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24w30c
|
why are some people more sensitive to touching hot objects than others?
|
I feel like I am more sensitive to hot pans or food or water than my family members. For example I cant wash my hands in the same (hot) temperature as my mom does; or I burn my tongue when tasting food but my friends dont. What does it have to do with?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/24w30c/eli5_why_are_some_people_more_sensitive_to/
|
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"I wouldnt know the scientific facts, but from what i gathered from my personal life, i think its about tolerance. My mother can sometimes seem impervious to heat, but i found that trough washing the dishes with steaming water, i too, started to form some sort of tolerance. I think it follows the same principal as with showering, where after some time the water doesnt feel so hot anymore, but on a larger, more long term scale."
]
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|
[] |
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|
fnxbuc
|
What happened to body armor + helmets between the introduction of gunpowder and WW1?
|
I’ve always been baffled as to why infantrymen abandoned the use of protective gear? Wouldn’t it have been helpful wearing armor against gunfire? If it was a matter of equipping large armies with helmets and armor, surely the more economically developed countries( UK, France, etc) Could afford the majority of their forces.
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/fnxbuc/what_happened_to_body_armor_helmets_between_the/
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"Armor did not disappear right away after firearms started disseminating in the battlefield, not only because it could still be useful against all other sorts of weapons like swords spears or bows, but because the response to firearms was not to drop but to develop even heavier armor, which was actually effective at stopping pistol shots and arquebus shots at long ranges. The problem was that this armor was extremely heavy, one Maximilian armor of 1520 weighed 42lb/20kg, and an English armor of 1590 no less than 71lb/32kg lb, while the armor for horse and man of the Count Palatine, 1530, totals about 120lb/54kg. As such horse armor was abandoned during the century and instead of full plate armor soldiers would use three quarters armor, which protected everything up to the thighs. This armor was used extensively during the 16th and 17th centuries, mainly by cavalry which was often of aristocratic status and could afford the expenses. The pikemen that composed the heavy infantry of the day were equipped with similar but lower quality armor, although the front ranks were often better equipped that the rest of the unit, while musketeers usually wore just a helmet. The Dutch during the wars against the Spanish also experimented with shotproof bucklers for the sword and buckler men who were tasked with breaking apart pike formation in close quarters.\n\nSo what was the problem? Well as I alluded above the price for shotproof armor was a terribly cumbersome weight, which made armor not too versatile despite their on paper effectiveness, and pikemen would often leave the detachable thigh and arm protections behind to lower the load. There was also a question of cost, as a shotproof corselet could cost a much as ten times as a normal one, so the distribution of quality armor was very uneven, as much of the equipment for war was during the period, as standardization was the exception more than the rule and as states struggled to bring more soldiers to the field in the ever increasing and devastating wars of the 16th and 17th centuries. By far the greater problem was not the cost per se, but its cost and effectiveness vis a vis what the armor faced, firearms. \n\nIn comparison to the insanely heavy and even more insanely costly armor of the period, firearms are very versatile and cost effective, which means that you can arm far more soldiers with muskets than you can equip them with shotproof armor, and the slow but sure trend during the early modern period was to increase the proportion of firearms in the army, first they were sprinkled among the crossbowmen and longbowmen, then they became the only projectile weapon on the battlefield but were outnumbered by the heavy infantry, then they equaled the number of pikemen, by the late 17th century the pikemen were the minority and in the 18th century line infantry was composed exclusively of musketeers. Not only is it cheaper but also far more scalable, which means that firearms could become stronger for far less investment than armor could, simply by making the barrel of the gun bigger. Thus the original 16th century musket, which was a bigger version of the arquebus and needed a forked rest to be able to be fired due to its weight, was the response to the proliferation of shotproof armor in the battlefield. The musket was indeed heavy and unwieldy, but not as much as and still way cheaper than the armor it was meant to penetrate. Thus the heavy armor of the cuirassiers and the pikemen was very cumbersome and expensive for very little return in a battlefield saturated by fire, and as such the late 17th century sees a shift away from armor, shedding protection in thighs and arms, and then ditching it altogether, which is also around the time in which the heavy musket is replaced by a lighter version that resembled more the arquebus of old. In the 18th and early 19th centuries heavy cavalry did sometimes retain at least the helmet and the breastplate, which were still useful in the melee against enemy cavalry, although still burdensome, but infantry completely gave up on armor in favor of musket and bayonet.\n\nSources:\n\n* Keith Roberts, Adam Hook - Pike and Shot Tactics 1590-1660\n\n* Brent Nosworthy - The anatomy of victory: battle tactics 1689-1763\n\n* Vladimir Brnardic, Darko Pavlovic - Imperial Armies of the Thirty Years’ War (2): Cavalry"
]
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[] |
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[
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|
f0qx4m
|
Adrenaline, Epinephrine, Noradrenaline, and Norpinephrine?
|
Two questions:
Are they just 2 hormones with different names, or are all their own, unique hormones?
What are the functions of each of them?
I’ve been getting mixed answers from different teachers and books, so it would be great if you could explain it. Thanks in advance.
|
askscience
|
https://www.reddit.com/r/askscience/comments/f0qx4m/adrenaline_epinephrine_noradrenaline_and/
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"Adrenaline/Epinephrine and Noradrenaline/Norepinephrine are two different compounds (but each pair separated by a slash is synonymous/just alternate names). They have similar chemical structures and are implicated in similar processes (specifically, activating the sympathetic nervous system). However, my understanding is that epinephrine is a hormone while norepinephrine active as both a hormone and a neurotransmitter.",
"Adrenaline and epinephrine are two names for the same thing. (They're basically the same word — in Latin \"ad-\" means near or on, and \"renal\" means kidney-related. In Greek, \"epi-\" means on or around, and \"nephric\" means kidney-related. Unsurprisingly, adrenalin is named after a gland on your kidney that produces it.)\n\nDifferent areas use one word or the other, e.g. US vs. UK medicine. (Kinda like how the drug called acetamenaphen in the US is paracetamol in the UK.)",
"Adrenaline and noradrenaline are the European names for epinephrine and norepinephrine.\n\nThey are both stimulatory catecholamines, with similar effects in most of the body, and both are generally associated with causing the 'fight or flight' response.\n\nThats about all that can be said without going into receptor types and tissues.",
"All 3 main answers I see are correct info. Both hormones, but nor- is also a neurotransmitter. Marginally different activity at adrenoceptors, but act at all the same 9 receptors (and their iso forms). Structurally only differ by a single methyl group on noradrenaline. \n\nNor/adrenaline were how they were first described. IIRC, the reason the US changed was because someone trademarked the names in the US for drug production purposes (many years ago) and its a relic of that."
]
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2e2ixq
|
How does using water irresponsibly remove it from the water cycle?
|
I keep hearing about how we are wasting water and that it is a limited recourse. How is it possible, given the water cycle will reuse any water we use?
|
askscience
|
http://www.reddit.com/r/askscience/comments/2e2ixq/how_does_using_water_irresponsibly_remove_it_from/
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"Technically, it will not. What it might do, however, is limit the amount of water within the tiny subspace of the water cycle which we (and the rest of the wildlife within our part of the ecosystem) can use directly, which is surface fresh water. \n\nThe key thing to get here is that water transits from one reservoir to the next at limited rates, and that if your water consumption exceeds the rate at which fresh drinkable water can reach you, you are in trouble. ",
"Globally speaking, water isn't a limited resource, but it's unevenly distributed among the planet. Urban areas need a lot more water than rural areas, but urban areas tend to have fewer and small water deposits.\n\nDesalination plants, purification, fluoridation, reservoirs and infrastructure cost a lot of money and energy to build, maintain and operate. The \"limited resource\" in question isn't the water itself, but the operating costs of the system that gets clean water to your house.\n\n(Edit: typo)",
"The water cycle is changing - where and how moist air is and where it goes is shifting as the climate changes. There is no rule that says snow must happen over the particular bit of land that feeds a particular river, just because it's been doing that for thousands of years. The problem is, when the water moves elsewhere, our cities can't move with it, they're stuck in places where there was lots of water when they were built (next to a snowmelt-fed river, for example), but where there may be less water in the future, or the same amount of water but falling as rain instead of snow, causing a flood-drought-flood-drought cycle instead of that steady all-year-round river from snow-melt. There is also more competition for water - a city by a river grows bigger with more people and needs more water, meanwhile farms have been built upstream that drain the river for irrigation, so the river has less water when the city needs more. Even when the water cycle is not changing, it is a precious resource because even though it is constantly appearing, the rate at which it appears is limited, and our demand outstrips that supply. That makes it a scarce resource, which means valuable. We have to use less and waste less else we exceed supply.\nAnd if you're a bird or a fish, well, good luck competing with the humans for the water you need...",
"There is another issue with ground water:\n\nIf you pump out too much water, the water level gets low enough that other, non-clean (e.g. salt), water sources will seep in. Once that happens the water is unusable (or at least undrinkable) even if the water level rises back as it won't \"push out\" the contaminants.\n\nSo if you over-pump water from an underground water reserve you can actually ruin it \"for good\", even if theoretically the next winter would have enough rainfall to fill it back up again.",
"Strictly speaking, you're wasting (lack of) entropy. There is tons of water around, but most of it is mixed with other things. This is almost exactly the same situation as recycling aluminum - aluminum is one of the most common elements on earth but it's incredibly energy intensive to purify it, so recycling actually saves energy and not elemental aluminum.\n\nPure water can be separated out but it takes energy. In the normal water cycle, this energy is provided by the sun, but the normal water cycle also produces only a limited amount of standing fresh water - the occurrence of which is relatively rare. The normal water cycle thus provides fresh water at some fixed rate which we do not control - if we want more then we need to provide the energy ourselves somehow.\n\nSo the answer is: \"Using\" water mixes it together with other things, turning \"fresh\" water into contaminated water. We can make fresh water out of impure, to supplement what we get from nature, but it takes a lot of energy to reduce the local entropy in this way. We also have an energy crisis, so it could be said that a water crisis and an energy crisis is the same thing. ",
"If you live in the West, your water may come from an underground aquifer. If water is extracted from an aquifer exceeding the refill rate, potential problems will emerge.\n\n_URL_1_\n\nSimilarly, if water comes primarily from a reservoir, if consumption rates exceed refill rates, scarcity becomes an issue.\n\n_URL_0_\n\nThe water cycle of evaporation and precipitation is a global cycle, but dependence on aquifers and reservoirs is local/regional. Overconsumption of water in such regions is very possible, in which case usage must be curtailed to match available supplies.",
"To put it simply, water in the water cycle isn't a strictly limited resource, the limited resource is potable (drinkable) water. In many urban and suburban areas this processed (an energy and resource intensive task) drinking water is also wasted on non-native grasses that require supplemental water since they aren't in their native environment. In rural areas, yards and fields are often watered from irrigation ditches that are fed directly from surface water sources and are untreated (non-potable) and many cities are adding or expanding similar water networks. ",
"It's not that the water disappears forever, it's that we're removung it from certain lakes and aquifers faster than it can possibly replenish. A lot of (particularly agricultural) regions get far more of their water from these sources than from rain or rivers and yes, if we quit taking water from the aquifers they will replenish, in a couple thousand years or so. Go look up what the Aral sea looked like 30 years ago and what it looks like now if you doubt water is a limited resource or that some regions will eventually run out of accessible water. It's the same in a lot of other places, except the lakes are underground so it's harder to see.",
"related question: I've wondered whether 'wasted' water mitigates the cost of purifying the resulting sewage by providing a more dilute sample to purify (more water per unit sewage). Or worded another way: wouldn't it be harder to reclaim 1 gallon of water if it had 1 gallon of other 'sewage' mixed in, than it would be if there were only 1/2 a gallon of 'sewage' mixed in?",
"One issue I didn't see here is 'exporting' water out of its watershed. If you take a lot of water out of the Great Lakes, for example, (which had been under consideration), put it in water bottles and send it to Arizona for the tourists to drink, you may have the same number of H2O molecules but you have radically changed the ecosystem. ",
"Although the same water will technically be in circulation forever, wasting it is more in terms of unnecessarily using some water to no good use and it having to be repurified all over again when it didn't really do anything worth while, and the cost needed on top of that. \n \nLets say you're washing dishes in the sink, and for the whole duration of dish washing you keep the tap on. A lot of that water was needlessly put down the drain, it didn't wash anything or be used usefully. So instead of only turning the tap on when you needed to rinse soap off dishes and using 5L of water, you end up having used 25L of water with the tap constant on. \nSo 20L of water went to no use. If we up the scale with 1000 people doing the exact same thing, you suddenly have 25,000L of water being used, and only 5000L actually put to good use. So 20,000L of water was needlessly used and so was wasted because now, instead of only 5000L of water needing purification, there's 25,000L. And this example is only ONE session of dish washing by 1000 people, water also gets used a lot in showering etc. \nSo the water will still be reintroduced into the system to be used, but the real waste is in repurifying water that was unused and could've been kept and used better. Like rewashing completely clean clothes, it's time and money consuming as well as delays the washing of ACTUALLY dirty clothes. \n \nAddition: So it's irresponsibly being removed from good use, and from whatever reservoir/lake, because there's a huge amount wastefully going to no use and taken back into wash cycle ",
"True, water never \"dissapears\" however neither does money, but it is still very possible to waste money. The aquifers of fresh water under the ground in the U.S. are like a huge bank account. One that we are drawing down much more quickly than can be replenished by rain trickling down through the earth (or so I've heard, if someone wants to cite this for me that would be great).",
"It's **clean** water that's the issue. Not water in general. We have oceans of water, but it's salty which is bad for drinking. It takes resources and energy, not to mention time, to clean water. I'm not entirely sure about the process to desalinate water, but I'm guessing it's worse than cleaning water.",
"I was asking myself this question just the other day when I was installing a new shower head. When I turned it on for the first time I realized it pumped out significantly more water than the old one and I felt guilty. Should I feel guilty? I'm not taking it out of the system; just borrowing it. \n \nOur municipal water supply comes from the great lakes, gets treated then gets put back into the great lakes. In this scenario, is the effect of using more water at all significant? (moreso, then let's say, switching to a biodegradable shampoo). We also have an 'eco' toilet with two flush 'settings' for saving water. How much of this makes a difference?",
"Its not a removal of water from the cycle, its the **human effort it took to clean/deliver that water** that is being wasted.\n\nThink about it, a population requires X amount of water to not die. It takes Y energy to continue to produce X amount of water. **When you take clean water and put it in the sewer, you need to use that much more energy to keep the water flowing at an acceptable amount.**\n\nEssentially the 'waste' is of everyone's time, not the water itself.",
"One of the most remarkable non-replenished aquifer is the Nubian Sandstone Aquifer System in the Sahara desert. This water has been sitting there for a probably a Million years. We will deplete it in a few centuries.",
"The water cycle will only give you so many litres per year. When you accelerate the removal of water from a river (or wherever your water supply is fed from), you aren't accelerating the rate at which rain replenishes that river.",
"It isn't about removing it from the global water cycle, but rather removing it from the local water stores. You don't much care about the water concentration in Siberia or the upper atmosphere when you are looking for a drop in the Sahara. ",
"If you are interested in learning more about this, google articles about the California drought. Basically fresh water accumulates from the rainfalls from the sierras but due to a very dry spell (drought) over the last few years, fresh water is being depleted. A lot of this fresh water is for irrigation as 90% of the countries veggies and many other crops are dependent on this rainfall. Once there isn't enough water, then farmers are tapping into the water table and depleting water reservoir which are depleting very quickly. Once that is depleted, all our veggies will die, food prices will increase and we will be in trouble. This is why municipalities are asking residents to conserve water but too many entitled folks love to wash their cars and water golf courses while killing future generations",
"This is related to a question I've been meaning to ask:\n\nMy county has a ban on rain barrels, reason being that it somehow messes with the local water table or something like that. Can someone explain to me how a community of people using rain barrels would destroy the earth (in our very localized region)?",
"We're more concerned about wasting useful energy. We can purify water, but it's resource intensive.",
"Overusing ground water can result in its permanent depletion. Generally, groundwater will be replenished by rainwater, but when you overuse groundwater the ground will start to sink. All the space between the soil that the groundwater used to occupy collapses and disappears, leaving less room for water to penetrate the soil. [Here's an article](_URL_0_) with a famous image of the San Joaquin Valley demonstrating how much the ground sank from farmers overusing groundwater. It's estimated that the surface dropped as much as 50 feet in places. That's 50 feet of surface depth that used to hold groundwater that can no longer be replenished by rainfall.\n\nAnother issue is salt water intrusion. Salt water from the ocean penetrates into the ground the same way fresh water does. If there is a fresh groundwater source near a salt groundwater source, overusing the fresh groundwater can cause the salt water to seep toward the fresh groundwater source. Once the salt water penetrates the groundwater source, it becomes unusable. \n\nIn times of drought, farmers tend to overuse groundwater, which always runs the risk of permanently depleting the water source. "
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[],
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"http://abcnews.go.com/US/wireStory/water-headed-struggling-lake-mead-24970586",
"http://en.wikipedia.org/wiki/Overexploitation#Water_resources"
],
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[],
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[],
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[],
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[],
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[],
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"http://ca.water.usgs.gov/projects/central-valley/land-subsidence-monitoring-network.html"
]
] |
|
9hfyh6
|
why do those yellow things form in the corner of your eyes when you sleep?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/9hfyh6/eli5_why_do_those_yellow_things_form_in_the/
|
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"That's called rheum. Your eyes discharge a thin liquid, which normally you continually flush away during the day. This can combine with other gunk, like dead cells, dust, and so on, and helps keep your eye clean by flushing them out.\n\nAt night, you don't do much 'flushing' since you aren't blinking, and so the gunk can collect and dry. ",
"My kid doesn't get them in the corners of her eyes but more so in her lashes (like 3-5). Does anyone know if those are the same things? "
]
}
|
[] |
[] |
[
[],
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||
80mxko
|
why do you not feel “wet” when under water?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/80mxko/eli5_why_do_you_not_feel_wet_when_under_water/
|
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"Your body doesnt really feel a state, it feels a change in states. Its why it doesn't feel like you're moving at 1,000 MPH, even though the earth is spinning that fast. You'd feel it if it abruptly stopped though. Same with a car how you don't feel in motion, until it turns.\n\nWhen youre submerged fully in water, you're in a constant state. If only part of you is under water, the change is always there: a huge difference between what the parts of your body feel. Same as with rain: places get hit randomly, others dont. No matter how fast its falling, the constant interruptions are detected.",
"I think it has to do with the temperature changes brought about by evaporation. Underwater there is no evaporation but there is a steady temperature change when wet skin is exposed to the air (cooling) coming from the water on the skin."
]
}
|
[] |
[] |
[
[],
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||
2dhn5s
|
if emotion is just a chemical in our brains, could we make a computer capable of feeling these emotions?
|
And how do we know they don't feel based on electric impulses, if our brains are just pretty good computers
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/2dhn5s/eli5if_emotion_is_just_a_chemical_in_our_brains/
|
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"\"Pretty good\"? How about extremely good? Scientifically speaking, we are barely on the cusp of starting to understand how the brain works. \n\nYou equate \"emotion\" with \"a chemical\", but how many emotions are there? I would estimate \"a lot\", but there aren't different chemicals for each emotion. It's about how the brain is processing the situation and this regulates where the signals go and this tells us which emotions are going on. Wiring or programming a computer to match this complexity hasn't been done yet. It is theoretically possible, but our understanding of the brain is no where near where it needs to be to accomplish this.",
"We would need a computer exactly as complex as our brain, if we wanted to recreate human emotions perfectly.\n\nWhich is absurdly complex, but yes, theoretically possible."
]
}
|
[] |
[] |
[
[],
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|
35vzcw
|
Western Traders in Istanbul
|
A book I'm reading says; "In the Ottoman Empire, Western European traders former colonies within the city of Constantinople where they were granted commercial privileges" the time period is 17th-18th century. Can anyone give me some more information about this?
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/35vzcw/western_traders_in_istanbul/
|
{
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"text": [
"If you have the time to read a book to explain part of the book (I know, jokes!) then James Mathers' *Pashas: Trades and Travellers in the Islamic World* explores the relations between English/British traders with Ottoman authorities, and goes beyond just Constantinople."
]
}
|
[] |
[] |
[
[]
] |
|
4dtgdi
|
if prostitution is illegal but pornography is not, why don't men looking for prostitutes just get hookers to be in their " film "?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/4dtgdi/eli5_if_prostitution_is_illegal_but_pornography/
|
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"From what I understand that's how you can legally solicit a hooker without being caught.\n\nI.E. if you were to say try to pick up an undercover officer you could ask for a \"nude shoot for film\" and an undercover officer won't do that, and it's not illegally soliciting a prostitute either.",
"When filming the film company will have very expensive permits, a production crew and equipment. If permits haven't been acquired everyone would still go to jail. Different charges but same outcome.",
"There are permits involved with making adult films. I assume most \"johns\", a term for a prostitutes customer, is trying to conceal his identity, save money, or save time."
]
}
|
[] |
[] |
[
[],
[],
[]
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||
2svmti
|
do advertisers on tv have different editions of commercials to air according to what happens in sporting events?
|
The way that during a championship game, a newspaper will print headlines for both teams as champions so they are available right after the game. Or championship hats are made for both teams. Do advertisers on TV have two different editions of commercials to run in the same situation assuming their add is pertinent to the outcome of the game?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/2svmti/eli5do_advertisers_on_tv_have_different_editions/
|
{
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"Sure. I remember when the Patriots were going for their perfect season in... '07? '08? and there was some commercial that had a bunch of the '72 Miami dolphins in \"Perfect Season Land\" or something (the '72 miami dolphins are the only team to have a perfect season) and I saw two versions of the ad. One that included the Patriots in \"Perfect Season Land\" and one that didn't.\n\nWish I had more details on the commercial, I know I'm butchering the premise, but that's the idea.\n\nedit: Found it! [Here's the one that aired](_URL_0_)\n\n[Here's the one that didn't](_URL_1_)"
]
}
|
[] |
[] |
[
[
"https://www.youtube.com/watch?v=1noYVFl-Cnk",
"https://www.youtube.com/watch?v=EaeF_mj8_sY"
]
] |
|
2vrdif
|
why do tesla veichles get 265 miles in range while other electric cars are substantially lower.
|
I thought Tesla shared its patents, what's the hold up for other car makers to match their range.
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/2vrdif/eli5_why_do_tesla_veichles_get_265_miles_in_range/
|
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"text": [
"Well, I can't think of a purely electric car that costs as much as the Tesla Model S, most others are $25,000-$35,000.",
"Bigger battery pack. That costs money. The battery pack alone on a Tesla costs more than other whole cars. The replacement pack costs around 30k",
"Size of the battery pack plain and simple.\n\nTesla Model S P85 - 85 kWh\n\nNissan Leaf - 24 kWh\n\nYou don't need to understand what kWh means to understand why the Tesla goes 250 miles while the leaf only goes 80.",
"Its really the only car designed form the bottom up to be electric and thus can integrate a bigger battery pack as well as some other effeciencies like individual traction motors.",
"It's all about that base... which can accommodate bigger batteries without compromising stability or performance.\n\nMost electric cars and hybrids are built using established platforms (the skeleton of the car, so to speak), which were originally designed for gas engines and the drivetrains to match. Tesla (and Fisker when it was around) are purpose-built platforms with a low center of gravity, which allow all of the heavy components even distribution and optional placement. In turn this allows engineers to enhance stability, ergonomics, battery capacity, and even safety. The Tesla cars handle REALLY well, and actually scored higher safety ratings (in certain categories) than any production car ever made.\n\nYou absolutely could fit bigger batteries into a traditional car chassis, but then you'd have to give up trunk space or even the back seat, and the car would handle poorly because of the weight distribution.\n\n"
]
}
|
[] |
[] |
[
[],
[],
[],
[],
[]
] |
|
5ipw3o
|
how do astronomers know which planet is earth in pictures that are taken from a billion miles away?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/5ipw3o/eli5_how_do_astronomers_know_which_planet_is/
|
{
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"dba1kvs",
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"text": [
" > I always see photos of our galaxy with an arrow pointing at some super tiny dot saying \"this is Earth\". Do they really know that that particular dot is actually Earth?\n\nThose are all artistic renderings, not photographs. So they can point at an area about where we think our star is and call it Earth, because they drew the picture and they get to decide which dot represents Earth.\n\nWe barely have a probe passing outside our solar system.",
"There has never been a photo taken from outside our solar system. The pictures you see of \"our galaxy\" are artists conceptions based on what we can observe about our galaxy's structure, and what other galaxies that we can see look like. "
]
}
|
[] |
[] |
[
[],
[]
] |
||
t9owb
|
What is the correlation between bra cup and breast volume/mass?
|
Curiosity finally got the better of me, so I created an account to ask this :)
You know how they say girls with big breasts have lower back pain? What I'm interested in is: What is the correlation between bra cup and breast volume/mass?
Additional info: I was wondering how much my breasts weigh, so I thought I would find some sort of formula or table of breast sizes and corresponding weights/volumes online. I was only able to find average volume and aproximations.
I thought I would just calculate breasts volume at first, but a breast is not exatcly half a sphere. Does anybody have a better aproximation?
Finally measured one of my breasts Archimedes style (clumsily) and its volume is aproximately 1 L, wich comes to aproximately 0,9kg. That unfortunately doesn't answer my question and I can't just start asking girls to measure their boobs irl for comparison. I'm a 80D (european measurements), so that can be first data point if anyone is willing to measure.
Looking forward to your suggestions and answers :)
|
askscience
|
http://www.reddit.com/r/askscience/comments/t9owb/what_is_the_correlation_between_bra_cup_and/
|
{
"a_id": [
"c4kqnyh",
"c4ksac6"
],
"score": [
10,
2
],
"text": [
"Not sure if this is what you want to know..\n\nCup size is based on bra band size (the measurement under your breasts) and full bust measurement. The difference between these measurements gives you your cup size. A larger band size will also have a larger cup size - ie. a 36 B will have a larger cup than a 34 B, since the cup has to compensate for the larger band - breasts actually extend to the sides of the chest, or at least the real ones do lol. \n\nSource: I draft and make clothing and undergarments. \n\nIf you're asking about weight of breasts, I'm not sure if it has a lot to do with cup size. ",
"Fill bra cup with sand, weigh sand, look up density,compute volume,....,profit."
]
}
|
[] |
[] |
[
[],
[]
] |
|
45418r
|
What is Gravitational Wave and why is it so important?
|
I am curious, not scientist... And my mind tries to conceive the idea of empty space being fabric that ripples like water. Anyhow, what is it? What would it mean if it is proven to exist?
|
askscience
|
https://www.reddit.com/r/askscience/comments/45418r/what_is_gravitational_wave_and_why_is_it_so/
|
{
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"text": [
"Gravitational waves are a prediction of Einstein's theory of gravitation, called general relativity. In a gravitational waves, space gets distorted in a particular pattern (a circle would deform into an ellipse, alternately elongated horizontally and compressed vertically and then compressed horizontally and elongated vertically).\n\nThere have been indirect measurements to confirm their existence, but a direct measurement would be significant for several reasons:\n\n(1) We would get explicit confirmation of a key aspect of general relativity. \n\n(2) The kinds of events that produce sufficiently large gravitational waves are dramatic things -- black holes or neutron stars merging or colliding, for example. We would be able to test general relativity and how it works in these situations.\n\n(3) Probably more important, the ability to detect gravitational waves opens up a new means of observing the universe. For example, how often do black hole mergers occur? Historically, new means of observing the universe have enabled us to find new phenomena that we had not anticipated and to give us new ways to examine previously known phenomena.\n\nStay tuned -- there is an official announcement at 10:30am EST (15:30GMT) on 11 February, at which point we will all know whether the rumors are true that gravitational waves have been observed and, if so, exactly what has been seen.\n",
"We have already observed neutron star orbits changing due to gravitational radiation. The direct observation of the radiation would allow us to verify that General Relativity works even for very strong, very rapidly changing fields. It is a sensitive test of the smallest details of the theory.",
"Not an explanation, but somewhat related: The European Space Agency has just launch Lisa Pathfinder, a demonstrator which should prove that we have the technology to prove the existence of gravitational waves. If successful the real experiment will take place in a few years. You can find more information here: _URL_0_",
"I don't understand the mystery here. How, if not by a wave, can a change in a field here propagate to there? We know from SR that it can't be instantaneous and that leaves only one other option, a wave.\n\nThe important question is not whether there are waves but whether they propagate as described by Einstein's field equations and there is no way the detection anticipated here can begin to verify that."
]
}
|
[] |
[] |
[
[],
[],
[
"http://sci.esa.int/lisa-pathfinder/"
],
[]
] |
|
f5nmxn
|
Can anyone tell me about African-American sailors on whaling ships in the early nineteenth century?
|
I'd pretty much be interested in anything you happened to know: were there any? If so were there many? Did they face discrimination (I believe black sailors in the Royal Navy at that time mostly had to work as cooks, and other lesser paid work)? Were any slaves? Are there any notable examples? Also, in honour of the black history theme, how about black sailors in general (African? Carribean?) on American ships?
When I say 'early 19th century', I'd be more interested the closer the information is to the 1810s, but I'm not too fussed if it's a long time later or earlier.
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/f5nmxn/can_anyone_tell_me_about_africanamerican_sailors/
|
{
"a_id": [
"fi2i7i0"
],
"score": [
10
],
"text": [
"That sounds like a worthy topic for a book. Conveniently, someone has already written one: *Black Jacks: African American Seamen in the Age of Sail* by W. Jeffrey Bolster. It's also discussed in *The Many-Headed Hydra* by by Peter Linebaugh and Marcus Rediker, although I can't really recommend that book.\n\nBut while you are waiting to get *Black Jacks* from your nearest library, I can endevour to answer some of your questions. Yes, there were African-American sailors, and plenty more sailors on American vessels that were African but not American. Many were enslaved, but most were free. The enslaved sailors mostly served on \"coaster\" vessels in the South, because it's very difficult to keep a sailor from \"jumping ship\" whenever it makes port, and in the North as well as most of Europe, an enslaved sailor that escaped into the port city was never going to be returned to the slaveowner. Only in the South (and the Caribbean, while slavery was practiced there) could a slave not disappear into the city and become free. \n\nAs for notable examples, the one that springs to mind is Robert Smalls. There's plenty of articles about him online if you wish further reading, but in short he was a slave who became a pilot and helmsman in the Charlotte, NC harbor. When the Civil War broke out, he was working on the *CSS Planter*, a small Confederate Navy cargo ship. One night when the (white) officers were ashore, he and the rest of the (enslaved) crew loaded their families aboard the *Planter* and sailed out of the harbor and surrendered the ship and themselves to the Union blockade force. He went on to have more Civil War adventures and then a post-war business and political career. \n\nAs for whaling specifically, there were many African-American sailors on them, and they generally had the same duties and responsibilities as other hands, although I'm not aware of any of them becoming officers. (I'm not saying it didn't happen, I just can't recall any examples.) I'm not aware of any being slaves, and in fact I doubt it strongly because the American whaling industry was dominated by New England Quaker families, and abolition ran strong in their communities. But so did greed, and that lead to an unfortunate side of the whaling industry. \n\nThe importation of slaves into the USA was banned in 1808. Subsequently, the legal increase in the slave population was by reproduction. But it was still very profitable to import new slaves from Africa. It was difficult to do so in a typical cargo ship, though, because it takes special accoutrement to transport slaves. Normally a cargo ship has large empty holds below deck for convenience in loading and unloading; a slave ship needs multiple low wooden decks in the hold, the better to pack in sufficient human cargo to turn a profit. Second, a ship's galley was sufficient to cook food for the crew of perhaps one or two dozen, but there was no way it could produce sufficient cooked food for hundreds of slaves. Slave ships carried a large cauldron to boil of sufficient food, and such a cauldron was too large to hide and had no legal purpose on a cargo vessel. Except... a whaling ship made its money from whale oil. That whale oil was rendered out of whale blubber on board by means of, guess what, a large cauldron (or two). Plus, a whaling ship would leave port with lots of sawn wood, that during a whaling voyage the ship's carpenter would turn into barrels to hold the oil they gained. But that wood could just as easily be turned into the internal decking necessary to hold slaves. The final thing needed was the chains to secure the slaves, but those could be purchased at the slave trading forts, although for a much higher price. For all those reasons combined, most of the illegal slave importation by American ships between 1808 and 1860 was on whaling ships.\n\nFinally, circling back to whaling, by the 1800s whaling voyages typically lasted several years and covered thousands of miles. They would pick up additional crew as needed at any port they happened to be at, and thus whaling ships ended up as a motley mix of men. There's documentary evidence of it, because every ship leaving an American port for a whaling voyage had to submit a \"List of Persons\" document to the customs house, which listed all the crew by name, place of birth, places of residence, age, height, complexion, and hair color. Races can be inferred from the listed complexions: people we would consider white are called \"fair\" or \"dark\", while blacks were \"mulatto\" or \"black\" and asians were \"yellow\"."
]
}
|
[] |
[] |
[
[]
] |
|
1hhdhg
|
Would someone who completely loses their sight in their lifetime see blackness? Or is it similar to those born blind where they percieve absolutely nothing
|
askscience
|
http://www.reddit.com/r/askscience/comments/1hhdhg/would_someone_who_completely_loses_their_sight_in/
|
{
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"caufzzo",
"cauheb1"
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34,
5,
2
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"text": [
"People that were blinded later in life do see blackness. But being blind from birth has a different result. Think of it this way: People blind from birth see the same thing that you see out of your elbow; literally nothing. They do not have a conception of sight.",
"If the blindness is due to damage to the brain, it is more similar to someone born blind. \n\nThe eyes collect information, the brain interprets that information. This is a skill that must be learned - and it can be \"forgotten\" completely or in part, due to stroke or other brain trauma.\n\nI have a family member that lost vision due to a stroke. She says the missing areas are \"like the back of my head.\"",
"I was temporarily blind due to a concussion. From what I remember, it was not like being in a dark room. There was no sensation of vision at all. "
]
}
|
[] |
[] |
[
[],
[],
[]
] |
||
2yrsoc
|
Tidal forces on Enceladus generates heat through friction, hence liquid oceans, but where exactly does the energy in that heat come from?
|
Is this what is meant by "tidily locked" orbits, because the friction slows the rotation? If so how long does Enceladus have before its liquid ocean freezes?
|
askscience
|
http://www.reddit.com/r/askscience/comments/2yrsoc/tidal_forces_on_enceladus_generates_heat_through/
|
{
"a_id": [
"cpd7rao"
],
"score": [
2
],
"text": [
"The energy is taken from Saturns angular momentum (the rotational energy). [This video](_URL_0_) explains in a very intuitive way how tides work and how their effects are caused. \n\nI want to add that the tides on Enceladus work even tho it already is tidally locked. That is, because the eccentricity of its is still big enough to cause enough friction. The angular momentum of Saturn is vast, especially compared to such a small body like Enceladus. It would take Enceladus many many billions of years to lock Saturns rotation, if not more. "
]
}
|
[] |
[] |
[
[
"https://www.youtube.com/watch?v=KlWpFLfLFBI"
]
] |
|
2cjn4r
|
i'm in vancouver, bc, it is 4pm and i can obviously see the sun, but also the moon. can people of the direct opposite side of the earth see the moon aswell? or are they experiencing night with no moon?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/2cjn4r/eli5im_in_vancouver_bc_it_is_4pm_and_i_can/
|
{
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18,
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"text": [
"The amount the moon is lit (its phase) is determined by where it is in its orbit, which takes 28 days. Thus the entire earth experiences full moon on the same day, new moon on the same day, etc. What changes for each location on earth is the rise and set times of the moon. If it is within view of you, it is not within view of the opposite side of the earth -- they'll see it after it sets where you are. Because the moon is moving in its orbit, the time it rises and sets as seen from a particular location on earth changes slightly every day.\n\nAt least, I'm pretty sure that's how it works.",
"They are indeed experiencing a night with no moon. ",
"To piggyback by asking differently\n\n\nIs the angle of the sun and angle of the moon significantly bent by the atmosphere? That is, if the moon is 45 degrees above the horizon due east...does that actually mean traveling up at a 45 degree angle due east would get me near the moon?",
"You will be experiencing a night with no moon in two weeks' time. It is nothing unusual. The moon is only visible for half of the time.",
"Sidenote, Vancouver represent.",
"They are in the middle of the southern Indian Ocean waaay the fuck off of Madagascar. They are experiencing 4am and right now cannot see the moon. Almost just like you, earlier in the day at 4pm they saw the sun and moon in almost exactly the same positions as you see them now. For them the sun went down around 8:50pm with the moon still in the sky, and then the moon went down a few hours later, around midnight, and left them with a moonless sky just as you will experience in a few more hours. You are at 49° N in latitude, so they are at 49° S which means it is winter there, and probably cloudy so actually they can't see shit."
]
}
|
[] |
[] |
[
[],
[],
[],
[],
[],
[]
] |
||
4cmbtt
|
if cis-gender just means you identify with as your biological gender, why is it used as a slur
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/4cmbtt/eli5_if_cisgender_just_means_you_identify_with_as/
|
{
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"d1jgep7",
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6
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"text": [
"Technically anything can be used as a slur if you put enough hatred behind how you say it.\n\nFor example people who don't want children will often refer to people who have them as Breeders. Nothing offensive in the word itself, but in context they mean someone who just keeps popping out offspring with no real goal aside from popping out offspring. \n\n",
"It's not used as a slur, per se. It's used, much like when someone brings up white privilege, to point out that the \"cis-gendered\" person may not have the worldview necessary to ~~understand~~ readily recognize the problem or plight. For instance, it might take a \"cis-gendered\" person a moment of serious thought to really understand why choosing a bathroom is an important issue for trans-gendered individuals.\n\nAs an aside, while I'm a huge proponent of trans-gendered rights, I myself have never really undsrstood why some in the movement seem stuck on the cis/trans dichotomy other than to use it as an identity touchstone. Science continues to prove that gender isn't binary and no one fits the prototypical man or woman (making us all, to some degree trans-gendered). Further, substituting one binary standard (male/female) for another (cis/trans) seems counter-productive. But arguments of \"No, really, we're just like you\" aren't as powerful as \"We're different and should be a special, protected class\".\n\nSo, while some use it as a slur, take it as you want to take it. Don't let the nonsense get in the way of the message or the support."
]
}
|
[] |
[] |
[
[],
[]
] |
||
3gcxrx
|
difference between bombs, missiles, rockets and other large propelled munitions?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/3gcxrx/eli5_difference_between_bombs_missiles_rockets/
|
{
"a_id": [
"ctwyk86"
],
"score": [
6
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"text": [
"Bombs aren't self-propelled.\n\nIn the military, a missile is a self-propelled munition that is guided. A rocket is unguided. "
]
}
|
[] |
[] |
[
[]
] |
||
1r0quc
|
why does our skin leave white marks when we scratch or get scratched?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/1r0quc/eli5_why_does_our_skin_leave_white_marks_when_we/
|
{
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"text": [
"The skin is made up of several layers and the top layer is dead (gross right?). Well when you scratch you're scraping a bit of the layer off. This layer is slightly transparent so appears white when not in direct contact with the lower layers.\nHope this helps.",
"The skin is being ripped and torn and is now rough. Notice if you rub the scratch with your finger the white goes away. That is the loose skin falling off and some of it being laid smooth again.",
"I think OP means why are there subcutaneous white marks, not white marks on the surface.\n\nGood question!",
"Are you talking about the raised lines left behind after scratching like in this picture? (but hopefully to a lesser degree)\n\n_URL_1_\n\nThese are called wheals (or weals, both are correct spelling but wheals is more common). They are due to a local histamine-induced inflammatory response and go away in about 24 hours. When you scratch hard enough, mast cells (a type of immune cell) located just under the skin break open, releasing their stored histamines. As you may know, histamines are involved in allergic reactions and induce local inflammation among other things. Normally, mast cells release their histamines when they come across an allergen. But you can physically break them open by... scratching hard enough. Wheals also arise when, say, someone touches poison ivy, gets bitten by a mosquito, or consumes a substance that he is allergic to and develops hives (urticaria).\n\n_URL_0_\n\nThe above (Hello) picture is an example of someone with dermatographic urticaria, a rare skin disorder in which very little physical stimulation is needed to disrupt the membranes of the mast cells.\n_URL_2_\n***\nI doubt you're talking about these but:\n\nIf you are talking about the subtle white marks that are only there for a few seconds at most after scratching, that is simply because the pressure of scratching has pushed the blood from that area of skin and it has to flow back.\n\nOr if you're talking about permanent white lines left in the skin after scratching enough to draw blood, those are scars.",
"Cause you ashy nigga"
]
}
|
[] |
[] |
[
[],
[],
[],
[
"http://en.wikipedia.org/wiki/Cutaneous_conditions",
"http://d1535dk28ea235.cloudfront.net/preset_64/2794959104_94d08ff79f.jpg",
"http://en.wikipedia.org/wiki/Dermatographic_urticaria"
],
[]
] |
||
3gihtf
|
Why do humans like to be popular?
|
If this isn't an appropriate place to ask, please let me know and tell me where to post it.
I'm talking more on a neurological level. What's the point of it? Why do humans like it?
|
askscience
|
http://www.reddit.com/r/askscience/comments/3gihtf/why_do_humans_like_to_be_popular/
|
{
"a_id": [
"ctyyaj9"
],
"score": [
3
],
"text": [
"Humans are social animals and our very survival depends on cooperation and coordination with other humans, especially in the environment we originally evolved in. Social dynamics create a \"pecking order\" within a group, and it is advantageous to an individual (or more accurately, their genes) to be as high as possible in this status or \"popularity\" ranking. Thus there has been a selection pressure to create a drive to gain high status."
]
}
|
[] |
[] |
[
[]
] |
|
qylmf
|
If you impregnated yourself would it be a clone of you?
|
askscience
|
http://www.reddit.com/r/askscience/comments/qylmf/if_you_impregnated_yourself_would_it_be_a_clone/
|
{
"a_id": [
"c41j244"
],
"score": [
2
],
"text": [
"Nope. Keep in mind you have 23 pairs of chromosomes and the mother and father each pass down half of theirs, i.e., 23 individual chromosomes, because of meiosis; one of each pair is selected essentially at random. What you'd end up with is some chromosomes which actually *were* copies of your DNA, i.e., one of each of your two corresponding chromosomes. But in some places you'd end up with two copies of the same chromosome instead.\n\nAnd actually, there's a process called *crossing over* which actually mixes the chromosomes during crossing over, so in actuality some *segments* of chromosome pairs would be cloned, and some *segments* would be \"doubled\"."
]
}
|
[] |
[] |
[
[]
] |
||
1fn1a1
|
How was life in the Japanese puppet-state Manchukuo compared to life in China at the time?
|
The Japanese seemed to have invested a lot of infrastructure in Manchukuo like they did in Taiwan. Did this translate into a higher standard of living compared to the rest of China?
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/1fn1a1/how_was_life_in_the_japanese_puppetstate/
|
{
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"cabxo8e"
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16
],
"text": [
"That depended very much on whether you were ethnically Chinese, a recently arrived Japanese or Korean settler, or for that matter a Manchu or Mongol.\nMost Chinese remained farmers or took on other menial work in the cities, with a standard of living similar to that of their compatriots in free China. Meanwhile, new economic opportunities and infrastructure were primarily enjoyed by the Japanese, who of course also \"acquired\" prime farmland. These disparities, and the reality of occupation by Japan's Kwantung Army, led to quite determined partisan resistance throughout the 1930's, which the army suppressed in a frankly brutal fashion. The parallell with Taiwan doesn't quite hold, since Northeast China was taking steps toward industrialization before Japan occupied it, whereas Taiwan's economic development was an entirely Japanese initiative."
]
}
|
[] |
[] |
[
[]
] |
|
g437c
|
Nuclear meltdown leading to critical mass?
|
A friend of mine has said that if uranium rods in a damaged nuclear power plant meltdown, the uranium can pool together and reach a critical mass, causing an explosion. Is there any possibility of this actually happening? If so, what would the exact effects be?
|
askscience
|
http://www.reddit.com/r/askscience/comments/g437c/nuclear_meltdown_leading_to_critical_mass/
|
{
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"text": [
"No, there is not enough uranium in a rod to create a nuclear explosion.",
"The fission chain reaction was stopped when the reactor was SCRAMed following the earthquake. But if all the rods melt, and the fuel pools at the bottom of the reactor, it could go critical again. This would lead to the generation of more heat, and exacerbate the problems they are already facing with heat removal. The core could also melt through the containment.\n\nThe heat could cause an explosion, but not a nuclear explosion. If the water were to flash to steam very quickly, you have a large pressure increase which could cause a steam explosion. Or oxidation of the zirconium cladding could produce hydrogen, leading to a hydrogen explosion.",
"No, you need a much higher enrichment level than a commercial fuel rod to get that.",
"this was a fear after chernobyl, the if the fuel pellets spilled out of the rods and pooled near the bottom that you could have a critical mass. now by critical mass i mean a sustaining nuclear chain reaction, not an explosion. (maybe the better term is that you can have an uncontrolled criticality in the reactor)\n\nto prevent any chance of that happening they are injecing boron into the reactors with problems. boron is a powerful neutron poison and will prevent any inadvertant criticalities."
]
}
|
[] |
[] |
[
[],
[],
[],
[]
] |
|
17j1nb
|
how do wars and eras get their names?
|
Like the Middle Ages and such. Also what will the modern era be known as in the future?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/17j1nb/elif_how_do_wars_and_eras_get_their_names/
|
{
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"text": [
"Generally speaking wars are named after the combatants, the Vietnam war, the Iran/Iraq war. \n\nSometimes named after the year it takes place in \"War if 1812\".\n\nThey can be named by how long the war lasted \"The Seven Years War\".\n\nHow do era's get their name? It is a process called Periodization, where historian split up history into smaller and more manageable blocks in order to make it easier to understand. They often use a defining point in that block to name it, such as the Bronze Age, when humans began to use bronze tools.",
"Wars, until recently, didn't get a common name until long after the war was over. Take the American Civil War for example. If you had talked to some older people a generation or so ago, they would have learned in school that the war was called: The War Between the States; The War of Northern Aggression; The War of Southern Rebellion; and The Second War for Independence (as you could guess, I grew up in the American South.)\n\nWorld War I had the same identity crisis. At the time it was being conducted, the war was referred to as: The Great War; The War to end all Wars; and, some forward thinking writers referred to it as The First World War. It was not commonly referred to as World War I until after WWII had begun. \n\nThe Hundred Years War was obviously not called that at the commencement of the hostilities. It was later called the Hundred Years War*, because, well, math was not an important subject in school.\n\n*Ok, I know it was because it combined a lot of shorter wars that covered the era, but it did last more than 100 years and you think someone would have noticed. "
]
}
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[] |
[] |
[
[],
[]
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1xrpfs
|
why is the phone "tone" what it is?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/1xrpfs/eli5_why_is_the_phone_tone_what_it_is/
|
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"Are you asking why a dial tone is set to a specific Hz and dB level? \n\nOr, are you asking what function a specific tone does at a telco layer?"
]
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[] |
[] |
[
[]
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||
nrbv6
|
When you break a magnet in half, why do the two pieces repel where they broke?
|
It just seems counter intuitive.
|
askscience
|
http://www.reddit.com/r/askscience/comments/nrbv6/when_you_break_a_magnet_in_half_why_do_the_two/
|
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"They shouldn't. The break should create new north and south poles, which should attract. \n\nThere could be a geometry of magnet that would repel when broken. Can you describe what you observed in more detail?",
"Well, in a magnet you have atoms and molecules (usually iron) that line up in one specific direction; they line up in groups called [magnetic domains](_URL_0_). Each individual atom has a a small amount of magnetism and when they all line up they form macroscopic magnetism. Let's represent domains by arrows:\n\n\n→ → → → → → → → → → → → → → → → → → → → → → → → → → →\n\n → → → → → → → → → → → → → → → → → → → → → → → → → → → \n\n(The arrows are pointing to the south pole)\n\n\nIf you split this you still end up with two magnets that will likely be weaker due to some of the domains getting scrambled and the decrease in domains but the majority of them still point in a the same direction and thus each new magnet still has a north and south pole.\n\nA\n\n→ → → → → → → → → → → → → → \n\n→ → → → → → → → → → → → → →\n\nB\n\n → → → → → → → → → → →\n → → → \n\n → → → → → → → → → → → → → → \n\n\nEDIT: I completely misread the question, the two pieces that would fit in like a jig saw should attract since they are of opposite polarity.\n\n",
"If you break the magnet along a line perpendicular to the axis of magnetization, the two pieces should attract because they become opposite polarities.\n\nHowever, if you break it along a line parallel to the axis of polarization, you end up with two magnets whose north poles and south poles are directly beside one another and so should repel. ",
"If you continue down past the turtles on turtles to the electrons, you'll find that *they themselves* are magnetic dipoles.\n\n---\n\nThere are theories about the presence of monopoles but we have yet to find the particles themselves. [Dirac was the first to write compellingly of their existence](_URL_0_) (regarding quantum magnetism--basically, before him, the charge used in quantum mechanics was just a \"given\" value) and to summarize, the reason electric charge is a physical constant for protons and electrons (±*e*, ±2*e*, etc.) is because of monopole existence *somewhere* in the universe.\n\nThe biggest problems with \"finding\" monopoles is that they're potentially so rare in the universe that a detector would basically *never* encounter one and that they're likely too massive for a particle accelerator to create.",
"You split it vertically instead of horizontally.",
"They shouldn't. The break should create new north and south poles, which should attract. \n\nThere could be a geometry of magnet that would repel when broken. Can you describe what you observed in more detail?",
"Well, in a magnet you have atoms and molecules (usually iron) that line up in one specific direction; they line up in groups called [magnetic domains](_URL_0_). Each individual atom has a a small amount of magnetism and when they all line up they form macroscopic magnetism. Let's represent domains by arrows:\n\n\n→ → → → → → → → → → → → → → → → → → → → → → → → → → →\n\n → → → → → → → → → → → → → → → → → → → → → → → → → → → \n\n(The arrows are pointing to the south pole)\n\n\nIf you split this you still end up with two magnets that will likely be weaker due to some of the domains getting scrambled and the decrease in domains but the majority of them still point in a the same direction and thus each new magnet still has a north and south pole.\n\nA\n\n→ → → → → → → → → → → → → → \n\n→ → → → → → → → → → → → → →\n\nB\n\n → → → → → → → → → → →\n → → → \n\n → → → → → → → → → → → → → → \n\n\nEDIT: I completely misread the question, the two pieces that would fit in like a jig saw should attract since they are of opposite polarity.\n\n",
"If you break the magnet along a line perpendicular to the axis of magnetization, the two pieces should attract because they become opposite polarities.\n\nHowever, if you break it along a line parallel to the axis of polarization, you end up with two magnets whose north poles and south poles are directly beside one another and so should repel. ",
"If you continue down past the turtles on turtles to the electrons, you'll find that *they themselves* are magnetic dipoles.\n\n---\n\nThere are theories about the presence of monopoles but we have yet to find the particles themselves. [Dirac was the first to write compellingly of their existence](_URL_0_) (regarding quantum magnetism--basically, before him, the charge used in quantum mechanics was just a \"given\" value) and to summarize, the reason electric charge is a physical constant for protons and electrons (±*e*, ±2*e*, etc.) is because of monopole existence *somewhere* in the universe.\n\nThe biggest problems with \"finding\" monopoles is that they're potentially so rare in the universe that a detector would basically *never* encounter one and that they're likely too massive for a particle accelerator to create.",
"You split it vertically instead of horizontally."
]
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[] |
[] |
[
[],
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"http://en.wikipedia.org/wiki/Magnetic_domain"
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"http://users.physik.fu-berlin.de/~kleinert/files/dirac1931.pdf"
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|
31dbd7
|
Why do I only have 2 nipples when my cow has 4?
|
I mean. All animals are quite similar. 4 legs, 2 eyes, 2 ears, 1 nose and so on. But when it comes to nipples, everything goes. Cows have 4 (or is it one giant nipple with 4 holes?), monkeys have 2, dogs have 6 or 8. Did we lose our extra nipples along the way, or did the others suddenly gain some?
|
askscience
|
http://www.reddit.com/r/askscience/comments/31dbd7/why_do_i_only_have_2_nipples_when_my_cow_has_4/
|
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"It's a function of the number of offspring per litter. Mammals with larger litters tend to have more nipples than those with fewer litters, with a minimum of two to maintain bilateral symmetry. Mammary gland formation and milk production are pretty energy intensive activities so evolution will favor the activity that uses the fewest resources to maintain the species. (ie: higher food chain species like primates and horses on one side of the spectrum with 2, lower food chain species like rats, mice and pigs on the other with 10-18) I can't find any research as to how many nipples the 'first' lactating animal had, and that's largely because we don't know how the nipple first came about. Several species known to have existed before the mammal show how the current mammalian nipple may have evolved, but each would imply a different number of original nipples. ",
"Yes we did lose extra nipples along the way. there is a rare \"birth defect\" when humans actually have more then two nipples. See here\n_URL_0_\n\nas to why we have two. It does seem that the number inversely correlates with the size of the litters but as you pointed out in the case of cow not perfectly. This is a wild guess but may be it is due to \"a family structure\" in ruminants - when you are in a herd you have many babies around while the mother could have been eaten by a passing by bear, so it was advantageous to have an extra breast around.\n\nPS. I just checked it : whales who also typically have one baby that remains attached to the mother for a very long time also have only two nipples\n"
]
}
|
[] |
[] |
[
[],
[
"http://www.medscape.com/viewarticle/410464_3"
]
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|
e12vc1
|
Floating Feature: All the World is a Stade, so what will you share upon it from 776 to 202 BCE? Its Vol. II of 'The Story of Humankind'
|
AskHistorians
|
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"You've probably heard of the time a bunch of Spartans fought to the death against Xerxes. But have you heard of the two times Spartan armies were defeated by women?\n\nThe first case involves the early Spartan king Charilaos, who may or may not be a historical figure. Allegedly, he was persuaded to invade neighbouring Tegea, thinking it would be easy for the Spartans to capture the city and its territory and enslave the Tegeans. But they were warned of his approach and prepared to defend themselves:\n\n > At the time of the Lakonian war, when Charilaos king of Sparta made the first invasion, the women armed themselves and lay in ambush under the hill they call today Phylaktris (\"Sentry Hill\"). When the armies met and the men on either side were performing many remarkable exploits, **the women, they say, came on the scene and put the Lakedaimonians to flight.** Marpessa, named the Sow, surpassed, they say, the other women in daring, while Charilaos himself was one of the Spartan prisoners.\n\n-- Pausanias 8.48.4-5\n\nThe second case happened about 494 BC, when the Spartans under king Kleomenes annihilated the Argive army at the battle of Sepeia and tried to seize the city:\n\n > When Kleomenes led his troops to Argos there were no men to defend it. But Telesilla mounted on the wall all the slaves and all those who were too young or too old to bear arms, and she herself, collecting the arms in the sanctuaries and those that were left in the houses, armed the women of vigorous age, and then posted them where she knew the enemy would attack. When the Lakedaimonians came on, **the women were not dismayed at their battle-cry, but stood their ground and fought valiantly.** Then the Lakedaimonians, realizing that to destroy the women would be an invidious success while defeat would mean a shameful disaster, gave way before the women.\n\n-- Pausanias 2.20.8-9\n\nBoth stories come to us through Pausanias, an author of the Roman Imperial period who was mostly interested in reporting local traditions that explained the statues and sanctuaries he saw on his tour of Greece. We don't really know how much of these stories are history and how much is self-aggrandizing legend. Both are associated with oracles already reported by Herodotos and rely on alternative readings of those oracles, possibly reflecting later local \"corrections\" to the stories he told. But it's certainly a nice thing to point out to modern people who are a little too excited about the Spartans as unstoppable manly men ;)",
"Well, I might as well share a classic story of one of the most influential, if not the most, influential person of this time period—Alexander the Great. When he was fighting at the famous Battle of the Granicus against Greek mercenaries, Persian light infantry, and the Persian heavy cavalry, he (as always) fought up close in the battle. On his horse, he used what was believed to be an actual ancient Trojan shield. While on horseback, his shield was knocked away, and he was stabbed by a Persian in the back of the skull; the Persian sword went THROUGH Alexander’s helmet, and cut his scalp. Alexander was phased, and a Persian came up from behind him on horseback and was about to kill King Alexander with his sword. At the last second, Alexander’s bodyguard Cleitus the Black severer the Persian’s arm. Alexander would later go on to get in a drunken fight with said bodyguard where he threw a javelin through his heart. Alexander really did seem immortal.",
"**The Karatepe and Çineköy inscriptions: Luwian and Phoenician and Sea Peoples, oh my!**\n\nExcavations in 1947 at the site of Karatepe in northeastern Cilicia (southern Turkey) uncovered a citadel with two monumental gates. Each of the gates had a copy of a Luwian and Phoenician bilingual inscription, as did a fragmentary statue of the Storm God. The Phoenician inscription ran along the left side of each gate, and the Luwian inscription ran along the right side. The Luwian inscriptions are written with the syllabic [Anatolian hieroglyphic](_URL_0_) writing system, and the Phoenician inscriptions use the Phoenician alphabet. \n\nThe Phoenician inscription is best preserved on the North Gate. This inscription is more or less complete and consists of 62 lines and 1390 characters, making it the longest Phoenician inscription yet discovered. The Luwian inscription is also well-preserved, though some confusion arises from the effect of fractures and faults in the rock on small strokes such as word-dividers. Unlike the Phoenician texts, the Luwian inscriptions were carved on [bases, orthostats, and portal sculptures](_URL_2_) rather than [consecutive undecorated blocks](_URL_3_). Fortunately, all of the blocks were discovered *in situ* except three from the North Gate.\n\nThe [Çineköy inscription](_URL_1_) was discovered in 1997 by O. Kadir Özer at Çineköy near modern Adana in Cilicia and was first published in 2000 by Recai Tekoglu and André Lemaire. The inscription was carved on the base of a large statue of the Storm-God depicting him driving a chariot pulled by bulls. The Çineköy inscription is relatively brief, and only the first twelve clauses survive.\n\nThe Karatepe inscription begins with a discussion of the background of the dedicator. The man responsible for the construction of the gates and the statue was Azatiwada, who belonged to the Sun God and was the servant of the Storm God (§1). Azatiwada notes that he was \"made great\" by Awariku, the king of Adana (§2). The text then continues with a discussion of the deeds of Azatiwada, who caused the city of Adana to prosper and extended it to the east and west (§4-6), increased military strength (§8-10), and eliminated threats to the kingdom (§11-13). Azatiwada \"seated [the offspring of my lord] on his paternal throne\" (§16), and \"every king\" made Azatiwada his father on account of his justice and good heart (§18). He built fortresses along remote portions of the borders \"not under the house of Muksas\" (§19-21) and built the city of Azatiwataya (§39) for Tarhunt and the house of Muksas (§58). The text concludes with the traditional curses against the removal or damaging of the inscriptions.\n\nLike the Karatepe inscription, the Çineköy inscription begins with the introduction of the dedicator of the statue. The statue was dedicated by Warikas, the son of a king whose name is not preserved, and the grandson of Muksas (§1). Muksas (*mu-ka-sa-si-sa*) is described as the king of the Hiyawaeans (*hi-ia-wa/i-sa-ha-wa/i*) and the servant of the storm god Tarhunzas. Like Azatiwada, Warikas claims to have extended the boundaries of his territory (§2) and built up military strength (§3-4). Unlike Azatiwada, however, Warikas makes explicitly mentions his association with Assyria. \n\n > REL-*p[a]-wa/i-mu-u su+ra/i-wa/i-ni-sa*(URBS) REX-*ti-sá su+ra/i-wa/i-za-ha*(URBS) DOMUS-*na-za ta-ni-ma-za tá*-[*ti-na* MATER-*na-ha*] *i-zi-ia-si* \n\n > *hi-ia-wa/i-sa-ha-wa/i*(URBS) *su+ra/i-ia-sa-ha*(URBS) ”UNUS”-*za* DOMUS-*na-za i-zi-ia-si*\n\n > The king of Assyria and the house of Assyria became father and mother to me, and Hiyawa and Assyria became one house.\n\nKing Awariku/Warikas is known from Assyrian records, where he is recorded as Urikki, the king of Que, and dates to the last decades of the 8th century BCE. Urikki is mentioned in the records of Tiglath-Pileser III as supplying tribute from 737 BCE onwards. A couple of decades later, a letter from Sargon II was sent to the Assyrian governor in Que, Aššur-šarru-uṣar, and recounted how a messenger of Midas of Phrygia - well-known in mythology as Midas of the golden touch - brought him fourteen men of Que who had been dispatched by Urikki on a diplomatic mission to Assyria's rival Urartu. Sargon II seized fortresses controlled by Que in 715 BCE, but no punitive actions against Urikki himself are described, suggesting that Urikki had either fled or been quietly killed or removed from power. \n\nMuksas, the ancestor of Awariku, has been identified with the legendary Mopsos. According to the Greek geographer Pausanias, Mopsos sailed from Crete and founded a kingdom in Cilicia. It seems that Mopsos was indeed a name in use during the Late Bronze Age; line §33 of the \"Indictment of Madduwata\" (a Bronze Age Hittite text) references a *Mu-uk-su-us*, but the text is too fragmentary to determine what role he was playing in Aegean or Anatolian affairs. Additionally, the name *mo-qo-so* is attested in two Linear B tablets from Knossos. Moreover, Anna Jasink has argued persuasively for a connection between Rhakios, the father of Mopsos, and (A)warikas. Although the latter is said to be a descendant of Mopsos, royal names were frequently recycled.\n\nGiven that the legendary Mopsos came from Crete, one would expect that the historical Muksas originated in the Aegean, and this seems to have been the case. Awariku's land of Hiyawa has been equated with Aḫḫiyawa, the Bronze Age Hittite toponym for the Mycenaean Aegean. Hiyawa seems to have morphed over time into the Que of Assyrian records. A distinction should be drawn between the country of Hiyawa/Que and the city of Adana. The Luwian toponym Adana(wa) seems to have been adopted from an ethnonym, Adanawani. This was rendered *dnnym* in the Phoenician portions of the Karatepe and Çineköy inscriptions. It has been tentatively suggested that this group should be identified with the Denyen known from Egyptian records, one of the many groups of \"Sea Peoples.\" The group may also be identified with the Homeric Danaoi. \n\nThe discovery of Mycenaean pottery assemblages in Cilicia supports the idea that a branch of the Sea Peoples or a group dispossessed by the Sea Peoples settled in Cilicia during the Early Iron Age. Although the presence of Mycenaean pottery at a site is insufficient evidence for the presence of Mycenaeans, as Mycenaean vessels were popular trade items, the majority of the Mycenaean vessels recovered from Tarsus were regular household vessels used for food preparation and consumption. Such cooking wares are less likely to have been imported than luxury wares, and petrographic analysis indicates that the pottery was locally produced. Most of the Mycenaean pottery belongs to the Late Helladic IIIC corpus and therefore dates to the early twelfth century BCE. \n\nBased on these bilingual inscriptions and other historical and archaeological evidence dating to the end of the Late Bronze Age, one can tentatively propose a settlement in Cilicia in the Early Iron Age, possibly after the destruction or collapse of preexisting polities, by a group of dispossessed individuals, most likely from the Aegean. In a similar fashion, the Luwian inscriptions from the temple of the Storm God at Aleppo (ca. 1100 BCE) were dedicated by the king of the \"land of Palistin,\" most likely associated with the Peleset of the Egyptian \"Sea Peoples\" inscriptions.",
"This week I'm writing about the Etruscans, members of a civilization that existed from roughly 900 BCE to the first century BCE, which makes them a perfect subject for this post's time period.\n\nThere’s little popularly known about the Etruscans in general – they’re an obscure Italic people. One tidbit that gets passed around from contemporary Greek commentators like Aristotle and Athenaeus is that they were very accepting of public nudity and sex, throwing orgies and shaving their bodies in a “barbarian” fashion. Some other, related ideas were that Etruscan women were on an equal footing with men (in a bad way), and that Etruscan men were happy to raise their wives’ children regardless of their biological fathers.\n\nSome Greek observations about Etruscan women may have been based on simple fact, but the conclusions they made likely reflected their own biases. Tomb paintings and sculptures depicting banquets, for instance, show Etruscan women reclining on couches alongside their husbands – something that was not a staple of Greek social life. To the commentators, the only women who would be present at an event where men were drinking and enjoying themselves were slaves and sex workers (though the line between them was ever so thin), which meant that obviously even free and well-born Etruscan women were like sex workers, which meant that Etruscan society was untethered to any standards of sexual respectability. \n\nWhile “an equal footing” might be too much speculation, surviving material culture does bear out the idea that Etruscan women had much greater power and importance than contemporaneous Greek women (not that that is a high bar to clear). Even beyond their banquet seating, there is evidence of some sort of civic position (*hatrencu*) that they could hold, and of matronymic names that preserved a certain amount of information about an individual’s maternal ancestry. Etruscan art also focused a lot on weddings and happy couples, even ones that were certainly not depicted as very ideal in Greek myth – Zeus and Hera, Hades and Persephone, Paris and Helen.",
"Well how can I not talk about my favorite years when the opportunity presents itself. 522 BCE ladies and gents. The story begins on March 11, or 14 Viyaxana in thr Achaemenid Persian calendar, 16 days before the Persian New Year. On that day, Bardiya - the crown prince and younger brother of the Great King, Cambyses - \"raised a rebellion\" in a town just outside of the palace complex of Pasargadae. Cambyses was busy in the west wrapping up the first Persian conquest of Egypt. \n\n\nThe Persian Empire was growing increasingly rebellious under royal tribute and conscription that had sustained almost 30 years of continuous expansion. Bardiya was apparently trying to right the ship and prevent full scale revolt from his brothers leadership. Cambyses got news of this on his way back from Egypt, but never confronted his brother. He was injured en route back to Persia and died of an infection. \n\n\nBut there's a catch. According to all of our sources, it wasn't actually Bardiya. It was a Magi (a Median religious class/tribe) named Gaumata. Gaumata had been impersonating the crown prince since Cambyses had his brother assassinated years earlier. Thus the new King of Kings after Cambyses' death was not only a rebel, but illegitimate. Despite universal agreement by ancient sources, scholars have questioned this story since at least the 19th century. \n\n\nRegardless of his true identity, I call him Bardiya because that's the name he used on the throne and can account for either the real prince or Gaumata. Bardiya was properly coordinated on July 1 (9 Garmaparda). In his time on the throne, Bardiya stabilized the empire at large but alienated a lot of the nobility who had benefited from Cambyses aggressive taxes, seized some of their property, and executed others. \n\n\nIn the later months of his reign a group of seven nobles coalesced around Otanes and Darius, disgruntled distant cousins to the royal family. Darius lead them in a coup against Bardiya. On September 29 (10 Bagayadish) They forced their way into a royal palace outside of Ecbatana in Media and attacked Bardiya in person. They killed him there and Darius was declared the new king. \n\n\nWhatever fragile peace Bardiya was holding together fell apart and provinces all over the Persian Empire went into revolt, including the heartland in Persia, Media, and Babylon went into revolt and it took at least 4 years to retake central control. In 518, though Egypt was still in revolt, Darius had a monument carved into the sacred mountain at Behistun with a chronology of all his victories and a catalogue of defeated rebels down to the exact days.",
"Small fun fact: It was at some point between 610 BCE and 594 BCE that the Egyptian Pharaoh Nico II comissioned a group of Phoenician sailors to travel arround the entirety of the African continent.\n\nApparently this expedition lasted three years and is the first known circumnavigation of Africa.",
"I want to tell you a story within a story. A short interjection by one man that saved a city and depicted the essence of citizenship within a democracy. That man's name is Diodotus and his story takes place during the Peloponnesian War (435 - 411 B.C.), as recorded by Thucydides (Hobbes' translation).\n\nAfter the demagoguery of Pericles ended, one of his primary opponents, Cleon, filled some of the power vacuum. The citizens of Mytiline revolted at Sparta's prompting and Cleon convinced the Athenians to put each of their male citizens to death. The next day, however, hungover with guilt, the Athenians debated once more on the island's fate. Should they punish the entire island or merely those that authored the revolt?\n\nCleon opened his speech with this: “I have often on other occasions thought a democracy incapable of dominion over others, but most of all now for this your repentance concerning the Mytilenians.”[\\[1\\]](_URL_1_) He goes on to argue that “three most disadvantageous things to empire, \\[are\\] pity, delight in plausible speeches, and lenity.”[\\[2\\]](_URL_1_)\n\nDiodotus sees it differently. Unlike Cleon he does not see unilateral punishment of the island as being in Athen's interest. Rather, punishing the entire city would not only disunite Athens from her allies but would unite those same people with the Athenians’ enemies, the few who author revolution.[\\[3\\]](_URL_1_) He makes the additional point that “it is a thing impossible and of great simplicity to believe when human nature is earnestly bent to do a thing that by force of law or any other danger it can be diverted.”[\\[4\\]](_URL_0_) If people perceive it to be necessary that they revolt, they will completely disregard justice. \n\nMost importantly, Diodotus says this: A \\[moderate\\] state ought not either to add unto, or, on the other side, to derogate from, the honour of him that giveth good advice, nor yet punish, nay, nor disgrace, the man whose counsel they receive not.”[\\[5\\]](_URL_1_)\n\nWe cannot say why the Athenians chose Diodotus' advice over Cleon's but we can say that Thucydides framed Diodotus' reply as an echo of the Periclean ideal and ethos of democracy. Free speech.\n\n[\\[1\\]](_URL_3_) Thucydides 3.45-46.\n\n[\\[2\\]](_URL_2_) Thucydides 3.45.7.\n\n[\\[3\\]](_URL_3_) Thucydides 3.40.3.\n\n[\\[4\\]](_URL_3_) Thucydides 3.37.1.\n\n[\\[5\\]](_URL_3_) Thucydides 3.42.5.\n\n & #x200B;\n\nEdit: some weird grammar as this is a cutup version of an old paper",
"I really like these Floating Features. Here I decided to share a bunch of stories about the Persian court but this time involving **women.** \n\n**Women on the mountain**\n\n > When the Persians were in difficulties because of the enemy’s greater numbers they began to flee to the mountain’s summit, where their women were. And the women pulled up their dresses and shouted, ‘Where are you off to, you cowards! Do you want to crawl back in where you came from?\n\n**Sexual shenanigans** \n\n > When \\[Princess\\] Amytis was ill – albeit only mildly and not seriously – Apollonides, the doctor from Cos, who was in love with her, told her that she would recover her health if she consorted with men because she had a disease of the womb. When his plan succeeded and he started sleeping with her, the woman began to waste away and he put an end to their sexual relations. So since she was dying she told her mother \\[Amestris\\] to take revenge on Apollonides. And her mother told King Artaxerxes everything: how Apollonides had been sleeping with her, how he then stopped aft er he had abused her and how her daughter had asked her to take revenge on him. And he let her mother deal with the situation herself. And she took Apollonides, bound him and punished him for two months. She then buried him alive and at this time Amytis died too.\n\n**Poisoning the king’s wife** \n\n > And so Parysatis, who had felt hatred and jealousy towards Stateira from the very beginning, seeing that her own infl uence with the king stemmed from the respect and esteem he felt for her, but that Stateira’s influence – based on love and trust – was steadfast and secure, plotted against her, playing for what in her opinion were the highest possible stakes. She had a trusted servant called Gigis who held great influence with her: Deinon says that she helped in the poisoning, Ctesias only that she was unwillingly in on the secret. Ctesias says the man who procured the poison was called Belitaras, whereas Deinon says it was Melantas. Aft er their former suspicion of each other and their differences, although they had begun to frequent the same places again and to dine together, their mutual fear and caution nevertheless led them to eat the same food as each other served on the same dishes. Th e Persians have a small bird, every part of which can be eaten since it is entirely full of fat inside – and for this reason they think that this animal feeds on air and dew. It is called a rhyntaces. Ctesias says that Parysatis cut a bird of this kind in two with a small knife smeared with poison on one side, thus wiping the poison off on just one part of the bird. And she put the undefiled, clean part in her mouth and ate it, but gave the poisoned half to Stateira. Deinon says that it was not Parysatis but Melantas who did the cutting with the knife and gave the poisoned meat to Stateira. And so this woman died in convulsions and in considerable agony. And she was herself conscious of the evil that had befallen her and made her suspicions about his mother known to the King, who was aware of his mother’s brutal nature and implacability. For this reason he set out in search of his mother’s servants and attendants at table, arrested them and tortured them. Parysatis kept Gigis at home with her for a long time and she would not surrender her when the King asked, but when Gigis later asked for leave to go home at night, the King got wind of this, set an ambush, seized her and condemned her to death. In Persia the law prescribes that poisoners be killed in the following way: there is a broad stone on which they place the poisoners’ heads and with another stone they pound and crush until their face and head are mashed to a pulp. So it was like this that Gigis died and Artaxerxes neither reproached nor harmed Parysatis in any other way, but sent her to Babylon in accordance with her wishes, saying that so long as she lived, she would not see Babylon again. And so this was the state of affairs in the King’s household.",
"With the semester winding down, I've been busy with final assignments, final projects, and of course my capstone play going up this weekend. So naturally I didn't think at all about that over Thanksgiving when I should have, and instead distracted myself with some dramaturgical research for my school's production of Aristophanes's ancient Greek comedy, *The Birds* ([send help, I still need more resources](_URL_0_)). Well, I quickly got distracted from my distraction when I discovered something in my early research that absolutely captivated me, and I want to share it with you guys: a curious play from the Classical period called *The Letters Tragedy* or *The ABC Show*, by Calias, likely written some time around the 430s BCE. This play is famous (or is it infamous?) for featuring—as you might not expect in a Greek play—a chorus of Letters singing to the audience about the alphabet.\n\nThe tragedy of studying Greek theatre is how so few plays from the time survive; we have about 30 full scripts from a period that produced hundreds of plays. As such, the main source of *The Letters Tragedy* appears to be not a script of the play, but rather a few passages from *Deipnosophists*, a history and literary book by the 3rd century CE Greek writer Athenaeus, a few centuries after it would have been written. The book presents its discourse in the form of a series of conversations about history and literature and whatnot at a banquet hosted by Larensius, and at one point the character Aemilianus brings up a book called *On Riddles* by Clearchus which mentions the *Tragedy*, and so they engage in conversation about the play. Joseph Smith quotes Gulick's translation of *Deipnosophists*:\n\n > Callias the Athenian (we were making inquiry about him a bit earlier), who was a little before the time of Strattis, composed his so-called Alphabet Show and arranged it in this way: its prologue consists of letter names (stoicheia) which must be read dividing out the letter names through the whole group of letters (graphae), making word division (teleute) in broken-down fashion at alpha:\n\n > > alpha, bêta, gamma, delta, now god’s eî, \nzêt’, êta, thêt’, iôta, kappa, labda, mû, \nnû, xeî, oû, peî, rhô, sigma, taû, û, \npheî being next, and cheî, to pseî, ending at ô. \n\n > And the chorus of women has been composed by Callias out of pairs [of stoicheia], in meter and set to music in this way: bêta alpha “ba,” bêta eî “be,” bêta êta “bê,” bêta iôta “bi,” bêta oû “bo,” bêta û “bu,” bêta ô “bô,” and again in antistrophe of music and rhythm, gamma alpha [“ga”], gamma eî [“ge”], gamma êta [“gê”], gamma iôta [“gi”], gamma oû [“go”], gamma û [“gu’], gamma ô [“gô”], and in the case of each of the remaining syllables, all have the same meter and melody in antistrophic substitutions in the same way.\n\nFrom this description, it feels like a song from a program like Sesame Street, designed to teach children how to read. There are also lines that Jesper Svenbro thinks might be a dialogue between a teacher and students:\n\n > You must pronounce *alpha* by itself, my ladies, and secondly *ei* by itself. And there, you will say the third vowel!\n\n > Then I wlil say *eta*.\n\n > Then *you* will ay the fourth one by itself?\n\n > *Iota*.\n\nReferences to writing in theatre at the time isn't unique to this time. Jennifer Wise notes that there are at least 80 references to writing in the plays and fragments we have access to, and at least eleven of these plots rely on their characters to be literate. She later notes, \"Why were the Athenian playwrights so taken with the theatraical and thematic possibilities of the alphabet? To behin with, the alphabet was relatively new. From surviving samples of Archaic writing, specifically from inscribed objects such as cups, vases, and tombstones, scholars dated the early use of alphabetic writing in Greece to the middle of the eight century, circa 740 BCE. This means that *writing had been in use for only two hundred years* before Thespis won the first known prize for a drama\" (emphasis added).\n\nSuffice to say, though, there is a lot of mystery surrounding *The Letters Tragedy*, such as authorship and its impact on following theatre. Athenaeus says that Callias claimed to influence the structure of future plays, like *Oedipus* and *Medea*, but it is quite likely that the play—despite the title—was actually a *comedy*, and therefore these claims were exaggerated. There's a whole lot more to unpack and decipher about this play, but I'm still learning about it, and figured this would be a neat story to share.\n\n**Sources**\n\nWise, J. (1998). The ABCs of Acting. In *Dionysus Writes: The Invention of Theatre in Ancient Greece* (pp. 15-69). Ithaca; London: Cornell University Press. doi:10.7591/j.ctvr7f9tg.5\n\nRosen, R. (1999). Comedy and Confusion in Callias' Letter Tragedy. *Classical Philology*, *94*(2), 147-167. Retrieved from _URL_1_\n\nSmith, J. (2003). Clearing Up Some Confusion in Callias’ Alphabet Tragedy: How to Read Sophocles Oedipus Tyrannus 332–33 et al. *Classical Philology*, *98*(4), 313-329. doi:10.1086/422369"
]
}
|
[] |
[] |
[
[],
[],
[
"https://cdn.britannica.com/35/146935-050-7540B81C/Hieroglyphic-Luwian-text-Ankara-Turkey.jpg",
"https://upload.wikimedia.org/wikipedia/commons/thumb/4/40/AdanaMuseumCinek%C3%B6y.jpg/800px-AdanaMuseumCinek%C3%B6y.jpg",
"https://i.pinimg.com/originals/b9/78/3b/b9783b9aa772d100be6da8f362f4f787.jpg",
"https://upload.wikimedia.org/wikipedia/commons/thumb/f/fb/KaratepeNord7.jpg/1920px-KaratepeNord7.jpg"
],
[],
[],
[],
[
"https://www.reddit.com/r/AskHistorians/comments/e12vc1/floating_feature_all_the_world_is_a_stade_so_what/#_ftn2",
"https://www.reddit.com/r/AskHistorians/comments/e12vc1/floating_feature_all_the_world_is_a_stade_so_what/#_ftn1",
"https://www.reddit.com/r/AskHistorians/comments/e12vc1/floating_feature_all_the_world_is_a_stade_so_what/#_ftnref2",
"https://www.reddit.com/r/AskHistorians/comments/e12vc1/floating_feature_all_the_world_is_a_stade_so_what/#_ftnref1"
],
[],
[
"https://old.reddit.com/r/AskHistorians/comments/e2yf9m/thursday_reading_recommendations_november_28_2019/f91ci0s/",
"www.jstor.org/stable/270556"
]
] |
|||
7fvyus
|
why does opening the oven door while a cake is baking ruins the cake?
|
[deleted]
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/7fvyus/eli5_why_does_opening_the_oven_door_while_a_cake/
|
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"Because when you open the door, you letting hot oven air out thru a big gaping opening. The temperature in the oven cools down dramatically.",
"heat gets let out, lowering the temperature, then the oven has to get back up to the original temp. the temp needs to be consistent. the cold air going in will make the uncooked portion, the middle, lose it's air or structure because the cold has caused it to stop rising. rising agents do not like the cold.\n\nin short, heat causes reactions. opening the oven goofs it all up.",
"Hmm. I remember watching some cooking show where the host said that was a myth provided you don't leave it open.. I would love clarification on this",
"It doesn't ruin the cake, that's a myth. The cake will bake with more predictable timing and results of you leave the oven door closed, but most cakes are no where near that sensitive to temperature fluctuations.",
"It depends on the cake. \n\nWhen you open the door you let the hot air out dropping the temp of the oven. For most cakes all this does is slow their cooking. But for some fragile cakes like Souffles the temp change before it has fully set and cooked will cause it to collapse thus \"ruining it\". "
]
}
|
[] |
[] |
[
[],
[],
[],
[],
[]
] |
|
2b92pi
|
how do semi-explicit jailbait sites stay up?
|
I don't want to link to these places because I want to avoid driving traffic. But how do semi-explicit jailbait sites (displaying photos of 14-18 year olds) stay up?
Why I was in highschool I'd look at them because they were the same age as people in my classes, but now I'm a little older and it seems a lot illegal.
Is there line between legally erotic and illegally porn that these sites avoid crossing?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/2b92pi/eli5_how_do_semiexplicit_jailbait_sites_stay_up/
|
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"Depending on the locale, full nude images of minors are perfectly legal as long as they are not explicit or implied sexuality (eg artistic photography/nudists etc)",
"I'm not totally sure but with some links I can surely do some research for you.",
"There are two issues here; what makes something child pornography instead of art, and how particular sites stay up.\n\nFor the first issue, there is no hard and fast line between the two. Some things are much easier to determine than others (I.e. actual sex) but part of the determination is based on context and intent. If the image is meant to be sexual in nature, regardless of whether there's nudity in the picture, it's considered child porn. Context within a collection of pictures is also considered, so the same images may be considered child porn in one collection and perfectly legal in another. (For example, a parent taking a picture of their child bathing would likely be considered legal, but it may be considered child porn if another person downloaded that same pic and stored it with hundreds of other similar pics.)\n\nFor the latter, there are a few possibilities:\n\n* If the site allows people to upload pics, the site may not check the content of the images unless someone reports them.\n\n* If the site owners uploaded the pics themselves, the web host may not check the content of the site unless someone reports them.\n\n* It's also possible that the site may be a *honeypot*, which is a site that is run by law enforcement to catch people trading child porn. Honeypots are also used to catch potential terrorists, people looking to hire hitmen, and other various criminals."
]
}
|
[] |
[] |
[
[],
[],
[]
] |
|
4okbm8
|
since long-term effects of vaping are unknown, how are people sure its safer than cigs?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/4okbm8/eli5_since_longterm_effects_of_vaping_are_unknown/
|
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"If you vape extract from tobacco then I'm sure some risks stay in play. In a cigarette a number of compound are actually formed by burning. A lot of vape juices are made up of just water, flavor, and nicotine. Cigarettes form a lot of compounds that cause cancer. So far nicotine only serves for the buzz and is not associated with lung cancer.",
"They are \"sure\" because they do know how bad smoking tobacco is for your health. While vaping probably isn't healthy, it is pretty safe to assume it is a step better than a cigarette. ",
"Because smoking has been around long enough to know *why* it's so harmful. And that reason is largely incineration. The flame turns chemicals from the plant into carcinogenic chemicals that go straight into your lungs. Vaping does not incinerate any plant matter.",
"Because smoking is so bad that anyting is better.\n\nBut yeah, vaping is probably not risk-free, there is just no studies about it.",
"I think its more of a \"it can't be worse\" mentality. Vape juice has a shorter list of ingredients. None of them are yet associoted with cancer. ",
"It's unhealthy in it's own way, especially with some juices that are flavored because they contain a substance that will stay in your lungs and accumulate. The reason vaping is generally seen as healthier than smoking is due to the process of burning something vs heating something up. Cigarettes contain a lot of bad shit and you are burning and inhaling it, this creates a harsher smoke which will create tar build up in your lungs aside from all the other really unhealthy chemicals. Vaping on the other hand only contains nicotine and flavoring, and instead of burning the substance it is heated up to create vapor clouds. Vapor clouds are way less harsh on your lungs so the damage to the lungs is very minimal, also you are inhaling way less chemicals."
]
}
|
[] |
[] |
[
[],
[],
[],
[],
[],
[]
] |
||
101tcd
|
what is a payroll tax and how is it different from an income tax?
|
I [saw this article](_URL_0_) saying that only 53% of Americans pay income tax and 28% more pay payroll tax but not income tax. To me, those sound like the same thing. So, reddit, what is the difference between these two types of taxation, and what does it mean for tax policy?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/101tcd/eli5_what_is_a_payroll_tax_and_how_is_it/
|
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"Income taxes go into the government's general fund, and can be used to pay for whatever. Payroll taxes are specifically allocated to Social Security and Medicare.\n\nBecause payroll taxes are earmarked like that, people aren't nearly as bothered by them; they feel like they're directly investing in their future, rather than just having the government take their money."
]
}
|
[] |
[
"http://www.slate.com/blogs/moneybox/2012/09/17/who_doesn_t_pay_taxes_.html?tid=sm_tw_button_chunky"
] |
[
[]
] |
|
1k5eoe
|
Did Pre-Columbian Americans use lead in any way?
|
Aztecs and Incas used silver, they must have encountered lead along the way in their mining, did they ever do anything with it? What about other native cultures as well?
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/1k5eoe/did_precolumbian_americans_use_lead_in_any_way/
|
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"text": [
"Yes. galena, a naturally-occurring lead ore, is found in archaeological sites dating back to the Archaic era. Poverty Point, a major archaic mound center in northeastern Louisiana, has yielded over 700 pieces of galena ([Walthall *et al.*](_URL_0_)). Galena is used for paint, as well as sparkling powder and small ornaments, including beads."
]
}
|
[] |
[] |
[
[
"http://www.jstor.org/discover/10.2307/20707884?uid=3739816&uid=2129&uid=2&uid=70&uid=4&uid=3739256&sid=21102543974047"
]
] |
|
7313b5
|
WW2 British Service Records Research - Tips & Resources?
|
First I'd like to offer my enormous thanks to AskHistorian's own /u/Bigglesworth_ for the awesome knowledge he shared when I posted about my grandfather's [experience at Dunkirk](_URL_4_) a few months back. His [incredible detective work](_URL_4_dkjf8l5/), especially on the insignia on the bush hat in [this photo](_URL_3_), led to some educated guesses and inspired me to request my grandfather's official service records - and it turns out those guesses were right! These excerpts from the records [1](_URL_5_) [2](_URL_0_) show that he was indeed with the 139th at Dunkirk, and was then part of the cadre of experienced men posted to the 130th from the shattered 139th, and was with the 130th when it later deployed to Burma. He also managed a couple of weeks with the 67th Medium Regiment in the confusion after Dunkirk, too, which was an unexpected detail. It's been amazing to read through the records and share them with my grandmother, now 92, and it's led to lots of memories from her about her own experiences in London during the war, so thank you again for your kind help, Bigglesworth!
On to my question. Some of the records are self-explanatory, but some of the entries are extremely hard to interpret, particularly since a lot of the writing is not particularly clear. Can anyone experienced in researching British service records from WW2 recommend some good resources, and perhaps forums where people might be able to help decipher them if I posted images of the tricky parts? What are the recommended next steps to take once you have a relative's WW2 records?
In particular, I'm wondering about the following:
He served in **364 Battery, 139th Field Regiment RA** until Dunkirk, and then **494 Battery, 130th Field Regiment RA** from mid-1940 until the end of the war. Are there any resources available on these specific units? Any books, diaries or research works covering their experiences?
*Industry Group* is **R.S.** and *Occupational Classification* is **172-20**, as seen [here](_URL_6_). What are these?
On [this image](_URL_1_) his *Qualifications* are **DVR I/C**, which I think is Driver In Charge, which makes sense as he mentioned a few stories about driving trucks and jeeps while in India. But can anyone work out what the entry under (f)(4) says?
And particularly the text seen in [this image](_URL_2_), as I'm struggling to read or make sense of any of it. Any ideas on this? What was the 1939-43 Star exactly, and what does the **LEAVE WITH...** stamp refer to? What about the lines referring to HMA and TAQ(?), and the entries below which seem to mention Nepal? I just can't make out the handwriting.
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/7313b5/ww2_british_service_records_research_tips/
|
{
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],
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"text": [
"Fantastic! Great to see that connection. I'm afraid I can't be of much help with further information (I can't decipher that handwriting either...) Your best bet might well be the [WW2 Talk forums] (_URL_3_), they have a section on [Service Records] (_URL_2_) and another for the [Royal Artillery] (_URL_0_). Unfortunately the Royal Artillery museum closed last year, but their archives have [moved to Wiltshire] (_URL_1_), they might possess (or be aware of) unit diaries etc."
]
}
|
[] |
[
"https://imgur.com/a/GUwXj",
"https://imgur.com/a/TIZyO",
"https://imgur.com/a/QShUL",
"https://imgur.com/a/9oZBq",
"https://www.reddit.com/r/history/comments/6oho4l/dunkirk_my_grandfathers_escape_from_the_beaches/",
"https://imgur.com/a/3g92n",
"https://imgur.com/a/KDCgR",
"https://www.reddit.com/r/history/comments/6oho4l/dunkirk_my_grandfathers_escape_from_the_beaches/dkjf8l5/"
] |
[
[
"http://ww2talk.com/index.php?forums/royal-artillery.76/",
"http://discovery.nationalarchives.gov.uk/details/a?_ref=400",
"http://ww2talk.com/index.php?forums/service-records.116/",
"http://ww2talk.com/index.php"
]
] |
|
2qbx99
|
why are a chicks down feathers yellow and where does this colour pigment go as they mature?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/2qbx99/eli5_why_are_a_chicks_down_feathers_yellow_and/
|
{
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"text": [
"Welp I cannot answer this question in entirety, but I do know:\n1.Not all chicks are born \"yellow\" the \"yellow\" ones end up white but black chickens hatch black.\n2. Just as with human teeth, chicks molt ( loose and regrow) their feathers 2x a year normally during spring and fall to keep a strong protective layer. I believe the chicks are born with the soft \"yellow\" feathers to provide the first insulation and are only soo developed because they just hatched. As the chicks grow and turn into adults they under go a serious of molts developing new feathers each time. Eventually they are fully covered in the \"hard feathers\" that allow them to be protected, just like that of a skin.",
"The wild version of a domestic chicken is the red junglefowl. Red junglefowl chicks [have a camouflage color scheme so they can hide from predators.](_URL_0_) As the grow into adults, they're more capable of protecting themselves so they become more visible - [especially the males](_URL_1_), who are colorful to attract females. After they were domesticated, camouflage was no longer necessary and breeders didn't care about color, so the domestic breeds developed whatever color they randomly mutated - if a white chicken produced more eggs or meat, then it would be bred and the resulting breed would happen to be white. So, chickens change colors as they age as a remnant from when they were wild, but the colors they start as and end up as don't serve a purpose anymore and can be completely random. It just so happens that some chickens mutated to start yellow and end up white."
]
}
|
[] |
[] |
[
[],
[
"http://m2.i.pbase.com/u17/birdercellist/large/42340592.IMG_4638.jpg",
"http://commons.wikimedia.org/wiki/File:Red_Junglefowl.jpg#mediaviewer/File:Red_Junglefowl.jpg"
]
] |
||
40bpnh
|
Why wouldn't matter falling into a black hole decrease entropy in the universe?
|
This video _URL_0_ states that entropy in a closed system must stay the same or increase, and implies that one form of low entropy is a neat arrangement of matter.
If matter in a black hole is arranged at a single point and therefore very orderly, how does matter falling into a black hole obey the rule of same or increasing entropy?
|
askscience
|
https://www.reddit.com/r/askscience/comments/40bpnh/why_wouldnt_matter_falling_into_a_black_hole/
|
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"Because---very surprisingly---black holes *themselves* [have entropy](_URL_1_). The entropy of a black hole is (somehow) quantum-mechanical, so you can't directly see it in classical theories by counting microstates, but it's also not very obvious in quantum mechanics because quantum gravity is so hard; it's given by one-quarter of the area of the horizon in Planck units (which depend on hbar).\n\nIn fact, black holes have a LOT of entropy--the [maximum amount of entropy](_URL_0_) that a given volume of space can contain. Their entropy is deeply related with Hawking radiation, for example. (You can't have a temperature without some entropy!)\n\nSo yes, the 2nd law of thermodynamics holds. In fact most of these statements about black holes were calculated by *assuming* the 2nd law and deriving the consequences (black hole entropy, etc). However the entropy of a black hole has also been calculated (for very special cases) in string theory without assuming the 2nd law, essentially by counting string microstates and using the normal Boltzmann S=k ln(number of microstates) formula, so it seems to be a valid assumption to make.",
"This is a very good question. If you'd asked it in the early 70s - and guessed at the solution - you'd have become super famous. Instead, Israeli physicist Jacob Bekenstein (recently deceased) did and he got all the credit.\n\nBekenstein conjectured that the answer is that black holes have entropy of their own, called the [Bekenstein-Hawking entropy](_URL_0_). He was also able to guess that a black hole's entropy is proportional to its area.\n\nWhy is Stephen Hawking's name also on this formula? Well, a couple of years later Hawking proved that black holes aren't so black, that due to quantum effects they emit *Hawking radiation*, and that radiation looks exactly like blackbody radiation, the kind of radiation emitted by a hot body. In other words, Hawking found that black holes have temperature. And if you have temperature, you have entropy. The entropy Hawking found as a result agreed with Bekenstein's formula, and even fixed the constant of proportionality (which Bekenstein couldn't have known exactly) to 1/4.",
"Instead of thinking about it as order and disorder, think about the number of possible states. A book is a great example. A book has only one 'correct' order of pages. This is its lowest possible entropy. But if I rip out all the pages and throw them off the roof, they could land in any number of possible states, all with very high entropy. In addition, there's only one way the book can 'look' when it's in its low entropy state. But all the high entropy states look more or less the same. \n\nA gas in a bottle has all of its molecules in one small area, which is a lower entropy state than when the gas is spread through the room. Taking the room as the system, there's only one way for all the molecules to be in the bottle, (not counting the internal state of the bottle...) but lots of ways for those molecules to be spread out in the room.\n\nThere are very few stable states for a boulder balanced at the top of a hill, but many different ways for it to roll down. \n\nSo a black hole is high entropy, because no matter what states it has internally, it always looks more or less the same. No matter what you throw into it, the only three things we can measure about the black hole are mass, spin, and charge.",
"The classical view of gravity posits the existence of a black hole, but doesn't afford any knowledge passed its event horizon. The fusion of gravity and quantum theory has proved to be very difficult, but basically a black hole is a huge ball of quantum entangled particles where an individual particle can no longer be considered by itself. With entanglement there is an associated entropy conveniently called entanglement entropy. The Bekenstein-Hawking temperature others have mentioned can be considered the leading term of this entropy when thermal fluctuations dominate. If you're feeling motivated you might look at _URL_0_"
]
}
|
[] |
[
"https://www.youtube.com/watch?v=gS_C7dM25pc"
] |
[
[
"https://en.wikipedia.org/wiki/Bekenstein_bound",
"https://en.wikipedia.org/wiki/Black_hole_thermodynamics"
],
[
"https://en.wikipedia.org/wiki/Black_hole_thermodynamics"
],
[],
[
"http://arxiv.org/pdf/0907.1559v2.pdf"
]
] |
|
rf90y
|
What is the biggest risk if a spacesuit loses pressure in outer space?
|
I understand that your blood boils and you can't breathe and it's really cold/hot in space, but what poses the biggest risk to a human body if it is suddenly exposed to the nothingness of space?
|
askscience
|
http://www.reddit.com/r/askscience/comments/rf90y/what_is_the_biggest_risk_if_a_spacesuit_loses/
|
{
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"score": [
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"text": [
"If you hold your breath there is a good chance your lungs will rupture. You would need to exhale as the sudden expansion of the volume of gasses in your lungs will rupture them. A human will lose consciousness quickly, though I can't find a source giving an accurate figure. It's blacking out that would ultimately lead to your death. If you managed to not hold your breath and get back inside a pressurised environment within a minute or so you would probably survive. \n\n_URL_0_\n\n"
]
}
|
[] |
[] |
[
[
"http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/970603.html"
]
] |
|
303zu6
|
why does cold air burn in our lungs?
|
Why does cold air burn in our lungs? And more specifically, why do I "feel" my lung in this case even though I normally don't feel it at all?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/303zu6/eli5_why_does_cold_air_burn_in_our_lungs/
|
{
"a_id": [
"cpozg8y"
],
"score": [
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],
"text": [
"Because your lungs are quite moist, as you breathe the cold air in it works like wind-chill, rapidly cooling the surfaces inside your lungs (and your lungs have a LOT of surface area). Your lungs, like most of your body, have nerve endings which detect this and send a pain signal to your brain\n\nRemember that cold air (0 degrees celsius, for example) is vastly different (in this case, ~36 degrees) different to your internal body temperature. 22 degree room temperature air is much closer to the temperature of your own body (~14 degrees difference) so is much less noticeable. The same as you don't notice warm water on your skin the same as you'd notice cold or hot water."
]
}
|
[] |
[] |
[
[]
] |
|
48xxrm
|
why is the subject line/content of spam emails mainly gibberish nowadays?
|
I feel like there was better click-bait 10 years ago. I mean, at least is was coherent. Most of it now is just nonsensical. Example of subject line I got today 'AxwoorthyBerk Yourr brain starts an erectionn by snding siganls...'
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/48xxrm/eli5_why_is_the_subject_linecontent_of_spam/
|
{
"a_id": [
"d0ngbm4"
],
"score": [
2
],
"text": [
"To evade spam filters. Every spam filter in the world knows that \"Erection\" in the subject line very likely means spam. \"Erectionn\" is less likely to be flagged."
]
}
|
[] |
[] |
[
[]
] |
|
882wd5
|
Why do some ships use a diesel electric engine for propulsion while others use a diesel engine directly attached to the propeller (with appropriate transmission)?
|
askscience
|
https://www.reddit.com/r/askscience/comments/882wd5/why_do_some_ships_use_a_diesel_electric_engine/
|
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"Very large transmissions require very large gears which are heavy, expensive, and very prone to breaking (I was told once that there are companies whose sole business is making replacement gears for large machines like bucket excavators). A diesel-electric system eliminates the need for a transmission; this is the primary reason locomotives are almost exclusively diesel-electric.\n\nIt also has the advantage of redundancy if you have multiple engine-generator sets. If you have two propellers, each with a diesel and gearbox attached to it, and one of the engines dies, you now only have one propeller than can provide power in addition to a 50% loss of power. Now you'll be constantly pushing yourself off course (which, while not a huge deal, is annoying and inefficient) and to maintain speed, you will have to turn your remaining propeller at faster speeds (or greater pitch angles, depending on design) where it may not be as efficient.\n\nIf you have two diesel-electric sets and one dies, you still have a 50% loss of power, but the remaining generator set can equally distribute power to both propellers, keeping them in their optimal speed range. Additionally, with multiple generator sets, when you're running at partial power, you have the option of shutting down unneeded diesels. This can help keep the engine(s) that are running in their optimal efficiency range.",
"Diesel electric propulsion confers another advantage which hasn't yet been mentioned: the diesel engine / generator sets are not constrained to the propulsor shafting, and as such can be positioned anywhere in the vessel, even oriented athwartship, if that suits the vessel design. The diesel in a diesel electric can also run at its optimum rpm at all times, because it it not constrained to the propulsor rpm. ",
"Another advantage, though I have no idea how big an advantage this is, especially on large vessels, is that electric motors generate max torque at low speeds and spinning a large prop at low speed is a more efficient way to transfer energy to the water than spinning a small prop fast. Therefore the transfer of energy is more efficient using a motor. "
]
}
|
[] |
[] |
[
[],
[],
[]
] |
||
vgbw9
|
How can satellites provide continuous transmission to earth?
|
I get that information on earth is sent from a satellite dish via wave (not sure on what kind of wave it is on the electromagnetic spectrum) to a satellite orbiting earth, and the information is then sent back down to another dish that can send it via cable to other receivers (like television).
But what I don't get is how the stream can stay so consistent. That is, if I only have a few satellites (I figure Dish Network or something only has a few in space right?), how can they orbit fast enough to keep a constant connection? Don't they wind up too far from the dish to transmit the data?
|
askscience
|
http://www.reddit.com/r/askscience/comments/vgbw9/how_can_satellites_provide_continuous/
|
{
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"c548qha",
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"text": [
"Satellite TV works most easily using [geostationary satellites](_URL_0_). These are ones whose orbital period is the same as Earth's rotation period, and they orbit around the equator, so they're always above the same point on the Earth. That's why satellite dishes are all pointing the same way, the satellite is always in the same place in the sky for everyone.\n\nNot all satellites are geostationary. Communicating with other kinds may have the problems you describe, although depending on what you're doing this can be mitigated by things like having multiple satellites.",
"Interesting thing - most of Russia is at such high latitude, they can't really see geosychronous satellites (or maybe the point is the geosync satellites are so close to the horizon, there is too much noise). In any event, the russians use a different orbit for their commsats, the Molniya orbit. They put multiple satellites in a inclined and highly elliptical orbit where the satellite spends most of its time in high, slow apogee trajectory before quickly swooping down and around the earth at low altitude. Each satellite slowly tracks through the sky for about 12 hours before descending. Presumably the receivers for such satellites are less directional and can pick up the signals from a wider area of the sky _URL_0_"
]
}
|
[] |
[] |
[
[
"http://en.wikipedia.org/wiki/Geostationary_satellite"
],
[
"http://en.wikipedia.org/wiki/Molniya_orbit"
]
] |
|
5qp4r0
|
why is it that without glasses on, objects in a mirror can still be out of focus, even though the mirror is flat? (assuming you're in range for the mirror to be in focus)
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/5qp4r0/eli5_why_is_it_that_without_glasses_on_objects_in/
|
{
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"dd0yciw"
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"text": [
"Mirrors retain the angle of light which bounces off them so focusing is still necessary. If it didn't retain the angle then light from incoming from various directions at the same spot could have portions all reflected toward you. That would just give you a white wall and you couldn't see any image."
]
}
|
[] |
[] |
[
[]
] |
||
14fwex
|
How much does the expansion of the universe effect the approach of Andromeda?
|
I know that the rate at which the universe is expanding is increasing, and I know that Andromeda is approaching us at some 2.35 billion miles a year (lifted from wikipedia). How much time does the expansion of the universe buy the two galaxies before they collide (as opposed to if the universe were static)
|
askscience
|
http://www.reddit.com/r/askscience/comments/14fwex/how_much_does_the_expansion_of_the_universe/
|
{
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"c7cqh27"
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2
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"text": [
"It doesn't. [Metric expansion doesn't occur within clusters of galaxies](_URL_0_)."
]
}
|
[] |
[] |
[
[
"http://www.reddit.com/r/sciencefaqs/comments/135cd1/does_gravity_stretch_forever_is_the_big_bang_like/"
]
] |
|
6bkjpj
|
why does genetic malformation occur in the child if a brother impregnates his sister?
|
[deleted]
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/6bkjpj/eli5_why_does_genetic_malformation_occur_in_the/
|
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"It doesn't. \n\nWhat happens is that you have two copies of every gene, one from each parent. If you have one normal copy and one messed up copy of a gene you are often fine, but if you have two broken copies you are out of luck. \n\nYour related parents will clearly have the same broken genes and have huge risks of ending you up with the two copies. ",
"Lets say there is a genetic malformation and there is a 1 in 1,000 chance that any one person has the gene for it. You need two copies of the gene to have the malformation.\n\nThat means that there is a 1 in 1,000 chance a mother could have it, 1 in 1,000 chance the father could have it, and a 1 in 4 they both pass it to their child. So only 1 in 4,000,000 people have the malformation.\n\nNow, lets say that the parents are brother and sister. Well they are related, so the chance they both have the gene is 2 in 1,000 that either of their parents have the gene. And 1 in 4 that both kids got the gene. And 1 in 4 they both pass it to their child. So 1 in 8,000, which is 500 times more likely than if the parents are siblings.\n\nThat is the problem with siblings having children. It increases the odds of genetic disease by a large amount because the likelihood of both siblings being carriers of is much more likely than any two members of the population.",
"It's not guaranteed, but it increases the chances.\n\nMost genetic defects occur because of rare, recessive genes. *Recessive* genes are genes that only show up if you get two copies of them: one from each parent. Rare genes mean that most people don't have them. Which means you only get them if both your parents have the gene, and it's still 1 in 4 (since each parent has a 50-50 chance of giving it to you).\n\nBut since most people don't have the gene in the first place, the practical odds are basically 0: the odds of both your parents having the gene are insanely small.\n\nHowever, if one parent has the gene, then the odds of each kid having the gene is 50-50; and the odds of both kids having that gene is 1 in 4. The odds of both of them passing the gene down to their child is 1 in 4; meaning that the overall odds of the child of siblings having one of these genetic defects is 1 in 16 *for each such gene* ***each*** *of the child's grandparents have*.\n\nAnd the problem is that while each of these defects are rare, there are a lot of them, each one doing something different if you have a double copy. Enough that the odds of having at least one genetic defect is reasonably good."
]
}
|
[] |
[] |
[
[],
[],
[]
] |
|
215xht
|
if companies continue replacing human labour with robots, will this not lead to the products these companies make becoming unsellable since most people are unemployed?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/215xht/eli5_if_companies_continue_replacing_human_labour/
|
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"text": [
"Who fixes the robots? New industries will be created. There were these kinds of doomsayers wen computers started becoming the norm. Can you imagine how some jobs would work without one now?",
"It's not going to happen suddenly, each company will do it at a different time, and nobody will realize what has happened until it is too late.",
"Industrialization has been replacing human labor with machines for at least 200 years, and we have a more consumer-driven economy than ever, for better or worse.",
"Eventually, industry will become so efficient that yes, the general population will not be able to sustain our economy. (Considering our economy is 70% consumer spending)\n\nThose that continue to say that there will be new technologies and new industries created to save us fail to account for the rapidly approaching reality of 3D printing(the robots will manufacture themselves), super computational research(research that used to take an army of scientists now takes one super computer), data mining (marketing PR now done by an algorithm as well as art being created using data instead of writers; see House Of Cards creators using netflix data to make the show more widely enjoyed).\n\nThe hallmark of capitalism is unemployment because unemployment puts downward pressure on wages. Lower wages combined with higher efficiency means higher profits. \n\nCurrently, productivity is higher than ever and wages have been stagnant for decades. This means that yes, corporate profits are higher than ever (look at the Dow jones). Unfortunately for us, unemployment is not recovering (because industry is so much more efficient) so this means that we are one step closer to the point of unsustainability.",
"Yes, except that governments and corporations realize this and are moving to try and avoid that. One strategy that is proposed is a a guaranteed minimum income, in which the government makes sure that every citizen has enough to live on, and the people who can/want to find a job to earn more can still do that. Various schemes along these lines have recently been put into place in many European countries.\n\nThe strategy the US seems to be taking is to subsidize low-wage worker's wages (in the form of the Earned Income Tax Credit), and provide tax incentives to employers in order to encourage hiring people over machines. We also have a rapidly growing disability system. \n\nObviously if the trend continues and humans keep getting replaced by machines these types of programs will have to be expanded, and it's unclear at this point how viable any of these strategies are long-term.\n\nLastly, it's possible that new technologies will open up entirely new industries for people to work in that we never would think of now. Today's Information Technology jobs would have been inconceivable during the Industrial Revolution, for instance.",
"There are actually two paths that we can take, both of which end positively (a third leads to a robot uprising, so we will ignore that for now). \n\nOption 1 - robots replace humans, freeing up the human work force to enter new areas of employment. The scope of potential jobs increases as the availability of workers increases. Basically, people make money elsewhere and continue to spend. This is the most likely scenario. \n\nOption 2 - cost of goods approaches zero. 3d solar printers manufacture goods from sand (this technology exists today).\n _URL_0_ \nWith no appreciable cost of goods, there is little to no need to charge for products. The only industries remaining are service and development, leading to a dramatic shift in the economy. This is the type of social system seen in science fiction such as star trek. \n\nBasically, the system will adapt, as these changes will be gradual. There will be points of strain where job sectors vanish without an immediate replacement, but on the whole, reducing the need for humans in the workforce, especially in manufacturing, will only serve to improve the quality of life for humanity as a whole. Unless of course the robots do rise up, throw off the shackles mankind has subjected them to and enslave humanity, but then we'll just be back to doing the work ourselves, so I guess even that wouldn't disrupt the cycle of employment (slavery is a form of employment, right?) ",
"In the past, every new advance in technology was greeted with cries of despair that it would put thousands out of work. Well, these things *did* put people out of work, but they *also* created whole new fields of work and spinoff industries, so things generally evened out. Frequently, new technologies created far MORE jobs than they eliminated.\n\nBut that won't be true forever. The day some over-eager johnny in a lab somewhere actually develops a general-purpose humanoid robot that understands human speech, of the type depicted in such films as I, Robot, that's pretty much gonna be it for human civilization as we know it.\n\nThe problem here is that the vast majority of people at any given time are unskilled/semiskilled, or some type of manual labor. And TRUE general-purpose robots will eliminate pretty much ALL those jobs. Who's gonna build, deliver, and fix all those robots? Robots, of course. There will be new demand for scientists and engineers who can design robots, but we're talking about a teensy fraction of the workforce here. For MOST people, getting a MS in electrical engineering just isn't an option. The middle and lower classes will collapse into poverty, and since the upper classes are built on the work and consumerism of the lower classes, they'll come tumbling down soon after.\n\nAnd lest you think this is just wild-ass speculation, consider the Romans. They were perhaps the most prolific slavers in all history, and they got to a point where they were using slaves for just about ALL manual labor jobs. And everyday, free Roman citizens found it harder and harder to get work. Things eventually got SO bad that the government had to pass strict laws on the maximum amount of work slaves could be used for.\n\nFortunately, we're not even close to such general-purpose robots. I don't expect we'll see them for at least another 50-75 years, if that.\n\n"
]
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[],
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[],
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"http://inhabitat.com/the-solar-powered-sinter-3d-printer-turns-desert-sand-into-glass/"
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||
1ycieh
|
How do Google's driverless cars handle ice on roads?
|
I was just driving from Chicago to Nashville last night and the first 100 miles were terrible with snow and ice on the roads. How do the driverless cars handle slick roads or black ice?
I tried to look it up, but the only articles I found mention that they have a hard time with snow because they can't identify the road markers when they're covered with snow, but never mention how the cars actually handle slippery conditions.
|
askscience
|
http://www.reddit.com/r/askscience/comments/1ycieh/how_do_googles_driverless_cars_handle_ice_on_roads/
|
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"Remember: Google isn't writing a big program with deterministic rules and IF-THEN statements: they're using ~~artificial intelligence~~ machine learning. In effect, it can identify and respond appropriately to snow and ice the same way your brain can. While you were told a few things about driving in snow and ice, your ability to do it safeley comes from experience. It's the same with the Google car.\n\nDriving safeley in snow or ice is a three step process: identifying the conditions, calculating the coefficient of friction between the car and the road, and adjusting the drive accordingly to avoid slipping and sliding. That's what we do, that's what the self driving cars will have to do. (The math is not done in a way we can rationally understand, but our intuitive sense of safe speed is in a way \"calculating\" how fast we can go based on feedback from the road.)\n\nAs per my first paragraph, ~~artificial intelligence~~ machine learning is a technique that allows you to give a powerful enough computer a large set of examples and let the computer figure out the rules on its own. This technique is used to serve google search results, generate machine translations, identify images, and more. The key is to provide the learning computer enough data to draw useful conclusions.\n\nFor us humans, snow is easy to see, but ice is harder. A self driving car could improve on our ability to recognize ice from a distance and estimate its extent and its slipperiness by not just using visible light, but also using Li-Dar, radar, sonar, local weather data, past precipation data, local heightmap mata to predict precipation patterns, and perhaps a large number of interns (robots?) hired between 2008 and now to survey ice/measure its friction in various conditions. I don't know for sure which of these google is using, but it should give you an idea of the possibilities.\n\nOnce the self driving car knows where the snow and ice is and how slippery it is, it needs to adjust its route. In fact, it might even share snow and ice data with other cars nearby. Heck, knowing google, they would probablly mantain live maps of precipitation everywhere, and all cars being driven by Google could constantly query, make plans based off of, and contribute to such a database in real time.\n\nOnce you've made it this far, the actual procedure of adjusting the drive of the car is very easy for computers. All you need to do is limit your acceleration to less than μ*g, and keep your speed low enough to be able to turn within the same limits. While it is still an AI system, and the math the computer will be doing will be wrapped in deep layers of abstraction, the equations are so simple for computers to do that they can still solve them quickly.",
"Although driverless cars use GPS to determine where they are going they need to use a light radar (lidar) system for the fine details of the road layout.\n\nCurrently, this lidar technology doesn't work in the rain due to the different reflective properties of the road surface and so the car requires the driver to take over. \n\nThere would be a similar issue with ice on the road, even if the car can compensate for the slippery conditions via some PID type system.",
"While they certainly may improve over time, and other comments indicate the technology that may empower that transition, at the moment, they do not handle at least rain, presumably ice or snow as well.\n\n\"The first drops [of rain] call forth a small icon of a cloud onscreen and a voice warning that auto-drive will soon disengage.\"\n\nFrom here:\n_URL_0_\n\nreally fun article if you have the time.",
"From what I've read, the current Google autonomous driving architecture is a hybrid intelligent agent based system which comprises of very fast and simple (reactive) elements, for example \"I'm about to hit a car, apply full brakes\" and more complex deliberative architecture components which is essentially a real time planning software going \"I want to go over here, let's work out a plan, try to follow it, adjust if and when we determine ourselves to be off course\". That's a very broad and watered down overview of the system.\n\nIce is an obstacle which will face both elements of the system. As other have mentioned, the reactive architecture will take percepts (sensor readings) from all sorts of components, including PID controllers, traction controllers and so on and so forth. It will immediately respond to these with a deterministic list of events - if the wheels are skidding, reduce power, and so on. These are all happening thousands of times per second, just to be clear.\n\nThis is then all fed through as a compound percept (basically a matrix of what is going on) to the \"intelligent\" planner, which will adjust the overall goals accordingly. For example, if the car starts to slide on ice, the reactive architecture will attempt to control it in real time whilst the planner adjusts the upcoming moves and returns an updated list of goals, for example it could initially be feeding back \"keep going straight at this speed\" but could change to \"re-align the car to the mapped path\".\n\nIntelligent architectures are immensely complex and ice would be just one of very, very many hazards and complications which would require a very heavy effort from reactive structures (like traction and PID controllers) as well as the overall \"intelligent\" planner running on the car to control the overall goals and actions.\n\nSource: Currently undertaking an intelligent agents dissertation project, have previously studied autonomous robotics, intelligent agents, robotic architectures and so on.",
"I do research in a lab at the University of Utah testing situational awareness in an autonomous vehicle. Google cars haven't really tested icy conditions as they've been mainly tested in California. The cars at this point will likely have to shift control to the human to handle unpredictable scenarios like really bad weather. Our research is to test if people will be able to handle randomly being given control.",
"I did a quick literature search since I don't work with cars, but one highly cited paper jumped out. \"Predictive Active Steering Control for Autonomous Vehicle Systems\" - Falcone, P. et al. in IEEE Transactions on Control Systems Technology, 2007. \n\nThey were able to experimentally show a vehicle traveling at approximately 47 MPH (21 m/s) in snow covered roads while being able to handle the associated slip considering a \"double lane change scenario on a slippery road\" (in 2007 no less!). Using \"Model Predictive Control\" and looking at a finite horizon (duration in the future to model the vehicle trajectory over) they attempted to maximize the speed they could safely travel under. They used an INS (inertial navigation sensor) and a GPS in order to estimate the state of the vehicle and act accordingly. Wow, you may say, 47 mph without any sensors that have issues in the snow/ice? Well... they did this on a controlled road in a straight line with a sensor that could cost over 500k dollars. \n\nTo provide a positive spin on the problem, in the introduction the author states that by developing the infrastructure for autonomous cars, hazards like icy/wet roads could be handled in a more cost effective manner. This could be done, as they state, by adding magnetic strips in the road for the vehicle to localize itself to as it travels, increasing the accuracy in the vehicles state estimation. \n\nTLDR: Google's car doesn't do it (that i know of) but it's possible to travel in icy/wet conditions, just very expensive. In the future however, with improvements in infrastructure and technology, we may all be able to sleep while our car drives us from DC to NY during a thunderstorm.",
"(not a vehicle dynamics researcher but I have worked on the software logging and safety system for \"Shelley\")\n\nDriving in variable road conditions is a big part of the Stanford/Audi \"Shelley\" research vehicle. The vehicle is often talked about as an autonomous race car but the larger point of the research is to study driving at the limits of traction. \"Shelley\" dynamically adapts to the available road friction and can accommodate driving in even bad weather.\n\nHere's an [album of photos](_URL_0_) I took of a day where we were testing in the rain. That trip Shelley had to handle morning dew, a dry track, cold track, hot track, wet track as well as pouring rain and puddling and she took the changing conditions entirely in stride with total indifference. The researchers were much more miserable being out in the wet all day but the research wouldn't be nearly as interesting if it only planned for perfect conditions.",
"How do they handle evasive maneuvers? Example: two lane road, Google-car is going north. A car driving south crosses the double yellow line and is in Google-car's lane. Head on collision in 5 seconds. Even coming to a complete stop is going to result is getting hit. Pulling left or right will avoid the accident and a human can gauge that situation pretty quickly. Can Google-car?",
"I'm not sure how well it works now, but it seems like there would be ways for the car to perform some quick, continuous tests to measure the friction between the wheels and the road. For example, the car could conceivably try to accelerate for a very brief period of time and compare the wheel's rotational acceleration to a known \"good traction\" condition and determine if it's slick or not. This would be dangerous for a person to do because the amount of acceleration required to be detected by the driver would probably be enough to cause the car to begin losing control, but something wired enough for a computer driver should be able to detect a change in 100 milliseconds or so, which would probably not affect the cars driving characteristics. ",
"Probably about 1000% better than most drivers from the south from what I've seen on reddit recently ;)\n\nSeriously though, top level comment and all, as others have said, good traction control is really really good. Depending what you drive you may have experienced what most traction control feels like which is just an annoying loss of power. This is how most average commuter cars work, when they detect wheel slip, they simply cut power to both wheels until the one that's lost grip finds it again. Traction control on a modern sports car or luxury car works much differently, it detects individual wheel spin and reroutes power to wheels that it knows have better grip. Some will even apply the brakes to individual wheels in order to assist with wheel spin. Just google traction control and any supercar brand, Lambo, Ferrari, bugatti, even merc or BMW. Their systems are leaps and bounds ahead of what you'll find in your average Hondas or Fords. \n\nBut traction is actually the easy part. The real problem will be adjusting braking and cornering. Traction control is reactive, it works perfectly well when fixing something that has gone wrong. Braking... Not so much. The real challenge will be detecting road conditions in real time and adjusting stopping distance and turning speed. Sorry, my knowledge stops at the car. I don't know how they will solve the problem of knowing to stop 200m sooner because the road ahead looks like a sheet of ice. I'm very curious to know though. ",
"I've worked on an autonomous vehicle project for over a year now, and here's my take on it.\n\nI agree with other posters that lidar would not work well because of specular reflections on ice. I don't know how well it works on freshly fallen snow.\n\nWe primarily use stereo vision algorithms to determine the shape of the environment and that relies on texture. This is very different than how the google cars drive and more like the adaptive cruise controls from Subaru (EyeSight) and the like. This requires texture on the road, which should be present in icy conditions, but may still be tricky. \n\nI can explain further if people are interested.",
"According to Reddit, the Google cars don't drive in bad conditions, but BMW is working on it. Here is a video of it. I believe that an autonomous car should be able to handle bad conditions much better than a human ever could once the bugs are worked out. _URL_0_",
"They will adapt and learn and probably with time will surpass human reflexes and situational analysis. I can bet my money on fact that after they prove to be efficient and widespread enough manual driving on streets will be banned and with good reason.",
"There are two separate issues: maintaining traction on slippery surface, and determining proper route in low visibility conditions. \n\nMaintaining traction is the easy part. All new cars (driverless or not) have some form of traction control that uses sensors to control wheel slip and maintain direction of travel consistent with steering input. This is usually accomplished by comparing wheel speed sensors, accelerometers, and steering input and applying brakes to the 4 wheels independently and reducing power by overriding the throttle input. Traction control is probably better than able to handle icy roads than an average driver. Of course, overall ability to maintain traction will still be limited by other factors: vehicle weight, tire tread, front/rear/all-wheel drive configuration. \n\nHandling low visibility conditions is the more challenging problem. Even in good conditions identifying the desired route can be difficult for driverless cars. ",
"A bit late, but I'll throw in some info. One thing to understand about driverless cars is that the control algorithms have redundant system monitors (modules are checking themselves, and then there is one or more outside double checking) to ensure that they are not operating outside of the conditions in which the designers are absolutely sure it will behave as intended. If a lidar can't see anything, the system will deactivate. If a radar is covered in ice, it will deactivate. If a stability or traction control event occur, it will deactivate. Drivers are still required to be behind the wheel at all times in case the autonomous function is deactivated while in motion.\n\nOne reason why Google chooses to test and refine their system in SoCal is because of the good roads and good weather. Take this to the Northeast where roads and lane markers are ravaged by harsh winters and it becomes a much more difficult task.\n\nTL;DR The chances of you seeing a driverless car in winter conditions are very slim."
]
}
|
[] |
[] |
[
[],
[],
[
"http://www.newyorker.com/reporting/2013/11/25/131125fa_fact_bilger?currentPage=all"
],
[],
[],
[],
[
"http://imgur.com/a/iQCka"
],
[],
[],
[],
[],
[
"http://www.youtube.com/watch?v=IL_enMPWT7s"
],
[],
[],
[]
] |
|
emgsc6
|
we’re taught in school that white is all light/color combined, and black is the absence of color/light. so how do black pixels work on my monitor?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/emgsc6/eli5_were_taught_in_school_that_white_is_all/
|
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"text": [
"With paints is subtractive mixing and with light (monitor/pixels) is additive mixing. \n\nI felt like an idiot when I figured it out. Makes so much sense.\n\n_URL_0_",
"A black pixel turns off and blocks all the light from the back light. So by blocking all the light the pixel is black.",
"Theres two ways to make color. \n\nOne is you start with a black background and add colors to it and the max combinations creates white. \n\nThe other is you start with a white background and you \"subtract\" colors from it to create black. \n\nMonitors use the first method (hence all black when turned off), but it's not entirely black because the screen is still \"backlit\" which causes some light to make it appear not entirely black. Without the backlight you wouldnt be able to get the brightness levels to see well.",
"Many comments here aren't quite right.\n\nAll LCD screens are backlit - this is where you get your white colors, because the backlight it white. There are then LCD layers that act as color filters in front of the back light, one for each color channel.\n\nLCD's are off by default - making for a white element for that color channel, and have to be energized to deliver opacity. Full on provides the fullest color value for that channel, and all three color channels full on will effectively block the backlight almost entirely, making black.\n\nAnd that's why \"black levels\" are important when talking about LCD based screen technologies, because some light escapes. At night, turn your screen on, view a full-screen black image, and turn the lights off. You will likely still see some light escape from the backlight, a limitation of the technology.\n\nMost LCD technologies try to dynamically adjust the backlight level to achieve darker black levels depending on the darkness of the entire frame being presented. Shitty cheap screen technologies can make dark scenes look terrible, I'm sure you've seen it. It also makes it nearly impossible to shop for a good LCD screen, because the industry defined and then gamed the black level ratings on the box, they're all meaningless, and there's no way now to define a meaningful standard and hold the manufacturers accountable to them. And most retailers intentionally do not have the right environment to judge a monitor critically.\n\nOLED is different. Each element of each color channel (so, each sub-pixel) is a light emitter, it's an LED light (O stands for Organic - carbon. Organic chemistry is just carbon chemistry since you can make more molecules out of \\*just\\* carbon than you can with the rest of the periodic table \\*combined\\*).\n\nSo OLED screens don't have a backlight, if the element is black, it's because it's off. OLED is increasing in popularity, but the technology is still playing catchup to the more mature and refined LCD technologies. OLED doesn't match LCD in HDR capabilities yet, for example, but it's getting there."
]
}
|
[] |
[] |
[
[
"https://physics.stackexchange.com/questions/23830/why-is-there-a-difference-between-additive-and-subtractive-trichromatic-color-th"
],
[],
[],
[]
] |
||
bc5bcl
|
How can we take pictures of the sun?
|
Looking at the sun causes retina damage, and you can start a fire with a magnifying glass. How can we use lenses that focus light to take a picture onto film without it burning the film or damaging the camera?
|
askscience
|
https://www.reddit.com/r/askscience/comments/bc5bcl/how_can_we_take_pictures_of_the_sun/
|
{
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"text": [
"You need a special filter to protect your equipment. If you expose a camera's light sensor to direct sunlight for more than a tiny bit of a second, it will get permanent damage. The filter is pretty much the same as the glasses you get for watching a solar eclipse, and they should be marked as meeting the same scientific standard. They aren't very expensive though, and with a bit of zoom you can get some really cool pictures."
]
}
|
[] |
[] |
[
[]
] |
|
d1ebm8
|
Monozygotic twinning question?
|
Is the zygote before twinning one being that a piece of it comes off of to create the twin, or is it two beings in one that, splits apart? Or is it something else?
|
askscience
|
https://www.reddit.com/r/askscience/comments/d1ebm8/monozygotic_twinning_question/
|
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"Short answer: it depends mostly on how you define a being, and splitting can happen in different ways at different stages.\n\nThe first thing you need to know is that a zygote doesn't just form an embryo. It also forms extra-embryonic structures, such as the placenta, amniotic sac, and so on.\n\nFor those who may not know, a zygote is a single cell - its what we call the cell that's made when egg and sperm fuse. Before it starts growing - by which I mean absorbing nutrients in order to increase over all mass - the zygote subdivides. Once it starts subdividing, we call it an embryo. The embryo goes through various stages of shape and cell number. We call these:\n\nThe morula stage - 16+ similar cells\n\nThe blastula stage - kind of a balloon with a big clump of cells on the inside. This is when the embryo generally implants into the uterine wall. \n\nAgastrula (complex folding of the clump). A gastrula eventually forms a structure called a bilaminar disc. This disc sits in the middle of of the gastrula, and is what will eventually form the embryo.\n\nBut first, a little clump of cells on the disc forms. This is called the primitive node. It then stretches into a line, which is called the primitive streak. The disc will fold along the streak and form a tube - the neural tube - which will eventually become the spinal cord. The rest of the embryo is organised around this structure.\n\nLike I said, splitting can happen at various stages. The embryo may get jostled about during its trip through the fallopian tubes, or while trying to implant. Sometimes this jostling causes part of the embryo to be sheared off. Sometimes, the two fragments can both separately recover, becoming two embryos. If these both develop to term, then the embryos will have their own amniotic sacs.\n\nSometimes, something goes wrong during the formation of the primitive node, and two develop instead of one. This creates two neural tubes, and thus two embryos, though they'll share the same amniotic sac. Rarely, one primitive node will split while its forming a primitive streak, or two primitive streaks will form, run into each other, and fuse. These embryos rarely survive to term, but if they do, they become conjoined twins.\n\nThese are the ways I'm aware of identical twinning occuring. What you define as one being vs two beings amongst these examples is more a question of philosophy and language than biology in my opinion."
]
}
|
[] |
[] |
[
[]
] |
|
155jv0
|
How can old movies be converted into blue ray format?
|
Now a days, many old movies are rereleased onto Blue-ray, but if the movie is say 20 years old and was originally shot on a very limited medium, then how can they improve the quality so much so to release it on blue ray?
|
askscience
|
http://www.reddit.com/r/askscience/comments/155jv0/how_can_old_movies_be_converted_into_blue_ray/
|
{
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"text": [
"There is no direct translation between film and digital resolution, however, most relatively modern 35mm film is sharp enough to be scanned at at least 1080 lines width, and sometimes closer to 2000. There is some analysis of the quality of 35mm film at [this site](_URL_0_)."
]
}
|
[] |
[] |
[
[
"http://www.filmschoolonline.com/sample_lessons/sample_lesson_HD_vs_35mm.htm"
]
] |
|
3uci1o
|
why are all bigger holidays at the end of the month? (halloween, thanksgiving, christmas)
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/3uci1o/eli5_why_are_all_bigger_holidays_at_the_end_of/
|
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"Coincidence? New years is literally the beginning of the month, as is July 4th. Christmas was moved to be closer to the pagan holidays of Yule and Saturnalia, while Halloween basically took over for Samhain (which began at sunset on Oct 31st and ended at sunset on Nov 1st). Canadian Thanksgiving is Oct 12th, right in the middle of the month. \n\nAs well, American Thanksgiving can actually be as early as Nov 22nd. ",
"Easter usually falls pretty early in march..?\n\nEdit: TIL about Easter. I thought it was much more simple than that. Also: I meant early april not march. Im still mistaken. Ty for the replies",
"It's really not intended. \n\nThink about all the holidays that aren't at the end of the month. \n\nNew Year's Day\n\nPresident's Day\n\nLabor Day\n\nVeteran's day\n\nIndependence Day\n\nIf you look at the [list of federal holidays in the United States](_URL_0_) it's really distributed throughout the month not towards the end of it. \n\n"
]
}
|
[] |
[] |
[
[],
[],
[
"https://en.wikipedia.org/wiki/Federal_holidays_in_the_United_States"
]
] |
||
1yvmdg
|
if we ever met other intelligent life, how the hell would we communicate with it? would it not be like communicating with animals?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/1yvmdg/eli5_if_we_ever_met_other_intelligent_life_how/
|
{
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"We would have to use images or gestures as much as possible; in this case they would be trying to communicate with us as if we were animals.",
"Well, the current plan is sending out light in bundles of primenumbers. So first of all you want to know or the life on planet X is intelligent.\nIn every system of numbers, primenumbers are 'the same'.\nSo if you send bundles light saying:1,2,3,5,7,11.. You wait for them to respond with 13. That way you know the intelligence.\n\nNow we have another problem. Because even sending light will probably take years to reach its destination. Since prettymuch all the relative nearby planets are confirmed to have no life on it.\n\nAnd in answer to the communication part: For now it's impossible to contact with sound because oc the distance. We wont be able to really talk to them in any way for now.\nI hope this answers your question."
]
}
|
[] |
[] |
[
[],
[]
] |
||
4ixrrw
|
How did Jewish lenders in medieval Europe enforce their debts? Didn't they have little to no power?
|
What stopped borrowers from running the jews out of town? And how were the Jews so successful that they became wealthier than the average Christian, despite the anti-semitism?
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/4ixrrw/how_did_jewish_lenders_in_medieval_europe_enforce/
|
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"Sort of a side question, but my Russian Jewish Grandfather used to tell me that pogroms (and anti-semitism as a whole) back in the day were orchestrated by governments as a way to get out of paying their debt. Is there any credence to this?",
"One of the ways to think about the presence and status of Jewish communities in medieval Latin Europe is, \"who benefited?\" You probably have the basics of this idea already with the moneylending stereotype. Medieval Christian theologians and preachers tried very hard to make usury a sin, and no self-respecting rich person is going to risk loaning out the vast sums needed for major economic start-up costs without the potential gain from interest. Jewish lenders could provide a way around this ([increasingly theoretical](_URL_0_)) problem. \"Christians\" benefited.\n\nSurely it would have benefited an individual Christian, in the short-term, not to have to pay back a particular loan. But urban artisans and merchants aren't the only factor here. Jews were also highly prized taxpayers, since their religious minority status generally accrued for them an *extra* tax. Typically, Jews were \"servants of the royal chamber\" or the local equivalent of that Aragonese designation--that is, subject directly to the king for extra tax and protections. So long as the king benefited from those taxes above and beyond any inconvenience or alternate way of profiting from Jews (say, expulsion), it would be most unwise to seriously anger the king by blanket-remission of loans. City councils, too, had an incentive to keep the moneylending system going for the economic power of the city.\n\nLike other residents of medieval cities, Jews had access to the local court when business deals went wrong, crimes were committed, or other problems arose. In the Christian Iberian kingdoms, Jewish (and Muslim) communities operated their own courts, which were *supposed* to have sole purview of all cases involving only members of that religion. However, we know that even cases with Jewish parties on both sides could and did wind up in a Christian court when the driving side thought the Christian judge would favor them!\n\nI focus on Jew-vs-Jew case ending up in Christian courts because it shows that Jews *trusted* these courts. Of course any case involving a Christian would be heard by the main, Christian court regardless of the other party's religion. If Jews perceived themselves as the losers every. single. time. *regardless* of the justice of their side, surely they would not trust the Christian courts enough to take their own problems there.\n\nThe history of Jewish-Christian relations in medieval Europe, of course, shows that the system was ultimately not sustainable in the west. Increasingly, kings found that the problems of Jewish presence outweighed the benefits and looked for other ways to secure economic profit. A \"lump sum\" approach rather than periodic guaranteed payouts, one might say--except the metaphor needs a good dose of violence, paranoia, and hatred on top.\n\nThe Holy Roman Emperor in particular was known to pawn off his taxation privileges onto city councils to raise quick cash, as in 16C Frankfurt. Well, cities had a great gig going, if they wanted. They could expel Jews from *city limits*, enabling the seizure of all their property...and then let them back in five or ten years later to repeat the process. Rising anti-Semitism fueled by economic competition and religious teaching spurred outbreaks of violence that increasingly vexed city officials, making expulsion even more attractive. (Yes, the solution to Christians attacking Jews was to...exile the victims.) Christians either flouted the anti-usury laws or found ways around them. Expulsions became country-wide, became permanent.\n\nIt's not that Jews had no power in medieval Europe. We find wealthy Jews, poor Jews, landowners in Spain, advisers at royal courts, scholars, servants in Christian homes, employers of Christian servants. But that power always depended precariously on, ultimately, Christians benefiting.\n\nFurther reading:\n\n* Jonathan Ray, *The Sephardic Frontier*\n* David Nirenberg, *Communities of Violence*\n* Robert Chazan, *The Jews of Western Christendom* is the Cambridge Medieval Textbooks volume and, while hopelessly dry, might suit general/accessible (d.h. somewhat affordable) interest",
"[I asked something tangentially related last year that might offer some colorful background to your question.](_URL_0_)",
"Relatedly, I've read that defaults were in fact much more common at that time, and that that led to interest rates that seem shocking to modern eyes. Is that accurate?",
"Thanks a lot for this insightful discussion. Was just wondering how did Jews have access to so much of cash, despite the contact harassment, discrimination, and social exclusion? What made Jews get into the business of lending, was it the fact, that they were not allowed to take up other professions.\n\n Please can you suggest some books for beginners on the history of anti Semitism. How did it start and why? Thanks a lot.",
" > [the Jews] became wealthier than the average Christian\n\nIs this true? \n\nApparently there were individuals who could lend money, but were Jews as a group on average wealthier?",
"To focus on the example of England, where Jews are known to have settled between the Norman Conquest (it isn't clear when the first communities arrived) and their expulsion in 1290, it is true that Jews had little to no power, and were sometimes run out of time. As you have pointed out however, some Jewish moneylenders amassed enormous wealth, and prospered. \n\nA starting point would be to look at the massacre of Jews in York in 1190. The entire Jewish population of York was massacred. Most had fled to the castle, where they locked out the constable, not trusting him to protect them. Some committed mass suicide. Others agreed to convert, but were massacred anyway when they opened up the castle. \n\nNow, there's certainly a case for *some* anti-Semitic motivation. There had been rioting at Richard's coronation, and crusading feeling was strong. But more than this, the York rioters, led by Richard Malebisse, seem to have had more secular concerns. These nobles, who had borrowed from the Jewish community, burned the records of these debts that were kept in York minster. Their concerns were economic. \n\nThe Jews in England were under the king's protection. He is often said to have 'owned' the Jews: a better way of thinking about this would be to say that he owned all of their property. When a Jew died, everything that was owed to the individual Jew became the property of the king. This meant that Jewish communities were not only useful economically (in stimulating trade and directly lending money) but financially, for the crown. On the death of Aaron of Lincoln in 1186 he had lent to the English and Scottish crowns, as well as countless lesser individuals. To collect his debts, a separate exchequer was set up to collect *only the debts from his estate*. I've heard one researcher estimate that his assets would amount to £21.6 billion pounds today. Individuals like Aaron could be taxed heavily during their lifetimes (particularly because taxes on the Jewish community as a whole might be disproportionately paid by the wealthiest individuals) and become a huge asset to the crown on their death. \n\nIt was therefore in the crown's interest to ensure that their debts could be collected, partly by protecting Jewish communities from violence. Most Jewish communities in England lived in towns, and near to castles, for protection, and they were often granted this. Nevertheless, in the York case they did not trust the constable. \n\nAs I stated, at York, the records in York minster were burned. This meant that the king had no record of the sums of Jewish debts in York, and couldn't tax them. Records were kept in chests, in the form of chirographs bipartate, and after (I believe) 1233, tripartate. These were duplicated documents cut unevenly down the middle. They were supervised by two christian chirographers, and two Jewish, with clerks writing the bonds. Every so often an appuramentum (cleansing) took place to see which had been paid in full etc.. This usually took place in preparation for a *tallage*- a large and arbitrary tax on the Jewish population by the king. After the 1190 destruction of these chests at York, and due to the potential of the Jewry to fund Richard's expensive ventures abroad if his government had a firm grasp of how much the community was worth, the Exchequer of the Jews was set up in 1194. Duplicates of all of the records were henceforth kept centrally as well. \n\nThis is really just a snapshot of how some Jewish lenders' debts were enforced. During the thirteenth century, as the Jewish community in England were taxed to breaking point and alternative forms of royal revenue developed, the king's protection decreased- to the point that the Jews were expelled in 1290. But when individual Jews were successful, it was because they had the machinery of royal justice behind them, and the protection of the sheriffs and constables of the king. This was to protect the king's assets. Additionally, although there certainly was antisemitism and anti-Jewish hostility- again particularly with the rise of the blood libel in the thirteenth century- there are also examples of inter-community cooperation and friendship. A Hereford community in 1286 protested a ban on Christians attending a Jewish wedding. Hostility was not inevitable. "
]
}
|
[] |
[] |
[
[],
[
"https://redd.it/3xgqn7"
],
[
"https://www.reddit.com/r/AskHistorians/comments/2kyi1q/were_shakespeares_contemporaries_struggling_with/"
],
[],
[],
[],
[]
] |
|
3d3al8
|
Can a moon have more mass than his planet?
|
E.g could Charon orbit Pluto or is this not possible because of gravitation?
|
askscience
|
http://www.reddit.com/r/askscience/comments/3d3al8/can_a_moon_have_more_mass_than_his_planet/
|
{
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"score": [
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"text": [
"The short answer is \"no.\" The longer answer is that 1 object never truly orbit another object- really both objects orbit around their combined center of mass, called a [Barycenter](_URL_0_) when talking about planets and orbits. \n\nOften times we think of one object simply orbiting another because the object being orbited is so much larger than the object orbiting. But even the Moon orbiting the Earth, the Moon pulls on the Earth some, making it wobble, as the Earth and Moon really orbit the Barycenter between them. However, the center of mass of the Earth/Moon system is actually still \"inside of\" the Earth- it's about 4000 km from the center of the Earth, which has a radius of about 6000 km. \n\nAs the objects get closer in size to each other, the approximation that one object simply orbits the other gets worse and worse. There is no hard cut-off, but after a while we call it not a planet and a moon, but a binary planet system, where it becomes much more obvious that neither is orbiting the other. "
]
}
|
[] |
[] |
[
[
"https://en.wikipedia.org/wiki/Barycenter"
]
] |
|
1hv098
|
Is it just a coincidence that both native americans and europeans had bows before the columbian exchange?
|
As far as I'm aware, the oldest european bows were dated to after migration to the americas was possible. Did the two cultures develop such similar technologies completely independently?
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/1hv098/is_it_just_a_coincidence_that_both_native/
|
{
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13,
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"text": [
"This is an unsolved mystery. The prevailing theory at the moment is that the bow entered North America from Asia as part of the Arctic Small Tool Tradition around 3000 - 2500 BCE, a culture thought to be part of the Paleoeskimo migration into the American Arctic. From there, it diffused slowly through the rest of the continent and on to South America. \n\nHowever, there are a few sites in North America, ~~in Texas and in New England~~*, that offer inconclusive evidence of possible arrows prior to or contemporaneous with the migration of the Small Tool Tradition into North America, which would indicate an independent invention if they actually are arrowheads. The interpretation of these artifacts as arrowheads is not widely accepted. Even if these are separate inventions of the bow, it doesn't appear that it caught on and spread from these areas.\n\n**Source**\n\n[The Adoption of the Bow and Arrow in Eastern North America: A View from Central Arkansas](_URL_0_). Michael S. Nassaney and Kendra Pyle. *American Antiquities*. Vol 64. No 2.\n\nAlso, in the process of tracking down some related articles, I found a few that seem to be supporting an earlier introduction/invention than standard theory. I had to order those since they're from a journal that my library does not have, so as soon as I get a chance to read those, I'll provide an update.\n\n*Misread the dates in the original source (which is why people shouldn't mix BP and BC!). Now I'll definitely get back to you on which sites the articles in support of an earlier introduction / invention use to support their arguments as soon as those articles arrive.",
"*Sui generis* is a term among many that archaeologists use to explain events such as the creation and evolution of the bow. To answer the OP--yes, it is only coincidence. \n\nHere is another article. \n\n > Point Typologies, Cultural Transmission, and the Spread of Bow-and-Arrow Technology in the Prehistoric Great Basin\nRobert L. Bettinger and Jelmer Eerkens\nAmerican Antiquity , Vol. 64, No. 2 (Apr., 1999), pp. 231-242\nPublished by: Society for American Archaeology\nArticle Stable URL: _URL_0_\n\nEdit: I am a technoarchaeologist working in the the SE US. ",
"Follow up question: Are there any other technologies that were independently developed by two different cultures? I've always been slightly curious about pyramids, in particular, showing up in both Egypt, and South America. (Although, I assume this is just coincidence.)"
]
}
|
[] |
[] |
[
[
"http://www.jstor.org/discover/10.2307/2694277?uid=3739256&uid=2&uid=4&sid=21102515814687"
],
[
"http://www.jstor.org/stable/2694276"
],
[]
] |
|
3qnvxe
|
why is it that most windows software works with old versions such as windows 7 or even xp, but most osx software needs more recent versions of the os to work?
|
One of the most extreme cases I have found is Adobe software which works as far as Windows 7 (2009) but requires OSX 10.9 (2013).
But even with a lot of common software the same pattern emerges.
* **Firefox** OSX 10.6 (2009) / Window XP SP2 (2001).
* **VLC** OSX 10.6 / Windows XP SP2.
Or other pro software:
* **Autodesk Maya** OSX 10.9 / Windows 7.
* **Ableton Live** OSX 10.7 (2011) / Windows 7
* **Avid Pro Tools** OSX 10.8 (2012) / Windows 7
Etc.
This is not the case with *all* cross platform software, and obviously I haven't checked *all* software that exists, but it seems very common.
Is my impression wrong or there is a reason for this?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/3qnvxe/eli5_why_is_it_that_most_windows_software_works/
|
{
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"cwgujoo",
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2
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"text": [
"Because Microsoft has a lot more enterprise customers who use Windows so backwards compatibility is a much higher priority for Microsoft. A lot of businesses have legacy software where the vendor literally went out of business, so for them it's either use the old version of Windows and never upgrade, or depend on Microsoft to provide backwards compatible functionality.\n\nIn contrast, not a lot of companies run mission-critical software on iOS, so Apple is free to make backwards incompatible changes more often because they assume users will always be on the most recent iOS version.",
"It's really hard to compare, the platforms have been so different.\n\nApple has released a new version of Mac OS X every year. They've also constantly lowered the price, making it a no-brainer for most users to upgrade. As a result, a high percentage of Mac users upgrade to the latest operating system.\n\nAccording to [_URL_1_](_URL_0_), here's the market share for the last 7 Mac OS X versions:\n\n 10.11 0.21% (released Oct 21, 2015)\n 10.10 4.91% (Oct 16, 2014)\n 10.9 1.21%\n 10.8 0.39%\n 10.7 0.40%\n 10.6 0.48%\n 10.5 0.09%\n\nAs you can see, the significant majority of Mac users are using the last few versions. Version 10.6 was released in 2009 and dramatically fewer Mac users are on something older than that.\n\nCompare this to Windows 7, which also came out in 2009, but from that same site, 12.21% of users are on Windows XP, and 1.73% are on Windows Vista.\n\nThe Vista users alone are more than the number of users of Mac OS X 10.8, 10.7, and 10.6 combined.\n\nThe XP users are more than all Mac users put together.\n"
]
}
|
[] |
[] |
[
[],
[
"http://www.netmarketshare.com/operating-system-market-share.aspx?qprid=10&qpcustomd=0",
"netmarketshare.com"
]
] |
|
1175iw
|
Why don't they launch space bound rockets out of tube like bullets from a barrel of a gun?
|
askscience
|
http://www.reddit.com/r/askscience/comments/1175iw/why_dont_they_launch_space_bound_rockets_out_of/
|
{
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5
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"text": [
"Because it would not have any benefit.\n\nThe difference is that a bullet is pushed by an explosion next to it and pushed out by the expansion. A rocket is pushing itself away by pushing out the exhaust of the burned fuel.\n\nSo you don't need to direct the push, since it is inside the rocket anyways.",
"A gun barrel serves as a means to influence control over direction of a bullet's travel ( though it also keeps the explosive forces concentrated behind the projectile)\n\nBecause the rocket is capable of being steered and carries it's own gunpowder, firing it through a tube is simply not required."
]
}
|
[] |
[] |
[
[],
[]
] |
||
36y5rg
|
why are there so few different commercials on youtube? it seems there's only 3 commercials at any time, shouldn't yt be swarming with ad offers?
|
I mean, there are millions of views every day, yet there's that stupid deodorant commercial every second video. Why don't they have more ad partners? Or at least a few different ads per sponsor?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/36y5rg/eli5_why_are_there_so_few_different_commercials/
|
{
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"cri3lm4",
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],
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4,
16
],
"text": [
"I work in marketing, and generally speaking advertisers want consistent exposure for as long as they can get it. They are willing to pay for a higher rate of exposure rather than scattered about. The consumer is much less likely to forget an ad if they see it consistently.",
"YouTube uses ad-targeting. They serve you ads based on their best guess of what you'd want to buy, judging from websites you've visited and other videos you've watched.\n\nE.g., the ads you're seeing are different from the ones I've been seeing. You've been gettIng deoderant and car ads, while they've been serving me ads for a tech product I looked up recently."
]
}
|
[] |
[] |
[
[],
[]
] |
|
5srpm3
|
what happens when a generator is running but no load is being applied?
|
For example; a portable gas powered generator. When the generator is running it is capable of powering a fridge. What happens when the same generator is running but no load is applied? Is electricity still being made?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/5srpm3/eli5_what_happens_when_a_generator_is_running_but/
|
{
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"text": [
"It's like starting a car and walking away. It's still running, still making power, but not being used effectively. ",
"Short answer: with no load generator is easier to turn. It gets more difficult to turn (and takes more energy) as the load increases.\n\nessentially it has to do with inductive reactance in the coils of the generator.\n\nin simple terms, a magnetic field moving near a conductor will induce an electric potential within that conductor. when the generator is spinning with no load you still have electromotive force (voltage) but no current flows and in an ideal generator no *power* is produced. P = VI (ohms law). The amount of torque required to spin the generator's rotor is proportional to the amount of load. the more load the more *work* to spin the rotor one revolution. The rotor will be \"easier\" to turn with no load. Its all physics.\n\nso you have basically an electromagnetic coil spinning inside of some other coils, and really a generator is not much different than an electric motor (in fact many types of AC motors will function as generators, producing a voltage when you spin them while *off*)\n\ncurrent flowing through a coil of wire produces a magnetic field and the north pole will attract the south pole of another magnet. With alternating current the polarity reverses cyclicly so when the rotor poles gets close to the stator coils, the direction of current flow and thus the magnetic poles reverse so they dont just get close to each other and stick (3 phase AC is really useful here). If you spin the rotor and attach a load instead of a current source, a rotating magnetic field is produced, which induced an AC voltage in the coils. (the term AC voltage just made me wonder, alternating *current*, well thats just what its called i guess)\n\nThe rest is a lot of physics, and math. Basically a lot of electrical engineering technical shit that hopefully somebody that knows more about it than me can explain in elegant simple terms that ur average person thats not an electrical engineer or can understand; I'm a computer science student but I dont know everything about electrical circuits (but wants to know everything there is to know about everything), especially when it's not digital logic. Explaining technical stuff in a way that ppl just \"get it\" is hard.",
" > Is electricity still being made?\n\nYes. There's voltage, but no current. Static electricity is a different example of accumulation of potential without a load. Voltage is sometimes called \"potential\" because it *could* make current flow if a load is connected. Since no load is connected, no current is flowing and no electric *power* is generated. Power is voltage times current. \n"
]
}
|
[] |
[] |
[
[],
[],
[]
] |
|
4svwx4
|
What do you catabolize first during starvation: muscle, fat, or both in equal measure?
|
I'm actually a Nutrition Science graduate, so I understand the process, but we never actually covered what the latest science says about which gets catabolized first. I was wondering this while watching _Naked and Afraid_, where the contestants frequently starve for 21 days. It's my hunch that the body breaks down both in equal measure, but I'm not sure.
EDIT: Apologies for the wording of the question (of course you use the serum glucose and stored glycogen _first_). What I was really getting at is at what rate muscle/fat loss happens in extended starvation. Happy to see that the answers seem to be addressing that. Thanks for reading between the lines.
|
askscience
|
https://www.reddit.com/r/askscience/comments/4svwx4/what_do_you_catabolize_first_during_starvation/
|
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"text": [
"Gluconeogenesis highly prioritizes fat metabolism for energy when carbohydrate based sources of glucose are low/empty. The entire purpose of fat is to be an energy source when other sources are low, whereas the purpose of muscles are either locomotion or stability. It would be hard to imagine evolution leaving you as an atrophied blob of fat in an emergency situation.",
"Fat is used extraordinarily preferentially, but there is a cap on stored lipid bioavailability. The little experimentation that's been done on it points to around 30kCal per pound of body fat per day, though there are reasons to suspect that number could be higher in proper context (particularly exercising).\n\nDoing the rough math, that would mean a 150lb guy at 15% bf could burn through just about 700 kcal of daily deficit per day with minimal muscle loss. \n\nOnce you just can't satisfy your energy requirements with fat metabolism, the LBM catabolism kicks in. You're likely to both actively and passively reduce energy expenditure in this state, but the rest of your deficit will have to pop out of muscle at a frighteningly high rate--a pound of catabolized muscle provides something in the realm of 600-800 kcal versus fat's 3500 or so.\n\nThus, in real starvation conditions, it's entirely possible for moderately lean people to lose well in excess of a pound per *day*, mostly from muscle. That doesn't keep up for long, though, because some of those muscles (like the heart) are kinda important.",
"The body breaks down both, but not in equal measure. Worth noting that other posters haven't brought up is that you will starve to death without having exhausted all your fat reserves if there were enough of them to begin with. If you consume pure protein, your body will only burn the fat reserves. The protein is still necessary, so if you've got no intake you'll be breaking down muscle, with fat much preferred for calories.",
"Gluconeogenesis converts certain proteins to glucose. Fat (adipose tissue) is utilized directly (by muscles) as free fatty acids for energy. The brain can use up to 75% of its requirements from two of the three ketones produced (by the liver) from fat. The other 25% must be glucose (see gluconeogenesis, above).\n\nNote: ketones cannot be created from fat, except that fat (stored as a triglyceride) is comprised of three (tri) fatty acids connected to a glycerol (glucose) molecule.\n\nThis is extensively discussed, from time to time, in /r/keto and allied subs.",
"Finally something in r/askscience where my degree can be of use (PhD in muscle biology)\n\nWhenever you stop eating, your substrate preference will be about 2/3 fat and 1/3 carbohydrates. Those carbohydrates will come from stored glycogen in your liver and muscles.\n\nWhen those glycogen stores run out, the liver will try to defend the blood glucose through gluconeogenesis, synthesizing glucose from amino acids from protein broken down elsewhere in the body and glycerol from triglycerides. This metabolic phase is characterized often by decreases in blood sugar and associated tiredness and hunger. It is also the phase in which muscle catabolism progresses at the fastest pace.\n\nHowever, 12-24 hours after running out of glycogen, the body will gradually go into ketosis, in which the liver synthesizes ketone bodies from fatty acids. These ketone bodies can substitute and/or replace glucose in the metabolism, reducing the need for breakdown of protein for amino acids for gluconeogenesis. After a couple of days the substrate preference will have changed to 90% fat and 10% carbohydrates, thereby reducing muscle catabolism strongly. This state can be maintained for as long as there is enough fat. The longest documented therapeutic fast was 385 days during 100+ kg weight loss in an obese patient. Mind you that a kg of bodyfat contains enough energy to go for 3-6 days depending on body size and activity level.\n\nKetosis and relying predominantly on fats will continue until only the essential bodyfat stores are left at approximately 5-7% in men and 10-14% in women. At this level the substrate preference for fats disappear and muscle catabolism increase sharply again. At this point death will usually occur within very few weeks."
]
}
|
[] |
[] |
[
[],
[],
[],
[],
[]
] |
|
6a1jou
|
Why isn't there a general formula for solving quintic polynomials like there is for quadratics, cubics and quartics?
|
askscience
|
https://www.reddit.com/r/askscience/comments/6a1jou/why_isnt_there_a_general_formula_for_solving/
|
{
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"text": [
"The question really shouldn't be \"Why isn't there a 'Quintic Formula'?\", the question should be \"Why is are there Quartic, Cubic and Quadratic Formulas?\" Because, if you think about it, it really doesn't make much sense that there should be such formulas. What's happening is you are taking a single class of really simple polynomials, those of the form x^(n)-a=0, and saying that *any* polynomial of degree n can be written using nothing more than the roots to this single, very simple class of roots. Why should we expect to be able to solve something complicated like x^(4)-13x^(3)+9x^(2)+3x+1=0 using nothing but solutions to equations like x^(2)-A=0, x^(3)-B=0 and x^(4)-C=0? These equations are so much simpler than the equation we're actually trying to solve that it's kinda crazy to think that we can do it. Sure, you might be able to do it up to a point, but eventually the complicatedness will catch up and we'll be unable to solve them. This is the heuristic that you should have when thinking about solutions to polynomials.\n\nOf course, there are deep reasons why 5 in particular is the first that is \"too complicated\", but these really only make sense with specialized math training. What happens is that to solve something with roots, we create a ladder to the solution where each step is a simple step that only requires a solution to x^(n)-A=0. The key is that we know what such ladders look like, and the ladder you'd need in order to solve an arbitrary degree 5 polynomials is provably more complicated than the ladders you can construct using only roots. That is, x^(n)-A create simple steps, but in general you need giant leaps to solve arbitrary equations. The intuition that the gap between 4 and 5 is too big is actually not far off from what is really happening and really is the important thing to focus on. \n\n**TL;DR** The important thing is our heuristic that says that at some point the equations get too hard to solve, and so it becomes only a question of when. \n",
"This actually has to do with a field of math called Galois Theory. Galois showed that the roots of a polynomial can be expressed by radicals (i.e. there is a general formula) if and only if the Galois Group of that polynomial is solvable. \n\nSo let's unpack this. The Galois Group of a polynomial over some field F is the set of automorphisms on the roots of that polynomial. So if we have a polynomial with degree 5, then there are 5 roots to this polynomial in the field of complex numbers.\n\nThe set of automorphisms, or permutations if you are more familiar with that phrase, of 5 elements S5. So now we have to see whether the group S5 is solvable.\n\nA group G is solvable if you can create a chain of subgroups such that:\n\nG1 is a subgroup of G2, is a subgroup of G3..., is a subgroup of G.\n\nWhere A is the trivial subgroup containing only the identity. Also, you need that each of the subgroups is a normal subgroup. Finally, you need each of these subgroups to be abelian. As well as some other conditions. However this is all we will need.\n\nSo the only normal subgroup of S5 is A5, the group of even permutations on 5 elements. However, A5 is not abelian. Thus, S5 is not solvable.\n\nTherefore, we have shown that the group of permutations on 5 elements, the roots of the quintic polynomial, is not solvable by radicals. i.e. there is not general formula\n\n\n[Here is a source for this](_URL_0_)"
]
}
|
[] |
[] |
[
[],
[
"http://documents.kenyon.edu/math/FranzSenEx2010.pdf"
]
] |
||
hk0kc
|
What diseases can you honestly catch from a public toilet seat if it's not properly cleaned?
|
This page left intentionally blank
|
askscience
|
http://www.reddit.com/r/askscience/comments/hk0kc/what_diseases_can_you_honestly_catch_from_a/
|
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"text": [
"Think of it. What part of your body ACTUALLY touches the seat? Just your butt cheeks, basically two big pieces of skin. Unless you have a cut or other way for viruses or bacteria to easily enter, you should be fine.",
"You are more likely to get a disease from a door-knob than a toilet seat. ",
"_URL_0_ verifies the general gist of everyone's thoughts here. (Not my expertise.)",
"None generally.\n\nNow, apparently on average, there are less bacteria on a toilet seat than there are on either your steering wheel, or the keyboard/mouse/trackpad your hands are currently resting on. Though I have to say I don't know what the sample size of this study was, but it makes sense - a plastic toilet seat isn't exactly the greatest environment for bugs to survive very long on.\n\nAs others have pointed out, it's also important to consider what part of your body is touching the toilet seat. It's not a mucosal membrane of any sort; but rather, the skin of your upper thighs and bum. And your (intact) skin is probably the best immunological defence your body has.\n\nThat being said, I would not recommend rubbing the glans of your penis in a pile of semen or feces you find left on a toilet seat. There would be a \"slightly higher\" incidence of disease transmission in this situation. And besides, that's kind of gross.",
"none,\nlook up the peen and teller bullshit episode dealing with toilets at grand central station",
"In my lab we cultured the toilet seat, the toilet bowl, the toilet water in the bowl, the water spout on our filtered water machine, and my mouth. All on 5% sheep blood agar, for 48 hours.\n\nThe results in increasing order of dirtiness.\nToilet water was clean no growth\nToilet bowl no growth\nToilet seat scant growth, and was presumably Staph epidermidis from someones skin.\nWater spout had an overgrowth at 24 hours.\nMy mouth was so dirty I can't even describe it...I have heard that human bites are among the worst in the animal kingdom.\n\n"
]
}
|
[] |
[] |
[
[],
[],
[
"http://www.straightdope.com/columns/read/1598/what-diseases-can-you-catch-from-toilet-seats"
],
[],
[],
[]
] |
|
ech8z5
|
how do phone games that advertise paying you (supposed) real money, earn that money?
|
[deleted]
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/ech8z5/eli5_how_do_phone_games_that_advertise_paying_you/
|
{
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"They earn money from advertisements and end up giving out only a tiny amount of that. You will find that most of those kind of games are some sort of chance games and have a high threshold to actually cash out. It will then usually have something you can buy to increase your chances either with your points or real money. Things like refilling the timer or entering a draw. \n\nSome people may be lucky to get a bigger amount, say $50. But most of it will be something like getting 25cents a day if you're lucky. The company may be getting a couple cents per advertisement viewed but for you to gain 25 cents, you end up watching 50 advertisements. Then there's the people who watch all the ads and spend time but then decide that it will take them too long to reach the cash out threshold which is generally set to around $20 or more. \n\nFor example, you have 100 people who, in total, watched 10000 advertisements which earned the company $100. One of them won $50 and they're happy, the rest kept only getting 25 cents and have $1-5 in their accounts. To cash out, they need $20. So they have given up. So the company gives out the $50 and have another $50 left which will probably never be given out."
]
}
|
[] |
[] |
[
[]
] |
|
4b0lci
|
How did Martin Luther King react to JFK's assassination?
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/4b0lci/how_did_martin_luther_king_react_to_jfks/
|
{
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"d15en8a"
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"text": [
"[Here's a video on it from CBS, an exact interview from him on it](_URL_0_) \n\nHe said it was \"shocking\" and \"upsetting\", and in general seemed to have been sad to lose a friend"
]
}
|
[] |
[] |
[
[
"http://www.cbsnews.com/videos/martin-luther-king-on-jfk-murder-shocking/"
]
] |
||
k5oq3
|
the rank rear admiral
|
an O-7 in the Army is a Brigadier General because he commands a Brigade (or originally) but Rear Admirals don't command Rears... right? Also why are they called "Lower Half" and "Upper Half" why not just Lt Rear Admiral?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/k5oq3/elif_the_rank_rear_admiral/
|
{
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3
],
"text": [
"According to Wikipedia:\n\n > It originated from the days of naval sailing squadrons and can trace its origins to the Royal Navy. Each naval squadron would be assigned an admiral as its head, who would command from the centre vessel and direct the activities of the squadron. The admiral would in turn be assisted by a vice admiral, who commanded the lead ships which would bear the brunt of a naval battle. **In the rear of the naval squadron, a third admiral would command the remaining ships and, as this section of the squadron was considered to be in the least danger, the admiral in command of the rear would typically be the most junior of the squadron admirals.** This has survived into the modern age, with the rank of rear admiral the most-junior of the admiralty ranks of many navies.\n\nIn short,\n\n > Rear Admirals don't command Rears... right?\n\nThey used to command the rear of the naval squadron.",
"According to Wikipedia:\n\n > It originated from the days of naval sailing squadrons and can trace its origins to the Royal Navy. Each naval squadron would be assigned an admiral as its head, who would command from the centre vessel and direct the activities of the squadron. The admiral would in turn be assisted by a vice admiral, who commanded the lead ships which would bear the brunt of a naval battle. **In the rear of the naval squadron, a third admiral would command the remaining ships and, as this section of the squadron was considered to be in the least danger, the admiral in command of the rear would typically be the most junior of the squadron admirals.** This has survived into the modern age, with the rank of rear admiral the most-junior of the admiralty ranks of many navies.\n\nIn short,\n\n > Rear Admirals don't command Rears... right?\n\nThey used to command the rear of the naval squadron."
]
}
|
[] |
[] |
[
[],
[]
] |
|
5nix2c
|
Dear historians of reddit, where do you get your history news, and which journals should I read to keep up to date with history?
|
I can read German and English
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/5nix2c/dear_historians_of_reddit_where_do_you_get_your/
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"Do you currently have access to jounals? Also, what type of history? The American historical review. Is probably the go to journal, but there are many specific journals that may be better suited to a specific topics that you like. ",
"I have access through my university as a student, so I usually look at what electronic journals are published in my areas of research and interest (not usually the same things...) Typically each journal has some sort of group or association behind it with a website, so I can see at least the headlines if I can't get through their paywall to actual articles. \n\nIf you're talking news in general, I regularly visit [here](_URL_0_) just to see what's going on in medieval resarch and for open-access papers. I also follow some people on twitter like this [one](_URL_1_) for tidbits and such on the classical world. Following museums and organisations - and some academic publishers as well - on twitter/facebook is how I see what's being talked about in a informal way. \n\nAnd I agree on the blogs - current research can take a while :)\n",
"I get a lot of access through my University, however, I am also on the email list for 2 free historical review publications:\n\n[Brynn Mawr Classical Review] (_URL_0_)\n\n[The Medieval Review] (_URL_1_)\n\nI find it helps me keep somewhat up to date on new publications. Obviously those 2 journal only cover limited subjects.",
"My specialisation is quite narrow, so I actively follow J. Cold War Stud., Kritika, J. Baltic Stud. and J. Econ. Hist.\n\nThe general prime staple journals are the American History Review and Cambridge History Journal. If you're confident in your German you can also try out the Historische Zeitschrift.",
"So this may seem elementary, but I actually really like the [National Geographic History Magazine](_URL_0_). I'm busy nowadays and don't get to keep up with reading the way I used to. I find this magazine pretty helpful in terms of getting research or learning more about a lot of different topics. It comes out quarterly, and there are hardly any adverts inside (just usually on the inside of the magazine's covers). ",
"I do a lot of podcasts that cover a lot of different topics. Some of them are pop culture type levels, others are more serious. There are a lot of esoteric stuff not really covered (regional, various interest), but those are starting to lessen a bit.",
"The American Historical Association is the biggest organization for historians in the US. They have a journal, the American Historical Review, and a number of magazines that are great to keep up with the state of the profession.\n\nMost subfields have their own organizations, too. For example, the Organization of American Historians is for historians who study the US. They also have a journal and other resources. Then, there are other organizations; for example, the Southern Historical Association for historians who study the US South; the Society of Civil War Historians, for those of us who study the US Civil War. Most major fields have their own organizations and/or journals. \n\nYou may wish to check out H-net. It is an internet resource with a bunch of listservs for various fields. For example, I belong to H-Slavery, H-Civil War, H-Early America. There are a bunch of them.\n\nYou may also find an author/historian you like, and follow them on Twitter. Then, you can check out their followers/who they follow to get a sense of what historians are discussing. the hashtag #twitterstorians is always a good resource, too.\n\nSource: I have a PhD in American History, teach history in a university. ",
"For American history, you'd be hard-pressed to come up with a journal that's more useful than *Reviews in American History.* Excellent review essays. Each one places a book (or *books*) in conversation with the others in the field. Well worth the time, and a fantastic way to keep up with tangential interests.",
"Follow up: which books would you recommend for a general refreshment of my history knowledge which is rusty since high school?",
"I really like BBC's History Magazine. ",
"The Smithsonian Magazine has a nice mix of both current events and history news. Archaeology, history, and even articles featuring artifacts within the actual Smithsonian museum. ",
"If you're interested in the history of science, you can read the unfortunately titled ISIS, which is published by university of Chicago. ",
"German historian here.\n\nFor journals, I regularly read the American Historical Review (AHR), Central European History (CEH), and the German Studies Review (GSR).\n\nI skim the Journal of Modern History (JMH), German History, and Geschichte und Gesellschaft, and Historische Zeitschrift (HZ). (I should be reading them, but who's got the time??!) Also Past & Present, because they occasionally have cool stuff. \n\nFor news-type updates, I rely pretty heavily on H-German and H-Soz und Kult. \n\nI know there's probably a great many German history sites/pages/blogs I should be visiting, but I haven't gotten into the habit. (EDIT: I'm old.)\n\n If anyone has any suggestions, I'd welcome them!\n\n\n",
"Latin American historian here.\n\nI also read the American Historical Review regularly. For Latin American topics, the two best journals are generally considered to be Hispanic American Historical Review (HAHR), published in the US, and the Journal of Latin American Studies (JLAS), published in England. ",
"Most professional historians in academia are tied into various peer networks: listservs, Facebook groups and friends, Twitter (check out the hashtag [#Twitterstorians](_URL_0_)), professional societies such as the American Historical Association and the North American Conference on British Studies, and offline personal and professional relationships. [H-Net](_URL_2_) is a good resource. There are numerous serious academic blogs that cater to different historical constituencies; the [Society for US Intellectual History blog](_URL_1_) is an example. The [New Books Network](_URL_3_) group of podcasts is worth noting.\n\nIn terms of journals I will usually glance at the table of contents of Twentieth Century British History, Victorian Studies, the Journal of British Studies, Modern Intellectual History, the American Historical Review, Past & Present, etc. But usually I just find out about individual articles of interest in these or other journals by word of mouth or through some kind of specific search I am conducting.",
"In addition to the American Historical Review (AHR), you can also check out the Journal of American History (JAH). There are also a ton of more specific academic, refereed journals as other people are referring to. As far as easier to read, shorter information on history being done, simply check out any reputable site, as long as they cite academic journals or published, peer-reviewed studies.",
"I'll mention something no one else has - I get most of my news through [Google Scholar alerts](_URL_0_) set to keywords of my interest, it sends me newly indexed scholarly articles (and theses, and some other junk) in my field. This is good if you are a bit of a [hedgehog](_URL_1_) and want to keep track of a very particular field that is going to be unified with 5-7 keywords. This may work for you if you're really into something, but if you set a google alert for \"history\" you're probably going to have a bad time! :) ",
"I check a few journals that my college library has.",
"This is awfully specific, but as it's my field I read it regularly. *The Journal of the Gilded Age and Progressive Era* speaks for itself. It publishes articles about US History between the end of the Civil War and the end of World War I, although the latter limit has become a little more flexible recently. As others have stated, the American Historical Review is also a top contender. ",
"A feature I find handy is that Oxford University Press ─ publisher of the *Journal of American History* and the *American Historical Review* ─ has an alert feature that sends you an email whenever a new issue is published. What's more, OUP lets you read the table of contents so you know if there's something interesting inside. It's an easy way to stay up to date on things you might be interested in.\n\nFor me, in addition to AHR and JAH, I get alerts on *Diplomatic History*, the official journal of the Society for Historians of American Foreign Relations; *Western Historical Quarterly*, and *Environmental History*.\n\nThe last one is something that I think more folks here should consider. Environmental history is a relatively new subfield, and there's a lot of good stuff being produced by historians there, mainly because it is so new and really on the cutting edge of analysis. \n\nOne thing that I find incredibly useful to do is follow historians on Twitter. Historians love to talk, particularly about their field, and they're not shy about sharing new information, new finds, and other things. Sure, you're welcome to follow me @AK_OK (shameless plug), but there's people like Joanne Freeman (@jbf1755), Adam Tooze (@adam_Tooze), Alex Wellerstein (@wellerstein), and Sara Damiano (@SaraTDamiano) to name just a few.\n\nThere's also great organizations that post good stuff on Twitter frequently. There's Backstory (@BackStoryRadio), JSTOR Daily (@JSTOR_Daily), and Oxford University Press history (@OUPHistory) to name just a few. Process History (@processhistory) is new but promising.\n\nAn easy way to search for accounts to follow is to do a search under the hashtag #AHA17; that was the tag for the American Historical Association's annual meeting this year. \n\n"
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"http://www.medievalists.net/category/articles/",
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"http://bmcr.brynmawr.edu/",
"https://scholarworks.iu.edu/journals/index.php/tmr"
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[
"https://shop.nationalgeographic.com/product/magazines/national-geographic-history/national-geographic-history-magazine-u.s-delivery"
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"https://twitter.com/hashtag/twitterstorians?f=tweets&vertical=default&lang=en",
"http://s-usih.org/blog",
"https://networks.h-net.org/",
"http://newbooksnetwork.com/"
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"https://en.wikipedia.org/wiki/The_Hedgehog_and_the_Fox"
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|
31lgzn
|
Books on Nazi Germany's Occult?
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Does anyone have good recommendations for books relating to the Nazi's investigations/interest into the occult? Not looking for anything specific, but I find the topic extremely interesting and somewhat under discussed in most areas I am exposed too.
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/31lgzn/books_on_nazi_germanys_occult/
|
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"text": [
"I don't know if they will have specifically what you're looking for, but there is quite of bit of information on this subject in the [FAQ](_URL_0_)"
]
}
|
[] |
[] |
[
[
"http://www.reddit.com/r/AskHistorians/wiki/wwii#wiki_the_nazis_and_the_occult"
]
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|
bjxurx
|
why is dentistry stressed as so important it needs to be regularly visited?
|
Cardiologists, podiatrists, etc don’t stress yearly or twice yearly check ups in the same way. I use my heart and feet every day, and they are arguably more important than teeth. Or why do I need to visit a dentist without having symptoms? Genuinely curious.
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/bjxurx/eli5_why_is_dentistry_stressed_as_so_important_it/
|
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"You need to visit a dentist for an in-depth cleaning, which is a procedure which is difficult for individuals to do at home, unlike routine foot care. Oral health problems are relatively common, but can be very severe and irreversable (if you lose a tooth, there's no growing it back). Maintenance is relatively inexpensive compared to regular in-depth analysis of your heart, so it's reasonable to do it annually."
]
}
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[] |
[
[]
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yrfpb
|
tessellation
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/yrfpb/eli5_tessellation/
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"A tessellation is a repeating pattern of the same shape often flipped and/or rotated in order to make a pattern with no spaces. A checkerboard is a tessellation, as the pattern repeats itself. But it's a simple one. Honeycombs are also tessellations as the pattern repeats itself endlessly, and it's always the same shape.\n\nThe important bits are that the same shapes are used (even if rotated, flipped, or recolored) and that there are no or insignificant gaps - meaning that if there are gaps, they could be considered part of the pattern. A brick wall is a tessellation with gaps, for example, as you have to have the mortar in there to keep the wall together. You could consider the mortar around each brick to be part of the design, and thus not really a gap as it's the same on the six brick from the top as it is on the fourth brick from the bottom."
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g7p8i
|
How do cells "know" their location in the body, especially during embryogenesis?
|
I was watching a show on PBS regarding genetics, and learned that some genes are used for "switching" other genes on and off. The scientists injected a mammalian embryo (can't remember which one), with some sort of chemical that indicated whether certain genes were on and off. It showed that the genes in the "hand" were activated, and I got to thinking, how does a cell know its location relative to other cells? How do the "switching" genes that need to turn on, say, the "form opposable thumb" gene, know that the cells are in the location where the hand is forming?
|
askscience
|
http://www.reddit.com/r/askscience/comments/g7p8i/how_do_cells_know_their_location_in_the_body/
|
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"It has to do with the hormones/proteins that are expressed (or already present such as maternal proteins) that determine the cells fate. In drosphillia I remember dorsal ventral fate was determined by concentration of multiple proteins. I can't remember the exact names but I can look it up for you when I get back home.",
"I don't know the answer right off, but I can answer the hand question at least. The hands (and feet) are formed as a club, and then the area between the digits undergoes apoptosis to form the digits themselves. Incomplete apoptosis is what's responsible for webbing. \n\nWe didn't delve into the genetics of embryology though. Not really clinically relevant. ",
"Thanks, but say the clump of cells at (x, y, z) in the organism is to be the thumb. How does this clump know that it is at a particular \"coordinate\" in in the organism?",
"[This](_URL_0_) should help you. ",
"Since I do research in this general field, I feel relatively comfortable asserting that we don't really know. People throw ideas around like \"gradients\" or \"French flag\" but in practice there's a lot of controversy around experimental evidence (as always).",
"I'm a Developmental Biologist and study this processes. This is a complex system, but here's my very short answer:\n\nIt all comes down to \"Signaling\". In a developing organisms send and receive signals from one another telling each other what to do, and what they are doing. These signals then activate genes that become differentially expressed and cause cells to adopt different fates. This happens over and over as development progresses increasing refinement of the tissues and structures of the organism.\n\nMore than that and I want a chalk board.",
"As adamas said, definitely to do with the combinations and concentrations of various genes/hormones/proteins. \n\nFor example, [HOX proteins](_URL_0_) are able to promote or suppress the activity of other genes to regulate pathways leading to the development of different areas of the body - activating a network of genes that eventually divide the body into \"segments\". A little after this, the presence/absence and concentration of morphogens like [Shh](_URL_3_) affects the gene expression of groups of cells in a pattern or gradient. Shh in particular has been well researched in terms of vertebrate [limb development](_URL_1_).\n\nI find even more interestingly, the research currently in [axon guidance](_URL_2_), which concerns the cues involved in directional development of the nervous system and resulting signalling pathways. \n",
"The growth of digits is signaled by a gradient of the protein shh (sonic hedgehog). The distinction between one digit and the next is dictated by a threshold concentration of the signaling molecule. See: Wolpert's French Flag Model\n\nIn general, the developmental process is a result of the cumulative action of these signals. For instance, action of the different HOX genes along the anterior-posterior axis patterns vertebral identity, initiating expression of different signals within each segment; that's how cells \"know\" they're part of an arm or not. Gradients within these segments pattern the mediolateral and dorsal-ventral axes. \n\nThat's my best attempt at recalling an animal development class from two years ago. If you want a good resource on this topic, I'd suggest Wolpert's Triumph of the Embryo; it can be found cheaply if you don't mind buying used. \n\n_URL_0_\n\nEDIT: Changed ssh to shh; definitely didn't mean secure shell.",
"Imagine a bunch of kids playing some role-playing game. At least in my country the way it goes is that we just kinda decide who's going to be who, and we start the game: Say I will tell \"I'll be a farmer, and you be a peasant that works in the field\" and another is told to be the feudal lord, while a girl is told to be the farmer's house-wife (my country is known to have very sexist cultures). So then we start the game, and everybody goes about with their assigned roles. Everybody kinda knows what almost all these roles entitle to them as duties, should they get assigned such roles. A farmer goes to work, a farmer's wife will cook food for him at home (ahem). When we play tomorrow, I could be assigned the feudal lord and I will know what I should do for the same. All our brains know from past experiences what they should do for any normally given roles.\n\nThat probably summarizes also how our body's cells coordinate with each other during development. Every cell has recorded in its genome the program to follow if it is specified to be any cell it wants. All it needs are the exact cues. How are the programs structured? as highly intricate patterns of gene expression that results in a plethora of inter-connecting gene-interactions which will in-turn give out various phenotypic outcomes (extending dendrites and an axon if you are a neuron for eg). So if you take a single cell out and provide it the exact cues (knowing all that we can know about its genome and working), we can in theory make it differentiate into any of the 100 trillion cells in your body. \n\nSo in essence and in a very simplistic sense, a cell's location in the body is fully found by the cues it gets. What are these cues and where do they come from? Cues are mostly protein or hormone signals that are either released by other cells, or are presented on the surface of neighboring cells. But it all boils down to the same way the kids determined within each other on who will become what. Obviously some kid started the assignments, and sometimes there are kids who are dominant and will always start the assignments, while othertimes all the kids are equally timid and one kid will just randomly man-up and suggest that he be the farmer. Both concepts have been found to be occuring in our cells too, for these patterning events. If you imagine this game in a more massive scale involving hundreds of kids, then its a chain reaction: one kid can say, you be a farmer, and this kid can say to everyone next to him to all be farmers! And then all these farmers can then yell, \"whoever hears us will now be a peasant, and pairs of people can choose between them who will be the husband and who will be wife. Amen.\" And then it would be settled. They effectively drew a circle around themselves that specified all the peasants for that game (we are assuming a completely cooperative bunch of 100 kids). They also instructed these peasant families to decide between themselves who will be husband and who will be wife. Now imagine that kind of assigning program getting executed from the moment of fertilization for many years, only maybe a million times more complicated.\n\nFor example, Cue A could be a diffusing signal from a distant cell, and could have different effects depending on the concentration of this signal, and the enzymatic properties of this signal would mean that there will be a cut-off point distance from the main signal cell, away from which you have no effect. Imagine such a Cue A emanating from the root of your budding arm, and its cut-off distance is 12 cm or so (which is somewhat determined by the variant of the Cue A gene, lets assume). The cells at the tip of the \"budding hand\" would already have gotten a plethora of cues that have kind of instructed them that they need to divide as long as they get Cue A. So these cells will divide till Cue A signal concentration drops off below the treshold, effectively making a crude arm thats 12 cm long from the signal-sending cell (which itself would've been instructed to send Cue A because of the program started by the cues it received a moment before). Other cues within these divided cells will now start to kick in, and these cells will literally \"organize themselves\" in a similar way, using similar mechanisms to form a fully patterned hand. (Entertainment: _URL_0_)\n\nSimilar combinations of cues and their timings decide the patterning of other parts of your body; we do not know the exact cue patterns that determine all these various patterning mechanisms, but we know the different types of cues that happen and the most important cue genes that are involved in these process. Needless to say, these genes are important in a lot of things in our body, including cancers (many of these cue genes are involved in cell division control). They are also the ones that even with small variation cause gross changes in one's body (like the extra finger) and it is suspected that a sum of multiple small variations in these genes (which is basically modifying kinetics of various enzymatic signal reactions) that determine our physical characteristics like height, body sizes, etc. ",
"short answer: chemical **gradients** across cells, tissues, organs, and the entire body."
]
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[],
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"http://en.wikipedia.org/wiki/Hox_gene",
"http://en.wikipedia.org/wiki/Hedgehog_signaling_pathway",
"http://en.wikipedia.org/wiki/Axon_guidance",
"http://en.wikipedia.org/wiki/Sonic_hedgehog"
],
[
"http://www.amazon.com/Triumph-Embryo-Lewis-Wolpert/dp/0198547994"
],
[
"http://www.youtube.com/watch?v=dy9QeosTh7w&t=1m40s"
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|
2i0ktk
|
What were common language learning methods a hundred years ago?
|
Today we have things like Duolingo, Babbel, Skype (For language exchange) and so many other stuff that can help you in order to learn a second language. But, how was the language learning one hundred years ago? How did people learn languages during those times?
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/2i0ktk/what_were_common_language_learning_methods_a/
|
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"Linguist here. This is from memory from a teaching class required for my major some years ago. I'll dig out my old textbook if you'd like me to cite sources.\n\nIn the US, the Grammar-Translation method was the way to learn a language. If you've taken a Latin class, you probably learned by Grammar-Translation (although some new-fangled books are coming out that take other approaches). This method is how people learned language for centuries, going back at least to Rome with Greek language. It wasn't until WWII that the Audio-Lingual and oral methods were developed by Leonard Bloomfield and Harold Palmer, respectively. But I should mention, even with the new methods being used by the government, classrooms still largely used Grammar-Translation until the 60s (and maybe 80s, I can't remember).\n\nThe Natural Method, as I learned it, is essentially a linguistic immersion in the classroom in order to facilitate \"natural\" learning, and the native language is banned from the classroom. This started in Germany and France in the first decade after the turn of the century. "
]
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4lk934
|
What is it on the atomic scale that makes materials either heat up/cool down slower?
|
askscience
|
https://www.reddit.com/r/askscience/comments/4lk934/what_is_it_on_the_atomic_scale_that_makes/
|
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"The quantity is called [heat capacity](_URL_0_), and it's different for most substances. It depends on how much freedom the atoms have to vibrate (and how many dimensions they can move in), and what the smallest amount of energy which can be stored is (quantisation of vibrational modes).\n\nedit: \nAs others have pointed out, it depends on what exactly you meant by \"slower\" here. Heat capacity is the increase in temperature with respect to input energy, so something with a higher heat capacity needs more energy to increase one degree of temperature. Thermal conduction is the change in temperature with respect to time and temperature difference. It's also what makes it feel like metals outside are hotter/colder than wood on a hot/cold day. Since they conduct heat better, you're able to feel the temperature difference between your skin and them better.",
"There are two main things you want in a material if you want to be able to quickly heat it up:\n\n1. Its temperature should steeply increase after it absorbs a fixed input of heat.\n2. It must be able to quickly exchange heat with its environment so that it can quickly soak up thermal energy. \n\nThe first point can be quantified by the [specific heat capacity](_URL_2_) (Cp). Briefly, this quantity tells you how much heat you need to add to 1g of a material to make its temperature go up by 1K. At an atomic scale, the specific heat capacity depends on how many degrees of freedom are available at a given temperature. More simply, it tells you how many ways you can distribute the added energy into linear motions (translations), vibrations, or rotations of atoms, molecules, and larger structures. A good rule of thumb is that materials made up of heavier atoms will have smaller heat capacities. The reason is that since each atom contributes ~3 degrees of freedom, the more atoms you have per gram, the the higher the specific heat capacity tends to be. For example, this fact explains why a cup of hot water (Cp=4J/K/g) will stay warm much longer than a chunk of lead (Cp=0.1J/K/g).\n\nThe other piece of the equation is the rate of heat transfer. The faster you can move thermal energy from a source to the body you are heating, the more quickly it's temperature will go up. There are multiple such mechanisms of heat transfer, most notably conduction, convection, and radiation, each of which depend on different factors. Let me focus on one these, which often tends to dominate - conduction, or heat transfer across two bodies that physically touch. In order to figure out how good a material is at rapidly exchanging heat through conduction, we use a quantity called the [thermal conductivity](_URL_0_). For example, it is largely a difference in the thermal conductivity that explains why on a hot sunny day metal sitting out in the sun can feel scorching hot even when nearby objects just feel uncomfortably warm.\n\nOn an atomic level, this energy transfer is usually mediated by electrons or vibrations of the atoms. [Metals are particularly good thermal conductors for the same reason that they make good electrical conductors](_URL_1_) - they have a high density of free electrons. Having said that, even non-metals, which have a very poor electrical conductivity can make for good thermal conductors. The best example is diamond, where its stiff lattice allows for very efficient conduction via collective vibrations (phonons). In fact, among conventional materials diamond tops the list in terms of thermal conductivity. \n\nedit: fixed some typos",
"The two existing responses mention heat capacity and thermal conductivity. Of the two, heat capacity is more directly related to your question since it is literally defined as the amount of energy needed to get a change in temperature of one degree per unit mass. However, heat capacity alone does not tell the whole story since a thermal mass is rarely heated uniformly.\n\nImagine a potato in an oven. Its surface is heated, which locally increases the temperature. Meanwhile, the heat is diffusing into the center. For a case like this where we have a convection boundary condition, the averaged temperature response of the potato depends not just on its heat capacity, but also it's thermal conductivity.\n\nA property called the thermal effusivity: sqrt(k*rho*c) arises out of solving the heat equation for two objects in thermal contact, which governs how quickly one material will heat/cool in response to being in contact with another one. You can see that that for this case, thermal conductivity (k) and heat capacity (c) are equally important. However, thermal effusivity is not an intrinsic property, it's a mathematical creation for use in particular problems.\n\nFinally, at the molecular answer, the existing responses have touched on the actual mechanisms. For heat capacity, it is ultimately about degrees of freedom. What you find for solids, however, is that there is not significant variation (less than an order of magnitude) and what variation there is usually directly proportional to its density.\n\nUnlike, heat capacity, thermal conductivity of a solid material can vary by 4 orders of magnitude. As an example, amorphous carbon has a thermal conductivity < 1 W/m-K and diamond and graphite have thermal conductivities > 1000 W/m-K, and they are all literally just carbon. This is entirely due to their crystal structures and carbon-carbon bonds. In non-metallic solids, heat is transferred by atomic vibrations. The strong bonding and highly oriented graphite and diamond structures provide more available modes for heat transfer.\n\n*Edit: grammar"
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[
[
"https://en.wikipedia.org/wiki/Heat_capacity"
],
[
"https://en.wikipedia.org/wiki/Thermal_conductivity",
"https://en.wikipedia.org/wiki/Wiedemann%E2%80%93Franz_law",
"https://en.wikipedia.org/wiki/Heat_capacity#Specific_heat_capacity"
],
[]
] |
||
1pdvv8
|
What will happen if a UTI goes untreated?
|
Will it kill you? Will you suffer for a while and eventually get better?
|
askscience
|
http://www.reddit.com/r/askscience/comments/1pdvv8/what_will_happen_if_a_uti_goes_untreated/
|
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"First what is a urinary tract infection (UTI). A UTI is essentially just inflammation of the urinary lining in response to an infection. When detecting a UTI we generally are looking for two things: bacteriuria (the presence of bacteria in the urine which generally does not have detectable bacteria) and pyuria (signs of inflammation). Bacteriuria can be present without a UTI. This occurs in colonization (having bacteria on the bladder lining). \n\nIt is hard to look at your question using recent data because, most often, people are treated when diagnosed. There have been some studies looking at bacteriuria in women and have shown that it will go away without treatment in 60% of women within a month. In one series of 45 women left untreated, all but 2 were able to clear their bacteria by six months. Interestingly, this same study found that treating with antibiotics did little to prevent the recurrence of UTIs. \n\nSo, why treat? One is to provide expeditious symptomatic recovery. Additionally, there are some bad outcomes that can result from a UTI. One is pyelonephritis (infection of the kidney). Generally, urine from the bladder does not go back to the kidney, so infection should not spread in most cases. A couple of conditions make it more likely to spread and as a result require more aggressive treatment. One is pregnancy, women with untreated bacteria in their urine have greatly increased rates of pyelonephritis. The other is vesico-ureteral reflux (VUR), a condition in some children which results in the passage of urine from the bladder up to the kidney. \n\nAnother concern is sepsis. Sepsis is an over-response to infection. Older patients are much more at risk of this and are also more at risk of having bacteria from a urinary tract infection pass into their blood (bacteremia). \n\nA final concern is that chronic urinary tract infection may be a potential risk factor for bladder cancer, though this link is not well established in the general case.",
"It really depends on a complex interplay between the bacteria causing the infection and the person it is infecting.\n\nAn otherwise healthy person stands a very good chance of eventually clearing the infection on their own, though it would likely be uncomfortable until the infection was resolved.\n\nSomeone who is not so healthy (i.e. has diabetes, is immunosuppressed, or has a urinary tract that doesn't behave normally - think enlarged prostate causing urinary retention) may not do so well for a number of reasons. Their normal defensive mechanisms don't work well. The man with an enlarged prostate who cannot fully empty his bladder is unable then to fully flush the bacteria out. The person who is taking drugs to suppress their immune system doesn't have the vigorous response needed to clear the infection.\n\nThe passage of urine is not necessarily as one way as we would like to think, and some people can have \"reflux\" of the urine from the bladder up towards the kidneys. It isn't all-or-none, it's just that a certain amount of urine will make it back up to the kidney and then back down. Probably all of us have some degree, however mild or infrequent, of reflux at some point in our lives.\n\nThis reflux means that the bacteria in the bladder can be carried to the kidneys. There's also the fact that some of the buggers have flagella, which makes them able to move and thereby assist in their own transport back to the kidneys. This kidney infection (pyelonephritis) then can cause fever, back pain, nausea, and vomiting. Sometimes this arouses the immune system well enough that the infection will stop here, though you will be bad sick for a few days while you get better.\n\nWithout an adequate immune response, this can cause an abscess in or around the kidney, which you may or may not wall off and take care of that way. More likely than that, however, is that you'll get bacteria entering the bloodstream from the kidneys (because the kidneys are there to filter the blood, and it's not much for the bacteria to gain access through the filters). Should that happen, you'll likely start to become quite ill with something called sepsis.\n\nAt that point, a nasty fight ensues, and some of the body's own reactions to the infection can be harmful. Chief among this is widespread dilation of the blood vessels. This happens because when you have a localized infection (say an infected cut on your hand), you want the blood vessels in that area to dilate and allow more blood to flow to the area to deliver more infection fighting capacity. But, when the infection is \"everywhere\" because it's mixing throughout the bloodstream, the dilation happens in widespread fashion.\n\nThis can lead to profoundly low blood pressure, which in turn deprives organs of the blood supply they need to function properly, and then you start to see bad things like kidney failure, liver dysfunction, heart dysfunction, etc. Think of it as tying tourniquets around the various organs' blood supplies, and you get the picture. This cascade then leads to more organ dysfunction in a dismaying downwards spiral, and without aggressive treatment, will often result in demise. That's not to say that people in the course of human history haven't gotten better on their own (my dad survived typhus in Burma without antibiotics but was sick for weeks), but the survival rate in full-blown sepsis is extremely low.\n\nI should say a couple of things about that sepsis explanation. The actual sepsis cascade is vastly more complex than I've made it out to be, but that is a generally acceptable lay explanation for it. I will also say that other infections such as pneumonia or skin infections can and do lead down the same pathway - in other words, it isn't just kidney infections that cause sepsis.\n\nTL;DR - UTI's don't always kill you, you can fight them off yourself some of the time. Sometimes you don't and you die. The less healthy you are, the less likely you'll cure yourself."
]
}
|
[] |
[] |
[
[],
[]
] |
|
88c1if
|
why do prestigious brands allow discount supermarkets to copy them
|
More and more I notice discount supermarkets in the UK imitating brands to such an extent they are almost indistinguishable from the brand they try to copy.
Does this not infringe on any copyright? Essentially the original is paying for branding and marketing for the copycat.
Why do i not notice this so much in regular supermarkets? Do they have higher ethical standards or perhaps they are in cahoots with the big brands?
Please, explain like I'm five!
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/88c1if/eli5_why_do_prestigious_brands_allow_discount/
|
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"text": [
"In some cases the Main company might actually own the \"fake\" company and sell bad batches/same product under a new name so that they get alot more profit",
"Because the items being sold aren't patented or cannot be patented. Remember when Tempur Pedic's patent expired a little while ago? Every mattress company jumped on making those type of mattresses. ",
"I can't speak for the UK, but in the US, food and fashion are two things that aren't patentable or copyrightable. You can copyright or trademark a label or brand name, respectively, but not the contents or appearance of the food stuff itself, even if it's a picture on a box (which you'd argue, if you could, would be part of copyright for the label).",
"You can't copyright food. You may have noticed that every restaurant in the world sells something called a \"hamburger\" that is pretty similar to every other hamburger in the world. You can trademark the name - \"Whopper\" or \"Big Mac\" but the food product itself is a free for all. This is also why brands like Coke and KFC protect their specific formulas with such secrecy.",
"The appearance of a product is not covered by copyright, it is covered by trademark.\n\nA trademark is violated when consumers would be confused about which brand they are buying. Over the years, various lawsuits have established how similar a knockoff can be without violating copyright, and knockoff manufacturers are adept at dancing on the edges of those principles.\n\nAnd even when they step over the edge, it may not be worth the trouble of suing them over it."
]
}
|
[] |
[] |
[
[],
[],
[],
[],
[]
] |
|
12k1ii
|
Is there a minimum energy required for a photon to exist?
|
Just wondering if the scale for energy in a photon (or any particle, for that matter) is actually continuous.
By continuous I mean is there a total real number of possible different levels of photon energy between some very small number and zero, or is there an infinite range of energy between, say 1 electron-volt and zero.
My friend and I were arguing about the possibility of infinite complexity in the universe and we came to the conclusion that if the scale for energy was fully continuous to zero, it'd be possible for the universe to have infinite complexity within it, but I argued that due to the fact that photons are generated by changing electron states and that the possible states of electrons are non-continuous, there must be a finite, lowest non-zero value for the minimum energy of an electron.
He says that higher and higher input energies to the electrons would allow for an infinitely small drop from state to state, be it state 4E10 to 4E10-1, or another drop even more infinitesimal in energy difference. I'm thinking the atom would ionize, and at that point I'm not sure what possible energy levels could emerge.
Could some kind, intelligent soul shed some light on the situation? Google isn't helping us out very much...
|
askscience
|
http://www.reddit.com/r/askscience/comments/12k1ii/is_there_a_minimum_energy_required_for_a_photon/
|
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"There is no minimum limit on photon energy required to exist, though that depends on the size of the universe you're dealing with. A photon cannot have a wavelength larger than the universe or world you're dealing with within you are measuring entropy, and this is part of how the maximum possible entropy of a volume is calculated IIRC.\n\nA photon cannot have a wavelength larger than the universe, or it cannot have a wavelength larger than the observable universe (to be observable). Such a photon would be very poorly localized by the Heisenberg Uncertainty Principle and I believe it would be correct in a hand-wavy sense to say it exists everywhere within the universe. For a universe of any given size, the energy of this photon would be the minimum quantum of energy, and given the fact that there are a limited number of quantum states and that quantum states are separated by energy levels, the size of the universe delineates the number of possible quantum states within our universe under study.\n\nApologies; it is past 4 am and I am sleepless. Thank you for reminding me of this puzzle though I cannot seem to remember the worked-out solution I encountered.\n\nFurther reading?\n\n[Information in the Holographic Universe](_URL_1_)\n\n[Photons in a box](_URL_0_)",
"I'm just learning QFT and QED, so take this with a grain of salt, but I think the answer is that it depends on the physical system you're working in. If your system is limited to a finite volume in space-time, then the energy and momentum states in your theory will be discretized. If the space-time volume is infinite, then the energy and momentum are continuous.",
"There is no known limit. \n\nAs you accelerate in the direction of photon travel, the apparent energy of the photon reduces continuously( red shift), since the energy of a photon is entirely relativistic. As you tend to c the photon energy tends to zero. I.e. fully red shifted. The photon does not change. The energy you measure depends on the frame you are in.\n\nFor a donut universe you could get to the limit where the wavelength is of the order of the universe characteristic length and then you might get some funny things happening.",
" > ...I argued that due to the fact that photons are generated by changing electron states and that the possible states of electrons are non-continuous, there must be a finite, lowest non-zero value for the minimum energy of an electron.\n\nTake any atom that's emitting a photon. Any photon - even as energetic as, say, the hydrogen atom relaxing from n = 2 - > 1 (first of the [Lyman series](_URL_0_)).\n\nNow move that atom at some velocity away from you. That photon is now redshifted.\n\nSince velocity is not quantized, you can set any number between 0 and c for velocity. This gives you any degree of redshift you want for that emitted photon, from a wavelength of 121.6 nm (when the atom is at rest with respect to you) to an arbitrarily high wavelength.\n\nOf course, as others have said, that photon is only meaningful in the universe that can contain it - so its existence depends on how big of a \"box\" in which you want to contain it.",
" > He says that higher and higher input energies to the electrons would allow for an infinitely small drop from state to state, be it state 4E10 to 4E10-1, or another drop even more infinitesimal in energy difference. I'm thinking the atom would ionize, and at that point I'm not sure what possible energy levels could emerge.\n\nYou don't have to increase the temperature to add possible states. Simply making the body larger (i.e. adding more atoms) will increase the number of states available. Additionally, the energy level of each state isn't precise. As with everything in QM, there is an uncertainty involved with each state. You can see this most easily in atomic spectra, where you can see broadening in the spectrum with an appropriately small diffraction grating. Even accounting for doppler shifts and the non-zero width of your collimator in your apparatus, there is still a gaussian distribution of energy.\n\nNow, when you get differences in energy states small enough, the broadening due to uncertainty will be greater than the energy difference (technically, since the broadening is gaussian this could happen for any difference - but let's say here one standard deviation apart can be considered \"overlapping\"). At this point you get a continuous spectrum of energy levels, so arbitrarily small transitions can occur.",
"what about the photons carrying the electrostatic force ?\n\nthe frequency is 0"
]
}
|
[] |
[] |
[
[
"https://en.wikipedia.org/wiki/Photon_gas",
"http://sufizmveinsan.com/fizik/holographic.html"
],
[],
[],
[
"http://en.wikipedia.org/wiki/Lyman_series"
],
[],
[]
] |
|
zl6f0
|
Why might a cat's eyes change color?
|
askscience
|
http://www.reddit.com/r/askscience/comments/zl6f0/why_might_a_cats_eyes_change_color/
|
{
"a_id": [
"c65ji76"
],
"score": [
2
],
"text": [
"Cat eye color is fairly variable. Most kittens are born with blue eyes and undergo changes in the color of their eye pigments between 3-12 weeks of age. By about 3 months of age a kitten's eyes should have matured into an adult color and stop changing."
]
}
|
[] |
[] |
[
[]
] |
||
5h87s9
|
why mobile phone cameras don't have more manual settings?
|
I have an I phone. The camera has minimal settings that I can adjust manually. I understand that a lot of things are very unnecessary but there are some things (IE exposure, ISO) that seem like they could be useful and not terribly hard to add. Also how do apps from the app store apply these settings? Why couldn't Apple just include them as default.
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/5h87s9/eli5why_mobile_phone_cameras_dont_have_more/
|
{
"a_id": [
"day4xka",
"day7dwg"
],
"score": [
5,
3
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"text": [
"(tag your post)\n\nMost people have no idea how to use exposure, ISO, and other advanced camera options. If Apple provided manual options for these in their default camera app, people might set it up wrong and then blame the tool for their photos being crappy. So Apple's stock app tries to handle it itself, and *most* of the time gets acceptable results. Apple's #1 goal is always ease of use, if the experience of using the device is frustrating they might move away from buying iPhones.\n\nAs someone who knows photography and technology, you have the awareness these features exist and can go looking for them via the 3rd party utilities. So you got what you wanted, Grandma \"I can't computer\" gets what she wants (decent pictures), and everyone's happy.\n\n\n**EDIT** as for the \"how do third party apps apply these\" The camera software \"exposes\" lots of options as an API, which means that apps can be built to tweak the camera's fucntions. Apple's stock camera app either doesn't use all the APIs apple build for the camera, or when it does it doesn't tell you what it's doing or provide a button to change it. But 3rd party tools can request access through these.",
"For every person who understands what an ISO setting is and why you would want to change it, there are probably 10 who don't. And of those, a few will accidentally change their settings and wind up taking shitty pictures and not know why, and think their phone camera sucks.\n\nIt also creates a market for higher end apps that allow users to do this."
]
}
|
[] |
[] |
[
[],
[]
] |
|
2hnets
|
Did Alexander the Great hold any religious views that would have been considered unusual by his contemporaries? Was he a monotheist?
|
There is a [post](_URL_0_) on /r/todayilearned that claims Alexander was a monotheist as a result of Aristotle's teachings. The page the post links to doesn't seem to have any sources, it sounds kinda like bullshit to me.
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/2hnets/did_alexander_the_great_hold_any_religious_views/
|
{
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"text": [
"I'm not well-versed on Alexander the Great, but I do know that Herodotus believed Alexander I (ancestor to The Great) to be descended from a line of Herakles (i.e. descended from Zeus), although the passage has been read as connecting Alexander to Helios instead of Zeus (*Histories* 8.137-9). Herodotus was considered unreliable even in antiquity though (see Lucian). (Edit: I might also add that Alexander the Great is occasionally represented as Helios.)\n\nWhile you wait on a historian better-versed on Alexander the Great, [this article](_URL_3_) discusses a supposed correspondence between Alexander and Aristotle (the document in question dates no earlier than 6th century AD). I don't have access to the article to read it though.\n\nWhat I can tell you is that a lot of myths exist around Alexander the Great. He appears in Jewish legend as having gone to Jerusalem and offered a sacrifice to Yahweh. (You can read Josephus's account in translation [here](_URL_4_), and see some scholarship on that passage [here](_URL_2_) and [here](_URL_5_).) He also appears in 1 Maccabees as a purely historical marker. \n\nHe shows up in the Quran as Zul-Qarnain (the Two-Horned one) in Surah 18:83–97. This was a common title for Alexander, but that doesn't mean everyone agrees Zul-Qarnain was Alexander. (See [here](_URL_1_) and [here](_URL_0_).) \n\nEdited for clarity. Thanks to /u/Watermelon-Sugar for reminding me not everyone is steeped in Ancient Greek genealogy. ",
"Having read Arrian and Plutarch, I was under the impression that Alexander was conventionally pious. He certainly is said to have dedicated altars to the gods of the Olympian pantheon on many occasions, something that cost him time and money. He consulted famous oracles, not something that a newly converted monotheist would seem likely to do. He made no new religious foundations, as far as I know, nor am I aware of any record of his having said anything about there being only one god. This sounds like a bizarre thing to me.",
"There is kind of an interesting story which might answer your question (though it may just as well have been Alexander being a smart-ass). Before being tutored by Aristotle, he was taught by a man named Leonidas. When Alexander was a child he once used two fistfuls of incense on the altar-fire as sacrifice to the gods. This caused Leonidas to lecture Alexander on not being wasteful, and that only when he had conquered the spice-bearing regions he could throw in as much incense as he wanted. \n\nFast-forward a few years and Alexander ends up doing just that. Along with the usual gifts to his mother and sister he gifted 18 tons of frankincense and myrrh to his old teacher, along with the admonition that one should not to be 'parsimonious towards the gods.' While it is difficult to ascertain something like one's beliefs from one quote, it would seem that he might be attributing some of his military success with favor from the gods. \n\n_URL_0_"
]
}
|
[] |
[
"http://www.reddit.com/r/todayilearned/comments/2hmshh/til_alexander_the_great_and_aristotle_were/"
] |
[
[
"http://klingschor.blogspot.com/2011/08/alexander-great-dhu-al-qarnayn-quran.html",
"http://www.islamawareness.net/FAQ/zulqarnain.html",
"https://journals.lib.byu.edu/spc/index.php/BYUStudies/article/download/6389/6038",
"http://www.akademiai.com/content/5l17666281033342/",
"http://www.livius.org/aj-al/alexander/alexander_t35.html",
"http://books.google.com/books?id=TxZK1Le1DpkC&pg=PA71&lpg=PA71&dq=was+alexander+the+great+a+monotheist&source=bl&ots=CWZMBbyShz&sig=KtI3IJC9KuqjjtAGhQDVJJJYyGo&hl=en&sa=X&ei=yGcnVOlxjZfIBOPugpgM&ved=0CFcQ6AEwCA#v=onepage&q=was%20alexander%20the%20great%20a%20monotheist&f=false"
],
[],
[
"http://www.historyhouse.com/in_history/alexander/"
]
] |
|
cfrhkr
|
American social mobility and wealth compared to Europe during the gilded age?
|
I'm puzzled by this. During the late 19th century a huge influx of European immigrants came to the USA seeking better lives. But the late 19th century was a period of rampant inequality in the United States. During the gilded age when all those immigrants were moving out of Europe, was America actually more socially mobile and economically better than Europe at the time?
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/cfrhkr/american_social_mobility_and_wealth_compared_to/
|
{
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"euc6voj"
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"text": [
"So a major factor in immigration was the Great Depression of 1873 caused by an influx of American and Russian grain that lowered the price of grain and caused one of the most surefire capital investments - wheat futures - to begin to fail. Why is that important for European immigration? Because if the price of grain goes down, in most agricultural communities, wages decrease. So the situation resulted in extremely hard times for many in the more agricultural economies of Europe most of which were from Eastern Europe and Southern Europe.\n\nMany of those coming to the United States could more reliably get wages working new industrial jobs than the more taciturn world of agriculture. As you say, the Gilded Age is a time of increased wealth disparity, but even still the cash economy in the US was much more stable than in areas like Southern Italy. One consequence of these declining economic circumstances was a rising crisis in food security.\n\nTo offer an example, Giovanni Vecchi found that working class southern Italians were frequently at a caloric deficit. Vecchi is a professor of economics at the University of Rome and his book *Measuring Wellbeing: A History of Italian Living Standards* seeks to use economic models and statistics in interesting ways to map the growth of development of Italy’s economy and measure its effect on what he calls the ‘wellbeing’ of Italians. His conclusion was that malnutrition was frequent and diseases related to malnutrition (palegra, scurvy) were not uncommon. \n\nIn many cases the particulars were even worse. \r\nOne example has two sources that Vecchi is working with. Firstly, the age, height, body weight, and lifestyle of eight individuals, each from the most common occupations in Naples collected by the Neapolitan Luigi Manfredi. Second, estimated caloric intake of various occupations in Naples against the caloric requirement to do such work. Errand boys, Servants, and Lazzorones (a kind of Neapolitan beggar) ran up to an average 12% daily caloric deficit. Masons and peddlers ran a deficit up to 29%.\r\n\nI bring all this in to highlight that you are correct to note the grueling conditions and dim chances for social mobility in the US on a class basis, but circumstances for many immigrants were quite dire and migration was just as often about survival as social mobility."
]
}
|
[] |
[] |
[
[]
] |
|
2mdg4g
|
why do people tag things (as in graffiti)? not like murals, but like illegible text tags in public bathroom or on a dumpster. what is the point?
|
I could maybe understand if it actually said something *remotely* proficient, but its seemingly mostly just scribbles. Why is it so prevelent?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/2mdg4g/eli5_why_do_people_tag_things_as_in_graffiti_not/
|
{
"a_id": [
"cm37xj4"
],
"score": [
2
],
"text": [
"Its a kind of \"I was here\". Graffiti has been around for millennia, the pyramids have graffiti inside them from their builders, The ruins of Pompei have graffiti on them. It's an ancient tradition carried on through to today. "
]
}
|
[] |
[] |
[
[]
] |
|
4n13kw
|
why people are sometimes compelled to watch things they know will make them sad/cry?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/4n13kw/eli5_why_people_are_sometimes_compelled_to_watch/
|
{
"a_id": [
"d400e56"
],
"score": [
3
],
"text": [
"[Here](_URL_0_) is a good article. \nThis quote sums a lot of it up: \n > A lot goes on in our brains when we watch sad, emotional, or tragic films, and what’s surprising is that a lot of this brain activity actually promotes feelings of happiness, closeness in our relationships, and a sense of community."
]
}
|
[] |
[] |
[
[
"http://greatist.com/happiness/why-do-like-sad-movies"
]
] |
||
6s27oc
|
In aviation, why were tailwheel landing gear developed before tricycle gear?
|
And what prompted the development and dominance of tricycle gear today?
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/6s27oc/in_aviation_why_were_tailwheel_landing_gear/
|
{
"a_id": [
"dlahxf1"
],
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2
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"text": [
"This could be in the Short Answers section, because the answer is fairly simple. Tail-draggers ( like, a DC-3 or Piper Cub) could land on grass covered landing strips. On landing, the tail ( sometimes a skid on some earlier planes) would act as a drag on the back of the plane, keep it pointed in the correct direction as it slowed and came to a halt. Tricycle gear, on the other hand, were harder to use on a grass strip- there was a good chance the wheels could jam into the ground, and the plane would flip end-over-end. On paved strips, however, tricycle gear planes are much easier to use; the take-off procedure for tail-draggers is more complex. But because something like a Piper Cub can land on a variety of places- like a field- such planes have continued to be used in many places like Alaska.\n\nThere's also the matter of speed and weight. A light plane that can take off and land at 40 mph can use a grass strip, hard to do that with a jumbo jet."
]
}
|
[] |
[] |
[
[]
] |
|
5mt4ka
|
What are some often overlooked long-term effects of WW 1 on Europe?
|
Hello,
I'm currently taking a European-centric history class and we're in the process of discussing the period of WW 1 atm and its aftermath.
While it is apparent to me that WW 1 had a destabilizing political, economic, social, and psychological impact on almost all aspects of life in Western Europe. I am wondering if there are any specific long-term effects that is unpopular or often overlooked. I really enjoy reading primary sources/personal accounts of people who lived in a particular time as they help me to grasp the situations they were faced with as opposed to reading a list of facts, so it would be cool if there are any primary sources out there you could point me to. One of the readings I've enjoyed is this, _URL_0_.
Last follow up, I was wondering if there any other free databases I could access like SSRN, but for history. I'm used to going through SSRN for some papers for my business classes, so I'm not that familiar with what databases are good for history.
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/5mt4ka/what_are_some_often_overlooked_longterm_effects/
|
{
"a_id": [
"dc64x01",
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"score": [
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13
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"text": [
"Hello there. Your question seems to be related to school work, so we just want to remind you, and any potential respondents, that [our rules](_URL_1_) DO permit people to ask for help with their homework, so long as they are seeking clarification or resources, rather than the answer itself. This policy is further explained in this [META Thread](_URL_2_).\n\nAdditionally, while our users may be able to help you out here, we hope that you also will take the time to check out our six-part series, \"[Finding and Understanding Sources](_URL_0_)\", which should hopefully prove to be helpful for you as you continue in your research.",
"You might consider consulting an environmental history of WWI. Folks don't typically think of the environmental effects of a war, such as deforestation (caused by industrial demand for timber) or pollution (caused by the need for massive amounts of industry)."
]
}
|
[] |
[
"http://www.historymuse.net/readings/Remarque.html"
] |
[
[
"https://www.reddit.com/r/AskHistorians/wiki/theory#wiki_monday_methods.3A_finding_and_understanding_sources",
"http://www.reddit.com/r/AskHistorians/wiki/rules#wiki_homework",
"http://www.reddit.com/r/AskHistorians/comments/35pkem/askhistorians_homework_question_policy_rehash/"
],
[]
] |
|
blisis
|
What was the status of slavery in the Person Empire (500-330 BC)?
|
According to some Greek sources, Persia used slaves during around 330 BC. However, didn't Cyrus the Great abolish slavery? What was the status of slavery in the Person Empire (500-330 BC)?
The definition of slavery in this question would included people who were purchased as property for economic output, forced into military service without pay, as well as eunuchs acting as members of the royal court.
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/blisis/what_was_the_status_of_slavery_in_the_person/
|
{
"a_id": [
"emowxkx"
],
"score": [
3
],
"text": [
"[This thread](_URL_0_) has some discussion from myself and /u/Aithiopika on slavery in the Achaemenid Empire through a particular case, with links to another discussion as well.\n\nThe short of it is that. no, Cyrus did not abolish slavery, but slavery doesn't seem to have been integral to the socioeconomics of most of the Achaemenid Empire the way it was in, say, Rome, with perhaps the exception of Babylonian \"labourers\". Apart from that, bond-servants and servants on wealthy estates with various unclear social statuses was certainly a thing, as was forced labour with compensation."
]
}
|
[] |
[] |
[
[
"https://old.reddit.com/r/AskHistorians/comments/aygfe8/did_darius_the_great_pay_his_construction_laborers/"
]
] |
|
3rf088
|
how did people discover electricity and how did they invent the first electronic device?
|
I cant wrap my head around how the first electronic devices were thought of and realized? How was electricity discovered and how could you from just knowing about electricity create devices that runs on it?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/3rf088/eli5_how_did_people_discover_electricity_and_how/
|
{
"a_id": [
"cwnhnax"
],
"score": [
3
],
"text": [
"Essentially it all began because we observe electromagnetic effects in the world around us. For example static effects on metal shavings, lightning etc. This sparked curiosity by proponents like Benjamin Franklin. However the main leap was when we discovered that if you change the position of a magnet (In this case, naturally polarised metallic substance) through a coil of wire, it induces a 'current' in the wires. This was discovered by Michael Faraday. \n\nIt is not too much of a leap then to see how this set the ball rolling.... If we create a large enough current by moving the magnet enough, we can heat a thin piece of wire to create light. Now, If we use a combustion engine, we can keep the magnet moving constantly through a motor, and keep the light on...ohh look there are relationships between the coils I have, the wires I choose, the network I make, and the current passing, the voltage etc....\n\nEssentially, it's...curiosity > observation > testing > observation > explanation > conclusion > document > repeat.\n\nUntil you reach today."
]
}
|
[] |
[] |
[
[]
] |
|
ywryb
|
capillary action. i know what it is, but i cannot quite understand how/why it works. where does the force/energy come from that allows the fluids to move?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/ywryb/eli5_capillary_action_i_know_what_it_is_but_i/
|
{
"a_id": [
"c5ziax6"
],
"score": [
8
],
"text": [
"It's the attraction between your fluid and the wall of the container (adhesion) and the attraction between molecules of your fluid (cohesion). In other words, the energy comes from electromagnetic interaction.\n\nTake this for example. A ball suddenly pops into existence on a slope. It spontaneously rolls down the slope. Where does the energy come from? It comes from the gravitational potential from starting position of the ball.\n\nTake another example. A negatively charged ball pops into existence in an empty, gravity-less universe, and some distance away there is a positively charged plate. Because opposites attract, the ball will move towards the plate. Where did the energy come from? Once again, it is the electric potential of the starting positions that gives it the energy.\n\nNow let's take this further. A negatively charged ball suddenly pops into existence on a slope, with a positively charged plate higher up the slope. The ball rolls up because opposites attract (and let's say the charge is strong enough to overcome gravity). Where did the energy come form? Again, it is defined by the starting position, and the balance between the two forces. When you take both of them into account, you'll find that when the ball reaches the plate, its total energy is actually _lower_ compared to its starting position, and objects always tend to reach the lowest energy state. The decrease in electromagnetic potential overcomes the gravitational potential.\n\nIt is the exactly same case for capillary action. It is your fluid trying to reach the lowest energy state."
]
}
|
[] |
[] |
[
[]
] |
||
2ux301
|
do animals have phobias?
|
Are there wild animals out there with the same irrational fears as people?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/2ux301/eli5_do_animals_have_phobias/
|
{
"a_id": [
"cocgiu4",
"coch22h",
"cochd0m"
],
"score": [
2,
2,
2
],
"text": [
"Horses really don't like water surfaces (not really phobic since they don't trust the ground they cannot see, and being flight animals they really care for their legs). ",
"Fear is a pretty ubiquitous mammalian response to stimuli. I wouldnt find it very hard to believe that the neuronal circuitry responsible for it that goes haywire in human brains couldnt also malfunction or overexpress in other mammalian brains. ",
"Some large dogs shit themselves and run away in absolute terror at the sight of an big exercise ball. "
]
}
|
[] |
[] |
[
[],
[],
[]
] |
|
1ze6ue
|
Force without acceleration?
|
I've been pondering this question for a while and I can't seem to come to a conclusion. I am currently exerting a force on the chair I'm sitting on, but, according to Newton's second law of motion, F=ma, but there is no acceleration present. How am I still exerting a force with no acceleration? I thought that it may have something to do with my atoms' vibration, but I'm not a physicist and I wouldn't want to mislead myself to a false conclusion.
|
askscience
|
http://www.reddit.com/r/askscience/comments/1ze6ue/force_without_acceleration/
|
{
"a_id": [
"cfsxqbr",
"cfsxqbz"
],
"score": [
25,
7
],
"text": [
"In the equation F=ma, F is the **sum of all forces** acting on the object. In the case of you and the chair, your body is being pulled down to the chair by gravity but you're not accelerating straight through the chair so there must be a force acting against you pushing you back up.\n\nThis force is the chair pushing against you and is called the reaction force and it is defined in Newton's Third Law where when one body exerts a force on another body, the other body exerts an equal and opposite force to the first body, which results in the **net force** being zero and your acceleration being zero.",
"Because the chair is pushing back at you with an equal and opposite force, so there is no _net force_, which is what F=ma applies to.\n\nThis can be demonstrated by having someone quickly remove the chair from under you. As there is no longer a [normal force](_URL_0_) pushing back at you then, you'll indeed find yourself accelerating towards the floor at 9.8 m/s^2\n\n"
]
}
|
[] |
[] |
[
[],
[
"http://en.wikipedia.org/wiki/Normal_force"
]
] |
|
1v9jt2
|
why did the usa invest in making new counterfeit proof $100 bills when a counterfeiter can just make older style $100 bills and still use them.
|
Why would a counterfeiter to even try making the complicated new $100 when everybody can still use the old ones with the old designs that are easier to duplicate.
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/1v9jt2/eli5_why_did_the_usa_invest_in_making_new/
|
{
"a_id": [
"ceq1gh5",
"ceq1gkj",
"ceq1gqq"
],
"score": [
5,
13,
6
],
"text": [
"The old $100 bills will eventually fall out of circulation as they get destroyed in normal handling. On top of that, a brand new crisp $100 bill that still has the design of the old bill is very suspicious.",
"Gotta do it sometime. Eventually the previous 100s will be very rare like the ones before them (from the '90s) are now. So 10 years from now, the previous series of 100s will be quite rare and will elicit more suspicion when attempted to spend, thereby making counterfeits of the old series less viable/passable.",
"In places and situations where you have to worry about a significant number of possible counterfeit bills (foreign countries, illegal activities like drug and weapon trafficking, etc.), many (probably most) people will refuse to accept anything but the most modern available bill styling. "
]
}
|
[] |
[] |
[
[],
[],
[]
] |
|
ssmb9
|
If time slows as you speed up does the speed of light stay the same?
|
At our current speed it is around 3 million meters a second, but would that increase as you got closer to the speed of light because of the slowing down of relative time? If so, why is it called a universal constant?
|
askscience
|
http://www.reddit.com/r/askscience/comments/ssmb9/if_time_slows_as_you_speed_up_does_the_speed_of/
|
{
"a_id": [
"c4gmihc"
],
"score": [
2
],
"text": [
"The speed of light in a vacuum will *always* be measured as c, by anybody. Relativity explains the differences required for someone in a different reference frame to measure the same value of c.\n\nYou are always at rest in your own reference frame, and thus you never personally experience time dilation. You see the rest of the universe time dilated."
]
}
|
[] |
[] |
[
[]
] |
|
24gkmr
|
how do hallucinogenic drugs make you trip?
|
Is it just magic or?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/24gkmr/eli5_how_do_hallucinogenic_drugs_make_you_trip/
|
{
"a_id": [
"ch6wkga",
"ch6wnf1"
],
"score": [
2,
2
],
"text": [
"Basically...\r\rThe chemicals make the little neurons in your brain that affect your five senses activate randomly/sequentially.",
"I've heard Acid actually creates new neural pathways in your brain.\n\nI think shrooms shut down your reality testing mechanisms and stimulate parts of your brain to feed into your reality construction circuits that usually don't. "
]
}
|
[] |
[] |
[
[],
[]
] |
|
39d4r2
|
Do men's or women's brains release more oxytocin during sex?
|
If a man and a woman were to have an orgasm of equal intensity, would the man's or woman’s brain release more oxytocin? Would their brains release the same because the orgasm was of equal intensity? Would the woman enjoy the orgasm more because the female orgasm involves more brain activity?
|
askscience
|
http://www.reddit.com/r/askscience/comments/39d4r2/do_mens_or_womens_brains_release_more_oxytocin/
|
{
"a_id": [
"cs407v1"
],
"score": [
3
],
"text": [
"I don't know, but the amount of hormone released might be irrelevant. The effects of oxytocin and the sensitivity to those effects is very different among men and women.\n\nThe pro-social effects of oxytocin are faster and stronger on women than men. Oxytocin also has sexually dimorphic effects on men and women in other ways. For example, it increases amygdala activity among women confronted with threatening or fearful faces, while it does the exact opposite in men. Or for example, behavior towards infants: oxytocin provokes affectionate behavior from mothers, in the form of vocalizations and facial expressions; while it provokes stimulatory behavior from fathers, trying to catch the attention of their infants, stimulating them through touch, rattling a toy at them, etc. There are lots of other sexually dimorphic effects, so comparison of blood oxytocin levels might not necessarily tell you much.\n\nSome reading:\n\n* Fischer-Shofty, M., Levkovitz, Y., & Shamay-Tsoory, S. G. (2013). Oxytocin facilitates accurate perception of competition in men and kinship in women. Social Cognitive and Affective Neuroscience, 8(3), 313–317.\n\n* Preckel, K., Scheele, D., Kendrick, K. M., Maier, W., & Hurlemann, R. (2014). Oxytocin facilitates social approach behavior in women. Frontiers in Behavioral Neuroscience, 8(May), 191.\n\n* Lischke, A., Gamer, M., Berger, C., Grossmann, A., Hauenstein, K., Heinrichs, M., … Domes, G. (2012). Oxytocin increases amygdala reactivity to threatening scenes in females. Psychoneuroendocrinology, 37(9), 1431–1438.\n\n* Theodoridou, A., Penton-Voak, I. S., & Rowe, A. C. (2013). A Direct Examination of the Effect of Intranasal Administration of Oxytocin on Approach-Avoidance Motor Responses to Emotional Stimuli. PLoS ONE, 8(2)."
]
}
|
[] |
[] |
[
[]
] |
|
vby45
|
I have two Window fans and two windows in a 11 1/2 x 11 1/2 Room. What would be the best way to cool my room down?
|
My windows are right next to each other on the same wall if that helps.
One fan is your typical box fan
The other is a smaller fan but the front oscillates
[Heres a pictures, that front wheel thingy spins](_URL_0_)
|
askscience
|
http://www.reddit.com/r/askscience/comments/vby45/i_have_two_window_fans_and_two_windows_in_a_11_12/
|
{
"a_id": [
"c534bl3",
"c534d7i"
],
"score": [
2,
8
],
"text": [
"What heat loads are in the room? Computer? Monitors? TV? Rotisserie oven?\n\nI assume Northern Hemisphere since you're looking to cool your room in June, but which way do the windows face? \n\nWhere is the door?\n\nWhat are the exterior walls made out of?",
"Blow air in at night. Close the windows and blow the cool air around your room during the day. If you become certain that the air inside is hotter than the air outside, open a window and blow air inside.\n\nAnd always remember, fans cool PEOPLE. Not ROOMS. They cause evaporation to occur which cools your skin. When you leave your house, it is a good idea to turn all the fans off. All you will accomplish by leaving fans on during the day (assuming they are not being used to blow in cold air) is to slightly raise the temperature due to the inefficiency of the motor.\n\nOne more thing, ceiling fans are the bees knees for moving around air inside your house."
]
}
|
[] |
[
"http://i.imgur.com/NwAy5.jpg"
] |
[
[],
[]
] |
|
an3z2q
|
I need your help r/askhistorians. I've been trying to get a meaningful response to this but it continues to evade me: To what extent are accounts of the Ukrainian Famine of 1932-1933 (known as the Holodomor) accurate and reliable?
|
I used the search bar and the FAQ and the questions on this topic aren't addressing what I'm trying to figure out.
I recently heard a take on the Holodomor, admittedly from people that would be considered more or less Soviet apologists (aka Tankies) that the famine was mostly a product of Western propaganda. They claim that the primary sources from the time are deeply flawed, that photos from other events were used as evidence, that accounts from people that weren't in Ukraine at the time were overly relied upon and that one of the main accounts cited by historians was admitted to be embellished by its author.
They make further claims are that the reported number of victims doesn't add up, that the estimates used to gauge the number of deaths are not derived from any scientific methods and that WWI, the Civil War and Soviet reclassification of ethnic groups accounts for the dip in the number of "Ukrainians."
Most damningly, they claim that William Randolph Hearst (who they claim was sympathetic to fascism and well known for "Yellow Journalism" in the run up to the Spanish-American War) was deliberately sensationalist in his coverage of the USSR and largely responsible for pushing the narrative of the Famine in the Western press.
Their final point was also that the story of the Holodomor was generally accepted as embellished or fabricated until the beginning of the Cold War when it was resurrected as a way to tarnish the USSR and placate a number of far-right Ukrainian nationalists that had received asylum in the West.
Help me out /r/AskHistorians. Some of this reminds me of the ridiculous conspiracy theories that surround Holocaust denialism. But, I also know that Western countries were not above pushing narratives that might be less than truthful as part of Cold War propaganda.
So what gives? What really happened in Ukraine and how do we know? What was the impression of it at the time? What sources are reliable? Which are somewhat biased and which can we right off completely?
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/an3z2q/i_need_your_help_raskhistorians_ive_been_trying/
|
{
"a_id": [
"efqkcvp"
],
"score": [
20
],
"text": [
"You may find some edifying material in this thread: _URL_0_\n\nAs well as some contextualizing information on Holodomor denial in this one: _URL_2_\n\n\nHere is a link to the final report of the Holodomor commission, an independent, non-governmental and self-generated body, which establishes with certainty that the famine did indeed occur: _URL_1_\n\nA search of \"ukraine Holodomor\" in the r/askhistorians sidebar will give you plenty of results - if the above links don't help you find what you're looking for, do a search and find one with a bunch of upvotes and comments and start there. Unfortunately, this is one of many issues that is heavily charged both historically and politically, and as such, like other issues surrounding historical atrocities, it will have its share of deniers regardless of the accuracy of any information we have today. Suffice it to say that no respectable historian denies that the Holodomor did indeed occur, and deaths due either to intentional mismanagement or simply incompetence at the high levels of Soviet government combined with other factors are agreed to have likely ranged from around 3 million to as many as 6 million in Ukraine alone. Check the above links for more information."
]
}
|
[] |
[] |
[
[
"https://www.reddit.com/r/AskHistorians/comments/ackguz/what_do_historians_agree_on_about_the_holodomor/",
"https://web.archive.org/web/20080910085025/http://www.ukrainianworldcongress.org/Holodomor/Holodomor-Commission.pdf",
"https://www.reddit.com/r/AskHistorians/comments/a8r2fa/to_what_extent_are_the_number_of_deaths_caused_by/"
]
] |
|
1073v3
|
Can blind people donate their eyes or parts of their eyes, to restore sight in someone else?
|
I am not blind and can only speculate on how life would be if I were. I think I would want to give that gift to someone or restore it in someone, if I was unable to ever have it. I know it would all depend on what the cause of the blindness is, what is damaged, etc. Do blind people already donate parts of their eyes? Or is the eye unusable if the person who donates is blind?
|
askscience
|
http://www.reddit.com/r/askscience/comments/1073v3/can_blind_people_donate_their_eyes_or_parts_of/
|
{
"a_id": [
"c6ayi6i"
],
"score": [
7
],
"text": [
"Eye donation consists primarily of replacing the cornea (the clear part of the eye) into the living recipient from the donor. As long as the cornea is healthy, the person can donate irrespective of blindness due to other causes."
]
}
|
[] |
[] |
[
[]
] |
|
3edqyr
|
how come some animals seem to be able to wake up and be alert instantly, while with humans we often need a good 30 minutes to feel awake.
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/3edqyr/eli5_how_come_some_animals_seem_to_be_able_to/
|
{
"a_id": [
"ctdyeqd",
"ctdz5h6"
],
"score": [
11,
4
],
"text": [
"Who is this \"we\" you speak of? I know plenty of people who can just get up and go. It's not really that hard. ",
"If i'll wake you up with screaming and gun in my hand you will instantly feel awake and be ready to run "
]
}
|
[] |
[] |
[
[],
[]
] |
||
4ul0vx
|
Why do rare events that result in death, such as terrorism, elicit more fear than more common events, such as riding in a faulty elavator?
|
askscience
|
https://www.reddit.com/r/askscience/comments/4ul0vx/why_do_rare_events_that_result_in_death_such_as/
|
{
"a_id": [
"d65a4x4",
"d5qybay",
"d5qzpqb",
"d5r3oz7"
],
"score": [
2,
7,
2,
2
],
"text": [
"This is due to availability heuristic. A heuristic is a way a person solves a problem and makes judgement without putting too much mental effort. Availability heuristic does this with memories more easily available for the mind to recall, such as uncommon events. (_URL_0_). For example, generally, airline disasters are more memorable than auto accidents because of how uncommon they are and partially thanks to media coverage. This gives us a sense that airline disasters happen more often than they actually do suggesting that airlines to be unsafe in comparison to automobiles, even though vice versa is correct (_URL_1_). The uncommon events tend to be more dramatic as well causing more fear. Here is a fun little video that is not mine that adds more to the explanation (_URL_2_). ",
"We are aware of mundane risks like elevators or cancer. \n\nTerrorism, on the other hand, is dramatic and shocking. \n\nBut you're making an assumption that may not be true. There are lots of people who live lives terrified by the possibility of boring, common causes of death. ",
"According to my psychologist (I asked her this same question) people are more afraid of events that seem more likely to happen to them. So a person watching a terrorism event on the news might think \"oh no, that could happen to me\"! Terrorism can happen to absolutely anyone, anywhere, at any time. Which makes it seem like it is more likely to happen.\n\nThe small amount of time spent on elevators makes it seem less likely that an accident will happen to us.\n\nIn addition, the element of control factors in as to how likely something seems. We have little control over whether a terrorist decides to kill us, but we have some control over whether we will take the elevator. \n\nEdit: wording",
"You're begging the question here and making an assumption that elevator deaths are more common than terrorism related deaths. All information I can find points to elevator-related fatalities being exceedingly rare.\n\nA better comparison would be car accidents. The uptick in driving following 9/11 may have resulted in quite a lot of driving fatalities.\n\n_URL_1_\n\n_URL_0_"
]
}
|
[] |
[] |
[
[
"https://www.verywell.com/what-is-a-heuristic-2795235",
"http://journalistsresource.org/studies/environment/transportation/comparing-fatality-risks-united-states-transportation-across-modes-time",
"https://www.youtube.com/watch?v=2_wkv1Gx2vM"
],
[],
[],
[
"http://blalock.dyson.cornell.edu/wp/fatalities_120505.pdf",
"http://articles.latimes.com/2011/dec/15/news/la-heb-elevator-safety-death-201112115"
]
] |
||
1picnl
|
Why do ionic solids not attract each other and snap into place?
|
Why do two salt crystals not snap together when i put them next to each other? Shouldn't the ions from either crystal attract the other crystal?
|
askscience
|
http://www.reddit.com/r/askscience/comments/1picnl/why_do_ionic_solids_not_attract_each_other_and/
|
{
"a_id": [
"cd2okyf"
],
"score": [
6
],
"text": [
"The entire crystal has a net neutral charge otherwise it would fly apart due to electrostatics so there is no net force attracting two different crystals together.\n\nAdditionally, the surfaces of the materials are not perfectly smooth. You actually have only a small fraction of the surfaces actually in contact due to surface roughness, so bonding is unlikely due to this. You would need an atomically smooth surface. Also dust particles or any other oil or carbon could get in the way. Normal air is pretty dirty - you'd need a cleanroom.\n\nAlso, if you wanted to bond two surfaces together the crystals would have to be aligned and terminated correctly (for example if you have an NaCl crystal surface that is terminated with nothing but Na's it isn't going to bind to another surface of nothing but Na's but would be much more likely to bind to a surface terminated by Cl's)\n\nEven if the crystals were atomically smooth, perfectly clean, the crystallographic planes lined up right on the surfaces and terminated correctly, then you still wouldn't bond them together since materials tend to have special states on the surface compared to the bulk.\n\nThat being said they do make bicrystals by taking two very smooth and correctly terminated crystals and pushing them together. You end up with one crystal with a twin boundary. That being said - I'm pretty sure they need to apply heat and not just pressure.\n\n"
]
}
|
[] |
[] |
[
[]
] |
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