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[
"Is our circulatory system one giant loop that involves all blood vessels or is it composed of many smaller loops which don't connect to each other?"
] |
[
false
] | null |
[
"All blood vessels are connected to each other. This becomes obvious when you realize that all our blood vessels have to connect to our heart, which is the pump for our circulatory system."
] |
[
"The circulatory system is actually ",
" separate sets of tubes: one big closed loop (the blood vessels), and a second, open-ended, one-way system (the lymphatic system) that reclaims and conveys any fluid that leaked out of the blood vessels (about 3 liters in a day) back to the heart to rejoin the blood loop.",
"Also, during a single \"lap\" of the body, your blood goes through the heart twice: first through the right half of the heart, which takes the blood coming back from the body's tissues and pushes it into the lungs to get oxygenated; then back through the left half of the heart, which pushes freshly oxygenated blood out to the body's tissues again. So the heart is actually two completely separate pumps, although joined together side by side and pumping in synchrony (and part of the same loop).",
"The fluid-reclaiming lymphatic system, incidentally, empties into the blood system at the \"start\" of the loop, where the blood is about to enter the right half of the heart and go get oxygenated."
] |
[
"Many smaller loops, but all connected to each other. Really simply: Arteries lead away from the heart, branching off to different parts of the body getting smaller as they get further out. The smallest vessels are capillaries where the blood actually perfuses the tissues. The blood then returns via veins. Initially the veins are small but as they get closer to the heart and different veins merge they get larger."
] |
[
"Can cravings for specific food be a symptom of deficiency?"
] |
[
false
] |
[deleted]
|
[
"There are some deficiencies that seem to have an effect on what we crave, such as low iron, calcium, zinc, and sodium. E.g. we crave meat for the iron, salty foods for the sodium (rare), etc. It appears there is some evidence to support these, but the research shows it is not the case for all (or even most) nutrients, and even those few that seem to have a link are up for debate.",
"TLDR: If there is a link it is not significant.",
"",
"Sources:",
"Pica w/ pregnancy 1",
", ",
"2",
"Here's a good article on it if you'd like to learn more: ",
"https://www.healthline.com/nutrition/nutrient-deficiencies-cravings"
] |
[
"Not having enough sodium in your diet being rare seems like the understatement of the decade."
] |
[
"It's weird how the article is not mentioning sugar when having a low blood sugar level. That's the one I most commonly seem to have."
] |
[
"How fast can germs travel?"
] |
[
false
] |
Obviously - as small as they are - viruses, bacteria and fungal spores use larger animals as their primary means of transportation. But given a sterile surface, if contaminated in one spot and no other interference, how long before another spot - say 6 inches away - is actually contaminated?
|
[
"Pretty much only bacteria have a means of traveling on their own. Viruses need a host to move, although sometimes they can infect bacteria and be transported that way. Fungal spores also don't move by themselves, instead spreading based on air or water currents, mostly. Protists, another class of single-celled organism, also move, but have about the same range as bacterial motion. The range of bacterial motion varies from 2 microns/sec up to 200 microns/sec, in solution. So, assuming there is enough water on the surface for the bacteria to move through, it would take between 12 minutes and 21 hours."
] |
[
"Is it not also the case that bacterial motion is rather randomized in terms of where they are going?\nI remember from my Microbiology lectures at university that they kind of zigzag around the place, not ever moving in a straight line for very long.\nIf so, the minimum of time for the bacteria to move the given distance in a film of water would likely be higher than 12 minutes, no?"
] |
[
"I was just trying to give a theoretical minimum time. Yes, there is a lot of random motion, but bacteria also do follow chemical and other signals with impressive accuracy and purpose. There are cool videos of them and other cells following various trails and signals online."
] |
[
"If we can see light emitted from the big bang, could we hypothetically \"hear\" the big bang at a considerably shorter distance?"
] |
[
false
] |
I've wondered this for a while. If the observable universe stretches 46 billion light years in every direction (a figure I just took off Wikipedia). Could we, knowing the difference in the speed of light and sound, calculate approximately where the "sound" from the big bang currently is? Thanks!
|
[
"Actually, the earliest light we can see is from the CMB. The CMB is roughly 380,000 years after the Big Bang. Prior to that, photons did not last long enough to travel any distance.",
"In the Big Bang model for the formation of the universe, Inflationary Cosmology predicts that after about 10−37 seconds[6] the nascent universe underwent exponential growth that smoothed out nearly all inhomogeneities. The remaining inhomogeneities were caused by quantum fluctuations in the inflaton field that caused the inflation event.[7] After 10−6 seconds, the early universe was made up of a hot, interacting plasma of photons, electrons, and baryons. As the universe expanded, adiabatic cooling caused the plasma to lose energy until it became favorable for electrons to combine with protons, forming hydrogen atoms. This recombination event happened when the temperature was around 3000 K or when the universe was approximately 379,000 years old.[8] At this point, the photons no longer interacted with the now electrically neutral atoms and began to travel freely through space, resulting in the decoupling of matter and radiation.[9]",
"Also, sound travels via a different mechanism than light. It is not possible to hear the sound of the big bang."
] |
[
"WTF is going on here? Space isn't a perfect vacuum, but there are particles - and at higher redshift, more and more. The density of matter scales like (1+z)",
" so space had the density of air at a redshift of about a billion (a lot, but the universe was still ~30 seconds old, so it's after Big Bang Nucleosynthesis, for instance. We know there are sound waves in the early universe ",
"which is imprinted on the galaxy distribution today",
". ",
"And hell, there are sound waves in the spaces between galaxies in clusters",
"So if you lived at high z, you could certainly hear sound waves in space (assuming they were at the right frequencies). The downside is that the CMB would burn you to death right quick (since it'd be a COB or CUB, maybe even CXB)."
] |
[
"The one thing that no one is mentioning is that the Big Bang is not an event that happened at a place, so you can't somehow figure out where it happened. It happened all at once everywhere in the universe, which as far as we can tell is infinite in extent."
] |
[
"From my 7 year old: Do the things in our bodies ever get tired? Like cells and antibodies? Do they have to rest?"
] |
[
false
] | null |
[
"Excellent question! ",
"Cells themselves don't need to rest in the way that the entire body does, but some organs and body parts do. Cells use a molecule called ATP to make stuff happen. Food + oxygen is turned into ATP and carbon dioxide. When you feel tired, what you are feeling is low amounts of ATP or other molecules made as byproducts from your body working. ",
"Your muscles for instance don't work as fast when they have low amounts of ATP, and the way you experience that is the feeling of tiredness. ",
"When you are sick, your white blood cells are working hard to fight the infection, so they are using up heaps of ATP. This also results in the feeling of tiredness.",
"Your brain however, does need to rest as a whole. Your brain needs 7-9 hours of sleep per night to rest so it can continue working well the next day! It actually changes the way it works (like changing the channel on the tv) to rest and recover.",
"Hope this answers your question!",
"Edit: Clarity"
] |
[
"The basis of recommended amount of hours per night of sleep an average human should obtain is based from studies, both observational and experimental. Essentially researchers just took a bunch of data and analysed/compared which group functioned better. Some people need more, some less.",
"As for why, there are many reasons, some even still being discovered today. ",
"The brain uses insane amounts of energy just to function, let alone do any strenuous cognitive work. About 25% of your daily energy is used by the brain just being 'on' so to speak.",
"The by-products of cerebral metabolism need to be cleared/dealt with, certain circuits within the brain need to either be switched off or altered in order to let that happen. (Like an electrician needing to shut off the power to fix the wiring). Have a google about the glymphatic system if you're interested.",
"Certain circuits are always going around in your brain. Sleep, while not fully understood yet, seems to have an effect on the health of those circuits. There are measurable changes throughout the stages of the sleep cycle in those circuits and interruption of said circuits can have profound effects not only cognitively but physiologically too, like muscle weakness, immune modulation and GI issues.",
"Complex answer to a simple question but the tl:dr version is needs a chance to clean and 'reset', which takes time, apprx 7-9 hours per night to be precise."
] |
[
"Can you explain why the brain needs X hours of sleep?"
] |
[
"What’s the reason head lice prefer the head and pubic lice prefer the pubic area? Hair is just hair isn’t it?"
] |
[
false
] | null |
[
"If you look at a diagram of pubic lice vs head lice you will notice the claws of pubic lice are bigger and more suited to thicker hair. The species is more likely to stick on the host in their respective regions because of this difference but that does not mean there’s zero chance of finding pubic lice in the eyebrows or a beard. ",
"Hair can also have different thickness or coarseness depending on region. Pubic hair tends to be thicker and coarser than the head."
] |
[
"I hate you for making me learn I could potentially get pubic lice in my eyelashes"
] |
[
"The hair spacing of eye lashes serves pubic lice fairly well too.",
"Not seen it yet myself but colleagues in the eye clinic have."
] |
[
"Does rinsing fruits/vegetables with just water really clean them?"
] |
[
false
] |
So I buy an apple, bring it home, rinse it and rub it a little with my hands, dry it off and then eat it. Does this really take everything off that should worry me? I've heard of a "vegetable wash" for this task.. Is that necessary?
|
[
"Sort of. It'll get rid of any pesticide residue and dirt on the outside, but it's not the best at removing bacteria. Bacteria aren't all that water soluble in the first place - there's a reason you use soap when washing your hands, and it's not because it smells good. Worse yet, a lot of produce has nooks and crannies that you can't really clean well just by rinsing it, most notably leafy stuff like spinach. There was just a big listeria recall for bagged, prewashed spinach. So, it's better than nothing, but not exactly sterile.",
"The good news is that most produce is perfectly safe, and even if it isn't, it takes a huge load of bacteria to make it through your stomach to make you sick. With the Listeria above, it's unlikely to cause any problems, Listeria isn't much of a risk to anyone with a functioning immune system."
] |
[
"I'm not an expert on exactly which pesticides are used, but when I worked on a farm, all pesticides had half-lives, either from them washing away or degrading. Guys in white suits come through, spray the place down, nobody is allowed in for 48 hours. After that, it's deemed safe, no special washing required.",
"Pesticides and herbicides aren't meant to keep a field completely free of pests, they're meant to control them. You don't have to keep protection on 24/7, you just need to knock down the population enough that it doesn't get out of control."
] |
[
"Why would farmers use pesticides which wash off when it rains? I assumed that they would be specifically designed to be non-water soluble."
] |
[
"How does scuba gear keep the water pressure from crushing your lungs?"
] |
[
false
] |
[deleted]
|
[
"The scuba gear itself doesn't really do that. There are two pressure regulators, one on top of the tank and the second one as a part of the mouth piece. These combine to deliver air from the tank at atmospheric pressure i.e air equal to the \nthe pressure of the water around you.",
"The air in the lungs will always be at the exact same pressure as the surrounding water, it is this air pressure that keeps the lungs from being crushed by the water pressure."
] |
[
"To expand on this, the deeper you go scuba diving, the more compressed the air in the tank and in the lungs (and gas in your blood), so the same amount of expansion of lungs in response to a breath will draw in a greater amount of more compressed air. Thus, the deeper you dive, the quicker you consume air. ",
"The BCD (buoyancy control device, i.e. the inflatable vest) helps you to adjust your buoyancy by filling your vest with more or less air. As you go deeper, the air in your BCD compresses more, so you sink further, as such, you need to compensate by inflating the BCD. Conversely, if you are rising to the surface, you deflate your BCD so as to not rise too fast as the air expands.",
"So ultimately, a big part of scuba diving is regulating your speed of ascent and descent so that you are not badly effected by the pressure change, and controlling buoyancy levels underwater which effects air consumption."
] |
[
"more compressed the air in the tank and in the lungs",
"Technically the air in the tank isn’t compressed. Since it’s in a rigid container the pressure of the air inside depends only on the volume of the tank, the temperature of the air and how much air there is in the tank. It only really compresses in you body! I’m just splitting hairs, though..."
] |
[
"How do Americans get 115V?"
] |
[
false
] |
Well obviously from a plug socket, but I digress. In Europe, our power is generated in 3 phase (Red, Blue, Yellow, all 120 degrees apart), and when it's transformed down to its consumer power level, the voltage across any two phases is 400V. When there is a star load, you can take power from a single phase relative to the star point, and that comes out as 230V. How does America get 115V? Is it transformed down from 230V at some point? Is the 3-phase voltage different? Is there some other witchcraft going on?
|
[
"most of us do get 240V to the home, as a single phase- but that phase is \"split\" - the transformer that supplies the house is center-tapped, that center is pinned to ground, so there's effectively a +120 and a -120. obviously not really positive and negative since it's a/c, but they're 180° out of phase. so some circuits get one polarity, some get the other, and if we need the full 240 (like for an air conditioner or the stove, etc) we use both."
] |
[
"You sound fairly knowledgeable for power in europe, so I can make this quick.",
"Is it transformed down from 230V at some point? Is the 3-phase voltage different?",
"That is the 3 phase voltage. Utilities will deliver 240V, 3 phase, at the transformer. Once inside a structure, the wiring will center tap resulting in 2 120V lines.",
"Appliance designers will design for 115V +/- 10%. Even though 120V is delivered, there will be some line losses.",
"Is there some other witchcraft going on?",
"Witchcraft is saved for ",
"frequency changing",
"."
] |
[
"Hey, just a heads up- but making comments on askscience which don't contribute to the discussion is frowned upon. A post explaining the rules can be found ",
"here",
", and if you're intent on trolling- I'd suggest just taking it somewhere else, because you'll just get your comments deleted and your account banned from the subreddit if you do that here."
] |
[
"Can a camera record different frequencies of light at the same time? For example, can one camera with a single lens record visible light and infrared at the same time?"
] |
[
false
] | null |
[
"Keep in mind that every color you see is actually a different frequency, so a color image is an example of a picture in more than one frequency. The lens does matter a bit as glass, for example, can make a great lens for optical, but is opaque to infrared, so infrared cameras will have lenses made out of things like quartz, I believe.",
"Really, what you care about isn't the lenses, it's the detector. That can either be what frequencies film is sensitive to, or what frequencies a CCD is sensitive to in a digital camera. I think this works for most digital cameras, but they're usually able to pick up a bit into the infrared, to see the beam that your tv remote uses to change channels. It's actually a ",
"neat way to check",
" and see if your remote is working or not, by seeing if the infrared lights are working that send signals to the tv."
] |
[
"This bit about the material is interesting! Say you have a glass lens. Is it a gradual transition into opaque as you go toward infrared, or a sharp cut-off/transition? "
] |
[
"Yes, they certainly can.",
"I'm solely going to focus on digital cameras in this answer, as they are by far most common today.\nA camera sensor with a Bayer-filter array (red, green and blue micro-filters), captures electromagnetic radiation around the visible spectrum. It can capture near infrared radiation because the red filters don't have a sharp cut-off point, allowing some infrared light to reach the sensor as well. They can capture ultraviolet radiation for the same reason, the blue filters also don't have a sharp cut-off point, hence some ultraviolet radiation can reach the sensor.",
"Since most people only want to capture visible light, a band-pass filter is mounted in front of the sensor. This filter blocks IR and UV, but let visible light pass. In some cameras, this filter can be fairly easily removed, converting the camera to a full-spectrum camera. This is commonly done to consumer cameras to be used for astro-photography, where you're interested in more than just the visible light.",
"However, light of different frequencies focuses at different distances, when focused by a simple lens. Advanced lenses with special materials are needed to bring both near-IR, visible and UV into focus. Btw, this is even a problem in visible light photography, very simple lenses cannot bring red and blue light into focus in the same plane. This is called chromatic aberration. Achromatic lenses are lenses that can bring two wavelengths (usually red and blue) into focus in the same plane, apochromatic lenses can bring three wavelengths into focus.",
"Full-spectrum cameras that don't require modification does exist, and are commonly used by forensic photographers (as they can reveal evidence that cannot be seen by the unaided eye). Those cameras usually don't have the Bayer-filter, so they can capture a wider range of spectrum.",
"Some relevant wikipedia links:",
"http://en.wikipedia.org/wiki/Full-spectrum_photography",
"http://en.wikipedia.org/wiki/Bayer_filter",
"http://en.wikipedia.org/wiki/Band-pass_filter",
"http://en.wikipedia.org/wiki/Chromatic_aberration",
"http://en.wikipedia.org/wiki/Achromatic_lens",
"http://en.wikipedia.org/wiki/Apochromatic_lens"
] |
[
"Would fireworks look the same on mars?"
] |
[
false
] |
Would the color be different, the way they look or would they look the same?
|
[
"They would look the same, the colors you see are the result of a chemical reaction occurring in the materials of the firework itself. Fireworks include their own oxidant, so they would burn the same on Mars as they would on Earth or even in space.",
"When they explode, they would probably spread out farther due to the decreased gravity on Mars. As far as looks go, that is likely the only difference you would notice. The report however, would sound different due to the much thinner atmosphere."
] |
[
"Yes, the thinner atmosphere would make the report sound muffled.",
"HERE",
" is an approximation of the difference between sound on Earth and Mars."
] |
[
"How would the sound be different? Would it just be fainter?"
] |
[
"How do we define the strength of the fundamental forces?"
] |
[
false
] |
I understand that the force between two objects each with 1 coulomb of charge is stronger than two 1 kilogram objects, but how could we say that the electromagnetic force is stronger than gravity? If we used different units (Like nanocoulombs and megagrams), would we say that gravity is stronger?
|
[
"The only reason gravity beats EM at large scales is because protons and electrons almost universally balance each other out, making macroscopic things electrically neutral for the most part. If you had a macroscopic ball of protons (somehow), and one of electrons, the force exerted between them would still absolutely dwarf gravity at large distances."
] |
[
"Of course not, since people can, and do, use very different unit systems. ",
"The relative strengths of interactions can be compared fairly well by considering their coupling constants. They are unitless quantities and thus independent of the unit system used.",
"Alternatively, on a more basic level, you can for example compare the Coulomb forces exerted by a pair of electrons to the corresponding Newtonian gravitational forces. If you simply consider the ratio of these forces, the result is again a unitless quantity.",
"A reasonably good, more down-to-earth example is that you can hold a small object in the air with a regular bar magnet and not have it fall off: When doing that, you are acting against the gravitational pull of the Earth. "
] |
[
"You're exactly right, the relative 'strength' of the forces is not the most fair comparison. These relative strengths are based mainly on their relative forces on an atomic scale. The strong nuclear force dominates here, holding the nucleus together, with electromagnetism not far behind, trying to tear the protons away from each other. On this scale, gravity is undetectably weak (around 10",
" weaker than strong nuclear, on a particle-particle basis).",
"This provides a convenient way to get around the question of what units to use in the comparison, since you don't need any consensus to measure the properties of fundamental particles, but it also stacks the comparison against poor gravity, which is a very relevant force on a large scale, but seems like just a rounding error on the atomic scale."
] |
[
"If you see through a colored filter, will the brain eventually adjust and reprocess it normally?"
] |
[
false
] |
[deleted]
|
[
"if the filter is broad enough that it lets through light that can stimulate all three types of cones, then you could probably adapt enough to be able to discriminate colors again, but not as well as without the filter; if it's a narrow filter (e.g. that is strongly red or blue), you won't be able to see color normally through it, adaptation won't do much for you.",
"as an extreme case, consider a filter that only lets 'red' light through, i.e. wavelengths longer than 600nm. at this cutoff, you could still use your M(medium wavelength) and L(long wavelength) cones to discriminate some colors; and with adaptation, the M would become relatively more sensitive and the L would be come less sensitive, so your discriminations would improve a bit over time. but the S cone, which allows you to discriminate Blues from Yellows, and mediates green sensations, would be completely dormant - it is totally unstimulated by wavelengths longer than 600nm. so you could never see 'blue' through such a filter, and you'd lose your sensations of 'yellow' - everything would look different shades of brownish red.",
"adaptation in the retina comes down to changes in gain (related to adjustable rate of production of photopigments), but the range of frequencies that are detectable is genetically fixed. however, deeper in the nervous system (i.e. in the brain), ranges of selectivity (e.g. to perceived direction) are much more plastic, since they come down to network connectivity rather than some fixed physical component."
] |
[
"Such a phenomenon definitely exists, and is called ",
"chromatic adaptation",
". This process can can be illustrated by the concept of ",
"color balance",
" in photography. The key is that our brain carries out quite a bit of processing when you viewing a scene, one effect of which is to make a scene appear rather constant even when say the ambient lighting changes. For example, a room illuminated by tungsten lighting will have a bluer hue, while one illuminated by sodium lamps will have a more orange hue. However because our brain carries out a color correction of sorts based on contextual cues, such as the green of plants or the color of human faces, the scene will be perceived to change much less than would be noticeable from say looking at the actual spectral data. When one takes a photograph, on the other hand, it ",
" the spectral data that is recorded (at least as can be recorded via the three color channels), such that looking at uncorrected photographs the difference can be quite stark. For this reason white-balance adjustments are carried out to compensate for the change in ambient lighting in a process analogous to that carried out automatically by our sensory system."
] |
[
"Just put on tinted ski goggels for a few hours. The first 5 minutes look a little distorted, but then it all returns to \"normal\". Then after a while, the same happens when taking them back off. "
] |
[
"Do insects have things similar to digitigrade, plantigrade and unguligrade feet?"
] |
[
false
] | null |
[
"Walking insects generally use tarsi (5 segments) at the end of their legs to contact the ground. Most insects have a specialized 5th segment for grasping that features claws or hooks. There is tons of variation in the insect world though, given the vast number of species compared to other animals. I'm sure some use specialized mouthparts or the like to walk. Nice question."
] |
[
"There's some modification that I can think of, but it's in insects without true legs, i.e. prolegs or creeping welts."
] |
[
"Here's",
" an interesting video talking about how some insects and other animals differ in what parts of the leg are used in locomotion. In particular, it introduces the idea of the \"distributed foot\" comprised by, for example, the spines on cockroach legs - structures that amplify the contact between the insect and the surface it's walking on, providing a way to get across rough terrain quickly. Also, applications for robotics!"
] |
[
"Does the gravity of the outer planets., viz Gas giants and Ice giants, influence the positioning of earth? What would have happened to the structure of solar system if the Outer planets where not there initially."
] |
[
false
] | null |
[
"As others have posted the gravitational effects of the outer planets on Earth are dwarfed by the sun's effects, but the Outer Planets are important in fact that they are so massive they suck in many large objects passing through the Solar System that could hit Earth and disrupted the formation or continuance of life as we know it. So even if they don't mess with our orbit too much, we need them as a sort of \"Bodyguard in Space\".",
"But you're question of how the Solar System would be like if they weren't there originally would have some interesting consequences.",
"Background Info:\nA new theory has been rising out of the idea that Neptune and Uranus aren't where they should be. They formed in an area really far out of the Solar System where there shouldn't have been enough material for them to form, so a current explanation is that they formed actually close in the solar system, and Jupiter and Saturn flung them out. ",
"The theory goes is that Jupiter and Saturn were in a 1:2 resonance orbit, which means that for every orbit Saturn did, Jupiter did 2. The issue with this is that the resonance kept pulling other objects out of orbits. One of the large effects is that this pulled Neptune and Uranus out of their orbits and threw them out into the outer solar system. ",
"But of course your question was about what if ALL the outer planets were gone, not just Jupiter and Saturn. ",
"The thing is that 1:2 resonance, as well as launching out Neptune and Uranus, is also theorized to have knocked out many other planetesimals and torn them apart (some of these could have formed into other planets). These pieces of rocks dust would form either the Asteroid Belt, or have been launched out and made into the Kuiper belt or Oort Cloud. As well as this major shifting in the Solar System could have lead to the Late Heavy Bombardment Period, essentially a period in Earth's and the Moon's history where they were bombarded by thousands or millions of meteorites. This pretty much destroyed the Earth's crust and heated it up again to a more liquid state, delaying the formation of a solid crust by a couple hundred million years.",
"So without the Outer Planets at the beginning of the Solar System would have lead to a very different Solar System. First of all their would not be any belts, or at least of the ones we recognize today. Secondly their would be a larger clutter of things in the Inner Solar System because all those planetesimals thrown out by the Outer Planets would still be there. Those could have formed into more planets, or have crashed into one of the currently forming ones (the latter would almost certainly happen many times). The constant bombarding of objects would have implications that I'm not quite sure what they would be. It may in some way delay or even stop the formation of life on Earth, and the Earth would certainly be different than how we know it today, at least being a bit more massive. And even if the Earth survived through the clutter and began forming life, it would constantly be disrupted by events in space (even more so than has happened in the actual Earth's history) because of the likelihood of something hitting the Earth has increased greatly, from both in the Solar System (more clutter), and out of it (no bodyguards).",
"So in short the Outer Planets are in a way essential to the formation and survival of life on Earth, by giving the Earth a clean space to form life undisturbed, and by keeping that space clean.",
"Video- ",
"https://www.youtube.com/watch?feature=player_detailpage&v=5eXR1nvQm5s#t=702s",
"Theory- ",
"http://en.wikipedia.org/wiki/Nice_model",
" "
] |
[
"The gravitational influence of other planets is dwarfed by that of the sun. If the outer planets were not there, Earth's orbit would probably be slightly changed, but not noticeably. "
] |
[
"F = GmM / r",
"G = gravitational constant (6.67384×10",
" m",
" kg",
" s",
"m = mass of Earth (5.9736×10",
" kg)",
"M = mass of Jupiter (largest of the outer worlds) (1.8986×10",
" kg)",
"r = distance (closest is 5.88e9 m, force will be lower as distance increases)",
"Force = 2.189e22 N",
"which sounds like a lot, but that is a pull on the Earth of 3.66e-3 m/s"
] |
[
"What is the science between wine reduction?"
] |
[
false
] |
[deleted]
|
[
"It simply evaporates. The goal is to concentrate the compounds that lend wine (or whatever you're reducing) its flavour by reducing the total volume, creating a very tasty broth. Reduction here does not refer to reduction in the chemical sense of reduction/oxidation reactions."
] |
[
"A few other details that aren't totally off topic.",
"First, unless the reduction is carried to completion (meaning that the liquid is entirely evaporated), there will be some alcohol left. It will be less than before, but the common assumption that the alcohol boils off first is incorrect.",
"Second, the alcohol, because of its volatility and ability to solvate many of the flavoring agents in the food, makes the food taste better since the flavoring agents are now effectively more volatile. This is the reason that we have such oddities as \"vodka sauce\" popping up on Italian menus. The vodka doesn't add any flavor, but it sure makes the tomatoes taste a lot better.",
"EDIT: added the last sentence."
] |
[
"Hmmm I wish it did! How disappointing."
] |
[
"How did people do spacewalks from these small crew capsules without losing their air?"
] |
[
false
] |
At the time where people started to go to space they made these small spacewalks from the crew capsules but how did they do that? I think they needed some kind of airlock so they don't lose their air but how does an airlock fit inside these small capsules? Or did they just had a tank of air to fill the vacuum after the spacewalk? I'm sorry if my sentences sound wierd. English is not my first language but I hope you understand what I mean. Understanding it is easier than writing. I also didn't know what flair to use for my question because there was none for spaceflight or something similar so I just used the Physics one
|
[
"There was two main ways. The first spacewalk by Alexei Leonov was done using an inflatable airlock. It looked like a tube that inflated from the side of the spacecraft. You can see it ",
"here on a painting by the man himself",
".",
"The American early spacewalk were done from the Gemini spacecraft. In that case both astronauts were wearing suits and the whole capsule was purged of air. After the spacewalk it was filled again with compressed air.",
"Part of the issue with venting the whole capsule is that you need to have reserve air but also you need to make sure your instruments will work under vacuum. One of the challenge is to make sure they don't overheat when there is no air to take the heat away. The early Soviet designs notoriously did not want to deal with this which is why they had the inflatable airlock system."
] |
[
"You can get pretty sturdy/stiff inflatable structures if they are designed correctly. Leonov had huge issues with suit pressure that made his suit balloon up and very hard to bend. It made it hard to get back into the tiny airlock. The first spacewalk nearly ended in a catastrophe and he had to vent his suit to quite a low pressure to get back in. Of course being the USSR this story was hidden for years."
] |
[
"The risk of failure is debatable. The inflatable modules are something like 30cm thick once inflated, consisting of many layers of Kevlar, ballistic nylon, and other materials. It’s basically built up like a really thick ballistic vest. In earth based testing, it survived hyper velocity impacts much better than the traditional modules."
] |
[
"Is it possible to graph 4 variables on one graph?"
] |
[
false
] |
On a 2d graph, you can graph 2 variables and you get a line. On a 3d graph, you can graph 3 variables and you get a surface. Is it possible with a "4d" graph, you can graph 4 variables and get some other visualization? This may be stupid, but it just popped into my head.
|
[
"One nice way of graphing an additional degree of freedom is to use a colour scale and colour your graph according to the value of that last variable. I used this a lot in my dissertation by graphing 3D plots (a surface) without actually rendering anything in 3D, just by using a top-down flat view of a coloured image.",
"Often, complex functions of complex variables are graphed using hue for the argument (angle) and lightness for magnitude. Then you get things like ",
"this",
"."
] |
[
"I have a bunch like ",
"these",
". They're pixelated but that doesn't really change the concept.",
"I also have some like ",
"these",
", which used to be in the form of the above (just not pixelated), which I turned into contour plots because I felt they looked better in print, but I kept the colour scale. I hope it shows what I had in mind."
] |
[
"Can you post a picture example of one of your graphs, just to give us a better idea of what you mean?"
] |
[
"What could be beyond the outermost galaxies?"
] |
[
false
] | null |
[
"There's no way to make it intuitively sensible without resorting to math, I think. However, there are an awful lot of people on askscience who are smarter than I, and perhaps someone will make a better 3D analogy."
] |
[
"There's no way to make it intuitively sensible without resorting to math, I think. However, there are an awful lot of people on askscience who are smarter than I, and perhaps someone will make a better 3D analogy."
] |
[
"The idea of a finite but boundless universe was presented by Hawking in A Brief History of Time. In his example he compared the expanding universe to the surface of an inflating balloon. \"Up\", in that case, is the arrow of time. However, this model requires curved space. Since that book was written there have been attempts to detect a curvature of space. If it exists it's too small to measure with available technology. ",
"In regards to your question, we must be careful to distinguish between the universe and an observable universe. The observable universe is finite, but the universe as a whole may or may not be. In the absence of evidence for curvature, it's commonly held to be infinite. For each observer there is an observable universe, but because we're all so close together here on earth, for practical purposes, it can be said that we share the same observable universe. As the expansion of space is metric, the greater the distance between two objects the faster they tend to recede from each other. Beyond a certain distance objects are receding from us faster than the speed of light. So we are surrounded by an event horizon. Sufficiently distant regions cannot communicate, or effect each other. Now it may be that there are only a finite number of galaxies occupying a finite region of space(larger than our observable universe), surrounded by an infinite void, but the cosmological principle is commonly assumed, so it's generally thought that space outside of our observable universe is like the space inside our observable universe. "
] |
[
"Why do electrons and protons have exactly the same charge magnitude even though their masses are different by a factor of nearly 1,000?"
] |
[
false
] | null |
[
"I guess I asked the question badly. My question seemed to imply that mass and charge are related.",
"What I'm saying is, I can understand that the masses of two different particles would be completely different, as there doesn't seem to be any reason for them to be the same. ",
"So why should a property like charge magnitude be exactly the same for completely different particles?"
] |
[
"\"why is charge quantized?\" I'm sure you'll get plenty of interesting reading, with an ultimate answer of \"nobody knows.\"",
"Actually, there is a really interesting answer. At least more interesting than that. If there were magnetic monopoles, ie. a \"magnetic charge\", then not only would the Maxwell equations look completely symmetric, meaning you could exchange E and B arbitrarily, but it would also imply that the electric charge must be quantized. In fact, even one single monopole in the observable Universe would be sufficient. ",
"Unfortunately, no one has seen any monopoles so far."
] |
[
"\"why is charge quantized?\" I'm sure you'll get plenty of interesting reading, with an ultimate answer of \"nobody knows.\"",
"Actually, there is a really interesting answer. At least more interesting than that. If there were magnetic monopoles, ie. a \"magnetic charge\", then not only would the Maxwell equations look completely symmetric, meaning you could exchange E and B arbitrarily, but it would also imply that the electric charge must be quantized. In fact, even one single monopole in the observable Universe would be sufficient. ",
"Unfortunately, no one has seen any monopoles so far."
] |
[
"Why does taking a hot shower temporarily relieve the symptoms of many minor human illnesses?"
] |
[
false
] |
Colds, the flu, a nasty sore throat, a cough, a hangover: a hot shower seems to take away the pain, soreness, exhaustion and general discomfort for at least a while. I understand the medical reasons why a hot shower might help soothe a cough, just like a humidifier, but what's the effect it has on the rest of the body? Would just getting hot, like under an electric blanket, do the same thing? Or is there something about the running water that creates the sensation of relief?
|
[
"The short answer would be vasodilation provided by heat. That would increase blood flow to affected areas and reduce pain and soreness and general discomfort. As far as a hot shower alleviating exhaustion, I don't know the precise mechanism behind that. ",
"There may also be a degree of psychology (placebo effect) involved because we've associated a hot shower with symptom relief, hence one possible reason why people feel better after such. ",
"- ice "
] |
[
"That doesn't really hold up as if you have a hot shower you will sweat more to reduce your body temperature however this will have no effect due to the high humidity and constant exposure to the hot water. You also don't absorb water through your lungs. ",
"One thing that does occur is any mucus in your lungs and nose will be hydrated, thinning it, allowing far easier removal from your lungs or anywhere it is helping to block with the added inflammation. "
] |
[
"Another thing that contributes to some extent is the hydrating effect of being exposed to that much water vapor, since a pretty good amount of that will be breathed in."
] |
[
"Trampolines in low gravity"
] |
[
false
] |
If all other things are equal, would a trampoline jumper achieve a different height in lower gravity? I.e a Moon base with full atmospheric pressure and a very high ceiling vs a similar setup on Earth.
|
[
"The trampoline is just a spring and just returns any energy put into it. So the question is really, \"Can people jump higher when there is lower gravity?\" The answer is definitely yes. With less gravity, the gravitational acceleration is lower. That means with a given initial velocity upwards, it takes longer to decelerate you to zero speed at the top of your trajectory and than bring you back down. So you can definitely jump higher on the moon. You can see this easily if you ever watch any of the Apollo moon videos. Depending on the gravitational field of a given body, there is a given escape velocity, which is the initial speed you have to start with to never fall back down. The weaker the gravity, the lower the escape velocity. In other words, the lower gravity, the higher you can jump, progressing towards the limit of an infinitely high jump when you exceed the escape velocity (because the gravity is so weak)."
] |
[
"You will jump higher because the velocity of a projectile follows a parabolic function. If you jump up at two meters per second gravity will decelerate you to zero, then it will reaccelerate you to two meters per second exactly when you hit the trampoline. In this aspect, it is completely unimportant what the magnitude of gravity is because you will always hit the trampoline at the same velocity you left it. The catch is lower gravity will just take longer to decelerate and reaccelerate you to that initial velocity. If you want to think of it in a different way, think of dropping objects off a building. The higher you go the faster the object hits the ground (assuming terminal velocity isn't reached which would be insane for a trampoline). Since we know the earths gravity is stronger than the moon's, we can infer we would have to drop it from higher on the moon to reach the same velocity as we did on earth. And since we know a final velocity right before the bounce must equal our initial velocity we can conclude that we would bounce higher on moon, however the frequency of the bounces would be much slower"
] |
[
"You are assuming that he would bounce around like an inanimate object, a human however is using the leg muscles when jumping, so given the right timing the jump will be pretty high, also any follow up jumps would be just as and higher as you will keep using your legs"
] |
[
"Why do red and purple look similar when they’re at opposite ends of the spectrum?"
] |
[
false
] | null |
[
"Purple is a non-spectral colour, being a mix of red and blue. Violet is the name for the pure spectral colour beyond blue, and the reason it looks slightly red is that red cones have a small secondary peak of sensitivity at around that wavelength:",
"https://midimagic.sgc-hosting.com/huvision.htm"
] |
[
"Your perception of color is related to the wavelengths of various visible light, but it's not a linear scale, the information is translated into color to emphasize important distinctions you might see in the world, rather than give you a precise accounting of wavelengths.",
"Somewhat separately - violet and purple are not the same color, and only violet is part of the EM spectrum. Purple pigment is a combination of red and blue, so it does resemble both colors."
] |
[
"Perhaps a more informative way to phrase the original question would be \"Why is pure violet perceived as similar in color to a mixture that includes red?\". I found an explanation at ",
"https://web.archive.org/web/20170226011606/http://gene.bio.jhu.edu/violet/violet.html",
"."
] |
[
"Is time the same on Mars?"
] |
[
false
] |
[deleted]
|
[
"If you're talking about relativistic effects, they are effectively negligible. We're talking less than a part per million difference. In terms of timekeeping, the conventions on Mars are different because the days aren't 24 hours."
] |
[
"the day on mars is roughly 24 hours and 40 minutes. i think a human would have little problem adjusting to that cycle. other than that i don't know what factors would effect human behavior differently to how they would on earth.\n",
"http://en.wikipedia.org/wiki/Mars"
] |
[
"The engineers at NASA working with Curiosity are on a Martian sleep cycle."
] |
[
"What happens when sound waves outside the human ear's range make contact with us? And why don't we perceive them?"
] |
[
false
] | null |
[
"Bear in mind that we often still perceive such soundwaves, but just not as sound (e.g., the feeling of really deep bass at a concert).",
"Incoming sounds produce a traveling wave which propagates down the basilar membrane (to which the hair cells are attached, which in turn traduce motion into electrical discharges). As far as I know a very high frequency sound will still cause the eardrum to vibrate, but the wave will disapate almost immediately. Low frequency sounds ought to travel the entire length of the membrane, and may cause sounds to perceived at higher harmonics of the fundamental frequency. As you approach the audible range, you may find that a section of the basilar membrane is strongly excited by the soundwave, but that there are simply no functioning hair cells attached to the membrane (e.g., due to cell death, caused by ageing/smoking/etc.). Here there will be nothing to transduce the motion into electrical signals, so nothing will be perceived."
] |
[
"There are tiny hairs in your cochlea ",
"I think it's important to note that these aren't actually hairs, but are actually stereocillia. They are commonly referred to as \"hair cells\", but are orders of magnitude smaller than the hairs on your head.",
"Those sounds outside of our range of hearing produce less pressure then our ears are able to detect. ",
"Not exactly. This suggests that if you were to increase the intensity to a certain point, you could hear a 30 kHz tone. That's not the case. There simply isn't a point on the basilar membrane where these frequencies will resonate and disturb the hair cells. Even if there were a way to get the energy into the hair cells, I don't know if the auditory system could properly encode that high of a frequency."
] |
[
"I think it's also important to mention that is seems that the human auditory cortex has evolved to interpret human speech, so those are the frequencies to which the Basilar Membrane is most responsive. We have hair cells beyond the range of speech frequencies to give us environmental cues, but the natural resonance of the ear canal and the structure of the auditory cortex are centered around speech understanding. "
] |
[
"My 5 year old asked me \"daddy, how does a medicine know where to go once it gets to the stomach?\" after watching me take a pill for a headache. That got ME thinking and now I'm curious cause we always take it so normal on the everyday life."
] |
[
false
] |
[deleted]
|
[
"Medicine doesn't \"know\" where to go (at least, not yet). Ingested chemicals are dissolved in the body and reach areas they are able to go. In your case, a pain-reliever (like an NSAID) dissolved in your stomach, was absorbed into your blood stream, was distributed across the systems in your body, including crossing the blood-brain barrier, and had an effect on your brain. Because it had an effect on your brain and you felt its effect, you perceived that it \"knew\" where to go when in reality it went many places, you were just unable to perceive all of them."
] |
[
"The field of working out how to make drugs go to a specific place is called ",
"targeted drug delivery",
" and is a very active field of current research, especially for new cancer therapies. There are a variety of methods under study for doing this, which are pretty well summarized by the Wikipedia article. ",
"On top of that, you can also accomplish some less-specific drug targeting based on knowledge of cell metabolism. For example, some of my colleagues use a fluorescent version of glucose to detect cancer cells, since cancer cells uptake more glucose than non-cancerous cells."
] |
[
"There are already examples of this just entering common use now ",
"http://en.wikipedia.org/wiki/Antibody-drug_conjugate",
"In this case, the antibody provides the targeting for a general poison."
] |
[
"Why do we seem to discover periodic table elements only in sequence of the number of protons in the nucleus?"
] |
[
false
] |
[deleted]
|
[
"Couple of reasons. The main one is that the reaction cross section (probability of creating) for making these super heavies falls very quickly the larger the nuclei. So we simply have not done enough measurements to even see the much larger ones. In addition, the target and beam are chosen to yield a specific one. Currently, they are starting at the easier to make super heavies because they know they should get a few over the course of the measurement. ",
"They have tried uranium on uranium bombardment, but they have yet to see a really large super heavy out of that. "
] |
[
"Anywhere I can read about that last thing?"
] |
[
"I would have to search for the papers. Those type of experiments were mostly done in the 60s and 70s"
] |
[
"Is it possible to have a completely clean eye in a cyclone?"
] |
[
false
] |
The fantastical artic hypercane in the movie "The Day After Tomorrow" are shown with a completely clean eye that allows a clear and quite spectacular view of the surrounding eyewall. Now is this actually possible in reality, can real life tropical cyclones present a completely clean eye? I ask this because in all the videos and photos taken from the ground it seems that the eye presents a low layer of clouds that prevents the vision of the surrounding eyewall. In this video you can see something that looks like what is shown in the film, at 1:53 minute, but there is still a thick layer of haze and low clouds that prevents a clear and distinct view.
|
[
"I hesitate to even answer this question based on how horrifically unrealistic the science is in that movie. So in case anyone unfamiliar with the movie's \"science\" is reading this, I'll just start by linking to ",
"this brief list of some of the many things wrong with that movie meteorologically",
".",
"For actual hurricanes that can physically happen in our world: yes, it is possible to look up and be able to see blue sky. It is infuriatingly hard to find actual images taken from inside the eye (due to a few factors, namely eyes tend to become disrupted and cloud-filled as they make landfall, and that people tend to evacuate from an area that is being hit by a storm strong enough to have a clear eye), but just from ",
"images of Florence at peak intensity",
" there are many patches of blue ocean that are visible from space, so it would follow that the sky would be visible from the ground/ocean within the eye. And indeed, ",
"this video from the eye of Hurricane Nicole",
" shows that, at least in some storms, you can see some blue sky within the eye.",
"Is it possible to have a ",
" clear eye with an unobstructed view of the full eyewall?. There is nothing that would make this physically impossible. But it is highly unlikely, and would likely require perfect conditions to make it happen. ",
"This last section is kind of rambling and probably far too detailed, but I thought I'd include my thoughts in case you or anyone else wanted me to elaborate further on what those \"perfect\" conditions might be. Among the conditions I can think of that would need to be satisfied:",
"annular hurricane",
"this image"
] |
[
"Wow thank you so much. This was exactly the kind of answer I was looking for. For the movie, I actually have some background in meteorology, and I know how terrible it is in scientific terms, I used it as an example just to visualized my idea of a completely calm eye. ",
"Thank you so much again",
""
] |
[
"To get back to you a bit later, today's landfall of Hurricane Michael saw a good portion of the eye cloud-free. Here is one video: ",
"https://www.facebook.com/Stefan1126/videos/10156491591296138/",
" I did not think it would be possible for a storm of this intensity, but you can see almost the entire eyewall from the ground!",
"Updon discussion with a colleague on this topic she was able to dig up another video from a storm in 1985: Hurricane Elena ",
"https://www.youtube.com/watch?v=4qNkGH5Fviw",
". Not completely clear, but a good portion of blue sky is visible."
] |
[
"Interesting biology work for a high school student?"
] |
[
false
] | null |
[
"Find out if there's any colleges nearby that have bio labs. If you ask a professor if you can volunteer in their lab you'll learn a bajillion times more, actually get to do real research, don't have to pay anything, and get something that looks REALLY good on resumes/college apps. Tell your parents helping you get to/from there can be your birthday present. ",
"Disclaimer: you WILL get stuck doing bitch work (e.g. dishes, filling pipet tip boxes, etc). Everyone does in a lab. You might find some labs that won't let you do anything besides that. But if you find a professor who actually likes teaching, they will be thrilled to have an excited, interested young mind to mold. If you can't find anyone who will let you help, check again around May when all the college students leave and there's no one left to work in the labs. "
] |
[
"Where does it belong?"
] |
[
"Not here. This subreddit is for scientific questions, not questions about science related jobs. "
] |
[
"Why do I only seem to get itchy and antsy right before I fall asleep, this causing me to move and become uncomfortable?"
] |
[
false
] | null |
[
"Hello,",
"We can't speculate about this here."
] |
[
"Ok where can we? "
] |
[
"You could try ",
"/r/answers",
"."
] |
[
"How do we know what makes up the center of the world?"
] |
[
false
] | null |
[
"The primary way that the different layers of the earth were discovered was through seismology. An earthquake creates a wave that begins near the Earth's surface and propagates outwards in all directions, all the way across the planet if it's strong enough. With sensitive detectors you can feel earthquakes from all over the planet. These waves don't just go out in a uniform circle though, at the interface between two layers the wave is refracted and reflected, like light hitting water. By carefully studying how seismic waves travel through the planet's interior, we can infer the density and thickness of the layers.",
"As for the actual composition of the layers this can be more difficult, the density can be relatively straightforward but then you still need to know exactly what materials are down there. Once we know the temperatures and pressures to expect at different layers we can perform experiments on materials to see how they behave under those conditions and determine what makes up each layer. The mantle also comes out of the surface every once in a while as lava, so that helps. The core is the least well understood simply because it's so far down there, but the idea that we have an iron core is supported by the presence of a magnetic field, meaning there's gotta be something conductive moving around down there."
] |
[
"This is definitely the correct answer, I just wanted to add on a couple of things (which I’m sure you know, but for the benefit of other readers):",
"The mantle also comes out of the surface every once in a while as lava, so that helps",
"These are known as mantle xenoliths (literally ‘foreign rocks’) and are an important direct source of information about mantle composition, as opposed to the high pressure-temperature experiments also mentioned. Even though the vast majority of lava at the Earth’s surface was generated in the mantle, this is a partial melt of mantle material and so the original composition has to be inferred based on which minerals get melted. Mantle xenoliths are comparatively rare, but there’s enough of them from around the world that we can confidently say this is the stuff that the mantle is made from (at least the upper mantle anyway). ",
"Fun fact: mantle xenoliths are various types of peridotite - a rock made almost exclusively from the mineral olivine, which gives it a striking green colour. Mantle xenoliths stand out from the dark coloured lavas which encase them, making it look like a sort of mint choc-chip rock, ",
"example",
"the idea that we have an iron core is supported by the presence of a magnetic field, meaning there's gotta be something conductive moving around down there.",
"The iron core hypothesis is also supported by the fact that we know iron to be cosmically abundant due to it being the end product of normal fusion in stars; abundant in our own solar system as confirmed by analysis of meteorites (which represent building blocks of the early solar system); the fact that metal meteorites are iron-nickel (thought to represent cores of early planetesimals which were then smashed apart); aaaaand don’t forget the simple fact that the Earth’s total mass indicates there is a load of much higher density material somewhere inside, more than can be accounted for by mantle material or planetary compression of such material. We would have known that last fact since the time of Newton. "
] |
[
"A fancy way is to actually \"x-ray\" the Earth. A normal x-ray picture works since bones absorb gamma rays differently than muscles/flesh etc. If you want to \"xray\" the earth you will need a particle type that isnt absorbed so easily on the whole distance. So ",
"people use neutrinos for that",
"\nThis kind of measurement directly provides the integrated density in the earth core (the averaged lets say) but dependent on which way the neutrinos went you could get a detailed map of the earth.",
"I imagine those people fix the detectors (large tanks of water with scintillators basically) and fire with a neutrino gun from different spots on earth into those detectors. Pretty fancy I find."
] |
[
"Is the Montreal plan to dump sewage into the St-Lawrence river actually that bad for the environment or is opposition to it just people trying to get environmental brownie points?"
] |
[
false
] | null |
[
"Outside of my field off expertise, but just to get things started, here is an article from 3 days ago where a researcher comments on the whole thing (",
"http://www.lapresse.ca/le-nouvelliste/actualites/environnement/201510/07/01-4907728-deversement-deaux-usees-a-montreal-luqtr-va-etudier-les-effets.php",
") - since it is in french, I'll get out a few of the highlights:",
"The \"sewage dump\" is the equivalent of 0,5% of the flow in the river;",
"This event is \"business as usual\" and should be no worse than what the river has to deal with day-in/day-out;",
"The plume will go through an extensive network of marshes in the Bourcherville area which will act as a natural filter;",
"There remains a valid question as to what will happen to large unfiltered objects;"
] |
[
"Can't speak to the situation in Montreal, but dumping raw sewage into rivers is a pretty common issue in larger cities with older sewer systems. The sewer lines (sanitary sewer) are where the water goes when you flush your toilet/run your sink/where any water goes down a drain. This water flows to a treatment facility where it is treated (cleaned). The problem occurs during storm events where water can infiltrate into these older sanitary sewer lines or is (illegally) piped from downspouts into sanitary sewer pipes. The treatment facility cannot handle this drastic increase in flow and the excess mix of sewage and storm water has to be deposited into a nearby stream. \nDEP has already begun a plan to fix these lines, but it is a very large scale project. So dumping sewage into the river is a dangerous health issue for aquatic life and civilian health, but it is also a rather common issue."
] |
[
"So ",
"according to the professors from the Polytechnique engineering school, the dump is no big deal.",
"Its total volume is 0.5% of the river's flow, so the dilution factor alone lets us breathe easier. This means if you released it all in one second, the \"clean\" river would still dwarf the waste. The experts also raise the issue that most of the chemical/pharmaceutical/hormonal contaminants are not usually treated anyway, so no biggie. ",
"On the topic of large objects, they theorize they will sin at the bottom close to the release point, so they shouldn't cause a problem downstream."
] |
[
"Why do we talk & act like we're drunk when we become exhausted?"
] |
[
false
] |
As someone who's had plenty of nights drunk & also had work days that seemed to never end (not at the same time)... I've always wondered this. Can anyone explain this to me? EDIT: thank you kindly to those that replied with intent to truly answer my question. Best response (& scariest) so far, by cough_e: When you are sleep deprived your body still produces GABA. Caffeine or other energy stimulants typically work to increase excitatory neurotransmitters, but the effects of GABA will ultimately outwork these supplements, especially in the brain. O_o...
|
[
"Although this thread seems to be a downvote magnet, no one has really answered the question.",
"Although there are other factors at play, the main reason your body feels tired is because an increase in the neurotransmitter gamma-Aminobutyric acid, or GABA. This is an inhibitor that blocks the normal excitability of neurons throughout the body. ",
"When you are sleep deprived your body still produces GABA. Caffeine or other energy stimulants typically work to increase excitatory neurotransmitters, but the effects of GABA will ultimately outwork these supplements, especially in the brain. As your body attempts to fall asleep (despite your paper being due tomorrow morning) GABA begins to shut down your brain's control of the physical functions it uses when awake.",
"The cerebellum is a major brain segment that controls really basic tasks, such as walking and talking. Since these are only useful when awake and the cerebellum is at the bottom of the brain, it gets targeted first by GABA. It's clear to see why when someone gets overly tired, their abilities to walk and talk would become a bit impaired. If they became even more sleep deprived, their abilities to think and reason would also begin to shut down.",
"Not surprisingly, alcohol also increases the production of GABA, which is why it is a depressant. All the same consequences of sleep deprivation are equal to and amplified by the intake of alcohol. From losing \"inhibitions\" to losing balance and slurring speech, GABA increase leads to the shutdown of basic brain functions."
] |
[
"Please read the ",
"AskScience guidelines",
" before posting. Top level comments are reserved for expert panelists or comments that provide factual evidence with appropriate sources. ",
"Thank you!"
] |
[
"/r/askscience",
" is not ",
"/r/funny",
" "
] |
[
"Why do we stop feeling hungry when we're nauseous?"
] |
[
false
] |
I currently have some sort of stomach bug and I've been having diarrhea all day (TMI, sorry). All I've eaten today is a granola bar (and about half a bottle of powerade) and I don't feel hungry at all. I am just curious what's going on in my body - are the mechanoreceptors in my stomach cells somehow less sensitive? Are the signals trying to tell me that I'm hungry being interrupted? Is my immune response telling my body that I shouldn't eat or I'll throw up? If so, how? How does being sick affect the body's ability to process information that might ordinarily tell me I should eat?
|
[
"Your gut is highly connected with your central nervous system and controlled by the parasympathetic nervous system. My assumption would be that if you feel sick your nervous system will be preoccupied and the same centre that controls appetite (Hypothalamus) will not be responding typically. This in turn will be related the the immune response to whatever 'bug' you've caught. "
] |
[
"Well, to answer ",
" we stop feeling hungry, it's an evolutionary trait to try to prevent anything else from entering your system that might cause you harm. If you've recently eaten something that's contaminated (or you're likely to... contaminate your surroundings) it may be best not to want to eat. Things that are gross or disgusting similarly make us lose our appetites.",
"I think you're actually looking for ",
" we stop being hungry, as you said in your post, but you'll have to wait for someone else to come along to answer that."
] |
[
"Thanks for the insight! Sounds like that might be a hormonal response, then."
] |
[
"When we're out of oil. Will there still be plastics?"
] |
[
false
] |
I mean - will there always be some oil to drill up to make plastics, or will we have to move to similar materials? I have for example seen very much looking like plastic material made out of corn starch. Are there alternatives?
|
[
"Oil will probably never run out in the sense that it becomes impossible to find a single drop left anywhere on earth. Most parts of oil can be ",
"synthesized",
" from coal, gas or even biomass. So oil-based products will simply become gradually more expensive and replaced by alternatives where it is viable. If a particular industrial application absolutely requires oil-based plastics, it will always be possible... it's just a matter of how expensive they will be."
] |
[
"Yep There are tons of different Bioplastics as they are called. some examples incluce... polylactic acid (PLA), Polyhydroxyalkanoates (PHAs). The wikipedia article does a good good of summerizing some of the common ones. If a chemical can be polymerized chances are we can turn it into a plastic for the right price. The reason why we arn't using them right now is because oil is still sooooo cheap compared to biological and renewable sources. ",
"Also I'm just going to go out on a limb and suggest that in addition to bioplastics we will go back to using nature's polymers, aka wood and stuff like that.",
"http://en.wikipedia.org/wiki/Bioplastic"
] |
[
"In addition, recycling and extracting oils from waste plastics may be utilized more."
] |
[
"How likely is it that the \"Big Crunch\" is the ultimate fate of the universe? What sort of evidence led to this theory?"
] |
[
false
] | null |
[
"Given that the Nobel Prize in 2011 was given to the people who made the discovery that the universe is expanding at an accelerating rate, I would say not very likely. \nThe evidence so far suggests that the universe is expanding, and as it expands more dark energy is created. The mechanism that would lead to the big crunch is the gravitational interaction between baryonic matter, pulling everything together. However, while the amount of matter in the universe is set, it would seem that Dark Energy keeps increasing, expanding the universe. \nWe see evidence of all of this in modelling the expansion of the universe in the past. There is the initial expansion, which then slowed, making a plateau or saddle point roughly 5-billion years ago. This saddle point corresponds to the point where The amount of dark energy and matter were equal. From where we are now in history, we are seeing more dark energy than matter and, as far as we can guess, dark energy will continue to dilute the amount of matter we have.\nSo what is the ultimate fate of the universe? Everything will separate from everything else and the universe will expand forever."
] |
[
"So what is the ultimate fate of the universe? Everything will separate from everything else and the universe will expand forever",
"Trying to prevent the spread of this misinformation.",
"This isn't true, the ultimate fate of the universe is not known.",
"Accelerating expansion does not imply A big rip. We require an accelerating acceleration of the expansion of the universe.",
"What an accelerating expansion implies is that stuff we can see now (distant galaxies) will be redshifted out of sight eventually but this is also implied by a constant expansion. ",
"The simple way to think of this is that our other forces are accelerations and are often much much stronger than any acceleration caused by the expansion of the universe, which is tiny except at extreme distances. We thus need an increase from the current value of the accelerating expansion to a value which is comparable to that of our other forces at shorter distances. The expansion (and it's acceleration) are currently only relevant at distances far exceeding those associated with a big rip.",
"We are still gravitationally bound to a lot of the universe, the whole of our local group and infact the entire virgo supercluster, consisting of many thousands of galaxies, will not be ripped from us with the current value acceleration of the expansion of the universe. Not even close. This, incidentally, comprises the entirety of what you can see in the sky at night.",
"What we need to determine is whether a factor, called omega, which is the ratio between the dark energy pressure and the dark energy energy density, is less than -1. We currently measure it to be exactly -1 but with enough uncertainties to make either >-1 or <-1 a possibility.",
"TL;DR The big rip is a possibility but not one which current evidence points to. Accelerating expansion does not imply big rip as other accelerations (such as gravity or electromagnetic) are stronger at short distances (less than many megaparsecs)."
] |
[
"Is it just me or does a big crunch sound more optimistic than ever-expanding-into-darkness-and-cold? It'd be an epic end to the universe, maybe spawning another. I don't see how expanding forever is anything but terribly depressing."
] |
[
"Two probably nonsensical questions on spacetime from a layman."
] |
[
false
] |
Total relativity novice here. I understand that mass somehow "warps" the fabric of spacetime, thus massive objects "experience" time differently. What I am curious about is the underlying reasoning for this. What I am thinking of is that: it is harder to move a mass through physical dimensions of space (i.e. more energy required), and is that somehow analogous to moving a larger mass through time? That is, is the relationship of mass to spatial dimensions similar to (in underlying principle) the relationship of mass to the temporal dimension? And an unrelated follow-up! Does time "stop" for photons because they move at the speed of light? I.e. if I was a photon, would time be meaningful to me? And if it does "stop," that really wigs me out because photons clearly travel through space over time... so would they experience their origin and end (assuming they were sentient!) all at once?
|
[
"Spacetime doesn't really care about the difference between space and time. Remember the length contraction and time dilation in special relativity? These arise because different reference frames have different conceptions of which directions are spatial and which is time. Time in my rest frame is going to be some combination of space and time dimensions in the rest frame of someone moving relative to me, much like if I take an x-y axis and rotate it, my new x axis is a combination of the old x and y axes.",
"All of which is to say that nature can't differentiate between the two without picking a preferred frame. So once we know that mass and energy bend space, they ",
" to bend time as well, at least in most frames. And since our velocity through spacetime is constant, moving differently through time means you experience time differently - at least as an outside observer would see it.",
"As for the unrelated follow-up (a contradiction in terms, no?): time \"stops\" for photons because every object has a constant velocity through spacetime, and photons use up all of that velocity in spatial directions. There's just no velocity left to move through time. If you'd like, you can think about this as time dilation: relative to an outside observer at rest, as your speed increases your clocks slow down. If you look at the mathematics, you see that this asymptotes as your speed reaches the speed of light. So if you were a photon, you simply wouldn't experience any time. This is why the concept of a \"sentient photon\" simply doesn't make sense."
] |
[
"Wow, that's a very good article. Not only that, but most of the articles it links to are clearly written and highly accessible. Physics is so much better on Wikipedia than my field."
] |
[
"I meant that more as an apology than a complaint. I really should get back on Wikipedia."
] |
[
"Why do the eyes of some blinded people lack pigmentation?"
] |
[
false
] |
Is there a reason some eyes appear to be a grayish-blue color when blind?
|
[
"The lens becomes cloudy and occluded, making it appear white: ",
"http://en.wikipedia.org/wiki/Cataract"
] |
[
"You might be thinking of cataracts, which can cause blindness.\n",
"Image"
] |
[
"Right, the eyes don't lack pigmentation. Eyes that lack pigmentation such as in ",
"Albinism",
" appear red or purple."
] |
[
"Is it genetically possible for a mutation to occur that would give us superhuman properties? (i.e. something like Spider-man or the X-Men)"
] |
[
false
] | null |
[
"Well, consider that it was a series of mutations that advanced humans above the fray of primates amongst which we evolved. Compared to modern chimpanzees our powers of speech and problem solving could be considered a super power. ",
"So the possibility of future mutations endowing future humans with new capabilities is greater than 0, but the likelihood of a ",
" mutation giving us awesome x-men claws or web-spinning organs is probably close to 0. "
] |
[
"This is probably the essential difference between the X-men and actual genetics. In the X-men universe, there's a single mutant gene that enables all of the special powers. In reality, it'd typically take mutations in a large number of genes to give someone a super-human feature."
] |
[
"Wolverine actually had bone claws before they were covered with adamantium.",
"http://en.wikipedia.org/wiki/Wolverine_(comics)#Powers_and_abilities"
] |
[
"Are K+ ATP dependent channels active or passive transport?"
] |
[
false
] | null |
[
"So... what is the definition of active transport again? Rather, what is active transport ",
" on?"
] |
[
"Active transport is movement that requires the input of energy. I'm not sure if this involves the input of energy however. The channel is open if there is no ATP bound to it and closes when ATP binds to it. My concept of it is that ATP is acting as an allosteric inhibitor by binding, not by phosphorylating. "
] |
[
"Ahh, that does make it more confusing! I would say that it is not active transport because the ATP is not being hydrolyzed for energy. The channel is ",
" by this hydrolysis I'm sure, as being hydrolyzed will turn it back to ADP (much like in a G-protein that is active with ATP and then hydrolyzes it to ADP to become inactive again) but it isn't ",
" by this hydrolysis. ",
"These papers might help (I found the latter more useful than the former) your understanding:\n",
"How ATP Inhibits the Open KATP Channel",
"A universally conserved residue in the SUR1 subunit of the KATP channel is essential for translating nucleotide binding at SUR1 into channel opening",
"edit: derped on formatting "
] |
[
"Is there a Bayesian analog to the frequentist chi-square goodness of fit test?"
] |
[
false
] | null |
[
"Dude this is askscience. Not being elitist or anything but its for people who have specialist knowledge to put forward their opinions on a questions asked, not for people to add 'whimsical' comments. "
] |
[
"Dude this is askscience. Not being elitist or anything but its for people who have specialist knowledge to put forward their opinions on a questions asked, not for people to add 'whimsical' comments. "
] |
[
"Well the Bayesian point of view is somewhat simpler. You can't just reject a null hypothesis, you instead pick the best, i.e. MAP, hypothesis from a set. So you calculate P(Model|Data) for all models, and pick the best one.",
"Are you looking for Bayesian examples where normal distributions are tested, or where the chi squared distribution turns up?"
] |
[
"How do audio books, printed books, and videos differ in terms of how our brains retain and process the information?"
] |
[
false
] |
[deleted]
|
[
"I know video and books are definitely different. but paper books and audio books are processed in the mind almost identically. so when you listen to an audio book it is nearly as if not better than reading the book and handled almost identically in the mind.",
"Better with a particularly good reader as they can help you engage better.",
"it seems reading words and listening to words uses the same \"portion\" of the brain.",
"http://nymag.com/scienceofus/2016/08/listening-to-a-book-instead-of-reading-isnt-cheating.html",
"there is a forbes article back to 2011 saying the same thing but I can't read it any longer (ad block blocker)"
] |
[
"Learning style typically has no effect on performance, although we believe it does.",
"Here's an article published by one of my colleagues in the British Journal of Psychology ",
"http://onlinelibrary.wiley.com/doi/10.1111/bjop.12214/abstract"
] |
[
"Learning style typically has no effect on performance, although we believe it does.",
"Here's an article published by one of my colleagues in the British Journal of Psychology ",
"http://onlinelibrary.wiley.com/doi/10.1111/bjop.12214/abstract"
] |
[
"Could we use photons to create a black hole?"
] |
[
false
] |
If I understand it correctly photons have a mass. If I put a large convex mirror in front of the Sun could the photons in the focal point create a black hole? And how large would that mirror have to be?
|
[
"\"Ball-lightning\" is just a name here, not saying that the weather phenomenon is related to black holes."
] |
[
"Doesn't ball lightning last for more than a nanosecond? Wouldn't a black hole of such tiny mass evaporate so quickly it'd be nothing more than a burst of energy radiating out? "
] |
[
"Doesn't ball lightning last for more than a nanosecond? Wouldn't a black hole of such tiny mass evaporate so quickly it'd be nothing more than a burst of energy radiating out? "
] |
[
"If we sent a probe into space away from earth at the speed of light, would it be able to transmit data back to us?"
] |
[
false
] | null |
[
"You can't accelerate an object with a non-zero rest-mass to the speed of light as this would violate special relativity. You can, however, accelerate the probe arbitrarily close to the speed, in which case it would still be able to transmit data just fine, although the time it would experience would be much slower than the passage of time on Earth due to ",
"time dilation",
" (i.e. if the spacecraft were designed to emit a signal every hour, then once it is at a speed close to the speed of light, an observer on Earth would only receive the signal with a time separation of say years). "
] |
[
"another problem would be the red shift if the probe was going at clsoe to the speed of light. At some point the wavelength would be too large to be detectable anymore."
] |
[
"IF you could get a spacecraft to 1c, ",
"Then anything you like could happen. You can't answer a question with our current understanding of physics if you start with an assumption that violates that understanding."
] |
[
"(This question is bathed in ignorance): The speed of sound of an object?"
] |
[
false
] |
Forgive me for not having the original thread available to reference, but the question posed to was something about setting gears up around the planet and how long it would take for a rotation to reach the other side. The general assumption is that it is instantaneous; however it in fact was not and had to do with the "speed of sound" of the material being used. One of the analogies in the response was using a stick, having one end held by someone on earth and the other end being held on the moon. When earth tugs on the stick, moon doesn't feel it for a few moments, the length of time being dependent on the "speed of sound" of the material. I thought this was amazing and shared this with my boss today at work, who then asks, "How can they prove that?" Now, I trust a proper physicist to understand that theory behind such a response must be pretty sound to be perpetuating it, so I never looked in to it prior to his asking and promised to come back with something next week. So I suppose the tl:dr is: Thank you.
|
[
"1) What is the \"speed of sound\" of an object?",
"The speed of sound ",
" an object is just the speed at which disturbances travel. The air is an object, the speed of sound in air is about 340m/s. In other objects it is different.",
"2) What theories or hypothesis are used to come to this conclusion?",
"A variety of theories can be used to work out the speed of sound in an object, depending on whether it is a gas, liquid, solid etc. There's a good outline ",
"here",
"3) What experiments can be or have been done to prove this conclusion? (Not necessarily something I or he can try; a reference is fine)",
"I'm not quite sure what you mean here. Are you asking how we have verified that different objects transmit sound at different speeds?"
] |
[
"For Q3, the aforelinked wikipedia has a good summary on methods for measuring the speed of sounds in solids and gases."
] |
[
"Were you thinking of ",
"this post",
"?"
] |
[
"Can stars exist outside of galaxies and still be visible from Earth?"
] |
[
false
] |
Are there any known stars that are: a) bright enough to be seen from or near Earth with any kind of equipment; b) outside of the Milky Way Galaxy; and c) known to not "belong" to another galaxy or are in transit between two? How prevalent are these stars (if they have been observed)? If they haven't been observed are they theoretically possible/likely? Thanks.
|
[
"I searched this subreddit for \"stars\" and perused all the askscience posts that came up from the last month and didn't find any similar questions. If anyone else can bring a similar thread to my attention I'll try and delete mine. Thanks for the notice."
] |
[
"I searched this subreddit for \"stars\" and perused all the askscience posts that came up from the last month and didn't find any similar questions. If anyone else can bring a similar thread to my attention I'll try and delete mine. Thanks for the notice."
] |
[
"Thanks MathGrunt, I'll remember that!"
] |
[
"Using only Bronze Age technology, how would you charge a mobile phone?"
] |
[
false
] | null |
[
"Using acidic fruit wouldn't work. While you can get a volt or two from a lemon or potato, the amperage is essentially nil. "
] |
[
"My thinking was you might be able to make a battery with lemons or potatoes (depending on where you land) in series with copper and tin/zinc electrodes, strung to the charger by copper filaments. If acidic foods are not available, maybe a galvanic cell of sea water with copper and tin/zinc electrodes?",
"Then what? I suppose introduce agricultural technology and metallurgy, language and writing? However it goes in Civilization, I suppose."
] |
[
"Hmm, so maybe a wet battery is in order. I wonder how many orchards of lemons would be necessary for the necessary current."
] |
[
"What does /r/askscience think of the Gaia Hypothesis?"
] |
[
false
] |
What is your opinion of the ? The Gaia hypothesis, also known as Gaia theory or Gaia principle, proposes that all organisms and their inorganic surroundings on Earth are closely integrated to form a single and self-regulating complex system, maintaining the conditions for life on the planet. ...The Gaia theory posits that the Earth is a self-regulating complex system involving the biosphere, the atmosphere, the hydrospheres and the pedosphere, tightly coupled as an evolving system. The theory sustains that this system as a whole, called Gaia, seeks a physical and chemical environment optimal for contemporary life.
|
[
"pedosphere",
"I had to google it, it just means the part of the Earth that's made of soil."
] |
[
"As far as I know — and I know only what I've been told — there are actually two.",
"One is too trivial to deserve the name \"hypothesis.\" It just says that a large, complex system like the Earth will oscillate naturally around some sort of equilibrium state. This is of course true … right up to the point where it's not.",
"The other idea of the same name is that the Earth, taken as a whole, ",
" This strikes me as being a particularly useless idea."
] |
[
"It does have a lot of unnecessary \"junk\" in it (and I was dismissive towards it before I started interacting with atmospheric science professors). But on the other hand - it's actually ",
" in its simplicity. It's even included in several atmospheric science textbooks because it wonderfully (and simply) describes the nature of albedo feedback cycles on Earth - particularly the carbon-silicate feedback cycle (if you increase the solar insolation, the temperature ",
" stay constant for as you increase it UP to a certain point due to feedback processes - this follows our predictions for the evolution of Earth's average temperature over the last billion years - with some modifications of course - since Earth hasn't gotten warmer even when the solar luminosity evolved from 94% of its present value to 100% of its present value)"
] |
[
"If light is both a wave and a particle, are distant stars' light particles affected by gravity of the galaxies they pass by on their way to us?"
] |
[
false
] |
Does this bend the light of distant stars so they may not actually be where we perceive them to be?
|
[
"Yes! This is more of a general relativity thing than a quantum mechanical thing, but still it's true. This effect was the source of the first evidence in favor of general relativity (a certain star was at a different position in the sky during a solar eclipse because the sun deflected the star's light), and a form of this effect called ",
" (which I recommend looking up) is used to measure the mass of large objects, and to study extremely distant objects like quasars.",
" to answer the rest of your question, stars in our own galaxy are, for the most part, exactly where it looks like they are. Gravitational lensing which we can observe is mostly in the context of very distant objects being lensed by something very massive like a galaxy or a star cluster."
] |
[
"Wow thanks! The wiki on gravitational lensing is exactly what I was wondering. It makes you feel so small... in a good way."
] |
[
"It makes you feel so small... in a good way.",
"I know what you mean. At those times I like to read up on subatomic particles to make myself feel really big! "
] |
[
"How come light travels \"in one direction\" in transparent materials?"
] |
[
false
] |
During high school physics I seem to remember being told light travels slower in materials such as air than in vacuum because the photons keep getting absorbed (forcing an electron to increase its energy level) and then transmitted (returning the electron to a lower energy level) again after a brief period of time. My question is why the transmitted photon has the same (or almost the same) direction, in transparent materials.
|
[
"Feynman's QED lecture",
" focuses a lot on this. You're asking an important question.",
"The short answer is: photons are continually being absorbed and reemitted by atoms in the medium. They're emitted in ",
" directions, but amazingly, ",
", the photons tend to cancel out in all directions except for a very narrow range. This is the \"direction of propagation\"."
] |
[
"But photons still do travel in other directions. ",
"Consider this image",
". It's a photograph showing the total internal reflection of light. As you can see, the laser is reflecting within the material and traveling in straight lines. But the camera still captures the image, showing that a significant number of photons do travel around and deviate from that path.",
"So, yes, the strongest or most intense beam travels in one direction, but a great number of photons still travel out in all directions, thus allowing us to view phenomena as shown in the image."
] |
[
"Layperson here. I'll give some simple answers and let the experts expound on it if desired.",
"In response to your first point, absorbed photons are converted to heat. That's why black surfaces get hotter than white ones when exposed to the same amount of sunlight.",
"In response to your second point, some materials are transparent to high energy photons which are opaque at optical wavelengths. This is why we can image our skeletons using x-rays. The x-rays used for imaging have enough energy to pass through our soft tissues, but not enough to pass through bones, so the images you see on an x-ray film are essentially the shadows of your bones."
] |
[
"Is there an organism whose genetic material lacks one of the four bases?"
] |
[
false
] |
I was once told about an organism (or virus, if you don't consider them organisms) whose main genetic material used only three of the four bases. I can't remember if the genetic material was DNA or RNA, but I assume it was single-stranded, logically. I believe that when he told me about this, he said that the organism had plasmids that contained the missing base, and that this was spliced into the main genetic material as needed. So ... WTF? Does this thing exist? If so, what's it called? I can't find anything about it.
|
[
"watch out, that research is highly controversial:",
"http://www.physorg.com/news/2010-12-critics-nasa-arsenic-bacteria.html"
] |
[
"I've taken quite a few genetics classes, and I've never heard of it either. Google isn't helping, so here are some things that might help you decide whether to believe it or not.",
"If it is a virus whose genome has been split into several sections (\"plastids\") then it's likely an RNA virus. Some have extremely small genomes - just a few thousand bases which code for <10 proteins. Still, I'm not aware of a single protein, let alone an essential one that doesn't require several amino acids, and that's a problem here.",
"If it's missing a Uracil or an Adenine, then it isn't possible to have a stop codon. I'm pretty sure that means those virus' aren't viable. If it's missing a Cytosine, then the amino acids S, P, L, A, N, T, H aren't possible (yes, I did arrange them to spell that). If it's missing a Guanine, then D, W, C, G, R, A, V, E, S are out. Those comprise a pretty huge swath of amino acids. It seems impossible. But what if it somehow \"splices them in as needed\"?",
"At first I thought that was total BS, but then I remembered that viruses do have recombinases that could conceivably pull this off. ",
"So I'd have to say extremely unlikely but perhaps just barely possible. "
] |
[
"Just to point out, if it was missing 1 base, it would probably be missing 2. Pairs generally only bond to their \"opposite.\" This would result in only a few possible amino acids being made, fewer than is required for life."
] |
[
"How much alcohol would an average 6ft tall 185Ib male have to consume to die?"
] |
[
false
] | null |
[
"There's something called the \"LD50 value\", which is how much of something you can drink before you have a 50/50 chance of dying from it. For alcohol, it's about 5-8 g per kilogram of human weight. For 185 lb (= 84 kg), that's about 420-670 g of pure ethanol. Basically, an entire pint of pure ethanol.",
"So if you had something that was 10% alcohol (lower end for wine), you'd need to drink 10 pints of it in a short period of time to have a 50/50 chance of death. For something that's 5% alcohol (lower end for beer), you'd need to rapidly drink 20 pints."
] |
[
"Tiny change. LD50 refers to the dosage of a chemical that kills (lethal dose) 50% of the test animals and it's scaled up by weight. It doesn't necessarily relate to probability of it killing a human, that's just a guess."
] |
[
"Thats 2 x 4 x 3 = 24 shots btw. That is a lot of shots for one party for most people"
] |
[
"How does VLF radio \"push out\" the Van Allen belts?"
] |
[
false
] |
I just read but I don't understand exactly what's going on. Are the VLF waves actually "pushing on" particles in the radiation belt? Is there some sort of "magnetic bubble" or something going on?
|
[
"So I've read the papers directly related to this research (",
"here",
" and ",
"here",
" - they're probably paywalled, sorry), and to answer your question, no, the VLF waves are not actually \"pushing\" on the particles.",
"As I understand it, what is happening is that the \"bubble\" of VLF waves form a region in which ultra-relativistic electrons (i.e. several MeV) are very easily scattered into the Earth's ionosphere, where they lose all their energy and are \"lost\" from the radiation belts. These particles only travel inwards slowly, so the scattering ensures that they are never around long enough to build up any significant population.",
"I will note that this is all still very recent research, so bear in mind our understanding may change as we learn more and more about the radiation belts."
] |
[
"Actually, having done some reading, this really isn't \"new\" science at all. The idea of man-made VLF waves causing scattering of electrons has been hypothesised since the early 80s, but until recently it was though to be contained to energies <500 keV. All that has happened recently it that the Van Allen Probes have given us very strong evidence to suggest that VLF waves can, in fact, scatter ultra-relativistic electrons.",
"To answer your questions:",
"I guess you could think of the electrons as being eaten, though it's closer to the truth to say that they're being thrown into the ionosphere.",
"As to your second question, I have to point out that your link is a little misleading - the top of the VLF region doesn't correspond to the bottom of the VA belts (that's significantly lower). Regardless...",
"You'd think the wave power would drop of to the inverse square, but the problem is that we're dealing with electromagnetic waves in plasma, which is much more complicated than waves in a vacuum. The short answer is that as the VLF waves get further out, they approach a sort of resonance with the radiation belt plasma, and get absorbed.",
"it's interesting that you mention the bouncing off the ionosphere, actually, because that's exactly what the VLF waves are intended to do. The VLF waves we see in the radiation belts are more of a side-effect due to \"leaking\" of the waves through the ionosphere."
] |
[
"Thanks for answering! (Those articles are totally paywalled, but thanks for the links.)",
"So the VLF sort of \"eats\" the Van Allen belt because the electrons in the VLF-affected region are removed from the belt?",
"The link in my original question suggests that the top of the VLF region corresponds to the bottom of the VA belts. The fact there's there's a top to the VLF region at all surprises me. Shouldn't it fall off as inverse-square? Or do you suppose that the VLF is being reflecting off the VA belts similar to how HF radio propagates over the horizon by bouncing off the ionosphere?",
"I understand this is fairly new science, and you may not have a meaningful answer. Thanks all the same!"
] |
[
"Mixing Helium and Hydrogen for balloons?"
] |
[
false
] |
As far as I can understand Hydrogen is better for balloons than Helium because Hydrogen gives more lift and is cheaper than Helium. But Hydrogen is pretty explosive so that's why we don't use it anymore? Helium on the other hand is a noble gas so it dosen't explode or even react with fire. But would it be possible to mix the to gases to get a mixture that is cheaper than 100% Helium but without the exploding hazard of 100% Hydrogen? The extra Hydrogen would lower the cost and add lift power to a balloon. Like 50% Helium and 50% Hydrogen? Or perhaps this is already done?
|
[
"Part of the problem in what you're suggesting is answered in your understanding of noble gases. As Helium is such, it won't bond or interact with Hydrogen in any real way. ",
"The poster was not suggesting anything that implied any such thing either.",
"What you'll end up with is a balloon which over time becomes \"layered\", with lighter hydrogen occupying the upper portion of the balloon, and heavier Helium settling more-or-less around the bottom.",
"No. Thermal motion at ordinary temperatures is easily able to keep two so light gases mixed.",
"This might be a feasible scenario, if it was found that the main risk of explosion came from the passenger compartment",
"Balloons don't have passenger compartments. Maybe you're thinking of zeppelins or something, but when people talk about helium balloons they usually mean the kind you have at parties, not the USS Macon."
] |
[
"Pure hydrogen doesn't explode; as with (most) other flammable gases, you need a ",
" of air (or just oxygen) and the gas to get an explosion. A balloon filled with pure hydrogen will burn quickly and rather violently in air, but not explode the way it'd do with a mixture. ",
"What's known as the upper and lower explosive limits tells you what percentage (by volume) of a gas you need mixed in with air to get an explosion. For hydrogen the explosive limits are 4-75%. ",
"Anyway with no oxygen and nothing to react with the hydrogen won't explode then. But it will still burn, so the're still a significant danger there, and you're not really that much better off diluting the hydrogen with helium than having just pure hydrogen."
] |
[
"What you'll end up with is a balloon which over time becomes \"layered\", with lighter hydrogen occupying the upper portion of the balloon, and heavier Helium settling more-or-less around the bottom.",
"I don't think this follows. Mixtures of gases do not spontaneously separate in general because of a difference in molecular weight, because entropy of the mixed state is much higher. The theoretical energetic loss because of gravitational settling would not offset. This is why nitrogen and oxygen never separate in air."
] |
[
"Why does pressure decrease as velocity decreases?"
] |
[
false
] |
Using the equation A1 v2, we know that velocity and Area are inversely related. Using the pressure equation, we can say A = F/P. We can then say (F1/P1) v2. Shouldn't velocity and pressure be directly related?
|
[
"In your approach you ended up introducing the force acting on the fluid at each cross section of the pipe, which is a number you don't know.",
"Instead, let's look at the more general equation for incompressible fluid flow - Bernoulli's equation.",
"1/2 ρ v^2 + ρ g h + P = constant\n",
"where ρ is the fluid density, v is the flow speed, g is gravity, h is the height of the fluid, and P is the pressure. ",
"This equation looks really similar to a statement of conversation of energy (1/2 m v",
" + m g h = constant) but with mass replaced by density. Bernoulli's principle is basically conservation of energy but for fluids, with an additional term 'pressure.' You can almost think of pressure like an 'internal energy' of the fluid - in fact, if you multiply pressure by volume you get units of energy. In this sense, pressure is like an 'energy density,' similar to how we're using ρ to talk about the mass density of the fluid. ",
"So what does this mean? Since you know Bernoulli's equation is equal to a constant, you can write: ",
"1/2 ρ v1^2 + ρ g h1 + P1 = 1/2 ρ v2^2 + ρ g h2 + P2\n",
"thus allowing you to relate the behavior of the fluid at one point in your system to another. Now let's suppose you have a horizontal pipe. In this pipe, h1=h2, so we can cancel that gravity term ",
"1/2 ρ v1^2 + P1 = 1/2 ρ v2^2 + P2\n",
"Now, suppose the pipe gets narrower between point 1 and point 2. Given the continuity equation (A1 v1 = A2 v2) we know that v2 must be bigger than v1. This just means the fluid flows faster in the narrow pipe. ",
"Now, returning to Bernoulli's equation, you'll notice that if v2 is bigger than v1, then (1/2 ρ v2",
") is bigger than (1/2 ρ v1",
") - if the 'kinetic energy' term is bigger at point 2, then in order for both sides of the equation to be equal you'll have to find that P1 is bigger than P2. Effectively, this means that pressure and velocity are inversely related. In order for your fluid to speed up, the pressure must decrease. ",
"This brings us back to the conservation of energy interpretation of Bernoulli's equation. Energy just changes forms, it's not created or lost. So you can think of pressure almost like a reservoir of energy for changing the speed of the fluid. In order to increase the speed of the fluid you have to decrease the pressure a bit. Conversely, if you want to slow a fluid, that energy won't be lost, it will just become an increased pressure. "
] |
[
"As for your title, velocity decreases as pressure increases. ",
"The other explanation with bernoullis law is correct. You can look at it as converting energy stored as pressure to kinetic energy and vice versa.",
"Intuitively, what will increase pressure? Impeding the flow of a fluid which decreases the velocity. "
] |
[
"Also gotta point out difference between total pressure and static / dynamic pressure. Total pressure would be more equivalent to the energy density comparison you made and is the addition of static and dynamic pressure. So if your pipe diameter decreases, your velocity increases, which causes a drop in static pressure with an increase in dynamic pressure. ",
"(EDIT: dynamic pressure, q, is q=1/2(rho)v",
" , which is sort of the \"kinetic energy\" part of the equation. As pointed out below static pressure is what you would feel as if you were moving within the airstream so the air is \"static\" or not moving relative to you; total pressure is what you would feel if all that air came to a compete stop on your hand or abdomen or whatever as it has that added momentum.)",
"Now if you increase your diameter back to the original size, your velocity will drop to where it was, however static pressure will be slightly less than it was. This is due to entropy and the irreversible nature of the process; total pressure always decreases as energy is lost due to friction in the pipe boundary layers. "
] |
[
"When I'm on an airplane and I look straight ahead during takeoff or landing, I feel like I can see that the plane is pointed up or down. Can I really, or does my brain just extrapolate based on other information to create this illusion?"
] |
[
false
] |
My relative position in the plane stays the same in takeoff or landing, so why am I able to see that we are pointed up or down when I'm just looking straight ahead?
|
[
"You can do this, but not with great accuracy.",
"Your visual perception is certainly affected by gravity, which like other accelerations, acts upon the vestibular organs in your inner ears.",
"We have a very fast neuron arc from these sensors to the neural circuitry that controls eye movements. Here's a simplified outline that may describe your scenario: Nose of the plane rises (which you also notice with sensory modalities other than vision), you tilt your head forward to compensate (probably incompletely). To keep your gaze on the thing you were looking straight ahead at, your eyes automatically elevate by the same amount. You now feel like you are looking upwards, and this can affect your perception of location in rotational threespace.",
"As to my opening comment about accuracy, this is not an ability you would ever want to have to bet your life on. This is why pilots have an artificial horizon instrument; there are endless cases (NTSB accident reports) about pilots who chose to believe their ears and eyes rather than an objective measurement."
] |
[
"On that last point. Pilots are trained to trust their instruments absolutely, if they are unsure of their attitude at night or in bad weather.",
"Your senses can very easily be confused or deceived. This ends up with a pilot thinking he's pointed up, down, or in a bank, when he is in fact doing none of those things. The reverse is also possible.",
"If at this point, the pilot ignores his instruments, which would tell him his actual attitude, and relies on his flawed sensory inputs, he can very easily take a safely flying airplane and place it in a very dangerous position. He could exacerbate a gentle climb and stall the plane, initiate a dive into the ground in an attempt to counter a perceived climb, or he could roll the plane significantly in order to cancel out a perceived roll. All of these maneuvers can, if continued for long enough, cause a plane to stop flying.",
"Looking down at the artificial horizon in the cockpit will give a pilot a visual reference point that displays the planes attitude and allows the pilot to safely fly the plane, even if he was disoriented. The artificial horizon also allows the brain to recalibrate itself and helps the brain to ignore false sensory inputs. "
] |
[
"This happened to me during pilot training. Your inner ear can \"reset\" to a non-level attitude so that it treats it as though it were level. You then perceive yaw, pitch, and roll based on this internal idea of \"level.\" I would have bet any amount of money my instruments were lying to me. Good thing I was with an instructor."
] |
[
"Is it possible to create a device similar to an electronic device that uses photons instead of electrons?"
] |
[
false
] | null |
[
"Yes! Photonic and optical devices are increasingly used in place of electronic devices. Light has particular advantages when it comes to transmitting information, creating 'high quality' resonators, or interacting on a quantum level. ",
"Some examples:",
"fiber optics",
"Silicon-based optical waveguides",
"quantum computers",
"optical gyroscopes",
"protein detectors for medical diagnostics",
"a lot",
"",
"You're less likely to see an optical device that say, drives a motor, or a heater, as it's typically much more efficient to do these applications with electronics. But there ",
" mechano-optical devices, like ",
"optical tweezers",
". "
] |
[
"Yes, and people are. The biggest roadblock, in my view, is a lack of photonic memory at the moment. Storage times on the order of milliseconds are state of the art in a photonic integrated circuit.",
"Also shameless plug for my sub that is dedicated to this topic ",
"/r/siliconphotonics"
] |
[
"The most fundamental part of electronic devices is a transistor, essentially a small device that can be switched from conducting to insulating. There have been demonstrations that this can also be done for light: One beam either goes through or not, depending on whether the other beam is on. But I imagine you see at this point why a transistor for light is much harder to build than one for electrons. Two electrons will interact, but two photons will not. You have to make a significant additional effort with special materials and quantum tricks to make it work. "
] |
[
"Does a fish ever see it's tail?"
] |
[
false
] |
Settle a dispute my friend and I are having. And we're talking about a standard fish here, nothing fancy. I'm pretty sure they can, because their eyes are on the sides of their heads, but he's saying that their peripherals, are not as good as I am thinking. Thanks and much love ( :-*)
|
[
"Unfortunately, I can't seem to find any direct report of whether fish can see their tails but we can still try and figure it out.",
"The most convincing evidence of fish-seeing-own-tail is this ",
"video of a betta fish biting its own tail",
". At times the tail is covering the eye and therefore must be perceived by it. However, I wasn't sure if betta's fell under the category \"standard fish\" or not, so I continued my search. ",
"From the tail biting video we learn that there are two factors at play here, 1) the visual abilities of the fish and 2) the flexibility of the fish. Even if the fish has a very small field of view, it could see its own tail if it was flexible enough. ",
"This image shows a fish's field of vision",
" ",
"(Source)",
". The site states that fish have 330 degrees of peripheral vision (and 30 degrees of binocular vision) ",
"(Additional source for field of view)",
". It is now clear that if our fish is facing straight forward it will not be able to see its own tail.",
"A fish can see 165 degrees to each side (330/2) and its tail natural rests 180 degrees away. So if a fish can bend its tail more than 15 degrees (180-165) it should be able to see it's own tail. First let's see some visual aids: ",
"Goldfish bend",
", ",
"trout bend 1",
", and ",
"trout bend 2",
". I'd certainly estimate that these fish are bending more than 15 degrees but its hard to measure angles from a picture. However, I did find a study that tracked the tail angle of blind cave fish approaching walls. ",
"This figure",
" shows that the fish bent their tails up to 20 degrees in order to avoid the wall ",
"(full article)",
". We can now conclude that fish can likely see their own tails, if they bend their bodies first (presuming that cave fish are not unusually flexible). [EDIT: Thanks to ",
"/u/atomfullerene",
"'s comment below, we can be certain that most fish can bend into a C-shape]",
" Fish cannot see their own tails while looking straight ahead but if they bend their tails they can likely see them."
] |
[
"A fish doing a ",
"c-start",
" (which is something nearly every fish can do as an escape response) would definitely be bending more than 15 degrees and therefore would likely be able to see its tail."
] |
[
"AH thank you! I knew fish could absolutely bend their tails quite a bit but I couldn't find any info about it beyond pictures of fish. Searching \"c shape\" gave me nothing useful, but \"c-start\" is exactly what I needed! ",
"This article",
" states that they can bend almost 180 degrees!"
] |
[
"If the surrounding temperature is higher than a surface's temperature, does radiation occur ?"
] |
[
false
] |
I know that q_rad = C*(T_s -T_surr ), but I'm not sure about what happens if the object's temperature is lower than the surrounding temperature, is it considered irradiation in this case ?? meaning that heat transfers into the object ?
|
[
"That equation is about the ",
" radiation from a surface. If the right side is positive, the surface has more radiation leaving it than it is absorbing. If it is negative, there is more radiation being absorbed than emitted. In the negative case, there is still radiation leaving the surface in the form of photons leaving, there's just more energy inbound.",
"If there was no outbound radiation at all, then, for example, you would not be able to see an icecube in a warm room, and a hot stovetop in a dark but very hot room would not glow red."
] |
[
"you would not be able to see an icecube in a warm room",
"Is reflection the same principle as radiation?"
] |
[
"Radiation = beam of photons. You're right that in principle, photons are not reflected, but a lot of times, the scattering theory describes physical phenomena very well, so it's often described like that.",
"On the main topic: Every (real) object emits thermal radiation. If two objects are the same temperature close to each other, object 1 emits the same amount of radiation as object 2 and both absorb each others radiation. That's what is called equilibrium.",
"Edit: Spelling"
] |
[
"How do spacecraft/rovers/space probes communicate back to earth from such long distances?"
] |
[
false
] | null |
[
"On the far ends, they have a low power (20w) radio transmitter with a highly directional antenna pointed at Earth. At this end we have very sensitive radio receivers connected to HUGE and highly directional radio antennae pointed back at the spacecraft. Transmissions from Earth to the spacecraft are sent at a much greater power level."
] |
[
"In case of rovers and landers, they use orbiting satellites as relays (for example Mars rovers communicate directly to orbiters and then orbiter sends data back to Earth)"
] |
[
"It's probably also worth pointing out that the transmission datarates are also extremely slow by our modern terrestrial standards, which improves the signal-to-noise ratio dramatically. New Horizons now transmits at less than 1 kbps at its current distance.",
"EDIT: ",
"Here's a lovely picture of one of the enormous directional antennae we use to communicate with probes in deep space",
".",
"EDIT II: ",
"The guy with the DSN photo apparently has a ton of other cool astrophotos as well."
] |
[
"Hot water and the urge to urinate: What's the deal?"
] |
[
false
] | null |
[
"If I assume by your question that you mean the \"hand in warm water\" trick or something similar, then I couldn't really find a valid answer to the question, or any literature associated with it. ",
"Immersion diuresis",
" is the closest thing I could find relating to the phenomenon, but it involves full submersion in colder temps and not what your question asks.",
"I could hazard a guess and say that the warmer water relaxes the muscles that controls the passage of urine from bladder to urethra, but it would be purely speculative."
] |
[
"I would also speculate that it has to do with warm water inducing muscle relaxation, specifically of the pelvic floor, which is a precursor to urination."
] |
[
"Not a totally scientific answer, but Mythbusters have tried it and have called it Busted. You don't get the urge to pee, at least while sleeping, if they submerge your hand in warm water."
] |
[
"How does matter \"remember\" that it is moving a direction after an initial force is applied to it?"
] |
[
false
] | null |
[
"Momentum is conserved."
] |
[
"Where? So to speak. "
] |
[
"Everywhere, all the time. Whatever momentum an object has in one instant of time will be the same in the next instant of time, if there is no net external force acting on the object.",
"If there is an external force ",
" acting on the object, and its momentum at time t is ",
"(t), then in the next instant of time, the momentum will be ",
"(t + Δt) = ",
"(t) + ",
"Δt, assuming Δt is small."
] |
[
"Do sleep walkers still get the same, sufficient amount of recuperation as if they slept soundly?"
] |
[
false
] |
After watching the reaction video of the mother who was treated to a video of herself sleepwalking (for what I assume is the first time), I was curious if the brain can still recuperate as efficiently when someone is sleepwalking as if they had slept soundly.
|
[
"No, sleep walkers generally walk during the SWS (slow wave sleep) phase of rest and require a higher level of consciousness than is typically seen during REM (rapid eye movement) because their brain is partially engaged during the walk.",
"But, this varies depending on the complexity and length of the sleep walk. Sleep walking can be as short lived as 30 seconds or as lengthy as 30 minutes. ",
"Given a sleepwalker with a complex walk (such as walking about the house and re-arranging things) and lengthy walk (30 minutes), their brain may miss the benefits of an entire REM cycle and feel as if they have slept for 1.5 hours less than a non-walker. ",
"On the opposite end of the spectrum, a sleep walker that sits up on their bed for 30 seconds may not feel any different than any other non-walking night.",
"So, the answer is no sleepwalkers do not get the same amount of rest as compared to a night where they sleep soundly, but it really depends.",
": Misread the question.",
": Yes, there are no empirical facts here but it is well-understood that a lengthy interruption of REM sleep (being the most vital cycle in feeling well-rested) will cause the individual to feel lethargic the next day. This can safely be inferred. But, as to some of the shorter sleep walks it would be scientifically responsible to map the brain waves of the sleepwalker and determine if the short walks cause enough interruption to interfere with sleep cycles in any meaningful way.",
"The point is, lengthy sleep walks are very likely to cause the sleepwalker to feel the effects of the interrupted sleep the next day. "
] |
[
"That said, would lucid dreamers then have a similar amount of recuperation as a normal person?"
] |
[
"Lucid dreaming is somewhat of a misnomer and a contradiction. ",
"So, lucid dreaming wave patterns (higher concentrations of beta frequency band: 13-19 Hz) interrupt the predominant wave patterns of REM sleep (higher concentrations of delta frequency band: 0.5-2 Hz) and effectively remove the sleeper from strict REM. The dorsolateral prefrontal cortex, which is inactive during REM, is reengaged during lucid dreaming and allows the sleeper to realize they are asleep and dreaming.",
"While the mind can continue dreaming, the dreamer becomes aware. It is a point of contention as to whether or not the dreamer becomes capable of \"guiding\" the direction of a dream upon awareness. This is in effect, lucid dreaming. While it is a well-established niche of parasomnia, it is very different from the REM segment of the sleep cycle that provides the feeling of recuperation.",
"The answer is ",
", lucid dreamers would not have a similar amount of recuperation to a normal sleeper/dreamer, certainly not if they were exhibiting high concentrations of beta frequency during the period of sleep when they should be exhibiting high concentrations of delta frequency in the full cycle.",
"Edit: Spelling and clarification."
] |
[
"How valid is the Myers-Briggs Type Indicator?"
] |
[
false
] |
I'm also not sure if this is a proper question for askscience, but I didn't know where else to go. is this test an accurate determination of a person's psychology profile? If not, what makes it inaccurate or wrong? In anecdote, I've always found that this test can accurately describe myself and close friends I've had take it, without being purposely vague or broad/generalized.
|
[
"Pretty much bunk.",
"See:",
"Key passages:",
"\"The test does have some severe inherent problems. It's been found that 50% of test takers who retake it score differently the second time.\"",
"\"From the perspective of statistical analysis, the MBTI's fundamental premise is flawed. According to Myers & Briggs, each person is either an introvert or an extravert. Within each group we would expect to see a bell curve showing the distribution of extraversion within the extraverts group, and introversion within the introverts. If the MBTI approach is valid, we should expect to see two separate bell curves along the introversion/extraversion spectrum, making it valid for Myers & Briggs to decide there are two groups into which people fit. But data have shown that people do not clump into two separately identifiable curves; they clump into a single bell curve, with extreme introverts and extreme extraverts forming the long tails of the curve, and most people gathered somewhere in the middle\"",
"\"From reviewing the literature, I do find one common theme among mainstream psychotherapists where the use of the MBTI is advised, and that's as a conversation starter. It's a fine way to give people a quick snapshot of what their strengths and weaknesses might be, and of those with whom they interact. To get the dialog going, this is a perfectly valid tool. But as a tool for making career decisions, relationship decisions, or psychiatric assessment, no. \""
] |
[
"Some researchers have interpreted the reliability of the test as being low. Studies have found that between 39% and 76% of those tested fall into different types upon retesting some weeks or years later.",
"So, perhaps not very accurate."
] |
[
"Personality does change a little over the course of your life, and more so when you're younger, but a high number like 83% would be entirely inconsistent with what we know about people. This would mean that people were constantly having significant personality overhauls, and we know that this isn't true.",
"However, this isn't what the paragraph above is referring to. It's discussing a statistical test known as \"factor analysis\", which (to put it very simply) is a test that attempts to identify a number of variables that explain the data. For example, if we have data points that indicate that people who respond \"yes\" to questions like \"Do you prefer your own company over being in groups of people?\", \"Do you feel drained after hanging out in crowds?\", \"Do you sometimes feel overwhelmed in social situations?\", etc etc, are all grouped together on a variable, we could label that variable \"introversion\". ",
"What psychometric tests do is to find all of the major variables and try to use them to predict the future behavior and outcomes of people who score in a certain way on those variables. What the result you've described above is suggesting though, is that the \"personality types\" described by the MBTI (I-E, S-N, T-F, J-P) only account for 17% of the data. In simple terms, I guess you could say that it tells us practically nothing about the vast majority of our personality.",
"In a more practical sense, what this means is that knowing that someone is \"intuitive\" (according to the MBTI) is not very helpful at all, as it only accounts for such a small aspect of our personality and is unlikely to be very predictive at all."
] |
[
"Is there a difference between Cytotoxic T cells (killer T cells) and Natural Killer (NK cells)"
] |
[
false
] |
I know they are both WBC's but are they different types of lymphocytes?
|
[
"NK cells are an interesting part of microbiology. To put it simply:",
"Cytotoxic T cells recognize a major histocompatibility (MHC) I complex which contains foreign protein fragments on the surface of the cell using a TCR on a T-cell's surface. The foreign protein has been digested and broken down within the affected cell. When a foreign protein is detected, cytotoxic T-cells release granules of perforins that cause apoptosis (basically little packets of things that cause the cell to kill itself).",
"NK cells are an interesting cell, as they don't quite fit in innate (non-learned) or acquired (learned) immunity, but for all intensive purposes, we'll place them within innate for now. NK cells do NOT need to have prior exposure to an \"antigen\" (or foreign fragment), do not exhibit memory, and do not undergo clonal expansion. They do not possess a TCR, and recognize their \"prey\" using a MHC receptor, which recognizes \"self\" receptors, as opposed to foreign ones. They also have \"stress receptors\" that look for certain \"stress proteins\" on the surface of cells, indicating an issue. Should an issue be detected, granules are released. "
] |
[
"Actually there is a growing body of evidence indicating that NK cells may in fact form memory populations ",
"1",
" ",
"2",
"."
] |
[
"This makes it super clear to me!! Thank you!"
] |
[
"What is different between Earth and Mars that gives Earth a Magnetic field, while Mars does not?"
] |
[
false
] | null |
[
"The molten semi-liquid core, made primarily of iron, for the most part. Mars's core is iron, but it is not in a liquid state, rather solid. It has to do with the fact that there is circulation, or \"rotation\" within it. That is mostly what generates a magnetic field, movement of a magnetic conductor."
] |
[
"The reason Earth's core is still liquid but the core of Mars isn't is that Earth's core is more massive, and so it still retains some of the heat from planetary formation and radioactive decay of heavy elements while Mars' core cooled off faster due to the planet's smaller size."
] |
[
"Both planets have a crustal magnetic field, roughly the same order of magnitude nT. The Mars crustal field is distributed around the south pole in a pretty interesting way. This implies there was a core field at some point in the past, since we don't think it was made by impacts.\n(Earth crustal field: ",
"http://geomag.org/models/MF6.html",
" )\n(Mars crustal field: ",
"http://www.planetary.org/blogs/emily-lakdawalla/2008/1710.html",
" )",
"For the core magnetic field, we assume that Mars has roughly the same structure as the Earth, with a crust, mantle, outer core, and inner core. We think the outer core is liquid (",
"http://www.jpl.nasa.gov/releases/2003/32.cfm",
") although we don't think its as large as Earth's outer core, and this result is still a bit debated. And its really the vigorous convection in Earth's liquid outer that gives Earth a magnetic field. If Mars' outer core is similarly convecting, but is much smaller, it would be much weaker. Or, if it is not convecting nearly as strongly as Earth's, that would also make a much weaker field. We don't really have constraints on which it could be. We're sending a mission in 2016 to try and determine just how large the internal layers are within Mars. (",
"http://www.dailygalaxy.com/my_weblog/2012/08/deep-probe-nasa-to-explore-mars-core-liquid-or-solid-.html",
") But in general we would expect somewhat less vigorous outer core convection because we think its cooler than the Earth."
] |
[
"What happened before the Big Bang?"
] |
[
false
] |
I'm relatively ill-educated in physics, but I'm interested in the topic. I was thinking about the Big Bang and realised that, whilst I knew that this event was acknowledged as the beginning of our universe, that I didn't know what occurred before it. So I ask, what happened before the Big Bang? Is there a scientific consensus as to the answer, or is any answer pure speculation? If this has been tackled previously then I apologise.
|
[
"the current accepted answer to that question is \"that question doesnt make sense.\" there was no \"before\" the big bang. Now some people beleive we live in a sinusoidal universe meaning before what we know as the universe was another universe that that crunched down to a point then big bang to our universe."
] |
[
"No, it's not beside the point. It ",
" the point. You've conflated \"north\" with \"up\" here, and you're imagining that moving north somehow is equivalent to increasing your altitude.",
"Cut that out. Stop thinking of the Earth as a ball hanging in space. Focus your attention solely on the ",
" of the Earth. We establish a set of coordinates such that one particular point becomes the \"north pole,\" and from any other point on the surface it's possible to move northwards. But when you get to the pole, \"northwards\" ceases to have any meaning. You can't continue moving northwards, because there isn't any more ",
" to move into.",
"It's not that anything is \"beyond your understanding.\" It's just that you're trying to think about it in the wrong way, and your brain — which is more clever than you seem to think it is — is throwing up a red flag and telling you you're not making any sense. Because you aren't, because your mental model is flawed."
] |
[
"Since our every experience is constrained to the constant of time, what happens outside of that isn't describable it a way we could understand or relate to.",
"No. This is completely the wrong way to look at it. You're thinking of it as something ineffable, mysterious, beyond comprehension. That's wrong. You're just trying to answer, for yourself, a question that ",
"What's 13,746,383 times 577,869,992,389.06?",
"You haven't the foggiest idea, nor do I. But because we both understand the fundamentals of how arithmetic works, we have no problem accepting that there's a single, sensible answer, even though we don't know what it is.",
"What's effervescence divided by the square root of tumbleweed?",
"That's not a question that \"isn't describable in a way we could understand or relate to.\" It's just gibberish! It's just a bunch of words strung together to form nonsense. And this fact troubles us not at all, because again, we both understand arithmetic, so we have no difficulty rejecting any arithmetical statement that's not in a valid form. Effervescence and tumbleweed aren't quantities, and they can't be operated on mathematically, and that's fine.",
"The phrase \"before the Big Bang\" is nonsense. It's words which — like \"effervescence\" and \"tumbleweed\" — are perfectly sensible on their own, but when you put them together in that order you get a phrase that's grammatically sound but semantically degenerate. The phrase ",
" has no meaning, and cannot be interpreted correctly.",
"This hurts your head to think about because you're trying to force your brain to assign meaning to meaningless statements. That's where your difficulty is coming from. It's not that you're trying to wrap your head around ",
" It's that you're feeding your brain gibberish, and it's balking."
] |
[
"I've heard it said that we should use hand sanitize less frequently because it encourages the evolution of sanitizer resistant super bacteria. Why is this not a concern with traditional hand washing?"
] |
[
false
] |
If both hand washing and hand sanitize get bacteria off of your hands (away from where they want to be), couldn't hand washing encourage the evolution of soap-and-water resistant bacteria?
|
[
"Traditional hand washing removes bacteria from your hands rather than attacking it chemically (unless you us anti-bacterial soap), so the bacteria does not develop the d same kind of defense. "
] |
[
"Is this actually a concern with proper hand sanitizers which are just ethanol and water with a little gelling agent? "
] |
[
"There are actually some bacteria which are more resistant to ethanol than others, probably due to a different cell wall structure. It's not clear whether or not ",
" are breeding resistant bacteria by using ethanol. Even if we are, it's probably still less of an issue than specific anti-bacterials. ",
"http://www.ncbi.nlm.nih.gov/pubmed/2178781"
] |
[
"[Chemistry] Is Cupric Sulfate + Methanol dangerous?"
] |
[
false
] |
I want to mix (I bought the type that is not anhydrous) with some methanol (Wikipedia says it dissolves). Cupric Sulfate is what they use in fireworks and flame tests to make green fire, so I am planning on filling a water gun with this solution and shooting it at a bonfire in a couple weeks. First, would this solution be toxic after it is burned up and would it be bad for the environment?
|
[
"Also worth noting that one of the problems with using alcohols in flame tests is that they burn and give off their own emissions, which can sometimes drown out the color you're trying to use. Methanol is better for this than ethanol, but water is clearly the better choice here."
] |
[
"Why do you want to mix it with methanol? If you're shooting at a flame, water would do just fine to change the flame colour. What you're trying to make is a flame-thrower - which is dangerous. Methanol may also be less spectacular than you think, since its flame is faint and burns quickly - the fact that it's faint may add more danger as well."
] |
[
"It'll even be better if you can modify the nozzle so it sprays a mist instead of a jet. Better yet, just use regular cleaner spray bottles. This way you won't accidentally kill the flame."
] |
[
"Are solar panels that are glass-faced (for protection) significantly less efficient at creating energy than bare panels because glass prevents the transmission of UV light?"
] |
[
false
] | null |
[
"One, only a small portion of the energy in sunlight is in the UV.",
"Two, photovoltaic cells work by turning one photon into one electron-hole pair. A photon with too little energy (too long a wavelength) will produce nothing. A photon with excess energy (a short wavelength) will \"waste\" that excess. Single-junction solar cells have the energy threshold (the band gap) \"tuned\" for maximum overall power, which further reduces the contribution of UV wavelengths to their power.",
"So while the glass will reduce solar panel efficiency, it will be a modest reduction.",
"Multi-junction solar cells, which have multiple layers with different band gaps, have higher overall efficiency and could get more energy from the short-wavelength radiation. They are currently more expensive on a power per dollar basis so they are primarily used where power per mass or power per area are more important, such as aerospace applications. Panels using such cells might well consider UV transmission in any facing material. (But even then, in principle a UV-opaque material that gives the required durability for low mass could give better Watts-per-kg than a UV-transparent material that needs to be more massive to meet the durability goals).",
"https://commons.wikimedia.org/wiki/File:Solar_spectrum_en.svg"
] |
[
"Good answer. Readers should note that in the linked spectrum, it's the red curve that's relevant--the atmosphere already reduces the UV significantly.",
"The spectrum there is available as a data file at ",
"https://www.nrel.gov/grid/solar-resource/spectra-am1.5.html",
" If you take 350 nm as the cutoff of glass (it varies with the type of glass but that's reasonably typical), and add up the energy in the spectrum for wavelengths 350 nm and shorter, it's only 1.8% of the spectrum. But in terms of number of photons (which is what matters as explained in the comment I'm replying to), the UV in that range is only 0.8%",
"Not only is there little to be gained by allowing more UV through, but there's also the ",
"potential for degradation",
" of the encapsulant material and/or the cells themselves."
] |
[
"Something that hasn't also been specifically mentioned is that the UV energy that is partially blocked by the glass also improves durability of PV modules.",
"While UV energy only a small portion of the overall energy, the large photon sizes make it the primary cause of polymer photodegradation. A slight reduction in efficiency can improve the overall efficiency over time by protecting components from that energy."
] |
[
"Would it be possible, given a person's prescription, to create an altered image that would appear normal to that person?"
] |
[
false
] |
[deleted]
|
[
"I was refraining from answering before because I'm not a full expert in the field, but I've got some experience, and given the other... not very helpful \"answers\" below, I'll give it a shot.",
"Blurriness from bad vision, while looking at a flat plane (computer monitor), is a convolution filter on an image (a gaussian blur in photoshop is another example of a convolution). I'm not sure exactly how your eye geometry works in that I'm not sure what your eyeball's defocus filter looks like (i.e. it's probably not a gaussian blur, it's probably not a box filter - it's probably closer to a defocus filter, but again, I'm not sure what that looks like mathematically).",
"I'm not sure how helpful this is, but it at least gives you a starting place to start a-googlin.",
"So, the inverse of convolution is deconvolution, you're essentially asking whether it's possible to find the deconvolution function to undo the blur that your eye does. I... believe convolutions are commutative, so it's identical to the \"real question\" of: can you find a convolution function to pre-apply to an image such that the eye's blur is that function's deconvolution. I definitely don't have the math background to tell you the full answer to that, but I would guess NO.",
"Certainly you cannot do it for the general case, for any image that a monitor could display. For example, a fully white screen with a fully black dot in the middle of it would be impossible to deconvolve so that your blurry vision made it sharp again, since you need some of your pixels to go darker than black and whiter than white. But if you added some constraints to the problem (for example, if your eyes aren't super super blurry, the image is very low contrast, etc.), perhaps it is possible to get close (or perfect?)",
"Really you need an mathy expert to help you out, but you can do some googling on \"deconvolution\" if you are interested."
] |
[
"Ok, my theory seems to not be incorrect. However the contrast achieved using this method is very limited since we can't have negative intensities.",
"http://i.imgur.com/3mIRy.png",
"For reference i first show the process of restoring a blurred image. The convolution kernel is a combination of a disk and a Gaussian. Note that this result is so good because I'm not introducing any noise other than rounding errors.",
"Then I show what the preprocessed image might look like. since it's initially complex valued I've taken out the real part and added an offset to fit as much as possible of it within the 0..1 range.",
"The reblurred image, this is what it might look like compared to the preprocessed image for someone with exactly the error in vision corresponding to the filter I used in the first step.",
"Since one could conceivably just use higher intensity monitor I show the result amplified. ",
"To see how sharp the reconstructed image actually is, I show the image fitted to the full visible range. Showing that the idea posed in the question is theoretically plausible.",
"In conclusion: ",
" that one could, with good enough technology, create an image that is actually sharper than expected at a certain focus distance. It would though, be very limited in contrast and practically ",
" hard to implement. (A lot of things has to be known)",
"(I have not taken a full model of the blurring in the eye in consideration, it might be more complex than a convolution)"
] |
[
"Adding to this. (from a signal processing background) ",
"A convolution filter (like blur, defocus etc) is the same as multiplying the ",
" function in the frequency domain (fourier domain)",
"This means that the only information truly lost is for frequencies where the transform of the blurring filter is zero. (on below the noise floor)",
"Implementable low pass filters (filters that removes small details) tend to not have many zero points, if any. So there is actually an inverse, just 1/F(",
") that could bring back more or less all of the original image fully after a blurring operation.",
"This is used in practice for image enhancement. However, the limitation is that if you add noise after the blurring operation (like all real systems do) it will be amplified by an almost infinite amount in frequencies where the blur transform is close to zero. So real image enhancement use some tricks to limit that effect.",
"Now, i hadn't before thought about the possibility of preprocessing an image so that it will appear normal after a softening convolution. It would of course be limited by the intensity range as pointed out with the white dot on black example. ",
"If you accept that the end result will be a low contrast image, the answer to the initial question might actually be ",
", if you know the exact shape of the blur (you would have to know the size of the pupil, the lens distortion and the distance to the screen. ",
"This is not at all what I expected opening this thread, thought it was entirely unfeasable. "
] |
[
"What's the correlation between sexual abuse and trauma and it causing mental illness (specifically long term mental illness and emotional damage)?"
] |
[
false
] |
I am aware of women both in my family and in extended relationships that endured sexual abuse at some point in their lives that led to long-standing mental illness, be it borderline personality disorder, manic depression, anxiety disorder, post traumatic stress disorder, etc. One person in particular has basically been left mentally incompetent and has had a tremendous change in her person, leaving her unable to work and in a very low income position. She is legally disabled because of her mental state. She experienced frequent and brutal sexual abuse over the course of years during her time in a military branch as a younger woman. I often wonder if these events led to her being homeless and so unstable because of the emotional damage. Are there figures that indicate how many people suffer mental illness after being sexually assaulted? Is a person more likely to experience mental illness as a consequence from sexual abuse more so than other physical or verbal abuse? Are there any studies related to this?
|
[
"This is a really complicated question. TLDR at the bottom.",
"One of the most famous scientific controversies in the history of the United States arose from a question very similar to yours. It's called the ",
"Rind et al. controversy",
" (link to wikipedia). Rind et al. wrote a paper about the self-reported harm caused by childhood sexual abuse (CSA). Their paper made a lot of procedural points (for example, that the working conceptualization of childhood sexual abuse was massively flawed and theoretically unworkable), that largely got left by the wayside because their findings were misinterpreted as somehow ",
" sex abuse.",
"Basically, they found, and I'm simplifying here, that based on the definition of CSA being used by researchers at the time, that there weren't really these massive negative psychological effects caused by CSA. A lot of the variation had to do with other factors: was it coerced? Was it forced? How old was the victim? The biggest finding wasn't that CSA doesn't cause traumatic effects, but rather that the conceptualization of CSA was so poorly constructed that a true test of their hypothesis wasn't possible.",
"The paper was condemned by the United States congress, something that had never happened before or since.",
"The main findings of the paper were replicated by ",
"Ulrich et al.",
".",
"So here's the problem: CSA was such a vague construct that it included diverse behaviors like the rape of toddlers and a minor male high school student having uncoerced (which is not to say consensual, I'm not trying to debate that here) sex with his teacher. So of course those are going to have different long-term effects! Researchers were basically lumping together really, really, obviously different behaviors into one category called \"CSA,\" and Rind et al. essentially pointed out that doing so was stupid.",
"TL;DR the available evidence suggests that childhood sexual abuse does not predict long-term mental dysfunction, but the researchers who published that evidence would probably argue that that is because \"childhood sexual abuse\" is a limited construct and we need more precise definitions to properly assess the question."
] |
[
"That was a really well-written break down. Really interesting that the study was condemned like that."
] |
[
"Thanks. It was a really big damn deal at the time because politicians basically ",
" to vote to condemn it or their opponents would make them look like sympathizers of child-abusers. But at the same time, politicians have practically zero qualification and literally zero authority to tell scientists that they're doing bad science, so a lot of scientists were uneasy with that decision to say the least. This happened to coincide with the tail-end of the \"memory wars,\" during which there was an epidemic of people reporting that they recovered previously repressed memories of satanic ritual childhood sexual abuse---and scientists and researchers who designed experiments to show that these \"repressed memories\" were likely the result of suggestive psychotherapy techniques. As might be expected, many alleged victims of satanic ritual abuse felt like they were being personally victimized or attacked by these scientists.",
"In other words, skeptical scientists were in the public eye, the role of science in the law was in the public eye, and people were used to scientific evidence attenuating their sympathy for alleged victims. A very controversial time for social science."
] |
[
"If you were locked up and only had access to 1 litre of water, how should you comsume it in order to survive the longest?"
] |
[
false
] | null |
[
"A still requires material that were not part of the original conditions."
] |
[
"Before drinking any of it, store your urine if it's dilute. You're probably pretty hydrated already, so you'll be losing a lot of water through there. When your urine starts to get darker(Probably only after 1 piss), stop, and start drinking small amounts of water. Concentrated urine will be very bad for you, and is counter productive for quenching thirst. When you run out of water, drink the dilute urine. It'll give you a little more emergency water.",
"There's not really anything you can do. Your body has you covered though. As you get dehydrated you'll begin to release hormones like ADH to help you preserve more water. ",
"But basically, there's no magic trick to make a litre of water last you over a week. Depending on heat you'll probably dehydrate in about 4 days, provided you were properly hydrated before you started."
] |
[
"A evaporating chamber with a connected cooling chamber. Usable in deserts with two 2l plastic bottles and tape to turn urine of any colour into clear water. Put sand over the cooling chamber. "
] |
[
"At one end, photons experience no time. Is there anything at the other end which has experienced more time?"
] |
[
false
] | null |
[
"Photons do not have a rest frame. So the statement \"photons experience no time\" is meaningless.",
"This thread in the FAQ answers your question.",
"https://www.reddit.com/r/askscience/wiki/physics/exceed_speedoflight",
"edit: This second one might answer your question more directly.\n",
"https://www.reddit.com/r/askscience/wiki/physics/light_and_time"
] |
[
"I thought time stood still at c. What do you mean by rest frame?"
] |
[
"The rest frame of a massive particle is one in which it is not moving. Photons always move at ",
", and so they do not have a rest frame. So it is meaningless to ask questions like \"what does a photon experience\"."
] |
[
"Is there such a thing as \"hangtime\" during jump?"
] |
[
false
] |
i often hear commentators in various sports comment about certain players ability in air and how they get hangtime in air, or ability to stay in air for longer than opposition while being shorter. Is it simple physics of having a better jump or is there a special technique or variable that allows you to outlast someone in a jump with superior height?
|
[
"To a limited extent, yes. By moving your limbs in particular ways you can alter where your center of gravity is. While the center of gravity will always follow parabolic path, your body doesn't always have to. A classic example of this is the Fosbury flop used by high jumpers and pole vaulters. "
] |
[
"I think the perception of hang-time is mostly driven by how far horizontally the player moves during the jump. It's the flattening of the top of the parabola that seems most impressive to me."
] |
[
"Height has nothing to do with time spent in the air, though being taller does improve your reach. Strength of the jump is basically the only factor in the time you spend in the air. The other things like limb position affect it a little bit but usually not to a noticeable amount."
] |
[
"Similar to increasing wealth gap, are we experiencing an increasing educational gap? Are well-educated getting more educated and under-educated staying under-educated?"
] |
[
false
] |
Edit: Thanks everyone for many different perspectives and interesting arguments! One statistic brought up was global educational attainment rising overall, which is a quite well-known development, and I'm glad it is taking place. Another point brought up was education and degrees. In this question, I don't necessarily equal attained education with received degrees but rather with actual acquired knowledge, including knowledge gained through non-institutional education. I realize we need quantifiable ways to measure educational attainment and awarded degrees is one of them. Though imperfect, it is better than non-existent. One just has to be careful about interpreting what exactly that number tells us. It also begs the question: What is the best way to measure acquired knowledge? An educational gap has existed in some form since the dawn of formal education. However, in case there is a trend of a growing educational gap, what concerns me is the possible emergence of an . Depending on the definition of "educational divide" and high-quality data available, such divide might potentially be underway.
|
[
"TLDR: Yes and no. There is no direct connection between having and education and then getting more education as a result. However, education leads to more money and more money leads to more opportunities for education and more success in obtaining education, both for an individual and for that individual's children. It would be perfectly correct to say that the Wealth Gap has created an Education Gap because the American education system is so dependent upon local economies.",
"Sociology professor here.",
"It can be stated as a scientific fact that ",
"wealth inequality exists in America.",
". It can also be stated as a scientific fact that ",
"wealthy individuals are more likely to graduate high school, graduate college, and obtain advanced degrees",
". Therefore, the wider the inequality in wealth the wider the inequality in education.",
"However, there is a worse problem that's hidden in that statement. Education attainment is not a perfect indicator of how educated a person is. That's sort of counter intuitive, so here is an example:",
"Group A) A poor section of town has low property values which means less taxes that fund schools. This then means that the school cannot hire the best teachers because it cannot pay very well. This means that the education being received by students is delivered by average or below average teachers, that textbooks and campus facilities are more likely to be outdated, and that after-school activities and extra curriculars are more likely to utilize sub-par equipment.",
"Group B) A wealthy neighborhood has high property values which means plenty of funding for schools. They can afford high salaries, so many teachers apply to work here, meaning the school can select the best of the best. They also have money to keep their facilities and extra curricular activities up to date.",
"Now if both Group A and Group B have a perfect 100% graduation rate, can we say that the students that graduate have the same education? Yes and no. They passed 12th grade, but in one situation the academics were more rigorous and the education included more than just the bare minimum. So on one hand we can point to statistics that say America's graduation rates are increasing, so we must be smarter. On the other hand, our schools are getting less funding and in some neighborhoods the curriculum are more lax, therefore the graduation rates increasing may be showing that our schools are getting easier to pass.",
"Some studies have shown that ",
"private schools emphasize critical thought and leadership, while public schools are more likely to emphasize discipline, cooperation, and obedience",
". Is this a disparity? In a way. Leadership and critical thought are skills needed in management and entrepreneurial jobs, while cooperation and obedience are more useful in menial labor. This isn't specifically tied to school funding, but it is worth noting that education quality will affect job prospects and success.",
"Lawmakers and policy makers are well aware of these trends. To correct for this, America has the \"No Child Left Behind\" law which forces all public schools to meet at least a minimum standard of education. The problem is that some schools barely meet it, while other (well funded) schools exceed it by leaps and bounds.",
"Some states also have a \"Robinhood\" law which takes excess money from wealthy neighborhoods and redistributes it to poor neighborhoods to keep schools from becoming too polarized. These are effective, but not perfect, and I'm not an expert on this area so I'll leave it at that.",
"However, all of this just says that the wealth gap creates an education gap. So the next question is, does higher education create more education?",
"For an individual, no. Most people seek a particular degree, and then stop seeking education. If education snowballed like the OP implies that then we'd have individuals who obtain dozens of Ph.D's, and that's pretty rare.",
"It is common, though, that ",
"educated parents are more likely to raise educated children",
" (pay wall). There's a lot of different factors here, mostly having to do with parent's higher education meaning more income and more free time. At the same time, this social fact is why colleges have programs set aside to specifically help first generation college students. People who go to college when their parent's hadn't gone to college are ",
"half as likely to graduate",
" as students whose parents do have a degree.",
"In summary, the answer is a soft yes. There is an education gap in america and it is growing, but it has more to do with the wealth gap and school funding than with education specifically."
] |
[
"The question is about education disparity among classes, not the general trend of educated populations."
] |
[
"I think you need to define \"we\". This would be very different for each countries laws. Things like access to education, ability to use that education to actually benefit lifestyle, etc, will dictate the answer to this question."
] |
[
"Why do neutrinos oscillate but electrons don't?"
] |
[
false
] |
Are there any interesting theories as to why neutrinos would oscillate but not electrons given that they're both leptons?
|
[
"By definition.",
"Basically take ",
"this answer of mine",
" and replace the up-type quarks (u,c,t) with the charged leptons (e,μ,τ) and replace the down-type quarks (d,s,b) with the three neutrinos. Exactly the same thing happens with the leptons.",
"(There's a difference from quarks in that the neutrinos could also be Majorana. Plus other complications. But the general conclusion of that answer still holds in that case. See ",
"u/majoranaspinor",
"'s comments there)."
] |
[
"So ",
"u/rantonels",
" answer is correct but assumes you are familiar with quarks; I will assume you are not. ",
"Okay so basically the reason is that we have to be careful about what we call a particle when we right down a Quantum Field Theory. The definition is basically something like \"If I can seperate this thing infinitely far from everything else, will it keep on being the same thing, then I can call this a particle\" ",
"Now when particles have all the same properties sometimes we cannot tell them apart. For example if we had two neutrinos with the same mass any linear combination of them would be a valid particle. ",
"Now charged leptons (muons, electrons, and tauons) all have different masses. This means we are stuck. Speaking loosely: there is no freedom. This is what ",
"u/rantonels",
" meant. The thing we call an electron is defined so that when its all on its own it keeps on keeping on. It does not oscillate. ",
"The trouble is that interactions dont always let particles stay particles. Specifically in this case a charged current interaction causes an electron to become a neutrino or vice versa . ",
"http://www.twinkletoesengineering.info/feynman_diagram3a.jpg",
"\n(here time is going up) ",
"This makes it tempting to label the neutrinos by the charged lepton names: Electron neutrino, muon neutrino, and tauon neutrino. This makes keeping track of things easy. Even better if all of those guys turn out to be massless then any linear combination of them will no oscillate. ",
"We have cleverly defined our particles so that there is a one-to-one correspondence with charged leptons. This makes them easy to identify in the lab. ",
"Unfortunately we cheated, neutrinos turn out to have mass. This means we cannot take any linear combination of them, but rather are stuck with the labels provided by their masses. Now charged currents might do something like this: ",
"When an electron comes in there is a 20% chance the lightest neutrino comes out, a 40% chance the medium neutrino comes out, and a 40% chance the heaviest neutrino comes out. ",
"Now how to actually explain oscillations? For this you need quantum mechanics but it is basically this. If we have an electron incident which interacts via the charged current then we can consider our initial state",
"[; |\\psi(t_0)>=|\\nu_e>=a_1 |\\nu_1> + a_2|\\nu_2> + a_3|\\nu_3> ;]",
"where we re-wrote the electron neutrino as a linear combination of the true particles. This then evolves like ",
"|\\psi(t_0)>=|\\nu_e>=a_1e^(iE_1) |\\nu_1> + a_2e^(iE_2)|\\nu_2> + a_3e^{iE_3}|\\nu_3> ;]",
"So each guy evolves with a different time dependent phase. This is basically all of the physics involved. Everything else is just turning the crank. "
] |
[
"As you said within the standard model the flavour of a neutrino is defined by the charged leptons it produces in a weak interaction. The question is if there is a possibility assuming beyond the standard model physics.",
"There is a fantastic paper by ",
"Akhmedov",
" that discusses everyting about the oscillations of charged leptons ! very well written paper in my opinon (like most of akhmedov papers).I could give a tl:dr of the paper but I think it is worth to look at it if oyu are intersted in this topic !"
] |
[
"How do stem cells know how to arranges itself in space, defining tissues boundaries and shapes?"
] |
[
false
] |
Hi! I was always intrigued by how stem cells work together to build a complete organ, and parts of the human body. Like, for example, to build an arm, how do stem cells "know" that they have to go X cm lenght to start to build the wrist. And moreover, how do that X cm lenght converts to Y number of cells. I know it's not that simple, it's not a formula that works that way, that chemicals rule the building and spacial orientation of each cell in the process. But it's so curious how these chemicals give this spacial "conscience" and define the boundaries. Like, how body knows it's time to end the arm, when it should create a curve for the hand, etc. Thank you for any information that can give a light to this question =)
|
[
"It all comes down to chemical reactions and signals, like you said. At the most general level, cells will differentiate one way or another based on a presence of a signal, which usually means that the signal needs to reach a certain threshold for something to happen, and if it doesn't reach that threshold, then another thing happens. ",
"There are some relatively simple mechanisms for altering the amount of signal present that cells utilize. You can produce more signal (translating more proteins or more enzymes that anabolize a signaling molecule), control how much the signal propagates (different diffusion depending on tissue/cell composition, or presence or absence of protein channels to let the signal into the cell), destruction of signal (specific tags that are recognized by some cells and not others for destruction, or just general catabolism), and what the signal can do (different wiring in the cell based on the same signal depending on what proteins already exist).",
"The last point is crucial. It's how a single hormone can affect different cells differently and give rise to complex phenotypes. For example, if you are making a finger from a small stub, and the signal for \"more finger\" comes in a form of a hormone, that hormone can give the signal for just cell division if you have a certain class of receptors in the middle, but the same signal could be interpreted as \"elongate on an axis\" by cells that are on the boundary and are expressing a different receptor. These are just examples.",
"The truth is that we know some of these but not nearly all. Biology is not neat. Evolution uses the tools it has (which is just a few general mechanisms - chemical reactions) and then wires them in different ways to achieve results. Some of these pathways are pretty complicated and are interconnected in ways that are not designed intelligently (forgive the pun). Here is an example of a very well studied pathway for ",
"cell proliferation",
". Each arrow represents an interaction (a chemical reaction) and each bubble is a protein. You can see that figuring out what a signal will do is not easy, and more importantly, changing what that signal will do by removing or adding another protein ",
" easy. So cells respond to a lot of queues differently based on what their state is, and these differential responses can lead to differentiated structures.",
"The astute observer would then point out that all cells start from one cell, so where does the inhomogeneity begin? Well there are multiple explanations, but a really neat breakthrough came from Alan Turing, the mathematician, and Enigma code breaker. He postulated that within a homogeneous population an interaction as simple as two molecules that can affect the rate of synthesis or breakdown of each other (very common thing in biochemistry) you can generate patterns that can lead to inhomogeneity. The wikipedia ",
"article",
" gives a good introduction and if you have a decent background in chemical kinetics, differential equations, and linear algebra, then the ",
"paper itself",
" is not too hard a read. The most impressive part is the diffEQ calculations he did by hand on all of the examples. This is not exactly how differentiation works usually, but the general mechanism is what causes a mass of uniform cells to create spacial differences that lead to cell differentiation and eventually specialization."
] |
[
"Chemical markers/messengers. Cells spew out molecules that other cells “read”. Based on what molecule it is the cell differentiates itself into a particular type of cell, e.g., liver or neuron. Then in turn it spews more messenger molecules for the other cells to “read”. Imagine a soup of these messenger molecules."
] |
[
"I would like to add to the other answers here that the signals which cells use create order structures (tissues and organs) are not purely chemical, they can also be mechanical. For example, an epithelial cell (the epithelium being the surface of a tissue) should be surrounded on all but one side by other cells, and the pressure it feels from those other cells on all but one side can serve as a crucial signal that this cell is supposed to be an epithelial cell. Specific signaling transduction pathways are unfortunately beyond my expertise, but I made a quick search for one and found a ",
"review on cadherins",
", which are theorized to transduce mechanical signals when they are deformed by tension. As a general rule, anything which can change a protein's shape can theoretically be used as a signal, and probably is used at least somewhere in the vast realm of biology.",
"Cells can also keep track of the number of times they have divided and then stop after a certain number of divisions (though I'm not sure how well understood this phenomenon is). The model organism ",
" - a nematode - for instance, ",
"has exactly 1031 or 959 cells",
", depending on whether it is a male or a hermaphrodite, respectively."
] |
[
"If skin sheds and regrows daily, then why do scars develop?"
] |
[
false
] |
Scar tissue seems much different than normal skin tissue. It almost seems more fragile. Why would replacement skin grow if it's weaker or a different texture? Follow up: what leads to scars forming? I got a paper cut on my forearm, and it's still red, although it'll disappear after a couple of days. Yet picking small scabs can lead to scarring on me.
|
[
"The short answer is that the body is mainly concerned with patching the hole in the skin as fast as possible. It does this with fibrous tissue as opposed to the normal skin cells, which then makes up the scar. The smaller cuts can be tightened and heal without the need for scar tissue formation.",
"As to the picking of scabs and scar formation, a wound bed heals from the bottom up, with the scab acting as a roof/shield. When you pick this, you are reopening the wound and restarting the inflammatory healing process, which rushes more of the scar tissue fibers to the site. There are some images on google that help illustrate this, just google wound healing (careful, there's some gnarly wounds in that search). I'd link them but I'm on mobile at the moment."
] |
[
"Heres a hopefully clearer explanation. There are multiple layers to your skin. The top layers are made of the cells you're thinking of as skin cells, or keratinocytes. These cells form a barrier that helps keep water in and the environment out. These cells are linked by proteins and as they mature they're shed. This is the part that keeps replacing itself with normal wear and tear.",
"Below these cells is a much thicker layer of fibrous collagen and other proteins that provide both strength and elasticity. This tough layer is organized outside of fibroblasts that recycle the old proteins, but follow the original protein scaffold as a guide.",
"If you damage the keratinocytes- like down to below a friction blister, paper cut, etc, the collagen layer is still intact, no scar as the keratinocytes fill the gap back in. Deeper wounds disrupt the collagen network, the deeper the injury, the less of the original pattern is left. To repair the gap, fibroblasts lay new collagen fibers. The wound contracts along the fibers to close the edges as much as possible, but it wont be perfect. The result is new collagen fibers in the remaining gap that are less organized and weaker as well as less elastic. So you're right, at most scars are ~80-90% the strength of the original skin.",
"The original structure is created as the fetus develops, so there isn't a way we heal deep wounds other than with scar tissue. The main difference is extension and expansion in the fetus vs. cutting through existing mature collagen fibers in the middle."
] |
[
"The body leaves the scar tissue because there's no reason to replace it as far as the body is concerned. The scar is actually not fully healed for a long time after the wound is closed, the pinkish hue that can be seen in the scar is capillaries continuing the healing/modeling process. ",
"The 'scarred' cells don't get replaced. A scar can soften a bit over time and with proper care during the modeling phase but the fibrous tissue will be there until removed."
] |
[
"How effective are two dose vaccines if you get the second dose long after the recommended time interval?"
] |
[
false
] |
This has become relevant due to Biden’s plan to release COVID-19 vaccines that were being previously reserved as second doses. Let’s say you receive the first dose of a vaccine and it is recommended to get the second dose one month later. But instead you do not receive the second dose for multiple months or even a year later. How does that impact the effectiveness of the vaccine ? Do you have to start the dosing schedule over again (i.e. receive a third dose at the correct time interval after the second dose) to achieve immunity? Obviously there isn’t data yet to understand how this would impact COVID-19 vaccine effectiveness. But I’m wondering if there is data on other vaccines that can be used for comparison.
|
[
"Well there is some research. Mainly being that just getting the one dose is only around 50% effective at preventing covid, so really you aren't very protected until you get the second dose when protection effectiveness is like 95% or more \nAs far as other vaccines that area two shot series, it's a difficult comparison as this is the first rna vaccine so other vaccines work on different science. The mmr vaccine is one that's a 2 dose vaccine, and there is no need to restart if you don't follow the schedule, but the second dose for it is considered more of a booster for long term immunity. The effectiveness of a single dose of mmr tho is 93% for measles, 78% for mumps and 97% for rubella so there isn't as much of a gap in prevention between the shots as there is for the covid vaccines."
] |
[
"so really you aren't very protected until you get the second dose",
"It's not really as clear-cut as that. Looking at the ",
"initial report",
", it looks like the 50% figure is from observing:",
"After the first vaccination, PsVNA responses were detected in less than half the participants, and a dose effect was seen (50% inhibitory dilution [ID50]: Figure 2C, Fig. S8, and Table 2; 80% inhibitory dilution [ID80]: Fig. S2 and Table S6). However, after the second vaccination, PsVNA responses were identified in serum samples from all participants.",
"But there are a few issues in reading too much into this, whether positive or negative:",
"This was the result of testing 14 days after the first dose, but we're comparing against tests taken on day 36+ (7 days after the second dose) - but part of this may simply be that the body has simply had 22 days more time for the immune system to get going. For all we know you'd have got similar results on day 36 even if you ",
" administered the second vaccine. There isn't data about what happens if you test the response of a single dose subject after 36 days, because that wasn't how the study assumed it'd be used.",
"Conversely, it looks like testing the day 14 tests only involve testing for a PsVNA response - further tests with pseudovirus and live virus were only performed after 2-doses, so it's worth noting that we're only checking for the producion of neutralising antibodies here and assuming that translates to the same levels of effectiveness.",
"So really, it's hard to say - it may be somewhere between 50% and 100% of the 2-dose effectiveness, but it's hard to say exactly where, and even that's not certain."
] |
[
"Out of curiosity, what happens if you get the 2nd vaccine shot 2 or 3 days after getting the first one. I might be able to book a 2nd appointment 2 days after getting the first one and am not sure if I should or not?"
] |
[
"What causes galaxies in our universe to move?"
] |
[
false
] |
[deleted]
|
[
"The predominant motion of the universe depends on what scale you're looking at. If you look at small scale motion then gravity dominates the motion. So we see all the familiar gravitational phenomena. For example, the Milky way has a smaller galaxy, known as a satellite galaxy, orbiting it called the Ursa Minor Dwarf. The Milky Way is also headed for a collision with the Andromeda galaxy. The largest gravitationally bound object we know of is the Laniakea supercluster, defined in Sep 2014.",
"On a larger scale, the expansion of the universe dominates the motion of galaxies. To understand this, imagine a balloon with ants on it. As we inflate the balloon the ants will get further apart, even though they are stood still on the balloon. This can also be described as the space between galaxies expanding and the effect is larger the further away the other galaxy is. So at scales too large for gravity to have a noticeable effect, all galaxies are moving away from every other galaxy."
] |
[
"So space kind of expands \"from under us\" and the reason, e.g., galaxies are getting further apart is that the forces binding them are unable to compensate for the rate of expansion, however the reason we are still the same size is that the bonds that make us up can counteract this expansion?"
] |
[
"Yeah, that's right. Worth noting though that you wouldn't get bigger, you would be pulled apart since all the particles you're made of would get further apart. Just a technicality."
] |
[
"Where can I find a good explanation of String Theory?"
] |
[
false
] | null |
[
"You might try Barton Zwiebach's book ",
", which is geared towards advanced undergraduates."
] |
[
"This is cool. (short add first) NOVA on PBS\n",
"http://video.pbs.org/video/1512280538/"
] |
[
"String theory is very (very) mathematical, what sort of mathematical background do you have?",
"I found that with all areas of physics there is a lack of good material for advanced laypeople, ie. material for casual reading more advanced than say \"The universe in a nutshell\" that is not undergrad level."
] |
[
"Time dilation question"
] |
[
false
] | null |
[
"In your calculations for [1] and [2] you use the distance between Neptune and the Earth as seen by the stationary observer on Earth (Captain Kirk) and the velocity of the ships Alpha and Omega (again measured by Captain Kirk). This is the time that Kirk will age before the ships pass Earth. There is nothing more than that. ",
"Then you use time dilation in [3] to calculate the time compression factor for the moving frame. Multiplying this factor by the time that Kirk has aged during the ships' transits does not logically follow. 2.4004 and 1.1547 are the factors by which, respectively Alpha's and Omega's clocks run slow as compared to the stationary frame.",
"If you want to learn Special Relativity the easy way. Learn about the \"",
"Invariance of the Space-Time Interval",
"\". It's a much easier way to understand and solve almost all SR problems as compared to calculating time dilation factors and trying to think about just who is moving relative to whom. The Space-Time interval for all observers (Kirk, Alpha, Omega) is the same."
] |
[
"One additional question - how would you calculate the age of Kirk from the frame of reference of each ship?",
"You take the fact that when Omega (for example) passes Earth Kirk is 8.06 hours old, then calculate his age at any moment using the fact that Earth time is slowed by a factor of ~0.87 in Omega's reference frame. Also the fact that Omega's travel took 8.06 * 0.87 hours, from its point of view.",
"In particular, that means that since Kirk aged by about 6 hours during Omega's travel, he was 2 hours old when it launched. More precisely, that was in its inertially moving reference frame, after the acceleration completed, which means that Kirk rapidly aged by 2 hours during the acceleration (no matter how short it was).",
"The real fun fact is, of course, that if Omega were to rapidly decelerate immediately after getting to cruise velocity, in its reference frame Kirk would un-age back 2 hours to just being born. The notion of \"current time at a remote point\" is kinda virtual in SR."
] |
[
"Gah, ok, that makes sense (that my assumptions are incorrect). I do want to learn Special Relativity the easy way, so thanks for providing a learning resource, and thanks for the response. "
] |
[
"How and when does a virus cross over to another species?"
] |
[
false
] |
Crossing over requires another host with similar evolutionary lineages, but that's about the extent of my knowledge.
|
[
"In many cases, viruses evolved to be well adapted to a certain species. This is true of several steps in its life cycle: how it's transmitted, what surface proteins in binds with to gain entry into the cell, which proteins it can interact with to replicate, how it shuts down the immune system, etc. This is why it can be very difficult for a virus to jump species; they just don't have the right tools.",
"To be able to jump species, it needs to be able to at least infect and replicate inside the new host even if its poorly. As the virus replicates and evolves, over time it will mutate to become better at infecting its new host.",
"For example, let's take a look at the Coronavirus responsible for SARS (SARS-CoV). ",
"This paper",
" describes how the virus was able to jump from bats to humans. Most forms of the virus isn't able to infect humans because it can't bind to the ACE-2 protein very well, something that is required for entry into a cell. By sheer genetic variation and luck, one strain was able to bind to ACE2 and infected a person. We can tell from phylogeny that as the virus replicated and evolved inside people, it also became better at infecting people."
] |
[
"You have to remember than the \"virus\" is just some genes in a protein shell. Everything it does is dictated by chemistry and physics; it doesn't really \"decide\" anything. Take avian flu for example: a duck sneezes out droplets filled with virus. Wherever that droplet goes, that's what the virus will try to infect. If a person inhales that droplet, then that's the virus' entry point. If it can't find a cell within the human to grow inside, then it dies. ",
"Or take Ebola: a certain strain of virus infects a bat. The bat gets killed and eaten by a human and bam! There's your patient zero. We suspect that people in Africa often come in contact with the virus, but transmission and adaptation of the virus in humans is difficult which is why Ebola outbreaks only happen once every few years."
] |
[
"Thank you, I found your explanation helpful. Can you provide any insight as to when a virus crosses over? As in, when does it \"decide\", so to speak, that there is a need to jump species? Or is it by sheer chance? Because if the crossing over doesn't work, isn't that equivalent to suicide?"
] |
[
"Without a cataclysmic event like the Cretaceous–Paleogene extinction event, would intelligent human life still developed and if so would it have happened millions of years later?"
] |
[
false
] | null |
[
"We also run ",
"/r/AskScienceDiscussion",
" which would be a good bet."
] |
[
"Thank you for your submission! Unfortunately, your submission has been removed for the following reason(s):",
"For more information regarding this and similar issues, please see our ",
"guidelines.",
"If you disagree with this decision, please send a message to the moderators."
] |
[
"Thank you. Sorry to not meet the criteria. Is there another sub for this sort of question, like a \"sciencewhatif\"?",
"Thanks."
] |
[
"Why won’t the rocket equation give the same answer for simple conservation of momentum?"
] |
[
false
] |
you know how the ideal rocket equation says Delta V = Vexh ln(m0/mf)? If I use it for a very simple example, like a bowling ball with an ice skater, I get two different result, and I don’t know why. Here’s what I mean: Say that a 50kg ice skater with a 10kg bowling ball launched the ball at 10 m/s in one direction. From the conservation of momentum, the ice skater should go 2 m/s in the other direction right? But if I plug that into the rocket equation (Vexh = 10 m/s, M0 = 60 kg, Mf = 50kg), I get like 1.82 m/s. Why is there a discrepancy? Isn’t the derivation for the rocket equation just based off of conservation of momentum?
|
[
"In the situation you describe, the change in mass is being treated as an impulse, while in the case of the rocket equation the mass is being expelled continuously as a function of time.",
"Referencing ",
"this",
" derivation of the rocket equation, you can see that the differential equation",
"m dV/dt = -v",
" dm/dt",
"is being solved by separation of variables, where you can \"rearrange\" dm/dt.",
"But if you instead assume dm/dt is an impulse rather than a continuous function, you can arrive at the result that you'd use for conservation of momentum problems in introductory physics.",
"Specifically, assume",
"dm/dt = -Δm 𝛿(t).",
"This means that the change in mass of the ice skater is -Δm, and it happens impulsively at time t = 0.",
"Now the differential equation reads",
"m dV/dt = v",
" Δm 𝛿(t),",
"and you can integrate both sides over time from any time before the impulse to any time after the impulse, and you get",
"m ΔV = v",
" Δm.",
"This is just the usual conservation of momentum, expressed in terms of the ΔV and v",
" variables that you'd see in the rocket equation.",
"If you plug in the numbers you gave, m = 50 kg, Δm = 10 kg, v",
" = 10 m/s, you get that ΔV = 2 m/s."
] |
[
"Just as a notational thing, I wanna be clear that by δ(t), is that referring to the Dirac delta function at t=0?",
"Yes.",
"In that case, would the units still be in seconds? I’m just trying to make sure that the units make sense when you preform the integration since you’d be multiplying both sides by dt.",
"The units of the delta function are the inverse of the units of its argument. So 𝛿(t) has units of [time]",
".",
"So I would use that derived “introductory” version if essentially the mass was constant and being ejected all at once. If the ice skater were to chop up that bowling ball into 2 at threw both at once, that would still give us a deltaV value of 2 m/s right? Would it always stay at 2 m/s and only jump to 1.82 m/s once we have a smooth differentiable function that describes the mass flow rate? Or would we “see” that 2m/s value change at approach 1.82 as we chop up that ball into finer pieces? I’m sorry if this is a weird follow up question, I’m pretty satisfied with the response you gave me. I guess I’m just being a little lazy by not thinking this through so I’m just looking for an easy, intuitive answer.",
"I'd say to try it as an exercise.",
"I'll work it out for the case where the mass is cut in half and expelled as two impulses at different times, then you can generalize it to N times, and see what happens when you make N very large.",
"For the first step, you have m = 55 kg, v",
" = 10 m/s, and Δm = 5 kg, which gives ΔV = 0.91 m/s.",
"Then for the second step, you have m = 50 kg, v",
" = 10 m/s, and Δm = 5 kg, which gives an additional ΔV = 1 m/s.",
"So the combined ΔV is 1.91 m/s, not 2 m/s anymore.",
"You can see that the ΔV at each step is inversely proportional to m, which is the remaining mass of the \"rocket\" after the impulse. So it's in your favor to make that small as fast as possible. Expelling the propellant as a single impulse is more efficient than breaking it up into multiple impulses."
] |
[
"In that case, I guess one could say that you could come to very close values for delta V by just using algebra and conservation of momentum, with no need for calculus. Or maybe if you could write a program or something and come to a good value with just introductory high school physics. Also this is the first time I’m seeing a real life example of the Dirac delta function, so that’s pretty cool. Thanks for your time"
] |
[
"How is gender (not sex) biologically structured? Why does gender dysphoria exist?"
] |
[
false
] | null |
[
"I wrote something like a year ago on the epidemiology of Gender Dysphoria for an assessment in my abnormal psychology unit. It might be of some use to you.",
"Gender dysphoria is the experience of distress resulting from an incongruence of a person’s psychological and emotional gender identity and their biological sex (Yarhouse, 2015). While the debate over the possible causes of gender dysphoria is ongoing, there are two predominate classes of theories. The first are ‘Brain-Sex’ theories which focus on prenatal hormones. It has been established that the presence of testosterone in utero leads to the development of both male genitalia and a male differentiated brain (Yarhouse, 2015). These developments however occur via two distinct processes and occur at different times during fetal development (Yarhouse, 2015). It is hypothesized that a discrepancy can occur where only one of the two processes occurs in full, leading to the development of either female genitalia with a male differentiated brain or male genitalia and a female differentiated brain.",
"The second class of theories are multifactorial models that give greater weight to early psychosocial factors in childhood whilst still taking into account the prenatal sex hormone considerations associated with the Brain-Sex theories. (Yarhouse, 2015). Proponents of such theories believe that there is a cognitive process by which a child comes to know and understand his or her sense of gender and associated behaviours. Parenting and observational learning plays a role in this process as both influence what is witnessed, modelled and reinforced by parents, family and peer groups (Yarhouse, 2015). Following this view, several possible risk factors are thought to be associated with gender dysphoria. These include: inhibited/shy temperament, separation anxiety, late in birth order, sensory reactivity and sexual abuse (Yarhouse, 2015). Additionally, risk factors associated with parents include parental indifference to cross-gender behaviour, reinforcing cross-gender behaviour, insufficient adult same-sex role models and parental psychiatric issues (Yarhouse, 2015).",
"I only had 300 words to use for that section but I believe I got a 35/40 for it.",
"Determining the precise prevalence rates of gender dysphoria is somewhat of a challenge. There exists a multiplicity of gender variant expressions and identities (agender, androgynous, transgender etc.) and it is not clear that all who describe themselves in such a way should necessary be diagnosed as gender dysphoric (Yarhouse, 2015). It would therefore not be possible to gain accurate prevalence statistics through analysis of the self-classificatory terms that individuals in the public use to define themselves, a one on one diagnosis of gender dysphoria needs to be made. Unfortunately, everyone who might be so diagnosed is not guaranteed to see, or even have access to, a health care provider who is knowledgeable in this diagnosis (Blosnich et al., 2013). This means that even if we had perfectly accurate diagnosis records, they would only be rough estimates. The majority of the prevalence statistics that do exist are based off the number of those who have sought treatment for gender dysphoria. As everyone does not receive treatment, or is even diagnosed, these numbers too can only be seen as very rough estimates (Blosnich et al., 2013). Further complicating matters is that the DSM-5 diagnostic criteria for gender dysphoria differs from the criteria of gender identity disorder in the DMS-IV. This means that previous research into the prevalence rates of gender identity disorder cannot been seen as an accurate reflection of gender dysphoria prevalence (Dickey, Fedewa & Hirsch, 2014).",
"A very broad estimate for gender dysphoria is given in the DSM-5 which purports rates of 0.005-0.014% in adult natal males and 0.002-0.003% for adult natal females throughout Europe (Kraus, 2015). These estimates unfortunately are based on people seeking out specialty clinics for treatment, and thus can only be considered modest estimates (Kraus, 2015). ",
"Psychological intervention can offer positive outcomes. Individual client treatment is focused on understanding and coping with gender issues. Group, marital, and family therapy can also provide helpful and supportive environments throughout treatment. ",
"A recent study (2015) on sexual quality of life before genital reassignment surgery indicated that hormonal therapy may improve sexual satisfaction. 67 male-to-female and 37 female-to-male gender dysphoric adult participants who had not yet undergone genital sexual realignment surgery (SRS), (39.8% receiving cross sex hormonal treatment and 30.1% with breast augmentation or reduction) were tested with validated measures of sexual quality of life (QoL, WHOQOL-100) for negative feelings, hormonal treatments, partner relationships and personality (Revised NEO-Five Factor Inventory). This test concluded that before genital SRS about half of gender dysphoric subjects perceived their sexual life satisfaction as ‘poor dissatisfied’ or ‘very poor, very dissatisfied’ (Bartolucci et al, 2015). No data for these participants sexual life satisfaction after genital SRS is available. This limits the ability to make conclusions about the success of SRS on gender dysphoric people in this case. ",
"A 2-phase investigative process occurs for patients seeking this surgery (Carroll, 1999)",
"Adolescents desiring SRS must demonstrate the following:\n• A lifelong cross-gender identity that increased at puberty \n• Absence of serious psychopathology \n• Social functionality free of significant problems ",
"Treatment may include: Luteinizing hormone–releasing hormone (LHRH) agonists, Progestational compounds, Spironolactone, Flutamide, Cyproterone acetate, Ethinyl oestradiol, Conjugated oestrogen, and Testosterone cypionate (Carroll, 1999).",
"Cross sex hormonal therapy (CHT) achieves physical modification in gender-non-conforming persons and induces and maintains desired sex characteristics, meeting the individuals goals and expectations, and Improving quality of life increasing sense of wellbeing and easing gender dysphoria,",
"SRS is not prerequisite to CHT. \nComprehensive baseline assessment includes medical history, physical examination, general laboratory tests, hormonal profile, sexually transmitted disease, genetic assessments, bone mineral density, ECG, FtM (pap test, lower abdomen), \nMtF (venous system examination, thrombophilia and prostate cancer screening). Monitoring of physical and mental health is ongoing in CHT. (Fabris, Bernardi, Trombetta, 2015).",
"CROSS SEX HORMONE-TREATMENT USE & HEALTH RISK",
"Sex steroid use may be associated with potential adverse effects such as acne, venous thromboembolism, atherosclerosis, hypertension, hyperlipidemia, prostate hyperplasia; and may cause or exacerbate neoplasia of the prostate, breast and ovaries.\nCross-sex hormone therapies increase serum triglycerides in MF and FM and have a trivial effect on HDL-cholesterol and systolic blood pressure in FM. Data about patient important outcomes are sparse and inconclusive ",
"Post surgical transsexuals are an at risk group that need long-term psychiatric and somatic follow-up. Surgery and hormonal therapy alleviates gender dysphoria, however it does not appear to reduce the high rates of morbidity and mortality of transsexual persons. It is therefore crucial that care for transsexual people post sex reassignment is improved.",
"Bartolucci, C., Gomez-Gil, E., Salamero, M., Esteva, I., Guillamon, A., Zubiaurre, L., Molero, F.\n& Montejo, A. L. (2015). Sexual Quality of life in Gender- Dysphoric Adults before\nGenital Sex Reassignment Surgery. The Journal of Sexual Medicine, 12, 180-188. Doi:\n10.1111/jsm.12758.",
"Blosnich, J. R., Brown, G. R., Shipherd, J. C., Kauth, M., Piegari, R. I. & Bossart, R. M. (2013).\nPrevalence of gender identity disorder and suicide risk among transgender veterans\nutilizing veterans’ health administration care, American Journal of Public Health, 103,\n27-32. Doi: 10.2105/AJPH.2013.301507.",
"Carroll, R. A. (1999). Outcomes of Treatment for Gender Dysphoria. Journal of Sex Education\nand Therapy, 24, 128-136. Doi: 10.1080/01614576.1999.11074292.",
"Dhejne, C., Lichtenstein, P., Boman , M., Johansson, A. L. V., Langstrom, N. (2011). Long-\nTerm Follow-Up of Transsexual Persons Undergoing Sex Reassignment Surgery: Cohort\nStudy in Sweden. PLoS ONE 6. Doi:10.1371/journal.pone.0016885.",
"Dickey, L. M., Fewewa, A. & Hirsch, A. (2014). Diagnostic changes: gender dysphoria.\nCommunique, 42, p 1. Retrieved from:\n",
"http://ezproxy.lib.swin.edu.au/login?url=http://go.galegroup.com/ps/i.do?id=GALE%7C",
"\nA393517552&v=2.1&u=swinburne1&it=r&p=AONE&sw=w&asid=c317abd6d87cc3ca7\n20208fc3f7aecee.",
"Elamin, M.B., Garcia, M.Z., Murad, M.H., Erwin, P.J. & Montori, V.M. (2010). Effect of sex\nsteroid use on cardiovascular risk in transsexual individuals: a systematic review and\nmeta-analyses. Clinical Endocrinology, 72, 1–10.",
"Fabris, B., Bernardi, S. & Trombetta, C. (2015). Cross- sex hormone therapy for gender\ndysphoria, Journal of Endocrinological Investigation, 38, 269- 282. doi: 10.1007/s40618-\n014-0186-2",
"Kaplan, A. B. (2012). The Prevalence of Transgenderism – an update. Retrieved from\n",
"http://tgmentalhealth.com/2012/02/13/the-prevalence-of-transgenderism-an-update",
".\nKraus, C. (2015). Classifying Intersex in DSM-5: Critical Reflections on Gender Dysphoria.\nArch Sex Behavior Archives of Sexual Behavior, 44, 1147-1163. doi: 10.1007/s10508-\n015-0550-0",
"Yarhouse, M. A. (2015). Understanding Gender Dysphoria. Illinois, Westmont: InterVarsity\nPress"
] |
[
"First theory: you get two \"doses\" of testosterone production while in utero. It may be that the timing or administration of these doses is abnormal. "
] |
[
"The second believes there is a critical time in early life development where environmental factors influence gender identity. Parents reinforcing opposite gender roles or stereotypes, abuse, or other abnormal situations during this time period may disrupt the normal \"sense of self\" time period "
] |
[
"How many generations (or time) back would we have to go before being unable to produce fertile offspring with one of our ancestors?"
] |
[
false
] |
Bonus question: What determines wether or not two organisms can reproduce?
|
[
"For the first question, ",
", but ",
" at least ",
" ",
" 500,000 years (sorry, I forgot about Neandethals when I was first writing this answer...silly me).",
"Let me answer the bonus question next, and then I'll give a few thoughts on your main question.",
"The place to start is with the genetics. An offspring gets one copy of each gene from each of it's parents, so generally two organisms will fail to be able to reproduce if there are any genes that they contribute are somehow incompatible with one another. There are two principal kinds of genetic incompatibilities: those which impact ",
", and those which impact ",
". If it's ",
" that is impacted, this can be at any point during the course of the organism's development, up until sexual maturity. So for example you could have some combination of genes that causes embryos to abort early in development, or causes death or severe disability in early childhood or adolescence, etc. Alternatively, you could have a genetic combination which does not interfere with the offspring's survival, but just makes them infertile. Maybe they produce sperm that swim in circles or eggs which don't start developing when fertilized.",
"The simplest genetic model you might think of for an incompatibility is the following. At some particular gene there are two different alleles: the A allele, and the a allele. Individuals who have two copies of A, or two copies of a are normal and healthy, but individuals who have one of each (i.e. ",
"heterozygotes",
") have some defect, due to the two different alleles interacting with one another negatively (for any of the reasons discussed above). This is called ",
". Examples of it are rare in nature however, for the following reason. If there are both A alleles and a alleles in a population, then one of them must have formed via mutation from the other (e.g. let's say the a allele is derived from the ancestral A allele). When that mutation first occurred the first individual to carry the new a allele would necessarily be heterozygous, and therefore at a disadvantage. The new a mutation is thus unlikely to spread, and never gets off the ground. Most mutations which cause genetic incompatibilities ",
" likely are not of this kind.",
"Instead, genetic incompatibilities between species generally involve at least two loci. For example, imagine a case where all individuals in species X have A alleles at gene 1 and B alleles at gene 2. Then, imagine species X splits into two different populations, and in Population 1 theres a mutation to an a allele at gene 1, which eventually spreads through the population, such that all individuals have aaBB genotypes. In Population 2 on the other hand, a mutation to a b allele at gene 2 eventually spreads through the population, so that all individuals have AAbb genotypes. When individuals from Population 1 and Population 2 try to produce offspring together, some of the offspring will have both a and b alleles together, which may interact poorly and cause reproductive isolation. These are called ",
"Dobzhansky-Muller incompatibilities",
", or \"DMIs\". DMIs also don't have to be pairwise. You could also imagine having three way interactions in which some three locus genotypes are bad, but others are ok. It's believed that these higher order interactions may contribute to speciation, but they are generally very hard to detect, largely for statistical reasons.",
"You can flip the above scenario around a bit and have a good explanation for how a descendant population could come to be reproductively isolated from their ancestors. Imagine the ancestral population all had aaBB genotypes, and then the A mutation swept through the population, replacing the a allele, so that everyone was AABB. ",
", the b allele sweeps through, replacing B, so that everyone is AAbb. If these individuals somehow had the opportunity to try to reproduce with their aaBB ancestors, they would produce some offspring that have a and b alleles together, resulting in bad things and therefore reproductive isolation. It's also worth noting that in general a lot of the time it's probably not single pairwise interactions completely shutting down reproduction on their own, but likely many such interactions, all of which add up to cumulatively cause severe problems.",
"Now, back to your main question. The reason I say 500,000 is because that represents a good bound on the divergence of modern humans from Neanderthals, and ",
"we know that all modern non-Africans have about 1-4% Neanderthal DNA in their genomes",
", and ",
"we know that the interbreeding happened about 50,000 years ago",
", so we know that modern humans of that time were interfertile with Neanderthals. There is also evidence that ",
"regions that are under stronger functional constraint have lower amounts of Neanderthal introgression",
", suggesting that there has been selection against Neanderthal genes in modern humans, and thus that partial reproductive isolation may have already begun to evolve."
] |
[
"I would just add that an important factor for fertility of offspring is chromosome number. Mules are perfectly functional as individual animals but are sterile because their parents had different chromosome numbers, so it is nearly impossible for them to pass on a complete haploid genome. The great apes, other than man, have a diploid chromosome number of 48. We have 46. When did this change (two chromosomes fusing) happen? If there are any specialists with knowledge of this issue, please chime in."
] |
[
"I can't access your final link (it goes to the UCDavis library login), but cheers that's an awesomely detailed answer."
] |
[
"When will energy be free?"
] |
[
false
] | null |
[
"Electricity will only ever be \"free\" if it is covered by taxes.",
"People are needed to produce electricity, or at least produce the objects that produce electricity, and they need salaries to continue to work. So it won't be free."
] |
[
"We're getting bombarded by free energy all the time. The issue is transforming that energy into a form that does useful work. If it is cold outside, I am getting \"free\" heat by standing out in the sun, which serves a useful purpose of heating me up. However, unless I had the means to transform that energy into something like electricity to power my house, then I am limited to what I can do with that free energy."
] |
[
"you're assuming the current \"capitalist\" configuration of society. That's akin to saying a couple hundred years ago that slavery will never be outlawed, or saying even a hundred years ago that landing on the moon is inconceivable."
] |
[
"I've learnt that bacteria can become spores and preserve themselves for thousands of years, but how do they survive if DNA has a half-life of 521 years?"
] |
[
false
] |
[deleted]
|
[
"One thing to remember with the decay of DNA is that it's not necessarily a radioactive decay. The decay is typically from the molecular bonds being broken. This is commonly caused by chemical reactions involving water and oxygen. When these bacteria go into stasis, they are still alive but chemical reactions typically cease, which protect the DNA. I do not know the exact actions of the process, but by being in stasis and preventing chemical reactions, the half life may be increased. ",
"Article about DNA half-life"
] |
[
"Carbon-14 makes up about 1 ppt of the total carbon in the world. Some of it will inherently become incorporated into DNA, when it decays it decays by beta emission and becomes Nitrogen-14. This would probably break up the ring structure of whatever base pair or sugar it is incorporated into in the DNA. ",
"Furthermore about .012% of the potassium inside of living organisms is K-40. K-40 decays by high energy beta emission, so there's a chance that a high energy electron would occasionally strike an atom in a strand of DNA and ionize it, which would also likely lead to breaking up of the DNA strand.",
"Its not hugely likely to happen, but any event that has a non-zero chance will eventually happen over a long enough time period."
] |
[
"Carbon-14 makes up about 1 ppt of the total carbon in the world. Some of it will inherently become incorporated into DNA, when it decays it decays by beta emission and becomes Nitrogen-14. This would probably break up the ring structure of whatever base pair or sugar it is incorporated into in the DNA. ",
"Furthermore about .012% of the potassium inside of living organisms is K-40. K-40 decays by high energy beta emission, so there's a chance that a high energy electron would occasionally strike an atom in a strand of DNA and ionize it, which would also likely lead to breaking up of the DNA strand.",
"Its not hugely likely to happen, but any event that has a non-zero chance will eventually happen over a long enough time period."
] |
[
"Should we see a mild flu season?"
] |
[
false
] |
In theory, should we be seeing a lower than average amount of flu cases this year due to the enhanced social distancing, mask wearing, and sanitization? Will we actually? Why or why not?
|
[
"Influenza cases in the Southern Hemisphere’s flu season were extremely low, and so far in the Northern hemisphere cases have been far below average. ",
"Following widespread adoption of community mitigation measures to reduce transmission of SARS-CoV-2, the virus that causes COVID-19, the percentage of U.S. respiratory specimens submitted for influenza testing that tested positive decreased from >20% to 2.3% and has remained at historically low interseasonal levels (0.2% versus 1–2%). Data from Southern Hemisphere countries also indicate little influenza activity. … The community mitigation strategies implemented to prevent the spread of COVID-19, including both community and individual-level measures, appear to have substantially reduced transmission of influenza in all these countries.",
"—",
"Decreased Influenza Activity During the COVID-19 Pandemic — United States, Australia, Chile, and South Africa, 2020",
"Influenza viruses are about half to a third as transmissible as SARS-CoV-2 (R0 of influenza viruses is around 1.5; of SARS-CoV-2, about 3-4), so measures that suppress COVID will be even more effective against influenza."
] |
[
"My hospital posts statistics daily due to Covid and we are behind the number of flu cases this year in comparison to the last ten years."
] |
[
"It's almost like washing your hands, using hand sanitizer, and staying away from other people can reduce the transmission of the flu virus too!"
] |
[
"On Jupiter, will more superstorms the size the Great Red Spot eventually form, or are the positions and types of storms relatively constant?"
] |
[
false
] |
Hurricanes and big storms on Earth move around and change size, but does that happen on Jupiter?
|
[
"I'd expect that Jupiter's weather calculations would be even more chaotic",
"I did my PhD dissertation running climate models of Jupiter. Surprisingly, this is ",
" the case.",
"Earth is actually the planet with the hardest weather to predict. That's because we live on the only planet with atmosphere and oceans and continents and clouds and ice caps and rain and snow and they interact in very non-linear ways. ",
"On Jupiter, there's atmosphere and clouds. If you know where the Great Red Spot was last week and where it was today, you can very accurately predict where it will be 6 months from now. Imagine trying to do that with a hurricane on Earth.",
": Something else makes Earth much harder to model, too. In atmospheric dynamics, we talk about something known as the \"deformation radius\", essentially how big a vortex can get before it starts splitting up into separate vortices. On Jupiter, the deformation radius is quite a bit smaller than the planet's circumference, so you can pack quite a few vortices on Jupiter and still have them play nice together. On Earth, though, the deformation radius is actually a lot closer to Earth's circumference; you can only pack about 6 or so around the planet, and they all get in each other's way and make a big messy pile of turbulent interactions.",
"My old advisor used to say: Picture 6 prima ballerinas on the stage, jumping and pirouetting around...it's beautiful and ordered. That's Jupiter. Now pack these same 6 ballerinas into an elevator and ask them to perform - that's Earth."
] |
[
"The great red spot has been a standout feature of Jupiter for at least a couple hundred years, possibly a lot longer. Clearly it's not a short-lived feature like storms and hurricanes on Earth.",
"But as for its evolution and the formation of other storms like it, that's all unknown AFAIK. Understanding our own atmosphere is hard enough, understanding Jupiter's very different atmosphere (with much more limited data) is very difficult.",
"In recent years, the spot ",
"has been shrinking",
"."
] |
[
"Sorry, bit too much personal info in there to share publicly. The part of my dissertation that was about Jupiter (the majority was actually about Uranus) summarized, though:",
"Until recently, the Great Red Spot (GRS) was the only massive vortex on Jupiter that was also red. It's very unclear why this is the case - is there material welling up from the deep like in an Earth hurricane, coloring the GRS? Or is it compounds we see everywhere else on Jupiter that get pushed very high in the atmosphere, where ultraviolet light is much more intense and can create all kinds of interesting photochemistry, a sort of photochemical tanning? (In fact, we don't even know what chemical compound actually makes it red...though this is a separate-but-related research question known as the Jovian chromophore problem.)",
"That all changed in 2006, when the second largest vortex on Jupiter, oval BA, suddenly turned red. This is clearly some kind of big clue about what's going on. Through both climate modeling and careful retrieval of wind speeds by tracking clouds in various spacecraft images, you can actually discern between the two likely scenarios (deep welling vs. photochemical tanning) by looking at wind speeds. If there's new stuff welling up from the deep, you'd expect vertical velocity to have increased, which creates a stronger high pressure system at the center and thus faster horizontal wind speeds around the perimeter. A higher cloud top explanation, however, doesn't require faster wind speeds - just slow growth through vortex cannibalism (yes, vortices \"eat\" each other through merging) and time for the material to tan.",
"I found that the wind speeds hadn't changed before and after reddening, so it seems likely that photochemical tanning is likely the right explanation here. ",
"This also fits our most accepted model of how these big vortices work better; it turns out that the GRS and oval BA are probably nothing like hurricanes on Earth. In the Northern Hemisphere, hurricanes on Earth actually spin counter-clockwise near the surface towards a pressure low, winds rise up in the middle of the eye, producing a pressure high aloft at much higher altitudes in the atmosphere around which the winds then spin clockwise. That's a lot of vertical structure to maintain, and one thing that will kill a hurricane quickly is having a strong ambient vertical wind shear; if the surrounding winds blow at different speeds near the surface than at altitude, then the whole hurricane quickly falls apart, as it just can't maintain that complicated vertical structure.",
"On Jupiter, we're fairly sure there is some pretty strong vertical wind sheer (based on our one measurement from the Galileo probe as well as considerations of temperature gradients in latitude), so maintaining a vortex that has a pressure low at depth bring material up to a pressure high farther up seems pretty difficult. A much better model for the GRS seems to be an isolated blocking high with no pressure low beneath it, similar to the ",
"omega block",
" that led to California's drought the past few years."
] |
[
"Why don't candles smell until you blow out the flame?"
] |
[
false
] | null |
[
"TLDR: The stuff you smell is being burned up while its lit. "
] |
[
"Complete combustion turns all the components of the candle into gases, which is why expensive candles tend to run very little. The wax and wick mixture is perfect for a virtually perfect, clean flame. ",
"In combustion of the solid wax, first it must be vaporised. This vapour normally rises into the blue core of the flame, where heat from combustion reactions prior, and oxygen drawn in by the riding current of air, create the light and cause continued combustion. ",
"When we interrupt this process by essentially removing the combustion in process, the vapour has already risen, and much of the wax on the surface is still hot enough to vaporise for a moment longer. The coolness also creates a small amount of incomplete combustion, which requires less heat, and is not sustainable. That is, it's still hot enough for the vapour to react with the air, but not so well. ",
"The vapour and the dirty products of incomplete combustion smell. ",
"Cheap candles, and candles with a sooty flame are also prone to being a bit smellier, as the additives may require a hotter flame, which the candle can't achieve in a normal oxygen environment. "
] |
[
"Ask science is not the place for guesses, especially ones as wrong as this.",
"Read the rules for the subreddit!"
] |
[
"What does the SEIR model of infection actually tell me?"
] |
[
false
] |
There are so many formula's but it doesn't mean much to me. I have a definition for most part of the model but I can't seem to put them together. I there a succinct way to describe it? Phone grammar
|
[
"The SEIR model is one way of projecting how many individuals in a population are ",
"usceptible ",
"xposed ",
"nfected and ",
"ecovered when considering an epidemic that allows an infected individual to immediately transfer the parasite to another individual. ",
"Some parasites have latency periods where an individual can be infected, but cannot infect another individual. These epidemics are covered by other models such as the SEIS model.",
"The equations you see are the calculations needed to obtain these values: ",
"http://en.wikipedia.org/wiki/Epidemic_model#The_SEIR_model",
".",
"The terminology for each symbol can be found in a table at the top of that page: ",
"http://en.wikipedia.org/wiki/Epidemic_model#Terminology",
"."
] |
[
"It allows you to model the rate at which an infectious disease spreads through a population, and as such the impact an infectious disease will have on that population. Will it be a minor outbreak or a full blown epidemic? What happens if the disease mutates such that it becomes more contagious, or what happens if a vaccination program is introduced.",
"In contrast to the SIR (Suspectible-Infectious-Recovered) model, SEIR also allows for modelling of diseases where there is a pre-infectious stage (",
"xposed) where the person has caught the disease, but is not yet infectious. Thus it is possible that they can be removed from the general population before they infect anyone.",
"The mathematical formula are just about how many people move from one stage to another (eg. Susceptible to Exposed) at a given time step."
] |
[
"It's a way of describing how the population is divided (into the SEIR categories) in relation to a particular infection, and how individuals transfer between categories. Just like with any model, if you know a few parameters (for instance, the proportion of the population in each category, or the rate that individuals move from one category to another) then you are able to predict a load of cool things (for instance the basic reproductive number Ro), and derive equations which will tell you about specific dynamics (i.e. the pattern of spread of the infection). Each disease is unique in its dynamics and characteristics, and the SEIR model helps us to simplify this a little. "
] |
[
"Even though we share 98% of our DNA with chimpanzees, we can not interbreed. Since it is known that Humans (Homo-Sapiens) interbred with Neanderthals, is there any estimate on how close of a match our DNA was?"
] |
[
false
] | null |
[
"A recent estimation is that 7.9% of the differences between humans and chimps occurred after the split from Neanderthals, so that would put the estimate of differences in our DNA from Neanderthals at around 0.2%. In other words, modern homo sapiens share around 99.8% of their DNA with Neanderthals.",
"http://humanorigins.si.edu/evidence/genetics/ancient-dna-and-neanderthals/sequencing-neanderthal-dna"
] |
[
"According to my Anthropology text (A Human Voice Exploring Biological Anthropology) on pg. 270 it states that it varies based on location with some areas being as high as 62% (",
"Sankararamann et al, 2014",
") and in others as low as 0.1%."
] |
[
"Do you mean that the genetic similarity between the two species varied across homologous genomic loci?"
] |
[
"Does the mirror test really prove consciousness or self-awareness?"
] |
[
false
] |
And does failing the test really show that you aren't conscious or self-aware? It seems like an incomplete test to me, but maybe I'm missing something. I feel like an animal can be conscious but still lack the reasoning power to realize that the animal in the mirror is himself. Conversely, I feel like an animal can be intelligent enough to realize for some reason that the animal in the mirror is him, but not have awareness. But maybe I'm missing something.
|
[
"Posted this photo on my facebook last month:",
"Forcing Trunks to accept the fact that he's a dog. He wishes he took the blue pill instead.",
"We showed my dog the mirror for a while while interacting with him to help him understand that he was the one in the mirror. We don't have any ground level mirrors in the house, so this is the first time in his life that he's really seen himself and others in a mirror.",
"He looked genuinely sad the rest of the night, like he was contemplating his non-human nature.",
"Just thought I'd share."
] |
[
"I'm not sure I'd call the mirror test a measure of ",
", but that's more of a philosophical matter. It certainly ",
" a measure of self recognition, of course - or, more accurately, a certain ",
" of self recognition. ",
"Animals that normally fail the mirror test may still possess a degree of self awareness; take ",
"this paper from a few months back about Rhesus monkeys.",
" They fail the standard mirror test, but when there's an additional form of stimuli (a head implant) they're apparently able to recognise themselves in a mirror. The authors thus concluded, and I'm inclined to agree, that they had found evidence for \"an evolutionary continuity of mental functions\"; it may be less useful to divide animals into \"self-aware\" or \"not self-aware\" than it is to categorize them as ",
" or ",
" self-aware."
] |
[
"haha awesome story",
"poor thing, probably thought he was gonna grow up to have hands, stand up, and eat at the table and everything."
] |
[
"Gravity Probe B has essentially perfectly spherical gyroscopes that are supposedly only 40 atoms out at any point. Would these be, relatively, the roundest objects in the universe?"
] |
[
false
] |
If the gyroscopes are the size of ping pong balls (~2.5 cm diameter) and only have an error of a maximum of 10 nm, relatively, they would be flatter than neutron stars would they not (an error of up to 5 mm over a diameter of somewhere around 15 km)? Is anything more round and spherical than this?
|
[
"The gravity probe b website claims they are topped in sphericity by neutron stars ",
"http://einstein.stanford.edu/TECH/technology1.html",
". If you want to stretch the definition of object slightly, I believe electrons are the most spherical things ever measured ",
"http://www.youtube.com/watch?v=yYZhNBYYmLk"
] |
[
"The associated charge distribution does, and that's what has been measured to exceptionally high precision ",
"http://www.nature.com/news/2011/110525/full/news.2011.321.html",
". When you get right down to it though, nothing really has a shape; everything is just a charge/mass distribution on some level."
] |
[
"If for \"round\" you'll accept a circle rather than a sphere, then a possibility is the orbits of some binary pulsars. Due to gravitational radiation, they naturally circularize their orbits over time. We can measure the eccentricity of the orbits from pulsar timing experiments. ",
"One pair in particular(pdf)",
" has an eccentricity of 1.283(5)×10",
" which corresponds to a fractional difference in axes of 8.23×10",
" That means a deviation of 80.3(5) cm out of an orbital radius of about 9.8 million km."
] |
[
"Why does Venus rotate so slowly?"
] |
[
false
] |
I remember reading that Venus rotates at a rate much slower than Earth and have been wondering what the cause of this is.
|
[
"It took me less than 5 minutes to do the reference trail on the Wikipedia article, which leads to ",
"two",
" ",
"articles",
" by the same authors that describe ",
" and ",
" conclusions that lead to the points about tidal locking and thermal tides. Laskar is a well respected researcher, but two papers a consensus does not make.",
"Didn't take much longer to find ",
"several",
" ",
"news",
" ",
"articles",
" describing Venus Express measurements showing that the rotation rate is slowing and that nobody knows why, though theories in those links directly refute those of Correira and Laskar (i.e. that thermal tides actually slow the planet down rather than speed it up).",
"TL;DR Nobody really knows why. Wikipedia lies."
] |
[
"http://en.wikipedia.org/wiki/Venus",
"according to wikipedia its because the atosphere is so dense it has a tidal (like the sea on earth) effect on the planet, where its rotation actually switches direction over billions of years, it is currently a retrograde motion, but slowing again. eventually it may rotate at a speed where only 1 side ever faces the sun."
] |
[
"Sources please."
] |
[
"Why do airplanes seem louder when it's really cold outside?"
] |
[
false
] | null |
[
"Hey guys,",
"I've come up with some possible explanations for the loud airplanes. While we're all waiting for the airport people to call me back, I thought I'd share some with you.",
"Imagine you bought a McChicken sandwich but couldn't eat it for a few days. Your next move? Put it in the refrigerator. Deliciously preserved even over a length of time. Same deal with sound waves, except they're deliciously preserved over a time of <i> length </i>",
"Planes aren't actually louder when it's cold. they use special cold weather fuel. It makes their engines louder. It's like one of those scammy fuel additives for high mileage jets. ",
"Tiny ice crystals in the air vibrate against each other, creating a domino effect. The cascading ice crystals move in waves, perfectly mimicking the sound itself. Ice waves make for a remarkably efficient mode of transportation. Just ask a surfer in Duluth. ",
"When it's cold, jets have to fly closer to the ground to find the proper air density to achieve adequate lift. You ever see Superman nearing the Fortress of Solitude? Dude's altimeter is at like 12 feet. So like, the planes aren't louder, they're just closer.",
"Planes aren't actually louder when it's cold. Our ears are simply more sensitive due to seasonal affective disorder and it's dark and life is pointless. ",
"Summer things absorb sound: micro organisms, insects, dog poop, green grass and other vegetation, bomb pops, lakes and streams, children's laughter. ",
"*edit - wow this blew up overnight. thanks for the gold!"
] |
[
"I am going crazy. Somehow, cold air is more dense than warm air. I'm trying to imagine a hot air balloon here. Obviously understanding the answer to this has opened up a pandora's box of science questions which is revealing that I can't remember anything from my high school science courses. Yikes. "
] |
[
"I am going crazy. Somehow, cold air is more dense than warm air. I'm trying to imagine a hot air balloon here. Obviously understanding the answer to this has opened up a pandora's box of science questions which is revealing that I can't remember anything from my high school science courses. Yikes. "
] |
[
"When I look straight up into a perfectly clear, blue sky, What Exactly am I looking at?"
] |
[
false
] | null |
[
"i'll give some nonstandard answers to this relatively standard question. (standard answer is that you're looking into the great void, and the blueness is merely scattered light from the sun, rather than the 'color of' something, which glosses over the fact that everything else you look at outside in the daytime is also visible by virtue of scattered light from the sun).",
"maybe you're looking at the ",
"Earth's atmosphere",
", which can be blue (and usually is from your point of view) but also takes on other colors depending on where the light is coming from.",
"maybe you're looking at ",
"white blood cells",
" tumbling through your retinal blood vessels.",
"maybe you're looking at ",
"floaters",
", stuff suspended in the transparent vitreous stuffing of your eyeball(s).",
"maybe you're looking at scintillating phosphenes from a ",
"migraine aura",
".",
"perhaps you're looking at the ",
"afterimage",
" of the sun, or simply daydreaming.",
"using the same expansive definition of 'looking at' that qualifies the standard 'great void' answer (where 'looking at' doesn't imply 'seeing'), you're almost certainly looking at a star, and depending on exactly where on earth you're standing and what time of day it is, it might be a famous one; you might even be looking at a planet. you MIGHT even be looking straight into the alien eyes of another sentient creature standing on the surface of its homeworld, or its prisonworld, or whatever, if only for a brief moment, but that is very unlikely."
] |
[
"You're looking at outer space!\nThe blue color comes from a phenomenon called ",
"Rayleigh scattering.",
" This is the elastic scattering of photons, or more simply put, scattering in which the photons keep their original energy. This scattering is caused by the atmosphere. Now, as for the color, blue and violet are at the high-energy end of the visible light spectrum. This high energy visible light is scattered by the atmosphere the most, giving the sky its characteristic color."
] |
[
"Yeah!",
"Also lots of little moving dots, many of which execute a sine-wave wiggle motion. Those are white blood cells which form gaps in the blood-filled vessels in front of your retina. ",
"Scheerer's phenomenon",
" or \"blue entopic phenomenon.\" The wiggle-motion is actually a capillary, and if you watch for awhile, you'll see another dot make the same wiggle in the same place in your visual field.",
"Also a fuzzy colored X-shape in the exact center of your vision ...a pair of bluish patches, with a pair of yellowish patches. ",
"Haidinger's Brushes",
". It's caused by polarized light of blue sky in a wide band 90deg from the sun's apparent location. It works best with dark blue sky when the sun is low. For added benefit, spin your body around while gazing upwards, and the pattern will remain still while your eyeballs turn."
] |
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