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[
"Is it possible for sperm to break through the walls of non-egg cells?"
] |
[
false
] |
I doubt the shape and motion of sperm is enough to puncture a regular cell wall, but what about the enzymes? If I remember correctly, sperm have an enzyme that helps it work through an egg's barrier. Could that or any other mechanism allow a super-potent and super-confused sperm enter one of the body's other cells? If possible, what would the effect be? I assume it would just spill the cell's contents. Might the hole it creates instead seal itself? How severely would the victim cell's normal function be impaired?
|
[
"No, it could not. Digestive enzymes from the sperm's ",
"acrosome",
" are not super-enzymes capable of digesting anything. They are only capable of digesting the very special (and very digestable) glycoprotein membrane of the egg cell, called the ",
"Zona pellucida",
"."
] |
[
"In fact, the egg plays a much more active role in fertilization than is usually depicted - it kind of grabs on and reaches out for the sperm."
] |
[
"You would also have to induce the ",
"acrosome reaction",
" in the first place."
] |
[
"Does the Earth's atmosphere rotate at the same speed as the planet?"
] |
[
false
] |
Does the atmosphere around the Earth 'turn' in sync with planet? So does The North Pole or England or anywhere else always have the same atmosphere 'above' it?
|
[
"The atmosphere \"slips\" relative to the surface of the Earth. There is a \"boundary layer\" where there atmosphere meets the surface of the Earths that creates all sorts of atmospheric phenomena (turbulence, uplift, jet stream, ...).",
"There are also large scale currents in the atmosphere: the Hadley cells.",
"So no, the atmosphere does not corotate like a rigid body."
] |
[
"So does the earth's crust rotate at the same speed as the underlying magma? How about the core?"
] |
[
"There must be some amount of differential rotation going on, but that is on a much longer timescale. Differential rotation is needed (AFAIK) to drive the magnetic dynamo in the core."
] |
[
"On the anatomy and physiology level what does stretching actually do?"
] |
[
false
] |
As in, does stretching pre-flood chemical gates or lower the threshhold of said gates so that it takes less time/effort to move said muscles? And how does it actually reduce cramping later or have people just convinced themselves that it's true?
|
[
"Quick physio lesson time: The force producing units of muscles are called sarcomeres, and they work somewhat like a ratcheting mechanism where closely interdigitated protein filaments (actin and myosin) form chemical crossbridges that promote relative sliding of the myosin and actin chains. As a result, the amount of force produced by an individual sarcomere depends on the number of actin/myosin interactions that sarcomere can form, and this in turn varies depending on the sarcomere length. This is often referred to as the length-tension curve , which although different from muscle to muscle, generally looks like an upside-down parabola (with length on the x axis). Too long and a sarcomere cannot form cross-bridges, too short and you get a whole lot of intereference between filaments which hinders crossbridge formation as well. ",
"Hence, every muscle has a sweet-spot in terms of the length at which it can maximally generate force. One of the key ideas behind stretching is to lengthen muscles that have overshortened and reset their sarcomere length to a more optimum position (and thus increase possible force generation). ",
"there are a whole host of other effects as well, for example the golgi tendon organ (a load sensor in the muscle tendon) can shut down neural activation of a muscle during high loading (which would occur in a stretch), and the effect lasts some time longer than the stretch itself (minutes i believe). So if you have a tonically overactive muscle group you can turn down its contribution to an activity performed immediately after stretching it. In the long term it is likely you retrain your golgi tendon organ, and muscle spindle to operate at a new set point (allows proprioceptive feeling of muscle length, and involved in reflexive movement as well as inhibition of antagonist muscles during a coordinated action).",
"Edit: my husband (a medical student) typed all that out while logged into my account. "
] |
[
"Yes this is all true, but the act of stretching has to do with ",
" length changes, whereas the LT curve you reference above (your husband) is active (as in, actively creating force with muscles). ",
"Passive length-tension has to with ",
"titin",
" at the sarcomere level, but mostly with extracellular tissues at the whole muscle, whole limb level. Stretching may alter crimp angles in the collagens in these tissues. ",
"Jury is still out about the benefits, though...there are loads of competing studies."
] |
[
"That same golgi tendon inactivation is why you don't static stretch before an exercise, you do a dynamic stretch, a warm up. A static stretch causes the golgi inhibition which temporarily creates that new set point for a \"stretch\", much closer to the injury threshold. So if you stretch the ankle before running, a missed step isn't felt by the body until too late and injury becomes more likely. "
] |
[
"I fill the bottom of a bottle cap with my blood and let it dry overnight. Then I put the dried disc in a cup of water. the color leaves the disc and seeps into the water. I'm left with a translucent, slimy material. What is it?"
] |
[
false
] |
[deleted]
|
[
"It's fibrin mesh, made from fibrinogen and the end result of the clotting cascade. It's a protein that polymerizes to form a hemostatic plug to stop bleeding and allow wound healing. "
] |
[
"There seems to be a little confusion/questioning about what you're left with after the water step, fibrinogen or albumin so I looked up the blood contents",
"Conveniently there is this image at wikipedia, which is pretty fascinating:",
"https://upload.wikimedia.org/wikipedia/commons/c/cb/Blood_values_sorted_by_mass_and_molar_concentration.png",
"All the way to the right you can see the things present in the grams per litre range",
"Albumin 40-50 g/L\nGlobulins 25-35 g/L\nFibrinogen 2-2.5 g/L\nTransferin 2-3 g/L\n",
"Interestingly these are all \"big\" things in that they are all proteins with fairly high molecular masses. Just about everything else in your blood (< 1 g/L) is a small molecule. There are some exceptions (proteins with names ending in '-in') but they are vanishingly rare and not worth considering here.",
"So what happens with your mildly gruesome process/experiment? The blood in your bottle cap will undergo 2 processes that \"dry\" it off, some of the water will evaporate off and the prothrombin/thrombin will get on with coagulating your blood.",
"Thrombin converts the fibrinogen (soluble) in your blood to fibrin (insoluble). The fibrin can bond to itself and will form a loose sticky mesh. This mesh forms the main structural matrix of a blood clot or scab. Embedded in this meshed will be any large items in your blood; blood cells (red & white) and proteins.",
"White blood cells and most proteins are pretty rare so the mesh will mostly contain red blood cells, albumin, globulin and transferrin.",
"Your next step is to move the coagulated disc to water. It is not completely clear to me what happens at this step. Certainly all the haemoglobin (the red stuff) leeches out of the disc and back in to the water due to the osmotic gradient. There seems to me to be two processes this could happen.",
"First, the fibrin mesh is sufficiently loose so the red blood cells just dissolve back to the water. Red blood cells are pretty big, if this is the case then you'd also expect all other trapped water soluble elements (proteins, small molecules) to also return to the water. This means your remaining slimy material is almost certainly just the remaining Fibrin mesh with nothing else",
"Alternatively the water you've added may lyse (break open) the red blood cells, due to the osmotic pressure. In this case the haemoglobin will dissolve back in to the water but leave the detritus of the red blood cells trapped in the fribin matrix. Albumin and haemoglobulin are all around the same molecular weight (approx 60KDa), so if the haemoglobulin can dissolve back to the water then so can most of the other blood proteins. In this case the slimy material left is the fibrin mesh with the remains of the red blood cells trapped in it. Globulins can range up to 1000s of KDa so perhaps they might remain trapped in the mesh too.",
"Edit: As pointed out below overnight drying may just rupture all the redblood cells. I don't know whether the fibrin network will trap enough water to prevent this. So perhaps the latter outcome is most likely"
] |
[
"It's not very different from a scab, both are made of fibrin and other detritus, but a scab is dehydrated and so it's more brittle."
] |
[
"Why does a space shuttle arch as it leaves earth?"
] |
[
false
] | null |
[
"In order to orbit the earth, you need massive amounts of \"sideways\" velocity; just going straight up means that you'll fall straight back down when the rockets finish firing.",
"So the shuttle needs initial vertical lift just to get off the ground, and then gradually shifts to horizontal acceleration in order to enter orbit (which is nothing more than constantly falling while moving so quickly to the \"side\" that you always miss hitting the Earth)."
] |
[
"Nice.",
"It's worth expanding this a bit: the only reason for the shuttle to go ",
" at all is to get above the atmosphere, to prevent drag. The reason it has to do that is because it needs ",
" lateral speed to be in orbit. Only a tiny fraction of the rocket fuel is used for going up -- essentially all of it is for going sideways."
] |
[
"So stupendous, in fact, that if you look at the altitude data for the shuttle's climb to orbit, it actually begins falling back to earth about 2/3 of the way up to gain velocity.",
"http://www.spaceflightnow.com/shuttle/sts124/fdf/124ascentdata.html",
"At T+5:37, it begins losing altitude, having peaked at 356,955 ft Above sea level, and descends at an average of 5,000 feet per minute (peaking around 12,000 feet per minute instantaneous) for 2 minutes until T+7:52 at 336,393 ft.",
"As drzowie said, it only needs to get above the atmosphere. Why fight gravity when you can use it to your benefit. In that 2 minutes 15 second time, the Shuttle accelerates from 12,629fps (8,611 mph) to 22,780fps (15,533mph).",
"Once it starts gaining altitude again, it only burns for another 30 seconds, and at MECO (main engine cut-off), is still climbing in an elliptical orbit. Once it reaches altitude (approximately half an hour later), the OMS (orbital maneuvering system) rockets light to circularize the orbit. "
] |
[
"What technological advancement would make Thermoelectric Cooling a realistic substitute for conventional refrigeration systems?"
] |
[
false
] | null |
[
"One of the major issues facing thermoelectric cooling (via the Peltier effect) is the low efficiency and inability to handle large heat flux. The theoretical maximun rate at which heat can be carried away by a Peltier device is determined by the Peltier coefficient (property of the materials used) and the current that's driving the device. It is more common to use a quantity ",
", called the thermoelectric figure of merit. When this dimensionless number is larger, a thermoelectric device is more efficient. It's estimated that ",
">3 is required to compete with traditional refrigeration. Currently no materials with such ",
" are known. So the struggle is to engineer such materials, and that's where a lot of research is being done. ",
"The figure of merit is the product electrical conductivity times Seebeck coefficient squared times temperature divided by thermal conductivity. So the challenge is to find materials that conduct charge well and heat poorly. This is arguably a challenge of materials science for the most part, as well as physics. Researchers generally look at semiconductor based materials, since they offer sufficiently high electrical conductivity while limiting thermal conductivity due to the low carrier concentrations. Amorphous materials are also attractive because they naturally suppress heat transport via phonons. But some crystal structures may offer suppressed thermal transport as well. ",
"I guess the tldr is some magic material needs to be found! ",
"There may also be improvements to be had on the engineering side to eg. improve heat transfer away from the Peltier device on the hot side. ",
"Edit: Wow glad to see this was interesting for folks! Lots of great follow up questions, many of which have been answered by other folks already. I'll try to add more responses where I think it's merited. ",
"I spent about two years working on experiments with thermoelectric thin films during a masters doing film deposition and thermal conductivity measurements. Went on to work in a different area of condensed matter physics through my PhD so I had to brush back up to make this response. Been working outside of academia for almost 3 years now so it's always a pleasure to go back to my physics roots!"
] |
[
"Thanks for the elaborative answer. I hope researchers keep looking for that magic material.I worked on two projects in school, one where we tried to cool an enclosed space using 8 Peltier modules with huge heat sinks attached to the hot side, and it was good enough to produce the cooling effect quickly, but reached a point where the temperature would not go low enough to replicate the refrigerating effect. For the second project, we designed a water cooler/heater, which was able to dispense water at 7C and warm water at 45C. It was fun working on those projects as a student, since this technology wasn’t known to me as much then. Now, I constantly keep looking if there are any breakthroughs in this area."
] |
[
"it's a physics and materials problem, not a problem of making things tiny like computing.",
"that said, a crutch solution is faster heat transfer away from the hot side (better heatsinks) but that's only one third of the solution."
] |
[
"How do phones keep cool with small heatsinks and no fans?"
] |
[
false
] |
[deleted]
|
[
"They have a lot of surface area and they throttle their performance if they are too hot. This is a major constraint for mobile VR, phones have a lot of computing power but they can't use it at 100% for extended periods due to heat."
] |
[
"Also it should be noted that most phone chips are very low wattage. The snapdragon 835 (A very powerful mobal chip) only pulls about 3.5 watts. most intel/AMD X64 chips pull 65 watts With the very high end ones pull over 200"
] |
[
"It may depend on the material, but in general yes. Most cases have a rubber interior to prevent damage to the face, which would act as a thermal insulator and reduce the amount of heat the phone can transfer to the environment. A metal case may, in theory, slightly improve the heat transfer of the phone by offering increased surface area, but the contact resistance between the phone and case as well as small air gaps due to imperfections between the two surfaces (this is why computer heat sinks use thermal paste) may actually result in a decrease in cooling, despite increased surface area and good thermal conductivity."
] |
[
"What is the difference between saturated, unsaturated, and trans fats, and how does it affect our health?"
] |
[
false
] |
I know c.10 years ago every "medical expert" and their mother was touting the cholesterol-lowering benefits of unsaturated fats, particularly the all-holy "omega-3 fatty acids," but I've since heard quite a few different testimonies saying otherwise, from 's "saturated fat is fine as long as you get it from the half-dozen eggs you eat every day" to the and lowered his LDL cholesterol 20% in 10 weeks. My only direct concern with this is whether my parents are really better off taking "fish oil" pills to help lower their LDL levels (which haven't changed much since they started taking the pills a year and a half ago), but I'd also like to know the current medical consensus on different fats' health effects as a whole.
|
[
"The health effects of different fatty acid classes are always under debate. IMO there is little consensus in the field, if by consensus you mean something everybody agrees about.",
"It's a personal interest of mine (I'm just a dilettante), so I can give you a very brief overview of the subject. I can provide references for any individual claim, or resources for further reading if you're interested.",
"Main dietary fatty acid classes:",
"By the way, fish oil does not lower LDL levels, but might lover triglycerides a bit."
] |
[
"Saturated fats have only single-bonds between carbon atoms (the molecule is saturated with hydrogen atoms).",
"Unsaturated fats contain at least one double-bond between carbon atoms (the molecule is not saturated with hydrogen atoms).",
"Trans-fats are a specific type of unsaturated fats that contain only \"trans-isomers\" (E-isomers) of unsaturated fats.",
"From a chemical perspective, saturated fats and trans-fats are to be avoided because they are relatively thermodynamically stable. Thus, saturated fats and trans-fats are more difficult for the body to break down into simpler molecules and to utilize the energy from the bonds of these fats.",
"As for you question about cholesterol, I do not possess the required expertise."
] |
[
"Thus, saturated fats and trans-fats are more difficult for the body to\nbreak down into simpler molecules and to utilize the energy from the\nbonds of these fats.",
"I don't think that's true for saturated fats. Mitochondria are quite happy to burn saturated fats, and in fact high-saturated fat diets are therapeutic for mitochondrial disorders like heart failure in lab animals (while high-PUFA diets are not)."
] |
[
"What happened to my defined jawline?"
] |
[
false
] | null |
[
"Hi Double_Joseph thank you for submitting to ",
"/r/Askscience",
".",
" Please add flair to your post. ",
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] |
[
"Human body"
] |
[
"Thank you for your submission! Unfortunately, your submission has been removed for the following reason(s):",
"/r/AskScience",
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"guidelines.",
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] |
[
"Are there materials that only emit Alpha radiation? My Geiger counter only detects beta and gamma."
] |
[
false
] | null |
[
"Pure alpha sources exist, but you don't need one to discriminate between alpha counts and beta/gamma counts in the detector. Given the very short range of alpha particles in matter, you'll only be able to detect alpha particles when the detector is held very close to the source.",
"So if you hold the detector close, you get the count rate for alphas, betas, and gammas. Then if you move the detector back a few inches, the alphas will have all more or less stopped in the air between the source and detector, leaving only betas and gammas. ",
"So looking at the difference in count rates at the two positions, correcting for the difference in geometric efficiency, you can determine what the count rate is for just alpha particles."
] |
[
"So you're saying that my Geiger counter claims to only detect beta and gamma rays, but it can actually detect alpha rays also? But that's because alpha rays don't travel very far, so it doesn't claim to detect the alpha radiation?"
] |
[
"So you're saying that my Geiger counter claims to only detect beta and gamma rays, but it can actually detect alpha rays also?",
"No, I'm assuming you're using a model which has a thin enough window to detect alphas, or everything above is irrelevant.",
"But that's because alpha rays don't travel very far, so it doesn't claim to detect the alpha radiation?",
"Yes, because alpha particles travel very short distances in matter (~ microns in solids and liquids, and ~ centimeters in air). Unless the detector is specially designed to have a thin window for alpha particles to penetrate, they won't reach into the active volume of the detector."
] |
[
"Why in arthropod species where females are larger than males and sometimes consume potential mates, do the males not grow larger to evade this threat?"
] |
[
false
] | null |
[
"I think another way of looking at it is this: is it really a net positive for the species as a whole for the male to evade being consumed? Let's try to think about it from a perspective that isn't anthropocentric.",
"Consider: if the male did his job in the reproductive act, what other purpose does the male serve in this situation? Seems like providing sustenance for the female provides a larger benefit for survival of the species as a whole than being able to evade the female for the survival of an individual.",
"So it seems to me that you could just say that there is no evolutionary advantage for the male to grow larger or to evade (though I do know that some do develop strategies for evasion and survival, and some are cool)."
] |
[
"Or that the evolutionary advantage is actually in favor of the male who does not evade, because it helps the female in the species more. Or even that it's more selective, in that the female will only mate with males who are small, the larger ones don't get the chance to reproduce."
] |
[
"If males and females eat the same food, and it is in short supply, then the male may actually be doing his genes a favour by dying off, so that his girlfriend can eat better and raise some strong, healthy kids. In the short term, anyway -- which is the term that natural selection sees."
] |
[
"Does the Dzhanibekov Effect occur with throwing knives?"
] |
[
false
] | null |
[
"If it has three different principal moments of inertia, yes. But rotations around the principal axes with largest and smallest moments are stable."
] |
[
"Doesn't any macroscopic object have three different principal moments of inertia?"
] |
[
"No. If the object is symmetric, two or more of its principal moments may be equal in value."
] |
[
"psychologically speaking, why do we sometimes laugh when presented with sad or unfunny things?"
] |
[
false
] |
For example, "shock jokes" are meant to make you laugh by saying something you wouldn't expect. Also, that video of the boat spinning around the whirlpool during the Japan tsunami made me laugh, even though there shouldn't be anything funny about that. Do we laugh because we don't know what else to do, because we are trying to cope, or is it something else? EDIT: I probably should have started out by asking "why do we laugh?" I thought laughter was a purely human act in response to something funny, but it seems more complicated than that.
|
[
"These quotes are all very nice, but I was hoping for something a little more substantive."
] |
[
"Radiolab, Laughter"
] |
[
"\"It's annoying when people answer difficult questions with well known aphorisms.\" -- Me"
] |
[
"Is it actually healthier to go braless?"
] |
[
false
] | null |
[
"In other contexts, guys making studies on bouncing boobs would be frowned on.",
"What are you trying to insinuate here? It's one thing citing the author saying that the study might not be representative. It's another inserting your own insinuations into the study.",
"If the movement of the breasts is necessary to develop the muscle tone and provide natural support - the claim being discussed here - why does it matter what it would seem like in other contexts? It is relevant in ",
" context.",
"\"Just a thought\" is probably one of the most weaselly phrases one could utter."
] |
[
"In other contexts, guys making studies on bouncing boobs would be frowned on.",
"What are you trying to insinuate here? It's one thing citing the author saying that the study might not be representative. It's another inserting your own insinuations into the study.",
"If the movement of the breasts is necessary to develop the muscle tone and provide natural support - the claim being discussed here - why does it matter what it would seem like in other contexts? It is relevant in ",
" context.",
"\"Just a thought\" is probably one of the most weaselly phrases one could utter."
] |
[
"A comprehensive analysis would not necessarily lead to different results. I think the issue here is one of data collection. The benefits cited are purely cosmetic. No health claims are made, other than anecdotal self-reported evidence of less back pain.",
"So, to answer your question in the most scientific way possible, we don't know."
] |
[
"Are there stars that do not emit light on the visible spectrum?"
] |
[
false
] |
Are there stars that we cannot see with are make eye? If so, how did we find them and how are we able to tell?
|
[
"There are stars that are too cold to emit visible light and emit mainly infrared radiation instead. These are called brown dwarves, and are kind of on the edge of what we'd classify as stars because they don't have hydrogen fusion in their core (some have deuterium fusion though). These can be detected with infrared telescopes.",
"There are also stars that emit visible light but are just too faint to see with the naked eye. Proxima Centauri, the closest star to the sun, is a red dwarf that is invisible to the naked eye."
] |
[
"Short answer, No",
"Longer answer, depends on what you call a star. Brown Dwarfs emit mostly infrared light. Depending on who you ask, they’re not really stars though because they don’t sustain fusion. For any “real” star, they would emit visible light. This is because stars emit what’s called Blackbody Radiation. That means they emit light across all wavelengths. Colder stars would peak in red light and hotter in blue light, but they’re always emitting light across all wavelengths. That’s why even though the sun peaks in green light, it appears white because it’s still producing all other wavelengths."
] |
[
"There are also stars that emit visible light but are just too faint to see with the naked eye.",
"99.999999999...% of the stars in the observable universe are in that category. We see a few thousands out of 10",
" or so. That just means they are too far away. If Proxima Centauri would be closer we would see it as red star."
] |
[
"Did dinosaurs evolve into birds because flight became necessary?"
] |
[
false
] |
It seems to be accepted that dinosaurs evolved into modern day birds. Most birds can fly. Most dinosaurs could not. What was the mechanism by which birds were selected to fly when their predecessors could not?
|
[
"Nope. The evolution of flight and the evolution of birds are very much decoupled from each other; flight occurred in non-avian dinosaurs as well.",
"There are a few characters we strongly associate with flight: feathers, hollow bones, and a ",
"unidirectional airflow system in the lungs",
" that makes respiration highly efficient. All of these show up prior to the emergence of birds ",
" the origin of flight; these unique lungs are likely even ancestral for archosaurs. While they do create the perfect scenario for flight, they also clearly conferred their own advantages individually, and they're also deeply entrenched in these dinosaur lineages.",
"\"Bird\" is actually sort of a fuzzy term at this point because there isn't much that makes a bird morphologically distinct from its close relatives. Birds inherited their wings and feathers, among many other things, from increasingly more inclusive taxonomic groups of dinosaurs:",
"Asymmetrical flight feathers show up in Avialae (a lot of theropod workers consider all avialans to be \"birds\" while others only include crown-group Aves).",
"Maniraptorans have ",
"semilunate carpals",
" in their wrists, a backwards-facing pubis, a bony sternum, and pinnate feathers on the forelimb. ",
"This paper",
" looks at the evolution of the semilunate carpal and says:",
"The original selective advantage of this enhanced mobility is not clear, but cannot have related to pennibrachial folding unless relatively basal tetanurans had elongated feathers on the forelimb. [Note: the pennibrachium was basically the wing, but termed differently because the authors weren't sure it was used for flight.] Such a possibility should not be dismissed entirely. Specimens representing this grade of evolution have not been recovered from sediments that preserve extensive soft tissue, and filamentous integumentary structures [e.g. feathers] have recently been reported in a basal ornithischian (Zheng et al. 2009). However, it is likely that mobility of the wrist was initially associated with other functions, such as predation (Padian 2001). ",
"Feathers are present for sure ",
"at least in Coelurosauria",
", and either feathers or a similar integumentary structure show up even earlier in some dinosaur lineages and possibly into pterosaurs (which are related to but ",
" dinosaurs). ",
"Theropods have a ",
"furcula",
" (wishbone) and hollow bones.",
"A ",
"unidirectional airflow system in the lungs",
" that makes respiration highly efficient that goes beyond just dinosaur evolution and ",
"shows up in crocodylians",
".",
"Paleontologists ",
"have reconstructed the brains of birds",
" and non-avian dinosaurs and found that the enlarged forebrain that we associate with the neurological ability to fly shows up earlier than we thought (the original paper is ",
"here",
"). This enlargement shows up multiple times to create an overarching trend in theropods.",
"Birds are all of these things: archosaurs, theropods, coelurosaurs, maniraptorans, and avialans, and it's all reflected in their anatomy. At this point these characters are smeared so far down the dinosaurian tree that there is no magic point at which a dinosaur becomes a bird, and there is certainly no point at which a bird would cease to be a dinosaur. ",
"Given the level of detail at which we've been able to document about the evolution of birds, at this point the most useful definition of \"bird\" probably lies in the crown group, which is a group that contains the common ancestor of all living birds and every descendent of that ancestor. That's usually how Aves is defined. The thing that sets crown-group birds apart from their immediate relatives is the ",
"complete loss of teeth",
" in the beak, and possibly the complete fusion of the ",
"tibiotarsus",
", but teeth are lost and tibiotarsi are fused in several other lineages. So right now there's nothing morphological that sets a the crown group apart. For this reason, like I mentioned above, the group Avialae is so bird-like that many people do refer to them as \"birds\".",
"There were flying theropod dinosaurs before there were birds (not pterosaurs - pterosaurs are not dinosaurs and evolved flight independently!). An excellent review of feathered dinosaurs (many of which didn't fly) can be found ",
"here",
". Some examples are ",
", ",
", and ",
".",
"As for flight, if you look into its origin within dinosaurs you may hear that the dichotomy for the origination of flight is either ",
"\"tree-down\" or \"ground-up\"",
". This widely regarded by paleontologists to be a gross oversimplification of things, in large part because there was a lot of diversity in the group and they were doing a lot more than just climbing up or falling out of trees. There were both ",
"cursorial feathered dinos",
" and ",
"arboreal feathered dinos",
". ",
"Here",
" is a source on the origination of flight, although keep in mind that at this point more fossils have been found.",
"In short, flight developed because a bunch of traits that are found much deeper in dinosaur evolution were co-opted into something that could be used to fly. Because it opens up a whole new ecological niche, it was selected for."
] |
[
"The statement \"dinosaurs evolved into birds\" is very misleading. It's kind of like saying \"mammals evolved into whales\". ",
"It's better to think of it this way. Birds ",
" dinosaurs. They are the one group of dinosaurs that survived the KT extinction event. All the dinosaurs you know of (T-Rex etc.) have no living descendants. These did not \"evolve into\" birds.",
"As far as how flight evolved, there is no consensus yet. ",
"Wikipedia",
" is a good place to start. We are not sure when powered flight started (as apposed to simply gliding). It may be that feathers initially evolved for display and then later evolved for use in gliding and eventually flight."
] |
[
"There's no proportional difference between flying dinosaurs and birds. Birds ",
" flying dinosaurs. If you're asking why most birds fly and most extinct dinosaurs did not, it's because all birds today are descendents of a group of flying dinosaurs. Flightless birds are secondarily flightless. Flight was not the ancestral condition for all dinosaurs."
] |
[
"What is an explanation for the rapid increase of Autism Diagnosis in the past few decades?"
] |
[
false
] |
Can it be attributed due to innovations of technology that allow us to accurately diagnosis cases, in which may not have been diagnosed in the past due to limitations on technology or just plain out factors that we still have yet to fully grasp - environmental, genetic defects, etc. ?
|
[
"There was a big increase in the recognition of autism after Rainman came out in 1988. Before then autism was hardly known outside a the circle of a few notable pioneer researchers and parent groups e.g. The national autistic society in the UK. For example, in the 1970s it was thought that autism was a rare condition, affecting perhaps 5 in 10,000.",
"Then 6 years later the criteria for autism was greatly widened in 1994 in the DSM-IV, a manual that defines the criteria for diagnosis of mental disorders. This meant that many milder cases, including Asperger’s Syndrome and pervasive developmental disorder - not otherwise specified (PDD-NOS), and another disorder now no longer linked with autism (Retts Disorder) where included in autism statistics. About half of the increase was due to Asperger’s Syndrome and PDD-NOS. ",
"The was was also an parallel recognition that many people previously diagnosed as only mentally retarded in fact also had severe autism, so as cases of severe autism increased as cases of only mental retardation decreased. For example about 5-10% of people with Downs syndrome also have autism, and over have of people with Fragile X have autism. In total 5% of autism cases are due to Fragile X. ",
"There's also a economic and educational reasons behind the increase, parents found that diagnosis of autism or Asperger’s Syndrome brought financial and educational supports for a child they wanted to attend mainstream school. It's not uncommon that a child will be diagnosed as autistic for school supports but parents will tell relatives and friends that their child has Asperger's syndrome, as there's less of a stigma. ",
"The newest version on the DSM-5 merged autism and Asperger's into autism spectrum disorder and it introduced a 3 point scale of severity, partly because autism and Asperger's are too similar, but also to reduce parental shopping for a diagnosis.",
"So to sum up, in the 1970s, only the most severe, typical and obvious cases of autism were diagnosed. Autism was wrongly assumed to be rare and possibly related to schizophrenia. Then as time went by, people became more aware of milder cases and less typical presentations, these were diagnosed with an autism spectrum disorder. The current estimate is about 1 in 110. But understand that this includes people who are very severe and mute, all the way to eccentric scientists who are educated to PhD level."
] |
[
"This is very nice explanation of the most important reasons why autism diagnoses seem to be going up. It's also summed up in ",
"this article in Nature",
". ",
"In short, we can explain about half of the increase we are seeing. Apart from better recognition and awareness of autism by both clinicians and parents, we also know that increasing parental age explains a bit of the increase (parents over 35 years are more likely to have a child with autism). And in a few cases, there seem to be some local clusters, such as in West-Hollywood in California and the Eindhoven region in the Netherlands. ",
"However, that only explains about half of the increase, and we don't know lot about the other half yet. There are a lot of ideas out there, but very few that have scientific support at the moment (though, for instance, ",
"air pollution",
" seems one possible explanation). Mostly, we have been ruling potential explanations out, such as vaccines and ",
"assisted reproduction",
"."
] |
[
"That's a good article, very interesting. I met one of the people mentioned in the paper, Terry Brugha. I'm inclined to think that Terry's idea that autism a has always been the same is more likely than a partial real increase; he supported this idea with a door to door survey that found a similar incidence of autism in adults as in children.",
"But it's possible there might be a slight real increase. Autism and schizophrenia are related conditions of the social brain (see Crespi and Badcock 2008). They seem to share similar though occasionally opposite risk factors. For example, the offspring of Afro-Caribbean immigrants to the UK have a vastly increased rate of schizophrenia and possibly autism. This might be linked to a Vitamin D deficiency. There's also an unexplained autism cluster amongst Somali refugees in the US, the cases then to be severe autism only rather spanning spectrum, we might see a schizophrenia cluster as children grow up. Vitamin D might be just one of the causes of a possible increase, in both schizophrenia and autism i.e. one cannot increase without the other also increasing. So has schizophrenia increased in parallel with autism? That would be interesting to find out.",
"Brugha, T. S., McManus, S., Bankart, J., Scott, F., Purdon, S., Smith, J., ... & Meltzer, H. (2011). Epidemiology of autism spectrum disorders in adults in the community in England. Archives of general psychiatry, 68(5), 459-465.",
"Crespi, B., & Badcock, C. (2008). Psychosis and autism as diametrical disorders of the social brain. Behavioral and Brain Sciences, 31(03), 241-261.",
"Edit: Spelling"
] |
[
"Can anyone help me understand why my post is being taken down??"
] |
[
false
] | null |
[
"All posts are placed in a mod queue and released manually. Please read the posting guidelines."
] |
[
"it was a question on replication of virus. I dont know how it violates any guidelines"
] |
[
"It is likely still in the queue waiting for a mod with the relevant background to review it."
] |
[
"Is there any non graphic proof that when n appoaches infinity, |(x^n)| + |(y^n)| = r is a square?"
] |
[
false
] |
I've been playing with online cartesian drawing tools. When n=1, it is a rotated square at half PI. Then it will transform into a circle while rising n slowly towards 2. Then, an interesting thing began. Any increase in n will make it more square-y but will never become a complete square. Will it became a true square when n reaches infinity? What is the proof?
|
[
"Let's use r=1. You can ask for which x,y does |x",
"| + |y",
"| converge to 1. Let's say x,y>0, r=1 and x=cy for 0<c<1, the other cases can be treated using symmetry or they are trivial. Then |x^(n)| + |y^(n)| = y^n (1+c^(n)). For y<1 this converges to zero, for y>1 this diverges, for y=1 this converges to 1.",
"If you use a different r then you never get convergence to r of a point, but you can still show that you get the closest to r at this square."
] |
[
"For any point (x',y') where |x'|<1 and |y'|<1, you can show that that point lies inside the |x",
"|+|y",
"|=1 curve for all sufficiently large n. ",
"Basically you show that for any fixed 0<k<1, k^(n)-->0 as n-->infinity, and apply that to both x' and y'. ",
"Is \"every point in the interior of the [0,1]",
" square is also in the interior of |x",
"|+|y",
"|=1 for sufficiently large n\" the same thing as \"|x",
"|+|y",
"|=1 becomes a square for infinite n\"? Sort of. It pays to be precise with what \"approaches infinity\" and \"approaches a square\" means."
] |
[
"The function f(x,y) = (|x^n| + |y^n|) ^ (1/n) is often called L_n, or the n-norm.",
"For n=2, L_2 is the usual Euclidean distance from the origin to point(x,y)",
"For n=1, L_1 is the Manhattan distance, that is, if you have to travel from the origin to point (x,y) but you can only walk alongside the \"grid lines,\" as you would in Manhattan.",
"For n really large, say 1000, then if say x > y, then it almost doesn't matter what y is. All that matters is what x is. So for n -> infinity, then L_n approaches max(x,y). We can prove this formally using sequences, but once you understand the reason and intuition why it's that way, the rest is just formalism.",
"So now you have a curve that says max(x,y) = r. Err that sounds like a square doesn't it?",
"Bonus: for n -> 0, L_n approaches sqrt(xy). This can be proven too. At that point the graph is like the graph y = 1/x but replicated along all 4 quadrants. ",
"As n continues to decrease to negative numbers, the graph is like L_0 but even skinnier. ",
"And as n -> negative infinity, L_n approaches min(x,y). The graph is just a \"plus sign\""
] |
[
"Weight of potential energy?"
] |
[
false
] |
The energy put into compressing a spring, does it have measurable weight (no matter how miniscule, theoretical question)?
|
[
"Note that in practical situations, this weight increase is so small that you would not notice it on a scale."
] |
[
"Note that in practical situations, this weight increase is so small that you would not notice it on a scale."
] |
[
"So, i'm not actually sure about this. Maybe it's true for a spring - for mechanical potential energy - but is it true for gravitational potential energy? I think not, right?",
"And in the case of the spring - where precisely is that additional mass stored?",
"Does this also imply that the mechanical stresses in the earth's crust add to its mass?"
] |
[
"Do the holes on a dice which represent the numbers affect the chances of getting different numbers?"
] |
[
false
] | null |
[
"Yes they do!",
"If you look at the regular dice you get from, say, a Monopoly game, you'll find many things that can change the chance of rolling a specific number.",
"First your question: The mass on the 1 side (with one hole) is higher than from the opposite, the 6 side (with six holes), so the 1 side is the heaviest side and therefore a 6 is slightly more likely.",
"Now to other things:",
"The dice are usually made out of wood or white plastic or other materials you can't look through, so you can't see if the dice are manipulated (a weight on the 1 side to make the 6 side more likely for example).",
"The edges/corners are round and, without proper measurements, you won't be able to know if the edges/corners are identical. If you grind specific edges/corners down, you can increase the chance of a specific side.",
"There's one more: Dice get used up after a while. You may not see it on a wooden die, but it will get little scratches, which also changes the probabilities.",
"Now you may think, how do casinos prevent it? They have special dice.",
"They are usually made out of acryl, so you can look through. The edges and corners are very sharp, so you can easily, without measurements, tell if one edge/corner is grinded down and, IMO the most awesome thing: The holes get filled with a material that has a density as close as possible to the acryl.",
"They handle the tear in an easy way: They simply change out the dice pretty often.",
"If you want high quality dice, get casino dice.",
"I have five of them (though, not quite casino quality, I paid 15€ for all of them, so 3€ each) and you can see all the points mentioned very easily, even the scratches on the edges and the broken off corners. I've used them somewhere between 15 to 20 thousand times. If you'd like to, I can take a few pictures of mine with the scratches, otherwise you can simply google \"casino dice\" to see pictures of them.",
"Edit: I took some pictures, ",
"they aren't great",
", but I hope you guys can see what I mean with used casino dice. Look closely at the corners and edges.",
"/u/Macinapp",
"/u/Azurphax",
"2nd edit: I was stupid enough to forget the link to the pictures."
] |
[
"I can't speak to the physics, but I can tell you that dice used in gaming license venues adhere to pretty strict balance properties, and are constructed with this in mind. No single set of dice is ever used for too long for the same reason.",
"Cheap dice do not adhere to these rules, and are often unbalanced, so I think there is a good chance the indentations do factor into the dice performance."
] |
[
"Dice used in gambling do have their pips (the names for those holes) filled in, negating whatever small influence they might provide, but the real factor that makes them expensive is that they are machined to a certain tolerance where cheaper dice are injection (edit: or compression) molded and then polished to take away the sharp injection molded seams. The polishing process can often change the weighting of a die significantly. "
] |
[
"If one identical twin gets a cancer of the blood, and they share blood with the other twin, do they 'catch' the cancer?"
] |
[
false
] | null |
[
"Completely and utterly wrong.",
"'blood cancer' is actually reliant on bone marrow to produce the cells which cause the cancer. This is reliant on a number of things and simply sharing blood is not going to mean you 'catch' cancer. "
] |
[
"You made a few errors, I'm afraid"
] |
[
"Quite right on both counts, my mistake.",
"In my defence it's 5:45 in the UK and I have yet to go to bed.\nI meant to say metastatic instead of malignant."
] |
[
"Does every object that has mass have a Schwarzschild radius, even sub-atomic particles/fundamental particles?"
] |
[
false
] | null |
[
"Yes, it's just a function of mass.",
"Massless particles do not."
] |
[
"The issue is that you can't Lorentz-transform to a frame where they're at rest. There is a gravitational field for a massless particle, which agrees with the limit of an extremely Lorentz-transformed Schwarzschild solution.",
"The paper on this claims \"On this plane the Riemann tensor has a δ-like singularity and is exactly of Petrov type N.\" but I don't know what that means."
] |
[
"Wikipedia says that, but Wikipedia is not necessarily right. In fact, most things on Wikipedia about Planck units are wrong. That page also states that nothing can be localized to smaller than its Compton wavelength, but the radius of the electron is known to be more than 10 orders of magnitude smaller than that.",
"What is true is that when you start getting to that size you'll have to take quantum gravity into account."
] |
[
"How did chemists first calculate bond angles?"
] |
[
false
] |
Was it based off of the molecular structure?
|
[
"Bond angles were first measured by analyzing the infrared spectra of a molecule to determine at which frequency the bond vibrations resonate with the frequency absorbed by said IR light. With this information, you could assume that the bonds act like springs and the atoms as weights and determine the angles of the bond. (this is what I understand of it, at least).",
"The NEW way to measure bond angles (and lengths) is to use molecular orbital techniques to calculate the energies of each occupied molecular orbitals. With these calculations, it is possible to determine the orbitals' size and shape to then determine the \"exact\" distance/angle (theoretical/average) of one nucleus relative to another of the same molecule."
] |
[
"/u/alexryan94",
" is correct in saying that the first bond angle measurements were based off vibrational absorptions seen in IR spectroscopy. However, this method is not particularly robust and is considerably more difficult to apply to larger structures.",
"Röntgen won the Nobel Prize in 1901 for discovering X-rays, and later von Laue would discover that crystals diffract X-rays. Shortly after this discovery by von Laue, Bragg did his groundbreaking work on X-ray crystallography. In brief, X-rays are diffracted on the molecular level by crystalline solids. A focused beam of X-rays through pure crystals would yield a specific diffraction pattern, from which the crystal structure of compounds can be discerned (via geometry based on the varying light intensities along the pattern). This was the original method of directly measuring bond angles and determining structures."
] |
[
"XRD has been used to determine molecular structure with precision for quite a while now, so I'm not sure what you mean."
] |
[
"How does supersymmetry solve the hierarchy problem?"
] |
[
false
] |
Hoping for an explanation that doesn't require me to learn too much extra notation. I understand the basics of supersymmetry, and I understand the "fine-tuning" problem that exists without it, but it seems like the claim that it solves the hierarchy problem is passed over without much attention, or it involves crazy math. I realize that this question may involve too much math in order to be explained on this site. Thanks in advance.
|
[
"The solution rests on the non-renormalization properties of supersymmetry, which cause quadratic divergences in loop diagrams to cancel out. Naively, the Higgs mass (which we expect to be around the weak breaking scale, and which perhaps is around 125 GeV) would receive quantum corrections proportional to the square of the ultraviolet cutoff scale, which without any other physics, we would expect to be something like the Planck scale, which is way, way, way too high (10",
" TeV vs. ~.1 - 1 TeV). Supersymmetry provides a cancellation of these quadratic terms, so that we don't get Planck scale correction to the Higgs mass."
] |
[
"To expand on this, fermions and bosons contribute to the Higgs self energy with opposite signs. In supersymmetry, the fermions and bosons in SM have partners with opposite spin which makes δm",
" almost zero (not Λ",
" )."
] |
[
"You have to look at the diagrams that contribute to the renormalization of the Higgs mass. The coupling between Higgs and two fermions can produce a H->H diagrams in which you have fermions running in the loop. The quartic coupling of 2 Higgs + 2 bosons give you another loop diagram with the bosons running inside.",
"It turns out that in a supersymmetric theory, the relation of the coupling constants is such that the square of the yukawa coupling to fermions is proportional to the coupling constant to bosons, so that doing the computations, all these diagrams cancel each other, provided that they have the same masses."
] |
[
"Why is the human body homeostatic at ≈36.8°C?"
] |
[
false
] |
I know it's bad for sperm production. Is this a good temperature for certain chemical reactions? Is it in response to climate? Why not 30°C? Or 40°C?
|
[
"Well, first of all your body temperature does fluctuate throughout the day and can be different depending on the person, time, where you measure, etc.",
"That said, there is a general set point that does indeed exist that probably arose out of evolution. The really famous study that you'll probably encounter is here: ",
"http://mbio.asm.org/content/1/5/e00212-10.full?sid=3927b57a-d112-452b-bbce-e1e1f4743e1d",
"The study seems to suggest that the temperature is an optimal balance for avoiding fungal infections (which the frequency of decrease with increasing temperatures) and fitness. Check it out. "
] |
[
"While I agree with what you'd said it's also extremely important for you to note what InbredScorpion had added. That is, that the protein action inside our bodies is most efficient at this temperature. They work most rapidly, without the risk (most) of denaturation at this temperature."
] |
[
"I am not sure if this is an inherit reason as to why the body is homoeostatic at 36 - 37°C but... proteins work optimally at around 37°C. Increasing or decreasing the temperature too much (not in the case of spermatozoa, which sits around 33°C) will cause the proteins to denature.",
" "
] |
[
"Suppose two people with different copy number variations(CNVs) mate . . ."
] |
[
false
] |
Say guy has 5 copies of a gene (homologous) and girl has 7 copies (homo.) What will child have? I ask this in the context of autism, which seems to be related to CNVs in at least some cases.
|
[
"If we're talking about the same gene, then think about it this way:",
"It depends how many copies are on each chromosome. If the guy has 4 copies on one homolog and 1 copy on the other homolog, the child can either inherit either the chromosome that has 1 copy or the chromosome that has 4 copies. Same with the mother- it depends how those 7 copies of the gene are distributed between the two maternal copies of that chromosome. The child could, in the end, have any number of copies of that gene from 2 (1 from each parent) to 10 (4 from Dad and 6 from Mom). ",
"It's possible that recombination could occur during egg or sperm development, too, increasing or decreasing the number of copies that the child inherits. This happens quite often, especially when the amplified sequences are flanked by repetitive sequences. "
] |
[
"Yep!"
] |
[
"That rather depends on which chromosomes they're on and how many on each. genes/sequences that are on the same chromosome tend to violate mendelian genetics rules of thumb because the closer two sequences are to one another, the more likely it is that they'll be inherited as a group rather than independently. If all five in the guy's genome are localized on the same chromosome very near one another in the genome and the child inherits the other chromosome in the chromosome pair that has no copies in it, then the child won't inherit those copies at all from the guy. The same is true of the girl. So without knowing the specifics of where each of these CNVs are, it's at best statistical."
] |
[
"How are electrons shared in compounds?"
] |
[
false
] |
Since electrons orbit the atomic nucleus how can an electron be shared between two nucleus? Does it do a figure of eight between them and is it always the same electron that is shared?
|
[
"The electron ",
" is delocalized from the atom. There is still charge neutrality since there is the same number of positive and negative charges, but the electrons are no longer electromagnetically confined to a single atom. Don't think of them as individual particles orbiting, but a probability cloud that is spread out over many atom cores."
] |
[
"Different atomic electron shells have different shapes arising from the probability of the electron to be found in different places. When we talk about books between now than one atom we consider the electron orbital of the atoms to be overlapping, in effect the electron is now free to move about both atoms in this overlapping orbit. In a molecule you will have a number of orbits all joined by the overlaps in neighbouring atoms to form what is known as a molecular orbital, and these are much more complicated than the single electronic orbitals "
] |
[
"Electrons of atoms don't really follow Newtonian mechanics, they follow quantum mechanics. So when they are shared, they're shared by probabilities rather than by orbits.",
"Quantum mechanics was an unexpected solution to the problem of the electron spiraling into the nucleus, and also the so-called ",
"ultraviolet catastrophe",
", and eventually led to the concept of electron probability clouds.",
"http://www.chem1.com/acad/webtut/atomic/WhyTheElectron.html",
"An electron, unlike a planet or a satellite, is electrically charged, and it has been known since the mid-19th century that an electric charge that undergoes acceleration (changes velocity and direction) will emit electromagnetic radiation, losing energy in the process. A revolving electron would transform the atom into a miniature radio station, the energy output of which would be at the cost of the potential energy of the electron; according to classical mechanics, the electron would simply spiral into the nucleus and the atom would collapse.",
"By the 1920's, it became clear that a tiny object such as the electron cannot be treated as a classical particle having a definite position and velocity. The best we can do is specify the probability of its manifesting itself at any point in space. If you had a magic camera that could take a sequence of pictures of the electron in the 1s orbital of a hydrogen atom, and could combine the resulting dots in a single image, you would see something like this. Clearly, the electron is more likely to be found the closer we move toward the nucleus.",
"http://en.wikipedia.org/wiki/Ultraviolet_catastrophe",
"According to classical electromagnetism, the number of electromagnetic modes in a 3-dimensional cavity, per unit frequency, is proportional to the square of the frequency. This therefore implies that the radiated power per unit frequency should follow the Rayleigh–Jeans law, and be proportional to frequency squared. Thus, both the power at a given frequency and the total radiated power is unlimited as higher and higher frequencies are considered: this is clearly unphysical as the total radiated power of a cavity is not observed to be infinite, a point that was made independently by Einstein and by Lord Rayleigh and Sir James Jeans in the year 1905.",
"Max Planck solved the problem by postulating that electromagnetic energy did not follow the classical description, but could only be emitted in discrete packets of energy proportional to the frequency, as given by Planck's law. This has the effect of reducing the number of possible excited modes with a given frequency in the cavity described above, and thus the average energy at those frequencies. The radiated power eventually goes to zero at infinite frequencies, and the total predicted power is finite.[2] The formula for the radiated power for the idealized system (black body) was in line with known experiments, and came to be called Planck's law of black body radiation. Based on past experiments, Planck was also able to determine the value of its parameter, now called Planck's constant. The packets of energy later came to be called photons, and played a key role in the quantum description of electromagnetism."
] |
[
"How is it that our visible light spectrum can be displayed via a ciclic representation (the color wheel) when the light spectrum is linear?"
] |
[
false
] |
The 'break' would be between red and blue, I assume. But it is able to seamlessly circle back through purple. I'm curious as to how that fits in with the linear representation of visible and non visible wavelengths of light. On that note, what would a color wheel look like if it integrated non visible light?
|
[
"The color wheel is based on what people see rather than the whole spectrum. It would be better to think of it less as a wheel and more of a triangle. And even better to think of it as ",
"this weird shape",
". There very much is a break between red and blue.",
"For each additional frequency of light you integrate, you'll need to add one more dimension. Someone who can see four colors would need a color sphere. Though it would be as close to a sphere as that thing I showed you is to a circle. Someone who could see five would need a color 3-sphere (or 4-sphere depending on how you count them) etc. If you want all the colors, you'd need a hypersphere embedded within infinite dimensional ",
"Hilbert space",
" or something like that."
] |
[
"Interesting addition to that weird shape.(which in itself is a cross section of a 3d shape, iirc the hidden dimension relates to brightness) that edge there that is marked with numbers from 460 to 620, those are pure wavelengths in the spectrum and their positions in the graph correspond to those colours. Colours in between are mixes of those pure colours.\nThe straigth line edge of the picture corresponds roughly to what we'd perceive as fully saturated purples.",
"RGB monitors can only represent colours formed by a triangle the corners of which correspond to the wavelengths of its 3 colours.",
"Distances between coordinates in the graph only vaguely correspond to perceived differences in colours. A different colourspace would be more suited for such comparisons."
] |
[
"The main reason why we represent the colors as a wheel or some other two-dimensional graphic is that we have three different color sensing cells in our eyes, the ",
"cone cells",
".",
"Any of the colors on the \"color wheels\" only represent the ratio of the three colors we perceive - if you look at the picture ",
"/u/DCarrier",
" linked you will notice that no dark colors are represented, since dark colors are the same as the bright ones on the picture, only at a lower light intensity.",
"As a result, if we only could percieve one color, we would only need a dot to represent all of them. Two colors has to be a line, since the ratio of one color to another can have any mixture from 1:0 to 1:infinity - a line from zero to infinity, or whatever numbers you feel are appropriate. Three colors, as a result, need the extra, 2",
" dimension added to show the new complexity - if you start at one color, say red, you can go in one direction to add some blue and arrive at a more purple color, or you can add green to get a more yellow color. In the center of his picture there is white - a mixture of equal amounts of all the three colors we perceive."
] |
[
"AskScience AMA Series: We are building the national quantum network. Ask Us Anything about the #QuantumBlueprint"
] |
[
false
] |
Last Thursday the to build a national quantum internet. This #QuantumBlueprint is meant to accelerate the United States to the forefront of the global quantum race and usher in a new era of communications. In February of this year, DOE National Laboratories, universities, and industry experts met to develop the blueprint strategy, laying out the essential research to be accomplished, describing the engineering and design barriers, and setting near-term goals. DOE's 17 National Laboratories, including Argonne National Laboratory and Fermilab will serve as the backbone of the coming quantum internet, which will rely on the laws of quantum mechanics to control and transmit information more securely than ever before. The quantum internet could become a secure communications network and have a profound impact on areas critical to science, industry and national security. (Fermilab Scientific Computing Division) and (Argonne National Lab's Center for Molecular Engineering) will be answering questions about Quantum Computing and the Quantum Internet Today at 2 PM CST (3 PM ET, 19 UT). AUA! Usernames: ChicagoQuantum
|
[
"My understanding is Quantum computing is done at very low temperatures - is this required for a quantum internet and how can this be achieved over distance?"
] |
[
"A: Not necessarily. Some quantum processors may need to operate at very low temperatures. But the quantum internet is designed to transmit quantum states to different places. Scientists typically use photons as the vehicles to transmit quantum states. Photons are transmitted either in telecom fibers or in free space. The devices that handle photon transmission can typically operate at normal temperatures. (Wenji)",
"A: As Wu said, the transmission will very likely be at room temperature, apart if cooled superconducting wires become wide-spread across cities and continents. However, the quantum internet will require a quantum repeater to boost the signal across long stretches of fiber (if not using satellites), similar to a classical amplifier. This repeater is very much like a barebone tiny quantum computer, meaning that it will require low temperatures in most cases. (Gary)"
] |
[
"It's my understanding that creating the entangled particles is hard to do. How will you handle the extremely large amount of connections being made?"
] |
[
"Can our bodies tolerate environments without oxygen?"
] |
[
false
] |
What I mean is, if we have access to a normal breathing atmosphere through some sort of breathing apparatus, would our bodies otherwise tolerate being in an atmosphere (same pressure as normal) devoid of oxygen? The only answers I was able to produce while searching related to what happens to our bodies in space or on different planets, and that our skin doesn't "breathe", but still absorbs oxygen. So just as an extreme example, if we were to find another planet with the same pressure and composition as ours but lacking oxygen, or if our own somehow ran out of oxygen, would there be a limit to how long we could stay outside without a suit, aside from the oxygen required to breathe? Or in other words, what would happen to our bodies if the respiratory system was the only part of us that had access to oxygen (most of the time)? (not sure if right tag)
|
[
"As long as your body intakes normal air, and the atmosphere outside is the same pressure as our atmosphere, then I would think that nothing of significance would happen. Being submerged in water and having a breathing apparatus, but not a full diving suit is possible already, so long as the pressure differential isn't significant. Breathing pressurized air deep underwater and then rising up too quick is dangerous due to gas expansion, as well as nitrogen saturation. As for long term side effects, I don't believe it has been tested before in a study. Could be wrong on this though."
] |
[
"Yup, for anyone interested, many SCUBA divers use wetsuits which trap a layer of water inside that your body heats up to keep you warm even in somewhat cold waters. Drysuits keep the water out but are less comfy and are for more extreme cold temps, usually < 50°F (you get cold faster in water so even 50° is dangerous if unprepared)"
] |
[
"Yes, when doing gas work we have to enter low oxygen areas with a breathing apparatus of course. The low oxygen doesn't affect your body. However without the breathing apparatus and no suitable oxygen to breath then your body will not be triggered to expel carbon dioxide and you will just not be able to breath at all which will lead to death. But to answer your question yes our bodies can tolerate 0 oxygen areas."
] |
[
"Why do the variables in cosmological equations have the values that they do?"
] |
[
false
] |
[deleted]
|
[
"Really, nobody knows why the universe has the properties it does. Gravity could be arbitrarily stronger without \"logical\" contradiction but we live in a universe where it has the strength that it does.",
"The cosmological constant, before it was measured, was derived from quantum electrodynamics. Then it was measured and found to be 10",
" times smaller than predicted. This is one of the worst predictions in the history of science."
] |
[
"Because it's off by 120 orders of magnitude."
] |
[
"Because it's off by 120 orders of magnitude."
] |
[
"Was Venus ever within the habitable zone of our Sun?"
] |
[
false
] |
It is a known fact that main sequence stars increase their luminosity over time, as helium accumulates in their cores. Even though our own sun will be around for ~5 billion more years, it will have gotten bright enough 500 million years from now to have boiled away our oceans. So what if we turn back the clock? Was there a time, say, 3 billion years ago, when the current orbit of Venus would've been within the habitable zone? Would it have been in the habitable zone at the time (considering how chaotic the early solar system was, it's likely that all of the planets moved at least a little bit, IIRC)? Is it still within the habitable zone now? EDIT: Torn between "astronomy" and "planetary science" flairs.
|
[
"Venus is actually in the habitable zone, however its thick atmosphere prevents temperatures for life as we know it to exist. While studying astronomy, one of the things a professor pointed out was that if Mars and Venus were to be swapped, both would likely be able support life."
] |
[
"This always is asked about Mars. I have read enough responses to feel like I can answer. Solar wind has stripped away the atmosphere on mars already. That’s why it’s so thin. But it took millions of years to do it. It’s because Mars doesn’t have a liquid rock and rotating iron core like Earth does and this means Mars can not generate a Magnetic field to keep the solar wind from having a atmosphere reducing effect. Switching solar positions wouldn’t increase the amount of solar wind too much. It’s a considerable change in distance yes, but not overall compared to the rest of the solar system. ",
"We can terraform Mars one day when we develop the technology to do so as long as we can produce a greater global effect than the rate of which the solar wind strips it away. But the effect is pretty gentle. We would have more of an issue with radiation from solar flares sterilizing away our hard work. ",
"It’s all pretty exciting stuff!",
"Edit: on my iPhone and sometimes sentences make sense in my head but the thumbs fail to translate. "
] |
[
"Wouldn't Mars's extremely thin atmosphere likely have been blasted away by solar wind if its orbit was swapped with Venus's?"
] |
[
"What is the chemical signaling process for memory in the brain?"
] |
[
false
] |
[deleted]
|
[
"Memory is an emergent property of several interacting signaling processes. It is thought to be encoded in the connectivity of neural networks, including signaling strength between neuron pairs. This process is guided by several different mechanisms, but the most general description of them is hebbian learning and neural darwinism. Neurons and circuits that are used grow stronger together, while neurons that aren't die.",
"A process called long term potentiaion (LTP) is often involved in learning that leads to memories, as are genetic expression processes that create more receptor channels on post synaptic neurons. There are also signals to microtubules that cause the microtubule to invade a particular dendritic spike. Little package delivery proteins, called kinesin use the microtubules as a highway, bringing materials that help to increase the dendrite's surface area and post-synaptic receptor count. All this leads to strong connectivity between that dendrite and the bouton."
] |
[
"How does calmodulin relate to memory, mechanistically?"
] |
[
"Calmodulin is all over, in multiple sites around cells. When associated with ion channels, it can prolong spiking in cells by holding those channels open, which can facilitate LTP. Calmodulin has also been shown to participate in transport of AMPA receptors that turn silent synapses into active ones. It probably does about 100 other things that I don't know about, as well."
] |
[
"Two questions regarding the limiting power of the speed of light"
] |
[
false
] |
I realize that these questions resemble that of "troll physics" but I was curious anyway. If I were to have a unbreakable, massless stick of 1 light-minute in length, and I used that stick to poke somebody 1 light-minute away, would it take exactly 1 minute for them to feel it? If so, could somebody explain why? If I were to take that same stick, and move it in an arc over my head at, from my perspective, 90% the speed of light, how would the end of the stick behave?
|
[
"If you had a massless stick, it would have to be moving at the speed of light. All massless particles move at the speed of light.",
"But lets say you had a stick of 1 light-minute in length with mass. If you push one end of the stick, the pressure wave from the push would propagate at the speed of sound, not light, and it would take a really long time for the end of the stick to feel it.",
"As for two, the stick would just bend."
] |
[
"when you push on your end, the atoms in the stick need to \"talk\" to their neighbors by pushing on them. And so on down the line. The fastest they can possibly communicate (push on each other) is at the speed of light. ",
"This is slightly more challenging to answer, you mean the end of the stick on your end is traveling with some tangential velocity at .9c (the standard way of representing portions of the speed of light). If those atoms are moving like that, they have to pull their neighbors as well, and those neighbors would have other time dilation effects, so my guess is the whole thing would \"bend\" (since it can't break)."
] |
[
"It would take as long as it takes a sound wave to propagate through the stick, which is how fast the poke would travel. The fastest speed of sound I know of is about 20 km/s, but I think neutron stars might have interior speeds of sound approaching the speed of light.",
"It would follow an arc, with the tip trailing behind your hand. The shape of the stick would change as it gets length-contracted."
] |
[
"After doing a repetitive task for hours on end, sometimes you close your eyes and you can see it. What is going on here?"
] |
[
false
] |
I'm talking about after those late nights of playing games, you close your eyes and see DotA 2 behind your eyelids. Or if you spend all day picking fruit, take a shower and close your eyes only to see apples everywhere. Anyone know what gives?
|
[
"The Tetris effect (also known as Tetris Syndrome) occurs when people devote sufficient time and attention to an activity that it begins to overshadow their thoughts, mental images, and dreams. It is named after the video game Tetris."
] |
[
"Excellent. Thanks for the reply! Any idea how it actually works? Also, it would be interesting to learn if the hallucinatory nature of this phenomenon is caused by the same thing that causes ",
"GTP",
"."
] |
[
"is this akin to \"highway hypnosis\", where, after a long stretch of highway driving, your internal 'speed sensors' are out-of-whack and higher-speeds feel slower than actual?"
] |
[
"If a person with a certain communicable disease dies of it and is buried, do the said pathogens continue to live, multiply and spread in the soil?"
] |
[
false
] |
By extension, like how vaccination improves herd health, shouldn't incineration be a preferred mode of disposal of the dead rather than burial?
|
[
"This will depend on the pathogen in question. Some examples:",
"Anthrax can survive in soil after the host is dead, although the bacteria aren't actively multiplying (instead, they form spores).",
"Prions can also persist in soil (\"survive\" is the wrong word here because they're not alive)."
] |
[
"Mortuary worker here, embalming/sterilizing (which you can't really guarantee to be 100% sterile) isn't required for burial at all, and even for most diseases (Hep C, AIDS, MRSA etc.) it isn't required by the funeral home or the law (at least in Colorado, USA). There are some EXTREME cases such as Ebola where the health department will get involved and tell us what needs to happen, but for the most part embalming or cremating aren't ever required for people with \"certain communicable diseases\".",
"Also, AFAIK, most of these diseases aren't going to get very far through a casket, vault, and 6 feet of soil and live to infect someone.",
"EDIT: Also, we never take out organs at the mortuary, that is only done for autopsies. We would never do it of our own volition as it makes embalming a pain in the ass."
] |
[
"If something can multiply in soil and infect humans at the same time then it is everywhere anyway."
] |
[
"If an object is dropped in a vacuum and pulled down toward Earth, changing its gravitational potential energy into kinetic energy, does it lose any of this energy as heat?"
] |
[
false
] |
The way I understand it is that every time energy changes form, some of the energy is lost as heat energy. However, in this situation, what would cause the production of heat without friction from air resistance?
|
[
"If it is a perfect vacuum then no, there would be no drag and thus no gravitational energy converted to heat. It will lose all of its kinetic energy to heat when it smacks into the edge of the vacuum vessel though...",
"Edit: Clarity"
] |
[
"The source could have been anything. cpxh just means that any object with a temperature greater than 0K emits blackbody radiation, regardless of if it is caught in a gravity well. In an ideal system such as your example, the transfer of energy from potential to kinetic will be 100% efficient, so no lost energy will become heat. In a real-world example there will always be some loss to do things like not having a perfect vacuum, tidal forces, etc. this loss of efficiency manifests as heat."
] |
[
"The object would still be radiating heat to the walls of the vacuum, but thats not really what you were asking about. "
] |
[
"If we take all of the world's CO2 emissions and compressed it to a diamond, how big would it be?"
] |
[
false
] | null |
[
"The world emitted 36 gigatons of CO2 in 2014. A CO2 has a molecular mass of 44.01 g/mol, while carbon has a molecular mass of 12 g/mol, meaning that 27% of the weight of CO2 is carbon, meaning that that CO2 emission produces 9.8 gigatons of Carbon. If this was compressed into diamond it would still weight 9.8 billion tons",
"Diamond has a density of 3.51 g/cm³ which means 9.8 gigatons of diamond would take up 2.8x10",
" cm",
" . How big is that? Pretty damn big. It's a cube about .8 of a mile or 1.4 km on each side. It would form a crystal basically exactly the same size of Mount Everest. It would be really really big.",
"EDIT: A lot of people are taking me to task on the Mount Everest claim. And I totally see their point. However, the references comes from Wolfram Alpha.. which is pretty reliable:",
"https://www.wolframalpha.com/input/?i=2.8x10%5E15+cm3",
"After trying to find some sources, I see that it's kinda difficult to really say what the volume of mount Everest is, as it's impossible to say where it starts. Certainly, the diamond will not have the same volume as an equalateral square pyramid with a height of 8.8km. I think a lot of the \"weight of Mt Everest\" and \"Volume of Mt Everest\" come from starting at base camp."
] |
[
"Love ",
"/u/NeuroBill",
" 's answer, but here's another way of looking at it: if you're an average American, your personal diamond weighs 4.5 tonnes, and measures about 4 feet by 4 feet by 3 feet. And you create a new one every year."
] |
[
"This is also a really nice answer, I like this personal perspective."
] |
[
"Would it be possible to build a large double slit experiment to examine the behavior of gravitational waves? If so, would that be proof that gravitons exist?"
] |
[
false
] | null |
[
"No, even ignoring the technical challenges of building such a contraption, it couldn't be used to prove the existence of gravitons. The reason is that the double slit experiment is most directly related to the wave-like properties of a field. For example, the general properties of light as a wave, including things like interference and diffraction were known far before we figured out that light was made up of discrete bits of energy that we now call photons. Similarly in the case of gravity, we now (as of a week) can safely say that it can propagate through waves, and theoretically we know that these waves should also interfere with each other. However, observing such effects can't directly prove that gravitons exist."
] |
[
"And the technical challenges are pretty intense: you need to find a material that can block disruptions in spacetime - which also would be resistant to all of relativity, including gravity. "
] |
[
"There are no opaque materials for gravatational waves, so there is nothing for them to diffract off of."
] |
[
"Why can we see objects millions of light years away?"
] |
[
false
] |
If I have this right, photons travel in a straight line. So, if you imagine a crude drawing of the sun, with sun beams coming off of it, the further these sun beams get from the center, the more spread out they become. Even if a star is giving of Billions upon billions of photons. wouldn't their distance to each other become so spread out that it seems unlikely that we should be able to detect them, let alone get a complete picture out of them? Am I just not comprehending how MANY photons are let off, that it does still spread, but not enough, even millions of light years away? Or is something else happening that lets us see such distant objects?
|
[
"It's crazy, but that's exactly right.",
"Let's think about the Sun for a moment - its luminosity is on the order of 10",
" watts. Half of that power (more or less) is in the visible spectrum, and a visible photon has the order of 10",
" J of energy. That means that the Sun emits on the order of 10",
")=10",
" visible photons ",
".",
"Ok, now let's travel a million light-years away. Those photons are distributed more or less evenly on a sphere with that radius - it turns out that the radius is almost exactly 10",
" m",
" So at a million light years, a telescope with a radius of x meters",
" would receive about x visible photons per second.",
"Now, that doesn't seem like much, but we can actually detect that kind of signal (with very long exposures). And you also have to consider that many of the things we look at (and all of the ones that are -really- far away are -way- brighter. We're talking as much as ",
"2 trillion",
" times brighter. (edit: actually, reading more closely, the brightest known quasar is more like 140 trillion times brighter) ",
"So yeah, these things just produce a lot of photons, and the definition of whether we can see it (assuming there are no obstructions) is whether they're dense enough to produce a measurable signal at this distance."
] |
[
"Because they're really big and bright. "
] |
[
"Not quite. A long exposure is always useful in gathering more photons, but the age of the galaxy itself is irrelevant. The light that reaches us is millions of years old (for example, the light from the Andromeda galaxy is 2.5 million years old when it reaches us, as it is 2.5 million light years away). Howoever - the photons are travelling at a constant rate, so if the star only burnt for 3 minutes, we would see if for 3 minutes on earth. Whether you can see it or not with the naked eye is just a function of how many photons are coming from it (and at what wavelengths). ",
"Take a look at a light bulb. it has a surface area, and every point on the surface area is emitting photons towards you, as well as in all other directions. Stars are just much much bigger versions of that. "
] |
[
"Is there any such thing as gravity wave interference?"
] |
[
false
] |
Could gravity waves from all of the sources in the universe interfere with each other destructively/constructively? Also, I was reading about effect created by colliding kinetic waves, and I wonder if colliding gravity waves could interact in a similar way to produce a repulsive effect, and could that effect be a contributor to the expansion of the Universe? These are questions founded on bodies of knowledge I don't possess, and for that I apologize--but I'm curious nonetheless.
|
[
"Like any other kind of wave, gravitational waves can certainly interfere with each other.",
"I don't know about the tractor beam thing specifically, but people have put forth the idea that gravitational waves are responsible for the accelerating expansion. The answer as I recall is that you can get a small effect but it's not nearly enough."
] |
[
"Bonus questions: is space expanding in all dimensions? Are any dimensions contracting? ",
"I'm told that ",
" is expanding like the skin of a balloon, and the galaxies, nebulae and other objects within are like dots drawn on the surface--but if \"space\" is expanding, where is the \"new space\" coming from? This rhetoric seems to imply a material nature to the behavior of space, and if it's stretching is it getting \"thinner\"? If yes, how? If no, how?"
] |
[
"Yep, space is expanding equally in all directions, at least as far as we can tell.",
"It's a matter of some debate among philosophers whether or not space is like a \"material,\" that is, whether or not all those questions you just asked make any sense. From a physical point of view, it doesn't matter too much. The expansion of space doesn't mean you're making space out of nowhere, we don't even know for sure that space is stuff. Space is the background on which things happen, and when it's expanding, what's really happening is that the way we measure ",
" is changing, such that two objects staying in the same locations in space will measure their distance to each other to be growing and growing."
] |
[
"What's the difference between a chelating agent and a surfactant?"
] |
[
false
] | null |
[
"A surfactant reduces surface tension, usually between water and air or oil. These surfactants have a hydrophilic end and a hydrophobic end. The hydrophilic end sticks into the water and the other end either faces the air, or sticks into the oil. If it's being used for oil on water, the surfactant molecules will surround droplets of oil, enabling an emulsion with the water.",
"A chelating agent works at a more atomic level. It's a large molecule that will bind to a metal atom, surrounding it and removing it from further reactivity by forming a water soluble complex with it."
] |
[
"I'm sure someone else will come along but in general:",
"Chelation is the sequestering of metal ions by a compound so it is not available to react with anything else. ",
"Surfactants lower the surface tension of a liquid. "
] |
[
"Quick difference:",
"Chelators keep metals in solution real good.",
"Surfactants help oily stuff and watery stuff stay together in solution real good (in addition to the surface tension effect everyone else mentions).",
"Yes, I know that this is very hand-wavy but I'm trying to skip a bunch of technical stuff. Also, terrible grammar everywhere."
] |
[
"What would happen if it unexpectedly rained a lot in a desert?"
] |
[
false
] |
[deleted]
|
[
"This is actually how it works in some deserts. They don't have small amounts of rain for a while but huge bursts of rain. This can lead to flash floods (southern california, arizona, other areas). ",
"Part of the problem for deserts is the lack of rain, but also sand and \"large grains\" of soil don't really retain water so plants can't really grab up the water before it's gone. "
] |
[
"The plants that do adapt to it, like saguaro cacti, can suck up a huge amount of water from a single storm. I don't remember which BBC doc it was that did this, but I remember seeing a time lapse shot of a cactus swelling with water from a storm. "
] |
[
"something like this",
" perhaps ... \nI am not 100% sure if that is the type of desert the OP has in mind (i guess he means more of sand dunes and similar...)"
] |
[
"How is gravity \"weak\"? What scale are we using to compare the forces?"
] |
[
false
] |
I've heard the example of being able to counteract the gravity of the entire earth merely by picking something up, but that is a subjective description of weak. In what way can four forces be compared that makes us wonder why gravity is weak, and why would we expect them to be similar? In other words, why do we need an explanation as to its relative weakness? I hope this question makes sense...
|
[
"For example, if you consider the attraction between an electron and a proton, the electrostatic attraction is about 10",
" times as strong than the gravitational attraction."
] |
[
"Randal Munro (author of XKCD) recently addressed that exact scenario in his feature ",
"Proton Earth, Electron Moon",
". The calculation works out that the repulsive force created by that many charges, so densely packed, would represent energy that itself would have gravity.",
"I highly recommend checking out his workup to see which dynamic wins out."
] |
[
"The way I heard it explained is, imagine how large the earth is. Now imagine how all of it's gravity would be acting on a small 1cmx1cmx1cm iron cube. Now imagine how a small magnet could lift up this cube. A tiny magnet could cause more force on the cube than the earth. Im sure this is oversimplified and it's more complicated than this but it's how I learned it."
] |
[
"What exactly is spin in quantum mechanics?"
] |
[
false
] |
None of the explanations get traction in my head.
|
[
"This is a fun question that pops up a lot from people first getting into quantum mechanics. From the point of view of electrons, electrons have intrinsic angular momentum. We know this because electrons have tiny magnetic dipole moments, which we know because you can send electrons through a magnetic field and they will deflect in different directions (this was originally done with silver atoms, I believe). In order to have a magnetic dipole, there has to be charge moving in a loop, so classically, this would logically lead us to believe that the electron itself is some tiny thing with non-zero radius that is itself spinning.",
"Well it turns out that when you do calculations to figure out how fast the electron is spinning (based on the measured magnetic dipole moment and using a radius called the “classical electron radius”, which is actually somewhat leaning towards being an overestimate), the outer portions of the electron would literally have to travel faster than the speed of light, which we know (or are pretty sure, at least), is not possible. The only explanation we really have for this is that quantum mechanics is weird and that electrons just have intrinsic angular momentum for some reason.",
"As with many things in quantum mechanics, applying classical principles to quantum systems will just make things into confusing gobbledygook. We know that the electron isn’t literally spinning, but we still call it “spin” because we associate angular momentum with spinning."
] |
[
"It’s not spinning like a classical object, its just carrying an intrinsic angular momentum, just like it carries charge and mass."
] |
[
"It just represents itself. As unintuitive as it is to our classical minds, it's just an intrinsic property of the particle, like mass or electric charge."
] |
[
"How could I solve this problem I made up that deals with time dilation and constant acceleration?"
] |
[
false
] | null |
[
"120 meters per second squared",
"RIP travellers. Anyway, these calculations are pretty straightforward and there's a few online calculators that do them for you.",
"http://i.imgur.com/D5whW7N.png",
"http://nathangeffen.webfactional.com/spacetravel/spacetravel.php",
"0.5588 meters per second",
"I assumed this was 0, relative to the speed of light, it pretty much is."
] |
[
"Thanks for that calculator; I didn't find it in my searches."
] |
[
"Thanks for the help; that makes sense!"
] |
[
"In an old fashioned prop fighter plane, how do the machine guns on the nose not shear off the propeller?"
] |
[
false
] |
This confounds me. Is it a mechanism that only lets the firing pin engage at a certain prop angle? This seems sketchy. One mistake and kaput.
|
[
"There is indeed a mechanism to guarantee this. It's called the ",
"interrupter gear",
" and it makes it physically impossible to fire into your own propeller.",
"Good question!"
] |
[
"The earliest planes actually had armor plating on the back of the prop, before the interrupter gear was developed. "
] |
[
"there was a mechanism that would link the machine gun to the cycle of the engine so that the bullets would pass through the propellers instead of hitting them. the system was not perfect though, in a few instances pilots shot off their own propeller "
] |
[
"Why is the atmospheric pressure on Venus so high?"
] |
[
false
] |
Venus being about the same mass as earth, why is the surface atmospheric pressure is so high? Is there a general formula one could use to predict this? What are the parameters/variables involved in determining the basics of a planet's atmospheric values? Any insight would be appreciated! TIA!
|
[
"Okay the formula stuff I dont know, but the reason for the high ground pressure I do know. Basically all the water on the planet was turned to gas, clouds. CO2 built up from volcanic activity. Soot and other crap got launched into the air. The gravity of the planet kept the atmosphere from drifting off into space. Now you have a green house effect on steroids. The heat from the sun comes in but cant escaoe due to the clouds. So it is basically like a giant pressure cooker. Thus high ground level pressure."
] |
[
"Thank you!",
"I now see how to visualize this!",
"So, if I understand you correctly, the atmosphere of Venus is more like a..... colloid, a soup, a fog, as compared with our atmosphere, yes?",
"Thank you ",
"/u/omnescient",
"! I think I get it :)",
"However, another question comes to mind:",
"Hypothetically, how could you increase the pressure of Earth's atmosphere? \nFor some reason, I have always envisioned that as you added more stuff/mass/gases to the atmosphere, this would just increase the rate of \"evaporation\" into space. \nIn other words, the only variable in the steady state of an atmosphere is the planet's gravity (and I just learned, whether or not it has a magnetic field to protect against solar winds)."
] |
[
"Thank you!",
"I now see how to visualize this!",
"So, if I understand you correctly, the atmosphere of Venus is more like a..... colloid, a soup, a fog, as compared with our atmosphere, yes?",
"Thank you ",
"/u/omnescient",
"! I think I get it :)",
"However, another question comes to mind:",
"Hypothetically, how could you increase the pressure of Earth's atmosphere? \nFor some reason, I have always envisioned that as you added more stuff/mass/gases to the atmosphere, this would just increase the rate of \"evaporation\" into space. \nIn other words, the only variable in the steady state of an atmosphere is the planet's gravity (and I just learned, whether or not it has a magnetic field to protect against solar winds)."
] |
[
"Why hasn't life on Earth sparked into existence more than once?"
] |
[
false
] |
As far as I know life has "sparked" into being just once on Earth. I realise that theoretically life could have started multiple times and become extinct through history. But why don't we have multiple branches of life with multiple "alphabets" instead of "only" the GACT alphabet. If the conditions on Earth where so Goldilocks-like why don't we have different branches of life? Doesnt the idea that, despite the excellent prerequisites, life began only once on Earth throughout Earth`s history make the likely-hood of life being created elsewhere in the universe even more unlikely?
|
[
"It might have. Any new life that appeared would probably be unable to compete with existing lifeforms, and would be wiped out pretty quickly."
] |
[
"Well, first off, it's probably best not to speak of life \"sparking\" into being. I presume this notion may come from the oft repeated bit about lightning striking the \"primordial soup\" and giving enough energy to create some new biomolecule or something. This new thing wouldn't suddenly have been \"alive\" though.",
"Life almost certainly developed out of some sort of rather messy, uber simplistic replicator molecules which were probably so simple that we would not really think of them as alive. ",
"Hypercycles",
" are one example of the sort of process by which this might have happened (I don't know my abiogenesis all that well, so that's just one of the few things I remember from when we discussed it in a seminar course I took). ",
"Whatever these replicators were, they would have very gradually increased in complexity over the course of many many many generations (it is perhaps hard to talk about \"generations\" when you don't have a strictly defined organism or \"cell\", but you get the idea), until they eventually resembled something we would today classify as a \"living organism\".",
"So, let's imagine some of these really simple replicators managed to arise today. They have two characteristics which pretty much guarantee that they wouldn't make it:",
"They would almost certainly be made out of something that is certifiably delicious to today's current microorganisms (amino acids, nucleic acids, lipids, something like that...)",
"They would be so simplistic, at least initially, that they would not be able to defend themselves against these modern day micro-predators, who would just scoop them up for their nutrient value.",
"In short, \"new life\" just couldn't compete with the life that's already here."
] |
[
"No, species adapt to their environment (including other species). They've evolved alongside each other to be highly competitive in their niche. Any new life would be starting out from scratch with no adaptations, which would most likely be a fatal disadvantage.",
"Edit: I'm a bit disappointed to see technotaoist getting downvoted for asking a question. We should be encouraging discussion here."
] |
[
"Does anyone know of any decent studies done on the effects of tea that use subjects that actually drink tea as opposed to taking highly concentrated amounts of the things in tea?"
] |
[
false
] |
From what I have found, a lot of the health claims around tea (for better or worse) seem to be unsubstantiated or backed up with studies done either with large amounts of tea extract or concentrated components found in tea (caffeine, polyphenols, l-theanine), or reference research done on animals. Are there any conclusive studies done just on people drinking tea itself, or is this still kind of a fuzzy area?
|
[
"Studies have indeed been conducted on the prevelence of disease in tea drinkers compared to none tea drinkers. Once these showed that there may be health benefits, the mechanism behind them (what you seem to have found) is now being investigated.",
"This journal article seems to sum it all up pretty well and references studies of tea drinking populations as well as research into how tea might be helping.",
"http://jn.nutrition.org/content/130/10/2409.full"
] |
[
"Thanks!"
] |
[
"You presumably enjoy it, and it's fairly clear that it's not bad for you (unless perhaps you add lots of sugar), so does it really matter? How would it change your behavior if you knew you could take a pill to get the same effect?"
] |
[
"Equations for AskScience"
] |
[
false
] |
Would it be possible to get embedded LaTeX or something for AskScience so we can make our equations easier to read? Edit: I guess I'm looking for server-side solutions so everyone doesn't have to install the same plugins.
|
[
"http://latex.codecogs.com/gif.latex?(latex",
" code goes here, then copypaste the whole thing into address bar)"
] |
[
"Using TeX:",
"Firefox/Opera",
"Chrome",
"Instructions"
] |
[
"So you have to link a new page? I was hoping more for something that could be embedded in the comments.",
"Edit: ",
"test",
"\nAlso, that is a neat site; I will have to play around with it."
] |
[
"How is it that human brains work so much more differently than any of the others in the animal kingdom?"
] |
[
false
] |
I was taking a look at this video today of .. and it got me wondering - this is actually some very elementary problem solving skills for even a human teenager - yet how is it that elephants, with their large brain sizes, aren't able to "implement" something as simple as maybe use a branch to get the calf to hold onto and pull to dry land, or maybe entwine their trunks to get a good hold and pull, or maybe the ones with the longest trunks loop their trunk around the leg/knee of the calf and pull to the shore. I know that maybe the calf was waaaay too stressed to think cogently or listen to its mama's "explanations" - I'm sure they must have been "speaking" in elephant speak, but still... Is it that human brains have "evolved" so much that we are, these days, natural born problem solvers, and that other animals in the animal kingdom haven't had the need to get to humans' levels? What is preventing any other animal species from putting a man on the moon, or winning the Olympics or any other equal field where humans today have the sole hold over? The movie story of Rise of the Planet of the Apes comes to mind - have humans, in any way, prevented any other species from becoming an apex predators of the our planet? Or are humans ready for one?
|
[
"I'm not able to answer all your questions, particularly around our ability to limit other animals becoming apex predators (or indeed, more intelligent), but I can address some of your questions regarding our brains.",
"I should state, that we have not got a definitive answer as to why humans are so much more intelligent than other animals. We probably don't understand the brain well enough yet to be able to find the exact cause. ",
"One possible explanation is that we simply have larger brains, and this is true in comparison to many animals, but elephants and many cetaceans have much larger brains, but don't appear to build spacestations. Other theories suggest that mankind has a higher brain mass:body mass ratio than other animals. It is larger than might be expected (",
"source",
"). Another potential explanation is that our brains (specifically the outer layer of the cortex where most of the neurons are) are more \"folded\" than other animals, increasing surface area and hence the number of neurons, our brains certainly are littered with gyri and sulci (",
"source",
").",
"The problem with both of these theories, is that counter-examples can be found for each. Shrews have a much higher brain:body ratio than us, and \"dumber\" New World monkeys have a higher one than chimpanzees (",
"source",
"). Cortical folding doesn't correlate perfectly either.",
"However, from the same source, it appears that humans have a very high ",
" of neurons within our cortex, and actually have the highest number of cortical neurons. Furthermore, our neurons are more myelinated (insulation which speeds conduction) than elephants and cetaceans, so it may be that we have more neurons, which can \"talk\" to each other faster than other animals. Thus giving us our intelligence.",
"It's interesting to note here, in regards to the latter parts of your question, that cetaceans and elephants, which both branched off from us long before the lower-order monkeys, are substantially more intelligent than those monkeys. Possibly they are at a similar level to the Great Apes. That is, intelligence has evolved in parallel in several species (suggesting a strong selective pressure for it, in many environments), so it may be reasonable to speculate that there is nothing uniquely human about intelligence, or that other animals may, with time, evolve similar levels."
] |
[
"This is a lot of questions here. I think the best way to answer this is to say that humans, unlike most animals, are specialized tool users. Every solution you mentioned involves a tool of some kind, the cognitive understanding in how to use it, etc. This is not the core competency of an elephant.",
"Also, I don't think trunks are as strong as you think they are. The little elephant weighs hundreds of pounds. The trunk isn't that strong. They seemed to have saved the baby in a smart way. First offering their rear leg, which is strong, for the baby to grab onto. Then quitting and just going in the water and pushing him out. They've in some enclosure or barrier so they know that barb wire fence (electric?) and moat are serious business, so its probably why they didn't try that first. It also makes sense not to risk the lives of other to save one. There's no shortage of articles about multiple humans drowning to save one person, so stupidity, risk assessment failure, etc knows no bounds.",
"As far as why humans are better puzzle solvers, well that's how we evolved. A large part of our evolution is the need to use tools to survive against more powerful predators and to hunt. There was some evolutionary pressure on us at one time to be better with tools because whatever other approach wasn't working. Note this approach isn't superior in all scenarios, just the ones we're familiar with. Imagine some kind economic or biological disaster. Lots of animals would survive and thrive, but humanity might not. Tools build upon tools. Your average adult is an Excel jockey, not a master of spear hunting. Our approach comes with its own fair amount of risk."
] |
[
"Also, our problem solving and intelligence would look comparitively less advanced compared to other 'animals' if other ",
" species were still extant."
] |
[
"Why is it sometimes that something that interests me at first, will later leave me completely cold?"
] |
[
false
] | null |
[
"Science cannot answer your question directly, sorry. We can speak to how groups of people act at different time scales, but not you specifically. "
] |
[
"I only took myself as an example. I'm assuming I'm not the only person who has this. I was just wondering why people do this in a more general sense"
] |
[
"feel free to phrase a repost in a general way that can be answered scientifically"
] |
[
"How much of one's body weight is being lifted during a push up?"
] |
[
false
] | null |
[
"I think what you mean is \"how hard do I have to press down with my arms to raise my body when doing a pushup.\"",
"This is a problem of leverage. Your feet are the fulcrum. Your shoulders are the point where the force is applied, and you can think of all your body weight as sitting at your center of mass, which is a little below your navel.",
"Let's say that your center of mass is thus at 50% of your height, and your shoulders are at 80% of your height. During a slow pushup you are barely accelerating, so we can treat this as a statics problem.",
"We solve this problem by knowing the downward force of gravity, F_grav = mg , acts downward on your center of mass, while the force from your arms (F_arms) and from your feet (F_feet) act upward from their respective connection points. All of these balance if you're not accelerating. Just as importantly, you're also not \"angularly accelerating\" either, ie your \"turning about some rotation point\" is constant. ",
"We get to pick a rotation point, and things are nice if we pick that point to be at your feet, because then F_feet doesn't contribute to the torque equation. Torques are \"force times distance from rotation center\" (which we've chosen to be your feet), so the torque balance equation gives ",
"F_arms*(0.8*height) = F_grav*(0.5*height),",
"where the part in parentheses is the distance of that force from your feet.",
"Your height cancels in that equation, so we have",
"F_arms = (0.5/0.8)*F_grav = 0.625*F_grav.",
"Finally, we have our estimate: your arms have to push with about 65% of your body weight, to do a slow pushup. ",
"You can test this on a bathroom scale; I got more like 70%, which I consider rather close given the rough numbers used in the estimate!"
] |
[
"Good point, see reply to ",
"u/rooka8",
" ; I suspect it's a little bit arm weight, a little bit stability (for free weights), but it would be interesting to hear from expert physiologists or similar what they think."
] |
[
"Doesn't that include the weight of your arms? Or rather, how much you put on a bar to bench disregards the weight of the arms?"
] |
[
"Could our universe be contained by a much larger system that obeys different laws of physics? And if so, could they interact?"
] |
[
false
] |
So, the analogy would be the relationship between the quantum realm and classical realm. This probably has been asked and answered before but I wasn't able to find it. Thanks!
|
[
"Theoretical physics deals with that kind of stuff all the time and is the very definition of not immediately verifiable (or falsifiable)."
] |
[
"There are quite a few possibilities here, I'll summarize some of the more well-known ones. Note that all of this amounts to speculation, and none of it is proven, but it's not my speculation, but rather that of physicists working in these areas:",
"First, just from a mathematical perspective, if our universe is embedded in some greater hyperdimensional space, the most likely scenario is that we could not affect that \"external\" space but it could affect us. To understand this, imagine the 2D world on a sheet of paper: a creature confined to the 2D surface of the paper can't do anything in the 3rd dimension, but we can poke our fingers through the paper and have a significant effect on their dimension. See ",
"Flatland",
" for more along these lines.",
"The ",
"Many Worlds Interpretation",
" (MWI) of quantum mechanics basically says that every quantum event has every possible outcome, resulting in an infinite number of \"parallel\" universes. In this case, interaction might occur at the quantum level. Quantum computation pioneer David Deutsch, an MWI proponent, has posed the question of where quantum computations run, since they are able to explore far more possibilities than classical computations - his answer is that they must run in other universes. In that case our interactions with other universes might include receiving a bill from those universes for resource usage...",
"String theory gives rise to the speculation that we may live in a ",
"brane world",
", in which our 3+1 dimensions are a subset of a more complex space. In that case, various kinds of interactions might occur between branes, such as collisions and leakage of forces across branes, although as in bullet #1 above we'd be unlikely to be able to do anything to affect things outside our brane.",
"More generally, string theory also speculates that ",
"extra dimensions",
" may exist. One possible reason we don't experience them is that they may be \"compact\" - too small to detect. An interesting aspect of these hypotheses is that in principle, some versions of it could conceivably be testable.",
"Some hypotheses about the Big Bang suggest that our observable universe is only a part of the universe that happened to undergo inflation, and thus grow exponentially larger than other parts of the universe. See e.g. ",
"Eternal inflation",
". In that case other uninflated regions of the universe would be inaccessible to us - too far away, and too small.",
"That's off the top of my head, I probably missed some..."
] |
[
"No. It doesn't. Experiments are the essence of science. Models and theories are developed to explain available observations and must be able to make ",
" predictions. Without that, you're left with a very mathy way of blaming stuff on gremlins. ",
"Things involving strings or the embedding of our universe in larger structures and the like fall into that category. It can't be tested now or for the foreseeable future. It can't be science. It's metaphysics. "
] |
[
"What happens to gravity at the very centre of a planet?"
] |
[
false
] |
My friend and I were talking about gravity and we couldn't figure out what happens to gravity at the centre of a spherical mass. Does it disappear at the centre? Does it get weaker going towards the centre as there is less mass underneath you pulling things downwards? Say you're 'standing' at a point in the earth around the boundary of the inner and outer core, would there be less gravity there than on the surface of the planet? Does the mass above your head pushing down count as gravity even though it's pushing and not pulling?
|
[
"There is a very relevant fact proved by Newton called the \"",
"shell theorem",
"\". It implies that inside any spherically symmetric shell, the total gravitational force is 0 wherever you are - even if you go much closer to one part of the shell than to the rest. ",
"Then you can use this to work out the gravitational force inside a solid object. You decide what point you want to evaluate the force at, then consider all of the bits of the planet where the radius is greater than that point to be a \"shell\", then by the theorem you can just forget it altogether! In other words, as you go closer and closer to the centre, it's as if the ground above you is disappearing into thin air, as far as gravity is concerned.",
"When you get to the centre, the whole planet is effectively a shell around you so there's no force at all."
] |
[
"If there could somehow be a hollow sphere at the center of the earth, and if you were in the sphere, you would be essentially weightless because the mass of the planet would be pulling equally from all directions, sort of like a weird Lagrange point. ",
"Imagine two perfectly equal sized planetary bodies orbiting each other in a circular orbit. If you were perfectly equidistant from both planetary bodies and not moving in relation to them, you would be pulled equally by each planet and would stay at that location in space. \nNow imagine with 4 planets on the same X axis, and then with an infinite number. Then imagine the same thing on the Y and Z axis. "
] |
[
"That is really fascinating thank you!"
] |
[
"What sorts of problems does asymptotically safe gravity face as a potential quantum gravity solution?"
] |
[
false
] |
I've recently by Ethan Siegel over at Forbes (he also blogs at Starts with a Bang) on asymptotically safe gravity as a possible alternative to string theory. I read the author's blog from time to time, and he's described the potential benefits of asymptotically safe gravity, as well as the apparent prediction of a 126 GeV Higgs Boson years ago. My question is, what sorts of challenges does this idea face when it comes to quantum gravity? I feel like the buzz generated by an extremely accurate Higgs prediction, coupled with the ability to avoid adding entities like extra dimensions and supersymmetric particles, would be a huge positive in favor of asymptotically safe gravity. That being said, I do see much written on the subject and I wonder if that might be related to inherent problems or skepticism in relation to the framework.
|
[
"First of all, asymptotically safe gravity did not predict the Higgs' mass, since it has nothing to do with that. Also, string theory absolutely does not require low energy supersymmetry and large extra dimensions. They are very cool things that were easily accomodated into strings, and it would have been cute if they were true, but they were absolutely not predictions. Theories of quantum gravity don't make any reasonable low energy prediction 99% of the time. There is a lot of trashy popsci on this so let's make sure this is clear.",
"Now, asymptotic safety for gravity is based on the existence of a fixed UV point. There is no proof, nor evidence, of this. That's the main criticism.",
"Point two would be that this is a scale invariant theory and so predicts a volume-intensive entropy. As far as we know, all semiclassical development (i.e. black hole thermodynamics) until now requires area-intensive entropy. This whole program seems strongly at clash with everything we already know about quantum gravity.",
"Finally there's a bit of a subtle point about nonlocality. This one might be more controversial. It is understood that nonlocal phenomena must be involved in some way with any theory of quantum gravity. These appear both in strings and in loop quantum gravity. Asymptotically safe gravity cannot handle this since it's a local quantum field theory."
] |
[
"Point two would be that this is a scale invariant theory and so predicts a volume-intensive entropy. As far as we know, all semiclassical development (i.e. black hole thermodynamics) until now requires area-intensive entropy. This whole program seems strongly at clash with everything we already know about quantum gravity.",
"Asymptotically safe gravity is not scale invariant, it just contains an (RG unstable) scale invariant UV limit. The IR theory obviously has a scale - the Planck mass. Same story as QCD, which has some energy scale in the IR, but contains a scale invariant (actually free) UV fixed point. Asymptotic freedom can be thought of as a special case of asymptotic safety, though the latter almost always refers to nontrivial UV fixed points."
] |
[
"Arguably, unless you have a very developed imagination, it is not possible to make up a scheme through which information is conserved through collapse to black hole -> Hawking radiation which only involves local evolution.",
"Essentially, at the Planck scale we expect spacetime to be \"foamy\" and the causal structure to be emergent in the classical limit. Not everyone agrees on this."
] |
[
"What would happen if there were no locks on the Panama Canal?"
] |
[
false
] |
[deleted]
|
[
"Yes, that's how a river works. However, what would actually happen is that both sides would drain towards each ocean. As you can see ",
"here",
" , What the locks actually do is get from level sea, up over the continent, and back down to the other side. The Pacific wouldn't flow to the Atlantic, or vice versa, you'd end up with a river draining into each. "
] |
[
"The reason for the locks is primarily that the canal level is higher in-between as it goes over land. If you removed the locks, water from the Gatun lake in the middle would run out both ends, and you'd ultimately be left with perhaps some small streams."
] |
[
"Actually, without locks there would be saltwater flow since the atlantic is about 20cm lower than the pacific there."
] |
[
"Question on preferred methods for suicide for each gender"
] |
[
false
] |
Looking up some statistics on suicide, I've found that the most common forms of suicide in men are firearms and suffocation, and in females it is poison (drugs, ect). My question is what is the reason why men tend to use guns, and women tend to use drugs? Some related facts. Men successfully commit suicide 4 times as much as women, but women attempt suicide 2 to 3 times as often as men. I assume they attempt it more because they are more likely to not succeed with drugs, which is why i think this might be relevant to why they use drugs.
|
[
"That answer does sound pretty good, but I would like a source."
] |
[
"Source(s)?"
] |
[
"There's debate in the field. Some claim that women use suicide attempts as a cry for attention, without an intent to succeed, much more often than men, and therefore choose less lethal and more discoverable methods. Other claim that men simply have an affinity towards 'macho' methods such as guns and driving cars off cliffs from due to cultural conditioning (action movies and the like)."
] |
[
"Do gamma rays have radiation pressure too? If so, how?"
] |
[
false
] |
I can understand alpha and gamma rays exerting pressure because they have mass but, IIRC gamma rays are photons which are massless, so they can't exert a pressure.
|
[
"You're right, they are photons, but photons can exert ",
"radiation pressure",
" because they have a momentum, p = E/c, where the energy E = hf for a photon of frequency f, even though they have no mass. c is the speed of light and h is Planck's constant. Because they have a momentum, you can figure out the momentum imparted on an object in a unit of time, which is a force. If you know that force per unit of area of the object, that's a pressure."
] |
[
"The first comment is spot on, but I'd just add that the equation for momentum that OP is probably thinking of is the non relativistic one which of course doesn't predict that photons should have momentum. ",
"The proper equation for momentum includes a term that doesn't",
" "
] |
[
"It's worth noting that the momentum is only imparted to an object if the photon interacts with that object by scattering or being absorbed. The simplest case (as in the figure in your wikipedia link) is reflection, where the momentum imparted is up to twice the photon's momentum (the direction changes while the magnitude stays the same, and x - (-x) = 2x).",
"But gamma rays very weakly interact with most matter. And typically only by being absorbed by electrons in atoms. And when that happens, ionization happens (an electron is kicked off from the atom). The gamma ray can then either be totally absorbed, or re-emitted at a lower energy (having lost energy by giving it to the electron), a process called Compton scattering. ",
"In both cases there's momentum change to the photon, and so a radiation pressure, but there's also change in the electron's momentum. This makes it more considerably more complicated than more typical cases, like shining a blue laser at a mirror."
] |
[
"When a nuclear bomb goes off, is the area immediately irradiated?"
] |
[
false
] |
I realize that it's almost instantaneously burned, but I'm wondering if the radiation comes from the initial blast or entirely from the fallout, which I thought was just ash.
|
[
"I realize that it's almost instantaneously burned, but I'm wondering if the radiation comes from the initial blast or entirely from the fallout, which I thought was just ash.",
"Short answer: yes.",
"The initial radiation takes the form of gamma and neutron radiation - this radiation dissipates relatively quickly (lasts about the length of the explosion). Very few injuries would result from initial radiation alone - as most people affected by this also happen to be close to ground zero and have other worries (e.g. giant fireball).",
"Fallout is what comes next. There are hundreds of fissile products that can be formed from a nuclear blast - some with a very short half-life (like iodine 131), and some that will stick around for months or years (like strontium 90). This can come from the weapon debris (e.g. \"leftover\" plutonium), products from the fission itself, and much of it will be from irradiated soil (assuming you're detonating it near the ground).",
"So, I think your question is more about the after-effects - so to answer: the radiation you're seeing that has long term effects is from the fallout.",
"edit: Grammar - as per Vanabrus :)"
] |
[
"Irwin Redlener on surviving a nuclear attack. Actual instructions being at 17:30",
"\n",
"http://www.ted.com/talks/irwin_redlener_warns_of_nuclear_terrorism.html"
] |
[
"Irwin Redlener on surviving a nuclear attack. Actual instructions being at 17:30",
"\n",
"http://www.ted.com/talks/irwin_redlener_warns_of_nuclear_terrorism.html"
] |
[
"Why can't we test for mental illness like we can for other diseases?"
] |
[
false
] |
If we know depression for example is cause by a chemical imbalance in the brain, why can't be test the chemicals in the brain like we test for various things in the blood? By say looking for related animo acids, looking for trademark electrical signals of a reaction, or looking at metabolites. It seems very crude that we diagnosis such complex diseases using questions, not biologically.
|
[
"If we know depression for example is cause by a chemical imbalance in the brain",
"It really isn't. That's an oversimplified explanation used by pharmaceutical salespeople and ",
" doctors. ",
"The real situation is much more complicated and not very well understood. We know that inhibiting reuptake of serotonin improves depression symptoms in many, but not all, people with depression. It's not as simple as sticking a needle in the brain (which carries a risk of infection), taking a sample of neurotransmitters, and saying \"You have depression\" or \"you have bipolar disorder\"."
] |
[
"Part of the problem lies in our diagnostic system, which is built on observed combinations of symptoms and prioritizes reliability over validity. In other words, if you go to three different doctors, they should all come to the same diagnosis. However, the typical example of how this is imperfect is that a diagnosis of major depressive disorder requires 5 of 9 symptoms, four of which can go in opposite directions (insomnia/hypersomnia, increased/decreased appetite, increased/decreased weight, psychomotor agitation/retardation), so you can have two patients who have the same diagnosis, but no symptoms in common. That's just the overt symptoms, ignoring any putative causes, such as genetics, altered levels of neurotransmitters, altered neurotransmitter receptor sensitivity, hypothalamic-pituitary-adrenal axis dysfunction, chronic inflammation, positive reinforcers in the environment, social support, etc. There are many overlapping symptoms between diagnoses and many people receive multiple diagnoses, blurring the lines between categories even further. Most, if not all research to date has relied on this imperfect diagnostic system. The good news is that the National Institutes of Mental Health is embarking on a herculean effort to build a new system for understanding mental illness. The Research Domain Criteria initiative seeks to understand clinically relevant phenomena (e.g., sensitivity to punishment/reward, fear of future threat) across multiple levels: genes to chemicals to cells to neural pathways to more gross levels of physiology to behavior to self-report to greater the context. This bottom-up approach should eventually yield a diagnostic system that is much more accurate, clinically useful, and may even allow for the sort of testing that you are asking about."
] |
[
"The real thing missing though is the word \"yet.\" There is a huge field pushing advances in areas just such as this. ",
"The brain (well the body as a whole) is just a difficult place to study. There are countless entwined systems all affecting each other and each has to be taken into account. While some diseases may have specific chemical markers and others may not, the field really just isn't to the point where we have defined a measurement to do so reliably. "
] |
[
"My dad doesn't believe that the light we see from stars originated thousands-millions-billions of years ago. Or that some of the star light we see comes from stars that died. How can I prove it?"
] |
[
false
] |
I've explained to him through a few ways such as if I fired a gun but then put the gun away, the bullet is still traveling in the same trajectory it was fired regardless of what happened to the gun afterwards and if I wrapped a fiber optic cable around the earth a trillion times, and shined a light in one end and saw it come out the other, there would be a delay. Also that the speed of light is some number in terms of meters per second which literally means it can only travel a certain number of meters per second. What can I show him?
|
[
"You will need a microwave and a large bar of chocolate and a ruler. (Your dad must first understand that microwaves and visible light are all part of the electromagnetic spectrum.) Take the rotating plate out of your microwave. Unwrap your chocolate bar and place it into the microwave. Turn the microwave on for between 30 seconds and a minute, make sure the bar does NOT rotate. What you should see are two, maybe three very specific spots of melted chocolate (this is why you need to be careful how long you heat the chocolate for, you don't want to melt the lot). The \"hot spots\" are formed where the microwaves meet hence the distance between two spots is half the wavelength of a microwave. Measure this distance and double it to get the wavelength of the microwaves (needed in units of metres). Your microwave oven will be running at a frequency of about 2.45 GHz (2.45 x10E9 Hz). Plug these numbers into",
"speed of light = wavelength/frequency ",
"and hey presto! You'll have proved to your dad the speed of light! Should be around 3x10E8 m/s"
] |
[
"Try explaining that the sun's light is 8 minutes away. If he can accept that, then he can accept that pluto's light is however far. From there, a simple map that shows scale should be sufficient. I'd say the 8-minute sun is the first example.",
"You can also say that we've PROVED the sun's light is 8 minutes away by sending satelites up to space and going around the sun a few dozen times and recording things. Making sure the clocks were 100% matched up, both on take off and landing, and that the data the satelites took prove the sun's light is 8 minutes away. ",
"If he asks how exactly they proved it, could say certain big sun flares that our satelites photographed 8 minutes before they were received on earth. "
] |
[
"Most of the comments here are assuming that your father's problem lies in a refusal to accept science. But after looking into actual stars and finding that most of the notable ones are within 100 lightyears, I think he's making the much more reasonable argument that we can't actually see stars that are that far away. ",
"In that case, perhaps this ",
"article from NASA",
" will help. It's discussing stars visible via telescope, however. ",
"If you're only talking about stars visible with the naked eye, you're certainly going to need to take conditions into account. But a more managable question might be \"How far away is the most distant star visible by the naked eye under ideal conditions?\" Hopefully someone here could fill us in. ",
"Assuming he accepts E=mc",
" (particularly the \"c\" part of the equation, as it stands for the constant speed of light) as well as the fact that a light-year is a measure equal to the distance light travels in a year, you should then be well on your way to convincing him that the light from at least ",
" stars has travelled a long time to get here.",
"Another relevant question would be \"How far away is the average star?\" Hopefully someone here could answer that as well, because I'm curious."
] |
[
"Which creature increases in body size most since birth?"
] |
[
false
] |
I'm wondering if you took the ratio from the mature adult form of an animal, and divided it by it's birth form what would have the highest ratio? Is it something huge like the blue whale, or is it some form of insect that (relatively) grows massively? Is it approximately the same for all animals? Thanks Ask Science.
|
[
"From what I know, in terms of length the largest growth % is likely the Lion's Mane Jellyfish, which starts off as a tiny clump of cells around one millimetre in length and eventually grows to be up to 37 metres long. This is a growth of around 3,700,000%, an change in order of magnitude of 10",
" .",
"In terms of mass, I have no idea."
] |
[
"While some jellyfish certainly are, the Lion's Mane is not."
] |
[
"A colony organism is an organism that is actually made up of several seperate entities. A good example of this is coral, which is actually made up of thousands of separate polyps.",
"The Lion's Mane Jelly is not a colony organism."
] |
[
"What is happening chemically when cooking oil is heated past its smoking point and it begins to smoke?"
] |
[
false
] |
Wikipedia's explains how the fat is broken down into glycerol and free fatty acids, but I'd like to see an example chemical equation. Also, what are the health risks involved in consuming oil that has gone beyond its smoke point?
|
[
"It's pretty straightforward reaction. ",
"Here's a triglyceride with fatty acids and glycerol labeled.",
"Upon heating, oxidation occurs at the ester bonds, releasing glycerol and free fatty acids.",
"It's also possible that high heat can increase the presence of free radicals, which are highly reactive. Additionally, high heat can introduce double or triple bonds in the fatty acid chains, increasing the amount of trans fat.",
"The health effects of any of the above are unsettled scientifically."
] |
[
"That reaction may very well occur, but it isn't the cause of the smoke. The smoke is caused by pyrolysis of the resulting fats and alcohols, leading to decomposition of the molecules by scission of C-H (and probably C-C) bonds, which re-form as small (usually toxic and bad-tasting) organic molecules by reaction with themselves and oxygen. These molecules then decompose further to form soot. Additionally, part of the 'smoke' is condensed oils and fats which have been volatilised in the high heat and subsequently formed small droplets upon contact with the (relatively) cooler air."
] |
[
"So, what is the result of repeated heating and cooling cycles on such a material? Assuming it is kept below the smoke point or thermal decomposition point."
] |
[
"There has been a lot of anti-ADHD rhetoric going around lately. Do we have proof that ADHD (especially in adults) is actually a disorder? Or are people like me truly just lazy, awful people?"
] |
[
false
] | null |
[
"ADHD is listed on the ",
"DSM",
", which means that it is considered a real clinical disease at the moment. However, that does not mean it will always be so (homosexuality was listed on the DSM in the past). But given what we know about ADHD, it is likely a 'real disease'. For example, there is a significant genetic component, with greater concordance between monozygotic vs dizygotic twins. A number of genes have been implicated, but no single key regulator has been found. There are some neuroimaging findings (average brain volume smaller in some areas), but we don't use it for diagnosis - it's entirely a clinical diagnosis based on the signs and symptoms. With that said, it's also possible that ADHD is overdiagnosed in some circles (though there are ",
"data",
" suggesting that ",
"this is actually a misconception",
")."
] |
[
"It is probably a \"real disease\" but the problem is that it gets over-diagnosed for children and adults that don't actually have anything wrong with them:",
"http://www.sciencedaily.com/releases/2012/03/120330081735.htm",
"The study showed that child and adolescent psychotherapists and psychiatrists tend to give a diagnosis based on heuristics, unclear rules of thumb, rather than adhering to recognized diagnostic criteria. Boys in particular are substantially more often misdiagnosed compared to girls.",
"But see:",
"http://www.psychiatrictimes.com/adhd/content/article/10168/1926348?pageNumber=1",
"Faced with severe payer and clinical time constraints, many physicians diagnose ADHD by emphasizing a present oriented, cross-sectional symptom evaluation.6,25 This type of evaluation may result in overdiagnosing ADHD, or underidentifying ADHD in children with complex and comorbid presentations...",
"The public’s fear that ADHD is overdiagnosed and that stimulants are overprescribed is not generally supported by the current scientific research. Reasons for the continued controversy include fears of stimulant abuse and diversion, physician overprescribing, limited payer resources to support evidence-based standards of ADHD evaluation and treatment, and continuing unease as to the legitimacy of the ADHD diagnosis. "
] |
[
"For example, there is a significant genetic component, with greater concordance between monozygotic vs dizygotic twins.",
"The same could be said for ",
"homosexuality",
", so I'm not sure your evidence for \"real disease\" for ADHD logically follows."
] |
[
"Is there a \"minimum\" viscosity for the shatter effect to take place?"
] |
[
false
] |
Extremely high viscosity liquids shatter when struck with enough speed and pressure. Would low viscosity liquids appear to shatter in a similiar way if viewed on an incredibly ultra high speed camera is stuck withenough speed or force? Or is there a "minimum" viscosity for the shatter effect to take place?
|
[
"I can't directly answer your question. First instead of the shatter effect I'm going to use the term brittle fracture. The phenomenon you're referring to is known as shear thickening which occurs in some non newtonian fluids. During shear thickening, the viscosity of a fluid increases with increased strain rate. With this increase in viscosity, the modulus of elasticity increases. Materials with high modulus's tend to fail in a brittle manner. ",
"viscosity=(a material constant)*(shear rate)",
" When n is greater than 1, the material exhibits this shear thickening phenomenon. When n is less than 1 it exhibits shear thinning, aka with increased strain rate the viscosity decreases. Shear thinning is much more common than shear thickening. So there is no magical viscosity. The viscoelastic behavior and non newtonian behavior depends on other material properties. "
] |
[
"First off we're likely talking about polymers where the traditional crystal lattice and slip do not exist. Second we're clearly talking about viscoelastic non newtonian fluids. The definition of shattering does apply. When you pull silly putty quickly it shatters, fractures what ever you want to call it. We all know what it means, theres no confusion. You claim tit looks like shatter. If its not shattering what is it? You ask about the temperature the forces applied and density. All of which don't matter. You know what he's asking. Don't be a dick explain the principal causing the behavior or shut up. If professors responded to questions like you we'd all be fucked and english majors. "
] |
[
"Please explain to me how shattering could mean anything other than brittle fracture. I think if the person asking the question knew the exact nomenclature to use they'd also know the answer to the question. Viscoelastic behavior is a pretty materials concept. "
] |
[
"Does a method exist for organisms to prevent mutations from occurring?"
] |
[
false
] |
Are there safeguards to prevent mutations from occurring, either by killing off cells with an faulty gene or repairing damaged DNA? Are there organisms that are more capable at this than others?
|
[
"Yes, actually most (if not all) living being with dna possess quite effective process that repair dna, ie cancel mutations by returning the dna into its pre-mutation form.",
"This page from the nature website, explain the most well-known of them : ",
"http://www.nature.com/scitable/topicpage/dna-damage-repair-mechanisms-for-maintaining-dna-344"
] |
[
"Yes, and the best example is actually the naked mole rat. It sounds made up, but its basically immune to cancer. Some other animals are very prone to cancers. ",
"Even within the same species, the sexes can have different kinds of cancer protection. Men have a much higher chance of brain tumors because we do not have a certain gene that protects us. The vast majority of women have this gene. It means men have increased brain inflammation, while women have far less. "
] |
[
"This, nearly all organisms have various proteins involved in replication that \"spellcheck\" DNA looking for things like physical bumps or kinks caused by mismatching base pairs. Humans have multiple proteins that work on DNA during replication and protein production that have the ability to cut out or \"excise\" incorrect segments which then get patched up later. There are several other mechanisms mentioned below that more involved with cancer."
] |
[
"Can film exist in a format that isn't a series of still frames? Whether analog or digital?"
] |
[
false
] |
Instead of many still images creating the illusion of motion, are there other ways of depicting film without a film reel with separate negatives (analog) or a video file (digital) without frames?
|
[
"If you're asking about the storage of video, there's no need to keep each frame stored separately. Normal video codecs today only store some frames called keyframes. For all other frames, only the difference between the precious frame is stored, as this can be compressed more efficiently.",
"You could theoretically store video in many other ways. For example, you could store the different color values of the first pixel across all the frames, and then the same for the second pixel and so on. It would be highly inefficient, but it could still work.",
"If you're asking more about having the time dimension of video being discrete, I guess you could store the video in a continuous format. You could, for each pixel, store a continuous function of time giving the color values at any given time. That way you would not be bound to any frames. But defining these function would be highly non-trivial, either it would be very slow to compute or it would be very lossy (probably both)."
] |
[
"Regarding the last paragraph, there would exist a Fourier series whose partial sums would approximate the brightness of the pixel at each time as close as you wanted.",
"In fact, instead of Fourier series, one could use wavelets. Further, one might use \"different\" wavelet bases (? not sure if this is the correct term, it's been a while) for the different dimensions of film. That is, one can use wavelets which are discontinuous in space (modeling the sometimes abrupt changes of color between two objects in frame) but continuous in time (modeling the fact that movement through space is continuous ... but not modeling cuts well)."
] |
[
"If you ignore the fact you're viewing it on a computer screen (which has a refresh rate and therefore 'frames'), vector animations can sort of do this.",
"Something like a flash animation - you don't store each frame normally, you store each object's start point and end point.",
"So if I had a square at T-0 Seconds, I can tell it at T+10 seconds I want it 15cm to the right. I've not given it any frames, it has no frames stored in it - there are not 100 other location storage data between those two points - it just interprets everything in between - and what we see is motion, if we've done it fast enough.",
"Now once you ",
" that out - then it's stored as a movie with a frame rate, but the initial data doesn't have that."
] |
[
"Are there examples in nature or experiments where animals with less desirable traits but more resources attract more mates?"
] |
[
false
] |
The title sums it up, less desirable traits being things like older age or weaker physical attributes, and more resources I guess meaning food stock piles or superior "housing" setup. Of course, in nature if a weaker or older creature has resources, the more fit one will usually just take them so that's why I wonder about this experiment. Trying this again as first was marked spam for some reason.
|
[
"I forgot the name of the bird but it collects anything that is blue to put in its nest to attract females ( saw it on planet earth)"
] |
[
"Sunfish have a weird little ternary arrangement where colorfull super alpha males make and guard nests and drab beta males mimic females and fertilize eggs just as the real female produces them by sneaking into the nest at the strategic moment. ",
"Not sure if it counts by your standards."
] |
[
"Most animals don't have 'resources' the way humans do. Many species, including chimps, will trade food for sex directly. Many birds create elaborate nests to attract mates, which I guess could be considered a 'resource', but is more of a costly display in line with a peacock's tail.",
"Beyond that, I'm not sure what other 'resources' animals have."
] |
[
"What does it feel like to be given high doses of radiation?"
] |
[
false
] | null |
[
"\"Radiation\" isn't one single thing. Some are massive particles, while others are massless. Some are a ionizing, some aren't.... You get the idea.",
"What kind of radiation?"
] |
[
"I suppose gamma radiation. Or something along the lines of chernobyl."
] |
[
"Chernobyl is an unwieldy case to use, since the death toll varies wildly by source. Unless your question is really nuclear power-based, it looks like what you're asking about is ",
"Acute Radiation Syndrome",
", or radiation poisoning. It's a quite complex array of symptoms, depending on how much exposure to where; I'd recommend reading over the chart behind that link. ^"
] |
[
"Is a singularity reactor possible?"
] |
[
false
] |
I have been thinking, and it seems something like this would be theoretically possible. It all comes down to Hawking radiation and the evaporation of black holes. Large black holes evaporate incredibly slowly, but small black holes (like the kind the LHC might create) evaporate incredibly quickly. What if this effect could be harnessed? Imagine using an array of very powerful lasers to create a micro-singularity. Almost immediately, it starts evaporating. But you don't let it collapse. You keep feeding matter onto it, such that the mass flow cancels out the mass loss due to hawking radiation. It would seem to me that with such a setup, you've just made the perfect energy source. You have a system that converts mass to energy with 100% efficiency, much better than fission or fusion. You could use a reactor like this to produce abundant energy ANYWHERE. You don't need fossil fuels, sunlight, uranium, or deuterium; any mass will do. You could probably power a relativistic spaceship with it, gathering mass from the interstellar medium as you go. Any thoughts on this?
|
[
"The problem is, you'd have efficiency losses both maintaining the singularity and capturing the energy from the Hawking radiation. Furthermore, we don't even have the technology to create a sustained fusion reaction, and what you're talking about would be several orders of magnitude more difficult.",
"So is it possible? Yes. But is it a viable method of energy generation? I'm not so sure the engineering challenges can be overcome."
] |
[
"You could use a reactor like this to produce abundant energy ANYWHERE. You don't need fossil fuels, sunlight, uranium, or deuterium; any mass will do. You could probably power a relativistic spaceship with it, gathering mass from the interstellar medium as you go.",
"Did you not see what happened in ",
"?"
] |
[
"I love that movie. I am fully aware that it is silly. I don't care."
] |
[
"Why do i sneeze when i go outside and its really bright out?"
] |
[
false
] | null |
[
"Some people have a ",
"photic sneeze reflex"
] |
[
"Sneezing as a result of looking into a bright light is known as the \"photic sneeze reflex,\" and is a genetic trait that about one third of all humans have.",
"The last I checked, however, there was no definitive explanation as to why it happens. If anyone has some good documentation on the subject please post it - I'm at work currently."
] |
[
"In medical school physiology one instructor said it was probably because of the proximity between two nerves - the nerves which constrict the pupil may \"crosstalk\" to stimulate the nerve that senses touch inside the nose.",
"Looking for sources just now, I also found ",
"this",
" describing a similar sneezing phenomenon associated with sexual arousal. "
] |
[
"If the photo \"pale blue dot\" (a photo of the earth) was taken from 3.7 Billion miles away, how does it not contain the rest of our milky way galaxy in the photo?"
] |
[
false
] | null |
[
"The image only covers a small angle - much like how zooming in on your camera means you don't see as much background."
] |
[
"I see. So is the image magnified that much that the next closest planet is out of the field of view? "
] |
[
"Very much so! It really is quite zoomed in on Earth.",
"Perhaps more interesting is the \"updated\" image that was taken by the Cassini mission, ",
"here",
". The Sun is behind Saturn, which is what you're viewing the back and rings of, with Earth being the dot between the bright inner rings and middle faint ring on the left (",
"this shows where, if you can't find it",
"). This image is actually a 9x3 mosaic of wide-angle photos from the Cassini probe. Venus and Mercury are presumably too dim to see, or obscured by Saturn."
] |
[
"Are there nerves in the umbilical cord?"
] |
[
false
] |
I'm talking about the human umbilical cord, specifically, and I'm curious whether newborns feel anything when it's cut.
|
[
"No. The only structures in the umbilical cord are two arteries and a vein, unsurprisingly called the umbilical arteries and the umbilical vein. The cord's not even made of muscle or skin. It's composed, apart from those blood vessels, of a substance called Wharton's jelly, which is the same kind of stuff that fills your eyeballs."
] |
[
"Umbilical cord contains 2 arteries, 1 vein and a substance called Whartons Jelly that gives the cord its shape and protects the arteries/veins from being occluded.",
"The next part is me thinking to myself, and not a scientific answer... the cord is not meant to contain any nerves, yet for breech births and cord prolapse we are taught to ",
" touch the cord, or as little as possible as it could cause it to spasm. Therefor blood flow will reduce/stop and separation of the placenta could commence prematurely. If there are no nerves how could that happen?",
"Edit: cannot word."
] |
[
"The umbilical cord and placenta are tissue produced by the fetus. That should answer your hypothetical."
] |
[
"How does a master key work?"
] |
[
false
] | null |
[
"The master key itself is nothing special, the trick is in the locks set up to accept the master key. Most locks have a set of metal bars called pins, that prevent the lock from turning. A regular key pushes these pins to a precise height, moving them out of the way and allowing the lock to turn. Locks set up for a master key have two sets of these pins on top of each other. One set is properly aligned when the normal key is inserted, the other set is properly aligned when the master key is inserted. ",
"For a more in depth explanation, check out ",
"https://unitedlocksmith.net/blog/how-master-key-systems-work"
] |
[
"Bingo. You have two possible correct heights to pick each pin to, instead of just one."
] |
[
"Does that mean that a lock with a master key is easier to pick, because there are more correct combinations of pins?"
] |
[
"Can humans breed with any other species?"
] |
[
false
] |
[deleted]
|
[
"Some relevant reading"
] |
[
"Non-coding DNA is quite a bunch of stuff: flow control, dead code, comments, noops, and stuff which you didn't even know could parse and sure as hell are not going to touch."
] |
[
"HIV was almost certainly contracted from ",
"bushmeat",
", since chimps and apes are both occasionally hunted for food in certain parts of Africa. The rates of transmission for HIV through sexual intercourse ",
"actually aren't terribly high",
", which is why behavioral patterns which increase risk through repeated exposure are so important in controlling the spread of the disease."
] |
[
"Is there a difference between long-term memory that gets used daily and memory that doesn't, and is it possible to have brain damage which causes loss of memory that doesn't?"
] |
[
false
] |
Is is possible to have severe head trauma that causes nearly complete loss of long-term memory after three to six months, and are there any other symptoms (possibly ASD-like) that would result from this kind of injury? I've just heard of short-term and long-term memory loss, but never this medium-term kind of thing, and looking over Wikipedia implies that the brain doesn't work this way and it shouldn't happen. So we're curious, that's all.
|
[
"In a way yes, I just saw an article about how the brain has mechanisms for long term memory and for memory loss. Heres the article, it also has other cool info too. ",
"http://brainblogger.com/2015/11/08/best-and-worst-of-neuroscience-and-neurology-october-2015/"
] |
[
"As far as I am aware there's only retrograde and anterograde amnesia, but nothing in between in regard to TBI. Generally, I believe that newly formed memories are more fragile than older ones, but I think it can also depend on the strength of the connections. Memories you don't use as often would be more fragile than something you use every day. ",
"Could you be thinking of dissociative amnesia? It fits the description, but the issue there is that in order for it to be dissociative amnesia there can't be an organic cause. A TBI, drug use, or neurological condition would all be organic causes."
] |
[
"No the article described had nothing to do with amnesia but only the natural mechanisms of filtering out memories so that the brain can save energy and become more efficient."
] |
[
"What is physically different between the brains of people with \"good memories\" versus those with \"bad memories\"?"
] |
[
false
] |
Some people naturally have stronger memories than others, is there a difference in the physical structure of two peoples' brains with varying strengths of memory recollection? Some people are very good at remembering conversations, obligations, directions and events. However some people can be the complete opposite. Is there a difference in the anatomy or function of their two brains that cause this?
|
[
"The ",
"hippocampus",
" is a part of the brain that plays a very important role formation of new memories. If a person has structural damage to the hippocampus, that causes issues with forming new memories. Alzheimer’s disease, for instance, is associated with ",
"hippocampal damage",
"--and memory loss is consequently an early symptom of Alzheimer's. ",
"So ",
"research shows",
" that higher hippocampal activity at encoding (the time when something enters memory) predicts better recall of the information later. But it’s not just neuronal activity that matters, it's how ",
". There’s something called “functional connectivity,” which is the correlation between the activity patterns over time between different brain areas. There are a ton of ways of measuring this, but basically if the neurons in part A of the brain activate at the same time points as neurons in part B of the brain, we say that they have high functional connectivity. There are ",
"studies that show",
" that hippocampal functional connectivity predicts memory performance. ",
"This is even shown",
" when you look at people’s functional connectivity when they’re just resting, awake, not trying to remember anything—i.e. a person who--when not thinking about anything--has highly in-sync activity in their hippocampi is more likely to remember things than a person who has out-of-sync activity in their hippocampi."
] |
[
"Thanks for answering!"
] |
[
"Great question!",
"This is a new direction of research from my ",
"former post-doc advisors lab",
". ",
"Daniela Palombo",
" developed a survey called the Survey of Autobiographical Memory that allows people to rate themselves on their memory for personal experiences - episodic memory, facts - semantic memory, spatial thinking and future imagining, all abilities of the hippocampus that ",
"u/viajackson",
" describes. They found that compared to laboratory tests of memory, people were pretty good at rating themselves across these abilities. ",
"In a follow-up ",
"Signy Sheldon",
" found that people's subjective ratings were related to the ",
"intrinsic connectivity of the hippocampus to other parts of the brain",
", again similar to ",
"u/viajackson",
" comment. In that study, they found that the connectivity pattern of the hippocampus depended on whether someone rated themselves as having superior episodic vs semantic memory. In particular for remembering experiences like you describe in your question, the brains of individuals who were good at that were well connected to the parts of the brain that process our perceptual experiences (the sights, sounds and other sensory experiences from your life).",
"If you're hoping to improve your own memory for past experiences researchers have found the ",
"MEST",
" to be fairly successful in different patient populations. Otherwise, as with most cognitive skills, rehearsal has been shown to help improve abilities, so you could take up journaling and not only have a record of the past but help you to work on your memory."
] |
[
"How likely is the Fukushima nuclear crisis able to cause a worldwide environmental catastrophe?"
] |
[
false
] |
[deleted]
|
[
"I think you missed some of the question. If any of the reactor buildings were to collapse and cause loss of shielding over the spent nuclear fuel, you may not be able to get humans in the area anymore. Abandonment of the site could release radioactive particulate several orders of magnitude beyond Chernobyl. That said it is only an absolutely worst case scenario. The reactor building including the fuel pools is actually supported by the containment structure, not the building walls, so it is very unlikely it would collapse in an earthquake. "
] |
[
"Reason being, Fukushima already avoided a meltdown",
"Full nuclear meltdown in Fukushima admitted by Japan"
] |
[
"I guess if you can't dazzle them with brilliance, baffle them with bullshit. How does any of this justify giving dangerous medical advice or intellectual dishonesty?"
] |
[
"What is an example of two very similar chemical formulas behaving very differently?"
] |
[
false
] |
I remember someone illustrating this for me with a very good example but I forget what it was. I have someone arguing that baking soda is like lye because the formulas are similar... EDIT: He's saying that baking soda dissociates to lye in water.
|
[
"There are many examples of this. The chemical formula itself is often not a good indication of its properties, rather, a compound's structure is often important. Take for example the formula C4H8O2. Two ways that we can arrange those atoms is as ",
"ethyl acetate",
" or ",
"butyric acid",
". Those two compounds have the ",
" formula, but entirely different properties: one being an ester and one a carboxylic acid. "
] |
[
"I think thalidomide is one of the most famous examples. It was used as a morning sickness drug in the fifties or sixties. It is a chiral compound, meaning the same molecule has two configurations which are non super-imposable mirror images of each other. (Think your left and right hand.) One configuration was successful at easing morning sickness symptoms but the other caused terrible birth defects. Google image search thalidomide babies if you are interested."
] |
[
"Cisplatin, the anticancer drug, versus transplatin, which is almost chemically identical, but extremely ineffective as an anticancer drug."
] |
[
"Physicists, what are your opinions about the Feynman Lectures? Are they still worth reading?"
] |
[
false
] |
I have all of them and I am interested in self-learning physics, as I am doing with differential equations and linear algebra. Are these good books, or should I find something else?
|
[
"Great books. Totally worth working through."
] |
[
"Hey, a QFT specialist! I have a question for you specifically. If you somehow had the money to support your living expenses (say you inherited a large sum from your distant Nigerian relative), would you be able to study QFT or any other form of mathematical physics by yourself, provided that you could get almost any book you needed or could ask question of people who knew the answers? I mean, you are doing math, so provided that you don't have to gather or crunch data, is there any reason you HAVE to get an advanced degree in physics to learn QFT or any other subjects in math or physics? "
] |
[
"Do you need an advanced degree? Gerard 't Hooft has posted a ",
"list of resources",
" that might get you to the point of learning what you need to learn. I don't think you need an advanced degree ",
", but I don't think I could have learned to be a theoretical physicst without having been in a university environment. It's not just about being able to ask people questions, although that is certainly somethng not easy to do outsde a university environment; it's about being around people doing science, hearing their seminars, hearing ",
" people ask questions at those seminars, sitting around with others thinking about research ideas, etc. It's about seeing all those minds at work, thereby learning how to think. (Others may have different opinions on this; I am only speaking of how I've learned.)",
"There is also a sociological question: How do you get taken seriously if you don't have credentials? I'm not saying it can't be done, I'm just saying that the system is set up so it's easy to be taken seriously if you're working \"within the system,\" but ifyou're outside the system, that's just an extra hurdle to get past. The key would be to get some established people to take you seriously, from which a chain reaction could ensue. "
] |
[
"How much would celebrities net worth weigh in $100 bills?"
] |
[
false
] | null |
[
"Here's a photo of a billion dollars.",
"http://3.bp.blogspot.com/_jhf-7wU76qc/TGmkUNmohuI/AAAAAAAABXY/rJnOh2MYi9Y/s640/billion_dollars_cash_3.jpg",
"Bill gates is worth about 80 of these. Or roughing it up a bit, about 1000 of those individual pallets of $100 bills."
] |
[
"This is pretty easy, since a ",
"bill weighs about 1 g",
". So, according to ",
"this page",
":",
"George Lucas = $ 5.1 billion = 51 metric tons (of 100 dollar bills)",
"Steven Spielberg = $ 3.5 billion = 35 metric tons",
"Oprah Winfrey = $ 3.2 billion = 32 metric tons",
"Wolfram-Alpha tells me these masses are comparable to large dinosaurs."
] |
[
"A dollar bill (any denomination) is about 1 gram, Which gives you about 454 bills per pound. Using $100 bills, that's $45,400 to the pound or $90,800,000 to the ton.",
"Bill Gates' net worth is $79.2 billion. $79,200,000,000 divided by $90,800,000/ton gives you 872 tons.",
"$1 million (in $100s) is about 22 pounds. $1 billion (in $100s) is about 11 tons. That should be enough to gives you a quick way to figure the amount for anyone else you're curious about."
] |
[
"Does gravity have a range or speed?"
] |
[
false
] |
So, light is a photon, and it gets emitted by something (like a star) and it travels at ~300,000 km/sec in a vacuum. I can understand this. Gravity on the other hand, as I understand it, isn't something that's emitted like some kind of tractor beam, it's a deformation in the fabric of the universe caused by a massive object. So, what I'm wondering is, is there a limit to the range at which this deformation has an effect. Does a big thing like a black hole not only have stronger gravity in general but also have the effects of it's gravity be felt further out than a small thing like my cat? Or does every massive object in the universe have some gravitational influence on every other object, if very neglegable, even if it's a great distance away? And if so, does that gravity move at some kind of speed, and how would it change if say two black holes merged into a bigger one? Additional mass isn't being created in such an event, but is "new gravity" being generated somehow that would then spread out from the merged object? I realize that it's entirely possible that my concept of gravity is way off so please correct me if that's the case. This is something that's always interested me but I could never wrap my head around. Edit: I did not expect this question to blow up like this, this is amazing. I've already learned more from reading some of these comments than I did in my senior year physics class. I'd like to reply with a thank you to everyone's comments but that would take a lot of time, so let me just say "thank you" to all for sharing your knowledge here. I'll probably be reading this thread for days. Also special "thank you" to the individuals who sent silver and gold my way, I've never had that happen on Reddit before.
|
[
"Yes, gravity has infinite range and changes in gravity propagate at the speed of light. It's a very analagous with electromagnetism, ie electric/magnetic fields and electromagnetic waves.",
"Every piece of matter in the universe is attracted to every other piece of matter in the universe. And when wild things happen, like neutron stars merging, the hiccup in gravity you feel from them spiraling into each other at half the speed of light arrives in almost lockstep with the light from the explosion from the matter they fling off."
] |
[
"If you’re wondering why would gravity waves just so happen to have the same speed as light, even though they would not seem to have a direct relationship, it’s because the speed of light is not actually specifically about light; it’s about ",
" Calculations show that if any kind of information-bearing phenomenon whatsoever were to travel faster than this, causality would be violated. Which would mean that consequences could precede their own causes — i.e. time travel. ",
"This YouTube video",
" has an excellent explanation of this. ",
"Light is what we normally refer to for this speed simply because it’s readily accessible/understandable, and is relatively easy to measure. But in general, any wave in any massless field ",
" propagate at the speed of light (causality); only phenomena that are associated with mass are ever able to travel slower than that. ",
"This video",
" from the same channel explains this part really well.",
"Edits: typos"
] |
[
"This is because there are no negative mass particles. Electrical shielding works because dipoles in the material can arrange themselves to cancel out an external field. Without negative mass particles, you can't have a gravitational dipole."
] |
[
"Have we ever observed an object (such as an asteroid or comet) from another solar system come into our solar system?"
] |
[
false
] | null |
[
"We did for the first time last year",
"https://en.wikipedia.org/wiki/%CA%BBOumuamua"
] |
[
"Basically,",
"is only travelling at 17 km/s",
"plane of the ecliptic",
"approached the solar system at a completely different angle"
] |
[
"How do we know it wasn't a perturbed object from our own system that was sent on a hyperbolic trajectory before we discovered it (e.g. A comet or asteroid that had an accidental 'gravity assist' from a giant planet)"
] |
[
"Assuming that the universe is expanding, what would happen with a light beam, which is emitted from a star, who is located at the horizon of the expanding universe, in the direction of the horizon?"
] |
[
false
] | null |
[
"or do my questions or assumptions not make sense at all?",
"It's a common misconception that the universe is expanding \"outwards\" like a balloon. The universe is expanding at all directions and there is no single point of origin for the expansion. The only horizon we observe is from the ",
"observable universe.",
"You can learn more about this in the Wikipedia article on the ",
"metric expansion of space",
".",
"It is an intrinsic expansion—that is, it is defined by the relative separation of parts of the universe and not by motion \"outward\" into preexisting space. ",
" A frequently used analogy is the expansion of the surface of an expanding rubber balloon. In this analogy the universe has two spatial dimensions (the surface of the balloon) rather than three. As the balloon expands, any two points on its surface get farther and farther apart. Another common analogy is a rising loaf of raisin bread—as the loaf expands, the raisins inside it move farther and farther apart from each other.",
"As such, I will not release this question because your question is based on an erroneous premise.",
"Thanks"
] |
[
"thanks for the answer but i am aware that the universe is not expanding outwards. but i didnt want to use the term \"observable universe\" either, because observable universe only means that we can observe it. I am talking about a Star at the \"end\" of the universe (assuming that the universe is finite)"
] |
[
"There is no \"edge\" of the universe per se as covered: - ",
"http://www.reddit.com/r/askscience/comments/mbw2x/what_would_happen_when_you_reach_the_end_of_the/",
" ",
"http://www.reddit.com/r/askscience/comments/kn075/does_the_universe_have_an_end_what_would_it_look/",
"\n",
"http://www.reddit.com/r/askscience/comments/goy44/what_really_is_at_the_edge_of_the_universe/"
] |
[
"Should the Observable Universe be Described as Three Dimensional or Four Dimensional?"
] |
[
false
] |
I ask because I have always thought it would be considered 4D (length, width, depth, and time as the forth). But I often find myself seeing things that refer to only 3, then the extra-dimensions in regard to string theory, and time is dumped in at the end. Since time is observable should it be counted in with length width and depth? is the most recent example of an article that list things in the manner I'm questioning.
|
[
"Personally, as a physicist, I prefer to ",
" our universe is 3-dimensional to the layman. This is because the temporal dimension is related to the spatial dimensions in a different",
" way than the spatial dimensions are related to themselves. I'm very hesitant to call the universe 4D because of this, because there are some things people extrapolate that they shouldn't because they envision time as a 4th ",
" dimension.",
"Ultimately, though, both are correct. When someone says the universe is 3-dimensional, they mean 3 spatial dimensions. When they say 4-dimensional, they mean 4 total dimensions. It is something to note that the quoted total number of dimensions ",
"includes the temporal dimension",
" in String Theory, but it doesn't mean that when we're dealing with anything else you should stick to \"4D\".",
"Bottom line, we all should know what you mean when you say the universe is 3D or 4D. Neither is incorrect.",
" Second sentence of the ",
"spacetime",
" article on Wikipedia. The three spatial dimensions are Euclidean, but spacetime is hyperbolic because of the temporal dimension."
] |
[
"If you do tell laymen that the Universe is 3D, especially a group of laymen as interested as the ones on askscience, I'd suggest at least mentioning the caveat about diffeomorphism invariance, i.e., that there's no unambiguous way to slice the Universe up into 3D constant time slices. I think most interested laymen are perfectly capable of understanding, so long as it's explained well, that this means all four dimensions are physical and are tied up together and should be treated on somewhat equal footing."
] |
[
"Three extended spatial dimensions, one time dimension, and possibly six or seven compactified spatial dimensions (if string theory is correct), so it just depends on what you mean when you say \"dimension.\""
] |
[
"What is the current \"standing\" of cosmic inflation, specifically re: BICEP 2's findings?"
] |
[
false
] |
I've been digging about on Google, but I was hoping that some folks here might have better resources and info.
|
[
"It's not any different than before BICEP2 first announced their results. Most working cosmologists still think it's (by far) the best theory of the very early Universe we have to date, because it does predict a lot of the very specific features we've observed in the CMB's temperature fluctuations.",
"But as for the ",
" fluctuations (specifically the so-called B-mode polarization) which has been called a \"smoking gun\" of inflation, the state right now is wait-and-see. BICEP's position on this is that they stand by their results (which seem pretty robust), but they originally underestimated how bad the dust contamination might be. So how you ",
" those results - whether they're due mostly to inflation or entirely due to dust - remains to be seen.",
"BICEP2 and Planck, a CMB satellite, are collaborating right now to tackle that problem and should have results fairly soon (i.e., this year). Planck can help for two reasons: one, it will do a full-sky map, and two (and most importantly), it has multiple frequencies. By looking at the polarization in the same patch of sky at different frequencies, you can more easily separate out real CMB signal from foreground dust, as they have characteristic behaviors."
] |
[
"Basically, and someone more familiar with the experiments can explain further, it's this:",
"BICEP2 released their results, on arXiv.",
"Critics point out that if the dust foreground was much much bigger than what they assumed it would invalidate their findings.",
"BICEP2 pointed out that they did take dust into account using data from the Planck mission, and it's insignificant compared to their observed signal.",
"BICEP2 paper is published in a top physics journal essentially unchanged.",
"Planck says that they're working on results for the effect of dust in the particular part of the sky that BICEP2 looked at, and to stay tuned for their results."
] |
[
"Critics point out that if the dust foreground was much much bigger than what they assumed it would invalidate their findings.",
"BICEP2 pointed out that they did take dust into account using data from the Planck mission, and it's insignificant compared to their observed signal.",
"BICEP2 paper is published in a top physics journal essentially unchanged.",
"This is a much rosier outlook than even the BICEP2 people are saying. They admit they underestimated the potential foreground levels, and the published version is quite a bit more restrained in their conclusions than the arXiv preprint. The data are the same, but the interpretation is less certain.",
"The big change is that they used ",
" Planck data (in the absence of anything better) to make their initial foreground estimates. Planck has since released some data (though not data covering the patch of sky BICEP2 observed) which show that there's generally more foreground contamination than was previously anticipated in similar (low-dust) regions.",
"One of the PIs, John Kovac, gave a talk about this at a recent cosmology conference in Chicago, and you can see a nice summary of developments since their initial announcement in March on page 39 of ",
"his slides",
"."
] |
[
"Why do bee stingers come off?"
] |
[
false
] | null |
[
"Human skin is very thick and they get stuck. When they sting other things, they do not get stuck."
] |
[
"https://en.m.wikipedia.org/wiki/Bee_sting",
"See the honey bee section"
] |
[
"Oh really?\nCan you show a example?"
] |
[
"How do optical illusions appear to be moving?"
] |
[
false
] |
like these
|
[
"I'm an artist who creates optical illusions. The big reason this particular type of illusion works is because the value of the lines lead the eye. Other moving illusions can force the perspective with the thickness of the lines. It is the same principle shown in ",
"this famous illusion",
" but much simplified. If you look at that one you can see the white color on one side and the black on the other. When you focus on one part of the drawing, your area of view is much smaller and your brain then imposes what it thinks should be in that place instead. It's similar but not quite exactly like the lens of a camera rack focusing. The big difference is that your brain also interpolates what it thinks it should be seeing. "
] |
[
"If I stare at an optical illusion long enough, will I get used to it, and see it as a regular, picture which doesn't move?"
] |
[
"No, though if you allow your eyes to unfocus and see the picture as a gestalt it will stop moving."
] |
[
"Is the habitable zone of a 2-star system further out than a single-star system like ours?"
] |
[
false
] | null |
[
"Depends, but often not really.",
"Binary star systems can have any of a huge variety of separations, from so-called ",
"contact binaries",
" to a decent fraction of a light-year (Proxima Centauri is ~0.21 ly from Alpha Centauri A&B). Or maybe more (Fomalhaut gets silly).",
"If the stars are similar in mass/luminosity, and close together, then you can have a circumbinary habitable zone that's a bit farther out than would be normal for a single star. As stars can vary enormously in luminosity (even ignoring high mass and post main-sequence ones), you could potentially have a binary where this is unimportant. Similarly, if the system is at all spread out (more than a handful of au), a planet around one star will be far enough from the other that the other star will do little to heat it."
] |
[
"Fomalhaut B is 0.28 pc (0.91 ly) from Fomalhaut A. Fomalhaut C is 0.987 pc (3.22 ly) from Fomalhaut A.",
" Figuring out that Fomalhaut was a multiple star system was slightly difficult because the components are separated by ",
"."
] |
[
"Fomalhaut gets silly",
"What are you referring to?"
] |
[
"A question about human population movements"
] |
[
false
] |
While I was listening to NPR's science Friday, they were talking about the evolution of human languages. One of the languages they featured was Hawaiian and I thought of the following question for you guys... How did human beings manage to populate all of the remote Southern Pacific islands? When all of this happened they had no way of knowing that if they sailed out into the ocean in a small boat that there was anything there. Was it just trial and error? It seems like it would take a lot of voyages of multiple people to succeed if people just randomly launched ships.
|
[
"Wikipedia Link to Polynesian Navigation",
"Since you mentioned Hawaii, Polynesians were a pretty extensive sea faring civilization, so it wasn't a matter of launching a boat and risking it never coming back.",
"Rather than looking at it as a haphazard jump in a boat and see what happens situation, think about it as a group of expert navigators raised to look at explorers as heroes.",
"They could range hundreds, even thousands of miles from their launching point and still have a decent idea of how to get home.",
"They developed innovative methods of locating nearby islands, ranging from observing currents and wave formation to using shore spotting birds and as a result it was a lot less random than you think."
] |
[
"The people you are talking about are Polynesians, they lived on small islands around the pacific and had developed ways to navigate to other islands. For example clouds tend to cluster around islands, navigation by stars, direction of swells.",
"Then again you need results for any rules so I suppose originally it would have been random.",
"Heres a good map: ",
"http://upload.wikimedia.org/wikipedia/commons/9/93/Pacific_Culture_Areas.jpg"
] |
[
"TIL Polynesians were the equivalent of ancient astronauts."
] |
[
"If our sun were a white dwarf, would it still be the brightest in our night sky? If not, where would it rank?"
] |
[
false
] | null |
[
"If it were a white dwarf, it wouldn't appear in our night sky. Night time is when you're facing away from the sun.",
"Source: any dictionary ever written."
] |
[
"A typical white dwarf has absolute magnitude between 10 and 15 (where a higher number, counterintuitively, means a lower brightness), so the apparent magnitude of a white dwarf at the distance from the Earth to the Sun ranges from about -16 to -21. The Sun has an apparent magnitude of about -26, so a white dwarf would be 100 to 10,000 times dimmer than the Sun.",
"However, that's still pretty darn bright - as you can see ",
"here",
" the next brightest object in our night sky, the Moon, has an apparent magnitude of only about -13 at full brightness, which is 100 to 10,000 times dimmer than a white dwarf."
] |
[
"Of course - I was just comparing it to something you know, since that seemed helpful for visualizing a white dwarf in our Sun's place."
] |
[
"What is polarized light?"
] |
[
false
] |
I came out of Jurasic Park 3D the other day, and noticed that the 3d glasses were polarized when I saw them black out the screen on my phone. What differentiates polarized light from regular light?
|
[
"So as a photon travels along the x-direction, it has a magnetic field which oscillation in the y-axis up and down and an electric field which oscillation in the z-axis ",
"see here for visualization",
"So the photons are still travelling along the x-axis ",
" you, but can be angled differently. ",
"Taking only the electric field. we have some polarization plains.\n",
"see here",
"One filter only allows vertically electric field photons through, the other filter only allows horizontal electric field photons through",
"Light which is all oriented the same way is polerised.",
"Video to help",
"Using two polarization filters to block out 100% of the light"
] |
[
"Your second link really clears it up nicely. The light wave is in 2d, but it is rotated around the Z axis. So does this mean that unpolarized light (like sunlight) consists of a multitude of photons coming at you at random angles?"
] |
[
"Related question, when a polarizing filter allows a light to pass through is it the electric field which is aligned with the filter or the magnetic field?"
] |
[
"Because of the commonness of depression in humans, is it probable that it has some adaptive quality that has been selected for?"
] |
[
false
] | null |
[
"Not depression, per se, but the kinds of kinds of personal traits needed during difficult times -- existential worry, stress over resources, deep concern over abstract problems -- are far less adaptive when there is no current emergency. Living, as most people do, with the relative certainty of long life and relative comfort means that the ability to worry about abstract problems is misplaced, but we don't get to turn it off. Robert Sapolsky talks about this, adaptations that were once key to survival, like the stress response, now leading to chronic conditions in humans. We see depression in a number of other species so we know it is part of the cost of a complex nervous system and deeply related to stress. ",
"No one is certain, I'm just trying to convey what Sapolsky believes."
] |
[
"Mental illness, at least, as we experience it, basically doesn’t exist in hunter-gatherer societies. We are not built for the world we have created any more than cheap food suits our diets, cheap housing suits our needs, and work suits our bodies.",
"The sooner we acknowledge that and begin actually building a world that suits our needs instead of what is easy, the sooner we’ll realize that many of our ills are diseases of civilization instead of some inherent flaw in ourselves."
] |
[
"Off the cuff, I doubt it. Modern life, at least in wealthier countries, has effectively eliminated selection pressure in humans in terms of fitness. I suspect the prevalence of depression has more to do with work, diet, and other stressors that we weren’t really “built” for.",
"Or maybe there’s a very successful breeding population of brooding poets living amongst us.",
"EDIT: To clarify, I do not mean to suggest that depression and GDP are somehow correlated. My specifying that I was referring to wealthier countries is limited to selection pressure, not prevalence of depression, and to be ",
" clear I only limit my statement to wealthier countries because my realm of experience is limited and speculation to that end would only reveal my ignorance on the matter."
] |
[
"Why is it that some tasks are much more easily performed while not thinking about what you're doing?"
] |
[
false
] | null |
[
"The short answer is that your consciousness is rather limited in processing power compared to your subconsciousness. If you practice a task enough while using your consciousness, a lot of the specifics in the task will be transferred to the subconsciousness. Until the task is practiced enough, you won't be able to perform it correctly without thinking.",
"Since thinking about how to perform tasks has a lot to do with memory, a good place to look at a for a bottleneck in processing is memory itself. For ",
"example"
] |
[
"http://en.wikipedia.org/wiki/Procedural_memory#Expertise-induced_amnesia",
"A reported 16.6 million Canadians watched Sidney's goal, and it's safe to assume that most of them would have been able to easily recollect the details, but not Crosby; he was immersed in an automatic state that at least temporarily blocked his ability to remember.",
"Maybe blocking goes both ways... since using procedural (implicit) memory to do something seems to block your ability to form a declarative (explicit) memory, maybe trying to form a declarative memory blocks your ability to access your procedural memory."
] |
[
"upvote for hockey reference."
] |
[
"I have a booklight with a fluorescent light bulb that, when turned on, will not light up if the room is darkened. It lights immediately if the room is itself illuminated. What exactly is going on here?"
] |
[
false
] | null |
[
"My specialty is lighting and optics. I have never heard of this happening without a photosensor being involved.",
"Is the book light plugged into the wall or battery operated? Are you absolutely sure the start up time of the lamp is faster when exposed to other light than when in the dark? Is there a small photovoltaic cell on the book light?"
] |
[
"as a test, i would suggest you actually time this, with a cold bulb (i.e. one that was not on previously, for perhaps 12-24 hours prior)",
"1) first condition - time how long it takes for the bulb to come on, from cold, in the dark.\n2) second condition - time how long it takes for the bulb to come on, from cold, in a room already lit\n3) third condition - time how long it takes for you to turn the bulb on in a dark room, with you THEN going over to flip your light switch on and off.",
"my suspicion is that the times for all three are the same, using a cold bulb. the difference between conditions 1 and 3 being that you are not counting the time for you to get up and walk over to the light switch.",
"or, as laserhorse has mentioned, it has a light sensor that modifies its response time.",
"without data, it is difficult to answer your question."
] |
[
"I can answer most of these. Number 1, the answer varies. Sometimes it takes 5 seconds, sometimes it takes as long as 30 seconds. It actually kind of depends on how run-down the booklight's batteries are. I should have mentioned this before, but this effect only starts happening when the batteries (4 AAs) are run down slightly. If the batteries are newly charged, the bulb lights up immediately when turned on (the way it's supposed to).",
"Number 2, if the room is lit, the bulb turns on instantly. Number 3, the booklight turns on the instant I turn on the room light. ",
"It's not a coincidental timing thing; turning on the room light ",
" causes the booklight to turn on; I've tested it dozens of times."
] |
[
"Do Iodine tablets prevent radiation sickness?"
] |
[
false
] |
Saw Iodine being administered in two separate TV shows. Does it really help? How does it work?
|
[
"Not exactly, a large amount of the radiation dose from a nuclear explosion comes in the form of a radioactive isotope of iodine. You take large doses of safe iodine and that means your thyroid won't absorb the radioactive one, and you'll just piss it out instead of ending up with a radioactive thyroid."
] |
[
"Iodine supplements only protect against one particular way in which fallout can hurt you. It does no good against acute radiation sickness or other radionuclides other than 131I. But it's cheap and easy, and protecting against one thing is better than protecting against zero things. ",
"Think of it like wearing a hat when you're hiking. It won't protect you from falling and breaking your leg, or getting eaten by a bear, or eating a poisonous berry, or getting lost and freezing to death; but it ",
" protect you from sunburning your face and maybe against heatstroke, so it's worth doing."
] |
[
"This is actually not that uncommon of a treatment type. For example, if you drink antifreeze accidentally, one treatment is for you to drink a bunch of normal alcohol, because it keeps your ",
" liver busy while the antifreeze passes (antifreeze isn't toxic in and of itself, but what your liver creates after processing it is)."
] |
[
"Would a lander be able to land on Io, Jupiter's volcanic moon?"
] |
[
false
] | null |
[
"Yes, but the thin atmosphere requires retrorockets to slow a lander for soft landing, and strong radiation shielding.",
"Here",
" is a mission profile."
] |
[
"Would something like Curiosity's Sky Crane be suitable for such a landing?"
] |
[
"Possibly, but before the sky crane deployed Curiosity, aerobraking was done with a parachute. Mars has between 2 million and 20 million times the atmosphere of Io, so there's still a significant challenge in shedding velocity."
] |
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