title list | over_18 list | post_content stringlengths 0 9.37k ⌀ | C1 list | C2 list | C3 list |
|---|---|---|---|---|---|
[
"What is considered the absolute zero speed point of the universe? In other words, what are the speeds of galaxies relative to?"
] | [
false
] | When measuring speed, we always have something relative to it. When driving a car we use the Earth, when measuring the speed of the Earth, we use the sun, and when measuring the speed of our sun or solar system, we use the supermassive black hole in the center of our galaxy. But when measuring galaxy speeds, what do we... | [
"Generally when we talk about something's speed or velocity, we mean relative to Earth. For galactic motions, we can look at them relative to our own galaxy. There is no single \"correct\" reference frame."
] | [
"Yep. You can ",
"see for yourself",
" how fast it's moving relative to us."
] | [
"Current theory attributes most of the speed of galaxies ",
" the expansion of the universe. In modern cosmology, there are 2 framworks for length: comoving length, and proper length. Comoving length is fixed. Every galaxy is always at the same point in comoving coordinates, and the time in comoving coordinates i... |
[
"Is scar tissue more likely to sunburn/ more susceptible to sun damage?"
] | [
false
] | null | [
"Burn surgeon here, and I can answer at least as far as burn scars are concerned…\nGenerally speaking, scars have a multiple phases of formation. To overly simplify there’s an early phase where the scar is forming and then a later phase where it is maturing and ultimately reaching its “final form”. This process can... | [
"Dr. of biomedical engineering here. I'll take a stab at this question.",
"Generally speaking, scar tissue is formed when fibroblasts, which are variant of your white blood cells, invade an area and start to deposit collagen. This is done to close up a wound and prevent further infection. Collagen is a globular p... | [
"Not burn scars but I had a serious case of chicken pox as an adult and have little white scar dots all over my body.",
"When I tan (never been sunburned since), my skin will become darker but the white scars stay very much white and stand out even more. So is any sunburn hidden as such by the scar tissue?"
] |
[
"How do diseases like mumps spread through vaccinated populations?"
] | [
false
] | Let me say up front that I abhor the anti-vaccination movement and this is in no way some anti-vax just-asking-questions nonsense. The National Hockey League is in the midst of a mumps outbreak in which at least 15 players across 5 teams (in Anaheim, Minneapolis, Pittsburgh, Newark and New York City) have contracted th... | [
"Herd immunity doesn't provide any real immunity, it just means you're less likely to bump into an infected person in a region where most people are vaccinated. If you're unlucky enough to bump into an infected individual then herd immunity doesn't provide you any kind of shield.",
"Considering sports players ar... | [
"Vaccinating a population (assuming it's an effective vaccine) doesn't necessarily prevent infection, but limits transmission. So assuming the people who caught the mumps were vaccinated, they likely were exposed to someone who was infected and not vaccinated. The non-vaccinated person will generally have a more se... | [
"In addition to what has already been said, it's important to remember that vaccines are not perfect. They aren't just \"not foolproof\" or \"occasionally fail\"-- most of them have pretty low effectiveness rates compared to what the common belief is. We think of them as \"making us immune,\" but in reality, the ... |
[
"Why can't hashing algorithms be reversed?"
] | [
false
] | For instance, the hexadecimal representation of the SHA256 hash of the title of this post is Why can't I just create a new algorithm that is the "reverse" of the one used to generate that string and input it to get the original post title as the output? I'm assuming it's not as simple as , but that's what I'm basing my... | [
"That's called hash collision and it's a real problem. Collision resistance (the difficulty of constructing multiple inputs that map to the same hashcode) is an important trait for a good hash function.",
"MD5 was a common hash function until ~2005, but was abandoned because it's too easy to create collisions.",... | [
"This is not super relevant in a lot of cases. Being able to find hash collisions (two inputs that produce the same output) should be just as difficult as inverting a hash function if your hash function is secure. The \"hardness\" of inverting a hash function does not come from the fact that it maps an infinite set... | [
"No, they're hashed. At least they should be.",
"You suggested storing encrypted passwords but that's a much greater risk: if the server can decrypt them to check them, then anyone who compromises the server gets all the passwords."
] |
[
"How dangerous is turbulence when flying in a commercial plane? Exactly how bumpy can a flight get before it becomes a problem?"
] | [
false
] | null | [
"Airplane are designed to a maximum g-load (\"load factor\") they have to be capable of handling. For airliners, this load factor is +2.5g",
"source",
" This means that if you were sitting in the plane and it was pulling +2.5g, you would feel 2.5 times as heavy. You've (hopefully) never felt that before, at lea... | [
"Commercial aircraft are designed so that the wings can handle 140% to 155% of the maximum take-off weight. Turbulence doesn't create anywhere near that amount of flexion on the wings, because the aircraft is moving forward either straight or at a very shallow angle. Hypothetically, an aircraft can pass through a l... | [
"How are wings attached to the plane? How are they so strong?"
] |
[
"How is it like to be a scientist?"
] | [
false
] | null | [
"\"scientist\" is a very broad term and how things work can be quite different in different fields and different countries",
"In general, you start by going to university after high school to become educated in the field of your choice. The main transition to doing actual research is typically when you're doing y... | [
"Hi ",
"/u/diogocp27",
" ,",
"A better place for these open-ended questions is our sister sub, ",
"/r/AskScienceDiscussion",
". Have a look. Most of our panelists and mods also hang out and moderate there, so hopefully you'll get quite a few answers.",
"Cheers!"
] | [
"I checked the guidelines and poated this on ",
"r/physics",
", afterwards i got responses to post this on ",
"r/askacademia",
" and ",
"r/sciencediacussion",
" (or something like that, i didny know there wrre so many subreddits like this, thank you."
] |
[
"What happens to atoms that emit Gamma radiation?"
] | [
false
] | I'm learning about radiation right now and I found something to be confusing about Gamma radiation. If the equation of a Gamma radiation emission is 'the isotope -> gamma radiation (represented by Y with 0 mass and atomic number) + the isotope', how is the energy conserved? What about the isotope changes when the Gamma... | [
"Before gamma emission, the nucleus is in an excited state, the protons and neutrons are arranged such that they have higher than normal energy. If this state is semi-stable, it's called a nuclear isomer. When they relax to the ground state, they emit a gamma ray.",
"Nuclei end up in an excited state either by ab... | [
"Yes, there are energy levels for nucleons. ",
"http://en.wikipedia.org/wiki/Nuclear_shell_model",
"A gamma ray is just what we call a photon that comes from nuclear processes, or sometimes just one that is very high energy (there's not clear-cut difference between x-rays and gamma rays)."
] | [
"What about the isotope changes when the Gamma radiation is emitted?",
"The excited state relaxation that ",
"/u/iorgfeflkd",
" mentioned also manifests as a change in the mass of the atom: the atom gets lighter when emitting a gamma ray. ",
"Mass is really a form of energy, so the two are conserved togeth... |
[
"If I cut my hand and foot open, and held them together, would they heal together?"
] | [
false
] | null | [
"Rotationplasty",
" - Cut off leg above knee, remove knee entirely, attach foot backwards.",
"Great toe to thumb transfer",
" - What it says. (Gore)"
] | [
"Wow. Modern medical science is both awe-inspiring and utterly terrifying."
] | [
"That rotationplasty video was astonishing"
] |
[
"Why is Occam's Razor a valuable tool?"
] | [
false
] | What is it about the nature of a simple theory that makes it better than a complex one? The way I'm thinking about it, perhaps if you thought that the creator of the universe were very busy, then maybe he'd have written down the physical laws very quickly and so he would have made them as simple as possible. But otherw... | [
"Occum's Razor",
" is not so much abut selecting the simplest explanation, but the principle that generally when selecting between competing hypothesis you should select the one that ",
", when the hypotheses are equal in other respects.",
"This isn't always the simplest explanation, but rather the one has th... | [
"People tend to forget that what we choose remains a hypothesis and that Occam's Razor makes no statement about the truth of something or proves anything."
] | [
"I like to think about Occam's Razor in the context of formal logic.",
"Background on \"Sequent Calculus\"",
", which is a family of systems, also called ",
" systems, that correspond to natural inference in a pretty intuitive way.",
"The general idea is that you can make a statement (called a ",
") by wr... |
[
"How does a photovoltaic cell replenish its electrons?"
] | [
false
] | null | [
"It doesn't really lose electrons. When light hit the cells it energizes the electrons and they start moving/\"flowing\" in the same direction. As they leave the cell and enter the circuit, electrons leave the circuit and enter the cell from the other end."
] | [
"That's not a terrible metaphor. ",
"Imagine the solar cell as a two level ball-pit with a ball outlet at the top level and an inlet at the bottom. At the beginning, many of the balls are in the bottom level (valence band - electrons bound to atoms). A jackhammer (sunlight) kicks some balls across the vertical di... | [
"picture a bunch of balls at the bottom of a hill, these are the electrons before they get excited by a photon. When they do get hit by a photon, they (the balls) jump up the hill and roll back down to the bottom from whence it came, releasing potential energy then entire way down. photovoltaic cells are just a w... |
[
"What would happend to the rope in orbit?"
] | [
false
] | Imagine we have a rope of significant length, let's say 100 meters. Then we position it in such a way that one end of the rope is 100 meters lower than other in altitude, what would happen to the rope after some time? | [
"The rope will rotate about its center. It's a phenomenon in microgravity where each point of the object is on a slightly different orbit. ",
"Small objects in the space station also \"orbit\" each other over the course of an orbit because of this. "
] | [
"Where can i read up on this? It doesn't quite make sense to me, i assumed it would wobble maybe, or will come at rest at some altutude, but rotate?"
] | [
"It's a bit counterintuitive. \"Rotate\" means at the same rate it translates around the Earth, effectively pointing to Earth at all times.",
"You can read about ",
"Tidal locking",
" and ",
"Gravity-gradient stabilization of artificial satellites",
". Wikipedia gives a nice overview, while ",
"this pdf... |
[
"What impact (if any) will the new higher threshold for overtime pay have on postdocs, lab techs, and other grant funded research positions?"
] | [
false
] | I know certain industries are exempt from overtime pay requirements (transportation sector primarily)... are there statutes in place in the research world? Thanks! | [
"While they are salaried, the salary is frequently less than 50K which would mean that they need to get paid overtime per the new regulations"
] | [
"That's a good point, 2015 year 0 starting salary for postdoc training grant is ~42k (",
"http://grants.nih.gov/grants/guide/notice-files/NOT-OD-15-048.html",
"). There was discussion / recommendation of raising it to a 50k minimum, but that hasn't happened yet. ",
"I wonder if the new rules apply to \"stipen... | [
"I feel like there must be some technicality that will let the universities off and continue to pay postdocs shit but that'd be pretty amazing if you could get overtime. Though I feel like the real effect would be supervisors having the same expectations for the quantity of work that needs to be done and simply sa... |
[
"what’s the difference between rh-null and rh-negative?"
] | [
false
] | i’ve fallen down a rabbit hole of blood types and stuff lately. i know rh-null is extremely rare. around 50 people in the world have it if i’m correct. if rh- neg means it doesn’t contain the rh antigen, then isn’t that just rh-null | [
"When we call someone Rh+ or Rh-, it is a shorthand to indicate whether that person is +ve or -ve for one particular blood group antigen, the Rhesus D antigen. There are more than 300 blood group antigens (I looked it up - 342!), 49 of which are Rh antigens. However, these other antigens aren’t used in the common b... | [
"Someone who is Rh null would be able to donate blood to anyone, but they would only be able to receive blood from another Rh null donor."
] | [
"thanks."
] |
[
"Are there any known human diseases that come from archaea?"
] | [
false
] | [deleted] | [
"I'd check this link out for more info and sources: ",
"https://www.reddit.com/r/askscience/comments/h4ws4/why_arent_archaea_human_pathogens/",
"I think it basically boils down to the environments that archaea typically populate and their comparison to humans, as well as genetics of archaea vs. bacteria, specif... | [
"Sure, ",
"here",
" is a nice review about phages in nature. Phages, or more specifically bacteriophages, are viruses that infect bacteria. They act like regular virus - they use the bacteria to replicate themselves. Eventually they may kill the host cell, releasing themselves into a bacterial colony to continu... | [
"Would you mind expanding on the role that phages have in infection?"
] |
[
"Is it possible for our brains to \"run out of memory\"?"
] | [
false
] | null | [
"I asked this question 11 days ago ",
"here",
"Might have some answers if you don't get any here :) I'm still very curious about it myself."
] | [
"But during our lifetimes, it's unlikely we'll end up \"running out of memory\"."
] | [
"Yes. Whether you mean information a la plank's energy per mass of the brain compared to information in the universe or just how stupid you are to ask such an open ended question with no definition of memory such as this...it is definitely possible."
] |
[
"I've only been able to cry out of one eye for a week now, and that eye constantly waters if I'm laying down. Is there any scientific reasoning behind this?"
] | [
false
] | null | [
"I called my doctor a couple days today concerning some reactions to a different procedure we did on Monday (medial ranch nerve block... Yay needles in my neck), and mentioned the eye watering-ness. Just kinda waiting on a call back.. Or something. My next appointment with that doctor is next week."
] | [
"I called my doctor a couple days today concerning some reactions to a different procedure we did on Monday (medial ranch nerve block... Yay needles in my neck), and mentioned the eye watering-ness. Just kinda waiting on a call back.. Or something. My next appointment with that doctor is next week."
] | [
"I'm sorry, but we don't do medical advice. You should talk to your doctor."
] |
[
"How does Trans-cranial magnetic stimulation(TMS) work?"
] | [
false
] | I read about TMS in a neuroanatomy book and am under the impression that it basically works by the principle of electromagnetic induction and this is exactly what I cannot seem to understand. For an electric potential to be induced there are two requirements- 1) Changing magnetic fields and 2) There should be a conduct... | [
"How this works, I’m not exactly sure, but physics states that the ions in question would be physically affected by the field, so it’s possible that the electromagnetic field affects the quantum vibrations of the ions. This could have a very real effect; the new field of quantum biology attributes olfactory percept... | [
"The electric fields induced by TMS drive currents within the neurons themselves. A ",
" is any movement of charge; in metals we think of currents as electron flows but currents can be carried by ions as well. Currents in the neurons can drive membrane voltages above the depolarization threshold and cause action ... | [
"Everything is a conductor. Some things have low conductivity and are called insulators; others have very high conductivity.",
"Brain tissue is quite conducive because neurons function by transmitting electrical impulses."
] |
[
"Does the speed of light apply only to velocity, or velocity and acceleration?"
] | [
false
] | null | [
"Acceleration does not have the same units as speed, so what do you even mean?"
] | [
"Can an object ever accelerate at 299,792,458 m/s",
" or faster?"
] | [
"Absolutely. A particle in a particle accelerator accelerates much, much faster.",
"The point is 299,792,458 m/s2 has no relation to 299,792,458 m/s. They are not comparable, they have different units. If you change system of units, they will not have the same numerical value.",
"299,792,458 m/s2 is ",
" the ... |
[
"Would two different volumes of water freeze at the same rate?"
] | [
false
] | Say you have two pools of water, one of 1000 L and the other of 10000 L. If both are subjected to a temperature of -10 C, will they freeze at the same rate? | [
"As the quantity of liquid is bigger it will take longer to freeze because more energy will have to be used. There is a state of matter that water has witch is called super cooling this is where the water is at a freezing tempture but ice crystals haven't be formed correctly."
] | [
"Try it yourself! Science is all about exploration and observation!",
"There will be a number of factors that can effect how fast each volume of water will freeze. If everything else is equal, the larger volume should take longer... But why?",
"What kinds of containers are they in? A big flat metal pan might f... | [
"This. Depending on how the volumes are exposed ten thousand liters could freeze much faster than a thousand. Example: 10kL is placed in a massive circular pan with a depth of 1mm if the entire surface is exposed to an isothermic boundary of -10 deg C this will freeze pretty fast, conversely if you put 1kL in a cyl... |
[
"AskScience: I live close enough to a major roadway that I hear quite a bit of noise. As electric cars become more prevalent will the sound get lower or am I mostly hearing road noise?"
] | [
false
] | Just curious if at high speeds do we mostly hear road noise or engine / exhaust noise? | [
"Just off the top of my head, I can tell you that road noise is far more significant than engine noise at highway speeds. I don't have exact numbers but this would be a pretty easy and illuminating experiment that someone could run (get an SPL meter, compare a stationary car revving its engine, to the same car driv... | [
"they will be the last to go electric",
"Or the first to go nuclear! ... Hey, a man can dream, can't he?"
] | [
"they will be the last to go electric",
"Or the first to go nuclear! ... Hey, a man can dream, can't he?"
] |
[
"If you get knocked out, will you have a concussion?"
] | [
false
] | If a boxer gets knocked out, or a person gets knocked unconscious. Does that mean you will have a concussion? | [
"Yes, concussion is defined as \"...a head injury with a temporary loss of brain function,\" which is what exactly happens when someone is knocked out due to strikes to the head. "
] | [
"Being knocked out is one of those conditions that is treated really poorly by films and TV. Its very common to see the hero take a blow to the head, collapse to the floor, and a few hours later to wake with a bit of wooziness and a \"where am I expression\" but no real side effects. In reality, if you are struck h... | [
"By definition any loss of consciousness with preceding trauma = concussion. Concussion does not require LoC (and in fact usually lacks it), but LoC secondary to head trauma does mean concussion."
] |
[
"Does liquid medicine work faster than pills?"
] | [
false
] | There is a new sleep medicine that is liquid and contains Diphenhydramine. Would this work faster than taking the regular pills and how would liquid capsules compare? I appreciate any insight. | [
"I doubt you would be able to really notice a difference. If anything it would only be quicker by a small amount, pills are designed to dissolve quickly where they are needed to. The \"rate limiting step\" of drug absorption is passing the membrane of GI cells (mostly in the small intestine). When you take a pill i... | [
"It all depends on the drug in question, and its solubility in the blood stream. A pill, even though it is a solid may have a higher solubility once in contact with the blood stream. Versus a liquid which might have a comparably less solubility in blood, but is a liquid due to the solvents used in the capsule.",
... | [
"Depends if they are slow release to work longer or if they are 4 hour or similar. I don't think you would notice a difference."
] |
[
"Do bird lungs work the same as human lungs?"
] | [
false
] | null | [
"Bird lungs are very different from mammal lungs, including humans.",
"With mammalian lungs, the lungs are basically two big sacks. Inhaling and exhaling are driven mainly by the diaphragm (with assistance from chest and abdominal muscles), but really it's just the two sacks inflating and deflating. There's compl... | [
"You're welcome! I could add that, because bird-lung air sacs occupy space within the skeleton, they leave identifiable traces on the bones. Traces we have also found in fossil dinosaurs (theropods, like ",
", and sauropods, like ",
" and ",
"). Flow-through, highly-efficient bird-style lungs are probably a b... | [
"Wow, thank you for the awesome response. "
] |
[
"If light is made of alternating electric and magnetic fields, why can neither and electric nor a magnetic field interact with light?"
] | [
false
] | null | [
"Just to extend the first sentence, if it's not obvious why EM fields can only apply a force to charged particles, think of this: can you create a wave in water that can deflect another wave in water?"
] | [
"Just to extend the first sentence, if it's not obvious why EM fields can only apply a force to charged particles, think of this: can you create a wave in water that can deflect another wave in water?"
] | [
"We don't use gamma rays to talk to our mars rovers because radio does it just as fast and much more cheaply.",
"All light, regardless of energy can experience diffraction, reflection or any sort of wave interference. However, with x-rays or gamma rays, we don't have any readily usable materials which can reflect... |
[
"What is the hottest object known to man, and what's the temperature?"
] | [
false
] | null | [
"Inside the LHC, the collision of atoms produces particles with a temperature of 5.5 trillion kelvin, which is what the book of Guinness world records considers to be the highest temperature achieved.",
"However negative temperatures have been obtained (",
"http://www.sciencemag.org/content/339/6115/52",
"), ... | [
"The negative temperature thing is still an active area of debate; there have been a lot of papers since that Science one debating what it actually means, particularly with regards to two competing definitions of temperature (Boltzmann vs Gibbs). This paper was published recently in the American Journal of Physics ... | [
"Inside the LHC, the collision of atoms produces particles with a temperature of 5.5 trillion kelvin",
"how do they measure that?"
] |
[
"What is the difference between linear and non-linear microscopy?"
] | [
false
] | I know that linear microscopy consists of light microscope, confocal microscope, fluorescence microscope etc, and that two-photon is non-linear. The only explanation I can find, without explaining too much about the physics is that non-linear is the combined energy from multiple photons to get an image. Does anyone hav... | [
"In one-photon excitation, the fluorescence intensity has a linear dependence on the excitation intensity (up to saturation). If it takes more than one photon to generate the excited state, the fluorescence intensity scales with the excitation intensity raised to the power of the number of photons needed. So, for t... | [
"Linear: fluorescence microscopy: a single photon excites an electron into an excited state. When that electron decays to the ground state, it emits a photon with slightly less energy (longer wavelength) then the initial photon.",
"Non-linear: two photon microscopy: two photons impinging on electron almost si... | [
"What does linearity actually mean when it comes to wavelengths? Does non linear just mean it uses two photons as energy source instead of one? "
] |
[
"Do Pirahnas and Dolphins Cohabitate?"
] | [
false
] | When I was younger, I remember reading or hearing the statement "if you see dolphins in the water, its safe to swim, since dolphins and pirahnas don't swim together". Is this generally true? I did a little bit of research and and their diet includes pirahnas as well. That obviously means they swim together, but the pir... | [
"Piranhas are a freshwater fish. The most common forms of dolphins are saltwater mammals. So these species don't have a lot of contact. There are, however, river dolphins that inhabit fresh and brackish waters. In fact, river dolphins are listed as a common predator of piranhas."
] | [
"I don't personally know the answer. I did find this quote...",
"\"Piranhas rarely attack people. Many experts believe they are actually timid fish, and shoal for protection. Even the most aggressive are thought to be not really dangerous until they are trapped and confined, and then attack in self defense.\"",
... | [
"Do you know if groups of piranhas actively / aggressively fight back when they're attacked by a river dolphin?"
] |
[
"Does an object lose mass by giving off a smell?"
] | [
false
] | [deleted] | [
"It absolutely does lose mass - take a look at an air freshener at some point, particularly the cone-shaped-jelly ones. They will visibly and measurably lose mass as they evaporate and produce the scent you purchased them for.",
"Most things are not so dramatic - the air freshener will include other ingredients t... | [
"Smell is your body's perception of airborne molecules. So yes, if given substance has a smell, it is losing ",
" mass in order to come into contact with your body.",
"That said, the strength of the smell is not always related to the quantity of particles in the air; because \"smell\" varies person to person AN... | [
"Well, technically, yes, but it would only be such a tiny amount that it would be barely perceptible, even over a long period. Consider it akin to how we shed skin every day, but lose very little mass, overall, from that.\nAs for strong smells, that depends. Some scents are stronger because they react more readily ... |
[
"When do adult teeth develop enough to be seen on an x-ray such as panorex? Do they all appear at the same time?"
] | [
false
] | null | [
"Prenatally."
] | [
"there are precursors in the maxilla and mandible at birth. In time, they will become more radio-opaque as they accrete enamel. "
] | [
"Yea at a relatively young age you can see the whole set of teeth ready to come thru. Pretty neat. If your close with your dentist just ask to show you a pediatric panorex...pretty awesome how the body is."
] |
[
"When humans need DNA for cell replication (adenine thymine etc), do we form it on the spot, or are we supposed to eat something and take the bases from there?"
] | [
false
] | Also if we dont form it, then who does? Do microorganisms do it and then it goes up the food chain? | [
"Normal cell respiration results in carbon dioxide. Every cell that has access to oxygen (which is most of them except in states of exercise or fatigue) can produce it easily. When your body breaks down protein, it needs to remove an amine group through a process called deamination. This produces ammonia, which ... | [
"The liver is the major organ of synthesis of DNA nucleotides. The components are derived from biosynthetic precursors of carbohydrate and amino acid metabolism, and from ammonia and carbon dioxide."
] | [
"Carbon dioxide is made in every cell through normal respiration."
] |
[
"How do some fruits that have been bred to not grow seeds (like mandarines) how do they reproduce?"
] | [
false
] | null | [
"You can find the basic answer with a simple Google search / on wiki. Please start there and come back with a more specific question."
] | [
"I asked here cuz my Google results didn't result in much..."
] | [
"Try \"how do seedless plants reproduce?\""
] |
[
"If two astronauts are traveling half the speed of light away from each other, and looking behind them, what would they each see?"
] | [
false
] | null | [
"So first, let's clarify the situation a little. I'm assuming you mean you are standing \"at rest\" (aka- in your own frame, you are not moving) and two astronauts move away from you at 0.5c as measured in your own frame. Whenever we start dealing with relativity, you have to be careful saying what frame you're dea... | [
"And to run the numbers:",
"Call the \"stationary\" observer in the middle M.",
"Call the person moving to M's left at .5c L (for Left).",
"Call the person moving to M's right at .5c R (for Right).",
"From L's perspective, M is moving to the right at .5c and R is moving to the right at some speed that must ... | [
"In relativity, one of Einstein postulates says that the speed of light is constant in all reference frames. If you use the equation, (x-vt)/sqrt (1-( v",
" / c",
" )), the answer will approach a number close to c, the speed of light, but never will get to c, as this general formula states. "
] |
[
"Will a balloon inflated with air SINK if forced deep enough then released?"
] | [
false
] | going down (being dragged down by a diver say) it will compress into a smaller volume. Will it get to a point where the volume of the inflated balloon will be less than the volume of water displaced thereby making it sink further? I'm already half thinking this will be a density thing not a volume thing, but I'm still ... | [
"For a constant mass of air, density and volume are directly (if inversely) linked. As the pressure of the surrounding water increases, the volume of the balloon decreases and the temperature increases according to the ideal gas law, PV = nRT (mostly, since it's not an ideal gas). If we assume that the mass of the ... | [
"This would happen if you added weight to the balloon. The same effect occurs to scuba divers when they descend; their BCDs compress and instead of neutral buoyant they start sinking, so they have to inflate their BCDs more to remain neutral as they descend. So a diver with a BCD with enough inflation to float on t... | [
"FYI I imagined this with a goon sack not a balloon. don't know why; I'm doing the drowning section of online pre-questions for a first aid training course tomorrow, there's nothing in the notes about goon sacks.."
] |
[
"Biology : Why are apes and primates so much stronger then humans?"
] | [
false
] | [deleted] | [
"The amount of Motor Neurons per muscle spindle! Apes have less motor neurons per muscle fiber than humans, so they activate larger groups of muscle tissue when they flex. This causes them to be stronger but as a result their dexterity suffers. It is helpful to think of their muscle contraction as an all or noth... | [
"Just to make a quick note about your title: humans are both apes and primates, so you would say \"Why are non-human apes/non-human primates...\" :)",
"Anyway, the Smithsonian has a ",
"short and sweet blog post",
" on this. It actually links a study or two as well, if you're interested. Basically it has to d... | [
"Motor neurons are activated by signals from the spine which often originate from the brain. It's your standard action potential that travels down the axon of the neuron right to the muscle. At the end of a motor neuron, there's a \"neuromuscular junction\", or a space where the neuron can act on the muscle directl... |
[
"How do forensic experts go about identifying bodies that have been exposed to the elements for extended periods of time (i.e. the MH17 victims)?"
] | [
false
] | We've all seen characters on shows like CSI and Hannibal be able to quickly and accurately identify decomposed bodies using forensic science, but they rarely go into detail about the process and techniques. I'm wondering what kind of workflow the experts working on identifying the MH17 victims will be using? Dental r... | [
"Dental records are a fantastic way to identify bodies. Teeth survive just about anything and are distinct enough to identify people. Plus, most people (in Europe at least) have dental records sitting in an office somewhere; i doubt that most people have their DNA on file."
] | [
"I regularly read forensics journals, I'll outline the basic process of recovering/identifying remains.",
"Recovery of human remains has basically 3 phases: ",
"locating the remains",
"mapping out remains and the entire area of interest",
"retrieving remains properly, while labelling, and securing transport... | [
"DNA is really only useful when you have a known sample to compare it to, so until the forensic lab obtains either known samples from the subjects or their immediate family, they'll likely investigate other modes of identification.",
"The exact order of tests will depend on the lab, but I think we can look to the... |
[
"If stars are different colors based on how hot they burn (our sun being yellow), why is the light that we get from it white?"
] | [
false
] | If white is a combination of all the visible spectrum of light, and our sun is yellow because of the temperature at which it's burning, why isn't the light more yellowish? Why wouldn't a planet orbiting a blue star have more bluish light? Or would it? | [
"The sun is actually white. The sun ",
" yellow because the sky is blue (it scatters blue light by Raleigh scattering). The peak output of the sun is actually in the green range: ",
"http://solar-center.stanford.edu/SID/activities/GreenSun.html"
] | [
"How does color not being a physical property mean that the Sun is not any color? I mean, this is partly a semantic issue, but the Sun has a color the same way that incandescent lightbulbs have a color."
] | [
"The Sun is not actually any color, because color is not a physical property, it's a way that our eyes and brain interpret electromagnetic radiation. We see \"white\" when ",
"all three color bands (R, G, & B)",
" are receiving significant amounts of light. We see yellow when primarily R & G are being stimulate... |
[
"In Terminator, when they say skynet \"begins learning at a geometric rate,\" what does that mean?"
] | [
false
] | null | [
"A geometric progression, or geometric sequence, is a sequence of numbers where each number is obtained by multiplying the previous number by some constant.",
"For example:\n1, 2, 4, 8, 16, 32, ...\nEvery next number is twice the previous number.",
"But the following is also a geometric sequence:\n1, 0.9, 0.81,... | [
"Rannasha explained quite effectively what a geometric rate is. I'm answering in case you are asking more generally what learning at a geometric rate implies. I'm not too familiar with the Terminator universe so I'll speak in general terms.",
"One way a software system could learn at an increasing rate (using thi... | [
"They could very well have been using it correctly in terminator, because we dont know if they were truly learning ay a geometric or exponential rate.",
"Exponential would assume that the change in happening in the exponent. For example: 3",
" You can see that 3",
" will grow much faster than x",
" or 3x.",... |
[
"Is there a way to separate white sugar and table salt that have been thoroughly mixed together?"
] | [
false
] | null | [
"Yes, but It's hard to do at home. Salt and sugar crystallize out of solution at different temperatures, so if you dissolve the mixture, then hold the solution at the right temperature, one will crystallize out. Draw off the remaining solution, and let it evaporate. You should end with two containers, one with sa... | [
"Thank you :) do you know the temperatures?",
"\n(I'm going to try)"
] | [
"Sugar has a density of 1.59g/cm",
" and salt has a density of 2.17g/cm",
" So if you find a fluid with a density between those that will dissolve neither of them, then you can use that fluid to separate them. I'm not sure anything suitable is readily available for home use."
] |
[
"Could there ever be organisms or any other living beings born with \"organic\" metal parts?"
] | [
false
] | What stops an organism from evolving to have a metal organ? It seems like it would be very helpful for an animal or other type of creature at a lower level of the food chain to have a stronger defense against predators. For example, a rabbit that, instead of fur and skin, has a metal housing on the outside. Or even ... | [
"Some mollusks have magnetite radulas, made out of an iron compound, and some bacteria extrude metals as a byproduct of metabolism...this is what makes bog iron, for instance. I think most organisms don't bother with metal shells because metal is pretty hard to come by compared to carbon and oxygen and materials l... | [
"Thanks for the informative reply! That's really interesting, and you explained it nicely."
] | [
"I've wondered this too, could it be possible to create some form of biological radio?"
] |
[
"If I drop my phone into distilled water will it get damaged?"
] | [
false
] | If distilled water doesn't conduct electricity could it still damage electronics? | [
"What about salts or other possibly conducting materials residing on the electronics? If they were to dissolve, wouldn't that increase the conductivity of the distilled water and cause short circuits?"
] | [
"Depends on a few factors - including permeability and solubility of the electronic components. Metal and plastic do not undergo significant, immediate damage due to exposure to air. Assuming 'perfect' distillation, water acts as a fairly good insulator, but I'm not sure what effect it would have on integrated circ... | [
"Yes, because water can oxidize or otherwise alter and destroy metal connections."
] |
[
"What animal evolution experiments could reasonably be done at home?"
] | [
false
] | Whatever you've got. I was thinking of continually breeding insects and then spraying them with some sort of pest spray to try and create a breed of insects immune to it. | [
"those 3 day lifespan (mayflies?) were used for some experiments.. but why would you want to test things like the toxicity of chemicles on anything?"
] | [
"You can do natural selection on fruit flies pretty easily. ",
"Here's a fun one: Train flies to fly either left or right to get food (always the same direction). After about half the flies have learned which way to go for food, kill all the flies which go the correct direction and breed the rest. Repeat. Afte... | [
"Antibiotic resistance in bacteria and perhaps even environmental selection in bacteriophages."
] |
[
"What defines what the universe is and at the edge of the universe, what is on the other side? An infinite expanse of nothingness or something else?"
] | [
false
] | null | [
"The universe is believed to be infinite. However, even if it is finite, it still won't have an edge but would be a 3d version of the 2d surface of a sphere (i.e. a straight line through space in one direction will end up where it started)."
] | [
"That's insane."
] | [
"Nobody knows for sure, however in Hawking's ",
" he explains how our current theories are that the universe is infinite in distance, yet finite in area, similar to how you can walk forever in a straight line on Earth even though the Earth isn't infinite. The exact shape of the universe is debated a lot, also."
] |
[
"Smallest indivisible unit of time?"
] | [
false
] | [deleted] | [
"No, it's not a smallest indivisible unit of time. Let's just say it's a time scale where physics, as we know it, doesn't work so well. If space-time is discrete (which isn't a part of any mainstream-accepted theory at the moment) and it's discrete in a specific way (of the more accepted proposals, it tends to be d... | [
"That's not actually a property of Planck time. There's a misconception that Planck length and Planck time represent absolute minimum values, but there's nothing in quantum mechanics that says that."
] | [
"Someone who knows more than I will hopefully correct me if I'm wrong, but just based on reading the Wiki:",
"One Planck time is the time it would take a photon travelling at the speed of light to cross a distance equal to one Planck length. Theoretically, this is the smallest time measurement that will ever be p... |
[
"Why does lead absorb radiation so well? Do other materials do the same?"
] | [
false
] | null | [
"Lead is good shielding for high-energy electromagnetic radiation because of its high atomic number. Any solid material with high atomic number will do well. Lead, tungsten, etc."
] | [
"The photons are primarily interacting with the atomic electrons rather than the nucleus (except in the case of pair production). So it’s the size of the ",
" which is relevant rather than the size of the nucleus (the atom is 100000 times larger in diameter)."
] | [
"There are three main processes by which high-energy photons interact with matter (meaning atoms). There’s the photoelectric effect, where the photon interacts with an atomic electron, freeing it from the atom, and being destroyed in the process. Then there’s Compton scattering, where the photon scatters off of an ... |
[
"Why is there no gravitational analog to magnetic fields?"
] | [
false
] | So, an electric charge creates an electric field, a moving charge creates a magnetic field and an accelerating charge creates electromagnetic radiation. A mass creates a gravitational field and it is very likely that an accelerating mass creates gravitational radiation. So where is the gravitational analog to the magne... | [
"There is: See ",
"http://en.wikipedia.org/wiki/Gravitoelectromagnetism",
"It's just incredibly hard to detect"
] | [
"Electricity and magnetism can be linked together with special relativity (explained below), so it would make sense for every force to have a magnetic component.",
"Imagine you are standing next to an electrically neutral wire, carrying current. A large amount of electrons are moving in this wire, but you see sa... | [
"ah ok thanks, so there is a theoretical gravitomagnetic field. I guess I should've explored wikipedia before I asked. But today, someone was trying to tell me that there was some fundamental difference between gravity and E&M that prevented the presence of gravitomagnetic fields. And I was thinking that there is p... |
[
"What specifically causes the bull's eye rash of Lyme's Disease?"
] | [
false
] | I was reading about Lyme Disease and I got curious about a bull's eye rash forms. | [
"It's an inflammatory response (minus neutrophils) in response to the infection at the site of the bite. Tick saliva has immune disrupting compounds that allow the spirochete to develop an initial infection, once these are dissipated, the immune system can attack the infection. This causes the bullseye rash. As I ... | [
"The \"bulls-eye rash\" is called ",
"erythema chronicum migrans",
", which is Latin for \"chronic migrating redness\". Interestingly, the rash begins as just a red spot and then slowly spreads outwards, like a fire in a field, with redness on the outside, and white (or burned grass/ash in my example) on the i... | [
"The CDC thinks that about ",
"70-80%",
" of people infected with lyme disease develop the characteristic rash. It's not very sensitive, but it's extremely specific for lyme disease."
] |
[
"Would it be possible for a snake to eat itself? Or how far could it go before it has to stop?"
] | [
false
] | [deleted] | [
"from a more practical point of view, I would say there are two possible limiting factors: the stomach size/capacity and the minimum radius of curvature achievable by the snake. In the case of stomach size, it will insert its tail until it's no longer able to do so, which is not very interesting. In the other case,... | [
"From a topological point of view, you could get a snake to \"eat itself\" by turning it inside-out, like the sleeve of a reversible jacket. "
] | [
"Video",
"Apparently this behaviour isn't entirely unheard of. It can happen if the snake over heats."
] |
[
"Why are there metals near the surface of Earth?"
] | [
false
] | I apologize if this has been asked before, although my quick search came up with no results. My question is, why are there metals, such as iron, gold and copper to be found near the surface of Earth? Considering, that Earth was fully molten in its history, and all the dense elements fell into Earth's core, why can we f... | [
"We have no idea if Earth was ever fully molten or not. The leading idea is that we had a global magma ocean but how deep it goes (ie does it go to the core mantle boundary or not) is still up for debate. From the more recent results that I've seen it probably did not go to the core mantle boundary in which case me... | [
"Yes. You were right in regards to the molten earth idea, and when these elements combined with the impurities, they rose to the molten surface. After some time, they cooled and solidified to the ore we know today. "
] | [
"Usually, these metals are not found in the conventional \"metal\" state that you think. Rather, the ore (that these metals are smelted from) arises when the molten form of the elements are combined with elements (such as oxygen and sulfur) and are cooled within the outer crust of the planet. "
] |
[
"Do predators have a faster rate of mutation than prey?"
] | [
false
] | Out of curiosity, I wrote a simple DNA simulator to see if there was an optimal rate of genetic mutation in a predator/prey environment. I was not surprised to see that there was, and that the predators evolved a rate of mutation that was close to the prey's. However, I was surprised to see that the hunter's rate of ... | [
"Depending on the environment and the species evolution can move in an almost cyclical manner. This is referred to as the Red Queen Hypothesis (in reference to Alice in Wonderland). Not sure what parameters you're using to write your simulator but if you're not familiar with the Lotka/Volterra equations you shoul... | [
"Thank you. This is helpful because I'm trying to eliminate factors that may contradict my original hypothesis that a species' rate of mutation should be the same as the mutation rate of the environment. My simulation showed that the predator's mutation rate should always be slightly greater than the mutation rat... | [
"Thanks! i'm an old EE/CS dude, so for me the game of life was cathartic! In my experience the chronological order was (CS:the game of life) --> (Psych 201:the selfish gene) --> (pre-Cana) --> (atheism). Thank you Mr. Dawkins, you changed my life for the better! I never got past Chapter 3 of the God Delusion be... |
[
"In hot summer days, why is it that the air in the distance looks blurry or kind of on fire?"
] | [
false
] | null | [
"Short, sort of useless answer: it is caused by vertical turbulent flux of sensible heat.",
"Long answer:",
"Hotter air is less dense (by the ideal gas law)",
"Less dense air = lower index of refraction",
"Different indices of refraction of visible light look different.",
"Now if the air were perfectly un... | [
"Heat in essence is the random average motion of particles. When something is hotter, all that really means is that it's particles are moving around more, bumping with all its neighbours. When air gets hot, say above a grill or fire (most prominently through convection), this random motion becomes apparent by obser... | [
"Thank you!"
] |
[
"How does the size of an atom change as you move through the periodic table?"
] | [
false
] | I know that the mass of an atom is due primarily to the nucleus and the make up of its nucleus determines the atomic number. Since mass and density goes up as we go along the periodic table, I would assume that the overall volume of the atom itself must not increase in a linear way. i.e. an atom with 10 times the mass ... | [
"See ",
"here",
"."
] | [
"The size of an atom has little to do with the mass, rather the principle quantum number, which is why size increases as you follow a column down.",
"We can divide the electrons into two types, core electrons (inner/lower energy electrons) and valence electrons (outermost electrons).",
"The trend from left to r... | [
"Atoms rarely exist in isolation; they're bonded with other atoms, and that tends to change their sizes. For example, Oxygen picks up two extra electrons and this bloats it enormously. Beryllium gives up two electrons, and that shrinks it enormously. Here's a ",
"table that shows both the isolated and the ionized... |
[
"According to an article engineers have created a 1nm transistor, the article said they used molybdenum disulfide because it has \"heavier electrons\" that don't suffer quantum tunnelling, what do they actually mean? Surely electrons are electrons?"
] | [
false
] | Here is the article and the paragraph in particular Berkeley Labs refers to molybdenum disulfide (MoS2), commonly used as an engine lubricant, as its other key material. While electrons travelling through Silicon gates of under 5nm would be "out of control" due to a quantum mechanical phenomenon called tunnelling, the ... | [
"You're right that electrons are electrons, and every electron has the same mass. I think the article is saying mass when it means ",
" mass. When you apply a force to a free electron it accelerates according to a=F/m, where m is just the normal mass of the electron. In a material, the electron is constrained by ... | [
"You might want to fix your formatting, type d^(2)E/dk^(2). The parentheses keep your exponents from getting out of control. And yes I just checked my quantum mechanics notes and that's the relationship. So the dispersion relation of of the electron determines it's effective mass, and the dispersion relation is det... | [
"You might want to fix your formatting, type d^(2)E/dk^(2). The parentheses keep your exponents from getting out of control. And yes I just checked my quantum mechanics notes and that's the relationship. So the dispersion relation of of the electron determines it's effective mass, and the dispersion relation is det... |
[
"Do any other animals besides humans store information externally?"
] | [
false
] | Humans have developed written language. Is this unique? The only example I can think of is territorial animals that "mark" their territories. But I was wondering if there are instances of learned behavior and not instinctual. | [
"Only possible example I can come up is use olfactory cues when marking territory. Not sure if it used as memory aid. ",
"How about this: ",
" ",
"http://www.pnas.org/content/109/43/17490"
] | [
"If i recall ants use pheromones to mark a path the others should follow, and also ants do some interesting things, so i'd have to say check that. Aside from that nothing comes to mind.",
"edit: ",
"Link to wiki"
] | [
" I do recall seeing an article a while back that some monkeys (or other primates) had written something on a leaf using a stick and passed it onto another, which then ate it, but presumably read it first.",
"Would this count? I would think so. I'm not sure if it's the best example, but it at least displays the c... |
[
"How do prions cause illness in cannibalistic humans?"
] | [
false
] | If humans consume other humans' brains, they can get a disease called kuru which leads to death. Prions cause this disease. So please, what are prions, how do they work, and how do they cause this illness? Does the human brain already have prions in it that are not active unless ingested? If you eat a human brain, is i... | [
"Prions are basically proteins that are in a weird conformation. Weird meaning different than their usual/physiological conformation, while the normal protein mostly has α-helices (a usual secondary structure element) the pathological form consists of lots of β-sheets (also a regular secondary structure element). T... | [
"I've always found the meaning of the 'oid' suffix really cool:",
"a suffix meaning “resembling,” “like,” used in the formation of adjectives and nouns (and often implying an incomplete or imperfect resemblance to what is indicated by the preceding element):\nalkaloid; anthropoid; cardioid; cuboid; lithoid; ovoid... | [
"another fact you may or may not find interesting, Kuru seemed to affect the elderly, women, and children far more than men in the affected tribes in Papua New Guinea. This is because men would get the prime cuts (muscle) while the rest would get the less desirable parts like the brains as part of their \"funeral c... |
[
"What controls the increase/decrease of blood flow to different parts of the body?"
] | [
false
] | null | [
"Excellent, thanks for the info."
] | [
"Well arteries contain smooth muscles in their walls, these muscle cells account for artery distensibility meaning that they can contract/dilate. "
] | [
"No problem. If you're really feeling ambitious look up windkessel effect. It is a crude model to account for shape of arterial blood pressure waveform."
] |
[
"My six year old daughter asked after clapping her hands, \"How does the sound come out?\""
] | [
false
] | Can you help me explain it to her? | [
"There's actually ",
"a paper about that",
". The sound is produced by the air escaping from between the palms as they come rapidly together. It's like a little explosion.",
"You'll notice you can clap very softly with your fingers, but the loudest clap is palm to palm. The palms are slightly cupped, and the... | [
"There's an excellent magic school bus episode about how sound is made that I think would explain this really well. Ms. Frizzle takes all the kids to a sound museum, and they illustrate sound waves and how they are generated from everything, and how there are different vibrations and wave lengths to the sounds.",
... | [
"Thanks for answering the question, which wasn't \"how do we hear sound,\" but rather \"how does clapping make that sound.\""
] |
[
"Why do our muscles get sore when we get sick?"
] | [
false
] | null | [
"This is often due to your body ramping up its immune system and inflammatory cytokines and hence your muscle fibers can become inflamed. A good example of this is a viral myositis when you get the flu or another viral infection. "
] | [
"The whole reason pain exists is because it's beneficial to us."
] | [
"Thanks. I have strep and I'm super sore. I appreciate it. "
] |
[
"Is String Theory falsifiable?"
] | [
false
] | String theory has been around for decades now, but I don't know how it suggests any observations that deviate from those suggested by the Standard Model. So my question is: is String Theory falsifiable? If not, isn't just mathematical philosophy and not science? | [
"Not yet. It's not ready. It can take a long time to figure out what a theory implies.",
"However, if you generalize your question and ask \"Can string theory as a technique make predictions about a non-stringy universe\" then the answer is yes: you can use holography to make predictions about heavy ion collision... | [
"Only the specific phenomena. It does not tell us that the universe is stringy, just that those specific predictions are accurate.",
"To make an analogy, we can think of the \"little men\" theory of friction, wherein little men living on surfaces push against any objects trying to move across the surface. This th... | [
"So these 'non-stringy' predictions... would their accuracy give support or not give support to String Theory? Or would they have nothing to say about String Theory as such, only the specific phenomena of heavy ion collision and quantum entaglement?"
] |
[
"Compared to when I exercise, when do I lose fat / build muscle?"
] | [
false
] | [deleted] | [
"Your body will use the most convenient source of energy first. If you recently ate a meal, the sugar and fat from that meal will be in your blood stream and will be preferentially used to supply energy to your body. If you do high energy demand or anaerobic workouts your body will primarily consume glucose since i... | [
"Wouldn't it effectively be the same? You can do an hour of low energy exercise and burn however much fat, or do some higher energy stuff and burn off the calories that you've taken in during the day? Burn off the glucose so it never becomes fat?"
] | [
"Yes, if you are active you can burn the calories you eat rather than store them for use later, so you won't be accumulating fat. But this doesn't translate to burning the fat already stored in your body. ",
"Its two separate concepts. One is using the energy stores already in your body to supply the energy for e... |
[
"If Alex Rodriguez has really been taking anabolic steroids for a decade or more, what will be the long-term effects on his health?"
] | [
false
] | null | [
"\"Anabolic steroids\" is really a blanket term for many different chemical compounds, some with controllable side-effects and some without. If he took high grade steroids, stacked them right, and cycled correctly, which he most likely did considering his income, then probably nothing. He's much past the dangerous ... | [
"This is a pretty spot on description. There seems to be a really big misconception that steroid use automatically = dangerous. I've known a few people who have used steroids; some of them had cycled them for an extended period of time. None of them have had adverse health effects, and quite frankly aside from o... | [
"You could say with a high degree of certainty that his doping certainly didn't give him the side effect of being able to get a goddam hit in October. "
] |
[
"If you have 2 perfectly flat pieces of metal, and you put them together in a vacuum with no air and nothing between the 2 pieces of metal. Could you technically weld them together using no fire, just because there is nothing separating the two pieces."
] | [
false
] | null | [
"This process is called ",
"cold welding",
", and it is used. With this term, you should be able to research to your heart's content. "
] | [
"Yes, you can. You need to make sure they are cleaned of any oxide or other surface layers, however, as those inhibit the welding process."
] | [
"Just to clarify, this ",
" performed in certain situations today. "
] |
[
"Does hair actually absorb vitamins, proteins... from shampoo?"
] | [
false
] | [deleted] | [
"Most of the claims in the UK are positioned as \"makes your hair ",
" healthier\"",
"Then in teeny tiny font at the bottom briefly you'll see \"67 out of 100 people agreed with this statement\"",
"Their claims are almost always based on majority statement to fixed questioning."
] | [
"Your basic idea is right. There's a few chemicals that can help keep the individual hair scales all smoothly aligned but the hair itself can't be 'nourished'. As for vitamins the best answer is to eat a diet that provides the vitamins you need rather than relying on supplements."
] | [
"Just came to add that when taking vitamins (like a pill or other oral supplements) be careful how much of what you are taking. Some vitamins are water soluble, meaning if you take more than your body needs you will just pee out the extra. For example, too much B vitamin turns your pee a fluorescent yellow color. B... |
[
"Are there organic compounds on other planets?"
] | [
false
] | [deleted] | [
"Yes, absolutely! Anything carbon based in the universe, such as methane (which is contained in many extraterrestrial atmospheres), is considered organic."
] | [
"Organic compounds in the chemistry sense of the word (hydrocarbons and so forth) absolutely exist all over the universe. There are organic compound containing asteroids flying around out there, there are methane atmospheres, et cetera.",
"If you mean organic compounds as in compounds of life, we'll need to get a... | [
"Oceans of Hydrocarbons on Titan."
] |
[
"Does Adinovirus-36 significantly contribute to human obesity?"
] | [
false
] | I recently heard that Adenovirus-36 might be implicated in at least some part of the modern obesity epidemic. Looking into it, the claim seems to be that The DNA (genetic material) of the virus gets into the fat cells of the person or animal and causes them to bring in more fat and glucose from the blood and to make fa... | [
"I have no desire to feel morally superior to fat people, some would call me fat. \nI was just trying to point out, that to me it seems like many fat people try to shift the responsibility for their condition, so that in the end they are powerless to do anything about their weight (and yes i realise there are certa... | [
"I would argue that the \"obesity epidemic\" is more about life-style and dietary choices and less about a nasty virus making mankind fat."
] | [
"So is this something we should be vaccinating kids against routinely, especially considering the ongoing obesity epidemic?"
] |
[
"Why does water, when kept in a fridge or freezer, have a funny taste to it?"
] | [
false
] | I notice this a lot with ice. When you take tap water, and freeze it, or put a jug of it in the fridge, it comes out with the slightest funny taste to it. I also notice that some bottled water has the same funny taste to it. | [
"Some molecules in the fridge dissolve into the water. When it freezes over, some molecules also physisorb onto the ice."
] | [
"The former. It has to do with the more volatile components of whatever is in the freezer.",
"You can try this experiment. Put something fragrant in the freezer beside an ice cube tray with water. Perhaps freshly chopped onions, say. Once everything freezes over, the ice cubes will pick up a very small amount of ... | [
"Thanks for that :) I think it's time to do some science!"
] |
[
"How can same volume engines have different HP/torque/etc.?"
] | [
false
] | null | [
"The displacement of an engine is not the only factor contributing to work done by the engine. The compression ratio for one will change the power output (the more you squeeze the air and fuel the more power you get out). Intake and exhaust manifolds will affect how effectively air can enter and exit the combusti... | [
"The list goes on. Heads can have different flow rates and differences in camshafts, valve size and design, as well as rocker arm design change the flow characteristics into the combustion chamber. There are a variety of combustion chamber designs that will affect the combustion event and consequently horsepower.... | [
"Engine displacement is a measure of the volume swept by its pistons.",
"Now, what creates work in an engine is the expansion of combusting gases against the piston. So naturally, given ",
" pressure, you can combust a larger volume of fuel/air in an engine with a larger displacement, allowing that engine to pe... |
[
"After going through a modern embalming, how long does it take a body to decompose once buried?"
] | [
false
] | I've always wondered what our bodies look like a week/month/year after being buried... Any thoughts? | [
"As a funeral director, this would depend on the condition of the body prior to embalming. Obesity, trauma, advanced decomp and other factors influence the efficacy of the formaldehyde. Also, the strength of the embalming fluid (mixed by the embalmer) will determine how long a body holds up. In summary, it depends.... | [
"Your cells die, but after you come back to life your body will slowly try to heal itself unless there is brain damage. Then it will try but fail."
] | [
"Your cells die, but after you come back to life your body will slowly try to heal itself unless there is brain damage. Then it will try but fail."
] |
[
"Is the QM two slit experiment done in a vacuum? Why or why not? Does it matter?"
] | [
false
] | Wondering if ambient molecules in air impacts outcomes. | [
"The double slit experiment with light doesn’t need to be done in vacuum, but with electrons it does."
] | [
"The double slit experiment is not exclusively a thought experiment. It did very much happen and the result is exactly what was so earth shattering."
] | [
"The double slit experiment is not exclusively a thought experiment. It did very much happen and the result is exactly what was so earth shattering."
] |
[
"Having read a couple academic papers from a fellow redditor, plus some Wikipedia etc...it is still hard to get an idea of risks posed by dental amalgams and mercury. What sayeth r/askscience?"
] | [
false
] | null | [
"My own meta-analysis found that most studies show no statistically significant risks from dental amalgams and a few dissenting papers questioning common methods. In short, there is no convincing evidence that dental amalgams have negative effects, but there is a possibility that future studies will refute this. It... | [
"depends on what you consider a problem. if anything short of 'death' is no big deal, then yeah. if losing your short-term memory is no big deal, likewise. ",
"the part about autopsies being done on cadavers with and without amalgams, and those with amalgams having higher levels of mercury in the brain, seemed in... | [
"no it's not, when it cites research papers itself. the quality of an article depends on sources, not merely whether it is on a certain url or not."
] |
[
"What are the stringy bits on egg yolks?"
] | [
false
] | [deleted] | [
"those are chalazas (see: ",
"http://en.wikipedia.org/wiki/Chalaza",
")\nBasically, they keep the yolk in place."
] | [
"I could be wrong but if i recall correctly from my hospitality class, it starts at the bottom of the egg, connecting from the shell to the yolk, then from the yolk to the top of the egg, holding the yolk in the middle. "
] | [
"thank you"
] |
[
"The human heart is asymmetrical, which is why it is felt more easily on the left side of the chest (fairly consistently in humans). During fetal development, what signals do the individual cells use to \"know\" which side is left vs. right while differentiating to make the organ?"
] | [
false
] | I've been thinking about this topic, and it makes sense how cells can "know" (please excuse the terminology) up from down, as there is gravity. However, in making asymmetrical organs such as the heart, how do the cells distinguish left from right before differentiating to develop the organ? | [
"Through signalling molecules. Roughly speaking, all cells have the potential to be the \"anchor\" cell by producing signalling molecules. Once one random cell started producing a signalling molecule, all the other cells \"understand\" that someone has taken the initiative, and won't \"volunteer\" themselves into a... | [
"That's an interesting reply thanks. But, it still leaves the questions of why the vast majority of people are oriented the same way left/right.",
"I know some people have their insides left/right flipped. Given your explanation, I'd expect it to be an even 50/50 of people with the heart on their left vs people w... | [
"What happens if multiple cells choose to become anchor cells before detecting another?"
] |
[
"why do we go red when we are embarrassed?"
] | [
false
] | [deleted] | [
"Capillaries in your face dilate, bringing blood close to the surface of your skin and giving it a reddish tint.",
"It probably evolved as a social signal, people see that you are embarrassed and then try to help you. "
] | [
"To expand upon your original answer, in 2009 Dutch psychologists Corine Dijk, Peter de Jong and Madelon Peters conducted an experiment showing that there were socially beneficial properties to blushing. Their hypothesis as to its use is the same as yours above, namely that:",
"Publicly conveying embarrassment or... | [
"Citation? I'd like to see this study."
] |
[
"Why did we go from a Delta variant of COVID straight to Lambda? What happened to Epsilon, Zeta, Eta, Theta, Iota, and Kappa?"
] | [
false
] | According to there is now a lambda variant of COVID that is impacting people mostly in South America. This of course is coming right in the middle of the Delta variant outbreak in the United States and other places. In the greek alphabet, Delta is the 4th letter and Lambda is the 11th. So what happened to all the lette... | [
"They didn't skip them. There are variants that use the other greek letters. Lambda is just a variant making a larger impact. You won't hear about all the variants unless they were influencing more public action."
] | [
"Yep, all the other variants are out there, they just aren't on the news. \nThere's a site which is collecting and providing genetic information for all of it here-\n",
"https://nextstrain.org/ncov/gisaid/global"
] | [
"Correct. ",
"Because mutations are random, and not all of them result in something worse."
] |
[
"Do animals respond to harmonies and dissance the same way humans do?"
] | [
false
] | I sing in a choir and it is pretty easy to tell when someone isn't singing the right notes by the dissance created around them. I was wondering if animals interact in the same way. | [
"There is a short and long answer.\nThe short answer is maybe.",
"The long answer explains why:",
"First off, lets get one thing straight, if I think you're talking about what you're talking about, you mean \"dissonance\" instead of \"dissance\". ",
"Now, lets explain why dissonance has such an unpleasant or ... | [
"When ever I record music and my dog is in the room he ignores us until we start to harmonize, then he howls. He can only hit 2 or three notes but he tries. "
] | [
"Dissonance"
] |
[
"Why does \"Alternating Current\" have a live and neutral wire and why are they not the same?"
] | [
false
] | null | [
"Voltage measures difference in electric potential. This will help you a lot: ",
". Lets call the points ",
".",
"When we say this circuit is 230V AC, its 230V AC ",
".",
"Now we need 2 wires to close a circuit from our source to the load, in simpler words: ",
" from the 2 poles of our source to the 2 p... | [
"Think of a person holding the end of a piece of rope, shaking it around and creating waves on the rope. If you are just looking at the rope, you can't necessarily tell which direction the waves are coming from. But there is still one end of the rope where the force is being applied, and one end where it's just dis... | [
"Your house has a transformer",
"The transformers that derive 120V/240V supplies for houses are owned by the power utility and are mounted either on utility poles or on concrete pads near the street. One transformer will serve several houses.",
"In-building transformers are typically only found in apartment bui... |
[
"How does the immune system defend from airborne infections?"
] | [
false
] | If I understand things correctly: COVID-19 attaches to ACE2 receptors available in your airway. So it doesn't need to go through your bloodstream at any point to cause an infection, then once it infects a cell, it releases a protein that suppresses that cell's ability to release cytokines, which is responsible for sign... | [
"When you first get exposed to a virus, your body has little defense. It isnt geared up to produce antibodies, so the virus rapidly reproduces and brings the viral load up, which basically general to any body tissue. ",
"The body then produces antibodies versus that virus, and when it detects and active infecti... | [
"Yes but it’s less likely. A respiratory infection is looking for a moist area with a thin and active membrane. This happens in your lungs where gas exchange takes place. It’s also why respiratory infections can’t go through your outer skin. The lungs also have macrophages secreted into the fluid lining since it’s ... | [
"Mucous will entrap viral particles where they can be destroyed by the digestive system. One type of antibody, called IgA, is specialized to fight pathogens on mucosal surfaces. This antibody has receptors to transit through your epithelial cells into your mucous spaces. Additionally, some blood plasma is filtered ... |
[
"Can someone tell me what I was looking at last night?"
] | [
false
] | Hey guys, I hope this question is ok. Last night around 8:15 PM I was outside and at about 298 deg NW (according to my Iphone compass) and about 15 deg above the horizon (my best guess), there was an extremely bright "star" in the sky. Was this a planet? Also, I live just NE of Atlanta, Ga. I tried to google for any in... | [
"The \"brightest star\" in the Northern sky right now is ",
"Venus.",
"I will double check the positioning in Stellarium for you.",
"EDIT: Jupiter was just setting at that time. You likely saw Venus right above it.",
"http://i.imgur.com/1XocWwl.png",
"The horizion goes along the direction label axis."
] | [
"Nope, it was Venus. Jupiter is rapidly setting behind the Sun, while Venus is rising from behind the Sun higher into the sunset sky each night. Venus is currently higher than Jupiter right now as of the conjunction last week, and is always about 5 times brighter than Jupiter."
] | [
"http://spotthestation.nasa.gov/",
"Enjoy :)"
] |
[
"What happens when you test the intermediate axis theorem in 4 dimensions? Can it even happen, since there are two, or do they both rotate?"
] | [
false
] | null | [
"Rotation in 4 dimensions is not characterized by an angle and a single axis. That is, there is no such thing in 4 dimensions as \"rotation about a given axis\". So this is mostly a meaningless question. Additionally, the intermediate axis theorem is a consequence of the Euler equations for a rigid body, which very... | [
"there's plenty of this i don;t understand, but thanks anyway :)"
] | [
"Well, rotations in higher dimensions required advanced math to understand. In two dimensions, things are as simple as they get. There is really only 1 type of rotation, and that's it. In three dimensions, we can just talk about rotations about each of the three principal axes, and that's it. Very simple both to un... |
[
"Does high-end hardware cost significantly more to make?"
] | [
false
] | I work with HPCs which use CPUs with core counts significantly higher than consumer hardware. One of these systems uses AMD Zen2 7742s with 64 cores per CPU, which apparently has a recommended price of over $10k. On a per-core basis, this is substantially more than consumer CPUs, even high-end consumer CPUs. My questio... | [
"Of course, some factories use expensive processes, some use cheap processes, and thus their CPUs will be more expensive or cheaper to make in general. But not within the same Factory (Fab line). It costs exactly the same to make the different CPU models there. The issue is yield. Just like diamond mining. An exens... | [
"The way I tell people is you're not paying for the one you get you're paying for it ",
" the ones they had to make to get that one",
"With high end chips with large core counts the likelihood of having errors increases exponentially. Taking your 500 8core chips,that's 2000 cores if you use 64 core you'd be at ... | [
"Most of the cost of server chips is markup for the datacenter/HPC market. Compare the price of your EPYC 7742 to an Intel system with a comparable core count and see why AMD doesn't feel pressured to charge any less. Like all businesses, AMD charges what the market will bear.",
"AMD Zen in particular is configur... |
[
"Is there a general function to find the shortest distance from a point to some arbitrary function, f(x)?"
] | [
false
] | [deleted] | [
"The euclidian distance between point (x,y) and (x',f(x')) is sqrt( (x'-x)",
" + (f(x') - y)",
" ). Take the derivative of this function with respect to x' and look for zeroes to find a minimum."
] | [
"Use a ",
"Lagrange multiplier",
" to find the minimum of the function D(x,y)=(x- x_0)",
" + (y-y_0)",
" (a justifiable simplification of sqrt((x- x_0)",
" + (y-y_0)",
" ) ) subject to the constraint f(x)-y=0."
] | [
"UncleMeat's answer is the simplest: the distance",
" from (x_0, y_0) to a point (x, f(x)) is given by",
"(f(x) - y_0)",
" + (x - x_0)",
"You want to set the derivative of this to zero (which is reasonable cases should give you a minimum, rather than maximum, of the distance), which yields",
"df/dx (f(x) ... |
[
"What plant dominated the grasslands and steppes BEFORE modern grasses (Poaceae) evolved?"
] | [
false
] | That is, in climates dominated by grasses today, what plants would have dominated these regions before angiosperms began taking over ~60 million years ago? | [
"Lycopods. Oldest extant vascular plant division, first spotted ~410 mya. May not have \"dominated\" exactly at the specified time - wiki says during the carboniferous era (360-300 mya). Still cool. ",
"http://en.wikipedia.org/wiki/Lycopodiophyta",
"There are still a few around today, but most have gone extinct... | [
"What he likely refers to is what's known as the ",
"irst ",
"ppearance ",
"atum, aka ",
"FAD",
".",
"\nThe FAD is simply the oldest known point in time that a fossil has been seen. When you know the age of a rock, such as a mudstone, you can infer the age of the fossils found inside it. That rock is 39... | [
"During the Jurassic period Ferns were incredibly common.",
"I'm not very well educated in this subject, but when I was a younger teen I was obsessed with Sauropods.",
"Ferns were common in the Jurassic and food favorite of Diplodocus. They had peg shaped teeth that were well adapted to stripping ferns of their... |
[
"Why do we use CMYK (Cyan, Magenta, Yellow, Black) for printing rather than primary Blue, Red, Yellow?"
] | [
false
] | Also, why RGB for screens, instead of RYB? | [
"CMYK is purely a printing scheme, which is why we are using yellow and not green.",
"Light is additive, if you have 100% red, green, and blue you get white, this is what most people are familiar with. In this way the three color pixels in your screen can generate pretty much any color. There are some that have... | [
"The RYB primary color scheme everyone learns back in school is outdated and there are a few colors you can't form by using it. We really shouldn't be teaching it anymore.",
"The primary benefit of CMY is that each color overlaps ",
"two cone cells",
" in your retina. Cyan activates your blue and green cells,... | [
"If you were to print with RGB you would be unable to produce yellows, if you were to create a screen with RYB you would be unable to produce greens.",
"Thank you very much! I was wondering this too, but that makes a lot of sense.",
"Only thing though: ",
"isn't it read and green that make yellow in light?"
] |
[
"Why isn't it always light?"
] | [
false
] | On a clear night, without light pollution, I can follow the path from Cassiopeia to the Andromeda galaxy, which appears as a dim smear of light. I assume that the closer I travel towards Andromeda (as impossible as that is) the brighter and more visible it will be and therefore it stands to reason that if I am Androme... | [
"Suppose you had several floodlights on stands, at varying heights and set a distance apart but angled so that they’re pointing at the same place. A person walking up to the spot at which they’re pointing would, for awhile, just see a wide swath of very bright light. But at some point, they would get close enough t... | [
"This is a great answer and has made me feel dumber (in a good way) for not working that out myself. ",
"I guess if I look at a distant city from a hilltop I can see an indistinct glow but if I'm ",
" the city I can still find \"dark\" spaces. That kind of thing?"
] | [
"It is always light. The stars bathe the planet in light 24 hours a day. It's not enough for your eyes to see with, but we have cameras which can easily.",
"Human eyes are designed for sunlight which is many magnitudes of brightness more intense, not starlight. Good thing too, because otherwise daytime would perm... |
[
"Can this spider running around on my desk hear my music but not comprehend it?"
] | [
false
] | [deleted] | [
"I'm sorry but I'm not sure if I quite understand the question.. Could you clarify if my answer is not sufficient? ",
"Spiders can't quite hear in the same manner as humans, but they can feel and interpret or react to vibrations. with hairs on their body. (",
"http://www.smithsonianeducation.org/educators/lesso... | [
"I will share my personal story",
"That's not the best way to start out a top-level comment on ",
"r/askscience",
". See the sidebar, disclaimer under the comment box, and obnoxious red box that appears when you hover over the save button for more details."
] | [
"I will share my personal story",
"That's not the best way to start out a top-level comment on ",
"r/askscience",
". See the sidebar, disclaimer under the comment box, and obnoxious red box that appears when you hover over the save button for more details."
] |
[
"What leads us to believe that time is moving in only one direction?"
] | [
false
] | It's occurred to me that all our perspective on the passage of time is based on our memories. That is to say there has been a change between something we had known in the past and the present we now inhabit.The problem with this is all of it is biochemically based. If time were really running in reverse (from the end o... | [
"Time is not symmetric in our universe. The relationship between the dimensions of space is purely symmetric; you can move either from left to right and from right to left. Both \"forwards\" and \"backwards\" are equally meaningful in all three spatial dimensions.",
"But time is not symmetric that way. Worldlines... | [
"Thanks, as always this gives me a lot to think about. But as the universe doesn't especially care about galaxies or stars or hedgehogs why is it \"future directed\"? What keeps time moving one way regardless of the effects?",
"Edit: Nevermind, you've already ",
"answered this"
] | [
"The disorder here is more specifically the disorder in energy. Thermal energy is just a random motion of particles and so, is very disordered. So although it may seem like you would have a perfectly ordered \"soup\", you would actually have all the atoms in your system zipping around in random directions, with ran... |
[
"Why are fires primarily red? Why don't fires naturally burn violet or green?"
] | [
false
] | [deleted] | [
"The flame you see from a candle or wood fire has several colors in it, but most of the upper flame is a red-orange color. The light from that section of the flame is mostly coming from blackbody radiation emitted by the recently formed soot particles. Most flames you see heat the soot to a similar temperature rang... | [
"Fires have all sorts of colors. It depends on the element that is burned, not the fire itself. ",
"This is also how fireworks are made. Various salts/metals are combined with black powder to create the different colors you see when it goes boom. ",
"For instance, strontium burns bright red, while magnesium bur... | [
"while magnesium burns completely white",
"Does it mean for this case magnesium burns a multitude of different colours in spectrum which results in the white colour?"
] |
[
"Is it possible to travel faster than the apeed of sound through a liquid?"
] | [
false
] | Has it been done before? What would that look like? Would there be anything cool to see like when planes pass through the sound barrier and that vapor wall builds up? Thanks. | [
"Shoot something with sufficient velocity into a liquid. There is a good chance you get ",
"supercavitation",
" and the object gets surrounded by a thin shell of evaporated liquid (=gas).",
"With a looser interpretation: Small particles like electrons and ions can travel at thousands of times the speed of sou... | [
"Not:",
"[faster than the speed of light] [in a liquid]",
"but:",
"[faster than] [the speed of light in a liquid].",
"Nothing can travel faster than the speed of light in a vacuum, but it is possible to travel through a medium faster than the light speed of that medium."
] | [
"This is not true, though the correct explanation of how light travels slower through matter involves some more complicated wave stuff that I don't understand, so I hope someone can follow up with a better explanation."
] |
[
"Why is a pendulums period constant.. until it isn't?"
] | [
false
] | One of the labs I did years ago in highschool involved the measuring of a pendulums period. We all know that a pendulum has a period which is constant regardless of its amplitude. You hold a weight on a string off its axis and it will swing from period to period, and take exactly the same amount of time to move end to ... | [
"In the small-angle approximation, a pendulum behaves like a simple harmonic oscillator, which has a constant frequency. Outside of the small-angle approximation, the differential equation of motion for the pendulum is nonlinear, and the period is amplitude-dependent."
] | [
"We all know that a pendulum has a period which is constant regardless of its amplitude",
"This is only approximately true for small angles.",
"What is happening that causes this phenomenon? ",
"When they derived the equation that they gave you they made the assumption that sin(x), which is hard to deal with,... | [
"equation of motion for a frictionless pendulum with a rigid weightless string holding up a mass is mw\"=-mg/l sin(w) where w is the angle between the position of the mass and the gravitational force vector (in radians of course). The Taylor expansion for sin(w) is w-w",
"/3!+w",
"/5!-... The infinite expansion... |
[
"The antibiotic Cefuroxim has an half life of only 80 minutes and is given twice daily. Why does it still work, even if half of it is eliminated in the body after such a short time?"
] | [
false
] | My guess is, that its dosage is so high, that the minimum inhibitory concentration of some bacteria is still achieved over a day, far beyond the MIC. But why is it, that my brother gets 500mg twice a day and I just 250mg twice a day? What serum level is necessary to achive a sufficient MIC? Should a higher dosage do no... | [
"So at the half life 1/2 of the compound will still be floating around in your blood. At twice the half-life you have 1/4th. 3 times the half-life 1/8th. So twice a day is every 12 hours, at that point you would only have 0.2% of the compound remaining. This isn't the whole story though because the half-life on... | [
"Most antibiotics (the bactericidal ones anyways) display a really cool property known as the Post Anti-Biotic Effect (PAE). Basically, after the drug has been eliminated from your body, the bacteria don't multiply (I have no idea how that works, and I think the science community in general are still thinking about... | [
"I have no idea how that works, and I think the science community in general are still thinking about it as well.",
"Actually, we've a decent idea. The beta-lactam core and attached ring of penicillins, cephalosporins is similar enough in character to the peptidoglycan subunits which the penicillin binding protei... |
[
"How far does sunlight travel through the atmosphere when I watch the sunset?"
] | [
false
] | Hi, I got curious during some research on Rayleigh-scattering. I was wondering: If the sun appears red for us at sunrise and sunset, how much further does the light travel through the atmosphere for the shorter (blue-appearing) wavelenghts to be scattered to near-invisibility at mornings/evenings compared to noon? Let'... | [
"I quickly whipped up a ",
"sketch of my solution.",
" Basic idea is the distance is equal to the square root of the thickness of the atmosphere squared plus two times the radius of the earth times the thickness of the atmosphere. (d = sqrt(a",
" +2",
"R)). In my diagram the inner circle is rhe Earth, t... | [
"Awesome, thank you! That's a good tip."
] | [
"Note that you can intensify the effect by watching the sunset from high altitudes with good visibility. The sunlight has that much more air to plow through before reaching your eyes. I flew into Detroit once right around sunset with no clouds, and the sun was just this blood red orb in the sky, looked like the ey... |
[
"Would it be possible to artificially create an atmosphere like Earth has on Mars?"
] | [
false
] | null | [
"Mars has an atmosphere, its just kinda shitty for life.",
"Think about what an atmosphere is. It's an razor thin envelope of gas that wraps around the surface of a rocky planet. There's no way to fake that. You don't want an artificial atmosphere, so much as you are actually asking for a real ",
" atmosphere."... | [
"Does the lack of magnetosphere hurt the process? I was under the impression that without one, solar wind would blow the atmospheres away from the inner planets."
] | [
"Not that much, the lack of magnetosphere allowed the atmosphere to erode for at least a billion years if I recall correctly. In human terms it wouldnt change much while we \"set up shop,\" but in the spirit of your question yes we would have to undo about a billion years of atmo decay. For practical purposes thoug... |
[
"At what size does a wire mesh stop acting as a Faraday cage?"
] | [
false
] | Wire meshes can often be used as Faraday cages to shield the inside from exterior electromagnetic waves. At some point, the mesh should stop being a Faraday cage if the holes keep getting bigger. So at what size of mesh does the mesh stop being effective at screening incoming waves? | [
"Faraday cages stop being effective as the mesh size approaches the wavelength of light. For microwaves, notice that the protective wire mesh has mm-sized holes in it. If they were cm-sized, it wouldn't screen the microwaves as effectively."
] | [
"The holes of the cage have to be considerably smaller than the wavelength they should shield against. I dont think there is a cutoff point but the bleedthrough increases as the hole size comes closer to the wavelength size.",
"Taking the example of microwaves: At ~2.4Ghz they have a wavelength of 12,5cm. The hol... | [
"Faraday cages stop being effective as the mesh size approaches the wavelength of ",
" ",
"the wavelength of the waves you are considering."
] |
[
"Is gravity infinite?"
] | [
false
] | I dont remember where I read or heard this, but I'm under the impression that gravity is infinite in range. Is this true or is it some kind of misconception? If it does, then hypothetically, suppose the universe were empty but for two particles of hydrogen separated by billions of light years. Would they (dark energy... | [
"Gravity does have infinite range. So if you had two atoms of hydrogen, at rest with respect to each other, separated by billions of light years in a static universe, then they would eventually hit each other.",
"However, if they're in any sort of relative motion, they would instead end up in some (probably ridic... | [
"The ",
" of gravity doesn't propagate; it's intrinsic to the local geometry, so it's indistinguishable from being instantaneous.",
" in gravitation propagate at the speed of light. But it gets complicated when you start talking about the aberration effect, which has to do with the difference between where a mo... | [
"Let's say a big heavy thing is moving along inertially at some significant fraction of the speed of light. A nearby — but not too nearby — smaller object is orbiting it. You might naively expect, because the big thing is moving that the orbit would be unstable, because the satellite object is always falling toward... |
[
"Why do people have different sized pupils? Does this imply a significant difference in perception?"
] | [
false
] | Some people naturally have larger pupils than others. Some are "beady" eyed. Does the amount of visual information perceived vary between the two? | [
"The size of the pupil is determined by a complex balance of sympathetic and parasympathetic drive. AFAIK, there is no simple predictor of pupil size, although it can be altered by things like drug use. ",
"OTOH, a ",
" in pupil size (right v. left) can be caused by a brainstem tumor."
] | [
"Regarding perception: the major difference is how much light is allowed into your eye. If you've ever had your pupils dilated at the opthalmologist/optometrist, you'll know what this means. There is not a noticable change in what you see; rather you become very light sensitive and can see more in low light setting... | [
"Right, but someone can have differing pupil size in the same lighting conditions. For example if you are interested in something you are reading, or someone you are talking to your pupils dilate, so how would one separate the pupil responses from caused by emotional states from the ones caused by lighting conditi... |
[
"Why do bombers make immediate 90 degree turns after releasing a nuclear weapon for detonation?"
] | [
false
] | Wouldn't it simply make more sense to continue on the same path? You'd lose speed and be closer to the explosion by making a 90 degree turn? Edit: so here's the video that got me interesting in asking the question last night. At about 39 seconds you see the bomb being dropped with a parachute, and the bomber making a (... | [
"The nuke doesn't just drop down from the plane, it drops while traveling at the same horizontal speed as the plane, which means that continuing to travel forward would be the absolute worst thing you can do — you'd stay directly above the nuke for the most part."
] | [
"I made a simple ",
"paint sketch",
". It should make it quite clear. The circle is just for reference, or it can symbolize the..danger zone!"
] | [
"Can I ask where you got the information that bombers with nuclear payloads turn 90 degrees after release?",
"When the bombs were dropped on Hiroshima and Nagasaki, the pilots turned their planes 159 and 155 degrees respectively. To quote the pilot of the Enola Gay, Paul Tibbets:",
"He [Dr Norman Ramsey, physic... |
[
"Do you weigh less at the equator because of centrifugal force?"
] | [
false
] | I am always confused be centrifugal and centripetal force. I am just going to state my thinking and help me point out the problem. At the equator your body is traveling fast in a circle and the inertia of your body makes you continue to move out-word, this is the centrifugal force. At the poles you are moving not at al... | [
"Yes. In addition, you also weigh less when you move east than when you are stationary, and more when you move west. This is the Eötvös effect."
] | [
"Yes, if the Earth were a perfectly rigid sphere (so ignoring the fact that the Earth itself bulges at the equator, also due to the centrifugal force), then your “effective weight” at the equator would be a little bit (less than 1%) smaller than your effective weight at the poles. And it is due to the centrifugal f... | [
"And also a bit because at the Equator you are a bit further away from the center. But even combined, the difference in weight is negligable"
] |
[
"Does the rise in our planets surface temperature cause increased volcanic activity?"
] | [
false
] | It makes sense to me that when the surface of an object heats up so would the core of the object, if only through less heat loss. Is this the case? Would this make magma more fluid and does it manifest as more volcanic eruptions and earthquakes? | [
"The increase in surface temperature is entirely negligible, and only impacts near-surface temperatures. As a rule of thumb...",
"At 1m depth, ground temperature is unaffected by daily fluctuations of surface temperatures.",
"At 5m depth, ground temperature is unaffected by seasonal fluctuations.",
"At 10m de... | [
"So it's something that you might notice on a sphere that was much much smaller, but being huge it has no noticeable affect. Cool, thanks!"
] | [
"Earth is a terrific insulator. Heat from the sun doesn't really penetrate that deep into the earth. Volcanism is largely caused by either plate subduction or core/mantle boundary interactions. Energy from insolation is inconsequential."
] |
[
"How did geneticists first discover which parts of the human genome were \"exons\" and which were \"introns\"?"
] | [
false
] | In the human genome only 1.1% of the genome is spanned by exons, whereas 24% is in introns, with 75% of the genome being intergenic DNA. How was this discovered? How exactly did we find the exact regions for exons? | [
"Introns were first discovered -- as with much of eukaryotic genetics -- via viruses. Viruses are much more manageable than a gigantic human genome, can be separated out easily and manipulated, but generally follow the same rules as the host genome they mimic for replication purposes. ",
"The discovery of intro... | [
"I don't know how introns were first discovered however your question in the comment seems slightly different whether you realise it or not.",
"Exons have well defined bases in certain places so we can do DNA sequencing then run them through a computer that can pick out introns and exons with reasonble accuracy. ... | [
"Exons have well defined bases in certain places",
"How do we know all exons have well-defined base patterns? Simply testing each of them? "
] |
[
"What is the relationship between information entropy and thermodynamic entropy? (Maxwell's Demon)"
] | [
false
] | Building on this discussion: On the Wiki page for Maxwell's Demon, it says that one way to account for it would be increasing information on the part of the "Demon" which would delay the increase of (thermodynamic) entropy until it ran out of storage capacity for the data. How does this work? We can just "dump" thermod... | [
"No, your intuition for the relative amounts of entropy is just wrong. The information entropy of the minimum amount of data Maxwell's demon needs to store (in order to reduce the box's entropy to X) is ",
" the difference between the box's current entropy and X. It's not that deleting the data somehow compensate... | [
"You don't just have the information floating around disembodied; you have to physically ",
" it somehow. And it turns out that the information entropy is a theoretical lower limit on the amount of physical entropy you need to store a given amount of data.",
"Now, erasing the data is also a physical process. If... | [
"And it turns out that the information entropy is a theoretical lower limit on the amount of physical entropy you need to store a given amount of data.",
"Ah, this makes more sense. So any information that is stored... is stored on a physical medium of some sort so there must be some physical entropy, no matter h... |
[
"Why us low intensity exercise better for fat burn and high intensity for cardiovascular health and how significant is the difference?"
] | [
false
] | null | [
"There are two types of physical activity: exercise and NEAT (fidgeting, daily activity). These activities burn calories, more specifically ATP.",
"...",
"ATP can be generated through a variety of means: metabolism of lipids, glucose, or protein. For this discussion we will ignore protein, as it is only metabol... | [
"This is an awesome answer, thank you!"
] | [
"You are most welcome.Thank you for the gold! Let me know if you need anything else."
] |
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