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1xzib1
|
how do scientists/anthropologists explain the seemingly quick ascent of the human species?
|
The wheel was created around 3500 BCE and within roughly 5000 years, humans have been to the moon. What is the explanation for such quick progress in a species? Dinosaurs were around for millions of years and never accomplished even a fraction of the technological progress as we have. I have heard that opposable thumbs is an explanation, but many other species have this feature without the same results. I have also heard our high protein diet allowed our brains to grow larger than other animals in proportion to body size, but other animals have similar (if smaller) brain to body ratios. Chimpanzees are often compared with humans and we do share many genetic traits, but why, after being around for as long as us, have they only learned to use sticks to catch ants, while we have started to transition into a type I civilization (on the [Kardashev Scale](_URL_0_)?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/1xzib1/eli5_how_do_scientistsanthropologists_explain_the/
|
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"text": [
"[Punctuated Equilibrium, my man. Evolution of species or ideas shouldn't be be viewed as a gradual and constant change but as a series of leaps and bounds interspersed with periods of stability.](_URL_0_)",
"Am I the only one who thinks that in the grand scheme of things, 5,000 years is a really short span to have achieved so much? I mean language helps but other animals have been proven to communicate. I can see how written language would help our advance even more but is that the real explanation for going from the wheel to spaceships in 5,000 years, cause its hard to believe. "
]
}
|
[] |
[
"https://en.wikipedia.org/wiki/Kardashev_scale#Type_I"
] |
[
[
"http://en.wikipedia.org/wiki/Punctuated_equilibrium"
],
[]
] |
|
3ow34m
|
Is it possible to tack into the solar wind the same way we can sail into the wind on earth?
|
askscience
|
https://www.reddit.com/r/askscience/comments/3ow34m/is_it_possible_to_tack_into_the_solar_wind_the/
|
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"text": [
"If you mean sailing in the opposite direction as the wind (i.e. to the Sun) then yes, it is possible, though not in the same way nor for the same reasons. Orbital dynamics are crazy and amazing :)\n\nYou can use [radiation pressure](_URL_0_) with a solar sail or the solar wind with an [electric sail](_URL_1_). In the rest of this comment I'll assume you have either of them.\n\nYour spacecraft is initially in orbit around the Sun (assuming it's already escaped Earth's gravity). If you're orienting your sail at an angle, so that the net force on your spacecraft points in a direction opposite to its velocity, then you're causing it to slow down. Orbital dynamics mandate that an object in orbit that loses speed will come closer to the central attracting body (i.e. migrate to a lower orbit). If you keep losing and losing speed it will end up spiraling inwards.\n\nFun fact: even though the sail will cause it to lose speed, while getting closer to the Sun gravitational potential energy is released in the form of kinetic energy, effectively speeding up the spacecraft. The second effect is more significant; slowing down while in orbit actually makes the spacecraft move faster.\n\n"
]
}
|
[] |
[] |
[
[
"https://en.wikipedia.org/wiki/Radiation_pressure",
"https://en.wikipedia.org/wiki/Electric_sail"
]
] |
||
2u1fvs
|
why do boobs in classical artworks look so different from those sported by today's models? [nsfw]
|
I've always wondered about this. Did Titian, Rubens and the like have different ideas about how nice boobs were supposed to look? Were they going for some "classical ideal" of nice boobs, and if so, what was it? I've read that beauty comes from an evolutionary instinct towards healthy, child-bearing figures, so surely boobs should look the same down the ages. What gives?
Some examples:
[Venus of Urbino by Titian](_URL_2_)
[Maja desnuda by Goya](_URL_0_)
[Nell Gwyn by Simon Verelst](_URL_3_)
And purely for comparison purposes:
[Rhian Sugden](_URL_5_)
[Libby Smith](_URL_4_)
[Sammy Braddy](_URL_1_)
(none of these are surgically enhanced; maybe a bit of Photoshopping)
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/2u1fvs/eli5_why_do_boobs_in_classical_artworks_look_so/
|
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"The models have all had surgery, or are naturally big-breasted. \n\nIn antiquity, it was considered more attractive to have smaller breasts, so the artists chose smaller-breasted women.",
"I'm sure there are models with similar breasts that attract less attention in today's society due to a difference in culture.",
"Small boobs were very much considered to be more attractive in those time periods.\n\nAlso size of the breast says nothing about the ability to produce milk for offspring. A small breasts woman might produce as much breastmilk as a bigger breasts woman. (and breasts generally grow a cupsize or two during pregnancy and breastfeeding anyway). So evolutionary speaking there is no basis for preferring big breasts over small breasts. "
]
}
|
[] |
[
"http://upload.wikimedia.org/wikipedia/commons/7/74/Maja_desnuda_%28museo_del_Prado%29.jpg",
"http://imgur.com/r/Page3Glamour/EOAW9G1",
"http://upload.wikimedia.org/wikipedia/commons/b/bb/Tiziano_-_Venere_di_Urbino_-_Google_Art_Project.jpg",
"http://i.dailymail.co.uk/i/pix/2011/10/18/article-2050520-0E6D16CB00000578-335_634x864.jpg",
"http://imgur.com/r/Page3Glamour/16yLBFu",
"http://imgur.com/r/Page3Glamour/Oemsn7Q"
] |
[
[],
[],
[]
] |
|
3jqs5y
|
why was the race to the moon more important than the race to the first man in space?
|
[deleted]
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/3jqs5y/eli5_why_was_the_race_to_the_moon_more_important/
|
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"They know him in Russia. \n\nBecause the Soviets sent a man into space first, the achievement was downplayed in the West, and then the Moon Race was really hyped up to compensate. ",
" \"It reminds me of the heady days of Sputnik and Yuri Gagarin when the world trembled at the sound of our rockets. Well, they will tremble again — at the sound of our silence.\"",
"Primarily because the US had the first man to the moon and Russia had the first man in space. Naturally, the US would want to emphasize the one that made them better. I imagine there were other reasons. For example, the first man on the moon was heavily publicized beforehand and broadcast live to the world. This would have gone badly had the mission ended in disaster, but the US put the extra effort in to make sure that most likely wouldn't happen. Russia didn't have the budget for that, so they had to perform the missions in secret until one of them succeeded."
]
}
|
[] |
[] |
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[],
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|
1z2qtn
|
how was the bureau of census measuring population before sampling?
|
I'm currently reading about Dr Deming's early work at the Bureau of Census and it says
> many of the users of census data were willing to accept sample results, but some of the old-timers at the Bureau of the Census were opposed to the idea of sampling
I'm new to this section of history. I may guess they were measuring the whole population but I might be wrong so ELI5.
EDIT: And (how) does sampling measure the whole population since it's a limited number of examined people?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/1z2qtn/eli5_how_was_the_bureau_of_census_measuring/
|
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"The census counts every person, or at least tries to, every ten years.\n\nHe is talking about people using the data collected - some of them insisted on using everything which, before modern computers could be a monumental task."
]
}
|
[] |
[] |
[
[]
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|
dh60c4
|
how is airport security regulated and kept consistent around the world
|
Like do all the countries agree on regulations somehow, or could you theoretically get away with something by boarding a plane with something in one country and connecting to a different country. (I’ve never flown international so idk anything)
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/dh60c4/eli5_how_is_airport_security_regulated_and_kept/
|
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"No, it’s highly inconsistent from country to country.\n\nUS is the worst for sure, I hate travelling there. Its the only place they make us remove your shoes.\n\nAtm im in Nepal, and they only pass your luggage in a scanner, barely look at it, everyone pass the metal detector, everyones beeping and they dont give a fuck.",
"It is not. \n\nEvery single country sets up their own rules and regulations, as well as how they enforce these rules and regulations. There are some countries who have treaties with others that set certain requirements for flights between said countries, but these are not always well enforced."
]
}
|
[] |
[] |
[
[],
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|
6eawqj
|
What happens to the parts of the brain which control amputated body parts?
|
askscience
|
https://www.reddit.com/r/askscience/comments/6eawqj/what_happens_to_the_parts_of_the_brain_which/
|
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"Op, the brain will began to adapt new brain cells to communicate with it, whatever is near in the somatosensory cotrex, that means if you cut off a finger the section of brain that used to respond to that will begin strengthening it's connections to still firing neighboring cells.",
"They exist, and can even be \"tricked\" into thinking an arm is still there which is basically phantom limb syndrome; it's also the basis for some robotic prosthesis which wouldnt work if the brain didnt retain those faculties; there are some local neurons that likely need to be developed, but the brain remains entirely undisturbed."
]
}
|
[] |
[] |
[
[],
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||
3rf3qu
|
what is the benefit of a water-cooled pc?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/3rf3qu/eli5_what_is_the_benefit_of_a_watercooled_pc/
|
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"Generally superior cooling due to both heat absorption of liquid and a lack of stale warm air in the case. \n\nAlso quieter ",
"Water cooling is more efficient, which allows the CPU and GPU to run at a higher frequency without overheating. Depending on how the cooling is set up it can also be less noisy. Last but not least it's just plain cool.",
"Water has a higher specific heat than air. Thus its able to more quickly transfer heat away from the CPU. ",
"It permits you to transport the heat away from the core at a rapid pace, to a radiator which can be much larger than any reasonable air cooled heatsink. \n\nAir cooling has made great strides with the use of heatpipes to carry heat away from the source.",
"I imagine that you've put your hand in an oven at 400 degrees or higher before to remove a pizza, lasagna, etc. You can leave your hand in the air in the oven for a few seconds before it starts to feel uncomfortable. Now try putting your hand in a liquid at 400 degrees. It's going to burn your skin within milliseconds, right? This is because liquids take heat away from (or give heat to) objects faster than gases can.\n\nThis is what computers take advantage of. If you only use a heat-sink and fan on a computer, the metal from the heat-sink has to transfer heat from itself to the surrounding air, which is inefficient. However, if a liquid replaced the air, then it's going to transfer heat much more efficiently and quicker. "
]
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|
[] |
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1r7qm7
|
why group mentality is so powerful
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/1r7qm7/eli5_why_group_mentality_is_so_powerful/
|
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"text": [
"Human nature to belong and conform to social groups, empathy, and natural fear of exclusion.\n\nIt's kind of instinctual, that's why the weak minded are susceptible to group mentality. Case in point: Reddit."
]
}
|
[] |
[] |
[
[]
] |
||
49av6o
|
Are protons in nuclei wiggled by electrons "flying" around them?
|
Protons and electrons attract each other. And I hear that an electron is like wave around the nucleus. Waves oscillate so they should shake the proton.
|
askscience
|
https://www.reddit.com/r/askscience/comments/49av6o/are_protons_in_nuclei_wiggled_by_electrons_flying/
|
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"This is better answered by answering each sub-question.\n\n > Are protons in nuclei wiggled by electrons \"flying\" around them?\n\nYes, in the system both motions contribute to the actual state. But, the nucleus is very much heavier than the electron, so it's the electron that does most of the moving. Analogously, a swing with one heavy person and one light person moves so that the heavy person moves little. For most calculations it can be and is assumed that the nucleus is stationary.\n\nAs for other than electric force, not. A proton and an electron don't \"collide\" classically, which is a feature that now takes this scenario into quantum mechanics. Protons and electrons are different particles, so they don't occupy the same quantum state, and don't repel each other through the [exchange interaction](_URL_0_) like two electrons. So, when an electron flies headfirst into a nucleus, it will simply go through it like a ghost. This is exactly what happens with the *s* orbitals: [the nucleus has the highest electron density](_URL_1_).\n\nThis isn't as weird as you'd think. Consider a classical analogy: loose balls of yarn and double-pointed knitting needles. I think we can agree both are solid objects. Yet, you can pretty easily stick a needle right through a ball of yarn, even if you can't force another ball of yarn through.\n\n > Protons and electrons attract each other.\n\nYes, but what is also necessary to understand that when an electron is accelerated, *there is nothing to stop it*. So, when it flies right at the nucleus, it will simply fly through and keep going, doing another loop on the other side. This system is stable over long times.\n\n > And I hear that an electron is like wave around the nucleus. Waves oscillate so they should shake the proton.\n\nNot really, in the dynamical sense you imagine. The reason quantum mechanics is called \"quantum\" is that there is the smallest possible quantum of energy, and only a restricted number of stable states. An electron forms a standing wave around the nucleus. In a similar way, the nucleus has its own mini-standing wave. The energy of this oscillation is very well-defined. In order to disturb it, you'd have to supply the full energy needed to raise it into a higher state. Smaller energies can't do much.",
"u/RRautamaa gives a good answer, stating that \n > yes both motions contribute to the actual state\n\n but\n > For most calculations it can be and is assumed that the nucleus is stationary.\n\nA very important example of when this perturbation is important is conventional superconductivity. In this quantum state electrons (which should repel each other) become attracted to one another and pair up in twos (Cooper pairs). This attraction is mediated by the nuclei in the lattice. Namely, when an electron travel through the crystal, the local nuclei are attracted towards the electron. Thus as the electron moves, it leaves behind it a trail of extra positive charge from the higher nuclei density in its wake. Another electron is then attracted into this potential and becomes bound to the first.\n "
]
}
|
[] |
[] |
[
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"https://en.wikipedia.org/wiki/Exchange_interaction",
"http://wps.prenhall.com/wps/media/objects/3081/3155040/blb0606/6.20.gif"
],
[]
] |
|
3q4huh
|
how is the milk of a cow so beneficial to humans?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/3q4huh/eli5_how_is_the_milk_of_a_cow_so_beneficial_to/
|
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"Because it contains fats, proteins, and sugars, making it a very energy-packed beverage. Now granted, if you're lactose intolerant than you don't make the necessary enzyme to make use of the sugars, lactose, and that can lead to a fair bit of intestinal distress so...there is a downside for some people.",
"It's not just cows. Milk of many mammals is as beneficial to humans (and, on a side-note, that benefit *is* debatable, and many humans are, in fact, *not* able to process it). \n\nCows are just the animal we domesticated and started using for milk in a way that is ubiquitous in Western culture. In other cultures, other animal's milk is more widespread. That includes goats, camels, even donkeys. Also remember that much of Human population is lactose-intolerant. ",
"You can get all the nutrients you get from milk from other sources that are better for you health wise, so in relative terms it's not that great for us. People first started drinking the stuff specifically because of the calcium. Back before people had well established trade routes and high tech farming technology, sources of calcium in Northern climates were rare. The main way that humans are supposed to get our calcium is from green vegetables and fish. Not having green vegetables available for a large part of the year could mean death due to calcium deficiency for those people in the North, so they ended up with an adaptation that allowed them to drink milk from other animals that could eat the greens that grew in the area. Cows can eat grass and get the calcium that way. \n\nIn reality, all the healthy things that milk gives us like calcium, protein, and essential vitamins, you can get by eating green vegetables and meat. Even for the people who do have the ability to drink milk, eating greens and meats is actually healthier than getting those same nutrients from drinking milk because there's less sugars and fats. "
]
}
|
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||
cl55sk
|
Was the Indo-Aryan migration truth or fiction?
|
In most Indian schools, students are taught Indian history (and world history to a certain degree) as a compulsory subject until the 8th grade. In the 5th grade I remember being taught about the Vedic period in India brought on by the Aryan tribe who had begun settling in the subcontinent after the Indus Valley Civilisation met its end.
About 10 years later I stumbled across a YouTube comment that said that the Indo - Aryan migration was a myth and that it was British propaganda. I was very surprised after reading that because the only thing I had read about my culture until that point was that I am Indo-Aryan and that my Hindu roots come from the teachings during the Vedic period.
So my question is: Was the migration a myth? If so, why would that be British propaganda and how would it have helped them remain in control over the subcontinent?
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/cl55sk/was_the_indoaryan_migration_truth_or_fiction/
|
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"The Indo-Aryan migration is absolutely true, insofar as Indo-Aryan - a branch of the Indo-Iranian language family, which itself is a branch of the Indo-European family, which originated somewhere in the Pontic Steppe (around modern Ukraine, Crimea, and southern Russia) - is not indigenous to India. Anyone who claims that it was, including anyone who references the Indus Valley civilisation as an Indo-European one, is participating in nationalist pseudoscience. We know this from the method of [comparative reconstruction](_URL_3_), which shows that Proto-Indo-European, or the common ancestor to all Indo-European languages, had words relating to the material culture and natural environment of the Pontic steppe (for example, “salmon”, “birch tree”, and a whole host of words relating to horse domestication), but few or none indicating a culture that might have arisen in modern Pakistan (“elephant”, “lion”, and notably any words to do with the urban life that the Indus Valley people lived); those words were innovated or borrowed within Indo-Iranian or Indo-Aryan, and therefore don’t share any common ancestor with their equivalents in other Indo-European languages. With the addition of material archaeology, we can us the Indo-Europeans as being, or at least being related to, the [Yamnaya culture](_URL_1_), and thus certainly not related to the contemporaneous Indus Valley culture or any other culture of the Indian Subcontinent. This conclusively shows that the original speakers of Indo-Iranian, and thus their descendants the Indo-Aryans, migrated into Central Asia, then Iran and the Subcontinent at some point. The Indus Valley people, for their part, have been connected to the indigenous [Dravidian](_URL_0_) or (for a fringe hypothesis) [Munda](_URL_2_) peoples, but the relatively slim evidence doesn’t allow us to make a firm conclusion either or neither way; what’s certain is that originally, or at the time we generally associate them with, they weren’t Indo-Aryan.\n\nThe question that follows - and here the mainstream historical perspective differs from both the conflict-based Anglo-German colonial narrative *and* the unitarian Indian nationalist one - is what kind of migration this was: was it, as nineteenth- and early twentieth-century European historians generally assumed, a mass migration with violent conquest and population replacement, or a gradual, mostly-peaceful assimilation from a relatively small founding group based on trade and intermarriage? This is an important point, because the migration in general is a complex facet of human history - the Anglo-Saxon migration into Britain and the Slavic migration into Southeastern Europe are disputed along similar lines - and one we don’t have a complete answer to. Certainly it appears that the Indus Valley civilisation had a gradual but eventually total decline in the first half of the second millennium BC (from about 1900 to 1600), which coincides with the rise of the Indo-Aryan language family in the area. But whether the Indo-Aryan presence was a *cause* of the Indus Valley’s decline, or an *effect* of a decline caused by a more fundamental ecological or political collapse, is very much disputed. Modern history tends more toward the latter, as it does with the analogous but much later Anglo-Saxon and Slavic migrations, and some kind of synthesis between the two seems like the most plausible account of the period.\n\nAs for *why* Anglo-German historians preferred the idea of a violent migration over a gradual dispersal, the cause is not as fundamentally propagandistic as Indian nationalist historians assume; their arguments were based (for the most part) not in an effort to keep the various Indian peoples disunited and in conflict, but rather on a faulty scholarship that valued textual sources and those who produced them (i.e. the Vedas and Brahmins) over concerns of how, when, and why those texts were produced, leading to the impression of a united and distinct “Aryan” people - who supposedly neatly coincided with Brahmins themselves - opposed to a vague mass of *mleccha* indigenes. This, of course, was thoroughly amplified by the “scientific” racism of the time, and encouraged Anglo-German historians to interpret Indian history as one of Indo-Europeans (to whom they conveniently belonged) as a conquering people who subjugated the indigenous peoples of the Indian Subcontinent. The connection with race ideologies of the nineteenth and twentieth centuries is obvious, and still colours Indian history from both European and Indian perspectives to this day.\n\nOverall, both the nationalist idea that the Indo-Aryan language family and early Hinduism were always indigenous to India and the Anglo-German colonial idea that Indo-Aryan represented a sudden and violent population shift are fundamentally discredited. The real answer lies not somewhere between the two, but through a subtler and more historically comprehensive understanding of “migration”.\n\nA good layman’s source for the Indo-European migrations is David W. Anthony’s *The Horse, the Wheel, and Language*. Additionally, the [Wikipedia article](_URL_4_) on the Indo-Aryan migration is surprisingly and gratifyingly comprehensive, so I’d recommend it at least over the Internet."
]
}
|
[] |
[] |
[
[
"https://en.wikipedia.org/wiki/Dravidian_languages",
"https://en.wikipedia.org/wiki/Yamnaya_culture",
"https://en.wikipedia.org/wiki/Munda_languages",
"https://en.wikipedia.org/wiki/Comparative_method",
"https://en.wikipedia.org/wiki/Indo-Aryan_migration"
]
] |
|
1p4cai
|
If photons are smaller than atoms, why don't they pass through solid matter?
|
Aren't atom's mostly empty space, between the nucleus and the electrons? Shouldn't photons pass through those spaces and penetrate basically any form of matter?
|
askscience
|
http://www.reddit.com/r/askscience/comments/1p4cai/if_photons_are_smaller_than_atoms_why_dont_they/
|
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"The closest thing to \"size\" for a photon is its wavelength. Different types of light have different wavelengths: x-rays have really short wavelengths, while radio waves have really long wavelengths. Visible light is somewhere in the middle.\n\nIf the wavelength is small compared to whatever we're dealing with, then you can treat the photon like a particle - i.e. it's a \"bullet\" that either hits, misses, or bounces off whatever we're dealing with. Visible light is 100s of nanometres in wavelength, which is way smaller than say, a window, and so you can think of it as a bunch of light \"particles\" flying towards the window: some of the particles go through the window, some bounce off the frame etc.\n\nBut if the wavelength is *big* compared to whatever we're dealing with, you really need to treat the photon like a wave - i.e. instead of a bullet being fired at a solid object, imagine a bunch of objects floating around in the ocean being shoved around by a water wave. This is the case for visible light and atoms. Visible light is 100s of nanometres in wavelength, but atoms can be even smaller than 1 nanometre. So you can't really \"miss\" with visible light - the photon passes through hundreds of atoms at the same time. This means there is definitely some interaction going on, and so the photon can be changed a little by the atoms, and that allows you to \"see\" the atoms when the photon hits your eye.",
"Light is basically just waves of electrical and magnetic fields lined up perpendicularly. Astrokiwi made the solid point that 'size' of the wavelength and material it is passing through basically defines how far it can go through. i guess size is a simplification of it, but it comes down to some E & M constants called permittivity and permeability (I think that's them... represented by epsilon and mu for electric fields and magnetic fields, respectively) that essentially define how those fields pass through materials. Everything has a certain value for these constants, from vacuum to rock. For the most part, the combination of these values allows certain wavelengths to pass through, and others to be blocked to some extent. The extent to which they pass through is referred to as the skin depth: something like wood has a skin depth that is almost nonexistent, while air has a skin depth of miles (no idea the exact value), and water is somewhere in between.",
"Some do : X-Rays and Gamma rays, for instance, will pass through a lot of different kinds of solid matter...all depends on the photon's wavelength and the atom's structure. One visible light photon MAY pass through a wall, but your eye would not be nearly sensitive enough to detect it. Read 'QED: The Strange Theory of Light and Matter' By Richard P. Feynman. It's wicked cool!",
"Photons can interact with atoms over a long range through the electronic force. Every material interacts with photons differently, sometimes they absorb and sometimes they let photons pass uninhibited (they actually slow down the photons but don't do much else).\n\nThe amount of photons absorbed is calculated by Beer's law:\n\nA=εcL\n\nWhere A is the absorbance, ε is the extinction coefficient at that specific wavelength, c is the concentration (in solution, but I assume we could also use density for solids if the extinction coefficient was given units to match) and L is the path length through a material. The extinction coefficient will vary based on many things related to the material, but it also varies based on the actual wavelength.\n\nI know I may have given you more questions than answers, but I hope this points you in the right direction.",
"The interaction of light and matter has for centuries been treated with heuristics such as those among the replies here. However, in the mid-20th century a much more comprehensive theory (quantum electrodynamics) was developed, and the story is much more interesting. If you want to explore this further, I highly recommend Richard Feynman's slim volume \"QED\".",
"The real reason some light doesn't pass through some matter is that the electrons have electric charge and so they can interact with the electric and/or magnetic field of the light. if the electrons are able to absorb the energy carried by the photon, then it'll absorb that photon. otherwise the light will carry on (mostly) unharmed. The amount of energy in a photon is inversely proportional to its wavelength. but what light is absorbed and what light is transmitted is a very much dependent on what kind of stuff the light is hitting. \n\nNeutrons on the other hand, don't have electric charge and so they almost always pass straight through. ",
"Feynman answered this in [QED: The Strange Theory of Light and Matter](_URL_0_). \n\nIn it he contradicts commonly held ideas such as light is a wavicle and explains why the double slit experiment isn't a paradox. He categorically states that photons and electrons are particles that behave in a probabilistic fashion. \n\nTo answer your question, a photon can travel through matter if it's probable that it will do so. \n\nWhat that means is the photon that enters an object interacts with the electrons in the object. It gets absorbed and a little later a photon gets spit out. When a photon gets spit out, the direction it's most likely to be headed depends on how energetic the photon was. If the energy level the photon has corresponds to a direction parallel to the original direction, we say the object is transparent because we can see most of the photons that made it through the object.\n\nFeynman described the wave/particle duality in terms of the photon being a particle that has a probability of being detected at various points in space. Map the probabilities and you map a wave-like structure.\n\n He spends a good part of the lectures trying to shake people away from the idea of a wavicle which given the wide-spread acceptance of the Copenhagen interpretation of quantum mechanics is a really tough sell. \n\nIf you buy his interpretation however, a lot of QM starts to make sense instead of being \"ooo that's so weird!!!!\"",
"they do at high energy/short wavelengths. gamma rays can pass through matter till it loses energy through pair production, compton scattering and when they get to a low enough energy level they are absorbed. ",
"I thought that the whole thing about photons was that they DO pass through SOME solid matter. I mean, that's literally the entire reason why *sight* is a thing:\n\nPhotons can easily pass through a lot of gases, like nitrogen and oxygen, but less easily through solids, carbon-based organisms, and especially metals. Gases whirl around at insane speeds, mostly at \"lowish\" concentrations. As such, there's less likelihood that photons will impact large enough amounts of the gas-particles to be visible to the human eye, and so many gases are colourless and few, if any, are opaque. Metals, on the other hand, are more concentrated. The whole tightly mashed structure of metals in general is what allows current to so easily flow through, and as such a \"smooth\" chunk of metal is less permeable to photons than most other things. And that's why metals are reflective! Not because photons CAN'T pass through, but because they meet a solid, dense layer of difficult-to-penetrate atoms, and so a lot of them reflect off of the metal's surface.\n\nOf course, the northern lights are an interesting case - here, a good way to put it is that electrons contain a lot more energy than normal, and so, EVEN WHEN THEY HIT \"invisible\", common molecules in the air, they become visible due to reflected photons.\n\nIs ALL colour a result of photons increasing the energy of an electrons orbit and then being unleashed once more upon the world in all its fearsome majesty? I only ever had 1 year of physics, so I don't know. Anyone?"
]
}
|
[] |
[] |
[
[],
[],
[],
[],
[],
[],
[
"http://www.futuretg.com/FTHumanEvolutionCourse/FTFreeLearningKits/01-MA-Mathematics,%20Economics%20and%20Preparation%20for%20University/001-MA01-HI00-High%20School%20Mathematics,%20Preparation%20and%20Recreational%20Science/13%20-%20Recreational%20Science/Richard%20Feynman%20-%20QED,%20The%20strange%20Theory%20of%20Light%20and%20Matter.pdf"
],
[],
[]
] |
|
5kbm2n
|
Did the concept of mutually assured destruction prevent the Cold War from going hot?
|
I understand the idea of MAD, but would the USSR really be willing to engage in all out war with NATO without nuclear weapons?
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/5kbm2n/did_the_concept_of_mutually_assured_destruction/
|
{
"a_id": [
"dbnsrgm"
],
"score": [
3
],
"text": [
"We really can't know the answer to complex hypotheticals like that. Smaller \"What ifs\" can sometimes be productive. But \"what if the strategic situation of the world was totally different?\" isn't something that historians can readily answer.\n\nWhat they can do is point out that, 1) the Cold War was plenty \"hot\" if you lived in one of the places consumed by proxy war or state interference; 2) \"mutually assured destruction\" as a condition did not really apply until the 1960s, arguably the 1970s, because the Soviet Union's nuclear capabilities were far undermatched against the USA's, though the question of whether deterrence broadly (which is not the same thing as MAD) mattered is still up for grabs; and 3) there is evidence that there is more than nuclear deterrence that kept the Soviets from initially pressing westward in the 1940s, and there is clearly more than deterrence with the US lack of interest in engaging the Soviets militarily (or with nuclear arms) prior to the Soviets having a truly compelling nuclear force (e.g. before the mid-1950s if you care primarily about Europe, the 1960s or 1970s if you care more globally). The \"nuclear taboo\" — lack of use of nuclear weapons — has applied even in non-deterrent, definitely non-MAD, situations."
]
}
|
[] |
[] |
[
[]
] |
|
12iqdn
|
How does pollution from mostly unregulated countries like China affect the rest of the world?
|
For example, if most of the western world attempts to curb the amount of pollution it produces, does China's disregard affect these nations? Is there anything the rest of the world can do about it?
|
askscience
|
http://www.reddit.com/r/askscience/comments/12iqdn/how_does_pollution_from_mostly_unregulated/
|
{
"a_id": [
"c6vgpzg"
],
"score": [
2
],
"text": [
"Long-range transport of air pollutants, including metals and pops, and is well-documented with ongoing research. While your last question seems mostly policy related, a large proportion of, but not all, nations decreasing use/production/emission of toxic chemicals does have significant effects in decreasing levels (sorry - turned your question around a bit).\n\nThe example I'm most familiar with is mercury - in its elemental form (Hg0), it forms a vapour and can be transported great distances. Ultimately, a lot of this winds up in the arctic, storing up over the winter and, upon polar sunrise, changing form (Hg2+), causing deposition, oral bioavailability, and toxicity. In recently chatting with a phd student working on mercury testing in arctic birds, she mentioned that mercury levels have begun to drop, although levels of other compounds either haven't/are increasing still. "
]
}
|
[] |
[] |
[
[]
] |
|
ckjlo7
|
Do I weigh less at midday than at midnight?
|
Does having the sun directly overhead make any difference to an objects mass on earth?
|
askscience
|
https://www.reddit.com/r/askscience/comments/ckjlo7/do_i_weigh_less_at_midday_than_at_midnight/
|
{
"a_id": [
"evocftd",
"evopfy8"
],
"score": [
9,
4
],
"text": [
"A point of clarification: Mass is how much matter makes something up, so it won't change mass.\n\nThe position of the sun will change your weight, but only very, very slightly. It's only a very small fraction of the influence from the earth, so all other things being equal, there should be a very slight difference, something like less than a tenth of a percent.\n\n_URL_0_",
"Let's ignore the Moon for now and assume that you are at the equator for simplicity. As discussed the mass doesn't change, but the weight does.\n\nThe weight has a minimum both at midday and at midnight a maximum at sunrise/sunset.\n\nYou are attracted by the Sun, but so is the Earth. Only the difference in acceleration matters. During sunset/sunrise you are at the same distance and the effect of the Sun cancels (there is a smaller effect from being not in the same direction, but that is increasing your weight). During midday you are closer to the Sun, you are attracted more (\"away from Earth\") - you feel a bit lighter. During midnight you are farther away, you are attracted less, or equivalently Earth is attracted more - again you feel a net effect away from Earth and feel lighter than you would without Sun.\n\nThe effect is small: (mass of Sun)\\*(gravitational constant)\\*(radius of Earth)/(distance to Sun)^3 = 2.4\\*10^(-7) m/s^(2) or 24 parts in a billion. The Moon actually has a larger effect as it is much closer: (mass of Moon)\\*(gravitational constant)\\*(radius of Earth)/(distance to Moon)^3 = 6.7\\*10^(-7) m/s^(2). Both together cause the tides."
]
}
|
[] |
[] |
[
[
"https://van.physics.illinois.edu/qa/listing.php?id=30395&t=effect-of-sun-and-moon-on-ones-weight-during-the-day"
],
[]
] |
|
5ec1tu
|
why does standing on a train tire me out?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/5ec1tu/eli5_why_does_standing_on_a_train_tire_me_out/
|
{
"a_id": [
"dab8eub",
"dab8fca"
],
"score": [
3,
2
],
"text": [
"It's the same thing as being in a car for an extended period of time.\n\nWhile you aren't really making a lot of *big* movements, you are making a *very very large amount* of *tiny* movements. Every second you're adjusting, balancing, making sure things are going smoothly, watching all of the people, etc - so while you aren't physically doing a whole lot, your muscles are constantly contracting/relaxing, and your brain is constantly thinking.",
"The train shakes and sways and changes speed while you're riding. A lot of muscles are constantly acting to absorb and counter that motion and that takes energy."
]
}
|
[] |
[] |
[
[],
[]
] |
||
22cjj1
|
When a star collapses into a black hole, does the density of the singularity continue to increase forever?
|
From what I understand, once the star exceeds the electron degeneracy pressure, there's no known force in the Universe that will prevent the star from not only collapsing but to *continue* collapsing. That being said, is the density of the singularity of Sagittarius A* higher than it was, say, yesterday morning if we had some way of measuring it?
|
askscience
|
http://www.reddit.com/r/askscience/comments/22cjj1/when_a_star_collapses_into_a_black_hole_does_the/
|
{
"a_id": [
"cglglli",
"cgllwkg"
],
"score": [
20,
2
],
"text": [
"It doesn't really make sense to consider the density of the singularity. You can consider the mean density of the entire black hole within the event horizon, which actually decreases as the black hole gets bigger. If you treat the center as a singularity, it has infinite density, like an electron has infinite charge density.",
"Piggybacking off of this question:\n\nIs it possible for large masses such as collapsing stars to collapse asymmetrically? If so, would such an object become unstable or exhibit properties that are strange in comparison to symmetrically collapsing entities?"
]
}
|
[] |
[] |
[
[],
[]
] |
|
xk1p5
|
LEDs vs Normal Bulbs - Environmental Impact Outweighs Benefits?
|
Hey,
So recently P-brand started to sell LED based lamps that can be screwed into the normal sockets, so even though it's still much more expensive than 'traditional' bulbs, it's not prohibitively so. In my view, the first real affordable LED solution for the everyday people.
I was talking about this with a friend, justifying the high cost by saying not only do you use less energy, because you buy less bulbs, an individual would produce lesser waste as well. Win-Win.
But then he pointed out what is essentially the 'Prius Conundrum':
The Prius' batteries have to travel around the world, arguably creating more environmental harm than the average car even before it took its first spin.
So, even though we may produce less rubbish, because LEDs are relatively new, it may be a more harmful pollutant because of what's inside.
I was wondering is anyone familiar with the subject could shed some light on that part. Are there any harmful 'exotic' materials used in everyday LEDs? Apart from less discarded 'volume' because you replace it less often, how is its 'pollution footprint' compared to existing bulbs?
(Note, I included the Prius example to highlight the train of thought. Let's not argue about that here. Thanks)
|
askscience
|
http://www.reddit.com/r/askscience/comments/xk1p5/leds_vs_normal_bulbs_environmental_impact/
|
{
"a_id": [
"c5n2mys"
],
"score": [
2
],
"text": [
"I work with LEDs all the time. If you live in the US, the \"Prius Conundrum\" could be applied to any imported product.\n\nAs far as [luminous efficacy](_URL_5_), the LED lights that you can buy *right now* at Home Depot etc are about the same as compact fluorescent lighting (CFL). What's inside a white LED (blue LEDs are used with a phosphor) are some small amounts of semiconducting material, usually [indium gallium nitride](_URL_3_) that is completely encapsulated and not a heavy metal. Some [Philips LED lights](_URL_1_) (Home Depot has those for $15) use a remote phosphor that is completely encapsulated in plastic. (The blue LEDs inside them are about 45% electrically efficient)\n\nLEDs will quickly over take CFLs in luminous efficacy and one can buy white LEDs now that are [significantly higher](_URL_0_) (+125 lumens per watt typical).\n\nWhat they don't have are the shorter life spans of compact fluorescent bulbs, which reduces the the conundrum argument, and the small amounts of mercury they contain and some states have [specific laws on their disposal](_URL_4_). \n\n_URL_2_"
]
}
|
[] |
[] |
[
[
"http://www.philipslumileds.com/products/luxeon-rebel/luxeon-rebel-white",
"http://1000bulbs.com/product/58963/LED-409946.html?utm_source=SmartFeedGoogleBase&utm_medium=Shopping&utm_term=LED-409946&utm_content=LED+Light+Bulbs+-+60+Watt+Equal&utm_campaign=SmartFeedGoogleBaseShopping&gclid=CMq7xKqIybECFQtThwodGFAAew",
"http://en.wikipedia.org/wiki/Compact_fluorescent_lamp#Environmental_impact",
"http://en.wikipedia.org/wiki/InGaN",
"http://en.wikipedia.org/wiki/Fluorescent_lamp_recycling",
"http://en.wikipedia.org/wiki/Luminous_efficacy"
]
] |
|
k74ie
|
Is their a chemical or other additive(like what I do not know, perhaps one that reacts with water) that could make paint dry faster?
|
would it be the same for both oil and latex based paints?
P.s. I just finished typing this and I think the real question should I guess be about dehydration... but thats as far as I have gotten.
|
askscience
|
http://www.reddit.com/r/askscience/comments/k74ie/is_their_a_chemical_or_other_additivelike_what_i/
|
{
"a_id": [
"c2i7xvh",
"c2i7xvh"
],
"score": [
2,
2
],
"text": [
"Many of the paints in use now take advantage of chemical driers or other systems to accelerate 'drying.'\n\nFirstly, not all paints are water-based. In the case of oil-based paints, 'drying' is actually not related to the evaporation of water, but instead to the slow chemical reaction of the oil to oxygen in the air that gradually [polymerizes the oil into a film](_URL_0_). This is a slow process compared to, say, how fast watercolors dry. But, there are things ([like cobalt](_URL_2_)) that can be added to speed up the process. There are also other types of [oil-based products](_URL_1_) that have been chemically treated to 'dry' faster.\n\nWater-based paints can be diluted with water-soluble volatile organic compounds (VOCs) that evaporate at a lower temperature than water, thus speeding drying, but this practice is generally frowned on (as it's never a good idea to inhale a lot of most chemicals). Most latex paints are water soluble (and, these days, low-VOC), so your best bet is to paint on a low-humidity day, open some windows and turn on some fans. \n",
"Many of the paints in use now take advantage of chemical driers or other systems to accelerate 'drying.'\n\nFirstly, not all paints are water-based. In the case of oil-based paints, 'drying' is actually not related to the evaporation of water, but instead to the slow chemical reaction of the oil to oxygen in the air that gradually [polymerizes the oil into a film](_URL_0_). This is a slow process compared to, say, how fast watercolors dry. But, there are things ([like cobalt](_URL_2_)) that can be added to speed up the process. There are also other types of [oil-based products](_URL_1_) that have been chemically treated to 'dry' faster.\n\nWater-based paints can be diluted with water-soluble volatile organic compounds (VOCs) that evaporate at a lower temperature than water, thus speeding drying, but this practice is generally frowned on (as it's never a good idea to inhale a lot of most chemicals). Most latex paints are water soluble (and, these days, low-VOC), so your best bet is to paint on a low-humidity day, open some windows and turn on some fans. \n"
]
}
|
[] |
[] |
[
[
"http://en.wikipedia.org/wiki/Linseed_oil#Chemical_aspects",
"http://en.wikipedia.org/wiki/Alkyd",
"http://en.wikipedia.org/wiki/Drying_oil#Chemistry_of_the_drying_process"
],
[
"http://en.wikipedia.org/wiki/Linseed_oil#Chemical_aspects",
"http://en.wikipedia.org/wiki/Alkyd",
"http://en.wikipedia.org/wiki/Drying_oil#Chemistry_of_the_drying_process"
]
] |
|
1ms1sy
|
When did the Byzantines stop wearing togas and other classical Greco-Roman garments?
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/1ms1sy/when_did_the_byzantines_stop_wearing_togas_and/
|
{
"a_id": [
"cccdgf7"
],
"score": [
39
],
"text": [
"They probably rarely wore togae in the first place. Togae were notoriously uncomfortable to wear, let alone in the stifling heat of the Eastern Roman Empire. Martial refers to work done during the day wearing the toga as 'toga work' (_opera togata_) and 'never ending' being such a pain. They would have official places, but according to Juvenal outside of Rome, everyone made do with more comfortable tunics or so forth instead - although the following is likely hyperbole, it reflects known attitudes towards the toga and its uncomfortableness. \n\n > \"There are many parts of Italy, to tell the truth, in which no man puts on a toga until he is dead. Even on days of festival, when a brave show is made in a theatre of turf, and when the well-known farce steps once more upon the boards; when the rustic babe on its mother's breast shrinks back affrighted at the gaping of the pallid masks, you will see stalls and populace all dressed alike, and the worshipful aediles content with white tunics as vesture for their high office. In Rome, everyone dresses above his means, and sometimes something more than what is enough is taken out of another man's pocket. This failing is universal here: we all live in a state of pretentious poverty.\n\n(Juvenal, Satire 3).\n\nSee also; [Roman Dress and the Fabrics of Roman Culture, edited by Jonathan Edmondson and Alison Keith](_URL_0_)"
]
}
|
[] |
[] |
[
[
"http://books.google.co.uk/books?id=QYo8kA3pJNAC&pg=PT212&lpg=PT212&dq=toga+uncomfortable+juvenal&source=bl&ots=hjNfkrY_Xr&sig=Mp_nFe1ZPnQkANvNBkcQKyHqxpg&hl=en&sa=X&ei=J9w8UoSFNqPM0QXYloGQBg&ved=0CDMQ6AEwAQ#v=onepage&q=toga%20uncomfortable%20juvenal&f=false"
]
] |
||
1ulku9
|
Was it commonplace for Royals of old to be highly learned and respected in Academia?
|
For example - 'Anti-Machiavel' by Frederick the Great. Was he an exception or was the publication of academic works by monarchs more frequent?
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/1ulku9/was_it_commonplace_for_royals_of_old_to_be_highly/
|
{
"a_id": [
"cejc354"
],
"score": [
3
],
"text": [
"It was generally not common. Certainly there were some monarchs who did have some scholarly abilities. Queen Elizabeth I translated Boethius's Consolation of Philosophy.\n\nBut the amount of training in languages and literature necessary to be a truly accomplished scholar was tough for a monarch to achieve. They tended to be more patrons of scholarship (like Charlemagne or Alfred the Great or Catherine the Great) than scholars themselves."
]
}
|
[] |
[] |
[
[]
] |
|
14pyjg
|
why is gold so expensive?
|
I don't see any obvious use for gold except for jewlery :/
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/14pyjg/eli5_why_is_gold_so_expensive/
|
{
"a_id": [
"c7fcbza",
"c7fccsr",
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"score": [
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26,
2,
2,
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2,
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"text": [
"[It is not used only for jewelry](_URL_0_), but what does it matter if it was? There is a limited amount of gold on earth. If there are a lot of people who want that gold, the price will go up. Lets say you only have ten pieces of gold, but there are a hundred people who want a piece. If you want to make money you are not just going to ask a fixed amount of dollars. You ask those people how much they want to pay for a piece of gold. ",
"_URL_0_\n\n > Gold emerged as a sort of inevitable global currency, before people even thought of it as currency. It is rare, portable, easy to identify, can easily be made into jewelry, and can be easily quantified (unlike, say, jewels or seashells, which are harder to treat as a \"substance\"). Once word got around that rich people like it, it became easy to barter with anyone, anywhere, for anything.\n\n > In the early stages, it was not really the same thing as \"money\", it was just an easy thing to barter. But it had money-like characteristics:\n\n > - If someone walked into your apple-orchard offering to trade a yellow rock for apples, you might look at them a little funny. What use does an apple-grower have for a yellow rock?\n\n > - But if you know that rich people in town covet this soft yellow metal as something they can make jewelry out of, then you might be happy to trade apples for it. \n\n > - Once *everyone* knows that rich people will trade for this stuff, it becomes something like actual currency: neither the hunter, the shoemaker, nor the fisherman in town has much use for it, but because they know they can redeem it for the stuff they *do* want and need, it becomes a sort of transferable IOU that can be redeemed anywhere, i.e., money. \n",
"1) There's not a lot of it. 2) People like the way it looks. 3) When 1 & 2 are true (limited supply and high demand) there is high value for something.",
"by actions taken over hundreds of years of history, societies have decided by fiat that gold is a reliable long-term store of wealth.",
"The reason that gold is so expensive is because gold has been expensive for a long time, and people want gold to remain expensive, so that the wealth invested in gold will remain. The value in gold is purely a social construct, and nothing more.",
"Because it has certain properties, many mentioned here, that would make it the default medium of exchange; people are valuing it at its current level because of all the debt (which will need money to be created in the future in order to pay) and money that has been created worldwide.",
"Gold is rare and cannot be cheaply or easily manufactured. It's compact and can be stored easily. It won't rust, rot or decay when stored in a safe place. It's also considered beautiful (hence the jewelry thing). Something rare, beautiful, resilient and _small_ (compared to it's relative value) makes it an excellent store of value or wealth.\n\nGold _does_ have some industrial uses but it's value derives mainly because it is _universally recognized_ as a store of wealth. If everybody suddenly decided it was useless, it would have little or no value."
]
}
|
[] |
[] |
[
[
"http://dollardaze.org/blog/pages/00063/GoldUses2005.gif"
],
[
"http://www.reddit.com/r/finance/comments/utf5u/where_has_all_the_money_in_the_world_gone/c4yg5it"
],
[],
[],
[],
[],
[]
] |
|
fwgbt2
|
how do options and shorts work for investments?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/fwgbt2/eli5_how_do_options_and_shorts_work_for/
|
{
"a_id": [
"fmo759j",
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2,
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"text": [
"For shorts, its better to think about what you're expecting to happen when you do it than how its actually executed in the market (which is more complicated, but ultimately unimportant to you, the trader).\n\nWhen you buy a stock, the *only* reason to buy it is that in the future you expect it to be higher than when you bought it. This is being \"long\".\n\nWhen you short a stock, the *only* reason you \"buy\" it is that you think the stock will be lower in the future.\n\nYour broker doesn't give a shit what you trade, they just facilitate the trade and take a commission (this is a bit untrue, but for these purpose its fine). When you short a stock, you potentially have a chance to lose more money than you have though, so they require these accounts to have some extra money to cover the losses in case that happens.",
" > Why do platforms allow shorting, doesn’t it make them earn less if the stock drops?\n\nMake who earn less?\n\nShort selling is a simple principle, you borrow stock from someone else who is holding it, sell it on the market, and then return it to them at some point in the future. If stock price goes down, you sell high then buy low, pocket the difference and return the share. If stock price goes up, you choose when you have to buy the shares back to give back to the borrower, here you sell low buy high, eating the loss. With brokers this is easier, they have a vast pool of people who hold shares that they can borrow from, as long as all of them don't sell at the same time there is always someone you can keep borrowing from.\n\nThe broker doesn't or risk anything here as long as you show the ability to buy back the share (posting sufficient collateral, if you don't then the broker will loan you money with interest which limits their risk), the person from who you borrowed generally loses (if they sell) but that was the risk they agreed to when they bought the share.\n\nOptions are a different thing than short selling but can accomplish a similar purpose. \n\nA call gives you the right to buy 1 shares at any point until some future expiration date at the strike price. A put gives you the right to sell 1 shares at any point until some future expiration date at a strike price. Do note that options are only sold in batches of 100. \n\nSay I buy a call for company A (whose share price is 10 dollars), with a strike price of 11 dollars and expiration date of next friday, costs me 1 dollar. If A's share price increases to 12 dollars, at expiration I just broke even, but if it rises to 13, I can buy a share at 11 dollars using the contract and sell on the market for 13, pocketing 2 dollars minus the 1 dollar I paid for the contract initially. If it stays stagnant at 10 dollars, or in general goes to less than 11 dollars, at expiration, it doesn't make sense for me to exercise this option so I don't it expires worthless and I lost the dollar I put in. \n\nPuts work similarly in the opposite way, think about how this works with selling. Puts are a bet that the stock goes down, try to apply the same logic as a call but with selling at a price instead of buying.",
"The idealized idea and general business model of a platform is indifferent to the types of position you take ie long or short because they function as a meeting place between buyer and seller. They make money off the volume of trade and (mostly) aren't the counterparty to your trade - ie one person going short means someone else goes long. They are concerned that the traders are \"reliable\" - ie that you fill your position and not run away with or have insufficient assets which is a higher risk to the platform in short positions.\n\nThat said, shorting is still not allowed by some governments (ie the stock exchange). Some feel that increases short term volatility and is a sort of \"bet on failure\". Others say that shorting delivers the right \"signal\" and that it allows for better price discovery - ie stocks prices reflect the market sentiment better. \n\nOptions are standardized contracts (ie legal agreement) between two parties to agree to trade (buy and sell) some stock in the future at a fixed price with an option (ie the right) to nullify the trade given to one party. The other party must complete the trade if the holder of this option so chooses. This \"option\" is clearly valuable and represents the price of that option.\n\nThe idea of the option is straightforward but the terminology used and liability involved is confusing. A put option is a contract where the option belongs to the seller of the stock (\"ie right to sell this stock on this date at this price\"). A call option is a contract where the option belongs to the buyer of the stock (\"ie right to buy this stock on this date at this price\").\n\nNow each type of option (put or call) contract has two parties. (again sometimes confusingly, the term buyer and seller are used again). The person who obtains the right is called the buyer of the option. The person who gives up the right is called the seller of the option. The reason for this terminology is the buyer of the option has to pay the seller because this \"right to buy/sell\" has value. \n\nBecause these option contracts are standardized (100 shares typically) and their value changes over time, there is a secondary market for these contracts - there are people who want buy and sell existing options contracts. And this is what is usually seen on trading platforms.\n\nExample: \n\n1) AAPL $200 Put June 2020. This is a contract that gives the right to sell 100 Apple shares at the fixed price of $200 on June 2020. \n\n2) AAPL $200 Put August 2020. This is a contract that gives the right to sell 100 Apple shares at the fixed price of $200 on August 2020. \n\n2) AAPL $200 Call June 2020. This is a contract that gives the right to BUY 100 Apple shares at the fixed price of $200 on June 2020. \n\nThe $200 is called the exercise or strike price, and the date is when the option contract expires (ie must be completed or nullified). To make matters worse, there are standardized so called \"American style\" or \"European style\" options contracts which give different rights. \n\nThere are MANY MANY moving parts to options - strike price, option expiry dates, puts or calls, the price of the actual shares (in the example Apple), the price of the option contract. These option contracts are time limited, highly volatile and (for some stocks) thinly traded. These are all risks that the traders in options must appreciate.\n\nLink to useful resource:\n\n [_URL_0_](_URL_0_) \n\nCheers!"
]
}
|
[] |
[] |
[
[],
[],
[
"https://www.investopedia.com/options-and-derivatives-trading-4689663"
]
] |
||
3e5z2m
|
Why is tungsten at room temperature so brittle? Since super cooled metals are more brittle, is this the same phenomenon but just at a much lower temperature because tungstens melting point is so high? Or is it something entirely different?
|
askscience
|
http://www.reddit.com/r/askscience/comments/3e5z2m/why_is_tungsten_at_room_temperature_so_brittle/
|
{
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"Basic answer is that tungsten is Body Centered Cubic (BCC) and therefore will go through a ductile to brittle transformation at certain temperatures. DBTT (Ductile to Brittle Transition Temperature) of tungsten is quite high, around 400K. Room temperature, or 273K, is way below this transition temperature, so the tungsten will be brittle.\n\nThe basic mechanics here is that below this temperature there isn't enough vibrational energy in the lattice to allow for slip. So the atoms are almost locked in place and are unable to slide past each other, therefore they will separate and the material will fracture. ",
"Yes. No? Something completely different. Explaining will require defining several different \"kinds\" of material strength.\n\nElastic modulus (E, in units MPa) describes how a material's chemical bonds respond to mechanical pressure. E is directly proportional to the chemical bond strength in KJ/mol; the stronger the chemical bond is, the stiffer the material will be. As temperature increases, the bonds will elongate a little, and vibrate more until the material melts. It follows that melting temperature is also approximately proportional to bond strength, as well as E.\n\nYield strength (YS) is the pressure (also MPa) a material can withstand before deforming permanently (e.g. bending a paperclip into a different shape). Yielding activates an entirely different deformation mechanism in metals than elasticity. When a metal bends, crystalline defects in the metal's structure called dislocations are pushed around. This involves the atomic planes of the crystal sliding and shearing past one another. YS is highly dependent of metal purity and microstructure. Yielding takes a lot of energy, but you still haven't broken any chemical bonds, you've only shifted them around. YS and E are two very important numbers in fracture mechanics, which (in a nutshell) is a field of engineering used to predict if a material with inherent defects will fracture or yield.\n\nDuctility (the opposite of brittle-ness) is the percentage of elongation (percent total increase in length for tension) that a material can withstand before rupturing and failing (breaking bonds). It is how much you can yield (see above) a material above its YS before it fails. Ductility can vary from low (~1% for very brittle metals) to high (approaching 40% for very ductile metals). Ductility can vary even in metals and alloys of the SAME composition, and depends highly on crystal structure, microcrystalline grain size, and orientation. It also depends highly on alloy purity and composition. Even some lower melting point metals are very brittle (e.g. pure Cr).\n\nNow we have that out of the way, I can answer your immediate question.\n\nFirst of all, the class of materials that exhibit the largest reduction in ductility at low temperatures is high strength steel alloys. This phenomenon is called ductile to brittle transition (DBT) and happens primarily with BCC crystalline materials (which tungsten is also). There are a few alloys (e.g. nickel alloys) that have higher impact toughness at lower temperatures.\n\nTungsten (W) is one of the strongest pure metals we know of, in terms of E and YS. Its metallic chemical bonds are strong, which cause it to have a high E modulus and melting point. However, it takes so much force to move dislocations in W at room temperature that it fails locally before much of the material can yield. Based on fracture mechanics, minuscule defects result in a far larger problem for a brittle material than for a ductile material. As the temperature increases, YS decreases to a point where dislocations can be push around more easily. One source reports this temperature threshold to be around 400 deg C [_URL_0_]. IMO, however it is unclear how the rate of loading (impact testing vs. tensile testing) would affect the ductility in the way I defined above.\n\nI should also point out that W has extremely good high temperature strength (creep resistance), but that is a completely different damage mechanism and I've already written too much.\n\ntl;dr: Melting point (bond strength ) is one way to qualify one of the many factors concerning material ductility. Crystal structure, purity, microcrystalline grain size, and defect occurrence are all sensitive factors as well.\n\nSources:\n\n[_URL_0_]\n\nDieter, Mechanical Metallurgy.\n\nPorter, Easterling, Sherif, Phase Transformations in Metals and Alloys.\n\nI am a metallurgical engineer.\n\n[Edit: Spelling]"
]
}
|
[] |
[] |
[
[],
[
"hal.archives-ouvertes.fr/jpa-00253413/document"
]
] |
||
1sxoss
|
can someone explain to me the pros and cons of capitalism?
|
I feel I know a bit of both, but not nearly anything when I really think about it. Help?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/1sxoss/can_someone_explain_to_me_the_pros_and_cons_of/
|
{
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"As far as economic history goes, there simply isn't a better set of institutions than capitalism to generate technological growth.\n\nCons: inequality - though this can be abated with a welfare state.",
"Capitalism: An economic system under which capital is controlled by private individuals.\n\nCapital: Productive property such as factories, farms, financial institutions, or other systems which create wealth.\n\nPros: In theory, it allocates capital to the areas in society where they are most useful. For instance, let's suppose Mr. White, Mr. Green, and Ms. Brown all own factories making T-Shirts. Ms. Brown finds a cheaper way to put the design on T-shirts, thus, she can make more of them while spending less money. Because she's spending less money, she is able to expand the factory, so more T-Shirts will be made in the more efficient way, benefiting society.\n\nCons: A lot of the money that goes to capitalists doesn't make its way down to the rest of society, and ends up not benefiting society in any particular way. For instance, after a few months or two, Ms. Brown is making enough money that she not only expands her factory, but also buys Mr. White's factory. Now she's making twice as much money (even though she isn't doing twice as much work as she was before). Now, most of her money is going to pay for luxuries and more capital. This isn't benefiting society, since it's silly to produce extravagant luxuries for the few when there are still people struggling to get things they need. Furthermore, Mr. Green has long since adopted the new way of making T-Shirts, so it no longer really benefits society that Ms. Brown is expanding her factories, because factories owned by her are no longer any more efficient than factories owned by anyone else. In fact, Ms. Brown doesn't even manage most of the factories anymore; she pays other people to do that. So in the end, the only one who has benefited from Ms. Brown having so much capital is Ms. Brown herself."
]
}
|
[] |
[] |
[
[],
[]
] |
|
wm6zb
|
What is the final form of energy?
|
So the Law of Conservation of Energy states that energy cannot be created or destroyed. Since that is true, what is the final 'form' of energy?
For example, a lot of energy is converted to friction (which is heat). But what about kinetics and sound? When I wave, chemical energy is transformed to kinetic energy, but what happens to the kinetic energy? Does it just disappear?
Thanks!
|
askscience
|
http://www.reddit.com/r/askscience/comments/wm6zb/what_is_the_final_form_of_energy/
|
{
"a_id": [
"c5eiw64"
],
"score": [
4
],
"text": [
"Heat (thermal energy) would be the closest to the answer you are looking for.\n\n_URL_0_"
]
}
|
[] |
[] |
[
[
"http://en.wikipedia.org/wiki/Heat_death"
]
] |
|
1t1wve
|
how does apple own the beatles?
|
I just saw the movie Jobs and have been obsessed with apple and Steve Jobs lately.. How does Apple own the rights to the Beatles when Paul McCartney is still alive? /How does all of that royalty stuff work?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/1t1wve/eli5_how_does_apple_own_the_beatles/
|
{
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"Apple Inc, the computer/device company, is different from Apple Records/Apple Corps Ltd, which is the record label created by the Beatles. Apple Inc doesn't own the rights to the Beatles music.",
"[The Beatles sold the rights to their catalog of music back in the 1960s.](_URL_1_) It's been owned by many people, most famously by Michael Jackson, who made almost as much money on Beatles royalties as on his own music.\n\nI don't know if Apple Computer has any ownership in Beatles music, but you might be confused by [Apple Records](_URL_0_). Long before Steve Jobs was in business, The Beatles named their record company Apple. There was actually [a lawsuit between the computer company and the record label, because of conflicting trademarks.](_URL_2_)",
"Actually, Apple Records IS owned by McCartney and Ringo and the estates of Lennon and Harrison.\n\nInteresting point to add:\nYou may remember that it was a big deal (well kind of) when iTunes started carrying the Beatles' music. Why the delay?\nThere was a lawsuit (as /u/PLJVYF stated) between the two in which the judge basically said that it was okay for the two companies to have the same name because the computer and music markets were completely separate. \nWell, as Apple computers started gradually including music as part of its market, it had regular legal clashes with Apple Records and they weren't able to reach an agreement to sell the Beatles' music on iTunes. Too much animosity between the two. It did eventually get cleared up though, and the Beatles were on iTunes in 2010."
]
}
|
[] |
[] |
[
[],
[
"http://en.wikipedia.org/wiki/Apple_Records",
"http://en.wikipedia.org/wiki/The_Beatles#Song_catalogue",
"http://en.wikipedia.org/wiki/Apple_Corps_v._Apple_Computer"
],
[]
] |
|
5vle6l
|
if in the vacuum of space there are no exterior forces acing on a spacecraft, why can't we continuously speed up the craft to light speed with constant thrust?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/5vle6l/eli5_if_in_the_vacuum_of_space_there_are_no/
|
{
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"It takes more and more energy to constantly accelerate a spacecraft. This means that as you approach C the amount of energy that you need to go faster approaches infinity. Sadly humans do not have access to infinite energy so we can never actually reach C.",
"Because of relativity, from your point of view on the ship it may seem like you are always accelerating but from the point of view of someone back on Earth, you will never reach the speed of light. From their perspective, the closer you get to the speed of light the more slowly you would seem to age, the more your length would contract in the direction you are moving and the more your mass would increase. Theoretically, your mass would become infinite if you could reach the speed of light. Since the amount of energy needed accelerate an object is proportional to its mass, you would need an infinite amount of energy to accelerate up to the speed of light.",
"The main major problem is it would take a massive amount of energy (i.e. fuel) to be able to produce enough overall thrust to even get *close* to the speed of light (ignoring relativistic implications of doing this). That fuel has to somehow be contained in a single spacecraft and that massive spacecraft has to be launched from Earth while also hauling that massive payload.\n\n > Why not just build the spaceship *in* space?\n\nIt would still require astronomical resources to ferry enough building materials, crew, and fuel using smaller crafts spread over hundreds of trips up to the theoretical shipyard. \n\nThe sheer amount of time it would take to accomplish the feat of building and launching such a spacecraft using existing technologies and fuel sources would probably equal the amount of time it will take humanity to discover new technologies that can accomplish the same thing cheaper and faster."
]
}
|
[] |
[] |
[
[],
[],
[]
] |
||
250f92
|
Hebrew language revival
|
I know very little about the revival of Hebrew as a modern language from the ancient version, so I was wondering if the reason of the revival was a part of building a national identity or for a religious identity. Was identity a part of the reason or was it purely religious?
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/250f92/hebrew_language_revival/
|
{
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"text": [
"It was about the national identity, not religious reasons. More religious segments of Judaism were historically (and often still are) skeptical of Zionism in general, of which the Hebrew revival was a part.\n\nFirst, some linguistic background. Hebrew went extinct by the 2nd century. But it remained in use in Jewish communities as the language of the liturgy, Jewish texts, and religious literature. Synagogues still generally used Hebrew biblical texts, religious learners still learned Jewish texts, Rabbis still wrote Hebrew commentaries. Jews were generally literate in Hebrew script, and used it for writing non-Hebrew languages in many cases.\n\nThe revival of Hebrew is an interesting linguistic topic. The father of Hebrew is Eliezer Ben-Yehudah. But the process began a bit before. During the 19th century, the Jewish literary revival involved making Jewish works of \"high\" literature, in both Hebrew and Yiddish. One product of this was a body of literature in Eastern Yiddish (Tevye the Milkman was a product of this, which of course became Fiddler on the Roof). Another was new literary writing in Hebrew, by authors like Chayim Nachman Bialik.\n\nIt's with this backdrop that we get a critically important, but sadly forgotten, Zionist named Ahad Ha'am (that was his penname--his actual name was Asher Grinsberg. Ahad Ha'am means \"one of the nation\"). There were several strands of Zionism in the late 19th century. His was sometimes called \"cultural Zionism\". He saw the establishment of a Jewish state as the ultimate expression of this Jewish cultural revival. Just as writing literature would revitalize Jewish writing, a Jewish state would revitalize all aspects of Jewish life. He saw Zionists like Herzl as being sort of half-assed. They wanted to help Jews, yes, but they didn't want to really make Jews a more vibrant nation. In essence, he saw Herzl et al as trying to create a \"state of Jews\", while he wanted a Jewish state. He didn't think it was practical to just get Jews to migrate to Palestine--you'd need a cultural revival to get people interested in such a national enterprise\n\nAnd he wrote these objections in Hebrew. One of his bigger essays, זה לא דרך (Hebrew for \"this is not the way\"), where he outlined his objections. Trying to build a state out of nothing is pointless--first, Jews have to be inspired by a revitalization of Jewish culture.\n\nAround this time Eliezer Ben-Yehudah started working to revive Hebrew. He did a few things to this end. He wrote a Hebrew-language newspaper based in Jerusalem. He raised his son as a native monolingual Hebrew speaker. He wrote a Hebrew dictionary, including a number of coined words for new concepts.\n\nTo address your initial question, there were religious objections to this. Hebrew was, in Jewish parlance, *lashon kodesh/loshn koshesh*, the Holy Tongue. It had a religious significance. And many objected to its use in daily affairs. It was a particular point of controversy for Eliezer Ben-Yehudah in Jerusalem, which had a large religious population.\n\nWith this intellectual and ideological backing, combined with someone doing the legwork, Hebrew slowly started to gain ground. In the early 1900s Zionists incorporated Revisionist Zionist lingo into the language arguement. They saw Yiddish as an exilic language, which was to be eschewed for the *real* Jewish language, Hebrew. This active objection to other languages, combined with the ideological advantage of a Jewish revival it provided, gave it strength.\n\nPerhaps the solidifying moment was in the establishment of the Technion. It's a scientific univerisity in Haifa. There were intense debates about what its language should be. On one hand, German was the language of scientific discourse at the time. On the other, it was a institution in the Jewish statehood enterprise, and it should use the Jewish language. Eventually, Hebrew won out.\n\nSo propelled by a couple pieces of Zionist ideology, Hebrew managed to become the language of what would become Israel.\n\nEdited to remove typo"
]
}
|
[] |
[] |
[
[]
] |
|
1fdnkv
|
What was the source of gunpowder for the colonial militias during the American Revolution?
|
Were they able to manufacture it themselves? Did they receive it from overseas? If so, from where?
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/1fdnkv/what_was_the_source_of_gunpowder_for_the_colonial/
|
{
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"I don't have much analysis that can add to their own words. From the Journals of the Continental Congress, Saturday, June 10, 1775:\n > Resolved: That it be, and is hereby earnestly recommended to the several Colonies of New Hampshire, Rhode Island, Connecticut and the interior towns of Massachusetts bay, that they immediately furnish the American army before Boston with as much powder out of their town, and other publick stocks as they can possibly spare; keeping an exact account of the quantities supplied, that it may be again replaced, or paid for by the Continent; this to be effected with the utmost secrecy and dispatch.\n\n > That it be recommended to the committees of the several towns and districts in the colonies of the Massachusetts bay, New Hampshire, Rhode Island, and Providence Plantations, Connecticut, New York, and the eastern division of New Jersey, to collect all the salt petre and brimstone in their several towns and districts, and transmit the same, with all possible despatch, to the provincial Convention at New York.\n\n > That it be recommended to the provincial Congress ∥convention∥ of the colony of New York, to have the powder Mills, in that colony, put into such a condition as immediately to manufacture, into gun powder, for the use of the Continent, whatever materials may be procured in the manner above directed.\n\n > That it be recommended to the committees of the western division of New Jersey, the colonies of Pensylvania, lower counties on Delaware and Maryland, that they, without delay, collect the salt petre and sulphur in their respective Colonies, and transmit the same to the committee for the city and liberties of Philadelphia; to the end, that those articles may be immediately manufactured into gun powder, for the use of the continent. ",
"The American colonists had very limited supplies of gunpowder and very limited capacity for manufacturing more of it (precise figures are in the link.) Had there not been a foreign source of gunpowder it is very doubtful that they could have been successful in their revolution. Who was this crucial benefactor? [Why the liberty loving King of France Louis XVI.](_URL_1_)\n\nIt's easy to forget that North America remained a side theater to European conflicts. Without France's self interested support there couldn't have been American independence.\n\n[Here's another link with more detailed figures]( _URL_0_)",
"This doesn't really answer your question other than saying the gunpowder wasn't made domestically.\n\nHowever, the first gunpowder mill in the US was the Eleutherian Mills near Wilmington, DE. It was run by the DuPonts shortly after the revolutionary war. It was also the start of their industrial empire.\n\nI can't link to anything currently, but there is a wiki page about the mill. You might also look into the Hagley Museum, which is located near the mill and contains loads of information about it."
]
}
|
[] |
[] |
[
[],
[
"http://penelope.uchicago.edu/Thayer/E/Journals/AHR/30/2/Supply_of_Gunpowder_in_1776.html",
"http://www.universityarchives.com/Find-an-Item/Results-List/Item-Detail.aspx?ItemID=54674"
],
[]
] |
|
ctl2kg
|
when cops and dea agents perform undercover drugs busts where do they obtain said drugs?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/ctl2kg/eli5_when_cops_and_dea_agents_perform_undercover/
|
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"I think most of the time they act as the buyers, not the sellers. They are trying to work their way UP the ladder, not down, so they want the dealers, not the end users. \n\nSo they just make multiple buys from a small dealer, then bust him, and try to flip him to be a double agent in exchange for less jail time. Then they try to get him to introduce them to the next step up the ladder and do some bigger buys from him, then bust him and try to flip him also. \n\nThen they just repeat this process as high as they can go, but the higher they go and the less productive the undercover operation is, as it takes much longer to gain trust, and get to the real kingpin instead of one of his flunkies or lieutenants, plus the buy quantity needs to keep escalating and it's hard to tell your boss down at the cop station, \"Hey, I need a million bucks to buy some drugs\" so there is really only so high they can go before it becomes completely unproductive.",
"I know of a movie/film prop house in Atlanta that makes fake drugs specifically for drug busts. Also film. They also specialize in high quality fake money for film which involved years of talks with the Secret Service to figure out what could be allowed. I guess that's part of where the connections were made for the fake drug supply stuff.",
"While the other comments here are are accurate, the DEA does keep a small quantity of drugs on hand if there is a need to have _actual_ drugs used in sting operations.\n\nThese drugs are obtained from other drug busts, and are simply not destroyed after the trial (as is customary for drugs seized as evidence)."
]
}
|
[] |
[] |
[
[],
[],
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] |
||
4qy10k
|
what happens to clothing that isn't sold?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/4qy10k/eli5_what_happens_to_clothing_that_isnt_sold/
|
{
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"text": [
"What you're asking about is the retail chain. For most products, it works like this:\n\nManufacturer makes a product, and markets it to retailers, who place orders in various quantities. They ship the orders, and the retailers sell it in line with their contract with the manufacturer. Using your example, Levi doesn't want to compete with itself or have the price fall so low it causes perceived value issues, so they may have a minimum price the jeans can be sold for.\n\nAfter a certain point, the unsold merchandise will go through a series of price reductions via sales, promotions, bogos, and ultimately end up on clearance.\n\nThe merchandise remaining after the clearance sale will be sent to the retailers distribution centers and bundled into lots. These lots are sold to discount outlets. For clothes, that would be places like Marshall's, Kohl's, TJ Maxx, etc.\n\nThey go through the same price reduction process as before, only becoming cheaper still. These places do hold on to merchandise for a considerable amount of time. You can find some relics at Big Lots, for example.\n\nIf the merchandise is still sitting unsold, it often ends up being put back in lots and re-auctioned to the bottom feeders of the retail chain - flea marketeers, eBay and Amazon wanna be moguls, etc.\n\nAt that point, the merchandise that doesn't sell is either so severely discounted, you are literally only paying for the shipping and storage, or it is finally liquidated via donation for tax purposes.\n\nOr, you fill a warehouse with it, wait a respectable amount of time, and light a match.",
"It depends there are a few companies that will dependent on the manufacturer's (or the company that had them made for them) wishes will either:\n\n- destroy them\n- remove all identifing features and sell them in some country where the manufacturer is not present in the market.\n- simply sell them in some far away country\n- or simply sell them off to clearence stores / dollar stores or similar",
"Something funny to think about is that they print \"Superbowl Champion\" shirts for both teams so somewhere in Africa, there are a bunch of kids running around in Seattle 2015 shirts.",
"I'm surprised there isn't more mention here about the companies that do just destroy and throw away the unsold clothes, it's actually a pretty large problem. Just so a quick Google, there's been a lot of flack about this lately.\n_URL_0_"
]
}
|
[] |
[] |
[
[],
[],
[],
[
"http://nymag.com/thecut/2010/01/hm_destroys_and_throws_out_per.html"
]
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||
7lc8hh
|
how is a single injection of a drug able to provide months of therapy?
|
My wife is getting a single shot of a drug that will stop her production of estrogen for a full three months. I read about "once a year" injections that can provide months of relief for various conditions. How can a single dose of a medication remain metabolically active for months at a time?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/7lc8hh/eli5_how_is_a_single_injection_of_a_drug_able_to/
|
{
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22
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"text": [
"Esterification of an injectable steroid basically accomplishes one thing, it slows the release of the parent steroid from the site of injection. \nThis happens because the ester will notably lower the water solubility of the steroid, and increase its lipid (fat) solubility. This will cause the drug to form a deposit in the muscle tissue, from which it will slowly enter into circulation as it is picked up in small quantities by the blood. Generally, the longer the ester chain, the lower the water solubility of the compound, and the longer it will take to for the full dosage to reach general circulation."
]
}
|
[] |
[] |
[
[]
] |
|
13hp7g
|
How does amputation early in life affect growth of the amputated limb?
|
askscience
|
http://www.reddit.com/r/askscience/comments/13hp7g/how_does_amputation_early_in_life_affect_growth/
|
{
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"c749t3m"
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"text": [
"Typically amputated limbs do not grow."
]
}
|
[] |
[] |
[
[]
] |
||
2johqv
|
Were legendary swords actually a thing?
|
In all the many years where swords were used in combat, were legendary swords actually a real thing?
I don't mean simply named swords, but swords that carried a reputation as being exceptionally well made or somehow powerful. I'd imagine given the beliefs of the time, they probably would have been seen to be magical.
If there were, was it well known who had them, and were they feared?
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/2johqv/were_legendary_swords_actually_a_thing/
|
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"Heya guys, just popping in here to issue a quick reminder as to the [standards we uphold in this subreddit.](_URL_0_) Not a single one of the answers so far has measured up to those standards, including posts along the lines of:\n\n* \"I don't know a great deal about this but as there are no other replies I'll have a go\"\n* \"This one (Wiki link)\"\n* \"Link to Youtube 'popumentary'\" (We've had 6 or 7 different posts linking to the Ulfbehrt video, which is about as far from academic as you can get.) \n\nAlso, please remember the three things to ask yourself before posting:\n\n1. Do I, personally, actually know a lot about the subject at hand?\n2. Am I essentially certain that what I know about it is true?\n3. Am I prepared to go into real detail about this?\n\nIf any one of these is answered with a \"no,\" then please think twice about posting.\n\nThanks so much for your consideration! :)",
"I know for sure there were coronation swords - for example Szczerbiec of Piast dynasty, the only surviving part of crown jewels of Piasts, currently displayed in Kraków. The name translates to \"Jagged Sword\" or \"Notched Sword\" and the legend has it the sword was chipped by Bolesław Chrobry against Golden Gate of Kiev during his capture of the city - purely a myth, as the capture took place in 1018, and the gate was constructed in 1037. The sword is a symbol of Poland, used throughout 20th century and to this day even by nationalists.",
"Here's a prior thread that addressed this topic: _URL_0_\n\nHope you find something you wanted to know, I thought it was a good thread.",
"Sorry OP: do you mean a real, existing weapons that hold high reputation, or simply a legendary or semi-legendary weapons (which existence is doubted)?\n\nIf it is the latter, I guess I'm going to mention a rather not-well known Asian weapon. The Javanese people in Indonesia has a huge fascination with *keris*, a dagger-like weapon. Back in the pre-modern times every Javanese man who is considered as adult, no matter whether he's rich or poor, always have at least one keris in his home. This tradition is well-documented in Tome Pires' *Suma Oriental*. Today we can still see the Javanese wield decorative keris in very formal events, such as weddings or, in case of Jogjakarta (a province in Indonesia which retains the autonomy for operating as sultanate), in sultanate-related events.\n\nOne famous legend is of the Keris Mpu Gandring.\n\nIt was wielded by Ken Arok, a bandit-turned-king. Once upon a time during his life he encountered Ken Dedes, a beautiful wife of Tunggul Ametung, a provincial of Tumapel. He told his mentor of this encounter, and the mentor told Arok that whoever man who took Dedes as his wife would be a king of prosperous kingdom. Arok, already infatuated with Dedes, then desired to murder Ametung, marry Dedes, and become a famous king. \n\nIn traditional Javanese belief, a man with high position such as Ametung is believed to hold a supernatural power. So Arok needed a special weapon to be able to kill Ametung. He asked Mpu Gandring, a famous keris-smith, to make such weapon. Gandring fulfilled Arok's request and asked him to wait several months. However after several months and a number of visits, Arok grew tired of waiting. So he took the keris (it's already exceptional at that time, just need some more imbuing with supernatural power), and murdered Gandring. With his last breath, Gandring cursed the keris, and told Arok that he and his seven generation of descendants will be killed by the same keris.\n\nLong story short, Arok murdered Ametung, married Ken Dedes, and built the Kingdom of Singhasari. However his rule was short, as Ametung's son, Anusapati, murdered him during his reign. Later on, Anusapati got murdered himself by Arok's son, Panji Tohjaya. Then Tohjaya's rule ended when Anusapati's son, Wisnuwardhana, rebelled. Tohjaya was wounded severely and died while seeking refugee.\n\nWhether they were all wounded and murdered by the same keris remains a question, but it is what the Javanese believed until today. The story of Arok's ascension, along with the murder of Ametung and the tragedy that followed are real though.\n\nThere are many other keris, like Keris Setan Kober, Keris Condong Campur, Keris Kyai Omyang, etc, but Keris Mpu Gandring is the most famous. Many are believed to have supernatural power. Keris Kyai Omyang, which was wielded by one of anti-colonial heroes in 19th century, Prince Diponegoro, now resides in Sasana Wiratama Museum, Jogjakarta.\n\nThe only source written in English I can recall dealing with this subject, albeit only briefly, is Benedict Anderson's *The Idea of Power in Javanese Culture*. Others I know unfortunately are in Indonesian.",
"Related question if anyone knows: Is Kusanagi (the Japanese national treasure) thought to still exist, or is it more likely to have been lost?",
"Does the Sword of Goujian count? It probably dates to 500-300BC, was owned by a king (since engravings on the sword itself says so), and is remarkable for being a copper/bronze-age sword that remains untarnished. Maybe this one doesn't count as legendary because it's an archaeological artifact and not mentioned in legends.\n\nOn Tiger Hill in Suzhou, China, there is a boulder called \"Sword Testing Stone\" and legend says that the boulder was split in half by one of the emperors who lived there using his legendary sword.\n\nSecondly, Guan Yu was a legendary General who wielded a legendary pole-arm. I'm not sure if this is only legend or historical. I was taught that it was real, but Wikipedia says that there's no historical evidence either way.\n\nI'm not a Chinese historian, but mention these as they either haven't been mentioned below or in similar threads. Hopefully a Chinese historian will be able to fill in the details and mention any other legendary Chinese weapons.",
"I really like this question - sure there have been a lot of named swords, but getting down to the reason why they're named is deeply fascinating when there's a story to be found.\n\nSo to answer directly - yes! There absolutely were swords that had reputations to go along with their names. The vast majority of them would qualify as being 'well made' or at least perceived so even if they failed and broke in some way. The truly legendary swords though, were believed to have something special about them though - whether some magic, an other-worldly quality or a personality all their own.\n\nOne such sword was Skofnung - the sword of the Danish King Hrolf Kraki. The sword in Kraki's time was revered for it's hardness, sharpness and was said to have been imbued with the spirits of twelve of his Berserks. It was also said to give a loud cry whenever it saw wounds. It had quite a reputation, and when Hrolf Kraki died, the sword was entombed with him in his burial howe.\n\nNow, in Scandinavian tradition it wasn't uncommon for valued possessions to be put to rest with it's owner rather than handed down. This led to a habit of retrieving weapons and armour from graves that is documented in a number of Norse sagas. These tales are often embellished with battles against the previous owner for the item, but they are at least rooted in factual history.\n\nSkofnung shows up in tales well after the time of Hrolf Kraki - notably in the hands of Skeggi of Midfjord who is said to have recovered the sword. It's at this time that we hear more about what makes Skofnung so special, and the particular way in which it has to be handled.\n\nSkofnung has with it a 'Life-stone' and it's said that a wound inflicted with the sword can only be healed if the life-stone is rubbed on the would first. Life-stones are mentioned in conjunction with a handful of other historical swords so while it isn't a unique feature, it does mark it as a special blade believed to have an otherworldly power about it.\n\nThen there are the rules to handling the sword. Skofnung came with a small bag on the pommel and it was said to never allow the sun to shine on the pommel directly. Also it was never to be drawn unless the wielder was ready for a fight. Then there was the little snake - when drawn the wielder should blow gently on the blade just below the guard and a little snake with creep out. When that happens the blade is to be inclined to allow the little snake to creep back in again. \n\nAs a side-note, the bit about the blade-snake isn't as crazy as it might sound. Skofnung was pattern welded from a number of metal rods, and made in several sections (typically three - a longer central section that was tempered to be softer and springier, and two hardened outer edges that were welded on). The metal rods were twisted and folded in the forging process which imbued a pattern in the blade. It is this pattern that, on Skofnung in particular, made a little 'snake' when the warm breath of a person in the cooler climate of Scandinavia, contacted the blade. \nNote: Googling 'pattern welded blade' will give you an idea of how the effect looks on a blade.\n\nThis is all very well explained because these are the things that weren't done when the famous sword was lent to a man named Kormac to fight a duel with a man named Bersi (who also had a sword, Hviting, which had a life-stone as well). Kormac ends up losing the duel and it's his failure to follow the sword's rituals that are blamed (which are believed to have imparted bad luck as he lost the fight when he cut the point off Hviting and it flew onto his hand, cut him and caused him to bleed first). \nFailing to observe the rules of the sword (and doing pretty much everything wrong) Kormac is forced to wrench Skofnung out of the scabbard and the sword was said to have come unwillingly and howling. It's also said that the luck of the sword was changed, which didn't work out so well for Kormac.\nIt's worth noting however that the sword served both Skeggi and his son for many years after this, with no mention of it's luck being damaged or changed in any way.\n\nSo, a long, somewhat rambling answer, but I think it covers off most of the points and shares a bit of an interesting story as well. I'd highly recommend checking out the sources I've listed below here - in particular Oakeshott's book is excellent.\n\n\nSources & Further Reading:\nThe Archaelology of Weapons, R. Ewart Oakeshott\n\nSkofnung on Wikipedia: _URL_0_\n\n"
]
}
|
[] |
[] |
[
[
"http://www.reddit.com/r/AskHistorians/comments/1jsabs/what_it_means_to_post_a_good_answer_in/"
],
[],
[
"http://www.reddit.com/r/AskHistorians/comments/15atks/are_there_any_examples_of_named_swords_in_history/"
],
[],
[],
[],
[
"http://en.wikipedia.org/wiki/Skofnung"
]
] |
|
4dcac6
|
how quartz crystal resonators work?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/4dcac6/eli5_how_quartz_crystal_resonators_work/
|
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"text": [
"They rely on a piezo crystal. These crystals have the useful property that they generate a voltage if you squeeze them, and expand or contract if you apply a voltage. They are commonly used in lighters (squeezing them generates a high voltage, which causes a spark), speakers and ultra sound transducers(a rapidly oscillating voltage contracts and expands the crystal) and kitchen scales (putting a weight on them generates a voltage).\n\nAs a resonator, the crystal is tuned like a musical instrument to oscillate at a certain frequency, and combined with a small amplifying circuit. If you turn it on, it starts oscillating at a precise frequency, and never stops. Imagine it like a tuning fork, only that it never stops humming as long as you apply a voltage.",
"Quartz is Piezo Electrical. Which means if it moves it generates power. Or if power passes though it, it moves.\n\nThe Quartz Crystal is placed in contact with metal wall. Power passes though, Quartz moves, power is cut off, Quartz moves back, power is back on. As long as the circuit has power it'll produce a predictable On/Off/On/Off hundreds of thousands time per second forever. ",
"Someone will be able to explain it better, however it basically oscillates at a specific frequency, if we apply a specific voltage. So, if we do apply that known voltage, we can count up its 'vibrations' so to speak, and we can use that to accurately measure time.",
"There is a great Air Force training video that explains it like you're five. \n\n_URL_0_"
]
}
|
[] |
[] |
[
[],
[],
[],
[
"https://www.youtube.com/watch?v=dUZFxMTEss0"
]
] |
||
7dy4xi
|
What are the best examples of forgiveness and philanthropy and self-sacrifice from history?
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/7dy4xi/what_are_the_best_examples_of_forgiveness_and/
|
{
"a_id": [
"dq15vbc"
],
"score": [
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"text": [
"Sorry, we don't allow [\"example seeking\" questions](_URL_1_). It's not that your question was bad; it's that these kinds of questions tend to produce threads that are collections of disjointed, partial, inadequate responses. If you have a question about a specific historical event, period, or person, feel free to rewrite your question and submit it again. If you don't want to rewrite it, you might try submitting it to /r/history, /r/askhistory, or /r/tellmeafact. \n\nFor further explanation of the rule, feel free to consult [this META thread](_URL_0_)."
]
}
|
[] |
[] |
[
[
"https://www.reddit.com/r/AskHistorians/comments/3nub87/rules_change_throughout_history_rule_is_replaced/",
"https://www.reddit.com/r/AskHistorians/wiki/rules#wiki_no_.22example_seeking.22_questions"
]
] |
||
4szktg
|
how does the 100 year old light bulb work?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/4szktg/eli5_how_does_the_100_year_old_light_bulb_work/
|
{
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"I believe you're talking about the firehouse lightbulb that is 100 years old.\n\nThe answer is a combination of several things- the bulb has been fairly gently used, the power that it running it is lower than standard, the bulb itself is of a sturdier design than its modern replacements would be, and, IIRC, the bulb is in a dangling wire fixture, which provides some protection against vibrations from nearby traffic, activity in the building, or earthquakes.",
"Lightbulbs work by running current through a wire, making that wire get white-hot and using that whiteness as light. The hotter a lightbulb is, the whiter, and brighter, the light. The thinner the filament, the more light you get for a given amount of electrical power. Therefore, an efficient lightbulb needs thin wires. Thin wires break easily. Long-living lightbulbs are less efficient, dim, reddish and therefore have many drawbacks over conventional 1000 hour bulbs. But it makes for some nice headlines.",
"It's actually nowhere near as exceptional as you think. A huge proportion of the wear on light bulb filaments is to to thermal expansion and contraction from being turned on/off (this is why bulbs only ever to fail when you first turn them on). These very old bulbs are bulbs that have been left on continuously, so they don't get that wear: they just sit there, at a steady temperature, not being stressed in any way, so they don't fail. "
]
}
|
[] |
[] |
[
[],
[],
[]
] |
||
fktct0
|
Why aren't you still contagious after you recover from a viral infection?
|
My understanding is that *recovering* from a viral infection is not the same thing as *removing* a viral infection. Even though you no longer show symptoms, the virus remains in your body forever - the only difference being that your immune system can keep at at bay effectively enough to keep you asymptomatic. If that's the case, why can't I spread the disease? Are there no longer any germs in my saliva or mucous?
Along the same vein, why don't people who develop autoimmune disorders get overrun by all the previously defeated viruses/bacteria in their body once their immune system can no longer keep up?
Thanks in advance for your help. I've always wondered this since I was a kid. Seems like too specific a question to google.
|
askscience
|
https://www.reddit.com/r/askscience/comments/fktct0/why_arent_you_still_contagious_after_you_recover/
|
{
"a_id": [
"fkxm3cs"
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9
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"text": [
"It is absolutely not true that viruses remain in your body forever. There are a small subset of viruses that do that, but the vast, vast majority of viruses are completely eliminated from your body by the immune system."
]
}
|
[] |
[] |
[
[]
] |
|
2fq2fb
|
Are there any magnets available commercially that will adhere to aluminum?
|
Just wondering. Is there anything like that available?
|
askscience
|
http://www.reddit.com/r/askscience/comments/2fq2fb/are_there_any_magnets_available_commercially_that/
|
{
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"text": [
"Magnetic effects generally arise from the interactions of unpaired electrons. Typically, magnetic materials (such as iron) are ferromagnets, which means that the the unpaired electrons the d-orbitals can spin-align under certain conditions. Aluminum only has s and p orbitals, and therefore no d electrons are available for spin alignment. Therefore, aluminum exhibits no intrinsic ferromagnetism.\n\nHowever, there are other means by which aluminum may magnetically interact. For instance, if one passes a current through an aluminum object, it will give off a weak magnetic field (Lenz's law), which will cause the aluminum to interact with a magnet. Other effects related to Lenz's law and electromagnetic flux may also cause aluminum to weakly interact with magnets (_URL_0_). So, in principle, one could apply a current to a piece of aluminum, and achieve a magnetic interaction with any commercially available magnet."
]
}
|
[] |
[] |
[
[
"https://www.youtube.com/watch?v=yk4ACjzDFRY"
]
] |
|
e7jnch
|
how does a fast charging plug charge faster when the socket has the same output when there's a regular plug?
|
[deleted]
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/e7jnch/eli5_how_does_a_fast_charging_plug_charge_faster/
|
{
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"fa0acfy"
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5
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"text": [
"The \"fast charge\" socket **does not** have the same output.\n\nThe voltage is the same, but the current available at that voltage is higher. This must be taken into account when choosing cables and connectors."
]
}
|
[] |
[] |
[
[]
] |
|
1br8vb
|
Generating electricity and rotating magnets
|
From what I understand, rotating a magnet inside a metal coil produces electricity.
Also while I was playing with my magnets I noticed that in certain configurations/distances if I rotated one magnet the others would rotate as well.
Building on these two things could we build one 'master' generator with a rotating magnet but then have that master rotating other magnets in other generators ad infinitum?
Hope that made sense!
|
askscience
|
http://www.reddit.com/r/askscience/comments/1br8vb/generating_electricity_and_rotating_magnets/
|
{
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6
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"text": [
"You could, but it wouldn't be beneficial. Any energy being used to cause rotation of the smaller magnets is not going in to generating electricity. You could be better off using your super magnet to generate electricity directly. "
]
}
|
[] |
[] |
[
[]
] |
|
53m6oc
|
In John Milton's Paradise Lost, Satan is sometimes read as the protagonist. While Milton obviously didn't intend this, did any of his contemporaries believe this?
|
By this I mean, do we have any writings or evidence to suggest that some people in his time viewed Satan as the protagonist, or at least a tragic hero.
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/53m6oc/in_john_miltons_paradise_lost_satan_is_sometimes/
|
{
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"[Yes.](_URL_0_)\n\nAs the source describes, Milton was a republican in the historical sense. It was during his lifetime that Oliver Cromwell, still a divisive figure in English history, rose to power after overthrowing Charles I. Milton supported this. Charles I was deposed, but after returning and making war throughout the 1640s, the English ultimately executed him in 1649. Following this, Cromwell is given the title of Lord Protector of the realm, although after his death, the monarchy is restored bloodlessly. Although Richard Cromwell was selected to succeed, he did not command the requisite respect and was booted out of office within a year, leading to the restoration of Charles II to the throne.\n\nFast forwarding to 1667, after Milton (unpopular for his Republican views, at this point blind, which was considered by some to be divine punishment for his support of regicide, or the killing of the king.)\n\n > England in 1667 was reeling from the events of the previous year, when plague and fire had swept the capital, causing a devastation many people thought was divinely inspired; a biblical epic from a blind, grim old controversialist was by no means certain of being sympathetically received, as the poet's wish that his poem might 'fit audience find, though few' (VII.31) perhaps recognises. In spite of this unwelcoming climate, when Paradise Lost appeared, it was hailed as a work of genius, even by Milton's political opponents. \n\nOne of the first adaptations of the poem is John Dryden's play, which \"outsold the original until the end of the seventeenth century.\"\n\n > Satan, who disdains servitude and tries to overturn his monarch, becomes in Dryden's rewriting an unmistakeable portrait of Oliver Cromwell, the king-killer. He also believed that the fallen angel, and not Adam, was the hero (in the sense of his structural position as the protagonist of the epic), and weighted his adaptation accordingly... Contemporary readers who thought there was a whiff of sulphur about the unrepentant republican poet were not surprised to find these sentiments in the mouth of the arch-fiend; and there were those who believed that Milton was in fact disowning his previous stance by associating it with Satan. Neither reading does justice to the complexity of Paradise Lost, but this does identify what was to become a recurrent theme in later responses to the poem: the contested interpretation of Satan, its eloquent anti-hero.\n\nThe most prominent later commenter on Milton who views Satan as the protagonist, William Blake, remarks that, \"The reason Milton wrote in fetters when he wrote of Angels and God, and at liberty when of Devils and Hell, is because he was a true Poet and of the Devil's party without knowing it.\"\n\nEssentially, opinions are divided: as the linked source would indicate, many at the time may have viewed Milton's poem as autobiographical in a sense, or as they say, that Milton was \"disowning his previous stance by associating it with Satan.\" Those who favored Cromwell were likely to favor it; even those who didn't agree with Milton like his political opponents \"hailed [it] as a work of genius.\" The role of Satan, then as now, was open to interpretation and disputation.\n\n\nSource:\n\nPeter Gaunt, *Oliver Cromwell*"
]
}
|
[] |
[] |
[
[
"http://darknessvisible.christs.cam.ac.uk/critics.html"
]
] |
|
3ap076
|
after their extinction, why did dinosaur type creatures not evolve all over again?
|
After the dinosaurs suffered the extinction event and life had to 'start over' to a degree, why didn't creatures similar to them evolve all over again?
If life had evolved as such to create all the dinosaurs creatures and they were seemingly wiped out by a disaster (rather than simply not being up to it as a species) then why didn't evolution see a repeat of that 'type' of species again?
Why did life find a different way?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/3ap076/eli5_after_their_extinction_why_did_dinosaur_type/
|
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"There are infinite forms for life to try. There is no trajectory of evolution except the historical lineage. Since the non-avian dinos were erased, there was no evolutionary history to build on. ",
"Evolution creates species that do better in there current environment than there predecessors. Dinosaurs or creatures like them didn't 're-evolve' because they wouldn't have survived in the post extinction environment better than the surviving species of there family/group.",
"Well, first of all, Dinosaurs never disappeared. Their descendants still roam this earth and are one of the most successful and widely spread types of animals on the planet: birds. \n\nWhatever species evolves after a massive extinction event like that is really down to a lot of luck and timing (having the right traits at the right time), what sort of competition is out there for those species, what kind of environment those species are evolving in, and none of those things are static. The ancestors of dinosaurs (archosaurs) had the right luck, the right timing, the right traits for dealing with their competition, and the right environment to thrive in after the Permian-Triassic extinction event (a mass extinction even bigger than the Cretaceous-Paleogene extinction event) which had wiped out *a lot* of the species competing with them for resources. But just because they were able to do that once, doesn't mean all those events lined up again. A lot had changed. Most giant dinosaurs were unable to deal with the impact winter that followed. And the smaller ones that could deal with that winter were either birds/bird-like (which, again, have turned into a hugely popular group) or were outcompeted by early mammals (which are actually descendants of synapsids, the group Dinosaurs once outcompeted after the Permian-Triassic extinction event). ",
"Actually many Mammals and Birds fill niches vacated by the Non-Avian Dinosaurs. Convergent Evolution seems to be a vastly under appreciated concept. ",
"The ecological niches formerly occupied by dinosaurs were taken over by the creatures that survived the mass extinction. So now instead of big dinosaur carnivores like t-rex, we have big mammalian carnivores like lions, tigers, polar bears, killer whales, and fish like great white and bull sharks.\n\nIf all mammals became extinct tomorrow, but amphibians survived, hundreds of millions of years from now there would probably be big amphibian carnivores and big herbivores.",
"Evolution takes place in an environment; different organisms compete to best survive (reproduce) in an environment, and it is their adaptation to it that drives evolution. \n\nThe environment of the earth after the dinoasaurs died out was different from that when they first evolved - for one thing, there were all those dead dinosaurs! That may sound silly, but that really was one of many factors that drove the evolution of the surviving species. Another major factor was the thing that wiped out the dinoaurs, the meteor impact that affected the global climate. If it was drastic enough that the living dinosaurs were wiped out, then it was drastic enough that any new evolutions that might be similar to the old dinosaurs wouldn't survive either. And there is the factor that organisms themselves are part of the environment. The dinosaurs could never evolve again because now there were other species that took their environmental niche. To regain that niche, the surviving descendants of dinosaurs had to evolve in to something different from dinosaurs (and that's what modern birds are).\n\nSimilar organisms can evolve in different places or times only if the environments are sufficiently similar. The earth is always changing, and was never similar enough to the pre-dinosaur environment, so similar species never evolved again."
]
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3bioer
|
I know of absolute zero at -273.15°C, but is there an absolute hot?
|
askscience
|
http://www.reddit.com/r/askscience/comments/3bioer/i_know_of_absolute_zero_at_27315c_but_is_there_an/
|
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"We don't know if there's a maximum temperature.\n\nIn certain models -- string theory is one of them -- there is a maximum temperature called the *Hagedorn temperature*. This arises because the number of possible high energy states increases sufficiently fast that as you put more energy into the system, it gets spread out over more and more states in such a way that the temperature decreases less and less for a given amount of heat put in. Net result is that there's a temperature that is the upper limit of the temperatures that can be reached.\n\nI'll add that even in string theory, some people think the Hagedorn temperature might not be an actual limit, but more an indication that there is a phase transition (like when a liquid turns to gas), but that's even more speculative.",
"If you're interested in \"what is the hottest temperature achievable\" that may be an unanswerable question (or at least one I cannot answer), but if you want to know the defined lowest temperature, it is -0K. \n\nIt turns out any negative temperature (in K, not C or F) is actually hotter than any positive temp. The temperature scale goes something like this:\n\n0K,... inf K, -inf K, ... -0K\n\nThis may seem odd, to answer why this is the case, you must understand a fundamental property of temperature. While temperature is defined as [T = dE/dS](_URL_0_), aka- Temperature is defined as the derivative of energy with respect to entropy. See, normally as entropy increases, energy increases, but you can arrange systems where the opposite happens, as entropy increases energy actually goes down. That means that temperature will be negative. \n\nSince we know from the Second Law of Thermodynamics that in a closed system, entropy will increase, that means that energy will flow from a negative temperature system to a positive temperature system, because when a system has a negative temperature, by decreasing the energy in the system (heat), the entropy will actually go up (and in a positive system, increasing energy will lead to increased entropy, so entropy goes up there too). \n\nAnd that's why negative temperature is hotter than positive- heat will flow from the negative temperature to the positive one, and a higher temperature item will have heat flow from it to a lower temperature one. ",
"The Planck temperature is 1.42 x 10^32 K.\n\nAt this temperature, the radiation emitted causes quantum gravitational effects. Lacking a unified theory of quantum gravity, our understanding of physics breaks down at or past this point.",
"In terms of the Universe, I guess there would be one we can say is a definite upper limit but it would be nonsensical. The max temperature would be equal to or less than the total energy content of the Universe. ",
"Ethan Siegel on his [Starts with a Bang blog](_URL_0_) wrote about this very question a few weeks ago...\n\nHe basically came up with 10^28 - 10^29 K as the maximum temperature because at this point you would be re-initiating the exponential expansion of the Universe (cosmic inflation).\n\nEthan says it would be like \"hit[ting] the 'reset' button on the Universe... resulting in the Big Bang starting all over again.\"",
"The black hole discussed by others in the tread is formed by a concentration of light so intense that it forms an event horizon and becomes self-trapped. This is referred to as a Kugelblitz. A kugelblitz is so hot it surpasses the Planck temperature. Both the Plank temperature and a Kugleblitz are listed at 1.41x10^41 degrees Kelvin. I haven't checked which is really hotter.",
"Oh, I didn't answer your question directly so here goes. The generally accepted maximum possible temp is the Planck temperature. There is an inverse relationship between temperature and wavelength of electromagnetic energy released by a heated body. We see this by heating a piece of steel. At one temp it glows a dull red. As it heats it shifts to orange and eventually white. If we had a material which was capable if infinite heat resistance we'd see UV, X-ray, gamma rays and on and on to the point where the wavelength of energy would be less than the Planck length which is a no-go. That temperature is on the order of 10^32 Kelvin. That's really really hot.",
"If there is an absolute hot, it is, surprisingly enough, -273.15°C. The reason for this is that temperature is defined based on how much energy it takes to make a marginal increase in entropy. If there is a maximum temperature, then there's some lower point with maximal entropy where temperature is infinite. When it gets hotter, adding energy starts reducing entropy, so the temperature is negative. As heat approaches the maximum, the temperature approaches zero from below.",
"Yess there is! It's the [planck temperature](_URL_1_) (141 * 10^30 kelvin). It's the point at which the radiation emitted would have a wavelength smaller than the [planck length](_URL_0_) (161 * 10^-33 meters). So it can get more energy but it can't get any hotter.\n\n[Cool video](_URL_2_)",
"Why, then, is life sustained at so close a temperature to absolute zero? The difference between absolute zero and temperatures on Earth's surface is minuscule compared with, say, the millions of degrees of the sun and entirely negligible when we're talking about the scales of any theoretical \"absolute hot.\"",
"Yes.\n\nIf you pack enough energy into a single point it turns into particles (thus removing some of the energy) meaning there's is an equilibrium in which temperature no longer increases as new particles are created as fast as you can pack energy.\n\nSimilarly you can't separate quarks. You just create new ones when you stress the gluon field enough.",
"Maybe.\n\nSteven Weinberg addressed this question in the 1996 updated version of \"The First Three Minutes\" (Afterword P 190-191)\n\n*...the continued success of the \"asymptotically free\" theory of strong interactions has by now made obsolete the speculations in Chapter VII about a maximum temperature of two million \nmillion degrees Kelvin (10^12 ºK). At higher temperatures, nuclear particles dissolve\ninto the quarks they are made of, and the matter of the universe behaves, quite\nsimply, as a gas of quarks, leptons, and photons. The description of matter only\nbecomes greatly difficult at the much higher temperature of 100 million \nmillion million million million degrees (10^32 ºK), where gravitation becomes as\nstrong as the other forces. Theorists have been speculating about the theory that\ngoverns matter at these temperatures, but we are a long way from any direct\nexperimental test of these speculations.\nThe most exciting speculative theories studied since 1977 have been the\nstring theories. These replace the description of matter in terms of particles with\na description in terms of strings—tiny one-dimensional discontinuities in\nspace-time. The strings can be in any one of an infinite number of modes of\nvibration, each of which appears to us as a different species of elementary \nparticle. Gravity appears not only naturally but inevitably in string theories; the\nquantum of gravitational radiation is one of the modes of vibration of a closed\nstring.* **There may be a maximum temperature in modern string theories, but it\nwould be in the neighborhood of 10^32 ºK, not 10^12 ºK.**\n\n*Unfortunately, there are thousands of versions of string theories, and we do\nnot know how to evaluate their consequences or why one string theory rather\nthan another should describe our universe. But there is one aspect of string \ntheories that is of great potential importance to cosmology. Our familiar \nfour-dimensional space-time continuum is not a truly fundamental ingredient of string\ntheories, but arises in the approximate descriptions of nature that only become\nvalid at temperatures below about 10^32 ºK. It may be that our real problem will\nnot be to understand the beginning of the universe, or even to decide whether\nthere really was a beginning, but rather to understand nature under conditions\nin which time and space have no meaning.*",
"So this will probably get buried and not answered but...\n\nHow do we know things can't get colder than Absolute Zero? Is that when particles stop moving? And even then what if it came down to quarks or strings, do those particles still move at AZ? And if those particles DO still move at AZ, then is it really AZ?",
"I'm going to start talking about speed, but I'll get around to temperature, so stick around. C is defined as light speed, and is also the maximum speed something can move at. The reason it's the maximum speed in this universe is that the energy required to accelerate something depends on its current velocity, and is exponential. This means it takes more energy to get something moving 50 mph up to 51 mph than it does to get something moving 25 mph up to 26 mph. This also means that there is a velocity where it would take an infinite amount of energy to get anything at that velocity to move any faster. That velocity happens to be C, light speed.\n\nNow, to temperature. What you're asking about is called specific heat, which is a linear equation (E = c*m*deltaT, where E is the energy required to raise the temperature, c is the specific heat constant of the material being heated, m is the mass, and deltaT is the change in the temperature). You'll also note that there's no place in the formula for starting temperature, meaning that it's independent of the starting temperature and the same amount of energy will net you the same increase in temperature regardless of initial conditions. This leads me to believe that, at least in classical physics, the view is that there is no maximum temperature a material can reach other than the maximum temperature the material can survive without being destroyed.\n\ntl;dr-Newton says the answer is no.",
"The [Planck temperature](_URL_0_) is the highest theoretically possible temperature, at 1.417x10^32 degrees Celsius. Matter at any specific temperature gives off radiation of a certain wavelength, with the wavelength decreasing as temperature increases. Matter at the Planck temperature gives off radiation with a wavelength of one Planck length, the shortest possible length.",
"Thermodynamics doesn't place a strict upper limit on temperature, although there clearly an upper bound if the universe is finite. Thermodynamically, temperature is dE/dS -- the fundamental relationship between energy and entropy. As it turns out, thermodynamic systems, by law, have monotonically increasing temperature with respect to increased energy. Well, by rearranging, TdS = dE. If T is huge, then a finite dS can require a dE exceeding the total amount of energy in the universe.",
"Temperature is the random vibration of atoms. It's essentially the combined kinetic energy of all the atoms in an object. So, the maximum temperature should be equivalent to whatever the temperature would be with all the atoms vibrating at 99.99999999999999999% the speed of light (or however fast they could vibrate with all the energy of the universe pumped into that object). ",
"I'll give this a try based on logic.\n\nSo temperature is nothing more than energy right? And we know that energy in the universe is finite. So therefore if there is a finite amount of energy then there must be a maximum temperature. Except I have no clue what that would be.",
"Interesting stuff, I don't understand it completely (was never very scientifically minded) but I just had a question of scale. Between - 273.15°C and the average human body temp of 36(?)°C and the suns temperature, which is in the thousands? How much hotter are we talking? Is the suns heat still only in the bottom 1%? Less? ",
"Planck temperature, denoted by TP, is the unit of temperature in the system of natural units known as Planck units.\n\nIt serves as the defining unit of the Planck temperature scale. In this scale the magnitude of the Planck temperature is equal to 1, while that of absolute zero is 0. Unlike Planck length and Planck time, which are defined as the smallest possible measurable units of length and time, Planck temperature is defined as the largest possible measurable unit of temperature. Other temperatures can be converted to Planck temperature units. For example, 0 °C = 273.15 K = 1.9279 × 10−30TP.\n\nThe Planck temperature in Fahrenheit is 2.55*1032 degrees Fahrenheit (255 nonillion degrees Fahrenheit)/1.417*1032 degrees Celsius (141.7 nonillion degrees Celsius).\n\n_URL_0_",
"Because the wavelength of light emitted by an object decreases as the temperature increases there is a theory that you couldn't go past a certain temperature because the wavelength would get smaller than Plank's distance, the smallest distance possible. I think it's 1.31x10^32 K, but don't quote me on that number, not sure if I remember exactly. ",
"I have a question. Does a total vacuum have a temprature? ",
"Not confirmed but I believe I read somewhere about the [Planck temperature](_URL_1_)\n\nI believe if you cross that limit, you run the risk of turning that area into a [kugelblitz](_URL_0_) , a black hole formed by energy. Of course, once a black hole is made it doesn't particularly matter if it was made from a star or not. ",
"All matter gives off electromagnetic radiation. Humans give off infared wavelength radiation; when something is hot enough, it gives off visible light.\n\nWhen something gets so hot that the wavelength of the radiation given off reaches the Planck Length, it technically can't get any hotter. This is called the Planck Temperature: 2.55 x 10^32 degrees Fahrenheit, or 1.417 x 10^32 degrees Celsius.",
"I thought just recently, probably a few months ago. They discovered something colder than absolute zero by actually heating it. It was something along the lines of heating it and as it's energy potential neared infinite (nature apparently doesn't like infinite things) it essentially reversed and dropped negative or something. Dropping it below absolute zero by .000001 or something rather minute, but interesting nonetheless."
]
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[
"https://en.wikipedia.org/wiki/Planck_units",
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||
j3oo0
|
programming and writing computer code (if it can be explained to a 5 year old) elim
|
Where to begin, how to do it, important programs and tools?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/j3oo0/programming_and_writing_computer_code_if_it_can/
|
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"text": [
"If you have a lot of time, I think a wonderful and engaging introduction is Harvard's [CS50](_URL_0_) course, and it leads you step-by-step through many of the questions you have. "
]
}
|
[] |
[] |
[
[
"http://cs50.tv/2010/fall/"
]
] |
|
8zaa51
|
how can google get fined by eu for practically promoting their own products/brand(google search engine & android/google search engine on android devices)
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/8zaa51/eli5_how_can_google_get_fined_by_eu_for/
|
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"How can they? The EU can impose a fine and refuse to let them operate in the EU until it is paid.\n\nWhy would they? Because it can be considered a breach in monopoly laws. Microsoft was indicted on the grounds of monopolization for bundling internet explorer with their OS. \n\nI may be a bit out of the loop but are you asking about what rule they might break or what rule they did break?"
]
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|
[] |
[] |
[
[]
] |
||
3yivi2
|
What was US espionage like from the Revolutionary War period through the Civil War? What sort of information was targeted and how was it collected?
|
Reposting this question since I didn't get an answer when I [first asked](_URL_0_).
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/3yivi2/what_was_us_espionage_like_from_the_revolutionary/
|
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"In the intelligence community Nathan Hale is often called \"America's first spy\". He was captured by the British in 1776 and executed, famously stating \"I only regret that I have but one life to lose for my country.\" \n\nHale's mission was to go behind the British lines and report on their movements. \n\nThis was the same for almost all human intelligence (HUMINT) gathering in those days. When battles were fought in formations the most valuable piece of information was at what point the formation would be weakest so that it can be penetrated/flanked/or used to flank. When the force was too large to fight, it allowed units to avoid engagement or retreat and re-engage under more favorable conditions. \n\nMore famous \"spies\" during the Civil War weren't actually conducting espionage as much as sabotage. The Great Locomotive Chase as an example, for which the first Medal of Honor was awarded. These men were executed as spies regardless. \n\nInformation of simple troop movements back in those days sounds useless with all the things the US intelligence community can do nowadays, but don't discredit its value. \n\nGeneral Beauregard of the Confederacy credits a spy from Virginia for the victory at First Manassas (First Bull Run). This spy was Bettie Duvall, and she rode from Washington to Fairfax to pass on those troop movements. Individual spies, same as scouts, could move much faster than entire units. However, scouts were uniformed and watched carefully. Spies were not uniformed and integrated themselves into local life. This was the advantage of a spy. \n\nMostly, the spies were just eyes. They went into an environment, kept an eye on things, and reported anything deemed valuable enough. None of this was centralized. \n\nAllen Pinkerton made the first attempt at centralizing intelligence. He built a counterintelligence (CI) network in Washington to counter Confederate HUMINT. He built up his own HUMINT operation in Richmond to keep eyes and ears open. However, its effectiveness is questionable. Pinkerton's intel was often bad and cost a few battles by convincing the commanders not to attack a force they thought was stronger, but wasn't. \n\n**TL;DR + Conclusion** - It was mostly a de-centralized network of eyes and ears in public. The targeted information was primarily troop movements, though other information like important infrastructure, routes, goals, and unit readiness were also valuable. "
]
}
|
[] |
[
"https://www.reddit.com/r/AskHistorians/comments/3xweqm/what_was_us_espionage_like_from_the_revolutionary/"
] |
[
[]
] |
|
nnv0t
|
computer shellcode (shell code)
|
Please ELI5 what malicious shellcode (Shell Code) is, how it works, and how it can be avoided. Thank you.
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/nnv0t/eli5_computer_shellcode_shell_code/
|
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"If you're not a programmer, the only thing you can really do is make sure that you consistently update your software, especially when it says it's for security reasons.\n\nIf you are a programmer, you should be aware that one of the most common types of security vulnerability is a buffer overflow. What this means is that if your program is not properly checking the length of data inputted by the user, the user can write past the boundary you have allocated for that particular data and overwrite different parts of memory. This becomes an issue when the user overwrites the code segment of memory, which tells the computer which instructions to execute. If a malicious user overwrites this area of memory with his own instructions, they can be executed instead. Commonly, a user will overwrite it with \"shell code,\" which is code designed to spawn a shell. A shell is basically the command line interface by which you can control your computer (cmd most closely resembles this in Windows).",
"This may be a bit past ELI5, but I'll try:\n\nSo first, let's define the shell: a way for the user to give the computer instructions.\n\nShell code is a way of creating a shell from somewhere else that I can use. Say I'm in New York and your computer is in Los Angeles, shell code gives me a way of opening a shell so I can control your computer over the internet.\n\nHow it works: The person trying to execute shell code gives a program some bad input that gets the shell code in \"the right place\" so that it runs next. Imagine I give you a piece of paper with a list of instructions:\n\n1) Go to the grocery store\n\n2) Go to the meat counter\n\n3) Ask how much the filets cost\n\n4) Walk back home\n\n) Write down the filet cost here: \n\nNow, the guy at the meat counter says, \"Oh, I'll make it easy, hand me your paper and let me write down the price.\" But he's malicious, so he writes down the price but also writes over your old instructions, so now step 4 on your list is \"Go see the banker and do whatever he says.\" He hands you back the list, and you see step 4 and go to the banker and wait for him to tell you nefarious things to do. (So the shell code would essentially be telling you to go to the banker.)\n\nHow it can be avoided: there are various approaches, but it's kind of an arms race. Generally it amounts to either checking the amount of input -- making sure that when the guy at the meat counter writes down the cost, he doesn't try to use more room than you gave him to write -- or putting extra data around the \"walk back home\" instruction to make sure it hasn't been altered.\n\nEdit: it occurred to me that you may have meant how can you avoid it as a user, not as a programer. Like smango said, basically, your best bet is keep all of your software up to date.",
"If you're not a programmer, the only thing you can really do is make sure that you consistently update your software, especially when it says it's for security reasons.\n\nIf you are a programmer, you should be aware that one of the most common types of security vulnerability is a buffer overflow. What this means is that if your program is not properly checking the length of data inputted by the user, the user can write past the boundary you have allocated for that particular data and overwrite different parts of memory. This becomes an issue when the user overwrites the code segment of memory, which tells the computer which instructions to execute. If a malicious user overwrites this area of memory with his own instructions, they can be executed instead. Commonly, a user will overwrite it with \"shell code,\" which is code designed to spawn a shell. A shell is basically the command line interface by which you can control your computer (cmd most closely resembles this in Windows).",
"This may be a bit past ELI5, but I'll try:\n\nSo first, let's define the shell: a way for the user to give the computer instructions.\n\nShell code is a way of creating a shell from somewhere else that I can use. Say I'm in New York and your computer is in Los Angeles, shell code gives me a way of opening a shell so I can control your computer over the internet.\n\nHow it works: The person trying to execute shell code gives a program some bad input that gets the shell code in \"the right place\" so that it runs next. Imagine I give you a piece of paper with a list of instructions:\n\n1) Go to the grocery store\n\n2) Go to the meat counter\n\n3) Ask how much the filets cost\n\n4) Walk back home\n\n) Write down the filet cost here: \n\nNow, the guy at the meat counter says, \"Oh, I'll make it easy, hand me your paper and let me write down the price.\" But he's malicious, so he writes down the price but also writes over your old instructions, so now step 4 on your list is \"Go see the banker and do whatever he says.\" He hands you back the list, and you see step 4 and go to the banker and wait for him to tell you nefarious things to do. (So the shell code would essentially be telling you to go to the banker.)\n\nHow it can be avoided: there are various approaches, but it's kind of an arms race. Generally it amounts to either checking the amount of input -- making sure that when the guy at the meat counter writes down the cost, he doesn't try to use more room than you gave him to write -- or putting extra data around the \"walk back home\" instruction to make sure it hasn't been altered.\n\nEdit: it occurred to me that you may have meant how can you avoid it as a user, not as a programer. Like smango said, basically, your best bet is keep all of your software up to date."
]
}
|
[] |
[] |
[
[],
[],
[],
[]
] |
|
66oskt
|
How does a king or queen end up with a epithet...such as Alfred the Great, Æthelred the Unready, Edward the Confessor, etc?
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/66oskt/how_does_a_king_or_queen_end_up_with_a/
|
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"A couple ways.\n\n1. They give it to themselves. *Every* Joseon Korean King styled himself \"the Great\"\n\n2. Others give it to them. Kings in Europe took their epithets personally and knew what they were in many cases. They all wanted a name like \"the Bold\", \"the Good\", \"the Brave\", or \"the Great\", or in rare cases \"the Lionheart\". Richard probably got a little woody when he heard the last one for the first time. It became standard practice for courtiers to assign such names and for even ordinary people to come up with ways to describe their King. Lots of them were neutral, like \"Barbarossa\" (Red Beard). Others, like \"the Thunderbolt\", referring to Bayezid of the Ottomans, were very accurate and referred to specific events, like Bayezid's racing his army between Europe and Asia.\n\n3. The state officially assigned names to monarchs and minted them on coins. Islamic countries did this a lot, with every Ottoman Sultan styling himself \"Gazi\" or some positive epithet. \n\n4. Historians and literati ascribe epithets after the reign of the monarch. No doubt very few would dare call Ethelred \"the Unready\" during his reign. That was an epithet made popular by later historians of England writing about their own country. The same case was for Timur the Lame, who in his day was called Timur the Great.\n\nUsually it starts with courtiers or literati genuinely praising a King or coming up with a witty, ironic epithet like \"the Confessor\". Then, it either catches on with contemporaries at the time, or with later writers."
]
}
|
[] |
[] |
[
[]
] |
||
1bnxah
|
Why do English translations of WWII German always leave the words "Reich" and "Führer" in German?
|
I'm a German major and as far as I'm aware "Reich" simply translates to "Empire" and "Führer" simply translates to "Leader".
So why do English translations almost always leave those two words (and a few others) in German? Why not simply finish the translation?
Thanks!
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/1bnxah/why_do_english_translations_of_wwii_german_always/
|
{
"a_id": [
"c98fknb"
],
"score": [
8
],
"text": [
"These words have entered the consciousness of English-speakers (and speakers of other languages) as having a specific connection to a certain object. There are dozens of German leaders, there is only one Fuhrer. This is the same with, say, Czar or Chief.\n\nSimilarly, sometimes words get extra meanings that are lost in translating. A South American Caudillo isn't just a \"war leader\" or \"head\", but a Caudillo. "
]
}
|
[] |
[] |
[
[]
] |
|
4smarr
|
how far ahead we are in achieving unified field theory ?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/4smarr/eli5_how_far_ahead_we_are_in_achieving_unified/
|
{
"a_id": [
"d5ag67d"
],
"score": [
4
],
"text": [
"Not very far unfortunately. Without going into the details (which I'd be crap at explaining anyway), string theory seems to be the most promising avenue. However, there seem to be virtually an infinite number of configurations of the math that leads to a consistent universe which makes it practically impossible to find the right equations that would give us the conditions for our universe. Without the math it's extremely hard to come up with experiments that would test the theory. There's also the problem of the theory being based on sizes near the Planck scale which are currently impossible for us to see. A few experiments or potential observations have been proposed which could provide evidence based on current or near future technology, but so far none have yielded any evidence.\n\nThere's also the problem that so far there is no experiment or observation proposed which could disprove the theory. For a scientific theory to even be considered a scientific theory, this is one of the most important features. (I.E. relativity could be disproved by there being no time dilation observed by clocks or observing something moving faster than light speed.) String theory so far has nothing like this after a couple of decades, and there has been debate about whether or not it should even be considered a scientific theory.\n\nThere are a couple of other possibilities being floated around, but so far they have yet to yield any results more promising than string theory."
]
}
|
[] |
[] |
[
[]
] |
||
1m77h4
|
Were there ground public transportation options before the advent of the automobile and the locomotive?
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/1m77h4/were_there_ground_public_transportation_options/
|
{
"a_id": [
"cc6n71f"
],
"score": [
2
],
"text": [
"One of the best known ground public transport options was stage coaches, so-called because they regularly changed horses with each stretch between changes being called a \"stage\". In Australia the best known and remembered of these is \"Cobb & Co\" although there were many other companies running coaches.\n\n_URL_0_ "
]
}
|
[] |
[] |
[
[
"http://australia.gov.au/about-australia/australian-story/cobb-and-co"
]
] |
||
1sod3n
|
how do generic brands work and why are they cheaper than their name brand cournterparts?
|
I've always wondered, as a frequent consumer of generic brands, I e always wondered what was it that made it so much more cheaper than the name brands. Like, is it made with cheaper ingredients or materials or is it just the reason that its not a name brand that its cheap? How do stores get their own generic brand like Kroger or best value? Do they have their own company manufacturing the products or what? Also, I'm talking about all types of products like food, contact lens solution, medication, anything generic. Ive just been curious about it.
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/1sod3n/eli5_how_do_generic_brands_work_and_why_are_they/
|
{
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"text": [
"My roommate used to work at Kraft foods. He said when they were making the \"Brand Name\" product, everything was added to the mix. About mid day they would change to the \"Store Brand\" product, and either remove an ingredient, or use lower quality ingredients, and just change the label.",
"More often than not there is no difference other than the packaging. Most \"generic\" batteries, for example, are produced on the same line as Duracell and just have a different label.\n\nThe rest of the time they have lower quality, either in terms of ingredients, fiber quality, etc., etc.",
"Typically the main difference is the amount of marketing the company puts in. Large brands put in millions of dollars into marketing while off brand counterparts usually advertise not at all. Sometimes they may even made in the same place as brand name products but it comes down to the advertising costs.",
"I think the story for generic drugs is a little bit different than other products:\n\nTypically, the \"brands\" (non-generics) are made by companies that have patents. These patents, in the United States, last 20 years. By having this patent, a company producing the drug establishes a monopoly. As a monopoly, it has considerably more **market power** because it is able to set the price of the good without having to deal with influence from competitors.\n\nWhen the patent expires, the monopoly status is lost. Competitors enter the market and now all of the suppliers will begin to play by the rules of the free market.\n\nOften, however, the brand name remains considerably more expensive. As an example of this: Lipitor costs about $152.00 for a one-month supply, while Atorvastatin (it's generic counterpart) costs about $14.00 (Source: Costco Pharmacy). Marketing plays a role at this point; the pharmaceutical companies invest on swaying prescribers to feel their drug is better. Or, they might just work to make their drug the most recognizable. It may even be subtle: if all you know furosemide by is Lasix, you may just start writing prescriptions for Lasix. If this happens to be paid by your insurance company, then nobody will make much of a stink about it and the drug company wins.\n\nAs an aside: The active ingredients in pharmaceutical generics are required by law to be identical or bioequivalent to previously patented brand-name drugs. However, the packaging (the materials in the capsule, for example) may vary as these aren't the active ingredients. For some patients with bad reactions to generic medications, providers may opt to continue prescribing the brand-name drug.\n\n",
"The scope of your questions is pretty broad. The difference between generic and brand name is different depending on the category of product (food, prescriptions, toiletries, fashion, gas ect...)\n\nCBS has an online article that answers the question for some of the categories (_URL_0_)\n\nI can tell you that a very large manufacturer of chips also makes chips for store brands. They do this for a few reasons. First they make sure that even if you buy the cheaper store brand they still make money. Second the can control the quality of the store brand. They can (and do) make sure that inferior quality ingredients are used. (Source: I worked for this company)\n\nThe same is true for a lot of dry pasta. They are made at the same factory. \n\nIn some cases there are factories or companies that make a product exclusively for store brands. In these cases the ingredients can be very different. "
]
}
|
[] |
[] |
[
[],
[],
[],
[],
[
"http://www.cbsnews.com/news/generic-and-store-brands-vs-brand-names/"
]
] |
|
3t2p0i
|
what is a runny nose supposed to accomplish? it seems so counterproductive
|
As soon as snot starts flowing into your nose, you're just going to sniff it back it. I've seen this reaction in every person, and even every mammal I've ever seen with a runny nose. Don't we just end up snorting all the germs back up into out internal snot chutes?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/3t2p0i/eli5_what_is_a_runny_nose_supposed_to_accomplish/
|
{
"a_id": [
"cx2jyjc"
],
"score": [
6
],
"text": [
"Your \"internal snot chutes\" empty into the stomach. The snot, along with anything that happens to get stuck in it, gets destroyed by stomach acid. So sniffing it back in, and then down into your throat, is the entire point."
]
}
|
[] |
[] |
[
[]
] |
|
4d134m
|
how can we know the size of the observable universe of we only just escaped the solar system?
|
I know we didn't really leave the solar system but I can't spell.
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/4d134m/eli5_how_can_we_know_the_size_of_the_observable/
|
{
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"score": [
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"text": [
"We can look at galaxies outside ours, and see how far away they are (using various techniques like standard candles, a particular kind of star with known brightness) and how fast they are moving (using techniques like redshift). When we do this, we find that (almost) everything is moving away from us, but the speed they move away is proportional to the distance away they are.\n\nIf we turn time backwards we would see them coming towards us. We can use maths to work out when they would hit us. This is ~13Billion years. Because we have turned back time, we can make it go forwards again and we see a Big Bang. So know we know the age of the universe. (I am ignoring dark energy, because I don't know what it is).\n\nBecause the universe is ~13billion years old, and light is the fastest thing in the universe, the furthest we can see is things which gave of light 13 billion years ago, thirteen billion light years away.",
"You can observe something without going there.\n\nFor instance, I can observe the city across a busy ship channel. It's clearly observable. However, I would not want to swim across the ship channel to go walk around in the city. I would need my own vessel capable of safely crossing the intervening waters to allow me to get there safely.\n\nIt's the same for space. We can observe it from earth with the naked eye. Stars are part of observable space. They're not in the solar system, yet we can see them without any equipment. But to visit them we would need a vessel capable of getting there safely. The people that launched it would be long dead before it reached its destination unless we drastically extend our lifespans, or faster than light travel happens.",
"_URL_0_\n\nlight travels fast, but not infinitely fast. a very short time after the big bang light was first able to travel in straight lines relatively unobstructed. we can only see as far away from our vantage point as the light gets to us.\n\nso if the universe is 13 billion years old, you would only expect to be able to see a sphere around us with about a 13 billion light year radius. That is simple way to think about the observable universe.\n\nbut the universe is still expanding, so it is a little more larger and more complicated than that, too.\n\n",
"The more important question that has been bothering me is, how exactly do scientists have the rough measurement of the size of the un-observable universe?",
"The current top reply is incorrect. Certainly if you were to assume a static universe, then knowing the age of the universe would easily give you an estimate of the size of the observable universe, but the response neglects dark energy, which vastly underestimates the approximation.\n\nWe know space has been expanding since the big bang, and we also know that the rate of expansion is increasing. This means that an object that is, say, a billion light years from earth will emit light that will have to travel much further than one billion light years to reach our telescopes, because the distance between the object and earth has been increasing. And when we get that light, we know that that object has since traveled even further away than it was before. A few calculations reveal that objects we'd think are 13.8B light years away are actually around 46B light years away, meaning in either direction the furthest things in the observable universe are 46B light years away, giving an approximate diameter of about 93B light years. \n\nAs to address u/tikhung01's question, we have a few very, very rough ideas of how big the entire Universe is, but as of right now there is no answer. Maybe the Universe is 100B light years in diameter, maybe its 10,000B light years, and maybe it's size is infinite. That may seem a little unsatisfying, but we just don't know.",
"The diameter of the observable universe is 92 billion light years centered around us. The oldest light we can see has been travelling for a little less than 13.7 billion years but the distance which it has traveled is **now** 46 billion light years. We know this because of the redshift of the light from the furthest galaxies is redshifted more than galaxies closer to us because of the expansion of space. It's analogous to someone throwing you a ball and then running away from you. By the time you receive the ball(light) the person(galaxy) is standing much further away. "
]
}
|
[] |
[] |
[
[],
[],
[
"http://i.imgur.com/83Qa2mU.jpg"
],
[],
[],
[]
] |
|
1mhpx8
|
why in germany or the netherlands the youth unemployment rate is under 9% while in countries such as greece, spain and portugal the same rate ranges from a 40% to 60%?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/1mhpx8/eli5_why_in_germany_or_the_netherlands_the_youth/
|
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"text": [
"Overall unemployment in Germany and the Netherlands is significantly lower, so without a lot of unemployed, experienced workers around, businesses have no real choice. They would either have to get into a bidding war with other businesses over older, already trained workers, or hire young people and train them themselves.\n\n\nIn Spain, Greece and Portugal, businesses have no need to take on younger, inexperienced workers because they can hire unemployed experienced workers cheaply. In addition to that, with the situation of the economy in those countries, businesses aren't expanding, so they're hiring fewer new workers to begin with. They may even be overstaffed already.",
"First of all, currently the situation in those countries with extremely high youth unemployment is exceptionally bad. For that reason alone you can expect it to be a quite a bit higher than usual.\n\nNext, you have to consider what youth unemployment actually means. It doesn't mean that 40-60% of 15-25 year olds are unemployed, but only those among this group who aren't in school, university or an apprenticeship are (i.e., it's the share of those who could take on a full time job tomorrow). So, while many among the unemployed youth indeed have already finished their professional training, the proportion of people without a learned profession (among the group relevant for those statistics) is higher than in an age group that is old enough to have a professional degree, because the ones still in training aren't counted while their peers of the same age but without professional training are. An economic crisis always hits untrained workers harder.\n\nFinally, Germany has a [different education system](_URL_0_) for vocational training. To learn a trade, apprentices split their time between trade school and (the larger part) on the job at a company. So, by the time they graduate, they've already been with a company for (typically) three years, which is more than just a foot in the door. ",
"It is often a statistical illusion (but not always).\n\nEmployment is calculated as \"number of people employed\" divided by \"ACTIVE population\" which is the population looking for a job.\nIn order to have high figure of employment (ie a low for UNemployment), you can either have a high number of people employed AND/OR a LOW active population.\n\nUnlike what most journalists say, an unemployment rate is not the percentage of youth NOT having a job, it is the percentage of youth IN THE ACTIVE POPULATION, not having a job. If almost no youth is in the active population, a high unemployment in that category is not a problem.\n\nCountries have VASTLY different active population, especially for the youth. \n\nIf in country A 80% of the youth are full time students not looking for work, and 10% are having a full time job, and 10% are looking for one, you'll have youth unemployment rate of 50% (only 20% are in the labour force, 80% are not so those are not counted to calculate the unemployment).\nIf in country B you have 50% of the youth as full time students, 40% having a job, and 10% looking for one (ie same overall figure as country A), you'll have a youth unemployment rate of 20%. \n\nBut is the country B in a better situation? Are the youth of country B working because they can't afford to study (because studies are too expensive) or because they finished them early (less education than country A) or because they have a better job market?\n\nOne needs to ALSO look at the employement/total population ratio. In some countries, it is very high (ie every one works, regardless of age and sex). In others it is very low (only few categories work).\n\n\nIf you look at this data:\n_URL_0_\n\nYou'll see for the 15-19 age bracket both sexes, VERY different Labour participation rates (ie the number of people actually in the labour force, having or looking for a job):\nGermany 28.5% and Greece 8% 2012. So youth unemployement rate of let's say 10% in Germany means 2.85% of total youth are looking for a job. The same 2.85% would mean 35% unemployement in Greece because of its much lower active population.\n\nIf you look at the real figures you have for 2012 in \n\nA. Employment/total population:\nFrance (9.7%) Germany (25.8%) Greece (2.8%) USA (26.1%)\n\nB. Labour force/population\nFrance (14.4%) Germany (28.5%) Greece (8%) USA (34.4%)\n\nC. Unemployment rate (A/B)\nFrance (32.7%) Germany (9.2%) Greece (65.7%) USA (24%)\n\nBut what does C represents in matter of total population? This is what is important to really gauge the scale of the problem. The number of youth looking for a job/total youth population, ie the UNEMPLOYEMENT/POPULATION. For Greece, this means 65.7% (very high scary figure) but of ONLY 8% of the youth (super low)\n\nHere is the result, ie the percentage of youth unemployed (ie looking for a job) of the total population of youth (and not only those in the active population).\n\nFrance (4.7%) Germany (2.7%) Greece (5.2%) USA (8.3%)\n\nSo the unemployment of youth concerns a much bigger part of the youth population in the US than in Greece... even though its unemployment rate is many times smaller (24% vs 65.7%)...\n",
"The Netherlands might be a bad example as all policies are aiming to keep this figure as low as possible.\n\nSome background information: Real estate values dropped a lot over the past couple of years and as a result in many households the mortgage is higher than the amount of money their house is worth. This difference easily hits tens of thousands of euros. These people can not move because even selling their house will result in a net loss. Plenty of people are currently losing their jobs. Since they can not go anywhere these people, with multiple years of experience, will gladly accept entry level jobs.\n\nEmployers prefer to hire these people because they get experienced people at entry level salaries. It is not uncommon to see entry level job ads requiring multiple years of experience. If you are currently starting on the job market, you're shit out of luck.\n\nNow here is the beauty of the system. In order to be counted as unemployed, you need to register with the government. This is the only way to get 'free' money. In order to be eligable you will have to follow training programs if requested and you'll have to apply for x jobs per week/month. You are required to take on any job that is actually offered. The problem with this is that applying for a job in your own field is hard if you are working in a factory 40 hours a week. Besides that, paying off your student debt with a minimum income is not going to give you a financially stable life.\n\nAs a result a lot of young people decide to stay in the educational system. They have already been studying for at least 4 years, and racked up some debt to persue a career. Most people are not going to give up on that, and will go and try to get a higher degree. Hoping that by the time they finish they can actually get a job they like.\n\nThis will become a problem as soon as the economy improves. All of those people who decided to stay in the educational system will come out at once. They will all be overqualified, and they all need a decent income to pay of their debts.\n\nSo it is not that the Netherlands actually has enough jobs for young people, the government is just really good at hiding this and postponing the problems.\n\ntl;dr There are no jobs, so young people stay in the educational system to study for jobs which might be available in the future. Students are not registered as unemployed therefore the unemployment problem is \"solved\"."
]
}
|
[] |
[] |
[
[],
[
"http://en.wikipedia.org/wiki/Dual_education_system"
],
[
"http://stats.oecd.org/Index.aspx?DatasetCode=LFS_SEXAGE_I_R"
],
[]
] |
||
2nsiiw
|
Why is the way in which colonial powers took over North America viewed today as "stealing", when similar scenarios are often seen as "occupying" or "invading" and then largely forgotten?
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/2nsiiw/why_is_the_way_in_which_colonial_powers_took_over/
|
{
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"text": [
"Can you give some examples, please? That would help."
]
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|
[] |
[] |
[
[]
] |
||
fgy10d
|
why is it harder to find veins for injection on someone who's feeling nervous about it ?
|
I was given an injection with a baby needle on my elbow pit. The nurse had to switch veins 4 times (twice in left arm, twice in right arm) and still didn't manage to give me the injection. I was told it was because I felt nervous so it made my veins "disappeared". How is that possible ?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/fgy10d/eli5_why_is_it_harder_to_find_veins_for_injection/
|
{
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"text": [
"Nervousness causes high blood pressure. One of the causes of high blood pressure is constriction of the blood vessels thus making them smaller and hard to find. Add in the fact that not everyone has the same body make-up, I.e. some people may just have naturally smaller/less flexible veins or their veins don’t run in exactly the same way, can also contribute.",
"Likely to do with vasoconstriction, which is the narrowing of blood vessels. When you get nervous, your body releases adrenaline into the bloodstream. This serves several purposes but one of the effects of adrenaline is vasoconstriction. This could lead to a smaller target for the nurse to hit with a needle. Also, adrenaline can cause increased body movement which can make it more difficult to be accurate with the needle.",
"So, from a theoretical perspective:\n\nYour body goes through something called sympathetic stimulus during stressful situations - it is colloquially called a \"fight or flight\" reaction. The body does several things with this, it reduces blood flow to your gut (don't need to be digesting things when running from a tiger), activates insulin (to get glucose into your muscles, where you are gonna need it to run from a tiger), dilated the pupils (so you can see the tiger better), increases blood flow to your heart, and increases heart rate (definitely need that with tigers around), and *decreases* peripheral blood flow (to prioritise the central organs, like your heart and lungs) by constricting your veins. Smaller tubes, less blood in them, more blood for your heart. This increases your blood pressure too.\n\nFrom a practical perspective, the venous constriction is actually relatively small, certainly compared to other factors affecting how easy it is to get a needle in, like hydration.\n\nYour nervous disposition also has an effect on the person putting the needle in. I am massively needle-phobic, and I really hate cannulating other needle-phobes, cos I know what they are going through, and it makes me feel under massive pressure to get the vein first time, which inevitably makes me miss."
]
}
|
[] |
[] |
[
[],
[],
[]
] |
|
2t5gal
|
how come when i dream something relevant happens in real world?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/2t5gal/eli5how_come_when_i_dream_something_relevant/
|
{
"a_id": [
"cnvviog"
],
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"text": [
"You dream many things per night and some of them are relevant. Or maybe they are not all that relevant, but can be interpreted in a strange way to make sense to you. Like in your example, it could have been your brother, your father, anyone calling, anyone on the TV etc. you just want it to fit, so it does. \nThis will be paired with the confirmation bias. You dream 99 nights without it fitting, after that, 1 dream seems to fit \"perfectly\" like your example and you remember this one but disregard the rest."
]
}
|
[] |
[] |
[
[]
] |
||
j2pol
|
explain me stocks (what i should look for, what types are there).
|
More specifically: I am spending a bunch of money in random stocks, but don't know what things I should be looking at. They are things like dividends and other technical terms. Also, there are many other types of stocks like mutual funds. Share your knowledge. (Also, I wasn't sure if this topic would be more towards Askreddit or this thread, but I will start here)
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/j2pol/explain_me_stocks_what_i_should_look_for_what/
|
{
"a_id": [
"c28ncf6",
"c28nnqq"
],
"score": [
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2
],
"text": [
"Honestly, this is your best shot at learning about [stocks](_URL_2_)\n\n\nThere is no easy answer to any of the things you asked.\n\nStop spending money as if it grows on trees. \n\nalso here are some important links that you might want to take a look at\n\n_URL_0_\n\n_URL_3_\n\n_URL_1_\n",
"You aren't smart enough to pick winners. Almost nobody is. You are best off buying an index fund like SPY or QQQQ, which contains hundreds of stocks so your risk is spread out and one company's trouble won't take down your retirement. As you get older you should have an increasing amount of your money in bonds rather than stocks. "
]
}
|
[] |
[] |
[
[
"http://www.djindexes.com/",
"http://www.standardandpoors.com/home/en/us",
"http://www.investopedia.com/university/",
"http://www.nasdaq.com/"
],
[]
] |
|
3k8zxw
|
how did people used to find their penpal, back in the day?
|
[deleted]
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/3k8zxw/eli5how_did_people_used_to_find_their_penpal_back/
|
{
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"cuvmu96",
"cuvmyf9",
"cuvpp2s",
"cuvx1wt"
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"score": [
5,
2,
2,
2
],
"text": [
"I found some in the back of a magazine called Stickers, for sticker collectors, back in the 80's. It was in the classified section where people could advertise that they wanted pen pals to write to them about the hobby.",
"There were penpal sections in newspapers, magazines and such. For example gaming magazines.",
"The United States Postal Service had a penpal program. Also highschool language classes used a service to pair up penpals from other regions of the world. ",
"We did them as a class project, so the teacher gave us the names and locations, it was somewhere in Guatemala as I recall."
]
}
|
[] |
[] |
[
[],
[],
[],
[]
] |
|
2pj3xi
|
why do police always show up to places with their sirens on?
|
Wouldn't it be beneficial to keep the element of surprise on your side without announcing your presence with loud noises and flashy lights?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/2pj3xi/eli5_why_do_police_always_show_up_to_places_with/
|
{
"a_id": [
"cmx5j7u"
],
"score": [
6
],
"text": [
"If police are doing something sneaky, like a sting, then they won't use a siren.\n\nBut the siren gets them through traffic, instructs the public to clear away, and can intimidate criminals (or potential criminals) to dissuade any further crimes. You might think twice about shooting a hostage if you know there are guys outside with guns drawn."
]
}
|
[] |
[] |
[
[]
] |
|
4332ig
|
why does "populism" have a negative connotation within democratic societies?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/4332ig/eli5_why_does_populism_have_a_negative/
|
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"text": [
"Wiki has this definition:\n\n > Populism is a doctrine that appeals to the interests and conceptions (such as hopes and fears) of the general population, especially when contrasting any new collective consciousness push against the prevailing status quo interests of any predominant political sector.\n\nBasically it's demagogy. Pandering and appealing to emotional knee-jerk parts of people, and tending towards short-term satisfaction, as opposed to logical, rational, long-term and sustainable planning. \n\n",
"This is fairly well explained by the tragedy of the commons, see William Forster Lloyd. Basically an individual person is likely to look out for themselves, with rational interest in short term success /safety. Their interest will not take into account what is good for the majority however. This is one of the arguments made against communism, for example. An Ayn Rand supporter would say that capitalism works because working towards your rational self interest is economically supported, jobs and taxes are levied as a byproduct of 'selfishness'. ",
"Populism is a political philosophy that is not truly represented by any of the candidates for President, and not accurately described by the posts so far. People seem to be defining populism based upon how they think it fits into their view of hour our government should or does work, while populism has been around for much longer than we have.\n\nIn its purest form, populism is a belief in the rights and power of the people against the privileged class who exploit them, especially through economic means. These \"elites\" typically are hold power in the government and work hard to maintain the status quo. One of their most successful tactics is to drive a wedge between the underclasses by convincing the middle class that the welfare class is their greatest enemy.\n\nFDR may have been the last, closest thing we have had to a real populist, not very popular with the upper classes. Nowadays, populism is used pretty much as a derogatory term, although people generally go further over the top. I heard someone the other day call Mr. Trump a populist, which left me shaking my head. Speaking to issues of concern to many of the middle and lower classes does not make one a populist, at least in the historical and philosophical sense.",
"It's generally associated with unconsidered, \"passionate\" mob rule as opposed to the carefully considered, respectfully debated consensus upon which democratic rule relies. It's generally thought of as the sort of dark side of democracy where people are led down a policy path based on their anger and frustration instead of peacefully reaching a consensus on an issue. "
]
}
|
[] |
[] |
[
[],
[],
[],
[]
] |
||
74z0xe
|
why do wifi routers need to be power cycled periodically? are there any that don't?
|
It seems like the older they get, the more often the procedure is necessary. I need to reset mine once a day or every other day.
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/74z0xe/eli5_why_do_wifi_routers_need_to_be_power_cycled/
|
{
"a_id": [
"do2b7lo"
],
"score": [
10
],
"text": [
"Routers do NOT need to be reset periodically. If you set it up correctly and installed its firmware then you shouldn’t even be touching it for months or years. If you have an older modem then it could possibly be set on DoD and you’ll need to figure out how to make it a permanent connection. "
]
}
|
[] |
[] |
[
[]
] |
|
3eofx6
|
why do towels have a band without fuzz on each end?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/3eofx6/eli5_why_do_towels_have_a_band_without_fuzz_on/
|
{
"a_id": [
"ctgw4zh"
],
"score": [
11
],
"text": [
"It is there so the towel does not fall apart over time. There are two reasons for using this stitch over the regular \"fold-and-stitch\" version:\n\n* the fabric is very thick so it would give a very fat fold at the end which does not look appealing\n* the frothing does not make it very easy to handle\n* as there is no front and back, there is also no side that you could hide this ugly part, eg. in contrast to clothes where usually the seams are on the inside"
]
}
|
[] |
[] |
[
[]
] |
||
1ntaga
|
If we know all the naturally occurring elements and how they combine, is there a finite number of compounds? Do we know them all? Have we synthesized all or most of them??
|
askscience
|
http://www.reddit.com/r/askscience/comments/1ntaga/if_we_know_all_the_naturally_occurring_elements/
|
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"text": [
"It's quite likely we know all naturally occurring elements, as all the ones heavier than those we know are naturally occurring are quite short-lived, and AFAIK it's not believed any more stable elements exist (even if an 'island of stability' may exist higher up, but then they mean _relative_ stability - they'd still be short-lived).\n\nThere's a finite, but very large number of compounds. You can build very long polymer chains and very large crystals, although their size is theoretically limited by entropy (although practical limits are far smaller). No matter how strong they're bonded, it's a finite strength, and if you make the chain long enough, it'll statistically be likely to break _somewhere_.\n\nWe do not know all possible compounds. Not at all. Although many of the possible ones are just quite boring variations. If you add another amino acid to a protein, you may have a protein that's never been synthesized, but it's not going to differ much in its properties from the original, or other proteins. Not in the way that small compounds are distinct from each other.\n\nHowever, there are even relatively small compounds we still don't know about, because it's not always easy to predict whether a molecule is stable or not (especially if it doesn't much resembles ones we know already), nor predict how stable it is if it exists. We're also discovering new states and properties of old and well-known elements, e.g. it was fairly recently discovered that stable compounds of Fe(VI) were existed, where it'd previously only been thought to exist as an intermediate in certain reactions, at most. \n\nThere are a number of 'theoreticals', compounds that are predicted to be stable, but which we don't know how to synthesize, often because they're high-energy compounds. One example is Td-N4, four nitrogen atoms should be able to form a (somewhat) stable tetrahedron, with each bonded to three others. Nobody has been able to produce it yet though.\n",
"Yes there are a finite amount of compounds. Most molecules will become unstable if they get too big, which limits the amount of bonds that can occur in a molecule. That being said, the number of possible compounds might as well be infinite. One tiny adjustment in the position of an element creates an entirely new compound. That, coupled with the sheer number of elements is mind boggling.",
"The concept that you're asking about is called \"chemical space\". There have been attempts made to ennumerate exactly how big it is for non-polymers (which hugely complicate things, but could conceivably be dealt with), and even with a search limited to 13 atoms and a select elements, the number is [huge](_URL_0_) (977 million compounds came to less than 0.01% of the total number, which was too large to calculate). A group at Pfizer tried to calculate how many compounds are possible with synthetic techniques we have right now, and came up with [10 trillion](_URL_1_). But it should be noted, these are a little limited to the organic chemists, and certainly underestimates the true number.",
"We know all the notes - C, D, E, F, G, A, B , plus their sharps and flats, and a few octaves either side. (Fewer than the number of elements!)\n\nAre we close to knowing all possible songs? Is this even feasible?\n"
]
}
|
[] |
[] |
[
[],
[],
[
"http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3447393/",
"http://pubs.acs.org/doi/abs/10.1021/jm0707727"
],
[]
] |
||
d0edar
|
Why do positron-electron pair not annihilate each other?
|
Ok so my current understanding of the formation of electrons at the big bang ish is from to colliding high energy gamma rays from black body radiation turning into a positron-electron pair to keep net charge 0 but as they are antimatter of each other so why don't they annihilate each other?
|
askscience
|
https://www.reddit.com/r/askscience/comments/d0edar/why_do_positronelectron_pair_not_annihilate_each/
|
{
"a_id": [
"ez9g9dn"
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"score": [
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"text": [
"To answer the question in the title: electrons and positrons do annihilate eachother.\n\nTo address the [different] question in the body of the post: the matter–antimatter asymmetry of the universe is an unsolved problem. Perhaps there are processes that violate lepton number or baryon number (key ingredients in generating the asymmetry), but we haven't observed anything like that yet."
]
}
|
[] |
[] |
[
[]
] |
|
5fiqj4
|
what are pilots checking during pre/post flight?
|
What is the checklist to make sure a plane is good to go and what could prevent that plane from taking off again?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/5fiqj4/eli5_what_are_pilots_checking_during_prepost/
|
{
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"text": [
"Im not a pilot, but as a truck driver i would assume you would check a lot of the same things as i do on my rig. Check your fluid levels, belts, guages, lights, and for leaks. I bet they check their wings and tail like i check my tires and steering. ",
"Not everything on the checklist will ground the plane, but some things can. For example, during flight a bird might have damaged a [pitot tube](_URL_0_). That wouldn't ground a plane by itself (unless *all* of them were damaged by a flock of birds), but you'd need to clean them out at the very least, and certify they were working properly before you could fly.\n\nOther items on the checklist make sure that the plane is ready for flight. Is it snowing/cold outside? Turn on engine anti-ice. Are your outboard lights on (so other planes can see you)? Are your radios setup on the correct frequencies? Did you program the flight computer? etc.\n\nAs for post flight, that's mostly to do with shutting down the electrical systems and engines in a safe manner. When you're on the ground, you're generally connected to ground-based power. You still need to switch the plane over to actually use this power, and ensure that things like the APU are not generating power. You also don't want to drain your batteries. Also, no sense in trying to pressurize the cabin when the door is open. The checklists exist to make sure you turn all the knobs and dials you're supposed to turn because despite the automation, there is still a LOT of settings that can/should be tweaked on a plane."
]
}
|
[] |
[] |
[
[],
[
"https://www.scientificamerican.com/sciam/cache/file/1B1FE816-FDF8-4284-AA1440243F4494AD_agenda.jpg?w=600&h=335"
]
] |
|
fw2yke
|
why does yawning temporarily make a headache go away?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/fw2yke/eli5_why_does_yawning_temporarily_make_a_headache/
|
{
"a_id": [
"fmmh5fa"
],
"score": [
2
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"text": [
"Headaches are mostly caused by misfiring nerves in your brain (migraines) or \"heartbeat\"/pressure headaches in the nerves/vessels/muscle that surround your brain.\n\nYawning causes a few things to happen in your body: it increases oxygen in your blood stream, increases blood flow around your jaw as you use the muscles (which is why you sometimes hear a \"whooshing\" as you stretch/yawn) and relieves pressure imbalances in your sinuses (when your ears pop). All three of these effects can impact headache pain.\n\nThe most significant \"immediate\" effects on your headache are pressure balancing and muscle stretching - especially for non-migraine headaches. Pressure in your sinuses can cause the sinus walls to trigger nearby nerves, making them to react in a throbbing pain that is relieved by a temporary release of pressure while yawning. The pain will, of course, come back when the pressure is unbalanced again\n\nIf your headache is caused by dehydration or a hangover, your brain has slightly shrunk and pulled away from your skull, alerting the nerves in a painful way (esp at your temples). By yawning, you are stretching the muscles in your jaw and temples, making nearby nerves fire a sense of \"pleasure\" that overrides the \"pain\" from dehydration - it's a very similar principal to rubbing an area near an injury to reduce the feeling of pain. Once you are no longer doing that, the pain returns. Yawning also stretches muscles that can be tight with painful tension (due to stress or exhaustion), and the temporary relax + stretch makes nerve firings associated with constricting your muscles go away.\n\nYawning during migraines is a little different because migraines are (to our current understanding) misfires of nerves within the brain itself. Yawing is usually a sign that a migraine is coming on, likely because the brain is reacting to random nerve firings the same way it reacts to exhaustion - by trying to get more oxygen. There is no real evidence that yawning lessens migraine pain in a physical way caused by an increase in oxygen, but the action may temporarily district you from your headache."
]
}
|
[] |
[] |
[
[]
] |
||
35wuj4
|
Is there a name for the feeling you get when you see something that makes you cringe?
|
Like the feeling you get when you see a graphic injury (bones sticking out, blood, etc.) Just thinking about it now is making me uneasy. What is going on in the brain that causes this reaction?
|
askscience
|
http://www.reddit.com/r/askscience/comments/35wuj4/is_there_a_name_for_the_feeling_you_get_when_you/
|
{
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"text": [
"_URL_0_ This is more about sounds like scratching, scraping etc., but it does cover where the reaction comes from",
"[Might not be what you're looking for exactly, but this site has a plethora of definitions that haven't been captured by words by an official dictionary yet. You might find a word that means that here](_URL_0_) ",
"Perhaps \"Neural Mirroring\" is what you're looking for.\n\nIt's an overhyped concept right now, but the concept itself makes sense.\n\n_URL_0_"
]
}
|
[] |
[] |
[
[
"http://psychcentral.com/news/2012/10/11/why-we-cringe-at-unpleasant-sounds/45935.html"
],
[
"http://www.dictionaryofobscuresorrows.com/"
],
[
"http://en.wikipedia.org/wiki/Mirror_neuron"
]
] |
|
6du8cw
|
How did Gen James Longstreet go from Lee's right-hand man to pro-Reconstruction Republican?
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/6du8cw/how_did_gen_james_longstreet_go_from_lees/
|
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"text": [
"In a word, Longstreet was a realist. He accepted that the South has lost, and was looking for the best way for her to bounce back. But while he wasn't alone in the former officer corps in his caution \"to accept the terms that are now offered by the conquerors\" following the implementation of Reconstruction in 1867, he was fairly unique in his advocacy for actual cooperation, which resulted in considerable vilification by Southern veterans and writers over the next few decades. Maybe if he had kept is views to himself it wouldn't have been so bad, but he put them in a letter that was published in a New Orleans newspaper. [I don't know if the entire text is available, but \"Lee's Tarnish Lieutenant\" has a fairly extensive quotation](_URL_0_). In short though, He was arguing that cooperation with Republicans was essential in order to best be able to mitigate the adverse effects of Reconstruction - \"if whites won't do it, the thing will be done by the blacks\" - and additionally that ensuring a Southern presence within the Republican party was essential to limiting the ability of the newly enfranchised African-Americans to have any real power with their vote.\n\nAs you can see, his views are still fairly offensive as far as our ideas of racial equality goes, but for a Southern audience, still smarting from defeat, and still *pretty* damn racist, he might as well have just waved a white flag. Most of them weren't willing to give even an inch, and of course, as the next few decades would bear out, the South was fairly effective in ensuring the failure of Reconstruction, and the continued subjugation of the African-American population under Jim Crow. It didn't matter to them that Longstreet firmly believed he was advocating in Southern interests, and for the continued marginalization of the Black population at that. The Republican Party was *the enemy*. It was everything that stood in opposition to white, Southern civilization. One of the most core aspects of the Southern views on their defeat was to ensure that their honor remained intact - defeated on the battlefield but not in spirit. Longstreet's path went against that, however much his long term view of the continuance of a white dominated South may still have aligned.\n\nLongstreet perhaps could have defended himself, but he simply never really tried, at least in the early days. A few private letters exist which speak to his commitment to white supremacy, but he never made strong, public statements to that effect in order to clarify his position. It didn't help that within a few months, he was granted his Federal pardon, which would allow him to again run for office, and of course led to accusations of abandoning the Confederate cause out of sheer self-interest. \n\nHe then just keep digging that hole deeper, endorsing Grant for the presidency, and then accepting a Federal job in the Port of New Orleans. This just only continued to feed Southern attacks on his generalship and character, and soon enough, Longstreet was essentially the sole cause of Southern defeat, having been made the lynchpin of defeat at Gettysburg, and in turn Gettysburg the lynchpin of defeat in the war itself. It was essentially a vicious cycle, with each side acting and reacting to further entrench the other's position. When, in 1896, he published his memoir and dared speak an ill-word of General Lee in defense of himself, well, he might as well have taken a dump on Jesus Christ himself as far as Southern audiences were concerned. While he wasn't exactly at Sherman's level, Longstreet had very much come to be a villain of the 'Lost Cause' narrative as it was formed in the late 19th century. \n\nJames Longstreet and the Lost Cause by Jeffry D. Wert, in The Myth of the Lost Cause and Civil War History, edited by Gary W. Gallagher & Alan T. Nolan\n\nLee's Tarnished Lieutenant by William G. Piston"
]
}
|
[] |
[] |
[
[
"https://books.google.com/books?id=n24-UIO3TuUC&pg=PA106&lpg=PA106&dq=%22My+politics+is+to+save+the+little+that+is+left+of+us,+and+to+go+to+work+to+improve+that+little+as+best+we+may%22&source=bl&ots=x_BhIJ2P4c&sig=glxeWPlkkGUE1MTyJT_c7NXYvfg&hl=en&sa=X&ved=0ahUKEwjq95X0qZPUAhXD4CYKHQ6NAlsQ6AEILjAB#v=onepage&q=%22My%20politics%20is%20to%20save%20the%20little%20that%20is%20left%20of%20us%2C%20and%20to%20go%20to%20work%20to%20improve%20that%20little%20as%20best%20we%20may%22&f=false"
]
] |
||
ryol9
|
hasidic judaism (or jewish mysticism)
|
What's the core of their belief and how are they different from other branches of Judaism?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/ryol9/eli5_hasidic_judaism_or_jewish_mysticism/
|
{
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"text": [
"Alright, first of all, not all Chasidim (-im generally means plural people in Hebrew) are mystics, nor are all mystics Chasidim. But you will usually find more Chasidic Kabbalah scholars than you will Reform. (Anecdotal evidence: I knew a Chabadnik who started Reform and eventually became Chabad.)\n\nChasidim (and especially the Chabadim, one of the most popular form of Chasidic Judaism in the US) feel that besides devotion to G-D, one must study G-D's ways as well. The Chabad movement took it further and said that it wasn't enough to just give G-D and Judaism your heart; you had to give your mind and your wisdom as well. No mindless devotion to the Law for them! They believe in studying always the Talmud (thousands of years of commentary on the Torah, the first five books of the Bible) and don't think that just saying the prayers and keeping the commandments are good enough. One has to always be learning.\n\nRabbis in the Chabad (and also most Chasidic movements) are not priests or superiors, so much as they are a supervisor of sorts. (One thing that drew me back to my family's Judaism was the idea that one is expected to argue with the rabbi, as that is one of the best ways to learn. True, he'll usually win, but that's not the point.)\n\nSo -- Chasidic Jews are Orthodox Jews who devote themselves to a strict interpretation of the Law. Chabad also devote themselves to learning, to spreading wisdom, and to a general appreciation of life. If you're ever at a Jewish meal, and there's one guy with long hair, a long beard, and a glass of vodka in his hand, telling you that G-D commands all to make three *l'chayim* (toasts) in his honor, that's the Chabadnik. \n\n(By the way, the 'ch' can be spelled or pronounced as 'H' and you won't be too wrong. But properly... pretend you have a hair in the back of your throat, and you're at dinner with your girlfriend's family, so you don't want to just cough it out in front of them. That gentle throat-clearing... THAT'S the Hebrew 'ch.')\n\nEDIT to finish your question: A general view of the other branches of Judaism:\n\nOrthodox: for all practical purposes, follows all the *mitzvot* or commandments. They keep all the dietary laws, they pray in separate rooms in the Synagogue (Men in one, Women in the other... it's supposed to keep your mind off the other sex), and do their best to live the way the Torah and the Talmud say Jews should live. Chasidic Jews are almost always Orthodox. The way they live and worship is generally the same since the Second Temple was destroyed in AD 70. (Of course, they use technology... except on the Sabbath. From sundown Friday to sundown Saturday, they will not drive, turn on (or off) any appliance, and do no work whatsoever. Most congregations have a \"Shabbos Goy,\" a non-Jew who will turn things off, lock up the Synagogue, and other little tasks that have to be done.)\n\nReform: this movement does their best to blend in with the surrounding population. They may or may not keep all the dietary or cultural laws, but they still say the prayers and practice Judaism. For a long time, they were the only ones who had female rabbis, but this is slowly starting to change.\n\nConservative: this movement sprang up as an answer to Reform Judaism, and is roughly a happy medium between the two. Many conservative will make small changes to the cultural laws in order to better live in society. There are Conservative female rabbis, now, and women in the congregation are more engaged. You won't see one firing up the barbecue to cook up some pork ribs on Saturday morning, but they may be a little more lax on the laws (on a personal basis) than Orthodox.\n\nEDIT #2: Meant to say that Chabad is *one of the* most popular forms of Chasidism in the US. "
]
}
|
[] |
[] |
[
[]
] |
|
3duro7
|
How do sun rays affect clouds and their changes?
|
Is it all about wind when clouds move, disperse, tear apart etc., or does sunlight also have any significant effect?
|
askscience
|
http://www.reddit.com/r/askscience/comments/3duro7/how_do_sun_rays_affect_clouds_and_their_changes/
|
{
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"text": [
"Well, sun is the energy source in the formation of clouds. Actually, sun is the main energy source of all atmospheric movements. But I assume that wasn't your question (if it was, let me know.)\n\nOnce the clouds are formed, sun rays don't affect them **directly** because clouds are poor absorbers of short-wave radiation (which is the lenghtwave in which the sun emits). Most of the incoming solar radiation gets reflected back to the top of the atmosphere by clouds, and they also scatter the visible light in a way that makes clouds appear white, but they don't get heated or evaporated by direct solar radiation. \n\nHope it helps. Sorry for bad english :P\n",
"The prior answer is quite right. The sun provides the energy to the earth system, so in that sense \"energy that came from the sun\" is responsible for heating the Earth and the air above it. This heating is one reason that air rises. When air rises, it cools. If it rises relatively quickly, it cools so fast that the water vapor becomes supersaturated - it then condenses out on small particles in the atmosphere. These small particles come from both natural sources (like sea spray or desert dust) and man-made ones (wildfire smoke, car or power plant exhaust). The droplets that result from water condensing on such particles are cloud droplets. This is essentially how a cloud forms. \n\nSome of these particles are colored (eg desert dust), brown (smoke), or black (soot from combustion). If these particles are at the heart of droplets within a cloud, they can cause the cloud to absorb energy from the sun - just like how wearing a black shirt on a sunny day makes you hotter than wearing a white shirt. The light energy absorbed by such \"atmospheric brown clouds\" can hear the air around them. This can actually cause the cloud to evaporate! \n\nThese types of brown clouds are not everywhere on the Earth - they are very common in South Asia. The clouds there form on particles produced by Asian deserts and also the seasonally common plumes of smoke associated with burning in the region (often controlled burns for agriculture). \n\nThis is definitely a special case, but it does give a real example of how direct sunlight can affect a cloud. The vast majority of the time, clouds reflect sunlight back to space, giving a cooling effect to the Earth. "
]
}
|
[] |
[] |
[
[],
[]
] |
|
89jpfh
|
Do wolves panic during thunderstorms the way domesticated dogs sometimes do?
|
askscience
|
https://www.reddit.com/r/askscience/comments/89jpfh/do_wolves_panic_during_thunderstorms_the_way/
|
{
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"Dogs panicking during thunderstorms only primarily happens because they aren’t conditioned to the sound before formative development in the brain stops. Dog trainers can suggest playing different sounds—cars honking, trains, thunderstorms, alarms, etc.—while puppies are young so they get used to the sounds and don’t panic when they hear an unfamiliar sound. Since wolves are in the elements 100% of the time, I assume pups hear the sound of a thunderstorm before that brain development cuts off, and are normalized to it. \n\nNot a zoologist or wolf expert—just have a puppy that I’ve done tons of research on so that he doesn’t panic during thunderstorms. ",
"Your question is stated in a way which makes it a bit hard to answer correctly. There is most likely a wolf somewhere in the world which panics during thunderstorms. But that is not very helpful. What I think you want to ask is \"Is it common for wild wolves to panic during thunderstorms?\" We restrict it to wild wolves as wolves in captivity tends to have a lot of weird behaviors...\n\nTrying to answer this question, I had a look around. I can't find much data on the behavior of wild wolves during thunderstorms (and I doubt many studies have been done on that subject). No paper I have read mentions wolves panicking, and if it was a common occurrence it would probably be mentioned somewhere. \n\nWhat I can find is that wolves are known to reduce their movements when there is [rain and other bad weather](_URL_0_). Data on howling and other social activities seems to be more [limited on days with bad weather](_URL_1_) (you can't hear them as well, and studying their behavior is harder when the guy collecting the data is cold and wet). But they may also reduce the frequency of howling...\n\nSo my guess from the papers I can dig up, and what I know of wildlife in general, is that most wild wolves don't panic during thunderstorms, but that they may take shelter to avoid the weather. "
]
}
|
[] |
[] |
[
[],
[
"https://watermark.silverchair.com/84-1-243.pdf?token=AQECAHi208BE49Ooan9kkhW_Ercy7Dm3ZL_9Cf3qfKAc485ysgAAAcQwggHABgkqhkiG9w0BBwagggGxMIIBrQIBADCCAaYGCSqGSIb3DQEHATAeBglghkgBZQMEAS4wEQQMRwH8V6yxoazOF12cAgEQgIIBd18Sa2tRpFN8okKsrtDztKt7CnibUmh7YFtCilYifQKS09s_viDxTkL8CAplaUnSKAGoQbaCHRuNa9R1hzgOGkQPGjYLF9Mrh5qmwL6B6sCLen2Jxo2nwCJy9BxoJT7fDkJ4Je2hNF_fzrQujaoQs4QLXJ_mPAsDjfnrKay5r6kesyz6Dcz7i8WcmpCU_GcYrGIOEJQ7la9fshHjn6cNJKBUDUXBBI2eXd-5aca44MPqMsfDVfM6cT0krXz66uHuGCtW8FQFgXY1ynPeqgk7iuyJSJGVoDj5A6xaB_XOKkU_es87s2ogCPAjEiDAfIQgisMt7xL_2UFSK5gjrXpVjjXHchabZ70oRTjjPEl7PFREFROVPBwQQJHcUzb3pAGDs1_IlcL64WR7IESn4gooMnW9vLU7FDt9YquF_1jeTPLd1CBjQWrG49R0_DWpsveoQl1Y59VxaWXdZOuwHqj5tpySXFG_eFML5xfwzmD-jJIY19H3Hpyr-g",
"https://www.researchgate.net/profile/Joern_Theuerkauf/publication/52006155_Howling_activity_of_free-ranging_wolves_Canis_lupus_in_the_Bialowieza_Primeval_Forest_and_the_Western_Beskidy_Mountains_Poland/links/54d061920cf29ca811012d64.pdf"
]
] |
||
4dauhr
|
why is the ph of water important for plants but not animals?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/4dauhr/eli5_why_is_the_ph_of_water_important_for_plants/
|
{
"a_id": [
"d1p97zd"
],
"score": [
3
],
"text": [
"My tomato plants that I'm growing hydroponically (i.e. in water) grow within a pH range of about 5.5-7.0\n\nMy fish grow in a range of about 6.5 - 7.0.\n\nSo I think pH of water is important for both plants and animals, and probably even more important for animals? But it probably depends a lot on which plants and which animals, are they're all likely to have different abilities to cope with different pH levels.\n\nWhich animals and plants were you talking about in your question?"
]
}
|
[] |
[] |
[
[]
] |
||
3r7grd
|
why do tomato based foods stain tupperware?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/3r7grd/eli5why_do_tomato_based_foods_stain_tupperware/
|
{
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"cwlkpsh",
"cwllrt4",
"cwmgr1p"
],
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23,
9,
2
],
"text": [
"Tomatoes contain a compound called lycopene that reflects light strongly in the red portion of the visible spectrum. The lycopene binds to the plastic in the container causing it to take on a reddish tint. ",
"You can prevent a great deal of the staining beforehand by using cooking spray to coat the plastic ware before storing the tomato based foods. You can remove some of the stains w/o ruining the containers by using a bleach soak - or a phosphate containing (commercial type) dishwasher detergent.\n\nTL:DR use a glass bowl to store your marinara sauce.",
"But the real question is do Italian families just have a shit ton of stained tupperware? Completely serious here."
]
}
|
[] |
[] |
[
[],
[],
[]
] |
||
10h7zb
|
dust
|
what is it made of? how does it get to all those weird spots? how does it get into virtually untouched spots it seems. What is dust
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/10h7zb/eli5_dust/
|
{
"a_id": [
"c6dh3ih",
"c6dql7g"
],
"score": [
17,
2
],
"text": [
"Dust is made of a collection of things: dead skin, dust mites, dust mite feces, pollen, smoke, soil, hair, and other materials. Dust particles are very small and light so they get blown around easily in the air. They spread out to fill a room top-to-bottom like a [cloud in a bottle](_URL_0_) but for your whole house.\n\nSome of the dust settles onto surfaces. Some surfaces, like doorknobs, you constantly touch which wipes the dust off the surface, before it builds up to a point where you can see it. If it's a surface that rarely gets disturbed, like the top of your television, it keeps building up until you grab a washcloth and wipe it down. ",
"How does so much of it wind up on top of and on the sides of my ceiling fan when it's been *on* for the past month?"
]
}
|
[] |
[] |
[
[
"http://www.wikihow.com/Make-a-Cloud-in-a-Bottle"
],
[]
] |
|
3ho54r
|
Before the arrival of the Magyars, who lived in Hungary?
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/3ho54r/before_the_arrival_of_the_magyars_who_lived_in/
|
{
"a_id": [
"cu95kff"
],
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14
],
"text": [
"The Iazyges were a nomadic Sarmatian tribe located in around where Romania, Ukraine, and Hungary meet today. They were a constant thorn in the side of the Roman Empire from the 1st Century BCE. They constantly resisted assimiliation and were among the last of the Dacian peoples to be quelled. In the late 1st Century CE, they crossed the Danube into Roman Pannonia and defeated Legio XXI Rapax (who were disbanded afterwards). It was only when Trajan took control of the Empire (and the war in Dacia) where the Iazyges were conquered. In fact, future emperor Hadrian was the one that forced them to submit. They were reduced to a client state of the Roman Empire after this (107 CE).\n\nEDIT: Professor pronounced them (ee-uh-zee-gees)\n"
]
}
|
[] |
[] |
[
[]
] |
||
frxto
|
Does the total volume of precipitation in the sky vary? If so, by how much?
|
askscience
|
http://www.reddit.com/r/askscience/comments/frxto/does_the_total_volume_of_precipitation_in_the_sky/
|
{
"a_id": [
"c1i66mi"
],
"score": [
2
],
"text": [
"Unsure what you are asking. Are you asking if the amount of water vapor varies? If so, it clearly does because humidity varies widely over the Earth."
]
}
|
[] |
[] |
[
[]
] |
||
30eh70
|
Before photo ID's how did people prove their identity? How would you get a check cashed?
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/30eh70/before_photo_ids_how_did_people_prove_their/
|
{
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"cprwxbu",
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"text": [
"More of a legal history perspective, but contracts historically were based on trust. Basically you could cash a check because you said you were the person on the account. You would only need to prove your identity if there was something wrong with the transaction (someone else claimed it, the check was returned, etc.). \n\nIf in court you needed to prove your identity, you would have to do so by a preponderance of the evidence, which is to say that you would prove that it is more likely than not that you are who you say you are. You would use whatever you had at this point, family bible, a deed, a birth certificate if you had one, etc. ",
"While there is always more that can be added, so I don't wish to discourage anyone from answering, you'll find that there are older threads which might interest you as a starting place at least. [Check 'em out here!](_URL_0_)",
"You might be interested in *The Return of Martin Guerre* by Natalie Davis. It's a historical analysis/reconstruction of a court case in 16th century France that deals explicitly with the subject of identity. A basic synopsis of the case is that after a man named Martin Guerre left his family, an imposter came and took his identity. After people started to figure him out there was a trial to determine his identity, and as if the whole situation wasn't dramatic enough, the true Martin Guerre returned in the middle of the trial. Davis' analysis reconstructs both the life of Martin Guerre and the trial itself using archival evidence and the papers of the judge who presided over the case and led the investigation. It's been awhile since I've read it so I'm murky on the specifics, nevertheless it should give an interesting perspective on your question. ",
"Missing from the comments below are notes, and the letter of credit. If you are a traveler, going from London to Madrid, you would go to a business or bank or even a friend in London who had a contact, branch or associate in Madrid. They could take your money, and provide you a letter for their associate saying, in essence \"this is George, give him 40 reals\". You would have some other documents, even letters of introduction, passes from the Spanish embassy, with you, showing your name was George. There would usually be a discount- i.e., they would give you a little less than your 40 reals, to make a profit. This is how you'd avoid hauling bags of gold with you.\n\nBut for more local transactions, especially with a scarcity of small money, there would be \"notes\". You build a doghouse for George Washington, he pays you with a note saying reimburse the bearer 2 shillings. You can then pay somebody else with that note, when you owe them. Eventually somebody will show up at Washington's house wanting the real cash, and he'd pay them...or tell them to come back Monday.\n\n\nThe important thing is, notes often did not require ID, anymore than money does today. BUT if somebody gave you a note, or letter of credit, and you doubted it was good, you could decline to accept it, or you could discount it heavily- give them much less than the face value. So, your note from Washington would be less discounted than a note from somebody totally unknown. If the note was for a specific person, you; you could sign it over to someone else, and they could then sign it over to someone else; and anyone could also refuse the note, or discount it.\n\nA check was essentially also a note, but instead of eventually presenting it to Washington, someone had to present it to the bank. And the bank itself could simply issue notes- which is where you get paper money being called bank notes. \nFrom here you can see how notes would be used as credit, loans, be traded, used as collateral...and it gets complicated.\n"
]
}
|
[] |
[] |
[
[],
[
"http://www.reddit.com/r/AskHistorians/wiki/dailylife#wiki_proof_of_identity"
],
[],
[]
] |
||
219vbr
|
Why is Australia so hot even though it is so far south of the equator?
|
I feel like this is a stupid question but yeah..
|
askscience
|
http://www.reddit.com/r/askscience/comments/219vbr/why_is_australia_so_hot_even_though_it_is_so_far/
|
{
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"cgb1vsz",
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2
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"text": [
"Australia isn't that far south - depending on whether you're talking Darwin or Tasmania, you're roughly looking at the same latitudes as northern hemisphere locales such as Syria, Iraq, Spain and Mexico - all fairly warm in their own right.\n\nAustralia's also affected by a strong warm-water current, the Eastern Australia Current (or \"E.A.C. of *Finding Nemo* fame). This is like the analog of the northern Atlantic's Gulf Stream, shunting warm equatorial Pacific water directly down Oz's eastern shore. So just as the Gulf Stream keeps the British Isles several degrees warmer than they would otherwise be (there are even a few palms in southern Ireland), the E.A.C. warms up that part of Australia that most Aussies call home.\n\nFinally, it's notably, remarkably, lacking in mid-continent bodies of water that might ameliorate inland temperatures.",
"To reinforce what Sierrajeff is saying, look at this [map](_URL_1_) or [this smaller one](_URL_0_).\n\nYou will notice that all of Australia is closer to the equator than most of Europe.\n\nIn fact, one of the Tropic lines pass right through the middle of the continent.\n\n"
]
}
|
[] |
[] |
[
[],
[
"http://go.hrw.com/atlas/norm_map/world.gif",
"https://www.lib.utexas.edu/maps/world_maps/txu-oclc-264266980-world_pol_2008-2.jpg"
]
] |
|
2r8mu5
|
why is murder always the most severely punishable crime?
|
Why is it that no matter how much pain and suffering you inflict to a living person you will always get a lighter sentence than if you killed someone quickly with a relatively short amount of suffering? Even if you torture someone and ruin their lives and they end up killing themselves later.
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/2r8mu5/eli5_why_is_murder_always_the_most_severely/
|
{
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4,
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"text": [
"It's simply the most permanent way to harm someone. I do agree that there are other ways to harm people that should result in harsher sentences. ",
"Because once your dead, that's the end of the road. To be taken from a life, no matter how miserable it may seem, or even be, is worse than a life sentence. Even a useless scum bag murderer gets to live, inside of a cage. ",
"In some cases Treason may be more serious than murder. ",
"Because in a human society, the human life is the most valuable. ",
"if reincarnation was proven true would murder still be as severe?",
"Imagine a society where there are only two capital crimes: murder and robbery. For the sake of argument let us say any crime with a surviving victim has a 75% chance of being \"solved\" and any crime with a dead victim has a 45% chance of being \"solved.\"\n\nIf you murder someone, there is a 45% chance you will be caught, tried, and then executed.\n\nIf you rob someone and then leave them alive, there is a 75% chance you will be caught, tried, and then executed.\n\nIf you rob someone and then murder them, there is a 45% chance you will be caught, tried and then executed. \n\nSee how murder just changed you chances of execution from 75% to 45%? That is exactly what a lawful society should avoid. You never want to make murder attractive for a criminal. You want, if possible, to maximize the chance the victim lives and the criminal is brought to justice. \n\nYour punishments should be tiered to reflect this. You want the criminal to think \"Killing this person isn't worth the smaller risk of much greater punishment.\" ",
"Your premise is flawed, I've seen plenty of people get convicted of second or 3rd degree murder and serve less time than people that were convicted of treason, kidnapping, arson or rape. You can get very long sentences or even life for those charges, second or 3rd° murder doesn't often mean a life sentence. "
]
}
|
[] |
[] |
[
[],
[],
[],
[],
[],
[],
[]
] |
|
4ub0s3
|
airplane formations
|
Other than the Geese/Mighty Duck flying V, why?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/4ub0s3/eli5_airplane_formations/
|
{
"a_id": [
"d5ob2l9"
],
"score": [
3
],
"text": [
"Different formations serve different purposes. Some just look good for display, and some are designed to maximize the aircraft's effectiveness in combat. \n\nEspecially in the pre-missile-and-radar days it was important for combat aircraft to fly in mutually supporting formations. Bombers flew in tight box formations to maximize the effect of their defensive guns. Fighters generally flew in 2-ship elements. You attack, your wingman watches your back. Other elements of the formation would stay high, to watch for enemy fighters, etc."
]
}
|
[] |
[] |
[
[]
] |
|
1j8cwm
|
Are there any well written/ researched historical books specifically about the America atomic dread and how it influenced culture and art?
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/1j8cwm/are_there_any_well_written_researched_historical/
|
{
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"cbc4owx",
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"text": [
"Hmm, if you're specifically interested in American art the catalog for the exhibition Under the Big Black Sun should have some material on the topic.",
"Indeed, there are!\n\nMy favorite, for its breath and scope, is Spencer Weart's _Nuclear Fear: A History of Images_ (1988). There is a revised/updated edition out recently as well, though I prefer the original. It covers public attitudes (in a number of countries) about radioactivity and nuclear energy from the 19th century through the 1980s. It is very well written and one of my favorite academic books.\n\nThe other big book on this, though its time period and geographical focus is much narrower, is Paul Boyer, _By the Bomb's Early Light: American Thought and Culture at the Dawn of the Atomic Age_ (1985/1994). \n\nThere are other books on this subject as well, though I think most historians would list these at the very top.",
"Henricksen, Dr. Strangelove's America: Society and culture in the Atomic Age\n\nOakes, The Imaginary War: Civil Defense and American Cold War Culture"
]
}
|
[] |
[] |
[
[],
[],
[]
] |
||
3ds72j
|
How did Jefferson Davis get out of treason charges?
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/3ds72j/how_did_jefferson_davis_get_out_of_treason_charges/
|
{
"a_id": [
"ct8i5jf"
],
"score": [
4
],
"text": [
"The short answer is there are a variety of reasons. This actually goes into law a little bit so I will be in uncharted territory.\n\nSo Davis was indicted for treason. But when he went before the judge his team argued that due to the 14th Amendment he was already punished for insurrection against the US, as under the 14th Amendment anyone who takes an oath of public office and commits an insurrection can no longer hold public office.\n\nHowever the chief justice gave him an interesting argument. As Davis was president of another nation, he wasn't technically a citizen and couldn't be tried for treason for that reason.\n\nIn the end, Andrew Johnson pardoned him and all ex-confederates anyways, so any outcome would have been moot due to this."
]
}
|
[] |
[] |
[
[]
] |
||
8m527b
|
why does light only penetrate 1000 meters of the ocean and not the entire ocean?
|
I read that light is detectable at a depth of 1000 meters, but photosynthesis is only possible at 200 meters. The verbiage used by the article I read was "significant light is only present at above 200 meters," but does "significant" mean the energy of the photons at that depth is diminished or simply that the frequency of photons hitting the sensors is decreased?
Is photonic energy simply absorbed by the ocean to the point where photons can no longer exist? Or does the "wave" of light energy dissipate into the ocean like a sound or shockwave would?
Moreover, are there other methods of gathering information through the medium of water that are more effective than light? For example, is the effective range of SONAR greater than that of, say, a light source? What about low wavelength vs high wavelength light?
Sorry if it seems like I'm asking for a 101 in photons and electromagnetic energy, never learned this stuff in physics.
Thanks in advance.
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/8m527b/eli5_why_does_light_only_penetrate_1000_meters_of/
|
{
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"Roughly speaking, every metre of water will reduce the light by a fraction. Let's say that after 10m half the light is gone. After 20m, only a quarter would be left. After 100m, only a thousandth of the light would be getting through. (Number pulled out of my thin air.) In practice, presence of creatures/debris/different pressures/etc will affect it, but broadly speaking it will decrease exponentially with depth.\n\nSonar is a wave in the water itself. As it propagates differently, it does not decay exponentially in the same way, allowing it to potentially propagate far longer distances. How it does propagate is rather complicated, and dependant upon a lot of variables, especially the frequency. Most frequencies would not work, sonar uses frequencies specially chosen for how well they function at the task.",
"Light runs into stuff and bounces off stuff. At some point there's no more light to continue.\n\nSame thing happens in space too. Space isn't completely empty, and over a large enough distance, the light can be obscured.",
"because water isn't 100% clear. it's pretty straightforward. just like paper isn't 100% transparent, or your hands aren't 100% transparent.\n",
"No one seems to be answering your question with photons:\n\nThink about light from the sun as a hail of lots of photons.\n\nEach photon travels until it hits something. Some things can “bounce” photons off them, some things just suck in the photon.\n\nLots of photons from the sun make it through the air and start travelling into the water. But seawater has stuff floating in it that absorbs photons. For each metre of water, some photons will hit something, and some will make it through without hitting anything.\n\nIf you look for photons 300 metres deep in the sea, you will only find the very lucky photons who made it through 300 metres of water without hitting anything, and hardly any photons are that lucky.\n\nEdit: I just thought of a good analogy – it’s like a crazy guy spraying a machine gun around in a forest. Bullets stop when they hit a tree, but some bullets can go quite far before they hit a tree. If you can get a mile away from the crazy machine gun guy, your chances of getting hit go down to practically zero.\n\nEdit 2: please stop accusing me of being an American.",
"The spectrum also dissapears in order from lowest to highest frequency. one color every 10 meters or so. \n\nROYGBIV\n\nSO at 50 meters its kind of blue green. ",
"Light or visible light is a spectrum, we will call it X.\n\nThe photosynthetic spectrum is a subset, we will call it Y.\n\nIt is possible for X to penetrate far deeper than Y. And for Y to require more energy to occur whereas simply detecting X requires far less energy.\n\n_URL_0_\n\n\n\n_URL_1_",
"Simply speaking there's only so many photons per square unit of measure. \n\nAs we travel deeper in the ocean, we pass more things. \n\nEach of those are dodged by photons until they are not.\n\nYou run out of photons eventually.",
"Here's something that nobody seems to answer: water isn't completely transparent, it's just very, very translucent. Even if the water was completely free of particles, after about 200-300m you wouldn't be able to see any light. Only a true vacuum can transmit 100% of the light that passes through it. And a true vacuum doesnt actually exist anywhere in nature that we know of. We can get close in a laboratory, but that's it. Even deep space sucks up light, because all of it has a tiny tiny bit of matter floating around in it, like a couple atoms per square foot or something. But that's enough to reduce light, if you look at it with enough space between it and you. That's one reason why, incidentally, that some stars appear brighter than others. If outer space didnt diminish light whatsoever, the entire sky on average would be aapproximately as bright as the sun. Any physical matter sucks up photons, given enough of it. It just takes about 300m of water to see that it's not actually transparent.\n\nAs for photosynthesis, it's a process that requires a minimum threshold of light to make it happen. Without that minimum amount of light, there isn't enough energy to break/create the chemical bonds that are required for that process.",
"Photon energy is determined by the frequency (color). When light get weeker in the ocean, it's the number of photons getting smaller.\n\nThe reduce of photon numbers in water could be scattering (thinking of photons bounced away by particles in water) and absorbtion by either water or other stuff in the water. Scattering and absorbtion are both frequency dependent.\n\n\"significant light is only present at above 200 meters,\" means for most frequencies, the photon numbers are much smaller after 200m.\n",
"I felt everyone else is explaining it complicatedly. The sea has lots of particles floating around and they take in some of the light. Now imagine a really fine siv. You can see through it but if you take 3 or 4 of them it makes it really hard to see all the way through. The particles are small but over so many metres of them they add up and crisscross each other that the light can't get through.",
"Easiest way to think about it. Let's say you are walking forward, through a forest and cannot turn left or right. But not just you, you and a million people.\n\nIf the forest is only a few trees thick, then there's a high chance you can make it without hitting a tree. So a few trees thick forest maybe 800k would make it without hitting a tree.\n\nBut add another row of trees. And another. And so on. Eventually the chances that even a single person could walk through the forest becomes 0 because there's too many trees in the way.\n\nSame goes for atoms and light. The light flies through and the atoms of water because there's mostly empty space. But once it goes through enough water the chances of light not hitting an atom becomes 0.",
"The deeper you go, the more dense the water becomes, making it harder for individual photons to travel a clear line to the bottom. Eventually the photons collide, or bounce and reflect and that is where the absence, or lessening of light occurs. Think of it (when there is no light) as throwing pebbles at a fine mesh, the holes are too small and it is to dense (in thsi case, compact) for the larger particles (represented from the pebbles) to penetrate this mesh. This is why clean shallow water is crystal clear and light as opposed to its darker forms in deeper spots. Sorry for bad English.",
"How does light make the ~93 million mile journey through space without the same thing happening? (There's lots of space dust/debris)",
"In space it is a tight ray. *makes tube with hands*\n\n\n\nWhen it hits the air, it has to wiggle through it. *Wiggles fingers like rain* That's called 'Diffusion'.\n\n\n\nWater is like 100 times thicker than air, so it diffuses faster. *spirit fingers*\n\n\n\nSONAR is an effective but messy way to detect things underwater. The S in SONAR stands for 'sound'. Light is made of photons. Water is made of Atoms. Photons have to go into an Atom and then warm it up enough to drive another Photon out, if it doesn't then it becomes heat. \n\n\n\n\nSound is a wave of energy that moves many Atoms. It's like with a train, when you push on the rear car it pushes all the ones in front of it. That force works on water Atoms too. If there is enough force it will bounce off solid objects and you can use the speed of sound underwater and the time it took for your sound to get there and back. SONAR can harm living things. There are different types of SONAR to try and make them safer to use. \n\n\n\nLIDAR is a fusion of the two. It uses a high intensity beam that bounces off objects to a receiver. It uses math and triangles to calculate distance. This technology is still young though.\n\n"
]
}
|
[] |
[] |
[
[],
[],
[],
[],
[],
[
"https://en.m.wikipedia.org/wiki/Electromagnetic_absorption_by_water#/media/File%3AAbsorption_spectrum_of_liquid_water.png",
"http://bio1151b.nicerweb.net/Locked/media/ch10/10_09PhotosynthWavelength.jpg"
],
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[],
[],
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[],
[],
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[]
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|
15hykv
|
If you have an addiction, and suddenly get amnesia, will you know what you crave, even if you can't remember it consciously?
|
Say you are addicted to cocaine. you then get whacked in the head, forgetting your entire life, or at least the parts filled with cocaine use. I assume you will have intense cravings, but will you know what for?
|
askscience
|
http://www.reddit.com/r/askscience/comments/15hykv/if_you_have_an_addiction_and_suddenly_get_amnesia/
|
{
"a_id": [
"c7mulqc"
],
"score": [
2
],
"text": [
"Amnesia, to my knowledge, only affects conscious memory, so you will still have the cravings but you most likely will not remember what you are craving."
]
}
|
[] |
[] |
[
[]
] |
|
2arj2i
|
doing x in your life decreases/increases your risk of getting y cancer by z%. how do they determine the percent risk?
|
For example, I'm personally reading an article that says "Men who drank 2 to 3 cups a day had a 10 percent lower risk of mortality, and those who drank 4 to 5 cups per day had a 12 percent lower risk." We also see things like "Smoking increases your risk of lung cancer by whatever% over that of nonsmokers!" How do they go about determining these values?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/2arj2i/eli5_doing_x_in_your_life_decreasesincreases_your/
|
{
"a_id": [
"ciy0wr3"
],
"score": [
3
],
"text": [
"They look at a sample of the population, made up of varying groups within that sample, and they look at their habits and the outcomes.\n\nIf they notice that some men are not getting cancer while others are, or some men are being hospitalized for similar reasons while others aren't, they then look at the similarities between the men are try to find a cause.\n\nOnce they have that cause, they try and look at why it might be the case.\n\nFor cigarettes they know that people who smoke and inhaling cancerous chemicals, and that's why their risk of cancer is increased.\n\nFor (I'm assuming coffee) drinkers, it might be because the caffeine is A) giving their heart a boost and a little work out by beating faster and therefore minorly improving cardio B) caffeine is a diuretic and therefore may flush stuff out of the body\n\nThey then run more tests to conclusively prove these theories and then release the information."
]
}
|
[] |
[] |
[
[]
] |
|
151lkv
|
baby boomers and the animosity towards them
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/151lkv/eli5_baby_boomers_and_the_animosity_towards_them/
|
{
"a_id": [
"c7ifm5x",
"c7ihz3x"
],
"score": [
10,
5
],
"text": [
"Copy-Pasta of my comment from [this thread](_URL_0_).\n\n > When the US had crushing debt after WWII, the top marginal tax rate was raised to over 90%(!!!). Our debt was far worse than today and the WWII generation was not willing to pass that debt on to their children. This WWII debt was paid off relatively quickly and responsibly.\n > \n > The boomer generation is very often criticized because they have been hesitant to take similar action in the public sphere. The Cold War again caused national debt to skyrocket, but instead of raising taxes, they lowered them and let the debt balloon. Instead of reforming programs that are on shaky ground, they insist the government not touch them.\n > \n > To many, they just seem awfully close to violating the Boy Scout Rule, not leaving the country better than they found it. The 60s-70s were no utopia, don't get me wrong, but people see problems they definitely could have solved or at least contained which they did not.\n\nTheir stewardship of the country has left a lot to be desired in many peoples' eyes.",
"The United States of America always had a tradition of sacrificing to make sure the world was better for their children. In World War II, for instance, people turned in bits of scrap metal and even tin foil to help the war effort, and dealt with rationing, etc. Example:\n\n_URL_3_\n_URL_2_\n\nThe same sacrifice was true with raising taxes to pay for debts, and so on.\n\nThen came the 1970s and the very bad problem the USA had to deal with was an oil problem. A man named Jimmy Carter was president and saw that we had another huge problem we needed to sacrifice for. He suggested Americans put on a sweater and turn down the thermostat so we could beat our dependence on foreign oil, and gave speeches like this:\n\n_URL_1_\n\nThe Boomers tossed him out of office in favor of an aging actor who told them everything was all right.\n\nThe Baby Boomers betrayed that sense of national sacrifice, and so today, we still have a lot of problems with oil dependence, and debt, etc. but compounded so badly they are leaving the world a worse place for their children. Instead of being a major sacrifice, wars are now fought as though they had no effect on the general population except for yellow magnets on cars like this:\n\n_URL_0_\n\nThe unwillingness to sufficiently address major problems and the betrayal of our traditions is why people feel the Baby Boomers were a dishonorable generation."
]
}
|
[] |
[] |
[
[
"http://www.reddit.com/r/explainlikeimfive/comments/mf3m4/eli5_the_baby_boomer_generation_and_why_they_are/"
],
[
"http://www.4thefight.com/media/catalog/product/cache/1/image/5e06319eda06f020e43594a9c230972d/p/a/patriotic_yellow_ribbon_support_our_troops_vehicle_magnet_1.jpg",
"http://www.pbs.org/wgbh/americanexperience/features/primary-resources/carter-crisis/",
"http://www.timemoneyandblood.com/images/posters/American/donate-scrap-metal.jpg",
"http://www.ohiohistorycentral.org/images/972.jpg"
]
] |
||
2meeum
|
Do bent space-time and gravitons both cause objects in space to attract one another?
|
I'm having a hard time understanding why there seem to be two different explanations for how objects attract one another.
|
askscience
|
http://www.reddit.com/r/askscience/comments/2meeum/do_bent_spacetime_and_gravitons_both_cause/
|
{
"a_id": [
"cm3fjmq",
"cm3hhn5"
],
"score": [
10,
7
],
"text": [
"They are different descriptions of the same thing. Changes in the gravitational field propagate as gravitational radiation, and quanta of gravitational radiation are called gravitons. The classical limit of a spin-2 massless (graviton) quantum field theory is general relativity.",
"Feynman's lectures on GR uses the graviton formulation by considering a fun hypothetical scenario: \n\nIn our own history, we discovered the classical forces, and developed classical field theories of electromagnetism and gravity (GR). Then we discovered quantum field theory, and in this context GR does seem like an \"odd man out\" since it's so unnatural to think of spacetime curvature in terms of quantum fields. \n\nFeynman then considers the perspective of a hypothetical alien species (he calls them Venutians from Venus) who discover all of the the quantum forces (quantum field theory) first. They understand the complete Standard Model (I'm updating Feynman here because his book is from the 1960s), and then they discover gravity. They naturally try to fit gravity into their framework of quantum field theory using the methods they know. \n\nIt turns out that they are successful. Feynman considers the measurable experimental consequences of gravity/GR, and then attempts to build up various quantum field theories, showing how certain attempts fail. Eventually he reaches the theory of massless spin-2 particles (gravitons) as the simplest QFT which gives all of the correct predictions, and then uses this as his definition of GR for the rest of the book, which covers the standard material in a GR course from the graviton theory. He later speculates about the Venutians eventually discovering the geometric formulation, which he calls unnecessary but marvelous (and related to gauge invariance)."
]
}
|
[] |
[] |
[
[],
[]
] |
|
3z1kmw
|
what is the purpose of the black paint under the eyes?
|
Also if historical context could be explained that would be great too!
Edit: the black paint used in sports
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/3z1kmw/eli5_what_is_the_purpose_of_the_black_paint_under/
|
{
"a_id": [
"cyih9zy"
],
"score": [
2
],
"text": [
"It reduces glare (reflection off your upper cheekbones) from the sun/lights and makes it so that you do not have to squint as much. Besides being used in many sports, it is also used by hunters and military/ warring peoples. As for historical context, it's been done for a very long time because it's copied from nature - many non-human animals like cheetahs and gazelles naturally have the useful glare-reducing darkness under their eyes. "
]
}
|
[] |
[] |
[
[]
] |
|
5d0chz
|
Why can an inner ear infection cause temporary taste loss?
|
I recently had a minor inner ear infection and along with the normal slew of symptoms (headache, earache, and overall discomfort) I experienced temporary taste loss in the front half of my tongue. After some googling, I discovered that ear infection can be accompanied by taste loss (_URL_0_) but I haven't yet found a source that explains why. Can anyone explain?
|
askscience
|
https://www.reddit.com/r/askscience/comments/5d0chz/why_can_an_inner_ear_infection_cause_temporary/
|
{
"a_id": [
"da1vh19"
],
"score": [
6
],
"text": [
"Oh so this is SUPER cool. Sorry, probably not for you, but I'm a huge dork.\n\nThere's a nerve called the chorda tympani which passes through the middle ear, and I'm making an assumption here that you actually had a middle ear infection, as they are far more common. It is one of three nerves that carry taste sensation from the tongue to the brain, and my bet is that irritation of this nerve leads to temporary taste loss.\n\nSource: ~~Medical student. But I haven't brushed up on my anatomy in a while. This is, of course, not medical advice.~~ Good 'ol [Netter's Anatomy Atlas](_URL_0_)"
]
}
|
[] |
[
"https://www.nidcd.nih.gov/health/statistics/what-numbers-mean-epidemiological-perspective-taste-smell"
] |
[
[
"http://hearinghealthmatters.org/waynesworld/files/2016/08/chorda_tympani-1.jpg"
]
] |
|
2514oc
|
Is an insect that lives for 1 hour much faster evolving than humans who reproduce every 657 000 hours? (30 years)
|
Let's say a mayfly lives for 1 hour.
A new human offspring always 1 step further in the family tree reproduces every 30 years.
This theoretically and optimistically leaves the mayfly the oppurtunity to reproduce further in the family tree about 657 000 times in the time the human reproduces 1 time.
Does that mean that the mayfly also goes through their evolution so much faster than the human? I understand that the environment doesn't drastically change as much as it would in 657k human reproductions, bit still...
Edit: spelling
|
askscience
|
http://www.reddit.com/r/askscience/comments/2514oc/is_an_insect_that_lives_for_1_hour_much_faster/
|
{
"a_id": [
"chd26g9",
"chd5h5o"
],
"score": [
2,
2
],
"text": [
"My brain is foggy, but there were many studies that get done on fruit flies for mutations because of their quick life span and how many offspring each can create.\n\nEDIT: Here is an example that goes into more details than I could ever remember: _URL_0_\n\nTo quote the article for the lazy:\n\n\"Since the early 1900s, multiplied millions of fruit fly generations have been bred in laboratories across the globe. Scientists performing these experiments have introduced fruit flies to various levels of radiation and countless other factors designed to produce mutations. Sherwin noted that over 3,000 different mutations have been documented in the fruit fly gene pool (n.d.). These mutations have caused such physical characteristics as eyeless flies, flies with different colored eyes, flies with legs growing from their heads, extra pairs of wings, various colored bodies, wingless flies, flies with unusually large wings, flies with useless wings, flies with twisted wings, etc. The list could go on for hundreds of pages.\"",
"Evolution is just change in gene frequencies over time. You don't need the environment to change for a species to evolve. Some traits drift, or you might get a mutation that allows them to interact with a pre-existing environmental factor in a novel way. \n\nBut yes, the rate of evolution is heavily dependent on generation time."
]
}
|
[] |
[] |
[
[
"https://www.apologeticspress.org/apcontent.aspx?category=9&article=2501"
],
[]
] |
|
d42crs
|
how are people able to salvage data that has been deleted?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/d42crs/eli5_how_are_people_able_to_salvage_data_that_has/
|
{
"a_id": [
"f06xo52",
"f06xpvn",
"f06y1zt"
],
"score": [
6,
2,
3
],
"text": [
"Data isn't actually deleted when you hit \"delete\". When you hit \"delete\", you're telling the Operating System that it is OK to overwrite the area the data is taking up. If you delete something by mistake, and you don't write anything to the disk, the data is still there, and you can recover the data.",
" Windows (and other operating systems) keep track of where files are on a hard drive through “pointers.” Each file and folder on your hard disk has a pointer that tells Windows where the file’s data begins and ends.\n\nWhen you delete a file, Windows removes the pointer and marks the sectors containing the file’s data as available. From the file system’s point of view, the file is no longer present on your hard drive and the sectors containing its data are considered free space.\n\nHowever, until Windows actually writes new data over the sectors containing the contents of the file, the file is still recoverable. A file recovery program can scan a hard drive for these deleted files and restore them. If the file has been partially overwritten, the file recovery program can only recover part of the data.",
"I'm not entirely certain of the process, but data that you delete doesn't simply \"dissappear\". It just gets marked as unused space and sits there and does nothing until it gets overwritten by something else. Data salvaging is just searching through that unused space to find the data you're looking for. I don't know exactly how they accomplish this though."
]
}
|
[] |
[] |
[
[],
[],
[]
] |
||
cydkv5
|
After WW2, Hirohito was allowed to remain as a symbolic head, Why?
|
I read that initially, he wanted peaceful solutions to international problems, but was he actively involved in giving orders to the armed forces during the war? Was his initial hesitancy responsible for the later treatment? Or did the common people of Japan have any attachment with the emperor or the Dynasty?
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/cydkv5/after_ww2_hirohito_was_allowed_to_remain_as_a/
|
{
"a_id": [
"eyrrqrr"
],
"score": [
3
],
"text": [
"/u/restricteddata previously answered [Why was Emperor Hirohito allowed to keep the throne after Japan's unconditional surrender in WWII?](_URL_1_)\n\n/u/vinco_et_praevaleo previously answered [How did Emperor Hirohito escape trial and death following the Second World War?](_URL_0_)\n\nEDIT: fixed typo"
]
}
|
[] |
[] |
[
[
"https://www.reddit.com/r/AskHistorians/comments/5omexl/how_did_emperor_hirohito_escape_trial_and_death/",
"https://www.reddit.com/r/AskHistorians/comments/4wozby/why_was_emperor_hirohito_allowed_to_keep_the/"
]
] |
|
d70rvp
|
why do some batteries puff up?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/d70rvp/eli5why_do_some_batteries_puff_up/
|
{
"a_id": [
"f0x1tct"
],
"score": [
2
],
"text": [
"A swollen battery is the result of progressive degradation of the chemicals that generate power. The reaction that pushes electrons through the circuit can't work the way they were designed to, and part of that failure involves *outgassing,* or the creation of gases and vapors where they're not intended. This swells the battery casing, and might cause a breach and leak of the battery's contents."
]
}
|
[] |
[] |
[
[]
] |
||
vnd2t
|
Is there a certain configuration for a wifi router's antennas to give better reception?
|
I am not 2 rooms away from my wifi router and I only get 2/5 bars. I have my wireless Rx on my wall and the router itself is also up high, however it is not on the wall. Is there a certain way that I can angle the antennas to give me better reception?
|
askscience
|
http://www.reddit.com/r/askscience/comments/vnd2t/is_there_a_certain_configuration_for_a_wifi/
|
{
"a_id": [
"c5603ya"
],
"score": [
3
],
"text": [
"You want to set up antennas perpendicular to the direction of motion of the signal. So, if you're in the room next door, you would want the antenna to be vertical. If your router was in the basement and you wanted signal directly above it on the roof, you would want the antenna to be perfectly horizontal. "
]
}
|
[] |
[] |
[
[]
] |
|
1mwg90
|
How does sound pass though objects, but light (mostly) cant?
|
askscience
|
http://www.reddit.com/r/askscience/comments/1mwg90/how_does_sound_pass_though_objects_but_light/
|
{
"a_id": [
"ccdcuaz"
],
"score": [
16
],
"text": [
"Sound waves are a series of uncompressed and compressed molecules. When you slam your book on your table, the molecules of the book pushes the table surface molecules down, which gets them pretty close to the next set of molecules. The first group then retracts since they don't want to be so close to the other molecules, and the same goes for the second set of molecules, except they push further down. This continues until the energy dies out, or when it reaches the other side of the table, except the molecules being pushed are air molecules, which will also continue until the energy is lost. This *is* a sound wave, so it's not the fact that sound waves are traveling through an object, it's that the sound wave is manifested *in* the object(s).\n\n"
]
}
|
[] |
[] |
[
[]
] |
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