title list | over_18 list | post_content stringlengths 0 9.37k ⌀ | C1 list | C2 list | C3 list |
|---|---|---|---|---|---|
[
"What about the dinosaurs made then unable to survive the K-T extinction?"
] | [
false
] | What is it about dinosaurs that made them die out to the K-T extinction, while other animals survived? How did the survivors survive? Was it just by sheer luck that the dinosaurs died out and mammals etc. survived through the extinction? | [
"This is an excellent, but incredibly complex question. But here goes: just a few notes on the subject but not at all a comprehensive answer:",
"First off, dinosaurs weren't the only casualties - lots of groups went extinct, from many of the planktonic foraminifera, on up to many groups of mammals (yes, mammals ... | [
"From wiki",
"\"A lingering impact winter... made it impossible for plants and plankton to carry out photosynthesis.\"",
"\"Yet the devastation caused by the extinction also provided evolutionary opportunities. In the wake of the extinction, many groups underwent remarkable adaptive radiations — a sudden and pr... | [
"Not all of the dinosaurs went extinct. The larger ones did, while many of the small species of dinosaur, mammal, reptile, etc survived. Large animals were more vulnerable because they couldn't find shelter from the impact and resulting firestorms, and would not have been able to find enough food afterward."
] |
[
"Smoking during pregnancy"
] | [
false
] | [deleted] | [
"The baby's source of oxygen and nutrients comes from the mothers blood. When the mother smokes cigarettes, all the harmful chemicals like cyanide, lead, etc enter the mothers blood stream. The two main chemicals responsible for most birth defects are nicotine and carbon monoxide. Nicotine narrows blood vessels m... | [
"What I have stated is true, and though it might be oversimplified, it does not make it any less true. Sure we don't know ALL of what happens, but we do know some.",
"Edit: If you want information from something besides \"one of those poorly run internet health sites\" ",
"here is an article from the CDC basic... | [
"Impaired fetal oxygen delivery is the BEST studied cause of problems in pregnant women who smoke. Like other posters said here, nicotine is a major factor. It causes vasospasm and acutely decreases intervillous perfusion (decreases blood supply to the fetus). ",
"It's also been ",
"suggested",
" that nicotin... |
[
"Is there anything interesting in our solar system that is outside of the ecliptic?"
] | [
false
] | null | [
"Pluto is probably the most well-known highly inclined object in the Solar System. Its inclination is over 17 degrees.",
"Ceres is inclined at about 10 degrees. The asteroid Pallas is inclined at almost 35 degrees, and there are a number of less-well-known asteroids of higher inclinations."
] | [
"High-inclination objects tend to be of interest ",
" of their high inclination.",
"Retrograde asteroids are very rare, whereas retrograde long-period comets are quite common. ",
"https://en.wikipedia.org/wiki/List_of_exceptional_asteroids#Orbital_characteristics",
"Eris is the most highly inclined dwarf pl... | [
"How do they stay inclined without falling? ",
"Revolving objects ",
", even ones with zero inclination. They are just falling so fast, they miss the sun entirely!",
"But seriously, inclined in comparison with what?",
"The sun's equator and the average plane of rotation of the solar system."
] |
[
"Question about Theorhetical Physics, Flatlanders, and Time."
] | [
false
] | Let me know if this is the wrong place for this. We understand ourselves to be perceiving three dimensions and sensing the fourth as Time. Now, lets imagine that we were flatlanders, only able to perceive two dimensions. Obviously, in this two dimensional space, we'd still be able to sense time - time would move forward, moments would progress from one to another. Would this be an instance of them "skipping" a dimension into the fourth, somehow utilizing the third dimension as their "time" dimension, or does it suggest that our assigning the fourth dimension as "time" to be relative only to our third-dimensional rationalization? (To go further: Flatlanders wouldn't understand the concept of depth., or how to move "deeper" into something. What if we call the fourth dimension Time, but there is in fact another "direction" that hypothetical fourth dimensional beings can move in, but are as alien to us as depth is to a flatlander?) | [
"I don't think you should consider time as a fourth dimension - and certainly not ",
" fourth dimension. ",
"If you lived in Flatland, you would have 2 dimensions, or using your line of thinking 3 with the 3rd as time. You wouldn't assume that there is a different 3rd dimension and time is #4.",
"Have you r... | [
"That is precisely how I've come to understand it; yet, people often describe the new direction in the fourth dimension as time: We can go forward in time or backwards in time, so as to move through the fourth dimension, analagous to our third dimensional ability to \"go deeper\" (as compared to a flatlander).",
... | [
"Try reading through my ",
"type-up of space-time",
". it may not be exactly what you're talking about, but while time is a dimension ",
" space, it's not connected in exactly the same way that the space dimensions are connected to each other. There's a rich, more general expression of geometry that can descr... |
[
"What is the general math behind L-points and the interplanetary transport system?"
] | [
false
] | I think I have a good grasp on how gravity assists work, but I've never been able to find anything but the most superficial article on the interplanetary transport system other than saying "it's complicated" and "needs a computer". Some questions include: If a probe were to do a flyby of lets say Earth-Moon L-1 what would be the ideal and realistic Delta-V gain and how is that calculated? How are the windows for L-points determined? What determines how long the probe spends in a Halo Orbit? What exactly is a Halo Orbit? How can it really be "zero" propellant for some routes? How do travel times compare to a Hohmann? Other than L-points and Gravity Assists what other landmarks are there on the interplanetary transport system? I know this is a lot but I just can't find any good mathy sources out there and I would love to crunch some rough numbers rather than just rely on iterative simulations. | [
"Good questions, and lots of questions; this will be long.",
"L-points, more commonly called Lagrange points, are a set of 5 locations between two large planetary bodies in which one orbits the other (although they both orbit each other, 1 of them has way more mass and only slightly moves). At these special Lagr... | [
"If you do get around to posting a video series I would love to see it. Maybe we could start an AskScience video lecture series for the public to help understand some of the more frequently discussed concepts here."
] | [
"The key is to do your calculations in the frame that rotates at the same rate as the large masses, and is centered on the center of mass of the system. Since this is a rotating frame, you have to consider not only gravity but also the (fictitious) centrifugal and Coriolis forces. When you consider the total force ... |
[
"How long is the free mean path inside an electron microscope tube?"
] | [
false
] | I figure it has to be at least as long as the vacuum chamber itself, from the electron gun down to the sample. But I'm wondering what the preferred value is. Twice the length of the chamber? Three times? And also, of course, why that's the answer. | [
"Mean free path is more important for uncharged particles than charged particles. Uncharged particles, such as photons and neutrons, travel a relatively long way before interacting, and give up a significant fraction of their energy each time. ",
"Electrons (and other charged particles) on the other hand, inte... | [
"I'll gladly tell you more, I'm not sure I made my point. I understand the interaction volume inside the specimen when you shoot it with an electron gun, and I understand the many scattering events that make up this interaction volume. This interaction volume is roughly 1-2 microns for a typical accelerating voltag... | [
"Right after I replied, I found the answer I was looking for. The equation was on Wiki, surprise surprise.",
"It says ",
"here",
" that the mean free path in a pressure of 10",
" mbar (which is about 10",
" Torr) is about 1,000 cm, or about 10 meters. So a gas molecule is going to bounce of the wall of th... |
[
"Do the harmful chemicals that are listed in anti-smoking ads come from the additives that the manufacturer adds or are they inherent to the tobacco itself?"
] | [
false
] | null | [
"Most of the stuff listed comes from pyrosynthesis, or incomplete combustion. Arsenic, what they call rat poison, comes from the fertilizers. Tar, is the total particulate matter caught on a filter pad, you can see it in the filter too, minus nicotine and water. Nicotine comes* from the plant as well, in addition t... | [
"Pack a day habit of most commercial brand cigarettes is equal(give or take a few either way) to 300 chest x-rays a year.",
"You're comparing apples and oranges, or in this case photons, alpha and beta particles.",
"Also worth pointing out the commonly used LNT model is pretty shoddy."
] | [
"Very nicely explained. Only missing one item: It's the dose which makes the poison. That's a fact which is conveniently ignored by the ads."
] |
[
"Why does low gear act as a brake when going down hill?"
] | [
false
] | Why does low gear act as a brake when going downhill? I understand when going uphill, low gear is needed for a higher force (torque) at the wheels. But when going downhill, the work comes from gravity, and the difference between low gear and high gear is at the same speed, the gears in the engine (before the gearbox) spin faster with less force (torque). Does it just rely on the resistive force in the engine to keep the car at a constant speed? What exactly is the resistive force? | [
"Most of the braking effect is actually due to vacuum caused by the closed throttle plate, the energy absorbed by compressing the air is mostly returned to the engine on the following expansion stroke, the air acting much like a spring."
] | [
"The resistive force is the engine compressing the air in the cylinders. When you use a low gear you are spinning the engine the fastest for your speed. Therefore the most compression events happen per time, and you get the most breaking. ",
"Tldr, your converting kinetic energy to hot air"
] | [
"Thanks for pointing that out.",
"I had a nagging suspicion that I didn't know what I was talking about.",
"I actually had no idea that diesels controlled their RPM via fuel regulation as opposed to air regulation in a gasoline engine.",
"You wouldn't happen to know the reason for the differing designs would ... |
[
"Do animal's limbs 'fall asleep' like human hands and legs and such do? My cat sleeps in weird positions but never seems to wake up with a leg 'asleep' but her motions."
] | [
false
] | What the title says. Why doesn't my cat sit there shaking her numb paw from it being in a weird position? | [
"This is a tough question to answer for sure since we can’t know how they’re perceiving things, and I apologize in advance that this is anecdotal and not sourced, but I believe that they do. Most mammals have roughly the same neurologic and circulatory structures as humans do so there’s no reason to suspect they wo... | [
"They absolutly can! They just move before it get worst. I work with cows and you see them with numb leg when they slept too long on one side. Most of the time, they switch side before this happen. We even need to do it ourself when one has an injury, because their weight can litterally cut off their blood circulat... | [
"Thanks for this, I enjoyed reading your answer. The conditioned to be uncomfortable, I really get that. I Akshay the time for this answer."
] |
[
"Viewing in the dark."
] | [
false
] | When I'm in the total dark with eyes open, are they focusing on something? Do they just act like an auto-focus camera that cannot focus on anything and keep trying? Also do eyes acts like a camera with respect of light? If I keep looking at a very little light up object in the dark, will I see it better over time? | [
"Your eyes aren't focusing on anything in total darkness, they will dilate to try to get as much light in as possible so you can see. No, you will not be able to see better."
] | [
"Also do eyes acts like a camera with respect of light? If I keep looking at a very little light up object in the dark, will I see it better over time?",
"Your retina won't continue to accumulate light over time, no. For one thing, your eyes are constantly moving in ",
"saccades",
", so the image would consta... | [
"Do you have any reference for this?"
] |
[
"Why does the colour of my eyes change?"
] | [
false
] | null | [
"Eyes don't change color. However, the iris may be ",
" as a different color based on lighting conditions, and even based on comparisons with surrounding colors."
] | [
"Updated from Wikipedia source:\nThe appearance of blue, green, as well as hazel eyes results from the Rayleigh scattering of light in the stroma, a phenomenon similar to that which accounts for the blueness of the sky. Neither blue nor green pigments are ever present in the human iris or ocular fluid.[3][5] Eye co... | [
"Do you have any sources that back that up?",
"The only thing I can provide this close to bedtime is Wikipedia:",
"Changes (lightening or darkening) of eye colors during puberty, early childhood, pregnancy, and sometimes after serious trauma (like heterochromia) do represent cause for plausible argument to stat... |
[
"MEDICINE Could healing gels be possible?"
] | [
false
] | null | [
"The trick is to constrict the healing effect to the wound, otherwise it will cause intergrowth. So just recreating the effect is not the way to go, but you'll have to increase the speed of the body's own effects."
] | [
"Hmm. Good point didn't even think about that. It's one thing to speed up healing but you have to stop it as well. "
] | [
"Cell based \"patches\" are already available and might be similar to what you're asking. Again, as a previous post mentioned, it'd be important to constrict the healing effect to the wound. However, more importantly, it's a cost vs. benefit thing. There are already patches which are able to heal chronic ulcers/... |
[
"Can color be heard?"
] | [
false
] | null | [
"Color is a psychological not a physical property. The human visual system gives rise to the experience of color and different experiences occur for different wavelengths or combinations of wavelengths. ",
"Pressure on the ear drum is experienced as sound and does not typically produce color experiences. ",
"S... | [
"\"Different experiences occur for different wavelengths or combinations of wavelengths\"\nAre these wavelengths different from sound waves? I know we percieve them different and they are different sizes, but is there a bigger difference between them?"
] | [
"Yes. These are properties of photons. Sound is the result of changing air pressure. Lots of things are spatial or temporal waves. I can draw a wave (e.g. a sinusoid) on a piece of paper. That too has a wavelength. It's kind of like saying \"my table has a width and my pencil has a width so is the table the same a... |
[
"Does commercial lumber contain enough infect fragments of DNA from the tree that produced it, for genome reconstruction and analysis?"
] | [
false
] | [deleted] | [
"Depends on how it is treated. But DNA analysis has been successfully used to track illegally logged timber. It seems more common to use other techniques to identify the origin, though, like isotope ratio analysis."
] | [
"That's a big maybe",
"That's a mostly yes with a lot of maybe, depending on how crazy you want to be. ",
"Forensic genotyping",
" of lumber to try and catch illegal timber has been around for years. Could you do this for an entire genome in every tree species? Probably not without a lot of fine-tuning. There... | [
"That's a big maybe. DNA degrades fast. There's probably not enough intact sequences left. But pinpointing the origin with an isotope ratio analysis could still work."
] |
[
"limitations of photon frequency?"
] | [
false
] | If I wave a magnet back and forth once per second, have I produced a light wave of 1 hertz? Is there a lower limit as to how low the freq can be using this simple method of generating light? Also is there an upper limit to freq of light? I think with very very high frequency gamma rays, they interact with the dirac sea and force virtual particles into reality - anyone know the ballpark of this upper limit? | [
"A photon's frequency is equivalent to its energy - the more energetic a photon, the higher its frequency - and at a certain point, called the ",
", we don't really know what happens. It's been suggested (as below, by QuantumBuzzword) that that might turn it into a black hole, but there are plenty of issues with ... | [
"If you look at Maxwell's equations, there's no real lower limit on EM radiation. What you're proposing should create an ultra low frequency radio wave. ",
"For pair creation, it comes in at an energy of 1.022 MeV, which is directly proportional to the frequency by E=hf. This process is actually quite common insi... | [
"An important point worth mentioning is that pair-creation requires that the photon interact with something ",
" than the vacuum/Dirac sea. This ties in with the second important point worth mentioning: assuming relativity is correct (as most do) there is no upper-limit to the photon's frequency ",
". In other ... |
[
"Do planets slowly grow in size?"
] | [
false
] | [deleted] | [
"The burial of archaeological sites is an indication of erosion and deposition (i.e. mass is transferred from one area to another) as opposed to growth of mass/volume of the Earth through time. Whether we are talking about archaeological sites or fossils, we have to consider that there is significant preservation b... | [
"It’s a redistribution of existing mass. ",
"Imagine it as a sand dune. If you place something on top of it and come back a million years later , that object will no longer be on top. Due to wind , rain, other factors. ",
"Now scale it up to an entire planet, with all of its forces acting upon it."
] | [
"This is mostly compensated for by the loss of atmospheric hydrogen to space. We lose ~3kg/s to space. This is about 300 tons per day."
] |
[
"Why are poison dart frogs brightly colored?"
] | [
false
] | How did it come to be that brightly colored frogs survived the processes of natural selection? Let's say that we have two frogs, both poisonous, one camouflaged, and one brightly colored. A predator would go for the one that it can see, the brightly colored one. The predator would die in either situation, but it would seem to me that selection would always favor camouflage as opposed to vivid coloration. I know that this is not the case as there are many poisonous species that have bright coloration, but I would like to know why such coloration gets selected. | [
"You have made a key assumption. Many poisonous animals dont necessarily kill their predator. Many make them very sick, and most simply dont taste nice and are spit back out.",
"It is to the advantage of the frog that the predator survives. There have been studies that show that if a bird eats a brightly coloured... | [
"Many poisonous animals dont necessarily kill their predator. ",
"That's it. Right there. I didn't even think of that. Thank you. It makes much more sense now."
] | [
"Glad to help."
] |
[
"Is the sun a black body?"
] | [
false
] | I know this is in an idealized context, but I've seen the sun described as a black body before. Does that mean it's in thermal equilibrium if it emits black body radiation? | [
"The plasma that makes up the \"surface\" of the Sun is in pretty good thermal equilibrium, so the sun's spectrum is pretty close to that of a blackbody. (I say \"pretty good\" because sunspots, for example, cause variations in temperature across the surface.) ",
"There is a bigger complication, though: at di... | [
"Don't forget about the absorption lines in the solar spectrum. That's how we discovered helium!"
] | [
"Absolutely! But that's a case of \"seeing to a different depth\"... at those wavelengths we are not seeing as deep into the sun, so the photons we do see come from a cooler, outer layer. (ie the cooler layer is absorbing photons at the line frequency from the hot inner layer, but is also re-emitting those in tho... |
[
"Dinosaurs in Space (as ejecta)?"
] | [
false
] | I read that the crater at Chicxulub is over 110 miles in diameter. I can't find estimates of the mass of ejecta sent into space at escape velocity. What would the math be to determine how much of it was dinosaur? Given current biomass per square kilometer, and assuming the volume of escape-velocity ejecta can be found, what are the chances? Additional questions: If a dinosaur did make it into space, what would the overall likelihood of it remaining in our solar system and not impacting another body for 65 million years be? Would it be recognizable or would exposure destroy it? | [
"I think the main issue would be the heat of the impact at ",
"the crater site",
":",
"\"The impactor had an estimated diameter of 10 km (6.2 mi) and delivered an estimated energy equivalent of 100 teratons of TNT (4.2×10",
" J). By contrast, the most powerful man-made explosive device ever detonated, the T... | [
"Ignoring the calculation to figure out what percent of the ejected matter had dino-origins, you should be aware that the ejecta gets completely fucked for a variety of reasons. I can think of 3 main sources:",
"Heat and speed of the projectile, as well as heating of the air underneath the projectile by compressi... | [
"It could have ",
"tea",
"."
] |
[
"Everything is expanding from the center of the universe. Can we see more or less depending on where we look?"
] | [
false
] | null | [
"The universe does not actually have a center. Everything (not gravitationally bound) is expanding away from everything else. Not a 'center.' ",
"Every direction we look is ultimately moving away from us, and it would appear that way from any other location as well."
] | [
"The ",
"cosmological principle",
" means that, when viewed over sufficiently large scales, the universe looks the same everywhere.",
"Also, there is no single \"centre of the universe\". To only slightly simplify: the big bang occurred at every point in space, and every point is moving away from every other ... | [
"And, might as well add a deep field image to this post: ",
"http://www.nasa.gov/images/content/690958main_p1237a1.jpg"
] |
[
"Can you see the curvature of the earth when looking at an ocean horizon?"
] | [
false
] | When I have gone to the beach I always thought that the horizon of the ocean looked curved, as if I were seeing the curvature of the earth. So is this true, or is there something wrong with my eyes? Also, if you can see this effect, but it is not in fact caused by the curvature of the earth, what is causing it? | [
"Searched",
"Relevant ",
"discussion",
"Original question by ",
"Sm3ulders",
"When looking at the horizon (at the beach, looking over at the ocean for example) you can see a distinct curve. Is this curve the curvature of the Earth, or the curve in your line of sight? Apparently you can only see things for... | [
"I don't know what this statistic is supposed to refer to, but it's somewhere between wrong and useless as stated. For instance, the sun is rather more than 30 miles away, and is quite visible."
] | [
"Thanks for that! And sorry, I know reddit's search is less than par, so used google unsuccessfully instead. This will make my trip to the beach next week more informed. "
] |
[
"AskScience AMA Series: We are Andrea Copping, Biological Oceanographer, Genevra Harker-Klimes, Physical Oceanographer, and Meg Pinza, Coastal Scientist. We study the environmental effects of marine energy at Pacific Northwest National Laboratory. Ask us anything!"
] | [
false
] | Hi Reddit!! Marine energy is a huge, largely untapped energy resource. So huge that more than 10% of Pacific states' electricity demand could be satisfied by developing a fraction of the wave energy available off the West coast. Imagine a future where we could harness ALL of our oceans' energy, including energy from moving water, like waves, currents, tides, and offshore winds. Renewable energy like this is not only immense, but its predictable nature allows power grid managers to offset more established, yet variable renewable resources such as wind and solar power. And on a regional scale, widespread marine energy has the potential to provide localized power sources in isolated coastal regions and areas susceptible to extreme events, such as hurricanes, flooding, and storm surge. But are there environmental costs to widespread installation of marine energy devices in our oceans? How does marine life react to these devices? And is this approach safe? At the U.S. Department of Energy's (DOE) Pacific Northwest National Laboratory, we are tackling these exact research questions . Ask us Anything! We're looking forward to this! We'll be on at 9 AM PT (12 ET, 16 UT). Ask us anything! | [
"Hello, thank you for taking the time to do an AMA with us! This is a really interesting topic. What sort of potential environmental impacts have you found from marine energy? Are there ways to mitigate them?"
] | [
"The main concerns are around what could happen to animals around rotating turbine blades, either collision risk or changes in behavior. Underwater sound from devices may also be a concern as this could interfere with navigation, hunting prey, and socializing. There are other lesser concerns, but most do not indic... | [
"Wind energy, particularly offshore wind energy, has progressed a lot in the last 20 years, with the cost reduced significantly. Marine energy is expected to follow the same pattern. European studies have suggested the levelized cost of energy with be in the range EUR 0.17/kWh and EUR 0.23/kWh by 2020. As arrays... |
[
"How do geese know which way north/south is?"
] | [
false
] | null | [
"Along with that, most birds have an extra sense, magnetoreception, which allows them to detect the Earth’s magnetic field, and therefor know which direction is north or south."
] | [
"Interestingly, there is some evidence that suggests that birds primarily use there magnetoreception not as a compass but as an altimeter. "
] | [
"It is most likely related to their ability to detect the intensity/density of the magnetic field as they fly through it. ",
"The further from the earth you get the weaker its magnetic effect."
] |
[
"Can anyone help us identify what kind of bone this is? My brother found it in northern Missouri and has no idea what animal it is from."
] | [
false
] | null | [
"All those pictures are thumbnails. Could you share larger pictures?"
] | [
"Crap. Sorry, this is my first post. "
] | [
"Fixed!"
] |
[
"How is gender evolutionarily advantageous?"
] | [
false
] | null | [
"No, it is advantageous to have sexual reproduction because new gene combinations lead to a process of natural selection. Genetically identical beings, such as in asexual reproduction, could all be wiped out from one external factor. The genetic differences in offspring underlying sexual reproduction allow for diff... | [
"In the literature on reproductive genetics the word 'gender' is commonly applied to male/female systems. Obviously 'gender' has a distinct meaning within psychology/sociology/anthropology, but this is not the context here.",
"No, it is advantageous to have sexual reproduction because new gene combinations lead t... | [
"Most species reproduce asexually. But the majority of life is too simple for sexual reproduction to even be a possibility. By numbers and biomass, bacteria and archaea far outnumber eukaryotes, and not all eukaryotes reproduce sexually. Horizontal gene transfer is common in prokaryotes, but shouldn't be confused w... |
[
"Why do particular foods such as bananas' phloem bundles (strings), eggo waffles, grape seeds/skins , and even some breakfast cereals sometimes leave a dry feeling in your mouth? (a dry that can't be wet if you know what I mean)"
] | [
false
] | null | [
"I think the sensation you're referring to is called \"astringency\" and is caused by tannic acids, which around found in a number of fruits, teas and wines. The tannins bind salivary proteins and cause them to precipitate, leaving a rough or dry feeling in your mouth.",
"http://en.wikipedia.org/wiki/Astringent"
... | [
"It's the buttermilk they use in their recipe.",
"Buttermilk as an oral astringent: ",
"http://www.ncbi.nlm.nih.gov/pubmed/16772560",
"Eggo ingredient list: ",
"http://www.kelloggs.com/en_US/kelloggs-eggo-buttermilk-waffles.html"
] | [
"Awesome, thanks for the info! But eggo waffles? I wonder is that is the same acids? "
] |
[
"Have we ever detected seasonal changes in spectrum (redshift / blueshift) from nearby stars due to the Earth's rotation around the Sun?"
] | [
false
] | As a rough estimate, the rotation of the Earth around the Sun changes its velocity relative to nearby stars as much as 200 km/s, as compared to its velocity six months later. While large compared to the speed of space probes, this is pretty small compared to the velocities of stars or galaxies relative to the Earth. Is it possible for us to detect the change in spectrum introduced by such as a small change in velocity? Has this been done in practice? | [
"Correction, our motion around the sun is about 30km/s.",
"The doppler shift from this motion is indeed imprinted on all radiation we receive. It's easier to see it in spectral lines than in the whole spectrum. It's even easier to see it in pulsar timing than in optical spectra."
] | [
"Thank you"
] | [
"It's too small.",
"It's easier to detect the parallax shift in nearby stars."
] |
[
"Can spiders walk backwards?"
] | [
false
] | I know this sounds stupid, but they don't have vision behind them. Can they purposefully move backwards? | [
"Species that use vision to hunt like wolf or jumping spiders do have vision behind them, and yes spiders can walk backwards, trapdoor spiders do this every time they drag a still struggling victim into their lair never to be seen again."
] | [
"Wolf spider"
] | [
"wolf [...] do have vision behind them",
"Sorry, what?"
] |
[
"How can a cell work so accurately on the molecular level?"
] | [
false
] | When I think of a human cell and it's inner workings I find it hard to believe how everything can work so accurately since the inner structures actually seem rather chaotic. For example, theres protein synthesis... First you have the extremely long DNA string rolled up, in a more or less randomly / unpredictable coil. Then, some protein floating in the, compared to the tiny DNA molecule, large space of the nucleus somehow manages to correctly attach to the correct spot of the DNA. When transcription is done, the mRNA somehow manages to correctly attach to the ribosome, which seems rather unlikely given the randomness of it's position and rotation.. The amino acid transporters, which also are flowing around randomly, then also correctly attach to the ribosome one after another... Mathematically, the chance of all this happening seems infintely small. I imagine this kind of like having a large bowl of water and throwing in an amount of different, small-ish LEGO structures - then shaking it wildly and hoping for the correct connections to form... It seems all so random, unpredictable and as if it shouldn't work at all.. So in short, my main question is: How can a cell, which is in itself rather chaotic - since the working proteines and enzymes are moving and rotating unpredictably - work so well? | [
"It's important to remember that cellular processes are not the result of a single enzyme finding a single substrate to react with. Pretty much every process is governed by many copies of the same enzyme circulating the cell, able to bind with many copies of the same substrate. While the individual probability of... | [
"Well, it ",
" quite chaotic. It's nothing like an engineered machine, where everything occurs in a precise, well-defined and stepwise order, where the parts play well-defined purposes and functionality is neatly separated, and so on.",
"It ",
" random. But that does not mean 'unpredictable', it just means th... | [
"How can a cell, which is in itself rather chaotic - since the working proteines and enzymes are moving and rotating unpredictably - work so well?",
"The high number of collisions guarantee the activity. Not only is ",
"what arumbar said",
" correct -that is, you're not shaking a single lego to bind with anot... |
[
"If I have 100g of Uranium 235 for one half-life, what determines which 50g decays?"
] | [
false
] | As half-life is the time it takes for half of a sample to decay, what determines which half will decay? Furthermore, what determines the part that will be around after 100 half-lives? | [
"As far as we can tell it's a completely random process. So \"nothing\" determines it, strictly speaking. "
] | [
"Half-life only really applies to bulk amounts of atoms, and cannot explain more than the relationship between quantities of starting materials/products vs. time (It's a bit like thermodynamics in that regard). It won't tell you which atoms will decay and when.",
"Spontaneous radioactive decay is what you want to... | [
"Physics is appropriate. Chemistry is the study of how different atoms interact. But if you are concerned with the nucleus of atoms decaying, that is physics.",
"Of your 100g of Uranium, the 50g that will have decayed will be interspersed among the whole amount."
] |
[
"\"Crappy beer gives me such a hangover.\" Is this true?"
] | [
false
] | If you drink a lower quality alcohol beverage will you get a worse hangover? And if yes, why? Thanks! | [
"barkeep in a beer-specialized bar here. (I never thought I'd cite my credentials on this subreddit :o)",
"'Quality' in beer is a difficult subject. There's a lot of pshychology involved but that aside lets look at the ingredients. All beer is made out of grains (mostley barley but wheat, maize and sometimes oats... | [
"What you would call a \"crappy\" beer will most probably contain more chemical additives than a quality beer. It is reasonable to assume that these additives will cause or aggravate some of the symptoms associated with hangover.",
"I can attest to that from personal experience. I'm Austrian but live in Australia... | [
"Quality in alcoholic beverages is very much more emotional than a taste thing.",
"So beer is to men as cosmetics is to women."
] |
[
"Why 100 neurons per \"pattern recognizer\"?"
] | [
false
] | In his latest book How to Create a Mind, Ray Kurzweil argues that the neocortex consists of 300 million pattern recognizers. Each of them is capable of recognizing just one pattern, consists of, on average, 100 neurons, and takes, on average, 8 inputs (page 196). I couldn't find an explanation of where these numbers come from, other than that the number of pattern recognizers is the estimated total number of neurons in the neocortex (30 billion) divided by the average number of neurons in each pattern recognizer (100). Wouldn't it be more logical to assume that each neuron is a pattern recognizer in its own right, and each synapse is its input, and so there should be 30 billion pattern recognizers with 1000+ inputs each? Is there any neuroscience research that supports Kurzweil's claims? | [
"It is generally believed that there is population coding going on in neurons, most likely to counteract noise, so it's not unreasonable to suppose that each neuron is ",
" \"a pattern recognizer in its own right.\" To explain this briefly (and very very inaccurately), imagine you have 100 neurons, each of which ... | [
"Is \"population coding\" a good term to search for? Are there good review papers, especially ones that address the degree of this \"redundancy\"? Is there any evidence for \"8 inputs per pattern recognizer\"?"
] | [
"Can't think of a good review right now, but there is a wikipedia article on it that might have some useful links. Regarding \"8 inputs per pattern recognizer\" that seems a bit nonsense. I assume that when he says pattern recognizer, he means \"filter.\" For example, filters in the visual cortex are reasonably wel... |
[
"Is human intelligence limited?"
] | [
false
] | null | [
"It depends on what kind of threshold you mean. It's very unlikely that any human being will be able to keep the whole of science and mathematics in his or her mind at once, for example. ",
"But if you're talking about the kind of intelligence where we can comprehend concepts if we put our minds to a particular c... | [
"There is no way to know if such concepts exist since we can't comprehend them in the first place. There may be things out there that a higher being (if it exists of course) can comprehend and we wouldn't even be aware of it; just like your cat and calculus example. So my answer would be yes, human intelligence is ... | [
"Considering that intelligence isn't very well defined, I'm not. That's why I took two alternate definitions to increase the chances that I wrote about the OP's definition of intelligence."
] |
[
"What is the speed of gravity (or a gravitational wave)?"
] | [
false
] | null | [
"The speed of a gravitational wave is the same as the speed of light. The best paper on this is ",
"this one",
" by Carlip."
] | [
"This isn't a good explanation, ",
"I'll link to the wiki",
".",
"Basically, this is more easily understood classically in terms of EM fields interacting with a polarisable medium, or in condensed matter quantum field theory terms as quasiparticles created by mixing of the electron and photon fields.",
"Try... | [
"The speed of light in a medium differs from c, but the paper states that the speed of gravity = c, which is constant. "
] |
[
"Is this a new theory of gravity?"
] | [
false
] | null | [
"Hello,",
"We don’t evaluate personal theories here.",
"Cheers."
] | [
"It's not a full theory just an interesting train of thought. I'm not asking for evaluations just conversations with other people who might find it interesting. "
] | [
"That is not something that we offer here."
] |
[
"How do polarised lenses block the glare from water?"
] | [
false
] | null | [
"Light wave energy can oscillate up and down, side to side, or any angle in between. The molecules in the lenses or lens coating allow only one angle of polarized light to pass through and block all others. If the angle is chosen to allow all vertical oscillations to pass, then any horizontal ones are blocked. Li... | [
"That's lot clarifying anything. There is absolutely no quantum physics going on here. 'Clarifying' polarisation of light by referring to the 'spin' of photons is almost always actually misleading the reader.",
"Saying a photon has spin is also technically incorrect because there are only 2 (linearly independent)... | [
"You did a great job of explaining that. Thanks for sharing some knowledge."
] |
[
"Would it be possible to have a planet (possibly gaseous) with an entirely flammable atmosphere?"
] | [
false
] | [deleted] | [
"You'd agree that the Hindenburg with its hydrogen was very flammable.",
"Similarly Jupiter is composed of about 90% hydrogen.",
"So, yes, Jupiter is flammable...",
"Except, since there is practically no oxygen, the hydrogen can't burn."
] | [
"The meteor impacts and constant lightning would help with that.",
"Hydrogen and oxygen can start combining on their own seemingly at random as well."
] | [
"Even if jupiter did have enough oxygen to burn the hydrogen I would assume that it would have caught on fire and burnt out early in its life?"
] |
[
"What makes the properties of elements?"
] | [
false
] | According to my gen chem teacher the number of protons makes an element itself. What makes Carbon, Carbon? How does the atomic makeup give every element such drastically different characteristics? | [
"Basically: electrons. How many electrons and their locations decide how an element interacts with other matter. Elements above and below any given element on the periodic table have similar electron arrangements, so they have similar properties. Strontium can substitute calcium in bones, for example. Silicon h... | [
"Thank you! She claimed it to be too advance for us, and I just really wanted to know."
] | [
"Okay, but how do protons, electrons, and neutrons, imbue elements with their ",
" qualities. I'm not talking about reactivity. I mean why does adding or subtracting subatomic particles fundamentally change something from gold to radon?"
] |
[
"If you crossbred all of the modern domestic dogs together, would you end up with their common ancestor, the grey wolf? Or is it more complicated than that?"
] | [
false
] | Would you end up with a wolf, or a generic looking mutt? If that would work, are there other interesting things we might be able to breed back? Like a saber tooth tiger or something? | [
"Very good question. Short answer: You get a generic looking mutt, more or less like many of the mutts you see in animal shelters or on Caribbean beaches.",
"The reason you don't get a wolf is that all modern dogs descend from a single domestication event and share certain evolved traits. There are ",
"dozens",... | [
"Humans didn't come from Neanderthals, they were a whole different sub species that went extinct"
] | [
"That's a pretty interesting idea, but unfortunately, it wouldn't work.",
"Dogs have ",
" (78 altogether). They get 39 from their sire and 39 from their bitc-... mom. Crossbreeding means that a dog gets 39 pairs of chromosomes from one breed, and 39 from another. This makes it impossible to crossbreed all the d... |
[
"Does quantum mechanics violate causality?"
] | [
false
] | First, how is causality defined? Secondly, does quantum mechanics violate causality? In what theories and interpretations is causality violated and in which is it preserved? Naming theories and interpretations is okay if you don't have the time to explain anything | [
"No, causality is not violated by entanglement."
] | [
"This has come up before, so I'm going to take what I think is a good guess: You're thinking of determinism, not causality. And yes, determinism is dead.",
"(There's room for a long and drawn-out discussion of the subtle differences between Laplacian determinism and unitary evolution, and knowing this place, that... | [
"No information can be transferred between the entangled particles. There is no violation of causality.",
"Haven't we had this discussion before?"
] |
[
"What is the typical carbon content of hot and cold rolled steel used in industry?"
] | [
false
] | null | [
"http://www.onlinemetals.com/productguides/steelguide.cfm",
"That is a quick primer on steel types from a supplier. As it notes, most commercially available steels are between 0.2 and 1.7% Carbon by weight. The alloys you are interested in are ductile so they are probably nearer the end 0.02%. If you know the nam... | [
"Depends on the industry and the application. The most common for piping carbon steels is 0.2 though."
] | [
"Thanks a lot"
] |
[
"Is it possible for a moon around a planet to have it's own moon in orbit?"
] | [
false
] | Say for instance Europa had a small moon in orbit around itself? Is that kind of thing just unstable? | [
"The magic astronomical phrase to Google here is \"",
"Hill sphere",
"\" - that's the volume around a body where the body's gravitation dominates the gravity of whatever it's orbiting around.",
"Anyhow, ",
"here",
"'s a pretty good explanation of the situation.",
"Short answer: yup. But usually they're ... | [
"A few additional points/details:",
"The Hill Sphere is based on the circular restricted three body problem in which there are two massive bodies in circular orbits about each other and the third body is massless. So, while the idea of the Hill Sphere is a useful concept it cannot be taken too literally if the or... | [
"Technically the same process occurs, but there's a huge difference in scale.",
"Earth and the moon can be called a binary planet system because they're relatively close in mass. The moon has about 1% as much mass as Earth, which is enough to make Earth wobble significantly. But the Earth is only 0.0001% as massi... |
[
"What’s the difference between anti-platelets and anticoagulants? In what circumstances do we use each of them?"
] | [
false
] | null | [
"This topic gets really deep, but here is a quick summary: Your body makes blood clots through a mechanism called the clotting cascade. This, very simply, begins with platelets clogging up the hole by forming a kind of mesh, and then different clotting factors reacting with each other to to finally form fibrin that... | [
"That was amazing, thank you"
] | [
"Antiplatlets generally prevent clumping and clotting just based on contact within blood vessels. Aspirin and plavix are 2 common examples. They work well for people with a little plaque build up and preventing platelets from snagging and forming a clot. Since they don't interfere with clothing based on signalling ... |
[
"Atmospheric Escape: Where would I end up?"
] | [
false
] | What does an atmospheric escape mean? If I were a single atom of helium, escaping Earth, where would I go? Is there a pool of Helium where it takes the least amount of energy to be, a sort of Helium suburb? Are Helium and Hydrogen the only chemicals which can escape within a human-livable period of time? | [
"What does an atmospheric escape mean?",
"Atmospheric Escape",
"If I were a single atom of helium, escaping Earth, where would I go?",
"Space.",
"Is there a pool of Helium where it takes the least amount of energy to be, a sort of Helium suburb?",
"The particles do not escape/collect because they have low... | [
"It achieves escape velocity, which is to say it is able to overcome the gravitational pull of the earth and shoot off into space. Essentially yes, it goes off in no particular direction. Since the gravitational pull of the planet cannot restrain it, it does not hang out in a spot near the earth."
] | [
"I appreciate the answer! It answers only half of my question, because of my own written shortcomings!",
"My real curiosity is if there is a particular spot in Space surrounding the Earth where the H/He might end up, like in the Thermospere, or perhaps in the area surrounding the Earth's atmosphere.",
"The core... |
[
"Is there any evidence that dinosaurs migrated like birds do now?"
] | [
false
] | Watched this video that shows the migration of a pair of Honey Buzzards from the Netherlands down to Africa. If dinosaurs migrated seasonally across vast distances, would there be any fossil evidence and does that evidence exist? | [
"Yes - there is rather good supporting evidence for this from stable isotopes in growth bands within teeth (a bit like tree rings). Continuous tooth growth served as a recorder of the O and C isotope signatures of feeding grounds, and cold vs warm areas have distinctly different and recognizable isotope signatures ... | [
"It is indeed rather neat that it resolves this way. Should have added that non migrating species don't show the variation in O and C isotopes in their own growth rings. ",
"There are indeed cool things slowly beeing resolved through new applications of research tools: dino pigmentation, the feathers thing, diet,... | [
"It is indeed rather neat that it resolves this way. Should have added that non migrating species don't show the variation in O and C isotopes in their own growth rings. ",
"There are indeed cool things slowly beeing resolved through new applications of research tools: dino pigmentation, the feathers thing, diet,... |
[
"\"In a universe with three time dimensions and only one space dimension for example, the speed of light would be the lower limit for all motion\", why is this?"
] | [
false
] | This is a line from the March issue of the BBC's science and tech monthly called Focus (I recommend it to anyone by the way). I understand, I think, the ideas being discussed here, such as in our universe time only has one dimension, one way that it can flow. But I do not understand why, if the space of our universe was a single dimension or a line, the speed of light would be the lower limit. Also, if this is the lower limit, is there another upper limit? | [
"That's a bit of mathematical wankery, really. It doesn't mean anything except in the most abstract, unphysical sense.",
"If you start with the laws of physics that describe kinematics, then ",
" that there could exist tachyons — particles with energy that can only be quantified in comparison to ordinary partic... | [
"Dirac predicted the positron based on what you might call \"mathematical wankery\". His equation gave negative energy solutions, but instead of declare them non-physical, he posited that the corresponded to an undiscovered particle."
] | [
"Didn't it often happened in the past, that mathematical wankery predicted some real things which at that time seemed absolutely surreal?"
] |
[
"Why did the matter that formed our solar system form 8 planets instead of clumping into a bigger star?"
] | [
false
] | null | [
"In short, because the protoplanetary disk was so large. When things are in orbit, they don’t just go straight towards the star; they can maintain that large distance. Any clumps of matter large enough would have a larger influence (gravity gradient) on their immediate environment than the sun(like how the moon pul... | [
"While this is true, you're missing out on a few things. First, that even though single objects to tend to fall into relatively stable orbits over time, a gas cloud would eventually collapse down onto the star due to collisions over time.",
"What keeps the gas from doing so however is that at a certain point afte... | [
"The main point is that not all the gas in the gas cloud has a chance to collapses into the star in the center because the gas further out is gonna take a longer time to collapse than the gas near the center. The material further out is still falling inwards but once a protostar has formed it start getting really h... |
[
"How have tardigrades survived five mass extinctions? Also, what makes them so resilient in extreme environments?"
] | [
false
] | I was watching Cosmos and Neil Degrasse Tyson mentioned that tardigrades have survived five mass extinctions (meaning that they've been around for hundreds of millions of years). They can survive in the most extreme conditions, including the cosmic radiation of space, 10 years without water, and intense volcanic heat. What makes them so good at surviving? | [
"Well, Tardigrades have the distinct ability to enter a really intense kind of hibernation. They eliminate nearly all the water in their systems before going into \"hibernation\", replacing it with a sugar trehalose, which both protects membrane as well as serving as a retainer for the water thats left in the tardi... | [
"Wikipedia: \"Tardigrade genomes vary in size, from about 75 to 800 megabase pairs of DNA.\"",
"^ That seems much more reasonable. "
] | [
"That's fascinating. Are tardigrades the only known organisms to use trehalose in this way?"
] |
[
"What causes this ring of fire from a Desert Eagle? *Link in description* (x-post r/woahdude)"
] | [
false
] | null | [
"that ring is a toroidal vortex, it happens because the jet of hot gasses leaving the muzzle shears past the stagnant air around the muzzle creating a ring of rotating air/gunpowder:",
" well illustrated here",
". ",
"I assume the flame in the ring is more visible because the hot gasses in the vortex ring bar... | [
"Short answer: The combustion products of the gunpowder (and some powder that is still combusting) mixing with ambient atmosphere. The ring itself is being pushed by the overpressure wave exiting the muzzle.",
"All firearms produce muzzle flashes. A flash hider/suppressor is sometimes used to redirect the gas int... | [
"Thanks for the link to \"Physics Girl\" - that's an awesome video (and series!) She is asking questions, testing processes, looking for reasons behind results.\nShe's got the Scientific Method included: observation, question, hypothesis, experiment, conclusion!",
"When I was in school, there just weren't girls... |
[
"How does long term, childhood trauma physically change the body? And are the effects reversible?"
] | [
false
] | null | [
"In many ways. For example, certain types of mental trauma can even show up on MRI scans.",
"To anyone who is interested in trauma and trauma therapy, I wholeheartedly recommend van der Kolk's book ",
"The Body Keeps the Score",
". It is brilliantly written, not very long, and well-researched. I also recommen... | [
"OMG ask me questions! I'm a NeuroAffective Relational Model practitioner and have been studying trauma for years. Anyway, ",
"yes long term childhood trauma can and does physically change the body, and yes it's effects are reversible to a degree. I actually started my career in trauma healing as a massage therap... | [
"What are you referring to? All the reviews seem to agree that it is a brilliant book. Obviously it contains case studies -- what kind of scientific work on the subject would not?",
"Edit: just clicked the link in the post I was responding to, and it seems to be some sort of self-help website. If you are interest... |
[
"How is the speed of a spacecraft measured? Is it the rate of increasing distance from earth? From the sun? Is it the affected by the earths orbit?"
] | [
false
] | Question sort of popped into my head today. When a spacecraft, or probe is traveling in our solar system, they often state that its traveling at x miles/second. Is that the rate of increasing distance from the earth? If the earth was orbiting away from the probe, would the probe then have a faster velocity compared to when the earth is orbiting toward the probe? Also, in the same vein, how are speeds of orbits or planetary rotations measured? Are the always referenced to the sun? This sort of stuff bothers me, like once in physics, a teacher asked me "how fast is the earth moving right now?", I responded "With reference to what? To us? Then its not moving at all" She stated I was wrong and spat out a number, and a few classmates laughed at me. Thanks for the help guys! | [
"It depends. If a probe is being sent from Earth to Mars, for instance, there are three phases of flight.",
"The first phase is where the probe is under the influence of the Earth. The orbit here will actually be what's known as a hyperbolic trajectory. It's an \"orbit\" that causes the object to escape the gravi... | [
"Just to add, the actual speed in relation with Earth is calculated by measuring the doppler effect in the radio communications with the spacecraft. "
] | [
"Awesome response, great information. Very interesting and not as straightforward as one might think. Thank you for your time!"
] |
[
"How do forward swept wings on an aircraft differ from a Delta wing and a straight wing?"
] | [
false
] | I know the basics of lift, however I was curious about how these wing types differ. Thanks! | [
"A straight wing is the basic configuration, it always stalls in the axis of symmetry first which is rather stable, is easy to manufacture structurally, and can hold a lot of fuel. Drawbacks are it's large lift induced drag coefficient, making it suitable for low airspeeds only. ",
"Delta wings allow big wing are... | [
"The wing designs change the aerodynamics of the aircraft. Most importantly, the wing configurations changes the stability of the aircraft under different flight profiles. Essentially, there's a trade off between speed, maneuverability and lift.",
"Each has its advantages and disadvantages, but at a high level: f... | [
"Straight wings are less suitable for high speed due to transonic and supersonic effects, rather than induced drag. In fact, straight wings can have much lower induced drag than swept or delta wings. Induced drag largely depends on aspect ratio, which is why gliders have these massive wingspans and straight wings."... |
[
"If we selectively bred mice for millions of years could we increase their intelligence similar to a human's?"
] | [
false
] | As in; We measure a group of mice's intelligence (through mazes or other tests initially), and selectively breed only the most intelligent. Over millions of years could we eventually breed mice with intelligence similar to a human's, or at least capable of abstract thought? | [
"Excellent, I was rewriting my population genetics notes last night.",
"Since I'm typing on a phone, the short of it is that there are limits to artificial selection. After enough selection, you'll reach the limits of variation for the trait you originally selected for, and while they ARE smarter than before, you... | [
"http://www.reddit.com/r/askscience/comments/ly72u/could_we_breed_another_species_to_our_level_of/",
"http://www.reddit.com/r/askscience/comments/kzd50/ethics_aside_how_long_would_it_take_to_breed_dogs/",
"http://www.reddit.com/r/askscience/comments/kitiq/could_you_selectively_breed_chimps_to_human_level/"
] | [
"Mice seem to have FOXP2",
".",
"\nedit: Also, with a time period of 'millions of years' mutations that have positive effects on intelligence are very probable. I'm far from an expert, but I think that with careful selection you'd get the maximum intelligence that's possible with mice' current genes in a couple... |
[
"How do trick candles work?"
] | [
false
] | What keeps them lit, or makes them able to re-light after being blown out? How does blowing them out NOT work? | [
"You know how when you blow out a regular candle there is still a little bit of a glowing ember at the tip of the wick? Well trick candles also contain in the wick some magnesium which ignites at the temperature that that ember is glowing at causing a flame which reignites the rest of the wick."
] | [
"The data you are looking at is for solid block magnesium. When powdered or finely shaved it is extremely flammable at very low temperatures. ",
"an MSDS"
] | [
"When a candle burns, it's not technically the wick that's burning, but rather the wax. Candle wax is generally made of paraffin which is the real fuel, with the wick acting as incident surface.",
"When lighting a candle, you're actually melting some wax at first, which vaporizes the paraffin fuel and causes a fl... |
[
"Are black holes literal \"holes\" or \"rips\" in space, or are they actual objects?"
] | [
false
] | I've read about black holes that can "move" across space, orbit each other, and revolve. I guess I always grew up thinking black holes were literally that: holes in space; that after enough mass has accumulated, that whole "collapsing in on itself" thing makes a hole, not an object. Am I mistaken? How could a "rip" or "hole" move around like an object without leaving a "tear?" | [
"We don't know what a black hole is made of, or if the question even makes sense; classical gravity theory tells us that it's a singular point, not a \"rip\" in space but a point where the curvature blows up, and there's no problem with that sort of thing moving around, because curvature can change. Compounded in t... | [
"A black hole consists of two things, really, a singularity and an event horizon:",
"The singularity is where all the mass in a black hole is concentrated in a single infinitely small point of space.",
"The event horizon is the sphere around the object inside of which nothing, not even light, can escape (ie whe... | [
"Where are you? Can you answer that without answering ",
" to something else? Any answer you give (i.e. 'my house', street address, city, state, nation, continent, Earth...) can still be questioned with \"but where is ",
"?\"",
"For most day-to-day purposes it's easy to forget that positions are all relative.... |
[
"How much time and what treatments is needed for the astronaut to fully recover after a long mission in zero gravity?"
] | [
false
] | Mark Vande Hei is back after almost a year on ISS. I wonder - how long will it take him to fully recover? Are there side effects of such a long mission that cannot be undone e.g. osteoporosis? | [
"Here's a pretty detailed document on a European astronauts reconditioning program after a 6 month mission. They tailor the things specifically to the astronauts though so the exact exercises won't necessarily be the same for each mission.",
"https://eprints.soton.ac.uk/405193/2/Postflight%2520reconditioning%2520... | [
"While ",
"/u/Skusci",
" has some good info, this is not true for bone and muscle. Long-duration space flight can lead to some significant bone and muscle loss, and while bone/muscle mass can be recovered to pre-flight levels, it usually isn't. Further, the quality of bone and muscle post-flight is often poor w... | [
"Thank you for your answer! :)"
] |
[
"how are earthquakes predicted?"
] | [
false
] | How exactly are earthquakes predicted? To what extent is the prediction based on past earthquakes? When people say the area is "due" for a large earthquake statistically how true is that statement. | [
"Earthquake prediction is in most cases an extremely difficult challenge. Almost all predictions are based almost entirely on how often the fault has ruptured in the past combined with how long it has been since it last ruptured. So it is ",
" fine to say you are \"due\" for an earthquake if it has exceeded the a... | [
"To add to the excellent answer by ReturnToTethys, another interesting aspect of earthquake \"predictions\" form a statistical perspective is the differing way they are presented. For example, the USGS will assess seismic hazard based on the things outlined in ReturnToTethys's answer, and then assign something like... | [
"In Japan there is short term \"prediction\", though \"detection\" is more accurate. A national network of sensors detects ",
"P-waves",
" kind of the first weaker part of the quake before the main S-waves hit(?) quickly analyzes them and if it looks major, sends a warning to radios and mobile phones (mandatory... |
[
"What's the best telescope for an ameteur astronomer?"
] | [
false
] | null | [
"Is this your first telescope? Have you tried (1) large binoculars (2) going to a local astronomy club and seeing through one of their telescopes? I say, try one of these 2 first or else you will be highly disappointed. Meade does not seem to offer the 8-inch Dobsonian anymore but I would always say that this or so... | [
"Are you located in the US?",
"If so, check out craigslist. I have found incredible deals on CL on decent scopes. My first scope was an 8 inch Odyssey that I picked up for 175 bucks, a few months later I found a 10 inch for 300 that came with an OIII filter(90 bucks by itself). I sold the 8 inch later for 200 ... | [
"My father has his own Meade. It's about ten years old, but he's lost all of the lenses but the broadest. I've used my fair share of telescopes, and look at the moon with binoculars when I can. I'll look at Meade ad what I can afford. Thank you."
] |
[
"Does notation exist for it possible to \"write\" any real number?"
] | [
false
] | [deleted] | [
"No. In fact, almost every number cannot be described using mathematical notation. If you were to randomly pick a number between 0 and 1, then there would be a zero percent chance that it will be describable. Same for any interval [a,b].",
"See ",
"Definable Real Numbers",
"."
] | [
"We're using math to pick it, not a computer. Math is independent of the universe, so it doesn't matter what ",
" can do in our limited existence, it matters what ",
" can do in it's existence where it doesn't have to worry about minor things like only being able to use pseudorandom algorithms. Math has true, w... | [
"See Definable Real Numbers.",
"At the top of that page:",
"This article's factual accuracy is disputed...",
"This article possibly contains original research...",
"This article needs attention from an expert on the subject...",
"This article includes a list of references, related reading or external link... |
[
"Is it theoretically possible to harness gravity waves? More specifically with Moscovium (Element 115)?"
] | [
false
] | null | [
"Are you looking for sources about gravitational waves or about superheavy elements? Because these two topics have almost nothing to do with each other."
] | [
"The longest-lived isotope of element 115 has a half-life of less than one second, so nobody is using it to propel anything, unless they can produce it on the fly. If that were possible, it doesn't seem like it would be a very efficient method of propulsion.",
"This website",
" has information about all of the ... | [
"I don't really even know; both? ",
"Full disclosure, and it's a bit embarrassing, but I'm a sucker for all things extraterrestrial (I know how tinfoil hat-ty this sounds). Bob Lazar, an area 51 whistle-blower, claims that he was part of the reverse engineering of certain air-crafts in the 70s. He also claimed ... |
[
"If I were placed into a hollow sphere with super-massive walls, would I experience time dilation but not gravity?"
] | [
false
] | null | [
"In Newtonian gravity, the gravitational field within a hollow, uniform sphere exactly vanishes. (This can be proven rather easily using the divergence theorem and noting that the field must be spherically symmetric.) Outside the sphere, the field is that of a point particle with mass equal to the mass of the spher... | [
"To clarify, that means someone far from the shell will observe time dilation of the people inside the shell, right?",
"So it's kinda like a plateau - flat, but at a different \"elevation\" to the rest of spacetime. The inside of the shell should also contain more space (that is, length contraction in all directi... | [
"Incidentally, it's the same principle that causes charged hollow spheres to have no electric field inside."
] |
[
"How are bacteria species differentiated if they reproduce asexually?"
] | [
false
] | null | [
"I found a very interesting paper on species differentiation in prokaryotes:\n",
"http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1764935/",
"A method which has been used a lot is the analysis of 16s ribosomal RNA, where above 97% sequence identity is considered within the same species.\nBut because this makes some... | [
"So all living things except viruses (Im a fan of saying that they are alive) make ribosomes, this is made with rRNA or ribosome ribonucleic acid, there are three of them, 5s, 16s and 23s where the number refers to their relative size. Since these genes are conserved for all living organisms, they are useful for d... | [
"Species vary by a number of characteristics, but mostly it comes down to genetics. The difference in the genetics between bacteria allow them to produce different proteins, and through those proteins they can have different effects on their environment.",
"Now you may be asking, how did they differentiate/evolv... |
[
"What would we observe if a micrometeorite traveling at relativistic velocities impacted Earth?"
] | [
false
] | [deleted] | [
"That's less energy than you might guess. A kiloton is equivalent to about four gigajoules, which is on the same order of magnitude as the energy released by a good-sized thunderstorm."
] | [
"The K-T event is estimated to have released about 10²³ joules. That was pretty interesting."
] | [
"It wouldn't do anything because it would be going into the atmosphere at that speed and burn up in the atmosphere due to frictional heating. It wouldn't arrive on earth in one piece."
] |
[
"Does increasing gravitational potential energy increase the mass of an object?"
] | [
false
] | If you add energy to an object, such as by heating it to add thermal energy, it increases very slightly in its mass. Does the same happen if increase an object's gravitational potential energy by changing its height? If this were the case, and the mass did change, how would the potential energy be affected, since mass factors into it? | [
"In the context of General Relativity, the answer is no. ",
"Gravitational potential energy is just a mathematical way to represent how masses behave in the presence of one another, and is a description of the local spacetime curvature around an object. "
] | [
"Is there another model where you can increase gravitational potential without actually increasing mass?"
] | [
"Gravitational potential increases with:\n- increasing mass\n- decreasing distance between masses ",
"And, pedantically, by mass I mean \"energy density\" which can be matter or energy...."
] |
[
"If the ice caps carrying on melting at their current rate, roughly when will Arctic shipping lanes become a major thing?"
] | [
false
] | This seems to be an advantage of global warming that I bet more than a few people would be willing to hop onboard with, but will it ever realistically be a thing? | [
"Somewhere around 2040-2060 according to a ",
"recent study",
". "
] | [
"North pole is just ice, south pole has land under not sea "
] | [
"that's like asking why there's a lot of land on the east side of Britain but not much on the west. There's a continent centered on the south pole called Antarctica. Since it's cold down there, Antarctica and the sea surrounding it are largely covered by glaciers and sea ice.",
"There is no such continent centere... |
[
"Why Does Sublingual Metals Help Fight \"Onion Tears\""
] | [
false
] | I heard this on Oprah years ago, that a paper clip in your mouth, under your tongue, was the best way to fight those tears when cutting onions. When my organic chemist Grandpa (from years ago, retired now...) was over for dinner last night I asked him why it helped and he was stumped. He did explain that you teared because sulfuric acid was being produced in your tear ducts - but didn't know what any metal in the mouth would have to do with anything. Probably un-related but I used that trick for years cutting onions for a job but later had my tongue pierced - since then, and I removed it over five years ago - I can eat raw white onions without it bothering me at all. Am I still getting some weird effect? Or is this whole metal thing an old wives tale anyways? | [
"There is no mechanism that can remove the irritant, ",
"sulfenic acids",
" that are the breakdown products of amino acids when cells of the onions are lysed. While metals are often good for catalyzing organic reactions, even if it removes the vaporized sulfenic acids, placing it under your tongue makes it impo... | [
"So it's more likely that the paperclip is sticking out of your mouth (while under the tongue) is the reason it works?"
] | [
"Even if the metal is catalytically active, it's highly unlikely a paper clip will work. There's a reason ",
"catalytic converters are built the way they are",
" - even if the metal catalyzes the reaction of something in the air into some harmless product, you need a high surface area in order for that to occur... |
[
"Why do scars never heal?"
] | [
false
] | If the body replaces all of its cells over a period of a few years why do scars stay with a person for life and never look like normal skin afterwards? | [
"This is my understanding. The difference in texture you notice between your regular skin and scar tissue is because of the way that the collagen is deposited by the fibroblasts that are healing the deep wound. Normally it is random, but in the case of scar tissue all of the fibres are aligned in the same direction... | [
"scars occur because the layer of skin 'stem cells' was interrupted. it then has this chasm it needs to fill. Unfortunately, there is no 'base' to rebuild the skin from. Therefore the adjacent skin stem cells start by filling in the base with granulation tissue. Unfortunately this not the same as the regenerating b... | [
"Normally it is random, but in the case of scar tissue all of the fibres are aligned in the same direction.",
"This sounds wrong. Do you have a source? From what I know from muskuloskeletal injuries, tissues like ligaments and tendons are the few that have extremely aligned collagen fibers. The reason they are ne... |
[
"What is the effect of bird flu on wild populations of birds?"
] | [
false
] | A cursory glance on google/google scholar didn't really answer this question, so I decided to ask it here. Basically I was wondering what the effects of highly pathogenic types of bird flu is on wild bird populations. Does it have significant ecological effects? I am mainly interested in this as it seems that the HPAI variants seem to have originated from domestic bird populations (or so I have been told). | [
"H5N8 bird flu has varying mortality rates among different birds, from 5% in some species to 39% in others",
"The effect of the bird flu among wild populations is theoretically similar to the effect it will have in humans if it becomes transmissible which is to say it kills them by the thousands",
"Birds have f... | [
"Birds with bird flu exhibit strange behavior, diahrrea, head swelling, and sometimes discharge from the eyes",
"Human flu is comparatively very tame. Some asymptomatic birds have been observed to still die spontaneously after contracting bird flu (likely stroke or blood clot)",
"https://www.petmd.com/bird/cond... | [
"Birds with bird flu exhibit strange behavior, diahrrea, head swelling, and sometimes discharge from the eyes",
"Human flu is comparatively very tame. Some asymptomatic birds have been observed to still die spontaneously after contracting bird flu (likely stroke or blood clot)",
"https://www.petmd.com/bird/cond... |
[
"Why does our sense of humor change as we get older? Specifically why do young kids enjoy slapstick and funny faces?"
] | [
false
] | null | [
"Yeah also neat little tidbit a lot of users in this sub reddit have tags next to their names of what they specialize in. I like to think they are full fledged scientists in lab coat speaking to us lessers for their entertainment."
] | [
"I still laugh at fart sounds and I am a first year medical student."
] | [
"Do we really gotta get that specific? Especially when this is a subreddit about many different kinds of science."
] |
[
"What is the average distance between individual pieces of \"space junk\"?"
] | [
false
] | I've seen the graphics of how much "space junk" is out there and I've also read that space is very large and is easy to underestimate this. My question stems from someone asking when there would be so much space junk that we would not be able to put more into space. So, just how far apart (on average) is the space junk? Does this figure exist somewhere? Without anymore knowledge than seeing a graphic and knowing how large the earth is, my guess would be that on average, individual pieces of space junk are 300 miles apart. How wrong is my intuition? | [
"It's probably within three or four orders of magnitude. I'm far too lazy to do the maths right now, but I ",
"worked this up",
" not long ago, based on the number of ",
" in orbit. If you had a couple of numbers, you could adapt the calculations to see how close or how far you are."
] | [
"Using his numbers I got about 1,600km, which seems about right. Keep in mind that is only how far apart they are on average, at any given moment. "
] | [
"While your post is interesting and related, for my poor mind it does little to answering my question. My horrible math just told me that they are 3,417,541,557 miles from each other based on your ratios. I'm quite sure I've done something wrong. "
] |
[
"Is the term \"bandwidth\" a dumb term?"
] | [
false
] | I have an annoying friend who always says the same complaint about the term "bandwidth" when it comes up in regards to networking. "Bandwidth is a stupid term. It has nothing to do with data rate." Then he goes into a vague, not fully educated explanation in regards to its meaning as used for signal bandwidth. I am certain that he doesn't even know an EM radiation goes about 300 million m/s. He is just regurgitating something a professor told him. Any suggestions on what I could say to shut him up? | [
"I see where you are coming from, that is, it is not the most explicit term, but it is not a stupid term. My understanding is that it goes all the way back to Harry Nyquist, who along with Shannon pretty much wrote the book of digital signals.",
"One of Nyquists most important and fundamental discoveries, is the ... | [
"This is a truly great answer. ",
"To be clear though, your friend may or may not actually be correct. It comes down to what he said ",
" The amount of information per symbol is based entirely on the noise distribution, and not changed by bandwidth. If your friend said the ",
" of the channel, instead of data... | [
"I already responded once, but I am going to use this as a warm up writing for the day. This will be a lot deeper and hopefully with the clarity of someone post coffee. Keep in mind that I absolutely love this stuff, so I might get off track at some points because it is just so gosh darn fun. There is also a word o... |
[
"Why does gunpowder need the three specific ingredients of charcoal, sulfur and saltpeter? What purpose does each ingredient serve?"
] | [
false
] | null | [
"Saltpeter (KNO3) is an oxidizer. Charcoal and sulfur are fuels. Together they will burn rapidly (exploding if confined)."
] | [
"To add to this: You need a oxidizer to start the combustion reaction. In most combustions, like in a bonfire or in an engine, your oxidizer is air, specifically Oxygen. Now Oxygen is a good oxidant, but if you want a faster burn, it's not good enough. That's where nitrates come in. Nitrates are nasty good oxidants... | [
"Oxygen is great, but as atmospheric gas you simply don't have enough. You need it as liquid or solid with the corresponding high density. Liquid oxygen would work, but then you have too cool your explosives."
] |
[
"[String theory] If energy is simply vibrating 1-dimensional points, what powers these vibrations?"
] | [
false
] | [deleted] | [
"Whoa, there's a lot of words in this question. Energy is energy, it's just a conserved number that doesn't have a physical realization, string theory doesn't change that in any way. But let's talk about particles first in order for you to understand what exactly string theory is about.",
"In string theory, parti... | [
"Let's put it like that: once a particle is created, it can exist forever if its stable. But if you want to describe why this particle appeared in the first place, then you need interactions. A particle can't just pop out of nowhere, it needs to have been created in some collision or as a decay process of some less... | [
"Interactions! Whenever you throw one particle against another (let's say you accelerated a proton at the LHC and threw it against other protons), you have this \"strumming\"."
] |
[
"With all the breakthroughs in genetically engineered plants, what's to prevent us from 'seeding' Mars?"
] | [
false
] | null | [
"Plants need a lot of light, water, warmth, and oxygen in addition to carbon dioxide. Mars is very limited in terms of (2), (3) and (4). The need for oxygen and water isn't really something that you can easily engineer out, and the fact that much of Mars is freezing cold makes it even worse."
] | [
"This has been removed because the question is too broad or too vague. If you’re still curious, please conduct some basic research and resubmit a more specific question.",
"For more information regarding this and similar issues, please see the ",
"FAQ."
] | [
"This question has been removed because highly speculative in nature. Exceedingly imaginary hypotheticals often invite non-scientific speculations.",
"For more information regarding this and similar issues, please see the ",
"FAQ."
] |
[
"What is the smallest thing we can see with an optical lens (i.e. without an electron microscope) and why is there a limit?"
] | [
false
] | null | [
"It depends on what you mean by \"see\". I will assume you mean optical imaging using traditional lensing. In that case, resolution is diffraction limited. Traditional lensing works on the principle of light acting like little bundles of rays that refract through lenses and can be focused. Unfortunately, light is n... | [
"As ",
"/u/cyprezs",
" said, there's a difference between resolving and seeing. A simple way to think about resolving is a two-point system. If we're trying to image two bright points, there's a limit to the separation between them where we can actually tell they're two distinct objects. Two bright dots that ar... | [
"chrisbaird gave a great answer about what the smallest thing we can resolve with an optical lens is, but it is important to keep in mind that there is a difference between being able to see something and being able to resolve it. To just see something, all you have to do is to detect light that it scatters or emi... |
[
"When pizza burns the roof of your mouth and \"skin\" dangles down, what is that? Is it actually skin? Some other type of membrane? Does it scar?"
] | [
false
] | null | [
"It's a layer of mucous membrane that's been killed by heat. Not skin, but similar.",
"Wounds inside the mouth tend not to scar too often or very much because most of the tissue in there regrows fast, and is kept moist while regrowing, which prevents scabs (which actually slow wound healing down a bit.)"
] | [
"It's more susceptible to the environment. Scabs are hard and keep things out."
] | [
"Why can't the rest of our skin function in a similar manner?"
] |
[
"How are the images on the Voyager probe kept?"
] | [
false
] | I've tried researching how they're kept, but all the sources say they're on the phonograph record. Are the images on film, a metal plate, etc? | [
"The so-called \"Golden Record\" included on the Voyager is pretty interesting in its own right. The record consisted of gold-plated copper, with a spiral array of grooves encoding all information. As such, the record was an early form of an analog video disk. The basic operation was fairly straightforward, you wer... | [
"The signal you read out would then correspond to a series of frames, each having 512 lines each having about 500 dots. As a result, in 12 seconds you could read out a grayscale image.",
"Exactly what I was looking for. I was so confused on how they actually stored the images. Thanks for the explanation! "
] | [
"Did they test this method using scientists who had no knowledge of what the info meant? I guess it would be impossible to truly test it since anyone capable of solving it would have a concept of record players and scan line image storage, but even so, I'm sure they would have put it through some trials."
] |
[
"Why does highway MPG decrease ~linearly with speed, when the power to overcome air drag goes up v^3?"
] | [
false
] | [deleted] | [
"The first thing to note is that miles per gallon is not a linear quantity; for example, which increase in fuel economy will give you save you more gas over a distance of 10,000 miles?",
"a) 10 to 11 mpg",
"b) 33 to 50 mpg",
"It's a trick question; they both would save you about 100 gallons over 10,000 miles.... | [
"Where are you getting that drag increases at the cube of velocity?",
"Power, not drag. Power due to drag is force times velocity, giving you another factor of v."
] | [
"Where are you getting that drag increases at the cube of velocity?",
"Power, not drag. Power due to drag is force times velocity, giving you another factor of v."
] |
[
"What causes the chaotic rotation of celestial bodies such as Pluto's moon Nix or Saturn's moon Hyperion?"
] | [
false
] | is a simulation of the rotation of Pluto's moon Nix. According to wikipedia, it's rotation can only be predicted 30 days into the future before it becomes too chaotic. What causes this chaotic rotation? | [
"Rotation about an object's intermediate principal axis in unstable. This is known as the ",
"tennis racket theorem",
", since it can be observed by holding a tennis racket face up and throwing it into the air so that it will spin end over end once to allow it to be caught by the handle. There's a good video of... | [
"It's a many-body problem. We can only fully solve 2 body problems - to approximately solve more than 2 (eg the planets) that we need assumptions like one body has essentially all of the mass (the sun).",
"When you have a dynamic system with more than 2 bodies, and the masses of more than one are non-negligible, ... | [
"It is not about working out the math, it is proven that you can not analytically solve the problem for more than two bodies."
] |
[
"Can optical circuits depend on when you check them?"
] | [
false
] | I've been absorbing information about quantum mechanics from various places, trying things out on paper, and I wanted to make sure I wasn't going off into lala land. So, consider . It's a bit like a with a cycle added to cause the photon to "decay" out of the circuit instead of exiting immediately. Note that the detectors don't contain information about when the photon was recorded, only if it was recorded. Also, suppose that it is not interacting with the outside world . The light source releases exactly one photon, we wait, then we check the detectors (at which point the system interacts with the outside world, of course, but before that it is isolated). My question is this: does the amount of time you wait before checking the detectors affect the proportion of times that the bottom detector goes off? My current understanding is that it does. If you wait a long time before checking then the result is basically equivalent to not having the loop, in which case the right detector never goes off due to destructive interference (because the detectors are not time-sensitive). But if you check early, say after three cycle periods, then your interaction creates a difference between earlier and later photon arrivals that reduce the destructive interference and so the right detector would go off a non-negligible proportion of the time. Is this understanding correct? In the idealized abstract scenario? In real experiments? Where can I find resources to answer this sort of question? | [
"Maybe I should go through the math of why I think they differ. Fair warning: this could be completely misguided.",
"The system starts out with a single photon being emitted, with the default amplitude of 1:",
"1 * |PhotonEmitted>\n",
"The photon travels to the first half-silvered mirror, where it is split. T... | [
"What do you mean by a detector that is \"not time sensitive\"? Real detectors (e.g. an avalanche photodiode) can certainly give you the photon arrival time.",
"My intuition would say that at late times only photons that circulated in the loop would contribute to the observed signal, so you would observe an equal... | [
"A detector that transitions to the exact same state no matter when a photon is received, allowing later receives to interfere with earlier ones.",
"I think the resolution to the question is \"the detectors are impossible\", meaning no interference. They violate reversibility."
] |
[
"How is it that gravity slows the passing of time?"
] | [
false
] | While looking into general and special relativity I read that gravity can slow the passing of time. Is that why time is considered relative, because this happen slower in different settings? How does that disprove the Euclidean view, and why is it not simply just understood as a property of physics that things just go slower with more gravity? Or am I just all wrong on my understanding of all of this... | [
"The speed of light c can be derived theoretically from electromagnetism, simple experiments which can be done in any inertial frame allow you to calculate the constants epsilon_0 and mu_0. The expression for c is this, \nc= 1/sqrt(epsilon_0 * mu_0). Because the experiments you perform to find epsilon_0 and mu_0 ar... | [
"Hmm, well firstly you will never feel your own time to slow down regardless, you cannot change your position in a gravitational field and see your watch slow down, you will always measure time ticking at a rate of one second per second. You will observe other clocks ticking at different rates dependent on their po... | [
"Gravity is the curvature of spacetime.",
"In a gravity well the photon needs to travel a longer distance than somewhere absent a gravity well. However, relativity says that we will ",
" measure the speed of light as a constant speed. The only way the photon can traverse this longer distance (which we usually... |
[
"Why do my bones ache when I get really sick?"
] | [
false
] | [deleted] | [
"usually when people with a flu describe \"bone pains\", its Myalgia, which is a horrible ache in the muscles, often the big groups; shoulders, back, thighs. ",
"I cant describe the exact chemistry of it, but these things are usually part of a generalized systemic response, often modulated by inflammatory media... | [
"Joint pain is also a common flu symptom, technically called ",
"arthralgia",
", and is a result of a viral infection.",
"If there is accompanying fever, it is more likely to be an influenza virus than a cold virus."
] | [
"When the body is fighting an infection it's common to see a set of characteristic behaviours (sickness behaviour) and physiological responses. This is to help to body fight the infection, one of these may be hyperalgesia by the release of IL-1. This increased sensitivity to nociception may explain part of the achi... |
[
"Generally in sci-fi movies, when 0g is activated, objects around the actors start floating with no force pushing them \"up\", is this scientifically inaccurate?"
] | [
false
] | null | [
"Not scientifically inaccurate, but suspiciously convenient. In zero gee, or free-fall as on the ISS, seemingly very little force is needed to push things around. Notice in videos from the ISS how everything is tied to the walls in some way, and when they try to \"hang\" a microphone, no matter how carefully they... | [
"If you're specifically referring to rocket launches where microgravity starts when the engines cut off, the way that works is this:",
"During the rocket burn, you are being accelerated forwards by some amount (let's call it a 1 G burn, 9.8 m/s acceleration.) Your body is being compressed back into your seat by ... | [
"I'll assume your question takes place on a spaceship, far away from the gravitational influence of any planets or stars, with 'artificial gravity' which is then suddenly 'turned off'.",
"To understand how object will behave in this scenario, imagine you had a weight resting on a spring, such that the spring is c... |
[
"If neanderthals and early humans mated and produced offspring, wouldn't that require that they are actually the same species"
] | [
false
] | Neanderthals and early humans interbred . Also, we group a species by their ability to mate and produce fertile offspring (wolves and dogs are the same species). Wouldn't that mean that these two species were actually the same species? | [
"Check the first couple sentences in wikipedia: ",
"http://en.wikipedia.org/wiki/Species",
"In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. ",
", the ... | [
"There is more that goes into the definition then just the ability to interbreed. The line that defines one species from another is subjective and is drawn on a case by case basis. Different scientists will draw the line in different places. Many factors go into deciding where this line should be. I will give you a... | [
"Again, people could argue this a number of ways. There are several things to consider. As of now, ",
"the dog",
" - (Canis lupus familiaris), is a subspecies of the gray wolf (Canis lupus). \"The domestic dog was accepted as a species in its own right until overwhelming evidence from behavior, vocalizations, m... |
[
"How bad is pure Nicotine for humans (without the tobacco/smoke)?"
] | [
false
] | [deleted] | [
"In Sweden many people (more tham a million at least) use \"snus\" pouches of tobacco under your lip which have twice the amount of nicotine of cigarettes. We have looked hard for harmful effects and found very few, it might raise your risk of mouth cancer but that risk is very small to begin with. ",
"So as long... | [
"Interesting. Is chewing tobacco permitted in the EU? It does increase the chance of mouth cancer quite significantly, but it sounds like the tobacco in Snus is contained and not masticated. "
] | [
"Snus comes in these little packets(as far as I know of the brands/varieties). \nSo yes it is contained and not masticated."
] |
[
"Why is it relatively cheap and easy to make Canine Rabies Vaccines while it is very hard and expensive to get a human Rabies Vaccine?"
] | [
false
] | null | [
"The human rabies vaccine is typically given after a bite, not before. Post-exposure, the vaccine will need to be given with a dose of rabies immunoglobin (rabies antibodies). This is the expensive part. It is derived from human blood, which needs to be screened for any diseases beforehand, and the antibodies thems... | [
"Does this mean if you’ve gotten the vaccine your blood can be used to help make the antibodies? I mean like as an ordinary rabies vaccinated citizen, is there a way I can help?"
] | [
"I looked it up and it seems like certain plasma donation centers specifically seek people with recent rabies vaccines. I also noticed that I might not qualify right now due to other adventure travel (malaria risk). I’ll definitely keep it in mind for the future if I stay up to date with my boosters and stay out of... |
[
"Ask Anything Wednesday - Biology, Chemistry, Neuroscience, Medicine, Psychology"
] | [
false
] | Welcome to our weekly feature, Ask Anything Wednesday - this week we are focusing on Do you have a question within these topics you weren't sure was worth submitting? Is something a bit too speculative for a typical post? No question is too big or small for AAW. In this thread you can ask any science-related question! Things like: "What would happen if...", "How will the future...", "If all the rules for 'X' were different...", "Why does my...". Please post your question as a top-level response to this, and our team of panellists will be here to answer and discuss your questions. The other topic areas will appear in future Ask Anything Wednesdays, so if you have other questions not covered by this weeks theme please either hold on to it until those topics come around, or go and post over in our sister subreddit , where every day is Ask Anything Wednesday! Off-theme questions in this post will be removed to try and keep the thread a manageable size for both our readers and panellists. Please only answer a posted question if you are an expert in the field. . In short, this is a moderated subreddit, and responses which do not meet our quality guidelines will be removed. Remember, peer reviewed sources are always appreciated, and anecdotes are absolutely not appropriate. In general if your answer begins with 'I think', or 'I've heard', then it's not suitable for . If you would like to become a member of the AskScience panel, . Past AskAnythingWednesday posts . Ask away! | [
"What species of mammal dies of starvation in the wild most frequently relative to death by other causes?"
] | [
"Seems like sea lions maybe. I wouldn't expect it to be anything lower in a trophic pyramid (e.g. prey animals), because those are more often eaten."
] | [
"How come sleep paralysis tends to predominately occur when laying on your back while sleeping?"
] |
[
"How much, if at all, have covid vaccines been improved since public release?"
] | [
false
] | This question applies to the vaccines available to the public. Are we still on version 1.0? Have formulas been improved as more variants are researched? Have we even made it to 1.0 considering that they were released under emergency release guidelines? Here in the US I only hear about Pfizer, AstraZeneca, and J&J. What are other promising vaccines and how do they stack up to the 3 I mentioned? Are other less reputable countries, like China and Russia, reporting advances in their vaccines and has anyone been able to verify the claims? | [
"You forgot about moderna. And from my uninformed point of view, I would think once you get a medicine approved by the FDA you can’t really modify it without having to go through the approval process again, that’s what would make sense to me at least. So id gander we’re still using the same version of the vaccines ... | [
"So far, none of the vaccines on the market have changed their formulations in any significant way. I assume, that minor production details may have changed to optimise yields and so on, but not to an extent that affects final product. ",
"BioNTech/Pfizer, Moderna and AstraZeneca are working on a booster against ... | [
"The vaccine formulation and production process is approved, which is a lengthy process. Once approved, the production protocol and formulation cannot deviate from what has been approved. Each year, the new vaccines then undergo an accelerated approval process.",
"For completely new influenza vaccines, they need ... |
[
"Would the sun be brighter if we could see UV rays?"
] | [
false
] | I'm in Physics 30 and recently have been learning about light waves. I understand that our visual spectrum is between infrared and ultraviolet, but hypothetically, if our spectrum could expand to view ultraviolet light, would the sun appear brighter due to the UV coming from it? All answers are appreciated, just started learning the basics of waves and struck some curiosity! | [
"Not really. UV radiation makes up ",
"less than 10% of the sun's light",
" at ground level: the majority of UV light is absorbed by the atmosphere. To give you an idea of how minor the effect would be, that's comparable to the change in brightness ",
"between July and January",
" due to Earth's elliptical ... | [
"There is no qualitative difference between sunlight in the winter and summer. It's really hard to say for sure whether your personal experience was real or just observational bias. There are many factors which might contribute to what you describe:",
"1",
"2",
"But again, it's really impossible to say how mu... | [
"I noticed that in the summer, colors are more vibrant on a sunny day and in winter it seems like colors have a duller look with a slightly blueish tint. Am I seeing things? "
] |
[
"Does artificially restricted breathing improve aerobic (or some other) capability like training weights would?"
] | [
false
] | I'm sorry, but I couldn't think of a more succinct way of putting it for the life of me! My question is this: if someone were to use, say, a gas mask while doing aerobic exercise, would it have any benefits at all? Would it be detrimental? Have no effect? By the term "training weights" I used in the title, I mean weights like the ones martial artists might use on their arms while training. I don't know if the example can even be applied to my question, but it's the closest analogue I can think of. The background to my question is practical - during service I used to go jogging with a gas mask on, and I enjoyed it. If I recall correctly, the one I was using let about 70% of air in compared to your normal breathing effort without it (because of the resistance of the filter). I've been curious about this for a long time, but I haven't really known who to ask. | [
"This is exactly what I was looking for. Thank you!"
] | [
"This is exactly what I was looking for. Thank you!"
] | [
"You could diminish oxygen, which would be like training at altitude. "
] |
[
"What's the \"lifetime\" of a water molecule?"
] | [
false
] | I saw on my Facebook feed just now, and it got me thinking. How long does the average water molecule last? I know that whenever hydrogen is burned, it combines with oxygen and the byproduct is water. I know that electrolysis and other water splitting processes happen all the time as well. And finally, there are nuclear processes that cause atoms to fuse and break apart happening too. So what are the chances that ANY water molecule has lasted 65 million years, intact, much less existing within my body right now? | [
"The chances are effectively nill. Water continually autoionizes.",
"http://onlinelibrary.wiley.com/doi/10.1002/bbpc.19550591020/abstract",
"This gives a figure of each water molecule doing that once every ten hours."
] | [
"In nature, photosynthesis is the only (large scale) process that splits water into Hydrogen and Oxygen",
"It might be the only one splitting water in oxygen and hydrogen, but not the only one using up water. Proteins, fats and starch all hydrolyze, that is, undergo decomposition by reaction with water. ATP is co... | [
"In nature, photosynthesis is the only (large scale) process that splits water into Hydrogen and Oxygen",
"It might be the only one splitting water in oxygen and hydrogen, but not the only one using up water. Proteins, fats and starch all hydrolyze, that is, undergo decomposition by reaction with water. ATP is co... |
[
"Realisticly, how far away are we from a robot that would be indistinguishable from a human being?"
] | [
false
] | I mean in terms of appearance and conversational ability. I'm not expecting this to be a specific timeframe, probably extremely vague, but I'm just very interesting to hear an expert's take on it. | [
"It can't be impossible. Surely we are just biological machines? We are proof that it is possible.",
"Or am I wrong?"
] | [
"This is hundreds, if not thousands, of years of. ",
"I would have to disagree with that. One thousand years ago the height of technology was the mill. From the mill to the microchip is a bigger jump by many orders of magnitude than from already having robots that are beginning to mimic humans, to them succeeding... | [
"Asking for a timeframe for computerized advancement is just asking for trouble. There's probably no other technology which people have predicted more incorrectly."
] |
[
"How do redox reactions actually work?"
] | [
false
] | [deleted] | [
"I don't know the mechanism there offhand, you'd have to look in the academic literature. Most likely it involves a number of pathways and intermediates. But the simplest would seem to be Mg + H2O +H",
" --> MgOH + H2, followed by MgOH + H2O + H",
" --> Mg(OH)2 + H2"
] | [
"I didn't think of it that way. Probably why my searches for H-metal bond turned up nothing."
] | [
"Well those (metal hydrides) exist. It's a possible intermediate too, although it seems unnecessary because if you have a proton and a water molecule, you can form the hydroxyl and H2 almost directly. Electrons move fast relative everything else."
] |
[
"Before the Riemann Sum was devised, how did people understand/visualize the integral?"
] | [
false
] | If differentiation and integration were practically invented/discovered together, how is it that the Newton Quotient was thought of but not the Riemann Sum? What did it even mean to integrate without the limit of the Riemann Sum? | [
"Mathematicians had been doing ",
" Reimann sums for centuries before Reimann came on the scene. In fact, Archimedes had found the area of a section of a parabola using an infinite series of triangles milennia before Reimann sums were invented. ",
"As far as integration goes, Newton had done something similar t... | [
"You might be interested in The Historical Development of the Calculus by C H Edwards. A lot of libraries have it and it offers some really interesting insights to this kind of mathematical development."
] | [
"\"If I have seen further it is by standing on the shoulders of giants\"",
"-Isaac Newton",
"This statement holds a lot of truth in mathematics (and thus all further abstracted sciences). Great examples of this can be Euclid's Elements which only established a rigorous and orderly arrangement of the rules which... |
[
"Why do mountains have peaks instead of having \"flat tops\"?"
] | [
false
] | null | [
"Largely because of erosion. Almost all erosional processes that are important in mountain environments (e.g. rivers, glaciers, hillslope diffusion, mass wasting) have a slope dependence, i.e. the rate at which they occur is at least partially dependent on slope and they generally proceed faster when slope angles a... | [
"In addition, not all mountains are peaked. Stratovolcanos like Mt. Rainier in Washington State are more like huge piles of debris, and have rounded tops. Longs Peak in Colorado is flat at the top because its top was once the bottom of the central sea in North America."
] | [
"Cape Town, South Africa also has a mountain called Table Mountain, and the top is pretty much completely flat"
] |
[
"What's the chemical/sensory difference between the spiciness of wasabi and that of hot peppers, for example?"
] | [
false
] | [deleted] | [
"Wasabi's spiciness comes methylthioalkyl isothiocyanates. Spiciness from plants in the genus Capsicum comes from capsaicin. ",
"Both compounds play with the neurons normally used to sense heat or damage (thermoreceptors and nociceptors). They bind to and open ion channels, thus allowing depolarization leading t... | [
"I don't know about the biological/perception side of it, but the burn from hot peppers comes from ",
"capsaicin",
", while the burn from wasabi (as well as mustard and horseradish) comes from ",
"allyl isothiocyanate",
"."
] | [
"To follow up: while true about wasabi, most wasabi products are actually horseradish. Horseradish is prohibitively expensive (and quite rare). I think wasabi (possibly actually truffles [also commonly replaced with cheaper/more accessible products in truffle oil]) are the most expensive foodstuffs (by weight, I th... |
[
"When traveling at relativistic speeds, do you feel more massive?"
] | [
false
] | As you travel close and closer to the speed of light you mass changes with the formula m=m0/(1-(v My question is this: if you travel close to the speed of light would you "feel" heavier" than if you were standing still. I ask because if this were true, there would be a way to determine how fast you were going relative to absolute space without needing an external reference point. | [
"your mass doesn't change with that formula. It's an old poor way of teaching relativity. What happens is that mass ",
" to be defined to be p=mv. But relativity said: p=(1-(v/c)",
" )",
" *mv. Well someone along the way decided to smush that first term and the mass term together into a \"relativistic mass.\"... | [
"No!",
"Think about it this way: There is a perfectly valid reference frame right now where you are travelling 99.9999999% the speed of light. Do you feel more massive?"
] | [
"No. The key part about relativity is in the name: everything is relative :). There ",
" any absolute frame, all reference frames are equally valid.",
"In your own reference frame you aren't moving, so you don't feel any relativistic effects."
] |
[
"Is pricing a product with a price ending in 5 (e.g. 29,95) as effective as prices ending in 9?"
] | [
false
] | [deleted] | [
"In some cases it's used to denote clearance or sale items or the such, my job that uses .99 for most of our prices uses .98 or .97 to denote clearance prices and in a few cases we have used .00 for other items but less frequently"
] | [
"When I worked in retail, prices ending with 95¢ were discontinued products, and those ending with 97¢ were final clearance items that we had to get rid of ASAP. And I think we'd set it ay 98¢ when we manually changed a price for a deal so that customer service would be aware that a deal was made if the customers t... | [
"I don’t know about effectiveness but in general there’s ",
"Benford’s law",
" which often shows up when you look at data."
] |
[
"Is there any way of knowing whether a proton is positive without comparing it to something negative?"
] | [
false
] | null | [
"Benjamin Franklin came up with the convention; he called the kind of charge from rubbing silk on a glass rod \"positive\", and the kind of charge you get from rubbing amber with fur \"negative\". As far as I know, there are no records of why he chose this convention."
] | [
"As Amarkov said, it's just a convention. We could just as easily have defined protons as having a negative charge and electrons as being positive.",
"(Edited for mistyping)"
] | [
"It would have made a lot more sense for modern electrical engineering. Electrons are the ones moving in electricity, but physicists tend to always consider current positive, so they often measure current in the opposite direction, leading to loads of student confusion and sign error."
] |
[
"Why don't long-distance runners have a lot of muscle in their legs?"
] | [
false
] | [deleted] | [
"Good example, ",
"here",
" the dark muscle is what the shark uses for long distance and the lighter for quick bursts. "
] | [
"While I'm not knowledgeable of the exact anatomy, I have a friend who is doing her PhD and has been a long distance runner for her university for years. Her explanation is that increased strength doesn't help a distance runner much, and the excess weight would be more of a hindrance than a help. This is why sprint... | [
"Sprinters also need more acceleration. Long distance runners are basically repeating the same motion over and over without concern too much for power.",
"It's like asking why not use a drag racer car for a 100km race [without pit stops]."
] |
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