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50iojj | What's going on structurally/microscopically when we bend some material? | Like a piece of metal or somethin'? | askscience | {
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"well the first thing is elastic deformation. One you you start trying to force something to be in a different shape you are either putting it in tension or compression, or a mix of both. So tension you're pulling atoms further apart, compression pushing atoms closer together as though on springs. But you can't keep doing that forever it takes more and more energy to push the atoms further out of equilibrium. \n\nWhen the energy needed to deform the material further gets to be high enough that its easier to create defects in the material structure than to compress the atoms further is when you reach the region of plastic deformation. Now the elastic deformation all goes back to normal when you stop applying force, but plastic deformation doesn't go back to to the way it was before. What you're doing is causing the motion of dislocation defects along certain crystal directions based on how you're applying force. Those dislocations are line defects. If you have a line moving in a direction that's not the direction of the line itself, its defining a plane. Basically as the dislocation moves through a crystal it offsets the crystal lattices on either side of the plane of motion by one atomic spacing. And these change the shape of the crystal in response to applied force because your force is causing them to move.\n\nIn some crystal systems dislocations can't move as well as others, and so deformation twinning is the more common form of deformation. And that's basically a region inside the material where the lattice changes directions to take up more or less space in one direction or the other. \n\nIf you keep trying to apply force after you exhaust the ability to move dislocations and create twins you can apply enough energy that its favorable to just create a free surface, and that's called fracture and it breaks apart. \n\nSo first, springy atoms hold energy, then the crystal lattice adjusts by using defects, finally create free surfaces and break apart."
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} | What's going on structurally/microscopically when we bend some material?
Like a piece of metal or somethin'? | [
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9w66me | How would you describe the Electroweak interaction to a middle school student? What does it do and how is electroweak symmetry broken? | askscience | {
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"It's very hard to explain the electroweak interaction and symmetry breaking without introducing many other concepts that a middle school student probably wouldn't be familiar with.\n\nBut to explain it in a few words, without any of the details, at high energies, the electromagnetic and weak interactions \"merge\" into a single force. Below those energies, they \"split\" apart into the two separate forces that we're familiar with in nature.\n\nIt's similar to a ferromagnet, where at high temperatures, it becomes unmagnetized, and has no preferred direction in space. At low temperatures, a magnetization develops in some particular direction. In a completely idealized situation of a rotationally symmetric magnet in zero external field, there is no preferred direction in space, yet the magnet \"chooses\" a particular direction for its magnetic field to point in. This is the simplest example of spontaneous symmetry breaking."
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} | How would you describe the Electroweak interaction to a middle school student? What does it do and how is electroweak symmetry broken?
| [
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9yi7v3 | How are these kinds of layered stones formed? (Image inside) | Some nine years ago, when I was still in school, I had found a strange looking stone with layered patterns. Recently looking at my old stuff, I found it again. Which makes me wonder how these kinds of layers are formed:
[Photo](_URL_3_)
Edit:
[Different angles](_URL_1_)
[With tape for scale](_URL_0_)
The sample is about 4 centimeters long, 3 centimeters wide and about 2.5 centimeters in height.
I found it in my school playground just lying in the dust among other things, and live in India, the westernmost part.
The color of the rock is actually yellowish to yellow-orange and slightly brown in some places.
[With Magnifying glass](_URL_2_) | askscience | {
"a_id": [
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"Retake the photo with a scale and a different angle or two. Where did you find it?",
"It's difficult to say without more information (scale, where you found it, multiple angles, etc.). We can make some educated guesses though. The first thing that comes to mind is foliation. This occurs in metamorphic rocks (rocks that have been subjected to heat and pressure, but not enough to fully melt them) and is a result of the minerals in the rock being free to assume their preferred orientation. Foliation usually forms at a right angle to the direction of maximum strain (if the rock is being compressed vertically, foliation will be horizontal). The green color of your sample (assuming it is not extensively weathered) is also a VERY loose indicator of metamorphic origin. \n\nIt is also possible that your sample is a result of sedimentary processes, where different rates of sediment deposition result in fine layers of sand/silt/clay being deposited on top of each other. This structure is then preserved upon lithification (sediments becoming a rock). I think this is less likely given the scale of the sample (I'm guessing it fits easily in the palm of your hand, making the layers very small indeed), but it's still a reasonable possibility. Provide some more info and I'm sure either myself or u/siliconlife can figure it out."
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"https://www.imgur.com/a/n5NLDJw",
"https://www.imgur.com/a/cAX5ecE",
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} | How are these kinds of layered stones formed? (Image inside)
Some nine years ago, when I was still in school, I had found a strange looking stone with layered patterns. Recently looking at my old stuff, I found it again. Which makes me wonder how these kinds of layers are formed: [Photo](_URL_3_) Edit: [Different angles](_URL_1_) [With tape for scale](_URL_0_) The sample is about 4 centimeters long, 3 centimeters wide and about 2.5 centimeters in height. I found it in my school playground just lying in the dust among other things, and live in India, the westernmost part. The color of the rock is actually yellowish to yellow-orange and slightly brown in some places. [With Magnifying glass](_URL_2_) | [
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mz1l5 | Does extreme physical exertion cause strain on the nervous system as well as the musculoskeletal system? | Can the neurons become depleted of ions to produce action potentials? Does the brain or CNS become fatigued during or after exertion? Are extreme levels of motor neuron activity in some way harmful to these cells? | askscience | {
"a_id": [
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"Central Fatigue is what you're talking about, as opposed to peripheral fatigue, which occurs at the neuromuscular junction or the muscle .\n\nDifferent tasks fatigue the body in different ways. Some fatigue just the muscle, and some fatigue the nervous system.\n\nOne way to test this is to fatigue the muscle, and then measure force output while a person contracts as forcefully as possible. During this contraction, you use an electrical stimulator to give a jolt to the muscle.\n\nIf the maximum force is less than when you're rested, we attribute that to muscle fatigue. If any extra force is evoked when we give you the electrical jolt, we say that's central fatigue. It indicates that your muscle is ABLE to produce extra force, but your nervous system wasn't able to activate that muscle tissue.\n\nJust like the health of your muscles is improved by exercising them, your motoneuron health appears to be improved by regular activation. Motoneuron activity following activity & with ageing relates directly to my research, so if you have any other questions give a shout.",
"Yes, the nervous system responds similiar to muscles in the sense that it adapts and improves to handle high stress tasks"
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} | Does extreme physical exertion cause strain on the nervous system as well as the musculoskeletal system?
Can the neurons become depleted of ions to produce action potentials? Does the brain or CNS become fatigued during or after exertion? Are extreme levels of motor neuron activity in some way harmful to these cells? | [
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2dpwvr | How am I able to comprehend a term completely in my mind, but when asked to define it I struggle to do so? | askscience | {
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"Language is comprehended via repeated experience i.e. you learn --most, probably all-- words from hearing them in context. You can comprehend a term completely in your mind, in the same way you can use correct grammar in your native language without ever studying your language's grammar i.e. without defining it. Forming a definition not only requires comprehension of a term being defined, but careful, conscious analysis of the context in which it is used, it's connotations, etc. Truthfully, every dictionary definition you read is woefully incomplete, moreso a painted picture than a graph, in terms of its associative exactitude. \n\nReally, there are no universal definitions, because everyone has different experiences with different words, i.e. different associations, therefore a different definition. It's just that usually the experiences are so similar that everyone's definition is practically the same. Only when attempting to neutrally converse with words that are primarily used to manipulate is this remedial linguistic principle abundantly apparent, e.g. in conversations about \"goodness\", or \"justice\", or \"right\", etc. \n\n\nIdk if you consider remedial linguists and linguistically applied semiotics to be science, though. But, the question is one of linguistics.",
"Don't think of this as a sign you don't fully comprehend the term. Learning an idea, even to the extent you can apply the idea and use it correctly, is a different skill than learning how to explain the idea to others. Explaining the idea requires not just comprehending the concepts themselves, but also modeling what's going on in another person's mind as you give the explanation. You have to seek out the right words, you have to construct a step-by-step breakdown of ideas that may very much resist simplification, and you have to remember and anticipate the various incorrect lines of reasoning that they might come up with. \n\nYou have to do all of these tasks simultaneously and quickly, keeping the complex term in your mind the entire time. You shouldn't be surprised that you find such a task difficult without any preparation. It's rather marvelous that we are able to do it at all! Some people are better at it than others and of course you get better with practice. As others have mentioned, the process of imagining how other people might approach a new idea often brings new insights to your own understanding.",
"I look at this from a language perspective (I'm a Speech-Language Pathologist). Receptive language skills (understanding) are developed before expressive language skills. So you are probably understanding the concept, like when a kid correctly knows what an apple is when you say \"apple\" even though it isn't yet able to label it him/herself. Hope that perspective helps."
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} | How am I able to comprehend a term completely in my mind, but when asked to define it I struggle to do so?
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2o7jdh | Looking for a material with unusual properties. Can anyone help? | So I am looking for a material (preferably a plastic or a coating that can go on plastic) that will fluoresce when illuminated by a wavelength of light not produced by fluorescent light bulbs, stay luminous for a brief amount of time after the light stops shining on it, and then go back to normal. Is anyone aware of something like that?
EDIT: Looking for floor tile sized pieces | askscience | {
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"text": [
"You might want something like this: _URL_0_\n\nThey light up under only specific wavelengths"
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} | Looking for a material with unusual properties. Can anyone help?
So I am looking for a material (preferably a plastic or a coating that can go on plastic) that will fluoresce when illuminated by a wavelength of light not produced by fluorescent light bulbs, stay luminous for a brief amount of time after the light stops shining on it, and then go back to normal. Is anyone aware of something like that? EDIT: Looking for floor tile sized pieces | [
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138e50 | Is this company, StemCell100, a scam? Is there any evidence that this product does what it says it does? What exactly makes it a scam or not? | _URL_0_
It would be cool if this was legitimate, but I have serious doubts. Considering it's not that popular at all. At least from what I have seen. | askscience | {
"a_id": [
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"After looking at their 'longevity research' page, I'm throwing my vote in for scam. They do a little *Drosophila* study (of which I am also highly dubious, but okay) but nowhere on that page do they **show** that their product has any effect on stem cells. They mention that *Astragalus membranaceus* inhibits mTOR and thus causes the animals to defy aging, but it's almost laughable to think that the solution to aging could possibly be so easy. *Plenty* of experiments have been done with mTOR and no spectacular results like this have been found.\n\nI'm not entirely ready to discredit the molecular activities of compounds found in traditional herbal remedies, as it's entirely possible that they do truly have some kind of effect. But to claim that they mixed up some herbs and it makes your adult stem cells live much longer and healthier? Utter fantasy.\n\nedit: Not a single reference on their 'stem cells' page. As a nascent *Drosophila* stem cell researcher, I am even more highly skeptical than before.",
"* Seems to fix a large variety of symptoms, basically general aging symptoms and I don't look/feel great\n* Not FDA reviewed\n* Throws out a lot of scientific words and goes into long winded explanations about how this makes you younger/healthier on the front page of the website \n\nThis seems to really be a pill that has a lot of health supplements that has been re-branded as a stem cell support. So it is plausible that there could be some health benefits gain from this, although I am going to leave a real analysis of that up to a nutritionist.\n\nTheir fly studies seem dodgy, the study was done by the company itself and their is no actual paper of the study, just some plots and then more talking about the benefits of all the herbs involved.\n\nI high doubt this is some wonderful stem cell aiding medicine, jut an herbal supplement",
"Complete and utter scam.\n\nThere are zero stem cells in this product. Even if their were, those stem cells would make you **SICK**, not better. \n\nIn order for stem cell therapy to work, they must be **YOUR** stem cells. Otherwise they would be recognized as foreign to your body cause an immunorejection reaction making you sick."
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} | Is this company, StemCell100, a scam? Is there any evidence that this product does what it says it does? What exactly makes it a scam or not?
_URL_0_ It would be cool if this was legitimate, but I have serious doubts. Considering it's not that popular at all. At least from what I have seen. | [
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uxkgp | Do castrated people lose their libido? | Since libido seems to be a testosterone/estrogen-based drive, does the dip in production eliminate a eunuch's sex drive? | askscience | {
"a_id": [
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"Yes. Your testicles are a driving force in testosterone production, which is key to having any sort of sex drive for males. Steroid users often use faux testosterone to get bigger, causing their body to stop making its own. So when they get off a cycle the have to block estrogen production and wait for natural testosterone to return. And hope they're T levels are in check with their estrogen levels. Thus normal libido."
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} | Do castrated people lose their libido?
Since libido seems to be a testosterone/estrogen-based drive, does the dip in production eliminate a eunuch's sex drive? | [
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1yfmi4 | Traveling in a closed box through space, how to know if it is moving or stationery? | Hello redditors, my first question here.
Imagine this scenario. You are in an air tight box with no windows or any method of seeing, contacting anyone outside. The box might be moving at a constant speed (no acceleration ) through outer space (no gravity, air resistance), or it might be stationary. What can you do to find out if the box is stationery or moving?, what items or instruments, that if you had would help you to determine that the box is moving or is stationery?
| askscience | {
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"Assuming you cannot contact the outside world at all, you cannot.\n\nInterestingly, even if you include a uniform gravitational field, you still wouldn't be able to make any determinations about your motion.\n\n(A non-uniform gravitational field would mean that gravitational acceleration would vary slightly between parts of your box, although you would need some very, very sensitive instruments to measure that)",
"According to the theory of relativity there is no such thing as \"motion\" (as in \"absolute motion relative to space itself\"), thus, as counterintuitive as that sounds, this question quite literally does not make sense.\n\nMotion is something that can only be defined in relative terms: You can talk about your motion relative to some other object, but not about \"pure\" motion without any reference.\n\nMathematically there is no fundamental difference between saying \"A moves with 5m/s relative to a stationary B\" and \"B is moving with 5m/s relative to a stationary A\", these are just two ways of expressing the same thing and in fact there is no way to distinguish the two cases at all.\n\nA consequence of that is that it is impossible for the traveller in the box to determine his or her own motion (relative to anything outside)."
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} | Traveling in a closed box through space, how to know if it is moving or stationery?
Hello redditors, my first question here. Imagine this scenario. You are in an air tight box with no windows or any method of seeing, contacting anyone outside. The box might be moving at a constant speed (no acceleration ) through outer space (no gravity, air resistance), or it might be stationary. What can you do to find out if the box is stationery or moving?, what items or instruments, that if you had would help you to determine that the box is moving or is stationery? | [
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18jjdg | What is the hard matter beneath spots? | Just a passing thought that I couldn't find a reasonable answer to on google:
What exactly causes the tissue to go solid beneath the head of a spot/zit that has swollen?
Is this something that used to increase our chances of survival? | askscience | {
"a_id": [
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"text": [
"Fluid and cells build up in the area in response to bacteria. It is a natural part of the immune response. Immune cells that are in the skin sense a foreign body and send out chemicals called cytokine and chemokines that cause the blood vessels in the area to become leaky. This brings fluid to the area but also allows for immune cells in the blood to pass through the walls of the blood vessels and into the area where the foreign body is detected. The result is increased turgor pressure in the area so that it feels hard."
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Just a passing thought that I couldn't find a reasonable answer to on google: What exactly causes the tissue to go solid beneath the head of a spot/zit that has swollen? Is this something that used to increase our chances of survival? | [
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t9ipv | Could someone skydive onto a quarter/half pipe? | Simplified title a little but says it all.
If someone jumped out a plane and reached terminal velocity, provided there's little to no wind and/or the person was a good enough skydiver to control their decent to line up the landing correctly, would it be possible for them to land safely, and if so how big would the curve have to be?
Sorry if this is a silly question, I just woke up, it seems to be one of those random thoughts your brain has in half sleep mode, I'd usually forget about it but then I remembered askscience! | askscience | {
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"Terminal velocity for most skydivers is something like 150 mph? In real units, that's 67 m/s.\n\nA \"comfortable\" landing would involve no accelerations greater than maybe 3x gravity, and \"safe\" would have a peak of maybe 10x gravity. I'll stick with 3x here.\n\nAcceleration toward the center of a circle is v^2 / r, where v is tangental velocity and r is radius. 9.81 x 3 = 67^2 / r, r = **152.5 meters**. After going through this quarter pipe, you're now traveling at 150 mph horizontally, so you'll have to deal with that somehow..."
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} | Could someone skydive onto a quarter/half pipe?
Simplified title a little but says it all. If someone jumped out a plane and reached terminal velocity, provided there's little to no wind and/or the person was a good enough skydiver to control their decent to line up the landing correctly, would it be possible for them to land safely, and if so how big would the curve have to be? Sorry if this is a silly question, I just woke up, it seems to be one of those random thoughts your brain has in half sleep mode, I'd usually forget about it but then I remembered askscience! | [
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iit5n | I want to build an aquarium with a deep sea exhibit. | What kind of pressures would the tank require to simulate the ocean floor and what would be the requirements for a window to view it? Would such an exhibit have any physical possibilities? | askscience | {
"a_id": [
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"Contact the Mystic Aquarium in CT. I cannot use my Google-fu well right now, but I assure you they have (perhaps had...) bioluminescent creatures in a special, pressurized tank. It was outside their main hall, in an exhibit you look down into. Just inside from the deep-sea vehicle and near the JFK exhibit."
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What kind of pressures would the tank require to simulate the ocean floor and what would be the requirements for a window to view it? Would such an exhibit have any physical possibilities? | [
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67m8ue | How did Tyco Brahe account for movement of Earth in his measurements? | If Earth did not rotate, it would be comparitively simple to face the same direction every time for each measurement, and mark the position of an orbiting object.
But Earth rotates as well as orbits. How did Tyco account for all of this?
Also, how could he tell objects were moving in an elliptical orbit? | askscience | {
"a_id": [
"dgrjqwo"
],
"text": [
"Simple - Tycho Brahe's model was not accurate. :)\n\nTo be more precise - in Tycho's model, the sun and moon orbited the (rotating and tilting) earth, but the rest of the planets orbited the sun. \n\nThe strength of his model was that he assumed the stars were fixed in position, and the rotation (and tilt) of the earth accounted for all of the apparent motion in the stars. This is close enough to correct that it took awhile to disprove. It was fifty-ish years later before Galileo famously made a better heliocentric model, and shortly after that it was widely accepted."
],
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} | How did Tyco Brahe account for movement of Earth in his measurements?
If Earth did not rotate, it would be comparitively simple to face the same direction every time for each measurement, and mark the position of an orbiting object. But Earth rotates as well as orbits. How did Tyco account for all of this? Also, how could he tell objects were moving in an elliptical orbit? | [
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9ca0kk | Why do groups alpacas defecate in a communal dung pile? | askscience | {
"a_id": [
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"text": [
"Having a communal dung pile helps prevent the spread of parasites. Worms can be shed in the feces, so animals like sheep that don't have communal dung piles can more easily pick up worms as they eat much closer to where they defecate. Why alpacas have a communal dung pile while other herd animals like sheep and cows don't, I don't know the answer to that. Perhaps the ancestors of alpacas spent more time in the one area, while sheep and cattle graze a larger area or continuing move on, thus more selection pressure for a communal dung pile in alpacas."
],
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"url": []
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"url": []
} | Why do groups alpacas defecate in a communal dung pile?
| [
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3klkpg | What is the difference between the U.S' BRAIN Initiative and the E.U's Brain Mapping Project? | I've heard there was some criticism that the Brain Mapping Project was too narrow. I was under the impression that both are trying to map every synaptic connection, is there more to either of the projects? | askscience | {
"a_id": [
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"The BRAIN Initiative is much more far-reaching and will fund many different fields in neuroscience and not just brain mapping -- e.g., everything from understanding how single neurons work to cognitive neuroscience in human subjects (where we can only observe activity of 1000s of neurons at once). By contrast, the Brain Mapping Project is *just* mapping all of the connections of the brain and nothing else."
],
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} | What is the difference between the U.S' BRAIN Initiative and the E.U's Brain Mapping Project?
I've heard there was some criticism that the Brain Mapping Project was too narrow. I was under the impression that both are trying to map every synaptic connection, is there more to either of the projects? | [
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5d8fjl | What is the etymology of Stoichiometry? | Stoichiometry is a term used in Chemistry and it pertains to the calculation of the quantities of chemical elements or compounds involved in chemical reactions. It is usually a 5-step process which uses ratios (generally, whole numbers) to determine mols or mass of a compound or element in a certain reaction. What is it's etymology? | askscience | {
"a_id": [
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"The first part, *stoichio*, comes from the Greek word *stoikheion*, which means \"the elements\" when used in plural form (in singular it means one of a row). *-metry*, of course, means process of measuring, which has roots in Middle English and Middle French (*-metrie*), Latin and Greek (*-metria*), and also *-metros* and *metron*."
],
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} | What is the etymology of Stoichiometry?
Stoichiometry is a term used in Chemistry and it pertains to the calculation of the quantities of chemical elements or compounds involved in chemical reactions. It is usually a 5-step process which uses ratios (generally, whole numbers) to determine mols or mass of a compound or element in a certain reaction. What is it's etymology? | [
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adb50h | Hipparchus is credited with discovering the precession of the equinoxes; but how can you measure such a slow process, especially in ancient Greece? | askscience | {
"a_id": [
"edgploa"
],
"text": [
"Careful observation, and checking against earlier sources:\n\n > The discovery of precession usually is attributed to Hipparchus (190–120 BC) of Rhodes or Nicaea, a Greek astronomer. According to Ptolemy's Almagest, Hipparchus measured the longitude of Spica and other bright stars. Comparing his measurements with data from his predecessors, Timocharis (320–260 BC) and Aristillus (~280 BC), he concluded that Spica had moved 2° relative to the autumnal equinox. He also compared the lengths of the tropical year (the time it takes the Sun to return to an equinox) and the sidereal year (the time it takes the Sun to return to a fixed star), and found a slight discrepancy. Hipparchus concluded that the equinoxes were moving (\"precessing\") through the zodiac, and that the rate of precession was not less than 1° in a century, in other words, completing a full cycle in no more than 36000 years.\n\n_URL_1_\n\nOne doesn't need particularly precise instruments to detect differences of a couple of degrees, and the ancient Greeks were developing relatively sophisticated technology for just that purpose, like the Dioptra.\n\n_URL_0_"
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"url": [
"https://en.wikipedia.org/wiki/Dioptra",
"https://en.wikipedia.org/wiki/Hipparchus#Precession_of_the_equinoxes_(146%E2%80%93127_BC)"
]
} | Hipparchus is credited with discovering the precession of the equinoxes; but how can you measure such a slow process, especially in ancient Greece?
| [
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iijyu | My friend is buying a house next to a Superfund site and wants to plant a vegetable garden. Should she? | [This](_URL_0_) is the site in question, and [this](_URL_1_) is the most current site assessment. Her future house is less than a mile north of the site, with a stream running downhill from the landfill on her property. Her house is on the bottom edge of a valley. I think it's a bad idea, but I'm not entirely familiar with the way groundwater flows or the ins and outs of Superfund cleanup. Is she safe to plant right in the yard? Thanks for your help! | askscience | {
"a_id": [
"c241ova",
"c241l4l",
"c244fmy"
],
"text": [
"I can't answer your question but one solution might be to build some big planter boxes, buy some topsoil from a store, and avoid the issue altogether.",
"I would be slightly uneasy about that, but it's probably fine. I think the biggest danger is contamination of groundwater if your friend has a well. If your friend has a municipal water supply I don't expect it would be a problem.\n\nI live about a quarter mile from a Superfund site which has polluted the groundwater and I get my water (although not drinking water) from a well. I looked at the groundwater flow and contamination charts that the EPA produced before buying the house. We also had our well water tested fairly extensively. Everything seems fine and we grow and eat vegetables on our property.",
"Short of getting a lot of independent tests and confirming that you are safe, I would say absolutely not.\n\nI've done some work in and around superfund sites near me and the general trend I see is that they are often inadequately contained, too small, and levels of pollutants are under-reported.\n\nGroundwater testing I've done around landfills have *always* resulted in plumes of VOC's which can have a range of health effects. The clay liners never seem to hold up.\n\nWhat's even more scary are times when the entity that caused the pollution still exists and is fighting the EPA. I've seen a 70-acre superfund site chopped down and sold to developers with no cleanup until just 9 acres are left due to pressure from the polluting comany. In this particular case, the neighborhoods around the site have seen huge spikes in cancer rates, oily films on their groundwater, and you can even smell the chemical in question (TCE) coming from springs on warm days."
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"http://www.epa.gov/superfund/sites/fiveyear/f2008010002556.pdf"
]
} | {
"url": []
} | My friend is buying a house next to a Superfund site and wants to plant a vegetable garden. Should she?
[This](_URL_0_) is the site in question, and [this](_URL_1_) is the most current site assessment. Her future house is less than a mile north of the site, with a stream running downhill from the landfill on her property. Her house is on the bottom edge of a valley. I think it's a bad idea, but I'm not entirely familiar with the way groundwater flows or the ins and outs of Superfund cleanup. Is she safe to plant right in the yard? Thanks for your help! | [
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1sxcqu | When is tracheotomy preferable to intubation in a clinical setting? | I've been watching a lot of *House* lately, which seems to me like one of the better researched and informed medical dramas.
It seems like when a patient is in respiratory distress, half the time they perform a tracheotomy, and half the time they intubate, and they never explain why they did it one way or the other.
I can understand a tracheotomy being done in the field because it doesn't necessarily require specialized equipment, but they often trach in a clinical setting, where the means to intubate is readily available.
Isn't intubation usually preferable because it doesn't require cutting? In what case(s) is it contraindicated, besides not having the necessary implements? | askscience | {
"a_id": [
"ce29be5"
],
"text": [
"First off, House is actually quite terrible in terms of accurate medical science, so I wouldn't assume that anything they do is correct. In this case, House probably features a lot of emergent cricothyrotomies because it looks more dramatic. Typically you would try either bag-mask ventilation and/or endotracheal intubation (sometimes with assist devices such as laryngeal mask airways), and only jump to the surgical solution if those don't work.\n\nWhen deciding between tracheostomies and standard oropharyngeal intubation, [there are pros and cons to each procedure](_URL_0_). Typically what we see is that patients are started with endotracheal intubation and then transitioned to a tracheostomy if prolonged mechanical ventilation is thought to be necessary. This has benefits for both patient comfort as well as ease of care."
],
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"url": []
} | {
"url": []
} | {
"url": [
"http://i.imgur.com/bhl0SsD.png"
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} | When is tracheotomy preferable to intubation in a clinical setting?
I've been watching a lot of *House* lately, which seems to me like one of the better researched and informed medical dramas. It seems like when a patient is in respiratory distress, half the time they perform a tracheotomy, and half the time they intubate, and they never explain why they did it one way or the other. I can understand a tracheotomy being done in the field because it doesn't necessarily require specialized equipment, but they often trach in a clinical setting, where the means to intubate is readily available. Isn't intubation usually preferable because it doesn't require cutting? In what case(s) is it contraindicated, besides not having the necessary implements? | [
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1016oy | So I've been pretty inactive for a few weeks, then I had to go hiking for ten days. The first hour was brutal on my cardiovascular system and muscles, but after that first hour I felt fine. What happened, exactly? | I'm an archaeologist and my job requires long hours of hiking up and down tough terrain. I've been in the office for months, living a sedate life, and recently I got the chance to do some fieldwork.
As stated in the title, the first hour or two was really hard. It felt as if my heart would explode, my lips and face throbbed with my pulse, my legs ached, and I was out of breath. By midday, however, I felt back to normal and could hike for hours without problem. The rest of the work session went by just fine.
Physiologically, what happened during the transition from being inactive to active?
Thanks | askscience | {
"a_id": [
"c69uclf"
],
"text": [
"Central fatigue is when your brain limits motor output to less than what would be predicted by classical models of fatigue (such as the AV Hill model). Some have suggested that this phenomenon could be adaptive, as it could conceivably prevent injury or other catastrophic consequences of over-exertion. One of the proponents of this idea (Timothy Noakes of South Africa) has come up with a whole literature surrounding the \"Central Governor\", which he hypothesizes is responsible triggering the cessation of exercise before injury as well as pacing of exercise. If true, it would mean that our brains make subconcious calculations about our energy stores, muscle capacity, the perceived duration of exercise (both performed and anticipated), and then sets a pace for exercise. When energy stores are becoming depleted, muscles are becoming over-stressed, and/or body temperature is becoming too high, the brain will terminate exercise by a variety of proposed mechanisms, including inhibition the motor cortex.\n\nUsing this to speculate on your experience, I would say that your brain was more \"out of shape\" than your body, and was not calibrated for intense exercise. When you settled into a sustainable pace, those impulses to stop were calmed. It is well known in rodents that exercise training alters the neurobiological correlates of fatigue.\n\nCentral fatigue is well studied in rodents, and we are honing in on the precise mechanisms (one well documented correlation is a change in the relative concentrations of dopamine and serotonin in brain regions such as the striatum) . \"Central Governor\" is as popular to cite as it is to refute, so take it with a grain of salt.\n\nI read a lot about this for my own work. I have hundreds of citations on my work computer, but I am typing this from home. I will edit in the morning if this thread has gotten any attention.\n\nTL;DR : It is probably a mix of physiology and psycholgy that made you feel so tired at first, then get over it."
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} | So I've been pretty inactive for a few weeks, then I had to go hiking for ten days. The first hour was brutal on my cardiovascular system and muscles, but after that first hour I felt fine. What happened, exactly?
I'm an archaeologist and my job requires long hours of hiking up and down tough terrain. I've been in the office for months, living a sedate life, and recently I got the chance to do some fieldwork. As stated in the title, the first hour or two was really hard. It felt as if my heart would explode, my lips and face throbbed with my pulse, my legs ached, and I was out of breath. By midday, however, I felt back to normal and could hike for hours without problem. The rest of the work session went by just fine. Physiologically, what happened during the transition from being inactive to active? Thanks | [
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aty5x7 | Can refractuve index of a medium be negative? | Is there a material which has a negative refractive index is yes then how will it effect the redaction of light? | askscience | {
"a_id": [
"eh4cdvz",
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"text": [
"Yes, for example a student of mine built a metamaterial out of paper and copper for a class which had a negative index of refraction for microwaves. By sending microwaves through the material he found that the refraction angle was inverted which can be seen by looking at Snell's law. Here's a Wikipedia article about them with a picture of one.\n\n_URL_0_",
"I don't think there are any homogeneous materials with a negative refractive index. But there are so-called metamaterials, carefully constructed composites, that can have negative refractive index, at least over some range of frequencies."
],
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} | {
"url": [
"https://en.m.wikipedia.org/wiki/Negative-index_metamaterial"
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} | Can refractuve index of a medium be negative?
Is there a material which has a negative refractive index is yes then how will it effect the redaction of light? | [
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nwu30 | About 20 years ago I stole a mortar & pestle from the science lab at school. If I use it in the kitchen now, will I die? | askscience | {
"a_id": [
"c3ckbze",
"c3ck5u0"
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"text": [
"What do you think your school would have used which have lasted 20 years and still been deadly in minute doses?",
"I don't think there were too many things that your highschool may have been mortar/pestle-ing that would be potentially fatal, unless you meant school as in University. Give it a good wash and you should be good. \n\n\nEDIT: If you really wanna be sure, use a bunch of different (safe) solvents. Acetone is a pretty good organic solvent, you could throw in an alkaline solution if you think there may be some acids still left from this 'lab', or vica versa."
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} | About 20 years ago I stole a mortar & pestle from the science lab at school. If I use it in the kitchen now, will I die?
| [
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mb2mv | How much power do I have over myself? | Essentially, my question is: "How much influence do our thoughts have over the chemical reactions going on in our brains?" For instance, if a person was diagnosed as clinically depressed, to what extent could they balance out the chemicals responsible for their happiness, through altering their thought processes? | askscience | {
"a_id": [
"c2zj0dh",
"c2ziaip"
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"text": [
"Since things like psychotherapy and mindfulness meditation are scientifically proven to improve the lives of depressives, even without medication, I'd say quite a bit.\n\nThis is a moral and philosophical beehive, however. How about those who are never able to get out of depression -- are they more sick, or simply too useless or unskilled to get their thoughts back on track? Is it *you* (whatever that means), or just a defense mechanism reacting when you try to turn those negative spirals?\n\nBut the short answer to your question is yes, kind of. You can change the release of neurotransmitters through thoughts (think happy thoughts: [1](_URL_1_), [2](_URL_0_), sorry for lack of full text) or actions (sex, workout). Then again, one of the documents linked discuss how personality and motivation is influenced by for instance genetic sensitivity to dopamine in the brain. And there are many more neurotransmitters than the famous few (serotonin, dopamine, epinephrine) that we haven't even studied much. So it's not that simple. \n\nBut if you meditate, focus on thinking about the good things in life and possibly talk to a therapist about it, and do actions that stimulate the right moods, chances are you'll be a happier person. Even if you're unhappy to begin with.",
"I'd like to add: How much power do we have over *worsening* our conditions? When one becomes overly cynical and pessimistic over years or decades, how can one break free?"
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"url": [
"http://www.ncbi.nlm.nih.gov/pubmed/10467897",
"http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2483304/"
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} | How much power do I have over myself?
Essentially, my question is: "How much influence do our thoughts have over the chemical reactions going on in our brains?" For instance, if a person was diagnosed as clinically depressed, to what extent could they balance out the chemicals responsible for their happiness, through altering their thought processes? | [
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34tnq1 | Why do we "bring down the power and take one from the power"? | For calculating the derivative function for simple polynomials its always been that rule. Can someone please explain how that works to get dy/dx? thanks | askscience | {
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"One way you can see this is by looking at the Product (or Leibniz) Rule. This says that if I have two functions , f and g, then the derivative of f(x)g(x) is f'(x)g(x)+f(x)g'(x). In general, if I have N-Functions, then to find the derivative of the product of all of them you pretty much take the derivative one at a time, then add it all together. For instance:\n\n* The derivative of fgh is f'gh+fg'h+fgh'\n\n* The derivative of fghk is f'ghk+fg'hk+fgh'k+fghk'\n\n* the derivative of fghkt is f'ghkt+fg'hkt+fgh'kt+fghk't+fghkt'\n\netc. An important thing to note is that if I take the derivative of N functions, then I'm going to be adding up N different terms, as in the examples. What happens if I have the product of N functions that are all equal to f(x)=x? The derivative of one of these is equal to 1, and I'll have N-1 left in each term. This means that each term is going to be x^(N-1), but I have to add N of them together, which means I get Nx^(N-1)\n\n* The derivative of x^(3) = xxx is 1xx+x1x+xx1 = x^(2)+x^(2)+x^(2) = 3x^(2)\n\n* The derivative of x^(4) = xxxx is 1xxx+x1xx+xx1x+xxx1 = x^(3)+x^(3)+x^(3)+x^(3) = 4x^(3)\n\n* The derivative of x^(5) = xxxxx is 1xxxx+x1xxx+xx1xx+xxx1x+xxxx1 = x^(4)+x^(4)+x^(4)+x^(4)+x^(4) = 5x^(4)\n\nThis is an interesting way to think of things, and it also helps reveal some stuff about [Taylor Series](_URL_1_).\n\n-----------------------------------------------------------\n\nAlternatively, you can think of the definition of a derivative. The derivative of f(x) is the limit of (f(x+h)-f(x))/h as h goes to zero. If you ever have a question about something that a derivative does, this should be a place where you look first, because this is what a derivative actually is! If f(x)=x^(r), for any real power r (not just integers), then we can use the [Binomial Theorem](_URL_0_) to write \n\n* (x+h)^(r) as x^r + rhx^(r-1) + h^(2)(*Some Function*). \n\nAn important thing about *Some Function* is that it's limit as h goes to zero is finite. What we get is f(x+h)-f(x) = rhx^(r-1) + h^(2)(*Some Function*) and so dividing by h gives\n\n* (f(x+h)-f(x))/h = rx^(r-1) + h(*Some Function*)\n\nTaking the limit as h goes to zero then gives rx^(r-1)."
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"url": []
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"url": [
"http://en.wikipedia.org/wiki/Binomial_theorem",
"https://postformalism.wordpress.com/2015/03/24/why-are-there-factorials-in-the-taylor-series/"
]
} | Why do we "bring down the power and take one from the power"?
For calculating the derivative function for simple polynomials its always been that rule. Can someone please explain how that works to get dy/dx? thanks | [
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24u0j6 | Is there a "Reynold's number" for electricity? | Is electrical transmission in wires somewhat analogous to fluid flow through pipes? | askscience | {
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"text": [
"Electrical transmission in pipes is somewhat analogous in the sense that if you look at the equations that describe pipe flow with no viscosity or boundary layer effects, those equations are exactly the same as the equations for electrical transmission in a line. \n\nHowever, when you add viscosity and boundary layers, the equations for fluid flow change dramatically and no longer resemble those in electrical transmission lines. For there to be a Reynolds number, there has to be a viscosity, and so the answer to your question is probably no, there is no analogous electrical Reynolds number because there is no analog for the equations of fluid motion that yield a Reynolds number. \n\nBut, and here I'm totally speculating, if you were to assume that a line had a transmission loss by resistance (Ohm's law), and that electrical mass was given by inductance through an inductor, I suppose you could define the quantity \n\nRe = L * omega / R \n\nwhere R is the resistivity, L the inductance, and omega the frequency. This quantity is dimensionless, and since this is something like \"inertial effects / viscous effects\", there may be an interpretation as a Reynolds number, but only in limited sense.",
"> Is electrical transmission in wires somewhat analogous to fluid flow through pipes?\n\nVery loosely. The conservation equations do end up taking rather similar forms.\n\n > Is there a \"Reynold's number\" for electricity?\n\nReynolds number is just one important non-dimensional parameter in the Navier-Stokes equations. There are other important ones, like Mach number, Prandtl number, etc.\n\nThere are important non-dimensional terms in Maxwell's equations as well. Things like Debye–Hückel length or relative permeability."
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} | Is there a "Reynold's number" for electricity?
Is electrical transmission in wires somewhat analogous to fluid flow through pipes? | [
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1kx1zl | How do adaptive optics work? | As its related to astrophotography/astrophysics/astronomy In particular, how does the lens bend to counteract the perceived turbulence in the atmosphere. | askscience | {
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"Well, we don't use lenses for AO, we use deformable mirrors. Using a deformable lens would be impossible; the number of sections you need to move independently in order to correct for atmospheric distortion is simply too much, and an optically relevant lens would be much too thick to really deform enough.\n\nThe basic idea of AO is to correct for atmospheric distortion, of course. What this amounts to is correcting the shape of the wavefront. Imagine \"sheets\" of light coming off a star and heading for Earth. The turbulence in the atmosphere acts to crumple these sheets up, which results in a distorted image. By correcting the wavefront, we flatten it and get all the light that hit the top of the atmosphere at the same time hitting our detector at the same time. Does that make sense? If it doesn't, imagine a rumpled sheet coming in. The leading parts of the sheet are going to hit the mirror first, and vice versa. To make it flat, we adjust the mirror so that the leading parts of the sheet hit the mirror last, etc. We do this in such a way as to exactly mirror all the bumps and deformations in the sheet, so that the reflected sheet is now flat.\n\nThere are essentially two levels of AO correction that go on in a system. The first is tip-tilt correction. Since the star image is bouncing all over the place, you need to hold it in one spot to get a good image. So we take one mirror and tip and tilt it back and forth to get the star in one spot. From the sheet analogy, imagine just holding it at various angles from the ground, without actually rumpling it. This is tip-tilt.\n\nNow we get to the nitty gritty of wavefront correction. Basically, for any optical system, there something called the point-spread function, or PSF. Basically what it tells you is what kind of image you get out the back of your camera, etc., if you take a picture of a point source. The PSF is also the source of things like bokeh. The atmosphere has a PSF, as does our telescope. The atmosphere's PSF really sucks (the sheets get all rumpled), but hopefully our telescope's is as close to optically perfect as can be (a nice [Airy disk](_URL_0_)). So what we do is analyze the shape of the PSF. We know how various distortions and aberrations affect the PSF, so we just calculate which ones are affecting the image and their strengths, and deform the mirror in the right way to counteract them. Then do it hundreds of times per second.\n\nThis kind of PSF manipulation is also why premium camera lenses tend to have so many elements. You'll have elements which are there specifically to counteract aberrations induced by other elements.",
"The optical satellite we test in our labs has hundreds of mirrors arranged in a parabolic shape (similar to a [reflective telescope](_URL_1_) ) such that it appears as one large curved mirror but is in fact hundreds of smaller mirrors.\n\nThese mirrors are attached to the dish by three electrical servos (a stick that moves in our out to push the mirror around) arranged in a triangle pattern underneath each mirror, allowing each mirror to have a wide range of potential angles depending on the extension of each servo. The telescope detects distortions in the image and can adjust the mirrors to correct for it.\n\nAs to the software algorithms to detect and correct distortions, I'll let somebody who knows more about that to speak to it. I only know about the mechanical side."
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"url": [
"http://en.wikipedia.org/wiki/Airy_disk",
"http://en.wikipedia.org/wiki/Reflecting_telescope"
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As its related to astrophotography/astrophysics/astronomy In particular, how does the lens bend to counteract the perceived turbulence in the atmosphere. | [
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lu8sf | Questions about an experiment described in the The Greatest Show on Earth by Richard Dawkins | Chapter 5, Forty-Five Thousand Generations of Evolution in the Lab (p 127 in my copy) -
Some biologists put the same strain of bacteria in 12 jars with some glucose. Every day a sample of the surviving bacteria from each of the 12 jars is put into a new beaker with new glucose. 12 pure lines of bacterial (no mixing between lines), about 2-3 generations a day for 20 years = 20,000 days and about 45,000 generations. Along the way they took samples to freeze as a "living fossil record."
Bacteria normally eat glucose so glucose was the limiting factor driving natural selection. However, the flasks also had citrate and around generation 35,000, one of the lines discovered the mechanism to eat it. The scientists theorized that it wasn't just one mutation that allowed this ability, but 2. "This might be a biochemical pathway in which the product of one chemical reaction feeds into a second chemical reaction, and *neither can make any inroads at all without the other.* This would require two mutations, call them A and B, to catalyse the two reactions. On this hypothesis, you really would need *both* mutations *before there is any improvement whatsoever.*"
That turned out to be true: A sample from each of the frozen "fossils" from that particular line were thawed and set breeding again. All samples from after 20,000 generations subsequently developed the ability to process citrate. None from before generation 20,000 did. Thus, around generation 20,000, a single mutation randomly developed and "primed" all future bacteria in the line to be able to accept the other random mutation and be able to process citrate.
My questions is, if the first mutation, A, was not beneficial by itself, why did it come to be represented in the whole population and why did it persist for that long? Wouldn't it have come and gone over the generations, dominating and scarce at random time?
| askscience | {
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"So, Richard Lenski's experiments are seriously cool. Every experimental evolutionary biologist has to be kicking themselves for not having the foresight to start a long term experiment like this 30 years ago when he did.\n\nAnyways, I'm not familiar enough with this experiment to know the actual identity of \"mutation A\" and \"mutation B\" (although I'm pretty sure that Lenski's lab has worked it out), but it's entirely possible that mutation A was, by itself, selectively neutral.\n\nIf we represent the mutation rate on a per individual, per generation basis by μ, and the population size by N, then there are Nμ mutations introduced into the population each generation. Each new mutation arrives at a frequency of 1/N, and if we assume the mutations to be neutral (which most are), then their probability of fixing (i.e. replacing all other alleles at it's genetic locus) is just equal to it's frequency, or 1/N. This may seem pretty small (especially given that population sizes in bacteria are astronomically high), but remember that the number of mutations introduced in each generation is also a function of population size (i.e. the more individuals there are, the more mutations there will be in the population): Nμ. \n\nSo the rate at which neutral mutations come to be fixed in the population is simply equal to Nμ * 1/N, or just μ, the mutation rate.\n\nNow, the mutation rate isn't all that high, but it's greater than zero by a large enough amount for this affect to be non trivial.\n\nSo it's possible that mutation A was entirely neutral, and just managed to be one of the \"lucky\" ones to fix just by random chance.\n\nThere's also a chance that that maybe mutation A rose to intermediate frequency in the population, bummed around there for a few thousand generations, and then mutation B happened in one of the cells carrying mutation A, and from there it was off to the races, so it's certainly not even necessary that mutation A fixed first.\n\nSo I guess the **TL;DR** is\n\n > was not beneficial by itself, why did it come to be represented in the whole population and why did it persist for that long?\n\nRandom chance\n\n > Wouldn't it have come and gone over the generations, dominating and scarce at random time?\n\nPretty much, yeah, with the spectrum of possibilities strongly skewed towards \"scarce\". The odds are actually stacked against any one mutation, but by way of rough metaphor: if something has a one in a million chance of happening, and you try a billion times, it's still going to happen a thousand times, even though we consider \"one in a million\" pretty poor odds.",
"If the gene has no benefit, then there is no pressure acting on it. In other words, some thing has to have a negative effect for it to be selected against.\n\nSince there was no pressure against it, over time it would be found in more or less the entire population. \n\nSo if out of 10 individuals, one has mutation A and that mutation has no positive or negative effect on the individual's ability to survive and reproduce. Since it has no negative effect, there is no reason (from this mutation) for the offspring not to spread mutation A to their own offspring. And those offspring will spread it to their offspring, etc. ~~The mutation won't spread as rapidly as a mutation with a positive benefit, but it will spread nonetheless.~~ (see jjberg2's comment)\n\n/Biology undergrad"
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} | Questions about an experiment described in the The Greatest Show on Earth by Richard Dawkins
Chapter 5, Forty-Five Thousand Generations of Evolution in the Lab (p 127 in my copy) - Some biologists put the same strain of bacteria in 12 jars with some glucose. Every day a sample of the surviving bacteria from each of the 12 jars is put into a new beaker with new glucose. 12 pure lines of bacterial (no mixing between lines), about 2-3 generations a day for 20 years = 20,000 days and about 45,000 generations. Along the way they took samples to freeze as a "living fossil record." Bacteria normally eat glucose so glucose was the limiting factor driving natural selection. However, the flasks also had citrate and around generation 35,000, one of the lines discovered the mechanism to eat it. The scientists theorized that it wasn't just one mutation that allowed this ability, but 2. "This might be a biochemical pathway in which the product of one chemical reaction feeds into a second chemical reaction, and *neither can make any inroads at all without the other.* This would require two mutations, call them A and B, to catalyse the two reactions. On this hypothesis, you really would need *both* mutations *before there is any improvement whatsoever.*" That turned out to be true: A sample from each of the frozen "fossils" from that particular line were thawed and set breeding again. All samples from after 20,000 generations subsequently developed the ability to process citrate. None from before generation 20,000 did. Thus, around generation 20,000, a single mutation randomly developed and "primed" all future bacteria in the line to be able to accept the other random mutation and be able to process citrate. My questions is, if the first mutation, A, was not beneficial by itself, why did it come to be represented in the whole population and why did it persist for that long? Wouldn't it have come and gone over the generations, dominating and scarce at random time? | [
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3ixuk9 | Where can I get some long, raw recordings of pulsars and FRBs? | I'm doing a project on powerful broadband phenomena such as pulsars and FRBs (fast radio bursts). I have a sound analysis software to study the oscillations and frequencies. I just need to know where to get the data itself. Where can I find extensive recordings of these two astronomical phenomena? | askscience | {
"a_id": [
"culh4j7"
],
"text": [
"You'll likely have some difficulty with this. The Parkes Radio Telescope releases all data (see [here](_URL_2_)), GBT will have data via the [NRAO archive](_URL_1_), and I found a few random pulsar data sets from Arecibo [here](_URL_0_) (I don't recall if Arecibo data are made public or not after a certain time). However, it takes a lot of expertise too turn raw files into something usable like you are asking (this coming from personal experience/woes). The Parkes page has a primer on some of the software used, or you can build your own, but beware that this takes a lot of time and effort (this coming from personal experience/woes). All I can say is that I wish you the very best of luck!"
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"https://archive.nrao.edu/archive/advquery.jsp",
"http://www.atnf.csiro.au/people/pulsar/index.html?n=Main.ANDSATNF"
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} | Where can I get some long, raw recordings of pulsars and FRBs?
I'm doing a project on powerful broadband phenomena such as pulsars and FRBs (fast radio bursts). I have a sound analysis software to study the oscillations and frequencies. I just need to know where to get the data itself. Where can I find extensive recordings of these two astronomical phenomena? | [
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slnht | Why are syphilis chancres painless? | askscience | {
"a_id": [
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"text": [
"I am not an ID specialist, but given that the bacterium that causes syphilis can go on to cause neuropathy in both the central and peripheral nervous system, local neuronal damage may be the reason. Damage to sensory receptors around the area could explain why the chancres indicative of primary syphilis are painless. Someone with better ID experience is more than welcome to weigh in on whether this is the case, or to explain it better.",
"Degenerative changes take place in adjacent sensory axon terminals - this is the current hypothesis as to why chancres are painless"
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} | Why are syphilis chancres painless?
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mdrrt | What are some sources where i can teach myself physics? | Im 16 and i fucking love physics. I was almost too happy when i saw there was a physics class at my high school.
i was excited at first, but so far all we have learned is velocity, acceleration, and the forces(Fn Fg etc.) i have to say im somewhat dissapointed. I understand these are important to physics, but i want to learn about electrons and the technical stuff for how shit works. So far pretty much all we are doing is re-learning trig.
Are there and good sources where i can learn about physics, maybe astrophysics and quantum mechanics too? I doubt there would be any free sources though. Thank in advance! | askscience | {
"a_id": [
"c303rxg",
"c303yc8",
"c30418r"
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"text": [
"One caveat - you will never get away from the maths :) Trig is a good start, but you if you want to get into physics you will eventually get deep into calculus and linear algebra and statistics. It will go better for you if you find things to love in mathematics rather than resenting it as a \"necessary\" part of physics :)\n\n*But*, you are lucky in that there are a *lot* of resources to learn about physics. Physics is sufficiently universal that everybody basically learns the same stuff at high school and the first couple years of university, so you can look almost anywhere for information.\n\nIf you're serious about learning deep proper physics, you can have a look at the free online courses offered by [MIT](_URL_0_) - however, you may find that a bit of a steep learning curve if you're just starting out.\n\nFunnily enough, for general concepts you can get a pretty good gist of things from wikipedia - as long as you take some of the claims with a bit of a grain of salt :)\n\nFor more general stuff, NASA is actually pretty good. [Here's](_URL_1_) some stuff on Dark Matter for instance.",
"[Khan Academy](_URL_2_) - the most glorious place on the internet",
"[Physics2000](_URL_3_) from University of Colorado at Boulder.\n\nSuperb graphics to help teach by intuition - resulting in instant understanding of many concepts without the maths."
],
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"http://www.colorado.edu/physics/2000/index.pl"
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} | What are some sources where i can teach myself physics?
Im 16 and i fucking love physics. I was almost too happy when i saw there was a physics class at my high school. i was excited at first, but so far all we have learned is velocity, acceleration, and the forces(Fn Fg etc.) i have to say im somewhat dissapointed. I understand these are important to physics, but i want to learn about electrons and the technical stuff for how shit works. So far pretty much all we are doing is re-learning trig. Are there and good sources where i can learn about physics, maybe astrophysics and quantum mechanics too? I doubt there would be any free sources though. Thank in advance! | [
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4s0nra | Does anxiety increase blood pH level? | The context of this question is related to exercise endurance, running more specifically.
I don't have a scientific background, but after reading different articles, I went to the following conclusion:
When a person runs at anaerobic level of effort, the blood pH decreases. However, if this person becomes anxious, due to the fear of lack of oxygen for example, the blood pH is increased metabolically, which basically extends the capacity of performing the exercise.
That can be the explanation of endurance, if the idea is correct.
Am I right, or if not, what's wrong? | askscience | {
"a_id": [
"d55kube"
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"text": [
"Anxiety in and of itself does not affect pH. However, hyperventilation that may be part of anxiety can cause respiratory alkalosis leading to an increase in blood pH. Acid base status is regulated mainly in the lungs and kidneys. The lungs are able to cause rapid changes in pH through hypo- or hyperventilation. The kidneys respond more slowly by excreting or retaining bicarbonate in the urine. Anxiety accompanied by hyperventilation can cause a rise in arterial pH (respiratory alkalosis) This is not metabolic alkalosis. \n\nAlkalosis, either by respiratory of metabolic causes, actually decreases the ability of hemoglobin to offload oxygen to the peripheral tissues. The [oxygen dissociation curve](_URL_0_) shifts based on pH (and other factors). This will actually have the effect of causing a tendency toward anaerobic cellular respiration, production of lactic acid, and a drop in pH back toward baseline. The body almost always has mechanisms to return to homeostasis."
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} | Does anxiety increase blood pH level?
The context of this question is related to exercise endurance, running more specifically. I don't have a scientific background, but after reading different articles, I went to the following conclusion: When a person runs at anaerobic level of effort, the blood pH decreases. However, if this person becomes anxious, due to the fear of lack of oxygen for example, the blood pH is increased metabolically, which basically extends the capacity of performing the exercise. That can be the explanation of endurance, if the idea is correct. Am I right, or if not, what's wrong? | [
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8k2vy1 | What is the difference between numerical relay and static relay? | askscience | {
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"An electromechanical relay uses the incoming flow to create an electromagnetic force, and then \"compares\" it against a reference force (a spring) to determine whether the circuit should be open or closed.\n\nA static relay uses transistors to change the incoming flow into a smaller electrical flow, and then compares it to a reference electrical flow to determine whether to open or close the circuit. It is called \"static\" because it has no moving parts.\n\nA numerical relay converts the incoming flow into a digital signal and then uses software to determine if the flow is outside the desired parameters to decide whether to open or close the circuit. Because it has a software level, a numerical relay has much greater flexibility in terms of the protection it provides (at the cost of greater complexity and expense).\n\nThere is apparently some fine distinction between a numerical relay and a digital relay, but I don't know what it is and I've seen the words used pretty interchangeably."
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} | What is the difference between numerical relay and static relay?
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3uokul | Hey, what kind of plant is this? | [removed] | askscience | {
"a_id": [
"cxgyn3y"
],
"text": [
"This looks like the fruit from an indian Lotus, [Nelumbo nucifera](_URL_0_).\n\n[edit] [Pictures](_URL_1_)"
],
"score": [
4
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} | {
"url": []
} | {
"url": []
} | {
"url": [
"https://en.wikipedia.org/wiki/Nelumbo_nucifera",
"https://www.google.co.uk/search?q=dried+lotus&tbm=isch"
]
} | Hey, what kind of plant is this?
[removed] | [
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1mw5m2 | Can we listen to the CMB? | As I understand it, the CMB used to be higher energy radiation and has decayed over time. Is it possible to turn that data back into radio waves and then listen to it? | askscience | {
"a_id": [
"ccdc1z7",
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"text": [
"You don't have to turn it back into radio waves. The CMB is currently peaked at a wavelength of around 2 mm, with the highest intensities between about 1 mm and 1 cm in wavelength. These are radio waves.\n\nIn fact, in an analog TV set, if you tune to a spot where there is no broadcast station, a fraction (if I recall correctly, around a percent) of the static you see is the CMB. And the way the CMB was first discovered was that Penzias and Wilson found that there was unexplained \"noise\" in their radiotelescope that they couldn't remove; it turned out that this was because their radiotelescope was picking up the CMB.",
"You could, but there's not much to hear."
],
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} | Can we listen to the CMB?
As I understand it, the CMB used to be higher energy radiation and has decayed over time. Is it possible to turn that data back into radio waves and then listen to it? | [
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ydly1 | a question on sound | A simple question. If there are two machines producing sound at 50 decibels each, does it produce 100 decibels?
Was talking about it at work today about or lawn cutting equipment.
Thanks! | askscience | {
"a_id": [
"c5ulxde"
],
"text": [
"No because it is a logarithmic scale, not linear.\n\nEdit: Here is a handy tool showing the mathematics used to convert back to a linear scale to manipulate in the way you need to. \n_URL_0_"
],
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} | a question on sound
A simple question. If there are two machines producing sound at 50 decibels each, does it produce 100 decibels? Was talking about it at work today about or lawn cutting equipment. Thanks! | [
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lu24q | Are brainwaves and brainwave entrainment psuedoscience/placebo effect? | Science is in no way an area that I excel in, so I can't very well explain the specifics of it. All I know is that we produce different brainwaves at different states of being. I'm curious if it's actually proven that you can artificially induce brainwaves via headphones. I've tried researching on my own via google, and have only gotten a biased opinion from someone trying to sell me their brainwave entrainment product. Is this stuff for real or only for the weak minded? | askscience | {
"a_id": [
"c2vplas",
"c2vmqi8"
],
"text": [
"BTW, the placebo effect isn't pseudoscience. You can measure a statistically significant difference in populations who were and were not subjected to a placebo. In fact, levels of depression appear to co-vary with the belief that an antidepressant will work, regardless of the effectiveness of the antidepressant. \n\nI don't have a link to the anti-depressant bit, that was in my psychopharmacology book in college, but here is stuff on the [placebo effect](_URL_0_)",
"Here is a link to a brainwave entrainment symposium at Stanford University _URL_1_\n\nEspecially see Dr. Budzynski's \"Clinical Guide to Light and Sound\" referenced on that page. You are right, there is commercial hype regarding entrainment, but that doesn't mean that the concept itself is nonsense.\n\nPeople have different levels of responsiveness to entrainment. Being weak-minded or strong-minded is irrelevant. It is more about an individual's innate responsiveness to rhythmic audio stimuli."
],
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"url": []
} | {
"url": [
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]
} | Are brainwaves and brainwave entrainment psuedoscience/placebo effect?
Science is in no way an area that I excel in, so I can't very well explain the specifics of it. All I know is that we produce different brainwaves at different states of being. I'm curious if it's actually proven that you can artificially induce brainwaves via headphones. I've tried researching on my own via google, and have only gotten a biased opinion from someone trying to sell me their brainwave entrainment product. Is this stuff for real or only for the weak minded? | [
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trdk0 | What is happening in this Eric Laithwaite gyroscope video? | I saw this in /r/videos today: _URL_0_
Why does the contraption weigh less when the disc is spinning than when it is not? | askscience | {
"a_id": [
"c4p2hm3",
"c4p2t77"
],
"text": [
"[Precession](_URL_0_)\n\nThe weight of the contraption is identical to before it was spinning and still acts down perpendicularly to the ground. However, notice he holds in that position before spinning the disc. \n\nWhen the disc starts spinning faster, it gains angular momentum around the spin axis of the disc (the axis is along the pole of the contraption).\n\nWhen gravity pulls down on the disc, it applies a force on the spin axis downwards. However, due to gyroscopic precession, the downwards force is converted to a sideways force instead. Notice that in the video, when he releases one of his hands, the whole contraption starts rotating around him. This is due to the downwards force being translated to a sideways force. This translation removes most of the downwards force due to gravity and will cause the contraption to feel weightless.\n\nThe link I provided has a good explanation on gyroscopic precession.",
"> Why does the contraption weigh less when the disc is spinning\n\nIt doesn't! It weighs the same either way. It is, nonetheless, easier to hold aloft, as it puts less strain on the wrist. See the excellent discussion at\n_URL_1_"
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} | {
"url": [
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]
} | {
"url": [
"http://science.howstuffworks.com/gyroscope2.htm",
"http://www.reddit.com/r/askscience/comments/kf9dr/eric_laithwaite_lifting_heavy_gyroscope_with_one/"
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} | What is happening in this Eric Laithwaite gyroscope video?
I saw this in /r/videos today: _URL_0_ Why does the contraption weigh less when the disc is spinning than when it is not? | [
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jyalo | Hey r/askscience. I read about Erwin Schrödingers "My view of the world". It seems to be heavy spiritual stuff. Since most here are rather materialists ( I guess ), what do you think about this book? ( more inside ) | askscience | {
"a_id": [
"c2g39b0"
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"There are a couple of issues that need to be considered to understand these quotations:\n\n1. These men lived a hundred years ago, and though they were brilliant, they still lacked an enormous amount of the additional mathematical theory work and experimental data that any modern student has at their fingertips. Keep in mind that making a correct conclusion requires both the correct data, and the correct mind to analyze that data. For example, Einstein maintained until the end of his life that [entanglement](_URL_0_) could not possibly function as all further studies and theoretical work have demonstrated.\n\n2. Anything that can be called \"science\" can be described mathematically. In particular, for the fathers of quantum mechanics, they were facing math that described a world for which they had no intuition. Heisenberg's quotation above means that he was able to develop some intuition for the meaning of his own equations from considering the spiritual; it does not mean that these spiritual traditions have any mathematical truth behind them or any particular capacity to correctly describe the phenomena that we encounter in reality.\n\n3. Many scientists will speak of \"god,\" or \"the spiritual,\" but mean it in a radically different context from the way that most laymen do. They are describing their sense of wonder, and their incomplete knowledge of the universe. They are also noting that some phenomena that are cleanly described by science also seem to coincidentally appear in the spiritual traditions of other groups. This doesn't mean that these scientists felt the need to appeal to the existence of anything supernatural to explain the function of the known universe."
],
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} | {
"url": [
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]
} | Hey r/askscience. I read about Erwin Schrödingers "My view of the world". It seems to be heavy spiritual stuff. Since most here are rather materialists ( I guess ), what do you think about this book? ( more inside )
| [
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1imtj7 | Van Der Walls Inter molecular forces question, Shouldn't they cancel out? | If Van Der Walls forces cause attraction by temporary dipoles from the electrons orbiting the nucleus and causing attraction randomly, wouldn't there be an equal chance of the molecules causing a repulsive temporary dipole? so the forces wouldn't attract each other at all, they'd just kind of vibrate a tiny bit closer, then a tiny bit away.
I thought it might be that when the hypothesized repulsive dipole was made the molecule would just turn and then attract?
Just a random question i thought that my chemistry teacher couldn't answer so thought Reddit could help :) Thanks in advance | askscience | {
"a_id": [
"cb601p9"
],
"text": [
"Van der Waals Forces can actually refer to a number of different intermolecular interactions, but what you're thinking of is the [London Dispersion Force](_URL_0_).\n\nOne way to think about it is that atomic nucleii are much, much heavier than electrons. When two atoms happen to run into each other, it is a lot easier for the electron clouds to shift than for the atomic nucleii to deflect each other. So if one atom happens to randomly have more electron density on the side facing the other atom, the other atom's electrons will be repulsed, making a temporary (attractive) instantaneous dipole."
],
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3
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} | {
"url": []
} | {
"url": []
} | {
"url": [
"https://en.wikipedia.org/wiki/London_dispersion_force"
]
} | Van Der Walls Inter molecular forces question, Shouldn't they cancel out?
If Van Der Walls forces cause attraction by temporary dipoles from the electrons orbiting the nucleus and causing attraction randomly, wouldn't there be an equal chance of the molecules causing a repulsive temporary dipole? so the forces wouldn't attract each other at all, they'd just kind of vibrate a tiny bit closer, then a tiny bit away. I thought it might be that when the hypothesized repulsive dipole was made the molecule would just turn and then attract? Just a random question i thought that my chemistry teacher couldn't answer so thought Reddit could help :) Thanks in advance | [
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30khy9 | I propagate yeast for homebrewing using a magnetic stir plate. What is the preferred method for best results, fast with large vortex or slower and little/no vortex? | I posted [this GIF](_URL_0_) on /r/homebrewing and /r/oddlysatisfying today and it started a lot of discussion about best practice for making yeast starters. I'm curious what the best method is.
As seen in the GIF, the dye stays in the vortex for a while and is finally dispersed, however I did drip the dye directly into the vortex. Do I want a fast spin with a strong vortex or a slower spin and low to no vortex?
What about stir bar size? The bar in the video is a 1.125", I had a 2" bar but my plate keeps throwing the bar. | askscience | {
"a_id": [
"cptfh2v"
],
"text": [
"Non-brewer yeast biologist here. \n\nAeration is important when you're growing yeast. Usually, if you're growing a yeast culture in the lab, you'll do it on a shaker rather than on a stir plate, and you'll use only about 20% of the volume of your flask (so 50ml of culture in a 250ml erlenmeyer flask). That allows the cells to be well-oxygenated, and so they will grow well. \n\nIn your case, I would say you should use a larger stir bar at a much slower rpm, which should help aerate the culture. Ideally you'd do it in a larger erlenmeyer, too. Yeast are pretty hearty, though -- if you're growing them in quite rich media (which I would guess you are), you're almost certainly getting to a saturated culture."
],
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"url": [
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"url": []
} | I propagate yeast for homebrewing using a magnetic stir plate. What is the preferred method for best results, fast with large vortex or slower and little/no vortex?
I posted [this GIF](_URL_0_) on /r/homebrewing and /r/oddlysatisfying today and it started a lot of discussion about best practice for making yeast starters. I'm curious what the best method is. As seen in the GIF, the dye stays in the vortex for a while and is finally dispersed, however I did drip the dye directly into the vortex. Do I want a fast spin with a strong vortex or a slower spin and low to no vortex? What about stir bar size? The bar in the video is a 1.125", I had a 2" bar but my plate keeps throwing the bar. | [
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rivkx | Do those electronic muscle stimulating devices that cause the muscle to spasm or contract up and release like what Bruce Lee used actually have any beneficial effect? If so of what is it? | askscience | {
"a_id": [
"c466ig9"
],
"text": [
"[This study](_URL_2_) showed that [electrical muscle stimulators](_URL_1_) did strengthen muscles:\n > The electrical-stimulation and isometric-exercise groups had statistically significant increases in quadriceps femoris muscle torque when compared with the nonexercised controls (p < .001). The data supported the use of this electronic stimulator as an appropriate device for strengthening skeletal muscle without voluntary effort. \n\n[Another study](_URL_4_) on rugby players showed that it improved muscle strength:\n > A 12-week EMS training program demonstrated beneficial effects on muscle strength and power in elite rugby players on particular tests. However, rugby skills such as scrummaging and sprinting were not enhanced.\n\n[This study](_URL_0_) done on sedentary people showed improved strength and aerobic levels:\n > These results suggest that EMS can be used in sedentary adults to improve physical fitness. It may provide a viable alternative to more conventional forms of exercise in this population. \n\nAnd just to throw you for a loop,[ this study](_URL_3_) done on college kids found that EMS caused no change on a bunch of measured variables:\n > Thus, claims relative to the effectiveness of\nEMS for the apparently healthy individual are not supported\nby the findings of this study."
],
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"url": []
} | {
"url": []
} | {
"url": [
"http://jap.physiology.org/content/99/6/2307.short",
"http://en.wikipedia.org/wiki/Electrical_muscle_stimulation",
"http://www.physther.net/content/63/4/494.short",
"http://www.hawaii.edu/hivandaids/Effects%20of%20Electrical%20Muscle%20Stimulation%20on%20Body%20Composition,%20Muscle%20Strength.pdf",
"http://www.ncbi.nlm.nih.gov/pubmed/17530954"
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} | Do those electronic muscle stimulating devices that cause the muscle to spasm or contract up and release like what Bruce Lee used actually have any beneficial effect? If so of what is it?
| [
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ca6lfz | Why our pankreas can't be "rebooted"? | So, I am a T1 diabetic and I'm really curious as to why can't our pankreas work again or be transplated once it stops working properly? I mean we have heart, kidney, liver transplatations etc..
If anyone can explain I would truly appreciate it, thanks! | askscience | {
"a_id": [
"et9y2ei"
],
"text": [
"I am not sure if I understood properly the question and I am far from being a specialist on the matter (only medstudent) but I ll try to give few answers. \n\nPancreas are transplanted. \n\nAs you probably already know, the auto-antibody target beta cells and kills them more or less slowly depending of the individual. The cells left can compensate the managment of glycemia. There is no known regeneration as far as I am aware (just like the heart, kidney and the majority of organs). I do not know the reason why some organs (like the liver) have impressive abilities to regenerate themselves when it is not the case for others.\n\n & #x200B;\n\nLet me know if you need more clarifications, i'll do my best (if I can answer them\\^\\^)"
],
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"url": []
} | Why our pankreas can't be "rebooted"?
So, I am a T1 diabetic and I'm really curious as to why can't our pankreas work again or be transplated once it stops working properly? I mean we have heart, kidney, liver transplatations etc.. If anyone can explain I would truly appreciate it, thanks! | [
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48xsf4 | Is it possible to integrate by parts with more than 2 parts, and if not why not? | askscience | {
"a_id": [
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],
"text": [
"Yeah, you have to iterate the process though. You could try deriving a formula for it using the product rule on 3 terms, like compute (fgh)', manipulate and integrate, but that formula will be messy to deal with.\n\nAlso it's math, so I mean you can do this yourself. Try integrating x/(1-x^2) by factoring and doing integration by parts (the integral is easy to do direct, it is -1/2ln (1-x^2) )\n\nEdit: actually that example may not be doable by parts. Do it in reverse, let f (x)= x e^x sin (x)\n\nDifferentiate, you get 3 terms, each of those terms you should be able to compute the integral of by parts. Integration by parts is the \"reverse\" product rule, derivatives of products of functions gives you stuff that you can then integrate by parts. This is a great way to generate practice problems too.",
"usually you'll do something like int ugh = int u(gh)\nand then have u as a derivative f' or something like that.\n\nkeep in mind that the method relies on you knowing how to antiderive some of the factors, so since\n\n(fgh)' = f'gh + fg'h + fgh'\n\nint f'gh = fgh - int(fg'h) - int(fgh')\n\nbegs the question whether you are better off doing that.\n\nit's really the same as treating gh as a single function:\nint f'gh = fgh - int(f (gh)')"
],
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| [
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13qrr9 | When I hold a weight motionless over my head, I'm not doing any work on it, but it sure feels like I'm using energy. | This is something I never really understood from my Physics classes. Imagine I hold a heavy weight completely motionless above my head. I'm not moving the weight, so there is no work being done, since work is the integral of F.dx over a path that consists of a single point. But my body is definitely using energy to hold it up, and if I hold it long enough I'll run out of energy and my arms will buckle.
So in other words, what confuses me is that I'm applying a force to the weight to keep it suspended in the air, but since it isn't moving, there is no work being done. But I feel like I'm doing work. Am I? | askscience | {
"a_id": [
"c76b0sm",
"c76az1i"
],
"text": [
"Well that really depends on your sense of scale, but once you get small enough, you bet. The tension in your muscles is being maintained by isometric contraction. The thick and thin filaments in your muscles are repeatedly undergoing so-called \"crossbridge cycles\" without actually slipping past one another. \n\nAn imperfect comparison would be to a rowing team matching the downstream current with their own upstream rowing. Each individual stroke requires energy (the work required to move the oar), even though the net work of the boat is strictly speaking null. In the sarcomeres of your skeletal muscle, each stroke of your thick filaments uses one adenosine triphosphate (ATP), converting it to adenosine diphosphate (ADP). In this way, it is identical to the process of isotonic contraction in which your thick and thin filaments actually do slip past one another, and result in grossly visible work as when you lifted the weights in the first place.",
"On a macro level you aren't doing any work since the weight isn't moving, but on micro level your muscle fibers are doing work against gravity keeping the weight up. While I'm not entirely sure, I believe they are having some up-down/to-fro micro-motions which you'd consider as work. And when the fibers run out of fuel, your arms buckle and you lose your hold. \n\nPS: Bad formatting may result since I'm using my phone to answer."
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"url": []
} | When I hold a weight motionless over my head, I'm not doing any work on it, but it sure feels like I'm using energy.
This is something I never really understood from my Physics classes. Imagine I hold a heavy weight completely motionless above my head. I'm not moving the weight, so there is no work being done, since work is the integral of F.dx over a path that consists of a single point. But my body is definitely using energy to hold it up, and if I hold it long enough I'll run out of energy and my arms will buckle. So in other words, what confuses me is that I'm applying a force to the weight to keep it suspended in the air, but since it isn't moving, there is no work being done. But I feel like I'm doing work. Am I? | [
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kp1h1 | Is it easier to relearn something you used to know but forgot? i.e. "it's like riding a bike" | I'm curious about this. Over the course of my life, I have learned many things, and forgotten a fair amount of them.
Let's use a simple example. I used to have memorized a table of around 25 phrases, numbered in order. I needed to use them quite often for my job at the time. Right now, I can't think of any of them offhand. If I needed to start using them again, would it be any easier for me than the first time I used them? It took me a week or so of using them on a daily basis to learn them all. If I wanted to re-learn them, would I be able to just look at a placard listing them and memorize it in a minute?
I guess the crux of my question is if a person used to know something, but forgot it, does that knowledge still exist somewhere in the brain so that a simple reminder can make them remember it, or is that knowledge gone so that it must be completely re-learned? It seems from my own experience that the former is correct, but I'd like to hear from an expert. | askscience | {
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"From _URL_0_ - I think these are someone's course notes... hence the fragmented sentences\n\n > information can be relearned faster if it was learned previously. This is a very sensitive measure of memory. The person to discover this is the father of memory research. He was Hermann vonEbbinghaus (1850-1909). His goal was to quantify memory and forgetting. He is the father of thenonsense syllables. (BAF, ZUP, TEJ) .\n\n > He used these made up words because no one will have ever seen or heard these words before - he took away a confound. He viewed his research as a true measure of memory. He created many lists of nonsense syllables. He had subjects study these words and memorize them. Then he would have them come back in and relearn the words. He conducted the study over two years (163 trials). He used himself as a subject (bias). He studied the list till he had two perfect recitations. If he met that criterion, he would stop studying. He keeps track of the length of time to meet criterion. This was the original learning time. Then he we would delay 20min to 31 days. He would then get this list again and time how long it took him to recite the list perfectly two times. He would track this time to meet the criterion as well. This was the relearning time.\n\n > Method of Savings: original learning – relearning time = savings (how much better you do to relearning something from having learned it the first time). Expressed as a percentage of learning time = savings/original learning time. Data can be plotted to discover trends (Dependent variable: percent savings, Independent variable: Elapsed Time). Curve goes down over time but not linearly. Very rapid forgetting early on. Relatively low rates of forgetting over time. After 20 over 50% remembered. After 1 hour, under 50%. After 9 hours, at 40%. Over time though, memory never got below about 30%.",
"Yes, re-learning is easier. I can't find the particular citation I'm thinking of right now, but I'll look later. Also be aware that \"learning\" and \"re-learning\" of physical vs. cognitive tasks have different implications."
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} | Is it easier to relearn something you used to know but forgot? i.e. "it's like riding a bike"
I'm curious about this. Over the course of my life, I have learned many things, and forgotten a fair amount of them. Let's use a simple example. I used to have memorized a table of around 25 phrases, numbered in order. I needed to use them quite often for my job at the time. Right now, I can't think of any of them offhand. If I needed to start using them again, would it be any easier for me than the first time I used them? It took me a week or so of using them on a daily basis to learn them all. If I wanted to re-learn them, would I be able to just look at a placard listing them and memorize it in a minute? I guess the crux of my question is if a person used to know something, but forgot it, does that knowledge still exist somewhere in the brain so that a simple reminder can make them remember it, or is that knowledge gone so that it must be completely re-learned? It seems from my own experience that the former is correct, but I'd like to hear from an expert. | [
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3fwbsi | Can you intend to forget? | I was talking to my friend about deep things and this question came up and we couldn't find an answer to this online. | askscience | {
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"It's not easy, if not impossible. When you intend to forget, oftentimes your mind CHECKS whether you have forgotten, making you remember the thing again.\n\nSome people ended up having OCD because of failing to do so. [Here's a glance of how they feel](_URL_0_)."
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} | Can you intend to forget?
I was talking to my friend about deep things and this question came up and we couldn't find an answer to this online. | [
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bh87lv | Size comparison: Simbakubwa Kutokaafrika vs Andrewsarchus Mongoliensis? | Recent news articles declare Simbakubwa to be the largest carnivorous land mammal of all time, beating out the polar bear. I was under the impression that this title was held by Andrewsarchus, but I can't find any sources comparing the size of each. Given that we only have limited fossil remains of these 2 enormous predators, which was likely the larger beast? | askscience | {
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"As interesting a topic as this is, it's pretty hard to make any definitive statements about the size of these animals. As you mention, both species are known from quite limited material; to quote directly from [Borths and Stevens 2019](_URL_4_) on *Simbakubwa*, the type specimen is:\n\n > KNM-ME 20A, left dentary with canine, p4, m3, and alveoli of p3, m1, and m2\n\nOr, to make that a bit more intelligible, it's the left side of a (40 cm long!) jawbone with a canine, premolar, and molar (as well as empty sockets for an additional premolar and two more molars). [Here's what it looks like compared to a lion's jawbone](_URL_10_). In addition to this specimen, there's also a small [section of the upper jaw](_URL_5_), a few [individual loose teeth](_URL_0_), a [heel bone](_URL_6_), and [two phalanges](_URL_7_) (all images are from the paper). And, that's all we have! I want to be clear that this is not at all an unusual situation; extremely few fossil vertebrates are known from complete skeletons, despite palaeontologists' best efforts. However, understanding what parts of the body we actually have concrete samples of goes a long way to explain why there is so much uncertainty and ambiguity in how reconstructions on these organisms are done. For the sake of comparison, *Andrewsarchus* is also known from just a single specimen, which is a [ridiculously large](_URL_14_) (83 cm) partial skull, missing the jawbone, that was collected and described by [Olsen in 1924](_URL_3_).\n\nBoth for scientific reasons and just because it's really cool, we of course want to know what the rest of these animals looked like. So, in the absence of more specimens, the best option we have is to compare these animals to related species that we have more complete records of. *Simbakubwa* is described by the authors as a hyaenodont, a group which fortunately has [many other representatives](_URL_9_) to choose from. I'm not sure if this is still the most up to date consensus, but as far as I'm aware, this group is generally considered as being [closely related to carnivorans](_URL_12_), but not actually a member of this group. *Andrewsarchus* has been a bit harder to place phylogenetically; it was originally considered a member of Mesonychia (an extinct group more distantly related to carnivorans, and closer to hoofed mammals), but is now usually considered to be more closely related to whales and hippos (as well as the extinct [entelodonts](_URL_2_)). [This phylogeny](_URL_8_) from [Spaulding, O'Leary, and Gatesy 2009](_URL_13_) shows this relationship (*Andrewsarchus* is about 1/3 of the way down).\n\nNow, to finally get on to size estimates. I actually already talked about this a bit in a comment in r/science a few days ago, but most of the discussion there ended up being about the first half of my comment which is not relevant to this topic (though you can [read it here](_URL_1_) if you want). As I said there, Borths and Stevens used three different models to estimate the body size of *Simbakubwa* by comparing it to other species. I'm not an expert in this or anything, but it works basically just as you'd expect; you compare the size ratio of a *Simbakubwa* body part you actually *have* to the analogous part in another species, and then extrapolate this ratio to the rest of the body. The three different models and their results are as follows:\n\n1. The first, based on [Morlo 1999](_URL_11_) (unfortunately not publicly available), uses a fairly simple linear regression estimate based on the average size of molars. The estimate for *Simbakubwa* using this model yielded a mass of 1308 kg. However, I think there's two points worth mentioning here. Firstly, as Borths and Stevens note while doing these estimates, this very same model predicts larger sizes for other species (*Megistotherium osteothlastes* at 1794 kg, and *Hyainailouros bugtiensis* at 1744 kg), meaning that if we are going to trust this model, there are bigger hyaenodonts than *Simbakubwa* anyway. More importantly though is the second point I want to make; the model used in Morlo 1999 (which I really wish I could show a picture of here), only includes species that range in mass from \\~1 to \\~50 kg. To speak in terms of mean molar length, which is the independent variable for this graph, they range from \\~6 to \\~18 mm, compared to *Simbakubwa*'s 44. *Simbakubwa* (and the larger species they test simultaneously) are way off the scale here. I'm not saying the authors are being dishonest or anything here; they're using the best size estimation techniques available to them to predict the size of their specimen. However, it may well be the case that this model is not well suited to such an extreme outlier and is not accurate if used to extrapolate beyond its original boundaries.\n2. The second model is based on Van Valkenburgh 1990 and yielded the highest estimate of 1554 kg. Unfortunately, I was not able to access this source, since it appears to be print only. However, it is stated that this regression was designed for members of the Felidae, which are a subset of carnivorans, and therefore I will remind you [do not include hyaenodonts](_URL_12_). I'm definitely not knowledgeable enough to say for sure what kinds of biases there could be in using a model calibrated to felids on *Simbakubwa*, but I think it's easy to imagine that there could be some. It's also very likely that the large hyaenodonts discussed in Borths and Stevens are again extreme outliers that rely on extrapolation of the model rather than interpolation, but without being able to see it I can't say for sure.\n\nTo be continued due to character limit...."
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"https://www.tandfonline.com/na101/home/literatum/publisher/tandf/journals/content/ujvp20/0/ujvp20.ahead-of-print/02724634.2019.1570222/20190412/images/large/ujvp_a_1570222_f0002_ob.jpeg",
"https://www.reddit.com/r/science/comments/bfoj4c/scientists_found_the_22_millionyearold_fossils_of/elf80xh/?context=3",
"https://en.wikipedia.org/wiki/Entelodont",
"http://digitallibrary.amnh.org/bitstream/handle/2246/3226/N0146.pdf;jsessionid=2E333DAAFCEF0CCD03FED54C70E19F0E?sequence=1",
"https://www.tandfonline.com/doi/full/10.1080/02724634.2019.1570222",
"https://www.tandfonline.com/na101/home/literatum/publisher/tandf/journals/content/ujvp20/0/ujvp20.ahead-of-print/02724634.2019.1570222/20190412/images/large/ujvp_a_1570222_f0003_ob.jpeg",
"https://www.tandfonline.com/na101/home/literatum/publisher/tandf/journals/content/ujvp20/0/ujvp20.ahead-of-print/02724634.2019.1570222/20190412/images/large/ujvp_a_1570222_f0007_ob.jpeg",
"https://www.tandfonline.com/na101/home/literatum/publisher/tandf/journals/content/ujvp20/0/ujvp20.ahead-of-print/02724634.2019.1570222/20190412/images/large/ujvp_a_1570222_f0008_ob.jpeg",
"https://journals.plos.org/plosone/article/figure/image?size=large&id=10.1371/journal.pone.0007062.g002",
"https://www.tandfonline.com/na101/home/literatum/publisher/tandf/journals/content/ujvp20/0/ujvp20.ahead-of-print/02724634.2019.1570222/20190412/images/large/ujvp_a_1570222_f0009_ob.jpeg",
"https://www.tandfonline.com/na101/home/literatum/publisher/tandf/journals/content/ujvp20/0/ujvp20.ahead-of-print/02724634.2019.1570222/20190412/images/large/ujvp_a_1570222_f0001_ob.jpeg",
"https://www.sciencedirect.com/science/article/pii/S0016699599800436",
"https://blogs.plos.org/paleocomm/files/2017/04/hyaenodont_phylogeny.jpg",
"https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0007062",
"https://upload.wikimedia.org/wikipedia/commons/c/c7/Andrewsarchusscull2.jpg"
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} | Size comparison: Simbakubwa Kutokaafrika vs Andrewsarchus Mongoliensis?
Recent news articles declare Simbakubwa to be the largest carnivorous land mammal of all time, beating out the polar bear. I was under the impression that this title was held by Andrewsarchus, but I can't find any sources comparing the size of each. Given that we only have limited fossil remains of these 2 enormous predators, which was likely the larger beast? | [
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j7yuu | How does the Loop of Henle in a nephron concentrate the urine? | I almost submitted this to LI5, but I get osmotic pressure, so better asked here. I just can't seem to wrap my head around the countercurrent multiplier. Please help! | askscience | {
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"Without writing a small essay, this [animation](_URL_0_) may help you understand it better.",
"I think the best way to intuitively understand how the multiplication works is to view it in terms of equilibriums. \n\nThe tendency in the descending limb (DL) will always be to make an equilibrium with the insterstial fluid (IF). Water will always leave the DL and enter the IF until both solutions have equal osmolarity. \n\nThe tendency in the ascending limb (AL) is to go away from equilibrium - specifically by shifting the osmolarity towards a higher (more concentrated) value. Via active transport, it removes solute but not solvent.\n\nSo if you zoom out and look at the nephron as a whole, you've got the DL which is constantly trying to play catch-up to an ever increasing IF concentration - its trying to catch-up but it can't because the AL cheats by using active transport!\n\nEvery time the fluid in the DL loses a bit of water in order to equalize its osmolarity with the IF, the IF suddenly becomes *more* concentrated by removing solute (thus concentrating itself more) from the AL, which causes an equilibrium shift where the DL has to catch up again.\n\nSo this passive process - the tendency for water to want to establish an osmotic equilibrium, is always trying to catch up to this active process that is constantly pushing the equilibrium towards a higher osmolarity. \n\nNow this doesn't continue indefinitely (i.e. doesn't concentrate the fluid passed a specified amount) because the active transport in the AL can only \"fight\" against so-steep of a gradient, but it certainly goes much higher than the concentration experienced in the proximal tubule."
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} | How does the Loop of Henle in a nephron concentrate the urine?
I almost submitted this to LI5, but I get osmotic pressure, so better asked here. I just can't seem to wrap my head around the countercurrent multiplier. Please help! | [
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4tzicr | How does the LIGO observatory compensate for all of the environmental factors i.e. storms, strong winds, human movement around the facility etc. ? | askscience | {
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"Summing up [this page](_URL_0_), this is how they sort out the signals at LIGO:\n\n* Observations - if seismometers, barometers, [weather rocks](_URL_1_), or other instruments detect a terrestrial disturbance, corresponding events at LIGO can be ignored.\n\n* Comparisons - there is more than one of those massive interferometers, located very far from each other, so something that only shows up on one of them is just a local disturbance.\n\n* More complicated things - algorithms that can separate signals and noise, models that predict what a gravitational wave looks like, etc."
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} | How does the LIGO observatory compensate for all of the environmental factors i.e. storms, strong winds, human movement around the facility etc. ?
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5vlp9w | What is the science behind the "Euler's Disk"? | If you don't know it, then it is pretty easy to look up. It's pretty damn mesmerizing and I've been wondering what the science is behind it | askscience | {
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"[Here's a Stand Up Maths](_URL_1_) video about it. The fun thing about it is how fast it wobbles near the end, and he discusses how this rate is related to the rate of the spin and the angle that it is inclined. What you get is that\n\n* (Rate of Wobble)\\*((1/cos(t)) -1 ) = (Rate of Rotation)\n\nwhere t is the angle that it is inclined. As t goes to zero the term ((1/cos(t))-1) goes to zero. If we then assume that the rate of rotation isn't changing too much as it starts to fall, then the rate of wobble has to increase to keep up with (1/cos(t))-1 going to zero.\n\nA lot of the physics of the spinning is explored in this [Vsauce video](_URL_0_), though not explicitly about the Euler disk, it discusses the relevant concepts of rotation."
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} | What is the science behind the "Euler's Disk"?
If you don't know it, then it is pretty easy to look up. It's pretty damn mesmerizing and I've been wondering what the science is behind it | [
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n40zc | Does "l'appel du vide" have an underlying psychological cause, and if so, what is it? | askscience | {
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"L'appel du vide specifically refers to that feeling you get when you're at the top of a tall cliff and consider jumping off. It can be considered a form of self destructive ideation. It's actually fairly anxiety provoking for most people to be in that kind of a situation, one in which you are quite literally a step away from death. When suicide notes are examined, more than half of actual or attempted suicides clearly involve an attempt to flee from an averse situation (1). \n\nWhile I was not able to find anything specifically using the phrase \"l'appel du vide\", if you consider it as form of self destruction, it can be understood as a way for your brain to cope with a naturally anxiety provoking situation. It's a way of establishing control over a situation, which is fairly elementary defensive mechanisms people engage in.\n\n(1) Acceptance and Commitment Therapy: An Experiential Approach to Behavior Change, Stephen Hayes et al."
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} | Does "l'appel du vide" have an underlying psychological cause, and if so, what is it?
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46lzba | What makes a black hole hungry? | This [Hubble](_URL_0_) article talks about the newly discovered supermassive black hole "feeding" and "resting." What turns on and off a black hole's appetite? | askscience | {
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"Black holes don't have 'hunger'. What they do, is draw in any nearby matter. Sometimes the surrounding matter is absorbed in 'chunks' .. and those cycles are called 'feeding' and 'resting'. It's not real though.",
"Black holes are always \"hungry\", but in reality, matter collects as an accretion disk around the black hole. In an accretion disk, material orbits the hole in a circular orbit.\n\nIn a circular orbit, in principle there is no reason for a particle to fall downwards. After all, the moon hasn't fallen to the earth despite the obvious attraction between the two: the speed of the moon compensates for its fall towards the earth, resulting in a stable near-circular orbit. Saturn's rings are an example of an \"accretion disk\" that has stayed stable for a very long time.\n\nBack to the accretion disk. For a particle to fall downwards, it must receive a kick from another particle with a higher or lower orbit. In cold matter, this won't happen, but in a black hole accretion disk, the material has been heated to extremely high temperature by the collision between the disk and incoming matter. This transports momentum and allows the material to fall into a lower orbit. Eventually, it falls so low it is eaten by the black hole.\n\nThis is a simplified picture. Real accretion disks aren't fully stable. They eventually \"decay\" from a near-circular orbit into an unstable mode, where much more matter is surrendered to the black hole as opposed to the normal situation. This causes increased collisions with the rest of the disc, increasing X-ray brightness. Once any \"excess\" matter has been dealt with, the accretion disk returns to normal. These are the \"feeding\" and \"resting\" modes."
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} | What makes a black hole hungry?
This [Hubble](_URL_0_) article talks about the newly discovered supermassive black hole "feeding" and "resting." What turns on and off a black hole's appetite? | [
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oak9c | Is there a measurable correlation between body weight and brain stimulation? | The brain uses 25% of our total metabolic energy, yet it is only a couple % of our total body mass. Do some people lack mental stimulation so much that it could possibly be a cause of being overweight?
I think the most relevant question about this possibility is if television has any substantial effect on lowering brain activity... | askscience | {
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"Check out this article:\n\n_URL_0_\n\nSo I think there's a slight relationship, although I would doubt it to be causal. I don't think that a lower IQ results in people being overweight - there are too many other factors involved. And you were asking brain stimulation, which isn't the same as IQ, although I imagine they're related."
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"url": [
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]
} | Is there a measurable correlation between body weight and brain stimulation?
The brain uses 25% of our total metabolic energy, yet it is only a couple % of our total body mass. Do some people lack mental stimulation so much that it could possibly be a cause of being overweight? I think the most relevant question about this possibility is if television has any substantial effect on lowering brain activity... | [
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393mum | What are the indicators in a reef-rehabilitation study? | tl;dr: I want to know what I should note/count for a before-and-after survey of a section of ocean floor for a garbage-removal study, but I don't know what to look for.
I'm an avid diver and have more recently gotten interested in ocean and reef health. Where I live, I know of a section of coast that, traditionally, has heavy-human traffic, and thus has a lot of trash in it dating back at least 3 decades.
What I want to do is do a baseline evaluation of the reef health and of the marine life that exists right now. Then I want to clean up all the trash and work with the municipality to help prevent future waste articles from entering the local ecosystem. Finally, I want to measure the ongoing health of the reef to see if it being rehabilitated and at what rate.
I've done some science before, but it's not my main field, so I'd appreciate any and all help that's available for this marine-biology-related activity that I want to pursue.
Thanks! | askscience | {
"a_id": [
"cs0381a",
"cs03qpu"
],
"text": [
"Easiest way is to divide the area into same sized squarE's. Document density , species, and anything note worthy in all squares. Coverage or percent coverage can also be used if you have 5hings like barnacles that likes to make a mat. Every time you take a measurement document water temp, salinity at various depth, light availability, oxygen content, if able take a water sample and preserve it.\n\n Make sure your sample area is representative. Especially for ocean floors a bit of debrir or ditches can drastically alter the fauna.",
"Where are you? Some reef systems have a massive amount of dead corals probably for very different reasons. /u/TachnicallyActually's list is awesome, but if you're in certain areas, documenting frequencies of living and dead corals would be well worth adding to the list."
],
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} | What are the indicators in a reef-rehabilitation study?
tl;dr: I want to know what I should note/count for a before-and-after survey of a section of ocean floor for a garbage-removal study, but I don't know what to look for. I'm an avid diver and have more recently gotten interested in ocean and reef health. Where I live, I know of a section of coast that, traditionally, has heavy-human traffic, and thus has a lot of trash in it dating back at least 3 decades. What I want to do is do a baseline evaluation of the reef health and of the marine life that exists right now. Then I want to clean up all the trash and work with the municipality to help prevent future waste articles from entering the local ecosystem. Finally, I want to measure the ongoing health of the reef to see if it being rehabilitated and at what rate. I've done some science before, but it's not my main field, so I'd appreciate any and all help that's available for this marine-biology-related activity that I want to pursue. Thanks! | [
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21t4g1 | Why exactly does production eventually experience diminishing marginal returns to labour in the short run? | askscience | {
"a_id": [
"cgh4kae",
"cghmb6b"
],
"text": [
"Depends on what you mean by \"exactly\", as you'll get a different story for each business.\n\nIn general, if you're holding other inputs steady, it's because there's only so much that can be done with the land and capital on hand. \n\nIf you're a trucking company with a certain number of trucks, then every time you add a driver, you can more or less operate another truck. Once you have a driver for every truck, adding more still helps some, since you can do better shift scheduling and keep them running for longer hours. Eventually, though, if you keep hiring people, they're just going to be sitting four to a cab watching cat videos on their phones almost all day.",
"The example from /u/AdamColligan is pretty good. I added one example and said what the basic model is.\n\nThe general model is production output as a function of labor and capital and you try to get the most output for the lease amount of money. Labor costs wages and capital costs rent. The idea here is when you increase labor without increasing capital, you won't be maximizing the output you can produce for the same cost. \n\nIn simple terms, if you have 5 people to work on one computer, it's much less efficient than if you had 3 people working on 3 computers. In this instance four people would work on pen and paper and calculators. Sure you can increase the labor and always have them produce more and more but after a while it makes sense to spend more on capital goods."
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} | Why exactly does production eventually experience diminishing marginal returns to labour in the short run?
| [
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1ljl0d | Is 'subsconcious' a misleading term? | EDIT: Just noticed the spelling mistake in the title. D'oh!
I recently read a [comment](_URL_0_) about how it is misleading to use the term 'subconscious' in discussions about psychology. Essentially, the commenter argued that 'subconscious' isn't a term used by psychologists, that is 'doesn't describe a testable hypothesis or construct', and that there are other specific terms that should be used: 'implicit', 'unaware', 'unintentional'.
I asked the commenter to elaborate but they seemed reluctant to, and just linked me to some dense primary literature on automaticity.
So, psychology people, could anyone offer an explanation of the difference between 'subconscious' and terms such as 'implicit', 'unaware' or 'unintentional'?
And, more generally, how might I, knowing little about psychology, be misled by use of the term 'subconscious'? | askscience | {
"a_id": [
"cbzx9zp"
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"The word 'subconscious' isn't really used in psychology, probably due to its association with Freud. Generally psychological processes/functions can be called either unconscious/non-conscious or conscious, however other words are used in more specific contexts. \n\nFor example unconscious knowledge (knowing something without being aware that you know it) is often referred to as implicit knowledge, as opposed to explicit knowledge. The word awareness is often used when talking about perception, e.g. visual processing occuring in the brain without you having any level of visual awareness. I haven't come across unintentional so much, but I would guess it refers to situations when people act without consciously intending to."
],
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} | {
"url": [
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]
} | {
"url": []
} | Is 'subsconcious' a misleading term?
EDIT: Just noticed the spelling mistake in the title. D'oh! I recently read a [comment](_URL_0_) about how it is misleading to use the term 'subconscious' in discussions about psychology. Essentially, the commenter argued that 'subconscious' isn't a term used by psychologists, that is 'doesn't describe a testable hypothesis or construct', and that there are other specific terms that should be used: 'implicit', 'unaware', 'unintentional'. I asked the commenter to elaborate but they seemed reluctant to, and just linked me to some dense primary literature on automaticity. So, psychology people, could anyone offer an explanation of the difference between 'subconscious' and terms such as 'implicit', 'unaware' or 'unintentional'? And, more generally, how might I, knowing little about psychology, be misled by use of the term 'subconscious'? | [
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1xajah | Does the human body have a OS of some sort and can we modify it? | What I'm asking is how does my brain receive and process everything I see in this world and know what to do with it. Does my brain have some type of software it lives by? Do we all have something hard wired in our brains when born and just keep adding to it as we grow and learn. Would it be possible to plug me into something and upload new information without actually studying? | askscience | {
"a_id": [
"cf9qhak"
],
"text": [
"Applying the concept of the an operating system to serve as a metaphor for how our brain processes information is a gross over simplification that doesn't really suffice. We are currently uncertain how or why activation of specific neural pathways/areas of the brain result in various kinds of processing for different types of stimuli (e.g. sight, sound, smell, etcetera).\n\nWe know to a certain extent we are hardwired to respond positively and negatively to certain kinds of stimuli (e.g., things that are extremely bitter are unpleasant to us taste-wise, so when we experience the sensation of overly bitter taste we tend to want to avoid this negative stimulus so we spit). So yes to certain degree our brains are hardwired to interpret certain kinds of stimuli as negative and positive. We learn as we grow and experience specific stimuli to avoid specific types of stimuli and to seek out those things act as positive stimuli. How this process occurs is an incredibly complex web of interactions between various parts of the brain responsible for processing different aspects of the stimuli we experience and those parts responsible for analyzing this processed data, and then determining a response.\n\nThe idea of plugging someone in and uploading information, with no need for \"manual\" input of sensory information is far from close. I suppose it's theoretically possible, but at this point with the level of understanding we have for what the different patterns of activation mean and the variation between individual people is so great I don't see it happening for an insanely long time. Definitely not in my lifetime. And I'm not sure if it ever would even be possible without messing something else up severely due to the greatly entangled nature of these various neural circuits."
],
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"url": []
} | Does the human body have a OS of some sort and can we modify it?
What I'm asking is how does my brain receive and process everything I see in this world and know what to do with it. Does my brain have some type of software it lives by? Do we all have something hard wired in our brains when born and just keep adding to it as we grow and learn. Would it be possible to plug me into something and upload new information without actually studying? | [
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isxd5 | Water is densest at 4°C. Could we exploit this property to use it as an energy source? | Water is at its densest at 4°C, so what stops us from extracting heat energy from it until it's frozen, and then using the kinetic energy of the ice that forms as it floats to the surface? Could we build some sort of submarine-type ship which travels at the appropriate depth, taking in water and then releasing ice which subsequently melts under the sun, and then sinking back down? I understand that extracting energy from hot substances is difficult and inefficient, but what are the other limiting factors? Is there simply not enough energy available, or else is it unfeasible for some other reason? | askscience | {
"a_id": [
"c26dj72"
],
"text": [
"you can't just extract energy: you have to have a *difference* in temperature between 2 points to do that.\n\nyou might be able to extract some energy by floating something with one end at the surface and the other end down in the warmer water but you wouldn't get much and you'd cause the water to freeze faster which could be good or bad depending on how much and where you used this."
],
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} | Water is densest at 4°C. Could we exploit this property to use it as an energy source?
Water is at its densest at 4°C, so what stops us from extracting heat energy from it until it's frozen, and then using the kinetic energy of the ice that forms as it floats to the surface? Could we build some sort of submarine-type ship which travels at the appropriate depth, taking in water and then releasing ice which subsequently melts under the sun, and then sinking back down? I understand that extracting energy from hot substances is difficult and inefficient, but what are the other limiting factors? Is there simply not enough energy available, or else is it unfeasible for some other reason? | [
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xnkgx | I bought salsa the other day and it just exploded in my face when I took it out of the fridge... why...? | So I bought a combo of salsa and bean-dip at costco the other day. The bean-dip container was stacked on top of the salsa contained and the two were wrapped together with plastic wrap. Anyways, when I took the salsa and bean dip out of my fridge, two weeks after buying them, I noticed that the salsa was bulging from its top and bottom. I take the wrapping off and my roommate comes in and gawks at the mutated salsa container. Then it just explodes. The cap flies off (found it behind my fridge), salsa splatters the entire kitchen, and I have a loud ringing in my ears for about 5 minutes... I don't understand how this happened, all I wanted were some chips and salsa... | askscience | {
"a_id": [
"c5nxbou",
"c5nxc7c"
],
"text": [
"When something starts to decompose, it releases gasses. So in the closed jar of salsa built up pressure. So when you released it all of the pressure released, Salsa was pulled along with the escaping gasses.",
"If your salsa was contaminated, bacteria could produce gasses which would build up in the container."
],
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} | I bought salsa the other day and it just exploded in my face when I took it out of the fridge... why...?
So I bought a combo of salsa and bean-dip at costco the other day. The bean-dip container was stacked on top of the salsa contained and the two were wrapped together with plastic wrap. Anyways, when I took the salsa and bean dip out of my fridge, two weeks after buying them, I noticed that the salsa was bulging from its top and bottom. I take the wrapping off and my roommate comes in and gawks at the mutated salsa container. Then it just explodes. The cap flies off (found it behind my fridge), salsa splatters the entire kitchen, and I have a loud ringing in my ears for about 5 minutes... I don't understand how this happened, all I wanted were some chips and salsa... | [
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1h72t4 | How to balance a centrifuge? | Doing an RNA extraction this morning, we were discussing the loading of a centrifuge. I suggested that we spread the tubes (even number) out as much as possible but another individual suggested that clustering them was better for the machine. I figured that by spreading them out the "stress" distribution would be equally split to all parts of the rotor but that is just my gut feeling. Perhaps as long as it is balanced, it is merely negligible?
What is the best way to load a centrifuge to minimize strain on the machine?
Here are the two example scenarios:
**EDIT: Better summary of the dilemma** [PIC HERE](_URL_2_) (modified from Stanford image below)
-
Colleague's suggestion: (_URL_3_)
My suggestion: (_URL_0_) and (_URL_1_)
Main comparison between the two views can be seen in the 4 tube example.
| askscience | {
"a_id": [
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"text": [
"There are now top level answers asserting all three possibilities with respect to balancing (spread is better, clustered it better and it doesn't matter) so I did a [quick Monte Carlo simulation](_URL_0_). It generates a million sets of 4 weights, calculates the resulting offsets in center of mass for spread vs. clustered and plots a histogram of the results. Blue is spread and pink is clustered.\n\nIt definitely makes a difference but I would say spread vs. clustered is not so cut-and-dry. Spread gives a higher expected offset but clustered has a longer tail so if your goal was to never exceed some fixed imbalance limit then spread could be better.",
"If the tubes are perfectly balanced it makes no difference, the net force is zero in each case. However, if the tubes are unbalanced then clustering them minimises the strain. You can see this by taking an example of balancing four tubes with masses of 1, 1, 0.5, and 1.5. In the limit of a rotor with a large number of spaces the two extreme cases are:\n\n1) arranging in a square\n\n2) clustering pairs next to (i.e. virtually on-top of) each other.\n\nIn case 1 the mean net force for all possible arrangements is (0.85v^2 )/r. For case 2 it is (0.5v^2 )/r.\n\nI think this is right, but would welcome corrections. :)\n\nedit: I should say that if you're balancing the tubes to within the design tolerance, it should make absolutely no difference to the rotor lifetime - they're designed to be safe for a specified length of time when used within specs and then be retired.",
"I never really think about it because the counterbalancing in most centrifuges seem to deal with +-1 tube just fine. But, it would seem to me that spreading them out as much as possible (\"my\" not \"colleague's\" model) would be better. The rotor is probably solid enough that it won't break no matter how imbalanced it is. It's the drive shaft that I would worry about. If you add up all the imbalances between opposite pairs of tubes, it's going to sum to one angle along which there is imbalance. \n\nImagine you have six tubes. Within each pair of tubes that balance each other there is probably some tiny amount of imbalance (1 or 2 ul). So, there are three different vectors that point toward the heavier tube in each pair. If you have them spread out, the vectors will be more or less pointing in different directions and slightly cancel each other out. If you have them clumped, they might cancel each other out, or they might all point in the same general direction and cause a lot of imbalance toward one side. \n\nIn other words, if you have one imbalance going up to the right ( / ) and one going down to the right ( \\ ), they will cancel each other out vertically and result in a smaller horizontal vector ( - ). If they were both in the same direction, there's a 50/50 chance of them being parallel (and adding) or antiparallel (and canceling). And I would personally prefer to hedge every time than sometimes have no stress and sometimes have a lot. And I feel like physics and rotation and something increasing as the square of something would back me up, but I don't quite know if that's true.\n\nBut, if you're doing short runs for a miniprep or something, it matters much more how easy it is to keep track of your tubes. So just order them in whatever way it's easiest for you.",
"Attach an accelerometer to the centrifuge and watch it's output on an oscilloscope. The configuration that minimizes the peak is best. I have to think the tubes should be distributed as uniformly as possible. I don't have any experience with lab centrifuges but I specialized in machinery vibration analysis for 30 years.",
"I suspect clustering them as your colleague suggests balances the rotor while minimizing the influence and any one tube's weight difference in comparison to the other tubes, since each weighted point has a higher overall weight."
],
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"url": []
} | {
"url": [
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"http://www.ars.usda.gov/sp2userfiles/ad_hoc/19000000SafetyHealthandEnvironmentalTraining/graphics/CenBalance3.jpg",
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]
} | {
"url": [
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} | How to balance a centrifuge?
Doing an RNA extraction this morning, we were discussing the loading of a centrifuge. I suggested that we spread the tubes (even number) out as much as possible but another individual suggested that clustering them was better for the machine. I figured that by spreading them out the "stress" distribution would be equally split to all parts of the rotor but that is just my gut feeling. Perhaps as long as it is balanced, it is merely negligible? What is the best way to load a centrifuge to minimize strain on the machine? Here are the two example scenarios: **EDIT: Better summary of the dilemma** [PIC HERE](_URL_2_) (modified from Stanford image below) - Colleague's suggestion: (_URL_3_) My suggestion: (_URL_0_) and (_URL_1_) Main comparison between the two views can be seen in the 4 tube example. | [
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2k4qhp | How does reCAPTCHA work, now that it only shows a single image? | Recently reCAPTCHA has started showing only a single image; house numbers. But how can that act as a CAPTCHA unless they already know the number? | askscience | {
"a_id": [
"clk51p3"
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"text": [
"Most probably they're showing the new images to a certain amount of people (50 should suffice) and treat every answer as incorrect and have them prove the validity of their first answer by making them answer a well-known image next.\n\nThis would mean that after those 50 displays of the new image, you'll end up with the correct answer having by far the most votes, which means you can now treat this image as a well-known image and have more people further confirm the correct value.\n\nDisclaimer: This is just an idea, I have no idea if they really work like this :)"
],
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} | How does reCAPTCHA work, now that it only shows a single image?
Recently reCAPTCHA has started showing only a single image; house numbers. But how can that act as a CAPTCHA unless they already know the number? | [
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142fl6 | Is there such a thing as 'cognitive atrophy'? | From what I understand, the term 'atrophy' refers specifically to the decline in condition of the body, either by way of disease or lack of use. Are cognitive functions subject to a similar process with regards to lack of use or 'exercise' leading to a decline in their functionality and if not, why not?
Thanks. | askscience | {
"a_id": [
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"text": [
"> Are cognitive functions subject to a similar process with regards to lack of use or 'exercise' leading to a decline in their functionality and if not, why not?\n\nThey are, but the use of the term \"atrophy\" is somewhat misleading here. Cognition is largely dependent on the connections between neurons in the brain that occurs through regulation of synaptic connections. When two neurons communicate they are able to regulate the \"strength\" of that connection through the synaptic connections. When neurons communicate often, they can often increase their synaptic connections, making it easier for them to communicate, and that can be demonstrated by increases in a cognitive ability. To some degree, when certain neurons don't communicate as often, they decrease their connections, and that can be demonstrated by decreases in a cognitive ability. \n\nObviously this is overly simplified, and there are a VAST number of variables and conditions and factors that go into this, but yes, activity and inactivity of cognitive functions is thought to be in part related to ability."
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} | Is there such a thing as 'cognitive atrophy'?
From what I understand, the term 'atrophy' refers specifically to the decline in condition of the body, either by way of disease or lack of use. Are cognitive functions subject to a similar process with regards to lack of use or 'exercise' leading to a decline in their functionality and if not, why not? Thanks. | [
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awhz2f | What's the difference between slab pull and subduction? | askscience | {
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"Subduction is the process of a lithospheric slab (ie. a tectonic plate) sliding beneath a neighbouring tectonic plate and descending into the deeper mantle. Subduction zones are the regions in which this happens, often depicted as a 2-D slice [like the upper diagram here](_URL_1_), though we should remember that the edges of plates undergoing subduction are hundreds to thousands of kilometres long, creating arcs of ocean trenches and volcanoes which can stretch [across large sections of the planet](_URL_0_). \n\nSlab-pull is the negative buoyancy force transmitted to the rest of the plate by the downgoing slab as it subducts. To put it another way, the slab only started subducting because it was denser than the neighbouring plate, and this density is now causing gravity to pull the subducting slab further into the mantle, dragging the rest of the plate with it. \n\nSlab-pull is the dominant force driving plate motion, the other major one is ridge-push (sometimes called ridge-slide). At [mid-ocean ridges](_URL_3_) buoyant upwelling mantle comes close to the surface and partially melts to create new oceanic lithosphere. \n\nThe raised temperature and higher elevation at the oceanic ridge compared to the colder, more dense plate material further away causes gravity sliding such that the elevated terrain at the ridge pushes away the lithosphere that lies further out. This is the plate seeking to establish gravitational equilibrium. Ridge-push can drive plate motion by itself, though plates with subduction zones move much faster than those without. In fact there is a clear correlation between the speed at which a plate is moving and the length of its edges which are subducting. \n\nThe now classic paper which first sought to quantify such forces is [‘On the Relative Importance of the Driving Forces of Plate Motion’, Forsyth & Uyeda, 1975](_URL_4_) in which terms like ridge-push and slab-pull are introduced. A very brief and much more accessible summary of the forces acting on tectonic plates can be found in [this short animation from MinuteEarth](_URL_2_)."
],
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} | {
"url": []
} | {
"url": [
"https://i.imgur.com/B8xXd5m.jpg",
"https://i.imgur.com/UOe4k07.jpg",
"https://youtube.com/watch?v=kwfNGatxUJI",
"https://en.wikipedia.org/wiki/Mid-ocean_ridge",
"http://www.dynamicearth.de/Lectures/Tekto.SoSe12/Vorlesung/fu75.pdf"
]
} | What's the difference between slab pull and subduction?
| [
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12qc1z | How do the calorie counters on exercise machines (treadmills, ellipticals, etc) work? | Does this mechanism allow for accurate reflection of the calories used in the activity?
And going further, how are the values in tables like this determined? _URL_0_ | askscience | {
"a_id": [
"c6xdmwj",
"c6xda6e"
],
"text": [
"The device measures or estimates the amount of work done and then factors in the (substantial) loss involved as your body converts chemical energy into mechanical work done by muscles.\n\nThe accuracy of the measurement depends in part on the type of equipment. Something like a stationary bike can just directly measure the amount of energy put into spinning the thing, while a treadmill likely has to make more assumptions because the amount of energy expended depends on such factors as bodyweight and running technique.\n\nAnother component of the reading is your baseline energy expenditure and the extent to which it is elevated during exercise. That number is just an estimate because a direct measurement would be impractical.\n\nHeart rate monitors can also produce calorie estimates based on heart rate alone. It's a statistical model that takes inputs such as your age, weight, and fitness level and looks up a calorie count that typically corresponds to a given heart rate.",
"A calorie is a unit of energy, which is the potential to apply force over a distance. In a treadmill, you apply a force with your legs over a distance travelled on the treadmill which correspond to a certain amount of energy. This transfer of energy is not 100% efficient, and varies depending on on a lot of factors such as weight, technique and overall fitness. The calorie meter and the table you linked probably uses a statistical mean of how much energy an average person use."
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} | {
"url": [
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"url": []
} | How do the calorie counters on exercise machines (treadmills, ellipticals, etc) work?
Does this mechanism allow for accurate reflection of the calories used in the activity? And going further, how are the values in tables like this determined? _URL_0_ | [
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11mp5f | Are solitons required to move forward, or can they remain stationary? | Just a thought I had earlier, couldn't find anything on my own for about five minutes. | askscience | {
"a_id": [
"c6nujhr"
],
"text": [
"It depends what kind of solitons you are talking about.\n\nThe term soliton was originally applied to certain solutions of the Korteweg-de Vries equation, discovered by [Zabusky and Kruskal](_URL_4_), who coined the term soliton. These solitons necessarily are moving; their amplitude is proportional to their speed. For solitons arising from the non-linear interactions in systems like this, the solitons must be moving. However, there are some systems like this that have [stationary solitons](_URL_1_) or stationary [multi-soliton bound states](_URL_0_), but to the best of my knowledge, these are unstable (but if there's an expert out there who knows otherwise, please add that information). This meaning of soliton is explored [here](_URL_3_).\n\nThere are other objects called solitons, which you will see, for example, in field theory. Many of these are what are called [*topological solitons*](_URL_2_); these are stabilized by their structure rather than interactions (an analogy: if I put a loop on the side of a broom handle, I can shrink it to a point, in principle, whereas if I put the loop around the broom handle, it is prevented from shrinking down like that). Topological solitons do not need to be moving.\n\nThere are also non-topological solitons that arise in field theory that can be stationary. [Q-balls](_URL_5_) are field configurations that are stabilized by charge conservation, having a lower energy-to-charge ratio than the particles of a theory. These types of objects would be balls of matter, and could be stationary or moving, just like any other ball."
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"url": [
"http://people.physics.anu.edu.au/~nna124/Txt/bound3572.pdf",
"http://arxiv.org/pdf/hep-th/9604122v1.pdf",
"http://books.google.com/books/about/Solitons_and_Instantons.html?id=SGtKSgAACAAJ",
"http://www.scholarpedia.org/article/Soliton",
"http://prl.aps.org/abstract/PRL/v15/i6/p240_1",
"http://adsabs.harvard.edu/abs/1985NuPhB.262..263C"
]
} | Are solitons required to move forward, or can they remain stationary?
Just a thought I had earlier, couldn't find anything on my own for about five minutes. | [
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lnbq4 | Is there a scientific explanation for "game head?" | I'm sure that's not a technical term. Basically, my friends and I have a set of symptoms that we call "game head" that occurs after we have played a video game for too long. It's especially bad if the player is trying to fall asleep too soon after playing.
Symptoms can be headaches or blurry/blown out vision, twitching, and the most aggravating one is when you close your eyes, you see the game being played again, as if you were still sitting in front of your console/computer. It can be very realistic, especially when falling asleep, and cause spasms and twitches that keep you awake.
Aside from my handful of friends, I'm wondering if other people experience this, and if there are any physiological reasons for it? Is it purely psychological, and if so, why are the symptoms all the same with my friends? | askscience | {
"a_id": [
"c2udpi3"
],
"text": [
"I've also gotten that feeling where the game plays out in my imagination! It's really surreal -- every time I closed my eyes after playing Halo 3 ODST for six hours straight, I couldn't stop seeing the game."
],
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2
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"url": []
} | Is there a scientific explanation for "game head?"
I'm sure that's not a technical term. Basically, my friends and I have a set of symptoms that we call "game head" that occurs after we have played a video game for too long. It's especially bad if the player is trying to fall asleep too soon after playing. Symptoms can be headaches or blurry/blown out vision, twitching, and the most aggravating one is when you close your eyes, you see the game being played again, as if you were still sitting in front of your console/computer. It can be very realistic, especially when falling asleep, and cause spasms and twitches that keep you awake. Aside from my handful of friends, I'm wondering if other people experience this, and if there are any physiological reasons for it? Is it purely psychological, and if so, why are the symptoms all the same with my friends? | [
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11svfe | What causes the increased capacitance with decreased separation between plates? | I understand why potential difference relates to distance between plates, and that larger plates will mean more capacitance, but what is happening (on the atomic or ionic scale) to cause the capacitance to increase with decreasing distance? | askscience | {
"a_id": [
"c6pax8m",
"c6papyb"
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"text": [
"Capacitance is defined as charge per voltage. A large capacitance means that you can store a lot of charge per voltage, and a small capacitance means you can store very little charge per voltage. Further, in most cases the capacitance of a system is defined purely by its geometry, and it doesn't change depending on how much charge you have.\n\nIn general, the way to figure out something's capacitance is to imagine you have a certain charge Q+ on one plate and Q- on the other plate, and then calculate the voltage difference between the two plates. For your parallel plate capacitor, this calculation is fairly straight forward, as the voltage is just the electric field times the distance between the plates (or, generally, the integral over the E dot ds). Thus for Q+ and Q- a small separation between the plates will mean a smaller voltage compared to a large separation (the separation doesn't change the E field except on the edges of the plate). Therefore in the low separation case you can store the same amount of charge at a lower voltage, which is the definition of increasing your capacitance.",
"I like to think of Capacitance as \"the ability to store energy\"...larger capacitance means it can store more energy. If you take two plates that are oppositely charged, they are attracted to each other. The closer they are together, the more attracted they are to each other...which corresponds to more energy."
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} | What causes the increased capacitance with decreased separation between plates?
I understand why potential difference relates to distance between plates, and that larger plates will mean more capacitance, but what is happening (on the atomic or ionic scale) to cause the capacitance to increase with decreasing distance? | [
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18zb8q | Medicine: Everytime I see a billboard or an advertisement to get a colonoscapy I think "That's doing it wrong" | askscience | {
"a_id": [
"c8je9w4"
],
"text": [
"Good question\n\nFew people get colon cancer before the age of 50 which is why screening colonoscopies begin at 50. If you have a first degree relative who developed colon cancer it is recommended that you begin screening 10 years earlier than the age which the relative developed colon cancer. (Eg. If your dad got colon cancer at 48 you should begin screening at 38). These are recommendations from the USPSTF (United States Preventative Services Task Force) and not just a money making scheme by GI doctors. \n\nThe vast majority of colon cancers develop from a polyp and it can take 5-10 years for a polyp to develop and turn cancerous. This makes most colon cancers entirely preventable if a polyp is found and removed before it degrades into cancer. \n\nThere are other screening options but none of them have proven to have the same level of sensitivity of a physician skilled in performing colonoscopies. For example there is a camera that can be swallowed which will take pictures of the entirety of your GI tract as it travels through. You still have to go through a \"prep\" for this so that there isn't a lot of stuff blocking the view if the camera. Also, there is no guarantee that the camera will always be oriented correctly and it may miss part of your colon simply because it wasn't in the field of view. There is also a method where a CT scan is taken of the abdomen and 3D images are reconstructed from the data and you can visualize any polyps that have formed in the colon. This method is approved as a screening method for colon cancer in individuals with no history of polyps and is actually pretty sensitive for detecting polyps but it still has its drawbacks. First it s requires a \"prep\" to clean out the colon. It is more difficult to visualize the colon wall if there is still poop in there. Also it is more expensive and many insurance companies won't pay for it because it has not proven to be superior to colonoscopies. In addition it subjects the patient to unnecessary radiation exposure, a bigger problem the younger you are. A mutual drawback to these and other \"less invasive\" screens is what do you do if you see a polyp? The patient will still have to have a colonoscopy to remove the polyp which necessitates a second bowel prep and more downtime. In most cases it is better to be able to treat at the same time you do the exam. \n\nYou pretty much can't get around the inconvenience of a bowel prep and there is really good evidence that screening colonoscopies prevent cancer and save lives so you should look forward to that when you hit 50. For some fun look up the column where comedian Dave Barry writes about his experience preparing for a colonoscopy. \n\nHope that helps Mithryn."
],
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} | Medicine: Everytime I see a billboard or an advertisement to get a colonoscapy I think "That's doing it wrong"
| [
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63a10q | For PRBS3 with clock input on each gate, how can you work out the sequence? | I've seen them described on Wikipedia, but I don't understand the process of working out the states, and the order that they repeat in. | askscience | {
"a_id": [
"dft3ej0"
],
"text": [
"What Wikipedia describes as \"PRBS\", and only clarifies in half a sentence, are sequences generated by [Linear Feedback Shift Registers](_URL_1_). [1] (not exclusively, of course)\n\nYou'll note that what the \"PRBS\" page refers to as \"common sequence generating polynomials\" [2]:\n\n| \"PRBS\" | Feedback polynomial | Period |\n---|---|----\n| PRBS7 | x^(7)+x^(6)+1 | 127\n| PRBS9 | x^(9)+x^(5)+1 |511\n| PRBS11 | x^(11)+x^(9)+1 | 2047\n| PRBS15 | x^(15)+x^(14)+1 | 32767\n| PRBS20 | x^(20)+x^(3)+1 | 1048575\n| PRBS23 | x^(23)+x^(18)+1 | 8388607\n| PRBS31 | x^(31)+x^(28)+1 | 2147483647\n\nare, in fact, _[maximal-length polynomials for shift registers](_URL_2_)_.\n\nThe 'state' of a LFSR is simply the contents of the register. The arrangement of bits (of the register) which influences its (next) state are called _taps_. Let's imagine the simplest shift register with no feedback: it accepts an external input, pushes it to the MSB, shifts all the other bits to the right, and outputs the LSB. Now take that and instead of providing an external input, wire the input to one of the bits of the register, i.e. _internal_. You have the simplest feedback shift register!\n\nSchematically, a LFSR may look like [this](_URL_0_). Note you can apply arbitrary transformations to the taps, but why XOR?\n\nThe finite field with p*_n_* elements is denoted GF(p*_n_*) and is also called the Galois Field. GF(p) if p is prime is the _ring of integers modulo p_. In particular, we are interested in GF(2) (why?). In GF(2), addition without carry is equivalent to XOR. Therefore by XORing taps e.g. 2 and 5 of a register we are forming a polynomial, x^6 + x^3. This is termed the _feedback polynomial_.\n\nBy following the very simple operation of a shift register, coupled with a predefined feedback polynomial to provide its input, we form a LFSR.\n\nGenerating the sequences produced by any polynomial is actually quite simple: the Fibonacci construction (see wiki) is the simplest, and directly corresponds to the description above: read register state, substitute to the feedback polynomial, feed it to the input, shift, repeat. The Galois construction is a bit more involved, but it's also faster. If you want to generate the entire sequence by a given polynomial, you can use an [implementation](_URL_3_) of mine, like so (the link points to Python code, but there's a C implementation in there as well):\n\n In [1]: from lfsr import GLFSR\n \n In [2]: g = GLFSR(0x100009, 1) # 1 is the initial state. For maximal feedback polynomials, any state will do.\n \n In [3]: sequence = list(g.states())\n \n In [4]: period = len(sequence)\n \n In [5]: period\n Out[5]: 1048575\n\nTo test out whether \"PRBS3\" is maximal, let's produce it:\n\n In [17]: hex(0b1100) # x^3 + x^2 + 0*x^1 + 0*x^0\n Out[17]: '0xc'\n \n In [18]: g = GLFSR(0xc, 1)\n \n In [19]: sequence = list(g.states())\n \n In [20]: sequence\n Out[20]: [0, 0, 1, 1, 1, 0, 1]\n \n In [21]: len(sequence)\n Out[21]: 7\n\nand we've verified we produce all the states possible (~~2^(8) - 1~~ 2^(3) - 1).\n\n[1] I have never before encountered either the abbreviation \"PRBS\", or such a lax \"definition\" of it, and I strongly suggest you avoid that wikipedia page altogether and the term \"PRBS\" - not all pseudorandom binary sequences are generated from LFSRs, and the term has a much wider meaning\n\n[2] The characterisation \"common\" is inaccurate and very misleading: most of these sequences are not good for any but specialised or teaching applications, and it is more likely you will never find them in a production system. They're unsuitable for cryptography (they're a linear system and thus vulnerable to known cryptanalysis techniques), ECCs, they're possibly good for scrambling or noise generation (can't check, sorry) but even if they were I see no reason to label them as common. One reason is their period - some of them have too small a period to be good - but mostly their statistical properties like autocorrelation, etc."
],
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} | {
"url": []
} | {
"url": [
"https://upload.wikimedia.org/wikipedia/commons/1/16/LFSR-F16.gif",
"https://en.wikipedia.org/wiki/Linear-feedback_shift_register",
"http://www.newwaveinstruments.com/resources/articles/m_sequence_linear_feedback_shift_register_lfsr.htm",
"https://github.com/mfukar/lfsr/blob/master/lfsr.py"
]
} | For PRBS3 with clock input on each gate, how can you work out the sequence?
I've seen them described on Wikipedia, but I don't understand the process of working out the states, and the order that they repeat in. | [
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pfbpx | Just about every part of the body has a technical name, right? What's the back of the knee called, and how was it named so? | askscience | {
"a_id": [
"c3owsed",
"c3owszi"
],
"text": [
"It is called the Popliteal Fossa - the literal translation from Latin is 'knee depression'",
"It's called the popliteal fossa. It's from the latin poples which means the ham of the knee, and fossa means a pit which is from the latin meaning dig.\nIt's formed from the popliteal muscle of the leg.\n(I'm a med student)"
],
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} | Just about every part of the body has a technical name, right? What's the back of the knee called, and how was it named so?
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q0gmq | Just had an idea for a night readable e-ink reader (without a standard backlight or lighted cover). | So, a while ago I bought my wife a Kindle 3G. She loves it and I think it's pretty cool as well. I bought the lighted leather cover, and it works great, but I was wondering about the ability of having the text be illuminated internally - not with a backlight per se, but somehow lit without using a light shining on the surface.
I also bought a sample kit of glow paint from _URL_0_. One of the colors/phosphors is called "Super Phos Green". That stuff glows for hours. Like 12 hours. When I wake up in the morning, the jar is still glowing from the night before. It is faint, but it is glowing still.
Anyway, I was thinking, what if the e-ink spheres were composed of black/phosphor. The phosphor side would have a slight greenish-yellow cast, but not terrible. The e-reader would have two modes; day and night.
Day mode would be normal - white page and black text.
Night mode would be inverted - black pages and white/phosphor text.
The way it would work is that the e-reader - when switched to night mode - would temporarily transition to an all black screen, exposing the white/phosphor side to the LED backlight. The LED backlight would temporarily turn on and charge the phosphor, then turn off. The screen would then go to the inverted text mode, and the text would glow green. At each page turn, the screen would transition through an all black screen for just a second before going to the next page and the LED backlight would come on and recharge the phosphor.
I guess the LED backlight would deplete the battery more than normal mode, but less than using an LED light that has to be continuously on to read.
Anyway, what do you guys think?
I tried to post this to [/r/technology](/r/technology) but apparently no text posts are allowed. That's cool.
| askscience | {
"a_id": [
"c3tsd7x"
],
"text": [
"I assume there would be mechanical difficulties with combining screen types that way. But in theory, yes, it can be done."
],
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2
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} | {
"url": []
} | {
"url": [
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"url": []
} | Just had an idea for a night readable e-ink reader (without a standard backlight or lighted cover).
So, a while ago I bought my wife a Kindle 3G. She loves it and I think it's pretty cool as well. I bought the lighted leather cover, and it works great, but I was wondering about the ability of having the text be illuminated internally - not with a backlight per se, but somehow lit without using a light shining on the surface. I also bought a sample kit of glow paint from _URL_0_. One of the colors/phosphors is called "Super Phos Green". That stuff glows for hours. Like 12 hours. When I wake up in the morning, the jar is still glowing from the night before. It is faint, but it is glowing still. Anyway, I was thinking, what if the e-ink spheres were composed of black/phosphor. The phosphor side would have a slight greenish-yellow cast, but not terrible. The e-reader would have two modes; day and night. Day mode would be normal - white page and black text. Night mode would be inverted - black pages and white/phosphor text. The way it would work is that the e-reader - when switched to night mode - would temporarily transition to an all black screen, exposing the white/phosphor side to the LED backlight. The LED backlight would temporarily turn on and charge the phosphor, then turn off. The screen would then go to the inverted text mode, and the text would glow green. At each page turn, the screen would transition through an all black screen for just a second before going to the next page and the LED backlight would come on and recharge the phosphor. I guess the LED backlight would deplete the battery more than normal mode, but less than using an LED light that has to be continuously on to read. Anyway, what do you guys think? I tried to post this to [/r/technology](/r/technology) but apparently no text posts are allowed. That's cool. | [
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1kc6oi | Is it correct to describe a Scientific Theory as a "best guess?" | askscience | {
"a_id": [
"cbngtwc",
"cbngfdf",
"cbngjqe",
"cbngnec"
],
"text": [
"I think 'best guess' is a little too speculative. I prefer \"most likely explanation\".",
"no, it's just the consensus on the subject.\n\n[Karl Popper page on Standford encyclopedia of Philosophy.](_URL_0_)\n\nI suggest particularly the chapter about the \"demarcation problem\"\n\nwhat's a \"best\" explanation? how could you know it's the \"best\" one in advance? the empiric/scientific method is not guarantee enough in itself.",
"I believe the confusion comes from everyday use of the word theory, and scientific use of the word theory. I'll take the example of another r/askscience question.\n\nSay you notice a spider in the corner of your house, and each day you mop it's web up and place it in a bundle near the spider. Each day the spider has built a new web, and the old destroyed web has disappeared. A *guess*, or your hypothesis could be that the spider is perhaps eating it. This can be an educated guess - eating it might make sense to help preserve energy, but you don't have any proof of this. \n\nYou can test this *hypothesis*(notice in everyday language you would call it a theory) by filming the spider and seeing what happens. Upon viewing the tape, you see that it is eating the web. Your initial hypothesis has been proven correct, but you can still do further tests to see if the web is actually digested -radioisotope labelling etc, and help build more information about the nutritional information of the web, and how the spider uses the energy, how it gets reabsorbed etc. Eventually testing out multiple hypothesis helps build the case for a theory. All the pieces of information fit together, and you can test how they fit with other accepted theories such as evolution or calorimetry(energy of chemical reactions) through more testing. \n\nEverything you discover can add or detract from the theory, and if you get unexpected results you may have to adjust or re-write the theory completely.\n\nThis is why one experimental result can always destroy a theory, it may have new information that is totally incompatible with the theory you have been working with. An example often used to combat religious fundamentalists is finding a rabbit fossil in the Jurassic.\n\nThese fundamental theory destructions have occurred quite often throughout history, but as we have advanced scientifically with a more coherent understanding, they are becoming less common -because we are narrowing in on the truth; by testing more hypothesises!\n\nEach test you make adds to the likelihood that your theory is the correct one. Things like evolution have been tested and confirmed so many times that it really is a \"fact\". And that's where the importance of theories begins to become really useful - you can use the theory to make predictions - which means more educated guesses!",
"By all means ping me for laymen speculation however the tone of the question makes me think a plain English explanation may be in order.\n\n\n\nThe definition of a scientific theory will vary depending on who you ask. You are likely to run into a few common elements:\n\n1) It explains all of the data that we currently have to do with a particular topic ie it can explain the past.\n\n2) It can be used to make predictions about what will happen when experiments are performed ie it can predict the future.\n\nSo yes its a best guess but one that provides an explanation for data gathered in the past and which can be used to make falsifiable predictions about data we'll get in the future."
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"url": [
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} | Is it correct to describe a Scientific Theory as a "best guess?"
| [
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3g915i | What causes black outs in stormy days? | Hi askscience, today during a storm the lights in my town switched off a couple of times (and soon you could hear long-lasting thunders). Does it happen solely if a lightning hits electric pylons? Are there side effects which cause black outs? | askscience | {
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"Reposting a similar answer I made [here](_URL_0_)\n\n > It's usually a lightning strike or piece of debris falling on a power line. Either of these will create a fault condition and trip the circuit breakers at either end of the line. After a trip, breakers try to close back in to restore power. If a lightning strike caused the trip, the fault clears quickly and you experience a quick flicker. If a physical object, like a tree branch, fell on the line it might take a few moments for the current in the line to burn off the object, causing the temporary loss of power.\n\n > The re-closing of a circuit breaker is governed by a reclosing relay.Each relay is unique to the circuit it is on, but a typical one might close something like 0-15-45-95 seconds after a fault. If after the fourth attempt at reclosing, if the breaker still trips out, it will lock open. We assume that the line is either down or incapable of clearing the fault without our help. A maintenance crew will usually have to go to the station and reset the breaker once the line has been cleared by another crew.\n\nAs for side effects, the only thing I can think of off the top of my head that would cause blackouts is load shedding. Essentially, overloading the grid causes the frequency of the grid to drop. If the frequency drops too much, (about 0.5 hertz), we start load shedding to keep the whole system from collapsing. Load shedding typically involves deliberately tripping circuit breakers, chopping swaths of people from the grid. In the developed world, load shedding rarely if ever happens (I think Texas had rolling blackouts a few years ago) and results in huge fines and lots of paperwork for the power company involved.",
"Often, the high winds cause branches and trees to fall on power lines, breaking the line until somebody can go fix it. This is why power goes out even in storms without lightning (like snowstorms)"
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} | What causes black outs in stormy days?
Hi askscience, today during a storm the lights in my town switched off a couple of times (and soon you could hear long-lasting thunders). Does it happen solely if a lightning hits electric pylons? Are there side effects which cause black outs? | [
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5oerek | How can a habitable zone be defined? | Hello i hope im on right place for my question here. I know that the definition of a habitable zone is complicated and depending on many parameters like size and light of the sun. Atmosphere of the planet and lot of other things.
But what i wonder about can u not maximal definr how far a planet minimal have to be from the sun?
How is it possible to say anything about maximal distance? I mean isnt biggest part of earths temperature coming from its core? Wasnt earth one a pure hot lava planet? Couldnt there be just some planet with a hoter core then earth which no mather how far from its sun provides itself with heat from its core and reaches just perfect Temperature conditions for liquid water by its own? Or a planet with heavy continous vulkano activity allowing some areas on the planet to be constandtly in that tempersture lebel thanks to magma? Would be happy to get some explanation why for example there couldnt be a hot planet as far from sun as pluto. | askscience | {
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"The typical modern definition of the habitable zone is simply the region around a star where liquid water can form on the surface given the brightness of the star and the distance from it. Too close and the water is too hot to be liquid. Too far and the water is ice. To a good first approximation, for a planet with an atmosphere, this \"Goldilocks's zone\" is really all that matters for whether or not liquid water is on the surface. The heat coming from the interior of the planet is usually very negligible, at least for planets like the Earth. For example, [here is a graphic comparing the different sources of heat flow onto the Earth's surface](_URL_0_).\n\nNow, you are right to think that perhaps we may find a planet in the habitable zone that can't sustain liquid water because its' core is too hot or it has too much volcano activity. Unfortunately, modern telescopes can't tell us that yet!"
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} | How can a habitable zone be defined?
Hello i hope im on right place for my question here. I know that the definition of a habitable zone is complicated and depending on many parameters like size and light of the sun. Atmosphere of the planet and lot of other things. But what i wonder about can u not maximal definr how far a planet minimal have to be from the sun? How is it possible to say anything about maximal distance? I mean isnt biggest part of earths temperature coming from its core? Wasnt earth one a pure hot lava planet? Couldnt there be just some planet with a hoter core then earth which no mather how far from its sun provides itself with heat from its core and reaches just perfect Temperature conditions for liquid water by its own? Or a planet with heavy continous vulkano activity allowing some areas on the planet to be constandtly in that tempersture lebel thanks to magma? Would be happy to get some explanation why for example there couldnt be a hot planet as far from sun as pluto. | [
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1k85hx | What's the equation in today's Google Doodle? | Today's google doodle has a picture of Schroedinger's cat with some sort of equation in it. What is this equation? | askscience | {
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"If it's [this](_URL_0_) then it's showing that the quantum state of the cat is (alive + dead)/sqrt(2) meaning that there's a 50/50 chance that the cat will be observed alive or dead."
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Today's google doodle has a picture of Schroedinger's cat with some sort of equation in it. What is this equation? | [
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1dumkt | Is there any evidence to support the idea that forbidding something only increases the desire for that something? | Was thinking about the behavior of children and also reading some stuff about prohibition and this idea is recurring but seems reasonable and absurd at the same time. | askscience | {
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"Yes. The underlying psychological phenomenon is called [*reactance*](_URL_0_), and it's [well documented](_URL_0_#References)."
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} | Is there any evidence to support the idea that forbidding something only increases the desire for that something?
Was thinking about the behavior of children and also reading some stuff about prohibition and this idea is recurring but seems reasonable and absurd at the same time. | [
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8egg6q | How does a doctor determine "you have a 5% chance of living" or x% chance of walking again, seeing again, and so on? | askscience | {
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"It's based on statistics of similar cases. \n\nIn medical research, a cohort is a group of patients who are experiencing similar symptoms, which may be monitored over a period of time. Detailed patient data and biological samples are usually obtained by all the patients, and analysed for trends.\n\nWhen a doctor diagnoses a specific case, they will compare symptoms and physiological characteristics with people in those cohorts. That will give them a good indication on how your disease or condition will progress. \n\nOf course, this is not a precise method there could be many characteristics missing from the diagnosis.",
"As a recent recipient of such a discussion, and having spent some time with the primary literature as a result, a doctor will seldom talk of \"chance of living\" but is more likely to say \"survive beyond 5 years\". This partly reflects the difficulties of funding followup studies of massively extended duration, and partly, I guess, the accumulating random factors over time that might effect the prognosis.\n\nBut in general, unless you are 'lucky' enough to be the first sufferer and have a condition named after you, or you are one of the first trialists of a radical new treatment that is destined to revolutionise survival rates for your condition, the estimates you get will be based on statistical analysis of the fates of all your predeccessors with similar conditions."
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l4s0b | How would I go about testing and documenting a theory/hypothosis without being a scientist? | I have theory ( food and health related) and I would love to do an official study with proper sample sizes, but I'm not a scientist, nor am I a student. I don't have the money or the resources to do such a study. What are some of my options. | askscience | {
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"One option is to contact a research centre at a local university/hospital/etc that performs research in the particular field, and attempt to get them on board. Unless it is blindingly obvious that your study would be beneficial, you will want to be extremely well prepared to have any chance of convincing them. Visit libraries/universities and do a thorough literature review so you have the necessary background knowledge to discuss the study at the level that will be expected from the researchers.\n\nResearch centres are approached often by non-academics with ideas, so you need to be thoroughly prepared, well-versed in the topic, and convincing to separate your proposal from the \"chaff\". Be polite if they reject your proposal. Most research fields are small communities and you don't want to develop a reputation that may hinder your chances of collaboration in the future.\n\nUnderstand that even a feasible study with little possibility of generating revenue via grants, etc or much recognition in the field is likely to be rejected. Resources are limited, and ultimately the centres have to channel their available resources into studies that keep the doors open."
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} | How would I go about testing and documenting a theory/hypothosis without being a scientist?
I have theory ( food and health related) and I would love to do an official study with proper sample sizes, but I'm not a scientist, nor am I a student. I don't have the money or the resources to do such a study. What are some of my options. | [
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1ixmdz | What is the significance of placing a grounding pad close to radiofrequency signals? |
I originally posted this in ELI5, but I'm hoping I can get an answer here.
I work in a clinic, and one of our most common procedures involves radiofrequency ablation of nerves. We essentially burn the nerve using this machine, which sends electrical signals into a wire and lesions the designated nerve at x degrees (usually around 80 degrees C). We always attach a grounding pad to the patient before each procedure. The physician also prefers that we place the grounding pad close to the site where the radiofrequency ablation will take place. I asked her why once, and she just said it created a more effective burn if the grounding pad was closer to the site of interest.
Can someone explain to me what the purpose of a grounding pad is, and why a radiofrequency ablation is more effective if the pad is close by? | askscience | {
"a_id": [
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"text": [
"The ground pads serve as the return path for the RF current. I would guess you'd want them close to the active electrode to minimize the distance the return current has to travel through the body.\n\nThis also likely minimizes the load impedance that the RF source sees, increasing the amount of power drawn.",
"RF systems must be examined via the theory of [transmission lines](_URL_0_). An RF signal, at any place, requires a ground against which its value has a meaning, at all places in the circuit. For a 200 MHz 3 V peak to peak wave, we may momentarily have a value at some place of 3V with respect to the 0V ground, [which is typically very close by](_URL_1_).\n\nAn effective ground in an RF system is necessary for one to have any control of the path of an RF signal at all. \n\nIf the ground in place is ineffective (or has loops), the RF may do just about anything. \n\nIn that case, it will not adhere to the tissue you want it to. You require that the RF passes through some particular region."
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"url": []
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"https://upload.wikimedia.org/wikipedia/commons/thumb/4/4d/Transmission_line_symbols.svg/220px-Transmission_line_symbols.svg.png"
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} | What is the significance of placing a grounding pad close to radiofrequency signals?
I originally posted this in ELI5, but I'm hoping I can get an answer here. I work in a clinic, and one of our most common procedures involves radiofrequency ablation of nerves. We essentially burn the nerve using this machine, which sends electrical signals into a wire and lesions the designated nerve at x degrees (usually around 80 degrees C). We always attach a grounding pad to the patient before each procedure. The physician also prefers that we place the grounding pad close to the site where the radiofrequency ablation will take place. I asked her why once, and she just said it created a more effective burn if the grounding pad was closer to the site of interest. Can someone explain to me what the purpose of a grounding pad is, and why a radiofrequency ablation is more effective if the pad is close by? | [
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1cwzkj | Why do bases feel soapy or slippery (other than the fact that soap is basic of course). | askscience | {
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"text": [
"When you touch a base it the fats in your skin to produce similar detergent compounds found in soap. Bases literally turn you into soap when they touch you. You are merely feeling the soap your skin has become."
],
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} | Why do bases feel soapy or slippery (other than the fact that soap is basic of course).
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2vhbhy | How do you round a number like 1.4999...? | I've always been taught that when rounding numbers, if the following number is 5 or higher you round up, and if it's 4 or lower you round down. So if I had the number 1.5 and I want to round to whole integers I would round up to 2, and if I had the number 1.4 I would round down to 1.
But what if I look at the number 1.4999..., with infinitely recurring 9's? The number following is a 4, so I should round down to 1. But isn't 1.4999.... equal to 1.5, in the same way that 0.999... is equal to 1? If so why are my two outcomes of rounding different, while the number is the same? | askscience | {
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"> But isn't 1.4999.... equal to 1.5, in the same way that 0.999... is equal to 1?\n\nYou answered your own question here. Such a number with a repeating decimal is equivalent to 1.5. So using your scheme, 1.4999... would round to 2.0 just like 1.5 would round to 2.0.\n\nJust remember, rounding is a human construct, a useful mechanic system to simplify numbers, losing accuracy, but gaining efficiency, or truncating false accuracy in favor of representing uncertainty.",
"The mathematical meaning of rounding is the following : if you have a number x, you will take \"the closest integer to x\".\n\nSo if x < 1.5 then you round down to 1, and if x > 1.5 then you round up to 2. \n\nFor numbers that are not equal to 1.5, looking at the first digit (in base 10) is sufficient to tell you on which side you are. So that gives you the \"first digit rule\". But the important thing is that it should not be confused with the definition of rounding (that works whatever the base)\n\nBut the problem is that \"the closest integer to x\" is not well-defined when x is exactly equal to 1.5. So as a *convention*, we said that 1.5 should be rounded up to 2. Note that it's just a convention. It does not break the \"first digit rule\" when we write it like that. \n\nHowever, as you said it breaks the rule when we write this number as 1.4999... But obviously, we could not have a \"first digit rule\" that would work for both representations. \n\n\nSo the rounding of 1.4999... is 2 by convention. It does not work well with the \"first digit rule\", but the rule should not be confused with the mathematical operation (taking the closest integer), which is not well-defined for 1.5.",
"As an additional question, if we scrap the repeating 9's and say the number is just 1.49, should that be rounded to 2?\n\nIn middle school, I would have assumed we round it to 2 because the the 9 makes the 4 round to 5, making the entire number round to 2. However, if we actually look at the .49 as clearly less than .5, it should round down, making the whole number round to 1.\n\nWould I be right in saying the latter is the correct way? I never actually had this clarified to me by any teacher/professor despite being in multivariable calc at the moment. One of those elementary things that just kinda gets neglected."
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} | How do you round a number like 1.4999...?
I've always been taught that when rounding numbers, if the following number is 5 or higher you round up, and if it's 4 or lower you round down. So if I had the number 1.5 and I want to round to whole integers I would round up to 2, and if I had the number 1.4 I would round down to 1. But what if I look at the number 1.4999..., with infinitely recurring 9's? The number following is a 4, so I should round down to 1. But isn't 1.4999.... equal to 1.5, in the same way that 0.999... is equal to 1? If so why are my two outcomes of rounding different, while the number is the same? | [
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rj9qe | Looking for a good metaphor for the blood vessels organisation | Hi Reddit,
I remember John Dorian explaining that the blood vessels have an organisation analog to tree branches. As this metaphor doesn't include anastomosis, I am trying to find a more precise one.
I thought of "the way a river flows", but the circulation is the other way around (I am actually considering the arterial circulation).
What can you think of? | askscience | {
"a_id": [
"c46b2ch",
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],
"text": [
"Nice objection to the tree analogy! I have two answers for you:\n\n[A strangler fig](_URL_0_) is a great example of a plant that can branch and re-fuse, all while getting smaller from a common trunk point. You can think of anastamoses in this way: connections between larger limbs as the larger limbs progress and send off smaller branches.\n\nAnother analogy is familiar to those driving across the USA. You are on a large freeway, moving fast, when you come upon a large-ish city (let's say... Kansas City) Suddenly, you have the option to exit the freeway (artery), which has lowered its speed limit progressively as more and more exits pass by. Each of these exits allow you to take many increasingly smaller roads (arteriolar highways, capillary city streets) while still only travelling in your original direction (eg, east to west) but, eventually, you make it back to the freeway (veins). If there's construction along any of the side roads, you can detour (anastamose) to a different one and continue on your way.",
"Rivers can branch both ways. In the upper course they have lots of small tributaries confluencing, in the delta they have lots of divergent channels. So rivers aren't a bad analogy to use."
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"url": []
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"url": [
"http://en.wikipedia.org/wiki/File:Strangler_fig_boulder_katandra.jpg"
]
} | Looking for a good metaphor for the blood vessels organisation
Hi Reddit, I remember John Dorian explaining that the blood vessels have an organisation analog to tree branches. As this metaphor doesn't include anastomosis, I am trying to find a more precise one. I thought of "the way a river flows", but the circulation is the other way around (I am actually considering the arterial circulation). What can you think of? | [
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2g92p9 | Why do people "declare" war? | Why don't they just attack the other? What is the reason to declare it? | askscience | {
"a_id": [
"ckgwm1s"
],
"text": [
"The act of war requires a legal reason. In medieval history this was known as casus belli. You couldn't just go to war with your neighbours without a valid reason otherwise you would be viewed as a tyrant in the eyes of third parties. Warmongering nations would often be victims of other nations to ganging up to stop their aggressive nature. \n\nExamples of valid casus belli include line of succession dispute, a religious crusade by the pope, \"peace keeping\", fighting on behalf of another nation for their independece, or defending against another nation. These days the general authority you have to submit casus belli to is the UN. If you don't give a shit about what other nations think of you (countries like NK), you can just attack them for the surprise advantage.\n\nThe problem is that in the modern world it is very difficult to mobilise forces without the potential target knowing you intend to attack. The advantages of declaring war are probably better than the impact of the surprise attack (the possible exception being acts of terrorism)."
],
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} | {
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} | Why do people "declare" war?
Why don't they just attack the other? What is the reason to declare it? | [
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rlcju | Constantly horny | askscience | {
"a_id": [
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],
"text": [
"Welcome to your wonderful teenage years! Don't worry bro, you'll settle down soon enough.",
"sounds like every 15 year old guy ever in the history of ever.."
],
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} | {
"url": []
} | {
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} | {
"url": []
} | Constantly horny
| [
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16cmyg | How can they call KOI 172.02 a "Super-Earth" already? | askscience | {
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"Well, there are really only two types of planets; rock and gas. And of the rocky bodies you either have liquid water or not. So if something is a large rocky body with the chance for liquid water then it's about as close to Earth in terms of definitions as you can get. Where you might be going wrong is in your assumption that 'Earth' means just like Earth, in any scientific context it really just means rocky body with water."
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} | {
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} | How can they call KOI 172.02 a "Super-Earth" already?
| [
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xzqsa | I was musing yesterday and caused a debate I hope /r/askscience can help me with. Can Usain Bolt, out accelerate a car? | Ok, obviously everyone's been discussing Usain Bolt's feats of awesomeness the last few days and I innocently asked if anyone thought he could out accelerate an old banger which sparked a massive debate between people who just don't know enough science and maths to prove it either way.
So my question is this, would Usain Bolt manage to outrun an old car (of your choice) over 100 metres? And if this is possible could he do it over 200 metres? If he loses in the 200 metre race at what point does the car overtake him?
Thanks guys | askscience | {
"a_id": [
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"For Bolt to beat a car to 100 meters that car has got to be about dead. Bolt's best time to 100 meters is 9.58 seconds. That's an average speed of 23.3 MPH, which is obviously very impressive. But any car that's only managed to average 23 MPH after almost 10 seconds of acceleration is in very bad shape.",
"Based on 20m splits from [Sports Scientists](_URL_1_) His maximal acceleration is the first 20 meters, from 0-25km/h in 2.89 seconds. This works out to ~2.4m/s^2. \n\nBased on [0-60 Times](_URL_0_) the acceleration of a 1985 civic is 0-96kmh in 11.8 seconds. That works out to 2.25 m/s^2. \n\nSo yes. At least for the first 20 meters.\n\nAs for your actual question, He would be passed before 100m was up. At 2.25 m/s^2, it takes 9.428s for the car to finish 100m. So no, the car would still win."
],
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"url": []
} | {
"url": []
} | {
"url": [
"http://www.zeroto60times.com/Honda-Vtech-0-60-mph-Times.html",
"http://www.sportsscientists.com/2009/08/analysis-of-bolts-958-wr.html"
]
} | I was musing yesterday and caused a debate I hope /r/askscience can help me with. Can Usain Bolt, out accelerate a car?
Ok, obviously everyone's been discussing Usain Bolt's feats of awesomeness the last few days and I innocently asked if anyone thought he could out accelerate an old banger which sparked a massive debate between people who just don't know enough science and maths to prove it either way. So my question is this, would Usain Bolt manage to outrun an old car (of your choice) over 100 metres? And if this is possible could he do it over 200 metres? If he loses in the 200 metre race at what point does the car overtake him? Thanks guys | [
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avf11x | Does every part of us become replaced over time? | askscience | {
"a_id": [
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"text": [
"Everything, except stable cells that don't actively divide: nerve, muscle, ligaments, cartilage undergo constant division. The cells with the highest turn over rate are our skin cells, and the lining of our gastrointestinal tract."
],
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} | {
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} | Does every part of us become replaced over time?
| [
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2u4cvd | What is beyond the observable universe? Or at least what physicians expect there? | Also if we travel at speed of light at the edge of big bang , can we reach the beyond the observable univerce? | askscience | {
"a_id": [
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"co5focs"
],
"text": [
"Physicists* physicians are doctors. \n\nThe stuff outside the observable universe is expected to be the same as the stuff in it. \n\nThere is no edge of the Big Bang. \n\nYou can't travel out of your observable universe.",
"Physicians are probably just a flummoxed as everybody else."
],
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} | {
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} | What is beyond the observable universe? Or at least what physicians expect there?
Also if we travel at speed of light at the edge of big bang , can we reach the beyond the observable univerce? | [
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12h9a0 | How much energy is in Sandy from a perspective of rotational momentum? | I asked this [yesterday](_URL_0_ "yesterday's attempt") of /r/backoftheenvelope. It had support/interest, but no responses, so now I askscience:
> Apparently some in Iran and Syria think that [Sandy is due to Iran's advanced technology](_URL_1_ "Imagine the power required!"). I think that's delusional, but it got me wondering...
How much energy is in Sandy due to the rotational momentum of all that rotating mass? (i.e., water, air)
I suspect the amount of energy required to set all that mass a-spinnin will dwarf the amount of energy humanity has ever used. | askscience | {
"a_id": [
"c6v2f2s"
],
"text": [
"From Wikipedia:\n\n > Scientists estimate that a tropical cyclone releases heat energy at the rate of 50 to 200 exajoules (10^18 J) per day, equivalent to about 1 PW (10^15 watt). This rate of energy release is equivalent to 70 times the world energy consumption of humans and 200 times the worldwide electrical generating capacity, or to exploding a 10-megaton nuclear bomb every 20 minutes.\n\n[source](_URL_2_)\n\n[NOAA Answer to a similar question](_URL_0_)\n\nEDIT: See also, this wikipedia page on orders of magnitude re. energy (scroll down in the table to 10^19 J):\n\n[Orders of magnitude](_URL_1_)\n\nYou'll see that the total energy released in 1 day by a single hurricane is on a par with the annual electrical consumption of the entire planet in 2008. It would be simply ridiculous to try and claim that anyone on this planet possesses the technology to cause anything like Sandy. It just isn't possible."
],
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} | {
"url": []
} | {
"url": [
"http://www.reddit.com/r/BackoftheEnvelope/comments/12eizn/how_much_energy_is_in_sandy_from_a_perspective_of/",
"http://www.cnn.com/2012/10/31/world/meast/syria-sandy-facebook-claim/index.html"
]
} | {
"url": [
"http://www.aoml.noaa.gov/hrd/tcfaq/D7.html",
"http://en.wikipedia.org/wiki/Orders_of_magnitude_%28energy%29",
"http://en.wikipedia.org/wiki/Hurricane#Mechanics"
]
} | How much energy is in Sandy from a perspective of rotational momentum?
I asked this [yesterday](_URL_0_ "yesterday's attempt") of /r/backoftheenvelope. It had support/interest, but no responses, so now I askscience: > Apparently some in Iran and Syria think that [Sandy is due to Iran's advanced technology](_URL_1_ "Imagine the power required!"). I think that's delusional, but it got me wondering... How much energy is in Sandy due to the rotational momentum of all that rotating mass? (i.e., water, air) I suspect the amount of energy required to set all that mass a-spinnin will dwarf the amount of energy humanity has ever used. | [
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rghs9 | Curious about evolution, mind vs body | I have a question about human evolution that seems to me to resemble the old adage of the chicken and the egg.
Would the human brain have evolved first and "built" a body to defend it or would the "mindless" body have evolved a mind to allow it to hunt/gather more effectively? | askscience | {
"a_id": [
"c45mfai",
"c45naur",
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],
"text": [
"Well you could say that the body developed first, since single celled organisms didn't have a nervous system (which is what the brain is part of). But the question doesn't make a lot of sense since they developed together.",
"Well first of all no complex animal is \"mindless.\" Our brains differ from other mammals only by degrees, not by some really fundamental divide, even if the difference in capability is large.\n\nEvolution works on the whole creature, and so mind and body are always going to be evolving as a combined unit. I suppose if I had to pick answer I would say the latter, since no creature can survive without an effective physical body, and obviously human levels of intelligence come very very late in the grand scheme of natural history. Specifically for us, we became bipedal and somewhat \"human\" before developing such things as tool use. But even later, once our ancestors were clearly the smartest creatures on the planet, they were much more physically imposing than the average person is today. Particularly the advent of farming has reduced the average size and muscle density of humans quite a lot in relatively recent human history. A fully grown male chimp, for analogy, can with ease lift a person over their heads and toss them.",
"You can't will evolution. I'm not 100% what you are asking but from what I can tell you are asking if \"humans\" got being brains then selected on their own to stand up right and all that. \n\nIf you look at early hominids you can tell they stand up right long before they use tools."
],
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} | {
"url": []
} | {
"url": []
} | {
"url": []
} | Curious about evolution, mind vs body
I have a question about human evolution that seems to me to resemble the old adage of the chicken and the egg. Would the human brain have evolved first and "built" a body to defend it or would the "mindless" body have evolved a mind to allow it to hunt/gather more effectively? | [
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14p0u6 | Some physics questions: spectra and blackbodies | What is the difference between a continuous spectrum and a discrete spectrum?
What is a blackbody?
I hate to be picky, but try explaining like I'm a third grader. I genuinely do not understand the concepts and the scientific explanations are NOT helping. | askscience | {
"a_id": [
"c7f3ujd"
],
"text": [
"A discrete spectrum arises from a process (such as atomic or molecular emission/absorption lines) which has specific values.\n\nA continuous spectrum (as arising from blackbody radiation or synchrotron emission) has values throughout the spectrum (or at least a certain segment of the spectrum).\n\n > What is a blackbody?\n\nAs you may already know, the atoms and molecules in matter are always bouncing and jittering around on microscopic scales. The hotter an object is, the faster those particles bounce around. However, they don't all move at the same speed, there's a spread. If I have, say, a tube full of some gas, then the speeds of the particles in that gas are described by a [Maxwell-Boltzmann distribution](_URL_0_) which can tell us what percentage of the particles have a certain speed.\n\nElectromagnetic radiation is created when a charged particle such as an electron or proton is accelerated. The particles in a gas, when they bounce off one another, cause some acceleration and release energy in the form of electromagnetic radiation. Since the particles have a variety of speeds, they release energy at a variety of wavelength (and hence at a variety of energies, since energy of an EM wave is proportional to 1/wavelength). The spectrum that is produced by such an object is known as a [blackbody spectrum](_URL_2_), because objects which we perceive as black tend to emit radiation that is more like a blackbody curve than light-colored objects.\n\nNow, no observed objects emit a perfect blackbody spectrum (Although black holes are hypothesized to do so through [Hawking radiation](_URL_1_), which is a whole other animal). Most object either do not have perfectly smooth temperature distributions, or they have emission or absorption lines. Molten metal is a pretty good approximation of a black body."
],
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} | {
"url": []
} | {
"url": []
} | {
"url": [
"http://en.wikipedia.org/wiki/Maxwell%E2%80%93Boltzmann_distribution",
"http://en.wikipedia.org/wiki/Hawking_radiation",
"http://www.globalchange.umich.edu/globalchange1/current/lectures/universe/blackbodyradiationcurves.png"
]
} | Some physics questions: spectra and blackbodies
What is the difference between a continuous spectrum and a discrete spectrum? What is a blackbody? I hate to be picky, but try explaining like I'm a third grader. I genuinely do not understand the concepts and the scientific explanations are NOT helping. | [
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1si6qb | How does a weld end up being stronger than the parent material? | What's the chemistry being the welding process that results in the weld being stronger than the parent material? Is it similar to a heat treating process? | askscience | {
"a_id": [
"cdxyla6"
],
"text": [
"Basically, the material the welding rods are made of has stronger properties (tensile strength, yield strength,...) than the material on which you are working. So, that part of the finished assembly will be stronger than elsewhere. This is a mechanical answer, on the chemistry side, I can't help."
],
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} | {
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} | How does a weld end up being stronger than the parent material?
What's the chemistry being the welding process that results in the weld being stronger than the parent material? Is it similar to a heat treating process? | [
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2pugx3 | How misleading is this product in science terms? | Look at this picture: _URL_1_
Source: [Kickstarter](_URL_0_) || [reddit thread](_URL_2_)
The toughness claims are questionable to me. If the creators claim it's really that tough, why did they have only **two of four** of the vehicle's (probably a pickup truck by the looks of it) wheels resting on their product, with the other two wheels on the floor? I speculated that part of the vehicle's weight is not resting directly on the product itself, and that the claim would be more believable if the creators demonstrated the user can literally park their vehicle on top of its product - as in, no wheels touch the ground directly.
I'm tempted to make a /r/shittykickstarters thread about it, but I would like to first know if the crush-proof claims are as credible as the creators claimed here. Thanks! | askscience | {
"a_id": [
"cn0bc5h"
],
"text": [
"Having a car sit on top of something and having a car drive on top of it are two very different things. It is the difference between statics and dynamics. Consider a baseball resting in your hand, now consider being hit in the face with a moving baseball, much different in terms of force. It is still fairly impressive, but this demonstration does not indicate how well the coffee maker would survive if dropped, which is a more likely situation than being driven over."
],
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3
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} | {
"url": []
} | {
"url": [
"https://www.kickstarter.com/projects/1217364508/the-coffeeboxxtm-the-worlds-toughest-coffee-maker?ref=nav_search",
"https://s3.amazonaws.com/ksr/assets/002/886/927/e25d02edf09c41cd5ff569485d48605f_large.png?1415656881",
"http://www.reddit.com/r/kickstarter/comments/2pp6a3/the_coffeeboxx_the_world%CA%BCs_toughest_coffee_maker/"
]
} | {
"url": []
} | How misleading is this product in science terms?
Look at this picture: _URL_1_ Source: [Kickstarter](_URL_0_) || [reddit thread](_URL_2_) The toughness claims are questionable to me. If the creators claim it's really that tough, why did they have only **two of four** of the vehicle's (probably a pickup truck by the looks of it) wheels resting on their product, with the other two wheels on the floor? I speculated that part of the vehicle's weight is not resting directly on the product itself, and that the claim would be more believable if the creators demonstrated the user can literally park their vehicle on top of its product - as in, no wheels touch the ground directly. I'm tempted to make a /r/shittykickstarters thread about it, but I would like to first know if the crush-proof claims are as credible as the creators claimed here. Thanks! | [
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vh5th | Can anyone tell me the name of this rock? | _URL_0_ | askscience | {
"a_id": [
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"c54ldp3"
],
"text": [
"Can you provide any more information? Where did you find it, how heavy is it, etc? More pictures might also help.\n\nThat being said it reminds me of a rock I once found which appeared to be porous obsidian. That had a similar structure but was more of medium-dark gray rather than the deep black the stone in your picture is. I really can't say for sure based just on the picture. Maybe someone with a better geology background will recognize it but more info would definitely help.",
"As entropy2057 said, we need some more info.\n\nI have seen graphite look like that, so if it doesnt mark paper I can't help you without maybe some more angles, where its from, etc."
],
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} | {
"url": []
} | {
"url": [
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} | Can anyone tell me the name of this rock?
_URL_0_ | [
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1v17jn | Could anyone explain me the Lennard-Jones potential? | No need to go too deep(studying pharmacy),it's a question on my physics exam and it's really giving me headaches. | askscience | {
"a_id": [
"cenq88x"
],
"text": [
"It's a way of describing interactions between neutral atoms or molecules. When the molecules are beyond a certain distance, there is a weak attraction when the positive parts of one atom attract the negative parts of another, and vice versa (dipole attraction). From the laws of electromagnetism, that attraction falls as the sixth power of distance. When they get too close to each other, there is a repulsive force basically due to the fact that two atoms can't occupy the same place. There isn't a set form for this repulsion, but it is often written as an inverse-twelfth power repulsion, which gets really big really fast as the radius gets small.\n\nSo a Lennard-Jones potential has a negative inverse-sixth-power attraction and a positive inverse-twelfth-power repulsion, with an equilibrium where the two cancel out."
],
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} | {
"url": []
} | {
"url": []
} | {
"url": []
} | Could anyone explain me the Lennard-Jones potential?
No need to go too deep(studying pharmacy),it's a question on my physics exam and it's really giving me headaches. | [
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35ypgu | Why do plumbing dielectric unions always fail? | I am a licensed plumber for 20 plus years. When I started, it was code to install dielectric unions everywhere in houses where copper connects to steel. every single union fails miserably by either leaking, clogging up completely, rusting to pieces with no water contact outside pipe or depositing rust in water.
The theory behind these is simple, you break the electrical continuity between steel and copper pipe in order to prolong the life of the pipes by stopping dielectric corrosion.
These fittings seem to cause dielectric corrosion, not stop it. and even if there is no steel touching the water, these fittings still make the water rust colored?
I am confused on what exactly is going on here can someone explain the science behind it?
furthermore, a dissimilar metal connection with a brass nipple seems to hold up perfectly between the two connections and there is zero dielectric corrosion at the fitting. brass and copper are close on the anionic scale. I dont understand why direct copper is so corrosive and brass which is 80% copper is not?
| askscience | {
"a_id": [
"cr9kb5e",
"cr9uoxt",
"cra54eg"
],
"text": [
"I hope someone answers this because I know exactly what you're talking about. I'm a GC for over 30 years and I've seen this countless times. It makes no sense. My own home has some brass to galvanized steel connections in the basement that I meant to change out years ago, but they are holding fine and give no sign of trouble. The connections are probably 75 years old. I've seen dielectric unions fail within 5 years. I really do hope someone can explain this.",
"Engineering physicist here. I have no experience with plumbing, what exactly is a dielectric union? Is is just a plastic fitting designed to break electrical contact, or does it have any other purpose?\n\nBasically, electrically insulating the two metals from each other is a good idea on paper, but will probably fail in reality. If there is any indirect electrical contact between the steel and copper, such as through the earth, the insulation will do nothing. If a kitchen tap is bolted to a steel sink, which is in contact with a stove which is electrically grounded, then it has electrical contact with the water mains in the earth, and the dielectric union will do nothing.\n\nI'm not sure why a brass nipple would work better though. Corrosion is quite easy to prevent with a sacrificial anode, often made from zinc. Galvanic corrosion will corrode the \"least noble\" metal first, i.e. the one with the lowest electrode potential, and zinc has lower potential than steel. Brass however has higher potential than steel, so the steel would still corrode first.",
"If ordinary brass (copper and zinc) is in contact with water, particularly if it is chlorinated, some of the zinc can leach into the water. To combat this, most brass used with potable water is Dezincification Resistant Brass (normally stamped CR, DZ or DZR). This type of brass includes tin in the alloy. \n\nTin forms a protective layer of tin oxide which helps to protect the zinc and prevent corrosion. Brass that is to be used in more corrosive environments is usually made with aluminium to form an aluminium oxide layer for the same reason. Naval brasses for use on ships for example.\n\n[Wiki on zinc leaching.](_URL_0_)"
],
"score": [
8,
6,
2
]
} | {
"url": []
} | {
"url": []
} | {
"url": [
"https://en.wikipedia.org/wiki/Selective_leaching#Leaching_of_zinc"
]
} | Why do plumbing dielectric unions always fail?
I am a licensed plumber for 20 plus years. When I started, it was code to install dielectric unions everywhere in houses where copper connects to steel. every single union fails miserably by either leaking, clogging up completely, rusting to pieces with no water contact outside pipe or depositing rust in water. The theory behind these is simple, you break the electrical continuity between steel and copper pipe in order to prolong the life of the pipes by stopping dielectric corrosion. These fittings seem to cause dielectric corrosion, not stop it. and even if there is no steel touching the water, these fittings still make the water rust colored? I am confused on what exactly is going on here can someone explain the science behind it? furthermore, a dissimilar metal connection with a brass nipple seems to hold up perfectly between the two connections and there is zero dielectric corrosion at the fitting. brass and copper are close on the anionic scale. I dont understand why direct copper is so corrosive and brass which is 80% copper is not? | [
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ccmul7 | Is gluconeogeneses reproducible outside of a body? | My knowledge of chemistry is iffy so This may be a stupid question. I'm trying to write a sci fi book, and this question came up as I thought about what kind of alcohol people in this world I'm creating may drink. I decided the more complex the better so I want to know if it’s possible to make alcohol out of fish. So meat has no carbohydrates in it and you can’t directly make it into alcohol. I’m wondering if there is some sort of chemical wizardry to make enough carbohydrates from protein through gluconeogeneses to then turn into alcohol. And to do so on a large enough scale the gluconeogeneses would have to occur outside of a living organism. So, is it possible? | askscience | {
"a_id": [
"etphw2o"
],
"text": [
"I don't think your book will make much sense but yeah, it's possible to use non-carbohydrate substrates to form glucose.\n\n & #x200B;\n\n[_URL_0_](_URL_0_)\n\n & #x200B;\n\nThe process would be incredibly, and I stress incredibly energy/cost inefficient but it is hypothetically possible. Your reclaimation rate would probably be about 0.001% of gross feedstock input. You would have to extract and refine glucogenic amino acids from the fish and then have that undergo amino acid catabolism. There's nothing different between biochemistry and chemistry if you can reproduce the same circumstances. Your drunk fish/mermaid people are better off getting high off of hallucinogenic fish."
],
"score": [
6
]
} | {
"url": []
} | {
"url": []
} | {
"url": [
"https://en.wikipedia.org/wiki/Gluconeogenesis"
]
} | Is gluconeogeneses reproducible outside of a body?
My knowledge of chemistry is iffy so This may be a stupid question. I'm trying to write a sci fi book, and this question came up as I thought about what kind of alcohol people in this world I'm creating may drink. I decided the more complex the better so I want to know if it’s possible to make alcohol out of fish. So meat has no carbohydrates in it and you can’t directly make it into alcohol. I’m wondering if there is some sort of chemical wizardry to make enough carbohydrates from protein through gluconeogeneses to then turn into alcohol. And to do so on a large enough scale the gluconeogeneses would have to occur outside of a living organism. So, is it possible? | [
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xnvsz | Can someone help me with a mass as money analogy? | Recently while talking with a my kids I threw out this analogy; if the entire solar system's mass was $100, then the sun would be $99.99 and everything else would be $0.01.
I couldn't carry the analogy any further, but I'd like to. So...
If the solar system was $0.01, the Milky Way would be what?
And if the Milky Way was $0.01, the entire universe would be what?
| askscience | {
"a_id": [
"c5o4wie"
],
"text": [
"This is the sort of problem with which [Wolfram|Alpha](_URL_1_) can help.\n\nFor example, the mass ratio between the milky way and the solar system is [3x10^12](_URL_1_input/?i=mass+of+milky+way+%2F+mass+of+solar+system). So in your money analogy, if the solar system were $0.01 then the Milky Way would be $30 billion.\n\nSimilarly, the ratio between the observable universe and the Milky Way is [5x10^9](_URL_0_), so if the Milky Way were $0.01 then the observable universe would be about $50 million.\n\nObviously there's a lot of approximation in the mass of the observable universe and the mass of the Milky Way, but those are good ballpark figures."
],
"score": [
3
]
} | {
"url": []
} | {
"url": []
} | {
"url": [
"http://www.wolframalpha.com/input/?i=mass+of+observable+universe+%2F+mass+of+milky+way",
"http://www.wolframalpha.com/",
"http://www.wolframalpha.com/input/?i=mass+of+milky+way+%2F+mass+of+solar+system"
]
} | Can someone help me with a mass as money analogy?
Recently while talking with a my kids I threw out this analogy; if the entire solar system's mass was $100, then the sun would be $99.99 and everything else would be $0.01. I couldn't carry the analogy any further, but I'd like to. So... If the solar system was $0.01, the Milky Way would be what? And if the Milky Way was $0.01, the entire universe would be what? | [
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2hmoeb | Why do ECGs look the way they do during heart attacks? | _URL_0_
Considering the image above, for reference.
I can see that the electrical activity drops very suddenly before the depolarisation. Does this mean that electrical charge 'builds up' instead of being released as normal?
Also, the depolarisation wave looks a lot smoother and longer. Does this mean that the electrical charge lasts for longer, and that hyperpolarisation does not occur immediately? Is the heart in constant contraction during this phase - and is that what's meant by the heart 'stopping'? And why?
Also, is there a big difference between an ST-elevation and non-ST elevation heart attack?
Thanks a lot! | askscience | {
"a_id": [
"cku3oms"
],
"text": [
"Yes there is a big difference between ST and non-ST elevation myocardial infarcts (heart attacks)! The major difference is that ST elevation myocardial infarcts imply that the entire thickness (transmural) of the heart muscle dies as opposed to non-ST elevation infarcts where it is only partial thickness (usually subendocardial). More tissue damage=worse outcomes after the initial recovery and puts you at risk of specific complications (heart rupture, heart aneurysm, heart valve dysfunction)."
],
"score": [
2
]
} | {
"url": []
} | {
"url": [
"http://patienteducationcenter.org/wp-content/themes/default/image.php?image=243458"
]
} | {
"url": []
} | Why do ECGs look the way they do during heart attacks?
_URL_0_ Considering the image above, for reference. I can see that the electrical activity drops very suddenly before the depolarisation. Does this mean that electrical charge 'builds up' instead of being released as normal? Also, the depolarisation wave looks a lot smoother and longer. Does this mean that the electrical charge lasts for longer, and that hyperpolarisation does not occur immediately? Is the heart in constant contraction during this phase - and is that what's meant by the heart 'stopping'? And why? Also, is there a big difference between an ST-elevation and non-ST elevation heart attack? Thanks a lot! | [
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0.270182549953460... | |
1923h4 | Explain to me the science behind something I witnessed this morning in my water bottle | I'm not really well versed on science, so you'll have to be patient...
Last night I left a bottle of water in the freezer, I meant to take it out but forgot to. This morning (8 hours later) I went to the freezer to get the water. When I opened I saw to my surprise that it wasn't frozen solid as it usually is, it still seemed to be all liquid, even with bubbles. I took it out of the freezer and before my eyes, the clear liquid transformed into mushy opaque solid (with around the consistency of snow cones).
Any explanations? | askscience | {
"a_id": [
"c8k4oq1"
],
"text": [
"You most likely experienced a [supercooling](_URL_0_) phenomenon. This happens, simplistically, when the liquid has nothing to grab onto (a bit of dust, something like that) to form crystals or other ordered structure like ice. When you took it out, you probably agitated it enough that it found something to form crystals around, and those ice crystals are what you saw (they're like snow, of course).\n\nPretty cool that you watched it happen!"
],
"score": [
3
]
} | {
"url": []
} | {
"url": []
} | {
"url": [
"http://en.wikipedia.org/wiki/Supercooling"
]
} | Explain to me the science behind something I witnessed this morning in my water bottle
I'm not really well versed on science, so you'll have to be patient... Last night I left a bottle of water in the freezer, I meant to take it out but forgot to. This morning (8 hours later) I went to the freezer to get the water. When I opened I saw to my surprise that it wasn't frozen solid as it usually is, it still seemed to be all liquid, even with bubbles. I took it out of the freezer and before my eyes, the clear liquid transformed into mushy opaque solid (with around the consistency of snow cones). Any explanations? | [
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1.1906126737594604... |
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