q_id
stringlengths 5
6
| title
stringlengths 3
301
| selftext
stringlengths 0
39.2k
| document
stringclasses 1
value | subreddit
stringclasses 3
values | url
stringlengths 4
132
| answers
dict | title_urls
list | selftext_urls
list | answers_urls
list |
|---|---|---|---|---|---|---|---|---|---|
816u82
|
“The Triumph of Christianity,” by Bart D. Ehrman, claims that socially, politically, and religiously, the Roman world was based on “dominance,” strong vs weak. The author also claims that Christianity brought the concepts of “charity” and caring for ones neighbor to Roman society. Thoughts?
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/816u82/the_triumph_of_christianity_by_bart_d_ehrman/
|
{
"a_id": [
"dv18ty1"
],
"score": [
18
],
"text": [
"In terms of 'charity' I would argue that this had existed for a while. Augustus in the *Res Gestae Divi Augusti* makes much of his free distributions of grain and money during times of crisis during his time as *princeps*, for example. Even during the late Republic, grain doles were being expanded, as the Gracchi introduced subsidised grain in the late 2nd century BCE and Pulcher's *Lex Clodia Frumentaria* (58 BCE) briefly introduced free grain for the poor before being reined in by Julius Caesar and Augustus later on. Juvenal's complaint about 'bread and circuses' (*panem et circenses*) was in part directed towards the use of grain distribution by the emperors to keep the masses sated.\n\nAdded to this was the emphasis on expanding entertainments seen among many emperors. Domitian (r. 81-96), whose Rome Juvenal wrote about, was one of the 'popular' emperors who certainly did a lot on the circuses front, with his introduction of more chariot teams (Cassius Dio, *Roman History* 67.4.4) and shorter races so as to fit more in one day (Suetonius, *Domitian* 4.3). Earlier, Augustus made much of the 8 gladatorial shows with 10,000 fighters and 26 animal games with 3,500 slain beasts which he put on, again in the *Res Gestae*. Baths, too, saw much expansion – 'Who worse than Nero? What better than Nero's Baths?' (Martial, *Epigrams* 7.34). It is notable that Domitian and Nero, two emperors usually reviled in the often pro-senatorial sources, were so invested in public welfare.\n\nFrontinus' *Aqueducts*, the edited notes of the administrator of the city water supply under Nerva and Trajan, sees much discussion of the establishment of effective management of this essential service. One thing noted is the expansion of the water services under previous emperors, Agrippa (a right hand man of Augustus') having left 240 slaves to the state for aqueduct maintenance, whilst the emperors since Claudius had furnished 460 more. Frontinus himself was not an un-'charitable' man, with much of his work narrating his countering of corruption by the water men, who for some time had been using obfuscatory measurement systems to hide the fact that they were using oversized delivery pipes and undersized distribution pipes, then selling off the excess to private buyers, thereby literally siphoning off the public amenities of the city for personal profit.\n\nSuggesting that Christianity brought 'charity' to the Romans forgets that for much of its existence, especially the early Principate, the Roman *state* was a very much a provider of amenities to the Roman public, and indeed the emperors, whom one would at first believe were the most 'dominant' of all, were often the providers of this 'charity'."
]
}
|
[] |
[] |
[
[]
] |
||
3ifby0
|
can we train our voices over time to get higher or lower?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/3ifby0/eli5_can_we_train_our_voices_over_time_to_get/
|
{
"a_id": [
"cufxd3p",
"cufy8wl"
],
"score": [
2,
3
],
"text": [
"Yes. Ever seen someone do impressions?",
"Yes, this is possible. In my job I have to sometimes raise the volume of my voice and realized that lowering the pitch allows my voice to be heard better. Since I've been doing this I've been able to lower to tone of my voice even more. Any voluntary muscle can be trained and strengthened to an extent. "
]
}
|
[] |
[] |
[
[],
[]
] |
||
au9147
|
Why did several Confederate states ratify the 13th Amendment right after the civil war?
|
_URL_0_
I see Tennesee, Arkansas, South Carolina, North Carolina, Alabama, Georgia. Why did they ratify it?
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/au9147/why_did_several_confederate_states_ratify_the/
|
{
"a_id": [
"eh6wsu9"
],
"score": [
15
],
"text": [
"Ratifying the 13th amendment was a precondition for rejoining the Union under presidential reconstruction. If states chose to ratify, they expected that they could regain the privileges of states in good standing, thus being equal again to northern states. Hence why South Carolina (and others) tried to send representatives and senators to the 39th congress in December 1865- they had ratified the amendment in November and expect things to go back to how they were. President Johnson seemed to be on board with this idea since he wanted to put things back to normal as quickly as possible. Johnson had fairly minimal requirements for reentering the Union- only that “state legislatures ratify the thirteenth amendment, nullify the states’ secession ordinance, and repudiate the Confederate debt.”(1) Congressional Republicans, however, did not support this plan and refused to recognize the senators and representatives from the former confederacy. \n\nBut why wasn’t there more resistance to ratification from the southern governments? Well for many of these states slavery was already effectively abolished long before the 13th amendment. As early as 1863 nearly half a million slaves had run off and offered their services to the union army on the South Carolina coast and in the Mississippi River valley, forcing the military to accept them as “contraband of war” (2). As Sherman made his march to the sea this number only grew. With the confederate army defeated, the government surrendered, and civil society in disarray, there was really no question that slavery could continue in its previous form. Slavery was over. Ratifying the 13th amendment did not end slavery, it merely acknowledged the present state of affairs and gained the states that did ratify it certain important privileges in return. \n\nAdditionally, ratifying the 13th amendment did not mean accepting black equality or civil rights. Many of the states you listed quickly passed black codes that tried to recreate systems of social control and economic exploitation (like imprisonment with hard labor as punishment for vagrancy) (3) These sorts of outrageous laws, which President Johnson allowed, were a large part of why congress turned on him and took over reconstruction, as well as the motivation behind the 14th and 15th amendments. \n\n(1) David Herbert Donald *The Civil War and Reconstruction* Norton: New York 2001, 522.\n\n(2) W. E. B. Du Bois *Black Reconstruction in America* The Free Press: New York 1935, 78.\n\n(3) Donald, 526.\n\n(I apologize for my surely improperly formatted citations. I am typing on a phone and have been out of academia too long to remember how to do it!) "
]
}
|
[] |
[
"https://en.wikipedia.org/wiki/Thirteenth_Amendment_to_the_United_States_Constitution#Black_slaves_and_their_descendants"
] |
[
[]
] |
|
4af8ha
|
Are there any 2 compounds which would react violently with each other in solid states?
|
askscience
|
https://www.reddit.com/r/askscience/comments/4af8ha/are_there_any_2_compounds_which_would_react/
|
{
"a_id": [
"d10j9vt"
],
"score": [
6
],
"text": [
"Caesium will react with ice above -116C. If you don't restrict yourself to just \"room temperature\", then that opens a wide variety of reactions. For instance, thermite, a mixture of iron oxide and aluminium powder, will react _extremely_ exothermically if you heat it strongly enough."
]
}
|
[] |
[] |
[
[]
] |
||
5p7wia
|
How "Secure" were borders (in Europe) in the middle ages
|
Say I'm a rich Spanish nobleman in the late middle ages. I'm planning on going on a trip north through English Aquitaine, West across Southern France, tour around Northern Italy a bit, and finally end up visiting my cousin in Bohemia. What kind of preparations would I need to make? Do I need any kind of identifying paperwork or special permissions to pass through all of these realms? Are there well established borders and guarded border crossings that I'd have to pass through, or is that all more of a modern development?
Furthermore what would the journey actually be like to cross Europe in the late middle ages? Would it be radically different for a nobleman than for a peasant?
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/5p7wia/how_secure_were_borders_in_europe_in_the_middle/
|
{
"a_id": [
"dcqo8q6"
],
"score": [
2
],
"text": [
"So, borders as we would think of them - that being a clearly demarcated, fortified line with manned checkpoints through which one must pass - did not exist, and neither did formal immigration systems. The state apparatus for maintaining them just wasn't there. You did have marches, such as on the English-Scots border, which were basically more-or-less militarized frontier zones, but the marcher lords were concerned with invading armies and raiding parties, not individual travelers. You might well be made to pay a toll for crossing bridges, and there were customs men in the ports laying fees on merchants importing goods.\n\n > Furthermore what would the journey actually be like to cross Europe in the late middle ages? Would it be radically different for a nobleman than for a peasant?\n\nI'm really not prepared to speculate as to what a typical journey would be like; there are too many variables involved. Certainly, your journey would probably be a bit more comfortable and secure as a noble than as a peasant, as you would likely have servants and/or armed followers with you, and you would probably be mounted. As to your original hypothetical, I would find it odd for a nobleman to take such a long and circuitous route; long distance travel for leisure was rare. It's much more likely that he takes ship somewhere like Bilbao or Corona, disembarks at a north German port, and proceeds to Bohemia from there."
]
}
|
[] |
[] |
[
[]
] |
|
r3fl9
|
What color would plants be if our sun was blue?
|
askscience
|
http://www.reddit.com/r/askscience/comments/r3fl9/what_color_would_plants_be_if_our_sun_was_blue/
|
{
"a_id": [
"c42lcpk",
"c42lf3f",
"c42lftw",
"c42lr0t"
],
"score": [
8,
3,
3,
2
],
"text": [
"Ideally, I think even the plants on Earth would be black in colour, to maximize energy absorption. There seems to be some debate over the reason why they're not though. Just wikipedia-ing: _URL_1_\n\nAlso, NB: the sun is white :) _URL_0_",
"Since our color perception is heavily influenced by the prevailing color \"mix\" this is very dificult to answer specificaly, so we will ignore this part and assume we continue to see color as now.\nThe explanation for the green colour of plants, is that it makes sence for the chloroplasts (sun absorbing part of leaves) to be of a color that absorbes the more prominent (energy rich) light frequencies in the suns spectrum, and reflect the less effective ones (from which we perceive the strongest as the leaves color).\n\nSo if our sun was red, plants might appear yellowish-green, if blue green or indigo. Now if the sun was white, since a perfect black is unlikely I would expect a greyish tint of whatevere color ends up being less needed for photosynthesis.\n\nAttached image shows some (very rough) color curves which can be used to mostly guess what color plants would be under different suns.\n\n[](_URL_0_)",
"Our sun emits fairly evenly across all wavelengths in the visible. However, there are some dips in the light that reaches the earth because of absorption and reflection in the atomsphere. It turns out that there is a large dip in green light, which is why plants prioritized absorbing other colors over green. It should also be noted that once you go into the infrared or ultraviolet you do not get much penetration to the atmosphere at all. This is why we evolved to see visible light.\n\nNonetheless It's not entirely clear why plants are currently green and not black. After all, they still would absorb more light if black. It's possible that maintaining all the necessary pigments to be black costs more than the extra light absorbed.\n\nSo if you change the light emitted by the sun, to say a single line. Say pure red light. Then plants would be anything but red, but they'd look black to us because only red light is around, and we probably would only have evolved to view red light. Same thing with any other pure color. If you removed all atmospheric absorption, so that all visible lights pass through evenly, then it's really hard to tell what the most efficient color is. \n\nLastly, if you really wanted to change plants from green, you would alter the atmosphere so that it passes green light. If you block some other light, say red, you'll likely get red plants. It's possible that you could even get blue plants by blocking blue light, although blues don't show up as often in nature as greens and reds.",
"This question can only be answered with speculation. To understand why, there are a couple important points to consider. \n\n\nFirst, evolution is not a perfect process. What I mean by this is that the best solutions to a problem are not necessarily what the process of natural selection selects for; very few, if any, organisms are perfectly adapted to their niche. Natural selection is not engineering, and this is evident when looking at many biological systems. Photosynthesis, for more reasons than one, is one example. One of the lesser \"imperfect\" aspects of photosynthesis is that leaves do not absorb light in green wavelengths as well as they do for blue or red. Most leaves can still absorb a good amount (about 2/3) of light in the green wavelengths. By all accounts that is fairly impressive, but why aren't the leaves black? \n\nThere has been some speculation about this question (see the [Wikipedia](_URL_0_) article), but strictly speaking, asking why leaves are green and not black is outside the scope of science. The best we can do is understand how they got to be green in the first place, and which underlying processes contributed to the dominance of green leaves.\n\nSecond, because evolution is a dynamic process concerned only with survival and reproduction, it is impossible to know for sure what color plants would be around different stars, or if they would be different at all. In our system, plants are green even though this may not be the ideal color. Why would they necessarily be the most optimal color in another system?\n\nAlso, I think you may be misunderstanding how colors and light work. The light from the sun is actually white in the sense that it is essentially composed of all colors. Maybe some of the other comments from astronomy and physics people can shed some more light (har har) on this for you."
]
}
|
[] |
[] |
[
[
"http://www.todayifoundout.com/index.php/2010/03/the-sun-is-white-not-yellow/",
"http://en.wikipedia.org/wiki/Chlorophyll#Why_green_and_not_black.3F"
],
[
"http://i.imgur.com/lKphk.png"
],
[],
[
"http://en.wikipedia.org/wiki/Leaf_green#Why_green_and_not_black.3F"
]
] |
||
48qsjg
|
Would water boil at 99°C? What difference does 1°C make?
|
askscience
|
https://www.reddit.com/r/askscience/comments/48qsjg/would_water_boil_at_99c_what_difference_does_1c/
|
{
"a_id": [
"d0mnu91",
"d0mul70"
],
"score": [
2,
6
],
"text": [
"AP Chem student here! So first off when you're heating water the heat is actually breaking the inter-molecular forces that keep the water molecules together. The closer they are affects their state, but if the bonds are broken then they enter gas phase (unless were dealing with non ideal gases, then some are still together). So that one degree might make a difference, but at that point the water would have began boiling (unless heat is distributed evenly). So I don't think it would. \nEdit: If I'm wrong tell me why, it could my scores in may.",
"The boiling point of a liquid is defined to be the point at which the vapor pressure (the pressure of a the vapor when it is in thermal equilibrium with the liquid) reaches the ambient atmospheric pressure. Temperature comes into play since increasing the temperature increases the vapor pressure. Before the boiling point the liquid will still vaporize, which is observable in things like hot cups of tea.\n\nIf you're at sea level, 99 degrees isn't enough to raise the vapor pressure of water to the ambient atmospheric level. At high elevations, it absolutely is. In space, you can boil water without supplying any heat at all, since there's not enough ambient pressure to keep it in liquid form."
]
}
|
[] |
[] |
[
[],
[]
] |
||
2q2dyi
|
Why does closer thunder sound sudden and sharp, while distant ones are more drawn out?
|
I thought the cause may be that different frequencies in the sound of thunder are carried at different speeds through the air, but wouldn't that mean I would be able to hear a difference in pitch?
|
askscience
|
http://www.reddit.com/r/askscience/comments/2q2dyi/why_does_closer_thunder_sound_sudden_and_sharp/
|
{
"a_id": [
"cn2d2tx",
"cn2h2df",
"cn2isoc"
],
"score": [
27,
3,
2
],
"text": [
"Mostly because of echoes/difference in path lengths. The farther you are away from a lightning bolt, the more chances the sound has to bounce off a few things (or not) before reaching you. The more a sound bounces around, the longer its path length, and the longer it takes to reach you. So, some of the sound goes directly to you while some of the sound bounces around a bit before reaching you. The different bits of sound from the original lightning strike reach you at different moments, so as a whole it sounds longer and more drawn out. \n\nYou can experience this same effect on a smaller scale. Stand in a very large, empty field and yell to a friend. There is very little opportunity for the sound to bounce around, so the sound either goes straight to you or gets lost out in the sky. As a result, your friend's voice sounds sharp and quick. Then go into a small canyon and yell to your friend. All the bounces the sound can take makes it more drawn out. The audio world calls this \"reverb\". ",
"From a musicians point of view, bass frequencies travel a farther distance that higher (treble) frequencies. I'm guessing The closer the thunder, the louder the \"clap\", or the higher frequencies heard in the thunder. The same reason you can hear a car with a loud system \"bumping\" from a block away. As far as the drawn out aspect, you're simply hearing the reverberations of the thunder, just as you would hear the reverberations in a concert hall. ",
"A lot is to do with damping (and to a lesser degree dispersion which is a phenomenon where different frequencies travel at different speeds). \n\nLow frequency sound is able to travel long distances without losing much energy. This is why whales for example use ultra low sound frequencies for communicating over very long distances. \n\nHigh frequency however is damped rather quickly (both when travelling in the air and when bouncing off things). \n\nThe effect is that the spectral content (what frequencies you hear) is related to the distance you are from the source. \n\nThe same thing is seen when you go to a big music event. Stand at the back and all you get is low frequency bass. \n\n\nEDIT: I may have misread the question! But this link is a good source of info. \n\n_URL_0_\n\nSource: Acoustician "
]
}
|
[] |
[] |
[
[],
[],
[
"https://www.ec.gc.ca/foudre-lightning/default.asp?lang=En&n=4EFD3A52-1"
]
] |
|
19j7x6
|
Are the background smattering of stars bright enough to illuminate two astronauts holding hands in deep space so that they could see each other?
|
I was wondering at what distance from the sun does it become too dark to see. Or is there a distance from the sun at which the human eye can no longer make out objects even on their weakly illuminated solar side? For example, standing on Pluto at midday, will it still be too dark to see your own hands?
|
askscience
|
http://www.reddit.com/r/askscience/comments/19j7x6/are_the_background_smattering_of_stars_bright/
|
{
"a_id": [
"c8oijpz"
],
"score": [
5
],
"text": [
" > Are the background smattering of stars bright enough to illuminate two astronauts holding hands in deep space so that they could see each other? \n\nWell even if the astronauts appeared pitch black, the eye would be acclimatised to the dark, and they would be able to make out their silhouette against the stars.\n\n > For example, standing on Pluto at midday, will it still be too dark to see your own hands?\n\nYes. It's 450 times less bright than earth, but still [brighter than the full moon from earth](_URL_0_) according to Dr Phil Plait, so you would be able to see your hands.\n\n"
]
}
|
[] |
[] |
[
[
"http://blogs.discovermagazine.com/badastronomy/2012/03/15/bafact-math-how-bright-is-the-sun-from-pluto/#.UTJNYTCNm8A"
]
] |
|
9gqglr
|
what do the "pill" terms mean when online asking to be "blue/red/black/etc pilled" on a certain subject/topic?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/9gqglr/eli5_what_do_the_pill_terms_mean_when_online/
|
{
"a_id": [
"e664hw0",
"e66as5o"
],
"score": [
15,
4
],
"text": [
"It is a reference to the famous scene in the Matrix when Morpheus offers Mr. Anderson one of two options. \n\n-Take a blue pill, the story ends wake up tomorrow back in your bed and fall back in line with whatever beliefs you have.\n\n-Take the red pill and experience the full unredacted truth of your existence, good or bad.\n\nIn terms of topics I've seen used in recent memes and discussions, being \"red-pilled\" implies no longer blindly believing the stance one holds regarding their allegiance to the political left.\n\n\"Black-pilled\" is a prophetic and usually apocalyptic scenario involving occultism, mysticism, and other topics of usually unbelievable proportions.\n\n\"Blue-pilled\" is the opposite of both. Essentially ignorance is bliss. Learn nothing of the true nature of things, but at the same time remain completely insulated in a false sense of security and we'll being.",
"There is actually a Wikipedia article about this:\n\n_URL_0_\n"
]
}
|
[] |
[] |
[
[],
[
"https://en.m.wikipedia.org/wiki/Red_pill_and_blue_pill"
]
] |
||
5f3f5f
|
how come when i'm dizzy my vision always spins to the right? do other people's spin left?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/5f3f5f/eli5_how_come_when_im_dizzy_my_vision_always/
|
{
"a_id": [
"dahc5bd"
],
"score": [
8
],
"text": [
"Inside your inner ears are structures and fluid that help you detect motion. The fluid in your inner ear moves when you move. After spinning around, for example, the fluid in your inner ear also spins. When you stop, the fluid keeps going. You feel dizzy because your brain is hearing conflicting stories from your eyes \"we stopped moving\" and your inner ears \"no we didn't\". \n\nThe eyes' muscles begin to work to stay focused on the environment which the inner ears are insisting is \"spinning\". \n\nSometimes dizziness is because of an infection or other condition that affects how the inner ear performs its job. \n\nAs for your vision spinning to the right, that often depends on which ear is affected. I have a condition that causes occasional vertigo and if my right inner ear's structures are affected, my eyes deviate to the right when I'm experiencing an episode. \n\nI'm sure there is a far more accurate explanation that could be given. This is just what I've been told. "
]
}
|
[] |
[] |
[
[]
] |
||
6iqreo
|
The first human head transplant is set for December 2017. Have we reached a point in medical technology were this is even possible?
|
I've read in various articles that a human head transplant is scheduled for December of this year. However, the odds of the patient surviving seem quite unlikely. Am I wrong? Has technology and medical innovation advanced to the point that doctors can connect a spinal cord from a head to another spinal cord on the donor body?
|
askscience
|
https://www.reddit.com/r/askscience/comments/6iqreo/the_first_human_head_transplant_is_set_for/
|
{
"a_id": [
"dja0nxz"
],
"score": [
5
],
"text": [
"Technology has advanced that we can attach all the individual parts however it's not because something is attached that it will work. We can transplant the head, attach all the nerves arteries without any problems. Thats just mechanical attaching. However that's the easy part. There are tons of problems, the primary being immune reactions like [graft versus host disease](_URL_1_\n) and [micro vasculitis](_URL_0_)\n\nTransplants as you know it mostly involve organs and skin. These are elements of our body that we don't actively controle and do their jobs via simple biochemistry. However when we have to transfer actual limbs it gets really complicated. You can compare it to copying an entire program on your pc then copy it to an unknown computer that you know has the same hardware, but you have no idea what edition the OS is on or if its even compatible x100 etc. ( nervus system ) The immune reaction is the antivirus on your PC. However we can controle this immune reaction with immunesupressants. But supressing your immune system also means - > you get sick more often and with more life threatening complications. \n\nI can go into detail about every single part of the process but that would almost make this a full blown paper. However if you have more questions on specific functioning or specific problems ask them and I will happily answer\n\n\n"
]
}
|
[] |
[] |
[
[
"https://medlineplus.gov/ency/article/000815.htm",
"https://medlineplus.gov/ency/article/001309.htm"
]
] |
|
7l7ird
|
Did prima noctis (the right of the first night) really happen?
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/7l7ird/did_prima_noctis_the_right_of_the_first_night/
|
{
"a_id": [
"drk66vc"
],
"score": [
5
],
"text": [
"/u/sunagainstgold answered [this question here](_URL_2_) and you should also check out this answer on [In Medieval Europe, if a female serf was very pretty would the Lord who owns her land simply take her as his wife? Even if she was already married?](_URL_0_) which are from the [FAQ on marriage](_URL_1_)."
]
}
|
[] |
[] |
[
[
"https://www.reddit.com/r/AskHistorians/comments/3zf3bh/in_medieval_europe_if_a_female_serf_was_very/cylltg5/",
"https://www.reddit.com/r/AskHistorians/wiki/women#wiki_love_and_marriage.2C_goes_together_like_a",
"https://www.reddit.com/r/AskHistorians/comments/77w2uz/true_or_false_monarchs_could_claim_newlywed/dopiwl0/?st=jayppjyi&sh=db9a467a"
]
] |
||
2liour
|
why is a 3d printer considered a printer?
|
I cannot understand how it's a printer or how it's not just an advanced manufacturing machine.
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/2liour/eli5_why_is_a_3d_printer_considered_a_printer/
|
{
"a_id": [
"clv564y",
"clv565d",
"clv56xi"
],
"score": [
4,
2,
2
],
"text": [
"It's mostly called a printer because that terminology is easy to understand to most people. The same way that an inkjet printer has a head which moves back forth across a tray to reproduce an image, a 3D printer has a head which moves back and forth across a tray to reproduce a shape.\n\nI can see your point, but this is a case of \"If it looks like a duck, and sounds like a duck...\" ",
"Because the way it deposits material is almost exactly the same way as an inkjet printer. All that happens is that the plastic gets stacked, allowing the printer to create in three dimensions, rather than just two.",
"It's more of a design. We understand the word \"Printer\". It sounds familiar and gives us a good idea of what it does. \n\nWe can also apply other logical semantics to it.\n\n*TO PRINT: to reproduce (a design or pattern) by engraving on a plate or block.*\n\na 3d printer reproduces a designt/pattern by engraving it not on a block or plate, but by printing it on itself.\n\nIt \"print\" layers upon layers of material to form a 3d image/item. a tower printed would start with a single layer, then the printer prints another layer on top of that layer, and then print another layer on top of that layer and so on and so forth until you have the entire tower. \n\n[you can see this process better in this video, albeit quite briefly](_URL_0_). there you see the builder scanning back and forth, adding a new layer to the material one inch at a time, like a normal printer would print out a normal page one line at a time. it's this similar motion and build process that we can recognize as a \"printer\""
]
}
|
[] |
[] |
[
[],
[],
[
"http://youtu.be/8aghzpO_UZE?t=2m39s"
]
] |
|
981aj2
|
What do the amplitude and frequency of a single photon actually represent?
|
In the classical view, light is the combination of an electric wave and a magnetic wave going up and down in phase. Here, what is going up and down is the square root of intensity of the electric and magnetic wave. So we clearly know what the amplitude and frequency represent.
The photoelectric effect proves that the classical EM wave theory of light is incorrect. Light exists in the form of particles / wave-packets called photons. These photons also have wave-like properties. Unlike previously theorized, the energy carried by light isn't given by the intensity of its wave but by the frequency of individual photons.
From my understanding, this is what I infer:
If something is wave-like and has a frequency *F*, then *something (X)* is moving up and down at that frequency.
If something is moving up and down at a frequency, then there is obviously amplitude involved. This represents "*by* *how much X has moved up or down at a certain point*". Let's call this *A*.
In the classical view, *X* was a measure of energy or **intensity**. And *A* gives the value of *X* at a point in time. And *F* was a measure of how quickly this intensity went up and down.
Let's get to the quantum, modern view.
According to the double slit experiment's results, photons land on the screen at random positions forming an interference pattern. This pattern seems to be the result of two radial wavefronts starting from the two slits. Now, if the interference pattern is represented by a wave function, then this would give us that *X* for a photon is the **probability** of it landing at that point of space.
This would mean that the frequency *F* of a photon measures the **speed at which this probability moves up and down**, which makes no sense to me. How does a shifting probability value give rise to colors (since colors are just photons at different frequencies)?
Does this mean that when I see blue, it's because the probability of a photon hitting my eye is **oscillating** at 650Hz!?
Sorry if I seem dumb.
|
askscience
|
https://www.reddit.com/r/askscience/comments/981aj2/what_do_the_amplitude_and_frequency_of_a_single/
|
{
"a_id": [
"e4crl8o"
],
"score": [
15
],
"text": [
"This gets to the heart of quantum mechanics, which is that the light is not a continuous thing but is instead quantized into discrete smallest-possible packets - the photons.\n\nYour question is continuing to take the principles of classical physics and apply them to the quantum realm, which you can't do. It makes total intuitive sense to do it, but experiment has shown that the world just doesn't work that way. The problem comes in thinking of a photon as a classical wave with amplitude and frequency. Photons have frequency, but they *don't* have amplitude. The amplitude of a classical E & M wave is more like the number of photons. A single photon is the smallest possible unit of light, so the amplitude doesn't vary from photon to photon. \n\nNow lets get to the photon frequency and the probability wave. The wavefunction is not what the frequency of the photon refers to. The frequency of the photon is equivalent to the energy of the photon, and is a property of the particle. I *think* (and someone who works in this field please chime in, I'm going off of grad classes), that the thing which oscillates is the direction of the EM field of the photon. If you have a photon in an EM field, the strength of that field oscillates with photon frequency, which can be measured with particles like electrons in the EM field. The strength of that oscillation is constant for photons of a given frequency, but is (I think) frequency dependent, so photons with more energy have stronger oscillations (I'm basing that on the energy density of a DC electric field and the energy of a single photon). "
]
}
|
[] |
[] |
[
[]
] |
|
1lsq7u
|
What are the most notable cities and locations during the viking-age (political, cultural, religious, economical and so on)
|
*Before I start: when I write Svitjod, I mean the region around lake Mälaren in sweden, since this was the name used in a book I recently read.*
I think I should explain what I have in mind so you get an idea of what I'm asking for: I'm doing research for a little project of my own. Basically, I'm thinking about creating my own "in-game" map of a hypothetical "Assassin's Creed" game set in ancient Scandinavia (around the same time Harald Bluetooth ruled). I'm only doing it for fun and only intend to post it to the Assassin's Creed subreddit.
So what I need now for planning for this project is basically some directions: what should be on the map. I have decided to make a few separate maps to make it more detailed. Here are the regions I will cover: Svitjod (The region around lake Mälaren in Sweden), Norway (The west cost of Norway, with the fjords), Denmark, Iceland and the Faeroe Islands
(I will also do a similar map around the English Channel, but I don't need help with that now)
I'm just going to use satellite pictures and use a colour filter, so I'm not planning to do a hyper-accurate map (otherwise I would have to count with the rising of land after the Ice age, and that would be too complicated)
**Now, to the actual question**
Within these regions (Svitjod, Denmark, Norway, Iceland and Faeroe Islands), what were the most notable locations and cities? I mean things like settlements, major burial mounds and tombs, temples or anything else you know of that was important for the Norse society. The more you can tell me about these places (like the population of the cities), the better!
So far, I only know that Birka was an important city in Svitjod, and the temple of Uppsala was a major religious site. That's all I know.
Thanks in advance!
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/1lsq7u/what_are_the_most_notable_cities_and_locations/
|
{
"a_id": [
"cc2dq3n"
],
"score": [
6
],
"text": [
"I could make a detailed description of the locations and characteristics of Harald Bluetooths Trelleborg fortresses, Jelling (which was recently subjected to new research, don't bother reading anything on Jelling (except the runestone) older than 5 years), Aarhus, Ribe, Haithabu/Hedeby, Lejre, and Kaupang/Skiringssal, but it would be much better to just obtain The Penguin Historic Atlas of the Vikings by Haywood; posting the map would be plagiarism/stealing but I'm sure you would be able to obtain it yourself, Viking-style or otherwise."
]
}
|
[] |
[] |
[
[]
] |
|
25w9cz
|
why is there no b#
|
Why is there no B# (or E-flat if you prefer)
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/25w9cz/eli5_why_is_there_no_b/
|
{
"a_id": [
"chlbdya",
"chlbf40",
"chlbpyp",
"chlbpyr",
"chlihrx"
],
"score": [
2,
7,
3,
3,
8
],
"text": [
"Not exactly sure why there isn't, but just to clarify about what you said about Eb, there is one. You meant to say C-flat. There also isn't an F-flat or E#.",
"There is\n\nB# is an enharmonic respelling of the note C. it all depends on the context its used. you wouldn't spell a G# major chord with a C in it, you'd use B#.\n\nalso, Eb is an enharmonic of D#.",
"An octave is broken up into 12 semitones (the smallest distance between notes that is used in Western music - not sure how much you know about music theory), but only 7 note names exist. Because of this, most non-accidental notes have a whole tone (2 semtones) between them. However, if all of them had a whole tone between each other that would make 14 semitones - 2 too many. So, B-C was made to be 1 semitone distance, and E-F.\n\nRealistically you can have a B# or a Cb, and would use it in certain situations, but it sounds the same as a C or B respectively",
"It is because there are only 12 notes in an octave.\n\nc, c#, d, d#, e, f, f#, g, ab, a, bb, b\n\nIt's somewhat arbitrary which notes have semi-steps attributed to them. \n/e: to clarify, I mean you could technically rewrite all music to go from c through k without any flats, whatsoever.",
"This is a really good question. If I understand it right, you're asking about the reason why the scale sounds good without a black note between e/f or b/c. There's a nice math-based answer.\n\nFirst, you need to know about \"beat frequencies.\" In short, if two musical notes have frequencies A and B, then the notes have *low* beat frequency with each other if you can write the fraction A/B using fairly small numbers. Low beat frequency sounds good to humans, and high beat frequency sounds bad. The fancy musical term for low/high beat frequency is \"consonance\" and \"dissonance,\" respectively.\n\nUnder this rule, what note pair should sound *the best*? Well, if your first note has frequency F, then you want your second note to have frequency 2*F. Then F/2F = 1/2, which can be written using small numbers, so it ought to sound good, right? This is an octave: every time you go up an octave on a piano, you double the note frequency.\n\nAside from octaves, what else should sound good? If our first note has frequency F, then the next best candidates should be, in order: (3/2)F, (4/3)F, (5/3)F, (5/4)F, (6/5)F. In a truly wild and beautiful coincidence of the universe, these fractions are approximately equal to: 2^(7/12) , 2^(5/12) , 2^(9/12) , 2^(4/12) , and 2^(2/12) . **The \"12\" in the bottom of those fractions is why music sounds good to humans!**\n\nSo now we know that it's a good idea to split the octave into 12 equal parts. That's why there are 12 notes (including black ones) in an octave. We also know that we should pay special attention to the 2nd, 4th, 5th, 7th, and 9th of these twelve notes. If the original note was a C, then these new notes are D, E, F, G, A. That answers one of your questions: **the reason there is no black note between E and F is that, by coincidence, the second and third low-beat-frequency powers of 2^(1/12) are only one away from each other.**\n\nB is a bit of a bastard child here. The reason it sounds good is that it has low beat frequency with D, E, and G, which obviously tend to appear a lot in the scale of C. Some classical composers went so far as to declare B a \"black note\" and not part of the major scale, but I guess now we've decided that it plays nicely with DEG and that's good enough for us. So that's why we allow B = 2^(11/12) into the white key club, and so there can be no half-step between B and C.\n\nQuick aside: There's a decent case to be made that we should use B flat = 2^(10/12) instead of B = 2^(11/12) . People do this, sometimes, and it's called a \"Dorian mode.\" Songs in Dorian have a very distinct melodic feel to them. A couple examples off the top of my head:\n\n[Love You Madly](_URL_0_)\n\n[Work It Out](_URL_1_)\n\nAnyways, I hope that helps!"
]
}
|
[] |
[] |
[
[],
[],
[],
[],
[
"http://www.youtube.com/watch?v=2uwjsG0cRf0&feature=kp",
"http://www.youtube.com/watch?v=kUw9Ej5VLnM&t=18"
]
] |
|
4or2mx
|
why do we sometimes have an urge to smell disgusting things?
|
Especially from our own environment.
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/4or2mx/eli5_why_do_we_sometimes_have_an_urge_to_smell/
|
{
"a_id": [
"d4ewmil"
],
"score": [
5
],
"text": [
"You mean like our poop? It's an evolutionary drive. Because animals often track other animals by scent, when we smelled our own poop we could gauge how strong the smell is and therefore gauge the level of danger we would be in after having defecated. The stronger the smell is, the further and faster it would travel and alert predators to our presence."
]
}
|
[] |
[] |
[
[]
] |
|
21ip1h
|
What was the connection between Osama bin Laden and the US government, prior to 9/11?
|
I always had thought that he was one of many operatives directly trained by the US government to raise an army to fight the Soviet invaders, but recently I've heard that this was not the case?
I've heard that his main motivation for 9/11 was because non-Muslim soldiers were stationed in Mecca. Is this true?
Apologies if this breaks the 20 year rule! I'm mostly wondering about 1994 and earlier, though.
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/21ip1h/what_was_the_connection_between_osama_bin_laden/
|
{
"a_id": [
"cgdq95y"
],
"score": [
5
],
"text": [
"I think your first question refers to the *mujahideen* in Afghanistan, who were a loose coalition of opposition groups to the pro-Soviet Democratic Republic of Afghanistan in the 1970s. As the backbone of the anti-Soviet insurgency, the US funneled supplies to mujahideen groups through the Pakistani intelligence service (ISI). But the insurgents received substantial support from other, non-Western groups; Osama Bin Ladin was the head of an Islamist group (Maktab al-Khidamat, or MAK) that recruited foreign fighters and raised money to support them. There's little evidence that MAK received direct funding from the American government - at any rate, the group played a very small role in the conflict, raising only $2 million and sending 100 foreign fighters to Afghanistan. **Bin Laden was never directly trained or funded by the United States government** - however, the CIA and ISI did directly finance Gulbuddin Hekmatyar, who was then one of the most powerful Afghani warlords. Today, he's one of the three main leaders of the anti-NATO forces, and has used his money and influence to launch attacks the coalition-backed government. \n\nAlthough the Afghani proxy war was wildly successful in entangling the Soviets in a war of attrition, it destabilized Afghani civil society. The country has been wracked by internal conflict pretty much since the Soviet withdrawal, and it can be argued that the resources made available to Islamist insurgents by the CIA (through the ISI) was one of the major factors that allowed the Taliban to be successful in their takeover of the government.\n\nIf you're interested in Bin Ladin's trajectory, I'd recommend Lawrence Wright's *The Looming Tower*, which does a fantastic job detailing the origins of al-Qaida and the motivations behind 9/11. \n\nIf you're more specifically interested in the history of *mujahideen* groups and US involvement with them, I'd check out Seth Jones's *In the Graveyard of Empires*. Both books are quick and easy reads, and together, they provide a great look at the poorly-understood roots of the conflict in Afghanistan and US counter-terrorism efforts over the last few decades. "
]
}
|
[] |
[] |
[
[]
] |
|
lpubd
|
how does hydrogen turn into people?
|
I know you've heard the quote--I saw fourteen of you use it today. But how? What's the chain of events that begins with hydrogen and ends with people?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/lpubd/eli5_how_does_hydrogen_turn_into_people/
|
{
"a_id": [
"c2umuk6",
"c2umweu",
"c2umzj8",
"c2unjl7",
"c2umuk6",
"c2umweu",
"c2umzj8",
"c2unjl7"
],
"score": [
2,
13,
6,
2,
2,
13,
6,
2
],
"text": [
"Don't think of humans as the end in mind. Start with a building block like hydrogen and consider that it will, through numerous processes like fusion, gravitation, electromagnetism and so on, eventually take on every possible configuration it can. Other elements, molecules, rock, water, planets, cells, stars, everything. We are merely one result out of infinite possibilities, and it doesn't end here.",
"Stars are bright and hot because in their cores they have nuclear fusion going on. Nuclear Fusion is when small elements are crunched together (fused) to form larger elements. Depending on the star, different atoms will be combined to create different elements. Some stars convert hydrogen into helium. Other stars convert helium into relatively light elements (like oxygen and carbon), and still other stars (usually very large stars that are in the process of dying) create heavier elements like gold and uranium. \n\nSome stars will explode when they die, spilling a chunk of their constructed elements out into the universe. These elements might form into other stars (creating more heavy elements) or they might form into planets. \n\nNow, what about your body? Your body is made up of cells, which are made up of molecules, which are made up of elements. Since you *aren't* made up of entirely hydrogen, every element in your body must have at some point been formed by a star.\n\nSo hydrogen turns into people, but in a kind of roundabout way. First hydrogen has to turn into helium (in a star), then the helium has to turn into even heavier elements (also in a star), then the heavier elements need to turn into a planet (after the star explodes), then that planet has to produce life (through abiogenesis(we're actually not quite sure how this specifically happened on earth)), and then that life has to turn into people (through evolution).",
"It's a pretty terrible quote, frankly.\n\nBut there are two important things you need to know about to understand this: baryogenesis and nucleosynthesis. Settle down, I'm gonna explain them.\n\nYou've heard of protons, yeah? Protons are one of the three particles that atoms are made of. Protons are particles called *baryons*; a protons is one type of baryon. There's another type of baryon that's also important: It's called a neutron. There are about a *zillion* other types of baryons that *aren't* important to us right now, but take all of these things collectively and we call them baryons.\n\nBaryons are not elementary things. That is, they're things which are made of other things. What are they made of? A variety of particles that are called *quarks.* The question, then, is how did quarks *initially* get together to make baryons? Or in other words, how did the first baryons come to exist?\n\nThe answer is the Big Bang. The Big Bang was the earliest period in the history of the universe, lasting from *zero* — what we call the time of the very first event that ever happened — to about 400,000 years later. Early on in the Big Bang, the universe was very hot and dense, so hot and dense that no matter could exist. Later, as the universe cooled, the first quarks appeared. But it turns out quarks, by themselves, are not stable, for deep and complicated reasons we won't go into here. Below a certain energy density, quarks are only stable when they link up in pairs and in threes. So as the universe cooled, those first primordial quarks did just that: They hooked up in pairs and in threes. The pairs we call mesons and we don't care about them right now; the three-particle collections of quarks we call *baryons*, and the proton is the lightest of all the baryons.\n\nBut when the quarks first congealed into baryons, the result was both baryons and *antibaryons*. You know, like antimatter? When a baryon of one type encounters an antibaryon of another type, the two particles annihilate each other, meaning they cancel each other out and release photons. When a *heavy* baryon and a heavy antibaryon get together, they release *very energetic* photons. Very energetic photons don't want to stay photons any more; they want to decay into lighter particles. We call these lighter particles *leptons*. The electron, which you've doubtless heard of, is a lepton.\n\nSo let's review what we've got so far: First the universe was very hot. As it cooled, quarks appeared. As it cooled further, quarks hooked up in pairs and triplets to form mesons and baryons and their antiparticles. But the mesons and baryons and their antiparticles all got together and mutually annihilated, releasing energetic photons which decayed into electrons. That's how both protons and electrons first came into existence.\n\nOf course, that raises the question: If all the baryons got together with all the antibaryons and annihilated to make photons and leptons … how come there are still baryons in the universe? I mean, we're *surrounded* by atoms made of protons and neutrons, and those are baryons, so how'd they get here?\n\nThe answer is called *baryon asymmetry*. See, way back when the free quarks first condensed into baryons and antibaryons, for every ten billion antibaryons that formed, ten billion *and one* baryons formed. So when all the annihilation happened, we had one baryon in ten billion left over with no partner to annihilate with. So those particles stayed around, and that's the origin of all the baryonic matter in the universe today.\n\nWhy did that baryon asymmetry exist? Nobody knows for sure. We already know about processes in nature that slightly favor baryons over antibaryons, so we know it's possible for that asymmetry to exist. But its precise nature is gonna remain a mystery for a while yet.\n\nAnyway, there we are, a bit after the start of the Big Bang. Quarks appeared, hooked up to make baryons, baryons annihilated releasing leptons and a *very slight* trace of leftover baryons. Meaning we had a universe that was filled with a hot gas of mostly protons and electrons and basically nothing else.\n\nAs this gas cooled, the protons — which have positive electric charge — and the electrons — negative electric charge — got together. You know what you get when you put a proton and an electron together, don't you? You get *hydrogen.* That's how hydrogen came to exist: The universe cooled, and all those free protons and electrons hooked up. So the universe went from being filled with a hot electron-proton plasma to a merely warm (a few thousand degrees) neutral hydrogen gas.\n\nWell, this hydrogen gas wasn't perfectly evenly distributed. It was denser in some places than in others. In places where it was denser, gravity started to pull the gas together to make it denser still. Once enough hydrogen gas gets together, a process called *nuclear fusion* can happen. Basically, if you squish two hydrogen nuclei — protons, in other words — together, they'll *stick* and make a helium nucleus. And if you stick two heliums together you get a beryllium, which is unstable and decays into a lithium … and so on. The trick is, none of these reactions can happen unless the hydrogen gas is really hot and really dense, which means you need a lot of it in one place. It took a few million years for this to happen, but once it did, you got *stars.*\n\nStars are where *nucleosynthesis* happens. You start with hydrogen and smoosh the nuclei together to make bigger nuclei, then smoosh those nuclei together to make still bigger nuclei … then the star explodes. Because those first stars that existed didn't live very long. They were really inefficient, so once they got to a point where they couldn't support themselves by fusing hydrogen into helium, they popped like balloons and scattered their contents through space.\n\nWhich meant now you had this big clouds of hydrogen *and helium*, which again started to collapse under their own weight and turned into the next generation of stars. These fused the heavier stuff inside them into still heavier stuff, then popped and scattered their fusion products through space, products like carbon and nitrogen and oxygen. These subsequent clouds collapsed again and formed stars … but that's not all. Those clouds also congealed to form things smaller than stars, made up of heavier elements that hadn't been present in the universe before, elements like iron and nickel and silicon, plus in at least one case a lot of leftover hydrogen that bonded with oxygen. We call these smaller things *planets* and the leftover-hydrogen-plus-oxygen *water*.\n\nAnd then one of those planets ended up having people on it.\n\nSo yes, in a sense hydrogen turned into people, first through the process of baryogenesis — where hydrogen appeared for the first time in the universe — and then through nucleosynthesis — where hydrogen got smooshed together to make more interesting things inside the cores of about three generations of stars and about ten billion years. But just saying that \"hydrogen turns into people\" somehow manages to throw away all the *interesting* stuff and leave just one mundane, totally uninteresting fact that's sort-of true but not really.",
"Our sun is in it's second life cycle, and is in the region of 4.5 billion years old. Before this, a much bigger star, made of 99.9% hydrogen a little helium and a pinch of lithium (all residue from the big bang,) was floating around in space somewhere. This star had enough gravity in its core to fuse hydrogen in to larger heavier atoms like oxygen, carbon, iron and everything else that makes up the earth. Being so big, this star went into supernova. Basically it exploded, spewing all these heavy atoms out into nowhere. Thicker parts of this cloud of atoms started to gravitate towards each other, slowly clumping together, getting hotter and increasing its gravitational pull. As this clump grew in mass, it began the process of nuclear fusion again. The birth of a second, much smaller star from what was left of the first.\nNow, still spewed around this young star is all the thinner regions of the cloud of atoms. The gravity of the star, combined with centrifugal (spinning) force, began swirling the cloud into orbit around the star. The cloud, little by little, got thicker in places where all these atoms started clumping together. By centrifugal force and the even pull of gravity, these clumps were shaped into spheres, and became planets. Those closer to the sun are mostly made of dense iron - being heavier it was pulled closer by the new star - and those farther away are made from light, less dense gasses. In the earth's case, a large body of molten iron was surrounded by a thin cover of mostly hydrogen and helium. As the earth began to cool, forming the crust, volcanoes were erupting intensely over the surface, spilling forth water vapour, carbon dioxide, methane and ammonia. A bit more cooling and bodies of water started to form, early oceans that were void of oxygen. \nThe earth was in this state 3.5-4 billion years ago. Through electrical activity (lightening), and the combining of early atmosphere gasses with the new oceans, and the odd atom of phosphorous that was kicking around, the first few basic building blocks of life were created. This pre-biotic soup, as it is known, consisted of a few amino acids and a couple of RNA bases. Add a few hundred million years, a few of these building blocks had formed into self-replicating molecules. A few of these molecules became bound together in an enclosed membrane, complete with instructions for copying itself, and life began. These very early bacteria - formed around 3 billion years ago - was the starting point for every living this on earth. Basic biological and biochemical processes were worked out. 2.7 - 2.2 billion years ago, the most important of biological process was worked out - photosynthesis. Suddenly, bacteria could create energy rich molecules using abundant CO2 and sunlight. But more importantly, they started mass producing oxygen. Oxygen changed everything. Much more energy was utilised when respiring with oxygen, and that meant life could replicate and diversify much much quicker. Bacteria started compartmentalizing regions of there cells, increasing efficiency. Some cells started collaborating, increasing survival, and some of these multi-celled organisms developed specialized regions, allowing them to out compete others. \nThe rest came down to survival of the fittest, with the most diversified most likely to reproduce and pass on those characteristics. Add another billion years or so, and that led to you.",
"Don't think of humans as the end in mind. Start with a building block like hydrogen and consider that it will, through numerous processes like fusion, gravitation, electromagnetism and so on, eventually take on every possible configuration it can. Other elements, molecules, rock, water, planets, cells, stars, everything. We are merely one result out of infinite possibilities, and it doesn't end here.",
"Stars are bright and hot because in their cores they have nuclear fusion going on. Nuclear Fusion is when small elements are crunched together (fused) to form larger elements. Depending on the star, different atoms will be combined to create different elements. Some stars convert hydrogen into helium. Other stars convert helium into relatively light elements (like oxygen and carbon), and still other stars (usually very large stars that are in the process of dying) create heavier elements like gold and uranium. \n\nSome stars will explode when they die, spilling a chunk of their constructed elements out into the universe. These elements might form into other stars (creating more heavy elements) or they might form into planets. \n\nNow, what about your body? Your body is made up of cells, which are made up of molecules, which are made up of elements. Since you *aren't* made up of entirely hydrogen, every element in your body must have at some point been formed by a star.\n\nSo hydrogen turns into people, but in a kind of roundabout way. First hydrogen has to turn into helium (in a star), then the helium has to turn into even heavier elements (also in a star), then the heavier elements need to turn into a planet (after the star explodes), then that planet has to produce life (through abiogenesis(we're actually not quite sure how this specifically happened on earth)), and then that life has to turn into people (through evolution).",
"It's a pretty terrible quote, frankly.\n\nBut there are two important things you need to know about to understand this: baryogenesis and nucleosynthesis. Settle down, I'm gonna explain them.\n\nYou've heard of protons, yeah? Protons are one of the three particles that atoms are made of. Protons are particles called *baryons*; a protons is one type of baryon. There's another type of baryon that's also important: It's called a neutron. There are about a *zillion* other types of baryons that *aren't* important to us right now, but take all of these things collectively and we call them baryons.\n\nBaryons are not elementary things. That is, they're things which are made of other things. What are they made of? A variety of particles that are called *quarks.* The question, then, is how did quarks *initially* get together to make baryons? Or in other words, how did the first baryons come to exist?\n\nThe answer is the Big Bang. The Big Bang was the earliest period in the history of the universe, lasting from *zero* — what we call the time of the very first event that ever happened — to about 400,000 years later. Early on in the Big Bang, the universe was very hot and dense, so hot and dense that no matter could exist. Later, as the universe cooled, the first quarks appeared. But it turns out quarks, by themselves, are not stable, for deep and complicated reasons we won't go into here. Below a certain energy density, quarks are only stable when they link up in pairs and in threes. So as the universe cooled, those first primordial quarks did just that: They hooked up in pairs and in threes. The pairs we call mesons and we don't care about them right now; the three-particle collections of quarks we call *baryons*, and the proton is the lightest of all the baryons.\n\nBut when the quarks first congealed into baryons, the result was both baryons and *antibaryons*. You know, like antimatter? When a baryon of one type encounters an antibaryon of another type, the two particles annihilate each other, meaning they cancel each other out and release photons. When a *heavy* baryon and a heavy antibaryon get together, they release *very energetic* photons. Very energetic photons don't want to stay photons any more; they want to decay into lighter particles. We call these lighter particles *leptons*. The electron, which you've doubtless heard of, is a lepton.\n\nSo let's review what we've got so far: First the universe was very hot. As it cooled, quarks appeared. As it cooled further, quarks hooked up in pairs and triplets to form mesons and baryons and their antiparticles. But the mesons and baryons and their antiparticles all got together and mutually annihilated, releasing energetic photons which decayed into electrons. That's how both protons and electrons first came into existence.\n\nOf course, that raises the question: If all the baryons got together with all the antibaryons and annihilated to make photons and leptons … how come there are still baryons in the universe? I mean, we're *surrounded* by atoms made of protons and neutrons, and those are baryons, so how'd they get here?\n\nThe answer is called *baryon asymmetry*. See, way back when the free quarks first condensed into baryons and antibaryons, for every ten billion antibaryons that formed, ten billion *and one* baryons formed. So when all the annihilation happened, we had one baryon in ten billion left over with no partner to annihilate with. So those particles stayed around, and that's the origin of all the baryonic matter in the universe today.\n\nWhy did that baryon asymmetry exist? Nobody knows for sure. We already know about processes in nature that slightly favor baryons over antibaryons, so we know it's possible for that asymmetry to exist. But its precise nature is gonna remain a mystery for a while yet.\n\nAnyway, there we are, a bit after the start of the Big Bang. Quarks appeared, hooked up to make baryons, baryons annihilated releasing leptons and a *very slight* trace of leftover baryons. Meaning we had a universe that was filled with a hot gas of mostly protons and electrons and basically nothing else.\n\nAs this gas cooled, the protons — which have positive electric charge — and the electrons — negative electric charge — got together. You know what you get when you put a proton and an electron together, don't you? You get *hydrogen.* That's how hydrogen came to exist: The universe cooled, and all those free protons and electrons hooked up. So the universe went from being filled with a hot electron-proton plasma to a merely warm (a few thousand degrees) neutral hydrogen gas.\n\nWell, this hydrogen gas wasn't perfectly evenly distributed. It was denser in some places than in others. In places where it was denser, gravity started to pull the gas together to make it denser still. Once enough hydrogen gas gets together, a process called *nuclear fusion* can happen. Basically, if you squish two hydrogen nuclei — protons, in other words — together, they'll *stick* and make a helium nucleus. And if you stick two heliums together you get a beryllium, which is unstable and decays into a lithium … and so on. The trick is, none of these reactions can happen unless the hydrogen gas is really hot and really dense, which means you need a lot of it in one place. It took a few million years for this to happen, but once it did, you got *stars.*\n\nStars are where *nucleosynthesis* happens. You start with hydrogen and smoosh the nuclei together to make bigger nuclei, then smoosh those nuclei together to make still bigger nuclei … then the star explodes. Because those first stars that existed didn't live very long. They were really inefficient, so once they got to a point where they couldn't support themselves by fusing hydrogen into helium, they popped like balloons and scattered their contents through space.\n\nWhich meant now you had this big clouds of hydrogen *and helium*, which again started to collapse under their own weight and turned into the next generation of stars. These fused the heavier stuff inside them into still heavier stuff, then popped and scattered their fusion products through space, products like carbon and nitrogen and oxygen. These subsequent clouds collapsed again and formed stars … but that's not all. Those clouds also congealed to form things smaller than stars, made up of heavier elements that hadn't been present in the universe before, elements like iron and nickel and silicon, plus in at least one case a lot of leftover hydrogen that bonded with oxygen. We call these smaller things *planets* and the leftover-hydrogen-plus-oxygen *water*.\n\nAnd then one of those planets ended up having people on it.\n\nSo yes, in a sense hydrogen turned into people, first through the process of baryogenesis — where hydrogen appeared for the first time in the universe — and then through nucleosynthesis — where hydrogen got smooshed together to make more interesting things inside the cores of about three generations of stars and about ten billion years. But just saying that \"hydrogen turns into people\" somehow manages to throw away all the *interesting* stuff and leave just one mundane, totally uninteresting fact that's sort-of true but not really.",
"Our sun is in it's second life cycle, and is in the region of 4.5 billion years old. Before this, a much bigger star, made of 99.9% hydrogen a little helium and a pinch of lithium (all residue from the big bang,) was floating around in space somewhere. This star had enough gravity in its core to fuse hydrogen in to larger heavier atoms like oxygen, carbon, iron and everything else that makes up the earth. Being so big, this star went into supernova. Basically it exploded, spewing all these heavy atoms out into nowhere. Thicker parts of this cloud of atoms started to gravitate towards each other, slowly clumping together, getting hotter and increasing its gravitational pull. As this clump grew in mass, it began the process of nuclear fusion again. The birth of a second, much smaller star from what was left of the first.\nNow, still spewed around this young star is all the thinner regions of the cloud of atoms. The gravity of the star, combined with centrifugal (spinning) force, began swirling the cloud into orbit around the star. The cloud, little by little, got thicker in places where all these atoms started clumping together. By centrifugal force and the even pull of gravity, these clumps were shaped into spheres, and became planets. Those closer to the sun are mostly made of dense iron - being heavier it was pulled closer by the new star - and those farther away are made from light, less dense gasses. In the earth's case, a large body of molten iron was surrounded by a thin cover of mostly hydrogen and helium. As the earth began to cool, forming the crust, volcanoes were erupting intensely over the surface, spilling forth water vapour, carbon dioxide, methane and ammonia. A bit more cooling and bodies of water started to form, early oceans that were void of oxygen. \nThe earth was in this state 3.5-4 billion years ago. Through electrical activity (lightening), and the combining of early atmosphere gasses with the new oceans, and the odd atom of phosphorous that was kicking around, the first few basic building blocks of life were created. This pre-biotic soup, as it is known, consisted of a few amino acids and a couple of RNA bases. Add a few hundred million years, a few of these building blocks had formed into self-replicating molecules. A few of these molecules became bound together in an enclosed membrane, complete with instructions for copying itself, and life began. These very early bacteria - formed around 3 billion years ago - was the starting point for every living this on earth. Basic biological and biochemical processes were worked out. 2.7 - 2.2 billion years ago, the most important of biological process was worked out - photosynthesis. Suddenly, bacteria could create energy rich molecules using abundant CO2 and sunlight. But more importantly, they started mass producing oxygen. Oxygen changed everything. Much more energy was utilised when respiring with oxygen, and that meant life could replicate and diversify much much quicker. Bacteria started compartmentalizing regions of there cells, increasing efficiency. Some cells started collaborating, increasing survival, and some of these multi-celled organisms developed specialized regions, allowing them to out compete others. \nThe rest came down to survival of the fittest, with the most diversified most likely to reproduce and pass on those characteristics. Add another billion years or so, and that led to you."
]
}
|
[] |
[] |
[
[],
[],
[],
[],
[],
[],
[],
[]
] |
|
4ff6q4
|
Why are rocket engines not able to throttle down all the way?
|
In the case of the Merlin 1D, it can throttle down to 70% max thrust. What is preventing it from going any lower than this?
|
askscience
|
https://www.reddit.com/r/askscience/comments/4ff6q4/why_are_rocket_engines_not_able_to_throttle_down/
|
{
"a_id": [
"d28kzao",
"d29pcmy"
],
"score": [
42,
3
],
"text": [
"I'm far from an expert, but I will attempt a little discussion.\n\nOne issue is that rocket engines tend to use supersonic flows. That is, the exhaust gases are moving faster than the speed of sound. The result is that nothing downstream can affect the combustion chamber.\n\nIf the engine is throttled down until flow is subsonic, then downstream acoustic effects are able to reach the combustion region. This can alternately accelerate and slow the combustion rate. Basically, the engine can whistle, with a major fraction of its power output going into oscillating thousands of times a second. This can result in rapid destruction of the engine.\n\nThere can also be challenges choking off the supply of propellant that runs the fuel/oxidizer pumps. It can be difficult to get stable flow through valves that are nearly closed. The whole engine can even develop surging instabilities, as the flow rate becomes sensitive to the pressure from the weight of propellant in the tanks.\n\nAll of these problems are solvable, but why bother? There is not much call to use a rocket as a cigarette lighter. Turn it on, or turn it off.",
"Hey,\n\nfor deep throttling you need variable geometry in the injector. This can and has been done, e.g. for the LEMDE in production, and I believe there were experimental RL-10 variants (done for potentially up-scaled moon-landings) as well.\n\nWhy this is the case is explained [here](_URL_0_) better than I could.\n\n\nThe reason it isn't done in general is that variable geometry:\n\n- Is more complicated.\n- More failure prone, cause above.\n- More costly, cause above.\n- Heavier, cause extra hardware.\n\nYou could argue that for the Merlins it'd make sense to have at least optional deep-throttling capability (say just for the centre engine). But either they were super confident that they could solve the control problem to land with T/W > 1.0, or the landing concept only appeared once engine and vehicle development had already solidified to the point that drastic changes were uncalled for.\n\nCheers,\n\nMichael"
]
}
|
[] |
[] |
[
[],
[
"http://www.yarchive.net/space/rocket/deep_throttling.html"
]
] |
|
1nt589
|
There are thousands of pigeons in central London. They don't seem to be eaten by birds of prey. What's preventing predation?
|
askscience
|
http://www.reddit.com/r/askscience/comments/1nt589/there_are_thousands_of_pigeons_in_central_london/
|
{
"a_id": [
"cclvdmb",
"ccm0yw8",
"ccm1oyx",
"ccm1ra6"
],
"score": [
256,
20,
7,
3
],
"text": [
"The volume of pigeons far outweighs the predatory ability of birds of prey.\n\nThat said, there are plenty of good examples of predatory birds making a living off of pigeons. \n\n[From wikipedia](_URL_1_) \n\n[One example: Pale Male in NYC](_URL_0_)",
"About 10 years ago, Trafalgar Square was infested with pigeons. Then-mayor Ken Livingston introduced a bylaw making it illegal to feed them. A few hawks now circulate around the area regularly to keep the pigeon population wary of returning. The combination of fear of predation and loss of ready food supply has kept the area mostly free of pigeons since.\n\n[A](_URL_0_) [few](_URL_2_) [sources](_URL_1_).",
"They are beginning to come back into London.\n\n_URL_2_\n\n_URL_1_\n\n_URL_0_\n\n\n\n",
"Places like stadiums in cities (Wembley for example) use trained birds of prey to clear pigeons from their rafters, stopping the nuisance of pigeons flying around, accumulating faeces and nesting. This is very much controlled though, a handler will bring the bird out to circle the stadium regularly and not just let it live free within the stadium."
]
}
|
[] |
[] |
[
[
"http://en.wikipedia.org/wiki/Pale_Male",
"http://en.wikipedia.org/wiki/Feral_Pigeon#Peregrine_Falcons_and_other_urban_predators"
],
[
"http://www.independent.co.uk/news/uk/this-britain/the-pigeons-have-gone-but-visitors-are-flocking-to-trafalgar-square-2041675.html",
"http://news.bbc.co.uk/1/hi/england/london/3275233.stm",
"http://londonist.com/2011/07/london-nature-notes-pigeons.php"
],
[
"http://www.theecologist.org/how_to_make_a_difference/wildlife/573303/urban_birdlife_encouraging_peregrine_falcons_in_london.html",
"http://www.inthenews.co.uk/news/parliament-new-home-peregrine-falcons-$1283142.htm",
"http://www.londonperegrines.com/plog/index.php"
],
[]
] |
||
2vwj59
|
when a nuclear warhead is de-commisioned, what happens to the nuclear material?
|
Is it re-used in any non military capacity (like in a nuclear reactor) or is it sent to a waste site like Sellafield?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/2vwj59/eli5when_a_nuclear_warhead_is_decommisioned_what/
|
{
"a_id": [
"coli69p"
],
"score": [
4
],
"text": [
"Both, actually. Usually used as fuel though, since it takes a whole lot less energy to repurpose it than make it from scratch."
]
}
|
[] |
[] |
[
[]
] |
|
2csq5y
|
Why is Byzantium not just called the Roman Empire and why isn't its fall considered the actual fall of the Roman Empire?
|
Why is Byzantium not just called the Roman Empire and why isn't its fall considered the actual fall of the Roman Empire?
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/2csq5y/why_is_byzantium_not_just_called_the_roman_empire/
|
{
"a_id": [
"cjin0b0",
"cjj3t6k",
"cjjc02z"
],
"score": [
3,
6,
5
],
"text": [
"See this [thead](_URL_0_) and a couple of other ones you get if you search the sub. As been rehashed many times, the \"fall of the Roman Empire\" wasn't an event but a process of receding territorial claims, political power in Rome, etc. But in the end, it was a clear, dramatic shift in the political structure that resulted in the loss of a capital, most of the land, and a reputation. That's enough to call it a \"fall,\" even if an emperor was still ruling under the same name.",
"Traditionally in the West, part of the differentiation is in language and the eventual split in religion - Latin vs. Greek - Catholic vs. Orthodox. The tail end of the Roman Empire and its western successor was Latin and Catholic while the Byzantines, the eastern successor was Greek and Orthodox. \n\n\nThe Byzantines in their minds never ceased to be Rome and be nothing other than Roman\n\n",
"Well to some of us the fall of Constantinople WAS the end of the last vestige of Rome. Clear and obvious. But I understand why others can't or don't understand and agree with that. Its also easier to differentiate between Byzantium and 'other' so called Roman Empires (Holy ones) by using the B name, especially when Rome itself was long out of its possession."
]
}
|
[] |
[] |
[
[
"http://www.reddit.com/r/AskHistorians/comments/14oins/at_what_point_did_the_eastern_roman_empire_become/"
],
[],
[]
] |
|
6gfk8j
|
Second time trying: I see a lot about sexuality in Greece and Rome but what about the Ancient Middle East?
|
Is there any scholarship about attitudes concerning sexuality and heteronomativity in Mesopotamia, Persia or pre-Islamic Arabia?
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/6gfk8j/second_time_trying_i_see_a_lot_about_sexuality_in/
|
{
"a_id": [
"dj0cfv0"
],
"score": [
2
],
"text": [
"This is actually a good question, does anyone know"
]
}
|
[] |
[] |
[
[]
] |
|
2lzq0v
|
how is spacecraft controlled over such long distances? how do scientists factor in obstacles such as asteroids?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/2lzq0v/eli5_how_is_spacecraft_controlled_over_such_long/
|
{
"a_id": [
"clzmgjk",
"clzmpkx",
"clzptid",
"clzs4qw",
"clzul9d"
],
"score": [
15,
13,
3,
19,
2
],
"text": [
"Preprogrammed commands with meticulous planning ahead of time. Asteroids are not obstacles space is tremendous and its hard to hit something on purpose and nearly impossible to hit anything on accident.",
"They dont factor in asteroids at all. There's a basically 0 percent chance you will hit one. ",
"We can calculate with a very high precision (read a few meters) where everything is going to be when the spacecraft may be at risk of colliding with it, so a path can be chosen that avoid them. However, it is also true that most of space is, you know, space, so as others have said, it will take some effort to even hit anything.",
"For most of their journey, spacecraft do not fire their engines. Engines are fired to put the spacecraft into a specific orbit, and then it is left to coast under the influence of gravity until it needs to be put into a different orbit.\n\n For example, to go to Mars you would first have to wait until Mars is in the right position, so that it will actually be there when you arrive. This occurs roughly once every two years. \n\nFirst the spacecraft would be put onto a very large rocket whose job it is to get the spacecraft into low earth orbit, for which it has to accelerate to about 8km/s. The vast majority of the total fuel required for the mission is spent achieving this.\n\nFrom there, the spacecraft needs to accelerate out of earths gravitational field. Spacecraft travelling faster than escape velocity will follow a hyperbolic path, and you can calculate the angle that the spacecraft will leave Earth at. From this, you time the burn so that the spacecraft will leave Earth travelling parallel to the Earths orbit. \n\nMars is further away from the Sun than earth is, so you now need to get into a higher orbit. To do this, you typically use a [hohmann transfer](_URL_0_). The aim is to get the spacecraft into an elliptical orbit with the perihelion(closest point to the sun) on Earths orbit, and the apohelion(furthest point to the sun) on Mars orbit. To do this, you need to make sure that the spacecraft leaves earth travelling at the right velocity, which factors into earlier calculations.\n\nWhen the spacecraft reaches Mars orbit, you hope that Mars will actually be there (which is why you can only launch when Mars is in the right position). However, the spacecraft may be travelling either too slowly or too quickly to be captured into mars orbit. Typically, you will fire the rocket engines again until you are captured into Mars orbit.\n\nThese calculations all have to be performed with very high accuracy in order to actually arrive at Mars, which considering the distances involved is actually a very tiny target.\n\nAsteroids are few and far between. Hitting an asteroid is far harder than not hitting one.",
"Specifically how Spacecraft are controlled over long distances:\n\nAll space craft are built with long range radios that can keep in touch with the earth. They will programmed to keep the radio pointed to earth and send back reports on where they are.\n\nThe people at mission control use the reports from the space craft to calculate exactly where the space craft is and what it is doing. They can plan to have it turn to face a direction or use its engines at specific times.\n\nWhen mission control has a plan ready to go, they send the plan to the space craft, which will wait until the time that it is told to, then it will follow the directions of the plan.\n\nSince most spacecraft are robots that are so far away that it takes light and radio signals several minutes or even hours to get to them and back, a lot of thought goes in to making the plans be exactly what has to happen to go where they want, and direct control is never assumed.\n\n(This is in contrast to something like Kerbal Space Program, where the player takes direct control of the space craft unless mods are used to add in more realistic elements)\n\nAs others have mentioned, it's HARD to hit things in space, even on purpose. basically, obstacles are not taken in to account because there is no way to react to them in real time and guidance systems are not really so powerful as to do so automatically, but there's little chance that they would need to in the first place.\n\nAn actual manned spacecraft, of course, would have a pilot and more powerful automatic controls that could allow it to avoid any obstacle that did arise unexpectedly."
]
}
|
[] |
[] |
[
[],
[],
[],
[
"https://en.wikipedia.org/wiki/Hohmann_transfer_orbit"
],
[]
] |
||
70kfe9
|
how do we know there weren't any intelligent civilization on earth before man
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/70kfe9/eli5_how_do_we_know_there_werent_any_intelligent/
|
{
"a_id": [
"dn3sv3w",
"dn3uu7v"
],
"score": [
7,
3
],
"text": [
"There would be evidence of it somewhere still on earth, and what we have found does not show that. Things like structures, metal tools, mass burials would be left behind somewhere. We have done a decent job of mapping things like extinction events as well as the growth of species over the last 540 million years, and there is no evidence of a species building an intelligent civilization. ",
"An intelligent, industrialized civilization would leave a huge amount of evidence behind, even if they died out half a million years ago.\n\nPlastics and concrete don't decompose very quickly. We don't find ancient pieces of plastic or pebbles made of concrete underground. We've made billions of tons of both in the last few decades, and the Earth will never be the same as a result."
]
}
|
[] |
[] |
[
[],
[]
] |
||
m5znb
|
american educational system
|
What is grad school? What is elementary? What is junior high? What is a community college? What is an university?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/m5znb/eli5_american_educational_system/
|
{
"a_id": [
"c2ydfb9",
"c2ydsd4",
"c2yjd6e",
"c2ydfb9",
"c2ydsd4",
"c2yjd6e"
],
"score": [
66,
4,
2,
66,
4,
2
],
"text": [
"Most children start school around 4 or 5 with kindergarten. This is the youngest level of school that the government says everyone must go to. Some parents put their children in preschool at an even younger age, but that's almost like day care and may not actually teach very much.\n\nAfter kindergarten is elementary school (they may both be part of the same actual school building). Elementary contains grades (or years) 1 through 6.\n\nAfter Elementary is Junior High (also called Middle School), which usually is grades 7 and 8, though it some areas it is 6 through 8, 7 through 9, or 6 through 9. Junior High is usually the first level at which students don't stay with one teacher for the whole day, but move from class to class. It's also the first time students may have some choice of what subjects they want to study.\n\nThe final level of school required by the U.S. government is High School, which usually is grades 9 through 12. These four years are often referred to as \"Freshman\", \"Sophmore\", \"Junior\", and \"Senior\" years, in that order. Highschool often gives students even more freedom that Junior High to choose what classes to take, but there are still some classes that all students are required to pass.\n\nAfter highschool, many kids feel they've had enough school and decide to go get jobs. Some, however, continue on to college. A college is a school for adults that offers specialized programs to study specific topics. Some colleges may only offer a few subjects, such as Science and Engineering, or various kinds of Art. Some, called Universities, are a group of colleges that all work together and teach a very broad range of subjects. Colleges are often very selective about who they accept, and only students who did well in highschool are likely to be allowed in. Community colleges are cheaper colleges that are often funded by local and state taxes, but allow students who might not qualify for more prestigious schools to still take classes and earn a degree.\n\nMost colleges confer degrees. A Bachelor's Degree usually takes around 4 years to earn, and is given in the specific field that the student choose to study. For example, a student who chooses Biology as a major would earn the degree \"Bachelor of Science in Biology\". An Associates degree is a similar, but easier degree that only requires around 2 years worth of work. Most students take additional classes beyond their specialization or major, know as general education classes.\n\nAfter earning a Bachelor's degree, some students choose to continue on to graduate school. Grad school, as it is often called, is a program within a college or university that confers even higher degrees. There are Masters Degree programs that require around 2 to 4 additional years of work, and Doctorate Degree programs that require from 4 to 7 years of work. Many Masters degrees and all Doctorate degrees require the student to do research and writing as part of the program, in order to show that they can contribute some new ideas or knowledge to their field. A student who earns a Doctorate degree (often called a Ph.D. - Philosophy Doctorate) can use the title \"Doctor\", although this does not make them a medical doctor (that requires going to a med school and earning an M.D. - Medical Doctorate).",
"[posted 1 month ago](_URL_0_)",
"In a nutshell:\n\n'grade school' is defined as grade 1 (6 yr old average) to grade 12 (18 year old average). 'Kindergarten' and 'Reddiness' are for 5 year olds or 6 year olds who are not socially or mentally mature enought for 1st grade. 'Pre-K' is the year before that and any earlier than that is 'childcare' as a generic.\n\nElementry is (again averages) grades K (Kindergarten) through 5 or 6. Highschool is grades 8 or 9 through 12. Middle School (Jr. High) is what's between those two.\n\nA College teaches one or more 'post secondary' degree programs. A University is made up of a collection of one or more specialized colleges. A Community College is the collage down the road from your house and is usually less expensive.\n\nDegrees come in multiple flavors too:\nAssociates of < something > = two year degree\nBachelors of < something > = four year degree\nMasters of < something > = Bachelors + 1-2 years\nDoctor of < something > = Bachelors + 2 or more years or Masters + one or more years along with a Dissertation. Heavy enphsis on 'or more' there. I know very few even of the brightest in the world that pulled off their Doctorate in only a few years. My cousin is working on his and has been for more than 15 years now.\n\nCommonly known Doctorates are Dental (DD), Medical (MD), Law (JD), Philosophy (PhD) and Science (ScD). A vast majority are Medical, Law or Philosophy.\n\nA Dissertation is (supposed to be) a new addition of knowledge to your field. It takes years of research and often a defense against a group of Doctors in your field. It is a huge deal.\n\nAnything above Bachelors is called 'Graduate School' - I.E. Masters, and Doctorial programs.\n\nOnce you have a Doctorate you go into what's called 'Post-Doc' which is generally research and some light teaching or you go straight for teaching with a hope for tenure.\n\nI think that covers everything EdgeOfDreams didn't.\n\n",
"Most children start school around 4 or 5 with kindergarten. This is the youngest level of school that the government says everyone must go to. Some parents put their children in preschool at an even younger age, but that's almost like day care and may not actually teach very much.\n\nAfter kindergarten is elementary school (they may both be part of the same actual school building). Elementary contains grades (or years) 1 through 6.\n\nAfter Elementary is Junior High (also called Middle School), which usually is grades 7 and 8, though it some areas it is 6 through 8, 7 through 9, or 6 through 9. Junior High is usually the first level at which students don't stay with one teacher for the whole day, but move from class to class. It's also the first time students may have some choice of what subjects they want to study.\n\nThe final level of school required by the U.S. government is High School, which usually is grades 9 through 12. These four years are often referred to as \"Freshman\", \"Sophmore\", \"Junior\", and \"Senior\" years, in that order. Highschool often gives students even more freedom that Junior High to choose what classes to take, but there are still some classes that all students are required to pass.\n\nAfter highschool, many kids feel they've had enough school and decide to go get jobs. Some, however, continue on to college. A college is a school for adults that offers specialized programs to study specific topics. Some colleges may only offer a few subjects, such as Science and Engineering, or various kinds of Art. Some, called Universities, are a group of colleges that all work together and teach a very broad range of subjects. Colleges are often very selective about who they accept, and only students who did well in highschool are likely to be allowed in. Community colleges are cheaper colleges that are often funded by local and state taxes, but allow students who might not qualify for more prestigious schools to still take classes and earn a degree.\n\nMost colleges confer degrees. A Bachelor's Degree usually takes around 4 years to earn, and is given in the specific field that the student choose to study. For example, a student who chooses Biology as a major would earn the degree \"Bachelor of Science in Biology\". An Associates degree is a similar, but easier degree that only requires around 2 years worth of work. Most students take additional classes beyond their specialization or major, know as general education classes.\n\nAfter earning a Bachelor's degree, some students choose to continue on to graduate school. Grad school, as it is often called, is a program within a college or university that confers even higher degrees. There are Masters Degree programs that require around 2 to 4 additional years of work, and Doctorate Degree programs that require from 4 to 7 years of work. Many Masters degrees and all Doctorate degrees require the student to do research and writing as part of the program, in order to show that they can contribute some new ideas or knowledge to their field. A student who earns a Doctorate degree (often called a Ph.D. - Philosophy Doctorate) can use the title \"Doctor\", although this does not make them a medical doctor (that requires going to a med school and earning an M.D. - Medical Doctorate).",
"[posted 1 month ago](_URL_0_)",
"In a nutshell:\n\n'grade school' is defined as grade 1 (6 yr old average) to grade 12 (18 year old average). 'Kindergarten' and 'Reddiness' are for 5 year olds or 6 year olds who are not socially or mentally mature enought for 1st grade. 'Pre-K' is the year before that and any earlier than that is 'childcare' as a generic.\n\nElementry is (again averages) grades K (Kindergarten) through 5 or 6. Highschool is grades 8 or 9 through 12. Middle School (Jr. High) is what's between those two.\n\nA College teaches one or more 'post secondary' degree programs. A University is made up of a collection of one or more specialized colleges. A Community College is the collage down the road from your house and is usually less expensive.\n\nDegrees come in multiple flavors too:\nAssociates of < something > = two year degree\nBachelors of < something > = four year degree\nMasters of < something > = Bachelors + 1-2 years\nDoctor of < something > = Bachelors + 2 or more years or Masters + one or more years along with a Dissertation. Heavy enphsis on 'or more' there. I know very few even of the brightest in the world that pulled off their Doctorate in only a few years. My cousin is working on his and has been for more than 15 years now.\n\nCommonly known Doctorates are Dental (DD), Medical (MD), Law (JD), Philosophy (PhD) and Science (ScD). A vast majority are Medical, Law or Philosophy.\n\nA Dissertation is (supposed to be) a new addition of knowledge to your field. It takes years of research and often a defense against a group of Doctors in your field. It is a huge deal.\n\nAnything above Bachelors is called 'Graduate School' - I.E. Masters, and Doctorial programs.\n\nOnce you have a Doctorate you go into what's called 'Post-Doc' which is generally research and some light teaching or you go straight for teaching with a hope for tenure.\n\nI think that covers everything EdgeOfDreams didn't.\n\n"
]
}
|
[] |
[] |
[
[],
[
"http://www.reddit.com/r/explainlikeimfive/comments/kpfv4/eli5_the_american_education_system/"
],
[],
[],
[
"http://www.reddit.com/r/explainlikeimfive/comments/kpfv4/eli5_the_american_education_system/"
],
[]
] |
|
3j1m43
|
If you were stuck between two planets with the same gravity at equal distances apart would you move or be stationary?
|
See, I know if you had two positively charged particles and a test positive charge is between them it will remain in place. However does this work for gravity?
|
askscience
|
https://www.reddit.com/r/askscience/comments/3j1m43/if_you_were_stuck_between_two_planets_with_the/
|
{
"a_id": [
"cum0989",
"cum1pgx"
],
"score": [
4,
2
],
"text": [
"It depends on the size of your body compared to the distance between the two planets. If you're a point particle, then you will just be stationary, since the forces from the two planets are equal and opposite. However, if the size of your body is large enough, you will start to notice that the bits of your body at your extremities are getting pulled towards the planet they're closest to, since your extremities are not at the centre. These are called \"tidal forces\", and will have the effect of pulling things apart.",
"The situation you describe is unstable: the slightest disturbance in either direction would send you towards one of the planets. What *is* stable is if a smaller body were in orbit around a larger, and then you were 60 degrees ahead or behind the smaller body, at a Lagrange point. Then you would be fixed, in the reference frame of the smaller planet."
]
}
|
[] |
[] |
[
[],
[]
] |
|
3agfpa
|
why do dark objects get hotter in the sun than lighter objects?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/3agfpa/eli5_why_do_dark_objects_get_hotter_in_the_sun/
|
{
"a_id": [
"csce2bi"
],
"score": [
2
],
"text": [
"Dark objects absorb light while light objects reflect it. The energy from the absorbed light becomes heat energy, which makes the darker object hotter. "
]
}
|
[] |
[] |
[
[]
] |
||
b50wgv
|
why does having a positive mind set help with sickness and pain?
|
[deleted]
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/b50wgv/eli5_why_does_having_a_positive_mind_set_help/
|
{
"a_id": [
"ejaennb"
],
"score": [
2
],
"text": [
"It doesn't. \n\nPraying does not help either.\n\nIt Just makes coping easier. "
]
}
|
[] |
[] |
[
[]
] |
|
3hz3jd
|
why can quicksilver and scarlet witch be used in marvel movies from two different intellectual property owners, such as x-men and the avengers?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/3hz3jd/eli5_why_can_quicksilver_and_scarlet_witch_be/
|
{
"a_id": [
"cubww23",
"cuc4fkt"
],
"score": [
49,
5
],
"text": [
"Quicksilver and Scarlett Witch are mutants, but they have also been a part of The Avengers team pretty much since its beginning. Fox have the rights for the X-men, but Marvel has the rights for The Avengers, and Quicksilver and Scarlett kinda fall in the middle, which gives both companies the right to use them - as long as Fox doesn't mention The Avengers, and Marvel doesn't mention mutants. ",
"The Marvel/Fox contract states that Fox can use any X-Men they want, which gives them the ability to use Scarlet Witch and Quicksilver. However, both characters are recognised Avengers which means that Marvel can use them in The Avengers films. This puts them into a grey area that both companies can use, however, it would cause issues if Marvel attempted to put them in Thor, or Iron Man, or Ant-Man and so on. They'd be fine for Agents of SHIELD and the Netflix stuff because Fox's rights are for films only. \n\nThe one absolute thing Marvel can not do is call them Mutants. So long as the origins are different, all is sweet.\n\n"
]
}
|
[] |
[] |
[
[],
[]
] |
||
2yvcvl
|
In WWI, what would happen to a Frenchman living in Germany or a German guy living in France? How did they deal with immigration?
|
When WWI was declared, what would happen with someone from a country opposed to the one he or she was currently living in? Do they fight for or against their country of origin or where they sent back to where they were from?
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/2yvcvl/in_wwi_what_would_happen_to_a_frenchman_living_in/
|
{
"a_id": [
"cpdj4d5"
],
"score": [
13
],
"text": [
"It really depends on the nation in question. For example, the announcement of war in Russia was greeted by anti-German rioting in 1914. In Moscow, there were riots in the streets and while at first the police tried to stop them, they gave up their attempts. Instead, they found all the German nationals in the city and evicted them, most likely saving their lives. The distrust of the Germans was enormous at the time. This posed problems for the Russian royal family too because the Tsar had married a German. Germans who remained behind lied about their origin - the source I'm using is a biography of Frederick Bruce Thomas, who had a German wife who at this point claimed Swedish ancestry. \n\nThis was in Moscow though - the Russian heartland. In the South, at Odessa, it was different. Odessa was a port city, with huge amounts of trade running through it, and consequently had a massively diverse population. It was filled with practically every nationality from Europe, and they were able to live there comfortably until at least 1916. In the case of Russia, I suspect this is because Odessa and Moscow had vastly different histories and cultures based on location.\n\nSource: *The Black Russian*, Vladimir Alexandrov."
]
}
|
[] |
[] |
[
[]
] |
|
2g5twe
|
How long will it be before the great attractor is visible and moves out from behind the center of the milky way?
|
askscience
|
http://www.reddit.com/r/askscience/comments/2g5twe/how_long_will_it_be_before_the_great_attractor_is/
|
{
"a_id": [
"ckg2gsn",
"ckg3tv3"
],
"score": [
3,
2
],
"text": [
"Depends what you mean by \"visible\". It'll still be in the plane of the galaxy, which is a hard region to observe at best. The Sun takes around 200 million years to do a full orbit of the Milky Way, so it will probably take of order 10^6 years for it to no longer be obscured by the bulge of the MW. It will still be hard to optically observe at that time, though.",
"Worst case scenario is that the great attractor is directly behind galactic center, so we need to move, let's say 90 degrees around our galaxy.\n\nIt's been said we take 226 million years to orbit the Milky Way, so 1/4 of that is around 56 million years.\n\nOf course, there's no guarantee that this thing is even visible in the first place! Is it a big blob of stars or something strange?"
]
}
|
[] |
[] |
[
[],
[]
] |
||
u2b1a
|
Shrimp have low levels of mercury and pollutants?
|
[Link](_URL_0_)
> Interestingly, when surveys have been done of the effects of pollution in fish shrimp come in very low on the list. They have one of the lowest levels of contamination by mercury and other pollutants of any seafood. At the same time much of the shrimp that you purchase today is farmed and is fed a shrimp feed.
I'm looking for more information about shrimp. I would love love a study to back this up!
Discrete questions:
How are shrimp able to pull this off? Are they unsafe in any way to eat? Should the fact that they are bottom feeders cause alarm since we eat them?
thanks!
|
askscience
|
http://www.reddit.com/r/askscience/comments/u2b1a/shrimp_have_low_levels_of_mercury_and_pollutants/
|
{
"a_id": [
"c4rpz23"
],
"score": [
5
],
"text": [
"Mercury levels in fish generally [depend on where they are in the food chain](_URL_0_). The ones at the top which live the longest accumulate the most mercury, because they eat smaller fish that have already accumulated mercury. Shrimp are small and are pretty close to the bottom of the chain, so they don't have time or the inclination to accumulate much mercury.\n\nHere's a page that [describes what shrimp eat in various scenarios](_URL_1_)."
]
}
|
[] |
[
"http://www.drgourmet.com/askdrgourmet/shrimp.shtml"
] |
[
[
"http://en.wikipedia.org/wiki/Mercury_in_fish",
"http://www.eaglewoodgourmetfood.com/what-do-shrimp-eat.html"
]
] |
|
21h5ga
|
the difference between techno and house
|
Electronic music is a bit confusing to me.
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/21h5ga/eli5_the_difference_between_techno_and_house/
|
{
"a_id": [
"cgeatdo"
],
"score": [
3
],
"text": [
"Start [here](_URL_0_). It's better than any ELI5 because it has audio examples. Although some of it is less factual and more a matter of opinion, it's fairly accurate overall."
]
}
|
[] |
[] |
[
[
"http://techno.org/electronic-music-guide/"
]
] |
|
3szo2g
|
why is it socially acceptable to vilify scientology and other religious sects?
|
This is something that has been done a lot of times, virtually everywhere on the Internet. Here on reddit "f**k Scientology" is an universally accepted narrative and I've never in my life seen anything like that being censored or anyone speak in that religion's defense.
Every single aspect of Scientology and other religious sects has been vilified, the people involved are being constantly humiliated, even if they are mere believers and are not anyhow involved into the things that higher-ups may or may not be doing.
So, this has been bothering me a lot recently. It is currently a widely accepted narrative in context of another religion that you must not judge 100% of the its believers by the acts and beliefs of 30%, no matter what those acts and beliefs might be. Then why do the very same people feel free to judge 100% of Scientologists and other cultists by the acts of less than 1% of them?
Why is it acceptable to ridicule one people's beliefs, but outright not acceptable to even question some other people's beliefs?
I am obviously not an expert like all the smart people who are in charge of making those written and unwritten rules, so please, do explain it like I really am five.
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/3szo2g/eli5_why_is_it_socially_acceptable_to_vilify/
|
{
"a_id": [
"cx1tsjb",
"cx1tuy1",
"cx1u3eg",
"cx1ynl2",
"cx2gd1n"
],
"score": [
7,
4,
6,
2,
2
],
"text": [
"The horrible things committed in Scientology come from the highest echelons of the organization, though, and no Scientologist that I know of has ever spoken out against crimes committed in the name of Scientology. They are all either complicit, ignorant, or coerced. It is a cult and a villainous organization through and through.",
"The Church of Scientology is an organisation. That organisation has its own actions. All Scientologists are paying members of that organisation, and so share in responsibility for that organisation's actions. Those actions include abuses of human rights, government infiltrations, and sabotages of health care organisations, leading to the Church being considered a criminal organisation in many areas. Anyone who criticises these actions is declared SP and expelled from the Church, making them no longer Scientologists. There's no such thing as a Scientologist who opposes Church actions, so it's not and cannot be an \"only 30% are doing this!\" thing.\n\nBuddhism, Christianity, Judaism, Hinduism are not represented by a single organisation to which every single member belongs; even when Buddhists, Christians, Jews and Hindus are part of an organisation they do not *have* to pay to support it; and there are many Buddhists, Christians, Jews or Hindus who oppose some behaviours of their organisations.\n\n(Scientologists who continue professing their beliefs after being expelled are termed 'Squirrels'; there are an estimated 150-200 of them worldwide and there is a unit of the church, the Squirrel Busters, dedicated to keeping them under surveillance.)",
"You're confusing the vilification of a belief with the vilification of an organization. It's generally not alright to vilify someone's beliefs. There are villainous beliefs, of course, like \"muahaha I believe tha I should torture puppies for no reason!\", but the basic tenets of Scientology aren't so prima facia villainous, and nobody deserves to be vilified for accepting them.\n\nOn the other hand, the Church of Scientology, as an organization, has something of a nasty record for dealing with its people. All sorts of stories have come out over the years, starting with what is effectively slave labor, then moving on to kidnapping, beatings, and of course financial ruin. Often the members of scientology are not seen as villains so much as victims, while the leadership itself is vilified.\n\nYour question compares this to Islam. The difference here is that Islam is no longer a Caliphate, and there is no single voice that speaks for the religion as a whole. I can't condemn a muslim as a bad person because some other person claiming to also be a muslim thinks that Islam means that he should do bad things. The first person hasn't done anything wrong and claims to have different beliefs than the second person.\n\nIf I were a Christian, and some other person screamed \"praise Jesus\" before blowing up a building somewhere, I wouldn't expect people to hate me for it, and I extend the same courtesy to others.",
" A gaggle of nut jobs waiting for instuctions from their alien overlords is inherently funny, sad and troubling all at the same time. ",
"There are three levels to this: individuals, religion, and organization.\n\nAt the level of individual, it is acceptable to recognize a person's religion (\"What religion are you a part of?\"), and to question them about the actions of an organization they are an active participant in.\n\nAt the level of religion, it is acceptable to question religious beliefs, the interpretation thereof, and to challenge those beliefs. Within certain limits, it is acceptable to parody or poke fun at beliefs.\n\nAt the level of organization, it is acceptable to question the actions of the organization, and the membership of the organization, especially when said actions are in service of the organization. And organizations are open to a much wider range of attacks, both in conversation, and in comedy.\n\nBasically, religion is most vulnerable to parody, organization most vulnerable to attack, and individuals protected to some extent from both\n\n\nThe problem is that in the case of the Church of Scientology, there is no clear line between the group of believers, the religion, and the organization.\n\nExamples: \n\n- Regarding Pedophile priests, it is not acceptable to question individual Christians (individual), nor other priests (religion), but it is acceptable to question the Church (organization)\n\n- Conversely, it's more acceptable to parody Christianity (religion) than any specific Church (organization). But parodying Christians for their belief is usually unacceptable, unless they are a member of an organization, or a public figure.\n\n- In almost all cases, individuals who merely attend religious ceremonies are insulated from the actions of both religion and organization.\n\n\nWith the Church of Scientology, there is a much less visible line between the religion of Scientology, the organization of the Church of Scientology, and the membership of the organization: partly because anyone who tries to practice Scientology outside of the Church is at risk of lawsuit. The Church of Scientology now is more like the Catholic Church in Europe before 1517 (when Martin Luther wrote his 95 Theses): there is no practical difference between the religion and the organization.\n\nA Christian today can exist separate from the Church, from all Churches even; and participation with one Church does not imply membership in that Church: I can attend a service any church in the city I live in without having any connection to that church. \n\nHowever, all Scientologists are both practitioners of the religion of Scientology and members of the Church of Scientology. Which means that individuals, group, and organization are all the same. And therefore are all subject to the full range of parody and questioning. Because the Church has done so much to maintain its control over the religion, and has required people who wish to attend services to join the organization, it has opened up itself and its membership to the full range of socially acceptable parody and criticism; which also allows both to be more pointed."
]
}
|
[] |
[] |
[
[],
[],
[],
[],
[]
] |
|
464sen
|
By Mycenaean standards of beauty, what would Helen of Troy have looked like?
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/464sen/by_mycenaean_standards_of_beauty_what_would_helen/
|
{
"a_id": [
"d02lmw0"
],
"score": [
966
],
"text": [
"We don't know much about Mycenaean beauty standards, as most of their writings revolve around record keeping and trade rather than literary works, news reporting, or other types of writing. The script of the Mycenaean Greeks, Linear B, was not very good at encoding Greek. It was successful as a script because the limited nature of employment of Linear B (in addition to experience/training and context) allowed scribes to understand what was being written, despite the origins of the script obviously being tied to another language. In short, you're not going to find an epic poem like the Iliad written in Linear B.\n\nOur best bet at answering your question will probably be by looking at the art of the Mycenaeans and how they depicted themselves. The Mycenaeans painted beautiful frescoes, such as [this one from the acropolis of Mycenae (ca. 13th century BC)](_URL_0_). Women are often depicted wearing colorful dresses and with their breasts exposed, quite different from the chiton or peplos that we usually imagine ancient Greek women wearing. We've also found artifacts like [this](_URL_1_), which depict the face of a woman, possibly with makeup."
]
}
|
[] |
[] |
[
[
"https://upload.wikimedia.org/wikipedia/commons/thumb/9/9b/La_Dame_de_Myc%C3%A8nes%2C_fresco.jpg/1280px-La_Dame_de_Myc%C3%A8nes%2C_fresco.jpg",
"http://40.media.tumblr.com/209b8cb8aa05ce037388e4bab64744fe/tumblr_nnjjlvJMjp1us8irco1_1280.jpg"
]
] |
||
pp0bi
|
How important is gravity for human embryo development?
|
I imagine no one was crazy enough to do actual experiments in space stations and whatnot, but what can we deduct from other animal tests and from what we know of human embryo development.
|
askscience
|
http://www.reddit.com/r/askscience/comments/pp0bi/how_important_is_gravity_for_human_embryo/
|
{
"a_id": [
"c3r3gtj",
"c3r3hi1",
"c3r3k3k",
"c3r3nco",
"c3r3nvv",
"c3r8dyr"
],
"score": [
146,
109,
4,
19,
9,
9
],
"text": [
"Saw a Nova episode that talked about this. Pregnant mice were sent to the Mir space station while the fetuses developed. The mice were brought back to earth to give birth. The infants could not determine which direction was up when dropped into water. \n\nI believe that this was the episode: \n_URL_0_",
"_URL_0_\n\n\" During space flight it is impossible to apply the existing countermeasures against microgravity deconditioning of the muscular and cardiovascular systems to the fetus. Absence of gravitational loading during the last trimester of gestation would cause hypotrophy of the spinal extensors and lower extremities muscles, reduction in the amount of myosin heavy chain type I in the extensor muscles of the trunk and legs, hypoplasy and osteopeny of the vertebras and lower extremities long bones, and hypotrophy of the left ventricle of the heart muscle. Because of decreased capacity of postural and locomotor stability, acquisition of the gross developmental milestones such as sitting, standing and walking could be delayed. In the authors’ opinion, only artificial gravity (rotating platform) during space flight will allow physiological development of the human fetus.\"",
"Here is a wired article on the subject [wired](_URL_0_)\n\nand here is the study that it cites [study](_URL_1_)\n\nSeems like from what they know right now fertilization can occur, but development does not progress properly.\n\n\n",
"So, would exposure to heavier than normal gravity during pregnancy result in super humans? Or would the difference from normal earth gravity cause havoc with development as well?",
"I learnt in reproductive physiology that gravity is important for the penetration point for the sperm in the egg, which has great sway in the migration of future cells and subsequent development of the embryo.\n\nHOWEVER\n\nWhen fertilising chicken eggs in space, when no gravity was present, light could be used as a basis for penetration required for fertilisation.\nThis is astounding as sperm obviously possess no known means for photoreceptivity.\n\nSo yeah, hope that helped.",
"_URL_0_ Article discussing Spacelab (Shuttle) experiment where frogs mated, fertilized eggs, and had them hatch into tadpoles while in orbit. Conclusion of the study was gravity did not seem to be necessary for embryo development, including humans"
]
}
|
[] |
[] |
[
[
"http://www.pbs.org/wgbh/nova/space/can-we-make-it-to-mars.html"
],
[
"http://www.ncbi.nlm.nih.gov/pubmed/15607544"
],
[
"http://www.wired.com/wiredscience/2009/08/spacebabies/",
"http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0006753"
],
[],
[],
[
"http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/1995/03/14/MN65100.DTL"
]
] |
|
2uoj7c
|
if i was to stop masturbating, eventually, would i simply stop producing semen or does my body dispose of the 'old' semen some other way?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/2uoj7c/eli5_if_i_was_to_stop_masturbating_eventually/
|
{
"a_id": [
"coa7t44",
"coa7tqd"
],
"score": [
4,
4
],
"text": [
"The unused sperm cells eventually break down and are reabsorbed by the body.",
"You always produce more semen, as the old sperm have a lifespan and will expire eventually (about 3 weeks in storage in the male body). If you don't get rid of them the body will either reabsorb them or purge them itself in a \"wet dream\"."
]
}
|
[] |
[] |
[
[],
[]
] |
||
14gzmj
|
is it plausible that a person from 1313 BC Britain would be aware of the existence of Egypt?
|
I once read a sci-fi story where a women from 1313 BC is brought forward to the present day. at one point she makes some sort of comment about electric lighting, that was along the lines of "surly even in pharaoh's court they don't have things this splendid" (but probably more poetic then that)
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/14gzmj/is_it_plausible_that_a_person_from_1313_bc/
|
{
"a_id": [
"c7cyyzk",
"c7d0jp6"
],
"score": [
2,
10
],
"text": [
"I would say it would be highly unlikely that the people of the British isles even heard of Egypt all the way back in 1313 BC. There has been evidence that the people of the British isles traded with Gauls across the channel dating back 150 BC though. And Julius Caesar didn't invade Britain until 55 BC, and then again in 54 BC. So it could be possible but I find it highly unlikely. ",
"*Feasible*, I'd say, but not very likely. There's decent evidence of trade between the Wessex culture and the Mycenaean world in the mid-2nd millennium (faience beads, gold cups with similarities to Mycenaean designs); no direct evidence of Egyptian trade, though.\n\nI did find one article from 1953 arguing that a faience bead found at Ballyduff in Ireland, dating to 1400 BCE, was probably imported from the eastern Mediterranean, with similar finds in Egypt, but I haven't turned up any more recent references to this, so it's not very definite.\n\nIf there was trade, it certainly wouldn't have been direct, anyway. It'd probably be best to imagine trade from Egypt first via the Mycenaeans, then up to the Black Sea, all the way up the Danube, and then to Britain (that's the route Mycenaean artefacts seem to have followed). Even if the Bronze Age Britons had artefacts imported from Egypt, or if the Egyptians had tin imported from Britain, they might well not know where they came from."
]
}
|
[] |
[] |
[
[],
[]
] |
|
1kql0f
|
how candlestick charts work and why they're useful
|
They're kind of confusing...
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/1kql0f/eli5_how_candlestick_charts_work_and_why_theyre/
|
{
"a_id": [
"cbrtjag"
],
"score": [
4
],
"text": [
"The \"bar\" of the chart shows you the opening/closing price for the day (often, modern charts will use a red color to show a loss for the day and green color to show a gain). The \"wick\" is showing you the highest/lowest price reached during the day.\n\nThis allow you to see, in one chart, what the overall gain/loss (lenght of the bar) was as well as what the overall volitility (variation of price over a day) was. These two pieces of information are equally important, as it give you greater insight into the riskiness of any given security. "
]
}
|
[] |
[] |
[
[]
] |
|
2g0yxk
|
why do we use water as a containment field for nuclear fuel rods, yet contaminated water is such a notable and talked about issue when a meltdown occurs?
|
Contaminated water is commonly talked about in a reactor meltdown (chernobyl, and fukishima) yet, most fuel rods are kept in a pool of water? Isn't that water then contaminated?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/2g0yxk/eli5_why_do_we_use_water_as_a_containment_field/
|
{
"a_id": [
"ckekz0i",
"ckel1q1",
"ckelh1i",
"ckeq3lp"
],
"score": [
5,
2,
2,
2
],
"text": [
" > Isn't that water then contaminated?\n\nYeah, but it's not in the water supply. Water is good at cooling things. Just because we want most of our wanter to not be contaminated, doesn't mean we avoid using some of our water for cooling spent fuel rods.\n\nThere is plenty of water used in a nuclear plant that's expected to be contaminated. That's fine, the problem is when the ocean or lakes get contaminated. That's not the plan.",
"Nuclear reactions give off tremendous heat. The heat must be absorbed somehow, and water is an excellent material for capturing/transferring thermal energy (heat), just like the water in your car's cooling system takes heat away from the engine block and is then cooled in the radiator to then go back and get heated again. Yes, the water is contaminated--but that's an inherent tradeoff of the overall system's design.",
"If we used a substance other than water to cool fuel rods, then whatever that substance is would be a notable and talked about issue when a meltdown occurs.\n\n\"Contaminated liquid nitrogen is vaporizing into our atmosphere! Why weren't they more prepared!\"\n\nWater has the advantage of being cheap, abundant, good at cooling things, and easy to store. Yes, we end up with contaminated water, but this is a more-or-less manageable waste product when the plant is running safely.",
"I'm not an expert but I think the issue is less the water itself and more that when the cooling is insufficient trace radioactive material breaks off of what is being cooled and can then be carried with the water in the event of a flash to steam explosion or if the water itself is flushed out.\n\nI think the other issue might be that some of these materials will combust at such high temperatures and then you get rain condensing from the radioactive ash produced when they burn."
]
}
|
[] |
[] |
[
[],
[],
[],
[]
] |
|
6dxloi
|
why are our names followed by our fathers' names and not our mothers'?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/6dxloi/eli5_why_are_our_names_followed_by_our_fathers/
|
{
"a_id": [
"di65446"
],
"score": [
2
],
"text": [
"Because for the longest time, marriage wasn't seen as something two equals did - it was seen as the woman \"leaving\" her family and joining her husband's family. Children of that union were considered part of the father's family. So everyone took the father's name. The exact details vary depending on country and time period, but marriage being an \"equal partnership\" is a relatively new thing (by which I mean in various societies and time periods, women may have had immense freedom and independence and political/economic power and in other times and places they were treated as little more than investments or products to be sold/traded, hence dowries and/or bride prices). \n\nMany people still do it out of tradition or beliefs. Many women don't and either keep their last name or hyphenate (or keep their last name, but hyphenate the kids'. Or keep theirs, but give the kids the father's name, etc)."
]
}
|
[] |
[] |
[
[]
] |
||
qgdci
|
What can we expect the world in terms of population, famine, resources to be like in 40-50 years?
|
What could the population be like in 40-50 years time? We've just reached 7 billion now and 80 years ago it was only 2 billion, a 350% increase in population. Will we see a similar growth or does the Earth have a 'natural' limit in terms of what it can handle in terms of food and resources?
Can we safely predict some nations will be stable and others without it / in strife?
|
askscience
|
http://www.reddit.com/r/askscience/comments/qgdci/what_can_we_expect_the_world_in_terms_of/
|
{
"a_id": [
"c3xehgi"
],
"score": [
5
],
"text": [
"There's a thing called the \"Rule of 70\". Basically, you take the \"human growth average\" (which is 1.1% at the moment) and divide it into the number 70. So, if the human growth average (HGA) stays constant for the next 70 years (which it definitely won't), it would take roughly 70 years for the human population to double.\n\nHowever, you may have noticed that countries around the world are starting to have a negative HGA. A good example is Germany. The reason why their HGA is now negative is due to their country's culture catching up with their technology. Here is how a country's population is affected by medical/technological advancement. \n\n1. pre-modern: both the child birth rate and death rate are relatively equal, and both quite high. \n\n2. early industrialization: Greater wealth means better food/health/sanitation. As a result, children don't die as much. However, the culture still calls for a massive birth rate. This creates a population explosion. \n\n3. Mature industrialization: The child birth rate declines because they aren't as much of an asset, and they're also getting more expensive. \n\n4. The child birth rate declines even further and matches the death rate. \n\nThe world averaged as a whole is currently at stage 3. \n\nIt's generally accepted that the world's population limit is ~11 billion with today's current technology. Possibly 12 billion if we realllly scrimp and save. However, it's also speculated by others that the population will hit a plateau at around 9 billion, optimistically. Keep in mind the 11 billion population is only possible if everyone has a vegetarian diet. \n\nIf the planet doubles in population and hits 14 million, we will not be able to support it (with current agricultural technology). Basically, the earth's carrying capacity depends upon human technology, rather than the environment so much. Take a look at the Green Revolution in the 40's. \n\nCan we safely predict some nations will be stable? Yes. Germany is an example of going \"further\" than stability, and is declining in population. The U.S. is also declining in its HGA (though is definitely still positive). Basically, just refer to the 1-4 step process. \n\nHowever, there are problems in Africa. They entirely skipped the early-industrialization period, and are basically between step 2 and 3. There is a problem because the technology came from the outside world, rather than within. Therefore, their culture is not changing, and their child birth rate is still ridiculously high, even though their death rate has plummeted. \n\nIf I got anything wrong, someone please correct me. I've got some notes on this that I can't find at the moment, and so this is from memory. (aside from some google searches on the current HGA and things like that).\n\nedit: Just a little factoid: There is only .76 acres of arable land **per person**, and that number is going to just keep on going down. Especially if we keep degrading the soil we use...but that's another story. "
]
}
|
[] |
[] |
[
[]
] |
|
7pvpsb
|
why does running just after eating cause cramps?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/7pvpsb/eli5_why_does_running_just_after_eating_cause/
|
{
"a_id": [
"dskdvg0",
"dsl4bkc"
],
"score": [
11,
3
],
"text": [
"When you're digesting, a lot of your blood is directed to your stomach and intestines.\n\n\nWhich means you have less available for your legs.",
"I used to get awful stomach (actually abdominal muscle) cramps often when we had to run laps in Gym class in elementary/middle school, and of course got no sympathy and was told to \"walk it off\". I don't remember if it was before or after eating though, I just always assumed I had shitty stomach muscles or something. Also, the joy of getting headaches almost every day because of side effects of allergy medications and getting ragged on by school mates (and teachers) whenever I complained about the pain."
]
}
|
[] |
[] |
[
[],
[]
] |
||
14hmkb
|
During WWII, were any German-Americans detained in the United States similar to the way Japanese-Americans were?
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/14hmkb/during_wwii_were_any_germanamericans_detained_in/
|
{
"a_id": [
"c7d7ktp",
"c7d7ufj"
],
"score": [
7,
5
],
"text": [
"In 1942, German Americans were the largest ethnic group in the USA, comprising approximately 20 % of the population. Irish Americans were the only group that came close to it in size. German immigration also began before the US was even an independent nation, and continued at a steady rate during the nineteenth century. Even after Germany became a united country that had the highest economic growth rates in Europe, more than a 100,000 Germans emigrated to the US each year from 1885 to 1914. Immigration became severly restricted to the US during the Harding Administration, so there were few \"new\" Germans living in the USA in 1942, and most of these German families could trace their ancestry back several generations. \n\nJapanese immigration was later and much smaller. They faced a lot more discrimination in the US than German immigrants did, and the hysteria about Japenese spies and sabatours was so great, the government over-reacted. They could round up 400,000 Japanese immigrants and put them in internment camps, but it would have been impractical for the US to incarcerate one fifth of its population that way. \n\nThe FBI did keep a close eye on Germans who might have been a threat to the USA. This surveilance was so close, that the FBI was quickly able to thwart Operation Pastoris, the only Nazi effort to land sabatours in the US. Eight Germans, who were trained in Berlin, were supposed to hide out among Nazi sympithizers while conducting a comprehensive series of sabatoge. The FBI nabbed them all within 48 hours. Source: Peter Hansen \"Hitler's Rail Wreckers\" pp 38-47 Classic Trains magazine, Winter 2001 ",
"Howdy, OP! You may also find these questions beneficial--[question one](_URL_1_) and [question two](_URL_0_)."
]
}
|
[] |
[] |
[
[],
[
"http://www.reddit.com/r/AskHistorians/comments/130kzd/regarding_the_japanese_american_internment_during/",
"http://www.reddit.com/r/AskHistorians/comments/z1nhl/how_were_japanese_german_and_italians_treated/"
]
] |
||
dpz4cm
|
How did the invention of the press affect the usage of parchment paper?
|
Prior to the development of the press, it was common practice for the copying monks to scrape the parchment and re-use it to write a different book.
I also remember Galileo, in The Assayer (1623) describing the printing of a book as something like "striking the paper multiple times with hot iron, leaving the page really hot" (I could search for the exact reference, but I know it's part of his athomists arguments in the book).
My questions are:
- were early methods of printing more permanent to parchment paper than handwriting?
- Was this at all discussed or am I being too anachronistic?
- Was the value of a printed book high enough that it outweighed the possibilities of the reusing the material?
- was the scraping of books largely confined to monasteries and didn't affect the beginnings of a book production?
Sorry for the many questions.
Edit: grammar and formating
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/dpz4cm/how_did_the_invention_of_the_press_affect_the/
|
{
"a_id": [
"f60jsbd"
],
"score": [
7
],
"text": [
"Well first, 'paper' doesn't mean any writing material. Paper is a specific material made out of cellulose fibers. (whether from wood, linen, cotton or hemp and other sources). Parchment is made from animal skins prepared into a thin scraped sheet (whether from goat, ox or other animal). Then there's for instance papyrus which is made from thin strips of papyrus pressed together. So paper is not parchment is not papyrus; they're different materials. (there's also vellum, which is a form of parchment so I'll skip that and just talk parchment. I'm also talking here about how historians use the terms; 'parchment paper' seems to be a marketing term these days but as far as we're concerned here those are two different things)\n\nParchment is more durable than paper, paper more so than papyrus, which is brittle and doesn't survive well in humid environments and didn't grow in much of Europe anyway. It was always far more expensive to produce parchment. First the raw material - animal hides - was more expensive, but it was also _much_ more labor-intensive to produce, with stretching, hair removal, scraping it to the right thickness, etc. In the Middle Ages, parchment was used for things intended to be permanent; psalm books, or illuminated manuscripts, or important treaties. Purely temporary notes were written on reusable wax tablets. Paper occupied a status in-between. \n\nDuring the Middle Ages, the art of paper-making spread in Europe, methods of producing it became increasingly sophisticated, and the quality improved. Thus parchment was being out-competed by paper by the end of the Middle Ages; parchment was still a better and higher-status material but good paper was just so much cheaper. As you say, parchment could be re-used (a palimpest) by washing and scraping, but so could paper, by methods that are in principle the same as how it's recycled today; by boiling it and freeing up the fibers which are washed and then added in with the fibers used when making new paper. Paper is really more easily reusable than parchment. (and had often been made out of recycled rags in the first place)\n\nWhen printing comes around in the mid-1400s, paper quickly proves itself to be a better material to print on. Only a very limited number of things early on were printed on parchment (i.e. some Gutenberg Bibles). Printing on parchment would never have been an option anyway, though - there simply was not a big enough supply of parchment to produce any significant print runs on it. Not to mention, paper-makers quickly adapted to produce papers that were made specifically to be good to print on. The fact that they _tried_ with parchment is a bit typical of _incunabula_ though; which is a term for the earliest printed works (defined as pre-1500). The reason those books have their own term is that much more work was put into them than later printed books, because they tried to imitate hand-written manuscripts. The main text body was printed but ornamentation, titles, decorative initials and flourishes and [even illumination](_URL_2_) were added in by hand afterwards. By 1500 or so, legendary printers like Aldus Manutius of Venice had developed typesetting into an art of its own. Some of the books they printed were [almost modern](_URL_1_) in layout. (note that paragraph breaks weren't really a thing yet, though)\n\nThe production of incunabula is an indicator that for a time at least, handwriting on parchment remained the ideal. But with printing spreading and more and more books being available in print, it became increasingly difficult to justify funding immense effort in producing a single hand-copied volume when the same money could be used to buy a dozen printed works. (not an exact number) One who tried, though, was the abbot and cryptographer Johannes Trithemius, who directed his monks in _De laude scriptorum_ ('In praise of scribes') in 1492:\n\n > Brothers, nobody should say or think: \"What is the sense of bothering with copying by hand when the art of printing has brought to light so many important books; a huge library can be acquired inexpensively.\" I tell you, the man who says this tries only to conceal his own laziness.\n\n > All of you know the difference between a manuscript and a printed book. The word written on parchment will last a thousand years. The printed word is on paper. How long will it last? The most you can expect a book of paper to survive is two hundred years. Yet, there are many who think they can entrust their works to paper. Only time will tell. \n\nIn a historic irony, _De laude scriptorum_ does not survive in any handwritten manuscript; we only know its contents today because of copies from when it was printed in 1494! It seems Trithemius' own work proved him wrong though about whether longevity was key to preservation; it seems quantity outweighed quality.\n\nThe development didn't stop for Trithemius or anyone though; so printing certainly played a part in killing parchment manuscripts, but skilled handwriting on parchment remained the higher-prestige option for centuries after. The advent of printing - but also the advent of more, better and cheaper paper - was significant to the decline of the handwritten parchment _book_. But not everything was printed or needed to be had in hundreds of copies. So parchment remained used for unique documents, papal bulls, treaties, other important legal documents; contexts where printing wasn't used but prestige and quality were important. For instance the US Declaration of Independence and Constitution were handwritten on parchment. To a limited extent there are still calligraphers using parchment to this day. Parchment and vellum also remained used in bookbinding, and a lot of that was reused; a not-insignificant amount of medieval texts have been found in the bindings of much later volumes. ([picture](_URL_0_))\n\nSo in summary; printing did affect the use of parchment but printing on parchment had little to do with it, as that was basically limited to some early experimentation. When it comes to recycling, paper was in fact cheaper and more reusable than parchment. But it was still quite expensive until the advent of paper making from wood pulp in the 19th century made paper became truly cheap and abundant. There was a real problem with people stealing book and documents to sell to merchants and manufacturers who needed waste paper to use as wrapping paper and for other purposes. For instance in 1801 they arrested a grocer in Södermalm here in Stockholm who'd been wrapping goods in important government documents; they found 37 volumes of stolen documents from the Svea Court of Appeals at the shop!\n\n(Trithemius quote from Evylyn B Tribble, Ann Trubek (eds.) _Writing Material: Readings from Plato to the Digital Age_ , Longman, New York, 2003)"
]
}
|
[] |
[] |
[
[
"https://medievalbooks.files.wordpress.com/2014/10/rolduc_library_fragment.jpg",
"https://i.imgur.com/xvVW3P3.jpg",
"https://i.imgur.com/wCXDARt.jpg"
]
] |
|
1rkdp4
|
how do moka coffee makers work
|
_URL_0_
These guys? I get that the water heats and expands, but how does all the water get up the top and how does all the air in the bottom get in?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/1rkdp4/eli5_how_do_moka_coffee_makers_work/
|
{
"a_id": [
"cdo4ysr"
],
"score": [
2
],
"text": [
"The water in the boiler is heated and some of it becomes steam. This expansion of the water increases the pressure in the boiler. In the top of the pot the pressure is lower. This forces the water at the bottom to raise through the filter with the ground coffee."
]
}
|
[] |
[
"http://www.theculinarylife.com/images/moka-pot-4.jpg"
] |
[
[]
] |
|
2odni2
|
Formations during the Sengoku period and how it evolved during this time?
|
I heard a lot of changes were made after their interactions with the mongols and that wars prior to the ones that occured during Sengoku period weren't as bloody, but I don't see many explaining why.
They were said to have fought completely disorganized in the past. During this time, were they more organized and better matched the 'ebb and flow' of Western warfare?
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/2odni2/formations_during_the_sengoku_period_and_how_it/
|
{
"a_id": [
"cmmthaq"
],
"score": [
6
],
"text": [
"Wars prior to Sengoku were between mounted archers - the samurai. The samurai shot at each other before joining for general melee. The reason they weren't as bloody was that 1) samurai numbers were small 2) mounted archery wearing samurai armor shooting against samurai armor had its limitations to cause casualties 3) there was a *tiny* bit of formality about it and sometimes warriors will announce names and challenges to fight each other, but all it all the focus was on individual prowess rather than a group killing machine 4) the squires didn't often enter combat\n\nThis was the case at the beginning of the Sengoku (kinda, generally speaking). As it became every samurai for himself, it got clear really quickly that numbers do matter. So more and more samurai called up more followers to fight, and started organizing them separately, and we got the Ashigaru.\n\nAshigaru were given bows and spears at first. The spears got longer steadily, and were by mid-late pretty much a 3 to 5 m pike. Samurai traded their bows for spears, and some dismounted and became officers while others became charge cavalry (they dismounted to fight on foot frequently though).\nBows also seem to get the short end of the stick for the Ashigaru as well. There kept being less and less bows and more and more spears. Then we get the introduction of firearms which resulted in less and less spears and more and more arquebus (but still less and less bows, some daimyo by the end put bows under \"others\" with porters and engineers). In the Mid Sengoku, gun numbers depended on how many you can afford with, unsurprisingly, central Japan and the western tip of Honshu and Kyushu having a lot, while eastern Japan having less.\nBy Sekigahara, with mass produced guns, the percentages were more stable at **roughly** 40% arquebus, 30% spears, 15% cavalry (though this include squires fighting on foot, roughly 2 to 3 squires to the samurai) , 5% archers, and 10% support troops like cooks, porters, and engineers (We can actually lower all those percentages somewhat if we include all the flag bearers drummers and horns they have, lots more than in Europe).\n\nOkay now that's out of the way, formations:\n\nA samurai unit fought in something called a sonae (meaning a preparation). It's designed to be the smallest unit capable of independent operation. Unlike Europe there's no standardization, because it depends on what each daimyo can field. Generally it's 300~800 men. A lord with 10 000 koku domain, the minimum baseline for a daimyo, can field one. Daimyos that can field more fielded multiples, and often a larger \"headquarter\" one surrounded by lots of normal sized ones.\n\nThe sonae unit would be by European standards incredibly loose formation. It has 5 distinct ranks, each being only one, maybe two deep and seldom shoulder-to-shoulder.\nThe first were the ranged troops. They started battle with missile exchange. They didn't seem to be arranged in one long line, but in small groups. Once these groups were mostly guns, archers were dispersed amongst them to give covering \"fire\" while the gunners reload.\n\nWhenever the commander decide the missile exchange was done, the first rank fall back and the second rank, the spears, move forward and form up, and lower their spears. Sometimes there's yet another rank of spears after this one but yeah. Anyway the spears then advance. I've read differing accounts of whether they charged or walked. I suspect both, depending on situation and commander.\n\nSo the spears on the two sides are at it. The \"cavalry\", including all those infantry squires, form the third rank. Their job is to charge weak points and prevent such charges from the enemy, and to pursue.\n\nThe fourth rank is the commander with his retainers/aids. They issued command and acted as reserve.\n\nThe fifth is porters, cooks, engineers and the like. They also acted as reserve, though in battle they're really there to either pursue a broken enemy or die while being pursued. In a formation with multiple sonaes, these folks from all the sonaes would form up to the rear of the formation.\n\nIn battle these sonae kind of work like battalions, while general formations function like division or corps (depending on how large, some daimyo only had one sonae). You send one to fight another one. If one break you replace it with another. Repeat until one side completely breaks and runs for it.\n\nWhen compared to contemporary pike-and-shot, the striking power would be low due to lack of depth or concentration. And no charger horses. And barely any artillery pieces (usually none at all). But it is well suited to the need to maneuver in the incredibly mountainous terrains of Japan. Also the generals constructed field fortifications, even for open battle, whenever the opportunity presented itself, to help on the staying-power front.\n\nSource \n*Samurai Warfare* - Stephen Turnbull, and some Japanese stuff."
]
}
|
[] |
[] |
[
[]
] |
|
aanblv
|
why can’t normal airplanes go to space?
|
I saw that our atmosphere is ~300 miles in depth. Normal airplanes can fly much farther than that so why can’t they just fly straight up for 300 miles at a slower speed than a space rocket? Or why not a supersonic jet? There’s something I’m not thinking about.
Edit: Thanks for all the info everyone! I knew ELI5 would know the answer!
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/aanblv/eli5_why_cant_normal_airplanes_go_to_space/
|
{
"a_id": [
"ectcd6r",
"ectcgw4",
"ectcj00",
"ectdji7",
"ectlqfo",
"ectnuxa",
"ectpde3",
"ectue3p"
],
"score": [
2,
108,
19,
3,
2,
7,
2,
3
],
"text": [
"Because the way airplanes work is that they take air in from the front of the engine and speed it up, shooting air out of the back.\n\nThe higher up you go, the thinner the air is, so at one point you won't get enough air going through the engine to keep the airplane flying.",
"Consider, why can't a swimmer swim into the sky? Because there is no water in the sky, and the water is what supports the swimmer.\n\nAirplanes \"swim\" through the air. The air is what supports them. So they can't fly somewhere without air.",
"Their engines rely on the oxygen in the air to let them burn fuel and their wings require air to generate lift. As they get higher and higher the air gets thinner and thinner which means their engines generate less thrust and their wings generate less lift until they reach a point where they can't make it any higher.\n\nAround 100km up a plane would have to be traveling at orbital velocities(thousands of meters per second) in order for their wings to generate enough lift to keep them airborne, but since most planes can't get much above 300 m/s they can't get close to that high.\n\nWe've made some rocket planes that can go up that high, but that's because they carry the oxygen their engine needs with them so the thin air poses less of an issue.",
"Saying that the atmosphere is 300 miles deep is very misleading. Two third of the atmosphere is bellow the summit of Mount Everest. The higher you get the less atmosphere there is. It is a matter of definition where the atmosphere ends and empty space begin. It just gets thinner and thinner the higher you get. Aircrafts need atmosphere to fly and if they go too high the atmosphere becomes too thin and they will no longer be able to generate thrust from their engines and lift from their wings. Different aircraft can climb to different altitudes. The experimental X-15 were able to go over 100km but were unable to stay up there for more then a few minutes. Similar with the current SpaceShip Two aircraft. The SR-71 and Mig-21 aircrafts were reportidly able to sustain flight at 25km by flying several times faster then the speed of sound and using specially designed engines built with exotic materials.",
"In order to escape the gravitational pull of the earth, a thing must travel at about 11.2 km per second. Travel less fast than that and you’ll stay on the earth, whether in a vehicle on the ground or in the air. So at minimum, your aircraft must travel that fast to go to space, and no airplanes do, even if we set aside the issue others have raised here of it being unable to fly at high altitudes due to lack of air. ",
"The way jet engines works has been explained, but you also asked why they can't just go straight up.\n\nLet's imagine a rocket that goes straight up into space and runs out of fuel. Once it's there, what happens to it? Gravity from Earth still effects it, in fact, it's still very strong at a mere 300 miles up. So it just falls back down to Earth. How do things stay in space without crashing back down to Earth, or in other words, stay in orbit?\n\nWe not only need to go up, we also needs to go sideways to orbit the Earth. When an object is in orbit it is still effected by gravity. In fact, without gravity it would not be possible to orbit anything. Our rocket needs to go fast enough that as it falls it keeps missing the Earth. If you do this at the correct altitude and velocity you'll orbit the Earth instead of crashing into it.\n\nOrbiting is a lot harder than it sounds, it's also counter intuitive. You're in orbit in your rocket, and just a few kilometers ahead of you is a space station you want to dock at. You're going at the same velocity as it, so to catch up you turn your engines on...and now you're going away from it!?\n\nBut you're pointing right at the space station, why are you going away from it? Simple, by increasing your velocity in the direction you are traveling you go into a higher orbit, and as you go higher in your orbit it will take longer to orbit the Earth.\n\nTo catch up to the space station you actually need to point away from it and turn your engines on to lower your orbit. You'll orbit the Earth faster than the space station. You'll then need to pass it up before going back up so you can meet it.\n\nIf you want to find out more about orbital mechanics there's a game called Kerbal Space Program that will teach you everything you want to know.",
"You need the atmosphere to generate lift and the atmosphere gets thinner the higher up you go. So eventually, you reach an altitude where the atmospheric density is inadequate.\n\nSpace rockets don't generate lift via aerodynamic interaction with the atmosphere so they aren't limited by a lack of it.",
"As you go higher in the atmosphere the air gets thinner. Even at the orbital altitude of the International Space Station there’s enough atmosphere that the station has to be boosted up several kilometers every once in a while due to drag.\n\nIf you can fly straight ahead for 300km at an altitude of 10km, which is where most planes fly you can sustain flight and counteract gravity with only 25% of the atmosphere at ground level. \n\nIf you want to double your altitude from 10km your plane would have to be **4 times** more efficient, when most planes are barley able to stay in the air at 10km. To reach space you would need a plane that can sustain flight with **100 times** more efficiency than an airliner, and on top of that it would need to be 70 times better at producing thrust (as atmospheric oxygen makes up roughly 70% of your burning fuel’s mass) in addition to generating the required lift to counteract gravity 100 times better.\n\nSimply put for an airliner to make it to what we recognize as the boundary of space it would have to be **7000 times** better at flying than it is at normal cruising altitude per unit of mass. Which based on current airliner designs and performance envelopes would mean it would have to have a range at normal cruising altitude of about 80 million kilometers without refueling. This is way beyond what can be done."
]
}
|
[] |
[] |
[
[],
[],
[],
[],
[],
[],
[],
[]
] |
|
7qonxp
|
why can a company take an erroneous payment from your account in a second but it takes them weeks to give your money back?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/7qonxp/eli5_why_can_a_company_take_an_erroneous_payment/
|
{
"a_id": [
"dsqq80r"
],
"score": [
2
],
"text": [
"My submission will most likely be dropped due to being too short, but...\n\nEach transaction costs money. When they take money from you, part of it goes to pay the transaction, so they can use faster forms of payment with higher fees.\n\nWhen they give money back, they lose your payment plus the transaction, so they choose the cheapest method, which takes time.\n\nAlso, companies don't want to make it easy to take money out, or everyone would be doing it. Some people just want to avoid the hassle, like mail in rebates."
]
}
|
[] |
[] |
[
[]
] |
||
7c1j6o
|
how does hit detection work in first-person shooters?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/7c1j6o/eli5_how_does_hit_detection_work_in_firstperson/
|
{
"a_id": [
"dpmfnjn",
"dpmg9c9",
"dpmgb33",
"dpmhw7y"
],
"score": [
44,
5,
13,
2
],
"text": [
"[check out this video by Gameranx that talk about bullet physics in games](_URL_0_)\n\nthe player basicly have a lazer pinting straight ahead, if a enemy is touching the lazer when the player press the trigger, the enemy will get hit. some realistic games have a delay from the player pulling the trigger to the enemy getting hit to give an effect of bullet travel time or bullet drop.",
"In terms of ping, hits are calculated on the server, not on the client, which is how come you might see rubber banding on your game but still get hit by someone.\n\nThe most basic games just simply draw a straight line from you to the target to see if you hit them. Some games take into account some physically effects. Star Citizen is the only game that I know of (though I'm sure there are others) that actually creates bullets as physical game objects and calculates physics on the bullets in that way. Pretty cool.",
"There are many solutions to this, but usually there is one computer that acts as the server (if it's P2P then it's the hosting player, if it's dedicated servers then it's the actual server itself). \n\nThe server is the only computer that calculates hit detection and has a complete picture of the whole game. Everyone else just sends and receives updates from it. So if you shoot someone, you don't actually do any calculations on your computer. Hell, you probably just tell the server that you pulled the trigger and it will create the bullet for himself and do all the necessary calculations without asking you for anything. \n\nAnd then, when the bullet collides (or not), it will just tell you that it collided (or not) and then your computer would draw the blood splash, or ragdoll the dead target, or whatever.\n\n The way ping factors into all of this is that:\n\nA) If you lag then it will receive you input message late and will spawn the bullet late, thus possibly missing your target. Nothing can be done about that.\n\nB) If your target lags, then it will need to do some smoothing to somewhat predict where they would be realistically, if they didn't lag at this very moment. Technically that is not hit detection, but should be mentioned anyway.\n\n",
"Send out a raycast in the direction the player is facing. Was there a collision? What's the Object type? Is there a function to handle that? Call it. \n\n\n"
]
}
|
[] |
[] |
[
[
"https://www.youtube.com/watch?v=nI2mlnKEKTQ"
],
[],
[],
[]
] |
||
5fvp6u
|
Can there be a star orbited by hundreds of planets? Thousands?
|
askscience
|
https://www.reddit.com/r/askscience/comments/5fvp6u/can_there_be_a_star_orbited_by_hundreds_of/
|
{
"a_id": [
"daob5kp"
],
"score": [
6
],
"text": [
"Our sun is orbited by millions of objects, although we have decided to only call 8 of them planets. Depending on the size and type of the star formed and the original mass of the protostellar cloud giving rise to the solar system, I think there could be sufficient stable orbits for far more than 8 planets. But planetary formation might favor fewer large planets over more smaller ones. That would decrease the number of viable orbits. In any case, I think a hundred planets as we define them is unlikely."
]
}
|
[] |
[] |
[
[]
] |
||
5vj4ql
|
the racehorses which always finish last - why do they still bother to compete if they know they'll always be the slowest?
|
The payout for them is also very high - if only because it's impossible for them to win. What's the theory behind entering the slowest horses? What's in it for the jockey's team?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/5vj4ql/eli5_the_racehorses_which_always_finish_last_why/
|
{
"a_id": [
"de2fpcq",
"de2g1db",
"de2grkk",
"de2i5ac",
"de2ip2b",
"de2otkx",
"de2tx4p",
"de2ymvv",
"de38r32"
],
"score": [
7,
28,
3,
3,
6,
5,
2,
2,
2
],
"text": [
"Even just entering some of these races will help out. Being in the Kentucky derby (even finishing last) is worth quite a bit to the horse owner. A large portion of their income is not from race winnings but from breeding rights. By having an official entry in a big race you've proved that your horse is within the top ten or so of the country, which is no small feat. Granted winning first place is worth more.\n\nPlus having your jockey and horse still 'practice' in these big races always helps and just keeping your name out there is good too. Also also who doesn't love a good race day in the owners' box?",
"I wouldn't say it's impossible. The \"long shot\" horses usually aren't really *that* off pace. You're unlikely to see a horse that's a legit 500:1 or 1000:1 odds, usually they're more like 30:1. These are still specially bred race horses, not some random mule.\n\nSo why are they there? It may be an inexperienced horse or jockey getting some real race practice in. It may be a breeder advertising that the horse can keep pace even if it's unlikely to win. It may just be a horse with little race history so bettors default to the \"dark horse\" odds.\n\nThe 30:1 horses still do win occasionally. The favorites get sick or run way off pace, horses stumble or get spooked, jockeys make mistakes. It's a highly random sport.\n",
"For some jump races there is always the chance that most of the other horses fail to complete the course. See Foinavon in the Aintree Grand National. That race has had two 100/1 winners in the past 50 years.",
" > What's the theory behind entering the slowest horses? \n\nFirst, there are different distances and track types. If your horse came in last going sprint distances on dirt, you try mile races on dirt. Still comes in last, you go classic distances on dirt. Still comes in last, you go long distances on dirt. If all those fail, you try the same distances on grass/turf. \n\nThere are different levels in horse racing, too. If the horse is always coming in last, they'll enter it in progressively lower and lower quality races. \n\nIf they still come in last, they'll get sold to someone and hope their training is more suited to the style/temperament of the horse, then they try all of the above. \n\nSo a horse can lose an awful lot of races and it's still valuable to see if they can win some other type of race. \n\nJockeys make a fee based on the purse money that is won, so they're obviously going to try to get on winning horses. But only the most elite jockeys have that much of a choice in which horses they ride. Even if they're pretty sure the horse will lose, they'll try their best hoping to get paid. \n\nTop level jockeys will also ride \"bad horses\" because they have relationships with certain owners or trainers and they want to keep that relationship a happy one.",
"Breeding rights man. The fastest horse in the world may be a boy, but to make a faster one it will need to bang the fastest lady horse. \n\nWhat better way to advertise the breeding of your horse than in a publicly recorded, heavily monitored official race. To post that last place time, the horse had to pass a physical, drug test, and have a verifiable pedigree. It establishes a history of the horse not just on a good day, but race day, showing it can put up that time on command. \n\nAlso, Sanchez has been working really hard with this horse and says it has a real chance today. The bookies are giving it 500:1 odds and we're totally gonna get rich when it breaks a personal record. ",
"First of all it's rare that a horse \"always loses.\" Most race horses, have a record of occasionally winning, or at least doing well enough to take home some prize money. \n\nEven horses that are sold off the track as riding horses specifically for being too slow usually have some starts and winnings. \n\nIt's generally thought that any horse has some chance of winning. The losingest horse in racing history, Zippy Chippy, was banned, not for losing, but because he wouldn't break from the gate. When the other horses would run, he would just stand there. The Jockey Club eventually felt it was misrepresentation to allow people to bet on him. He became an outrider pony for the track, and later retired to be a spokeshorse for a thoroughbred retirement group. \n\nBecause he was a bit of a fan favorite for his indomitable will not to run, he did some exhibitions after his ban. In a famous instance of slowness, Zippy lost a footrace with a minor league baseball player. \n\nEven with 100 starts and no wins, Zippy earned $30,000 in his racing career. 8 2nd place finishes, and 12 3rds. ",
"In horse racing, you need a field. There might be three or four favorites who are mostly likely going to win, but you need more horses than that for a proper race. \n\nSome of them are just filler. Local horses and jockeys who know they are unlikely to win, but are competent enough to run a good race. They get paid an appearance fee to do their thing, and sometimes if thing go just right, they might even finish in the money.",
"Depends on the number of races the horse has run. In the beginning it's not too bad, but if it loses too many then it's a trip to the glue factory.",
"it is like asking why the Cleveland Browns still play football. I mean the team is still composed of some of the best players in the world. Just not quite at the top. \n\nAlso some horses legitimately run better on some types of track, certain length of races etc. So they can be in the money for some races and trailing in others."
]
}
|
[] |
[] |
[
[],
[],
[],
[],
[],
[],
[],
[],
[]
] |
|
2pg78c
|
(not trolling) how is canada not just a better version of the us? it seems like all the problems we have aren't issues over there. am i missing something?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/2pg78c/eli5_not_trolling_how_is_canada_not_just_a_better/
|
{
"a_id": [
"cmwduoy"
],
"score": [
3
],
"text": [
"I wouldn't exactly say that we don't have our issues up here. We've got growing concerns over CSIS (our approximate equivalent of the CIA/NSA), immigration and refugee issues have sprung up from time to time, particularly refugee health benefits in the past year or so. While not as immense a problem as the US', neglect over Veteran's Affairs have been front and center recently. I think it was just last week there was a new sweep of calls of Members of Parliament demanding for the resignation of our Minister of Veteran's Affairs due to major cuts in services and spending, not to mention the minister's overall indifference to veterans (he skipped out on a meeting with WWII vets, then got angry at them when the vets complained).\n\nWhat else is there? Rising food costs for our northern territories, which caught a lot of media attention after some documentary footage showed people in the northern territories scrounging for food at a land fill. The minister responsible for affairs involving our northern territories was seen a few weeks ago reading a newspaper during a session of Parliament while other members were openly discussing and questioning the issue.\n\nAnd here's a fun one--our government has been pushing forward to create a massive 'Memorial to the Victims of Communism' which would be built right across the road from the Supreme Court of Canada - an area that had been slated for the construction of a new court building (which would have been named after former Prime Minister Pierre Elliot Trudeau, whose son is also the current leader of the Liberal Party of Canada and biggest threat in the next election)."
]
}
|
[] |
[] |
[
[]
] |
||
8makk7
|
why does our brain find patterns in random events?
|
[deleted]
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/8makk7/eli5_why_does_our_brain_find_patterns_in_random/
|
{
"a_id": [
"dzm2e2c",
"dzm50rx",
"dzm8a7u",
"dzmas64",
"dzmb3gm",
"dzmdyj8",
"dzmpwon"
],
"score": [
20,
353,
6,
17,
76,
2,
3
],
"text": [
"Afaik, it's evolutionary. Helps us to survive by linking events when interpreting our environment.",
"Suppose someone eats a berry, dies. Another person eats a berry, dies. The man who sees that there is a pattern here does not eat berry for fear of death. The person who does not see a pattern eats a berry and might die. So the pattern-finders survive and we keep this trait.\n\nIf the man was wrong, worst case scenario is we don't eat the berry until we're about to die anyway, so being wrong doesn't really punish people nearly as much, which is why you can overanalyze things sometimes",
"Every time your brain gets input from senses it compares to what you've experienced before so that you can understand what's going on. If you're experiencing something you've never experienced before your brain might try to link that new experience to something you've experienced before despite it being unrelated.",
"This question has a flawed sort of conception.\n\nOur brains find patterns. Patterns sometimes *emerge* in random events.\n\nFor instance, if I take a coin and I flip it and it comes up heads 10 times in a row, my brain would notice the pattern and say: \"Hey, I bet that coin is weighted.\" Since there was only a 0.1% chance of that occurring.\n\nBut it is fully possible that it was a normal coin and you just got a statistically unlikely sequence of coincidences that produced a pattern that seems non-random.\n\nThere's literally no way to tell which is the case - you can guess at the likelihood, but until you do some external measure, like weighing the coin itself, you will never know.\n\nHowever, were you to repeatably flip the coin, your certainty of the truth is likely to improve. 10 heads (or tails) in a row is a 1 in 1000 chance with a fair coin. 20 in a row is a 1 in a million chance. 30 in a row is one in a billion.\n\nIf you flip a coin and get 10 heads in a row, you can be *pretty* certain it's a weighted coin. If you get 20 or 30 heads in a row... yeah, you're pretty much guaranteed that it's weighted.\n\nThe outcome of random events will *tend towards* the random distribution after many occurances. But especially when you only take a few samples, it is quite possible for patterns to appear. Coincidental Patterns indistinguishable from true patterns. And since our brain picks out patterns - we notice them.\n\nNow, one related flaw with humans is that we might get a few samples of a process, determine a pattern that is more coincidence than underlying distribution, and then *fixate* on that pattern. If I got 10 heads in a row, but then the next 20 flips were a fairly even assortment of heads and tails... it is likely that the coin is a typical coin with little or no tampering. But if I anchored myself and said unequivocally: *\"No! This coin came up heads ten times in a row once! It's Definitely weighted!\"* I would probably be in error. I'd be privileging the results of my first impression, my initial trials, over the total results across all trials.\n\nWhich in and of itself also isn't the worst instinct. A departure from one behavior to a completely different behavior (seemingly weighted to seemingly fair) is itself a change worth noting. Maybe someone swapped out your weighted coin for a fair one while you weren't looking, to try and pretend the coin was fair all along? I mean, this concept is what a lot of magic tricks rely on. There's really no way to be certain. Just varying probabilities and expectations of those probabilities, based on models built from incomplete data.\n\nSo how do we balance it? How to we ride the line between appropriate skepticism indicating true changes, and coincidences that grab our attention but ultimately are worth discarding as notable? It's difficult, if not impossible to say. Humans do a *decent* job of balancing the two, all things considered. But nothing is perfect. ",
"Here’s an example I read once:\n\nYou know about pareidolia- seeing faces in random patterns? \n\nWhat would would be worse for our ancestors in the bush, seeing a face where there isn’t one, or *not* seeing a face when there *is* one? The second would be worse- it could be an enemy. It’s better to be safe than sorry, so pareidolia has remained a part of the human condition and wiring of the brain ",
"In addition to the evolutionary perspective: Our brain notices patterns to create schemas (short cuts). It is very labour intensive for our brain to have to work everything out from scratch all the time so we notice things and group them together. Say for example we know that a table has four legs, and a flat surface and is used to put things on. Rather than our brain having to take in all of these details individually every single time, we notice that pattern (that everything that looks like this gets used for this purpose) and creates a shortcut. You can then use this short cut to build upon for more complex variations (ie. a one legged table). ",
"Noam Chomsky was asked \"How do you deal with somebody, coming to you and talking about astrology?\" in the animated conversation/documentary Is the Man Who is Tall Happy. He had an interesting response-\n\n\"Astrology? I don't dismiss the person's interest in it. I mean, people have all sorts of irrational beliefs -- me too, you know. I may think they're irrational, but to them, they're meaningful. And, after all, some pretty smart people were interested in astrology, like Isaac Newton, for example. So, it's not -- it's not imbecility. I mean, humans have a -- kind of like an automatic -- in this case, instinctive -- drive to find causal relations, to explain things that are happening in terms of causes. When you can't see the causes, you postulate hidden causes -- I mean, infants do this. You can -- you do experiments with infants in which, you know, something is moving along and then something starts moving this way. They'll make up in their minds that there's some hidden contact there that you can't see, you know. And we just do this instinctively. I mean, if things are happening around us, we try to find some agent behind it... ...Often an agent, you know, like an active intelligence that's doing it, sometimes something mechanical. So it pretty naturally leads to beliefs like astrology, especially because you find -- I mean, life is full of coincidences. So you try to make a connection between the coincidences, and you find a pattern in the stars, or it's a full moon, so this is going to happen, and so on and so forth.\"\n\n\n"
]
}
|
[] |
[] |
[
[],
[],
[],
[],
[],
[],
[]
] |
|
bw491t
|
Why is it that Western Religions and Islam have had several major conflicts while East Asian Religions(Shinto, Buddhism, Hinduism, etc.) have had a much more peaceful existence.
|
I mean like, the crusades between Islam and Christendom, the reformation and 30 years war and World War Two were all mainly middle eastern and Western Religions, while in East Asia, there not been almost any major religious conflicts(besides the Hindu Muslim conflict).
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/bw491t/why_is_it_that_western_religions_and_islam_have/
|
{
"a_id": [
"eq9xyzu"
],
"score": [
21
],
"text": [
"Ho boy... there's three parts to this question that we need to answer one at a time and in order because there's a vastly incorrect premise here. \n\n* Did East Asian religions have a much more peaceful exisence? \n\n* Are East Asian religions inherently more pacific? If so, why? \n\n* Why do we perceive East Asians to be pacific and Abrahamic ones to be violent? \n\nSo let's start from the top: \n\n > Did East Asian religions have a much more peaceful exisence? \n\nAnd the answer to this is a resounding *absolutely not.* \n\nAs you can see from my flair, I specialize in Buddhism. A few weeks ago I answered a question regarding [wars based on Buddhist belief.](_URL_0_) And shortly after that there was a question regarding the [Slovenian Philosopher Zizek and his perception on Buddhism (somewhat related).](_URL_1_) Feel free to read those and get back.\n\nThe long and the short of it is that eastern religions, with a laser focus on Buddhist traditions there in that thread, have been no less susceptible to war, genocide, and explosions of violence than in Abrahamic traditions. \n\nGandhi's deep commitment to pacifism hasn't been universal. He was murdered by a radical Hindu. Of which there were many who advocated violent resistance against both the British and the Indian Muslims. The most radical of them, the RSS, formed the basis of various Right-wing Hindutva based political parties, leading up to the modern BJP (but that's sure as hell not a can of worms I'm interested in opening up right now...). \n\nWe don't even need to look at the modern day to look at violent Hindus. In the brief window between the Mughal Collapse and the British Raj, the Marathas took control of India, and were not shy about their use of violence against their enemies. Throughout Indian history, in fact, there was a whole segment of life (referred to as *yoga*) that specifically referenced wandering men in the \"war market\" of India. This market seems to have taken many *many* changes over the course of Indian history, culminating in the British roundly defeating, dissolving, and coopting these organizations (and the market entirely) when they conquered India. \n\nIn China, Confucianism and Taoism, sure, seldom advocated violence in any systematic manner (as far as I can tell), but Confucianism, which placed the Emperor at the center of a properly ordered world-society, could be argued to imply a violent correction of world order. Which I would argue, is exactly how dynastic China operated. When a Dynasty which had lost the Mandate of Heaven was being violently upset, a new Dynasty which had obtained the Mandate (or claimed to) violently established their order. \n\nBuddhism didn't seem to entirely temper the Tibetans (or Koreans, or Japanese) imperial ambitions. It's arguable *how* Buddhist the Tibetan Empire became, but even today the Three Ancestral Dharma Kings, whose deeds are mostly remembered for the first establishment of the Dharma in Tibet, are also known (much more generally) for their military accomplishments. \n\nThe Korean Silla and Goryeo periods are characterized by Buddhism, but are also known for dramatic abuses of power (including conquest and violence against other Buddhist powers). Japan's history, especially as regards Buddhism, is far too long in this thread, but Zen theology was used to justify wars against the Allied powers in World War II, straight up excusing soldiers for killing living beings, which of course, Buddhadharma is strictly against. (See above threads for better explanations). \n\n > Are East Asian religions inherently more pacific? If so, why? \n\nI would argue *yes,* but only marginally so. Buddhism, for example, places a much clearer prohibition against killing in the Five Precepts. This differs from the Ten Commandments' commandment against killing in two ways. \n\nFirst, as far as I'm aware, the commandment is usually interpreted as to refer specifically to 'murder' but excludes the more general term 'killing.' This is important, because while a Buddhist shouldn't murder, he also isn't supposed to slaughter animals, slap a mosquito, or kill in defense. All of which (and I'm not a Hebraicist) the Ten Commandments traditionally seem to allow. \n\nSecond, the Ten Commandments are *commandments*. They are orders distributed from a deity on high. The Five Precepts are vows that must be taken. Since God is universal (and yes, I'm aware that I'm paraphrasing and generalizing Abrahamic religions) his Commandments apply to all of humanity at all times. If we excluded all Christian soldiers fighting for the defense of their nation, we would be condemning a lot of faithful Marines, noble Crusaders, and good Minutemen to fiery hell. \n\nThis points to the difference in *soteriology* of Abrahamic and Dharmic religions. Followers of the Abrahamic God want to obtain some kind of union with him. The goal of Christianity, Islam, and Judaism, is to some degree to achieve an afterlife with God, and not apart from Him. \n\nThe goal of Dharmic religions is to achieve *liberation* from the cycle of suffering and rebirth. \n\nThe goal of Sinic religions (Taoism and Confucianism) is to achieve harmony and balance.\n\nThese all sound like they might be synonyms for each other, depending on how you want to define liberation, balance, and God. But they are fundamentally different. In Buddhism, one doesn't try to align their life with a deity's commands, but is trying to escape Samsara, which is the cycle of rebirth that leads one back to suffering again and again. Obtaining liberation from this is achieved by (usually) becoming a renunciate (monk or nun) and living a life between the extremes (called the Middle Path). \n\nGoing on a crusade would be *ludicrously* antithetical to this goal. Those Buddhists which engage in religiously motivated violence, usually do so by using Buddhism and Buddhist history as an identity marker, not as an odd theological reinterpretation of Buddhist teachings themselves (again, a vast generalization). Warriors who subscribe to Buddhism are... well, *very* common in Buddhist history, but the rules of a monastery are much stricter. Taking human life is one of the two breaches of Monastic conduct which can get a monk expelled from the Monastery, and one of the first acts of an Anti-Buddhist sovereign to destroy the Sangha is to force monks into the army, ending the possibility of the Sangha reforming. \n\n > * Why do we perceive East Asians to be pacific and Abrahamic ones to be violent? \n\nI think the simple answer to this here is education. Americans learn mainly American history with a bit of Europe thrown in during the Age of Exploration (i.e. the Western \"conception\" of the idea of America) and then disappears until the World and Cold Wars. In Europe, obviously, they have a different perspective, learning mostly their own history and a bit of American and African history as necessary to the telling of their own national, well, let's call it, \"epic.\" \n\nThis leads to a much *much* larger and longer conversation about the history of public education and history as propaganda, but in the terms of eastern religions, American and European histories don't have a long history with abuses or violence with eastern religions (the key word here is \"long\"). The equivalent would be classrooms in China, Thailand, and Bhutan asking why eastern religions have violent traditions but Catholic monks seem so peaceful, ergo, why are Christianity and by extension, Abrahamic religions so peaceful? Of course, Western history students with a long history of abuse from Christianity, both systematic and otherwise, know better. \n\nThere's other smaller reasons. I.e. Buddhism's and Hinduism's own image of themselves is as \"religions of peace\" even if they don't refer to themselves outwardly as such. Part of this is the emphasis, see above, on the Precepts which prohibit the taking of any life for monks (though see other threads I have written in on when those Precepts have clearly been bended or broken with few or no intra-religious consequences). The Dalai Lama XIV, for example, presents himself as a \"simple monk\" whose outward goals have been world peace, a self-determined Tibet (though not explicity independent, in fact he has written extensively on the importance of the Middle Way Approach), and the freedom of religion around the world. He, naturally, has come under fire, particularly from the Chinese Government for being a \"splittist\" and the religious minority of Dorje Shugden practitioners (a can of worms we don't need to get into here). Be that as it may, the Dalai Lama, in his promotion of a peaceful resistance against the Chinese takeover of Tibet, was awarded the Nobel Peace Prize in 1989. Thich Nhat Hanh is another very popular Zen Master who has been, arguable, the world's foremost promoter of Engaged Buddhism and World Peace, even nominated for the Nobel Prize in 1964 (no prize was awarded that year). Hindu yogis, though I'm not sure any have reached the high profiles of either His Holiness or the Venerable Thay, often times promote themselves in the same manner, or at least as animals of the same stripe - sitting by the Ganges and meditating upon extreme austerities, or singing Vedic hymns while practicing modernized yogic forms - but there's a long list of Yogis and Buddhist monks who actively flaunt or promote violence, particularly in recent times against Muslims, though we're quickly ascending into current events and out of history, but it's not like we can't find plenty of examples of Muslim/Buddhist-Hindu conflict pre 1999."
]
}
|
[] |
[] |
[
[
"https://www.reddit.com/r/AskHistorians/comments/bdbamj/wars_based_upon_opposing_buddhist_beliefs/el1syeh/",
"https://www.reddit.com/r/AskHistorians/comments/bu9cr8/what_exactly_is_slavoj_zizek_referring_to_when_he/"
]
] |
|
6aaygs
|
If we were on a spaceship traveling at a hypothetical 99.9% the speed of light and I spoke something to you, would you be able to hear me?
|
Since 99.9% the speed of light is faster than the speed of sound.
|
askscience
|
https://www.reddit.com/r/askscience/comments/6aaygs/if_we_were_on_a_spaceship_traveling_at_a/
|
{
"a_id": [
"dhd8mab",
"dhdaq2x"
],
"score": [
26,
16
],
"text": [
"The core principle of relativity is that the laws of physics do not depend on your frame of reference - they don't depend on your speed. This means that even the speed of light has to be the same for every frame of reference (i.e. as seen from every speed), and you have to change the laws of motion and velocity to make that add up correctly.\n\nSo if you and a buddy are in a space-ship moving at some high velocity, you can't even tell you're moving quickly without looking out the window. It's the same as driving in a car in a straight line at a constant speed - if you drop something, it falls straight down to the floor, and it doesn't fly backwards. The air inside the car or spaceship is moving with you, and so the sound doesn't \"know\" how fast you are going. From inside the ship, you should be able to talk perfectly normally and not have any issues.",
"Have you ever talked to someone on a plane trip? Have you ever talked to someone on the surface of a planet whose surface is spinning as fast as 1,000 mph (at the equator)? Yes you have. Speed is RELATIVE not absolute. You don't go 99.9% the speed of light. You go 99.9% the speed of light RELATIVE to some reference frame. Right now, as you sit there, relative to SOMETHING, say some far off galaxy, you are right now going at 99.9% the speed of light. Do you feel different? Switch your reference frame to the sun, BAM, now you're going 30 kilometers PER SECOND. Good stuff. Do you feel different? Switch the reference frame to your chair, now you're at rest. Do you feel different?\n\nThere is no difference between travelling at a constant speed and being at rest, they're the same thing, it's just a matter of switching reference frames. If you were on a ship going 99.9% the speed of light RELATIVE to the Earth, you, and the air in your ship, would still be at rest RELATIVE to you. So it'd be no different than if you were on a ship that was at rest relative to the speed of light. The only times things get interesting is if the air has a speed relative to you (which is wind). Or, of course, if you're going at 99.9% the speed of light relative to the Earth and you look AT the Earth, then you'll see some funny things going on on the Earth, but from your perspective you're at rest, so really it's the Earth causing it because it is the one going 99.9%. You're just sitting there in your space ship. Who's right? The Earth thinking it's stationary and you're going 99.9% of light, you think you're at rest and the Earth is going 99.9% the speed of light the other way? Both.\n\nThe weirdness of special relativity comes from the fact that light is the same in every reference frame, not that there are absolute reference frames. So if the Earth is heading towards you at a speed v, and sends a beam of light towards you, which relative to it goes c, you'd think that light would head towards you at v + c, but it doesn't it heads at c. And that's the crux. "
]
}
|
[] |
[] |
[
[],
[]
] |
|
3chzyz
|
what kept the heads of medieval arrows on the shaft
|
talking about arrow heads like the log bodkin which wraps around the outside of the shaft, not heads like the saxon heads that have a tang. i can't see any indication of nails having been used and surely they weren't simply glued on, but i can't seem to find anything on what keeps the friken arrow head from just falling off the shaft.
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/3chzyz/what_kept_the_heads_of_medieval_arrows_on_the/
|
{
"a_id": [
"csw3jn8",
"cswfwwl"
],
"score": [
6,
2
],
"text": [
"The arrow socket would have been glued to the tapered point of the shaft, very quick and easy to make. Arrows were disposable so didn't need to be made sturdy. Also if the head falls off after you've shot the arrow its much more difficult for your adversaries to shoot it back at you! ",
"Beeswax is often mentioned as the adhesive in question. The arrowhead is meant to come lose in the wound in english arrows. Heads that get stuck in bone are very likely to cause complications. Below is an article that quotes Bill, Joseph Howland, “Notes on Arrow Wounds,” American Journal of Medical Sciences, 154, 1892, p. 366.\n\n_URL_2_\n\nContrary to the claim above, arrows are quite sturdy (they need to be if shot from a +120# warbow, lest they blow up upon release or break when they hit something hard) and by no means disposable. Eastern military arrows usually have some sort of colour where the fletching (at the \"head\" of the arrow) is (red, orange or white), which helps to find them afterwards. They're also tanged, with sinew wrapping at the foot, which improves durability. \n\nThe shafts of the Mary Rose show remains of a verdigris compound around the fletches, which would have produced a bright green and could also have had conservatory purposes. These war arrows are quite sophisticed, basic info found here: _URL_3_\n\nMaking arrows is quite labour intense. To give you an idea, you need to season the wood, splitting it down, saw to scantling, planing, barreling and sanding the shafts, putting on the feathers, glueing horn inserts for the nocks, etc.\n\nI'm better versed in eastern tackle, so here's an article about bow and arrow prices in Qing China in 1802. You'll see that a single war arrow almost costs as much as a regular worker makes a day.\n\n_URL_1_\n\nQuite sophisticated: \n\n_URL_0_"
]
}
|
[] |
[] |
[
[],
[
"http://i.imgur.com/EMIbsa1.png",
"http://www.manchuarchery.org/bow-and-arrow-prices-1802",
"http://allthingsliberty.com/2013/05/battle-wounds-never-pull-an-arrow-out-of-a-body/",
"http://www.theenglishwarbowsociety.com/tudor-livery-arrow_EN.html"
]
] |
|
1yug5h
|
why do huge corporations have such a long interview process (i mean ... months and months)?
|
I'm a senior programmer, I applied for a job on a big tech company website -- if you listed the 5 biggest tech companies you can think of, it's one of those.
Had a phone interview in two weeks, three weeks later, interviewed with a local manager, three weeks later interviewed with a senior manager remotely, it's been a week again -- still waiting, wondering whats next
A friend who works for a different huge tech company told me for him from application to job offer took four months.
Why does this take so bloody long?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/1yug5h/eli5_why_do_huge_corporations_have_such_a_long/
|
{
"a_id": [
"cfnuyts"
],
"score": [
2
],
"text": [
"they are investing a huge amount of money and faith in you that they are very cautious over who they are going to invest in. Don't be surprised if you pass the senior manager you may be interviewed by the group before possibly being hired. "
]
}
|
[] |
[] |
[
[]
] |
|
2w3kuh
|
Did WWII Soldiers have a preference between the Pacific and European front?
|
I know many soldiers did not have a choice because they were drafted into whatever branch needed bodies, but did soldiers who enlisted normally lean towards the army because they would most likely get sent to western Europe or the Marines or Navy because they would most likely get sent to the Pacific?
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/2w3kuh/did_wwii_soldiers_have_a_preference_between_the/
|
{
"a_id": [
"conyuqo",
"coo9nbf"
],
"score": [
11,
2
],
"text": [
"The 2/1st battalion of the 6th division Australia fought in both North Africa, Crete and Kokoda in the South Pacific. Veterans of both have said that the pacific was far worse. They suffered greatly in the hot humid conditions. With the large amount of rain malaria and dysentery were common. The other thing was in such thick jungle and tiny paths seeing more then a couple of metres in front of you was next to _URL_0_ give an idea of the conditions here is a photo of the track.\n\n_URL_1_.\nSource australia goes to war 1939 to 1945 by Robertson J.",
"From my understanding U.S. GI's much preferred fighting in Europe to the pacific front. A major reason being the Japanese rarely surrendered. The Japanese also did not adhere to any standards of war, often targeting medics and casualty depots. It was perceived that the Japanese were fanatics and this caused a worrying sentiment in the allied pacific front. "
]
}
|
[] |
[] |
[
[
"impossible.To",
"https://www.awm.gov.au/collection/026852/"
],
[]
] |
|
wlonu
|
how china transfers power from one leader to another
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/wlonu/eli5_how_china_transfers_power_from_one_leader_to/
|
{
"a_id": [
"c5egsc5"
],
"score": [
3
],
"text": [
"Consensus among Politburo Standing Committee Members. Publicly, at the end of each Party Congress, the new lineup of PSCM suddenly appears on TV in a big showy event. \n\nIn reality, there is a lot of horsetrading going on among the Politburo members, making sure that someone from their own faction gets a seat or blocking the ascension of someone they dislike. So, essentially, the Politburo is a self-perpetuating elite group - they just pick their own successors.\n\nThe President, the Premier, the NPC Chairman (kind of like speaker of parliament) are limited to two 5-year terms. So there's that institutional framework which guarantees a new lineup of leaders every 5 or 10 years. The no. 1, 2, 3, positions in the party correspond to those state posts, respectively. The Party now prefers that state leadership correspond to party hierarchy. And there is an informal agreement among leaders to prepare to retire once they enter their 70s. \n\nBut beyond that, no one REALLY knows what goes on during Politburo meetings because it's all secret. \n\nOK, this makes more sense with some historical background: The current power transfer system was in reaction to the cult of personality and totalitarian excesses of Mao Zedong (r. 1949-1976) and the rather clever vision of Deng Xiaoping. Under Mao, succession was a mess. His first successor, Liu Shaoqui (the president of China) was unceremoniously deposed during the Cultural Revolution and then cruelly persecuted by the Red Guards until he died in prison. His second successor, Defense Minister Lin Biao, died in a plane crash in Mongolia, fleeing after plotting a failed coup d'etat against Mao. His third successor, Hua Guofeng, did end up assuming control after Mao's death, but he was a weak and uninspiring leader and within two years he was outmaneuvered and shoved aside by Deng Xiaoping. \n\nDeng Xiaoping (ruled c. 1978-1993 or 1997) is most famous for introducing free-market capitalist reforms which spearheaded China's remarkable economic growth that turned it into what it is today. But what is less remembered is that Deng was also the architect of a new political order and a new way to transfer power in China. He was surrounded by ancient party elders (people in their 80s or older), many hostile to economic reforms. He wanted them out of the way but he didn't want to go back to the violent intra-party struggles and purges under Mao. So instead he created the Central Advisory Commission and coaxed party elders to retire but still retain some prestige and influence through the CAC. Thus, Deng created a way for party leaders to leave office without fear of persecution or complete loss of power. Even today, Jiang Zemin and Li Peng (old retired leaders) still retain some influence on the Politburo and elsewhere.\n\nIn 1983, a new constitution was created which outlined the new rules for political office holding and such. Deng also was careful in picking future leaders that represented different party factions in order to force people to cooperate. So Jiang Zemin, his successor as party leader, was from the Shanghai faction but Jiang could not choose his own successor as Deng also made sure that a young guy named Hu Jintao was chosen as vice-president and then as the next leader. There is a rumor that Hu Jintao's successor, Xi Jingping, was not Hu's preference but the rest of the Politburo insisted on Xi's accession to prevent one faction from dominating the rest.\n\nThis is important to consider because the power transfer system in China is still a work in progress. The current transfer going on now is the first one not planned out by Deng and it already had a few hiccups (like the Bo Xilai scandal). Going back earlier, in 2003-2004, during the last transfer, there was another hiccup. Jiang Zemin was reluctant to relinquish all power - especially to Hu Jintao, a guy not chosen by him, from a rival faction. To the surprise of many, Jiang retained his final leadership post of Chairman of the Central Military Commission (I should explain - China's top leader since 1993 has always held 3 posts - President, Party General Secretary, and Central Military Commission Chairman. Jiang relinquished control of the presidency and the party but not the CMC). There was a mini-uproar among China's elites that Jiang is messing up the orderly succession plan laid out by Deng and a group of generals even published some sarcastic, nasty editorial articles criticizing the act. Eventually, Jiang did resign from his CMC chairmanship in favor of Hu Jintao. But it set a new precedent where the outgoing leader could hold onto the CMC a bit longer as Hu Jintao will do when he retires this year. \n\nThis makes more sense when we remember that under Deng Xiaoping, the military became much more important and autonomous as a political force. And direct control of the military is through the Central Military Commission. So in many ways, controlling the CMC was the key to real power in China. Even Deng Xiaoping, who famously never held any important post (except for a brief stint as Vice-Premier), always held onto his chairmanship of the CMC. \n\nSo, in conclusion, the new system of power transfer is to prevent a recurrence of another Mao-like dictator, ensure rotation of leaders, and presumably, stable political governance. \n\nIncidentally, not all Marxist countries are like this. In Vietnam, for example, they actually hold real elections within the Party to elect the top party leadership and there's all kind of politicking and campaigning. This is different from the \"elections\" held in China's Party Congress, which just ratify decisions made beforehand by the Politburo. "
]
}
|
[] |
[] |
[
[]
] |
||
9kq4f4
|
why do people buy sports video games every year despite them roughly being the same game as the previous year?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/9kq4f4/eli5_why_do_people_buy_sports_video_games_every/
|
{
"a_id": [
"e70wf7q",
"e70wlrt",
"e70wmcv",
"e70wwlu"
],
"score": [
5,
3,
2,
4
],
"text": [
"First of all the team lineup changes and so do the player stats. Second they put in enough new features for it to be worth the $60 they are asking. Third because people usually want the newest and best stuff, if they released a newer version of a game you enjoy and play a lot, odds are you will buy it even if it’s been only a year since you bought the last one. Fourth, it’s like saying why watch football? It’s basically the same game every time, well it basically is because the rules are standard and the plays themselves aren’t extraordinary from one game to another, but there are lots of reasons to watch a game even though you’ve seen 1000 football games, it’s not like if you have seen one you have seen them all.",
"Well, except for slightly better graphics and physics, you get updates for players, clubs, stadiums and other staff. You can look at this as a subscription for the current information. Expensive subscription, but you want to have latest info, right? \n\nBy the way, I always find it interesting to play the previous year FIFA, because I can buy a player who suddenly becomes a star in this year. ",
"You and all of your five year old mates like to play chase at playtime. Next year, you will grow up to unlock another playground, where all of the best chasers will go and play a new, slightly improved version of the same game, with the latest chase players and chase team kits. There will also be competitions and leagues happening that every chase player wants to partake in.\n\nAll of your friends will move up, and so can you, if you’re willing to fork out your lunch money for the privilege, otherwise you’re stuck playing in a playground with less games of chase.\n\nIt’s pretty much so that you can stay relevant, if you buy the latest sports games it’s highly likely you’re an avid sports fan and half the fun is playing as your favourite teams and players in their current state, that match the teams you watch in real life. ",
"**Roughly** the same is the important word.\n\nAnnual iterations in sports games usually do things like reflect player careers, transfers, a team's position in league or world rankings. There are minor refinements to the game mechanics and iterations on the graphics, too.\n\nBut it's the accurate representation of the actual players and personalities that are the real draw for sports fans.\n\nFor example: I like cricket. If I played a cricket video game, it'd be a bit incongruous to me if it had Andrew Flintoff and Graeme Swann on the England cricket team, Chris Gale playing for the West Indies, and commentary by Henry Blofeld because all those men are retired.\n\nFor soccer games you might have one team's star player who's now transferred to a completely different team. If you're playing the 2008 version of an NHL game then the Stanley Cup champions would be the Anaheim Ducks, but at the time of writing the most recent holders of that championship are the Pittsburgh Penguins.\n\nThat may not sound like a big deal if you're not interested in the game, but to the fans it makes a difference. \n\nTo translate it into more general gaming culture...\n\nImagine if you were playing an Elder Scrolls game set sometime after Skyrim, and suddenly the Nerevarine showed up.\n\nOr a Fallout game set in 2277, when suddenly you're visited by the vault dweller from Vault 13, the protagonist of Fallout 1, which was set in 2167.\n\nOr you're playing the latest Dragon Age and then King Cailan walks in the room fully alive and healthy. \n\nOr maybe you're playing Spider-Man swinging around New York when out of the blue a Green Lantern drops in and tells you that you've inherited Captain Picard's lightsaber, which you need to fix the TARDIS so the spice can flow.\n\nTL;DR - Think of it as updates to avoid clashing with the lore."
]
}
|
[] |
[] |
[
[],
[],
[],
[]
] |
||
3rvezy
|
why is there a difference in voltage between america and pretty much the rest of the world (240v vs 120v i believe) and what are the impacts of this in terms of energy transport/conservation and usage.
|
⚡⚡⚡ Wow, that's a lot of electric knowledge being passed around here. I'm buzzed! ⚡⚡⚡
ITT: Mostly discussions about water kettles.
For some really cool maps, click this link. ~~[Link](_URL_1_)~~
**Please don't click the [Link](_URL_0_) anymore, I'm afraid we are reddit-hugging the world's power grid to death. ( ͡° ͜ʖ ͡°)**
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/3rvezy/eli5_why_is_there_a_difference_in_voltage_between/
|
{
"a_id": [
"cwro6jk",
"cwrolke",
"cwrony4",
"cwrow44",
"cwroyna",
"cwrp0ec",
"cwrp0np",
"cwrpaa4",
"cwrqec1",
"cwrqim8",
"cwrqotd",
"cwrr2jv",
"cwrrcq4",
"cwrrpw2",
"cwrs9ns",
"cwrtbfg",
"cwrtg8y",
"cwrug22",
"cwruiby",
"cwrukvf",
"cwrv5nz",
"cwrvrsi",
"cwrw82z",
"cwrwira",
"cwrxa5u",
"cwrzrov",
"cws08pm",
"cws0uwm",
"cws1dh2",
"cws3oj7",
"cws40h4",
"cws54bt",
"cws5xhd",
"cws63zi",
"cws68di",
"cws9bw7",
"cwsc65o",
"cwscjyl",
"cwse79f",
"cwsgj2n",
"cwugbs6"
],
"score": [
2347,
3,
2,
25,
114,
37,
479,
13,
19,
8,
35,
13,
2,
2,
68,
2,
437,
2,
2,
2,
2,
2,
2,
8,
2,
2,
2,
3,
16,
3,
3,
5,
7,
4,
2,
6,
3,
3,
3,
2,
2
],
"text": [
"Every country developed their basic infrastructures independently with different scientists and during an era that communication between countries took days at best, weeks on average, and sometimes months if conditions were bad. As time progressed infrastructures and communications were improved and those countries that lived next to each other often started to share standards and even interconnect their infrastructures. The US being mostly geographically isolated kept its own standard. Our neighbors match our standards. ",
"120/240 V is the residential voltage standard, used over short local distances. It doesn't say anything about the voltages used for power transmission over longer distances. So, if you're looking for some kind of general conclusion about overall energy efficiency, you're not going to find one, I think. ",
"This is the main reason transformers have dual primary windings, so they can produce the same output for both 120v and 240v.",
"Bonus: Different rail way voltages through-out Pan-Europe.\n\n\"Likewise, electrification of lines varies between countries. 15 kV AC has been used in Germany, Austria, Switzerland, Norway and Sweden since 1912, while the Netherlands uses 1500 V DC, France uses 1500 V DC and 25 kV AC, and so on. All this makes the construction of truly pan-European vehicles a challenging task and, until recent developments in locomotive construction, was mostly ruled out as being impractical and too expensive.\"",
"The US were the first to build a large-scale power grid. At that point, ~110V was the maximum lightbulbs etc. could handle without burning out. As you want as high voltages as possible to keep losses, cable strengths, etc. down, this was chosen (instead of something arbitrarily lower).\n\nBy the time Europe electrified (around 1900, **not** post-WW2!), light bulbs could handle 220 volts. Or 230. Or 240. All three were in use in various European countries until the EU equalized everything to 230 volts.\n\n220+ volts has advantages. Why not switch?\n\n* Because it's expensive. The EU harmonization took *13 years*, and it was a minimal change for all countries involved (10V difference each). Converting from 110V to 230V is flat out impossible.\n* Because it, ultimately, doesn't really matter. 110/230 Volts is mainly used inside buildings, everything long-distance is running at several thousand (or tens of thousands) of volts. And even inside buildings you have three-phase sockets with 400V, if necessary.",
"the biggest impact I see for local low voltage wiring in the US (110V) compared to other countries (230V). To maintain equipment operating conditions, larger copper cross sectional area cables are required in the 110V system as the currents are (comparably) higher and therefore suffer more voltage drop. ",
"It's because of light bulb technology. The early bulbs could only operate at lower voltages (Edison settled on 110V) but later bulbs with metal filaments could operate at 220V. This meant that power could be transmitted at higher voltage, which is more efficient. The change was pushed by a German power company. [Per wikipedia:](_URL_0_)\n\n > In 1899, the Berliner Elektrizitäts-Werke (BEW), a Berlin electrical utility, decided to greatly increase its distribution capacity by switching to 220 volt nominal distribution, taking advantage of the higher voltage capability of metal filament lamps. **The company was able to offset the cost of converting the customer's equipment by the resulting saving in distribution conductors cost.** This became the model for electrical distribution in Germany and the rest of Europe and the 220-volt system became common. North American practice remained with voltages near 110 volts for lamps",
"So wait... American here, slightly confused. (Go figure) So when the rest of the world plugs in a toaster, you're plugging to 240v? What about plugging in a clothes dryer? Here in the USA we have \"split service\". 120/240vac. 2 legs come into the house from the same phase at 120 v leg to ground. Leg to leg however is 240v. We plug our toaster into 120v but our clothes dryer (and other things) into 240v. As to why, the other examples given make sense... lightbulb, tesla, and such. But I will say with 120v being less pressure, while higher gauge wire is required in the home it is nicer to be shocked by 120v instead of 240v. Not to mention our wire sizes for home are 14, 12, 10, and I forget for the clothes dryer but I think that's like 2. As far as the grid goes, that's usually 2 aut, 3 strand from the transformer to the house. Before the transformer depending on how old the part of the grid is you either have 4kv or 13kv. 13 is the more common one these days but you will find 4kv in some places still.",
"208-240v is what us run to almost every house in the states. All it is is two legs of 120v. And your 120v circuit is just one hot (120v) and a neutral wire which carries no voltage. \n\nThe main difference is the hertz rating they are generated at. The United states does 60 hz, most other places do 50 hz. \n\nThere are voltage differeces as well, high voltage commercial equipment in the states is 460-480v three phase. High voltage in Canada is 600v I believe. I'm not sure what their low voltage three phase is though, ours is 240v.",
"Some FYI\n\nJapan also uses ~~110V~~ 100V as their standard. I haven't researched the reason but will guess it's something to do with US influence after WWII.\n\nEDIT\n\nThanks to the responses. \n\nu/Sakuromp corrected me in that Japan uses 100V; not 110V.\n\nu/cmfg provided [a link](_URL_0_) which explains the history behind the 50 Hz and 60Hz difference within the country.\n\nu/AppleGel also explains that \"the electricity grids in Tokyo and Osaka are both old, it's the same reason as the U.S. Also Tokyo land area uses 50Hz whereas Osaka land area use 60Hz because they bought different systems in the beginning assuming grids would never need to be connected.\"",
"Most of Europe now uses 400V phase-to-phase, and 230V phase-to-neutral. Earlier 230V Isolated Terra (IT) 3-leader power system was the norm, but they are now using a 400V Terra Neutral (TN, with variances TN-C/TN-S/TN-CS) 5-leader power system where you have 3 phases and a terra leader split into protected earth (PE) and a neutral (N), which gives you 400V between phases and 230V between phase and neutral. Although it's true that you deliver high voltage to the transformer on each street and step it down there, you still have 100's of meters with low voltage cabling to reach each house, and this is enough to save power by going to 400V instead of 110V or 230V. Copper, which most low power cables are made of, is very expensive and so any incentive to reduce the thickness and amount of copper needed, is money saved. Alu-cables are used too, because they are much cheaper, but they don't conduct as good as copper so you have to increase their size and thicker cables are a nightmare to work with. There are several other advantages with this system too, like the size of earth fault currents, but I'll need more space and time to explain that.",
"Now all this is confusing me. When I wire a house we use 15 amp breakers on all plugs and lights except for kitchen and those are 20 amps (aside from big appliances) we run 120v (14/2) and 240 (14/3). It's neither 110 or 230.... I am only in my first year for my apprenticeship so I don't have much knowledge.",
"In Brazil, the voltage is different depending on where you are in the country. I'm 220v where I live but Rio and Sao Paulo are 110v, so you need to be careful when you buy electrical goods on the internet. A lot of the time you're just grateful to have any electricity as blackouts are pretty regular. ",
"Why does the uk and Ireland have different shaped plugs to the rest of Europe? \n\nFrance is so close to the UK but went for two round prongs instead of the UKs three square prongs. ",
"On a mildly related note, while researching this I found a cool map that shows the [US power grid frequency in real time.](_URL_1_)\n\nEdit: There's also one for the [whole world too.](_URL_0_)",
"The scanner I bought in America cannot be used when I am back in China even though I have bought three AC adapters! I have been frustrated.",
"First off, America uses a range of voltages for consumption. 120V is the most common for residential, though most houses also have 240V for larger appliances. 208V and 277V are the norm for commercial, and 480V and above can be found in industrial settings. So the US isn't homogeneously 120V everywhere. I'll return to this in a bit.\n\nSecondly, it's all irrelevant (mostly) for transport costs. This is because the end-user voltage (120 or 240) is only present for like the last 0.5% of the journey from the power station. Prior to that, the electrical power is transmitted at much higher voltages - up to hundreds of kV.\n\nBack to end-user voltages now. For residential (where there exists this US-global disparity), there really isn't a major difference in terms of conservation. The lower voltage requires higher current to drive similar devices, basically double in this case (but it's the same wattage regardless, so energy use is roughly equal). It's the reason commercial users typically need 208 or 277V service, because they have far more wattage on any given circuit (think of the lighting in a typical store compared to a house), so to reduce the current/heat/wire size they want higher voltage. Running larger wires over the longer distances in a store would be very expensive.\n\nHowever, in a house there isn't much distance from breaker panel to end outlet, and many electricians will just use larger-than-necessary wire sizes (#12 instead of #14 where applicable) to avoid nuisance tripping since the added cost isn't huge for such a small installation. And that's really it: for the small amounts of wire being used on any given house, the added cost of thicker wire isn't significant enough to be a huge issue. If we switched to 240V-all residential service, and shifted wire sizes down one step across the board, you'd be saving like $400/house.\n\nOn the other hand, those higher voltages (240V) are a lot more dangerous than 120V. While in a commercial setting you can be fairly sure some dumb kid isn't going to lick a receptacle or an idiot homeowner isn't going to try rewiring everything live, you can't be sure of that in residential. Going with the slightly more expensive but safer 120V makes sense.\n\nAlthough as others have pointed out, it started as a historical accident, the code could've been changed at any time, as it is almost yearly, yet we've stuck with 120V for residential all the same.",
"Besides the historical difference as others have mentioned, and how costly it would be to retrofit to different standards, 220v is intrinsically more efficient due to heat losses.\n\nFor given wattage, say a 1100W microwave oven, since Power = Current * Voltage (P=IV), for 110V @10A and 220v @5A.\n\nVoltage is Current*Resistance (V=IR).\n\nIf you manipulate the equations, P=I^2 R. [This equation solves the power lost as heat due to Joule Heating.](_URL_0_)\nTherefore, for given Current and conductor resistance, power lost as heat is HUGE as current increases.\n\nPower Received = Power Generated - Power Lost during transmission. \nTherefore if the sending voltage is low, the current will have to be high make up for low voltage, but it'll all get lost in the form of heat and not much will get to the end point. That's also the reason why it make sense for main power lines have extremely high voltage. ",
"Also worth mentioning that higher voltage can be carried through smaller wire, greatly reducing the cost of wiring. ",
"ELI5: Is one system superior to the other? I'm Canadian, but once had met a Kiwi electrician at a bar and through a drunken ramble he explained how our system was inferior but I didn't really understand his logic. ",
"I live in Toronto, Canada.\n\nIn the early 1950's our house and many others in the eastern part of the city had 25 cycle (Hertz) 120 Volt electrical power. Visitors coming from other parts of the city would comment on how our lights seemed to flicker.\n\nOne day a crew from the power company came and changed as many frequency sensitive devices as they could so that they would operate on 60 Hz. record players, clocks etc.\n\nWe didn't have a television at the time and I don't know how they remedied these devices. It would be interesting to hear from anyone else who also experienced this transition.",
"The 230V and 110V just matter for the end user since the ac voltage can be transformed up and down. Outside in the distribution network it doesnt matter overall. Benefits on both standards: 230V can deliver much more power on the same cable stength and so also can be used over greater distances. 110V ist less likely to kill you. \nAnother difference in the ac frequency. It can only be converted into another with expensive equipment, especially at high power like in the distribution net. Benefits: At 60Hz the voltage can be transformed more efficently. 50Hz has less transport loss in the distribution network, caused by the skin effect. \nSo both has it up and downs...",
"Just 16 miles off the coast of Canada, there are households with 220V outlets. I wonder how many Canadians know where that is and why? It was my rebuttal to some Canadians who were making fun of typical American knowledge of geography. Thank god for Google Maps.",
"There are pros and cons to both systems, as described in the linked article. Some of it is technical, but it should enlighten.\n\n_URL_0_\n\n\n",
"The higher the voltage, the smaller the wire needs to be to perform the same work. Watts are what is required to perform work. Wire size determines the Ampres that it can carry.\n\nWatts = Voltage * Ampres\n\nSo as Voltage goes up, Ampres goes down.\n\nIf your George Foreman Grill requires 1500 Watts, at 120 volts, that draws 12.5 Ampres. At 240 volts, that drops to 6.25 Ampres.\n\n(Yeah, I know P=E*I, but this is ELI5)",
"I'd be curious whether there's going to be a problem once low voltage LED lightning systems start getting integrated into new homes. Whether the larger step down at the house creates any extra inefficiencies.\n",
"How dangerous is it to run equipment on different loads than they're supposed to be? I was at a hotel working with electronics and their circuits were 126-129 volts...",
"European voltage makes my laptop conduct electricity and my headset hum when plugged in. Probbably bad but meh, no problems so far.",
"I live in Brazil..and it's weird. The voltages seem to be random.. sometimes 110, 127 or 220v.. Also the outlets are sometimes fitted like European style, sometimes American. Everyone carries around adapters.. This doesn't help explain anything. ",
"America : greater transmission losses(they can afford that though) and household appliances are safer. However greater risk of electrical building fires\n\nRest or world: lower transmission losses, greater risk of appliance fire but lower risk of building fire. \n\nHope you enjoyed the ELI5...",
"By the way, Canada, USA, an Mexico all three have 120volts, and in the US and Canada, equipment that uses more energy usually uses 240 volts. Things like clothes dryers, electric ovens, large air conditioners, and a lot of garage equipment like welders and large air compressors. Most mexicans dont even have 240 volt circuits.",
"A friend of mine who worked on power systems at one point in her career told me: \"the difference between 120 and 240 is about ten feet.\"\n\n(As in, how far you're thrown if you touch it.)",
"England developed their power lines to use a higher voltage specifically so their electric kettles would heat their water faster for afternoon tea. Kidding. \n\nBut actually, during popular televised events like football, power stations in the UK have to activate more turbines during commercial breaks because everyone gets up and makes tea at the same time.",
"120v is safer. That is why the US uses it. 120v provides enough power for small appliances at reasonablr currebt levels and is far less likely to electrocute someone. For large appliances we can simply use two 120v line 180 degrees out of sync and still get 240v.",
"I'm buzzed too. But that's from the day drinking. \n\nAnyway, great question. And thanks for the thoughtful discussion, all. ",
"Haven't seen anyone talk about the frequency differences yet, so I'll chime in. The US uses 60hz because it divides nicely into seconds:minutes:hours. In fact, many older clocks and pieces of industrial equipment used to take their timing directly off grid frequency, no timing circuit required.\n\nEverywhere else uses 50hz because it's a nice round number that makes doing higher order power calculations easier. Just like the metric system vs imperial system, easier math for the former, more relatable shorthand for the latter.",
"can I also add a question? whats the point of a neutral? can you get shocked by a neutral? I recently had to adapt a four pronged plug to a 3 pronged plug in 240 and I was told to just use the ground as the neutral as they were pretty much the same.",
"Something important to note about transporting electricity is that higher voltages transport energy more efficiently than lower voltages. In the Navy we generate power at very high Voltages to transport it around the ship, then step it down to lower voltages for major pieces of equipment (RADARS, AC plants, Ovens, etc), and step it down even further to the 120 you know and love to plug in your laptop or run a lightbulb.\n\nPractically this saves weight and money because metal is heavy and expensive. Think of how much electricity runs through power lines every day and how small those cables are. If you were to run a lower voltage the same distances you would need a MUCH bigger line which is heavier and more expensive to transport the same amount of power due to loss.",
"Not sure why everyone is giving you false information. Wattage is Amps*Volts, so at 240V the amperage for the same power usage is actually a little less than half of what it would need to be at 110V. There's a reason data centers frequently use 240v instead of the standard 110, and that's because it's more efficient, not less. No idea why America is so far behind the curve (likely fear, since 240V would be more of an immediate danger to someone being stupid around an outlet), sorry, but it was painful to read the blither of nonsense people are suggesting about 110V actually being the efficient solution. Do you really think the only country in the world that refuses to use international scientific notation is ahead of the curve in electrical infrastructure?",
"Just as a point of perspective, you shouldn't consider it America vs *all the other countries*. In broad terms, you should really only consider it North America vs Europe, which is about 400 million vs 500 million people, and 52 European-country-sized jurisdictions vs 20 some European countries.\n\nIt's not some sort of hold-out or anomaly, it's just two different standards with comparable utilization.",
"The higher the voltage, the thinner gauge wire that can be used due to less resistance. Higher voltages are more dangerous, but cheaper to implement. In very poor countries, 440V is sometimes used (\"illegally\") to reduce the cost of the wiring even further.\n\nAlso, Japan is also on 110V."
]
}
|
[] |
[
"http://powerit.utk.edu/worldmap/",
"https://www.reddit.com/r/explainlikeimfive/comments/3rvezy/eli5_why_is_there_a_difference_in_voltage_between/cwrs9ns"
] |
[
[],
[],
[],
[],
[],
[],
[
"https://en.wikipedia.org/wiki/Mains_electricity#History_of_voltage_and_frequency"
],
[],
[],
[
"https://en.wikipedia.org/wiki/Electricity_sector_in_Japan#Transmission"
],
[],
[],
[],
[],
[
"http://powerit.utk.edu/worldmap/",
"http://fnetpublic.utk.edu/gradientmap.html"
],
[],
[],
[
"https://en.wikipedia.org/wiki/Joule_heating"
],
[],
[],
[],
[],
[],
[
"http://electrical-engineering-portal.com/north-american-versus-european-distribution-systems"
],
[],
[],
[],
[],
[],
[],
[],
[],
[],
[],
[],
[],
[],
[],
[],
[],
[]
] |
|
109oey
|
What are some major disagreements among historians today?
|
I'm curious about theory, methodology, and things like that. I'm a history student, and whenever a professor goes over historiography, they tend to point out how things were done "wrong" before, but *now* we've got it right! Of course, every historian before them probably thought the exact same thing.
What about our understanding of historical events, people, and concepts? Are there many disagreements there? I can imagine that in ancient history there's a great deal to argue about, but what about better documented periods?
So what are the controversies, disagreements, and competing ideas modern historians are arguing over most often?
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/109oey/what_are_some_major_disagreements_among/
|
{
"a_id": [
"c6bll8q",
"c6blsax",
"c6blzng",
"c6bm6ix",
"c6bn0ri",
"c6bniw4",
"c6bo6iw",
"c6boa76",
"c6bobml",
"c6bow6n",
"c6bp757",
"c6bp79v",
"c6bpkhm",
"c6bpota",
"c6bq54j",
"c6bqqtf",
"c6bqtni",
"c6bt4r1",
"c6btxrp",
"c6bumay",
"c6bxoep",
"c6bxvxr",
"c6c2ufa",
"c6c675g"
],
"score": [
42,
32,
120,
84,
15,
7,
21,
6,
119,
78,
23,
10,
11,
4,
28,
5,
29,
2,
10,
7,
3,
3,
4,
2
],
"text": [
"Just a couple;\n\nBritish Historians debating the early Tudors, their legacies, intention, and powerful figures such as Cromwell and Woolsey.\n\nFrench Historians debating \"Marxist\" history of the French Revolution, against the modern revisionists. Mostly an older subject that has been all but settled, but never the less a good example of Historiography and how perceptions change.\n\nThere's also the infamous African American history, debating \"chicken or the egg\" style whether racism or slavery came first. Much of the works of earlier scholars that emerged in the early 20th century also hailed slavery as a peaceful institution based on journals and vivified the image of the benevolent, paternal planter. Wasn't until quite recently that modern scholarly understanding emerged (1990's~) with some modifications.\n\nIn the Middle East there's plenty of conflict between scholars over motivation of rulers, questioning whether they were a puppet regime, or just fucking batshit crazy. Really could go either way in about every case...However much harder to solve because Western countries have gotten incredibly good at manipulation.",
"Oy vey, my American history professor opens up every lecture with a discussion on Populist and Progressive historiography. Apparently, nobody's quite sure how reformist the Progressive reformers were, and whether or not they were really a bunch of insecure middle-class white men. For a more specific example, most historians think the Progressive Era started in the cities, but there's one political scientist, Elizabeth Sanders, who argues it started in rural areas. I find her argument fascinating. \n\nModern historians focus *far* more on marginalized groups than they used to, which is where I think a lot of that sense of \"*now* we've got it right!\" comes from. Like, yeah, a lot of the Progressive reformers really were insecure middle-class white men, but now historians have done research into women's activities and realized that there's a whole bunch *more* that went on. It's not that we're correcting the picture, but getting a more nuanced version of it, yeah? I'm quite interested in women's history, but 100 years ago, women's history wasn't a *thing* people studied. Nowadays, I can write \"modern women's history\" on my graduate school applications, and people will get it.",
"In Biblical Archaeology, there are issues debating the chronology of certain digs dated to the Iron I-IIa ages. Some dates simply don't match up, and Archaeologists are proposing their own explanations.\n\nIsrael Finkelstein, proponent of the \"Low Chronology\", says that some sites traditionally dated to the 11th-century BCE, should actually be dated to the mid 10th century BCE (Datings aren't always absolute, some are based on stratigraphy, and this kind of datings are relative).\n\nThe most prominent critic of the Low Chronology is Amihai Mazar, who proposes another solution, called the \"Modified Conventional Chronology\", which does other adjustments to the datings. It's pretty complicated stuff and the available material to common laypeople is scarse, but the implications of which choice to make aren't small - Finkelstein's proposal implies that King Solomon didn't exist, for example, and that his legend was created in the late 8th century BCE for political reasons.\n\nAnd then of course, are the scholars with an Orthodox Jewish vision of Ancient Israel, who believe everything in the Bible must be literally true, from Genesis and Exodus to the Chronicles of the various kings of Israel; these are rare, but very noisy.\n\nAnd in another extremist view, there are the Biblical minimalists, who claim that everything in the Bible is an invention dating to the Persian and Hellenistic periods; Don't pay too much attention to these ones, they're dismissing tons of existing evidence already.\n\nAnother debate is whether the ancient Israelites worhshipped goddess Asherah as a companion of Yahweh; William G. Dever is the proponent of this controversial hypothesis, explained further in his book \"Did God have a wife?\" (EDIT: It is accepted that Asherah was given cult, there is much evidence about it; but her relationship with Yahweh in cult is another matter).\n\nAlso, Dever and Finkelstein have had their disagreements regarding chronology, and at a point it went down to insults, with Finkelstein calling Dever a \"parasite\", and so on.\n\nImagine all these disagreements for the common man; it's a maze of opinions and you can't really distinguish the truth from extremist ideas and fanaticism. But the more you read, the more you realize that everyone (EDIT: except the orthodox and the minimalists) has valid points to make, so you have to read a lot to form your own opinion.\n\nI really recommend reading the book \"The quest for the historical Israel: Debating Archaeology and the History of Early Israel\", which contains articles from both Finkelstein and Mazar, where they explain their own viewpoints.",
"Periodization and particularly regnal dating make for a slow burning controversy that will probably never go away. Basically, is there any analytic utility in referring to periods based on who the monarch was (eg. Elizabethan, Jacobean, Victorian, Edwardian)? Especially in periods where the monarchy isn't exercising political power? And what about when someone reigned for such a long time that society changed dramatically underneath them-- aren't problems created by linking those changes with regnal periods? For instance, what if some of the key trends we think of as 'Victorian' began well before Victoria ascended or stopped while she was still on the throne and none of them had much to do with anything she was doing?\n\nHow do we chop up the past into chunks for the purposes of teaching and analysis? If we're doing it on the basis of perceived continuities or specific factors how do we decide which factors to use? What about instances where our perception of a significant change clashes with what people at the time thought or strove for? For instance, the 'Tudors' or a Tudor period. Undoubtedly there are huge revolutions in the constitution and administration under Henry VIII, but on the other hand Henry VII was quite keen to portray himself as a legitimate union/continuation of the Yorks and Lancasters. Calling them Tudors at all is in fact quite a modern phenomenon and none of the monarchs lumped into that category would have thought of themselves that way. So should we be doing that? \n\n",
"The Paraguayan War: was it caused by British Imperialism interests against the local power of Paraguay, or was it caused by the consolidation of the National States in Platine America?",
"My little corner of the world is thinking about the modern environmental movement: what caused it to surge in popularity when it did? Was is a suburban movement, a college radical movement, a philosophical turn, a result of new scientific vision, an urban anti-pollution movement, a place for foiled anti-war protestors to turn, or a direct reaction to insanely out-of-control mass consumer culture? *And*, did it matter? Has a modern environmental movement changed anything?\n\nI personally like the little fight people are having about whether we can say that an Industrial revolution happened, or if it's just too broad and diverse a thing to really label as a single event.\n",
"Other than the \"chicken or egg\" slavery and race question mentioned elsewhere, another major issue in my period is \"what caused the Civil War?\" Basically every historian has their own opinion and viewpoint, even though the general timeline is agreed upon by most.",
"In the study of history itself there are always debates between historians who focus on the importance of individuals and those who focus on the importance of trends. Do the times make the man, or vice versa? It is a bit like a chicken or egg debate.",
"Is oral history valid in academia?\n\nYou might just see a Historian throw a punch over this.\n\n",
"I'd say the BC/AD vs. BCE/CE battle continues. I'm in the camp that still uses BC/AD, because I think BCE/CE is just a goofy euphemism. It'd be more convincing as replacement terminology if it didn't use the same event for as the focal point.",
"History of Zionism/Israel post 1880s. The New Historians claim that Israel was the aggressor, the 'classical' historians claim that Israel was the aggressed. The New Historians claim that Israel started the exodus of Arabs from Israel; the 'classical' historians claim that it's a multi-factor reason on why Arabs left Israel. Never have I ever seen such [a large disagreement between two groups of academics.](_URL_0_) ",
"I love this question! There are so many active historical debates. My two favorites are: the cause(s) of the Cold War, and then my all-time favorite is of course whether or not Thomas Jefferson had an affair, and children, with one of his slaves (who just so happened to be his late wife's half-sister). There are so many huge implications to that question. It makes for a lively argument! I of course love the idea that TJ was capable of exploring an interracial relationship, while some of his known white descendants absolutely refuse to acknowledge the possibility, with historical experts landing on both sides of the debate. I won't lay out the whole historiography for you, but if you're interested send me a PM and I'll shoot you a copy of a 15 page historiography I wrote on the topic. It's very readable, and in my opinion, totally fascinating. ",
"Holocaust historians are divided into two major camps, the 'Structuralists' and the 'Intentionalists'. The former group argues that the \"Final Solution to the Jewish Question\" (the plan to industrialise the extermination of European Jews) evolved over the years, while the Intentionalists argue that Hitler and the higher Nazi echelon had more or less always planned to exterminate Jews.\n\nBoth sides have things going for them. The Intentionalists can point to Hitler's (and Goebbel's) earlier rhetoric, which points towards an intent to destroy the world of Jews. Nazi ideology argued that Jews were the main source of evil in the world and thus would need to be destroyed.\n\nHowever the structuralists have much more direct evidence to point towards. Secret Nazi documents strongly indicate earlier plans (prior to 1941) of forced migration. Furthermore, concentration camps were originally designed for political dissidents, rather than Jews.\n\nIt can get quite heated sometimes, with some Jewish intentionalists accusing structuralists or downplaying the significance/extent of the Holocaust",
"In my undergrad capstone I chose as a topic The Phalanx and the Othismos. It was on what actually happened in the *othismos*. *Othismos* in English means almost the same thing, it can mean physically pushing or it could mean a metaphorical push (i.e. the Americans pushed East, towards Germany in WWII) and there is little evidence or description of fights in classical greek warfare other than the word *othismos*. I tend to interpret the evidence as meaning a physical push and therefor the *othismos* was a formation of organized greek infant that fought in an organized manor, though some interpret it as an army vs army pushing match. So until we find a piece of papyrus in the Egyptian desert, historians have to make do with what little there is and fill the gaps with a little bit of logic (i.e. how do you move, let alone fight with a long spear, when there are in between 14 men. If it really was a pushing match why have such a long spear that would be useless at such a close distance?)",
"There are two major debates in South Asian History. \n\n1. How did the civilization of Harappan Culture, popularly called the Indus Valley Civilization come to an end? Some historians have a natural disaster theory, like a flood or conversely drying up and changing course of certain rivers. Others think it was a violent invasion by Indo-European people (Aryan Invasion), some Vedic texts point to the fact that on entering the country they destroyed several cities (I'm not sure of exactly which text). To make matters worse, there is evidence of writing but it has proved difficult to decipher thus far. \n\n\n2. The other issue for debate is more complex. It is also a collection of debates surrounding the historical authenticity of the two Hindu epics - the Ramayana and the Mahabharata. One particular debate centres on the city of Ayodhya in North India. Said to be the birthplace of Rama the protagonist of the Ramayana. It is here in the early ninetees that the debate temporarily left the realm of academics and was taken up by hooligans that destroyed a Mughal era mosque of the 15th (?) century, because of a claim that a temple to Rama had been demolished to build that mosque. The court case in which archaeological and historical debates have been used has been going on for about 5 decades. ",
"My history department was at war with post structuralism. ",
"There is a lot of debate as to whether or not Marco Polo actually went to China. While he was able to describe the Great Wall and chinese fabrics with great detail, he was incredibly off about other points (e.g. the way the people looked). It is speculated that he may have just asked various merchants along the silk road (a huge stretch of land where people from all places came to trade goods) what China was like and kept good documentation of it. Which, if true, would ruin a really fun game because I don't play games named after liars.",
"I'll just add my two cents. One problem always associated with the period 1640-1660 is how to define it. Was it a rebellion or a revolution? And which regional names can we use: just English or dare we use British (no!)? Historical trends keep changing what the vogue term to use is.\n\nAnother rather recent point of conjecture is the death of Charles I and how far was his execution planned. Sean Kelsey has written a number of articles since 2002 which convey a sense that the Rump parliament made the decision to execute rather late in January. For many years history students and academics have used his arguements as they were a fresh and new approach to this particular topic. However, in 2010 Clive Holmes embarked upon an article which systematically debunked Kelsey's arguement and even the evidence he used. Holmes' arguement certainly shed light on the matter and alluded to a much earlier date when the decision to execute Charles was made (early-mid January).",
"No one has mentioned my favorite disagreement so far. Which was more responsible for the Japanese decision to surrender, the atomic bomb or the Soviet invasion? \n\nI don't feel its worth rehashing here simply because I know that it's come up in a major thread in the last month or so but needless to say, I think it's a really interesting debate especially when we have access to primary sources from the Japanese military and diplomatic envoy to the USSR. \n\nI personally subscribe to the Soviet Invasion caused Japanese surrender view but I think both sides have really great arguments.",
"Some personal pet peeve disagreements I'd love to see answered someday:\n\nWas [Queen Elizabeth I]( _URL_2_) really a virgin?\n\n\nWho built the [Great Sphinx of Giza](_URL_0_)?\n\nWas [Lizzie Borden](_URL_3_) innocent or guilty?\n\nWho shot the \"[shot heard 'round the world](_URL_1_)\" and why?",
"I'm not sure if I would consider this controversy as I only observed this from two history professors. When comparing the present rate of globalization, one insists that it can be compared to past historical events while another believes that globalization in the 21st century cannot be compared to any past historical settings at all.",
"Regarding economic history, it all depends on which school of economics they belong to. My schooling was in New Keynesian, but I lean heavily towards classic Keynesian. Someone who prefers Chicago or Austrian will disagree with quite a bit of what I have to say.\n\nThere's pretty much a different opinion about how the Great Depression started, depending on the school. Chicago, New Keynesian and Austrian schools place the blame solely on the government, only with differing opinions on how much Smoot-Hawley played a role. Classic Keynesian includes the major lack of banking and finance regulations, such as corporations having the ability to print and sell stock with no accountability, and buying on the margin (basically taking a loan out to buy stock). The government gets blamed for pushing the Harding \"return to normalcy\" ideology, where American's were encouraged to buy with credit. Funny how history practically repeated itself over the past few decades. This is partly why famous economists, such as Bruce Bartlett (creator of Reaganomics), switched from Chicago school to classic Keynesian.\n\nWhile this may be a bit generalized, the best way I've been able to translate what each school's opinion will be on a particular era, is to summarize each school's basic ideology. Austrian will pretty much blame the government at all costs, this includes falsifying or omitting facts, just read a few articles on Mises and compare that to popular opinion to see what I mean. They push for laissez faire economics (free trade). This is why Austrian school is chalked up as a school of unproven theories, with no real basis in economics like the other schools (Hayek did earn a Nobel Prize, but that was due to McCarthyism, not because he was taken seriously). Chicago is very similar, but with a heavy emphasis on monetarist practices (centralized money control), they believe in supply-side economics (think if you build it, they will come). New Keynesian is like a combination of classical Keynesian and Chicago schools. It has an emphasis on supply-side economics, like Chicago, but believes in imperfect competition that effects prices (in other words oligopolies can heavily effect prices, like they do today). Classic Keynesian is certainly the least 'corporate-friendly' school, in that they believe in \"trickle-up\" (never use that term in front of an economics professor) or demand-side economics, in that if you redistribute a wealth glut that's formed at the top, then the people will sink it right back into the economy by buying products they demand, but often can't afford under normal circumstances. They also believe in imperfect competition and sticky prices. That's their opinions in a nutshell.",
"WWI: Who started it? Revisionists in the immediate decade following the war tried to absolve Germany, more modern scholars have placed a large amount of blame on Wilhelm II and his dismantling/retooling of Bismarck's policies/alliances to further more aggressive, expansionist policies.\n\nWWII: A-Bomb a war crime? Is the US only absolved because it won? \n\nUSSR: Was the revolution top down or bottom up? Intelligentsia or the people (or something else)? How do you explain the *fait acompli* that occurred when Petersburg and Moscow were successfully overthrown in light of any of these monocausal explanations given that the vast majority of the country didn't even know there was a revolution until as long as 2-3 years later?\n\nAztec/Mayan/Incan/etc. and Spanish conquest: Were the relatively quick and \"easy\" conquests of these regions the result of \"western supremacy,\" pure circumstance/situation (guns/germs/steal arguments about resources and ways society developed around their environments), the result of socio-religious structures (especially in the case of the Aztecs) that paralyzed the indigenous leader and populations, some combination, or something else entirely?\n\nThere are so many haha",
"Aside from the US and Turkey, just about the entire world recognizes the Armenian Genocide. [Hitler even referenced it with regards to the Holocaust.](_URL_0_)"
]
}
|
[] |
[] |
[
[],
[],
[],
[],
[],
[],
[],
[],
[],
[],
[
"http://en.wikipedia.org/wiki/New_Historians#Major_debates"
],
[],
[],
[],
[],
[],
[],
[],
[],
[
"http://en.wikipedia.org/wiki/Great_Sphinx_of_Giza#Builder_and_timeframe",
"http://en.wikipedia.org/wiki/Shot_heard_around_the_world",
"http://en.wikipedia.org/wiki/Elizabeth_I_of_England#Marriage_question",
"http://en.wikipedia.org/wiki/Lizzie_Borden#Murders"
],
[],
[],
[],
[
"http://upload.wikimedia.org/wikipedia/commons/1/1d/Hitler_Armenian_Quote.JPG"
]
] |
|
3fmie2
|
Do humans have skin inside their bodies?
|
For instance, on our lips or nostrils, as one proceeds from completely external areas to complete internal areas, is it all skin, or does it transition from skin to some other kind of tissue at some point?
|
askscience
|
http://www.reddit.com/r/askscience/comments/3fmie2/do_humans_have_skin_inside_their_bodies/
|
{
"a_id": [
"ctq2op3"
],
"score": [
8
],
"text": [
"Skin is only on the outside.\n\nDuring embryonic development, you go from a single cell, to a ball of cells (blastocyst), which then gastrulates or, folds inwards to form a sort of donut which contains three \"germ layers\" [[image](_URL_1_)]. \n\nThe cells around the outside of the donut are the [ectoderm](_URL_3_), which develops into skin as well as elements of the nervous system, the cells forming the inside are the [endoderm](_URL_0_) which develops into your gut, and the cells between the two are your [mesoderm](_URL_2_), which form skeleton and muscle tissue.\n\nThe endoderm and ectoderm meet at the mouth and anus with the inside of the oral & anal cavities being endodermal in origin. These are lined with mucous membranes and though they share some similar properties, they are biologically distinct from skin (germ layer origin, cell type, organization & structure).\n"
]
}
|
[] |
[] |
[
[
"https://en.wikipedia.org/wiki/Endoderm",
"https://b51ab7d9e5e1e7063dcb70cee5c33cf7f4b7bad8.googledrive.com/host/0Bx6hk6AUBHxDc2d4TDJZTFIyMGs/files/Bio%20102/Bio%20102%20lectures/Animal%20Diversity/Protostomes/Lophotrochozoans/Image7.gif",
"https://en.wikipedia.org/wiki/Mesoderm",
"https://en.wikipedia.org/wiki/Ectoderm"
]
] |
|
k53mk
|
what does the pancreas do exactly?
|
Just like the title says. I am trying to explain it to an 8 year old.
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/k53mk/eli5_what_does_the_pancreas_do_exactly/
|
{
"a_id": [
"c2hkspu",
"c2hkymd",
"c2hkspu",
"c2hkymd"
],
"score": [
5,
3,
5,
3
],
"text": [
"It helps digest food and also regulates the concentration of key molecules in the body - for example, blood glucose. That's why when the pancreas stops working properly, you can get diseases like diabetes.",
"Here's hoping the kid knows that hormones are... If not, just call them \"substances\" i guess. I'll use \"substances for the sake of simplicity. The pancreas is responsible for: \n\n1. storing energy (\"fuel\") in your body \n\n2. releasing stored fuel in your body \n\n3. or stopping the absorption of fuel when you're body has more important things to worry about. \n\nThe pancreas uses three different substances to do this. Substance 1 (insulin) takes the energy from your food and stores it in your body so you can use it later if you need energy but don't have food. Substance 2 (glucagon) takes that energy back out of storage when your body needs fuel but hasn't eaten recently. Substance 3 (somatostatin) kicks in when we're either have to fight or run for our lives. Basically, this substance tells your body \"we have bigger things to worry about than digesting food right now\" and stops digestion. The fight or flight response will also cause the release of Substance 2 (glucagon) to make sure that your body has plenty of fuel to either fight off the threat or run away from it.",
"It helps digest food and also regulates the concentration of key molecules in the body - for example, blood glucose. That's why when the pancreas stops working properly, you can get diseases like diabetes.",
"Here's hoping the kid knows that hormones are... If not, just call them \"substances\" i guess. I'll use \"substances for the sake of simplicity. The pancreas is responsible for: \n\n1. storing energy (\"fuel\") in your body \n\n2. releasing stored fuel in your body \n\n3. or stopping the absorption of fuel when you're body has more important things to worry about. \n\nThe pancreas uses three different substances to do this. Substance 1 (insulin) takes the energy from your food and stores it in your body so you can use it later if you need energy but don't have food. Substance 2 (glucagon) takes that energy back out of storage when your body needs fuel but hasn't eaten recently. Substance 3 (somatostatin) kicks in when we're either have to fight or run for our lives. Basically, this substance tells your body \"we have bigger things to worry about than digesting food right now\" and stops digestion. The fight or flight response will also cause the release of Substance 2 (glucagon) to make sure that your body has plenty of fuel to either fight off the threat or run away from it."
]
}
|
[] |
[] |
[
[],
[],
[],
[]
] |
|
g6rvj
|
Is gravity negative energy?
|
I was watching lawrence kraus video a universe from nothing where he seems to be saying the total energy of the universe is 0, so is it as simple as gravity cancelling out the other stuff in the universe?
thanks for the 4 answers given so far. Clear as mud.
|
askscience
|
http://www.reddit.com/r/askscience/comments/g6rvj/is_gravity_negative_energy/
|
{
"a_id": [
"c1lb576",
"c1lb76w",
"c1lbkqn",
"c1lbskr",
"c1ld1jg"
],
"score": [
5,
3,
2,
2,
3
],
"text": [
"The final value of energy is arbitrary. We can only measure energy differences, so if we offset the energy of everything by a constant value, nothing will change.",
"There are some formulations of the laws of mechanics where you write some terms with plus signs and some with minus signs. In the Lagrangian, for instance, kinetic energy has a plus sign and potential energy has a minus sign. But the equations would work exactly as well if you reversed those.\n\nThe central ideal is that whenever a *potential* exists, any motion of a particle within the potential will change the particle's of energy of motion by some amount, and change the particle's potential energy by the same amount. Which you deem positive and which negative is arbitrary.",
"_URL_0_\n\nConservative quantities are a zero sum situation.",
"If two objects are very far off (infinite separation distance), the gravitational attraction between them is non-existent, so it makes sense to call that a zero-energy state. Things in general have a tendency to move from configurations of high potential energy, to those with lower potential. And the gravitational force makes things masses attract, so small separation configurations need to have a lower energy than the large separation ones. This leads you to label any finite distance configuration with a negative energy.\n\nAll that matters is the difference in energy when you compare two configurations, so you could increment both their energies by some arbitrary number. You could label the infinite separation configuration with a large positive energy and have the finite separation configs with smaller +ve energies. (although, you'd eventually reach -ve energy when the mass got close enough)",
"Can someone please explain to me what Krauss means by a zero energy universe? This was never mentioned in any of my cosmology classes or books. I thought the consensus was that the universe's energy density is pretty much the critical density, which makes it greater than zero and the total energy content infinite, of course. Is he talking about Omega_k as total amount energy?"
]
}
|
[] |
[] |
[
[],
[],
[
"http://en.wikipedia.org/wiki/Zero_sum"
],
[],
[]
] |
|
7mqipv
|
What does the content of radioactive waste Disposal Containers (The yellow ones) look like?
|
askscience
|
https://www.reddit.com/r/askscience/comments/7mqipv/what_does_the_content_of_radioactive_waste/
|
{
"a_id": [
"drwsi8q"
],
"score": [
5
],
"text": [
"Depends on where they are coming from.\n\nCould be low level solid waste from hospitals or research labs. That'll mostly be bags of used gloves, paper towels and the like.\n\nCould be contaminated construction waste from renovation or decommissioning of a facility. That'll be hunks of wood, plaster and the like.\n\nCould be solidified liquid waste from a hospital, power plant or lab. That'll look like a drum of concrete or bags of absorbents like cat litter.\n\nUsually these drums get counted, sealed and then placed into a reinforced overpack container for shipping or intermediate storage."
]
}
|
[] |
[] |
[
[]
] |
||
3nf735
|
why do carnivores seem to prey mostly on herbivores and omnivores, and not on other carnivores?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/3nf735/eli5_why_do_carnivores_seem_to_prey_mostly_on/
|
{
"a_id": [
"cvnhykx",
"cvnhyrl"
],
"score": [
4,
2
],
"text": [
"Safety plays a major concern. Prey typically has a flight instinct and predators typically have a fight instinct. If you attack a Gazelle, it may kick you, but then it's going to run. If you attack a Lion, it's turning around to kill you. Obviously not always the case, but it's the majority.\n\nThe type of offense each brings is also important. Most prey animals kick, headbutt, blunt force things. The predator may get a broken bone, but that's relatively safer than scratched/ bit with infection ridden claws/ teeth. Then wandering around with an open wound for a few weeks.",
"Other carnivores tend to have things like sharp teeth and claws which may injure the attacker. They would rather go after targets which have a less chance to attack back."
]
}
|
[] |
[] |
[
[],
[]
] |
||
ha1s3
|
How do you figure out what neuroreceptors a chemical activates? Do we know how many neuroreceptors there are?
|
askscience
|
http://www.reddit.com/r/askscience/comments/ha1s3/how_do_you_figure_out_what_neuroreceptors_a/
|
{
"a_id": [
"c1tt8rq",
"c1ttavj",
"c1ttby0"
],
"score": [
3,
2,
2
],
"text": [
" > Do we know how many neuroreceptors there are?\n\nwell, yes and no. We have a basic guess of how many different types of receptors are in the brain or on neurons, but we don't know what they all do, and there are always new things coming up. \n\n > How do you figure out what neuroreceptors a chemical activates? \n\nThere are a few ways of doing this. The easiest is a simple binding assay. So for example, if I wanted to know if a compound binds to the dopamine receptor, I would isolate some tissue (and specifically the membranes holding the receptors) and add a dopamine ligand (a compound that binds to a receptor, in this case a dopamine receptor). Dopamine itself could be the ligand. Then I spike this ligand-receptor cocktail with some radioactive dopamine. I can then wash the membranes so that the only dopamine left is bound to the dopamine receptor on the membranes. A portion of this will be radioactive. Then I add my compound. If it binds to the dopamine receptors, the more compound I add, the more it will displace the radioactive dopamine, since they would compete for binding to the receptor. If the radioactivity stays put, then the compound probably doesn't bind the dopamine receptor. \n\nI've looked for an animation but haven't had much luck. ",
"You can isolate a receptor a few different ways. Perhaps the easiest from my history is to remove the receptor you think it might be through genetic methods. Then if the neuron no longer responds to the chemical or does so in a reduced manner you have isolated the receptor. You can also do cletus-cubed's method. If you know your receptor is a G protein coupled receptor you can make a transgenic G protein coupled receptor ion channel and start adding different mixtures of chemicals until you find a batch that causes an influx of ions into the xenopus oocyte you have expressed your protein in. Then you start splitting up the chemicals you are adding until you find one that causes the effect you are looking for. \n\nAs for how many receptors there are that isn't entirely known. We can guess at what may be a receptor based on its homology to known receptors, but we by no means know what binds every receptor or what the properties of every receptor are. \n\nYour best bet is going to be getting your hands on an introductory neuroscience textbook. That's about the only place you will see all the known kinds of receptors and the history of how they were isolated in one place. ",
"If the gene for a neuroreceptor is known, genetic knock-out animals can be generated that have either a poorly functioning or missing gene code. These animals do not produce 1 or more of the proteins that make up the neuroreceptor. If the animal no longer responds to the chemical, it's possible that chemical normally activates the now defunct receptor.\n\nThat being said, the real story is much more complex because the animal either developed without that receptor all along or had it temporarily knocked-out (more complicated genetic manipulations can allow this), so other pathways may compensate for this loss.\n\n > Do we know how many neuroreceptors there are?\n\nThe major categories that show up in the bulk of modern research are the monoamines (e.g. histamine, dopamine, epinephrine (adrenalin), norepinephrine, serotonin, etc), the glutamate receptors (AMPA, NMDA, metabolic) and cholinergic (acetylcholine). As cletus-cubed pointed out, we have no way of asserting that the list is ever complete."
]
}
|
[] |
[] |
[
[],
[],
[]
] |
||
5zyd6i
|
why do we feel nauseous when dehydrated
|
I don't understand why we feel nauseous and sometimes vomit when we are severely dehydrated. If we vomit, we are losing even more water and fluids. Why do we feel nauseous then?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/5zyd6i/eli5_why_do_we_feel_nauseous_when_dehydrated/
|
{
"a_id": [
"df20b2a"
],
"score": [
3
],
"text": [
"I am no physiologist, but I would hazard a guess that it has something to do with the ion concentration raising up and causing problems in the head, blood, and GI tract. Water also helps calm the stomach down while you are sick. "
]
}
|
[] |
[] |
[
[]
] |
|
et1xu8
|
Did Salieri actually hate Mozart and vice versa?
|
I'm doing a presentation on Mozart for my history club and there are just a couple of things I'm not sure about. For one, did Salieri and Mozart actually have a rivalry or is that just Hollywood bullcrap made up for the film Amadeus?
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/et1xu8/did_salieri_actually_hate_mozart_and_vice_versa/
|
{
"a_id": [
"ffedrrb"
],
"score": [
3
],
"text": [
"u/DGBD answered a [similar question about the film](_URL_0_)."
]
}
|
[] |
[] |
[
[
"https://www.reddit.com/r/AskHistorians/comments/d7k4zg/how_accurate_is_the_portrayal_of_wolfgang_amadeus/"
]
] |
|
7of9qr
|
What sources did medieval doctors use? Do we have copies of what books they studied?
|
European doctors in the medieval era are always seen as lunatics who think every medical problem could be solved by a paste of various plants and leeches, and a healthy dose of physical pain.
What sources and texts were these doctors learning these practices from? Have any been discovered? Were these stereotypical practices considered actual medical knowledge, or a sham?
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/7of9qr/what_sources_did_medieval_doctors_use_do_we_have/
|
{
"a_id": [
"ds9mjm6"
],
"score": [
3
],
"text": [
"In the early centuries of the modern university in the west, medicine was one of just three advanced (PhD-level) faculties: law, theology, and medicine. In addition to the university-trained physician tradition, there were numerous levels of medical practitioner from royal surgeon to urban apothecary and battlefield barber-surgeon to village herbalist. In addition to the wealth of formal medical texts inherited from Greek antiquity and the medieval Islamic world, increasing literacy in the late Middle Ages brought practical handbooks of medical knowledge into the hands of medical practitioners with less formal education. \n\nThe writings of Galen, Aristotle, and Hippocrates (that Hippocrates) underlay the theory and some of the major treatment routes in the Latin west. Of course, their shared \"four humours\" basis of human biology was completely wrong *as we understand today*. But ancient and medieval people did not. And so medieval medicine--treating diseases and disorders--was systematic and logical, but based on an incorrect framework.\n\nHence, for example, the much-maligned leeches and bloodletting treatment. If you believe that disease manifests itself through an imbalance in humours circulating within the body--too much bile, say--then bleeding out some of the bile will help restore the balance! Other means of purging, like enemas or blowing one's nose, could be construed similarly.\n\nDon't get me wrong, there's a lot of stuff in medieval medical writings that is a MAJOR head-scratcher today. But that doesn't mean that doctors were universally stupid or ill-trained. In fact, there is a long, strong tradition of medieval literature satirizing/complaining about *quacks*. Which is to say: medieval people definitely understood what a good and an effective medical practitioner was and could do, because they knew enough to denounce the bad ones."
]
}
|
[] |
[] |
[
[]
] |
|
d8c7ix
|
Who was Homer?
|
I don't mean what he did, I mean, who was he as a person? I've been poking around just for shits and gigs and there seems to be almost nothing known about his personal life, in fact, there's almost nothing that seems to be known about him beyond his works and accomplishments as a writer, so, who actually was he? what was his early life like? how did he get his education? did he ever have family? friends? was he charismatic and outgoing or more recluse? these are the kind of questions that interest me about famous historical figures
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/d8c7ix/who_was_homer/
|
{
"a_id": [
"f1ays7y"
],
"score": [
24
],
"text": [
"Simply put, we don't know.\n\nThe only relevant texts that survive in writing from the period the Homeric epics were composed are the Homeric epics themselves. Since these poems do not feature any autobiographical details, they tell us nothing about Homer as a person. From the roughly contemporary epic poems of Hesiod, we learn that Hesiod was an estate owner from a small town in upland Boiotia in Central Greece, but the Iliad and Odyssey contain no information about Homer. There is nothing else that can tell us anything about the man. Indeed, it's been noted that the dialect of Greek in which the epics were written is not consistent, so even linguistically it's not easy to pin down a historical Homer.\n\nIn Greek works written hundreds of years later, we get all sorts of fanciful stories about Homer's origins, his life, his afflictions (including crippling poverty and alleged blindness), and the era in which he supposedly lived. But none of this seems to have any basis in reliable historical knowledge. With the Homeric epics so central to the education of every Greek and to the formation of Greek identity, it was only natural that their author should become an almost mythical figure about whom many wise men claimed to know things that hadn't been known before. It is fair to say that the Greeks actually knew nothing about Homer from any local tradition or historical documentation.\n\nFor these reasons, many scholars in the past have doubted whether Homer was even a real person. Certainly, if he really existed, he wrote nothing down; he sang poems that gained a fixed form over time but weren't put into writing until several centuries later. Given this long process of oral tradition, it is quite possible that the figure \"Homer\" is just a later invention. The real composer of the epics may have had a different name, or it may have been a collective of poets, either combining their powers or improving on each other's works gradually over time until the final, canonical version came into being. Later admirers then declared that this story had been created from scratch by a single genius, a divinely inspired poet they named Homer.\n\nMost modern scholars are perfectly happy to use the name \"Homer\" as a shorthand for whoever actually wrote the epics. It's easier, and at least it reflects a long tradition about the origins of the works. But we don't even know if Homer was a real living poet, let alone any detail of his life."
]
}
|
[] |
[] |
[
[]
] |
|
3dpnmr
|
why is the gap in pay between genders a prominent political issue, when the gap in life expectancy between genders is not?
|
Obviously there are biological factors that contribute to the different life expectancy, but there are also undoubtedly biological factors (e.g. men being more aggressive negotiators) that contribute to the pay disparity - why are we willing to accept one but not the other?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/3dpnmr/eli5_why_is_the_gap_in_pay_between_genders_a/
|
{
"a_id": [
"ct7gkua",
"ct7gtdr",
"ct7gzct",
"ct7pime"
],
"score": [
6,
2,
4,
5
],
"text": [
"At the end of the day we may be able to influence our mortality, but some people live longer and some live shorter and that's life. No person or groups of people are actively making women live longer. On the other hand, wages are something that is 100% in the control of us as a population. It's something that is regulated and legislated, so if there is a bias against one gender (and I'm not saying there is), then it's because of people, and as such we have a ethical responsibility as a population to fix it. You can't really legislate life expectancy.",
"In my opinion the main reason a lot of men live shorter lives is because those men are less worried about their health.",
"The wage gap is constantly bought up because it fits into the 'women are always victims' political narrative. It's very profitable for people to make a big deal about it. Nobody makes money or gains political power from complaining about a gap in life expectancy between sexes.\n\nAlso, the wage gap is essentially a myth. Here's a good video to watch regarding the facts: \n\n_URL_0_",
"Women strongly object to being paid less than men, so they fight against pay disparity.\n\nMen don't seem to object as strongly to doing violent or foolhardy things - they would fight hard FOR their right to participate in extreme sports, to drink to excess, and to avoid medical treatment for their illnesses, and those are just a few examples of things that cause more deaths in men than in women and drive up the averages. They're also the ones most likely to be in favor of the next war. Men fight FOR their right to die younger.\n\nIf men want to fight for their right to live longer, I'll be very curious about whether they do that by trying to change the laws, or the culture. I think the latter would work better, but take longer."
]
}
|
[] |
[] |
[
[],
[],
[
"https://www.youtube.com/watch?v=BDj_bN0L8XM"
],
[]
] |
|
dafenw
|
how are about 1000 books the #1 best selling in new york?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/dafenw/eli5_how_are_about_1000_books_the_1_best_selling/
|
{
"a_id": [
"f1p8yjn",
"f1p9jkm",
"f1pb2ki",
"f1pcpsl",
"f1pd2ie",
"f1pdaek",
"f1peu5m",
"f1pfxu4",
"f1pgm9b",
"f1pgqey",
"f1ph5o6",
"f1phka6"
],
"score": [
2206,
72,
272,
25,
11,
3,
70,
4,
5,
3,
3,
2
],
"text": [
"I assume you are referring to the New York Times bestseller list. Those are for everywhere, not just New York.\n\nThe list goes out every week, so if a book is #1 for even a single week, it can call itself a #1 bestseller. So technically there could be 52 #1 bestsellers a year in each category (fiction, nonfiction, hardcover, paperback). Realistically there will not be that many, as books tend to stay on top for several weeks.\n\nAnother reason it might seem like every book is #1 is that the bestselling books are the ones you hear the most about... because they are bestsellers.",
"Slight tangent: those charts can be gamed. Meaning the title of bestselling author does not actually mean much. \nsource: Darknet Diaries, ep 27: Chartbreakers",
"The publishers know these lists exist and how many are roughly needed to be sold to get to the top of the list. When a book debuts, they might \"buy\" a few hundred or thousand copies for the book tour to get that moniker on the second run of books in a few weeks.",
"The simple answer is that there are like two dozen lists with 15-20 books each (e.g., bestselling children's e-books for grades 6-8), meaning at any given time there might be 400 \"New York Times Bestsellers\", with a significant number able to claim #1.\n\nThe more complicated answer involves the fact that people game the system to get their book on there for a week to earn that title, and the following fascinating quote from the Wikipedia article about it:\n\n > The Times countered that the list was not mathematically objective but rather was editorial content and thus protected under the Constitution as free speech.",
"Regarding people buying their own books, whenever a new L. Ron Hubbard book came out (while he was still alive, obviously) Scientologists would buy thousands of copies then ship them back to the publisher so they could be sold again.",
"The NYT bestseller list is not a list of books that sell a lot of copies, it’s an editor’s choice list.",
"Fun fact about the New York Times bestseller list: the reason there is a children's book list is because all the \"serious, adult\" authors got mad that the Harry Potter books were crowding out the top slots for weeks and weeks at a time (well, over a year, really!).",
"[Because the list doesn’t necessarily refer to actual sales but has a high degree of ‘editorial content.’](_URL_0_) \n\nSo some books may be on the list solely because the editors may find them significant, not because they sold better. And there are other ways to manipulate the list. Read the criticism and controversy sections of the wiki. I don’t pay attention to that list anymore.",
"So does anyone know of a list of good books to follow? Besides the NYT which, after reading some comments here, may be misleading?",
"In addition to what has been said, you often see **New York Times Bestseller** on a book, which sneakily implies that it was #1, without actually stating it. But what it actually means is that it simply made the bestseller list, or more accurately one of the many bestseller lists. \nSo an author or publisher could buy a relatively low amount to get it on the list and then blast New York Times Bestseller on the cover.",
"There are categories as well, not just the top 10 list. So it can be the #1 bestselling \\[children's\\] book or the #1 bestselling \\[thriller\\] book. Categories matter with those things. Oftentimes, the books are only claiming to \\*A\\* bestselling book, not the #1. So it could be #99 in the top 100 for one week and call itself a bestseller.",
"My favorite version of this is “award winning pizza”\n\nWhat award, where’s this pizza contest? Best cup of coffee? According to who?"
]
}
|
[] |
[] |
[
[],
[],
[],
[],
[],
[],
[],
[
"https://en.m.wikipedia.org/wiki/The_New_York_Times_Best_Seller_list"
],
[],
[],
[],
[]
] |
||
7g3qyd
|
how does being out in the cold increase your chance of catching a cold? if it doesn't, where does this misconception come from?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/7g3qyd/eli5_how_does_being_out_in_the_cold_increase_your/
|
{
"a_id": [
"dqg9zy8"
],
"score": [
2
],
"text": [
"Not fully the answer, but when you're cold you tend to touch your hands to your face/mouth/nose more often, introducing more germs into your body."
]
}
|
[] |
[] |
[
[]
] |
||
bllv6a
|
In the show 'Deadwood' there is whiskey being drunk in, it seems, more than half the scenes in the show. Was frontier whiskey watered down?
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/bllv6a/in_the_show_deadwood_there_is_whiskey_being_drunk/
|
{
"a_id": [
"ens4u2s"
],
"score": [
3
],
"text": [
"In the 19th century, \"whiskey\" was nothing like the whiskey we know. Very few distilleries actually sold directly to the public and there were many home distillers, usually farmers who realized that the surplus corn and rye they couldn't afford to ship to the market would be a lot more profitable if they turned it into liquor first.\n\n & #x200B;\n\nDistilleries would generally produce a high proof neutral spirit not unlike the commercial \"moonshine\" you see today, which would then be sold to rectifiers to further improve the product. The rectifiers would blend whiskeys, possibly do some aging, and often add things like coloring to make the product look more like whiskey. They sold this product to wholesalers (where any aging would be done, if it was), who then sold the product to saloons and stores that would sell to the end customer. The whiskey would be watered down to a lower proof, around 40-50% alcohol by volume, before it eve reached the customer. Otherwise it would be virtually undrinkable.\n\n & #x200B;\n\nA lot of unscrupulous rectifiers and wholesalers would adulterate the product to try and sell it for less. They might water it down more and then add things like acid and lanolin to give it more burn and body and disguise how much weaker it was. Saloon owners might mix two half-empty bottles to save shelf space with little regard to what product was getting mixed with what. You really had no clue what you were going to get if you went in blind."
]
}
|
[] |
[] |
[
[]
] |
||
3moea4
|
What is the relationship between (tensile) strength and hardness?
|
Iron rod is stronger than glass. But one cannot make scratches on glass surface as easily as on iron rod, hence glass is harder than iron rod. It is said that when glass shatters, it is not because of its poor strength, but because of a powerful shockwave passing through it. But then, why doesn't the same happen with iron rod? I mean, if an iron is dropped, a shockwave must be passing through it as well. Why doesn't it get shattered for the same degree of drop on ground? My question is what are the basic ideas of hardness and strength? They arise out of the same cohesive forces between atoms. Then why hardness and strength are generally inverselt corelated? Why the same atoms react with one strength if they are separated in one way (streching) and a different strength if they are separed in another way (scratching)? Also why diamonds are not extremely brittle? Is hardness only a surface property?
|
askscience
|
https://www.reddit.com/r/askscience/comments/3moea4/what_is_the_relationship_between_tensile_strength/
|
{
"a_id": [
"cvh7xsn"
],
"score": [
2
],
"text": [
"Usually strength and hardness show positive correlation.\n\n > It is said that when glass shatters, it is not because of its poor strength, but because of a powerful shockwave passing through it.\n\nNot really. Glass breaks when it's strength is exceeded, just like any other material.\n\n > But then, why doesn't the same happen with iron rod? I mean, if an iron is dropped, a shockwave must be passing through it as well.\n\nGlass exhibits poor impact resistance. One way of thinking of this is by looking at a [stress-strain curve](_URL_0_). Since glass is brittle, it does not strain much before fracture. The energy absorbed in deformation is equal to the area under the stress-strain curve, so it can be seen that glass is not able to absorb as much energy as a more ductile material of similar strength.\n\n > Then why hardness and strength are generally inverselt corelated?\n\nThis would not be the case if you compared similar materials. For instance, if you examine heat-treated steels, you'll find that strength and hardness are positively correlated.\n\nThis is because hardness measures how easily a material is scratched or dented. Take a look at the Brinell hardness test, which applies a large force to a steel or tungsten carbide ball, and examines the resulting size of deformed material. A material with a higher compressive strength will show a smaller dent, and thus will have a higher hardness on the Brinell scale.\n\n > Also why diamonds are not extremely brittle?\n\nDiamonds are brittle. Brittleness is not the same as weakness. As another example, consider quenched steel. A sample of steel can be heated and quenched, resulting in a harder metal, meaning it has higher tensile, compressive, shear, and bearing properties, but it is also made brittle, meaning that it doesn't strain as much before fracture. It will still take a higher load (meaning it is stronger), but it exhibits brittle failure. This is the case with diamond - it is extremely hard, very strong, and also brittle.\n\nIf you want more details about the grain structure of metals and more of the \"whys\" for this, pick up a materials science textbook."
]
}
|
[] |
[] |
[
[
"https://upload.wikimedia.org/wikipedia/commons/0/00/Brittle_v_ductile_stress-strain_behaviour.png"
]
] |
|
2b83zd
|
does it matter what time i brush my teeth?
|
I've always heard that we should brush our teeth twice a day. Once in the morning and once at night. But does it matter if we brush in the morning before we eat or after we eat? If we don't have breakfast in the morning should we wait until after we eat to clean off anything sticking to the teeth after the meal or brush before so the teeth are protected in the first place? Both? Or will brushing your teeth too much wear away enamel?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/2b83zd/eli5_does_it_matter_what_time_i_brush_my_teeth/
|
{
"a_id": [
"cj2p424",
"cj2r47o"
],
"score": [
6,
3
],
"text": [
"Brushing is about killing bacteria, hardening enamel and reducing plaque. You should concentrate on massaging gums though.\n\nYou shouldn't brush after eating, because acidity of your mouth is high, which makes it easier to damage enamel.",
"The most important time to brush IS before bed. Besides gook sitting there all night, you also salivate less at night worsening any bad effects. You can damage your teeth by brushing too much. A friend's daughter had OCD and had begun destroying her enamel brushing too much."
]
}
|
[] |
[] |
[
[],
[]
] |
|
avomef
|
why when we look to a thing or a photo long enough we see the negative version of it after stop looking it or after closing eyes?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/avomef/eli5_why_when_we_look_to_a_thing_or_a_photo_long/
|
{
"a_id": [
"ehgnw1q"
],
"score": [
2
],
"text": [
"Because the rods and cones and photoreceptors in your eyes have become over stimulated and desensitized to the image.\n\nBasically the specific receptors, out of the many in your eyes, that are used to process the colors and shapes of the image get over worked and shut down. Their being “off” causes an after image in the shape of the receptors and the information they receive, for around 30 seconds or so until the brain can click them back on and put them to work.\nThe brighter the light or more complex the image, the shorter time it takes to cause an “after image”"
]
}
|
[] |
[] |
[
[]
] |
||
9z7ql2
|
how does strong duct tape and other adhesives bind easily and permanently with almost anything, but easily detached from it's roll/container?
|
[deleted]
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/9z7ql2/eli5_how_does_strong_duct_tape_and_other/
|
{
"a_id": [
"ea6yjz7"
],
"score": [
5
],
"text": [
"Most rolled tape has what's known as Release Coating on the top layer (the non-adhesive side) that prevents it from being adhered to easily.\n\nDouble-sided tapes have a liner that will need to be removed, as well."
]
}
|
[] |
[] |
[
[]
] |
|
6s6p9w
|
is it technically possible for countries to 'build' a nuclear bomb, even if not given the technology by another nuclear country?
|
I was wondering whether North Korea, or any other country to that regard, even if not giving the 'technology' by another nuclear country would have been able to obtain nuclear power.
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/6s6p9w/eli5_is_it_technically_possible_for_countries_to/
|
{
"a_id": [
"dlafqxx",
"dlaj12w"
],
"score": [
7,
2
],
"text": [
"All the theory is well known, you can search it online right now. Nations are usually limited by the availability of weapons grade fissile material for the bomb itself and the elaborate detonators required, which are much harder to obtain or construct.\n\nTo make the bomb useful they also need a delivery system, which requires advanced ballistic missile technology that again is hard to build.\n\nSo the basic science is public knowledge, but managing to build your own nuclear detonation device with your own weapons grade uranium mounted on your own ICBM is a more difficult and costly.",
"The first country built it without being given the technology by another nuclear country; ergo, yes."
]
}
|
[] |
[] |
[
[],
[]
] |
|
avmhit
|
how do pharmaceuticals decide which of their medications will be available as a generic? what percentage do they make off them?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/avmhit/eli5_how_do_pharmaceuticals_decide_which_of_their/
|
{
"a_id": [
"ehg8s61",
"ehg93p1",
"ehg93zf",
"ehg9502",
"ehg96km",
"ehggg87"
],
"score": [
11,
4,
4,
3,
3,
3
],
"text": [
"A drug patent lasts about 20 years. After that anyone can snag the ingredient list and make a generic. The only money the original patent holder makes after that is if doctors still prescribe the brand name and pharmacists actually fill it instead of the generic. ",
"so the government has made a rule where companies that actually make the drug only have so much time from the moment they discover the molecule where the molecule is actually theirs. after that amount of time has passed, the molecule becomes available to everyone. kind of like public domain. so even though for the majority of this time the pharmaceutical company isnt actually making money off the molecule because theyre still putting money into research, development, and marketing. once the new drug is ready to be sold, they only have a few years to make that money back PLUS profit from it (which is why name brand drugs tend to be so expensive). once that time runs out, they go generic and anybody can make the drug as long as it is close to the original. a lot of the time the same companies that make the original drug have smaller companies that are a part of them that only make generic versions of their drugs and drugs that used to belong to other companies so they can still make some money off of them. the name brand version still gets made, however it is less profitable because once it goes generic there is competition with other companies who make it much cheaper. other companies are able to sell it for less because they dont have to worry about making up for the cost of all the research that went into developing it. \n\nedit: made it more readable and added a little bit of info. ",
"Drug companies spend many years and millions of dollars in research and trials to develop a new drug, once it's deemed acceptable and proven to do what it's supposed to do they have the right to sell it under a patent, that patent expires after 7-10 years and now everyone else can take that formula and mass produce it to sell to the public, so it's the exact same thing but cheaper, the original is sold for a much higher amount because they're trying to make their money back and a whole lot of profit. All that being said, I have 2 cousins that are doctors and they both told me to always go for the generic drug, it's exactly the same but cheaper",
"It has to do with the patents. Basically drug manufacturers will fund research for new drugs, and once it’s developed and proven and approved etc. The company that developed it has a patent on that drug and can essentially charge as much as they want for it. Prices depend on various things such as the potential pool of users (specialised drugs for rare diseases are more expensive because less users) and the amount spent developing the drug, etc. \n\nUntil the patent on a particular drug expires, no other manufacturer can produce it. \n\nAfter the patent expires, the formulation for the drug is fair game for anyone who wants to produce it. \n\nThis system is essentially in place because it’s very expensive to produce new drugs and pharmaceutical companies wouldn’t be willing to do invest any money into research and development if they couldn’t make any money off their drugs. \n\nA generic being available usually means the drug’s patent has expired, so there’s competition between companies for the same product and the price drops. Most insurance companies will only pay for a generic if there’s one available and there’s no medical reason why they should cover the cost of the brand name. ",
"If a drug company invents a new drug and gets a patent on it, only they can produce it for a certain number of years. Once the patent expires, other companies can use the recipe for the drug to make generic versions of the same thing. The original company still continues to sell the product under the name brand. ",
"Drug patents last 20 years in the US. Afterwards, the brand name drug is often still sold, but it's far less profitable.\n\nThere's two nuances to the 20 year rule:\n\n* First, it can take 8 years to get FDA approval so you only get 12 years of patent protection. \n\n* Second, there are ways to extend patents such as slightly reformulating the drug (worth 3 extra years), using a special extension designed to account for part of the FDA's approval time (worth 5 extra years), or trying to exploit the occasional legal loophole (these rarely work.)\n\nPharamaceutical companies try to keep their patents alive for as long as possible because 80% of their revenue comes from them. Generics either put brand name drugs out of business, or at least dramatically reduce their profitability. \n\nDoctors try to avoid prescribing brand name drugs and insurance companies try to avoid paying for them. Sometimes brand name prices come down, but other times, they use the AOL method where some elderly people are still paying for America Online dial-up internet because they forgot about it or are used to it. People often get used to the brand name drug and don't bother to switch to the generic. This is less common nowadays because insurance companies keep an eye out for it since they are the people who actually have to pay.\n\nThere are ocassionally some small benefits to brand name drugs. The actual drug is the same, but the other parts of the drug are different. So the brand name drug might use a capsule that is less irritating to your stomach or something. But it's also possible that it goes the other way where the generic drug is better for you. Doctors almost always suggest going with the generic drug if there's one available. "
]
}
|
[] |
[] |
[
[],
[],
[],
[],
[],
[]
] |
||
5vqro4
|
What happened in the Cretaceous-Paleogene Extinction?
|
The most famous theory presented that explains this event, which is widely known as the extinction of dinosaurs 65 million years ago, is a 6-mile wide asteroid that impacted the Earth off the coast of Yucatan Peninsula. I've learned that there are two ways that the asteroid could have affected the global temperature. One is that it cooled the Earth to freezing temperatures due to the debris that were flung off and suspended high in the atmosphere, or the materials that was blown away were super-heated rocks and set the surface ablaze to searing temperatures. Which off these scenarios have likely happened?
|
askscience
|
https://www.reddit.com/r/askscience/comments/5vqro4/what_happened_in_the_cretaceouspaleogene/
|
{
"a_id": [
"de5n78i",
"de5zhjb"
],
"score": [
3,
2
],
"text": [
"Both appear to be real effects. The \"flash & burn\", however, was at most local in its effects and seems to have been previously overestimated (See: [Belcher, C. M., Collinson, M. E., Sweet, A. R., Hildebrand, A. R., & Scott, A. C. (2003). Fireball passes and nothing burns—The role of thermal radiation in the Cretaceous-Tertiary event: Evidence from the charcoal record of North America. Geology, 31(12), 1061-1064](_URL_0_)), while the \"nuclear winter\" phenomenon was global. So, in regards to your question, it seems the cooling was by far the most consequential phenomenon.\n\nBut wait! There's more: 2 other important effects were more than a decade of acid rain and changes in the patterns of ocean currents & stratification. From [Pope, K. O., Baines, K. H., Ocampo, A. C., & Ivanov, B. A. (1997). Energy, volatile production, and climatic effects of the Chicxulub Cretaceous/Tertiary impact. Journal of Geophysical Research: Planets, 102(E9), 21645-21664.](_URL_1_):\n\n*\"These sulfate aerosols caused a second pulse of acid rain that was global. Radiative transfer modeling of the aerosol clouds demonstrates (1) that if the initial rapid pulse of sulfate aerosols was global, photosynthesis may have been shut down for 6 months and (2) that for the second prolonged aerosol cloud, solar transmission dropped 80% by the end of first year and remained 50% below normal for 9 years. As a result, global average surface temperatures probably dropped between 5° and 31°K, suggesting that global near-freezing conditions may have been reached. Impact-generated CO2 caused less than 1°K greenhouse warming and therefore was insignificant compared to the sulfate cooling. The magnitude of sulfate cooling depends largely upon the rate of ocean mixing as surface waters cool, sink, and are replaced by upwelling of deep ocean water. This upwelling apparently drastically altered ocean stratification and circulation, which may explain the global collapse of the delta 13C gradient between surface and deep ocean waters at the K/T boundary.\"*\n\nSo, in retrospect, the main effects which make the Chixculub impact stand out are: \n\n* a decadal scale nuclear winter effect, comparable to several \"years without a summer\" in a row;\n\n* a global pulse of acid rain, yet again in excess of a decade;\n\n* changes in ocean circulation and stratification.\n\nThe wildfires seem, in comparison, like an afterthought.",
"Whilst the Chixculub impact theory is the most well known idea amongst the public, there is actually another competing theory, namely involving the Deccan Traps Large Igneous Province (e.g. [Self et al, 2006](_URL_1_)). Large Igneous Provinces are formed by extended, prolonged periods of volcanic activity (not a single massive eruption) and they have been associated with many other mass extinction events so it is accepted that they are capable of driving mass extinction (through severe climate and environmental change). \n\nIt is likely that both the Chixculub impact and Deccan volcanism were responsible for the extinction. Many scientists are skeptical that the impact itself could be solely responsible for the mass extinction because extinctions began rising before the impact and continued well after the earth system should have recovered. It is possible that volcanism created a background of environmental stress that made it much more difficult for ecosystems to survive the additional stress imposed by the Chixculub impact. Additionally, [Renne et al \\(2015\\)](_URL_0_) suggest that the Chicxulub impact may have actually intensified volcanism, creating even more environmental stress."
]
}
|
[] |
[] |
[
[
"http://geology.gsapubs.org/content/31/12/1061.full",
"http://onlinelibrary.wiley.com/doi/10.1029/97JE01743/full"
],
[
"http://science.sciencemag.org/content/350/6256/76.full",
"http://www.ligo-wa.caltech.edu/~robert.schofield/Flood/HugeGasReleaseFromFloodBasalt.pdf"
]
] |
|
6ue0d4
|
If someone quits smoking without having contracted cancer, do their odds of getting cancer eventually return to those of non-smoker?
|
Or has some irreparable biological damage been done, which increases the likelihood of cancer over time?
*Edit: my bad for typo in title* :(
|
askscience
|
https://www.reddit.com/r/askscience/comments/6ue0d4/if_someone_quits_smoking_without_having/
|
{
"a_id": [
"dls4e2x"
],
"score": [
12
],
"text": [
"Smoking cessation will decrease your risk of smoking-related illness compared to continuing to smoke. However, your risk may not universally return to baseline. For example:\n\nAn average of 27 studies shows that your risk of COPD-related morbidity and mortality (\"illness\" and \"death\") probably decreases after smoking cessation compared to continued smoking, but the studies are small and the effect sizes are, too. (1).\n\nYour risk of coronary disease (heart disease) may never return to pre-smoking levels, but if a current smoker is at 3x elevated risk for heart disease, someone who quit smoking 1-3 years ago is \"only\" at a 1.9x risk. Most of that risk reduction happens within the first few years of quitting. (2). Of note, you really do have to quit for 20 years to return to \"normal\" or \"normalish\" levels of risk, especially for lung cancer. (3).\n\nFurthermore, that risk of lung cancer shows a \"dose response curve\", meaning that the more you smoked, the more likely you are to get lung cancer. So, if you smoked for 20 years and then quit for 3, you may have a higher risk of lung cancer than if you smoked for 3 months and quit for a week.\n\n[1](_URL_0_)\n\n[2](_URL_1_)\n\n[3](_URL_2_)\n\nI also study this stuff."
]
}
|
[] |
[] |
[
[
"http://erj.ersjournals.com/content/32/4/844.short",
"http://onlinelibrary.wiley.com/doi/10.1111/j.1520-037X.2007.06050.x/full",
"http://ajph.aphapublications.org/doi/abs/10.2105/AJPH.80.8.954"
]
] |
|
6jds4a
|
Why don't you feel an electric shock while touching a 9V battery but feel one with the fake pen and gum toys with button cells?
|
askscience
|
https://www.reddit.com/r/askscience/comments/6jds4a/why_dont_you_feel_an_electric_shock_while/
|
{
"a_id": [
"djdo3nv",
"djdotqi",
"djdp2wb"
],
"score": [
18,
3,
75
],
"text": [
"Those toys include a voltage multiplier curcuit which brings the voltage up to a point that a shock is possibly noticed. Very similiar to a electric ignition lighter in characteristics. Knowing the ohms law relationship V=iR, your skin is R and fixed around 500k ohm. If you can make V go up you are also increasing i. ",
"It depends on the resistance between the two leads and the voltage. If the resistance is too high or the voltage too low, you won't get any current flowing and thus not feel it. The voltage is pretty much set by the battery or the toy you are using and the resistance determined by where your hold the leads on your body.\n\nFor instance, touch your *finger* to the leads of a 9V battery and you feel nothing. Touch your *tongue* to the leads of a 9V and you'll get a nice jolt. Your tongue has a much lower resistance than you finger does.",
"Toys that shock you contain (typically) a capacitor that is charged by the battery, and then discharged, releasing the accumulated charge. Although all the current coming from the toy comes from the battery, it has been used to build up charge in the cap that can release at a higher voltage and current than the battery would do by itself.\n\nThe toys may use something different, like an induction coil, but the basic principle is the same - they extract more current over a shorter time.\n\nReddit loves a good half-baked analogy so: Consider comparing sitting under a leaky tap for an hour, vs filling a bucket from that tap for an hour, then pouring it on yourself - the basic result is the same, but the bucket provides a much faster delivery of the water, and a much faster change of state as a result - one that is probably more noticable."
]
}
|
[] |
[] |
[
[],
[],
[]
] |
||
1me7hb
|
Did Hitler ever give any thought to choosing a successor?
|
He obviously knew he couldn't rule forever; what were his (or other Nazi officials') plans for succession in the event of his death. The idea of a "Thousand-Year Reich" doesn't get you very far when your government dissolves into chaos and infighting upon the death of the Führer. There must have been some sort of thought given to the issue, even if it was kept intensely secret for security reasons.
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/1me7hb/did_hitler_ever_give_any_thought_to_choosing_a/
|
{
"a_id": [
"cc8g717"
],
"score": [
34
],
"text": [
"Yes. The original successor Hitler named at the beginning of the war was Herman Goering. However, Goering fell out of favor toward the end of the war when Hitler perceived him as being too eager to take power, and Karl Donitz was appointed instead in Hitler's last will. Donitz was commander of the Kriegsmarine (the German navy) and had distinguished himself with the U-boat campaign against Allied shipping; historians think he was appointed because he was the only commander left after all the generals had incurred Hitler's displeasure in various failed campaigns. In addition, in his will, Hitler returned to the Weimar Constitution by separating the offices of President (Donitz) from Chancellor (Goebbels, in Berlin, who killed himself a day after Hitler.)\n\nDonitz was in northwestern Germany when he found out about this. He ruled for several weeks, to \"save Germany from destruction by the advancing Bolshevik enemy\" (in his first public broadcast) and promote \"the bare survival of the German people\" (in his later autobiography). Seeing that the military situation was futile, he promptly tried to negotiate terms of surrender to the British and Americans. Eisenhower insisted on unconditional surrender to all three Allies, at which point Donitz seriously considered just stopping the war in the West and letting the British and Americans pour over Germany up to the Russian lines. Eisenhower in turn threatened to seal the Allied lines against civilians. At that point, Donitz surrendered unconditionally."
]
}
|
[] |
[] |
[
[]
] |
|
6oinh8
|
chip sealing of roads- taking a layer of asphalt covered in lose gravel that uses traffic to finishing smoothing out the gravel? why?
|
Why is this used? Is it harmful to cars? Outside of expense, what are the benefits long term to the road. I see on the wikipedia page, it is used for low traffic... but here it is used on all roads in our area outside of highway. (Milwaukee)
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/6oinh8/eli5_chip_sealing_of_roads_taking_a_layer_of/
|
{
"a_id": [
"dkhp6jf"
],
"score": [
3
],
"text": [
"A few reasons dealing with traction and the underlying soils. Some roads need more traction than asphalt for various reasons, some are laid on ground that moves with the weather, so asphalt is prone to cracking or potholes. Also, in the right conditions, a hot day can heat up the tar mix, allowing material to flow, and repair cracks in the surface. "
]
}
|
[] |
[] |
[
[]
] |
|
70z1aa
|
apparently glass never fully breaks down? if this is the case, then why aren't most deserts just filled with lightning glass, instead of sand?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/70z1aa/eli5_apparently_glass_never_fully_breaks_down_if/
|
{
"a_id": [
"dn6wqus",
"dn892w5"
],
"score": [
16,
2
],
"text": [
"Sand is glass... Its primarily silicate. Glass never fully breaks down but it does break, and gets smoothed, and gets smaller and smaller. So deserts are filled with tiny broken pieces of lightning glass, which is sand.",
"There's a lot of ground to cover here.\n\nThe defining property of glass is that it lacks any well defined crystal structure. \n\nIf you look at most sands under a microscope, they're definitely crystalline. Sands are most commonly quartz crystals but they can be formed from almost any minerals. For example, the white gypsum sands in New Mexico, or black basalt sands in Hawaii. Many beaches are made of crushed up coral and shells, limestone in other words.\n\nGlass isn't technically stable. Glasses will over time, absorb water and transform into hydrated silicate minerals such as clays. These typically have a very fine crystalline structure, but it's visible under a high power microscope. This hydration process takes a long damn time however. Hundreds of millions of years. Note that in some cases you can measure the process of hydration in obsidian (volcanic glass) to give a rough estimate of it's age.\n\nMoreover silica becomes moderately soluble in water at very high temperature and pressures underground This explains the formation of *Geodes* that are lined with quartz crystals. This also explains the formation of Quartzite rock, which is formed when sandstone is exposed to heat and pressure.\n\nMoreover, the composition of fulgurites (fused soil from lightning) varies greatly based on the soil composition. If it's formed from mostly silica sand, then what you have is slightly melted sand grains mixed with fused silica. Fused silica is not technically glass since it's still composed of very tiny quartz crystals which can be seen with a microscope. This isn't the case with glass. \n\nGlass is difficult to form without prolonged heating and mixing. In fulgurites, you would not expect to find much truly glassy material. Rather they tend to be heterogeneous like a ceramic, being only slightly melted.\n\nFulgurites tend to be quite delicate and break easily, so they're just as prone to mechanical erosion processes and breakage like any normal rock."
]
}
|
[] |
[] |
[
[],
[]
] |
||
13jh7h
|
Are there any plausible alternatives to the Big Bang Theory?
|
When I say the Big Bang Theory I include inflationary cosmology and all that jazz. Is there a single other theory that fits the observations? For example, are any plausible theories based around the idea of a steady-state universe or anything like that?
|
askscience
|
http://www.reddit.com/r/askscience/comments/13jh7h/are_there_any_plausible_alternatives_to_the_big/
|
{
"a_id": [
"c74ksw8",
"c74kvdy",
"c74lbcq",
"c74mq8d",
"c74r477"
],
"score": [
6,
12,
5,
3,
2
],
"text": [
"From a 2008 article. _URL_0_",
"As I understand it, the steady-state model of the universe was largely dropped in the early 1980s. Penzias and Wilson's observation of CMB radiation put the Big Bang model in the scientific mainstream and the steady-state model ended up with too many things it couldn't explain to remain relevant.\n\nThat being said, I don't know of any current theories about the formation of the universe that rival the Big Bang theory, but that's not saying too much in and of itself because there are still plenty of things that the Big Bang theory can't explain.",
"[The Cyclic Model](_URL_0_), which describes the \"big bang\"-like explosion or symmetry breaking due to colliding 11-branes.",
"The key piece in BBT is the red shift. [\"tired light\"](_URL_1_) was proposed in the past as an alternative explanation.\n\nIf light redshifts for some other reason than the recession of galaxies then you might not need a big bang or you could push the big bang further back. That would give more time for life to have formed and abiogenesis and panspermia become more tenable. \n\nYou would need to invent a good mechanism to do it....\n\n_URL_0_",
"I believe there is a component of m-theory which explains when two parallel branes collided it would produce a similar event to the BBT. They also claim the existence of background radiation as a prediction of their theory. The final tell tale sign of which theory is correct will be the existence of gravity waves. If they exist then the BBT is correct if they do not then M-Theory is the lead candidate."
]
}
|
[] |
[] |
[
[
"http://m.discovermagazine.com/2008/apr/25-3-theories-that-might-blow-up-the-big-bang"
],
[],
[
"http://en.wikipedia.org/wiki/Cyclic_model"
],
[
"http://news.sciencemag.org/sciencenow/2001/06/28-01.html",
"http://en.wikipedia.org/wiki/Tired_light"
],
[]
] |
|
l3tkf
|
how i can tell if someone is black simply by just hearing their voice no matter how proper they speak?
|
Any time anyone is on the radio and they're black I can always tell. Even people like Bryant Gumbke that act "white." or whatever people say about him. This is not a joke post, I just don't know how to put it any other way.
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/l3tkf/eli5_how_i_can_tell_if_someone_is_black_simply_by/
|
{
"a_id": [
"c2pjcyg",
"c2pjgh1",
"c2pjkf8",
"c2pjcyg",
"c2pjgh1",
"c2pjkf8"
],
"score": [
8,
3,
6,
8,
3,
6
],
"text": [
"Think about it, different races look different. This goes beyond skin colour, facial features (and by extension the features of the vocal tract) are also race-influenced. One race may tend to have larger noses and nasal cavities than another, or a bigger mouth. These things affect the acoustics and articulations of a person's speech and many of these characteristics can be prevalent throughout a whole race. ",
" > no matter how proper they speak?\n\nSo, black people don't speak properly normally?",
" > This is not a joke post, I just don't know how to put it any other way.\n\nAs a linguistics student--and my whole discipline would probably agree with me--most people are horribly under-educated when it comes to things related to linguistics and language, and this is probably for the worse.\n\nThat being said, you're doing better than most by at least asking. Keep it up.\n\n > How I can tell if someone is black simply by just hearing their voice no matter how proper they speak?\n\nFirst off, everyone speaks some dialect of a given language. Even if you \"don't have an accent,\" you most certainly do. If you \"don't have an accent,\" chances are you speak the prestige or standard dialect of a given area.\n\nFor example, I speak a relatively standard version of American English, the Midlands dialect. Many people would say that I don't have an accent. However, if I go to London, Ontario, it becomes obvious that I do have an accent. It is different then the one on TV, and people will likely be able to pick me out as an American. If I go to London, England, this becomes even more obvious.\n\nDialects that don't conform to the prestige or standard dialect end up having our biases towards other races, towards other cultures and subcultures, towards urban dwellers and rural dwellers, etc. applied onto them. The dialects in and of themselves have none of these traits; we apply them.\n\nAfrican Americans, then, do not speak \"broken\" or \"improper\" English any more so than you speak \"correct\" or \"proper\" English. Many African Americans speak [African American Vernacular English](_URL_1_) (hereafter AAVE), a fairly divergent dialect of English, related to the other dialects found in North America.\n\nThe grammar of AAVE is very different than the standard dialect in the USA, Midlands North American English (hereafter SAE), and any other North American English dialect. AAVE has a much richer system of expressing tense--the relative position in time from now when an action took, takes, or will take place. For example, you can distinguish between these two sentences:\n\n* I been bought her clothes.\n* I been buyin' her clothes.\n\nIn standard American English, these are ungrammatical. You might switch \"been\" to \"had\" in the first sentence to try and make it correct, and add a \"have\" in the second sentence to try and make it correct, but this would not be what these sentences really *mean* in AAVE. Here's a \"translation:\"\n\n* I bought her clothes a long time ago.\n* I've been buying her clothes for a long time.\n\nThere is really no way to express these meanings without a long phrase tacked on in SAE, but in AAVE, this is simply part of the regular patterning of how verbs work.\n\n > Any time anyone is on the radio and they're black I can always tell.\n\nThis is almost certainly confirmation bias at work. I would guarantee that at some point you have mis-categorized someone's race by the sound of their voice alone, and most likely, [you'd have categorized them as your own race](_URL_0_).\n\nThat being said, there are definite differences, some baseline physical differences, some more linguistic- or culturally-bound. On the whole, these have not been well investigated for any *a priori* distinction we'd think to look at--race (people seem to do okay with this from initial studies), gender (people seem to do well with this from initial studies), sexual orientation (people do quite badly at this from initial studies), etc.",
"Think about it, different races look different. This goes beyond skin colour, facial features (and by extension the features of the vocal tract) are also race-influenced. One race may tend to have larger noses and nasal cavities than another, or a bigger mouth. These things affect the acoustics and articulations of a person's speech and many of these characteristics can be prevalent throughout a whole race. ",
" > no matter how proper they speak?\n\nSo, black people don't speak properly normally?",
" > This is not a joke post, I just don't know how to put it any other way.\n\nAs a linguistics student--and my whole discipline would probably agree with me--most people are horribly under-educated when it comes to things related to linguistics and language, and this is probably for the worse.\n\nThat being said, you're doing better than most by at least asking. Keep it up.\n\n > How I can tell if someone is black simply by just hearing their voice no matter how proper they speak?\n\nFirst off, everyone speaks some dialect of a given language. Even if you \"don't have an accent,\" you most certainly do. If you \"don't have an accent,\" chances are you speak the prestige or standard dialect of a given area.\n\nFor example, I speak a relatively standard version of American English, the Midlands dialect. Many people would say that I don't have an accent. However, if I go to London, Ontario, it becomes obvious that I do have an accent. It is different then the one on TV, and people will likely be able to pick me out as an American. If I go to London, England, this becomes even more obvious.\n\nDialects that don't conform to the prestige or standard dialect end up having our biases towards other races, towards other cultures and subcultures, towards urban dwellers and rural dwellers, etc. applied onto them. The dialects in and of themselves have none of these traits; we apply them.\n\nAfrican Americans, then, do not speak \"broken\" or \"improper\" English any more so than you speak \"correct\" or \"proper\" English. Many African Americans speak [African American Vernacular English](_URL_1_) (hereafter AAVE), a fairly divergent dialect of English, related to the other dialects found in North America.\n\nThe grammar of AAVE is very different than the standard dialect in the USA, Midlands North American English (hereafter SAE), and any other North American English dialect. AAVE has a much richer system of expressing tense--the relative position in time from now when an action took, takes, or will take place. For example, you can distinguish between these two sentences:\n\n* I been bought her clothes.\n* I been buyin' her clothes.\n\nIn standard American English, these are ungrammatical. You might switch \"been\" to \"had\" in the first sentence to try and make it correct, and add a \"have\" in the second sentence to try and make it correct, but this would not be what these sentences really *mean* in AAVE. Here's a \"translation:\"\n\n* I bought her clothes a long time ago.\n* I've been buying her clothes for a long time.\n\nThere is really no way to express these meanings without a long phrase tacked on in SAE, but in AAVE, this is simply part of the regular patterning of how verbs work.\n\n > Any time anyone is on the radio and they're black I can always tell.\n\nThis is almost certainly confirmation bias at work. I would guarantee that at some point you have mis-categorized someone's race by the sound of their voice alone, and most likely, [you'd have categorized them as your own race](_URL_0_).\n\nThat being said, there are definite differences, some baseline physical differences, some more linguistic- or culturally-bound. On the whole, these have not been well investigated for any *a priori* distinction we'd think to look at--race (people seem to do okay with this from initial studies), gender (people seem to do well with this from initial studies), sexual orientation (people do quite badly at this from initial studies), etc."
]
}
|
[] |
[] |
[
[],
[],
[
"http://web.mit.edu/tkp/www/Perrachione_Chiao_Wong_ASA2008_Poster.pdf",
"http://en.wikipedia.org/wiki/African_American_Vernacular_English"
],
[],
[],
[
"http://web.mit.edu/tkp/www/Perrachione_Chiao_Wong_ASA2008_Poster.pdf",
"http://en.wikipedia.org/wiki/African_American_Vernacular_English"
]
] |
|
a9iyt6
|
why do american schools favor a 9 month school system that inhibits age-appropriate sleep over a more conducive full year schedule?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/a9iyt6/eli5_why_do_american_schools_favor_a_9_month/
|
{
"a_id": [
"ecjq5ev",
"ecjqtxq",
"ecjqxdz",
"ecjsgyk",
"ecjt9ir",
"ecju6i7",
"ecjuly7"
],
"score": [
35,
16,
4,
4,
12,
3,
2
],
"text": [
"The duration of the school year has no bearing on the duration of the school day and therefore no bearing on sleep. The school day is chosen based on the work day. It is structured such that parents can drop their kids off before work and then pick them up after their after school extra curricular.",
"historically its for harvest, same reason as most of the world. the kids get off school at the time historically when they would have been needed to help with the harvest. It adds the benefit of segmenting it into distinct years and giving a long break for the kids to partake in social and formative activities. \n\n\nIn what way do you feel it impacts or inhibits sleep?",
"It’s an outdated system. Originally people needed their kids to help with farming in the summer months. And schools weren’t climate controlled. Obviously neither of those things is true any longer. It makes much more sense to go year-round, but have breaks more often.",
"How does a 9-month school year inhibit age-appropriate sleep exactly?",
"Judging from OP's tone and responses, sounds like you have a serious chip on your shoulder and aren't just asking out of genuine interest.\n\nThe original reason had to do with farming families, which needed help in the summer. But actually the reasons go far deeper than just the help. Basically in America, the responsibility for a child's education rests primarily on the parents. A year-round school is just a step further than a very large majority of American parents are willing to take. The 3 months represents a time for parents to take their kids on vacations, send them to church functions, etc. So whatever reasons that it started, it's an ingrained part of most Americans' culture now, and is unlikely to change.",
"US teacher here.\n\nThe school day start times are an atrocious slap in the face to developmental science. Unfortunately, schedules are ruled by two things; athletics/activities and transportation. Sports are king in many parts of the US, and if the school day ends around 3pm, that leaves roughly 2-4 hours for practice before it starts getting dark out and families have dinner. If we moved the school day back so that the day ended at 5pm, kids would regularly get home after 8 or 9 and parents would flip out. Unfortunately it serves the needs of the few over the needs of the many.\n\nTransportation for mid-large districts requires that buses be available for 2-3 separate “rounds” of bus routes before and after school every. single. day. This means that start times are stretched out to facilitate those trips and get the most bang for your taxpayer buck with as few buses and drivers as possible. Public transit just isn’t common in the vast majority of the US, and most cities aren’t built condensed enough for all kids to walk/bike to school (or at least not reliably). We have legislation requiring buses be provided to kids living X distance from school, even if it means that someone’s entire part-time job is to drive one kid to and from school every day (which, yea, does happen).\n\nThe year-round thing is a whole different monster. I recommend watching the Adam Ruins Everything episode on it.",
"The reason American kids aren't getting enough sleep isn't because they \"only\" have 9 months of school a year. It's because the American education system is an inefficient piece of shit. Finland uses the same 9 month system but it still has the best education in the world and kids still have plenty of time to sleep. Source: I am Finnish."
]
}
|
[] |
[] |
[
[],
[],
[],
[],
[],
[],
[]
] |
||
d3xbvs
|
in the olden days before gyms were a thing how did people gain large amounts of muscle mass?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/d3xbvs/eli5_in_the_olden_days_before_gyms_were_a_thing/
|
{
"a_id": [
"f05qqyq",
"f05qsal",
"f05qujg",
"f05qwsh",
"f05rl2c",
"f05rzlm"
],
"score": [
16,
2,
8,
5,
304,
43
],
"text": [
"In general, they probably didn’t attain the amount of muscle mass you see on super “ripped” people today, but when you have to use your body to do heavy manual labor over long periods of time, especially repetitive tasks that work most of the body in some way, you get fit and muscular.",
"Working/Training with barrels, stones, ropes. Anything can approximate weights or other exercise equipment.\n\nBonus go watch Rocky 4! Beats the high-tech trained Russian by working out on a farm.",
"Unfortunately very simple answer. By working manual jobs. Look at the old old days, any kind of trade like lumberjack blacksmith etc. They'll be swoll asf.",
"Among other thing, physical labor from a tender age due to either an industrial or agrarian job from the tender age of 12 because of lax labor laws and few safety restrictions. You'd be surprised the kind of gains a 13 year old boy can expect stacking square bales of hay by hand for 10 hours a day.",
"Ever wonder where the term \"Dumbbell\" comes from? People noticed that bell-ringers were pretty ripped, an unusual thing back in the day. Lots of people were strong from manual labor, but the muscles would hardly be bulging. Bell ringers though, were *yoked*. \n\nSomeone realized that yanking on ropes connected to a few tons of bell was a pretty sweet workout, but you know... kind of impractical for most people. Even if you had the money, pissing people off by ringing a bell all of the time wouldn't work. So... someone figured out that you could use a system of pulleys, ropes, and counterweights to imitate the workout, but without the sound; this would be a silent (dumb) bell. \n\nOver time the workout gear changed, and \"dumbbell\" came to refer to the weights we're familiar with today.",
"Gigantic muscles, like we see in some of today's bodybuilders, weren't really a desired thing in the past. Muscles were certainly admired in some cultures, as well as strength, but typically people admired muscles that were strengthened in order to DO something, whereas today sometimes bodybuilders simply get big for the sake of being big. \n\n\nIn ancient Rome, soldiers and athletes of all kinds (including Gladiators) would practice a wide range of exercises designed to improve strength, speed, flexibility, fighting skills, etc. The types of exercises depended on the goals of the person, what sort of sport or fighting style they used. Some of the wealthier men also liked to go to local gyms, or train with slaves or employees, in order to keep fit and strong and stay up on their fighting skills. \n\n\nIn ancient Greece they had gymnasiums called xystos, where competitors in the Olympic games would get training for their specific sports like running, wrestling, etc. Wrestling is actually still a very popular sport and training exercise in cultures around the world. \n\n\nWe also have evidence of special \"athletic\" diets from certain points in history. Archaeologists working in what is now Ephesus, Turkey, found a grave containing the bones of 67 Gladiators dating back 2000 years. After careful analysis they discovered that these men were eating very little meat and high amounts of legumes, grains, and non-meat foods high in carbs and calcium."
]
}
|
[] |
[] |
[
[],
[],
[],
[],
[],
[]
] |
||
3lvmvx
|
Humans in arctic climates (such as parts of Canada and Greenland) traditionally eat a diet consisting of almost exclusively meat. Would a person of different ancestry (aka me, a white American) be able to thrive on such a diet or are genetics a factor?
|
askscience
|
https://www.reddit.com/r/askscience/comments/3lvmvx/humans_in_arctic_climates_such_as_parts_of_canada/
|
{
"a_id": [
"cva4674"
],
"score": [
16
],
"text": [
"There are relatively well documented instances where groups of Europeans subsisted on an Inuit-style diet for long stretches of time. One such instance is sir Ernest Shackleton's voyage on the Endurance, which left from the island of South Georgia on December the 5^th 1914 to the Weddell Sea in Antarctica.\n\nThey rapidly became icebound and the crew was trapped by an early winter; then the boat was crushed by the pack. They ran out of provisons and relied on eating penguin and seals. After much effort, including dragging a lifeboat across the pack ice which they used to cross to elephant island, they were rescued on the 30^th day of August 1916. \n\nOverall, they were away for 1 year, 8 months, 25 days. They kept a meticulous journal and report throughout their stay that they took quite well to their diet of seal and penguin. They stayed fit, played soccer, their morale was generally good and they do not report any dietary deficiencies or ill effects from the diet itself.\n\nNow, that beeing said, a recent study has shown that Inuit populations have special genetic adaptations to that diet ([Fumagalli *et al.*, 2015](_URL_0_)), so one might expect there might be some divergences in results over longer time periods and given a larger test population. But the différences would at first glance to be in the nature of optimisation and not of gross incompatibility."
]
}
|
[] |
[] |
[
[
"http://www.sciencemag.org/content/349/6254/1343.short"
]
] |
||
5x78wt
|
Did the bizarre practice of turning men into eunuchs (and then giving these men substantial responsibilities) emerge independently in many places, or do we have some evidence of it starting in one place and then spreading through cultural diffusion?
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/5x78wt/did_the_bizarre_practice_of_turning_men_into/
|
{
"a_id": [
"degiag9",
"degtrr4"
],
"score": [
297,
7
],
"text": [
"Sorry for the delay… I’d have gotten this last night but it appears IFTTT is down, and that’s how I get summoned to the subreddit! \n\nWell first let me spoil the ending here: we don’t know, you can definitely argue for a single-eunuch-creationism theory or a multiple-convergent-evolution theory, and historians certainly do, there are a few eunuch traditions we can argue were directly inspired (or instigated) by one culture to another, but in general this historian believes eunuchs are as close to a biotruth as anything else in human history. \n\nSO, to begin, let us begin nicely at the beginning, who were the first eunuchs? We don’t know, but it’s likely that eunuchs were born sometime before writing. The first records of eunuchs (meaning men serving a specific social/cultural role for which castration had qualified them, and not just merely castrated men, the difference is fine but very important) come from Assyria. Eunuchs in this society are documented pretty much exactly as we’d expect in any other era and place - serving as politicians/servants in the court. The funny thing is though, they basically spring onto the historical record fully formed, there is no “gradual” appearance of eunuchs, it’s just bloop, they’re there, like anyone else at court, and why wouldn’t they be? There is no explanation for them, their existence was apparently as obvious to the Assyrians as they are baffling to us. This indicates that they are older than their appearance on the record. But, since then, you can draw a pretty straight timeline from culture to culture in the area of the Cradle of Civilization of eunuchs, from Assyria down to the Ottoman Empire in the 1930s, and I think it would be hard to argue that the technology of eunuchs was ever really lost and rediscovered in that area of the world. So there’s a decent argument you can make that it was invented once, and meme’d its way around the world, and we just don’t know the particulars of how it was passed in all instances. There are more clear examples too – the Korean eunuchs would be the easiest; they were explicitly passed from China to Korea, who they had subjugated. \n\nThere are however, some oddities of eunuch traditions that you can’t easily draw a line from their culture to another to say how they invented it. China is the big one – some make the argument that China was inspired by the ~~Byzantines~~ Ancient Romans, but I find it hard to support, unless you’re just desperate to prove this nasty little eunuch habit came from someplace else. Chinese eunuchs, like the Assyrian ones, pop up more or less as if they’d always been there. Same for the Italian castrati, they also pop up at the end of the 16th century, already there casually leaning on the edges of history, with no explanation for themselves, like almost every other eunuch tradition. There’s a few weak attempts to say they got the idea from someone else (usually “The Moors,” a nicely convenient scapegoat of a different religion and ethnicity) but after years and years, I have found no good support for blaming the castrato phenomenon on anyone. [Here’s a link to an old post where I wrote in more detail about the theories of the origin of castrati in particular.]( _URL_2_) \n\nSeparate to all this… there is an argument that castration of humans was invented after the discovery of the benefits of castration in animals as part of the invention of agriculture, and you’ll see a few people arguing the jump went from animal to man. But for my money, I think they have it a bit backwards. Messing with private parts (circumcision and other stuff) is something close to a cultural universal, you see it in lots and lots of cultures, and not all of them agricultural. Men have external sex organs, they’re hard not to look down and notice, their function would be easy to observe through sex and accidents, nor is it hard to look over at your neighbor and think “hmmmm.” Castration is not exactly that complex of an idea, to be plain, you think it’s “bizarre” now but you also codex books are normal and that’s way more complicated of an idea. But there’s no reason eunuchs can’t be independently invented. \n\n[I believe this is the most recent work on Assyrian and Hittite eunuchs,]( _URL_3_) and free to read online! Discussion of the origin of Chinese eunuchs is good in [this book.]( _URL_0_) [Gary Taylor]( _URL_1_) works on the agricultural theory in this book… I, uh, have some Big Problems with this book, but maybe if you want a different opinion on the origin of castration. :) \n",
"Something tangential to your question that it might be useful to keep in mind is that the term \"eunuch\" is used for a wide variety of cases. A lot of different languages have different words that are translated to mean \"eunuch\" but that doesn't mean they are necessarily referring to someone who has been castrated.\n\nThere are a wide variety of biological intersex physical external genitalia traits that can result in people being called a term that historians and linguists translate into \"eunuch\" in English. I'm actually in the process of creating a podcast on this topic (the podcast is just about history in general but one episode is about gender identity concepts throughout history and the history of intersex surgical procedures).\n\nFor example, the term Hijra, used in South Asia to refer to a third gender, is sometimes translated as \"eunuch\" but that is an inaccurate translation. It's possible that some historical figures that are referred to as eunuchs, if there isn't a specific reference to their castration, were simply born with an intersex trait that made their society not consider them male (micropenis, undescended testicles, unfused perineal tissue that makes it look like they have a vagina, one of various disorders that cause lowered testosterone or lowered ability to utilize testosterone, or even just a self-identification as female or something other than male).\n\nMany of these conditions (some resulting from having extra chromosomes) have he possibility of making a person infertile, which is usually one of the more important things to have in a traditional eunuch (because if they can't have children they can't create their own dynasties and many cultures wouldn't even allow them to be considered as a possible head of state, even if they could control things behind the scenes). In addition to the traditional eunuch role, there are just a lot of people that have been referred to as eunuchs (like the Hijra) that don't serve as courtiers or attendants or administrators or any of the roles in which eunuchs are used in certain societies."
]
}
|
[] |
[] |
[
[
"http://www.worldcat.org/title/eunuchs-in-the-ming-dynasty/oclc/802534856",
"http://www.worldcat.org/title/castration-an-abbreviated-history-of-western-manhood/oclc/50079029",
"https://www.reddit.com/r/AskHistorians/comments/4c2u1j/what_led_to_the_invention_of_castrati/d1gn9un/",
"https://www.academia.edu/3882323/Eunuchs_in_Hatti_and_Assyria_A_Reassessment"
],
[]
] |
||
9hpjdg
|
Was Nazism considered a form of socialism? At the time or now?
|
So I got into a heated debate about whether hitler was socialist I think he definitely was using his own version of socialism but I coild be wrong. At the time was he considered to be using a version of socialism or is it considered now to be based in that. My logic is Stalin is considered communist even though he was mainly a dictator so why not hitler?
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/9hpjdg/was_nazism_considered_a_form_of_socialism_at_the/
|
{
"a_id": [
"e6dnfca"
],
"score": [
20
],
"text": [
"I am not looking to limit conversation here but /u/G0dwinslawyer provided an excellent answer to this previously.\n\nI would add that dictatorship isn’t a specific philosophy per se and that both Hitler and Stalin were dictators within their relative political frameworks. \n\n_URL_0_"
]
}
|
[] |
[] |
[
[
"https://www.reddit.com/r/AskHistorians/comments/4ydl63/why_did_the_nazis_call_themselves_socialist_when/d6mykrr/"
]
] |
|
1035s5
|
Did anyone ever figure out what caused the massive bird and fish deaths last year?
|
askscience
|
http://www.reddit.com/r/askscience/comments/1035s5/did_anyone_ever_figure_out_what_caused_the/
|
{
"a_id": [
"c6a1n6t",
"c6a1rcq",
"c6a1uaq",
"c6a5gm5",
"c6abyz8"
],
"score": [
788,
59,
75,
31,
2
],
"text": [
"I am slightly involved with research on some of the die-offs that involve marine mammals, or UMEs as they are known in the trade. (Unusual Mortality Events) Basically there are always die-offs, every single year, in every group of animals, somewhere in the world. That list for last year doesn't actually look unusual, and I was always sort of puzzled about why it hit the news that year and not in other years. There are a hell of a lot of animal diseases out there, and epidemics sweep through now and then. For marine mammals the most common causes are epidemic disease (for example morbilliviruses that sweep down fom the north now and then when northern seals sometimes stray south), and red-tide-related outbreaks of toxins like domoic acid and brevetoxin. See [here](_URL_2_) for a great review. In other taxa there are very similar issues. \n\nMarine mammal UMEs in the US are tracked by NOAA. (See [here](_URL_3_) for more info) but the monitoring program is not well funded and is very imperfect. UMEs often only get reported in areas were there's a good marine mammal stranding network and a good necropsy facility to look at the carcasses. Last year there was clearly a die-off going on of harbor seals in the Gulf of Maine, but it took forever to get it reported because nobody in Maine had any funding to compile the necessary evidence and send it to NOAA. There was also another pinniped dieoff in Alaska that had different symptoms, and sick sea lions in Calif. Anyway, the Maine harbor seals turned out to have a new strain of influenza A.\n\nBy far the UME of greatest interest is the one that occurred in the Gulf of Mexico starting *three months before* the BP oil spill began (see [here](_URL_1_) for NOAA's page on it), with mortality worsening rapidly during/after the spill - BP is going to try to play this into \"they were already dying, it wasn't our fault\" so there's quite a few people trying to figure that one out. Hornet's nest of lawyers and I personally wouldn't touch that case with a ten-foot pole, but that's another story.\n\nBacking up to the bigger picture: are epidemic disease outbreaks more common in wildlife than they used to be? Certainly a lot of introduced diseases like West Nile have, with human assistance, colonized new places where they didn't used to be. Climate change is likely accelerating spread of certain diseases to new areas, especially tropical diseases spreading slowly poleward. There's a lot of speculation about whether chronically stressed animals, or animals carrying high toxin loads, are more vulnerable to disease than they would have been otherwise (see [here](_URL_0_)). Probably stress/toxin load/etc do play a role - for example dolphins living in polluted estuaries are known to be more vulnerable to disease than \"cleaner\" dolphins (see above refs).\n\nSo it's probably not one thing. It's a bunch of different diseases and toxins that often are hitting stressed, vulnerable animals in polluted/degraded habitats.",
"I remember that there were some flocks of birds found dead after New Year's Eve, and a lot of people took this as a mysterious bad omen because they didn't know what killed them. Turned out it was fireworks giving overhead flocks of birds heart attacks.\n\n_URL_0_",
"Yes. It was a combination of slow news amplifying a small story (bird kill which turned out to be probably due to chemicals sprayed on roosting birds to kill them - as they do in the midwest to kill off various black bird species and starlings at their roosts to reduce competition for corn with farmers) which then became one of those fads that the news media is constantly propagating. So every animal kill around the world (fish kills are very common and occurr for a variety of reasons) suddenly was more likely to get coverage. This was self amplifying as people (audience and journalists) suddenly fell victim to the availbility heuristic and thought that an artefact of the way the media works was actually indicative of a mysterious and threatening real word trend.\n\n_URL_0_",
"Out here in Northern California we get water fowl die-offs every year. Particularly in the flooded rice fields in the Central Valley. It's usually an outbreak of cholera. The fish die-offs in the Yolo Bypass are due to entrapment of fish in basins after flood waters recede. Dept. of Fish and Game always goes out to do \"fish rescues\", but it's mostly just for good press and public relations. Most of the fish die whether they're \"saved\" or not due to the stress of the whole situation.\n\nSource: I'm a former Dept. of Fish and Game biologist",
"Related question: what about the bees?"
]
}
|
[] |
[] |
[
[
"http://onlinelibrary.wiley.com/doi/10.1111/j.1439-0442.2005.00693.x/abstract;jsessionid=10F0B937B687B5FED011B7C243516E7F.d02t02?deniedAccessCustomisedMessage=&amp;amp;userIsAuthenticated=false",
"http://www.nmfs.noaa.gov/pr/health/mmume/cetacean_gulfofmexico2010.htm",
"http://www.ncbi.nlm.nih.gov/pubmed/19902843",
"http://www.nmfs.noaa.gov/pr/health/mmume/"
],
[
"http://www.usatoday.com/news/nation/2011-01-05-arkansas-dead-birds-fireworks_N.htm"
],
[
"http://www.csmonitor.com/USA/Society/2011/0120/Bye-Bye-Blackbird-USDA-acknowledges-a-hand-in-one-mass-bird-death"
],
[],
[]
] |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.