title list | over_18 list | post_content stringlengths 0 9.37k ⌀ | C1 list | C2 list | C3 list |
|---|---|---|---|---|---|
[
"When someone says \"x is titrated against y\" which is in the burette and which is in the flask?"
] | [
false
] | null | [
"The titrand (or analyte) is the stuff in the flask.",
"The titrant is the stuff in the buret."
] | [
"No, no: The titrand is what is being titrated, and it's in the flask. ",
"X is in the flask. Y is in the buret."
] | [
"Thanks, I was still confused."
] |
[
"From a quantum mechanics perspective, why is a lower energy state more stable?"
] | [
false
] | Hi guys, Thus far my understanding (superficial though) comes from in which one user states that 'systems go to lower energy states when they share their energy with some other system' which in-turn has so many degrees of freedom that 'energy is divided into indiscernible small portions.' | [
"Without going into the math - as it doesn't really help drive the intuition here...",
"A higher energy state will always have a non zero probability of spontaneously shedding some energy to drop into a lower energy state (eg. an electron in an excited state can emit a photon). The reverse will only happen if you... | [
"This is true but the thing is the total state (electron + photon) still conserves the total energy. It’s just that we regard as being a “stable” state of the electron actually isn’t the electron. And we are ignoring the coupling of the atom’s Hamiltonian to the external background field. If you look at this entire... | [
"Sure, but it's possible to answer the question without going into qft. ",
"And it's nice to define your system such that the energy is constant, but if you're talking about the stability of the electron state, then it only really makes sense to talk about the energy of the electron state (although I admit this w... |
[
"What are trichomic prokaryotes, exactly?"
] | [
false
] | A google search doesn't reveal much at all. | [
"Trichomes are hair-like, or filamentous structures. Prokaryotes are single-celled organisms without a cell nucleus, i.e. bacteria. ",
"So trichomic prokaryotes are bacteria with a filamentous morphology."
] | [
"Would be so much easier to just call them \"Hairy Prokaryotes\" :)"
] | [
"Prokhairyotes."
] |
[
"Is there any theoretical/empirical support for the idea that creativity is \"noise\" (or chaos) among the otherwise orderly neural impulses in our brain? (X-post from /r/cogsci)"
] | [
false
] | null | [
"I haven't read iorg's link and this isn't really my specialty, but I can tell you that ",
"low latent inhibition",
" is correlated with creativity. In other words, individuals who are unable to ignore random sensory input (noise) tend to be more creative, especially when paired with high intelligence.",
"On ... | [
"There are some psychology-based theories that creativity comes from \"freeing up associations\". That is, you create a sort of chaos in the brain, and then when everything cools down, you're left with new links between things that hadn't been linked before. But you have to break from \"normalcy\" in order to creat... | [
"This might help: ",
"http://www.on-rampis.ca/xyz-strengths/creativity/crea007.pdf"
] |
[
"How dense is the plasma inside fusion reactors?"
] | [
false
] | null | [
"Either (1) very not dense, or (2) not very dense. There are two main types of fusion reactors.",
"Magnetic confinement fusion reactors (such as JET and ITER) contain hot plasma (around 10",
" K) with magnetic fields and generate continuous fusion. Typical plasma densities in MCF are about 10",
" g/cm",
", ... | [
"The standard density of the atmosphere is 1.2 * 10",
" grams per cm",
" so 10",
" g/cm",
" is actually 100,000 times as dense as the atmosphere."
] | [
"Ah, evidently I can google but I can't read"
] |
[
"If one were to fuse two hydrogen atoms together, would the resulting release of energy be visible to the naked eye?"
] | [
false
] | null | [
"Just the energy from two atoms fusing - no, you would never know it happened.",
"Let's calculate the energy in one hydrogen atom (doing this for the sake of simplicity, the actual energy released would always be less than the energy in two hydrogen atoms).",
"E = mc",
" ",
"= 1.6605402 x10",
" * 299 792 ... | [
"Thank you very much!"
] | [
"Energy as such is a concept, it cannot be seen.",
"Fusion of two hydrogen atoms releases helium, gamma rays and neutrinos, and energy in the form of kinetic energy. Those particules will likely interact with other particles and emit some photons at some point, which you will likely be able to see if you are in t... |
[
"Is it possible to view the moon landing sites through a powerful enough telescope?"
] | [
false
] | And if so, what can we make out? Can we see the lander? The buggy? I doubt we could make out the flag, though. | [
"Not through a telescope we currently have, no. (Well, not from Earth at least, the LRO did, but it was in orbit around the Moon). ",
"Here is an",
" interesting discussion we have about a week ago on this topic. "
] | [
"This",
" is about as much detail as we have so far....will we ever make a powerful enough telescope to see this? maybe..who knows. ",
"The problem is that the objects are quite small, and the moon is a ",
" way away. This heavily reduces the amount of photons being reflected by these objects, back to earth ... | [
"You don't have permission to access /squidoo/moon-landing-photos/photo-of-lunar-lander.jpg on this server."
] |
[
"Why is it that animals can eat rotten meat and drink filthy water, but people can't?"
] | [
false
] | null | [
"Some animals, such as vultures, have adapted to be able to eat rotting meat, or carrion. It looks like ",
"some people propose",
" that the vulture's extremely low pH aids in killing most pathogens, although it seems to be a hypothesis and more research needs to be done to look for other possible mechanisms.",... | [
"When I worked in a clinic (in vet school now), I would hear this myth frequently that dogs GI tracts can handle anything. And maybe it's true that they are somewhat more robust. However, a huge part of the practice was devoted to GI upset. Many many parasites were found in fecals. Sure, they are exposed to more an... | [
"Can I post a followup question?\nWould humans living as hunter gatherers thousands of years ago have been more resistant towards bacteria in rotting meat and dirty water?\nAre we simply more susceptible (assuming we are) towards these kinds of bacteria because we generally don't encounter them as much today?"
] |
[
"Is it possible to raise the temperature of a half-filled Thermos of water by vigorously shaking it for an extended period of time?"
] | [
false
] | null | [
"Yes it is! See ",
"mechanical equivalent of heat",
".",
"The SI unit of energy, Joule, is named after ",
"James Prescott Joule",
", who did some pioneering work on that topic."
] | [
"In a thermos the container wall is mirrored and surrounded by vacuum to minimize heat transfer to the outside (aka why it can keep you drink hot or cold for so long and why it can keep lN2 from evaporating rapidly.) ",
"So its still going to take a good bit of shaking to heat it (I certainly don't care to test ... | [
"Even though this is actually true (that if you shake something, you add energy and it will eventually get warmer by this), you need to consider that since shaking raises the heattransfer of the water to the containerwall, it is not likely you can get the water really warmer than the surrounding fluid (e.g. air) ju... |
[
"Why we don't see solar emission lines when we put sunlight through a prism but a continuous spectrum?"
] | [
false
] | When you put prism in the path of the sunlight you get a nice spectrum spread from red to violet (and beyond the visible part). Why do we get that spectrum? Why don't we see emission lines from hydrogen or helium? Where do other wavelengths come from? How do you "take out all those photons to see say He lines (how heli... | [
"Keep in mind, when we are looking at the solar spectrum, we are really looking for absorption lines, not emission lines. The sun is very very hot, and so mainly acts as a black body emitter, which has a continuous spectrum. However, after the black body radiation is emitted, the gases and materials in the solar at... | [
"These features were originally discovered in prism spectra, so they do occur there. However, the lines are quite narrow, which means that it's important to avoid as much blurring of the spectrum as possible.",
"The sun is not a point of light, but is extended with a diameter of half a degree. Light from each poi... | [
"It's useful to think about this in terms of ",
"optical depth",
". Think about looking something through some fog, for example. If there's not much fog between you and the object you can see it clearly, but as the amount of fog increases the chance of a photon making its way to you without being scattered away... |
[
"Why can't we cure cancer by combining 3-d Imaging and a robot controlled moveable sphere of low powered lasers that destroy only kill cells at their intersection, leaving tissues they pass through undamaged?"
] | [
false
] | So, you've got existing technology that seems to me could target any cancer in any shape in the body by combining Put that tumor model into a computer that remembers all the x,y,z points of tumor and non-tumor tissue Build a sphere/half sphere of low powered lasers targeting at one point, kinda like the so that neighbo... | [
"That is basically how radiation therapy works now. But your idea assumes that we can do all of those things precisely (i.e. with no uncertainty). There are several things that we are, in general, uncertain of:",
"1) We can identify gross tumor tissue to within a few mm. But we can't identify the exact microsc... | [
"Could you do the MRI like 20 minutes before the procedure to reduce changes?",
"There is something called ",
"real-time MRI",
" now, but its limitation is in the fact that it's 2D. Three-dimensional imaging requires reconstruction from many 2D slices, and the collection process itself is one limiting factor ... | [
"Ah, ok, as a video editor i know the hassle of waiting for renders. If it is at it's core a matter of computing horsepower, i guess the fact that computers get faster exponentially is hopeful.",
"As far as spatial resolution, i did find this ",
"article",
" on some new technology that can do this stuff on a ... |
[
"If a computer monitor refreshes at 60hz, and you are displaying 24fps video, how is this mismatch resolved?"
] | [
false
] | I've tried searching about this issue, and I saw people referring to 3:2 pulldown, but I'm not sure exactly what they mean. I'm just wondering how mismatched frame rates are resolved on a display. 30fps video on a 60hz monitor could obviously mesh well by simply playing the same frame twice, but what about when the re... | [
"Your monitor's internals refresh the screen at 60 times per second based on the signal on the input, your computer/video-card updates the signal on that input at, say, 24 times per second. The mismatch is not resolved.",
"Sometimes, when the monitor refreshes while the video card is updating,.. half (or part) of... | [
"3:2 pulldown is explained here ",
"http://en.wikipedia.org/wiki/3:2_pulldown#23pulldown",
". Basically, remember that for a television (conventional NTSC american TV), the vertical refresh rate for the video signal is just below 60hz (59.94hz). Originally, it was exactly 60hz, but since the powerlines run at... | [
"Tearing is a phenomenon that occurs when your video buffer is displayed half-way through a frame update. This rarely occurs when we're talking about video because the frame-rates are well-known and the decoder performance is well understood and optimized for a specific code-path. Video decoders use a specific pa... |
[
"Why don't we dream under a general anaesthesia?"
] | [
false
] | Why can't we dream under a general anaesthesia? | [
"We do dream under general anesthesia. Some patients report dreaming and, although it is not fully understood, some experience something called emergence delirium. If the sedation used is one that leaves the system rapidly, the patient can regain consciousness and be agitated, confused, and sometimes even violent. ... | [
"It actually varies a lot with the drugs we use. Propofol, which is the most commonly used anaesthetic drug in \"the west\" often gives quite vivid, normally pleasant dreams. This indicates that it not just gives sort of a controlled GABA overload, but actually triggers the intrinsic sleep pathways in some way.",
... | [
"Bizarre, The lights go out and you wake up again, but there was nothing in the middle, it's as if you didn't exist with no self awareness to yourself."
] |
[
"How are there still radioactive elements such as uranium on earth when they've had billions of years to decay?"
] | [
false
] | null | [
"Really simple answer: because they take more than billions of years to decay.",
"Uranium-238 has a half-life of about 4.5 billion years, which is (very roughly) the age of the Earth. That means we've only used up half of it."
] | [
"Long half lives of elements like uranium is only part of the answer. Shorter lived radionuclides such as carbon 14 or beryllium 10 are produced all the time when cosmic rays, often in the form of protons or neutrons, collide with other atoms and cause neutron activation or spallation reactions. This process can al... | [
"This seems like a semantics argument. How do you define the age?",
"If when the planet formed, was it there? Almost all, yes (small addition due to celestial impacts). ",
"If the uranium was formed in supernova before earth was formed? Yes, but so was the rest of the material considered earth. "
] |
[
"By what mechanism does male circumcision inhibit HIV infections?"
] | [
false
] | I've read in a number of places, and just recently heard Bono say on The Daily Show, that male circumcision can inhibit HIV infection in men. says infections can be reduced by more than 57%. Why would that be? Circumcision and exchange of fluids seem more or less unrelated to my layman's perspective. How could a circum... | [
"from ",
"http://en.wikipedia.org/wiki/Foreskin#Langerhans_cells",
"Langerhans cells are immature dendritic cells that are found in all areas of the penile epithelium,[52] but are most superficial in the inner surface of the foreskin.[52] A study by Szabo and Short (2000) targets Langerhans cells as receptors o... | [
"I just wanted to lend support to this answer, as current literature theorizes this is the reason. This has been shown in a number of studies, such as ",
"here",
"."
] | [
"In regards to the OP, it doesn't. Not really. It is a contested subject but I personally have seen no evidence to indicate it prevents infection of HIV.",
"A foreskin that has not been cleaned can allow bacteria to grow, but HIV is not a bacteria. The V stands for Virus, and those don't \"grow\" like bacteria... |
[
"If a photon has no mass, why doesn't it pass through objects like other forms of radiation?"
] | [
false
] | If a photon has no mass, why doesn't it pass through objects like other forms of radiation? Why is it reflected by a mirror instead of just passing through? Why can't we use a mirror to reflect Gamma radiation for instance? | [
"Mass has nothing to do with it.",
"Visible light is reflected by matter because it interacts with the electrons in the species that make up that material.",
"The frequency of the light determines how it will interact with various materials.",
"Radiowaves (photons) rarely interact with most materials, except ... | [
"Well in fact gamma radiation is composed of photons. It is electromagnetic radiation that is simply more energetic than the visible light photons. The reason that certain wavelength photons do not pass through certain objects is because their energies are just right to interact with the electrons in the matter.",
... | [
"You're getting into some seriously complicated physics with this question. If you'd really like to begin to grasp this subject, QED [Quantum Electrodynamics] is a series of lectures by Richard Feynman in book format. It's pretty popular because it's designed to explain this challenging subject to a layman, and i... |
[
"Why does food perish and how can suppliers so accurately put a date on when this will occur?"
] | [
false
] | [deleted] | [
"The date is actually rarely accurate. Most foods are good for several days (in some cases weeks or months) after the best before dates. If storage was not ideal, or the packing faulty things can also go off before their stamped date."
] | [
"There is also a difference between \"best before\" and \"use by\" dates. ",
"http://en.wikipedia.org/wiki/Shelf_life#Best_before"
] | [
"The dates listed on food are simply a required thing the FDA does. ",
"Lots of factors go into how long it takes food to spoil so there is no way to put a spoilage date on the food. ",
"The date is a \"sell by\" date most of the time which I think has more to do with covering the stores ass than it does with s... |
[
"About the 7 base SI units: \"7 is the number of physical quantities that are independent from one another. It comes from the fact that the number of quantities in physics is higher by 7 to the number of determination equations (definition equations and natural laws).\" -- Can someone explain this?"
] | [
false
] | Side question: How is the Candela not , since it is a measure of luminous power ( ) per solid angle (dimensionless)? Edit: Thank for the insightful inputs. I took that course for granted, but after going through the lectures again, and having passed the exam, I am now fully convinced that these guys have absolutely no ... | [
"Where did you read that statement? It sounds made up and not based on reality."
] | [
"To answer the side question, the candela is defined to be a unit of PERCEPTUAL intensity of light based on the sensitivity of the human eye. The definition takes into account the perceptual brightness of different wavelengths.",
"That's the difference between luminous intensity (candela) and radiant intensity (W... | [
"I have never heard such a statement. On the surface, it seems to suggest that there are, say, N+7 equations that \"determine physics\" with only N unknowns. Yes, that would mean there are 7 free parameters in that system of equations, but I'm not sure what equations the statements refers to or why they think 7 suc... |
[
"If I replaced the bones in my body with metal replicas what problems would occur?"
] | [
false
] | null | [
"Ok, so even if you get it done that all the tissue will grow onto it and it won't poison you etc...",
"Your ",
"bone marrow",
" would be missing.",
"As you see in the article, you would be pretty screwed without it.",
"So yeah. You would die."
] | [
"White blood cells are generated in your bone marrow, you'd probably miss those. "
] | [
"People already explained the lack of white blood cells and red blood cells because of the missing bone marrow. Another thing that can happen is the inability to heal. Bones can regenerate if a fracture occurs. If you get some type of crack within your metallic bone, you're screwed because eventually the crack will... |
[
"Detecting Observers - Is This Possible?"
] | [
false
] | I am by no means an expert on Quantum Physics, but I've been reading about the and the experiments, and I had an idea which I fully expect to be (gently) disabused of. Let's say you have a room that has a display device which consistently outputs information regarding which-path and/or which-slit photon results from re... | [
"I don't know if this really answers your question, but...\nFrom the observer effect wiki you linked:",
"This thought experiment was proved correct experimentally. The people conducting the experiment found that when the sensor was turned off, an interference pattern developed, but when it was turned on, the inte... | [
"From what I know about the observer effect, it does not have to be a human observing the experiment to interfere with the results.",
"Let's say you have a room that has a display device which consistently outputs information regarding which-path and/or which-slit photon results from repeated automated dual-slit ... | [
"Yes, this is the case. Observation really doesn't describe what is happening here. Observation means any sort of interaction, it has nothing to do with whether a human sees it or not. "
] |
[
"How are there still unsolved math problems from the '50s?"
] | [
false
] | [deleted] | [
"We understand the laws (we made them, after all), but not all the consequences of them. Fermat's last theorem is a great example of an extremely difficult problem which is nevertheless very simple to understand.",
"Could it ever be true, for some integers ",
" ≥ 3 and ",
", ",
", ",
" ≥ 1, that ",
" + ... | [
"How are there still unsolved math problems from the '50s?",
"It's worse than that ! There are problem that are thousands of years old. For example, the existence or non-existence of odd perfect number (we found evidence that this problem was considered by Nicomachus of Gerasa around 100 AD, and it's still an ope... | [
"That really depends on the problem. Fermat's has negligible impact outside of mathematics. Something like ",
"P vs NP",
" could potentially be huge for just about the whole of humanity if answered in the affirmative (although, it's likely that the right answer is ",
" affirmative)."
] |
[
"Is there a material that can block magnetic fields?"
] | [
false
] | I understand that magnetic objects create a field, and that a magnetic field can cause damage to certain electrical equipment or data storage. (Bonus Question: Why is that?) But is there a material that can create a barrier for magnetic fields, So if you put a paperclip on one side and a magnet on the other, the paperc... | [
"Any ",
"closed ferromagnetic surface will block magnetic fields",
". Basically, a hollow iron shell will divert magnetic field lines away from the inside of the shell and force it to travel around the outside of the shell.",
"In addition, ",
"superchilled superconductors will expel a magnetic field by auto... | [
"Type 1 superconductors will completely expel magnetic fields, type 2 allow magnetic flux through vortices with a quantized amount of magnetic flux in each vortex.",
"1"
] | [
"Over-unity or perpetual motion/free energy machines are impossible. Just putting that out there.",
"That being said, there are materials which can change the shape of a magnetic field. Check out mu-metals.",
"Bonus: Many forms of data storage today is achieved in the form of very delicate magnetic orientations... |
[
"When animal mothers \"adopt\" a newborn animal from another species, does the mother know that they are not the same species?"
] | [
false
] | [deleted] | [
"Probably not. Unless there is evidence that the animal is self aware, it would do well to think of what is going on as automated processes rather than a decision and that the adopted animal is hijacking this.",
"A good way to illustrate this is with parasitic cuckoos.The common cuckoo lays its eggs in the nests ... | [
"While we are on the subject of parasitic cuckoos, interesting side note: ",
"here",
" is an article about the Eurasian magpie which evantually figures out how to identify these eggs and deprive them. These birds do demonstrate some self recognition though so makes sense."
] | [
"So the cuckoo triggers an instinct in the parent bird to feed it. Wouldn't this be similar in some ways to humans adopting \"cute\" pets -- isn't the perception of something as \"cute\" part of our instinctive behavior to care for children?"
] |
[
"Does a Martian night sky look similar to our own? Do stars appear brighter since the atmosphere is thinner with less light, or are they substantially dimmer because of the dust?"
] | [
false
] | I'm riding the curiosity hype train right now. I know the colors in the pictures we get from Mars usually have false colors, but it always seems that visibility is usually slightly less than earth's, even though the atmosphere is thinner. | [
"Isn't it also clearer because there is 0 light pollution as opposed to earth's bright cities which block out some stars?"
] | [
"Isn't it also clearer because there is 0 light pollution as opposed to earth's bright cities which block out some stars?"
] | [
"\"Think\" is supposed to be \"thin,\" not \"thick.\" It confused me the first time I read it, too."
] |
[
"Is there a limit to how big a Rocky Planet like Earth can get?"
] | [
false
] | Like can there be a Earth type planet the size of the Sun. | [
"Others have described the physical limits. But there's another problem that will kick in earlier: such a planet will not even form. The protoplanetary disk that planets are born from contains mostly hydrogen and helium, with a small percentage of rocky material. Smaller, rocky planets like Earth don't have enough ... | [
"This answer is correct, but realistically, such a large rocky planet would be incredibly rare or maybe impossible, as any body that size would have enough gravity to begin drawing hydrogen and helium in from the proto-disk during its formation and inevitably become a gas giant of some sort."
] | [
"This answer is correct, but realistically, such a large rocky planet would be incredibly rare or maybe impossible, as any body that size would have enough gravity to begin drawing hydrogen and helium in from the proto-disk during its formation and inevitably become a gas giant of some sort."
] |
[
"How and why does a brain-dead body decompose?"
] | [
false
] | In the news lately, there have been several cases of brain-dead people being kept alive artificially, even though they are medically dead. In reading these articles, I've learned that an artificially animated body cannot stay that way indefinitely and will begin to decompose. How and why does this happen? If a person s... | [
"A person can be \"brain dead\" and the rest of the body \"alive\" as long as the body is kept breathing (ventilator) and given sustenance (gastric feeds). The body will waste away due to inactivity, but it won't \"decompose\" as such. The muscles will atrophy with misuse, the skin will break down from pressure sor... | [
"Without knowing all the details, it sounds like they were saying \"decomposing\" instead of \"wasting away\" (which is what I would say)."
] | [
"So my question is this, the woman from Texas was stated to be decomposing. Was that an exaggeration? I believe it was said by a family member. Or was it just her body not being in use, so to speak? Would it be easy to confuse the two? ",
"Sorry if this isn't appropriate, I'll delete if need be. "
] |
[
"If snow is just sub 0 precipitation, then why does it snow more in the winter than it rains in the spring/fall?"
] | [
false
] | [deleted] | [
"2 reasons. First, the colder it is the harder it is for the air to retain moisture. Second, snow takes up more volume because there is a lot of air in snow on the ground. 1 foot of snow is about as much as 1 inch of rain."
] | [
"Oh wow, that's cool to know, thank you!"
] | [
"There are also a lot of seasonal patterns at work. There are some places where this isn't the case. In a lot of places though, it's about the seasonal winds and how they interact. Sometimes you just tend to get more precipitation in the winter because of wind patterns"
] |
[
"[Astronomy]Is it possible to have an orbit around the earth and the moon?"
] | [
false
] | null | [
"Because the center of mass of the Earth-Moon system is inside the Earth, this would just be a distant orbit around the Earth. So in a sense, any orbit around the Earth farther than the moon would satisfy this. The upper limit of this, the region where the Earth's gravity dominates over the sun's, is called the Hil... | [
"So, just outside of the Hill Sphere, would an object then start to orbit around the Sun?"
] | [
"There important thing here is the word \"just\". The Hill sphere doesn't have sharp edges, instead, the stability of orbits around objects depends on whether it is prograde or retrograde and the masses of all involved bodies. Retrograde orbits are more stable than prograde orbits (about 70% and 50% of the Hill sph... |
[
"What happens to all the electrons that are flowing through an insulated power cord when you unplug it?"
] | [
false
] | Wouldn't that cause the atomic structure of the atoms to become unstable? | [
"A few reasons this isn't an issue:",
"1) Remember that you're starting with a material which is approximately neutral (i.e. same number of electrons as protons) and that electronic motion is in a circuit. So any electrons that exit are approximately compensated for by electrons that reenter; on average, you're n... | [
"Thanks for the detailed explanation. It's always intrigued me how current flows when the electrons barely move at all (especially in AC). How exactly does this happen? I have a vague notion of energy being passed down the line like a wave (or something), not really sure to be honest."
] | [
"It's just that there are a whole lot of electrons moving slowly, so the total current is actually pretty large.",
"In fact, the total current is the electron charge times drift velocity times electron density times the cross-sectional area of the wire. If you plug in numbers, say for a 1 mm diameter copper wire,... |
[
"If the human egg is the largest cell, and human sperm is the smallest... How big would a sperm cell be if the egg was the size of a basketball?"
] | [
false
] | It is just a question to which I have always wanted an answer. | [
"Egg Cell\n Diameter = 130 um\n Volume = (4 * pi * (130 um / 2)",
" = 1150000 um",
"Sperm Cell\n Diameter = 5 um\n Volume = (4 * pi * (5 um / 2)",
" = 65.4 um",
"Ratio of Diameters = 130 um / 5 um = 26\nRatio of Volumes = 1150000 um",
" / 65.4 um",
" = 17500",
"So, what's 1/26th the diamet... | [
"You are sort of missing the point."
] | [
"I'm sure he meant the largest cell in a human"
] |
[
"How exactly does White Blood Cell detect bacteria ?"
] | [
false
] | [deleted] | [
"The main white blood cells chasing bacteria are neutrophils. They have receptors on their surfaces that recognize what are called formylated peptides produced by bacteria. Formylated peptides are breakdown products of proteins made by bacteria, since bacteria begin all of their protein sequences with the modified... | [
"I did some googling to pin down the source of this gif, and it was apparently made by",
" David Rogers at Vanderbilt University sometime in the 1950s",
". The bacteria here is ",
" and the white blood cell is specifically a neutrophil. ",
"As you suggest, the neutrophil is following some sort of biochemica... | [
"This is severely incorrect.",
"B cells ",
" neutrophils or macrophages. Neutrophils and macrophages are leukocytes (white blood cells) that are in the myeloid lineage. B cells are completely different cell type which are also considered leukocytes, but they are in the lymphoid lineage. B cells are part of t... |
[
"If I kept my finger on an object for long enough, would the skin start growing to it?"
] | [
false
] | I am just wondering if skin can/will start growing to inanimate objects if it you kept it there for a long time? This may be stupid. | [
"No it will not. Think about piercings, I've had an earring in my tragus for over a year and skin has never grown onto it. ",
"This",
" is about how bodies reject piercings, but it talking about how the body rejects foreign objects is the same reason why your skin won't begin to grow on an inanimate object. It... | [
"Your piercing healed. If you have exposed wounds and it is in constant contact with a foreign surface, it would grow over it, would it not? Isn't this essentially how a graft works?"
] | [
"A (skin) graft is basically a bandage. It does not heal into new skin."
] |
[
"Why do nuclear bombs form this typical mushroom cloud and not just a ball shaped cloud?"
] | [
false
] | null | [
"The cloud is called a pyrocumulus and it is not specific to nuclear blasts - large forest fires and volcanos can cause it too - with a slightly different shape. It is very similar to the classical storm cloud - the cumulonimbus. Hot air rises and expands. Expansion cools it down. Eventually it reaches an equilibri... | [
"Mushroom clouds form in any case where there is a very hot central feature, causing a strong updraft shaft where that heated air rises. This rising against the stagnant colder air around the circular rising center \"stem\" causes swirling currents in the form of a muffin top or mushroom cap."
] | [
"Another reason not yet mentioned is that the shockwave may reflect off the ground, pushing the fireball into a donut shape, which helps catalyze the other effects mentioned. ",
"Here",
" is a slow motion video of this happening. If you think this is weird looking, I suggest reading about the ",
"rope trick e... |
[
"Why do you get a runny nose from eating spicy foods?"
] | [
false
] | Also, why do you get a runny nose from the cold? | [
"It's the same mechanism behind both instances, just triggered by different things.",
"The reason you get runny noses is increased blood flow to mucosal tissue that makes all that snot in the first place. More blood means more fluid being supplied to the mucosa meaning more fluid oozing out of your nose.",
"In... | [
"Can you comment on why \"the\" cold [temperature] (as opposed to \"a\" cold [virus]) would trigger a runny nose? It seems contrary to the idea that increased blood flow triggers it. I would think cold weather would cause arteries to restrict, causing less blood flow.",
"Edit: Punctuation"
] | [
"Yes actually! I'm glad you brought that up. That's a couple of other factors that are in play. One of the purposes of the nose is to filter and humidify the air that reaches the lungs. Cold air is much dryer than warm air as it's less capable of holding moisture, as anyone that's suffered dry skin in the winter... |
[
"Do insects perceive time differently than us humans since their reaction time and reflexes seem far superior than our brain can process?"
] | [
false
] | null | [
"This ",
"source",
" indicates that neural impulses travel at speeds of 2-200 mph. ",
"Neurons don’t transmit electrically like you would think; they use waves of ions chemically moving through the cell."
] | [
"Yes, not only insects but different species in general perceive time differently. We measure it by checking in what frequency of flickering light a species perceives it as a continuous (non flickering) light. For example the value is greater for dogs than humans so they will see every frame of a movie on a TV with... | [
"This is a fantastic answer for so many reasons. Distance that electrical synapses have to traverse matters: it’s a 2-way street. Upstream then downstream. The reason their reflexes are superior is precisely bc of that AND the fact that they’re not processing like higher order life does. Much of their response is d... |
[
"When a network \"loses a packet\", where does it go?"
] | [
false
] | [deleted] | [
"The packet is not lost in that we don't know where it went. Don't think of it as two cars colliding. It would be more accurate to say that the signal of the original packet is changed or becomes combined with the other and is then unreadable by the receiver. Packet loss can also be associated with attenuation(s... | [
"http://i.imgur.com/lq88U.jpg"
] | [
"http://i.imgur.com/lq88U.jpg"
] |
[
"In the context of nuclear reactions, what is the difference between prompt criticality and delayed criticality? Why does one result in a nuclear explosion while the other does not despite them both being supercritical reactions?"
] | [
false
] | I already understand the process by which nuclear reactors work to a fundamental level with the ideas of moderators and control rods sorted, but what I cannot seem to understand is the difference between prompt and delayed criticality. Like, both are supercritical so both should in theory result in exponential growth o... | [
"For each fission reaction, you have ",
" neutrons and ",
" neutrons. Prompt neutrons are emitted during the fission, so they come out on a timescale or effectively zero for engineering purposes. The delayed neutrons are the result of beta-delayed neutron emission, so they’re limited by the half-lives of the be... | [
"It's about timescale. Delayed criticality ramps up slowly enough that operators can control it, and also slowly enough that even if it isn't actively controlled it will be self limiting, as the increase in temperature disrupts the reaction.",
"By contrast, prompt criticality occurs fast enough that it releases t... | [
"It all depends on the equation you use and the assumptions with it. ",
"The period equation has some assumptions built in which are true when you are close to k=1, but results in this large step change in calculated period at prompt criticality. One of the assumptions is that k is near 1 and that you can change ... |
[
"Can pi be expressed rationally in a non base 10 number system?"
] | [
false
] | [deleted] | [
"No.",
"The definition of a rational number is that it can be expressed as the ratio of two integers. So a number X is rational if there exists integers A and B such that X = A / B.",
"Note that this definition is completely independent of the number system. "
] | [
"Regardless of the base, PI will always be irrational and transcendental. Properties of numbers hold regardless of base because the base is just a way of representing the number, not defining it. You could put 3 in any base you felt like and it would still be a prime odd number. "
] | [
"No, it doesn't. At its heart, pi is a ",
" having to do with the geometry of a circle, not a literal count. ",
"For example, 17 is a prime number in any base. Changing the base doesn't change the fundamentals of mathematics, it merely changes how you express it. If you try to use pi as the base, all you've re... |
[
"How exactly does radiation mutate DNA? Is there a specific mechanism behind it?"
] | [
false
] | null | [
"Directly, they cause faulty bonding within DNA strands",
". ",
"Indirectly, they ",
"create free radicals through homolysis",
"; the free radicals can then damage DNA."
] | [
"Radiation is often described as either ",
" or ",
" radiation, depending on whether its individual particles have enough energy to knock an electron off an atom. Ionizing radiation has enough energy to break molecular bonds and cause the chemical changes that ",
"/u/airbornemist",
" describes, and by doing... | [
"Pyrimidine dimers induced by radiation as mentioned above will produce mutations if not repaired by specific cellular mechanisms that exist to recognize these bulky bases and excise them. Pyrimidine dimers are suspected to be the main cause of UV-induced mutagensis leading up to melanoma.",
"Other forms of radia... |
[
"In \"The Martian\", a stranded astronaut lives off a daily multivitamin and 1200 calories worth of potato. Is this actually feasible?"
] | [
false
] | In the book, it's explained that he uses potatoes for energy, vitamins for his actual "nutrition", and supplements with a meager amount of protein from his nasa-supplied rations. Is this viable in the short term? In the long? What would prolonged subsistence on that diet do to a human over the course of a year or longe... | [
"This would not be viable for more than a year or so, as the astronaut would run the risk of protein deficiency and phosphate deficiency. ",
"Although potatoes contain acceptable amounts of phosphate, it's in a form that the human body is unable to digest. Specifically Inositol PolyPhosphates also known as Phytic... | [
"There are a lot of breakfast cereals and other prepackaged foods, that have added B-12. ",
"Also, as I mentioned a certain amount of B-12 is produced by gut bacteria. But anyone on a vegan diet should be aware of B-12 intake. ",
"Vitamin D deficiency can also be a problem for vegans, if they avoid milk produ... | [
"There are a lot of breakfast cereals and other prepackaged foods, that have added B-12. ",
"Also, as I mentioned a certain amount of B-12 is produced by gut bacteria. But anyone on a vegan diet should be aware of B-12 intake. ",
"Vitamin D deficiency can also be a problem for vegans, if they avoid milk produ... |
[
"Is it possible to make a region of space absent of atoms?"
] | [
false
] | I know that a perfect vacuum cannot be formed because of quantum fluctuations. But also when a compressible fluid is shaken with enough force, vacuum-bubbles can form. Are these completely empty? Can they suck in extra matter momentarily? Are they truly absent of any atoms? Edit: Because of the inertia of the fluid, th... | [
"I know that a perfect vacuum cannot be formed because of quantum fluctuations.",
"Not necessarily, but that's perhaps a bit off-topic. ",
"But also when a compressible fluid is shaken with enough force, vacuum-bubbles can form. Are these completely empty? ",
"Nope. Caviation bubbles can have a quite low pres... | [
"The best laboratory vacuum is about 1 nPa (nanopascal). Anything below 10 nPa is already quite state of the art."
] | [
"Thank you. This is the answer I wanted."
] |
[
"How likely is it that digital data we have right now (of music, movies, pictures, etc) are preserved and recoverable thousands of years into the future?"
] | [
false
] | null | [
"Such a question is difficult if not impossible to answer. There are too many variables; what country are you talking about for example, as a war or conflict could destroy data storage infrastructure. Which company because of how likely they would be to preserve data through acquisition or financial ruin. What is ... | [
"Probably not for very long. The lifespan of commercially produced DVDs and CDs is 25 years \"or more\" at best; those you can write at home are only 5 to 10 years. The problem is that the plastic in the disk will deteriorate and become impossible to read through. Perhaps we can imagine a future where the backing i... | [
"I disagree; I don't interpret this as a question about the course of history, but rather about the aging properties of digitial media. I cannot claim to be comprehensively knowledgable about this subject, however, I was able to hunt down this link,",
"http://www.auldworks.com/awserv/archcdr.htm",
"which says:"... |
[
"How does time dilation work in this scenario?"
] | [
false
] | The classic example is that Alice leaves earth on a spaceship traveling at some speed comparable to the speed of light. Bob however stays on earth. Special Relativity tells us that Bob will observe a clock traveling with Alice to tell time at a slower rate than one that Bob himself has. If Alice makes a round time and ... | [
"Alice turns around and stops. She feels this acceleration. Accelerated and rest frames are not equivalent; Bob does not feel this. This breaks the symmetry."
] | [
"Any inertial frame (one that is at a constant velocity) is equivalent to a rest frame. Alice saying Bob is moving one way is the same as Bob saying Alice moving the other way. However, accelerated frames are not equivalent to rest frames. Alice saying Bob is accelerating is not the same as Bob saying Alice is acce... | [
"There isn't a first or a second. Simultaneity doesn't exist when you compare between different reference frames. Differently moving observers don't necessarily agree on the order of events."
] |
[
"If you chip your bone from an injury, what happens to it?"
] | [
false
] | null | [
"This is also how moving teeth with braces works. Tugging on the tooth causes bone to break down in front of the tooth and new bone to be created behind it. So the tooth \"flows\" through your jaw to its new location. "
] | [
"If the cells in the chipped piece are still healthy and it's in the right place, I suppose so. Broken bones will reconnect when set after all. "
] | [
"Injury or no injury, bones constantly undergo breakdown and regeneration. There are two types of bone cells: osteoclasts break down old bone while osteoblasts create new bones. Hormones keep the actions of these cells in balance so that bones are kept in healthy density. Based on this, I would imagine that an inju... |
[
"How long has Earth had conditions that would be suitable for the survival of a 21st century person?"
] | [
false
] | Ignoring the complexities of getting to a said time period and ignoring the issues of surviving contact with the predators that exist in the time period, how far back can one go and survive? And I know that humans would probably succumb to any foreign illness, bacteria or virus eventually so for the purposes of this qu... | [
"First, as for the illness factor, 21st century humans have the most advanced diseases",
"What expertise/evidence do you have that it's useful to think about a linear progression of 'advancement' for infectious diseases over history? It's perfectly plausible that the host/parasite battle was simply at a qualitat... | [
"First, as for the illness factor, 21st century humans have the most advanced diseases. Any contact a 21st century time traveller would make with ancient humans would almost assuredly kill them off.",
"Looking at geological timescales, the first place to look would be atmospheric oxygen levels. This lecture see... | [
"I think this would also depend if you would consider the \"snowball earth\" ice ago 650 million years ago survivable. Though the theory does now include the probability of an equatorial \"belt\" that was not covered in ice allowing for life "
] |
[
"Would it be possible to make a bio-luminescent tattoo?"
] | [
false
] | Over in it was noted that are pretty cool, followed by discussion of how to make them. One idea was an implanted LED system, another more interesting one was injecting bio-luminescent fungi or bacteria. Would it be possible to do this? | [
"I couldn't find anything that had already been done the way you're looking for (UV tattoos have already been mentioned and I think you're looking for something that glows under any amount of light). So, I went about trying to figure out how this could be accomplished. The idea of bio-luminescent organisms was inte... | [
"I presume this person would like something that glows in natural light versus UV light like the one you linked."
] | [
"I presume this person would like something that glows in natural light versus UV light like the one you linked."
] |
[
"How are the polytropic constant, adiabatic index, and central density chosen for simple TOV neutron star models?"
] | [
false
] | I am a bit confused (and getting a little frustrated) trying to get a straight answer about these. For a bit of background, I'm a 3rd year grad student in physics but my program has not had a course offering in GR available since a year before I started. I have been trying to self teach basic GR, and have successfully ... | [
"But, there are three things I am still quite unclear about: the polytropic constant used for neutron star models (I've seen 0.25, 100, 5.38x109 and 1), ",
"Those are going to depend on the units you're working in. Someone might might use a dimensionless density (normalized by nuclear saturation), they might be u... | [
"Oh dang, thanks for the in depth reply!",
"I'll take a look at white dwarf modeling today!",
"Cheers!"
] | [
"I was under the impression we do not really have a good understanding of the equation of state for neutron star and hence the polytropic index was not really well known. Not really my area though."
] |
[
"Why do elliptical galaxies have a low abundance of heavy elements?"
] | [
false
] | null | [
"There are a couple of moving parts here to keep track of to understand their observation: the age of the galaxy, the shape of the galaxy, and the chemical composition. I'll try to circle around them all.",
"The distribution of elements in a galaxy, sometimes called its metallicity, is a function of its age. Th... | [
"Assuming you meant to say ",
" and not ",
" galaxies in your description I don't see the soundness of their reasoning. A typical elliptical galaxy has significantly ",
" metallicity than a spiral galaxy such as our own."
] | [
"Older stars. In general, the earlier a star formed, the less metals (in the astronomy sense, meaning anything heavier than hydrogen) it will contain. The interstellar medium hadn't been \"polluted\" with as much of the heavier elements as it has been today.",
"I don't know what they mean by full sized planets th... |
[
"Would the length of a Sidereal day change if the Earth had an orbital period of 6 months? How about a Solar Day?"
] | [
false
] | This is for an assignment in my astronomy class, as a heads up. This is not the direct question however (since I want to figure it out on my own, at least as much as I can). I know (or, think I know) that a Sidereal day is 23 hr 56 min, and is determined by the apparent location of the fixed stars. A solar day (I think... | [
"The sidereal day would remain the same. The relationship to the stars would not change.",
"The solar day would be shorter, because the earth would not have to rotate as far as at present to put the sun at the same position in the sky."
] | [
"Currently, the solar day is about 4 minutes longer than the sidereal day.",
"If the earth traveled twice as fast along its orbit, it would only have to spend have as much extra to make up the distance. So the solar day would be about 2 minutes shorter than it is now. "
] | [
"Thanks! To ask a follow-up, is there any way to tell how much shorter the solar day would be than the sidereal day? ",
"The way I understand it now, a year with the Earth moving around the Sun in 6 months would only be 182.625 solar days, is that correct? If so, does that make a solar day half of what it is dur... |
[
"BiologyDoes the CAS9 enzyme associate and disassociate with it's guide RNA like a regular enzyme with some known kd? or once it's formed the complex does the guide RNA just stay bound."
] | [
false
] | Also what are the ramifications of this for delivery of the enzyme to every cell in the body simultaneously. | [
"There's no such thing just \"staying bound\" if two things are not physically connected in any way. Guide RNA is a ligand like any other, so Cas9 will have some particular affinity for it, with accompanying on and off rates. ",
"This",
" paper states a Kd (so the lower the number, the higher affinity Cas9 has ... | [
"Thanks for the reply. I just wasn't sure about the structure of the complex since they look quite intertwined - it must be strong. 10 picomolar is crazy strong, getting into biotin/avidin territory. ",
"There's no such thing just \"staying bound\" if two things are not physically connected in any way. ",
"Do y... | [
"I think avidin/biotin is something like 1fM, but 10pM is nothing to sneeze at. One of the DNA-binding proteins I used to work on bound its highest-affinity sequence with a Kd of 200pM, which in our lab was extremely high affinity. "
] |
[
"What animal is this skull of?"
] | [
false
] | My family and I have found a skull during a hike in Germany, in the "Sächsische Schweiz" (near Dresden) to be exact. We're puzzled about what animal it could be. These are the pictures: Our first thought was a wolf or fox or something similar, but the molars aren't matching, and if it weren't for the fangs we would hav... | [
"Some kind of ",
"wild boar",
"? That was my first thought on seeing those lower teeth at the front. Seems kind of long and narrow, but there's at least one like that in a google pic search."
] | [
"That looks very much like it, indeed. The teeth and the size of the skull fit. Stupid that it didn't cross our minds, hehe. Thank you very much."
] | [
"I was thinking about this a little more, and it occurred to me that it might be a female boar skull. That might explain why a lot of those google images look more robust and fierce, because hunters go for males, which would have bigger tusks and a head built for fighting other males."
] |
[
"How/where do we find naturally occurring mercury?"
] | [
false
] | Does it appear in pools on the surface of the earth? Inside geodes? Especially in large quantities, it just seems strange that it is naturally occurring... Curiosity piqued by the frontpage post with the cannonball floating in mercury. Thanks in advance! Edit: Thanks, Science! Great answers. Some pokemon related. ... | [
"The liquid metal doesn't occur naturally, we extract it out of ores like ",
"cinnabar",
"."
] | [
"Native mercury can sometimes be found with cinnabar, actually. "
] | [
"Native mercury will locally be found as tiny blebs within pockets of cinnabar within mercury deposits or mercury-bearing polymetallic deposits. I've never encountered sufficient volume for pools to form, only the tiniest little balls clinging to a fracture surface or clogging some porosity. ",
"My understanding ... |
[
"Aren't all intercalating nucleic acid dyes (such as GelRed, SYBR Green) mutagenic to some extent?"
] | [
false
] | If so, how are they "less" carcinogenic as compared to EtBr ? | [
"Sorry to be linking bitesizebio (I like them a lot, and they do list sources), they are not exactly peer reviewed, but they had a really good article - OK it was in 2007, but still relevant:\n",
"Ethidium bromide - a reality check",
". Apparently EtBr isnt really even that bad, and may even be less toxic in m... | [
"Clinical molecular technologist here, I think a fume hood is completely unnecessary. As a powder, EtBr is unlikely to become airborne and once it is in solution...well. And as for the correlation to cattle, I understand where you are coming from, but I think this is a logical correlation. The mechanics of DNA are ... | [
"Being better safe than sorry is one thing, but it's also important to have a realistic understanding of a chemical's real hazard level. People go insane about EtBr in particular like it is some sort of superweapon. In some labs there are huge signs with skulls and bones wherever people use EtBr and everything that... |
[
"Suggestions for cheap fluorescent substance, to be used in science projects involving ultraviolet?"
] | [
false
] | I've plenty of projects to keep myself busy for a while, but I'm also adding to the queue. So right now I'm researching the N2 (nitrogen) laser, which appears to be one of the easiest DIY lasers to get lasing, but of course it's ultraviolet. So I need something to make UV visible. Some people recommend thick ultrawhite... | [
"Tonic water. The quinine in tonic water is fluorescent."
] | [
"Buy a bunch of highlighters, pull out the spongy bit, drop it in water. Classic college party \"decoration\" trick"
] | [
"Search glow in the dark or blacklight paints, or just go to a craft supplies store. There are plenty of products for a few bucks that are designed to fluoresce and in different colors too."
] |
[
"Do viruses stay in the human body forever after symptoms stop?"
] | [
false
] | I don’t remember where I had heard it from but I thought that it was impossible to get rid of all individual viruses from a body even after symptoms have stopped and the person has recovered. Is it true that all viruses stick around in the body for the rest of our lives after we’ve contracted it, just in very small, un... | [
"Some viruses become immortalized in the body, but not all. The biggest example is the Herpes family (Herpes 1&2, Chicken Pox/VZ, CMV, EB). They basically \"live\" forever inside a certain cell type and go through cycles of dormancy and activity usually mediated in part by the host's immune system and hormonal/stre... | [
"The vast majority of viruses are permanently eliminated from the body by the immune system. There are a handful of exceptions, but they are way in the minority. ",
"Examples of viruses that are permanently eliminated within days to weeks of infection: measles, mumps, rubella, yellow fever, polio, noroviruses, in... | [
"I agree with everything ",
"u/Grauzevn8",
" said! A good example of how retroviruses can stick with you forever is endogenous retroviruses in humans. Our genome actually carries the DNA of ancient, now extinct retroviruses that infected our ancestors and then after cleared the infection, their DNA stayed. The ... |
[
"Why does an epsom salt/magnesium sulfate bath help remove a splinter or other foreign body?"
] | [
false
] | My dog occasionally gets spear grass and splinters in his paws. If I don't check him after walkies and they become embedded under his skin, a little oozing bump appears and I have to go hunting with tweezers. A few times now I've had to go to the vet to get the things removed, and every vet I've talked to suggests gi... | [
"Here are some guesses on my part:",
"the magnesium sulfate solution has a lower water potential than your body, so water flows outwards into it. This would necessarily be through the hole created by the splinter and might help to dislodge it.",
"Magnesium ions reduce swelling and are used by muscles so that co... | [
"Osmosis",
"By submerging the paw in a bath solution that is saltier than conditions within the cells of said paw, you encourage the cells to flush out water (in an attempt to reach equilibrium between the saltiness of the water and the saltiness inside the cell). The excess deluge of fluid, flowing from inside t... | [
"I don't know either, but I could only guess it would dehydrate your skin, causing it to recede from the splinter."
] |
[
"If deep water is colder than surface water, then why does the water at the bottom of a lake not freeze before the surface water?"
] | [
false
] | null | [
"A few key things to keep in mind:",
"- Nearly all heat transfer to/from a lake occurs at the surface\n- It takes increasingly more energy to mix water masses of increasingly different temperatures\n- The maximum density of water occurs at 4º C\n- Less dense masses float on top of more dense masses\n",
"So, for... | [
"One of the things other people didn't mention pressure hinders water crystallization (One of the few exceptions. Most materials behave oppositely) and deep water tends to be under fairly large pressures. "
] | [
"Short version: same reason ice floats. ",
"Most things, the colder they get the denser they get, so the cold things sink to the bottom. With water, the solid form [near standard temperature and pressure] is less dense than the liquid so if the water starts solidifying it rises. The maximum density is at 4 deg. C... |
[
"Why are soap bubbles different colors?"
] | [
false
] | We have a soap bubble machine, and the bubbles come out in a range of colors. With no immediately discernible system of size, position etc to explain why some are orange, som bluish etc | [
"This is actually a physics question. Light gets reflected by both the inside and outside surfaces of the bubble and because these surfaces are so close together the light waves from each at able to interfere with each other depending on the thickness of the bubble each wavelength (color) of light may interfere con... | [
"It might not be discernible to the naked eye but there is probably slight size differences. This slight difference causes the white light that enters the bubble to refract at different angles in each bubble. Here’s the cool part, different wavelengths of light within the white light will refract at different becau... | [
"This phenomenon is also visible when liquids that don't mix with water are spilled into water (eg, gas, oils, etc). When you see a rainbow on a puddle, it's because the oil is very thin and not of a constant depth and so as its depth varies, you'll see a variety of rainbow colors."
] |
[
"Seeing as blackholes don't let light escape, how can we have quasars ?"
] | [
false
] | [deleted] | [
"The light escapes before it reaches the event horizon.",
"If too much matter is trying to fall in the black hole, it starts to bunch up in the accretion disk and to heat up.",
"When things get hot they emit light."
] | [
"To add, you actually get a lot of the emission you're seeing as synchrotron (spinning electrons in a magnetic field) on top of the thermal. The magnetic fields around the black hole also create collimated jets, and emission can come from these regions as well. You can see a model of quasar and the various areas of... | [
"This is a common question here - a search for something like \"light quasar\" would probably give you some high-quality answers.",
"I'll give a brief explanation though. The light from quasars isn't being emitted from the central supermassive black hole itself - it's actually being generated from an accretion d... |
[
"Possible to decompose function into non-sine waves?"
] | [
false
] | Fourier decomposition transforms a function into a superposition of sine functions with different amplitudes and phases. But is it also possible to decompose a function into other types of waves, for example triangular or square waves? | [
"/u/thephoton",
" is correct, and I'd like to mention a few details. If we have a set X, maybe a subset of the real line or ",
" or the complex plane or ",
", then there is a special set of functions called ",
"L",
"(X)",
". These are the functions f(x) from X to ",
" (or ",
") so that the integral ... | [
"Yes it is possible. There are many sets of functions that form a ",
". Any of these sets of functions can be used as the basis into which you can decompose any well-behaved function. ",
"One such set that is closely related to square waves is the ",
"Walsh basis",
".",
"I don't know of any such set that ... | [
"Conversely those sine waves can be decomposed back in to square waves so..."
] |
[
"Which greenhouse gas is worse? Methane or the fumes from burning it?"
] | [
false
] | null | [
"It burns into carbon dioxide and water. Methane is a worse ghg than carbon dioxide by itself. The epa's global warming potential numbers take the gases' lifetimes and decays into account.",
"But overall the question isn't burning it vs not, but retrieving it from underground storage and releasing it into the atm... | [
"The product of pure methane combustion is 1 CO2 and 2 H2O. for every methane molecule burned (with 2 Oxygens). Although water vapor is a greenhouse gas of it's own I will ignore it as the amount of methane burned should not really make a dent in the amount of water vapor in the atmosphere. So we can compare methan... | [
"Luckily this touches upon my area of expertise, as one of the things I am doing right now is genetically engineering methanotrophs for precisely the purpose of removing the need to vent methane into the air and to produce value added chemicals from the relatively cheap methane.",
"Now, onto your question, why is... |
[
"Would it be possible to put an Atmosphere on Mars?"
] | [
false
] | I started asking this question on the TIL about the giant water quasar. The people there answered that it is most likely possible but never provided ways that we could do it. They said that Mars doesn't have a magnetic field preventing it from retaining an Atmosphere. Would thawing out the core give it a magnetic field... | [
"Magnetic fields on planets are generated internally. Yes, if some method of remelting Mars' core could be devised, and the different layers would rotate, then yes Mars could start generating a planetary magnetic field. Of course there is no way known to do this.",
"Moving the planet would not help with the cor... | [
"If you moved Mars into the same orbit as the Earth I think you would need it to be 60 degrees in front of or behind the Earth's orbit to be stable.",
"You'd also need it to be much less massive than it is. L4/L5 orbits are only stable when one body is less than 1/25 the mass of the other."
] | [
"Doing anything to the planet's core isn't really possible. There isn't any way to make Mars have a magnetic field or more gravity, so any atmosphere you give it will be stripped away on the order of 100 million years. But Earth itself will become uninhabitable in a few hundred million years too, and that's obvious... |
[
"How would humans adapt to life in space?"
] | [
false
] | If humans had to colonize space, without ever finding a planet able to sustain life like Earth, how would humans evolve and adapt? What would be the most challenging obstacles? What kind of resources would become critical and how could they be created/supplied (I'm thinking oxygen, water; but what else?). How would hum... | [
"It would take millions of years to evolve and adapt to space life on another planet. It all truly depends on the planet we go to. If we go to a planet that is in the goldilock zone then theoretically we can go and live there, but if the planet is not then we would have to live there with special suits and other eq... | [
"The answer is really complicated. For example, microgravity exposure causes calcium to leech from the bones of astronauts."
] | [
"It's been shown that astronauts lose muscle mass and bone density just by being up in space a few months. If humans were to colonize space without having a planet to call home, the primary long-term goal would be some way to simulate gravity. ",
"However, if humans could indeed survive in zero gravity long term,... |
[
"How does Antivirus software work?"
] | [
false
] | I mean, there are ton of script around. How does antivirus detect if a file is a virus or not? | [
"While there are many different styles of viruses and attacks, a lot of antivirus software deployed relies on a currently known threats or vulnerabilities. It is hard to defend against an unknown vector of attack (I use virus here generically), but some basic attacks/detections are as follows:",
"An easy way to d... | [
"Excellent summary. You neglected to mention detection methods for encrypted viruses and metamorphic viruses though. As this expands upon your post, I'm not sure if I should add it as a reply to your post, or as a general reply to the original poster. Oh well.",
"Before going further, if you ware really intereste... | [
"I realize I missed this, and could not have better explained it myself. Very nice job covering the aspects I did not, and Szor's writings are definitely an excellent source if anyone would like to dive deeper into the subject of computer security. Up vote for you!"
] |
[
"Is there a cumulative benefits of flu shots?"
] | [
false
] | Is there any cumulative benefit to getting flu shots every year, beyond the current year? (ie if I get a flu shot every year for 20 years, am I any better protected than if I get a flu shot this year without any prior shots?) Maybe almost the same question, but also, what effectiviy, if any, does a flu shot from a pre... | [
"Stay with me, this is kind of like Cliff notes of immunology 101.",
"There is only benefit when receiving the same particular shot. ",
"The influenza virus is what the flu shot is attempting to protect you against. The trick is that the influenza virus mutates itself in order to outsmart your immune system, it... | [
"Are there any statistics known on this hit or miss? How often do we 'guess' correctly the new version of the mutated virus?"
] | [
"https://www.cdc.gov/flu/professionals/vaccination/effectiveness-studies.htm",
"It varies from year to year.\nThe most recent failure in memory would have been the H1N1 outbreak within the past decade. \nIn all matters of public health I would defer to the data collected by the CDC. "
] |
[
"Could a gun fire in the vacuum of space?"
] | [
false
] | Google seemed to almost unanimously say yes, but nothing was sourced and I don't know how reliable the guesses were. So, askscience, could you shoot someone in space with a standard firearm? | [
"Yes, the CCCP did it once, the space station Almaz had a cannon on it and they test fired it.",
" http://en.wikipedia.org/wiki/Almaz",
" "
] | [
"Yes, the majority of guns have the oxidizer built into the cartridge so don't need oxygen to fire. Some can also fire under water."
] | [
"Some poor bastard 50 million lightyears away will get a bullet in the back a very long time from now."
] |
[
"Is there a delay between a star beginning fusion and light becoming visible?"
] | [
false
] | So I've heard on various science programs that a photon of light takes thousands, even millions of years to reach the surface of the sun because it bangs into so many particles along the way. If I were an observer one AU away from a star the size of our sun, looking at it just as fusion begins would it take millions of... | [
"Aren't protostars usually surrounded by gas clouds and hard to see before fusion begins?"
] | [
"Aren't protostars usually surrounded by gas clouds and hard to see before fusion begins?"
] | [
"Fusion is reponsible for ",
" stars manage to remain hot and bright",
"There was an interesting calculation before people knew about fusion: If the Sun would get its energy purely from gravitational collapse it would be ~100 million years old. Short compared to its lifetime (and so short that it was in disagre... |
[
"How do scientists know where the mutation in a gene originated and how long ago the mutation occured?"
] | [
false
] | Title | [
"The way they track these mutations in time is by creating a huge family tree and puzzling the way back up. If a group of people is known to have split up e.g. 5000 years ago and none of them have that mutation, it likely occured less than 5000 years ago in the main population.\nIt's not perfect but with enough sam... | [
"Without getting into excessive detail: today we genotype or sequence DNA from many many people. We can cluster people into groups that have a higher than expected number of shared alleles (genetic variations). This happens when people share common ancestry because at some point their ancestors were isolated to an ... | [
"What do you mean where it originated? A mutation is stationary in a gene and doesnt move. Should a mutation occur in another location it is a seperate mutation. You cannot really time a mutation, however you can determine the homology between genes and their differences (could be referred to as mutations) and some... |
[
"How can we talk about vapor pressure before boiling point?"
] | [
false
] | In thermodynamics chapter we used to say in change of state for ex: h2o liquid at 50 degrees>h20 liquid at 100 degrees .then h20 liquid at 100>h2o gaz at 100 The 2 reactions are at 1 atm pressure, and temperature are in degrees celcius But now we're taking vapor pressure, hence there could be gaz before achievieng the... | [
"The water in the liquid phase is always in equilibrium with water in the vapor phase. This is why water can evaporate even when it's not boiling. ",
"The pressure of the water vapor in equilibrium with liquid water is the vapor pressure, and its value depends on temperature. The boiling point is the temperature ... | [
"I'm not sure of your question. Are you asking about what goes on at the horizontal line?... You are clearly adding energy and yet the temperature does not change. Its weird. The full description why is kind of complicated and requires Physical Chemistry concepts, not just general chemistry. This website kind of t... | [
"Evaporation also breaks hydrogen bonds, as those exist all over the place in the liquid and molecules are leaving the liquid in evaporation.",
"Vapor pressure is just the pressure (of a pure gas) at which the same number of molecules on average are leaving the liquid phase as entering it again from the gas. Ther... |
[
"Two plant-life questions about Mars."
] | [
false
] | [deleted] | [
"Genetic engineer specializing in plants here; this is my life career-goal. Although I previously believed that genetically modified microbial life was the best way to generate an atmosphere for Mars, I began taking astronomy courses to become better educated regarding potential hurdles.",
"I'm not certain (I'm ... | [
"So, can I ask you to be a little bit more clear about what we ",
" for certain here?",
"I mean, stuff like this",
"The lack of atmosphere would definitely affect plant life--this is visibly true when considering mountain tree lines on Earth.",
"-",
"I think the primary problem with \"less dense\" would b... | [
" This is reply post 1 of 2.",
"I split this into two posts because of length. For the second post, I thought people in this thread might like the snip of information without paying $140 each.",
"This paper is nearly twenty years old, but sadly still a good reference for terraforming theories because we've foc... |
[
"What revolves around what in the universe?"
] | [
false
] | So, satellites revolve around planets, planets revolve around a star, the star revolves around what? The center of the galaxy? If so, then what does the galaxy do? | [
"Moons orbit planets.",
"Planets orbit stars.",
"Stars orbit the galactic center.",
"Galaxies orbit other galaxies in their local group (if they have one).",
"Note that technically everything orbits a common center of mass which is not the actual center of the object. So, for instance, the earth and moon o... | [
"thank you sir"
] | [
"yes, the stars rotate around the center of the galaxy.",
"galaxy can be organized into clusters and they all affect one another. sometimes they are denser in the center and in that case they rotate around that, in other cases they all kinda just rotate around each other "
] |
[
"Why is Newtonian mechanics the most widely taught version of classical mechanics in the school room?"
] | [
false
] | [deleted] | [
"The other formulations of classical mechanics need a somewhat higher level of mathematical background (calculus of variations, PDEs), so it’s easiest to teach Newtonian mechanics at the introductory level.",
"And while Lagrangians and Hamiltonian are very aesthetically pleasing and convenient, they have some ugl... | [
"Just to add emphasis to your post, Hamiltonian and Lagrangian mechanics are ",
" of Newtonian mechanics. They say the same thing in different ways."
] | [
"Those other scientists did not independently \"come up with the same thing\" (putting Leibniz aside). They after-the-fact reformulated the \"fundamental\" physical theory of Newton, built from simple, empirical principles, into other mathematically useful forms. The physical theory is really Newtonian, although th... |
[
"\"Breakfast the most important meal of the day\"?"
] | [
false
] | I'm wondering if this is indeed the case? Does it matter (contribute to weight gain) if I have my first meal in the early afternoon, for example? Also, will eating a big dinner before sleep contribute to weight gain "because I am not burning off the calories"? I realise there's fitness subreddits but I am after a scien... | [
"This thread has 79 comments right now, and I see few references to actual scientific papers. For this reason, I feel like I need to describe the process of answering your question (which most people didn't attempt) well, while actually trying to answer it. Try using this outlined procedure on your own.",
"Step 1... | [
"I'm in school for dietetics. I might be able to shed a little light on this. Eating breakfast doesn't necessarily \"boost\" your metabolism in a way that would increase weight loss or anything like that, but it may help to curb appetites later. I grabbed this from the American Dietetic Associations 'Evidence An... | [
"Well, I don't know about the health benefits, but eating breakfast at the exact same time every morning is an excellent way to wake up at the exact same time every day."
] |
[
"Can you actually hear your thoughts?"
] | [
false
] | null | [
"So no, you are not actually hearing your thoughts in the sense that it is not going through the same sensory pathways as a normal auditory stimulus. "
] | [
"Yes! That's what I'm talking about, thank you :). So, what im wondering is when you are thinking or reading, is the temporal lobe showing similar activity?"
] | [
"Yes! That's what I'm talking about, thank you :). So, what im wondering is when you are thinking or reading, is the temporal lobe showing similar activity?"
] |
[
"What is the strongest muscle in relation to it's size?"
] | [
false
] | null | [
"It is the masseter in particular. The other masculatory muscles are accessory in one way or another (Medial Pterygoid, Lateral Pterygoid, and Temporalis). ",
"Some may argue that the myometrial layer of the uterus (seen in females) is stronger, but I exclude this since it is not present in both genders. "
] | [
"It is the masseter in particular. The other masculatory muscles are accessory in one way or another (Medial Pterygoid, Lateral Pterygoid, and Temporalis). ",
"Some may argue that the myometrial layer of the uterus (seen in females) is stronger, but I exclude this since it is not present in both genders. "
] | [
"It is the masseter in particular. The other masculatory muscles are accessory in one way or another (Medial Pterygoid, Lateral Pterygoid, and Temporalis). ",
"Some may argue that the myometrial layer of the uterus (seen in females) is stronger, but I exclude this since it is not present in both genders. "
] |
[
"How did scientists in the 1800's know that they isolated an element and that it wasn't a novel chemical compound?"
] | [
false
] | I feel like it'd be very difficult to first isolate an element, then to know that you have gotten to the element, rather than a new compound. It doesn't seem like there's any test you can do determine that without a lot of supporting evidence or advanced equipment. Were people mistaking compounds for elements as the... | [
"Trying a whole battery of reactions, basically. One of the most important is whether anything significant happened if you heated the substance up in a vacuum, as many compounds would tend to decompose on heating. But you can heat a chunk of carbon or phosphorus or metal and so on in a vacuum all day and nothing wi... | [
"It's also worth noting that once all known elements were ordered and indexed, the gaps in the periodic table gave scientists a pretty good idea of what to expect out of unknown elements which aided in their eventual identification. "
] | [
"Yea this all is good but you didn’t answer op’s most interesting question - how could Nikolay know that he has pure gas element atoms in a jar?"
] |
[
"Are the umbilical cord part of the mother or the child? Whose genes does it contain?"
] | [
false
] | null | [
"The placenta consists of a layer that contains maternal cells and a layer that contains fetal cells. The fetal layer of the placenta is connected to the umbilical cord. The umbilical cord consists of fetal cells."
] | [
"The umbilical cord is made out of fetal cells and that is why you can store the umbilical cord to be used as a source of stem cells should the person later need them!"
] | [
"No, these are not embryonic stem cells in that they are not totipotent and cannot differentiate into any cell type of the body. But they are very useful when needing to do research on blood or specific genetic disorders. ",
"EDIT: I'm just going to type this out here for help:",
"Totipotent: Embryonic stem cel... |
[
"Why cant we transmit wireless electricity for long range ?"
] | [
false
] | I know that tesla tried to do something like that back in his time. But its 2015 and still we depend on cable transmission of electricity. Are there any risks for doing this ? | [
"There are a lot of issues with transferring electricity through the air.",
"At the basic level, electricity is the movement of electrons. To get an electron to move through air you have to discharge it into the air. Electrons are pretty uncontrollable and they like to react in air - hence the giant electric spar... | [
"The concept has been proven time and time again the problem, however, lies in the efficiency of the system. Tesla was in fact successful in his quest to power small lights a distance away but this required an extremely large amount of power input. There is a company today that is trying to make a system that wil... | [
"The problem is that the energy radiated follows the inverse square law. The energy decreases with distance far too quickly to be of any use. You'd need an incredibly powerful transmitter, or transmitters every few hundred feet."
] |
[
"Could one interpretation of super symmetry be that part of the very early big bag/inflation consisted of a split where two universes were originally created, one based on antimatter and the other \"normal\" matter?"
] | [
false
] | null | [
"No, this is not what supersymmetry is. Supersymmetry is a very precisely defined property, not something with differing interpretations, and it is not a symmetry that relates matter and antimatter as duals. Supersymmetry pairs bosons and fermions, and does so in a way that is integrated into the existing spaceti... | [
"I suppose I was asking if it, at all fit our current scientific understanding, and established models, of such things. "
] | [
"I suppose I was asking if it, at all fit our current scientific understanding, and established models, of such things. "
] |
[
"How does light from an object in space update itself to us?"
] | [
false
] | For example, if a star is 200 light years away, it will take 200 years for that light to arrive here. When we see it in the future, it might look different. What determines the exact light we see once those 200 years are up? Also, once that light appeared, would the object just suddenly change, or would it be gradual p... | [
"Let's bring it to human scale.",
"Suppose that back in the 1600s (no fast communication), a king wanted to keep citizens in a distant city updated with the latest proclamations on a minute by minute basis. (Assume the king is crazy.) Obviously, being the 1600s, there is no form of communication faster than a fas... | [
"Basically, you would see what the object looked liked 200 years ago. If a star were to form quickly enough for a human to observe it within a lifetime, they would be able to see its formation gradually. "
] | [
"You are actually looking into the past when you look up at the stars. The light you see is actually 200 years old and the light you see the next second is 200 years and 1 second old. That star could already be destroyed but you wouldn't know until 200 years after it happened (ignoring all other ways of detection).... |
[
"How do plants \"know\" which way the sun is facing?"
] | [
false
] | Most of us have seen the timelapse video of plants moving with the sun as it moves across the sky throughout the day. Those of us with house plants see the same thing, except plants facing the windows. Plants in my apartment are even tilting their leaves to get the maximum surface area possible. How do they know which ... | [
"A chemical called auxin elongates cells furthest from the light.",
"http://en.wikipedia.org/wiki/Phototropism"
] | [
"These things in the cells called phototropins are responsible for allowing plants to detect light. UV light hitting them causes them to turn 'on', and blue light causes them to turn off.",
"As corey-- said, Auxin is the real workhorse in phototropism. Phototropins that are facing the sun will be more turned on, ... | [
"I'll try an analogy, hope it works: \n",
"Eyes have cells specialized in being excited by light stimuli. If you lay this cells in a straight line, then turn on a light source at the edge of the line the nearest cells would be more excited than the last cells in the line.",
"In a similar fashion, plants have a ... |
[
"Why is steam formed, when water is not at boiling point?"
] | [
false
] | Like when you make a hot drink, steam comes off the top, but the drink itself is not 100 degrees Celsius. | [
"What you see coming from the top of your hot drink is condensating water vapour which is NOT steam. Steam is 100 per cent pure water vapour and is invisible.",
"\nYou can see clouds in the sky (condensating water vapour) but can not see water vapour in the atmosphere until it condensates (forms clouds) and the ... | [
"Just to add to this: the molecules of water inside your drink do not all have the same amount of kinetic energy. The distribution of energy levels is determined by statistical mechanics, and is a direct function of temperature. So while the ",
" kinetic energy of the entire container of water may be at a tempe... | [
" NO. Steam is 100 per cent pure H ",
" O vapour. For pure H<sub>2</sub>O vapor to be produced the water has to be boiling - which is steam.",
"\nCondensation, water vapour and steam are three entirely different entities which is why they have different words to describe and define them.",
"Steam is pur... |
[
"Is computation without energy possible?"
] | [
false
] | Is computation without an expenditure of energy possible? If not, why exactly? | [
"This question is related to information theory and statistical mechanics.",
"First, ",
"Landauer's principle",
" states that any ",
" computation has to transform energy into waste heat. All ordinary computers are based around irreversible operations, e.g. taking two numbers and adding them (from just the ... | [
"Understood. But I don't see how computation can be performed at absolute zero."
] | [
"No, even if you had a mechanical computer, or even used pen and paper to compute, you would still move. Even with though, energy is required to think."
] |
[
"Can you be born with an allergy?"
] | [
false
] | null | [
"The simple answer is no. You cannot be born with allergy. You have to have a first exposure to the allergen in order to develop the allergy.",
"The real answer is more complicated....you can be born with a predisposition to becoming allergic, and you can (in rare cases) be born with a predisposition to become al... | [
"This is difficult to answer. Allergy is a broad term that covers many pathological immune processes. IMO the Gell and Coombs classification of hypersensitivity (type I-IV) doesn't cover every manifestation of allergy. Traditional teaching is that anaphylaxis-type hypersensitivity requires exposure to the antigen t... | [
"Allergy is specifically type 1 hypersensitivity, and they are IgE mediated. This is how it's ",
"defined",
". I wish I could give you a better reference than Wikipedia...but the only good reference I know of is Janeway.",
"Type 1 is not limited to anaphylaxis. Pollen allergies are (edit : TYPICALLY) type 1. ... |
[
"Weird reflection?"
] | [
false
] | So I installed a window film on my home windows with up to 70% UV blocking capacity so then the film reflects rainbow alike colors on the floor is the film working? | [
"Assuming this is a thin film, meaning in the order of micrometres and not some millimetre thick plastic thing you stuck on, it is probably ",
"thin film interference",
". It's the same reason soap bubbles and oil spills on puddles in the road have rainbow reflections. ",
"When light hits the thin film some i... | [
"Could be that too. I'm not sure exactly what OP has given his description. "
] | [
"Thank you for the information very much appreciated! I live in a very hot country and the window is from like 2007-2000? It's old one."
] |
[
"If we ever get to do brain transplants, what would happen? Would the person with the new brain have the new brain old memories, or would all memories be forgotten?"
] | [
false
] | Or... would he have he's old memories...?(I think thats impossible) | [
" it were ever possible, and that is a big if, you, and every conscious aspect of you, would be transported with your brain. Your mind is the product of the pink squish stuff between your ears. Move the squishy stuff around, and the mind follows.",
"Now, there would be some things that would probably not be trans... | [
"It's not really a case \"Memories are in the brain\" being established by a single study. It's the kind of thing that has evidence accumulating for hundreds of years, but some super important findings over the years... just papers off the top of my head:",
"Scoville and Milner (1957). \"Loss of recent memory aft... | [
"Oh, a couple thousand years of human endeavour.",
"But basically, like any good scientific theory, my basis is that there has never been any evidence to the contrary.",
"I'm not exactly sure which bit your picking at, but in general, if I make the statement \"the mind is a product of the brain\" the evidence t... |
[
"Would pi be as difficult to perfectly describe using a different number system?"
] | [
false
] | Such as base-12 or base-8 or something? Or are irrational, infinitely extending numbers just inherently that way? | [
"If a number is irrational in one base, it is irrational in every (integer) base.",
"The notion of irrationality doesn't depend on base as can be seen from its definition: A number is irrational if it can't be written as the ratio of two integers. Pi is irrational because there are no integers ",
" and ",
" s... | [
"Then you would never be able to accurately say you have ",
" ",
" of something. Which is a hell of a trade off. All other irrational numbers which are not a function of pi would still be irrational."
] | [
"One is 1 in every base since b",
" = 1. But you can't write any other integers than 0,1 and -1 accurately."
] |
[
"What is the difference in supernova types? Do they create a shockwave?"
] | [
false
] | If there is a shockwave, is it a big wall of fire? Or is it more of a compression wave? | [
"They wouldn't produce a shockwave so much because there is no speed of sound in space.",
"That's not correct. Space is not a perfect vacuum, which is why supernovae do produce shockwaves. Interestingly, these shockwaves play a vital role in star formation since they compress hydrogen gas in the interstellar medi... | [
"They wouldn't produce a shockwave so much because there is no speed of sound in space.",
"That's not correct. Space is not a perfect vacuum, which is why supernovae do produce shockwaves. Interestingly, these shockwaves play a vital role in star formation since they compress hydrogen gas in the interstellar medi... | [
"I'm sure you could read the wiki page of supernovae for details. Type 1a occurs when white dwarves explode. They siphon energy from nearby stars until they reach a limit and boom. Other types 2s are more normal explosions of big stars ending their lives with an implosion leading to an explosion. Their are other we... |
[
"What percentage of total world photosynthesis are plants responsible for?"
] | [
false
] | In learning about the global carbon cycle, I had always learned that plants are responsible for converting CO2 into O2 and organic compounds. What percentage of total photosynthesis are bacteria responsible for? Protists? | [
"http://en.wikipedia.org/wiki/Photosynthetic_efficiency",
"From a 2010 study by the University of Maryland, photosynthesizing Cyanobacteria have been shown to be a significant species in the global carbon cycle, accounting for 20–30% of Earth's photosynthetic productivity and convert solar energy into biomass-sto... | [
"From that article:",
"Using satellite-derived estimates of the Normalized Difference Vegetation Index (NDVI) for terrestrial habitats and sea-surface chlorophyll for the oceans, it is estimated that the total (photoautotrophic) primary production for the Earth was 104.9 Gt C yr−1.[13] Of this, 56.4 Gt C yr−1 ",
... | [
"And just to clarify, the terrestrial production is going to be almost all plants, while the oceanic production will be nearly all bacteria or protists"
] |
[
"What is transcriptional polarity?"
] | [
false
] | I've asked my prof a lot of questions recently and i'm kinda feel bad bogging him down with questions, especially over the weekend. However, since it is a short question I hope you the reader wont' mind answering it. In the context of virology, what is transcriptional polarity? image for reference by the way this image... | [
"It means that as the RNA polymerase is transcribing the viral 'operon' (I don't know the correct term), it has a chance of stopping transcription in between every gene. That means that genes closer to the beginning of the transcript are more likely to get transcribed whereas genes closer to the end of the transcr... | [
"Transcriptional polarity:\ngenes closest to the 3’ end of the genome are transcribed in greater abundance than those towards the 5’ end.",
"Happens in viral genomes at least"
] | [
"OH!!! does it mean that some genes are expressed more than others?"
] |
[
"How to make \"tv\" time-travel possilble, geometrically?"
] | [
false
] | null | [
"Wait...what are you talking about?"
] | [
"The fallacy of time travel is that no two points are physically in the same spot one moment to the next. Between universe expansion, earth rotation, universe rotation, earth's movement around the sun, and so on... if you moved forward or backwards a minute in time, you'll be quite a far distance away from where yo... | [
"The notion of two positions being the same at different instants in time depends on the observer / coordinate system... there is a frame for which Earth is really still. It's the frame of the Earth. There is no absolute notion of how much we moved from one second to the next."
] |
[
"How is a ship's weight distributed when it enters a body of water?"
] | [
false
] | I saw this article ( ) and started wondering about how strong that bridge would need to be. But what about when a ship is travelling over it? How does the fluidity of water affect the weight distribution of the ship throughout the water? Technically, isn't the water displaced the minute the ship hits the water, so it's... | [
"Think about it this way. If you balance a dish full of water on a point...say the top of a pencil eraser, and then place a piece of styrofoam or another object that floats at one of the extreme edges of the dish such that it is floating, what will happen to the dish?\nThink in terms of center of gravity (for the d... | [
"When an object is placed in a fluid (such as the image you posted) the water of water that is displaced is being replaced by the weight of the ball. No more no less. A way to visualize it is to imagine a balance scale with a glass of water filled to the brim on each side. If you were to add an object that float... | [
"The system would stay in equilibrium. I like your illustration, and can understand where the intuition disagrees. You mentioned reaction moment, lets run with that:",
"In this case, there is no force acting in the horizontal direction. ",
"Since there is no force in the horizontal, we are only concerned with v... |
[
"How do we know that space/ the universe is expanding and not matter \"shrinking\" in relation to space?"
] | [
false
] | How do we know that the universe is expanding and not matter "shrinking"? I have no physics background so as far I can see the observable effects would be the same: As matter gets smaller/is shrinking, but space is'nt, it would seem like every galaxy is moving away from us. Also there would be no need for dark energy e... | [
"When observing very distant objects, we observe the phenomena of red-shift, where the light waves from the galaxies and quasars have be stretched as a result of the expansion of the universe. Objects which are further away appear to be moving away much faster than objects which are nearer--the red-shift is more st... | [
"Expanding space and shrinking matter actually have very different effects:",
"The interesting thing about expanding space is that the further something is away from you, the faster it appears to move away from you. Think about ants on a soap bubble, the more distant two ants are on the bubble as it expands the f... | [
"All light moves at light speed, so no - there's no such thing a \"slow\" light (for a given medium, that is, light goes at different speeds in different media). Red-shifted light has less energy, however, and light red-shifts (and blue shifts) in many of the same situations where matter would speed up or slow dow... |
[
"[Biology] Do probiotics actually work?"
] | [
false
] | Full disclosure: I did study biochemistry and for that reason, I'm doubtful that probiotics actually work. I do have friends who have started a probiotic regimen and have seen results. Does the science back this up? | [
"They likely work for preventing C. Diff infection in patients who have been taking antibiotics, based on a ",
"meta analysis of 39 randomised controlled trials",
". ",
"The evidence for other benefits from probiotics is not as strong. There isn't a good standard for reporting such studies to disclose the str... | [
"Microbiome bioinformaticist here.",
"It helps with very few diseases if any besides C diff mildy. Might help your GI tract a tad.",
"Pretty much all the leaders in the field from the microbiome conferences I've been to seem doubtful at best that it does much more than that. Those probiotic species rarely estab... | [
"There's also the problem that if you create a perfect environment for the probiotic it becomes the only species, like a forest with nothing but pine trees. It's hard to fake biodiversity, especially when you don't know the desired population or the parameters they desire to be in. We were born with the assumption ... |
[
"What does radioactive waste look like?"
] | [
false
] | [deleted] | [
"Radioactive waste just looks like rods or pellets of metal. Reactor fuel comes in the form of rods of uranium or other nuclear fuels, and when they're used they look just the same. Also included in nuclear waste is irradiated equipment and more common waste, which just looks like normal except it's radioactive.",
... | [
"Interestingly, if you put radioactive waste underwater it will look different from normal materials: the water will glow ",
"as in this picture",
".",
"Radioactive waste emits highly energetic particles which we normally can't see, so the material looks no different than typical materials. However, when thes... | [
"Hi Nuclear Engineer from Canada here. I worked in the nuclear waste department and in Ontario we store our waste in ",
"these.",
" The are called Dry Storage Waste Containers (DSCs) and are essentially made up of high density steel reinforced concrete and all the spent ",
"fuel rods",
" are stored in them ... |
[
"Are neutrinos WIMPs, or a type of WIMP?"
] | [
false
] | They have (non-zero) mass, and don't interact electromagnetically. To this layman that sounds like a Weakly Interacting Massive Particle. In theory could dark matter be composed (at least partially) of neutrinos, or does the math just not work out? Heck, can we even do the math? Wikipedia says the neutrino's absolut... | [
"Current direct detection efforts searching for WIMPS have found some evidence for a 'low mass wimp' of around 5-10 GeV. A proton is almost 1GeV, for reference. I'm not well versed as to what astrophysical constraints say about a lower bound for the WIMP mass, but the point is that the mass has to be heavy enough t... | [
"Glad to have helped. Viridian's post is correct. You can see ",
"here",
" the masses that have been ruled out by experiment. To give you some idea, neutrinos have masses on the order of eV. Wimps need to have mass on the order of a billion eV."
] | [
"Excellent, good to know someone's already gone down that route and ruled it out. At least I'm not proposing zany ideas, just disproven ones. ",
"So how \"massive\" do these WIMPs have to be to make the math jive with the observations? Less than an electron, more than a proton, somewhere in between?",
"Also,... |
[
"What would an observer, moving faster than the local speed of light in a medium (eg. water), see?"
] | [
false
] | null | [
"This is an amazing question and one that requires a ton more though and devotion than I can give it here. Let me just make an observation or two about what dynamics this medium would support, ",
"Here's a spacetime diagram of this situation, ",
"https://i.imgur.com/pHdP0of.png",
"We have an x,t plot with t... | [
"that going faster than light is not the same as travelling backwards in space time",
"No, you heard right the first time. Faster than light ",
" as time travel in special relativity. The distinction here is that the light in a medium travels less than c, but information and causality is still bounded by c even... | [
"extrapolating the \"runs into own signals\", light emitting things far backward would appear to run in reverse as you are catching up on light emitted a while ago. So for example a dolphin would appear to swim in reverse."
] |
[
"Is parapsychology real? If so, then what's the evidence?"
] | [
false
] | null | [
"What is parapsychology?"
] | [
"Abilities like telepathy, photographic memory and other \"super-human\" abilities.",
"Or according to the internet it is \"the study of mental phenomena that are excluded from or inexplicable by orthodox scientific psychology (such as hypnosis, telepathy, etc.)\""
] | [
"Telepathy: no empirical evidence. Hypnosis and hypnotherapy are used and there are courses offered in mainstream clinical psych programs at large research universities. There are people who have photographic-like memory or are \"super-recognizers\" (very good memory for faces). I'm not sure what constitutes other... |
[
"Why is a kilo still a lump of metal in Paris? Why haven't scientists come up with a better kg, and what are proposed new kg?"
] | [
false
] | null | [
"We are building a new kilogram standard measurement that can be calculated rather than actually weighed so we will have a proper formula that will be constant. ",
"Look here",
"There are a few projects on in this area. "
] | [
"It'd be easy to define kilogram exactly by tying it to some natural constant. We could have easily done this decades (or centuries?) ago if we wanted to. The problem is that we can't measure those natural constants very accurately, but of course we can just define one to some exact value and be done with it. When ... | [
"'We' as in 'human society', 'scientific community' or are you directly involved?"
] |
[
"How sparse are the rings of Saturn?"
] | [
false
] | I know that was poorly worded but I can't think of a better way to word it so I'll hopefully explain better here. I found out a long time ago that the asteroids making up the asteroid belt are actually incredibly sparse and nothing at all like I initially imagined them. Can the same be said for the rings of planets lik... | [
"The Rings are Saturn are much more dense than the asteroid belt. The rings themselves are actually seven sets of concentric circles that circle the planet. There are gaps between each set of rings big enough that Cassini was able to fly between two sets of rings on its way closer to the planet. Flying THROUGH a ri... | [
"Yeah, the most of the rings are fairly compact the the exception of the sparse rings further from the ones in all the famous pictures (G & E rings apparently), but the space between them is pretty large. Large enough, at least, for the ",
"shephard moons",
" which were discovered in the last 30 years or so.",
... | [
"Voyager also passed through the rings. The answer to this question also varies depending on which ring set (and there are several of distinct composition) you're talking about. ",
"JPL's Voyager Saturn rings page",
" quotes several features: ",
"'The edges of the rings where the few gaps exist are so sharp... |
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