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warm fronts | Warm air moves to an area where there is already cold air.
As the warm air moves into the new area, it gets pushed up on top of the cold air.
Unlike cold fronts, the weather at warm fronts tends to be stable. In other words, as the warm air rises and cools, it becomes dense enough that it's not going to continue rising and rising.
Because of this, warm fronts tend to have lots of "stratus" types of cloud, that means layers of cloud (rather than big, bumpy clouds), and a warm front would normally be associated with persistent drizzle and rain (whereas cold fronts create lumpy "cumulous" clouds, and are associated with heavy rain showers). | [
"A warm front is a density discontinuity located at the leading edge of a homogeneous warm air mass, and is typically located on the equator-facing edge of an isotherm gradient. Warm fronts lie within broader troughs of low pressure than cold fronts, and move more slowly than the cold fronts which usually follow be... |
How did Einstein 'discover' time-dilation? | It was pretty well established by then that light acts like a wave. Now any other wave that we know about needs a medium to propagate through: ocean waves need water, sound waves need air. It was natural to assume that light needed a medium too, which they called the 'ether', but every experimental attempt to prove its existence failed miserably. The consequence of it having no medium means that there is no preferred frame for light, which given this and Maxwell's equations, means that the speed of light is constant for any observer. (As opposed to, say, me throwing a ball on a train: if I'm on the train I see it moving slowly, if you're off the train, you see it moving at the speed of the train plus the speed of the ball. If it was a photon, we'd BOTH see it moving at 3x10^8 m/s... weird but true). Time dilation and length contraction both come out of the math when you start formalizing these postulates, as in the Lorentz Transformations. Hope that helps - feel free to ask for clarification, and I'll do my best =] | [
"Einstein subsequently (1907) suggested an experiment based on the measurement of the relative frequencies of light perceived as arriving from a light source in motion with respect to the observer, and he calculated the additional Doppler shift due to time dilation. This effect was later called \"transverse Doppler... |
why does a weak am/fm radio signal result in a consistent static/fuzzy sound while a weak satellite radio signal results in intermittent high quality sound? | The simple answer is that AM/FM is an analog signal, which you can "kind of" pick up. Think of analog as a scale of 100-0 with the quality increasing or decreasing as you move from the transmitter.
Satellite radio is a digital signal. Think 1 or 0. It's either there, or it's not. The same holds true for satellite TV, where in a severe storm your picture will be perfect right up until it cuts out into nothingness. | [
"Reception of RF signals is sensitive to the size of obstruction in the path between the transmitter and the receiver. Generally speaking, if the size exceeds the wavelength the reception is interrupted. Since the wavelength is inversely proportional to frequency, it follows than that the higher frequency broadcast... |
why are anarchists and nihilists put on the same political wing as socialist and communists? | If you look at it economically, anarchism has strong ties to socialist/communist theory. Anarchists are pretty misunderstood, it's not all about no rules and complete chaos. Early anarchists believed that you should grow food, and whatever extra you had you should give to your neighbours for free, and vice versa. This idea is basically the opposite of capitalism, where you pretty much want to make as much money as you can off of your extra food. That is just one example of policy why it is on the left, rather than the right. | [
"Some forms of anarcho-communism such as insurrectionary anarchism are strongly influenced by egoism and radical individualism, believing anarcho-communism is the best social system for the realisation of individual freedom. Hence, most anarcho-communists view anarcho-communism itself as a way of reconciling the op... |
How long does it take for plant cells to grow? | This varies greatly from plant to plant, and it will vary based on the conditions. You also need to define 'grow' because cells can expand or divide to grow.
Plants that perform C4 photosynthesis (like grasses) tend to expand and divide rapidly under the right conditions, while plants that perform CAM photosynthesis (like cacti) will grow slower in an attempt to conserve water. There are [genes](_URL_0_) in some cultivars of rice that helps it keep itself above water when the paddy floods by rapidly growing to stay above water.
Many plants will halt growth if the conditions aren't right, and try to ride out the problem. Some plants will rapidly grow if they arn't getting enough sunlight in a sort of last-ditch effort not to die.
There really isn't a simple answer to your question, sorry.
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"Growing cells require synthesis of new nucleotides, membranes and protein components. These materials can be obtained from carbon metabolism (e.g. glucose metabolism) or from peripheral metabolism. The enhanced flux observed in abnormally growing cells is brought about by high glucose uptake.\n",
"Plants grow fr... |
How thin is the surface of a bubble? | Short Answer: Somewhere around 50-500 nano meters, depending on where you measure the bubble's thickness.
Long Answer: This can be measured using a very clever natural phenomenon, [thin-flim interference](_URL_0_).
So a bubble has two sides, the outside and the inside. Light coming from the sun hits the outside layer of the bubble, because light travels different speeds in a medium some of the light is reflected off of the outer layer of the bubble while most goes through it. This is a property of the index of refraction of a material, a small portion of light incident on a material with a different index of refraction that the lights original medium will reflect back.
The portion that goes through the outer layer then contacts the inner layer, again a change in the index of refraction causes some light to reflect back. So now we have two different rays of light that are exactly twice the thickness of a bubble out of phase from each other.
Now depending on the particular thickness of the bubble at that certain point the observer will likely see some color appear. This color occurs from what is called constructive and destructive interference. Destructive interference is when two waves that are 180 degrees out of phase come in contact with each other, this destroys the wave and no light is seen. Constructive interference is when two waves of the either 0 or 360 degrees out of phase come in contact with each other, this creates brighter light.
What we are seeing as color in the bubble is exactly a measurement of the thickness of that bubble. Say the color is purple and has a wavelength of 400nm. This means that the thickness of the bubble must be around 200nm, because the second beam of reflected light will constructively interfere if it travels and extra 400nm (in and back out) and destructively interfere if it travels any other distance.
Some discrepancies in the accuracy of the measurement occur when you include the light traveling at an angle into the bubble, but you get the idea.
This is also why thin layers of oil on water make rainbow colors. There are lots of uses of the phenomenon, such as infrared protective layering on the front of expensive camera lenses... | [
"A 1 mm bubble has negligible extra pressure. Yet when the diameter is ~3 µm, the bubble has an extra atmosphere inside than outside. When the bubble is only several hundred nanometers, the pressure inside can be several atmospheres. One should bear in mind that the surface tension in the numerator can be much smal... |
Did Romans really have those feathered things on top of their helmets? If so, why? | The "feathered thing" is called a crest and its usage depends on the time period:
In the days of the early republic, it was not common.
During the late republic (post 3rd century B.C.) it was very common among legionaries.
After the reforms by Augustus, only centurions were wearing crests.
In the later empire, they seem to be abandoned altogether.
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"The origin of these very elaborate helmets is uncertain but appears not to have been Rome. Various origins have been suggested, including a theory that they came from Rome's eastern provinces. They were produced from the early 1st century AD through to the mid-3rd century. Although they are relatively light, they ... |
how is something scientifically proven to be a fact? | Scientists don't tend to use the word "fact" for any generalized statement.
I dropped a ball from the top of a 100-meter building and I measured that it took 4.9 seconds to reach the ground. That's a *fact*. It's evidence consistent with the theory objects on Earth fall with an acceleration of approximately 9.8 meters per second squared.
The theory of gravity is our complete understanding of gravity based on all of the evidence we've collected. It takes into account things like wind resistance, so a feather falls more slowly than a brick. It takes into account the masses of the various objects involved, and it also takes into account Einstein's theory of relativity, which changes what happens pretty dramatically when the velocities involved are large.
The most important thing about a scientific theory, to me, is that it makes useful predictions. It says that given a certain situation, here's how to apply the theory to predict the outcome.
If it's right, it's a useful theory.
You can disbelieve the theory of gravity all you want, but that doesn't make it any less useful. If you can find a counterexample - some evidence that it's wrong under a certain set of circumstances, then the theory *must* change to incorporate that new evidence, if it can be reliably reproduced and the current theory is inconsistent with it.
In the case of 1+1=2, that's one of those things where as long as we all agree on the definitions of numbers and addition and equals, it's definitely true, but there are other scenarios where it's not true (like one cloud plus another cloud equals one larger cloud).
We don't talk about 1+1=2 just as an exercise, we talk about it because it's useful. We have problems to solve and math helps us get at the answer. If the answer we get is wrong then it's not very useful and then there'd be no point!
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"In science, a \"fact\" is a repeatable careful observation or measurement (by experimentation or other means), also called empirical evidence. Facts are central to building scientific theories. Various forms of observation and measurement lead to fundamental questions about the scientific method, and the scope and... |
feces being a major source of harmful germs,how is it the lower intestine isn't chronically infected. | The vast majority of the bacteria in your colon are (mostly) harmless organisms that have evolved to live with us. The high populations of these bacteria tend to suppress the growth of other, harmful bacteria. Think of an apartment building with 100 units. 98 of them are already occupied by quiet residents. Even if the other 2 units are occupied by hooligans, they can't cause a lot of trouble and that trouble can't spread.
Now these bacteria aren't completely harmless. The very common E. coli bacteria causes infections ranging from mild (simple urinary tract infections) to life threatening (sepsis of the blood) if it gets somewhere it isn't supposed to be.
When we kill off the friendly bacteria, sometimes less savory ones take their place. A bowel infection known as C. difficile colitis is typically caused when antibiotics kill off the benign bacteria, leaving it behind. And some bacteria are just bad actors (like Salmonella or Shigella) and can cause infections even in healthy colons.
The colon itself as another poster noted is resistant to invasion from most gut microbes. | [
"An infarcted or dead intestinal segment is a serious medical problem because of the fact that intestines contain non-sterile contents within the lumen. Although the fecal content and high bacterial loads of the intestine are normally safely contained, progressive ischemia causes tissue breakdown and inevitably lea... |
What led to Sulla's retirement after being declared dictator for life? | The sources are particularly lousy for this: the wretched Appian on the one hand, and on the other Plutarch, more interested in the morbid details of his wasting disease than any politics. Scullard and Keaveney both argued that Sulla simply got tired and decided that he'd done enough to ensure a return to Republican form. Sulla retired to Cumae, into a Campania that he had essentially remade from the ground up in the aftermath of the ravages of the Social War. It was a pleasant place, to be sure, and I don't think there's anything wrong with believing that Sulla went there purely because he wanted to relax and indulge in the proclivities which he seemed to cultivate.
But I don't think that's right. I don't think Sulla was "done," and in fact the actions of Sulla in some ways provided a rough draft for how the *principes* would elevate themselves above the machinery of the Republic later, starting with his protege Pompey. Striking coins with his image while he still lived (a no-no in the *mos maiorum*), not to mention the giant equestrian statue of himself in the forum, both suggest Sulla had grand designs. He left off the dictatorship in 81 and held the consulship in 80, probably thinking he was secure enough in his position to do away with the more odious form of authority. His old rival Marius had held consecutive consulships in the past, and Sulla might have had something like that in mind in lieu of the dictatorship. If so, it never came to pass. I think the old madman was probably gently ushered out by the younger Sullani, Pompey in particular, and convinced to let others have a turn. He could have fought on, and there were plenty of Sullan veterans in Italia that he could have stirred up, but he seems to have just simply got too tired. I don't like modern claims that he was "forced out" or the like. Nobody ever forced Cornelius Sulla to do anything. It was most likely a combination of satisfaction with his life's work, fatigue and sickness, and the gentle, careful, but insistent advice of his young proteges.
Check out Jenkins' little article, "Sulla's Retirement," 1994. See also, for a modern and interesting look at Sulla, Santangelo's *Sulla, the Elites, and the Empire* Brill 2007. | [
"In 79 BC, Sulla resigned his dictatorship, re-established consular government and, after serving as consul in 80 BC, retired to private life. In a manner that the historian Suetonius thought arrogant, Julius Caesar would later mock Sulla for resigning the Dictatorship—\"Sulla did not know his political ABC's\". He... |
Did the Romans ever face armies of horseback archers from the steppes or elsewhere? How did they fair? Did they ever experiment with or adopt the strategy? | Yes, Roman armies faced armies primarily composed of horse archers more than once. The fellow under me has referenced Attila the Hun. The Romans did technically defeat him at Chalons, but I'll admit to a small working knowledge of the late Roman army, so I'll focus on the earlier armies of the Republic and the Principate, and how they fared against horse archers.
In this time period, the two best examples I can come up with are both involving the Parthians. Crassus was famously defeated by the Parthians at Carrhae, and Antony led a failed invasion into Parthia while a triumvir.
The Parthian army was based on a feudal model, controlled by the king but in reality a large formation of many different strong noble families. Most of the army was composed of cavalry, mainly horse archers along with a smaller force of heavily-armed cataphracts. For example, the force of Parthian commander Surena that fought Crassus at Carrhae in 53 BC was made up of 10,000 horse-archers and 1,000 cataphracts. Parthian armies also included infantry made up from the poor, but these were never influential in any way at all and so have little tactical relevance. According to Lucian the basic unit of the Parthian army was a *dragon* of 1,000 horse-archers. The decimal model is quite prevalent in horse-archer armies, but we have no other evidence for this claim, and Lucian was no historian.
This cavalry force obviously operated in a very different way from Rome's infantry based army. We get a glimpse of Parthian tactics at Carrhae. In this battle, both sides expected an easy victory. The Romans had crushed every other eastern army they had faced with ease recently, and the Parthians were equally scornful of the Romans. Surena expected the Romans to be scared at the sight of his cataphracts, but was disappointed by the disciplined Roman infantry, who showed no signs of fear.
It seems that usually the Parthians simply expected the sight of their cataphracts to scare the enemy, and apparently they wore cloaks over their armour that they would discard right before battle, either as protection from the sun or to shock the enemy with a startling reveal of their glimmering scale armour.
Therefore, at Carrhae Surena had his horse archers bombard the Roman troops all day. Despite thousands of arrows, the Roman troops suffered relatively few casualties, mostly wounds, due to their armour and shields. Their morale stayed intact as well.
The Romans held up very well in spite of the horse-archer bombardment, and the troops were comparatively safe as long as they maintained discipline. However, Crassus made an ill-fated attempt to drive away the horse-archers, led by his son, who was cut off and killed. Dispirited, Crassus ordered a retreat, which soon degenerated into a routing mob as the horse archers surrounded the Romans, who began to panic. Carrhae was a decisive Roman defeat, and it made the Parthians very confident in themselves and scornful of the Romans. However, the Parthian army is often over-estimated in our sources, and they weren't truly as powerful as they would have liked to think.
Crassus's problem was that his army was unbalanced. Later Roman encounters with the horse-archers remedied this. For example, Antony brought many light missile troops with his Parthian expedition. A foot-archer will always out-range a horse-archer, and Antony's troops suffered little from horse archers. When the Romans were well prepared, usually the Parthians had to content themselves with shadowing the Roman marches, and depend on attacking their extended supply train. When Roman troops had enough supporting missile fire, they were very safe from horse archers, who became more of an irritant than a real threat.
Rome did sometimes have horse-archers in her armies, but it was never a major part of them in this period. I know that later Roman armies included more horse archers, but like I said I don't really know enough to be any authority on that. However in our period Rome tended to bring auxiliary troops into her army based on the native's methods of fighting, so many Roman armies in the east had horse-archer auxiliaries.
For example, Arrian's army that fought the Alans, a steppe people, had horse archers in it. However they were only really a supporting wing and the Romans never adopted this tactic beyond in a minor supporting role.
I hope that this makes sense, I can elaborate more if need be. I'm not very good at organizing my answers on this subreddit yet, haha.
Sources: Plutarch's *Life of Crassus* & *Antony*, Adrian Goldworthy's *The Roman Army at War 100 BC - AD 200*
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"There were also horse archers, who had the ability to shoot on horseback – the Parthians, Scythians, Mongols, and other various steppe people were especially fearsome with this tactic. By the 3rd–4th century AD, heavily armored cavalry became widely adopted by the Parthians, Sasanians, Byzantines, Eastern Han dyna... |
what are ghz and what do they mean when it comes to computer specs? | Hz is a measure of frequency- the number of times something happens per second. If something has a frequency of 3GHz, it means that it happens three billion times per second.
In the case of computers, that's the speed of its internal clock. A single operation in a computer can take multiple steps, and the clock speed tells you how long it gives each step to complete. A simple operation, like addition, might only take 1 clock tick to complete, while a more complex operation like trig functions, can take over 100.
Clock speed by itself doesn't mean much. You can use it to directly compare processors of the same series (so you can compare a 4th gen Core i5 with another 4th gen Core i5 processor), but different series of processors take different amounts of time to complete each operation, and a 3GHz processor that can finish a task in 100 clock cycles is faster than a 4GHz processor that takes 200 cycles to do the same work. | [
"BULLET::::- On August 31, 2011, in Austin, Texas, AMD achieved a Guinness World Record for the \"Highest frequency of a computer processor\": 8.429 GHz. The company ran an 8-core FX-8150 processor with only one active module (two cores), and cooled with liquid helium. The previous record was 8.308 GHz, with an Int... |
Do rockets use fossil fuels? Is there danger of running out of rocket fuel as we deplete oil reserves in the next 50-200 years? If so, are there alternative fuels that have the necessary power to take us into space? | We are in no danger of running out of liquid oxygen or liquid hydrogen, as they can be extracted from water. You can make a workable rocket with just those fuels, although a big fat first stage full of low density hydrogen has penalties.
Realistically, if absolute supply of kerosene or methane is an issue, we'll be too far gone to have the technical infrastructure to support spaceflights.
Helium is the real supply danger. It's irreplaceable as a pressurant and coolant and it is a nonrenewable resource. It's plentiful in space, but in limited supply on earth. | [
"energy). In chemical rockets, unburned fuel or oxidizer represents the loss of chemical potential energy, which reduces the specific energy. However, most rockets run fuel-rich mixtures, which result in lower theoretical exhaust velocities.\n",
"Since solid-fuel rockets can remain in storage for a long time with... |
when a hard drive sets aside space for a download, what is it filled with before it actually receives the data that takes up the space? | Logically, the filesystem is told to reserve the physical space for the new file.
Physically, the space of a hard drive that are reserved still contain whatever data was last in that space. | [
"When data is deleted from storage devices, the references to the data are removed from the directory structure. The space can then be used, or overwritten, with data from other files or computer functions. The deleted data itself is not immediately removed from the physical drive and often exists as a number of di... |
subjective vs. objective | Subjective is a judgement or experience. Objective is a reliably reproducible measurement. Both can be scientific. A good example is flavor versus chemistry.
A cherry is tangy, sweet. That's a subjective statement because everyone experiences flavor in a different way, but it's still important to science to characterize the properties of a cherry.
A cherry contains an average of 0.4 grams of fructose. That's an objective statement because we've distilled some measurement from an analysis.
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"Some have argued that the distinction between objective and subjective assessments is neither useful nor accurate because, in reality, there is no such thing as \"objective\" assessment. In fact, all assessments are created with inherent biases built into decisions about relevant subject matter and content, as wel... |
Do we have any concept of "infinite" I terms of time and space? | _URL_0_
> We now know (as of 2013) that the universe is flat with only a 0.4% margin of error. This suggests that the Universe is infinite in extent; [...] All we can truly conclude is that the Universe is much larger than the volume we can directly observe.
_URL_1_
> The size of the Universe is unknown; it may be infinite.
But
> how can it truly be without an end?
To imagine *that* it might be so is easy: Just look at e.g. Natural Numbers ([0,] 1, 2, 3, ...) - they go on without end, so why shouldn't something physical (like the size of space) be infinite (= go on forever)?
To imagine this infinity itself is probably forever impossible, but whenever I try to create a mental image of "Goes on forever. No, no just until that point - even further. And further.", I seem to find a new, more "correct" image of infinite space. Maybe I am re-using previous such mental images in the new one, like subroutines in a computer program. This can maybe never lead to an actual imagination of an infinite spatial stretch, but it feels like something new and awesome whenever I find a bigger mental image of this.
The actual question might be: Why should we be able to create mental images for everything that exists in reality? Maybe it just has to be accepted that reality is beyond our ability to mentally describe it (except by symbols and concepts). But don't let that discourage you from trying.
> When it comes to time, I know that we estimate the universe to be about 13.7 billion years old. I know we don't have a understanding of what was before that,
Well, that's an interesting problem, and I must admit that my musings in this regard might be unfit for /r/AskScience, but I dare write them anyway:
We (Mankind.) have found principles that reality follows, e.g. Quantum Mechanics, General Relativity etc. - and before we had found those, we had simpler, less accurate concepts of the principles that reality follows, and we had *more* of those because we didn't know yet what their underlying principle was. I'm saying that we had found a lot of small boxes, but nowadays we have a few larger boxes that each holds a lot of those earlier boxes. We keep searching for TheOneBoxToRuleThemAll™, the principle that all of reality follows.
But in the same way, when we look back further in time, we see a conceptually simpler and simpler universe. Our search for "the all-concept" and our search for what was at the beginning of the universe is a very similar one, it's ultimately looking for the same answer: What is reality ultimately really?
My take regarding the beginning of time is that the closer we'd get with our understanding to that point, the more we'd look at the all-unification of all things, the all-principle, and this would - my opinion - ultimately describe even what time is. Even what logic / cause & effect is. If that were so, then the beginning of time would be a singularity not just of space/matter/energy but also of all meanings. The question "what was before" would in this way not even have a meaning.
Just think of it this way: At some point in our mental journey to get closer to the root of the universe, we might find the explanation of what time is and how it works. And then? Well, and then there logically is no "before" any more. | [
"Aristotle also distinguished \"things infinite in respect of divisibility\" (such as a unit of space that can be mentally divided into ever smaller units while remaining spatially the same) from things (or distances) that are infinite in extension (\"with respect to their extremities\").\n",
"The basic premise p... |
how does trade between countries work in terms of currency? if country a buys millions of dollars worth of commodities from country b, how do they pay? do they give them cash? gold? bank transfer? | Think of countries as regular companies for this case.
Countries don't really buy things - it's state companies that are run (more or less) like private companies, think of train networks requiring trains, power grids require generators, water networks needing pumps, etc. - when they buy something - and it doesn't matter if its domestic or foreign - they'll agree on a price (and a currency - especially in countries with weak local currencies, a strong foreign currency is actually agreed upon even on domestic deals) with the seller.
On longer running deals, most companies (state or private owned doesn't matter) then pay some insurance to have their exchange rate fixed (especially if the exchange rate between the local and foreign currency is more volatile) so they'll pay the same amount in their local currency for the foreign product over a longer amount of time. | [
"By an accounting identity, Country A's NCO is always equal to A's Net Exports, because the value of net exports is equal to the amount of capital spent abroad (i.e. outflow) for goods that are imported in A. It is also equal to the net amount of A's currency traded in the foreign exchange market over that time per... |
counterfeit vs fake vs forgery for items | A forgery usually refers to a *specific* item, like a signature or an original painting. If you were two see two identical copies of the same original painting, you could conclude that forgery has occurred merely from the fact that there are two of them. You still might need an expert to tell which one is the forgery, though.
Counterfeit is for *categories* of goods, and usually means that the thing being faked is the *origin*, not the good itself. Counterfeit is often, but not always, related to IP infringement.
If you make a purse, that's fine. If you make a purse and call it a Louis Vuitton, then it's a counterfeit because Louis Vuitton didn't make it (regardless if it's good quality or otherwise identical!). If Louis Vuitton licenses you to make LV-brand apparel, then that same purse is now not counterfeit anymore. In contrast to forgery, there's nothing inherently suspicious about seeing a dozen identical Louis Vuitton purses.
Bank notes are also counterfeit, because the thing being faked is who made them. The country issuing them is what gives them the legal weight to be considered money. So what you're faking is the issuing authority, and the good itself only incidentally.
Counterfeiting banknotes may also require forgery because there's signatures and art. Also, *financial instruments* can be forged: things like checks and deposit slips and authorizations.
"Fake" is a pretty loose term. I'm not sure it's well-defined. | [
"Sometimes, forgery is the method of choice in defrauding a bank. There are three main types of cheque forgery: (a) Counterfeit. This is a cheque that has been created on non-bank paper to look genuine. It relates to a genuine account. (b) Forged signature. The cheque is genuine, but the signature is not that of th... |
How do you defend the purpose of Medieval History? | I don't actually feel as if I need to defend medieval history for its social relevance - the fact that I enjoy studying it is really enough for me. It should be obvious that medieval history presents special problems of understanding, in particular in relation to the number of sources, and I have always liked grappling with these.
I also don't buy the distinction you seem to be making between history which "has direct implications... and directly affects what occurs today" and that which doesn't. This is partly because I believe that the medieval period genuinely does affect today - you could think about the roots of the British constitution and legal system in terms of Magna Carta (1215); or the development of the English language via Middle English including the cultural legacy of the medieval period via Chaucer; or the way in which we link modern events to [those from medieval society](_URL_0_); or the ways that [modern culture](_URL_1_) draws on medieval tropes. Drawing this sort of distinction reduces history to a monocausal discipline which just considers immediate context, and I don't think that actually captures the past very well.
I'm also not sure how compelling a justification the one you use is. For one thing, I really don't think that people reading history necessarily apply the lessons of the past to the present - this is a bit crudely determinist for me.
A good introduction to the value of medieval history is Marcus Bull's *Thinking Medieval*. | [
"Medieval period oriented living history groups and reenactors focus on recreating civilian or military life in period of the Middle Ages. It is very popular in Eastern Europe. The goal of the reenactor and their group is to portray an accurate interpretation of a person who credibly could exist at a specific place... |
why do we still need sunscreen? why haven't we as humans adapted to the heat of the sun after all this time? | > Why haven't we as humans adapted to the heat of the sun after all this time?
It's not the heat that's the problem. It's ultraviolet light, which damages cells and can lead to skin cancer. And we *have* adapted. Tanning is our body's response to excess sunlight, and it helps reduce (but does *not* eliminate) sun-related damage.
But skin cancer from sun exposure generally happens late enough in life that it has no impact on someone's ability to reproduce, and if it doesn't affect our ability to reproduce, then there is no evolutionary pressure to change it (i.e. pretty much no one who is more prone to UV-influenced cancer is dying before they can have children). | [
"Sunlight has been shown to be beneficial in some skin conditions and enables the body to make vitamin D, but with the increased awareness of skin cancer, wearing of sunscreen is now part of the culture. Sun exposure prompts the body to produce nitric oxide that helps support the cardiovascular system and the feelg... |
Why did America develop a stable republic while most of Latin America developed weak, unstable republic? | I don't know that I can answer the question as written for "most of Latin America, from what appears to be independence to the present day", but I think I can point to some important differences that might help you think about the question you're asking. For the sake of brevity I'll stick to Spanish America, because Brazil is a whole different thing, and I'll just refer to "America" in your question as the US.
- The independence of the United States was a purposeful, top-down effort led by a motivated elite; it was deeply rooted in international instability, but not, I would argue, primarily caused by it. The independence of Spanish America was, in large part, a product of a power vacuum created by Napoleon's sudden conquest of Spain. In the important power centers of Spanish America, this meant that various groups surged uncertainly into authority over the 15-20 years of Napoleonic instability, including an explosive, highly intolerant attempt to re-assert authority by the recently restored Ferdinand VII with the support of other counter-revolutionary European regimes. So while in the British colonies you had a relatively brief period of war with a decisive end, and a (weak, but functional in important ways) independence government with reasonable legitimacy waiting to step in, in Spanish America the best case scenario was to be far enough away from a power/economic center that you were mostly left alone for the decades of warfare and disorder. Which creates a neat catch-22 since those remote locations like Costa Rica were not going to become the sort of regional powers people have in mind when they ask this question. Because we lack (afaik) comprehensive evidence for how generalized support for US independence was, it's tough to really track that ebb and flow, but as you'll see in the next points, at least it wasn't like the upper classes were hopelessly alienated from the middle and lower classes in terms of their goals, which were basically "change as little as possible and don't give an inch to the poor or underprivileged" more than broad ideas of independence. Why was this?
- The power vacuum situation in South America meant that, for all practical purposes, South America's major countries were simultaneously embroiled in the equivalent of the US Revolution and Civil War, at the same time, for a period of at least two decades on-and-off. That means issues of race, caste, class were being negotiated (Bolivar's rebranded independence movement after Haiti, Mexico's Hidalgo vs Iturbide branching paths, Peru's post Tupac Amaru II mentality was firmly in place, etc) simultaneously with basic questions of chain of command, forms of government, economic structure. This meant that people who Had Stuff in Spanish Latin America felt they were in a very scary place compared to US elites, and you can easily see why competing thrusts at low-consensus republics that shut out these new ideas or military dictatorships coming in and out of power would lead to difficult precedents, and far from "taking care" of major questions of governance like the eventual US Civil War, really only set in place the potential for cyclical discord, often tied to individuals rather than institutions, in many countries (see: *caudillismo*).
- Timing. Ideologically, the Euro-American world was a very different place in the early 19th century versus late 18th, due in no small part to the US revolution but also to the French Revolution and, importantly, the semi-successful revolt of enslaved persons in Haiti. Combined with the uncertainty and the outbursts of change in social order in various independence movements (again, Hidalgo and the undercurrents that would lead to Bolivar v2), and you have that situation I described in the first point. Which is that the leadership that would take power from Ferdinand VII's (unwilling) hands was, in most ways, profoundly conservative and reactionary in motivations that simply weren't present for US leaders/elites in their ascension to power.
I could go on, but that gives you three big things I think are important in considering the process of independence in the two regions. Why things evolved differently from there would really benefit from a country by country breakdown, as (for instance) Mexico's evolution into its 19th century and 20th century forms is much more deeply enmeshed with American intervention than, say, Argentina, to cite just one important factor in its "instability" over time. Apologies for the big generalizations above, but I hope they get the job done.
Further reading:
Rodríguez, Jaime E. The Independence of Spanish America. Cambridge University Press, 1998.
Halperin-Donghi, Tulio. The Aftermath of Revolution in Latin America. Harper Torchbooks, 1973.
Bulmer-Thomas, Victor. The Economic History of Latin America since Independence. 2nd ed. Cambridge University Press, 2003.
Some more specific works that do well addressing this question in their areas
Woodward, Ralph Lee. Central America: A Nation Divided. 3rd ed. Oxford University Press, USA, 1999.
Walker, Charles F. Smoldering Ashes: Cuzco and the Creation of Republican Peru, 1780-1840. Duke University Press Books, 1999.
Young, Eric Van. The Other Rebellion: Popular Violence, Ideology, and the Mexican Struggle for Independence, 1810-1821. 1st ed. Stanford University Press, 2002.
Jiménez, Iván Molina, and Steven Paul Palmer. El paso del cometa: estado, política social y culturas populares en Costa Rica (1800-1950). Editorial Universidad Estatal a Distancia, 1994.
| [
"Latin America's political independence proved irreversible, but weak governments in Spanish American nation-states could not replicate the generally peaceful conditions of the colonial era. Although the United States was not a world power, it claimed authority over the hemisphere in the Monroe Doctrine (1823). Bri... |
Why does water turn yellow when electric current passes through it for some time? | It's a physical reaction, not chemical, the electricity is causing it not an interaction of chemicals. Ions (atoms missing bits) come off the anode (positive side). If you leave wires connected to a battery in water for long enough you'll see one of them will eventually disintegrate. That's why you see metal for out doors that is anodized or galvanized . They put a metal coating that will degrade by giving up ions preventing the underlying metal from degradation. | [
"Water attenuates light due to absorption which varies as a function of frequency. In other words, as light passes through a greater distance of water color is selectively absorbed by the water. Color absorption is also affected by turbidity of the water and dissolved material.\n",
"BULLET::::- Pure water is near... |
if i keep the calories down but it's all mtn dew & chocolate & chips, will i lose weight or stay fat from all the sugar? | If you eat fewer calories than you use, you lose weight.
If all those calories come from soda, chocolate, and chips, you lose other things. Like muscle mass, hair, and vital signs. | [
"While you don't need to limit the sugars found naturally in whole, unprocessed foods like fresh fruit, eating too much added sugar found in many processed foods can increase your risk for heart disease, obesity, cavities and Type 2 diabetes. The American Heart Association recommends women limit added sugars to no ... |
Let's be honest: Is interstellar/intergallactic space travel possible at all? | You are pretty much correct in your analysis.
Long-term generation ships using nuclear pulse propulsion (or similar) could perhaps reach another star, but that technology is too far away to even say how far away it is. | [
"Intergalactic travel is hypothetical manned or unmanned travel between galaxies. Due to the enormous distances between our own galaxy the Milky Way and even its closest neighbors—hundreds of thousands to millions of light-years—any such venture would be far more technologically demanding than even interstellar tra... |
If we never see objects fall into black holes due to time dilation, how do black holes gain mass? | It's a somewhat tricky question, actually.
From the point of view of the infalling particle, time doesn't slow down at all as it approaches the horizon; in fact, it doesn't feel anything special at the horizon at all, and it continues to fall in as normal.
To the outside, however, it's true that infalling matter appears to accrue on the surface of the black hole, and this is fine: the exterior gravitational field of a black hole of mass M is the same as that of a black hole with mass m1 surrounded by a shell of mass M-m1 on the horizon. As far as we're concerned, it doesn't matter if the matter falls in through the horizon or asymptotically reaches it because you'll get the same gravitational field either way. | [
"As predicted by general relativity, the presence of a mass deforms spacetime in such a way that the paths taken by particles bend towards the mass. At the event horizon of a black hole, this deformation becomes so strong that there are no paths that lead away from the black hole.\n",
"To a distant observer, cloc... |
why does traveling to new places generally make people happy? | 1. Humans have an instinctive desire to explore. Following our instincts feels good.
2. It distracts us from our usual daily concerns, which aren't visible there.
3. We don't have so many chores or work to do when on vacation. | [
"The new travelers have traveled the world, they have seen the classic sites. Staying at a Western hotel is not attractive enough, and they are excited by the prospect of experiencing the authentic local way of life: to go fishing with a local fisherman, to eat the fish with his family, to sleep in a typical villag... |
how the conversion rates between currencies are decided. who, or what, decides these? | It works kind of like the stock market. Look up forex trading for details.
But basically a bunch of people make and take offers to trade one currency for another, and the rates those people are willing to trade at determine the exchange rate. | [
"Convertibility of a currency determines the ability of an individual, corporation or government to convert its local currency to another currency or vice versa with or without central bank/government intervention. Based on the above restrictions or free and readily conversion features, currencies are classified as... |
how does alka-seltzer work? | Stomach acid isn't there to break down your food, its primary role is to destroy bacteria in anything you just ate. The enzymes in your small intestine are responsible for most of the digestion.
Heartburn is caused by stomach acid finding its way up, and out of your stomach where it attacks the lining of your esophagus. Alka seltzer relieves heartburn by neutralizing that acid. | [
"It was developed by head chemist Maurice Treneer. Alka-Seltzer is marketed for relief of minor aches, pains, inflammation, fever, headache, heartburn, stomachache, indigestion, acid reflux and hangovers, while neutralizing excess stomach acid. It was launched in 1931.\n",
"Alka-Seltzer is an effervescent antacid... |
how does the opening bottle of wine in a shoe work? | Liquids don't compress. Holding the bottle upside down and striking the heel sends shockwaves through the bottle, which terminate in the spongey cork, causing it to move. Since it can't move into the liquids, it moves out of the neck. | [
"Wine bottle openers are required to open wine bottles that are stoppered with a cork. They are slowly being supplanted by the screwcap closure. There are many different inceptions of the wine bottle opener ranging from the simple corkscrew, the screwpull lever, to complicated carbon dioxide driven openers. The mos... |
Why are many diseases that are potentially lethal to animals harmless to humans (and vice versa)? | A couple points:
1) yes, the tree of life contains a wide spectrum of immune systems. The innate immune system (macrophages, granulocytes e.g. neutrophils, complement proteins, etc) varies across the animal clade. The adaptive immune system (T and B lymphocytes and the lymphoid organs) also become increasingly complex as you move from primitive to complex animals as well. Check out [this review](_URL_1_) ([pdf](_URL_5_)). Simple things like physical barriers also play a role. Our skin is tough plating of keratinized cells, exposed to the air and thus is quite dry. We are much less susceptible to fungal infections as a result (unless the skin is always kept moist, e.g. like in a shoe, allowing athlete's foot to take root). Amphibians, which are usually thin-skinned and wet, making some [fungal infections lethal to them](_URL_0_).
2) viruses, which rely on host cells to replicate and survive, are always specific for a surface receptor of some kind to invade a cell. If this receptor is absent, the virus cannot invade from outside. Viruses that can cross from one animal to another (influenza, which can infect all sorts of mammals and birds) can do so because the receptors it requires evolved back before our last common ancestor. Think about that for a second: if the flu can infect a bird and a human, it must be able to infect any other animal (that hasn't since lost these receptors) that also came from that last common ancestor. Snakes arose from that ancestor, too, so snakes should be able to get the flu, right? [Yep. They can.](_URL_2_)
3) bacteria aren't usually dependent on host cells so much as they need the right environment. Some hosts simply cannot provide the right environment for bacteria to live. Ectothermic animals like small reptiles don't keep their body temps where some bacteria grow best, but we do. Other bacteria don't grow well at high heat, so we're safer from them. In fact, this is why we have fevers when we get sick.
4) advanced parasites require very specific aspects of host biology to reproduce. [Malaria](_URL_3_) is a great example: it is adapted to live in the GI tract, then the salivary glands, of a biting mosquito. After injection into a host's blood stream, it requires erythrocytes to reproduce. Without complex interactions between the parasite and its host (which induce [complex changes in parasite biology](_URL_4_)), the parasite can't reproduce. The malaria parasite simply cannot interact with non-host physiology in a way that lets it reproduce. This is just one example of parasite/host specificity- the world of parasites is filled with far more complex examples.
Hope that answers your question! | [
"Susceptible animals include cattle, water buffalo, sheep, goats, pigs, antelope, deer, and bison. It has also been known to infect hedgehogs and elephants; llamas and alpacas may develop mild symptoms, but are resistant to the disease and do not pass it on to others of the same species. In laboratory experiments, ... |
How can exoplanets in systems whose planes do not allow transits visible to earth be detected? | There's a lot more methods to detect exoplanets. I'll summarize them :
1. Transit Photometry as you said. This detects only a tiny fraction of the exoplanets since you need aligned systems there could be tens of thousands of planets not seen because of misalignment. However this is the most successful technique right now with over 3000 detection (next best being radial velocity at around 750 detections).
2. Radial Velocity : The radial velocity method, also known as Doppler spectroscopy, is the most effective method for locating extrasolar planets with existing technology. The radial velocity method relies on the fact that a star does not remain completely stationary when it is orbited by a planet. It moves, ever so slightly, in a small circle or ellipse, responding to the gravitational tug of its smaller companion. When viewed from a distance, these slight movements affect the star's normal light spectrum. If the star is moving towards the observer, then its spectrum would appear slightly shifted towards the blue; if it is moving away, it will be shifted towards the red. Using highly sensitive spectrographs, we can track a star's spectrum, searching for periodic shifts towards the red, blue, and back again. The spectrum appears first slightly blue-shifted, and then slightly red-shifted. If the shifts are regular, repeating themselves at fixed intervals of days, months, or even years, it means that the star is moving ever so slightly back and forth - towards the Earth and then away from it in a regular cycle. This, in turn, is almost certainly caused by a body orbiting the star, and if it is of a low enough mass its a planet.
3. Microlensing : Microlensing is the only known method capable of discovering planets at truly great distances from the Earth. Whereas radial velocity searches look for planets in our immediate galactic neighborhood, up to 100 light years from Earth, and transit photometry can potentially detect planets at a distance of hundreds of light-years, microlensing can find planets orbiting stars near the center of the galaxy, thousands of light-years away. when the light emanating from a star passes very close to another star on its way to an observer on Earth, the gravity of the intermediary star will slightly bend the light rays from the source star, causing the two stars to appear farther apart than they normally would. If the source star is positioned not just close to the intermediary star when seen from Earth, but precisely behind it, this effect is multiplied. Light rays from the source star pass on all sides of the intermediary, or "lensing" star, creating what is known as an "Einstein ring". Even the most powerful Earth-bound telescope cannot resolve the separate images of the source star and the lensing star between them, seeing instead a single giant disk of light, where a star had previously been. The resulting effect is a sudden dramatic increase in the brightness of the lensing star. If a planet is positioned close enough to the lensing star so that it crosses one of the two light streams emanating from the source star, the planet's own gravity bends the light stream and temporarily produces a third image of the source star. When measured from Earth, this effect appears as a temporary spike of brightness, lasting several hours to several days, superimposed upon the regular pattern of the microlensing event. Such spikes are the telltale signs of the presence of a planet.
4. Astrometry : *Astrometry* is the method that detects the motion of a star by making precise measurements of its position on the sky. This technique can also be used to identify planets around a star by measuring tiny changes in the star's position as it wobbles around the center of mass of the planetary system. However, the precision required to detect a planet orbiting a star using this technique is extremely difficult to achieve and for this reason only one planet has been discovered by this method, although astrometry has been used to make follow-up observations for planets detected via other methods.
5. Direct Imaging : Direct imaging of exoplanets is extremely difficult, and in most cases impossible. Being small and dim planets are easily lost in the brilliant glare of the giant stars they orbit. Nevertheless, even with existing telescope technology there are special circumstances in which a planet can be directly observed.
For further reading see : [_URL_1_](_URL_1_) (you can see exact detection statistics here) and [_URL_0_](_URL_0_) | [
"The transit method of discovering exoplanets relies upon carefully monitoring the brightness of a star. If a planet is present and crosses the line of sight between Earth and the star, the star will dim at a regular interval by an amount that depends upon the radius of the transiting planet. In order to measure th... |
Why do we as humans often times feel he need to feed wild animals such as birds and fish when we get nothing in return? | Bear with me on this:
When our ancestors moved down from the trees and started to live in social groups out in the open this put selective pressure towards developing altruistic behavior. Some evolutionary biologists such as Robert Trivers argue that in humans this altruistic system is regulated by emotional dispositions. Altruism as a strategy makes sense for human-human interactions, whether we're talking symmetry-based altruism, attitudinal altruism or any other reciprocity mechanism. In this case let's focus on symmetry-based altruism with no cost to the giver, for example sharing the leftovers of a kill after you and your family are full instead of letting the remainder of it rot. There is no cost to you in sharing but you might get something in return later if you're nice and give the leftovers away to someone else. Fine and dandy. But how would this make sense for human-animal interactions? First consider that in the case above there is no cost to this behavior. Secondly we must assume that the emotional dispositions triggering the behavior isn't reserved for human-human interactions but in fact also apply in human-animal interactions. Seeing as there are no cost to sharing your spoils with animals there is also no selective pressure against this behavior. Now you may object to the assumption above stating that the emotional dispositions triggering the behavior isn't reserved for human-human interactions, but consider this: We find baby animals cute because there have been and is strong selective pressure towards bonding with our infant offspring. Recognizing infantile features in our children triggers this bonding, but a "side effect" of this mechanism is that infantile traits in animals also triggers a part of this system. We can assume the same has happened with our empathy, it was developed because of human-human social dynamics so we feel empathy for each other, but a "side effect" is that we also feel empathy for animals.
So then it follows that we feed animals because we feel compassionate towards them, and we feel compassionate towards them because there is selective pressure towards maintaining compassion and empathy in human-human interactions and no selective pressure against it from feeding animals with our surplus. It is likely that Ogg wouldn't feed the animals if he him self or his family were hungry, and so the extent of our compassion towards animals follows the same pattern as for human-human interactions, which is strongly regulated.
TLDR: Simpler explanation: we feel sorry for the hungry animals so we feed them or we feel good when we help them so we feed them. We feel this way for animals because we feel this way for each other. Biological Market Theory offer an explanation for why we feel this way and how these strategies developed over time as a result of natural selection. | [
"It is common for animals (even those like hummingbirds that have high energy needs) to forage for food until satiated, and then spend most of their time doing nothing, or at least nothing in particular. They seek to \"satisfice\" their needs rather than obtaining an optimal diet or habitat. Even diurnal animals, w... |
Can animals really predict disaster ahead? | The seizure sniffing dogs are a legit thing. They're a form of service animal that are *very* highly trained. I saw one assisting his "owner" (for lack of a better word in this context). About a minute before the guy started to seize, the dog did something (I didn't notice the signal, but apparently the guy did) to indicate that the seizure was about to start, the guy let me know what was about to happen and took a moment to roll his wheelchair over to an area with low foot traffic. The dog then kept guard on him for about a minute and a half while the seizure was happening, picked up the guy's dropped water bottle and put it back in his lap and gently nuzzled his hand once the seizure was ending. So, yeah, anecdotal, but totally legit.
As for animals detecting earthquakes, there was a really interesting segment on River Monsters where a Japanese scientist was studying the Nomazu catfish for signs of responses preceding earthquakes. Apparently, they will swim away from the bottom of the lake preceding an earthquake. I'm not sure how scientifically accurate the study was, as the fish were in tanks, but the implication and (presented) evidence seemed pretty strong to me. | [
"For centuries there have been anecdotal accounts of anomalous animal behavior preceding and associated with earthquakes. In cases where animals display unusual behavior some tens of seconds prior to a quake, it has been suggested they are responding to the P-wave. These travel through the ground about twice as fas... |
What is the correlation between decibels and sound waves? | I believe your confusion comes from thinking of decibels as being units used to measure sound waves. They aren't. The units typically used to measure sound waves are either micropascals RMS (for amplitude/pressure) or watts/meter^2 (for intensity). Decibels are, in general, just a convenient way to represent *ratios* that can vary over many [orders of magnitude](_URL_0_). In the specific case of sound pressure levels in air the decibels represent the ratio of the RMS pressure of the sound wave in question to the "reference level" which is by convention 20 uPa RMS.
So for example when someone says a sound is 60 dB they typically mean 60 dB re 20 uPa RMS which means that the pressure is 1,000 times greater than the reference level, or 20 millipascals RMS. That means that if you had a tiny and very sensitive pressure gauge and you watched the variation in pressure as the sound wave passed the reading on the pressure gauge would average out to 20 millipascals RMS. | [
"Sound is measured based on the amplitude and frequency of a sound wave. Amplitude measures how forceful the wave is. The energy in a sound wave is measured in decibels (dB), the measure of loudness, or intensity of a sound; this measurement describes the amplitude of a sound wave. Decibels (dB) are expressed in a ... |
Why does a wood stove burn more vigorously when the door is slightly ajar than when fully open? | It's air pressure. When the stove is completely open, air pressure is roughly equalized so oxygen being burned is immediately replenished. When the door is only slightly open, the fire is using up the oxygen in the oven causing an area of low pressure, so the atmosphere outside of the oven "rushes in" to attempt to equalize. So the fire is getting more oxygen dumped onto it, feeding it more oxygen to burn. | [
"The wood is very dense and produces a hot flame when burned, which functions as an excellent source of heat for barbecues and wood-burning stoves. However, the wood is not desirable for wood fireplaces because the heat causes popping, thereby increasing the risk of house fires.\n",
"The system is more efficient ... |
Did any ancient civilisation ever actually build the kinds of complex mechanical puzzles you see in popular fiction like Indiana Jones, Tomb Raider, Uncharted, National Treasure etc? | Hi, you may be interested in a couple of posts from [the FAQ](_URL_2_):
* [Were the tombs of South American civilizations the booby-trapped nightmare we see in entertainment?](_URL_1_) - South & amp; Central America, Egypt
* [Many fantasy/historical computer games and RPGs feature "dungeons", ie a large labyrinthian set of tunnels, rooms, traps etc. Is there any historical basis for dungeons?](_URL_0_) - various labyrinths & amp; catacombs
If you have follow-up questions, since these posts are archived, just ask here & tag the user's username to notify them | [
"The oldest known mechanical puzzle also comes from Greece and appeared in the 3rd century BCE. The game consisted of a square divided into 14 parts, and the aim was to create different shapes from these pieces. In Iran \"puzzle-locks\" were made as early as the 17th century (AD).\n",
"Eblong likened the game's p... |
What can we make using the 6 elements in the /r/askscience logo? | Pretty much none. Neon is a noble gas which won't form compounds with much and definitely not with all of these at any reasonable energy. You might be able to squeeze everything but Ne onto some long molecule all as substituted atoms, but even that would be a stretch. The only compound that sticks out containing two of these is potassium iodide though I'm sure cerium/scandium iodide are kicking around and maybe a few arsenic compounds as well. | [
"The company takes its name from scandium, the 21st element of the periodic table, alloys of which are used to make golf clubs and fishing rods. Element 21 claims that their use of scandium improves performance compared with that of other commonly used metals.\n",
"The symbols of chemical elements are evenly spac... |
When 'unlikely' animals tolerate the company of each other, what is happening at a psychological level? | A polite reminder. This is AskScience. No layman speculation, no guessing, no anecdotes, no jokes. Please check the sidebar if you're unsure whether your answer should be here or not. | [
"In real life situations, animals (including humans) have to cope with stresses generated within their own species, during their interactions with conspecifics, especially due to recurrent struggles over the control of limited resources, mates and social positions (Bjorkqvist, 2001; Rohde, 2001; Allen & Badcock, 20... |
Before their double-helixed DNA model, Watson and Crick made a "failed" model. What did this model look like? | Apparently it was a triple helix with three sugar-phosphate backbones in the middle with the Nitrogen bases sticking out.
_URL_0_
That is my google fu however not my expertise. I would not be a good person to describe what that would actually look like. | [
"Late in 1951, Francis Crick started working with James Watson at the Cavendish Laboratory within the University of Cambridge. In 1953, Watson and Crick suggested what is now accepted as the first correct double-helix model of DNA structure in the journal \"Nature\". Their double-helix, molecular model of DNA was t... |
Is remembering a dream the same mechanism as remembering something in real life? | Memory isn't as perfect as we'd like to think it is to begin with. Then, on top of that, the altered state of consciousness the brain is in during sleep can (essentially) shut down parts of the brain, particularly the prefrontal cortex. Since memory requires many neurons firing in concert, having fewer neurons functional while sleeping likely causes the memory not to be encoded. Further, dreams are influenced by experiences so there's probably blurring between reality and dreams when it comes to forming memories.
& #x200B;
tl;dr: Same mechanism, but fewer active neurons to encode memory. | [
"For some people, sensations from the previous night's dreams are sometimes spontaneously experienced in falling asleep. However they are usually too slight and fleeting to allow dream recall. At least 95% of all dreams are not remembered. Certain brain chemicals necessary for converting short-term memories into lo... |
If I shoot a car with an EMP gun, what would happen? | Devices like this exist and are being marketed to police departments around the world as a means for terminating dangerous car chases. I believe there is some safety cost/benefit calculation at work. The burning out of all electronics will effectively destroy/total the car. The driver may in fact lose control of the vehicle, but this is considered preferable to the alternative of allowing him to continue and put other people's lives at risk. There is also considerable shielding required for the police car to prevent the pulse from also destroying the police vehicle electronics. There is the possibility of other nearby vehicles in the path of the pulse also being damaged (although the range of the pulse is only 20-30 feet so it is not a major consideration). If you built one on your own, you might be able to get away with it, however, you might also end up disabling your own vehicle in the process and get identified as the culprit
| [
"BULLET::::- In the 2008 series \"Knight Rider\" the co-protagonist—a Ford Shelby GT500KR named KITT which is capable of driving itself, talking, and firing all sorts of offensive and defensive weapons—has a small EMP device on board. The car is most often seen deploying this weapon to disable vehicles that it purs... |
why when there is a silent we often hear a beep sound? | Yer not alone in askin', and kind strangers have explained that this is *tinnitus:*
1. [ELI5: what is the ringing noise we hear when there's silence? ](_URL_3_) ^(_ > 100 comments_)
1. [ELI5: Why do my ears ring in a quiet room? ](_URL_2_) ^(_12 comments_)
1. [ELI5: What is the beeping sound I hear sometimes when it's completely silent? ](_URL_1_) ^(_4 comments_)
1. [ELI5: What is happening when you randomly hear a weird ringing in one or both of your ears? ](_URL_0_) ^(_69 comments_)
1. [ELI5: Why do I sometimes suddenly hear a ringing in one of my ears? ](_URL_4_) ^(_86 comments_)
| [
"Beeps are also used as a warning when a truck, lorry or bus is reversing. It can also be used to define the sound produced by a car horn. Colloquially, beep is also used to refer to the action of honking the car horn at someone, (e.g., \"Why did that guy beep at me?\"), and is more likely to be used with vehicles ... |
how does the amazon go store figure out what you are purchasing exactly? | Holy crud, this is a neat idea. Here's some speculation, until we can get a concrete answer from Ol' Amazon themselves.
* since you need the app, and need to apparently launch it when walking in, that's probably how the store determines that you in particular are the person who just entered. Bluetooth might also be involved, as that's a short-range wireless technology that can provide a unique identifier and help it accurately ballpark who's where in the building.
* cameras in the store are connected to a computer system that can tell people apart (that'd be some machine learning bit right there) and since it knows who just walked in the door, can keep an eye on you as you move about the building.
* sensors on the shelves know when an object has been taken. If it detects that a pudding cup got picked up, and knows by the cameras that you are standing right in front of the pudding, it assumes that you're the person who did so. | [
"Amazon announced in June 2019, that Amazon shoppers will be able to pick up their purchases at designated counters inside more than 100 Rite Aid stores across the US. The new service is called Counter and launches in the US after finding success in the UK with the Next clothing chain and in Italy with Giunti Al Pu... |
how was the dnc primary "rigged"? | The DNC is supposed to be neutral. The e-mails released by wikileaks from the DNC showed that they were actively trying to help Hilary's nomination and hurt Bernie's. That was a violation of their charter. In addition, after the leaks and subsequent calls for her resignation, the head of the DNC, Debbie Wasserman Schulz, was immediately appointed as chair of one of Hilary's election committees. In short, it was not a fair primary for Bernie or his supporters. | [
"The Democratic National Committee (DNC) proposed a new schedule and a new rule set for the 2008 Presidential primary elections. Among the changes: the primary election cycle would start nearly a year earlier than in previous cycles, states from the West and the South would be included in the earlier part of the sc... |
why did slave owners/ traders feel it was necessary to convert slaves to christianity? if slaves were considered nothing more than property why was their salvation important? | All the answers here are correct for a certain historical period. However, it's important to remember that for the majority of the time the Atlantic slave trade was in operation, religious conversion was not a priority. There were a number of reasons for this:
1. In many colonies the average slave lived only 5-10 years, so conversion was deemed not worth the effort. This was especially true in the Caribbean. It was only when the mortality rate dropped and whites began to see established intergenerational slave communities that anyone thought it might be worth trying to make new converts.
2. In colonies with a higher proportion of slaves (e.g. Barbados, where whites numbered less than 10% of the total population) there was a constant fear of slave uprisings. The authorities wanted to restrict Christianity because they feared that some of the Bible's more humane messages might give their slaves some revolutionary ideas.
3. More generally, slave owners throughout the Americas were (kind of) concerned about the theological implications of making their slaves Christians. There are all kinds of warnings in the Bible and in Catholic and Anglican texts about enslaving co-religionists. Slave owners didn't think it would cause much trouble, but they were concerned that if they converted their human chattel there might be a chance that the authorities would then declare the enslavement of Christians unlawful. And that would be a very expensive mistake.
Now, in the British colonies in continental North America, the people who made religious decisions and the people who mad economic decisions were one and the same. So there was no danger of the local plantation owner having his slaves preached at by the church deacon, because there was a good chance that they were the same man. Religion at the time was about hierarchy, but, contrary to the responses here, the best way to keep a slave population at the bottom of the social hierarchy is to never initiate them into it in the first place.
What ended up happening (again, in the 13 colonies - my knowledge of non-British slave systems is patchy) was that in the early-mid 18th century, the first in a series of religious revivals swept across the colonies. Now religion was rendered less hierarchical, and people started to think that anyone could talk to (a) God, and (b) other people about God. So now it's not only the local vicar who can convert heathens, it's any God-fearing Christian.
The situation as it subsequently developed was not therefore of the slave-owning class's making. Zealous individuals converted slaves of their own initiative and against the express wishes of the colonial elite. Once that damage was done, the slave owners just had to make the best of a bad situation by emphasising (as others here have pointed out) the hierarchical bits of Christianity. But it's wrong to say that the beneficiaries of the slave system actively converted anyone.
**TLDR: Slave owners never really converted anyone because slaves were easier to handle if they weren't Christian. It was only at the tail end of the Atlantic slave era that any widespread conversions started to happen.**
SOURCE: *Inhuman Bondage* by David Brion Davis. | [
"Slave-owners weren’t keen to have their slaves baptised as Christian converts could not be sold. Mostly freed slaves were therefore baptised and could then become members of the Dutch Reformed Church in South Africa (NGK). This led to the directors of SA Mission Society establishing their own congregation. It was ... |
why there is a difference in the way medication is administered. specifically, what is the difference between pills and injections. | Injections, if through an IV, go straight into the bloodstream. Pills have to be digested before entering the bloodstream, so generally less gets in (or if something is meant to work in the gastrointestinal tract it would be taken as a pill.)
Certain injections might only have a local effect (like a corticosteroid injection for a joint,) which would necessitate injection into a specific body part. | [
"A wide variety of drugs are injected, often opioids: these may include legally prescribed medicines and medication such as morphine, as well as stronger compounds often favored in recreational drug use, which are often illegal. Although there are various methods of taking drugs, injection is favoured by some peopl... |
What happens to the blood in an uterus during missed periods? | Tl;dr the lining usually doesn't thicken in these cases
The causes of frequently irregular periods (oligomenorrhoea) or complete lack of them (amenorrhoea) are normally always hormones.
To put this into context with an example, breastfeeding results in high levels of the hormone prolactin, which then inhibits release of FSH and LH. These hormones drive oestrogen production, which is responsible for thickening the endometrium - the lining of the uterus. Without this, the uterus may never acquire a thick lining at all. Similarly excess stress releases hormones like cortisol which can also affect FSH and LH.
There are other, non-endocrine (non hormone related) causes but they're rare. Examples of such conditions include uterine agenesis (congenital - from birth) and endometrial fibrosis (acquired) but I'm not too familiar with those. In the case of the former, hopefully you can see that if the uterus does not form (agenesis) then its lining can't be thickened!
I don't know of the existence of a disease where the uterine lining remains but ovulation doesn't occur. Without progesterone formed by the corpus luteum post-ovulation, the lining would degrade anyway. Perhaps some sort of progesterone-producing tumour might do it but that would be mere speculation since progesterone has effects on FSH and LH anyway.
Anyway I've rambled on for far too long. Hope I helped! | [
"Couvelaire uterus is a phenomenon wherein the retroplacental blood may penetrate through the thickness of the wall of the uterus into the peritoneal cavity. This may occur after abruptio placentae. The hemorrhage that gets into the decidua basalis ultimately splits the decidua, and the haematoma may remain within ... |
Why do some cameras get really grainy when taking photos or videos in low-light/no-light? | Various kinds of noise. As the light goes down, you get less light (signal) but not less noise.
But what is the noise? One type of noise is read noise. Read noise is a constant caused by imperfections in the technology used to detect the light. For example, an amplifier might accidentally amplify stray currents and mix that in with the signal. This type of noise gets better with more advanced sensor technology.
Another type of noise is shot noise. Shot noise is caused by the fact that light is made up of photons. A bright light might shine billions of photons a second, but a very dim light might send 10s of photons a second. If you don't gater enough light to get lots of photons, you get noise.
The only way to reduce this is to capture more photons by increasing the size of the sensor/objective to gather more light or increasing the time of exposure.
Some cameras have larger sensors and larger aperatures meaning they gather more light.
There are other kinds of noise, but this shows noise levels in one device vs another is influenced by the quality of the sensor tech and the physical light gathering ability of the optics. | [
"Because the effect is caused by the relative motion between the camera, and the objects and scene, motion blur may be avoided by panning the camera to track those moving objects. In this case, even with long exposure times, the objects will appear sharper, and the background more blurred.\n",
"Some still camera ... |
the phrase 'have your cake and eat it, too.' | Once you eat the cake, it's gone. You don't have it anymore. You cannot have both | [
"The phrase \"Let them eat cake\" is often attributed to Marie Antoinette, but there is no evidence she ever uttered it, and it is now generally regarded as a \"journalistic cliché\". It may have been a rumor started by angry French peasants as a form of libel. This phrase originally appeared in Book VI of the firs... |
How do large batteries work (like the Tesla house unit)? and What are the barriers around efficient large scale energy storage? |
The tesla house battery is a basically a lithium Ion battery,same as yor phone just in Large. Here's a pretty good [link](_URL_0_) to how they work.
Barriers are :the low engie density in these types of. I think the Tesla battery weighs 100KG an can store up to 13.5 Kw/H. That equates to ~4KG of diesel.
Also the charge degrades over large time spans due to leak currents and even by high temperature.
With our current technologies storing electrical energie is quite inefficient and expensive. And likely to not change all to fast, after all li batterys were around ~1915.
Hower a a lot of money and manhours are Invested into research so we might see completely new technologies or a battery operating on simmylar principles but with different materials. | [
"Contrary to electric vehicle applications, batteries for stationary storage do not suffer from mass or volume constraints. However, due to the large amounts of energy and power implied, the cost per power or energy unit is crucial. The relevant metrics to assess the interest of a technology for grid-scale storage ... |
why is testosterone legally prescribed for transgender but not bodybuilding/muscle gain? | Because the trans man has a recognized medical condition and the dude just trying to bulk up doesn't. And because the trans man is only going to normal male levels of testosterone - which are relatively safe - not pushing it to dangerously high levels by adding more on top of typical male production. | [
"Transgender women, known as \"kathoeys\", have access to hormones through non-prescription sources. This kind of access is a result of the low availability and expense of transgender health care clinics. However, transgender men have difficulty gaining access to hormones such as testosterone in Thailand because it... |
Are there other cultures that have a long tradition of personal names appropriated from languages other than the ones primarily spoken by that culture? | Late Ancient Hebrew did this a ton. Many names were Greek. Variants of "Alexander" were especially popular. Other names were Aramaic, but the two languages are so similar that distinguishing them in names is often difficult. Yiddish does this two. Many of the names are Hebrew names or Hebrew words, and though some of them correspond with ones generally used in Europe, they come straight from the Hebrew, rather than through Latin and/or Greek, so they're not really recognizable. | [
"However, in some areas of the world, many people are known by a single name, and so are said to be mononymous. Still other cultures lack the concept of specific, fixed names designating people, either individually or collectively. Certain isolated tribes, such as the Machiguenga of the Amazon, do not use personal ... |
Why didn't any Ottoman Sultans perform Hajj when they declared themselves Caliphs of Islam? | It's mostly logistical issues. A sultan traveling from Istanbul to Mekka would need a huge army for protection. Traveling there and back would take months even years with a massive entourage which would destabilize the government back home and probably any province they pass through. | [
"When the Ottomans conquered Mamluk territory in 1517, the role of the Ottoman sultan in the Hijaz was first and foremost to take care of the Holy Cities of Mecca and Medina, and provide safe passage for the many Muslims from various regions who travelled to Mecca in order to perform the Hajj. The Sultan was someti... |
if the sun is on the other side of the earth at night, how does it stay so warm during the summer? | Okay, the only difference between summer and winter as far as heat goes is the angle that the sun hits the earth. With the axis, the sun hits at a steeper angle (ie. Straight up/down) which means greater concentration of energy, think: smaller area, same heat energy. That being said, the world and atmosphere absorb a ton of heat, and hold it as well, that is where the heat sticking around at night comes from. | [
"During winter in either hemisphere, the lower altitude of the Sun causes the sunlight to hit the Earth at an oblique angle. Thus a lower amount of solar radiation strikes the Earth per unit of surface area. Furthermore, the light must travel a longer distance through the atmosphere, allowing the atmosphere to diss... |
how does the fourth amendment prevent government reach into government cell phones? | Your quote provides the answer.
The constitution including the bill of rights defines what the government can, and can't, do. (It does not apply directly to private employers, of course.)
You don't automatically lose rights as a result of becoming a government employee; but you may waive those rights at times in exchange for something else, such as having a certain job. | [
"The bill then states: \"The Fourth Amendment to the Constitution shall not be construed to allow any agency of the United States Government to search the phone records of Americans without a warrant based on probable cause.\"\n",
"In November 2017, the United States Supreme Court ruled in \"Carpenter v. United S... |
why, in the event a hurricane or super storm heading for a vulnerable area, can't we launch and detonate explosives within the storm to disperse it? | I think you've been watching too much Sharknado. It doesn't work that way in real life.
Besides, hurricanes can be hundreds of miles across. There's no way enough explosives could be launched to affect that, especially without causing massive environmental damage. | [
"Certain targets, such as bridges, historically could be attacked only by manually placed explosives. With the advent of precision-guided munitions, the destructive part of the raid may involve the SF unit controlling air strikes. Air strikes, however, are practical only when U.S. involvement is not hidden.\n",
"... |
Why is the star in the "star and crescent" symbol of Ottoman Empire/Islam not exactly upright geometrically? | The design is specified by a 1930s law. The alignment of the star is such that one of the points of the star points directly left. So it's aligned "exactly" on a horizontal axis -- relative to the crescent -- rather than a vertical axis. See _URL_0_ and the sources cited therein. | [
"The star and crescent symbol became strongly associated with the Ottoman Empire in the 19th century, a symbol that had been used throughout the Middle East extending back to pre-Islamic times, especially in the Byzantine Empire and Crusader States which occupied the lands later assumed by the Ottoman Empire. By ex... |
what makes soda taste so bad when you leave it out for some time? | It doesn't taste bad at all, you're just losing the carbonation so there isn't that stimulating feeling. If soda was made without carbonation I'm sure there would be a lot less soda drinkers in the world | [
"A large number of soda pops are acidic as are many fruits, sauces and other foods. Drinking acidic drinks over a long period and continuous sipping may erode the tooth enamel. A 2007 study determined that some flavored sparkling waters are as erosive or more so than orange juice.\n",
"OK Soda had a more \"citric... |
why is it worthwhile to separate colors from whites in laundry? | In the past, you would often add bleach to whites to help clean them. However, it would destroy colored dyes, so you would need to separate them first. | [
"White fabrics acquire a slight color cast after use (usually grey or yellow). Since blue and yellow are complementary colors in the subtractive color model of color perception, adding a trace of blue color to the slightly off-white color of these fabrics makes them appear whiter. Laundry detergents may also use fl... |
why does peanut butter turn shiny after being spread? | The oil is more visible when the peanut butter is spread thin | [
"Peanut butter is a food paste or spread made from ground dry roasted peanuts. It often contains additional ingredients that modify the taste or texture, such as salt, sweeteners or emulsifiers. Peanut butter is served as a spread on bread, toast or crackers, and used to make sandwiches (notably the peanut butter a... |
i saw a commercial for a car dealership offering you a car for $88 down and $88 per month even if you have bad or no credit. what's the catch? how can they do this? | You will be paying interest on that car for decades. | [
"Depending on the type of car purchased and \"the difference in fuel economy between the purchased vehicle and the trade-in vehicle\", the amount of the credit given in the form of vouchers to eligible customers is either $3,500 or $4,500. New car dealers will be able to reduce the purchase price by the amount of t... |
Do dissolved solids (I.E. sugar in coffee) have the same volume as their constituents? | Generally, no. Archimedes does not apply when you're dissolving a solid.
Depending on the nature of coordination in solution, a solid can dissolve and displace more or less volume than the solid would. If everything behaved like an ideal solution, this wouldn't be the case, but mixtures involve [partial molar properties](_URL_0_) that take place and break away from additive properties like volumes.
Changes in water order can change the local volume in similar ways to how ice takes up more volume than liquid water. | [
"When a sugar solution is measured by refractometer or density meter, the °Bx or °P value obtained by entry into the appropriate table only represents the amount of dry solids dissolved in the sample if the dry solids are exclusively sucrose. This is seldom the case. Grape juice (must), for example, contains little... |
When light is reflected off a surface, is that same photon being bounced back or is that photon absorbed and then another one emitted? | To the extent I understand it, photons don't have an "identity", there is no way to know, and use whatever assumption works for the problem you are solving.
It is a very unsatisfying answer, but physics has a lot of that. | [
"Total external reflection is the situation where the light starts in air and vacuum (refractive index 1), and bounces off a material with index of refraction less than 1. For example, in X-rays, the refractive index is frequently slightly less than 1, and therefore total external reflection can happen at a glancin... |
- if deadly viruses, like ebola, ultimately kill the host, how do they evolve, or persist to an epidemic level? | It isn't a good way to spread a virus strain.
That's precisely why these epidemic diseases kill thousands and then burn out. They massacre their food supply and host by accident and die with them.
The most successful viruses have no symptoms. They live in you and transfer among humanity without alarming our immune system or killing the host.
Ebola and others like it have accidentally infected humans instead of their preferred animal hosts where they generate little to no immune response or symptoms. | [
"Generally, if a virus kills its host too quickly, the host will not have a chance to come in contact with other hosts and transmit the virus before dying. However, in serial passage, when a virus was being transmitted from host to host regardless of its virulence, such as Subbaro’s experiment, the viruses that gro... |
In my high school history classes, the fate of the USS Maine is usually described as a boiler-room accident or a deliberate "false-flag attack" to provoke war with Spain. What is the current academic consensus on the disaster? | **The current academic consensus is that there is no consensus.**
Let's review.
[There have been four major investigations into the sinking of the *Maine*:](_URL_0_)
* The first took place in 1898, immediately after the sinking. The McKinley administration created a naval board of inquiry that concluded unanimously that the ship was sunk "only by the explosion of a mine situated under the bottom of the ship at about frame 18, and somewhat on the port side of the ship."
* The second investigation took place in 1911. President Taft ordered the Army Corps of Engineers to study the wreckage. Never to do anything by halves, the Corps built a cofferdam around the ship's wreckage, pumped out all the water and examined the exposed hull. Hundreds of photographs were taken, and the Corps removed much of the wreckage. A revised board of inquiry reaffirmed that a mine sank the ship, but it concluded the mine had detonated at a different place.
* The third investigation came in 1974, when Admiral Hyman Rickover, father of the nuclear Navy, asked historians to re-examine the case. The historians dredged Spanish archives and consulted with foreign militaries about their own experience with internal explosions. They consulted professional engineers to analyze the 1911 photographs and took into context the "natural tendency to look for reasons for the loss that did not reflect upon the Navy." This study resulted in [*How the Battleship Maine was Destroyed*](_URL_1_). That book concluded the explosion was, "without a doubt," internal.
* The fourth investigation came in 1999 and was conducted by the National Geographic Society. NGS commissioned a study by Advanced Marine Enterprises, which conducted the first detailed computer modeling of the disaster. AME stated that a coal fire within a bunker could have raised the temperature within one of the *Maine*'s magazines to hazardous levels within a few hours. As to a mine strike, AME found that even a simple mine consisting of 100 pounds of black powder and a contact fuse could have sunk the ship. "If so, the mine must have been perfectly
placed, which under the circumstances would have been as much a matter of luck as
skill.”
While it did not discount either option for the *Maine*'s destruction, AME ultimately concluded (based on the 1911 photographs) that there was more evidence in favor of the *Maine*'s destruction by a mine.
[Let's review the competing evidence for each side, and you can make up your mind](_URL_2_).
For a mine detonation:
• The Maine carried a type of bituminous coal that rarely spontaneously combusted.
• Bunker A16 was not situated by a boiler or any other external heat source, and spontaneous combustion does not occur unless there is a heat source to speed up the process.
• When Bunker A16 was inspected the morning of the disaster, the temperature was only 59 degrees Fahrenheit.
• The Maine's temperature sensor system did not indicate any dangerous rise in temperature on the morning of the last inspection.
• Discipline on the Maine was excellent, and regular inspections of coal bunkers for hazards, as well as the implementation of precautions for preventing bunker fires, were diligently carried out.
• A number of witnesses stated that they heard two distinct explosions several seconds apart. If anything else besides a mine had triggered the magazine explosion, then witnesses would have only heard one blast, because the only explosion would have been that of the magazines.
• The only reason that two explosions would have been heard is if something besides the magazine had exploded, such as a mine.
• Divers who examined the bottom plates of the Maine reported that they were bent inward. This was subsequently confirmed with 1911 photographs.
• Divers spotted a large hole on the floor of Havana harbor, something that would not have occurred with a magazine explosion. Those are directed upward, toward the path of least resistance.
For an internal explosion:
• Spontaneous combustion of coal was a fairly frequent problem on ships built after the American Civil War. Coal was exposed to air, oxidized and began burning. The heat was transferred to the ship's magazines, causing an explosion.
• The *Maine*'s bituminous coal was more subject to spontaneous combustion than anthracite coal. Furthermore, higher moisture content increases the danger of spontaneous combustion. The *Maine* had spent most of the previous three months in Key West or nearby, where tropical moisture predominates.
• Bunker A16 had not been inspected since 8 a.m. The explosion occurred around 9:40 p.m. There was ample time (12 hours) for a coal bunker fire to smolder into a disaster.
• From 1894 to 1908, more than 20 coal bunker fires were reported on U.S. Navy ships.
• No one reported seeing a geyser of water thrown up during the explosion, a common sight when mines explode underwater.
• No one reported seeing any dead fish in the harbor and these would have been seen if there had been an external blast.
• Inward bending of the plates could have been caused by water displacement occurring at the same time the front of the ship was breaking away from the rear.
***
**ADVERTISEMENT:** Read and subscribe to /r/100yearsago | [
"USS \"Maine\" (ACR-1) was a United States Navy ship that sank in Havana Harbor in February 1898, contributing to the outbreak of the Spanish–American War in April. American newspapers, engaging in yellow journalism to boost circulation, claimed that the Spanish were responsible for the ship's destruction. The phra... |
why do tech manufacturers region lock their devices? | It's pretty simple, depending on the region you sell your product the highest price people are ready to pay for your device can differ quite significantly. If you have the same price all over the world you wont sell in some regions. If you have different prices and don't region lock people will just buy from the cheapest region. The "solution" is region lock.
Tl;dr: it's because of money. | [
"Adapters (sometimes called \"dongles\") allow connecting a peripheral device with one plug to a different jack on the computer. They are often used to connect modern devices to a legacy port on an old system, or legacy devices to a modern port. Such adapters may be entirely passive, or contain active circuitry.\n"... |
What are some unsolved problems in Computer Science? | The biggest and probably the most famous problem is the P-NP problem. It concerns decision problems (problems that can be answered with a "yes" or a "no"). There are two important classes of decision problems - P and NP. P problems are those which can be decided in polynomial time. NP problems are those whose solutions can be verified in polynomial time. It's simple to see that P is a subset of NP - if you can solve a problem in polynomial time, you can verify a solution in polynomial time just by solving it. The big question is, is P a proper subset of NP - in other words, are there decision problems whose solutions can be verified in polynomial time, but cannot be solved in polynomial time?
Another famous problem is the RSA problem - can a semiprime (a product of two distinct primes) be factored efficiently (in polynomial time)? This is related to the P-NP problem, but it's not a decision problem, so it's a bit different. It's called the RSA problem because the RSA cryptosystem relies on semiprimes being difficult to factor. If an efficient factoring method was found, RSA would be easy to crack, which would be bad. | [
"This article is a list of unsolved problems in computer science. A problem in computer science is considered unsolved when no solution is known, or when experts in the field disagree about proposed solutions.\n",
"Perhaps the most important open problem in all of computer science is the question of whether a cer... |
why did saber-tooth cats have such big fangs? | I'm just guessing here, but maybe it preyed on larger animals. Those fangs would have sunk deep into flesh. | [
"The different groups of saber-toothed cats evolved their saber-toothed characteristics entirely independently. They are most known for having maxillary canines which extended down from the mouth even when the mouth was closed. Saber-toothed cats were generally more robust than today's cats and were quite bear-like... |
when people say how fast something in space is moving what reference point are they using? | It is usually going to be with reference to the body that exerts the dominant gravitational force in the region.
The speed of a probe sent to orbit Europa would first be expressed with reference to the earth, then the sun, then Jupiter, then finally Europa. Possibly other planets or moons if a gravitational assist was involved. | [
"Alternatively, we could choose a frame of reference \"S′\" situated in the first car. In this case, the first car is stationary and the second car is approaching from behind at a speed of . In order to catch up to the first car, it will take a time of , that is, 25 seconds, as before. Note how much easier the prob... |
how do countries pay for maternity leave? | In France it is payed by the Social security (healthcare etc..), not the employer. | [
"Paid maternity leave is important for women to take time away from work to bond with a child without financial pressures. Of the 193 United Nations countries, only a handful do not have a paid-parental-leave policy: New Guinea, Suriname, the United States and a few South Pacific island nations. The international h... |
What is the Eastern Front known as in Russia? | This can be a bit confusing, so I will use *italics for Latinized Russian* and **bold for English translations**
If you're asking about the Eastern Front of WWII, the single massive continuous front (geographic area) is known by Russians as Великая Отечественная Война (*Velikaya Otechestvennaya Voyna*), meaning **Great Patriotic War**
The **Patriotic War** (*Otechestvennaya Voyna*) would be WWI, which is also sometimes known as Вторая Отечественная война (*Vtoraya Otechestvennaya Voyna*), or **Second Fatherland War**, with the **First Fatherland War** being the war of Napoleon's invasion, which confusingly was the original **Patriotic War**
Confusingly for English-speakers, the **Great Patriotic War** consisted of several military units also known as фронт (*front* in Latinized Russian), which in this case means a Soviet military formation equivalent to an army group of most other militaries, and not the geographic area you are asking about. You can see [the flag on the right in this video](_URL_0_) says "1 БЕЛОРУССКИЙ ФРОНТ" (*1st Belorussian Front* in Latinized Russian), which most accurately translates to **1st Belorussian Army Group** in American English
Because of the two meanings for "front", it would be confusing to read, "The **Eastern Front** had many *fronts*." The proper translation would be, "The **Great Patriotic War** involved many **army groups**, some of which were named *1st Belorussian Front* (**1st Belorussian Army Group**), the *2nd Belorussian Front* (**2nd Belorussian Army Group**), and *1st Ukrainian Front* (**1st Ukrainian Army Group**)." | [
"\"Eastern Front\" is a corps-level simulation of Operation Barbarossa, the German invasion of the Soviet Union in 1941. The player controls the Germans, in white, while the computer plays the Russians, in red. Units are represented as boxes for armored corps or cavalry, and crosses for infantry, an attempt to repl... |
How are new stars born following the death of old stars? Surely all the hydrogen has gone- or the previous star wouldn't have died? | Stars can only fuse hydrogen (and in the latter stages other elements) in their cores, where the temperature is high enough to start fusion. The vast majority of the hydrogen is outside the core (90% orso) and gets blown away when the star is dieing. This forms the material for the next generation of stars | [
"According to theories of stellar formation, as in other stellar nurseries, the stars in Henize 206 were created after a dying star, or supernova, exploded, sending intense shockwaves through clouds of cosmic gas and dust. The gas and dust were subsequently compressed into large groups, then gravity further condens... |
When did "Right by conquest" stop being a thing? | Actually way later, up until WW2 right by conquest was recognized as international law. "War of aggression" as a crime was only codified in the Nuermberg Principles after WW2 and made a UN resolution in 1974 (UN resolution 3314).
The principle of Right by Conquest was first diminished in the Kellogg-Briand Pact (1928) which was, in a very basic summary, a group of countries promising not to declare war to resolve their differences. It didn't work, the nations still went to war, they just didn't declare war, but it was a first step towards the establishment of "War of aggression" as a crime under international law. | [
"The right of conquest is the right of a conqueror to territory taken by force of arms. It was traditionally a principle of international law that has gradually given way in modern times until its proscription after World War II when the crime of war of aggression was first codified in the Nuremberg Principles. In ... |
It is said that Benedict Arnold died wishing to wear his Continental Army uniform, expressing regret at his betrayal. This may be legend, but do we know how he really felt in his later years about what he did, or his attitude towards the United States? | Not to discourage further discussion, but see /u/uncovered-history's answer in [this post](_URL_0_). He also addresses the Continental Army uniform question a little further down the comment chain. | [
"Benedict Arnold (June 14, 1801) was an American military officer who served as a general during the American Revolutionary War, fighting for the American Continental Army before defecting to the British in 1780. George Washington had given him his fullest trust and placed him in command of the fortifications at We... |
What is the relationship between C-reactive proteins and inflammation with depression? | Some cytokines can cross/be actively transported across the blood brain barrier. There are also cytokine receptors that stimulate the vagus nerve, providing feedback to the brain. There was a study specifically investigating the use of an anti-inflammatory drug, infliximab, which antagonizes tumor necrosis factor alpha (TNF-alpha), in people with treatment resistant depression. What they found was that overall, infliximab was not more effective than placebo. However, in those patients with high levels of CRP at pre-treatment, infliximab was more effective than placebo, while in those patients with low CRP, infliximab was *less* effective than placebo. [Here's a picture of that.](_URL_1_) What's noteworthy is that infliximab is too big of a molecule to cross the blood brain barrier, so any direct effects it has happen in the body. [Here's the full text of the source article.](_URL_0_) | [
"Various review have found that general inflammation may play a role in depression. One meta analysis of cytokines in people with MDD found increased IL-6 and TNF-a levels relative to controls. The first theories came about when it was noticed that interferon therapy caused depression in a large number of people re... |
What Slows a Computer Down? | This is a complicated question to answer.
First and foremost -- Did you upgrade OS versions in the meantime or are you running the same OS and exact same software as before?
If you upgraded the OS, then that could be part of the problem. Newer versions of Windows and OSX often are designed around newer computers. Older machines just can't keep up -- even if the OS is marketed as capable of running on older hardware. Sometimes newer OS versions fix and address the sins of previous versions, so they can get faster than older versions, but more often than not newer OS's are more "bloated". (Bloat is a general euphemism for bigger code that does more, fancier graphics and effects, etc -- all of it taking up resources at runtime and on the disk).
It depends on the exact OS release, basically. But the overall trend is towards newer OS = more of a resource hog.
Secondly, if you upgraded the installed programs in the meantime (via updates, etc) they can also be resource hogs for the same reason as the OS -- they get bloated over time as the programmers add features and subfeatures and noone complains because the software is assumed to run on newer machines that "can handle it".
Newer software assumes you are running a newer machine, so it takes up more CPU and RAM. Programmers sometimes don't bother to optimize their code when it runs "fast enough" on a newer machine. Or they allocate more memory than they need or use algorithms that are hungrier for resources.
Add to that the trend towards slower interpreted languages for more and more software (such as embedding javascript code or other scripting languages in applications to form part of the application logic, etc).
Another factor could be that your computer's hard disk is fragmented (usually an issue on Windows -- less of an issue on OSX).
Another factor could be that you have malware/adware or other background programs running that you accumulated over time as you installed more and more hardware and software. Some driver packages or other software you may install like to install all sorts of services and daemons, systray icons, toolbars you don't use, etc. My mouse for example came with an annoying systray icon utility that was absolutely useless but took up RAM and CPU occasionally for no reason.
Yet another factor is that if your computer is old, its cooling may be faulty. Your fans may be spinning slower and/or dust may have accumulated as a sort of 'blanket' on your motherboard/logic board. If your computer is running hotter, certain processors (such as Intel), will purposely slow down the CPU so that it doesn't heat up as much. To you, this will look like a performance hit.
It could be any or all of the above factors, basically.
But the computer itself, at least in theory, if kept clean inside and the fans are running, etc, doesn't "age" like a person does. It should run just as fast 10 years down the line as it did the day you bought it, assuming the hardware hasn't gone faulty (particularly read errors on the disk can delay things) and the cooling is working right.
| [
"It was possible to increase the speed of the computer by using POKE 65495,0 which accelerates the ROM-resident BASIC interpreter, but temporarily disables correct functioning of the cassette/printer ports. Manufacturing variances mean that not all Dragons are able to function at this higher speed, and use of this ... |
Are any mammals as sexually dimorphic as humans? | Male gorillas are over twice the size of female gorillas, probably the largest sexual dimorphism among primates. The big [silverbacks](_URL_0_) you see in zoos are all males. Big differences like this are also seen in orangutans, mandrills, baboons, proboscis monkeys, hamadryas.
Sperm whale males weigh about 3 times as much as females. Pretty much all pinnipeds (seals, sea lions) show huge sexual dimorphism, with males being much larger than females.
As for features other than size, it's probably because you're not used to distinguishing between members of other species. Humans are very much attuned to detecting small differences in the facial features of other humans. And not just other humans, we are even more finely attuned to detecting these differences in our own ethnicity or geographical neighborhood. I'm guessing a farmer or herdsman is better able to tell the sex of a domestic animal at a glance than the average person, or a vet, or dog or cat breeder, for example. But sexual dimorphism is very very common among mammals. | [
"The reduced degree of sexual dimorphism is primarily visible in the reduction of the male canine tooth relative to other ape species (except gibbons). Another important physiological change related to sexuality in humans was the evolution of hidden estrus. Humans are the only ape in which the female is intermitten... |
how do jets that are taxiing stop and start moving without trying their engines up or down ? | To get moving again, they DO spin up their engines.... modern high bypass turbofans have ridiculous thrust, just bumping them up a little from idle is enough to get an airliner moving again. To stop, they have brakes. These brakes are ridiculously powerful, more than enough to stop an airliner moving along a taxiway. Pilots are just careful to use _enough_ brakes to slow the aircraft, if they were to stomp or lean on the brakes hard enough people and improperly secured baggage would fly around the cabin.
In fact, one of the standard certification tests for a new airliner is a takeoff abort test, or a takeoff "reject". (this has nothing to do with your question, but it's super cool). If the plane hasn't reached the critical V1 takeoff speed by a certain point of the runway, they're supposed to abort the takeoff. This means slamming the brakes on and engaging the engine reverse thrust. But to certify, the brakes alone have to be enough to bring the craft to a halt. [Usually this will leave the brake discs red-hot and more often than not pop a few tires due to the heat. Its quite spectacular.](_URL_2_)
[Here's a 777 doing such a test. The brakes are literally on fire.](_URL_0_)
[787-8 rejected takeoff with some good explanation](_URL_1_) | [
"When taxiing, aircraft travel slowly. This ensures that they can be stopped quickly and do not risk wheel damage on larger aircraft if they accidentally turn off the paved surface. Taxi speeds are typically .\n",
"An airplane uses taxiways to taxi from one place on an airport to another; for example, when moving... |
How were crimes by ordinary people punished in Ancient Rome? | Roman law during the late Republic and most of the Principate made no distinction in punishment between free people of different social rank. By Roman law all Roman citizens were guaranteed the same legal rights, and the only important distinction in court was whether one was a Roman citizen or not. In cases of civil law (i.e. lawsuits) this was *the* only distinction, as slaves could not sue or be sued. In lawsuits the nature of punishment (which almost invariably consisted of a fine) could vary, depending on what exact crime had been committed--it was determined by the judge, either calculated by him or drawn from tables. This fine did not change according to the social status of a citizen at court, and such a distinction would've been both impossible and contrary to Roman legal ideals. "Plebeian" does not mean "anybody who's not a *nobilis*." "Plebeian" just means anyone not descended from one of the original senators, a very tiny hereditary club that got tinier over time and which had already lost pretty much all its privileges by the end of the 4th Century--the Conflict of the Orders is considered to have ended in 287 with the passage of the *lex Hortensia*, but in reality the major issues (plebeian right to run for magistracy, etc.) had all been secured fifty to a hundred years earlier. By Caesar's day only 14 patrician families still had existing lines, out of more than 50 that we know of originally, and the most of the members of the senatorial class were plebeians. Indeed, since legally one consul each year had to be a plebeian at least half of the consular *nobiles* were also plebeians. Such men of standing as Cicero, Pompey, Crassus, Cassius, Cato, Brutus, Lepidus, Antony, Hortensius, etc. were all plebeian, and it becomes immediately clear that during the late Republic social status was not equivalent to social order, and that the category of patrician and plebeian cannot have been useful in cases of determining punishment. In cases of criminal law the punishment was generally the same for everyone. As criminal law tried capital crimes (murder, treason, etc.) the penalty was almost invariably death, or occasionally *infamia* (loss of citizen rights). The manner of execution might differ according to what crime was committed and whether the convicted was a citizen or not, but beyond that there was no distinction.
I should mention exile separately, though. Exile was not an actual *punishment* during the late Republic and generally during the Principate. During the late Republic exile was not a punishment that could actually be sentenced in court, it was a voluntary punishment. A citizen could voluntarily go into exile to escape the death penalty in a criminal case. He could go into exile before criminal proceedings actually began, but generally exile occurred either shortly before sentencing or in the space between sentence and execution (the *trinundinum*, which could last up to a month or so). So we see, for example, Milo fleeing to Massilia to escape being put to death for the murder of Publius Clodius. By the late Republic anyone who fled a criminal proceeding or the execution of sentence by leaving Italy was considered an exile, but the status of "exile" was only applied after the fact, not before--after the criminal fled Italy an *interdictio* would be passed denying him the right to fire and water, that is to say the rights and status of a Roman citizen and a free (or even living, since the death penalty was applied to those who returned to Italy) person within Italy. Officially this was the only type of *exsilium* going way into the Principate, although in point of fact Augustus introduced a couple of new penalties that, while not legally exile, were essentially the same thing. The most common was *relegatio*, which existed during the late Republic but wasn't really used. Under the emperors *relegatio* is used far more often, and it consisted of banishment to a particular place (like the island that Julia was sent to). Tiberius introduced a slightly different version of this penalty, the *deportatio*. There were also a couple of other kinds of *de facto* exile that weren't really exile *per se* or were illegal--this includes fleeing proscription or the illegal (as it was a *privilegium*) *lex Clodia de exsilio Ciceronis* that exiled Cicero
This is not to say that social status and wealth did not matter as long as citizenship status existed. That's not really true. Obviously in cases of civil law the penalties imposed on the poor would generally be different (if the law allowed it) from the penalties on the rich. In cases of criminal law, though, all penalties were the same, although Roman citizens could not be executed by certain means (crucifixion). During the later part of the Principate, however, we start to see the establishment of the *honestiores* and *humiliores*, social groups that did not exist in the late Republic. The concept probably existed in the late Republic, but it was a social idea that members of the senatorial class or the equites, though largely of the same order as the rest of the population, were not really of the same class--only in the later Principate, especially among the Antonines, does the legal distinction between the two start to emerge. There appears to never have been a legal definition of an *honestior*, and since by the Antonines the social orders had long since stopped being meaningful and the acquisition of magistracies was no longer a good indication of social rank it appears that it was largely left up to the judgement of the court and the emperor. *Honestiores* were exempt from certain penalties in criminal cases, particularly a replacement of the death penalty with *rogatio* (the beginnings of this practice can be seen as early as Augustus). Oddly, by the Antonines it seems that crucifixion had been re-introduced as a penalty for some citizens--*honestiores* were exempt from it, but *humiliores* might be crucified, which was not allowed as a punishment for any citizen in the earlier Principate or the Republic. *Humiliores* could also be sentenced to *damnatio ad ludas* or *ad bestias* or *ad mortem*, whereas *honestiores* could not. But the legality of these proceedings is kind of fuzzy, and this period is not one that I'm especially familiar with--during the late Republic, which is what I know about, criminal penalty was the same for all citizens, no matter their social rank | [
"In ancient Rome, executed criminals were thrown into the Tiber. People executed at the Gemonian stairs were thrown in the Tiber during the later part of the reign of the emperor Tiberius. This practice continued over the centuries. For example, the corpse of Pope Formosus was thrown into the Tiber after the infamo... |
Can fish see color? And if not, why are they so colorful? | I know for a fact that at least some fish do. Some fish have a trade-off feature where they have a red belly which females finds attractive, but they are more visible to predators. Some marine animals also get their color from their diet, so maybe it has something to do with that? | [
"Mesopelagic fish are adapted to a low-light environment. Many fish are black or red, because these colors appear dark due to the limited light penetration at depth. Some fish have rows of photophores, small light-producing organs, on their underside to mimic the surrounding environment. Other fish have mirrored bo... |
How did the heavier metals on Earth end up in the Earth's crust and not all towards the Core? | Here's a [recent post where I answered a very similar question](_URL_0_). Basically it comes down to two things: solubility in different materials (silicates versus metals, which is why there are Uranium ores on the surface of Earth) and meteor bombardment during the early history of the solar system (which is why there's still some Gold, Platinum, Iridium, etc. in the crust). | [
"In early stages of Earth's formation about 4.6 billion years ago, melting would have caused denser substances to sink toward the center in a process called planetary differentiation (see also the iron catastrophe), while less-dense materials would have migrated to the crust. The core is thus believed to largely be... |
Was there any indication for a genocide in the Bosnia war from 1992-1995? | Oh, there's absolutely indication that they intentionally committed genocide.
In fact, it's internationally recognized as such today.
If you'd like background on the conflict itself, please check [this thread here](_URL_0_).
Edit: I realized it might be helpful to give you the account of what actually happened in Srebrenica, to make it more effective in explaining how the conclusions were made. My mistake, I don't know if you actually know them!
In 1993, the UN protection force in Bosnia (UNPROFOR) was tasked with protecting "safe areas". One of these safe areas was the Muslim enclave around Srebrenica. In March of 1994 (after agreeing in October 1993), the main force of the Dutch was deployed under UN command to this enclave. One company was stationed in the city, the other in the Potocari compound outside Srebrenica.
On the 5th of July, 1995, General Mladic of Republika Srpska (basically, the Bosnian Serb army) attacked the enclave. On the 11th of July, they took the city, and the Dutch troops in the city retreated to the Potocari compound. This caused a mass exodus from the area, with 5,000 staying inside the Potocari compound and around 27,000 outside. UN command determined that these people would have to be evacuated, so the Dutch commander began negotiating with Mladic for the evacuation. The Dutch also chose to expel the 5,000 staying inside the compound, which they have accepted responsibility for as being partially responsible for the deaths of those people. Over the next two days, Mladic's forces removed all the people outside and inside the compound via bus and truck, saying they were helping in the evacuation as promised. While they were removing them, they also conducted executions of men who were around military age, and rapes of women. Local UN employees were unharmed generally speaking, if they had UN cards (contrast this with the Rwandan genocide, where the Belgian troops were targeted gruesomely to get the UN to withdraw).
As people were getting onto the buses and trucks that were going to Bosniak-held territory, the men of military age were separated out. Some younger and older were also separated out, even as young as 14. They were killed, executed.
Witnesses also noted cruel killings of children who were crying, women, and other forms of sexual abuse and torture.
Some buses never made it to the Bosniak territory, and were seen driving away from the Bosniak territory, though it had women on it (not military age men, like the other killings). It's assumed that those on the buses who didn't make it were all killed.
The Serbs have admitted that they planned and carried out mass executions of the men of military age, which is damning evidence of genocide.
To get into some of the international recognition, first, before I explain why it was regarded as a definite genocide:
* [The US recognized the actions of Serbia in that entire 1992-1995 span as genocide in 2005](_URL_1_).
* [The ICTY tried Karadzic for genocide in 2010 [PDF Format!], and ruled that Srebrenica was a genocide.](_URL_2_).
* [The ICJ ruled that Srebrenica was a genocide, but that the Serbian government was not responsible or complicit in it](_URL_5_)
So we know that there's a pretty sizable agreement that this was a genocide. Even the [UN Secretary General agreed it was a genocide](_URL_4_).
Now, how do we know it was definitely a genocide? Let's look at some documents on the subject.
First, the US Congress resolution on the subject says this:
> Whereas Bosnian Serb forces deported women, children, and the elderly in buses, held Bosniak males over 16 years of age at collection points and sites in northeastern Bosnia and Herzegovina under their control, and then summarily executed and buried the captives in mass graves;
This is pretty crucial. The fact that they separated males over 16 years of age and then summarily executed them is evidence of premeditation in carrying out the massacre. Now, how is this a genocide? Alone, it might not be considered as such, because it's not carried out with the intent to destroy the whole group, or they'd have killed women, children, and the elderly. However, the genocide convention that defines genocide says this:
> ...any of the following acts committed with intent to destroy, in whole or in part, a national, ethnical, racial or religious group, as such:
> (a) Killing members of the group;
> (b) Causing serious bodily or mental harm to members of the group;
> (c) Deliberately inflicting on the group conditions of life calculated to bring about its physical destruction in whole or in part;
> (d) Imposing measures intended to prevent births within the group;
> (e) Forcibly transferring children of the group to another group.
There are a few things to note here. There is the question of preventing births, there is the question of destroying *in part* a group, which is clearly done in Srebrenica, and there is the question of severe physical and bodily harm done.
Now, let's look at the ICJ case.
The ICJ, while clearing Serbia of genocide, notes that it failed to prevent genocide. That is a *de facto* admission that it was a genocide. How did they reach this conclusion?
Its decision, for the record, said this:
> The Court concludes that the acts committed at Srebrenica falling within Article II (a) and (b) of the Convention were committed with the specific intent to destroy in part the group of the Muslims of Bosnia and Herzegovina as such; and accordingly that these were acts of genocide, committed by members of the VRS in and around Srebrenica from about 13 July 1995.
Now, again, how did they determine this to be genocide?
The case itself is [long [PDF Format!]](_URL_3_), so I'll try to slim it down for you to the important bits if I can. Of course, I recommend you read it; there's a lot of information I *won't* be able to cover.
> At the same time, it also endorses the observation made in the Krstic´ case that “where there is physical or biological destruction there are often simultaneous attacks on the cultural and religious property and symbols of the targeted group as well, attacks which may legitimately be considered as evidence of an intent to physically destroy the group."
This observation was made by the ICTY.
Now here's where it gets into the nitty-gritty. Page 190, if you're following along.
The Court pretty summarily rejects most arguments that relate to a lowering of the birth rate via male/female separations, rape, etc. It doesn't accept these arguments as constituting the genocide. However, it did examine the Srebrenica Massacre, on page 164 (it's mentioning the Appeals Chamber decision).
> By seeking to eliminate a part of the Bosnian Muslims, the Bosnian Serb forces committed genocide. They targeted for extinction the forty thousand Bosnian Muslims living in Srebrenica, a group that was emblematic of Bosnian Muslims in general. They stripped all the male Muslim prisoners, military and civilian, elderly and young, of their personal belongings and identification, and deliberately and methodically killed them solely on the basis of their identity. The Bosnian Serb forces were aware, when they embarked on this genocidal venture, that the harm they caused would continue to plague the Bosnian Muslims. The Appeals Chamber states unequivocally that the law condemns, in appropriate terms, the deep and lasting injury inflicted, and calls the massacre at Srebrenica by its proper name: genocide.
This is pretty damning. The court, in examining the actions of those involved, found this. And yes, that is how it went down. The men, as I said, were separated out, and killed in mass executions. Over 20% of the town's population was killed by the time it was over. Muslims were specifically targeted. Those who were deported or otherwise detained were either subjected to harsh conditions as refugees (as the Serbs knew they would be) or were held in camps that the ICJ notes were detestable in conditions and cleanliness and food/water provided.
There's little doubt that there was every indication for a genocide in Srebrenica today, and though the Serbian government has never officially said so (likely due to pride), it's a fairly clear-cut thing to most everyone who studies the issue. I highly suggest you look at the events themselves again and you'll see what I mean. However, just looking at the attempt to destroy a part of the population (the military age men, though it is also said that it was all men), it qualifies as a genocide under the Genocide Conventions.
Sources not cited in-text:
KILLINGS AT SREBRENICA, EFFECTIVE CONTROL, AND THE POWER TO PREVENT UNLAWFUL CONDUCT
Tom Dannenbaum
The International and Comparative Law Quarterly, Vol. 61, No. 3 (JULY 2012), pp. 713-728 | [
"In 2001, the International Criminal Tribunal for the Former Yugoslavia (ICTY) judged that the 1995 Srebrenica massacre was an act of genocide. On 26 February 2007, the International Court of Justice (ICJ), in the \"Bosnian Genocide Case\" upheld the ICTY's earlier finding that the massacre in Srebrenica and Zepa c... |
How did the Allies supply their armies in France in WWII in 1944 and 1945? | Logistics were always a key factor in the planning of Overlord. Prior experience showed that capturing ports was difficult as they were a natural focus for defensive efforts, and once captured extensive work would likely be needed to repair sabotage and demolitions carried out by the defenders. Supplies would therefore have to come over the beaches initially, assisted by the artificial Mulberry harbours, until sufficient ports could be taken and cleared. An initial plan was for US forces to have Cherbourg operating by D+11, with a push into Brittany to take Brest and construct a new facility in Quiberon Bay around D+54. (Figures from *Logistical Support of the Armies: May 1941 - September 1944*, Roland G. Ruppenthal).
As it was Cherbourg only fell at the end of June, and rather than three days it took three weeks for the port to be cleared; Col. Alvin G. Viney described the damage done to the port as "... a masterful job, beyond a doubt the most complete, intensive, and best-planned demolition in history." (*Cross-Channel Attack*, Gordon A. Harrison). The majority of supplies therefore came over the beaches until August when Cherbourg was fully operational, some minor Normandy ports were opened, and Operation Dragoon started to make southern French ports available. The beaches remained in use, though with less traffic as weather worsened, and as the Allies pushed east along the channel coast heavily fortified ports such as Le Havre and Rouen were besieged, captured and repaired.
After initial slow progress, behind initial estimates, the breakout from Normandy happened far quicker than expected; by mid-September, about three months into the campaign, Allied forces were reaching objectives they were only planning to capture after a year. Antwerp was captured at the start of September with its docks intact but could not be utilised until the Scheldt estuary had been cleared, which only happened in November, Market Garden proving something of a distraction in the meantime. Ports in Brittany were scarcely used, with Brest heavily damaged and the planned facility in Quiberon Bay not built; by 1945 Antwerp and the Southern French ports were handling about half the supplies being landed, the rest coming into Cherbourg, Le Havre, Rouen and Ghent (Figures from *Logistical Support of the Armies: September 1944 - May 1945*, Roland G. Ruppenthal).
Of course the supplies had to get to the front line after being landed, and the unexpectedly rapid advance caused major logistical headaches. The French railway system had been heavily targeted by the Allied air forces in the run-up to Overlord to prevent German reinforcements being rapidly deployed, and though plans were in place to reconstruct it these could not keep up with the speed of advance. Improvisation was therefore required, primarily in the form of truck convoys; the most famous route for these was the Red Ball Express from Cherbourg, though others including the White Ball from Le Havre and the ABC from Antwerp were also established.
For further reading Ruppenthal's *Logistical Support of the Armies* is available online ([Volume I] (_URL_1_) and [Volume II] (_URL_0_)), the planning and execution of Overlord being a major theme.
| [
"Conducted strategic bombardment of Axis targets in Europe. Between 29 August 1944 and 2 October 1944 division aircraft dropped food to the French population in liberated areas. It also airdropped food, equipment, and supplies to Allied forces engaged in the airborne attack on the Netherlands (September 1944), as w... |
Was there any study of economics pre-consumerism? | Yes.
Consumerism is generally linked to the rise of industrial production and wasn't a phenomenon (at least outside the upper class) until the late 19th century. Before then you had such figures as Adam Smith, David Hume, Ricardo, Marx, Quesnay, Colbert etc all writing on economics. Adam Smith is considered the defining founding father of modern economics and industrial era economics based much of its premises on the works of Smith and Ricardo. | [
"In the late 20th century, areas of study that produced change in economic thinking were: risk-based (rather than price-based models), imperfect economic actors, and treating economics as a biological science (based on evolutionary norms rather than abstract exchange).\n",
"Consumer economics concludes the family... |
What properties of charcoal cause it to be so useful in absorbing toxic compounds? | Can anyone actually explain this though! Yes it becomes more porous, yes it has active binding sites. But what is actually occurring here. Are particulates getting trapped? Are aldehyde/ketones groups protonating with particulates? Or what is the actual chemical manipulation of this? | [
"Activated charcoal is used to treat many types of oral poisonings such as phenobarbital and carbamazepine. It is not effective for a number of poisonings including: strong acids or bases, iron, lithium, arsenic, methanol, ethanol or ethylene glycol.\n",
"Activated carbon is used to treat poisonings and overdoses... |
Are Neutrino's really faster than light? | Because photons are light. To pass from the source to the detector, they are travelling through the earth. Light won't do that. | [
"Neutrino speeds \"consistent\" with the speed of light are expected given the limited accuracy of experiments to date. Neutrinos have small but nonzero mass, and so special relativity predicts that they must propagate at speeds slower than light. Nonetheless, known neutrino production processes impart energies far... |
why are there patterns and fractals in nature? | > Why are there patterns and fractals in nature?
Patterns and fractals are just the large scale result of simple repeating behaviors. Suppose you have a stem that will grow for a bit and then split, then those stems grow for a bit and split, etc. You end up with a branching pattern from simple base behaviors.
> Is math based off of nature?
Sort of, in the most simplistic sense it is a way to model reality. People start counting stones and math adopts the behavior that things don't just spontaneously appear or vanish. You pick up one rock and then pick up another rock you will have "two" rocks. At this point of abstraction the system takes off behaving with internally consistent rules which yield results consistent with reality (in many cases).
So while the internally consistent rules can yield things which have no real counterpart (such as imaginary numbers) the application of those rules can allow the deduction of behaviors of the universe which are not immediately apparent via observation. This is again based on the basic observation that the universe behaves according to internally consistent rules and that the fundamental rules of mathematics are based on easily observed behaviors of the universe. | [
"Some mathematical rule-patterns can be visualised, and among these are those that explain patterns in nature including the mathematics of symmetry, waves, meanders, and fractals. Fractals are mathematical patterns that are scale invariant. This means that the shape of the pattern does not depend on how closely you... |
What was President William McKinley's reasoning for his views on the issue of the annexation of the Philippines? | My understanding is he was sort of painted into a geopolitical corner. He hadn't really intended on taking the Phillipines, but now that he had them he couldn't give them to anyone else (because they'd just use them as a base for competition in China), couldn't give them back to Spain (because we had just beat the pants off of them and it would seem like a really pussy thing to do), and couldn't give them independence (because he thought they were a bunch of ignorant savages who couldn't govern themselves). Plus at that time period pretty much any island in the Pacific was useful as a naval coaling station and storehouse for supplies, much less somewhere like the Phillipines where there was the potential for a functional colony rather than just a lagoon and a beach to pile stuff on. | [
"A controversial aspect of McKinley's presidency is territorial expansion and the question of imperialism—with the exception of the Philippines, granted independence in 1946, the United States retains the territories taken under McKinley. The territorial expansion of 1898 is often seen by historians as the beginnin... |
Good books/movies/documentaries/websites/podcasts about Roman British history | British History Podcast. | [
"The History of Byzantium podcast by Robin Pierson is explicitly modelled after The History of Rome in style, length and quality; Pierson intended the podcast as a sequel to The History of Rome in order to complete the story. David Crowther of The History of England podcast has mentioned Duncan as an influence. as ... |
why do the ends of escalators and moving walkways have the blue or green light that shines through the cracks? | I may be wrong but I think it's a light from a sensor that stops the escalator, moving sidewalk, etc. when it sees that there is something caught in the treads e.g. a pantleg, or a shoelace | [
"Multi-coloured spherical lights in the trees were installed in 2005 by the Elephant Impacts project. The project has repainted and added feature lighting to a number of bridges and buildings in the area, including the adjoining railway bridges on Walworth Road and Newington Causeway, and to London College of Commu... |
will we ever see the national debt start going down or will it keep raising forever? | We'll likely see the national debt fluctuate up and down as this century goes on. The American economy is pretty robust and very very good at generating income. Without multi-trillion dollar wars to fight, and [hopefully] an upcoming rationalization of our economic, tax and social policies the debt will start to drift downwards.
However, it will almost certainly never go away.
This may sound wacky but - America's national debt is the chain that binds the rest of the world to America.
So long as the US continues to be THE place to invest money at a risk free rate (ie US Treasuries) the entire world has a vested interest in the US continuing to operate productively. In other words, the rest of the world NEEDS the US to be successful or their own economies will suffer. They need America to keep spending money, because America's economy is the beating heart that is pumping all the blood (re: dollars) through the rest of the world.
As an example, China's growth is impossible without billions of dollars of US money flowing into the country. That money is so critical that they loan that money back to us at pathetically small interest rates so we can keep buying.
The US is living in the best possible situation - we have the close to unlimited funds... and the appetite to match. | [
"According to the Treasury, \"failing to increase the debt limit would . . . cause the government to default on its legal obligations – an unprecedented event in American history\". These legal obligations include paying Social Security and Medicare benefits, military salaries, interest on the debt, and many other ... |
What are some examples of small disciplined forces defeating larger forces? | The winter war perhaps? _URL_0_
Little Finland beating off the might of Soviet Russia. 70k casualties against soviet 323k. | [
"Regular forces, in turn, may act in order to invite such attacks by concentrations of enemy guerrillas, in order to bring an otherwise elusive enemy to battle, relying on its own superior training and firepower to win such battles. This was successfully practiced by the French during the First Indochina War at the... |
why some, but not all, acquisition prices are disclosed . | In the USA, if a publicly traded company is acquired, the purchase price will have to be reported publicly in reports to the SEC. Acquisition of a private company won't have to be, although if it is bought by a public company then it will often show up in their SEC reports, although it may be obfuscated. In the case of a large company like Google or Cisco, they may buy so many companies that you won't be able to find the price of any individual one in their reports.
Whether or not to divulge purchase prices is usually dictated by the purchasing company, although the acquired company could potentially make it a condition of sale. I don't know what laws exist that cover acquisitions/mergers.
There are a variety of reasons to not want to divulge. But usually it seems to be avoidance of criticism. | [
"An acquisition/takeover is the purchase of one business or company by another company or other business entity. Specific acquisition targets can be identified through myriad avenues including market research, trade expos, sent up from internal business units, or supply chain analysis. Such purchase may be of 100%,... |
How do you feel about John Brown? Terrorist or freedom fighter? | He's both technically but in my biased opinion he's a freedom fighter. Though he could have planned the rebellion slightly more I believe, like asking a local slave in the dead of night on what he thought the slaves would do perhaps, but really Brown was never going to achieve the full liberation of the slaves as he wanted to. Regardless he's an inspirational figure. | [
"Brown claims to be a Muslim and jihadi who believed his actions were \"just kills\", or justified shootings, of adult males in retaliation for actions by the U.S. government in Iraq, Syria and Afghanistan. As he stated to authorities: \"All those lives are taken every single day by America, by this government. So ... |
how does my computer know how much time is remaining for a program to be installed? | It's an estimate based on how much data there is left to transfer and how fast it is currently getting done. | [
"Time Machine creates incremental backups of files that can be restored at a later date. It allows the user to restore the whole system or specific files from the Recovery HD or the macOS Install DVD. It works within Mail, iWork, iLife, and several other compatible programs, making it possible to restore individual... |
what does a company do with funds generated from selling stocks? | The go to various things, depending on the company and its business... the money does literally go into the company's bank accounts, minus fees paid to investment bank doing the underwriter, etc. They may use it to pay back debt, invest in expansion (factories, new stores, inventory), make acquisitions, pay bonuses to founders, etc. | [
"In a primary market, companies, governments or public sector institutions can raise funds through bond issues and corporations can raise capital through the sale of new stock through an initial public offering (IPO). This is often done through an investment bank or finance syndicate of securities dealers. The proc... |
why old film clips, like ones of ww2 almost always seems sped up faster than 1x? | As you probably know, the speed at which motion picture film runs through the camera determines its frame rate, given in frames per second (fps). When run through a projector (which you can think of as a backwards camera) at the same speed, the movement looks natural to us. If turned more slowly or quickly, however, it plays out in fast or slow motion, respectively (the terms "undercranking" and "overcranking" are still used for these techniques, derived from the literal cranking mechanism used to run early cameras and projectors).
Obviously this enthralled audiences, and early camera operators took advantage of this at times, but the cliche of its ubiquity happened more by accident. In the early days of the medium, both cameras and projectors were usually operated at a lower speed than the 24fps that later became the industry standard (particularly with the advent of synchronized sound in the late 1920s). I've shown silent films while working as a projectionist, and they're often distributed with instructions to be run at 18fps so that movement shows up normally. If shown at 24fps—which has often been done, either because of insufficient equipment or human error—you would be seeing everything at 1.5x the speed of the actual motion, hence the cliche of old films running in fast motion.
| [
"So a film recorded at 12 frames per second will appear to move twice as fast. Shooting at camera speeds between 8 and 22 frames per second usually falls into the undercranked fast motion category, with images shot at slower speeds more closely falling into the realm of time-lapse, although these distinctions of te... |
why doesn't north america see protests similar in size to other continents and countries? | [We took part in the largest protest in human history](_URL_0_), in 1995 the Million Man March had between 400,000 and 837,000 people, in 1993 the March on Washington for Lesbian, Gay and Bi Equal Rights and Liberation had between 300,000 and 1,000,000 people, in 1992 the "Save our Cities! Save our Children!" protest had 150,000 people, in 1989 the March for Women's Lives had 500,000. The list goes on, back through history. What are you basing your question's premise on? A guess? | [
"Some potentially vulnerable states that have not yet seen such protests have taken a variety of preemptive measures to avoid such displays occurring in their own countries; some of these states and others have experienced political fallout as a result of their own governmental actions and reactions to events which... |
What is the best way to determine if an exoplanet is suitable to sustain human life? | Part of the problem is we have a sample size of 1. Basically impossible to draw hard conclusions from.
One key metric I've seen talked about is the presence of free oxygen. Oxygen is very reactive, if it is present in large quantities in molecular form it seems reasonable to infer that a process like life is creating it (e.g. photosynthesis).
Liquid water also seems to be an important pre-requisite, as life needs a solvent in which to mix all its magical molecules.
If we spotted a planet at the correct temperature for liquid water that also had large amounts of molecular oxygen people would get very, very excited. | [
"The discovery of exoplanets has intensified interest in the search for extraterrestrial life. There is special interest in planets that orbit in a star's habitable zone, where it is possible for liquid water, a prerequisite for life on Earth, to exist on the surface. The study of planetary habitability also consid... |
why do dogs like the smell of cheese so much? | Cheese, that is, REAL, unprocessed cheese (although some types of pasteurized cheese included as well,) is naturally very pungent. Cut up a bit of Brie or aged white cheddar and tell me this isn't so. If we humans think cheese is very pungent, imagine how much more so dogs would be able to smell it. Dogs tend to have a much more potent sense of smell than we humans, since before dogs had been domesticated, their sense of smell was essential for hunting down their food.
Naturally, regardless of whether or not a dog would recognize that this powerful scent is coming from tasty food, dogs would be curious about the origin of the odor. Some dogs might not even need to witness a human or other animal eating the cheese to consider licking the strange, odorous object, if given the opportunity, to learn more about it. Once licking it, they may discover that it's tasty to them and consequently eat it.
To some dogs, it may be habitual as you say--like Pavlov's dog. Every time a dog smells this piquant scent, he tends to see a human eating the object the smell is originating from. Eating means food. Food is good to eat.
However, even if a dog recognizes the cheese to be a compound originating from lactose, but does not first see a human or other dog/animal eating it does not mean they will brush it off as "not food." This misconception people have that humans are the only mammals that continue to consume milk into adulthood has absolutely no basis in fact.
Cliche as it may sound, put a bowl of cow's milk you bought from the supermarket in front of a cat who has neither consumed processed milk nor seen anyone else consume it and tell me she won't drink it. I'm not promising she won't get sick, but 9/10 times, she will drink it, anyway. (And yes, I have tried this numerous times before hearing you're not supposed to do that, but the cat never got sick. Lol)
And it's not just cats. Many animals will drink milk if put in front of them because animals know it is rich in fat. From an evolutionary standpoint, fats are a delicacy since they are rich in energy and have only recently become so readily available to us that we haven't been able to turn off that insatiable craving for them yet.
TL;DR
1. Cheese is pungent, dogs have a good sense of smell.
2. We're not the only ones who like milk. Milk is rich in fat, and fat is tasty because we need it. | [
"Dogs have around 1,700 taste buds compared to humans with around 9,000. The sweet taste buds in dogs respond to a chemical called furaneol which is found in many fruits and in tomatoes. It appears that dogs do like this flavor and it probably evolved because in a natural environment dogs frequently supplement thei... |
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