title list | over_18 list | post_content stringlengths 0 9.37k ⌀ | C1 list | C2 list | C3 list |
|---|---|---|---|---|---|
[
"How do researchers \"control\" for various factors like education, income, etc. when trying to study some social or economic phenomenon?"
] | [
false
] | You often hear studies that compare disparate groups to look for specific differences between them, but in order to get reliable results, factors outside of those being researched are "controlled". (i.e. group X and group Y don't have gap Z after controlling for education, wealth, family status etc.) But how does one r... | [
"There are many methods, but ",
" is the most common technique that does not require changing the way the data was collected.",
"For example, suppose you want to see if race (R) predicts crime rates (C) by census district, but you want to ensure that race is not just a proxy for income (I), which is the real pr... | [
"Thank you for your response. I'll have to do some additional reading to fully understand your response, but trying to understand an answer can often be as illuminating as the answer itself.",
"It sound a bit like both recursion (running the same process for data and its components) and multivariable calculus (ho... | [
"You're welcome. Short version: predict the phenomenon of interest from all the factors you are trying to control for. Then predict the remaining error using the variable of interest."
] |
[
"Just how great was Einstein?"
] | [
false
] | [deleted] | [
"It's not that we don't hold Hawking in high regard. We do. We just know a ton of other great scientists too!"
] | [
"Einstein was fucking awesome. ",
"His contributions in the year 1905 alone are enough for 4 lifetime contributions to science. I mean, in that one year, he published the papers on photoelectric effect, brownian motion, the special theory of relativity, and E=mc",
" Each of these four papers ",
" the way scie... | [
"Both of them (it's ",
", by the way) have significant contributions in their fields - they just happen to be more well known in the non-scientific community. For anyone with a cursory study of chemistry, Einstein would be more well known for the photoelectric effect than relativity, and he'll be in similar stand... |
[
"Why does hair loss from chemotheraphy grow back but hair loss from male pattern baldness does not?"
] | [
false
] | [deleted] | [
"Because hair loss from chemo is due to the poison targeting the fastest growing things in your body, like tumors and hair. When the chemo is gone some of those hair cells start to function again. It’s temporary. ",
"But with say, male pattern baldness, it’s a genetic thing where your hair cells just start to run... | [
"Baldness occurs because the follicle itself dies/quits working due to having a specific type of receptor on its cell surface. This receptor is triggered by a specific type of Testosterone, which is always present in the blood, so the baldness never goes away. ",
"Chemotherapy does not permanently kill/incapacita... | [
"How come girls don't lose their hairs like men do? I've read that the tissue on men's scalp gets thinner as we age, is it because of DHT?"
] |
[
"We have found well preserved woolly mammoths from 10k years ago in ice. Is it realistic to hope to find well preserved creatures from 100k+ years ago in Antarctic ice?"
] | [
false
] | recent front page post reminded me of a question I'd though of a while ago. Would there be too much movement in the ice over that past 100k+ years to hope to find an animal from when Antarctica was only partially frozen over? | [
"Seems unlikely that animals would stray very far from the coasts (no food), so it is unlikely that they'd be buried in ice that would persist for 100k yr. like that in the interior."
] | [
"Ah, but Antarctica was once not ice covered. Then ice formed on it, spread outward, and eventually covered the whole thing. If something had gotten trapped when the ice was first forming, then it could be hidden away. ",
"Now, geology isn't my field so someone who knows more should tell me if these things cou... | [
"Mummified seals",
" have been found 40 miles inland and carbon dated as old as 2,600 years. "
] |
[
"What is the weird buzzing feel when running fingers across some plastic?"
] | [
false
] | Little difficult to explain, when I rub my fingers across the material on back of my phone and my iPod touch wheel it feels almost like there's a tiny current running across it, it feels like a vibration of sort. Why is this? Or does this not happen to anyone else and I'm just going a bit mad... | [
"Could it be a static?"
] | [
"I suspect it is the same as any other squeaky surface. Your finger is alternating catching and sliding, and that jittery vibration is causing the sensation."
] | [
"It doesn't feel like static, what it feels like, is my finger prints causing friction and that small resistance being felt as a vibration...it's difficult to explain."
] |
[
"What is more likely, there are some same molecules of air that were in my room 10 years ago, or every molecule is different than the ones from 10 years ago?"
] | [
false
] | null | [
"There are about 10 to the power of 26 air molecules in your room, and about 10 to the 44 in our atmosphere. That means that at a moment in time ten years ago, you had 10",
" / 10",
" of our atmosphere in your room, that's 10",
" . (0.0000000000000001% of the atmosphere)",
"Now, if you mixed up the atmosphe... | [
"Hmm - expanding out a little bit more, let's assume that there is about a mole of air molecules in every breath. That's a little smaller, so a breath represents 10",
" of the atmosphere.",
"That still gets a tiny probability for any breath containing zero air molecules from any given previous breath, on the or... | [
"We're assuming here that the population of molecules now and ten years ago are completely uncorrelated. That is, any molecule in the world is now equally likely to be in any location regardless of where it was 10 years ago."
] |
[
"What are the advantages/disadvantages of an engine with more cylinders compared to one with less cylinders but both have the same displacement."
] | [
false
] | basically i just noticed that most supercars have engines with a large amount of cylinders when compared to engines found in Trucks but both have the same displacement. (example, the ford powerstroke 6.0L V8 compared to a 6.0L Ferrari/maserati engine that is a V12. or the 7.0L V16 engine of a bugatti veyron and a 7.3L... | [
"One of the biggest advantages of having more cylinders (with the same displacement) is reduced vibration. An engine with more, smaller cylinders will generally vibrate less than a comparable engine with less cylinders because fewer cylinders means larger, heavier pistons are required to sweep the same volume.",
... | [
"The amount of air an engine can process dictates how much power it can make. Since two revolutions of the crankshaft pull through one 'rated displacement' of air, it follows naturally that increasing the maximum RPM an engine can operate at will allow it to generate more power.",
"Grab a 10 lb weight and make pu... | [
"Not necessarily the amount of cylinders, but one of the advantages to a shorter stroked engine is the increase in max rpm. Of course there are other factors that go into that, like valve train, but that's one of the big ones. "
] |
[
"Is it possible that the laws of physics vary slightly according to your position in the Universe?"
] | [
false
] | I don't know if the laws are based purely on mathematical proofs or physical observations. If they are based partly on physical observations, is it possible that our understanding of physical laws is local to our place in the universe? For example, could the speed of light be slightly faster or slower in another dista... | [
"In that case the laws wouldn't be laws, they'd be specific cases of more general laws.",
"So instead of F=GMm/r",
" , it would be F=G(x,y,z)Mm/r",
" .",
"Nobody really expects this to be the case though. There was some speculation recently that the fine structure constant varies by a tiny amount, but I hav... | [
"No, it's pretty simple really. They used two different telescopes to collect their data, and ",
" the data sets were different. What Webb et al. ",
" to have proved is that different instruments give different readings. Which we knew already."
] | [
"I don't know if the laws are based purely on mathematical proofs or physical observations.",
"This isn't answering your main question (iorgfeflkd has already done that, anyway) but it is a crucial point. Science is about making models (which are, at times, mathematical) of our physical universe. We may do a lo... |
[
"What is wrong in this assumption?"
] | [
false
] | null | [
"Keep in mind Newton's third law, and draw a diagram of the force vectors involved in your problem. The force the incline exerts on the sphere will be orthogonal to the incline, thus it will be at least (partially) opposing gravity. A steeper incline has a vector that points less vertically, and more horizontally."... | [
"Replace g with a, the equation you used only works in free fall. Different angles of the slope will lead to different net forces and therefore different accelerations. "
] | [
"thanks!that makes sense now"
] |
[
"How well does Isaac Newton's Principia hold up today? Is it 100% correct or were there errors and/or just plain wrong ideas/calculations?"
] | [
false
] | null | [
"Howdy! I've removed your post for its open-ended and speculative nature. I can redirect you towards ",
"/r/AskScienceDiscussion",
" which better suits such posts."
] | [
"oh I thought it was rather specific. Didn't think there would be speculation as I thought his book is pretty much seen as scientific truth and not hypotheticals"
] | [
"Your question lacks a conceptual basis--which is the more accurate reason I removed it. However, I do recommend reposting this to ",
"/r/AskScienceDiscussion",
" which is perfect for a question like this."
] |
[
"What is the most recent common ancestor of me and my cat? And do we know what it looked like?"
] | [
false
] | Kind of a random question really, but I need to know | [
"Edit: ",
"recent study",
"looked something like this.",
"A ",
"paper",
" \"reconstructed\" the genome of the hypothetical \"",
"boreoeutherian ancestor",
",\" a shrew-like creature that is the common ancestor to most mammals from ",
", though the exact date is unknown (for context, dinosaurs went e... | [
"According to ",
"this relatively recent story,",
" the common ancestor to placental mammals developed a little bit after the extinction of the dinosaurs, about 65 million years ago. So this is slightly more recent."
] | [
"If you find this interesting, I highly recommend the book The Ancestor's Tale, which explores the idea in great detail. It's a fascinating read. The quality of the writing and the material are both terrific. "
] |
[
"Is there a \"maximum loudness\"?"
] | [
false
] | This may seem like a silly question, but I'm genuinely curious: what's the very loudest something can possibly be? Is there a cap? | [
"Kind of. ",
"Sound is a pressure wave, the pressure oscillates up and down around the standard air pressure. This is around 100 kPa of pressure, so therefore the troughs of the wave can only be 100 kPa deep. A total pressure swing from 0 kPa to 200 kPa. This is about 194 dB. This is only for standard atmosphere ... | [
"Sound is a ",
"pressure wave.",
" There is a region of high pressure followed closely by a region of low pressure.",
"The minimum pressure is vacuum, which corresponds to about ",
"194 decibels",
" at STP. Anything beyond that is technically a shockwave, and has an increasingly large region of near-vacuu... | [
"I tried to google an answer, and I found this: ",
"https://www.reddit.com/r/askscience/comments/25q8o0/is_there_maximum_as_to_how_loud_a_sound_can_be/"
] |
[
"What effects do wind and solar energy have on climate if you ignore their effect on carbon usage?"
] | [
false
] | For example, do solar panels, by themselves, exert a downward pressure on temperature by taking light that would have become thermal energy and converting it into electricity, or do they tend to increase temperatures by darkening the Earth's albedo? Similarly, I keep thinking that windmills should reduce temperatures i... | [
"Remember that energy is conserved - so if you are pulling 1000 watts of solar power that is 1000 less watts heating your neighborhood. ",
"BUT that energy then powers the 1000 watt plasma TV in your house. Half of that energy directly becomes heat, and the other half becomes light and sound that is absorbed by... | [
"max_p0wer is correct, but there are some minor wrinkles.",
"Solar panels cannot destroy heat, but they can change the amount of energy absorbed by Earth the same way a stretch of blacktop does.",
"If you put a solar panel on your roof it will ",
"cool your home",
" because it is a lighter color than asphal... | [
"You're a little off here. The cooling effect of having panels isn't due to color, it's due to the fact that wind blows between the panels and your roof (so the heat is never transferred to your home). However, solar panels are black, so they will generally have lower albedo than any other roofing material. So t... |
[
"How do the 420 underwater cables that transmit all of the internet information work?"
] | [
false
] | I read that they're no wider than a can of cola. How is it possible that they send all of that information on that relatively small amount of wire? Do the signals transmit in one direction only or in both directions? Why is there no interference between signals being sent? Any other information would also be greatly ap... | [
"That's not how fiber actually works, well at least singlemode fiber that's used in trans oceanic cable.",
"In singlemode, the laser light goes in a straight line down the core, with minimal internal reflections. They can multiplex more data over one strand by using different colors of light (though it's all in t... | [
"They're optical cables, very thin and very long glass strands. Lasers are shot through them and they bounce until they reach the reciever. (Ever tried shooting a laser through a running tap? It makes a \"zig-zag\" line by bouncing inside.) That reciever then \"translates\" it to electrical impulse. By changing the... | [
"one thing to add is the need to place repeaters along the way. These devices are used to amplify the incoming signal and send it further. Without these the signal would be attenuated before reaching the other side of the Atlantic. The actual cables laid at the bottom of oceans are quite thick to resist external at... |
[
"Have ancient viruses ever been found?"
] | [
false
] | Obviously not like fossils, but maybe an insect millions of years ago had a virus and then got trapped in amber. I know the genetic material would be destroyed, but would we be able to learn anything about the virus? Would we even be able to tell the insect had been infected? | [
"somewhat relevant: there are actually \"ancient viruses\" found in our own DNA. Virus-like elements anyway... ",
"http://en.wikipedia.org/wiki/Transposable_element"
] | [
"Probably wouldn't be able to tell actually, unless it was a really big virus. All a virus is a a bit of nucleic acid in a very thin protein coat. The half life of DNA was recently determined to be about 500 years, so all of the genetic material would have degraded into other molecules. Proteins last a little longe... | [
"Super interesting read thanks for the link! It starts off by saying we wouldnt be able to clone t-rexs, wasnt Jurassic Park about cloning them from blood stored in bugs that were covered in amber? Would that be viable way to extract dna or would the temps have not been low enough for that to actually be viable? "
... |
[
"If I were to travel around a circle at a constant rate what would be the average degree I was at?"
] | [
false
] | [deleted] | [
"This is the realm of ",
"Directional Statistics",
". If we have a distribution on a circle, then quantities like \"mean\" are not defined. What we can do instead, is look at the circle as place onto the 2D-plane (typically the ",
"Complex Plane",
"), and instead of looking at our variable as just an angle,... | [
"What would be the difference between [a random distance between 0 and 2pi] and a [random distance between -pi and +pi]?",
"Both represent all the points on a circle, but the average of the first is pi and the average of the second is 0."
] | [
"It seems to me that this is sort of like asking what is the average number over all integers."
] |
[
"How could the big bang happen without space and time?"
] | [
false
] | null | [
"I was not a bang in the traditional sense. What it was was a rapid expansion of space and time from a single point. It expanded into nothing, just got larger."
] | [
"Thank you. But as I understood it, that space/time had to have a creation. As a subatomic particle suddenly existing, and expanding into nothing as the big bang. But if there was no space and time, how could the subatomic particle appear?",
"Edit: Can something pop into nothing, and be unaffected by the non-exis... | [
"That is a good point!\nConsider time to be a chain of causality. In other words, our concept of time can be described entirely by the notion of cause and effect. Since the Big Bang was \"before \" time, traditional notions of causality cannot be applied. The particle did not necessarily need a cause. We have a... |
[
"Do astronauts take their bodily waste back to earth?"
] | [
false
] | [deleted] | [
"Here's a ",
"recent article",
" about how it gets back to earth."
] | [
"I will assume this is a real question. ",
"This is a scientific notation of the number 0.00000000005 with units atm (atmospheres, 1 bar, 14.7 psi etc). ",
"the x10",
" literally means \"multiplied by 10 to the negative eleventh power\" which if applied mathematically would add 11 decimal points infront of th... | [
"I will assume this is a real question. ",
"This is a scientific notation of the number 0.00000000005 with units atm (atmospheres, 1 bar, 14.7 psi etc). ",
"the x10",
" literally means \"multiplied by 10 to the negative eleventh power\" which if applied mathematically would add 11 decimal points infront of th... |
[
"How do colliders aim atoms so that they actually hit each other?"
] | [
false
] | null | [
"More like two high precision sniper rifles.",
"I have done some beamspot measurements at the LHC, and the beams of particles at the collision point are narrowed down to be similar in width to a human hair."
] | [
"You pretty much nailed it. ",
"Here's some reading for anyone who's interesting."
] | [
"You pretty much nailed it. ",
"Here's some reading for anyone who's interesting."
] |
[
"Geomagnetic Reversals older than ~ 120Ma"
] | [
false
] | It's a fairly common explanation as to how we know when magnetic reversals occur - the , but oceanic crust only lasts for, on average before it gets subducted, . How then are chrons determined that go further back in geological time than say the Mesozoic? | [
"They're not, basically. As you say, the oceanic records only go back about 200 Ma. Between 170 and 200 Ma, the records aren't very reliable anymore, so any data you find will look like ",
"this.",
"What does happen though, is that a lot of experimentation is done with rotating spheres of liquid sodium, see for... | [
"As a professional geologist, I feel that you should be ashamed of yourself. Reading through that 'article' you posted is like a knife to my head. Nothing they have written about in that article is even close to the truth, it is either a misrepresentation of the facts (cherry-picking) or it is just making things up... | [
"PT is as much as a religion as gravity. The evidence for it is overwhelming, your reaction to that evidence is completely up to you. The article is too full of factual inconsistencies to really discuss in this forum, however if you state the main things that ",
" feel are the most inconsistent in plate tectonic... |
[
"Outside our solar system, are there more \"gas giants\" or small rocky planets? Why (if at all) is one more likely than the other to form?"
] | [
false
] | Does the size of the star they're orbiting, or the distance at which they're orbiting, have an effect? What about time of formation (i.e. was one more or less likely to form at the universe's earlier stages, etc.)? On a somewhat related note, is it coincidental that our solar system's gas giants are all relatively adja... | [
"The problem is that our detection methods are biased towards larger objects. We are also biased towards detecting things close to the star."
] | [
"Before we started detecting exoplanets, we were biased on what we though planetary systems would look like. We though smaller, rocky planets would form closer to stars and larger, gas planets would for further away. We also had models that would explain/predict this.",
"With the discovery of exoplanets, it seems... | [
"I suppose that makes sense, based on what little I know of those detection methods. Is the error margin on those methods currently too high to say anything meaningful about those planets' size and orbit at all? Or are we just unable to compare the number of planets of each type because we'd tend to understate the ... |
[
"If we’ve never actually been there, much less gotten even a fraction of the distance, how is it that we know what materials the core and mantle of the Earth are?"
] | [
false
] | null | [
"For all of those areas, we have direct measurements of their physical properties; in particular, we have good data on density distribution, heat flow, electrical and magnetic properties, and how these materials interact with seismic waves. This is the purview of the field of geophysics. In particular, ",
"seismi... | [
"Sound is one way to do it. In simple words, earthquakes, N-bombs, and volcanoes can produce seismic activity that can be recorded all around the world. By measuring the time it takes for sound travel we can figure out what material must be there for that to happen."
] | [
"To add to this-- We can also experimentally create the conditions of the lower mantle and core using ",
"diamond anvil cells",
". We use the cells to create minerals that only form in the lower mantle and core. From there, we can connect rocks of certain seismic properties in the lower mantle and core with min... |
[
"What is the significance of a dot product? What are some applications of it?"
] | [
false
] | null | [
"If you include linear algebra applications, you could do a couple of weeks of lectures on this question. However, suffice it to say that the dot product measures how two vectors are aligned with each other. If they have a dot product of zero, they are orthogonal, which is a powerful property for many reasons. If n... | [
"The dot product signifies the product of the components of two vectors that are parallel. ",
"Physics has many application of Vector operations. for the dot product, consider this. when a person moves an object, the objects potential energy increases by an amount that is proportional to its weight, W(a vector th... | [
"Dot product is a scalar given by multiplying 2 vectors.",
"Example: work (W) is a dot product of force (F) and displacement (d) vectors, this is why when you calculate work for a displacement not parallel to the force, you also multiply by cos(theta)."
] |
[
"Why does old ice in a tray in the freezer seem to shrink over time? Does the ice compress and take up less volume?"
] | [
false
] | I've seemed to noticed that ice in a tray seems to shrink from its original frozen volume after some time. Does the ice change from a solid phase to a more compact form? Edit: Thanks for the explanation! I was thinking sublimation, but I didn't seriously consider the effect of frost-free freezers and low humidity condi... | [
"Sublimation - ",
"http://en.wikipedia.org/wiki/Sublimation_%28physics%29",
"Ice cubes shrink when left in the freezer for a long time because of the process of sublimation. This is occurs when a solid mass changes directly into gas. This occurrence is not at all unusual for there are substances and conditions ... | [
"Good question.",
"If you're thinking that an individual molecule would pass through the liquid phase on the way from solid to gas, I will offer you this little nugget of wisdom: a single molecule ",
". Phases only apply to large collections of particles. So, if there were a liquid phase intermediate, you would... | [
"The ",
" ",
" molecules in the surface of the ice cube jump of to join the gas molecules floating in the air around them. The transformation of the ",
" ",
" molecules into gas cause the ice cubes to shrink over time.",
"FTFY"
] |
[
"Are there any elements which cannot exist in a certain state of matter?"
] | [
false
] | [deleted] | [
"A substance's phase is based on its pressure and temperature, which have no physical upper bound. (In theory, at least.) A substance can decompose or chemically react with itself under certain conditions, though, which limits the conditions where a substance can exist in equilibrium. The only way elements can d... | [
"I'm wondering where they are getting their Carbon melting point if it's at atmospheric pressure. ",
"Carbon sublimes at atmospheric pressure...",
". They must be deviating from atmospheric pressure on many of the points.",
"That being said, it can still be a liquid at high pressures, so it can still be solid... | [
"Yeah, that's odd... Carbon doesn't even melt at any pressure until about 4500 K. I'm not too confident about the data from that page any more...",
"Edit: Apparently that's ",
"the melting point for diamond",
", which explains why it's not on the phase diagram. Looks like it's not ",
", just misleading."... |
[
"How does turning on AC with heat actually help to defog a car windshield?"
] | [
false
] | From reading various tricks to help defog the car window, people recommend turning on the AC with high heat. However if it's set to heat the car, doesn't it bypass the AC condenser and just pump hot air from the radiator without the benefit of condensation on the condenser coils? | [
"AC is not just cooling;",
"Air conditioning (often referred to as AC, A/C, or air con) is the process of removing heat and ",
" from the interior of an occupied space, to improve the comfort of occupants. ",
"Wiki",
"The ac condenser coil is before the heater, the incoming air passes over the cold coil and... | [
"Hot air can hold much more water, in addition increasing the temperature increases the evaporation rate."
] | [
"This is also how the air conditioning system works",
" really great short explanation "
] |
[
"What is the smallest thing an ant can see?"
] | [
false
] | As most of the cells are impossible to see to human eye, would it be that hard for smaller and smaller animals to see it? | [
"So ants actually have pretty crappy vision and rely more on chemosensation (smell/taste) but I get what you're asking.",
"Visual acuity is not about the size of the eye but rather the density of cone cells. Humans average about 10k cones per mm",
"; birds have MUCH greater visual acuity with 100 cones/mm",
"... | [
"Adding onto the other great answer, there's a physical limitation to the size of things that can be ",
" in general. We can't ",
" things in the traditional sense that are smaller than the size of lightwaves themselves. Humans can see light waves that have a wavelength of between 400 - 700 nanometers, which is... | [
"This is a great answer!"
] |
[
"What are the real possibile outcomes if the #4 unit of the Fukushima nuclear plant fails?"
] | [
false
] | The nut jobs on the left are saying things like evacuate to the Southern Hemisphere and mass extinction and much of the mainstream media is ignoring the whole thing. It has gotten some coverage but it is all so contradictory I can't make sense of it. Does anyone have any expertise or knowledge they can share on this is... | [
"This is ask science where we don't speak in hyperbole.",
"Additionally, TEPCO, who has seismologists and earthquake engineers on staff, who are experts on seismic analysis for nuclear power plants, did an analysis showing that unit 4 can handle another earthquake similar to the one from March 11'th last year. Th... | [
"This is ask science where we don't speak in hyperbole.",
"Additionally, TEPCO, who has seismologists and earthquake engineers on staff, who are experts on seismic analysis for nuclear power plants, did an analysis showing that unit 4 can handle another earthquake similar to the one from March 11'th last year. Th... | [
"Here",
" is my writeup of it.",
"More or less, they determined through structural analysis that the building could handle another 9.0 if it happened, but they went and added more structural support just to be safe (in june/july last year), and are going to be adding more structural supports as they build the u... |
[
"Is there anything interesting about adding a \"small cardinal axiom?\""
] | [
false
] | I'm really not sure how to properly articulate this idea or if it is even meaningful, but ... we use the axiom of infinity to guarantee the existence of an infinite set with cardinality aleph-null, and we can use the power set operation to construct aleph cardinals greater than aleph-null. We can also add large cardin... | [
"So there's a few things wrong here that I'll try to explain. First though, you may be interested in the ",
"surreal numbers",
". It's the closest fit I can think of to what you might be looking at with \"infinitesimal cardinals.\" It's not really that at all but it is an interesting number system containing th... | [
"What if we give up the axiom of choice?\nAlso I am not sure I understand why the cardinal numbers must be exhaustive ...?",
"If we give up choice, we're in big trouble. What we really care about is the well ordering theorem, which is equivalent to AC and states that every set can be well ordered. Recall that any... | [
"so I suppose we can conclude therefore that this proposed axiom is fully inconsistent with all axiomatic systems, yes?",
"I'll qualify one of my previous statements. If we take the negation of AC to get an infinite cardinal that doesn't fit into the aleph numbers, it's still bigger than aleph_zero, but it may no... |
[
"How far from the Earth would an asteroid big enough to destroy all life be visible?"
] | [
false
] | [deleted] | [
"Visible to the best astronomical tools luckily pointed in the right direction, visible to back yard telescopes, visible like a star, or visible like the impending doom of a rapidly growing fireball?"
] | [
"Almost no asteroid could destroy ALL life. There are sulfer fixing bacteria at the deepest sea vents that are not dependant upon the sun."
] | [
"From ",
"the Wikipedia article on Asteroid-impact avoidance",
", impact by a 10 km asteroid would likely be an extinction level event.",
"For a solar system body, its ",
"absolute magnitude",
" (",
") is the magnitude it would have at 1 AU from the Sun and 1 AU from the Earth. It's ",
"apparent magni... |
[
"Why did humans evolve an ability to spot straight lines and square corners?"
] | [
false
] | Why do our visual systems seem tuned to spot perpendicular angles? Even young kids with no formal training in geometry can usually tell instantly if lines aren't straight or corners aren't square. Those shapes occur very rarely in nature. What evolutionary advantages could have motivated development of this ability? | [
" from a computational perspective, the visual system might be building up to representations of curvature by starting off with corners and small straight-line approximations which are in turn based on points (or center-surround regions) of light and dark. ",
"Here",
" is an illustration of such a hierarchical ... | [
"I'm going to approach this question not from an evolutionary standpoint, which is always a tricky proposition, but instead from a computational one. ",
"At the level of the eye, we have individual photoreceptors that are activated by photons. Photons are very very small. The receptors are essentially responding ... | [
"At an early level, it is suggested that we might detect corners by something called an ",
"end-stopped cell",
". This is a cell that is sensitive to not just oriented contrast (bar of light), but a bar of light that does not span the entire receptive field: a bar that ends half-way through. ",
"Here",
" is... |
[
"Is there a certain mass or density that a star has to reach in order to become a black hole?"
] | [
false
] | null | [
"Yes, ",
"http://en.wikipedia.org/wiki/Chandrasekhar_limit"
] | [
"That's for white dwarves.",
"http://en.wikipedia.org/wiki/Tolman%E2%80%93Oppenheimer%E2%80%93Volkoff_limit"
] | [
"It should be noted that both this limit and the TOV limit to which iorgfeflkd linked are ",
" collapse masses, after the star has shed much of its mass as a planetary nebula or supernova; the mass of the star prior to that event would need to have been quite a bit higher."
] |
[
"Why do we like the sound of rhyming words?"
] | [
false
] | In a song or a poem, why do humans find it pleasant to hear words that rhyme? Why do verses sound slightly off if they don't rhyme? | [
"Humans love patterns. There is a definite evolutionary benefit to be able to do so, from predicting the weather to understanding when plants are about to bear fruit, etc.",
"The way I understand it (and I'm sure someone more familiar with the reward learning literature could give a citation for this), the brain ... | [
"A creature found patterns confusing.",
"When trees had ripe fruit he was snoozing.",
"But his friends who liked rhyming",
"had much better timing.",
"They evolved into us--how amusing!"
] | [
"Rhythm and such. Rhymes are assembled by humans mostly, and assembled sets of rhymes are pleasant to us because \"we find beauty in something done well.\" ",
"https://www.ted.com/talks/denis_dutton_a_darwinian_theory_of_beauty.html"
] |
[
"How are the sensory areas of our brain structured?"
] | [
false
] | I have a vague idea of learning that that part of the area of our brain that deals with touch, for example, is structured so that an area of our body that feels touch corresponds roughly to an area of the brain that processes signals from that part of the body. Correct me if I'm mistaken. I also vaguely remember learni... | [
"Hey OP, sorry, I've been meaning to answer this, but life got in the way. The areas of the brain that respond to sensory stimuli utilize a hierarchal system whereby at the \"bottom\" level we have basic computation which leads to higher and more specific processes, branching outwards. ",
"You are correct in sayi... | [
"Wow, that's really remarkable! Especially the stain of the rat brain! Did these sensory areas within the same species evolve separately and converged on the same general structure, or are they 'copies' of each other that diverged to specialize?",
"You know what, I think I will get that text and add it to my read... | [
"Unfortunately I don't know enough about the evolution of the brain to speculate on that question - although I would like know myself. If you're interested I found a picture illustrating the columns of cells that respond to specific orientation in V1 ",
"here",
". :)"
] |
[
"Why is NH3 a polar molecular solid and not a hydrogen bonded molecular solid?"
] | [
false
] | null | [
"A hydrogen bond isn't just a bond that includes a hydrogen molecule -- it's the type of attraction that occurs when a Hydrogen nucleus ",
" a molecule is positively charged (due to donating its electron to another atom in its molecule), and that positive Hydrogen atom is attracted to a negatively charged part of... | [
"It has both polar interactions and hydrogen bonding interactions. I'm not sure which one dominates when. It clearly isn't as strong as water, since ammonia is a gas a room temp. That may be because ammonia has one lone pair while water has two lone pairs. So you might say ammonia hydrogen bonds half as much as wat... | [
"Polar Bonds are intramolecular forces (occur between atoms, not molecules) , Hydrogen Bonds are intermolecular (occur between molecules, not atoms).",
"",
"The bonds within an ammonia molecule, or any molecule, cannot be H-bonds."
] |
[
"Psychologists of reddit: Is the development of conspiracy theories a learned behavior or is there some innate reasoning why humans more readily associate events with some greater order of magnitude?"
] | [
false
] | Question sparked by an experience I had this morning which my mind immediately came up with some conspiracy type explanation. Basically people love conspiracy theories to varying degrees. Is there an explanation for this and is it explained by environmental factors or is there something innate within our psychology tha... | [
"go away."
] | [
"I'm not a psychologist and I hope a psychologist responds to this post, as I have always found your question interesting, but one theory is that conspiracy thinking arises from innate traits humans possess because of the survival advantages they are associated with. These traits are sometimes called ",
"patterni... | [
"Not a full answer but I have seen some research showing that more intelligent people are actually more likely to believe conspiracy theories. The hypothesis is that smart people are more used to their \"logical conclusions\" or things they figure out on there own to be correct. So when they come to an incorrect co... |
[
"If I make low-purity polycrystalline diamond, will I still get thermal conductivity that is far above copper?"
] | [
false
] | I want to make a lot of polycrystalline diamond. I mean A LOT (imagine 2 square yards). Buying that in the open market will cost you a cool $800 million (I'm not kidding, look it up). But... I only want thermal conductivity that's above copper, and not the hyper-pure stuff that most professionals want. So... if I make ... | [
"2 square yards, what thickness? If you don't need a big solid diamond, you can get grinding diamond for pennies on the dollar - about $200 for 2 pounds. ",
"Diamond has isotropic thermal conductivity, i.e. it's not like BN where it has high conductivity along one plane and low along another. As long as it's high... | [
"I looked up the conductivity for grinding diamond and it seemed to be awful! Was I mistaken? You're right about the matrix materials lowering conductivity. High temps are definitely not what I need. I want lightweight and fast heat dissipation. OK... boron and nitride filled ceramics. This sounds promising! Uhmmm.... | [
"I'm strictly an engineer (mostly electronics, a bit mechanical), so I can't really do much for you in the way of science literature. However, as always, ",
"Wikipedia",
" has an excellent write-up about BN.",
"BN is almost exclusively used as a filler material for injection molded parts. h-BN is the cheapest... |
[
"How would a quantum computer solve a simple 2-dimensional maze?"
] | [
false
] | in Data is Beautiful and someone jokingly made the comment Could a quantum computer do such a thing? How would quantum computing tackle a maze? | [
"Quantum computers don't work like how you think they work, and it's a common misconception that keeps getting repeated by the press that doesn't know how quantum computers work either. Quantum computer don't just \"try all possibilities at once\"",
"This blog goes into detail about the issue I'm talking about: "... | [
"Thanks very much for your clarification and link :) I will do additional research.",
"Edit: I watched the video linked to by the blog by ",
"Scott Aaronson",
" and it was very informative and well presented.",
"I recall having read this page before: ",
"http://en.wikipedia.org/wiki/Amdahl%27s_law",
"Gi... | [
"Essentially. The process has some randomness in it, but at the end of the day you only get one value back, ",
", and you can't guarantee that it's the 'best one' that you wanted, even if the odds of returning that value were nonzero. For some cases QM and interference effects ",
" be leveraged to make this hap... |
[
"How would one go about making their own antibiotic?"
] | [
false
] | I'm a huge fan of every kind of apocalyptic fiction and it seems to me that in these stories the two main things that everyone needs after the bomb drops or the zombies rise up is food and penicillin. I was wondering, when society crumbles is there a way to create an effective antibiotic from stuff that could be easil... | [
"Hey, so I typed \n\"How to make penicillin at home\" into google and one of the first links was ",
"this",
"It is advice for people called \"preppers\" and is intended \"only for use in a post-collapse scenario\" I have no idea what they're talking about but there's a pretty good protocol for growing penicilli... | [
"Almost all antiboitics are 'natural' in that they're isolated from organisms that 'naturally' use them to kill each other one way or another. Example: ",
"http://en.wikipedia.org/wiki/Streptomyces_griseus"
] | [
"I've got to agree, in an apocalyptic world, I'm not sure you'd be able to find everything you need to do things like this. Even today, I think I'd have problems getting my hands on all of that, outside of what I can get in lab. That said, there are other ways to treat surface infections that likely would be more... |
[
"If the surface of the Earth is cold and the Earth’s mantle is hot, how far down do I have to dig my cave house for it to be a cozy temperature?"
] | [
false
] | null | [
"The mean annual temperature of a location is a decent proxy for the temperature a few meters below the surface (daily and seasonal temperature variations will average out within the first few meters). From there, the ",
"geothermal gradient",
" is a decent proxy for how temperature will increase as a function ... | [
"Note that if you were to actually live there, you'd need to dig ",
" less than that, maybe just a few meters. This is simply because you yourself, and whatever appliances you'd have there, would generate enough heat to keep your burrow nice and cozy because heat loss would be very slow in the lack of windows. Ea... | [
"Woah this is amazing! Less than 1km actually seems achievable. I’m gonna start digging! 🦄"
] |
[
"When I Have A Bad Headache, Why Does The Pain Feel Like It's Pulsing?"
] | [
false
] | null | [
"Vascular theory was invented when they noticed that during migraine, areas that registered pain were particularly engorged with blood and that vasodilation must be in cause. The vessels were so engorged they throbbed (hence that pulsing feeling). Early medication like ergotamine and caffeine were used for their va... | [
"Vascular theory was invented when they noticed that during migraine, areas that registered pain were particularly engorged with blood and that vasodilation must be in cause. The vessels were so engorged they throbbed (hence that pulsing feeling). Early medication like ergotamine and caffeine were used for their va... | [
"Vascular theory was invented when they noticed that during migraine, areas that registered pain were particularly engorged with blood and that vasodilation must be in cause. The vessels were so engorged they throbbed (hence that pulsing feeling). Early medication like ergotamine and caffeine were used for their va... |
[
"Ask Anything Wednesday - Biology, Chemistry, Neuroscience, Medicine, Psychology"
] | [
false
] | Welcome to our weekly feature, Ask Anything Wednesday - this week we are focusing on Do you have a question within these topics you weren't sure was worth submitting? Is something a bit too speculative for a typical post? No question is too big or small for AAW. In this thread you can ask any science-related question! ... | [
"Why are some viruses contagious after death (like Ebola) while others aren't?"
] | [
"Happens in what sense? The reaction kinetics will change because of the kinetic isotope effect, but otherwise it will still behave the same. ",
"https://en.wikipedia.org/wiki/Kinetic_isotope_effect"
] | [
"What happens with an acid when you replace all the hydrogens with deuterium?"
] |
[
"Is it possible to build a river filtration system using a toroidal magnet to pull heavy metal waste from the water?"
] | [
false
] | null | [
"No. Unfortunately it is not. ",
"Most heavy metals are not in their elemental state when they are \"in the water\"- they exist as metal salts or (even worse) organometallic compounds. These salts and compounds are all non-magnetic. In most cases, the water itself is more paramagnetic than the salts so even i... | [
"Is it possible to traditionally filter water at a rate to keep up with a river?",
"EDIT: ",
"https://en.wikipedia.org/wiki/2015_Gold_King_Mine_waste_water_spill?oldformat=true",
" This article is actually inaccurate, heard on the radio in DC a caller from Navajo Nation during an interview about the emergency... | [
"Yes, it is possible to filter, but you need a lot of electricity and time. "
] |
[
"How can we possibly make out the shape of galaxies billions of light years away is the light per square meter available decreases by an inverse square law?"
] | [
false
] | [deleted] | [
"While the total amount of light does drop off as 1/r",
"2",
", the angular area of the object also drops by the same factor, so the amount of light per unit area (",
"surface brightness",
") does not drop. This is the same reason a person across the room from you does not look dimmer than someone right n... | [
"They produce an awful lot of light, but the really far galaxies require very long exposure times with a telescope-mounted camera to see. The Hubble Ultra Deep Field is based on ten days of camera exposure."
] | [
"A point source would have no angular area. That said, I'm not sure I understand your question, it seems to be missing a word"
] |
[
"Microwave heat?"
] | [
false
] | [deleted] | [
"Nitrogen is not polar, so no, it's impossible.",
"\nYou can read abt it here:",
"\n",
"https://en.wikipedia.org/wiki/Chemical_polarity"
] | [
"To elaborate, most of the heat from microwave ovens comes from the water molecule reorienting in response to the electric field from the microwave radiation, which oscillates back and forth billions of times per second. If the water molecules are free to rotate, the microwave radiation is absorbed and the tempera... | [
"Generally you need polar molecules for RF heating, and N2 is not polar.",
"You can sometimes use RF heating with non-polar substances because in some cases the dipole moment can be induced from the oscillating electric field due to irregularities in the electron distribution in the (otherwise non-polar) molecule... |
[
"Why does burnt food like milk stick to the bottom of the pot and why is it almost impossible to remove?"
] | [
false
] | [deleted] | [
"The milk contains proteins and sugar. The excessive heat applied to the pan caused the proteins to coagulate and bind to the source of the heat. The first amount of protein has thermal insulating properties that allow the pan to get even hotter, since less of the heat gets transferred to the water content of the... | [
"Heat denatures protein. Denatured proteins have lost their shape and will mold to almost any tiny surface. This makes them \"sticky\". On a pan, tiny strands get into all the microscopic crevices and then harden with the heat and localized dehydration in the burn."
] | [
"Every hear of horses, or other animals getting sent to the glue factory?",
"-source: Three Stoges",
"fml"
] |
[
"Is it possible for a star to only output light outside of the human visible spectrum?"
] | [
false
] | ...therefore the star would be nearly invisible to the naked eye. Are there any examples of such (or similar) known stars? | [
"A star at any temperature will emit radiation according to a ",
"Planck distribution",
", which is continuous and nonzero over all frequencies, for all temperatures.",
"So there is no temperature at which there's no visible light emitted.",
"Very cold stars",
", usually ",
"brown dwarfs",
", can emit... | [
"Stars aren't powered by chemical burning, but rather by nuclear reactions. And their emission spectra are dominated by a Planck function at some effective temperature."
] | [
"What about the material the star burning? For example methanol fire burns in a way where you can’t see the flames. Would such a thing be possible with this consideration?"
] |
[
"How does conditional statements in mathematical logic work?"
] | [
false
] | null | [
"Thanks for the help. I am starting to see what you are trying to say"
] | [
"But how does that apply though? Like for example if 3 is an even number, then 5 is an a even number. How does the condition remain true if both statements are false"
] | [
"A statement of the form \"if P, then Q\" is false precisely in one case: when P is true and Q is false. Why? The conditional is not satisfied. P is true, and so, according to the conditional, Q must also be true. But Q is false. So the whole conditional is false.",
"However, if P is false, then the entire condit... |
[
"Can space be a great sound insulator? See inside for question."
] | [
false
] | Hey guys, my question is; Sound needs a medium to travel in, and there's no medium in space hence no sound. Speaking in nonsense for better understanding, if there was this little device or a ball, 5cm in diameter and its causes a sound of 90 decibels. If it was inside a 10 cm ball and between the first and second ball... | [
"Sound cannot travel through vacuum, so vacuum is a very good insulator for sound. The problem is that your inner chamber almost always has to be attached to the outer one in some way or another, and the sound can propagate through that bridge but to a lesser extent. The same principle is behind things that insulat... | [
"If you placed a ringing alarm clock in some kind of chamber and pumped out the air, the sound will slowly fade away. Eventually it will be silent once all the air has been pumped out.",
"I suppose you could argue that the the alarm clock is still resting on some kind of surface. Sound vibrations could still be c... | [
"A magnetically levitating clock would work, though the magnets might mess with the circuitry."
] |
[
"Why do microwave ovens and wireless routers operate on the same frequencyrange (~2.4GHz)?"
] | [
false
] | [deleted] | [
"There's only so much electromagnetic spectrum available; the FCC doesn't regulate microwave ovens (the EM field they produce is just noise). The rest of the bandwidth is incredibly valuable, and all of it, essentially, has been claimed for other purposes. You can see the full chart ",
"here",
". A tiny fractio... | [
"Just to expand on this: that's the reason WiFi is in that band. The reason microwave ovens are in that frequency range is because it happens to be more efficient for dielectric heating of water and fats to occur. Dielectric heating--this is kind of going off-topic--takes advantage of the polar nature (asymmetrical... | [
"To be fair the first rotational transition ( J=22( 4,18)-J= 21( 7,15) ) of the vibrational ground state of water is at 8274.53190MHz.",
"The v2=1 ( J = 4( 2, 2)- J = 5( 1, 5) ) is at 2159.98000MHz.",
"v2 = 2 ( 4( 3, 1)- 5( 2, 4) ) is at 6332.83950MHz.",
"v1 = 1 (5( 2, 3)- 6( 1, 6)) is at 3523.69800MHz.",
... |
[
"What would happen to a laptop if you took a medical x-ray of it?"
] | [
false
] | Inspired by . Would the laptop take any damage? What if this were done while it was running? | [
"I have a little bit of experience fabricating radiation hardened circuity. The biggest threat to these chips is ionizing radiation (x-rays are ionizing) (",
"http://en.wikipedia.org/wiki/Ionizing_radiation",
"). This is because this type of radiation creates electron-hole-pairs (EHP) in semiconductors, which e... | [
"I don't ",
" it will do anything terribly bad. I don't believe the level of intensity used in medical imaging is high enough to do hardware damage by itself. Not really sure if hard drives are vulnerable, you'll need someone more familiar with the interactions of metals and x-rays for that. Solid-state drives... | [
"Just to remind you - airport X-Rays are equivalent technology.",
"So all the bad things of flipped bits in semiconductors (see SSDs today) can happen at your airport. That they show up rarely is due to error correction."
] |
[
"What is the apex predator of a typical backyard?"
] | [
false
] | null | [
"That's really going to depend on region. Even limiting ourselves to the US, it can vary. Coyotes are very common in some places. I have lived in typical suburban areas with mountain lions and bears. Are we including pets? Many suburban areas have predatory birds such as eagles and owls. "
] | [
"That's irrelevant though. Apex predators are the predators that sit at the top of the food chain with no other predators preying on them. Position in the food chain isn't determined by what an animal kills but by what kills that animal.",
"Cats are spree killers that murder a crazy variety of creatures but in pl... | [
"Depending on what bar you go to you're bound to find some decent ones in Virginia Beach."
] |
[
"Is an aerodynamic object inherently hydrodynamic and vice versa?"
] | [
false
] | null | [
"For the most part, yes. Small models in water flumes are often used to simulate the behavior of large vehicles in air. What matters is the ",
": Re = U L / nu, where U is the velocity, L is the size of the object, and nu is its kinematic viscosity. Situations with the same Reynolds number will have comparable... | [
"No not really. Sound travels quite a bit faster underwater, and water doesn't compress easily. The closest thing would be something like this:",
"https://en.wikipedia.org/wiki/VA-111_Shkval"
] | [
"Are you asking if something has low drag in air then would it have low drag in water? The answer is sorta. Streamlined objects are relatively low in drag in any medium. However, due to the large differences in Reynolds (and sometimes Mach) number (I recommend giving these a google), a body optimized for travel in ... |
[
"If I was deposited somewhere in the Milky Way, is there an easy way to figure out how to get back to Earth?"
] | [
false
] | Assume I only have what I'm wearing, so no laptop with a galaxy map, no reference material, and no Hitchhiker's Guide. A lot of things that come to mind are based on perspective which isn't super helpful when the sky I would see and Earth's are completely different. | [
"Get back to? You'd have to have one hell of a spaceship, and even if you could go at the speed of light, the trip might take a hundred thousand years if you're unlucky. And you have to be pretty unlucky if your light-speed spaceship has neither telescopes nor computers.",
"There are some great difficulties in fi... | [
"That was a very thorough answer. Thank you. I have saved your comment for future reading and reference."
] | [
"No, didn't you read the prompt, he's clearly going to be teleported to some random point in the galaxy and needs to get back home."
] |
[
"When I stack books on a previously rolled-up poster and it straightens out, what is happening on a cellular level?"
] | [
false
] | I am currently straightening out a poster with a large book, and it occurred to me that I have no idea how this actually works. When I apply pressure to previously rolled-up posters, what is happening on the small scale to each cell to make it yield to the pressure applied on the large scale? And just for fun, this is ... | [
"Nothing is happening at the cellular level, since there are no cells as such in printing paper. They all get destroyed or at least killed during the paper making process. On a molecular level it just shifts the point at which molecules are in their lowest energy state. When paper is rolled up, there are fewer mole... | [
"This is a great response, and it mostly makes sense to me, but I have to ask: what exactly happens in the paper-making process to convert cells into this non-cell status. I'm having trouble understanding materials made of atomic compounds, but not made of cells."
] | [
"Well a cell is a biological entity. When an organism is alive, it acts as a kind of chemical unit. It is enclosed in a membrane, which separates it from the external environment. Molecules on the other hand are non-living structures comprised of atoms which are bonded together. A cell contains and is made of molec... |
[
"If a vector goes from the origin to point (x,y,z), how do you determine at what coordinate location it intersects the unit sphere?"
] | [
false
] | null | [
"This question is pretty easily searchable and it sounds like it is likely a homework problem so it will be removed. (You can try ",
"/r/learnmath",
" if you wish)",
"I can give a hint, what happens when you divide the coordinates of a vector by it's length?"
] | [
"It's not a homework question and I wasn't having much luck searching it. I'm trying to do a transformation of coordinates to align the permanent dipole of a molecule with the cartesian z axis so that calculations of excited state transition dipoles will be easily comparable to the permanent ground state dipole. ... | [
"You're correct, the new vector will have length 1 which by definition intersects the unit sphere."
] |
[
"The apparent \"mixing\" of skin colour in humans defies everything I understand about mammalian genetics. Can someone explain how it differs from determination of fur colour?"
] | [
false
] | [deleted] | [
"Skin color is a polygenic trait, meaning it's controlled by more than one gene. It's also a continuous trait, which means that human skin can be a wide range of colors rather than a small number of distinct colors. Humans can be anywhere from albino white to Nigerian black and everything in between. Height is an... | [
"Actually in genetics there is something called Co-dominance and incomplete dominance. incomplete dominance is when a red flower is crossed with a white flower and produce a pink flower, and co-dominance is when the offspring is white and has red dots. ",
"In the case of humans, it might be that there is incomple... | [
"Just to clarify, your definitions of co-dominance and incomplete dominance are flipped. The examples with the flowers are still good ways of describing the two inheritance patterns though."
] |
[
"Ask Anything Wednesday - Physics, Astronomy, Earth and Planetary Science"
] | [
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! ... | [
"Thank you for doing this! A life-long question I’ve had is what does it means for time to be relative? I’ve heard about the experiment where one twin travels very fast in space and when he returns to earth he’s younger than his brother. Is that an example of what it means for time to be relative? If so how does ti... | [
"I hate the phrasing of \"time slows down for person X\" because it makes it sound like a person is moving in slow motion. A little more conceptually helpful, I think anyway, is to consider this. For me, I have a watch of some kind and I can perform an experiment and measure the ticks of the second hand take one se... | [
"Thank you. One of those Wikipedia links had a relatable analogy: “If two persons A and B observe each other from a distance, B will appear small to A, but at the same time A will appear small to B.” This is an analogy for time dilation: two people moving relative to each other each think the other’s time slowed do... |
[
"Can the United Kingdom change the way the new COVID-19 vaccine is administered without changing its efficacy?"
] | [
false
] | null | [
"What if I change the question to be more along the lines of \"How similar are the different Covid vaccines can they be used interchangeably?\""
] | [
"What if I change the question to be more along the lines of \"How similar are the different Covid vaccines can they be used interchangeably?\""
] | [
"There are similar questions recently."
] |
[
"How are rulers measured?"
] | [
false
] | null | [
"Traceability and calibration. The companies calibrate their machines using either physical length standards (gage blocks, micrometers, etc.) or a laser. In either case these standards are themselves calibrated (with equipment having a lower uncertainty than the standards) If you go far enough up the chain of calib... | [
"It sounds like the question you're asking is how is an inch defined. Not sure about inches, but a meter is, by definition, the distance light travels in a vacuum in 1/299,792,458 of a second."
] | [
"Rulers are made by calibrated machines. ",
"if the machine was designed and calibrated to make a 1 foot ruler then every ruler that machine makes is one foot."
] |
[
"If rain/rivers are constantly carrying salt from rocks into the ocean, how does the ocean not become salty to the point of uninhabitability?"
] | [
false
] | null | [
"Billions of organisms big and small extract minerals to make their shells and bodies, die and sink to eventually fix the washed-in minerals back into rocks like limestone and such. That’s not the only process, but it seems to be the biggest factor. Apparently, without life doing this, we’d not only see salinity ... | [
"Cycling of certain salts (especially calcium and carbonate) certainly does have the highest flux through marine organisms, given that plankton are the base of the food chain and exist in surface waters pretty much everywhere, though it’s important to remember that (1) as the plankton tests sink through the water c... | [
"This is one of the issues with climate change and the polluting of the ocean.",
"If we kill of the tiny life in the ocean these problems will lead to the planet becoming uninhabitable."
] |
[
"What is the largest living carnivore in the world?"
] | [
false
] | Hello Reddit, During lunch a colleague and I were having a discussion about what the largest living carnivore animal is. Since google has not returned a satisfying answer I was hoping someone here could help me. My colleague thought that the Sperm Whale is the largest carnivore while I thought that polar beers are the ... | [
"Depends a little on the definition of carnivore used as sometimes is used to only include animals that eat vertebrates, but strictly its animals that eat other animals. Since Sperm whales are bigger than polar bears and eat animals like squid, octopus and fish your colleagues answer is more correct. However, blue ... | [
"Blue whales spend their time hunting krill, amphipods, copepods, shoaling fish and the like - which 'aint exactly vegetables - making them the largest carnivore that has ever lived. ",
"The largest extant land carnivore is indeed the polar bear, weighing in up to about 700kg. The largest land carnivore that has ... | [
"Thanks for the explanation about the largest land animal. Did not that."
] |
[
"When I go to spit, am I collecting saliva already present in my mouth, or do I simultaneously create new saliva?"
] | [
false
] | because honestly I can't feel or tell the difference. | [
"wow. Weirdly cool question. I have thought about a lot of esoteric questions, but never this one!",
"So this answer is not based on research but on how I perform this behavior. I think the answer is both. Here is why. Try doing this without sealing your mouth. It seems impossible. Thats because i create a vacuum... | [
"You have a profound ability to make spit on demand. Have you ever had to vomit and noticed the copious amounts of spit beforehand? I once got very sick but it took a long time between feeling nauseous and the actual event, and I was shocked at quickly my mouth would fill with spit. I'd spit it out and in just a fe... | [
"I have no difficulty accruing a sizable pool of spit while keeping my mouth open. "
] |
[
"What positive research did the Nazis achieve?"
] | [
false
] | We all know the atrocities that the Nazi's were responsible for. We also know how they did medical experiments against their patient's wills. However, what positive research came from this, and how many lives were saved as a direct or indirect result of the experiments, if any? | [
"Please remember to keep any answers to this thread professional and based on fact - the morality of these experiments is not the topic of this question."
] | [
"This question has been asked before. ",
"This thread",
" has a lot of discussion. A few others are ",
"here",
", ",
"here",
" and ",
"here",
".",
"The conclusion seems to be that the experiments regarding hypothermia and exposure to low pressure / vacuum produced useful data, while a number of ... | [
"One thing that I know for sure is that they found out at what temperature the body goes through hypothermia and the effects of hypothermia."
] |
[
"How much better are we at treating Covid now compared to 5 months ago?"
] | [
false
] | I hear that the antibodies plasma treatment is giving pretty good results? do we have better treatment of symptoms as well? thank you! | [
"Lot of the initial data we got from China wasn't super helpful. We knew it was contagious, deadly, And had a brief idea of what symptoms looked like.",
"At first, treatment was shifted towards early intubation (no bipap, no hiflow oxygen) but patients were found to have a difficult time being extubated. Now we t... | [
"ICU doc who treats COVID-19 and research on COVID, and published on COVID both original research and editorials in reputable medical journals.",
"We are much better than previously.",
"Regarding COVID-19 specific therapies:\n1. The UK RECOVERY trial demonstrated a mortality benefit in intubated patients who re... | [
"Nailed it. Numbers wise the work you folks at the bedside have done has been heroic. Early Mortality when admitted to the icu in the early days was 80% now it is closer to 20%... we don’t need a miracle cure when we have smart miracle workers at the bedside. Thanks for your work on the frontlines!"
] |
[
"Why is isopropyl alcohol sold in a 91% solution?"
] | [
false
] | What not 90% or 100%? What's so special about 91%? It seems very random. | [
"According to ",
"wikipedia",
", isopropyl alcohol forms an ",
"azeotrope",
" with water at ~88%. This means that it is no longer possible to separate the water from the isopropyl alcohol by distillation. You have to use other methods."
] | [
"AFAIK 100% solutions would be very difficult (and probably expensive) to make, since at high concentrations (e.g. 95% and up) ethanol and water are azeotropic. I remember one of my professors told us about using benzene or some sort of drying salt to remove the remaining water, but then again I would expect the an... | [
"Absolutely correct on all counts sir. (chemist)"
] |
[
"Did lemons and oranges evolve from the same source? what about grapefruits and other citrus? did this parent plant have a name?"
] | [
false
] | null | [
"Did lemons and oranges evolve from the same source? What about grapefruits and other citrus?",
"All the citric plants (tangerine, lemon, lime, orange, etc.) have a single ancestor. While some of them are product of artificial selection, the rest are still wild relatives.",
"Take a look at ",
"this image",
... | [
"Everything evolved from the same source if you go back far enough. Citrus evolved from the same source about 15 million years ago. We don't name a species without actually finding a member of that species (even if it's just fossils), and I'm pretty sure fruit doesn't last 15 million years, so it doesn't have a nam... | [
"Citrus is one of those tree families that will happily hybridise with almost no help at all. A lot of the common citrus fruits are a hybrid, one way or another, of the papeda, the pomelo, the citron and the mandarin."
] |
[
"Carl Sagan and the pulsating cosmos."
] | [
false
] | In an episode of his Cosmos series, Carl Sagan briefly discussed the idea of a closed cosmos; a big bang is followed by expansion up until a point, then contraction, and eventually a new big bang. Rinse and repeat. He hinted that further examination of the total mass and gravity of the universe was needed to evaluate t... | [
"Not only have we been able to throw it out, we've discovered the exact opposite: rather than slowing down towards an eventual halt and recollapse, the expansion is ",
".",
"Now, take a moment for it to sink in just how weird that is. Even if the Universe weren't going to recollapse, its expansion should still ... | [
"Don't sell yourself short, you're probably at least 3/4ths that smart. You just need to apply yourself. "
] | [
"Don't sell yourself short, you're probably at least 3/4ths that smart. You just need to apply yourself. "
] |
[
"Why is a colour wheel a circle and not a straight line?"
] | [
false
] | null | [
"Color is not \"essentially a wavelength\". There are various color experiences we have that do not correspond to any single wavelength of light (non-spectral or extraspectral colors like pink, purple, and brown).",
"Our experience of color is the result of the interaction of light (combinations of wavelengths at... | [
"It’s so interesting that the government doesn’t sell shirts of these extraspectral colours. Only in foreign brown countries"
] | [
"Wow gee whiz it is like I am saying looking at a color gamut of a television may as well be a color wheel. Red+yellow does give orange and red + blue does give violet and green +violet does give blue. Just like adding waves destructive and constructive interference which they say light doesn’t do unless it’s polar... |
[
"If you have a lot of something can you control a market for that item?"
] | [
false
] | Let's say that there is a person in a free market that abides to common supply and demand laws so that most items are at a market clearing price. Now lets say that there is a person called Person A who owns twenty billion tons of gold. He knows that he essentially has a worthless pile of soft yellow metal but no one el... | [
"This is dependent on the thing you control, and what alternatives people have, their cost of switching over to the alternative, etc. For example, if you have a massive horde of wool...what applications are there where only wool is usable? Certainly clothes can be made out of many other things, so you're not going ... | [
"Simply yes. Considering you know the current demand for the gold market and you own all of the gold then you will be able to choose whatever price you want including the current market clearing price. Now if you don't own all of the gold in the market however you own a vast majority of the gold you could enter in ... | [
"Well, there's two sides to supply and demand. What you have in your scenario is one person in control of the supply side, but price is determined by the interaction between supply and demand. If no one wants it, it doesn't matter how much of it you have, or even that you have all of that thing in existence, it wil... |
[
"When I take a photo, am I taking a snapshot of only the colors within the visible spectrum of light? Or does more of the spectrum develop than we can note without other instruments?"
] | [
false
] | null | [
"The camera is designed to do that, but as a matter of fact the CCD also captures light from different wavelengths. You can google CCD sensitivity if you'd like some more detailed graphs on that, or check the wiki: ",
"http://en.wikipedia.org/wiki/Charge-coupled_device",
"As a matter of fact, today's digital ca... | [
"I know that cellphone's cameras can at least pick up infrared . You can see the light used on TV remotes if you point it at the camera. "
] | [
"Film is sensitive to the higher wave lengths of light such as x rays and gamma rays , but lucky most places aren't that radioactive. You can see this in some of the photos taken during the cleanup at Chernobyl, where the film was fogged because the ground was literally glowing in a spectrum that humans can't see. ... |
[
"Is there a closed form solution for all recursively defined sequences?"
] | [
false
] | Or if there isn't, is there a subset of recursively defined sequences which does? Has it been proven to be true or false? | [
"The Wolfram article covers this fairly well.",
" A linear sequence does have an analytic solution, but it's unknown/unproven whether nonlinear ones do."
] | [
"It depends on what you mean by \"closed form solution\". The linear recurrence",
"a(n) = a(n-4) + a(n-5)",
"has solutions all of the form",
"a(n) = Ar1",
" + Br2",
" + Cr3",
" + Dr4",
" + Er5",
",",
"where A, B, ..., E are constants and r1, r2, ..., r5 are the roots of the polynomial equation",
... | [
"A small subset of Difference Equations can be solved analytically. In fact, homogeneous (and some non-homogeneous) linear difference equations can be solved using some of the techniques for ODE.",
"Variation of parameters, Method of Undetermined Coefficients, and Summing Factors (analogous to integrating factor... |
[
"A 17 year old created a \"cancer killing nanoparticle\". What are the implications of this discovery, and what impact will it have on cancer treatments?"
] | [
false
] | gives the story of a high school student who won $100k in a Siemens sponsored science and technology competition. The winning creation was a nanoparticle which can target cancer cells. In laymans terms (as much as possible), can you explain why this discovery is important, how it may alter the treatment of cancer, an... | [
"I read the article and am familiar with the concepts she incorporated into her design. To answer your first question, this is not a discovery. Angela has simply combined the most promising developing treatments into a single particle. It's really all here in the title of her project:",
"“Design of Image-guided, ... | [
"All these are in current literature right now, with many more in active research. In fact, many are past the \"design\" stage, and are facing real world problems of synthesis and specificity.",
"So while this is a great idea and she deserves credit for putting it together, it's not a discovery or a development -... | [
"Usually when we hear things like this, there is a major catch. Cancer, as I understand it, is a very wide grouping of similar (yet different) conditions, which no one solution works for. Is this new treatment applicable to all cancers? To even many of them?",
"How well is it studied - is it actually reliably eff... |
[
"Are the polar regions of Venus significantly cooler than the rest of the planet, as on Earth?"
] | [
false
] | Would a lander have a greater lifespan on Venus' poles (assuming it could survive the pressure), or is the planet's average temperature relatively even, no matter the location? | [
"The planet's surface temperature is actually very constant. On Earth, the temperature difference between equator and poles is due to the fact that the equator receives much more solar irradiance than the poles do. On Venus, however, the extremely thick atmosphere redistributes the heat very well and keeps the surf... | [
"Also Venus rotates very slowly correct? Making one area get blasted by the sun for a long period?"
] | [
"It does rotate very slowly, but the very strong greenhouse effect means that the night side is nearly as hot as the day side. The whole planet is very well insulated."
] |
[
"If you were to sky-dive in the rain, would water hit your stomach, back, or both?"
] | [
false
] | null | [
"Assuming you jumped from below the height of the raincloud, and that the rain drop originated sufficiently high above you to already be falling at their terminal velocity, and that you are bellydown, you'd initially be struck by rain on your back. As you fall and gravity accelerates you, the rate that rain strikes... | [
"As you approach your terminal velocity, which is faster than that of a raindrop, you'll be catching up to raindrops ahead of you.. ",
"You will exceed the terminal velocity of the raindrop within ",
" of beginning your free fall."
] | [
"Skydiver here. The water always hits you from the direction you are falling. From the moment you exit the aircraft, you are \"falling\" forwards at around 70-90 knots typically. That is already fast enough that you will be striking water on the side of you facing the relative wind. From there, the direction of you... |
[
"Lewis Black asked it as a joke, but it got me thinking. If blood doping has such great effects...why don't we all do it?"
] | [
false
] | null | [
"Blood doping does improve human performance, but for a limited time and with a great deal of organisation.",
"Basically you need t have your blood drawn, wiat for your body to repopulate your blood stream with red blood cells and then take the old blood back in. However your body will recognise that you have too... | [
"The viscosity certainly is a concern as this makes the blood more prone to clotting or coagulation, which in turn increases the chances for stuff like heart attacks and strokes.",
"Another risk is if the blood is improperly stored and contaminated before being reintroduced into the body."
] | [
"If this increase in blood cells helps oxygen carrying capacity why don't our bodies produce more red blood cells naturally? Surely there is some downside, perhaps the blood is dangerously thick?"
] |
[
"If I hold a weight directly in front of me and don't move it, no work is being done as work = force*distance. So if no work is done why does it use up energy?"
] | [
false
] | Sorry for my teenage understanding of physics. | [
"You are not able to hold static loads without using energy. The cellular mechanisms that move your muscle fibers involve small combustion reactions rotating proteins. It is like trying to push on a wall with water from a hose, you need a constant stream of material to get a constant force.",
"Stiff objects do no... | [
"To make it explicit: the energy is being converted into ",
" energy inside the muscles, whereas work is usually converted into kinetic or potential energy. It's not terribly different from the way heating a cup of water uses energy, despite not doing any actual work (in the scientific sense) on the water."
] | [
"The combustion reaction is taking place one molecule at a time, inside your cells. The factors you can observe:",
"Large amount of heat produced",
"Oxygen input required",
"CO2 and H2O exhaust (you cant really see the H2O, but it is why you breath out CO2)"
] |
[
"Why would liquids in the garage not freeze for at -10C/+14F ?"
] | [
false
] | My inlaws have a garage that is separate from the house (maybe 20 by 20 feet?). They store extra drinks in the garage. They have beer, cokes, water bottles, etc. They are directly laid on a table or on the floor and not in any container. The garage is non-heated. Why would they when the thermometer inside the garage sa... | [
"There could be two different things at work, the first of which is that sugars and alcohols lower the freezing point of liquids. A typical can of soda or soft drink will have around 36 grams of sugar in it, so you can get a greatly reduced freezing point.",
"\nThe other is a phenomenon called ",
"supercooling"... | [
"A solution of water and sugar won't completely freeze until -9.5 °C (-15 °F). They form what is known as a eutectic system; you can find the phase diagram ",
"here",
". Even once the freezing point is reached, some additional cooling is necessary to nucleate ice crystals, and once freezing begins the latent he... | [
"I need!!!"
] |
[
"Does the 7.8 earthquake in Nepal mean that Mt. Everest just grew a little more?"
] | [
false
] | Given the location, type of fault line, etc... | [
"They can measure the height from an airplane down to the inches? What about snow cover?"
] | [
"They can measure the height from an airplane down to the inches? What about snow cover?"
] | [
"LIDAR won't help - it's only accurate for measuring relative heights. ",
"Conclusive evidence would probably require an expedition to place a differential GPS on the summit like an ",
"American team did in 1999.",
" Though it's possible that InSAR might be able to measure it - if there's accurate pre-quake i... |
[
"How do I find x,y coordinates in concentric circles?"
] | [
false
] | null | [
"Not the right sub for project help. Try ",
"/r/math",
" or ",
"/r/mathhelp",
" maybe "
] | [
"Mathematics"
] | [
"Mathematics"
] |
[
"Does the type of sand matter for glass production?"
] | [
false
] | Read a report that if not for plastic-glass hybrid vials, we nearly didn’t manage to mass produce vaccines in such a short time. I understand not all sand are created equal, for example, dessert sand is smooth hence not suitable for construction. Construction requires rougher/angular sand from rivers etc. Controlling f... | [
"We don't normally think of glass as soft, but it's not technically a solid",
"Glass in this context is an amorphous solid. It doesn't exhibit long-range ordering like a crystalline solid, but it doesn't flow with the relatively low viscosity of a liquid. It is definitely a solid."
] | [
"High grade silica sand for making glass is a special type of sand.",
"You can broadly classify manufactured glass as container glass, flatwear, fibre glass, table glass, and finally specialty/technical glass (used for pharma). The quality of the sand determines what type of glass is possible.",
"That global s... | [
"Generally laboratory glass is borosilicate. This is due to its toughness and resistance to a range of chemical agents. It contains at least 5% boric oxide.",
"So yes, it ends up mattering. Borosilicate is extremely tough, to the point where it can sometimes survive being dropped.",
"For reference the majori... |
[
"Are the claims in the linked article true? That only modern wheat contains the protein gliadin and that it increases appetite by \"binding to opiate receptors\"?"
] | [
false
] | and is the original article. Thanks! | [
"I'd be interested to see how many of them are from reputable peer-reviewed journals."
] | [
"According to ",
"this review",
", the citations don't actually support the claims they back. "
] | [
"Your overall assessment seems solid, but I have to wonder why you speak poorly of older papers? Even if the evidence is 30 years old, is it not still evidence?"
] |
[
"How do cells \"know\" their location in the body, especially during embryogenesis?"
] | [
false
] | I was watching a show on PBS regarding genetics, and learned that some genes are used for "switching" other genes on and off. The scientists injected a mammalian embryo (can't remember which one), with some sort of chemical that indicated whether certain genes were on and off. It showed that the genes in the "hand" w... | [
"I'm a Developmental Biologist and study this processes. This is a complex system, but here's my very short answer:",
"It all comes down to \"Signaling\". In a developing organisms send and receive signals from one another telling each other what to do, and what they are doing. These signals then activate genes t... | [
"but... how do they know what signals to send?",
"where does the chain start?"
] | [
"IIRC, this chain is first initialized at the formation of the zygote, when fertilization forms a diploid cell from the egg and sperm that then splits into non-identical cells. This process repeats itself and differences form exponentially."
] |
[
"What is this shape on my friend's laptop?"
] | [
false
] | is the image that my friend sent me about a week ago. I have noticed that the laptop screen had this weird shape caused by some sort of visual anomaly. Now the reason I'm interested in what causes that shape is that because I've created a simple code for a fractal which has a very similar shape and I have never seen th... | [
"It's called a ",
"Moiré pattern",
" but it can basically be thought of as aliasing. There is in an interaction between the spatial sample rate of the CCD on the camera and the spatial output rate of the monitor. Due to slight bends in the monitor, it's not perfectly regular."
] | [
"No, it's what happens when you sample (by a CCD in this case) a band limited signal (pixels over space) at a rate less than twice that of the highest frequency in the signal (i.e. the CCD resolution needed to be high enough such that each line of the screen was captured by two lines of the CCD). Look up ",
"Alia... | [
"Yeah, this is like digital signal processing 101. Like, literally, you'd probably get this either on the second half of the first lecture, or the second lecture. (and then they'd go over it again when they talked about Fourier Transforms)."
] |
[
"Are all solids frozen?"
] | [
false
] | Meaning, frozen is equivalent to a solid. Anything that can be melted into a liquid or freeze into a solid is considered frozen. | [
"To combat RobustEtCeleritas, I would say TECHNICALLY no, not all solids are frozen. ",
"This is a language thing, in the sense that when talking about freezing we are talking about a transition from liquid to solid. Not all solids have gone through a liquid to solid phase change, so they would not be considered ... | [
"No they aren't. Frozen means that something has undergone the process of freezing. If it hasn't gone through freezing, it isn't technically frozen."
] | [
"You actually are freezing the water contained in the steak. But I get what you are saying."
] |
[
"How long did recombination (photon decoupling) actually take?"
] | [
false
] | Ok, so in the beginning, the universe was too hot and energetic for nuclei to hold on to electrons. Therefore photons had a very short mean free path to travel, and the whole universe was opaque. So far, so good. Then, "378,000 years after the big bang", the universe had cooled down sufficiently for neutral atoms to fo... | [
"~10,000 years, pretty much the same 10,000 years everywhere. The probability that a photon didn't get absorbed any more increased continuously from \"nearly 0%\" to \"nearly 100%\" over this timescale.",
"I don't find a nice plot showing this now.",
"/u/Rumetheus",
": This is quite long on human timescales."... | [
"Ah. As noted in my comment, my knowledge of this topic was deficient to give totally accurate answers. Thanks for the more informed insight! Cosmologically insignificant timescale, but exceedingly significant in human lifespan terms. I was merely making an educated guess, but my use of human timescales as a descri... | [
"Edit #1: The best I’ve found on a quick google search is it happened “abruptly” ~380,000 years after the Big Bang. Which does make some sense to me for some measure of “abruptly” since the CMBr is effectively a map of “first light” for the whole universe. Probably safe to say that “abruptly” has wiggle room in tim... |
[
"If there was a Dyson Sphere around a star harvesting 100% of its energy, would we have any means of detecting it with current technology? What would we look for?"
] | [
false
] | null | [
"Gravitational effects I'd guess would be easiest. There would be a solar system orbiting \"nothing\". Also if the sun was large enough it may produce gravitational lensing where it effected the light passing around it even with the Dyson sphere. "
] | [
"One potential way would be if it passed in front of another object, we could see how big it is. That's one technique used to measure the size of exoplanets."
] | [
"One potential way would be if it passed in front of another object, we could see how big it is. That's one technique used to measure the size of exoplanets."
] |
[
"Why do people seem to get pain in their joints when the weather gets wet and cold?"
] | [
false
] | It appears whenever it gets cold and rainy, people complain a lot more about aching muscles and joints. I also have a knee, which I once hurt snowboarding, that starts aching a bit when it's cold and wet outside. Why is this? | [
"changes in atmospheric pressure"
] | [
"s8nlovesme is correct. Here is a source for a clinical research study pertaining to you question:",
"http://www.sciencedirect.com/science/article/pii/S0002934306010266",
"\nChanges in barometric pressure and ambient temperature are independently associated with osteoarthritis knee pain severity."
] | [
"It's a good question, and this research indicates that there's more to this than anecdote:",
"http://www.ncbi.nlm.nih.gov/pubmed/21334931",
"Here's the wiki page for 'barotrauma', it may be relevant:",
"http://en.wikipedia.org/wiki/Barotrauma"
] |
[
"What causes different consistency in semen?"
] | [
false
] | [deleted] | [
"It all depends on the fluid that comes out of the prostate and other sexual organs. The extra fluid coming with the sperm, ",
", is to deacidify the acid present in the vagina and the acid from the urine in the urethra. Pertaining to your question: the consistency of the semen would depend on how much extra flui... | [
"I've always found it tied to hydration personally. If I'm hydrated, it is more watery, but when I'm not, it tends to be thicker."
] | [
"All other things being equal, this is the largest factor. Increased sperm motility (and subsequent virility) is highly correlated with hydration. ",
"Of course, as RossTheColonel pointed out, the extra fluid from the prostate, etc can be depleted in one or two ejaculates, and if further ejaculations occur, they ... |
[
"Will the Earth be at the same position relative to the Sun, on 6:00 PM MST on 11/15/2013 as it was at 6:00 PM MST 11/15/1813?"
] | [
false
] | [deleted] | [
"The usual kind of year isn't exactly the time it takes Earth go around the Sun once, even discounting the mess with leap years. It's the time from one vernal equinox to the next. Because the axis of Earth changes slowly, the orbital position where vernal equinox happens also moves. This is called a tropical year a... | [
"No.",
"Aside from perturbative forces from other planets, the Earth's orbit is slightly eccentric (i.e., its orbital path is an ellipse that is not a perfect circle), and this ellipse precesses about the sun with a period of about 110,000 years. So the whole orbital path is gradually moving around the sun, if th... | [
"In an approximate sense yes, but it won't be exact. For starters, calendar years aren't exactly 1 astronomical year long; to takes 400 years for the Gregorian calendar to adjust to the mismatch here.",
"The Earth's orbit is also constantly being perturbed in small ways by the presence of other bodies in the sol... |
[
"Photon density emitted by a star?"
] | [
false
] | [deleted] | [
"Very approximately, at its surface the sun outputs about 10",
" photons per square meter per second. You would have to be roughly 10",
" solar radii away to get that down to 1. That is about 700,000 lightyears, about a third of the way to Andromeda."
] | [
"Semi-serious follow-up question:",
"To gather a metric (pho)ton of light (In the sense that light as energy changes the gravitational field.) from the sun, how long would one have to gather the sun's total output?"
] | [
"Like, a microsecond."
] |
[
"If including risk-taking and substance abuse, how do the genders compare in deliberate self-harm?"
] | [
false
] | Studies find that male suicide rates are far higher than women’s, across regions and countries. However, it seems that delibarate self-harm (DSH) is more prevalent in women throughout Europe, with Finland as a possible exception. But what is the case if one includes deliberate risk-taking activity—such as choosing the ... | [
"I don't think I can directly address your main point. However, here are my thoughts about your question, which in part get at why it's a hard one to answer:",
"You're right that rates for completed suicides are higher in men than women, but women are more like to attempt suicide than men (for review, see ",
"h... | [
"In order to design a study to address the broad idea that you're getting at, I might slightly alter the terms you're using. Rather than getting at deliberate self-harm, I would look at risk-taking behavior. By getting rid of the problematic \"deliberate\" part and focusing on just observable behaviors, we have a t... | [
"These are all excellent answers, and I am very grateful for you taking the time answering. I found that at least one of the papers was not hidden behind a pay wall, and began reading through it yesterday; it will give more depth to my proposal, when I finish it sometime this summer. I will read through your replie... |
[
"Can you change light spectrum with out prism?"
] | [
false
] | How could I make infrared or ultraviolet? | [
"You can change lights wavelength using Doppler shift or frequency doubling crystals but I don't think you understand what's going on with prisms.",
"Prism doesn't change light into anything, it merely splits the existing components of the light beam you shine through it. So if we shine white light through it, it... | [
"Is it that the energy gets adsorbed by the filters?"
] | [
"And if you sent white through it as it might be emitted by a modern TV screen, you'd get three distinct color stripes: Blue, green, red. Because that's how the impression of white is being created in the first place."
] |
[
"Are there any shapes of constant width that will tesselate the plane?"
] | [
false
] | This might be inherently impossible but I'm wondering. | [
"I'd been thinking for a couple of hours but I couldn't figure out how to rigorously prove the assertion that a convex shape that tiles the plane must be a polygon with a finite number of sides. But if we assume that, then it's impossible for a shape of constant width to tile the plane.",
"We have that ",
"all ... | [
"I'd been thinking for a couple of hours but I couldn't figure out how to rigorously prove the assertion that a convex shape that tiles the plane must be a polygon with a finite number of sides.",
"I'm not very familiar with these sorts of geometric arguments, but this one seems to me like it shouldn't be so hard... | [
"Well, you've got a positive length side that has to be shared by a finite number of other copies of the shape, and the sum of the shared parts of the side have to add up to the full length of the side. The sum of a finite number of non-negative values can only equal a positive value if at least one of them is posi... |
[
"Why are some metals magnetic, and not others?"
] | [
false
] | What are the properties found in iron, nickel and cobalt that cause them to be permanently magnetic, and not other metals, or another material for that matter? | [
"Those materials are ferromagnetic in particular, which is your typical attraction. This is caused by the spin of free unpaired electrons (remember that the valence electrons in metallic bonds are delocalized) lining up and producing a unidirectional magnetic field.",
"IIRC Only Cobalt Iron and Nickel have the pr... | [
"Besides Fe, Ni, and Co there are also Gadolinium, Terbium, Dysprosium.... but for Gd, Dy and Tb the Curie temperature is below room temperature so they are usually in their paramagnetic phase."
] | [
"There are also ",
"ferromagnetic polymers",
", but they are an active area of study and have no known applications at the moment."
] |
[
"[Physics] What would be the escape velocity for a planet with a radius of 46.2 meters and a mass of 3.14 x 10^15 kg? Assuming normal G."
] | [
false
] | null | [
"Escape velocity is given by sqrt(2GM/R). Just plug in the numbers. You get 95.25 m/s \n",
"http://www.wolframalpha.com/input/?i=sqrt(2*Gravitational+Constant+*+(3.14+*+10%5E15+kg)+%2F+46.2+meters)",
" ",
"Your discrepancy is probably a calculator error."
] | [
"Thank you very much!!!"
] | [
"Please post calculation requests to ",
"/r/estimation",
" or ",
"/r/theydidthemath"
] |
[
"Is it possible to directly observe the impact between two massive solar bodies occurring in real time? How often, if ever, has humanity been able to observe such an event?"
] | [
false
] | I ask because after getting lost in wikipedia, I came across the article about Rheasilvia (the tallest mountain in our solar system). I was thinking about how fascinating it could be to observe some sort of footage depicting an impact on that sort of scale. My initial thoughts are that an event like this is probably t... | [
"Doesn't matter. Time is relative and when we look at a star thousands of lightyears away and see something happening it is in real time for us."
] | [
"It wasn't a poor answer. This was the exact answer I came to give. Time is relative so OP has to clarify what s/he means by real time. If s/he meant us experiencing the event and watching it take place, it is possible but we would need to be looking at the correct portion of space at the right time."
] | [
"its technically possible, but given the very tiny portion of space that we monitor at any given time, it is unlikely. we would most likely only be able to see the sort term reaction well as in the case of a supernova (several of which have been documented through telescopes and naked eye observations)"
] |
[
"Could a dying sun's life be extended by combining it with another smaller sun which was much younger?"
] | [
false
] | Imagine an incredibly advanced alien planet's sun is dying. To keep the sun from going super nova and destroying their world, the aliens decide that they could capture a smaller sun and bring it close enough to their own so that their sun would pull the smaller sun's hydrogen to itself, thus allowing fusion to continue... | [
"That's why the second sun would have to be on the smaller side so that compared to the larger sun, it wouldn't have as much impact as on surrounding planets."
] | [
"The smallest sun you can possibly have would be a tad larger than Jupiter, and Jupiter has some severe effects on the solarsystem. Imagine drawing something of that size trough, I don't think that would go well :P"
] | [
"This can sorta happen in Binary star systems, one star will steal mass from another. If its a white dwarf (a star in its final stage slowly cooling) then the matter it can pull in enough mass to reignite fusion in its outer layer until it collects enough mass go nova or supernova which would obliterate our hypothe... |
[
"What determines the color of an object?"
] | [
false
] | Yeah you could say for instance "the red paint makes the firetruck red" but what makes the paint red, and what makes that red, and so on and so forth until you get to the root of red. I want to know what that root is and if it's common for all colors or if it's dependent on the material of an object. | [
"There are essentially 2 ways that something can ",
" a particular color: either it gives off that color light or reflects that color light more strongly. Both work off the same principle in the end - the cones in your eye, which detect red, green, and blue light are preferentially excited in different proporti... | [
"To add to this, the wavelengths which are reflected/absorbed/emitted by the object you are looking at is determined by the molecular structure of the the paint, or surface of the object. For example Iron (III) Oxide (Fe2O3) has ",
"this absorbance spectrum",
". See the dips near 800nm on the right side of the ... | [
"Yup, it's all about the energy contained at different wavelengths in the light hitting your retina. Your photoreceptors are differentially excited by different wavelengths of light, which provides the brain with the data it needs to calculate the energy profile of the incoming light."
] |
[
"How do we know what is in the middle of the earth?"
] | [
false
] | null | [
"We can use seismic waves from earthquakes to determine this. We are able to trace these wavepaths through the Earth and depending on what type of wave it is (either a P or S wave) they will behave differently through different phases of matter. I think that ",
"this gif",
" does a lot better job of describing ... | [
"If this is true, it may not have to do with \"how much we've explored\", but more with the fact that the centre of the Sun has to obey a stable but very delicate equilibrium condition (inward gravity versus outward thermal pressure), which could constrain more what its allowed properties are. ",
"Also, a descrip... | [
"Eventually it will be too hot. In theory one could encounter, C.H.U.D.S., Morlocks and Molemen."
] |
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