title
list | over_18
list | post_content
stringlengths 0
9.37k
⌀ | C1
list | C2
list | C3
list |
|---|---|---|---|---|---|
[
"There was an article about Germany and its excess of power posted recently. Would the electrolysis of salt water followed by running it through a compressor and using the H2+O2 reaction to send it back to water be a viable power sink?"
] |
[
false
] | null |
[
"Overly complicated. Storage of excess power, if necessary, is best done by the old fashioned \"pump water uphill and store it there\" method."
] |
[
"There's no good way to store H2, and the combined efficiency of even the best experimental-scale electrolysis methods and fuel cells is still lower than existing industrial-scale methods of storing power, such as pumped hydroelectric storage."
] |
[
"But why not store it? The problems that Germany has at the moment isn't so much that they can't get rid of excess power, but that these peaks in wind production are causing grid stability problems due to insufficient infrastructure. That problem would be better solved by, say, building some HVDC links between Germany its neighbors."
] |
[
"The expansion of the universe is accelerating and eventually some galaxies will be receding from us (redshifted) at greater the speed of light, making them undetectable. If gravity interacts at the speed of light, does that mean gravity also be \"redshifted\" away from detection?"
] |
[
false
] |
i.e., will they no longer have gravitational influence on our locality? I guess eventually the measurable mass of the perceivable universe would be limited to your own galaxy. s/greater the/greater than the
|
[
"A clarification: plenty of galaxies are apparently receding faster than light, but we can still see them fine, and galaxies with apparent speeds far greater than c. The reason is basically that the light from such galaxies traversed smaller distances early on in their paths to us, and those distances have since expanded so that the recession speed of their parent galaxies looks like c.",
"Anyway - the gravitational field itself doesn't really propagate at c, but changes do. This is why so-called superhorizon modes - perturbations in the density field left over from inflation that are bigger than the present size of our observable Universe - can still exist and gravitate. But if a galaxy is beyond the visible bit of our Universe and you start to shake it around, we wouldn't feel it because the gravitational radiation emitted wouldn't be able to reach us. Not that it matters all that much, though, we don't really feel the gravity from any individual galaxies except those ",
" close to us - what really matters is the cosmic density on the whole, and that's almost certainly the same both here and in parts of the Universe far removed from ours."
] |
[
"Oddly enough, some asked a version of this question as a top level question about two hours before you did:",
"http://www.reddit.com/r/askscience/comments/htyqw/is_it_possible_that_there_are_areas_of_the/"
] |
[
"Oddly enough, some asked a version of this question as a top level question about two hours before you did:",
"http://www.reddit.com/r/askscience/comments/htyqw/is_it_possible_that_there_are_areas_of_the/"
] |
[
"Research is suggesting that hormones in the womb are a major factor in determining a person's sexuality. Has there been any research on whether the hormones and hormone analogs we use in modern industrial society are influencing this process?"
] |
[
false
] | null |
[
"Birth control pills have had an impact on amphibians. A decent amount of the hormones in the pills are not absorbed into our bodies and instead make it into waterways. ",
"Podcast about birth control and amphibians",
"Article about a research paper on the same topic"
] |
[
"No he’s upset about a herbicide called atrazine, citing a fraudulent study by Tyrone Hayes."
] |
[
"So that's the context for that Alex Jones gay frog rant, I feel enlightened now."
] |
[
"Why does my skin do this when i drink alcohol?"
] |
[
false
] | null |
[
"Hives. Happened to me once, except all over my body and it lasted for two weeks. Worst two weeks of my life."
] |
[
"\"Itch\" does not begin to describe how hives feel. They drive you to madness, for reals. So if you don't itch, then I guess it's not hives."
] |
[
"\"Itch\" does not begin to describe how hives feel. They drive you to madness, for reals. So if you don't itch, then I guess it's not hives."
] |
[
"Can our ears/brain hearing system identify only left/right source of sound, or can we also locate the height (below/above) our heads and front/back axis?"
] |
[
false
] |
When I close my eyes and try to identify sound source location I seem to be able to deduce a direction on all axes, not just left/right axis. Is this real or an illusion? If real, how can this be done with only two ears? If an illusion, please explain what exactly we're experiencing.
|
[
"It is not an illusion. The pinna of the ear affects the perception of sound from different angles and permits localization. This can be demonstrated experimentally with prosthetic pinnas that disorient sound perception. Over time, these new pinnas can be adapted to, and sounds are able to be localized again.",
"edit: plural should probably be pinnae"
] |
[
"To expand on this, some animals, like owls, have ears positioned at slightly different height. This allows them to predict the vertical direction of a sound even more accurately."
] |
[
"Firstly, this type of sound illusion is very difficult to create at all with loudspeakers, most of the time it is intended for headphones.",
"This can be done in one of two ways: One is to record the sound source using a dummy head. A dummy head is essentially a head with artificial pinnae, and omnidirectional microphones where the eardrums would be. Sound sources picked up by the microphones are effectively filtered by the dummy head's head-related transfer function (HRTF) and when played back to a listener over headphones will appear to be in 3D space around the listener. (",
"http://en.wikipedia.org/wiki/Binaural_recording",
")",
"The second is by taking already-recorded sound, and processing it through an artificial head-related transfer function algorithm. This is how 3D audio is usually done in video game engines, for example. A filter is applied based on where the sound source should originate from, and when heard by a listener using headphones the effect should be relatively convincing. However, since HRTFs are unique, it likely wouldn't be real enough to fool an astute listener.",
"There are free databases of HRTFs available from research universities, one notable one here: ",
"http://interface.cipic.ucdavis.edu/sound/hrtf.html"
] |
[
"Why do children with a higher bmi start puberty earlier?"
] |
[
false
] |
I read that obese children, or children with a higher bmi start puberty earlier, and children who are underweight or have a lower bmi start later. Why exactly is this?
|
[
"Quick answer: additional fatty tissue can supply increased lipid levels, including cholesterol, which is the basis for sexual hormones synthesis. Moreover, fat tissue can itself synthesize some feminine hormone lookalikes that can trigger early puberty (this is also why obesity is a factor influencing male hormones)."
] |
[
"We understand that, but the endocrine system which evolved before Cheet-os doesn't."
] |
[
"Obesity is not an indicator that a child is well fed, it’s a sign the child is over fed. And many, probably most, obese children are malnourished because they’re not eating nutrient dense food. So they’re getting calories, but not vitamins and minerals."
] |
[
"In a timeline from the Big Bang to the present when did the heavier elements start appearing?"
] |
[
false
] |
ok Long Question: when did the Heavier elements start being made? I know that a lot of the heavier Elements are made during the collapse of stars seeing as these elements seem to be in most biological systems it seems that they may be required for life to arise within a system. so we calculate when these elements start being made when would they would have been around in sufficient quantities and we get the start of a timeline when life in the univers could have started. Right?
|
[
"Note: In astronomy, metal just means any element heavier then helium.",
"Well, many of the common metals (like iron, carbon, and oxygen) are actually made in stellar nucleosynthesis, not supernovae nucleosynthesis, but this is not important. Early stars are thought to have first appeared approximately 200 million years after the big bang. These stars are hypothesised to be population III stars, which contain virtually no metals, and lived very short lives (only a few million years). When these stars died, the metals they produced during their lives and in their supernovae ended up in population II stars, which also contained very little metals (not enough to support life as we know it). Again many of these stars died quickly and formed population I stars, like our sun. Population I stars contain enough metals for life to develop, and the first of these stars appeared about 1.5 billion years after the big bang (roughly).",
"I hope this answers your question, feel free to ask for any clarifications."
] |
[
"It's just convention, because its easier to say \"metal\" then \"elements that are heavier then helium\", and the chemical properties of the elements don't affect astronomers, for example stars are made of plasma. Also most of these elements are metals anyway.",
"Edit: Words"
] |
[
"The big bang actually. Hydrogen and helium were the two main elements produced in it, where as heavier elements come from stars (some lithium and beryllium also come from the big bang, but they aren't really mentioned because for the most part they don't fuse). Basically, metals are elements formed after the big bang in astrophysics."
] |
[
"Do plants prepare for the winter? What do they do? And what if the weather is totally different from the norm?"
] |
[
false
] | null |
[
"They essentially hibernate much like a bear! Actually it would in the case of plants be called dormancy. \nWhen winter comes, the woody parts of trees and shrubs can survive the cold. The above ground parts of herbaceous plants (leaves, stalks) will die off, but underground parts (roots, bulbs) will remain alive. In the winter, plants rest and live off stored food until spring.\nDuring summer days, leaves make more glucose than the plant needs for energy and growth. The excess is turned into starch and stored until needed. As the daylight gets shorter in the autumn, plants begin to shut down their food production.\nMany changes occur in the leaves of deciduous trees before they finally fall from the branch. The leaf has actually been preparing for autumn since it started to grow in the spring. At the base of each leaf is a special layer of cells called the \"abscission\" or separation layer. All summer, small tubes which pass through this layer carry water into the leaf, and food back to the tree. In the fall, the cells of the abscission layer begin to swell and form a cork-like material, reducing and finally cutting off flow between leaf and tree. Glucose and waste products are trapped in the leaf. Without fresh water to renew it, chlorophyll begins to disappear.\nWhat is the process of dormancy?\nDuring the active months of growth (April-August), each plant is using the photosynthetic process to change carbon dioxide, water, and certain inorganic salts into carbohydrates. These are used by the plant or stored for use during the winter. At the end of the season, plants begin to move these sugars and carbohydrates from the leaves down in the roots to nourish the plant for the winter months. Plants are no longer growing.",
"\nEach plant is transformed differently in the fall, but ultimately dormancy is the way plants conserve energy by using the stored sugars and carbohydrates they produced during the growing season to survive the winter.\nAs plants grow, they are affected by temperature and sunlight. These two forces act as signals to plants that winter is coming. As the day length shortens, plants begin to slow growth and the dormancy process begins in each plant. In spring, shorter nights encourage plants to actively grow. However, in autumn, longer periods of darkness (August-October) and typically cooler temperatures are obvious indicators to plants that winter is around the corner.\n",
"https://dyckarboretum.org/why-do-plants-go-dormant-in-the-winter/",
"https://www.sciencemadesimple.com/plants-in-winter.html#:~:text=When%20winter%20comes%2C%20the%20woody,off%20stored%20food%20until%20spring",
"."
] |
[
"Great answer! Is there a limit to how much it can store? Let’s say we had a freak year where it was mild summer temps all year round. The plant stored up starch but winter never comes. Can it get rid of that waste? And if so, how?"
] |
[
"It grows more. One of the ways that we can estimate the weather over centuries is by looking at the tree ring growth of very old trees like redwoods. The tree grows outward at the trunk every year. The period of dormancy versus the period of growth is what makes the rings of the tree. if a tree falls or is cut, you can look at the rings and count them to see how old the tree is. You can also look at ",
"historically harvested timber",
" for growth rings. ",
"In years where there was better growing conditions, the growth rings will be thicker. In bad years they will be thinner. For example, we can look at trees that are older than the volcanic eruption of Krakatoa and see that during the years immediately following the eruption, the growth rings are narrower. Scientists attribute this to particulate matter thrown into the upper atmosphere by the volcano that blocked sunlight and produced cooler years.",
"Tree-ring evidence for climactically effective volcanic eruptions"
] |
[
"Are there done any clear studies for mask's efficacy?"
] |
[
false
] | null |
[
"I also clicked on another study, which pretty much implied the results were inconclusive ",
"https://pubmed.ncbi.nlm.nih.gov/25336079/",
"\nIt makes me think that whoever gathered those studies did not even go any of those themselves, but just gathered links for the sake of it to support their opinion, figuring nobody else would bother to go through all those studies and just be awed by the whole amount of links thinking there's so much evidence, this opinion must be correct. How can I trust whatever their opinion is?",
"And I have already spent quite some time on trying to figure it out, how can one expect any layman to figure something like this out, without giving a clear cut study like this?"
] |
[
"I also clicked on another study, which pretty much implied the results were inconclusive ",
"https://pubmed.ncbi.nlm.nih.gov/25336079/",
"\nIt makes me think that whoever gathered those studies did not even go any of those themselves, but just gathered links for the sake of it to support their opinion, figuring nobody else would bother to go through all those studies and just be awed by the whole amount of links thinking there's so much evidence, this opinion must be correct. How can I trust whatever their opinion is?",
"And I have already spent quite some time on trying to figure it out, how can one expect any layman to figure something like this out, without giving a clear cut study like this?"
] |
[
"Hi Iayork, I did spend more than hour googling and everything, I even cited links I found googling for it, I did not find answer to this specific question unfortunately. I'm confused, I haven't found a single study that would look like that and make sure other factors wouldn't influence the results."
] |
[
"How does friction work if objects never actually touch?"
] |
[
false
] | null |
[
"Also as a pedantic point: the whole \"they never actually touch\" thing is kind of silly to claim. The quantum world behaves differently than the macroscopic world. No electrons ever \"touch\" in the quantum world. It's an entirely trivial statement to make. They're repelled by forces and perhaps Pauli-exclusion pressure before they ever \"touch.\" So as long as we modify to a very reasonable definition of \"touching\" as \"close enough for electrons to interact significantly\" then we're fine."
] |
[
"On the molecular level, friction is not a case of two solid surface mechanically bumping into each other. Rather, friction is caused by attractive electromagnetic forces between the atoms on the surfaces (mostly Van der Waals forces) due to permanent or induced electric dipoles in the molecules. "
] |
[
"At the plane of contact...",
"At the atomic level, there is no plane of contact. Atoms are not hard spheres with well defined edges that can touch. The outer parts of the atoms (the electrons) are quantum, extended, wave-like/cloud-like probabilistic wavefunctions that interact via the electromagnetic field.",
"this lack of flatness implies there will be small protruding parts of object B physically in the way of protruding parts of object A.",
"Actually, rougher surfaces often have ",
" friction because there are less points on both surfaces that are close enough to electromagnetically attract. In fact, if you get two surfaces of the same solid material very smooth, (and prevent impurities), you get effectively infinite friction. It's called ",
"cold welding",
". Friction is complicated and it depends on the materials involved and the amount of roughness."
] |
[
"Does potassium-argon dating work on organic fossils, or just rocks and minerals?"
] |
[
false
] |
For instance, I know Carbon-14 dating wont work on volcanic rocks and minerals because only organic matter contains carbon.
|
[
"You cannot use K-Ar dating to directly determine the age of a fossil but you can use it to determine the age of layers of volcanic material around the fossil. ",
"The main principle with K-Ar dating is that Ar is a gas so if you have a liquid magma or lava any argon present will just leave before the lava or magma cools and forms crystals. This means that at the time of crystallization there will be no argon in the crystals. Potassium is very common and will be present, some of the potassium will be radioactive and will disintegrate into argon. The new radiogenic argon will be trapped within the solid crystal structure.",
"The ratio of argon and potassium can be determined and used to calculate the time the crystal formed."
] |
[
"Very nice explanation. The initial amount of potassium doesn't matter, because the age is determined by the ratio, right?"
] |
[
"Thank you. Yes there just needs to be a measurable amount of potassium, the ratio is what matters."
] |
[
"Is it possible that all the information received from our eyes is stored in a part of our brain?"
] |
[
false
] | null |
[
"There are some people (after something of a worldwide search, all sources I've found identify 4) who remember every detail of everything they've ever done. There's a study currently looking at them. Here's some background: ",
"http://blogs.static.mentalfloss.com/blogs/archives/34971.html",
"http://www.usatoday.com/news/health/2009-01-27-mri-super-memory_N.htm"
] |
[
"From a purely evolutionary point of view, no, such storage doesn't exist. Apparently, if it exists, it is not doing much good as we can't recall information from the storage. And from an evolutionary standpoint a useless information storage is heavy to carry around, unnecessarily consumes energy, and requires nutrients to build. So it will not be realized in a species such as ours."
] |
[
"these people typically have other brain functions that are sacrificed as a result of their memory"
] |
[
"Do nerves grow when a person gets morbidly obese or do they stretch?"
] |
[
false
] |
My question is that when a person gets incredibly obese (like this ) does their nervous system grow with their increasing size, or does everything just stretch. Does this effect feeling in the hands and feet? I ask because under my knowledge your nerves can't regenerate, so I would assume they can't grow. To follow that logic further, when a persons size increases that much how does the rest of the body account for getting signals/blood/nutrients out to the extremities?
|
[
"When your body grows (either by cells growing in size or increasing in number), your cells release signals that act on other cells which are nearby. These signals, called ",
", cause the growth of structures such as blood vessels and nerves in the direction of the signal. This is the basis for growth of these systems in embryos. An important set of growth factors for neurons (nerve cells) is the ",
"nerve growth factors",
".",
"This also occurs in the case of normal growth and development in children; I see no reason why the growth of a person due to obesity wouldn't cause the same process.",
"I hope this helps, I'm a med student so can maybe answer some of your questions, but I'm sure someone more qualified could do better."
] |
[
"The specific reason this has been a significant hurdle is because of a process called glial scarring.",
"Glia are the helper cells of the CNS (Brain and spinal cord) and work on the CNS to help protect it after trauma. Like the outside of your body, after certain types of trauma, the healing process leaves a glial scar. This scar basically makes it impossible for the nerves to heal correctly and creates disconnection. However, there has been issues with the Blood-brain barrier being compromised without the scarring."
] |
[
"Hope this isn't a silly question. Why can we not make use of this to re-grow spinal Cords?"
] |
[
"Could somebody explain conscience through evolution?"
] |
[
false
] |
[deleted]
|
[
"There are two different mechanisms to explain altruism. The one you mentioned is ",
"Group selection",
". The other theory is ",
"Kin Selection",
" and has more evidence supporting itself than Group Selection.",
"Kin Selection simply states that: Because our relatives share our genes, any trait that would greatly help your relatives at a small cost to ourselves will evolve. Another way to say it is by helping out our relatives we are also helping out our genes that we share with our relatives. However, kin selection explains why we are altruistic to close relatives, but doesn't explain why we would be nice to a complete stranger."
] |
[
"There are two different mechanisms to explain altruism. The one you mentioned is ",
"Group selection",
". The other theory is ",
"Kin Selection",
" and has more evidence supporting itself than Group Selection.",
"Kin Selection simply states that: Because our relatives share our genes, any trait that would greatly help your relatives at a small cost to ourselves will evolve. Another way to say it is by helping out our relatives we are also helping out our genes that we share with our relatives. However, kin selection explains why we are altruistic to close relatives, but doesn't explain why we would be nice to a complete stranger."
] |
[
"And kin selection can evolve to extremes; take ant colonies, for instance. There is one \"queen\" who is the only one who reproduces. Everyone lives and dies to protect her. "
] |
[
"Why is iridium so rare on earth yet so abundant in asteroids?"
] |
[
false
] |
Every time I hear someone talk about impact events they always mention the tell-tale iridium left behind by the impacting object. Why is it that iridium is x1000 times more common in space than it is on earth?
|
[
"So it's a really ",
" metal, and it's a metal that likes to be bound up with iron, so what iridium is on Earth is likely to be in the core rather than the crust. (",
"wiki",
")"
] |
[
"Density isn't as important as geochemical behavior. Ir is a siderophile (iron loving) metal and prefers to dissolve in metal rather than bond with O or S.",
"Regarding the original question. Ir does not have very high absolute abundances (it's concentration is about 2 ppm in iron meteorites and 0.5 ppm in chondrites), but these concentrations are very high compared with the crustal abundance of about 0.0004 ppm."
] |
[
"Shavera is right - and to complete his argument, an asteroid will show higher grades of Ir than earth crustal rocks because the earth has differentiated and the asteroid has not. Differentiation is similar to an oil/water mixture separating, the lighter material floats on top of the denser stuff. Earths core should be enriched in Ir relatively to the asteroid."
] |
[
"How can someone with healthy body (or at least fit body), suddenly collapse after having a surgery? (story inside, please help me)"
] |
[
false
] | null |
[
"I'm so sorry to hear about your father-in-law. Unfortunately this is not a situation we can address, as there are just too many factors that go into someone's medical history. We'd be speculating, and we don't want to do that when someone's health is involved. We wish him all the best in his recovery. Please take care!"
] |
[
"He passed away yesterday. And thank you for the kind words"
] |
[
"Oh no. Please accept the mod team's condolences. We are so very sorry for your loss. "
] |
[
"Can kitchen knives with single-bevel designs really achieve stronger, sharper and thinner edges compared to knives with double-bevel designs?"
] |
[
false
] |
Note: I'm simplifying. German and french knives are "flat ground" with a symmetrical double bevel edge, most japanese knives are "chisel ground" with a single bevel edge instead. Knife sellers claim that chisel ground knives can achieve sharper, thinner and stronger edges compared to flat ground knives and browsing forums that seems to be the general opinion. Given the alloy used in the blade is constant, would you say the claim holds? Edit: updated picture.
|
[
"They are absolutely sharper. It’s a steeper angle at the edge of the blade. ",
"That said, they’re not for everything. You don’t always want the sharpest edge possible, as tougher things will dull them much faster. You usually see a single bevel used for chopping vegetables or sushi. ",
"A standard bevel may not get as sharp, but will keep its edge longer when cutting tough things like meat and root vegetables. "
] |
[
"Asymmetric knives are particularly useful in applications for cutting thin slices.",
"It isn't that they're actually sharper. On an equal included angle basis, an asymmetric grind is not sharper than a symmetric ground knife.",
"When cutting thin slices, the pressure on the flanks of your edge is not symmetrical. The material on the thin slice side of the knife (I'll call it the freed material) peels away from the knife when it is cut. ",
"Being thin, the freed material bends easily compared to the material on the opposite side which is backed by lots of uninterrupted material.",
"You will see asymmetrical blades in common thin cutting applications like chisels, carpentry planing blades, sushi knives. Basically all metal working and general machining applies asymmetric blades in that their rake angle \"attacks\" into the material while the relief side (trailing side) is nearly parallel to the material left behind. You rarely see symmetric cutting in spinning cutting tools because they cut thin chips.",
"If you use a symmetric knife while cutting thin cucumber slices, you'll find that the blade tends to steer out of your cut if you push your cut down the centerline of the blade. To achieve straight non steered cuts, you'll find that you have to angle the knife until the relief side of the edge is basically parallel to the material on the unfreed side. You will basically be cutting with a blade configuration like an asymmetric blade.",
"Getting more controllable cuts gives the general impression of sharpness even if the actual severing pressure is the same."
] |
[
"Unless the double bevel knives have the same angle as the single bevel. An isosceles triangle instead of a right triangle. "
] |
[
"Do butterflies recognize caterpillars as conspecifics?"
] |
[
false
] | null |
[
"This would be hard to test, considering that butterflies don't really have a reason to interact with caterpillars, with the exception of some butterflies that ",
"guard their young",
". Some other holometabolous insects do interact significantly with their young (bees, ants, many wasps, Bess beetles, etc) and while conspecific may be a bit abstract for those insects, they at least perceive the young as important to care for, and different from other species."
] |
[
"Yes! There are ",
"caterpillars",
" that smell like ant larvae to trick ants into taking care of them. In addition, certain kinds of ",
"bees",
" and and ants (",
"1",
" ",
"2",
") infiltrate the nests of other, often closely related species, where they lay their eggs to be cared for, with or without killing the host queen."
] |
[
"Can any of the insect that treat their larval stage as a significantly different relation from other non-related larva be tricked? ",
"I'm thinking like birds that lay eggs in other species nests to have them raise their young. And if so, do the trick young look similar to the true young, or is there just some non-specific imperative to care for any young within the nest/hive regardless of appearance (or pheromone or however the bees/ants/etc might identify their offspring)?"
] |
[
"What makes electomagnetic waves able to propagate without a medium and other not other waves??"
] |
[
false
] | null |
[
"You could say that electromagnetic (EM) waves ",
" propagate in a medium, if you take that medium to be the electromagnetic field. In this picture you can think of an EM wave (or a group of photons if you prefer) as an ",
" in the electromagnetic field that moves from one region of space to another.",
"In reality the way EM waves propagate is not all that different from how say a water wave behaves. Imagine you are sitting on the edge of a lake on a windless day and the water appears completely calm. If you throw a pebble into this lake, you will ",
"create ripples that will spread outwards",
". In other words, you are creating an excitation where water is both the medium through which the ripples travel and it is also the stuff that is jiggling up and down at every point as each ripple passes.",
"Deep down EM waves work pretty much exactly in the same way. For this analogy to click, the trick is to realize that no matter where you are in the universe, you are always surrounded by the electromagnetic field. This field is as big as the universe, it exists wherever space itself exists. Even in the depths of outer space, where at first it may seem like there is nothing around, if look more closely you will see that the EM field is still there and produces measurable effects (e.g. see the ",
"Casimir Effect",
").",
"Now just like the surface of that lake, the EM field normally looks still (in the sense that you won't detect any photons), but that doesn't mean it's not there. In fact you can still measure it and you can still interact with it. Just like you can throw a pebble to create a water wave, you can add energy into the EM field (e.g. by firing up a flashlight) and you will see this excitation spread outwards in the EM fields like the ripples in the lake."
] |
[
"Yes. The aether was thought of as a physical thing, like water, that jiggled to makes waves and otherwise was still. The electromagnetic field isn't physical in that sense, just like the temperature field of a room isn't something you can grab and jiggle. There was never any real explanation as to why it was physical, but never interacted with anything which was unsettling. ",
"But really though, the thing that killed it was special relativity. The aether theory meant you could measure light moving at different speeds in the same medium. Think walking along with a wave, you measure 0 speed but running towards the source it moves even faster than usual. We looked for that and didn't see it, so we ruled out aether. The electromagnetic field idea is constructed under special relativity, so you always measure light moving at one speed in a medium, just like we observe.",
"Adding a little addendum;\nNot only is the EM field relativistic, but it's also easy to quantise properly because of this, and so can be included into the Standard Model. When you quantise the EM field you get the photon, in the same way quantising the Higgs field gives you the famous Higgs boson. This wouldn't be possible with aether as quantum field theories have to be Lorentz invariant (at least up to energy scales we've currently measured)"
] |
[
"Yes. The aether was thought of as a physical thing, like water, that jiggled to makes waves and otherwise was still. The electromagnetic field isn't physical in that sense, just like the temperature field of a room isn't something you can grab and jiggle. There was never any real explanation as to why it was physical, but never interacted with anything which was unsettling. ",
"But really though, the thing that killed it was special relativity. The aether theory meant you could measure light moving at different speeds in the same medium. Think walking along with a wave, you measure 0 speed but running towards the source it moves even faster than usual. We looked for that and didn't see it, so we ruled out aether. The electromagnetic field idea is constructed under special relativity, so you always measure light moving at one speed in a medium, just like we observe.",
"Adding a little addendum;\nNot only is the EM field relativistic, but it's also easy to quantise properly because of this, and so can be included into the Standard Model. When you quantise the EM field you get the photon, in the same way quantising the Higgs field gives you the famous Higgs boson. This wouldn't be possible with aether as quantum field theories have to be Lorentz invariant (at least up to energy scales we've currently measured)"
] |
[
"How can a body accept an organ from a different person if they have different DNA?"
] |
[
false
] |
[deleted]
|
[
"Immune recognition of self vs non-self is a pretty complicated thing. Different organs and different protocols require different degrees of matching. For solid organs, you can get by with matching by the major blood ground antigen. For bone marrow, you need more.",
"Invariably, left untreated (barring autotransplantation or a kidney from an identical twin or something), there is always some rejection as there is always some degree of mismatch. Managing this is a key technique in transplant medicine. The general technique is to turn down the immune system. This starts during the operation, usually with big-gun anti lymphocyte (a type of white blood cell, consisting of T and B cells) medicines. The mainstays of solid organ immune suppression is steroids and other anti-T-lymphocyte drugs like cyclosporine (which revolutionized transplant medicine), or other newer drugs. When you turn down T-cells, you become more prone for certain infections, so post-transplant patients are often given antibiotics and antivirals to prevent these.",
"All organ transplant patients have regular assessments of rejection. In bone marrow, this may be monitoring blood counts and graft-versus host disease. In lungs, CT and bronchoscopy are used as well as pulmonary function testing. Liver and kidney are usually tested by serum chemistries and biopsies if necessary. In the heart, they may do endomyocardial biopsies and catheterizations. Certain things like infection or alterations of medicine may lead to a flare of rejection. In these circumstances, the usual action is to turn up the immune suppression."
] |
[
"Only genes that correlate to proteins expressed on the surface of cells matter for immune detection and \"acceptance\", and even then, not all of them matter. Read ",
"here",
".",
"The easiest thing to compare it to is blood type. When you donate blood, you only have to match the ABO protein set and the Rh protein set. Organs, since they're permanent, have to match a larger variety of \"types\"."
] |
[
"In general, the more genetically similar a donor and a recipient are, the better, because it means most of the recipient's surface proteins will share a lot of amino acid sequences with the donors, and reduces the chance of the recipients immune system recognising the donor cell surface antigens as \"foreign\". This is why immediate family are usually preferred donors for kidney/liver transplants. Certain antigens are more immunogenic than others, and so for some operations, for example, HSC (\"bone marrow\") transplants, matching ",
"HLA alleles",
" is usually the deciding factor for transplant success. It's so important for HSC transplants in fact, that it's preferable to use bone marrow from an unrelated person with matching HLA alleles than it is with an HLA mismatched sibling.\nUnless the donor and recipient are genetically identical though (for example, identical twins), rejection will happen eventually and so recipients need lifelong treatment with immunosuppressants (typically ciclosporin)."
] |
[
"What goes on in squirrel nests?"
] |
[
false
] |
A bit of context. I live in Eastern Canada, and grey squirrels ( ) are everywhere. They build , up in the canopy of trees. Naïvely, I accepted what I was told as a child, namely that those are where squirrels retire to hibernate for the winter... But here's the thing: not only do the nests seem a bit too small and flimsy to shelter the squirrels in any meaningful way in -30°C weather and winter winds, but the critters are scampering outside . So they manifestly don't hibernate. What exactly do squirrels actually do with those structures?
|
[
"Sleep and raise their young.",
"http://www.birdfeeders.com/blog/backyard-battles/squirrel-nests/"
] |
[
"Thank you both. I didn't know I had this question until it was asked."
] |
[
"Thanks for the link to that article.",
"I've watch those nests sway back an forth a good 10 feet in violent wind storm. Was fascinated that they stayed in place. That poor squirrel probably lost its lunch after that ride."
] |
[
"My Cell Bio professor and I were discussing whether or not there were viral species with both DNA and RNA. Are there any known species that have both DNA and RNA?"
] |
[
false
] |
I seem to remember reading an article in either Virology Journal or in Microbiology that there had been a handful of species discovered. Any help would be much appreciated. Edit: Thanks for the fast response guys. I've got to say this will definitely prolong our discussion quite a bit.
|
[
"Did you plan that timing?",
"This",
" post on ",
"this",
" paper."
] |
[
"Even if this paper is accurate, I think the answer is still \"no.\" The virus the authors found is a DNA virus that encodes a gene normally found exclusively in RNA viruses (but it's encoded as DNA in this DNA virus). So while it may be evidence of an evolutionary transition between RNA and DNA viruses, I don't think it's evidence for a virus with both an RNA and DNA genome."
] |
[
"no it isnt, the sugar backbone (ribose vs deoxyribose) and bases (ACTG in DNA vs ACGU in RNA) are different"
] |
[
"Please explain chromosomal polymorphism to me"
] |
[
false
] |
First off, I'm an atheist, and I accept evolution as the best explanation for the biodiversity on this planet. The reason for this statement is because I predict some people will see this as an attempt at trolling. "Macroevolution is impossible, microevolution is irrelevant," that sort of thing. Okay, I'm stuck on one thing. Horse + donkey = mule. My understanding is that mules are sterile because horses and donkeys have differing numbers of chromosomes (32 and 31 pairs, respectively). Similarly, horses and zebras can reproduce (sterile offspring), despite zebras having considerably more chromosome pairs. Most surprisingly, the Przewalski's Horse can interbreed with the domestic horse and produce semi-fertile hybrids. . The obvious first question is, how can this happen? My understanding is that sexual reproduction requires the "matching" of chromosome pairs to form the DNA of the offspring. If one side has many more than the other, what do they "match" against? I see some help in the wikipedia entry on , but I really don't understand how this is even possible. Please note, I don't doubt that as a matter of fact. Horses can breed with donkeys, never a miscommunication. My question is it happens at a genetic level. The reason I want to know is because I think it's important for my understanding of speciation. , it's hard to imagine how speciation can occur because it would be an all or nothing process. Example: A population of Species A exists. A newly conceived individual, due to random mutation, is now an entirely new species, Species B. But this is the end of Species B because this new individual has no one to mate successfully with. This situation does not describe reality (see Przewalski's horse, and I'm sure many other examples exist), of course, but it illustrates the importance of chromsomal polymorphism to me. , it seems like it would happen like this: Species A exists. Newly conceived individual has slightly more or less chromosome pairs, slightly more or less genetic information, whatever, due to genetic mutation. The difference is slight enough that this new individual can still breed with the rest of Species A. Offspring of this new individual might be sterile, but could be fertile, and might pass on the increased/decreased genetic information. Fast forward ten million years and the ancestors of that first abberant individual now constitute an entirely new Species B that can no longer interbreed with Species A. - I'd like to understand chromosomal polymorphism so I can explain speciation, occurs.
|
[
"To produce viable offspring, they typically need to inherit 2 copies of the genome, one full copy from each parent. In a cross between e.g. horse and zebra, the offspring gets a full complement of genes from each parent, it's just that the two parental genomes are divided into different numbers of chromosomes. The hybrid offspring will have a chromosome count intermediate between horse and zebra, but basically a normal complement of genes.",
"As for fertility of these hybrids, well these creatures are going to produce a lot of gametes with wacky numbers of chromosomes, but with luck you can get a few viable sperm out. Note that in the link you provide, the only horse hybrid that is described as being at all fertile is the male from the ",
" cross, which can evidently make enough decent sperm to fertilise a female horse."
] |
[
"Chromosomal Polymorphism is big trouble, you are right. But it is ",
". It creates confusing crap like ",
"Robertsonian translocations.",
"^ and reduces viability of progeny, however.",
"Speciation occurs with these translocations co-occuring and then fixing in the population so that they are no longer a problem. The species barrier is largely due to differences at the level of the gene through several well-described mechanisms:",
" ",
"As it turns out, there is a constantly evolving game up catch-me-if-you-can between sperm and egg and sometimes male genital and female genital. They \"Red Queen\" just like hosts and pathogens or predator and prey. ",
" For ridiculous \"Red Queen\" sexual examples, google \"duck penises\".",
"Species evolving separately accumulate genetic mutations that are neutral or nearl-neutral in their own genetic background. However, that doesn't make the genotype neutral among hybrids or the progeny of hybrids. This is well-studied in ",
", when the species both have 4 chromosomes. ",
"This is the model.",
" It is very complicated, but well-documented even in the absence of mechanistic explanations.",
"mechanisms I don't know much about.",
" on Robertsonian Translocations**",
"Here is a picture of the ways it can screw up meiosis.",
" It is important to note that one of three possible meioses in the example produces 4 top-quality gametes that will give rise to a healthy adult.",
"The best-studied of these RTs is a fusion between chr14 and chr21. In the figure above, group A produce two nonviables and two fetuses with Down's syndrome. Group B are nonviable. ",
". The progeny from C that inherit a Robertsonian have the same risk as above. The human-specific fusion that separates it from the apes is probably derived from ",
"something like a Robertsonian translocation",
". It's kind of a given that it was carried in the population as a polymorphism for awhile."
] |
[
"I can answer one more question that I mistakenly treated as implicit because I've studied genetics so long.",
"If one side has many more than the other, what do they \"match\" against?",
"They \"match\" by homologous recombination during meiosis",
" The DNA base pairs on one chromosome match to the base pairs on the homologous chromosome and vice versa. This is why crossing over happens.",
"In the RTs I talk about above, the RT chromosome matches against 2 normal chromosomes. They \"match\" fine. However, this becomes problematic during metaphase of meiosis I. Normal chromosome pairs can only form 1 structure at the metaphase plate. RTs can form 3. 2 out of 3 give rice to aneuploid (chromosomally altered) gametes. ",
" the process by which sperm and egg are made."
] |
[
"What's going on with technetium?"
] |
[
false
] |
Technetium, with 43 protons/electrons, is the first element in the periodic table with stable isotopes. But it's surrounded by perfectly normal elements, the next smallest completely unstable element is promethium, which is a lanthanide, and radioactive elements don't start coming with any frequency until polonium, which has nearly twice as many protons/electrons as technetium. What gives?
|
[
"This is actually a physics question. There a multiple things happening here. First, there are an odd number of protons. Protons/neutrons like to pair up. This is the pairing energy term in the ",
"semi-empirical mass formula",
". Now that does not explain everything. ",
"Part of the answer lies in the idea that it lies far from the ",
"nuclear magic numbers",
". Magic numbers impart additional binding that helps hold nuclei together. Now there is one more piece. Technetium is special in that it lies next to two elements that are unusually very stable (Mo and Ru). Because if this, nuclei of Tc will decay to the most stable configurations. This means they will beta decay to either Ru or Mo. ",
"It is important to remember what stable means. In many cases it means the isotope will not decay for a very long time. Many \"stable\" isotopes actually decay. "
] |
[
"It is important to remember what stable means. In many cases it means the isotope will not decay for a very long time. Many \"stable\" isotopes actually decay. ",
"If you want to go even deeper, what I find fascinating is that you could even say that the only ",
" stable nucleus is Ni-62. The reason is that as you know when you look at a chart of the ",
"binding energy per nucleon",
", Ni-62 sits at the very top, meaning that you could always release energy by allowing other nuclei to decay and fuse into Ni-62. But of course, in reality is point is almost meaningless since it would take a really, really, really long time for this process to occur. In ",
"a beautiful paper from a few decades ago",
", Freeman Dyson estimated that for all the nuclei in the universe to undergo such a process would take a whopping ~ 10",
" years!",
"And of course, even this last point is moot since we would never actually get to this situation. Almost all the modern theories we have suggest that ",
"the proton itself is unstable and that it can decay",
" long before that. Stability is never completely clear-cut but depends on the context and the timescale we are interested in.",
" This value was actually calculated for Fe-56, rather than Ni-62.",
": Thanks to ",
"/u/tauneutrino9",
" I corrected the answer to reflect that Ni-62 has the highest binding energy per nucleon; fixed units."
] |
[
"Fe-56 is not the most stable. Ni-62 is the most stable isotope. It is a common misconception since Fe-56 is produced in stars at a higher rate."
] |
[
"Why is there such a high disparity between the number of first and second doses for the COVID-vaccine in the UK?"
] |
[
false
] |
I was under the impression you have to get your second shot about 14 days after the first round of vaccination. According to the UK governments' website the number of first doses administered is about 17 million while only about 0.6 million people have gotten their second dose. What's up with that? Are these 17 million people still immunized?
|
[
"With a limited supply of doses and many bottlenecks in the shipment and distribution of vaccines, public health officials have to weigh the trade offs between two less-than-ideal scenarios:",
"Given that even only one shot of the vaccine does confer some resistance to severe disease and does reduce the likelihood of hospitalization and death, it seemed to be the better choice to give as many people as possible at least one dose now. Some protection is better than no protection at all. ",
"Everyone still ought to get a booster eventually and soon, but the demand for the vaccine is still much higher than the available supply, and so there’s no getting around waiting."
] |
[
"Most of these 17 million doses are the Oxford-Astrazeneca vaccine which should have the second dose 4-12 weeks after the first (with a new Lancet paper finding in review that best protection is found when the second dose is given closer to 12 weeks after the first). Also, most of these 17 million doses have been given in the last 4-6 weeks only."
] |
[
"\"A single dose of the Pfizer/BioNTech vaccine offers 92.6% efficacy in new calculations based on data submitted to the US Food and Drug Administration (FDA), researchers report.\"",
"https://www.medscape.com/viewarticle/946102?src=mkm_covid_update_210218_MSCPEDIT&uac=356354SZ&impID=3199592&faf=1"
] |
[
"Do foaming soaps work better?"
] |
[
false
] |
[deleted]
|
[
"Most of the time not. The purpose of most soaps/degreasers is to form ",
"micelles",
" around fat, oil and dirt, so these tiny \"bubbles\" can \"dissolve\" and be carried away by water. \nThe foaming is to give the consumer a good feeling about it, as they can see and feel it working. ",
"But the foaming does help spreading and holding the liquid in place, so it has a function in products like shaving cream, where the purpose is to keep the hair moist. ",
"Ever realized bread is a type of foam?"
] |
[
"I'm not sure most healthcare workers actually care all that much whether it's foaming or non-foaming, they just utilize whatever the hospital buys. And from what I've observed from purely anecdotal evidence is that the hospital will always buy the cheapest stuff possible."
] |
[
"on a related note, are \"foaming soap\" formulas anything more than watered-down liquid soap? the reason i ask is because i have found that i can turn any liquid soap into foaming soap using a garden variety foam dispenser and any watered down body wash/hand wash and i can't tell what the difference would be. it foams and it gets the hands clean, so i have been assuming the whole foam deal is just a gimmick unless i'm paying for the fancy pump. i'd love to know the story here."
] |
[
"Are there any brain disorders that disable one's folk psychological intuition of free will?"
] |
[
false
] |
I was reading on neuroscience and the law. It discusses our folk psychological belief in free will. It got me wondering whether there are any people who simply have that intuition of themselves and/or others? A quick googling revealed nothing helpful. What do you know, ?
|
[
"Given the vast array of mental issues in schizophrenia spectrum disorders, I think that's where you might find it. From reading some case reports from counselors, it seems that some schizophrenics may get into a state where they are so completely immersed in the feeling that they are being controlled by supernatural/exotic forces (ironically of their mind's own making) that they might lose all concept of self-determinism/freedom. Appreciate comment from a real psychologist...."
] |
[
"Would deficits in ",
"theory of mind",
" fit your question?"
] |
[
"Schizophrenia is a great example. This is a psychotic mental illness where there is a failure of 'reality testing,' which refers to one's ability to differentiate what is real/logical from what can exist only in one's mind/imagination.\nWith respect to the question about free will, many schizophrenics do not know if their thoughts, feelings or actions are coming from within themselves or from the outside world. Many of these patients will describe a sense that they are merging with other people or objects. In this way, they have a genuine sense that what they are feeling and doing is actually originating from the person they are psychically connected with.",
"Edit: I also want to comment on the topic of the article posted by the OP. This is a very relevant topic and neuroscience will undoubtedly continue to have an impact on the way we look at criminal behavior and how we ",
" it as opposed to ",
" it. I just want to add that while these authors focus on free will and how there may be disorders of free will, I believe a bigger issue is impairments in judgment. People have impaired judgment when they fail to appreciate the future consequences of their current behavior (drive drunk -> wreck car). There are many cases of organic causes of impaired judgment from brain damage and intoxication, but there is a high prevalence among many psychiatric disorders as well. A prime example is bipolar disorder where episodes of mania lead people to make completely irrational decisions like blowing their entire life's savings on a spontaneous vacation. As we learn more about how our brain makes decisions based on future consequences, we will start to see that we're all walking around with different innate and learned abilities in this function."
] |
[
"How do dialects form, and where is the highest density of dialects?"
] |
[
false
] |
I was thinking about how many dialects there are in the British Isles, and how the dialects can very from city to city. I was wondering if the British Isles came close to the highest density, and how all of the differences in language formed.
|
[
"Do you know about ",
"r/linguistics",
"? There would be more people there who could help, probably."
] |
[
"You'd have to define dialect, distinguish it from accent, and weigh the influence of ",
"idiolect",
". A useful place to start is to ask people whether they can tell a given speaker is from \"somewhere else\" or \"around here\".",
"The BIs have a high density of regional accents, but so also do the German-speaking parts of Europe. This sort of thing typically happens when you have a lot of people pretty much staying put in their respective communities and not traveling far or often, where they will hear how things are spoken in other areas. Fluctuations in one or more people's pronunciation eventually snowballs into a full blown separate language eventually."
] |
[
"Take a look here for some answers ",
"http://www.reddit.com/r/askscience/comments/o252a/how_did_the_first_dialects_ever_develop/",
"\nHighest density might be Papua New Guinea."
] |
[
"What is the most recent common ancestor of all organisms that require sleep?"
] |
[
false
] |
If it is unknown, are there reasonable hypotheses about this organism's characteristics? Could it have extant descendants that don't require sleep? Is there a taxon that contains all sleep-requiring organisms? Does it also contain non-sleep-requiring ones? Does it contain one or more taxa, which contain both sleep-requiring and non-sleep-requiring organisms?
|
[
"An alternative question. What is the most recent common ancestor of all organisms that can be awake?",
"There was a discussion not so long ago about sleep, and someone who seemed to know what he was talking about, argued that it's not obvious what evolved: the need for sleep or the ability to be awake.",
"Can we even meaningfully say that amoeba is awake? Or asleep?"
] |
[
"Organisms as basic as millimeter long round worms (that diverged 70 million years ago) have shown wat looks like daily bouts of inactivity..",
"Edit: I meant to type 700 not 70"
] |
[
"tbh it seems that everyone really wants to know more about sleep on reddit and that we just do not know that much about sleep."
] |
[
"How fast did the Earth spin when it was first formed?"
] |
[
false
] |
I've been thinking about the rotational velocity of the Earth, more specifically how it's changed over time. To the best of my knowledge, the Earth slows by 1.7 ms every century. If the Earth is 4.5 billion years old (45 million centuries), has it really slowed by 21.25 hours? Was a day really only 3.75 hours long when the Earth was formed? I'm guessing I'm just making some silly math mistake, but I can't seem to figure it out. I think it's also pretty amazing that the Earth slows down so little. It seems like an object the size of the Earth would lose a lot of energy over time to passing objects and various gravitational forces, but it seems to remain pretty stable in rotational velocity. Just being a nerd thinking about these things I guess...
|
[
"Thinking about it off the top of my head: It's hard to say with certainty, especially if you accept that the most likely explanation for the formation of the Moon is the giant impactor hypothesis: the rate of spin of the Earth was ",
" altered a great deal during the Moon's formation event. This makes its rate of rotation prior to the impact basically indeterminate. Changing the rate of rotation of the Earth prior to the impact may require the impactor to have arrived at a different angle, speed, or mass in order to generate the moon we currently have, but we don't know these variables. One could assume the impact parameters, and run a simulation to determine the rate of the Earth's rotation prior to the impact, or vice versa, but it's still a pretty big parameter space.",
" Just thought of something else which makes this hard to answer. You have to define the point in time in which you cease to have a proto-Earth, and instead have an Earth. Assuming that the consensus that planets form by slow accretion, when does the proto-Earth become Earth? When it has reached 99% of its current mass? 90%? 75%? etc. This point is somewhat arbitrary. "
] |
[
"the Earth slows by 1.7 ms every century",
"didnt know that, thanks"
] |
[
"Note: I posted this in the ",
"original",
" thread that was in AskReddit. I figure it will get more discussion here.",
"I don't really know what I am talking about, but here is what I thought after reading your post...",
"I believe that the tides are what slows the earth (friction forces of the water moving). Since the earth used to spin faster, the tides would also happen more often, meaning that the rotational velocity would be exponential, not linear.",
"The 1.7ms/century is how much the earth is slowing NOW (instantaneous slope), which is a very close approximation because of the many, many years it takes to actually slow.",
" I know I didn't really answer your question, but was pointing out that I think your 1.7ms*4.5 billion is flawed. That being said, it would be spinning much faster than your estimation."
] |
[
"Can you make a circle out of a bunch of triangles?"
] |
[
false
] |
hypathetically, if you were to put an infinite amount of triangles together, could you construct a circle?
|
[
"Yes. Consider a circle with radius of 1.\nThe area is found with the equation\n A = πr",
"\nWith a radius of one, the area is simply π.",
"The area of a regular n-gon can be found with the equation \n A = N/2 * sin(2π / N).\nNow find the limit of the function as N approaches infinity.\n lim_(N->inf) (N/2 * sin(2π / N)) = π\nSo, as the number of triangles approaches infinity, the area will approach π. Same area, same constant radius, same thing."
] |
[
"In a hypothetical situation, with infinite triangles, yes. However, being that a perfect circle has no edges whatsoever, a perfect circle does not exist. Period. Sure, we have really really really round things, but if you go deep enough, there are edges, curves, nooks, and crannies. "
] |
[
"You don't have to put a line on the outside. ",
"Since a circle is literally defined as an infinite number of points equidistant from a center, you could arrange an infinite number of triangles angle-out with the angles all equidistant from the center, and you would end up with a circle. ",
"Of course, I could be wrong - if so, please correct me! "
] |
[
"Ask Anything Wednesday - Economics, Political Science, Linguistics, Anthropology"
] |
[
false
] |
Welcome to our weekly feature, Ask Anything Wednesday - this week we are focusing on Do you have a question within these topics you weren't sure was worth submitting? Is something a bit too speculative for a typical post? No question is too big or small for AAW. In this thread you can ask any science-related question! Things like: "What would happen if...", "How will the future...", "If all the rules for 'X' were different...", "Why does my...". Please post your question as a top-level response to this, and our team of panellists will be here to answer and discuss your questions. The other topic areas will appear in future Ask Anything Wednesdays, so if you have other questions not covered by this weeks theme please either hold on to it until those topics come around, or go and post over in our sister subreddit , where every day is Ask Anything Wednesday! Off-theme questions in this post will be removed to try and keep the thread a manageable size for both our readers and panellists. Please only answer a posted question if you are an expert in the field. . In short, this is a moderated subreddit, and responses which do not meet our quality guidelines will be removed. Remember, peer reviewed sources are always appreciated, and anecdotes are absolutely not appropriate. In general if your answer begins with 'I think', or 'I've heard', then it's not suitable for . If you would like to become a member of the AskScience panel, . Past AskAnythingWednesday posts . Ask away!
|
[
"Yes, but it depends on how you want to define real.",
"Disincentives to companies breaking the law include: greater regulatory scrutiny, loss of public trust, loss of investor support, loss of support/purchasing from supply chain partners, potentially triggering regulators to enact new legislation that could negatively impact business operations, etc. There's more that i can't think off the top of my head, and more specific impacts related to certain industries. ",
"Edit: a couple examples",
"(1) Global banks post-financial crisis have had to implement internal controls and procedures under Dodd-Frank etc that are costly and result in greater regulatory oversight. Entire compliance oriented departments now exist that didn't exist prior, and this affects any bank that wants to continue doing business in the US.",
"(2) The Volkswagen scandal has resulted in a damaged brand, thereby hurting sales to consumers in the short and medium (and possibly long) terms. So in addition to billions in settlements they've agreed to, their business has been suffering and there is naturally behind the scenes reorganization going on which is time consuming and costly"
] |
[
"How can so many people simply be stuffed into 2 groups? ",
"Short answer: They can't be, not really.",
"Long answer: The US uses a voting system called \"First Past the Post\" in which the candidate that wins the plurality of the votes in a given district then represents that district. This strongly encourages the formation of a two party system. Think of it this way: Suppose that we had three parties, the liberals, the super-liberals, and the conservatives. In elections, the liberals and the super-liberals would always split their supporters and hand victory to the conservatives. Odds are the super-liberals would rather have a liberal representative than a conservative one so they strategically support the liberal candidate even though they prefer the super-liberal candidate. This happens across the ideological spectrum and basically pulls (mostly) everyone into a left-leaning party and a right-leaning party.",
"For a different perspective, look at the parliaments of many European nations (which don't use First Past the Post). They usually have several parties which run the ideological gamut. Germany has 5 political parties that currently hold seats in their parliament. "
] |
[
"If companies get fined when they break the law, is there any real disincentive to breaking the law if it earns them more money than they will be fined for?"
] |
[
"Linguists/NLP-ers; could we decipher alien text?"
] |
[
false
] |
I'll try and explain a bit more about what I mean. If we were to come across a body of alien text (I use alien simply to mean no one has seen it before) of sufficient volume (and here I assume the 'text' in question has a similar language structure to those on Earth; characters, words comprised of characters, and sentences), could we decipher it? Could we translate the language having no reference to check against? I'm assuming that the text in my hypothetical question does not have any 'pointers' like a picture of dog and associated labelling, just raw text (that isn't just random garbage characters). I'm aware of the , but i'm unclear as to if this answers my question...
|
[
"I would agree with themuffinking that the answer is no, given the conditions you stated. ",
"It's an important distinction though whether this text was written by humans, representing a natural human language, or comes from some other source. ",
"If it's the former, we might at least be able to start to make some progress on the basics if we knew beforehand what the text was about, or if there were pictures, or if we knew what language the language might be related to, etc etc etc. With none of these things to go on, no, we would not be able to decipher it even given a very large volume of text. ",
"If it's the latter, we really would need to bring in the cryptographers. It is extremely unlikely that a truly alien language would work ",
" like natural human language. Even artificial human languages are so different from natural language that you would probably not ask a linguist to help you decipher them (think of programming languages, though they fulfill a somewhat different function). I imagine that a team trying to decipher a non-human language would have a couple of linguists on it, but plenty of cryptographers, mathematicians, etc. as well.",
"Human languages only use a tiny subset of the conceivable mechanisms that could link form to meaning, and linguists focus almost exclusively on understanding that subset.",
" below someone claimed that with enough text, cryptographers can decipher just about anything. I'm not really qualified to confirm or deny that, but I would not have though that that was the case. ",
" RRC's post makes an excellent point about ",
"Linear A",
", which has yet to be deciphered but is definitely a writing system for a natural human language. I can't tell from the wiki article exactly how much raw text has been found though. "
] |
[
"The Voynich is an interesting case, because it's not actually known to be a language at all. It could be some kind of code, or possibly just a meaningless script created for artistic reasons.",
"But leave aliens out of it; no one has ever been able to translate Linear A, a script that was used extensively in the Greek isles some 3,000 years ago. And without the Rosetta Stone, it's entirely possible that most ancient Egyptian writings would be untranslated today."
] |
[
"Thanks for the answer. Kinda sucks that if we were to receive an alien transmission (of text, not some other kind of message medium) without any 'rosetta stone' of sorts to aid deciphering it, that we would very likely be unable to understand it."
] |
[
"Does the color of light shining on ice affect the melting speed?"
] |
[
false
] |
Hi! I was just ice skating and a bit bored when I saw the ice melting. (It is a really good ice rink! Not...) But I noticed colored lights shining on the ice and I wondered if they can speed up (or slow down) that spot of ice. I began thinking and I came up with this: I know white colored things reflect all colors of light. So if the ice is colored white it does not matter? But if the ice for example is colored red. Could not red light shining on it increase the melting speed? Becasue red objects absorb all light except red, they reflect that. And absorbing is also absorbing heat? Not? I was just wondering... Thanks!
|
[
"You are on the right track. Ice reflects and absorbs different wavelengths at different fractions. Looking at ",
"a graph of albedo vs frequency for ice",
", we can see that over most of the visible range, it is roughly constant, while towards the red end of the spectrum, it starts to absorb more. So, lower frequency light would be better for melting, given that the power is held fixed."
] |
[
"Before I make a goofball of myself, lower frequency definitely means near-infrared in this case.",
"As larger wavelength means... well lower frequency between the waves."
] |
[
"Yes."
] |
[
"How did pouch evolve on marsupials?"
] |
[
false
] |
Edit: And by "how" I mean "how", not "why" (yes it's for babies, everybody knows that :D). How did it evolve? What/how did it used to be before they have pouch like the one they have in present time? I tried Googling but all of the results appear to be creationism sites. Help!
|
[
"There are even marsupials today which don't have pouches. The babies just hang on to the fur next to the teat. If the skin is a bit loose in that area, it's probably easier to grab. A bit looser still, and you have a nice little fold. Expand the fold, and viola, a pouch!"
] |
[
"There is the common misconception that each animal alive is an improved version of another. Like us being a step above chimps.",
"The truth is that if it's alive, it's evolved. Just different. Just another branch of a very round tree."
] |
[
"It's not that uncommon! Out of the four orders of Aussie marsupials, big, bag-like pouches are only consistently found in the ",
": kangaroos, wombats, koalas, and possums. ",
"The other three orders have pouches that range from classic bag-like pouches (Bilby) to folds of skin that tuck up against the young (some of the Dunnarts, Kowari), to absolutely nothing, where the young just hold on to the nipples and hope not to be scraped off (Numbat, some of the Antechinus). "
] |
[
"Why is the Southwestern U.S. dry and the Southeast wet? How can different areas on the same latitude have such different rainfall amounts?"
] |
[
false
] |
I crudely understand how air and water currents work on this planet as well as how the Coriolis effect influences weather but I don't understand how different longitudes relatively close together on the same latitude can have such different average rainfalls.
|
[
"The jetstream brings moist air from the pacific northwest down to the southeast, ",
"here is an example"
] |
[
"Here's some:",
"Elevation, ocean currents, winds, mountains, and vegetation."
] |
[
"Also, the Southwest is on the opposing side of the Rocky Mountains. Much of the precipitation gets trapped on the eastern side, leaving the western side of the mountains relatively dry."
] |
[
"The first element of the periodic table is hydrogen, associated with the alkali metals and highly reactive - one of the most reactive elements of all, I believe? The second element is helium, a noble gas and a highly unreactive element. Why the massive difference between the first two elements?"
] |
[
false
] | null |
[
"Because the first shell holds two electrons. Hydrogen only has one, so it wants to gain a second. Helium has two, so it's full."
] |
[
"In that case, can I ask what's behind the first shell only holding two electrons?"
] |
[
"Quantum mechanics tells us that particles in bound states occupy orbitals described by discrete quantum numbers. Only a certain number of those exist, and only a one electron can occupy each available state due to Pauli exclusion."
] |
[
"Could a fuel alternative be synthesized to run in modern combustion engines?"
] |
[
false
] |
[deleted]
|
[
"Biodiesel is an alternative for Diesel fuel that uses vegetable oil as a base. In order to not affect food supplies, it has been proposed to use non-edible plant oils instead of typical vegetable you get at the store. While biodiesel produces similar greenhouse gasses to diesel, it's not as energy dense, requiring more fuel for the same amount of torque."
] |
[
"Around a decade ago, BMW built a few cars with internal combustion engines that could run on both gasoline and hydrogen. I think the cars actually had a switch on the dashboard to go back and forth between the two fuels. Using hydrogen in an internal combustion engine is far less efficient than using it in a fuel cell, though.",
"https://en.wikipedia.org/wiki/BMW_Hydrogen_7"
] |
[
"Natural gas engines are getting more common, although still a fossel fuel. Also there is promise for ethanol made from the cellulose of plants. Things like switch grass can be grown in marginal soils not suitable for other crops, or from staulks of other crops like corn. It is not as efficient as corn seed based ethanol production but you are using a product with little comercial value. Basicaly a byproduct. The issue is economic not technical."
] |
[
"So now that water ice has been confirmed at Mercury's north pole, how feasible would a manned base there (compared to the Moon or Mars) be?"
] |
[
false
] | null |
[
"It would still be impossible with current technology. The extreme temperatures alone are a huge deterrent.",
"Mars is pretty cold, and has almost no atmosphere. In mid-latitudes, temperatures range from about -60°C to 0°C . The Moon has no atmosphere, so there's no air temperature, but surface temperatures range from about -110°C to 130°C. Mercury has very little atmosphere, and has the highest temperature swings of any planet in our solar system, going from about -170°C to around 430°C. So temperature alone would be a nearly insurmountable obstacle. Based on temperature alone, Mars is probably the best contender.",
"The Moon is close to Earth, so it's relatively easy to get there, and one side always faces earth, so communication is relatively easy. The Earth-Mars distance is obviously greater, and varies largely. Mercury's closest distance is a little farther than Mars' closest distance. The Moon is the winner in terms of distance and communication.",
"Intense solar irradiance also makes Mercury a pretty forbidding place.",
"So in terms of feasibility, Mercury isn't really a good place for a manned base. The presence of water doesn't do much to aid with the harsh environment.",
"Edit: temperature. (I converted to F instead of C - thanks das_mime)"
] |
[
"I'm still holding out for cloud cities on Venus. But Mars will do."
] |
[
"Wikipedia says that Mercury's surface temperature ranges from 100 to 700 K, not 100K to 1070K like you stated."
] |
[
"Does humidity have any effect on odor, for example does a stockyard smell worse when the humidity level is higher? If it does smell worse is it because of how the odor carries in humid air or is our sense of smell effected by humidity levels?"
] |
[
false
] |
[deleted]
|
[
"Higher amounts of water in the air increases the binding affinity of \"smell molecules\" to \"smell receptors\" in your nose. So yes, humidity has an effect on ",
" odors. Try farting in the shower and you'll notice. Alternatively, smell your shampoo before turning on the shower and again while you're showering and notice the difference."
] |
[
"Thanks for the great answer, you just helped me win an argument:-)"
] |
[
"Wouldn't the rate of diffusion be higher in a high humidity environment? So smell molecules would travel faster and farther through the air, which would mean smell molecules are more concentrated where the smeller is than they would be when it was a lower humidity. Does that follow?"
] |
[
"What element has the highest specific heat? Additional, what compound?"
] |
[
false
] |
What element, and additionally what compound, has the highest specific heat? Also, since we're on the topic, what element and compound have the lowest specific heat? I sprang this question on a chem professor of mine the other day, but he said he did not know the answer. Thanks!
|
[
"Maybe this will help with the element question (Hydrogen is highest, Radon (natural)/Technetium (synthetic) is lowest:\n",
"http://periodictable.com/Properties/A/SpecificHeat.ssp.log.html",
"A quick search makes it seem like no compound is going to top gaseous hydrogen or get below Radon or Technetium."
] |
[
"I haven't spent a ",
" of time looking at it, but there's no obvious trend in how the elements are arranged, except that they tend to get heavier as you move left to right. Since the values are listed in units of J/kg-K, this is sort of what you'd expect -- it takes more energy to heat up heavier elements. However, if you multiply the values listed by the molar weight, then I'm guessing it'll be roughly the same for all of the elements (the Dulong Petit law). ",
"Edit: Just wanted to emphasize that this will change if you're talking about elements in liquid or gaseous form, and if they form diatomic molecules, etc, since they will have differing degrees of freedom. Also, as you're probably aware, specific heat can vary a lot with temperature, and for metals we generally have to consider the electronic and lattice parts separately. "
] |
[
"This will depend a LOT on whether you're talking about the elements in gas, liquid, or solid form -- as the chart ramk13 linked to shows."
] |
[
"How does basic light reflection really work? Confused."
] |
[
false
] |
Hey Reddit, So I'm trying to get my head around what's happening at a fundemental level when light reflects off of a highly reflective surface like a mirror. For a given photon, I'm assuming it doesn't "bounce" in any way when it reaches the atoms of the reflective surface (ie isn't repulsed), but rather is absorbed and re-emitted. What's confusing me is how the momentum / angle of reflection is maintained through the absorption / emission process. I kinda see it when viewing light as a wave, but picturing water bouncing off a containing wall doesn't help, because its not really absorbed + emitted in any way. Can anyone help me with what's going on? How does an electron absorbing the photon and jumping to a higher energy level maintain momentum? Thanks
|
[
"On an ideal conductor, the re-emitted photon has to cancel out the parallel component of the electric field. This results in a re-emitted photon that has to have the same momentum in the parallel component, and the opposite momentum in the perpendicular component.",
"Or, the angle in equals the angle out."
] |
[
"The way Feynman explains it, individual photons don't know or remember their momentum. It's just that, if you have a light source and a light sensor and a mirror, you will find that the photons are most likely to have followed the path that we expect from classical optics. The wave function of a photon taking a slightly more acute path cancels out with the wave function of a photon taking a slightly less acute path, and all we're left with is the proper",
"See Feynman's explanation here: ",
"http://vega.org.uk/video/subseries/8",
" He goes into your question early in part 2, but I recommend watching all 4 segments."
] |
[
"It's actually pretty mindblowing when you think about it.",
"When a photon is absorbed by an atom in, say, glass, it is re-emitted a very short time thereafter. The problem is: the direction it is emitted is random. How then does light reflect in one direction? Turns out that the phase of the photons in ",
" just about cancel out (\"just about\" to account for the fact that there are only a finite number of photons). Along such an angle, all photons constructively interfere, giving you the angle you expect.",
"Most modern undergraduate optics books will have a short section on QED in this respect. But Feynman does a great job too in the videos the others link to."
] |
[
"How the heck does quantum levitation work?"
] |
[
false
] |
I thought about magnets, but it seemed impossible as when you change the thingy's place, it locks at the exact place you leave it. And that's clearly against how the magnets work. Someone explain this.
|
[
"It is simple. The difference is that we are dealing with superconductors, so odd stuff happens.",
"Basically, when you change the magnetic flux through a metal, the metal will set up currents to avoid the change in the flux. Usually this current is held back by the resistance of the material.",
"Since this is a superconductor however, there is no resistance, so the eddy current and the superconductor pins the magnetic field lines.",
"I don't like the name quantum levitation as it adds needlessly to the mysteriousness of the phenomena. Its name is flux pinning as that is what happens. ",
"In review, superconductors pin the flux through them. If this was a normal conductor, the resistance of the conductor would not perfectly pin the flux and it wouldn't levitate."
] |
[
"Moving a magnet near a conducting material like iron will induce a current (electron flow) in the conductor, because the electrons will move to oppose the change in magnetic flux through the material. In normal conductors, the current is dissipated to heat fairly quickly by the resistance of the material. In a superconductor, there is practically 0 resistance, so the current persists in the material for extremely long times. The current produces a magnetic field that opposes any motion in the field of the magnet, preventing the magnet from moving. "
] |
[
"thanks for the explanation."
] |
[
"Do baryons other than neutrons become stable in atoms?"
] |
[
false
] |
Neutrons are unstable, but become stable in nuclei. Do any other baryons have this property?
|
[
"Here is one scenario in which this ",
" happen. ",
"Neutrons and protons are made of up and down quarks. Because free neutrons are only slightly more massive than free protons, as you say, neutrons can wind up stable in nuclei, because the binding energy overcomes the mass difference.",
"Now baryons with strange quarks are significantly more massive than baryons with just up and down quarks, so binding energy won't be enough to stabilize them.",
"However, it is thought that in the center of neutron stars, there may be another mechanism that causes strange quark states to be stable. Because of the exclusion principle, in the dense core of the neutron star, some of the ordinary quark matter would have to be in very high energy states, as all the lower energy states would be filled. Because of this, it is possible that the overall energy could be lowered by having the ordinary baryonic matter in higher energy states replaced by strange quark matter in lower energy states -- where the increase in mass from replacing a down quark with a strange quark is more than made up for by the decrease in energy of the state in which it sits. (Remember, the exclusion principle only acts between identical particles, so the ordinary quark matter doesn't affect which strange quark states are possible.)",
"There are some other exotic possibilities that might occur, driven by a similar effect (the interplay of the exclusion principle and the masses of the quarks)."
] |
[
"Thank you."
] |
[
"Ah, I seem to have failed to mention a scale that would seem big.",
"Protons are among the most stable composite things known. However if a physical theory predicts that in the heat death of the universe protons might start breaking that is not a absurd result which would make a theorist immidietly throw it into garbage.",
"a subatomic particle collection that lives for half a second might be termed \"long lived\". The most stable radioactive elements last some hundreds of years. However stars are inherently in a transient state but the transiton takes some millions/miljards of years somewhat depending on size (paradoxally small stars don't burn themselfs out so fast). If you would apply the standard used for elements to humans they would be very unstable, yet a clinically \"stable\" patient is expected to live atleast a day, but not centuries."
] |
[
"Why do we consider Neanderthals and Homo Sapiens different species?"
] |
[
false
] |
It is well-known that homo sapiens interbred with Neanderthals. If this is the case, then why do we consider the two, different species? This could also to apply to other species, such as homo erectus and other members of the homo group.
|
[
"There is not actually a strict definition of \"species\". Sometimes interbreeding populations of a species will diverge long/far enough to develop noticeably different features without ever losing the ability to produce fertile offspring together. It can be difficult to decide where an appropriate line is drawn. Among the species of homo, sapiens became distinct quite late, and although it could still produce fertile offspring with Neanderthals and perhaps others, there were enough genetic differences that it seems prudent to consider it a separate species."
] |
[
"The morphological argument seems weird and a bit elitist to me. We are perfectly happy to label bulldogs, chihuahuas, great danes, greyhounds, etc. all as the same species \"dog\". But when it's about us humans suddenly looks matter? It seems like a remnant of the racist times when we would label other human races as \"sub-human\".",
"Are there any other examples in the animal world where we make a clear species distinction based only on morphological differences?"
] |
[
"It’s somewhat arbitrary because the definition of species is more fungible than you’d think. It boils down to the species concept being used. ",
"The biological species concept is based on reproduction. The evidence of interbreeding is fairly clear which would mean you should consider Neanderthals the same species as us using this species concept.",
"However, they are morphologically distinct in a variety of ways, so some anthropologists categorize them as different species according to the morphological species concept. However, at least some of these morphological distinctions (occipital bun, swept back zygomatics, protruding midface, etc.) might be due to behavioral modifications, further complicating the matter. "
] |
[
"So if there is the phenomena of vanishing twins, and the possibility of multiple ovum being fertilized, what are the odds of these being fertilized by two different men, one vanishes, and the result having the DNA of both men after one absorbs the other?"
] |
[
false
] |
So as the question asks, some links to what i know: vanishing twin: heteropaternal superfundication: twins with different fathers: follow up: Is there a DNA test for this? and in a normal paternity test, will it match either man?
|
[
"I’m nowhere near qualified to answer this, but since it’s been 9hours without a response, I’ll make a go of it. The term I think you’re looking for is chimerism. In most cases, it refers to swapping DNA between mother and child but it also happens between twins. In one famous case, a woman named Lydia Fairchild nearly lost custody of her children because her DNA was not present in them. They later found out that she had absorbed some of her vanishing twin’s DNA, and it was that DNA that was the parent of the kids. So the DNA can be exchanged, however it also stays independent of the other DNA, even if they are now present in the same body. Hopefully my muddled through explanation makes sense."
] |
[
"So its possible, but as I understand can have serve consequences on child due to fusion of 2 DNA. Also it must happen really early in pregnancy cause if procces started we will have twins in 1 body. There are cases of this."
] |
[
"Interesting enough, House did an episode about this called, “Cain & Able”. Worth a watch."
] |
[
"Could someone go deaf from a sound he cannot hear?"
] |
[
false
] |
[deleted]
|
[
"Sounds are just pressure differentials that vibrate our eardrum, and the amplitude of the sounds is just the magnitude of the pressure differential between your inner and outer ear. We can only perceive a certain frequency range of vibrations, but that doesn't mean that something outside of our perceptible range doesn't effect our ears.",
"Take, for example, a pressure wave caused by an explosion. The initial wave is a single pulse (essentially a frequency of zero). That pulse is easily enough pressure to rupture your eardrum and deafen you permanently even though you wouldn't be able to hear it. "
] |
[
"I was just giving an example of how something outside of the audible range could damage the ear. I know it's not an example of normal hearing loss, but it is an example of how something that cannot be heard can deafen the listener (by physically rupturing the eardrum). "
] |
[
"I was just giving an example of how something outside of the audible range could damage the ear. I know it's not an example of normal hearing loss, but it is an example of how something that cannot be heard can deafen the listener (by physically rupturing the eardrum). "
] |
[
"How much does recycling actually save us, in terms of cost?"
] |
[
false
] |
I am not questioning the efficacy of the process, but is anything lost during it?
|
[
"Popular Mechanics has a nice article about recycling. ",
"Here",
"Summary: Environmentally there is no debate that it is worth it, even when including energy costs like pickup and sorting.",
"Aluminum, for example, requires 96 percent less energy to make from recycled cans than it does to process from bauxite. At the other end of the spectrum, recycled glass uses only about 21 percent less energy--but it still comes out ahead, according to a study by Washington-based environmental consultant Jeffrey Morris. Recycled plastic bottles use 76 percent less energy and newsprint about 45 percent less, he found.",
"However economically it does not always make sense. Just because it requires less energy does not mean that it is a cheaper process. For example labor costs may be more intensive for a recycling process. As noted in the article it really depends on the location, material, and demand for the material."
] |
[
"Aluminum recycling saves vast amounts of energy, 95% is the figure I've seen most often. Melting down existing cans versus mining bauxite, processing it through the Bayer process, etc. "
] |
[
"I can give you the economics of glass recycling and cite 20+ years of personal experience. As it's anecdotal I'll strive to be believable. ",
"Firstly, glass is economical to use in construction for such things as including as part of road base / tarmac. It's simple matter to crush it up and mix it in. ",
"It's economical to reuse to make new low quality glassware in low cost labour situations. If bottles can be sorted into ",
" source bottles then they can be remelted into a uniform batch with relatively consistent properties. ",
"The reuse of bottles as bottles, just as they are, is problematic. Let's say beer bottles. If you wish to bottle beer in a plant you need large numbers of identical bottles. There is a cost associated with sorting many diverse bottles in order to extract just the ones that are standard size and colour.",
"\nNow comes the cost of rejecting bottles with foreign intrusions.",
"\nThink syringes (visible), chemicals and poisons, et al. You can use camera vision systems and high temperature steam flushing etc. but there ",
" be a rate of failure to detect.",
"\nThere is a ",
" cost associated with failing to detect poison or a syringe in a beer bottle. The PR backlash is enough to kill the project. ",
"Remelting glass bottles (crushing, then fritting) seems like a good idea but this also has quality control issues for consistent production. Glass isn't just glass. Have a look at the glass article in wikipedia. There are many many types of glass that vary in colour, thermal resistance, and thermal expansion coefficients. Getting a consistent batch from random inputs is hard and costly. ",
"Now. The other side of the coin. The raw materials for glass are actually cheap and plentiful. The major part of most glass is sand. We don't have a sand shortage and the greatest energy cost by a huge factor is the need to heat that sand (along with fluxes) to roughly 1200 degrees Centigrade for an extended period. ",
"That cost is the same whether you make new fresh glass with raw materials that you can readily Quality Control or whether you remelt old bottles with a mixed background that need a large amount of sorting and testing to ensure consistent results. Making fresh new bottles is therefore cheaper. ",
"That said, if you've access to a large number of wine bottles or beer bottles that have been discarded they do make excellent \"bricks\" for inclusion in rendered walls or stacked upright to make a building slab. The trapped air makes for good insulation."
] |
[
"How does our DNA code for the creation of mitochondria if it is thought that the mitochondria was once a separate entity that \"migrated\" in to a cell?"
] |
[
false
] |
Mitochondria also have their own DNA. Did their DNA somehow combine with the cell's when it "moved in" or something? Am I just not properly understanding how it came to be or what? Thanks.
|
[
"No, the mitochondrial DNA is in the mitochondria. They're pretty much cells-within-cells. (and yes, originated as such) They have their own ribosomes too.",
"But our nuclear DNA does have quite a bit of genes for mitochondria-related stuff. One example I know is the enzyme Cytochome C Oxidase, an important metabolic enzyme in the mitochondria. In bacteria (who don't have mitochondria), it only has 3-4 amino acid chains, out of which only 2 really do the work. The human CcO, on the other hand, is ",
" bigger, consisting of 13 chains. ",
"Here's the interesting thing: Only 3 of those chains (including the two that do the work) are encoded in the mitochondrial DNA. And if you look at the structure of just that part, it's very similar to the simple CcO enzymes in bacteria (",
"comparison",
", from ",
"this",
" nice page on the same thing). In other words, the other 10 chains that are encoded in our nuclear DNA are basically just some customization that our cell made later to get this cell-within-the-cell to act more like it wanted it to.",
"It's quite cool. And a strong bit of evidence to support endosymbiotic theory!"
] |
[
"Nice answer. I'd add one more thing which is that the nuclear genome actually does include quite a lot of mitochondrial DNA in the form of functionless copies of mtDNA. Over evolutionary time, mitochondrial genes often jump into the nuclear genome, and then stay there permanently. Often a big chunk of mtDNA ends up in the nucleus (sometimes landing in a nuclear gene and messing it up). These sequences are called \"numts\" (pronounced \"new-mites\", nuclear DNA sequences of mitochondrial origin). ",
"Here",
" is a nice review, and ",
"this ref",
" is specifically about numts in humans and chimps. Humans have about 450 numts, including one that includes a whopping 90% of the entire mitochondrial genome."
] |
[
"This topic is very interesting which upon a quick inspection of askscience search history I do not see a good explanation. So as a resident nonexpert I'll try my bestest to explain.",
"As it is there are mitochondria in our cell ",
". These mitochondrial organelles are an unbroken line of mitochondria (similar to how we are an unbroken line of cells) which means when our cells divide some mitochondria go to one daughter and the rest go to the other daughter. ",
". There are ",
" genes that we have, as Platypuskeeper points out above, that are encoded by our DNA that exploit the mitochondria (or more precisely work with the mitochondria). This is really where science punches you in the face. We have mitochondria in our cells which do their own thing and we have proteins which we specifically create to go out and interact with the mitochondria and improve upon it. ",
"This breaks the dogma we see in other major organisms. If you were one of the original cell biologists the answer to your question would have actually melted your face. Essentially there is a cell-like organelle within each of our cells which carries its own DNA and our DNA codes for proteins which are enhance it. Without the mitochondria our cells would be nothing, without the DNA encoded programs there would be decreased efficacy. ",
"I often like to give information outside the question to really drive the point home. I think most people understand at least the basics of genetic inheritance. Mitochondrial inheritance breaks the mold as you might expect from my 3rd and 4th statement. ",
". To take a very, very simple example imagine your mother's cells were filled with 8 good and 8 bad mitochondria. When her gamete divides it splits these up. You get some combination of these mitochondria. The amount of disease is dependent upon the amount of 'bad' mitochondria you get. Essentially Mendelian genetics breaks down with these diseases. This is not to mention that suddenly there is an interaction between the cell DNA and mitochondrial DNA which makes this whole ordeal even more \"non-Mendelian.\"",
"tl;dr Mitochondria will melt your face."
] |
[
"How do calculators compute fractional exponents (square roots, cubic roots, etc.) of numbers that are not perfect squares/cubes/etc. ?"
] |
[
false
] |
The square root of a number (n that is not a square number (4, 16, 25) results in an irrational number. (For example: sqrt(2) = 1.4142135...) The same goes for other fractional roots. How does a calculator (or a human for that matter) go about calculating these numbers?
|
[
"There are many ways to calculate a square root, dating back as far as the Babylonians. As far as how modern calculators do it (i.e. which method they implement), that is maybe more of an engineering question, but I can run down a couple of the methods.",
"Given a number ",
", finding it's square root is the same as finding solutions of ",
". Take an initial guess ",
". Assuming our first guess isn't correct, there will be some error ",
", i.e. ",
". We can expand this expression:\n",
" and solve for ",
":",
"We assume the error is small compared to x, and so we have",
"Now, to get a better guess, we take",
"and repeat the process over and over, i.e.",
"until reaching the desired accuracy. This is a special case of Newton's method, which I'll come back to later.",
"In Calculus courses, students learn another way to (sort of) do this with Taylor series. In particular, it is possible to approximate the square root of x via polynomials. For instance, the square root of a number x between 0 and 2 can be approximated by",
"1 + (x-1) / 2 - (x-1)",
" / 8 + (x-1)",
" / 16 - 5(x-1)",
" / 128",
"This method isn't that practical though - given a particular number you want to find the square root of, you'd have to find a series that worked (e.g., to find the square root of 15, my formula above won't work), and it won't converge that fast either (in terms of amount of work vs. accuracy).",
"Another thing students learn about in calculus (and then forget) is Newton's method. You need to understand how to take a derivative of something, but barring that, it's straightforward. Again, we phrase the problem as wanting to find the value of ",
" so that ",
". Then Newton's method says that if we start with an initial guess of ",
", and define iteratively ",
"x_{n+1} = x_n - f(x_n) / f ' (x_n)",
"then (under some other mild hypotheses), this process will converge to the correct result.",
"For our square root problem, this is the same as the Babylonian method, as f ' (x) = 2x in this case. But it can be used to solve more general types of problems, for instance if we now want to solve your ",
" root problem, we choose the function to be f(x) = x",
" - S, and go from there. In this case, f ' (x) = 3 x",
" and so the Newton's method iteration is",
"x_{n+1} = x_n - [x_n",
" - S] / [3 x_n",
" ]"
] |
[
"To be fair, most calculators CAN divide. By 2, 4, ... -- bitshifting is a funny thing."
] |
[
"I once had a math teacher who would always ask the question \"Can a calculator divide?\" and when the student would answer yes he would respond with \"They did a good enough job tricking you didn't they?\"",
"The reason he would always pose this question is that calculators really can only perform functions like add and subtract. But they are able to add and subtract in a way that gives you an approximate answer for what you want. ",
"For the vast majority of the functions on a calculator it is done by using one of various kinds of approximation methods which can write the function of interest in a way the calculator can handle. A simple example of one of these functions might be newton's method",
"https://en.wikipedia.org/wiki/Newton%27s_method",
"You could use that to derive the iterative function",
"a_(n+1) = (a_n",
" + r)/(2a_n)",
"All you do is insert the number you want the root of, enter a guess value as the initial value of a_0, and loop this function until it converges. For this method all you need to be able to do is add, multiply, and divide. ",
"Now in modern calculators they use slightly more sophisticated methods to ensure fast convergence without some of the headaches (Newton's method does have its flaws), but they work of the same principal: Write a function that converges to your desired root and make sure it can be easily handled by a calculator. "
] |
[
"What is the fastest a human has ever travelled?"
] |
[
false
] |
What is the fastest speed in MPH, relative to earth that a human has travelled?
|
[
"Or 39,897 km/h for us metric lovers."
] |
[
"http://en.wikipedia.org/wiki/Apollo_10",
"24,791 mph"
] |
[
"To provide some context, this speed is about Mach 32.4 at STP, or about 10x the regularly stated operational speed of the SR-71 Blackbird spyplane. The Earth's equatorial circumference is 24,900 miles, or slightly more than an hour's travel time at this speed.",
"While certainly impressive by normal standards, it is still a small fraction of the speed of light, 670.6 million mph, or 27,050x greater than Apollo 10."
] |
[
"What is the mechanism for thermal radiation?"
] |
[
false
] |
For instance, the sun emits a continuous spectrum consistent with blackbody radiation of around 5000k. However, the Sun primarily consists of Hydrogen and Helium, so I would assume we would see only emission lines for H and He's discrete energy levels. Why do we see a continuum? Or any other blackbody source, if the energy is exciting and de-exciting electrons, why is the radiation continuous? And if it is not electron excitement, what drives the conversion of thermal energy to e&m energy? Thanks for the help!
|
[
"Since they don't have to fall into specific energies, they're free to have a statistical distribution of velocities, and so, emit a continuous spectrum.",
"If I'm reading the question correctly, it's the mechanism behind this process that the OP is asking about. In other words how the velocity distribution gives rise to a continuum distribution of photons. It's something I've wondered about for a while now, but hasn't bothered me enough to seriously look for an answer.",
"Thinking on it now, my first stab at an explanation would be that in a collision between two atoms (or molecules or whatever the substance is comprised of) charges are accelerated, which produces a photon. The distribution of velocities gives rise to a characteristic distribution of photon energies.",
"That still seems very hand-wavy though, and could even be wrong. "
] |
[
"Radiation from emission lines and thermal radiation are two different things: the first one occurs when an electron falls from a discrete energy level to a lower one - it looses potential energy which gets emitted as a photon. This is a random process that can always happen when there are electrons in raised energy levels (and they get there by being excited by other photons or kinetic collisions beforehand).",
"Thermal radiation, on the other hand, exists because whenever a charged particle is accelerated, it emits an electromagnetic wave. Temperature is an averaged measure of the individual chaotic movements by a group of particles - since those particles move in random directions, they constantly collide with each other. Each collision changes their velocity and direction, which is in fact a form of acceleration, thus generating an electromagnetic wave. The frequency of that wave depends on the amount of acceleration, and since that is pretty random, the spectrum is continuous."
] |
[
"Discrete energy levels only occur for sufficiently \"cold\" atoms. In the case of H and He in the sun, their electrons are sufficiently hot that they're excited beyond any given energy level for these atoms. Since they don't have to fall into specific energies, they're free to have a statistical distribution of velocities, and so, emit a continuous spectrum. That's a bit of a hand waving explanation, but it's the general mechanism, basically, electrons no longer attached to nuclei.",
"However, that's not to say they're all free. You can still see H and He spectra in the sun, but I think it's mainly absorption spectra that are seen."
] |
[
"Calories vs. Vitamins"
] |
[
false
] |
When a person takes too many vitamins our bodies remove the extra we don't need why don't we do the same for calories?
|
[
"In the evolutionary environment which shaped the traits of early humans, it was disadvantageous to waste valuable calories by excreting compounds providing them. Instead, these calories were stored for times of food shortage. Furthermore, since humans were generally engaging in much more physical exertion, they were expending more calories, making excreting 'extra' calories even more unwise.",
"In contrast to vitamins, calories are needed in much larger amounts, and cannot be metabolically recycled. Therefore, the excretion of compounds providing calories was not favored by natural selection, and the cellular 'machinery' necessary for this process is not present in modern humans. The obesity 'epidemic' is a modern phenomenon, but the human body has evolved to suit its previous environment, in which calories were a much scarcer commodity. "
] |
[
"The other comments answer the question, but I just want to add that getting rid of a vitamin surplus isn't trivial, and there's ",
"maximum doses",
" for each vitamin. In fact, the side effects of a consistent overdose are pretty serious. "
] |
[
"This is not the case for the majority of vitamins. There is actually a ceiling for how much of certain types of vitamins your body can absorb."
] |
[
"Is strength always directly correlated to muscle size, or are there other factors as well?"
] |
[
false
] | null |
[
"No.",
"Ask yourself this, why aren't olympic weightlifters the same definition and muscle size as bodybuilders?",
"Check out the theory (more of a hypothesis) for ",
"Myofibrillar vs. sarcoplasmic hypertrophy",
" ",
"Basically it says that you can build the muscle and/ or the amount of fluid in the muscle. Most athletes want the fluid gone, it's just extra weight with no benefit. Bodybuilders want the fluid.",
"David Prowse (the body of Darth Vader) wrote a great article on this, if you want I'll see if I can find it."
] |
[
"Just to add on,",
"Sarcoplasm = space in muscle volume that contains basically anything but the fibers doing the actual contracting. Bodybuilders increase this because it's easier. Their muscles are huge, but you won't catch them being used for anything other than very specific weight-lifting routines. Ask a bodybuilder to throw a baseball, and they may pop a bicep.",
"Myofibrillar = the actual fibers that contract, or the part that actually adds strength. Muscles with lots of Myofibrillar but little sacroplasm are \"dense\", meaning that most of the volume of such a muscle is involved in actually moving whatever body part its attached too.",
"A muscle with lots of Myofibrillar but not much sarcoplasm is likely a lot stronger than a bigger muscle with mostly sarcoplasm.",
"This is the leading theory among weightlifters and trainers, based on the differences in results between low rep/high resistance vs high rep/low resistance exercises."
] |
[
"No, higher weight with low reps is myofibrillar, and low weight with more reps is sarcoplasm. Most strength training (myofibrillar) is done with 1-5 reps, and training for size (sarcoplasmic) is usually done with 8-12 reps."
] |
[
"How does the gate bias in a Tunnel Field Effect Transistor align the conduction band of the intrinsic region with the valence band of the P region?"
] |
[
false
] |
I understand that once aligned, the electrons can tunnel through the boundary, but I don't understand how the applied voltage at the gate "aligns" the two bands.
|
[
"You might remember from high school chemistry that electrons can only exist at certain discrete energy levels around an atom corresponding to the orbitals, and that no two electrons can be at the same energy level and spin. Well when we stick multiple atoms together to form a solid, these energy levels shift a little bit so that no two will directly overlap in energy, but can still hold just as many electrons. When a ton of atoms are put together all of these energy levels are spread out into a discrete range, and we call that range a band. Thus you can think of a band as a range of energy that electrons in that solid are allowed to have.",
"As you might imagine, there are many different band configurations found in different materials. It's these band configurations that govern the electrical properties of the material.",
"One way of envisioning band structures is by thinking of clear boxes that may or may not contain water. The band structure will look like a stack of boxes separated by space in between. The bottom boxes are all filled with water and the top boxes are all mostly empty (because the electrons preferably fill the lowest energy levels first). Where it gets interesting is at the boundary.",
"Materials can be generally categorized into 3 groups electrically: conductor, insulator, and semiconductor. Conductor band structures have their top-most band half filled; their hightst-filled box is half water and half air. Thus it's really easy to slosh water from the left of the box to the right (analogous to conducting electrons along a metal wire for instance).",
"Insulators have their highest-filled box completely full, so there's no air, only water. It's therefore impossible to slosh water from left to right, those electrons have nowhere to go. Thus materials like this are terrible at conducting electricity and we call them insulators.",
"Semiconductors, like insulators, have their highest-filled box completely full as well. The difference however is that the next empty box above it isn't very far away. In fact with a little bit of effort, we can splash some water into the next higher box, and all of a sudden we can move that splash from left to right again (conducting electrons) in that next box up. The box full of water below is called the valence band because it is made up of all the valence electrons from the atoms. The empty box above is known as the conduction band because there's enough room up there (energetically) for electrons to conduct back and forth.",
"Interestingly, if you imagine we splashed some water into the conduction band, we actually left a little air in the valence band as well (where that water used to be). These bubbles left behind can also conduct from right to left and create a meaningful current as well. In semiconductors these bubbles are known as holes.",
"Now an integral part of semiconductor physics is the concept of doping. If you can replace some of the atoms in your material with an atom that normally has extra electrons, it can (if the energy is right) donate that electron to the conduction band to allow a current to pass. Think of an eye dropper sitting just below the bottom of the conduction box that squirts water up a few centimeters. Doesn't take much energy to squirt up that much and now you have some electrons you can use for conducting! This is known as n-type doping.",
"Similarly you can put an eye dropper just above your valence band and take up a little bit of water into it, leaving some bubbles (holes) in your valence band. These can also be used for conducting! This is known as p-type doping.",
"All of semiconductor physics revolves around engineering these concepts to create useful things. By combining different semiconducting materials, with different band levels, with different doping regions, with some insulators and conductors, we can create all sorts of devices such as solar cells (photovoltaics), LEDs, MOSFETs, lasers, etc. Semiconductors are the real stars of the electrical devices world because of how varied and manipulable their properties are."
] |
[
"You might remember from high school chemistry that electrons can only exist at certain discrete energy levels around an atom corresponding to the orbitals, and that no two electrons can be at the same energy level and spin. Well when we stick multiple atoms together to form a solid, these energy levels shift a little bit so that no two will directly overlap in energy, but can still hold just as many electrons. When a ton of atoms are put together all of these energy levels are spread out into a discrete range, and we call that range a band. Thus you can think of a band as a range of energy that electrons in that solid are allowed to have.",
"As you might imagine, there are many different band configurations found in different materials. It's these band configurations that govern the electrical properties of the material.",
"One way of envisioning band structures is by thinking of clear boxes that may or may not contain water. The band structure will look like a stack of boxes separated by space in between. The bottom boxes are all filled with water and the top boxes are all mostly empty (because the electrons preferably fill the lowest energy levels first). Where it gets interesting is at the boundary.",
"Materials can be generally categorized into 3 groups electrically: conductor, insulator, and semiconductor. Conductor band structures have their top-most band half filled; their hightst-filled box is half water and half air. Thus it's really easy to slosh water from the left of the box to the right (analogous to conducting electrons along a metal wire for instance).",
"Insulators have their highest-filled box completely full, so there's no air, only water. It's therefore impossible to slosh water from left to right, those electrons have nowhere to go. Thus materials like this are terrible at conducting electricity and we call them insulators.",
"Semiconductors, like insulators, have their highest-filled box completely full as well. The difference however is that the next empty box above it isn't very far away. In fact with a little bit of effort, we can splash some water into the next higher box, and all of a sudden we can move that splash from left to right again (conducting electrons) in that next box up. The box full of water below is called the valence band because it is made up of all the valence electrons from the atoms. The empty box above is known as the conduction band because there's enough room up there (energetically) for electrons to conduct back and forth.",
"Interestingly, if you imagine we splashed some water into the conduction band, we actually left a little air in the valence band as well (where that water used to be). These bubbles left behind can also conduct from right to left and create a meaningful current as well. In semiconductors these bubbles are known as holes.",
"Now an integral part of semiconductor physics is the concept of doping. If you can replace some of the atoms in your material with an atom that normally has extra electrons, it can (if the energy is right) donate that electron to the conduction band to allow a current to pass. Think of an eye dropper sitting just below the bottom of the conduction box that squirts water up a few centimeters. Doesn't take much energy to squirt up that much and now you have some electrons you can use for conducting! This is known as n-type doping.",
"Similarly you can put an eye dropper just above your valence band and take up a little bit of water into it, leaving some bubbles (holes) in your valence band. These can also be used for conducting! This is known as p-type doping.",
"All of semiconductor physics revolves around engineering these concepts to create useful things. By combining different semiconducting materials, with different band levels, with different doping regions, with some insulators and conductors, we can create all sorts of devices such as solar cells (photovoltaics), LEDs, MOSFETs, lasers, etc. Semiconductors are the real stars of the electrical devices world because of how varied and manipulable their properties are."
] |
[
"Small correction: increasing voltage ",
" the electron potential energy, due to their negative charge. In this case, the potential energy of the intrinsic conduction band is lowered by increasing voltage, until it is down to the level of the p-type valence band, allowing for tunneling."
] |
[
"Since the International Space Station is in the thermosphere and that is where auroras occur, has the ISS ever been engulfed in an aurora? Or is it too far away from the poles?"
] |
[
false
] |
Ah sorry, more Googling found this: (the answer is yes it has, though that video looks more like "over" and not "through") Not sure if I should delete the question or leave it?
|
[
" Yes they can be ",
" The ISS is around 330-410km above earth ",
"1",
", and the Aurora is around 90-100 km high ",
"2",
", but can go up as high as 600km ",
"3",
" you can get great views of them from the ISS.",
"Here is a BBC video of the auroa",
"Here is a NASA photo from ISS",
"This infographic"
] |
[
"Series 4 Episode 2 of BBC Stargazing had an interview with Chris Hadfield in which he discussed being on a spacewalk right in the middle of the Aurora Australis. Not been able to find a video myself, but it must be out there somewhere. He talks about having the 'rays' of it both above and below."
] |
[
"There is certainly aurora higher than 100km. 90-120km is the altitude range for the 558nm emission, the 630nm emission goes up quite a bit higher; 300km is normal, ~450km isn't that unusual and some observations see it up to ~600km. That infographic is really bad w.r.t. auroras. Emissions below 50km? Ridiculous. Aurora even down to 80km would need ",
" high energy electron precipitation."
] |
[
"What would happen if I stuck a really long pole into a black hole?"
] |
[
false
] |
Would the part that is in the event horizon break off if I pulled back on the pole? Would it get sucked in instantaneously or would it take time?
|
[
"So here's you, chillin', hanging out ",
" at rest relative to the black hole.",
"And not just any black hole, right? A ",
" black hole. A black hole that is not boiling and seething with a highly energetic stretched horizon.",
"You begin lowering your pole. Unseen by you, the stress on the pole begins to climb. Soon, there's insane internal stress on the pole, due to the difference between four-acceleration where you are and where the end of the pole is.",
"Then snap. Pole breaks. And it will always break ",
" That is, it will break ",
" the four-acceleration on the end of the pole goes infinite at the event horizon. The fragment or fragments that break off fall toward the black hole and vanish; the bit you're holding on to remains intact until you either pull it back, or lower it farther until it, too, breaks.",
"Don't ask what would happen if the pole were infinitely strong. Everyone always does, and the answer's always the same: you can't have infinitely strong materials and black holes in the same universe."
] |
[
"He and I are saying the same thing, we're just considering the problem in slightly different terms.",
"But just to clarify, no, black holes ",
" They are not cosmic hoovers. They're just gravitating bodies like any other, as long as you don't get ",
" close to them. Once you get ",
" close, their unique properties become apparent. But aside from that, they're just like anything else. Things will ",
" but they don't "
] |
[
"Wow, no, we're very far off the mark here.",
"First of all, put the idea of \"touching\" a black hole out of your mind. It's not an object. It's a region of spacetime with distinct properties.",
"Remember that in your thought experiment, you are at some fixed radial distance from the black hole's barycentre. If you lower the pole such that its far end lies at some smaller fixed radial distance, there will be a stress on the pole of a certain magnitude. The farther you lower the pole, the greater the magnitude of the stress. When the far end of the pole reaches a point where the stress exceeds the tensile strength, the pole breaks. The piece or pieces that break away fall toward the black hole and vanish. The remainder, which you are still holding, is still intact because the stress across its length is now less than its tensile strength."
] |
[
"Lenses bend light in the visible spectrum; are there materials that bend frequencies above and below the visible spectrum? If so, is it used for anything?"
] |
[
false
] | null |
[
"There's this thing called \"snell's law\". It describes how light bends when it comes to an interface between two materials (like air and water, for example). How much the light bends depends on the \"index of refraction\" of the materials in question. ",
"In physics 1, they tell you that every material has one number that describes this bending. That's false. Every material has a ",
" that describes the bending. This function depends on wavelength (or frequency)",
"So, to some degree, every material bends every wavelength of light according to this function. Some materials bend certain wavelengths more than others, but ALL materials bend ALL wavelengths to some extent.",
"Mostly, the uses are restricted to the IR through UV parts of the EnM spectrum. That's because we use IR, visible, and UV light for a lot of things. There are some applications for focusing Xrays, mainly for scientific research. I haven't heard of any applications for refracting microwaves, radio waves, or gamma rays, but there could be. "
] |
[
"I just wrote a lab report on lasers that centered around Snell's law. We used red lasers and green lasers and just proved penisgoatee's post. Go science!"
] |
[
"X-ray Crystallography",
" uses fresnel lenses made of gold"
] |
[
"Why is it that toothpaste and other minty things alter the tastes of foods such as oranges, but don't alter other foods such as bread?"
] |
[
false
] |
I'm drinking some fresh squeezed orange juice this morning minutes after brushing my teeth. It's so tart I'm having a hard time drinking it. However, my slice of toast hardly changed in terms of taste except for the subtle backdrop of mint. What is it about mint that changes your tastebuds and make orange juice so tart tasting?
|
[
"The chemical that makes toothpaste foam up also blocks your taste buds that detect sweet things, so your toast (which is not sweet at all) tastes the same but your orange juice (which is a log of sugar = sweet, and acid = sour) tastes much more sour/tart. "
] |
[
"A quick DuckDuckGo search tells me this is because of sodium dodecyl sulphate (SDS).",
"SDS is a surfactant that causes the toothpaste to foam up. Due to its shape, it inhibits your sweet taste buds. It also breaks down phospholipids on the surface of the tongue, which themselves inhibit bitter taste buds.",
"As after you brush your teeth, your ability to taste sweet things is deadened and your ability to taste bitter things is supercharged."
] |
[
"SDS is soap, fyi. The technical term is surfactant, in case anyone was curious."
] |
[
"Could you create a vacuum with a centrifuge?"
] |
[
false
] |
If you had water or air in a spinning cylinder, and it spun at a high enough speed, would the centrifugal force be enough to, I guess, cause cavitation in the center for water.
|
[
"Yes. Let's assume you put the water in a flexible cylindrical container. Let's assume that the container is made of spring-steel or something so that when it rotates, it can bulge out and increase in volume to the approximate shape of a whiskey barrel. Caution: when performing this experiment the container could burst and cause loss of life. When you start spinning, the centripetal acceleration will start to bulge the container, causing cavitation in the central axis of the cylinder. If the container is rigid, then the incompressibility of water will prevent much of interest from happening, until of course you get to high enough RPM (and thus pressures) where water is compressible again :D"
] |
[
"of course, the cavitated water in the center won't be a \"vacuum\" it will just be low-pressure steam at room-temperature."
] |
[
"If you have a liquid in the container it will vaporize (cavitate) when the pressure gets low enough. At the center, if you have vapors or gas, you would have to spinning really fast to overcome the average kinetic energy of the gas molecules at room temperature. The ",
"RMS speed",
" of gases at room temperature is ",
"~200-2000 m/s",
". If you imagine a gas molecule bouncing off the other molecules near the center, you'd have to spinning very fast to keep the bouncing ones from making it to/through the center."
] |
[
"Can light cast a shadow?"
] |
[
false
] |
I'm not exactly sure the best way to articulate this question but maybe someone can give some information on the subject. Can the flame from a candle block the light from a light bulb? Do photons bounce off each other? Do they pass through in a straight line or is the light refracted?
|
[
"In order for light itself to block other light, two bits of light would have to interact with each other. Since light consists of photons, which are bosons, and because light carries no electric charge, light never directly interacts with other light. So no, light itself cannot directly block other light and therefore cast a shadow. In other words, photons do not bounce off each other or deflect each other.",
"However, photons can interact indirectly. One way is for each photon to turn into an electron-positron pair, which then interact with each other. But this only works for extremely energetic photons that have enough energy to turn into electron-positron pairs and is very rare and exotic. Another way is for light to interact with other light indirectly by altering the medium that both bits of light are traveling through. For instance, an intense light beam can ionize air, causing it to turn from transparent to reflective, which then redirects a second light beam. This effect is used to create air waveguides - essentially one light beam is used to control where the other light beam travels by altering the air. In short, one beam of light can certainly block another beam of light and create a shadow by altering the medium that both travel through. All-optical computing circuits (photonic chips), which may some day be the CPU's of our computers, depend on light interacting with light indirectly by changing the material. Read more ",
"here",
".",
"Lastly, you need to realize that a candle flame is a lot more than a beam of light. A candle flame contains small solid bits of soot. This soot can definitely absorb light, so a candle flame can indeed cast a shadow. The flame also contains heated air, which will tend to deflect the light via refraction and also contribute to the formation of a shadow."
] |
[
"Yes."
] |
[
"Thank you for that excellent response. I should have worded the question more about the light photons themselves and left the candle bit out. I guess the root of my question is would two light photons traveling directly at each other just simply pass through each other as if the other was not there?"
] |
[
"Before European contact in the Americas, did any other wayward vessels make it across the oceans?"
] |
[
false
] |
People have been making very fine seafaring vessels for a very long time. We have also been losing these at sea for just as long. Why haven't I heard about ancient armor or trade goods in, say, a 200 BCE tomb in Guatemala or Han lacquer in some Northern California cave. Additionally, would anything like that pop up in relevant mythology?
|
[
"Well, there was ",
"that time the Vikings tried to colonize Canada",
". That's an interesting bit of history more people should know about. The settlement in Vinland didn't last long but yes, there really were Europeans here before Columbus.",
"However, we know that nobody successfully introduced smallpox or anything else obviously European before Columbus got there which puts this bound on how much contact there could have been.",
"Archaeologists don't find every last item either. Things break down with time (or get used until they're completely broken or lost in a swamp) and there's a lot of continent to search for a population of artifacts that just can't be that high.",
"If you want ",
" about people finding stuff like this then you won't be disappointed. Some of them are ",
"fascinating",
" but they are ",
"pretty obviously mostly hoaxes, wishful thinking and false positives",
" once you examine them for more than a moment."
] |
[
"They ",
" have made it across but if there was only one boat, and no settlement, and no-one got back to tell the story, the evidence is likely hard to find.",
"We still haven't managed to beat wind and wave power over long distances. No mechanically propelled vessel can keep up with a sail-powered racing yacht for a circumnavigation, not even with nuclear power or refuelling stops (doubtless this will force people to WTF straight to wikipedia so I will save you time, the page you wanted is ",
"here",
")"
] |
[
"I remember I had an anthropology class where the professor talked about remains of humans in south america that were 20,000+ years old and had to have gotten there by boat. Any truth to this?"
] |
[
"How old is Cancer?"
] |
[
false
] |
[deleted]
|
[
"Cancer is, in simple terms, cell division gone ",
" wrong. New cells are not perfect replicas and their differences don't matter in the short run, but very rarely some change in hamrful ways: they end up dealing damage to the organism by keeping surrounding tissue from functioning properly as the mutated cells keep growing, using ressources, space and so on. So, cancer is just a little younger than multi-cell-based life."
] |
[
"Curing cancer is possible once it happened. Keeping it from appearing at all means making every single cell replication perfect, which is equal to biological immortality, which is pretty hard to archieve. However, you can reduce the risk of being affected by e.g. not smoking, exposing yourself to the sun too much and so on."
] |
[
"The earliest physical evidence of cancer are bony tumors in the mummified remains of ancient Egyptians.",
"Actually...",
"\"scientists found that a fossilized foot bone, dating approximately 1.7 million years old, showed signs of osteosarcoma, an aggressive form of bone cancer. The fossil, located in South Africa, appears to have belonged to an ancient human.\"",
"If we ignore humans, ",
"tumors have been identified much much earlier in history.",
"\"Scientists have unearthed the first fossilized facial tumor.\" \"The fossil -- dated between 69 million and 67 million years old -- hails from the Late Cretaceous period.\" "
] |
[
"Could an asteroid field like the one in Empire Strikes Back exist?"
] |
[
false
] |
Could a very dense asteroid field of large asteroids like the one in Star Wars: Empire Strikes Back exist? link to picture of said fictional asteroid field: Do we know of one in any other system? From what I can tell from wikipedia there's nothing like that anywhere in our solar system. Would a dense system like that grind itself into dust very quickly/be stripped by the gravity of nearby planets and suns?
|
[
"Just consider this: if any collisions are happening frequently enough to be seen casually, it would have ground itself to dust billions of years ago."
] |
[
"Also, in the process of grinding down to dust, the velocity of the bits would gradually average out to the same direction so it would end up as cloud of dust/ pebbles going roughly the same direction.",
"The a messy asteroid field could probably exist shortly after some interesting event, but it would not persist for very long."
] |
[
"Even Saturn's rings are thought to be a relatively short-lived phenomenon, lasting maybe a hundred million years."
] |
[
"How can a fish (salmon, say) live in both fresh and salt water?"
] |
[
false
] | null |
[
"Fish are limited in their ability to live in fresh or salt water due to osmotic diffusion - sticking a freshwater fish in salt water will cause it to \"dehydrate\" as it loses water due to the hypertonic solution. Conversely, salt water fish will bloat when placed in a hypotonic solution - water flows into cells. Both these situations adversely affect normal biological functioning of the fish.",
"Salmon (only certain species) is capable of osmoREGULATION, which means that it can actively control the salinity of it's cells to adjust to both fresh and salt water. The term for this migrating life cycle of fresh to salt water is \"anadromous.\" "
] |
[
"In this, I am not an expert.",
"But to partly answer, skin cells are partly porous and are still subject to osmotic pressure, which is why they swell when sitting in the tub (the human body is big on water, but it also contains other things, including NaCl)."
] |
[
"As a follow-up: how does this compare to what happens in mammalian epithelial cells? Presumably keratinised epithelial tissue is simply impenetrable to water? Although, then, what happens when we spend too long in water and our finger-tips wrinkle? Also, how are squamous and other types of non-keratinised epithelial cells affected by changed local salinity?"
] |
[
"Is there a point in space where there is no gravitation at all?"
] |
[
false
] | null |
[
"Absolutely there are points where the gravitational force of all the stuff surrounding you balances out to exactly zero. But points like that aren't terribly interesting. That's because all the objects around you are moving so the point where this happen isn't going to remain a zero gravity point for any length of time. ",
"Lagrangian points are interesting because at those you'll remain stationary relative to two objects revolving around each other. But gravity does not sum to zero at any of these points, that is not at all what Lagrangian points are."
] |
[
"I disagree. Superposition of two or more gravitational point charges can easily lead to a net field of zero at a point, line or surface. This would be a unstable equilibrium, but none the less it exists. "
] |
[
"No. It will never equal to zero.",
"g = GM/r",
"This can never equal zero, as r (the distance between the bodies) increases the strength will be smaller and smaller but it will never hit zero",
"EDIT: If M was 0 then yes, the overall would be zero. But you get my jist o-o"
] |
[
"How accurate are calorie counts on nutrition labels or at restaurants?"
] |
[
false
] |
You would think that companies could use some method to lower calorie counts and deceive the public. Such as smaller portions.
|
[
"In the U.S., the FDA regulates the labels. Serving sizes are often smaller than what people typically eat in one sitting, which is something the new labels are changing. You can easily Google this, but I believe calories can be off by as much as 20% legally. Also, if there is less than 0.5 g of something like saturated fat, the label can show 0 g."
] |
[
"Legally yes calorie counts can be off by 20%, but there was a study a while back which tested the label vs lab results and found most food products were actually within about 8% of the label value on average if I recall correctly.",
"I'll see if I can fish that study out again and edit this post. ",
"That said if you are watching calories, you probably shouldn't rely on just the food label. ",
"Edit 1: Not the study I was looking for, but here is one on the topic",
"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3605747/"
] |
[
"In my experiancr, they will probably be higher- not as much of a product of deception but of bad practice. 1/2 cup of cheese turns into a small handful to a large handful really quickly. ",
"Also,In general food nutrition facts are based on manufacturing and probably have certain levels of confidence associated to their process. "
] |
[
"How does the \"plug\" of skin cut out by injecting someone with a hypodermic needle or IV not clog the needle and then get pushed into the blood stream and cause problems by clogging capillary blood vessels?"
] |
[
false
] |
From my understanding the needle is hollow with a pointed end, and it seems like this would act like a leather punch and cut a disk of flesh out, which would then clog the needle and be forced into the bloodstream when the medicine is injected. How does this not cause problems when it enters the blood stream? Do needles not work that way?
|
[
"In some ways it's better to think of a needle as a knife, not a punch. It has a beveled end, and a newly uncapped needle is ",
". In fact, in surgeries we sometimes use small (e.g. 30ga) needles as microknives, just to cut something without ever intending to punch into it.",
"So ideally the needle splits the skin and enters the desired tissue \"clean\". You can also help this process, when necessary, by applying slight positive pressure to the syringe that is on the back end of the needle; this pushes material away and stops anything from plugging the tip. This technique is used, for example, in a related kind of procedure called whole-cell recording (where the \"needle\" is actually a pulled glass pipette, with a subcellular sized tip).",
"Edit: fixed minor typos. Also, it's worth mentioning that needles commonly are not bare metal, but have an ultrathin coating that reduces friction, thereby also lessening the chance of material getting stuck to the tip.",
"Also, while I'm on a roll, there can be a ",
" decrease in effectiveness after a needle is first used. They are not meant to be reused."
] |
[
"We used to pull glass pipettes to use as capillary tubes for thin layer chromatography... We would have competitions to see who could pull one the farthest. ",
"One of our older professors saw what we were doing and chuckled. He walked up and held one over the meker burner... rotating it slowly for about 45 seconds. Then he pulled it as fast and as far as he could, stretching it across his chest so his arms were behind him. It measured 2.5 meters even though he was roughly 2 meter tall. We were all lucky to get one 1 meter in length."
] |
[
"Take a look at what the end of a hypodermic needle looks like ",
"here",
"",
"As you can see the angle of the hole in the needle means that the skin is pierced by the pointy bit before it ever really comes into contact with the hole.",
"",
"Pierced. Therefore, not hole punched."
] |
[
"Is it a given that all patients with COVID will have some degree of long-term damage?"
] |
[
false
] |
Anybody have a research-supported opinion on this? Or any articles that you can share on this? Thank you
|
[
"Around 1 in 10 respondents testing positive for COVID-19 exhibit symptoms for a period of 12 weeks or longer",
"—",
"The prevalence of long COVID symptoms and COVID-19 complications",
"That says that 90% of COVID patients do ",
" have long-term symptoms. You could assume that some of those 90% may have some kind of undetectable damage that might show up later, but there’s been no surge in late-appearing complications from people infected 9-10 months ago, so that seems unlikely to be a major factor."
] |
[
"https://www.mayoclinic.org/diseases-conditions/coronavirus/in-depth/coronavirus-long-term-effects/art-20490351#:~:text=COVID%2D19%20symptoms%20can,within%20a%20few%20weeks",
".",
"tl:dr most people see lingering effects of organ damage from the virus during their recovery. These can last weeks to months. Plain and simple we don’t know the long term effects because the virus is too new. The lasting effects of the virus will be revealed in time"
] |
[
"It's worth noting that many studies are only looking at people who have had sufficiently severe symptoms to at minimum get tested and at maximum be hospitalised. There is a significant fraction of cases where people either get no symptoms at all or where the symptoms are mild enough that they don't recognise it as COVID. ",
"So be aware that stats you may see in terms of '1 in 10 people with lingering effects' or whatever could be referring to 1 in 10 overall or just 1 in 10 of those with serious symptoms, which makes a huge difference. Worth checking the methodology behind the gathering of said stats so you get a clear picture."
] |
[
"Does the flow of time have a constant?"
] |
[
false
] |
Maybe I'm not asking the question right but I'll try to clarify. We as humans measure time based on a rotation around the sun (in terms of years, days, hours and seconds). Is there something more fundamental then this? Is there a constant like the speed of light in a vacuum or Planck's Constant for time?
|
[
"The speed of time is not constant. It is relative. Hence Einstein's theory of relativity which has been experimentally confirmed. The faster you're moving the slower time moves for you, compared to someone moving more slowly.",
"This visualization should help.",
"https://youtu.be/mgkyxZSYnVE",
"If you're standing inside the cart you see the photon bouncing up and down. You see it traveling the distance between the top and bottom of the cart.",
"If you're looking at it from outside, not moving with the cart, you see the photon traveling a zig zag pattern which is a longer distance.",
"Because the speed of light (the photon) is the same for both the person on the cart and the person not on the cart, the only other variable that could be changing is how fast time is passing. Same speed of the photon but longer distance (not on the cart) means more time has to pass therefore time is moving faster to the person not on the cart.",
"If you could travel on a ship near the speed of light for a year (from your perspective) many years would pass for those not traveling with you.",
"This would essentially be time travel for you. You could travel near the speed of light for a year and come back to Earth and many years would have passed on Earth. "
] |
[
"That is an optical clock."
] |
[
"It's really as simply as using a formula. The clocks onboard GPS satellites already do this. They corrected for both special and general relativistic time dilation effects so that they run at the same rate as clocks on the surface of the Earth (as observed from the Earth's surface)."
] |
[
"If subatomic particles have a size, how is it theorized that the universe and all matter was at one point infinitely small?"
] |
[
false
] |
Prior to the Big Bang.
|
[
"Particles aren't really \"solid\" the way you'd expect. The apparently solidity of objects -- if you smack your hand against a table, it certainly feels solid -- is (at everyday energies) due to the electromagnetic force. The electrons on the surface of your hand are strongly repelled by the electrons on the surface of the table, and so you can't push your hand into the table. It has absolutely nothing to do with the \"size\" of the particles, merely that when electrons are very close together they push against each other very powerfully.",
"The electromagnetic force is ",
" strong, and you aren't even remotely close to being strong enough to overcome that force, but it is possible to overcome it in high-energy situations and squeeze matter together more tightly than its apparent solidity would suggest. You'll encounter other forces, such as electron and neutron degeneracy, which keep you from compressing the matter further, but each of those forces is only finitely strong and therefore can be overcome. With sufficient force, it is possible to overcome these forces and squeeze particles even tighter together.",
"So far as we know, there is no force strong enough to prevent particles from being crammed into an arbitrarily small space. They really, ",
" don't want to do that, and push back with unbelievable force, but as long as you squeeze them together with an equally-unbelievable pressure, you can overcome their reluctance to do so and crush them down to a tiny point. That's what a black hole is -- the result of an unbelievably strong gravitational pressure overcoming neutron degeneracy pressure, and at that point there is no force we know of strong enough to keep the matter from being pushed together further."
] |
[
"As far as we know they don't have size, and the universe was never an infinitely small point."
] |
[
"People are giving more complex answers than necessary. Sub-atomic particles didn't exist for several pico-seconds until after the Big Bang. "
] |
[
"How does human strength compare to that of other animals?"
] |
[
false
] |
It's my understanding that humans are abysmally weak for their size in comparison to other great apes, but is that because other great apes are very strong, or are humans just weak? What i'm asking is, how does our strength compare to other animals of equal weight? Particularly mammals and other chordates.
|
[
"In ",
"this",
" paper, they compare the jumping power of a male bonobo vs a human male athlete.\nThey are able to generate almost exactly the same amount of power, despite the bonobo weighing 34 kg and the human 61 kg, where humans at the same time have larger leg muscle mass in proportion to total bodyweight than the bonobo.\nThey suspect that, either the maximum muscle contraction velocity is higher for the bonobo, or that the specific force of the contractile material is higher (or both).",
"TL;DR it has nothing to do with muscle mass, but the ",
" the muscles contract."
] |
[
"we are weaker than other primates of comparable weight.",
"Could you provide some numbers on this?"
] |
[
"we are weaker than other primates of comparable weight.",
"Could you provide some numbers on this?"
] |
[
"Why aren't Hybrid vehicles being produced en masse as a transitional technology to EVs?"
] |
[
false
] | null |
[
"Thank you for your submission! Unfortunately, your submission has been removed for the following reason(s):"
] |
[
"How is the premise this question \"fundamentally flawed\"?"
] |
[
"I work in the energy industry BTW, so I'd love to hear how my question is \"fundamentally flawed\"."
] |
[
"E=mc^2 always?"
] |
[
false
] |
Does E=mc always, or is that just understood in some specific context, and there are other factors added in? What I'm trying to ask is whether it's true that all energy is "stored" as mass. When I pick up a brick and set it on a shelf, does that brick have more inertial mass because it has more potential energy? Is a hot pan heavier than a cold pan because of the relativistic movement of the atoms? Just something I've been wondering, thanks! (Wondering since long before I knew anything about relativity, actually. :-)
|
[
"So the actual equation is",
"E",
" = m",
" c",
" + p",
" c",
"where p is momentum. Thus E = mc",
" is only for objects at rest.",
"As for energy being \"stored\" as mass, something like that happens. IIRC, mass does increase (imperceptibly) when an object is heated due to the thermal energy in it. But a better example is to look at the binding energy of quarks. If you compare the masses of ",
"quarks",
" to the masses of ",
"protons and neutrons",
" you can see that almost 90% of the mass comes from the binding energy holding the quarks together."
] |
[
"Better to say that rest mass (this is the more appropriate term than inertial mass) is a form of potential energy."
] |
[
"No, it means that all energy is represented as mass. There's no point in picking one example and by implication doubting the others."
] |
[
"How big can an all-liquid-water planet be? (no/mininal solid core)"
] |
[
false
] | null |
[
"About 3 or 4 Earth radii. ",
" (Edit: I shouldn't make statements I can't back up.)",
"Figure 5 from Lissauer et al. Nature 470, 53–58 (03 February 2011)",
"Figure 4 from Seager et al. Ast.J. 669:1279-1297 (2007 November 10)",
"Let me know if either of these is blocked by a paywall."
] |
[
"Related Question: Is there any mechanism by which an earth size planet principally made up of water would form?"
] |
[
" water. Once pressurized enough, water becomes solid (see ",
"here",
"). You have to calculate the pressure as a function of depth for a planet with the density of water, then solve for the radius with a pressure of around 1 GPa. Use ",
"this",
" to find the pressure as a function of depth. ",
"You get R = sqrt( 3 P_max / 2 pi G rho",
" ), giving an answer of R = 2 675 km or about twice the radius of the moon. "
] |
[
"At what point would one find a parity between the performance of a Diesel Electric engine, compared to a Diesel Mechanical engine?"
] |
[
false
] |
Let's say you could build two engines to propel a vehicle, a Diesel (with traditional 5/6-speed transmission) or a Diesel Electric. At what displacement would both engines make comparable horsepower, torque and fuel efficiency?
|
[
"Side by side the actual diesel engines would effectively be the same. The overall thermal efficiency of a diesel engine won't improve solely based on the driven equipment. It is the friction and thermal losses in the driven equipment that will have the biggest impact on which is the better option. The task that needs to be performed is the biggest driving choice as to whether gears, electric or hydraulic drive is the best option and even then there still may not be a clear winner. "
] |
[
"A diesel electric engine would surely be heavier than a regular diesel engine with the same torque, though?"
] |
[
"The engine itself no. There is no difference in engine size. The engine doesn't care if you hook up a generator or mechanical transmission. You could make the weight of either setup close enough to make it insignificant."
] |
[
"[Astronomy]Binary Systems (Star-Black Hole)"
] |
[
false
] |
[deleted]
|
[
"Orbital motions care about the mass of the system's constituents -- so if a star is orbiting a 50 solar mass partner, the star doesn't care if its partner is a black hole or a regular ol' star. But there are other considerations we need to note for your hypothetical situation.",
"For one, the planet would most likely be orbiting around the star, as planets form as a result of star formation -- though I suppose it would be possible for the planet to orbit the black hole, any existing planets may be annihilated during supernovae. In this situation, the black hole would never come between the star and the planet, making an eclipse impossible.",
"If the planet does orbit the BH, the orbital planes have to line up. In our solar system, the Sun, the Earth, and the Moon live basically in the same plane -- so you can have solar and lunar eclipses. The Earth can come between the Moon and the Sun along a single line of sight. This would need to be the case for your BH-Star-Planet system. The planet could have a totally different orbital axis as the star-BH -- if that's the case, no eclipses would occur.",
"As for what you'd see on the planet... the size of a black hole is not really well defined (outside of extreme general relativity) except for its event horizon. In the rare case that the black hole is orbiting the black hole, I honestly don't know how the eclipse scenario would look, other than speculate that ",
"gravitational lensing",
" would occur.",
"Black holes are typically observed because they have accretion disks -- were it not for our observations of their effects on surrounding matter/objects, we wouldn't know they were there at all. We can't \"SEE\" black holes."
] |
[
", but I use the term \"plane\" rather loosely. You don't have lunar eclipses every month because the Moon ",
" slightly different, though damn close (within 5%). If the system were somehow perfectly in the same plane, they'd happen as frequently as the planet orbits the black hole -- if its orbit was significantly faster than the BH-star orbit.",
"I think the planet would always be freezing because it is not orbiting a luminous object. This would not be a habitable planet for humans."
] |
[
"Hey thanks. Im guessing that if the BH/Star/Planet where on the same plane, with the planet orbitting the BH, eclipses would be pretty much yearly events wouldnt they? Probably get pretty damn cold for most of the 'year' when the planet is not in perihelion to the star, and absolutely freezing when the planet is on the far side of the BH?"
] |
[
"Would thorium be a candidate for use in an atomic bomb?"
] |
[
false
] | null |
[
"Thorium is not a fissile element (like Uranium or Plutonium), meaning hit it with a neutron and it doesn't split, which doesn't release any energy.",
"Thorium is a fertile element, so that neutron you hit it with gets absorbed, and \"breeds\" the thorium into a completely different element. It becomes protactinium 233, which has a half life of about 28 days. So if you shot ten thorium atoms with ten neutrons and had ten absorptions, you'd have ten atoms of protactinium, and 28 days later you would (on average) have 5 atoms of protactinium and 5 atoms of uranium-233.",
"Now, uranium 233 is fissile, you can theoretically make a bomb out of it. It is the fuel that would get 'burnt' in a thorium reactor. ",
"There is a problem though. Any time you are 'breeding' thorium into protactinium 233 in order to eventually make more U-233 you can't help but make some protactinium 232. The same neutrons that would hit a thorium atom and get absorbed sometimes hit a protactinium 233 atom. In whats called an (n,2n) reaction, the neutron hits the protactinium, but instead of splitting or absorbing the neutron it just spits out two neutrons. This turns protactinium 233 into protactinium 232, which has a half life of only 1.2 days before decaying into Uranium 232.",
"Uranium 232 decays into some isotopes that emit very high energy gamma radiation which is difficult to shield against, quickly causes radiation poisoning, breaks down chemical explosives and fries electronics. It also shows up on satellite sensors. ",
"Now if someone is hell bent on making a bomb from thorium and had the expertise and equipment to do so, they might be able to process the protactinium before much 232 could form, then try to filter out what did get into the mix by purifying the 233 every few days. But you have to remember that they would be working with a very very radioactive very very hot substance and even then they can only minimize how much 232 they filter out. And if they have all that expertise and equipment and access to reactor technology they are much more likely to build a bomb the conventional way, using U-235, U-238, or Pu-239.",
"So can thorium be used to make a bomb? Yes. It it as easy to make a bomb from thorium as it is to make one from natural uranium or plutonium? Probably not."
] |
[
"No, IIRC if you try to enrich thorium it gives off too much radiation and screws up your electronics and explosives, as well as giving away your position.",
"You might be able to do it, but it's certainly not practical."
] |
[
"Thank you for the very in depth response! I was genuinely curious."
] |
[
"What type of technology is used to determine if there are inhabitants on remote planets (e.g. Kepler-20F)?"
] |
[
false
] |
If said technology does not exist, what would it take to determine this?
|
[
"Well we could listen for radio transmission with radio telescopes. If they have particularly bright spacecraft drive systems we might see that as well.",
"Short of that sort of thing we don't have a way to tell. Certain signs of life could be detected with spectroscopy done by a probe in the planetary system, but if you want to check for a pre-industrial civilization you're most likely going to have to take photos from orbit."
] |
[
"Well since it's around 1000 light years away, it's faster to wait and build a faster probe than to send one with existing technology. The future technology is hard to predict, but definitely more than 1000 years from the launch date."
] |
[
"This is why I hate humanity so much. We've got all that space out there to explore, but we're too damn busy arguing about the apparent lack of it here. So disgusting."
] |
[
"If I'm phoning an alien in another galaxy, whose relative position is unknown, is it possible to tell them what we mean by left and right just by talking?"
] |
[
false
] | null |
[
"Yes, in fact it is possible to universally define \"handedness.\" Before explaining how you can do so, realize that this situation was by no means obvious and in fact for a long time it seemed impossible. The reason is that in general physical laws tend to be pretty symmetrical. In this case, the relevant symmetry is ",
"parity",
", or the flip of one (or multiple) directions in a coordinate system, e.g. going from (x,y,z) to (-x,-y, -z). Most physical laws (including gravity, electromagnetism, and the strong force) behave exactly the same when you change the parity of a system. Now while there are certain natural examples that break this symmetry, e.g. chiral biological molecules or the asymmetry of human bodies, these differences are a mere coincidence of evolution and the physics would work essentially identically if you just flipped everything. ",
"However, there is one major exception which is universal: the ",
"weak interaction",
", which ",
" always conserve parity. In practice, this makes the decay of certain particles have a certain handedness, ",
"as shown here",
". If you know the spin of the particle, you can now universally define a direction as left vs right. with respect to the result of the decay. So to explain what we mean by left, all you have to do is to explain to the alien how to set up this experiment and they will get the same result."
] |
[
"Richard Feynman gave a lecture on precisely this topic and gave an answer substantially similar to yours. He points out that if the alien were composed of anti-matter in a region made primarily of antimatter, the alien would not know that it was made of antimatter and reverse left and right due to the reversal of spin in radioactive decay.",
"The conversation about the alien begins at 40m.",
"https://www.youtube.com/watch?v=zQ6o1cDxV7o"
] |
[
"However, there is one major exception which is universal: the weak interaction[2] , which does not always conserve parity. In practice, this makes the decay of certain particles have a certain handedness, as shown here[3] .",
"That's amazing. Do we have a model for what causes the asymmetry?"
] |
[
"Why do humans perceive minor musical scales as \"sad\" sounding and major scales as \"happy\" sounding?"
] |
[
false
] | null |
[
"Music composition/theory student here: A lot of it has to do with the way you've been raised on music. If it weren't for the tonal system of music that we use today, you might perceive music completely differently. There are tones in music that we call \"tendency tones\"; due to the way we've been raised to listen to music, we have come to expect the resolution of these tones to other tones. You can \"try\" this for yourself by singing the first 7 notes of a scale; if you were to ask someone what the next logical note in the sequence would be, they would likely repeat the first note in the scale you sang, up an octave.. This is not due to innate human nature; it's a result of the musical system you've internalized your entire life.",
"Another possible component of this is the fact that the major third is less dissonant than the minor third, and the third is the scale degree that defines the major or minor mode. Because the minor third (the interval between the first and third notes of a minor scale) is technically more dissonant than a major third (first and third notes of a major scale), this may play into the psychology of it as well. ",
"Another interesting thing to think about; we are not limited to minor and major modes. There are a multitude of different scales musicians used in ancient music (and still use today); check out music written in \"Dorian\" mode(or any church mode for that matter; Dorian, Lydian, Mixolydian, Phrygian, Locrian, to name a few). It's a fundamentally minor scale, but the music that results isn't always sad sounding. It has a very interesting, very gothic/old feel to it. ",
"Finally, the guy below has a point. Your question is sort of fundamentally flawed; you can make very sad sounding music using major scales, and you can make very happy music using minor scales. It depends on the context the scale is put in, and that isn't always as black and white as happy/sad. Music can be whatever emotion you interpret it to be, that's why it's awesome :)"
] |
[
"There is also a bit of convention. There is nothing stopping you from writing \"sad\" music in sharp, or in any scales apart from the conventional western ones. Minor scale is one shorthand for \"sad\" music, but tempo, rhythms, instrumentation &c. also play a role."
] |
[
"Beethoven's Ninth Symphony, fourth movement is a good counterexample to minor pieces having to sound sad. Do you have any other well known counterexamples off the top of your head?"
] |
[
"Easy question on pronunciation from an undergrad physics major."
] |
[
false
] |
So I have to give a presentation on a project I'm working on later today...in part of the background, I will briefly mention applications of the general field I'm working on. Of course, most of these are some super high level topics that I don't know much about, but I do need to mention them My trivial question is: how do people say "AdS/CFT dualtiy" in general speech. Do people actually just say the letters A D S C F T? Or is it more common to use the full name. I don't really wanna make an ass of myself... Thanks
|
[
"Anti Conformal Sitter De Field Theory"
] |
[
"\"Ay dee ess see eff tee.\"",
"About half the time, it's said in the right order. The rest of the time the letters are mixed up, but everyone's too polite to call attention to it."
] |
[
"I don't think I've ever heard someone saying \"anti de-sitter conformal field theory\", so yes, A D S C F T is the norm, at least here :)"
] |
[
"Looking for reading material for the moon."
] |
[
false
] |
hoping i do this right. I'm looking for information on the moon and it's effects if any on the earth other than tides. Also curious about orbits, rotations, revolutions etc. I'm not even an amateur astronomer, i was just curious about the moon lately and wanted to find some reading material. Thanks.
|
[
"Dude, you are not an astronaut looking for some good reads to take with you on your secret trip to the moon? Fuck!"
] |
[
"Where do you live? I may be able to mail you a book, if you're interested"
] |
[
"I live in Ohio. Just curious though. While it's generous of you to give away a book, I'm wondering why?"
] |
[
"Our brains are very good at to recognizing faces in the images we see. Is there anything else that our brains are especially good at picking out from what we see?"
] |
[
false
] |
[deleted]
|
[
"Yes, we have numerous \"pre-cognitive\" patterns that we can discern as it relates to pattern recognition. A few of these include size, solidity, and fate (direction) of an object as it relates to other objects near it. Check out Dan Roam's work in visual communication for more juicy details. "
] |
[
"Basically you have specialized image processing all over the visual cortex combined with color vision, which in itself isn't that great.\nBut almost all kind of patterns have an dedicated orientation.\nIf you're interested I'd recommend reading papers by Hubel Wiesel.\nContrast detection is something humans are quite good at."
] |
[
"Sort of on topic, I've always wondered if there is a way of formulating problems in such a way as to be able to easily solve them by taking advantage of our built in hardware acceleration. Facial representation of math problems has a nice ring to it."
] |
[
"Why hasn't the gas on Jupiter fully mixed together yet? Why is it covered in visibly distinct regions of gas rather than being a single color like Neptune or Uranus?"
] |
[
false
] | null |
[
"This question gets asked a lot here - repost of my answer when this was previously asked:",
"The atmosphere ",
" well-mixed (hydrogen and helium), but that's pretty much colorless. The clouds, on the other hand, have lots of different colors - what you're seeing is clouds being continually formed and destroyed as they cycle through the atmosphere.",
"For the primary whites and browns that cover most of the planet, note that almost everything you see when you look at Jupiter is ammonia clouds, which on their own are bright white. Some latitudes are regions of upwelling (zones), and have high ammonia cloud-tops, while other latitudes are regions of downwelling (belts), and have low ammonia cloud-tops, as shown in ",
"this diagram",
". In between these high and low heights sits a thick brown hydrocarbon haze (not shown in the diagram), very chemically similar to smog. The cloud-tops in the zones are sticking up above most of the haze and thus appear fairly white. The cloud-tops in the belts, though, lie below the haze layer, and thus appear colored brown by the overlying haze.",
"For the occasional bluish regions seen just to the north and south of the equator (as indicated by the arrow ",
"here",
"), these are some of the rare cloud clearings that occur in very strong downwelling regions. We're actually peering through the ammonia top cloud layer, and perhaps even down through the ammonium hydrosulfide middle cloud layer and the bottom water cloud layer. So, in those regions we're looking at just clear air, which has the exact same color as it does one Earth, blue. This is entirely due to Rayleigh scattering, the same reason that Earth's sky is blue.",
"Then there's the reds, notably in Jupiter's Great Red Spot, although also occasionally seen in another big vortex here and there. As of right now, we ",
" what makes the Great Red Spot red - this is generally known as the Jovian chromophore problem. Since this color is only seen in very large vortices, it's believed to be caused by some mixture of compounds already present on the planet getting pushed very high in the atmosphere by these vortices. In three dimensions, the Great Red Spot is essentially shaped like a wedding cake, so the cloud-tops at the center of the spot are at very high altitudes where there's a lot more ultraviolet light. You can end up producing all kinds of odd substances through UV photochemistry of trace substances in the atmosphere, and the working hypothesis at this point is that it's some kind of ",
"imine or azine",
"."
] |
[
"Jupiter is essential a giant ball of super heated gasses",
"By mass, Jupiter is mostly liquid metallic hydrogen. The term \"gas giant\" is actually a misnomer.",
"it's massive magnetic field means it laughs at the sun's attempts to blow off atmosphere with the solar winds.",
"Oof, you're not repeating the myth that \"a magnetic field is required to retain an atmosphere\", are you? A quick look at Venus should tell you that's not true."
] |
[
"Saturn, Uranus and Neptune have lower temperatures in the upper atmosphere because they are further away from the Sun, so the gas moves less between areas.",
"Neptune has the highest recorded wind speeds anywhere in our Solar System, so...no."
] |
[
"Do the bodily fluids necessary for conception of an offspring originate from an area between the spine and the ribs?"
] |
[
false
] | null |
[
"Not unless you want to get really generous with the definition. Seminal fluid is made up of secretions from the testes, seminal glands, prostate, and bulbourethral gland. The ones besides the testes hang out around the bladder, which is certainly around the tail end of the backbone, but is further down our bodies than our ribs go, by a long shot. The yellowsish fluid would be from the seminal vesicle."
] |
[
"No, fluids involved in conception in females do not come from the breast or rib/chest area. There are some vaginal secretions, but nothing coming from the part of the body you reference."
] |
[
"(Proceeding from between the backbone and the ribs.)... the ribs of the woman, which is referring to her chest.",
"Does the rib/chest area in females release a drop or fluid as the text from Ibn Kathir's exegesis says? Are there any fluids released from that area that are integral to conception (as the spermatozoa made in the testicles?)"
] |
[
"Why is the bending of light by gravity a consequence of general relativity?"
] |
[
false
] |
Okay, so I know a little bit about this. The thought experiment goes that if you pretend you're in a gravity-free elevator or something and it's accelerating upward and light comes in one side and travels to the other side, it'll hit the other wall at a lower height because the system is accelerating upward and then by the equivalence principle, gravity must do the same thing. BUT Why is this also not the case in an elevator that is simply moving upward and not accelerating upward (aka, a non-inertial frame)? It seems like the fact that it's accelerating doesn't matter, only the nonzero velocity.
|
[
"If you imagine the elevator is full of fog and think about it geometrically, when the elevator is accelerating the path of the light is curved. One could draw a straight line between where the light begins and where it hits the opposite wall, and in Euclidean space this would be a shorter path than the one light takes. Because light takes the curved path, it suggests that the path of minimal time (which light follows) is not the straight one.",
"At constant velocity it doesn't matter because the path is a straight line anyway."
] |
[
"Light travels in a \"straight line.\" However general relativity states that mass \"warps\" space. The warping of space time can be thought of as making \"straight lines\" curved. It's much like an aircraft on earth. The shortest distance between two airports is along the major circle containing both. Even thought the plane \"goes straight\" along this path, the path itself is curved."
] |
[
"Why is this also not the case in an elevator that is simply moving upward and not accelerating upward (aka, a non-inertial frame)?",
"Remember, all motion is ",
". Let's look at it from two different reference frames: the elevator's reference frame, and the ground's reference frame.",
"In the elevator's reference frame, the elevator is at rest (so, neither moving nor accelerating). If the light enters the elevator at a perpendicular angle (parallel to the elevator's floor), it will hit the other side at the same height it entered at, simply because the elevator ",
" moving, and the light has no motion in the up-down direction.",
"In a \"ground\" reference frame (where the elevator is moving upward, but still not accelerating), the elevator has up-down motion, but so does the light. Whatever ",
" velocity the elevator has in the up-down direction, the light also has that much ",
" velocity in the up-down direction. An observer on the ground will see the light travelling at an angle which is not perpendicular to the elevator's walls, but will still see the light hit the second wall at the same height it entered the first wall, because the elevator is moving along with the light.",
"Hope that helps.",
"(Edits: Silly mistake.)"
] |
[
"About the 100 foot fissure in Yellowstone. What could that mean? What are the consequences of it opening up so suddenly?"
] |
[
false
] | null |
[
"The crack is not in Yellowstone, it's near Yellowstone. This is significant, because ",
"it's in the Grand Tetons",
" an ",
"actively exhuming mountain range characterized by steep, rocky hillslopes",
", where cracks like this are exceedingly common. A good analogue for this feature this are the ",
"exfoliation joints that that lead to rockfalls in Yosemite",
". I'm not sure of the rock type in the specific area of the crack (i.e. whether it is technically an exfoliation joint in a granitic rock like those that are common in Yosemite), but regardless of the exact rock type in this area, features like this are 1) common in steep, rocky landscapes, 2) develop overtime through a variety of surface weathering processes, e.g. ",
"freeze-thaw cycles",
" but can propagate rapidly (e.g. this ",
"video from Yosemite",
" of an exfoliation joint propagating somewhat violently in a few seconds) and 3) have nothing to do with the Yellowstone caldera."
] |
[
"Ah that is much more informative than anything I've seen on it. Everything I read made it seem like it was a huge deal and right near the volcano. Thanks for clearing that up!"
] |
[
"USGS is the go-to source for rocky drama in the USA.",
"Even ",
"IFLScience had a good piece",
" on it, with source from everyone's favourite \"nope\" volcano doc, Janine Krippner."
] |
[
"What happens when you shoot a proton into Bose-Einstein condensate?"
] |
[
false
] | null |
[
"You would likely introduce enough energy to ensure that it is no longer a BSE."
] |
[
"A lot of different things ",
" happen, depending on how hot the golf ball is and how big the swimming pool is and a variety of other factors. But there's nothing inherent to golf ball-swimming pool interactions that would permit a general answer."
] |
[
"Because it's not particularly interesting. If you add too much energy to a Bose-Einstein condensate, it will stop being a Bose-Einstein condensate. That's hardly unexpected."
] |
[
"What is the minimum number of pre-filled spaces on a standard 9*9 sodoku puzzle that will give a single solution?"
] |
[
false
] |
Sudoku puzzles vary by difficulty, usually based on how many of the spaces are filled in beforehand. Logically, there must be some minimum number of these spaces that can be filled before more than one solution to the puzzle becomes possible. How would this be calculated?
|
[
"Seventeen",
". "
] |
[
"Besides, a proof is a proof. Not all of them have to be elegant, it is irrelevant."
] |
[
"Besides, a proof is a proof. Not all of them have to be elegant, it is irrelevant."
] |
[
"AskScience AMA Series: We're Experts Here to Discuss Zoonotic Disease. AUA!"
] |
[
false
] |
Zoonotic diseases, those transmitted between humans and animals, account for 75% of new or emerging infectious diseases. The future of public health depends on predicting and preventing spillover events particularly as interactions with wildlife and domestic animals increase. Join us today, May 27, at 2 PM ET (18 UT) for a discussion on zoonotic diseases, organized by the American Society for Microbiology (ASM). We'll discuss the rise of zoonotic diseases like COVID-19 and Zika, monitoring tools and technologies used to conduct surveillance, and the need for a One Health approach to human, animal, and environmental health. Ask us anything! With us today are: Links:
|
[
"Hello, thanks for the AMA!",
"What do you make of the recent mysterious disease originating in Canada, which was tentatively labeled a prion disease?"
] |
[
"The risk of zoonotic diseases in humans can be mitigated, but not entirely eliminated, since zoonotic pathogens persist in animals irrespective of whether humans are part of the picture. I can’t think of a single zoonotic pathogen that has been ‘eradicated’ in human populations. ",
"The historic low in influenza cases this year was brought about because of global dampening in human to human transmission. But reducing a pathogen’s spread once it has already spilled over into humans is different from reducing initial spillover risk, which originates from contact with animal reservoirs. Reducing human to human transmission will keep spillover events from turning into epidemics, but it will not eradicate the spillover events themselves from occurring from the animal reservoirs. ",
"There are many effective strategies for reducing this risk of spillover transmission, for avian influenza and other pathogens, many of them targeting the nature of human contact with potential animal reservoirs. ",
"Here are two great papers about this: ",
"Plowright et al. 2017. Pathways to zoonotic spillover.",
"Sokolow et al. 2019. Ecological interventions to prevent and manage zoonotic pathogen spillover."
] |
[
"How would the number of zoonotic diseases decrease if factory farming would cease to exist?",
"\nAnd how much would it decrease if humans were to not eat any animal products, therefore (I assume) destroying the breeding grounds (farms) and transmission opportunities (contact of humans to other animals) for zoonotic pathogens? ",
"Would it go close to zero or is a big number of these diseases also transmitted in ways other than via farmed animals?",
"\nAdditionaly: Would the ratio of 'more dangerous' and 'less dangerous' zoonotic diseases change in such a situation?"
] |
[
"Do objects orbiting one another travel in straight lines through curved space?"
] |
[
false
] |
Or vice versa? Does gravitational attraction make them travel in an arc?
|
[
"There are three spatial dimensions: x, y, and z. ",
"So far as we can confirm, yes.",
"Time is a non-spatial dimension",
"Yes.",
"that allows events to occur.",
"Erm...maybe?",
"It can be thought of analogously as a ever-increasing stack of independent \"moments\".",
"In the most general spacetimes, this actually isn't true. You can't, in general, split all of spacetime into a series of \"space\" bits that then advance through time. You can do it over small regions for a short time, but in general there just isn't any way to make that splitting.",
"We can look at these discrete moments and see that three dimensional space changes from one to the next",
"Yes. In a region like that in our solar system, this is definitely doable.",
"although we don't understand how time itself progresses.",
"I'm not sure that's true, mainly because I'm not sure what it means.",
"Space is curved in all four dimensions.",
"Space",
" is curved, yes.",
"Even time is affected, in the sense that the rate of passage changes progressively with the curvature.",
"Not ",
" like that; if you take what one persons considers to be \"space\" and \"time\" and then go find another observer, the second one will often think of \"time\" as some combination of the first observer's directions. Time dilation is something that happens when people compare clocks, meaning that they separate and then come back together. This coming back together is important as it allows them to be sure they're using the same notion of \"space\" and \"time\".",
"We don't really understand how matter-energy curves space",
"This is a sticky point. We don't really understand how ",
" works; all we have are models that accurately predict the future behavior of systems.",
"the finest minds, and models of our universe, can make very educated guesses. ",
"Our models for gravity are quite accurate, yes.",
"And to answer my own original question, objects travel in straight lines through curved four dimensional spacetime. ",
"Again, you have to be careful what you mean by straight line. In the common parlance that is correct, but it's not nearly so simple as just taking a line on a flat surface and \"bending\" it around a curved one."
] |
[
"In a word, Yes.",
"The orbits are straight in a ",
" sense: the elapsed relativistic proper time (the time measured by a perfect wristwatch affixed to one of the objects) is invariant under small changes in the orbit. Non-inertial trajectories don't have that property: in any orbit other than the inertial one, changing the trajectory slightly would change the proper time along the trajectory. ",
"This view of curvature is fundamental to the ",
", which is about finding curves with certain invariance properties. You can use the calculus of variations to find straight lines in normal Euclidean space -- in Euclidean space, \"the shortest distance between two points is a straight line\" is equivalent to \"a straight line is the curve whose length is invariant under small perturbations of its shape\", because Euclidean space has no curves that are local ",
" of length -- only local ",
", so any curve whose length is invariant under infinitesimal changes must be a local minimum.",
"Einsteinan relativity uses hyperbolic space, so the inertial path is actually a local ",
" in proper time -- if you follow any course other than the inertial one between two events in spacetime, your wristwatch will show ",
" elapsed time than if you followed the inertial trajectory. Just like, in Euclidean space, if you follow any curve other than a straight line between two points, you'll find ",
" distance covered than on the straight line path.",
"That notion of curvature is tied very deeply into the shift from classical mechanics to quantum mechanics: we now understand classical mechanics to be due to constructive interference from a ",
" of possible trajectories taken by any object. The observed trajectory of a large object like ISS or a Soyuz must be a trajectory whose total phase shift (a measure of elapsed proper time) is stationary under perturbations, because that property causes constructive interference of the possible paths taken by the object. That sounds spooky and weird at first, but it's exactly analogous to the construction of ray optics from the theory of electromagnetic waves."
] |
[
"The phrase \"straight line through curved spacetime\" is actually a bit ambiguous. A more precise statement would be that they are following the curved spacetime analogue of a straight-line. That is, there is this thing called a geodesic, which is a curve that obeys certain rules related to curvature. In a flat space, this looks like a straight line. On a sphere, this looks like a great circle (such as the equator or lines of longitude). In a curved spacetime, you watch an object following such a path, you will see (in some cases) that it moves in an orbit like those of Earth about the Sun."
] |
[
"If Helium is the second most abundant element in the universe then why is there a shortage on earth?"
] |
[
false
] |
Is it even possible to harvest from space?
|
[
"Two reasons, 1) helium is very light, which means that helium atoms can easily ",
"escape the atmosphere",
", and 2) because helium, because it is a non-reactive ",
"noble gas",
" is not incorporated in many other compounds and minerals.",
"To start off with the first point, every astronomical body has a characteristic escape velocity, which is given by ve=sqrt(2GM/R), where ve is the escape velocity, G is the gravitational constant, and R is the radius of the body. Note that the escape velocity does not depend on the mass of the particle that is escaping! On the other hand, the average ",
" distribution of gaseous particles is almost identical and is described by the ",
"Maxwell distribution",
", which looks ",
"like this",
". The kinetic energy in turn is described by KE=1/2mv",
" , where KE is the kinetic energy, m is the mass of the particle, and v is the velocity. This means that for a given average energy, lighter particles will have a higher average velocity. Putting everything together, lighter particles, such as helium will have a higher velocity and heavier atoms/molecules, and so will have a much higher chance of having enough energy to escape the atmosphere. The same is true for the most abundant element in the universe, hydrogen, which in the atmosphere exists in the form of H2, which is even lighter than He and therefore can escape even more readily. However, this is less of a problem because...",
"2) Hydrogen because of its chemical nature is incorporated in a vast set of organic and inorganic compounds and minerals. Therefore, there is no shortage of hydrogen in various forms lying around. Helium on the other hand is a noble gas and is not very reactive. Therefore He mostly likes to remain in its atomic form, which as we saw tends to float away and out of the atmosphere. In fact, most of the helium that currently exists on Earth is not a remnant from the Earth's formation, but has actually been produced as a result of radioactive decay. Some of this helium was then trapped in pockets of natural gas, from where it can be ",
"extracted for commerical use",
". "
] |
[
"Helium have the lowest boiling point of any element. So it is widely used for extreme cooling "
] |
[
"And the use for this that you're most likely to run into is the superconducting magnets that make MRI machines possible. We use helium to cool the magnets down to their superconducting temperature."
] |
[
"Why are world leaders constantly pushing green energy like solar and wind, but seem to completely ignore nuclear?"
] |
[
false
] | null |
[
"Why someone does something isn't a science question. Perhaps try a politics related sub"
] |
[
"No, it’s the question of why isn’t nuclear energy being pushed by the scientific community? All I’ve been seeing is a large push for other renewables like wind and solar. I’ve heard barely a peep from nuclear. Almost as if everyone’s trying to go away from it."
] |
[
"Not the right sub for such questions. Perhaps try ",
"/r/asksciencediscussion",
" or ",
"/r/askreddit",
"."
] |
[
"What exactly is a field in physics?"
] |
[
false
] |
I understand what field is in these terms: However, what constitutes a field? Also, if I understand it correctly, if particles are a manifestation of excited field in certain region, does that mean a) all particles are basically just one same particle? b) how many different fields/particles are there (Standard model 12 ones or are there more?). I apologize for somewhat confused question, since I can't even properly ask a question without further explanations.
|
[
"Searched",
"Relevant ",
"discussion",
"Original question by ",
"renots",
"Sort of a follow up from ",
"this",
". What I learnt is basically that you cannot see vibrations \"moving\" in the EM field because, well, they always \"travel\" at c and you cannot take a POV where you are moving(following that vibration) at c.",
"So, isn't this sort of like saying that you can see the water but not the ripples in it?",
"Top comment courtesy ",
"ViridianHominid",
"There are actually multiple technical definitions of the word field.",
"In physics, a field is an object which is defined as a function of space and time.",
"A day-to-day sort of example would be a field which describes the temperature in your room. This isn't a fundamental field, because temperature is the result of the motions of many particles averaged together.",
"Another example of a field could be one which describes the direction and velocity of air-flow at any point. This sort of field is a vector field, precisely because it's values are given by a magnitude and direction. A way to visualize this field is to imagine a small arrow at each point in space that points in the same direction as the wind, and the length of the arrow is proportional to the speed of the air.",
"The electromagnetic field is something more fundamental, though- it's not something that arises from the motions of atoms. (Although it may be affected by them) It simply exists everywhere. For each point in space, there is an electric field vector and a magnetic field vector.",
"The standard model of particle physics, which is the current consensus (albeit incomplete) on the underlying objects which make up all matter, frames all objects in terms of fields. There is, for example, an electron field that tells you where electrons are.",
"The mathematical object known as a 'field' is a sort of algebraic structure. My guess is that you weren't particularly asking about that, so I'm not going to elaborate. It's an entirely separate concept from a field in physics.",
"Relevant follow-up courtesy ",
"zeug",
"Mathematically, one can just think of a field as a number defined for every point in space and time. A simple concrete example would be the water height (h) at every point in space and time on a pond. This would be a 2+1 dimensional field as you have two spatial dimensions, the east/west (x) and north/south (y) coordinates of the place on the pond, and one dimension for time (t).",
"For example, a wave traveling to the east on our water height \"field\" could be represented by the mathematical function, where time is in seconds and height in meters.",
"h(x,y,t) = 2 sin( x - 2t ) + 5",
"This wave has an amplitude of two meters, and is moving east at 2 meters per second. The average depth of the water in the pond is 5 meters.",
"Now, to make an analogy with sight, you would \"see\" other boats in the water by feeling their waves hit you. A canoe paddling nearby would produce waves, and later on you would \"see\" it moving past by the shape of the waves it produced. How big the waves were would be how \"bright\" the canoe looked, and the \"color\" of the canoe would be how close the waves were packed together, which might be related to how fast they were paddling.",
"Seeing things in reality is just letting electromagnetic (EM) waves hit your eyes. This is a bit harder to visualize as the electric and magnetic fields encode a number for each point in 3D space, i.e. (x,y,z), and for time t. Plus the E (electric) and B (magnetic) fields each encode three numbers for each point as they are \"vector\" fields.",
"An electromagnetic wave might look like this mathematically:",
"(x,y,z,t) = sin(z - ct) ",
" + 0 ",
" + 0 ",
"(x,y,z,t) = 0 ",
" + (1/c)sin(z-ct) ",
" + 0 ",
"where c is the speed of light.",
"In the \"normal\" understanding of space and time, you can speed up and overtake a wave, or at least have it be moving slower with respect to you. However, it is an experimental fact that EM waves always move at c, even if you try to catch up with them.",
"In \"normal\" space and time, this is mathematical nonsense. So the idea behind special relativity is to change the basic relationship between space and time so that anything going at c is going at c relative to any observer."
] |
[
"I love you"
] |
[
"a) Particles are like ripples on the sea: even if there is only one sea, there can be a lot of ripples.",
"b) There is one field for each kind of particle. In the standard model, there are 3 leptons (electron, muon, tau), 3 neutrinos, 6 quarks (u, d, c, s, t, b), one photon (EM force), 3 bosons for the weak force (W+, W-, Z0) and 8 gluons for the strong force. And last but not least, a Higgs boson. In the end, there are at least 25 fields."
] |
[
"Do devices use noticeably different amounts of power based on the volume that audio is played at? Is this still the case if the speakers are external and self-powered?"
] |
[
false
] |
When I turn up the volume on a device like my phone, does that increase the power that is being used to play that audio? For example, would a muted but still playing song be noticeably different than the same song playing at full blast? As a follow up, does any effect of volume still exist when I’m playing the music through my car’s speakers instead of the phone’s/headphones?
|
[
"Sound is produced by speaker's driver moving back and forth. The bigger amplitude of that movement is, the louder sound it emits. And to move the driver further, you need to apply more voltage. So technically it does drain the battery faster. Though it shouldn't make a huge difference.",
"In your car, however, speakers are powered by the car's battery and ",
" the voltage sent through that cable is tiny. So the difference between low and high voltage in that scenario is negligible. "
] |
[
"The power of sound waves is surprisingly small - the volume does have an effect on power consumption, but not a large one."
] |
[
"Where the loudspeaker moves back and forth you get pressure waves created at both sides of the driver. At low frequencies (where they are most inefficient) these waves diffract around the cone and cancel the waves at the other side."
] |
[
"In the theory of relativity, time dilates and space dilates. Does mass ever dilate?"
] |
[
false
] | null |
[
"Thank you. "
] |
[
"Thank you. "
] |
[
"Thank you. "
] |
[
"It seems to be universal (at least in the English language) that when asking a question, one's voice is raised at the end. Is there any reasoning behind this, scientifically?"
] |
[
false
] |
I'm Ron Burgundy?
|
[
"It isn't universal to all languages, and not really even to English. My first impression is that the voice is only raised when part of the statement is meant to be uncertain. Here are some phrases that can be said normally without the rise (some can go either way):",
"\"Where are you?\"",
"\"What time is it?\"",
"\"What would you like to drink?\""
] |
[
"In Chinese inflection can actually change the literal meaning of the word (not just the meaning of the sentence).",
"http://en.wikipedia.org/wiki/Cantonese_phonology",
"An upward inflection at the end of a question actually might mean you turn your question into a completely different sentence (which might not be a question)."
] |
[
"In addition, a raised voice generally means something requires your attention or response.",
"It could also be an attempt to make yourself heard, because you are in greater need of the conversation than the answerer.",
"The Japanese add the word \"ka\" at the end of the sentence to transform it into a question. However, even here, there is a raised voice for question."
] |
[
"If I put different size wheels on my car, will it affect the accuracy of my speedometer?"
] |
[
false
] |
And would it be a large amount?
|
[
"If the rolling radius (the radius of the wheel and tyre on it) changes, then yes. How much? By the percentage change in the rolling radius."
] |
[
"Here's a calculator online. Simply put in your factory tire size and the size of your new tires.",
"\nIt calculates the circumference and I believe gives you a percentage difference between the two. If you need help finding your tire size you should be able to look up your factory tire size on tirerack.com\n",
"http://www.miata.net/garage/tirecalc.html"
] |
[
"Yes. The speed reading usually relies on a ",
" speedometer which measures the rpm of the driveshaft, so if you increase the diameter of the wheels, you render it (and the mileage and speed calculations based on it) incorrect. The precise difference will carry according to what size the original tyre was to what it is replaced with. You could very easily calculate it though simply by working out the original circumference and the new one, and find the difference between them.",
"It's worth noting there will likely be a number of other knock-on effects on things such as wear and tear and fuel economy"
] |
[
"Has nuclear testing during the 20th century contributed to climate change, and if so, to what extent?"
] |
[
false
] | null |
[
"For a short while; it’s proposed that it would have cooled our climate off slightly from suspended particulate matter scattering insolation. An interesting fact though, radioactive dust deposited fairly uniformly around the world, so we can still see this layer in ice sheets which helps narrow the window for dating “older ice”."
] |
[
"Also I will add that when I said “proposed”, I meant that it is fairly we’ll documented and agreed upon by climate scientists that nuclear testing did have an impact on global temperatures. The impact would not have been regional, but probably would have been contained to the northern hemisphere due to atmospheric circulation patterns. Great question!"
] |
[
"In a way, yes. There is talk in the field of geo-engineering about suspending aerosols (sulfates) in the stratosphere which yield a similar effect that volcanoes produce. This effect is short lived (2-3 years) and has other consequences. For instance, these aerosols may lower our global temperature, but they do not effect the root cause of climate change. This method could be used in tandem with attempting to reduce C02/CH4 emissions to buy us some time. It is very complicated both scientifically, politically and ethically."
] |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.