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fiq51
|
Why does my skin look different under different lighting conditions?
|
I noticed this while in the gym this morning. When I went into the raquetball court, my skin looked blue/grayish, and blemishes along my arm became more noticeable. I thought perhaps it was some type of weak x-ray, and I was getting the bluish hint of my bloodstream.
Google returns talk of this, and what types of light make your skin look better, but nothing scientific. (Vanity wins over science again)
I appreciate any clarification, thank you.
|
askscience
|
http://www.reddit.com/r/askscience/comments/fiq51/why_does_my_skin_look_different_under_different/
|
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"text": [
"Different kinds of lights are composed of different wavelengths of light. That is some lights have more red others more blue etc. When these reflect off your skin which reflects different colors differently you get different colors. It has nothing to do with x-rays. ",
"Exactly what the appropriately named UV Catastrophe said.\r\n\r\nRegular light bulbs are composed of all wavelengths at different proportions, like a bell curve. Fluorescent lights--due to the specific way they generate light by electrically exciting gas molecules--emit only very specific wavelengths of light, usually mostly green and some red. That powdery coating on the inside of a fluorescent bulb is supposed to smooth it out a bit, but optical detection and analysis shows it doesn't do that well.\r\n\r\nThus, anything that is blue, green, or red is going to stand out proudly, and everything in between looks sort of muted and gross.",
"This may also be a case of color theory. For example, if you stand in the bathroom (which usually has a yellowish light) you teeth may look pretty white. But if you were to hold a mirror in front of you while outside (where the light has less yellow in it) your teeth would look more yellow. If you were to step into a blue light, it would be exaggerated even more. It has to do with color compliments and works the same with the tints of color in your skin. Certain lighting is going to bring out reds or yellows etc. Think about when you shine different color flashlights on different samples of colors. Similar effect. \n\nYou should check out a decent color theory book. Interesting stuff.\n*Edited for grammar",
"On a side note, your blood is never blue. That's a common misconception that is not true. Anyone who has ever given blood can see that deoxygenated blood comes right out of your vein dark red. The reason it appears blue under the skin is because the light undergoes [Rayleigh scattering](_URL_0_) as it passes through tissue. This is a frequency-dependent effect and shorter wavelengths like blue scatter more, which is also why the sky appears blue."
]
}
|
[] |
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[
[],
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"http://en.wikipedia.org/wiki/Rayleigh_scattering"
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|
cg0tvi
|
if the polar ice caps were developed during the last ice age, why is it so bad that they are melting now? isn’t that more of a return to where we were rather than an anomaly?
|
I’m talking bad for the Earth itself; I get that coastal cities are screwed.
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/cg0tvi/eli5_if_the_polar_ice_caps_were_developed_during/
|
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"text": [
"I believe that the issue is that since the last Ice Age there have been a number of cities created right along the coast. Prior to that we don’t really have as far as I know anything archaeological evidence of cities on the coast. As the ice packs melt the water level rise which will drown most of the cities near the coast and additionally this may also impact the earths seasons or at least what cools off regions of the world and what helps regulate the temperature",
"It reflects sunlight, it influences ocean currents, it insulates the air, it keeps methane at bay, it limits severe weather, and it supports native Inuit people and wildlife.",
"The earth doesn't give a shit what's happening to it. You do along with all the things that live on it because they've adapted to the conditions that existed after the last ice age and they don't want to adapt again to rapidly changing conditions because that means a lot of them and their offspring are going to die.",
"It’s bad because there are billions of humans now. Changes in sea level will greatly affect the lives of millions people, especially those residing near bodies of water. Additionally, we have modified these bodies of water to accommodate more people (i.e., reclaimed areas).",
"Earth abides. Global warming is a blip for it. But global warming will kill people and destroy a lot of human-built stuff and cause many animal species to go extinct, and that’s bad. The changes being experienced on the earth by global warming are catastrophically fast, and mature can’t adapt that quickly, hence the extinctions."
]
}
|
[] |
[] |
[
[],
[],
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|
darqv0
|
With the massive influx of gold miners immigrating to California during its gold rush, was there enough food and water grown locally for them? Was food sent in? The miners obviously weren’t growing their own food.
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/darqv0/with_the_massive_influx_of_gold_miners/
|
{
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"text": [
"Water was usually not a problem - the California Gold Country has plenty of streams and rivers. During the drier times, miners had to wait for enough flow to \"wash dirt\" - the method used to expose gold, but there was always enough to drink.\n\nMiners spent a lot of time hunting. I co-edited the [letters of the Grosh Brothers](_URL_0_) - placer miners in the California Gold Rush. They described how two of their group would wash dirt while one or two others would go hunting. They would then share everything that each was able to produce during the day - food and gold. That was the typical approach for the first miners in the Gold Country.\n\nThere were also those who farmed. The Grosh Brothers gave up mining at some points and took up agriculture, but the lure of gold always brought them back (and they eventually died in the effort). There was also a great deal imported to California. Ships were repeatedly making the trip to Mexico and South American, bringing back passengers (and the mail!), but also a great deal of food grown in those areas. Costs were inflated in Gold Rush-era California, but acquiring food was not difficult.\n\nAs the Gold Rush went through its cycle of initial rush, depletion of gold, and then retreat from the Gold Country, infrastructure improved and more people were involved in agriculture, exploiting the rich natural resources of Northern California, which continue to feed the nation. Acquiring food was never that big of a problem; the real question was a matter of distribution and cost, but since the first years were \"flush\" with gold, money was no object."
]
}
|
[] |
[] |
[
[
"https://www.amazon.com/Letters-Allen-Shepperson-Nevada-History/dp/1943859019"
]
] |
||
7529i2
|
How have the eyes of animals that need clear vision in and out of water evolved to cope with the varying refractive indices?
|
For animals where it's arguably just as important for them to be able to see clearly in air and water (e.g. sea otters, penguins, crabs), has their vision evolved to cope with this somehow, or can they still see much more clearly in one medium than the other?
|
askscience
|
https://www.reddit.com/r/askscience/comments/7529i2/how_have_the_eyes_of_animals_that_need_clear/
|
{
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"text": [
"Anableps fish just have eyes that are half-and-half divided, with the top half working well out of water and the bottom working well in. It's _weird_. \n\nSeal pupils contract in the bright light of the surface, and their eyes focus better in air. In dim light (like they experience underwater) the pupils expand and the eyes focus better underwater. But at night on land, their pupils expand and their eyes can't cope well with seeing through air, giving them terrible night vision. It's apparently pretty entertaining to walk around a beach where they have hauled out at night....they know you are there but can't actually see you well at all."
]
}
|
[] |
[] |
[
[]
] |
|
n1ucn
|
why, when most people orgasm, they instinctively want to vocalize their excitement/expressions?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/n1ucn/elif_why_when_most_people_orgasm_they/
|
{
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"text": [
"No scientific answer here, but I can only assume it is like any other \"unexpected\" rush of emotions or feeling. When you step on a nail, you shriek. When you burn your hand, you shriek. Just like anonoman925 said, it is probably an involuntary reaction to too much stimulus.\n\nTL;DR: Too much stimulus = Involuntary reaction.",
"No scientific answer here, but I can only assume it is like any other \"unexpected\" rush of emotions or feeling. When you step on a nail, you shriek. When you burn your hand, you shriek. Just like anonoman925 said, it is probably an involuntary reaction to too much stimulus.\n\nTL;DR: Too much stimulus = Involuntary reaction."
]
}
|
[] |
[] |
[
[],
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||
gsa3i
|
What would happen if a MAGLEV train lost power?
|
Since MAGLEV trains rely on electromagnets to stay off a rail, what happens when they lose electricity? Do they have some kind of skidpad or emergency wheels to rely on?
|
askscience
|
http://www.reddit.com/r/askscience/comments/gsa3i/what_would_happen_if_a_maglev_train_lost_power/
|
{
"a_id": [
"c1pwyrr"
],
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15
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"text": [
"They have wheels."
]
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|
[] |
[] |
[
[]
] |
|
5aatfz
|
how would the space agencies respond if they detect an incoming asteroid large enough to cause damages?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/5aatfz/eli5_how_would_the_space_agencies_respond_if_they/
|
{
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"text": [
"The space agencies would report it to the public. They are in no position to keep anything like that a secret and in no position to do anything about it. The only thing they can do is warn people the best they can in the hopes that people might get to safety. The only thing anyone might be able to do about it is to launch a nuclear ICBM against it in the hope that it will break up and cause a number of smaller less dangerous meteorites. The space agencies does not have ICBMs as they are used by the military but the space agencies will hopefully be able to help in such an event. We have not tried such a thing either and have no idea if an ICBM can fly the radically different flight path needed or what a nuclear device does to an asteroid.",
"There are a number of ways of responding to a potential threat that have been theorised. The most common is to use a nuclear detonation to destroy or deflect the object away from Earth. Other alternatives include using a kinetic impact in a similar way, a laser array to disintegrate the object or even use a normal rocket to push the object away.\n\nThese all have pros and cons and are untested. The likely outcome is by the time we identify the object it's likely too late to do anything to change it."
]
}
|
[] |
[] |
[
[],
[]
] |
||
414ogf
|
how are news outlets and online articles able to be so misleading and sometimes downright wrong with their stories?
|
[deleted]
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/414ogf/eli5_how_are_news_outlets_and_online_articles/
|
{
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"Back up a bit and imagine a government body who's job is to decide what is and isn't true, and to censor or fine news agencies that it believes are wrong. \n\nA) It would be incredibly unconstitutional, as freedom of the press is a critical right that we all have.\n\nB) Consider the possibility of abuse. Is it staffed by people? If yes, then its entirely possible that they'll bring in their own biases, and start shutting down points of view that they disagree with.\n\nC) What is true or false. We can all think of blatant examples, as that's easy. Where do you draw the line. Could an organization be punished for a mistake? How about a matter of opinion, which much of the news media focuses on. Are you willing to give a government agency the ability to silence reporters because their opinions are \"wrong,\" or because the person they're interviewing is wrong about something.\n\nSuch a thing could never be safely or effectively implemented in a free country."
]
}
|
[] |
[] |
[
[]
] |
|
dzh7f9
|
why do injuries tend to hurt more in winter than in summer?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/dzh7f9/eli5_why_do_injuries_tend_to_hurt_more_in_winter/
|
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"text": [
"One reason is that when your immune system is compromised, your body amplifies pain signals to trick you into staying in bed. It's one reason why you're achy and weak when sick. Since your immune system tends to be weaker in the winter when your body is expending a lot of energy to stay warm. This effect happens more often in winter.",
"Generally speaking, we feel more pain in the cold because there is a relationship between blood circulation and nerve pain. When its cold outside and you aren’t dressed up for it, it’s very difficult for your body to heat itself because your heart rate slows in the cold as a way to survive. Our nerves are a network that send signals to the brain -ouch- that hurt! As circulation and heat increase our nerves calm down. The cold is more painful because it increases pressure on our nerves and stiffens soft tissues- such as your muscles. This in itself can increase your likelihood of injury (which is why runners do warm ups and wear sweats!)"
]
}
|
[] |
[] |
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[],
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||
299b58
|
How can moons get "captured" by planetary bodies without having done a "retrograde burn"?
|
I've heard of planets capturing satellites before, but I recently read about Triton likely having been captured into Neptune's orbit, and I realized such a free-body capture would be pretty difficult/impossible to reproduce in "Kerbal Space Program" because you'd always need a retrograde burn to reduce relative velocity.
Is it just that the correct trajectory for free-body satellite capture has completely escaped my intuitions about gravity? Or perhaps KSP's gravity modelling is inadequate?
|
askscience
|
http://www.reddit.com/r/askscience/comments/299b58/how_can_moons_get_captured_by_planetary_bodies/
|
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"The reason that KSP requires retrograde burns to have a captured orbit is because KSP does not accurately simulate multi-body gravity. When you orbit Kerbin, you only experience Kerbin's gravity. However, when orbiting Earth, a decent chunk of the gravity you experience is the Moon's, with a little left over for the Sun and everything else. This acts as an extra force on the object.\n\nHere is a good example. \n_URL_0_\n\nIf you watch closely, you can see that the object (which is believed to be an old Apollo spacecraft part) accelerates extremely quickly as it passes closely to the moon on both its first and last approach to the system.",
"Triton is Neptune's captured moon. To go into orbit, Triton still had to lose momentum somehow, just as you do a burn to get captured by Duna (or, perhaps get your orbit adjusted by Ike). In KSP, the moons and planets are all on rails, but in real space, you would transfer some of your momentum to Ike to get captured by Duna. Your orbit will still intersect Ike's, so you'll either get ejected or eventually settle into a resonance.\n\nNeptune probably didn't have a large moon for Triton to transfer momentum to -- but Triton, like Pluto and many other outer solar system bodies, was probably a binary object. So Triton's partner got sped up as Triton slowed down, letting Triton get captured by Neptune while its partner got boosted to higher-energy orbit."
]
}
|
[] |
[] |
[
[
"http://upload.wikimedia.org/wikipedia/commons/3/39/J002e3f_orbit.gif"
],
[]
] |
|
1sjqgz
|
How did the Merchant Republics in Italy arise in isolation while the rest of Europe seems steeped in Feudalism?
|
Did they have any long term effects on the rest of Europe? Why does there seem to be little connection between these early Republics and later ones? Why didn't or did other feudal lords view them as competition and dangerous to their position?
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/1sjqgz/how_did_the_merchant_republics_in_italy_arise_in/
|
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"text": [
"I'm not sure the question as it's posed will yield a satisfactory answer. Feudalism and a republic aren't mutually exclusive, as the former isn't a type of government. Besides, the republics present in Italy weren't the kinds of republics we think of today. They were essentially city-states dominated by elites and ruled by particular noble families (e.g. the de'Medicis in Florence). The Dutch republic and the state of Novgorod functioned in much the same way.\n\nFor more info, I'd check out Daniel Waley and Trevor Dean, [_The Italian City-Republics_](_URL_1_) and Perry Anderson's [_Passages from Antiquity to Feudalism_](_URL_0_).\n",
"A big question, particularly around the 90's (after the fall of one of the last multi-ethnic empires: the Soviet Union), was how the world came to be entirely divided in nation-states as it seemed right then. Was it coincidence? Was there something inherently more effective about nation-states? Fukuyama famously declared it the end of history, others were more reserved, but there was a general agreement that it was in fact the case now, but clearly it had not always been like that.\n\nAnd this is the context that generated a lot of interesting literature on the structure of medieval politics. One of the most interesting ideas imo, comes from Charles Tilly in his work \"Coercion, Capital, and European States\". He argues that European history (after 990 AD) essentially knows two bases for political power: a concentration of capital, and a concentration of potential for coercion (money and swords, so to speak). Capital, he argues, tends to be concentrated in cities. So, is his notion, during most of the middle ages in rich, urban regions of Europe (most notably northern Italy, but later also the Low Countries and parts of north Germany, I think) monied elites formed the basis of local regimes, whereas in other parts of Europe power was based on control over the military class, with a lot of pressure on regimes to get control over both sources of power.\n\nHe leaves lots of room for criticism, at least partially by being very thin in the specifics, but I think he makes a strong point for the fact that the presence of lots of money hugely impacted the course of history for northern Italy."
]
}
|
[] |
[] |
[
[
"http://books.google.com/books?id=NE9qw3_yCRgC&printsec=frontcover&source=gbs_ge_summary_r&cad=0#v=onepage&q&f=false",
"http://books.google.com/books?id=CQbdAAAAQBAJ&printsec=frontcover&source=gbs_ge_summary_r&cad=0#v=onepage&q&f=false"
],
[]
] |
|
3alku1
|
what causes that characteristic "grandma scent?"
|
Assuming I even want to know the answer...
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/3alku1/eli5_what_causes_that_characteristic_grandma_scent/
|
{
"a_id": [
"csdqheh"
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"text": [
"technically it's described as:\n\n* floral\n* aldehydic (a sub category of floral, think soapy and citrusy)\n* musky\n* powdery\n\nTo ELI5, it's typically Chanel No 5 with a slight baby powder note."
]
}
|
[] |
[] |
[
[]
] |
|
b9cdfr
|
what would happen if you took laxatives for an entire week?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/b9cdfr/eli5_what_would_happen_if_you_took_laxatives_for/
|
{
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"text": [
"I assume hemorrhoids at the very least. \n\nThis is a form of bulimia. And the long term effects are more concerning then the week your on them. At some point (not sure if it’s after one week or more prolonged used) you’ll start to have loose bowels because your body hasn’t been needing to work on its own. ",
"Former laxative abuser here. Assuming you are talking about stimulant laxatives, while continuing a normal diet, the only weight loss would come from holding less waste in your body and dehydration, as your body still digests the food normally. You may experience severe muscle cramps, intestinal bloating from inflammation, joint pain, a sore raw butthole, and headaches from the dehydration. Continued prolonged laxative abuse will also cause nausea, weakness, and can lead to seizures from electrolyte imbalance. Not to mention the normal intestinal cramping from the laxatives itself. There were instances where the nausea and pain were so intense that I would also throw up while having a bowel movement. While taking the laxatives, bowel movements can also become unpredictable, and experiencing random \"leaking\" is very common, which is usually triggered around half an hour after eating. Your body can also get used to the dose you have been taking, and to continue having the desired effect, you may have to up your dose. Aside, taking stimulant laxatives regularly without continuing to eat can cause you to poop stomach bile, which burns like the fires of hell all the way out. Once you stop taking them after such a period of time, you will experience constipation, as your body has come to rely on the effect of the stimulant laxative to eliminate waste. The constipation will last anywhere from a few days to weeks depending on the individual's response to detoxing from the laxatives.",
"It depends on the type of laxative. For example doctors regularly prescribe Miralax, Colace etc. for daily usage by people who have constipation problems. Those laxatives work by drawing water into the large intestine to soften the stool so its easier to pass. On the other hand, laxatives with Bisacodyl as the active ingredient force your intestines to contract,. So your body \"pushes\" the poo out. Just one regular dose can make you extremely uncomfortable. Taking a higher dosage will be extremely painful. I did this once, it was really really bad. I lost 13 pounds of mostly water. People do use it for weight loss though, especially to make a weigh in. This happened all the time during PRT season in the Navy. But, long term abuse can cause a whole host of problems including permanently messing up your ability to poo without assistance. "
]
}
|
[] |
[] |
[
[],
[],
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||
3nd8kh
|
if we can't see atoms how did ibm make a movie with them?
|
I'm curious about what we are seeing on the movie with the boy and his pet atom ! (A boy and his atom)
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/3nd8kh/eli5_if_we_cant_see_atoms_how_did_ibm_make_a/
|
{
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"text": [
"Those are Carbon Monoxide molecules. \n\nFor that note, electron microscopes can operate pretty much on an atomic scale. "
]
}
|
[] |
[] |
[
[]
] |
|
chmd6d
|
were little old people always little or do they shrink as they age?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/chmd6d/eli5_were_little_old_people_always_little_or_do/
|
{
"a_id": [
"euv1a4l"
],
"score": [
3
],
"text": [
"Most people do shrink as they get older and their bodies degenerate.\n\nThe very little old people you're thinking of were short to begin with and shrivel up more."
]
}
|
[] |
[] |
[
[]
] |
||
65tbjt
|
Why do some places show a long-term decline in sea level and others a rise?
|
There's a sea level monitoring site in Alaska that [shows a long-term decline in sea level](_URL_0_).
I don't understand how this can happen? If there is a global sea level rise shouldn't everywhere be rising?
Genuinely curious. Thanks.
|
askscience
|
https://www.reddit.com/r/askscience/comments/65tbjt/why_do_some_places_show_a_longterm_decline_in_sea/
|
{
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"text": [
"Measuring sea level is actually tricky business and we're not really *that* good at it currently.\n\nAdditionally, there's global sea level and local sea level. Global sea level is mostly affected (at least on human time scales) by the volume and temperature of the ocean (which is mostly affected by melting of surface ice). But the land on Earth is not static, so local sea level ends up being even more complicated with a lot more factors going into it. A major factor around river mouths, for example, is subsidence. The land there is soft, and it settles over time (to simplify) so even if nothing about the ocean changed the water depth at a particular point in a river delta might get deeper over time. Similarly, material deposition can have the opposite effect.\n\nAn important factor today is that the Earth only recently, in geological terms, came out of an ice age. For a period of about a hundred thousand years vast ice sheets covered much of the northern land masses. The current location of Boston would have been under more than a kilometer of ice, for example. Those ice sheets were, of course, massive and the water that made them up came out of the oceans, which is why the sea levels were lower during that period. Additionally, the weight of those ice sheets pushed down the continents, which float on the solid but plastic mantle. When the ice sheets retreated with the end of the ice age about ten thousand years ago the water raised the global sea level significantly (flooding a lot of low lying areas) but it also reduced the force that was weighing down the areas of the continents where the ice sheets were. As a consequence many northern land masses have been experiencing a long period of \"post-glacial rebound\", as slow geologic forces push them toward a different equilibrium elevation than when they were weighed down by glaciers.\n\nThis movement is actually large enough to be measurable, and it's highest in places like Norway and Northern Canada. And, of course, Alaska. Southern Alaska is rebounding at a rate of several millimeters per year. Global sea level rise is smaller than this movement so local sea level change in regions still experiencing post-glacial rebound is negative, the sea seems to be going down (though in fact the land is going up). You can see the same thing in [Oslo, Norway](_URL_0_) for example.\n\nBut if you look at areas that never had local glaciation and aren't experiencing post-glacial rebound, like [Mumbai, India](_URL_1_), you see a different trend, one of increasing sea level. However, if you look at the sea level trends for a lot of different port cities at low latitudes you'll find that the rates of sea level increase are all over the place, from just a single mm/year up to several mm/year. A lot of that is due to different rates of subsidence. The land moves (both up and down), so trying to measure one moving thing from another moving thing is a very challenging problem.\n\nWe've been measuring the sea level with satellites for decades, but even that is not without it's fair share of problems. The main one being that we can't seem to calibrate the measurements of the satellites sufficiently well to actually have much confidence in the exact values of the trend data. We can be fairly certain that there's a global sea level rise but it may be as low as 0.5 mm/year or as high as 2-3 mm/year, it's hard to be certain.",
"A process called isostatic rebound causes land uplift resulting from the lack of ice that was once present which caused large depressions over an area. This uplift, or rebound, is greater then the rate of sea level rise. A classic example of this process can be observed in north eastern Europe, where historically the land was covered in ice kilometres in thickness, similar to present day Greenland. It is very important to note that sea level change is a very complex science with dozens of factors contributing to a net rise or fall for example, water temperature, air pressure, and water currents trends. All of which change on annual, decadal, centennial, and millennial scales. The max and min sea level difference globally is a much as 70m from what I remember, all due to local factors mentioned. \n\nSource: Have a bachelors degree in physical geography"
]
}
|
[] |
[
"https://tidesandcurrents.noaa.gov/sltrends/sltrends_station.shtml?stnid=9451600"
] |
[
[
"https://tidesandcurrents.noaa.gov/sltrends/sltrends_global_station.shtml?stnid=040-321",
"https://tidesandcurrents.noaa.gov/sltrends/sltrends_global_station.htm?stnid=500-041"
],
[]
] |
|
87cvi4
|
How do we measure gas levels of an exoplanet's atmosphere?
|
Methinks this would be impossible with current technology since we have to use a host star to even theorize an exoplanet's existence.
|
askscience
|
https://www.reddit.com/r/askscience/comments/87cvi4/how_do_we_measure_gas_levels_of_an_exoplanets/
|
{
"a_id": [
"dwc0qdw"
],
"score": [
10
],
"text": [
"Molecules have characteristic absorption lines in the electromagnetic spectrum. The width of these absorption lines depends on the optical thickness of the gas. Meaning, with more gas in our line of sight we will have a stronger (wider) absorption band. \nIn order to measure the atmosphere of a planet, the planet needs to orbit infront of the star. Then some light of the star will pass through the planets atmosphere. We can then compare the spectrum of the star with the planet and without. The difference between the two spectra allows us to see the effect of the atmosphere of the exo planet on the spectrum. By using some sophisticated data and error analysis it is theoretically possible to estimate the content of the atmosphere. However in order to reliably do this you need very high resolution spectrographs and you need to be able to estimate all the other parameters that can also broaden the spectral lines. This could be thermal doppler broadening of atmospheric molecules, broadening due to the rotation of the planet, shifts due to the motion of the planet around its host star, pressure broadening, etc. etc. It is not a trivial process and this kind of technology is not very far yet. However our technology improves every year and we make theoretical advances every year so soon we should be able to characterise exoplanet atmospheres more reliably. "
]
}
|
[] |
[] |
[
[]
] |
|
2wt17g
|
Education in post war Germany?
|
In the UK we're taught about how Hitler planned to continue his Cult of Personality by teaching the Nazi Party ideals in schools (Jews are evil, Arians are superior, Hitler is sehr gut, this is what -insert race here- look like). But what happened after the war to everyone who had been socialised into believing this? How valued were their qualifications?
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/2wt17g/education_in_post_war_germany/
|
{
"a_id": [
"cotxydn"
],
"score": [
2
],
"text": [
" > How valued were their qualifications?\n\nIn West Germany the folks behind the racial science of the nazi regime [kept teaching their subjects](_URL_0_) using their skills to, for example, measure the skulls of the Canary Islanders. The continuity of West German elites would be a major issue both to East Germany and in the West German public.\n\n > But what happened after the war to everyone who had been socialised into believing this?\n\nwhat was done to \"reeducate\" or \"denazify\" Germans has been asked before so here's a primary source on the opinions immediately thereafter:\n\n > Report No.12 (28 June 1946) \n > ATTITUDES OF SOME BAVARIAN SCHOOLCHILDREN\n > Sample:250 schoolchildren between the ages of 12 and 18 in\nRegensburg, Weilheim, Pirkensee, and Burglengenfeld\nInterviewing dates:not specified. (6 pp.)\nAlthough 88 per cent of the children had belonged to Nazi youth\norganisations, only 12 per cent were members of a new youth\norganisation. Thirty-seven per cent of their parents had belonged\nto the NSDAP,a figure about average for the American zone. Eightyfour per cent of the youth were Catholic. Most (48%) would vote\nfor the CSUif they were old enough, 18 per cent for the SPD, and\nthree per cent for the KPD. Almost a third (29%), however, said\nthey would not vote even if they could.\n\n > Their principal concern was obtaining food. Thirty per cent said\nthat the type of aid Germany needed most was food, and 26 per\ncent reported that their greatest wish was for more food. They also\ndesired peace and freedom for their brothers who were prisoners\nof war. Their secondary concern were jobs, clothing, and shoes.\nThe children seemed to be in good health. Reading, sports, and\nhandicrafts provided recreation.\n\n > Almost all the children (98%) claimed to like school. Most (66%)\nthought themselves to be average students. About one-third\nconsidered themselves to be good students. Only a few (3%)\nadmitted that they were bad students. Although they were interested\nin a wide variety of subjects, they liked best mathematics, German,\ngeography, history, biology, and English. Seventy-four per cent\npreferred to learn English rather than some other foreign language.\nThe employment aspirations of the youth were generally low.\nThe girls wanted to be saleswomen, dressmakers, clerks, teachers,\nor hairdressers. The boys wished to be bakers, electricians, or\ncarpenters. None of the boys wanted to teach. More girls (7%)\nthan boys (3%) hoped to become physicians or dentists.\nThe most common reason given (36%) for Germany’s loss of\nthe war was the overpowering strength of the enemy. Second\n(30%) was Germany’s lack of material. When asked to name the\nthree greatest Germans, about ten per cent named Hitler, a\nquarter mentioned monarchs, and a third poets. When\nquestioned as to what the respondent would do if he alone knew\nthe secret of the atom bomb, the most common answer given\n(36%) was to keep it a secret. Democracy to these youths meant\nfreedom for the people (23%) and government by the people\n(10%). Forty-eight per cent, however, had no opinion when\nasked what democracy meant.\n\n > Almost as many (35%) liked the American soldier as disliked\nhim (39%). More than half of those who disliked the American\nsoldier mentioned his general behaviour as a reason.\nMost of the youth expected a good, lasting, or just or wise peace\nfrom the Allies. Fifty-nine per cent did not expect another war\nsoon. Of the 41 per cent who did expect war, most thought it would\nbe with the Soviet Union."
]
}
|
[] |
[] |
[
[
"http://en.wikipedia.org/wiki/Ilse_Schwidetzky"
]
] |
|
ygvyn
|
Can house flies, fruit flies, or other insects see the microscopic organisms or bacteria on stuff that we can't see?
|
askscience
|
http://www.reddit.com/r/askscience/comments/ygvyn/can_house_flies_fruit_flies_or_other_insects_see/
|
{
"a_id": [
"c5viylr",
"c5vj2mn"
],
"score": [
65,
20
],
"text": [
"I don't believe they can. Their eyes, [compound eyes](_URL_1_), are not intended to see high detail images because their largest threats are larger than they are (ie, a cow's tail or your hand trying to swat them). Instead, they are intended to see fast movements over a large angular resolution, they can see movements from more angles than we can (again, the cow's tail or your hand coming in from a weird angle) however, their eyes lack [visual acuity](_URL_0_).",
"No. A smaller eye does not automatically make the eye see sharper.\n\nA less advanced compound eye does not see sharper than a more advanced octopus eye.\n\n~~Human eyes can easily see very small things floating on the eyes surface, but its generally very out of focus and highly transparent, irrelevant and therefore unnoticed.~~\n\nEverything else is just a matter of focussing, its easy to see something small on a short distance if the eye allows for it. Since eagles must be good at this, i wonder how a hawk/eagle eye can see a nearby non-moving water surface."
]
}
|
[] |
[] |
[
[
"http://en.wikipedia.org/wiki/Eye#Visual_acuity",
"http://en.wikipedia.org/wiki/Eye#Compound_eyes"
],
[]
] |
||
r384j
|
why do some people enjoy massages but it causes pain for others?
|
Whenever I get massaged around the neck (Scalene muscles, I think) it really, really hurts. But a lot of people really enjoy it. I'm told it's because I'm not used to it but that sounds weird. Please help, I know it's stupid but I've wondered about this forever.
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/r384j/eli5_why_do_some_people_enjoy_massages_but_it/
|
{
"a_id": [
"c42jzr8",
"c42mfpx"
],
"score": [
3,
2
],
"text": [
"There is a huge difference between massages just for the feeling of someone rubbing your back with some more force in it and massages for relaxing muscles. I have a rather high pain tolerance, but if my muscles are really tense, having them massaged hurts *a lot*. I can't give you a good explanation for that (any physicians/medicine-students around here?), but this is one reason why a lot of people do not enjoy massages meant for really relaxing the muscles. And if my muscles are really tense, even slightly pressing them will hurt, so maybe your neck is just ridiculously tense? In this case I'd recommend going to get a medical massage. I've known folks running around with muscles that were never really relaxed for years. They didn't even know what a relaxed back feels like, so they didn't miss it.\n\nMassages for relaxing the muscles are generally made harder, so they might even hurt slightly if your muscles are not tense and you are not \"used to it\" (meaning your pain tolerance to this kind of pain is very low). Another possibility: The guys giving you a massage didn't know, what they were doing. A wrong massage hurts too, but it will only tense your muscles even more.",
"Secretly, some people are masochists."
]
}
|
[] |
[] |
[
[],
[]
] |
|
8p8ln3
|
When was the highest % of the global population enslaved and did ancient societies with more slaves have an economic advantage over their rivals?
|
I'm not asking anyone to put forward any arguments for slavery, I think the moral arguments against it are obvious enough.
Nonetheless my question more or less has 2 parts:
A) What was greatest % of the human population that was enslaved at any one point in history?
and
B) Did societies that had more slaves have an economic advantage over those that had less? If there was a strong advantage, then surely every nation would seek to acquire as many as possible in an endless quest to gain an competitive edge over their neighbors.
Thank you for your help :)
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/8p8ln3/when_was_the_highest_of_the_global_population/
|
{
"a_id": [
"e09o6di"
],
"score": [
10
],
"text": [
"Follow-up: Did areas with high percentages of slaves have poor freemen angry over economic woes? It seems like there would be a shortage of paying jobs when the wealthy could simply buy slaves to fill almost every role from farmhands to pedagogues."
]
}
|
[] |
[] |
[
[]
] |
|
fvtxzk
|
why is it easy to pick up a child that weighs 40 to 50 kilograms but very difficult to pick up a 40 to 50 kilogram weight?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/fvtxzk/eli5_why_is_it_easy_to_pick_up_a_child_that/
|
{
"a_id": [
"fmkiqae",
"fmkl60o",
"fmkmo5i",
"fmkmr6d"
],
"score": [
23,
9,
3,
6
],
"text": [
"The weight of the child is spread out over a large area compared to the relatively small area of the weight, making the child appear easier because it uses more muscles.",
"On top of what others have said, there’s usually a bigger incentive not to drop the child, so you try harder.",
"Well you're using both hands and your legs. You don't just grab a kid by the shirt and hoist it up with one arm. You bend down, grab the kid with both hands and use your legs to lift.\n\nWhen you pick up a dumbbell you're using one hand, which means the weight is to your side, which means it's an unbalanced lift, you have a hard time using your legs on an unbalanced lift, etc.\n\nWhen you pick up a barbell (this would be an empty bar), it's long an ungainly.\n\nWhen you pick up a box it's a smooth-sided surface with nothing to grab onto.\n\nThere are very few parallels to picking up a child. Picking up a lumpy piece of equipment like a kitchen mixer, desktop PC or a microscope is similar I suppose. Not hard if you can get a good grip on it.",
"Because a child doesn't weigh 40-50kg, that's around the weight of the average 14-17 year old male\n\nObjects typically are harder to pick up also because they are lower to the ground, a child with outstretched arms you're only picking up from around thigh/waist height"
]
}
|
[] |
[] |
[
[],
[],
[],
[]
] |
||
nfyfp
|
If an Amnesia victim has lost their memories for a significant amount of time and recovers their memories, will they regain their original personality or keep the amnesia personality?
|
I'm really curious about this. If an amnesia victim turns into basically a different person after memory loss, like in the movies. Will they be more like the "new" person after the memories come back, or return to the original person they were before amnesia.
|
askscience
|
http://www.reddit.com/r/askscience/comments/nfyfp/if_an_amnesia_victim_has_lost_their_memories_for/
|
{
"a_id": [
"c38s564",
"c38s564"
],
"score": [
11,
11
],
"text": [
"What we observe as personality is the product of variance in regions of the brain- this study, for example, shows the correlation between neuroticism and amygdala variance- _URL_0_ . An individual's personality is quite stable over the long run- see here _URL_1_ and here _URL_2_ . \nAmnesia, specifically in your case retrograde amnesia, impacts the brains ability to utilize its episodic memory system. From the wikipedia article on amnesia- \"This type of amnesia first targets the patient's most recent memories, the amount of memories lost depends on the severity of the case. The person may be able to memorize new things that occur after the onset of amnesia (unlike in anterograde amnesia), but is unable to recall some or all of their life or identity prior to the onset. The effects of retrograde amnesia (RA) occurs on fact memory on a lower degree than its affects on autobiographical memory, which can be affected over the whole lifespan of the patient by RA.\" \nSo, to answer the question, personality wise, they would be the same throughout. If their memories returned, their personality wouldnt change- all that would change is their ability to recall the memories they had \"lost\". ",
"What we observe as personality is the product of variance in regions of the brain- this study, for example, shows the correlation between neuroticism and amygdala variance- _URL_0_ . An individual's personality is quite stable over the long run- see here _URL_1_ and here _URL_2_ . \nAmnesia, specifically in your case retrograde amnesia, impacts the brains ability to utilize its episodic memory system. From the wikipedia article on amnesia- \"This type of amnesia first targets the patient's most recent memories, the amount of memories lost depends on the severity of the case. The person may be able to memorize new things that occur after the onset of amnesia (unlike in anterograde amnesia), but is unable to recall some or all of their life or identity prior to the onset. The effects of retrograde amnesia (RA) occurs on fact memory on a lower degree than its affects on autobiographical memory, which can be affected over the whole lifespan of the patient by RA.\" \nSo, to answer the question, personality wise, they would be the same throughout. If their memories returned, their personality wouldnt change- all that would change is their ability to recall the memories they had \"lost\". "
]
}
|
[] |
[] |
[
[
"http://journals.lww.com/neuroreport/Abstract/2005/11280/Amygdala_gray_matter_concentration_is_associated.7.aspx",
"http://www.ncbi.nlm.nih.gov/pubmed/4078676",
"http://www.jstor.org/pss/20182303"
],
[
"http://journals.lww.com/neuroreport/Abstract/2005/11280/Amygdala_gray_matter_concentration_is_associated.7.aspx",
"http://www.ncbi.nlm.nih.gov/pubmed/4078676",
"http://www.jstor.org/pss/20182303"
]
] |
|
42vwtc
|
can alcohol turn you into a different person?
|
[deleted]
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/42vwtc/eli5_can_alcohol_turn_you_into_a_different_person/
|
{
"a_id": [
"czdj6yw"
],
"score": [
3
],
"text": [
"In my experience, alcohol just loosens inhibitions. So people who \"get mean\" when they drink are just mean people who usually keep it together. Just like I get really sentimental when I drink; I'm a sentimental guy, it's just normally under the surface."
]
}
|
[] |
[] |
[
[]
] |
|
58gmu0
|
Like Google Maps...but for History
|
Since it's Thursday again, I have yet another question about teaching tools.
I teach World History. My students are first year undergraduates from many different countries. This week I have learned the hard way that even 'obvious' historical facts, like say, what the Roman Empire was, is not obvious to all my students who after all come from all over the world.
I have found Google Maps an immensely useful tool. Now I can simply point to a place on the globe, and explain that during this period that empire ruled over roughly that territory.
There are of course several problems with this approach: The globe has modern states and modern borders on depicted on it, and my hand-waving is vague at best.
So my question is, is there some kind of historical globe that I can use? Ideally one where I can set the date and show (roughly) what the world looked like during various periods of time. I know several computer games by Paradox can do this, but booting up EU IV in class is hardly professional (aside from not being 100% accurate).
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/58gmu0/like_google_mapsbut_for_history/
|
{
"a_id": [
"d90f823",
"d90f8ri",
"d90r4zn",
"d90uv9o"
],
"score": [
25,
6,
2,
3
],
"text": [
"The website [GeoCron](_URL_1_) is a good place to start. You can skip to any year and it will show you roughly what the world looked like. It is not entirely accurate at some points, like sometimes the author just places a circle and the name of the civilization where he may not have much information. However, it is a good place to start and gives a good visual of empires, the first civilizations, and the such.\n\nOf course, more detailed maps can be used in collaboration with GeoCron to give your students a better understanding. I have found [Euratlas](_URL_0_) to be a decent sources for maps of different European regions in 100 year increments. So a bit of big stretches between maps, but decent if it has one near the year you are interested in.",
"Chapel Hill has the [Ancient World Mapping Center](_URL_0_). It's a little tricky to use - I've been able to generate maps for one of my chapters, but I haven't figured out how to get a persistent link and I have no bloody clue what the citation will be. Right now they're jpgs of screenshots. Should be fine for lecture though.\n\nSometimes the names of places are tricky. I think it prefers Rubico to Rubicon for some reason; some other places prefer to use the Latin or Greek forms in idiosyncratic ways. Probably fine for your needs though.",
"I find that [Talessman's Atlas](_URL_0_) maps are very good for teaching about the ancient and medieval periods indeed. Hope they can be of some use for you, too!",
"Google Earth has a [timeline feature ](_URL_0_) in the top bar. It only goes back to the 1940's in most cases and generally only in urban centers. \n\n[How To](_URL_1_)\n\nIt uses early aerial photography from the 1930's to the late 1990's, at which point satelite imagery kicks in. The oldest shots are in Texas around Spindletop, mapping oil fields.\n\nI use it to research & demonstrate growth and historic context of neighborhoods we do projects in. You can literally pick a spot, scroll back & forth watching change happen decade by decade."
]
}
|
[] |
[] |
[
[
"http://euratlas.net/",
"http://geacron.com/home-en/?&sid=GeaCron70960"
],
[
"http://awmc.unc.edu/wordpress/"
],
[
"http://www.worldhistorymaps.info/maps.html"
],
[
"https://support.google.com/earth/answer/148094?hl=en",
"https://support.google.com/earth/answer/148093?hl=en"
]
] |
|
1xws9k
|
modulo
|
All of the explanations I can find on this assume the reader is smart. I'm not.
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/1xws9k/eli5_modulo/
|
{
"a_id": [
"cffaljj",
"cffanex",
"cffd3s7"
],
"score": [
2,
3,
2
],
"text": [
"Modulo returns the remainder of integer division, rather than trying to fiind a decimal answer.",
"Mod is basically the remainder of a division problem.\n\n50mod7 is 1 because 50/7 = 7 with a remainder of 1. 7*7 = 49. 49 + 1 = 50. 50mod7 = 1.\n\n39mod5 = 4\n\n100mod12 = 4\n\n92mod3 = 2",
"Division with Rest and the result is only the rest.\n\nLets take an example: 5 / 4 = 1,25 or 1 And a rest of 1, because 5 - 4 = 1\n\nThat means, that 5 Mod 4 is 1."
]
}
|
[] |
[] |
[
[],
[],
[]
] |
|
1ywegq
|
Why have no new phyla developed since the Cambrian Explosion?
|
askscience
|
http://www.reddit.com/r/askscience/comments/1ywegq/why_have_no_new_phyla_developed_since_the/
|
{
"a_id": [
"cfombp2"
],
"score": [
4
],
"text": [
"This is because of the way that phyla (and other taxonomic groups) are defined. Phyla are essentially arbitrarily-defined groups, and there is no particular amount of structural or genetic divergence that causes us to classify a particular group as a phylum. However, like other taxonomic groups, scientists do strive to make phyla represent monophyletic groups (groups of organisms that contain a common ancestor and all of its descendants). This means that in order for a new phylum to be recognized, we would have to split up a currently recognized phylum, possibly into several groups."
]
}
|
[] |
[] |
[
[]
] |
||
458msk
|
Before French and Latin, has there been any other lingua franca?
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/458msk/before_french_and_latin_has_there_been_any_other/
|
{
"a_id": [
"czw0fwy",
"czw0y59",
"czw0yma"
],
"score": [
56,
26,
12
],
"text": [
"Greek! The Romans themselves were Grekophiles, and most well-educated Romans would be expected to know Greek. Greek was the lingua franca of the eastern Mediterranean (and was also widely spoken in many western mediteranean settlements like Massalia and Emporion) and continued to be the primary language of communication there up to the fall of the Byzantine Empire. [You can read more here](_URL_0_).",
"Imperial Aramaic would be an example of a lingua franca pre-dating the use of these two languages in that capacity.\n\nAfter and amongst the disruptions of the end of the Bronze age Aramean semi-nomadic tribes migrated throughout the Near East establishing new kingdoms and often overrunning existing ones. Babylon was sacked at one point and the Hebrew Bible is replete with references to Aram-Syria menacing Israel and Judah. They never were able to conquer Assyria (northern Iraq) though and ultimately Assyria brought most of the Near East under its control. As also referenced in the Hebrew Bible the Assyrians were quite fond of forced deportations and ultimately a lot of Aramean speaking peoples were settled in areas like Mesopotamia that already had a strong Arameans influence in certain areas. Ultimately, the dialect of Aramean spoken in Mesopotamia (Imperial Aramaic) became the \"lingua franca\" of the (Neo) Assyrian Empire. Assyria fell and was briefly replaced by a resurgent Babylon, which didn't knock Imperial Aramaic off of its pedastal since the Babylonians were speaking Aramaic by that point anyway. Once Cyrus the Persian overthrew the Babylonians and the Medes, he and his successors were practical enough to continue using this dialect in the administration of their empire. Koine Greek would steal some of the thunder of Aramaic after the conquests of Alexander the Great, but it was still widely used in the Near East at the beginning of the Common Era (the Christian Bible, while written in Koine reflects that Jesus spoke a form of Aramaic) and only stops being used as a lingua franca in parts of the Near East after the \"Arabization\" associated with the Muslim Conquests.",
"Yes, actually. One such language was Koine Greek.\n\nOne consequence of Alexander's conquests of Asia and Egypt was a process called Hellenization, the transference of Greek culture into the newly conquered territories. Greek architecture, philosophy, technology, literature, and religion were spread throughout the kingdoms that emerged in the wake of Alexander. \n\nKoine Greek became a *lingua franca,* though obviously that term would not have been used. In the Middle East, Koine Greek was even still used as a common language after the arrival of the Roman Empire. This is actually the reason that the New Testament was written in Koine Greek: anybody who could actually read could probably read Greek, and those who couldn't read Greek would still have understood it when it was read aloud. It was this common language that helped spread Christianity throughout the Empire.\n\nAfter the fall of the Roman Empire, Koine Greek continued to be used in the Byzantine empire as a written language (although at this point, the language was in a period of transition between Koine and Modern Greek, a period called Medieval Greek). It would only be a few centuries after that before Arabic was introduced to the region and Koine's dominance came to an end.\n\n---\n\nNikolaos P. Andriotis, *History of the Greek Language.* \nElizabeth Pollard, *Worlds Together Worlds Apart.*"
]
}
|
[] |
[] |
[
[
"https://www.reddit.com/r/AskHistorians/comments/22lf33/why_are_there_so_few_countries_that_speak_greek/"
],
[],
[]
] |
||
1dxk2g
|
Why does it spread germs/illnesses to leave a bathroom with hands unwashed, yet oral-genital contact is not regarded as a surefire way to get the same illnesses?
|
askscience
|
http://www.reddit.com/r/askscience/comments/1dxk2g/why_does_it_spread_germsillnesses_to_leave_a/
|
{
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"c9uuhuv"
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"Washing your hands after using the bathroom is not just about the germs gathered during the time using the bathroom. Ingraining that habit into people while they are at a sink with water gets them to clean away other germs they may have picked up without having to make a special trip to wash. \n\nHuman fecal matter is the real germ problem, not the human genitals. The genitals themselves, if clean should carry no more germs than the rest of the skin. Ineffective wiping however leaves fecal matter, and potentially it ends up on the hands. Washing removes it. In reality a male standing to pee, or either gender who doesn't wipe at all shouldn't be gaining any more germs on their hands than from any other activity. Its just easier to train people to always wash after a bathroom event so the bases are covered. It has the added benefit of removing other germs gathered before the bathroom event."
]
}
|
[] |
[] |
[
[]
] |
||
9w9iot
|
how can i invest and grow my money without knowing how to invest?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/9w9iot/eli5_how_can_i_invest_and_grow_my_money_without/
|
{
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"The market overall is down right now, so it makes sense that you lost some money. The three main things you need to know: Investment gains are slow; it wouldn't be a surprise for it to take a year or so before you make $10 on $500. The safest way to invest is to diversity; buying shares of an index fund or an ETF will let you invest in hundreds of stocks at once rather than putting all of your cash into one or two companies. Third thing to consider is what pre-tax investment options you have. See if your work offers a 401k plan; any money you put into that wont get taxed until you take it out, and some employers will give you extra money for contributions you make to it.",
"There are people who do this as their job. They are the much-reviled and lambasted \"investment bankers\" and they will invest and grow your money for you. In order to enlist their services you can talk to your bank where you are likely already keeping your money, and they will direct you to their specialists on staff for just such a purpose.",
"Exceptionally few people \"know\" how to invest. Most people use things like 401k from their company as their main investment, which requires minimal to no knowledge, and generally thats the first stop for most.\n\n > How can I take $500 and put it somewhere and after a reasonable amount of time, have more than $510?\n\nNot sure if example or not, but if you are thinking of investing $500 (the fact that you even used such low number as an example scares me), you should not. Thats **way** too low of an amount to consider investing in anything. Generally amounts less than $10k of very liquid, you really don't need it, no chance you'll need it would be even the bare minimum to consider investing at all (outside of 401k stuff).",
"the layperson should be funding a 401k, funding a roth IRA, and putting any additional investment funds into a major index fund. Personally I like the vanguard 500; you can quibble over fund management but vanguard's fees are low and no comparable product meaningfully outperforms them.\n\napps like acorn, betterment and so on are really less about investment choice than they are about finding inventive ways to start saving; they're fine if they help you, but you still want to be sure you're using the change they set aside in the best way possible",
"Go to r/wallstreetbets. Look at what they think is the right move. Now invest $500 in the opposite. "
]
}
|
[] |
[] |
[
[],
[],
[],
[],
[]
] |
||
73qc72
|
what is the difference between the various semi-automatic gun mechanisms?
|
I know roughly how they work (the expanding gas is used to push the slide or bolt back) but I have no idea the difference between short vs long blow back, blow forward, direct vs indirect impingement, recoil, etc. I can't find great visual differences, and the Wikipedia articles are pretty technical and assume that I know more about the internals than I do.
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/73qc72/eli5_what_is_the_difference_between_the_various/
|
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"The most simple form is straight blowback\nStraight blowback works by having an unlocked bolt behind the round in the chamber. when the gun is fired the gas pressure exerts a force on the bolt and it is forced away from the chamber. As it moves rearwards the empty case is pulled out. When the bolt reaches the rear of it's travel it moves forward again using the force stored in the recoil spring. On the way forwards it strips a new round from the magazine and pushes it into the chamber ready to fire again. The main disadvantage of blowback firearms is that the only thing keeping the bolt in battery (against the chamber) is the inertia of the bolt. In order to be safe the case needs to be supported in the chamber until the pressure in the chamber has dropped (after the bullet has left the barrel). As the power of the round being fired increases the mass of the bolt must increase. \n\n\nDelayed blowback is similar in operation except there will be some mechanism that will increase the inertia of the bolt without adding mass. For example the roller delayed blowback system used in the HK MP5 sub machinegun and G3 rifle or the lever delayed system used in the FAMAS rifle. The mechanism generally works by having a two part bolt having some method of forcing one half to move faster than the bolt face thus giving the bolt assembly more inertia than a one piece bolt of the same mass.\n\n\nBlow forward is the opposite of blowback. The bolt is in a fixed position and the drag of the bullet travelling through the barrel pulls the barrel forwards off the empty case. As the barrel reaches the end of it's forward travel the empty case is ejected and the barrel returns under spring pressure. As it travels back it collects a new round and chambers it. This method of operation is extremely rare and was only used in a few firearms\n\n\nRecoil operation means that when the gun is fired the bolt and barrel both move backwards together. This gives the bullet more time to leave the barrel than a blowback design. There are two main types of recoil operation: short recoil and long recoil.\n\n\nShort recoil operation means that the barrel and bolt are locked together when in battery and only travel a short distance before the barrel unlocks from the bolt. After this happens the barrel stops and the bolt continues. The empty case is ejected and the bolt returns forward collecting a new round and chambering it. The bolt gets to the barrel and moves it forward into the locked position ready to fire again. Most semi-auto pistols use a short recoil action with a browning tilting barrel design which works by locking the barrel into the slide via locking lugs above the chamber. As the barrel moves rearward it drops down which disconnects it from the slide. For example see the 1911. Other short recoil systems include the toggle locked (luger pistol) and rotating barrel (gsh18, beretta px4).\n\n\nLong recoil operation means that when the gun is fired both the bolt and barrel travel all the way to the end of travel. At this point the bolt stays at the rear and the barrel returns to the forward position. When the barrel slides off the empty case which is held by the bolt the case is ejected and the bolt then moves forward collecting a new round and chambering it. An example of this is the Browning A5 shotgun.\n\n\nGas operated firearms use tap some gas from a port in the barrel and use it to operate the gun. Gas operated firearms can be put into 2 categories: direct impingement and piston operated.\n\n\nDirect impingement firearms work by blowing gas directly at the bolt carrier which then moves rearward unlocking the bolt and ejects a round. For example the AG m/42 rifle. \nAn alternative is the system used in the AR10 and AR15 rifle which is where gas is tapped off the barrel and directed into the bolt carrier via the gas key. Once inside the carrier it expands in the space behind the bolt (which has a gas piston and rings at the rear) causing the bolt carrier to move rearward and unlock the bolt and then carry it the the rear. If memory serves this system was originally called an \"expanding gas system\" but is usually called direct impingement now.\n\n\nGas piston systems work by directing gas from the barrel and using it to push a piston which moves the bolt carrier to operate the firearm.\nThere are two types: short stroke and long stroke systems.\n\n\nShort stroke is where the piston only travels a short distance just enough to give the bolt carrier a kick which sets it into motion. Examples of this are the HK G36 rifle, FN SCAR rifle and the Steyr Aug Rifle.\n\n\nLong stroke is where the piston is attatched to the bolt carrier and travels all the way to the rear and all the way forward again. For example the AK47 rifle and M1 Garand rifle.\n\n\nTwo different ways that the bolt can unlock are by tilting or rotating. All the rifles I mentioned previously as examples of gas piston systems all have rotating bolts. Examples of tilting bolts are the VZ58 rifle and the FN FAL.\n\n\nOther actions exist too, I forget the name but there is a gun that used a combination blow forward/blow back action. Also check out the Mateba auto revolver."
]
}
|
[] |
[] |
[
[]
] |
|
4cwroj
|
sound. yes i get that is a wave but how is a wave able to encode so much variety (voice, instruments, sound effects)?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/4cwroj/eli5_sound_yes_i_get_that_is_a_wave_but_how_is_a/
|
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"text": [
"If it were a single wave, it would not convey so much. But sounds like you describe are a series of waves, spread out over time and interpreted by an excellent computer -- your brain. ",
"Frequency. The rate and fluctuation of which your' auditory cortex is inundated with sound hitting it determines the way you interpret it. If I hit something once it's a sharp whack, but hit it 1000 times per second it's a steady tone. Just like how a dog whistle cannot be perceived by humans, but dogs with more superb hearing can register the sound which basically isn't real to humans.",
"You can encode a huge amount of information in a single wave. This can be done due to a property called *waveform addition*. If you take the sound of a voice and the sound of a piano, you can record them both individually as separate waveforms. You can then add them together to produce a more complex single wave. Here is a simple version of adding 2 waves together. _URL_0_\n\n",
"The simple answer is just that waves are incredible complex and the sounds you describe look nothin like the sine waves one thinks about when thinking about waves. Just [look](_URL_0_) at the difference between a plugged guitar string and a cymbal crash.",
"Dunno if I can answer your question directly but I'm a music major undergrad taking beginning audio. Basically all we talk about is the science of sound and how we can manipulate it. \n\n\nSound, or better yet, specific tones vibrate a certain amount of times in one second. For example the tone A440 will vibrate 440 times in one second. Beyond that though are overtones and partials (basically the same thing) where you will have other tones sort of inside the principal tone. It's easier to explain with a drawing, but a quick google search of the overtone series should give you plenty of info. Anyway, the reason A440 will sound different on a piano than a guitar is because of timbre. This is essentially the overtone series put to work. Different instruments will have different overtones to create their characteristic sound. Furthermore, if you are tech savvy and have a DAW (Digital Audio Workstation) you can manipulate these overtones to either make a guitar sound like a piano, or create whole new fictional instruments based on acoustic ones we already have. They will do this for movies based on sci-fi books and the like. \n\n\nSomeone else correct me if I'm wrong. To be honest I've had seven exams this week, it's Friday, and I'm high af. ",
"There are different frequencies, tones, pitches, and densities very much like the variety in types of waveforms. If you look at the waveform visualization of an audio you can see the differences in volume and such. "
]
}
|
[] |
[] |
[
[],
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"http://clas.mq.edu.au/speech/acoustics/waveforms/waveadd01.gif"
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],
[],
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||
mpd38
|
Is this any intuitive way to think about normal distribution function ?
|
Normal distribution density function is given by: f(x) = (1/sqrt(2*pi*sig2)) * e(x-mi2 / 2mi2))
Is there any way to visualize why there is pi,sqrt and esome stuff there ? I remember great answer for making sense out of Euler formula some time ago here on AskScience I wonder if there is similar way to make sense of normal distribution density function. One other thing... How do I go about arriving at the formula ? I am interested in arrival process, not proving that it's correct once given. I try to figure out how people figured to put e, pi and sqrt in there to describe normal distribution curve :)
(I will probably understand most math thrown at me given time so even some "higher level" intuitions would be very useful).
|
askscience
|
http://www.reddit.com/r/askscience/comments/mpd38/is_this_any_intuitive_way_to_think_about_normal/
|
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"text": [
"The gaussian distribution is e^-x^2. It is the heart to the shape that is called the normal distribution. The pis, the sigmas, the various other values are just adjustments. \n\nThe constant term in front of the exponential is just a multiplier to make the area under the curve equivalent to 1 (so that the sum of the probabilities is 100%.))\n\nThe x-a term in the exponent is to shift the function right or left. Ie if you set a to 5, the function would peak at 5.\n\nThe sigma is widening the curve.",
"The gaussian distribution is e^-x^2. It is the heart to the shape that is called the normal distribution. The pis, the sigmas, the various other values are just adjustments. \n\nThe constant term in front of the exponential is just a multiplier to make the area under the curve equivalent to 1 (so that the sum of the probabilities is 100%.))\n\nThe x-a term in the exponent is to shift the function right or left. Ie if you set a to 5, the function would peak at 5.\n\nThe sigma is widening the curve."
]
}
|
[] |
[] |
[
[],
[]
] |
|
53uhvi
|
How different were the peoples of northern Spain culturally, linguistically etc from people in southern Spain during the rule of the Umayyads?
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/53uhvi/how_different_were_the_peoples_of_northern_spain/
|
{
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"So what you're talking about here is a really long period. I happen to have a decent source that discusses this topic at length in some parts, but I might wander a bit here and there.\n\nSo to the beginning. If we look at the early days of conquests in the 8th century, even then the actual conquering force of al-Andalus wasn't uniform ethnically at all. When they crossed the straits of Gibraltar in 711 the troops were mainly composed of Arabs and Berbers, being ruled from Damascus by the (Umayyad) Caliph. They were *very* much a Berber-dominated force, and Maribel Fierro (p8) reports that the number of actual Arabs among them was pretty small, and they had a fairly privileged status being Arabs. At that time there was a fairly strong link between being Muslim and being Arab which was broken down over the years, but in those days it was still quite strong. This meant that people who weren't arabs adopted the status of clients (mawali) of an Arab tribesman or of another convert who already had a patron. Freed slaves were clients as well. So in these days islamicization went hand in hand with arabicization but there were still distinct Berber and Arab cultures. \n\nIn 739 there was a pretty big Berber rebellion in northern Africa and the Caliph sent some troops to put an end to it. Without getting too much into detail about this - it led to a big influx of Arabs around Ceuta as a Syrian commander named Balj ibn Bishr al-Qushayri, initially refused passage, managed to negotiate with an Andalusi military governor who was attempting to deal with his own Berber rebellions. I could go on and on about the political consequences of al-Qushayri arriving in al-Andalus for an entire post , but suffice to say they brought their division of Qays and Yemen (northern and southern) arabs with them, although the precise meaning of this conflict in the islamic world back then is still debated. Again, without going into too much detail they were settled (with a lot of argument and dispute) in Granada (Elvira), Seville & Niebla, Malaga, Jaen, Algeciras, Sidonia, Beja and Tudmir. \n\nSo the Berbers also had their own culture and existence and how arabicised & islamicised they were depended on whether they were urban or not. So the real cultural divide at that point wasn't necessarily *just* northern/southern, but also urban/rural. The Berbers did however mostly settle in tribal groups in rural areas along the frontier. Please remember that when I say \"frontier\" here it's in the context of the early 8th century, where the frontier was in what we would consider to be fairly southern in modern Iberia. From what we understand they were mostly autonomous although it's difficult to pull the details out of obscurity with limited archaeological work. But for example, Fierro points out that some patterns of irrigation we find can potentially be linked to Berber tribal organisation, and the existence of these tribal, autonomous Berbers in the northern rural regions is highlited whenever they rebelled against the Cordoban ruler or representatives below him. \n\nSome of these tribal berbers in al-Andalus actually continued their existence well into the Umayyad era of al-Andalus and actually outlived it - some of the taifas after the fitna of al-andalus (the huge civil war that caused the Cordoba Caliphate to collapse from around 1009-1031) were ruled by those who gained power because of Berber tribal military resources & organisation - i.e. the Zirid taifa formed by Zawi bin Ziri. From what I understand, most of these guys survived even the reconquista and the inquisition and although they eventually lost their unique cultural identities, their descendants still live in Spain & Portugal today. But, if you were an urban Berber, you were much more likely to have been a state administrator or a scholar and thus very arabicised and islamicised. \n\nNow, if we look briefly at the christians - sometimes you see them called in secondary sources as \"mozarabs\" (as arabicised christians) but really I don't like this term, especially because they certainly didn't identify as this and afaik none of the actual Andalusi literature ever uses that term. This term appears in the very late Christian sources as a term they used for Christians who emigrated to the north of Iberia but who spoke Arabic and culturally resembled Arabs rather than those with Visigoth ancestry. But it's not an accurate label as it lumps them all together culturally and linguistically, when in reality a lot of them didn't really share those histories or backgrounds. \n\nAnyway, the vast majority of the Andalusi Christians, like the Berbers, lived in rural areas with fairly limited contact with the Arab settlers & conquerors. Ibn Hawqal in the 10th century, translated by Fierro, wrote an interesting section about these relatively autonomous Christian Andalusis:\n\n > In al-Andalus there is more than one agricultural property on which dwell thousands of people who know nothing of urban life and who are Hispano-Romans professing the Christian religion. There are periods in which they rebel and some of them take refuge in fortresses. They put up a stiff fight, for they are fierce and stubborn. When they cast off the yoke of obedience, it is hard to make them return to it, unless they are exterminated and that is a difficult, prolonged process.\n\nSomething I'd like to point out about the \"extermination\" here that needs to be understood with context is that the history of al-Andalus is also the history of a series of governments dealing with a long series of rebellions. These included arab muslim rebellions, tribal berber rebellions, and many others - so they weren't trying to 'exterminate' Christians per se, Ibn Hawqal is more referring to rebels that can't be negotiated with and so must be defeated by conquest. \n\nNow, Ibn Hawqal doesn't speak about what language the rural Christian spoke but it was likely a Romance language descended from Latin since the local Andalusis weren't monolingual until the mid-to-late 11th century, and even then it wasn't truly monolingual demographically until the 12th century. So yes, between urban and rural areas, and the south to the frontier, there were certainly linguistic divides - with Romance/Arabic bilingualism being common for Christians. Indigenous Christian converts were often called muwalladun - in the way it was used then it referred mainly to people who weren't Arabs ethnically, but were born into Arabic culture and were raised as Arabs. That could be anybody, without a specific indication of religion. Jews in al-Andalus were also very arabicised and in their case, it enabled them to flourish and also paradoxically to preserve their language and ethnic identity. \n\nDespite the rural/urban divides in culture and language throughout the early centuries of al-Andalus, by the time of the establishment of the Caliphate of Cordoba under the reign of Abdul Rahman III, an era that was one of stabilising and unifying the region, a common Andalusi identity finally emerged through the work of scholars but also through the fierce advocacy of the muslim traditions of egalitarianism which Abdul Rahman III was a particularly big supporter of. In those days there was a concerted attempt to eradicate the idea of Arab supremacy (particularly in politics), although it was an uphill battle and never quite manifested in the way that was hoped and muwallads hardly ever managed to maintain the power or positions that they were given by Abdul Rahman III in place of ethnic Arabs.\n\nThis is already a pretty damn long post, so I'm going to cut it off here. I would close by saying that yes, the frontier - that changed over time - certainly did see an impact culturally but I would argue that just as big was the divide was between rural and urban areas."
]
}
|
[] |
[] |
[
[]
] |
||
58z8bx
|
This Week's Theme: The 14th Century, AD
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/search?q=flair%3A14th+century&restrict_sr=on&sort=relevance&t=all
|
{
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"\n**Current**: 14th Century AD\n\n**On Deck:** Resistance and Conformity\n\n**In the Hole**: Propaganda",
"*I send a pestilence, a plague*\n\n*Into your house, into your bed*\n\n*Into your streams, into your streets*\n\n*Into your drink, into your bread*\n\n*Upon your cattle, upon your sheep*\n\n*Upon your oxen in the field*\n\n*Into your dreams, into your sleep*\n\n*Until you break, until you yield*\n\n*I SEND MY SWARM*\n\n*I SEND MY HORDE*\n\n*THUS SAITH THE LORD*",
"Oh cool! The 14th century is such an interesting time in Mesoamerica. You have the Mexica arriving in the Basin of Mexico, the uacusecha (I think) arriving in the Patzcuaro Basin, the Caxcanes, who also worshiped Huitzilopochtli and spoke Nahuatl, arriving in Jalisco, the end of Chichen Itza and the rise of Mayapan in northern Yucatan. Maybe someone will ask questions about these topics or others. \\*hint hint, nudge nudge*"
]
}
|
[] |
[] |
[
[],
[],
[]
] |
||
22ve03
|
Do the descendants of the major Japanese clans (Tokugawa, Oda, etc) still have influence or command respect? Are their any clans that still 'exist', so to speak?
|
I was wondering because their have been so many events in Japanese history that could erase these clans and their descendants, such as the Meiji Restoration and even World War Two. Thanks.
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/22ve03/do_the_descendants_of_the_major_japanese_clans/
|
{
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"text": [
"According to popular belief, The Meiji Restoration was an effective wipe out of samurai nobility. Instead, the surviving samurai heads (that is, the heads of all the major clans excluding the Hojo, Takeda and Chosokabe) accepted the new order of the emperor. The 15th shogun of the Tokugawa shogunate, Tokugawa Yoshinobu, wanted to reform the shogunate and began the Boshin War, which also marks the beginning of the Meiji Restoration. Following the shogun's surrender and resignation, he retired and disappeared from public view for the majority of his later life. While the Emperor allowed him to create his own house for his family, his descendants do not retain the influence of their clan.\n\nOda Nobunaga's death at Honno-ji by the hands of his general Akechi Mitsuhide was the start of the end of the Oda clan. Central Japan soon fell into the control of another general, Toyotomi Hideyoshi. This left no substantial record available to prove bloodline, similar to many other clans that existed before the Meiji Restoration. \n\nWhile there have been many claims of relationship to the major clans, another note to bear in mind is that over a long period families tend to create a new name for themselves after a fall from grace or due to an unknown heritage - a good example of this is the widespread family name of Takeda and Suzuki.",
"After the Meiji restoration, the clans were [converted into noble families](_URL_1_), along the lines of European nobility. Their domains were [converted into prefectures](_URL_0_), with a centralized authority, though they were allowed to keep 10% of the province's revenue. If you're interested in this time period, there's a great biography of Saigo called (unfortunately, due to the horrible Tom Cruise Movie) *The Last Samurai*, by Mark Ravina. It's a really good read.\n\nThe nobility was finally eliminated in 1947, though their descendents continued to do pretty well for themselves. ([This book](_URL_2_) is pretty much exactly what you're looking for.) After WWII, they maintained an elitist status, referring to non-former-nobles who became rich as *nariagari* (upstarts) or *narikin* (nouveau riche). They were criticized for being ostentatious with their wealth (austerity was a virtue in old money families, with many boasting their maids wore better kimono than their own daughters). "
]
}
|
[] |
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[
[],
[
"http://en.wikipedia.org/wiki/Abolition_of_the_han_system",
"http://en.wikipedia.org/wiki/Kazoku",
"http://f3.tiera.ru/ShiZ/Linguistics/japanese%20books/Above%20the%20Clouds%20-Status%20Culture%20of%20the%20Modern%20Japanese%20Nobility.pdf"
]
] |
|
svvxi
|
Ionized water
|
Can someone please explain, in easy to understand terms, the process of ionizing water and the consequences/repercussions of exposing skin to ionized water?
|
askscience
|
http://www.reddit.com/r/askscience/comments/svvxi/ionized_water/
|
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"text": [
"Could you be more specific? In general, anyone claiming to make \"ionized\" water is running a scam, but depending on what device they're selling, it may produce any of a number of things."
]
}
|
[] |
[] |
[
[]
] |
|
x2ylk
|
why do i get these rashes on my throat after i've shaved?
|
And is there anyway to prevent this? I've tried alcohol based after shave and i always shave downwards.
_URL_0_
EDIT: Im using Gilette Deep Blue for men shave gel sensitive. And after i've shaved i use AXE dark temptation AFTER SHAVE. I have also tried Gilette soothing moisturiser with no luck.
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/x2ylk/eli5_why_do_i_get_these_rashes_on_my_throat_after/
|
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"text": [
"it's just razor burn, and it's common. There's a facial hair softener you can buy that may work. are you using shaving cream? It's quite important",
"A few years back I switched to a brush+lather shave and never looked back. Canned shave gel is total garbage.\n\nThis made all the difference in the world to me. That and picking up a safety razor.",
"_URL_0_\n\nYou're welcome"
]
}
|
[] |
[
"http://imgur.com/bLGEs"
] |
[
[],
[],
[
"http://www.reddit.com/r/wicked_edge"
]
] |
|
3a7zto
|
what is tickling? why do we have places like on our sides and armpits that makes us laugh out of panic when there is no real danger?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/3a7zto/eli5_what_is_tickling_why_do_we_have_places_like/
|
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"I am not 100% certain why this is the case... But to my knowledge it's due to the \"surprise factor of the person touching you. Think about it this way. When someone is tickling your mind is thinking \"they're touching me, but where\". I believe this unpredictability of the situation causes you to squirm and panic. But if you tell the person hey touch my armpit here, the effect is not the same.",
"This is just a short explanation based on the video at the end of my comment:\n\nSmall tickling (like from a feather) is called knismesis. It makes you scratch/touch places. This is to make us get rigd of insects, spiders and other stuff we don't want to have on our skin. Many animals are ticklish too so it shows us our evolutionary history.\n\nThe more rough version (e.g. from fingers poking you) is called Gargalesis. It is something all primates have and might be there to teach each other self defence without hurting each other. It makes you react to something that might hurt your most vulnerable parts. \n\nSource: SciShow about this topic.\n_URL_0_"
]
}
|
[] |
[] |
[
[],
[
"https://www.youtube.com/watch?v=Sjyl-ti3xAY"
]
] |
||
3vll58
|
Why does some music just sound... Old? Is it recording quality, or were instruments constructed differently?
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/3vll58/why_does_some_music_just_sound_old_is_it/
|
{
"a_id": [
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"text": [
"Can you shoot some examples of what recorded music you're thinking of? "
]
}
|
[] |
[] |
[
[]
] |
||
4k5u38
|
why is nuclear fusion considered the "holy grail" of nuclear power compared to fission?
|
I know the difference between fission (atom's nucleus splitting) and fusion (atom nuclei combining), but I fail to understand why fusion is safer, cleaner, and produces more energy. I thought fusion required very high energy input to even occur, whereas fission occurs naturally on its own in unstable elements.
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/4k5u38/eli5_why_is_nuclear_fusion_considered_the_holy/
|
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"Fusion is controllable and sustainable. If your fusion reactor is getting too hot, shut off the fuel source. If your nuclear reactor is going critical and the safeties have failed, pray. ",
" > but I fail to understand why fusion is safer\n\nBecause it requires extremely specific circumstances to occur. The second those conditions are lost, the reaction can't physically happen. If you don't have enough heat in the system, the fuel won't have enough energy in it to fuse.\n\n > cleaner\n\nIt doesn't use radioactive fuel and the radioactive byproducts are extremely minimal.\n\n > produces more energy\n\nThis is the same system that powers the sun. You're using E=mc^2 basically. Fission is just using the radioactive release of heavy elements to heat water. Fusion converts the entire atom to energy (well not exactly but that's not important for this discussion).\n\n > I thought fusion required very high energy input to even occur\n\nIt does initially but the hope is that once you get it running the power output is larger than the input. And NO this does NOT break physics, the input merely allows for the output to occur, it doesn't magically double itself or whatever.\n\nAnother bonus: Fuel is easy to come by. It uses light elements, which are the most common in the universe. There's enough hydrogen in the ocean to last us beyond the heat-death of the universe.\n\n_URL_0_\n\n"
]
}
|
[] |
[] |
[
[],
[
"https://en.wikipedia.org/wiki/Fusion_power#Economics"
]
] |
|
bcq96k
|
why are white americans not called european americans? similar to asian americans and african americans.
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/bcq96k/eli5_why_are_white_americans_not_called_european/
|
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"text": [
"We should not use any of these segregating terms. \n\nWe should simply use the term Americans instead.",
"Because some other white people got mad about us calling black people black. So they made up a new term, even though not all black people are African, and not all African people are black.",
"Historically, “American” was used by people in power in the US to refer to white Americans\n\nSomething else-American was to identify non white people. White people were the default, essentially\n\nNow, we say white Americans because we know white shouldn’t be assumed. Many people prefer black Americans instead of African Americans because that’s actually what people mean. Not all people from Africa are black\n\nCaucasian is the white equivalent of African American\n\nDoes that make sense?",
"African-American is a relatively new term and part of what is commonly termed a 'Euphemism Treadmill'. What happens is that you've got a word to describe a group and that word acquires negative connotations from that association. So you change the word and the process starts all over again. A better example would be how we refer to the mentally disabled, where yesterday's word becomes a slur about every 2 - 3 decades because there's never going to be a polite way to say \"dumber than average\".\n\nHowever, African-American also falls into this category. Neither 'colored' nor 'black' are strictly offensive in the way that 'retard' or 'imbecile' would be, but they were viewed as being negative terms so we got a new one.\n\nAsian-American is slightly different. A first generation immigrant would almost never refer to themselves this way because it's vague to the point of meaninglessness. People from Bangalore, the Hmong highlands or Seoul have no real unifying characteristics - they're from wildly different cultures with dramatically different appearances and Old World experiences. However, despite the presence of large numbers of people with Asian ancestry in the U.S., no single cultural group from Asia makes up a significant percentage of the population.\n\nThus, Asian-American became a political term of art to amplify the importance of the faction. \"People of Color\" or \"LGBTQ\" are similar in nature - they merge wildly disparate groups with wildly disparate interests and backgrounds in an attempt to create common political cause (with minimal success in the former case and slightly more success in the latter)."
]
}
|
[] |
[] |
[
[],
[],
[],
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||
5wpa9x
|
why were trains invented so much earlier than cars? it seems like trains would be harder to manufacture and create.
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/5wpa9x/eli5_why_were_trains_invented_so_much_earlier/
|
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"Imagine a car running a steam engine, burning coal in a furnace, using the heat to heat up water, pump that water, and turn the wheels. Also storage for coal to be able to go hundreds of miles.\n\nThis is easier to go in a 200 tonne stab of metal than a tiny box with people inside. \n\nAlso no need for steering, just turn wheels and drive forward. ",
"Trains have some advantages that make them more cost effective and essentially a lower technology level to run.\n\n1) no steering system. This simplifies manufacure and design of the suspension.\n\n2) they're larger. This means that heavy, large engines and gearboxes can be used. While these might be individually more expensive than those used in cars, they are more efficient and can be simpler to manufacture than smaller parts.\n\n3) They usually used steam engines, which are dramatically more efficient and simple than internal combustion engines, but less responsive. Because of these qualities, steam engines are far better for pushing somethig a log way at a constant speed (like trains), but are kind of crappy for the stop-and-go driving that cars do a lot of."
]
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|
[] |
[] |
[
[],
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] |
||
anr40s
|
what's the difference between cs (computer science), cis (computer information science, and it (information technology?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/anr40s/eli5_whats_the_difference_between_cs_computer/
|
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"Oversimplified, but here we go.\n\n* **Computer Science** - the science of creating computer programs. Algorithms and data structures. Almost entirely focused on writing code.\n\n* **Computer Information Science** - How to use computers to organize and make use of data. A little higher level than CS.\n\n* **Information Technology** - How to use technology to solve business problems. This can involve CS and CIS but is more problem focused.",
"This will vary on the program you are enrolled in: \n\nComputer Science = learn programming to eventually become a developer building apps, services, and automation.\n\nComputer Information Science = you learn a technical curriculum with the intent on becoming an IT manager or Program Manager. You basically manage projects and have some technical insights.\n\nIT = tech support with some PM skills, maybe dabble in programming. ",
"Computer Science in essence is academic, research focused, scientific. It concerns studies of AI algorithms, network protocols, security research, ... Not many people who study CS continue in this theoretical field, since the demand for practical applications is enormous. \n\nCIS is the part of CS that deals with information gathering and processing. Again, there's a huge practical interest, given what Facebook, Google, etc. do. Smaller companies all try to implement their own versions. But there is also tons of research to improve their algorithms.\n\nIT is a bit different, in the sense that its core business is managing computer infrastructure. They make sure all employees have the correct and up-to-date software installed, the servers keep running, the network is secured, etc. This is almost purely practical.\n",
"Since we're here, where does Computer Engineering falls?",
"**Computer Science** : It’s the science (mathematics) of how computers inherently work. It would have an answer to this question: If I had a bunch of random numbers, what would be the fastest way to sort them, is it the fastest way? And why is it the fastest way. It often requires writing code but only to verify and quantify an idea.\n\n**CIS**: I’ve got this gigantic set of numbers and letters and words and other data. CIS will answer this question (amongst many other): How can I make sense of this data to find how they’re interrelated\n\n**IT**: I’ve got a business to run that requires selling lemonade. But because I’m a genius lemonade maker and the biggest one in town, I’ve set up many lemonade stands around town that are completely automated. IT answers this question: How can I effectively tie in all these lemonade machines to work seamlessly and serve customers without a moments delay? What computers do I need? How shall I set up my storage? What’s the ideal internet connection to use?\n\nEdit: well shit, good morning to me. Glad this is my most upvoted comment! And thank you for the gold and silver!\n\nEdit 2: Because some of y'all asked me to ELI5 some more, so here's my take: \n\n\n**Software Engineering**: The customers of Lemonade Inc. need an app to order their favorite kind of lemonade right to their door step. A software engineer would be able to: Make an app that's easy to use, and can be installed on the customer's phone. \n\n\n**Data Science**: Data science is (amongst other things) using lots of data to draw conclusions about a specific topic. If Bob opened the app made by the software engineer, given his previous purchases, which lemonade flavor can I suggest to him that he is most likely to buy? Also, can I perhaps make him buy another one by showing his wife's favorite lemonade right next to his so he would remember to buy her one as well? \n\n\n**Computer Engineering**: Computer Engineering deals with actually making the physical computer that will physically run the programs made by the computer scientist or software engineer. Example: Hey computer science guy! I hear you want to run that new number sorting method on a set of 1,873,347,234,123,872,193,228 numbers! Oh, are current processors too slow because they need to do 10x more work than required for this specific task? Ok let me see what your method is, and let me perhaps build a custom processor for you to efficiently do everything in as much time as you expect. (Warning: this is a gross oversimplification of computer engineering, and they dont go around making new custom processors for everyone. I've tried to keep it simple and in line with the examples above!)",
"Also, how does Information Systems relate to these?",
"There seems to be plenty of answers, but I figured I would throw one more in there for you. I majored in MIS (management information systems) for a bit. It was a lot like the CIS but more focused on software used in businesses. In my short time studying it they really seemed to put emphasis on not only knowing technical side of how to make the software, but also knowing the business side of things so you could make the most effective software for the customers needs. ",
"I have never heard of the term CIS in my field. As for the two other, they are vastly different.\n\n & #x200B;\n\nComputer science relates to the science of how to translate a task in a way that a computer can do it. Example: you take a map and decide how you are going to drive your car from point A to point B while avoiding congested areas and accidents. How can a computer do that (like google map)? It involves modeling a mathematical formula, a logic per se, that will allow a computer to determine the best path. Or say you have a sheet of metal and you need to cut shapes into it, how do you make sure select which shapes to cut and in which angles to minimize the material loss?\n\nIt's not dependent on programming language, even if selecting the rigth language for the right task is essential.\n\n & #x200B;\n\nInformation Techbnologies is geared toward business applications. From designing interfaces, business applications and understanding business processes and how to automate them or support them with a software, to infrastructure and server installation and maintenance. Web design, maintaing a company's computer fleet, it's all IT.\n\n & #x200B;\n\n & #x200B;",
"Programmer, data scientist, and admin. \n\nOne writes code. One manages and manipulates data. One keeps a computer system up and users happy. ",
"CS: You write a program to see how often that guy picks his nose\n\nCIS: You use that program to gather the data and determine what is actually a true nose pick\n\nIT: You set up the computers and cameras and network them so that you never miss a nose pick again.",
"I see so many things I disagree with here. Terms aren't always used correctly or consistently so don't get too hung up on them.\n\nThe way I see it:\n\nComputer Science: is the study of how computers work. It is typically a program offered at universities. \n\nIT: Is the career of working with computers. This is most often done by people with Computer Science or related degrees.\n\nComputer Information Science: Is a subbranch of computer science.\n\nSoftware Engineering: Is another subbranch of computer science, however with more focus on engineering aspects. ",
"Went to school for CS. \n\nWish I would have gone to school for CIS. I did not know the difference. I don't have the interest in or dedication to math that it took to make it into Calculus 4 and differential equations. \n\nOf course, the real secret is you don't need a degree to do what the pros do in this specific field. No other STEM field has such a lack of academic requirements for the pay we receive, and that's because there's an incredibly high demand for us. I didn't graduate and am making top tier salary as an SRE in silicon valley. What matters is what you can demonstrate. Certifications and code reviews weigh a lot more than a degree in this particular occupational field. And we tend to get lots of office perks too.",
"Absolutely no difference to 90% of the people out there.\n\nPeople: \"What do you do?\"\n\nMe: \"I develop software.\"\n\nPeople: \"So you are in IT?\"\n\nMe: \"No. I develop software. Which means I USE a computer and a network, but I do not spend my life maintaining a network of computers. If I have a computer problem I phone my IT department and go for coffee.\"\n\nMe: \"No I cannot help you with your computer, WIFI, printer, or networking problem.\"",
"**Computer Science** - Math behind creating computer programs and systems.\n\n**Computer Information SYSTEMS** - This is what businesses called Information Technology in the '70s and '80s. It is a set of things working together to control information on computers. Databases, file servers, etc. \n\n**Information Technology** - Basically the same as computer information systems. The technology we use to process information from fax machines to smartphones.",
"Imagine you have a lemonade stand with 3 people working it.\n \nOne person understands how lemonade works. They research better ways to make the lemonade, better ratios of ingredients, different lemons, design better pouring methods, hell maybe there is a BRAND NEW stand we could be creating. This is like in computer science where people are researching more efficient patterns and algorithms, and more broad computing concepts. \n\nThe second person is responsible for building the lemonade. They understand the best mugs to use, understand those better pouring techniques and how to use them (but may not understand WHY they are better or how), and everything involved in building your lemonade stand and delivering the lemonade to the customer. This is Computer Information Systems. They design the programs that are used, using concepts laid out by computer science (over simplifying for the ELI5).\n\nThen the final person is essentially the middleman between the lemonade stand and the customer. They may not sell the lemonade (that would be product or sales), but have interactions with the customers. If a customer isn't liking their lemonade, or can't even drink it for some reason they can contact this person to help fix the problem. They have some idea of how everything works, but don't typically design it themselves. This is IT.",
"My rough take; each answers a different fundamental question:\n\n* Computer Science: What is a computer? (What can a computer do?)\n* Computer Engineering: How can we build a computer?\n* Computer Information ~~Science~~ Systems: What can the computer tell us about this data?\n* Software Engineering: What problems can we solve with the computer?\n* IT: How can I ~~keep~~ make all these computers ~~working~~ efficient and secure?\n\nEDIT: I did not expect this comment to get so much attention! Please, do not base your academic or career decisions on these ELI5, one-sentence breakdowns. I think if you study in any of these fields you can learn enough to jump to any other in practice. Most of what you will actually use every day you will learn on the job or on your own time (if that scares you, you will have a harder time making a jump). The key is to learn *how to learn on your own*.\n\nPlease consult with people actually working in the industry. I myself have an electrical engineering degree, work mostly as a software/controls engineer, and have a passion for computer science. On a daily basis, most of my time is spent working with teams to solve practical problems where software is simply one tool in the box. Feel feel to ask me anything about these areas.",
"Honest answer: It's all marketing buzzwords to promote more degrees. Professors in universities push this so they can get funding and more $",
"Simply put, the difference is what people studying each field focus on.\n\n- Computer science primarily focuses on the specific science of \"computing\", which is to say, how to make computers \"do\" specific things. It's the core \"academic\" approach to computing, and the most theoretical\n- Computer Information Science is related, but focuses more on the data and how it can be analyzed and used. It's very closely related to computer science and is an academic approach to computing too, but focuses on a different aspect, with a slightly more business oriented approach too\n- IT is more practical and focuses on the actual hardware in a \"real world\" environment: it's the \"business\" approach to computing\n\nCS/CIS are quite closely related, along with other fields like Cybersecurity - a lot of people who study one of these fields started with CS, and usually there's a chunk of crossover between modules/classes studied: eg a CS major will do some CIS-type modules (often without the CIS label) and a CIS major will almost certainly take some CS modules.\n\nIT is much less related to the other two, and is more like the IT department at a school or business.",
"Oversimplified but....\n\nComputer Science = Study of computers and computer systems. You design the system, parts of the system or ways to use the system.\n\nInformation Science = How to turn data into valuable information. You take the data that the system collects, clean it, organize it and turn it into something that makes sense, like a report or chart. \n\nInformation Technology = Set up / maintenance / administrative. You put the system together, install the software and set up permissions/security. \n\n",
"CS: We make things.\n\nCIS: We manage things.\n\nIT: We fix things.\n\nThis might be more ELI3...",
"Someone at universities figured out that there is a lot of money to be made since a lot of students study computer related courses. At least at a grad level, it’s mostly a money making scheme with basically the same courses being offered.",
"CS = Computer Science - The focus is on the theoretical basis of computing. What makes computers work the way they do\n\nCIS = Information Systems - The focus is on the systems (including humans) and how they are used to support business\n\nIT is the one everyone else (especially computer scientists) tend to get wrong. So I will refer to the formal definition according to the ACM / IEEE curriculum statements for these fields.\n\n_URL_0_\n\nI quote:\n\nInformation Technology is the study of systemic approaches\nto select, develop, apply, integrate, and administer secure\ncomputing technologies to enable users to accomplish their\npersonal, organizational, and societal goals. \n\nMy shorter version: \n\nIT = Information Technology - The focus is on technology and how to apply CS theory to help improve solutions within IS systems (kind of).\n\nIf you think about it in terms of cars:\n\nCS is equivalent to Physics working out the \"rules\" of what makes a car work\n\nIS is equivalent to car manufacturers that analyse the needs of humans in various environments and design what our cars should look like and how we want to use them etc\n\nIT is equivalent to Engineering who works closely with IS to build cars, engines, etc, according to the rules the physics people discovered to meet the specifications of the designs the IS people came up with.\n\nThe above is of course not nearly as clear cut since all of these overlaps in many aspects. The primary focus of the degree is different though. A CS graduate will always have advanced math, and IS graduate will always know a lot more social science theory, and IT graduate will always be somewhere in between CS and IS.\n\n",
"Computer Science is a branch of mathematics that got rich enough to afford its own building. Everything else is about doing practical stuff with computers.",
"I think of IT guys as mechanics. They do the grunt work of keeping them running and troubleshooting shit.\n\nYou dont have to learn how to create, you learn how to maintain what's there ",
"Computer scientist: I’ll tell you how you might fix it, if certain assumptions are true.\n\nComputer information systems expert: I’ll tell you how many fixes are needed, how long they’ve been in queue for a fix, and what category of fix is needed.\n\nInformation technology worker: I’ll fix it.",
"(Generally speaking, in practical terms)..\n\nComputer science is centered around fundamental research of software and hardware concepts and the development that springs forth from it.\n\nComputer information systems is centered around how the developed software and hardware interacts in an applied sense.\n\nInformation Technology is just a department title for whatever group in an organization is responsible for putting what's developed in 1 and structured in 2 into action to achieve some sort of defined goal.\n\n & #x200B;",
"I don't think any of these responses are actually understandable by a child. Here's my take. \n\nComputer science is about how to make computers do what they do. \n\nComputer information systems is about how to make computers do useful work for business. \n\nInformation technology is about how to fix broken computers and make healthy computers stay healthy longer. ",
"**Computer Science** = theoretical, philosophical, foundational understanding of computing in general\n\n**Computer Information Systems** = teaches some of the theoretical (not always to the same extent as CS), but also mixes in how it ties into real-world business\n\n**Information Technology** = practical business application of tech knowledge",
"CS: How computers work\n\nCIS: How this computer works\n\nIT: How these computers work together",
"Many answers here incorrectly associate computer science with building software or writing code. Computer science is best understood as a field with significant overlap with pure and applied mathematics. Very broadly, computer scientists seek to understand claims about the nature of computation.\n\nFor example, it is known that if you're only allowed to perform comparisons, sorting a list of n numbers cannot be done without performing at least C * n * log(n) comparison operations in the worst case. Here C is some constant number that depends on how you implement your algorithm (for example, whether you chose to execute the algorithm on pencil and paper, or whether you wrote a computer program to execute the algorithm for you). After specifying a model of computation (and some other details), this claim can be proved rigorously using mathematics.\n\nThe result above is a classic example of a lower bound type result. It tells you that no matter how clever you are, you cannot avoid doing a certain amount of work if you want to compute a solution to some problem. More generally, lower bound type results tell you that given an input to a problem of size N, your algorithm must perform at least C*f(N) computations to find a solution to the problem in the worst case, where C is some constant that depends on the way you implemented the algorithm, and f is some function of the input size. (The question of how to measure the \"size\" of an input is very important, but I've chosen to ignore it here.)\n\nAlthough there is considerable diversity even in computer science, I believe the above example is more representative of what computer science involves and the things computer scientists think about.",
"When I went through college CS was algorithms based, very computer science/engineering heavy. \n\nCIS was out of the computer science department but had business electives required.\n\nMIS was out of the business department but had computer programming and databases electives required. When I was in the Unix lab there were a group of MIS students in there doing a database project and one of the guys was not understanding it and said loudly and smugly, \"I don't know why I have to learn this, I'm a MIS major, the people doing this will be working for me.\"\n\nI didn't know him but sometimes wish I knew what happened to him.",
"As far as degree programs go, this is how it was at my major university.\n\nCS: Writing Code and applications, the science of computers (binary logic, etc.)\nCIS and IT were the same thing basically but with different electives: Web development, Databases, Networking, OS Management (active directory, etc.)\n\n",
"*In academia:*\n\nCS/CIS/IT are largely dependent on schools. For example, there are some schools where CIS is more theory/math than another school's CS program.\n\nTo keep things simple we're going to go by the largest national accrediting body for computing (abet)'s [criteria](_URL_0_) \\- there are three specialties: Computer Science (CS), Information Systems (IS) and Information Technology (IT).\n\nThey define CS as:\n\n > Apply computer science theory and software development fundamentals to produce computing-based solutions. \n\nand IS as:\n\n > Support the delivery, use, and management of information systems within an information systems environment.\n\nand IT as:\n\n > Identify and analyze user needs and to take them into account in the selection, creation, integration, evaluation, and administration of computing-based systems.\n\nPretty vague, right? Academically it's not really strict like you would see in medical, engineering, law or business. There's essentially a handful of courses that a school's faculty puts together, then calls the degree whatever it most aligns to. There's a ton of overlap. Typically the curriculum with the most math and theory courses becomes Computer Science, then the one with the most business courses becomes (computer/management/nil) Information Systems, and then the remaining one becomes Information Technology. Another important distinction is in which section/school the program is in. The business school, liberal arts school, the math department, or the engineering school?\n\nNow, I did say typically. I have seen ivy league-tier schools that would offer a degree like \"Computer and Information Science: concentration Computer Science\" that is just a very rigorous CS degree with a long name.\n\n\\---------\n\n*In industry:*\n\nCS is a degree that HR looks at for software engineering positions. To a lesser extent they look at related degrees like electrical engineering, math, information systems, and information technology. Sort of confusingly, the IT industry (not the degree) is mostly a customer-facing support kind of role. In summary: traditional engineers create computers and maybe some software, software engineers create software like algorithms, and IT people utilize those creations to benefit the business.",
"The CS descriptions so far leave a lot to be desired. CS grew out of electrical engineering, mathematics and logic. Although it does involve coding, and some fields within it are more focused on this, the computer and coding are more of a tool used by the computer scientist to work on their more abstract, general concerns. Which are: \n\n- What is theoretically possible to compute? \n- How long will such a computation take? \n- What algorithms (descriptive 'how to' recipes) describe this computation, and are how many different ones exist and how efficient are they compared to each other?\n- What data structures (data storage techniques and representations) are best suited for a computation? What are their pitfalls and benefits?\n- What languages can we create to describe and instantiate these computations?\n\nCS Is a very broad field that spills over into more practical applications like software engineering and computer engineering, data science, and even IT when it comes to the application of cryptography for security measures. But on its own it has much more in common with theoretical math and logic than engineering. Its fundamental concern is the theoretical computer (a Turing Machine), to analyze what can be computed, and the algorithms possible and their efficiency. For example, there are some problems that can be solved, but they would take the lifetime of the universe to solve. And there are others that are easily solved if given the answer, but deriving it takes forever, like factoring numbers. ",
"IT - Keeps your sock drawer in working order\nCIS - Keeps your sock drawer organized\nCS - Answers the question, what is a sock?",
"Don't forget **Computer Engineering**, which is about the physical construction of computers. It's how you get from \"sparky wires\" to \"ones and zeroes,\" and eventually to \"I can run Doom on this thing.\"\n\nSource: I'm a Computer Engineer and it's cool as hell.",
"Computer science doesn't require a computer. Paper, a pencil, and a good eraser are all you need to write proofs.",
"Oooh, I'm way late to the party but I've always enjoyed my take on this very question, but people rarely ask this question. This is only based on my observations at the school I got my MIS degree at, so your mileage may vary.\n\nI don't know where IT falls in here. But for the rest, I think of it as a spectrum that looks like this:\n\n < CS---CIS---MIS---BA > \n\nWhen I use those acronyms I'm thinking Computer Science, Computer Information Systems (Maybe same as IT?), Management Information Systems (which is a terrible name for this degree, but it's an awesome degree, and Business Administration.\n\nThat spectrum also loosely equates to the kinds of classes you take:\n\n < Computer--------Business > \n\nSo computer classes will be like intro to comp sci, networking, programming, database design, etc. \n\nBusiness classes are like marketing, management, finance, etc. \n\nSo when I think back to the original spectrum I gave you:\n < CS----CIS----MIS----BA > \n\nand\n\n < Computer------Business > \n\nIn the CS degree, you get almost all computer classes and no business classes. With CIS you get some business, but still mostly computer. With MIS you get mostly business with some compsci classes, and BA you get all business classes.\n\nSo why would someone do any of this? Wouldn't it be better to specialize either in CS or BA? Why have those two in the middle? First, I would say the two in the middle are largely interchangeable in the business world. If you have a job that wants a CIS degree, your MIS will work, and vice versa. But those two play an **important** role in a business setting because to be frank: a CS and a BA don't know how to talk to each other. The CIS/MIS person knows enough of both sides of the world to translate between the two.\n\nThey know how to take the BA's business requirement and translate it into SQL code, or java, or whatever. They probably aren't doing the actual programming, but they can work closely with the CS person to ensure what they're doing matches what the BA wants. They can also help temper both sides' priorities. CS will want to do everything perfect. BA will want to do everything cheap. The CIS/MIS person will help the two negotiate.\n\nI'm an MIS major because I actually love doing this kind of work. I also lean more towards the business side, so that's why I took the MIS classes. When I graduated, I had to give an oral presentation on a subject in order to qualify for my Summa Cum Laude, and I gave it on this very topic (to which I passed). \n\nI've lived this role for 15-ish years in Corporate America and it's important, but not well understood or valued. But you'll get things done better when all sides are accounted for in a project. \n",
"Most of the answers are incorrect regarding what computer science is (even the top comment at the moment says it wrongly). \n\nIt is basically just mathematics (it split off of math because it is such a huge subject). Computer science is NOT about computers, it is about maths but using computers as a tool, just like astronomy is not about telescopes.\nWe learn about linear algebra, discrete maths, algorithms and datastructures, design of digital circuits, numerical methods, etc. \nThe goal of compsci is to quantify problems and solve them in an efficient manner using maths.\nIt is about the fundamental principles behind everything. For example encryption is basically just calculating enormous prime numbers (Diffie Hellman) and it finds application in the TCP protocol. Computer scientists develop the fundamental theory behind everything.\n\nSource: I am a cs student",
"The way I look at it. Do you want to me a programmer, data analyst, or sys admin?",
"CS: STEM undergrad, graduate school\n\nCIS: Business undergrad\n\nIT: community college, university dropout\n\nTongue in cheek, but it's more true than not.",
"I'm in IT and I stumbled across this explanation a while ago:\n\nThink of a car manufacturing company.\n\nYou have designers that work out what they want the car to do and perform tests to see if it can be done -*at all*. That's Computer Science. Possibly *creating* the bleeding edge of new innovations in the industry. Likely simply working for someone to reduce the business impact of a stupid decision of an executive.\n\nThen you have the mechanical engineers, who take the above information, and turn it into a car that can actually make it to market. That's Computer Information Science. . Might get a chance to *use* bleeding edge tech. possibly coming up with apps and using the teh to make something really cool, but more likely going to just be coding for an organization to make their weird payroll scheme work efficiently with outdated tech.\n\nThen you have several disciplines that are overlooked in the original question:\n\n- The guy who decides what size all the bolts in the car are going to be - that's hardware manufacture (how large should this server rack be?).\n\n- The guy who makes sure that the airbag isn't going to kill someone - That's bug testing (weird offshoot of IT)\n\n- and a few more, including other weird offshoot disciplines (White hat hacking, network design, software support, etc.)\n\nUntil you finally get to:\n\nThe greasy mechanic. Fixes the cars every day - solves problems, performs scheduled maintenance, and generally keeps them running. He is a Sysadmin, and he works in the IT department. BUT - \"what kind of IT?\" you may ask.\n\nMaybe he works for a company that has a nice fleet of high-end vehicles. That's IT at a nationally-recognized company headquarters. Seriously important, but not the main focus of the business, so no job security. Someone can replace him easily. Someone is likely *trying* to replace him.\n\nMaybe he works for a company that has vehicles, but not a ton, but he's still really important. That's IT at a small/medium business. The business would grind to a halt without him, but he's reliable and keeps the pretty lights blinking.\n\nMaybe he works in that weird place that doesn't seem like it *belongs* in the ghetto, but holy shit they get a lot of business - all your friends know that he does great work, but somehow has bad reviews on FB. That's a IT at a **M**anaged **S**ervice **P**rovider. The business has computers, but no IT department. They hire this other company to come and do maintenance/crisis management every once in a while. There might be a long-term contract. Maybe not.",
"One thing's for sure, taking any of these courses will make you never forget to end your open parenthesis. Trust me, I know."
]
}
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"https://www.acm.org/education/curricula-recommendations"
],
[],
[],
[],
[],
[],
[],
[],
[],
[],
[],
[
"https://www.abet.org/wp-content/uploads/2018/02/C001-18-19-CAC-Criteria-Version-2.0-updated-02-12-18.pdf"
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||
6dhsz8
|
Historical Fencing in the US of A
|
I am a practitioner or historical European martial arts (HEMA), and have been attempting to research the historical use of swords and bayonets in the USA, but so far lack the academic tools to do so; I have only found one manual online on the use of the saber from the early 20th century.
I am interested primarily in fencing manuals from any point in US history (say, pre 1917), as well as historical accounts of hand to hand combat in 18th and 19th century America. Does anyone with a background in any of these periods either have any sources like this or any advice on where and how to look?
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/6dhsz8/historical_fencing_in_the_us_of_a/
|
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"Matthew J. O'Rourke, a captain of volunteers on the Union side during the Civil War, published a treatise on the use of the saber in 1872, which was adopted as the Army's standard. You can get a free ebook of the manual here: _URL_0_\nThe first half of the the book is \"the Manual,\" regulations for how to draw a sword on parade, etc. The Part you're probably interested is the second half, \"the Exercise,\" which contains the actual fencing. If you're familiar with other 19th century military sabre systems, say from the U.K., its fairly similar, but with a few differences.\n\n",
"There are few resources over on r/Hemascholar that might be in the area you're interested in, although the materials there tend to be eclectic. You might also ask over at r/wma.\n\nSome resources from the US military side of things:\n\n- Matthew W. Berriman's [The Militiaman's Manual: And Sword-play Without a Master : Rapier and Broad-Sword Exercises](_URL_2_) (1861)\n\n- William Gilham's [Manual of Instruction for the Volunteers and Militia of the Confederate States](_URL_3_) (1861)\n\n- Philip St. George Cooke's [Cavalry Tactics; Or Regulations for the Instruction, Formations, and Movements of the Cavalry](_URL_5_) (1864)\n- A. J. Corbesier's [Principles of Squad Instruction for the Broadsword](_URL_1_) (1869) [PDF]\n\n- A. C. Cunningham's [Sword and Bayonet](_URL_4_) (1906)\n\n- [Provisional Regulations for Sabre exercise](_URL_0_) (1907)\n\n\n",
"I thought I should add that Captain O'Rourke published a previous version of his work during the civil war itself.\n\n Some more sources for 19th American military fencing:\n\nMajor Wayne, a former fencing instructor at West Point, published a manual intended for military use, unlike O'Rourke he includes a section on fencing with foils in preparation for a more \"thrusty\" weapon, as well as a broadsword or sabre section.\n_URL_0_\n\nThe Militiaman's Manual (Full title: The Militiaman's Manual: And Sword-play Without a Master : Rapier and Broad-sword Exercises, Copiously Explained and Illustrated : Small-arm Light Infantry Drill of the United States Army : Infantry Manual of Percussion Musket : Company Drill of the United States Cavalry\"), a work intended for Militia officers, contains fencing lessons for both thrusting and cutting weapons, perhaps intended, as the subtitle suggests, for people without access to a fencing master. The book sandwiches fencing instruction in with drill and the manual of arms for percussion musket, basically everything a militia officer would need to know.\n_URL_1_"
]
}
|
[] |
[] |
[
[
"https://play.google.com/store/books/details?id=M-ksAAAAYAAJ&rdid=book-M-ksAAAAYAAJ&rdot=1"
],
[
"http://www.anesi.com/prsefs.htm",
"http://www.navyandmarine.org/cutlassmanual/1869cutlass.pdf",
"https://books.google.fr/books?id=3moDAAAAYAAJ",
"https://books.google.fr/books?id=TPwlU_S_02YC",
"http://www.scribd.com/doc/14747784/Sabre-and-Bayonet-by-A-C-Cunning-Ham-USN-1906",
"https://books.google.fr/books?id=SjtFAAAAYAAJ"
],
[
"https://books.google.com/books/about/The_Sword_Exercises_Arranged_for_Militar.html?id=zS8PAQAAMAAJ",
"https://books.google.com/books/about/The_Militiaman_s_Manual.html?id=3moDAAAAYAAJ"
]
] |
|
fhvfuu
|
In high and late medieval Europe, German & Yiddish-speaking Jews had very high rates of literacy. However, was this isolated to Hebrew literature or could most Jewish people also read the Latin alphabet?
|
It's 1300. A German-speaking Jewish man is shown a phonically similar sentence rendered in Yiddish with Hebrew characters, and in German with Latin characters. Can we reasonably expect him to comprehend both?
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/fhvfuu/in_high_and_late_medieval_europe_german/
|
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"Gotz Aly (Why the Germans, why the Jews) explained that having extremely limited opportunities, European Jews invested heavily in and prioritized education. Whether their own religious education or secular education. As a result, they often had a mastery or at least understanding of multiple languages.\n\nBeing persecuted and discriminated against, Jewish people needed the ability to communicate with the Non Jews they were living with. Accordingly, they had to be able to read and talk in the language of their neighbours."
]
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[] |
[] |
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ni22i
|
what does the death of kim jong-il mean for north korea/the rest of the world?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/ni22i/eli5_what_does_the_death_of_kim_jongil_mean_for/
|
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"Functionally nothing as power had already been transferred and his death was expected. It's mostly important in relation to the cult of personality that existed in NK and how they will respond. I seriously doubt anything is going to change though.",
"Not much in any real sense, North Korea's leadership had already more or less been transferred to his son. \n\nMaybe his son will be less extreme then him but so far that has not been the case. ",
"Too soon to answer that BUT all indications are that his son has been groomed and will likely continue ruling NK in the same manner. Stay tuned.",
"Imagine you are playing a game called \"Crazy Dictator\" on your Xbox, and the person playing the game dies for some reason. Someone else then picks up the controller and continues where the previous player left off. Kim Jong-Il is dead, but the game will continue.\n\nBut North Korea has a mythology that surrounds their \"dear leader\" much like a comic book, wrestler, etc. has their own made-up backstory. Thus, they will have to let their crazy mythology \"absorb\" Il's death.",
"No one knows. That's the problem.",
"Long term, it's kind of up in the air. The US and ROK army over here in SK have been put on alert, however.",
"It's very hard to say at this point. There is very little information out about Kim Jong-un and we have no clue whether the regime will be better or worse under him. One of the many problems that analysts have outlined is that it isn't just the outside world that is unfamiliar with Kim Jong-un. Most North Koreans, outside of his name, aren't familiar with the successor either. Analysts say that this could lead to the government making drastic moves in order to make the North Korean people embrace the new ruler and the most obvious way in which a North Korean leader can gain approval is through aggression towards South Korea. Another cause for concern is the issue of having a power vacuum in a state possessing nuclear weapons. No one is sure as of right now whether North Korea is even dealing with a power vacuum as Kim Jong-Il's illness was well known and Kim Jong-un was being prepared to succeed his father. However, if there is, this situation could lead to disaster as potentially, many people could have access to these nuclear weapons. \n\nEDIT: Another interesting note that may or may not be important in predicting what Kim Jong-un's regime will be like is the fact that he was educated at an international school in Berne, separating him from his NK-educated father and grandfather. This could mean that he will have more western principles and as a result, he might not be as radical as his predecessors.",
"As has been stated, not much is likely to change. Even so, with how quiet and backroom the nature of politics in the DPRK are, it's not likely that everyone is excited about Kim Jong-Un replacing his father. As with any power-shift, there are almost certainly people in the background planning to use this as an opportunity to gain some power and influence of their own. \n\nFor the record, I'm not saying that they're going to go in and kill Kim Jong-Un or something; I'm just saying that I doubt Kim Jong-Un will find his power as entrenched as his father's was. \n\nOne final note: It's important not to think of the entire DPRK's population as brainwashed. That's a very simplistic (and generally untrue) way to think about things. A good chunk of North Korea''s southern population is exposed to South Korean TV, and there has been some quiet political organizing/questioning of the establishment at universities in the country throughout this past year, so don't think that the entire population of the DPRK is just sitting back, unthinking. ",
"Kim Jong-il had a unique combination of shrewdness, ruthlessness, and crazy that allowed him to rule North Korea with an iron fist while keeping the rest of the world at bay.\n\nChances are, his successor will not be as good at this game as he was. He may have to deal with the rest of the world in order to stay in power, or he may not be able to stay in power at all.",
"This was a paper that someone wrote in 2009 about the matter. These are all speculations about the possible outcomes of KJI's death. _URL_0_ It's a lot to read and it's not really ELI5, but i'm sure someone can break these situations down and explain much better than I could.",
"This is a stretch, but here goes.\n\nImagine you are at a your school. Now imagine that there is another kindergarten room, and nobody is allowed in there except that class of kindergarteners and their teacher. The teacher (Kim Jong Il) tells his students that he is the best teacher ever, and all the other classes (western countries) are teaching wrong things, and all the other teachers and students are evil. The principal (China) lets this one teacher get away with all of this as long as the teacher makes everything look ok, and keeps the kids in his room. Sometimes kids try to leave the room, but the principal quietly ushers them back to their room, where they are never seen or heard from again.\n\nThe rest of the school knows that there are many bad things happening in this room, but can't do anything about it because the principal is protecting them. \n\nNow imagine that the teacher dies, and leaves one of his students in charge. The student isn't known very well at all to the rest of the school outside the classroom, just that he might have been [playing with some fireworks](_URL_0_) last year. \n\nThere might also be a few teacher's pets left in the classroom (generals) who don't like the idea of this student being left in charge, because he is not as \"perfect\" as the teacher. So they might be planning something to get rid of him.\n\nThe rest of the school is not really sure what will happen because they don't have very much knowledge about what was really happening in the classroom. They can't burst into the room because the principal is still looking out for the secret class, so the best they can do for now is watch very closely to make sure nothing too bad comes out of the room and hurts anybody else.\n",
"\"**There is a 50-50 chance that the regime can survive. There is a huge chance that the regime can fall into implosion, explosion, or complete civil war. Anarchy type activity.** This is absolutley something that the people that are planning for right now. This means a lot of military involvement for both South Korea and United States. Probably lead by the South Korean military with support from the United States and this is a very real possibility and this is why the north korean regime process is the fourth threat\" Bruce E. Bechtol, Jr May 23 2011\n\n\n_URL_0_\n\nI will summarize some of Bruce E. Bechtol key points\n\n1. In North Korea there is no such thing as hierarchical organization of government. It is more like a guy in the center of a circle and all of the institutions feed into him. Since Kim Il-sung took over. He set up the government that way for his son Kim Jong Il. He had 20 years to do that since 1974 to 1994 when the process started. You cannot run that country unless you control the party, the military, the security services and that Byzantine entity known as the Kim family inner circle. Kim Jung Il controlled all of them. It all started in 1974. By 1992 he was a 5 star general in the army even though he never served in uniform. He was the head of the organization and guidance department for the party. Which is the organization that controls not only what happens in the party but the controls promotions for the military. He was the head of State Security Department and the Ministry of Peoples Security the 2 biggest security services of about 8 security services. His father also purged all of his relatives that he was out of favor with. **None of this has happened for Kim Jong-un yet.** His father is trying to set him up as a general in the army but he is not there yet. He is in the party and has a place in the OGD (Organization and Guidance Department) but he is not running it yet.**There have been problems with him getting along with people in the security services and there have been problems with the fact there have been reports of him trying to have his older brother assassinated.**\n\n\n2. Nobody outside of Kim controls more than a few staff members. In the army if you are a general commanding a core or a colonel commanding a regiment on your left shoulder you have a guy from the State Security Department overlooking that you are doing things politically correct and on your right shoulder you have a guy from the General Political Bureau making sure you are not going to try and overthrow the government. So unlike China and the Soviet Union where they have a political officer in every unit and in North Korea if you want to rebel you have to kill 2 guys and they answer to 2 separate chains of command. So Kim has built the power base in the country so nobody controls enough power so someone can come in and take control a coup d'etat.\n\n\n3. **In order for his son to take over his dad has to build a power base for him in the party, army, security services and the Kim family regime. Has he been able to do that? He has not been able to do that yet. It took 20 years for Kim Jong-il's father to do that for him.** There is a good chance Kim Jong Il will die in the next 5 years so he doesn't have much time to prepare his son unlike his father did for him.\n\n4. The generals would like the succession of the son to work because they know they will hanging on meat hooks Mussolini style if the country implodes. They would like to see a family succession to work for selfish reasons. Because of the way the military is set up it would be almost impossible for a general to throw a coup d'etat because the party watches the military too closely.\n\n\nThe lecturer Bruce E. Bechtol, Jr., is an associate professor of political science at Angelo State University and served as a visiting adjunct professor at the Korea University Graduate School of International Studies in Seoul, Korea. A former intelligence officer with the Defense Intelligence Agency and a retired Marine, he has lived and worked in Korea. He is the author of Red Rogue: The Persistent Challenge of North Korea, as well as numerous articles in peer-reviewed journals relating to Korean security issues.",
"A fatter version of Kim Jong-il keeps on playing the game.",
"On another thread, here's a \"explain like I'm an intelligence agent\" answer:\n\n_URL_0_",
"It means that Kim Kardashian is free to reign as the \"evilest Kim alive\"",
"Functionally nothing as power had already been transferred and his death was expected. It's mostly important in relation to the cult of personality that existed in NK and how they will respond. I seriously doubt anything is going to change though.",
"Not much in any real sense, North Korea's leadership had already more or less been transferred to his son. \n\nMaybe his son will be less extreme then him but so far that has not been the case. ",
"Too soon to answer that BUT all indications are that his son has been groomed and will likely continue ruling NK in the same manner. Stay tuned.",
"Imagine you are playing a game called \"Crazy Dictator\" on your Xbox, and the person playing the game dies for some reason. Someone else then picks up the controller and continues where the previous player left off. Kim Jong-Il is dead, but the game will continue.\n\nBut North Korea has a mythology that surrounds their \"dear leader\" much like a comic book, wrestler, etc. has their own made-up backstory. Thus, they will have to let their crazy mythology \"absorb\" Il's death.",
"No one knows. That's the problem.",
"Long term, it's kind of up in the air. The US and ROK army over here in SK have been put on alert, however.",
"It's very hard to say at this point. There is very little information out about Kim Jong-un and we have no clue whether the regime will be better or worse under him. One of the many problems that analysts have outlined is that it isn't just the outside world that is unfamiliar with Kim Jong-un. Most North Koreans, outside of his name, aren't familiar with the successor either. Analysts say that this could lead to the government making drastic moves in order to make the North Korean people embrace the new ruler and the most obvious way in which a North Korean leader can gain approval is through aggression towards South Korea. Another cause for concern is the issue of having a power vacuum in a state possessing nuclear weapons. No one is sure as of right now whether North Korea is even dealing with a power vacuum as Kim Jong-Il's illness was well known and Kim Jong-un was being prepared to succeed his father. However, if there is, this situation could lead to disaster as potentially, many people could have access to these nuclear weapons. \n\nEDIT: Another interesting note that may or may not be important in predicting what Kim Jong-un's regime will be like is the fact that he was educated at an international school in Berne, separating him from his NK-educated father and grandfather. This could mean that he will have more western principles and as a result, he might not be as radical as his predecessors.",
"As has been stated, not much is likely to change. Even so, with how quiet and backroom the nature of politics in the DPRK are, it's not likely that everyone is excited about Kim Jong-Un replacing his father. As with any power-shift, there are almost certainly people in the background planning to use this as an opportunity to gain some power and influence of their own. \n\nFor the record, I'm not saying that they're going to go in and kill Kim Jong-Un or something; I'm just saying that I doubt Kim Jong-Un will find his power as entrenched as his father's was. \n\nOne final note: It's important not to think of the entire DPRK's population as brainwashed. That's a very simplistic (and generally untrue) way to think about things. A good chunk of North Korea''s southern population is exposed to South Korean TV, and there has been some quiet political organizing/questioning of the establishment at universities in the country throughout this past year, so don't think that the entire population of the DPRK is just sitting back, unthinking. ",
"Kim Jong-il had a unique combination of shrewdness, ruthlessness, and crazy that allowed him to rule North Korea with an iron fist while keeping the rest of the world at bay.\n\nChances are, his successor will not be as good at this game as he was. He may have to deal with the rest of the world in order to stay in power, or he may not be able to stay in power at all.",
"This was a paper that someone wrote in 2009 about the matter. These are all speculations about the possible outcomes of KJI's death. _URL_0_ It's a lot to read and it's not really ELI5, but i'm sure someone can break these situations down and explain much better than I could.",
"This is a stretch, but here goes.\n\nImagine you are at a your school. Now imagine that there is another kindergarten room, and nobody is allowed in there except that class of kindergarteners and their teacher. The teacher (Kim Jong Il) tells his students that he is the best teacher ever, and all the other classes (western countries) are teaching wrong things, and all the other teachers and students are evil. The principal (China) lets this one teacher get away with all of this as long as the teacher makes everything look ok, and keeps the kids in his room. Sometimes kids try to leave the room, but the principal quietly ushers them back to their room, where they are never seen or heard from again.\n\nThe rest of the school knows that there are many bad things happening in this room, but can't do anything about it because the principal is protecting them. \n\nNow imagine that the teacher dies, and leaves one of his students in charge. The student isn't known very well at all to the rest of the school outside the classroom, just that he might have been [playing with some fireworks](_URL_0_) last year. \n\nThere might also be a few teacher's pets left in the classroom (generals) who don't like the idea of this student being left in charge, because he is not as \"perfect\" as the teacher. So they might be planning something to get rid of him.\n\nThe rest of the school is not really sure what will happen because they don't have very much knowledge about what was really happening in the classroom. They can't burst into the room because the principal is still looking out for the secret class, so the best they can do for now is watch very closely to make sure nothing too bad comes out of the room and hurts anybody else.\n",
"\"**There is a 50-50 chance that the regime can survive. There is a huge chance that the regime can fall into implosion, explosion, or complete civil war. Anarchy type activity.** This is absolutley something that the people that are planning for right now. This means a lot of military involvement for both South Korea and United States. Probably lead by the South Korean military with support from the United States and this is a very real possibility and this is why the north korean regime process is the fourth threat\" Bruce E. Bechtol, Jr May 23 2011\n\n\n_URL_0_\n\nI will summarize some of Bruce E. Bechtol key points\n\n1. In North Korea there is no such thing as hierarchical organization of government. It is more like a guy in the center of a circle and all of the institutions feed into him. Since Kim Il-sung took over. He set up the government that way for his son Kim Jong Il. He had 20 years to do that since 1974 to 1994 when the process started. You cannot run that country unless you control the party, the military, the security services and that Byzantine entity known as the Kim family inner circle. Kim Jung Il controlled all of them. It all started in 1974. By 1992 he was a 5 star general in the army even though he never served in uniform. He was the head of the organization and guidance department for the party. Which is the organization that controls not only what happens in the party but the controls promotions for the military. He was the head of State Security Department and the Ministry of Peoples Security the 2 biggest security services of about 8 security services. His father also purged all of his relatives that he was out of favor with. **None of this has happened for Kim Jong-un yet.** His father is trying to set him up as a general in the army but he is not there yet. He is in the party and has a place in the OGD (Organization and Guidance Department) but he is not running it yet.**There have been problems with him getting along with people in the security services and there have been problems with the fact there have been reports of him trying to have his older brother assassinated.**\n\n\n2. Nobody outside of Kim controls more than a few staff members. In the army if you are a general commanding a core or a colonel commanding a regiment on your left shoulder you have a guy from the State Security Department overlooking that you are doing things politically correct and on your right shoulder you have a guy from the General Political Bureau making sure you are not going to try and overthrow the government. So unlike China and the Soviet Union where they have a political officer in every unit and in North Korea if you want to rebel you have to kill 2 guys and they answer to 2 separate chains of command. So Kim has built the power base in the country so nobody controls enough power so someone can come in and take control a coup d'etat.\n\n\n3. **In order for his son to take over his dad has to build a power base for him in the party, army, security services and the Kim family regime. Has he been able to do that? He has not been able to do that yet. It took 20 years for Kim Jong-il's father to do that for him.** There is a good chance Kim Jong Il will die in the next 5 years so he doesn't have much time to prepare his son unlike his father did for him.\n\n4. The generals would like the succession of the son to work because they know they will hanging on meat hooks Mussolini style if the country implodes. They would like to see a family succession to work for selfish reasons. Because of the way the military is set up it would be almost impossible for a general to throw a coup d'etat because the party watches the military too closely.\n\n\nThe lecturer Bruce E. Bechtol, Jr., is an associate professor of political science at Angelo State University and served as a visiting adjunct professor at the Korea University Graduate School of International Studies in Seoul, Korea. A former intelligence officer with the Defense Intelligence Agency and a retired Marine, he has lived and worked in Korea. He is the author of Red Rogue: The Persistent Challenge of North Korea, as well as numerous articles in peer-reviewed journals relating to Korean security issues.",
"A fatter version of Kim Jong-il keeps on playing the game.",
"On another thread, here's a \"explain like I'm an intelligence agent\" answer:\n\n_URL_0_",
"It means that Kim Kardashian is free to reign as the \"evilest Kim alive\""
]
}
|
[] |
[] |
[
[],
[],
[],
[],
[],
[],
[],
[],
[],
[
"http://www.nps.edu/Academics/centers/ccc/publications/OnlineJournal/2009/Dec/vandermeerDec09.pdf"
],
[
"http://www.smh.com.au/world/north-korean-dictatorinwaiting-linked-to-deadly-artillery-attack-20101123-185p1.html"
],
[
"http://www.c-spanvideo.org/program/300124-1"
],
[],
[
"http://www.reddit.com/r/AskReddit/comments/ni1wp/i_am_south_korean_can_someone_coolheaded_explain/c39bec1"
],
[],
[],
[],
[],
[],
[],
[],
[],
[],
[],
[
"http://www.nps.edu/Academics/centers/ccc/publications/OnlineJournal/2009/Dec/vandermeerDec09.pdf"
],
[
"http://www.smh.com.au/world/north-korean-dictatorinwaiting-linked-to-deadly-artillery-attack-20101123-185p1.html"
],
[
"http://www.c-spanvideo.org/program/300124-1"
],
[],
[
"http://www.reddit.com/r/AskReddit/comments/ni1wp/i_am_south_korean_can_someone_coolheaded_explain/c39bec1"
],
[]
] |
||
3egrm9
|
what the suds in dish soap do and how they work.
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/3egrm9/eli5_what_the_suds_in_dish_soap_do_and_how_they/
|
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"Dish soap is made out of special molecules are both polar (slight charge) and non-polar. This property allows them to form a microscopic \"bubble\" called a [micelle](_URL_0_) around non-polar molecules (such as fat and oils) which can then be dissolved in water. The reason it is so hard to get things like oil off of your hands without soap is because they are non-polar and do not dissolve in water. Using a soap helps to dissolve the oils and they can then be washed off of your hands with water. "
]
}
|
[] |
[] |
[
[
"https://en.wikipedia.org/wiki/Micelle"
]
] |
||
2byil2
|
Atlatls VS bows in the Americas
|
I've read that bows were late on the scene for many NA indian tribes.
Can anyone supply a time-line for the introduction and spread of the bow in the Americas?
Also: was the atlatl wide-spread before the introduction of the bow?
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/2byil2/atlatls_vs_bows_in_the_americas/
|
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"[This post](_URL_0_) has it that bows and arrows emerged between 3-4 thousand years ago, probably independently, in a number of locations in North America. To my knowledge, atlatls were widely spread throughout North America both before and after bows were in use.\n"
]
}
|
[] |
[] |
[
[
"http://www.reddit.com/r/AskHistorians/comments/1i1y9d/did_the_native_americans_have_bow_arrows_by_1000bc/"
]
] |
|
l2hdz
|
What is the limiting factor in human eyesight?
|
The scenario I'm picturing is some future eyesight technology that would push biology to its limits--but I'm wondering about the point at which is it no longer possible to enhance human eyesight. Where would it be?
Would it be when the rod and cones in the eye are all receiving the maximum amount of information they can pass on? Or is there more bandwidth possible in the optic nerve than they can provide? Is there a point where the visual cortex has more information than it can handle?
|
askscience
|
http://www.reddit.com/r/askscience/comments/l2hdz/what_is_the_limiting_factor_in_human_eyesight/
|
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"To sum up several responses, there are several limiting factors, several of them intertwined:\n\n1. How much information hits your retina: the limit cause by the circular aperture of your eye and the imperfections in the lens.\n\n2. How much information that hits your retina actually gets converted into electrical signals: the limit caused by the number of photoreceptors.\n\n3. How much information that your photoreceptors generate actually gets passed on to the cortex via the optic nerve: the limit caused by the number of outgoing axons (note: we have only 1 million. Sounds like a lot, but remember that a 1 megapixel camera has 1 million pixels. This limit is also related to the preprocessing done by the retina, which consists of several layer of cells)\n\n4. How much information that reaches your cortex is processed into actual visual experience: the limit caused by the amount of cortex dedicated to visual processing.\n\n1. Given that the diffraction limit should allow us to see bacteria etc. I don't think this is the current bottleneck.\n\nI can't immediately eliminate any of the other 3, but I am fairly certain that evolution would prefer a system in which all of these channels are fairly well balanced against one another. That is to say, if you increased the number of photoreceptors, then you would also increase the diameter of the axon and the amount of cortex. There is no reason to believe that our cortex has the ability to process far more visual information than it currently does. \n\nSeveral have cited examples in which cortex being used for processing one modality can adapt to processing another. This is not evidence of increased bandwidth: it is very likely that those that learn to see using their tongues are actually processing _less_ information than they were before.\n\nSome evidence for the close balance would be the retinotopic organization of the first place input from the eye goes. There seems to be a tight correlation between the number of photoreceptors and the number of neurons for different parts of the visual field, evidence of the fact that we are spending just enough on building optic nerves and V1 neurons to deal with the input we are getting from the amount of photoreceptors we have. Every where the density of photoreceptors goes up, everything else goes up as well. Likewise for increasing the bandwidth at 3 and 4\n\nIn summary: the limiting factor in human eyesight is likely everything besides the diffraction limit. You probably won't see an improvement on the ability to recognize objects using the same light input to the eye without making improvements everywhere along the processing chain.\n",
"To sum up several responses, there are several limiting factors, several of them intertwined:\n\n1. How much information hits your retina: the limit cause by the circular aperture of your eye and the imperfections in the lens.\n\n2. How much information that hits your retina actually gets converted into electrical signals: the limit caused by the number of photoreceptors.\n\n3. How much information that your photoreceptors generate actually gets passed on to the cortex via the optic nerve: the limit caused by the number of outgoing axons (note: we have only 1 million. Sounds like a lot, but remember that a 1 megapixel camera has 1 million pixels. This limit is also related to the preprocessing done by the retina, which consists of several layer of cells)\n\n4. How much information that reaches your cortex is processed into actual visual experience: the limit caused by the amount of cortex dedicated to visual processing.\n\n1. Given that the diffraction limit should allow us to see bacteria etc. I don't think this is the current bottleneck.\n\nI can't immediately eliminate any of the other 3, but I am fairly certain that evolution would prefer a system in which all of these channels are fairly well balanced against one another. That is to say, if you increased the number of photoreceptors, then you would also increase the diameter of the axon and the amount of cortex. There is no reason to believe that our cortex has the ability to process far more visual information than it currently does. \n\nSeveral have cited examples in which cortex being used for processing one modality can adapt to processing another. This is not evidence of increased bandwidth: it is very likely that those that learn to see using their tongues are actually processing _less_ information than they were before.\n\nSome evidence for the close balance would be the retinotopic organization of the first place input from the eye goes. There seems to be a tight correlation between the number of photoreceptors and the number of neurons for different parts of the visual field, evidence of the fact that we are spending just enough on building optic nerves and V1 neurons to deal with the input we are getting from the amount of photoreceptors we have. Every where the density of photoreceptors goes up, everything else goes up as well. Likewise for increasing the bandwidth at 3 and 4\n\nIn summary: the limiting factor in human eyesight is likely everything besides the diffraction limit. You probably won't see an improvement on the ability to recognize objects using the same light input to the eye without making improvements everywhere along the processing chain.\n",
"Even light microscopes have a limit. \n > The resolution limit of a light microscope using visible light is about 200 nm.\nFrom Wiki\n \nHere's what we could see if we had super lenses in our eyes.\n\n_URL_0_\n",
"At some point, the eye will be diffraction limited (see Rayleigh Criterion and Angular Resolution [here](_URL_0_)). Even if your eye was physically perfect/ideal in every way, your vision is still limited by the size of the circular aperture of the eye. \n\nI actually did a presentation on this for a lower division physics class and can send it to you if interested, but I can't do that until tomorrow (have to get the file from a lab computer).\n\nEDIT: [Link to said small presentation](_URL_1_). Only three slides, and only one really discusses the physics.\n\nSecond edit: I do remember attending a talk where the speaker discussed using a clever algorithm to combine input from multiple lenses (i.e. two eyes) to beat the diffraction limit, but it didn't provide a huge increase in resolution by any means. Will try to hunt down the abstract.",
"Depends on the augmentation technology. For something that projects into your retina, you'd be limited by the number of rods and cones (the \"resolution\" of your eye) - there's a finite number of cells there and each cell can only detect a finite amount of information. \n\nIf you replace the retina and directly interface with the optic nerve (like some of the cochlear implants do), there'd be a limit on the \"bandwidth\" of the nerves. It's a pretty large bundle of nerves though.\n\nThe real limit would be how much optical data your brain can process. The brain filters out a lot of details and picks up on motion, edges, faces, shapes and distance, etc. That's all hard-wired either genetically or soon after birth. So if you want 6 eyes positioned on all sides of your head, I'm not sure your brain can process that. ",
"It's a function of the physical size and design of the eye. This affects the properties for the diffraction of light. Not so much the rods/cones.\n\nHere you go:\n_URL_0_",
"I can give a partial answer - we don't exactly know how the eye passes visual data to the brain, but we do know it isn't as simple as a response level being reported by each rod or cone every 1/24 seconds. The eye does a lot of preprocessing and sends signals that encode what patterns of rods and cones have fired. If I recall correctly, the eye actually does edge detection.\n\nThe brain appears to do motion detection, shape recognition, facial recognition, and colour detection in distinct steps - and in that order, I believe.\n\nA sufficiently advanced knowledge of how all that works might lead to an understanding of how to 'game' the optic nerve to shove more information through, but the brain isn't really equipped to deal with it and we don't know the limits of its plasticity when it comes to dealing with additional sensory input. \n\nWhat we do know is that people who have lacked a sense since birth don't like it when you fix the problem, because their brains haven't developed the capacity to deal with the information. I imagine you'd get a similar effect from increasing the complexity of information shoved through an existing channel.\n\nWe do already have (in its infancy) the technology to overlay an artificial retina over a failing natural retina. I can imagine a day when such an artificial device would do something like shift the spectrum you can see by interpreting UV or IR with false colour, or maybe insert an overlay to give you augmented reality.",
"I'm no expert, but I used to run a research and differential diagnosis laboratory for a large medical university's department of ophthalmology.\n\n\nBasically I found that during an electro-occulogram study that the occipital lobe would register information about 200 micro seconds after retinal stimulation. This was also borne out in an electro-retinogram study, as well. These were not just my findings, but well know standard data transfer rates in humans.\n\n\nWhat that means is that photonic light energy incident upon the retinal pigment epithelium was transduced into electrical impulses along the rods and cones and passed to the optic nerve bundle, and then moved from the eye through the brain to the occipital lobe (back of your head) and processed to some degree of recognition within about 200 microseconds.\n\n\nThe studies I mentioned include either stimulation of the retina by an image of a shifting pattern or by stimulation by a narrow band and intensity controlled light pulse. You can ask me how we acquired the data, but it's ghoulish and boring.\n\n\nWhat you really need is a Redditor who is either a physcho-physicist who specializes in visual stimulii studies, or an ophthalmologist who is focused on retinal degenerations, diseases, and other such dystrophies. I've been out of the game for about 20 years now, even though I like to think I try to keep current due to the fascinating nature of the topic.\n\n\nUmmm... Good question.\n",
"Density of photoreceptors (rods & cones), and bandwidth along the optical nerve.",
"There are a few interesting posts in here discussing processing within the brain. I won't comment on how that could fit in with future technology, but I can say that the limiting factor for human eyesight is retinal physiology. It comes down to the spacing of cones within the fovea, which is where they are most densely packed and responsible for fine detail vision. If you assume perfectly clear media (cornea, lens, vitreous), then the theoretical limit of human visual resolution is something on the order of 20/8. Anything that subtends a smaller angle on the retina just can't be resolved by individual cones.",
"What does 'enhance human eyesight' mean? That is the key part of answering this question.\n\nIf you are talking about angular resolution, well, that's easy: you give the eye magnifying lenses. Surgeons regularly use magnifying loupes to give them better resolution for fine operations. Or, in the case of most ophthalmologic procedures, they use a stereo microscope.\n\nIf you are talking about total bandwidth to the brain, that's a much different issue. There is a lot of signal processing and compression that takes place before information is sent along approx 1.2 million nerve fibers per eye.\n\nSo what do you mean by 'enhance eyesight?'",
"Wow, did I get lost after reading this article.\n\n_URL_1_\n\n > But adaptive optics will be most useful when it can be used to correct vision permanently outside the lab. That's why eye surgeons are so interested in Williams' work. His technique is fairly easily translated to surgery (and may also work for contact lenses). A laser surgeon can follow the map of errors revealed by the wavefront sensor, making minuscule, precise corrections on the corneal surface. No longer will laser surgery be limited to the big aberrations that surgeons can now eliminate: It could erase every error in the eye.\n\nWhich of course did not work out in the real world as well as they imagined.\n\n_URL_0_\n\n > Technology designed to have 100% of patients freed from corrective lenses. \n\nThe ALLEGRETTO WAVE Eye-Q customizes every treatment to the patient's individual prescription and cornea while aiming to improve what nature originally designed. The Wavefront Optimized TM treatment considers the unique curvature and biomechanics of the eye, preserving quality of vision and addressing the spherical distortions that can induce glare and may affect night vision.\n\nThey aren't saying everyone will have 20/10 vision, but at least it'll be good enough to not need corrective lenses.\n\nHonestly, I'm curious as to what the issue was this technology isn't more advanced by now? With how fast processing power, imaging sensors, lasers, and other supplemental technologies have progressed, after reading about this 10+ year old technique I'd figure 20/10 vision would be something you could get for $10 from a kiosk at your local pharmacy by now...",
"How about we just re-order the retina, and put the [photoreceptors first](_URL_0_)?\n\nWhy mess with technology when we can use biology?",
"So, I've seen a few replies saying there would be a limit to seeing small things with the eye do to...x...; however, the limit would have to be the same limit of a microscope. Since we can project what's on the microscope...\n\nAs far as the rest of the question I'm not sure, I just came to find out from the experts. (giggidy)",
"The density of air is the reason the focal length is what it is. If you aim for a better length then you get \"heat haze\" effects from the air.",
"Even light microscopes have a limit. \n > The resolution limit of a light microscope using visible light is about 200 nm.\nFrom Wiki\n \nHere's what we could see if we had super lenses in our eyes.\n\n_URL_0_\n",
"At some point, the eye will be diffraction limited (see Rayleigh Criterion and Angular Resolution [here](_URL_0_)). Even if your eye was physically perfect/ideal in every way, your vision is still limited by the size of the circular aperture of the eye. \n\nI actually did a presentation on this for a lower division physics class and can send it to you if interested, but I can't do that until tomorrow (have to get the file from a lab computer).\n\nEDIT: [Link to said small presentation](_URL_1_). Only three slides, and only one really discusses the physics.\n\nSecond edit: I do remember attending a talk where the speaker discussed using a clever algorithm to combine input from multiple lenses (i.e. two eyes) to beat the diffraction limit, but it didn't provide a huge increase in resolution by any means. Will try to hunt down the abstract.",
"Depends on the augmentation technology. For something that projects into your retina, you'd be limited by the number of rods and cones (the \"resolution\" of your eye) - there's a finite number of cells there and each cell can only detect a finite amount of information. \n\nIf you replace the retina and directly interface with the optic nerve (like some of the cochlear implants do), there'd be a limit on the \"bandwidth\" of the nerves. It's a pretty large bundle of nerves though.\n\nThe real limit would be how much optical data your brain can process. The brain filters out a lot of details and picks up on motion, edges, faces, shapes and distance, etc. That's all hard-wired either genetically or soon after birth. So if you want 6 eyes positioned on all sides of your head, I'm not sure your brain can process that. ",
"It's a function of the physical size and design of the eye. This affects the properties for the diffraction of light. Not so much the rods/cones.\n\nHere you go:\n_URL_0_",
"I can give a partial answer - we don't exactly know how the eye passes visual data to the brain, but we do know it isn't as simple as a response level being reported by each rod or cone every 1/24 seconds. The eye does a lot of preprocessing and sends signals that encode what patterns of rods and cones have fired. If I recall correctly, the eye actually does edge detection.\n\nThe brain appears to do motion detection, shape recognition, facial recognition, and colour detection in distinct steps - and in that order, I believe.\n\nA sufficiently advanced knowledge of how all that works might lead to an understanding of how to 'game' the optic nerve to shove more information through, but the brain isn't really equipped to deal with it and we don't know the limits of its plasticity when it comes to dealing with additional sensory input. \n\nWhat we do know is that people who have lacked a sense since birth don't like it when you fix the problem, because their brains haven't developed the capacity to deal with the information. I imagine you'd get a similar effect from increasing the complexity of information shoved through an existing channel.\n\nWe do already have (in its infancy) the technology to overlay an artificial retina over a failing natural retina. I can imagine a day when such an artificial device would do something like shift the spectrum you can see by interpreting UV or IR with false colour, or maybe insert an overlay to give you augmented reality.",
"I'm no expert, but I used to run a research and differential diagnosis laboratory for a large medical university's department of ophthalmology.\n\n\nBasically I found that during an electro-occulogram study that the occipital lobe would register information about 200 micro seconds after retinal stimulation. This was also borne out in an electro-retinogram study, as well. These were not just my findings, but well know standard data transfer rates in humans.\n\n\nWhat that means is that photonic light energy incident upon the retinal pigment epithelium was transduced into electrical impulses along the rods and cones and passed to the optic nerve bundle, and then moved from the eye through the brain to the occipital lobe (back of your head) and processed to some degree of recognition within about 200 microseconds.\n\n\nThe studies I mentioned include either stimulation of the retina by an image of a shifting pattern or by stimulation by a narrow band and intensity controlled light pulse. You can ask me how we acquired the data, but it's ghoulish and boring.\n\n\nWhat you really need is a Redditor who is either a physcho-physicist who specializes in visual stimulii studies, or an ophthalmologist who is focused on retinal degenerations, diseases, and other such dystrophies. I've been out of the game for about 20 years now, even though I like to think I try to keep current due to the fascinating nature of the topic.\n\n\nUmmm... Good question.\n",
"Density of photoreceptors (rods & cones), and bandwidth along the optical nerve.",
"There are a few interesting posts in here discussing processing within the brain. I won't comment on how that could fit in with future technology, but I can say that the limiting factor for human eyesight is retinal physiology. It comes down to the spacing of cones within the fovea, which is where they are most densely packed and responsible for fine detail vision. If you assume perfectly clear media (cornea, lens, vitreous), then the theoretical limit of human visual resolution is something on the order of 20/8. Anything that subtends a smaller angle on the retina just can't be resolved by individual cones.",
"What does 'enhance human eyesight' mean? That is the key part of answering this question.\n\nIf you are talking about angular resolution, well, that's easy: you give the eye magnifying lenses. Surgeons regularly use magnifying loupes to give them better resolution for fine operations. Or, in the case of most ophthalmologic procedures, they use a stereo microscope.\n\nIf you are talking about total bandwidth to the brain, that's a much different issue. There is a lot of signal processing and compression that takes place before information is sent along approx 1.2 million nerve fibers per eye.\n\nSo what do you mean by 'enhance eyesight?'",
"Wow, did I get lost after reading this article.\n\n_URL_1_\n\n > But adaptive optics will be most useful when it can be used to correct vision permanently outside the lab. That's why eye surgeons are so interested in Williams' work. His technique is fairly easily translated to surgery (and may also work for contact lenses). A laser surgeon can follow the map of errors revealed by the wavefront sensor, making minuscule, precise corrections on the corneal surface. No longer will laser surgery be limited to the big aberrations that surgeons can now eliminate: It could erase every error in the eye.\n\nWhich of course did not work out in the real world as well as they imagined.\n\n_URL_0_\n\n > Technology designed to have 100% of patients freed from corrective lenses. \n\nThe ALLEGRETTO WAVE Eye-Q customizes every treatment to the patient's individual prescription and cornea while aiming to improve what nature originally designed. The Wavefront Optimized TM treatment considers the unique curvature and biomechanics of the eye, preserving quality of vision and addressing the spherical distortions that can induce glare and may affect night vision.\n\nThey aren't saying everyone will have 20/10 vision, but at least it'll be good enough to not need corrective lenses.\n\nHonestly, I'm curious as to what the issue was this technology isn't more advanced by now? With how fast processing power, imaging sensors, lasers, and other supplemental technologies have progressed, after reading about this 10+ year old technique I'd figure 20/10 vision would be something you could get for $10 from a kiosk at your local pharmacy by now...",
"How about we just re-order the retina, and put the [photoreceptors first](_URL_0_)?\n\nWhy mess with technology when we can use biology?",
"So, I've seen a few replies saying there would be a limit to seeing small things with the eye do to...x...; however, the limit would have to be the same limit of a microscope. Since we can project what's on the microscope...\n\nAs far as the rest of the question I'm not sure, I just came to find out from the experts. (giggidy)",
"The density of air is the reason the focal length is what it is. If you aim for a better length then you get \"heat haze\" effects from the air."
]
}
|
[] |
[] |
[
[],
[],
[
"http://i.imgur.com/TkNNF.png"
],
[
"http://en.wikipedia.org/wiki/Angular_resolution",
"http://imgur.com/a/10xAa"
],
[],
[
"http://en.wikipedia.org/wiki/Angular_resolution#Explanation"
],
[],
[],
[],
[],
[],
[
"http://www.ttuhsc.edu/i-see/ladarvision.htm",
"http://www.slate.com/articles/health_and_science/superman/2003/03/i_spy_with_my_eagle_eye.single.html"
],
[
"http://en.wikipedia.org/wiki/Retina#Vertebrate_and_cephalopod_retina_differences"
],
[],
[],
[
"http://i.imgur.com/TkNNF.png"
],
[
"http://en.wikipedia.org/wiki/Angular_resolution",
"http://imgur.com/a/10xAa"
],
[],
[
"http://en.wikipedia.org/wiki/Angular_resolution#Explanation"
],
[],
[],
[],
[],
[],
[
"http://www.ttuhsc.edu/i-see/ladarvision.htm",
"http://www.slate.com/articles/health_and_science/superman/2003/03/i_spy_with_my_eagle_eye.single.html"
],
[
"http://en.wikipedia.org/wiki/Retina#Vertebrate_and_cephalopod_retina_differences"
],
[],
[]
] |
|
2vw6t9
|
is it true that the 1960's-1970's middle east was super civilized and progressive, and if so, what the hell happened?
|
We see quite often reddit posts to imgur albums of [1960's Afghanistan](_URL_0_) or [Iran](_URL_1_) or [Pakistan.](_URL_2_) Iraq and Syria seemed to be more conservative, but also far more stable and structured back then. I'm aware of the Iranian Revolution in 1979, and the Soviet-Afghanistan war from 1979-1989, and the Taliban government in the 1990's, and maybe the independence of East Pakistan (Bangladesh) in 1971, but what else might have caused the dramatic falter of progress back then, how did the seemingly minor ultraconservative groups influence their entire nation in that short of a time? And how did the super awesome 1960's era in these nations come to be? The stereotype is that these countries have always been violent shitholes, but this is clearly not the case.
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/2vw6t9/eli5_is_it_true_that_the_1960s1970s_middle_east/
|
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"Other contributing factors were the series of wars between Israel and essentially the rest of middle east in the 60s, the OPEC embargo, Foreign intervention, the rise of extremism, among other shifts in both Middle Eastern and international politics. There are still some last vestiges of stability in the Middle East such as Jordan, UAE, Qatar, and even Saudi Arabia.\n\nMuch of the stability came from independence efforts, especially after the fall of the Ottoman Empire, coupled with oil wealth. Ultra-right groups took power in the 50s and 60s in Egypt, Iraq, Syria and Libya, and soon the Soviet Union and other international powers got involved, and sparked/facilitated a lot of the pre-existing tension.",
"There are lots and lots of reasons.\n\nOne major factor is they were involved in a number of proxy wars between the US and Russia during the cold war, and that caused all kinds of damage, because both sides supported the militant rebel types, because they were the ones who would actually fight.\n\nThe school of thought seemed to be \"destabilized is better than communist/capitalist\"",
"My own personal opinion, based on what I have read, heard and know, is that most nations, especially Middle Eastern nations, are just pawns in a huge game of political chess among the superpowers. When it comes to the case of Iran, the US backstabbed the Shah and supported the current regime to get power so that they could stand against communism and send Iran back in progress. Note that this was during the Cold War when a lot of shit took place in the Middle East.",
"Same thing that happened in East Asia in the 50s and 60s. And Latin America in the 60s-80s. Uncle Sam arrived with his two best friends, freedom and democracy.",
"It was less about it being progressive, and more about being run by dictators who were friendly to the west. They were superficially trying to emulate some their ways, but without the underlying freedom and democracy.\n\nSure, women could wear short skirts and go to school, but everyone still get throw in jail for criticizing the gov't.",
"Pakistani here!\n\nIn the 60s, we were very progressive. Free market economy, thriving banking sector, largely secularist (Alcohol, clubbing and everything was part of society). Then the cold war happened.\n\nIn the mid 70s Prime Minister Bhutto, a socialist, was forced to outlaw alcohol by pressure from the Islamic clergy. He gave in to several other of their demands and that's when the left begun to fall. Bhutto was also anti American, opting to ally himself with the Soviets and China. So naturally, when the Shah (Pro US) was overthrown in Iran by the Shia religious faction (Anti US and Saudi), it was time for Bhutto to bite the dust. The US helped the then Chief of Army Zia ul Haq to take power and ousted Bhutto. Bhutto was hanged shortly afterwards.\n\nNow Zia was super Islamist and nationalist. And the US wanted to deter Soviet influence in the then Socialist Republic of Afghanistan. So then came the Afghan Jihad. The US and Pakistan Army started the Al Qaeda and the Taliban to fight the Soviets in Afghanistan. To strengthen this, massive nationalistic and Islamist propaganda and policies were introduced. This included lashing in public, making it mandatory to wear Islamic clothing (people wore western before the 80s), making it mandatory to learn government dictated Islamic studies and Pakistan studies (wasn't even a subject in school before this) and all sorts of policies to radicalize the masses. He also introduced heavy Islamic laws such as blasphemy and sharia. Basically, Pakistan went from being bad to worse in the 80s to pump propaganda and control the masses. The cold war ended, the US left and in the 90s, Pakistan was left in shambles with a radicalized public and a poor economy.\n\nWhen Musharraf came to power in 1999, he introduced liberal and free market policies. Bless that man otherwise Pakistan would be a complete shithole like Iraq or Afghanistan now. Today, urban Pakistan is progressive and liberal whilst rural Pakistan is still Islamist and radicalized. Issue is, it's difficult to de-radicalize two generations of people indoctrinated with religious and nationalistic propaganda in the rural areas while it was very easy to do so in the urban areas within a decade where people have access to free media and western education. So there's a rift in Pakistan now. Rural folks see urban folks as *shameless* and westernized whilst urban folks look at them as backward and blame them for pulling the country back.",
"One thing to keep in mind when you see those photos of mini skirt-clad women in Kabul or Tehran is that they were not at all representative of their countries at the time. Women may have been able to wear shorter skirts in Kabul in the 60's, but the majority of Afghan women still lived in very conservative areas and had little to no autonomy or access to education. The same generally holds true for Iran (also, Iran wasn't \"progressive\" under the shah--just because your wife wears western dress, that doesn't make your repressive monarchy somehow enlightened or moderate).",
"I am a secular middle class Iranian but the photos you show were only a specific segment of Iranian society at the time. Back in the 70s, we were only 40-50% literate and I'd dare say the majority had a poor standard of living. There was a huge clash between the modernized, westernized Iranians and the traditional, religious ones. For example, bazaar owners hated the new shopping malls, the religious populace disliked some liberal notions of Iranian society at the time (we even had nudity in films back then), and cabarets, bars and casinos were targeted. Honestly, those regions were always quite religious; it just didn't come to the fore as much at the time because of extremely strong dictators. Iran in the 70s was in a peculiar place; we had a bunch of educated intelligentsia who wanted more political freedoms, with an illiterate and religious populace who were controlled by the clerics. Left wingers and moderates idealistically thought that social freedoms would be a given, in addition to the new found political freedoms, as soon as we would overthrow the king, heck my parents even thought the same (remember, the 1979 revolution was political Islam's first victory in modern history). As history has shown, we eventually lost both political and social freedoms. Instead of banding together against the fundamentalists, they sided with them, before the Islamists turned on them, executing them by the thousands. The unsung heroes of this story? The Iranian military generals. They could have sent us straight into civil war, right before the eve of Saddam's invasion, but they decided to make the military neutral. The troops were ready and able to shed some blood, and they had already done so during the revolts. The generals themselves were executed a few months later by the revolutionaries. Really, if there ever was a practical application of Animal Farm, Iran would be it. The movie Persepolis kind of captures the feeling of the time.",
"The middle east has always had ultraconservative people, even back in the 60s and 70s. Likewise, there are still progressive minded people living in these countries today.\n\nBack then, these countries were overwhelmingly rural. The cities visited by westerners (i.e. where most of these pictures were taken) were typically inhabited by a well-educated, western-leaning elite, that wasn't representative of the views or lifestyles of the population at large. \n\nIn the past 40-50 years these countries have become far more urbanized (as an example, [Iran](_URL_0_) went from being 37.5% urban in 1966 to being 71% urban in 2011). As the rural population moved to the cities, they brought their ultraconservative views with them, and became much more visible to outside observers.",
"TL;DR: Cold war. Can't fight directly? Build proxies. ",
"In 3 words, the cold war.\n\nThis was when pretty much any tin pot dictator, revolutionary or convenient idiot would be propped up in power by one or the other sides (US/Russia, but other countries can't be absolved ether).\n\nThis usually split the population of the countries - left/right, religious/liberal etc. There's really no way a puppet regime can be in place without a bogeyman, real or imagined. \n\nThen suddenly, cold war ends. Geopolitical objectives shift and a lot of the countries in question are left with either a power vacuum since their puppet no longer has any strings, or suddenly needing to shift allegiances to a regional power. You'd think this is good, but a couple of decades of erosion of democratic institutions and weakening of the bureaucracy means that pretty much anyone can now step up to the plate. More often than not, the one who step into the vacuum isn't democratically elected, but has the backing of various institutions (army, security forces, regional powers, religious factions etc.), all with their own agendas not necessarily involving the progression of the country.\n\nMany times, the cold war government was good at suppressing internal disputes. With no government suppressing them, a lot of countries experienced civil wars, low level insurgencies, or just flat out shit the bed.\n\nNote that the images you're talking about don't really represent the countries. Mostly, urbanisation led to people being more liberal, but there were still substantial rural populations.\n",
"If you read carefully the responses below, the answer seems to boil down to this : American foreign policy happened.\n\nIs that really it? Did we sow the seeds that led to the War on Terror? Íf we did, is this karma?",
"The US and other powers meddle in the affairs of other countries for their own gain without any knowledge of how they're causing chain reactions that go back to them",
"The U.S. and Soviet Union approached the Middle East without properly understanding the cultures. Those areas have heavy cultural aspects intertwined with their behavior. The majority of the Middle East was ruled by tribes and Bedouins. Tribal culture it very different than the town life of Europe. Revenge is very strong a motive their. \n\nFor example, Syria was called communist at one point, before Assad's father came to power. One of the reasons was because he was trading with the Soviet Union, because the west betrayed the Arab countries by not fulfilling the Treating of Sykes-Picot (sp?). This angered a lot of Arabs, adding to it the betrayal they felt with the exodus of Palestinians and the formation of Israel. This made them go to war with Israel. \n\nIran had the Shah who was overthrown because Iran wouldn't share their oil with Britain and the U.S. This led to a coup and the western powers installing the strongest contender, who at the time was Khomeni. The rest is history. ",
"Hey, Pakistan is still pretty progressive once you get past the headlines. Just give to give you some quick examples, [This literature festival happened last week in Karachi](_URL_3_). No one really reported anything on that, because it's pretty much normal news. Plenty of similar events take place in big cities, Lahore, Karachi, Islamabad pretty much on a regular basis if you follow Pakistani news.\n\nHere's a video of the [fasion week event](_URL_0_) that takes place in Islamabad yearly.\n\n[Here's an article and video](_URL_2_) about popular musical \"Grease\" being staged in a Pakistani theater for the first time.\n\nAs far as education is concerned, [over 60% of all Pakistani university students](_URL_1_) are women.\n\nOf course, not trying to paint a rosy picture. Immense problems do exist in terms of inequality and conservatism in rural areas which is generally due to patriachal society and lack of education. Much needs to be done. But it's an evolving society and far more vibrant than people give it credit for, especially in the urban areas."
]
}
|
[] |
[
"http://imgur.com/a/LdHsL#0",
"http://imgur.com/a/psI0l",
"http://www.npr.org/blogs/pictureshow/2012/08/20/159338659/picturing-pakistans-past-the-beatles-booze-and-bikinis"
] |
[
[],
[],
[],
[],
[],
[],
[],
[],
[
"http://en.wikipedia.org/wiki/Demographics_of_Iran"
],
[],
[],
[],
[],
[],
[
"https://www.youtube.com/watch?v=t1WzWQgsN9w",
"http://en.wikipedia.org/wiki/Women%27s_education_in_Pakistan#Summary_of_statistics",
"http://www.bbc.com/news/world-asia-25763330",
"http://www.dawn.com/news/1162492/a-look-back-at-karachi-literature-festival-2015"
]
] |
|
1eejcg
|
What are some good books about US Armored Forces in WWII
|
I recently read "Death Traps" by Belton Cooper, which is a memoir of his role as an ordnance officer in the 3rd Armored Division. In it, he talks about how woefully inadequate the M4 Sherman was. The US had already developed the M26 Pershing, and according to Cooper could have replaced the M4 as the main battle tank in time for the invasion. He blames Patton for rejecting the M26 in favor of the M4 based on a strict interpretation of Armored Forces Doctrine. I was wondering if there is a book about the strategic and tactical histories of the US Armored Forces in WWII. Not necessarily as the main focus, but similar to "Masters of the Air" or "Shattered Sword" if you are familiar with those works. I know what I'm asking for is kinda vague so anything you can suggest would be greatly appreciated.
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/1eejcg/what_are_some_good_books_about_us_armored_forces/
|
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"text": [
"More generally Band of Brothers and Citizen Soldier are two great books if you want more of a narrative than a by-the-numbers historical account. Do realize that with books by Steven Ambrose you would do well to research what may or may not have been plagiarized. The core message is still solid even if Ambrose had sticky literary fingers.\n\nSteven Zaloga (being lazy, linking wikipedia for a book list here _URL_1_) is a good source for discussion of US tank tactics and strategy in WW2. \n\nForty too. _URL_0_\n\nTo elaborate a bit on the M4 and the M26, Patton personally had very little to do with the delay- he was no stranger to the inadequacy of the M4 and even ordered his own troops to engage in on-field modifications to effectively upgrade M4's to their Jumbo Sherman counterpart. He wasn't even in a position to decide what did and didn't get built. \n\nUnfortunately US tank doctrine was decided by a career artilleryman, and intended as a reaction to Blitzkrieg tactics; dedicated tank fighting groups were separate from the main US forces and intended to move from fire fight to fire fight (which explains why the US was the only major nation in WW2 building tank destroyers with very light armor, fully operational turrets *and* open tops) while the M4 Sherman was intended as an infantry support tank. In that sense it was a fantastic tank- it excelled at the same role that the Panzer 4 was intended for (the soviets and the British had no clear contemporary tanks) but was grossly inadequate at fighting late war tanks like panthers and tigers. That was a job intended for the M10, M18 and M36.\n\nUS tank doctrine was largely inflexible because everything had to be shipped 3000 miles from US factories to the European front. Which is why the M26 joins a laundry list of potent tanks that never made it past prototype phases or saw only limited production. "
]
}
|
[] |
[] |
[
[
"http://www.barnesandnoble.com/c/george-forty",
"http://en.wikipedia.org/wiki/Steven_Zaloga"
]
] |
|
14y0p2
|
I'm interested in the history of the addition of Hawaii to the United States. What was the reasoning behind it? Did the people accept it with open arms?
|
This is something that has bothered me for a long time, and I don't really see it being talked about in too many mainstream History textbooks, as they more-or-less gloss it over and just accept it as thought it was destined to happen. What was the real story?
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/14y0p2/im_interested_in_the_history_of_the_addition_of/
|
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"Hawaii was a major importer of sugar to the United States in the mid and late 19th century. However, after the McKinley Tariff (1890), which raised taxes on imports significantly, the sugar growers realized that they could bypass the costly tariff by becoming annexed into the US. They staged a rebellion against the local regent, Queen Luliokalani (who was staunchly against foreign influence in Hawaii), and with the help of US marines, forced her to abdicate. President Grover Cleveland, however, had not authorized the action, and after various inquiries into the legitimacy of the uprising (and as something of an anti-imperialist), refused to annex the ripe territory. Hawaii, despite pressure from the US to reinstate Luliokalani to the throne, remained the Republic of Hawaii (ruled essentially by the American sugar plantation owners) until in 1898 William McKinley signed an annexation treaty, largely motivated by Hawaii's usefulness as a staging area in the Spanish-American War. Hawaii remained a US territory until 1959 when Eisenhower signed it into the union as a state, and the residents of Hawaii accepted accepted the referendum nearly unanimously. ",
"Besides the obvious economic interest, Hawaii was geopolitically important as the last major piece of land that a naval fleet attacking the West Coast of the United States would have to pass. Thus after the acquisition of Alaska, getting Hawaii all but secured the US from Pacific assaults. \nSource: _URL_0_",
"To add to KingCharlesMarlowes' answer, the sugar plantation owners formed the Annexation Club and a Committee of Safety. This group lobbied the US to annex Hawaii. Not all sugar plantation bosses were enthusiastic about annexation because at the time the contract labor regime was still in place and would probably be outlawed if Hawaii joined the US because it violated the constitution as a form of slavery. Nevertheless, on Jan 16, 1893, Minister Stevens landed troops in Honolulu. The Monarchy was easily overthrown. There were unsuccessful counter revolts attempted. On February 1, 1893, Minister Stevens declared Hawai'i to be a protectorate of the US. The \"revolutionaries\" sent a delegation to Wahington to negotiate an official treaty with the US, which was signed by lame duck President Harrison. However, President Cleveland withdrew the treaty and disavowed the annexation when he took office in early March of 1893. Cleveland then appointed James Blount to conduct an investigation of the overthrow. He concluded US diplomatic and military reps had abused their power. Annexation was temporarily put on hold. In 1896 McKinley defeated Cleaveland. On June 16, 1897, a new annexation treaty was concluded, but it could not get the 2/3rd approval of the Senate. The opposition was slip into differing groups. Some thought the initial overthrow of a sovereign government was an injustice, others felt the US had enough trouble dealing with the mainland Native Americans and weren't enthusiastic about adding more indigenous. The Senatorial and House debates are a fun read if you're looking for contemporary accounts. \n\nThe Spanish-American war began in 1898 and the military advantages of annexing Hawai'i became clear. While it was unlikely necessary votes for a treaty could be obtained, a straight majority was possible. So, on May 4, 1898, nine days after fighting began in the war, Rep Newlands of Nevada introduced in the house a joint resolution to annex Hawa'i. This only required a simple majority in both houses to pass. It passed the house by a vote of 209 to 91 and the Senate by a vote of 42 to 21 with 26 abstentions. President McKinley singed it into law on July 7, 1898.\n\nI'm on my IPad right now and about to eat. I'll add sources later and edit grammar. Was just really excited to finally be able to contribute to my favorite subreddit.",
"u/KingCharlesMarlow and u/dumbassthenes have provided the details here, and they look fine to me. \n\nBut I would add that the annexation of Hawai'i needs to be understood as a part of the larger, contemporaneous groundswell for overseas expansion and what we now call the new imperialism. So the actions of the White House and Congress here should be understood in the same political moment that produced American interest in trade with China, expansion of merchant and military coaling stations throughout the Pacific, and the Spanish-American war. A meaningful number of congressmen, foreign policy intellectuals, and the general public were supportive of actions that seemed to support the expansion of trade overseas, including both access to resources and access to potential markets.\n\nN.B.; I am not saying that the annexation of Hawai'i is a *part* of the Spanish American War; instead I'm saying that the mindset and rationalization behind the annexation has roots in the same set of ideas.\n\nOn this, I like Michael H. Hunt's *Ideology and U.S. Foreign Policy*.\n\n_URL_0_\n\nBut there are certainly other works on the same topic; I think that Michael Krenn has something that's similar."
]
}
|
[] |
[] |
[
[],
[
"http://www.stratfor.com/analysis/geopolitics-united-states-part-1-inevitable-empire"
],
[],
[
"http://books.google.com/books?id=pgDioChXoMgC&printsec=frontcover#v=onepage&q&f=false"
]
] |
|
zmla7
|
why do (most) countries have a tomb of the unknown soldier?
|
How far back does this practice date? Did one country, or ancient peoples, start this tradition?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/zmla7/eli5_why_do_most_countries_have_a_tomb_of_the/
|
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"It's mainly just a respect thing. War leaves a lot of dead bodies that no one can identify. I think the British or the French started the tradition around WW1.",
"Quite some time. A famous example from antiquity is the [monument at Thermopylae](_URL_0_), although that hasn't survived."
]
}
|
[] |
[] |
[
[],
[
"http://en.wikipedia.org/wiki/Battle_of_Thermopylae#Monuments"
]
] |
|
2q4otu
|
the perceived animosity of the nypd towards bill de blasio.
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/2q4otu/eli5_the_perceived_animosity_of_the_nypd_towards/
|
{
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"text": [
"The mayor has repeatedly come across as being in support of those who are angry with the police, even in instances where that anger is not justified. The mayor isn't seen as being on the side of his police force."
]
}
|
[] |
[] |
[
[]
] |
||
3j649h
|
Where does the energy go when particle-antiparticle pairs spontaneously appear and annihilate?
|
Still trying to wrap my head around Hawking Radiation, but I was wondering about those particle-antiparticle pairs that are spontaneously appearing.
If they appear and annihilate (elsewhere in space, not related to black holes), wouldn't that release energy? I thought energy could not be created, but wouldn't the annihilation of those particle pairs release energy into the surrounding space, increasing the total energy of the universe? Where does the energy go?
|
askscience
|
https://www.reddit.com/r/askscience/comments/3j649h/where_does_the_energy_go_when/
|
{
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"text": [
"The energy doesn't go anywhere, because there was zero energy to begin with and zero energy after.\n\nThe particle-antiparticle pairs you're referring to are called *virtual particles*. They aren't real particles, and they don't actually exist. They're mathematical tools that are used in calculations, but they fail to have many of the properties of real particles. In particular, *real* particles have a relationship between their mass, energy, and momentum: E^2 = p^2 c^2 + m^2 c^4. In particular, their (mass+kinetic) energy is always positive. That relationship is not true for virtual particles, and one of the pair of virtual particles just has negative energy (so the pair has total energy zero).\n\nBut--just to reiterate because this causes so much confusion--virtual particles aren't real. They're just a mathematical tool."
]
}
|
[] |
[] |
[
[]
] |
|
1xq3rl
|
How many molecules wide are the sharpest blades?
|
Thinking about samurai swords, chef's knives, and titanium razors... anyone with information on what the blade edge is like on a microscopic or molecular level... maybe even how they work so well at shaving and slicing.
|
askscience
|
http://www.reddit.com/r/askscience/comments/1xq3rl/how_many_molecules_wide_are_the_sharpest_blades/
|
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"Obisidian blades can be mere molecules thick, the preferred tool of optometrists. I'm not sure if its the SHARPEST but it is practically impossible to not cut yourself on one\n\nSource: History of art professor, the first hand experience.\n[and wikipedia as source](_URL_0_)\n\nEdit: as others pointed out its actually Ophthalmologists",
"There is a process called 'Ion milling' in which a material is put into a vacuum and single ions are shot at it until it is electron transparent. If I had to make the thinnest, sharpest blade I could, that is how I would do it. Limited info [here](_URL_0_). Wish I had more specs on it. Hopefully someone else can help out.\n",
"One atom thick. \n_URL_0_\n\n_URL_1_\n\nI could have a sheet of graphene which would be a single atom thick blade.",
"I work in a research lab with access to some pretty spectacular electron microscopy equipment. Sadly, for most surgical blades all you need is an optical microscope to inspect the edge. A single crystal diamond blade is among the highest quailty blade you can get, and has an edge radius of about 1 micrometre, though it is very difficult to measure accurately - we did some work recently which involved measuring the edge radius of a few types of surgical blades.\n\nI also know that incredibly sharp blades are used to prepare sample for transmission electron microscopes, perhaps someone else who knows more about these could speak to them.",
"I used to do tech support for a company that produced RF chips. The machines that sliced the silicon wafers used a graphite-diamond blade that would crumble at the slightest touch, yet would slice you about 100 times in the time it took you to jerk your hand away. Ask me how I know. ",
"There is a great NOVA documentary on samurai swords : [here](_URL_0_)\n\nThis covers is great detail the metallurgical details in the crafting of samurai swords.\n\nHowever the prowess of samurai swords (Katanas) has been grossly embellished by Hollywood, and their effectiveness as weapons is indeed limited, as briefly summarized by Lindy Beige [here](_URL_2_)\n\nIf you are interested, I highly recommend watching [Reclaiming The Blade](_URL_3_) and [Secrets of the Viking sword](_URL_1_), they cover in great detail the physics of blades and swords, and well as the martial arts needed to use them. What sticks out in my mind from this documentary(the Viking sword), is a demonstration of a bastard sword, with no sharp edge at all (designed so), cutting various pieces of wood and fruit, clean in half with a single stroke.\n\nSorry if this is off topic, and more about history and weapons, but I thought it was relevant. \n\n**TL:DR blades do not need to be sharp to cut things.**\n\n*Edit : spelling and additional link*",
"Just a nitpick, since the experts have the main part of your question answered, but \"titanium\" razors aren't made of titanium, they're coated in titanium nitride or titanium carbonitride.\n\nTitanium itself it much too soft to make a good blade. Even 6Al4V alloy, AKA Grade 5, which to my knowledge is the best alloy for tools is significantly softer than a cheep steel you'd find in a $5 gas station knife. There are people that make blades out of it, but mostly dive knives or similar, things where steel would likely rust. Though that's less of an issue with modern nitrogen alloy steels like H-1 or N680. \n\n",
"My father worked on this technology in the late 80s and early 90s at a research lab. At the time, they were able to get a needle 3 atoms wide, as proved by a photo somewhere stored safely in his house. The best info I can find is from this abstract : _URL_0_",
"To specifically answer your question:\n0.1 mm = 1 000 000 ångströms\n[This](_URL_3_) site mentions 0.1 mm blades, which ~~we can assume are~~ aren't likely to be the amongst the thinnest on the market, but probably amongst the thinnest blades for shaving. [Tungsten carbide](_URL_0_) is a durable material often used in (razor-) blades, composed of carbon and tungsten. Now, a carbon atom is about 1.82 Å in diameter, while tungsten atoms are around 2.82 Å ([Source](_URL_2_)).\n\nI wouldn't have a slightest clue as for how dense the atoms in a tungsten carbide molecule are, nor how tightly the molecules stack on the edge of a blade - but, ~~judging from~~ using the [structure illustration on Wikipedia](_URL_1_), ~~I'd **guess**~~ I've calculated that the molecule is around ~~15x11~~ 17x11,5 carbon atoms, which equals 30.94x20.93 Å. To allow a fairly simple estimate, let's assume now that the molecules are stacked tightly on top of each other *in the same fixed angle*. Depending on the angle, this gives us:\nA) 1 000 000/30.94 = **32 320 molecules**\nor\nB) 1 000 000/20.93 = **47 778 molecules**\n\nThese must not be considered accurate calculations, but it's damn sure the closest I can get.\n\nEDIT: I was on my phone when I first posted. I've now measured the image in Photoshop for a (much) more accurate molecule size estimation.\n\nEDIT: Using the above numbers you can also calculate that in a tungsten carbide blade, there are A) ~3 molecules per nanometer or B) ~2 molecules per nanometer."
]
}
|
[] |
[] |
[
[
"http://en.wikipedia.org/wiki/Obsidian#Current_use"
],
[
"http://en.wikipedia.org/wiki/Ion_milling_machine"
],
[
"http://en.wikipedia.org/wiki/Scanning_tunneling_microscope#Probe_tips",
"http://en.wikipedia.org/wiki/Scanning_probe_microscopy#Probe_tips"
],
[],
[],
[
"https://www.youtube.com/watch?v=LtulTGxJdDc",
"https://www.youtube.com/watch?v=nXbLyVpWsVM",
"https://www.youtube.com/watch?v=XLWzH_1eZsc",
"http://www.imdb.com/title/tt0961079/"
],
[],
[
"http://scitation.aip.org/content/aip/journal/apl/57/14/10.1063/1.103451"
],
[
"http://en.wikipedia.org/wiki/Tungsten_carbide",
"http://en.wikipedia.org/wiki/File:WCstructure.png",
"http://www.cafeconleche.org/slides/sd2003west/handsonxslt/examples/sortedatoms.html",
"http://fortisblades.com/home/"
]
] |
|
273t89
|
how is it possible to have a hole in your heart, and not die of internal bleeding?
|
With all blood being distributed/circulated through, and by, the heart; how is it possible for someone to live with the hole. Is it just an expression or is there literally a hole? How does something like this develop?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/273t89/eli5_how_is_it_possible_to_have_a_hole_in_your/
|
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"Its not an expression, it is literally referring to a hole somewhere in the heart that there isn't supposed to be. Now bear in mind this doesn't mean there's a hole straight through the heart, or that the hole leads to the exterior of the heart. What it usually entails is that there is a defect in the walls that separate the chambers in the heart, or between the major vessels leading out of the heart.\n\nI presume your curiosity was piqued because of that AMA about the kid and his hole-in-the-heart. Without knowing the exact details of his condition, basically the kid has a hole in the wall between one of his atrium and the adjacent ventricle (there are four chambers in your heart, two atrium and two ventricles). In a healthy heart, the atrium contracts and pushes blood into the ventricle, and then ventricle contracts and pushes the blood out of your heart (either to your lungs or the other organs). The hole between the atrium and ventricle means that when the ventricle contracts, some of that blood gets pushed backwards, back into the atrium.\n\nYou can have holes elsewhere in the heart, but the results are usually the same. The flow of blood is disrupted as some of it backflows through the defect.\n\nThese are always congenital defects."
]
}
|
[] |
[] |
[
[]
] |
|
ovo3v
|
Is there a scientific reason that the hexagon is 'nature's shape'?
|
I saw this [picture](_URL_1_) in Earthporn, and this one of [Devil's Postpile](_URL_0_) and it reminded me hearing somewhere that the hexagon is nature's shape. Is there a scientific reason for this?
|
askscience
|
http://www.reddit.com/r/askscience/comments/ovo3v/is_there_a_scientific_reason_that_the_hexagon_is/
|
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"Good intention, bad wording. Hexagon is not natures shape. Nature has no shape as nature encompasses many amorphous blobs rather than shapes. HOWEVER!!! In organic chemistry there is are two molecules that are extraordinarily common in nature and they are cyclohexane and benzene, both of which are in a [on a general level] hexagonal formation. The molecules in question are so common in life because the six membered carbon ring structure is at almost the perfect bonding angle for carbon, and hence enjoys a unique stability. ",
"Hexagons represent the shape with the lowest possible energy when nested / packed. If you imagine a soap bubble, it pulls itself into a sphere for the same reason - the sphere is the least possible surface area which contains the maximum volume - the lowest energy shape. If you subsequently nest soap bubbles together, the membranes between cells pull themselves into straight walls forming hexagons, as this is the lowest energy configuration. Similarly, this is why bees evolved to construct honeycomb cells in their hives. The close packed hexagons use the least amount of wax in their construction than any other possible shape, conserving energy.",
"For one thing, a hexagonal grid is the perimeter-minimizing partition of a surface. This is why honeycombs are hexagonal: it takes the least wax to build them. The [honeycomb conjecture](_URL_0_) has been around for a long time, but was proven to be the case in 1999.",
"Here are also some curious hexagons and geometric patterns in nature: [Jupiters axis](_URL_1_), and [acoustic pattern formations](_URL_0_)",
"It's simple energy minimization and mathematics, imagine you have a surface broken by some sort of a boundary. That boundary could be a bubble or a grain boundary or honeycomb or whatever, where that boundary splits it is most likely to split in two. At this point we have a three sectioned point, like a banana interior or something, whatever. If that split is uneven then it's energy potential is greater than an even split, imagine holding an acute angle in a bubble for instance. So mathematically and energetically it makes sense for every corner of an equilibrium system to be a three sectioned 120 degree split. Continuing this line of reasoning, exclusively 120 degree angles imply regular hexagons. Q.E.D.",
"Do not forget the lowly [snowflake.](_URL_0_)",
"Does it make a difference to this matter that radius of a circle is the same lenght as the sides of the largest hexagon that can be fitted into that circle. In a way this is obvious, but this is mathematically relevant because hexagons are easily drawn inside a ring by a drafting compass.",
"First of all, it's incorrect to say that hexagon is \"nature's shape\". While I say this - there are a lot of events in nature where the hexagonal shape is preferred over any other shape. However, if you analyze the first picture you presented, there are also a lot of pentagons and heptagons as well. With a scientific mind, you should ask yourself, \"If there are also a lot of pentagons, hexagons, and heptagons... then the issue here should not be the overall shape, but how the shape is formed.\" Think cracks and angles.\n\nSo again, it would be a great risk on your scientific integrity to say \"hexagon is nature's shape\"; the better way to say it is, \"hexagon occurs very frequently in nature\". \n\nYou have to analyze this from a different perspective - how the shapes are formed. The pictures you show are defined by cracks on the ground or on volcanic rock as it dries/cools. This means that cracks begin to form.\n\nWhat is scientifically accurate is that cracks break into 120 degree angles because that provides the greatest amount of stress release. Consider how cracks are created; they're created when the surface tension of any material gains tensional stress - aka, when water evaporates from dirt or when hot lava cools suddenly. Each line begins to break in 120 angles. \n\nTry this on your own: Start with a line, begin dividing that into 120 angle split. After that, at any line starting point, continue dividing only in 120 splits. You'll soon realize that the smallest shape you can accomplish is a pentagon - but this requires for two cracks to gain length with \"cracking\", or relieving stress, for a while. \n\nTo emphasize why hexagons are more common than pentagons, consider this crude Madden-like drawing I have created. \n\n_URL_1_\n\nLet the black lines be the cracks and let the red arrows represent the direction of tension created by the process of evaporation or cooling. As the black line grows longer, the overall directional tension begins to accumulate. When the tension reaches a certain threshold (I don't know that much into geology), the crack splits since it requires less energy to do so. I haven't included it in the picture, but this also means that at the point of crack. This isn't the whole picture, obviously, but this is a general idea.\n\nIn other words, for pentagons to be created - there needs to be less cracks. Less cracks indicates that each line has to be longer, which also means a greater build up of surface tension. \n\n_URL_3_\n\n\nAs for mentioned in post about the honeycomb - this is relatively different. Hexagons aren't created in honeycombs because of cracks... although tension is a relevant topic. Honeycombs are created in that shape because a 3D hexagonal shape provides the greatest area for the least amount of surface area - or in other words, the most volume for each amount of wax used to create the structure. \n\n_URL_2_\n\nAbove is quite a difficult read. \nThis is a more general overview: _URL_0_\n\nHow do bees know that hexagons are the best structure? No idea... you'd probably have to consult a biologist. ",
"It's one of the most efficient ways to pack circles.\n\nIf you take a bunch of elastic circles, put them in a box, and apply pressure to them, they will naturally form to hexagons in order to reduce empty space between them.",
"Hopefully this isn't perceived harshly and downvoted but I always wonder the exact reasoning behind why the triangle is the strongest shape and why they aren't encountered more in nature. Can anyone help? Not to deter from the main question...sorry.\n",
"I agree with everything else posted here about conservation of energy in boundaries, etc. The reason honeycomb cells are hexagonal is exactly the same as why, for instance, convection cells are hexagonal, even though they are arrived at through different processes - in both cases it is the minimization of boundaries through natural feedback processes and so forth.\n\nAnyway, to your larger question: The term \"nature's shape\" is clearly rhetorical, and has perhaps no technical meaning (something the antihexagonalists here can't seem to acknowledge), but it is of course accurate - or at least can be said to reflect an accurate sentiment. (Indeed, it is entirely possible you heard that phrase from me, as I'm responsible for much of the pro-hexagonal material on the internet today, and it is a phrase I've used often.) The reason for this - to the extent the mysteries of the hexagon can be distilled to intelligible levels, and from there reduced even further to a single unitary principle - I think comes down, ultimately, to the fact that the hexagon can be understood as a two-dimensional projection of three-dimensional space. And representing the lowest dimensions that are capable of containing meaningful complexity, it becomes the archetype of _all_ ascent through dimensionality (and thus the ascent through all sets, and thus through all more complex orders of mathematical objects).\n\nTo understand this, consider the relationship between the cube and the hexagon. The hexagon as you are no doubt aware can be inscribed in a cube, and the cube can be projected as a hexagon. But there is a deeper relationship here when you consider centered hexagonal numbers. That is, in the fashion of square numbers, or triangular numbers, you have the number created by a figure consisting of a central hexagon surrounded by _n_ rings of additional hexagons. So the first such number n1=1, the second n2=7, the third n3=19, and so on in the fashion of adding (_n_-1)*6 to the previous number. Anyway, the interesting thing about these is that then the sum of all centered hexagonal numbers from 1 to _n_ equals the cube of _n_. So 1+7=8=2^3 , 1+7+19=27=3^3 , 1+7+19+37=64=4^3 , 1+7+19+37+61=125, et cetera. This can be understood by visualizing a cube vertex-on, projected as a hexagon. The centered subcube at the closest corner can be considered the first, centered hexagon of centered hexagonal number n1, the shell of 7 cubes around that corner cube can be thought of as the second number n2, and likewise out from there, in shells of additional cubes. (This helpful video should demonstrate it, sort of: [A Series of Cubes](_URL_0_)).\n\nAnyway, changing gears a bit, what is PARTICULARLY INTERESTING then is that the hexagon is a member of a class of polytopes known, somewhat bizarrely, as permutohedra. The _n_-dimensional permotohedron is characterized by having vertices that correspond to all possible permutations of the coordinates in n+1 dimensional space. So for instance a hexagon inscribed in a cube, which cube can be considered representative of three dimensional space, has the vertex coordinates 1,2,3; 1,3,2; 2,3,1; 3,2,1, 3,1,2; and 2,1,3. (This picture is demonstrates this clearly: [Perumutohedron order 3](_URL_1_).) One can do this for any dimension, so in 3 dimensions it is the truncated octahedron, which can be inscribed in 4-dimensional space with all possible permutations of 1,2,3,4, etc. What is particularly poignant about this - to me at least - is that in all dimensions these permutohedra correspond to the omnitruncated simplex in that dimension. That is, just as the hexagon can be seen as a truncated triangle with its ends removed, so the truncated octahedron can be considered a form of truncated tetrahedron - a regular truncated tetrahedron re-truncated again to turn the remaining triangular faces into hexagons. Thus they can be thought to emanate, in a sense, from the same triangulo-hexagonal symmetry that gives rise to the hexagon in two dimensions. Permutohedra in all dimensions also form a space-filling regular tessellationa, as the hexagon and the truncated octahedron can be tessellated in their respective spaces.\n\nSo because of their permutation-based vertices, every _n_-order permutohedron has n! vertices. (And here I should clarify that the hexagon is actually order-3, because it permutes the vectors of the three-dimensional space, not 2. The permutohedron is of the order of the dimension one higher than itself.) Likewise, the number of outer facets of every _n_-order permutohedron equals 2^_n_ -2. (8-2 for the hexagon, 16-2 for the truncated octahedron, etc.) For those who are paying attention, this fact ties back into the cube/centered hex number thing above. For if all permutohedra can tessellate space, and, having 2^_n_ -2 outer facets, is bordered by 2^_n_ -2 neighbors, it stands to reason that 1 initial permutohedron, plus the shell of 2^_n_ -2 permutohedra, plus the inner one on the second shell, will equal 2^n . Thus forming the gnomon of the _n_-dimensional cube for any order-n permutohedron. If that makes sense. For instance, the truncated octahedron, plus a truncated octahedron surrounded by 14 neighbors (which could be considered the order-2 centered truncated octahedral number), equals 16, which is 2^4 , in the same fashion that 1+7 hexagons = 2^3 . QED.\n\n(Bear in mind also that all two-dimensional faces in all permutohedra are, as with the truncated octahedron, either squares or hexagons - not only do these shapes bring the concept of hexagonality to higher dimensions, but they are themselves, in a sense, \"constructed\" with hexagons.)\n\nAnyway, my time grows short. All of this demonstrates to me, based on my hexagonal studies, that the hexagon is some sort of archetype or ontological primitive that defines or characterizes the nature of space and indeed perhaps existence itself on the most fundamental level. I would even conjecture that the universe itself may be a hexagon, and that as we become aware of our hexagonal nature, we will, as a species, move into a transcendental hexagonal future, when all will become a hexagon.\n\n[Edited to fix unexpected behavior vis-a-vis superscripting of carets.]"
]
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[] |
[
"http://www.appstate.edu/~marshallst/photos/boone_photos/devils_postpile/Devils_Postpile-030.jpg",
"http://www.flickr.com/photos/lagodigarda/96477237/sizes/l/in/photostream/"
] |
[
[],
[],
[
"http://en.wikipedia.org/wiki/Honeycomb_conjecture"
],
[
"http://www.asc-alchemy.com/imageEHO.JPG",
"http://api.ning.com/files/H8LqTcjGXTO9m7niIy4coO*zrjp4ILErubxEpS9LXVw*eajopJeeUI*8iE36nwZ6JXyM6XTMaNiGlO82xinGI2rufCvgovuA/cassini_saturnhex286x300.jpg"
],
[],
[
"http://www.google.com/search?hl=en&sugexp=pfwl&cp=10&gs_id=11&xhr=t&q=snowflakes&safe=off&rlz=1R2ADBS_enUS332&gs_sm=&gs_upl=&bav=on.2,or.r_gc.r_pw.,cf.osb&biw=1664&bih=887&wrapid=tljp1327486159980016&um=1&ie=UTF-8&tbm=isch&source=og&sa=N&tab=wi&ei=5tQfT_H0FeOlsAKM05XKDg"
],
[],
[
"http://www.maa.org/features/mathchat/mathchat_6_17_99.html",
"http://imgur.com/wnjN3",
"http://arxiv.org/pdf/math/9906042.pdf",
"http://www.nature.nps.gov/geology/usgsnps/depo/dpgeol5.html"
],
[],
[],
[
"http://hexnet.org/library/video/cubes",
"http://en.wikipedia.org/wiki/File:Permutohedron_order_3.svg"
]
] |
|
1ssojv
|
how do airlines know the exact departure and arrival times for flights months out in advance?
|
I've always wondered how they manage to coordinate thousands and thousands of flights ahead of time while somewhat sticking to the schedule. (Especially before computers were so common).
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/1ssojv/eli5_how_do_airlines_know_the_exact_departure_and/
|
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"Plane routes don't change often. The same flight goes from NYC to LA everyday and comes back everyday. To do the same thing tomorrow. Pretty much only time schedules change is when some airline starts a new route. Or shuts down a route",
"They build the schedule first (months in advance). Sales & marketing does a lot of work to figure out when they want to be where.\n\nThen they assign types of airplanes to different flight segments (\"fleet assignment\"). That's how you can see what type of aircraft you'll be flying on, usually, when you book your ticket. \n\nIt's only very close to the flight that they actually assign a particular aircraft, and that might change right up to departure."
]
}
|
[] |
[] |
[
[],
[]
] |
|
4ypn1f
|
why are all of our fingers different lengths?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/4ypn1f/eli5_why_are_all_of_our_fingers_different_lengths/
|
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"Having all fingers the same length would decrease dexterity and grip strength. When we were brachiating from the treetops this would have been a great disadvantage. The thumb in particular is very strong. The neural output equates to all other fingers combined and its ability to oppose helps with fine motor skills and precision grips. Different finger lengths also helps in creating a good fist which delivers a more forceful blow. The difference between the fourth digit and second digit is due to greater exposure to androgens in utero which has been linked to other physical and behavioral traits. ",
"[I made a quick video to answer your question](_URL_0_)\n\nIf you prefer reading here is what I ran over:\n\n- That it's due to evolution, we need it to improve our grip. We started using tools millions of years ago and we need the grip to use them! We still need the grip to date obviously, for items such as pens, tools and even phones. Try and grab an orange yourself and you will find that you can grip it so well due to the curvature of your fingers, and how because of the different length of each finger you end up holding it in various places which makes for great grip.\n\n- We also need different length fingers to make fists to use as a defensive weapon. We wouldn't be able to make a fist if all our fingers were the same length! \n\nTake it easy!",
"They evolved to match the thumb. Each of them is the optimal length for pressure against the thumb when the thumb is rotated to meet that digit. Because the palm has more flexibility on the index and pinkie, those two are significantly shorter. \n \nI made this up because everything else in this thread makes no sense, so why not."
]
}
|
[] |
[] |
[
[],
[
"https://www.youtube.com/watch?v=7zlA8tWqOXg&feature=youtu.be"
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||
ezbl6h
|
During the decolonization of Africa, was there any serious discussion/suggestions for the redrawing of colonial borders? (3rd try)
|
And by that I mostly mean in the sense of redrawing to better fit pre-colonial and/or ethnic lines.
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/ezbl6h/during_the_decolonization_of_africa_was_there_any/
|
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"I touched on this answer in [this thread](_URL_3_), and I discussed the [OAU charter and Cairo Declaration here](_URL_2_). [This thread](_URL_4_) focuses mainly on the formation and adjustment of borders in french Africa, but I do touch on origins of anti-colonial nationalism in the WW2 era.\n\nThose answers amount to this observation: the leadership of newly independent African states were interested in either promoting a coherent Nigerian or Tanzanian & c. national identity, or were interested in a pan-african unionist project. By and large, political leaders feared and opposed \"tribalism\" and sought to equate it with backwardness, while multi-ethnic nation-state and cross-ethnic national solidarity were vehicles to modernity.\n\nAt the same time, Marxist or Maoist revolutionaries also condemned tribalism or ethnic chauvinism. For example, here is a Muleleist manifesto from _les Cahiers de Gamboma_, from 1965:\n\n > Tribalists think, more or less consciously, that the men and women of\ntheir tribe and clan are superior to others, and that as a result the others\nshould serve and obey them. The tribalist tries to impose the hegemony,\nthe predominance ol his tribe and his clan. In practice, tribalist ideas and\nfeelings are used most often to create a clientele who can help them to\nsatisfy their selfish interests and ambitions. Tribalism is expressed in\ndifferent forms, of which the following the main ones:\n\n > 1 The tribalist constantly exaggerates and boasts about the qualities,\nmerits and good deeds ofthe people ofits tribe and its clan; on the\nother hand he refuses to recognise their faults,and even tries\nsystematically to hide them. With respect to other tribes, exactly the\nopposite attitude prevails [...].\n\n > 2 The tribalist indulges freely in liberalism and favouritism towards the people of his tribe and his clan [...]. By contrast, he is in general very\nsectarian towards people of other tribes and other clans [...].\n\n > 3 The tribalist tries to grant all the privileges and posts of responsibility\nto the people of his tribe and his clan [...].\n\n > 4 Conversely, the tribalist seeks to exempt his own people from their\nduties and obligations, from any difficult work, or from the most\ndangerous, difficult or humiliating missions\n\n > 5 The tribalist practises this favouritism in the division of material\nbenefits and the distribution of services [...].\n\n > 6 Occasionally, the tribalist even believes that those who are not of his\ntribe and his clan are too rich and fortunate to deserve his help [...]\n\n > 7 Some extend tribalism as far as preferring marriage between black\nwomen and white men to marriage between tribes [...].\n\n > 8 In politics, the supreme expression of tribalism consists of demanding\nthe formation of so-called independent republics which in fact have a\ntribal basis; failing this, tribalists demand ‘federation with regional\nautonomy’ with the distribution of political and administrative power following tribalist lines.\n\nSo, you have both Nationalist leadership and Marxist/Maoist revolutionaries condemning tribalism as obstacle in the path towards liberal nationalist or socialist modernity (respectively).\n\nNationalist leaders adopted a variety of strategies to contain or channel ethnic consciousness. For example, colonial Northern Rhodesia the territory of the Lozi monarch (Barotseland) was treated as a protectorate, associated with Northern Rhodesia but granted substantial autonomy. When Northern Rhodesia gained independence in 1964, President Kenneth Kaunda quickly negotiated the Barotseland treaty of 1964 which amounted to continuing recognition of autonomy of Barotseland.\n\nOn the other hand, in Algeria, the 1962 constitution declared the national language to be Islam. This led to a systematic program of enforcing Arab language education in schools, and use of Arab language in public life. This program led to the \"Arabization\" of the substantial Berber minority, and a backlash in the 1980s with the rise of Berber rights movement.\n\n---\n\nSo, all of this is to say that despite efforts of Liberal Nationalist, Maoist or Marxist Leninist governments to get beyond tribalism, and encourage people to think in terms of national or class consciousness; ethnicity continued to have a political logic. With the ratification of the OAU charter and Cairo declaration, national governments pledged themselves to the principle of only adjusting national borders through mutual agreement from the respective states involved. No military conquest to adjust borders. \n\nIn that scenario, the process of negotiating border adjustments to either bring the territory of an ethnic group into the state, or to cede territory (thus excluding an ethnic group from your state); would have been seen by the public through the lens of ethnic political calculus.\n\nTo use a hypothetical example: the state of Cameroon entered independence with a heavily Muslim population in the north, and a Christian or Animist population in the south of the country. At independence, leaders from the Northern, muslim portion of the country had power in the country.\n\nNow, let's imagine that the [Fang population](_URL_1_) in the south of Cameroon would like to live in a state with kinsmen in Equatorial Guinea and Gabon. Gabon and Equatorial Guinea are on board to adjust the borders. \n\nHowever, the non-Fang population in the south, and their politicians, all oppose the deal in Cameroon. They decry it as a trick by Northern politicians to weaken the southern opposition, and castigate their Fang colleagues for leaving them out in the cold.\n\nThe deal goes through, but now with a politically weaker Southern population, the [Baka and Gur](_URL_5_) also want to exercise the \"exit option\" and become part of the Central African Republic. But let's imagine that the government of Central African Republic is uninterested in negotiating, because Baka and Gur are opponents of the current government and that would strengthen Baka and Gur power. \n\nWhat are the Baka and Gur to do now? Do they secede? OAU and Cairo declaration pledge African states to oppose secessionism. And there is some doubt about how viable such a small secessionist state could be.\n\nOr, from a completely different perspective. What are we to make of populations like the Fula/Fulani? They are primarily herders, and their populations and herds move, and cross borders. Ditto, the Tuareg exist across borders in Mauritania, Mali, Algeria and Niger.\n\nThere is also the issue of what to do about ethnic diasporas who live in cities. Immediately before the start of the Nigerian Civil War, there were pogroms against Igbo bureacrats and merchants who lived in the Middle Belt and in northern Nigeria. In an imagined scenario where Biafra seceded peacefully, what would be done about this Igbo commercial diaspora living outside Biafra? Would they be repatriated? We can look to the historical example in Uganda and Tanzania where South Asian merchant communities were persecuted or forced into exile for being \"outsiders\" who threatened African merchant enterprise.\n\n---\n\nSo, that is the logic of the Cairo declaration of accepting existing borders, and many African leaders probably supposed that seeking border adjustments might inflame tribalist sentiments.\n\nHowever, there is the example of Somalia, which is the big exception. Somalia sought to encourage secessionist movement of ethnic Somalis in northeast Kenya from 1964-1967 in the Shifta war. Later, in 1977 Somalia invaded Ethiopia in order to annex the Ogaden region which had an ethnic Somali population. Both of these actions were in pursuit of the idea of [Greater Somalia](_URL_0_). However, these actions managed to anger Kenya and Ethiopia over Somali expansionism and drove those two countries into alliance with each other to thwart Somali aims.\n\nBoth Kenya and Ethiopia wished to keep Northwest Territory and Ogaden region as part of their states, despite viewing the Somali population of these regions as subversive elements. Partly this was a concern with natural resources in the region, partly it was a belief that the population *could* be Kenyan or Ethiopian as long as they kept in line. Partly it was a matter of national honor, where Haile Selassie or Jomo Kenyatta would not want their respective countries to be smaller. In the case of the Derg in Ethiopia in 1978, their Marxist-Leninist reaction to socialist Somalia invading was 1) feeling of betrayal that a socialist neighbor would put the Derg's nascent revolution in danger by invading. 2) that Siad Barre was a national chauvinist who would suborn the greater goal of spreading socialism in East Africa to the lesser goal of creating a larger Somali state. In the Derg's analysis, nationalist chauvinism was a deviation from the goal of transcending ethnicity and achieving socialism for all."
]
}
|
[] |
[] |
[
[
"https://en.wikipedia.org/wiki/Greater_Somalia",
"https://africa.uima.uiowa.edu/peoples/show/Fang",
"https://www.reddit.com/r/AskHistorians/comments/6cmwvl/why_havent_borders_in_africa_changed_since_the/dhw9qf0/",
"https://www.reddit.com/r/AskHistorians/comments/b9u4y7/why_didnt_more_postcolonial_african_leaders_try/",
"https://www.reddit.com/r/AskHistorians/comments/d7tmhe/why_are_former_french_colonies_in_north_africa/",
"https://en.wikipedia.org/wiki/Niger%E2%80%93Congo_languages#/media/File:Map_of_the_Niger%E2%80%93Congo_languages.svg"
]
] |
|
18yvyf
|
What did Lucifer, as a Roman God, represented for the people of Rome?
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/18yvyf/what_did_lucifer_as_a_roman_god_represented_for/
|
{
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"c8jea9k"
],
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13
],
"text": [
"Lucifer was not a Roman god."
]
}
|
[] |
[] |
[
[]
] |
||
t9evf
|
Plate Tectonics on Venus
|
I've read that Venus lacks plate tectonics like we see here on earth.
I wonder, especially given how similar Venus is in size and mass to Earth, why that is the case.
|
askscience
|
http://www.reddit.com/r/askscience/comments/t9evf/plate_tectonics_on_venus/
|
{
"a_id": [
"c4koc39"
],
"score": [
3
],
"text": [
"Interesting explanation here: _URL_0_\n\nEssentially, it doesn't have Earth like plate tectonics because it's too hot. It's a definitions issue, not a process one."
]
}
|
[] |
[] |
[
[
"http://www3.imperial.ac.uk/earthscienceandengineering/research/iarc/theplanets/platetectonicsonvenus"
]
] |
|
82bf59
|
why do anesthetic needles hurt so much when numbing a nerve?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/82bf59/eli5_why_do_anesthetic_needles_hurt_so_much_when/
|
{
"a_id": [
"dv8twaf",
"dv8w8q5"
],
"score": [
7,
4
],
"text": [
"Because they fairly directly poke the nerve (or very close to it) before injecting. Poking a nerve directly tends to hurt.",
"The way I had it explained by my doctor is that local anaesthetic doesn't actually \"numb\" your nerves. Instead it *over-stimulates* the nerves, so that the subsequent cutting/stitching pales in comparison. It's like the nerve is so full of the original pain that any other intrusion just doesn't register at all."
]
}
|
[] |
[] |
[
[],
[]
] |
||
9ofw28
|
why do addicts of hard drugs tend to lose many of their teeth?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/9ofw28/eli5_why_do_addicts_of_hard_drugs_tend_to_lose/
|
{
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"text": [
"Drug addicts don't typically have the best hygiene. Depending on the drug of choice, they may have no appetite and end up malnourished. ",
"Addicts can tend to have bad hygiene practices and ingest things that aren't good for their teeth. ",
"Option 1: Getting super high causes you to disregard general hygiene practices like bathing and brushing, and bad teeth are very obvious.\n\nOption 2: Some drugs contain corrosive/basic substances that will cause tooth decay over prolonged usage that will eat away at your enamel and cause decay to occur faster.",
"In the case of meth, there's physical effects of the drugs and behavioral effects of addiction. In the first case, the drug dries your mouth out - saliva has antibacterial properties but if your mouth dries out, bacteria has an easier time eating and multiplying in your mouth causing cavities. It also makes you twitchy and prone to grinding your teeth which weakens the enamel. Together, this results in increased amounts of cavities which, left untreated, leads to tooth decay and ultimately dead teeth (and worse). \n\nAll of this is made worse by the fact that an addicted person is usually much less likely to take care of themselves. That means dental hygiene is not observed, compounding problems. You're more likely to eat crappy, sugary foods which makes the damage the bacteria do when they feed on it worse. ",
"short version: instead of spending time caring for their teeth \"they spend their time under the influence or trying to acquire more drugs.\" [source](_URL_2_)\n\nadditional stuff: \n\nMany drugs cause dry mouth which increases the risk for tooth decay, because saliva protects your mouth.\n\nSome drugs can even affect oral health which makes the affect worse.\n\nSome drugs may cause grinding of the teeth which damage them.\n\nDrugs are expensive, and addiction is a real problem, so instead of paying for the dentist to address issues, they use the money to buy drugs.\n\n\nedit: [webmd](_URL_3_)\n\n[better health](_URL_1_)\n\n[delta dental](_URL_0_)"
]
}
|
[] |
[] |
[
[],
[],
[],
[],
[
"https://www.deltadentalins.com/oral_health/drugs.html",
"https://www.betterhealth.vic.gov.au/health/ConditionsAndTreatments/teeth-and-drug-use",
"https://americanaddictioncenters.org/health-complications-addiction/drugs-affect-teeth-health/",
"https://www.webmd.com/oral-health/drug-abuse-mouth"
]
] |
||
278eq5
|
Why are bike wheels so big?
|
Why are bike wheels bigger than car wheels? I don't think it's friction because surface area is not a factor in friction. The only reason I can think of is the added mass for gyroscopic stability, what do you guys think? Also I'm taking about road bike that ride on smooth surfaces not mountain bikes.
|
askscience
|
http://www.reddit.com/r/askscience/comments/278eq5/why_are_bike_wheels_so_big/
|
{
"a_id": [
"chyvfd3"
],
"score": [
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],
"text": [
"It is partly because mechanically it offers the opportunity of higher road speeds on a pedal bike without having to pedal furiously or without the need of excessive gearing.\nAlso, larger wheels traditionally were used before bike had suspension to try to smooth out the uneven roads that bikes were used on when they were first invented. \nsurface area is a factor in dynamic friction because the surface area of the wheel determines the shear strength of the surface of the wheel, so a thinner/smaller wheel will skid easier, whereas a wide wheel will skid and leave marks less easily, which is why rear wheel drive sports cars and motorbikes have larger rear tires.\nbut not all bike wheels have a large diameter, city bikes that pack up into a suitcase have much smaller wheels for obvious reasons."
]
}
|
[] |
[] |
[
[]
] |
|
1pxg6c
|
why do public women's toilets have lids if they're never going to be lifted up?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/1pxg6c/eli5_why_do_public_womens_toilets_have_lids_if/
|
{
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"text": [
"Standard parts for efficient manufacturing.",
"Do you mean seats? You'd have to lift up a lid to use the toilet, regardless of sex. Seats keep people from falling into the toilet while sitting down, which women have to do 100% of the time they use the toilet. ",
"Because it is cheaper to have 1 manufacturing process and mass produce it than it is to have 2 manufacturing processes. It also saves money in inventory; instead of keeping track of 2 items, you only need to keep track of 1.",
"Women might like clean toilet bowls too but also ease of manufacturing",
"you could lift it up in order to vomit"
]
}
|
[] |
[] |
[
[],
[],
[],
[],
[]
] |
||
2o2xiq
|
what is isis trying to accomplish with the beheading incidents and how do they release the videos?
|
What benefits them with the videos? How do they release the videos? They don't just upload them to YouTube.
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/2o2xiq/eli5_what_is_isis_trying_to_accomplish_with_the/
|
{
"a_id": [
"cmjdosl"
],
"score": [
3
],
"text": [
"ISIS believes that they can punish the US for conducting air strikes against itself, by executing American citizens who are so unfortunate as to fall into their hands, and that when America sees that it has been punished for its crimes, it will feel suitably remorseful and will then refrain from its criminal activities in order to avoid further punishment. I would say that this is a misreading of American psychology which is not generally inclined to surrender to extortion.\nReleasing the videos is not difficult. A large fraction of the world's population has the means to release videos if they so desire, and ISIS has many sympathizers around the world who would assist in such a release."
]
}
|
[] |
[] |
[
[]
] |
|
bs0vv2
|
how do frogs, toads and other amphibians know how and where to find new bodies of water?
|
We’ve got a new pond which must be half a mile away from the nearest lake/river yet frogs and toads have populated it almost immediately. How do they know where to find these new habitats?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/bs0vv2/eli5_how_do_frogs_toads_and_other_amphibians_know/
|
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"text": [
"Amphibians explore and migrate during cool moist weather. They can cover a lot of distance that way, especially if they can find damp places to take shelter in between stages of their journey.\n\nMost animals (including us) are also perfectly capable of smelling water from a good distance. Wind blowing across a body of water will have more moisture in its air than the surrounding air. An exploring frog that smells water on the wind will likely come to check it out.",
"I heard it's because of birds too. They walk/swim through water and might get some eggs stuck on their legs. Then when they visit your pond, they might lose some. Eggs hatch and you have toads and frogs. \n\nAlso some of your neighbours might have a pond too so they might not have migrated that far at all.\n\nEdit: spelling",
"well when birds land in one body of water, the eggs of amphibians/fish can stick to the birds and be transported to another body of water. Also, amphibians do explore land and can travel some pretty good distances on damp evenings, nights, mornings.",
"Tornadoes, strong storms and floods can carry animals like fish, and fish eggs from other bodies of water as well.",
"a lot of stuff that lives in water will lay eggs capable of sticking to ducks and other water foul. Frogs don't need to walk from one pond to the next. they just need their eggs to stick on bird feet.\n\nEventually you'll find fish or minnows in your pond.",
"The answer most likely lies in the taste and odor chemicals 2-MIB and Geosmin. They can be detected in such small quantities and are produced by Cyanobacteria and algae. The smell that makes a lake smell like a lake.",
"Did you post your pond on Twitter? There you go.",
"We have a few water tanks (maniacs ponds) on our deer lease that somehow always have turtles in them. No idea where they came from or how they find them but they always do.",
"People are explaining how animals can sense water, but another thing to think about is how many animals just die. If frogs from a pond head in several different directions, some will find new water and others will just die, either from dehydration or from predation/accidents along the way. \n\nThis kind of reminds me of the relatively frequent question about how animals manage to eat raw meat or drink stagnant water without dying, while humans can’t. And the answer is that many of them do die, and that humans could do the same if we were willing to have a much higher mortality rate.",
"I trunk it has encoded in their instincts. We really depend more on our technology now verses our natural instincts today. The same way salmon instinctively know how to find their original breeding grounds, sea turtles travel thousands of miles to the beaches they hatched from and so on...",
"There are toads that live in the desert where they hibernate for most of the year in these weird sacks that preserve their moisture underground. When it rains the few times a year, they wake and reproduce, but most of the time they are underground.",
"Insects and some animals take notice of polarized light which is what happens when light reflects off of a body of water especially at night. A full moon over a still pond becomes like a beacon to them. This is how mosquitoes know where to lay their eggs.",
"When I lived in southern Georgia as a kid, the subtropical rain would leave water standing in ditches and low places for months. Invariably small minnows and crayfish as well as the typical tadpoles would appear. I always attributed it to the white heron (egret) who loved to mill about these places and maybe somehow transported eggs along on their feet. Just a guess though..",
"Little known fact: frogs can fly when we're not looking.\n\nSorry, just had to throw that out, it was a great question, one I've often wondered about, and the first answer by TheSecretMe is right on the money.",
"You know, I’m kinda pissed. I tried making an ELI5 post about animal behavior about a week ago, and it was automatically removed because animal behavior questions are against ELI5 rules. Instead I had to search for 3 different subreddits who would take my question, and none of them answered as sincerely as ELI5 would have, so I basically never got my question answered. But this person?? And many others here??? Can all have their animal behavior posts put up and not taken down. I’m fricken sick of feeling like my posts get targeted for removal by bots when other people can get away with exactly the same kind of benign posts. TOO MANY RULES!"
]
}
|
[] |
[] |
[
[],
[],
[],
[],
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|
55n7k7
|
How easy was to get new identity and "vanish" at the end of WW2?
|
How easy was to "vanish" at the end of WW2 in Europe? Let's say its year 1945 , end of war in Europe and i need new identity.
If I just throw away my documents, pick new ones from a nearby corpse and start a new life what will be the chance i am ever discovered?
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/55n7k7/how_easy_was_to_get_new_identity_and_vanish_at/
|
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"text": [
"Follow up: If there were people that did this and were caught, what would the punishment be? ",
"Follow up: How plausible would it have been for an American to do this, during the Korean War, a la Don Draper from Mad Men?",
"Were there cases of Allied solders vanishing to avoid criminal charges at home or bad marriages for example?",
"Kathrine Hulme mentions in \"The Wild Place\" that they had Russians pretending to be Poles in the displaced persons camps. They were able to get DP papers because \n\na) there had been ethnic Russians in the old borders of Poland, so it was a bit easier to blend in, and there were similarities of language \n\nb) with the Soviet occupation of Poland, there was no way to check to see if they were who they claimed to be, & \n\n c) those few Russians in the camps got along well with the Poles, and so the Poles covered for them. \n\nFrom this, 1) you had to be plausible for that ethnic/social group. (Can't claim to be French and not speak it.) \n\n2) The harder it was to check out your new identity, the better. (The Nazi party archives were captured intact, with member photos. Hunted groups like the SS had unique blood type tattoos under their arms, and allied soldiers almost always checked prisoners for those. \n\n3)You better have sympathetic locals willing to hide you or at least overlook any discrepancies. "
]
}
|
[] |
[] |
[
[],
[],
[],
[]
] |
|
1yqhi6
|
how effective medical marijuana is. is it actually useful compared to other meds? or is it just used to get people to see the good side to marijuana
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/1yqhi6/eli5_how_effective_medical_marijuana_is_is_it/
|
{
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"text": [
"To be clear I'm not bashing marijuana or those who use it in any way. I'm just curious if medical marijuana is actually effective compared to other meds or if it's more a propaganda related ordeal to stop people from falsely accusing marijuana as some 'terrible drug'. \n\nFeedback from people who have used medical marijuana before would be greatly appreciated! ",
"A simple example would be people undergoing chemo. Sometimes they can get nauseous and have trouble eating. Other illnesses cause this as well. Marijuana brings back their appetite. ",
"Hey! I have Crohn's disease, which is essentially a disease of the gastrointestinal system that has varying effects on the people afflicted. For me, when my Crohn's \"flares\" as my wife calls it, I am unable to properly digest anything. As a result, I have severe diarrhea, stomach cramps, and a loss of appetite. These symptoms started around 15 years of age, but symptoms weren't really severe until I was in college. \n\nPrior to trying marijuana, I would have no appetite during my flare ups. It was not uncommon for me to lose 30 pounds in 2 weeks, simply because while you're stomach is in intense pain, food just is not palatable. I live in a state where it is not medicinal yet, though it will be on the ballot this fall, and I was really hesitant because of the illegality. Three years later, I am glad I did. It saved my life because it saved my friendships and my marriage.\n\nThere are a few medications on the market for Crohn's, from corticosteroids to immune modifiers to dietary supplements... though none of them are as effective for me as marijuana, and all of them presented different side effects that were equally troublesome as the Crohn's to my everyday life. For example, the steroids gave me increased blood pressure and occasional, serious mood swings.\n\nFor me, weed doesn't solve my stomach problems. I still have diarrhea, I still have cramps and stomach pain. What weed does is something more beneficial than any other medication I've been exposed to; it removes my pain from my focus. I am still in pain, but I don't mind it. I still gush water out of my asshole and, eventually, end up showering instead of wiping because my ass is raw, but my mind ignores the pain more easily because I'm focused on whatever else I am doing. It also gives me an appetite, not enough of one that I can't control myself, but just enough to make food taste enough that I don't get nauseous trying to swallow it.",
"I have tried anti depressants of a billion varieties through my childhood; nothing has allowed me to function on a day to day basis as well as marijuana. It does not eliminate, but mitigates my symptoms."
]
}
|
[] |
[] |
[
[],
[],
[],
[]
] |
||
79x9le
|
To what extent can parents' DNA be reverse-engineered from their child's DNA?
|
A child obtains 50% of their genetic material from their mother and 50% from their father. If a child's genome is mapped, how much of their parents' genomes could be reliably inferred from this? Can we determine more about their mother's genome than their father's?
I'm guessing that in terms of genes, we will know what the parents contributed together, but not which parent contributed which allele? What effect will recombination have?
|
askscience
|
https://www.reddit.com/r/askscience/comments/79x9le/to_what_extent_can_parents_dna_be/
|
{
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],
"text": [
"research engineer here:\n\nA haplotype (haploid genotype) is a group of genes in an organism that are inherited together from a single parent.\n\nAs the human genome consists of two homologous sets of chromosomes, understanding the true genetic makeup of an individual requires delineation of the maternal and paternal copies or haplotypes of the genetic material.\n\nRecognizing the importance of haplotypes, several groups have sought to expand our understanding of haplotype structures at the level of both populations and individuals. Initiatives such as the International Hapmap Project and the 1000 Genomes Project have attempted to systematically reconstruct haplotypes through linkage disequilibrium measures based on populations of unrelated individuals. However, the average length of accurately phased haplotypes generated using this approach is limited to ~300 kb. Alternatively, genotyping parent-child trios can determine whole-genome haplotypes in the child, but such methods are constrained by their higher cost and the sample availability of the two biological parents.\n\nNumerous experimental methods have also been developed to facilitate direct haplotype phasing of an individual, including long-fragment-read sequencing, mate-pair sequencing, fosmid sequencing, and dilution-based sequencing. At best, these methods can reconstruct haplotypes ranging from several kilobases to about a megabase, but none can achieve chromosome-spanning haplotypes. Whole-chromosome haplotype phasing has been achieved by sequencing based on fluorescence-activated cell sorting, chromosome-segregation followed by sequencing and chromosome microdissection–based sequencing. However, these methods only phase a fraction of the heterozygous variants in an individual, and more importantly, they are technically challenging to perform or require specialized instruments. Recently, whole-genome haplotyping has been performed using genotyping from sperm cells; however, this approach is not applicable to the general population and requires the deconvolution of complex meiotic recombination patterns.\n\nComputational analysis has shown that an important factor in haplotype reconstruction from DNA shotgun sequencing methods is the length of the sequenced genomic fragment. For example, longer haplotypes can be obtained using mate-pair sequencing (fragment or insert size, ~5 kb) compared with conventional genome sequencing (fragment or insert size ~500 bp) (Supplementary Fig. 1a). However, it is technically difficult to isolate and sequence DNA fragments that are longer than what is already obtained using fosmid clones. Hence, using existing shotgun sequencing approaches, it is difficult to generate haplotype blocks longer than 1 million bases, even at ultra-deep sequencing coverage.\n\nIn the human cell line, ...they obtained chromosome-spanning haplotypes at ~81% resolution with an accuracy of ~98% using just 17× coverage of genome sequencing. These results establish the utility of proximity ligation and sequencing for haplotyping in human populations.\n\n[source 1](_URL_0_)\n\nsource 2: I've modeled genetics and complex protein interactions for my job"
]
}
|
[] |
[] |
[
[
"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4180835/"
]
] |
|
74hz97
|
If you shine a white light through a blue filter, does it actually change the wavelength of the color?
|
As in, could you use plain old colored plastic filters to shift the color of a white or daylight LED light to wavelengths more friendly to plant growth?
|
askscience
|
https://www.reddit.com/r/askscience/comments/74hz97/if_you_shine_a_white_light_through_a_blue_filter/
|
{
"a_id": [
"dnyzieg",
"dnzexgt"
],
"score": [
4,
7
],
"text": [
"Filters do exactly what their name implies: they filter certain wavelengths of light. In general, light can do one of three things when interacting with a surface. First, it can be absorbed. This is what happens when you see things that are black in color, especially things like [Vantablack](_URL_0_) that actually trap the light. Second, it can be reflected. This is what objects do for you to see their color. It reflects the light into your eye so that you perceive it as a certain color. Third, the light can simply pass through, like with a clear object such as glass (note that clear objects may absorb wavelengths that are not in the visible spectrum). White light, such as sunlight, is made of the visible spectrum and can be split out like with a prism. A blue filter will take out the blue from the white light, leaving you with the other colors, meaning that theoretically the light will shift towards a more yellow color. This is actually similar to why the Sun might appear yellow: the blue light is being scattered away! Hope that helps!",
"Filters *remove* certain colors from the light beam. White light has all the colors mixed together: the blue filter removes everything but blue.\n\nIf the color isn't there to begin with, the filter can't add it. You can test this by getting a red laser pointer (which is *only* red) and shining it through a colored liquid like, say, apple juice or Mountain Dew. It'll change the brightness of the laser, but it'll stay red."
]
}
|
[] |
[] |
[
[
"https://en.wikipedia.org/wiki/Vantablack"
],
[]
] |
|
3ysjjh
|
Do certain activities increase/decrease brain activity during sleep?
|
I was wondering if certain activities before bed, like reading, exercising, watching TV, etc. might impact dream activity.
Over the last few weeks, I've been reading more right before bed (about 2 hours a night), and over the same period I've had very vivid dreams every night. Of course, my first reaction is to link the two, but more generally, I'm curious if there are certain things you can do to increase or decrease dreaming.
|
askscience
|
https://www.reddit.com/r/askscience/comments/3ysjjh/do_certain_activities_increasedecrease_brain/
|
{
"a_id": [
"cyimfrp"
],
"score": [
2
],
"text": [
"One of the main functions of sleep and dreaming is to consolidate (new) memories and reorganise the brain's neural architecture accordingly. Because of this, dream experience seems to have a strong relation with what you have experienced and encoded in waking life.\n \nIt is not entirely clear if there are reliable causes of more intense dreams, but some possibilities might be inferred. Firstly, one could argue that the novelty, emotional valence, and arousal related to your novel experience could translate to a necessarily more 'thorough' reorganisation, and vivid dream experience, if the emotion and arousal of episodic events are co-activated during dreaming.\n \nSecondly, one could argue that especially meaningful experiences could lead to more vivid dreams, if we assume meaningful experience to translate to more diverse and informative connections with existing memories/information in the brain.\n \nThe latter is based partly on the perspective that consciousness -and thus dream consciousness too- is dependent on a state of integrated information, which is still well possible during dreaming (as 'proven' by the fact that there's a subjective dream experience). To emphasize though, the above are not scientific knowledge, but a hypothesised answer based on it!\n\nHope the answer was satisfying, happy dreaming!\n\nSources: \nStickgold, R. (2005). Sleep-dependent memory consolidation. Nature, 437(7063), 1272-1278.\nTononi, G. (2008). Consciousness as integrated information: a provisional m\nWamsley, E. J., & Stickgold, R. (2011). Memory, sleep, and dreaming: Experiencing consolidation. Sleep medicine clinics, 6(1), 97-108."
]
}
|
[] |
[] |
[
[]
] |
|
31y38c
|
how do you enter a gas giant?
|
Ok, talking about the planets here, how does that work?
Would it be like an airplane descending into clouds (taking away things like their gravity), or would there be some type of contained atmosphere. I know thats the wrong word to use here, as they all have atmospheres, but is there a uniform boundary or is it just Space and then the planet kinda just "starts"?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/31y38c/eli5_how_do_you_enter_a_gas_giant/
|
{
"a_id": [
"cq630aw",
"cq63p6b"
],
"score": [
2,
2
],
"text": [
" > but is there a uniform boundary or is it just Space and then the planet kinda just \"starts\"?\n\nAtmospheres tail off roughly exponentially as you go up in height. Earth's does too - there's no sharp \"you're suddenly in space\" line for Earth, either.",
"Basically, at the top it's like the Earth: gently fading from vacuum to thin air to thicker air. \n\nBut the air just keeps getting hotter and denser and at higher pressures. "
]
}
|
[] |
[] |
[
[],
[]
] |
|
688f4v
|
what does the f/stop in a camera do?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/688f4v/eli5_what_does_the_fstop_in_a_camera_do/
|
{
"a_id": [
"dgwin0c",
"dgwiqg1",
"dgwjbmr",
"dgwje4q",
"dgwkpdf",
"dgxixfz"
],
"score": [
4,
4,
6,
2,
2,
2
],
"text": [
"It determines the size of the aperture which then, along with the shutter speed determines how much light reaches the film or sensor. A larger number means a smaller aperture, which means less light, but also a wider depth of field (how much of the image is in focus)",
"when you take a picture there are two things you need to tell the picture to do. how long to keep the lenses open and how much light to let into the camera. F/stop tells your camera how much light to let in",
"Building on the other two responses... \nThe F/stop works with the shutter speed to get the appropriate amount of light on the film. The smaller the F/stop number, the more light is being let in at once, and the larger fraction on the shutter speed, the longer time the light is allowed to reach the film. \n\nSo if you turn the F/stop up (closing the aperture more) you need to turn the shutter speed down to keep the same amount of light on the film (the same exposure). And if you turn the shutter speed up, you need to turn the F/stop down (opening the aperture) to keep the same exposure. \n\nFor fast moving objects, you'll want a fast shutter speed to cut down on blur, so that means you'll need a wide open aperture to match. \nBut the more open the aperture, the shallower depth of field you have. Depth of field is how far in front of and behind what you're focusing on is also in focus. If you have a very shallow depth of field, pretty much only the specific thing you're focusing on is sharp; everything else is fuzzy. If you have a deep depth of field, things are in focus for a long distance before and behind your subject. \nSo you need to decide how much you want in focus for how big you want your aperture, which affects the shutter speed you need. And you have to take into account how fast you need to take your picture for motion blur, which affects the F/stop you can use. It can be a frustrating dance. ",
"Think of it this way.\n\nIt takes a very precise number of photons to create a photograph in a camera. Too few and the image is all black, too many and it's all white. To control the number of photons that enter your camera when you hit the button, there is a shutter.\n\nYou can control this shutter in two ways. You can control how long it stays open for when you hit the button (obviously longer let's in more photons), or you can control how wide it opens. The F stop sets how wide the shutter should open. A low F number means that when you press the button, the shutter opens all the way and stays open for however long you set. A high F number means that when you press the button the shutter opens just a fraction and stays only this far open for however long you set before closing. Obviously, when the shutter opens all the way it let's in more photons in the same time than when it opens only a fraction.\n\nThe reason there's two different ways of controlling the amount of photons is that each one involves a compromise. Opening the shutter wider makes the camera harder to focus, while keeping the shutter open longer makes it harder to prevent blur. If you are shooting in below maximum daylight you have to choose between motion blur or some degree of out of focus. You use the shutter speed and f stop to control this trade off.\n\n",
" The smaller the f/ is the wider the aperture f/1.4 has opens the lens as wide as it will go whereas f/32 is narrow so it won't let in much light. Think of it's like the pupil in your eye, when it's dark it gets bigger and when it's a bright sunny day it's small. When set correctly the aperture with shutter speed and ISO can also be referred to as ASA on older cameras makes the foreground stand out and give a 3D effect this is called depth of field. _URL_0_",
"Always remember that the number in the f stop is the *denominator* in a fraction that describes the size of the hole letting light in.\n\nWhen i learned this, i totally got it after a long struggle with understanding it.\n\n1/1 (doesn't exist as far as i know) would be a fully open aperture with nothing impeding the intake of light.\n\n1/22 is a very tiny number and is thus a very tiny hole letting light in."
]
}
|
[] |
[] |
[
[],
[],
[],
[],
[
"https://www.slrlounge.com/wp-content/uploads/2015/04/photography-shutter-speed-aperture-iso-cheat-sheet-chart-fotoblog-hamburg-daniel-peters-11.jpg"
],
[]
] |
||
6ue285
|
Is there such a thing as space coordinates?
|
Let's say we wanted to broadcast some message into space, for possible detection by intelligent life anywhere. How could we communicate our location in the universe?
|
askscience
|
https://www.reddit.com/r/askscience/comments/6ue285/is_there_such_a_thing_as_space_coordinates/
|
{
"a_id": [
"dls2b61",
"dls2qi8"
],
"score": [
13,
6
],
"text": [
"There aren't any absolute coordinates in the universe. However, you can broadcast our location relative other parts of the universe. For example, if you wanted to send a message within our [local group](_URL_1_), such as communicating our location to a civilization in the Andromeda galaxy, you could send our galaxy's location relative to others in the local group, [like this](_URL_0_). Then you could include a second message communicating our location within our own galaxy. ",
"There are really two parts to this answer: it would basically be impossible for another planet to use our current coordinate system, the [galactic coordinate system](_URL_0_) since we define \"north\" to be towards the galactic center from where the Sun is in the galaxy. In other words, we do have coordinates for 3-dimensional space, but they are based on the Sun. Luckily, we have already figured out and sent a message out into space showing our coordinates on board the Voyager spacecraft, etched onto [golden plates or records](_URL_2_). We etched on a bunch of lines that is actually is a 3-d visual representation of the [pulsars](_URL_1_) in our neighborhood to scale. Pulsars are super useful because they are relatively bright but more importantly they have a very regular period to their rotation, or pulse (hence the name). Unfortunately pulsar beams can only be seen along the axis of the neutron star/white dwarf emitting them, but may be otherwise detectable with more advanced technology. If the extraterrestrials know which pulsars we are referring to on the etching, then they can deduce our location! Hope that helps!"
]
}
|
[] |
[] |
[
[
"https://upload.wikimedia.org/wikipedia/commons/1/1c/Local_Group_and_nearest_galaxies.jpg",
"https://en.wikipedia.org/wiki/Local_Group"
],
[
"https://en.wikipedia.org/wiki/Galactic_coordinate_system",
"https://en.wikipedia.org/wiki/Pulsar",
"https://en.wikipedia.org/wiki/Voyager_Golden_Record"
]
] |
|
1blxym
|
What is the probability of a couple having identical non-twins?
|
Scenario: A couple plans on having 2 children which are not twins. What is the probability that the two children will have the exact same genetics?
|
askscience
|
http://www.reddit.com/r/askscience/comments/1blxym/what_is_the_probability_of_a_couple_having/
|
{
"a_id": [
"c97v867"
],
"score": [
8
],
"text": [
"Here's [my answer](_URL_0_) to this question from about a month ago. The figures I give are for the probability of being unrelated (or rather of being substantially less related than the expectation), but the calculation is symmetric, so those probabilities are the same for the other half of the distribution.\n\nIt's not explicitly impossible, but the probability is so low that it basically won't even happen."
]
}
|
[] |
[] |
[
[
"http://www.reddit.com/r/askscience/comments/18nfrw/if_one_child_of_two_human_parents_receives_one/"
]
] |
|
39jqe6
|
why do people stand along roads holding signs to promote sales of some stores? (e.g. furniture stores, stores going out of business, etc.,.) is there a law against posting signs?
|
I always wonder why these people stand outside and hold signs for the store in all types of weather. How much do they get paid? And why can't the store pay the town to post flyers on telephone poles or in the land?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/39jqe6/eli5why_do_people_stand_along_roads_holding_signs/
|
{
"a_id": [
"cs3y9t6"
],
"score": [
2
],
"text": [
"Generally yes it is illegal in many towns to post signs and flyers because no one ever removes the signs later and they usually become trash in the streets, but that is not why they do it. They do it because people like you notice them. How many signs and posters do you stop to read that are posted to telephone poles and taped to windows? Unlike those signs that you don't even see any more, sign spinners get noticed, commented on and even talked about. Being noticed boots sales.\n\nThey, like most other simple jobs get payed minimum wage."
]
}
|
[] |
[] |
[
[]
] |
|
jt9c9
|
how / why water goes "bad" when you leave it out but is fine in bottles?
|
Why is it that water begins to taste bad when you have left it out, in a glass for instance, when one may think that since it is water it can't necessarily "go bad" yet it tastes distinctly different.
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/jt9c9/eli5_how_why_water_goes_bad_when_you_leave_it_out/
|
{
"a_id": [
"c2exs6k",
"c2exs6k"
],
"score": [
3,
3
],
"text": [
"Actually, water in plastic bottles CAN and does go bad (look at the expiration date!)\n\nExposed water will have dust settle in it, it will have smells and other floating stuff fall in to it, etc. Bacteria might get in it and start to multiply.\n\nBottled water will stay fresher longer, but since plastic does have very small pores/holes in it, eventually contaminants with find their way through the plastic in to the water (over the span of several years).",
"Actually, water in plastic bottles CAN and does go bad (look at the expiration date!)\n\nExposed water will have dust settle in it, it will have smells and other floating stuff fall in to it, etc. Bacteria might get in it and start to multiply.\n\nBottled water will stay fresher longer, but since plastic does have very small pores/holes in it, eventually contaminants with find their way through the plastic in to the water (over the span of several years)."
]
}
|
[] |
[] |
[
[],
[]
] |
|
1zmv28
|
why does a doughnut get nice and fluffy after 20 seconds in the microwave but hard after 40 seconds?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/1zmv28/eli5why_does_a_doughnut_get_nice_and_fluffy_after/
|
{
"a_id": [
"cfv4cgw"
],
"score": [
4
],
"text": [
"Microwaves act by making water molecules bounce around faster (increasing its kinetics) \n\n\nThe energy from this movement is released through the form of heat and it is dispersed evenly through the body of what you are heating.\n\n\nIf you overdo it you just completely dry out the object of the microwaves. Your doughnut becomes dehydrated."
]
}
|
[] |
[] |
[
[]
] |
||
17em7e
|
why do i have horrendous farts after a night of drinking?
|
They are horrible and basically constant (every 2 minutes). I have to clear my schedule for the entire day sometimes, because holding them in while around others would will cause stomach pains.
Also, loose stool. Just thought I'd throw that in there
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/17em7e/why_do_i_have_horrendous_farts_after_a_night_of/
|
{
"a_id": [
"c84t1ln",
"c84tn0b",
"c84ud7e",
"c84uh71",
"c84unkb",
"c84vzow",
"c84wavv"
],
"score": [
65,
18,
6,
3,
31,
3,
2
],
"text": [
"You have bugs in your stomach that like to eat carbohydrates. When they eat they produce gas. Alcohol contains carbs. The diarrhea is probably a side effect of not eating as well as you should while drinking.\n\nIf this happens every time you drink, you should see a doctor. ",
"TIL I am not alone.",
"This happens to me whenever i have an early shift at work. By early i mean like 0530. Any idea if this is related?",
"Think of what you eat on the night you're drinking. Are you eating a nice home cooked meal or greasy fast food, or even worse nothing at all. If your diet is ok, it might just be your stomach reacting to he alcohol in a weird way.",
"If you're five, you really shouldn't be drinking so much.",
" > Also, loose stool. Just thought I'd throw that in there\n\nI got nothing to add.",
"You may be sensitive to wheat or have some sort of yeast overgrowth. Are you on antibiotics or any other medication?"
]
}
|
[] |
[] |
[
[],
[],
[],
[],
[],
[],
[]
] |
|
6vet8s
|
how are digital devices functional in an mri room? how do they operate the mri in that strong magnetic field?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/6vet8s/eli5how_are_digital_devices_functional_in_an_mri/
|
{
"a_id": [
"dlzoyti"
],
"score": [
2
],
"text": [
"For the most part, magnetic fields are not as bad to electronics as people would lead you to believe. Specifically, magnetism isn't an important thing in the operation of electronics, and it doesn't somehow stop them from working. Really traditional hard drives are the only thing in a modern computer that has any meaningful sensitivity to magnets.\n\nElectronics however do use electricity, and current is directly tied to magnetism, specifically a change in current by definition generates a change in the magnetic field, and a change in a magnetic field generates a change in current (that could have a huge effect on electronics). In an EMP, there is a rapid change in magnetic fields, and that's how an EMP destroys electronics. In an MRI though, it's really just one big constant magnetic field, never changing. A magnetic field that doesn't change really has a minor effect on electronics.\n\nAnd finally to mitigate whatever sensitivity is left, we use [Mu-Metal](_URL_0_), basically you can make a case of metal, and the magnetic field lines will go through the case, not inside it (letting you make a hole of low magnetic field, inside a stronger one). Stop just put your computer inside a case made of Mu-Metal and it's thousands of times less sensitive to magnetic fields."
]
}
|
[] |
[] |
[
[
"https://en.wikipedia.org/wiki/Mu-metal"
]
] |
||
1clprr
|
Stem Cells for Rejuvenation
|
Can we take stem cells from our body, clone them and then re-implant them, wherever? Would this replenish and rejuvenate our body?
|
askscience
|
http://www.reddit.com/r/askscience/comments/1clprr/stem_cells_for_rejuvenation/
|
{
"a_id": [
"c9i2tsq"
],
"score": [
3
],
"text": [
"Cells from your body (eg your skin) can be manipulated and turned into [induced pluripotent stem cells](_URL_1_). These cells are, in theory, stem cells that can become any other type of cell in your body. Under the proper conditions, they can be induced to become neurons, blood cells, or any other cell type.\n\nIn theory, this technology could be used to produce organs (hearts, kidneys, livers) that could replace your organs as they became worn out over time. This would be difficult to do for complex organs that have multiple types of cells (the heart must contain muscle cells, blood vessels, nerves, etc.) This is the end goal of current research- however, this branch of research is still in its infancy, and it will be some time before it is ready for clinical application.\n\nIf your question is whether stem cells themselves can be injected into a patient and have them 'do their own thing' at the site of injection, it is unclear whether this will work or not. Wikipedia has a good [article](_URL_0_) describing potential treatments, although this line of research is also in its preliminary stages, and may or may not be successful in practice. It is currently being attempted for spinal regeneration and a few other areas.\n\nIf your question is whether the injection of a whole bunch of stem cells could rejuvenate someone in terms of reversing the aging process, this is unlikely. Stem cells, in general, do not have properties that are related to 'youth'- they are capable of becoming any type of cell, and they are capable of dividing infinitely, but they have no intrinsic properties that would remove wrinkles, restore cartilage, remove cholesterol buildup, etc."
]
}
|
[] |
[] |
[
[
"http://en.wikipedia.org/wiki/Stem-cell_therapy",
"http://en.wikipedia.org/wiki/Induced_pluripotent_stem_cell"
]
] |
|
3h6us4
|
when an app crashes and i send a report, what exactly does that do, and how is it used?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/3h6us4/eli5_when_an_app_crashes_and_i_send_a_report_what/
|
{
"a_id": [
"cu4rgft"
],
"score": [
15
],
"text": [
"It tells the developer that the app has crashed, first of all.\n\nBut it can also tell the developer what you were doing, what screen you were viewing, what data you were using, what route you took to get to that screen, and so on.\n\nAll of this can help fix the bug. Obviously the developer needs to know what screen you're looking at. But it's not uncommon to find find bugs where the app crashes every time you enter a \" character, for example. By sending the data to the developer, the developer can look at the report from dozens or even hundreds of similar crashes, and can realise that the \" character is the common denominator.\n\nObviously this has privacy issues - it's up to you to decide whether your privacy is worth sacrificing in order to help make the app better. If you use the app for banking or drug dealing, then probably not. If you use it for looking at pictures of cats you might be happy to share this data."
]
}
|
[] |
[] |
[
[]
] |
||
ycgf8
|
Why do trash cans smell even after they've been washed?
|
My plastic kitchen trash can smelled bad. Really bad. So I took out the trash, and washed it with soap and hot water. That didn't remove the odor. So I bleached it -- I sprayed it with a bleach solution, making sure to let it sit for 10 minutes before I rinsed it. Still have smell remaining. I washed it again. Still there.
I've asked around, and this seems to be a pretty common phenomenon (anecdotal, of course).
So what's going on? Is soap and water just not good enough for the kinds of decay processes going on in trash cans? Or is there some kind of residual odor in the can?
|
askscience
|
http://www.reddit.com/r/askscience/comments/ycgf8/why_do_trash_cans_smell_even_after_theyve_been/
|
{
"a_id": [
"c5ub058"
],
"score": [
3
],
"text": [
"I can only speak in generalities -- but I think it's pretty reasonable that those smell molecules have simply diffused into the plastic. At the molecular level, the plastic will be quite porous."
]
}
|
[] |
[] |
[
[]
] |
|
a8avg2
|
why does closing a credit card account hurt your credit?
|
I recently read that closing a credit card account can damage your credit. Wouldn't less credit card accounts be better?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/a8avg2/eli5_why_does_closing_a_credit_card_account_hurt/
|
{
"a_id": [
"ec968x2",
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"ec9c0dk"
],
"score": [
2,
8,
3
],
"text": [
"Having less credit cards is easier to manage, but people looking at your credit score don’t care how you do when things are easy, they want to see that you can have multiple lines of credit and balance them wisely. Also, closing a credit card could be saying “I’m in over my head” and they don’t want to see that either. ",
"Actually, to build great credit you want to have as much available credit (and **debt**) as possible. \n\nYour credit score is a reflection of how trustworthy you are with credit. It's based on how **reliably you pay off your debt**, not how little debt you have. If you have a lot of credit cards, you use them all, and you pay the recommended amount on the recommended time schedule without fail, you are building your credit score. \n\nClosing a credit card account means you're willingly lowering your maximum credit and debt situation, which tells lenders that you don't want that credit/debt, which hurts your overall ability to lend in the future.",
"It hurts your score for a number of reasons:\n\nCredit utilization goes up, meaning the percentage of your balance relative to overall credit line. This is one of the biggest factors in credit score. Let's say you have a $1000 balance on your cards, and your 2 cards have a total credit line of $10,000. Your utilization ratio is 10%. Now, you cancel a card with a $4000 line, and your utilization jumps to 17% with the same balance.\n\nAverage credit age might go down. Removing an account that has been open a while can reduce your average credit age, which is a factor in your score.\n\nYour number of accounts goes down. Showing more accounts, all in good standing, helps your score. It's better to show more accounts, and different types of accounts, than to have fewer accounts... provided they are all current and in good standing. Your rationale for thinking that fewer accounts is better actually plays more into the utilization rate mentioned above, where they don't want to see you maxed out/over extended on accounts."
]
}
|
[] |
[] |
[
[],
[],
[]
] |
|
3mzyr6
|
why aren't there bigger pushes to abandon the political party system?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/3mzyr6/eli5_why_arent_there_bigger_pushes_to_abandon_the/
|
{
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"Because it would be impossible. What are you going to do, ban people from working together?",
"Originally there were no parties. Like- minded individuals formed parties organically.\n\nIf they got rid of the current parties the only thing that would happen is new ones would form, officially or othrwise it doesn't matter.",
"[*This ended up being a long answer. Sorry.*]\n\nYou can't make anyone \"abandon\" the system -- there's no constitutional way to tell people they can't work together. How could you prevent a group of people from saying \"we're not all going to run for president, but instead we'll vote amongst ourselves to select just one person to run, and then the rest of us will support that person\"? That's what a political party is, and you can't stop people from doing it.\n\nThe more realistic solution would be to end the two-party system and provide more options than just Republicans and Democrats, such that alternative parties could also compete. However this would be very difficult to do.\n\nWe currently have a plurality system (rather than a majority system). This means that you don't need to win half the vote, only have more votes than anyone else. If we have three candidates, and one gets 40% and the others each get 30%, the person with 40% would win...even though 60% of the voters voted against them! \n\nThe problem with this system is that if a third-party candidate runs, they're actually *taking votes away* from the major-party candidate closer to their interests. And we've seen both parties lose elections as a result. In 1992, Ross Perot ran independently, however he was a fairly conservative candidate -- his appeal was with Republicans looking for an alternative to George Bush. Clinton won with 43% of the vote, however it's very likely that the majority of Perot voters (who made up 19% total) would have preferred Bush as their second-choice. This means that having a second conservative candidate actually gave the election to the one liberal candidate. And the inverse happened in 2000, when Ralph Nader ran for the Green Party. Nader only took 1 or 2% of the vote, however Nader was even more liberal than Al Gore -- clearly anyone who voted for Nader would have taken Gore as their second-choice over Bush Jr, and that small difference would have given Gore Florida and won him the election. So this time, splitting the liberal vote gave the conservative candidate the election.\n\nSo as it stands, it's generally a bad idea to run a third-party candidate. You may not like the Republican or Democrat, but if you run a third option, you'll likely be taking votes away from the major candidate who you prefer (i.e. if you're liberal but dislike Hillary Clinton, running Bernie Sanders as a third-party candidate would split the vote and give the election to Republicans; if you're conservative but dislike the Republican candidate, running Trump will split the conservative vote and give the election to Democrats).\n\nThe solution would be to have a majority system, which means that you cannot win until you get at least 50%+1. There are two main ways to do this:\n\n* You can hold a run-off election between the top two vote-getters. Let's say the totals for 4 candidates are 40%, 30%, 25%, and 5%; we hold a run-off between the candidates who got 40% and 30%, and the remaining 30% of voters can recast their vote in order to get the candidate most preferred by everyone.\n* Alternately, you can allow voters to select a second choice on election day. Polls would initially tally the first choices, however if no candidate gets more than 50%, then we go through some process of switching to second choices.\n\nEither of these would insure that the ultimate winner is the one most agreed upon by the electorate. It may not be everyone's top choice, but we wouldn't have a situation where more than half the electorate voted against the winner.\n\nBut here's the problem: more than 95% of our politicians are from one of the two major political parties. Currently, the worst case scenario for either party is to be the *second*-most powerful party at any given moment, which means neither party has any interest in changing the system. In order to change our voting process, you would need support from enough politicians to push through such legislation...but why would they want to do that? While Republicans and Democrats are at odds over a lot of things, one thing they both agree on is that the two-party system (and the voting process that supports it) is in their best interests, because it keeps both parties powerful and relevant.\n\nThis is why you didn't see Republicans pushing to change the voting system after Ross Perot cost them the 1992 election, even though a different system would have given Bush Sr. a second term. They recognized that, yes, they did lose this one election, but in the long-term, they'd rather keep that system and always be #1 or #2 than to change the system and potentially lose power not only to the Democratic Party, but also, perhaps, the Libertarian Party, Tea Party, and Green Party.\n\nTL;DR: you can't get rid of political parties, but you can change the electoral process that gives rise to a two-party system. Unfortunately, the politicians capable of changing that system are in their positions because of that very system, so they have no interest in changing it.",
"All that would happen is instead of having parties outright youd just have a lot of \"wink, wink, nudge, nudge\" going on. Oh, no im not a memeber of the liberal party, parties are illegal, but im a liberal and all my political signage is in red and im going to work with all of the other liberals who use red signage. ",
"What you're proposing makes no sense. The term \"party\" is just a label. A party is just a group of people who share similar ideas. Your friends are a party. Vegetarians are a party. Christians are a party. Political parties are simply people who share similar ideas in the political sector of society. ",
"If you wanted to get rid of the two party system in the US you could do these two things:\n\n1) Switch to approval voting. When you vote, you can vote for as many candidates as you want. Whoever gets the most votes wins.\n\n2) Switch to an additional member system for Congress. Basically this means that is some political party gets a substantial percentage of the vote nationwide and doesn't win any seats, you add some seats. The party fills those seats however it wants.\n\nThose two things would make a huge difference in how things happen in the US.",
"A political party gives a politician brand recognition. But more importantly it gives their opponents brand recognition. \"He's a democrat/republican/NDP/liberal/conservative so he's got my vote/he's a crook\". I'm from Toronto-- one of Rob Ford's favourite tactics is/was to call anyone who criticized an NDP hack, even though municipal politics doesn't have a party system and the provincial and federal parties rarely speak on municipal matters, but it played to his base who thought there was a vast left-wing conspiracy behind everything allegedly wrong with the city.\n\nAs far as why the US has had a two-party system for such a long time, I think it has to do with the perceived stakes by all voters of their less preferred candidate winning that they don't want to split the vote by voting for a third party candidate, and with the overall trend of binary logic in American culture: there are only two possible diametrically opposed and exclusive solutions to any problem and a consideration of nuance or flexibility is a sign of indecisiveness.",
"The below video really helped me understand how political parties in America work and why we only really have two. I'm not sure this is what you're looking for, but it's definitely worth a watch or three. \n\n_URL_0_",
"It's not a system. The only system is, people vote for their representatives.\n\nCandidates then freely associate into parties for brand recognition and simplicity. People don't have to know everything about a candidate - just that they share the main goals of their party and will work towards them.\n\nIt makes voting more efficient for the public, and then during actual legislating, being in organized groups with common goals gives you more weighg to demand, compromise, and get things passed.\n\nIt's just a valuable spontanious self-assembly.",
"Same reason we still have an electoral college. The only people who have the authority to stop it are the people who gained that authority through the current system. So they have nothing to gain by changing it."
]
}
|
[] |
[] |
[
[],
[],
[],
[],
[],
[],
[],
[
"https://www.youtube.com/watch?v=s7tWHJfhiyo"
],
[],
[]
] |
||
49a9ti
|
where does energy go in a short-circuited battery?
|
Wouldn't all the electrons just go from the negative to positive terminal immediately, without any conversion of energy besides a bit of heat from the wire? Assuming the wire is superconducting, how would the energy be used up?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/49a9ti/eli5_where_does_energy_go_in_a_shortcircuited/
|
{
"a_id": [
"d0q8sw2"
],
"score": [
6
],
"text": [
"It all turns into heat. Short out a battery, and it'll heat up and get warm, hot, or even on fire.\n\nAll batteries have internal resistance. That is to say, the inside of the battery isn't superconducting. So even if you had a superconducting wire shorting the battery, it would still get hot."
]
}
|
[] |
[] |
[
[]
] |
|
742pry
|
why does falling down hurt more/ longer when you get older
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/742pry/eli5_why_does_falling_down_hurt_more_longer_when/
|
{
"a_id": [
"dnv0bta",
"dnv0fbz",
"dnv9nvc"
],
"score": [
3,
13,
2
],
"text": [
"* your body is frailer and takes more damage\n* you are less able to react and control how you fall, meaning you are more likely to fall hard\n* any injury you suffer from the fall will heal more slowly",
"As you get older, you get taller. As you get taller, more of your body gets farther away from the ground. As they get farther from the ground, they have farther to fall. \n\nKnock a three year old over.\n\nThen hold that same three year old up to where his head is level with yours and drop him.\n\nDon't actually do that unless you record it. For science.",
"I'm 60, if I get cold I get stiff. If I stumble I'm not as good at balance or catching a stumble and recovering so sometimes I flail around to land on the ground in a heap. Very frustrating and now I'm not as limber and strong as I once was so a impact hurts more, does more damage and takes longer to heal, also Many aches and pains seem to heal to 90% but linger and become part of my life.\n\nSometimes I remember doing a activity and think I am as good as I ever was until I am out for a fast walk and get passed by old people or on the bicycle. Cleaning the eves troughs, moving a ladder, simple things that now take more concentration and am sore for days."
]
}
|
[] |
[] |
[
[],
[],
[]
] |
||
61jsas
|
why are salmon from the pacific prone to parasites while salmon from the atlantic safe to eat raw?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/61jsas/eli5_why_are_salmon_from_the_pacific_prone_to/
|
{
"a_id": [
"dff4dp1",
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"dffwnp3"
],
"score": [
335,
119,
39,
62,
4,
7,
3,
5,
6
],
"text": [
"I don't believe this is actually a thing? Atlantic Salmon also frequently have warnings put out about parasite risks. [The NHS publishes warnings in the UK](_URL_0_) about it. \n\nNow you can get sushi-grade fish, of course, but that's fish that has been flash frozen to kill any potential parasites in the fish. That can also be done with Pacific salmon. ",
"I used to work in an industry servicing Atlantic breeding farms and I can tell you, salmon here is not, in any way, parasite free. I would regularly see salmon swimming around with large pieces of skin and flesh missing. They do have methods to kill off the parasites in the breeding rings, though.",
"Interesting video on a sushi chef discovering a fish contaminated with parasites:\n\n_URL_0_",
"What information are you basing your question on?\n\n99.5% of Atlantic Salmon is Farmed salmon. There is no longer a commercial Wild Atlantic salmon fishery. \n\nPacific salmon is Wild. There is a large fishery in Alaska, BC, Washington, Oregon and California. \n\nAtlantic Salmon are more susceptible to disease because they are raised in Pens. I believe there biggest challenge is Sea Lice, which they are sharing with the Wild Pacific Salmon (not good).\n\nWild Pacific Salmon is as good as it gets. Salmon truly support the whole ecosystem of the West Coast and I will be eating salmon I caught off the west coast of Vancouver Island last summer for dinner tonight. \n\n\n",
"Is there a way to see it in a cut up filet in the supermarket? I often see some stringy white stuff after my salmon is cooked, but I'm not sure if it is a parasite... ",
"there is no such thing [US] as \"wild\" Atlantic salmon in the market. In fact something like 70% of salmon in all US markets that are labeled wild are actually farmed. Why does this matter? Farming conditions for salmon increase the risk of parasites\n\n\n_URL_0_",
"GF works for a large fish distributor and wants me to tell you guys that parasites, not only in salmon but fish in general, are ubiquitous. It's not about if there are parasites but how big and how many.",
"I saw something recently about using computer vision and FRICKIN LASERS to combat sea lice on salmon in Norway...\n\n_URL_0_",
"This may be unrelated, but in Norway they have little robots that live in their oceans that shoot lasers at parasites so fish are less likely to have them. This is not a joke.\n\n_URL_0_"
]
}
|
[] |
[] |
[
[
"http://www.nhs.uk/Livewell/homehygiene/Pages/salmon-parasite-warning.aspx"
],
[],
[
"http://youtu.be/c9xOf4Ku39E"
],
[],
[],
[
"https://dinersjournal.blogs.nytimes.com/2009/04/10/the-bottom-line-on-salmon/?_r=0"
],
[],
[
"http://spectrum.ieee.org/semiconductors/optoelectronics/licehunting-underwater-drone-protects-salmon-with-lasers"
],
[
"http://spectrum.ieee.org/semiconductors/optoelectronics/licehunting-underwater-drone-protects-salmon-with-lasers"
]
] |
||
1k3395
|
how can a spinning top stay upright while it's rotating?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/1k3395/eli5_how_can_a_spinning_top_stay_upright_while/
|
{
"a_id": [
"cbkv6vh",
"cbkx1af",
"cbkyy05"
],
"score": [
15,
4,
9
],
"text": [
"When something spins, it has inertia just like an automobile and just like an automobile, it is very easy to move it in certain directions in respect to the direction of the movement and difficult in other directions. The trick is that with a top, the inertia isn't all in one direction, it is in all directions along a plane. Shifting that plane up, down, or to the side takes very little energy, but turning the orientation of it requires disrupting the inertia, so you will experience a force if you try to do so. As long as the force which tends to topple the top is less than the force resisting it, the top will stay up.",
"This is called the law of Conservation of Angular Momentum.\n\nImagine you are spinning a bike wheel. If you want to completely stop its rotation and spin it the other way, that will require some effort, right?\n\nNow imagine that instead, as it is spinning you turn the bike wheel 180 degrees around (like turning a coin on its edge.) This would be surprisingly difficult. The reason is that the wheel is now spinning in the other direction. The law of CoAM requires that you have done as much work as in the previous scenario where you totally stop the wheel and spin it the other way. The faster the spin, the stronger this effect will be.\n\nOk, now you are spinning a top. Gravity wants to pull it down. That will tilt the top and change the axis of rotation, like you did with the bike wheel. Since the top is spinning, it resists this change. Again, gravity has to work for any change in the rotation like it was doing it \"by hand.\" So as long as the top is spinning fast enough, it can stay upright.\n\nTL;DR It is difficult to change the rotation of a spinning object.\n\nThis is also how gyroscopes work.",
"An object can be balanced on a point without spinning, but it's fiendishly difficult to do. By spinning the object fast, you are, in a sense, constantly averaging the centre of gravity about the axis, so a slight unbalance in one direction is quickly moved before it has a chance to fell the top in that direction. Instead, you just get a slight wobble as it continually self-corrects. \n\nThe angular momentum comments are true, but this is ELI5."
]
}
|
[] |
[] |
[
[],
[],
[]
] |
||
5nx04a
|
does my breastmilk have healthier properties if i eat healthier food?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/5nx04a/eli5_does_my_breastmilk_have_healthier_properties/
|
{
"a_id": [
"dceydap"
],
"score": [
6
],
"text": [
"Regarding healthy and unhealthy fats:\ngenerally speaking: the membranes of your cells always feflect the stuff you eat. Of course the body has its own fattyacid metabolism and can contribute here. but regarding the fats the general rule applies: you are what you eat.\nOn the other hand: the milk you produce contains still certain healthy components eitherway. like omega3 fats that are important for the brain of the baby. Thats a propriety of breastmilk that should not be influenced by diet."
]
}
|
[] |
[] |
[
[]
] |
||
1w4mn7
|
is it possible to have a mind like sherlock holmes?
|
Using the new Sherlock BBC series as a reference, can a mind like that exist? Where you are able to think so fast that it appears that time slows down for you, and you are able to analyze and execute moves perfectly from looking at a situation?
Edit: Or having a mind after taking the Limitless drug.
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/1w4mn7/eli5_is_it_possible_to_have_a_mind_like_sherlock/
|
{
"a_id": [
"ceyo81h"
],
"score": [
2
],
"text": [
"That doesn't really happen in the BBC series so much. Deductive reasoning is a real thing. I'm sure you're not seriously asking if you can slow down time with your mind though."
]
}
|
[] |
[] |
[
[]
] |
|
2kwo7h
|
Did any groups still cling to the Roman deities after the fall of Rome?
|
Even though Rome had been technically Christian for a century or so prior to its collapse (western empire at least). I assume it would have still been some time before Chrisitianity was universal around the empire?
Were any peoples or groups known to have held on to the belief in the roman deities post-collapse?
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/2kwo7h/did_any_groups_still_cling_to_the_roman_deities/
|
{
"a_id": [
"clpmt7m"
],
"score": [
13
],
"text": [
"The Roman Empire was of course not entirely Christian by the end of the fifth century, but it was pretty close. Pagans were never wiped out, but pretty much all our sources for this period and later were written by Christians, so we can't be entirely sure if they are accurate in their accounts of surviving pagans or not. I've written fairly detailed answers on paganism in the later Roman Empire and the early Byzantine empire [here](_URL_1_) and [here](_URL_0_), outlining in broad terms the evidence for pagans in a Christian empire. If you have any questions, I'll do my best to answer them :)"
]
}
|
[] |
[] |
[
[
"http://www.reddit.com/r/AskHistorians/comments/2bs9zl/when_christianity_became_dominant_in_the_roman/cj8gvv7?context=10000",
"http://www.reddit.com/r/AskHistorians/comments/2bs9zl/when_christianity_became_dominant_in_the_roman/cj91m8a"
]
] |
|
95jj8g
|
How did the ancient Romans think of what we today call race?
|
I understand that the Roman empire was a cosmopolitan and multi-ethnic empire, and that as time went on, more and more people in the empire were integrated and granted citizenship. How did the Romans conceptualize race? I'm asking this in the broadest sense -- any information you have on it. Other questions: did they have any conception or prohibition against miscegenation? Was Rome itself open to all peoples across the empire, or strictly for the residents?
I remember reading a while ago a post here or in /r/history about how colonizers viewed race. I can't find it now, but it had to say that one view was that race was emergent of the food that locals vs foreigners ate. I'd like to reference that post, but I can't find it anywhere.
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/95jj8g/how_did_the_ancient_romans_think_of_what_we_today/
|
{
"a_id": [
"e3tdbqm"
],
"score": [
10
],
"text": [
"Some previous answers to this question while we wait for any further answers: \n\nfrom /u/cleopatra_philopater -\n_URL_3_\n\nAnd another from cleopatra_philopater with further links to the origins of race perception -_URL_0_\n\nFrom /u/medieval_pants - \n_URL_2_\n\nAnd some consolidated links from the FAQ - _URL_1_"
]
}
|
[] |
[] |
[
[
"https://old.reddit.com/r/AskHistorians/comments/6w5xda/when_romans_conquered_africa_did_they_see_blacks/",
"https://old.reddit.com/r/AskHistorians/comments/2z3k1u/slavery_during_roman_times_is_portrayed_in_media/",
"https://old.reddit.com/r/AskHistorians/comments/4gzfbf/how_true_is_the_statement_race_is_a_modern_idea/",
"https://www.reddit.com/r/AskHistorians/comments/6s918x/given_the_recent_furore_concerning_dr_mary_beard/dlb36xx/?st=j6i9x7qd&sh=3a7e9ee3"
]
] |
|
1108nf
|
Can someone explain the dark trail in front of a plane in the sky?
|
Sorry if this is the wrong subreddit for this, but since you guys seem like such a smart group of people, I'd like to get some possible answers.
I'm wondering if someone can explain the dark line that seems to be leading a plane in the sky. I've seen this strange thing happen before, but never this apparent.
In the image, you can see the plane's vapor trail, and then a darker line in front of the plane's path.
Image: _URL_0_
|
askscience
|
http://www.reddit.com/r/askscience/comments/1108nf/can_someone_explain_the_dark_trail_in_front_of_a/
|
{
"a_id": [
"c6i6bgr"
],
"score": [
6
],
"text": [
"It's the contrail creating a shadow in the low haze.\n_URL_0_"
]
}
|
[] |
[
"http://imgur.com/GpL4R"
] |
[
[
"http://www.atoptics.co.uk/atoptics/contr1.htm"
]
] |
|
27wwvs
|
When an atom emits a photon, is it one blob of energy shot out like a bullet? Or is it a radiating wavefront coming from any one side of the atom? Or does the wave carry in a full sphere around the atom? Does the nucleus cause an eclipse?
|
askscience
|
http://www.reddit.com/r/askscience/comments/27wwvs/when_an_atom_emits_a_photon_is_it_one_blob_of/
|
{
"a_id": [
"ci56bdo"
],
"score": [
2
],
"text": [
"The photon at atomic scales can be thought of like a blob of energy, representing an excitation in the [discrete nature of the electromagnetic field](_URL_0_). It's only at larger scales that light appears to behave like a classical wavefront."
]
}
|
[] |
[] |
[
[
"http://en.wikipedia.org/wiki/Quantization_of_the_electromagnetic_field"
]
] |
||
4qnfeo
|
Why were siege engines not used more often in ancient times?
|
I've recently started reading a book about Roman generals and breaching into a city seemed a real problem (I'm thinking Numancia, Alesia, Cartago Nova, etc). If defenses were such a problem why didn't they destroy them with siege engines? Specially in cases where diplomacy failed several times why did they choose to starve the enemy out instead of just destroying the city from the outside?
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/4qnfeo/why_were_siege_engines_not_used_more_often_in/
|
{
"a_id": [
"d4uh8k5"
],
"score": [
4
],
"text": [
"Siege engines were expensive in terms of expertise to design, materials to gather for construction and (for some types) ammunition, time to build, and men to operate. They were also difficult to move and ranges were limited. [This interview with Peter Vemming](_URL_1_) discusses his work recreating a 22-ton trebuchet that was expected at the time to have a range of about 300m (about 328 yards). His was not the first attempt to recreate a medieval trebuchet, either, suggesting that despite our knowledge, authentic trebuchets required a great deal of knowledge to build properly.\n\nOn the topic of the range, a siege engine in the wrong place might be targeted by archers either trying to pick off crew or to damage or destroy the siege engine. CJ Longman wrote in 1894 of [attempts to replicate claims of longbow ranges above 300 yards](_URL_0_), and while he never quite reached it, he opined that a trained longbowman could probably reach 350 yards. Add in a little more distance due to shooting from a height (either a wall or a tower) and the range of the trebuchet suddenly becomes a potential problem."
]
}
|
[] |
[] |
[
[
"https://www.archerylibrary.com/books/badminton/docs/chapter24/chapter24_1.html",
"http://archive.archaeology.org/online/interviews/vemming/"
]
] |
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