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[
"Red and blue images on my phone look 3D through my corrective glasses. What gives?"
] |
[
false
] |
Normally I wear contacts constantly. One night a few months back I was giving my eyes a rest, wearing my glasses while perusing the web on my old first gen Moto Droid. I opened an image and was shocked to see a red typeface practically leaping out at me from a darker blue/black background. I thought it was neat, but easily dismissed it as an optical illusion. Today the same thing happened, and the red in the image was so intensely 3D that I decided to do a GIS for "red on blue." I looked through a dozen images, all with the same result - they appeared to be 3 dimensional, with the red or warmer colors leaping forward, and the more blue, cooler images receding in the background. I took my glasses off to see if the effect persisted - it did not. Finally I had my girlfriend come and try my glasses to see if the effect was replicated for her. It was, she was amazed. Next I went to my computer monitor to see if I got the same effect - nope. The only combo that works is my glasses with my cell phone. What gives? TL,DR: My glasses seem to create the illusion that images on my phone are 3 dimensional. Why? How?
|
[
"It looks like the polarizer on your phone and the anti-glare coating on your glasses Real interacting to create a ChromaDepth effect.",
"This website explains the phenomenon quite well:",
"http://jaredjared.com/chroma.html"
] |
[
"Fascinating, thanks! "
] |
[
"This effect ",
" be visible all the time while wearing glasses, though interaction with the phone screen may be accentuating the effect.",
"Traditional lenses bend light of different wavelengths by different amounts, meaning, in stereo vision, that different colours appear at different depths.",
"I can see the effect quite clearly on my laptop screen - the orange 'up votes' text in the top right is clearly closer than the blue 'down votes' text. Even the individual letters in black text appear at slightly different depths, I assume because of sub-pixel rendering."
] |
[
"When a boat travels over an aquaduct, does the aquaduct carry more weight?"
] |
[
false
] |
I think this would have something to do with buoyancy and water displacement, but that is beyond my knowledge.
|
[
"The boat displaces an amount of water equal to its mass. So, the answer to your question depends on where the displaced water goes. If any of it remains on the aqueduct, then the aqueduct carries more weight. This will happen only if the water level rises when the boat goes onto the aqueduct, which doesn't seem like the normal state of affairs.",
"I'm ignoring the boat's wake and other wave phenomena."
] |
[
"Dropping a boat into a body of water (or, just adding more water) causes the water to rise everywhere. Try stepping into a half-full bathtub, and note that the entire water level rises simultaneously. But that's a simplified description. In more detail: suddenly adding more volume to a body of water will create a very fast (hundreds KPH) wave which communicates to distant parts of the water any changes in pressure/depth.",
"So, when the boat was first lowered into the water far away from the aqueduct, that's the time when the water level in the aqueduct rose a tiny, tiny bit."
] |
[
"The displaced water would be displaced along the entire length of the aquaduct and the rest of the canal, so if it was 10 miles between locks and the aquaduct was half a mile long then it would only have to bear the weight of a twentieth of the boat and that weight would spread evenly over the entire aquaduct. "
] |
[
"Can the Universe be bigger than we think it is?"
] |
[
false
] |
I was working in a R&D lab over my coop and was chatting with my boss when he mentioned that one possible explanation for dark energy & dark matter was that the currently cited and used approximation for the size of the universe was incorrect. According to him if we adjust the calculations for how big the universe is then dark energy and matter are just the effects of gravity acting from beyond the limit of our currently defined universe. I don't think he would just bullshit a claim like that, is there any evidence to support such a theory?
|
[
"we know that it's bigger than the observable universe for sure. Most likely, it's infinite in size."
] |
[
"Can the Universe be bigger than we think it is?",
"Many physicists believe the universe is infinite. So no.",
"According to him if we adjust the calculations for how big the universe is then dark energy and matter are just the effects of gravity acting from beyond the limit of our currently defined universe.",
"Gravity propagates at the speed of light. Matter outside of the observable universe would not interact with us gravitationally because the universe has not existed long enough for its gravity to propagate this far.",
"Also we have imaged dark matter, using gravitational observations. We know where the dark matter is. ",
"Its gravity has been used in gravitational lensing observations.",
" So... dark matter exists. I don't know what your boss is talking about.",
"/physics major"
] |
[
"For staters, we currently think (inasmuch as a whole cohort can think alike) that the universe is infinite in size. However this isn't something that's testable, as we will never be able to observe this, which makes it more a question of philosophy.",
"As for dark energy and matter being explainable by more matter - there are several problems with this. The observable universe is something like 45 billion lightyears in radius. If expansion of space didn't occur this would simply be 13.5 billion years. Secondly, anything more than ~90 billion lightyears away couldn't affect anything that we can see (as they can never have interacted). Thirdly, at these scales the universe is effectively uniform and isotropic. Which means, if you apply Gauss's law to gravitation, that anything outside of the observable universe effectively has no impact on a spherical cavity within, because all effects cancel eachother out (as a corollary, if you replaced the core of the earth with a void, you would experience no gravity in there)."
] |
[
"How do plants \"out-compete\" algae in my aquarium?"
] |
[
false
] |
In freshwater planted aquariums, controlling algae growth is a big problem. Some people use high light, injected CO2 and fertilisers to promote healthy plant growth and it that when your plants are growing happily, algae is not a problem. It is often said that the plants "out compete" the algae. I am not a biologist and my understanding of this is lacking, I'll try and explain why. In an aquarium in which plants grow happily, it seems like there is no competition for resources. CO2, oxygen and nutrients all exist as a concentration in the water, are all in excess and are never totally consumed. Light, too, would seem to be abundant. For example, if you consider a square inch of the front glass of the aquarium, that square inch would seem to have everything algae needs to grow in excess. Yet aquariums seem to reach a balance in which plants grow happily and algae does not. The square inch of glass does not become covered in algae despite having lots of light, CO2, oxygen and nutrients available to it. In this case, how do the plants out-compete the algae? Or perhaps a better question is why does the algae not grow?
|
[
"This is a really interesting question, and there are several possible contributing factors. Plants can in fact out-compete algae for some nutrients, basically starving them. CO2 can be limiting in a brightly lit aquarium with no supplemental gas added. Rooted plants especially have access to nutrients below ground, which can give them an advantage over algae. It's also generally thought that dark periods help plants compete against algae. Plants have an advantage of being able to store nutrition in their tissues for overnight use. And finally it is possible that plants release some chemicals detrimental to algae, but I don't know anything about that specifically in aquariums."
] |
[
"And finally it is possible that plants release some chemicals detrimental to algae",
"To me this is the only thing that makes sense. If both algae and plants have all the things they need to grow, but only plants are growing, it seems like there must be another factor at work. However, I have asked on an aquarium forum and they said that this possibility has been discounted by using activated charcoal in the filter media - supposedly removing any algaecidal chemical that may be produced by the plants."
] |
[
"True, activated charcoal should absorb most kinds of algacidal compounds. I wouldn't be so quick to discount the possibility of nutrient competition though. It's quite well documented in various aquatic situations, though usually between species of algae, for simplicity's sake. Unfortunately, the specific name of the phenomenon slips my mind at the moment. But basically, if species A (say, a plant) can survive at lower concentrations of nutrient than species B (an algae), then both will grow until nutrient concentrations are low enough A will outcompete B. And in closed systems like aquariums, there is plenty of opportunity for various resource to be depleted."
] |
[
"Is there any place in the solar system that one can see a moon as big as ours?"
] |
[
false
] |
I assume gas giants would be quite spectacular to see in the sky from their moons. But where else in the solar system would be a good place to watch the sky from a glass dome?
|
[
"Pluto's moon, Charon, orbits at only 19500 km from Pluto. That's much closer than our Moon at 380000 km. Even if Charon is considerably smaller, it should look very big from Pluto.",
"If I didn't mess up with the math then the angular diameter (apparent size) of Charon seen from Pluto should be 3.76 degrees. Compare this to our Moon, which is only half a degree seen from Earth."
] |
[
"As far as I can tell, the only moon that would appear bigger from the surface of its primary than our Moon is Io as seen from the surface of Jupiter (whatever that means). But only about 15% bigger in diameter compared to the Moon as seen from Earth.",
"However some moons as seen from another moon do appear bigger than that. Io as seen from the next moon of Jupiter Europa, at their closest pass, would look about 50% bigger by diameter than what the Moon looks from Earth. Saturn's moon Tethys as seen from the moon Enceladus would look almost twice the diameter of the full moon. Uranus' moon Ariel as seen from Miranda would be about the same.",
"I didn't go through all the minor moons of the gas giants, but some of them may pass very close to each other so despite being very small, they could appear quite big from the surface of one another. One pair that caught my eye were Pandora and Prometheus, moons of Saturn. They're fairly similar in size around 80 km in diameter. From the surface of the other, they each would appear around 3 to 4 times the diameter of our Moon. Especially Prometheus is very irregularly shaped so the long side could be up to 5 times the diameter of the full moon."
] |
[
"Does Charon count as a moon now that Pluto isn't a planet?"
] |
[
"Is it possible to learn something without being consciously aware that you have ever learned it?"
] |
[
false
] | null |
[
"Yes! In fact, I'd argue that most learning is like this. Here are a few examples of what you might have in mind though:",
"Statistical learning: picking up regularities in the environment. We do this all the time naturally, but we can do this in the lab as well. ",
"Fiser and Aslin (2001)",
" showed participants little picture of symbols arranged in a grid. The symbols came from a library in which they were organized into groups (e.g. a + always above an O), but when displayed in the grid, all of the symbols were equally spaced and the groups were not defined in any way. After passively viewing a long sequence of such grids, participants implicitly learned spatial associations between the symbols (which ones formed a group) such that that when presented, during a test, with a group (+ above an O) and a non-group (X to the left of a -), they were more likely to judge the group as familiar. There were several other interesting experiments in that paper and there are plenty of other experiments on statistical learning. ",
"Statistical learning is also thought to be an important component of language learning. To an infant, it is not obvious where word boundaries are in a speech stream -- as we are talking, we don't really pause between words, making a continuous stream of sound. How do infants learn when one word ends and the next begins? It turns out that the frequency with which certain phonemes appear next to each other differs depending on whether they are within a word or are the end and beginning of two words. 8-month-old infants can pick up these differences (",
"Saffran, Aslin, and Newport, 1996",
"). Infants heard streams of syllables like bidakupadotigolabubidaku... some syllables always followed another (\"within word\") like \"bida\" and others only followed each other some of the time (\"between words\") like \"kupa\". That is, \"da\" always followed \"bi\", but \"pa\" only sometimes followed \"ku\". Infants just listened to this stream of syllables for several minutes and were then played a sequence of words (regular transitions between syllables) and non-words. Infants spent more time listening to the non-words, which is often interpreted in the infant literature as meaning that that stimulus was unusual or different from the other stimuli. ",
"Both of these examples of statistical learning are about pattern detection when the pattern is present in the world and it's just a matter of learning what features to look for. Sometimes this is told to us explicitly: \"this is what a fracture looks like; study this x-ray and identify fractures in other x-rays\", and sometimes we acquire this knowledge implicitly. However, in both cases, all of the information is there and available to us, we just need to learn what features are important. However, there are examples of learning where we are not able to detect features at all and can learn from them anyway!",
"In ",
"Watanabe, Nanez, and Sasaki (2001)",
", participants were shown a sequence of black and gray letters and had to remember the gray ones. In the background, a bunch of dots were moving in random directions, with some small percentage of them moving in the same direction. The percentage of dots that were moving coherently was so small that participants couldn't identify the direction (in a separate experiment). So in the main experiment, the dots were just background -- participant weren't told anything about the dots, didn't have to pay attention to them, and were only doing this letter task. Nevertheless, even though the dots weren't attended to and even though the motion direction of the dots was imperceptible, the participants who performed the letter memory task became better at discriminating the direction of moving dots (in a different experiment) than participants who were not shown the dots during the letter task and this improvement was only in the direction in which the dots were moving during the letter task. In other words, subjects were able to improve in a motion direction discrimination task from passive exposure to a stimulus that they couldn't even detect. Pretty cool. See ",
"Di Luca, Ernst, and Backus (2010)",
" for another example. ",
"Finally, there was cool study a few years ago on learning with fMRI feedback (",
"Shibata et al. 2011",
"). BOLD response in early visual cortex was measured for gratings at different orientations. A classifier was trained so that based on the pattern of activity, it would be able to determine which grating the participant was looking at (i.e., it could distinguish between patterns of activity that corresponded to a left-tilted vs. a right-tilted grating). Participants then came back and were shown a green circle on the screen and were instructed to try to change their brain activity to make the circle bigger. Which is a mad crazy instruction! What they actually did was make the circle bigger whenever the pattern of brain activity resembled the pattern corresponding to a particular grating orientation from a previous scanning session. The participants didn't know this though -- so, unbeknownst to them, the circle got bigger every time they (somehow) reactivated the parts of the brain that corresponded to a grating tilted in a particular direction. After this training (without actually seeing any gratings!), participants became better at discriminating grating orientations around the orientation that was trained, but not around any other orientations. That is, if the circles got bigger whenever the activity resembled that of a 45 degree grating, the subjects later became better at discriminating 45 from 47 degree gratings, but not 120 from 122 degree gratings. ",
"I think these examples touch more closely on what you meant by \"not aware\". However, I would argue that it is very rare that we are actively trying to learn something outside of a school, study, or training setting. Think about, for example, getting better at some video game. Often you just play and get better. You didn't sit there with flash cards or read a bunch of strategy blogs (although of course you can learn explicitly that way). This happens all the time. "
] |
[
"The patient HM is an interesting example of this. HM had severe epilepsy and underwent a lobotomy to decrease the frequency of episodes. An unfortunate side effect of the surgery was he lost the ability to form new memories. He could recall things before the surgery, and his short term memory was still working, but he could no longer transfer short term memory into long term memory. HM ended up being one of the most studied patients in the history of memory studies.",
"One of the tests he participated in involved mirror drawing. The person is sat at a table with a mirror and a screen directly in front of them and a double-lined shape (in this case a star) is placed in front of the mirror. The task is to draw a line between the lines while looking only in the mirror. A person with normal memory will be able to do this within a few trials and then retain that skill on new trials after a period of time. HM could also perform the task as well as a normal person. However, each time he could come in to do a new set of trials, he would have no memory of learning the skill or ever performing the previous trials."
] |
[
"Indeed. In the Saffran paper, they refer to relationships between syllables as transition probabilities, but I didn't want to get into it in the post. This is also the idea behind ",
"artificial grammar",
" learning. ",
"Here",
" is a paper on extracting structure using such models from natural languages in an unsupervised manner. And ",
"here",
" and ",
"here",
" are Bayesian spins on learning word boundaries. ",
"This",
" is another interesting paper."
] |
[
"How did the dinosaur destroying asteroid affect the aquatic life at that time?"
] |
[
false
] |
[deleted]
|
[
"The Cretaceous-Paleogene (K-Pg, or sometimes still referred to as the Cretaceous-Tertiary, K-T) Extinction event killed off both marine and terrestrial species. You can get a sense of the variability of organisms which died out in the ",
"wiki article on the extinction event",
". As described there, in the marine realm, significant numbers of species of nanoplankton, corals, cephalopods, echinoderms, bivalves, and some cartilaginous fish went extinct (it was especially hard on nanoplankton). ",
"For the latter half, are you asking whether it's possible there are organisms we think went extinct across the K-Pg, but are still alive in the deep ocean? If yes, in general, when considering the extinction of an organism, we're talking about it disappearing from the fossil record across a boundary. So it's unlikely that that an organism would disappear from the fossil record across the K-Pg and yet still be alive somewhere today (i.e. individuals of this species would have to avoid being fossilized for 65 million years of Earth history)."
] |
[
"Only in underground bunker. The entire world was hot as a pizza oven within a few hours of impact. Our ancestors were burrowing critters."
] |
[
"The heat was temporary. An asteroid that size carries the energy of many, many nuclear bombs. That fades rather quickly though, and then the 'nuclear winter' situation kicks in."
] |
[
"How to turn HCl into Citrate Salt?"
] |
[
false
] | null |
[
"What is the chemical in question? We can't answer the question without that knowledge."
] |
[
"I've added Phenethylamine HCl to Sodium Carbonate (Washing Soda) Water, \nseparated the Oil on top, \nThen added the Oil to Citric Acid.",
"I'm pretty sure that did the job."
] |
[
"Phenethylamine ",
"Why did you bother? Chloride in your diet?"
] |
[
"Atomic mass is calculated by averaging the masses of all isotopes of an element in their natural ratios. Could the natural ratios fluctuate as we explore and colonize places in the universe where the amounts of different isotopes may be different than in our solar neighborhood?"
] |
[
false
] |
If so, will whatever atomic mass that is printed on our periodic tables today have to be revised?
|
[
"Sure. This is how we know certain rocks are probably from Mars, for example. ",
"Here's one paper in specific."
] |
[
"Yes they can, and yes the accepted values in the textbooks will have to be revised. Some of this is due to the atomic age and all the radioactive stuff that has been let loose on earth recently. But the revision won't be by much. But it is enough to be able to prove that cognac really is 100 years old and not a fake, because the isotope ratios changed after the 1940s.",
"There is no guarantee that isotope ratios elsewhere are the same as here. We have nitrogen-14 being converted to carbon-14 constantly in the upper atmosphere, but there is no guarantee that a methane world or an atmosphereless planet would have as much as we do."
] |
[
"That mass is used because that's the mass that's important in doing chemistry on Earth. If it turned out that the abundances varied widely in the universe, the periodic table as it is would still be useful to chemists on Earth. "
] |
[
"Why does a shortage of hormons like estrogen or testosteron lead to depression?"
] |
[
false
] |
I'm curious. Everywhere I searched for an answer to this question they never brought up reasons for it, only the notion that it does cause depression or at least gives you a shitty mood (I'm not sure if it was the clinical definition of "depression" or the "depression" that many people talk abotu when they "only" feel down) What is the cause behind this? Is it to complex for a layman to understand? Are these hormons providing anything needed or blocking something you don't want to have? Does science know for sure yet?
|
[
"The endocrine system is highly integrated with itself, meaning many hormones are involved in pathways and often times one hormone will signal the release or inhibition of a 2nd hormone. I can't remember off hand what the steroids may or may not initiate but most likely reduced hormones will cause reduced levels of serotonin and melatonin to be released. Cortisol is another factor to consider (the stress hormone)"
] |
[
"Low testosterone levels in men manifests itself in a lot of the same symptoms that are common in depressed people: fatigue, low sex drive, muscle loss, fat gain, brain fog."
] |
[
"Low testosterone levels in men manifests itself in a lot of the same symptoms that are common in depressed people: fatigue, low sex drive, muscle loss, fat gain, brain fog."
] |
[
"Could a natural nuclear fission detonation ever occur?"
] |
[
false
] | null |
[
"Not quite, but close.",
"For a detonation to occur, you need a nuclear bomb, which is a very complex and precise machine. This is probably too complex to be assembled by random natural processes. The closest which happens naturally is when Uranium ore deposits form, and then reach a supercritical concentration of fissile isotopes, which is rare. Then, you get a runaway fission reaction. It doesn't go \"Boom\", but it releases a lot of heat and radiation, as well as daughter isotopes.",
"The best known examples occur in ",
"Oklo",
", in Gabon.",
"It has been discussed in previous posts:",
"https://www.reddit.com/r/askscience/comments/2mup5t/what_would_the_oklo_natural_nuclear_reactor_in/",
"https://www.reddit.com/r/askscience/comments/rcprg/could_the_natural_nuclear_fission_reactor_in/",
"https://www.reddit.com/r/askscience/comments/z9533/could_a_nuclear_detonation_occur_on_a_planet_via/",
"https://www.reddit.com/r/askscience/comments/mc9hq/there_is_a_natural_nuclear_fission_reactor_in/",
"We're getting a lot of posts in the thread along the lines of \"How is it possible that the formation of a nuclear bomb by natural processes is impossible when the formation by natural processes of complex intellects such as our own has occurred?\" ",
"This is a false equivalency. In simplest possible terms: both examples are not under the action of the same processes. The concentration or fissile material in ore deposits is under control of the laws of inorganic chemistry, while our own existence is the product of organic & inorganic chemistry, plus Evolution by natural selection. Different processes obtain different results; and different degrees of complexity ensue.",
"That being said, the current discussion is about natural fission and whether it may or not achieve detonation by its own means. Any posts about the brain/bomb equivalency will be ruled off-topic and removed."
] |
[
"Don't the isotope purities have to be much higher in a bomb so that the energy release is very quick? Like the difference in taking apart a building Brick by Brick or hitting it with a wrecking ball."
] |
[
"There is that. But mostly, you have to factor in that depositional processes in ore deposits are incremental, so that when a supercritical mass of fissile material is reached, it will be marginally so, not massively so. And of course, a lot of gangue will be involved which would interfere with any kind of bomb-like behavior.",
"The best analogue would be a ",
"nuclear fizzle",
" than a nuclear bomb."
] |
[
"Why are the rings of Uranus turned sideways?"
] |
[
false
] |
I understand that the going theory is that Uranus orbits with its poles nearly level with the plane of the solar system because of a collision with significantly-sized body. But why would that turn the rings as well?
|
[
"You're assuming that its rings were present when it first got its tilt. It could have easily picked up its rings long after it got blasted over on its side or they could have formed from the debris of the impact itself coalescing around its (repositioned) equator. Uranus and its system has been around and evolving a LONG time and our current belief is that many of Uranus' rings are very young because the material they're made of wouldn't remain there for long periods of time, so they seem to require constant replenishment. ",
"There's no reason the rings had to predate the axial tilt. There's no reason they couldn't, either, but most of what we're seeing is that the rings are relatively new, so it makes far more sense that the rings formed in place with their current alignment perpendicular to the planet's axis than being present before the current tilt and somehow being dragged into the new alignment as the planet rotated beneath them into its current position."
] |
[
"Thank you!"
] |
[
"If the rings were formed from debris from the collision (or I guess from moons that were formed from debris from the collision and then got within the Roche limit and disintegrated), then their alignment with the equator of Uranus makes sense. But it sounds like you're referring to another possibility when you say that it could have \"picked up\" the rings at some point. If the rings were \"picked up\" from a process that had nothing to do with the impact that tilted Uranus, why would they be aligned with its spin instead of the ecliptic? Would tidal interactions be able to drag it into alignment?"
] |
[
"Is there a limit to the size of an element?"
] |
[
false
] |
I saw that the four new elements were recently discovered. I was wondering, is there any limit to the atomic mass an element can have? Sorry if this is a repost!
|
[
"Well, you can theoretically have an atom of any size, but the larger it is, the weaker it is at holding itself together. ",
"So yes, you can have an atom some huge, 10th row element if you want, but only for a few nanoseconds. "
] |
[
"To add on, this is because nuclei contain protons, and protons repel each other. However, there is a stronger force, the \"Strong Force\", which causes attraction between protons and neutrons, holding the nucleus together. However, this force is a very short-ranged force, so the larger the nucleus, the weaker it is compared to the electrostatic repulsion between protons. Hence larger nuclei are more unstable. "
] |
[
"No, the strong force does hold gluons together but it is the residual strong force that provides attraction between nucleons. It is sort of analogous to the way neutral atoms are internally held together by EM forces, but neighboring neutral atoms can still attract each other via Van der Waals forces.",
"The weak interaction plays a role in decay of nuclei by allowing quarks to change flavors (so neutrons can decay into protons) but it isn't holding the nucleus together."
] |
[
"Could we just send a couple \"cleaner\" bots to Mars?"
] |
[
false
] | null |
[
"No the current rover Curiosity (and the next one) are nuclear powered."
] |
[
"Most of the cost of a mission is just landing something on the planet. It is vastly more interesting to design a whole new robot that can do much more than what Opportunity did than sending a cleaning robot that would cost 75% of the price to build, launch and land. "
] |
[
"right, but I'm assuming that whatever the next robot we sent is, it'll have the same problem eventually right? Or is technology just expected to progress at a rate that by the time any rover runs down it'll be about time to replace it anyways?"
] |
[
"Does a heightened sense of smell in dogs mean they smell *more things*, or that all things have a *more intense* smell?"
] |
[
false
] |
And if it's the latter, are they absolutely freaked out by certain smells?
|
[
"Both. Their threshold for most compounds is lower than ours. Therefore, some things we cannot detect at all (below human threshold), are detectable by dogs. Some things we do detect (above human threshold) will probably be more intense for dogs because of their lower threshold.",
"Although, how odour concentration and chemoreceptor sensitivity integrate into subjective 'intensity' is poorly understood and a damn slippery thing to study."
] |
[
"Both kind of, dogs smell all smells individually, like if you’re in a restaurant and you get steak, but at the table next to you a man’s been farting all night, and 3 seats down someone is smoking weed, we smell the blend of weed and steak and farts as one smell, a dog smells weed as it’s own thing, farts as their own thing, and the steak as it’s own thing. ",
"This separation of smell means that practically speaking they can smell any singular smell far better than we can, but aside from that they also have really strong sense of smell to the point that they can smell a drop of a single substance in a barrel of water a mile away or something like that (I can’t remember the exact figures but it’s pretty kind boggling)."
] |
[
"Does a heightened sense of smell in dogs mean they smell ",
", or that all things have a ",
" smell?",
"A dog's sense of smell supercedes its sense of sight! That is, a larger portion of a dog's brain is devoted to its nose than its eyes. ",
"Oddly enough, this is something that some dog researchers overlook. They conduct studies to eliminate inadvertent visually cueing (citing the Cleaver Hans Effect) without eliminating inadvertent cueing via a dog's sense of smell."
] |
[
"How long to disrupt for?"
] |
[
false
] |
I am running a DNA extraction protocol on rat liver, and we are starting off the protocol by using a disruptor with bead to grind up the sample. A piece of tissue will be in the tube along with extraction buffer (water, Tris, NaCl, and SDS) and of course the bead. We are using the Scientific Industries Disruptor Genie and will be using it at full speed, but I can't find anywhere online how long we should run this for. Thanks!
|
[
"Haven't used that, used a sonicator before though... I just blasted the damn stuff until it was a liquid goo with no pieces (only took a short time though like 30 seconds maybe). Varies depending on tissue though.",
"Happy homogenising!"
] |
[
"dunno, but thanks for sciencing! We need all we can get."
] |
[
"When I've homogenized cells in the past using a rotor-stator homogenizer, I think I only needed around 15 seconds. But that was cultured cells, not tissue. If I were doing your experiment, I'd start with 30 - 60 seconds as a guess. (Actually I'd call the company and ask them before actually doing it.)"
] |
[
"Why does an open cut sting when alcohol is applied to it?"
] |
[
false
] |
[deleted]
|
[
"There are special cells called VR1 receptors that tell your body when your skin is getting hot. If you hold you hand over an open flame or boiling water these receptors trigger to let you know it's hot.",
"When alcohol and these cells meet, they react chemically and the alcohol reduces the threshold needed for these receptors to fire. So it thinks you are getting burned at ambient temperature. ",
"This is a similar but not exactly the same reason why alcohol burns going down your throat."
] |
[
"This is a similar but not exactly the same reason why alcohol burns going down your throat.",
"Why does it burn when swallowed?"
] |
[
"Does this relate to when you've consumed alcohol, your body doesn't feel cooler temperatures that well?"
] |
[
"Given our knowledge of the formation of elements in stars over the course of the existence of the universe, what is the earliest time we should have expected to see life as we know it to come into existence."
] |
[
false
] |
As I understand it, the first stars that were formed produced only hydrogen and helium which was used, after those stars went supernova, to form new stars which in turn used those elements as fuel to make the rest of the gamut of elements with carbon being one of the earlier ones. Given that information and our knowledge of the age of the universe, can we make general assumptions as to the earliest possible time that life could have existed? Thanks for any help in answering this question.
|
[
"Wouldn't \"give or take a few billion years\" be a rather significant deviation, given the accepted age of the universe?"
] |
[
"What are population I/II stars?"
] |
[
"Pretty much when when it did. The heavy elements that make up our planet had to form in population II stars and our sun needed to be a population I star.",
"I've not seen any compelling evidence that the Earth could have formed any earlier than it did, perhaps give or take a few billion years."
] |
[
"When in a dark environment, why does objects which you are looking at directly appear darker and harder to see, but objects which you see at the corner of your eye or in the peripheral vision appear brighter?"
] |
[
false
] | null |
[
"The answer has to do with how different types of photoreceptros are distributed in your eye. There are two main types of photoreceptors that are responsible for human vision called ",
"cones",
" and ",
"rods",
". Cones come in three main varieties, which allows us to see the world in color under well-lit conditions. Rods on the other hand come in one main form but have the advantage that they are more sensitive than cones, as you can see ",
"in this diagram",
". As a result under low-light conditions (called ",
"scotopic vision",
"), the rods kick in to allow us to see a scene much better than we could using cones.",
"Now to get at the heart of your question, look at how ",
"cones and rods are distributed in your eye",
". Notice that cones are mainly clustered around your fovea (so you can see well directly ahead), while there are more rods to the side. As a result, at night when you scan a scene, it may appear to be brighter through your peripheral vision than it does right in front of you. On the flip side, the lack of cones in your peripheral vision also explains why your peripheral vision is black and white even under well-lit conditions!"
] |
[
"That blind stop is called the ",
"physiological blind spot",
" and it exists in all vertebrates. The reason it exists is that as you can see from ",
"this diagram",
" in our eyes there are nerve fibers that sit in front of the retina (where all the photoreceptors are). At one point these fibers link kink inwards where the optic nerve exits the eye. At that point there are no photoreceptors, so we can't see anything. ",
"As for your question about whether such an arrangement is advantageous, I would argue that the answer is no, and that this configuration is more of an evolutionary accident. For instance, the same diagram on the right shows that cephalopods (e.g. octupi), have an inverted arrangement, where the nerve cells sit behind the photoreceptors and as a result they don't have such a blind spot."
] |
[
"accounting for 80% of total supplied oxygen in humans.",
"Perhaps I'm misunderstanding what you were saying, but I'm fairly certain that is not even close to correct. Could you elaborate or provide a source? "
] |
[
"Are there any positive effects of stress?"
] |
[
false
] |
There are many books and articles about how stress can hurt your mental and physical health over time. However, like most things there seem to be positive effects in addition to negative ones.
|
[
"Actually, stress is very important in our lives. It activates our adaptation systems and allows us to learn, to adapt and to survive. There is of course bad stress, dis-stress, and good stress, eu-stress. Too much of anything is bad for you but in moderation can be beneficial. Look up the work of Hans Selye, he was a pioneer in the study and mechanisms of stress. Stress sets off a cascade of events in our bodies, hormone release, heart rate, pupil dilation etc.. Without stress we might not be here today to discuss the benefits of stress. "
] |
[
"I watched a science documentary on TV some time ago, that linked moderate amounts of stress (not prolonged), being hungry (lowering food intake to bare minimum) and drinking red wine (because it has ",
"Resveratrol",
") to a longer lifespan. All i can remember is that it was on Discovery and a Viasat channel.",
"Apparently, there are A LOT of pseudo-medical mambo jambo on the net, but i think ",
"this is a good article on the topic",
"."
] |
[
"Ah thank you, that article was very interesting and seems to flesh out much of the question. I suppose that there is healthy stress and unhealthy stress."
] |
[
"Is there a proof to say why the sum of all the digits of every multiple of 9 results in a multiple of 9?"
] |
[
false
] |
eg 56*9=504 5+0+4=9
|
[
"NB.: X mod Y or X%Y is the operation where you integer-divide X by Y and take the remainder.",
"This is trivial for single-digit numbers.",
"For two digits, the number AB is equal to 10A+B. If we write it as 9A+(A+B) we can see that (A+B) mod 9 will be the same as AB mod 9, or more related to your question, if a+b mod 9 = 0 (perfectly dividable by 9) then so would be the number AB.",
"We can see how this extends to more digits: ABC = 100",
"B+C = 99",
"B+B +C = (99A+9B) + (A+B+C) -- see how the first part is perfectly dividable by 9, and the second part is the sum of all digits?",
"The formal process to extend this to arbitrary number of digits is called 'induction', and I won't go into it now. It's not complicated, but I think the above paragraphs will give you enough."
] |
[
"/u/dontspillme",
" gave a short and correct explanation but I'm going to try and be more precise and formal, in case anyone wants to see an actual proof.",
"When we write a number as a series of digits, we actually write it as a sum of powers of 10. Take for instance 2014: it's TWO times 10",
" plus ZERO times 10",
" + ONE time 10 + FOUR times 1.",
"So let's take an arbitrary number N, and denote its number of digits as n + 1. We write N as N(n-1) N(n-2) ... N(0), by which we mean that:",
"Now we can prove by induction that for all n and p, both integers :",
"In particular for p = 10 :",
"For instance if n = 5, this relation becomes :",
"So you can see that it is in fact fairly obvious.",
"What this relation tells us is that ",
" for all n. Now that we have established this, let's write our number N as :",
"For instance :",
"The first series of terms are all multiple of nine ! So we can write :",
"where M is an integer. For instance :",
"2014 = 9 * (111 + 11 + 1) + 2 + 0 + 1 + 4",
"2014 = 9 * 123 + 2 + 0 + 1 + 4",
"If N is a multiple of 9, N - 9M is also one and thus N(0) + ... + N(n-1) is a multiple of 9. Conversely if N(0) + ... + N(n-1) is a multiple of 9, N(0) + ... + N(n-1) + 9M is also one and thus N is a multiple of nine."
] |
[
"More generally, for any base N, it works for any factor of N-1. For base 10, the only factors are 1, 3, and 9. For base 16, it works for 1, 3, 5, and F. Basically, the proof given by ",
"/u/dontspillme",
" shows this. The number AB in base N is N*A + B, which becomes (N-1)*A + (A + B). If (A + B) contains any factor of (N-1) then AB divides by that same factor."
] |
[
"What kind of geological processes must occur for terrain of this sort to be produced?"
] |
[
false
] |
I saw of Phong Nha-Ke Bang Park in Vietnam, and thought about it a little in a geological context. I noticed the flatness of the pasture below, but the steepness of the hills. It almost doesn't seem natural, as if they are meteors, covered in foliage. I figure they're probably not, but have no idea what causes terrain like this. What's going on in Southeast Asia that causes such flat marshes, and such steep hills jutting from the surface of the Earth?
|
[
"I love you. I love askscience. I love reddit. I love science. I just can't believe how I can ask a question about a picture I was interested in, and have someone teach me things I never knew I never knew!",
"Thank you so much."
] |
[
"Being easily impressed just makes life that much more exciting!"
] |
[
"This type of landscape is called ",
"karst",
". The underlying bedrock is usually limestone. These ",
"towers",
" develop when dissolution by water charged with ",
"carbonic acid",
" proceeds along fractures, causing them to widen. Other weathering processes widen the fractures further. In this picture, the towers surrounded by floodplain deposits from an adjacent river. You might also enjoy pictures of the karst landscape of ",
"Stone Forest in China",
"."
] |
[
"Why does the human immune system not have a cummulative effect?"
] |
[
false
] |
To be more specific, shouldn't our immune systems become more efficient as we get older and our body recognizes more and more pathogens? For example, i believe its true that you cannot get the same cold virus twice because your system remembers the virus, and has the antibodies to kill it. Why does this system not accummulate as we get older, and become more effective?
|
[
"There are a couple of things here. For one, your immune system does get better as you get older - to a point. Once you hit a certain age, though, your body begins to deteriorate. That's why we age. Cells mutate, they die. There's no getting around that, and it plays a pivotal role in our immune systems. But it's not just being old. Infants can't have honey because fungal and bacterial spores lie dormant in honey, and can cause an infection to a baby with an immune system that isn't \"experienced\" but the same honey won't make a toddler, child, teen or adult sick (with some exceptions) because their immune systems have become more functional. The flu primarily kills very young children and the elderly because both groups have weaker immune systems than the rest of the population. Babies because they haven't had time for their immune systems to fully come around, and the elderly because their immune systems are weakening due to age.",
"To understand the immune system's memory, you need to understand the very basic principles. I'm keeping this SUPER basic. There are two \"branches\" to the immune system. The nonspecific branch, called the innate system, that is always active. It's composed of neutrophils, complement, macrophages, etc. It's active all the time, antibody and complement binding up foreign antigens and the phagocytic cells (macrophages, neutrophils) eating cell debris and foreign bodies. The second, and the one we think of most, is the adaptive immune system - T cells and B cells. The adaptive immune system is what confers immune memory in the body. Your adaptive immune system, in theory, has the ability to recognize an infinite amount of antigens. However, due to your genetic make up and a number of other factors (see allelic exclusion), your adaptive immune system will not be able to. The receptors undergo a recombination event during cell maturation, leading to a very certain specificity for an antigen. When the immune cells are activated upon contact with their HIGHLY specific antigen, they undergo a proliferation and physical change. This takes a short time to ramp up to full immune power, but once it's up and running, it's a powerhouse. Upon changing they go from naive cells to memory cells. From then on, they will always exist as a memory cell until they die. For more info, Janeway has an amazing immunology book. I believe it's in its 7th or 8th edition now. ",
"Another issue is that there are a plethora of viruses to cause colds, bacteria/viruses/fungi to cause illness and disease. One bacterium can have a number of different virulence factors responsible for disease, and the only way to be protected fully is to have been exposed to all of them, in theory. On top of having an arsenal of virulence factors, the organisms are constantly evolving to beat our immune system, and our immune system to beat them. It's an arms race, as we like to say in the lab. On top of all this, when you get a cold, you may not be getting the same virus. In all likelihood it's a different virus - you are just getting the same symptoms. Do you know how many illnesses, both relatively benign and life-threatening, have \"flu-like symptoms\" as their initial signs? I don't have a number because it would take way too long to count them all. ",
"Again, this was just the basics. I've probably missed something as it's late here, but this is a good starting point."
] |
[
"Thank you so much for taking the time to answer this is such detail. Also, thank you for setting this up very simply for me. Immunology is not my area of expertise. ",
"So, my next question, in the adaptive branch of our immune system, do we find an overall strengthening during our lives until we reach an apex, and then it becomes less and less effective?"
] |
[
"Glad I could help! I'm by no means an expert in immunology. I study bacterial pathogens, and I prefer to understand how the bacteria is doing its thing. ",
"That being said, your immune system doesn't really hit an apex.It strengthens because it recognizes a certain antigen, and then the T cells and B cells proliferate. Those T cells then become memory T cells that will circulate the body \"hunting\" for any cell presenting the antigen on its MHC molecule (the T cell receptor recognizes a major histocompatability [MHC] molecule that has the antigen exposed - think of this like the MHC is the keyholder, the antigen is the key and the T cell receptor is the keyhole - they all have to fit perfectly for it to work). B cells turn into plasma cells and produce antibody that is specific to an antigen, or they become another type of memory cell important for T cell activity. In both cases, when the naive T cell or B cell is activated, it becomes a memory cell and then creates a large amount of clones. You end up with an army, for lack of a better term. There was a theory for a long time about your body being a \"bucket\" in that you only had a finite amount of space for memory and that memory cells for antigen B will eventually take over and the cells for antigen A will die and go away. We now know that not to be true. Dave Masopust at the University of Minnesota works on this stuff. It turns out your body seems to keep a balance on all the memory cells, ensuring that you will always have the memory if you can keep it, and that you will be able to keep adding new immune memory when you experience new illnesses and pathogens. It's pretty cool. ",
"Your immune system reaches its apex, as you put it, when it hits a certain age. It's not so much that the immune system has hit a plateau, more that aging has caused your DNA and your entire body to deteriorate. All of your cells are dying and weakening, immune cells included."
] |
[
"Black holes swallow light. However, do different wavelengths of light behave differently when reaching the event horizon?"
] |
[
false
] | null |
[
"Not so much. Light travels at the same speed regardless of wavelength because photons are massless, so all colors of light are equally affected by the black hole's gravitational field. ",
"This paper",
" summarizes previous experimental efforts to put an upper bound on the mass of the photon (and the graviton), and so far it seems that the photon mass is pretty darn close to zero. If the photon mass were nonzero, then photons at different wavelengths ",
" travel at different speeds, and this might have significant effects on our observations. For example, black holes would appear to be different sizes depending on what spectrum you observed them in. Observations in a \"slower\" spectrum would show a larger black hole than those in a \"faster\" spectrum.",
"One might think to turn this idea on its head and try to measure the effect on black hole sizes to see if the photon mass is different from zero. So far however, there have been no direct optical observations of a black hole, only indirect observations of their gravitational effect on nearby objects or ejection of ",
"relativistic jets",
"."
] |
[
"Because ",
"systems of particles may have mass, even if the individual particles may be massless",
". In fact, most of the \"normal\" mass in the universe comes from all the gluons in protons and neutrons, and gluons are massless."
] |
[
"not really. They blueshift (relative to some external observer) on the way in, but they all fall in and add to the mass of the black hole."
] |
[
"Will a spacecraft coated with Vantablack be “blind”?"
] |
[
false
] | null |
[
"This hypothetical questions is probably be better suited for ",
"/r/AskScienceDiscussion",
"However, here are some things to think about:",
"black body",
"pinhole camera"
] |
[
"Thanks for the feedback, viscence! Much appreciated :) Following your suggestion, I have posted this very same question in AskScienceDiscussion.",
"As for your comments, I will certainly look into the pinhole camera idea. While on Earth, to be sure the pinhole camera is not very cost-effective, for the aliens would need to cool it constantly--therefore a more cost-effective system, say echolocation, would be used instead to solve this issue, right? However, in the void of space, the cooling system would be free for sure. "
] |
[
"Quite the opposite I'm afraid. The vacuum of space may be cold (in places) but it's an excellent insulator. That's why vacuum flasks can keep stuff warm for so long. ",
"The three main ways of transferring Heat are conduction, convection, and radiation:",
"Black things radiate thermal radiation very well, which is why your black spaceships need a cooled surface in the first place. You could select which surfaces to cool depending on what direction you don't want to be seen from.",
"While echolocation isn't a very precise system, it draws some interesting parallels to the stealth of submarines. Active echolocation is very detectable: your ships emit a very loud noise (it would have to be if you want it to travel far enough) and listen for echoes. This is the pinging sound you know from submarines. \nPassive echolocation is not really detectable: essentially you have some microphones and when something makes a noise you can figure out where it came from, but maybe also where it bounced off things.",
"In either case, echolocation will probably have a very low resolution and since the speed of sound is 300m/s in air, active echolocation will only know about objects that are 300m away after 2 seconds (1 second for the sound to get there, 1 for the echo to get back).",
"Passive echolocation is more complicated. You'll know about an object making a sound 300m away after 1 second, but if that sound bounced off something the delay before you detect that object depends on where it is.",
"Needless to say echolocation does not work in space."
] |
[
"Does increased mass at high speed also increase an objects gravity?"
] |
[
false
] |
For example, if I took the earth/moon system and accelerated it to some appreciable fraction of light speed, would it cause the moon to 'fall' to earth?
|
[
"To answer you example question, no. It doesn't matter what speed the Earth Moon system is travelling at, you can always go to the Earth Moon rest frame where the Earth Moon system is stationary.",
"To answer your question, things don't gain mass at higher speeds, they gain energy and momentum."
] |
[
"This answer seems to contradict some other upvoted ones given on Reddit and elsewhere.",
"From another question on the /r/askscience front page right now",
":",
"mass is energy, and ",
" The stress-energy tensor is what creates gravitational fields in GR, and some components of the stress-energy tensor for a point particle -> infinity as the particle approaches the speed of light.",
"A PhysicsForums.com thread",
":",
"Energy density (effectively the \"same\" as relativistic mass) does indeed contribute to gravity. However, momentum also contributes to gravity",
"(Here he means gravity will be affected, but not in the simple Newtonian way.)",
"An ArXiv paper - S. Carlip, at U.C. Davis",
":",
"Am I misunderstanding you? I apologize, but I feel more confused!"
] |
[
"I_know_physics_AMA is absolutely correct. ",
"Only if there are relative differences between two systems does the energy/momentum effect on gravitation matter. If an ",
" system is accelerated to any speed whatsoever, the physics ",
" that system will be unchanged - no different than if the system was \"at rest\". Indeed, the system would still be \"at rest\" according to itself, no matter how fast you think you've accelerated it to from an outside frame of reference."
] |
[
"Chemical that reacts with Rust to ‘seal’ a surface?"
] |
[
false
] |
Has anyone come up with some type of sealant or protectant that can be applied directly to a rusty surface and the chemical actually reacts with rust itself to create the sealant? Whereby the rust itself can be converted to something better? Iron oxide must have some “potential” to it and not need to be removed every time?
|
[
"The problem is that if the rust is at all thick you end up with a brittle coating which can shear off when stressed. A surface which has had the majority of the rust mechanically removed (e.g. by wire brushing) can be painted on. Historically, red lead was the primer of choice for such surfaces as it reacted to form azeolates which are protective, but the safety implications of lead-based coatings mean that it is not used these days. Other specific chemicals are used, but you don't get as good a life from them as you would on a blast-cleaned surface."
] |
[
"There are commercial products that combine a rust reducer with primer. One was sold as NeutraRust. The rust is converted to a black substance, probably either a sulfide or Fe3O4, and when it dries you have a paintable surface. But I doubt there is anything that does it without the paint-sealer additive doing most of the work."
] |
[
"Basically phosphoric acid. You can also purchase phosphoric acid for this purpose as a thin liquid that can be brushed on."
] |
[
"Is the nucleus best visualized as many discrete quark triplets or as a sea of quarks?"
] |
[
false
] |
Since gluons mediate over both inter- and intranucleonic distances, which is the better mental model: Many quark triplets (protons and neutrons) reasonably spaced apart, or rather a largely seamless sea of quarks? Looking up the relative sizes of say a uranium nucleus and a proton, it seems like it could cut either way.
|
[
"Quark triplets (properly termed Baryons). We have another type of material that's a seamless sea of quarks, called a Quark Gluon Plasma."
] |
[
"It's best visualized in terms of protons and neutrons. You can understand pretty much all you need to know about nuceli without quarks"
] |
[
"It really depends on the nucleus. For small (light) nuclei, you can cleanly resolve different nucleons, and those are the \"optimal\" degrees of freedom. As you move towards larger nuclei, the relevant degrees of freedom are collective modes. A good depiction of this comes from Scidac-UNEDF collaboration, (",
"http://www.scidacreview.org/0704/images/unedf04.jpg",
")"
] |
[
"Frost on your car occurs when there is direct line-of-sight to space (e.g. no clouds or carport). Why is this?"
] |
[
false
] |
I've heard it has to do with something called latent heat of radiation (maybe?). What does this mean and how does it work?
|
[
"Overnight cloud cover tends to keep the underlying area warmer than if there were no clouds. The clouds absorb outgoing longwave radiation and emit them both to space and back to the surface. While it is certainly still possible to have frost occur, it may be less likely because those surfaces (i.e. Car) may not cool as readily to its frost point as during a clear night."
] |
[
"It's loss of heat by infrared radiation. We usually think of heat being shed from an object by it heating up its surroundings by direct contact (air, anything touching it). But heat is also shed radiatively, which is how infrared imaging devices can pick up on body heat, etc., from a distance. The wavelengths are too long to be seen visually, but a warm object is basically giving off light the whole time.",
"If there's anything to reflect or absorb this, then the local surroundings stay warmer, but if there isn't (direct line of sight to the sky, as you note), then this radiation heads straight out into space and is gone forever. This radiative cooling can take an object down below the dew/frost point pretty quickly under a clear sky.",
"As a telescope owner, I can testify to being driven nuts by this on humid nights with a clear sky, as my equipment films over with moisture just as things are getting going. Even a piece of black paper taped around the end of the telescope tube can slow this down enough to buy some more observing time."
] |
[
"Thanks for your answer! I'm still a little confused though. I was under the impression that, given 2 overnights where both reached, say, 20 F, one with clouds and one without, it's only going to frost the car on the night without clouds. This seems to be the case given my observations, but I never wrote these down or anything, so I might be wrong.",
"Does the infrared radiation change the dew point? Or is the surrounding air actually that much warmer (or i guess brighter on the infrared spectrum)? Maybe my car cools down slower and the frost doesn't form?"
] |
[
"If gravity is so weak, how did things even start attracting each other in order for new stars and etc to form?"
] |
[
false
] | null |
[
"The strong and weak forces have very short ranges, so they're effectively zero on the length scales relevant to this simulation. And as for the electromagnetic force, when you have a cloud of matter which is macroscopically neutral (all charges cancel out), electromagnetic forces effectively have a very short range too.",
"So by process of elimination, the only force which \"survives\" is gravity. So even though it's a weak force, it's the only one that significantly affects dynamics on the relevant length scale."
] |
[
"So by process of elimination, the only force which \"survives\" is gravity.",
"But it's extremelly weak in that scale of mass, so it's also effectively zero"
] |
[
"No, that's not true."
] |
[
"Based on existing and practical theoretical methods and texhnologies, To what extent can we realistically expect to lessen our dependence on fossil fuels?"
] |
[
false
] |
[deleted]
|
[
"Entirely dependent in economics: it would cost an enormous sum, but we could do it almost immediately if we were willing to abandon all existing fossil fuel infrastructure. I'm assuming that bioethanol is considered a fossil fuel for this, since burning it produces carbon dioxide just like traditional fuels.",
"Replace all gas vehicles with hydrogen or electric, terminate gas stations and replace them with charging stations.",
"Create large batteries to handle off peak generation of soar, wind, and hydro power (they just scale back the burning at coal and gas plants).",
"Massively and recklessly expand solar and wind installations without regard to environmental impact or efficiencies.",
"Large aircraft would have to be temporarily outlawed, as no high energy-density fuel replacement is readily available.",
"All of this is DOABLE, it just isn't SENSIBLE, and would require a catastrophic shift in public opinions and world economies to make happen.",
"Imagine a doomsday scenario where, instead of aliens, we fight weather phenomena by reducing our carbon emissions. If we truly threw everything we had at the problem, we MIGHT be able to fix it quickly."
] |
[
"Actually, biofuels are generally able to be produced in a carbon-neutral manner, since the carbon burned was extracted recently from the atmosphere. "
] |
[
"I know this is anecdotal but there is nothing here yet so it may give the OP somewhere else to look. Also, I think this is a technology question, not a science question.",
"As a technologist, I have to say that technologies are adopted not because they are the best solution but for many other reasons. Humans detest change and this alone is a major barrier to technologies being adopted. I recently tried to file patents for improvements to the Internal Combustion Engine (only to find that major manufacturers had filed these less than a year previously) but in my analysis I decided that the automobile was a solution in search of a problem. But people like automobiles a lot, so geting people to surrender their automobiles is going to be far harder than simply improving those automobiles.",
"I am not sure who would be qualified to answer your question. It involves technology, politics, socio-eceonomics etc."
] |
[
"If you could have a conversation with a founder of your field: who would it be? What would you like to ask them? What would you love to be able to explain to them?"
] |
[
false
] |
[deleted]
|
[
"Alan Turing",
", to tell him that things will get better for homosexuals.",
"(Sorry, not really about the state of his field, but I'm just saddened by the way he died. Who knows what more he might have contributed)"
] |
[
"Darwin. I imagine that he'd cry at the elegant beauty of the underlying mechanisms of reproduction, inheritance and the expression of traits - the double helix, meiosis, and the genetic code - and the vindication that genetics has brought to his ideas. And I imagine him having a good chuckle when told that he had a copy of Mendel's work all along on his bookshelf, buried in a book on gardening and plant breeding."
] |
[
"Depends on what you call 'his field', but, well, the languages used in the software industry could have actually ",
" ideas from math and computer science. Specifically(I don't really know what else is useful for languages), lambda calculus, categories. Languages exist like ML, Haskell, lisp, but aren't all too widely used. (Lisps are sort-of 'anarchistic' in the sense that you want to easily do whatever you want with the code, though most lispers use a neater subset. Anything can be expressed in s-expressions and therefor parsers should provide s-expression output for those wanting to analyze the code.)"
] |
[
"Is there a limited number of protons, neutrons and electrons or they are created all the time?"
] |
[
false
] |
If they are limited, can they be destroyed?
|
[
"TL;DR: This is an unsolved problem.",
"If the universe was in thermal equilibrium at very early times, there would have been equal amounts of matter and antimatter. As the universe cooled, they would have nearly completely annihilated, leaving a universe with very little matter (and an equal amount of antimatter). That is not what we observe. We see much more matter than the naïve theory predicts, and essentially no antimatter.",
"Th leading theory of the origin of this asymmetry is the breaking of a symmetry (called \"CP symmetry\"). Quarks are known to violate this symmetry, but not by enough to explain what we see. It is possible that neutrinos violate the symmetry by enough. This is one of the main foci of neutrino physics nowadays."
] |
[
"Creating a proton, neutron, or electron, requires creating the corresponding antiparticle at the same time. Destroying them requires annihilation with an existing antiparticle.",
"It is easier to create electrons and positrons, because they are much less massive than protons and neutrons, so much less energy (mc",
") is required. It is a common astrophysical process."
] |
[
"Protons and Neutrons can be converted into one another in fusion and fission processes."
] |
[
"What specific qualities/personality traits do you need to be successful as a researcher?"
] |
[
false
] | null |
[
"Hm, OK. I understand what you're saying - that there's also a lot of both creativity (in coming up with ideas) and \"grunt work\" (in setting up experiments) involved.",
"However, if I may, I'd like to say that these also require honesty: Finding the questions that really challenge your hypothesis (not like what homeopaths do: \"Are people satisfied with the service they receive\" instead of \"Does the shit work\") and not tweaking your data or repeating measurements until you got something you wanted, or choosing the wrong statistical tools, \"forgetting\" to include corrections for multiple testing, etc. etc. - there are a lot of possibilities where a researcher can fool himself, and it requires a certain amount of critical thinking for seeing that... and honesty to draw the right conclusions.",
"Can we agree?",
" I'm thinking of \"honesty\" more in terms of \"trying hard not to fool oneself\", although I admit that I focused on the \"accepting failure\" part in my original comment."
] |
[
"dedication and endurance,",
"ability to accept mistakes and learning from them,",
"critical thinking,",
"and, because you asked \"succesful\", not \"good\": from my experiences unfortunately it often requires a lot of brown-nosing or at least playing the \"social games\" (until you reach a certain position of course)"
] |
[
"I think by far the most important quality is intellectual honesty, which supports ",
"critical thinking",
". You have to be able to accept that your favourite hypothesis was ",
", if the evidence shows so.",
"But even with that, success is not guaranteed. You have to be a bit lucky, too, and get to work on projects that \"lead somewhere\"."
] |
[
"Is it possible to completely eradicate human diseases?"
] |
[
false
] |
I heard smallpoxs was completely eradicated declare by WHO, but they still exist, so can it reappear back?
|
[
"It is highly unlikely to the point of not possible. Smallpox was eliminated as a disease in the human population with the last cases being in 1978. There are two official samples left in highly controlled labs where they will not get out and will eventually be destroyed.",
"However there have been at least two cases of smallpox or smallpox related material found in the last decade that could provide a source of new infections. One was some scabs in a book and the other some vials in an FDA lab that no one knew were there. They were labeled so appropriate precautions were taken. ",
"There is small chance, very small chance, that there are other samples mislabled or lost that could start an infection. As time goes on the likelyhood gets less and less since the virus in the sample would become unviable unless properly maintained. ",
"Even if someone found a vial of the virus in some abandoned lab, it was mislabled and they got infected from it they are likely the only one that would suffer from it. We know how to vaccinate for smallpox and the scabs from the first infected person would be used to vaccinate those in contact with that person so it would not spread beyond them.",
"The fearmongers in the military/espionage fields also like to bring up that maybe some country kept some virus and will one day use it as a bio-weapon. There is no evidence any country has such stocks but the people paid to be paranoid are paranoid about it."
] |
[
"Right. And even if you completely eradicated all humans many of their diseases would live on, living with other vectors. ",
"The only reliable way to completely eradicate all human diseases would be to completely eradicate all of life."
] |
[
"Probably no. There are so many kinds of disease (genetic disease, infectous disease etc.) and they operate in such a complicated system. If you erdicate one type of infectious microorganism you can bet on that there will be another one taking it's place sooner or later. The same goes for genetic disease. DNA will continue the make mistakes during replication, and even though you probably could learn to cure many of these diseases you could never get you DNA replication to never make mistakes."
] |
[
"Apparently Jupiter has around 67 moons, would you always see at least one full moon if you were standing on the surface looking up?"
] |
[
false
] | null |
[
"No. If you are at the equator at noon then all the moons you see are closer to the Sun than you - they are at most half full. The full moons are behind Jupiter. You can only see full moons if you are on the night side.",
"While Jupiter has many moons most of them are small and far away. Io is similar to Earth's moon in terms of distance and size. Europa, Ganymede and Callisto are large but quite far away already, and everything else is much smaller, and nearly all of the other moons are also farther away. \"Full moon\" isn't that impressive if you have a 2 km rock 20 million km away - you don't even see it with the naked eye.",
"Here is a list",
"."
] |
[
"\"Full moon\" isn't that impressive if you have a 2 km rock 20 million km away - you don't even see it with the naked eye.",
"Just to add a couple specifics: Io is curiously almost the exact same diameter as our Moon, as well as almost the exact same distance from its parent planet. As a result, it would look about the same size in Jupiter's sky as our Moon does in Earth's sky.",
"All the other Galilean moons would appear smaller, as they're somewhat larger but substantially farther from Jupiter. The only moons outside of the big 4 that you could see as more than just a point source with the unaided eye (though not much more) would be Amalthea and Thebe; they're both much smaller, but are closer to Jupiter than Io."
] |
[
"Metis could be recognizable as extended (and non-spherical) object if you are somewhere near the equator. 130,000 km semi-major axis, subtract 70,000 km equatorial radius so its closest approach is 60,000 km. With its size of 60 km × 40 km × 34 km the long axis is 1:1000 and the short axis is 1:2000, similar to 1 mm and 0.5 mm at 1 m distance."
] |
[
"Do the viruses that cause the common cold leave lasting damage to any part of the body like covid variants do?"
] |
[
false
] | null |
[
"Post viral syndrome/Post viral fatigue",
" are both quite nasty and can be quite like long lasting and can happen after colds/flu.",
"I was ill for ~6 months after a particularly bad bout of flu. Probably wasn’t completely right for 18 months or so. ",
"After a bad cold one year I had post viral fatigue for about three months. Literally would come home from work and just go straight to bed most nights."
] |
[
"Yes, any infection has the potential to cause long lasting disease or damage, either by harming tissues ( like polio) and/ or never being fully eradicated ( like mono and Lyme).",
"In my opinion the biggest silver lining of this pandemic is that we are recognizing that infections can can cause long term complications after the main infection. For way too long we have only technically known this, but ignore the information when someone goes to the doctor for strange long lasting problems. It is time to start connecting the pieces for all these \"unexplained\" illnesses."
] |
[
"Wow, on first reading this comment I was very surprised to hear that microtubules have any relationship to CoV-2 infection, but it seems like it is indeed hypothesized to be involved in part of the replication cycle, e.g.",
"https://doi.org/10.1371/journal.ppat.1009246",
"Very cool!",
"I am interested in your suggestion that Omicron behaves differently, and that these differences may be seen in data on clinical outcome. I haven't been able to find any literature yet published on differences in Omicron replication mechanisms re. TMPRSS2/the cytoskeleton/cell fusion, would you mind dropping a few links?",
"As far as I was aware, the data collected thus far on mortality with Omicron can be explained equally well by higher vaccination rates, partial immunity from prior infection, and reporting issues, but I may be missing something recent. ",
"I know that there are some data suggesting that the lung/respiratory tract titers are different from Delta, but would you consider that convincing enough, from public health standpoint, to say that omicron is 'Gremlins mutated back into Gizmo'?",
"Thanks, have a good one!"
] |
[
"Is there a process to reverse electrolysis of water?"
] |
[
false
] |
I'm curious if there is a way to combine hydrogen and oxygen to form water in a way that is as simple as electrolysis of water.
|
[
"Yes, it's called a match. It's even simpler than electrolysis, actually. ",
"But, if you want a method that's about as complicated as electrolysis, you're looking for fuel cells."
] |
[
"This",
" looks like a fine introduction.",
"If it was the first part you wanted elaboration on: mix two parts hydrogen and one part oxygen. Light match. Products are water and a ",
" big boom."
] |
[
"Specifically, oxidation of the Hydrogen through combustion."
] |
[
"How do we know the amount of carbon in the atmosphere in the past?"
] |
[
false
] |
I understand ice cores from deep glaciers can tell us the makeup of the atmosphere for the last few hundred thousand years but how do we know what makeup of the atmosphere from before the glaciers existed?
|
[
"I'll assume by \"carbon\", you're primarily interested in CO2. Beyond air bubbles trapped in ice (which gives us a direct measure of CO2 concentration), there are a range of different proxies used to reconstruct ",
"pCO2",
" of either the atmosphere or ocean. A (probably non-exhaustive list) of common proxies are 1) stomatal density of leaves and other aspect of leaf morphology that vary as a function of pCO2 (e.g., ",
"Bacon et al., 2016",
", ",
"Steinthorsdottir et al., 2016",
"), 2) changes in carbon isotope ratios preserved in a variety of calcified organisms related to changes in pCO2 (e.g., ",
"Lisiecki, 2010",
"), 3) various techniques related to compound specific carbon isotopic analysis of biomarkers that change in relation to pCO2 (e.g., ",
"Pagani, 2014",
", ",
"Witkowski et al., 2020",
"), 4) changes in isotopic ratios of boron that reflect oceanic pH and thus pCO2 (e.g., ",
"Honisch & Heming, 2005",
"), or 5) a variety of other geochemical proxies (e.g., ",
"Berner & Kohavala, 2001",
"). All of these come with their own uncertainties and challenges, so it's pretty common that many of these are applied in concert with each other (e.g., ",
"Seki et al., 2010",
") or require additional geochemical context to be interpreted (e.g., ",
"Gavin et al., 2007",
"), but applying multiple proxies in different locations on deposits of similar age has allowed us to reconstruct (at least to a first order) the pCO2 history for much of the Phanerozoic (e.g., compilations of different proxies like the one in ",
"Royer et al., 2004",
"). I imagine someone who specializes in paleoclimate can provide more nuance to this answer."
] |
[
"Are there any methods based on carbon content in sedimentary rock? Or is that too imprecise?"
] |
[
"Depends on what you mean by \"carbon content\". Some of the proxies discussed above rely on carbon isotope ratios in particular minerals from specific sedimentary rocks, specifically, paleosols (e.g., ",
"Cerling, 1991",
")."
] |
[
"Matter can be neither created nor destroyed. What then is happening when Atoms smash together in the Large Hadron Collider? Is matter then destroyed?"
] |
[
false
] |
I see the collisions on shows like 'The Universe' and everything seems to go out of existence. Is this matter being destroyed?
|
[
"Matter can be neither created nor destroyed.",
"This assumption isn't true -- matter is created and destroyed all the time in ",
"pair production",
" and ",
"annihilation",
" processes.",
"What you are probably thinking of is that ",
" can't be created or destroyed -- and the law of conservation of mass itself is only approximate and is not exact (though for many applications, like chemistry, it is close enough to be considered exact). Mass is a form of energy, and energy is capable of changing forms (for example, from mass into kinetic energy, or vice versa) under the right conditions. Only the more exotic conditions allow it though -- for example, if antimatter is present, or very large amounts of excess energy are available to create new massive particles.",
"The exact conservation law here is conservation of ",
". ",
" cannot be created or destroyed. It can change forms, and the particles which ",
" energy can be created and destroyed as long as the energy is conserved in some other way.",
"What then is happening when Atoms smash together in the Large Hadron Collider? Is matter then destroyed?",
"Not exactly, but indirectly, yes -- the LHC smashes together protons (and lead nuclei). In these collisions, the particles are ripped apart into the particles they are made up of (quarks), which for technical reasons creates many new particles in the process. And then these particles often decay into other particles, themselves being destroyed in the process. So there is creation and destruction of matter going on, but the details are quite complicated. The original quarks that make up the protons probably still exist and are not destroyed, but it is true that the original protons that collide no longer exist in a whole form. Kind of like if you take apart a boat, and use each of the pieces in building other boats -- the original boat doesn't exist anymore, but all of the pieces that were part of it still exist.",
"In other particle accelerators that collide matter and antimatter together, though, yes -- matter is directly destroyed frequently in these collisions. Just not at the LHC specifically, because of the particular types of particles that the LHC smashes."
] |
[
"Only the more exotic conditions allow it though",
"Allow what exactly?",
"If energy is produced, then mass is lost. It's true for matter/antimatter reaction, of course, but it's also true for fusion and fission, and even for chemical reactions (even if the change of mass is too small to be measured). A CO2 molecule is (very slightly) less heavy than an atom of carbon + an O2 molecule."
] |
[
"Allow what exactly?",
"Conversion from mass-energy to other forms of energy (edit: in significant amounts), or vice versa.",
"If energy is produced, then mass is lost. It's true for matter/antimatter reaction, of course, but it's also true for fusion and fission, and even for chemical reactions (even if the change of mass is too small to be measured). A CO2 molecule is (very slightly) less heavy than an atom of carbon + an O2 molecule.",
"I assume you are talking about kinetic energy here, since total energy is never produced -- it is always conserved. As you say though, when you exclude energy that is radiated or otherwise carried away, the mass of the system decreases (because its total energy decreases). I did point this out in my previous post, when I said that the law of conservation of mass is only approximate, but is close enough to be treated exactly for many applications such as in chemistry. Whenever the difference is not close enough to be neglected, there are usually exotic conditions present, such as enough energy/pressure being available to fuse nuclei, or a specially triggered fission chain reaction, or antimatter which annihilates with a part of the system, etc."
] |
[
"If you spin or flip in zero-gravity, would you get dizzy?"
] |
[
false
] | null |
[
"Yes, they would eventually get dizzy. Dizziness is caused by the centrifugal acceleration while their body is rotating, and centrifugal acceleration is not caused by gravity."
] |
[
"Didn't you mean ",
" acceleration?"
] |
[
"Sorry, yes."
] |
[
"Why does the oxidation of a hydroxy group to a ketone (like morphine to hydromorphone or codeine to hydrocodone) make the drugs more potent pain killers?"
] |
[
false
] | null |
[
"The answer is quite simple these little tweaks cause they drug to become more lipid soluble. These drugs can only act mu1, mu2, kappa and delta cells if they can get there. \nThe blood brain barrier only allows the nonionized (another factor) lipid soluble drugs through."
] |
[
"Morphine is lipid soluble, but not as lipid soluble as for example fenantyl, and sufentil even more so"
] |
[
"I’m a microbiologist who has never even taken a neuroscience course, so this is not a definite answer. That being said, this seems like enough of a basic biology question that I think I can chime in.",
"People talk about protein-substrate binding as a lock and key model, where the substrate “key” fits inside of the binding site “lock”. While that’s a really good way to think about the concept, it doesn’t hold up perfectly. Most proteins have some degree of “promiscuity”, meaning that they can bind slightly different molecules. A great example of this is how mutations in the SARS-2 spike protein don’t necessarily prevent it from binding to ACE2 receptors. ",
"Protein specificity (at least with things that are closely related) is usually a question of rates rather than a binary one. To simplify a very complicated concept, if one ligand binds better or it stays bound longer, whatever the activity of that protein is will be more pronounced. I imagine that the ketone on those opioids fits better in the receptor than the alcohol and thus the drugs have a stronger effect."
] |
[
"How do animals evolve to blend in with their environment?"
] |
[
false
] | null |
[
"A whole bunch of mutations happen. Lots of things change. Some of those help and some don't. If the organism reproduces, all of those changes are passed on. Some might be tweaked even more while others might not. Over time (generations) the changes that help accumulate and may be pushed further. That's the rough idea behind natural selection. The wiki page on it is pretty thorough."
] |
[
"Ones that have mutations that make them blend in a bit better are slightly less likely to get eaten than ones that stand out. Their children are also more likely to survive and reproduce and pass on those mutations and additional ones if they look even more like their environments, etc."
] |
[
"That makes sense, but how does the body know it’s the color it is that helps instead of other factors?"
] |
[
"What is the evolutionary advantage to having a \"shy bladder\"??"
] |
[
false
] | null |
[
"That isn't how evolution works. Why do people have Parkinson's, what is the reason for that? Evolution works through random mutation. A new variation of a gene is created, and if it makes the person better able to reproduce, it gets passed on more. Sometimes bad genes get passed on too, and lots of them are neutral, like attached or detached earlobes."
] |
[
"You're making the mistake of assuming every random variation in genes and brain chemistry only occurs because it has a survival advantage. There are plenty of quirks that have nothing to do with survival or reproductive success. Your question should be \"",
" an evolutionary advantage to having a shy bladder?\" ",
"To answer that: maybe. You could argue that a wild creature to be more alert while in such a vulnerable state is an advantage, but you seem focused on humans specifically. In that case I would say there is no benefit. We don't really have an environment or predators or any sort of scenario that would benefit from having a shy bladder."
] |
[
"You are quite vunerable to attack from predators while actively excreting waste, in addition to leaving a nice smelly marker for predators to help track you. "
] |
[
"Salt: Sodium or Sodium chloride?"
] |
[
false
] |
I'm not a chemist or scientist, but I thought salt was = sodium chloride. Yet most of the general public calls salt, "sodium". Is this just a general and accepted misuse of the word, or am I confused here?
|
[
"It's just a general and accepted misuse of the word, table salt really is sodium chloride."
] |
[
"Table salt is sodium chloride, but to a scientist, salt usually refers to a group of compounds of which sodium chloride is one. In nutrition (as I understand it) sodium content is what's important not necessarily salt content, so that is probably why people use them interchangeably."
] |
[
"In chemistry, ionic compounds that result from reacting an acid and a base are called salts. The \"salt\" we eat, table salt, is sodium chloride. Of course, there are also other sodium compounds that isn't sodium chloride, such as baking soda. So the \"label\" in the nutritional data includes all sodium compounds."
] |
[
"Why do some people have photographic memory, yet a normal person without one can still remember a huge quantity of information, such as the meaning of hundreds and thousands of words? What's the scientific difference between those two types of memory?"
] |
[
false
] | null |
[
"i'll second the \"photographic memory is a myth\" post. there's no such thing. there are great ",
"mnemonists",
", usually people who have developed/trained a method for quickly organizing information to be recalled later. some of these people have extraordinary skill for memorizing visual scenes, e.g. ",
"stephen wiltshire",
", but their abilities are often mischaracterized as \"memory at a glance\" when they've actually taken some period of time to methodically commit a scene to memory."
] |
[
"The correct term for this is 'highly superior autobiographical memory' or 'hyperthymesia'. There are a very few individuals who exhibit the ability to accurately recall very specific details of their lives. It's not precisely the same as the mythical 'photographic memory', however. For example, they could tell you what they had for breakfast on any random day in the past, or what the major news headlines were, but they cannot recite word-for-word a book that they have read. HSAM is interesting, but limited."
] |
[
"The correct term for this is 'highly superior autobiographical memory' or 'hyperthymesia'. There are a very few individuals who exhibit the ability to accurately recall very specific details of their lives. It's not precisely the same as the mythical 'photographic memory', however. For example, they could tell you what they had for breakfast on any random day in the past, or what the major news headlines were, but they cannot recite word-for-word a book that they have read. HSAM is interesting, but limited."
] |
[
"Why might one's hands and feet get excessively cold and damp when they're a little bit chilly?"
] |
[
false
] |
[deleted]
|
[
"The dampness is likely just a perception. Many people have an excessive vasoconstrictive response to a mild cold stimulus called Raynaud's syndrome."
] |
[
"What do you mean by \"just a perception\"? "
] |
[
"Sometimes when digits get cold they feel damp even if they're not. The vasoconstriction in Raynaud's can have goofy effects on sensory nerves, so for instance your feet might get way too cold in relation to the ambient temperature and they'll feel damp but if you feel them with your hands they'll be dry."
] |
[
"If space is expanding outwards, would part of the night sky eventually get darker?"
] |
[
false
] |
Mainly referring to stars that are getting farther away but also other factors if relevant. If everything is moving away from a point, would that point eventually be darker/emptier than the rest of the sky?
|
[
"Our galaxy is not expanding, because its stars are gravitationally bound. The sky will go dark eventually, but because of the decrease in available fuel for fusion reactions, not because of the expansion of space. "
] |
[
"Everything is not moving away from a point. Everything (at intergalactic scale) is moving away from each other. Except that things are not really moving but the space itself is stretching so the distance between large-scale objects increases. As ",
"u/Heavensrun",
" said, \"small\" scale structures like individual galaxies will stay gravitationally bound. The light from distant galaxies will eventually redshift to oblivion."
] |
[
"This is not true. Like sharlinator pointed out, light is redshifting because of the Expansion of Space. Light from Stars of other Galaxies will eventuelly redshift out of the visible spectrum and all one can see will be Stars from ones own galaxie and probably the respective cluster."
] |
[
"Is there any real difference in sexual desire between males and females? Is something like this even possible to measure?"
] |
[
false
] |
[deleted]
|
[
"It's actually a topic of scientific interest for many social/gender psychologists. The short of it, is we still don't know. While physiological signs of sexual excitement (e.g., blood flow to the vagina or penis) are relatively easy to measure, the emotional differences that the two genders attach to sex are extremely difficult. Yes, there are theories that men are more easily stimulated visually and women are more easily stimulated verbally (which is why they are more likely to read trashy romance novels than porn), but the deeper differences between the two genders are extremely difficult. Add to that that gender is more thought of today as a sort of spectrum (than two polarized sides) and you've got even more complications. ",
"From what I've learned in various classes, this is what I will tell you. The different social attitudes in men and women towards sex are thought to be created by a variety of factors. At the root of it is biology, for two reasons. Men are more easily sexually stimulated, which is simply biology. But men and women are also treated differently by society because of their biology (i.e., social expectations differ because of whether or not you have a penis/vagina). Go beyond that, and you've got social processes. Women and men are socially expected to act differently towards sex. They are psychologically conditioned to act differently. And various cultures widely differ on expectations, and men and women can have differing attitudes because of their cultures. Especially for women, you will see a wide spectrum of interest in sexuality based on the culture they come from. It has been hypothesized that this is because mental attitudes factor more into sex for women than men; e.g., if a woman is worried that having sex is 'improper', she can't enjoy it as much--even if that is a subconscious worry. ",
"However, this barely scratches the surface. After years of gender/personality/cognitive/biological psychology, I can tell you the one thing we do know: we don't know. Different areas of psych love to say 'we can explain this'. But every different area of psychology differs in what that area is. Welcome to the fun black box that is human psychology!"
] |
[
"This isn't how science works. Just because it sounds plausible to you doesn't mean anything at all. Which is why a lot of bullshit is circulated as facts relying on Just-so explanations to justify."
] |
[
"I have mixed views about evolutionary psychology. I think most psychology nerds do. The problem is, evolutionary psychology often stretches itself past reasonable/supportable ideas into some ideas of downright silly. It seems to often switch sides to make evolution fit a theory rather than theory fit to evolution. Meaning that often the theories conflict and use evidence as it suits its purpose and ignores evidence as it doesn't. Pretty much for every sexual theory (polygamy, cheating, rape, etc.) you will find evolutionary evidence for all opposing sides. ",
"Although I specialize in neuropsychology, I think that social psychology has a rather impressive ground work for different sex theories. I wish I had my book with the greatest psychological sexual theories I have ever read on me, but it's not. I'll check my journal database tonight for a review. For now, have a link to a meta-analysis that says essentially what I did--there are not too many between gender differences. Humans fall on a spectrum, and it's hard to classify 'solid gender differences'. Here ya go for now though: ",
"http://psycnet.apa.org/journals/bul/114/1/29/",
". Excuse me while I finish some work on psychometrics. Yey for forever in school. "
] |
[
"How strong is human skin relative to other animals?"
] |
[
false
] | null |
[
"A human raised in similar conditions to animals winds up with very thick skin on the hands, feet and sun exposed areas. ",
"Look at the skin on the feet of individuals who regularly walk barefoot and it's often quite thick, then combine that with the increased need for thick skin on uneven, rocky ground.",
"Most mammals have relatively similar skin, with examples like rhinos, elephants and other savannah animals being an exception due to the increased need for protection from sun and predators, as well as the need for water retention.",
"The average indoor human, though, has thinner skin than we otherwise would have, being more similar to subterranean or nocturnal animals like moles and mice."
] |
[
"It's important to consider scale. To a rhinoceros horn you're not very thick at all, but on the scale of insects we are quite tough. There are areas of your skin that are tough enough that a mosquito can't bite you there, for example. We are definitely more vulnerable than most mammals, but to some creatures we are quite resilient still!",
"The skin of an ancient human who likely had more scars, callouses, and weathering, would likely be much stronger than ours. But we live pretty easy lives, and usually prefer softer skin over tougher skin."
] |
[
"Would the same apply to domesticated animals like cows and pigs that live a pretty sheltered life compared to their relatives in the wild?"
] |
[
"In programming, we can manually define functions for computers to perform tasks, but how do we program computers to actually understand what multiply, divide, add, subtract and equal actually mean and how to use them?"
] |
[
false
] | null |
[
"Circuits. We have something called an adder circuit. This can take two inputs in binary and output them added together, in binary. Multiply is just short hand for adding. Indices are just short hand for multiplication. And there's a way to subtract by adding which I don't fully understand but it's a thing. ",
"As for equal, we have something called an \"and\" gate. I this can take two binary digits and compare them. If both are 1s the output is 1. If u compare all the binary digits in one number to that of another and they match up, you've got a, does this equal this? ",
"There are also other gates like OR, NOT, XOR which all have there uses. ",
"As for how we use them. We can do anything that can be turned into maths! Want to use letters. Say A is 0, B is 1, C is 2. There u go. U can now use letters and store them. Want to create realistic physics. Go ahead, physics is just maths right! This is why I love programming. With the right mind anything is possible. "
] |
[
"Subtraction can be done through addition by negating the sign of the second operand, so a-b becomes a+(-b). Changing the sign of a number is quite easy in two’s complement, the system most computers use to represent integers in binary (it’s also very simple for IEEE-754 floating point numbers, the standard for real numbers)."
] |
[
"Computers don't understand anything. They flip bits according to the instructions we give them. Just like your washing machine doesn't understand the concept of clean or dirty clothes. It just goes through its wash cycle according to its computer chip (washing machines are computers these days) and the instructions we give it."
] |
[
"Does the delayed choice quantum eraser experiment necessarily imply retrocausality or determinism?"
] |
[
false
] |
I'm talking about where what I've called the "first" photon hits D0 and the "second" photon hits one of the other detectors. Won't the first photon of an entangled pair hitting a detector in a certain way mandate that the second photon's action, either passing through a splitter or being reflected, is a non-random event? Or that the random event of the second photon passing through a splitter or being reflected mandates how the first photon hits a detector? All in spite of the fact that the correlations between entangled photons can only be known after both have been measured (thus barring any FTL transmission of information)? Am I missing something fundamental about entangled particles? (Also where I'm talking about determinism I mean absolute determinism)
|
[
"A few more details here. (trying to explain the phenomenon more simply). A photon passes through the double slit and doubles into two photons. One of these photons quickly hits detector D0. After some time, the second photon passes through its mirrors and beam splitters and lands in some detector D1 through D4. ",
"At the end of the experiment if we take all of the photon hits at D0 that had a correlated hit on D3 or D4, we will see one type of pattern in the D0 photons. The D0 photons will look like they have definitively either passed through the \"blue\" slit or the \"red\" slit. They will not look like interference patterns.",
"However, If you take all of the D0 photons that are correlated to the D1 and D2 detection events, these D0 photons will look exactly like a 2-slit interference event.",
"The key is that the D0 photon hits that detector ",
" and then the \"information carrying\" photon hits one of those detectors. So essentially we've run two experiments simultaneously. We've run an experiment where we can't know which slit the photon passed through, and we've run an experiment where we can know. The detectors D1-D4 just let us know which data point belongs to which experiment. What's remarkable about the whole thing is that D1-4 can't tell us until ",
" D0 has already been recorded. "
] |
[
"I've been thinking for a long while about this question, trying to answer it best. I may be entirely wrong in the answer I'm about to give, so I welcome criticism if that's the case. ",
"The answer is that it's philosophical, not scientific. A rigorously pragmatic view of science says that science can only tell us what measurement outcomes will be. What happens between measurements is, by definition, unknowable. We propose ",
" of quantum mechanics, but they're just philosophic games of connecting the dots between measurement points. Is there wavefunction collapse? Is there a universal wavefunction with object and measurement apparatus in superposition? Are there probability waves that propagate backwards in time and interfere with forward propagating waves to create measurement? (Copenhagen, Multi-World, and Transactional interpretations respectively)",
"But remember that all of these interpretations are just philosophical in nature. The irony of it all is that we're discussing this problem in the experiment that explicitly shows it's a problem. We know a photon is on one side of two slits, then we next measure it on the other side. But we don't know which slit it passed through. Every test you can think of to determine which slit it passes through changes the setup in such a fundamental way that the results are completely different. ",
"Just to stress here, it has nothing to do with a conscious observer as well. A double slit experiment is ",
" than a double slit experiment with a \"which slit\" detector. ",
"takeaway: Between two observations we can't ",
" what happened with certainty."
] |
[
"If I'm not understanding your answer correctly or have made any mistake in my writing below please disabuse me of my ignorance.",
"I guess what I'm more interested in is the mechanism. If we think about this in terms of wavefunction collapse I don't understand the experiment. The first photon hitting detector D0 has made some final measurement even if we're ignorant as to which slit the original photon passed through (until we correlate it with the second \"information carrying\" photon). ",
" Can there be a superposition of measurements on detector D0 after the first photon has hit but before the second photon has been detected? Otherwise wouldn't the reflection/non-reflection of the second photon at the splitter in the interim be a non-random event?",
"I understand that we can't see an interference pattern in D0 or figure out which slit the original photon went through until we correlate D0 with the other set of detectors. I'm getting tripped up in how to define the experimental system in the interim between when a photon hits detector D0 and before the second photon goes through a splitter. Thanks! "
] |
[
"Is there a limit on how small the wavelength of light can get?"
] |
[
false
] |
I was thinking about 'no preferred reference frame' and blue shifting - is there a limit on how blue-shifted light can get?
|
[
"none that I'm aware of."
] |
[
"I dunno, I'm really not strong on electroweak forces. (pardon the pun)"
] |
[
"none that I'm aware of. For exactly the same reason as OP. You can always change your frame of reference such that the wavelength shifts smaller or larger."
] |
[
"What causes your tongue to appear 'furry' and how can you counteract this?"
] |
[
false
] |
And I am not talking about oral thrush, I know what that looks like and entails, are there other environmental factors, food or lack of ceratian minerals, vitamins, love to know :)
|
[
"Brush your teeth, use mouthwash, and stop smoking."
] |
[
"You mean the white stuff that builds up on your tongue? You can get rid of that by just scraping it with a toothbrush. Will make your breath a ",
" fresher."
] |
[
"Thrush?",
"http://www.medicinenet.com/thrush/article.htm",
"or",
"http://www.medicinenet.com/hairy_tongue/symptoms.htm",
"http://en.wikipedia.org/wiki/Black_hairy_tongue"
] |
[
"Why do certain musical scales sound happy, scary , eerie, etc?"
] |
[
false
] |
Some of my oldest memories is of being scared and saddened by songs in minor scales, and cheered up by songs in major scales. Is this something learned or in our DNA?
|
[
"i am not a scientist, but a reasonably educated musician.",
"the associations with scales is largely cultural. minor scales are not sad in all cultures. however, minor scales, because of how the notes compare to the harmonic series, tend to resolve downward to structural pitches rather than upward, which accounts for a lot of the difference.",
"there are also modes of the major scale. a mode is the same pitch relationship starting on a different pitch. natural minor is the 6th mode of the major scale, meaning you start on the 6th degree and play all the notes in the octave. lydian (major, aka ionian with a raised 4) is the brightest mode, and you can hear how bright and \"up\" it is in for example the simpsons theme song or in the 3rd movement of ",
"beethoven's op 132, (starting at 19:24)",
"(EDIT: and for the record, that string quartet is one of the finest chamber works ever, in my opinion. the third movement is the high point of the work, but it's worth listening to the whole thing. there was such a stir about it, that schubert requested to hear it his deathbed, and his response was \"after this, what is left for us to compose?\" AND beethoven was stone deaf for years before he wrote it. impressive guy.)",
"i'm afraid the ability to scientifically determine what's going on once and for all is rather limited at this time, because in addition to physics/acoustics, we have to deal with psychoacoustics (how our brains process sounds, deleting and adding content from different combinations of pitches and harmonics), cultural training, and personal associations.",
"EDIT: thanks to z3ugma for the youtube link that takes you to the right spot in the video."
] |
[
"Im not aware of a ton of work in this area, but one guy who is sorta studying this is Gilden at UT Austin. Though he mostly focuses on the nature of musical \"groove\". It's a bit of a new line for him, but he talks briefly about it on his site (",
"http://homepage.psy.utexas.edu/homepage/group/GildenLAB/groove.htm",
"). The guy is crazy smart though, so if you're interested keep up with him. Used to be an astrophysicist trained by a nobel laureate before switching to psychology. As for pop science, you might check out an Oliver Sacks book called Musicophilia if you haven't already. Also, there's this scientific american article from a while back, ( ",
"http://www.scientificamerican.com/article.cfm?id=why-does-music-make-us-fe",
" ). I dunno how particular an answer you're looking for, but hopefully something there will interest you more than being called a dumb fuck."
] |
[
"I'm not sure how well versed in music you are, but the primary difference between a major and minor scale is the 3rd note of that scale. Most of the others stay the same (the rules changing depending on the type of minor scale, but that is more of a music theory question than a psychology question). ",
"So let us focus a second on the third note of the scale. Basic chords are made up of the root note, the third (be it major or minor), and the 5th. In a well tuned instrument, the 5th has a pitch ratio of 3:2, meaning that for every 3 vibrations of the upper note, the lower note will vibrate two. This creates a generally pleasing effect as the waves that make up these notes restart at the same place every 6 cycles. ",
"Now we look at the major 3rd, which has a pitch ratio of 5:4, which is also pleasing as we hear a sync with the root every 20 vibrations. The minor 3rd, which has a pitch ratio of 6:5, is somewhat less pleasing. ",
"So you may be asking what this has to do with speech. In normal conversation, the notes our voice makes are rarely larger than an octave. In fact, most speech is within a half octave range (I don't have a source for this, sorry). That means that in order to convey meta-information, we must listen to the subtleties of voice inflection. One who is sad is less likely to add emphasis to certain non-monosyllabic words, thus dropping the pitch, raising the pitch ratio, etc. etc.",
"Think of Eeyore from Winnie the Pooh, and the way he says his name. I'm sure if you say it his way, and then say it as if you were happy to be saying the name, you'd be dropping a major 3rd rather than a minor 3rd. ",
"We have become quite adept at picking out these subtleties. Here's a paper on how good we actually are: ",
"http://psycnet.apa.org/?&fa=main.doiLanding&doi=10.1037/a0017928",
"Sorry if this is a bunch of disjoint ideas. Hopefully it helps!"
] |
[
"What exactly happens when an acid touches something? Specifically, how does a protonation work and cause damage?"
] |
[
false
] |
I was trying to find some stuff online and on here, but couldn't find much aside from mentions of Bronsted and Lewis acids (I think proton donation only happens with the former)? Thank!
|
[
"There are 3 types of acids:",
"Essentially the acids are very reactive, and they're \"unhappy\" in their current energy state, so they want to move to a lower energy state by giving energy to another molecule in the form of a proton (let's exclude Lewis acids for this discussion). Now when the receiving molecule becomes protonated, it too may not want to be in a high energy state, so it also wants to release the energy by breaking a chemical bond in it's structure, and maybe forming a new one with another molecule.",
"",
"For example, take a look at this reaction of tert-butanol with hydrochloric acid.",
" HCl is our acid which donates a proton (in the form of a hydronium ion H3O",
" since H",
" doesn't exist in water) to the -OH group to form -OH2 (water). -OH2 doesn't want to be bonded to the carbon, so it leaves to form a positively charged carbon (carbocation) which reacts with the Cl",
", forming a new molecule.",
"Now for a more real example to your question: plastics are essentially long chains of organic molecules linked together, not too unlike the molecules in the reaction above. Take ",
"polycarbonate",
" for example, if you were to introduce hydrofluoric acid (HF, very corrosive) to it, it would break the bonds linking the polycarbonate together, causing plastic degradation.",
"",
"TL;DR: Acids are \"unhappy\" and reactive so they give their unhappy energy as protons to other molecules which causes them to form other bonds and break apart."
] |
[
"Great question. I'm a little unclear what you're asking specifically, but I'll try to explain the best I can.",
"Strictly speaking ionization is just taking an ",
"uncharged molecule and removing an electron",
", but acids don't generally release electrons. They may cause the formation of anions have unbonded electron pairs, but the electrons generally don't ever leave the atoms because it requires ",
"a ton of energy",
". Ionization energies are measured in hundreds or thousands of kJ, while the enthalpy of acid-base reactions are measured in tens. However, I do see your point, heat or high-energy light can cause the formation of ions such as ",
"in the formation of free radicals",
", which is why if you leave plastics outside, they will degrade due to UV light from the sun breaking the chemical bonds holding the polymer together.",
"Now, our definitions of an acid above are very basic. There are actually a lot of factors that makes a molecule acidic relative to other molecules. For example, induction, ",
"resonance",
", charge, electronegativity, and hybridization all help stabilize the negative charge on the conjugate base when H",
" leaves. That's basically what makes something an acid is how willing the molecule would rather kick off the H",
" and stay negatively charged.",
"So in conclusion, ionization and acidity are related, but not the same, and acidity is a complicated property that is influenced by its neighbors."
] |
[
"This is going to sound a bit foolish on the surface, but how is this different from ionization? Aren't they essentially the same thing, only high energy radiation strips away an electron vs a chemical interaction? Wouldn't that mean ionizers change what makes something an acid? "
] |
[
"What is the feeling of falling when laying in bed caused by?"
] |
[
false
] | null |
[
"It's called ",
"Hypnic Jerk",
" and according to a study done by the Mayo clinic in '06, over 70 percent of the human population of the earth experiences them. ",
"They seem to happen more frequently in people who are having trouble sleeping/irregular sleep patterns/reasonably severe lack of sleep. ",
"Researchers believe that the lack of sleep from sleep anxiety or sleep deprivation confuses the muscles and the brain. The muscles continually attempt to relax and shut down for rest, while your brain remains awake creating continued “misinterpretations” of falling or loss of balance.",
"Scientists and researchers continue to study sleep twitching and jerking in a small capacity, but state that the sensation is completely normal for our bodies and is of little medical significance. [Last two paragraphs from ",
"this article",
" on the subject.] "
] |
[
"I speculate that he'd be unhappy if any scientist was freed from the burden of proof."
] |
[
"Tsk. It's just speculation. Take it with a grain of salt. It's not science without evidence."
] |
[
"Why are plants mostly green and solar panels mostly black?"
] |
[
false
] | null |
[
"The difference is due to the fact that solar cells and plants have simply have different requirements. The key goal of a solar cell is to convert as much sunlight as possible into electrical energy, which means that the ideal solar cell will absorb all incoming light. While we never get to this ideal case, the most common solar cell uses a slab of crystalline silicon will absorb most light past a threshold (determined by it's bandgap) at 1000nm, so common solar cells will look ",
"black or grey or slightly bluish",
", the slight difference being due to the choice of anti-reflection coating used.",
"In contrast, plants have different additional problems that they need to deal with. Go back to the case of silicon, because the material is so simple and robust, you can throw a solar cell on the roof of your house and it will keep working for years, even as it is blasted by scorching sunlight. Plants, on the other hand are far more fragile as they consist of a large number of less stable organic compounds arranged into complex structures. For this reason, in addition to harvesting enough light for photosynthesis, plants also need to worry about disposing of excess sunlight to avoid photodamage. You can get a glimpse of this process from what is called a ",
"PI curve",
", which represents how the rate of photosynthesis depends on the intensity of the incoming light, ",
"as shown here",
". Notice how at low intensities, the photosynthesis scales essentially linearly with the intensity of the light, but at a higher light level, photosynthesis begins to plateau or even to drop off. In other words, at higher intensities, photosynthesis already becomes quite wasteful, since much (in some cases most) of the incoming sunlight is not used for photosynthesis. For these reasons, while ",
"plants can be black",
", most are not, since in most cases they simply do not need to be optimized to absorb all available sunlight."
] |
[
"Very informative. TIL, thank you :)"
] |
[
"the slight difference being due to the choice of anti-reflection coating used.",
"And the crystallinity (monocrystalline having the most favourable orientation and no grain boundaries causing both internal and external reflections), as well as the depth of doping (thinner active areas look progressively reddish, then greenish, then bluish)."
] |
[
"How is gravity capable of bending light? And does this mean it can change light's speed?"
] |
[
false
] |
Okay, first off, in classical physics, Newton taught us that gravity was the inherent attraction between the centers of two masses. Einstein elaborated upon this by saying that matter warps space time, and the change is perceived by us as an attraction in gravity, like the age old analogy of placing a bowling ball on a trampoline. And I know new revisions on Einstein's work are created by physicists all the time. But what I still don't understand is how light can be affected by gravity. I know light can act as a wave and as a particle, and that the "particle" of light has a mass of zero, and according to (at least how I understand it) there must be at least two masses for a gravitational force. Light doesn't have that. And yet I know that even light can't escape black holes because of their immeasurable gravitational pull, and that scientists can detect stars behind their planets because the planets bend the light around to reach us, and in one sense that makes sense to me, but I don't know why. For my second question, accepting the premise of the first question, does this mean that gravity can change the speed of light? If gravity can bend light with centripetal acceleration, wouldn't it naturally follow that it could cause linear and/or angular acceleration? But according to what I've heard, the speed of light is constant and cannot be changed. Is this true, and if so, why? I've always chalked it up to being the foundation of space-time and left it at that, but I'd really really like an explanation that gives my brain some peace. Perhaps I can't wrap my head around this because I've stuck myself in the comfortable world of Newtonian physics, where everything is tangible, and I don't feel so insignificant. Thanks. tl;dr - just read the whole thing otherwise you'll just confuse me with an unclear answer. also I'm not sure if this goes in physics or astronomy so perhaps someone can tell me conclusively?
|
[
"This ",
"comment",
" I made a few weeks ago should mostly cover it. Let me know if there's anything that needs following up on:",
"Light does exhibit both particle-like and wave-like behavior. However, photons (light particles) are massless. It is for this reason that they move at a constant c, the speed of light.",
"The speed of light is a constant, so light doesn't ever go faster or slower than it. However, photons are affected by gravity.",
"While we normally just think of gravity as a force, gravity is actually curvature in spacetime. You may have seen images like this one: massive objects bend space, and other objects fall toward them. This includes light.",
"So while gravity does not make photons go at any speed other than c, it does change the direction in which they're moving.",
"When dealing with very massive objects, this can have interesting effects, such as gravitational lensing, when massive object act as lenses and change the light we observe to a noticeable degree."
] |
[
"I think you have it, but your summary isn't quite right.",
"\"It's an absolutely necessary requirement for the universe to function\" doesn't really make much sense. It's how the universe fundamentally works. There's nothing that must be done to keep it that way, and there's nothing that could be done to change it and \"stop the universe from functioning\".",
"Gravity isn't really altering \"our perception\", it's actually changing the direction of the light. The confusion is because \"straight line\" doesn't really mean anything in curved spacetime. To see this, consider a globe. What is a straight line on a globe? If you travel along a line on a globe, you'll be changing directions. ",
"And that's exactly what gravity does. Globally, the universe is (seemingly) flat, and straight lines act how we expect them to. Gravity introduces regions of curvature, where \"straight lines\" actually change direction."
] |
[
"Newton's law of universal gravitation is a nice description but it's not the whole picture. For that you need ",
"general relativity",
". Gravity is the warping of spacetime. It doesn't change the speed of light, it just changes its direction."
] |
[
"What if we cannot find the Higgs?"
] |
[
false
] |
What would be the implications of not finding the Higgs boson? To be more specific, not that we don't find it, but we it simply isn't there or even exists? What would this mean to particle physics and quantum theory? What branches or theories would benefit from it "not existing" and which ones would it hurt (if any at all)?
|
[
"Quantum mechanics and all are completely fine. The Higgs mechanism specifies a lot of things for the Standard Model, though, which is our current understanding of how all the particles we've seen get their masses, and our best explanation for the ratio between the masses of the W and Z bosons, among other things.",
"So, people like me have a lot of work to do. Yeah, there's already people working on various Higgsless theories, but they're not as fully fleshed out or as promising as the Higgs mechanism. "
] |
[
"Theorists would have a lot of work to do."
] |
[
"One immediate implication is that unification probably doesn't work like we think is does. ",
"The higgs boson comes from what is effectively a phase transition (symmetry breaking). When the symmetry group of E&M and the weak interactions is broken, U(1)XSU(2) (ie they are no longer the same force), the higgs boson condenses. ",
"The process is well understood in other areas of physics and is well known. As I said symmetry breaking is what drives phase transitions *. ",
"One of the most celebrated examples of this is conventional (BCS) superconductivity. In BCS theory the cooper pair breaks the E&M Gauge Symmetry of the system. In this case the boson that condesnes ** is a 'cooper pair' of electrons. The electrons form a bound state that is a scalar particle instead of a fermion (what the electrons are). This process is actually the process that inspired the great minds of the era to suggest that the 'Higgs Mechanism' could fix the problems that were apparent with the quantum theory of weak interactions. ",
"So while there are issues with the Higgs Boson, they physics of symmetry breaking, which is what cause the particle to condense is well understood, and in fact known to happen in other systems. If this isn't what is happens with the weak interaction then we truly have alot to learn. ",
"*I don't work with first order phase transitions so off the top of my head I am not sure of the details of those, so when I say phase transitions I specifically mean second order. ",
"** In general we call these bosons Goldstone or Nambu-Goldstone Bosons. "
] |
[
"How do jets know they've been locked onto?"
] |
[
false
] |
in movies, the pilot always has a warning when theyve been locked onto. is this real or just hollywood? how would it work?
|
[
"Check out ",
"this post",
"."
] |
[
"https://en.wikipedia.org/wiki/Radar_warning_receiver"
] |
[
"IR seekers still get an initial lock from the radar of the airplane that is carrying it. After the jet locks radar, information is sent to the missile so it knows where to look for its target. "
] |
[
"It is said we are 99% genetically similar to chimpanzees. But also that siblings are 50% genetically similar, cousins 12.5% etc. Can someone explain the different metrics of 'similarity' being used in each case?"
] |
[
false
] | null |
[
"None of the answers here have given the correct answer. The 50% number refers to genetic similarity directly through descent, while the 99% number refers to just how similar the genomes are when compared base by base.",
"When we say, for example, a son shares 50% of his DNA with his father, what is actually meant is that 50% of their DNA is Identical By Descent. That means 50% of the DNA, 50% of the ATC and Gs, were inherited directly from the Dad, with the other 50% coming from the Mother (keep in mind we have two copies of every gene, one from father and one from mother). Similarly, siblings share an average 50% of their DNA by descent, as they both inherited half their mothers and fathers genome, but got some of the same bits and some of the different bits of their parents genomes by chances. And you can do the maths for half-siblings, cousins, 2nd cousins etc to work out how much they share due to inheritance. This is an important concept when we discuss inheritance, for example these percentages make it possible to calculate the likelihood of certain relatives sharing a specific mutation, and predict the effects of inbreeding. However, since our Mother and Father's genome are highly similar themselves (both being humans and not chimps or bananas), the actually percent of DNA the son shares with his father is close to 100%. If you line up all their genome how many ATC and Gs will be the same at the same spot, most will be the same, and the percentage will be much higher than chimps, bananas etc. ",
"So if we look at a given gene in the Son, lets say the gene for haemoglobin, he will have received one copy of that gene from his father and one from his mother, so half came from each parent (the 50% figure). But if we compare the gene sequences we will find they are almost identical (the >99% figure). In cousins they will have a 25% chance of sharing one of these gene copies from their common grandparent, but again regardless of who they inherited their gene copy from, their two genes will be almost identical. ",
"Hope that makes sense!"
] |
[
"For a given DNA strand, the entire strand is 99% identical between humans and chimpanzees. For siblings, of the DNA that can be different between people, approximately 50% is identical, so about 99.5%. And so on. The general idea is that there are unspoken assumptions when you compare between species, between siblings, and so on. "
] |
[
"It's actually about 96% with chimps. But in reality that means practically nothing. We share 5o% of our DNA with bananas. \nHumans share about 99.8% with each other and the percentages listed for differences between cousins and distant relatives are all within that .2% "
] |
[
"Why is Rabies treatable up until it reaches the Central Nervous System? What exactly happens during this time to make it untreatable?"
] |
[
false
] | null |
[
"One major problem is that there is something called ",
"blood-brain barrier",
" - and ",
"once the virus gets beyond that the immune cells are ineffective on it",
".",
"The other problem is of course that the virus is causing major damage once in the CNS - generally even with the ",
"Milwaukee protocol",
" the survival rate seems to be very small (and seems to depend more on the aggressiveness of the virus and on the amount of antibodies that the body was already producing before the virus got into CNS)."
] |
[
"Thank you for your response and that was a very good read. "
] |
[
"Is this essentially the same mechanism that makes the eradication of the herpes virus in the body impossible since it hides in the nervous system? I am not knowledgeable enough to understand where exactly that is (not in the brain?), although it sounds like the peripheral nervous system has its own version of cerebrospinal fluid that is protected by the same process...",
"http://en.wikipedia.org/wiki/Endoneurium"
] |
[
"Why are our fingers of different lengths?"
] |
[
false
] |
My brother guessed that it is because this way we can better distribute our weight when hanging from something, because our center of gravity would be at the center of our hands, which allows us to balance better. Is that correct?
|
[
"Varying lengths of fingers give us more agility holding objects with odd shapes,they also promote better balance on hands."
] |
[
"As common in biology, form fits function. Looking at other ape hands you see orangutans with long palms and fingers fit for excessive hanging. As for humans, i'd guess this is just what an apes hand looks like if it isn't used for swinging through trees all the time. Our structure is better fit for holding objects than that of other apes. But, the difference is mainly in the palm size, and this causes one style to be more fit for gripping than the other.",
"Here is a web page with a picture of ape hand comparison, so you can see the difference: ",
"http://www.biog1105-1106.org/demos/106/unit08/8a.primates.html"
] |
[
"Was gripping tennis balls an environmental factor that influenced our evolution? What's the advantage of having your fingers line up when you grip something? When I grip my tennis racquet the tips of my fingers don't line up at all."
] |
[
"How do they determine how many calories any specific food has?"
] |
[
false
] |
For example, a strawberry, how do we know how many calories are in a strawberry?
|
[
"They burn it in a calorimeter to measure how much heat it generates. Heat = energy = calories.",
"It's horribly inaccurate though. You absorb fewer calories from a rare steak than a well done one, fewer calories from wholefoods than the processed version, fewer calories from raw food than cooked food. But the calorimeter will tell you they're all the same. They're not."
] |
[
"In short, the food's composition is determined through various means and through knowledge of the caloric content of each of those components, the caloric content of the total food is obtained.",
"The food Calorie (big C) is equal to 4.184 kJ, which is the heat energy required to heat up one kg of water one degree centigrade. When discussing food caloric content, the analogy of combustion is often used. This is because the overall reaction of respiration (sugar + oxygen -> carbon dioxide + water) is the same overall reaction as if you had burned sugar in air. However, your body doesn't burn food, and in a combustion reaction, a lot that energy released from the process is 'wasted' to heat the surroundings. Living things draw out the process over several steps instead of one big 'whoosh' to try to extract out as much usable energy as possible.",
"One could just burn some food in an instrument in a calorimeter and find out how much heat energy is released from the combustion reaction, and this theoretically would give you an idea of the maximum amount of energy available in the food, but there are a couple big problems with this. The biggest problem is that not everything that can burn can be used by the body for energy, such as fiber/cellulose. The more commonly used approach is to determine the food's composition through varying steps and then use those \"pure\" components energy value to sum up to the energy value of the entire food (for reference, 1g of carbs or protein gives 4 Calories and 1g of fat gives 9 Calories).",
"Protein content has traditionally been determined through elemental analysis, which gives the carbon, hydrogen, and nitrogen content of a material through a process of ",
" burning the material and analyzing the products. The majority of the nitrogen content from food comes from protein, so using some estimations, the approximate weight% of protein can be determined in the food. There are various complications with this method including: not everything with nitrogen in the food is protein (though most of it is) and bad actors may add adulterants to increase the apparent protein content by adding in high nitrogen non-food items.",
"Fats are usually determined through extracted triglycerides. Since fats are not soluble in water, they can be extracted using an organic solvent. The organic solvent is evaporated, and the fat content of the food is determined. The main source of error here is that there will b some non-fat water-insoluble content, such as cholesterol or various vitamins, but the majority of any fat present will be dietary fat.",
"Historically, carbohydrate content has been determined as a \"the remaining difference\" (i.e. initial weight - water - fat - protein - ash = carbohydrates). The water is determined by drying the food and the ash is what remains after the food has been burned to completion. However, this method has a significantly higher error than the estimations used in the determinations of the other components. Carbohydrate determination often requires specific chemical reactions that are specific to certain types of carbohydrate; this allows the analyst to distinguish sugars from things like cellulose.",
"Once you know the %weight of protein, fat, and carbohydrate in the food, you can find out the caloric content per unit weight."
] |
[
"The average calories in the four major energy-providing macronutrients (protein, fat, carbs, alcohol) was determined by burning a bunch of different molecules and seeing how much heat it generated. These values were then (",
") corrected to account for the actually biologically extractable energy by subtracting away the amount of energy lost in waste matter. This gives the average amount of energy that humans can get from one gram of typical carbs, fats, or proteins. The calorie content of foods is then determined by adding up the amount of carbs, fats, and proteins in it. In some cases where the only things going into the food are basic ingredients like sugar and oil it's very easy to add them up. In most cases you need to do laboratory testing to determine the chemical makeup and figure out what macronutrients are in it.",
"This is called the ",
"Atwater system",
". It's important to do it this way, breaking down foods into basic categories of nutrients, since not all organic molecules are digestible. For example, if you burn a strawberry the fiber will also produce heat, but fiber cannot be digested and provides no useful energy to humans. ",
"It should be noted that nutritional information is just a rough estimate. There's a lot of places where errors can occur. For example, not all carbs have the same energy content but all carbs are assumed to provide the average 4 cal / g. And similarly, not all strawberries are the same and some will have more sugar than others. However, generally the errors due to taking averages everywhere will cancel eachother out over time so that the average provides a good estimate. Whats more tricky to account for is metabolic effects (the thermic effect of food means that although protein provides 4 cal/g, some of this is used for digestion itself and the actual usable energy is lower) or the effect that cooking or otherwise processing food has on its caloric content"
] |
[
"3D Graphics Over 2D Footage Match-Move Conundrum"
] |
[
false
] |
I've noticed a strange thing in every 3D engine I've ever worked with. If I have three identical objects in a line in front of me such that when viewed from the top, the arrangement of myself and the three objects is that of the "T" shaped Tetris piece, in the real world, the objects on the left and right should appear slightly smaller than the one in the center since they're slightly further away, but in a 3D engine, all three objects are identical in size. I understand the linear algebra for why this is so (shape of frustum), but my question is how does this not negatively affect compositions of 3D effects superimposed over 2D motion pictures where the 3D art is match-moved to the video? I feel like a more lifelike virtual camera would have curved near / far clip planes.
|
[
"Hmm, you've really got me thinking. You're talking about overlaying 3D effects over 2D video. I think it's possible that the output of a typical 3D engine does accurately reflect the output of a typical camera, or at least, an ideal pinhole camera, if not the human eye.",
"Looking at some perspective equations on wikipedia, it appears that the width/length of an item will scale only with the perpendicular distance to the camera. It seems to me that these equations should be exact for an ideal, pinhole camera. (",
"http://en.wikipedia.org/wiki/3D_projection#Diagram",
")",
"I took the following picture of 3 butter knives:\n",
"http://imgur.com/vAaQlZr",
"The camera points directly at the center knife, with the outer knives at 30 degree angles or so. Taken from close-up, not far away and zoomed in.",
"Assuming a 30 degree angle, the outer knives should be 2/sqrt(3) times farther from the camera than the center knife, by simple trigonometry. This should make the outer knives appear (sqrt(3))/2 = 0.86 times the length of the center knife, by your logic.",
"I didn't count pixels, but they sure look the same length in the image to me. Certainly the outer ones don't look 15% shorter.",
"What do you guys think? If someone more knowledgable could confirm this, that'd be great. If I keep the camera stationary, but turn it 30 degrees to point directly at one of the outer knives, what happens? Would the outer knife then appear smaller in this new image, since its perpendicular distance to the camera is now larger?",
"I realize that I am asking a followup question as much as suggesting an answer. As for my non-layman qualifications to make a top-level comment, I did write my own 3D engine from scratch a few years back."
] |
[
"I've done similar tests by pointing my cell phone camera at a grid of tiles in my bathroom. I feel like I should see some curving in the lines that are created by the tiles but I don't. I know I have seen this effect in other images where the photographer used a fish eye lens, I guess I just thought the effect would be present to some degree with all lenses."
] |
[
"I found a youtube vid of a 3d engine that does exactly what I was imagining (taken to extremes)!",
"I'd imagine making a 3d game engine that does this with raytracing would be rather taxing on a system and destroy performance, but do you think this effect could be achieved with a post-process effect?"
] |
[
"Are the feelings in dreams really happening at the same time in real-life body?"
] |
[
false
] | null |
[
"This is from Dr. Stephen LaBerges book Exploring The World of Lucid Dreaming:",
"The experiments just reviewed supported the conclusion that the events you experience while asleep and dreaming produce effects on your brain (and, to a lesser extend, your body) much the same as if you were to experience the corresponding events while awake. Additional studies uphold this conclusion. When lucid dreamers hold their breathes or breathe fast in a dream, they really do hold their breathes or pant. Furthermore, the difference in brain activity caused by singing versus counting in the waking state (singing tends to engage the right hemisphere, and counting the left) are nearly duplicated in the lucid dream. In short, to our brains, dreaming of doing something is equivalent to actually doing it. This finding explains why dreams seem so real. To the brain, they are real.",
"TL;DR: Yes, feelings in dreams really happen at the same time in real-life body.",
"Also, I recall an explanation of how the brain causes paralyses while sleeping so your body doesn't actually move when you do while sleeping but I couldn't find it in my short search.",
"Edit: Spacing"
] |
[
"Your body and mind is not separate. It's not like your brain shuts off from the rest of the body when you're sleeping. The two are still interacting, and the rage/sadness/happiness you feel while dreaming is happening in the same way it would when you're awake."
] |
[
"Does this mean a dream could cause PTSD if it was traumatic enough?"
] |
[
"Why is oxygen so special?"
] |
[
false
] |
I'm not just talking about for life. For instance, why does combustion require oxygen specifically? Why can't things burn without oxygen? I get that because of the number of electrons in its outer shell it's really reactive, but shouldn't sulfur and selenium behave the same way, given their position on the Periodic Table? Are they just rarer, so that's why oxygen gets all the attention? Or are they actually less capable of filling the role oxygen does in things like combustion? (That may be a very stupid question, but my degrees are in psychology and history, not chemistry... obviously. :) )
|
[
"Things can burn without oxygen, it's just not as common. Most compounds/gases that are more powerful oxidizers than oxygen are rare in nature, since they've reacted already.",
"Oxygen isn't a uniquely powerful oxidizer, but it does have a unique feature, which is that it has what what we call a 'triplet ground state'. Two of its valence electrons ",
"are unpaired",
" and 'spin' in different directions. (electrons have a property called 'spin' that can be either of two values. It doesn't actually have anything to do with their actual motion though)",
"That gives it a magnetic moment - oxygen is ",
"paramagnetic",
". ",
"Here's a nice demonstration",
". Most materials and molecules have all their electrons paired up nicely (half with one spin value, half with the other) and virtually no magnetic moment (they're ",
"diamagnetic",
"). ",
"This matters a lot to oxygen chemistry, because the 'rules' say that - in most cases - the total spin is ",
" in a chemical reaction. So while you can write the reaction 2H_2 + O_2 --> 2 H_2 O , things can't actually happen that way. Because on the left side you have two unpaired electrons from oxygen, but on the right side of the arrow, you have two water molecules were all the electrons are paired.",
"That means combustion of hydrogen gas into water can't occur directly. For the reaction to occur, oxygen first has to flip the spin of one of its electrons, pairing it up. This takes quite a bit of energy (about 30 kcal/mol IIRC). ",
"For this reason, it takes quite a bit of heat/energy to get combustion started, even though it liberates lots of energy once it's happening. It's the same reason why compounds like F2 and Cl2 are uncommon in nature, because they're not only powerful oxidizers, they also react quite easily, unlike oxygen. ",
"The reason that spin is (often) conserved, is because it's related to angular momentum. So the reason we're not spontaneously combusting right this second is related to the textbook example of why you spin faster when you pull your arms in. (It's not an absolute rule that spin is conserved, because in some situations you can have a corresponding change of electron's angular momentum to compensate. The total of the two is strictly conserved)",
"All of that is, in turn, related to the fact that the universe works the same way no matter how it's rotated (Noether's theorem), but that's getting a bit off topic."
] |
[
"You have a pretty good feel for what's going on. Because of the number of electrons, sulfur and selenium can form the same type of molecules as oxygen. H2S (hydrogen sulfide) actually forms in combustion processes if oxygen isn't around. Hydrogen selenide (H2Se) is similar.",
"For another piece of the puzzle, we should look at how much energy is in the bonds. The standard notation for energy is kJ/mol which is the amount of energy to break a mole worth of bonds, or how much energy is released when the bonds are formed. It's not terribly important beyond knowing that bonds with larger values are stronger than ones with smaller values, and that elements generally will form molecules with the strongest bonds.",
"So ",
"from here",
", we have at standard earth temperatures and pressures,",
"This means that if a hydrogen atom has to choose, it's going to go to H2O. Now as for why the bonds are stronger for oxygen, I think I know the answer, but I'll let an actual chemist respond to make sure I don't misinform.",
"There's one last piece of the puzzle. On earth's surface, oxygen (O2) is a gas while Sulfur and Selenium and the rest of the elements in that period are solids. That means oxygen is a lot more mobile, and therefore it is a lot easier to create a combustion process with oxygen than the other solids."
] |
[
"Things can burn without oxygen, it's just not as common. Most compounds/gases that are more powerful oxidizers than oxygen are rare in nature, since they've reacted already.",
"And oxygen (gas) hasn't simply because photosynthesis keeps producing more? Or is it just that there's much more oxygen out there (on Earth or in the universe) to be left unreacted than other, similarly powerful oxidizers?",
"Oxygen isn't a uniquely powerful oxidizer, but it does have a unique feature, which is that it has what what we call a 'triplet ground state'.",
"I'm not sure I followed the spin part, at least insofar as why that explains oxygen's \"specialness\" as an oxidizer (which is, I guess, what I was really asking). Unless that was all leading to this part...",
"For this reason, it takes quite a bit of heat/energy to get combustion started, even though it liberates lots of energy once it's happening. It's the same reason why compounds like F2 and Cl2 are uncommon in nature, because they're not only powerful oxidizers, they also react quite easily, unlike oxygen. ",
"...in which case, I'm confused, because I thought oxygen ",
" react quite easily. I thought that's what makes it so dangerous/poisonous in high concentrations.",
"Thanks for the reply!"
] |
[
"How can the universe have a shape? This is mind-boggling to me..."
] |
[
false
] |
I cannot understand the concept of If something has a shape than that something "borders" something else. Please read the link above (it's from NASA's official website). It considers three possibilities: 1) The universe is spherical 2) The universe is curved like the surface of a saddle 3) The universe is flat "like a sheet of paper", and infinite in extent In the first scenario, the universe being a sphere, what surrounds that sphere? It does not say that it is infinite, so there must be a "beyond it", right? I could say more or less the same to the second "saddle" hypothesis. In the third case, if the universe looks like an infinite sheet of paper, I understand we couldn't travel to its extremities to reach the end of its extension, but how about traveling "up" or "down" its "height"? Does that make any sense?!? Please help, I'm having an existential crisis... (hopefully the matrix will open up)
|
[
"Actually, the terminology is somewhat confusing, but they are not talking about the shape of space but its global curvature. The universe could have a global curvature that is like that of a flat sheet of paper, i.e. zero, but it doesn't have to be a flat sheet of paper.",
"Also, the universe could actually have a shape on top of having a curvature. Take a toy universe you are probably familiar with if you have played computer games. If you wander around on the map of an old final fantasy game or an asteroids game, if you keep going in one direction, you'll just pop up on the opposite side of the map at some point. All those maps are flat, but have a toroidal \"shape\"."
] |
[
"First, we don't have an exact measurement of the curvature of the universe.",
"Second, you're talking about different parameters. The ",
" is zero for a flat universe, negative for a hyperbolic (saddle) universe, and positive for an elliptical (sphere) universe. The ",
" is 1 for a flat universe, greater than 1 for an elliptical universe, and less than 1 for a hyperbolic universe."
] |
[
"First, we don't have an exact measurement of the curvature of the universe.",
"Second, you're talking about different parameters. The ",
" is zero for a flat universe, negative for a hyperbolic (saddle) universe, and positive for an elliptical (sphere) universe. The ",
" is 1 for a flat universe, greater than 1 for an elliptical universe, and less than 1 for a hyperbolic universe."
] |
[
"Would electron degenerate matter behave similarly to a solid, gas, or liquid?"
] |
[
false
] |
In the book “The Collapsing Universe” by Isaac Asimov, he claims that degenerate matter would behave like a gas. He explains that while the electrons are compressed into a free flowing goo, the nuclei still remain relatively spaced out, and would thus act like a gas. Given that this book was written in the early ‘70s, is this an accurate statement, or do we have a better understanding of degenerate matter?
|
[
"The answer is basically yes, but it depends on your point of view. It's hard to imagine the kinds of forces involved that would cause the material to flow. Under such forces, normal matter wouldn't stand a chance.",
"Note the compared to the confinement pressure required to create EDM, the forces of molecular bonds in ordinary materials are of no consequence. ",
"Under such forces and pressures, things like tungsten or diamond behave more like gases themselves. In fact the density of EDM's are believed to be on the order of 10,000,000 g/cc. If you fired a small pellet of EDM at a tungsten block, the EDM would hardely flinch, and might as well be passing through a rarefied gas for the difference in density. The tungsten wouldn't have a problem flowing out of the way, then then consequently destroying itself in the process.",
"So EDM's are extremely ",
"This is if course assuming a small pellet of EDM would be stable, which it wouldn't be.",
"EDM is incredibly dense and at least from the perspective of the properties of normal matter, extremely hot. It isn't stable by itself, but exists because the immense gravity of a stellar remnant (a white dwarf) keeps it confined. If you took a small sample of EDM out of the confinement of a white dwarf, it would explode in a spectacular fashion. "
] |
[
"Electron degenerate matter is supported against further collapse by the degeneracy pressure of the electrons in the material being unable to occupy the same quantum states and isn't very dependent on temperature. As the material cools eventually the motion of particles in the material will slow and the blackbody radiation emission will diminish, but bulk properties such as density won't change that much. In principle, if you were to wait long enough (very, very long), all the nuclei in the EDM will eventually fuse into iron nuclei but this shouldn't really affect the electron pressure support."
] |
[
"I do work simulating neutron stars, which are composed of neutron degenerate matter, but the same concepts apply to electron degenerate matter. It's best to say that matter under these conditions acts as a fluid, something that in physics terms encompasses both gasses and liquids. All this means for the most part is that the material can easily flow under applied forces and isn't locked into one specific shape.",
"The extreme conditions of degenerate matter in compact stellar remnants aren't required to see this sort of effect though. If you look at the phase diagram of any material you can see that the distinction between the gas and liquid phases eventually ends as pressure and temperature increase and the material simply becomes a fluid that isn't really gas or liquid."
] |
[
"What happens to your eyes when you look straight at the sun?"
] |
[
false
] |
Just wondering what exactly damages your eyes from looking at the sun
|
[
"Same thing that happens to the rest of your body. They get sun burned. Also known as photokeratitis. ",
"And just like your skin. Your eyes will swell and burn and the cells will die off and shed. ",
"You’ll need to get antibiotics because if your eyes get infected they can scar over and become opaque. ",
"Usually it clears up in a couple days (much like sunburn on the rest of the body). ",
"Continued excessive sun exposure to the eyes can lead to cataracts and cancer. "
] |
[
"Does this just happen to the outer surface of the eye, or can it damage the retina as well?"
] |
[
"Are you talking about all the warnings that were given with the eclipse?"
] |
[
"What caused all the giant underwater reptiles to die out at the Cretaceous Mass Extinction but not other ocean life?"
] |
[
false
] |
Basically, what caused underwater dinosaurs to die specifically?
|
[
"Two things. Firstly, it’s important to remember that the Mesozoic Era, the ‘Age of Dinosaurs’ lasted 190 million years. The Cenozoic, or the ‘Age of Mammals’ has only lasted 65 million years. During the Mesozoic many different groups of plants and animals waxed and waned, and they did not all exist at once. Secondly, none of the marine reptiles during the Mesozoic were Dinosaurs; instead they belonged to six main groups:",
"Sauropterygi (which includes the Plesiosauria)",
"Thalattosaurs",
"Ichthyosaurs",
"Squamata (includes modern lizards and snakes, but also the Cretaceous Mosasaurs and Aigialosaurs)",
"Crocodylomorphs ",
"Chelonia (Turtles)",
"The latter three groups are still around, and all three groups contain marine species such as sea snakes, sea turtles, marine iguanas and salt water crocodiles. In saying that, aside from the Sea turtles, all the modern marine groups are more recently descended from terrestrial organisms. I’m also going to ignore the Thalattosaurs, because they died out at the end of the Triassic and weren’t around for most of the Mesozoic. ",
"The first major group of marine reptiles during the Mesozoic was the Ichthyosaurs. The Ichthyosaurs evolved really early on, at the beginning of the Triassic, and survived a major extinction that happened at the end of the Triassic. The Ichthyosaurs looked remarkably like dolphins, with highly streamlined bodies and gave birth to live young. During the Triassic and early Jurassic they were extremely successful. During the late Jurassic however, they went into decline, and they went extinct during the mid-Cretaceous, some 25 million years before the K/T extinction event. ",
"It is hypothesized that the rise of the ‘ray-finned’ teleost fishes led to the decline of the Ichthyosaurs; this group includes the modern pelagic fishes that outcompeted the ichthyosaurs preferred prey belemnites. Predation by larger marine reptiles, such as the pliosaurs and mosasaurs may have also lead to the extinction of the ichthyosaurs. A third hypothesis is that a major anoxic event in the world’s oceans around 91 mya knocked them out. ",
"The Plesiosaurians were the second major group of Mesozoic marine reptiles. They became successful following a mass extinction event at the end of the Triassic, which wiped out many earlier groups of marine reptiles (with the exception of the Ichthyosaurs). While there were many types of Plesiosaurians that flourished early on, two main groups became established, and stuck around for the rest of the Mesozoic; the pliosaurs and plesiosaurs. ",
"Loosely speaking, the plesiosaurs were the ‘long-necked’ ones such as elasmosaurus, while the pliosaurs were the ‘short-necked’ ones such as liopleurodon (which starred in Walking with Dinosaurs). These two groups thrived during the Jurassic and became increasingly less common during the Cretaceous. ",
"Some of the pliosaurs grew to be quite massive, and probably occupied an ecological niche similar to that of the modern orca. Despite their successes, the pliosaurs were wiped out around the same time as the Ichthyosaurs, possibly due to the same anoxic event around 91mya. The pleisosaurs were probably slow swimmers, perhaps ambush predators and lasted until the K/T mass extinction. ",
"The third main group of marine reptiles during the Mesozoic was the Mosasaurs. The Mosasaurs were descended from lizards (think monitor lizards), and were very much late comers, entering the marine environment only 20 million years before the K/T event. The mosasaurs took advantage of the vacant ecological niche left by the then extinct pliosaurs and ichthyosaurs. Despite their short period of success, they grew to massive sizes- up to 15m long, and were apex predators of the time. ",
"So by the time the asteroid strike that wiped out the last of the dinosaurs came, there were only the pleisosaurs and the mosasaurs left, in addition to the crocodilians and the sea turtles. And when the K/T event actually happened, neither of these groups were doing particularly well, because by the end of the Cretaceous the world’s sea levels had massively regressed, drying up much of the shallow continental shelves which they would have inhabited. So it’s likely that these groups were doing poorly prior to the asteroid impact, and the asteroid impact was the final nail on the coffin for these groups. ",
"Selected sources:",
"Ancient Marine Reptiles",
"Oceans of Kansas ",
"Book",
" / ",
"Website",
"Benson, R.B.J., Butler, R.J., Lindgren, J., Smith, A.S.\nMesozoic marine tetrapod diversity: Mass extinctions and temporal heterogeneity in geological megabiases affecting vertebrates\n(2010) Proceedings of the Royal Society B: Biological Sciences, 277 (1683), pp. 829-834. "
] |
[
"This theory has been around for a long time, and was pretty prominent before the discovery of the iridium rich K-T boundary and the tsunami deposits in the Carribean and the Gulf of Mexico. I'll try to address each of the points in turn, and keep in mind that geology is a subject that is always open to new evidence:",
"1) Not really sure what he means here, the K-T boundary is only exposed in a few places and those tend not to preserve fossils well. There are extensive sedimentary deposits all around the Gulf of Mexico which are consistent with a massive tsunami (a jumble of sand, boulders, and petrified wood). ",
"2)Some were, some weren't. Like redmeansTGA said, the pliosaurs were on the ropes, but the mosasaurs were doing quite well. A lot of the big lizards, who had ruled the world for 150 million years and survived multiple previous extinction events, vanished, but others survived. Crocodiles are an example of this, but an even better one is birds- birds ARE dinosaurs, just the lucky ones who had feathers and could fly and regulate their body tempature better.",
"3)I would argue the exact opposite- turtles have been around for 220 million years and have survived numerous cataclysmic extinction events, including the K-T event. T-Rex, on the other hand, only existed for about 5 million years before the K-T event, and would have required massive ammounts of food based solely on their body size.",
"4) There's really just no evidence to favor this theory. It's more based on a lack of evidence that a pathogen ",
" kill them off. Viruses and bacteria aren't preserved in the fossil record, so no one can ever debunk him, but it can't be proven either.",
"So on the one hand, we've got a rock layer rich in an element that's extremely rare on Earth, but common in the asteroids, a crater off the coast of Mexico that dates to 65 million years ago, roughly when almost all dinosaurs disappear, and sedimentary deposits consistent with a massive tsunami all around the Gulf of Mexico from the same time. On the other hand, there's a lack of proof that he's wrong. That said, it's possible that a pathogen contributed to the extinction, much like the Deccan Traps in India likely did."
] |
[
"I have a side question for you:",
"I remember seeing an show on the history channel (i think, looking for it now) and they interviewed a paleontologist who was making the case an asteroid didn't cause the kill off of the dinosaurs. His basic reasons was, ",
"1) lack of dinosaur fossils in the ash layer. ",
"2) that the majority of dinosaur populations were already declining or disappearing before the asteroid ",
"3) that the climate change caused by the asteroid wasn't sufficient enough to have caused the extention. His evidence of this was that turtles are highly sensitive to climate change and as he said \"if you can't kill the turtles, you can't kill a T. Rex\" ",
"He claims a pathogen was responsible for killing them off. ",
"Is there much of a founding for this idea, or is just a crazy idea to try and get on tv? "
] |
[
"What causes Ice ages?"
] |
[
false
] |
[deleted]
|
[
"We should distinguish between ice ages, which are long term cold periods, made up of many glaciations and interglacials. The current ice age started 2.58 million years ago, but the present interglacial only started about 11,400 years ago. ",
"For glacial and intergacial cycles, the ultimate driving factor appears to be Milankovitch cycles, which are variations in the tilt, obliquity, and eccentricity of the Earth. There's a more minor contribution, in the long run, by solar activity and occasional input from other factors such as volcanism or impact events. These changes are the forcing on Earth's many feedback mechanisms, such as greenhouse gasses.",
"The long term changes--your question about ice ages--is probably also related to Milankovitch cycles, but may be the combined influence of many factors. There may be different causes to different ice ages as well. "
] |
[
"There is widespread agreement from paleoclimatic and modeling evidence that Pleistocene glaciation cycling is driven by small, periodic changes in our movement and position relative to the sun called ",
"Milankovitch cycles",
". These changes are amplified in the climate system by feedbacks, such as albedo and greenhouse gases. The behavior of the Atlantic Meridional Overturning Circulation (AMOC) and ice sheet dynamics play significant roles. However, the exact processes at every step of the way are not completely understood. ",
"The short version is that changes in the duration and intensity of high latitude Northern Hemisphere summertime insolation due to Milankovitch cycles determine the extent of snow and ice cover. Changes in the extent of snow and ice result in albedo changes, temperature changes, changes in atmospheric CO2 and CH4, changes in vegetation, changes in sea level, etc. ",
"Note: There are completely separate phenomena wherein near total glaciation of the planet lasting millions of years occurred (popularly referred to as Snowball or Slushball Earth events). These episodes have different drivers for their inception and deglaciation. ",
" ",
"Brovkin, V., A. Ganopolski, D. Archer, and G. Munhoven (2012), Glacial CO2 cycle as a succession of key physical and biogeochemical processes, Clim. Past, 8(1), 251–264, doi:10.5194/cp-8-251-2012.",
"Calov, R., A. Ganopolski, C. Kubatzki, and M. Claussen (2009), Mechanisms and time scales of glacial inception simulated with an Earth system model of intermediate complexity, Clim. Past, 5(2), 245–258, doi:10.5194/cp-5-245-2009.",
"Hays, J. D., J. Imbrie, and N. J. Shackleton (1976), Variations in the Earth’s Orbit: Pacemaker of the Ice Ages, Science, 194(4270), 1121–1132, doi:10.1126/science.194.4270.1121.",
"Huybers, P. (2011), Combined obliquity and precession pacing of late Pleistocene deglaciations, ",
", 480(7376), 229–232, doi:10.1038/nature10626.",
"Köhler, P., R. Bintanja, H. Fischer, F. Joos, R. Knutti, G. Lohmann, and V. Masson-Delmotte (2010), What caused Earth’s temperature variations during the last 800,000 years? Data-based evidence on radiative forcing and constraints on climate sensitivity, Quaternary Science Reviews, 29(1–2), 129–145, doi:10.1016/j.quascirev.2009.09.026.",
"Raymo, M. E., and P. Huybers (2008), Unlocking the mysteries of the ice ages, Nature, 451(7176), 284–285, doi:10.1038/nature06589.",
"Vettoretti, G., and W. R. Peltier (2011), The Impact of Insolation, Greenhouse Gas Forcing and Ocean Circulation Changes on Glacial Inception, The Holocene, doi:10.1177/0959683610394885."
] |
[
"I'd say that estimate is a bit dodgy. Ignoring the effects of global warming is like saying \"other that that, did you like the show Mrs. Lincoln?\" Human contributions at the present are the overwhelming effect. Moreover, the end of the interstadial is not really well dated, some people think it would naturally have already ended, were it not for human contributions (although I think it is a distinct minority view).",
"But the human capacity to cope with climate change is a very real question. The whole of human civilization has been predicated on Holocene stability in climate. If we lose that stability, we probably lose agriculture. While that would not likely cause human extinction, it would take our population down to a global population of a few hundred million, living as hunters and gatherers."
] |
[
"Earth is made up of tectonic plates, will the number of these plates ever change over time?"
] |
[
false
] |
Earth conists of a number of tectonic plates that, as far as I know, seem rather stable. However, will some plates subdivide into new plates over time? Will current plates combine into larger "superplates"? Or is Earth just not geologically active enough for the tectonic plates of Earth to change? On a slightly related question, the tectonic plates present on Earth seem to be identical to the ones of Pangea, so is it possible that the number of tectonic plates has been stable for quite some time?
|
[
"Neither the number of plates or the geometry (i.e. their sizes/shapes) of plates are fixed. It's first worth noting that even the current number of plates is somewhat contentious and depends on how the criteria / data used to define them (e.g. ",
"this paper",
" which both lays out a set of criteria for defining 159 plates and also includes a summary of some prior efforts and criteria to define plates). There are similar discussions about how plate numbers and size may have changed with time (e.g. ",
"this paper",
", which mainly focuses on the best way to describe the variation in plate area, but considers the implications of changes in plate number and area a bit). ",
"Regardless of the exact number either now or in the past, there are a variety of processes that can change the number of tectonic plates (the second paper I linked to discusses this a bit more as well). For example, however, the number of plates can be reduced by the formation of mountain belts and the ",
"'suturing'",
" of plates together (e.g. while still separate, the ",
"Indian",
" plate is in the process of being sutured to the Eurasian plate in the process of the Himalayan-Tibetan orogeny). The number of plates can be increased by the ",
"rifting",
" of a plate (e.g. the ",
"Somalian",
" plate was formerly part of the ",
"African/Nubian",
" plate prior to formation of the East African Rift). "
] |
[
"This is completely fascinating. When a plates rift/suture, is this process quite catastrophic with volcanoes/earthquakes or is it so long that its effects aren't directly observable?"
] |
[
"It is a process that happens slowly, over geological timescales - for example, the Indian plate moves northeast at about 5 cm per year, while the Eurasian plate moves north at about 2 cm per year. It isn't really observable much on human timescales with the naked eye, but definitely measurable.",
"Especially the process of surturing, because it forces the plates to bend and deform, is however associated with earthquakes - the boundary between the Indian and Eurasian plates is one of the more seismically active regions of the world."
] |
[
"How much power could you generate if you put a water wheel in urinals that when spun generated electricity?"
] |
[
false
] |
Every guy wants something to aim at when he pees at a urinal. What if you put a pinwheel that spins when hit by the force of urine and generates electricity? Assuming you placed one at a bathroom at Disneyland to ensure a constant supply.
|
[
"But a lot of microscopic things don't add up to jack. ",
"Disneyworld has 52million annual visitors. Assume half are men and they average 2 pees per day that's 52million total pees. ",
"80mW * 30s gives you 2.4 joules/pee. Multiply by 52million and you get the energy saved per year, for which ",
"Wolframalpha gives some good conversions",
". ",
"Where I'm at that would save them $4.42 worth of electricity per year. It's also about equal to the energy in 1 gallon of gasoline. That's absolutely negligible compared to the cost of these devices and the energy required to create all of them. ",
"Simple calculations like this show why almost all \"energy recovery\" systems you see advertised are a scam. ",
"Edit: Oh, and this is assuming the device is perfectly efficient. It probably won't be much better than 20% so divide everything by 5. "
] |
[
"If you have 500 grams of pee that fall half a meter over the course of 30 seconds, you have about 80 milliwatts of power. Not much."
] |
[
"This would be a game-changer and allow us to send a manned spaceship to Alpha-Centauri every week."
] |
[
"What causes aftertastes? Why don't all tastes occur immediately?"
] |
[
false
] | null |
[
"Taste is caused by molecules in food binding to receptors on the tongue (plus a lot of scent stuff but we'll simplify that away for now because it's a similar mechanism anyways).",
"Some of those molecules stay bonded for a longer time than others."
] |
[
"Because probably the \"tasty\" molecules from the food are not bonded to the taste receptors on the tongue as long as the \"nasty\" molecules are."
] |
[
"But how does the aftertaste taste completely different to the original food? If I eat something with Stevia, for example, it tastes ",
". But maybe a minute later I get the aftertaste and it's vile, filthy, ",
". Why the big difference?"
] |
[
"Why don’t hotspots in the earths mantle move with the continental plates?"
] |
[
false
] |
I’m currently taking a geomorphology class in college and we were talking about plate tectonics. Our professor said that the plates move due convection of magma within the earth. However, hotspots tend to stay in place and cause volcanoes as the plate moves over them. Why are the hotspots not effected by convection?
|
[
"The mantle and the crust are - at least partially - decoupled.",
"In the most simplified way you can imagine the mantle as a convecting fluid, with rising portions (mid ocean ridges), coooling surfaces (oceanic plates) and sinking portions (subduction zones). Movement is in the order of 0.01 - 01 m per year. ",
"Hot spots are* vertical point instabilities in the mantle. The mantle is ~ 3000 km thick. With convcection cell speed at 0.1 m/y you're looking at 30,000,000 years for material to reach the surface from a deep mantle hot region. Do mantle plume 'wobble' - sure. But they are point events in a much broader structure."
] |
[
"Just to add a bit on the 'plumes wobbling', there is a pretty vigorous debate on the extent to which plumes are fixed either at their base or their surface expression, as just one example ",
"Tarduno et al, 2009",
" (and references therein) argue that the surface location of plumes can be influenced by a variety of factors, including deflection by 'mantle wind', i.e. convection currents, but also by things like the proximity of a mid-ocean ridge and motion of the base of the plume. Coincidentally, the paper I linked to is hosted on a ",
"curious website",
" devoted to debating whether hotspots are caused by plumes. ",
"In general, the fixed nature of hotspots is one of many 'convenient lies / simplifications' that are discussed in introductory level geology courses, but you typically don't really need to worry about whether hotspots are truly fixed until you get into very detailed reconstructions of plate motions. It is possible to define a reference frame for plate motion based on moving hotstpos, e.g. ",
"Wang and Liu, 2006",
" or ",
"Doubrovine et al, 2012",
", but it's not clear if these are even internally consistent, e.g. ",
"Wang et al, 2019",
", even to the point where we 'know' that hotspots are not really fixed, but they are fixed enough that you will still see many plate reconstructions done in a 'hotspot-fixed reference frame'."
] |
[
"It seems like there is a little misunderstanding here. First of all, the evidence of convective cells is at least in some places not quite given. Also plates are also to a large part moved by ridge push and slab pull, but this is besides the point.",
"Commonly Hotspots are theorised to originate at the Mantle-Core boundary. While the Outer core is indeed liquid, it is much denser and also hotter than the mantle. As a result, mantle material can be heated up and as a result rises up (same principle like a lava lamp really). Now you have a column of hot material in the mantle and since the core and mantle are relatively stationary to the crust (there is some evidence, that Hotspots can shift too), this column is relatively stable. At a certain depth, the temperature of this material in the \"heat column\" will be enough to melt that rock. Again; under normal circumstances the rock is solid in the mantle, but if a specific temperature limit is crossed, material is melted. This magma is now again lighter than the surrounding mantle rock and will rise up. Eventually the magma will break through the crust and from Volcanic rocks and (again) since the mantle and core is relatively standing still in relation to the moving plate, the Hotspot seems to wander around.",
"Hope that answers your question."
] |
[
"Is sugar content higher in ripe vs. unripe fruit?"
] |
[
false
] |
You have two bananas, one ripe, one green and unripe. The ripe banana will taste sweeter, leading me to believe it has more sugar, but I would assume both bananas have the same total calories.
|
[
"In the case of bananas, commercially produced bananas are almost always treated with ethylene gas which acts as a plant hormone that helps the fruit ripen (it's also responsible for the yellow colour). When this happens, enzymes in the fruit convert starch to sugar, which makes it taste sweeter and also makes the fruit softer. ",
"So yes, the calories are the same, but the way you absorb and metabolize them will be different (starches vs. sugars).",
"Essentially ripening is a process where the walls of the fruit cells break down into various water-soluble sugars which makes the fruit squishier and sweeter."
] |
[
"Don't know how this went off on a tangent regarding ethylene gas... Yes, when most fruits ripen, the starches in their tissues are lysed to form sugars. This, along with changes in color, is in order to attract animals which will eat the fruits and spread the seeds."
] |
[
"Don't know how this went off on a tangent regarding ethylene gas... Yes, when most fruits ripen, the starches in their tissues are lysed to form sugars. This, along with changes in color, is in order to attract animals which will eat the fruits and spread the seeds."
] |
[
"What is the relationship between energy savings and visible light reduction when dimming incandescent light bulbs?"
] |
[
false
] |
Levitron makes the following claim about their incandescent light dimmers. It appears on the dimmer package and : If "Dimming" means decrease in light output, then I find these claims hard to believe. As the filament cools down, emission shifts towards infrared and the light bulb becomes less efficient at producing visible light. Because of this, I was expecting much less of an energy consumption decrease. Is the table reasonably accurate? If not, can I find more accurate information elsewhere? I realize that different light bulbs would behave differently. I'd prefer information for something common, like 120V 60W or 100W incandescent bulbs. Edit: I just found some information at : For a supply voltage V near the rated voltage of the lamp: This means that a 5% reduction in operating voltage will more than double the life of the bulb, at the expense of reducing its light output by about 20%.
|
[
"I'd assume based on my EE knowledge that \"reducing power by 10%\" is actually just increasing resistance by the correct amount to give 10% less power. Basically every dimmer switch utilizes a sliding resistor as seen ",
"here",
"."
] |
[
"That was my EE suspicion as well. However, I wouldn't be surprised if that decreased power traveling to the light bulb itself did actually increase the lifespan of the filament as the OP's PDF suggested. "
] |
[
"You are right!",
"I suspect dimming by 10% means reducing power by 10%; not reducing light output by 10%. The light probably reduces by even more. But I am curious to know the answer as well. Upvote!"
] |
[
"What is the basis for having a sense of rhythm?"
] |
[
false
] |
It seems to be more involved than just good coordination. Has neuroscience ever studied it?
|
[
"Yes :) in my undergrad developmental psych class, we read a book that compiled a doctor's experiences after working in the emerging field of children's psychological trauma (boy who was raised as a dog, all the trigger warnings). There's plenty of research available indicating that musical training in some way accelerates or coordinates brain development. Google scholar is a great resource. But this book was different because the doctor's accounts reflect that children whose brain development was halted by severe neglect experienced discoordination muscularly in a severe way. Underdeveloped cerebellum. After rhythm training in the form of dance classes, that cerebellum re-entered a period of rapid growth and coordination long after the typical sensitive period. It is possible that rhythm is deeply related to our movements in general since it has a massive effect on the cerebellum."
] |
[
"This is less my area, but an exciting new paper just dropped looking at the genetics of a sense of rhythm. It's open access, so you may find many interesting answers to your question in the introduction and discussion sections.",
"Choice bit from the Abstract: \"Genetic correlations with breathing function, motor function, processing speed and chronotype suggest shared genetic architecture with beat synchronization and provide avenues for new phenotypic and genetic explorations.\"",
"\"Genome-wide association study of musical beat synchronization demonstrates high polygenicity\" ",
" \n",
"https://www.nature.com/articles/s41562-022-01359-x"
] |
[
"I read the book This Is Your Brain on Music way back in high school and the author did say that rhythm originates from the cerebellum, which is the part of the brain that controls rhythmic motor skills like your gait while walking and I think also our passive rhythms like breathing and heartbeat. It's the most \"basic\" part of the brain, which even reptiles possess. I don't have the book with me anymore, but you could find it and see what the author, Daniel Levitin, has cited."
] |
[
"So the colors we see can be placed on a linear chunk of the electromagnetic spectrum, red to violet. Why can we represent them in a circular \"color wheel\" then?"
] |
[
false
] |
So rainbows and images like show that red corresponds to low wavelength and violet corresponds to a high wavelength. Then how the heck is it that when we look at a color wheel ( for instance ), the difference in color between red and purple (massive difference in wavelength) looks about equal to the difference in color between red and orange (significantly less)? For that matter, why does combining red and purple give you a reddish-purple and not, say, cyan, the average of their two wavelengths?
|
[
"What it comes down to is that ",
"magenta isn't a real color",
", not in the same sense as all the other colors. See that article for a better explanation."
] |
[
"There is a great ",
"MinutePhysics",
" that may answer your question."
] |
[
"What it comes down to is how your brain processes color. We only have red, blue, and green photorecptors in our eyes. For whatever evolutionary reason (probably for better visual contrast), the brain mixes the red, green, and blue signals to try to recreate an original color rather than showing you a superposition of the three at a single point. For example, instead of seeing equal amounts of red and green at a point simultaneously, we see yellow which is the average of the red and green wavelength. The \"red\", \"green\", and \"blue\" colors are represented in your brain as a weighted average of what is being sensed. So equal amounts of red and green appear as yellow, and equal amounts of green and blue appear as cyan/turquoise. This does a very good job at allowing us to view the entire visible spectrum as different shades of color, however, it leaves one unnateral superposition: red and blue. No single wavelength of light will excite both the red and blue photoreceptors in your eye, yet the brains model cannot show you a superposition of colors, so it makes a weighted average between the two shades to give you magenta/pink, a color which cannot exist as a single wavelength.",
"tl;dr: its the way your brain interprets superpositions of colors which creates an artificial color... magenta/pink."
] |
[
"If projectiles were launched at Escape Velocity from an electromagnetic gun, wouldn't they eventually loop toward the Sun, regardless of which way the Earth was facing at the time they were fired?"
] |
[
false
] |
[deleted]
|
[
"Escape velocity from Earth's orbit around the Sun is about 43 km/s. But the Earth is already orbiting the Sun at about 30 km/s. So if we shoot something \"forwards\", we only need to give it an extra 13 km/s for it to escape the solar system - otherwise it goes into orbit. If you want the junk to fall into the Sun, that's actually ",
". The Sun is very small compared to the size of the solar system, so you basically need to drop your speed to 0 to drop into the Sun. So you need to shed 30 km/s of speed rather than gaining 13 km/s.",
"As a side note, this produces some interesting apparent paradoxes for Mercury. Mercury is, on average, the closest planet to the Earth (which is already counter-intuitive). But, because it's so close to the Sun, it's also the most difficult planet to reach in the solar system.",
"As for the railgun/coilgun/EM-gun idea, it's only really practical if you combine it with conventional rockets. It's not efficient to accelerate to extremely high speeds at sea level and then coast into space, because you lose huge amounts of energy to the thick lower atmosphere. It's better to start slower, and accelerate as the atmosphere becomes thinner and drag becomes weaker - which the opposite of what an EM gun does. The practical designs for this sort of thing are generally about using an EM gun to launch the rocket at something like the speed of sound, and then using a conventional jet engine or rockets to accelerate into upper earth atmosphere or space.",
"The other practical concern of launching waste into space is that you really need a very very low failure rate. Rockets are safer than they used to be, but failure rates of even 1-2% are not really acceptable if you're making routine launchings of nuclear waste, given the damage it would cause if the EM gun misfired or the rocket exploded."
] |
[
"It's incredibly difficult to actually shoot something into the sun. One of your qualifiers is that you don't want it to \"go into orbit around it (the sun)\", but everything on earth is already in orbit around the sun because the earth is. So you have to launch something off of earth, then you have to \"de-orbit\" it relative to the sun using energy so that it can \"fall\" straight into the sun. If it has any orbital movement it won't fall straight into the sun, it will just accelerate faster and faster toward the sun, but also in whatever direction it was already moving resulting in a highly elliptical orbit that you are probably already familiar with from some comets."
] |
[
"Besides the technical problems there is one relatively simple rule of orbital mechanics: If you are in an orbit, you will encounter the same point over and over again.",
"That means, if you shoot something away from Earth and it escapes the Earths gravitational pull, but doesn't fall into the Sun or escapes the Solar system, it will have a very high probability to collide with Earth in the future. You cannot shoot it into an orbit that does not cross the orbit of Earth. For nuclear material, it would be better to shoot it into the Moon if you just want to get rid of it."
] |
[
"Perceiving an object moving near the speed of light..."
] |
[
false
] |
[deleted]
|
[
"Sally goes to a point 5 years away traveling at < C and comes back immediately. 10 years have passed and Bob experiences more time has passed depending on the speed.",
"Bob experiences 10 years no matter how fast Sally is traveling.",
"So he would see the spaceship moving slower than it actually is?",
"No, he would perceive it as moving at whatever velocity it has relative to him. We can perceive any velocity up to but not including C."
] |
[
"Bob experiences 10 years no matter how fast Sally is traveling.",
"Well, if she's going much slower than c then he'll experience quite a bit more than 10 years.",
"For example, if she's traveling at 0.5 c, then he'll experience 20 years before her return while she'll experience about 17.3."
] |
[
"Maybe I'm misunderstanding OP's question. It's inconsistent, but I'm not sure what OP was intending to ask."
] |
[
"In a rear-end collision is it better to be slightly further away from the car in front? Or really close?"
] |
[
false
] | null |
[
"Please follow road safety and vehicle rules. It is always best to be as far away as necessary to have enough time to react and brake effectively.",
"For homework problems and calculations, please submit questions to another subreddit like ",
"/r/HomeworkHelp",
", etc.",
"Thank you."
] |
[
"This isn’t a homework problem, so I’m not sure if it belongs there. It’s just a question about physics I have wondered about. I imagine a rear end collision kind of like That little Newton’s cradle toy you put on your desk. But always wanted to know the science behind it. Sorry i rarely post on reddit so if it’s the wrong place let me know. "
] |
[
"/r/askscience",
" is probably not the right venue for getting a lecture on mechanics. I would suggest going through a textbook (elastic/inelastic collisions, conservation of momentum, etc) first, then submitting a more specific question for our Physics panelists.",
"Cheers."
] |
[
"Are black holes traveling through space?"
] |
[
false
] |
From what I understand, all heavenly bodies travel relative to each other through space. When a star collapses, does this change, or does the black hole continue moving through space? If so, how? If not, why not?
|
[
"Yes, they will. They have momentum relative to other objects and that will be conserved. In addition, we see evidence of supermassive black holes in orbit around each other."
] |
[
"There is no such thing as absolute motion (excluding for massless objects). Each black hole is either moving or not depending on your reference frame."
] |
[
"Yes. Due to conservation of momentum, a black hole will (ignoring asymmetries in the supernova) still have the same momentum that the star it was formed from had. Additionally, they are affected by gravity just like any other object with mass."
] |
[
"If I took a spoonful of a neutron star and pulled it away from said star, would the spoonful expand to a larger size? What would the matter look like (metal, glass, gas, liquid)?"
] |
[
false
] |
I heard a spoonful of matter in a neutron star weighs the same as Mount Everest. Would a spoonful of the stuff expand to that size?
|
[
"Neutron stars have a density of around 10",
" kg/m",
" which means that the total mass in a teaspoon is somewhere on the order of 10 billion tons. You'd want to take the scoop from the center of the star as the outside layers are more likely to be heavy elements and stuff.",
"So lets assume we can teleport a spoonful of neutron star into our cargo hold and steal it. Assuming we don't pressurize our cargo bay or container - the neutron star matter is no longer struggling between gravity and the degeneracy pressure which prevents collapse into a black hole.",
"The matter immediately explodes upon arrival in the cargo hold. The gas pressure is huge as the matter expands explosively. If the cargo bay holds then you're likely to have created a volume of matter with a density 10 million times that of solid rock. Do not stand in the cargo bay during this phase.",
"But it gets worse... The degeneracy pressure that was preventing the gravitational collapse of the star also prevents the neutrons from decaying. And when they decay they release energy. So the whole lot is going to explode ... again.",
"Our teaspoon of neutron star matter decays with the same amount of energy output that our whole Sun puts out over 2-3 seconds (roughly 10",
" J). This is about the equivalent of a trillion megaton nuke.",
"I strongly advise wearing protective gear when handling neutron star material."
] |
[
"I didn't fully answer the question... ",
"Here",
" is a wiki article that may help.",
"What would the matter look like (metal, glass, gas, liquid)?",
"It depends on the temperature of the object. ",
"Right now, at the current age of the universe, all neutron stars are gonna be pretty intensely hot. It takes a great deal of time (multiple times the age of the universe) to cool down - but eventually they will since neutron stars have ceased fusion. Assuming the neutron star avoids gravitational collapse into a black hole then we are left with a extremely dense and dark object (just one without an event horizon).",
"So if we took a teaspoon scoop right now it would essentially look like very much like star material. And then it would explode ... at least twice. It would be extremely high energy output so wear protective eye glasses.",
"If we waited until it cooled down a lot (leave the degenerate matter to cool for several times the age of the universe before applying frosting) then essentially the material would look black ... and then it would explode ... at least twice."
] |
[
"There wouldn't be any other light in the universe by the time neutron stars have cooled down. So you might describe it as translucent, maybe shiny if you shine a light on it or just black - due to the extremely low energy levels (at that stage of the universe) and cool temperature under intense gravity.",
"Of course it would immediately ignite (due to neutron decay) and dramatically inflate if allowed to escape that densely packed gravitational lockdown."
] |
[
"Why Do Beef and Lamb Have Such Distinctive Tastes?"
] |
[
false
] |
Just a thought I had: they both have pretty much the same diet (grass) so there can't be a huge amount of different compounds going into their diet and yet lamb tastes completely different to beef. Is it some chemical that one species produces that the other doesn't? Fat content? Thank you for any answers
|
[
"You're looking at this the wrong way. It is coded in their DNA, of course, but not with the evolutionary goal of tasting great to humans.",
"If you imagine asking the question \"why do sheep look different from cows?\", or \"why do cows and sheep smell different?\". Your question is essentially the same: the difference is a by product of animal ancestors evolving into different species in response to isolation, and environmental pressures leading to promotion of various genetic traits. Some of those traits are tasty, son.... and some taste different from others."
] |
[
"Because of differences in the number and type of long chain fatty acids that each animal tends to produce and store. "
] |
[
"Actually, if you try grass fed beef. It tastes different from corn fed beef."
] |
[
"Why is infrared radiation usually associated with heat even though UV, X ray, and gamma radiation are much higher energy?"
] |
[
false
] | null |
[
"Ugh this is such a cool question! The answer get's at some very real-life applications of quantum mechanics. ",
"The basic answer is infra-red radiation is a more effective way of heating up common materials (water, plastic, organic things) because photons in the infra-red part of the electromagnetic spectrum are more heavily absorbed by these compounds, but this is only part of the answer! The next obvious question is: why is that? Why for instance doesn't the visible and UV radiation from sunlight cause even more heating since it's higher in energy? The reason for this has to do with a couple concepts: 1) what exactly is happening on the molecular level when electromagnetic radiation is absorbed and turned into thermal energy and 2) the concept or resonance and how this translates into absorption spectra of various compounds. ",
"Let's get into the first idea. Several things can happen when electromagnetic radiation is absorbed by a material. Classically we are taught in science class that electrons in lower energy orbitals are pushed up into higher energy orbitals when they absorb EM radiation but this only really tells a small part of the story (this is what causes the classic \"absorption spectrum\" of various chemical elements - so valuable to astronomy). It turns out EM energy can actually be absorbed in myriad other ways, however to increase the temperature of a substance, it has to be absorbed in such a way as to increase the kinetic energy of the molecules making up that particular compound, since temperature is our perception of the average molecular kinetic energy of a substance. To accomplish this, the EM radiation will typically increase the vibrational energy of the chemical bonds present in this substance, though interactions which increase the rotational energy or flex the bonds will increase kinetic energy as well. In the case of your microwave for instance, a machine that projects high intensity EM radiation (in the microwave area of the spectrum - hence the name) the way kinetic energy (a.k.a. heat) is imparted on your food is by increasing the vibrational energy between the hydrogen-oxygen bonds in water. That's why you'll notice that the more water-filled portions of food you heat in the microwave often heat up disproportionately compared to other parts! ",
"This takes us to #2, why is infrared the part of the spectrum that is responsible for temperature changes, not other parts of the spectrum. Well this has to do with quantum resonance. Let's take the example of water again as we just discussed. Imagine a water molecule, with two hydrogen atoms and one oxygen atom. The hydrogen atoms and oxygen are mutually attracted to each other (if you're curious why, look up covalent bonds on wikipedia). Their mutual attraction exists such that there is a perfect distance at which they will be at their lowest energy state; where the attraction they experience due to their electronegativity (another chemistry concept) is balanced by the repulsion their positively charged nuclei experience towards one another. This is their \"bonding length\". In school we make models of molecules with balls and sticks, which implies bonding length is constant, but in reality, the hydrogen and oxygen in water are bouncing between each other as if they are on springs, constantly oscillating between attraction and repulsion. ",
"Remember earlier that increasing the vibrational energy of a chemical bond will in turn result in an increase in that molecules kinetic energy (resulting in a net temperature increase for the compound as a whole) so consider for a second what it would take to increase that vibrational energy. You would need the right amount of energy to perfectly increase that \"bouncing back and forth\" oscillating motion between the hydrogen and the oxygen atom. If the photon that interacts with this system is too high in energy, it will either disrupt the system violently (i.e. the way ionizing radiation works) or simply not be absorbed at all. Alternatively, a photon with too little energy will not have sufficient \"oomph\" (read: energy) to significantly affect the vibration of the oxygen and hydrogen. But a photon at just the right wavelength and frequency can add energy to the system by imparting just enough energy into the chemical bond as to increase the frequency and amplitude of the vibration, and lead to an increase in kinetic energy. It is primarily infra-red and microwave radiation that exists in this \"sweet spot\" of energy to interact so strongly with the chemical bonds of most common organic compounds in a way that produces heat. Other kinds of radiation simply are too energetic or not enough. This is the concept of \"resonance\" and I think it's an apt word to describe it. ",
"Another way of thinking about this is what something looks like when it does NOT absorb a part of the EM spectrum. Let's take water for example. Water barely absorbs visible light (compared to something like ink for example), so it appears clear. When visible light interacts with water molecules, it is hardly absorbed so the waves largely pass through it unhindered (they are in fact \"refracted\" but let's not get into that right now) and as a result it appears transparent. In contrast, water would appear \"black\" in the infrared spectrum since it heavily absorbs these wavelengths. Interestingly if you take this logic a step further, you could infer that black objects, which absorb the entirety of the visual spectrum, are essentially doing what water does to infra-red energy; they are absorbing it and transforming it into kinetic energy. If you want to test this theory, take two water bottles, one filled with pure water, and another filled with india ink out into the sunshine on a bright sunny day. Both bottles have similar infra-red absorption since they are largely filled with water, but the one with ink in it will additionally absorb most of the visible spectrum. It should be noticeably warmer at the end of the day. ",
"tl;dr: Infra-red energy is absorbed by chemical bonds in most common organic compounds, increasing their vibrational energy and leading to higher average kinetic energy of the molecules making up that compound (i.e. tempearature); other areas of the EM spectrum are either too high energy or too low energy to interact with chemical bonds in this way!"
] |
[
"Because the black-body emission spectrum at room temperature peaks in the infrared region."
] |
[
"Welding torches can give you a suntan. They are one of the few common objects hot enough to emit significant UV through blackbody."
] |
[
"Does the earths rotation have an influence on our weight?"
] |
[
false
] |
In other words, would we weigh more/less if the earth spun faster/slower due to centrifugal force or other factors? Is this difference significant? What might we weigh if the earth did not rotate?
|
[
"It does, but the effect is very slight. ",
"At the equator, where the apparent centrifugal force is strongest, it causes you to weigh about 0.3% less than you otherwise would.",
" ",
"Also, the same centrifugal force causes the Earth to be slightly oblate, i.e. it bulges out at the equator. The Earth's gravity is thus slightly weaker, because you're farther away and the gravitational force decreases with the square of the distance. That takes off about another 0.2% of your weight."
] |
[
"I believe you are off by a factor of 10. Earth's rotation makes you 0.0034 Gs lighter so you are only 0.5 lbs lighter"
] |
[
"I believe you are off by a factor of 10. Earth's rotation makes you 0.0034 Gs lighter so you are only 0.5 lbs lighter"
] |
[
"Why can you see fire when the US Navy railgun shoots?"
] |
[
false
] |
a video of it :)
|
[
"What you are seeing is known as shock heating. The projectile is travelling fast enough that it is compressing the air in front of it to extreme pressures which creates heat as energy is given up to the air. The air around the projectile heats rapidly to the point that it becomes plasma. This is the same effect that occurs during atmospheric reentry of space vehicles."
] |
[
"Precisely, I was simply referencing the heat of compression specifically."
] |
[
"The same phenomenon is responsible for the light you see with lighting or other electric arcs like ",
"this one",
" : the air recieves a considerable amount of energy which is converted into considerable levels of heat, resulting in a plasma."
] |
[
"What is the current thinking on the relationship of Arthropods?"
] |
[
false
] |
I know that it's been a matter of debate as to whether hexapods and myriapoda or hexapods and crustaceans are more closely related. The last I read was that crustaceans were the more likely, but with constantly evolving theories, it can be hard to locate the current thinking using the web. I presume Chelicerata are still classed as an outgroup. Any thoughts on where Trilobites would fit in? Also, I read that what we formerly classed as hexapods might no longer form a monophyletic group... Any info on that? Sources, as always, appreciated :)
|
[
"Phylogenetic data seems to be coming down firmly on the side of ",
"pancrustacea",
". Usually you have to take these studies with something of a grain of salt because of a myriad of artefacts, such as long branch attraction (which is widely responsible for the misconception that eubacteria are monophyletic. Yes, you may down vote me now.) However, the 2.6 megabases of 75 genome used to construct the tree is quite respectable. All chelicerates were still outside Mandibulata; however, chelicerates may not be monophyletic. Obviously no trilobites sequence was included to allow their placement within the tree, and I am not at all farmilur with the literature on trilobites. "
] |
[
"Thank you. I actually found this paper quite enlightening (I found it myself in the time between posting and your reply XD)",
"As for the trilobites, further investigation seems to put them within arachnomorphs as opposed to Mandibulata... Although the evidence for this is rather sketchy, as you might expect for a long extinct species.",
"Also, eubacteria aren't monophyletic?"
] |
[
"Yah, well, the monophyly of the eubacteria is only supported by molecular evidence, and I'm just not sure I trust molecular evidence any further than I can throw it when it comes to resolving events older than 2 billion years or so (the origin of eukaryotes). There is a group of bacteria with a membrane surrounding their DNA, and I have grown suspicious that they are paraphyletic to the rest of the bacteria (i.e. that they are more closely related to you and I than to other bacteria). Cavalire-Smith doesn't think they are ancestral to eukaryotes, and you should probably believe him over me, but even he puts the root of life inside the eubacteria, rather than between eubacteria and (archea / eukaryotes). So, it is just my crazy belief which is likely too strongly influenced by the opinions of protistologists. "
] |
[
"If a gamma ray burst had hit earth in the past, could we detect it in the crust of the earth?"
] |
[
false
] |
Or would that have happened so long ago, it's now a moot point.
|
[
"I seem to recall seeing something on this very thing on [a SciShow Space episode](",
"www.youtube.com/watch?v=inIFO5ZvdqM",
"\n) not long ago. ",
"Anyway, the gist of it was that scientists noticed something weird in some ancient tree rings, and ice cores from the same period.",
"I guess that's not exactly the Earth's crust, but even so... Worth a watch, though I haven't triple-checked their sources. They're usually okay, though. :)"
] |
[
"The problem becomes in finding a strata of rock/sediment to do so. Depending on how long ago it would have been, evidence might be eroded away by environmental processes. And then half life of the ionized / isotopes need to be considered.",
"Not an easy task, but plausible!"
] |
[
"The problem becomes in finding a strata of rock/sediment to do so. Depending on how long ago it would have been, evidence might be eroded away by environmental processes. And then half life of the ionized / isotopes need to be considered.",
"Not an easy task, but plausible!"
] |
[
"Why do healing wounds itch?"
] |
[
false
] |
I recently had some minor surgery and the area is itching like crazy. I know this is generally a good sign, but why does it happen?
|
[
"There are several theories that explain why scabs itch. There are histamines in scabs that irritate the skin around the wound. Some doctors think this is the body’s way of getting rid of the scab which is no longer needed. When it itches, you scratch it and it is comes off. There is a flaw in this theory, because sometimes the scab itches before the wound is healed.",
"A second theory has to do with nerves in your skin that are cut when the skin is cut. When a wound is healing, the new skin is very thin, so the nerves are even more sensitive. As they are healing, their signals may be affected and the brain gets the wrong type of signal. The brain may interpret it as an itch and want to respond by scratching it.",
"Another theory is that as the wound heals, the scab pulls on the new skin, and that causes the area around the scab to itch.",
"Lastly, dryness could be a reason for itching. When the wound occurred, the skin, nerves, and oil glands were affected, and without oil, the skin would become dry.",
"Source:\n",
"http://anatomyinmotionapp.tumblr.com/post/41520642698/why-do-wounds-itch-when-they-are-healing"
] |
[
"There is a flaw in this theory, because sometimes the scab itches before the wound is healed.",
"Why is that a flaw? Perhaps that mechanism is good enough, better than the alternatives, or even beneficial."
] |
[
"Do scars itch for similar reasons? If so, can these reasons explain why the itching can come and go, even years later?"
] |
[
"How can the sum of infinite rational numbers be an irrational number?"
] |
[
false
] |
There are convergent series where every term is a rational number, and the sum (the limit of the sequence of partial sums) is an irrational number. An example is the serie formed by the sequence 1/n!, whose sum is e, an irrational number. On the other hand, the sum of two rational numers is always a rational number. How is this possible?
|
[
"This is actually how the reals are defined: the reals are defined by a collection of values such that for each value v some series of rationals that \"Cauchy converges\" (roughly, a series where all partial sums sufficiently far into the it are all arbitrarily closer to each other) cannot be separated from v.",
"For example, let's consider the series 3 + .1 + .04 + .001 + ... = 3.141... If we were to write out more digits, we'd get more digits of π. While for every rational r we can say that this number is some positive distance from r, we construct the reals so that there is now some value π we can associate with this series which we cannot say it is separated from. Of course, any real number (rational or irrational) can be written in as a series using its decimal expansion, so the same works for any other rational/irrational number.",
"Underlying all of this is the philosophical question of why we need the real numbers. Why aren't the rationals enough? As the Greeks found out long ago, even simple right triangles with length-1 legs cannot have the length of their hypotenuse expressed as a rational. Any rational number you pick is either too small or too big. We thus fill in the gap with real numbers: those values that can only be reached by taking smaller and smaller increments of the rationals infinite times. Now there are no more such holes where some value is somehow either too big or too small compared to all numbers. The reals are, in both a formal and intuitive sense, the completion of the rationals.",
"TL;DR: It's defined that way, because we want infinite sequences in the rationals that seem to approach a value (in the sense that the terms all bunch up in the end) to actually have a number to converge to. Those values they converge to are called the reals, which includes rationals and irrationals alike."
] |
[
"One way that's helpful to think of things: The rational numbers are the numbers that can be constructed through a finite sequence of arithmetic operations (+, -, *, /) on integers (or really, just from the number 1). Any rational number has some arithmetic sequence that constructs it. Anything that can't be constructed with such a finite sequence, is defined as an irrational number. In other words, irrational numbers are those whose arithmetic construction (if it exists)",
" must be infinite. ",
"So, irrational numbers are the numbers whose arithmetic description is necessarily infinite. And an infinite sum of rational numbers is an infinite arithmetic description. Now makes sense that some of those numbers are irrational, right?",
"tl;dr Infinity does strange things, and irrational numbers are one of those strange things.",
" It does always exist, but you should prove that, not assume it. You can construct an infinite arithmetic sequence for any irrational by using its decimal expansion."
] |
[
"It is not, in general, true that properties of the partial sums are also properties of the limit.",
"Consider 1+1+1+... : every partial sum is finite, but the limit is infinite.",
"Or, x",
" in [0,1] : this function is continuous for all n, but the limit as n->infinity is discontinuous."
] |
[
"Are our toes thumbs?"
] |
[
false
] |
Did our big toes evolve from thumbs into the toes we know today? If so, why? Did we sacrifice having awesome feet thumbs in order to walk upright?
|
[
"Our big toes and thumbs develop from the same genes, as shown in experimentation by taking these genes, modifying them to produce blue phosphorescent dye, and injecting them into fetal mice."
] |
[
"here is an article from wikipedia",
"\nFoot ",
"Main article: Foot",
"\nThe human foot evolved to act as a platform to support the entire weight of the body, rather than acting as a grasping structure, as it did in early hominids. Humans therefore have smaller toes than their bipedal ancestors. This includes a non-opposable hallux, which is relocated in line with the other toes. Moreover, humans have a foot arch rather than flat feet. When non-human hominids walk upright, weight is transmitted from the heel, along the outside of the foot, and then through the middle toes while a human foot transmits weight from the heel, along the outside of the foot, across the ball of the foot and finally through the big toe. This transference of weight contributes to energy conservation during locomotion."
] |
[
"I actually recall seeing someone whose thumb was amputated and replaced by their second toe. I'm on my phone right now, so I can't look it up, but it was an interesting story."
] |
[
"Do all planets with magnetic fields have iron cores, or can they have cobalt/nickel cores instead? If they can, how common are these planets?"
] |
[
false
] |
When talking about terrestrial planets, we seem to always assume an iron core to the planet - is this simply because Earth has an iron core, or are there other factors involved that mean planets always form around an iron core?
|
[
"No it does not have to be Iron. A good example would be Jupiter which is thought to have a core of hydrogen in a form called metallic hydrogen. The crazy pressure compresses the hydrogen gas to the point it can conduct. So providing a planet has an internal core made up of something conductive it is thought a magnetic field can be produced.",
" ",
"But wait this is not the end of the story! Venus has been observed to have an externally produced in the ionospheres interaction with solar winds. Venus however does not have a very strong magnetic field as a result of this."
] |
[
"No. Metallic hydrogen is either a solid or a liquid. It's no different than iron or mercury. It's not some new state of matter. ",
"However, it's a new state for hydrogen. Like diamond and graphite are states of carbon. "
] |
[
"Are the metallic versions of matter considered a phase like gaseous, liquid, frozen and plasma?"
] |
[
"AskScience AMA Series: We study Animal Weaponry, Fighting Behavior, and Narwhal Tusks, Ask Us Anything!"
] |
[
false
] |
Hi Reddit! We are two behavioral ecologists who study the evolution, diversity, and function of animal weapons! Weapons such as elk antlers, beetle horns, and crab claws are fascinating (and badass) structures that puzzle us because of their extravagant sizes, shapes and colors. In the broadest sense, we use a combination of observational, experimental, and theoretical studies, to understand everything and anything that relates to animal weapons. Although we both spend most of our time working with animals that are easy to catch and study, we recently studied one of the most charismatic animals in nature: the narwhal. Narwhal tusks are perhaps one of the most bizarre traits that exist today. Why bizarre? Well, the tusk is actually a modified tooth that can grow up to 8ft in length and protrudes from the head of male narwhals (females rarely have them). So, you can imagine how it would feel to walk about doing your daily business with a pool stick sticking off the top of your head. Despite being bizarre, little is known what the narwhal tusk is used for. Some researchers suggest that the tusk is a hunting tool, while others suggest it is a weapon used during fights. Dozens of hypothesis regarding the function of the tusk have been proposed. In our study, we examined the growth and variation of 245 male narwhal tusks to gain insights on this mysterious structure. We found that that the largest male narwhals have disproportionately long tusks, and that there was immense variation in tusk length within males. These trends align with what would be expected of a structure that has sexual functions, whether it be as a weapon use in male combat, or a signal used in female choice (or both). Furthermore, we know that male narwhals often have a lot of scars on their heads, which may have resulted from "tusking" behavior, where two male narwhals will display and cross their tusk. This study is just one example of how we both try to learn about animals and their unique weaponry. So, if you are interested in learning about animal weapons, fighting behavior, and narwhal tusks, join us at 14:00 PST (17:00 EST, 21:00 UTC), and will try to answer as many questions as possible! Usernames: zagraham0, palaoro-av
|
[
"Speaking of teeth: wild boar have tusks and domesticated pigs don't. If a domesticated pig turns feral, does it develop tusks or not? If so, does it do so immediately or does it take a few generations before it comes back?"
] |
[
"How does being raised in captivity effect size of animal weapons? Someone mentioned tusks in pigs, but without domestication is there any effect? Elephant tusks, narwhal or rhino horn?"
] |
[
"This is actually true. It is not necessarily adaptation, but it is what we call developmental plasticity. This plasticity is just a fancy word to say that some structure is a bit maleable during development, so it can change depending on the environment the animal is raised.",
"Check two-legged goats: ",
"https://www.newsflare.com/video/139466/animals/goat-born-with-only-two-legs",
" ",
"Their hips change because they don't have forelegs"
] |
[
"If looking into the night sky is the same as looking into the past (speed of light from star/galaxy etc. reaching earth), what if you shot a camera at the speed of light at the object you were looking at?"
] |
[
false
] |
Would you see a time lapse of the object as the camera got closer or would you just see the object in its present state or something else i cant think of? What would you see?
|
[
"Sorry good sir, I won't lose the sir stuff. I have way too much respect for you and for the answers you provide to this forum.",
"Then have some respect for the fact that ",
" Get me?"
] |
[
"This is not right. There's no physical way to talk about going at the speed of light for massive objects. You also don't take into account time dilation, which can let you perceive things at an arbitrarily high rate, depending on your speed."
] |
[
"Cameras can't go that fast."
] |
[
"If a choir of people sing a note off pitch (some above, some below) would you hear the \"average\" of their pitch as a whole?"
] |
[
false
] |
.
|
[
"Musician here. I expect this answer will be modded away because I'm not linking to anything (I'm in an old iPad) so grab it while you can.",
"What you would hear is the central note - the pitch around which the voices are singing - with a shimmering timbre called the chorus effect. This is due to interference between the sound waves produced by the singers. Not everyone is singing at the same pitch, and not everyone starts their note at the same time, so you end up with not-quite-identical versions of the same waveform sliding around each other. Some of these waves boost each other's peaks and deepen the troughs, but not as much as if they were pitched and timed identically. Others lag behind a little, causing near-identical repetitions at millisecond intervals which produce a sound called comb filtering, so called because if you look at the sound spectrum, the resultant peaks are spaced like the teeth of a comb. The net result of all these near-identical waves washing about is the glorious, shimmering chorus effect.",
"The effect is so valued that there are electronic simulations of the effect used in music production. For example, Andy Summers of The Police often put his guitar signal through a chorus effect pedal."
] |
[
"Wow. Really intuitive answer. Thanks so much !"
] |
[
"Gonna add to this guys answer with some physics. When the waves interact they interact in either a destructive or constructive way. So if the waves are out of phase, they can destroy each other. In phase, they increase amplitude."
] |
[
"How much of the Earth's water is floating around in the atmosphere?"
] |
[
false
] |
We all know around 70% of Earth is covered in water, but how much of Earth's water is up in the atmosphere?
|
[
"Only about 0.001% of all the Earth's water is in the atmosphere",
".",
"If all of the water in the atmosphere rained down at once, it would only cover the globe to a depth of 2.5 centimeters, about 1 inch."
] |
[
"To make sure there's no confusion, it 70% of the surface of the earth that is covered in water. The earth is not 70% water by mass (like the human body), it's much much less. It's certainly less than a percent. Some unverified web searches pull up 0.02%."
] |
[
"I didn't realise the percentage of earth's surface and water was that close to the percentage of the human body and water.",
"Edit: added the word surface for clarification and to avoid confusion. Thank you ramk13"
] |
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