title list | over_18 list | post_content stringlengths 0 9.37k ⌀ | C1 list | C2 list | C3 list |
|---|---|---|---|---|---|
[
"What happens between the time a zit \"isn't ready\" and the time it is?"
] | [
false
] | [deleted] | [
"Increased levels of DHT causes an increased production of sebum, which in turn increases the activity of keratinocytes (a type of skin cells). Increased cell to cell adhesion due to keratinization interferes with normal desquamation (shedding) of the skin. Cellular debris and sebum produced by the skin starts accu... | [
"It's a \"side effect\" of the hydrolytic enzymes secreted by macrophages originally intended to be used against the bacteria."
] | [
"So popping is the \"desired\" result that the immune system is looking for? Or is there another reason to weaken the follicular wall?"
] |
[
"Why do exercises such as running that increase your heart rate make your heart stronger, but heart rate increase from stimulants such as Adderall, or excitement from video games, not make your heart stronger?"
] | [
false
] | null | [
"The same question was asked a few months ago, here is the answer:",
"\"Because when you exercise, you release a lot of catecholamines and other stress hormones. They are good in short bursts and they actually desensitise your body (in this case the receptors in the heart are lowered) to them over time; so that w... | [
"Please cite your ",
"source",
" whenever you directly quote anyone. Thanks!"
] | [
"I'm not sure I accept this. Professional athletes train for much longer daily than, say, amphetamine's half life.",
"I believe the vasoconstrictive properties of stimulants are to blame here, for raising blood pressure much higher than a person exercising at the same heart rate, simply putting too much stress on... |
[
"Is there any example of electromagnetic force affecting gravitational force?"
] | [
false
] | [deleted] | [
"There are things that could happen, but that we haven't detected. Examples are the gravitational field from electromagnetic radiation or fields. The magnetic fields of neutron stars might contribute non-negligibly to their gravity. There have been searches on Earth for violations of the equivalence principle, wher... | [
"It doesn't really make sense to say that a force has gravity. You could say system bound by the electromagnetic force has a gravitational field."
] | [
"My Newtonian worldview says that if gravity bends light, then the source of the gravity has to be affected as well because of conservation of momentum. Is this incorrect in GR?"
] |
[
"Is it strictly the force of Gravity which causes fast spinning object to \"fly apart\"?"
] | [
false
] | A sample video: This video is on a macro scale. Does it work the same on a micro scale? Is this experiment with magnets dealing with centripetal or centrifugal force? What's the difference? It seems counter-intuitive that the same force that "crushes" sub-atomic particles to over come the strong nuclear force can also ... | [
"Gravity doesn't really have anything to do with the tops flying apart. Let's consider one ball in the top. It's going in a circular motion around the axis of the top. For it to do that, there needs to be a force constantly pointing in the middle. If there was no force, then the ball would move in a straight line, ... | [
"Centripetal force is the real force, and it's the force that pulls an object inward (centripetal means center seeking) to prevent it from flying away as it moves in a circle.",
"You FEEL centrifugal force when you spin an object, say a ball on a string, because the ball pulls outward trying to travel in a straig... | [
"Centripetal and centrifugal forces are closely related concepts, but viewed from different frames of reference. When something rotates or turns, the velocity changes direction. This is an acceleration, even if the object doesn't speed up or slow down. From Newton's laws, that means there must be a net force. ",... |
[
"Do seeds carry more nutritional value than their flesh/meat?"
] | [
false
] | Let me clarify that I have no idea what to call the edible parts of a fruit like orange or watermelon therefore I’m referring to it as flesh/meat. As for the question. I am wondering if seeds in fruits carry more nutritional value than their flesh. Someone I know told me that grape seeds carry more vitamins and phytonu... | [
"I mean seeds do have some good nutrients. The endosperm of seeds are basically stored nutrients for the actual \"baby\" plant inside.",
"Sometimes theyre too densely packed to actually have us utilize tho. That or they are toxic to people and arent worth the time.",
"All grains are the endosperm of plants and ... | [
"I think the key thing you need to understand is that fruits are not all the same. This is true for grapes but not always for others, so please don’t start eating cherry pits. ",
"You have to look into each one individually to see whether the “I heard from someone” statements you’ll hear throughout your life are ... | [
"I am not debating whether the seed of one fruit or another is edible, but if the seed itself has generally speaking more nutritional value than the fruit itself."
] |
[
"Why can't we know the velocity and the position of subatomic particles at the same time?"
] | [
false
] | null | [
"I wasn't comfortable with this concept until I saw it demonstrated like ",
"this",
"Once you start thinking of particles as summations of waves, uncertainty follows quite naturally."
] | [
"It's not that we can't know them at the same time, it's that we can't know them to ",
" at the same time. This is the uncertainty principle, which comes about because position and momentum (related to velocity) are non-commuting operators. One very loose way of thinking about this is to use the fact that particl... | [
"This is a property of all waves. A real wave is this thing that has wiggles of length W and the wave extends over some distance L. The velocity is related to the length of wiggles W and the spread in position is just the distance L.",
"If you wanted to know the position of a wave accurately, then you want L to b... |
[
"Are there any animals that display a sense of humor?"
] | [
false
] | I know animals like to play and sometimes do things because of the conditioned response they get out of us. But I was thinking there's got to be some animals that do things just for shits and giggles... for instance, slapping another animal in the face repeatedly and enjoying the easy game... or "laughing" at another ... | [
"Definitely. just take a look at this and tell me the monkey has no humour",
"http://www.youtube.com/watch?v=MdA-y6J-KnY"
] | [
"I don't have a link to the journal article on-hand, but I am aware of at least one documented case of this.",
"In order to keep the bonobos of the Iowa Great Ape Trust in line, every now and again, caretakers dress up in a gorilla suit and make some random appearances around the borders of the faclity. Basically... | [
"Not humour but definitely playing:",
"http://www.youtube.com/watch?v=TMCf7SNUb-Q"
] |
[
"I'm a global warming skeptic, here are some of my points. Where am I wrong?"
] | [
false
] | [deleted] | [
"Look at the temperature fluctuations in the last 5000 years. You'll realize the mercury bouncing up a few degrees isn't uncommon, at all.",
"Response",
".",
"If you glance at any graph, you'll realize that the temperatures rose 800 years before the CO2 levels started rising",
"Response",
".",
"Other gr... | [
"First off, please use the search function, all of these points have already been addressed, multiple times in fact. We've had many long discussions on this topic. I'm not going to rehash all of the calculations here, sorry.",
"I will say this, please don't take this as an insult it's not meant to be, but you're... | [
"First off, he has to be reading a certain brand of sources if he's going to state that \"Volcanoes alone exceed that number [6.5 Gt]\". The real figure are more something like 26.4 Gt (human, per year, including land use) compared to 0.3 Gt from volcanoes. ",
"What the OP claims as evidence, isn't evidence acco... |
[
"What makes cats go crazy over catnip?"
] | [
false
] | Do other animals have similar effects to it? Are there any other known things that cause a similar effect in different animals? | [
"What is catnip, anyway?\nCatnip is a member of the mint family, which has about 250 species. The essential oil in catnip, nepetalactone, has a powerful effect on cats who are sensitive to it, turning even the most sedentary couch potato into a flipped-out ball of ecstasy.",
"Smelling vs. eating\nThe most intense... | [
"For more clarification, it actually mimics feline sex pheromones, and that's why cats are are so into it. I'm not aware of any other animals that like it, but it would interesting to test it out on various types of wild cat as well as animals that are very closely related to cats...",
"For more info:\n",
"http... | [
"Valeriana officinalis is also used as catnip the valerian acts as a a GABA-analog and binds with GABA therefore reducing GABA activity. This results in a hypnotic or sedative state. There is not an extensive amount of research on this though. "
] |
[
"Using a telescope, how likely is it that we could someday be able to see an event that took place, say, 50 years ago?"
] | [
false
] | null | [
"Like in space ? You can do that by simply looking at a distance of 50 light years away and you will see what was happening 50 years ago.",
"What we see of the sun is 8 minutes old. When we look at proxima centuri we see what was happening 4 years ago. ",
"If you are referring to what was happening on earth. Th... | [
"It is technically true that, if there happened to be an enormous mirror 25 light-years away, any light from earth that reflected off of it and came back to the Earth to be observed by telescopes would be from 50 years ago, and would depict events that happened at that time.",
"In practice, that's totally impossi... | [
"Most of the stars you can see with the naked eye are over 50 light years away. You see the light they emitted over 50 years ago. Once in a while a supernova is visible to the naked eye, in that case you can see \"live\" an event that happened thousands, maybe even hundreds of thousands of years ago.",
"An event ... |
[
"What are the ingredients to create human stomach acid(s) and why do we always have enough of it?"
] | [
false
] | I eat quite a lot but almost never drink anything other than water. So I don't take any liquid acids. What are nutrients/sources for the body to generate stomach acids? I can imagine that some fruits and vegetables, being very high in water content and often acidic, could be a source. What else is there? What about mea... | [
"There are cells in the stomach lining called gastric chief cells which secrete acid using a system of ",
"ionic pumps",
". This results in the net transfer of hydrogen and chloride ions being transferred across the stomach lining. These together are known as hydrochloric acid, a fairly strong acid (HCl). Chlor... | [
"Salt is sodium chloride (NaCl). When they break apart, the chloride is used to make hydrochloric acid. Yes a lot of water comes from your food: vegetables and fruit having lots of water. Meat, not so much, as you could tell. Now please go drink some water."
] | [
"You can form an acid and a base from a salt. It's the reverse of a neutralization reaction. Acids and bases aren't conserved - they can be neutralized, created and destroyed in multiple ways.",
"Separately, it doesn't make sense to separate your consumption of solids and liquids, since so many foods are mixtures... |
[
"Can some shoot some numbers and maths at me regarding how big a melting glacier has to be to raise sea levels?"
] | [
false
] | I am finding it very hard to see how one ice shelf or glacier melting could raise the sea levels by a measurable amount... Or any number of glaciers really. I just feel like the oceans are too big for the levels to be raised several ft. It doesn't seem like we have enough ice on the planet to do that compared to the si... | [
"OK, so area of the oceans is 361 million square kilometers.",
"We'll ignore sea ice (e.g. north pole ice cap) as that is buoyantly floating. However, we do need to consider ice which is sat on top of land. That is primarily Greenland (2,166,086 km²) and Antarctica (14,000,000 km²).",
"So, we've got about 16 mi... | [
"No worries. People tend to vastly underestimate how thick ice can be in these places, and how big Greenland and Antarctica really are."
] | [
"Thank you, I hadn't considered some of those factors. It just seemed as though something was missing. "
] |
[
"How can adrenaline slow your bleeding?"
] | [
false
] | So I recently just found out that adrenaline can actually be injected into you. I thought it was just something your body produced, and apparently it can be used to slow your bleeding. So with that knowledge here is my question. If adrenaline makes your heart pump faster then why or how does it slow down bleeding if yo... | [
"ER tech here. Adrenaline, or epinephrine as we call it in medicine, is responsible for the fight or flight response. In addition to raising the heart rate, it is a vasoconstrictor, ie, it causes your peripheral blood vessels (as well as those in your digestive organs) to constrict, slowing down the blood flow to t... | [
"Vascular surgeon here. I’m sorry, but the latter half of your statement is just not true. Vasospasm and vasoconstriction is far more pronounced in the arteries. In some cases, it is the only thing that slows bleeding enough to allow for hemostasis and can give us time to find a more permanent treatment.",
"Now d... | [
"Surgeon here. Everyone’s saying no, and the correct answer is probably no, but honestly if you are in the hospital and your blood pressure is low because you are hemorrhaging, and we can’t catch up quickly enough with blood transfusions to get your blood pressure up, we’re going to give you a medication very simil... |
[
"If two fermions with the same spin can't occupy the same position, how 'close' can they be?"
] | [
false
] | I'm almost certain I'm not grasping even the basics here, but does 'position' in this sense mean the same spot in space, or space-time? Or is this some other meaning of position that isn't quite like the colloquial use? | [
"Two identical fermions can have the exact same spatial wavefunction, as long as they have different spin projections (or some other quantum number different).",
"If they have all other quantum numbers the same, in principle their spatial wavefunctions can be arbitrary unless they're exactly the same. So they can... | [
"It’s because of the way fermions are defined. Identical particles must either have totally symmetric or totally antisymmetric state vectors under particle exchange in order for the system to have the right permutation symmetry. Fermions are defined to be the ones that are antisymmetric. The Pauli exclusion princip... | [
"Why is that? "
] |
[
"Would it be possible for a human being to actually walk on water? [Please, bear with me]"
] | [
false
] | During a discussion about magicians last night, someone made the argument that they feel that if a human being can float on water whilst on their back without any aides, it might be possible for a human being to train themselves to 'float walk' on water. Instinctively, I said this wasn't possible but the idea behind it... | [
"Only if it's frozen. Otherwise, you'd have to displace your own weight in water before you started to float. You'd but in up to over your neck in fresh water. A bit less in very salty water, which has a greater density."
] | [
"You could walk on liquid water if: you were not on earth...",
"If you were on a planetary body with a minute fraction of earth's gravity, and enough pressure for liquid water to exist, I could see it happening. Of course the 'splashing' from your steps would basically turn the room into a giant mixture of churn... | [
"In that video, the illusionist is clearly standing on a platform about 5-10 cm below the surface of the water. You can't see the platform due to the reflection of the sky and other incident light.",
"They rarely show a close up of is lower legs but when they do, you can see that his feet are totally submerged. H... |
[
"How is it that we can we control some of our body's 'automatic' functions (blinking, breathing) but not others (heartbeat, sweating, digestion, hair growth)?"
] | [
false
] | What's going on in the brain that stops us controlling the others/everything? | [
"Simply put, we're not wired that way. Grandiose oversimplification incoming...",
"There are two descending (that is, information and instruction that starts in the brain and descends to the organ in question) forms of motor control (that is, contracting muscles to effect a physical change) in the body. There is ... | [
"That all makes perfect sense, thanks! :)",
"So in a nut-shell: Autonomic systems run themselves, but some varying degrees of Somatic 'override'. Right?",
"So really a more interesting question might be; what happens when those 'overlaps' aren't normally developed? If mix-ups can happen with something like syne... | [
"Your nut-shell description is more or less correct, though I think I've committed a few cardinal sins of neurology in general by using the broad terms.",
"The question you've provided is is poetically possible (though in the below example not due to developmental pathology) and fascinating to see; one case comes... |
[
"When you fold a piece of paper, are you actually putting stress on any chemical bonds?"
] | [
false
] | null | [
"I can't imagine any significant protein content making it through a pulp and paper mill... paper is made primarily of cellulose, a polysaccharide. "
] | [
"I can't imagine any significant protein content making it through a pulp and paper mill... paper is made primarily of cellulose, a polysaccharide. "
] | [
"Yes. However a polymeric material like paper will first try to relieve stress by changing the organization of the polymer chains in the material. You can think of it like pulling on a pile of spaghetti. You are untangling things, but eventually you reach a point where you are breaking spaghetti. This would be bond... |
[
"What gives rise to the phenomenon of friction?"
] | [
false
] | [deleted] | [
"At the atomic scale, even the smoothest surfaces will be very rough and jagged. Also, two surfaces will never touch, they always have some gap between them. So say we have two surfaces with atomic \"spikes\". Due to the electrons in the atoms, the edges of these spike will carry a slightly negative charge. So, mov... | [
"As a physicist, I'm not completely happy with that explanation, since friction costs energy. If you have on stationary charge and you push another one (with the same sign) along it, at first, when you're approaching, you need to do work upon it, but you get the same energy back when you're past the stationary char... | [
"The loss of energy comes from the deformation of the two solids as they slide across each other, and from the heat and (sometimes) light created as well."
] |
[
"How different is our vision from the other apes?"
] | [
false
] | null | [
"Depends on the ape. Overall, humans and other apes have comparable visual acuity, color sensitivity, and capacity for object recognition, but ",
"here are a few differences",
":",
"Humans possess slightly different ratios of cones (cells that respond to different wavelengths of light and allow us to see colo... | [
"Yeeaaah that occurred to me as I was writing it but ball is life man and I got committed to the characters"
] | [
"At least to me, that example doesn't really seem to emphasize a difference in vision or understanding of context, but in experience. ",
"The human only knows it's a fake rubber nose because he has seen a fake rubber nose before, the orangutan only thinks it's fruit because he has seen fruit before. Had the human... |
[
"Why are there things i can only remember when i'm doing it?"
] | [
false
] | For example, game mechanics. | [
"Humans have several different \"kinds\" of memory. ",
"Autobiographical:",
" Your memories of events that have happened to you personally. ",
"Semantic:",
" Your knowledge of facts. ",
"Procedural:",
" Your knowledge of how to perform certain tasks. ",
"Procedural memory is very interesting, and can ... | [
"Great answer. But isn't it also ",
"priming",
"?"
] | [
"Quite possibly. Most of my priming research involves semantic priming, but there could well be some response priming in OP's scenario. "
] |
[
"(Geology) The \"polar wander hypothesis\" was debunked, but isn't the phenomenon of a wandering pole an actual thing since we've observed that magnetic North moves?"
] | [
false
] | My textbook says As paleomagnetists sampled and measured older and older rocks, . This was called the “polar wander hypothesis” at first. But then they ran into a problem. Each continent had a completely different polar wander curve, which only converged on a common magnetic pole today. These data seemed to suggest tha... | [
"Your book is correct that the idea of a wandering magnetic pole as the primary reason for variations in the orientation of remnant magnetic field that differ from today's orientation has been rejected. Within this, there is some nuance that is not reflected in the passages you highlighted, and generally are things... | [
"Thank you so much for such a great reply! I'll definitely be checking out that paleomagnetism text you mentioned."
] | [
"Awesome reply. I didn't even know I was interested in this, but I'll be damned if I didn't find that an interesting read!"
] |
[
"Does 'bracing for impact' actually help during minor impacts?"
] | [
false
] | Even mentally? | [
"Many people here talk about grabbing onto stuff etc. but there's a much simpler view.",
"Bracing for impact does help. You basically do this by contracting mucles and breathing out, anything else is optional or rather situational. \ncontracting muscles prevents impact from deforming your organs and helps muscles... | [
"Bracing may help reduce traumatic brain injury by increasing the blood in the veins surrounding the brain. The Valsalva maneuver is increasing the pressure in your lungs (i.e. \"bearing down\") which causes some blood to back up into the venous system. There's a collar is development for contact sports which recap... | [
"I did a summary of the studies they ran about it on my blog, haven't done much recently though, I'm on a little hiatus due to being balls deep in board exams\n",
"https://thedrugdebrief.wordpress.com/2016/06/19/the-q-collar-protecting-your-brain-from-your-skull/"
] |
[
"What exactly would the landscape of the British Isles have looked like prior to human cultivation?"
] | [
false
] | When you look at the landscape of the United Kingdom today, the vast majority of it consists of either towns or farmland. The human race has left an enormous impression on what Britain looks like, perhaps more so than most other nations on Earth. What would Britain have looked like during, say, the middle Paleolithic? ... | [
"This is actually an area of ongoing debate. In the past, it has generally been assumed that Britain was largely covered by forest - primarily because forest is seen as the inevitable result of succession given the ecological conditions in Britain. Note that in most of Britain this climax community is temperate bro... | [
"(and sorry for the essay)",
"I come here for the essays! Nothing more frustrating than an answer that has a couple of sentences for an answer and barely hints at the reasons behind it. This was very interesting."
] | [
"Scotland is still mostly preserved.",
"Just to jump in here, this is very much largely not the case. Whilst of course there are fragments of native woodland in Scotland, the landscape of the highlands is largely artificial/human-derived. Much of the heath and moorland is a result of human factors that result in ... |
[
"How come some moon phases can be seen during the daylight and some can only be seen at darkness?"
] | [
false
] | [deleted] | [
"The Moon is always half lit and half in darkness - the lit half is the half that faces the Sun. We see different phases because we are seeing the Moon from different angles, so sometimes we see more of the lit half, and sometimes we see more of the dark half. As the Sun is much further away than the Moon is, the S... | [
"This is basically a geometry problem",
"The Moon is always half lit and half unlit. The half that's lit will always be facing the Sun. So basically, when you look at the moon, remember that the lit side is pointing at the sun.",
"So, if you can see a full Moon, or something close to a full Moon, the Sun must b... | [
"When the moon is full, it's on the opposite side of the Earth from the Sun; when the moon is new, it's on the same side. As the moon waxes from new towards full, it will rise and set later and later after the sun. So a waxing crescent moon would be seen in the western sky shortly after sunset. As it grows more... |
[
"Is it possible to change a specific base for another specific base, at a specific location within the genome? What is the most common method to achieve this?"
] | [
false
] | I've read a bit about site directed mutagenesis but just wondered if we can mutate a specific base for another. Thanks in advance. | [
"Hmm, are you talking about humans or just in general? I'm not sure of a technique that would allow you to change one specific base for another precisely, but this is possible with common techniques. For instance, you could use a CRISPR-Cas9 type system to target a specific region in the genome and then use a PCR... | [
"I assumed the process could be applied to a variety of species. It did make sense, thanks. Is site directed mutagenesis most commonly carried out by PCR based method? "
] | [
"Well I work with drosophila (fruit fly) and we use a similar method so I suppose you could apply it to most species in vivo. But yes, most site directed mutagenesis is going to be based around PCRs because that's one of the easiest ways (that I know of, anyways) to cause a mutation in a gene and introduce it to a... |
[
"How can Mars ever be colonized without a protective ozone layer, thick atmosphere, and a strong magnetic field?"
] | [
false
] | null | [
"Hi plokijuhytrew thank you for submitting to ",
"/r/Askscience",
".",
" Please add flair to your post. ",
"Your post will be removed permanently if flair is not added within one hour. You can flair this post by replying to this message with your flair choice. It must be an exact match to one of the f... | [
"Planetary Sci"
] | [
"I am on mobile using Redditisfun. I have no idea how to flair, or if I did, flair what.",
"Is this some sort of cult?"
] |
[
"Why are sunburns, chemical burns, and burns from high heat all burns?"
] | [
false
] | Sunburns, chemical burns, and burns from high heat all look and feel similar, but their causes are very different. What do they all have in common, and more broadly what makes an injury a burn rather than something else? | [
"Medical terms (both casual and formal) are based on symptoms, not cause. All those mentioned result in pain, inflammation, and possibly scarring in the skin."
] | [
"UV radiation, caustic chemicals, and flames all cause tissue damage that leads to inflammation. Free radicals are produced, white blood cells invade, and dendritic cells become active. The pain is often due to spillage of inflammatory mediators that trigger nociception in the local area. This can be done through t... | [
"They are all related by the type of pain felt. Burns have a burning sensation as opposed to stabbing, itching, or other sort of pain. It is really more a quirk of the English language than anything. There are probably languages that are more specific words for different the types of pain and related injuries which... |
[
"Is the digestive process always first-in, first-out, or can quickly digestible meals \"pass\" slower digesting meals in the intestines?"
] | [
false
] | Google searches only seem to bring up information on constipation. | [
"Yes, the muscle ring between stomach and small intestine is coordinating some interesting stuff, like a bouncer in a club.\nLiquids in general go through the stomach faster, because they can flow through the muscular fissures of the stomach lining (like a motorcycle ignoring the traffic jam by driving around the c... | [
"Basically yes. Slower digesting foods, complex carbohydrates such as sweet potatoes and grains, will stay in your system breaking down longer than quicker digesting carbohydrates (sugars). The foods all break down as soon as they're in your stomach and interact with enzymes so it's not based on first in first out ... | [
"To add to what ",
"u/easyson",
" said, it's important to realize that a \"meal\" or even \"food\" really ceases to exist shortly after exiting the stomach. At that point you just have chyme, which is food + bile salts + water, and your small intestine starts the major nutrient absorptive process. So slower-d... |
[
"Why is it that the days I don't go to the gym I get extremely depressed?"
] | [
false
] | null | [
"First, please talk to a doctor. You seem to be treating your depression with exercise. While this may work in the short-term, it is obvious that you haven't completely controlled the problem. This is serious, and you require the opinion of a trained professional.",
"In terms of why exercise might help your de... | [
"Well, the post was removed, but here's a ",
"relevant scene from ",
"."
] | [
"thank you for the response"
] |
[
"Why do we always try to stop the swelling that occurs upon spraining or breaking a bone?"
] | [
false
] | [deleted] | [
"Just a nurse here, but unmitigated swelling can lead to vascular compromise i.e. compartment syndrome. This can lead to ischaemia and tissue loss. The body uses inflammation as a blanket response to injury until a more appropriate response can be delivered. I'm at work and unable to really delve into it deeper, ... | [
"Not only that but depending on the injury, the swelling could \"fix\" (as in, immobilise) the area in an awkward fashion, making addressing the injury harder. Take a joint dislocation - it's often said that it needs to be addressed before joint swelling kicks in otherwise manipulating the limb/extremity back to wh... | [
"The swelling might cut blood supply to the area due to pressing blood vessels, which then leads to that area start dying off due to lack of oxygen. ",
"In another case the swelling can crush organs and essentially damage/kill them, or prevent their proper function (imagine having swelling in your lungs, which wo... |
[
"why does the LHC have to be so big?"
] | [
false
] | cant you aquire the same data on a more efficient and less costly scale? | [
"The goal of the LHC is to collide particles at very high speed. So you need to make the particles travel a long distance in order to have enough time to accelerate them before the collision. That's why the LHC is circular: the particles travel several laps and are accelerated frequently.",
"But a particle moving... | [
"For the LHC, it's simple: they took the tunnel used by the previous collider (the LEP). Cheap and fast.",
"For the LEP, it was a compromise between \"how big do we want our collider to be?\" and \"how many billions euros can we get?\"."
] | [
"Sadly, scientists must sometimes deal with the fact that money is not infinite. By using the old LEP tunnel and not digging a new one, CERN managed to save tons of money that could then be spent on other areas of the LHC budget."
] |
[
"Can a deaf-blind person learn how to speak? If so, how?"
] | [
false
] | Assuming full deafness and full blindness from birth, can someone be taught to speak? Assuming speaking involves some acceptable measure of pronunciation, grammar, etc. If this is possible, how? Primary evidence would be highly appreciated. | [
"Yes. I have a friend who was born deafblind and he speaks, albeit not well. ",
"Teaching people with this condition to use their voice is an extremely difficult task. They feel the larynx and the breath coming.out of the nose on closed-mouthed consonants like M and N....",
"I have immense respect for the deafb... | [
"Thank you for the first-person response. Learning language with only one sense sounds like an incredibly arduous task.",
"I theorized that if a blind person can turn braille (touch) into language, and a deaf person can turn sign language (sight) into language, then it seems possible that a blind-deaf person cou... | [
"Helen Keller was not born blind and deaf; it was not until she was 19 months old that she contracted an illness described by doctors...",
"I'm aware of Helen Keller, but she wasn't born blind and deaf. She had 19 months worth of exposure to language and seeing the world before she lost her hearing and sight."
] |
[
"With growing water shortages, will we ever see water tankers crossing the globe like we see oil tankers today?"
] | [
false
] | null | [
"There is plenty of fresh water, and it is pretty easy to make it from sea water...the issue is one of transport, not supply.",
"The current water delivery infrastructure is based mostly on gravity...divert water from uphill to where you want it to be downhill. The problem is the ocean is as downhill as you can ... | [
"The technology for desalination isn't the limiting factor, it is an abundant source of cheap energy. No matter which desalination technology you choose, either some form of vacuum-distillation (probably ",
"multi-stage flash distillation",
") or a membrane based technology like ",
"RO",
" they all take qu... | [
"The cost of energy to desalinate will be superseded by the cost of fresh water and/or transport fresh water from one place to another "
] |
[
"How much would life on Earth change if the Earth's axis was tilted at 24 degrees?"
] | [
false
] | [deleted] | [
"A tilt of 24",
" is ",
"within the normal range of axial tilts",
" the Earth experiences. Over 41,000 years, our tilt varies from 22.1",
" to 24.5",
" and back again. This axial tilt range is quite a bit smaller than that experienced by some other planets - for instance, Mars' axial tilt has ranged anywh... | [
"We're currently at 23.5",
" and headed for smaller tilts. ",
"The cycles don't line up to set the stage for another glacial period for ",
"another 50,000 years",
", but there's also good evidence that we've pumped enough CO2 into the atmosphere that ",
"we'll be skipping glacial periods for at least 500,... | [
"Where are we at right now as far as tilt?"
] |
[
"Why do jet streams only occur at high altitudes?"
] | [
false
] | Additionally, do jet streams remain constant or do they 'die out' like gusts of wind? | [
"Jet streams are driven by differential heating between the equator and mid-latitudes that is then modified by the earth's rotation via the Coriolis force. The flow is at all levels of the atmosphere but there less friction at high altitudes so the flow is stronger there. Friction at the ground reduces the flow c... | [
"Would the friction at ground level be due to physical objects such as trees and buildings?"
] | [
"Yes, but also the ground itself and topography. The variability of the Jet Stream is amplified by flow over mountains."
] |
[
"As an example, if Penicillin gets inhibited by penicillinase, why don't we take another drug beforehand that would inhibit penicillinase so that Penicillin would be an effective antibiotic again?"
] | [
false
] | College Bio student and I just thought of this, of course someone else probably already though of it but I just want to know the reason why it doesn't work | [
"It does work. This is a common strategy for improving the effectiveness of certain antibiotics. Augmentin is an example of an antibiotic that uses this strategy. It's a combination of a pencillin derivative antibiotic (ampicillin) and a compound (clavulanic acid) designed to inhibit the enzyme that some bacteria u... | [
"It definately isn't as easy as you make it sound out to be. Developing a drug against an enzyme usually involves years of research by medicinal chemists. And even if a suitable compound has been identified it can be impossible to make it properly bioavailabe. ",
"The compound might even have severe side effects ... | [
"There are many different ways that bacteria biochemically resist antibiotics. They can break down the antibiotic, they can change how they express certain proteins that the antibiotic targets, they can produce more pumps to remove the antibiotic from their cells, etc. ",
"In some cases we understand how the meth... |
[
"Why do eggs become hard when boiled while potatoes become soft?"
] | [
false
] | [deleted] | [
"Regarding the eggs, Harold McGee explains it well in ",
" ",
"Page 1",
", ",
"Page 2",
"I'm not sure about the potatoes.",
"FYI though, cooking at or bellow 100°C mostly changes hydrogen bonds, very few covalent bonds are effected. Most of cooking therefore comes from protein denaturation, which is wha... | [
"Proteins have hydrophobic (water insoluble) and hydrophillic (water soluble) regions on the strand of amino acids. A protein is folded in such a way that the insoluble regions associate and interact with other hydrophobic regions while the hydrophillic regions are capable of solubilizing the protein in an aqueous ... | [
"Potatoes are composed primarily of starch(carbohydrates, combination of amylose and amylopectin) while egg, both white and yolk, are protiens in a native form. ",
"The native form of the starch is a hard, crystalline granule. When heated in the presence of moisture, the granule first swells, then 'gelatinizes'. ... |
[
"Why did evolution through natural selection favour putting testicles in a scrotum rather developing more heat resistant sperm."
] | [
false
] | [deleted] | [
"Probably just the testes were slightly external by some mutation, and this gave slightly higher sperm survival rates and it snowballed from there. However your phrasing of the question suggests that you are thinking of evolution as making concious choices. The only real reason that evolution 'picks' one solution ... | [
"Evolution pushes towards local peaks rather than global maximums. "
] | [
"Evolution pushes towards local peaks rather than global maximums. "
] |
[
"If a woman's eggs are fully formed at birth, why does having children later in life increase the risk of developmental disabilities?"
] | [
false
] | null | [
"source: biomedical sciences major with a few courses in genetics.",
"the simple answer is, eggs aren't fully formed at birth. i believe they become arrested at... metaphase I? then after menstruation, eggs continue to go through the first phase of meiosis and stop again into meiosis II until fertilization does (... | [
"you're right, but i wouldn't say that ",
"paternal age",
" holds much of a candle compared to ",
"maternal age",
". at age 40, there's a 1 in 100 chance a woman's child will have down syndrome.",
"why down syndrome in particular? that one's pretty cool, actually. down syndrome is one of the few chromosom... | [
"Men's children are at greater risk later in life as well. I'd assume this is mostly due to replication errors in the germ cells that produce sperm. "
] |
[
"How does restricting Internet work?"
] | [
false
] | Now when Net Neutrality is in the news all the time, I'm wondering how restricting the content works? Can it be avoided with a VPN? | [
"There are plenty of ways to deny service, particularly so if it is done by the operator providing the service.",
"Connectivity. You may be connecting to some sort of access point, like a WiFi AP, which does not provide service unless you follow specific procedures. This is usually some trivial registration or au... | [
"Wow, wouldn't have thought I'd get that detailed answer, thank you very much! Very interesting topic indeed, and (if possible) now I'm even more concerned about net neutrality..."
] | [
"It's worth noting that your ISP probably knows you're using a VPN and could just as easily throttle your internet for that reason."
] |
[
"Where do dead bacteria go?"
] | [
false
] | For example, when you cook meat to kill all of the bacteria, aren't you technically eating dead microorganisms? This could be a really stupid question, but I was always curious about it. Does your body use the dead bacteria it eats for any purpose or does it just flush it out during excretion? | [
"Sort answer : yes you eat the dead microorganisms. They are digested and passed just as other organic matter. ",
"Longer answer : furthermore, you actually eat live microorganisms all the time. Bacteria are everywhere! Additionally Your gut is actually full of a microbiome containing one of the densest concentra... | [
"In some cases, antibiotics can knock out most, but not all of the bacteria in our gut. That leaves the few bacteria remaining to thrive because there is no competition. This is the case with Clostridium dificile infections. They usually only happen after taking antibiotics. "
] | [
"Great questions! Clostridium is a great example. Most of our bacteria are good and outcompete the bad bacteria for resources. If too many of the bad bacteria outcompete the good, you will get sick. This also happens in food poisoning. \n Yes we have a wonderful immune system constantly monitoring our gut bact... |
[
"If dark matter (the non-baryonic kind) is real, does the theory predict that dark anti-matter should also exist?"
] | [
false
] | null | [
"There are people who believe that dark matter is baryonic anti-matter. The idea is strange antimatter formed into stable quark nuggets when the universe formed. Because they're so dense they can account for the dark matter, but still be rare enough to be \"dark\" to us. This model solves two problems, the matter/a... | [
"There are some people who think that dark matter is actually positrons and are looking for evidence of its annihilations.",
"There are a lot of theories for what dark matter is; some may have antiparticles and some may not. The general term for a particle that's its own anti-particle is Majorana, and there is re... | [
"There are many theories of what dark-matter is. None are completely accepted. The easiest explanation is that right now our models of galactic motion that are based on the physics we currently know fail in a consistent way. In trying to explain this discrepancy, we need a label to talk about it. \"Dark matter\... |
[
"Could a purely analog video signal hold enough data to transmit a 1080 high res video?"
] | [
false
] | I've been watching a bunch of videos on how old tv works and it got me wondering. If we hadn't developed digital signals, could analog signals be pushed to HD levels or is there a physical limit? Also, wasn't sure if this fit the physics flair, sorry ahead of time. | [
"HD video ",
" transmitted as analog signal - e.g. the Japanese HDTV standards that started in 1960s (that's not a typo). E.g. the system introduced in 1972 had 1125 lines. E.g. the MUSE/HiVision standard from the 1980s was like this too, fully analog, delivering 1125 lines (1920x1035 resolution) interlaced at 6... | [
"Yes, it would be possible to transmit a high-resolution analog signal, it would just require an absurd amount of power. Both analog and digital are transmitted via ",
"electromagnetic radiation",
", the major difference between the form in which they are encoded. \nIn specific, digital signals can use ",
"er... | [
"As a ballpark, the uncompressed bandwidth of a 1080p 60hz video is roughly 30 times greater than a standard-definition video signal (480i 30hz or thereabouts).",
"So yes, you could broadcast high-def TV using the old analog system, but there would only be enough bandwidth in the VHF and low UHF radio spectrum fo... |
[
"If Cavendish bananas were targeted by a disease not unlike the Gros Michel bananas, what would be the next species in line to replace the Cavendish?"
] | [
false
] | [deleted] | [
"Heeyyyyy I just spent two months in Central America researching this exact question and consulting with the experts of banana pathology and the top figures of the banana industry. First, I must say that your hypothetical scenario is already happening. Panama disease (Fusarium oxysporum cubense) is what wiped out... | [
"so the bananas that we buy at the market are genetics clones of each other. there's a fungal plant pathogen called ",
" that causes banana wilt, and since the bananas are all clones of each other (ie no genetic diversity) a strain of ",
" could potentially wipe out all the bananas.",
"I should say that Caven... | [
"There is really VERY little export of Gros Michel. The chances are tiny that if you're strolling through a market, you'll encounter one. I can't find them in the US. When I was in Central America, I worked with one organic farmer who sold some to a company that made baby food with them in Germany. I don't know... |
[
"How can the diameter of the Universe exceed its age?"
] | [
false
] | The Universe is 13.8 billion years old and the observable Universe is about 93 billion light years across. How is this possible? If I had to guess, I'd wager that the Universe must have expanded faster than the speed of light at some point in its evolution. I'm not sure if that makes sense though, and details would be ... | [
"I think the most concise answer is \"expanding faster than light\" means nothing since the amount of expansion does not have units of velocity.",
"The amount of expansion from time t to today (t_0) is given by the ratio between the size today and the size at time t. This is a dimensionless ratio and cannot reall... | [
"The diameter of the ",
" universe might be infinitely large. Because of that, for any finite rate of expansion there are always parts of the universe that ",
" to be moving away from us faster than the speed of light. However, the diameter of the ",
" universe is set not by the expansion alone but by the far... | [
"If that photon had started out as red light, it would have shifted to a different frequency of microwave background as photons that started out as blue light, correct? ",
"Correct. The redshift defines the ratio of the wavelength now to what it was then, so it is a scaling factor.",
"Can we learn anything from... |
[
"How common are gaseous planets?"
] | [
false
] | Is there any way to know how often gaseous planets are formed rather than rocky planets? What are the reasons? | [
"Based on observations by the Kepler Space Telescope, smaller radius (rocky) planets are more common than large radius planets. See Figure 2 in Borucki et al. 2011 (",
"ApJ ADS link",
", ",
"arXiv PDF",
")."
] | [
"Kepler candidates are possible planets (not only those that we think might be habitable) detected using the transit method. After accounting for observational biases (for example, how smaller planets are harder to observe (which is why the number drops off at small radius) and orbital geometry (the planet has to p... | [
"The paper ",
"The Snow Line and the Frequency of Giant Planets",
" might well answer your question. (Continue to read until \"[...] shows the likelihood of a star harboring at least one gas giant planet as a function of stellar mass for our baseline model.\")"
] |
[
"Does sugar-free gum (with sugar alcohols) produce an insulin response?"
] | [
false
] | I have a pack in front of me right now. It contains Maltitol, Sorbitol, Mannitol, Aspartame, Acesulfame-Potassium, and Sucralose. Would this be diabetic-friendly, in that it would not cause a blood sugar spike that would in turn cause/require an insulin response? | [
"The sugar alcohols you listed (maltitol, sorbitol, mannitol) all can potentially cause a change in blood sugar and affect insulin response, although usually to a much less degree than \"normal\" sugar. They can also give you diarrhea (a common question that diabetics get asked if they present with diarrhea is if ... | [
"It's same with xylitol. It does not absorb as fast as sugar, so it does not increase blood sugar levels or hyperglycemia in humans. ",
"For dogs it's different thing. Hypoglycemia that can kill from 100 mg/kg and if it goes over 500 mg/kg it can cause liver failure. "
] | [
"In some cases, the body is conditioned to release insulin upon receiving a sweet tasting stimulus (think Pavlov's Dogs), meaning your body will prepare to process incoming sugar."
] |
[
"There's been a lot of speculation about whether people who have received the Covid-19 vaccine may still spread the virus to others. Is this common for other vaccines?"
] | [
false
] | I understand that everyone wants to be careful about over promising what the vaccines may do for us until the data is in, but I was wondering whether this is just erring on the side of caution of if there's a history of vaccines for other diseases protecting the recipient from getting sick but not preventing them from ... | [
" viral vaccines ",
" block transmission, or greatly reduce it - smallpox, measles, mumps, rubella, polio, etc etc. ",
"Influenza vaccine is not sterilizing, and does allow some transmission even in vaccinated people. (Influenza is always an exception to other viruses. Because it’s an exception, it’s exceptiona... | [
"Thanks for the in-depth response.",
"Regarding your last paragraph, I agree 100% and I certainly wasn't trying to infer any sort of \"the sky is falling\" feeling on my part. I was genuinely wondering if this is a common precaution to take because we've been burned by vaccines in the past, if it's just erring on... | [
"A lot of it is also the question of \"how do we stop a pandemic\" rather than \"well, what's safe enough for something fairly rare?\"",
"For something like measles, most people are vaccinated, and it's pretty rare that you'd encounter someone who has recently been exposed to the measles virus anyway. So a vaccin... |
[
"Questions about Origin of Life/Evolution"
] | [
false
] | As far as I know, it is thought that all living creatures on Earth descended from one organism. Essentially, when life began, it happened only that one time and all other life afterwards has evolved from it, right? Why, in the more than 3 billion years since life began on Earth, has it not begun again (and again and ... | [
"Great questions and without answering it directly, I'd like to point out viruses which are very much 'life-like' with an independent origin. Perhaps if we found viruses on another world we would then consider them true life. ",
"I think a lot of it has to do with the statistics of the situation. Life has origina... | [
"I guess I never though of it that way. Once life began, anything coming after it has almost no chance of surviving due to competition from what already exists. Thanks!"
] | [
"Well, you pose an interesting question. Let's start with life. Most of the scientific establishment agrees that life started out in what was called an \"",
"RNA world.",
"\" RNA (a similar molecule to DNA) is capable of acting like an enzyme (like proteins). This activity is referred to as ribozyme activity. T... |
[
"What is your brain doing when you're trying to remember something?"
] | [
false
] | Specifically if you know you know something and are trying to search through your thoughts for the answer? | [
"The short answer is that a precise answer is waiting further research. The most compelling answer today is that declarative memories are enduring patterns of changes in connectivity between neurons in association neocortices. These areas are indexed by the hippocampus (if they are fairly recent) or by the prefront... | [
"The top post, which was removed because it was both speculative and inaccurate, cited Kurzweil."
] | [
"Folks, this is ",
"/r/askscience",
". If you don't have some level of expertise in the subject, or don't have a scientific source to back up your ideas, then don't comment. ",
"As always, please refrain from anecdotes, speculation, jokes, and off-topic discussion.",
"Thanks."
] |
[
"Is there any evidence that prehistoric man suffered from acne?"
] | [
false
] | Fighting with my teenage daughter to wash her face. Her defense included her reasoning that prehistoric man didn’t have face wash, since no cave drawings depict acne, so she doesn’t need to wash her face. I know, I know. Ridiculous. I’ve already countered with the fact that they didn’t have pollution in the air, their... | [
"Acne prevalence is correlated with westernization of societies. Here they found no prevalence of comedones in Kitavan islanders in Papua New Guinea and Aché hunter gatherers in Paraguay.",
"https://jamanetwork.com/journals/jamadermatology/fullarticle/479093",
"Moving from a rural lifestyle to an urban lifestyl... | [
"We published a little paper a few years ago about the human Acne bacterium P.acnes being found as a endophytic inhabitant of the domestic grapevine",
"There are a few interesting calculations there on the time when symbiosis began between humans and grapevines.... And P. acnes",
"If you have trouble finding it... | [
"Acne isn't really caused by improper facial hygiene. It's caused by hormonal imbalances that cause over secretion of sebum from the sebaceous gland in your hair follicles which clog them and provide a good microbiome for P.acnes bacteria to proliferate. The best treatment for that is topical or systemic antibiotic... |
[
"If protons sometimes include the heavy charm quark, does it mean proton mass fluctuates?"
] | [
false
] | I read from this how it was discovered that protons sometimes contain the charm quark and antiquark which themselves are "heavier than the proton itself". I don't know what to make of this. Doesn't it mean that proton mass changes? | [
"These quarks are heavily \"off-shell\" -- they don't always have the same values of certain parameters (like mass) that regular (\"on-shell\") quarks have. They can exist in this way because they are \"internal\" to a reaction; they are created and then absorbed again on very short timescales, rather than propagat... | [
"These are \"virtual\" charm quarks. Quantum mechanics permits quantities like energy and mass to be violated for very short intervals. Given that the proton lives for a very long time, its mass must be stable. The charm quarks it contains, however, can only appear and disappear basically instantaneously. This happ... | [
"There is no \"sometimes\" involved here. The proton mass is constant and doesn't change because energy is conserved.",
"The situation is similar to e.g. an electron in an atom. It has a wavefunction, which can be interpreted as probability density to find the electron at a given spot ",
" you measure its posit... |
[
"How does the body deal with artificial sweeteners such as aspartame, acesulfame and etc? In the end is it more healthy or less than real sugar?"
] | [
false
] | Different sweeteners carry different properties and health issues. But in general will you be better of just having regular sugar or using artificial sweeteners? A lot of people claim you will get more fat from drinking diet coke, some say you won't get fat at all. Whats the truth here? And how does it work? I know too... | [
"It depends on which artificial sweetener you're talking about. Aspartame is broken down normally and has caloric content, there's just so little (compared to an equivalent sweetness of sugar) that you get a small fraction of the calories in a traditionally-sweetened beverage.",
"There's no evidence that artific... | [
"All I can tell you is that there's really no evidence that diet coke is bad for you, or that any of the ingredients are bad (unless allergies or something uncommon). Nor diet drinks in general. Even caffeine has pretty good evidence of being generally good for you. As long as you're getting plenty of water and n... | [
"I think the discussion was more based on the effects they have in terms of nutrition and digestion, but it's important to consider dental health, too."
] |
[
"Is it possible to have a region of a gravitational field with non zero curl?"
] | [
false
] | Yes curl as in mathematical curl in the vector field. In what situation(s) would this happen, if it is possible? | [
"Gravity is a conservative force (hence path independent) so it has no curl. If it had curl, you could have an infinite power generator in that region, where you climbed up a gravity well in one direction, moved around, then fall back down the gravity well in another direction, and could extract energy along the wa... | [
"So, gravity is a ",
"conservative force, so it's curl will always be zero",
". But I'm curious, what sparks such a question, because the answer might be boring, but the reason to ask might lead to something much more interesting."
] | [
"I was just curious, I am studying mathematics at university but due to the coronavirus I am not having any classes (not even online), but I always have enjoyed studying maths, I am currently studying calculus III and differential equations, amongst some other things"
] |
[
"Why is space in the Cassini \"Pale Blue Dot\" picture bluish instead of black?"
] | [
false
] | is a marvel, but it does leave me with the question: why is the empty space there bluish instead of pitch black? and while we are at it, why is the outermost ring a very bright purple while the rest are varying shades of brown? | [
"Just to avoid confusion: that is not the \"Pale Blue Dot\" picture. ",
"This",
" is. Your image is called \"The Day the Earth Smiled\"."
] | [
"Have a look here: ",
"http://www.jpl.nasa.gov/spaceimages/details.php?id=PIA17171",
"Things to note: ",
"While ",
"/u/localhorst",
" is right that many space picture have altered colours, this one here is a natural-color image, according to the image description.",
"The blue glow emanates from the brig... | [
"NASA explains how it's done with the Hubble pictures:",
"http://hubblesite.org/gallery/behind_the_pictures/meaning_of_color/"
] |
[
"Question about Inflation (in cosmology) and the Big Bang"
] | [
false
] | [deleted] | [
"So very early in the universe there was a very brief period of very rapid accelerated expansion. This is called inflation. Then after inflation there was a period of radiation domination, then after the universe cooled some more there was a period of dark matter domination. During both of these periods the expansi... | [
"It's fair to say there are phases, but it's not fair to say they correspond to different forces. It's all gravity, it just depends on what type of energy is the most dominant in the universe at that time.",
"And yes I did mean to say dark matter. The phases go",
"Inflation (Cause = unknown, effect = rapid acc... | [
"It's fair to say there are phases, but it's not fair to say they correspond to different forces. It's all gravity, it just depends on what type of energy is the most dominant in the universe at that time.",
"And yes I did mean to say dark matter. The phases go",
"Inflation (Cause = unknown, effect = rapid acc... |
[
"Why does a neutrophil have a lobed nucleus?"
] | [
false
] | None of the biology teachers at my college could answer this question, and now I really want to know. So, why does a neutrophil have a lobed nucleus? | [
"The multi-lobed nucleus of the neutrophil arises during its formation, and is an artifact of the genetic events which occur during cell differentiation. During the differentiation of eukaryotic cells, the genetic activity of many regions of the genome is down regulated (transcriptional silencing) through a wide va... | [
"Side question...",
"Are some, all, or any of those regions still known to be present & identifiable after NET formation? Or do all the histones come off? Or is that even known?",
"That is, say you have an inflamed area in which NET formation is likely, and you have DNA free in the area. ",
"Is it possible to... | [
"Ah, that would be a problem. Well unfortunately now we’re getting to an area where your guess would be as good as mine. I can tell you that the dense chromatin packing unfolds to produce a chain of nucleosomes in NETs, so you wouldn’t be able to compare it to live cell DNA. I have seen papers where they identified... |
[
"What is the purpose of eye color?"
] | [
false
] | Overall, what does eye color do and what was its purpose in evolution, many species of animals don't even have eye color. | [
"well brown is one of the darkest colours and therefore provides the largest amount of protection (people from areas of high sun intensity tend to have brown eyes). The brown colours comes from Melanin. So far so good.",
"Blue and green though come from ",
"Reyleigh scattering",
" on the iris. Essentially the... | [
"UV Protection",
" two evolutionary means of protecting your cells that are absorbing light. Either replace them or protect them. Melanin or other pigments absorbs the UV light providing protection for the interior receptors. ",
"Pretty much the same reason for skin colour! (question below: yes melanin is respo... | [
"Huh, that's pretty cool to know! Thanks for the answer! But do you have any idea why specifically brown or blue or green etc.? Maybe brown I could understand because Melanin is brown in many other cases, but blue or green seems kind of out there, as Melanin is brown in ",
" cases, could you shed any light on tha... |
[
"How is energy conserved for a redshifted/blushifted photon?"
] | [
false
] | When a photon is emitted from a moving source it's frequency (and hence energy from the Planck relation E=hf) changes depending on whether or not the light source is moving towards or away relative to the observer. (Ignoring gravitational redshift to make it simpler) For a blue-shifted photon, eg the frequency is doubl... | [
"There is no extra energy. You are confusing measurements made by different observers. Suppose I emit a photon of some freuency f, corresponding to some energy E. You are moving at some speed away or towards me, and so you see a different frequency, and hence different energy. ",
"Conservation of energy does not ... | [
"How is energy conserved for a redshifted/blushifted photon?",
"It depends on the mechanism underlying the redshift/blueshift -- there are three different ones, and whether/how energy is conserved is different for each.",
"In your question, you seem to be asking about ",
", which is one of the three types. "... | [
"Will a sufficiently rapidly rotating disk hanging on the ceiling illuminate a room?",
"Does a fast moving solar panel generate electricity at night?"
] |
[
"Why don't any states use carbon monoxide smothering as an execution method?"
] | [
false
] | I know this is morbid as all hell, but my mind goes into dark places when I'm severely bored. I am aware of the irony involved: trying to kill a person as painlessly as possible seems to be a contradiction, but once again, I'm not here to discuss morality other than minimization of suffering in the condemned. Ignoring... | [
"There's no need to flood a chamber with CO, that's a little silly. There's no reason we can't sedate someone and give them a breathing mask that delivers CO or N2. That would definitely be more effective and less painful than our current methods."
] | [
"True, but the OP was asking about monoxide, which should work. Nitrogen would at least be less dangerous when venting the chamber after use."
] | [
"Oops. Yes - misread."
] |
[
"Does sunlight lose energy as it travels?"
] | [
false
] | Why does the sun heat heat a planet like mercury more than a planet like Neptune? If space is a vacuum, where does the energy go that is lost between the sun and a planet? | [
"The flux from the sun, the amount of energy landing on a given area, is inversely proportional to the square of the distance. ",
"If a certain amount of energy per square meter is received at some distance, say 1 million kilometers, then at 2 million only ¼ the energy per square meter would be realized. 10 milli... | [
"The flux from the sun, the amount of energy landing on a given area, is inversely proportional to the square of the distance. ",
"If a certain amount of energy per square meter is received at some distance, say 1 million kilometers, then at 2 million only ¼ the energy per square meter would be realized. 10 milli... | [
"Likely not on the scale of the solar system, but it's still good to point it out to avoid misconceptions like space = vacuum everywhere."
] |
[
"What if there was an infinite slope of snow, and a snowball started rolling down it, picking up snow as it went at the rate of S. As it is constantly increasing mass, would it ever reach terminal velocity?"
] | [
false
] | [deleted] | [
"What about the increasing diameter of the snowball? I guess we could throw \"infinitely sticky snow\" onto the list of assumptions, but if we didn't, wouldn't the snow on the outside of the snowball eventually be moving so fast that it would fling itself off at a rate equal to the rate the snowball was picking up ... | [
"No.",
"Terminal Velocity occurs when an object falls through a fluid at such a velocity that the Force due to Gravity is equal to the upward Force of Drag.",
"Force of Drag increases with velocity until you reach a velocity at which the forces acting on the object are in balance causing a constant velocity (no... | [
"Good job, but you're forgetting that drag force also increases with cross sectional area, which should go like mass",
" (assuming the snow doesn't compress significantly), so both forces have direct mass dependence. However, since the exponent is larger for gravity (1>2/3) your conclusion stands."
] |
[
"What causes adhesion between ultra-smooth surfaces?"
] | [
false
] | I recently re-glued a rear-view mirror to a windscreen. A small bit of solvent completely removed all the residue of the old bond and the surfaces seemed completely flat and clean. The new bond is completely solid. this made me wonder about how the adhesive worked and led me to do some reading. It wouldn't seem to ... | [
"Structural adhesives form covalent bonds along many branched chain polymers. If the surface can be chemically bonded too, it doesn't matter how smooth it is to a certain extent. Surely, a rougher surface has much more surface available for the adhesive to form a better bond, but the strength of the bond for a rear... | [
"So, if I understand, you're saying that structural adhesives rely on chemical bonds rather than mechanical adhesion? "
] | [
"Most adhesives that people deal with (Elmer's/wood/super/etc) are mechanical adhesives. They work by filling small voids in the surface before hardening and mechanically locking the adherands together. Stronger (i.e. structural) adhesives work generally by forming a network of covalent, polar or hydrogen bonds wit... |
[
"If a parent's DNA is damaged after birth, will the DNA passed onto offspring contain similar damage?"
] | [
false
] | [deleted] | [
"Depends where the damage occurs. Even before birth only DNA damage that occurs in your parents gametes (reproductive cells) may be passed down to offspring. Any other DNA damage to all other cells do not affect the offspring (not counting for any epigenetic effects of course [which is a newer area of genetics not ... | [
"Just to add to this, we use the terms somatic cells and germ line cells. Somatic cells are simply everything that isn't part of the germ line. The germ line are those cells that eventually undergo meiosis and divide into sperm (for example).",
"If germ line cells are damaged, then yes, it will be passed on.",
... | [
"Just a stab in the dark... you don't happen to program in lisp, do you? ;)"
] |
[
"In light of water shortages around the world, could we simply dehumidify and purify water to make it drinkable? Or gather water droplets from heat and desert areas?"
] | [
false
] | The core of my question being "what is the easiest way of producing water depending on where you live?" Obviously this heavily varies around the world but in areas where heat gathers could we simply not 'harvest' the water? Secondly, what could be the effect worldwide if we began to dehumidify large areas like forests ... | [
"Yes, but it requires a lot of energy to cool to below the dewpoint, and the environment you’re in is going to need to have a fair amount of humidity. There just isn’t any humidity in the desert. ",
"places that have humidity, and the temperature is fairly close to the dewpoint so that you don’t need to use a lo... | [
"Good sources you beat me to it "
] | [
"IF the temperature of the moist air drops below the dewpoint at night you can use ",
"fog nets",
", else, if you ",
" have humidity in the air, you can use a dehumidifier, but that is energy intensive (5 litre/kWh?). "
] |
[
"Why does Thermus thermophilus have reverse transcriptase capability?"
] | [
false
] | I realize the title is oversimplified, and also that asking why a particular organism evolved in a certain way is sort of missing the point but I had to shorten it for the title. I'm taking a molecular diagnostics class and we are discussing the use of the Tth polymerase enzyme isolated from for reverse transcriptase P... | [
"Interesting question, and unfortunately my answer won't be conclusive, just intuitive. It seems from what ",
"wikipedia",
" and a ",
"vendor",
" say on their websites, the polymerase is a normal DNA polymerase that has RT activity. But, it only has that activity in the presence of manganese. Manganese isn'... | [
"I was sort of wondering if the gene to make Tth polymerase might be viral in origin from early in the evolution of ",
"- obviously viruses have the ability to implant their own genetic material within other organisms and of course it would make sense for an RNA virus to have a reverse transcriptase enzyme and co... | [
"Well I should add the caveat that I don't know a lot about the T. thermophilus natural habitat. Maybe it's full of manganese. ",
"But anyway, for enzymes that turn over substrate, the assumption is usually that magnesium is the physiological cofactor. I know Mn is in some enzymes as part of a permanent prostheti... |
[
"Why does the Higgs mechanism give the same mass everywhere?"
] | [
false
] | So symmetry breaking via the Higgs mechanism gives certain particles mass, right? But the symmetry breaking can happen in more than one way. I mean, that's what it essentially means, right? An arbitrary quantity becomes 'special', which breaks the symmetry, and the arbitrary quantity is part of a family of equally vali... | [
"Ok. Thanks for entertaining this string of questions."
] | [
"Ok. Thanks for entertaining this string of questions."
] | [
"Ah ok, so then in the case of the Higgs mechanism, you get the same vacuum expectation value of the higgs field regardless of the way the symmetry breaks, right?",
"Is there a form of symmetry breaking in the Standard Model that gives you different results depending on how exactly it happens?"
] |
[
"If gut bacteria in mice can effect obesity, presumably some similar effect can be manufactured in humans."
] | [
false
] | I read this article about gut bacteria transplants from obese mice, resulting in increased obesity in the recipient mouse; There are also some interesting articles about fecal transplants which are readily findable on google. This makes me think that someone should get right on a human analog straight away. Find some h... | [
"In regards to the paper you reference, they don't quite show what you are proposing. They show that microbiota from obese mice to normal mice promotes obesity, but they don't show the reverse; that microbiota from normal mice can revert obesity in obese mice. Since that is a simple experiment and it's not included... | [
"well at the very least, I would be interested in the mechanism by which the bacteria were causing the host to act in ways that resulted in obesity.",
"I guess the simplest mechanism would be for the gut bacteria to directly inhibit the vagus nerve, basically the opposite of this;\n",
"http://www.popsci.com/sci... | [
"I would be surprised if bacteria were causing their effects directly through the nervous system, particularly because obesity is much more than just impaired satiety and overeating. Additionally, you have to have dysregulated and skewed metabolism that promotes the accumulation of fats which is typically the resul... |
[
"How does a flamethrower prevent the back flow of combustion as it shoots a stream of ignited fuel?"
] | [
false
] | In a flamethrower like as the fuel gets shot out of the barrel, it gets ignited creating stream of fire. I'm assuming the fuel gets ignited after it exits the barrel, cause in the gif, theres no visible flame at the tip of the barrel. But how does the flamethrower prevent the flame from spreading into the barrel and i... | [
"This device has no barrel - it's a torch with a two handed grip, plain and simple. Fuel and air mix outside of the fuel hose, which allows combustion. Inside the fuel hose, there is nothing but fuel, so combustion cannot occur."
] | [
"Things need the fire triangle to burn. These are heat, fuel, and an oxidizing agent (for simplicity oxygen - O2). These 3 items all have minimum values they need to support their function. Example a little heat might not cause combustion but add a little more to the fuel/O2 and you get fire. The liquid fuel in the... | [
"Trying to think of a fuel that burns in the liquid state, but having trouble thinking of one, maybe you can help out? Gasoline, diesel, and kerosene does not burn in the liquid state. I don't even know if there is a liquid state of carbon, or if it would burn in that state. Paraffins doesn't burn in the liquid sta... |
[
"Can vaccines be made for any pathogen?"
] | [
false
] | null | [
"Cancer is not a pathogen. Pathogen is an infectious agent. ",
"https://en.wikipedia.org/wiki/Pathogen",
" ",
"Although some cancers are proved to be caused by viruses we can't do vaccine against cancer per se. We only can make vaccines against microorganism that cause cancers as we did against human papillom... | [
"We can make vaccines for every pathogen available. But it's not the fast process. Sometimes it's really hard to isolate the antigens.\nBacteries and viruses mutate therefore making of vaccines is very time and money consuming process. So scientists concentrated of making them for most dangerous pathogens which kil... | [
"Viruses (like HPV) tend to cause cancer because they have the ability to insert their DNA into the human genome. This can interrupt otherwise normal gene and cause misformed proteins to be made. Most vaccines are made by pinpointing a viral/bacterial “antigen” or protein expressed by the virus that immune cells ca... |
[
"Why does the earths core generate a magnetic field? "
] | [
false
] | null | [
"The rotation of liquid metals in the earths core is thought to create the magnetic field. This is known as the ",
"Dynamo theory"
] | [
"Probably an old e&m book?",
"The Earth-core Dynamo is much better understood today than back before the 1970s. Modern modeling even produces the chaotic pole-flipping. A few different teams are even building physical models (",
"sphere full of liquid metal",
", sodium pumped through tubes, etc.)"
] | [
"Just wanted to thank you for that interesting word."
] |
[
"Does soapy water flow through pipes more quickly than plain water?"
] | [
false
] | null | [
"Observations. It's not always true (for example, in low-pressure or low-density situations). But you can put tracer particles in a flow and watch how they move."
] | [
"Fluids obey the so-called ",
" condition, meaning that the fluid's velocity at surface of the pipe is exactly zero.",
"I've never studied fluid dynamics before but how do we know that fluids have a no slip at the boundary condition?"
] | [
"Fluids obey the so-called ",
" condition, meaning that the fluid's velocity at surface of the pipe is exactly zero.",
"I've never studied fluid dynamics before but how do we know that fluids have a no slip at the boundary condition?"
] |
[
"When were dates invented? And if it was a long time ago, how did they calculate 365 days for the earth to rotate around the sun?"
] | [
false
] | null | [
"It is quite easy to note the day of the year with the longest or shortest hours of daylight. All one needs do is count between two successive midsummer days and you'll get the number of days in a year.",
"We use the ",
"Gregorian calendar",
" adopted on 24 February 1582, itself a variation on the precursor J... | [
"As for your second question, ",
"Hipparchus",
" calculated the year to be 365 days by counting the days between two equinoxes using a ",
"armillary sphere",
"."
] | [
"Try ",
"/r/AskHistorians"
] |
[
"How fast would a spaceship need to go to reach Alpha Centauri in 1-2 months, and is that speed physically possible?"
] | [
false
] | null | [
"You would have to go 24-48 times the speed of light and that is not physically possible."
] | [
"I see. What about at 50% the speed of light with 8 years or 25% at 16 years?"
] | [
"It's four light years away."
] |
[
"If I stick my head out of a car window at 65 mph and try to look directly ahead I’m effectively blinded by the air rushing passed my eyes. How does a cheetah see and track prey when running at top speed?"
] | [
false
] | null | [
"Full disclosure, I'm an optometrist for humans, not for cheetahs.",
"It's because they (and many birds and reptiles) have a ",
"Nictitating Membrane",
".",
"It is a transparent ‘third eyelid’ that covers the eye and allows them to see while also maintaining protection over their cornea. From SeaWorld's web... | [
"Bunnies have a nictitating membrane as well. They use it to protect their eyes in a fight.",
"This can be problematic if you're trying to bond bunnies and they start going at it with each other which means you need to get in there and separate them. If they put down their membranes it messes up their already bad... | [
"I think, in addition to the nictitating membrane that ",
"/u/slevayyoung",
" mentioned, (Edit: actually, having thought about it, I'm not sure the nictitating membrane is involved at all) it also has to do with the amount of air being displaced by a car. A car is obviously much larger than a cheetah, so a larg... |
[
"Why don't solid things react?"
] | [
false
] | [deleted] | [
"No, its not true. ",
"There is an entire field of people",
" dedicating to studying the chemistry of the solid state. "
] | [
"Solids can react with liquids. ",
"Sodium reacts violently with water",
", for example."
] | [
"Cesium ",
"fucking explodes",
" when exposed to water. Does that count?"
] |
[
"Could Dark Matter explain Neutrinos traveling Faster Than Light?"
] | [
false
] | I was just musing to myself and thought of this...is it possible that Neutrinos have been observed by the OPERA experiment traveling faster than light because the emitted photons have been caught up and re-emitted by Dark Matter? The neutrinos, being highly non-interactive, would then arrive at the detector more quick... | [
"If photons interacted with dark matter, it wouldn't be dark."
] | [
"Dark matter is characterized by the fact that it doesn't interact with electromagnetism AT ALL, including the absorption and re-emission of photons. Light passes right through it unaffected."
] | [
"A little clarification on what seems to be your thoughts: c, the speed of light, is the speed that massless particles are thought to move at in our universe. When you hear talk of 'the speed of light in a vacuum' being different than the speed of light in a substance, that is a macro level observation of the aver... |
[
"Why is Planck temperature the hottest that something can get and what is happing to the atoms at that point?"
] | [
false
] | null | [
"The Planck temperature T_P is the scale of temperature at which quantum-gravitational effects are dominant. Quantum gravity prevents you from overcoming T_P (within an order of magnitude), making it a type of \"absolute hot\".",
"A way to heuristically understand that temperatures T quite larger than the Planck ... | [
"At temperature which I guess are around the 10",
" K mark even nuclei are unstable.",
"I don't think this is even close, to have K_b T equal to the binding energy of a nucleus you would need temperatures of the order of 10",
" K, 4 orders of magnitude higher. I suppose the real calculations would need to c... | [
"you're right, I knew I'd get that wrong. I moved it up to 10",
"K, I guess it's a more reasonable ballpark."
] |
[
"]The moon rotates the earth slow enough that it doesn't seem to move in realtime. Are there, or is it likely that there are planets in the universe where an observer like us would see an orbiting object move in realtime? Basically a faster moving moon or sun that I'd visibly moving to the naked eye."
] | [
false
] | The moon rotates the earth slow enough that it doesn't seem to move in realtime. Are there, or is it likely that there are planets in the universe where an observer like us would see an orbiting object move in realtime? Basically a faster moving moon or sun that is visibly moving to the naked eye. | [
"Here",
" is a real-time video of Mars' moon phobos transiting in front of the sun."
] | [
"The moon is visibly moving, you just aren't patient enough, or zoomed in enough, or watching for events that make it noticeable. Astronomers regularly watch ",
"Lunar Occulations",
" where the moon passes in front of a star. Many are ",
"naked eye events",
" since the star is quite bright. Like the upcomin... | [
"That's neat, thanks. So if I was on Mars I could see phobos moving like that?"
] |
[
"Why is it that if you run your hands under warm water after they have been outside in the cold, they get itchy?"
] | [
false
] | Im talkin like if you had a snowball fight, with bare hands. Then went inside and warmed them with hot tap water. | [
"Check out articles on \"urticaria.\" Your body could be releasing histamines in response to the sudden rise in body temperature. The kind of urticaria this falls under would be cholinergic urticaria. ",
"Edited to include a good link on how this works"
] | [
"The mostly likely explanation is that the rapid change in temperature either directly depolarizes the nerve cells responsible for sensing itch, or the change in temperature causes a nearby cell type to release itch mediators such as histamine, which would then go activate the aforementioned nerve cells. given the ... | [
"Yes this. This just a personal anecdote, but I live in a colder climate and whenever I go to run, for the first five minutes my legs get brutally itchy. Apparently it's somewhat common among runners."
] |
[
"Is it incorrect to say that something is from a 'different dimension' or 'parallel dimension'? Wouldn't it be from a different point on a dimension that everything is in?"
] | [
false
] | I think of a dimension as being like an axis on a graph. You're located , rather than , per se. So there could be a universe parallel to our own, meaning that it's located at a different point on some dimension, but to speak of a 'different dimension' or 'parallel dimension' is incorrect, right? This has always bot... | [
"yeah the sci-fi meaning of dimension is very different than our scientific one. ",
"this is what we usually mean"
] | [
"Part of your problem is that 'parallel dimension' is not a scientific term, did you mean parallel universe? So it appears you are making an argument about a term that a scientist wouldn't use.",
"A scientist would definitely be interested in finding additional spacial dimensions or parallel universes. But those ... | [
"Yeah, that was actually my point, that they say 'parallel dimension' when such a term is meaningless. They really mean a parallel universe, meaning that it's a universe located at a different point on some dimension beyond the first 4 (including time), to our own.",
"That's what I thought anyway, I was just seei... |
[
"Why aren't there an excessive amount of fossils right at the KT Boundary?"
] | [
false
] | I would assume (based on the fact that the layer represents the environmental devastation) that a large number of animals died right at that point but fossils seem to appear much earlier, why? | [
"If a mass extinction occurs over, say, 100 years, there are probably actually fewer deaths during that century than in the previous century. Over the course of any given century, pretty well every animal living at the start will have died. In a stable population, these will be replaced by new births and there will... | [
"To put it a different way, the number of animals alive at any one time is relatively small compared to the amount that die within a geologically identifiable period of time."
] | [
"The premise is false: ",
"66-million-year-old deathbed linked to dinosaur-killing meteor: Fossil site preserves animals killed within minutes of meteor impact -- ScienceDaily",
" ",
"Consider that fossilization is rare, so such finds will be rare, but it only takes one to comprise \"an excessive amount of f... |
[
"Do we have a wider field of view when our pupils dilate in the dark?"
] | [
false
] | In the dark our pupils get wider, which I would imagine means there is a larger angle of light that we can see, and the opposite for our pupils shrinking in brightness. Is this actually how it works? | [
"Your field of view is determined by a patch of light-sensitive receptors that activate neurons on the back of your eye. Additionally, the stereo image collection of two eyes. ",
"While more light is collected, the opening of your pupil does not significantly affect your maximum field of view. ",
"Think about i... | [
"The fact that lots of most commenters miss is that, unlike a camera which has a fixed sensor that is more than covered in a field of light going through the lens, the eye has a retina (\"film\") that covers the entire inside of the eyeball forward to roughly the midline. This is why ophthalmologists dilate your ey... | [
"Fish don’t have larger field of view because of eyes further apart - it’s because their eyes point different directions. Our eyes pointing the same direction trades the larger field of view for better depth perception in our limited field of view"
] |
[
"Why does defogging windshields require outside air?"
] | [
false
] | If I use the recirculate option with the air pointed at the windshield, it seems like the glass gets foggier, but if I use air from the outside, the fog goes away very fast. Why is this? | [
"The air inside has higher humidity, due to your presence.",
"When you run the defogger, it automatically uses the air conditioner, which removes humidity. If you turn it to the hot position the heat added from the engine cooling system overwhelms the cooling effect of the AC, but the moisture has been removed a... | [
"It is more important to blow dry air on the inner surface of the window than warm air",
"What about your rear defroster? (as we call them in the US) In many cars, mine included, this works purely on the principle of heating the window such that the temperature of the window is above that of the dew point of air... | [
"Indeed, but this is designed for the external frost. It also repels the internal fog, but is pure inductive heating by electric elements, not something you would ever get in a front windshield."
] |
[
"How to properly cite someone's work in a blog?"
] | [
false
] | null | [
"Thank you for your submission! Unfortunately, your submission has been removed for the following reason(s):",
"This is not a science-based question.",
"If you disagree with this decision, please send a message to the moderators."
] | [
"I am having hard time finding suitable subreddits. Cna you recommend? Thanks.,"
] | [
"Not really sure. Maybe ",
"/r/askacademia",
"."
] |
[
"Why are some substances easily absorbed by the skin while other substances are not?"
] | [
false
] | null | [
"It all about fat solubility and to a lesser extent molecular size. The more fat soluble a substance is the easier it is absorbed through the skin. That's why you can have fentanyl and GTN patches and steroid creams. A paracetamol or aspirin patch wouldn't get through the skin very easily. "
] | [
"And to supplement this correct answer, some papers:",
"Frasch, H. F. (2002) ",
"A random walk model of skin permeation",
". Risk Anal. 22, 265-276 (Obligatory immature comment: what a journal name!)",
"Potts, R. O., and Guy, R. H. (1992) ",
"Predicting skin permeability.",
" Pharm. Res. 9, 663-669",
... | [
"So is it because steroid creams are considered cholesterols that they are able to be absorbed through the skin more readily as compared to an aspirin patch?"
] |
[
"Is there a point where walking becomes more efficient that cycling when going up a steep hill?"
] | [
false
] | null | [
"This is an interesting question from a high school physics perspective. I'm not sure it is entirely answerable, because a lot would depend on how efficient the two machines are, how heavy the bike is, how heavy the runner is, coefficient of friction of tires, shoes, etc, which would require a few assumptions.",
... | [
"You also have to consider the bike wanting to roll back downhill. Friction holds you in place on foot, on a bike you are constantly fighting gravity pulling you back. It's the difference between picking something up and putting it on a shelf vs. holding it."
] | [
"That exact question is addressed in David Wilson's \"",
"Bicycle Science",
"\" book. Don't have the reference handy, but it is an interesting read."
] |
[
"Why don't we experience G forces from relative motion?"
] | [
false
] | I know that we are travelling an indeterminate speed through space due to Earth's rotation, it's orbit, the sun's galactic orbit, ect. My question is, since that motion constantly changes in direction due to it's circular nature, and acceleration is what causes us to feel G forces, why does changing velocity relative t... | [
"You've just discovered the equivalence principle.",
"The bottom line is that a change of direction or relative velocity is ",
" an acceleration … and being relatively stationary is not necessarily the absence of acceleration."
] | [
"Think of it this way: how do you feel a G-force when in a car taking a hard turn? You feel it in several ways, such as a pressure on your internal organs, the fluid in your inner ear rushing to one side, etc. You can feel these things because the car is only pushing on you from the outside, which changes the press... | [
"The equation is a=(2 pi/T)",
" r, where T is the time of the orbit and r is the radius.",
"Earth: T=24 hours, r=6380 km, a=0.003 g.",
"Sun: T=1 year, r=150 million km, a=0.0006 g",
"Galaxy: T=200 million years, r=30000 lightyears, a=0.00000000003 g"
] |
[
"Half life period of radioactive substance?"
] | [
false
] | I know that half life period is the the time required for a substance to decay half of it's initial amount.My question is that many radioactive element have a huge life time in order of billion years.so how some atoms of the radioactive substance stays without decaying for such a long time. radioactive elements are uns... | [
"...radioactive elements are unstable and and gain stability by decay process so why not every atom decay as fast as possible.",
"For the same reason any other kinetic process has varying lifetimes. Imagine a ball on a hill. It could be a very, very steep slope, so the ball rolls down quickly. It could be such a ... | [
"All atoms of a single element, yes. Atoms of different elements no. "
] | [
"I was under the impression OP was asking specifically about atoms of the same long half-life element.",
"So, the downhill ball example is not appropriate to explain why some atoms of the same element decay early and others not. ",
"The ball example is a classical view and the classical example does not provide... |
[
"Why does fire behave differently in zero gravity?"
] | [
false
] | I came across from another post and was wondering why gravity has any affect at all on fire. | [
"Ever blown on a lit candle? Notice how, by moving the air around the candle, you can get it to point different directions? That's because the shape of a flame is due to ",
" - hot air is less dense than cold air, thus will rise to the top, while cold air from the surrounding is drawn to the base of the flame.",
... | [
"Follow up question, would I be able to smoke a cigarette in space ?"
] | [
"Clarify; are you asking about in a vacuum, or in a space ship/station?"
] |
[
"When measuring length contraction/time dilation of an object in a medium other than a vacuum; do you account for the reduced speed of light?"
] | [
false
] | null | [
"No! The fact that it's light that travels at ~300,000km/s is irrelevant to special relativity; it was only the motivation behind it. What matters is that ",
" can travel ",
" than that speed. In fact, it's possible that light itself doesn't even travel that fast: There are experiments trying to determine (indi... | [
"How do they travel faster than light?"
] | [
"So say they are electrons and they have a couple MeV of energy, and their rest mass is only 1/2 MeV. That means they must be traveling at some 0.97c, where c is the cosmic speed limit ... regardless of how fast photons or light waves or anything else travels. If you're in a medium where light waves propagate at 0.... |
[
"If light can be interpreted as a stream of photon particles, then these particles' momentum must be subjected to the uncertainity principle. Does this mean the speed of light varies a little bit, or do these particles form an exception?"
] | [
false
] | null | [
"The momentum of a photon isn't based on its speed, it's based on its frequency or energy. The relationship is basically p=E/c=hf/c where p is momentum, E is energy, c is the speed of light, h is Planck's constant, and f is frequency.",
"As to whether the wavelength of light jiggles due to uncertainty; I don't ac... | [
"When you you introduce relativity then it becomes related to energy in the expression I just posted, instead of just p=mv. If m=0 then the relationship is just E=pc. If p=0 then the relationship is the familiar E=mc",
" ."
] | [
"E",
" =p",
" c",
" + m",
" c"
] |
[
"How can light put force on objects?"
] | [
false
] | So in my physics class our teacher mentined that up until Albert Einstein, Light were considered an electromagnetic wave-form (Translation may be incorrect, im swedish) but he found out that light can also be considered a particle (the photon). He showed this by taking a cameraflash or something, which light up very st... | [
"Could you elaborate on the sound a bit more? I find it very hard to believe that a flash or light could transfer enough momentum to a cymbal to make it sound. It could be more of a thermal effect, but even then that is unlikely.",
"The sound could have been the capacitor in the flash mechanism recharging. ",
"... | [
"which leads me to think that the photons would have had to slow down when transferring some of its momentum",
"This is where the problem comes from: momentum is only velocity dependent for massive objects. For light, the momentum is ",
" dependent. When light strikes an object and transfers some momentum to th... | [
"Does that also mean that higher frequency gives higher energy?"
] |
[
"How would different musical instruments react to being played in a zero gravity environment?"
] | [
false
] | For example, a piano, a guitar, a trumpet. | [
"Looking at a piano and how the keys work, it seem like the hammer striking the wire might be affected by gravity. Specifically, after it strikes the wire, it appears to fall back to its initial position due to gravity. (I know nothing about the internals of a piano except what the ",
"picture on wikipedia",
... | [
"This ",
" column",
" may answer your question."
] | [
"An issue may be one of stance. For instance a trumpeter may be able to propel themselves backwards."
] |
[
"Why do certain vaccines require a booster?"
] | [
false
] | Prevnar requires a booster called Pneumovax. From my understanding, the reason it requires a booster is that Prevnar and Pneumovax target different agents and, therefore, it creates different antibodies. In the case of shingrix and its booster, I don't think that the shingrix booster targets different variants of the d... | [
"It's to boost your titer high enough. After initial exposure to a challenge, you'll have a high response then scale back. Look at it like the US before we decided to keep a standing army. You build up your forces and after you win you don't want to be spending a bunch of money on an army for an enemy that is gone,... | [
"Certain vaccines such as the diphtheria vaccine do not produce absolute immunity. Instead it is a protective antitoxin vaccine (it contains the diphtheria toxoid) that lasts about 10 yrs, hence why a booster is needed once a decade. Tetanus vaccine as well delivers the tetanus toxoid and must be “boosted” to conti... | [
"Different pathogens and toxins have varying degrees of antigenicity, which is the ability\nto stimulate an immune response. \nIt might be about size or about glycoproteins on the coat.\nIf an organism has a very high degree of antigenicity, a booster vaccine may not be necessary.\nMost often it is best to challeng... |
[
"What is the minimum molecular density required to conduct sound?"
] | [
false
] | Everyone (I should think) knows that there is a relationship between molecular density and the potential for acoustic conductivity (I'm not a scientist, so forgive me for using the best descriptive terms I can muster.) For example: As I understand it, we hear sound "better" under water because water has a higher densit... | [
"Great question, and there's a surprisingly simple answer.",
"Basically, if you want sound to be supported, you want the medium to look \"continuous\" to the wave. Otherwise, too much of the energy gets scattered and turned into heat. The more continuous, the better the wave will conduct.",
"Of course, \"contin... | [
"As far as I know, there is no minimum, at least for sound in the purest sense (there is undoubtedly a minimum density required for your ear drums to register sound waves, but that doesn't seem like the question you're asking). \"Sound waves\", or acoustic oscillations as they're generally called outside the realm... | [
"So cool. Appreciated!"
] |
[
"What is the lowest radio frequency?"
] | [
false
] | Is there a minimum frequency for electromagnetic radiation? Below a certain frequency, would the energy of each photon be below some quantum limit? Do AC power lines emit photons of 60Hz (50Hz) radiation? Would there be any effects one could test for to exhibit the particle nature of such low frequency radiation? | [
"There is no lower limit to radio frequency. All radiation has a quanta of hv, where v is the frequency and h is planck's constant.",
"Below a certain energy, it gets hard to detect individual photons, so then radiation is detected with antennas. Antennas need to be a good fraction of the wavelength of radiation... | [
"I can think of one minimum, but it's not very helpful: 2 attohertz = 2x10",
" Hz. Any oscillatory process that radiates photons with a frequency smaller than that would take longer than the age of the universe to complete.",
"In principle, there's no lowest frequency, but very low frequency photons are very h... | [
"Wikipedia: Communication with submarines",
" (with pic)"
] |
[
"Does fat spoil in the body? Does the body keep track of what fat is newer, and \"rotate stock\", so to speak?"
] | [
false
] | null | [
"Fats are also called lipids (I will use this term later). When fat spoils, it is called ",
"rancidification",
". Fat in our bodies is stored in special types of cells called ",
"adipocytes",
". ",
"When our bodies store energy, these adipocytes take up more fat, and they can proliferate, too. When ou... | [
"This is a wonderfully understandable reply. I especially loved \"Again, you are not going to wake up one day and find that the fat in your butt has gone rancid because you didn't ingest enough antioxidants.\""
] | [
"Brave, but stupid."
] |
[
"If everything in the Universe is constantly expanding, can/do we measure changes in size/space on an atomic level?"
] | [
false
] | null | [
"No. The expansion only applies on the largest scales. On smaller scales where you have things like galaxies and planets, there is no real expansion.",
"But be careful, because this is the sort of question that often gets people saying things which are completely incorrect. As a rule of thumb, if someone says tha... | [
"No, the expansion of the universe only effects objects that are not bound by other forces. In this sense everything in our own galaxy and the galaxies around ours are not effected by expansion. Only galaxies and clusters not gravitationally bound to one another are effected by the universes expansion."
] | [
"At what scale does expansion stop (assuming no cosmological constant)? To me, it doesn't seem right that there is a sudden discontinuity between expansion and non-expansion. Shouldn't there be galaxies in between, that are weakly expanding?"
] |
[
"Is there a way to describe the growpattern of a tree mathematically?"
] | [
false
] | Im interested in the texture cuts have for cg reasons. The wood texture generator is really bad though since there are no rings for branches in vertical cuts and so on... If someone has already done it, where can I find it? If not, why is it so hard to do? | [
"i did a research project in college that studied the reiterative nature of tree branches and showed that stresses on a tree branch (both from environmental factors and the weight of previously grown offshoots) affected the future growth patterns of the branch"
] | [
"Not completely accurately but there a few different ways. I think the best way to generate something that looks like a plant or tree is an L-system.",
"http://en.wikipedia.org/wiki/L-system",
"I'll just mention this because I can't remember how it works but power series have some deep relation to botany. I bel... | [
"Yes, this. You don't want fractals or L-systems, those are hacks that react to some of the observed shapes of trees. Instead, to make accurate CG trees, you need to \"grow\" them, as their shapes are very strongly influenced by their lifetime history of light, nutrients, water, and (most appropriate to your questi... |
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