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4dh2hf | why is there a massive interest in virtual reality lately, isn't vr around for decades already? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/4dh2hf/eli5_why_is_there_a_massive_interest_in_virtual/ | {
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"Sort of? In clunky forms that nobody ever found immersive or anything other than a gimmick. The recent change is that it's actually *good*.",
"It's been around, but it's been lacking in the \"reality\" in a very significant way. For example, VRML from the late 90s was interesting in that it was easy to create a 3d world and navigate it, it wasn't going to be a compelling experience for entertainment, and wasn't going to be immersive as a user experience. There is _some_ sense that we've reached a critical mass of hardware and software capabilities to make the vision of VR something that can be compelling to everyday folk.",
"Been around but never in a small compact size that anyone can use. That also seems to be of high quality.",
"These things get rediscovered from time to time and sometimes they finally stick and other times they fizzle out. Take 3D motion pictures for example, it has had at least three periods of popularity, but each time it went away.\n\nAnother example is the portable touch-screen computer. It went through decades of being \"the future\", but it took the right marriage of electronics, software, and marketing plus a merge with cell phones for something like the iPhone and now it is everywhere.\n\nVR might make it this time since we have better display technology, better graphics processors, and everything is just cheaper. It might also just be a fad that isn't ready to be appealing for people for a long time. We likely won't know for a while yet as we are only just now seeing actual products ship.",
"Does VirtualBoy count? Because it shouldn't.",
"the expense was also a huge part. A good VR headset and hardware from the late 80s early 90s was hundreds of thousands of dollars and required dedicated hardware and software.",
"New technology goes through a pretty predictable pattern, like this:\n\n_URL_1_\n\nGenerally they go through a quick peak of hype, but aren't mature enough initially to live up to expectations. We've recently gotten into the \"slope of enlightenment\" phase for VR. It still needs to mature some before is widely adopted.\n\nNote that adoption rates follow a trend too: _URL_0_",
"We are now at a convergence point for all of the technology required for good VR.\n\n Screens good enough that they can produce a convincing image even when just a few inches from our eyes.\n\nGyroscope tech accurate enough to keep us from getting sick. \n\nHead tracking, motion controllers, computers powerful enough to render realistic looking environments at high frame rates. Everything is just now coming together to form an enjoyable VR experience at a price point the mass market can afford. ",
"Proof of concept has been around forever, but a practical, affordable consumer product has not. All the pieces finally fell into place to make it something that exists outside of niche, expensive projects and something that can be priced at the same level as a new smart phone.\n\nSince it's affordable and there are dev tools available, startups and others an actually make games/movies/apps for it.\n\nIt's like the difference between the first computers many decades ago, and the desktop computer revolution in the 90s. Regular people can get in on it, basically."
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1jydi7 | What AMA Topics would you like to see? | We have quite a few AMAs coming up this month, as you can see in our Upcoming Events schedule, but we're always eager to have more. We're sure you are too, so we'd like to get your opinions on what topics you'd like to see as an AMA.
Hopefully, one of our resident experts will see the interest and volunteer or we may just track down an outside expert willing to participate. Word of advice for potential volunteers though, we like to have our AMA participants vetted first, so if you don't have flair yet, check out the [Panel of Historians](_URL_0_) thread to see how to correct that. | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/1jydi7/what_ama_topics_would_you_like_to_see/ | {
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"I've been getting quite heavily into Japanese history over the past year or so, so I'd love to see our Japanese flaired users come together for a larger panel. We had Japan covered at the end of last year along with China and Korea but there was only one historian who, granted, managed to do a great job in the circumstances but a little more specialisation isn't to be sniffed at.\n\nEDIT: I'm counting 13 flaired users with a hand , leg or whole body in Japanese history. Surely we could cobble something together on this?",
"I'd really like to hear more about Argentina! We all know it's a regional power, so I'd like to hear more about that, but I would also love to hear how they affect the world in general.",
"Andean archaeology. Tell /u/Pachacamac he needs to get on board. ",
"I would really like to see an economic history panel AMA. We have quite a few people who do economic history in certain areas and I'd love to band them all together for a big economics party. Any flaired users in those areas who'd like to volunteer? ",
"There are a still a lot of flaired historians here that have been consistently contributing, but haven't done an AMA yet. I'd love to see them doing one, but you have probably messaged them already.\n\nI'd personally really like to see an AMA on 19th c. American history, or more specifically on the Westward Movement, Borderlands, American West etc. \nA lot of users have 19th c. U.S. history flair, but I don't see them posting often as there aren't too many questions.",
"I think AskHistorians should go big and go for big names, see if we can't get a recent Pulitzer Prize or Wolfson Prize winner to come on. I know this is almost certainly more work for you guys (sorry) but I think it would be awesome.\n\nAlso, I'd love if there were Napoleon (really French Revolution through Waterloo) panel. /u/LeftBehind83, /u/Talleyrand, and a bunch of other of our Europeanist could surely add to it.\n\nI'd also love a Medieval Europe panel, because a lot of people have questions about this, but maybe I'm saying this just because /u/whoosier is one of my favorites. There are a lot of users specifically flaired \"medieval\", and I think there are more (like /u/owlett and /u/gingerkid1234) who could contribute beyond that.",
"I'd be happy to do one on pornography again..the one I did before I had to post, then do something, and then come back, so I did not manage to give it as much attention as I would have hoped.",
"I'd love to see an AMA on the history of theater and/or literature. \n\nAlso, South Asia. It's a historically rich region that is not discussed too often here.",
"Trade and economics during the middle ages in Europe",
"Turning points. \nThis could be something large, such as the Protestant Reformation, to something more regional such as the Meiji restoration. Or possibly even smaller. The PornMeister could talk about the importance of one \"Deep Throat\", and a 1970's scholar could expound on the other. Point being that there's something for every specialty.\nThis could bring to life things that most of us are vaguely aware of, and enlightening us as to *why* and giving us a better appreciation for the event(s) in question. \n\nedit:expand and clarify\n\n\n\n\n",
"Cool panels could consist of Science/Technology/Medicine, Colonies and Empires, Environment, Food, Cultural History (with a theoretical orientation). ",
"I'd love to see something on Canadian history. Also, I love anything about the history of science and technology.",
"I've suggested this now with [u/rosemary85](_URL_1_) and I've also messaged [u/Daeres](_URL_0_) about it, although he has yet to get back to me. I've been noticing a lot of scattered threads recently asking about the Homeric Poems, their origin, their significance, and their relevence to actual historical events. But they're all over the place and we really need to have some sort of panel to get a good comprehensive look at the subject. Rosemary norrowed down the subject of our possible AMA into:\n\n > the historical development of Greek epic and mythology, linguistics, and the relationship between these things and our evidence for historical practices\n\nAnybody up for this? Want to give us a hand? I'd like to get some more people on board before I submit the proposal to the mods.",
"I do not find that AMA's are more useful than regular questions.",
"Something like the recent [Apollo program experts AMA](_URL_0_), only for the space shuttle.",
"We had one once a year ago, one of the earliest AMAs. Time for another? Middle eastern history AMA (anywhere in the region of early modern - 20th century) would be awesome.",
"I would like to see an ancient Egypt AMA. ",
"Religion. I'd love to see an AMA panel about religion throughout history.",
"On the process of obtaining a degree in history. What the classroom is like, job opportunities, challenges, things we should be aware of. \n\nEdit: Also, what's the average work day like for a historian? Is it spent mostly analyzing documents? Teaching? Are a lot of historians also archaeologists? Is that a romanticized/misunderstood view of a historian's job? ",
"Just because it's such a huge topic everyone hears about all the time, I'd suggest at least one Hitler and the nazis AMA. but a more interesting one would be on the history of germania(streching from the germanic tribes to the modern german state. basically an AMA about the history of the territory.). Germanic tribes would be an interesting topic in and of itself."
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1dlgdb | dante's inferno | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/1dlgdb/eli5_dantes_inferno/ | {
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"Inferno is the first part of the epic (the literature meaning) poem *Divine Comedy*. In the story the author, Dante, describes his trip to Hell while guided by the Roman poet Virgil, who takes him through the 9 circles of Hell which were as follows: \n\n1. Limbo\n2. Lust\n3. Gluttony\n4. Greed\n5. Anger\n6. Heresy\n7. Violence\n8. Fraud\n9. Treachery",
"As Jim777PS3 said below, it's the first part of the *Divine Comedy*. \n\nIn *Inferno*, Dante is taken through Hell by Virgil, and he sees what happens to people who commit various 'sins' during their lives, ranging from pretty mild (like not really being a serious Christian) to more serious (violence, betrayal etc). The punishments given to people in the most part reflect what their sins were. \n\nThe *Divine Comedy* is an attempt by Dante to explain how the whole earthly world and afterlife is set up according to his understanding of Christianity. It's considered a hugely important work for lots of reasons; just as a poem, in terms of language and ideas it is amazing; it brings together a whole lot of strands of intellectual and artistic thought at that time; it actually *does* explain the Christian theology of Dante's time. Plus more reasons I don't really know about."
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x4u6g | music recognition software like shazam. | This sounds extremely stupid, but I was wondering how exactly music recognition software recognizes music. I have been able to tag music from the radio, in the mall, and even off of TV with people talking over it. I know it's not "magic" but I want to know how it's able to do that. | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/x4u6g/eli5_music_recognition_software_like_shazam/ | {
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"Remember how, when you were a kid, you'd try to hastily sketch someone's face? When you were young, the face probably looked pretty silly - the features wouldn't be proportionate, the eyes would probably be uneven - you'd barely be able to tell it was a face, right? Then, as you grew older, your ability to draw faces got better. With the same amount of time and using the same amount of lines, you could draw a better face than before, this time taking into account the unique features that separate people's faces and carrying them over to the paper.\n\nThink of music recognition like that. Services like Shazam need to get that song recognized, but they can't just send a clip of the whole song and compare it; that would take incredible processing power and quite a while for the database to locate the correct song. Rather, music recognition focuses on a song's *acoustic fingerprint*, which is a property unique to every piece of music. Instead of trying to draw the whole 'face', the acoustic fingerprint picks up tell-tale features like the song's spectral flatness (how the audio deviates from pure noise), tempo (speed), zero crossings (where the sound waves go from positive to negative/vice versa), bandwidth (the difference between upper/lower frequencies), and so forth. Think of these as the easily recognizable facial features; two songs may sound very similar, but their acoustic properties will be very different. \n\nNow, once you've stripped away everything but those few recognizable details, you can easily search through a database. Each detail works to narrow down the search; for example, there are millions of songs, but only thousands of them have a tempo similar to, say, Led Zeppelin's Black Dog. And only a few dozen of them have similar zero crossovers. \n\nAs for how the audio recognition is able to pick out music even through background noise; background noise is generally highly random and can't be analyzed as anything more than that, noise. Music, on the other hand, is rhythmic and easier to isolate. It's still possible to confuse audio recognition enough by making noise over the song it's trying to recognize, which is why services like Shazam generally listen for ten seconds or so to get multiple samples in case one of them has background noise.\n\nEDIT: Also, the above reasons are why music recognition services can't pick up the sound from live performances; even if the song sounds exactly the same to the human ear, the acoustic characteristics will be vastly different, making it impossible to identify."
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hfelg | Is there a nutritional difference between eating a fruit and drinking the juice of said fruit? | askscience | http://www.reddit.com/r/askscience/comments/hfelg/is_there_a_nutritional_difference_between_eating/ | {
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"Depends on what you mean by the juice.\n\nFresh squeezed whatever, all you are losing is probably some fiber.\n\nIf you're talking supermarket juice, well they add a lot of sugars and what not so the calories are really through the roof, like on the same order as soda!",
"While, as nallen said, the nutritional content might differ in the amount of fiber, think about the following:\n\n* Can you drink a cup of orange juice in 10 seconds? That's easy.\n\n* Can you eat three oranges in 10 seconds? That's a challenge."
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32vnk2 | in the us, are egyptians, algerians, tunisians, moroccans, white south africans considered african americans? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/32vnk2/eli5_in_the_us_are_egyptians_algerians_tunisians/ | {
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"Technically, yes. Being ignorant or unaware, we tend not to consider them \"African American.\" Generally, we use \"African American\" as the politically correct way to say \"black.\"",
"No they would not be. Most would consider them to be arab, while african american is used as a more politically correct way to say black",
"Here in the US, our society can be ignorant. We refer to most black people as African Americans even though most were born in the US. If you came from any of those countries you would technically be an African American, but if you are white you will probably be referred to as an American (if you mean said person gets citizenship), foreigner/tourist, or South African/Tunisian/Egyptian/etc. If you are a tan skin color, then you will probably be referred to as Arab, Muslim, or your country's origin (so again, South African/Tunisian/Egyptian/etc.). I do not mean to be racist in any way with this comment if someone interprets it in that way.",
"No, we don't think of them in those terms even if it is technically accurate. When we say \"African-American\" here we are referring to people descended from sub-Saharan races, what you think of when you hear \"black people.\"\n\nI guess we tend to lump North Africans together as Arabs, but I suspect that's not an accurate term for the eastern North African races. I don't know any Moroccans, so it's not a question I've ever really faced.\n\nReally \"African American\" was created specifically as an acceptable term to refer to blacks in aftermath of the main surge of the civil rights movement. It was born of the struggle for the descendants of slaves to finally get their government to quit shitting on them.\n\nI'm a white person trying to address issues of race in which I still have a lot to learn. If anyone else thinks I need a schooling in these matters, I'm happy to take criticism."
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yj0uj | Would Dinosaurs have been red or white meat? | askscience | http://www.reddit.com/r/askscience/comments/yj0uj/would_dinosaurs_have_been_red_or_white_meat/ | {
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"Red vs. white meat is largely a function of how the specific muscles are utilized. The 'red' in red meat is from high amounts of myoglobin for oxygen retention and mitochondria that are used for aerobic respiration and are generally found in higher abundance in slow-twitch muscles that are used for extended periods of time. In contrast, fast-twitch muscles that require rapid bursts of power but fatigue quickly tend to rely on anaerobic respiration more and therefore have less myoglobin and fewer mitochondria, making them more whitish in appearance. In fact, most animals have both types of muscles (analogous to white meat vs dark meat in chicken). \n\nThis, combined with the fact that chickens and other birds descended from dinosaurs, would seem to indicate that different dinosaurs would have different ratios of slow-twitch and fast-twitch muscles. This means that dinosaurs would have both white meat and dark meat, just like chicken!\n\nGoing further, it's more likely that dinosaurs that were grazers or persistence/pack hunters and moved around all the time would have more red meat and smaller dinosaurs that perhaps would rely on their speed to escape from predation or to catch prey themselves would have more white meat. \n\nSource: medical student with a lifelong fascination of paleontology. ",
" > I'm guessing white due to their close relationship with birds.\n\nThe relationship to birds is irrelevant. Ducks are birds, but they have dark meat. [What gives meat its color](_URL_0_) discusses this: slow-twitch muscles used for sustained activity are red (\"dark\"); fast-twitch muscles used for short bursts of activity are white. \n\nThe primary legs of dinosaurs would have been dark meat, at least.",
"Ok. I have to say it. This is by far my favorite askscience question ever.\n\nWhat kind of person do you have to be before you even think of a question like this?"
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ocgxz | How do we produce hot and cold air from our chest? | When we breath out, we can make it warm but if we blow, it's cold. Surely it all comes from the same place, so what's the difference? | askscience | http://www.reddit.com/r/askscience/comments/ocgxz/how_do_we_produce_hot_and_cold_air_from_our_chest/ | {
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"Actually the difference is the volume of air that you blow.\n\nWhen you blow air with a \"haaaaaaa\" its warm because the air is coming from your lungs, and moving slowly. \n\nWhen you blow air with your lips puckered you are blowing only a small amount of air from your lungs at a high speed, this causes the air around your lips \"room temperature\" to get carried along with it. A venturi effect also happens at higher velocities where when the air leaves your lips it expands, which causes the gas to cool down.\n\nTry blowing very slowly with your lips puckered and you will notice it is warm, but blowing fast makes the air seem cooler.\n\nThis effect combines with the moving air's heat transfer through convection based on speed."
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f47kw | Biologically, do we see in 2D or 3D? | I mean: Do our eyes perceive in 2D and our brains then calculate the depth based on the distance between our eyes or do we basically just see in 3D thanks to our eyes being round? | askscience | http://www.reddit.com/r/askscience/comments/f47kw/biologically_do_we_see_in_2d_or_3d/ | {
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"The eyes just take in light. They're not doing anything fancy, they just send a signal to your brain when they get hit with a photon. The brain most certainly does take that information, use the slight differences between the eyes to give some depth information (okay, and a bunch of other, more subtle, clues), and then places those objects it sees in some representation of the space around you. That is *precisely* what makes the scene '3-D'.\n\nA single eye can't give depth information in the same way. You can still get a decent sense, especially if you lose an eye well after you learn what the world looks like, but only by sensing relative scales based on how large you know objects to be, differences in repeating patterns, et cetera. Or, I suppose, my moving your head back and forth to see what parallax does to the object.\n\nNot sure if that's what you're looking for, but hopefully it helps somewhat.",
"Our eyes individually see in 2-D images, like a camera. Our brain can combine those two images to get a 3-D perception of what we are looking at.",
"There are other cues for distance besides the different images in the two eyes. For example, our brain knows that water falls at a constant rate. If we see a waterfall in the distance our brain can judge how far away it is. Or just moving through space, and seeing objects from different angles tells us how far away they are. We do all of this automatically. This meant that though our retinas are surfaces, we experience the world as being 3D (even if you have only one eye)."
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16yqwb | Traveling to Paris, Munich, and Vienna this spring! Any not well known historical gems you'd recommend I see? | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/16yqwb/traveling_to_paris_munich_and_vienna_this_spring/ | {
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"Munich is home to some truly excellent museums. \n\nThe Glyptothek has an excellent collection of classical sculptures, and the Staatliche Antikensammlung is also great ([This masterpiece of Roman glasswork](_URL_2_) is a highlight.) \n\nThe Alte Pinakothek has [Dürer's famous self portrait](_URL_1_), Altdorfer's *[Battle of Issus](_URL_0_)*, and the world's largest collection of Rubens paintings. \n\nThe Lenbachhaus, which has been closed since 2009, will reopen in May of this year. Here you can see a great collection of works by artists from Die Blaue Reiter movement, including Kandinsky, Franz Marc, and August Macke, in the intimate setting of a former villa.\n\nThen there's the Haus der Kunst, built by the Nazis to serve as a museum of \"Aryan\" art - it's now a contemporary art gallery.\n\nOf course there's also the utterly cavernous Deutsches Museum, the world's largest museum of science and technology. [Eight floors](_URL_3_) full of exhibits covering everything from mining (there's a full scale, immersive mine in the basement) to astronomy. \n\nEdit: Fixed link to Dürer's self portrait; Reddit's markup doesn't like parentheses in URLs. ",
"Paris:\n\n* [Musée de Cluny](_URL_3_ang/homes/home_id20392_u1l2.htm) (new name *Musée national du Moyen Âge - Thermes et hôtel de Cluny*) is Paris' best kept secret in terms of museums. Forget the massiveness and crowds at the Louvre or the Musée d'Orsay (impressionists). Musée de Cluny has everything to offer on **medieval life in France**. It's housed in the [Hôtel de Cluny](_URL_4_), formerly the town house (hôtel) of the abbots of Cluny. \n\n It is partially constructed on the remains of Gallo-Roman baths dating from the third century (known as the *Thermes de Cluny*), which are famous in their own right and which may still be visited. In fact, the museum itself actually consists of two buildings: the frigidarium (\"cooling room\"), where the remains of the Thermes de Cluny are, and the Hôtel de Cluny itself, which houses its impressive collections.\n\n The [English-language website](_URL_2_) is rather sparse, pending overhaul, but the [French-language site](_URL_3_) offers glimpses into the permanent and temporary exhibitions. If you manage to get there before March 4, you can still catch [\"Art of Games - Games in Art. From Babylon to the Medieval West\"](_URL_3_images/affiche.png)\n\n* [Musée des Arts décoratifs](_URL_0_): around the corner from the Louvre and an ideal place to escape the crowds. The highlight of the permanent collection are the period rooms, such as this [Art Déco bedroom](_URL_7_) and [bathroom](_URL_8_), or this [late 15th century bedroom](_URL_1_).",
"I've visited Munich and have to say it's a wonderful city.\n\nNow some of these may be \"well-known\", but I'm a German major so my perception of \"well-known\" may be different than the average person. \n\nNot really Munich, but it's a must. [Dachau](_URL_4_). It was a concentration camp about 16 km North of Munich. It's indescribable. Everyone should visit a concentration camp at least once.\n\nThe [Glypothek](_URL_14_) was built by Ludwig I from 1816-1830 to house his Greek and Roman statues. Today it's part of the [Kunstareal](_URL_0_) (Art District). Which has a ton of museums and is worth checking out.\n\nThe [Olympic Stadium](_URL_1_ which was built for the 1972 Olympics. Very cool. If you head to the top of the [Olympic Tower](_URL_13_) you get a great view (including the Alps if you're lucky with the weather). On a side note, the [BMW Headquarters](_URL_16_) are right next door, it's insanely cool and there's a BMW museum inside. It was actually declared a protected historical building in 1999.\n\nIt's a bit mainstream, but [Marienplatz](_URL_5_), it's a must. This is where the famous [Glockenspiel](_URL_3_) is. If my memory serves me correctly, there's a tourism office there where you can grab maps and get some more information. The [Frauenkirche](_URL_10_ is next door.\n\n[Odeonsplatz](_URL_6_), there's some cool architecture and it was the site of one of the fatal gun battles of the 1923 Beer Hall Putsch. I also had heard Hitler later gave a speech here, but it was just casually mentioned and I can't be sure if it's true.\n\n[Sendlinger Tor](_URL_7_), one of the three remaining Gothic gates, along with [Isartor](_URL_9_) and [Karlstor](_URL_15_).\n\nThe [White Rose Memorial](_URL_2_), the memorial to the White Rose movement.\n\n[Michaelskirche](_URL_12_). I think you can get up the tower for free which has a great view. Ludwig II (Neuscwanstein) is buried here. Along with a few other Bavarian Kings and other high ups.\n\nCheck out the [Englischer Garten](_URL_8_), I *believe* it's larger than Central Park. Even if it's not, it's historical, beautiful and very much worth a visit.\n\nIt's just outside Munich, but make sure to see [Schleissheim Palace](_URL_11_). Baroque and very impressive. Watch out for the swans though, they're mean!\n\n\nMunich is an absolutely amazing city. I plan on living there in the near future. It's very green and the great thing is that although you're constantly walking through history it's still a modern city. You'll have a blast and I'm pretty jealous of you! No matter where you go, you'll find something interesting. Let me know if you have any questions!\n"
]
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"http://en.wikipedia.org/wiki/The_Battle_of_Issus",
"http://en.wikipedia.org/wiki/Self-Portrait_%28D%C3%BCrer,_Munich%29",
"http://upload.wikimedia.org/wikipedia/commons/c/c5/Roman_diatretglas.jpg",
"http://www.deutsches-museum.de/en/exhibitions/overview/map-of-the-exhibitons/"
],
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"http:... | ||
2th8b6 | If you spun a centrifuge wheel in an empty universe, would the contents spin to the outsides or not? | Hope the question says what I mean it to say. I remember having this thought experiment brought up to me, but never resolved. This question itself may be a tautology, my primate brain can't easily grapple with relativity:
If you are inside a spinning drum (or space station), you are pulled to the outside, because your inertia drives you to travel in a straight line, relative to an outside reference point.
However, if you remove all matter that could serve as a reference point, from the reference frame inside the centrifuge, there is no way of knowing if the wheel is spinning or standing still. We know there is no ether or universal frame of reference, so then if it is spinning, are the contents drawn to the outside, or not? Does the universe need to have something else in it in order for a centripetal system to exist? Does direction become meaningless unless matter exists elsewhere? Help! | askscience | http://www.reddit.com/r/askscience/comments/2th8b6/if_you_spun_a_centrifuge_wheel_in_an_empty/ | {
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"text": [
"Imagine a spinning drum in space. Imagine a person floating still somewhere in the middle of it (not touching the walls). The person stays where they are; there is no centrifugal force.\n\nThere is however a centripetal force: if the person touches the wall of the spinning drum, then the friction will cause the person to start spinning with the drum. Once you're already spinning with the drum, due to inertia, your velocity will try to carry you radially away from the drum, but the drum wall exerts a centripetal force on you that keeps you in the drum.\n\nYou experience a centrifugal force if your frame of reference is rotating, and only if your frame of reference is rotating. You can tell whether or not your frame of reference is rotating by if you see a centrifugal force.\n\nHere are a few animations that might make it clear how a rotating frame of reference leads to the appearance of a centrifugal force:\n_URL_1_\n_URL_0_\n\nIt is worth reiterating that a rotating frame of reference is non-Newtonian. Things do not follow Newton's laws of motion in a rotating frame of reference. However, the addition of \"fictitious forces\" such as centrifugal force allows us to think of the system as Newtonian anyway."
]
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"https://www.youtube.com/watch?v=49JwbrXcPjc",
"https://en.wikipedia.org/wiki/Rotating_reference_frame#mediaviewer/File:Corioliskraftanimation.gif"
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43c1qv | what is all this i'm reading about 'negative interest rates' in banks around the world? does this mean that if you leave your money deposited in the bank, they will start to take your money away from you? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/43c1qv/eli5_what_is_all_this_im_reading_about_negative/ | {
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"text": [
"its happened. Its central bank rates, its unlikely that any consumer account would go negative, they would have to eat the spread as a cost of doing business.\n\nBut banks dont have any options to stick their cash under the mattress like people do. So they are enticed to lend that money at low rates which spurs commercial activity."
]
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[]
] | ||
e4poq4 | Why does mustard almost always list its calories as 0 on food labels? Surely it has some calories, yes? If so, what's the real number? | askscience | https://www.reddit.com/r/askscience/comments/e4poq4/why_does_mustard_almost_always_list_its_calories/ | {
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"I think a packet of yellow mustard has 3-4 calories but FDA allows them to round down. As calories are a measure of energy it is true there is calories in mustard just not many. \n\nThere are also some foods that are '0 calories' because even though there is energy in bonds making up the food it is not broken down by humans well and thus we do not utilize those calories so we count them as 0 i think. I am not as sure about this last part",
"Under US law,\n\n > The terms \"calorie free,\" \"free of calories,\" \"no calories,\" \"zero calories,\" \"without calories,\" \"trivial source of calories,\" \"negligible source of calories,\" or \"dietarily insignificant source of calories\" may be used on the label or in the labeling of foods, provided that:\n\n > (i) The food contains less than 5 calories per reference amount customarily consumed and per labeled serving. \n\n_URL_0_\n\nThis means some foods that claim a very small serving size can under US law label themselves as 0 calories.\n\nOther countries' laws differ. The UK for example requires nutrition information to include values per 100 grams or 100 ml.\n\nWe can see for example from a UK retailer's website that French's mustard contains 72 calories per 100 grams, which would be 3.6 calories in a 5 gram teaspoon. (Note that food recipes can also differ between different countries, the French's mustard sold in America might not be the same.)\n\n_URL_1_"
]
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[],
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"https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?fr=101.60",
"https://www.tesco.com/groceries/en-GB/products/256363765"
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244wsf | how do tv channels know the number of people that watched a show? and if i record a show and watch it later, do i still count as a viewer (can they also track that?)? | Always wanted to know this. For instance, if theres a series I cant watch live but i record it and watch later, do they know it has more viewers?
(sorry for bad english) | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/244wsf/eli5_how_do_tv_channels_know_the_number_of_people/ | {
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"There's a company called Nielsen that tracks the TV watching behavior of a bunch of households. Based on what those households are watching, the extrapolate that behavior to the rest of the country.",
"The Nielsen Company collects traditional television ratings data by choosing a cross section of sample households and giving these viewers a set-top Nielsen box. The Nielsen box keeps a digital record of what these so-called \"Nielsen families\" are watching. \nWhat many consumers don't know is that in addition to retrieving scheduling information, they also share data about what you're watching and when. You might remember the notorious Janet Jackson \"nip slip\" during the 2004 Super Bowl halftime performance. After the incident, TiVo released a statement calling it \"the most TiVo'ed moment,\" as TiVo users paused and replayed that clip more times than any other moment in the history of TiVo up to that point [source: Reuters]. While that in itself is interesting, the underlying point is even more revealing: TiVo and other DVRs collect your viewing information, and DVR companies are even using that data to release their own ratings numbers for recorded programs.\n\nTIVO/DVR tell when you watched the show & networks track how many watch for up to a week. So if you watch the recording within a week it gets counted. What I don't know is if it monitors to see if you fast-forward through the commercials."
]
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[],
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8i0svb | how can amazon echo pick up the "wake word" if it doesn't listen to you all the time | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/8i0svb/eli5_how_can_amazon_echo_pick_up_the_wake_word_if/ | {
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"text": [
"When they say it's not listening, they mean it's not uploading everything you say to the internet. It can check locally for the Wake word and then send what follows up to the Internet."
]
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[]
] | ||
6wtwmh | What determines the length of the unburned wick remaining above the candlewax? | Say you're burning a candle, why is the sticking out bit of wick that specific size? Is it related to the temperature of the flame or viscosity of the molten wax or something else unrelated? | askscience | https://www.reddit.com/r/askscience/comments/6wtwmh/what_determines_the_length_of_the_unburned_wick/ | {
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"text": [
"It should be governed by the burn rate and the capillary action drawing the wax up the wick. \n\nThere ends up being an interplay between everything though, so say you have a candle with a long exposed wick. That gives lots of surface area to burn, so the wax on the wick is consumed quickly, the wick itself burns up instead, shortening the wick. BUT, the larger flame during that process melts more wax, making more free to be drawn up the wick, so it also increases the wicking rate. If this causes the wax to substantially drip, the loss of the wax pool exposes more wick, increasing the surface area, making the flame hotter, melting more wax (which again drips) further growing the wick size, etc. This is why sometimes a cheap candle will burn down very quickly. \n"
]
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[]
] | |
mws53 | Is it possible to create a black hole with photons? | If you concentrated enough radiation into one area, would it be theoretically possible to create an event horizon, even though there is no mass present within the black hole? | askscience | http://www.reddit.com/r/askscience/comments/mws53/is_it_possible_to_create_a_black_hole_with_photons/ | {
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"Theoretically, yes and such a thing is called a [Kugelblitz](_URL_0_).",
"Apparently, yes! (See langfan's post.) There's nothing physically wrong with it, as long as the energy density of your light is sufficiently large that it fits within the associated Schwarzschild radius, you'll get an event horizon at which point you're forced to get collapse to a black hole. But it doesn't matter for the resulting black hole that a photon is massless, because as far as gravity is concerned mass and energy are on equal footing. So if you have a bunch of photons with total energy E that form a black hole, its mass would be - you guessed it - E/c^2 . The black hole will show no signs of whether matter or radiation went in, or even what type of matter or radiation it was. Black holes have [no hair](_URL_0_).\n\nFun fact: though there's almost certainly no realistic astrophysical mechanism to create such a thing today†, the gravitational effects of light have had a huge effect on our Universe; in fact, for the first few tens of thousands of years after the Big Bang, light was the **dominant** gravitational source in the Universe! The gravitational properties of light determined how the Universe expanded and evolved, and this is qualitatively different from what happened later when dark matter became the dominant source of gravity.\n\n†In the very early Universe, primordial black holes may have formed due to certain regions being so dense that they collapsed back on themselves. These wouldn't form purely from radiation because there is some matter floating around, but at those times radiation is certainly the dominant mass-energy component, so they would be something along the lines of a \"kugelblitz.\"",
"Theoretically, yes and such a thing is called a [Kugelblitz](_URL_0_).",
"Apparently, yes! (See langfan's post.) There's nothing physically wrong with it, as long as the energy density of your light is sufficiently large that it fits within the associated Schwarzschild radius, you'll get an event horizon at which point you're forced to get collapse to a black hole. But it doesn't matter for the resulting black hole that a photon is massless, because as far as gravity is concerned mass and energy are on equal footing. So if you have a bunch of photons with total energy E that form a black hole, its mass would be - you guessed it - E/c^2 . The black hole will show no signs of whether matter or radiation went in, or even what type of matter or radiation it was. Black holes have [no hair](_URL_0_).\n\nFun fact: though there's almost certainly no realistic astrophysical mechanism to create such a thing today†, the gravitational effects of light have had a huge effect on our Universe; in fact, for the first few tens of thousands of years after the Big Bang, light was the **dominant** gravitational source in the Universe! The gravitational properties of light determined how the Universe expanded and evolved, and this is qualitatively different from what happened later when dark matter became the dominant source of gravity.\n\n†In the very early Universe, primordial black holes may have formed due to certain regions being so dense that they collapsed back on themselves. These wouldn't form purely from radiation because there is some matter floating around, but at those times radiation is certainly the dominant mass-energy component, so they would be something along the lines of a \"kugelblitz.\""
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"http://en.wikipedia.org/wiki/Kugelblitz_(astrophysics\\)"
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"http://en.wikipedia.org/wiki/No-hair_theorem"
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6045of | isn't the freshwater we have to work with just going in a cycle? how are we losing fresh water? | You are told not to take long showers because you're wasting water, but the water goes through the sewers and is cleaned and returned to the water supply, right? Same thing with toilet water, dishwasher, sink, washer, etc? So, where are we actually losing water when we use it? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/6045of/eli5_isnt_the_freshwater_we_have_to_work_with/ | {
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"When the water ends up in the oceans, it slows down the cycling a lot. Water in aquifers (the stores under the ground that we access when we use wells) and water on Earth's surface are the cheapest to use. We have been either polluting these (surface) or using them too fast for new water to filter in. We have also allowed a lot of water to go to the ocean(storm water runoff from developed areas) , rather than slowly go into the aquifers through the ground. So the result is we are using aquifer water faster than they are getting refilled. When that water is depleted, all water will become more expensive. We will still have it, but it will either be salty, polluted, or far from where it needs to be, and all of the fixes for this cost money.\nSorry if this isn't too coherent, I haven't finished my first cup of coffee for the day.",
" > the water goes through the sewers and is cleaned and returned to the water supply, right?\n\nProbably not. I'm my city there is no treatment at all, just a pipe 200m (656ft) long that goes into the ocean. Other cities have various levels of treatment before dumping into the ocean or river. I think it's rare for a city to have enough treatment to make the water drinkable again.",
"If you live somewhere you depend on rainwater filling a tank for water then as long as your tank is big enough and it rains often enough and you don't overuse water you are fine.\nBut throw one thing out, too small a tank, too little rain, too much water used... you got a problem. No problem, just build a real big tank and be careful about useage and it'll rain eventually...\nThen you have some people move in, water useage goes up 600% instantly, you can't afford another tank and it's still not raining.\n\nTake that to the city and everyone on mains supply water is just sharing a big tank. City gets too big, wastes water or it just doesn't rain for ages and the whole city has a supply problem.\n\nThe cycle of water was providing excess water to use in places it was collected, that isn't the case everywhere now. The weather can't provide enough rain in some places.\n\nMore people and industry using more water all the time. There is still more fresh water than needed for all the people, but not necessarily where the people are.",
"In a typical case, water that is \"cleaned\" by municipal treatment facilities is clean enough to be released back in rivers or the sea. It's not clean enough to be used directly. For example, read [this] (_URL_0_) about how Las Vegas gets its fresh water from Lake Mead, but treated water is not put straight back in to the lake. Instead, it is released in to something called the [Las Vegas Wash], a river / wetland complex where natural processes work on the water over time, and impurities are broken down or filtered out. \n\nWhich is fine if you have created a lake to supply you, but the situation in California is different. Much more fresh water is used than the natural sources can supply. So e.g. the Colorado River has basically stopped flowing by the time it reaches the Arizona/California border, and Lake Mead is largely to blame. The \"water table\" under parts of California is being drained more quickly than it's being replenished, making it harder to find fresh water.",
"We aren't necessarily \"losing\" freshwater. We are simply using the limited supply we have at a greater rate than nature replenishes it. ",
"We have a major problem with this in Florida. As we draw more and more freshwater from the aquifer, the amount of rain and time needed to \"refill\" the aquifer is insufficient. As freshwater levels fall in the aquifer, seawater filters in to fill the space. This process was especially bad in and around the Tampa area, where they finally had to build a desalination plant on Tampa bay in order to meet the needs of the population. As Florida continues to grow, we will continue to see the gradual encroachment of seawater into the aquifer, eventually leaving it completely unuseable."
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4nul23 | how is the uk so prominent and how has it been such a big factor in history despite its small size? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/4nul23/eli5how_is_the_uk_so_prominent_and_how_has_it/ | {
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"Kicked off industrial revolution, thus was able to industrialize before anyone else, and claim the advantages that came with it.",
"Being an island the UK developed a large powerful navy in order to protect itself, this then had several consequences:-\n\nFirstly by being relatively safe from attack less money was required for an army or other defences compared to mainland Europe. Being protected from invasion people were more inclined to take on long term projects, like land drainage, industrial development and scientific studies and with less money being needed to fund the army surplus investment was available for this.\n\nSecondly a large navy in peacetime meant that the UK dominated maritime trade at a time when moving goods across land was very expensive due to the dire state of roads. This of course generated extra wealth and income, this in turn meant that the UK was constantly looking for new markets especially concerning countries outside of Europe.\n\nAs a result of improved agriculture population boomed, however with improved agricultural technology less people were needed to work the land. This led to city and industrial growth and at the same time people travelling abroad to the new colonies to seek their fortune.\n\nThis is a very brief look hope it helps.",
"tbh the naval power is the main thing and we the uk taking over country's. ie india, alot of caribbean, parts of africa. i mean we own a 1/3 of the world landmass at one point. not bad for a country that is smaller then several states in america. then the industrial revolution aswell",
"A combination of several factors that led into one another\n\n1) Naval power: As an island nation (after losing it's French lands after the 100 years war), the \"UK\" (which I will include the English Kingdoms before the UK formally formed) figured out that they can't be invaded by any army if no army could ever actually land on it's shores. So, starting sometime shortly after the 100 years war, the UK government invested heavily in an effective navy. This allowed English Privateers (basically pirates officially backed by a country against their military foes in ) could prey on Spanish gold shipments from the New World, hold off invasion attempts like the Spanish Armada, and most importantly, defend it's colonial interests (more on that in a minute). When UK did participate in European land wars, their homeland wasn't devastated by battles or the looting of hungry armies, they were shielded from many of the horrible economic destruction wars wrought.\n\n2) Colonial interests: At it's height, Britain's colonial Empire was [MASSIVE](_URL_1_) (although do be aware it didn't hold onto all these colonies at the same times). In the Caribbean they had sugar producing island, tobacco producing plantations in the 13 colonies, and eventually came to have a monopoly on many of the Indian Ocean spice trades. All these new lands also gave the UK a much bigger tax base and customer base for it's various manufactured goods. The British East India Trading company was absurdly powerful, and had the legal right to even wage wars in the name of higher trade profits. Once again, with the UK's unrivaled naval powers, the rest of Europe really couldn't do much to oppose the UK's empire (France tried in the seven years war, and lost big time). All this colonies, trading, and massive/expensive naval warfare dictated the development of...\n\n3) Finical institutions: So many aspects of finance we just take as a given today, such as stocks, bonds, and central banks were either invented in England or stolen from the Dutch and refined. This gave the UK massive tools to grow economy that many other European nations only could dream of. This all made the UK the perfect place for...\n\n4) The industrial revolution. While the steam engine is actually is [thousands of years old](_URL_0_), it was finally put to good use in the UK. First just to drain out mines, but soon to power machines that no amount of muscle could move. Factories popped up, massively increasing how much consumer goods a given amount of human effort could produce.",
"What it mostly comes down to is they are an island: they have a moat.\n\nThis means they were protected from any land based war/invasion for the last 1000 years.\n\nWhenever any other European country found itself weakened due to internal struggles, or because they screwed up an invasion themselves or because they just were in the way, they had foreign troops at home and were occupied or even absorbed.\n\nNo such thing for the English. Invading them required a huge upfront investment of not just an army big enough to do an occupation, but also a navy big enough to bring them over.\n\nThe English didn't have to worry about Mongols and Turks and Moors. The didn't have to worry about foreign intervention when they split off from the catholic church (something that devastated the rest of Europe for centuries). When they had their War of the Roses, when they had their long string of rebellions when the nobility drove the free yeomen off their land to start capitalism, there was no neighbour that could take advantage of the situation.\n\nThe English could also afford to change side in alliances whenever they saw fit because of that. Its not like the one they screwed over could punish them easily. The English-French animosity that lasted for centuries never resulted in French troops English ground. The long lasting French-German animosity had both sides winning an losing over centuries.\n\nThis protectedness by a moat also allowed the English to have periods without having to spend much on armies for protection. It also allowed them later to have much more army abroad for colonization and not worry about home protection.\n\nThis also shaped the nature of their internal politics. Protection from foreign invasion was a far greater responsibility for the continental rulers. Continental populations saw strong much more Kings as a necessary protection, while on the island the strong kings and their armies where much more freely used and seen as a tool of oppression.\n\nThere hasn't been a real thorough cleansing of the English/British upper class since the Norman conquest. Pretty much the same families that came into power back then still hold most of the land and wealth and most of the positions of power. Just that they are much more inbred and degenerate today now, and feel much more at home fucking kids together with their Arab sheik friends in the same London hotels than with Birmingham rowed house dwellers."
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xb2bw | how can north korea compete in the olympics? | Title pretty much says it all. How were they allowed out of North Korea? I imagine that they would be followed by guards the whole time and not allowed to socialize with the other athletes. | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/xb2bw/how_can_north_korea_compete_in_the_olympics/ | {
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"Well their families probably have guns to their heads currently. All hail dear leader",
"North Korea wants to appear normal to the rest of the world. They also want to appear better than the rest of the world.\n\nWhat better way than to compete in the Olympics. The government wants these athletes to compete. They probably send along an entourage of guards to keep them company.\n\nAccording to Vice (not the best source I know), they make it obvious to the individual leaving the country that the government could arrest the individuals family at any time, so they have an incentive to behave while outside.\n",
"Do they show the Olympics on television in North Korea?",
"Their athletes are loyal party members. ",
"Certain North Koreans are allowed to leave the country with permitted visas, believe it or not.\n\nIn fact, many North Koreans were living and working in Libya for the North Korean government during the revolution there, and because of what they witnessed, they were banned from travel back to NK.\n\nBelieve it or not, many North Koreans don't actually want to leave. There are a good number of them that believe and agree with the message of the government, and it's these kinds of people that typically get sent overseas for anything from the Olympics to FIFA to work contracts.",
"Sorry OP but I'm going to piggyback this thread because I have a similar question. Do north korean athletes get punished if they do poorly? \n\nI was watching a women's soccer game earlier and the north koreans lost 5-0 and I just kept thinking about what happened to the [men's Iraqi soccer team years ago](_URL_0_).\n\nI figure that since north korea really wants to show the rest of the world how amazing they are they probably will want the absolute best from their athletes.",
"I imagine everyone in here is going to get a PM saying \"you have been banned from posting in /r/pyongyang\".",
"Some athletes hail from [Japan](_URL_0_). I remember there was a prominent North Korean soccer player who would travel from Japan to play internationally with the North Korean team.",
"North Korea, for all it's stunning flaws, is very normal in a lot of ways we don't often think about. People come and go all the time. There are a lot of North Koreans who travel for business. Many of their kids have toys. They watch TV. They live.\n\nEven if they can't fool any one into thinking they are normal, they can at least seem less bat shit insane by showing up at the olympics.",
"Followup question: since they are worse than South Africa, which got kicked out, why aren't they banned for diplomatic reasons?",
"Compete? They've already won everything!"
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ro9gy | how can cereals like fruit loops and captain crunch claim to be "part of a balanced breakfast" without getting sued? | It seems to be incredibly misleading if you look at the actual ingredients.
Related: How is a "balanced breakfast" defined? (And, who defined it?) | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/ro9gy/eli5_how_can_cereals_like_fruit_loops_and_captain/ | {
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"There is no strict definition of a balanced breakfast, which is part of how they get away with it. They also advertise it as \"*part* of a balanced breakfast.\" That way, they can say, \"Well, the cereal provides the calories, while the rest of your balanced breakfast provides all the vitamins/minerals.\"",
"There is no standard definition of \"balanced breakfast\". For some food terms, such as \"fat free\", the FDA has established guidelines on how and when the term can be used. But nobody has established what \"balanced breakfast\" means.\n\nFurthermore, \"part of a balanced breakfast\" is a delightful bit of weasel wording that allows them to get away with nearly anything. You'll probably notice that when the full balanced breakfast is shown, there's usually orange juice, toast, milk, and sometimes fruit. \n\nAs a side note, here's a link from the FDA on what you can and cannot claim in your food labeling. It's interesting reading, but definitely not ELI5:\n\n_URL_0_",
"Also, why isn't Captain Crunch sued for the bodily harm they cause. When I eat it I feel like someone is taking shards of glass and slicing the roof of my mouth to pieces."
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uhpkz | How would ships be able to move in space? | I don't understand the physics of what would make a ship move in nothingness. If you shoot out a jet of air, doesn't it need to meet some resistance from something to make you move? | askscience | http://www.reddit.com/r/askscience/comments/uhpkz/how_would_ships_be_able_to_move_in_space/ | {
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"Conservation of momentum. If we're using a jet of air, in your example, we're expelling large amounts of particles at high velocity, and as such it has momentum. This momentum has to be conserved and is done so by moving the object doing the shooting (your space ship) in the opposite direction.\n\nConsider yourself out in space face to face with your buddy, not moving with respect to each other. What do you think will happen when you push him? ",
"The rocket engine's combustion chamber and nozzle act as interface between the exhaust and rocket, the gas pushes the back of the chamber and nozzle prograde while escaping in the opposite direction.",
"From what I understand it's like shooting a gun. There's that recoil that pushes you back. So everything has recoil like that. Like the earlier reply, you push your friend that causes him to travel say 10 mph. Hell go 10 mph in one direction, and you'll go 10 mph in the other",
"[Check out this diagram of a rocket nozzle](_URL_0_)\n\nThere is pressure on the walls of the rocket nozzle. There's also pressure on the combustion chamber but that mostly cancels itself out. The pressure on the rocket walls have a forward component that can be summed to find the rocket's thrust force. \n\nThis is also the same the \"conservation of momentum\" answer because force is equal to the rate of change of momentum. So those force vectors that make up the pressure force (pressure = force/area) are the same as momentum velocity vectors. We refer to momentum as \"p\" and force is dp/dt."
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3a3q17 | Has the double slit experiment been performed on things other than electrons? Would an interference pattern appear if, for example, single atoms of hydrogen were used? | Just curious if the double slit experiment has been performed with atoms or even molecules, and what the results were. I'm assuming there wouldn't be an interference pattern but I'd like to know if it's been tested anyway. | askscience | http://www.reddit.com/r/askscience/comments/3a3q17/has_the_double_slit_experiment_been_performed_on/ | {
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"The double slit experiment was performed with a beam of light in 1802 by Thomas Young. Interference phenomena occur with all sorts of waves, including [water waves](_URL_0_).\n\nIn terms of the \"quantum\" version of the double slit experiment, it has been performed with atoms and molecules and even [buckyballs](_URL_1_).",
"It has been done with progressivly more massive particles, as we have been able to reach higher and higher energies. \n\nI could be remembering things wrong, but I believe my quantum mechanics professor told me we have even been able to diffract molecules. I believe she said buckyballs."
]
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j6hv1 | According to the Hubble constant, the Universe is expanding at around 70 km/s. Does this mean an advanced civilization could go past the 'end' of the Universe, and if they waited, see everything start coming towards them? More ?'s inside. | I just watched [Everything](_URL_0_) by BBC and am left a bit dumbfounded, and actually have a few questions to ask and things to clarify. I've most likely interpreted things horrible wrongly, so forgive me.
Light moves faster than 70km/s, so is it possible for light to reach the 'edge'? If so, does it just disappear? I would think that it cannot, since you cannot create or destroy matter, but if it somehow rebounded then the whole universe would be filled with light, correct? And that doesn't make sense. So why can light not reach the 'edge'? (Sorry for contradicting myself but I don't understand.)
How can it be that objects are still expanding outside of our observable universe? It makes sense that objects moving faster than the speed of light after the big bang would not be seen, but I'm confused on how objects can still be moving outside of our observable universe. If we could see that light earlier, how can we not see that light today?
If you were on an object at the very edge of the entire universe, would you only be able to see your observable universe's light from one side of the object, and the other side would be completely black?
At the end of time, big freeze, whatever you wish to call it, will anything still be near where the big bang occurred? Will any atoms exist there? Or will literally everything have expanded far away from the 'center'?
These questions are a little out there and will probably be hard to explain, but if anyone has knowledge on this subject I would love to learn!
| askscience | http://www.reddit.com/r/askscience/comments/j6hv1/according_to_the_hubble_constant_the_universe_is/ | {
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"The metric is expanding at 70km/s *per Megaparsec* (a megaparsec is a unit of distance). At higher distances, the metric expands faster. At shorter distances, it is slower. Points at the edge of the observable universe are receding from us at the speed of light. This is why it is called observable - light from outside could never reach us.\n\nThe universe (which is different from the observable universe) is believed to be infinite, with no edge.",
"The current understanding is that the Universe is infinite and flat, with no edge. It just keeps on going ang going. This infinite Universe is expanding also. Light can therfor never hit a wall and bounce back.\n\nBut sure current understandings of the Universe might change with future data.",
"Wow... just about everything about this question is wrong.\n\nFirst of all, the Hubble constant is 70 km/s/megaparsec. Farther-away things move faster away from us. Second, there is no \"end\" of the universe. And third, even if there were, it's space itself that's expanding, so with respect to the surrounding \"stuff\", each galaxy sees itself as stationary. They're not flying apart from some explosion. It's more like the surface of a balloon expanding.",
"The metric is expanding at 70km/s *per Megaparsec* (a megaparsec is a unit of distance). At higher distances, the metric expands faster. At shorter distances, it is slower. Points at the edge of the observable universe are receding from us at the speed of light. This is why it is called observable - light from outside could never reach us.\n\nThe universe (which is different from the observable universe) is believed to be infinite, with no edge.",
"The current understanding is that the Universe is infinite and flat, with no edge. It just keeps on going ang going. This infinite Universe is expanding also. Light can therfor never hit a wall and bounce back.\n\nBut sure current understandings of the Universe might change with future data.",
"Wow... just about everything about this question is wrong.\n\nFirst of all, the Hubble constant is 70 km/s/megaparsec. Farther-away things move faster away from us. Second, there is no \"end\" of the universe. And third, even if there were, it's space itself that's expanding, so with respect to the surrounding \"stuff\", each galaxy sees itself as stationary. They're not flying apart from some explosion. It's more like the surface of a balloon expanding."
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44ecgn | would modern medicine (such as antibiotics) have similar effects on the human body as you go further back in time? | I'm essentially asking if you could treat something like bronchitis with today's medicine or would the medicine have to be tweaked in any way? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/44ecgn/eli5_would_modern_medicine_such_as_antibiotics/ | {
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"Modern antibiotics would likely be even more effective in a world without antibiotic resistant bacteria. Some medicines and dosages would obviously require tweaking to account for the generally very poor health (by modern standards) of historical people."
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5zecg4 | why can we put plates in the microwave but not things like silverware? | I know there are microwaveable plates and such but I want to understand why and how something is not okay to out in the microwave.
| explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/5zecg4/eli5_why_can_we_put_plates_in_the_microwave_but/ | {
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"You actually can put metal in a microwave, as long as its smooth. The walls of the microwave are, after all, made of metal. Metal reflects microwaves. The problem arises when you get thin edges, such as forks or foil. The microwaves can generate a strong electric field along these edges, and because metals have lots of free charge carriers (electrons; this is what makes them good conductors) you can get a heavy charge build up on these edges. This can then arc to nearby edges. \n\nCeramics don't have free charge carriers, they are strong insulators. So electric fields can't build up charge. Couple that with their smooth edges, and you can put a plate in a microwave just fine. \n\nEDIT: please note I am NOT advocating putting ANY metal in a microwave - better to be safe than sorry.",
"Microwaves are essentially high-powered radio waves, so think about how your radio works -- you have a long, pointy metal part that sticks up from your radio that \"soaks up\" radio waves from the air, and turn it into electrical flow that, in your radio, gets turned into sound.\n\nThose long, straight forks and spoons you put into the microwave will do the same: soak up the radio waves and turn it into an electrical charge. Unfortunately, they're relatively large, compared to the interior of the microwave, and the microwave is beaming 500 - 1000 watts of energy into the enclosure. All those watts start building up on the silverware, but unlike the food, the silverware isn't getting hot -- it's building up an electrical charge.\n\nThat charge is going to arc to ground when it builds up a whole lot of energy; that spark will jump off the pointy end of your utensil to something and cause a bunch of damage at the points it touches. \n\nYou'll note that microwaves are, well, made of metal, and some microwaves even have a metal rack or thermometer that can go inside; those are there because they are designed for microwaves; your fork is an unexpected thing that hasn't been designed around, so it's going to throw things off."
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ek3q6h | Why can feathers come in pretty much every color, but fur is always black, gray, white, brown, orange, or yellow? | askscience | https://www.reddit.com/r/askscience/comments/ek3q6h/why_can_feathers_come_in_pretty_much_every_color/ | {
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"There's no technical reason why fur couldn't be any color that feathers come in. It's just a matter of evolution and mutation. A mitation for lime green fur just hasn't occurred in an instance that was beneficial.",
"Evolution made it that way. Science is designed to answer questions about what and how, but not really *why*. We can look at the evidence and make our best guess, but the fact is no one really knows for sure because we can't ask genes and molecules what they meant by deciding to be black in pigment rather than bright blue.\n\nWhat we can *observe* is that bright colors in birds often play a role in helping them attract mates, but they also make these males easier targets for predators. Many mammals don't *seem* to take color into account when selecting a mate but use other factors, and so perhaps there was no need for male mammals to use the reproductive strategies of birds to secure mates.\n\n*Edit: fixing a hilarious autocorrect.*",
"Feathers use structural coloration, where as furs, skin, ect mostly use pigments. Structural coloration can produce a greater range of colours bc it exploits the properties of light; by creating microscopic structures small enough to interfere with light this form of coloration can produce nearly any colour without any changes in chemical composition.\n\nPigmentation on the other hand is chemical. It is the colour it is because that compound absorbs all other wavelengths of light. \n\nIn order for an organism to add a new colour to its self with a pigment, which cannot be produced by combining already available pigments or changing their concentration, it would have to expand it's chemical library. The organism must build a new metabolic pathway to produce the new pigment. Getting new colours out of structural coloration is much easier because the chemistry is already there; the organism changes how it builds the microscopic structures that give it colour, but not what those structures are made out of.\n\nEdit for clarity",
"Blue and green feathers get their color from structural coloration which uses selective interference of light waves rather than pigmentation. Most fur doesn't have the nano scale structure needed for interference effects. The golden mole is one exception, but it is a dull orange-brown. There are other examples. There's no reason it couldn't become more common if it was advantageous."
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32554h | When Prussia was unifying Germany, why didn't it invade and annex the German-speaking Cantons of Switzerland? | Considering how Prussia went to war against the Second French Empire for Alsace-Lorraine, I find it strange how Prussia didn't invade Switzerland for the German-speaking Cantons. | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/32554h/when_prussia_was_unifying_germany_why_didnt_it/ | {
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"The Prussians wanted a Prussian-dominated Imperial Germany - and they wanted it to come from the top. All the rulers of Germany - counts, dukes, princes and kings were to voluntarily submit to the Emperor in order for the state to be legitimate. \n\nIt was Prussia that took Alsace-Lorraine from France, not Germany.\n\nThe German-speaking cantons of Switzerland had no desire to join Germany and no high nobility or rulers that could do it for them. Since the cantons did not vote to join. Germany did not want them.\n\nNote that there were plenty of Germans in Bohemia, Moravia and Austria that were not asked to join, since their ruler, the Austrian Emperor Franz Joseph did not want to join."
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3y7lrg | einsteins definition of insanity as "doing the same thing over and over again, but expecting different results”. | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/3y7lrg/eli5einsteins_definition_of_insanity_as_doing_the/ | {
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"He is just saying that if you want things to change, yet you don't change your own actions, you are being foolish. Repeating the same actions will probably lead to the same outcomes. Change must come from trying something different.",
"What's not to get? What's being said is: a person can be considered insane when they repeat actions over and over and expect something different to happen even though nothing has changed in the process. It's only funny or witty because he's a scientist. As a Chemistry major I've run some of the same experiments multiple times, doing the same distillation on 4 separate days to get the same yield or mixing the same reagents and hoping to make gold when all you make is some shitty alkene. He's making fun of science, he's implying that scientists are insane because they meticulously track and repeat experiments looking for something different to happen and create an out of the norm result. ",
"Einstein is the sort of person people like to attribute quotes to. That particular quote actually comes from a 1981 text of Narcotics Anonymous. I imagine it was intended to get people to join Narcotics Anonymous, since they presumably hadn't yet.\n\n[Insanity](_URL_0_) is actually a legal term meaning mental illness of such a severe nature that a person cannot distinguish fantasy from reality, cannot conduct her/his affairs due to psychosis, or is subject to uncontrollable impulsive behavior. I am not a psychologist, but I don't know any mental illness that results in you doing the same thing over and over again but expecting different results. Doing the same thing over and over again sounds like OCD, but I don't think it makes you expect different results.",
"I have a friend who has been a jailer since 2009. In 6 years he's been passed up for promotion 4 separate times. How he goes about it is the definition of insanity; He goes to work on time, works his full shift, only calls off when necessary, then goes home when his shift is over. \n \nBut that's it, that's all he does. He doesn't pick the brains of the people holding the position he wants. He doesn't do physical improvement. He doesn't even volunteer for extra shifts, or agree to take the shit shifts to make his boss's job easier. All he does is his job, then applies for the promotion when it's available. \n \nYou get passed up once, maybe someone was more qualified. Twice, and maybe you should start finding out why and work on that. Four times or more? If nothing has changed since the first time, being hopeful that the outcome will be different is just an insane way to think. "
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eeg3o5 | what is the use of inductors in a circuit? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/eeg3o5/eli5_what_is_the_use_of_inductors_in_a_circuit/ | {
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"An inductor is like a resistor that only works with alternating current. When a changing current pass through a coil it produces a magnetic fields, and when that current is changing, the magnetic field induces voltage in the opposite direction. \n\nInductors are often used in conjunction with capacitors to create an LC circuit. Inductors make the changing voltage in a circuit lag behind the current, while capacitors make the current lag behind the voltage. The amount of lag changes with the frequency of the AC. At the right frequency these lags cancel each other out, resistance drops and a resonance is created. This is how radio tuners select just one signal while rejecting interference for all the others.",
"As previous poster mentions, it can be used in several configurations in conjunction with resistors and capacitors to form filters and with variable inductors or capacitors - tuned filters. These are essential to \"select\" certain frequency ranges from a signal and is the core of FM/AM radio etc. \n\nIn modern electronics, inductors are generally used as \"chokes\" - the ferrite bead you sometimes see on a charging cable (or more usually built into the power connector nowadays) is and example. Chokes are used to block high frequency noise from one device to another or from one circuit to another. \n\nIn high power circuits, these chokes allow devices to turn on and off safely without generating large spikes that might otherwise trip/damage other devices connected to it."
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h5z93 | If you pressed a gun against somebody's head and pulled the trigger, would their head act as a silencer? | askscience | http://www.reddit.com/r/askscience/comments/h5z93/if_you_pressed_a_gun_against_somebodys_head_and/ | {
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"Suppressors work by reducing the intensity of the sound wave produced by the propellant/gases being expelled from the barrel. Logically, putting an object against the barrel would do the trick. However, soft tissue is not strong enough to resist the pressure of a muzzle blast. Contact gun shots are usually accompanied by a star-shaped lesion at the entrance wound, due to gases trying to escape from the barrel. What ends up happening is that the entrance wound allows gases to enter soft tissue, and from that point forward it would follow the path of least resistance.\n\nSource: Undergraduate forensic pathology (so you can take it with a grain of salt)\n\nWarning, graphic image below:\n\n[Here](_URL_0_) is what a contact gunshot wound looks like, from a post-mortem photograph.\n\nEdit: Not to mention another major source of noise is the sonic boom produced by the travelling bullet."
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ljejs | how does rfid encryption work? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/ljejs/how_does_rfid_encryption_work/ | {
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"You're going to have to provide more details in your question here. Do you mean encryption on cards that prevents anyone with an RFID reader from reading the card?",
"Encryption in RFID comes in two flavours, one involves securing the data held on the tag, and the second is securing the trasmission of that data.\n\nSecuring tag data is essentially the same as the encryption methods used to secure digital data in other areas of computing. \nPlain text held on the tag is turned into a cipher using a specific algorithm and it is deciphered back into plain text using the same algorithm by the software supporting the reader. Adding encryption to the tag adds overheads in both the time it takes to process the information and memory required to store the information.\n\nSecuring the transmission is a little more of an obtuse definition of encryption. Radio is not the most secure transmission medium around. An RFID tag can essentially be interrogated by any reader broadcasting on its frequency. To get around this you can employ methods which force the tag to respond only if a specific code is transmitted to them. Adding this sort of functionality to a tag increases the processing requirements of them, thus increasing their cost. Securing the transmission also increases the time it takes to read tag data. \n\n\nGenerally most RFID implementations do not employ encryption. RFID tags need to be cheaply mass produced and readable in the thousands. The additional cost in time and money to add encryption is often not worth it. It is often not required either. Most RFID tags only contain a string of alphanumeric characters only relevant to the supporting software, so intercepting and reading their information is pointless. \n",
"You're going to have to provide more details in your question here. Do you mean encryption on cards that prevents anyone with an RFID reader from reading the card?",
"Encryption in RFID comes in two flavours, one involves securing the data held on the tag, and the second is securing the trasmission of that data.\n\nSecuring tag data is essentially the same as the encryption methods used to secure digital data in other areas of computing. \nPlain text held on the tag is turned into a cipher using a specific algorithm and it is deciphered back into plain text using the same algorithm by the software supporting the reader. Adding encryption to the tag adds overheads in both the time it takes to process the information and memory required to store the information.\n\nSecuring the transmission is a little more of an obtuse definition of encryption. Radio is not the most secure transmission medium around. An RFID tag can essentially be interrogated by any reader broadcasting on its frequency. To get around this you can employ methods which force the tag to respond only if a specific code is transmitted to them. Adding this sort of functionality to a tag increases the processing requirements of them, thus increasing their cost. Securing the transmission also increases the time it takes to read tag data. \n\n\nGenerally most RFID implementations do not employ encryption. RFID tags need to be cheaply mass produced and readable in the thousands. The additional cost in time and money to add encryption is often not worth it. It is often not required either. Most RFID tags only contain a string of alphanumeric characters only relevant to the supporting software, so intercepting and reading their information is pointless. \n"
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adc2qx | Pre-Archaemenid and pre-Median Iran | What was the political structure of pre-Archaemenid and pre-Median Iranian Plateau?
Did it consist of city states like in early Sumer and Assyria, nomadic tribes, or was it inhabitated by highly-urbanized though disorganized tribes like in Levant? | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/adc2qx/prearchaemenid_and_premedian_iran/ | {
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"Can you clarify? Do you mean before the establishment of the Achaemenid Empire or before the Medes and Persians migrated into West Iran in the first place?"
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ms8zd | Why we dont put to sleep hard drug-addicts for two months to detoxify their body without pain and mental distress? |
That way all the withdrawal process to eradicate the addiction can be done without any suffering, almost unconsciously.
Can it work? | askscience | http://www.reddit.com/r/askscience/comments/ms8zd/why_we_dont_put_to_sleep_hard_drugaddicts_for_two/ | {
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"Others have brought up some relevant points, but the short answer is that it's an unnecessary risk. An induced coma is not routine, and the negatives (risk, cost, medical resources required) outweigh the positives (making detoxification *easier* on the user)",
"Induced comas have lots of risks. The inducing drugs have negative effects on the body. The person becomes completely dependent on others for things like food, water, breathing, even just moving around a little bit every few hours to prevent bedsores. Even in the best ICU, problems will develop in some and there will be complications, including lethal ones.",
"Others have brought up some relevant points, but the short answer is that it's an unnecessary risk. An induced coma is not routine, and the negatives (risk, cost, medical resources required) outweigh the positives (making detoxification *easier* on the user)",
"Induced comas have lots of risks. The inducing drugs have negative effects on the body. The person becomes completely dependent on others for things like food, water, breathing, even just moving around a little bit every few hours to prevent bedsores. Even in the best ICU, problems will develop in some and there will be complications, including lethal ones."
]
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201ykw | What exactly is Brahman? | Sorry if this is the wrong subreddit, but I didn't know which one to post this. I've heard about if, and have done some research, but I cannot seem to get a grasp on the concept. | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/201ykw/what_exactly_is_brahman/ | {
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"You'd probably be best taking his to /r/religion or /r/hinduism. "
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[]
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1lp335 | Wednesday AMA: Australian History Panel | Greetings! This Saturday, Australia will be holding an election to decide who will govern our federal government for the coming four (or so) years. With this in mind, now seemed a good time to open up and try to answer any questions about Australian history you have.
Today's panel consists of myself (/u/w2red), /u/Algernon_Asimov and /u/thebattlersprince.
I am a postgrad student currently researching the Great Depression and issues of class and gender in labour during the 1930s. I've previously worked on the Australian Communist Party and Australian politics post-Federation.
/u/Algernon_Asimov's expertise focuses on the period of the federation of Australia: from 1880 to 1910. However, his knowledge includes government and politics before and after that period.
Meanwhile, /u/thebattlersprince is currently their final year of university studying Primary Education but specialising in teaching history.
> As a teacher, you have to have a jack of all trades attitude when it comes to teaching history to children, so I suppose you could classify my interest in Australian history as such. The largest complaint that children have with Australian history is that they perceive it to be "boring" (particularly compared to other countries) and my aim is to change that attitude. There is so much to the history of Australia than just convicts!
> With a military family history going back four generations, I also have a keen interest in Australia's military history, particularly the concepts of Anzac and it's influence on society.
I'm sure this panel will provide a comprehensive coverage of Australian history from pre-Federation through to the early-90s. There is [a list of previously asked questions available here](_URL_5_) (though I think we need to update it!) that you may like to look at and perhaps build upon.
* [British emigration to Australia and New Zealand post-WWII](_URL_8_)
* [Why did the six colonies of Australia decide to federate?](_URL_2_)
* and as a follow on, [Is it true that New Zealand was nearly a part of Australia?](_URL_4_)
* [What was life like for a prisoner recently transported to Australia?](_URL_6_)
* [Was the Australian government as brutal towards indigenous peoples as the US Government was?](_URL_0_)
* [What historical reasons lead to the different treatment of Maori culture in New Zealand to the treatment of Aboriginal culture in Australia?](_URL_3_)
* [Why was the east coast of Australia more settled by Europeans instead of the closer western coast?](_URL_1_)
[And, as always, read the sub rules before posting and commenting](_URL_7_). | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/1lp335/wednesday_ama_australian_history_panel/ | {
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"Why were women given the vote via act of parliament but Aborigines via referendum?",
"australian elections feel more and more presidential as they come around. has the office of prime minister always been seen this way or was there a time where the PM was seen as just one position in a potential cabinet?",
"What are your views on the National History Curriculum? I note that the Coalition has indicated they want it revised because it doesn't include narratives that support their ideology.",
"Is it true that before the Referendum, Aboriginals were classified as flora and fauna?",
"Got a few questions:\n\n1. How did the Whitlam Dismissal affect UK-Australian relationship and do you give credence to the idea that that America played any part in the dismissal? (Might be outside the panel's expertise) \n\n2. How socialist was the labor party at conception? \n\n2. How serious was West Australian nationalism? \n\n3. What do you think of the Australian Frontier wars? Was it a prolonged military engagement? \n\n4. What was America's relationship too Australia prior to Federation? \n\n5. Similarly, What was America's relationship too Australia prior to WW2?\n\n6. Why did the Australian Temeperance movement fail in Australia?\n\nedit: \nHistiographical question, do you think Australian history is looked down upon in Australia? \n\n \n\n\n\n\n\n",
"What was the public perception of the Whitlam dismissal? Was there outrage, were they in favour of it, apathy?",
"Why did Queensland get rid on the upper house and end up with a unicameral system? Has there ever been a serious attempt to reintroduce an upper house? ",
"This is fantastic that Australian History is taking the spotlight for this, and i am glad that you guys are helping me with my History Extension Work!:D\n\nMy question is this:\n\nMany Historians have debated about whether the British landing at Botany Bay and subsequent settlement should be defined as an Invasion. How has this view changed over the last 200 years and how does it link (If at all) to the concept of Terra Nullius that was applied in 1838?",
"There seems to me to be a gap in pre european australian history. Apart from the very basics little of this is taught in schools. The recent abc doco \"first footprints\" gave an interesting overview on this eg migration, technology and art development, conflict etc\n\nWhy isnt more of that sort of thing taught? Can you point me in the direction of a good book on the subjects?",
"I have more questions: \n\n1) Why did Robert Menzies introduce the communist dissolution bill? \n1a) What was the public reaction? \n\n2) How much influence did non-australian communists parties have on the Australian Communist Party? \n",
"* How did Britain's prior colonial experience in the North America influences its colonial policies in Australia, both with regard to the colonists and with regard to the indigenous population?\n\n* Can you give some notable examples of how Aboriginal Australians resisted (both militarily and politically) to colonization? Any notable cases of Aboriginal Australian peoples initially profiting from the arrival of Europeans, as some Native American nations did in North America?\n\n* Who are some notable Aboriginal Australian individuals in history and what makes him or her notable? Are these figures well-known in Australia (would you expect an average teenager to have picked this information in a history class)?",
"First up, thanks for this.... so many questions!\n\nI have a my grandfathers Iron Mongers and Munitions Workers union book from when he migrated here from Italy in 1948. What was the union participation rate of European migrants in the post-war era, and how left leaning were they? Was Communism or Socialism an attractive proposition to them? "
]
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"http://www.reddit.com/r/AskHistorians/comments/1l7e2b/were_the_canadian_andor_australian_governments_as/",
"http://www.reddit.com/r/AskHistorians/comments/1ks8t9/why_was_the_eastern_coast_of_australia_more/",
"http://www.reddit.com/r/AskHistorians/comments/1kec88/why_did_the_six_colonies_of_australia_decide_to... | [
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29eq5t | How did Eastern and Northeastern Europe become predominantly Orthodox rather than Catholic, when prior to their conversion they had been Slavic religions next to Catholic kingdoms? | The only center of Orthodoxy was the Byzantine Empire, right? | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/29eq5t/how_did_eastern_and_northeastern_europe_become/ | {
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"Yes the byzantines were the center of Orthodoxy. It was mostly due to them and the First Bulgarian Empire that Orthodoxy along with the cyrillic alphabet spread in Eastern, Northeastern Europe and Russia. I do not know much about the byzantines, but the bulgarians at that time invested a lot of money and resources in translating and spreading Christianity north and northeast. The tight trade connections and interactions between byzantines, bulgars and the various Rus and slavic states and the common slavic language also helped.\n\nSource: mostly \"History of Bulgaria\", Bulgarian Academy of sciences,"
]
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[]
] | |
2bjdk3 | Was any "Golden Age" in history recognized as such at the time? | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/2bjdk3/was_any_golden_age_in_history_recognized_as_such/ | {
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"At the risk of being close to contemporary, the phrase *Pax Americana* has been used many times in the past 100 years to describe the success of United States' influence over the Western Hemisphere then much of the European/non-aligned bloc even during the Cold War.\n\nCompared to other golden ages, we can obviously see far more of the concept's weaknesses. Bear in mind that this phrase refers specifically to the foreign policy and political aspects of the relative period of stability afforded to much of the Western bloc after World War II, not to the far more tumultuous state of domestic affairs or civil rights especially in the United States which did not reach its landmark accomplishments until the late 1960's.\n\nAthens also reached a definite period of triumphalism after the Persian Wars, forming the Delian League to aggressively pursue a level of influence over the Greek city-states not seen in centuries. Pericles, one of Athens' most powerful statesmen, helped to embody the sense of this age which also fostered the corresponding rise of Western philosophy (and its fascinating organic interaction with Athenian politics). It's worth noting however, that this \"golden age\" quickly precipitated hostilities with Sparta's own league of city-states, a devastating plague, and the end of Greek hegemony as Macedonian military supremacy rose."
]
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17vmi6 | - american government (congress, the house of representatives, etc) | I'm from the UK and interested in politics over here. I am totally confused with the USA's government and would like it if someone explained it, please.
Thanks :) | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/17vmi6/eli5_american_government_congress_the_house_of/ | {
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"The UK has a parliamentary system; the US has a presidential system. The differences are pretty minor. The biggest one is that in the UK, the head of the government is a legislator, while in the US he isn't.\n\nIn the US, all our federal laws are made by the Congress, which is roughly equivalent to Parliament. The Congress is made up of two houses, the House of Representatives and the Senate. The House of Representatives is roughly equivalent to the House of Commons; the members come from defined places (\"constituencies\" in the UK, \"districts\" in the US) and are elected by the people who live in those places.\n\nThe Senate, however, is *not* roughly equivalent to the House of Lords. The Senate was originally meant — back in the 1790s — to be in many ways the opposite of the House of Representatives. Members of the House are elected by the people; members of the Senate were appointed by the state governments. Members of the House are elected to short terms of office; members of the Senate were appointed to long terms of office. And so on.\n\nBut over the years, various changes have been made to make the Senate more \"democratic.\" For instance, today the members of the Senate are elected by the people directly, and are no longer appointed. That kind of thing.\n\nBut the *mandate* of the Senate is still the same: It's to balance the will-of-the-people aspect of the House of Representatives by being more deliberative and circumspect. If the Senate and House were people, the House would be the enthusiastic, idealistic teenager, and the Senate would be the mature, wise and slightly cynical adult.\n\nOur head of government is a separately elected person called the president; his role in government is *sort of similar* to the PM, but first and foremost he is not a legislator. He makes no laws, doesn't participate in the legislature, and so on. His job is *exclusively* to do what the Congress tells him to do. The Congress sets policy, and the president (through his truly vast organization of employees) carries out that policy.\n\nThere's also the judiciary, but the differences between how that works in the US and UK aren't important enough to go into. There are courts and judges. No surprises there.\n\nThe *real* difference between the government of the United States and the government of the UK, however, is that the government of the United States is tiered.\n\nYou know about home rule, right? It's the idea that, for example, Scotland is politically part of the UK and is subject both to the Crown and also to Parliament … but at the same time, Scotland now (since 1999) has its own parliament, and some degree of limited self-rule.\n\nIn the US, home rule is the *norm,* not the exception. The US is a federation of fifty sovereign and semi-autonomous states. Those states voluntarily joined together to form one political entity called (unimaginatively) the United States, establishing a layer of government *on top of* the sovereign governments of the states. For example, I live in California. I am subject to the laws of California. I pay my taxes to California, I participate in elections to choose the government of California, and so on. For all intents and purposes, the \"country\" of which I'm a citizen is California. But California is part of the United States, so there's this other thing on top that also affects me, albeit quite seldom and indirectly.\n\nSo in a sense, the government of the United States is to me as the EU is to you. It's there, it affects you, but it's not the most important legal system in your life. That's not an exact analogy; Washington is more important to an American than Brussels is to an Englishman, say. But it's pretty close to how things really are."
]
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33tqss | how are nuclear power plants resistant to various nature attacks? (tornados, lighting) | I live relatively near a power plant and am not really worried about it getting tornadoed, but I am interested in learning how they are protected from nature. Any information is appreciated! | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/33tqss/eli5_how_are_nuclear_power_plants_resistant_to/ | {
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"Nuclear power plants are structurally very secure. There are various layers of steel and concrete to shield radiation and protect against natural disasters. Lightning is not even a threat unless it somehow manages to overload the electronics running the plant. Tornadoes do not have the force to rip through several metres of concrete. Barring large natural disasters i.e. Earthquakes, man-made activities i.e. Missile strikes and acts of god nuclear plants are structurally very secure.",
"Nuclear plants are, especially in the reactor, heavily protected by concrete (up to several feet). This minimizes the damage from impact or winds. They are grounded in some way to prevent damage from lightning. As a general rule reactors are very safe. The Fukushima disaster was an extreme case of an old reactor hit by an intensely powerful event. ",
"Tornadoes and Lightning do immense damage to residential-grade construction - thin walls, minimal cost, lowest bidder, etc. Neither tend to do noteworthy damage to thick, steel reinforced concrete structures. A 1/2\" copper rod can safely conduct the majority of lightning strikes *without* damage. We know how to mitigate all but the most extreme natural events, it's just not cost effective most of the time, so most structures are not built that way.",
"Lightning isn't an issue. Worst case, lightning causes you to lose your switchyard/offsite power. The reactor automatically scrams and the emergency generators start up for decay heat removal and inventory control. This happened at the LaSalle nuclear plant a few years ago. Lightning arced and caused the switchyard to disconnect the plant from the grid. \n\nTornados won't affect the reactor directly due to the containment system being designed from several feet of concrete as a missile shield. However tornados can damage offsite power and portions of safety equipment required for plant shutdown. In general, every plant will be able to cope with this type of event for at least 24 hours until offsite equipment can be delivered for safe shutdown. Most onsite equipment is protected by shield or missile barriers to prevent tornado and missile based damage. One of the analysis performed a few years ago was \"smart tornado\" which is a tornado that causes any vulnerable or common mode failure equipment to all fail simultaneously unless it's in a missile proof bunker, and every plant had to demonstrate they can cope until offsite equipment is available. \n\nI'm a nuclear engineer and I've worked on some of these designs/analysis. "
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1lnf4a | Can my dog distinguish between my whistle and another persons whistle? Is there anything distinct about a whistle like there is with a voice? | askscience | http://www.reddit.com/r/askscience/comments/1lnf4a/can_my_dog_distinguish_between_my_whistle_and/ | {
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"The answer is yes with an asterisk. At least some working border collies can distinguish between the whistles of different people, but they have been being selected for for about 430 years to be able to understand language and whistles. Other breeds would be less likely to be apt at this skill. It also depends whether you are asking about a mouth whistle or an actual device whistle that you use. Whistling with your mouth would have more variability, and thus be more distinguishable.",
"I don't know about a dog but definitely people can distinguish whistler's distinct 'voices'. See for example: _URL_0_\n\nNotice F never asks, \"who's whistling?\" he can likely tell the 'voice'."
]
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[],
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"http://www-01.sil.org/mexico/chinanteca/sochiapam/13i-Conversacion-cso.htm"
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dsm5z1 | does a polyglot learn languages differently than an average person? | Also, is it possible to anyone to become a polyglot? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/dsm5z1/eli5_does_a_polyglot_learn_languages_differently/ | {
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"At around age 12, on average, our brains stop “acquiring” language and begin “learning” language. These are seated in different parts of the brain. There’s an interesting case where an anglophone man who learned Spanish later in life was in a terrible car accident and had brain damage. He stopped being able to speak his native English but could still speak Spanish. So there comes a point where you can no longer become a ‘native’ speaker of a language and are instead translating in your brain. Many languages are related though. I speak French and English myself but I can easily understand spanish and some Italian as they are both very similar to French - Latin-based. The more languages you know, the easier it is to understand and learn another because it’s likely related to a language you already know."
]
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[]
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4dditv | howcome a bag of chips bought at a highschool lunch are much more empty compared to when buying the same brand of chips at a store? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/4dditv/eli5_howcome_a_bag_of_chips_bought_at_a/ | {
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"they are sold by weight not by volume. there's empty space for padding. so are the weights the same?",
"Chips are sold by weight, not volume. So you need to compare the weights of the bags not how full they are. ",
"A) The larger the bag the less air they need to add by percentage of volume to protect the chips. \nB) size of bag is irrelevant since you're buying weight, as has been noted \nC) It's probably a perception thing since you might be hungrier on the lunch line. \nD) Stop eating Doritos at school. Drink more water."
]
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s6m9r | the pangea theory. | Explain it like I'm five. | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/s6m9r/the_pangea_theory/ | {
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"Think of the surface of the Earth as thin plates of dirt and rock, sitting on a giant ball of magma. These plates are constantly sliding around (very slowly, at about the same rate as our fingernails grow), but sometimes they can shift suddenly and create an earthquake. By tracking the current movement of plates, and by comparing [similar fossils](_URL_0_) and similar kinds of rock in certain places, we can see that at one time, all of the plates were together in such a way that there was one big continent on the Earth, called Pangea."
]
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[
"http://upload.wikimedia.org/wikipedia/commons/2/22/Snider-Pellegrini_Wegener_fossil_map.gif"
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6qagfp | If I donate blood, then later need a blood transfusion, what are the odds that I'm receiving my own blood? | askscience | https://www.reddit.com/r/askscience/comments/6qagfp/if_i_donate_blood_then_later_need_a_blood/ | {
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"Actually the odds are better than they used to be that you will at least receive *some* of your own blood.\n\nThe reason is that donated blood is now separated into their components: plasma, red blood cells, and platelets. The individual components are then pooled with those from other donors for use.\n\nHere's a non-technical [article](_URL_0_) on it with interesting photos.",
"As whole blood, nil after 30 days. As blood products, depends. Some plasma products are stable for a year or more and you might be treated with them. Most donated blood is pooled and used for blood products such as platelets."
]
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[
"http://www.thejournal.ie/tracing-the-blood-line-heres-what-happens-to-your-blood-after-you-donate-1363177-Mar2014/"
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bpwsk2 | what is superflat? what does it mean both as an art style and as an idea? | I have a hard time understanding Superflat art and what it is supposed to mean. I see examples of it when I google it (ie Murakami) but most attempts to explain it leave me more confused. | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/bpwsk2/eli5_what_is_superflat_what_does_it_mean_both_as/ | {
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"It's basically a word Murakami uses to describe his own work, and people use to describe similar art. It's loosely defined but the general idea is he takes some japanese pop commercial art (anime/manga/toy figurines/model building) and mixes it with a shocking or out of place element (often something grotesquely sexual or violent) \n\n & #x200B;\n\nIt's a little weird now, because so much time has passed and his most famous works are decades old. A lot of the grotesque imagery he was working with got absorbed over time into actual japanese mainstream so it's less obvious he was doing anything but drawing 4chan posts. \n\n\nLike in 1996 taking an manga drawing of a small hello kitty style child and making them into a grotesque monster made of breasts and vaginas was a more out there take on the sexualization of manga and of children in media and stuff because it was so over the top compared to other things. But like, now \"X rated hyper violent cute animal manga\" is it's own section in the book store so a lot of context is lost compared to when he started."
]
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11mk66 | why do some devices and game consoles use those shitty enormous power adapters? | Plenty of devices do not use those ridiculous things. Why do any of them require them instead of a normal power cord? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/11mk66/eli5_why_do_some_devices_and_game_consoles_use/ | {
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"Things like games consoles don't run using power straight for the mains. It's voltage is too high and in order to prevent the device from being fried, it needs to be stepped down by a transformer. The same goes for PC's but you don't see the big bricks because they are inside the case. With consoles, space is at a premium so many designers use an external transformer on the actual cord. The added bonus is that it also deals with the heat problem: Power suppliers throw out quite a lot of the stuff and running too hot is not a good thing for electrical devices. By having it externally you can make a more attractive/compact form factor and not have to worry about overheating so much.",
"**tl;dr**: Miniaturization costs money. Consoles are cheap.\n\nSmallness costs money, in the form of better engineering and more expensive components with better electrical and magnetic properties. In the old days power converters were pretty straightforward - you would use a transformer to step down the wall's AC voltage (and isolate the device), and a four-diode rectifier and giant filter capacitor to make D.C. out of the low voltage A.C. The rectifier just allows the A.C. current to pass into your D.C. circuit in one direction, so you get pulsing D.C, and the capacitor stores a tiny amount of energy to keep you going during the times when the wall socket voltage is zero. (every 1/120th of a second in the U.S., every 1/100th of a second everywhere else). But supplies like that develop \"ripple\" - they don't give a perfectly steady output voltage. So people developed fed-back dissipative regulators, which you can still buy today -- the \"7805\" chip, for example, accepts ripply 7 volts DC and gives you clean 5 volts DC.\n\nMaking that kind of power supply more, well, powerful means making it bigger. Old stereos have huge ones, with gigantic, heavy transformers, big hulking filter capacitors, and rectifier diodes the size of vitamin C tablets.\n\nAlong about the 1980s people developed something called a \"switching power supply\" that can generate more regulated power with less waste. Switching power supplies switch a transistor \"ON\" and \"OFF\" very quickly to dispense small amounts of charge into a capacitor, either directly from the mains or from a transformer. The transistor switches at very high rates -- tens of kiloHertz to megaHertz. Discrete-component switching power supplies are about the size of a box of animal crackers, and (famously) got used in the Apple ][. That technology is now very cheap and well-understood, and is what gets used for game consoles. In the \"animal cracker box\" size, this type of supply can produce up to 20-30 Watts of regulated power.\n\nHigher power densities require better parts: better induction coils, better capacitors, more carful circuit design. Laptop computers use modern high-density switching power supplies that can handle more like 100 Watts. Apple is famous for making very efficient switching supplies that have very high power densities -- a MacBook Pro supply is rated at 85 Watts and can actually supply over 100 Watts without much effort, and the 10W iPad/iPhone chargers are miracles of miniaturization. But all that costs money.\n\nGame consoles have to be cheap, so they use the cheapest supplies that they can -- either direct rectifiers or low-power-density switching supplies based on that 1980s/1990s technology. That means the included power supplies are big. \n"
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79jwbc | how do we know what's happening in complex biochemical reactions? | I'm not sure how to phrase this... I'm studying pharmacology which obviously involves a lot of biochem. It blows my mind how many enzymes and chemicals and reactions there are. How did we discover all the individual enzymes and reactions that take place in the Citric Acid Cycle, for instance? How are we observing cellular metabolism? It seems so complicated and amazing. | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/79jwbc/eli5_how_do_we_know_whats_happening_in_complex/ | {
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"There's two parts to your answer.\n\nOne is that we isolate the chemical, or even random chemicals, and add them to reagents to determine what they do. You add X to Y and it produces a specific amount of Z you can say it's an enzyme with a specific power of activation. This is how the citric acid cycle was *originally* worked out.\n\nThe 2nd is computer modeling - we understand the subatomic and quantum physics much better than we understand most biological molecules. So we can run massive computer simulations of various types (monte carlo, ect) only knowing the initial composition of the protein and a general guess as to what it does. This is getting more accurate by the day but it's not perfect - you then verify the models in the lab.",
"This is a bit of a complex question, and I wish you'd asked it in askscience... but nonetheless...\n\nWe need to go very historical on this, or otherwise this explanation will be circular.\n\nI'm not going to use the citric acid cycle as an example, because as you pointed out, it is very complex.\n\nInstead, I'm going to talk about the Cytochrome p450 enzymes, which as a pharmocologist, you are going to learn a lot about.\n\nScientists knew that compounds in the body got broken down. They knew this because, for instance, if someone got a fright, they had lots of adrenaline in their blood, but rapidly that adrenaline disappeared from the blood. They also thought that adrenaline might get broken down into something called noradrenaline, because they could put adrenaline onto a mush made of fresh liver, and get noradrenaline. Because other scientists had said that this reaction shouldn't happen very fast without help, the scientists suspected that there must be an enzyme that did this. By carefully measuring the amount of adrenaline added, and the amount of noradrenaline formed, they found that for every molecule of adrenaline added to the liver, they got one molecular of noradrenaline formed. This really strongly suggested that the adrenaline was being converted to noradrenaline (rather than adrenaline causing the release of noradrenaline).\n\nBy using centrifuges, and various other simple chemical techniques, they were able to make relatively pure samples of this enzyme. Once that happened, then real progress could be made.\n\nFor instance, we already knew that enzymes can be \"saturated\". That means that if an enzyme is doing a chemical reaction, by converting compound A into compound B.. if you add more of compound A the transformation into compound B goes faster. However, if you add too much of compound A, the transformation into compound B cannot go any faster. You can think about this like if you were making a sandwich: If I gave you two pieces of bread, which you converted into a sandwich, you could do that. If I gave you two pieces of bread every half hour, you could make a sandwich every half hour. Now if I gave you the bread faster, say every five minutes, you could make a sandwich every five minutes. However, if I gave you two pieces of bread every second, you could not make a sandwich every second. You are now \"saturated\" with bread. No matter how much more bread I give you, you cannot go faster.\n\nSo the scientists investigated how this enzyme in the liver which converts adrenaline to noradrenaline behaved, and they found just that. That once they gave it lots of adrenaline, it could not make noradrenaline any faster. But they found that if they added another compound (which I can't remember right now), the enzyme was able to break that compound down. How could you explain that? If you were busy making sandwiches as fast as you could, and I all of a sudden asked you to make oatmeal, you couldn't. The only explanation was that there were actually TWO kinds of enzymes. One that broke down adrenaline, and one that broke down the other compound. The scientific word for this is \"competition\". The adrenaline and the other compound were not \"competing\" for the same enzyme. Scientists continued to do experiments like this. If chemical A was saturating the enzyme, and chemical X could still be broken down, then the enzyme that broke down chemical A and chemical X were different. However, if the enzyme was saturated with chemical A, and now chemical Y could not be broken down, then chemical A and chemical Y were broken down by the same enzyme. By doing a lot of these experiments, scientists were able to discover that the original \"enzyme\" that was isolated was actually hundreds of different enzymes. They were all of the same family, as certain chemicals were able to block all of them, but they were all different, because they liked different compounds. This family is now called the cytochrome P450 family.\n\nSimilar experiments were done to reveal all the enzymes in the citric acid cycle. Basically, they knew that certain compounds were being converted to other compounds. They found that certain chemicals could stop this, and when they did that, they found that instead of getting the conversion of compound A into compound Z, they got compound A turning into compound F... hence they thought that compound A turned into compound F, which then turned into compound Z. They did this kind of experiment with better and better chemicals, until the whole cycle was revealed.\n\n"
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8aw6ws | why does the "wind" generated by electric fans feel like it comes in waves? | The blades are spinning at a constant speed but the airflow seems to come in bursts. Why? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/8aw6ws/eli5why_does_the_wind_generated_by_electric_fans/ | {
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"Because it do.\n\nThe blades are spinning at a constant speed, but the wind is really only pushed forward from the part of the fan where the blade is. The blades are constantly coming in and out of an area due to the rotation and since the wind is perpendicular to the blades spinning, so does the wind. ",
"What you're feeling is pressure pulsations in the fan wake.\n\nWhen a blade of a fan travels through the air, a vortex is constantly shed off the blade tip. The vortex is caused by differing air pressures of the airflow on either surface of the blade. As the two airflows come together, they start to mix. The mixing forms a vortex. The center of the vortex is of lower pressure than the surrounding (ambient) air.\n\nNow, because the fan blade is spinning around, that vortex forms the shape of a helix behind the fan. The helix travels for a rather long distance behind the fan before it breaks up and dissipates.\n\nNow imagine you're standing in the wake of the fan. You'd feel this helical vortex hitting you as a wind buffet. After all, wind is air flowing from high pressure to low pressure. So as this low-pressure vortex passes by you, you'd feel the wind. Because the helical vortex spins around with the fan blade, you feel a periodic wind pulsation.\n\nBut a fan wake doesn't feel perfectly periodic, right? There's two reasons for that. One is that there are any blades on a fan, and each blade sheds a vortex. The network of shed vortices interact with each other more the farther downstream you go, which messes things up a bit. The second reason is that the vortices spin around with turbulence, meaning that the flow is not all that smooth. This also messes things up a bit. As a result, the fan's wake is a bit chaotic, but there's still a lot of periodicity and order to it.\n\nThis phenomenon is linked to anything that spins with blades. For example, have you ever noticed how a helicopter can make a thwump-thwump-thwump sound (or however you want to call it)? That's the shed vortex of each rotor blade hitting a following rotor blade and making a noise. Ever notice how loud a jet engine can be? A lot of that is the noise of the jet, but another factor are the vortices shed from the fan blades up front hitting what are called the \"fan exit guide vanes\" behind them, which also creates noise. In both the helicopter rotor and the jet engine, the noise frequency is related to the spinning speed of those helical vortices.\n\nYou wrote a great question, PARANOIAH. The answer is a building block to understand one of the big problems facing rotorcraft and jet aircraft today -- how do we make helicopters and other aircraft quieter? Keep exploring, dude!"
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287v1d | For birds; why does it seem like wing flap rate lowers the larger a bird you find? | I've observed a simple thing:
Small birds = High wing flap rate, like a hummingbird
Big birds = Low wing flap rate, like an eagle
Any physics related explanation, or was this supposed to be biological? | askscience | http://www.reddit.com/r/askscience/comments/287v1d/for_birds_why_does_it_seem_like_wing_flap_rate/ | {
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"I love scaling questions like this one. I'll take a shot. Consider a bird of characteristic size L, and we'll scale that bird up.\n\n(This isn't a great approximations for real birds, as a hummingbird's geometry is a lot different than an eagle's but what the heck, this was tagged physics, not biology.)\n\nThe mass of the bird scale as the volume, L^3. The force which can be generated by muscles scale as their cross-sectional area, L^2.\n\nIf we were to model the wing as an undamped harmonic oscillator, its frequency of oscillation will scale as the square-root of the force divided by the mass. However, this would be a lousy design for a bird: you want the work the bird is doing to go into pushing air, not waggling a heavy wing around. So I'll assume that birds are well designed, and we'll assume the wing is over-damped.\n\nAir resistance is tricky, but I'll take the simple approximation that it's linear in the wing area (L^2) and proportional to the square of the velocity. See _URL_0_ for more details.\n\nPlugging in our above numbers, this gives a wing flapping velocity that's independent of scale. As the distance the wing moves per beat will scale as L, the frequency of beating should scales as L^(-1).\n\nThus, small birds have a high flap rate, and big birds have a low flap rate. I'd expect this to scale as the bird's length to the -1 power."
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39p5r7 | what's the diference between eating 500 calories of vegetables and 500 calores of butter? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/39p5r7/eli5_whats_the_diference_between_eating_500/ | {
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"Volume, there's a lot more vegetables for 500 calories than there's butter. Also there's not a lot of nutrients like vitamins in butter that are in vegetables. ",
"500 calories would be 28 cups of radishes, or 5 tablespoons of butter. You'd feel full after just three or four cups of raddishes, but probably not after 5 tablespoons of butter, so you want fats for calories and vegetables so you can be satisfied and stop eating."
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2b17va | Is the name 'Greek-Roman Empire' used by historians? | I was in Greece a few days ago and the tour guide called it by the above name, separate from the Byzantine Empire.
Is this common from Greek historians?
Is there any substance behind this claim? | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/2b17va/is_the_name_greekroman_empire_used_by_historians/ | {
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"Not in my experience. A common term is 'the Greco-Roman world', which is employed when discussing cultural stuff (for example, \"Homer was the preeminent poet in the Greco-Roman world\"), but 'Greek-Roman Empire' would imply that the Mediterranean Roman-led hegemony was some kind of mutually arranged joint-enterprise, which is false, since the Romans subjugated the Greek mainland and wider 'Hellenistic kingdoms' with varying degrees of force.\n\nHowever, the term has been used to describe the Byzantine Empire *as* a 'Greek Roman Empire' by some scholars, but not as *the* Greek Roman Empire, if you can see the distinction.\n\n**Further reading:**\n\n[W. Mayer (2007), 'A Greek Roman Empire: Power and Belief under Theodosius II (408-450) (review)'. The Catholic Historical Review Volume 93, Number 3.](_URL_0_)"
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b2guz7 | how does frequency(hz) affect loudness(db)? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/b2guz7/eli5_how_does_frequencyhz_affect_loudnessdb/ | {
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"They're unrelated in terms of objective measurement, however you will perceive different frequencies at different volumes due to the old Fletcher Munson curve. ",
"It doesn't, but humans don't have a flat hearing curve so we hear some frequencies louder than others.\n\nSometimes you see the audio level expressed in dBA which means the A curve was used, giving a closer approximation to actual hearing that raw dB. There's actually many different loudness curves.",
"Most of the other answers are sort of correct, but there is a lot of detail to be missed.\n\n\"Loudness\" is a subjective, *psychoacoustic* measure, i.e. one that results from how your brain perceives sound, not from physical properties of sound. It does not directly relate to any physically measurable quantity, and it is not measured in decibels (dB). \n\nThe quantity that is measured in decibels is called the *sound pressure level*. Any sound is just pressure differences in air, and the SPL simply measures how much the pressure differs from the ambient air pressure. For example, speakers work by having a vibrating membrane that causes those pressure differences. If you turn up the speaker's volume, the membrane will vibrate to a larger extent, causing a sound with higher pressure level. The sound pressure level also correlates with the energy needed to produce the sound, measured as the *sound intensity level*.\n\nThe *loudness* of a sound is measured in *sone*, which is a somewhat obscure unit. The idea is that if one noise has a loudness of 1 sone, then another noise that sounds twice as loud *to you* (or to some other test person) will have a loudness of 2 sone.\n\nThe sone is not a very useful unit in practice because the loudness of a noise can only be determined by having test persons actually listen to the noise, as well as other noises with known loudnesses, and comparing them. It is impossible to build an even remotely accurate physical \"loudness meter\", as the loudness of a sound depends on:\n\n- the sound pressure level\n- the frequency or frequencies of the noise\n- harmony: sounds that don't harmonise well will sound louder than ones that do\n- time: if you hear a noise for a long time, your brain may \"drown out\" the perception of that noise, or it may be enhanced\n- the environment the noise is playing in (in snowy areas noises generally sound quieter)\n- other noises playing at the same time\n\nThere are some alternative more complex measures that approximate the actual subjective loudness, for example the \"loudness level\" measured in *phon*, which only takes into consideration the sound pressure level and the frequency. If you have those two values, you can look up the loudness level in a [diagram](_URL_0_). For example, a sound at 250 Hz and with a pressure level of 30 dB will have a loudness level of 20 phon.\n\nThe problem with determining the loudness level is that it can only be done within the limits of this diagram, and that the diagram is empirically determined (i.e. by experiments with people, not mathematically). So for most practical purposes, an even simpler approach is used called \"weighting\", where you have mathematically exactly defined [curves](_URL_1_). You would look up the frequency in the curve you want (A weighting is pretty much the only weighting used in practice), and add it on to the sound pressure level you measured. So in our example above, the weighting would result in a difference of about -8 dB, so the 30 dB(SPL) sound at 250 Hz would be about 22 db(A).\n\nSo to conclude, the frequency absolutely does affect the loudness of a sound. It does not affect the sound pressure level measured in dB, unless you use a weighting method that modifies the dB value based on the frequency.",
"Humans need to hear the vowel and consonant sounds when little humans cry out of hunger or pain. To cry, those little humans shoot air violently across their vocal cords and out their mouths. We evolved over time so that our ears pick up the frequencies of those sounds all the better to hear and help the little humans.\n\nIf you want a human to pay equal attention to sounds outside of that frequency range, you have to shoot more air at them more violently than the little human did.",
"Lower frequencies lose less energy to attenuation in the atmosphere, so they may travel farther. lower frequencies also absorbed more easily, rather than reflected, so they might lose more energy in an enclosed space, such as a hallway. When an airplane is at high altitude, it sounds low frequency, but when it's at low altitude it has more of a whine to it, right? This is why. \nGood answer here:[_URL_0_](_URL_0_)"
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7m8hue | Concerning Holocaust Denial/Revisionist Claims | Apologies in advance if this has been asked before but I know a guy who considers himself to be a "revisionist" and I was hoping to find some really good knock out point to persuade him out of it.
He's significantly more knowledgeable in WWII than I am and his main claims are that the numbers are vastly overstated and there was no actual policy of the the final solution. He also denies the existence of gas chambers.
I suspect he's primarily motivated by antisemitism but claims to be approaching it from an open minded and objective point of view. Am I just wasting my time on him? Any advice, answers, or a good resource would be a greatly appreciated. | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/7m8hue/concerning_holocaust_denialrevisionist_claims/ | {
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"Sadly, there is [a rather large section of the FAQ on Holocaust denial](_URL_0_). Some of the answers that seem a bit more relevant to your question are [this ELI5](_URL_2_) by /u/Elm11 and [this Monday Methods post](_URL_1_) by /u/commiespaceinvader.\n\nI recommend reading some of those posts, and more info would be helpful here, but here's a section of /u/commiespaceinvader's linked post that seems relevant:\n\n > Given how Holocaust denial is part of a political agenda pandering bigotry, racism, and anti-Semitism, combating it needs to take into account this context and any effective fight against Holocaust Denial needs to be a general fight against bigotry, racism, and anti-Semitism.\n > \n > At the same time, it is important to know that the most effective way of fighting them and their agenda is by engaging their arguments rather than them. This is important because any debate with a Holocaust Denier is a debate not taking place on the same level. As Deborah Lipstadt once wrote: \"[T]hey are contemptuous of the very tools that shape any honest debate: truth and reason. Debating them would be like trying to nail a glob of jelly to the wall. (...) We must educate the broader public and academe about this threat and its historical and ideological roots. We must expose these people for what they are.\"\n > \n > In essence, someone who for ideological reasons rejects the validity of established facts is someone with whom direct debates will never bear any constructive fruits. Because when you do not even share a premise – that facts are facts – arguing indeed becomes like nailing a pudding to the wall.\n > \n > So, what can we do?\n > \n > Educate ourselves, educate others, and expose Holocaust Deniers as the racist, bigots and anti-Semites they are. There is a good reason Nazism is not socially acceptable as an ideology – and there is good reason it should stay that way. Because it is wrong in its very essence. The same way Holocaust Denial is wrong at its very core. Morally as well as simply factually.",
"If you're interested in a good resource on confronting Holocaust denialism I'd recommend *Lying About Hitler* by Richard Evans. It revolves around a libel suit which ultimately resulted in Evans having to prove now noted Holocaust denier David Irving was a holocaust denier in court, and really does a great job in showing how disingenuous those pushing the Holocaust denier narratives are in regards to the evidence they use to support their arguments.\n",
"Well because I am a machoist I occasionally argue with people like this and am currently in a debate with a holocaust denier right now.\n\nThe best point I've found because it's so based in numbers and fact is where are the Polish Jews? Poland pre-war had a Jewish population of 3.1 million Jews, Poland now has around 1,000. Directly after the war in 1946 the Polish government counted 240,000 Jews, 200,000 of which were deportees being returned from the Soviet Union. So where are the Polish Jews? Now most deniers will say they went to Israel! So lets look at that Israel at the time of independence has 800,000 people in 1948, in 1946 the Polish government counted 240,000 Jews so where are the missing three million? True almost all of the 240,000 emigrated to Israel but Israel right now has a population of 6 million Jews so are half of all Israelis descended from Poles no, and for more fun 1 million of those 6 emigrated from the USSR and former USSR, so prior to 1991 that would be 5 million Jews in Israel, so were 60% of Israelis descended from Yiddish speaking Poles in 1991? Are 50% now decedents of Yiddish speaking Poles, no they aren't we can look at the current Jewish populations of Israel and Poland and determine that neither can possibly hold the demographics claimed, those 3 million are missing because they were murdered by Nazi Germany. \n\n\n\n\nCitations: Witold Gadomski, Spłata długu po II RP. _URL_1_\n\n\"Jews in Poland Since 1939\" (PDF) Archived November 7, 2006, at the Wayback Machine., YIVO Institute for Jewish Research, The YIVO Encyclopedia of Jews in Eastern Europe, Yale University Press, 2005\n\nGłówny Urząd Statystyczny Rzeczypospolitej Polskiej, drugi powszechny spis ludności z dn. 9.XII 1931 r. - Mieszkania i gospodarstwa domowe ludność\" [Central Statistical Office the Polish Republic, the second census dated 9.XII 1931 - Abodes and household populace] (PDF) (in Polish). Central Statistical office of the Polish Republic. 1938. p. 15. Archived from the original (PDF) on 2014-03-17.\n\nSurvivo s of the Holocaust in Poland: A Portrait Based on Jewish\nCommunity Records, 1944-1947 (Armonk, N.Y., 1994)\n\n_URL_0_"
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6x1mmf | how were ancient astronomers able to accurately predict cosmological events using a geocentric model of solar system? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/6x1mmf/eli5_how_were_ancient_astronomers_able_to/ | {
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"There was an idea of \"epicycles\", where each planet did not orbit directly around earth, but rather orbited in a circle around some central point which was itself orbiting around earth - or perhaps just a point *near* earth, which was assumed to be stationary. See [this helpful Wikipedia image](_URL_0_). As observations got more accurate, the epicycle system had to become an ever-more-complex system of circles within circles to account for the observations. The first heliocentric theories actually also used epicycles, since it was at first assumed that orbits had to be circles. But eventually Kepler showed how the data could be easily explained using elliptical orbits, greatly simplifying the theory.",
"You don't have to know how something works to recognize patterns in it.\n\nJupiter takes 12 years to travel the constellations of the Zodiac. Venus takes 584 days to go from being the morning star to the evening star and back to the morning star again. If you see an eclipse, you will see a nearly identical eclipse 54 years and 34 days later.\n\nThose numbers check out whether you think the earth goes around the sun, the sun goes around the earth, or the earth is on the back of a giant tortoise and the sun carried by a golden chariot chased by a dragon.",
"You can describe the motion \"as seen from Earth\". That makes the motion very complex, and you need many contributions that have to be added to give the total motion, but it is possible.\n\nThe only thing that was predicted very accurately were eclipses, they only involve the Moon (which actually orbits Earth) and the Sun (where the relative motion between Earth and Sun is quite simple)."
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1e8mhw | Does anyone know any sources on lynching in the US, seen from the white man's perspective? | I am particularly interested in sources, emphathizing with the white people, but anything will be helpfull.
EDIT: I may not have expressed myself clear enough. The main reason is, that my English speaking abilities are not the best.
I am looking for someone who takes the white mans party.. I know that they were afraid that the black people would steal their jobs and stuff like that, but i can't seem to find any source that explains why the white men needed to do these horrible acts, if such sources exist.
And thank you very much for your inputs! | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/1e8mhw/does_anyone_know_any_sources_on_lynching_in_the/ | {
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"By white man's perspective, you mean like [Theodore Roosevelt's?](_URL_0_) \n\nEdit: Pres. Roosevelt was an outspoken opponent of lynching and on more than one occasion took the opportunity to publicly voice his opinion. The link above contains the transcript of a speech that gave of an event at Arlington Natl.Cemetery in 1902. In the speech, he compares the outrage expressed by some over the atrocitities reportedly committed by US forces in the Phillippines to the blind eye turned towards lynching in their own country. TR stated that lynching was barbarous and cruel to the victim and brutalized even those who were guilty of the act. For context, the inhumanities perpetrated in the Philippines were being hung around TR's neck by his political opponents, most of them being southern states democrats. Notably, the article in the link also responds to critiques of the propriety of even bringing up the topic of lynching in a presidential address. The cynical reader might believe that Roosevelt merely used the topic of lynching to distract from the Phillippines.While Roosevelt stifled himself regarding lynching later in his presidency for political reasons, his record of public and private communication demonstrate his dedicated opposition to the practice. ",
"Hmmmm. Published defenses of lynching must be few and far between, and when you would find a newspaper editorial or some other piece of writing condoning violence, I would imagine that they would most likely very carefully coded and indirect. Lynching was extra-legal, not explicitly supported by institutions or individuals who could be held accountable. So I would assume that sources explicitly defending lynching would be rare and from outside the mainstream.\n\nOne surprising recent discovery that documents lynching in an incredibly impactful and disturbing way was a collection of lynching postcards. It turns out that professional photographers took photos of lynchings and sold them as postcard souvenirs to attendees; some of these postcards were then mailed with writing on the back, and eventually archivists collected them. The resulting book, *Without Sanctuary*, reprints both the photos and some of the text from the postcard backs; the text is just incredibly disturbing, with some writers describe the picnic or holiday atmosphere of the lynching and some just not even seeming to acknowledge that they're sending a picture of an inhuman atrocity to their loved ones. Warning; it's an incredibly brutal book to read; the images on the website are pretty small, but disturbing; seeing them at high resolution in the book is just soul-crushing.\n\n_URL_0_\n_URL_1_\n\nIt's such an interesting set of sources; it's a good example of how historians seeking to document something that by definition didn't produce documents need to look to innovative, and in this case, ephemeral sources.\n\n",
"At a very high level, the pro-lynching sources tend to fall into a narrative of horrible unnatural brutish crime (committed by a black man) partially redeemed by *purifying* violence at the white male. However, lynching evolved over the years; the ways it was seen by whites (perpetrator, supporter, bystander, or denouncer) changed meaningfully as society changed.\n\nThere are several good books on lynching that make extensive use of passages from primary sources. Here are a few I've used:\n\n* *100 Years of Lynchings* is a collection of newspaper accounts of lynchings. Many contain quotes from white sources and many paint an overall narrative of justified retaliatory violence. I think it's important to realize that newspaper accounts were not some sort of \"objective\" recounting, but often were part of creating the narrative that enabled the violence: they made judgments about what was OK/not OK within mob behavior, they validated the idea of social control through fear and violence, they reinforced and accepted anonymity on the part of the perpetrator but repeated with little questioning the idea of guilt on the part of the victim, they valorized the idea of \"rough justice\" as an all-American institution, etc. \n\n* *Lynching and Public Spectacle* makes use of and partially reproduces primary sources but also provides a framework for understanding how lynching was understood by whites who were spectators but not direct perpetrators. \n\n* *Under Sentence of Death: Lynching in the South* is a collection of academic essays covering lynching from a historical and a sociological perspective.\n\nIf you don't mind sharing, is there any particular reason you are looking for this?"
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1jtwcy | Irradiated Water | What happens to radiations when irradiated water evaporates ? | askscience | http://www.reddit.com/r/askscience/comments/1jtwcy/irradiated_water/ | {
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"That depends, is the water *contaminated* or *activated*?\n\nTo be *contaminated* means the water just has other radioactive stuff in it.\n\nTo be *activated* means the nuclei of the atoms in the water molecules have been transmuted/excited and are radiating themselves.\n\nIf the water is contaminated, I guess the contamination would just stay where it is, like when you evaporate salt water you get a bunch of salt lying around.\n\nIf the water is activated, it'll continue to be radioactive even as a gas."
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6u8itl | why is it illegal to film a single person but journalists are allowed to do so and publish it, even using hidden cameras? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/6u8itl/eli5_why_is_it_illegal_to_film_a_single_person/ | {
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"Illegality depends on locality. Here in Idaho, we are a single pay consent when it comes to recording. "
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74bgix | how do we biologically "lose" energy as we age? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/74bgix/eli5_how_do_we_biologically_lose_energy_as_we_age/ | {
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"You don't lose energy in the physical sense of energy. However as you get older your metabolism slows down, your muscles become weaker, your blood can become less capable of carrying oxygen, your joints become less lubricated, your bones become weaker, the list goes on and on. All of these factors combined help contribute to the loss of vitality seen in older individuals. ",
"Cells are like tiny little earths in your body, they are lovely little peaceful worlds, but need to be taken care of with strict policing. Because of this fact, oxygen is jealous and wants to infiltrate the cell to find a home of it's own, but oxygen is a muslim and doesn't integrate well. All these god damn oxygens ever want to do is come in for a free ride, but they never help out, they are always just destructive to the cell community. \n\nThe human cell voted trump and decided it had had enough and it was time to act for the security of the cell. \n\nThe human cells are alerted that oxygen is approaching and sends out troops to the cell border in a defensive front line. The cell government builds a wall to keep out the oxygen. A horribly violent battle at the cell border ensues with a high number of casualties on both sides. \n\nMany cell troops lay dead, and many oxygen terrorists are also deceased. The wall has been knocked down and some oxygen managed to infiltrate the cell. The cell government sends builders to remake the wall for the next push, but the cell has already lost some of it's best men. It is unclear how many more front line assaults the cell can handle before it is oxidized. \n\nSurely, at this rate, there will not be enough troops or builders to stop the cell from destruction within say 100 years.",
"You don't lose energy, but your body becomes less efficient at everything. Your body is ultimately a biological super machine, but after decades of living you accumulate toxic substances in your organs, wear out joints and bones and the tiny 'mistakes' that your body makes when it repairs and renews it's cells accumulate. Exactly like an old cards vs new car."
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2fnkz6 | What happened between the time that a piece of gold was mined and the time that the gold atoms were generated which caused them to be located next to one another? | I gather that gold atoms (among other heavy atoms) are generated in supernovae. Are they generated in big "chunks" which then just happen to end up next to one another when planets are formed, or are they tossed off as individual atoms and some geological process brings them together during planet formation?
Super interested in this topic - would appreciate any suggested reading. Thanks! | askscience | http://www.reddit.com/r/askscience/comments/2fnkz6/what_happened_between_the_time_that_a_piece_of/ | {
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"Perhaps you mean how do chemical elements end up concentrated in the soil?",
"To be clear, you're asking how [mineral veins](_URL_0_) are created?",
"The latter. The elements produced by a supernova are pretty well mixed with the hydrogen/helium gas clouds; there are no \"chunks\" of gold at this point. When the solar system formed, planetary bodies got differentiated by gravity, with heavier rock sinking into the core. So on Earth, most of the gold, uranium, etc ended up in the core of mostly iron and nickel. The crust is mostly silicates and other light rocks.\n\nBut the same differentiation happened in dwarf planets, some of which got shattered and contributed to the asteroid belt. So there are asteroids that are made mostly of metal and are relatively rich in the heavy platinum group metals and gold. When those hit Earth after its formation, it enriched parts of its crust with these metals. Finally, geological and chemical processes resulted in concentration of certain elements, such as gold in veins. You can read more about it here:\n\n_URL_0_\n\n_URL_1_",
"I'm nervous about posting in this the most moderated of subreddits, but since there have been no responses I'll give it the old college try. \n\nI'm not sure about the first part of your question, but I seriously doubt physical chunks is the best way to think about the immediate results of nucleo-synthesis. I'm sorry I don't know enough about the process to give you anymore information there. \n\nOnce planets have formed elements can be concentrated by a variety of processes. One that would be particularly important early in the Earth's life, when the planet was thoroughly molten, was [planetary differentiation](_URL_4_). A process in which dense elements like gold would have sunk deeper into the earth's interior and lighter elements would have risen. This process is responsible for earth's dense metal core. In our cooler/ more solid earth this trend toward distinct layers of homogenous minerals is continued by [fractional melting/ crystallization](_URL_2_). \n \nHowever, none of this explain why dense elements exist in earth's crust at all. In fact this is a topic of some debate. With some people [arguing](_URL_3_) that gold exist in the crust only because it was delivered by meteorite impacts after the cooling of earth's crust (As SnickeringBear points out below which physical processes are responsible for the anomalous heavy element in our crust isn't really settled). \n\nThe nuggets of gold we think of grizzled prospectors finding wouldn't have been meteorites them selves. The exact process would have varied by case but a common means of ore concentration would have been hydrothermal activity. This would take the form of really hot water carrying dissolved gold from the deeper in the earth and implanting it in available spaces as it cooled. This would explain why gold is very frequently found in quartz veins which are created by the same process. \nGold can also accumulate along fault planes as differences in pressure and temperature allow the dissolution of elements in high pressure and temperature areas and their deposition in areas of lower pressure and temperature. Lastly if an ore bearing rock formed via either method reaches the surface it is susceptible to erosion which will redistribute the contents of the rock as sediments which can then be mined. These are called [placer deposits](_URL_1_). \n\n[This](_URL_5_) wiki article does a better job of addressing all this than I can.\n\nUnmentioned in the wiki article is theory that microbes that concentrate gold may play a role in ore formation, but I don't really know enough about that to talk about it.\n\nWhat I've written above for the most part represents the accepted wisdom about gold ore formation, but [recent analysis](_URL_0_) of Australian gold nuggets shows they didn't form at temperatures achievable near the surface suggesting a deeper origin. \n\nedited: to reflect the uncertainty about the exact history of heavy elements in our crust. Also Snickering bear is right about microbial gold concentration. \n\n"
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"http://www.csiro.au/Organisation-Structure/Divisions... | |
4qnojw | is the longer average lifespan of humans due solely to medical/technological advancements, or are we just built sturdier than we used to be? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/4qnojw/eli5_is_the_longer_average_lifespan_of_humans_due/ | {
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"It really has to do with lower infant mortality, thanks to better medicine. In the Medieval era, those making it to puberty would have lifespans comparable to ours, it's just so many babies died to drag down the average.",
"I read a Harvard study (I think it was math based albeit) that said that death is advantageous to a species as it allows for more rapid genetic drift and adaptation to an environment. I think that our lifespan is a careful balance between giving our species rapid adaptation and allowing us time on an individual level to raise offspring really fucking well. I think that the recent rise in lifespan is due to insuring that more people reach the balance point age of 60-80 where genes potentially help waste our bodies away. I don't think that the actual viable lifespan is changing. It's just that more people are reaching it due to medical advancements. \n\nEdit: I think u/Trolling_From_Work hit it right on the head with changes in infant mortality. We are not extending our lifespan. More people are living to it because of medical advances.",
"Sanitation is a huge factor in lifespan. We have clean water, we don't spread cholera like we used to, etc etc. Infections don't occur as easily. Don't underestimate how much more sanitary societies are these days and how it affects our lifespan. ",
"It's scary to think that before antibiotics and antisepis (awareness that cleanliness prevents infection), you could die from a mosquito bite or hang nail. ",
"It's technology. We're not built sturdier. In fact there is evidence to suggest humans are more fragile than we used to be. For example bones of modern humans are more brittle than that of prehistoric humans.",
"To state that any one thing or event is responsible for longer lifespans is foolish. Everything is integrated. There is no way to isolate any one issue since sanitation is both a technological advancement, a mind set, a medical issue, and a form of pest control. Pest control is a medical issue and a need of civilized development and a concern of world wide trade. All the issues affect infant mortality and birth rates. Education and learning to read enabled people to understand the lifespan issues, develop the technology and take steps that would enable them to live longer."
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2blddr | a nuclear apocalypse | Not just the general theory, but also an example of a realistic scenario in this current day and age? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2blddr/eli5_a_nuclear_apocalypse/ | {
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"Likely scenarios would be: \n\n1. The conflict over the Kashmir between Pakistan and India going nuclear\n\n2. Tensions in Europe (currently Ukraine, but also for whatever other reason) causing a nuclear exchange between Russia and Western Europe and/or the US\n\n3. A crisis in Asia over Taiwan or Japan or North Korea causing a nuclear exchange between China/North Korea, Russia and the West.\n\n4. Tensions in the Middle East causing Israel to use its nuclear weapons, likely against Iran\n\n#1 and #4 will probably not cause a total nuclear apocalypse in the form of nuclear winter / the complete collapse of civilization worldwide, but it may harm the ecology enough (global dimming and widespread fallout causing famine and agricultural collapse) to make life on Earth extremely unpleasant for the next decade or so.",
"Not current, but the Cuban Missile Crisis is a good example. Lets say it unfolded differently. Kruschev doesn't back down. Kennedy sends in bombers to take out the missiles (I've heard that planes were over Cuba with weapons armed when the recall order came so we were pretty damn close to this). So the US has now killed Russian soldiers. Russia retaliates, we retaliate back, things escalate and one of us launches their nuclear missiles, the other one launches back. The dust, ash and fallout kill most life on Earth. A good movie about this is \"13 Days\".\n\nI also read a study a while back that looked at a possible limited nuclear exchange between Pakistan and India. The environmental impact of that would apparently have global repercussions.",
"It is a nuclear war among allies of nations. the threat of nuclear war still exists today, with a number of countries possessing the capability of deploying such destructive devices. In addition to threats from the explosion and radiation, there are also indirect effects such as contaminated food and water supplies, poor air quality, destruction of power grids affecting communication and transportation, and nuclear winter.\n \nIt’s been theorized that detonating nuclear weapons will cause large amounts of smoke, soot and debris to enter Earth’s stratosphere, reducing sunlight for months or even years. Such a nuclear winter would result in severe cold temperatures and interference in food production. In 2007, scientists Brian Toon and Alan Robock concluded that if India and Pakistan were to launch 50 nuclear weapons at each other, the entire planet could experience 10 years of smoke clouds and a three-year temperature drop.\n\n",
"On a semi-related note, Russia had their Dead Hand system made during the cold war. Pretty scary stuff. Basically it meant that even if we completely and suddenly obliterated all of their command, the light and radiation would trigger a launch of all of their nukes at us. Completely autonomously. It may still be operational and in place.\n\n_URL_0_"
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2xirx5 | why does extreme muslim " isis" only attack islamic state (one after another) but never directly attack israel. | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2xirx5/eli5_why_does_extreme_muslim_isis_only_attack/ | {
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"One because geography they don't control any territories directly boarding Israel other countries aren't just going to let them bring their forces through.",
"Unlike the other countries, Israel has a functional military.",
"Because they don't have that kind of power yet. They are a loosely organized band of hyped up hadjis, no way they could stand a chance against the disciplined, organized, well funded, and battle tested Israeli military. They understand that they would get slaughtered. Same reason they don't commit an open attack against the US. There are grossly outgunned."
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282alr | laser guided missile systems | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/282alr/eli5laser_guided_missile_systems/ | {
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"The missile head has a sensor, looking for a laser. The fighter or ground spotter points a laser at the target, the laser hits the target, then the light (may not be visible) scatters in all directions. The seeker head of the missile sees the light and aims at it, moving the body to follow.",
"The best analog I can give you is this: [Cat and Laser Pointer](_URL_0_)\n\nThe cat's eyes are the sensor in the missile. The feet/muscles/claws are the rocket motors/control surfaces.",
"Oh, \"missile following the laser\" is so quaint and old-school.\n\nMore modern systems aim parallel beams at the butt of the missile, and when the human (or computer) manually aiming at the target all during the missile's flight moves his targetting reticle as the target moves, the missile sees that the lasers are moving, and adjusts its ailerons in order to stay in the beam all during its flight.\n\nThis way, the target never knows that it's being targeted, until it goes kablooie.\n\nSOURCE: did my military service in an anti-air missile battery."
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234hwg | Does gravity still 'work' when scaled down? | Assuming these numbers are right:
Humans are 668 times bigger than ants and that the circumference of the earth is 40,075km
Then if we made planet with a circumference (and everything else) scaled down to make ants the same size as humans, a planet with a circumference of 72km. Would this planet have enough gravitational pull on the ants to keep them on (lets imagine that ants are just like humans and cant climb and stick onto stuff)?
And also would this planet be strong enough to keep 70% of its area covered with water using gravity? If not why? | askscience | http://www.reddit.com/r/askscience/comments/234hwg/does_gravity_still_work_when_scaled_down/ | {
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"a human is 20 million times bigger than an ant when talking about mass which is the property gravity is dependent on(as well as distance between two objects) To answer you question, in the middle of space with no other masses to interfere, any two masses will attract, no matter how small, so yes a tiny 'planet' could hold ants onto it or water on its surface. ",
"A neat thing though that most people don't realize is how small of a force gravity is. Let me give an example. If you take 2 decently strong magnets that fit in your hand and put them together, you are not strong enough to pull them back apart(you might be able to slide them apart), but you can lift someone off of the earth if they are your size, so you can give enough force to counteract gravity of a planet that is 8000 miles in diameter, but not enough force to pry apart 2 things held together by the electromagnetic force."
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4e42xt | What was Russia's overall objective in declaring war on Sweden, starting the Great Northern War? | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/4e42xt/what_was_russias_overall_objective_in_declaring/ | {
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"Peter the Great's primary reason for starting the Great Northern War was to gain for Russia permanent access to the Baltic. \n\nWhen Peter became Tsar in 1682, Russia's only means of access by ship to the rest of the world was the port of Archangel, which was frozen over more than half the year and a long way from the Russian heartland. As a young man, Peter had acquired a love of ships and sailing (even learning how to build ships himself), and was determined to make Russia into a significant maritime power.\n\nOther than Archangel, Russia had essentially two ways out into the world's oceans: north through the Baltic, or south through the Black Sea, the Dardanelles and the Mediterranean. During Peter's reign, the Ottoman Empire was much too powerful for Russia to confront (after the Battle of Poltava, in fact, Peter would fall into Ottoman hands and be forced to yield what little progress he had made in the southern direction). The northern route for Russia was blocked by the fact that the Baltic was essentially a Swedish lake. So this meant war with Sweden, a risk Peter was willing to take because he (very inaccurately) calculated that the young Swedish king Charles XII would be an easy opponent.\n\nSource: Robert K. Massie's *Peter the Great: His Life and World*"
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set1p | Historical record in the digital age | Much of our knowledge of ancient history comes from clay tablets, scrolls, carvings, etc. In other words, we rely heavily on physical materials and evidence in order to learn more about the past.
These days, everything is becoming much less physical and trending towards the digital end of the spectrum. The digitized world is in many ways more efficient and better organized, but I can't help but feel it's all too easy to destroy or damage.
If something were to happen to our society, what would archaeologists have at their disposal centuries down the line in order to construct their knowledge of our civilization? | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/set1p/historical_record_in_the_digital_age/ | {
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"I've thought about this a bit myself, especially after an episode a decade ago where I lost a lot of my own writing after being unable to transfer it across from my previous word-processing program to a different word-processing software. \n\nElectronic data does not persist. It can be edited almost without trace. It can be deleted the same. \n\nAlso, how is a historian in 1,000 years going to know how to decipher the data on a flash drive (assuming it's still physically readable after all that time)? It's all very well to see a lot of 0's and 1's, but you'd need some digital version of the Rosetta Stone to know how to translate that into readable text.\n",
"Note: I'm not a historian, but I am a sysadmin. \n\nFor the sake of clarity, are you talking about a collapse of civilization? Because if that lasted long enough, the hardware itself would corrode to the point where it's useless. If you're talking about the continuity and preservation of data, I could probably expound on that aspect some more.",
"There is a free book on this subject. Part of digital history is making stuff free, which is why places like _URL_0_ allow for the creation of free history websites. \n\nGreat Resources Here: _URL_2_\nFree book on digital history here: _URL_1_",
"There is an excellent article on this subject that my students read for their research methods course - Roy Rosenzweig, [\"Scarcity or Abundance? Preserving the Past in a Digital Era.\"] (_URL_0_) (2003)."
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j9kqd | when/why major/minor 7th chords work in a progression. i use them a lot, but i've no idea why they sound good. | I play guitar, and up until a year ago I exclusively played metal (I still play Protest the Hero/Between the Buried and Me), but lately I've moved into the jazz/blues area. From this I've begun to use somewhat more "exotic" chords (well, more exotic than I was used to before), the 7th chords especially. I know a little bit of theory so feel free to ELI12 if it comes to it.
Cheers! | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/j9kqd/eli5_whenwhy_majorminor_7th_chords_work_in_a/ | {
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"I'll give this a try (if I understand your question).\n\nIn western music, an octave is divided into 12 semi-tones. People worked out that you could pick 7 or so of those tones to create a scale (or 5 say for a pentatonic \"blues\" scale), and that those notes sounded good when sequenced into a melody.\n\nThe example we'll use is C Major. A major scale is the old Do-Re-Mi scale, and you could say it has a fairly bright happy sound to it (as opposed to a minor scale).\n\nC Major is convenient because the notes are white keys on the piano: C D E F G A B. No sharps or flats.\n\nThey also noticed that playing certain notes simultaneously (a chord) sounded harmonious, some don't work so well.\n\nThe gap between notes (the number of semitones) is called an interval.\n\nProbably the cleanest (most harmonious) interval is a perfect 5th. For example C and G. This is incidentally a \"power chord\" in rock music.\n\nOther intervals are a little more dissonant, but still sound good. Such as a Major 3rd (4 semitones) or a minor 3rd (3 semitones).\n\nThe basic chords (triads) in a given scale are created by starting at one note, skip one, next note, skip one, next note. For example C Major is C-E-G.\n\nIn the key of C you can play all the triads in the scale on a piano by playing the white keys in this pattern (note-skip-note-skip-note).\n\nSo you start with C Major: C-E-G. \n\nNext is D minor: D-F-A.\n\nThen E minor: E-G-B\n\nThen F Major: F-A-C\n\netc...\n\nAs it turns out, a Major chord has 2 intervals: A Major 3rd with a minor 3rd on top.\n\nA Minor chord is the reverse: A minor third with a Major 3rd on top.\n\nNow, if you want to stack an additional note on your triad, you skip a note then play the next note.\n\nSo you might have C-E-G-B. Which is called a C Major 7th. It's a slightly dissonant chord (or colorful perhaps) because you've got two notes, B and C, that are only a semitone apart. The intervals are Major 3rd, minor 3rd, Major 3rd.\n\nOne chord that is especially popular and fairly harmonious is a 7th chord at the 5th note of the scale. In the key of C Major this would be G7. The notes are G-B-D-F. The intervals are Major 3rd, minor 3rd, minor 3rd. That top F note is a full-tone (two semitones) away from the G tonic. So it's smoother sounding than the above example of C Maj 7.\n\nOf course, you don't need to only stick to the notes of a scale, you can use accidentals or whatever you want so long as it sounds good.\n\nTL;DR; You can add an additional note to a basic triad for color. 7ths, Maj 7ths, 6ths, etc. The difference in sound relates to the intervals between the various notes.",
"I'll give this a try (if I understand your question).\n\nIn western music, an octave is divided into 12 semi-tones. People worked out that you could pick 7 or so of those tones to create a scale (or 5 say for a pentatonic \"blues\" scale), and that those notes sounded good when sequenced into a melody.\n\nThe example we'll use is C Major. A major scale is the old Do-Re-Mi scale, and you could say it has a fairly bright happy sound to it (as opposed to a minor scale).\n\nC Major is convenient because the notes are white keys on the piano: C D E F G A B. No sharps or flats.\n\nThey also noticed that playing certain notes simultaneously (a chord) sounded harmonious, some don't work so well.\n\nThe gap between notes (the number of semitones) is called an interval.\n\nProbably the cleanest (most harmonious) interval is a perfect 5th. For example C and G. This is incidentally a \"power chord\" in rock music.\n\nOther intervals are a little more dissonant, but still sound good. Such as a Major 3rd (4 semitones) or a minor 3rd (3 semitones).\n\nThe basic chords (triads) in a given scale are created by starting at one note, skip one, next note, skip one, next note. For example C Major is C-E-G.\n\nIn the key of C you can play all the triads in the scale on a piano by playing the white keys in this pattern (note-skip-note-skip-note).\n\nSo you start with C Major: C-E-G. \n\nNext is D minor: D-F-A.\n\nThen E minor: E-G-B\n\nThen F Major: F-A-C\n\netc...\n\nAs it turns out, a Major chord has 2 intervals: A Major 3rd with a minor 3rd on top.\n\nA Minor chord is the reverse: A minor third with a Major 3rd on top.\n\nNow, if you want to stack an additional note on your triad, you skip a note then play the next note.\n\nSo you might have C-E-G-B. Which is called a C Major 7th. It's a slightly dissonant chord (or colorful perhaps) because you've got two notes, B and C, that are only a semitone apart. The intervals are Major 3rd, minor 3rd, Major 3rd.\n\nOne chord that is especially popular and fairly harmonious is a 7th chord at the 5th note of the scale. In the key of C Major this would be G7. The notes are G-B-D-F. The intervals are Major 3rd, minor 3rd, minor 3rd. That top F note is a full-tone (two semitones) away from the G tonic. So it's smoother sounding than the above example of C Maj 7.\n\nOf course, you don't need to only stick to the notes of a scale, you can use accidentals or whatever you want so long as it sounds good.\n\nTL;DR; You can add an additional note to a basic triad for color. 7ths, Maj 7ths, 6ths, etc. The difference in sound relates to the intervals between the various notes."
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7saqko | how do condoms not work other than when they break? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/7saqko/eli5how_do_condoms_not_work_other_than_when_they/ | {
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"When you use them wrong, like putting two on (which causes a break), or if you tried to reuse it, or use it with the wrong type of lube.",
"besides breaking (tearing) they can still dislodge or just plain fall off.\n\n > A survey of more than 1,000 men in India has concluded that condoms made according to international sizes are too large for a majority of Indian men.\n\n > The issue is serious because about one in every five times a condom is used in India it either falls off or tears, an extremely high failure rate.\n\n_URL_0_",
"- Using the wrong size. By using a condom that is too big for you, you run the chance of it slipping and sperm leaking out.\n\n- By using them incorrectly like putting on two over each other or reusing them. \n\n- By not pulling out quickly enough afterwards. Though it can be tempting, if you are using a condom, you really should pull out, take off the condom and throw it away fairly quickly after orgasm. If the penis gets entirely soft inside of the condom, there is also the possibility of it slipping.\n\n- By not leaving some room at the tip while you put them on. You should always leave a little receptable where the sperm can go. Without that, there is also a much bigger chance of it leaking out. (especially if combined with staying in too long or the wrong size)\n\n- Using the wrong lubes. Not every lube is compatible with condom usage! Condoms are made of latex and oils or petroleum jelly can break that down.\n\n- Condoms expire. In an expired condom, there is no guarantee the latex is still in proper form. Don't risk it, and just toss out those expired old condoms. Similarly, though they tell you to always keep a condom in your wallet just in case, that is also not the best idea. The heat (especially if you carry it against your body) and the constant bending and tearing can also create invisible micro tears."
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8puj2f | in a cup of coffee, why does the top of the liquid leave a stain ring, whereas the rest of the liquid does not? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/8puj2f/eli5_in_a_cup_of_coffee_why_does_the_top_of_the/ | {
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"The air is where it the coffee dries up and the solids inside the water from the coffee can leave the water and stick to the edge. ",
"When you pour yourself a mug of hot coffee, you typically let it sit for 5-10 minutes until it cools down to a potable temperature. During that time, when the coffee is at its hottest, there is rapid evaporation at the surface of the liquid and coffee solids will accrete at the boundary between the evaporating liquid and the dry inner mug surface.\n\nThen, when the coffee is drinkably cool, it is both at a lower temperature (= less evaporation) and you're drinking it faster (= less accretion at any liquid depth than when you had a full cup).",
"That's called 'coffee ring effect'.\n\n > The coffee-ring pattern originates from the capillary flow induced by the differential evaporation rates across the drop: liquid evaporating from the edge is replenished by liquid from the interior.[1] The resulting edgeward flow can carry nearly all the dispersed material to the edge. As a function of time, this process exhibit a \"rush-hour\" effect, that is, a rapid acceleration of the edgeward flow at the final stage of the drying process.\n\n_URL_0_",
"That is where evaporation acts to remove water while leaving behind suspended material. Oxidation can the help it set.",
"If you put milk in your coffee, the fat from the milk rises to the top and sticks to the cup. It's like the ring in the bathtub. Grease, baby.",
"Evaporation happens from the surface I.e. top of a liquid. Since coffee is hot when poured, evaporation of water from the coffee is faster. This causes the coffee level to go down ever so slightly, while the cup tries to pull the liquid surface upwards around the edges where it comes in contact, causing the coffee to dry up faster along the edges leaving a trail of dried coffee aka stain. As we drink the coffee it cools and the evaporation slows down, plus we are drinking the coffee faster than the edges get time to dry to a stain at this point. If you leave a half drunk coffee alone long enough and then sip it you will see the stain at the new level as well. \n\nP.S: some cup materials are better at pulling the coffee up and making it stick while the water evaporates and coffee dries than others and can affect the staining. ",
"Say the coffee is 180°F when brewed. It will drop in temperature to 120°F much more rapidly than from 120°F to 80°F and a good percentage of this energy loss occurs through evaporation. So as it drops to a drinkable temperature, many insoluble solids are left caked to the vessel. ",
"the stain ring contains the most oils, which float at the top, along with other impurities or insolubles.\n\nif you cook sauces or need to reduce stocks and broths you will observe the same phenomenon.",
"Coffee contains natural oils. The oils sit on top of the water and that RING is the concentration of oils and fine coffee particulate. ",
"[Here’s a good answer](_URL_0_)\n\nThe answer has to do with how the fluid moves around in the drop while it’s drying. Coffee has round particles that don’t disturb the drop’s surface. As they float around, the pile up at the edges of the drop. "
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2t2amd | Schrodinger's cat question- is the cat actually both dead and alive and we change it with our current observation methods, or is it "really" either dead or alive and we may someday invent a measuring device that we could use to find out without disturbing it? | This is something I never really wrapped my head around- is there a more "real" state that it exists in that is actually one or the other that we just can't currently know? Or does it exist as "truely both" and only flip to one or the other when observed no matter how good our techniques will ever get?
I'm sure I used incorrect terminology, so please forgive if I'm even mixing up the current understanding (I only have a basic college intro science background and that was s long time ago)
Thanks! | askscience | http://www.reddit.com/r/askscience/comments/2t2amd/schrodingers_cat_question_is_the_cat_actually/ | {
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" > Or does it exist as \"truely both\" and only flip to one or the other when observed no matter how good our techniques will ever get?\n\nIt does that. It exists in a superposition of both states at once. Your other scenario would imply that the state is decided before the observation which isn't true.",
"OK, so one thing to remember about quantum mechanics is that even physicists don't agree on what the equations really mean. They know that the equations work and that they make excellent predictions, but nobody really has a firm grasp on what is actually happening in reality.\n\nWith that in mind, there are many different interpretation of quantum mechanics. Some say reality *is* a wavefunction in superposition. Some say that reality is a set of many branching worlds. Others say that we should just 'shut up and calculate'.\n\nSchrodinger's Cat was a thought experiment that Erwin Schrodinger made up, in order to show that he thought it was wrong to treat reality as if it were existing in multiple simultanous states. To Schrodinger (and Einstein too), the cat is most definitely *either* dead *or* alive in reality, rather than being in a state of superposition that included both possibilities.\n\nAs to who is right and wrong on the issue, it's unclear. Some would say Schrodinger and Einstein were clearly right, others would say they were clearly wrong, and others still would say we have no way of knowing. It's one of those issues in physics where there simply isn't any sort of broad consensus. There's lots of opinion and lots of very interesting ideas, but no solid reason to think that one is any more likely to be true than another.\n\nFiguring out what the quantum mechanics equations actually represent is still very much a frontier of modern science."
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yxgr5 | plutonium (nuclear?) power, specifically in the curiosity rover | I was reading [this article](_URL_0_) and it mentioned that Curiosity's laser uses "...more than a million watts of power in a five-billionth-of-a-second burst..." and gets its power from a plutonium reactor. How does this work?
I've been searching for an answer in earlier ELI5 posts, and nuclear power seems to be harnessing the energy to heat water and spin a turbine. Is this how Curiosity's reactor works? How can such a small system produce so much power? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/yxgr5/eli5_plutonium_nuclear_power_specifically_in_the/ | {
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" > I've been searching for an answer in earlier ELI5 posts, and nuclear power seems to be harnessing the energy to heat water and spin a turbine. Is this how Curiosity's reactor works?\n\nThe reactor on Curiosity converts a heat differential directly into electricity. As the radioisotope decays, it generates heat, which makes the inner chamber warmer than the outside chamber. This temperature differential is used to generate electricity directly, without the use of water and turbines. The phenomenon is called the [Seebeck effect](_URL_0_), although it is way beyond an ELI5 level.\n\n > How can such a small system produce so much power?\n\nIt doesn't produce that much power - only about 110 W. The generator is used to slowly charge the battery, so when it's time to use a power-intensive instrument, there is an excess of charge available.\n\nKeep in mind that when it says \"more than a million watts of power in five-billionth-of-a-second burst,\" that is a _really really short burst_. Power is a term used to describe energy over some time, and you can obtain a very high _power_ by shortening the duration to a very small number, even if you keep energy constant.\n\nTo put it in perspective, a million watts of power over five nanoseconds only has 0.005 Joules of energy. It takes the 110 W power supply 45 milliseconds to provide the equivalent amount of energy."
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1zhwnt | why do i feel so much joy when the bass drops? | I don't know if joy is the right word... but I just get so much satisfaction felt when the bass drops, especially when it's done right. | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/1zhwnt/eli5why_do_i_feel_so_much_joy_when_the_bass_drops/ | {
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"Usually before the bass drops, theres a buildup. You just know it's coming and when it comes, it floods the songs with bass. Its almost like an orgasm. A lot of good songs have this build up model, like how \"i believe i can fly\" builds up to that church chorus."
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40taii | why do we get 'weak knees' at the edge of a cliff or facing horror? isn't adrenaline meant to enhance strength/perception? | And sometimes other parts of the body feel useless in different intimidating circumstances. | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/40taii/eli5_why_do_we_get_weak_knees_at_the_edge_of_a/ | {
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"As far as weak kness goes, it is actually caused by adrenaline, as blood is pumped to the parts that need it the most from the legs, heart, brain muscles which causes the weak kness/jelly feel.",
"Okay so it's partly what /u/McPubes said, that our body takes blood away from our extremities and pumps it to our vital areas, the heart, the brain, and our vital organs. This means that our legs have less blood in them, and are less oxygenated and thus weaker.\n\nHowever, there is a much larger mental component to it. The fear response that we feel at the edge of a cliff is designed to put us into \"fight or flight\" mode. Although the physical response of \"fight\" and \"flight\" as part of fear are pretty much the same (both give you more rapid heartbeat, increased adrenaline, quicker response times, etc.), the mental responses can be very different. This was how it explained to me by a psych professor I had. Essentially, when you get scared, your body doesn't know why. It just says \"oh shit, we're scared now, battlestations everybody!\". But your body doesn't run away or fight without your mind telling it to. \n\nMeanwhile, your mind analyzes the situation, and depending on what's going on, decides to use its now increased strength, speed, reflexes, and heartrate for running, fighting, or both. It comes down to two questions: \"Is this something I'm scared of DOING or something I'm scared of NOT doing (or fighting/being around)\" and \"Is it going to stop the problem faster/better if I run or if I fight?\" Now these aren't conscious questions you're asking yourself, this is a decision made by your brain based on (generally pretty obvious) contextual clues. As my professor said, \"Your mind, even in its dumbest, most split-second moment, knows that it's not going to do any good to get pissed off at a cliff edge and to try and fight the cliff edge. It knows that it just doesn't want to be NEAR a cliff edge. So your brain can then interpret the less-oxygenated, weaker knees as a sign that you probably shouldn't use them right now, hence the feeling of weaker knees. It's the same response, just a different reaction.\n\nNow, depending on how your brain instinctively interprets a situation, that can determine what exactly your response is in a given situation, which is why some people run and some people fight in the same situation. Sometimes your brain learns not to be scared in certain situations too, like with mountain climbers who don't fear heights."
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2qri98 | why don't they track the cell phones of the passengers of the missing airasia plane? | Wouldn't it be likely that at least one of the passengers has a GPS phone? Why can't their phones be tracked? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2qri98/eli5_why_dont_they_track_the_cell_phones_of_the/ | {
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"The phones are submerged therefore inoperable.",
"GPS isn't a two-way signal. You can tell where you are, relative to some satellites, but those satellites aren't receiving any signals from your device.\n\nIf your phone is underwater, it's usually going to stop working.\n\nAs far as the plane, various people have asked about the search several dozen times already. The short answer is that finding a plane in the ocean is harder than you think.",
"cell phones don't have a signal when you're 500 miles from land. they won't be able to send datat out."
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1rky8r | Does the double slit experiment work with sound waves? How can you make the appearance of stereo sound with only mono? | Obviously disregard the particle wave duality conclusion of the double slit exp. I want it know if there are the same interferences with sound as with light and how does that change the sound we hear? | askscience | http://www.reddit.com/r/askscience/comments/1rky8r/does_the_double_slit_experiment_work_with_sound/ | {
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"Yes it does. Any type wave, like surface waves in a lake, etc. There's nothing mystical or spooky about it.",
"The two slit experiment is based on wave physics, so it works with sound waves, light waves, water gravity waves, etc. It's most noticeable when the wavelength is on the same order as the distance between the slits, and the slits are small with respect to the wavelength. For example, if I wanted to do this experiment with sound with a 1 m wavelength, then I'd want the slits no more than 10 meters apart, and I'd like the slits to be less than 10 cm.",
" As the double slit experiment is based on a wave model, sound waves and even ocean waves show this too. Even in nature, you see the same effect when a wave goes through two rocks:\n_URL_0_"
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cmlkud | how does our body know to swallow liquids and foods down the esophagus (and not the windpipe) 99% of the time? | [deleted] | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/cmlkud/eli5_how_does_our_body_know_to_swallow_liquids/ | {
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"Easy: We aren't adapted to swallow into our lungs. I mean, how often do you really think you need to *swallow air*? It is simple for the body to simply divert anything swallowed via the typical muscle contractions of the esophagus down into the stomach.",
"When ever you swollow a peice of muscle/tissue called the epiglottis will close over the trachea (windpipe), preventing it from going down.",
"We have a flap in our throat called the epiglottis. It automatically closes off the path to the lungs when you swallow. That is why you can’t swallow and breath at the same time"
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rbpa9 | why does my cat smash his face into the wall when he sleeps? | If he's in the window, its smashed against the side. If he's on my lap, its smashed against my arm. In bed, smashed against my leg. It is comforting? For warmth? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/rbpa9/eli5_why_does_my_cat_smash_his_face_into_the_wall/ | {
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"The better question is, why don't you?",
"My guess is that it's for protection: if he's attacked by a predator while sleeping, his face and belly are protected (since the predator can't reach them), and only the less-vulnerable backside is exposed.\n\nOr, he knows it's adorable and is trying to help you gain karma."
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c4ok11 | Superheroes seem to be an uniquely American phenomenon. How was it born? What specifics of American culture led to the Superhero being created there? | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/c4ok11/superheroes_seem_to_be_an_uniquely_american/ | {
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"Superheroes are a global phenomenon: the word itself dates to 1917, and at least two characters, the French Nycalope and the Japanese Golden Bat, are clearly superhuman adventurers who have abilities far beyond normal humans published well before Superman's debut in 1938. So, I must assume this question is asking about the specific form superheroes have taken in American culture as exemplified in the works of Marvel and DC Comics, as superheroes in the sense of \"heroic characters who are superhuman\" remain present worldwide and are not particularly like the American form. (One should be familiar to most are the Japanese sentai \"ranger\" shows and action-oriented magical girl shows of the type *Sailor Moon* pioneered.)\n\nHere, we have to dig into history and the panic over violent and gory content in comic books spurred on by books like Fredric Wertham's *Seduction of the Innocent*. At this time, mystery, true crime, and horror comics were very popular as well as pulp adventure and superheroes. While there had been a prior attempt at an industry association and self-regulating the content of books published (the Association of Comics Magazine Publishers) it was not successful as a number of publishers either refused to join, or pulled out of participation. Wertham's book, and the subsequent Senate hearings, spurred a second attempt (the Comics Magazine Association of America) which implemented the Comics Code Authority. Only comics that obeyed the strict rules of the CCA could bear the CCA stamp, and the intent was self-regulation was preferable to wholesale banning.\n\nMany of the features associated with American superheroes came about because of the restrictions of the Code, or (much later, in the 1980s on) as a reaction to those restrictions. For example, since the Code had provisions against showing anything related to crime as alluring, and criminals could never be shown sympathetically, one could not show antagonistic characters with subtle nuance. Instead, the antagonists would have to be shown as over-the-top, evil, and malicious as possible. Another provision was \"good must always triumph over evil and the criminal punished\", while excessive violence was prohibited, the crimes had to be either nonviolent or grandiose. The heroes themselves had to be clear avatars of good (as defined by the status quo of the day). How this leads to the heroes and villains in American superhero media and the morally black and white world they portrayed naturally follows, with nuance and subtle character development being added as the Code changed, weakened, and finally vanished, becoming a non-factor by the early 2000s.\n\nOther things common to the American style of superhero arose from the origins of being published on low-quality paper in weekly installments. \"Spandex\" costumes derived from drawing essentially naked figures and coloring them in, instead of the more time-consuming method of properly drawing flowing cloth. Simple, primary colors were favored owing to the cheaper printing process used by comic books.\n\nSo, in short, while superheroes are not at all a unique American phenomenon, the specific style of superheroes exemplified in the works published by the \"big two\" of Marvel and DC arose from specifically American cultural factors and demands. Since the fall of the Code there has been further deviation from that template, although an extended discussion of that is outside the 20-year rule of the sub. Even in the 1980s and 90s, though, the hold of the Code and the necessity for a comic book to be Code-approved had lessened, leading to experiments such as the Vertigo imprint used by DC.",
"I will preface this with the fact that I am not an historian, but I am a professional artist who has studied graphic arts, including comics, in a serious way for over 20 years.\n\nSo, while I concur that the \"Superhero\" as a concept goes back a long, long way (Moses?) there is something to be said for the influence the Great Depression and the Jewish immigrant experience had on the emergence of a singularly American style hero and basically the template for the comic book superhero as the West knows it today.\n\n[As this article makes clear](_URL_1_), Jerry Siegel and Joe Schuster imbued their Über-mensch with many characteristics drawn from their Jewish, immigrant heritage: his abandonment and separation from his home, his difficulty in relating and assimilating to his new surroundings... I don't know that they were trying to make his Jewish influence explict, but it's certainly obvious with even a cursory glance at the creators. [Jerry Siegel himself even mentions imagining a way to fight back against anti-semitic oppressors (namely the rising Nazi Party in Germany).](_URL_0_)\n\nSecondly, I would argue that Superman also grew out of a desire for the \"little guy\" in American society to have a voice and an ability to fight back against the powerful elites who were seen (rightly or not) to have plunged the country into dire straights. Superman's earliest stories see him fighting against all sorts of oppressors like landlords and moguls, even down to small-scale oppression like domestic violence. As u/aliasi mentions, Superman was much more violent and brutish early on; the boy scout stuff doesn't come until much later. But the powerlessness of the American working class during the Depression certainly explains the appeal of a hero who doesn't take any guff from the crooked boss or the greedy landlord. [This article (seemingly biased given the url but fairly citation dense)](_URL_2_) offers more proof that Superman was the personification of the New Deal rhetoric offered by Roosevelt: fairness and equality for the down-trodden everyman.\n\nLastly, the depression itself provided fertile ground for the development of the comic book itself. Cheap, action-packed escapism was a welcome distraction from the woes of everyday life and the superhero explosion soon after the invention of the medium proves that the market was hungry for such stories. I think it's probably important to note that the Golden Age superhero boom also began to implode right after the end of WWII, which suggests that the post-war boom years led to a hunger for different kinds of comic stories, notably science fiction and horror. Though the perennial favorites like Superman and Batman would continue to publish during the 50s, it wouldn't be until the inception of the Marvel Universe in 1961 that superheroes would experience another boom in popularity (tellingly by focusing on story elements that made superheroes seem like everyday people with problems!)."
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"https://www.supermanhomepage.com/comics/comics.php?topic=articles/new-deal-symbol"
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55ihb4 | If a decimal number is constructed as {0 . D1 D2 D3 ...} where Di = Random(0..9), for i = 1 to ∞, does such a number "exist" in the Real Numbers? Or in other words, do completely random numbers exist in the Reals? | askscience | https://www.reddit.com/r/askscience/comments/55ihb4/if_a_decimal_number_is_constructed_as_0_d1_d2_d3/ | {
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"All finite numbers are in the reals, including your random number. In fact, a randomly chosen real on any finite interval will [almost surely](_URL_0_) have random digits. Most reals look like your example number. We will never be able to write down or even fully describe any of these real numbers because knowing all the digits is effectively the same as knowing the outcome of an infinite number of coin flips (which means almost every real number effectively contains infinite information).",
"It sounds like you are asking, \"do all imaginable [irrational numbers](_URL_0_) exist among the [real numbers](_URL_2_)?\" If that's the question, then the answer is yes, and in fact, [almost all](_URL_1_) real numbers are irrational.\n\nHope that helps.",
"The reason any decimal exists is due to the completeness of the real numbers. \n\nAs an example, consider pi - 3 = .14159... \n\nThe set {.1, .14, .141, .1415, ...} is a nonempty set of numbers that's bounded above by 1. Therefore it has a least upper bound, which is in fact pi - 3.\n\nThe [completeness property](_URL_0_) of the real numbers says that any nonempty set of reals that's bounded above has a least upper bound. In other words there are no \"holes\" in the real numbers. \n\nThat's why every infinite decimal expression must converge.\n\nAlmost all such expressions are random in the sense that there is no algorithm or computational procedure to crank out the digits. You might get lucky and pick, say, .3333.... = 1/3. But there are only countably many such lucky expressions corresponding to algorithms (since there are only countably many Turing machines). But there are uncountably many real numbers. So \"most\" real numbers are random, having no algorithm that generates them.\n\nA sharper argument along these lines is that the measure of the unit interval is 1, but the measure of the computable reals is 0. \n\nYet another viewpoint is to consider binary representations. For example 1/3 = .01010101... Then you can imagine each binary digit as the outcome of a fair coin toss. The probability of any particular bitstring is 0. With probability 0, there will be some algorithm that predicts the coin flips (namely the bitstrings corresponding to the computable reals). With probability 1 (restricting to the unit interval) a random bitstring will not correspond to any algorithm.\n",
"You ask a very interesting question, because it is about randomness of an individual object. If you throw a dice 5 times, then the outcome of (1,1,1,1,1) is equally probable as (4,3,4,2,1), but the second one seems more 'random'. \n\n'Random' is a procedure of obtaining objects, but once you have the object, the way it was obtained is not part of the object any more.\n\nOne way of defining randomness of objects is by the length of its shortest description. \nA number is 'random' if it has no finite description. For example ( 1/ pi ) = 0.3183098862 .. is not random, because it can be described as `1/pi', which is very short.\n\nAssuming this definition of randomness, random numbers must exist, because in every reasonable algorithmic language, only countably many representations exist, and we know that there exist uncountably many real numbers.\n\nB.t.w. The theory of randomness of individual objects, based on shortest representation, is called [Kolmogorow Complexity](_URL_0_)."
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3djz4h | why aren't people getting sick from using their phones in the bathroom? | With all of the people using their smartphones while on the toilet, at the gym, etc and then later while eating, why aren't more people getting hepatitis / other illnesses? It seems that touching a phone with dirty hands, pocketing it, then using it later would be almost as bad as not washing your hands | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/3djz4h/eli5_why_arent_people_getting_sick_from_using/ | {
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"The real issue is that washing your hands in the bathroom isn't as crucial to avoid illnesses as you'd think. It's just that washing your hands IN GENERAL is, and reminding people to do so after using the bathroom is easier since you're already in a place with a sink.",
"Many of the diseases you're thinking of have very limited lifespans when they are outside of ideal environments. Since they are pathogens, ipso facto their ideal environment is inside us. Outside, they have a pretty rough time of it. Now, this is only generally; there are of course Bad Things that are infectious for quite some time.\n",
"1. Your hands are still clean when you're using your phone. I don't know of anyone who will sit down on a toilet, wipe their ass, and *then* grab their phone and take a shit. By the time you wipe, your phone is probably already put away again.\n\n2. (Most) phones are made out of metal and glass, and a few are made of plastic. Metal and glass (and most plastics) are non-porous - they don't absorb stuff, and bacteria won't survive on them very long, if at all.\n\n3. Our immune systems are actually pretty good. Chances are, you wouldn't get *seriously* sick even if you never washed your hands after using the washroom. That being said, there's a lot of other really nasty stuff that gets on your hands that you *do* need to wash off, like salmonella, e-coli, or other really dangerous bacteria. You should wash your hands regularly to protect yourself from this, and teaching a kid to wash their hands whenever they use the washroom is very convenient.",
"There is literally shit on almost everything you touch. There are germs fucking *everywhere*. Phones are not making the problem any worse than it always has been.",
"I honestly rarely wash my hands in general. Yeah if I touch raw meat or some nasty (visually dirty) surface or I can see that they are dirty. I usually get a minor cold every once a year and that's its. No serious illness.\n\nIf your concerned about germs on your phone, you shouldn't even keep your tooth brush near your bathroom.\n\nIt's just like the people who cover the toilets with that paper that is provided. It does nothing!!! ",
"If your own poop has hepatitis in it, then **you already have hepatitis**.\n\nYou probably should not lick strangers' phones. Especially not if the stranger has hepatitis, and the phone is covered in poop."
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2zby57 | why can't politicians be contractually obligated to fulfill their basic campaign promises? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2zby57/eli5_why_cant_politicians_be_contractually/ | {
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"Well the simple and to the point answer is that lying is not illegal, and the type of campaign promises politicians make are not under oath, so there is no consequence to them not following though (or doing the exact opposite).",
"We can always vote them out unless we prefer the lies they tell us.",
"Other than the obvious \"it's impossible\" or \"they cannot be punished for lying\", the simple matter of the fact is, a single politician is merely a voice in the crowd. Sure they have a louder voice than us regular citizens, but it's still a crowd nonetheless.\n\nOne can claim to do A while running for office, and when they finally get into office and try to perform A, other people in the congress can be like, no, that's now what we promised our people. Then A is scrapped and the politician is left in the dust. \n\nFor something to happen, the majority must agree. That means if the person running for office wants to fulfill his campaign promises, he must make campaign promises that the majority of the congress will agree upon. But the reason why people are voting up new congress members is for change. If you're presenting ideas that are agreeable by congress, nobody will vote for you. If you're presenting ideas that are not agreeable by congress, people will vote for you (if that's what the people want).\n\nTL;DR: Politician wants to legalize weed, people vote him up, politician promotes weed legalization to congress, gets rejected, campaign promises unfulfilled.",
"Leaving aside the obvious \"the people who would put rules into place to stop this are the people who benefit from not having a rule in place\" aspect, there actually is a good reason. Life is complicated, and looking after a country moreso. The circumstances someone makes those promises in are rarely the circumstances in which they have to act on them.\n\nA simple example; you pledge to reduce taxes. And you mean it! You've run the numbers, and you've figured out how to do it. The people get behind you, you get voted in, and, you start figuring it out. Then a bomb is dropped, literally. Now, you need money to rebuild, but you worked that into your finances, that's fine... But now you're under pressure to go to war. In fact, you know it's the right thing to do, you'd be putting your nation at danger by not responding. But war is expensive. So are you going to push ahead on your tax reduction, knowing that you'll be sending an ill-equipped under-funded military out to fight? Or do you put aside your tax-reduction plan and get them what they need? Lives... Or money?\n\nAnd this is assuming that everyone else is playing nice. Here's another one; you're clearly going to win, so while they're still in charge they put in place a bunch of popular but expensive policies to get people on their side. If you win anyway, your tax-reduction plan is no longer feasible. You may not legally be able to undo their policies, and even if you can, that makes you the asshole who eliminated the \"food for orphans and veterans\" bill to push through your pet agenda.\n\nSo making it punishable not to follow through on your plans wouldn't work, because it would put politicians in the position of choosing to do what's best at the time but getting in trouble for it, or avoiding punishment by honouring old promises that aren't in anyone's best interests anymore.\nDoes this get abused to allow people to make promises they have no intent of following through on, or even know how to do? Hell, yes, but we can't solve it by forcing them to. My suggestion? Force politicians to put up implementation plans on how they plan to make things happen. Show us where the money is coming from. Give projections of the impact of the plan. Have them cite sources for their claims. Make those things mandatory, with punishment for not following them.",
"Because you'd have to convince politicians to make it illegal.\n\n'Hey, you guys, want to make your life harder?'",
"I think the contract is that if you promise things & don't deliver, the voters will elect someone else in your stead. \n\nIf you wanted to hold politicians criminally responsible for changing their minds based on better information or underestimating entrenched structural obstacles, I don't see how the result would be better. \n\nI honestly want politicians explaining why they've changed their positions more often, but voters tend to punish politicians for being anything but suredly obstinate. ",
"In the grand scheme of things you don't want inflexible politicians. pre-2008 [ish] it might have been a good idea to be a budget-reductionist but then the banking \"crisis\" happens and you need to inflate the currency to keep things moving.\n\nIn reality, people are fairly stupid and will believe anything their favourite politician tells them. That's why \"no new taxes!\" and \"the other guy eats babies\" works.",
"Because as a UK politician said once:\n\n\"Election promises are not subject to legitimate expectation.\"\n\nMeaning that everything they say should be expected as a lie.",
"What if circumstances change and what was originally promised is no longer the best alternative?\n\nWe need to have politicians who analyze issues and respond accordingly, not robots who press predetermined buttons.\n\nTrue, many campaign promises get broken for less that stellar reasons, but that's the trade-off for giving them the flexibility they need.\n",
"\"Contractual obligations\" are legal questions enforced by the court system.\n\nWhether a politician has fulfilled their campaign promises is a *political* question. The court system cannot rule on political questions and must leave them to the political process (i.e. the next election).",
"Because they aren't a King who has total control. Obama has tried to close GITMO, but the Republicans have stopped him several times. That's what happens in politics.\n\nNot to mention that this is a stupid idea as things change between a campaign and when a politician is in power. Obama campaigned on getting troops out of Iraq (which he largely did). Now ISIS is a thing and he might need to send troops back. Do you want his hands tied by something he said in 2007?",
"It's a combination of things:\n\n1. Not all campaign promises can be achieved, some are realistic and some are not, others just don't come to fruition for unexpected reasons.\n\n2. Those who make the promises are not always representative of the entire political party they stand for and as such any promises they make are not necessarily going to be carried out by the current government.\n\n3. In most democracies what's stopping the current government from passing legislation isn't their unwillingness to do so, but instead the opposition who refuse to pass it into law. We see this particularly in US politics.\n\n4. Extenuating and unforeseen circumstances such as war, climatic events, civil unrest or other uncontrollable things can often prevent the government from focusing its attention on fulfilling campaign promises. Sometimes resources just must be distributed in emergency situations.\n\n5. And lastly, it is just wildly impractical. Every politician and government would be scrutinized if they failed to achieve even the most insignificant of their campaign promises. Who would be the judge of such failures and how do we remedy such a situation? These are all questions that need to be answered before holding governments completely accountable based on their manifesto's.",
".....why do you think we have a SECOND AMENDMENT??"
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46vrli | Is the human body designed to be herbivore, carnivore or omnivore? | askscience | https://www.reddit.com/r/askscience/comments/46vrli/is_the_human_body_designed_to_be_herbivore/ | {
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"Omnivore. There arent any animals that can digest plantstuff (cellulose) without the aid of microbacteria that do it (which we have), and our bodies can process meat, which is an important part of our diet, which makes us omnivores"
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c7fk4d | Why not blockade Japan by sea in WWII? | Everyone seems to agree that invading Japan at the end of WWII would have caused millions of casualties, but by mid-1945, wasn't Japan's navy and air force pretty much gone? Instead of using nuclear weapons, or actually staging an invasion, why couldn't the US (or the US and the USSR together) simply blockade Japan and starve it into submission? | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/c7fk4d/why_not_blockade_japan_by_sea_in_wwii/ | {
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"So until 1943 that was actually sorta the plan. Just about every iteration of War Plan ORANGE from the 1910's on contemplated one or a series of major fleet clashes between the Philippine Sea and the Home Islands. After that the fleet would blockade Japan into submission or at least to the bargaining table. As aviation technology advanced the new warfare domain was incorporated into the plan, strategic bombing, fighter sweeps, aerial mining all could tighten the noose.\n\nBut by 1944 into 45 several things had changed. Namely the perceived resistance of any willingness to negotiate on the part of Japan. Truman's, when he took office, desire to enforce the Potsdam terms strictly(no haggling about the Emperor for instance), and exact an extra measure of blood and vengeance from Japan, all while managing political support as many just wanted to turn towards peace as 1945 ticked on. Those factors seemed to all point to either a major time commitment to try starving Japan out and breaking political leadership or national will, or the need to put boots on the ground. With an eye looking North towards the potential of the USSR throwing a scrapped together force of a few divisions ashore in Northern Japan in the Fall to assure themselves of an occupation zone post war. \n\nOf course underpinning this was the desire to apply maximum force to defeat Japan as soon as possible, with the idea that more blood up front would end the war sooner, and prevent a sustained baseline of loss as the war continued. A conference in Quebec in 1943 suggested it could be 1947 before the Allies were ready to land force on Japan itself though! But the collapse of the IJN, and a self imposed deadline to attempt to bring Japan to terms within 12 months of Germany accelerated things. The post war US Strategic Bombing Survey suggested that without an invasion and with a failing harvest Japan could have been brought to terms in late 45 into early 46, but remember this is US Air power saying US Air power could have ended the war on their own!\n\nIn the end though it came down really to service rivalry. Hitting the beaches was the one way the Army could bring about Japan's surrender, under MacArthur of course! While the Navy under King and Nimitz were not excited about sitting off invasion beaches as a mostly fixed target and were far more supportive of the old blockade plan. Planning continued through the summer of 1945 with the first landings set for November 1945, but in the face of evolving intel estimates the Navy still had their doubts. Truman could absolutely have faced a split between his most senior military leaders and forced him to pick sides and own it. \n\nNuclear weapons would have featured in either eventuality, with a slow trickle of 2ish per month through the end of 1945. Though had plans for invasion continued there was a debate over saving them up to use in more direct support of landings against transport hubs, HQ's, etc. But the 'other use' as a tool of strategic bombing against populated cities was not discarded either, though the realities of its impact deeply impacted Truman and his willingness to allow them to be used.\n\nHasegawa's Racing the Enemy is very much a go to work on the end of the war in the Pacific, and does examine the USSR's role far more than I have.\n\nThe every wonderful Restricted Data has his amazing blog which I would point you to for his ease of access to numerous primary sources and memo's/transcripts, along with his own works.\n\nWar Plan Orange by Edward S. Miller is a masterwork on the evolution of US strategy for fighting Japan leading up to 1941 and its application. Warning it is dry as the Sahara though."
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1jzv8a | what happens to the bodies of asylum seekers who die en route to australia? | I'm sure there's some sort of process to follow with this sort of thing. Do we fly them back? And to who? Considering it's possible for whole families to die on the same boat, and identification of the bodies would prove to be difficult seeing as their aren't any official documents.
Not generalising to Australia. | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/1jzv8a/eli5_what_happens_to_the_bodies_of_asylum_seekers/ | {
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"I'm sure that the government would likely either burn or bury the bodies at the point. Here's a better explanation of how it works in the US, and I feel it would be no different for asylum seekers as there would be nowhere else to send the body (_URL_0_). If documentation did exist, next of kin from the country of origin may be tasked with flying the body back or paying for burial in the asylum country."
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37u3xy | how different coloured light affects plants and why? | For instance a standard coleus or tomato plant. So why would a light affect a plant in which way, is light just different wave lengths? Then why would a plant be more inclined to reflect a 520nanometer wavelength (green) than a 650nanometer wave length (red)? So what would be the most catalyzing (for growth) colour? Violet? Why?
Bonus question: Is this the same for plants that aren't green? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/37u3xy/eli5_how_different_coloured_light_affects_plants/ | {
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"The different colors are produced (more or less) by different wavelengths. It's a little bit more complicated than that since vision is complicated, but that's close enough.\n\nThe green color of plants comes from chlorophyll, the chemical that allows plants to capture sunlight to produce energy. It just so happens that it's good at absorbing blue and red light, but not as good at absorbing green (which gets reflected or goes through). Strictly speaking, there are several types of chlorophyll, but most plants limit themselves to two, which are green and yellow.\n\n > So what would be the most catalyzing (for growth) colour?\n\nI would speculate and say blue, since that's the color chlorophyll most strongly absorbs. But there could be other factors at play - I'm not a botanist.\n\n > Bonus question: Is this the same for plants that aren't green?\n\nMost plants that aren't green still have chlorophyll of the same kind, they just have other pigments that change their color. So yes, it should be the same. There are a few exceptions: some algae and cyanobacteria use different forms of chlorophyll that are different colors and absorb different wavelengths of light, usually because they live in environments where blue light doesn't penetrate well."
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5ibctp | why are shock waves more dangerous in water than air? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/5ibctp/eli5_why_are_shock_waves_more_dangerous_in_water/ | {
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"Water is not compressible but air is. So, in air, a lot of the energy of a shock wave will be wasted just compressing the air. But, in water, the energy of the shock wave gets directly transferred into your body because none of it was wasted compressing the water.\n\nImagine you were swinging a paddle at someone across the room. If there was just air in between you then the force would dissipate before it made it to your victim. However, if you used that paddle it hit an incompressible object like a long metal rod, the force would be transferred much more efficiently to the other side.",
"Water doesn't compress, so doesn't absorb the energy like air does. \n\nThe way to think of is like being hit around the head by a sponge, and then bit hit around the head, at the same speed, by a brick. One will do **way** more damage. ",
"This has to do with how momentum is transferred in a collision: If you have one steel ball hitting another of the same size, it will transfer all its momentum, and with it all its energy, to the other ball - as in Newton's cradle. But if it hits a much heavier steel ball, it will be deflected, and with it most of its energy.\n\nShock waves behave in a very similar manner: A shock wave in air hitting a human will be reflected almost entirely, whereas a shock wave in water is able to pass right through a human, simply because water is very similar in density and elasticity to tissue. \n\n"
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d97hjg | how are impossible burgers healthy with all the chemicals to make it look and taste like meat? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/d97hjg/eli5_how_are_impossible_burgers_healthy_with_all/ | {
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"everything is a chemical of some kind, including meat and vitamins. The chemical used in food products were tested and confirmed to be safe or beneficial."
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[]
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5i4qwq | purpose of warming car up during winter? i keep reading crap online today that says its a myth and doesn't apply to today's cars & my ignorance doesn't know what to believe. | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/5i4qwq/eli5_purpose_of_warming_car_up_during_winter_i/ | {
"a_id": [
"db5bpcg",
"db5bt2y",
"db5bupr",
"db5n0h1"
],
"score": [
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"text": [
"The heating element inside the car uses the engines coolant for its heat source. If the engine hasn't been running for a while, the coolant will not be hot, and you will have no heat inside the vehicle until the coolant warms up from the engine.",
"with modern cars, warming up an engine is not necessary. Electronics control fuel/air mixture allowing for correct combustion, so idling is just wasting gas. \n\nNOW, you don't want to red line it around town, be more gentle with it until your temp needle comes up to at least a quarter of the way. BUT the fastest way to do that is to put a load on the engine (driving it). ",
"The purpose of warming the car up has a couple features:\n\n* in really cold weather, the oil and transmission fluid can be thick and sluggish, and isn't fully lubricating the parts of the engine very well until they get a little warm. \n\n* create heat so you're comfortable in the car.\n\nThe second version is the primary reason. By 'get a little warm,' the fluids are pretty good even below freezing, and there's little difference between an idling engine and driving down the street at city speeds. Were you to head straight out on the highway at 70mph, there's the potential for more wear than usual, but generally things in the engine and transmission are designed to allow a little bit of time between the engine first starting and everything getting lubricated to normal operating levels.",
"It's not a myth. Your engine has more friction when cold and can shut right off if it's not warm enough to keep combustion happening. This has happened to me hundreds of times. Then again where I live the temperature can be -30 C."
]
} | [] | [] | [
[],
[],
[],
[]
] | ||
2ixs5g | Do spiders learn web-making or is it something innate? | I was watching a spider building a web a few days ago, and was impressed by how quickly and methodically it worked. Are these techniques "hard-coded" into the spider's being, or could web-making be considered a form of culture? The existence of spiders that produce specialised forms (funnel-web, trapdoor) makes me feel that it may be the latter, but I really know very little about this subject. I'm also aware of experiments that looked at how a variety of psychoactive drugs affected web construction, and wondered if these shed any light? | askscience | http://www.reddit.com/r/askscience/comments/2ixs5g/do_spiders_learn_webmaking_or_is_it_something/ | {
"a_id": [
"cl6imrz"
],
"score": [
12
],
"text": [
"Most web building spiders do not provide a great deal of offspring care, and I am fairly confident that spiders are able to build webs without observing other spiders building webs.\n\n[Web structure and strategy is fairly consistent within clades](_URL_1_); orb weavers build or webs, funnel web spiders build funnel webs, and so on, suggesting a strong genetic component.\n\nI'd also argue that the neurology of a spider is sufficiently simple that a fair bit of the web building behavior would need to be programmed.\n\nWe can [use genetic algorithms to predict web building behavior](_URL_0_).\n\nThat said, if a spider is catching prey reliably and needs to rebuild its web, it may build [a smaller web on the next go-round](_URL_2_) (more energetically efficient), so there is some plasticity in what they do based on conditions. This could be an algorithmic behavior, though, rather than outright learning."
]
} | [] | [] | [
[
"http://www.sciencedirect.com/science/article/pii/S0022519396903069",
"http://icb.oxfordjournals.org/content/12/3/445.short",
"http://www.sciencedirect.com/science/article/pii/S0003347299913271"
]
] | |
29cnez | Have we ever discovered rogue stars in open space? | By this I mean, singular stars located outside the confines of a galactic body in intergalactic space. | askscience | http://www.reddit.com/r/askscience/comments/29cnez/have_we_ever_discovered_rogue_stars_in_open_space/ | {
"a_id": [
"cijnlgx"
],
"score": [
2
],
"text": [
"Yes! We already dicovered [stars outside of galaxies](_URL_0_). There are actually three ways how stars outside of galaxies can form, however the linked article only states two of them. Besides these two ways (galactical collision and ejection by supermassive black holes) the third way is by forming of intergalactic gas clouds. However most of the intergalactical gas is too hot for forming stars and it is still hypothetical at the current state. \n\nThe ways of ejecting stars by black holes or due to galaxy collisions is good confirmed so far, as we already found several stars and even star clusters outside of galaxies, which serve as prove for these theories."
]
} | [] | [] | [
[
"http://en.wikipedia.org/wiki/Intergalactic_stars"
]
] | |
4llktp | How does melanin protect us? | askscience | https://www.reddit.com/r/askscience/comments/4llktp/how_does_melanin_protect_us/ | {
"a_id": [
"d3ob652"
],
"score": [
11
],
"text": [
"Melanin absorbs visible and ultraviolet radiation, converting it to heat when it might otherwise excite more delicate chemicals in the cell. It's like insulation against light radiation - it sucks up the photons instead of them passing through and messing up things below. The melanin molecule can then spontaneously return back to normal by [thermal relaxation](_URL_1_), with the net effect being heat generation, in lieu of chemical damage. \n\nIt tends to absorb in the short-wavelength visible and near-UV range, [peaking around 335nm](_URL_0_). This absorbs the radiation and keeps it from reacting with more precious biological materials like proteins and especially nucleic acids.\n\nIt does so because it has a gap between resting and excited states that matches the range of wavelengths that are relevant for some of sun-induced damage. With a peak absorbance in the near-UV, the molecule absorbs a lot of this radiation. It doesn't do much for the more energetic UV radiation, though, so sunscreen is always still a good idea!\n\nedit typos"
]
} | [] | [] | [
[
"http://www.cl.cam.ac.uk/~jgd1000/melanin.html",
"https://en.wikipedia.org/wiki/Relaxation_%28physics%29"
]
] | ||
3fhiqk | how do we know the "observer effect" in quantum physics is real? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/3fhiqk/eli5_how_do_we_know_the_observer_effect_in/ | {
"a_id": [
"ctonmq5",
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"score": [
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"text": [
"Exactly how to understand the observer effect depends on your interpretation of quantum mechanics. To the degree we \"know\" it's real it follows from the simple double slit experiment. Measure/observe which slit the particle is in and the interference pattern disappears. ",
"A measurement is *always* an interaction with the system we want to measure. And an interaction *always* changes the system. Thus, it follows logically, than an observation will *always* change the system."
]
} | [] | [] | [
[],
[]
] | ||
4nahme | Is there a limit to how many photons you can pack into a beam of defined width? Or to ask the other way - can an infinite number of photons occupy the same space? | askscience | https://www.reddit.com/r/askscience/comments/4nahme/is_there_a_limit_to_how_many_photons_you_can_pack/ | {
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"d42c8fj",
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"score": [
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"text": [
"Yes there is. After a certain amount of photons of specific energy are put in a volume of space, the space itself starts interacting with the said photons. So while you techinically can have an unlimited amount of energy in any point in space (up until the black hole situation that was mentioned), you cannot have a beam with unlimited energy density. \nThe maximum energy density of any beam of photons depends on their wavelength.",
"/u/RobusEtCeleritas is correct, you could create a black hole.\n\nAnother thing that will likely happen is [photon-photon scattering](_URL_1_). When the intensity gets large enough, [the Schwinger limit](_URL_0_) makes the electric field nonlinear: photon-photon scattering becomes possible, leading to nonlinearities even in a vacuum. The Schwinger intensity is much smaller than the intensity necessary to create a Kugelblitz, and will hopefully be reached in our lifetime.",
"Wouldn't spacetime itself breakdown at some energy density of photons, and transform the photons into matter/antimatter?\n\nI always thought this was the reason for E=MC^2. That spacetime itself has an energy density limit, and after that limit, energy of any sort \"crystallizes\" into matter.\n",
"If the photons are traveling through a medium (air, water, etc.) and there is enough photon flux in a small area, they will create a plasma. This plasma will reflect photons. In fact the plasma will move closer to the source of the light if there is enough photon flux, and reflect the photons even sooner.\n\nThis limits the amount a photons in a specific space when traveling through a medium (not empty space).\n\nThis is how laser eye surgery works. The laser cut is actually performed by a supersonic shock-wave created by the plasma."
]
} | [] | [] | [
[],
[
"https://en.wikipedia.org/wiki/Schwinger_limit",
"https://en.wikipedia.org/wiki/Two-photon_physics"
],
[],
[]
] | ||
vw8nd | please see the "huge bubbles" video in link below. you can see when a soap bubble pops at one end, the "popping" travels all the way to the other end till the bubble is completely popped. what determines the speed of popping? | _URL_0_ | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/vw8nd/eli5_please_see_the_huge_bubbles_video_in_link/ | {
"a_id": [
"c586cnm",
"c58axa5"
],
"score": [
2,
2
],
"text": [
"The speed at which the bubble pops is determined by the elasticity of the bubble material. There are forces holding the bubble together that are in equilibrium, acting on all sides of the bubble. When the bubble is popped, it no longer has that equilibrium, and rapidly approaches a chaotic state.",
"Thank you for showing that video it was amazing. Sorry I can't add to the answer."
]
} | [] | [
"http://www.youtube.com/watch?v=3i-zYdOPG2k&feature=fvwrel"
] | [
[],
[]
] | |
5h2mxz | can you explain turkey's constitutional changes in terms of the presidency and what it means for the us (and likewise, what does the us want)? | Struggling with completely understanding this topic, thought I'd try and tie up lose ends with the help of Reddit. | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/5h2mxz/eli5_can_you_explain_turkeys_constitutional/ | {
"a_id": [
"daxj5do"
],
"score": [
2
],
"text": [
"Turkey's political structure currently has a president (head of executive branch) and prime minister (head of legislative branch). \n\nCurrently the constitution states that a president elect must cut ties with his/her political party before taking on the role, constitutionally making presidency a nonpartisan role. \n\nThe proposed changes will eliminate this requirement allowing the president to stay loyal to his party. Currently parliament is elected though a general election, the prime minister is then elected privately by the ruling party in parliament. The president is elected in a separate election.\n\nIn a completely free and fair system this is not principally a problem. If on the other hand there is widespread corruption this will allow a single figurehead to rule both the legislative and executive branches of government, and thus appoint yes-men to the judicial branch, effectively ruling the entire government unilaterally. \n\nFor the US this doesn't mean anything special. It doesn't allow the Turkey to gain any extra power and if Trump continues with his America First approach than there is no concern with Turkey at all. They do not hold any leverage over the US and we have no special interest in them."
]
} | [] | [] | [
[]
] | |
2jpvhu | how are the "leaf stains" on concrete formed? | During fall, there are usually dark brown stains from leaves on the sidewalks. Sometimes they're perfectly in the shape of a leaf but later they get smudged. How are they formed and what are they made of? Why do so many form? I can't seem to find anything online besides advice on how to remove them. | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2jpvhu/eli5_how_are_the_leaf_stains_on_concrete_formed/ | {
"a_id": [
"cle1bv7"
],
"score": [
8
],
"text": [
"it's like acid etching but in reverse, concrete is acidic and decaying plant matter has an alkaloid base which results in staining upon exposure. "
]
} | [] | [] | [
[]
] | |
1pkusw | What formed the revisionist claim that slavery was not the cause of the Civil war, and when was it formed? | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/1pkusw/what_formed_the_revisionist_claim_that_slavery/ | {
"a_id": [
"cd3jkya"
],
"score": [
2
],
"text": [
"Could you elaborate? Or maybe give an example of that claim? I've read articles with titles like that, but it usually just turns out to be a headline for an article explaining the complexities of the economic and legislative factors - all centered around slavery in some way - that led to the southern states' secession.\n\nI'm not trying to argue that claim has never been made, in fact I'm sure it has. I'm just not familiar with it, except perhaps in apologist post-war Confederate propaganda."
]
} | [] | [] | [
[]
] | ||
88ju2o | why aren't orbits thrown off when two planets get near each other? | The planets in our solar system have had constant orbits for billions of years. When Earth, for example, is closest to Mars, why doesn't this slightly change the orbits of both planets? Wouldn't Earth's gravitational force on Mars (and vice versa) be different when they are nearest to each other versus farthest from each other? How does this not affect their orbits? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/88ju2o/eli5_why_arent_orbits_thrown_off_when_two_planets/ | {
"a_id": [
"dwl6xuz",
"dwl743p",
"dwlgi4l",
"dwlhn5o"
],
"score": [
3,
11,
3,
2
],
"text": [
" > The planets in our solar system have had constant orbits for billions of years. When Earth, for example, is closest to Mars, why doesn't this slightly change the orbits of both planets?\n\nIt does, and it has been stable for billions of years. \n\n > Wouldn't Earth's gravitational force on Mars (and vice versa) be different when they are nearest to each other versus farthest from each other?\n\nSlightly, yes, but they really don't get that close.",
"It absolutely does. The change is just small that over the course of human existence which is only a few hundred thousand years, let alone the few hundred years that we've been able to reliably measure, the difference is too small to matter. The orbits of the planets are stable over long periods of time, but dynamic over cosmic time-scales. We can only predict them with any confidence out to a few tens of millions of years. ",
"They do and these changes are what helped us locate some of the outer planets. Uranus was discovered by accident, but then someone cross checked the orbit that was observed versus one calculated, it was off. These discrepancies pointed astronomers to start hunting for Neptune. ",
"All celestial bodies have what is called a \"Sphere of influence\" meaning that their gravity dominates the behavior of everything in that sphere.\n\nAll planets fall within the Sun's sphere of influence and none of them pass close enough to each other to enter the sphere of influence of one another so their impacts on each other are relatively small.\n\nOver millions of years and thousands of orbits their paths will change but that is a very long time scale and since they're so far apart they won't result in drastic changes but just slight nudges this way or that\n\nAt their closest approach, Mars is accelerating towards Earth due to gravity at just 1.33 x 10^-7 m/s^2, its accelerating towards the Sun at 2.543x10^-3 m/s^2, that's over 10,000x greater"
]
} | [] | [] | [
[],
[],
[],
[]
] | |
1y0hwo | How do electrical signals instigate contraction in muscles? | What is the mechanism behind the contraction of voluntary muscles due to electrical signals being sent from the brain? Does the same mechanism apply to involuntary (smooth, cardiac) muscles? | askscience | http://www.reddit.com/r/askscience/comments/1y0hwo/how_do_electrical_signals_instigate_contraction/ | {
"a_id": [
"cfgb5f9",
"cfgbxhc"
],
"score": [
2,
2
],
"text": [
"A signal travels down the membrane of a muscle cell until it reaches membrane-bound calcium channels, which are stimulated by the electrical signal to transport calcium into the cell. The calcium further stimulates ryanodine receptors on the sacroplasmic reticulum to causes release of even more calcium ions into the cell. The contraction of the muscle fibers inside the cell is dependent on calcium.\n\nSee [here for cardiac muscle summary](_URL_1_) and [here for skeletal muscle summary](_URL_0_).",
"It's all about ATP binding. [Here](_URL_0_) is a link that explains the role of ATP and calcium ions in muscle contraction and explains how the nervous system is responsible for ATP actuation."
]
} | [] | [] | [
[
"http://droualb.faculty.mjc.edu/Course%20Materials/Physiology%20101/Chapter%20Notes/Fall%202011/chapter_12%20Fall%202011.htm",
"http://droualb.faculty.mjc.edu/Course%20Materials/Physiology%20101/Chapter%20Notes/Fall%202011/chapter_13%20Fall%202011.htm"
],
[
"http://faculty.southwest.tn.edu/rburket... |
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