title list | over_18 list | post_content stringlengths 0 9.37k ⌀ | C1 list | C2 list | C3 list |
|---|---|---|---|---|---|
[
"Is using electronics such as iPads actually better for the environment than using paper?"
] | [
false
] | [deleted] | [
"I think this only holds if you are talking about using the iPad exclusively as a notebook, which is not how they are typically used. What about if you use it as an e-reader that replaces books, magazines, and newspapers? What about if you use it and e-mail/other electronic messaging services to replace postal mail... | [
"I think this only holds if you are talking about using the iPad exclusively as a notebook, which is not how they are typically used. What about if you use it as an e-reader that replaces books, magazines, and newspapers? What about if you use it and e-mail/other electronic messaging services to replace postal mail... | [
"No; but it really depends what you mean by better.",
"First: Paper isn't inherently bad for the environment. Unlike wood the majority of paper within a first world country comes from virgin pulp farms, tree farms planted and harvested every 4-5 years specifically for the use of paper. In fact we have more trees ... |
[
"Why are allergies seemingly so much more prevalent today then in previous decades?"
] | [
false
] | It seems to me that, say, 20 years ago peanut allergies (for example) weren't nearly as commonplace as they are today. Peanuts were served on airplanes, practically everyone ate peanut butter and jelly sandwiches in elementary school, etc. Now, planes serve pretzels and many schools have banned peanut butter campus wide. Is there an environmental effect here? is it the way we process or breed peanuts? Whats going on here? One thought I had was that they might have been just as prevalent, but now are just more widely acknowledged, but that doesn't seem to match up with what I've observed. Peanuts being just a common example. I know there are plenty of allergies out there. Thanks for your expertise! | [
"This is a variation on the on-again off-again \"Clean Baby Hypothesis\" or \"Hygiene Hypothesis\". It is quite controversial, and has been for a long time. I used to work in allergic airway diseases back in the late 90s, early 2000s. This stuff was on the fringe when I started, got popular in the early 2000s, peak... | [
"This is a variation on the on-again off-again \"Clean Baby Hypothesis\" or \"Hygiene Hypothesis\". It is quite controversial, and has been for a long time. I used to work in allergic airway diseases back in the late 90s, early 2000s. This stuff was on the fringe when I started, got popular in the early 2000s, peak... | [
"Essentially yes. Your immune system is a thing that is continually changing throughout your life.",
"It's quite possible through repeated exposure to an allergen to develop an allergy, this is seen occasionally in bio labs where people pick latex allergies to the latex gloves. It is also quite common to slowly b... |
[
"Are all snowflakes really unique?"
] | [
false
] | I understand that there are many different formations of snowflakes, but there are also a lot of snowflakes in the world. Thinking about it with respect to the birthday problem en.wikipedia.org/wiki/birthday_problem isn't it almost certain that some snowflakes are the same? | [
"They are nearly unique. Think about this - watervapor combines with dust particles to form snowflakes..and the path taken by the watervapor and the dust particles it comes in contact with determines the shape of the snow flake.. Endless combinations are possible"
] | [
"Right. We need to be careful not fall into a pedantic trap here though.",
"One could extend this to state that essentially no macro structures are identical or that all are unique. There are nearly endless combinations of shape available depending on the level of detail you wish to examine and even regular struc... | [
"Depends, of course, to what degree of accuracy you want to consider 2 to be \"the same\".",
"You will find many that will be \"almost identical\" for any reasonable definition of almost."
] |
[
"How can Fourier expansions be made an integral?"
] | [
false
] | I see how a discrete Fourier expansion works by forming a linear combination of orthogonal functions. And when we write such an expansion, we are working in a basis of those orthogonal functions. So when we use the integral Fourier transform, are we working with a continuous distribution of basis functions? If so, are these continuous bases related to infinite dimensional matrices? | [
" In all, if you have a function F(x) from some domain D into the complex numbers, you can perform a Fourier Transform of it by comparing it with one of the fundamental functions from D into the unit circle inside the complex plane, which we can call E",
"(x). These functions fundamental functions will be paramet... | [
"Instead of thinking of uncountable collections of basis functions, I think it's better to view both of your examples as a special case of what is called a \"Pontryagin dual group\".",
"If G is a locally compact abelian group (such as the real numbers modulo 1) , we call a function chi mapping G to the complex un... | [
"All Fourier ",
" do the same thing. Take a function and find another function using properties of integrals (and sums) using it.",
"Take, for instance, periodic functions. We can wrap a periodic function around in a circle, so that it becomes just some function from the circle into the real or complex numbers... |
[
"Is it possible for a beneficial virus to exist?"
] | [
false
] | Upon being infected, we become stronger, or increased mental capacity, etc. Does not have to be a virus specifically, could be bacteria or something else that usually is associated with causing sickness. | [
"Pretty sure Bacteriophages count",
"http://en.wikipedia.org/wiki/Bacteriophage",
"They are viruses that specifically target bacteria. They have been used as anti-biotic treatments and are also used to help keep food fresh since they kill the bacteria that might make it go bad."
] | [
"I know of a few interesting examples but not any that perfectly resemble what you are talking about.",
"Retroviruses are viruses that add their DNA to the infected cells. Most of the time this just causes the cell to create new Retroviruses. However these bits of DNA can be passed on and become valuable parts of... | [
"Wow thanks for all the info. Are there any known retroviruses that are naturally transmitted (air/water/etc.)?"
] |
[
"Why does orange \"A\" taste bitter, but orange \"B\" is sweet?"
] | [
false
] | [deleted] | [
"Fruits develop and ripen individually regardless of what tree they're on or when they're harvested. In early stages of growth they're bitter/sour to discourage creatures from eating them before they're ready to spread their seeds.",
"In oranges in particular, as they ripen citric acids become diluted, the variou... | [
"So every time I go to buy one, I am rolling the dice as to getting a ripe vs unripe orange? =/"
] | [
"Pretty much, but they're loaded dice in your favor. Producers do try to get them at the right point of ripeness, but they don't check each fruit - they harvest whole trees, as there's no other way to produce in volume."
] |
[
"Are there any animals that do not feel physical pain? If so, how does this work?"
] | [
false
] | null | [
"There is a genetic disorder in which some people are pain insensitive due to a problem producing pain fibers.",
"http://en.wikipedia.org/wiki/Congenital_insensitivity_to_pain_with_anhidrosis"
] | [
"what about animals?"
] | [
"In general, we can only judge this behaviorally, so it's hard to tell. We measure pain in terms of response to potentially damaging stimuli. More or less anything you'd want to call living demonstrates averse responses to certain stimuli, so there's a case to be made for calling this pain.",
"One can take this... |
[
"Are asymptomatic people meaningful vectors of transmission of COVID-19?"
] | [
false
] | Two of the main symptoms of the flu are sneezing and coughing. These symptoms also help A LOT in transmitting a respiratory disease. Considering that COVID-19 asymptomatic people don't sneeze or cough, are they really meaningful vectors of transmission? | [
"Yes. Numerous studies have shown that the SARS COV 2 virus is aerosolized, which means it is emitted in infectious quantities in normal breathing and talking. No coughing or sneezing is necessary for transmission."
] | [
"Agreed. This is why Covid-19 is so dangerous. If people were sneezing and coughing they would know to quarantine. In this case they don't and become great spreaders."
] | [
"Sure. Here's a review paper that has links to multiple studies throughout. ",
"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7293495/",
".",
"Another",
"Another",
"Another",
"And here's the October update to the ",
"CDC guidelines",
" where they finally acknowledged aerosolized transmission.",
"Ma... |
[
"How do we know that certain animals are colorblind?"
] | [
false
] | Any examples of testing animals, as obviously they can't talk? | [
"If by this, you mean that the whole species cannot see a certain color, instead of say an abnormal individual: ",
"We have different proteins called opsins found in each type of color-sensitive cone in our eyes that are responsible for us being able to see these colors. These proteins absorb light most effectiv... | [
"Oh thank you for an awesome reply!"
] | [
"You could look for the opsin genes but I would look for the protein in an actual specimen to prove that it's there and potentially functional. You would fix the animal in paraformaldehyde, get a thin slice of its eye, and then do some immunohistochemistry. You would use a primary antibody to detect the three opsin... |
[
"If a male has very high-functioning Aspergers Syndrome (to the point that it isn't even noticeable by others), how much more likely are his children to have an autism spectrum disorder?"
] | [
false
] | null | [
"Good question, I'm also interested in the answer. My son has Aspergers and it's pretty apparent, though his is by no means crippling. I'm going to suggest when he's a teen to really consider reproducing though because he also has Neurofibromatosis 1, which is 50% inheritable."
] | [
"Here's a Wired article",
" about the rising prevalence of Autism-spectrum disorders in Silicon Valley, which some attribute to lots of geeky people (who have some but not all of the traits associated with ASD) having kids with each other. There's probably some relevant information for you in there."
] | [
"I'm not here to give you medical advice. ",
"But I will tell you what I know about autism inheritance patterns: it's complex and we don't know as much about it as we do for, say, cystic fibrosis. The inheritance pattern isn't all simple mendelian genetics - it's a heterogenous mix of inheritance processes. ",
... |
[
"What is the most efficient way to breath while running?"
] | [
false
] | null | [
"I ran track through college (sprinter). I generally found that your body is going to tell you what it needs, and you are going to breathe correctly no matter what. One thing you probably already do naturally is breath in rhythm with your stride, and I feel that is important. \nThat being said the other two comment... | [
"If you breathe in through your mouth you get more air in, but if you breathe in through your nose, the conchae/sinuses etc warm and humidify the air, conditioning it for your lungs. Breathing out doesn't require the same, as it remains conditioned until it leaves your body.",
"Breathing in through your nose will... | [
"Inhale deep through the nose and exhale through the mouth. "
] |
[
"How do you feed someone in a coma?"
] | [
false
] | null | [
"Med student here. There are a few options depending on the needs of the patient and how long they are in a coma for.\nMost of the time we will run a tube from the patient’s nose, down their throat and into their stomach. We then run a complete liquid formula through the tube that provides the patient with all the ... | [
"The digestive system is basically a mechanism for breaking food down into microscopic nutrients that are so small they can cross into the blood stream in the small intestine. The large intestine's main function is to provide water and salt balance in the blood stream as well as removing waste particles (like dead ... | [
"Wow thank you!",
"I'm betting all of these processes are quite costly...",
"regarding the last option, how is blood getting the nutrients able to support the entire body?"
] |
[
"What in physics is fundamental?"
] | [
false
] | Okay so I've had this question for a long time and got a variety of answers. If I were making a list of the fundamental laws of the universe, what equations, constants, and background knowledge would need to be on it? Would it just be Einstein's field equations and the standard model (can you write the standard model in one equation)? Would any equations that explain quantum or newtons laws be necessary or are these derivable from more basic laws? How bout the speed of light? Can everything we know be summed up in one equation like the photo posted? Thanks for any insight you can offer | [
"Nothing we know ",
" to be on the list of fundamental laws. The image you posted, by Sean Carroll, is a compact writing of the theories that so far describe just about every observation we've ever made. But this is only an ",
", meaning it only works below some energy scale. That's the meaning of the \"k < Λ\"... | [
"From what I can see, that says ",
" equals a whole bunch of other squiggly lines and stuff. What does the ",
" represent?"
] | [
"As ",
"/u/RobusEtCeleritas",
" said, you'd be hard-pressed to find a better explanation than Carroll's. But that is probably geared at a lower level than physics undergrad, so for that audience, I can add a few things.",
"First, the part labelled \"quantum mechanics,\" as well as the \"W\" on the left-hand s... |
[
"telescopes"
] | [
false
] | perhaps this is a stupid question, but I don't understand optics very well and I was just curious about this: if you shine a flashlight forward through a telescope, what would happen? And backwards? | [
"Less concentrated than at its source though."
] | [
"if you shine a flashlight forward through a telescope, what would happen?",
"If you hold a flashlight up to the eyepiece of the telescope, its light will be sent up wherever the telescope is pointing.",
"And backwards?",
"If you put a flashlight in front of a telescope's primary mirror/lens, the light will m... | [
"will it in any way concentrate the light?"
] |
[
"Is there any REAL difference in retention between audiobooks and hardcopy books?"
] | [
false
] | I've searched for evidence and cannot really find anything compelling. I often hear it suggested that reading ebooks results in lower comprehension and retention, but I was not able to find any good studies comparing either modality to audiobooks. I know there are people who are auditory learners vs. others who are visual learners so I would expect that makes the question harder to study. I was hoping some of our psychology friends could chime in! Thanks. | [
"What you found is comparing e-journals to print journals, I think OP wants to know if there's a difference between audio and print"
] | [
"Yep! That’s what I’m looking for and NCBI/Google Scholar searches aren’t coming up with much. "
] | [
"You haven't found anything very compelling because there's not a ton out there that's conclusive! Part of what needs to be considered is HOW we're measuring those differences. In the body of your question, you talk about comprehension and retention - which are two good metrics for understanding individual differen... |
[
"Why would an increase in mean free path mean an increase in thermal conductivity?"
] | [
false
] | If I'm understanding this correctly, mean free path is the distance an energy carrying molecule must go before a collision, which is when the energy is transferred. If the path is longer, wouldn't that mean energy is transferred less often or efficiently, making it a better insulator? | [
"Remember that the units of thermal conductivity are W/m/K. Thermal conductivity measures how quickly heat is allowed to travel across a length of a substance. If energy carriers (electrons and phonons in solids, molecules in fluids) have a large mean free path, that means that they're allowed to travel a long dist... | [
"Here is an approximation-heavy perspective.",
"Suppose quanta of heat jump around the lattice ",
"randomly",
". Thus the distance traveled after a time t is ",
"*sqrt(",
"*",
"), where ",
" is the average jump distance and ",
" is the average jump rate. By analogy (explained on the wikipedia page) ... | [
"means that the energy gets spread around a larger distance in the same amount of time.",
"But why is it the same amount of time? Shouldn't it take longer because it's farther to travel? "
] |
[
"Do electrons \"teleport\"?"
] | [
false
] | I assume the answer is a resounding "no," so other possible titles: "How do electrons pass through nodes", "How do electrons 'move'", Do electrons "move"? I may be exhibiting a supreme ignorance here, as I know it's all a lot more complicated than I begin to understand, but it's my (flawed, I think) understanding that electrons exist, delocalized, in a probability state (definitely wording that wrong). That meaning that at any given time an electron in a certain orbital has a certain percentage chance of being at any of a number of locations in relation to the nucleus. Now, there are some locations, nodes, that the electron cannot possibly be at - ever. In order to "cross" this node, does the electron not have to move in some way other than "through space" as we know it? Finally, it is also my understanding that that probability curve of the location of the electron at any given orbital is asymptotic. Does this mean that at any given time there is a > 0 probability that an electron in a given atom can be a lightyear (or any distance, really) away? I'm working off of two years of high school chemistry, a year of high school physics and a year of college chemistry and a healthy dose of curiosity and personal research. (Also: I know that if they did "teleport" that would not conform with "nothing can travel faster than the speed of light" which is why I'm thinking I'm flawed somewhere in my "logic." I'm hoping someone can show me where I'm flawed rather than just tell me that I'm flawed.) | [
"In order to \"cross\" this node, does the electron not have to move in some way other than \"through space\" as we know it?",
"This is something of an interpretational question. The more common view would be that there's simply no meaning here to the idea that the electron has a definite location. The location-p... | [
"It's not the electron is in some particular place, and we just don't happen to know where. The electron is in the entire orbital, and it is literally meaningless to talk about which ",
" of the orbital it's \"actually\" in. There is a probability distribution, but that just describes the locations the electron c... | [
"I think you are thinking about the electron wave as being like a \"standing wave\". That is a good way to visualize....but there is one fact that you should keep in mind. The \"wave\" is quantized in terms of \"energy\" and not position. So the nodes and anti nodes are in energy and not in positions as such. The s... |
[
"When betting on the result of a flipped coin, is it always probabilistically advantageous to bet on the opposite of the most recent flip, given that in each iterative flip it's less likely that it will continue to be that same result?"
] | [
false
] | null | [
"This is the very ",
" of the gamblers fallacy. "
] | [
"Granted.",
"So let's use a caveat of the Gambler's Fallacy. Let's say that instead of betting on an individual coin flip result, you're betting on a streak. Let's say you're betting that the coin will land on heads ten times in a row. Or twenty times. Or thirty times.",
"At what point does it become statistica... | [
"Betting on a series of events is equivalent to betting on the individual events sequentially. This is because of the independent nature of the trials.",
"You are confusing yourself because you are trying to use the probability of the sequence, in place of the probability of the next flip. Specifically letting ",... |
[
"Is it possible to build a circuit or electronic device in such a way that it wouldn't matter which way you insert the batteries?"
] | [
false
] | I tried googling this answer, but all I got was tutorials for beginner circuitry projects. | [
"Note that this also wastes a significant amount of power, as there's a voltage drop over the diodes. Even if you use ideal diodes (circuits that approximate the behavior of a diode with no voltage drop), it still consumes something.",
"Edit: The term \"ideal diode\" seems to make a lot of people upset. It has tw... | [
"Note that this also wastes a significant amount of power, as there's a voltage drop over the diodes. Even if you use ideal diodes (circuits that approximate the behavior of a diode with no voltage drop), it still consumes something.",
"Edit: The term \"ideal diode\" seems to make a lot of people upset. It has tw... | [
"Yes, a simple filament bulb doesn't care about polarity. ",
"This circuit",
" functions identically if you flip the cell around. ",
"But more complicated electronic circuits (definitely anything that starts to resemble a computer) will almost certainly contain diodes and other components which require curren... |
[
"What happens if you shine a laser while you're at light speed?"
] | [
false
] | null | [
"You can't go at light speed. When you fire a laser it will always appear to go the speed of light in your reference frame, unless you fire it through a medium where it travels slower."
] | [
"Nothing would happen. You would observe the light moving away from you at the speed of light, as per usual. Your velocities wouldn't compound. Space and time will deform in a way that you and the light emitted from your laser will both move at the speed of light."
] | [
"I'm not certain that the electronic components would function the same way once they are made of energy instead of matter."
] |
[
"For years I have sporadically experienced something that I have called \"blink sleep\" for lack of a more technical term. Can anyone tell me how it works?"
] | [
false
] | [deleted] | [
"While I agree that staying only in Stage 1/2 NREM would explain the continuation of thought, I wouldn't describe it as a variation of normal, and I'm not sure it explains the other aspects of OP's experience. That said, I don't have a better explanation, other than noting that people have repeatedly been shown to... | [
"While I agree that staying only in Stage 1/2 NREM would explain the continuation of thought, I wouldn't describe it as a variation of normal, and I'm not sure it explains the other aspects of OP's experience. That said, I don't have a better explanation, other than noting that people have repeatedly been shown to... | [
"It's not very accurate; it goes based on the idea that you're going to move around more depending on your place in the sleep cycle. Actigraphy has been shown to correlate to standard polysomnography, but I'm not sure how well established that is."
] |
[
"Was Tesla really that good?"
] | [
false
] | [deleted] | [
"I am pretty sure that all of Tesla's discoveries would have been found without him, but his personality brought them into existence. He had some great ideas he also had some very strange ones. The use of alternating current vs direct current for electrification of society certainly is his greatest acknowledged con... | [
"I'm pretty sure all of every great scientists discoveries would eventually been found without him. Newton's work? Revolutionary, but would've been figured out shortly afterward. Darwin? Someone else had actually figured out his exact same theory at the same time. Watson and Crick? They just got lucky, Linus Paulin... | [
"Hardly \"all but forgotten\". I still remember the ",
"Tesla coil",
"."
] |
[
"Why do different elements vary in color/properties if they're all made out of electrons, neutrons, and protons?"
] | [
false
] | null | [
"Why don't all buildings look the same if they're built out of bricks and girders? Because there are different ways of arranging them. The same applies to atoms.",
"The vast majority of the properties of atoms (including colour) come from the arrangement of their electrons. Atoms are electrically neutral, so they... | [
"Going along with this, the different amount of electrons and electron shells affect how the atom absorbs and reemits or reflects photons in the visible light spectrum. Simply put, an atom with many electron shells will affect light of a certain wavelength, whereas an atom with less electrons will affect light of a... | [
"So, with materials one way that the properties differ is how the atoms are bonded together. For instance, graphite and diamond are both made solely of carbon atoms. But they ar very different, due to the structure of how the atoms are joined. With graphite the atoms arrange more in a layer structure, meaning they ... |
[
"Can someone please explain why escape velocity is necessary?"
] | [
false
] | So here's my thought: if I have a rocket (let's pretend for the moment it has infinite, weightless energy with which to move) and I take off at say, 100 kph. If I keep a constant velocity what will prevent me from leaving the planet? | [
"If I keep a constant velocity what will prevent me from leaving the planet?",
"Nothing. Escape velocity is the velocity required to leave earth orbit without any further thrust, i.e. it's the velocity you would need to throw a ball with so that it would leave earth orbit (ignoring air resistance). If the ball ha... | [
"Escape velocity is important when, say, traveling to the moon",
"Actually, the Moon is in orbit around the Earth, so in theory you can reach it just with a Hohmann ellipse travelling a bit slower than escape speed. It won't be a lot slower though.",
"Escape velocity is important when travelling out of Earth's ... | [
"Escape velocity is the velocity you have to shoot out of the planet (or some other mass) so that the distance grows and the gravitational pull weakens faster than the gravitational pull slows you down i.e. the speed never turns negative because of that gravitational pull (with smaller speeds you would eventually f... |
[
"If I was in a cave 1000 miles below sea level, would I feel heavier, lighter or the same?"
] | [
false
] | [deleted] | [
"Heavier, but only by a tiny bit.",
"Where you would normally experience ~9.81 m/s",
" acceleration due to gravity on the surface, at 1,000 miles deep, you would experience ~10.0 m/s",
"\nThis is due to the varying density of the Earth. As an example, if you were to be 2,500 miles deep, you would experience t... | [
"Adding to your point, if the earth's density ",
" constant throughout, gravity would strictly decrease as you got closer. This is because \"if [a] body is a spherically symmetric shell (i.e. a hollow ball), no gravitational force is exerted by the shell on any object inside, regardless of the object's location w... | [
"It's called the ",
"Preliminary Reference Earth Model"
] |
[
"What does \"cooking\" dynamite into \"grease\" mean?"
] | [
false
] | Big fan of Prohibition-era non-fiction and in a memoir I read of a safecracker, he talks of the explosives -- aka "grease" -- he would use to open safes: He doesn't mention anything else about it and I've Googled this from every angle I know how. What does he mean by "cooked"? Literally, in an oven or on the stove? What is all even in that "grease"? Is it soupy or solidified? EDIT: I'm now aware of Nobel having made nitroglycerin safer by inventing dynamite so that's cool. | [
"\"shooting\" is blasting slang for detonating. \"A box\" is referring to either the safe or the case of dynamite. \"Grease\" is a reference to nitroglycerin mixed with any number of additives that were used in manufacturing dynamite . Nitroglycerin can be made from saturated fats, so \"grease\" is an apt slang ter... | [
"Nitroglycerin is also very unstable. A bottle of it could explode if dropped or even jostled too hard. Dynamite was helpful because it was fairly stable - it needed a blasting cap to explode."
] | [
"I mean, dynamite is essentially a filler to keep the explosives stable, and the reason is: In 1864, Alfred Nobel filed patents for both the blasting cap and his method of synthesizing nitroglycerin, using sulfuric acid, nitric acid and glycerin. On 3 September 1864, while experimenting with nitroglycerin, Emil an... |
[
"Are explosions additive or multiplicative?"
] | [
false
] | I've always wondered this. Is the explosion caused by 2 sticks of dynamite twice as big as the explosion caused by 1, or does it scale by some factor? As kind of a corollary, if two sticks of dynamite go off in rapid succession (within ms of each other) does that follow the same pattern, or does it act differently? | [
"I don't actually know precisely how they scale, but generally, for dimensional reasons, quantities cannot scale multiplicatively unless they are dimensionless."
] | [
"Not a specialist but I'd say that it's less than additive, the raw energy liberated is twice as much if you take 2 sticks of dynamites. But the energy then spread in 3D, therefore it's only going to be 2",
" more powerfull."
] | [
"An explosion is a rapid increase in volume and release of energy. ",
"Both are ",
" and are additive for independent, noninteracting subsystems.",
"So yes it's additive, this is why you can get TNT equivalent for big explosion like the one cause by a nuclear bomb. ",
"However, note that in the definition ... |
[
"Why is the air drier in the mountains?"
] | [
false
] | null | [
"At higher elevation the vapor pressure is lower, and moisture tends to evaporate quicker. This makes the air seem dryer. In fact, the air at higher elevation will hold less water than at sea level because it is less dense -- it takes less water to reach 100% humidity."
] | [
"Thanks, makes sense!"
] | [
"Its not. Mountains usually create a rainshadow effect. Air encountering the mountains on the windward side drops moisture (the Pacific Northwest in the US and canada is largely temperate rainforest and a good example of this). This air is able to top the mountains and proceeds to the leeward side much much drier (... |
[
"Where do air planes dump their fuel for emergency landings?"
] | [
false
] | In the news this morning, a United Airlines flight from Honolulu to SF had to make an emergency landing because the engine was sparking. The plane had to dump it's fuel, so where do they do it? What's the environmental impact, and couldn't the act of dumping the fuel cause more of a chance for an explosion because the engine is sparking? Source; | [
"No to mention the fuel all spills out into the environment anyway if the plane crashes because it was too heavy. "
] | [
"If you have to dump fuel, and an ocean is available, you do it over the ocean. You don't dump it from the engine; you dump it from the fuel tank, which is nowhere near the engine, so it doesn't matter if the engine is sparking. You dump fuel because you can't land with that much weight, not because you think it mi... | [
"Because the mechanical stresses of landing are different from those of takeoff. Most commercial aircraft are engineered to withstand landing stresses at lower weight limits than takeoff stresses, because that's the way 99.99% of your flights will be flown. It's only the emergency situations that arise at takeoff w... |
[
"Is there a name for the point where gravity shifts from Earth to the Moon?"
] | [
false
] | There must be some threshold between the Earth and the Moon where an object on one side will gravitate toward Earth, but on the other side of the line is affected more by the Moon's gravitational pull. I have done some Googling, but could not find the answer. Does anyone know if there is a term for this point and/or line? Similarly, is there a general name for this type of line between other celestial bodies, such as Mars and the Sun, etc.? | [
"The ",
"Hill sphere",
" is the (approximate) region of space around a body where its gravity dominates that of whatever it orbits. So outside of the moon's Hill sphere, Earth's gravity is dominant, and Earth in turn has a Hill sphere relative to the sun."
] | [
"L1",
"There are five ",
"Lagrange points",
" where an object can orbit the earth and keep the same position relative the the moon. I know that isn't quite what you asked. You were asking just about gravity, while the Lagrange points also consider the centrifugal force due to movement of the moon."
] | [
"This and ",
"Sphere of Influence",
" are the most appropriate answer to OP's question, in my opinion."
] |
[
"Is there a material that conducts heats easily, but is highly electrically insulating?"
] | [
false
] | It seems like electrical conductivity and heat propagation are often related in materials. I have a project that would benefit from a material that wouldn't conduct electricity easily, but would propagate heat easily. It would be a plus if this material were something that could be cast into a mold as well. (Like a ceramic, cement etc.) | [
"Mica",
" is what is typically used when you want to put a heatsink on a transistor with an exposed back. It's a naturally occurring rock that is notable for it's high thermal conductivity and low electrical conductivity. "
] | [
"If you want a good thermal conductor that is a good electrical insulator the formula is based on a strong covalent bond and a relatively close match in size/mass between the anion and cation, or like diamond a single atom.",
"Some great examples of these materials are diamond, beryllium oxide (careful of toxic d... | [
"Diamond is another material that meets the specified criteria. From Wikipedia, \"diamond has the highest hardness and thermal conductivity of any bulk material\" and \"some blue diamonds are natural semiconductors, in contrast to most diamonds, which are excellent electrical insulators\". ",
"Teflon (Polytetra... |
[
"One of the many definitions of Joule is defined as the energy required to increase the temperature of 1 kg of water by one degree centigrade is equal to one Joule. Is this definition independent of pressure of the environment?"
] | [
false
] | null | [
"That is not the definition of the joule. The joule is defined so that 1 J is exactly equal to 1 kg m",
"/s",
". The joule is a composite SI unit defined in terms of the base units kilogram, meter, and second."
] | [
"There is no mention of pressure in what I wrote. "
] | [
"There is no mention of pressure in what I wrote. "
] |
[
"Physically speaking, what is a memory?"
] | [
false
] | What physically happens in the brain when it stores memories? How are they stored? Is it like burning a CD? If someone were to replace a piece of my brain with the same piece of someone else's brain, would I be able to experience that person's memories, or would my brain not be able to process it? | [
"Moser, MB / Trommald, M / Andersen, P, PNAS, Vol. 91, No. 26, Dec 20 1994, page 12673-12675",
"Moser EI, Krobert KA, Moser M-B & Morris RGM (1998), Impaired spatial learning after saturation of long term potentiation. Science, 281: 2038-2042.",
"Whitlock et al., 2006, Science, 313:1093-97.",
"http://www.scie... | [
"There are many different types of memory but the memory people think of is declarative memory. This is processed in the hippocampus and stored there for a short term through LTP. Long-term Potential (LTP) is when a neuron produces a long-lived enhancement in the postsynaptic cells response to a subsequent single-p... | [
"[citation needed]",
"It has been established that LTP is the process through which memory is formed."
] |
[
"How can spacecraft safely enter orbit of other planets?"
] | [
false
] | After reading the question about New Horizons and Pluto, I was curious about aerobraking around planets that have atmospheres. The cheapest way to land on Mars or Venus, I assume, is to use their atmospheres to slow your craft down. But how well do we really understand the physical characteristics of their atmospheres, and how? Can we tell the altitude-density relationship using ground-based optical telescopes? Can aerobraking be done "conservatively", so that e.g. the craft has a 95% chance of entering some orbit, which can be tuned with further aerobraking? Lastly, before we flew close by them, how could we tell the mass of Mercury and Venus, that have no moons? Was it just a guess based on volume? Can magnetic fields (implying iron content) be observed from a distance? | [
"The cheapest way to land on Mars or Venus, I assume, is to use their atmospheres to slow your craft down.",
"Absolutely! But as you imply, it's not quite as simple as it sounds.",
"Firstly, as you're probably aware, there is a critical angle for aerobraking - below which the spacecraft will 'skim' the atmosphe... | [
"Just a small detail to add, which you probably omitted because it is a bit obvious but clarifying does no harm:",
"Aerobraking",
" is the technique of using atmospheric drag to decrease the speed and migrate to lower orbits, possibly through several successive atmospheric \"scraps\". This has already been perf... | [
"I can't answer all your questions but here is a few:",
"But how well do we really understand the physical characteristics of their atmospheres, and how? Can we tell the altitude-density relationship using ground-based optical telescopes?",
"There is several techniques to see what the atmosphere of a planet is ... |
[
"Is it possible to use light to transmit a voice over a fiber cable without using a speaker, microphone, etc?"
] | [
false
] | Using simple objects that I'd probably have lying around or could easily get, is it possible using a battery, etc? I want to be able to speak into one end and have my voice be sent to the other end using light sent down a fiber cable. | [
"So what could be used in lieu of a traditional microphone? "
] | [
"What do you mean no microphone? I've seen audio transmitted via a laser to a speaker. It isn't a \"simple object\" set up though."
] | [
"Well, not a commercial microphone, is what I mean."
] |
[
"Why is there a breathalizer test for alcohol levels but there isnt one for any other drugs? Do other drugs not escape through the lungs like alcohol, and why does alcohol exit the lungs?"
] | [
false
] | null | [
"Breathalyzer tests detect the presence of acetaldehydes that are the result of alcohol being metabolized and are passed easily out through the lungs. Other drugs just don't result in the same sort of molecules. The metabolites of THC are present in urine for weeks and that's what the tests look for. "
] | [
"The answer is obvious: they ",
" arrest people for having detectable THC metabolites in their blood or urine, despite not being presently intoxicated (e.g. they smoked earlier, but are not intoxicated at present). It's a controversial issue in states that have legalized recreational use.",
"Source:",
"http:... | [
"No, that's what an oral swab is for. That can tell if you've smoked recently."
] |
[
"How can we see galaxies that were formed shortly after the big bang if matter cannot travel at the speed of light?"
] | [
false
] | I just read a article about a galaxy that shouldn't exist. And mabey I don't understand the big bang enough but how did we get ahead of the light to see a galaxy that was formed 3 billion years after the big bang? Edit : | [
"because matter can travel away from other matter at speeds close to but still slower than the speed of light.",
"In fact, cosmological expansion can result in recession velocities that ",
" the speed of light.",
"Link the article. What do you mean shouldn't exist?",
"The article is ",
"this one",
". Hu... | [
"Yes. The most remote galaxy we can see is ",
"UDFj-39546284",
". The light we're seeing from it right now was emitted about 460 million years after the big bang.",
"The surface of last scattering was the moment/event where the universe became transparent. For the first 370 thousand or so years, the universe ... | [
"At the surface of last scattering, light was emitted from ",
". It continued to be emitted from any light-emitting source after that. About 3 billion years after last scattering, this galaxy was sufficiently far away that light emitted at that time took about 10.6 billion years to reach us."
] |
[
"How is our sense of touch able to differentiate between things such as wet and dry or hot and cold?"
] | [
false
] | I would highly appreciate an answer that describes the exact interaction between molecule and nerve-ending when for example when a finger touches something wet/dry/hot/cold down to what happens on an atomic scale and describes the way this information goes up my arm to the brain to be interpreted as accurately as possible. | [
"Not really, as there is very little evidence for direct chemoreceptors in the skin, as that would require an exposed neuron that is not capped by the epidermis, or protected by mucus secretions, and thus would be subject to abrasion and dessication from the outside environment. ",
"Also, think about something li... | [
"I don't think it is an atomic interaction that governs differentiation between these characteristics, but a combination of different sensory input and the prior experience to tell the subtle differences.",
"For instance, there are several different types of skin touch sensors. Their differences include the place... | [
"Not really, as there is very little evidence for direct chemoreceptors in the skin, as that would require an exposed neuron that is not capped by the epidermis, or protected by mucus secretions, and thus would be subject to abrasion and dessication from the outside environment. ",
"Also, think about something li... |
[
"An experienced runner and someone who is very out of shape run a mile. Do they burn the same amount of calories?"
] | [
false
] | If we assume their weight and the circumstances of the run are the same, and the experienced runner runs slow enough for the inexperienced one to keep up, so the question comes down to: is there a difference in how efficient calories are used? | [
"Several factors indicate the out of shape runner will burn more calories:",
"Two factors contribute to the fit runner burning more calories:",
"Overall, the first two unfit factor can result in large amounts of extra calories burned, while the other factors are weight dependent or only impact BSM. So the unfi... | [
"I have run a few marathons.",
"\nThe inexperienced runner will burn more energy, because:",
"The inexperienced runner almost certainly has bad running form, which would waste more energy. ",
"The experienced runner has better muscle energy efficiency, the efficiency is defined as output_mechanical_energy/co... | [
"Note that while caloric expenditure correlates with heart rate, it does so negatively with VO2Max, which might strike your first point."
] |
[
"Why do so many chemical compounds manifest as clear, colorless liquids or white powders?"
] | [
false
] | [deleted] | [
"Color is based off the absorption of radiation in the ultraviolet-visible region (200-800ish nm wavelength). Since this is a sliver in the wavelength spectra, not many compounds have the necessary \"chromophores\". The most common are conjugated double bond systems, though metals of certain oxidation states absorb... | [
"it's not even inexplicable - if our eyes had rods and cones that responded to different frequencies of light, we would indeed see things as coloured that we see as colourless now (and vice versa)."
] | [
"They already do. Sometimes you have to add external input like a specific wavelength light. UV light, for example, can assist one in telling different white paints.",
"Some counterfeit goods can be detected via UV because their plastics are of different composition than original plastics.",
"To add to the li... |
[
"What is the commonest cause of death in common laboratory mice?"
] | [
false
] | I'm primarily interested in the commonest cause of death in mice in life-long studies in which mice are left to live out their lives without major interventions. For example, common lab mice, say a C57BL/6 strain, are placed on a normal diet and monitored until they die, what is the most likely cause of death? I think neoplasia may be the most common cause of mortality, but I'm having trouble finding sources clarifying the details. Can anyone help? | [
"Here's a relevant manuscript ",
"http://vet.sagepub.com/content/early/2013/09/06/0300985813501334.full",
" with an excerpt below. Cancer is common in older mice and kills a percentage of them. But other degenerative organ changes can also occur and lead to death such as cardiovascular problems and kidney probl... | [
"This paper discussed mouse deaths at upenn. Most frequent cause cited was spontaneous death of unknown origin.",
"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3838613/"
] | [
"Very helpful, thanks!"
] |
[
"What exactly happens when you fire ceramics?"
] | [
false
] | As in, what happens to the clay particles in high heat that makes them harder and waterproof? Is fired clay chemically different than unfired clay? And if not, is it theoretically possible to un-fire ceramics? | [
"Yes, it is chemically different.",
" Fully fired clay takes the particles, drives off the chemically bonded water, and takes the aluminum and silicates of each particle and binds them into a continuous whole. The finished ceramic is chemically changed from the beginning clay.",
"As such, it is impossible to ... | [
"Not to my understanding. Ground up ceramics are called \"grog\" and used to provide structure in larger ceramic sculpture. It's still ceramics, just ground finely.",
"Purely physical changes, like grinding, aren't going to affect chemical changes. The process described in the link I posted also lists other th... | [
"If I understand correctly what you say, if you theoretically ground up ceramics really thinly and somehow chemically bond water to it, wouldn't it be \"un-fired\"?"
] |
[
"What makes some clouds have a flat underside while the rest of the cloud is puffy?"
] | [
false
] | null | [
"As air rises, warmed up by the ground, the temperature falls by adiabatic effect (fall in pressure) to an average rate of 0.65 C per 100 m of altitude.",
"At 15 C (the average temperature worldwide) a cubic meter of air can contain 14 grams of water. No more.",
"As the rising air cools down, it has less and le... | [
"The base of the cumulus is flat because it is exactly the place where the air reaches the dew point.",
"So the altitude of where the clouds begin is a function of relative humidity. Never thought of it that way. Interesting."
] | [
"In reference to the dew point and the formation of clouds there are also other factors involved such as the amount of cloud condensation nuclei (CCN) which are basically particles like dust. It is actually very difficult for water vapour to \"spontaneously\" change state to liquid water in the atmosphere; a relati... |
[
"Could those advanced scanners that view the \"layers\" in very old paintings be used on certain scratch-off lottery tickets?"
] | [
false
] | I am referring to the scratch tickets that have multiple choices. | [
"I have access to all the tools, XRF, XRD, Auger, TOF-SIMs, FIB, Raman, environmental-SEM, you name it. If anyone here on Reddit can propose an experiment, I will review and maybe carry it out for you."
] | [
"While interesting, this link provides no assistance in answering OP's question. Just a reminder to all that top-level comments should help in the scientific discussion related to answering OP's question. All the best!"
] | [
"I remember back in the late 80's where a few people who worked in a hospital or something in the US were using the x-ray machine to see the correct boxes to scratch. They got caught and scratch tickets went through a technology change to address the problem. I'd search for the original story but I'm such a lazy."
... |
[
"Increasing displacement is velocity. Increasing velocity is acceleration. So what is increasing acceleration? Does it go even further?"
] | [
false
] | null | [
"First, a technical point: velocity is the ",
" of position, and acceleration is the ",
" of velocity. These can act to ",
" as well as ",
" (when you hit the breaks, you're accelerating in the direction opposite your direction of motion).",
"To your question, the rate of change of acceleration is called ... | [
"But, really, there's no standard name for these things.",
"Sure there is! d",
" x/dt",
" "
] | [
"It's called \"jerk\"."
] |
[
"If the Moon is moving away from Earth, will it eventually escape Earth gravity?"
] | [
false
] | null | [
"Warning! Back of the envelope calculations below.",
"Every billion years, the moon will be 1x10",
" * 3.8x10",
" = 38,000 km farther away from us. When the sun turns into a red giant and engulfs the inner solar system, the moon will be 4 x 38000 = 152,000 km farther away. Currently it's 384,400 km out so whe... | [
"No. The Moon is gaining orbital velocity (and as such a higher orbit) at the expense of Earth's rotational energy. Eventually the Earth and Moon will become tidally locked and the orbit will stabilize."
] | [
"The only reason I'm aware of for why the Moon is moving away from Earth is because of the differences between the rotation of the Earth and Moon, which are slowly becoming more and more similar. Eventually the Moon and Earth will become 'synced'. The time it takes for the Earth to rotate once (one day) will equal ... |
[
"If someone was partially submerged in water and otherwise unable to drink, would they absorb the water through their skin?"
] | [
false
] | Assuming it is fresh water. | [
"I remember this was asked more recently, but this is the most recent version I found:\n",
"http://www.reddit.com/r/askscience/comments/k4szf/if_someone_were_sitting_in_a_bathtub_full_of/"
] | [
"There is absolutely no mechanism that I know of to allow this. While there are some vitamins and such that we can absorb through our pores, they absolutely cannot absorb water for the purpose of hydration."
] | [
"A person can be floating in water, and die of thirst, so ... no.",
"People afloat in the ocean, after a boat sinking, often know better than to drink salt water, so there have been recorded cases where a person surrounded by water, immersed in water, can die of thirst, or become very dehydrated."
] |
[
"Why (or how) does gravity bend light?"
] | [
false
] | Light moving near a massive object causes light to bend around the object (or in the case of black holes into it,) my question is since a photon is a massless particle how is it bent? Is it space time curving which causes this and the photon "thinks" it is going in a straight line? Or are any of my assumptions incorrect? Any elaboration on this would be much appreciated. | [
"Is it space time curving which causes this and the photon \"thinks\" it is going in a straight line?",
"I think you have it."
] | [
"Yeah. Objects follow paths called geodesics, and the shape of a geodesic is influenced gravitationally by massive objects."
] | [
"It's actually not too big of a feat to travel 0 distance instantly in a timeframe. I just did it right now."
] |
[
"Do any animals show signs of actual homosexuality?"
] | [
false
] | Ive been told that humans are not the only species with homosexuals but no one has ever shown me proof. | [
"Homosexual behavior in animals wikipedia page."
] | [
"2003 Ig Nobel Prize in Biology",
"Film: (",
"http://www.improbable.com/2009/10/08/minimovie-homosexual-necrophiliac-duck/",
")",
"About the award winner: (",
"http://improbable.com/about/people/KeesMoeliker.html",
")",
"Edit: award winner not author"
] | [
"Maaaaybe. There are some animals that will definitely do things that look homosexual, but it's complicated by the fact that with a purely behavioral observation it's very difficult to tell the difference between a cis-gendered gay duck, a transgendered straight duck, and a duck that for some reason just can't tel... |
[
"How do S-Waves react upon non-newtonian substances?"
] | [
false
] | If shear waves have a difficulty traveling through liquids, and non-Newtonian fluids solidify upon application of pressure, what happens when the two meet? Do the shear waves travel through undisturbed? Does the wave make it some way without failing? Or does it just not cause enough stress for the fluid to solidify in the first place? | [
"Just saying 'non-Newtonian' is really too broad of a term, as there are many different behaviors that fluids can have in response to shear that are not Newtonian. When you say 'non-Newtonian fluids solidify on application of pressure', that actually doesn't really make sense. Whether a fluid is non-Newtonian or ... | [
"Hmm, that's a good question. I would guess the induced shear from an earthquake might cause it to harden to some extent, but I don't think you would see the weird patterns like in the video I linked to earlier. The frequencies in an earthquake are much much longer than what a loudspeaker is producing, and it is ... | [
"Sorry about the incorrect wording in the post. I'm not the best at understanding science. ",
"Is the effect that appears in the video you posted the same effect you would observe from a collection of cornstarch during a 6.0-7.0 magnitude earthquake? Just out of personal curiosity."
] |
[
"What is the difference between an inner monologue and auditory halucinations from disorders like schizophrenia?"
] | [
false
] | null | [
"The major difference between internal dialogue and 'schizophrenic dialogue' is the parts of the brain active when the 'messages' are interpreted. A brain scan showing internal dialogue in a mentally healthy person will depict relatively active areas in the prefrontal cortex, areas associated with logic and reason.... | [
"That seems more like 'intrusive thoughts'. A condition where an otherwise normal person is experiencing thoughts they don't want to. ",
"http://en.wikipedia.org/wiki/Intrusive_thoughts"
] | [
"Wait, so voices that are experienced as being internal but more or less uncontrollable wouldn't be a symptom of schizophrenia?"
] |
[
"At what point do you think that humans will be unable to comprehend their own theories and models about the universe?"
] | [
false
] | As our models of reality become more and more mathematical and complicated, fewer and fewer people are able to understand them. As time goes by, more and more previous knowledge and understanding is needed for us to have access to the limits of human knowledge. Do you think there will be a point at which very few people are capable of pushing the boundaries? Will we design computers capable of using the scientific method and trying countless possibilities, effectively carrying our original research that may be beyond us? Vague, amateurish questions I know, but I would like to know what some of the very smart and thoughtful people here think. Thanks! Added: Do you think that understanding the mathematics behind something (complex numbers, for instance) amounts to understanding the concept itself? I guess we are also limited by language itself. | [
"In my opinion (and I'd say that of almost all mathematicians of physicists) the regrettably-named \"imaginary\" numbers are no more or less imaginary than real ones. In itself, i * i = -1 is not more abstract than 2*4 = 8. Both can be visualized fairly easily and used to represent many ordinary things. It's just t... | [
"I understand what you're saying, kind of. And I'd say we are already there.",
"Look at the wavefunction of a quanton, Psi (x,t) for example. Most of the time, these functions involve complex numbers and mathematical ideas that humans just don't have the ability to comprehend. ",
"Quantum mechanics is already a... | [
"Do you think there will be a point at which very few people are capable of pushing the boundaries?",
"Advances at the edge of physics and technology ",
" a level of creativity and skill that very few people can master. But that is true in any skilled profession. ",
"If you were to talk about composing music ... |
[
"Why are there Valence electrons? Why don't electrons just keep creating new shells around an atom?"
] | [
false
] | null | [
"As you add electrons to an atom, the Pauli exclusion principle forces them to pile into higher and higher shells. All electrons in the outermost shell are called \"valence\" electrons. So I'm not sure I understand the question."
] | [
"I'm asking why there is an outermost shell. Why can't there be another shell formed after the last electron shell is filled? Do the protons stop attracting electrons past where the valence shell is? "
] | [
"A nucleus with Z protons will only be able to grab onto Z electrons (forgetting about negative ions). Wherever the outermost ones lie is the valence shell."
] |
[
"Where can I get cheap/used lab supplies?"
] | [
false
] | So, first of all, I'm not cooking meth or anything illegal. Just curious. I work in a lab, and so often I think to myself how useful some of the glassware and things could be at home. Example: I found a 2L erlenmeyer flask at a goodwill, and I now use it as a goldfish tank. Example 2: I want a grad. cylinder to put a rose in as a table centerpiece when cook dinner for my also-nerd girlfriend. I know what stuff usually comes in contact with labware, and if I were to get anything used you have to assume the worst re: chemical residues, but there are plently of safe uses for those who know how to deal with this stuff. Does anybody know where/how I could get anything like this? | [
"Ebay. You can get any of the glassware you mentioned and more super cheap. Not just common stuff either, I bought a soxhlet setup for almost nothing."
] | [
"Interesting... As I understand it, the soxhlet extractor could be used for example to extract oils from something like plant matter, correct? It looks like an incredibly simple apparatus to accomplish such a useful task. I suppose once you extracted the oils you'd just need a method of separating it from the solve... | [
"Yep, it continuously extracts for as long as you run it. For separation I use isopropyl alcohol which evaporates. I use it to make plant extracts like kava kava as well as marijuana hash oil."
] |
[
"Can single-celled organisms become cancerous?"
] | [
false
] | [deleted] | [
"No, they can't",
". Basically, cell division in a unicellular organism is just reproduction, and they don't have any real internal reason to regulate it (external reasons include things like resource availability). Multicellular organisms, on the other hand, need to regulate just how many of each type of cell th... | [
"Except the human is external to the bicycle; the bicycle didn't break down, the human did. The bicycle is fine and will work fine again when the human starts pedaling again."
] | [
"not even all vertebrates or mammals afaik are susceptible to cancers.",
"All multicellular life is susceptible to cancer, though some have more defenses against it than others.",
"I suppose that single-celled eukaryotes could technically get something akin to 'cancer' if a mitochondrion or a plastid began repr... |
[
"Is it actually possible for a camel to go through the eye of a needle if it goes fast enough, or do I just not understand relativity?"
] | [
false
] | Because of length contraction under special relativity, if we accelerate a camel at a high enough speed, shouldn't we be able to make it go through the eye of a needle (theoretically)? | [
"But is the contraction still real?",
"It's very real.",
"Let's say there's a train longer than a tunnel. If the train goes fast enough, is it possible for all the passengers of the train to be under the shade of the tunnel at the same time?",
"You need to specify reference frames. Let me see if I understand ... | [
"Length contraction happens in the direction of travel only. A high-velocity camel going past you forwards would be observed not to be very long from nose to tail, but just as wide and as tall as the more common nearly-stationary camels."
] | [
"In other words, a 10 meter long train could fit within a 5 meter barn if it was going fast enough, but the barn would still have to be as tall and wide as the train."
] |
[
"When a person feels \"run down\", what systems or internal processes are creating that feeling?"
] | [
false
] | [deleted] | [
"I am far from an expert on this but there is a class of molecules called cytokines that are likely the culprits. These are signaling molecules within the body that serve a variety of functions; however, four in particular (interleukin-1, interleukin-6, tumor necrosis factor-alpha, and interferon-gamma) are respons... | [
"Burning through your neurotransmitters that need good sleep to replenish, micro-tears in muscles, a general lack of down time where the vagus nerve does its thing and you digest food and heal. ",
"Humans evolved for a hunter gatherer lifestyle, that's low stress socialising that can be done while gathering and ... | [
"connection between fatigue and inflammation ",
"I occasionally wonder if my autoimmune disease (Crohn’s) is somehow linked to all the severe mental stress and fatigue I went through in college. It surfaced not long after."
] |
[
"If I tied a bag around my head, how many plants would I need to put in the bag for me to be able to breathe comfortably?"
] | [
false
] | [deleted] | [
"might be better phrased if you were in a sealed room as I think it would have to be a mighty big bag."
] | [
"According to ",
"this TED talk",
", you'll need at least 4 areca palms, 6-8 mother-in-law tongues, and 1 (maybe more? he didn't specify) money plant per person."
] | [
"It did conjure up a pretty funny image, though."
] |
[
"If a fish's gills can extract oxygen from water, why can they not extract oxygen from the air?"
] | [
false
] | null | [
"It's not just about extracting oxygen, but also about releasing carbon dioxide.",
"So, when a fish is out of water, its gills are wet with a film of water that quickly gets saturated with carbon dioxide, and the gas exchange between the water and the air isn't sufficient/fast enough for the fish to survive.",
... | [
"An essential step in the process is the gills excreting ammonia into the seawater. This lowers the pH of the blood. ",
"The decreased pH changes the distribution of electric charges on hemoglobin molecules in the blood. This physically changes the shape of hemoglobin and allows it bind or unbind oxygen",
"A s... | [
"Last time this question was asked the top answer was that they can breath the air just fine but their gills collapse because they don't have the water to help keep them up.",
"So which is it"
] |
[
"Why do the lights dim sometimes when large appliances come on?"
] | [
false
] | I noticed that when the air conditioning comes on in my house, I can see the lights dim a little bit, for maybe half a second. What causes this? All I can find on Google is that the appliances "pull" a lot of current- I remember enough from college physics that this is way too vague for me, but not enough that I can come up with any more satisfying answers myself. Is there some part of the power supply process where the voltage is being reduced because the current is too high? Is this some alternating-current shenanigans I am not familiar with? | [
"Former AC technician here. What you're witnessing is the effect of the motor in the appliance drawing ",
"\"locked rotor\" current",
". As others have already pointed out, when the motor first comes on in your AC unit (actually there are two in the condensing unit outside -- a fan motor and a compressor motor ... | [
"I suspect it is more that many devices draw more current when they are first turned on. Motors coming up to speed would be an example."
] | [
"Well I install tile and I know when we use the drill and wet saw at the same time but staggered you notice a dip in power for both. I think it's the fraction of time it takes for the power in the house to level out from the extra load the circuit received. It can totally handle it, it just takes a bit out of the r... |
[
"What is the optimal amount of degrees to throw something?"
] | [
false
] | null | [
"Is this a homework question?"
] | [
"Nah man im just wondering"
] | [
"Neglecting drag, the best angle is 45 degrees from the horizontal.",
"Including drag, the problem becomes a lot more complicated."
] |
[
"If I was in a completely airtight room by myself, how many trees/plants would I need to never run out of oxygen?"
] | [
false
] | null | [
"This guy, ",
"Kamal Meattle",
" from India, has been studying precisely that for past past couple of decades. They have been using combinations of ",
"areca palm",
"(Dypsis lutescens) for producing oxygen during daylight hours, ",
"snake plant or mother in law's tongue",
"(Sansevieria trifasciata) for ... | [
"Not only that, but if it were actually sealed, you'd have a hard time getting other stuff like nutrients for yourself and your new-found plant buddies. Look no further than the ",
"Biosphere 2 closure experiments",
" for a prime example of our biggest attempts (and failures) at creating a completely sealed-off... | [
"Not only that, but if it were actually sealed, you'd have a hard time getting other stuff like nutrients for yourself and your new-found plant buddies. Look no further than the ",
"Biosphere 2 closure experiments",
" for a prime example of our biggest attempts (and failures) at creating a completely sealed-off... |
[
"A box is heated from the inside to 600 deg. C. If it’s made of aluminium, the inside is starting to melt. If it’s made of lead, the outside is starting to melt. Why the difference?"
] | [
false
] | null | [
"His wording is poor, or at least a bit terse. Pb melts at much lower temperatures (327°C) than Al (660°C), and the outside of the box is always cooler than the inside. 600 C is nearing the melting point of Al, so the inside would be getting gooey but the outside wouldn't get to that temperature very quickly (perha... | [
"My impression is that the reader thought (if my reading of \"Why the difference\" is correct) \"if it's lead, it's melting on the outside\" implicitly means it is not melting on the inside, and thus behaving in a different fashion than the aluminum. A simple enough misunderstanding."
] | [
"Me too, but I blame the writer, not the reader. The wording simply wasn't that explicit. "
] |
[
"Is there such thing as a seismographic camera?"
] | [
false
] | I want to know if there is a camera that can detect seismographic activity in the ground? If so, how does it accommodate for the base, user, or instrument holding it? Is it an algorithm that differentiates between the movement of the base, user, or instrument and the ground? And how does it build this predictive modeling to accommodate for this? | [
"Ok, so if the question is very specifically, \"Is there a type of camera that we can point at the ground that can record details of passing seismic waves in the same way as a seismometer?\" then the answer is no, and we're done (and the follow up questions become irrelevant because the hypothetical device/method d... | [
"InSAR can be (and is) used to measure changes in the ground surface regardless of the cause. In detail, we use InSAR to measure ground deformation related to earthquakes, interseismic strain accumulation between earthquakes, movement of magma within volcanic systems, movement of groundwater, etc. There are limits ... | [
"InSAR is primarily useful for short term changes to surface elevtions, so wouldn't have too many applications in this regard."
] |
[
"How long can footprints stay on the moon?"
] | [
false
] | Since there is no wind on the moon and very little atmosphere, how long can something (such as footprints) remain on the moon? The link below is a footprint on the moon: [ ] | [
"Given the absence of any significant atmosphere to cause traditional weathering, a food print could last dare I say indefinitely.",
"So let's look at what could affect footprints.\nFirst would be lunar dust accumulation acting in the same manner as snow covering footprints here on earth. You would have to ask NA... | [
"Second would be vibrations leveling out the dust. The moons core is inactive so that leaves impacts from asteroids.",
"there is actually seismic activity on the moon independent of asteroid collisions, the most powerful recorded moonquake was 5.5 on the Richter scale."
] | [
"Do you have a reference? I'd like to learn more about how moonquakes are detected & measured, you've piqued my curiosity."
] |
[
"It's my understanding that the vast majority of the energy humans produce ultimately ends up as heat, does that heat have a measurable effect on the planet?"
] | [
false
] | null | [
"A disc with the same radius, provided it is perpendicular to incident sunlight, will absorb the same energy that a sphere does. That's why the oversimplification of treating Earth like a disc was ok for this comparison.",
"The difference is how that energy is distributed. On a disc it will be uniform (in W/m",
... | [
"The world's energy consumption in 2008 was 143,851 TWh",
". This number may have changed today but not much. A simple calculation shows that this is equivalent to less than 1 hour of sunlight on Earth's surface. Our heat is really minuscule.",
"The greenhouse effect is another story. That one's big enough to g... | [
"So around 1/100th of a percent, that's quite a bit less than I thought it would be. Awesome, thanks for the reply. I couldn't find any information on how much solar energy is absorbed by the Earth and its atmosphere in a given time period."
] |
[
"Why is caffeine, a polar molecule, soluble in supercritical carbon dioxide?"
] | [
false
] | I am under the impression that caffeine wouldn't be very soluble in super critical carbon dioxide due to the difference in polarity, yet it a ver popular method for extracting caffeine from coffee beans. Is this something special about supercritical fluids? | [
"Caffeine is actually pretty soluble in a lot of nonpolar solvents - another common method for extracting caffeine is to use dichloromethane, a nonpolar solvent that doesn’t mix with water. I would reason that since caffeine lacks significant hydrogen bonding, it doesn’t interact with itself strongly enough to prev... | [
"Yeah, it’s not something you wanna have in your food and drink. CO2 is nontoxic (relatively) and any leftover would just evaporate away when it’s returned to normal pressure."
] | [
"Supercritical fluids, namely CO2 (the most used SF), are not static solvents with a constant polarity. ",
"If you take Hansen/Hildebrand solubilities, you'll see that organic solvents have solubility parameters that are function of temperature, and that SC-CO2 has a solubility parameter that is a function of pre... |
[
"Why do Tyrosine Kinase Receptors come in pairs?"
] | [
false
] | I'm a Junior in molecular-cellular biology, and I am currently learning about endocrinology. In every diagram I have seen of the receptor and its mechanism (basic diagram ) It shows them, after binding with the desired signal, aggregating before actually phosphorylating proteins, but in none of my books/ lectures I remember explain why it does this. Is there an added benefit to combining/ can it not function as a single unit? Any enlightenment is appreciated. | [
"The intracellular kinase domains of single RTK monomers are not catalytically active. Binding of ligand to the extracellular domains of these monomers causes a conformational change that induces dimerization of two monomers. This dimer then undergoes subsequent autophosphorylation of tyrosine residues in its int... | [
"English translation (not being sarcastic, this is just in case any nonspecialists want to follow this nice answer):",
"The part of the receptor that sticks into the cell normally can't do anything. But when a hormone molecule floats by and binds to the part that sticks outside the cell, this causes the receptor ... | [
"Thank you!"
] |
[
"How did early composers know to put low frequency notes \"under\" other notes on the scale, if they didn't know about frequency and sound waves?"
] | [
false
] | null | [
"I'm going to point out that the choice of frequency rather than period (that is, cycles per second rather than seconds per cycle) is equally arbitrary. That is, 440 Hz could be called 2.27ms, in which case higher numbers represent lower frequencies. "
] | [
"Well, this is essentially a question of etymology.",
"When singing, the resonance space for low pitches (chest) sits below the resonance space for higher notes (oral cavity, sinuses). This may give a physical reason for calling them \"lower\" and \"higher\", respectively.",
"I wonder what the literal meaning o... | [
"But translating energy levels to a direction ",
" completely arbitrary. There's no reason \"higher energy\" has to correspond with \"up\" - when we sort a list, we usually put higher numbers at the bottom.",
"Since everyone so far is already speculating, I'd guess it's as simple as \"your adam's apple moves up... |
[
"Lets say we find aliens, and we somehow speak the same language (or have some sort of translation available)"
] | [
false
] | How could we communicate something as simple as a unit of time to them? If our time system is based upon our distance from the sun, then wouldn't their definition of a "second" or a minute (never mind days and years) be completely different than ours? Does this mean that time is relative to where you originate? IE a person from the planet Omicron Persei 8 could have calculated their second to be equal to 1.5 of our seconds, who's "right"? Is there some sort of standard unit of time that is simply based on something other than the sun? Wikipedia says a second is: the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium 133 atom. Not sure what that means, and an explanation would be cool too. But what I'm really wondering is how we got to that number, 9 billion some odd periods of radiation seems like such an arbitrary figure. Sorry if these questions seem dumb, its just something that hit me out of nowhere that I couldn't think of an answer to | [
"All units are arbitrary. There aren't any special magical units of anything.",
"If you wanted to tell someone how to measure a second, you'd just describe the method for doing so. Same way you'd have to describe the definition of any other unit you might care to imagine. (Except the kilogram. \"It's a lump of me... | [
"Yes but it would be useless as a time unit because it's incomprehensibly short."
] | [
"In SI all scientific units are ",
" based on universally observable experiments. For example the second is defined as ",
"which is something you could describe to an alien over the phone. The other units are similar excluding the kilogram which is currently being worked on.",
"With this it's trivial to agre... |
[
"What drives the movements of tectonic plates?"
] | [
false
] | null | [
"There are three main drivers of plate motion, listed in approximate order of importance/strength they are (1) slab pull, (2) ridge push, and (3) basal traction. Slab pull is the force imparted from the negative buoyancy of the edges of oceanic lithosphere/plates which have started to sink into the mantle at ",
"... | [
"If you don't mind I would like to ask several additional questions. 1. Why doesnt the Cascadia subduction zone create a trench I thought all subduction zones made trenches. 2. Which countries are likely to get hit by M9 earthquakes in the foreseeable future. 3. If california is moving west why isn't is a subductio... | [
"Just wanted to comment as well a cool fact that the Juan de Fuca plate off the north west of america is actually the last remnant of an ancient plate known as the Farallon Plate which has completely subducted underneath the north american plate. ",
"In fact it has been over run so deep by the NA plate that it's ... |
[
"if i used a relatively cheap telescope that can be store bought and if i use it to look at alpha centauri. would i be able to see the star move relative to other stars every 6 months?"
] | [
false
] | null | [
"Not by eye. If you made really precise measurements of the stars' angular position over long periods of time, you may be able to measure the parallax. Alpha Centauri's parallax is like a 4000th of a degree."
] | [
"Apparently Bessel used a 6.2 inch diameter heliometer that looked like ",
"this",
" to measure 61 Cygni's parallax. Pretty impressive."
] | [
"Bessel was able to do it in 1836 but I don't know what kind of telescope he had. Looking through his original letter, it says he used magnitude 11 stars as reference, so maybe that can be used to figure out the size of telescope required."
] |
[
"If I scramble my dogs medicine with eggs, is it possible the heat will alter the compound and make it ineffective or even dangerous?"
] | [
false
] | null | [
"We do not offer any sort of medical, safety, nutritional or really any sort of advice on this sub. Please see the guidelines. If you have a concern, please speak with a physician."
] | [
"im not really asking for advice, but rather if heat of the temperature range provided by a stovetop applied to a compound will/could materially change the compound"
] | [
"The answer to that general question is yes -- that's cooking. We can't answer a specific question about your dog's medicine / advise about safety."
] |
[
"Can cameras be built with extended color range? Are any currently available?"
] | [
false
] | null | [
"https://en.m.wikipedia.org/wiki/Full-spectrum_photography"
] | [
"Yes there are infrared and uv cameras"
] | [
"Misses my point. I don't want an IR camera or a UV camera. I want a camera that converts IR to red and UV to blue, so an 800-300nm spectrum could be converted to traditional RGB colorspace."
] |
[
"Did all trees that have thorns come from a common ancestor or did trees in different regions across the world with thorns all develop them on their own naturally through evolution?"
] | [
false
] | I hope I'm wording this right. | [
"What we commonly call thorns encompasses a lot of different structures with different origins. Proper thorns are derived from side branches, like for example in Gymnosporia species. The thorns on roses, on the other hand, are properly called prickles, they are derived from the epidermis. And then there's spines, w... | [
"This answer is correct, but massively understates things. Thorns, spines, and prickles are different things that evolved differently, but let's take a look at proper thorns. Did proper thorns evolve once, or many times?",
"The ",
"wikipedia page for thorns",
" lists three plants with proper thorns. Let's lo... | [
"Awesome answer. Thank you so much ;)"
] |
[
"How does Quantum Field Theory explain things like Rayleigh Scattering?"
] | [
false
] | null | [
"What level of depth are you looking for in an answer, and what kind of background do you have?"
] | [
"I have a little more than a foundation understanding, I'm aware of bosons and fermions, and the excitation of various quantum fields with which ",
" particles may react while others react to different fields.",
"My understanding is that light hits the atom and subatomics with the atom react to the energy they ... | [
"The coupling between the photon fields and the charged particle fields allows excitations of the fields to exchange energy and momentum with each other. Because momentum is a vector quantity, whenever momentum is exchanged, the particles involved will generally change direction."
] |
[
"Are chemicals produced within the body carcinogenic, and to what degree? Does the body use common Organic carcinogens (for instance formaldehyde) as part of its molecular machinery?"
] | [
false
] | null | [
"The main carcinogenic byproduct of chemical reactions in our body are oxygen free radicals (superoxide, hydrogen peroxide, etc.). Fortunately, we are well equipped to deal with those under normal circumstances. We have enzymes like superoxide dismutase and coenzymes like glutathione to turn those free radicals int... | [
"An excellent answer, and I have only one question to ask as a matter of clarification. I was wondering about the reactions between oxygen free-radicals and DNA. Since the assumptions made during PCR include that DNA is negatively charged due to its sugar-phosphate backbone, it makes sense that a oxygen free-radica... | [
"You are absolutely right about reactions occurring with the bases themselves. The most common examples are pyrimidine dimers (cytosine) associated with free radicals from UV light that lead to melanoma, though there are many others as well. ",
"Wikipedia",
" has a decent summary of pyrimidine dimers, though it... |
[
"Have cancer rates gone up? Or has the technology to detect cancer gotten much more advanced?"
] | [
false
] | I feel like it's most lily a bit of both... Search 'cancer' on wolfram alpha and you will see where I am coming from. | [
"Multiple things here\n1) Yes - detection is much better\n2) People live longer, so other things that killed people - infections, trauma,etc - aren't bringing down the average age of death. So since people are living longer, we are seeing that people are dying of cancer (at a much older age) and at an increased in... | [
"so do you feel the toxins that we are putting into our bodies increase cancer rates. for example there was a company out there (sponsored by ciggaret companies) proving that smoking was not bad for you, and finding the positive sides. Point 2, oldest woman that lived to date smoked 2 cigs a day! Does the sun real... | [
"Cigarette smoke has repeatedly been linked with increased risk of cancer both in human epidemiological studies and animal model experiments. Anecdotes shouldn't be confused with scientific evidence, saying that cigarettes don't cause disease because she didn't die of cancer is like saying all people should live t... |
[
"Aren't we technically still in an ice age?"
] | [
false
] | e.g. over Earth's history, having permanent ice at the poles is an anomaly, not the norm (receding from it's peak where ice reached as far south as Ohio at the height of this ice age). From my understanding, we are technically at the tail end of the last ice/glacial age. Losing ice at the poles is inevitable, is it not? The Earth has had ice free poles over the majority of history that life has existed, true? Am I missing something? | [
"Hopefully this will help with some of the professional jargon. We are currently in an interglacial, as opposed to an ice age or glacial time. The somewhat informal term in the literature for an ice free Earth is a \"Hot House\" period. This is contrasted to periods with stable polar ice referred to as an \"Ice Hou... | [
"The Earths glacial - interglacial periods follow closely to the Milankovitch Cycles which in a general sense act on 26000, 41000 and 100000 cycles which effect the global ocean temperature, global surface temperature and sea level which in turn drive the glacial cycles. These cycles will keep occurring, but the ef... | [
"This is the scary part of the future as we're moving into uncharted territory with anthropogenic ejection of greenhouse gases into the atmosphere. ",
"Bad things may happen sooner rather than later. We have presage to guide us in making recommendations to governments, but as of right now most governments are ign... |
[
"Is there an increase in the average IQ of people born after the worldwide ban of leaded gasoline?"
] | [
false
] | We know lead hinders brain development, and makes us a little bit slower. Some have argued that leaded gasoline was responsible for reducing the iq of generations of people. It has now been a while since leaded gasoline has been banned worldwide. Do we see any non-negligible difference in levels of intelligence in people before and after the lead ban? (I know IQ is an imperfect measure of intelligence it is just one data point. And I use it for a lack of a better metric) | [
"Lead exposure is directly linked to developmental issues and lower IQ:",
"- ",
"https://today.duke.edu/2017/03/lead-exposure-childhood-linked-lower-iq-lower-status",
"We also know for a fact that levels of lead in blood decreased significantly following the phase out:",
"- ",
"https://www.ncbi.nlm.nih.go... | [
"It's not a case of IQ going up so much as fewer children were suffering developmental and cognitive issues. So it's like asking \"are we running faster now that we've stopped putting landmines everywhere and blowing off legs?\"",
"\"children with blood lead levels of 10 micrograms of lead per deciliter of blood ... | [
"IQ relative to previous generations has also increased due to iodized salt (iodine deficiency used to be very common). So there are several factors at play here, not just leaded gasoline."
] |
[
"What is the relation between electrons, photons and electromagnetism?"
] | [
false
] | First of all, English is not my first language and it has been a while since I actually had education in that area of physics so the following is what I udnerstand and is only partially correct. As far as I understood, photons are the particles that "spread" the force in electromagentism, as electromagnetic waves. I also know that electrons have electric charge and moving electrons cause a magnetic field. Does that not mean that electrons are also an "electromagnetic" particle? Following up, does the wave particle simultanity principle hold for electrons as it does for photons? Does that mean electrons are also "electromagnetic waves"? Additionally, why do we call "light" or photons "electromagnetic waves"? Are all photons electromagnetic waves or does it depend on wavelength/energy or the source? Thank you for any corrections and clarifications of my thoughts. | [
"Electrons are particles. We think they are fundamental particles, which means they aren't made up of any smaller particles.",
"Electrons have electric charge, which means that they interact with each other (and with other charged particles) through the electromagnetic field. This is a field that fills up all of ... | [
"A good way to think of these fields, starting from the sort of formal setting and working our way down...",
"A field is a function f(x,y,z,t) that has either a vector or scalar associated with every point. A good example of the former is the wind velocity on Earth, where each point on the globe has a vector repr... | [
"Electrons—and all other particles—exhibit ",
"wave particle duality",
" and can be described as waves as well as particles."
] |
[
"can anyone answer this, has the amount of water on earth been constant from when it was created till now? or has it grew or got less?"
] | [
false
] | null | [
"The prevailing geologic theory is that the vast majority of water on Earth was deposited here by asteroids and ",
"planetecimals",
". From that point, the amount of water on Earth has been relatively constant with only a few losses. Atmosphere, including water vapor, is occasionally vented to space, losing som... | [
"Comets",
" have water in them. Every time one hits the Earth, it adds to the amount of water on the planet. Multiply by billions of years, and a lot of water has been added."
] | [
"I have a question about this theory. Did water not exist on earth while it was solidifying? If, theoretically, no comets or asteroids hit earth whatsoever, would there be no water on earth?",
"Also, how many water containing comets would be needed to have striken earth, so that three quarts of our planet is cove... |
[
"Is a collapsing EM wave function capable of producing only a finite number of photons? If so, is the distribution manipulable?"
] | [
false
] | I read and because I was trying to figure out how an "observer" (e.g. my car radio) of an EM signal might affect the strength of that signal for a nearby "observer." I sort of understand that it's not just photon bullets shooting out at some initial density per square centimeter that dilutes as radius increases. So I started thinking about how or if we could see strange behavior of this wave function collapse due to interaction with a physical object. Let's say that there's a star out in intergalactic space that is not terribly bright/energetic. Its light is interacting with physical objects which are uniformly but sparsely distributed in a sphere around it at an extreme distance but still energetic enough to barely excite the atoms it hits on those objects. There's only empty space between the star and these objects. If we came from outside this distance limit and started placing more objects only on one portion of the spherical limit, would it affect the way the light on the other sides of the star interacted with the other objects? If we moved our artificially-placed objects closer to the star than any of the other objects, would that affect the way the light interacted? Probably meaningless background on what made me think of this: I was driving through a pretty sparsely populated area and noticed that as I approached hills the radio signal I received from the town toward which I was driving would drop off. Obviously the hill was getting in the way and absorbing some of the radio signal. While in the car and before I had looked up much on this to learn about wave function collapse I was thinking about how the "radio photons" were probably randomly energizing bits of rock and dirt and worms in the hill instead of my radio antenna. That got me thinking about if we could "cheat" on "focusing" light from a long way away by using the things we know about how weird photons act during e.g. the . Like setting up a double slit or finding one in space and then placing antennas at the "constructive interference" points to get a boosted signal we wouldn't otherwise be able to sense. And now I'm here thinking about lonely stars. | [
"The thing about \"wave-particle duality\" is that the limit where a quantum objects acts as a particle is very different from the limit where it acts as a wave. I use \"wave-particle duality\" in scare-quotes because the real description is a purely quantum one which does not act exactly like classical particles o... | [
"Are you referring to definite photon states or coherent states? Either way, presumably the best resources are quantum optics textbooks which I'm not really familiar with (though I have an electronic copy of Glauber's). I mostly learned about these states while taking and teaching various quantum courses; quantized... | [
"what you are doing is thinking about light which is very close to the wave-like limit",
"What pops into my head when I read this is a \"massive army charging\" scene from a movie. The horn is sounded, everyone starts charging ",
", and from afar the camera just sees a wave of humanity rushing forward. Then a... |
[
"The sun appears to move faster during sunrise or sunset. Why?"
] | [
false
] | null | [
"It's an optical illusion based on you being able to scale it against objects on the horizon. When it's in the air, you can't judge its movement nearly as well. If you photograph it every few minutes, you'll see it go across the sky at even intervals."
] | [
"You are seeing the projection of the sun’s rays refracted through the layers of atmosphere. It amplifies the visual size so that gives the illusion it is traveling faster. (it also appears bigger when it also appears faster, right?)",
"Someone else can probably explain it better than me. Is there an ",
"/r/Ast... | [
"Im not very familiar with any scientific reason this would happen but throughout the day we see the sun move across the sky over a blue medium. When the sun is setting you can still see the sky ex. but your also able to see the sun progressively getting smaller and smaller as the horizon cuts it off. Sunrises and ... |
[
"Approximately what magnitude earthquake would it require to destroy the Hoover Dam?"
] | [
false
] | In the trailer for the movie San Andreas they show the Hoover Dam collapsing as a result of a super earthquake. Has there ever been an earthquake in history that would have been capable of destroying a structure like the Hoover Dam? What would the absolute minimum magnitude on the Richter scale be for a quake that could cause destruction such as that, assuming it happened as close to the dam as possible? Edit: here's an that kind of covers the premise, but seems to cover the question in terms of what could realistically happen. I guess I'm more wondering what could happen. | [
"Buried ",
"deep within this pdf of a powerpoint presentation",
" on the Hoover Dam are a few statements about the dam design with respect to ground motion from earthquakes. It was designed to withstand horizontal ground acceleration up to 0.1g. ",
"Correlating ",
"peak ground acceleration",
" to a scale ... | [
"Some citations are always helpful for instances where someone \"cannot be true\". ",
"There are several papers documenting ground peak ground acceleration for the Great Alaska quake and they're all significantly lower than what you might expect. A lot of them are unfortunately not easily found online, for exampl... | [
"0.1g is too low. I was about to say that in Greece dams are more robust, but I came across a rather small dam (but with gold mining waste), whose study uses arbitrary PGAs per section, starting with a very reasonable 0.85 and falling until 0.19g, which is too small for a dam on the hanging wall of a normal fault 3... |
[
"How do new stars form out of the dust from older exploded stars that were out of fuel?"
] | [
false
] | null | [
"When these older stars go supernova (or, in the case of less massive stars, just expel their outer bits in a non-explosive kinda way), they enrich the interstellar medium with the metals they produced. Basically there's a lot of gas between stars, and these explosions add to that gas, giving it more heavy elements... | [
"To add to this explanation, if necessary: the interstellar medium is full of hydrogen, and the enrichment by heavy elements is relatively. So the newly formed star has plenty fuel again.",
"Also, slightly off-topic, when astrophysicists say metal, they mean anything heavier than He. So, carbon is a metal to, in... | [
"Astrophysicists are traditionalists :)",
"That explains so much."
] |
[
"Ligo gravitational observatory and nuclear bombs?"
] | [
false
] | Could a nuclear bomb trigger ligo? Would we know what it was? | [
"Yes it would trigger ligo but they back check all their data with siesmologists because nuclear explosions will read on the richter scale like an earthquake. ",
"And fun fact even large trucks can set off ligo which is one reason they constantly check with each other to eliminate the possibility of false positiv... | [
"Even ocean waves hitting the Louisiana coast line more than 100Km away have to be accounted for in their noise calibrations."
] | [
"LIGO detects gravity waves, but it detects them using EXTREMELY sensitive equipment. The detector sends out laser beams and then measures if there is an interference pattern in the lasers. The distances measured are a ",
" of a proton (I believe, talking from memory). There are even signs at the facilities to... |
[
"Would a mirror reflect radiation from a nuclear disaster?"
] | [
false
] | null | [
"Wouldn't that mean that the mirror is not reflecting the radiation then? Since it did not wipe the film."
] | [
"Right on! Thank you! "
] | [
"That's exactly what he said.. but thanks. "
] |
[
"Virtual pair production at the event horizon is often used to explain the mechanism behind Hawking radiation. This is usually accompanied with a disclaimer that it is not representative of the actual math that describes the phenomenon - so what is?"
] | [
false
] | null | [
"You can have a look at Hawking's ",
"original paper",
" to read some of his thoughts on this issue. In particular, he describes the way that one can picture the black hole radiation with a pair of virtual particles coming into existence, and says:",
"It should be emphasized that these pictures of the mechani... | [
"Hawking radiation is not unique to black holes (the more general concept is called ",
"Unruh radiation",
", and is just a result of quantum field theory), and so it is naturally misleading to couch a description of it in terms of black holes. It's really just required for consistency of looking at particle dec... | [
"Its also my understanding that the simple virtual pair explanation cannot be right because it would lose the information stored at the event horizon of the black hole.",
"Moreover there is the issue that we have never actually observed a blackhole dissipate, and so experimentally we cannot say this has happened ... |
[
"How did we make the first generation of precision tools before precision tools existed?"
] | [
false
] | In order to make something precise you need to use tools capable of making stuff with a high degree of precision which themselves need to be precise. So how did we overcome that leap before we had high precision tools to make the first set of tools capable of making things to a high degree of precision? A very simple example is needing a ruler to make a ruler but really it applies to manufacturing equipment and machine tools just as well. | [
"One example of how precision tools work is simple gearing. If you can produce an accurate worm gear to turn a screw to move a cutting tool, then you can count how many turns of the first gear are needed to move the tool one centimetre, and you can then easily apply a scale to the first gear to work out how to move... | [
"It may sound self-evident, but precision tools evolved to support industries that required manufactured parts that had close tolerances and were interchangeable to a degree. One such industry was watch making. ",
"Britain was the early volume leader in the manufacture and export of watches. British watches were... | [
"You don't need a ruler to make a ruler, the first ruler you make is the one that defines the unit. (most modern units are defined by physical properties, though)",
"You don't need high precision manufacturing to create precision tools. Tools and machinery can be calibrated and reach a higher precision than the t... |
[
"Is there a sensible theoretical design for a DIY Ecosphere?"
] | [
false
] | Without having to perform an experiment myself, is there data regarding the correct balance limits for a long term sustainable self-contained ecosystem? Most designs I've heard of begin simply with shrimp of one species or another (cherry or Hawaiian), algae (unknown species), and a certain amount of normal atmosphere. However some sources claim this is really a slowly collapsing system, with the shrimp slowly starving to death over the course of years. Light is the only energy source into the system. If anyone has any data suggesting the best structure and size for such a thing, I'd really love to know. (Side-topic: Would it be better to structure an ecosystem first, or just mix stuff together and let the ecosystem try to balance itself? Is there a tipping point or healthy ecosystem range in which a system naturally balances itself out? Is more species better or worse?) | [
"If I had the spacetime for it, I'd be setting up dozens of little DIY ecospheres and figuring out how to make them work long-term. ",
"Any fully closed ecosystem will slowly collapse, it's just the nature of entropy. The lifespan of one will depend on size and how it's put together (and what you define as \"co... | [
"Why boil the wood?"
] | [
"hey thanks for the positive feedback on my idea. :D",
"if i count them up it looks like i have spent the last ~18 years of my life (since 10) running various aquariums, terrariums, paludariums, etc. ",
"Currently have a beautiful 3 year old Red Slider i got as a hatchling (still had her egg tooth) "
] |
[
"Is Climate Change a Hoax?"
] | [
false
] | null | [
"Thank you for your submission! Unfortunately, your submission has been removed for the following reason(s):",
"/r/AskScience",
"/r/askscience",
"Also consider looking at ",
"our FAQ",
"For more information regarding this and similar issues, please see our ",
"guidelines.",
"If you disagree with this ... | [
"I directed you to do a bit of searching on this sub, but here's a few more resources to check out as well:",
"\n",
"https://www.reddit.com/r/AskScienceDiscussion/comments/2f45iy/so_i_have_two_questionswhen_it_comes_to_global/ck5rzhm",
" ",
"In short, climate change is real and it is most likely driven by ... | [
"Thank you for the information. I'll do more researching "
] |
[
"What is the effect of diet on LDL levels?"
] | [
false
] | So, what I was taught in my Nutrition class some years back, was that dietary cholesterol doesn't really affect LDL levels, but fat intake, especially saturated fat intake, is the main culprit in elevated LDL levels. However, I was reading the faq, and it claims that saturated fat intake does not increase LDL levels. So what's current consensus on the causes of elevated LDLs? | [
"Saturated fatty acids as well as trans fatty acids increase LDL levels by downregulating hepatic LDL receptor activity. The ",
"hepatic LDL receptor",
" is important for regulating the serum levels of ",
"cholesterols by reuptake",
"."
] | [
"In addition to saturated fatty acids, diets high in fructose can promote higher de novo lipogenisis from the liver and promote higher LDL production. This combined with the decreased LDL receptor activity of the liver mentioned above can promote higher circulating LDL if other tissues are unable to compensate for ... | [
"Saturated fats in general DO increases LDL cholesterol, however not all saturated fats increase cholesterol to the same degree. The worst types of saturated fat are the short-chains such as the C12 found in palm and palm kernal oil. These short chains fats are preferentially converted to cholesterol and raise LDL ... |
[
"Is it theoretically possible to create a sound so loud that its waves could be physically dangerous, or even lethal, to a person?"
] | [
false
] | null | [
"Absolutely. I mean, there are always the warnings against listening to music that's too loud because it can damage your ears, but really any shockwave is fundamentally the same as a sound wave. Explosives produce these kinds of shockwaves, but a significant portion of the force is outside of human hearing range.... | [
"Every object has a frequency that it vibrates most powerfully with, called its resonant frequency. It's the reason why standing next to a speaker that plays a sound with no bass hardly makes you vibrate at all, but a sound with heavy bass makes your insides feel like they're churning. The sound with more bass is c... | [
"Great answer! Thanks! "
] |
[
"Do animals get/have mental disorders?"
] | [
false
] | I know some animals can experience PTSD from traumatic events, but things like OCD/Bipolar/Autism etc... | [
"OCD, bipolar disorder and autism are all complex disorders (heterogeneous causes, heterogeneous presentation), but there absolutely are animal models for these as well as other mental disorders. Most of the work is done in genetically modified mice examined within a laboratory setting as a way to better understand... | [
"I study primates, and I know that things like depression (see Harlow's horrifying work from the 1950's) can be induced. Captivity can also cause stereotopies and self injurious behaviour, including things like \"floating limb syndrome\" and reacting to things that aren't there (captivity is truely, truely awful).... | [
"Mostly lab primates (usually macaques) suffer the most (where the goal is to just use them, not provide for them). In studies of self injurious behaviour (things like biting themselves, picking, etc.) it was found that rates didn't go down just because cage size increased (ie they weren't acting out because of la... |
[
"How are the Covid19 vaccines progressing at the moment?"
] | [
false
] | Have any/many failed and been dropped already? If so, was that due to side effects of lack of efficacy? How many are looking promising still? And what are the best estimates as to global public roll out? | [
"They're all progressing steadily - no major failures have been reported yet, but this will take time. Best estimates are initial/topline data by year end, with a potential approval shortly after. Global roll out to public is unlikely till around June or so next year (due to a combination of manufacturing times, ap... | [
"Like I said above, the statement from the CDC is generally not agreed upon by the scientific community including Pharma companies, who stand to lose a lot more (trust, brand value) by rushing a vaccine to market. It's unclear to the reason behind the CDC's communications on this, but from a rigorous scientific p... | [
"Why has the CDC said something about distribution by October or November? Is this just political pressure to get a false statement out? If so, won’t the ramifications be bad when nothing happens in October/November or if a bad vaccine is approved? ",
"Is there any possibility at all that we could get a good vacc... |
[
"How is a drug made ?"
] | [
false
] | null | [
"Hi Averysweetpotato thank you for submitting to ",
"/r/Askscience",
".",
" Please add flair to your post. ",
"Your post will be removed permanently if flair is not added within one hour. You can flair this post by replying to this message with your flair choice. It must be an exact match to one of th... | [
"'Chemistry', 'Biology', 'Engineering'"
] | [
"Thank you for your submission! Unfortunately, your submission has been removed for the following reason(s):",
"/r/AskScienceDiscussion",
"Please see our ",
"guidelines.",
"For more information regarding this and similar issues, please see our ",
"guidelines.",
"If you disagree with this decision, pleas... |
[
"Why do Males have 10% more water content than Females?"
] | [
false
] | [deleted] | [
"It's not about what males have more of, it's that females have a higher fat content than males do. I'm sure someone can give you a more detailed answer, but as far as medical school is concerned, that's as much detail as we were given.",
"Interestingly we didn't learn the body water compartment ratios are differ... | [
"It's the added piss and vinegar. (j/k) But I suppose why would one expect them to be exactly the same. They have different distributions and quantities of different tissues types. Different types of tissues hold water at different concentrations."
] | [
"It's the added piss and vinegar. (j/k) But I suppose why would one expect them to be exactly the same. They have different distributions and quantities of different tissues types. Different types of tissues hold water at different concentrations."
] |
[
"How can we be sure that the laws of physics hold throughout the entire universe?"
] | [
false
] | Let me clarify. I was talking to my dad last night about why x-men are an impossibility, due to conservation of energy etc. and he asked how we can be sure that CoE holds everywhere? Well that sorta got me thinking. I understand that by definition, the laws of physics hold in any inertial frame of reference, but with how friggin enormous the universe is, are we absolutely sure? If so, how do we know we're right? | [
"So there are a couple aspects to this.",
"First, ",
" (I'm capitalizing them so you know they are important) are the way the universe really works. By definition they must hold everywhere and every time, or else they wouldn't be ",
". That doesn't mean everything must behave the same everywhere. For examp... | [
", by definition, are complete and inviolate. That doesn't mean they have to be deterministic, however. There is nothing wrong, in principle, with randomness as in quantum mechanics. That randomness is still constrained by ",
".",
"If some of our \"laws\" fail in certain situations, that is just an indicatio... | [
"Yeah many of the rules, like conservation of energy-momentum hold from Noether's theorem and we would expect to be universally true. But other things, like the strengths of interactions and such are free parameters. The best we can say is that our best measurements have indicated these parameters have had the same... |
[
"I feel the consensus is that poor dental hygiene is extremely conspicuous when dealing with people. Did people, before the advent of good toothpaste, just have to accept that everyone had bad breath, or was it somehow less noticeable?"
] | [
false
] | I do realize there are things that help in similar ways to toothpaste that people might have used, but was that really ever as widespread as toothpaste is now? | [
"I think this goes some way towards an answer: \"Until [Listerine began to be marketed], bad breath was not conventionally considered such a catastrophe.\"",
"http://en.wikipedia.org/wiki/Listerine#History"
] | [
"Before the advent of refined foods, our teeth were significantly healthier than they are now."
] | [
"Thank you! Best answer yet."
] |
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