title list | over_18 list | post_content stringlengths 0 9.37k ⌀ | C1 list | C2 list | C3 list |
|---|---|---|---|---|---|
[
"Why is it a lightbulb can light up a room more than a fireplace, but the fireplace radiates a lot more thermal energy? . Or atleast so it feels like."
] | [
false
] | Question is basically in the title. I just wondered since thermal radiation is basically electromagnetic waves right? Or am i missing something? And shouldnt the intensity light=intensity of heat.. Only thing i could think of would be that the fireplace maybe is radiating a lot of its heat in the invisible spectrum? Just to make no confusion, since many answered this part. I meant that the radiating part of heat alone is stronger from a fireplace than a lightbulb. I know that the fireplace for obvious reasons will transfer also a lot of heat through convection/conduction too that a lightbulb won't do as much of because for one it's smaller. Some did answer what I was looking for though, specially thanks to them and thanks to everyone else who answered :) | [
"Radiation of thermal energy (as opposed to conduction of thermal energy) ",
" light, so when you say a fire feels very warm, it's because it ",
" producing lots of light, just not in the visible spectrum. ",
"Light bulbs were specifically designed to use materials that produce most of their radiation in the ... | [
"I was going to downvote you for the ridiculous '100% or more efficient' bit, but it turns out that these LEDs absorb heat from their surroundings to produce the extra light, so if you are only considering the electrical input and not the heat input this is technically correct. Interesting!"
] | [
"Not true. LEDs are capable of producing 100% or more efficient optical light emission. ",
"Source"
] |
[
"Does a car run more efficiently on a full tank vs. a half-full tank?"
] | [
false
] | if not, is there a point where driving is less efficient? ex. 1/4 of a tank or almost empty | [
"The less gas in the tank the less the mass you have to lug around meaning it is always more efficient to carry less. That being said a full tank of gas weighs about 100lbs while a car weighs 4,000lbs so the difference in efficient is quite small. About 1% at a 1/2 tank assuming 20mpg."
] | [
"In modern cars the fuel flow is tightly controlled. Pressure from the tank should have no influence on the fuel injection system. (Much) Older carburettors might be more susceptible to the feed pressure although where the sweet point is would depend on the particular car."
] | [
"If I remember correctly it is the fumes the gas gives off that is the combustible part of the gas not the liquid itself therefore as long as you have a large volume of the fumes the amount of actually liquid doesn't matter."
] |
[
"What is our current progress behind Stem Cell research and what would its immediate uses be?"
] | [
false
] | I'm curious to how close we are to using stem cells for applications in which they would apply to. From the little that I do know about about them I recall that we produce them from cloned fetuses and genetically engineering them (not sure about this one). I only remember that they have the potential to regrow parts of the human body, would things like healing scars, regrowing teeth and limbs be possible? I have no idea what the most up to date information is on it, are we close? | [
"Stem cell research has boomed over the last few decades, resulting in a large amount of possibilities for cures in human bodies. Stem cells are found in their best conditions in embryos, and growing these stem cells in controlled conditions can result in beating hearts, functioning lungs (when placed into a human ... | [
"What is big right now is the use of 3D printing to \"print\" out new organs using a scaffold and the appropriate cells and growth media. I imagine we'll see huge strides in the next 10-15 years.",
"One of the major problems with stem cells is that certain individuals are not comfortable with human embryonic stem... | [
"That's intriguing that you could live much longer with the use of them and that governments would look down upon that. Almost seems reminiscent of that movie The Island. I suppose with increasing research and experience with stem cells the cost for growing the cells will become more reasonable."
] |
[
"Why and how can Parrots and a few other birds talk?..and is there any animals that talk that the common person doesn't know about?"
] | [
false
] | My main point is to get a good understanding of how a bird learned to talk through the evolutionary timeline and why? | [
"That's a bad example. Lyrebirds are fantastic mimics with zero understanding. ",
"However, many other species don't act that way. So for example, African Grey Parrots will use words from humans but won't generally try to imitate sounds around them unless they are actively from living creatures. so an African Gr... | [
"Corvids are considered some of the most intelligent birds on the planet.",
"Studies on magpies show that they possess self awareness, and many people speculate crows and ravens (cousins of magpies) possess the same cognitive behavior. There have been multiple studies on the intelligence of Crows and Ravens. Most... | [
"By talk do you mean repeat human sounds? Lots of animals talk, just not in English. Animal communication encompasses visual, chemical, auditory, and vibrational signals. In most birds, vocalizations like song and calls convey information, and in some species (e.g. mockingbirds, starlings, lyrebirds) females pref... |
[
"Can the black and white TV static create a picture momentarily through randomness?"
] | [
false
] | null | [
"Hi PsychSpace 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 foll... | [
"'mathematics'"
] | [
"'Mathematics'"
] |
[
"Why does hot water freeze faster than cold water?"
] | [
false
] | null | [
"Out of the box, hot water does not freeze faster than cold water:",
"The cold water froze about 10 or 15 minutes faster than the hot water, and there was no detectable difference between the boiled water and the other kind. Another old wives’ tale thus emphatically bites the dust. Science marches on.",
"--",
... | [
"Absolutely not unusual. Our scientific knowledge is vast but the Universe is far vaster, so our knowledge is actually remarkably thin almost everywhere. There are innumerable commonplace phenomena that you only need to dig into a few steps to find a mystery that is currently unanswered by science (like, for exampl... | [
"I’m so shocked at the fact that we don’t know. I mean, us humans don’t know everything leading to the unknown mysteries. ",
"The idea of this question is so simple, but scientifically so complicated. ",
"Thanks for the responses. I’ve been thinking on this question for weeks beyond end. I’m so glad humanity ha... |
[
"Is there a scientific explanation for a beer gut? Are they even real, or the result of being inactive?"
] | [
false
] | null | [
"Beer contains a high amount of calories. That is really why beer became popular. Back in the old days it was a good way to store cereal and grain crops to keep them from spoiling while maintaining the nutritional value. Many of the variations in styles of beers can be attributed to what grew well in particular ar... | [
"At least according to this study, no causal link between beer consumption and abdominal obesity, at least not as opposed to consumption of wine/liquor. ",
"http://www.nature.com/ejcn/journal/v57/n10/full/1601678a.html",
"BBC news article about said study.",
"http://news.bbc.co.uk/2/hi/health/3175488.stm"
] | [
"Yes. It's important to note that alcoholic beverages contain a lot of calories, both in the sweeteners used to combat alcohol's bitter taste (sugar is 4 calories per gram) but also the alcohol itself. Alcohol contains almost as many calories as fat (7 calories per gram versus 9 calories per gram). 4 oz of vodka... |
[
"What are the velocities of the arms of the milky way?"
] | [
false
] | [deleted] | [
"Something that you need to consider here is that the arms do not spin like a pin wheel. Rather the stars orbit the center of the galaxy independently of the arms. The arms are like compression waves in a traffic jam. Measuring the speed of the stars will not tell you the speed that the traffic jam is moving. "
] | [
"The arms and the orbit of the stars aren't the same thing, basically. It's not a group of stars spinning around in the arm like a pinwheel, the 'arm' is a wave moving through the disc of the galaxy, bunching stars up locally.",
"There are animations on the wikipedia page that should help. ",
"https://en.m.wik... | [
"The arms of a spiral galaxy aren't really \"objects\" though so I'm not sure it's even meaningful to assign them a speed. They are areas of higher stellar density caused by the cumulative motion of individual stars around the galactic core (and up and down through the galactic disc). Put another way galactic arms ... |
[
"What are the differences between comets, asteroids, meteors, and meteorites?"
] | [
false
] | Seriously? Is it the size, what they're made of, what? Please, science, enlighten me! | [
"Asteroids are from the ",
"Asteroid Belt",
", located between Mars and Jupiter. Asteroids are mostly rocky. Some asteroids have migrated from the Asteroid Belt region. If an asteroid is in near-Earth space, they're called a Near Earth Asteroid. If it moved to the region between Jupiter and Neptune, it would be... | [
"I agree with you except for the last part. You say pluto and eris are astroids (or comets) that are big enough to be dwarf planets but aren't pluto and eris kuiper belt objects and not astroids?"
] | [
"You're right, they definitely aren't asteroids. Some people will call Eris and Pluto comets, which is why I put them in that list meaning for them to be understood as part of the '(and comets)'."
] |
[
"O.k., I've heard this a thousand times, that burr grinding will make a better cup of coffee because the grounds are more uniform. Does this really matter in a French press application if there is just as much total surface area touching the hot water?"
] | [
false
] | null | [
"If coffee is over-exposed to hot water, the water extracts bitter compounds from the grounds. The more finely ground the coffee is the less time it takes to extract the bitter compounds, and the faster your coffee turns bitter. The coarser the coffee is the longer it takes to extract the desirable coffee flavor.",... | [
"The reason I asked in the first place is that I've just not found that to be true. ",
"I do pour out all the coffee after pressing into a separate container; I don't find that any slurry is making it more bitter as it sits. Perhaps because it's not in an insulated container and gets too cool to make a difference... | [
"I already wrote a brief answer but deleted it once I started having second thoughts.",
"My initial answer was that yes, uniformity matters greatly because each ground dissolves individually. If you have a mixture of ground sizes, the finer grounds will produce overextracted coffee by the time the larger grounds ... |
[
"Will hot tap water contain more minerals or chemicals than cold tap water?"
] | [
false
] | I've heard from someone that warm tap water will collect minerals or chemicals from the pipes that cold water will not or it will carry more of them. I've googled it a little and people are saying it has to do with solvency of the particles in the water or that hot water has been in the pipe longer. Others say that it is/was actually leaching lead from the solder used before 1988. What it boils down to is this, is this an old wives tale or is there some evidence to support using cold water over hot water from the tap? Are there more minerals in hot water versus tap? Is/was it just an issue with lead, but people continue it even though lead isnt in solder any more? Is there something I'm missing entirely that supports (or refutes) this? Thank you, scientists, for your help! Edit: thanks again for the help. I was hoping for more of a comparison as well. For example, all tap water travels through X amount of pipe, before some of it goes into the hot water heater. Where ever this water is coming from, wouldnt it also be sitting in some tank or pipes or w/e. Is the difference from sitting in the water heater, or being heated up and then going through pipes significant when compared to cold tap water? | [
"Most hot water tanks have a sacrificial anode made of magnesium or aluminum. The anode is designed to purposely corrode and prevent rust in the rest of the tank. So yes, water coming from a hot-water tank will contain a higher mineral content then cold water. That is my understanding of why things like coffee ... | [
"Do these minerals have any ill effects when ingested in higher quantities? My grandmother always freaked out when I used hot water from the tap to mix my daughter's bottles - is there a legitimate concern there?"
] | [
"In both thermodynamic and kinetic terms, hot water is able to dissolve more things at a faster rate than cold water."
] |
[
"Is the Earth's gravity lessened by it's spinning?"
] | [
false
] | [deleted] | [
"The momentum granted to you by the spinning of the Earth does have a tendency to move you away from the Earth, and without gravity it would certainly fling you into space. With the effect of gravity, it has the effect of slightly resisting gravity.",
"But the spinning of the Earth creates more than a centrifugal... | [
"A small additional note - those 2 trillion kilograms may seem a lot to us, but compared to the mass of whole Earth (~6*10",
" kg) it isn't much. Those 2*10",
" kg are just a ",
" of Earth's mass."
] | [
"I wish you hadn't said that, I wanted to make it sound like a big deal."
] |
[
"Why does hydrogen not exist naturally as a metal?"
] | [
false
] | Lithium with only 2 extra protons is a solid at room temperature (and is a metal). Why could hydrogen protons not be connected in a lattice with shared electrons bonding them (like a metal)? | [
"Such a state is theorized to exist, possibly in great amounts in Jupiter and Saturn. It requires extreme pressure like what is found in Jupiter and Saturn, and is a liquid. Actual observation is disputed. ",
"http://en.wikipedia.org/wiki/Metallic_hydrogen"
] | [
"When you're talking at an atomic scale 2 more protons is a decent amount of weight and it's not just protons there are also neutrons which is why Lithium has almost 7 times the atomic weight of hydrogen. Basing the ability to be solid at room temperature on weight/proton content would also disregard other elements... | [
"Makes sense. How come Lithium doesn't bond with itself given that it also has only one electron in its outer shell?"
] |
[
"Why does steam come off of my water container?"
] | [
false
] | I drink my water out of a metal bottle thingy. When I put extra cold water in it from the sink it appears that steam is coming off of it. A) anyone else experience this? and b) what is it? | [
"A) Yep",
"B) It should happen when you open your freezer on a humid day. It's just water vapor in the air getting cold enough to condense into little water droplets that look like wisps of steam."
] | [
"It is analogous to what happens to your breath in cold days. Moisture in your breath condenses down because of the colder air outside cools down the air you just expelled. ",
"In your water thingie you're probably seeing convection currents but I guess you probably live in a very humid place. "
] | [
"Thanks! That was bugging me"
] |
[
"[Q] Can a strong immune system in a female negativly affect chances to become pregnant?"
] | [
false
] | . | [
"Semen contains chemicals that suppress the immune system.\nSperm are treated as non-self by the body\nhere is an abstract on the topic; the article is not free.\n",
"http://humrep.oxfordjournals.org/content/10/7/1686"
] | [
"Most definitely, both in the stages of becoming pregnant, and in the stages of pregnancy itself. Although I wouldn't use the term 'strong' immune system, as it's a bit of a misnomer, there are immune complications that can affect chances of becoming pregnant. ",
"Leaving auto-immune diseases aside, as they affec... | [
"That's a great source, thank you!"
] |
[
"At what point along the evolutionary track did humans become sentient? What makes a species sentient?"
] | [
false
] | What differentiates homo sapiens from homo neanderthalensis in terms of intelligence? What about their common ancestor, homo heidelbergensis? What are the prerequisites for sentience, for example clothing or hunting techniques? | [
"There is no way of exactly knowing if an animal has ",
"theory of mind",
" yet we can try to find out by using carefully constructed behavioural tests as well as including observational data on day to day behaviours of individuals. One example might be ",
"the mirror test",
": \"to determine whether an ani... | [
"What an amazing response! Thanks so much!"
] | [
"Just a clarification: ",
" are \"the group consisting of all modern and extinct Great Apes (that is, modern humans, chimpanzees, bonobos gorillas and orang-utans plus all their immediate ancestors).\" The last common ancestor for all these species (i.e. what would have been considered the first \"great ape\" liv... |
[
"Is their a theoretical limit to how big a supermassive black hole can be?"
] | [
false
] | I was reading article about attempts to measure the actual radius of black holes. It got me thinking...is there a limit to exactly how big a black whole could be? Could one, assuming it ate enough matter, become as big as entire solar systems or larger? If not, what would happen once it reached some limit? edit: and yes I know I used the wrong 'there' in the the title. | [
"Currently, there is no theoretical limit on how large a Black Hole could be. If it ate up a billion galaxies worth of matter, it wouldn't have any stability issues. ",
"If this got you thinking, read ",
"this",
". "
] | [
"There's no limit as far as we know."
] | [
"Depending on your definition, the universe has some properties of a black hole."
] |
[
"If capsaicin attacks our taste buds directly, what about spicy foods make us physically hot or sweat when eating them?"
] | [
false
] | [deleted] | [
"What do you mean \"attacks our taste buds directly\"?",
"You don't get physically hot from capsaicin. IT binds to and activates the TRPV1 heat receptor. Your brain just thinks you're hot. (This has been asked and answered many times before)"
] | [
"Self recycled answer:",
"Capsaicin acts by by turning on the ",
"TRPV1 receptor",
". This receptor is sensitive to heat and several other chemical stimuli, but is not limited to the tongue. TRPV1 is present in the entire central nervous system. The trick to alleviateing the burning sensation (Remember that... | [
"I'm not so sure about sugar water, but milk certainly works. Capsaicin is hydrophobic and doesn't get washed away well with water. Milk (specifically caseins in the milk) has a detergent effect on capsaicin. "
] |
[
"What else could the amount of energy that a human uses be used for?"
] | [
false
] | I.E. would the amount of energy used by a single person be enough to power a computer, a car for a day - and similarly how many peoples energy would you need to power something like a boat, an office block or a nation? | [
"Assuming 2000 Calories for daily intake:\n The energy would be equivalent to 1/16 the combustion energy of a gallon of gasoline. Which would drive my truck about 1 mile. "
] | [
"Really? downvoted for an on-topic joke that isn't an anecdote, layman speculation, meme or medical advice?",
"Agent Smith must have an account on Reddit ..."
] | [
"Or the matrix for about .0005 seconds."
] |
[
"How do denatured proteins in cooked food get absorbed and \"used\" in the body?"
] | [
false
] | What I mean is: Proteins are essential components in the body for building all kind of things like building enzymes....I also know that proteins denature at high temperature and that this process is irreversible as you destroy the disulfide bond between the amino-acids. So if you cook your food for example an egg you are destroying the proteins conformation. How can it still be used in the body? Does the body regenerate the aminoacids for usage? | [
"You already solved it - proteins are made from amino acids. Denaturing a protein just changes the conformation (shape) irreversibly. Your body would do that when you eat it. You need 22(?) essential amino acids in your diet that your body can't produce. Your body breaks down those amino acid chains and reconfigure... | [
"There are 8 that cannot be synthesized by the human body: ",
"isoleucine",
"leucine",
"lysine",
"threonine",
"tryptophan",
"phenylalanine",
"valine",
"*methionine",
"There are 2 which can be synthesized, but studies have suggested insufficient productions (especially in infants):",
"*arginine "... | [
"There are only 8 or 9 \"essential\" amino acids for humans. The rest of them can usually be made by the body when necessary."
] |
[
"Why do clouds stay in \"puffs\" rather than just diffusing out all over the sky?"
] | [
false
] | Specifically nice big well defined clouds - what is keeping the water vapor or temperature difference from just equalizing? | [
"I'm a meteorologist. Hopefully I haven't screwed this up but I'm a bit out of practice since I spend most of my time at work looking at satellite pictures, radar, and weather models. Not on the science.",
"I believe the simplest answer is that in these clouds, the rate at which water vapor mixes out of a cloud t... | [
"Hi. You did teach me something about clouds and I am very thankful for that. "
] | [
"Do you have any source of that? It almost seems like it would make sense, but I'm doubting it. I would think that the water molecules are too spread out in water vapor. It feels like an effect due to \"water tension\"/\"airborne tensions\" would be negligable or nonexistent. ",
"Edit: Wow... ",
"/u/Pyreload",
... |
[
"Genetic diversity between dog breeds?"
] | [
false
] | [deleted] | [
"There is so much to unpack in that question (of what makes a species) that I don’t think I can really do it justice, because there are entire areas of biology devoted ONLY to that question. So I’ll tackle the easy one: Yes, presuming that the physics of inserting tab A into slot B didn’t get in the way, a Great ... | [
"What makes two breeds different is a collection of phenotypical traits. There are genes that control the appearance of the hair, the color of the hair, the shape of the head, the set of the ears, and so on. Different breeds have different collections of genes, and they have been bred so that they ONLY have that ... | [
"The only difference between a Great Dane and a Chihuahua is that of phenotype.",
"",
"I have a different question. A German shepherd and a Eurasian wolf look much more similar to each other than Great Dane and Chihuahua do. Also the former pair can interbreed and I am not sure about the later. How do we decid... |
[
"Why do immune reactions take place in the lymph nodes closest to the site of infection?"
] | [
false
] | From what I learned in high school, every B cell in every lymph node is entirely unique since the structure of the surface receptors is randomly generated, causing each B cell to recognise a different antigen. However, whenever there is an infection in the body, it always seems like the closest lymph nodes are the ones active, eg. under the jaw during a cold, or under the armpit after a vaccine. Wouldn’t there be just as much chance that the B cell able to identify your sore throat antigens lives in a lymph node further from the site of infection like the groin, ect.? Does the B cell travel to a closer lymph node once activated? Or are there many different B cells that can recognise an antigen to varying degrees, and the closest ones mount the fastest immune response, even if a B cell further away could do a better job? | [
"Your body has dendritic cells in basically every tissue, so when an infection happens the dendritic cell will mature and lose its adhesion to the tissue. After that it will follow a chemokine trail to the nearest lymp node where it will present the antigen to mature B and T cells in the lymph node. Your lymp nodes... | [
"The last sentence you wrote is essentially correct. The b cell that gets activated first, regardless of affinity, is the one that gets clonally replicated. Those clones have some randomization of their antigen matching site -> the ones that bind better get selected for future cloning -> ad infinitum until infectio... | [
"In addition to the other answers, antigen naive (i.e. never-before activated) B and T cells circulate constantly between lymph nodes and blood. This maximises the chances of B and T cells finding their antigen and responding, even if the antigen is only found in those lymph nodes nearest to the infection."
] |
[
"It is said that the universe has no end, and is ever-expanding. But, assuming that we had a way to travel to (and possibly even beyond) the \"edge\" of the universe faster than it was expanding, what would we expect to be there? What would it look like? What would it even feel like?"
] | [
false
] | null | [
"This question can be found in our FAQ, along with others you may find interesting. Please take a look and let us know if you have any follow up questions. "
] | [
"This exact question? Not to be rude, but I can't find it. "
] | [
"You're asking what the universe is expanding into. There's a section on the ",
"expansion of the universe",
", including ",
"this post",
". "
] |
[
"How do quantum dots (>20nm) absorve and release vidible light (<400nm) if they are smaller than the visible light wavelength?"
] | [
false
] | Actually as I'm writing this question I also don't understand how we see materials, we do obviously see them but the atoms are smaller than the wavelength we see, so what is happening? Can atoms emit wavelengths bigger than their size? How? Or do we just see the cristaline structure of a bunch of atoms? | [
"Part of this answer is simple: the wavelength of radiation an object can emit is in no way limited by their size. Let's take a simple analogy, imagine you are standing on the short of a still lake with stick in your hand. If you tap the water periodically, you can create ripples that will radiate outward. You can ... | [
"I also don't understand how we see materials, we do obviously see them but the atoms are smaller than the wavelength we see",
"But you don't see the individual atoms, you see a material consisting of billions of billions of atoms. A material does ",
" behave just like a large pile of atoms, virtually all prope... | [
"For example the blue halo in nuclear reactors comes from accelerating electrons. ",
"Their acceleration is not the relevant point. To emit Cherenkov radiation they just have to move faster than the speed of light in this medium. Sure, they lose some energy doing so, which changes their speed, but that's not the ... |
[
"Is there a sequence of moves that can be applied to a Rubik's Cube that results in iterating the cube through every possible state exactly once?"
] | [
false
] | null | [
"No. Take two moves, a and b, that don't commute, that is, doing a then b results in a different state than doing b then a. For example, twists of two adjacent faces. Now say that your magic move, g, done m times, results in a, and done n times, results in b. Now ab=(g",
")(g",
")=g",
"=g",
"=(g",
")(g",
... | [
"It always fucks with me when someone solves a problem using group theory. It's so simple and yet I have zero intuition for it."
] | [
"The second one is called Hamiltonian circuit and if you ask google about that, it says that yes, it exists, ",
"for example",
"."
] |
[
"Do small things (such as flies) view the movement of larger things (such as humans) as \"slower\" than we perceive it?"
] | [
false
] | I was thinking about how in movies and whatnot you will have something massive swing its fist and it will seem "slower" than a normal fist swing because of the relative distance it covers (for you it covers a large distance, for the massive thing it covers a short distance). Does this relative difference make the perception of the speed of the object any faster or slower? | [
"They can move across a landscape quicker than the speed of light in the same way a shadow can move quicker than the speed of light. Here is a wikipedia article with references: ",
"Faster-than-light: Light spots and shadows"
] | [
"Hundreds of experiments with cockroaches reveal they suck at bullet time.I'm sure someone else will time how long it takes a survival impulse to travel to an insect's legs and make their tiny muscles do things for their size that would make them superheroes; and who knows how a lack of a consciousness would make t... | [
"I'm sorry I have to shut you down like this, but deadly space lasers are beams of light in the first place, and can't go any faster than it's own speed. Sorry again!",
"Just wanted to clear it up in case some poor redditor didn't already know this."
] |
[
"Why do humans have different eye colors? Were they ever an evolutionary advantage?"
] | [
false
] | To my knowledge eye color doesn't affect your vision, and the only role I can imagine it plays in selection is an aesthetic one. Or is it perhaps desirable eye colors are linked to other desirable traits? | [
"A bit off-topic:",
"You should take a step away from the idea that evolution only 'creates' something because it would be advantageous to the species. Evolution is much more chaotic than you may think. Things just happen more or less by accident (mutation), and if these mutated species somehow survive (even if t... | [
"There is some material on blue eyes in Cochran and Harpendings ",
"The 10,000 year explosion",
". I'll try to summarize:",
"\n75% of eye color variation in Europe is caused by a single allele of the OCA2 gene. It's a very new allele, only between 10,000-6000 years old, so it must have a strong selective adva... | [
"Further, why is it that only those of European descent (read: white people) have shades of eye colour different than dark brown? I've read that blue, green and grey eyes originate from Northern Europe, but that's about it."
] |
[
"Is neural activity affected by quantum uncertainty? Or are neurons too big for that?"
] | [
false
] | As far as I know, things are pretty much predictable at our level--you can predict a bullet's trajectory, whereas it seems you can't really predict a photon's. However, if it turns out that neural activity occurs on a small enough scale that things like quantum tunneling come into play, then perhaps our minds will never be predictable. | [
"We don't know. People have argued on both sides, and there isn't any evidence supporting quantum implications in neural activity in a major way. ",
"My opinion, as someone educated in QM, is that it's very likely no. The brain is too warm and the molecules too big for quantum behaviour to be a dominant part of t... | [
"This is just a technical point, but it is often missed by people who have not heard of chaos before. A chaotic system is ",
" unpredictable in the strict sense of the word, since it is deterministic. It is just very difficult to guess the behaviour of a chaotic system for one set of initial conditions based on t... | [
"(Computational condensed matter researcher here). As current theory goes, decoherence starts around mesoscale, unless you're pretty close to 0 K (",
"http://www.nature.com/news/2010/100317/full/news.2010.130.html",
"). Due to blood flow, the brain should be at a higher temperature than the rest of the body, ... |
[
"Do satellites, like the Hubble Telescope, get dirty?"
] | [
false
] | I just saw a question asking about the remaining lifespan of the Hubble Space Telescope, and I was wondering if there is anything in space that causes satellites to get dirty, or rust, or otherwise deteriorate. | [
"Yes.",
"The space environment is pretty nasty. Atomic Oxygen, UV Radiation, Meteoroids/Orbital Debris all cause pretty severe surface degradation.",
"Here's a video explaining the effects of atomic oxygen ",
"https://youtu.be/bjyv7bK9X74",
"Here's a video explaining the effects of radiation on spacecraft "... | [
"This is one reason Gold is used in Satellites. It Reflects radiation and does not corrode. ",
"If you see a Satellite that looks like it is wrapped in a gold Mylar Blanket that is not gold it is a Polymer called Kapton with an aluminum backing which is a different type of Mylar Blanket and is an MLI, Multi Laye... | [
"Surface degradation isn't really the same thing as being dirty though. Dirt can be cleaned, in principle. Degradation is irreversible without replacing degraded parts."
] |
[
"There's still time to start a project for the first Reddit Science Fair, hosted by AskScience!"
] | [
false
] | To all those forty thousand redditors who have joined AskScience since this was posted... You remember science fairs... a bunch of kids do science experiments, and present the results. It's the same thing here, except on Reddit, hosted by ! The Reddit admins have agreed to donate some awesome prizes, and AskScience will give you some sweet flair on our subreddit. Create and run an experiment by November 28th at 11:59 PM! This fair is all about , not . Make sure you're answering a question, and make sure you remember to hypothesize. Plan your experiment and complete it, making sure to spend no more than $40 US. After your experiment is done, write it up! Tell us what you did, what you learned, and what your conclusion is. Make sure you sum up the whole project in a one-paragraph abstract, too! Then post it to , again by November 28th at 11:59 PM. Make sure you do it before the deadline. After some judging-time, we'll make a post with some awesome prizes! Keep an eye out, because the AskScience panelists will be doing weekly workshops on Doing Science The Scientific Way (things like coming up with questions, making graphs, looking at data). These workshops will be at . ** and to keep up-to-date with the latest AskScience Fair developments!* Creativity! DIY materials! Testable ideas! Graphs! Pictures! Analysis! Friends or family! (Teams are ok, and so's doing it by yourself!) There's no age limit. There's no subject limit , but here are some things that aren't ok: Experiments with humans without their written consent aren't ok. Experiments that threaten community safety are not ok. No experiments with DEA-controlled substances or potentially hazardous biological agents. Unless you need to ask us about whether an experiment is ok, there's no need to tell us what your experiment's going to be. If you need help, feel free to post on . There are quite a few AskScience panelists who've volunteered to help out with questions. AskScience panelists are not eligible to compete. Judges are AskScience panelists who have agreed to help out on a volunteer basis. . While things you have lying around don't count as part of your $40 budget, keep in mind that following the spirit of the budget rule (intended to keep everyone on a level playing field) is a factor in scoring. Be creative! Judges might want some proof that you've stayed inside the cost limit. Keep your receipts. Projects need to be posted as threads on before to be considered. No late submissions. Your project must be developed for THIS contest, not something you've been working on for 4 months already. Give us anything you want in terms of format (link to a picture, link to a PDF, link to a Google document, link to the past), but it must include an "abstract" at the beginning telling us briefly what you did and found. An abstract is a short paragraph or two summarizing the main points or important ideas presented in your project. Try to avoid long youtube videos. In fact, try and avoid presenting your project in youtube format at all, unless you feel it really adds something. : When the deadline's passed, the projects will be randomly assigned to three judges each. That way it's not the same panel dealing with each project, and there won't be as much effect from individual scoring styles. Judges will be volunteer AskScience panelists. Each project will be scored by the scoring rubric, and the top three projects by score will receive prizes. Each judge will score projects to a maximum of 100 points, awarded as follows: Judges may post or PM questions to the entrants if they'd like further clarification. In addition to the top three projects by score, there'll be a few . These are: Judges' Choice: Presented to a particularly creative or all-around well-executed project that might not have made it to the top three. Best Research Question: Presented to the project with a really well-formed and creative research question. Best DIY Spirit: Presented to the project that best sticks to the spirit of the $40 limit - the "Doing The Most With The Least" award. Most Inventive Methods: Presented for ingenious investigative methods. Most Rigorous: Presented for best following the ideals of scientific rigor. Best Analysis: Presented for particularly fine analysis of data. Best Presentation: Awarded for excellent, clear, and impressive presentation of the experiment and results. | [
"Narf! I don't know if the top of your head would be the best platform for launching pumpkins, Brain. Poit!"
] | [
"Tis the season for pumpkin launchers! There has to be an experiment in that somewhere!"
] | [
"Closer to 50k now, I think."
] |
[
"What actually happens when I change the radio station in my car? How does my antenna know when I switch from 88.5 Newstalk radio to Oldies 101.1? Bonus points: why are FM stations odd numbers?"
] | [
false
] | null | [
"The antenna picks up the whole FM band. It gets amplified, then it gets combined with a variable Local Oscillator in a non-linear mixer which outputs the difference between the two signals to create an intermediate frequency at (typically) 10.7 MHz. So for 88.5 MHz the LO is 99.2 MHz. For 100.1 it is 110.8. That's... | [
"Inside the radio is an electronic circuit that resonates in a certain narrow frequency range. A signal recieved from the antenna at the resonant frequency is strengthened by resonating, even before any other amplification, whereas other frequencies do not resonate.",
"An ",
" is a simple example of a resonant ... | [
"The spectrum is divided into various bands. Avoiding interference is the main reason for spectrum regulation. I don't know why they chose 88-108 MHz for FM, but it was big enough to provide for 50 stations in each metropolitan area, but low enough for inexpensive receivers which all used vacuum tubes."
] |
[
"Won't landfills become fossil fuels in the future?"
] | [
false
] | Obviously assuming they are met with the same geologic phenomena that created existing fossil fuels. Essentially they are big piles of organic waste and plastic, which are already hydrocarbons. I guess I'm just curious as to what a future geologist would find when studying an area that was a landfill. | [
"There are organic and inorganic components, but the organic components do end up degrading. \"True\" fossil fuels usually require ",
"significant heat and pressure to form",
", but methane does get produced by bacteria breaking down organic material, and plenty of landfills capture this methane to burn or sell... | [
"It’s a possibility but many of the conditions needed to make fossil fuels in the first place are no longer around. Coal cane from trees that died before bacteria or fungus existed to eat it, so it just piled up. Oil is created differently but I assume nowadays the process is no longer viable naturally. "
] | [
"I didn't consider dams, but we are thinking on different time scales here, thousands of years from now yeah, there will still be a pretty big visible impact from what people have done so far. But millions of years from now? Rivers by their nature are ever changing, buildings will break down, radioactivity will d... |
[
"If weight is the measured effect of gravity on an object, and gravity is stronger the closer to the object’s center of mass the measuring object is, do objects high in the atmosphere weigh less than those on the ground, from a physics standpoint?"
] | [
false
] | null | [
"Yes, but the difference isn't very big. The radius of the Earth is about 6400 km (depending on where on Earth you measure). So if you're 10 km high in the atmosphere (the cruising altitude for long haul commercial aircraft), you're only 0.15% further away from the center of mass.",
"Since gravity is proportional... | [
"Provided the scales are calibrated well enough to reach the desired level of accuracy, yes. About a quarter of a kilogram for an 80 kg person."
] | [
"So I weigh myself on a scale at the airport and directly as soon as we reach cruising speed, there will be difference??"
] |
[
"How do epidural shots work?"
] | [
false
] | I know that they block nerves but could anyone provide a more in depth explanation? (i currently am doing my first anatomy course in University and I've done a couple pharmacology course but this question didn't cross my mind until recently) Also, additional questions! What sort of receptors does it act on? What nerves do they block? what do the nerves usually innervate?? what sort of chemical is contained in an epidural shot?? how likely is someone to die/suffer an injury from an innaccurate / excess dose? | [
"I’m currently in anesthesia school and have been trained on epidurals. ",
"Some minor corrections to your comment.",
"Epidurals do not pierce the dura mater. They are EPI (above) durals. The needle pierces through the supraspinous ligament then the interspinous ligament then the ligament of flavum. The epidura... | [
"Here’s a very general layout (not a med professional, but have taken anatomy)",
"Your brain has 3 membranes surrounding it. \nThe Pia-Mater (soft mother) is right against the grey & white matter (grey matter “thinks”, white matter “conducts”).\nArachnoid membrane (called that because it has the blood vessels in ... | [
"Wow, thank you so much for that detailed response! Really appreciate it! :)"
] |
[
"Can you make a waterproof Shear-Thickening Fluid?"
] | [
false
] | Ok, as many of you are probably aware, the military uses a shear thickening fluid on kevlar to create pierce-proof body armor. They use Silica Nanopowder (or Calcium carbonate nanopowder) dissolved in Polyethylene Glycol, then they dilute it with ethanol, and soak the kevlar in it. Then they bake the kevlar to make the ethanol evaporate, leaving the Shear Thickening Fluid behind, between all of the fibers of the kevlar. Well, my question is this: Can you make a waterproof shear-thickening fluid that would do the same? I was considering using Polydimethylsiloxane silicone fluid that has dissolved calcium bicarbonate in it, and then try using Boric Acid to create the solidity needed? (This would be a variation of Silly Putty) And then maybe dilute it in pentane, dip a shirt in and bake the pentane out? Would this work? Is there a better waterproof liquid + calcium carbonate nanopowder that would make a better, or stronger Shear-Thickening fluid than the one I presented? Any help in this endeavor would be appreciated! | [
"You might want to try asking this question at ",
"r/AskScienceDiscussion",
" instead, since it's more of an exploratory question. I doubt anyone can tell you the answer to this simply because nobody's tried it before!",
"With that being said, a few things to consider: kevlar is already very strong even witho... | [
"Two questions: how hydrophilic is the current kevlar armor, and why is it this way? ",
"I recommend you look into why a hydrophilic solvents are used before you consider alternatives. Changing the solvent you soak your kevlar could affect a lot of things (swelling the fibers, for example). Not saying an answer d... | [
"I think the problem with this process would be that the desired nanostructure that makes the coating what it is would not work. This is purely off the top of my head but i believe you will have trouble with the nanopowder actually setting into the fibers. Also possibly the carbonate reacting with weak acids in rai... |
[
"With all the issues that chemical batteries have, why aren't capacitors used to replace standard batteries?"
] | [
false
] | null | [
"Is there something I am missing?",
"Yes. While capacitors have high power density, they have very low energy density, which is what you want in your batteries. In a water-electricity analogy: batteries would be like a swimming pool, and capacitors would be like a big bucket. Sure, you can dump the bucket out ... | [
"I see, so the watthours of capacitors suck?"
] | [
"That's correct. Capacitor energy is usually measured in Joules, which is = 1/3600 Wh. A large capacitor you might find in a flash camera can only hold around 5 Joules. "
] |
[
"Could sea creatures that live at great depths survive at 1 atm?"
] | [
false
] | Do they have higher internal pressure to counter the external pressure on their bodies? If so, would this cause then to swell and possibly “lyse” at the surface? | [
"That's actually the way many deep sea specimens are collected. If they are slowly acclimated to the decreasing pressure they can be brought to the surface alive. Live deep-sea squids and octopi caught by the Monterey Bay Aquarium Research Institute have been exhibited at the Monterey Bay Aquarium for short periods... | [
"Many deep sea organisms can not tolerate 1 atm. Take for instance the blob fish:",
"https://i.imgur.com/pOMKdLl.jpg",
"This is in fact a somewhat normal looking deep sea fish whose tissues swell and lose structural integrity when they are brought up to the surface. This is a fairly common outcome for many atte... | [
"Suppose such animals are brought up slowly, similar to divers who decompress after being at great depths. Could they survive? "
] |
[
"If hurricanes in the northern and southern hemisphere spin different directions, what happens if one crosses the equator?"
] | [
false
] | Does it slowly change direction? Or does it die out, or continue in its old direction? | [
"They essentially can't cross the equator. Hurricanes rotate due to the Coriolis effect; the lack of such the closer you get to the equator means a tropical cyclone couldn't form at the equator, and would most likely die long before they reached it. Since records began, no tropical cyclone (nor a discernible remnan... | [
"Hurricanes can't ",
"cross the equator",
".",
"Essentially, within about 5 degrees of the equator the Coriolis effect essentially disappears. A hurricane forms because the rising hot air imparts a spin on the storm's motion. The spin creates the powerful winds and can helps absorb energy from the ocean's sur... | [
"To be technical and nitpicky, it's less that hurricanes can't physically cross the equator so much as that it's very unlikely. But hurricanes can and do form and survive near the equator; Typhoon Vamei in 2001 is a great example.",
"Also the poleward movement of tropical cyclones is due to the beta-effect, posit... |
[
"Why does the speed of light squared have anything to do with the equivalence of mass and energy?"
] | [
false
] | [deleted] | [
"Just to make it clear to the OP, when we say \"speed of light\" we really mean \"the universal speed limit of spacetime\". Light really has nothing to do with relativity aside from light happening to have no mass, it playing a historical role in the discovery of relativity, and it being an easy way to teach relati... | [
"Just to make it clear to the OP, when we say \"speed of light\" we really mean \"the universal speed limit of spacetime\". Light really has nothing to do with relativity aside from light happening to have no mass, it playing a historical role in the discovery of relativity, and it being an easy way to teach relati... | [
"In terms of units of measure, the unit for energy is equal to the unit of mass, multiplied by the unit for speed, squared. What we call \"energy\" is just mass, times speed squared - and this is true everywhere, not just in relativity.",
"1 Joule = 1 kg * 1 (m/s)",
"For example, the kinetic energy of any movin... |
[
"Do all animals have distinct tissues?"
] | [
false
] | This question came up in my biology class, and I thought it was a tad vague. I would argue that they do not all have distinct tissues (granted a large majority of them do). If I understand correctly, porifera lack "true" tissues. If they do not have "true" tissues, is it fair to say that they would refute the notion that all animals have distinct tissues? I very well could be over-thinking this question. Thanks for the help! | [
"Porifera do lack tissues, although they do have several different cell types. The different cell types do not organize into specific tissues, however."
] | [
"I am pretty sure mesohyl isn't a tissue. It's more of a matrix made up of collagen and other fibres. Porifera have specialized cells with flagella and what not but true tissues are endo-, ecto- and meso- derm. Some animals with true tissue lack a mesoderm but all animals with true tissue have endo- and ecto- derm.... | [
"I am pretty sure mesohyl isn't a tissue. It's more of a matrix made up of collagen and other fibres. Porifera have specialized cells with flagella and what not but true tissues are endo-, ecto- and meso- derm. Some animals with true tissue lack a mesoderm but all animals with true tissue have endo- and ecto- derm.... |
[
"Why does smoking increase your risk of getting cancer in so many different areas of the body, not just your lungs?"
] | [
false
] | null | [
"Literature has definitely established a dose-response relationship between smoking cigarettes and lung cancers. This can also be said regarding cancers of the mouth and throat (as the cells are also directly exposed to the carcinogenic chemicals). While I am not well-versed in the literature relating the risk of s... | [
"Finally, a question I can answer. The lungs are composed of alveoli, small sacs with super-thin absorptive cells that facilitate gas exchange. The lungs are also HIGHLY vascularized, and the carcinogens themselves can enter through the lungs and travel through the bloodstream to virtually any target in the human b... | [
"The jury is still out on coffee. Working out doesn't because it has both things that would increase cancer and things that decrease it."
] |
[
"Isn't SETI pretty much useless if aliens are using some kind of digital transmission?"
] | [
false
] | Or am I understanding this wrong? | [
"Here is the basic premise of SETI:",
"Listening is better than not listening.",
"No matter how many resources we put into SETI, no matter how broadly we search, you can construct all kinds of scenarios SETI won't find the aliens. But that does mean we can't make some reasonable assumptions about what an alien... | [
"No. If they were transmitting \"1\" at 110 MHz and \"0\" at \"90\" MHz then we could detect periodic spikes at 90 and 100 MHz."
] | [
"relevant?"
] |
[
"What is the mass of the universe and how is it calculated?"
] | [
false
] | null | [
"The mass of the universe is only a meaningful question if you restrict it to the observable universe, or some other reasonable subset of the universe. You then have to define what you mean by mass - baryonic mass? (i.e, regular matter), matter mass? (regular matter + dark matter), total energy? (regular mater + da... | [
"Depends where your head is.",
"First, we need a cosmological model of our universe. Let's assume, three things. The universe is homogeneous (the same everywhere), isotropic (the same in all directions), and is governed on large scales by general relativity. Then what we get is the ",
"FRW model",
", and the ... | [
"The amount of mass in the universe is calculated by how it affects (ie slows down) the expansion of space which is measured by the speed with which galaxies are receding from us. If there was a lot of mass in the universe the expansion would slow down and ultimately reverse (\"big crunch\") as gravity wins the cos... |
[
"If time slows down around a black hole then does the person falling in see a vastly sped-up outside universe before succumbing to tidal forces? How far does this go - seeing non local stars move around and disappear? Heat death of the universe?"
] | [
false
] | null | [
"Yes, pretty much so.",
"Perhaps the most surprising fact is that you don't need a black hole to see time outside speeding up. This effect has been demonstrated right here on the surface of earth.",
"The ",
"Mössbauer effect",
" has been used to measure gravitational redshift and it's one of the proofs of E... | [
"GPS wouldn't work if we didn't account for the fact that time flows faster in space than on the earth."
] | [
"It's both, but the time dilation due to gravity is more important. Time on the satellites is slower by 7 microseconds per day due to special relativity (their relative speed), and faster by 45.9 microseconds per day due to general relativity (the Earth's gravity)."
] |
[
"What is the air inside a bell pepper composed of?"
] | [
false
] | null | [
"Copied from an earlier question: source ",
"/u/danby",
" ",
"For peppers, The air in the void mostly has the same composition as the atmosphere and the air got there largely by diffusion through the fruit's tissues as the fruit (and the space) grew bigger.\nWith regards peppers; wild peppers are small and fa... | [
"So ant man could theoretically live inside a pepper? Would it convert his CO2 to O2 within the pepper void so he could treat it as a diving bell?"
] | [
"No idea what all the crazy talk is here but there are small holes near the stem so air can flow freely. Seriously put a pepper under water and give it a gentle squeeze. "
] |
[
"Is the radiation from a microwave oven considered a photon?"
] | [
false
] | null | [
"It's a stream of photons, yes. If the average photon has an energy of about 1.65-2.00 electronvolts (eV, a unit of energy) we call it \"red light\", if it's 2.75-3.26 eV we call it \"violet light\", if it's got 0.000001 eV to 0.001 eV we call it \"microwave\". There is no difference beyond that, \"microwaves\" ... | [
"A classical light wave is not a photon. It's a coherent state with indefinite number of photons. You can't say exactly how many photons there are, it's in a superposition of different photon numbers. The probability distribution for the number of photons is a Poisson distribution. So you can talk about the average... | [
"What do you mean? Because the wavelength of a microwave is on the order of centimeters? As ",
"/u/RobusEtCeleritas",
" pointed out, a classical EM plane-wave like so:",
"https://en.wikipedia.org/wiki/File:Electromagneticwave3Dfromside.gif",
"is not made of a single photon. In fact, if you have a microwa... |
[
"Would it be possible or even beneficial to flood the Sahara?"
] | [
false
] | I was reading about some theories in th 1800s and 1900s to flood a part of the Sahara which, if i understood correctly, would turn Northern Algeria, Tunisia, and the lands north of the Atlas Mountains into islands and cover a relatively depopulated area into a sea. The water's evaporation would make the rest of the sahara more humid and improve agriculture. Until recently i would have dismissed this as either impossible or disastrous until someone told me that terraforming Mars to make it habitable was scientifically possible. If its possible to create conditions for plant life on Mars along with large bodies of water is it possible to reduce the Sahara and make it green here on earth? edit: What's with the downvotes? Are you afraid of a little intellectual curiosity? Nobody's saying it's a good idea or an idea that should be petitioned for and implemented. This is just a feasibility study. It'd be interesting if there happens to be an expert at who is an expert in meterology, large scale engineering, ecology, any field really. I'm curious if anyone's got an idea, it seems some do. You can downvote a wrong answer not a wrong question. | [
"Perhaps possible, with enough $, time and resources, but I think it is worth revisiting why the Sahara exists where it does. ",
"Global circulation atmospheric circulation is complex, but looking at a satellite image of Africa, one can observe large bands of arid desert roughly centered on the Tropic of Cancer a... | [
"Never knew about that, so I went looking. Found this about ",
"flooding the Qattara Depression",
" near Cairo.",
"And then there's ",
"this paper about Saharan paleo mega lakes",
". ",
"Lake Megachad",
" once had a surface area of 361,000 km",
" , compared to Lake Superior at 82,100 km",
" ."
] | [
"I would tend to agree. The amount of money and resources necessary to sustain this project would be exhaustive. The effects that we as humans could have in this region directly would likely not be enough to counteract the global circulation and tendencies to keep the region dry."
] |
[
"Do any animals respond to music in ways similar to how humans do, such as rhythmic foot-tapping (paw tapping?), etc"
] | [
false
] | null | [
"This is not very rigorous, but an example of animal response to music can be read in ",
"this",
" discovery article. The jist of it is that most animals will not have a reaction to music at all unless it's tailored to their ears, though some will be calmed by certain types of music. Many farmers believe that c... | [
"Actually, yes it is, it's just not statistically significant. It's a data point. But taken in aggregate,",
"Schachner and her colleagues next studied thousands of YouTube videos showing animals dancing. The researchers checked to see which species had rhythm and could align their movements to musical beats. They... | [
"Actually, yes it is, it's just not statistically significant. It's a data point. But taken in aggregate,",
"Schachner and her colleagues next studied thousands of YouTube videos showing animals dancing. The researchers checked to see which species had rhythm and could align their movements to musical beats. They... |
[
"Could a beam from a flashlight cause motionless smoke to move in a 0g vacuum?"
] | [
false
] | null | [
"Hi DronesForYou 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 fo... | [
"'Physics'"
] | [
"Physics"
] |
[
"Why do several citrus fruits have pre-made slices?"
] | [
false
] | I know it's a common question, but I haven't seen the answer yet. | [
"Pictures and discussion on attempting to eat wild oranges",
". ",
"Like most plants in grocery stores, oranges have been changed massively by selective breeding. Wild relatives are harder to separate and are often so acidic that they're capable of causing chemical burns - not to mention uglier and seedier. ",
... | [
"I'm a biology undergrad taking a Taxonomy of Flowering plants course so I can explain it in rather layman's terms. The type of fruit that come with \"pre-made slices\" are called hesperidium which includes the Rutaceae family(citrus fruits). What's happening is that during development of the fruit, ovules(immatu... | [
"What was the evolutionary pressure for the slices? They seem incredibly useful for human-like hands."
] |
[
"AskScience AMA series: Geochemistry and Early Earth"
] | [
false
] | Today I am here to (attempt to) answer any questions you may have about early Earth, lunar history (particularly the late heavy bombardment), 9 million volt accelerators or mass spectrometers that can make precision measurements on something smaller than the width of a human hair. I am a PhD student in Geochemistry and I mostly work on early Earth (older than 4 billion year old zircons), lunar samples, and developing mass spectrometers. I have experience working in an accelerator mass spectrometry lab (with a 9 million volt accelerator). I also spend a lot of my time dealing with various radiometric dating techniques. So come ask me anything! | [
"There are several reasons but the strongest is: No one was around to watch it happen.",
"All we can do today is collect samples from Earth, Moon, and other bodies in the solar system (including meteorites) and compare them. What we know is Earth and Moon are identical in many isotope systems that have been measu... | [
"So the first contender is two approximately equal mass bodies (1/2 earth mass) merged and then in that collision a moon formed. My gut suggests that this is unlikely and if you shift the mass ratio too far one way or another you end up with a moon that is not the same composition as Earth. The saving grace to this... | [
"That is a great question and the answer is it depends on the transition. For example between the Hadean and Archean there is no real transition or boundary, people even dispute when it is at the 100 million year level. It is not at all clear that there is a meaningful distinction between the Hadean and Archean (th... |
[
"Is it true that there is only \"one\" actual photon/particle that exists?"
] | [
false
] | The question will seem a little odd but bare with me. I'm reading a book which, to enhance story line, mentions feynmans integral formulation and explains how a particle, say, a photo will take every possible path through space-time to go from A to B. It then goes on to say "there is only one photon in the entire universe, and that photon, spread across all of creation in a vast probabilistic smear, that one photon is responsible for all the light we see." I understand that particles will undergo all possibilities and will only show one when observed but i assumed that there were still a number of particles, not one expressing itself in many different outcomes. I was just curious if through some quantum science-y thing this actually was true and how. The book is "How to live in a science frictional universe" if anyone was wondering. Edit: Have to apologies for the bad english, writing isn't my strong point. | [
"No. That's a ",
" melange of the path integral maths formalism and the principle of indistinguishability.",
"The path integral formalism is just a way of doing maths. The technical details won't be helpful here, but you can think of it as being an application of Lagrangian mechanics to quantum physics, with an... | [
"Chemistry would have a hell of a hard time if there could only be one electron at any given instant!",
"I think he means ",
"this",
". Of course this is not true either, but in the early days seemed possible. From what i read this was supported by the existence of positrons which are mathematically viewed to... | [
"You may have ruined the book for me but damn i feel a lot more educated.",
"Cheers and upboat for you."
] |
[
"Neptune hasn't \"cleared its neighborhood\" since Pluto regularly enters it. Doesn't that technically make Neptune not a planet according to the official definition by the IAU?"
] | [
false
] | null | [
"Clearing the neighborshood doesn't mean there's nothing else in it's orbit - by such a definition, Earth wouldn't be a planet, since there are asteroids which cross Earth's orbit. So we need a less draconian definition.",
"One approach is to divide the mass of an object by the mass of everything else in that or... | [
"Kupier belt objects are within Pluto's \"neighborhood\", their mass is significant when compared to Pluto causing it to fail that criteria."
] | [
"The orbits of Pluto and Neptune don't actually cross. Pluto's orbit is highly tilted so they will miss eachother and they're in a 2:3 orbital resonance.",
"Lots more details and pictures on Wikipedia"
] |
[
"Does tanning really age you?"
] | [
false
] | Or is it just that it damages your skin? | [
"Age is a constant thing... you'll never be older than 20 or 30 or whatever actual age you are. ",
"But you can APPEAR older than your actual age if you damage your skin, abuse your body, etc. ",
"If you're asking if the changes from a tanning bed are reversible, they aren't. Once the damage is done, it's perma... | [
"UV rays break down components of your skin like collagen and connective tissue, leading to earlier wrinkles and a dried-out, leathery appearance. ",
"The UV rays can also break down the DNA in the basal layers of your skin, potentially leading to skin cancers. "
] | [
"The dried-out, leathery appearance: is that aging or just damage?"
] |
[
"If Chimp and Human DNA are so identical, why can't they produce a hybrid offspring similar to mules and zebroids?"
] | [
false
] | [deleted] | [
"Infertility is a result of the specific genetic differences between two species, not a result of the overall %genetic difference, much less the placement into same or different genera. As for why humans and chimps can't produce hybrid offspring, well, one crazy russian guy did some research back in the first half... | [
"Horses and donkeys also have differing chromosome numbers."
] | [
"Horses and donkeys also have differing chromosome numbers."
] |
[
"Radiometric Dating: How do we know the parent:daughter isotope ratio was initially 100:0?"
] | [
false
] | A few simple questions about radiometric dating: I would gladly take articles about the last two questions with open arms if people could point me in the right direction. Thank you. | [
"Firstly, it's really important to distinguish between ",
" dating (which is what you're referring to) and ",
" dating. Radiocarbon dating is just one technique in a whole suite of radiometric techniques, which all work in slightly different ways and are appropriate for different timescales (e.g. radiocarbon da... | [
"Going to piggyback off this, just to add a little bit to this excellent answer in regards to other radiometric dating techniques that are appropriate for rocks. ",
"In regards to the no preexisting daughter product (i.e. no inheritance) assumption, the answer depends on the radiometric system in question. For so... | [
"The other comment covers radiocarbon dating pretty well, so I'll just drop a few comments of my own:",
"In some cases the daughter isotope is a different element from the parent isotope, and so the two will have different chemical properties. This means that certain minerals can form with only the parent isotope... |
[
"How does Electro-Convulsiveshock Therapy work? How does it cure things like depression?"
] | [
false
] | As I'm currently looking down the ECT barrel due to what my psychiatrist called "treatment-resistant depression," I was wondering how exactly it does what it does. Unsure if this post will get disqualified due to rule 1, but I'm looking for all the chemistry/biology, maybe even a little psychology behind it. I've heard the whole "it restarts the brain" thing, but I want to know the entire process behind it. | [
"The exact mechanism by which ECT works is not fully known. If we knew that research would probably try to find alternate ways to accomplish the same thing that don’t require anaesthesia. There are some things we do know though:",
"The hippocampus and amygdala are parts of the brain involved in many processes inc... | [
"ECT has been around for almost a century, Psychedelic-assisted treatments are barely starting in this last few decades. So the difference in \"amount of studies\" is a red herring.",
"It's not a red herring. There are strict standards for medical procedures and the research required for it to be considered effic... | [
"ECT has been around for almost a century, Psychedelic-assisted treatments are barely starting in this last few decades. So the difference in \"amount of studies\" is a red herring.",
"It's not a red herring. There are strict standards for medical procedures and the research required for it to be considered effic... |
[
"If someone wore glasses that made everything you see shades of red/blue, how would they perceive the world if it was removed after 50 years?"
] | [
false
] | null | [
"It is a misconception that we have one cone that detects red color, one that detects blue color and one that detects green. It is true that each type of cone is ",
" sensitive to the wavelengths of light that correspond to those colors but for almost all colors at least two cones are going to activate.",
"For ... | [
"Is this speculation or do you have something to back up your claims?"
] | [
"Is this speculation or do you have something to back up your claims?"
] |
[
"How does compressing air lead to no temperature change theoretically?"
] | [
false
] | null | [
"In a ",
" compressing air ",
" lead to a temperature change. If you compress the air relatively slowly, though, you can let heat escape and the temperature equalize with the environment, keeping the gas temperature constant. Expansion and compression ",
" be adiabatic (no heat transfer), but don't have to be... | [
"I understand that the temperature can equalize while it is in the compressor tank. But excluding all external factors and just looking at this in terms of pressure, volume and temperature why is it that when I reduce the volume of a gas by half and increase the pressure by a factor of 2 the temperature stays exact... | [
"If you aren't allowing heat transfer, then that's not what happens. If you reduce the volume by a factor of 2, in an adiabatic compression, then the pressure will go up by MORE than a factor of 2 because the temperature will go up too. You've got one constraint and 2 dependent variables, you can't predict the end ... |
[
"How closely related are cherries and plums?"
] | [
false
] | I was eating cherries today and several of them looked like miniature plums I have eaten in the past. I know they are related, but how closely? When did the plants diverge and become separate enough evolutionary to identify or did they evolve separately from two different species? I would assume that being in the same genus they share a common ancestor. | [
"Here's",
" a recent article on the molecular phylogeny (i.e. \"evolutionary history\") of ",
". "
] | [
"Cherries and plums are from the same genus, ",
".",
"In the way scientific classification works, it's likely that they came from a common ancestor and diverged due to different evolutionary pressures - whether it be from different geographical areas (allopatric speciation) or whatnot. ",
"If two different or... | [
"Almonds, peaches, plums and apricots seem to be one clade, and the cherries (sweet, sour, bird, laurel) a separate clade, within the prunus genus. So plums and cherries would not share a common ancestor (directly)."
] |
[
"Is body fat percentage correlated with how long someone can endure starvation before death?"
] | [
false
] | Let's say two people wash up on a deserted island. One with 7% body fat and one with 32% body fat. They have access to a reliable water source however there is no food on the island. Would the individual with a higher body fat percentage be able to survive through starvation longer than the other? Logically I would assume that because there is more energy stored and available for use they would survive longer, however I've not seen any meaningful data supporting that notion. | [
"Largely, yes, more body fat would enable you to live longer without eating.",
"",
"The answer is more complicated than that. The human body needs many nutrients and minerals to function properly which do not occur in body fat, and both people would become vitamin deficient at roughly the same rate. Such defic... | [
"Wow thank you for the response! Sorry for the late reply, I was busy the last few days and haven't had a chance to look at the post. Seeing the Math really put that in perspective. Also I can't imagine how much it would suck to have to take multivitamins on an empty stomach every single day. "
] | [
"There is a case of Angus Barbieri, who fasted 382 days and lost 125 kg in process.",
"He was supervised by a doctor and regular check ups were done. He was getting the vitamins, potassium, sodium and yeast.",
"The case is also well documented in medical literature.",
"Here is the ",
"link",
" and ",
"m... |
[
"What molecular properties determine a material's heat capacity?"
] | [
false
] | null | [
"If by \"material\" you mean a solid, then this is an incredibly complex question. In a nutshell, the specific heat of a thing (solid or otherwise) is determined by the number of places energy \"can go\" or \"be put\". In a mono-atomic gas, this is easy, 3 places: kinetic energy (i.e. motion) in the x direction, ... | [
"Ironically, even though the underlying principles are very complex, for many crystalline elements near room temperature, the heat capacity is approximately constant at 25 J/K/mole."
] | [
"Well for \"regular\" materials there's always some level approximation you can utilize. For phonons for example you can use the Debye or Einstein models, but you can crash a google server with violations of expectations from the Debye model."
] |
[
"Tomorrow in Europe there is a solar eclipse. So is the moon today anywhere near the sun, in the sky, as sort of an almost-eclipse?"
] | [
false
] | null | [
"Yes, if we can call that an \"almost-eclipse\". We actually have a new Moon (or we're close to it). The eclipse will happen after about 14h (it's 19:50 in Central Europe at the time of writing this comment). The Moon moves 12º per day on the sky, so right now it must be nearly 6º west of the Sun. It must have set ... | [
"It is pretty much as close as it is on every orbit a day before a new moon; the only difference is that usually new moons miss the sun a bit (passing either \"over\" or \"under\" the sun) so they don't cause an eclipse."
] | [
"Yep! In fact, the moon gets very close in the sky to the sun every month, at new moon. Usually it is a little north or south, but when the orbits line up nicely, you get an eclipse."
] |
[
"How dangerous is alpha-Methyltryptamine?"
] | [
false
] | [deleted] | [
"Had to poke around some articles.\nOnly found one I could really use (Clinical toxicology [1556-3650] Hill yr:2011 vol:49 iss:8 pg:705 -719)\nBasically, there isnt enough research to know what the long term effects of this drug are specifically, but because of it's similarity to other drugs some inferences can be ... | [
"Good place to start is here:\n",
"http://www.erowid.org/chemicals/amt/amt.shtml"
] | [
"Thank you very much. That's very useful."
] |
[
"Can you die from drinking from a long enough straw?"
] | [
false
] | null | [
"Physics"
] | [
"Physics"
] | [
"No."
] |
[
"Why didn't NASA plan the trip to Pluto to arrive in the prehelion, wouldn't that be a quicker trip?"
] | [
false
] | null | [
"Pluto takes 248 years to orbit the Sun, it was at last at it's closest point to the Sun (perihelion) in 1989, since we missed that opportunity, we would have had wait till 2237 to launch New Horizons, the next perihelion. That's too long."
] | [
"It also implies that it's currently not very far from it's perihelion. There would be very little to be gained by waiting until 2237."
] | [
"Perihelion was in 1989. It took 25 years from the initial proposals for a Pluto mission in 1990 for NASA to get this mission there in 2015 after numerous changes and an outright cancellation in 2000. They would have had to have started planning in 1964. ",
"NASA is also not in full control of its budget. Congres... |
[
"How do scientists know how long the events after the Big Bang took?"
] | [
false
] | [deleted] | [
"We could reconstruct the evolution of the scale factor (how exactly the Universe expanded in time) by exploiting the Friedmann equations and measurements for the relevant parameters (Hubble's constant, deceleration parameter, density parameters etc) at the present time. Integrating the Friedmann equations back in ... | [
"I hear the big bang means that it all started out from a point",
"that's wrong. What happened is pretty subtle. Not mysterious, just really unintuitive.",
"Basically the point is that the Universe is in ",
", not the content. It's not that spacetime is inert and galaxies are flinging out from an explosion po... | [
"They most definitely never did, it's a popscience misconception.",
"Can you elaborate a bit on this? I hear the big bang means that it all started out from a point, but from what I've read the movement of the stars can't be reverse-traced back into a single point.",
"Just how big an area is a \"point\" that th... |
[
"Why do all the bubbles in a pint of beer tend to originate from specific points in the glass?"
] | [
false
] | After pouring a cold one, all the air bubbles that float through the glass seem to keep "spawning" from particular points wishing the class container. Why does this happen? | [
"Beer is carbonated so when it's made in a brewery they shove more carbon dioxide into the solution than would normally be able to dissolve at normal atmospheric pressures. This causes the solution to be supersaturated with CO2 once the beer is poured or opened. The CO2 in solution wants to find a way out so it doe... | [
"Bubbles may originate from small scratches or faults in the glass surface, but more commonly, they're produced by small sediment particles, either in the beer or adhering to the surface of the glass. ",
"This is more common with beers brewed with added wheat which can lend cloudiness and thicker head due to the ... | [
"I also think that once a bubble forms, the disturbance it creates enhances more bubble formation.",
"A similar but 'opposite' reaction is found in supersaturated salt water, like that found in brine holes in Death Valley, out in the Devil's Golf Course. The surface if the water is perfectly smooth, the color yel... |
[
"Why does this calorie math not check out?"
] | [
false
] | null | [
"A food \"Calorie\" is 1000 thermodynamic \"calories,\" or a kilocalorie."
] | [
"That is assuming perfect efficiency.",
"Humans turn chemical calories into mechanical work at about 20% efficiency.",
"The mechanical work -> electricity is ~40%.",
"An electric kettle (most efficient way to heat water) ~70% efficient.",
"That's around 300 kcal, which is on the order of 20-30 minutes of ex... | [
"The most common mistake with things like this, is that a dietary calorie is actually 1000 calories, enough to heat a ",
" of water by 1 degree Celsius."
] |
[
"How can digital numbers control path of electricity? (i.e. computers, microcontrollers...)"
] | [
false
] | For instance you can program a microcontroller to have power at a certain port. How can a line of code affect path of eletricity? Thank you for answers. | [
"With ",
"transistors!",
" They are clever little circuits that let one electrical current turn on or off another one. That line of code is really just a set of electrical activity in some electrical switches, that flip other electrical switches, that flip other ones, and so on. ",
"Transistors in computers w... | [
"There is a very nice book about these basics, called ",
"CODE",
" by C. Petzold. He starts from very basic concepts and thus it can be understood by laymen. "
] | [
"I will second this. I believe that CODE is the single best book written on computers and computer science for laypeople. "
] |
[
"Why is the integral of 1/x = ln(x)+C?"
] | [
false
] | I mean I get that you cannot integrate it normaly as in: x-1 --> (x0 )/0 because you obviously cannot divide by zero. So why does this just happen to equal ln(x)? | [
"First of all, you mean to ask why the ",
" of 1/x is ln(x) + C. An ",
" is a limit of Riemann sums, i.e., a single number, and it has various interpretations: area, volume, probability, etc. The fundamental theorem of calculus simply provides a link between integrals and antiderivatives. But the two objects ar... | [
"Nice man! Thank you. I did not even know about the term antiderivative because my maths teacher only uses \"integral\"",
"That is unfortunate and quite common actually. We happen to use the same symbol ∫ for antiderivatives and integrals, and the fundamental theorem only further blurs the distinction. So teacher... | [
"Nice man! Thank you. I did not even know about the term antiderivative because my maths teacher only uses \"integral\". This makes sense to me so thanks for explaining!"
] |
[
"Are there studies that tested placebos on babies?"
] | [
false
] | Or people young enough to not know that medicine is supposed to be good for you? | [
"AFAIR both babies and animals are susceptible to placebo effects. It is a common alt-med trope to claim that they aren't, but this sort of argument forgets (at least) two things:",
"Babies and animals may not have a concept of medicine, but they ",
" realize that they receive attention and that somebody cares ... | [
" \nI just read through a couple pages of a PubMed search on placebo and infant. They seem to use them relatively often. From the handful of abstracts I peeked at it looks like placebo is being used as having \"no effect\". "
] | [
"That's why good studies are double-blind."
] |
[
"Do kidneys adjust to water intake or is there a sweet spot?"
] | [
false
] | null | [
"Hello,",
"We can approve this if you edit out all of the personal details.",
"Best."
] | [
"I have no idea what personal details you're referring to. There's no age, gender, name, location, etc. Can you clarify?"
] | [
"The whole question is about ",
" water drinking habits, and how it will affect ",
" body. The question can’t be specific to you."
] |
[
"When passing the event horizon of a black hole there are no paths leading away from the center, but are there longer or shorter paths towards the center?"
] | [
false
] | null | [
"Yes there are, depending on your angular momentum."
] | [
"Is there any way to elaborate on that? I only have a loose Newtonian grasp of physics."
] | [
"Well, you can go straight towards the center, or curve around and spiral in."
] |
[
"How can a relatively small river like the Virgin River cut a 2000 foot deep Canyon (Zion) while an enormous river like the Mississippi doesn't cut a canyon at all?"
] | [
false
] | null | [
"Because a canyon requires flow over rock and a significant elevation drop over the distance of at least the length of the canyon. The Zion canyon is cut into rock by a river constantly flowing over it with the vertical drop of 2000 feet.",
"The Mississippi River has only about an 800 foot elevation drop from its... | [
"There are various factors involved in erosion, but I think the most important one here is that the Virgin River starts in the mountains, and so can gain a lot of energy from gravity which can be used to erode sediment. The Mississippi starts pretty low, so it can't gain much energy, and can't cut too deeply until ... | [
"There is also the essential factor that the whole Colorado Plateau area has been uplifted due to tectonic forces over the past few million years. This is the reason why you get such spectacularly deep canyons - the vertical drop of rivers from source to mouth is maintained despite constant the downward erosive for... |
[
"What state are dissolved molecules in?"
] | [
false
] | Would the dissolved molecules count as a liquid or does it matter on the starting phase. For example if gas is dissolved in water does that gas stay in gas phase? | [
"The entire solution is the same phase--the phase doesn't describe each component, but rather the whole thing. In your example, a gas dissolved in water is a liquid. You can also have solid solutions (e.g. a metal alloy) or gaseous solutions."
] | [
"a gas dissolved in water is a liquid.",
"No. No no no. No.",
"Things that are dissolved are in the dissolved \"phase.\"",
"Its not a phase like solid/liquid/gas. Those phases are distinct ways of organizing matter. A solution of carbon dioxide in water is a liquid, yes, but the carbon dioxide is NOT a liquid... | [
"In a water molecule, the oxygen has a slight negative charge and the hydrogens have a slight positive charge. When salt dissolves in water, the slight negative charge on the oxygen is attracted to the positively charged sodium ions and likewise with the hydrogens and the negatively charged chloride ions. So in the... |
[
"Do humans have any special physiological defenses against fire/high heat?"
] | [
false
] | [deleted] | [
"Not likely. That kind of defense would come from a population regularly plagued by fires generation after generation. It’s easier to just move to a place that’s not constantly on fire. Although I say that living in California, so take it with a grain of salt."
] | [
"Our defence is management and avoidance, so we don't need a physical one."
] | [
"What do you mean by high heat?",
"If you mean high environmental heat, like in a desert, then humans have very good physiological defences: they can sweat, all over, and have little hair on most of their body so the sweat can evaporate well. Humans are very good at cooling themselves compared to most other anima... |
[
"Has anyone ever actually physically performed the double slit electron experiment where the electron is both a particle and a wave or is it just a thought experiment that is backed up by the math?"
] | [
false
] | null | [
"This has absolutely been done, many times. You can read about various such experiments ",
"here",
". ",
"You can even see video of the data collection of a recent such experiment ",
"here",
"."
] | [
"While I agree with the facts in your post, to be fair to op, physics has quite a bit of untestable currently or perhaps untestable ever ideas that are supported by math. I'm thinking of Hawking's argument about blackholes storing information at the event horizon or string theory in general."
] | [
"Nice thanks for the links."
] |
[
"Guilin Karst is a famous example of limestone mountains. Do limestone mountains occur elsewhere in the world? If not, why not?"
] | [
false
] | Google says that limestone occurs under marine water, but I've never heard of limestone mountains anywhere else? Am I misunderstanding? | [
"There are numerous examples of mountains comprised primarily of the marine minerals limestone (CaCO₃) and dolomite (CaMg(CO₃)₂).",
"Some examples:"
] | [
"As mentioned in this thread, there are a variety of mountain ranges that have significant amounts of limestone within them. For collisional mountain ranges (e.g., Himalaya, Alps, etc), limestone is pretty common because the formation of the mountain range itself represents the closure of an ocean basin, first thro... | [
"Thank you for the examples!"
] |
[
"How do they use CED-13 mRNA to trigger the change to increased longevity in a cell?"
] | [
false
] | Specifically; how do they use CED-13 instead of EGL-1 or what is the process to switch from EGL-1 to CED-13 triggering? Can I, as a human, activately promote the change of using the CED-13 as a trigger? I have no formal study in biology (just a mild interest) so if you could make it fairly simple that would be great. (sorry I don't have full text only the summary) | [
"You, as a human, do not have the CED-13 gene and its mRNA would probably have no effect in your cells given that it is a C. elegans gene. This is a nematode worm, which i spent many years studying (they are awesome). Had a look on worm base and couldn't find a direct mammalian homologue. One reason why I changed o... | [
"In answer to your first question. They are describing a pathway that uses many components of the intrinsic apoptosis pathway, which is shown on the left hand side of the figure, activated by mtROS and CED-13 which leads to increased levels of longevity. There is no switch between EGL-1 and CED-13, they are activat... | [
"Okay, this was a bit tough to wrap my head around. Definitely in over my head with this stuff. So the study is more about observation of the pathway than changing the the pathway by adding or replacing genes? Or am I way off?"
] |
[
"Why can't electricity be economically generated from the heat energy in the air?"
] | [
false
] | It seems that all the energy we need is all around us, without needing to resort to fossil fuels, wind, hydroelectric or nuclear power. Shouldn't it be possible to concentrate heat energy from the air enough to boil water / turn a turbine and generate electricity? If the temperature of millions or billions of cubic feet of air were lowered, even by a degree or two, isn't that a lot of energy that can be used to generate electricity? Even if it's pretty inefficient to do so, it doesn't really matter if the energy is essentially free and doesn't need to be mined, drilled or transported. Is it simply that energy required to extract heat from the air exceeds the energy that could be generated? If so, how close are we to closing this efficiency gap? My understanding is that stirling engines can generate rotational force with a temperature differential of only a few degrees. Perhaps this is a starting point, with the cooler earth used as a large heat sink. Can this be deployed en masse? Is a heat differential strictly required? Thanks! Edit: spelling | [
"Try this",
". a Hilsch vortex tube. It separates the fast moving(hot) molecules in the air from the slow(cold) molecules. "
] | [
"Have you studied thermodynamics yet? To get energy into a useful form you generally have to have a ",
"heat source and a heat sink",
". See the ",
"disadvantages",
" for Stirling engines.",
"Even if it's pretty inefficient to do so, it doesn't really matter if the energy is essentially free and doesn't... | [
"Right.. there's no overunity here. All air has fast moving molecules and slow moving molecules, mixed. It uses centrifugal force to separate the denser cold air from the hot air. hot air comes out one end, and cold air out the other. You have to supply it with compressed air for it to do its thing. "
] |
[
"How much of a body could a person survive without?"
] | [
false
] | I have read that (for example), a severed head would be unable to survive even if bloodflow and nutrients were provided to it. But a person with no limbs can otherwise be healthy, and people can survive with only one kidney, lung, part of their liver, etc. How much of your body is the minimum amount needed to sustain "life"? | [
"White blood cells do not cross the blood brain barrier anyways. Immune functions in the brain are performed by permanently resident microglia cells. But otherwise, you are right, obviously you would need some exchange system to provide the brain with O2 and glucose. "
] | [
"You also need something to circulate blood and filter waste products.",
"At this point, it's no longer really surviving with just a head; it's surviving with a head connected to some minimally-sufficient body -- just that the body is artificial instead of natural."
] | [
"Follow up: why can't we sustain just a head?"
] |
[
"Could a habitable moon potentially orbit a gas giant?"
] | [
false
] | null | [
"Yes, of course. However, in our solar system, the gas giants are outside of the habitable zone, and no extrasolar satellites have yet been detected, so at present, this is only science fiction. But conceptually, as long as the moon has an atmosphere, water, a stable orbit, happy temperatures, lacks excessive volca... | [
"Depends what you mean by habitable. Jupiter's moon Europa is currently thought to be about the most likely place to find life in our solar system. Ice with water underneath, heated by Jupiter's gravitational forces etc."
] | [
"Well, in billions of years when the sun goes into the red giant phase Europa might just become a nice place to live."
] |
[
"How does the human body anticipate how much force to use when lifting/pulling/pushing an object, and why are our bodies often momentarily confused when something weighs less than we had expected?"
] | [
false
] | null | [
"Your brain uses memory as a way to anticipate the effort required in these situations. There is a book called ",
"On Intelligence by Jeff Hawkins",
" that discusses this. You've opened thousands of doors, lifted thousands of objects. Your brain remembers how it felt to engage in that activity. So when you ... | [
"Awesome, i figured this was a pretty stupid question but thanks for your reply!"
] | [
"I work with people after injuries some injuries correlate with that momentary misjudgment- like when you expect another step and it's not there, the muscle length is wrong to accept your weight and adjust the joint position, so you pull muscles, ligaments or fracture bones. "
] |
[
"Where can I begin learning the history of particle physics and cosmology?"
] | [
false
] | [deleted] | [
"I think ",
"A Short History of Nearly Everything",
" might be what you are looking for.",
"Not sure it will 100% meet your needs but a great book nonetheless and worth a read."
] | [
"You could try Coughlan's ",
" ",
"Don't have a recommendation for cosmology. :-("
] | [
"This looks interesting, I will check it out. Thanks alot."
] |
[
"How big would the sun appear to the Voyager 1 at the distance it's at now?"
] | [
false
] | null | [
"It would appear about the same ",
" as the diameter of a human hair, held at arm's length. ",
"http://www.wolframalpha.com/input/?i=%28diameter+of+sun%29+%2F+18%2C534%2C175%2C964+km+*+1+m"
] | [
"In terms of luminosity it's about 1 watt per square meter, still brighter than the moon appears on Earth."
] | [
"An interesting question! I'm going to do a little rounding to make the math slightly easier.",
"Voyager 1 is 18500000000km from the Sun. The sun is 1391000km in diameter. The angular diameter of the sun is 2xarctan(1391000/(2x18500000000))= 15.509 arcseconds. The human eye's angular resolution is about 1 arcminu... |
[
"Why don't the mirrors, crossbars, supports, etc. in a reflecting telescope block some of the image?"
] | [
false
] | I've always wondered this about telescope designs that place a mirror in the path of the incoming light (e.g. the ). Doesn't the mirror (and whatever is being used to hold it in the middle of the telescope) block some of the incoming light from reaching the viewpiece? Would this show up as a black space on the observed image, or is there some way of compensating for it? | [
"They do block some of the incoming light, so the image is dimmer than it would be without them. Telescope manufacturers try to minimize the light loss to such obstructions.",
"You don't see a black space because the part of the optics that is unblocked is capable of showing a full image. This is easy to see if y... | [
"The reason is that the image is out of focus ",
". Think about how a pinhole camera works. The entire view is obstructed except for a very tiny hole. How is it possible for the entire image to fit through that tiny hole? It's out of focus when it passes the hole. The light rays passing the hole are travelin... | [
"Not a black space,",
" but the obstructions are visible in photographs."
] |
[
"Why is it so much easier to balance on a bicycle when moving than sitting still?"
] | [
false
] | null | [
"I can't believe all the confusion surrounding bicycle dynamics.",
"To my ",
" dismay, it has even been the subject of at least one PhD dissertation.",
"The reason for this confusion seems to happen when the rider's active steering input is neglected as a causative factor. Jeez.",
"To clarify the forces inv... | [
"You can further confirm how neglible gyroscopic forces are and how important steering correction is with two experiments.\n1) If you build a bike with tiny, lightweight wheels, like those found on a razer scooter, it can still be easily ridden despite the almost non-existent gyroscope effect.\n2) If you tighten th... | [
"The reason for this confusion seems to happen when the rider's active steering input is neglected as a causative factor. Jeez.",
"You can see this happen by launching a pilotless bicycle and watching it turn into its fall as it falls over, every single time.",
"You can also see that a riderless bicycle in moti... |
[
"Why can we control voluntary muscles but not involuntary muscles?"
] | [
false
] | In other words, what is different between the two that allows us to control one but not the other? | [
"There are several different types of nervous innervation. Your autonomic nervous system which controls involuntary function has General Visceral Afferent (sensory, send impulses to CNS) and General Visceral Efferent (motor, send impulses away from CNS) fibers (there are special fibers as well). Somatic Efferents... | [
"Happy to elaborate!",
"First, a basic explanation of muscle contraction via a change in membrane potential. Each cell has a standard resting membrane potential at which activity is static. Ligand gated channels (and other mechanisms) have some influence on membrane potential, but voltage gated ion channels are... | [
"Thanks for the great answer! If you could explain what you mean by \"cardiac cells have the ability to depolarize spontaneously and without nervous system input\" I would be very thankful."
] |
[
"\"Neutron moderator\" materials slow down fast neutrons so they can successfully interact with radioactive materials to continue the fission chain reaction. How exactly do \"neutron moderators\" slow down the neutrons? Thanks."
] | [
false
] | [deleted] | [
"Graphite has a decent mass match to the neutrons, can tolerate fairly large amounts of damage to the lattice before losing strength, has few possibilities for activation (nuclei capturing an incident neutron instead of scattering it, leading to radioactive by-products), and is fairly easy to manufacture. Light nuc... | [
"The wiki article on this is actually really good: ",
"http://en.wikipedia.org/wiki/Neutron_moderator",
"The basic idea is that hot (i.e fast moving) neutrons will elastically collide with a bunch of cold moderator nuclei. Overall, the temperature and therefore speed of the neutrons will drop, by transferring t... | [
"Not being a nuclear engineer, I cannot give insight into the engineering trade-offs. However, a quick perusal of ",
"http://en.wikipedia.org/wiki/Neutron_moderator#Materials_used",
" suggests that there are lots of choices, graphite being only one or even a minority (esp. after Windscale)."
] |
[
"Why do all the planets in our solar system lie approximately in a plane?"
] | [
false
] | null | [
"All the planets have an inclination (orbit tilt) within a few degrees of each other. ",
"Mercury is the most tilted",
" relative to Earth at 7 degrees.",
"They also all circle the sun in the same direction in orbits which are approximately circles. ",
"This is because it all condensed from the same ",
"p... | [
"Basically the planets and our sun formed from a single spinning cloud of matter. Everything formed perpendicular to the axis of the spin and collapsed to planets and the sun due to gravity and fluctuations in the density of the cloud."
] | [
"Essentially the same reason our planets are on similar planes is the same reason Saturn has rings, right?"
] |
[
"Why can't Helium freeze?"
] | [
false
] | If you drag the temperature scale to 0 Kelvin, every element except Helium becomes solid. Helium, for some reason, stays liquid... I'd imagine every element should be completely solid at absolute zero. | [
"You have been misled by the idea that temperature is a measure of energy. While this is approximately true at high temperatures, it is not correct at low temperatures. Temperature is actually a measure of entropy (actually, its derivative).",
"At very low temperatures, quantum mechanical effects become importa... | [
"Internal energy."
] | [
"Yes.",
" Above roughly 3.2 MPa Helium-3 becomes solid at high pressure. For Helium-4 it will become solid above ~2.5 MPa."
] |
[
"How do we know we’ve discovered a new species of human based on a single fossil, and not just a really ugly dude?"
] | [
false
] | This claims they’ve discovered a new species of human, which is awesome, but since the claim is based off a single fossil, how do we know that it wasn’t just one person with some sort of genetic defect? | [
"I'll start by saying that we actually don't know if this is a new human species or not. The authors who found this fossil argue that it is because:",
"\"A combination of primitive and derived features in the Harbin cranium establishes a good set of diagnostic features that were used to define a new Homo species.... | [
"Thank you!! This was such a clear explanation. You have to think of course the authors are gonna be biased and want it to be a new species so always great to have a neutral perspective."
] | [
"That article repeats the ",
" of the team that found the skull \"",
"\", but also puts it into the context of other old human remains discovered in the region.",
"Dragon Man joins a number of early human remains uncovered in China that have proven difficult to categorise. These include remains from Dali, Jin... |
[
"If the speed of light(C) is the universal speed limit, what would happen to the end of a pole sticking out of the Earth, whose radius is so long its circular velocity exceeds C?"
] | [
false
] | I've taken Calc 3 and University Physics, and this question popped into my head while using the restroom. | [
"The pole would bend.",
"This would only be a problem if the pole were infinitely rigid, but as you can imagine, that's not possible. The pole is made up of atoms, bonded together electromagnetically, and those interactions are all restricted by the speed of light limit. In reality any speed it reached would be f... | [
"Sure. The problem is \"perfectly rigid\" isn't physically possible, so you can't really say what physics would predict in that case. But there's probably some limit in which that's what happens."
] | [
"I like your thought process but unfortunately most of the answers you wrote aren't really correct. The bending that occurs due to super relativistic effects don't put extra pressure on the material because it's space 'bending' not the material. So if it was perfectly strong it would just bend forever in a spiral... |
[
"What ultimately causes death with Alzheimer's Disease?"
] | [
false
] | Assuming a person with Alzheimer's had some incredible caregivers and survives all of the safety challenges and also has all of their basic needs met, what ultimately causes death? Even assuming "everything that can be done" is done (e.g. someone who has progressed to the point they lose the response to eat goes on "tube feeding") what will ultimately cause death? Do organs eventually shut down? | [
"Usually aspirational pneumonia. Alzheimer's patients tend to have worsening impulse control issues, and as a result they may swallow or vomit in a way that fails to protect their airway, which leads to aspirational pneumonia, respiratory failure, and then death. Even when they have a gastric tube (i.e., a \"feedin... | [
"thank you!"
] | [
"Most Alzheimer's disease die from infections secondary to aspiration"
] |
[
"Why do we use uranium as the primary atom in nuclear reactions?"
] | [
false
] | null | [
"Because it's relatively plentiful and it's big and unstable enough to undergo the necessary decays to generate power."
] | [
"The only fissile atoms are",
"(from wikipedia)",
"Fissile means the material is ",
" of critical mass and maintaining the nuclear reaction w/out an outside neutron source.",
"Notice, only U-235 is naturally occurring AND fissile. Plutonium and uranium-233 both require being bred through neutron capture (i.... | [
"I assume you mean electrical power. Electrical power is generated from a working fluid which is cooling the nuclear fuel. So, yes, you would. In fact, in commercial power plants towards the end of their core life, much of the fission reactions taking place are from plutonium, which was bred from Uranium 238 ini... |
[
"If we can't see the whole universe and are continuously seeing more of it, does that mean the universe expanded faster than the speed of light?"
] | [
false
] | We talk about the edge of the "observable universe" and how its continuously growing further as light from sources further away finally reaches us. If we can't see the whole universe and are continuously seeing more of it, does that mean the universe expanded much faster than the speed of light following the big bang? | [
"Here is a very relevant ",
"article."
] | [
"You can use ",
"Hubble's constant",
" to calculate that the matter at the edge of the universe (radius ~46 billion light years) is moving away from us at more than 3 times the speed of light. ",
"Calculation",
"."
] | [
"Here is an article concerning many of the popular misconceptions of the big bang and the expanding universe theory: ",
"Lineweaver Paper"
] |
[
"Using molecular vibration to degrade molecules?"
] | [
false
] | Hi Reddit, I was wondering if it is possible to use the molecular vibration of a molecule to help i'ts degradation. Let's say i have a salt, and i know the exact IR band at which light is absorbed at the ionic bond. Could i make an IR lamp with a bandpass filter and excite the molecules enough to cause increased dissociation? Does it make sense that if the molecule is in an exicted state, especially at the ion bond, it would dissociate faster or easier? Or would any dissociation just be becuase of the increase in energy of the molecule due to the temperature increase of absorbing tha IR radiation? Thanks. | [
"I don’t think salts are IR active... typically IR spectroscopy takes advantage of the polarity differences of covelent bonds. Since salts have ionic bonds they wouldn’t be affected by it. This is assuming you’re using a non-organic salt, like NaCl, rather than NaNO3, of which the NO3- would be active.",
"That be... | [
"There is IR activity for some salts, but it tends to be pretty minimal to non-existent for many of the single atom salts often with defects/impurities causing the absorption. ",
"Which is why we use salt plates as a surface to take IR measurements for organic samples. Because they transparent in the IR region."... | [
"Yes, \"it is possible to use the molecular vibration of a molecule to help its degradation.” But as ",
" points out: ",
"I don’t think salts are IR active.",
"Simple salts do not absorb in the infrared range, and in fact they are ",
" transparent in the IR that ",
"salt plates",
" are used to hold the... |
[
"Ask Science: do any hair restoration things actually work?"
] | [
true
] | null | [
"what kind of dr did you see? a dermatologist? or just your general Dr?",
"It seems like from what I'm reading online that propecia is the way to go"
] | [
"what kind of dr did you see? a dermatologist? or just your general Dr?",
"It seems like from what I'm reading online that propecia is the way to go"
] | [
"did you feel any hormonal effects? libido etc"
] |
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