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1ckr8t
|
Do any historians use the Holocene Era calendar in their work? (current year = 12013 HE)
|
After going to a museum exhibit about the Qin dynasty in the 3rd century BC, I became confused and irritated about dates going backwards, since I don't normally think that way. I had heard a while ago about the [Holocene Calendar](_URL_0_), proposed in 1993 to solve this issue.
It has increasing dates for all of human history (and no missing year between 1BC and 1AD). It starts approximately at the beginning of the Holocene, and it's easily converted to and from the Gregorian calendar.
So has anyone seen a real historian using it?
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/1ckr8t/do_any_historians_use_the_holocene_era_calendar/
|
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"Would this really solve things? It's still arbitrary and yet western-centric. I agree it's inconvenient having a date system that reverses at one point, but it's still better than the traditional reign-year system they still use in Japan.\n\nFWIW, I've taken history courses (India, China, Japan, Korea) and anthro courses (Native American, Mesoamerica) where we dealt with dates in the BC/BCE, and none of them used them. Some of them have dates that would be in the BHE as well.\n\nClearly the best solution is to adopt the [Juche Year system](_URL_0_) of Best Korea.",
"Honestly, it doesn't take long to get used to the dates going backwards. This is absolutely pointless. And what about the poor Palaeolithic specialists? They'd still have to count backwards in the \"Human Era\" system."
]
}
|
[] |
[
"http://en.wikipedia.org/wiki/Holocene_Era"
] |
[
[
"http://en.wikipedia.org/wiki/North_Korean_calendar"
],
[]
] |
|
3wluk0
|
what are the specific characteristics that define classical music?
|
Can a piece composed in 2015 be considered classical? Also, can the soundtracks of video games such as Skyrim or Dragon's Dogma be considered classical music?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/3wluk0/eli5_what_are_the_specific_characteristics_that/
|
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"In the broadest sense, \"classical\" music can mean any type of Western \"art music\" played by acoustic instruments, particularly the violin family, and with less emphasis on improvisation and repetition than folk or popular music.\n\nStricter definitions only include music from the classical period (1730 to 1820). Earlier composers were Baroque, and later composers were Romantic. However, Baroque and Romantic music are considered to be classical by classical stations, record stores, and common speech. \n\nA piece from 2015 could be classical by one definition, but it would be more proper to call it \"symphonic music\" or \"art music.\"\n\nAs for characteristics, classical music uses frequent dynamic loudness variation, frequent tempo and key changes, complex melodies, and complex instrumentation, while most other musical styles use a more uniform approach. At the same time, classical music tends to be very rehearsed, without much room for improvisation (as in jazz or rock.)",
"Among people who like the sort of music you are thinking of, \"classical\" refers specifically to music from around 240 years ago (Mozart, for example). After the middle ages the eras go, roughly, Renaissance, Baroque, Classical, Romantic; then you start to divide styles by schools rather than eras, but people might talk about Impressionism, post-Romanticism, Modernism, Expressionism, Minimalism...\n\nYou definitely still refer to people who work with that kind of music as \"classically-trained\", though. That is, even if when they compose new work it sounds very different, they've learned to play an instrument or conduct an orchestra in the way perfected during the classical era.\n\nA piece composed on 2015 would probably be identified as \"contemporary\" or else identified with the school of the composer.\n\nThe people who do the scores of films and video games are certainly accomplished musicians, but they generally go to a different sort of conservatory where they train specifically to work for film. The soundtrack for Skyrim might be considered contemporary orchestral music (is that what it is? I've never heard it), just like something written to be performed as a symphony, but the musicians and composer may not have any profile in the music world. There are exceptions, though. Ennio Morricone is widely recognized as a genius for his scores. There was a movie called \"The Red Violin\" that I think was scored and performed by classically-trained musicians."
]
}
|
[] |
[] |
[
[],
[]
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1b5ym3
|
Is there any form of Earthly life deriving energy that did not originate from the sun to fuel itself?
|
A few years ago, I took my first molecular biology class in college, and my professor asked us 'what constitutes life.' Occasionally I've gone back to that question and adjusted my answer (things that contain carbon based (on Earth at least) genetic information and can replicate), but I've always struggled to come up with a concrete definition. I guess there are probably many components to what constitutes life, so a nice, concise definition might be difficult to establish.
I was thinking about it today, and wondered if maybe the best definition is organisms that consume energy either directly from the sun or from these photosynthetic precursors. All consumed caloric energy that I can think of originated from photosynthesis, then trickled down the food chain. Are there any organisms that somehow thrive without some form of energy from the sun?
Writing this, I am realizing that this new definition is also deeply flawed, as many nonliving things consume energy that originally came from the sun (our cars for example), but perhaps a definition could be made by combining the two possibilities I've discussed above (carbon based genetic material that can be passed on and requires light energy for sustenance/reproduction). Thoughts?
|
askscience
|
http://www.reddit.com/r/askscience/comments/1b5ym3/is_there_any_form_of_earthly_life_deriving_energy/
|
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"The Earth's centre is primarily heated by radioactive decay (it also had a kick-start due to gravitational heating). Anything that gets its energy from thermal vents is getting energy from a non-solar source.",
"In addition to what Astrokiwi posted, there are many kinds of organisms that extract energy from inorganic chemicals. They are known as 'chemolithotrophs', and, depending on the species, can extract energy from such varied sources as iron, sulfur, and uranium. ",
"To help with your definition of life, the 5 criteria commonly used are\n\n* growth\n* reproduction\n* consumption of energy (whether from light or from chemicals)\n* mechanisms that maintain homeostasis\n* response to internal or external environmental stimulus\n\nAll five criteria must be met, hence robots and zombies are not alive."
]
}
|
[] |
[] |
[
[],
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[]
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|
1b6lf6
|
Sources of steel/iron in medival Europe.
|
So, I have this image in my head (thanks mostly to fantasy novels and movies) of medieval Europeans using steel and iron for everything from armor and weapons to tools, horeshoes, and nails. Is this accurate? If so, where did they get all this steel? Was iron ore gathered/mined and processed (refined, smelted, whatever you call turning a rock into a peice of steel...) locally, or only in a few places and then traded throughout Europe? Just how available was steel? Would peasants have had access to steel tools, or was it only affordable to the upper classes?
Also, I have similar images of bronze being just as ubiquitous in ancient Rome. How did the procurement and use of bronze in Rome differ from steel in medieval times? When and why did steel surpass bronze as the metal of choice in Europe?
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/1b6lf6/sources_of_steeliron_in_medival_europe/
|
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"In early times, a lot of iron ore resources came from swamps [bog iron](_URL_0_). For example the Vikings and the Russians this was a major source of iron. The time period you're describing is medieval times, by then a lot of rich iron ore resources would be discovered already and much trade was present in Europe, therefore distributing iron ore (raw steel ready for further tooling) would be possible.",
"In England during Roman times there were several iron mines with fairly advanced techniques. After the Romans, in the Early Middle Ages, these shut down and most of the iron was bog iron, which can be found as large chunks of high grade ore by probing in bogs. During this time iron and steel were scarce. Weapons were still made from it, and some craftsmen's tools would have used it, but for the most part a \"peasant\" would have used wood tools. Swords were steel, most other objects were plain iron as steel was difficult and expensive to make.\nAs you get into the High Middle Ages some of those old Roman mines are starting to be worked again, although with poorer mining technologies. This saw an increase in the availability of iron and a reduction in the cost of iron products. This meant more iron weapons, tools, nails, etc. At this time pieces of the [plows](_URL_0_) that a peasant would have access to were made from iron. \n \nThe Romans had both bronze and steel just like Europe did in the Middle Ages, in fact they had a far more efficient mining and transportation system that let them mine far more than was possible later on. I am not an expert on Rome, but I am pretty sure that Roman weaponry was steel. Bronze looks really nice though so it is possible it was used for a lot of decoration, or maybe movies just like it for this purpose. Also bronze tends to be more expensive than iron, since both copper and tin are needed to make it and they are often not co-located. The Romans, with their vast empire, had access to both copper and tin mines so could make bronze."
]
}
|
[] |
[] |
[
[
"http://en.wikipedia.org/wiki/Bog_iron"
],
[
"http://en.wikipedia.org/wiki/Carruca"
]
] |
|
5nsg2k
|
why do so many train tracks run along creeks and rivers?
|
[deleted]
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/5nsg2k/eli5_why_do_so_many_train_tracks_run_along_creeks/
|
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"Rivers tend to form in places that have a long, continuous, mostly-gradual path from high to low places. This is exactly the sort of path trains need, as they cannot climb (or safely descend) very steep slopes.\n\nSome rivers do have steep bits (rapids, waterfalls), and in these bits the train will of course take a different route.",
"Rivers tend to connect developed industrial centers, so following them aids in connecting towns and allows relatively easy transition from sea/water to land movement of freight and passengers.",
"Railway engineers had to design tracks which stayed dry and did not get washed out. The natural solution is to build a ditch capable of handling water beside the track. The water has to go somewhere sometime, so it needs a creek or river to drain into. It works just as well to run the rail line down a real creek or river along the bank.",
"There are several reasons why train tracks were developed close to water.\n\nBefore railroads, the primary way to transport large amounts of cargo was by canal. First, it was barges pulled by horses that ran along the side of the canal. Later, with the advent of steam power, you had steamboats as well.\n\nAs steam locomotives were developed, they initially competed with these canals and steamboats along the same routes, and so they laid track along these same routes.\n\nAnother reason is that steam locomotives need water, and lots of it. For this reason, it made sense to locate the tracks and stations close to major water sources.\n\nAnd finally, as trains expanded westward across the mountains, they needed to choose the easiest routes with the smoothest grades. Over millions of years, waterways had carved routes through the mountain ranges, so it made sense to just follow the smooth grade that the river had already formed."
]
}
|
[] |
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[
[],
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|
77en1w
|
why are some words pluralized with an "i"?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/77en1w/eli5_why_are_some_words_pluralized_with_an_i/
|
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"text": [
"Those are words of Latin origin of male gender ending in -us. \n\nThe ~~declination~~ declension of those words demands an -i in the plural. \n\nSee [here](_URL_0_) for a full list of all forms of the second ~~declination~~ declension in Latin. ",
"Those words are:\n\nA) Relatively recent additions to the English language (late 1500s to early 1600s)\n\nB) Are simply stolen, without change, from Latin.\n\nAnd one of the way Latin words form plural is by changing -us to -i",
"They are words that came into English from other languages. Here are some common examples:\n\n| Singular | Plural | Origin | Plural pattern\n:---|:--:|---|--:\ncactus | cacti | Latin, from Greek kaktos, kaktoi | os- > oi / us- > i\nradius | radii | Latin | us- > i\nfungus | fungi | Latin | us- > i\n(originally spaghetto but not used in English) | spaghetti | Italian | o- > i\nmafioso | mafiosi | Italian | o- > i\n(originally blin but not used in English) | blini | Russian | nothing- > i\n\nQuite a few languages form plurals with \"-i\". Often you have to remove some letters from the singular form before adding the \"-i\".\n\nIn Latin it's common to have \"-us\" in singular and \"-i\" in plural. Also Greek words would often form plurals in \"-oi\", but we ended up giving them a Latin plural form in English so they also end in \"-i\".\n\nAdd to that the fact that Italian, which is descended from Latin, still forms many plurals in \"-i\", and you end up with a lot of Greek, Latin and Italian words in English that have this ending. I should point out that a lot of Italian words such as \"piano\" would have originally been \"piani\" etc but now have a regular English plural."
]
}
|
[] |
[] |
[
[
"http://thelatinlibrary.com/101/Declension2.pdf"
],
[],
[]
] |
||
73golv
|
how can carbon, hydrogen, and oxygen be rearranged to make up so many different things?
|
For example, the formula for sucrose (sugar), is C6H22O11, while ethanol (alcohol) is C2H5OH. Sugar and alcohol are very different, yet they are comprised of the same elements. How can this be?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/73golv/eli5_how_can_carbon_hydrogen_and_oxygen_be/
|
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"Actually hydrogen cannot be arranged too differently. It can be H2, the gas. When combined with oxygen it can form water, H2O, or a hydoxyl group which will react with something. It is when these two types of atom combine with the carbon which normally has 4 bonds available. Substituting the hydroxyl group for a hydrogen atom in methane, substituting it more than once, suddenly give methanol, then ether. The carbons can link in a chain, in long chains, in a loop to form cyclo-hexane, then more and more things. It is the carbon which makes organic chemistry so rich.",
"Much like a basic set of LEGO blocks, if you have enough pieces you can build all sorts of things. There are only 26 letters in the alphabet and yet we use them to fill out all the books in the world. With just two digits we can convert all of that into binary. And with just binary we can code the entirety of the internet. \n\nIt’s all a question of quantity, even with very simple building blocks, given enough of them an incredible number of different things can be built. With a nearly unlimited amount of building blocks, such as C O and H, A fantastical number of things can be built. "
]
}
|
[] |
[] |
[
[],
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21sjwu
|
Why doesn't a plane naturally go in circles when one engine fails?
|
It seems like the thrust only coming from one wing would cause it to go in circles kind of like when you paddle a boat from one side. Or is it possibly naturally doing that and the pilot counters it?
|
askscience
|
http://www.reddit.com/r/askscience/comments/21sjwu/why_doesnt_a_plane_naturally_go_in_circles_when/
|
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"Thrust always acts relative to the center of mass, so in the event of an engine loss, the plane will tend to rotate \"away\" from the active engine. The pilot (or autopilot) will counter this using trim in the case of normal asymmetries, or the control surfaces in the case of large, or emergency imbalances.",
"It is true the the plane will tend to yaw to one side This especially applies to\nplanes that have the engines under the wings. Since they are further\naway from the center of mass, they will create more torque. \nThe plane is designed in such a way that the pilot can keep the \nplane straight by using the rudder.\n\nThe most critical event is a an engine failure during take off just after\nV1 (decision speed). At that moment, the remaining engine needs to have\nmaximal power (in order to be able to take off on time), while the rudder\nis still relatively uneffective (due to the low speed of the plane).\nThe size of the rudder is designed for this situation.\n\nPlanes with engines under the wing have bigger rudders than planes withe\nengines in the rear, because failure of an engine will create bigger torque.\n\nThe boeing 747 is designed in such a way that it can cope with failure of one\nengine. However, it could not cope with failure of two engines. \nWhen El Al flight 1862 lost two engines on the right side on 04.10.1992, it was able\nto fly only in circles. \n[Map](_URL_0_).\n\n"
]
}
|
[] |
[] |
[
[],
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"http://en.wikipedia.org/wiki/File:Bijlmerramproute.png"
]
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|
1xl630
|
if i file for bankruptcy....
|
ELI5:
If I file for bankruptcy what happens to all of my debts?
How are the people that I am indebited to get affected by this?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/1xl630/if_i_file_for_bankruptcy/
|
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"The people you owe money to get screwed.\n\nThe Court (assuming they agree to your claim of bankruptcy) will gather up all of your assets and sell them off, paying out the proceeds to your debtors.\n\nThis never ends up being worth it to them, they get pennies on the dollar. ",
"Bankruptcy actually stays on your credit for 10 years not 7(unlike other outstanding debts). The answer to your question also depends on whether you file (and are granted) a chapter 7 or chapter 11 bankruptcy, but generally the people you owe get nothing or very little of what you owe them. The longer the BK has been on your credit report the less it affects your chances of being granted credit. You can still have a bank account, you just probably will not be approved for a credit card or loan for a few years. Also it should be noted that federal student loans, child support and backed taxes will never be waived in any BK.\n",
"If you file for bankruptcy and follow all of the rules, most (if not all of) your personal debts will be \"discharged.\" This means that the creditors cannot attempt to collect on the debts; it's like the debt doesn't exist anymore.\n\nNot all debts can be discharged, though, and there are several different types of bankruptcies that you could potentially file, each of which has different rules and requirements for getting a discharge."
]
}
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[],
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74yav2
|
how are us military units numbered? if there's a 501st battalion, are there 500 others active at the same time?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/74yav2/eli5_how_are_us_military_units_numbered_if_theres/
|
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"The military gets bigger and smaller over time. A lot of units are disbanded based on requirements or the most decorated and acomplised ones are kept when others are cut but they keep their names. \n\nSame reason for MI5 and MI6, as far as I recall there were something like 14-17 (british) MI (military intelligence) units at the height of ww2 some were merged and others disbanded. ",
"It means there were likely 500 other batallions *at some time*\n\nDuring WWI and WWII lots of divisions and battalions were created. During WWII the US had 90 divisions, but infantry division designations went up to 106 and armored divisions went up to 20 which is well over 90, so why? Because there were a few dozen \"phantom\" divisions, divisions that existed only on paper and were \"deployed\" to locations to free up real divisions that were about to go on the offensive without the enemy intelligence knowing that an area was now undermanned.\n\nToday the US still has some extremely high numbered divisions like the 101st Infantry Division, also known as the 101st Airborne Division. Today the US only has 17 infantry divisions yet the 101st Airborne division retains its high number in recognition of the unit's service during WWII. Letting a unit live on under the same number, or spawning a new one under an old number is sort of like retiring a jersey number, its about respect despite screwing up the count"
]
}
|
[] |
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[],
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d1unev
|
Is there value in viewing history through a lens of modern morality?
|
What I mean by this is often I'll see people defend atrocious acts or now condemned opinions of past peoples or simply ignore as "A product of the time".
an example being H.P Lovecrafts writings are often considered racist and this is handwaved as a product of the time but it's still there in his works it hasn't and won't go anywhere.
Is there value to judging past actors by today's standards? or is it better to try and maintain an air of neutrality or objectivity towards it?
If I've phrased this awkwardly or it doesn't belong here, I do apologise.
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/d1unev/is_there_value_in_viewing_history_through_a_lens/
|
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"**NSFW Warning, Quotation From 1910s Letter With Racist, Anti-semitic Language, Be advised**\n\n > **What I mean by this is often I'll see people defend atrocious acts or now condemned opinions of past peoples or simply ignore as \"A product of the time\".**\n > \n > **an example being H.P Lovecrafts writings are often considered racist and this is handwaved as a product of the time but it's still there in his works it hasn't and won't go anywhere.**\n\nThis is a viewpoint which is more prevalent among certain fans than scholarship. The major critics and writers on Lovecraft, such as S. T. Joshi, have never made a point of denying, hiding, or downplaying his racism. In fact, they have contributed hugely toward our understanding of Lovecraft and his prejudices by continuing to push for the unexpurgated collections of his correspondence and essays, showing how Lovecraft expressed his prejudices to various friends and correspondents versus pieces written for public consumption, and how those views changed throughout his life.\n\nNow, there were Lovecraft scholars like Dirk W. Mosig who argued that Lovecraft should not be considered a racist *in the contemporary sense*. Mosig was writing in the 1970s, after the Holocaust and the Civil Rights Movement in the United States, and he was referring very specifically to the fact that Lovecraft, who died in 1937, was expressing views and opinions from a very different time period, even if only a few decades separated him from when Mosig was writing.\n\nLovecraft lived at a time when racial segregation was legal, and interracial marriage often wasn't; he saw the rise of the second Ku Klux Klan and Adolf Hitler and the Nazi party, the opening salvos of what would become World War II with the Italian invasion of Ethiopia and the Japanese invasion of Manchuria, but not the end; he was alive when the Immigration Act of 1924 established the quota system, drastically reducing immigration into the US on racial boundaries, and he was alive when \"Yellow Peril\" literature reached its height.\n\nSo it is absolutely the case that Lovecraft should be considered within the context of his time. It is not *remarkable* given when and where he lived that he should have had prejudices against various ethnicities, against African-Americans, Jews, LGBTQ folks, etc. It is also not surprising that the scientific racialism and events of his era helped shape his views: he uses many of the common classifications for races of Thomas Huxley, for example; during World War I he became more fervently patriotic and xenophobic; several of his specific comments can be traced directly to events and writings of his day.\n\nNone of which excuses the fact that he did hold those views. Just because you are raised in a society where racism is common does not mean you *have* to be racist. Lovecraft could have known better - arguably should have known better. He had more progressive friends, most notably James F. Morton, who was an early member of the NAACP and author of a tract titled *The Curse of Race-Prejudice* (1906), who would argue with Lovecraft on the subject. The scientific racialism which Lovecraft used to buttress his prejudices was being disproven while he lived by biologists like Franz Boas, and Lovecraft ignored or downplayed the findings, claiming the research was skewed by sentimentality.\n\nWhich is to say that the \"man of his time\" argument is not, or at least should not, be used as an excuse or apologia. It is not the case that Lovecraft could not have held any different opinion on race - and this is obvious because his opinions were not static throughout his life. Although he did hold some of the prejudices from a very young age (by his own accounts in his letters), his exposure to different peoples and points of view throughout his life did cause him to rethink and refine his thoughts on race...\n\n...but prejudices die hard. People don't change often, and when they do it isn't by much. Lovecraft was never \"not racist\" by our contemporary standards. Neither was he notably \"virulent\" by most of his contemporary standards (with the possible exception of his wife). What is remarkable about Lovecraft's racism is that we have such a *record* of it - because he was a prolific letter writer, and as many as 10,000 of his letters were saved and many have been published (and are still being published), and because Lovecraft is still being *read*. There are dozens of pulp writers who published fiction which is as prejudiced or much cruder in terms of race than anything that Lovecraft wrote, but their work is nowhere near as popular or influential - they are all but forgotten, and so they do not attract the same attention.\n\nSo all that being said, let's hit on the rest of your question:\n\n > **Is there value to judging past actors by today's standards? or is it better to try and maintain an air of neutrality or objectivity towards it?**\n\nLovecraft is still being read. He is long dead; his opinions cannot change, he needs neither demonization or excuses. It is for us the living who read and respond to his work to do something much more difficult: try to understand."
]
}
|
[] |
[] |
[
[]
] |
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2n20a0
|
Are there lone groups of "planets" in the distance between stars?
|
askscience
|
http://www.reddit.com/r/askscience/comments/2n20a0/are_there_lone_groups_of_planets_in_the_distance/
|
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"Groups? Doubtful. Rouge planets do get kicked out of solar systems during their formation, or systems with complicated and unstable orbits can eventually kick out a planet (or gravitational interaction with a nearby stellar mass object). There's an article on r/science where they measured Saturn's gravitational influince on the inner planets, they found that if saturn's orbit was inclined by 20 degrees from the ecliptic, Mars would get kicked out. At 30 degrees, Earth would get kicked out too.\n\n_URL_0_",
"There may be more rogue planets between the stars than there are stars in our galaxy. _URL_0_\n\nIt seems likely some of them could be in orbits with each other."
]
}
|
[] |
[] |
[
[
"http://www.newscientist.com/article/dn26601-saturns-calming-nature-keeps-earth-friendly-to-life.html?utm_source=NSNS&utm_medium=SOC&utm_campaign=twitter&cmpid=SOC|NSNS|2014-GLOBAL-twitter#.VHBphckrrJh"
],
[
"http://blogs.discovermagazine.com/badastronomy/2011/05/18/the-galaxy-may-swarm-with-billions-of-wandering-planets/#.VHDBNsktzOM"
]
] |
||
1n6ane
|
How does a DDWFTTW vehicle actually get energy to move in a straight line directly downwind faster than the wind behind it?
|
I'm familiar with sailboats that tack to go faster than the wind, but a DDWFTTW vehicle appears to be able to do it in a straight line with the wind directly behind it. I can grok the sailboat example, but I don't get how a vehicle being pushed only from behind by wind of 10mph can reach 25+mph. To my mind (and I'll admit I can be a pretty stupid cookie) when it's going 25mph downwind in a 10mph downwind it's actually running against a 15mph headwind. Can anybody give me some hints so I can intuit this in my head, because all I see online is academic acceptance of the working, but I don't 'get' the physics.
|
askscience
|
http://www.reddit.com/r/askscience/comments/1n6ane/how_does_a_ddwfttw_vehicle_actually_get_energy_to/
|
{
"a_id": [
"ccfz4f8"
],
"score": [
3
],
"text": [
"In analyzing the system, you can look at either forces or energy. In either case you must not come up with a contradiction.\n\nIn looking at forces, we have the force of the propeller against the air and the force of the wheels against the ground (call these F_p and F_w). I define a sign convention such that if F_p is positive then that is the propeller pushing the car forward (i.e. acting like a fan) and negative is the propeller pulling the car back (i.e. acting as a turbine). Similarly, if the wheels are propelling the car forward then I define that as F_w being positive, but if the ground is being used to drive the wheels--meaning that the F_w is in a direction to slow the car--then F_w is negative. Thus, the car can move forward at a steady state if and only if F_p + F_w > 0.\n\nIt must be greater than zero since there will be some friction forces from rolling and wind resistance to be overcome. Now, the intuitive thing to do here is to say that F_p is negative and F_w is positive--the wind is blowing the propeller, the propeller is spinning the wheels, and the wheels are driving the car forward. However, it is actually the case that F_p is positive and F_w is negative--the wheels drive the prop, which pushes on the air to make the car go forward.\n\n\"Surely this is an affront to conservation of energy!\" one might object, so let us now look into energy. Bear in mind that at this point we have taken that |F_p| > |F_w|. When we look at energy (or, more conveniently in this case, power) we can simply multiply a force by a velocity. The wheels produce energy at a rate of F_w\\*25 mph, while the propeller only takes F_p\\*15 mph to run; F_p can be greater than F_w but still satisfy the energy balance since the relative wind speed is less than the ground speed. The steady-state energy balance works out.\n\nNote that if we had assumed the opposite signs of F_p and F_w then we would have found that F_p\\*v_wind must be greater than F_w \\*v_ground and we would have had that |F_w| > |F_p|. This works out in a situation where there is, say, a 10 mph wind and the car is traveling at only 3 mph--a 7mph tailwind. We get that F_p\\*7 mph > F_w\\*3 mph. \n\nThe math gets dicey when traveling close to the speed of the wind, but there is no requirement for a steady state solution at the same speed as the wind. A car can be propelled across that boundary (if it exists) by either gusts or flywheels."
]
}
|
[] |
[] |
[
[]
] |
|
axbmmj
|
why is it okay for us to eat raw eggs but not raw chicken?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/axbmmj/eli5_why_is_it_okay_for_us_to_eat_raw_eggs_but/
|
{
"a_id": [
"ehshl02"
],
"score": [
9
],
"text": [
"It is not okay to eat raw eggs in every part of the world. Some places have the same salmonella problems with eggs as they do with chicken. It is not universally safe to eat raw eggs in the US."
]
}
|
[] |
[] |
[
[]
] |
||
anacdl
|
what does ping 127.0.0.1 do?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/anacdl/eli5_what_does_ping_127001_do/
|
{
"a_id": [
"efrwo52",
"efrwq72",
"efrwsfy",
"efrwv6s"
],
"score": [
2,
4,
3,
2
],
"text": [
"127.0.0.1 is the “loopback” address, which basically means it points to the machine sending the request (your own computer). Pinging that address has no real purpose, other than maybe testing hardware speeds. ",
"The network stack processes the packet, and goes \"oh, that's for me! Better see what's inside. A ping request? Great, I'll send a ping response to the sender! Which is me.\"\n\nThe packet is never physically transmitted over the wire. You can test this yourself by unplugging the Ethernet cable - ping 127.0.0.1 will still work.",
"127.0.0.1 is the loopback address. It is your machine sending a ping to itself, which can happen totally within software. So a ping to 127.0.0.1 allows you to test software by eliminating the variables of hardware, drivers, and the network.\n\nIf you can't get a response from 127.0.0.1 your IP software is borked.",
"127.0.0.1 much like 10.x.x.x, is a reserved IP number that refers to the local network /computer.\n\n\nAnother example of this is your router which is is almost always 168.192.x.x ... so you use this IP to connect to your router. Since it’s reserved, you can’t get to your router from outside your network.\n\n\n\nAs for the pinging... you’re trying to ping a local host.\n\n\nTo really explain what’s going on, I’d need to know more about what you’re trying to do. "
]
}
|
[] |
[] |
[
[],
[],
[],
[]
] |
||
bj0y3l
|
How did Christians reconcile their hatred of sorcery with the stories of Merlin and the quest for the Holy Grail?
|
I have been reading Le Morte D'Arthur and have also been getting into Dungeons and Dragons recently. I was curious why the figureheads of the Satanic Panic during the 1980s related the stories of fantastic heroes in a medieval setting hunting dragons and going on great quests with the worship of Satan rather than the stories of the Knights of the Round Table. As I thought about it more I also became curious about how the nuance between good and evil sorcerers in the stories became ignored during witch trials, where it seems to have been assumed that anyone who is accused of sorcery was in league with Satan.
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/bj0y3l/how_did_christians_reconcile_their_hatred_of/
|
{
"a_id": [
"em4t20t"
],
"score": [
9
],
"text": [
"I have an answer to an earlier question along the same lines (one of my favorites!):\n\n* [If the use of magic was seen as heresy in the Catholic church, why was Merlin, a renowned wizard, seen as a good and admirable figure from the Arthurian legends?](_URL_0_)\n\n~~\n\n[1/2]\n\nLancelot is the great tragic hero of the Middle Ages--the Knight of Hearts, *defined* by his love for the woman he can never permanently have. Gawain is the chivalric warrior par excellence, the greatest knight of the Round Table. And yet, in the early 13C *Quest of the Holy Grail*, one volume of the cycle that basically codifies the 'full' story of King Arthur and his knights, Lancelot spends the whole book doing penance for his adultery, spiritually divorcing himself from his defining characteristic, and still doesn't truly reach the Grail. Gawain doesn't have any opportunities to prove himself worthy. No, boring AF Galahad, Perceval, and Bors plod through their quest and receive the Grail-vision victory. Court-based \"Fanfction\" writers all over Europe take Gawain off on his own riotous adventures of ladies and war--while the rewrite and consolidation of the overarching tale works even *harder* to make everything a Christianized spiritual quest. Thomas Malory in the 15C, of course, will have none of this, thus reifying Lancelot and Guinevere's romance as the beating heart of Camelot.\n\nThe point is, western medieval Europe loved Arthur and his knights, and so the stories mattered. Because they mattered, people fought over them--both in and out of the texts. The presentation of Merlin throughout later medieval Arthuriana is a fantastic illustration of the tensions in play amidst changing social ideals of order, purity, and Christian orthodoxy.\n\nMerlin has both an in-universe and meta-literary backstory when Geoffrey of Monmouth drops him into his rough outline of the Arthurian saga in the 12th century. Geoffs had a bit of an obsession with the legendary wild man who evidently walked around spewing prophecy to anyone with a pen, in fact--he translated a book of prophecies attributed to Merlin from Welsh into Latin before composing the *Historia*, and followed it up with a separate biography of just Merlin.\n\nGeoffrey's new and improved backstory for Merlin already starts to show some of the tensions over supernatural power acting in the world. He borrows part of a biography of yet another legendary character--and then twists it completely. Instead of being a teenager with an unknown father (who turns out to be an ordinary Roman), Geoffs lets one character interview another as to Merlin's parentage. Merlin's mother implies the father was some sort of spirit in the *shape* of a young man, and Vortigern's advisor-sorcerers generally agree it was a demon. This is hearsay, this is supposition, it allows Geoffrey to avoid the question of the relationship between his prophet and magic, his prophet and demons.\n\nMerlin's magic or \"magic\" in the *Historia* is equally ambivalent. Geoffs certainly implies it--or does he? Are Merlin's \"contrivances\" that enable him to move Stonehenge all by himself, 'merely' physical? How closely were \"medicines\" tied to supernatural rather than natural power in the 12th century imagination? Is Merlin transforming Uther into Gorlois, or just giving him really good makeup advice? And--is the apparent ambiguity to us simply a modern imposition on a 12C worldview that didn't differentiate?\n\nThe popularity of Merlin beyond the developing Arthur tale, and the evident popularity of the character within it, made a serious impact on late 12C and early 13C readers. The first group I'll discuss is, like Geoffs, the scholarly-ecclesiastical elite: Latinate churchmen, at the forefront of crystallizing orthodoxy and stamping out what they label heresy (at this point: basically anything seen to threaten Church power; heretical \"belief\" is kind of a wash in an era where the bishop agreed to let the demon-possessed lady keep preaching and shouting in church until Hildegard of Bingen could get there to perform the exorcism).\n\nYou might think that, with the Church doubling down on Church-ifying and controlling lay belief from the late 12C on, clerics would frown on Merlin and vernacular writers composing romances for the laity would know what sells. Well, as Facebook might say, *it's complicated*.\n\nPerpetual crankypants John of Salisbury made little secret of his distaste for Merlin. John differentiated between contemporary, chosen-by-God prophets like Hildegard and Elisabeth of Schonau on one hand, and misguided diviners (that is, those who sought supernatural knowledge by themselves) of \"futile/worthless authority\" whose false prophetic powers came from demons. But when John criticized Merlin explicitly, he did so in response to a colleague who had cited him authoritatively.\n\nAround the turn of the 13th century, William of Newburgh had even harsher words about Merlin. Writing passionately that no true words can come from the devil, which is Merlin's source *even according to Geoffrey* (in Will's account), the Augustinian jeers:\n\n > It is plain that whatever things [Geoffrey] published, writing about Merlin, are lies, made up to gratify the curiosity of those without prudence/virtue.\n\nAround the same time, however, Gerald of Wales thoughtfully placed Merlin's Welsh-pagan roots in the context of the current fad towards Christianizing classical pagan texts and ideas (a time-honored medieval obsession). Gerald pointed out that, for example. pre-Jesus seers like the Sibyl nevertheless prophesied his birth (...roll with it). Orderic Vitalis had gone even further, pointing out that some of Merlin's prophecies had been fulfilled and more would be! God speaks through his saints; surely he has the power to speak through others even in the contemporary world. Still, Gerald must be cagey:\n\n > ...By what spirit such prophecies are made possible, I do not necessarily say that it is demoniac.\n\nThrough the twelfth century, the general idea of \"King Arthur\" and the Round Table knights grew into a gelatinous, disorganized blob. Around 1200, authors with a keen eye towards what was popular with readers started to work to change that. Among the most important, certainly of those whose (probable) name survives, was one Robert de Boron. Robert is probably best known for weaving the Grail into Arthurian legend not as a mysterious floating dish but as the Holy Chalice/Holy Grail brough to England by Joseph of Arimathea--in other words, a lot of the responsibility for the Christianization of Camelot's questing is on his shoulders. And, or maybe and yet?, his other major passion (at least, to surviving text appearances) was *Merlin*."
]
}
|
[] |
[] |
[
[
"https://www.reddit.com/r/AskHistorians/comments/68jwfl/if_the_use_of_magic_was_seen_as_heresy_in_the/"
]
] |
|
c199va
|
In the Ancient times, how did they know what time it was, and if they had a meeting, like the senate in Rome, how did they know what time it was and was it normal that people was late because they had different views on time?
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/c199va/in_the_ancient_times_how_did_they_know_what_time/
|
{
"a_id": [
"ercg3g1"
],
"score": [
78
],
"text": [
"There is already a great answer by u/Celebreth here ( [_URL_1_](_URL_0_)) on Ancient Greece - I will try to do the same for Rome.\n\nIn Ancient Rome, things were somewhat complicated. While everyone could more-or-less agree on what time it was *right now*, your idea of time shifted depending on where in the world and when in the year you were.\n\nOriginally, things were imprecise. At least in the city of Rome itself, time seems to have been reckoned originally by looking at where the sun was in relation to certain landmarks - the Roman writer Pliny, around AD 79, records that a herald would be dispatched in the Forum to announce when it was noon, based on seeing the sun 'between the *rostra* and the Graecostasis'. This exact measurement cannot have been particularly ancient, however, since the Graecostasis was only built around 160 BC.\n\nIn the middle Republic, the system of 'hours' was developed, dividing the day into twenty-four blocks of time, twelve between dawn and dusk and twelve between dusk and dawn. The first hour after dawn, therefore, was *prima hora* \\- 'the first hour' - or sometimes *prima hora diei* \\- 'the first hour of the day', and so on for eleven more. The first hour after dusk was similarly *prima hora*, usually called *prima hora noctis* ('the first hour of the night') - though as we shall see in a minute, this was rarely necessary. \n\nThere is an obvious problem with always marking the period between dusk and dawn as twelve hours, which is that the length of a day changes sharply from season to season - as such, an 'hour' could be anything between 40 minutes and 1 hour 20 in our modern system, and would be different in the day compared with the night. \n\nThe consul Valerius Messalla brought a *solarium* \\- a Greek sundial, now re-named in Latin - back from war in Sicily in 264 BC, but it cannot have been calibrated for Rome's latitude and at any rate would not have worked with the Roman system of reckoning hours. There were quite a few of these around the city - Augustus famously built a tremendous one on the Campus Martius in 9 BC, whose *gnomon* (the bit that sticks up and casts a shadow) is now in the Piazza di Montecitorio. Others can be found around the city and Italian towns, often on other buildings - in a fictional text called the *Satyricon* from around AD 60, the aristocratic author Petronius has the boorish character Trimalchio plan to have one put on his tomb, to ensure that everyone would look at his name written beneath it.\n\nFrom the 2nd century BC, *solaria* could be used to calibrate water-clocks - *clepsydrae,* a name which gives away the Greek origin of the technology, was Latinised into *horologium* - which had the advantage of working when the sun could not be seen. The basic idea was to make a cylindrical 'hourglass' filled with water, fill it up in at dawn, mark how far the water level had fallen by dusk, and interpolate. This could be done at various times of the year - Carcopino says that they would mark twelve vertical lines, one for each month, and then mark a set of horizontal lines on each one as above. I am not however sure of his primary source for this and his writing sounds like he is working out how they 'must have done it' rather than referring to anything empirical. At any rate, we know that it was never an exact science - Seneca, around AD 55, suggests that 'it is easier to find two philosophers who agree than two water-clocks'.\n\nAt night, things were more usually done by 'watches', timing by the four rotations of the city or camp watch, each marked by a trumpeter. So when sources talk about things happening at night, they much more usually talk about which 'watch' it was (and in other words, only give the time accurate to about three hours) than the 'hour' - because the *solaria* would be useless and few people had a *horologium* (a retainer of our fictional friend Trimalchio picks it out as a status-symbol that will wow his upper-class guests).\n\nThings got even more complicated if you ever travelled - I have seen something somewhere about how people noticed that you could travel West 'faster' than you could travel East, in that you might set off going West at the 'first hour' and arrive to be told it had only just gone the the 'second hour', but then turn around and find that the 'third hour' had been some time ago when you arrived - of course, the problem was that the sun rose later in the western town than it did in the East. However, I cannot for the life of me find the source.\n\nOne imagines that Romans would develop a keen sense of time, much like many people who rely on keeping regular time-limits do today - watch a chef or teacher at work to see that. For an analogue, you can think of the Guugu Yimithirr in Australia, whose language traditionally has no egocentric directions - only 'north', 'south', 'east' and 'west', and so who develop a keen sense of direction without necessarily being able to articulate how they know which way is 'north'.\n\n**Sources**\n\nPliny's recollection of sun-watching in the Roman Forum is recorded in his *Natural History* at 7.60. Seneca's quip about water-clocks is in the satirical work *Apocolocyntosis*\n\nOn Roman 'clocks', see the entry under 'time' in Matthew Benson (2002) *Encyclopedia of the Roman Empire*\n\nThere is also a lot of useful information in Jerome Carcopino's 1936 *Daily Life in Ancient Rome* \\- dated, yes, but this sort of 'nitty-gritty' factual scholarship largely escaped the major overhauling that came with the theoretical shift in Classical scholarship, and has not been of particular interest to many scholars since.\n\nOn the Guugu Yimithirr, see Guy Deutscher's 2011 'Through the Language Glass' - though it is worth pointing out that their system has all but died out in the face of modernisation."
]
}
|
[] |
[] |
[
[
"https://www.reddit.com/r/AskHistorians/comments/69knux/time_keeping_in_ancient_rome/",
"https://www.reddit.com/r/AskHistorians/comments/69knux/time\\_keeping\\_in\\_ancient\\_rome/"
]
] |
||
5pj6bd
|
which symptoms of the flu are caused by the virus itself and which are caused by our body trying to destroy the virus?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/5pj6bd/eli5_which_symptoms_of_the_flu_are_caused_by_the/
|
{
"a_id": [
"dcrkxc2",
"dcrlifu"
],
"score": [
81,
16
],
"text": [
"Symptoms of the flu are actually often caused by your body trying to rid itself of the virus; high fever is a way to try and kill the virus by essentially cooking it, but in the process destroys a lot of your own cells, which can make you feel tired and shitty.\nIncreased mucus production is a way to try and expel the virus from your system by trapping it, then sneezing or coughing it out. Tiredness can also be a result of energy being funnelled into your immune system to try and combat the virus.\nThe virus affects you by invading your cells, reprogramming them to create more viruses, then lysing (exploding) them, which can result in overall reduced physiological function.\nNausea, vomiting, and diarrhea are also a bodily response to try and expel the virus.",
"for almost any disease, most symptoms will be a result of your immune system activating, and the cytokines produced from that activation- fever, aches, fatigue, etc. \n\n\nthese symptoms are grouped as \"flu like symptoms\", and are very common and somewhat useless to diagnose anything without other symptoms- you might have a mild stomach virus, a cold, or something far worse. \n\nother symptoms depend on what cells are being attacked. \n\nrespiratory attacks present coughing, excessive mucus production in the nose or lungs, sneezing, and the like. flu, cold, pneumonia, etc.\n\ngastrointestinal attacks result in vomiting, diarrhea. \"mild stomach virus\", cholera, etc. \n\nlymph node swelling can occur for two reasons- normal immune response and increased fluid movement in that system, or the virus attacking the nodes. \n"
]
}
|
[] |
[] |
[
[],
[]
] |
||
53h3rp
|
How did the nazi leadership, SS and death squads justify/rationalise the holocaust?
|
Unless every single person involved in the holocaust was a psychopath with no capacity for empathy (i know many if not most of them were) i have difficulty understanding how an entire state of people could be capable of such a massive atrocity. How did the Nazis manage to dehumanise the Jewish people and other groups so much that mass extermination could be seen as an acceptable option? Did they manage to convince even otherwise normal people?
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/53h3rp/how_did_the_nazi_leadership_ss_and_death_squads/
|
{
"a_id": [
"d7t2esz"
],
"score": [
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"text": [
"The Final Solution underwent many different forms and changes before we finally arrive at the terrible conclusion that takes the form of the death camps like Auschwitz and Treblinka, and much of what was done to exclude and expel the Jewish people (among others) from pre-war German life, like the 1935 Nuremberg Laws, laid the groundwork for greater, more extreme measures to be taken during the war itself. As the Nazi state become much more emboldened and the SS began to assume more of a direct responsibility in physically eliminating \"undesirables\" in initiatives such as the T-4 euthanasia program and the deployment of *Einsatzgruppen* during the invasion of Poland, created the blueprints for much of methods used in the death squads and camps in Russia, such as the use of gas vans. This set a precedent of what was capable, and permissible, in the East in regards of extermination of enemies of the state, and launched the Final Solution into it's final phase in 1941/42 from the forced emigration of Jews from Europe into ghettos to extermination.\n\nIn terms of how the Nazi's made this awful notion of the persecution of an entire people not only acceptable but considered an ideological imperative, a staple of Hitler's racial ideology on the grounds that the existence of a Jewish conspiracy threatened Germany, and what role the ordinary German person played in purporting this idea is the subject of much debate. By the time World War 2 began, the German people had been subject to 6 years of state anti-Semitic propaganda, which waxed and waned in it's ferocity, occasionally bursting out into violence like at *Kristallnacht* in 1938, which did much to dehumanize and degrade the Jewish people. This highly charged environment, combined with greater autonomy the SS received in the resolution of the Jewish question in 1941, with a highly motivated and highly anti-Semitic leadership at it's core and with the support if not the official blessing of Hitler himself, allowed for the Holocaust to occur. \n\nSources: \"Hitler, the Germans and the Final Solution\" by Ian Kershaw 2008"
]
}
|
[] |
[] |
[
[]
] |
|
17upcm
|
Why don't Britain, Israel & New Zealand have written constitutions?
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/17upcm/why_dont_britain_israel_new_zealand_have_written/
|
{
"a_id": [
"c892mbj",
"c892qki",
"c892t3i"
],
"score": [
11,
6,
6
],
"text": [
"I can't speak intelligently about Israel or New Zealand, but Britain does have a written consitution (for the most part). However, it is not a single document, but rather a large body of laws, court decisions, treaties, etc, with a large dash of custom thrown in for good measure. \n\nThe main point to remember here is the doctrine of [parliamentary supremacy](_URL_0_): parliament is supreme, can not be overruled, and whatever it decides according to its own rules of procedure is the highest law of the land. There isn't much point in codifying the body of constitutional law into a single document when the next parliament can change it so easily:\n\n > Parliament means, in the mouth of a lawyer (though the word has often a different sense in conversation) The King, the House of Lords, and the House of Commons: these three bodies acting together may be aptly described as the \"King in Parliament\", and constitute Parliament. The principle of Parliamentary sovereignty mean neither more nor less than this, namely that Parliament thus defined has, under the English constitution, the right to make or unmake any law whatever: and, further, that no person or body is recognised by the law of England as having a right to override or set aside the legislation of Parliament.",
"The treaty of waitingi is new Zealand's founding document and almost acts as a constitution for the country, in that legal claims are still fought against the state based on the rights given within the treaty. For example at the moment the government is attempting to sell off state assets such as a hydro power company and several Maori have launched legal action based on the water rights provided within the treaty.\n\n_URL_0_\n\nThere's no single new Zealand constitution but several important documents including the treaty make up the supreme laws of the nation I believe. I think one of the reasons why a constitution wasnt so important was that we inherited the British justice system and laws so that there were already established legal precedents and rights granted for individuals as a colony.",
"I can answer about Israel, though I'm basing it on the education I got in high-school and what's written in the Knesset site to [back me up](_URL_0_).\n\nBasically, When Israel was created there was a lot of debate going on about a written constitution. Some wanted the declaration of independence to be a constitution, Others said that we cannot have a constitution since Israel is still changing and forming itself, and others argued about the nature of the constitution itself and what will be included in it. They eventually decided to postpone discussion since, you know, Israel was invaded by everybody around it.\n\nSo on 1950 they began arguing once again, mainly because no one could agree on what kind of constitution we want - a civil one, a liberal one, a more religious one, etc. Meanwhile, the religious factions argued that the Torah is Israel's constitution and they wont recognize another, and others said that since most Jews don't live in Israel, it would be wrong to write a constitution before most Jews migrate here.\n\nSo what they ended up doing is drafting a bunch of \"basic laws\". Separate laws with constitution-like statues that will grow and evolve over the years and eventually be bunched up into a constitution. And that's what's been going on here since. Former supreme Justice Barak tried to change this and move Israel closer to a constitution, but he's been replaced since then and the constitution is pretty much in limbo for now."
]
}
|
[] |
[] |
[
[
"http://en.wikipedia.org/wiki/Parliamentary_sovereignty"
],
[
"http://en.wikipedia.org/wiki/Constitution_of_New_Zealand"
],
[
"http://main.knesset.gov.il/Activity/Legislation/Pages/BasicLawsAndConstitution.aspx"
]
] |
||
32kk7c
|
The universe is expanding, and people would too if not for gravity, electromagnetism, and the nuclear forces. Where does the energy to resist the "expansion force" come from?
|
Every point in the universe is "moving" away from every other point because space is expanding. This includes the space between the sun and earth, the space between me any you, and the space between my own atoms. So two atoms in my body (for example) are constantly being moved away from each other, but electromagnetism pulls them back together. Where does the energy required to do this come from?
|
askscience
|
http://www.reddit.com/r/askscience/comments/32kk7c/the_universe_is_expanding_and_people_would_too_if/
|
{
"a_id": [
"cqcixbr"
],
"score": [
3
],
"text": [
"*\"Every point in the universe is \"moving\" away from every other point because space is expanding. This includes the space between the sun and earth, the space between me any you, and the space between my own atoms.*\"\n\nI don't think your premise is correct. While it is true that galaxies are moving away from each other at an accelerating rate, I don't believe this is true for atoms."
]
}
|
[] |
[] |
[
[]
] |
|
3o21e9
|
Were Slavs a single people at one point? Or did they just share a single language?
|
I've noticed that my friends from other Slavic tribes and I have a fairly easy time understanding each other in our native tongues. So this got me wondering if at one point all Slavs were essentially one ethnicity or if we just happened to share a common language. I'd really appreciate any input on this. Thanks in advance!
|
askscience
|
https://www.reddit.com/r/askscience/comments/3o21e9/were_slavs_a_single_people_at_one_point_or_did/
|
{
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"text": [
"The answer lies in your question already; in short: we share similarities because we were once a single people with single language and due to migrations that happened in the past the language differences were created. Slavs share common language root of Proto-Slavic language and \"present\" languages belongs to Balto-Slavic group (which then is divided into Eastern, Western and Southern and Baltic groups). The mutual intelligibility of Slavic languages lies in common history of people who where living by centuries in Central and Eastern Europe - similar thing happens in Germanic language group. Moreover, the parent group of European languages in linguistics gathers all our languages under common ancestor of Proto-Indo-European language, so in fact all our languages are in some way related to each other and if you look deeply you'll see similarities too.\n\nThese links may interest you\n[1 - Indo-European Languages: Balto-Slavic Family](_URL_0_) /\n[2 - The Slavic Ethnogenesis /\nIdentifying the Slavic Stock and Origins of the Slavs](_URL_1_) /\n[3 - What Is the Origin of the Slavs?](_URL_2_) /\n[4 - Mutual Intelligibility among the Slavic Languages by Robert Lindsay](_URL_3_)"
]
}
|
[] |
[] |
[
[
"http://www.utexas.edu/cola/centers/lrc/general/ie-lg/Balto-Slavic.html",
"http://www.andrzejb.net/slavic/",
"http://blog.ut.ee/what-is-the-origin-of-the-slavs/",
"https://robertlindsay.wordpress.com/2010/11/06/mutual-intelligibility-of-languages-in-the-slavic-family/"
]
] |
|
1fhr85
|
Are some breeds of dogs, such as pitbulls, truly more aggressive than other breeds? Or is it a case of nurture where they tend to be raised by people who get them to be guard dogs, for example?
|
I was just reading [this news article](_URL_0_) about a pit bull attacking a woman who had raised him since he was a puppy. She expressed surprise about the attack and insisted the dog had never shown violent tendencies. Unsurprisingly the article reignited the debate about nature vs nurture with certain dog breeds, and in some countries (especially European countries) some of these breeds are now banned.
We know that certain dog breeds tend towards certain types of behavior, most books about dog breeds describe what you can likely expect if you get, say, a border collie versus a golden retriever. So my question is:
Is there scientific evidence that certain breeds, such as pit bulls, are prone to aggression, including towards their owners? Are some dogs simply less suitable to be pets, just as some breeds of animals can or cannot be domesticated well? Or does the evidence show that aggressive behavior in certain breeds is the result of a self selective ownership, where people who are interested in training dogs to be aggressive (guard dogs, fighter dogs, etc) tend to pick those breeds, for example due to their appearance?
|
askscience
|
http://www.reddit.com/r/askscience/comments/1fhr85/are_some_breeds_of_dogs_such_as_pitbulls_truly/
|
{
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"text": [
"[Click here](_URL_0_) for an overview provided by the AVMA of the current status of scientific study into the role of breed in dog bite risk. The overview provides references to 53 analyses published in peer reviewed journals. Here is their conclusion:\n\n > Maulings by dogs can cause terrible injuries and death—and it is natural for those dealing with the victims to seek to address the immediate causes. Serious bites occur due to a range of factors in which a dog's size and temperament are known to be the risk factors. Also important are dog management factors such as neutering and tethering, and child care factors such as supervision around animals.\n \n > Given that **pit bull-type dogs are not implicated in controlled studies**, and the potential role of prevalence and management factors, it is difficult to support the targeting of this breed as a basis for dog bite prevention. If breeds are to be targeted, a cluster of large breeds would be implicated including the German shepherd and shepherd crosses and other breeds that vary by location.\n\nThe source most often cited by lay persons who disagree with these conclusions is the [Clifton report](_URL_1_). I bring this up only to clarify that the Clifton report is an unscientific tabulation of dog attacks from newspaper reports that does not track other potentially contributing factors (such as dog size, temperament, neutering, tethering, etc.) and is neither published nor peer reviewed.",
"Along the same lines: are there any phenotypes that indicate a greater natural threat of being attacked by a breed compared to other breeds or a specific individual when compared to the rest of its breed?\n\nSince dogs are often bred for specific qualities and abilities this might be possible. However, it also seems misleading in that perhaps the breeding just emphasizes specific efficiencies or advantages related to specifically desired outcomes for a dog trained to perform a given task. A dog bred for that outcome is more likely to be trained for that scenario, thus a skewed perception. (E.g., why train a Chihuahua to bite when there are other breeds that can be trained to bite better. Now the other breed has a reputation for biting due to availability heuristics.)"
]
}
|
[] |
[
"http://www.dailymail.co.uk/news/article-2334412/I-treated-like-kids--Woman-lost-arms-eye-ear-attack-pit-bulls-calls-tougher-control-breed.html#comments"
] |
[
[
"https://www.avma.org/KB/Resources/Backgrounders/Pages/The-Role-of-Breed-in-Dog-Bite-Risk-and-Prevention.aspx",
"http://images.bimedia.net/documents/Dog+attack+stats+with+breed+2012.pdf"
],
[]
] |
|
5h6oyz
|
Do Godel's Incompleteness theorems currently have use whatsoever in Physics? If not, might they some day?
|
I am plowing through Godel Escher Bach for the second time at the moment (amazing read) and I was curious as the what connection (if any) the strange incompleteness of formal systems has with the physical universe.
|
askscience
|
https://www.reddit.com/r/askscience/comments/5h6oyz/do_godels_incompleteness_theorems_currently_have/
|
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"text": [
"From a philosophical point of view, it limits the notion of determinism. Even if we give a completely axiomatic description of a natural phenomenon, there will always be theorems you essentially cannot prove. \n\n\nAlso, a proof similar to the proof of Gödel's theorem (at least the proof I know of the theorem) may be used to establish the NP-completeness of the [boolean satisfiability problem](_URL_0_). This, in conjunction with some graph theory allows you to connect this satisfiability problem with wildly 'different' problems, such as the groundstate energy of the classical Ising model (in an arbitrary lattice).\n\n\nEdit: The relevance of the second paragraph is that this connection between the Ising model and boolean satisfiability allows you to establish the Ising ground-state energy as a hard problem (in the sense that it is NP-complete).",
"Generally they do not. Theoretical physics isn't at the point where it can be axiomatized the way pure mathematics can be. There was a [paper last year](_URL_0_) about how a certain problem in quantum mechanics is undecidable, which you may find interesting.\n\nI should add though that some of the deeper mathematical foundations of physics are beyond what I, and most PhD's outside that area, have studied.",
"It's not really a *use*, but it does have the unfortunate consequence that there may be results we want to prove or disprove, but won't be able to.\n\nJ. R. Lucas and Roger Penrose have both used the incompleteness theorems to argue that human minds cannot be (modelled as) Turing machines. Penrose goes further to suggest that this gives clues as to the fundamental physical laws (specifically that they are deterministic, but not computable). But AFAIK, his research programme has not enjoyed much support or empirical success; and the broad consensus is that the Lucas-Penrose argument does not work.",
" > Do Godel's Incompleteness theorems currently have use whatsoever in Physics? \n > ...what connection (if any) the strange incompleteness of formal systems has with the physical universe. \n\nDistinction must be made between \"physics\" and \"the physical universe\". \nThe first is a (partial) description of the latter. While physics may be 'Gödel incomplete', the universe/nature/reality is probably not - if only because nature does not describe what it does, rather it just does. ",
"I asked the author about this some years ago,\nand he suggested that Godel's proof only works\nfor discrete mathematical structures, not continuous\nones. ie. it applies to elementary arithmetic, but\nnot to geometric calculus. Hence, not to Newtonian\nphysics, ever--perhaps as per the Principia, or for some \nproblems in quantum physics--but not to contemporary \nreal world physics.\n\nGodel's proof involves mapping all possible proofs\nabout numbers on a number line, to numbers on a \nnumber line. Always makes me think of a snake\nswallowing it's own tail. \n\nI've seen it argued that all you need is to axiom-ize\na system for Godel to apply. But I have never understood\nthat claim. It seems to me to be likely to be true, but\nI don't see how the proof works, because I don't see\nhow you can claim there's a mapping to a specific, but \nunreachable proof without a discrete number line, or\nsome discrete-number-line-like entity to\nattach all possible proofs to.\n\nTarski did seem to provide a twisty way to suggest\notherwise, which I haven't managed to understand, but\nit might be worth your time checking out.\n\n _URL_0_\n\n\n",
"Goedel's incompleteness theorem is not all encompassing. Euclidean geometry is both complete and consistent. You could think of the physical universe as having a true model like Euclidean geometry, and atop that context humans construct formal structures that Goedel's incompleteness theorem does apply to, like arithmetic with natural numbers, even though natural numbers aren't part of the underlying Euclidean geometry."
]
}
|
[] |
[] |
[
[
"https://en.wikipedia.org/wiki/Boolean_satisfiability_problem"
],
[
"https://arxiv.org/abs/1502.04573"
],
[],
[],
[
"http://math.sfsu.edu/smith/Math800/Units/Goedel&Tarski.pdf"
],
[]
] |
|
15vp54
|
modern, postmodern and all that other art that i really don't get.
|
Stuff like Jasper Johns and Robert Rauschenberg have never really made sense to me. I try, but I just don't get it.
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/15vp54/eli5_modern_postmodern_and_all_that_other_art/
|
{
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"text": [
"In terms of paintings.\n\nOne thousand years ago:\n\nPeople hire artists to make pictures of themselves looking handsome and wise, and to make their enemies look evil. Or to record facts and stories. Artists are craftsmen.\n\nSix hundred years ago (Renaissance):\n\nPeople decide that good artists can be more than craftsmen. Now artists are supposed to be a little more independent.\n\nOver time artists start to use their art to do things like try to focus on expressing emotions, rather than simply record events or tell stories.\n\nA hundred and fifty years ago:\n\nPhotography starts to create a problem for art, because the photograph can take over the job of recording things.\n\nA hundred years ago:\n\nIn part because of photography, and in part for other reasons such as industrialization, artists and people who buy art begin to move qucikly away from \"thing that records\" towards \"thing that expresses whatever I want it to\".\n\nFor the next sixty years or so art continues to explore what it can be. People are excited by every new twist and turn, because it shows that art is limited only by the human imagination.\n\nSixty years ago or so:\n\nAbstract Expressionism happens, centered around NY after the war. This is pretty much the pinnacle of paint not telling a story, but instead just being paint that you should value for being colors.\n\nOnce that point was reached, artists started talking about human stories and things again. That's what Jasper Johns and Robert Rauschenberg were doing, they were saying \"yes, abstract expressionism is cool, but what if we use the lessons we learned in abstract expressionism and apply them towards human experiences again\". Others said \"what if we have abstract paintings, but with these paintings the audience is very aware of their own presence in the room and relationship to the canvas\" (minimalism). And more.\n\nGoing on, identity politics started happening. People realized that there were often more than one human story going on in a country at the same time. Yes, there was a white male straight story, but there was also a black story, a female story, and so on. This is postmodernism, where people start to challenge the idea of a single story that art should be telling.\n\nFrom then on things obviously get a little fuzzier because art can be about anyone's story and can be made out of anything. But basically right now art is understood not as \"a picture book on canvas\", but instead as \"anything that makes you think differently about the world around you, as long as it's presented to you as art\".\n\nNote: the above is really vague, not entirely accurate, and is about painting and \"fine\" art alone. Postmodernism can mean different things in different fields.",
"Zirconium did a very good job, but I'll try put in some examples. If we are talking about visual art, think about war\n\nLook at a painting like [this](_URL_2_). How does it make war look? It sort of gives the impression of war being noble and almost bourgeois, and that certainly doesn't sit well with a modern artist. But it's technically brilliant- it realistically portrays the scene. So you need to paint something that isn't really \"there\"\n\nNow look at [this](_URL_1_). Notice how everything is less \"realistic\" in the technical sense, but the painting is far more powerful (well, at least to my mind). It seems to be \"truer\" to what war is like\n\nFinally, look at [this](_URL_0_). Now that doesn't resemble anything in reality at all, but still manages to be (relatively) clearly about war, and has just as much if not more emotional impact then the Goya painting, and certainly more than the first one. Emotionally, this painting best represents what war is like while least depicting it visually. Linking to what zirconium said about the impact of photography, modern art is art playing to its strengths: it can be emotionally true in a way a photo isn't necessarily \n"
]
}
|
[] |
[] |
[
[],
[
"http://en.wikipedia.org/wiki/File:PicassoGuernica.jpg",
"http://en.wikipedia.org/wiki/File:El_Tres_de_Mayo,_by_Francisco_de_Goya,_from_Prado_thin_black_margin.jpg",
"http://en.wikipedia.org/wiki/File:Velazquez-The_Surrenderof_Breda.jpg"
]
] |
|
3zuqle
|
How do nocturnal animals produce vitimin D without sunlight?
|
askscience
|
https://www.reddit.com/r/askscience/comments/3zuqle/how_do_nocturnal_animals_produce_vitimin_d/
|
{
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],
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"text": [
"Some nocturnal animals sleep in areas that have sun exposure, like sloths. Others, like bats, apparently are [deficient](_URL_0_) in vitamin D, but it doesn't seem to impair their metabolism or serum mineral concentration. [Cows](_URL_1_), while not nocturnal, can synthesize it even through fur coverage. But most animals who are nocturnal would get it from their diet, by eating organs or plankton which are rich in vitamin D."
]
}
|
[] |
[] |
[
[
"http://www.ncbi.nlm.nih.gov/pubmed/12899852",
"http://www.ncbi.nlm.nih.gov/pubmed/20412916"
]
] |
||
2355ko
|
why are some perfumes and colognes so expensive?
|
Hundreds of dollars for a couple of ounces of fluid? What gives?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/2355ko/eli5_why_are_some_perfumes_and_colognes_so/
|
{
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2
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"text": [
"They're luxury goods and status symbols. The same goes for designer clothes and jewelry. You're paying for the name and the prestige.\n\nThey do generally use better quality ingredients, but they definitely make a big profit. On the flip side, there's not a very big market of people who'll pay, so it evens out.",
"Because some people will actually pay that much. "
]
}
|
[] |
[] |
[
[],
[]
] |
|
bvlq52
|
the difference between curies, roentgen, rad, rem, sieverts, grays...
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/bvlq52/eli5_the_difference_between_curies_roentgen_rad/
|
{
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"text": [
"Curie measures the radioactivity or radioactive decay of a material and is outdated as a unit (modern unit is the becquerel).\n\nRoentgen (named after the German physicist who identified xrays) is another outdated unit used to measure radiation exposure levels in air or other material. The modern unit is coulombs per kilogram. \n\nRad is a measure of absorbed dose (typically in tissue), but the modern unit is the Gray.\n\nRem is a measure of effective dose, or the potential for the radiation to do damage to biological tissue based on tissue type, quantity of exposure etc. One would use the effective dose multiplied by the tissue weighting factor (different tissues have different levels of radiosensitivity) to calculate the equivalent dose, measured in Sieverts. Both Rem and sievert are still used today: 100 rem = 1 sievert (Sv).\n\nRadiation workers in the US like xray techs, nuclear medicine techs, radiologists, etc have annual dose limits of 50 mSv and most of us do not even reach 10% of that in a year.",
"Thank you\nTried to search this out after the Chernobyl docudrama and could find an easy answer."
]
}
|
[] |
[] |
[
[],
[]
] |
||
3gnoz5
|
Why is the German Panther tank (49.4 short tons) classified as a medium tank while Allied tanks with the same weight, such as the M26 Pershing (46 short tons) and IS-2 (51 short tons) classified as heavy tanks?
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/3gnoz5/why_is_the_german_panther_tank_494_short_tons/
|
{
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"It had a lot to do with the function of the tank. A Medium Tank, at this time, was meant to function in most roles, primarily in combined arms, being able to take out enemy tanks while at the same time being fast, armored, and versatile enough to perform its shock operations. In comparison, light tanks were used as infantry support or blitzkrieg purposes, and heavy tanks were primarily used for infantry support as well, but were generally too slow to lead an armored assault. \n\nThis means that Medium Tanks will have less armour, and less powerful armaments, than that of their larger Heavy Tank cousins, but will be faster. Weight is a by-product of Heavy Tanks being heavy due to all of their armor and weaponry. Usually, the weight of a tank is heavily related to its type, and in many ways, the Panther *was* much like a Heavy Tank than a Medium one. However, the Germans built their tanks much differently, much more skilled labor, time, and effort went into making them. They were over-engineered (at times), and very complex, which meant they were on average much heavier. To put it into perspective, you listed the two main Heavy Tanks on the side of the Allies. The German Tiger I was 54 tonnes, and the weight of the Tiger II was a whopping 68.5 tonnes. German tanks overall were much larger and much more complex, which meant they were, at the very least, much heavier than their rivals of the same class. In the case of the Panther, its weight seemed to suggest it was more of a Heavy than a Medium tank, but its function was much different.\n\nThe importance here is then that the Panther's speed was around 55km/h, and later was reduced to 46km/h in its later stages as more armor and armaments were added. The M26 Pershing had a speed of only 25mp/h, the equivalent of around 40km/h. The IS-2 was even slower at 37km/h. The Panther, therefore, was much faster than both.\n\nThe guns of the IS-2 and the Pershing were both larger than the Panther, however. While the Panther gun had *superb* penetration and velocity, it remained a 75mm gun, most aptly used against other Tanks. The IS-2 122mm gun and the Pershing 90mm guns meant that they had a larger explosion, and were more effective against infantry and fortifications. \n\nThe Panther is, as far as I am concerned, more aptly classified as a Main Battle Tank than as a Medium or Heavy Tank. The Panther had the armor and firepower (more or less) of a Heavy Tank but the speed and versatility of a Medium Tank. Many, rightfully, consider it a predecessor to the concept of the Main Battle Tank.\n\n"
]
}
|
[] |
[] |
[
[]
] |
||
2je7cp
|
when to adjust iso versus shutter speed versus aperture?
|
I understand what each of them do independently, but I don't really understand how one knows which times to adjust what.
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/2je7cp/eli5when_to_adjust_iso_versus_shutter_speed/
|
{
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"It depends on what you want the image to look like. If you know what they do independently, you should be able to figure out what you're prioritizing. It depends what you're taking pictures of and how you want it to look.\n\nIf you want to do long exposure / star trail stuff, do a long shutter speed. If you want to do something in focus and the background blurred, do a large (small #) aperture. If you need the speed and can't open the aperture anymore, increase the shutter speed.\n\nDo you have a more specific example?\n\ne: For example, I shoot both a lot of street and portraits. Street stuff the ISO is usually locked in at 200 (I usually use a film rangefinder), and I set the shutter speed to 1/250 as it's enough to freeze most motion. From there, I just adjust the aperture based on how light or dark the scene is.\n\nFor portraits I just use aperture priority mode, and set that near open to get a nice blur (usually f1,1 to f2) and the ISO stays as low as possible (to be clear as possible), and the shutter speed adjusts itself accordingly. If it's too dark (shutter speed to low), the ISO raises up to compensate.\n\nIn general, keep ISO as low as possible, and shutter speed / aperture will depend what you are shooting and how you want it to look.",
"**ISO:** The lower the better, because low ISO makes for smoother, less noisy pictures.\n\n**Shutter speed:** The faster the better, unless you're trying to make something blurry, show movement, or capture light trails.\n\n**Aperture:** In general, the wider the opening (and the lower the f number) the better. This lets in more light and allows for lower ISO and higher shutter speeds. If you want more things to be in focus, increase the aperture."
]
}
|
[] |
[] |
[
[],
[]
] |
|
fjspm
|
Interpretations of Quantum Mechanics
|
Is there a preferred interpretation of quantum mechanics among the majority of physicists? I'm only somewhat familiar with some of the more basic undergrad level mathematical calculations surrounded QM and never really got into understanding any of the wider epistemological considerations.
Are there any ongoing experiments that are designed to distinguish between the different interpretations of quantum mechanics (e.g. Bohmian mechanics, transactional interpretation, Copenhagen, Many Worlds, etc...)?
|
askscience
|
http://www.reddit.com/r/askscience/comments/fjspm/interpretations_of_quantum_mechanics/
|
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"The Copenhagen interpretation is by far the most accepted among physicists. While theres a certain appeal to the many worlds interpretation, there's no reason to invent multiple universes that we can't interact with if we don't have to.\n",
"It's important to remember that interpretations of quantum mechanics are just that: *interpretations.* They're philosophy, not actually theories in and of themselves.\n\nA physicist who thinks the Copenhagen interpretation is God's own revealed truth (and is therefore *right)* and a physicist who believes that Many Worlds is something other than the silly daydreaming of someone who collected too many copies of *Astounding Stories* as a child (and is therefore *wrong)* will work through the maths of quantum theory and come out the other side with exactly the same predictions.\n\nThe theory doesn't care how we feel about it. It just takes initial conditions and spits out predictions.",
"The Copenhagen interpretation is widely the most accepted. To be honest, there may not be any scientifically distinguishable differences between the various interpretations.\n\nFrankly, I find the Copenhagen interpretation unsatisfying because it just says that the wave-function collapses without really mathematically defining that process well. I'm a big fan of a many-states transactional interpretation myself. But again, these aren't scientific differences so much as philosophical ones. ",
" > Are there any ongoing experiments that are designed to distinguish between the different interpretations of quantum mechanics?\r\n\r\nI doubt it. The different interpretations are more like meanings that people have prescribed onto the maths.",
"It seems to me you could pretty easily distinguish between Copenhagen and MWI by reversing a state reduction. Of course, this is quite practically impossible on a macro scale, but perhaps someone will find a way to do it for a smaller system. The Copenhagen adherents would respond in a no-true-Scotsman-like manner that whatever you did didn't count as a \"real\" observation of course, but given enough mythical sci-fi technology you'd eventually be able to force them to admit that they're wrong.\n\nThe truth is though that no one in the physics community is working on this because they don't care about that sort of thing. They all decided long ago that they had more important things to do like search for a TOE. I have seen some musings (most notably from Roger Penrose, although he has a silly belief in objective state reduction) that maybe the current lack of progress in TOE-finding is due to everyone abandoning research in QM before it was \"finished\", but still I wouldn't get my hopes up."
]
}
|
[] |
[] |
[
[],
[],
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|
bs1nna
|
Why is gold used on connector ends, like on usb-connectors for gaming mice, when copper has lower electrical resistivity?
|
I'm reading about electrical components and a table in my book describes "Resistivities of common conductors". Here ideal resistance is described by:
& #x200B;
Resistance = rho (material resistivity) \* L (length of wire) / A (area of cross section of wire)
& #x200B;
With unit \[10\^(-8) Ohm meters\] copper is cited as having a value of 1.7 where as gold has a value of 2.4. Is the principle of gold connectors just a marketing hoax?
|
askscience
|
https://www.reddit.com/r/askscience/comments/bs1nna/why_is_gold_used_on_connector_ends_like_on/
|
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"Gold doesn't tarnish as easily.",
"Copper oxidises and oxidised copper conducts less electricity witch means after some time the digital signal from mice will cause problems and eventually die. Alternative connector coatings are nickel that basically do the same thing as gold, but will oxidise after decades.\n\nWhile it does not matter what material the wire is made of as electrons travel the same speed, what matters is the signal clarity and that the voltage does not drop (long cables heat up, voltage drops and at some point digital signal is not strong enough to receive. Suggested USB cable length is 5m and if you go longer, the signal might not go trough).\n\nSo having gold connectors means the signal is the clearest at the connectors.\n\nOh, and resistivity is by wire length, so having few molecule thick layer of more resistive metal changes nothing.\n\nBut why the marketing put it on the box, it's because people value gold more.",
"The outer layer of electrons on a gold atom is \"full\". Therefore it does not react chemically with much of anything, especially Oxygen. Therefore it never tarnishes or oxidizes. Therefore, it never loses conductivity. Also, Gold can be pulled into smaller wires and hammered into thinner sheets than Copper.\n\nedit: spelling",
"Simple, gold does not corrode. Most gold connectors are only gold plated anyways, the point is that they will last for decades with no contact faults / fusing together and other gnarly things cheap materials tend to do when decades pass and air/oxygen/moisture does its thing. \n\n\nIf conductivity was the reason there would be so many cheaper alternatives.",
"It's not just gold; it's electroless nickel immersion gold (ENIG). It's needed because gold does not oxidize as readily as bare copper. Copper oxidation is a serious, tangible problem with cheap connectors, because sooner or later, the male and female connectors get oxidized to a point when it stops conducting or it conducts intermittently due to vibrations. A lot of older cars and motorcycles have this problem when they get old, the connectors magically get oxidized and stop conducting. Sometimes the increased resistance will even melt the connectors solid.\n\nThe Prius Gen II is notorious for having this issue. The HV battery harness connectors are not ENIG plated and 5 years to 10 years later, the whole friggin thing is full of copper oxide that prevent proper conduction of power. A Prius I worked on got its HV harness connector melted and caught a bit of fire, but thanks goodness the fire was self limiting.",
"The effect on resistance of such a thin layer of material is so small that for typical uses it makes no difference - the resistance of a typical cable run for example will be much larger.\n\nWhat gold does provide over cooper and other metals is a material that will not tarnish and oxidise - if you use copper terminals, over time the material can degrade and eventually the connections will become unreliable, whereas gold doesn't tarnish and remains in good condition, so your connections will have much more longetivity and reliability.\n\nThis is one of the reasons why gold became such a valuable material - it remains shiny where other materials such as silver will tarnish and lose their lustre and sparkle.",
"Gold does not tarnish or corrode, while copper corrodes very rapidly, and the actual conductivity of gold is not significantly lower than copper, but the kicker is that the coating is so thin that it does not increase the resistivity of the whole circuit by any relevant amount.\n\n & #x200B;\n\nThere is absolutely no benefit gained by keeping the last 0.1mm of a cable copper, when the benefits of anti tarnish/corrosion are so important to the reliability and lifespan of a product,",
"There's a couple of things that are being missed here... \nHistorically, gold plating has lower friction and you can mate the cables etc easier. These days, you can get close (not quite as good) with tin plating.\nOn the flip side, not so much in audio/video industry, but higher current applications cause heat, which causes metals like tin to 'reflow' and solder themselves. Great for electricals, but bad for unmating and reuse. \nWith that issue, the added benefit of a very resistant anti tarnish and the legacy idea that gold is better, gold wins. Remember though, all this talk it's about plating, the core remains copper.",
"Gold doesn’t corrode as everyone else mentioned. However, gold is also very ductile. So when two good surfaces come in contact, the surfaces deform themselves and result in a greater surfaces area of gold to gold contact. Contacts made out of something like platinum, which also does not corrode but is much harder, would result a higher contact resistance unless you increased the contact pressure substantially.",
"I believe it's been said, but really it's because of the resistance gold has to the elements. Copper will corrode quickly when exposed and Current is running through it. The surface corrosion will cause increasing amounts of resistance. Gold lasts longer and in comparison has lower resistance after a period of time",
"I work at a company that builds PCBA's. So 1st, no board uses copper connections. Copper becomes \"contaminated\" way too easily when exposed to air and other chemicals that are used during the manufacturing process. So while all the traces in a board are made of copper, they are generally covered by tin, HASL (basically tin/lead solder) or gold. Since most of our products are LF and/or RoHS, we have to use gold to meet the requirements. Gold is also great in that it doesn't really get contaminated and it provides the flattest surface. Which when you are placing parts that are literally the size of a piece of rice, you want as flat of a surface as possible. Hope this helps answer your question.",
"I had the same question in the 80s when Lexus had a TV ad touting the gold-plated leads on its airbag trigger mechanisms. I’d learned that silver was a better conductor and I thought that they were just using gold because “gold is best.”\n\nBut as others have said: gold doesn’t rust. You can go to a museum and see gold jewelry from thousands of years ago and it is still shiny, where most everything else looks like it’s turned to stone. \n\nIf the leads on your cables oxidize in the open air, with all its humidity, then in theory they may not make the best contact. The majority of the conductor in the cable is wrapped in plastic which protects it from the air, so it doesn’t have this problem. But the leads are exposed, so gold makes some sense.",
"Gold is more resistant to corrosion. Corrosion causes poor continuity and high resistance in a circuit, and can cause major problems.\n\nCopper is used in most male-female harness connectors because they're easy and relatively inexpensove to replace. In contrast, a computer module with corroded pins is costly and often time-consuming to replace, which is why gold is used instead.",
" Gold is very resistant to corrosion and doesn't degrade easily, unlike copper, which turns to dirty alloys, weird amalgams, and funky oxides in air. Although copper contacts initially may provide a circuit that flows electricity with less resistance than gold, many of copper's compounds are not conductive. Copper, when exposed to air, immediately starts to interact with it and form a surface layer of non-conductive or resistive oxides.\n\n So then, in a fairly short time, the contacts would degrade to the same conductivity as gold, then worse and worse far more rapidly than gold would, until it were cleaned. Electroplating gold onto the surface of copper traces and wires requires only a tiny amount of gold, and can be scaled up very economically and rapidly. Keep in mind, the amount of gold applied to any finished product is on the order of a few milligrams at most.\n\n Even though gold is worth almost 500 times as much as copper, if the product is 99.95% copper, the .05% of not very pure gold that coats the surface of plugs and pins only adds a miniscule cost of time, electricity, and material. For that added small fraction of expense, electrical resistance, and effort, you get a product that requires substantially less maintenance and is significantly more reliable.\n\n Gold is only one of many materials that can fulfill this need, along with a few other pure elements, like platinum, palladium, and alloys of many others for other purposes. Beryllium, (which conducts thermal energy very well, but resists electricity), can be alloyed and used for thermal energy dissipation, and even electromagnetic radiation shielding, which becomes more and more of a concern as transistor design continues to inexorably shrink into the nanoscale. As machines get smaller, it's much easier for them to be negatively affected by ionizing radiation, even here on the surface of the planet, it's a valid concern.\n\n Depending on the environmental conditions, physical requirements of the device needed, cost fluctuations of materials needed for production, politics, metallurgical technologies, material availability, skill level of involved metal workers, interest and awareness of client side goals and preferences, and consumer aptitude, gold may be eventually replaced or modified as an alloy or amalgam, or replaced altogether for this purpose.\n\n Should humanity find a several trillion ton asteroid made of solid platinum or palladium before we find one made of gold, or even less likely; Should we find an undiscovered easy to reach deposit on Earth, we might see connector design move away from gold, at least somewhat anyway.\n\n I mention an asteroid as more likely than finding an undiscovered deposit on Earth because we have mapped out the rest of our Earthbound resources pretty well at this point. We need to start looking out at asteroids, Luna, and all of our nearby cosmic objects. We are running out of materials on Earth, and these are the very same materials that will be needed to expand off-planet.\n\n If we don't use these resources to go get more, we will likely never be able to go and get more. Eventually our Earth will become uninhabitable, one way or another, but we have a way to get past that, if people could just bite the bullet and invest in space science and infrastructure. If we spent anywhere near as much on space as gets spent on war, we could be sending thousands to build a moonbase within a year or 2.",
"There's something called electron migration, where the electrical signal conducting through a material actually transports some of the atoms of copper, this can cause welding and can enhance oxidation, sometimes gluing terminals together. More likely gold is used for it's anti oxidative properties, but it also does not succumb to this electron migration phenomenon like copper does.",
"The one thing i havent seen touched on is galvanic corrosion. Im not finding a standard for whether USB housings must be made out of steel, aluminium, tinned copper, or even gold plated metal. \n\nFor the manufacturer, making your side gold plated guarantees you eliminate galvanic corrosion due to mismatched reactive metals. \n\nBut mostly the need for gold is marketing and will not impact the product over its life except in niche circumstances for corrosive environments.",
"The resistance listed in all tables are for pure, non-oxidised metal.\n\nAnd this is where gold shine. Copper oxidise fast. And the oxide is a good electrical isolator. Gold do not oxidise.\n\nYou can have a perfect conductor, but if it's surface is an insulator then nothing will pass, even if you have such a perfect conductor. The tiny layer there block everything.\n\nThis is why you have gold plated connectors. You get the best of both world: good and inexpensive for the bulk of the cable, tiny bit of expensive gold to plate the contact surface, which now won't oxidise.\n\nSo really, it is just a question of rust/oxide.\n\n\nNow, for the second part, for normal cable, no, it is not a marketing hoax, it is literally day and night for plated vs non-plated. HOWEVER, I have seen some optical cable with gold plated connector 'for improved sound quality'... That one is scam pure and simple. The signal never even come close to the plated part! It is a red led shining on the end of an optical fiber, that conduct the light to a phototransistor on the receiver side. Gold, or any other metal or anything non-transparent, would block the light, thru would kill the signal... It does however make the cable look like it is of a better quality as it look better.",
"Work for a connector company.\nThe typical plating scheme on a gold plated connector is base copper alloy, with a nickel plating, and gold on top. On cheap connectors, the gold is very thin flash around 3 microinches thick. Military connectors use 50 microinches min.\n\nThe gold has many purposes. It is a noble metal and does not corrode. It does not form non-conductive oxide layers like tin and copper. The surface characteristics of gold to gold contact allows for low normal force down to 10g while still offering less than 2 milliohms of resistance at the separable interface. This helps to reduce mating force. \n It is also good for durability for high mating cycles. \n\nThe nickel plating layer is used between the copper and gold as copper diffuses through gold quickly and will create corrosion once the concentration is enough. Copper diffuses through nickel at a much slower rate. Even with the best plating, there are always pores, so the thicker the nickel layer and gold layers, the harder it is for copper to travel to the surface and start corrosion.",
"The resistance added by gold film is incredibly smal because the \"length of wire\" in that equation is something like 50 nanometers thick.\n\nAs others have said, it is to reduce resistance caused by bad electrical contact from corrosion. Gold doesn't tarnish or corrode.\n\nAlso, digital signals aren't greatly affected by increases in resistance. The resistance has to be quite high to matter",
"You usually don't even find bare copper conductors inside a data cable. A lot of the time it will be tin over copper because tin is easier to solder to terminals and doesn't require cleaning prior to soldering.\n\nAs stated before, gold is used on terminals because of it's corrosion resistance."
]
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|
[] |
[] |
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[],
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[],
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|
2cbqq4
|
If you freeze soda water, will it still be carbonated when you unfreeze it?
|
Or does the carbon dioxide get removed in the process?
|
askscience
|
http://www.reddit.com/r/askscience/comments/2cbqq4/if_you_freeze_soda_water_will_it_still_be/
|
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"It depends.\n\nIf you freeze a carbonated beverage in a sealed container, and the container remains sealed and doesn't leak, then yes the CO2 will re-enter the beverage once it is a liquid again. This is because the contents will still be under pressure, and the pressure forces the CO2 into the beverage. \n\nIf you freeze soda in an unsealed container, then no. The process of crystallizing forces the CO2 out. \n\nSomeone asked what happens if you flash freeze coke. So I dropped a bottle into Liquid Nitrogen (for science) and made a video. Feel free to AMA on this, but its friday afternoon, so don't be surprised if it takes me until monday to respond. \n\nVideo: _URL_0_",
"Carbon dioxide can be dissolved in water, but like most gasses, it is far less soluble in solids than liquids. \n\nFreezing forces the gas out, creating often explosive pressure on the can/bottle. This same pressure also tends to help force the gas back into the water when thawing.\n\nFun facts: tiny holes caused by the gas being pushed out of the freezing liquid is what gives frozen soda it's slushy appearance.\n\nSome of the co2 binds with the water forming carbonic acid. If you drink soda in a chamber that's pressurized to the same level as what's inside the can, the gas can't escape (the room is just one big effective can), but you will still feel that burning sensation in your mouth/throat when you drink it, proving that it isn't the bubbles causing the pleasing irritation."
]
}
|
[] |
[] |
[
[
"https://www.youtube.com/watch?v=fz94wsj0T1A"
],
[]
] |
|
2v709g
|
if we have telescopes that can see galaxies light years away, what's the reason we focus them on nearby planets to take a look at their surfaces?
|
Typo! I mean't to ask "what's the reason we *don't* focus them..."
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/2v709g/eli5_if_we_have_telescopes_that_can_see_galaxies/
|
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"I think you forgot a 'don't in your question.\n\nI have no idea what the answer is, I'm guessing it has to do with resolution. I have wondered a similar thing about pointing telescopes/cameras at the moon and taking pictures of the equipment left behind after the lunar landings, just to shut up the conspiracy goobers that say it was a hoax.",
"Telescopes take images of far away galaxies by taking a *really* long exposure (allow light in for a long time), in some cases, like the Hubble Deep Field, for weeks at a time. Bodies closer to earth move so much compared to the telescope which makes the image blurry.\n\nIt's kind of like how if you take a picture of someone running 100 yards away from you will be clear but someone running just a few feet in front of the camera will be blurry.\n\nETA: Here is a [What If](_URL_0_) from XKCD that explains it more.",
"Nearby planets don't emit light like stars do. They only reflect light, and they are much further away from the sun, so they are not as bright as stars in distant galaxies.\n\nThey are also very small, very far away, moving very fast, and usually rotating.\n\nIt's like taking binoculars to a baseball game. They work pretty well for watching the game because the field is well lit, the players are moving relatively slowly, and they are pretty big relative to the field of view of your binoculars.\n\nThey don't work very well at all if you want to follow what the mosquito 6 rows away from you is doing. He is NOT well lit, he is moving very fast, and he is very small compared to the field of view of the binoculars.",
"Galaxies are **unimaginably** huge, and produce their own light.\n\nIt's like asking how you could use a pair of binoculars to see a cluster of billions of candles on a hilltop ten miles away (a galaxy full of billions of stars light years away), but couldn't use the same binoculars to see details on the surface of a grain of sand 10 feet away, illuminated by the light of a single candle in your hand (a planet in our solar system illuminated by the sun)."
]
}
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[] |
[] |
[
[],
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"https://what-if.xkcd.com/32/"
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[],
[]
] |
|
27t4um
|
When I turn in a flashlight, am I creating photons, or turning 'on' photons that are all around me, or something else entirely?
|
askscience
|
http://www.reddit.com/r/askscience/comments/27t4um/when_i_turn_in_a_flashlight_am_i_creating_photons/
|
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"The simple answer is that a photon is a form of raw energy. If something is moving, it has kinetic energy. If slows down, it now has less energy, so that energy had to go somewhere. One of the ways it can go is as a photon. Similarly, if the thing gets hit by a photon, it might absorb it, and now it goes faster because it has more energy. In general, though, a photon is a \"packet\" of energy, and that's about all it is! The packet can have any size. Some photon energies are in the visible range, which is of course the primary goal of the flashlight. Others are much higher-energy or much lower-energy. A photon is actually \"made\" of electric and magnetic fields in a particular pattern, not \"stuff\".\n\nWhen you turn on a flashlight, you're using energy to excite some stuff -- usually atoms or electrons -- and, since stuff usually wants to have lower energy, it will generate a photon to get less excited. By the use of mirrors and the right materials, the thing gets excited to a degree where, when it gets less excited, the photon it shoots off has the right amount of energy to be visible. In the case of an incandescent bulb, the filament is heated, which means that the atoms in the filament (usually tungsten) start to move faster -- that's what heat is, particles moving around randomly. When they slow down, which they do for various reasons (called blackbody radiation), they emit a photon whose energy depends on how much they slowed down. An incandescent bulb attempts to raise the filament's temperature such that the photons that get emitted are in the appropriate energy range, but the spectrum is actually very wide, so most photons are not in the correct range. This is why incandescent bulbs are so inefficient. It takes a lot of energy to heat them, but most of that energy doesn't go into emitting visible photons.",
"Photons are just tiny packets of energy that take the form of light waves. When you wrap your head around that part, you can start to understand where they come from.\n\nDown to the atomic scale now:\n\nWe don't need to go into detail on the atomic model, all we need to know is that electrons move in orbital paths (loose term) around the nucleus, that there are multiple levels of orbitals, and that the higher the level, the more energy the electron has.\n\nAn electron cannot exist between orbitals. When an electron gains energy, it has too much for the orbit it's in and it \"jumps\" to the next level. This level may not have a stable amount of electrons, so it will jump back down. When it jumps down it needs to get rid of some of the energy that it had. This energy is released as a packet of energy we call a photon. This is how light is created.\n\nIn a fire, there's thermal and chemical energy stimulating electrons, and when they jump back down they release photons.\nDifferent elements have different energy levels per orbital, meaning the packet size varies resulting in different wavelengths.\n\nWhen you turn on a light, electricity moves through a filament which resists the energy flow. Some of the electrons passing through will jump between orbitals of the filament's atoms, releasing their energy as light when they jump down.\n\nIn a fluorescent tube, electricity is passed through a gas. The atoms of the particular gas used (not sure myself) gain and lose electrons rapidly, many of which end up jumping between orbitals and releasing photons.\n\nTo summarize, a photon is a packet of energy that propagates as a wave. The packet size is not defined in the definition of a photon, and there is no known limit to the amount of photons that can exist (except for all the energy in the universe).",
"My two cents: In the standard model, there is an electromagnetic 'field', which fills the entire universe and photons are excitations of that field. So in a sense it is a lot like a speaker playing a sound, kinda like the photons are all around you and you're turning them 'on', kinda.\n\nBut, quantum mechanics says that these vibrations in the electromagnetic field are quantized. That is, countable. And these countable photons make up the vibration that you are creating and so yes when you turn on a flashlight you are creating photons. \n\nThis article might help\n_URL_0_\n\n",
"Short answer is you're creating photons. The specifics of how a particular type of flashlight is more of an engineering problem so I'll only describe the fundamental event in any type of flashlight. \n\nLight is emitted from the atomic level. Atoms have electrons that are at various energy levels. If a photon 'hits' an electron it will increase the electron's energy level, which means the photon's gone. If the electron drops back down to a lower level it will emit a photon.\n\nEnergy levels for various atoms are fixed, which means they can only give off photons in certain frequencies since energy is directly proportional to frequency. This determines the color you see if it's in the visible spectrum.",
"When you run electrical current through something that thing will heat up, it will heat up more the more power you run through it and the more resistance the object has.\n\nEVERYTHING will emit photons when hot, the hotter something is the more energetic the photons it will emit. You and I are currently also giving off light, but the photons aren't energetic enough for us to see. The photons we emit can however be viewed through an Infrared camera (the photons we emit we refer to as \"infrared\").\n\nWhen you turn on a flashlight the current heats the material in the lightbulb causing it to emit photons energetic enough for us to see. If you were to make this material even hotter (without it melting and breaking the circuit) you'd eventually have an ultraviolet flashlight, then x-ray, then gammaray. In practice however the material will melt and break the electrical circuit long before that.\n\nBonus fact: Because everything emits photons and the photons get more energetic as something gets hotter AND because of there being a shortest possible length (known as the Planck Length) there is also a maximum achieveable temperature.\n\nAs you make something hotter the photons it emits will be more and more energetic and as such will have shorter and shorter wavelengths. The point where the material is so hot that the photons it emits have a wavelength equal to the Planck Length (about 10^-35m) is where you have your maximum achievable temperature. This is known as the Planck Temperature (about 10^32 degrees Kelvin).\n\n",
"It seems I'm pretty late to the party, but I will chip in regardless as I don't think the question have been properly answered yet. u/BigWiggly1 came close, but he and others claim that photons are \"just packets of energy\", which I think is misleading. By calling something \"just energy\" you haven't really said very much. Like someone asking you what art is, and you reply that it's \"just a concept\" :)\n\n**What is a photon?** \nFirst, let's talk about the *electromagnetic field*. It is a field that exists all around us, binds us together. Quite literally - the electromagnetic force is what holds electrons in orbit near the atomic nuclei, and the reason that atoms combine into molecules. \n\nMany fundamental particles, including electrons, have a property called electric charge. It can be positive or negative, and the universe has the strange property that like charges attract eachother and opposite charges repel. If you put a single charge somewhere in space, the particle will move in a direction determined by the value of the *electromagnetic field* at that point. The information of charges around the universe is somehow carried in this field.\n\nNow, imagine that you take a charge, say an electron, and you shake it back and forth. This creates a *wave* in the EM field, which will propagate in all directions at the same time. The wave will also have a certain energy, depending on how vigorously you shook your charge. The wave will propagate in the field at the speed of light. \n\nWhy at the speed of light? Because that's what light is! Waves in the electromagnetic field, also known as **photons**. Higher energy means higher frequency of the wave, which corresponds to the colour of the light. What we call \"visible light\" are photons in a certain range of energies, corresponding to the colours of the rainbow. Blue light has a higher energy than red light, for example. There are plenty of photons around that we can't see with our eyes - if it has higher energy than we can see, we call it *ultra-violet*, and if the energy is too low we call it *infra-red*. \n\nBy turning on your flashlight, you are causing an electrical current to run between the poles of the battery through some light source. There are several types of flashlights of course, but in all cases the photons coming from the flashlight are created as a result of electrons changing energy. If something is glowing red-hot, for example, it means that it is hot enough that the electrons are being shaken back and forth (ie. heat) sufficiently vigorously that it produces photons in the visible range. There are quantum mechanical subtleties to all this, briefly introduced by some other posters in here, such as the packets of energy being quantized and such, but I believe I have answered the question now.\n\nRecommended: [Richard Feynman talks a bit about photons](_URL_1_) (and [\"seeing\" in general](_URL_0_))\n\nMore in-depth information on \"producing photons\": [How Light Works: Producing a Photon](_URL_2_)"
]
}
|
[] |
[] |
[
[],
[],
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"http://en.wikipedia.org/wiki/Quantum_field_theory"
],
[],
[],
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"https://www.youtube.com/watch?v=1qQQXTMih1A",
"https://www.youtube.com/watch?v=eebWoZkN3FQ",
"http://science.howstuffworks.com/light7.htm"
]
] |
||
2rpkg5
|
what exactly is going on in my digestive system to make beer shits so awful?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/2rpkg5/eli5_what_exactly_is_going_on_in_my_digestive/
|
{
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"Just talked about this yesterday. They are terrible but my God are they satisfying. ",
"Drinking draft? More carbonation equals more gas...more gas equals more explosive shits. Try bottles and pizza if you want to pass a nice, solid submarine."
]
}
|
[] |
[] |
[
[],
[]
] |
||
35k2a4
|
how do dogs and cats easily determine each other's sex?
|
When I'm looking at animals, even animals I'm very familiar with, I have to check their junk to tell their gender. And with cats, sometimes I still get it wrong. I know that there are subtle differences in size and stuff, but what are the distinguishing features that help my dog determine male from female in other dogs?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/35k2a4/eli5_how_do_dogs_and_cats_easily_determine_each/
|
{
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"They can tell in the same way we do, there are certain traits (other than genitalia) which the different sexes have0. Sexual dimorphism (the difference between sexes) is actually less in humans than it is in most other species. Things like boobs seem like a big difference but they actually aren't that big of a difference unless you're actively looking for them.\n\nWe aren't \"wired\" to notice the difference between a girl dog and a boy dog, but dogs are.",
"They do it the same way you can tell a man from a woman - they look. You aren't able to discern because its not important that you be able to. This does not mean that boy cats and girl cats look the same, it just means they look the same TO YOU.\n\nPlus, the balls are a dead giveaway. But...they know long before that just like you know before you see boobs.",
"A lot of it would be smell and pheromones wouldn't it? That's why male dogs go nuts when female dogs are in heat - they can smell the pheromones they're giving off (from some distance away I might add)."
]
}
|
[] |
[] |
[
[],
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|
34loc9
|
What is flux?
|
Learning about magnetism and electric fields and this was brought up. I also am confused why you need to take an integral of "B dA " if that makes any sense.
|
askscience
|
http://www.reddit.com/r/askscience/comments/34loc9/what_is_flux/
|
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"You can just compare it to the flux of a liquid. \n\nLet's say you want a number, that describes how much of a liquid flows through some cross section of a pipe in a given time. You would need to know two things: \n- the velocity of the liquid\n- the area of the pipe\n\nIf you multiply them, you get the volume of liquid per time that passes the cross section. \n\nNow, what happens if the velocity is different at different positions of the pipe? You would need to look at a differential part of the cross section dA and multiply it by the velocity at this point of the pipe. Then you need to sum all those little pieces v\\*dA and therefore integrate over the whole cross section. (In the general case, the velocity doesn't have to be perpendicular to the cross section. Then you take the integral over the scalar product of **v** and the normal vector **n** of the surface and integrate over < **v**, **n** > dA, where < .,. > denotes the scalar product.)\n\nNow we can easily generalize this to arbitrary vector fields (the velocity of a liquid is a vector field! Why?) by just defining the flux as the integral over F dA. [(This can serve as a visualisation)](_URL_1_)\n\n*Magnetic flux* is just the so defined flux of the magnetic field B. But what does it mean? If you visualize a vector field with field lines, the flux through a surface is proportional to the number of field lines that pass through it. \nFurther read: [(wikipedia)](_URL_0_)",
"You can think of flux as the amount of something travelling through a given area.\n\nLet's take, for example, Gauss's law. Imagine a charged particle, which is emitting an electric field. Gauss's law says: \"If we measure the amount of electric field coming out of a surface, we know how much charge there is in the center generating it.\" You integrate the field, dotted with a surface element (dA), to figure out how much field is coming out around the closed surface.\n\nDoes this make sense?"
]
}
|
[] |
[] |
[
[
"http://en.wikipedia.org/wiki/Flux#Flux_as_a_surface_integral",
"http://upload.wikimedia.org/wikipedia/commons/d/d2/Flux_density.svg"
],
[]
] |
|
j37hc
|
If I sat in a computer chair with a freely rotating seat on the north or south pole, after 12 hours would I be looking the exact oppsite direction as I started?
|
Assuming no to almost no friction in the rotating part of the chair of course...
|
askscience
|
http://www.reddit.com/r/askscience/comments/j37hc/if_i_sat_in_a_computer_chair_with_a_freely/
|
{
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"At the moment you put the chair there, you are already rotating (because you stand steadfastly on the rotating earth) and thus the chair in your hands is already rotating. Similarly, when you sit down your body is already rotating and the chair's seat plane is already rotating. So even if the is no further friction between you and the ground, you will keep rotating in perfect synchronicity with the earth due to conservation of momentum. Thus you will always look in the same direction (relative to the earth, that is - relative to the stars, you will of course have turned 180 degrees like everything else on earth).\n\nThere might be other effects from the way the surrounding air moves (basically wind, etc.) that I am not sure about right now, though."
]
}
|
[] |
[] |
[
[]
] |
|
3i8jtq
|
why are netflix original sitcoms not exactly 30 mintues?
|
Netflix is a platform that doesn't air commercials and does not need to allow time for advertisments. So, why are their original sitcoms - that weren't filmed to be on NBC or the like - still less than an even 30 minutes long?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/3i8jtq/eli5_why_are_netflix_original_sitcoms_not_exactly/
|
{
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"cue7hm5",
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"text": [
"Netflix doesn't have their own studios. They finance and greenlight these new series, and as a result, they get the exclusive rights for a period of time to them -- pretty much the exact same way a traditional television network works.\n\nBut after that time, the studio can sell the show to others, and most of their customers will want commercial time. So, this is almost certainly a concession that Netflix made with the studios so that they would be able to remarket the shows after they've appeared on Netflix.",
"Shows broadcast on TV need to be editied to fit inside a 30 minute time slot with a set number of commercials. Normally, they're only 24-25 minutes long.\n\nShows for Netflix don't need to have an exact length. If the story they're telling only needs 22 minutes, adding a few minutes of filler isn't going to make the show any better. If they *really* need 32 minutes to fit everything in, they could do that too."
]
}
|
[] |
[] |
[
[],
[]
] |
|
9bq33j
|
How do you STRUCTURE a historical essay?
|
If it's about a historical event do you summarise it from start to finish in one paragraph then flesh it out with body paragraphs?
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/9bq33j/how_do_you_structure_a_historical_essay/
|
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"text": [
"If I may recommend a book that greatly helped me through my undergrad - Mary Lynn Rampolla's *A Pocket Guide To Writing in History.* There are plenty of different ways you could write an historical essay but, on the most basic level, what you want to do is craft an *argument.* Historical facts and their relevancy hinge on an interpretation, because causation and significance cannot be proven in history (and these things are often in dispute), so you have to argue why your interpretation is correct ",
"Based on your question, I am going to assume you are getting your feet wet in the history department of your college or some similar situation. If so, welcome! In any case, Rampolla's Pocket Guide as mentioned in an earlier comment is an excellent resource and very short while giving you the basic look and feel of an essay. Your general \"introduction body conclusion\" system from other courses or High School is broadly correct (I can't say for sure without knowing your situation a bit better) but does vary. My addition here is I recommend you make an outline. The \"top\" is your introduction, the big argument you are making. The \"body\" then breaks your arguemnt into a couple sub-points that support that argument with sources and analysis, which all gets wrapped up with a bow in the conclusion. If your professor has given different instructions or expectations, follow them. This paper should be one story or argument that some random classmate can read and follow your train of thought, outlines help keep that straight while writing. \n\nThe other thing I would add is that, depending on your course expectations, you should take some time and be sure to integrate your sources to neatly fit within the \"story\" you are telling. Primary or secondary, be sure to introduce and describe these sources in the paragraph they are being used in, especially if they are a major lynchpin for your essay. Don't just drop a quote into a paragraph! Sources and evidence are the bulk of your paper, but the paper shouldn't be a big collection of quotes. Analyse them and put them into the story you are telling in your paper, make them your own. If you pick up Rampolla's book, look at Chapter 6 for details on avoiding plagarism, and Chapter 7 for using sources well.\n\nHappy writing!\n\nEDITED for grammar.",
"This depends very much on the specifics of the assignment, and I strongly suggest you take this question to your teacher, professor, or TA, because they are ultimately the one you need to please. With that proviso I'll tell you what I look for from a student and some common mistakes, with less attention to a strict structure.\n\nAt the top I want a road map to your paper. I want to know what your problem is, what your conclusion is, and how you are going to get there. If you're set on a 5 paragraph structure I want your first paragraph to tell me what's in paragraphs 2, 3, 4, and 5. I want the problem and your conclusion, and the steps of your argument to reach your conclusion. If there's a debate in secondary sources that needs describing, this is where I expect to see it mentioned first.\n\nWhen I was grading papers, I told students that this introduction should probably be the last bit of the paper they edit, because it's hard to do the work I want to see there if they hadn't done the rest of the paper. It's a sort of cheat: if you tell your reader what your paper is going to do, they can't bring their own expectations to it very easily unless you depart drastically from the assignment.\n\nAfter that introduction is done, the rest of the paper is easy to read. I expect historical claims to be backed up by citation, with direct quotes where appropriate; I do not want your opinions aside from historical conclusions. If you said you were going to address things 1, 2, and 3 in the introduction, I expect to see those things addressed in full. And I expect your conclusion to recap your argument.\n\nThe common mistakes:\n\nI don't need a hook. If you're working with an assigned topic, you're not writing for a general audience. You're writing for an audience that is already interested in your assignment, otherwise they would not have assigned it. I certainly don't want to see a hook that involves \"the beginning of time\" or \"a universal truth.\" A lot of my students told me they were taught in high school to open an essay with a broad statement and over the course of their introduction narrow their subject down to a specific claim. Historians are historians of specific times and places. Universal claims\nintroduce a load of assumptions that just fall apart on even a shallow inspection.\n\nPersonal opinion. Personal opinion means I want to know what you think, but it doesn't mean you can make things up. You can't tell me a story and claim it's \"my personal opinion\" when you get a bad grade. You can have your opinion and should show it, but it should be grounded in evidence that you provide in your text. It probably belongs in your intro and conclusion.\n\nQuotes and paraphrases. When you give a direct quote you should tell your reader why you're quoting it and what to look for in the quoted passage. Don't leave your reader guessing at what your evidence is supposed to show. If you paraphrase, you should cite the exact passage and represent it accurately. A sloppy paraphrase might represent as the author's opinion something they are actually arguing against - a sin I am guilty of myself (don't paraphrase from memory!).\n\nBasically, leave as few choices of interpretation of your paper open to your reader as possible, and have good evidence for everything. I do think the intro is the most important part of a strong paper in this sense. Anything more on an actual structure depends on the assignment which you haven't shared with us. Nevertheless I hope some of these comments will be useful to you.",
"I reckon you're a fresh university student and not someone simply asking about other's personal approaches out of curiosity, so I will mention things that might sound a bit obvious to some.\n\nThere are multiple approaches (e. g. German, Anglosaxon, French schools...), so it largely depends on what you adhere to. In Europe, Umberto Eco's *How to Write a Thesis* – pretty much freely availible on the internet – is universally accepted as a guide that you can always follow within humanities/social sciences. The way I personally do it:\n\n**Preparation**\n\n1. Come up with a main research question\n2. Come up with a hypothesis that could be used to answer it\n3. Work with primary and secondary sources to to reject or confirm the hypothesis (in historiography there is little reason to write about rejected hypotheses, so make sure your reasoning makes sense before you start writing)\n\n\n**Structure**\n\n1. Write a short chapter explaining the nature of your research question, providing necessary historical background (only) where needed.\n2. Write a chapter examining your hypothesis and especially the theoretical approach you are using to explain the phenomenon you are studying.\n3. Write a varying number of chapters (depending on the topic and purpose of your essay) about the actual subject. Make sure you always *explain* and *answer questions* relevant to that chapter. Simple accounting of facts is not a historiography, that's writing an encyclopedia. Don't stray too far from your topic, make sure to use references and footnotes if you want to mention additional information not directly relevant to you research question. The order doesn't need to be chronological, you can divide the chapters by topics, models etc.\n4. After finishing writing the content of your essay, write a conclusion that summarises your findings and basically all that was done. Here avoid suddenly raising new questions that would sound like they should have been included in your work in the first place, but you can suggest what kind of further research could follow. \n5. Finally write an introduction. Yes, it may sound unintuitive, but if you write this part first, you will 100% end up rewriting it anyway. Make sure to include all formalities required by your receiving institution. The introduction, the body and the conclusion should often repeat themselves – that's not an issue, it is actually desirable. Many people first read introductions and conclusions before deciding whether they want to spend time actually studying the work in detail and these parts should tell them everything about your theoretical approaches, your work methods, your findings and such. \n\nEdit: Typo",
"For your main body paragraphs I recommend this old technique - PEEL.\nP- point - what is the point or argument?\nE - evidence - provide quotes, data, sources of evidence to support your point.\nE - explanation - explain how the evidence supports your point\nL - link - back to your overall argument, thesis or hypothesis. "
]
}
|
[] |
[] |
[
[],
[],
[],
[],
[]
] |
|
9ii5ux
|
What lead to the end of hangings in the USA?
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/9ii5ux/what_lead_to_the_end_of_hangings_in_the_usa/
|
{
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"text": [
"We talking judicial or non-judicial?",
"While you're waiting for an answer, you can start with this recent [post](_URL_0_) regarding the State of Michigan. \n\nEdit: Ok, so a robot politely told me to leave this here too: /u/PartyMoses"
]
}
|
[] |
[] |
[
[],
[
"https://www.reddit.com/r/AskHistorians/comments/93ri8x/the_state_of_michigan_abolished_capital/"
]
] |
||
9fn6i4
|
if the universe is infinite why are there estimated to be only 100 billion galaxies? surely the number of galaxies would also be infinite?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/9fn6i4/eli5_if_the_universe_is_infinite_why_are_there/
|
{
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"Are you sure that you're not just confusing the fact that the universe is infinite, but there are only 100 billion galaxies in the observable/known universe?",
"2,000,000,000,000 (at least) galaxies. \n\nThere are certainly more, but they lie beyond our ability to see them. So, to me, anything beyond what we can detect would be only an inference.",
"The estimation is not for the whole universe but only for the observable universe. \n\nObservable universe is like is say the part of the universe we can observe. So it is a sphere where light have had time to reach us since the big bang. Because of the expansion of the universe the object from where light needed 13.8 billion years to reach us since the big bang is today 93 billion light years away \n\nThe estimation today of the number of galaxies is from 200 billion to more the 2 trillion. the larger number is from more recent observation and models. Because we have manage to look farter and farther back in time it is likely that the higher estimation is closer to the real number. It looks that the number have grown from 200 billion in 2005 to at least 2 trillion in 2016,\n"
]
}
|
[] |
[] |
[
[],
[],
[]
] |
||
2ne6au
|
What was the Supermarine Spitfire's role during the Battle of Britain?
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/2ne6au/what_was_the_supermarine_spitfires_role_during/
|
{
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"cmct1am"
],
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"text": [
"That question is very vague and general, do you have something specific in mind? The Spitfire was a fighter aircraft, and thus was tasked with shooting down enemy aircraft. Of the two principal fighter types available to the RAF during the battle, the other being the Hawker Hurricane, the Spitfire was the more modern, and was capable of engaging the primary German fighter aircraft, the Bf-109E, at even terms. The Hurricane was an older design and was at a disadvantage against the Bf-109 in an even dogfight; the ideal tactics were therefore to concentrate the more capable Spitfires against the enemy fighters while the Hurricane squadrons went after enemy bombers with their slower, but more stable aircraft. In practice, however, air combat was very fluid, so you would often have Spitfires attacking bomber formations, Hurricanes taking on fighters, etc. Like I said, is there something more specific you would like to know? A fighter aircraft is tasked with shooting down other aircraft, not much more to the role than that."
]
}
|
[] |
[] |
[
[]
] |
||
jo1g3
|
If my car was struck by lightning while I was driving, would I/my passengers be grounded by the rubber tires?
|
They wouldn't take my question on Car Talk, so it's all down to you guys. If I was driving along and my vehicle was directly struck by lightning, what would be the results - ie what would happen to the car and what would happen to its occupants? Would the rubber tires ground the vehicle?
What about if lightning struck directly next to the vehicle (parked under a tree, let's say?) Would there be any effect to the car or its occupants?
Would the type of surface being driven over have any effect (ie a bridge or elevated highway vs a regular road)?
Not planning on being struck by lightning or anything, but lightning struck about a quarter of a mile in front of us while we were driving during a storm last week and that got us debating ... hoping you guys canbring some resolution.
Thanks.
|
askscience
|
http://www.reddit.com/r/askscience/comments/jo1g3/if_my_car_was_struck_by_lightning_while_i_was/
|
{
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"text": [
"No, the rubber insulating you is a common misconception. The lightning has already gone through the entire swath of air between you and the car, and a little rubber is a much smaller deterrent. What actually happens is the [skin effect](_URL_0_) in which the current goes around the outside of the car to the ground, instead of through you. Make sure all the windows & doors are closed and don't be touching them if you get struck by lightning in a car.\n\nNot sure why askscience is your last resort though. You do have Google, don't you?\n\n_URL_2_ \n\n_URL_1_ \n\netc",
"For fun, Top Gear tried this out:\n\n_URL_0_",
"I've seen this experiment myself at the Boston Museum of Science's Tesla coil, and it agrees with [this source](_URL_0_). The metal body of your car will act like a [Faraday cage](_URL_1_). Provided you were not touching anything metal inside the car, everyone would be okay. The electrical charge would pass from your car to the ground--either through the tires, or by arcing directly. Your car could be damaged (see the pictures in my first link), and the electronics on board could be pretty messed up, too. \n\nIf lightening were to strike the ground near you, you'd be fine. The Earth is really good at dissipating electric charge. You'd probably smell ozone. The main risk if lightning hit a tree near you would be that a branch might fall on your car.",
"I was actually struck by lightning in my police car. I was in a parking lot, just sort of watching the big thunderstorm, when Zap!.. The car went dead and would not re-start.\nWhen the storm passed, we found a burn-mark on the visi-bar (the red light display).\nNever felt a thing. It did kill all the computers in the car though; thing sat at the Ford dealer (it was a Taurus) for some time.",
"No, the rubber insulating you is a common misconception. The lightning has already gone through the entire swath of air between you and the car, and a little rubber is a much smaller deterrent. What actually happens is the [skin effect](_URL_0_) in which the current goes around the outside of the car to the ground, instead of through you. Make sure all the windows & doors are closed and don't be touching them if you get struck by lightning in a car.\n\nNot sure why askscience is your last resort though. You do have Google, don't you?\n\n_URL_2_ \n\n_URL_1_ \n\netc",
"For fun, Top Gear tried this out:\n\n_URL_0_",
"I've seen this experiment myself at the Boston Museum of Science's Tesla coil, and it agrees with [this source](_URL_0_). The metal body of your car will act like a [Faraday cage](_URL_1_). Provided you were not touching anything metal inside the car, everyone would be okay. The electrical charge would pass from your car to the ground--either through the tires, or by arcing directly. Your car could be damaged (see the pictures in my first link), and the electronics on board could be pretty messed up, too. \n\nIf lightening were to strike the ground near you, you'd be fine. The Earth is really good at dissipating electric charge. You'd probably smell ozone. The main risk if lightning hit a tree near you would be that a branch might fall on your car.",
"I was actually struck by lightning in my police car. I was in a parking lot, just sort of watching the big thunderstorm, when Zap!.. The car went dead and would not re-start.\nWhen the storm passed, we found a burn-mark on the visi-bar (the red light display).\nNever felt a thing. It did kill all the computers in the car though; thing sat at the Ford dealer (it was a Taurus) for some time."
]
}
|
[] |
[] |
[
[
"https://secure.wikimedia.org/wikipedia/en/wiki/Skin_effect",
"http://www.weatherimagery.com/blog/rubber-tires-protect-lightning/",
"http://www.lightningsafety.com/nlsi_pls/vehicle_strike.html"
],
[
"http://www.youtube.com/watch?v=ve6XGKZxYxA"
],
[
"http://www.lightningsafety.com/nlsi_pls/vehicle_strike.html",
"http://en.wikipedia.org/wiki/Faraday_cage"
],
[],
[
"https://secure.wikimedia.org/wikipedia/en/wiki/Skin_effect",
"http://www.weatherimagery.com/blog/rubber-tires-protect-lightning/",
"http://www.lightningsafety.com/nlsi_pls/vehicle_strike.html"
],
[
"http://www.youtube.com/watch?v=ve6XGKZxYxA"
],
[
"http://www.lightningsafety.com/nlsi_pls/vehicle_strike.html",
"http://en.wikipedia.org/wiki/Faraday_cage"
],
[]
] |
|
19fcws
|
what's stopping me from succesfully starting up an internet company that offers better services at cheaper prices than what is currently available?
|
You may all know that AT & T/time warner etc offer shit service at high prices with huge profit margins? I'm struggling to understand why there aren't other companies that are able to compete with them?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/19fcws/whats_stopping_me_from_succesfully_starting_up_an/
|
{
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"There's a *gigantic* entry cost to providing Internet service. You must have agreements in place to let your users send and receive data from literally every other computer on the Internet; you can't start an ISP that only lets people connect to servers in Texas, and then expand outwards from that. So there's no real way to build an ISP from scratch, unless you are Google and can just straight out buy all the infrastructure.",
"AT & T, Time Warner, Cox, Verizon all have thousands of miles of fiber optic cable in the ground, hundreds of trucks and engineers to manage that cable, and thousands of support reps to sell and support that service.\n\nDo you have any of those things?\n\nBig companies have decent margins on some products, but only because they're grouping offerings together to share cost. JUST selling internet or JUST selling TV or JUST selling phone is HARD, and the margins really aren't as pretty as you think they are.\n"
]
}
|
[] |
[] |
[
[],
[]
] |
|
5wdibv
|
why/how do actors choose their "stage names"?
|
Do celebrities choose stage names for some small piece of privacy or is it always about marketing themselves?
What makes some names "better" or more marketable than others?
Do they pick them themselves or is it usually a PR person?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/5wdibv/eli5_whyhow_do_actors_choose_their_stage_names/
|
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"text": [
"In the old days it would be done by actors with foreign sounding names who didn't want to be thought of as foreign. Today it's usually just someone with a hard to pronounce or complex name",
"In a few instances it's because the Screen Actors Guild requires its members to have unique working names. E.g. Michael Keaton's birth name is Michael Douglas but that name was already taken.",
"Jamie Foxx actually chose his stage name because he noticed that female comics usually perform first so he chose an ambiguous name to perform earlier.",
"Many reasons! Some pick their own, some are given one.\n\n* Avoiding confusion with someone else, sometimes per Screen Actors Guild rules. There was already a Diane Hall, so Diane Hall became Diane Keaton. \n\n* Hiding national/ethnic background, especially in the past. Margarita Cansino didn't want to be stuck with \"exotic\" roles, so she became Rita Hayworth.\n\n* Hiding family background. Francis Ford Coppola's nephew Nicolas didn't want people thinking he'd only made it on his uncle's coattails, so he became Nicolas Cage.\n\n* Some names are odd or difficult to spell, or don't seem marketable. Archibald Leach was given the name Cary Grant, Marion Morrison was given the name John Wayne, Maurice Micklewhite chose Michael Caine. (He had previously been going by Michael Scott, but there turned out to be another Michael Scott, so it's sort of a two-level stage name.)"
]
}
|
[] |
[] |
[
[],
[],
[],
[]
] |
|
xxl8x
|
what causes, or, what IS, that centre chest pain associated with guilt/being hurtful?
|
askscience
|
http://www.reddit.com/r/askscience/comments/xxl8x/what_causes_or_what_is_that_centre_chest_pain/
|
{
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"text": [
"I've found a possible theory on the cause of psychological chest pain:\n\n(_URL_0_)\n > According to a 2009 study from the University of Arizona and the University of Maryland, activity in a brain region that regulates emotional reactions called the anterior cingulate cortex helps to explain how an emotional insult can trigger a biological cascade. During a particularly stressful experience, the anterior cingulate cortex may respond by increasing the activity of the vagus nerve—the nerve that starts in the brain stem and connects to the neck, chest and abdomen. When the vagus nerve is overstimulated, it can cause pain and nausea.\n\n > Recent studies show that even experiencing emotional pain on behalf of another person—that is, empathy—can influence our pain perception. And this empathy effect is not restricted to humans. In 2006 a paper published in Science revealed that when a mouse observes its cage mate in agony, its sensitivity to physical pain increases. And when it comes into close contact with a friendly, unharmed mouse, its sensitivity to pain diminishes. \n\nConsidering that this happens in other animals, I'd say this might be more common than we think.",
"This has been posted recently: \n\n_URL_0_\n\nI know, the search function sucks. But I commented on it before, so I looked thru my old comments to find it. Happy reading!"
]
}
|
[] |
[] |
[
[
"http://www.scientificamerican.com/article.cfm?id=what-causes-chest-pains"
],
[
"http://redd.it/vccv6"
]
] |
||
1x52tf
|
How did the nursing/lactating relationship evolve?
|
So many small incremental steps are involved in evolution. A creature develops a gland that secretes something (probably not nutritional). A youngling is born that needs early nutrition without the ability to eat available food. How does this complex relationship develop incrementally?
|
askscience
|
http://www.reddit.com/r/askscience/comments/1x52tf/how_did_the_nursinglactating_relationship_evolve/
|
{
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"text": [
"A bit old, but quite worth a read, [this paper](_URL_0_). Their proposed mechanism is: \n\n > * 1 Evolution of egg-incubation behaviour in a mammal-like reptile, \nfollowing development of hair, endothermy, and cutaneous glands. \n\n > * 2 Evolution of a well-vascularized incubation patch on the ventral \nabdomen. \n\n > * 3 Enhancement of egg survival through the anti-microbial properties of \nsecretions of cutaneous glands of the incubation patch. Offspring survival also \nmay have been enhanced at or following this stage through ingestion or egg absorption \nof the weakly-nutritious secretions, which constituted a supplement to vitelline (yolk) \nnutrients. \n > * 4 Hypertrophy of cutaneous glands of the incubation patch, with produc- \ntion of a somewhat more copious secretion. Hormonal control of glandular \nhypertrophy and secretion may have been developed by this stage. \n > * 5 Gradual evolutionary shqt towards maternal secretion of a more \nnutritious product, associatedfirst with a supplementation and then with a \nreplacement of yolk nutrient provision. The beginning of this evolutionary \nchange may have been concomitant with the trend towards cyclically hypertrophied \nlacteal glands. The mammary-gland prototype evolved synthesis capabilities in part \nthrough co-optation and modification of existing synthetic pathways, enzymes and \nend-products, The trend towards production of nutritious secretions may have been \nassociated with a general shift from facultative to obligatory provision of extra-vitelline \nnutrients, as evidence suggests has occurred in non-mammalian matrotrophy. \n > * 6 Concomitant increases in milk-nutrient content, ingestion emciency \n(suckling.), and delivery eficiency (areola formation, hormonal control of \nmilk expulsion). The similarities of monotreme and therian lactation, as demon- \nstrated in publications by Griffiths and his colleagues (Griffiths, 1965, 1968, 1978; \nGriffiths et al., 1969, 1973) indicate that these features evolved prior to divergence of \nmonotremes from therians.\n"
]
}
|
[] |
[] |
[
[
"http://www2.trincoll.edu/~blackbur/1989-Blackburn++Lactation.pdf"
]
] |
|
1hzn5v
|
why tv ads are so important in american politics
|
For example, the ["Harry and Louise" ad](_URL_0_) that hurt the Clinton health care plan. From what I've read, US Congress members become cozy with special interests because they need campaign money, and they need campaign money to buy TV advertising slots so they don't get defeated come re-election time. Is American political life nothing but what comes out of a glowing rectangle (for 30 seconds at a time)?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/1hzn5v/eli5_why_tv_ads_are_so_important_in_american/
|
{
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"text": [
"A thirty second commercial is a lot easier for someone to remember and internalize than a paragraph from a speech or an op-ed. It's not entirely attributable to national culture, it's just that we're visual creatures and good at remembering visual things.\n\nHowever, a campaign's expenditures aren't just TV ads. A lot of it is operations for phone banks, volunteers knocking on doors (and sometimes driving voters to the polls), polling operations, and now social media. TV advertising is good for some demographics in some areas, but is becoming increasingly cost-ineffective. For a great example; Karl Rove and the Heritage Foundation spent about 200 million dollars on races in the 2012 cycle and lost almost all of them.",
" > Is American ~~political~~ life nothing but what comes out of a glowing rectangle (for 30 seconds at a time)?\n\nFTFY.\n\nIn all seriousness, the average American is not going to sit down and carefully consider every candidate's position on all the currently important issues under contention, and then make an informed choice as to who best represents their views. The average American either votes along party lines without thinking about it, or votes based on who they've heard good things about from sources they rely on, or who they haven't heard bad things about from sources they rely on. Most of the time, those sources are TV/radio, and this is particularly true of older generations. A 4 second soundbite cooked up by someone with a marketing degree is, sadly, much more effective at developing a following than delivering a cogent 15 minute speech."
]
}
|
[] |
[
"http://www.youtube.com/watch?v=CwOX2P4s-Iw"
] |
[
[],
[]
] |
|
1yzlvg
|
I have always been told that we dont know how people were able to construct the ancient pyramids. I have never thought about it from a critical perspective until today. Do we know how the pyramids were built?
|
I know pyramids have been found on in different countries continents. If that is a problem lets talk about the ones in Egypt, but now question is really about all of them.
What I have been told is that they are too big, and that the building materials should not have been available at the time, and that the cuts of stone are too precise, and that they did not have the scientific basis for creating a saw that would last.
Now I am curious to hear if I have been wrong all this time and that we know perfectly well how they built them.
|
askscience
|
http://www.reddit.com/r/askscience/comments/1yzlvg/i_have_always_been_told_that_we_dont_know_how/
|
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"I studied it briefly in my history class last term. There was a huge labour force available to the Egyptian govt at the time. Scientists today replicated a small scale pyramid with the same size blocks in a NOVA pyramid experiment. There are limestone quarries near by, it is believed that they used rollers possibly logs, to get them to the sight. How they moved them up to the higher levels was either via ramp or levers (lifting it up with them). The ramps in some cases would wrap around the pyramids because if they didn't it would be too long. How pyramids were build really varies from pyramid to pyramid, and some are stil debated. It is definately doable. Link to Nova pyramid experiment: _URL_0_",
"I'll have to find the link to the video i posted on my face book like a year ago. This guy said he figured it out and damn if it didn't look like he had. on the video he moves a stone that is like 40'x8'x8', the trick was to use 2 vulcrums. To move it laterally he rotated it around the 2 points. Then he gets this huge block into position next to a pit. again used two vulcrums. He put weight on one end so the far end lifts off one vulcrum. puts another log onto op the vulcrum then moves the wieghts to the other end. he see saws it up. always adjust one of the vulcrums and gets it way up and tilts it over into the pit. gets it to stand straight up all by him self.",
"Brute force and labor for the most part. Egyptians were masters of simple machinery. The inclined plane, wedges, levers etc. They used ramps to move limestone blocks up the side of the pyramid. These were carved from the quarry and rolled on logs to the build site. There are theories however, that the Egyptians might have used a limestone type of concrete. This would have allowed them to cast the blocks on site using a mold. \n The Egyptians were very innovative and you don't seem to be giving them much credit. They invented a lot of the things we still use today. Breath mints, toothpaste, shaving and hair care, boats/sails, door locks, bowling. They had their own written language. The Egyptians also had access to obsidian. Obsidian is a volcanic glass that leaves a 3 nano meter edge when flaked. Over 100 times sharper and smoother than stainless steel scalpels used today. I'm not sure if this could have been used for a \"saw\" as you stated above but feasible none the less.",
"Well, [Jean Pierre Houdin's theory](_URL_0_) seems to be the most recent and sensible explanation of the building of the pyramids. In short, he claims that an internal ramp was constructed in the pyramid at the edge of each level. Imagine it being like a spiral that twists on itself as levels go up and become narrower. Some [density measurements](_URL_1_) that were done in the 80's IIRC are actually quite similar in pattern to the [design of internal ramps](_URL_2_) Houdin came up with. Further simulations seem to support the theory. Though for some reason, at lest according to Houdin, the Egyptian government has not granted permission to investigate for those internal ramps, so as far as I know, there's no solid evidence for their presence. Either way, watch the the video. It explains it better than I do. ",
"We don't have any unambiguous records of the *exact* methods, but--contrary to the claims of the loon fringe--there are no \"unexplained mysteries.\" We can come up with plausible scenarios for the whole process: cutting the stones, transporting them, putting them in place, all with the materials, math, engineering, and tools of the period.\n\nI particularly like this guy's methods:\n\n_URL_0_\n\nHe's come up with ways of muscling around big-ass blocks all by himself, using nothing but bronze-age technology. Did the builders of the pyramids or Stonehenge use this? We don't have a clue. But they *might* have, it's entirely plausible.\n\nThe bottom line here is that you can can do this kinda thing when you have thousands and thousands of workers (NOT slaves, BTW, that's a myth). It would be *nice* to know exactly how they did it, but invoking space aliens is simply not necessary.\n",
"One theory was they were made from a simple concrete.\n\n_URL_0_\n\nIt removes the need for tools - which has always been a big flaw in the argument of building from pre-cut blocks. The sheer number of soft bronze chisels required to make something the size of a pyramid would be enormous. ",
"Give me a lever long enough and a fulcrum on which to place it, and I shall move the world.\n\n-Archimedes\n\nSimple machines were understood by the ancients. In fact they were very good at using them creatively. Each pyramid was built over several decades as a jobs project for farmers and workers between crop cycles. ",
"Ya see, we have a hard time coming to grips with ancient wonders, because we believe we are the smartest, wisest, be-all, end-all, end product of tens of thousands of years of accumulated knowledge. Rather conceited, if you ask me. Here's a great example: Renaissance painters struggled to figure out perspective, but the Romans knew how to do it. (One of the fantastic revelations I had when visiting Pompeii)\n\nAncient Egyptians were able to construct the pyramids because they had a reasonably sound knowledge of math, geometry, architecture, etc. etc. A lot came from the rise of agriculture, and more from the simple act of actually building other things.\n\nWhat you really need to build something as ambitious as a pyramid is time, and manpower. Something the Egyptians had an abundance of.\n\nCut some stone, build some scaffolding, get some logs to roll the stone up to the site, wait a while for martians to take note of what you're doing and come down to help, and a few decades later you've got yourself a bona fide Pyramid, that will last for millennia, and confound later civilizations for generations!\n\nJolly good fun!\n\n",
"You can debunk each of the claims of the \"it must be aliens!\" quite easily. One at a time. Everyone is doing so, I'll just tackle one more.\n\n\"How could primitive man make perfect 90 angles without lasers and surveying equipment etc.?!\"\n\nBasic geometry. You can make a perfect 90 angle with just 2 sticks and some string by drawing circles.\n\n1. Draw a circle. Mark the center before you remove the center stick.\n2. Put the old center stick on the circle edge, draw another circle.** The second circle should overlap the first circle in 2 places (like a locking rings magic trick) Mark the center of the second circle before you remove the stick.\n3. Use the string to make a straight line between the centers of the first circle and second circle.\n4. Use the string to make a straight line between the 2 places where the circles intersect.\n5. Voila, you have just made a cross with perfect 90 degree angles. \n\nNo aliens required. You can just do this at home on paper with a compass if you like.\n\nFrankly, to believe aliens did it requires an almost willful ignorance of the most basic math and physics that even an amateur carpenter knows. You can show this to them, even have them do it themselves, and most will just keep claiming only aliens could *really* make 90 degree angles, even after doing it with their own hands before their own eyes...\n\nAnd the fun part is, as long as your string isn't stretching, the bigger you make the circles, the *more* accurate your 90 angle will be!\n\n**You really can start drawing the second circle almost anywhere and it still works as long as it intersects the first circle, this way is just easier to explain.\n\nedits: format"
]
}
|
[] |
[] |
[
[
"http://www.pbs.org/wgbh/nova/pyramid/"
],
[],
[],
[
"http://www.youtube.com/watch?v=YTgxGJfXRQ0",
"http://khufu.3ds.com/fileadmin/kheops/images/gallery/microgravimetry1.jpg",
"http://patentpending.blogs.com/.a/6a00d83451c56869e20162fdb1d310970d-pi"
],
[
"http://www.youtube.com/watch?v=pCvx5gSnfW4"
],
[
"http://en.wikipedia.org/wiki/Joseph_Davidovits"
],
[],
[],
[]
] |
|
2f32ua
|
What caused the social revolution of the 1960s, with the resultant movement towards more liberal attitudes regarding race, women and sexuality? If it was WW2, why didn't similar things happen after previous major wars?
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/2f32ua/what_caused_the_social_revolution_of_the_1960s/
|
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"text": [
"No revolution, social or otherwise starts overnight. For most social revolutions in 60s, the spark was long in place before WWII came, but found itself greatly assisted by the war and the post war period. For race relations in America, the [Double V campaign](_URL_0_) was a real eye opener for Americans. Blacks, just like everyone else, were being drafted to fight in a war sold as a defense of liberty and freedoms--that many of them, especially those living in the segregated South did not enjoy. Organizations like NAACP (founded 1909) were also quick to point out the hypocrisy found within the US."
]
}
|
[] |
[] |
[
[
"http://www.learner.org/courses/amerhistory/resource_archive/resource.php?unitChoice=19&ThemeNum=3&resourceType=2&resourceID=10106"
]
] |
||
1jquu3
|
how do those who engage in illicit trafficking via tor know the entire network isn't an elaborate trap set up by the state department?
|
I'm relatively new to posting to Reddit, so apologies if I somehow break etiquette here, but I've searched ELI5, Tor, and SR and haven't found a complete answer. Here's what I have found:
-The US Navy and State Department have both publicly backed Tor.
-There are no huge security clearances required to run a server that relays communications via Tor.
-Hypothetically, the State Department would be able to facilitate dissent in non-democratic countries, monitor "secure" communications between enemies and allies alike, and elect either to tolerate (drugs & sex) or enforce (child porn) instances of trafficking.
I'm not normally the conspiracy theory type, but the possibility seems plausible enough to scare anyone whose anonymity and liberty have depended on Tor.
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/1jquu3/eli5_how_do_those_who_engage_in_illicit/
|
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"I don't know much about TOR because I'm still learning cryptography. However it is my understanding TOR is split into three different segments.\n\nYou have your entry nodes. (A node is a device on a network.) Your computer will make it's initial contact to an entry node.\nThen you have your relay nodes. Nodes that relay do exactly that and only act as a middleman connection.\nThen you have your exit node where your connection leaves the TOR network.\n\nSo for example, your on the TOR network. You're trying to access the hidden Wiki.\n\nYou load up TOR, your computer establishes a connection to the entry node. The entry node then contacts a relay and asks to route your connection through the thousands of other relay nodes. Once your relay node connects with the exit node of where The Hidden Wiki is hosted, it then connects you to the website.\n\nThe idea is to have a massive chain of connections, making it impossible (almost) for you to be traced. However the problem lies with encryption itself.\n\nEntry and exit nodes can be set up to monitor all connections. Relay nodes cannot monitor connections, they just pass through traffic. However entry and exit nodes are responsible for establishing and maintaining connections.\n\nThat's the way I see it, someone who understands TOR better will probably give a better explanation but I'll try and answer your questions:\n\n- Recent NSA leaks show that using TOR is more likely to put you on the authorities radar. \n- This is true. Any one can set up a exit node and monitor what goes on. That's why you are advised to ensure you change your browsing habits and not to be stupid. If your worried about your privacy, don't log into Facebook on TOR. It's just dumb and it gives LE something to work with. No personally identifying information means nothing to work with.",
"Basically, it's for the same reason that we trust encryption technologies like AES. Even though such technologies are developed by the government initially, they are effectively open standards for anyone to use and implement into their own programs. \n\nBasically anybody can peer into and inspect the code and algorithms [(see here)](_URL_0_) that make-up Tor and verify for themselves there is no 'backdoor' exploit built-in that compromises the network.\n\nOf course, it is theoretically possible for someone to purposely use techniques to obscure/obfuscate a back-door exploit such that it is impossibly difficult to figure out what that section of code does by just browsing through the source. But at the same time I imagine the code for such an exploit would end-up looking very unusual and would probably stick-out like a sore thumb (thus should have been detected relatively early on).\n\nAssuming there are no government back-doors, the only other vulnerability with Tor occurs if one particular group/institution (such as the US Government) operates (or has control over) a large percentage of relays and exit nodes. In this case, they have the potential opportunity to both trace traffic back to its original source and the ability to look-through any Internet-bound data traffic which is not encrypted (sites using HTTPS/SSL would still be secure). This is obviously a huge vulnerability, but considering tons of institutions (including, for example, schools) around the world run relays and exit nodes, it makes it very unlikely that any one institution will be able to trace traffic back all the way to its origination point.",
"Basically, it was. Except that the U.S. government didn't know it was a trap when they started it. They helped build it, for anonymous communication, but they did not foresee it's eventual use of trafficking child pornography and other illegal things.\n\nNow, (ten years after it was first published), they were like, this thing is full of CP! Let's try to catch one of the larger hosting services. They helped design the original tor, so it stands to reason that they have the technical knowledge and skill necessary to attempt an attack on Tor. And they did.\n\nThe fallacy you're proposing is that they planned the entire thing, they have complete control of the tor network, and they can arbitrarily de-anonymize more people in the near future. They cannot, they found one vulnerability and in order to infect people on tor, they had to compromise a tor server that people were visiting. The attack on this server actually had nothing to do with tor and still nobody is clear on how they pulled it off.",
"If you want to do internet crime (or not be killed in your country for political bs):\n\n[*] Don't use your home internet connection (use an open wifi or sit out in your pedo van and crack the encryption to some different ap's). Check for security cams in the area and map your route(s) of entry and exit mentally.\n\n[*] Use a computer/laptop purchased (or stolen) from someone else. Don't use it at home. This is your war machine.\n\n[*] Don't use your real identity. Make one up and pretend it's the new you. The real you doesn't exist to this identity. (don't search yourself, don't login to any actual personal accounts, don't cross contaminate). \n\n[*] Treat it like a game of chess. Create a flow chart if need be. Visualize each path and their respective outcomes. (Take the path that gets you to your goal while minimizing risk).\n\n[*] Being a sociopath helps... a lot.",
"Because Tor is open source. Anyone can look up the code, and make improvements on it.",
"If secret US government programs can find backdoors or crack a code, so can competent foreign governments. It is in the interests of US agencies to recommend things that they can't get into because they know it is unlikely that other states will be able to get into it either. Tor is completely secure, the recent events were because javascript is not, and various government agencies recommend script blocking.\n\nGenerally, if you follow all the US government's recommendations, you're reasonably safe from the US government (because it is in their interests to do so). It also kills two birds with one stone because it encourages paranoid people trying to hide from the government (like drug traffickers, terrorists, and child pornographers) that the best practices are \"being watched\" and thus they use less effective security measures that FBI, NSA, etc are capable of breaking. If it's good enough to keep dissidents safe from the Chinese government, it's good enough to keep you safe from the NSA."
]
}
|
[] |
[] |
[
[],
[
"https://gitweb.torproject.org/tor.git"
],
[],
[],
[],
[]
] |
|
699wag
|
How did ancient cities like Jerusalem expand with massive walls?
|
Did they start building vertically?
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/699wag/how_did_ancient_cities_like_jerusalem_expand_with/
|
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"A common misconception about walled cities is that dense constructions were built right up against the walls. Although the city centers were almost always dense and crowded, it was common for there to be open spaces like gardens and orchards between the city walls and the inhabited center. \n\nI wrote about [population density within the walls of Renaissance Florence here](_URL_1_) and also wrote about [wall construction in some Italian cities here](_URL_0_). \n\n",
"I know your question is \"like\" Jerusalem and so you mean to cover this more generally, but in the case of Jerusalem specifically a few things are worth noting:\n\n1. The current walls of the Old City of Jerusalem are relatively recent, they were built by Suleiman the Magnificent in the 16th century. Though the Crusades-era walls would would have been similarly imposing, for much of Jerusalem's history over the past 2000 years the walls were in various states of ruin.\n2. Until the 20th century, Jerusalem didn't actually expand very much at all. The population of the city remained in the low 10s of thousands, and sometimes single-digit thousands for the vast majority of its history in the past 2000 years.\n3. As a result, it wasn't actually that difficult for the entire population of Jerusalem to live within the old city. The population of the old city today is still about 35,000, so the population expansion has all been outside the walls. The old city is certainly dense, but it's not exactly teeming (this is more obvious at night than during the day when it's flooded with tourists/shop vendors/etc) and certainly hasn't required modern high rises to accomplish.\n",
"Walled cities would limit their expansion with, well, walls. \n\nJerusalem, for instance had its walls and the seven (six functional) gates to lead people in and out of the city. As u/cptbuck specified, the walls were rebuilt in the 16th century, but the new structures wouldn't have compressed the size of the city and reduced its area. Jerusalem still had other parts of the city that we read of in the Bible such as the Garden of Gethsemane and the Mount of Olives that were outside the city walls. \n\nBased on historical description, Golgotha, where Jesus was crucified was an open space but when you visit the Church of the Holy Sepulchre, there is no sign of a hill. This seems to indicate that even 2000ish years ago, there was tons of space within and outside the walls of the city for expansion and to accommodate more people. \n\nAt a macro level, the human population globally remained under the 300 million mark until the 13th century, resulting in less pressure for expansion in walled cities to adjust for population growth. "
]
}
|
[] |
[] |
[
[
"https://www.reddit.com/r/AskHistorians/comments/5t12oi/im_a_governor_of_a_roman_city_my_city_has_been/ddjzzf2/",
"https://www.reddit.com/r/AskHistorians/comments/4jxwid/how_crowded_were_the_streets_and_markets_of/d3bmasq/"
],
[],
[]
] |
|
1ta99f
|
what is the point of the 'press any key' screen in games?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/1ta99f/eli5_what_is_the_point_of_the_press_any_key/
|
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"The game just wants to make sure you are actually there. Usually the stuff that happens after a press any key screen is something that the game doesn't want you to miss because you'd have a bad experience otherwise. So, next time you see a press any key screen, maybe watch what happens after you press the key, then think about what a bummer it would have been if you hadn't actually been there during that part.",
"_URL_0_\n\nBecause console manufacturers require you to. Imagine that you load a PS3 game at a mall and leave it there... do you want the game to just sit in the main menu? That's why console games (and hence PC ports of said games) have a 2 layer system. They have the \"press any key to continue\" screen that displays the main game branding details and possibly loop in some cool video. Once you do press something, they can then figure out which controller pressed it (so they know who's playing), and they know that someone is actively attempting to play a game, so they go ahead and now load the actual menu components."
]
}
|
[] |
[] |
[
[],
[
"http://gaming.stackexchange.com/questions/18780/why-do-console-games-require-a-button-press-before-showing-the-main-menu"
]
] |
||
6e05yp
|
how is it that illiteracy still exists in the united states?
|
Given that school is required for kids how is it that not everyone has become literate by now in the United States?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/6e05yp/eli5_how_is_it_that_illiteracy_still_exists_in/
|
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"text": [
"They can make you be physically present in school until you're 18 and gain your full rights as a person. What they *can't* do is make you pay attention or remember anything, that part is up to you.",
"Illiteracy still exists because: Some kids actively refuse to learn to read, and they manage to fake it well enough that they fall through the cracks of the schooling system. Others are severely dyslexic and so are really only partially illiterate, or they have severe mental handicaps preventing them learning to read. \n\nBut statistically these people make such a small percentage of the population that we do have a fully literate society for all practical purposes. ",
"Academic Ken Robinson suggests that Western Education Systems should nurture, and not kill creativity, and that an inappropriate model may have undesirable consequences...including drop out rates, increased reports of ADHD etc\n\n[TED Talks](_URL_0_) \n\nSuch a view is consistent with Ivan illich's [deschooling theory](_URL_1_) \n\n\"\nThe pupil is “schooled” to confuse teaching with learning, grade advancement with education, a diploma with competence, and fluency with the ability to say something new. His imagination is “schooled” to accept service in place of value. Medical treatment is mistaken for health care, social work for the improvement of community life, police protection for safety, military poise for national security, the rat race for productive work. Health, learning, dignity, independence, and creative endeavour are defined as little more than the performance of the institutions which claim to serve these ends, and their improvement is made to depend on allocating more resources to the management of hospitals, schools, and other agencies in question. \"\n"
]
}
|
[] |
[] |
[
[],
[],
[
"https://www.ted.com/talks/ken_robinson_says_schools_kill_creativity",
"http://ektr.uni-eger.hu/wp-content/uploads/2015/11/deschooling-society-a-brief-summary.pdf"
]
] |
|
19l14n
|
why do medicine bottles say you shouldn't crush or dissolve the pills?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/19l14n/why_do_medicine_bottles_say_you_shouldnt_crush_or/
|
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"text": [
"Because you shouldn't crush or dissolve the pills. Some pills contain ingredients that may harm your mouth if you chew them. Some pills are designed to work after digestion.",
"Medicine is designed to release at a steady rate over time, if you break or dissolve the capsules you can skrew with that release schedule ",
"Some medication has a special coating that breaks down slowly so that the medicine is kept from being digested in the stomach and only in the intestine, it would really depend on the medication though"
]
}
|
[] |
[] |
[
[],
[],
[]
] |
||
an97nt
|
Why do nails stick in car tires instead of being shot out due to tire pressure?
|
askscience
|
https://www.reddit.com/r/askscience/comments/an97nt/why_do_nails_stick_in_car_tires_instead_of_being/
|
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"There is a lot of friction between the tire tread and the sides of the nail. There is only a very small surface area (the end of the nail) for the pressure to act on, so the net push outwards is very small, not enough to overcome the friction against the sides of the nail.",
"Apparently, 2.4mm is roughly the diameter for \"13 gauge\" nails, commonly used in construction. So 1.2mm would be the radius, and we can calculate the area at pi \\* r^2 . Also, my tire pressure is roughly 207kPa.\n\nThe cross-section of the nail and tire pressure on that area will tell us how much pressure is being put on the nail, trying to push it out.\n\nA = 2 \\* pi \\* 0.0012m = 0.0000090 m^2 .\n\nForce (in Newtons) = 207kPa \\* 0.0000090 m^2 .\n\nF = 1.87 Newtons, which is about the amount of force that something 200 grams exerts, just sitting there due to Earth's gravity. That's not a lot of pressure pushing it out.\n\nThe force pushing the nail out is based on the cross-section of the hole, and so the radius of the nail itself. The friction holding it in is based on its circumference. The area increases with the square of the radius, while the circumference increases just with the radius. So, the larger the nail, the more likely it is to be pushed out by tire pressure, since the pressure pushing it out will increase quicker than the friction holding it in."
]
}
|
[] |
[] |
[
[],
[]
] |
||
9qq6fe
|
how fast can a quasar star spin?
|
I just read in another post that some quasars spin in 1.4ms. That seems impossibly fast - if I could stand on the surface, would I be going close to the speed of light? What's the limiting factor?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/9qq6fe/eli5_how_fast_can_a_quasar_star_spin/
|
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"text": [
"The fastest millisecond pulsars are in the 1.5 milisecond (670 Hz) range. Assuming they're of typical size (~20 km in diameter) that gives you an equatorial speed around 43 million m/s.\n\nPretty fast, but light is *300* million m/s.\n\nSo how do you spin up a neutron star even faster? Pile more rotating mass! These milisecond pulsars gain their immense speed by sucking mass off another star and spiraling it down to the surface.\n\nThis leeches the orbital and rotational momentum from the victim star and adds it to the pulsar.\n\nSo what's the limit? The fastest we've ever seen is a 716 hz screamer, but in theory they can get a little faster.\n\nOnce you approach 1000hz, the deformation of the pulsar is so bad that there's no real way to add mass and energy faster than you're consuming energy distorting the star and the space around it a thousand times a second.\n\nAdd too much mass and the intensely powerful gravity overcomes light itself and the object becomes a stellar mass black hole instead. The rotation of black holes is not well understood.\n\nAlso, standing on a pulsar is not recommended."
]
}
|
[] |
[] |
[
[]
] |
|
22l4e1
|
how did the different english accents come about? when did american english begin to change and when did the australian accent differ from england's english.
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/22l4e1/eli5_how_did_the_different_english_accents_come/
|
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"text": [
"go over to r/linguistics they talk about this kind of stuff a lot",
"Language evolves all the time: you almost certainly don't speak exactly the same way your grandparents did when they were your age.\n\nLanguage changes in different ways in different areas -- even today, when we have the mass media and increased mobility. But in former times it was much more obvious: people couldn't hear how people at the other end of the country or on the other side of the Atlantic were speaking, so dialects and accents changed in different ways in different places.\n\nAnd it's not at all the case that American English changed while British English stayed the same: both changed, but in different ways.\n\nBut the language didn't change at the same speed everywhere. For example, if you want to get a general idea of how English speakers might have sounded at the time the first settlers arrived in the New World, you would actually benefit from listening to Yosemite Sam. His dialect preserves many of the features of Elizabethan English, including the very strong retroflexive \"r\" (the same \"r\" sound used by people pretending to be pirates) and the use of words like \"varmint\".\n\nThat's not to say everyone on board the Mayflower spoke like a cartoon character, but Yosemite Sam's speech is closer to Elizabethan English than, say, Walter Conkrite's speech, or even Benedict Cumberbatch's.\n\nEDIT: Added Benedict Cumberbatch to prove that I have my finger on the pulse; a.k.a. mid-life crisis.",
"The English accent that I speak with today probably sounded nothing like the 17th Century English accent. ",
"Well, most of this has been covered already so I won't repeat. However, the latter part of the question presupposes 1) that all English people speak the same English, and 2) that the English speaking migrants who went to Australia all came from England. Neither of these suppositions is correct. But, yeah, language changes over time and are subject to a combination of centripetal and centrifugal forces. The further you are from the centre, the faster your version of English is going to deviate from the norm of English English (whatever that is).",
"Im from Donegal in Ireland, If I drove half an hour to Derry, you would hear a different accent. \n\nIts crazy how many different accents there are in a country as small as Ireland. ",
"Not only have we got the perpetual accent change that others have mentioned, but there's never been a point in England's history when it had a homogenous accent. For the past 2000 years, since the Angles and Saxons slaughted most of the native Britons and exiled the rest to Wales, the \"English\" have been completely different from county to county. Yorkshire sounds fundamentally different to Somerset, which is again completely distinct from Kent's accent. Residents of my home town say its name differently to people who live ten miles away.\n\nThis is why it drives Brits mad to hear the phrase \"British accent\". We can pin eachother's origins down to the village they were born in, just by how they order a pint in the pub, *and it's always been that way*. So it's no wonder that if you throw a random selection of us into a colony, a distinct new accent will arise (Bostonian), but throw in another random mix and you'll get another different accent pattern (Aussie). Add in other nationalities (because the British weren't the only ones with colonies) and you'll get South African, Yoopers, and a myriad other sounds, all bubbling to the surface in the English Accent Gumbo."
]
}
|
[] |
[] |
[
[],
[],
[],
[],
[],
[]
] |
||
6jfrb8
|
What is the advantage of creating bipedal walking robots?
|
After watching the video of OSUs Cassie here: _URL_0_
I was wondering why so much interest in making robots able to walk on two legs. What could a two legged robot do that a drone/wheeled/four legged robot couldn't?
|
askscience
|
https://www.reddit.com/r/askscience/comments/6jfrb8/what_is_the_advantage_of_creating_bipedal_walking/
|
{
"a_id": [
"djexd43"
],
"score": [
2
],
"text": [
"A bipedal might go most of the places a person could, and do most of the things in a world built for people. A quadruped might have difficulty reaching beyond legs. Wheels might not negotiate obstacles so well. Drones might not lift as much and be less energy-efficient. "
]
}
|
[] |
[
"https://www.youtube.com/watch?v=Is4JZqhAy-M&feature=youtu.be"
] |
[
[]
] |
|
33uigr
|
How Fast Are Calories Absorbed?
|
I was watching a documentary that presented some "facts" that seemed a bit fishy.
This documentary stated that foods high in fiber such as "almonds" remain in digestive limbo for longer then sugary foods, which are "instantly" converted to fat.
My question is this, are foods eaten allocated for calories needed to live before being stored as fat? If i eat a sugary snack or a high fiber food and i was in a caloric deficit, would that food be used for energy before being saved for fat?
|
askscience
|
http://www.reddit.com/r/askscience/comments/33uigr/how_fast_are_calories_absorbed/
|
{
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"cqokmt2",
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"text": [
"Yes. There is an intricate system of enzymes and metabolic pathways that are arranged to make sure that the current energy needs are met, and that we only store energy when we have excess amounts of it. Fatty tissue in our body serves as an energy reserve, and fatty acid synthesis will only occur when you have more energy than you currently need.\n\nThat being said, the documentary is right in saying that certain foods are absorbed from the GI-tract faster than others. They also require different amounts of energy to break down before the organism can get a return on its investment. Most sugars are generally absorbed and broken down very fast, while proteins, fats and special sugars often take longer. Fiber is a good example of a substance we can't digest in any significant amount, and most of it gets excreted as faeces or is metabolized by the bacteria in our gut.",
" > This documentary stated that foods high in fiber such as \"almonds\" remain in digestive limbo for longer then sugary foods, which are \"instantly\" converted to fat\n\n**I watched that same documentary this morning!!!**\n\nI'm only a freshman with a nutrition major but /u/fake_lightbringer basically summed up what I was going to say. Fiber/fats are digested slower than carbohydrates. \n\n > however what the documentary was implying is that people can become overweight simply by eating only sugary foods, regardless of the caloric value. \n\nI didn't like that attitude of the documentary because its misleading. If someone is doing keto(low/no carb diet) and they still take in more calories than they burn, they will gain weight. The documentary had a very \"Its the governments fault your fat\" and \"most people can't help being fat\" vibe to it. \n",
"Calories are just a measure of net energetic resultant intake of foods. As such, you don't really ingest or absorb calories, but rather the products that are measured in calories.\n\nHigh-fiber compounds indeed stay longer in your digestive tract. While they may have a high caloric value, it takes longer for the nutrients to be absorbed and processed in your body.\n\nAdditionally, depending on the nature of the food, it takes longer for some things to be enzymatically converted in energy molecules such as ATP. While I don't know which is faster, proteins and fats are processed differently and at different rates. Sugars as well. \n"
]
}
|
[] |
[] |
[
[],
[],
[]
] |
|
5tx32e
|
why does one get heavy sweating before getting healed from a fever?
|
I usually dont sweat much when I get a fever but suddenly I get drenched in sweat the night before I get cured, why does that happen?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/5tx32e/eli5_why_does_one_get_heavy_sweating_before/
|
{
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"ddps3iz",
"ddq4u0f"
],
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4,
2
],
"text": [
"A fever isn't actually the illness, it is the response. \n\nWhen you are feeling sick, your body will commit more energy towards immune response, and one symptom is a fever. What your body is doing is basically ramping up your body temperature in order to kill off whatever pathogen is ailing you. The danger of a fever is that it can kill you by denaturing (breaking down) the proteins in your brain and body (Think of cooking a hamburger). Your begin to sweat as a mechanism to prevent your immune system from killing you off. Sweating actually cools the body, and occurs as the body attempts to cool down once the fever has \"broke\".",
"In your brain, in the hypothalamic area, a set body temperature is determined based on the physiological state. When you encounter a pathogenic agent(bacteria or whatever) your immune system will secrete molecules called prostaglandins which will cause elevation of the set temperature. When your immune system killed the \nPathogens your set temperature is returned to normal. Sweating is a mechanism by which your body dissipates heat. Sweating is a good sign (when referring to the typical fever caused by e.g flu), it means you are almost healed. "
]
}
|
[] |
[] |
[
[],
[]
] |
|
3hryjv
|
Why does the amount of oxygen in our atmosphere remain stable?
|
We saw how variable oxygen levels have been in the past as they where building up in the atmosphere. Now we seem to have settled at ~20%.
I've read that even 5% more would dramatically increase how readily things would combust (likely would cause some pretty big problems), and 5% less would effect our breathing, and also make things much less likely to combust.
So it seems we have a good balance of the stuff. My question is, why does this number remain stable instead of rising or falling more often? Is it likely that we ever might upset this balance somehow?
|
askscience
|
http://www.reddit.com/r/askscience/comments/3hryjv/why_does_the_amount_of_oxygen_in_our_atmosphere/
|
{
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"cua59rd",
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8
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"text": [
"The % oxygen has varied a lot over the lifespan of the earth, but it is much like climate where it very seldom changes dramatically in a short amount of time (short in relation to the lifespan of earth) at some point, as the atmosphere diminishes, it will decrease in % oxygen.",
" > 5% less would affect our breathing\n > So it seems we have a good balance of the stuff\n\nIt's not that we got lucky and our atmosphere has the correct balance of oxygen for us to live. Organisms that are alive today have been optimized through evolution specifically for our current oxygen blend. \n\nIn prehistoric times, many types of insects grew to be gigantic by today's standards due to a [higher percentage of oxygen in the atmosphere at the time] (_URL_0_). Essentially, the pace of evolutionary change has historically been able to keep up with atmospheric changes of oxygen in the atmosphere.\n\nThat's one of the reasons why climate change caused in the last hundred years or so is such a big deal. The changes we've been observing recently are happening way too quickly for most species to be able to re-optimize, including ourselves!"
]
}
|
[] |
[] |
[
[],
[
"http://news.nationalgeographic.com/news/2011/08/110808-ancient-insects-bugs-giants-oxygen-animals-science/"
]
] |
|
fl956q
|
Why were there so many soldiers in WW1 battleships?
|
I’m very interested in history but not well-versed. I have found the battle of Jutland to be very interesting but one thing that I couldn’t figure out is why the battleships had over 1000 men on them? Did it really take that many to run things? Or were they doubling as transports? Or is it something else that I’m completely missing?
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/fl956q/why_were_there_so_many_soldiers_in_ww1_battleships/
|
{
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"text": [
"It was mostly because yes you did need that many people for doing everything that needed to be done, to the margins acceptable for both the heat of battle, and running a massive warship 24/7.\n\nIf the ship just needed to fight for a few hours and then nothing else you could get away with a smaller crew. But you also needed it manned and sailing before and after the battle. Those are watches to be manned, work centers and stations to be crewed all day every day. The engines alone might require 100's of men at a time, and while the era of shoveling coal into furnaces was giving way to oil it was not gone entirely. And oil brought a whole new series of machinery that required constant monitoring and maintenance. \n\nAdditionally there was still relatively little automation in many processes. Massive shells for the main guns had powered or hydraulic lifts, but still required men to haul them out of the magazines and same for the bags of powder as most designs had separate shell and propellant. \n\nShips also had a nasty habit of taking damage in battle. Damage Control parties were also needed when preparing to go into battle. While every man could help, having these men set aside to respond as needed could be crucial, and another requirement for bodies, often these men would be drawn from men who were in the off watch but werent needed at their normal work center or task. \n\nAnother potential addition would be a Flag Staff. An Admiral in command of a squadron or other fleet element would have a staff with him, officers responsible for various parts of planning, and enlisted men to serve as attendants, communications staff, etc. \n\n_URL_0_\n\n/u/thefourthmaninaboat had a wonderful breakdown of Royal Navy battleship crews in WW1, and some of the unique aspects for the Royal Navy vs other nations. Each one had their own quirks but for the combatants in WW1 there was in essence something of a unified tradition in the seagoing services, they were alike in a staggering variety of ways. Part of it cultural in origin, part just because they represented best practices.",
"Battleships and battlecruisers had large crews because they needed that many men to operate them. A large par of this was because the ship required manning around the clock. The majority of the crew were divided into two watches, named port and starboard. These were further subdivided into two quarters, as only a quarter of the men needed to be on duty at any time when the ship was in harbour. The watches were on duty for four hours, then had four hours off. The one exception was the two dog watches, which were two hours long. The dog watches meant that men did not have to stand watch at the same time each day. However, there were exceptions to the watch system. The stokers (engine room crew) were divided into three watches. There were also daymen, which comprised groups such as the stewards, cooks and medical staff. These positions did not have to have someone on duty 24/7, and so were not divided into watches. Each watch was divided into four main groups, the 'parts of the ship'. In a hangover from the warships of the age of sail, these were called the forecastle, foretop, maintop and quarterdeck. Each part was responsible for their particular area of the ship. When not in action, they would keep this area clean and tidy, as well as performing other routine duties. These other duties included look-out duty, manning the helm, maintaining the magazines, or manning the boats in case of man overboard.\n\nIn action, a large part of the crew would be operating the armament. Taking the example of the 15in Mk I mounting that was used on the *Queen Elizabeth* and 'R' class battleships at Jutland, these had a crew of roughly 70 men. Each of the two guns in the mounting had a crew of eight men: a gun layer, two loaders, a rammer, a breech operator, an ordinance artificer (a trained mechanic present in case of a jam), and the Captain of the Gun, who led the gun crew, plus an 'interceptor operator' who was there to disable the gun in the event of an emergency. Two other men were in the main gunhouse - the trainer, who controlled the facing of the turret, and the 2nd Captain of the Turret. Four men were in a control cabinet at the back of the gunhouse; a rangefinder operator, a periscope operator, a communications rating and the Captain of the Turret. Below the gunhouse was the 'working chamber', where the shells and charges were transferred from the hoists that ran to the magazines and shell rooms to the hoists that ran to the turrets. This had a seven-man crew. The magazines, which contained the propellant charges, had a crew of 19, while the shell rooms had a crew of 21. There might also be others present to run emergency generators or to replace casualties amongst the crew. The *Queen Elizabeth*s and 'R's had four turrets each, totalling ~280 men in the main armament alone. The 12in and 13.5in turrets used on older ships would have slightly smaller crews, mainly in the shell rooms and magazines. However, ships mounting these weapons often had more turrets, so a similar number of men would be manning the main armament on each ship. Then we must consider the secondary armament. Most ships mounted either 4in or 6in guns as a secondary armament for use against torpedo boats and destroyers. These had a crew of four, plus up to six loaders, with ships mounting between 14-16 of these weapons. Then there were more men in the magazines and shell rooms used by these weapons. Ships also carried a torpedo armament. Depending on the size of the armament, this might require up to a hundred men to man it (though this is confused by the fact that the RN's torpedo branch was also responsible for low-power electrical engineering aboard ship). Finally, there were 25 men manning the fire control positions. As such, roughly half of the crew would be manning the weaponry in action. \n\nAnother significant fraction of the crew would be manning the engines. The typical battleship had about 200 men as its engine-room crew. Not all of these were needed to operate the engines in action. Instead, roughly a third would form damage control parties, along with other seamen who had no useful duties during a battle. Some men, like the ship's carpenters, blacksmiths and shipwrights, would be part of these parties as a matter of course. Still more men were needed on the bridge. This included not just the officers who commanded and navigated the ship, but also lookouts and spotters, signallers and searchlight operators. This might include up to 100 more men. If the ship was the flagship of a squadron or division, this number might climb even higher. Typically 1-200 of the ship's complement were Royal Marines, providing the ship with a landing party in case of need. The Royal Marines usually also provided the ship's police and sentries. However, in action, they would be manning one of the turrets and a portion of the secondary armament, and should not be double-counted.",
"It’s such an interesting and short lived period in naval history. Thank you for the additional info!"
]
}
|
[] |
[] |
[
[
"https://www.reddit.com/r/AskHistorians/comments/61sad5/the_hms_barham_had_1184_crew_what_are_the_duties/dfgzeab/"
],
[],
[]
] |
|
9wp949
|
Since horses are not native to the North American continent, how did they become available to Native Americans before Europeans came over?
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/9wp949/since_horses_are_not_native_to_the_north_american/
|
{
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"Horses went extinct in North America at the end of the Pleistocene (about 12,000 years ago). They didn't return to the Americas until Europeans arrived. While small numbers of horses escaped or were targeted specifically for capture in conflicts between various European and Native nations throughout the colonial period, the major turning point on the Great Plains came in 1680. The Pueblo Revolt ended ~~nearly 70~~ 82* years of Spanish occupation in New Mexico, and drove the Spanish frontier south for about a decade. Throughout New Mexico, the Spanish had trained local people to care for their horses, and now that the locals were back in charge, they could do what they pleased with those horses. Large numbers were sold off to people on the southern Plains, such as the Comanche who had recently come down from the north. Through raiding and trading, horses spread northward through the Plains, so by the early 1800s - when the United States claimed the Plains through the Louisiana Purchase - the vast majority of Plains cultures had adopted the horse and undergone considerable social shifts to maximize their usefulness. The Lakota, for example, were semi-sedentary hunters and farmers before the horses showed up and allowed them to follow bison herds regularly. \n\n*I was thinking the Spanish conquest of New Mexico was in in 1608; it's actually 1598."
]
}
|
[] |
[] |
[
[]
] |
||
192nnq
|
Did World War One trenches extend north to the sea/south to the mountains?
|
What happened to the trenches at the extreme north and extreme south of the fronts during World War One? Did they extend all the way to the sea/Switzerland along the western front? How about the eastern? Anywhere else? Pictures would be cool, too, as I can find none on google.
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/192nnq/did_world_war_one_trenches_extend_north_to_the/
|
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"I remember seeing a photograph of the extreme northern end of the front which had wooden barricades with barbed wire extending out onto the beach. They probably would have only needed a single machine gun supported by a company of infantry to defend that particular section. I could have sworn I saw that picture somewhere around reddit, but I too can't find it with a regular search.\n\nThe better question is what happened when the front reached the Swiss border? Did they just build fences and agree to fight away from neutral territory?",
"For the Swiss end, read [here](_URL_0_). The Swiss army had to prevent that neither the German nor the French army could gain an advantage by attacking the adversary over Swiss territory from the back – by using the convenient roads in the Largue pocket or on the Réchésy – Courtavon (Ottendorf) axis. The map shows clearly how easy that would have been for both adversaries. Therefore: 6 checkpoints along the border, 3 blockhouses in the Largue forest and at the Larghof-farm plus 2 observation towers were established.\n\nToday, only few traces can be found of these positions. The MOST SOUTHERN FRENCH BUNKER OF THE WESTERN FRONT is called “Villa Agathe” and is situated in the forest “Bannholz” south of Pfetterhouse. The blockhouse for 2 machine guns covered the road from the Largue Bridge to Pfetterhouse and is well conserved. There are rests of trenches around the blockhouse. The MOST SOUTHERN BUNKER OF THE WESTERN FRONT is the German Bunker in the wood opposite the Larghof farm. A shelter and a machine-gun position can be found just next to it.",
"I asked a similar question last year. You might be interested in the responses there.\n\n_URL_0_",
"Pretty close. Here are some maps of the Western Front at different times during the war. You can see why the war turned into a stalemate so fast--with entrenched positions throughout most of France there was simply no way for the Germans to break through. With the Germans bringing up reinforcements from their side there was no way for the French to break through. \n\nThe only thing keeping the trenches from going all the way to the Mediterranean was the neutrality of Switzerland. \n\n[1914](_URL_1_)\n\n[1916](_URL_2_)\n\n[1918](_URL_3_)\n\nAs a side note, I'd like to point out that the siege of Petersburg in the American Civil War developed in a way that very closely resembled the trench warfare of WWI.\n\n[Petersburg trenches](_URL_0_)\n\n[Dead Confederate soldier in trench](_URL_4_)\n\nI'd also like to point out that the development of the massive trench system was an organic thing. The first trenches in WWI started out as single foxholes, which were then connected to each other during the siege, then those connections were widened and as the Germans tried to encircle the army they were expanded to prevent them from being outflanked. \n\n\n\n"
]
}
|
[] |
[] |
[
[],
[
"http://www.schweizer-festungen.ch/1914-18_ww1.htm#border"
],
[
"http://www.reddit.com/r/AskHistorians/comments/t8svx/what_did_the_intersection_of_the_swiss_border_and/"
],
[
"http://i.imgur.com/y5cWQtT.jpg",
"http://sunnycv.com/steve/ww1/images/westpoint11.jpg",
"http://www.worldwar1.com/maps/wfsp1916.jpg",
"http://www.sunnycv.com/steve/ww1/images/westpoint18.jpg",
"http://i.imgur.com/BkXay5c.jpg"
]
] |
|
5z3ffw
|
why was the transition of germany into a democracy in ww2 so smooth (for the most part) compared to the attempted transitions in middle eastern countries?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/5z3ffw/eli5_why_was_the_transition_of_germany_into_a/
|
{
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"text": [
"Remember, self rule is not absent in German history. Under the Kaiser, the Reichstag stood as a parliamentary system, and under Bismarck, universal male suffrage was implemented. In practice, the Reichstag didn't have terribly much power, but it still existed.\n\nImmediately before WW2, Germany was already a republic, the Weimar Republic, which was actually fairly prosperous before the Depression hit.\n\nAlso, Europe has split between the Soviet Union and everyone else, and as such, the new German republic after unification didn't have to deal with danger from any of its Western neighbors.",
"Several reasons:\n\n1. The borders of modern middle eastern countries were not determined by the people who lived there. They were drawn by European and American powers who had little vested interest in stability (sometimes actively undermining it). As a result, a whole bunch of people who hate each other and have hated each other for a thousand years have been crammed together.\n\n2. Democratically elected governments in places like Iran have been toppled by the CIA because they were doing things the US didn't like. They were replaced with dictators who would sell oil and do what America told them to.\n\n3. Many people in the region don't believe democracy is in their best interests. Colonialism has given western ideas a bad name in the region, and local power brokers like things the way they are. Remember that the instigators of the revolution in the US were the rich and powerful who thought that they could be better off with a democracy than with royal rule. In Germany, disgust with Hitler and pressure from the US made the idea of another dictatorship laughable, and democracy tends to maintain itself once it exists in a good form.\n\n4. Petty dictatorship is the natural way of the world. For almost all of human history, tyrants of one kind or another lorded over peasants. Democracy is a fairly new thing. Even though the Greeks and Romans invented and used it, the US ( < 250 years old) was the first real nation state with a democratic government. I recommend reading The Dictator's Handbook by Bruce Bueno de Mesquita for a more in depth look at how various kinds of government evolve, survive, and die. ",
"Germans see themselves as Germans. They might have sub-cultures or regions they are from but they all first see themselves as German. \n\nSomewhere like Afghanistan people are loyal to their tribe over their country and are also split into Sunni and Shi'ite Muslims as well. They mostly see other tribes as either enemies or something or at best just don't care about them. \n\nThey don't want to be led by anyone other than someone from their tribe and especially not by someone from a different subsect of Islam. They don't want to pay for a military to protect other areas or pay taxes for social programs to help other tribes. \n\nIt's just a shitty situation for trying to have a unified government and the only real way to have any kind of unity there is with force. "
]
}
|
[] |
[] |
[
[],
[],
[]
] |
||
6ttsqj
|
what performance difference can we see between an athlete that warms up and one that doesnt before a race?
|
I would like to know specifically about cyclists
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/6ttsqj/eli5_what_performance_difference_can_we_see/
|
{
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"text": [
"Well I'm no expert but I do play hockey. When I myself do not warm up the first half period of my game is warm up, and I only start playing at my full potential around 2/3 of the way through. Also I notice I have significantly less stamina the entire game, and it feels like I didn't get enough sleep. I'm sure It has something to do with circulation perhaps. Warming up also tends to put me into a mental mindset to where I at least feel more awake and focused.",
"The most important reason for doing a warm up is to allow the body to prepare steadily and safely, thus preventing the possibility of an injury during the performance. In case an athlete didn't do the warm up exercise and an injury like a hamstring strain did occur that will obviously affect the performance, otherwise a considerable difference in performance is highly unlikely. Basically it's a matter of safety, gradually increasing the heart rate and circulation thus loosening the joints and increasing blood flow to the muscles. There is also a psychological factor that helps athlete when doing warm-up because it's an opportunity for the athlete to prepare mentally for the performance ahead. ",
"In short, warming up brings the body from its natural state of rest closer to its exercising state during training, performing etc. Essentially, it makes the transition from rest to exercise much more efficient as our heart rate is already substantially increased due to warming up. Our blood circulation is subsequently increased, leading to increased delivery of oxygen and removal of metabolic waste products from working muscles. Warming up allows athletes to jump straight into performance without having to worry about the stage known as oxygen deficit, where the body literally needs to take in a greater amount of oxygen to satisfy the increased demand for oxygen by the muscles. \n\nSo to answer your question, a cyclist that has warmed up will be able to cycle harder and faster as their heart rate, blood circulation, respiratory rate and more are already substantially increased. A cyclist that has not warmed up will need an increased amount of oxygen delivered to working muscles to satisfy the sudden increase in demand. ",
"Interestingly enough there might not be much of a difference. There was a study done with runners that showed that people who did warm up and stretch before running had the same rate of injuries as those who didn't. "
]
}
|
[] |
[] |
[
[],
[],
[],
[]
] |
|
1a15qe
|
Is there a limit to the amount of information that could theoretically be stored in the universe? Can you store more than one bit (piece) of information using a single particle?
|
I have no educational background in how information is stored / quantum computing, but it struck me that the at the very least you would need at least one particle, in a certain position, to store one piece of information. Does that mean that there is somehow a maximum amount of information that could be stored, being that there is a finite amount of matter in the universe? I'm hoping that someone can answer both sides of this question, as I am not sure if this question is worded correctly, or exactly what I am asking.
|
askscience
|
http://www.reddit.com/r/askscience/comments/1a15qe/is_there_a_limit_to_the_amount_of_information/
|
{
"a_id": [
"c8t6iq1",
"c8t6kx6"
],
"score": [
8,
2
],
"text": [
"Related to your question is [Landauer's principle](_URL_0_) which has to do with the minimum amount of energy needed to change a bit. Essentially, the laws of thermodynamics can be used to prove that changing a bit of information requires a certain minimum amount of energy to be used. Combining this idea with some of the encryption algorithms we have, we can actually say that they are impossible to brute force crack, even if some alien race with technology we've never seen before arrived and tried to crack it, because in doing so they'd need to convert all the energy in the universe into heat.\n\nI hope this won't get downvoted or deleted. I don't know the answer to your specific question, but it seems like you'd be interested in this if you're interested in the theoretical maximum information that the universe could store.",
"The [Bekenstein bound](_URL_0_) is an upper limit on the entropy of a finite region of space, varying by its temperature.\n\nAs it turns out, in a certain precise way, entropy corresponds to the number of possible distinguishable states internal to the system, which is also the maximum number of states of information that could be stored in the system.\n\nAny finite region of finite temperature therefore has a massive but finite possible information content."
]
}
|
[] |
[] |
[
[
"http://en.wikipedia.org/wiki/Landauer's_principle"
],
[
"http://en.wikipedia.org/wiki/Bekenstein_bound"
]
] |
|
1sltba
|
what is the clunking noise that cars make in movies when they die?
|
There's always this noise when a car comes to a stall in almost every movie.
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/1sltba/eli5_what_is_the_clunking_noise_that_cars_make_in/
|
{
"a_id": [
"cdyv1je"
],
"score": [
2
],
"text": [
"The car is briefly \"dieseling.\""
]
}
|
[] |
[] |
[
[]
] |
|
abtj05
|
Would a creating artificial gravity through a centrifuge impact something like a watch's time over a period of time?
|
If someone had 2 very accurate clocks and one was placed in a centrifuge to create strong artificial gravity, would the clock in the centrifuge eventually be measurably ahead of the other one?
|
askscience
|
https://www.reddit.com/r/askscience/comments/abtj05/would_a_creating_artificial_gravity_through_a/
|
{
"a_id": [
"ed5ruhh"
],
"score": [
6
],
"text": [
"The clock in the centrifuge would measure behind the other one. If you observe the system in the external frame, the time dilation observed for the centrifuge clock is equivalent to that predicted by special relativity.\n\nIf you're in the centrifuge, the time dilation experienced would appear to be due to \"gravitational\" time dilation from the centrifugal force.\n\n[This paper](_URL_0_) shows the doppler shift of absorption lines of a sample in an ultracentrifuge, and it is consistent with our expectations from relativity. "
]
}
|
[] |
[] |
[
[
"https://journals.aps.org/pr/abstract/10.1103/PhysRev.129.2371"
]
] |
|
xwapa
|
how does the mars rover curiosity transmit data over such uber long distance?
|
How does Curiosity transmit data over such long distance: satellites? What type of equipment is used?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/xwapa/how_does_the_mars_rover_curiosity_transmit_data/
|
{
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"c5q4pzw",
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],
"score": [
27,
12,
2
],
"text": [
"Rover tone transmit - > mars orbiter - > earth satellite - > JPL",
"I worked with signal equipment in the military so I know a little about earthly communications. Maybe someone else can answer how spacey communications work. I know the voyager 2, which is at the edge of our solar system, uses a wavelength that's measured in inches ~~(realllllly low frequency.)~~ correction -- this isn't that low after all! thanks @BlackCow\n\nDifferent frequencies serve different purposes.. We use ultra high frequency radios for short distances of 1-2 miles, and lower frequencies in a log periodic antenna that can serve maybe 30 miles (they look like old TV antennas.)\n\nFor even longer range, we use antennas that beam radio waves up in the atmosphere and bounce them back down thousands of miles away. There's a weird \"dead zone\" immediately around these antennas because the signal doesn't bounce back so near to the source.\n\nI'd imagine that the difficulty of communications in space is mostly calculating where to point your antenna. Even on earth we need to aim our antennas at each other to get a good signal. Imagine trying to aim a beam of light at a target so far away it takes light 14 hours to reach it! In other words you have to take into account that the earth has MOVED by the time your signal gets there. Mindboggling!",
"In simple terms: Imagine that you are taking a picture with your cell phone. Your cell phone embeds and encodes image, and then we introduces a new signal to make an \"envelope\". This envelope makes it so that we can transmit the data through an antenna. Now the power it would take to go from Mars to Earth would be really high because the signal will decay in terms of signal strength. So there is a satellite around Mar's orbit, it's job is to take that signal, boost or re-envelope it, and redirect it towards the Earth. Once it's close to the earth, it gets taken in once more by a satellite, re-envelopes it again and then gets set to NASA. \n"
]
}
|
[] |
[] |
[
[],
[],
[]
] |
|
2jrmn7
|
if sugar, fat, and salt play to our dopamine levels, what do spices (like black pepper, cumin, cinnamon, tumeric, etc) do to our brain?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/2jrmn7/eli5_if_sugar_fat_and_salt_play_to_our_dopamine/
|
{
"a_id": [
"cleg6ty"
],
"score": [
3
],
"text": [
"with pepper, and spicy things in general, they also release dopamine and other chemicals. I think it's your brains natural response to the pain. "
]
}
|
[] |
[] |
[
[]
] |
||
1b9z0t
|
what physics are behind this "stunt"?
|
[I'm blown away](_URL_0_),I have no idea how this is possible. He attempts to explain it but I still don't get it (I wasn't a very good physics student)
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/1b9z0t/eli5_what_physics_are_behind_this_stunt/
|
{
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4,
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"text": [
"What I've been able to find through googling this experiment is that it has something to do with \"the conservation of angular momentum\".\n\nI found a video of some high schoolers doing different things to exploit this property and found the bike tire thing at 0:45 to be the most interesting.\n\n_URL_0_\n\nUnfortunately I suck at physics so I can't really explain this black magic.",
"It's an effect called Gyroscopic Precession. I apologize in advance, but I don't know if I can explain it to a 5 year old, and an 18 year old is a stretch, as it involves some fairly complicated vector mathematics/physics. Hopefully someone else can. Pictures help immensely so instead of doing much explaining I'm going to link to some other sites later. \n\nBasically, Gyroscopes (like a top) behave oddly. Intuitively, a top should never stand on end. However, when spinning, it can resist gravity and stand up until it slows down. Another effect is when you try to rotate an object that's spinning, the rotation will happen in a completely different direction. He's taking advantage of that for a really cool trick I'd never seen. \n\nThis [How Stuff Works](_URL_0_) is probably the simplest, pages 2 & 3 specifically. [This explanation](_URL_1_) is very good, but very technical. \n\nAlso, [here's a simpler version of the trick.](_URL_2_) The wheel is spinning in one direction and gravity wants to make it fall (rotate) in a second. Instead of falling, it spins vertically. ",
"Hey one other fun thing related to gyroscopes you might enjoy (just for fun): _URL_0_"
]
}
|
[] |
[
"http://www.wimp.com/spinningdisk/"
] |
[
[
"http://youtu.be/UZlW1a63KZs"
],
[
"http://science.howstuffworks.com/gyroscope.htm",
"http://www2.eng.cam.ac.uk/~hemh/gyroscopes/onetofour.html",
"http://www.youtube.com/watch?v=lvPAjr_a6Jg"
],
[
"http://www.youtube.com/watch?v=cRJv6z_bxQg"
]
] |
|
gcf9b
|
DAE think maybe Dark Matter is the new Luminiferous Aether?
|
I don't hold a degree or anything but I try to follow physics as a hobby, can someone try to explain dark matter to me? All I ever see about it is that it's deduced and unobserved.
**EDIT** Thank you all very much. Askscience might be my new favorite reddit. I find this stuff fascinating. Can anyone recommend any books on the subject for the layman?
|
askscience
|
http://www.reddit.com/r/askscience/comments/gcf9b/dae_think_maybe_dark_matter_is_the_new/
|
{
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"text": [
"You have the gist of it, pretty much.\n\nThe general consensus, so far, is that some sort of extra, non-luminous matter best explains what we see in the rotation curves of galaxies and globular clusters, as well as what we observe from gravitational lensing.\n\nIt can't be normal matter we already know about, though. Gas and dust would light up in some part of the spectrum by reflecting light from nearby stars. There just aren't enough neutrinos produced by the stars to account for the extra mass (stellar fusion is one of those things we know absurdly well). It can't just be some cold, massive rocks, because having that much extra normal matter would screw up with Big Bang Nucleosynthesis, another one of those things we know absurdly well.\n\nSo, at least for now, we think that it's something we've never seen before. Not only that, but it seems to be stable (or at least, it's long-lived enough to last a long while). Many physicists and astronomers are focusing on this idea, which you may sometimes hear referred to as \"cold dark matter.\"\n\nThere are dissenting opinions, of course. Some advocate a modified form of gravity, including those advocating MOND (Modified Newtonian Dynamics) which postulates modifications to Newtonian gravity at large distances. This position is mostly disfavored though... but I don't know enough to tell you exactly why.\n\nPerhaps RRC will come by and correct/expand on this description? :)",
"Luminiferous ether wasn't a particularly dumb idea, it just happened to be wrong.\n\nBasically, we know that either our understanding of orbital is wrong, or our understanding of interstellar composition is wrong. Keplerian motion holds true (with some corrections) for every planet and moon in the solar system, every planet outside the solar system, and the thousands of double star systems throughout the galaxy. It's much more likely that we're not aware of some component of the universe, and we're calling that dark matter until we figure out what it is.",
"If you look at a disc-type galaxy — one that's rotating in some overall way, like a spiral galaxy for instance — from some angle that's not directly along its axis of rotation, you'll find the stars on one side of the galaxy's core are moving toward you and the stars on the other side are moving away from you. You can tell this by first noting the galaxy's overall redshift (which is an artifact of the expansion of the universe, and needs to be factored out for this observation), and then looking at the spectral emissions of the stars on *this* side of the galaxy and comparing them to the emissions of the stars on *that* side of the galaxy. Since emission spectra are very well understood, and it's not *that* hard, in practice, to make very precise measurements of them even over intergalactic distances, in this way you can get some really surprisingly reliable data about how the different parts of that galaxy are moving relative to each other.\n\nNow, if you did this to our solar system — went out into distant interstellar space and looked at the spectra of the individual planets — you'd find that there's a fairly simple relationship between orbital motion and distance from the sun: orbital speed is roughly proportional to the *inverse* (Thank you, Veggie) square root of the distance. This all follows naturally from everything we know about how gravity works, and it makes perfect sense.\n\nBut the data collected from observations of galaxies isn't like that at all. The orbital speed of a star around the center of its galaxy isn't proportional to the square root of its distance from the center. Instead, it's damn near *constant.* If you plot the data on a graph, showing distance from the center along the horizontal and orbital speed along the vertical, instead of seeing a line that slopes downward in a curve from left to right, you see something that looks like a cliff: pretty much flat most of the way across, then dropping fairly suddenly.\n\n(This has been done about a billion times over recent years. A google image search for \"[galactic rotation curve](_URL_0_)\" will show you what I mean.)\n\nNow, the most obvious conclusion is that there's something wrong with gravity. Not *gravity* gravity, but our mathematical description of it. If the equations say *X* and reality says *Y,* then the equations are wrong, right?\n\nWell, it's not really that simple. See, if gravity were just simply wrong, we'd see deviations from theoretical predictions here within our own solar system. The fact that we don't means that gravity's *at least* right on the small scale. Which technically leaves open the possibility that it's wrong on the large scale.\n\nBut there's a problem with that. See, the laws of physics don't actually distinguish in any intrinsic way between small scales and large scales. There's no term in any of the equations — equations that are *known* to work — that says \"The answer is *X* but *only if* the radius is less than a parsec,\" or whatever. Of course, we could write the equations that way, but not without being just totally arbitrary about it.\n\nAs Doner Kebab (who always makes me hungry) notes, there have been attempts to go back to the drawing board on gravity and find a way to explain galactic rotation curves that doesn't just amount to putting a bit \"if *r* < some big number\" fudge-factor in. But there's not really been any success there that's worth talking about. Those theories are hellishly complex, introducing multiple mutually-interacting massive scalar fields and other such things, and they can't explain the most basic gravitational phenomena, like the geodetic effect or orbital precession or gravitational lensing.\n\nBut it turns out that we can keep the laws of gravity exactly as they are and still explain observed galactic rotation curves to a ridiculously high degree of precision *if we assume that there's stuff in the universe we can't see.* If you assume that every galaxy — well, most galaxies anyway — is surrounded by a very large, very diffuse but very *very* massive cloud of gravitating matter, then the motions of stars within that galaxy line up just about perfectly with our observations.\n\nGreat! Sorted! Now we know that the universe is filled with huge amounts of stuff that's invisible, undetectable, and that is found in places where no matter has any right to be.\n\nHm. Okay. Maybe not *totally* sorted after all.\n\nThis is probably where your objection comes in. Making up this magical invisible stuff to explain a failure of theoretical prediction smacks of *bad science* all around. Except that's really not what's going on at all. You see, the properties of dark matter aren't arbitrary. It's not like we're making stuff up out of whole cloth here. All we have to do to get dark matter that behaves in ways that match what our theory *predicts* should be there is postulate that there exist some type of matter that's four things: massive, weakly interacting, cold and stable.\n\nDark matter has to be massive in order to have the gravitational effects we've observed. That one's obvious.\n\nIt has to be weakly interacting — that is, participating exclusively or mostly via the weak interaction, not the strong or electromagnetic interactions — in order for it to be invisible. Matter that interacts via the electromagnetic interaction will either emit or scatter light; stars emit light, and clouds of dust scatter light, and we can see both of those things if we look hard enough. But we can't see dark matter *at all,* so it has to be electromagnetically inert.\n\nIt has to be cold in order to be where it appears to be. Matter with a lot of momentum — hot matter, in other words — wouldn't be found in these large, well-defined halos around galaxies. Gravitation is so tenuous at such distances from the galactic centers — hundreds of thousands of light-years — that matter with any significant momentum would be at galactic escape velocity, and wouldn't be found in halos.\n\nAnd it has to be stable because we see the effects of dark matter halos around galaxies that are *very* widely separated in time, on the order of billions of years. The dark matter halo around a galaxy we observe when it's five billion years old appears to be pretty much the same in character and composition as the dark matter halo around a galaxy that's ten billion years old. So dark matter has to stick around for a while.\n\nSo in order for dark matter to do what it appears to do, it has to have all four of those properties. None of those is unprecedented! We can find examples of all of those properties all around us. We've just not yet found all four of them *together.*\n\nProtons are massive, cold and stable, but they're not weakly interacting. They participate in both the electromagnetic and strong interactions, which means they scatter light and form nuclei. They're not what we're looking for.\n\nNeutrons are massive, weakly interacting and cold, but they're not stable. A neutron off by itself only lasts for about a quarter of an hour before decaying into things that aren't weakly interacting.\n\nNeutrinos are weakly interacting and stable, but they're neither massive nor cold.\n\nAnd so on. If we wanted, we could make a chart with four columns for the four known gross characteristics of dark matter, and then list all the known elementary and composite fermions, putting checkboxes where they qualify. We wouldn't find any that have four checkboxes.\n\nBut that doesn't mean none exist. It just means that the Standard Model of particle physics doesn't predict any. It's widely accepted that the Standard Model is a damn fine start, but not a complete theory of particle physics. It's been extended all the time, as new ideas are explored. One of these ideas is called *supersymmetry,* and includes the notion that each boson should have a fermionic analogue called a \"superpartner,\" and vice versa. One approach to this idea includes the prediction that the fermionic superpartners of the neutral bosons — the photino and zino and possibly the higgsino — should all have the same quantum numbers, and thus should be able to form mixed states called *neutralinos.* Neutralinos would be massive (on the order of a hundred to a thousand proton masses), weakly interacting (that is, lacking electric charge), cold (by virtue of their mass), and stable (in the lowest energy state).\n\nI counted 'em twice on my fingers and twice on my toes, and unless I screwed up the arithmetic somewhere, that's *four checkboxes.*\n\nSo it's pretty much universally agreed that particles with the necessary characteristics to be dark matter *can exist.* They're not, like, forbidden by the laws of nature or anything. Is the lowest-energy neutralino the stuff of galactic dark-matter halos? Nobody knows, but it seems like the general consensus right now is \"probably.\" If it turns out the supersymmetric models that predict neutralinos are off and such particles don't actually exist, then clearly dark matter must be something else. Even if the models are absolutely dead-on, it's not unreasonable to expect that it'll be thirty or forty years yet before the lightest neutralino is unambiguously detected. And even that might be foolishly optimistic, given how reluctant they must be to interact and thus how hard they must be to detect if the models are right about their properties.\n\nBut in general, no one seriously doubts that dark matter exists, and that it has properties consistent with what we observe, and that we've never detected it directly so far because those properties all add up to make it pretty darned inconspicuous until you put tons and tons of it together and let it change the basic structure and shape of the universe as a whole."
]
}
|
[] |
[] |
[
[],
[],
[
"http://www.google.com/images?q=galactic%20rotation%20curve"
]
] |
|
fgkoez
|
why is it more pleasing to listen to my favourite songs when they randomly play on the radio rather than picking them myself in music streaming apps?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/fgkoez/eli5_why_is_it_more_pleasing_to_listen_to_my/
|
{
"a_id": [
"fk54ghj"
],
"score": [
2
],
"text": [
"Because it's reassuring, pleasant, and/or exciting to feel that someone else shares your taste in music. \n\nYou kinda feel vindicated, which doesn't happen when you're doing the choosing."
]
}
|
[] |
[] |
[
[]
] |
||
8juq9v
|
court stenographer machines can capture entire conversations in real time but no one uses them as computer keyboards? why? are they harder to use?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/8juq9v/eli5_court_stenographer_machines_can_capture/
|
{
"a_id": [
"dz2ke5m",
"dz2l0vv"
],
"score": [
6,
3
],
"text": [
"[A stenotype machine](_URL_0_) isn't just a quick way of typing, it's also a form of [shorthand](_URL_2_). It's not a 100% accurate way of recording things, it's just a really good way to capture things quickly. You have to do some work after the fact to make it readable.\n\nThere are [chording keyboard](_URL_1_) layouts but they're not particularly popular because it's much harder to learn key combinations than a 1:1 connection between symbols and keys.",
"They are harder to use because the user must know shorthand and know how to use the keyboard. People usually needed professional training in order to learn and use a stenography machine. There are less keys, and you have to press multiple keys at once to “spell” the shorthand words. It’s like having to learn a new language combined with learning a musical instrument. \n\nWith a typical QWERTY keyboard, the user just needs to know how to write in their language, making it incredibly user-friendly and accessible. A stenography keyboard requires training and entirely new skillsets. "
]
}
|
[] |
[] |
[
[
"https://en.wikipedia.org/wiki/Stenotype",
"https://en.wikipedia.org/wiki/Chorded_keyboard",
"https://en.wikipedia.org/wiki/Shorthand"
],
[]
] |
||
2ctuib
|
why does taking precautionary antibiotics after something like surgery help pathogens to become drug-resistant?
|
I has surgery on my foot and the podiatrist put me on antibiotics for the week after the surgery. When this was mentioned to my best friend's mom, who is a nurse practitioner, she made it very clear how against it and what a bad idea it is. I understand how starting an antibiotic and stopping before you've taken the full dose can do it when you actually have an infection, but how when you have nothing?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/2ctuib/eli5_why_does_taking_precautionary_antibiotics/
|
{
"a_id": [
"cjixjbu"
],
"score": [
2
],
"text": [
"Antibiotics help create drug resistant infection by exposing the infection to the drug.\n\nThey then mutate to be able to work against the drug, and become drug resistant.\n\nSimilar to how humans were once prey, and then evolved to be able to fight against our predators because the ones that were unable to fight back got eaten."
]
}
|
[] |
[] |
[
[]
] |
|
2vzg0f
|
How did the sun get to be made primarily out of Hydrogen, while the planets are not?
|
I understand the Solar System came from a nebula, but how did the Sun end up to be mostly Hydrogen? Is it just the size and other planets have a proportional amount of it? And why are the planets closest to the sun mostly rock, while the further away they get, they are mostly gas?
|
askscience
|
http://www.reddit.com/r/askscience/comments/2vzg0f/how_did_the_sun_get_to_be_made_primarily_out_of/
|
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"When the universe cooled sufficiently after the Big Bang, matter started to form: hydrogen, helium, and a bit of lithium. All, other elements are created in the interiors of stars via fusion. So far, there has been enough time for about 1% or less hydrogen and helium to be converted. \n\nHydrogen and helium are very light gasses. To retain them, you need a good bit of gravity and fairly low temperatures.\n\n\n",
"Actually, to say that the planets are not mostly hydrogen is not entirely correct ([Jupiter](_URL_0_), [Saturn](_URL_1_), [Uranus](_URL_3_), and [Neptune](_URL_5_) are all mostly hydrogen.) All of the Jovian planets (planets past mars that are the 'Gas Giants') are mostly hydrogen.\n\nSo I suppose the real question is: \"why are the planets closest to the sun not mostly hydrogen?\"\n\nBasically, the solar nebula is very warm at the center, but cooler at the ends. The [frost line](_URL_4_) in the solar nebula is the point at which ices (like hydrogen) can actually condense. Inside the frost line only heavy materials like metal and rock can condense, whereas outside of the frost line hydrogen is capable of condensing, and because it is the most abundant element, it makes up the majority of the planets where it is able to condense. The end result of this is that the closer planets were not able to condense hydrogen due to the heat, so they have very little hydrogen comparatively.\n\nEDIT: As for [star formation](_URL_2_), stars tend to be almost entirely hydrogen and helium because Stars fuse hydrogen into helium during their [main sequence](_URL_6_) which makes up most of a stars life and is really how we view stars.\n\nFUN FACT: If Jupiter were bigger it would likely be a star as well due to its composition, alas it is quite a ways off size wise from enabling fusion.\n\n\"Since the critical mass needed to set off the nuclear reaction that powers stars is 0.06 times that of the sun, Jupiter would have to be 60 times bigger to become a star.\" Ronin, A. Colin. The Universe Explained. Holt,1994: 77.",
"This will probably answer your question: _URL_0_\n\nBasically, colder, more massive planets more easily retain light gases like hydrogen and helium. Less massive & warmer planets cannot retain light gases due to less gravity to hold them at high kinetic energies. \n\nThis simulator / plotter should be helpful.\n\n_URL_1_"
]
}
|
[] |
[] |
[
[],
[
"http://en.wikipedia.org/wiki/Jupiter#Composition",
"http://en.wikipedia.org/wiki/Saturn#Physical_characteristics",
"http://en.wikipedia.org/wiki/Star_formation",
"http://en.wikipedia.org/wiki/Uranus",
"http://minerva.union.edu/parkashv/planets.html#Frost_Line",
"http://en.wikipedia.org/wiki/Neptune",
"http://en.wikipedia.org/wiki/Star#Main_sequence"
],
[
"http://astro.unl.edu/naap/atmosphere/atmosphere.html",
"http://astro.unl.edu/naap/atmosphere/animations/gasRetentionPlot.html"
]
] |
|
avml9r
|
why does stress and sleep deprivation lower your libido?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/avml9r/eli5_why_does_stress_and_sleep_deprivation_lower/
|
{
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"text": [
"Sex makes babies.\n\nBabies make stressed and lose sleep.\n\nIf already tired and stressed, your body no want add babies.",
"Cortisol is released during stress. It has an adverse affect on your health (including sex drive). Rather than giving you a random internet person’s knowledge on a subject they aren’t very well versed in, id urge you to google cortisol, stress, and the impacts that both can have on your health. \n\nAll we are doing on a day to day basis is reacting to the world and managing it. Our body releases chemicals based on that. It’s pretty simple in the most frustrating way possible if you come to realize that. "
]
}
|
[] |
[] |
[
[],
[]
] |
||
9jwxan
|
how do geologists record historic and pre-historic tsunamis?
|
After reading about the 2018 Indonesian Tsunami (prayers to the affected), I checked Wikipedia for list of the tsunamis. There were records of tsunamis all the way from ≈7000–6000 BCE. How do they record/identify those kinds (up to 1001 CE, I guess)??
& #x200B;
P.S.: I didn't know if Physics flair was correct for this.
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/9jwxan/eli5_how_do_geologists_record_historic_and/
|
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"text": [
"Tsunamis are huge waves, whose height can exceed tens of metres. The insane amount of energy in the wave lifts up boulders, carrying them all the way upshore. The heavy rocks are then dropped in a semi-neat line where the wave finally ran out of energy and changed directions.\n\nGeologists can identify the boulders as part of a tsunami wave deposit, then measure how high the Boulder is above sea level and make estimates on the height and energy of the tsunami.\n\nIf fossilized plant matter is found, carbon dating can be used to determine when the tsunami happened.",
"Googling ‘orphan tsunami japan washington’ or something like that should get you to a news article wherein Japanese records show a tsunami in the 1700s that agree with a corresponding earthquake in the Cascadia subduction zone around the same time, for which evidence was found back in Washington state. \n\nHere is a link to a journal article that talks about methodology and gives more examples. \n\nEdit: insert link...\n\n_URL_0_\n\nDetective work! We’re fortunate that we can interpret the rock record, and fortunate that throughout history, people like to write down interesting things, like giant, unexpected floods. \n\nSometimes those floods come with actual evidence. "
]
}
|
[] |
[] |
[
[],
[
"https://www.researchgate.net/publication/277576680_Tsunamis_as_Paleoseismic_Indicators"
]
] |
|
bl7qxa
|
What are the common "old age" failure modes of computer microprocessors?
|
We all know that mechanical devices fail due to their moving parts wearing out, but what about solid state electronics? If you used an a modern computer microprocessor everyday within its rated specifications until it failed, what wold be the most common failure modes and how long might it last?
|
askscience
|
https://www.reddit.com/r/askscience/comments/bl7qxa/what_are_the_common_old_age_failure_modes_of/
|
{
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"text": [
"Not sure about lifespans. Even manufactures might have trouble quantifying that. Usually the biggest problem is accidental overheating, but they have automatic protection built in. And running it within it's designed specs and not overclocking makes that unlikely. Thermal shock is always bad but unlikely. \n\nFor semiconductors, Electromigration is one failure I know of that is out of your hands. Unless the manufacturer used a barrier metal like nickel when plating before dicing and packaging. When I was still working in semiconductor very few were going that extra step. TI still does as far as I know. The problem is mitigated with other techniques now but I would not count on anything modern lasting as long as well built stuff from the 90's. I bet that Nintendo NES on my desk will outlive any PS or Xbox but I would still expect a few decades to prove that."
]
}
|
[] |
[] |
[
[]
] |
|
eyry3u
|
how do gene editing techniques target the whole tissue/organ/organism?
|
There are very good ELI5s on how novel gene editing techniques work. However, editing the DNA of a single cell doesn't seem that useful. How does the edit become expressed in multiple cells? Can this only be achieved during development?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/eyry3u/eli5_how_do_gene_editing_techniques_target_the/
|
{
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"text": [
"There are multiple options for trying to genetically engineer tissues/organs/organisms.\n\n1. Get them early -- if you can genetically modify them when they are a single cell (like you said, during development), then once they grow into the complete organism you should have modified the whole thing.\n2. Use something that gets into cells non-specifically. The thing about these is usually they only work well over a defined area that you have a lot of control over -- so more like a tissue or part of a tissue, and not usually like an organ.\n 1. Electroporation, which involves using electric current to disrupt cell membranes and push DNA into the cells, can be used on organisms (though it isn't always very gentle!). I've used electroporation to introduce plasmids into the neural tube of chicken embryos, for example.\n 2. Lipofectamine, which is a lipid-y positively charged tangle of stuff that goops onto the DNA and helps it get into cells.\n3. Viruses. You can package the genetic info you want to deliver into a virus. A popular kind right now are called AAVs, adeno-associated viruses. They're a little small, so you can't fit in really big stuff (for that you need a retrovirus maybe, or a lentivirus). There are lots of different strains of AAVs, and they typically have cell types that they prefer to infect. Because different tissues and organs often (but not always!) have different cell types, you can kind of pick your AAV of choice and have some of your DNA end up in those cells. This has (IIRC) been successfully used in mice to genetically modify parts of organs. There are potential issues in using viruses, centered around the potential for the immune system to clear them before they really get to infect your cells in reasonable numbers.\n4. Synthetic (nano)carriers. These would be around the same size as viruses, would carry your DNA of choice, and would probably use things like aptamers, targeting peptides, or antibodies to be selective to cell types and tissues. These are still in preclinical development, I'm not sure there have been successes in vivo yet. I think most success has been in modifying mammalian cells in tissue culture.\n\nI recognize this isn't really an ELI5, my bad."
]
}
|
[] |
[] |
[
[]
] |
|
4whknh
|
why does the text in older movies always move?
|
For credits or title screens the text never seems to stay in one place. It always slightly moves. Why is that?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/4whknh/eli5_why_does_the_text_in_older_movies_always_move/
|
{
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"text": [
"Because the text was applied to each frame of the film separately. That is an imperfect process so ... with a little difference in location of the text from frame to frame you've got what essentially amounts to a little animation!",
"With older film to video methods (called telecine) each frame was projected and captured by a video camera. Projectors use sprocket holes to keep the image stable but they have to move the film then hold it steady 24 times a second. Plus the film's holes are a little bigger than the sprockets so the image can move around. \n\nThe text was added in an optical printing process which added its own jitter. \n\nNewer methods use line scan methods which move the film continuously and the sprockets are optically sensed by the scanner. That reduces the playback jitter somewhat. "
]
}
|
[] |
[] |
[
[],
[]
] |
|
4ocbou
|
Can an object teleport because of Quantum Mechanics?
|
Correct me if i'm wrong but from what i know, every object has a wavefunction that has a value at every point in space, and the square of the amplitude is the probability of finding the object at the place. So if an unfathomable number of events were to take place in a universe, can an object teleport due its probability of being far far away from its original position?
|
askscience
|
https://www.reddit.com/r/askscience/comments/4ocbou/can_an_object_teleport_because_of_quantum/
|
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"text": [
"In answer to your question, yes, but I wouldn't consider this to be teleportation. The \"location\" of an object is really only defined in any sense by the exact value of its wavefunction over space, and while its true it could have some probability amplitude very far away from where you'd think of its location as being (maybe the expectation of its position, or a mode), it's not really teleportation in the standard sense- the particle was \"already there\".\n\nThere is a different and more interesting concept however, called \"quantum teleportation\". If I have, for example, an electron or some other spin-1/2 system, then it is possible to use quantum measurements (and a little classical communication) to teleport that piece of quantum information elsewhere in the sense that my copy is irrevocably damaged, and the teleportation destination obtains a particle exactly identical to the one I started with.",
"When the location of an object becomes fixed due to an interaction, as far as we know, the location is picked randomly based on the wave-function of the object. This means that an object can 'appear' at a position even if it's wave function at that position is very small. \n\nOne could think of an example in which we have a quantum ball in a two-box system. The wave function of this quantum ball is strongly peaked in box 1 so 99% of the time we'll find it in box 1 when we measure it's position. But 1% of the time we find it in box 2. It seems as if the ball occasionally 'teleports' to box 2 but this is not really the case. What's actually happening is that the ball is mostly in box 1, but a little bit in box 2 as well. In fact, any measurement that does not fix the ball's position will behave as if the ball is in box 1 and box 2 at the same time, with the apropriate distribution.\n\nTeleportation, also often called tunneling, is therefor just an illusion created by the fact that we tend to neglect the parts of the wave function that are very small. However, it is a usefull illusion. If we take the above example, it can sometimes be very annoying and difficult to carry that 1% of the wave function that's in box 2 through all our reasoning. It doesn't really add any insight into the 'normal' behavior of the system but every time we do a prediction we also have to make a prediction for the 1% that's in box 2. Because of this, we often simply neglect the fact that there's 1% of the wave function in box 2 in most of our calculations and instead we treat the system as if the ball will occasionally tunnel (the technical term for this kind of teleportation) to box 2. It's not a totally correct way of handling things, but usually it's good enough and a lot easier to work with. The bonus is that you can still use the concept of tunneling when you don't exactly know how much of the wave function is in box 1 and 2, as long as you know that most of the wave function is in 1 box. On the other hand, if you know that the wave function is distributed roughly equally over both boxes you can treat the ball as if it's in both boxes at the same time, which is a concept called \"delocalization\"."
]
}
|
[] |
[] |
[
[],
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|
aisjgz
|
Could the language i've spoke growing up influence on how my voice sound?
|
Could the way i use my vocal chords scar, or develop them so my voice would sound totally different if i grew up speaking another language?
|
askscience
|
https://www.reddit.com/r/askscience/comments/aisjgz/could_the_language_ive_spoke_growing_up_influence/
|
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"The answer to your question is mixed, and really depends on what you mean by \"voice\". When a speech-language pathologist (aka speech therapist) refers to voice, we generally view it as breaking down in three main aspects: vocal quality, intensity/loudness, and pitch. In turn, these aspects are controlled by three systems: the respiratory, phonatory (the vocal folds/cords and associated muscles), and resonatory (everything above the vocal folds which are manipulated to change sound waves to form different speech sounds). Therefore, a nuanced answer to the question requires that we investigate the different vocal aspects to see if they are impacted by the language a person speaks.\n\nIn terms of quality (things like roughness, breathiness, and strain), there is some [relatively new research](_URL_1_) that suggests that the language a person speaks can impact vocal quality. This research seems to indicate that tonal languages (in which changes in pitch contribute to meaning) have higher variation in vocal quality than English. However, the more significant and obvious differences between people in terms of vocal quality can often be attributed to personal vocal health choices (e.g. excessive drinking or smoking causing rough, hoarse vocal quality) or pathologies (e.g. cancer, vocal nodules). To comment on the scarring of vocal folds part of your question, it is unlikely that speaking a different language will \"scar\" your vocal folds or cause them significant damage unless you're engaging in poor vocal practices when trying to speak the other language (e.g. yelling or using a hard vocal attack in which the vocal folds are smashed together really violently when initiating speech).\n\nUnfortunately, I wasn't able to find any research regarding differences in vocal intensity/loudness across different languages. At least for me, the question of the impact on speaking one language or another on vocal intensity remains unresolved.\n\nOn to pitch/frequency. This a very mixed answer. The fundamental frequency--the pitch generated by the vocal folds before passing onto the resonatory system--of a person's voice is largely determined by anatomy. People with longer, thicker vocal folds will have lower fundamental frequencies (i.e. lower voices), while people with shorter, thinner vocal folds will have higher fundamental frequencies (i.e. higher voices). However, [Mennen, 2012](_URL_0_) (couldn't find it non-paywalled, sorry)] showed that fundamental frequency is impacted by what language a person speaks. So the answer is somewhere in the middle from a fundamental frequency perspective: anatomy has a large role but there is some variation based on language.\n\nGiven previous comments, it also seems worthwhile to comment on some of the language differences that we may perceive as impacting a person's voice, even though as a speech-language pathologist I would categorize them as differences in phonology (i.e. differences in sounds that are present in the languages). Each language has a set of sounds which are used in that language. When someone learns a new language, especially later in life, it is difficult for the brain to set up and execute the different motor pathways for contorting the articulators (tongue, teeth, lips, palate) that are required for correct production of sounds which occur in the new language but do not occur in the native language. In many cases the speaker will instead use the closest sound they possess in their native language to the intended sound in the new language. This difference contributes greatly to what we perceive as a \"foreign accent\". While technically not a difference in \"voice\" per se, these differences in sounds used in languages certainly do contribute to people \"sounding different\" when speaking a non-native language.\n\nEdit: hyperlink formatting"
]
}
|
[] |
[] |
[
[
"https://asa.scitation.org/doi/abs/10.1121/1.3681950",
"https://linguistics.ucla.edu/people/keating/Keating_2016_LSA.pdf"
]
] |
|
sv879
|
Does EM radiation create overtones?
|
Sound waves create overtones, but has anyone ever studied the possibility that light waves do as well? If so, couldn't microwaves cause overtones of such a "pitch" that they would be ultraviolet rays? I couldn't find any info on the web about this.
|
askscience
|
http://www.reddit.com/r/askscience/comments/sv879/does_em_radiation_create_overtones/
|
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"text": [
"I'm not sure about the answer, but I do think it's more appropriate to say a *source* of EM radiation may or may not create EM overtones. A single-frequency EM wave itself will not create overtones as it propagates; that would violate conservation of energy. But a source of EM radiation may emit a complex wave comprised of a certain base frequency *and* overtones of that frequency, or it may emit EM radiation over a broad spectrum (the way the sun does), or just a single frequency (such as in a laser).",
"Light can create overtones in specially engineered instances. In fact, if you own a green laser pointer, the green light is a overtone. In optics, this is called frequency doubling (or tripling, etc), and requires a crystal with very specific optical properties, called \"nonlinear crystals\" or \"electro-optic crystals\". Two photons of light combine in the crystal to create one photon at double the frequency of the original photons. \n\nIn a green laser pointer a \"seed\" laser (Nd:YAG) provides light at a wavelength of 1064 nm which then passes through a frequency doubling crystal. The crystal doubles the frequency, and thus halves the wavelength to give you light at 532 nm, which is green. There currently exist no green lasers, but rather you must start with a different laser and frequency double the light to get green.",
"I work with high-powered RF systems, so I have plenty of experience with this. The following applies to radio frequency systems; I'm not qualified to comment on terahertz, optical, etc. systems.\n\nYes, EM radiation sources create overtones. A source that outputs a continuous wave (CW) signal will output harmonics at progressively lower powers. So if you have a signal generator outputting a 800 MHz signal, you will also get a lower powered signal at 1600 MHz (first harmonic) and an even lower power signal at 2400 MHz (second harmonic). The better quality of the source, the lower these harmonics will be.\n\nNow, if you start [mixing signals](_URL_0_), you'll get mixing products equal to the sum and difference of the input frequencies. In practice, you also get various distortion products when mixing. Mixing allows you to convert a signal from one frequency range to another by using a [local oscillator](_URL_1_) as one of the inputs.\n\nWhen putting multiple signals into an amplifier, not only do you get harmonics, but you also get distortion products. Where those distortion products are exactly depends on the spacing of the input signals. The power they're emitted at depends on the power of the input signals, and their rate of power increase with relation to the input signals depends on where they're at in relation to the input signals. The power of the first distortion product increases 3 dB for every 1 dB of output power increase from the amplifier. Eventually, the signals will (theoretically) be radiated at the same power as the input signals. This theoretical value is called the [third-order intercept](_URL_2_) because the signal being measured is the third-order distortion product.\n\nEverything gets much messier once you start modulating signals and/or working with large numbers of signals. Most applications try to run their components powers well below their rated value to limit distortion products, but once you start getting into applications where high power is a must, things get pretty interested (and hard to predict), especially if you're operating over wide bandwidths."
]
}
|
[] |
[] |
[
[],
[],
[
"http://en.wikipedia.org/wiki/Frequency_mixer",
"http://en.wikipedia.org/wiki/Local_oscillator",
"http://en.wikipedia.org/wiki/Third-order_intercept_point"
]
] |
|
6sbqr9
|
how is the production cost for each game of thrones episode $10m, when they have 5 actors who are each receiving $2m per episode this season?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/6sbqr9/eli5_how_is_the_production_cost_for_each_game_of/
|
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"Every episode has it's own budget based off the budget the studio gives those showmakers. Let's say, like Game of Thrones, you have an 8 episode season, but you just have these 5 characters. The studio would give you $120,000,000 for that season, $40 mil goes to paying the actors, and the other $80 mil is separated into 8 pieces and used on each episode. That way each episode has it's own budget, and the actors are still payed ridiculous amounts of money that hardly seems fair.",
"Where did you get that $2M figure? It was more like $300k per episode max in season 6, but they negotiated hefty raises for seasons 7/8 (up to 1.1M)... which have fewer episodes probably partly to compensate. Also, it's Game of Thrones - you can bet some of those \"tier A\" actors are going to die and/or just not be in all the episodes."
]
}
|
[] |
[] |
[
[],
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] |
||
6hcpnz
|
why is testifying under oath a big deal?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/6hcpnz/eli5_why_is_testifying_under_oath_a_big_deal/
|
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" > I don't see how this oath thing is going to stop these politicians from lying again.\n\nLying under oath is a criminal offense. If they are caught lying then they can be stripped of office and go to jail for a long time.",
"Because if you're caught out in a lie, that has a legal consequence called perjury. Basically you can go to jail for lying under oath, a consequence that isn't present in everyday life. This means that the person under oath has less wiggle room when it comes to lying and can be used as a way to actually catch them out in a lie, enforcing a legal consequence for unethical behavior.",
"Because lying under oath is called perjury and its very illegal. Meaning if someone says a provable lie under oath then they can be face perjury charges. Perjury is what ended up getting Clinton facing impeachment. "
]
}
|
[] |
[] |
[
[],
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||
33s2co
|
why is the term "retarded" considered offensive?
|
Why do people consider the terms "retarded", "mental retardation", etc. offensive? The definition of 'retard' is "delay or hold back in terms of progress, development, or accomplishment." This seems like a very good word to be using to describe someone with a mental deficiency. Why or how did it become offensive to people?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/33s2co/eli5why_is_the_term_retarded_considered_offensive/
|
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"text": [
"Definitions of words aren't really important in deciding what people find offensive. F**got and homosexual both mean the same thing, but only one is considered offensive. \n\nWe view words as offensive when people begin to use them as an insult. This is why \"negro\" was once considered the proper way to refer to black people, but has since been used as an insult and is now considered offensive.\n\nWhile the word retarded wasn't originally offensive, people began using it as an insult so it became offensive. ",
"It's funny how euphemisms become offensive and so new euphemisms have to be invented, again and again. Idiot and moron used to be medical terms used by doctors. Then retarded. Then mentally deficient. Now I'm seeing people use the expression \"exceptional individual\" in a sarcastically offensive way, too. The neverending chain of ephemeral euphemisms.",
"Anything is offensive if society deems it to be offensive. When I was in school retarded was a general term used for special ed kids and a word we also used in place of stupid. Times change and so does language.",
"In the field of education and psychology we use the term \"intellectual disability\", in the medical field they still use \"retardation\". I believe we in the education field prefer intellectual disability because it is tied to IQ and can better assess their needs in a classroom. There are four categories for intellectual disability tied to standard deviations from the mean IQ score where 68% of the population scores. Two deviations ( < 70) means mild intellectual disability. Less than 50, moderate intellectual disability. Less than 35, severe intellectual disability. Less than 25, profound intellectual disability.\n\nObviously using the term retardation does nothing to help teachers and psychologists since there is a large spectrum of iD. Classes are divided along this categories now, because each group has special needs and capabilities.",
"Context. If you use \"retarded\" as an insult to a mentally challenged person or to insinuate that a person is mentally challenged, then it's offensive. If you use it to say, for example, \"The progress on our development of the analysis was retarded because of...\" then it's not meant in an offensive way.\n\nPeople tend to assume that words often used in euphemisms mean the same thing everywhere else, hence why we also have double entendres and people unable to take the word \"balls\" seriously, amongst others. I went to an English school when I was younger and did a double take when I saw \"faggots and mash\" on the lunch menu once. I later found out they meant sausages, but there you have an example."
]
}
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|
1hcvle
|
the offside rule in football
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/1hcvle/the_offside_rule_in_football/
|
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"text": [
"When a defensive lineman moves before the center snaps the ball into play. If an offensive lineman moves before the ball is snapped, it is called a false start. It is possible for the person snapping the ball to be called for false start, somehow.",
"The offside rule is one of the hardest to grasp, even some players don't know the exact definition. But I'll skip the former definition of the rule and explain it easily, you're still 5 after all...\n\nBasically you cannot pass the ball to any of your teammates that is above the last opposite player (not counting the goalkeeper). Unless you're beyond that last opposite player yourself, in which case you can. The reason for this is quite simple: if you were allowed to kick the ball to someone standing far from the last defending man of the opposite team then he would have an easy job scoring 1v1 against the goalie.\n\nIMHO the offside rule makes the game much more interesting and team based, you HAVE to get to the goal through you opponents, you can't just throw a cannon ball and hope for your one man attack line...",
"If an attacker is closer to his opponents' goal line than both the ball and the second last defender before the ball is played, he is in an offside position. If he gains an advantage from being in that position, he has committed an offside offence and play must be stopped, with an indirect free kick given to the defending team.\n\nA player cannot be offside in his own half.\n\nNot really an explanation for a five year old, but with a bit of thinking you can work it out.\n\nSource: Level 3 referee with 6 years experience + FIFA Laws of the Game\n\n_URL_0_",
"I like how everyone went for soccer except one person. In American Football, offside occurs when the ball is snapped and a defensemen is over the line of scrimmage. A player is allowed (under certain circumstances) to jump across the line of scrimmage and jump back without incurring a penalty; the penalty only occurs if the defensemen is over the line of scrimmage when the ball is snapped. If the defensemen is over the line of scrimmage and touches a player it is encroachment. If the defensemen lines up in the same line as the football (neutral zone), it is a neutral zone infraction. If the defensemen runs across the line of scrimmage and is making a beeline for the quarterback, it is unabated to the quarterback. Same basic premise but many different penalties."
]
}
|
[] |
[] |
[
[],
[],
[
"http://www.fifa.com/aboutfifa/footballdevelopment/technicalsupport/refereeing/laws-of-the-game/law/newsid=1290867.html"
],
[]
] |
||
95g9rh
|
how do passports from foreign countries (not american) wotk?
|
I thought a passport allowed someone to legally travel outside their native country. I recently heard that some European passports don’t allow travel to the USA. For example, my friend knows someone from Slovakia, whose passport allows her to travel only throughout Europe. And that person has no criminal record, deportations, etc.
Are there different passports for different types of travel?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/95g9rh/eli5how_do_passports_from_foreign_countries_not/
|
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"In Canada we basically have the same passport that you do - it's a book with lots of pages for visa stamps, and our photo.\n\nIf you have a European passport, it's the same deal.\n\nYour friend probably doesn't have a passport. Slovakia is in the Schengen agreement, which allows border-free travelling between the 26 European countries who are members of the agreement. If your friend wanted to go to Sweden or France or Germany, they wouldn't need a passport, just their national Slovakian ID. ",
"Someone is misunderstanding something here.\n\nA Slovakian passport is definitely valid for entry to the US.\n\nWhat your friend may be thinking of is the Schengen Area. The Schengen Area is an agreement between 26 European countries to allow citizens to travel freely between those countries without having to pass through immigration controls.",
"A passport is identification. It identifies the person named in it. \n\nA passport can contain a stamp for a visa. A visa is permission to enter a foreign country. Some visas are granted on arrival. Others need to be applied for in advance. \n\nSometimes, governments will have agreements with each other allowing their citizens to enter each other’s country without a visa, and only a passport. This is called visa-free travel. It isn’t always reciprocal —sometimes it’s just one way. For example, a US passport holder can enter a large number of countries without a visa, even if the US requires the other country’s nationals to have a visa. That’s because the other country gets an economic advantage by making it easy for American citizens (and their money!) to easily enter their nation. ",
"A Slovak passport actually allows a Slovak citizen to visit almost 180 countries without a visa, so yes it sounds like your friend doesn't have an actual passport but rather just a document that allows her to travel between Europe.\n\nIn some countries, like in Russia (Russia might be the only one left actually) citizens get an \"internal passport\" - historically these were used solely for traveling *within* the Soviet Union and they were used to restrict where people could travel in the USSR. But now it's mostly a bureaucratic holdover from those times - a citizen's travel within the country isn't restricted any more like it used to be, but they still use the \"internal passport\" as a form of identification (similar to how we use driver's licenses in the US).",
"Foreign passports work exactly the same as American ones do: they provide identification for the passport holder as well as a valid document issued by a government that said person is a citizen of the given nation and that the information presented is valid. \n\nSome nations will allow passport holders of certain nations to enter with minimal effort. Some will outright reject travellers holding a passport from a specific nation. This has little to do with the passport and more to do with international diplomacy: functionally passports follow some semblence of a standard and are virtually the same, only with a different color and coat of arms on the front. \n\nIf your friend can only travel around Europe that indicates they don't have a passport at all, at best a drivers licence or national ID. A large section of european nations (some 26 of them) have no internal border control. You can walk from the southern tip of portugal to the northen tip of Sweeden and never once be asked to present a passport. However once your friend wants to actually leave this border union they'll need to present a passport."
]
}
|
[] |
[] |
[
[],
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|
b4w2b7
|
how does p2p encryption work?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/b4w2b7/eli5_how_does_p2p_encryption_work/
|
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"Whenever you send a message, the message is locked (encrypted) using a key . The key is unique in the sense that you and only the intended recipient has the key to that lock. Thus, only the recipient can unlock (decrypt) the message.",
"I can't tell you the exact math of it, but that wouldn't be eli5 anyway.\n\nBasically they use math problems that are one-way. By one-way it means that you can easily get a solution when you start, because you know all the parts. But, there are so many possible combinations, that it's very hard to get the original parts when all you're given is an answer. Like this: X+Y+Z=21289745127828972. There are many different combinations of X,Y, and Z that would give you the same answer. But to actually decrypt the message, you need the exact same ones that were used to create it.\n\nKeys are kind of like the X,Y, and Z in the example (but much more complicated.) There are generally two keys: public and private. A private key contains all of the information needed, usually the public key is derived from the private key. A public key only has enough information to create a math problem that can be solved using the information in the private key (encrypting the message.) But not enough information to go backwards (decrypt) the message.\n",
"If it's peer to peer, imagine it like this:\n\nYou own a lock box. If someone wants to send you a letter, you tell them the lock box number to send it to. In fact, everyone can know your lock box number, no big deal. Someone sends a letter and now you have a message in your box. Since you're the only one with a key and the box is impossible to break, you're the only one who has access to that letter. If the key gets lost, you have to get a new lock box because there's only one key ever. \n\nThe lock box is the \"public key\". It's a unique code that allows anyone to encrypt a message but only to you (since it's your personal box). The lockbox key is your \"private key.\" It's the only thing that can decrypt the message (open the lockbox). It would take someone a long long time to recreate your lockbox key, so there's no point to trying. \n\n",
"Here’s the old school way it worked.\n\nYou have a lock box that has two latches for padlocks.\n\nYou put your message inside the box and lock one latch with your padlock. Nobody else can now open the box but you.\n\nYou send the locked box to the recipient using a courier.\n\nThe recipient can not open the box, but they can place their padlock on the other latch. Nobody else can unlock the recipients padlock other than the recipient.\n\nThe recipient returns the now double locked box back to you. You remove your padlock, and send the box back to the recipient. \n\nThe recipient can now remove their padlock and open the box."
]
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|
[] |
[] |
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[],
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3afpnf
|
How can black holes emit gamma and x-ray radiation if light can't escape from them?
|
askscience
|
http://www.reddit.com/r/askscience/comments/3afpnf/how_can_black_holes_emit_gamma_and_xray_radiation/
|
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"It's not the black holes themselves that are emitting radiation - it's the matter falling into the black holes. Diffuse matter (gas and dust) in the presence of a compact massive object forms what's known as an [accretion disc](_URL_0_). Matter in the accretion disc falls into the black hole, it experiences a strong gradient in gravitational potential. This heats up the gas through friction. Less massive objects (such as stars) can only heat the surrounding matter enough to emit in the infrared, but more massive objects (such as black holes) can heat matter to the point of emitting in the X-ray."
]
}
|
[] |
[] |
[
[
"https://en.wikipedia.org/wiki/Accretion_disc"
]
] |
||
31tg0k
|
What happens whith the excess of kinetic energy that isn't being acumulated when a rocket is flying at light speed and keeps thrusting in perfect vacum?
|
I'm sorry, another light speed question.
What happens with that energy? Does it just disappear?
|
askscience
|
http://www.reddit.com/r/askscience/comments/31tg0k/what_happens_whith_the_excess_of_kinetic_energy/
|
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"Well, a rocket can't fly at light speed so the question doesn't really make sense. ",
"If a rocket is flying just under light speed but continually being accelerated (so its kinetic energy must increase), the kinetic energy will increase without bound without the rocket ever reaching the speed of light. The full equation for kinetic energy is KE = mc^(2)/sqrt(1-(v/c)^(2)) - mc^(2), which reduces to KE = mv^(2)/2 for v much smaller than c, but goes to infinity as v approaches c.\n\n[Here's a graph](_URL_0_) which plots KE + mc^2 as a function of velocity if you want to see how it looks."
]
}
|
[] |
[] |
[
[],
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"http://newt.phys.unsw.edu.au/einsteinlight/jw/images/totalenergy2.gif"
]
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|
4kczk0
|
why have we (humans) advanced so much in the last 150 years or so compared to the thousands of years before?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/4kczk0/eli5_why_have_we_humans_advanced_so_much_in_the/
|
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"more resource/knowledge = more advancement in a same period of time\n\nadvancement against time is an exponentially increasing curve",
"Knowledge helps you generate more knowledge. \n\nTake something simple, ancients believed the world was made of 4 or 5 elements, earth, wind, fire, water and sometimes ether or some magic spirit. And that was fine for along time, because they had no knowledge or technology to study it further. \n\nIt took a long time to go from the idea that gold isn't just dirt mixed together with a combination of air, fire, water, and some magic spirit but it's own unique element. \n\nIt took someone figuring out that earth is made up of different kinds of dirt. From there dirt is made of different kinds of small rocks (sand), and sand is made of different minerals, minerals is made of various molecules, molecules is made of atoms, atoms is made of smaller stuff and so on. \n\nNow that we have that knowledge, we can go back and make gold by smashing other elements together. (obviously not cost effective) \n\nOr look at the Chinese and their invention of black powder. Had it for a long time, until someone said, hey put it in a pot, throw a rock on top. Use that rock to hit someone or something. \n\nOnce the idea of a primitive canon was made, a series of other people made perpetual tweaks to it, to now we have machine guns that can fire a lot of bullets per second. But to get to building a machine gun it took a lot of other people inventing stuff in other fields at the same time. Metalurgy, chemistry, manufacturing, engineering, etc. \n",
"Exponential growth. Once the Guttenberg press kicked off you had the entire European continent working together. Then the World Wide Web, and it's been constant growth through teamwork. ",
"It's actually more like the last 250 years or so. The reason is that 250 years ago is when the Industrial Revolution happened.",
"Complexity. The amount of knowledge that can interact with all other knowledge grew exponentially.",
"Look at each innovation as a Lego block.\n\nTwo lego blocks can be combined to create a new type of block. This block in turn can be combined with all blocks before it and perhaps create a new one. As the amount of blocks increase so does the amount of combinations - exponentially. In comes Minecraft and suddenly the blocks can be shared at (almost) no cost online. Suddenly almost all of earths population has the potential to further the block movement and pursue new combinations. On and on we go and soon that starter hut that almost got blown up by a creeper turns in to the Death Star. ",
"I think it largely started with the industrial revolution. Once we had the combustion engine, the mindset changed to focus on efficiency > craftsmanship. Using the assembly line, we were able to speed through production like never before. It was with this mass production that allowed us to innovate at a rate not seen prior in human history. In under a century we go from learning to fly, to putting men on the moon. \n\nBut looking back in history, we can see that the human race seems to hit it's stride when we are not spending our days focused simply on survival. Ancient Rome is an excellent example of a fast technological incline in a condensed time spread. \n",
"This is a long read, but you will understand the exponential grows of knowledge afterwards:\n\n_URL_0_\n\nHope you enjoy the article as much as I did.\n",
"If you have to spend all your time gathering food to feed yourself and your family you don't have time to advance human knowledge and technology.\n\nBut as some tech gets invented and just a few less people have to work full time to get food other people can work full time with governance and science. This makes a positive spiral. The more tech you have the more people you can have making new tech which in turn makes even fewer people able to feed the entire population letting more people work in tech and on it goes.\n\nThen you also have a similar effect with technology facilitating the creation of new technology. This is probably going to keep exploding with the coming advancements in AI.\n\nEdit: Who knew that thinking out loud for 60 seconds would be my highest rated reddit comment. < 3 you all",
"I cannot recommend this enough, [Connections](_URL_0_) by James Burke. He's a technology historian and a brilliant narrator, trying to answer exactly your question; and there's many answers! In short, more people are in connection with more people than ever before, like a global neural net that's getting faster every day. Each of us is a neuron, and globalization means that the Earth's brain is now in complete communication.",
"Access to information has expanded exponentially over the past 200 years.\n\nBut the largest driver of advancement is excess. People no longer have to spend every single moment of their day working for their next meal. That spare time is crucial for development of ideas.",
"I think it has to do with how much easier it has become to communicate and exchange ideas. From telegraphs to the internet, nothing sparks new ideas and inventions like being able to talk to other people with vastly different educations and life experiences.",
"The invention of the scientific method constrained development into a productive direction.\n\nThe inventions of mathematics, particularly integral and differential calculus, gave us a big and widely applicable lever to enable the progress of science and engineering (contribution by /u/Dekar2401)\n\nThe principles of equality, liberty and brotherhood (liberté, égalité, fraternité), helped removed constraints that limited who had access to knowledge.\n\nThe invention of writing enabled knowledge to persist.\n\nThe invention of printing enabled knowledge to reach more learners for every teacher ( a gain or amplification).\n\nThe development of communications systems, postal services and electrical methods speeded up and widened the distribution of knowledge.\n\nImprovements in manufacturing methods, from [Matthew Boulton](_URL_0_) to the invention of the 2D semiconductor manufacturing process that reduced significantly the constraints on the construction of complexity.\n\nThe feedback of knowledge and inventions into improving the scientific method, recording and distribution of knowledge, and manufacturing methods.\n\nA long time before this many changes from the taming of fire (cooked food enabled bigger brains), the development of trading, the specialisation of skills, to the organisation of big societies and money, provided the foundation for a great leap forward.\n\nTL;DR The right constraints, techniques, forms of persistence and mechanisms of gain have finally come together to enable knowledge and inventions to feedback and improve the constraints, techniques, persistence and gain.\n \nN.B. I don't have any academic references to back this up, I think this is not far from the truth, and criticism is welcome.",
"It's a convergence of 3 factors:\n\n1- Let's remember that there weren't many ways to quickly share knowledge until the mid 1800s, with the apparition of steam-powered large volume printing presses. Then we have real-time communications speeding this up even more as we progress technologically.\n\n2- Let's also remember that it took until 1804 to have 1 billion humans alive at the same time. Realistically, it takes a large proportion of manual workers to support mental workers. So, more people alive means more people sharing more ideas... which requires, well, many people.\n\n3- Let's say one in a hundred of your friends is really, really smart. If there's only a few humans alive, there's going to only be a few really smart ones. At the opposite end, more humans alive = more chances for really smart ones to be alive and have really smart ideas.\n\nPut all these things together and you have it: exponential growth in human population, coupled with hyper-efficient communication channels = way more really smart humans sharing ideas with each others while driving humanity's progress forward faster than ever.\n\nTL;DR: statistically speaking, there's more Da Vinci/Newton/Tesla/Einstein type of top-level smart people alive and sharing ideas together today than the sum of them between the start of humanity up to something like the industrial revolution.\n\n",
"Industrial ammonia syntheeis. I'm a chemical engineer by training, so I'm a little biased, but this process is what started industrial farming.\n\nProportion of time and people needed to collect food dropped significantly in the early 1900s and gave people time to get betrer educations and pursue academic stuff in general \n\nIndustrial farming - > more food + more time - > more, better educated people - > more ideas - > more idea sharing - > tech advancement \n\n",
"People figured out how to figure out things. We call this the Scientific Method.\n\nPrior to that it was mostly guesswork and many people guessed wrong.",
"“Throughout history, poverty is the normal condition of man. Advances which permit this norm to be exceeded — here and there, now and then — are the work of an extremely small minority, frequently despised, often condemned, and almost always opposed by all right-thinking people. Whenever this tiny minority is kept from creating, or (as sometimes happens) is driven out of a society, the people then slip back into abject poverty.\n\nThis is known as \"bad luck.”\n\n― Robert A. Heinlein\n\nStarting in the 18th century, we saw a lovely rise in personal liberty and industrialization. That was a good thing.\n\n",
"Exponential growth and zero marginal cost distribution of ideas, especially freethinking, skepticism, and science (not necessarily in that order). We've stopped using humans as a form of kinetic energy and shifted to using them more for mental energy (processing power).\n\nThis has occurred despite hinderance from dogmatism.",
"It's because progress is exponential. A lot of the progress we made has been in math, science, media, etc. And they feedback upon each other.\n\nIn fact people have been postulating that there will be an eventual technological \"singularity\" for decades now.\n\nWhat does this mean? Technology is advancing fast and on many fronts; and the speed of advance is constantly increasing too.\n\nThere will come a time when the advances will be so quick and so far reaching that the society we live in will become unrecognisable even to people who were born into it - you already see this to some extent with elderly people, but the \"bewilderment age\" will drop ever lower. Perhaps a day will come when noone ever feels truly comfortable because as fast as we learn and adapt (And children are the best at this) society will be changing even faster. We will all be in a constant state of future shock (See Alvin Toffler).\n\nTo put it simply: Part of the progress we have been making is in how to progress - and so our progress is progressing ever faster.",
"As has been said... exponential growth. It is best explained in a Ted talks by Ray Kurtzweil. Although to be honest his talking style is somewhat distracting. The pertinent part starts at the 5:33 minute mark. \n\n_URL_0_\n\nIf you wait for it, he says some very interesting and very far out things. \n\nRemember this talk was given almost ten years ago. And although his name is not a household name. In the world of technology he is very well known. He created the first flatbed scanner and the speech to talk technology that you use every day in your phone. And Google hired him a few years ago as the director of engineering. ",
"I would guess its improvements in communication. The telegraph then the phone, then the internet. That you can have a conversation in real time with anyone around the world in the comfort of your hom now is kind of insane. There is near infinite amount of information i can find on the type of work i do on the internet. ",
"Because humans build on past advances to increase the speed at which it takes to discover new ones. The process is only going to get faster, as far as we know there are limits to what computers can do but we still have a long way to go. \n\n_URL_1_\n_URL_0_",
"Since no one mentioned, Mastering risk.\n\nAfter development of probability theory and risk analysis, people no longer felt that future is completely unknown. They were funding/investing ship voyages in the past and businesses during Industrial Revolution which led to more wealth, thereby more further investments, and possibilities. \n",
"I saw a graph showing human population growth in relation to use of fossil fuels. That also could be a byproduct of various technological advances ushering people to do more than just field work.",
"Steam Power and Electricity. Ever play Age of Empires, or Civ-type games? And if so you know how you'll jump from age to age after getting certain technology? Well we jumped, and it was a big jump, like fire and the wheel big, and it's into one of the later ages where you get spaceships that we landed. Some people still just have javelin throwers and farms while we have tanks and pollution to clean up now. Once we unlocked the base tech to start the new age the advancement rolled forward. But for us, it's like living in the first decade we tried farming as a species. ",
"If you play Civilisation here's a decent illustration:\n\nThe first several dozen turns are spent mucking about trying to survive, get a slight edge on the barbarians and other nations, and slowly building up a baseline level of competence and capability.\n\nShit can be real slow at the start because you haven't unlocked anything, and you don't have enough resources of any kind to really get anything started.\n\nBut then as you hit the mid-late game you've already built up a sizable amount of land, you're raking in some serious moolah every turn, you have enough units that you've stopped trying to use all of them every turn, and your research trees have exploded and allowed you to do pretty much everything. This is the snowball period where every single turn causes change on a massive level.\n\nSo that's exactly how it is with us.",
"Better technology makes better technology so we can use that technology to make even better technology.",
"The short of it is that the Industrial Revolution happened, and we've had incentive structures that encourage innovation since then.\n\nThe economist Deirdre McCloskey's hypothesis for why the 'great fact,' as she calls the leap, happened in 18th-19th century England rather than any other developed time or place was the combination of a general increase in economic freedom and a level of social honour and dignity for those who innovate.",
"One word: Industrialisation. \n\nBy increasing the efficiency of food production through industrialisation, people's time to do 'other things' like develop new technology or generate intellectual capital (scientists and scholars sitting around inventing stuff and coming up with new ideas) increased dramatically. This effect has multiplied with every proceeding generation, coupled with an explosion in the population of humans. This has allowed us to move leaps and bounds in terms of productivity. \n\nEventually, some believe that with the advent of A.I and robots we'll reach a 'technological singularity' whereby we'll increase productivity to the point where technology will learn how to do things better than us and self-learn and problem solve.",
"Boolean logic isn't the only reason, but it's a big nugget in the pipeline. It influenced how modern mathematicians and logicians thought about truth, and it laid the groundwork for the computer.",
"Think of history like a walk through the woods. Is there one particular way to go? No, there are many ways to walk through the woods. But whichever way we go we feel like we're progressing. In what way is the path we have chosen progress in comparison to the other paths we could have chosen? In part it is because we are already on this path, and other paths feel like a divergence from the logic which leads us down this particular path.\n\nRecently we have started running down this path. Our own speed has become a large part of our reason for thinking that we are progressing. Yet we continue to move through a forest that has no end point and we leave many paths untraveled. I'm not so sure that is advancement in the sense that you are using the term.",
"There are a lot of minor small things that ended up giving us a huge boost, that in turn boosted us even more.\n\nFirst up - The Loop we started that grows bigger on every turn:\n\n* In the last 150 years we got a lot of that nation stuff organized. Nations are great at building infrastructure.\n\n* Improved infrastructure made information and trade more available for all people. Combine this with some ideas around freedom of the individual, the rights of man and the likes, we suddenly have a large base of learned individuals, with some ideas about how life should be lived, spread over an entire nation.\n\n* More Trade and more knowledge made people specialize, and this makes for more efficiency across the board. More food, more clothes, more medicine, more everything.\n\n* With this wheel rolling we now start getting new problems that lead to more innovation. How to transport stuff faster, safer, more efficiently . Once transporting an item a far way was insanity, soon it was profit to be chased after.\n\nThe above is the loop that keeps giving improvement. Below are some key technological breakthroughs that help sustain the loop, and prevent it from being broken.\n\n* Rifling/gunpowder - Up until around 200 years ago, any nation with the same technological weaponry that existed in the Spartan wars, could invade and crush your nation. Gunpowder, in its advanced form, reset that form completely. Sacking a nation now required that you advance yourself to their level of technology. \n\n* Self-propelled vehicles in all forms - Trains, cars, boats, planes. They massively reduced the need for people and freed up labor for innovative usage. (This is the idea that things can move, without being pulled, the idea that something can move of its own accord, if given the power to do so)\n\n* The Green Revolution - Without this change, we would not have had food to grow our labor force to the size it currently is.\n\n* Electricity - This is the glue that we never had before. Nothing has tied our world together, and improved our technology, if not for this fundamental discovery.\n\n\nAll these technologies and the above-stated loop work came together to cause the massive boost you see today. When people say it's all going to end, what they usually mean is some \"event\" will cause the loop to stop spinning. This is usually being argued to be one of the following:\n\n* Run out of energy - The loop if fueled by constantly having more energy thrown into it. If we cannot give it more energy, it will stop spinning or slow down. (run out of oil/gas/coal)\n\n* A breakdown in the human factor - Too many (overpopulation) / too few (run out of food) or Unable to sustain the quality of human that is needed for the loop to improve. (Inequality in one form or another)",
"I don't know if this has been said yet or not, but I highly recommend watching Neil deGrasse Tysons' Cosmos: A Space Odyssey. It is a very fine introduction to the few brilliant minds that made way for todays scientific advances",
"The real ELI5 here;\n\nWe have less to worry about and more tools to help us advance quicker. Technological advancement is exponential",
"All of these explanations are good. And as far as why are tech boomed in the last 150 years, therefore advancing us faster than anytime in the past is the human thirst to kill each other. Let me explain.\n\nAfter each war man has ever had, the tech used to win the war is obsorbed by the civilians. Whether it is in better metal refining to make better swords to making better clothes to endure the elements of the battlefield. \n\nWW1 marked the first use of mechanical warefare. Using tanks and airplanes on the battlefield. Afterwards all the countries started to race towards making better mechanical implements of war. Better tanks and airplanes, hey let's make troop transports. Of course the civilians say, hey that tank, just a few modifications and I could dig a big hole in hours that would take 10 people a week or more to dig. That airplane that is being built to drop numerous 500 pound bombs, if we put 50 people on it we could get more customers to fly coast to coast reducing the cost of having 3 planes do it. Of course don't forget all the electical components upgrading with each one.\n\nAnd here we are. Since 9/11 how fast has our tech increased due to military's need to win the day? And how much of that had been obsorbed in to civilian life to make your life easier?",
"Porn dude. Now that we have something worthwhile to accomplish, namely watching people do the deed in interesting and exotic ways, we finally have a reason to develop things like TV, cell phones, the internet. Porn.",
"Because every technological invention or improvement speeds up the process of making the next. A rule of thumb you'll hear on science oriented forums and such is that every year of improvement equals the amount improved in the ten before it, implying the same for the next year and so on.\n\nThat is to say: technological advancement is exponential, not linear. ",
"It all started with the printing press. That's the most significant invention of the last millenium. Printing was probably the most potent accelerant that science ever received. The rest is a result if that. ",
"If I had to name one thing it would specifically be the printing press. It was what kicked it all of because sharing people's ideas became so much easier and therefore it was easier to build of what another had started.",
" A man named James Burke wrote a book in the 1970s. That book, connections, was made into a television series in I believe 1977? The television series does a fairly decent job of explaining exactly how mankind advanced based on technological advances building on each other.\n\n_URL_0_",
"Seems like it follows that saying \"It takes money to make money\".\n\nAs in, \"It takes technology, to make technology\".",
"I am going to share an alternative meta-physical explanation based on Baha'i religion. In short and to my understanding the Baha'i religion says that all major religions have prophecy about this special period of human existence and when Baha'u'llah founded Baha'i religion it was from a Divine Catalyst that has infused a new life into humanity. The purpose of the Baha'i Faith is to unite humanity closer in a social and political relationship that transcends nationality, race, denomination and such. Along with His advent, God has infused all humanity with intense spiritual energies. One of the first evidence was the telegraph machine that was used within hours of birth of the [New Religion in mid 1800's](_URL_0_). If you look at technical development of mankind the fastest travel time was by train in mid 1800's. Not very fast. But now about 150 to 200 years later we travel 25 times the speed of sound. The Baha'i believe that the arts and science that exist is born out of human endeavors inspired to make tools for Unification of the humanity so it really will be considered one family. \n\nThis is an unusual religious POV but it is one that is embraced by many. The internet was anticipated by Shoghi Effendi in the 30's as a tool that would help further the cause of unity.\n\n > A mechanism of world inter-communication will be devised, embracing the whole planet, freed from national hindrances and restrictions, and functioning with marvellous swiftness and perfect regularity. A world metropolis will act as the nerve center of a world civilization, the focus towards which the unifying forces of life will converge and from which its energizing influences will radiate.\n\n[That was written in 1936](_URL_1_). So in short all the amazing advances we see are the result of the Manifestation of God appearing on earth and rejuvenating and re-ordering the life of humanity. As of now humanity really does not understand what to do with the technology except applying the technology to system antiquated and harmful to the humanity. But Baha'is believe humanity will progress in spiritual areas as it has in material and scientific arena. \n\nI am not trying to debate but I wanted to share this because it is a very basic axiom in Baha'i religion. There are several \"millennial\" religions from mid 1800's that also have alternate explanation for explosion of technical and scientific advancements since mid 1800's. ",
"i think newton said it best: \"if i have seen farther than any other man it is only because i stand on the shoulders of giants\"\n\nbasically all of science builds on what has come before, the process of determining what is real and what isn't has been a long one. and the key to it: communication.\n\nit is by speech that humans were first able to share information and teach people how to do things beyond simply showing them as our ape ancestors would have done, this allowed information to flow from one person to another and later to be written down allowing people in the past to teach those in the future, it allowed us to catapult ahead from our dark ages after finding the works of the ancient greeks and romans. \n\nthe next big thing was the printing press, allowing even more communication, now people in germany could teach people in england...so long as they can read the language (\"sorry darwin\"~gregor mendel's ghost) or get it translated. \n\nand the next big discovery: science! the scientific method, coupled with the new printing press greatly advanced our ability to discern what is most likely true. \n\neach new discovery built on previous ones and created new ways to communicate, telegraphs, the internet.\n\nand this is why our advancement has been largely exponential, each discovery builds on the last. \n\nand of course communication is useless without people to communicate with, advances in medicine and agriculture have decimated (that's not right...more than decimated...obliterated) infant mortality, from near 80% to less than 1% so there are a LOT more of us. if only 0.1% of all people go on to make great contributions to science that is still 7000000 people making advances in science, network these together so they can share their discoveries and you got a progress machine. \n\nby comparison in the middle ages you would have around (IIRC) 2 million people...on earth....meaning in all the earth you might have 2000 people who could make a meaningful advance in science, and they have no means of communicating, a discovery could be made in europe (say glass making techniques) which wouldn't be available to a person in china. knowledge was very land locked.",
"[This](_URL_0_) article really gives a cool opinion on why, and one that is backed up with some evidence. I think the main reason is exponential growth, this just means as technology increases it allows us to increase technology faster",
"The old quote is, \"From one thing, learn ten-thousand things.\"\nOr, \"One door leads to many others.\"",
"I'd say recent advancements can really be credited to two things: engines (industrial revolution), and communication (internet).",
"Starting from scratch, humans were hunter-gatherers, with barely any technical skills or inventions per se. \nThen came the first wave of inventions and discoveries, namely the use of tools like clubs and such, wheels and fire. \nThese enabled the precursors to develop newer things, newer, better tools. I'd say that the next step was with the metal ages, namely the bronze and iron ages, which succeeded the stone ages. With better tools and techniques being formulated and discovered, humanity began to progress a wee bit faster. \nHumans dabbling in materials, especially in the medieval age people 'working out' alchemy eventually probably led to scientific enquiry, most notably the birth of chemistry. \nWith riding standards of living, people had more time on their hands I suppose, which is why we ended up with rich Lords and counts experimenting in their laboratories. \nChemistry, botany and the physical sciences advanced. \nUp till this point humanity had been steadily gathering skills, tools and resources that would enable them to create and develop far more complex tools, machines even. \nIt's something like the bottom-up hierarchical design flow that one follows in designing electronics and ICs. \nArmed with all this knowledge that was obtained from previous successes (and failures) humanity was poised to attain a much faster growth rate. \nEnter the industrial revolution. The explosion was almost exponential. Every new development and invention in turn spawned the creation of 10-15 others, and so on and so forth. \nThis rate has never slowed ever since. \n\nHence, the rapid growth in the last two centuries, compared to earlier, simpler times.",
"Throwing off the idea that magic exists. Seriously, the further we get from the idea that 'fairies do it', the more diligently we work to understand what we're observing.",
"Storage of knowledge enables faster advancement.\n\nThink of it this way. Before books, you could only learn if someone with more knowledge than you wanted to explain something to you - their audience is relatively limited and they can only teach so many.\n\nThen came books. Then the ability of more people to read those books. Then came the print press which enabled more book production. Then we developed sound recording devices, then video, then the internet... you get the idea. You can now find more knowledge at your fingertips than ever before in history.",
"I give credit to [ James Clerk Maxwell ]( _URL_0_ ). In 1862 he laid down the [foundation for all electronics](_URL_1_ ). After that, there's no mystery, just difficult, but doable engineering problems.",
"Humanity has advanced because a decision was made to allow a growth in conciousness in preparation if a great event, that would paralyze the entire earth with fear and cause grown men to drop dead in the street at its sudden appearance. The secrets of the occult alchemical Masonic witchcraft are now widespread, to prepare the earth and its group consciousness for the literal physical presence and earthly kingdom of Satan himself. Revelation of the Method had to occur, so the hoodwinked can know the extent they've been fooled, to cheerfully magnify and amplify the effect. So technology and science had to be spread. As it says in the Rosicrucian manifesto \"the stones shall rise and give service.\" \"Everything lies veiled in numbers\" asserts the Zohar, and counting and measuring and qauntifying all leaves no more room for a God. This is why the metric system is promoted. To slap God in the face. To take us away from the natural, to pin down earth energies, slaying dragons. It alienates humans from the proper scale and scope of life. But it's another sacrifice. If/then has to work reliably, or there is no Must/be.\n\nThat's what I would tell my five year old.",
"The industrial revolution happened. We figured out how to make technology to make us more productive.\n\nBut that just puts the question a level deeper. Why did the industrial revolution happen at the time and place that it did? (around 1800 in England)\n\nAnd that question is much, much harder to answer. Economic historians have spent a lot of time and ink arguing this, and my understanding is that there is no easy, simple, single answer. Many plausible sounding answers seem like they should have applied to China centuries earlier.\n\ntl;dr: Technology from the industrial revolution. But no one knows why exactly the industrial revolution happened in 1800 in England, rather than during the Roman Empire or Chinese dynasties.\n\nEdit: Whoops, realized this was supposed to be ELI5. Oh well, I'll leave it just in case others find it worthwhile.",
"This is a great question, but a bad question for this format. ELI5 is good for scientific or plainly factual issues, but this is really very unclear and is probably a combination of so many factors that any single answer will be totally inadequate.\n\nFor instance, one guy essentially responded that technology has freed us to become more creative, but that alone is inadequate because it fails to explain why technology has suddenly improved so much. Perhaps it is the development of modern capitalism in the 17-18th century? But then perhaps not, and even if it is we would then have to explain the emergence of modern capitalism which is equally controversial.",
"The exponential nature of technocultural progress.\n\nI can see that rapidly improving from here when I think what can and likely will be dramatically improved in the near future; mindshare is still suboptimal, automation heavily short of what it could be, human-computer interfaces still relatively primitive, real AI nonexistent, disease and death ubiquitous.\n\nWe're used to the geometric improvement of computers, but there are wildcards such as the 3D printer that I can't even imagine the implication of.\n\nEDIT: I guess 3D printers will allow more intricate infrastructure, supporting denser populations, which in turn could be freed by automation, and devoted to further advancement. That is perhaps a decent example of naturally accelerating progress.",
"Two words: steam engine. For the first time in history we were easily able to do manual labor with little to no effort from humans/animals. Instead of entire teams doing a large and potentially dangerous task we only needed a couple of engineers and fuel/water.",
"It's called \"The Industrial Revolution\", and it took place mid-late 1800's. \n\nEssentially though, it comes down to civilizations sudden use of fossil fuels. Prior to that time, there was a spike in whale oil use, but really the only power behind agriculture and commerce was animal and human. Ox plowed fields and moved heavy things. Horses moved people. There were water and wind mills, but they could not produce nearly as much output. \n\nSuddenly this amazing source of energy arrives, and it changes everything. At first, it was coal, and the secondary application of steam power. Suddenly huge amounts of work can be done in a small time. Suddenly farms that fed a few hundred people can feed thousands. And that meant a drop in hunger and an increase in population. Goods can be shipped across huge distances in a relatively short time thanks to steam locomotives. All this industry created millions and millions of jobs, and that created a faster and more diverse economy. \n\nWhen electricity arrived (although still fossil fuel based) culture changed again. Things at home changed. Things like doing laundry became easier with machines. Refrigeration's arrival meant food lasted longer and caused less illness. \n\nThen the wars...both the world wars resulted in massive advances in technology, as well as advances in how we THOUGHT about technology. \n\nThis is why it is thought that if society were to collapse, say in a Walking Dead type of scenario..that we would not go \"back to the stone age\". Instead we would go back to the mid 1800's. ",
"Because we embraced empiricism and rational thinking among a larger portion of our population than merely the academics. Once a sizeable number of humans considered evidence based pursuit of knowledge to be a virtue, the information age ignited. ",
"TLDR: People stopped asking religious or philosophical questions and started asking about the natural world.\n\n\nThere are a lot of reasons on here, which do make sense, but one of the things changed everything was the type of questions that were being asked.\n\nAbout 1,000 years ago the world was focused on religion, and getting into heaven. This meant that the questions that were asked were faith or philosophy based, and thus really slow to contribute to the knowledge of the world. A great example of this the story of Francis Bacon...\n\n\"In the year of our Lord 1432, there arose a grievous quarrel among the brethren over the number of teeth in the mouth of a horse. For thirteen days the disputation raged without ceasing. All the ancient books and chronicles were fetched out, and wonderful and ponderous erudition such as was never before heard of in this region was made manifest. At the beginning of the fourteenth day, a youthful friar of goodly bearing asked his learned superiors for permission to add a word, and straightway, to the wonderment of the disputants, whose deep wisdom he sore vexed, he beseeched them to unbend in a manner coarse and unheard-of and to look in the open mouth of a horse and find answer to their questionings. At this, their dignity being grievously hurt, they waxed exceeding wroth; and, joining in a mighty uproar, they flew upon him and smote him, hip and thigh, and cast him out forthwith.\"\n\nMen who thought they were very smart spent a lot of time having philosophical discussions that did not contribute to the advancement of society, but did questions the Kings divine right to rule. To stop this a King (forget which one) banned these types of discussions. The rich, left with nothing else to do started investigating the natural world. Only experiments that could be reproduced were accepted, and the beginning of the scientific revolution had begun.\n\n",
"Religion often held advancements in medicine and technology to a minimum especially in the dark ages were religion was king ",
"The most succinct way to describe this phenomenon comes down to the law of accelerating returns. \n\nAs other's have mentioned, once we developed a strategy to enable a non-nomadic way of life - humans were able to focus on advancing their ways rather than simply sustaining life. Agriculture satisfied just that - it enabled humans to produce our own food without the need to follow seasonal migratory patterns (think herd animals and pack animals)\n\nOnce we were capable of surviving in one place, we threw our weight at issues beyond simple survival. Fast forward to the industrial revolution - we began devising strategies to do the work for us. Now some of the \"leg work\" was undertaken automatically by machines. Think about the time it takes to do a calculus problem without a calculator versus with a calculator. \n\nFast forward again to today - we are at a point where the mechanized tools help us answer questions so fast they are essentially to a point of developing the questions themselves (and then answering them)\n\nContinue in this pattern until you're a a point where things happen so fast it's almost intangible (the hypothetical singularity)\n\nThis is a TED Talk that you may find interesting. _URL_0_\n\nEdit: in addition, as the saying goes - necessity is the mother of invention. Even though nomads technically had more free time than farmers, farmers had new problems that required innovation to solve.",
"\"Why have we (humans) advanced so much in the last 150 years or so compared to the thousands of years before?\"- Porn.",
"we understood another fundamental force enough to use it everyday. \n\n\nbefore about 1862. we had only understood gravity. and mechanical things.\n\nthen in 1862 we learned to mathematically model a new force, electro-magnetism. \n\nit is like having one tool box with a hammer. \n\nand suddenly getting another tool box with copper wires and volt/ammeters.\n\na person could solve problems they never knew existed. \n\nI cannot wait until we figure out how to use the strong and weak nuclear force for more than just power generation! \n\nand having a whole third and maybe fourth tool box to worth with. ",
"Oil. The ratio of energy produced for energy expended is something we never ever had before. ",
"Human advancement, population growth, etc are directly correlation with energy access/sources/exploitation. We have advanced significantly in the past 150 years because we found a way to exploit fossil fuels ( particularly oil ). Particularly in the 1850s, the settlers in ohio/illinois/midwest/etc found oil that the natives were using and news spread and people realized how valuable it was. That's where guys like rockefeller came from. \n\nYour national power and wealth is also directly correlated with oil use. The greatest nation in the past 150 years was the US because we used the vast majority of the oil. From 1850 to 1950, we accounted for the vast majority of oil production and use. We are still one of the major producers of oil at nearly 10 million barrels a day and we are by far the biggest consumers of oil. \n\nThink of it this way, one barrel of oil produces about 24000 of man hours of work. \n\nIf you look at the chart of US economic growth or world population growth, you will see things started to really rise after the oil boom. \n\nWhether you are talking about ant colonies or bacteria growth or human civilization, they are all dependent on energy/resource acquisition and exploitation. \n\nPretty much every single thing you can think of - from medicine, computers, smartphones, fertilizers, toothbrush, etc - are dependent on oil and its by products. Modern human civilization is oil civilization. That's why nations fight wars for oil. WW2 was a war about oil. ",
"I'm not really satisfied with the top answers, so I'll post, though it'll likely not be seen at this point.\n\nThere was a radical change in agriculture toward the end of the middle ages, we moved to a new system that produced a lot of extra food. This, in itself, is not why we have advanced, but is a good starting off point. This created extra labor, that then was able to move to cities (urbanization) and work in factories (industrialization.) This was coupled with the Age of Enlightenment when education, republicanism, free-enterprise, and science were becoming much more common. Globalization was also on the rise, meaning raw materials were everywhere, and pretty cheap. So, people made factories and machines to make goods cheaper, increasing demand. Bam, industrial revolution.\n\nI'd also argue humanity has been advancing since civilization started. You can see technological advancements throughout all of history. What we have now is explosive technology of a different kind.\n\nIf you start from the last 150 years, we're looking at the 2nd half of the industrial revolution. Cars, airplanes, electricity, etc,... all came from about this time period. They are technologies with real impacts on life. That's really the big difference. A new press, makes printing books easier. That's a moderate impact on society. But a telegraph makes communication instantaneous. That's HUGE. An airplane makes travel much quicker, that's HUGE. Electricity means we can have electronics in the home, that's HUGE. \n\nI'd argue for that for the 2nd half of the Industrial Revolution, the technological advancements have been massive impacts on life, and as a result seem to move faster. They're also much deeper technologies. I mean, you can only go so far with a printing press. A hundred years after the television was invented, we still have big technological advancements that make tv's seem much different then they were even 10 years ago. The technological advancements of the past 150 years are mostly all life changing in ways no earlier technological advancement really was.",
"It's like when you're working on a hard jigsaw puzzle.\n\nThe first few edge pieces are kinda easy but then you have to start putting the middle together and it just looks like a bunch of random colors and patterns and takes you forever to find matching pieces.\n\nBut after a while, a pattern emerges. You get enough pieces together to start to recognize the shapes and patterns and suddenly you start speeding up your progress.\n\nKinda like that.",
"Here's a really interesting article by the guy at Wait But Why: _URL_0_\n\nHe explains that humans are standing at the point of exponential growth where horizontal progress begins to turn into vertical progress. Long read, but worth it",
"A big piece of this is math. We lost a lot of math when the library of Alexandria was razed. So we spent a lot of time rediscovering mathematics that were already discovered by the Greeks and Romans. We know that society develops in correlation to mathematics. Had the library not been burned, we might have had computers and such much sooner",
"Humans are barely any smarter(if any) than humans of 5000 years ago. It's technology and an educational system that has advanced. The industrial revolution brought machinery to farming which has allowed for more crops and more animals for slaughter. The readily available food has allowed humans to be more specialized in non-hunter/gatherer endeavors. Technology has advanced through the efforts of the truly talented and intelligent scientists and engineers. The average human however has remained basically a tool user instead of an innovator. Drop the internet and computers on a human 5000 years ago and they'd do the same thing as humans do today, sit around eating processed food and staring at their mobile devices and giggling like ninnies on Reddit and Facebook.",
"Think of it like a tech tree in any game. You figure out one new thing and that spawns a few more that you can do off of that. Then each one of those spawns even more. We just managed to figure out a few simple things, that further experimentation caused to blossom into more technology. It just keeps going. ",
"Part of it has to do with [Moore's law](_URL_0_)\n\nExponential growth in computing means as things get faster, the rate they get faster also gets faster. But as other commenters have pointed out, this is more universal, advancements allow us to make bigger and greater advancements faster. (better manufacturing tech not only means you can make more complicated things faster, it also means you can make better and more complicated manufacturing tech, and on and on and on)\n\nThink of advancement as a train that's still accelerating, we haven't even reached top speed yet, we are moving forward, but the speed we move forward is still growing, so as you look back to how fast you were going, it seems really slow, but I bet even 2 hundred years ago those with enough history knowledge had similar thoughts about their rate of advancement vs the past.",
"The technology we have developed in the earlier portions of that 150 years you mention has allowed us to do a couple of things; namely, we learn quicker now, and have access to more knowledge than ever thought possible. There is a lot less \"reinventing the wheel\" that has to happen in order to make something new, and push the limits of what we have. Cutting off that time alone has allowed us to more quickly develop new things, which only help with that yet more. Most technology is developed to save time or make something more efficient, only compounding this further.\n\nAlso worth noting, the world has never been smaller, both in travel times around the world, and in communication. We can communicate ideas, and thoughts to people across the world who help us to develop our ideas. The greatest minds of a generation can sit down, from opposite sides of the world and move us forward.\n\nIt is the technology that we have developed that has created this curved rate of growth.",
"Energy. We started burning fuels from underground. And that powered up everything. Machines started making food, other machines, laundry. They gave us transport of matter and information.\n\nAdvances like this happened before. People learned how to use fire. Then animals. Then wind and water. These gave solved many problems and gave more power to humans.\n\nBut burning fossils to power up machines gave so much energy so humanity almost exploded. But we survived and advanced. Wanna predict new era of advance? See where we get energy. Fusion reactors will do some stuff.\n\nBut AI may make a revolution too. Because our level is how much energy we have multiplied by how good we use it. And AI will use it wise.",
"A few reasons, of which I am no expert but I'll give you what I know. For one, strong capitalist societies placed great value on new, helpful inventions. One example is air travel. There was money to be gained on flights like those across the Atlantic, which brought a lot of money into aircraft advancement for instance. Another, more direct reason is world wars. When the top 10 most powerful countries come together, you get things like the Manhattan project, which brought the greatest scientists in the world together and gave them virtually unlimited resources. Aircraft went from rickety wood planes to complex metal bombers. When your society and way of life is on the line, you get great advancements in many areas. \n\nChemistry and physics came a long way becuase industrialization valued the uses of things like oil, dynamite, and medications.\n\nGlobal communication also played a part. European inventions came to America and vice versa. This allowed more than one country & #39;s scientists to improve each other & #39;s invention. The internal combustion engine is a perfect example. \n\nTo tie it all together, the conditions were perfect for scientific advancement. Communication, war, and excess resources made great invention possible.",
"We reached a point with the Industrial Revolution and Scientific Revolutions which, together, turned many of life's necessities into commodities. In the process, vast swathes of humanity have been able to move up just one notch on Abraham Maslow's Hierarchy of Needs, and that's all it really takes. \n\nIt's a loose answer but I think one of the best. \"Luxury\" is now a commodity for two billion people. \n\nHuge disparities continue to exist across regions but a blueprint of how to accomplish the feat is now firmly in place in economic literature and practice with governments following along, some more adeptly than others -- with religion, superstition, and convention being the prime factors mitigating against progress.",
"I would say a lot of advancement was held back due to religious oppression. We should be more advanced than what we are, but the powerful religious oppression of the old days held us back tremendously. ",
"Well, your question has been answered pretty well, and this may get buried, but scrolling down a lot I did not see anyone talk about the [Malthusian Trap](_URL_1_) named after Thomas Robert Malthus, a legendary economist who hypothesized that income (measured by estimations of GDP per capita, which is basically how much a country makes per person in their country) was, on average, not changing for all of human history up to 1800 CE or so, when the Industrial Revolution took place around the world. Some economists argue the exact date of the Industrial Revolution, but my point still stands. Essentially, the Industrial Revolution allowed each person to produce more output, meaning that they were more productive. Also, [property rights](_URL_0_) were more solidly formed in the IR. This gave people the incentive to invest in the economy and try to be as productive as possible in order to increase their profits/income. The more they produced, the more $$$ they got.\n\n\nBasically, the Industrial Revolution spurred a ton of growth, which combined with better property rights, led to increased investments, which led to more capital, which (more or less) means more money for everyone! I am not going into a lot of detail, but all of this spurred people to invent more, and now in 2016 we have grown exponentially. If anyone sees anything wrong in my assessment please let me know and I'll edit it :)",
"1620 Bacon sorts out the scientific method. Let's say you learn something using that. Great. You have learned a thing. Let's say you learn another thing. Now you have two things. Perhaps those two things together help you learn or do something else. Now you have three things. Meanwhile other people have learned three things and you're sharing info. So between say 5 people you have 15 things that you've learned but it only takes two things to learn another thing. So one of your \"results\" can be used with the other 4 peoples 3 results and the same is true of their results. The knowledge grows exponentially. Over the course of several hundred years many more people get into science and it grows even more. The industrial revolution is a big factor but it's a result of that growth from the scientific method. You can also throw in a couple world wars into that mix where the side with the best things wins and then an arms race to build the best nuclear weapon delivery device (The race to the moon) and the growth of knowledge become so exponential that it takes off. ",
"We have more people, with a lower need to work for basic things necissary for life. Food, shelter, clean water, healthcare, we can get that all with relatively few people working on it.\n\nThis leaves a lot of people with a lot of time to do things.\n\nBTW, it has been argued several times that we always have advanced at a more or less exponential curve. If you went back in time 300 years ago and looked at your recent history, it would still look like you were advancing at breakneck speed. You go back to the 1400's, and look how far your society has advanced in the last 300 years, it would still look amazing. Exponential curves always look like something is amazing happening in your time, because the rate of growth is always getting faster.",
"It's possible that we were much more advanced in the past, but extinction level events forced us to reset.",
"Not really sure if it's just a misunderstanding of compound interest. It's kind of like saying how come my brokerage account made so much money in the last few years before I started taking money out of it. Well it didn't make so much money or rather it did but it probably made the same percentage of money as it did in the previous years. So really I don't think it's that Humanity has achieved so much in the last 150 years they have probably achieved about the same percentage increase in efficiency as they did in many of the years previous to that however it looks like a ton of progress because of how compounding percentages work.",
"Everyone is familiar with the law of diminishing returns, but fewer people are aware of the law of accelerating returns. The law of accelerating returns states, quite simply, that as developments begin, the first stages are slow as innovation in the area is new and the path ahead is unsure, but as the new situation normalizes progress rapidly grows as more minds are tasked with advancing it. \n\nIn the last 150, or as some comments say 250, years we've seen new \"gateway\" technologies come into play such as engines, electricity, and communications technology such as telegraph and telephones. These all generated new fields of technological advancement which were profitable to invest into. More minds sought to improve them, and in improving them generated new technologies, which then created more innovators and so on. It snowballs into what you have today where even though everyone likes to joke that the only thing different about the new iphone is that it's smaller than the last, that in itself speaks volumes about the advancement of computational abilities that it could shrink in physical size but maintain similar processing ability in the course of a year of two. \n\nedit: said the first stages were short instead of slow because I'm posting this late.",
"Think about it, we have made is so everybody has to dedicate their life to a certain profession and study pretty much as soon as they are born. Its pretty fucked up if you ask me.",
"It's like compound interest but with knowledge. At first it starts off slow but eventually it builds off itself faster and faster to where it begins to grow exponentially.",
"Several factors:\n\n1) Improved farming technology meant that a higher proportion of the population could live in cities. At the time of the founding of the US, 90% of people in the US worked in agriculture. Today, it is 2%.\n\n2) Increased population. The more people there are, the more technology they can produce. #1 and 2 both served to greatly inflate the number of people who could be involved in the production of new technology.\n\n3) Improved methods of communication made it much easier to share discoveries.\n\n4) Increased levels of public education meant that there was a much larger population to draw new production capabilities from.",
"capitalism: (a free market for labor)\n\nthe death of religion and the rise of nation states: \n\nthe industrial revolution: (the ability to harness fossil fuel for power)\n\ngentle commerce: (stopping war and beginning cooperation)\n\n"
]
}
|
[] |
[] |
[
[],
[],
[],
[],
[],
[],
[],
[
"http://waitbutwhy.com/2015/01/artificial-intelligence-revolution-1.html"
],
[],
[
"https://en.wikipedia.org/wiki/Connections_(TV_series\\)"
],
[],
[],
[
"https://en.wikipedia.org/wiki/Matthew_Boulton"
],
[],
[],
[],
[],
[],
[],
[
"https://youtu.be/IfbOyw3CT6A"
],
[],
[
"https://en.wikipedia.org/wiki/Technological_singularity",
"https://en.wikipedia.org/wiki/Bekenstein_bound"
],
[],
[],
[],
[],
[],
[],
[],
[],
[],
[],
[],
[],
[],
[],
[],
[],
[],
[
"https://en.m.wikipedia.org/wiki/Connections_(TV_series)"
],
[],
[
"http://www.bahai.org/beliefs/god-his-creation/ever-advancing-civilization/",
"http://reference.bahai.org/en/t/se/WOB/wob-56.html"
],
[],
[
"http://waitbutwhy.com/2015/01/artificial-intelligence-revolution-1.html"
],
[],
[],
[],
[],
[],
[
"https://en.wikipedia.org/wiki/James_Clerk_Maxwell",
"https://en.wikipedia.org/wiki/Maxwell%27s_equations"
],
[],
[],
[],
[],
[],
[],
[],
[],
[],
[
"https://www.ted.com/talks/ray_kurzweil_on_how_technology_will_transform_us?language=en"
],
[],
[],
[],
[],
[],
[],
[
"http://waitbutwhy.com/2015/01/artificial-intelligence-revolution-1.html"
],
[],
[],
[],
[
"https://en.wikipedia.org/wiki/Moore%27s_law"
],
[],
[],
[],
[],
[],
[
"https://en.wikipedia.org/wiki/Property_rights_(economics)",
"https://en.wikipedia.org/wiki/Malthusian_trap"
],
[],
[],
[],
[],
[],
[],
[],
[],
[]
] |
||
37f23y
|
How did the inverted cross (Cross of St. Peter) come to be a symbol of anti-Christian imagery?
|
The inverted cross come from a tradition that told us Simon Peter was crucified upside down. It is believed that Peter requested this form of crucifixion as he felt he was unworthy to be crucified in the same manner that Jesus died. So we could actually see some churches having an inverted cross instead of the regular Latin cross.
But in popular media today we see the inverted cross as a symbol of satan, anti-Christianity, etc as featured in movies like The Omen and Annabelle. How did this happen?
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/37f23y/how_did_the_inverted_cross_cross_of_st_peter_come/
|
{
"a_id": [
"crmbnt7"
],
"score": [
18
],
"text": [
"According to Origen of Alexandria (185-254 CE) and the apocryphal [Acts of Peter](_URL_2_) (200 CE), Peter asked to be crucified upside down as he believed himself unworthy of the same death of Jesus Christ. This is typically seen as an expression of his Christian humility. The Acts of Peter (which includes, wonderfully, a *Sword & The Stone*-style magical face-off between Peter and Simon Magnus) were enthusiastically adopted by Christian Gnostics and in them, Peter uses the cross as a rhetorical device to emphasise the illusionary nature of the physical world:\n\n > For it is right to mount upon the cross of Christ, who is the word stretched out, the one and only, of whom the spirit says: For what else is Christ, but the word, the sound of God? So that the word is the upright beam whereon I am crucified. And the sound is that which crosses it, the nature of man. And the nail which holds the cross-tree unto the upright in the midst thereof is the conversion and repentance of man.\n\nHere, then, the Cross of St Peter takes on a significance unique to Christian Gnosticism (a significance beyond martyrdom).\n\nBy the beginning of 4th Century, Gnosticism was increasingly marginalised by the Church hierarchy - books were banned and practice was criminalised in the Roman Empire.\n\nThe first uses of the Cross of St Peter in something close to your anti-Christian context comes in the 19th Century with the French Occult Revival, which incorporated elements of esoteric belief as part of its opposition to the authoritarian and illiberal French government, of which the Catholic Church was a staunch pillar. \n\nAs British poet, mystic and Tarot deck co-creator AE White details in his wonderfully titled *Devil Worship in France* (1896):\n\n > Martinists, Gnostics, Kabbalists, and a score of orders or fraternities of which we vaguely hear about the period of the French Revolution, began to manifest great activity; periodicals of a mystical tendency—not spiritualistic, not neo-theosophical, but Hermetic, Kabbalistic, and theurgic—were established, and met with success; books which had grievously weighted the shelves of their publishers for something like a quarter of a century were suddenly in demand, and students of distinction on this side of the channel were attracted towards the new centre. \n\nGnostic revivalists such as Eugene Vintras (1807 – 1875), a former cardboard box factory foreman who founded the Eliate Church of Carmel, began to use the Cross of St Peter as part of his faith - and he's [pictured](_URL_0_) wearing one on his robes. The University of Sussex's Richard D. E. Burton, writing in *Blood in the City: Violence and Revelation in Paris, 1789-1945*, states that for Vintras, the traditional crucifix represented the \"Reign of Suffering\", while inverting it symbolised the beginning of the \"Reign of Love.\"\n\nClaiming to be a reincarnation of the Prophet Elijah and receiving messages from the Virgin Mary and Archangel Michael, Vintras was condemned by the Pope and accused by a follower in 1851 of homosexuality, conducting black masses in the nude, and masturbating at the altar. \n\n'Satanic panics' aren't a modern phenomenon - France experienced them in the 17th Century and fear of sexually charged sorcerous ceremonies re-emerged in the 19th, partly as a reaction to the perceived danger posed by figures like Vintras and his correspondent-turned-rival Abbé Joseph-Antoine Boullan (1824 – 1893). Boullan was a former Catholic priest whose dabbling (including exorcisms) was so widespread and notorious that he was accused of Satanism and child-murder.\n\nThese colourful figures in turn informed the depiction of the blasphemous rites in writing and art. [This 19th Century engraving](_URL_1_), for example, shows a 17th Century black mass, depicted the heretical abbot engaged in an infant sacrifice with an inverted cross upon his cassock, while Joris-Karl Huysmans' 1891 novel *Là-bas*, contains an account of French Satanism supposedly based on rituals he observed with Boullan. \n\nHuysman even directly models on character on Boullan, Dr Johannes, who he describes as wearing:\n\n > \"A long robe of vermilion cashmere caught up at the waist by a red and white sash. Above this robe he had a white mantle of the same stuff, cut, over the chest, in the form of a cross upside down.\"\n\nIt all got a little too much for Huysmans, who in 1892 converted to Catholicism and retired to a Trappist monastery (for a cold shower and a lie down, perhaps).\n\nThis imagery not only caught the attention of writers, artists and horrified clergy, but directly inspired and influenced a whole new crop of mystics, among them Aleister Crowley, who spent time in Paris in 1902. The figurehead of English ritual magic described the protagonist of *Là-bas* (modelled on Huysmans himself!) as a prophetic portrait of a future Crowley, while in 1908, British writer W Somerset Maugham, somewhat dismissively recalled of the 'The Wickedest Man in the World':\n\n > At the time I knew him he was dabbling in Satanism, magic and the occult. There was just then something of a vogue in Paris for that sort of thing, occasioned, I surmise, by the interest that was still taken in a book of Huysmans', *Là-bas*.\n\n**EPILOGUE**\n\nErroneously, the peace symbol is referred to as the 'Cross of Nero' to try and denote a link between the 20th Century hippie movement and SATAN \\m/ 666 because it apparently represents an inverted crucifix which has been 'broken' by the Emperor Nero (35-68 CE). \n\nThis definition is cited in *Investigating Religious Terrorism and Ritualistic Crimes* by Dawn Perlmutter and *Occult ABC* by Kurt E. Koch, for example, but its origin is an article by the John Birch Society in June 1970 issue of American Opinion, which claimed:\n\n > In America thousands of radicalised youths parade that same symbol, the heretics of The Christian have all but adopted the 'sign of the Anti-Christ' as their own. And you can be absolutely certain the Communists planned it that way.\n\nSource: *Symbols: A Universal Language* by Joseph Piercy, *Eliphas Lévi and the French Occult Revival* by Christopher McIntosh, *Satanism, Magic and Mysticism in Fin-de-siècle France* By Robert Ziegler and *Blood in the City: Violence and Revelation in Paris, 1789-1945* by Richard D. E. Burton\n\nEDITED: For clarity and Crowley (I needed to bring the point home)."
]
}
|
[] |
[] |
[
[
"http://www.bibliotecapleyades.net/sociopolitica/codex_magica/images/dcodex_39.jpg",
"http://cache1.asset-cache.net/gc/163236247-affair-of-the-poisons-black-mass-of-abbot-gettyimages.jpg?v=1&c=IWSAsset&k=2&d=3ZEia0D%2bt0oQsflLnnkojpyK3yyUjrEEC%2bd4NNvv3phonTp7FJOBsn1CiVctiGyPpNLWNsthGDPSF6liDPRLpw%3d%3d",
"http://www.gnosis.org/library/actpete.htm"
]
] |
|
2pfrx5
|
It is known that a massive supernova exploded in 1054 A.D. that was visible on Earth even during the day. Do any specialists know from there studies if any civilization recorded this phenomenon?
|
It is known as a handful of Europeans recorded that there was a massive blast that happened during this time, so massive in fact that it was visible during daytime, but were they the only ones?
Are there any recordings from civilizations or people throughout the world, like the Maya, East Asians, Middle eastern Civilizations, specific European nations, and/or anyone else that mentioned what is now known to have been a supernova?
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/2pfrx5/it_is_known_that_a_massive_supernova_exploded_in/
|
{
"a_id": [
"cmwb9le",
"cmwhnn0"
],
"score": [
26,
28
],
"text": [
"[Ancestral Pueblo pictographs](_URL_0_) in Peñasco Blanco, Chaco Canyon are believed to refer to the supernova.",
"Seems the Crab Nebula supernova event (that's the 1054 event you are enquiring about, right?) was probably noted by the Arabs, the Chinese (on the Suzhou planisphere) and the Japanese. Ibn Butlan, a christian Baghdadi living in Cairo also reports it. \n\nSee:\n\nGeorge W. Collins, II, William P. Claspy, John C. Martin, 1999. *A Re-interpretation of Historical References to the Supernova of 1054 AD*, Publications of the Astronomical Society of the Pacific 111 (761): 871–880 ([link to article](_URL_0_))\n\nand\n\nBrecher, K.; Fesen, R. A.; Maran, S. P.; Brandt, J. C., 1983. *Ancient records and the Crab Nebula supernova*, The Observatory, vol. 103, p. 106-113 (1983). ([link to article](_URL_1_))"
]
}
|
[] |
[] |
[
[
"http://www.hao.ucar.edu/education/archeoslides/slide_20.php"
],
[
"http://www.jstor.org/stable/10.1086/316401",
"http://articles.adsabs.harvard.edu/full/1983Obs...103..106B/0000106.000.html"
]
] |
|
22ck67
|
In big cities, before cars, where did people keep all those horses?
|
There must have been a great deal of horses in cities like London, and with overpopulation such a problem in the 19th century where were all those horses housed?
Here's a cool clip from the 19th century:
_URL_0_
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/22ck67/in_big_cities_before_cars_where_did_people_keep/
|
{
"a_id": [
"cglhvsc",
"cglmmyu"
],
"score": [
19,
4
],
"text": [
"Horse ownership was nowhere near as ubiquitous as auto ownership today. The figures I have handy (from Clay McShane's book *Down the Asphalt Path)* are for big US cities, and they indicate about one horse for every 23 people. Nearly all of those were owned by businesses for delivery purposes, and those businesses did have stable buildings in industrial areas or lower-rent districts near downtown.\n\nOnly a few very wealthy families had their own horses, carriages, and stables.",
"It was uncommon to own horses (England 17th-early 20th c) , but it was quite common to hire them as one would hire a hire-car today. Hence the origins of pub names like 'the Coach House' these establishments were once combination Inns and stables where travellers could rest one horse and take another on their onward journey. \n\nThere's a pub near me that still has signs up warning punters that horses left unattended and not stabled are liable to be sold by the Landlord. \n\n_URL_0_"
]
}
|
[] |
[
"https://www.youtube.com/watch?v=fkHMwPeG1LY"
] |
[
[],
[
"http://en.wikipedia.org/wiki/Coaching_inn"
]
] |
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