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[
"How can medication increase or decrease the rate of metabolism?"
] |
[
false
] |
For a long time, I've had Hashimoto's hypothyroidism, which means my metabolism is unusually slow. I can sort of understand what that means, but I don't get how my medication could speed up my metabolism. How do medications change the rate of metabolism?
|
[
"I realize that I made a mistake in my above explanation.",
"One cause of Hashimoto's hypothyroidism is autoantibodies against the TSH receptor (again, there are multiple different autoantibodies that can cause Hashimoto's hypothyroidism). If, for example, we block the receptor that receives the message (TSH) telling the thyroid to secrete T3 and T4, it won't. Therefore, serum levels of T3 and T4 will be low and this causes low metabolic rate. ",
"One currently accepted treatment for Hashimoto's thyoiditis is, as you state, levothyroxine. ",
" This is because with loss of thyroid function, the pituitary gland in the brain produces more TSH to try and \"kick\" the thyroid into functioning. We don't want to elevate levels any higher by adding exogenous TSH because that might be dangerous. ",
"Some references in the Wikipedia article: ",
"https://en.wikipedia.org/wiki/Levothyroxine",
"Levothyroxine is a synthetic form of T4. If we administer T4 to ANYONE, Hashimoto's thyroiditis or not, it will do its job of relaying \"boost metabolism\" signals. The body can't tell the difference between T4 it produces and T4 we've synthesized in a lab and administered. \nWe do not give T4 to people WITHOUT Hashimoto's thyroiditis because that would cause something akin to Grave's disease, the condition mckinnon3048 describes. ",
"- ice "
] |
[
"The reason for this is because Hashimoto's hypothyroidism is caused by antibodies blocking TSH receptors",
"So the medication for this, a levothyroxine, would only work in this specific case? It doesn't necessarily increase the rate of metabolism, but it stops the factors that cause the original decrease?",
"In other words, the levothyroxine taken would only increase the metabolism rate for someone with Hashimoto's, and would only really negate the Hashimoto's. By itself, a levothyroxine cannot increase the rate of metabolism. Am I right?"
] |
[
"No you would treat the symptoms of it (low serum t4) the above example is basically saying if you had some other drug to replicate the hormone that stimulates T4 production. You could essentially ask the thyroid many more times for responce (it's be like calling with 7 phones at once when calling number ten wins to increase the chances of you're adage getting thru. In practice with that disease that doesn't work. ",
"I have the opposite condition. Graves' disease, my immune system was basically attacking the thyroid causing stored T4 to be released by destroying the cells containing it. I had it abated with radio iodine therapy and now take levothyroxine to replace the T4 my no longer existing thyroid would produce. \nAs for OP question, before they increased my levothyroxine dose to a more appropriate level after my thyroid had be destroyed, I gained 50lbs in 2 months and had basically no energy. The T4 stimulates most of your tissues to actually do their functions at a reasonable rate. (Endocrinologist said my basal rate went from 8500cal daily with serum levels 1000x higher than they should be, down to 1200 at my lowest once the full effect of the radio iodine had killed my thyroid tissue)",
"(Side note, the radio iodine they used therapeutically for me is the exact reason why after nuclear accidents they distribute iodine tablets, in the hope that by saturating the thyroid with stable iodine isotops it doesn't absorb any or many of the rapidly decaying harmful ones from the fission products. "
] |
[
"Planck's Constant isn't clicking for me. Could anyone explain it to a layman who has yet to go to college?"
] |
[
false
] |
I was watching a video ( ) on Heisenberg's uncertainty principle which was really interesting but the young man in the video didn't go in depth explaining the math behind the principle. He shows the formula, and that clicks in my head just find, but when I dug a little more to try and understand Planck's Constant which is used in Heisenberg's formula, nothing that I watched ( ) or read ( ) came together for me. So I was hoping that someone here could explain Planck's Constant to a 30 year old who is going to be a freshman in a few months and only has a foggy memory of how Algebra and Geometry works. Who's up for the challenge??
|
[
"It's the constant of proportionality between the energy and the frequency of a photon. It's kind of like how pi is the constant of proportionality between the circumference and diameter of a circle. For a circle we can write",
"C = pi D",
"Similarly, for a photon we can write",
"E = h f",
"Basically it's a number that you multiply the frequency of a photon by to figure out its energy."
] |
[
"I'll give the simple explanation, someone else can try to handle the more complex stuff.",
"Planck discovered that the energy of a photon is directly proportional to its frequency. The problem is that the units don't work out. Energy is in Joules, and frequency is in hertz. You need to stick some number into the formula so that you have",
"Energy [Joules] = something [Joules / hertz] * frequency [hertz]",
"And, since hertz are actually \"cycles per second,\" [Joules / hertz] is just [Joules * seconds].",
"That's how you get the ",
" for Planck's constant. The other problem is that the numbers don't line up correctly. Scientists do this all the time. They realize that they have an equation that makes sense, and the units line up, but the numbers themselves are off. You need some correcting factor, which happens to be ~6x10",
", in order for the units to be correct.",
"So, that's h. It's also often useful to talk about angular frequency instead of cycles per second, so we use ħ, the \"reduced Planck constant,\" which is just h/2pi. ħ is useful in wave equations like the Schroedinger equation (which is what the uncertainty principle is derived from), because angular frequency corresponds naturally to wave behavior.",
"edit: angular frequency, if you don't know, is useful when you're using trigonometric functions like sine and cosine. sine and cosine go through one cycle after 2pi radians, so if we want a sine function to go through one cycle every second, we use the angular frequency w instead of the \"regular\" frequency f, under the relation",
"w = f * 2pi",
"so, if I have a sine function dependent on time, and I want three cycles per second, I'd use",
"sin(6pi * t)"
] |
[
"Other comments are focusing on a particular aspect of h, but it shows up in several important roles. ",
"It relates the energy of a photon (E) to the frequency (f) of the associated electromagnetic wave. E = h*c. ",
"So, it's actually connecting the particle and wave nature of light. ",
"It also relates the momentum of a particle (p) to its ",
"de Broglie wavelength",
" (bl). bl = h/p. ",
"Here, it's connecting the particle and wave nature of matter. ",
"It's...weird to have a physical constant play different roles for different things. And, yeah, in any other situation that would be a serious problem. ",
"It turns out both these things grow out of a deeper, more significant meaning of h. ",
"h is the quantum (e.g. discrete value for) of the physical notion of ",
"action",
". ",
"Like some other things, 'action' in Physics has a different meaning than in everyday conversation. ",
"Action is important (like, fundamental) and hard to explain for the same reason: it touches on pretty much everything. So, I'll let the wiki article take over and stop here. "
] |
[
"What happens when a bruise heals?"
] |
[
false
] |
I understand that bruises are formed by small amounts of blood being released into the tissue beneath the skin, but where does that blood go as the bruise fades?
|
[
"The short answer is that a number of cells are recruited to “eat” and otherwise break down the debris, especially the erythrocytes, which are ultimately either recycled in part or excreted as waste after processing in the liver/spleen. In particular the “eating” is carried out by leukocytes which are recruited to the area via the inflammatory process. Depending on severity and location of the bruise there might be some residual staining from the liberated iron, but that will usually also fade with time in a healthy person."
] |
[
"To add on to others, the reason your skin tends to look yellow as bruises progress is because of biliverdin (green pigment)/bilirubin (yellow), 2 intermediate products in the breakdown process of the heme group, which is the iron-containing, red pigment, O2 carrying part of hemoglobin in red blood cells (RBCs).",
"This is in essence the same reason people with liver failure and hemolytic disease (diseases that destroy RBCs) tend to have yellowing of their skin and eyes (jaundice). Macrophage (big eater) cells in the spleen/liver eat and break down old RBCs, and the resulting bilirubin is conjugated into a soluble form and excreted in bile, which helps emulsify fats in your small intestine.",
"We can take this even further- the bilirubin is eventually converted by gut bacteria into stercobilin, which makes poop brown, and urobilinogen, which is partly reabsorbed and leaves through the kidneys as urobilin, which makes pee yellow. So as you can see, that heme group in hemoglobin responsible for coloring a lot of our fluids."
] |
[
"Bilirubin",
" is a brown/yellow compound produced by the degradation of hemoglobin. Various concentrations lead to various fading colours",
"Edit : see the answer of ",
"SadandFurious",
", it is much better"
] |
[
"Why do stars explode in an \"hourglass\" shape?"
] |
[
false
] |
I'm referring to picture for example. Why does the explosion go in two ways, why not just expand in every direction at the same speed?
|
[
"I'm not an astrophysicist (but I am a physicist), so I may be able to use some intuition to help you out here. Stars contain vast amounts of ionized gases called plasmas, where the heavy, positively charged nuclei of an atom are separated from the light, negatively charged electrons. Due to their differences in mass (nuclei are often thousands of times heavier than electrons) the motions of these particles are very different, and it is not uncommon for a plasma to become locally non-neutral, meaning that it has an overall electric charge.",
"When the surface of a star blows off in a nova, it can send vast streams of charged particles away from the surface at relativistic speeds. One thing we know from classical electrodynamics is that moving charges create magnetic fields, and the faster they go, the stronger these fields get. In the case of a stream of particles, the effect of the magnetic field is to focus the path of the particles into a single jet. This is known as the ",
"pinch effect",
"). Part of my research recently was studying the focusing power of semi-relativistic proton beams, so believe me, this is a real effect.",
"In the case of a star, I assume that it's these magnetic fields created by the moving plasmas and gases themselves which focus the blast into a semi-directed stream. As for why you have two streams going the opposite direction, the star needs to maintain conservation of momentum. So in its rest frame, it needs to throw off an equal amount of plasma in opposite directions in order to not break the laws of physics.",
"If a legitimate astrophysicist wants to come and explain it better, I'd be glad to be corrected."
] |
[
"I don't know the actual reason, but I'm pretty sure this part is incorrect:",
"As for why you have two streams going the opposite direction, the star needs to maintain conservation of momentum. So in its rest frame, it needs to throw off an equal amount of plasma in opposite directions in order to not break the laws of physics.",
"There's nothing wrong with one jet from a momentum conservation perspective, the star itself would just have to recoil. This is how rockets work."
] |
[
"Supernova remnants are usually quite irregular, as example ",
"the crab nebula",
" but when a non-super massive star (like our Sun) dies it just loses its outer hot gas layers into space, this is called later a Planetary Nebula, these hot gases expand following different kind of symmetries really basen on the initial conditions of the dying star like rotation speed, nearby stars, etc... The resulting nebula not exclusively takes your \"hourglass\" shape, but also are common ",
"spherical symmetries",
", ",
"irregular shapes",
", and ",
"totally awesome structures",
".",
"\nBTW those examples are IC3568, NGC6326 and NGC6543."
] |
[
"How well regarded is the concept of negative mass?"
] |
[
false
] | null |
[
"Hi SymphoDeProggy thank you for submitting to ",
"/r/Askscience",
".",
" Please add flair to your post. ",
"Your post will be removed permanently if flair is not added within one hour. You can flair this post by replying to this message with your flair choice. It must be an exact match to one of the following flair categories and contain no other text:",
"'Computing', 'Economics', 'Human Body', 'Engineering', 'Planetary Sci.', 'Archaeology', 'Neuroscience', 'Biology', 'Chemistry', 'Medicine', 'Linguistics', 'Mathematics', 'Astronomy', 'Psychology', 'Paleontology', 'Political Science', 'Social Science', 'Earth Sciences', 'Anthropology', 'Physics'",
"Your post is not yet visible on the forum and is awaiting review from the moderator team. Your question may be denied for the following reasons, ",
"/r/AskScienceDiscussion",
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" on asking questions as well as our ",
". Please wait several hours before messaging us if there is an issue, moderator mail concerning recent submissions will be ignored.",
" ",
" "
] |
[
"Physics"
] |
[
"'Physics'"
] |
[
"Is there anything particularly unique about the elements in the F block? Like the Lanthanides and the Actinides?"
] |
[
false
] |
[deleted]
|
[
"It depends what you mean by \"unique\" or \"interesting\".",
"The lanthanides don't have particularly high oxidation states -- usually +3, sometimes +2 or +4. The actinides can reach higher states.",
"The varying configurations in the f-electrons can make for some interesting magnetic and photophysical properties. Many phosphors and luminescent dyes are based on lanthanides."
] |
[
"In the lanthanides, the 4f orbitals are quite close to the nucleus, so they don't participate very much in chemical bonding in compounds. However, a partially filled 4f orbital has a huge magnetic moment, which is why the \"supermagnets\" are alloys (or intermetallic compounds) containing lanthanides. They can also be used for amplifiers or repeaters in optical fibre based telecommunication.",
"Even the pure elements can have very complex physical properties. For example, cerium has a \"volume-collapse transition\", a phase transition in the solid state where, upon cooling, the volume changes by about 15 % (!!!) iirc, because the 4f orbitals suddenly start to form a metallic bond.",
"The 5f orbitals in the actinides are more extended than the 4f orbitals in lanthanides, so they may or may not contribute to bonding. The actinides and their compounds can have very complex physical properties because the 5f electrons can, and often will, do whatever the hell they want. Chemically and physically, the actinides are quite different from lanthanides, in that e.g. often they can have different oxidation states, etc."
] |
[
"ooo ok"
] |
[
"What communicates the strength of an odor to the brain? The number of particles? Or some property of the particle itself?"
] |
[
false
] |
Unless I'm mistaken, I believe I read on this subreddit that the sense of smell is communicated through special receptors in the nose. What actually determines the signal that's sent by those receptors? The sheer number of particles in the presence of them or some property of the odorous particle itself? EDIT: alternatively, what determines the quality of smell? Fresh baked bread vs. rank garbage
|
[
"Number of particles. more particles = more receptors triggered = stronger smell."
] |
[
"What about theons (think I did that right), those in much smaller concentrations, and less amounts of particles, produce a very powerful odor?"
] |
[
"Certain odors are certainly more pungent or foul than others. That is probably more due to how our brain and smell receptors have evolved. Things that smell bad generally are bad for us to eat. So at one point, an ancestor species had a mutation that caused rotting waste to smell bad, and that ancestor was more successful at spreading its genes because it didn't die of poisoning."
] |
[
"Do trees die of old age?"
] |
[
false
] | null |
[
"The answer, of course, is sort of. Like another poster said, old age is technically a secondary cause. What happens when a tree gets old is that it can't protect most of its inner heartwood or exterior. It certainly does not fight damage as well. ",
"Woody plants heal through CODIT (",
"http://en.wikipedia.org/wiki/Compartmentalization_of_decay_in_trees",
") in four steps, called walls. This is originally from a study where a guy named Shigo axed a bunch of trees and watched them heal. ",
"The four walls are explained in the wiki, but I'll simplify it. ",
"Wall 1: the tree prevents the wound/infection from spreading up and down the tree by blocking the transport tubes on either side of the wound.",
"Wall 2: the tree prevents the wound/infection from spreading inward by building up a ring to act as a barrier",
"Wall 3: the tree prevents the wound/infection from spreading circularly by sectioning the wound laterally. This basically means the wound/infection can't spread left or right. After wall 3, the would should look like a piece of pie.",
"Wall 4: the new growth rings seal off the wound/infection so it doesn't spread outward, as the trunk grows.",
"So in old age, the trees lose the ability to compartmentalize their wounds and eventually die. When wall 4 fails, you'll find a standing tree with a hollow inside- it's not uncommon to see them with leaves still. But unless wall 4 has succeeded just in the nick of time, the tree will die soon.",
"Another way trees die is they girdle themselves because they get too big or something that is sucked up by the roots get caught in the xylem and phloem. Think of it as getting a piece of food caught in your throat. It slowly chokes and dies.",
"Girdling is also a cause of death from insects and beavers. Most animals and insects only eat the newest part of the tree, where the xylem and phloem channels are active. This area, just under the bark, is called the cambium. When this cambium is eaten, the tree has no way to pass water/food/nutrients up and down the tree, essentially starving.",
"When a tree is old enough for the bark to start falling off simple weathering is enough to damage the flow of food/water/nutrients and that is as close to dying of old age as a tree can get, in my experience.",
"Lastly, some trees literally have no ceiling of growth (redwood, white pine) except for when the atmospheric pressure prevents the tree from getting its food/nutrients/water to the roots or leaves. In this case, they eventually die because they weaken and can no longer transport at a functional rate.",
"As an edit: when trees get unhealthy, you'll see weird sucker sprouts along a normally bare stem, or lots of leaves in clusters in weird spots.",
"source: professional ecologist"
] |
[
"I remember in nursing school we read an article about how nobody dies of old age. People die from heart failure, cancer, etc (natural causes), or infection, trauma, and such. The article went on to follow cases of several people who lived into their 100s and who when died, baffled medical examiners, as they were unable to find a \"cause\" of death. I'm sure I have the article hidden somewhere in my room."
] |
[
"I remember in nursing school we read an article about how nobody dies of old age. People die from heart failure, cancer, etc (natural causes), or infection, trauma, and such. The article went on to follow cases of several people who lived into their 100s and who when died, baffled medical examiners, as they were unable to find a \"cause\" of death. I'm sure I have the article hidden somewhere in my room."
] |
[
"How can the gases (the structure) of the gas cloud Pillars Of Creation have such evident shadows and areas of brightness (E.g the top) when stars are everywhere shining on it?"
] |
[
false
] |
Edit: Friggin thing looks like it's backlit or something...
|
[
"Same reason it's brighter during the day than at night, even though around the same number of stars are shining on Earth at both times. The really close by ones outshine the others, and create areas of intense brightness. "
] |
[
"Exactly. In this ",
"full frame image",
" of the eagle nebula you can see the young blue star cluster that illuminates the pillars, which usually doesn't fit in the high magnification images."
] |
[
"Awesome visual - saved it too! This really gave me a great look into what ",
"/u/Rocket_stuff",
" was describing! "
] |
[
"Why are blue and red primary colors in both light (additive) and paint (subtractive) color mixing, yet yellow and green change status from one system to the other?"
] |
[
false
] |
Never really made sense to me, curious to know if it has something to do with the light wave properties or anything else
|
[
"To clarify a few things, the primary colors of light are red, blue, and green (the ",
"RGB model",
"), while the primary colors of pigmentation are cyan, magenta, yellow, and black (the ",
"CMYK model",
"). So it's not that red and blue retain their status in both models, it's just that magenta and cyan look a lot like red and blue.",
" This has to do with the biology of the eyes. Your retinas contain two types of photoreceptor cells (light sensors): ",
"rods and cones",
". Rods (~125 million in one eye) are very sensitive, but don't detect color. Cones (~7 million) can be divided into three types -- guess which? That's right: ",
". The stimulation of a combination of these cones give you all the colors of the rainbow. (red+blue=purple, red+green=yellow, etc.)",
" This has to do with the nature of pigments. You're not adding light together -- you're taking light away. Pigments take away colors from white light (which contains all the colors of the rainbow) and leave certain colors that get reflected into your eyes. So if a certain paint absorbs all colors except red, you perceive that paint as red. The primary colors in this case are the direct opposite of light.",
"Hope this helps!"
] |
[
"Just to clarify... the black is only there because its unfeasible to make perfect pigments so you end up with muddy dark brown unless you include a specific black ink. So it isn't inherent to the color model as much as it's just a hack to overcome technology issues. "
] |
[
"Just to clarify some more, the K in CMYK stands for 'Key', and it's primary role is to save money (one ink for text instead of three), and because it's hard to keep 3 inks in register (perfectly aligned), across a sheet of paper that moves and stretches as it rolls through a printing press and gains wet ink."
] |
[
"If there was an imaginary city called Alphabet city and all the buildings were made in the shape of letters?"
] |
[
false
] | null |
[
"F would be difficult too, as would P."
] |
[
"Z would be difficult also."
] |
[
"Ok so I'm thinking, not difficult but would they be impossible, like could we make a 100 story Z?"
] |
[
"Could entropy be measured on a scale or with units?"
] |
[
false
] |
For example, maybe a single movement of a single particle within a planck length or something similar?
|
[
"It depends on how you define entropy, in everyday thermodynamics, entropy has units of energy per temperature degree, for example Joules/Kelvin. However you don't have to treat entropy this way, you can recognize that the units energy per temperature degree represent a conversion factor, one you can simple ignore. This leaves you with dimensionless entropy. Either formalism works perfectly fine mathematically as long as you remember which one you're using.",
"If you're curious as to what entropy actual is, we'd have to discuss the matter further."
] |
[
"The fundamental definition of entropy is the logarithm of the number of accessible states; such a quantity is dimensionless (unitless)."
] |
[
"Well... typically entropy is defined as",
" = ",
" ln(",
")",
"where ",
" is the number of states and ",
" is the Boltzmann constant. So, in common use, entropy does have dimensions. This seems to have happened (historically) because there isn't a good way to experimentally link temperature to energy over a wide range. This caused temperature to have different dimensions from energy. Since temperature is defined as",
" = d",
"/d",
" has to have non-null dimensions for ",
" and ",
" to have different dimensions.",
"I do think ",
" having dimensions is silly though. ",
" should be dimensionless and the factor of Boltzmann's constant should be in the definition of ",
".",
"Of course, this is all dealing with entropy as used in physics. In a straight up information theory discussion entropy is dimensionless."
] |
[
"How exactly does alcohol damage dendrites in the brain?"
] |
[
false
] | null |
[
"Well alcohol consumption causes thiamine defficiency in a number of ways: ",
"-Inadequate nutritional intake: alcoholics tend to intake less than the recommended amount of thiamine",
"-Decreased uptake of thiamine from the GI tract: active transport of thiamine into enterocytes is disturbed during acute alcohol exposure",
"-Liver thiamine stores are reduced due to hepatic steatosis or fibrosis",
"-Impaired thiamine utilization: Magnesium, which is required for the binding of thiamine to thiamine-using enzymes within the cell, is also deficient due to chronic alcohol consumption. The inefficient utilization of any thiamine that does reach the cells will further exacerbate the thiamine deficiency",
"-Ethanol per se inhibits thiamine transport in the gastrointestinal system and blocks phosphorylation of thiamine to its cofactor form (ThDP)",
"So basically ",
" is probably going to lead to thiamine deficiency and thus cause neural damage. I think you're trying to find out whether alcohol directly causes damage to neurons, I don't think there is any evidence supporting this, and I don't think there is any evidence that occasional alcohol consumption leads to neural damage. "
] |
[
"Anything a casual drinker (say a few drinks per night) do to mitigate this? Take a B complex supplement?"
] |
[
"This ",
"article",
" has most of the information you need to know. Basically alcoholism is associated with malnutrition, and malnutrition is associated with thiamine deficiency, and thiamine is needed for normal brain signalling and for the activity of some of the enzymes in the brain (alpha-ketoglutarate dehydrogenase). When alpha-ketoglutarate dehydrogenase does not work properly, neuron loss may occur. Also a low level of thiamine is associated with an increase in oxidation stress in the brain, which can lead to damage to neurons. ",
"tl;dr low thiamine"
] |
[
"Is there any way to use the polarization of electromagnetic radiation to transmit information?"
] |
[
false
] |
I'm currently educating myself about electromagnetic radiation, mostly with a focus on environmental and health concerns, but hopefully with a solid physics background. I just read about how EM-waves are modulated in three ways for the transmission of information in technical applications: amplitude modulation (AM), frequency modulation (FM), and phase modulation. Light is also a kind of EM-wave, and I remember from chemistry class, that light has another characteristic feature: polarization. I suppose this also applies to other kinds of EM-waves. Is there any sort of application, where the polarization of EM-Waves (like radio waves) is used to transmit information? Is this even theoretically possible? I would really like to learn more about this subject. So please enlighten me! (pun definitely intended)
|
[
"People are just giving irrelevant information in this thread about how some radio applications use different kinds of polarized emissions, but in none of these applications does the polarization itself convey information, which is what I think you are asking.",
"The answer is no, there is no application where, for example, a vertically polarized pulse is considered a 0 and a horizontally polarized pulse is considered a 1. The reason for this is that polarization can be randomized when radio waves interact with matter, in ways that amplitude, frequency, and phase are not, so radio communication relies on those for modulation rather than polarization."
] |
[
"Yes, many LEO satellites used to use circular polarization to increase signal to noise ratio & somewhat keep out nosey listeners.",
"The transmitted signal used helical antennas in a way that emits an end on beam which exhibits circular polarization, either left handed, right handed or sometimes both from two antennas.",
"Receiving antennas use a similar system of RH & LH helical antennas that are mixed such that the signals are in phase & will automatically filter common mode & unpolarized noise.",
"This was at relatively low UHF frequencies where electron scatter & other effects that could alter the polarization were minimal."
] |
[
"Similar to the other reply about low earth orbit, In geosynchronous satellites, Polarization is used to enable simultaneous transmit and receive on a single SATCOM antenna. Otherwise, one would be forced to use 1 antenna each for TX (transmit) and RX (receive). This also means the TX and RX can be done using the same frequency. ",
"In the case of horizontal polarization, TX and RX are 90 degrees apart. In the case of circular polarization, TX could be Right hand, RX could be left hand polarized. The exact LH or RH is opposite what your distant end puts out. ",
"No experience here with LEO. Source: I was a SATCOM terminal operator."
] |
[
"Is the earth a cold or hot planet?"
] |
[
false
] |
I hear a lot about these incredibly hot or cold temperatures in space. I was wondering what is the temperature of our solar system or the earth compared to the rest of the universe. Is the earth a hot planet? Is it a cold planet?
|
[
"We can only compare the Earth to other planets in our solar system; we're a long way from knowing the surface temperatures of extrasolar planets.",
"Earth's temperature range is warmer than Mars and Pluto. The gas giant planets don't have surfaces per se, and while their internal temperatures are still speculative it's believed that they're substantially colder than on Earth. Venus has an extremely high surface temperature (around 860 °F) due to a runaway greenhosue effect. Mercury's surface temperature ranges from extremely cold to extremely hot, depening on whether you're facing towards or away from the Sun."
] |
[
"You can define \"hot\", \"cold\" or \"lukewarm\" however you want in this case. Temperature is measured on a somewhat arbitrary scales that were developed to relate to daily life, not planetary geology."
] |
[
"It depends on what you're comparing it to. Interstellar space? Hot. Intergalactic space? FUCKING HOT. Mercury? Cold. Etc."
] |
[
"Why aren't all the planets in a solar system made of similar mixtures of elements?"
] |
[
false
] |
Curious if it has to do with the formation spreading out the matter based on density or energy levels or something to that effect. If so, would that support the theory that the same distance from a similar sized star would be a similar fraction of elements to support life?
|
[
"The principle control is the temperature gradient present in the protosolar nebula, with high temperatures near the Sun and low ones in the outer regions. The planets formed as ",
"materials condensed",
" (solidified) out of the hot gases in the PSN.",
"At about 5 AU from the Sun, temperatures were low enough for frozen water to condense (water was very abundant in the PSN); this is sometimes called the ",
"\"frost\" line",
". This allowed the outer planets to gain mass quickly and become large. Their increased gravity let them retain primordial gases such as H and He."
] |
[
"I would expect identical behavior in any forming stellar system. This being said, once the planets have formed (or while they are still forming) odd things can happen like ",
"planetary migration",
", which brings planets formed in the outer portions of the nebula close to the star (i.e., ",
"hot Jupiters",
").",
"The location and width of the ",
"habitable zone",
" largely depends on the distance from a star and the type of star. The zone is defined by the possibility of having liquid water, and its location is independent of the earlier processes acting in a stellar nebula. The origin of Earth's water/oceans is still under debate, it clearly formed too close to the Sun for water to freeze out. The two best possibilities for the origin of Earth's water are addition by comets late in its formation history, and from outgassing for water from its interior."
] |
[
"Basically it has to do with the distance from the sun and at what temperature materials leave a gaseous state. When the solar system formed, the heavier materials solidified closer to the sun, since they become solids at higher temperatures. As you progress further away (past the asteroid belt), the room temperature gases start to solidify and coalesce into planets and moons. So on Venus, you'll likely find more dense materials than on Earth. However, you still find atmosphere on the closer planets, because once the core of the planet was formed, it had enough gravitational pull to grab some elements that solidify much much lower temperatures."
] |
[
"Is the universe guaranteed to end?"
] |
[
false
] |
I've always been told that universe will eventually come to an end but what is the possibility it could last forever?
|
[
"Based on what we currently know about the universe, it seems like ",
"dark energy behaves like a cosmological constant",
". It also appears that the ",
"universe is flat",
". This is important, because the nature of dark energy and the curvature of the universe fundamentally determines the future of the universe. Given the apparent geometry of our universe, if dark energy is indeed a cosmological constant, it implies that the universe will likely continue to expand forever. The alternatives, such as the ",
"big crunch",
" or the ",
"big rip",
", are all currently disfavored. The most likely scenario seems to be the ",
"big freeze or heat death",
" of the universe."
] |
[
"The decay time for a supermassive black hole of roughly 1 galaxy-mass (1011 solar masses) due to Hawking radiation is on the order of 10",
" years,[22] so entropy can be produced until at least that time.",
"oh good. So I have a little bit of time to put my affairs in order then."
] |
[
"I quickly wondered if a observable flat universe that appears to be expanding could possibly be a local observation of a Torus. Sure enough the wik mentions that. I might hold onto that thought until we're able to observe, or at least offer an elegant proof, that it's otherwise. I don't actually know if the latter hasn't already been done."
] |
[
"What has the Large Hadron Collider discovered so far?"
] |
[
false
] |
The lhc was started back in 2008 and taken offline due to electrical faults. On Nov 2009 the lhc became fully operational, but I haven't heard of any discoveries or important findings from CERN. What has the lhc discovered during its years of operation? Edit 1: As someone who is not a particle physicist I appreciate all the information. I think the lhc is one of the most interesting research projects around the world, and I am excited to see what results will be published by the physicists at the lhc in the coming years. Specifically, I hope more light will be shed on supersymmetry and the Higgs boson.
|
[
"I found an answer to your question ",
"here",
": ",
"[...] At this point, the LHC has collected only approximately 1/200th the data collected at the Tevatron, but at higher energies. This means that the LHC at the moment can basically only see what the Tevatron has already seen. This is why nothing significant has been discovered yet.",
"But think about what an accomplishment this is: In a matter of a year, the LHC results are already comparable to results at the Tevatron, which has been running for 15 - 20 years.",
"Also, even though the data collected at the LHC so far has not uncovered anything new, revisiting previous results seen at the Tevatron (such as the discovery of the top quark) is very important in demonstrating the functionalities of the LHC detectors. These measurements also add precision to our knowledge of Standard Model physics. None of these results are earth shattering or particularly newsworthy, but they are incredibly exciting to particle physicists. More data is being collected as we speak, and by the end of the year, we will have about 20 times more data than we have now. At that stage, we will probably start seeing some indication of new physics.",
"Rest assured, a lot of work is being done at the LHC experiments, but the media or TED talks are probably not going to pick up on these things unless some anomalies are discovered (actually some anomalies have been discovered, but I'm not the best person to explain them). Stay tuned over the next decade! ",
"Disclaimer: I'm no physicist."
] |
[
"The amount of raw data that's been recorded at the LHC is 1/200th of the raw data that the Tevatron has recorded, but since the LHC operates at higher energies, it is more easily able to generate the interesting and heavier particles that the Tevatron took a longer time to find.",
"Consequently, what the Tevatron was the first to discover in 1995 (the top quark) was almost immediately found at the LHC."
] |
[
"how does \"1/200th the data collected at the Tevatron\" translate to \"LHC results are already comparable to results at the Tevatron\"?"
] |
[
"Could someone please explain to me the incompleteness theorems?"
] |
[
false
] |
I have a slight problem understanding Kurt Gödel's incompleteness theorems, as I don't have any higher education in such fields. It seems to me that it tells that math, and science by extension, can never describe the whole truth. Am I completely off the chart?
|
[
"Math is kinda like a game. You set your rules and then see what kinds of games you can play. These rules are \"",
"Formal Logic",
"\" and \"",
"Axioms",
"\". You can change the rules, but it then changes the flavor of math you play.",
"The axioms are, basically, statements that are assumed to be \"true\". Logic allows you to go from true statements to other true statements. A \"",
"Formal Proof",
"\" of a statement is then a string of these \"moves\", ending with the statement you're trying to prove. The game of math is then played by starting with axioms, doing valid \"moves\" allowed by your logic in order to arrive at various statements. These statements and proofs do not look like the statements and proofs in a typical math textbook, they're nothing but symbols. The goal is to formally and irrefutably prove something, not informally prove + provide explanation as with the proofs you see elsewhere in math. ",
"Here",
" of what such a proof might look like. It's not very illuminating to the reader, but it is true using the explicit rules and language of the math-game.",
"Godel's First Incompleteness Theorem says that for any sufficiently powerful consistent system of axioms, there are formal statements that cannot be proved or disproved. That is, there are statements so that there is no set of \"moves\" that will end at the statement or its negation. Informally, there are non-provable statements.",
"Godel's Second Incompleteness Theorem deals with consistency. That is, if we have a set of axioms, can we determine whether or not we can prove a contradiction using our allowed moves? The Second Incompleteness Theorem says that, in a sufficiently powerful system of axioms, if your system is consistent, then you cannot prove it. So, if you have such a system and you find a proof that it is consistent, then it is inconsistent. Essentially, it is like the First Incompleteness Theorem, but provides us with a particular statement that cannot be proved, and that statement is \"This system is consistent\".",
"This can have implications in math, but it is very, very rare for a mathematician, who isn't a logician, to encounter unprovable statements. So it isn't some damning statement telling us that math is futile or anything. We do math because it is fun, not to categorize all universal mathematical truths or anything. If you encounter an unprovable statement, then a proof that it is not-provable is just as good as a proof of the statement.",
"It even has less impact in science. Math can be used to approximate and predict the world through science, but there are lots of weird things in math that have no impact in real life because math is a made-up game rather than something required for the universe to function. Science, by its very nature, cannot describe reality with 100% truth or certainty. Science is merely a process used to refine our approximations and predictions about the real world, you'll never get the whole \"Truth\" from that. Math and Godel have nothing to do with it.",
"The fields where it has the most impact are in Mathematical Logic and Computer Science, outside of that it's just a good thing to learn.",
"I'm no logician and there is obviously a lot of subtlety to everything involved in mathematical logic and the Incompleteness Theorems, so I'm sure a lot of my statements and analogies are flawed. I invite ",
"/u/completely-ineffable",
" to come in and tear apart and correct everything I said."
] |
[
"I'm also a mathematician, but not a logician (far from it). There are a couple of issues I've always had with the way the first incompleteness theorem is typically interpreted and described in laymen terms:",
"\"Sufficiently strong\" while maybe technically correct, seems a misleading way to describe which theories the theorem applies to. It applies to any set of axioms that express arithmetic (along with the arithmetical tools Godel used in his proof, including induction I think?). There are plenty of rich theories that ",
" complete. For example, the theory of the real numbers as the unique complete, ordered field is complete (the word complete meaning two different things in that sentence). Hence a large portion of analysis (that which doesn't use induction or a few other arithmetical tools, I suppose) is complete. Correct me if I'm wrong.",
"It's really not a big deal for a theory to be incomplete. The theory of groups, of fields, of metric spaces, of measures, of topological spaces are all incomplete and we don't bat an eye about it. Why is it such a big deal that arithmetic is incomplete. A large difference, obviously, is that it's easy to construct undecidable statements in those theories (eg, a+b=b+a for groups). My understaffing is that explicit undecidable statements have been discovered in arithmetic as well. So let's just think of it in the same way we do group theory, no biggie. "
] |
[
"Whereas - for our readers - Clifford Spector proved (published posthumously in 1961 IIRC) that second-order arithmetic (in which the reals can be formalised) is consistent, no proof yet exists that it is complete. I don't keep up to date, though, so I could very well be wrong. Nonetheless, your point is true. For another instance, the theory known as 'true arithmetic' consists of all true statements about the standard integers in the language of Peano arithmetic. This theory is consistent, and complete, and contains a sufficient amount of arithmetic (heh). However, it does not have a recursively enumerable set of axioms, and therefore does not satisfy the hypotheses of Gödel's theorems, they do not apply.",
"The key omissions when summarising Gödel's first theorem are usually 1) Robinson arithmetic must be contained within the system in question, and 2) the distinction between consistency and completeness. ",
"This is true, and I doubt there are many who would claim otherwise, unless the topic is actually the foundations of mathematics instead of what we mere mortals are concerned with. It is a much bigger deal for a theory to be inconsistent, because then it would be impossible to tell whether a proven theorem is valid or not."
] |
[
"What role does anecdotal evidence play in science?"
] |
[
false
] |
I'm leaving this a bit open-ended because I'm curious to see what redditors think. I've heard a lot of debate on this subject.
|
[
"It may point towards a line of inquiry, I can't really think of any circumstances under which it's a good idea to draw conclusions from it though. Except for anecdotes like \"be careful with the high voltage source, Bob was screwing around and got shocked badly\""
] |
[
"Orac recently wrote about this.",
" His basic point was that anecdote is all that medicine had in the centuries prior to the last one, and it got us nowhere. Anecdote allows a pathway for human fallibility (confirmation bias, regression to the mean, etc.) to cloud our judgment, which is exactly what we don't want when evaluating possible treatments or interventions."
] |
[
"You should consider bringing this up at ",
"/r/philosophyofscience"
] |
[
"Soda bottle cap lock"
] |
[
false
] |
What causes a soda bottle, once opened, to lock the lid? Last night, I went to open an old coke bottle, about 3 days old, and I had to use pliers to open it: hand grips, gloves, nothing worked. I looked for dried sugar on the bottle lip, I tried to account for the increased internal pressure and none of it made sense.
|
[
"The caps are initially screwed on to a certain tightness. When you put them back on, you are over torquing it. Easier to close than open! ",
"Also, I am not a soda bottle professional."
] |
[
"Not an expert, but why wouldn't the internal pressure come into play here? If you tighten the cap when you put it on, and internal pressure builds, it will try and push the cap upwards. The threads on the cap will push against the threads on the bottle, perhaps so much that it becomes difficult to twist the cap. You could always try and reproduce the problem, but this time spray a little cooking spray on the bottle's threads and see if it opens easier next time."
] |
[
"The bottle itself is fairly rigid plastic, but the cap is made of softer stuff. When you torque the cap down you're actually heating the material of the cap through a combination of friction and compression, which deforms the threads slightly. On resting, the cap material becomes more rigid and grips the bottle threads more tightly."
] |
[
"When light is incident on an oblique surface, only a portion of that energy is imparted. Why? What is happening at an atomic level, and where does the remaining energy go?"
] |
[
false
] | null |
[
"Whatever part of the wave is not transmitted into the second medium is reflected at the boundary."
] |
[
"The statement above remains true whether you imagine the system macroscopically or microscopically.",
"If you send a classical light wave at a boundary, some of the wave will be reflected and some will be transmitted.",
"If you send a beam of photons at a boundary, some of the photons will be reflected, and some will be transmitted."
] |
[
"Understood, I’m just (poorly) trying to understand the micro! Thanks for your patience, kind reddit person. ",
"If I imagine atoms as billiard balls, a photon hits a surface perpendicularly - let’s say it hits atom A directly (ie the photon axis is right through the centre of A).",
"Why is this scenario different to one where the surface is now at 45deg to the incident photon, but the photon still hits A directly (axis through the centre)? Astro radiation calculations imply this imparts less energy. ",
"Is it the billiard ball assumption which is wrong? Or does atom A interact with the photon in some way which also involves the atoms surrounding it (ie so it knows it’s orientation)?"
] |
[
"Are there any gasses that are more dense than any liquid and would therefore sink in said liquid?"
] |
[
false
] |
This makes me wonder...are there ANY gasses that are more dense than ANY liquid? I know that someone might think this is a stupid question but I know there are liquids that are more dense than water (lead in it's liquid form for instance) and liquids that are lighter than water, such as oil. Same goes for gasses. Helium is lighter than breathable atmosphere but there are heavier ones too. So, are there any gasses that are more dense than any liquid and would therefor sink in said liquid?
|
[
"There do exist some very dense gasses which are more dense at room temperature than water. I once had the misfortune of working with one such fluorinated gas. I was working in organic solvent (THF if I remember correctly) at the time and the gas and the solvent were miscible so there was no separation to allow sinking. If I had substituted that solvent for one much less favorable then yes, I would have observed the gas sink into the liquid."
] |
[
"There aren’t any gases that are as dense as water at room temperature and pressure, which would be necessary to see a gas sink in water. Organic solvents will be the same order of magnitude of waters density so that wouldn’t help either.",
"WF6 is one of the densest known gases and it has a density of 0.0124 g/L, roughly 1% that of water."
] |
[
"Good question, but no. The best way I can think to explain it is that liquids have a whole lot more cohesion than gases--their molecules stick together more.",
"In fact, the main difference between gases and liquids is that gases will readily change their density based on the pressure around them. That's why tanks of pressurized gases (helium, carbon dioxide) are pretty common.",
"Gases that won't mix can 'layer' themselves in containers, with more dense gases 'sinking' to the bottom but, at normal pressures, any liquid will be more dense than any gas.",
"It might be possible to design a pressurized container where liquid is suspended on top of a gas, but gases are never going to 'sink' like you're asking. The gas will always bubble up."
] |
[
"In trials of psychological interventions, what is used as a placebo? Is there a \"sham talk therapy\"?"
] |
[
false
] | null |
[
"Clinical trials against placebo are unethical when there is an existing treatment that is superior to placebo. Ethical clinical trials compare a novel therapy to the current best available therapy. (This is generally true in medicine, not just in mental health research.)",
"(There are a few exceptions to this, but none apply to what you asked about.)"
] |
[
"As ",
"u/airbornemint",
" stated if there are existing treatments shown to be more effective these are provided in a TAU (treatment as usual group) so typically in applied psychology the benchmark isn't just better than placebo its better than current standard treatment.",
"If there is a theoretical experiment on some aspect of talking therapies researchers might look for very small changes in a general population sample between an experimental group and the control group will typically be a congenial therapist who actively listens and possibly provides some generic advice similar to the non-critical parts of the experimental group.",
"For example an experimental group might present active listening, rudimentary advice and a mindfulness exercise, whereas the control just the first two. "
] |
[
"It's like ",
"/u/airbornemint",
" and ",
"/u/ThomasEdmund84",
" said. Rather than a placebo-controlled trial, something like a noninferiority trial is often used. This is basically a comparison between the novel intervention and a well understood intervention as a positive control. More often than not, this is the first line treatment.",
"This isn't just in the context of psychological interventions; this model is also used in drug development and with novel surgical interventions."
] |
[
"Based on the CDC web site the total number of cases of coronavirus im the us is 746,625 and the total deaths is 39,083. That is a death rate by my math of 5.2%. Why is the fatality rate being reported at 2-2.5%?"
] |
[
false
] | null |
[
"The reported death rate depends on multiple factors. The most important one is testing. The less you test, the higher will be a) the apparent death rate, because deaths you will notice and record and b) your actual death rate, because patients don't get the medical attention they need. Both are (still?) huge issues in the US specifically. Other countries like Germany or South Korea have a much lower rate due to more widespread testing where many more mild cases are reported also.",
"Another factor is the demographic groups that are affected. The more old people and people with chronic medical conditions become sick, the higher the death toll will be as well. So protect your elderly.",
"Initial serological studies showed that the actual mortality rate may be even lower at about 0.37%, but that again also depends on the initial factors I mentioned. Both prevalence and mortality are also not evenly distributed across the country (see NYC as an extreme example), which is also something you should account for when calculating averages."
] |
[
"The number of cases is the cases that have been diagnosed. There will be an unknown number of people who have the disease, don't get tested, and recover. The 2 - 2.5% number will include an approximation of how many cases have not been detected.",
"Your calculation also omits those who have the disease now and may die."
] |
[
"How does this number vary depending on access to healthcare or lack thereof?"
] |
[
"How is zero gravity different from weightlessness?"
] |
[
false
] |
Is there any difference? Are there any mathematical differences between the two scenarios?
|
[
"If there is no gravity, definitely you are weightless.",
"If you are weightless, either there is no gravity or you're in freefall (or you have no mass, but you do).",
"If you're in freefall in a uniform gravitational field, you can't tell if there's no gravity or if you're freefalling. So freefall in a uniform field is the same as no gravity. (This is \"the equivalence principle\".)",
"If you're in freefall in a NON-uniform gravitational field, you can tell because you will feel tidal forces.",
"So basically weightlessness and no gravity are the same except for weightlessness in a non-uniform gravitational field."
] |
[
"I could be wrong here but let me see... Zero gravity should include the assumption that gravity is not acting on you by anything or at least just a negligible amount. Weightlessness can occur on Earth (in the atmosphere) by just falling. Even in the ISS, they are experiencing weightlessness by traveling around the earth really fast to counteract gravity. This makes them feel weightless."
] |
[
"the feeling of weight doesn't actually come from gravity, but rather the contact force between an entity and the surface it lies on. The feeling of weightlessness occurs whenever there is no normal force that gives the feeling of weight. Zero Gravity occurs whenever there is no large mass like a planet to create a force of gravity. Weightlessness is the feeling, zero-g is a situation, mathematically zero-g doesn't have a force of gravity on any objects and no opposing forces due to gravity."
] |
[
"Do the planets ever align in a straight line and if so how often?"
] |
[
false
] |
Assuming no planets "year" is an exact multiple of another, given enough time the planets should align shouldnt they?
|
[
"The planets will never align in a straight line. First, they are on different planes so there is no reason that even if they are at the same angular position they will form a line. Second, they will never be in the same angular position",
"",
"In fact, the planets would ",
" have years that are rational multiples of each other in order to ever align. ",
"This page",
" includes a relatively easy to understand proof of this. Of course with two planets, there will be alignments pretty frequently. However, as soon as you add a third you realize that all three can ",
" align if their angular frequencies are rational multiples of each other (meaning their \"years\" are also rational multiples), and this would continue to be true for more than 3 planets. The author continues to consider alignments of planets ignoring the sun, which will occur for 3 planets but then does not necessarily occur for 4 or more, though there can be close approaches."
] |
[
"They do have rational multiples of each other, though, to any desired precision. "
] |
[
"That was the point of my comment, what do you mean?"
] |
[
"Can anyone identify this piece of equipment? I need to find the brand, model, and model #. I think its a piece of chemistry equipment since the owner, my friend, is a chemist."
] |
[
false
] | null |
[
"Take a couple more photos of the circular bit on the right and any plaques on the machine (don't forget underneath). Also, if there are any access panels there might be an ident on the inside."
] |
[
"Yea. If I could see it in person I'd be able to figure it out easily but he is in Kentucky and I am currently in Michigan unfortunately."
] |
[
"My money is on gas chromatograph but I'm just making shit up"
] |
[
"Why are high temperatures bad for a cpu?"
] |
[
false
] |
I know it reduces the life span, but why?
|
[
"Heat effects the actual material of the cpu. Cpu's are silicon doped with ions. These ions allow the semiconductor to have a charge based on the chips designs to make them behave a certain way. When atoms get hot, they tend to diffuse around.",
"There is a phenomenon electro-migration where ions move around in an electric field. Over time, ions move to places where they become useless for their intended design. It goes even faster when the chips are hot.",
"http://en.wikipedia.org/wiki/Electromigration"
] |
[
"In addition to what others have said, there is another, more immediate effect. CPUs are tested before being sold to make sure they can run at a certain frequency without experiencing something called \"timing violations\". Basically, you need to make sure data can get through a part of the CPU in less than one click cycle so that it's ready in time. If timing violations happen you get bad data.",
"When the CPU gets hot, the mobility of electrons goes down, making every logic gate slower. This can cause timing violations which were not present at lower temperatures. You could sometimes see data corruption happening on screen if your graphics card overheats, though I don't think that happens much anymore."
] |
[
"For most/all transistors the mobility is limited by phonon scattering (lattice vibrations). Phonon scattering goes up with temperature, mobility goes down."
] |
[
"How is weight actually lost in the human body?"
] |
[
false
] |
When a person uses up more calories than they consume they lose mass. How does this occur exactly?
|
[
"The main by products of respiration of sugars and fats are carbon dioxide and water. Carbon dioxide is expelled via the lungs and water is lost via sweat, the lungs, urination, many places, reducing your mass.",
"Did you have a particular aspect of this you were curious about?",
"Edit. Moderators or automod deleted your reply.",
"http://www.nature.com/scitable/topicpage/nutrient-utilization-in-humans-metabolism-pathways-14234029#",
"This covers some of the basics of sugar metabolism. As a basic overview, a lot of chemical processes that break down larger molecules into smaller molecules release energy that we can use. Smaller molecules tend to be gases at room temperature since they have less points of contact to be attracted to each other (intermolecular interactions and van der waals forces are a large and complicated topic I won't go into), so a solid going to a gas is normal."
] |
[
"When most people talk about weight loss they are trying to lose fat. ",
"When you eat the food is broken down into many different products that feed into your metabolism, one of the main products being glucose. The cells in your body, especially those in the brain require glucose in order for them to survive. If you are not providing enough glucose to the body one of the processes that occurs is that the body makes glucose by breaking down other molecules such as glycogen and also fats. These then are processed by a series of enzymes and are eventually turned back into glucose that can be used by the brain."
] |
[
"I read some physiology a few years ago, I might mix the stuff up. But I think it's something like: A cell needs something like ATP to activate, and a calorie has 20 of those. What we usually mean by the word calorie is usually kilocalories though, so one of those is worth 20000 action potentials. Many of those are spontaneous - brain, heart, dietary tract for example. When hungry, insulin makes blood sugar. When full, some other protein makes fat that is being stored for a rainy day. Muscles use more ATP, so gaining muscle mass is a good way to increase your passive energy burning. When \"used up\" the rest products are excreted through the normal ways (mouth, skin, 1, 2)"
] |
[
"When pairing two electronic devices (like my phone via Bluetooth wireless speaker), is there a difference in power consumption if the volume is turned up on the phone or speaker?"
] |
[
false
] |
I'm sure the difference, if any, is negligible. Still, these types of questions keep me from thinking about better questions.
|
[
"The amount of power consumed by the speakers is obviously higher if the volume is turned up.",
"But the amount of power consumed to transmit data from the phone to the speaker is the same regardless of the volume settings."
] |
[
"I don't have experience with Bluetooth beyond consumer use, but I'm an acoustician and I've studied audio. So I did some research. Here's what I found.",
"Obviously, if you turn up the speaker, the speaker will use more power. I think that you knew that part. (You may be interested to realize how much more power is required to increase the loudness. A 3 decibel increase is equivalent to a doubling of the power, but is only considered a \"Just Noticeable Difference\" (JND) to the loudness.)",
"But what you're asking is \"Does turning up the volume from the source mean that the Bluetooth device is sending a more intense signal?\" Let me know if I'm wrong about that. So I looked up how a Bluetooth device actually sends a signal. The answer is found in two protocols: the ",
"Advanced Audio Distribution Profile (A2DP)",
" and the ",
"Audio/Video Remote Control Profile (AVRCP)",
". In my research, these appear to be the profiles used in pairing a phone with a Bluetooth speaker or similar device. If I'm wrong about that, the actual profiles used should be listed on ",
"this page somewhere",
", so feel free to check my work.",
"A2DP is the how the signal is actually sent. It sends the file as-is in MP3, WAV, etc. There is no volume control provided by that profile. The volume control is achieved through the control profile, AVRCP. When you hit \"pause\", or \"skip\" or when you adjust the volume, it's AVRCP that communicates the change. This change isn't an adjustment to the audio waveform intensity, it's an instruction to the audio player.",
"It seems that the only additional power consumed would be through the sending of the signal, instructing the media player to turn it up. So turning up the volume shouldn't have any more drain to your phone's battery than hitting \"pause\"."
] |
[
"And what happens if the phone is connected to a set of headphones? They'll draw power from the phone, so will the battery empty faster when the volume is higher?"
] |
[
"A free neutron has a half-life of about ten minutes. Suppose we were to somehow get a kilogram or so of free neutrons together before they decayed. What sort of physical properties would this mass have?"
] |
[
false
] |
The half life of free neutrons is around . This suggests it might be possible to accumulate a large enough mass of neutrons to study their emergent physical properties. The lack of net electrical charge seems to suggest that "neutronium" would behave very differently than normal matter. My thoughts on what this might be like: The lack of electron degeneracy pressure means that it would likely be very dense. It also would not emit or reflect light. I believe only electrons can emit and absorb photons. I'm assuming it would be transparent. Not sure if it would refract light or not. It would probably diffuse through ordinary atom-based matter, making a mass of free neutrons difficult to contain. This is again because of no electron degeneracy. Not sure how well it would conduct electricity. It's probably an extremely good insulator, like a vacuum, but the presence of particles probably interferes with field and thermionic electron emission, making it an even better insulator than a vacuum. It would be chemically inert. So what is "Neutronium" like at standard temperature and pressure before it decays?
|
[
"Neutrons don't bond well, so it would act like a very radioactive (and radiogenic) cloud of gas. Then (if it were large enough) it would act like a very hot cloud of hydrogen."
] |
[
"Exactly. And the one thing you can be sure of is that it would be ",
" since neutron decay releases energy!"
] |
[
"So while the question has been here for a while, I thought I would comment on the assumptions you made.",
"Now: I think theres 2 ways to talk about this. ",
"1: How would a bare neutron interact / a few in a reasonable area? And interestingly enough, they do interact quite a bit. And even though you might think they would be innert, they still do interact with materials, and we use neutron scattering a lot in the study of materials. (Studying high temperature superconductors for instance: by shooting neutron beams at the sample and measuring how they reflect off) ",
"Also, if you were to just try to collect this stuff, you would get the ideal gas / that bubbles away quickly as it releases the stored energy. (that has been answered by other people here)",
"And 2: A larger mass (on the order of 10",
" -> 10",
" neutrons), and this would just be super radioactive, and hard to manage and contain. But if you could, it would still be crazy energetic and would interact with everything that came close to it i suspect. (which is what I continue to talk about below, since no one really mentioned it too much?) ",
"The lack of electron degeneracy pressure means that it would likely be very dense.",
"This is true, and in the sense of getting enough of this stuff together, it becomes a neutron star. (The density is about the same as the density of the nucleus in an atom) In fact, a neutron star is just a big ball of neutrons, held together by gravity. Why does a neutron star not decay then? It's because the gravity is so strong its actually making neutrons the stable result. (Imagine a whole bunch of hydrogen atoms at first, that were pulled in by gravity so much that the protons + electrons combined to make neutrons (electron capture / inverse beta decay)) ",
"Now: why dosen't something this strongly pulled together not just become a Black hole? Well because there is 1 more thing it needs to fight against, just as you assumed, a degeneracy pressure. In this case: of the neutrons themselves. (Degeneracy pressure applies to all fermions, not just electrons, due to the pauli-exclusion principle)",
"It also would not emit or reflect light. I believe only electrons can emit and absorb photons. I'm assuming it would be transparent. Not sure if it would refract light or not.",
"I think it would do both of these things as electrons are not the only thing that can emit and absorb photons. It turns out that electrons' motion is predominantly the source of light that we see, but that is just because of the energy scales at hand. This Neutronium ball would probably be a very highly energetic, unstable, material which would most likely explode (if some immense pressure is not pushing it down). And now under such a high pressure, it will have to be SUPER hot. This heat will radiate out from black body radiation. So now we have a ball literally hotter than the sun, glowing due to its temperature. ",
"In terms of the absorption / reflection cross-sections, to be honest I don't know the mechanics of this quark/gluon mess that will be going on inside of these neutrons/the energetics that are keeping this thing together, however I will assume it will reflect high energy light (like x-rays). These x-rays can be absorbed by neutrons even in atoms, if they are energetic enough to interact with the quarks, as quarks that make up the neutrons have charge.... For visible light, I'm a little less sure, as this would be a very hard QM problem to solve, I would suspect with all the things that are going on, there has to be some mechanism for it to at least weakly scatter light, but I have no good guesses there. Also, it is worth mentioning, because this thing will be so amazingly energetic and radioactive, it will be creating electrons on its surface that will be constantly popping into and out of existence. These vacuum fluctuations will create electrons that would probably interact with the low energy light as well. ",
"It would probably diffuse through ordinary atom-based matter, making a mass of free neutrons difficult to contain. This is again because of no electron degeneracy. ",
"I think this would not happen at all, If any ordinary matter came in contact with this super dense mass they would likely be absorbed. Most likely with whatever process you are using to hold it together will also allow it to capture this matter and turn it into neutrons (eg. if its gravity, it would pull it in, and would turn it into a plasma on the surface, and start the same electron capture process in the atoms). If for some reason you shot a beam of electrons at it, then I can imagine them passing through in some super special circumstances... but ... because its so energetic, the electrons/protons that would be bubbling on the surface would be interacting with any thing you sent at it as well.",
"Not sure how well it would conduct electricity. It's probably an extremely good insulator, like a vacuum, but the presence of particles probably interferes with field and thermionic electron emission, making it an even better insulator than a vacuum.",
"Conduction of electricity would... be something that would be ... actually surprisingly interesting to measure in my opinion. Using the simple definition of resistance from applying a voltage source (assume putting this in between a parallel plate capacitor i guess), and ignoring the sources and sinks of charge that will be happening all over the place... I suspect that you could polarize the object, pulling the electrons along the surface, and protons in the other direction. Also, because of the super high temperature of this object it might have a very high resistance, tons of collisions etc... but honestly its hard to tell. This confusion comes to me because not only is it super hot, its also a quantum object... And that can mean weird things can happen, eg. the electrons might not interact, and can go straight through the big bulk of neutrons and actually prove to be a surprisingly good conductor. But, this is just hard to tell and i suspect that we need a plasma expert to talk to us about conduction through plasmas. ",
"It would be chemically inert.",
"This one... I have no idea how to talk about really. I suspect because it is such a highly radioactive and crazy material, that it would probably destroy anything that came in contact with it...",
"-- Sorry about such a lengthy reply, im in lab and bored... And this was an interesting idea to think about. "
] |
[
"Is \"The Pill\" an abortifacient?"
] |
[
false
] |
Hello everyone. I asked this on but the community seems rather small and there are probably more important questions they're answering pertaining directly to peoples health. So I figured I'd just ask it here as well. I tried to look this one up on my own, but I seem to keep reading conflicting information from different sources. Therefore, I'm not entirely sure what I can trust as reliable information. The argument for it being an abortifacient I've seen thus far is that in some cases "the pill" prevents implementation of an already fertilized egg in the lining of the uterus. If this occurs than it's pretty much causing an abortion, correct? The only argument I've seen to refute this is that in the event of a breakthrough ovulation the endometrial pattern of a women returns to normal, which I guess would counteract the "less than hospitable" endometrium that was initially caused by the pill. I've also checked out a wikipedia article that says the issue of the pill being an abortifacient is still a topic under debate and that no conclusive answer has been reached yet. If this is the case then I'm obviously fine knowing that. Although, it would be interesting to know if their is a particular direction scientists are leaning due to more evidence being present on one side than the other. Anyways, thank you for all responses/replies. I appreciate everyone taking the time to answer. Also, don't worry about "offending" me or anything like that. I'm not religious or anything so I don't really care what the answer is, I just want to know if the pill does have an abortifacient potential.
|
[
"This is kind of a loaded question. The debate over it depends on how you define the word \"abortion,\" and there is no one definition that makes everyone happy. I'm going to give my considered opinion as a nurse, but it's not a universal truth.",
"First off, oral contraceptives generally prevent ovulation. That's what is going on the great majority of the time. Only ",
" ovulation occurs anyway, and ",
" the ovum becomes fertilized, and ",
" the blastocyst would otherwise have successfully implanted, does it even become meaningful to ask the question.",
"That said, my answer is no. A blastocyst is not a viable organism, and not every blastocyst goes on to successfully implant and become an embryo, so I say it is not valid to consider nonimplantation a form of \"abortion.\"",
"My understanding is that this is a more common view than the other side, but that may be just due to my sample selection (my region of the country, or whatever)."
] |
[
"However, if we could go hypothetical for just a minute",
"Sorry, I'm not going to go into hypotheticals for this question. There's too much opportunity for misunderstanding."
] |
[
"I can understand your viewpoint that the blastocyst itself is not a viable organism. ",
"However, if we could go hypothetical for just a minute and validate the \"life begins at conception\" argument, just for arguments sake, then birth control could be a potential abortifacient, correct?",
"According to this article I'm reading the blastocyst forms approximately 5 days after fertilization or \"conception\". This would mean that if ovulation occurs, the ovum gets fertilized, AND the blastocyst would have successfully implanted otherwise then this would technically qualify as an abortion for someone who thinks \"life starts at conception\", right? ",
"Again, I understand the way you define abortion, but if we define it in the way I just mentioned then it's possible for the pill to have an abortifacient potential, correct?",
"Also, thank you very much for responding."
] |
[
"Court rules that MMR vaccine causes autism, how can I reply to anti vaccine supporter?"
] |
[
false
] | null |
[
"Take a look at the investigation done by Brian Deer.",
"It's pages and pages and pages highlighting why the original study pointing this out was fraudulent, and how no scientific study after has been able to replicate those findings.",
"Also, I'd point out that a court ruling is not scientific evidence. "
] |
[
"A court decision has no scientific weight. Judges and juries are not scientists and are not qualified to determine the veracity of the science. The arguments used to convince the court may have value, but merely stating a court's decision changes nothing and hardly constitutes 'proof'."
] |
[
"Scientifically, that makes no sense. How do you determine causality by looking at one case without some sort of control? Especially since the mechanism for a link between vaccination and autism has not been established? The best they could reasonably say is that the onset of disease was temporally related to the vaccination, but that's pretty much meaningless. The news article itself is a ridiculous sensationalist piece as well, with no scientific backing and obviously biased rhetoric."
] |
[
"Will an electromagnetic wave move a positively charged particle?"
] |
[
false
] |
With many waves it molecules will move up and down with the wave like a buoy in water but doesn't move forward. With an electromagnetic wave, there is an Electric field and a magnetic field. I was thinking that if a positive particle was on the x-axis of propagation, that it would move up on the z-axis with the E-field, but now having a velocity the magnetic field in the y-direction would cause the particle to move forward in the x-axis. Can someone confirm or talk a little bit more about it?
|
[
"An EM wave will move both positive and negative charges. The - charges will move in one direction, and the + charges will move in the opposite direction."
] |
[
"A positive charge will move in the direction of the electric field. A negative charge will move in a direction opposite the electric field."
] |
[
"What direciton is this? up and down? or along the x axis? "
] |
[
"Would the Tesla Model S get better range between charges if it had a transmission with multiple gears?"
] |
[
false
] |
I was reading about the Tesla Model S today, and I was somewhat perplexed to learn that it has a single speed transmission. For daily commutes the relatively short range of ~270 miles wouldn't come into play given regular overnight charges, but would the car see a range increase if it had a transmission with multiple gears?
|
[
"If anything introducing new sources of friction like a transmission would reduce its efficiency."
] |
[
"Probably not. The multiple gears used for internal combustion engines compensate for the [relatively] narrow ",
"power band",
" of those engines, and how power output varies by engine speed. The same thing doesn't happen with ",
"electric motors",
" so, as 7Geordi ",
"mentioned",
", extra transmission bits would only worsen performance, and increase costs."
] |
[
"With electric motors the amount of power used really depends on the amount of mechanical work the motor has to do. At high RPM parasitic losses are slightly greater because of friction in the motor, but this is not very significant. For an internal combustion engine, however, fuel consumption depends to a large extent on the rate at which the cylinders are fired. At low revolutions you use less fuel.",
"So in answer to your question: not really."
] |
[
"is Sulfur hexafluoride corrosive to gallium?"
] |
[
false
] |
Edit:Does Sulfur hexafluoride interact with gallium in any way?
|
[
"Edit: Well then again, not. There is virtually no reaction chemistry for sulphur hexafluroide. It does not react with molten sodium, but reacts exothermically with lithium."
] |
[
"well the idea is that if you don't have a way to fill a whole working environment with nitrogen you could always use hexafluoride by placing the object you don't want to interact with other gases inside of a bin of some kind and just fill it up with the gas but not need it to be sealed or pressurized or vacuumed exc exc.. it's not gonna go anywhere. I don't know can you do that with nitrogen but my understanding is it's lighter than air but not oxygen specifically but they are bout the same and I suspect the nitrogen would quickly dissipate as ambient air moves in the room."
] |
[
"Sulfur hexafluoride is typically a pretty stable gas. They use in the casting of Magnesium which is a high temperature process."
] |
[
"Why are elements like iron clustered in the ground, rather than distributed randomly?"
] |
[
false
] |
My friend just said: "Isn't is crazy that wood just.. grows? It's so hard! And metal kinda grows too. What's up with that?" He's sober as a bird, for the record. But it does bring up an interesting question: Why is it that an element like iron, lead, or gems like garnet, or whatever else, commonly show up together, in clusters in the ground? For products of organic matter, like oil, it makes sense that it would be in one place. But my understanding is that atoms of iron, lead, or carbon are created in explosive fusion, and this mess gets pulled back together via gravity into hot, hot planets. So why aren't planets just uniform solutions of elements? When everything is soupy, do elements like to hang out together? I hope I've made my question clear, but I'm happy to offer clarifications if needed.
|
[
"Generally speaking, elements are clumped up in the Earth by dissolving and un-dissolving. To a lesser extent, they're clumped up by gravity.",
"First, gravity. On the very large scale, heavy materials tend to sink under gravity, and light materials tend to float. So the Earth has a layer of dense iron at the center, less-dense rock above that, water above that, and air on top.",
"... but your question was more about ore bodies. Typically, when some sort of hot liquid (water, magma, whatever) comes into contact with rock, it will dissolve some chemicals more than others. When the liquid cools, some chemicals will precipitate out faster than others. So you tend to get the least-soluble minerals where the liquid was hottest, and more-soluble ones are found where it was cooler. If the liquid evaporates, or its chemistry changes, the same thing happens: some minerals precipitate out early, others late.",
"Suppose I take some salt and sand and mix them up in a jar. It's easy to separate them: I just pour water into the jar, pour off the salty water, and let it evaporate.",
"Almost all useful mineral ores are either the dissolved material, or the stuff left behind -- the \"salt\" or the \"sand\" in this example.",
"Iron, which you asked about, is a particularly interesting example. 3 billion years ago, the Earth's atmosphere had no oxygen in it, and the Earth's oceans had huge amounts of iron dissolved in it. But when oxygen photosynthesis started up, the oxygen changed the ocean chemistry so the iron was no longer soluble, and sank as iron oxide to the seafloor. This formed most (but not all) of the major iron ore bodies we rely on today."
] |
[
"Bingo. This covers it. Density, sedimentation layers, solutions. This is both intuitive and authoritative. Thank you. Where did you learn about it so that I can reference something?"
] |
[
"Some of this is accurate, but some is not. Most heavy elements did not come here by meteor and are not on the surface. There is a huge amount of gold, uranium, etc. in the earth's core and mantle - much more than is on the surface. Exactly what \"rose\" and what \"sank\" (and in which ratios) is complicated, but certainly the vast majority of the Earth's composition was already present when it was first forming.",
"Things like ore veins are primarily created through geologic and hydrologic processes. Water plays a key role - most veins are created by water depositing minerals over time. When there is a location that is well-suited to a particular kind of deposit, you'll get a lot of that kind of mineral accumulating, as the geological circumstances usually don't change for a long time."
] |
[
"Why did there evolve to be both males and females of a species rather than just one organism?"
] |
[
false
] |
Why would there be two different versions of every species that need to mutually co-operate in order to procreate rather than just one party that reproduces on its own? I know of some creatures that don't need another party in order to procreate, but how and why could it come to be that, seemingly more practical process, isn't the norm?
|
[
"http://www.reddit.com/r/sciencefaqs/comments/my6to/how_did_sexual_reproduction_evolve/"
] |
[
"Evolution might be \"random\" in the sense of random mutations, but adaptive evolution is far from random and actually completely logical, because the entire concept of survival of the fittest is not random at all: things that fit survive, things that don't fit, die. Therefore, anything that evolves does in fact have a reason: it created better survival. We can't always actually work out exactly why something like male and female were more fit than clonal reproduction, but it had to be for it to happen.",
"In this case, it's clear that part of the reason sexes evolved is because they created the ability for gene recombinations that produced more fit offspring."
] |
[
"More practical is actually sexual reproduction.",
"A-sexual reproduction and cell/bacteria reproduction take a very very long time to change the genetic code. It just replicates the original DNA and slight variations occur due to mutation.",
"However with sexual reproduction you have two sets of DNA which contribute to a whole new line of DNA; add that with possibility of still random mutations and you should understand why sexual reproduction is so prevalent.",
"Variation occurs much quicker, now when I say quicker I do not mean time-scale wise, but generation wise. Multi-celluar organisms live much longer and take much longer to reproduce so every generation is much longer than say a cell dividing every day for example. So timescale wise bacteria and cells can outdo us, but going by variation we beat the hell out of them generation by generation.",
"With the timescales involved for multi-celluar organisms, for us to be a-sexual we would never be able to keep up with other types of reproduction because we would barely change in comparison to timescales bacteria reproduce at."
] |
[
"If ants use a \"scent\" trail to find their way around, how do flying ants find their way?"
] |
[
false
] |
I'm just curious. Thanks guys!
|
[
"Flying ants are those leaving the nest, never to return. So they don't need a way to find their way back, they're only interested in distance. They're the male drones and new queens off to mate and start a brand new colony."
] |
[
"Just to build on what LincolnImp68 said, not only are they leaving, but pretty much the only time at which they will fly if for the mating flight. This is a selective event where relatively weaker males compete for access to females. During the flight, the males are indeed using still their scent to guide themselves to the females, following the trail of pheromones wafting from their objective. If ever you see mating flights, they even sort of have a probabilistic bell curve shape, where males are distributed as pixels according to how storng is their flight, with the female somewhere at the top. ",
"Once mated, the females just fall to the ground where they may and take their chance. The males die off.."
] |
[
"awesome. Thanks."
] |
[
"Particle velocity in a plane wave can be described as ui=Ui*e^j(wt-kx), Why does the sign of the kx term determine direction of travel of the wave?"
] |
[
false
] |
Some more information to help clarify things: Ui is the velocity amplitude t is time x is the horizontal location w is the angular velocity k is the wave number (k=w/C) where C is the relative wave propagation speed for the material. j is imaginary I just do not understand why the kx term is the only factor which describes the direction of wave travel. To me it seems that both the angular velocity w, time t, position, x, and the wave number k would contribute. Why is kx term the only term associated with direction of travel?
|
[
"(This sounds vaguely like homework, but there's a good change it's not. So I will probably just not release the question to be safe. But I will give you enough to point you in the right direction. If you need more help with a specific problem, a homework help sub is good place to ask.)",
"The phase of the wave in the form you have written is",
"Q = wt - kx",
"The phase velocity ",
" of the wave is the velocity of a point that has constant Q. Hence the velocity of such a point satisfies dQ(x,t)/dt = 0, where x is considered a function of time. So you have",
"0 = (dx/dt)(∂Q/∂x)+(∂Q/∂t) = (v)(-k)+w",
"Solve for ",
" to get",
"v = w/k",
"So the direction of the velocity is determined by the sign of w/k, not just k. Let's look at multiple dimensions.",
"Q = wt - ",
".",
"(Typically the phase is written with the opposite sign, but it doesn't matter.) Since grad(Q) = -",
", we see that wave crests increase in a direction parallel to ",
". If the phase is constant, the velocity of the wave satisfies:",
"0 = (d",
"/dt).(∂Q/∂",
")+(∂Q/∂t) = ",
".(-",
") + w",
"So you get",
".",
" = w",
"which means that |",
"| = w/|",
"|. Since the velocity is parallel to the wavenumber vector, we get",
" = w",
"/|",
"|",
"Again, you see that the direction of ",
" is determine by both the direction of ",
" and the sign of w."
] |
[
"Oh I see now. I was thinking too simply, only considering the particle motion as apposed to the wave motion. Thank you very much."
] |
[
"I added a few lines on the phase velocity in multiple dimensions."
] |
[
"How does an engine prevent a chain reaction that consumes all it's fuel from happening?"
] |
[
false
] | null |
[
"The combustion chamber and the fuel storage areas are separate. They used to be isolated from each other by the intake valves that would allow the fuel air mixture into the engine only during the intake cycle. With direct fuel injection, the injectors themselves act as tiny valves, isolation the fuel from the combustion chamber during ignition and exhaust cycles. Though, it would be very difficult for a spark/ fire to travel back through the fuel lines and into the gas tank. Even if that were to occur, there would be very little oxygen in the gas tank. Oxygen is necessary to burn fuel, so any ignition would likely be small and extinguish quickly. I honestly can't see this happening unless it was modified to behave differently. Intake valve sticking open during the compression and ignition cycle on an older car would still have to push the air/ fuel mixture through the venturi (an extremely small hole) to get back to the fuel tank. It is more likely to blow the air/ fuel mix out of the carburetor through the butterfly valve instead. No idea if this has ever happened, but I've never heard of it. "
] |
[
"If fuel was allowed unmetered into your engine it would blow up or flood itself and choke out from all the fuel and not enough air to burn it. Fuel injectors are valves that open and close in thousandths of a second. I would suggest looking up some videos online to better explain how those open and close and the further mechanics of an engine. Fun videos are diesel engine runaways where the engine is consuming its own oil and running on that till it blows up. "
] |
[
"There are diesel engines that can\"runaway\", this is because their pump is driven by the motion of the engine itself, so if your fuel valve fails, it will just pump its own fuel and usually, since that valve also controls flow of fuel, it will speed up until it gets too fast and explodes apart. ",
"https://en.wikipedia.org/wiki/Diesel_engine_runaway"
] |
[
"When a star becomes a black hole, does it happen gradually or suddenly?"
] |
[
false
] | null |
[
"Black hole formation is a very rapid process, both in stellar timescales and human timescales. Depending on what part of the process you define as \"becoming a black hole\" the process takes about two weeks, or it takes significantly less than a single second. ",
"All stars undergo fusion: the process by which light elements combine into heavier elements and release energy. The tremendous heat given off during these fusion reactions exerts an outward pressure that is constantly balanced against the inward pressure due to gravity. If the star gets hotter then it will expand, since there is more internal pressure. If the star gets cooler it will contract, since there is less. A traditional black hole forms when the internal pressure can no longer prevent gravity from completely collapsing the star.",
"Most fusion during the lifetime of stars creates very light elements: helium, carbon, oxygen, nitrogen, etc. As light fuels start to run out the heavier elements start to fuse as well: carbon fuses into neon, oxygen fuses into silicon, and many other reactions. These later reactions also release significant energy as well, so a star that can support itself by burning hydrogen, or burning carbon, etc. depending on the specific circumstances. Interestingly, a star is somewhat self-regulating: a reduction in energy generation inside the star leads to contraction, which leads to higher densities inside the star, which leads to more fusion of heavier elements and more energy release. A star changes temperature, size, and color depending on what kind of fuel its burning, but the star's basic structure is more or less stable all the way up until the very end.",
"However, one of these reactions is very special, which is the production of iron. Iron is an extremely stable element, which means that from a nuclear fusion point of view it's a dead-end state. Once iron is created inside a star it has squeezed all the energy it can out of those particular protons, neutrons, and electrons. Now this mass is sitting around in the star and contributing to a strong gravitational pull, but not contributing any energy towards supporting the star, so the star contracts a little. As more and more iron is created, the star continues to contract. ",
"So this gives us one answer to your question. If we define a normal healthy star as one that is not contracting, and the start of contraction as the start of a black hole, then it makes sense to say that that fusing iron is the physical event that starts the formation of a black hole. We can put a number on that process. Normal stars will burn for millions of years without creating any iron, but once iron creation begins they will only burn for two or three more weeks (depending on the initial mass of the star) before their cataclysmic end.",
"If you're curious, the luminosity of the star does not change significantly during this time. Iron formation is happening deep in the interior of a star, and other forms of fusion are still occurring within the star, but the scales are tilting internally towards collapse. However, neutrino generation is soaring off the charts, so neutrino detection projects may in the future allow us to predict when and where stars will collapse. ",
"However, there's another event in the evolution of a black hole which you could also point to as the actual formation. After enough iron has accumulated the star will undergo iron core collapse, which is the point at which so little energy is produced by fusion in the star's core that the force of gravity overcomes the normal electromagnetic forces that keeps regular matter as separate, regular elements. When this occurs, the ",
" of the star begins collapsing faster than the ",
" of the star. The star's core will begin falling in on itself at speeds up to a quarter the speed of light.",
"At this point half of the core has collapsed inward, and the other half is trying to catch up. The first half now hits a new physical limit of neutron degeneracy pressure: there are simply too many neutrons trying to occupy too little space at the same time, and the strong nuclear force repels the neutrons away from each other, stopping contraction and supporting a solid mass of neutrons. If the star is not massive enough then this is where the story ends and the result is a new neutron star. However, for heavier stars this is not a long-lived state, as the second half of the core comes crashing down, raising physical densities to incredible values and initiating the collapse into a black hole. Gravity overwhelms everything, even the strong nuclear force, and the matter in the core is squeezed into a singularity. Some of the star falls into the singularity with the core, while the rest is ejected in a violent display of the laws of conservation of momentum. ",
"This whole process, moving multiple stellar masses of material around at large fractions of the speed of light, takes significantly less than a second. Before this process happens you have a large ball of normal looking matter with a high iron content, a second later you have black hole and a rapidly expanding cloud of neutrinos and matter that we call a supernova. Estimates I've seen put the length of this process at a few hundred milliseconds.",
"I should point out that lighter stars undergoing this process will end up as white dwarfs instead of neutron stars or black holes. These stars are supported by another repulsive effect based in quantum mechanics called the electron degeneracy pressure. The temperature and pressure is high enough to disassociate the electron shells from atoms, but not high enough to force electrons and protons to combine into neutrons (as happened above). Thus, once enough fuel is burned the star becomes a big soup of free atomic nuclei and free electrons. The star is not massive enough to kickstart the fusion of heavier elements such as carbon or neon, so once the star burns all of its hydrogen and helium it is burnt out. It is however still extremely hot, and will continue to glow bright white for a long time as it cools into a black dwarf. This process takes so long that no black dwarfs are expected to currently exist (interestingly, this also means that the coolest observed white dwarf gives us a lower bound on the age of the universe). ",
"I'll also point out that this just describes the creation of star sized black holes. There are larger objects such as intermediate black holes and supermassive black holes that are suspected to form much differently.",
"The reference I used for time values:",
"https://arxiv.org/abs/astro-ph/0601261"
] |
[
"That was amazing, thanks for your time. "
] |
[
"Black holes lose mass via Hawking radiation, but the process is ",
" slow even on an astronomical scale. If our sun became a black hole, total evaporation (10",
" years) would take far longer than the current age of the universe."
] |
[
"Electrostatics phenomenon: moving charge lights up a fluorescent lamp.?"
] |
[
false
] |
I'm messing around with electricity for a class on electrostatics. I have a toy latex balloon (about 8 inch diameter blown up) and an unmounted fluorescent bulb, specifically an F8T5 lamp, which is about 12 inches long. It seems I can light up the tube just by moving a charged balloon around nearby. Can you explain this? I charge the balloon by rubbing it on my shirt. The lamp is held in one hand at one end. In my other hand is the charged balloon. Now if I just wave the balloon around, or back and forth, the fluorescent lamp will glow, bright enough to see in a room with dim lighting. It also works if the lamp is laid on a table and the balloon waved around it a few inches away. If the balloon is not moving relative to the tube there is no light. I don't understand what is causing the light (presumably a discharge in the tube) when I wave the balloon around a few inches away. There are no sparks or audible crackles that I can perceive. The balloon needs to be moving just a few inches per second to make the lamp light up, and can cause the light from a distance of 5-10 inches.
|
[
"The florescent bulb's terminals are not connected, so there is no circuit and no magnetic flux going through a circuit... So there's no EMF involved.",
"By moving the balloon he's creating linearly polarized radio waves with very long wavelength, which can be though of as a quasi-static electro magnetic field. When the balloon is placed in a distance such that the electric field of this wave is inside the bulb, it induces a current in the bulb."
] |
[
"The florescent bulb's terminals are not connected, so there is no circuit and no magnetic flux going through a circuit... So there's no EMF involved.",
"By moving the balloon he's creating linearly polarized radio waves with very long wavelength, which can be though of as a quasi-static electro magnetic field. When the balloon is placed in a distance such that the electric field of this wave is inside the bulb, it induces a current in the bulb."
] |
[
"You call this an \"electrostatics phenomenon\" but you said you are moving the charged balloon. This motion of charge produces a magnetic field.",
"To fully explain this I think we need to know whether you're actually getting light emission from the gas inside the tube, or whether it is simply the fluorescent coating on the bulb that is glowing."
] |
[
"From how far away can light from Earth be seen?"
] |
[
false
] |
I was hearing about exoplanets and how difficult they are to be spotted since they don't produce any of their own light, and I became curious. How far away could you be and still see light emitted from Earth?
|
[
"Honestly it's pretty much impossible to answer this question. As long as you're close enough so that ",
"/u/kasahito",
"'s issue doesn't apply, theoretically you can see light from anywhere. In practise, stars tend to outshine the reflected light from planets.",
"This is the problem we have with finding exoplanets - even the very big ones are far outshone by all of the stars around them, so finding them is a matter of having very accurate and very precise visual telescopes. ",
"So really, the limiting factors on how far you can see light from are twofold",
"1) Being close enough that the expansion of the universe doesn't outpace the light being emitted. You'd have to be pretty far away for this to be a problem",
"2) Having sufficient technology to distinguish Earthlight from Sol's light. That's an open question."
] |
[
"I will note that ",
"there are a few",
" exoplanets which we have been able to detect from their own light."
] |
[
"A few, and of those, almost all of them are much, much larger than Earth except one, which is only twice as massive.",
"There's also a few that we don't know their mass accurately.",
"I'm not sure whether we found the smaller ones by reflected light or not, though."
] |
[
"While I yawn, why does the music I'm listening to speed up?"
] |
[
false
] |
Today, I was listening to some music with an absolutely constant tempo (electronica), and I yawned, and while I was in mid-yawn the tempo of the song sped up by a few beats per minute. This isn't the first time this has happened - this is noticeable most times I yawn and listen to music, but I was reminded of the effect when I did it a few minutes ago. Is there any explanation?
|
[
" 's assessment is correct. There is not a shift in pitch, but changes in relative amplitude due to yawning altering some properties of the middle ear. ",
"The problem, however, is that the OP is not referring to amplitude or pitch changes. Fortunately, rhythm researcher ",
"Marilyn Boltz",
" has examined a few interactions of amplitude and and pitch shifts on perceived tempo: it appears that listeners rate tempi of stimuli as having increased tempo when a comparison stimulus has a lower amplitude. "
] |
[
"I'm not sure that the apparent pitch does change. Sound may be conducted differently before it reaches the cochlea, but the frequencies of those vibrations wouldn't change by my figuring. And the cochlea is filled with fluid, so the wavelength of the vibrations in the cochlea won't change. I think frequency wouldn't be shifted.",
"What will change is timbre or shape of the sound, meaning, the relative amplitudes of different frequencies. This may be enough to account for what the OP is asking about."
] |
[
"Which properties does it alter? ",
"I've tried it with earbuds and with speakers, and in both cases the music sounds quieter to me. The paper you furnished appears to suggest that if the music gets ",
" it sounds faster, but it doesn't sound louder and faster to me, it sounds quieter, faster, and with a constant pitch. "
] |
[
"Why is there a certain amount of electrons allowed in each orbital, when orbitals are not clearly defined?"
] |
[
false
] | null |
[
"Orbitals are not defined by some volume of space, where point-like electrons can freely flow into when they \"occupy\" that orbital, which is possibly how you're imagining it.",
"Rather, orbitals are mathematical solutions that describe the electrons themselves. When we say an electron occupy an orbital, we're saying that there is this equation, given by these set of quantum numbers, that describe its behaviour. One of the properties is probability distribution in space, which gives rise to the shapes that you see when it comes to atomic orbitals. However, that is very different from what I said in the first paragraph - the reasoning is completely opposite. That is, we don't determine which orbital an electron is by where it is in space - rather, it's the other way around.",
"Those shapes often are just some volume where there is some probability of finding the electron inside it. They are not hard-drawn lines where if an electron is inside it, we say it occupies that orbital. This is even more clear in examining multiple electrons - different atomic orbitals have significant overlap, so you can't just point to somewhere in space and say \"this point belongs to 1s orbital, so if I found an electron there, it is a 1s electron\"."
] |
[
"This is a great answer. Very well explained.",
"I find it helpful to realize this implication of the above:",
"An electron in the 3rd orbital can and is found in the space typical of electrons in the 1st orbital. And an electron in the 1st orbital can and is found in the space typical of the 2nd orbital. And so on.",
"As rupert1920 said, it's all about probability (quantum mechanics, yaaaay). The orbital of an electron gives us a prediction about how likely we are to find an electron in a particular space, but it is not a hard and fast rule."
] |
[
"Orbitals are clearly defined as solutions to the Schrödinger's equation, which are probability amplitude distributions labeled by the quantum numbers (eigenvalues of the equation). Since electrons obey the Fermi's distribution, only one electron can occupy a give state labeled by the set of quantum numbers."
] |
[
"Why do wind turbines have 3 blades? Wouldn't 4+ blades generate more torque?"
] |
[
false
] |
I would assume more blades would equate to more surface area, thus more torque? Or is there an equilibrium of energy generation efficiency at lower rotation speeds?
|
[
"I'm by no means an expert, but from what I've read, more blades does not necessarily mean more torque imparted by wind. In fact, more blades can negatively effect the efficiency of the turbine. As each blade sweeps through the air, it leaves behind a turbulent wake which can disrupt the following airfoil. By reducing the number of blades, you ensure cleaner air for the following blade so the wind can effect more work upon the surface. Also, more blades equals more weight and cost, so reducing the number of blades to the minimum needed for efficient work would allow the cost of the whole assembly to be recouped quicker. Also, if the turbine blades cause too much resistance against the airflow (due to the inertia needed to overcome static friction among other factors) then the air would naturally divert around the assembly also reducing efficiency. Betz's Law states that the maximum amount of energy that can be extracted from a turbine in a fluid is 59.3%. Most turbines only seem to come close to half this value. So by making the turbine as efficient as possible, the lifespan of the turbine and it's costs are kept at acceptable levels.",
"Furthermore, an even number of blades introduces instability in the design as airflow is not constant over the entire face of the area covered by blades. Also, the tower itself introduces a wind shadow. Airflow is generally strongest at the top of the arc. In a 4 bladed design, you have one airfoil in the area of strongest airflow while the other passes into the wind shadow of the tower. This introduces asymmetric forces upon the turbine shaft, causing increased wear and noise. By using an odd number of blades, you assure that when one blade is in the area of highest flow, there is no blade in the wind shadow, and vice versa.",
"(Apologies in advance if this answer is not deemed acceptable, as I have rarely been in a position to provide an answer)"
] |
[
"I can confirm this and add on to it. As an Engineering student, we were tasked with finding the best possible configuration for a wind turbine. Three blades is best for generating electricity for the reasons ",
"/u/TigerRei",
" mentioned.",
"More blades, however does produce more torque, so turbines with more blades are sometimes used, just for other things than wind turbines."
] |
[
"From what I've been reading, more blades becomes useful the smaller the turbine gets, or the more viscous the fluid."
] |
[
"How long does marijuana/weed/THC stay detectable in the body?"
] |
[
false
] | null |
[
"Drugs have a half life in the body. For THC, the half life is about one day. ",
"Here's a ",
"1995 study",
" that showed detection windows for THC were only a few days. If you are staying clean for 4 months, you should be OK. Even 1 month, you should be OK. One week and you are cutting it close."
] |
[
"I will disagree based on my own experience within the past few years. Whether detection methods have changed or I'm abnormal I can't say. From my own experience, leave at least 30 days to clean out."
] |
[
"30 days for urine, 90 for hair."
] |
[
"Why do cells split?"
] |
[
false
] |
I understand they split for reproduction purposes, in order to sustain life, but what triggers the cell to do so? Are there certain processes that take place prior to the actual action of the split?
|
[
"There is a cycle set up in the cell where it will produce more and more of a certain protein, and eventually the protein will reach a density point to where it interacts with another protein and forms new molecules which begin the process of cell division. It is like a molecular symphony of events, which is programmed into the cell. ",
"Mind you, this only occurs in Eukaryotic cells, which are much more complex, have bigger genomes, and more elaborate cellular architecture. Prokaryotic cells on the other hand (think bacteria) divide using different mechanisms. I'm not as familiar with what triggers cell division in the simpler Prokaryotic cells though. As a rule, Eukaryotes often have much more genetic controls in place, and that's what makes their division processes so regulatable. I'd imagine something similar goes on in the Prokaryotes, but I don't know for sure. ",
"Edit: the proteins is question are called Cyclins and Cyclin-Dependent Kinases. You can read a bit about them here: ",
"https://en.wikipedia.org/wiki/Cyclin",
"In effect its a signaling system which can be manipulated to cause a cell to divide or not divide, and on a certain time schedule. "
] |
[
"So I think you are askign what \"triggers\" a cell to divide right? When cells grow in the Gw phase they will either commit to divinding or they will in a sense \"drop out\" of the cell cycle. At this point of the cycle its called the Start or restriction point. So if the cell is like nah I aint gonna divide it goes to a G0 phase and this is usually because it did not recieve the apropriate growth factor signal telling to to divide. But if the cell is like hell yeah ima divide it goes into the S phase. ",
"So basically the best way i can say it is the cell goes through various checkpoints. At these checkpoints certain signals are given that either say go divide or no stay. "
] |
[
"Why/how does it decide to split? Very far fetched, but I am actually trying to connect it to the atmosphere. Firm believer in everything is connected, and there are storms that do split, so just maybe there is a link between the two. Just maybe. "
] |
[
"How did people not contract consumption from their spouses in the 1800s?"
] |
[
false
] |
I'm reading The Terror by Dan Simmons right now, and one of the characters marries a woman in maybe 1815 in England. She already has "the consumption" (which I almost always interpret as TB) when they're married, and they produce a child in the two years before she dies. This book is somewhat historically accurate, and I've read lots of other accounts/stories of people with loved ones/spouses who are dying of the disease (also lots of movies, Moulin Rouge springs to mind). The people seem to interact with the sick normally (no masks or quarantine) up until their death, but they don't contract the disease. From what I know, TB is airborne and contagious, and the above is NOT how we'd respond to "consumption" today. Ninja edit: I forgot to ask about vaccination. I highly doubt it, but were there immunizations available for TB/consumption back in 1820? I'd assume not, given that it was still vaguely understood as an umbrella TB type infection, and referred to only as consumption.
|
[
"https://www.mayoclinic.org/diseases-conditions/tuberculosis/symptoms-causes/syc-20351250",
"TB is rather hard to catch. ",
"TB often includes an 'inactive' stage where the carrier shows no symptoms, and is not contagious. This may last for years.",
"A healthy immune system is capable of dealing with tuberculosis bacteria without producing life threatening symptoms. "
] |
[
"Latent TB",
" probably affects about 30% of all people and we don't really know why sometimes it become virulent. So it is entirely possibly that those spouses had the TB bacteria, but not full blown TB."
] |
[
"As a modern figure, about 1 in 5 people in \"close contact\" with an infected person will also contract tuberculosis. However, one would imagine that in the past, with worse hygiene, and the disease going untreated for years, maybe that rate approached 100%.",
"But then, only 5-10% of people who contract tuberculosis develop overt signs of the disease, though again this is a modern figure, and may not reflect 19th century populations.",
"As for whether \"consumption\" always meant \"TB\"... maybe? The bacteria that causes the disease was only identified in the late 1800s, and prior to that, the diagnosis was made based on purely symptomatic criteria. Essentially, if you have an obvious lung ailment, couldn't stop coughing, and were losing weight, you had consumption. This probably missed a lot of atypical and asymptomatic cases of TB, as well as included a lot of people with other diseases.",
"(all I did was read some of the sources for the Wikipedia article on tuberculosis)",
"Edit: As for immunization, TB vaccination only started in 1921, and did not become common until 1945."
] |
[
"Shouldn't the sun's spectroscopy only show the lines for hydrogen and helium? Why does it give off the entire rainbow when passing through a prism?"
] |
[
false
] |
Since the sun is mostly hydrogen and helium, when is passes through a prism, shouldn't only the lines for hydrogen and helium be visible? Isn't that the basis for spectroscopy and how distant star composition is determined? How is it that the full rainbow is seen?
|
[
"Most of the light the sun emits is from standard ",
"black-body radiation",
" of a body of 5777K, which produces a huge range of frequencies. It's actual spectrum can be seen in ",
"this",
" chart: as you can see, while it isn't a perfect black-body, it fits fairly well."
] |
[
"The Sun's spectroscopy should have all of the colors ",
" for the hydrogen and helium lines. ",
"The Sun (and really, all hot objects) emits ",
"black-body radiation",
" which is \"white\" in the sense that it emits all wavelengths (but it has a peak wavelength near yellow). However, the hydrogen and helium lines are absorbed by the elements in the Sun. "
] |
[
"It isn't, but black-body radiation is a pretty good fit for it's emissions (there really isn't a perfect black-body in nature that we know of, although black holes and the cosmic microwave background are extremely close)."
] |
[
"How was Newton's gravity equation derived if we didn't know the specific quantities involved? How could you check your math with the evidence to verify it's correct? (Such as the masses of planetary objects or the distance between them?) Said another way, how did we compute the masses of planets?"
] |
[
false
] |
In Newton's equation for the force of gravity, he derived F = GmM/r and then that has been used to calculate, say, the masses of the planets in our solar system as well as the sun. What i don't understand is how that was able to be accomplished considering you need all of the values except for one in order to solve the equation (for a specific value). So, for example, if I want to know the mass of the moon, I need to already know the mass of Earth, its distance to the moon, the gravitational constant as well as the force of gravity between the two! Which quantities became known first in order to figure out these things??
|
[
"Newton actually didn't know the masses of the objects in the solar systems, because astronomically you can only measure GM, and he didn't know the value of G. Only like a hundred years later did someone manage to measure the gravity between two big lead balls of known mass and determine G from that; this experiment was known as \"weighing the Earth\" because it allowed people to find out the mass of the Earth.",
"What Newton did was to figure out that in general, an attraction that goes like 1/r",
" produces elliptical orbits with the Sun at the focus. Since Kepler had already figured out that the orbits are elliptical (using Tycho Brahe's data), this gave Newton confidence that his law was right, even if he didn't know all the numbers."
] |
[
"Your intuition is correct. Newton didn't get hit by an apple and then write down GMm/r",
" and say \"this is gravity\". That's not what he did or what it meant.",
"At the time of Newton, the orbits of celestial objects were known to very accurately follow Kepler's laws:",
"https://en.wikipedia.org/wiki/Kepler%27s_laws_of_planetary_motion",
"However, at the time, these relations were simply seen as empirical fits. They were laws with their source in geometry, but not justified by any physical mechanisms. No one knew WHY they were true and they seemed fairly obtuse and arcane in terms of what they were saying. In a sense they took the incorrect idea of \"planets go in circles around the sun because... reasons\" and replaced them with an equally unjustified set of statement of their motion.",
"It is intensely debated to this day whether it was Newton or Robert Hooke who first postulated the idea of an inverse square law. Regardless, what Newton DID DO, what his big \"drop-the-mic\" discovery was, was that he showed that he could DERIVE Kepler's laws from the assumption of an inverse square force of attraction. ",
"That was his big discovery, to distill these \"orbital shapes by fiat\" approach that prevailed and showed that they were the result of one very simple guiding cause, masses attract like an inverse square of their distance."
] |
[
"You can determine the ",
" masses of different objects by the magnitude of the acceleration they cause. As for determining how much mass corresponds to how much gravitational acceleration (i.e., the gravitational constant), you need to start with known masses. And believe it or not, this can be done by taking very heavy objects in a lab and measuring the tiny force between them."
] |
[
"What's the difference between 'Imaging optics' vs 'non-imaging optics'?"
] |
[
false
] |
Hello, hopefully explaining at a high school level or below, can someone help me understand the difference? Is one about mirrors and the other about lenses? Thanks so much! :)
|
[
"Imaging optics try to make an image of the field of view. Information of the spatial distribution of targets as well as their intensities are recorded in the image. Your CCD cameras come under this category. The spatial distribution of the signal strength will be recorded in the spatial distribution of the sensor's response.",
"Non-imaging optics is the theory of thermodynamically efficient optics and as such, depends more on thermodynamics than on optics. Non-imaging optics is the branch of optics concerned with the optimal transfer of light radiation between a source and a target. Unlike traditional imaging optics, the techniques involved do not attempt to form an image of the source; instead an optimized optical system for optimal transfer of radiation from a source to a target is desired. These make use of devices called imaging concentrators (See ",
"Concentrator",
".pdf)). Examples of non imaging optics are : solar energy concentration which is maximizing the amount of energy applied to a receiver, typically a solar cell or a thermal receiver, Collecting radiation emitted by high-energy particle collisions using the fewest number of ",
"photomultiplier",
" tubes.",
"My knowledge in this field is also quite limited, but I hope I provided some basic insight into this!",
"Edit : Added link"
] |
[
"Collecting radiation emitted by high-energy particle collisions using the fewest number of photomultiplier tubes.",
"Typically you want to know where the light comes from. It doesn't always have to be imagining, but usually you want more information than just \"there was light\"."
] |
[
"Thanks I think I get what you're saying: Imaging optics have to do with directing light/an image without distortion, whereas non-imaging optics have to do with concentration and directing light. (right?)",
"",
"So if someone is saying they are using a combination of non-imaging optics and imaging-optics for designing a lightbulb, they are probably saying that they are combining the two in a way that takes advantage of both techniques?"
] |
[
"Is there any type of animal whose nervous system isn’t based on neurons?"
] |
[
false
] |
As I understand it, all nervous systems are based on neurons: axons, action potentials, synapses, etc.. Broadly similar in all animals. Is there an alternative to this model that works in different way and still works quickly? My first thought would be chemical messaging but that is essentially hormone regulation. That’s not something you could “think” even in the most rudimentary sense.
|
[
"Sponges (porifora) are considered animals, and have no nervous system and no neurons, but do have cells that are ",
"similar in function to neurons",
". Cnidarians (Jellies) have nerves, but no nervous system or brain, more of a nerve network.",
"Placazoa",
" are animals that have no tissues or organs, and no nerves. The trichoplax is one example of a Placazoa, and there are two others. It's an oddity. The most recent classification puts placazoa as a cousin of sponges and jellies. A sponge is more closely related to us than the trichoplax.",
"So basically, sponges and Placazoa.",
"Edit: I realize I didn't answer your question. The nervous system, by definition, is comprised of nerves, which are comprised of neurons. So, there are no animals with a nervous system comprised of anything other than nerves.",
"Sponges rely on cells that can do some chemical signaling that secrete chemicals, called secretory neuroid cells, but they lack anything like a synapse.",
"There are other types of chemical signals that could serve similar functions. One could think of a mycelial network as a giant complex chemical signaling system between interconnected mushrooms like a nerve network. But then it's hard to draw the line, as almost anything could be considered a chemical signals system. When your body secretes insulin and it's carried in the blood and then attaches to a receptor, we wouldn't call that a nervous system."
] |
[
"I also want to note that the nervous system is not just comprised of neurons- there are several other types of cells (collectively called “glia”) that are part of the nervous system and critical to its function."
] |
[
"I know you said animals, but there is a lot of research going on right now on things that are not animals. For example, look up slime molds. Another interesting area is many plants have very complex ways of signaling other plants about an invader. Some plants have ability to move, such as the Venus fly trap (Via purely chemical means). There are also fun experiment such as this one player a researcher noticed Pavlovian response in Mimosa plants (built a roller coaster for the plants) ",
"https://dustandtribe.com/2020/11/09/pavlovian-plants/",
"Flatworms have a very simple nervous system, but have some very cool tricks. You can teach one a trick, cut it in half, each half regrows into a new worm and both know the trick. Moreover, you teach a worm a trick, cut it up into little pieces, feed these pieces to other worms, and all of these worms end up knowing the same trick as the one they ate."
] |
[
"Why do we use Caesium in atomic clocks?"
] |
[
false
] |
[deleted]
|
[
"Caesium is a fun element because it is easily excited. To say it more properly, it's easy to ionize, you can do so with visible light (so it works as a photoelectric material), and it can easily be ionized by an electrically powered source of microwave radiation.",
"In addition to having a single electron in its outer non-filled shell (some other elements also have that), caesium has a higher energy difference between electron states. More accurately, caesium has a larger hyperfine structure, which, in terms of an atomic clock, means that the changes in electron state that the clock observes happen more often. Since an atomic clock counts those changes, that means that the more they happen, the more accurate the clock can be.",
"This allowed, some decades ago, to precisely define a second as, SI definition follows, \"the duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom.\""
] |
[
"I answered it about a month ago here:",
"http://www.reddit.com/r/askscience/comments/1i8j8n/why_was_caesium_picked_to_define_the_second_on/",
"In a nutshell, reproducibility.\nStandards need to be reproducible, so that any lab anywhere can re-create the standard on their own. Caesium has a few properties regarding its hyperfine transition that give it advantages over other elements. Additionally, nearly 100% of the caesium found in nature is a single isotope, which nearly eliminates isotopic purity concerns."
] |
[
"Wikipedia:",
"A caesium standard or caesium atomic clock is a primary frequency standard in which electronic transitions between the two hyperfine ground states of caesium-133 atoms are used to control the output frequency. The first caesium clock was built by Louis Essen in 1955 at the National Physical Laboratory in the UK.",
"Caesium clocks are the most accurate commercially produced time and frequency standards, and serve as the primary standard for the definition of the second in SI (the metric system). By definition, radiation produced by the transition between the two hyperfine ground states of caesium (in the absence of external influences such as the Earth's magnetic field) has a frequency of exactly 9,192,631,770 Hz. That value was chosen so that the caesium second equalled, to the limit of human measuring ability in 1960 when it was adopted, the existing standard ephemeris second based on the Earth's orbit around the Sun. Because no other measurement involving time had been as precise, the effect of the change was less than the experimental uncertainty of all existing measurements."
] |
[
"Is there a logical explanation for the effects of Sheldrake's experiments with Morphogenetic Fields?"
] |
[
false
] |
[1] [2] I've been looking into these after I played a video game where they were a main part of the plot. I don't agree with the conclusions Sheldrake made, but I don't know what another reason for his results could be. Was it because of poor testing protocol? Has anyone repeated these experiments and gotten similar results?
|
[
"Possibly of interest - ",
"http://www.skepdic.com/morphicres.html",
" - "
] |
[
"Sheldrake's experimental protocols are very rigorous, IMHO. I have examined the folks who tried to debunk Sheldrake; in my opinion, they were illogical and question-begging. I have also looked into some of the folks who checked Sheldrake's work; they seem to be solid. ",
"Sheldrake worked with Trinity College of Cambridge up to 2010, and they are known for their attention to detail; we can be certain that there are quite a few folks reproducing his tests, but many of them won't get published.",
"http://www.sheldrake.org/Articles&Papers/papers/morphic/index.html",
"Now, Radin and Emoto put out some similar work at:\n",
"http://www.scientificexploration.org/journal/jse_22_4_radin.pdf",
"But perhaps what Radin and Emoto found was not exactly what Sheldrake found. "
] |
[
"thank you very much! I enjoyed your links"
] |
[
"How is the CMB be the most distant thing we can see when there is a cosmic horizon?"
] |
[
false
] |
Hi ! I'm watching the PBS Spacetime series on the Cosmic Microwave Backround and something's nagging at me that I was hoping you could resolve. I get the gist of the following facts: When I think about it, points two and three seem to be in conflict with each other. It seems like the CMB will always be the most distant thing we can see since the light it released was the first light ever produced in our universe. So a billion years ago the CMB was the most distant thing able to be detected, and a billion years from now the CMB will still be most distant thing view-able, since the the universe began releasing light more or less everywhere at once, and so we're seeing today the CMB at a distance of 13.2 B light years, a billion years ago one would be able to see it at a distance of 12.2 B, and a billion years from now one will be able to view it at a distance of 14.2 B light years. But doesn't this contradict the idea of a cosmic horizon? If, in the future, we will actually be able to see less of the universe because it is expanding faster, wouldn't the furthest away objects we see actually be closer to us today than they will be (lets say) a billion years from now? Wouldn't the CMB "we" see in a billion have had to have been released from a point closer to us than the CMB we are seeing today since the universe is expanding and today's most distant objects will have fallen behind the cosmic horizon, and we would therefore have seen it already, and not a billion years from now? My apologies if I'm being a bit inarticulate, even speaking about this in a way that makes sense to me is difficult, so let me know if I can clarify any part of my question. Please ELI've taken an intro to physics and a few calc classes, along with having watched some PBS Spacetime episodes. Thank you all in advance!
|
[
"The CMB we saw a billion years ago (well... would have seen) was emitted by matter closer to us. In a billion years we'll see the radiation from matter so far away that we can't see its radiation yet. At the same time we can follow what happened to the matter later that emitted the CMB we see today.",
"The matter that emitted the CMB we see today was about 42 million light years away from us at the time of emission. If you do the same calculation for other times then you get a sphere that expands over time. Very early in the universe this radius increased by the speed of light, now it increases by 1/1100 the speed of light (corresponding to the redshift of the CMB since its emission). If you wait long enough this radius will increase to 55 million light years or so. Didn't calculate it precisely. Anyway: It will approach a finite value. We'll never see light from matter more distant than that."
] |
[
"The intensity will never reach zero, mathematically, but it will be redshifted more and more until it becomes too weak to observe."
] |
[
"The further away from us a photon starts the longer it takes to reach us. For a photon from behind the CMB to reach us it has to travel for a longer time than the photons in the CMB. Thus it has to be older than the CMB. There are no such photons to see.",
"Basically the CMB is equivalent to the cosmic horizon of light. There is a 'X year horizon' for any amount of time at which all of the things we see at some distance are X years old. The larger the value of X the further away it is. Thus the oldest photons are the furthest."
] |
[
"Solar system element abundances - why are elements with even atomic number more abundant than elements with odd atomic number?"
] |
[
false
] |
As shown in this diagram:
|
[
"So you know how electrons in orbit around the nucleus like to pair up? One spin up, one spin down for each suborbital? Well the nucleus behaves very similarly. For heavier nuclei, they're more stable when they have even numbers both of protons and neutrons.",
"Otherwise, lighter nuclei are most stable when the number of protons equals the number of neutrons (so there will be an even number of total nuclei in this case as well)"
] |
[
"The easiest way to think of it is that it's the lowest energy state.",
"For a very (overly perhaps) simple approach: Spin up is like a little tiny magnet with the north pole pointing up. Spin down is like south pole pointing up. They like to be aligned in this manner. To do otherwise would require extra energy."
] |
[
"okay, so while any process that's energetically allowable to happen probably will, there are certain... coins that nuclear physics likes to trade in. Bear with me for the following analogy.",
"First you have your penny, the proton. Technically you can make anything out of it by sticking enough of them together (and letting a few decay into neutrons). But it's kind of time consuming and there are a lot of little steps. Then you've kind of got your standard workhorse coins deuterium and tritium/He",
" say like your nickels and dimes. Deuterium's nice because it has one of each, and tritium has an extra neutron, and He",
" an extra proton. But the real heavyweight, the coin that gets things built, the quarter, is the Alpha particle. The He",
" nucleus. The most stable nucleus you can assemble. 2 protons, 2 neutrons, ground state energies. Fantastic. So when you want to build a carbon atom you're going to put together 3 alphas. (2 alphas go to Mg, and a third goes to carbon)",
"Now carbon does an interesting thing in addition within stars. Carbon catalyzes the production of more alphas. Tack a proton onto C",
" , and you get N",
" . N",
" decays into C",
" . Tack another proton on and you get N",
" , which is stable. Tack a proton to that, and you get O",
" which decays down to N",
" . Tack a proton onto that and it binds to the 1 proton and 2 neutrons (they were the protons that had previously been added, and decayed) and we get a 2 proton-2 neutron ensemble that ",
" off the N",
" to bring it back down and around to C",
" . Those 2 protons and neutrons? Alpha. This is known as the ",
"CNO cycle",
", and it's one of my favorite things in astronomy."
] |
[
"Does a standard vacuum cleaner create static electricity and does the vacuuming of dust cause a buildup as well? /r/techsupport wants to know."
] |
[
false
] |
Hey askscience, needs your help! We are having a discussion on the cleaning of a device and the question of vacuuming came up. Some texts say it is fine to vacuum your computer, I would disagree, after watching components being damage from static discharge from the end of a vacuum hose. Though that is my own account and cannot be used as a strong source to prove whether or how static build up on the end of a vacuum hose when vacuuming dust. We need some solid science to figure out what is right and what is wrong. Here is a link to the thread.
|
[
"I can't answer the question of whether it's ever possible for it to arc, but if you hold the front of the nozzle, as well as the computer case, all static build up should disappear. People are pretty good conductors after all, and your case is grounded. To be extra sure, you could attach a metal wire around the nozzle, and run it to a radiator."
] |
[
"No, don't run it to a radiator. What you want is to have it at the same potential as the rest of the computer, and the only fool and murphy proof way of doing that is by connecting the ground wire to your computer cabinet."
] |
[
"Any time two dissimilar insulating materials move across each other, there can be a ",
"triboelectric effect",
", causing a voltage to build up between them. This can happen even with air moving across things, like plastic. It is very hard to make predictions about this effect; measurements and observations are better. Even things like the air humidity will change how much charge builds up. ",
"If you can see an ElectroStatic Discharge (ESD) spark (which I ",
" you are saying you've seen), then I believe that the voltage is probably ~4kV or higher. That is more than enough voltage to damage things if there is enough current to go with it...that's going to depend on the capacitance of the hose, and how much charge has built up. That's going to vary, so there's no simple yes/no answer. Could there be an ESD event strong enough to damage a device? Sure. Is it going to happen in a particular circumstance? Very hard to say. ",
"The air itself won't easily charge up much as it moves towards the hose. So as long as you keep the hose well away from everything there's not much risk. Or use a metal vacuum nozzle, preferably one that is grounded. "
] |
[
"What happens to all of the kinetic energy from matter falling into a black hole?"
] |
[
false
] |
[deleted]
|
[
"when you go into the center-of-momentum frame, the kinetic energy is part of the total mass of the object-blackhole system, so it should contribute to the black hole mass when the object is absorbed. it's not like this energy comes out of nowhere either, if you have two masses separated at a distance from each other there's (in newtonian terms) potential energy in the system, which is converted into kinetic energy when you let go of them (due to their gravitational attraction). that potential energy is also part of the total mass of the system."
] |
[
"There is no center of a black hole for an in falling object. Even, after it crosses the event horizon, it will continue to fall inwards, technically for ever, so there won't be an impact."
] |
[
"There is no center of a black hole for an in falling object. Even, after it crosses the event horizon, it will continue to fall inwards, technically for ever, so there won't be an impact."
] |
[
"What is the etymology of modern Black names like LaKeisha, Devonte, Shanice, D'Andre, etc?"
] |
[
false
] |
Firstly, I wanna make it clear: I am *not* trying to exotify or mock Black names or Black culture. I am *fully* in support of Black parents being able to name their kids what they want. I think that coming up with non-slave-names is a powerful reclamation of what was stolen from them. Mocking these names (or ) is straight-up racist. What I'm curious about: why were *those* names chosen in particular? I know the trend of Black name reclamation started in the 60s, and it rose with the Black Power Movement. I know that a lot of Black people took Muslim names, or names from SubSaharan cultures. But the names I'm talking about (LaKeisha, Devonte, Shanice, D'Andre, etc) don't seem to have roots in SubSaharan or North African cultures. EDIT: to clarify: I'm wondering where the name "Devonte" came from. Or names that start with La or D', etc. These unique names aren't completely random. There are trends amongst them, trends that were picked up by Black families nationwide. This implies they have shared roots and/or influences. So what are those roots/influences? the names have French origins, starting in New Orleans. I can see the French influence for sure (La, D', etc)... but most Black people in this country don't come from New Orleans. ), but most don't come from New Orleans or even French Louisiana. So why did Black families nationwide begin adopting French-inspired naming conventions, starting in the same decade? Hope this question makes sense. Thanks for your response!
|
[
"I’m no expert but I read an article about this recently: ",
"https://theconversation.com/a-brief-history-of-black-names-from-perlie-to-latasha-130102",
"The gist of it is that there have always been distinctly “black” names in the US and the names do t necessarily have a distinct old world cultural tie to, say, Africa."
] |
[
"This is true far more broadly. Those who have benefited from the status quo are more conservative, have less variance from norms, and want to preserve the status quo.",
"Those who have been unsuccessful in the status quo have more variance, less commitment to traditions, and are in general less trusting of the social contract."
] |
[
"There’s a chapter in Freakonomics about this. Essentially it boils down to education, socio-economics and cultural identity, according to the authors. Wealthy educated people are more likely to pick common names for their children, whereas parents who are poor and have less education will seek a more unique name."
] |
[
"Why is there no red-blue colorblindness?"
] |
[
false
] |
There is the common red-green colorblindness which makes green and red hard to distinguish, and the rare blue-yellow colorblindness which makes blue and green hard to distinguish, why isn't there a red-blue colorblindness that makes red and blue hard to distinguish?
|
[
"Yes, this is called \"Anomalous trichromacy\". There are three type - protanomaly, deuteranomaly, and tritanomaly, corresponding to anomalies in the L ('red), M ('green') and S ('blue') cones respectively. Deuteranomaly is the most common type of colour vision deficiency."
] |
[
"Can you be short of cones or have them not work as well or are they always just missing?"
] |
[
"Can you be short of cones or have them not work as well or are they always just missing?"
] |
[
"Is there a real difference between real and artificial light when growing plants?"
] |
[
false
] |
Secondary question, can a light source affect its natural attributes on how it grows?
|
[
"It depends on the light. As long as an artificial light emits the same color light, meaning the same intensity of each wavelength, and the overall intensity matches that of the sun, and the duration of daylight is the same, the plant will grow just as it would outdoors.",
"However, not all light sources match the sun - in fact, most are quite different. Generally speaking, grow lights are tuned to be similar to sunlight, but something like a fluorescent light would be very different.",
"Edit: and regarding your second question, yes, the light source will definitely affect the plant growth. Dimmer lights will usually cause plants to stretch as they climb higher for brighter light. Certain techniques like aiming bright LED lights at stems of plants keep can keep the plants dense and compact."
] |
[
"grow lights are tuned to be similar to sunlight, but something like a fluorescent light would be very different.",
"Grow lights are often fluorescent, especially for plants that prefer full sun."
] |
[
"Yes, good catch. However, a ",
"typical fluorescent light has a couple large spikes",
" and low light in other bands, compared to a ",
"pretty even spread for sunlight",
".",
"Also note that newer fluorescent lights use coatings that have several elements, giving more peaks, and a more even, more sun-like spectrum. The above fluorescent spectral plot is one such light. The older-style fluorescent lamps (especially yellow ones) don't have as many peaks, and tend to have a more narrow spectrum (corresponding to the emission lines for mercury and phosphor).",
"Blacklights",
" are an even better example, having only two peaks. "
] |
[
"Why is water not considered a reactant/product when you have an aqueous solution?"
] |
[
false
] | null |
[
"For the same reason the plate your food on isn't part of dinner. It is the medium in which the reaction takes place, but not a part of the reaction its self."
] |
[
"Because the water takes no part in the reaction. Similar to the reason a catalyst ins't listed in a chemical equation(Though they take part, they are not altered in any way)."
] |
[
"This would have been my guess, but I wasn't sure. Thanks."
] |
[
"Using a black hole, could you effectively 'stop' a photon?"
] |
[
false
] |
I mean to say: is there a point at or around a black hole where gravity would bend space to the point where it would effectively cause a photon to 'stand still' in location? The attraction to the black hole == the forward movement of the photon and it would just 'sit' there?
|
[
"The closest thing to what you're thinking is the photon sphere, a region at 1.5 times the event horizon where light travels in a circular path. Otherwise, light either reaches the horizon or escapes to infinity."
] |
[
"Thanks! Gonna read up on ",
"them",
"."
] |
[
"No. Photons always travel at the speed of light. As a photon travels away from a gravitational object like a black hole it doesn't slow down, it loses energy and will red shift to ever longer wavelengths, but it always travels at the speed of light. It's impossible for a photon to travel at anything other than c. "
] |
[
"What part of the observation of the quantum level causes the wave function to collapse ?"
] |
[
false
] |
I never found a description about of the observation causes the wave function to collapse. I also believed the "consciousness causes collapse" theory was proven wrong? But as I don't find any theory of other causes it seems to me that this would be the current most realistic thesis this science area came up with by now, and that seems pretty weird to me. It may be a stupid question or badly described. Would be great if someone could answer.
|
[
"Observer Effect",
"For an electron to become detectable, a photon must first interact with it, and this interaction will change the path of that electron. It is also possible for other, less direct means of measurement to affect the electron."
] |
[
"\nBut then what I didn't understand was why it works at all, isn't there interaction by default already ? I mean I thought this was valid everywhere so what about sunlight ? That's what I meant with",
"isn't nearly everything interacting with photons more or less",
"Sorry if I'm a bit of a newbie here but I'm sure I could understand it with a little help because I didn't find an answer on that anywhere."
] |
[
"How do you see something, anything, if not by photons? You see, observe, when a photon hits your retina. That photon was produced when some particle gave off energy as a photon. The energy it gave off it absorbed from a flashlight that you pointed at it, so that you could observe it.",
"Or consider sonar. You want to see what's around you. You send out a ping; that is your equipment sends out a sound wave. That wave hits something (that's your interaction), and then a new soundwave is reflected back to you. You do some fancy math and now you've observed your surroundings.",
"The act of observation, by definition, requires having some sort of interaction between the observer and the observed. It could be photons, sound waves, electrons, whatever. Photons usually have the least amount of inherent energy, and thus they disturb the observed the least, but there's still energy there.",
"Or consider this. How would you go about observing something without interacting with it at all? How would you transmit information from some thing to you with no intermediary?"
] |
[
"Does the brain have a clock, like a CPU?"
] |
[
false
] |
A CPU has a centralized clock which in which instruction(s) are executed in each clock cycle. Neural oscillation, or "brain waves" are repetitive neural activities where the firing of the neurons are usually in synchronization with the oscillation. From what I've read, these are the following known waves and frequencies: My question is, how do CPU clocks and brain waves differ? They both synchronize the operations being executed, and they are for the most part, central as well. A brain would better analogous to a GPU than a CPU, since it's massively parallel, but a GPU still runs on a clock. One more question, would "overclocking" a brain (increasing the frequency) necessarily make it faster, like it would for a CPU?
|
[
"A little knowledge is a dangerous thing.",
"There is no significant evidence for the brain having a clock, at least in any fashion that is comparable to clock in a microprocessor. There may be some neural behaviour that is based on rhythmic neuronal behaviour/oscillations, but that is not equivalent to the clock on a microprocessor. In order to understand why they are not analogous, you need to understand what they both are.",
"A clock in a microprocessor is obviously based around a piece of vibrating quartz, a frequency multipliers and so on... but we can abstract it to a square wave generator, that is a voltage switching between high and low. The logic gates inside a microprocessor a built up of transistors, and they do not need a clock unit to work: an AND gate will perform it's function at any rate, up until the transistors simply do not have enough time to respond. HOWEVER, in order for large numbers of logic gates to work in parallel, they must be synchronized, both on the input (both inputs to an AND gate arrive at about the same time) and on the output (the output from an AND gate and and OR gate might need to arrive at another gate at the same time). This is, in essence, achieved using something like a 'register', which stores a binary value, and spits it out when it is asked, which is the next clock cycle. That is, the gate performs it's function, the value is put into a register, and then the next clock cycle, the register supplies that value to the next set of gates.",
"The brain does not work in a comparable fashion. There is no central clock. There are no registers. Neural function does not happen in a synchronous fashion. However, if one was to FORCE the analogy, it would be a network of logic gates with no registers. When a complex pattern of inputs (sensation) arrives at the input nodes of the logic gates, then perform their functions which then cascade as fast as the logic gates will allow through the network, and produce an output (movement).",
"So then, this might make you wonder what these EEG oscillations are? I think the most useful analogy is to simply think of them like the sound of your cars engine. When you car performs it's task, that task necessitates the generation of sound. Those sounds reflect the underlying task (low rumble: idle. Load roar: acceleration. Ticking: engine cooling) but they are not fundamental to the task. There are some neuroscientists who disagree, but I have never seen any actual evidence that proves that this is not the case."
] |
[
"I realize this is not the same as a CPU clock, but how does my brain know exactly how long it's been? For example, I can lay down and say \"I need a 25 minute nap\" and I wake up after 24.5 minutes. If I need to wake up at 5am, I wake up at 4:58, always within a minute or two max. How does it know? "
] |
[
"This simple answer is: we don't know. And certainly over lengths of time that large, we have no idea. There have been a variety of studies looking into this, and they usually are done by training an animal to do something, then pause for a given length of time, and then do something else. If they pause for the correct length of time, they get a reward. Depending on the area and the task, scientists have shown the activity of neurons building up during that pause, and also the activity of other neurons decreasing during the pause. If we assume that these neurons are causative to the pausing behaviour (which not all studies demonstrate), this simply moves the problem: well how do those neurons know how to measure time? It is my understanding we have no answer for this."
] |
[
"Is there a possibility of human experiments or devices accidentally generating a black hole?"
] |
[
false
] | null |
[
"The Large Hadron Colliders have a non-zero possibility of doing that. "
] |
[
"Sure"
] |
[
"Wow, and here I thought this was only going to be a concern for future generations. Do you have a source?"
] |
[
"Why does childhood seem so much better? When even the simplest stimuli provided a great sense of well-being?"
] |
[
false
] |
I'm not really looking for a "we get used to it as we get older" answer, but perhaps a more scientific reason that has to deal with neurochemistry.
|
[
"I'll start by saying I can't help you directly but might point you in a reasonable direction;",
"Dopamine plays a major role in the brain system that is responsible for reward-driven learning. ",
"http://en.wikipedia.org/wiki/Dopamine#Learning.2C_reinforcement.2C_and_reward-seeking_behavior",
"\"The dopamine system, which plays a crucial role in reward processing, is particularly vulnerable to aging. Significant losses over a normal lifespan have been reported for dopamine receptors and transporters\"",
"http://www.pnas.org/content/105/39/15106.full",
"Hope that helps."
] |
[
"Thanks for the studies. Makes me think that childhood is evolutionary a crucial learning/development phase that needed a more sensitive reward system to gain more knowledge. Too bad there isn't more discussion for this...hoped this would blow up"
] |
[
"There is a theory that I read about a while ago (Maybe someone can site me on this) but it says that since we are young an experience makes up a greater amount of our total experience (life) so comparatively it seems better. While we can take a 40 year old and have them go through the same experience but comparatively it will not be as great to the overall experience.",
"I know this is essentially the \"we get used to it as we get older\" but I just wanted to clarify a little."
] |
[
"Why oxygen cant be sustitued by any other gas in combustion reactions?"
] |
[
false
] |
Im working on a project that involves combustion and pyrolysis, and now I know how important is oxygen concentration for combustion reactions but, why cant any other gas take its place in this reactions? what makes oxygen so special?. Also, i've just realyse that fire is not as common in other planets due the lack of oxygen in their atmospheres, fire is more special than you think!
|
[
"but, why cant any other gas take its place in this reactions?",
"It can and does.",
"Oxidants for combustion have high oxidation potential and include atmospheric or pure oxygen, chlorine, fluorine, chlorine trifluoride, nitrous oxide and nitric acid. For instance, hydrogen burns in chlorine to form hydrogen chloride with the liberation of heat and light characteristic of combustion",
"https://en.wikipedia.org/wiki/Combustion",
"Of course, oxygen is so abundant combustion with other oxidants is rare in comparison.",
"Nitrous oxide is used in place of oxygen for combustion in some internal combustion engines:",
"https://en.wikipedia.org/wiki/Nitrous_oxide_engine",
"Hydrogen peroxide is used for combustion in rocket engines:",
"https://en.wikipedia.org/wiki/Hydrogen_peroxide"
] |
[
"Things can burn in chlorine and fluorine too. They are both more potent oxidizing agents than oxygen because of their ability to accept electrons and end up with a complete outer shell. A broader definition of oxidation and reduction is the loss or gain of an electron rather than reaction with oxygen. For instance fluorine and chlorine can pull electrons (oxidize) from platinum which does not happen with oxygen."
] |
[
"The determining factors here are rather the ionisiation energy and electron affinity, i.e. the energies necessary to remove an electron or gained by adding one. And chlorine has a significantly higher electron affinity than oxygen.",
"The electronegativity plays a role in the polarisation of covalent bonds."
] |
[
"What is stopping us from having a functional, manned spacecraft and larger space installations?"
] |
[
false
] | null |
[
"Money. ",
"The only major scientific roadblocks would be the effects of low-g on health and radiation. But with money, you can afford to send up enough shielding, at least for a panic room. And with money, you can build a big enough crew compartment to rotate to provide gs."
] |
[
"Like people said - money.",
"But also - we have lost the ability to accept deaths as part of exploration.",
"Every time someone dies in the space program it's a huge issue, years of investigations, and tons of more money and redesigns to make sure it doesn't happen again.",
"You can't safely explore new frontiers. We have to accept that \"once every few flights something bad'll happen and people will die\", and just go on after that.",
"But we're no longer at that place as a society :("
] |
[
"Interestingly, this is something that came up in my discussions with my girlfriend on the topic. A lot of pushes in our transportation technology and exploration of our planet came with huge death tolls - colonizing America was hard, difficult and a lot of settlers died, either from the sea voyage, from starvation or disease when they got here or from the various wars. I'm sure a lot of people died developing: sea-worthy vessels, airplanes, faster-than-sound jets, deep-sea vessels, etc. Heck, how many people die to car accidents?",
"It's interesting how we'll accept millions of car deaths as something \"normal\" but we won't accept the death of a space shuttle crew."
] |
[
"Does pressure effect evaporation?"
] |
[
false
] | null |
[
"Yes, at lower pressures liquids will evaporate faster."
] |
[
"that's what I thought. I was taught today that the pressure does not matter and that temperature is the only factor. Can you explain why it does matter?"
] |
[
"Decreasing pressure brings down the boiling point, so the fraction of molecules that have enough energy to vaporize increases."
] |
[
"Hi, my name is jack, I'm 14 years old, and I love Baseball. I would like to know when a pitcher throws a baseball, how does it curve?"
] |
[
false
] |
I found this gif on my front page as soon as I made an account here so it kind of helps me make the question more clear. Here is a pitcher throwing what is known to be a "Knuckleball" and it has a lot of breakdown to it, I want to know what makes a ball curve like this. Thank you everyone. And remember science rules!
|
[
"Hi Jack, a baseball can curve for a number of reasons.",
"For a knuckleball, the ball moves around as it approaches the catcher because it isn't spinning. Spinning helps stabilize the ball, and prevents small turbulent effects from affecting its flightpath. A non-spinning ball isn't perfectly spherical, so as the air comes off the face of the ball, it creates turbulence in the air, and causes the ball to move erratically. You can see an example of vortex shedding here:\n",
"https://www.grc.nasa.gov/www/k-12/airplane/Images/mix.gif",
"For something like a curve ball, the spin of the ball is what causes it to move in a certain direction. As the ball spins, one side goes in the same direction as the air passing the ball, and the other side goes in the opposite direction of the air passing the ball. The side that moves in the same direction accelerates the air slightly (imagine the surface being rough, and acting to push the air as it goes by). The side going in the opposite direction slows the air slightly. As air accelerates, the pressure drops, and as it slows, the pressure rises (this is how planes fly). The net result is that the ball gets pushed by this pressure difference. With a top spin, you'll see the ball dropping, and with a backspin, you'll see the ball rising (or at least not dropping as quickly). If you apply this to a side spin, it'll cause the ball to curve from left-to-right or right-to-left.",
"It's worth noting that fluid dynamics is super complicated, but that's a pretty simplified explanation.",
"EDIT: THANKS FOR THE GOLD!"
] |
[
"Just a tiny typo correction (I think) to avoid confusion for me and Jack.",
"\"For a knuckleball, the ball moves around as it approaches the pitcher because it isn't spinning.\" ",
"Should be...",
"\"For a knuckleball, the ball moves around as it approaches the ",
" because it isn't spinning.\" Yea? Just want to make sure Jack and I have it clear in our heads.",
"Edit: Thanks for the edit :) "
] |
[
"That's fair, also a note to jack...the more wind, the more the knuckleball moves when in flight, towards the catcher. The more turbulence, the better for the pitcher."
] |
[
"How do opiates cause euphoria in the mesolimbic pathway?"
] |
[
false
] |
Could you please explain the mechanism of action of opiates. I don't understand how opiates produce a euphoric effect and hence dependence. Thank you in advanced.
|
[
"While cocaine inhibits the reuptake of dopamine as you say, opiates like heroin increase the amount of dopamine released overall. Normally, neurons regulate the release of dopamine by releasing the inhibitory neurotransmitter GABA. However, opiates bind to mu opioid receptors (as an agonist) on these regulatory cells to inhibit the release of GABA. Less GABA means less inhibition, which results in more dopamine. ",
"I hope that's the level of specificity you're looking for!"
] |
[
"Thanks for your answer. I appreciate your answer, but I was wondering how activating opiate receptors in the brain causes a euphoric effect.",
"So for example, I understand that cocaine inhibits the reuptake of neurotransmitters into pre-synaptic nerve terminals, leading to extended action of neurotransmitter in the mesolimbic pathway.",
"But what do opiates do to alter levels of neurotransmitter in this pathway?"
] |
[
"In the case we've been talking about (disinhibition of dopamine release), the receptors lie on presynaptic neurons at a synapse. For a more in-depth explanation, see ",
"here",
".",
"Opioid receptors can also be found post-synaptically, but that location isn't generally responsible for the euphoric effects of opiates. For example ",
"one study",
" suggests that mu-opioid receptors in the VTA influence cardiac activity via the vagus nerve."
] |
[
"What does askscience think about using n-back training to increase working memory."
] |
[
false
] |
I've read a little about using n-back training to increase working memory, like this one The wikipedia page suggests there is actually something to this, what does the evidence say?
|
[
"This whole idea was torn to shreds at this year's psychonomics. Apparently, some of the original work is spurious, where only 1/12 experiments showed an effect.",
"Part of this criticism came up in a recent Frontiers paper on video games and cognition, I believe.",
"The n-back alone won't increase your working memory. Working memory capacities are pretty stable. "
] |
[
"what does the evidence say?",
"You may not have noticed, but the link you posted links to five scientific papers indicating that it works. Those are the primary sources describing the evidence, and the basis of any credible answer you'll get here. If you'd like help understanding the content of e.g. ",
"this",
", askscience can probably help. Just try to be specific about your question(s)."
] |
[
"What do you think about the 2 studies linked to in the second paragraph here ",
"http://brainworkshop.sourceforge.net/",
"that are claimed to have replicated the results of the original work?"
] |
[
"How does localized anesthesia work? Why doesn't it just enter the bloodstream and travel everywhere?"
] |
[
false
] |
When the dentist gives me a shot in the mouth, why does the medicine stay there? I thought everything was connected via blood vessels.
|
[
"It doesn’t only stay there. It definitely gets into the bloodstream and is distributed. For example, when I numb up a patient prior to surgery with lidocaine + epinephrine, I have to tell anesthesia how much I gave so they can watch for the cardiovascular effects of these two drugs. ",
"The trick to it all is that you’ve got a large dose of lidocaine relatively localized to a region you want to anesthetize. When it starts to disperse through diffusion and blood flow, the effects wear off, and it’s diluted in a relatively large volume of blood. Because drugs like lidocaine are concentration-dependent for their effects, they don’t cause local anesthesia throughout your entire body. In fact, one of the reasons we give lidocaine with epinephrine is that epi is a local vasoconstrictor, which reduces blood flow to the area and reduces the speed at which lidocaine diffuses away, lengthening the effect of the local anesthesia.",
"The pharmacodynamics are a little more complicated, but in general, drugs like lidocaine rely on their ability to block sodium channels in nerve axons to produce their anesthetic effect - the nerve can’t propagate about action potential without sodium channel activation, so the pain signal never makes it to your brain."
] |
[
"No doubt. IV lidocaine is a little bit outdated (but still used) drug for advanced cardiac life support, and that takes advantage of the cardiac effects of lidocaine in lower concentrations to restore normal heart rhythms. ",
"Route of administration is tremendously important in the effects that drugs have."
] |
[
"The route contributes to this too, right? If you gave lidocaine intravenously it would be distributed throughout the body pretty quickly, but if you gave it subcutaneously it would take a much longer time to reach the larger blood vessels."
] |
[
"Can an organism be both venomous and poisonous with the same substance, and if so, what is the correct way to refer to that?"
] |
[
false
] |
I'm gonna give some extra context here: I'm working on a game with a few other people, and we are working on descriptions for stuff in the game and are voting on them. As part of that, we have an animal that is going to be associated with toxins, and all of the descriptions people have put forth refer to it having poison glands, but then go on to referring to the substance inside of them being venom. Now, I know poisons are ingested/inhaled absorbed (IE: passive), wheras venom are injected (active). Is there any way for this situation to be definitionally correct? My understanding is that while it's possible for a particular substance to be both a venom or a poison, and for an organism to use said substance both as a venom and a poison, it's not possible for a poison gland to contain a venom since if it's a poison gland, then the produced substance is categorically a poison, and not a venom.
|
[
"Toxin is a more general term, so if it's ambiguous as to whether the substance produced is being used as a poison or a venom, you could just call it a 'toxin gland'? I think this situation is a relatively rare in nature, so there isn't a widespread common term - if it does occur, you would probably name the specific gland/substance involved. "
] |
[
"Well, toxic gland is what I first thought of but it doesn't really sound great in the actual description.",
"Is \"venom gland\" by itself an accurate term? "
] |
[
"Yeah, venom gland is an accurate term. It's not especially helpful in most scientific applications because 'venom' has evolved independently many times, so the term doesn't mean much more than 'a gland that produces a venom'. For example, ",
"snake venom is modified saliva",
", and therefore produced in the salivary gland; platypus venom is produced by the ",
"crural gland",
". "
] |
[
"Why do we see \"beams\" of light when we squint at bright lights?"
] |
[
false
] |
For example, at night, if you look at a street lamp, it might seem a bit blurry. If you squint, you will see "beams" of light coming out of the lamp's light. Generally it's a straight line, and to both sides. I don't know how to describe it better. Why does this happen?
|
[
"It works kind of like the single-slit experiment.",
"The light travels through the slit (your narrowed eye), and forms a diffraction pattern on your retina, which you perceive as a bright streak of light."
] |
[
"Yes and you can attach certain lens covers to cameras to make this effect look like different shapes. ",
"Bokeh"
] |
[
"I will link to my other extensive comment on diffraction lines",
".",
"But in short, these streaks of light are the same reason cameras ",
"show sunstars at smaller apertures",
" and why stars ",
"show crosses when imaged by the Hubble telescope",
".",
"Depending on your iris shape or myopia and the brightness/apparently size of a street lamp may naturally form streaks; when you squint the diffraction lines are increased as the light try to pass around your eyelashes."
] |
[
"In Space (or freefall or whatever) What would an oil/water mixture do?"
] |
[
false
] |
Would it stay as one sphere and be two layers or would the layers separate into two different spheres?
|
[
"The most energetically favorable single-body arrangement of an oil-water mixture is to have a sphere of water contained within a spherical shell of oil. Water has a surface tension of 72 dyne/cm, about twice that of oil (~0-30 dyne/cm), so it will want to minimize its surface area more than the oil will and thus occupies the center. The concentric spherical arrangement also minimizes the surface area of the oil-water interface (since oil is hydrophobic). Having two separate spheres of oil and water is more energetically favorable for small quantities of oil/water, but larger amounts would assume the concentric spherical configuration."
] |
[
"Interesting. Can you calculate the radius at which you change over from two drops to concentric spheres?"
] |
[
"You'd have to know the surface tension for the interfaces between oil and atmosphere (a), water and atmosphere (b), and oil and water (c), which depend on the type of oil and the pressure. Once you know that it's just a matter of finding the point where the sum of the energies of the oil-water and oil-atmosphere interfaces in the concentric sphere configuration is lower than the surface energy of separate oil and water spheres with the same volume: c R1",
" + a R2",
" < a R3",
" + b R1",
", where R1 is the radius of the water drop (would be the same in both configurations), R2 is the outer radius of the oil shell and R3 is the radius of the oil drop. Of course, you have to enforce the condition that the volume of the oil shell is equal to the volume of the oil drop: R3",
" = R2",
" - R1",
"Edit: I could simplify this some more, since the volume of oil and water and therefore R1 and R3 are given:",
"R2 = (R1",
" + R3",
")",
"So the transition lies on the curve",
"(c - b) R1",
" + a (R1",
" + R3",
")",
" - a R3",
" = 0",
"If you have an equal volume of oil and water, R1 = R3 = R, so you can solve for the transition radius:",
"(c - b - a) R",
" + 2",
" a R",
" = 0",
"R = (-2",
" a / (c - b - a))"
] |
[
"What happens to light that crashes into a black hole?"
] |
[
false
] | null |
[
"Thank you for your submission! Unfortunately, your submission has been removed for the following reason(s):"
] |
[
"Sorry but whar r u talking about?"
] |
[
"Do not post a question multiple times. It's seen, it will be reviewed. There's no need for a second, or Nth, one."
] |
[
"Is albinism just skin deep?"
] |
[
false
] |
Like would the muscles/fat of an albino tiger look the same as the muscles/fat of a normal tiger?
|
[
"\"There is also no evidence that the amount of melanin in internal organs correlates with the amount of melanin in the skin. For example, the amount of melanin in the substantia nigra is normal in albinos (Siegel et al. 1989: 755)\"",
"Found here: ",
"http://www.csicop.org/si/show/magic_melanin_spreading_scientific_illiteracy_among_minorities"
] |
[
"Fun side fact : albinism is not only diagnosed by skin pigmentation. One does not have to be perfectly white. There are several other factors in determining if you're an albino, such as eye function.",
"Source : my albino gf"
] |
[
"Poor eyesight or extreme sensitivity to light?"
] |
[
"Can reintroduced, formerly native species become invasive?"
] |
[
false
] |
If for example, a particular species has been extinct in a particular environment, could it's reintroduction lead to further disruption of the ecosystem? If yes, what factors would play into it being invasive?
|
[
"Unless you’re talking about resurrecting mammoths or dinosaurs, no.",
"“Reintroductions” normally refer to species that were pushed out of a region by human activity in historic times (within a few thousand years), usually much more recently (within a couple centuries).",
"Now is it possible that habitat is so limited, or prey is so limited (due to modern human activity) that those reintroduced species (particularly a large predator like a Grey Wolf or Brown Bear) won’t thrive in that region anymore? Sure. ",
"Is it possible the reintroduced species will make farmers or other people angry, for a variety of reasons? Sure.",
"But ecologically, they’re not invasive, and if the habitat of the region was still intact, a reintroduction would never be considered an invasion—not by science, anyway."
] |
[
"Ecologically, a former native species can't be invasive. If the species can't compete with other species in the niche the non-native niche holders would be invasive.",
"But there is a chance that the reintroduced species can carry diseases with them that would destroy other native populations. Then it could be considered too damaging to reintroduce."
] |
[
"Thanks for the response! I'm curious, aside from the possibility of carrying diseases to other native populations, what other possible factors would make reintroduction too damaging?"
] |
[
"To what extent can the behaviour of sex offenders be attributed to sexual abuse in early years? Hypothetically, what effect would raising a whole generation without any sexual abuse have on the prevalence of adult sex offenders?"
] |
[
false
] | null |
[
"This is a very complex issue. There has been a lot of study on the link between history of sexual abuse and development of deviant behavior but there is not a definite and general consensus on the question. ",
"The first thing that need to be said is that very few people that have been sexually abused in their childhood will become sexual offender later.",
"When we look at studies on sexual offenders and their history of sexual abuse, the percentage of sex offenders reporting sex abuse will vary greatly from a study to another one, depending on the methodology (definition of sex abuse, sample coming from prison or not). The fact that most of theses studies rely on self-report from sex offenders is a big bias: sex offenders might report sex abuse history to excuse or justify their behavior. In a study",
" the searcher put the sex offenders in two groups: In both group sex offenders were asked if they have been sexually abused in their childhood, but in the second group, they were asked while monitored with a polygraph. 67% of the first group reported sex abuse in their childhood as opposed to 29% in the group monitored with a polygraph.",
"Still, the prevalence of sexual abuse history in sex offenders seems to be be constantly higher than in the general population, but at different degree depending on the study. Being sexually abuse might play an important role in the later development of sexual deviation, but it's definitely not a good predictive factor.",
"So to answer your question, if we kept a generation from being sexually abused, it might reduce the prevalence of sex abuser but it will definitely not eliminate sexual offenders as many of them don't have an history of sex abuse.",
"Sources:",
"-I have a degree in sexology, had a whole course on sex abuse. Have many references in my notebook, can give you some if needed.",
"1-Freund, Kurt; Watson, R.; and Dickey, R. (1990). \"Does sexual abuse in childhood cause pedophilia: an exploratory study,\" Archives of Sexual Behavior, 19(6), 557-568."
] |
[
"Are other kinds of abuse linked to sexual abuse?",
"Couldn't the self-reporting bias go either way? If Bob was sexually abused as a child, he might not want to acknowledge it because doing so would be an admission that his own abusive actions was wrong. Conversely, as you point out, Bob claiming that he was abused as a child could serve as an excuse for his abusive behaviour.",
"The difference seems to be whether or not the sex offender regards sexual abuse as wrong. I would be interested in knowing what a sex offender says if asked: \"Is sexual abuse morally wrong?\", \"Have you commited sexual abuse?\" and \"If yes, do you believe these actions were morally wrong?\""
] |
[
"I don't have any study about the perception of sexual abuse from the sex offender in my notes, but in the same study mentioned earlier, they checked if there was a difference between sex offenders who deny their crime and those who acknowledge it. Those who acknowledge their crime were more likely to report sexual abuse during their childhood than those that deny their crime."
] |
[
"Is there a generally accepted scientific definition for brainwashing in the psychology field?"
] |
[
false
] |
You see a lot of people talking about brainwashing on reddit- particularly when talking about politics. Is brainwashing generally accepted as being a real and measurable phenomenon, or just a loose concept?
|
[
"I think the field calls active attempts to change someone's point of view \"coercive persuasion\"; \"brainwashing\" in the public sphere, I think has spilled over into things like what is termed Stockholm Syndrome and group dynamics. ",
"This group has apparently made a scale to measure",
" how coercive groups are. There's also a decent literature on power, persuasion and group dynamics."
] |
[
"No, there is not a medical or scientific definition for brainwashing that I'm aware of.",
"Thus, any discussion of brainwashing can mean any of a dozen different things, from ",
"/u/dtmc",
" 's \"coercive persuasion\" to ",
"/u/ash_modeus",
" 's \"hypnosis\" to general reddit usage as a synonym for propaganda.",
"In stricter terms I think brainwashing would be defined as \"changing someone's opinion without convincing or coercing them\" and I think that has no scientific evidence that it exists."
] |
[
"Hmm that's an interesting position and I have to agree it kind of fits, but I think the limited nature of foot-in-the-door and other techniques like it kind of underwhelm compared to the hollywood \"stare at this for 20 seconds and become a dedicated assassin\" effect that people associate with the term brainwashing.",
"You're absolutely right that it doesn't fit in the \"not brainwashing\" category either though.",
"This is exactly why science develops so many of its own definitions. You look at stuff, realize how complicated it is, and quickly need a whole new vocabulary to even discuss what you've seen."
] |
[
"How Much Alcohol Comes Out in Your Pee?"
] |
[
false
] |
Exactly the way it sounds. I've searched to interwebs and found nothing but fetish websites and the like. If you're having a drinking evening, will it all be absorbed by your body, or will some of it come out in your urine? I'm interested in the metabolization rate here.
|
[
"I suppose I'll have to learn to keep my trap shut when I don't know enough."
] |
[
"This is not correct.",
"Ethanol metabolizes to acetaldehyde",
", which is processed in the liver. Kidneys do not \"break down alcohol\".",
"This site",
" claims unoxidized (metabolized) ethanol will escape in urine.",
"Through oxidation, alcohol is detoxified and removed from the blood, preventing the alcohol from accumulating and destroying cells and organs. A minute amount of alcohol escapes metabolism and is excreted unchanged in the breath and in urine. Until all the alcohol consumed has been metabolized, it is distributed throughout the body, affecting the brain and other tissues (1,2)."
] |
[
"The great majority of the alcohol you consume, over 90%, is broken down and used for energy. The full process is complicated and involves several steps, but in the end, the ethanol molecules get turned into water and CO2.",
"The remaining 10% or less gets excreted unchanged. Some of it comes out in urine, some in sweat, and some as vapor that you breathe out. (This last is why breathalizers work.) The exact mix of those routes depends on the situation-- e.g., how warm the environment is, and how well hydrated you are-- but saying that they are about equally divided is not a bad rule of thumb to work with.",
"So, it's reasonable to estimate that about 3% of the alcohol you drink will come out in your urine."
] |
[
"Where does a gust of wind start? How far can it travel?"
] |
[
false
] |
[deleted]
|
[
"Differences in atmospheric pressure generate winds. Due to localized heating of an area (by greater sunshine or other reasons) the air in that area is heated. Warm air is less dense so it rises, which lowers atmospheric pressure near that portion of the Earth's surface. When this happens air from the surrounding will rush in to fill that void and voila - winds and storms!",
"Once you have strong gusts of winds, there are a number of factors that determine how far it can travel. On of them is ",
"Coriolis effect",
", caused by the Earth’s rotation.",
"The Earth contains five major wind zones: polar easterlies, westerlies, horse latitudes, trade winds, and the doldrums. Each of these travel far and wide across the Earth."
] |
[
"Would you say that wind pushes or pulls?"
] |
[
"This is something that might sound silly, but if it were true I wouldn't be surprised.",
"When you say wind rushes in to fill the \"void,\" I picture a very fluid looking..\"simulation\" I guess, where air is essentially flowing like water. ",
"If it does flow like water the way I'm picturing, do winds coming in to fill the void (picture a drain with water coming in from all sides for this next question) slam together like water?",
"I hope this was a clear enough question!"
] |
[
"why can't a photon of appropriate energy enable P->N conversion?"
] |
[
false
] |
i understand that the uud structure of the proton is the lowest allowed energy state of three quarks, and thus it can't decay (supersymmetric theories aside). the neutron, meanwhile, is udd and can (when by itself, or in the right kind of nucleus) undergo beta decay to a proton via spontaneous emission of a massive, charged W boson. furthermore, i understand that for instance non-spontaneous fission occurs when a neutron of sufficient energy interacts with the nucleus, bringing it to an unstable energy level. u235 is close to this level, and thus fissions when interacting with a neutron of even thermal energy, whereas u238 needs a higher-energy neutron to fission. high-energy photons can furthermore knock nucleons out in photodisintegration. 2.78MeV differentiate the up and down quark. This energy ought be readily available; the excited Ni60 metastate decays with a 1.33MeV γ, about half this value. Why don't we see protons transmuting to neutrons when such gamma rays hit them, especially in e.g. a plasma where there are no electrons to get in the way (at nuclear distance scales)? sorry, i am merely a dumb computer scientist.
|
[
"Well it actually can :) If you have a photon of the right energy (or several) you can turn a proton into a neutron+positon+electron_neutrino",
"see this paper which discusses this subject in the regime when absorbing several photons ",
"https://iopscience.iop.org/article/10.1088/1367-2630/abf705/meta"
] |
[
"well yes, I would of course expect a positrrn to emerge, p + gamma -> n + e+ and probably some neutrino for momentum conservation or whatever it is neutrinos do"
] |
[
"well hey, there we go! thanks much =]"
] |
[
"How is amplitude related to energy?"
] |
[
false
] |
E=h c/λ where c is also a constant, but two waves with the same v or λ are not equal in energy if they have different amplitudes...help?
|
[
"Those equations are the energy of an individual photon, which is completely based on the frequency of that photon.",
"However, a light wave is made up of many, many photons. The number of photons (and their energy) will determine the amplitude of that light wave. This is why with the ",
"photoelectric effect",
" you need to have a high enough frequency of light to get any electrons to be kicked, and if it's too low, upping the intensity of the light doesn't matter at all (however, if the frequency is high enough, then upping the intensity will increase the rate at which electrons are kicked)."
] |
[
"Yeah the first line was enough, that piece of info was missing lol, thank youu"
] |
[
"Are you saying that a single photon can't be thought of as a wave? I think it can. And since a wave's energy is proportional to its amplitude squared, the amplitude of a single photon would be proportional to the square root of its frequency. Two photons of the same frequency would necessarily have the same amplitude."
] |
[
"Askscience AMA series: I am an astrophysicist specialising in galaxy formation and evolution"
] |
[
false
] |
[deleted]
|
[
"Good question :)",
"The ultimate fate of a galaxy is to exhaust all the fuel available for star formation, which means that no new stars get formed. It then just ages, getting more and more red. The lifetime of the oldest stars is longer than the Universe however, so we haven't yet seen any galaxies totally 'die' (and, like astrokiwi says, it's not really clear what this means, anyway). They just hang around getting redder and redder. ",
"They are colloquially known as 'red and dead' galaxies...\n",
"http://www.universetoday.com/23282/with-no-smoke-or-mirrors-spacecraft-hunts-for-active-galaxies-with-central-black-holes/red-and-dead/"
] |
[
"The thing about my field is that there are 'average' days, interspersed with very un-average days, where you find yourself on top of a mountain in Chile or Hawai'i -- basically, my job is 90% computer/office type work, with the occational observing trip thrown in.",
"A typical day at the office would go something like...",
"astro-ph"
] |
[
"What do you consider the most important breakthroughs/discoveries in your field of the last ~25 years?"
] |
[
"We have made paint that absorbs over 99% of the light spectrum. Do we have paint that reflects over 99% of the light spectrum? It is that just common white paint?"
] |
[
false
] | null |
[
"White paints typically reflect only about 80% of visible light, and they still absorb ultraviolet (UV) and near-infrared (near-IR) rays, which warm building\n",
"https://www.sciencemag.org/news/2018/09/cooling-paint-drops-temperature-any-surface#:~:text=White%20paints%20typically%20reflect%20only,)%20rays%2C%20which%20warm%20buildings",
".",
"Remember, we have mirror's which reflect nearly 100% of the light."
] |
[
"Spectralon",
" basically does this.",
"You can hit the upper 90's by adding barium sulfate to white paint. It's a way to make a lower cost calibration standard.",
"https://www.triticeaecap.org/wp-content/uploads/2011/12/Barium_Sulfate.pdf"
] |
[
"That magazine article is a little misleading regarding that 80% number. The ",
"peer reviewed article that it's based on",
" says that the typical ",
" reflectance of white paint is 85%, and explains that the reason it's not higher is that it absorbs UV and IR radiation. In other words, its visible reflectance is significantly higher than 85%. ",
"Paints with higher visible reflectance in the 90-95 range are readily available from regular paint stores, without going to special optical coatings described in other comments. In paint jargon, the visible reflectance is called LRV. For example, Behr ",
"\"Ultra Pure White\"",
" lists its LRV as 94."
] |
[
"Where's all the geothermal power?"
] |
[
false
] |
I don't know too much about geothermal power except that I never read about it or see it in the news. Why (seemingly anyway) isn't geothermal being researched more than it is? It seems like the most reliable and powerful energy source we would be able to get! It's not like the earth gets cold sometimes.
|
[
"There are lingering doubts about the long term effects with respect to tectonic stability. ",
"Example",
".",
"Even if there is no hard scientific evidence that it can cause worse earthquakes, can you imagine the shitstorm of lawsuits that will follow an earthquake in an area with a lot of geothermal power?"
] |
[
"Actually geothermal isn't all that uncommon. Here in Indiana both the high school and the college I went to now have geothermal systems. Here is a link to information about the geothermal project at Ball State University:",
"http://cms.bsu.edu/About/Geothermal.aspx"
] |
[
"Similarly, my old middle school (environmental charter) had a pretty good geothermal system for heating. This is in Illinois, which I don't think anyone would call terribly volcanically active (at least on a recent geologic scale). ",
"Linky to info: ",
"http://prairiecrossingcharterschool.org/about/LEED"
] |
[
"Why is the brain almost always located in the head of living things?"
] |
[
false
] |
Seeing as the brain is the most important organ in any living organism. Why is it exclusively located in the head amongst living things? I have a feeling there are some things that exist where the brain is not located in the head that I am unaware of. But I'd still ask why has evolution lead to most superior species having a brain in the head, what advantage does this provide over say a brain located in the chest/abdominal region?
|
[
"Evolution. First to evolve were simple light sensors in simple organisms (such as flat worms). Because these organisms move along a surface, and light sensors are useful for finding food and avoiding competition, the sensors evolved on the front side of the organism. This stayed this way throughout development of fish and amphibians.",
"Early brains also developed on the same end because that's where primitive eyes already were. When animals moved to land and started standing up, they gained more utility from their eyes by standing up with eyes high, so bipedalism developed to keep eyes high."
] |
[
"The brain need to be near the sense organs. Signals travel quickly through the nervous system, but if the senses needed to travel through several feet of nerves to reach the brain, it would greatly reduce efficiency, and there would be sufficient lag and loss of clarity to create real problems. So then you ask why our senses need to be on our head, and the reason is perspective. If our eyes are not the highest point on our bodies, we limit what we can see, and how far. If they're in the middle of our body, we need to constantly scan in all directions to be sure our body is safe. Imagine how many times you would hit your head if your eyes were in your chest, or if you happened to look up to see what your head was doing, you trip on something with your feet. Your ears would hear less distant noise at your feet, and what they do hear would be drowned by your feet rustling in the grass. Mouth and nose should be together, and if they were in your stomach while your eyes were on your head, eating would be very difficult and messy. So, all of the senses, and the brain, have to be together at the top and front of your body, and on an appendage so you have freedom to move them. Therefore, head."
] |
[
"The evolutionary trend of the brain and sense organs to come together in the same location is known as cephalization, and has been discussed, studied, and observed at length through the entire history of evolution. Your own observation should confirm this trend. There is no research into the reason evolution did this, because evolution is not an intelligent entity that can explain itself. Any time a question is posed in science beginning with the term \"why,\" we are forced to combine our observations with logic. Scientists with much more authority than myself have theorized (meaning formed a logical model that requires few assumptions and fits all known observations) that the reasons I mentioned above give organisms an advantage to survive. In my opinion, it doesn't require a stretch of the imagination to understand why. But yes, beginning with an observation and then using logic to find the reason for that observation, then testing that hypothesis if possible is essentially how evolutionary science, like many others, is done. Unless you want to go have a conversation with evolution and report back to us. "
] |
[
"Why when dropping a cold bottle of water, with no ice in it, do ice crystals appear?"
] |
[
false
] |
When I pulled a cold bottle of water out of the garage fridge I dropped it on the cement floor, causing it to bounce a couple times. When I picked it up there was a copious amount of ice in it. I opened an identical bottle, no ice, at this point I grabbed a few more and dropped them. All of them had ice after they bounced. What is the reason behind this? Sorry it's a bit long I didn't know how else to get the point across.
|
[
"Your bottle of water was cooled below its freezing point, but since there were no nucleation points, ice was not formed. This is called supercooling.",
"Dropping the bottle creates nucleation sites that led to rapid crystallization of the water. Often, the act of opening the bottle, shaking the water, squeezing it, etc. is enough to cause crystallization.",
"It is a common phenomenon and a ",
"quick search on Youtube",
" shows many examples."
] |
[
"Thanks for the answer. I will now use this to amaze and educate friends. "
] |
[
"Impressive? Yes. Disappointing? Yes. :("
] |
[
"How many different 800x600 pictures possible?"
] |
[
false
] |
If I get a camera that makes 800x600 8 bits (256 colors) pictures and start to randomly fly across the infinitive universe and take photos of EVERYTHING, how many I will take before the photos start to repeat? It sounds crazy but think: There is 480,000 pixels, each pixel display one of 256 colors at any time, there is some maximum number of possible combinations - maximum number of unique photos. I'm bad at math and it's 2am here, can Reddit help me?
|
[
"If an algorithm ran that generated all 256",
" images, you'd have pictures that would document every single event that had ever happened or could ever happen. For every picture that showed Washington crossing the Delaware, there would be one of Washington and Lincoln in a three-way with your mom. There would be pictures of you and pictures of me, pictures of Hitler wearing the Shroud of Turin, all the frames of a slow-motion video of Queen Victoria dancing on the Dome of the Rock. Anything you can imagine represented perfectly in 800x600 pixels.",
"Of course, there'd be quintillions of images of noise, but don't let that ruin your imagination. "
] |
[
"256",
" , an absurdly large number"
] |
[
"You would be arrested for producing kiddy porn"
] |
[
"Why don't we just eat calorie bombs that have the reccommended daily intake instead of spending money on low carb, expensive foods?"
] |
[
false
] | null |
[
"A few quick answers: "
] |
[
"Actually long-mission astronauts really get a boost from interesting, tasty food. Each supply mission comes with treats and the personal payload often includes hot sauce because freefall dulls taste. We can see the bottles in the ISS food prep area."
] |
[
"So... meals?"
] |
[
"Why do electrons and protons have exactly opposite charges?"
] |
[
false
] |
[deleted]
|
[
"Electrons are fundamental particles, protons are made up of quarks. These particles are very different and are not made up of the same things. ",
"Essentially, the smallest free unit of charge we have is the charge of the electron. We can see this in other charged particles in the standard model. This is because of something known as gauge theory, which is a mathematical way of describing the different aspects of the standard model. ",
"There is really no answer to why on a deeper level these theories are like that, it's just what we have observed. "
] |
[
"I wish more people had answered this because it's a fantastic question and I tend to agree; it seems too coincidental. FYI (if you didn't know): protons are made up of three quarks and ",
" quarks dictates the electric charge of the particle (proton +1 vs. neutron +0, mainly). That's all I know though. I'm not aware of any fundamental relationship between quarks and electrons. Surely ",
" must attempt to explain why the crazy coincidence?"
] |
[
"Interesting... So by the current model the perfectly matching yet opposite charges of electrons and protons is a coincidence...? This seems too perfect to be a coincidence. "
] |
[
"Do all plants metabolize (convert CO2 to O2) at the same rate or do some plants generate O2 more efficiently than others?"
] |
[
false
] |
I'm wondering if some plants can generate more oxygen with less sunlight, or if crating sugars faster than other plants would yield more oxygen.
|
[
"There's variation among plants generally, but specifically an alternative carbon fixation pathway called Crassulacean Acid Metabolism (CAM) used in plants that are found in arid climates that is less efficient, but with the benefit that it allows the plant to shutdown respiration during the day when heat and dry air pose a threat of substantial water loss."
] |
[
"Is there any relation to that and the C-4 trait that certain crops like corn have? "
] |
[
"CAM is less efficient in the sense that the plants expend more energy to fix the same amount of carbon (not accounting for photorespiration), but that's not related to oxygen production which happens as part of the light reactions that are essentially the same in the CAM, C3 and C4 pathways.",
"There's a direct correlation between light absorption and oxygen production and light absorption certainly varies depending on chlorophyll concentration and leaf surface traits like the hairs or waxes that change overall leaf reflectance. So in a rough sense the more green you can see when looking at the leaf the more oxygen will be produced from a given amount of light hitting it."
] |
[
"Is it possible for the sun to create a new element?"
] |
[
false
] |
I have limited knowledge on science but I have a question that for some reason I always think about. Since the natural elements were created from the destruction of stars is it possible that when the sun's life ends that it to will create an element? And if it has the possibility of creating an element can we figure out what the type of element it will be before the sun is destroyed? I am not certain that this is a good question but it is something I have often thought of and have never been able to find an answer.
|
[
"I think you're a bit confused then, those \"naturally occurring elements\" were completely new elements created in stars via fusion. That list of elements is by no means complete, any new element would simply be one we haven't found yet. Hydrogen is about the only \"naturally occurring element\" that primarily formed outside of stellar fusion. "
] |
[
"Every element and almost all matter comprising the Earth was created by fusion in a star before it exploded and ejected them out into space, those elements then coalesced into planets under the pull of gravity. Those elements don't generally occur in the universe through any other processes. "
] |
[
"New in what way? New as in unknown to us, or new as in an element that wasn't previously in the star? Stars fuse elements together constantly throughout their lifespan to create new elements, but we've cataloged a great deal of the existing elements we know of as well as a few possible elements on our periodic table. It's of course possible that there are a few we haven't yet encountered, but they likely exist already throughout the universe and in other stars as well. "
] |
[
"How do proteins that are build inside the cell and localize to the cell wall know where to go?"
] |
[
false
] |
Does the protein just bounce around inside the cell until it becomes imbedded in the wall, or is there some mechanism that causes it to move in the correct direction (outwards from the nucleus).
|
[
"Of course, I'd completely forgotten about vesicle sorting and how the proteins inside the vesicle (pointing inward) become extracellular-facing proteins when the vesicle fuses with the cell's membrane. ",
"What about proteins that aren't assembled inside the lumen of the ER? Say, a protein that is assembled by a free ribosome. I know some proteins' production is halted until the ribosome moves to the ER. Does the ribosome-protein complex bounce around until it hits the ER? ",
"I guess what I'm trying to get at is that I'd always learned that proteins are so much larger than molecules like water, peptides, amino acids, sugars, etc, that they can be treated as though they were not moving when considering collisions between those small molecules and the proteins. If this is a valid way of thinking about it, how do these large macromolecules localize anywhere in the cell? Do they just bounce around more slowly, but eventually reach their destination quick enough to be relavent to the functioning of the cell?"
] |
[
"Of course, I'd completely forgotten about vesicle sorting and how the proteins inside the vesicle (pointing inward) become extracellular-facing proteins when the vesicle fuses with the cell's membrane. ",
"What about proteins that aren't assembled inside the lumen of the ER? Say, a protein that is assembled by a free ribosome. I know some proteins' production is halted until the ribosome moves to the ER. Does the ribosome-protein complex bounce around until it hits the ER? ",
"I guess what I'm trying to get at is that I'd always learned that proteins are so much larger than molecules like water, peptides, amino acids, sugars, etc, that they can be treated as though they were not moving when considering collisions between those small molecules and the proteins. If this is a valid way of thinking about it, how do these large macromolecules localize anywhere in the cell? Do they just bounce around more slowly, but eventually reach their destination quick enough to be relavent to the functioning of the cell?"
] |
[
"My key question involves when you say \"the stop/transfer sequence in the mRNA targets the ribosome-mRNA complex to an SRP receptor on the ER.\" When you say targets, do you mean that the ribosome-mRNA complex actually travels in the direction of the ER? Or do you mean that the complex moves through the cell randomly until it hits the ER, upon which time it remains there through some binding mechanism?",
"Sorry if I'm not being clear!"
] |
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