title list | over_18 list | post_content stringlengths 0 9.37k ⌀ | C1 list | C2 list | C3 list |
|---|---|---|---|---|---|
[
"I have a problem understanding a certain aspect of radiation dating"
] | [
false
] | I understand the concept that over time the isotopes in various substances decay over time, but my question is why our bodies, and also igneous rocks, have always got 'fresh' isotopes in them. Why don't all these substances contain the same amount of depleted isotopes? I apologise if this has a really obvious answer I'm overlooking, but it occurred to me that I couldn't explain this to another person to my own satisfaction, which, I think, means I have an incomplete understanding. | [
"When rock melts and is in lava form, any argon it contains is released. That resets the clock. Once the lava solidifies into igneous rock, any argon resulting from potassium decay remains trapped in the rock. You can then date the time the rock was formed by the ratio of K-40 to Ar-40 it contains."
] | [
"Argon dating is a complicated matter (This is my research field). Potassium 40 decays to Argon 40 and then you measure the potassium and argon and calculate an age. There is a complication to this which is that usually we irradiate samples to turn 39K into 39Ar and then measure a 40Ar/39Ar ratio (it's just a bette... | [
"Every time you ",
"eat a banana",
", you consume radioactive isotopes. Also, new radioisotopes can and are produced every day in nature, such as ",
"carbon-14",
", which can end up in plants. Which we eat (such as bananas) or are eaten by animals, which we then consume. "
] |
[
"What causes the Mushroom shape of the cloud during a large explosion?"
] | [
false
] | null | [
"The ",
"Rayleigh-Taylor instability",
" does a pretty good job of explaining the formation of a mushroom cloud in terms of fluid dynamics. Also there is a good wiki article on mushroom clouds ",
"here",
"."
] | [
"The air that is blasted out by the explosion rushes bak in pushing the soot created by the explosion in from all sides-- this pushes up the smoke/other stuff into a mushroom cloud. "
] | [
"Thanks this was exactly what i was looking for"
] |
[
"If Earth has a close call with an asteroid, could it affect our orbit enough to change the way we calculate time?"
] | [
false
] | The referenced article about the New Horizons spacecraft states, "To balance the books, Jupiter lost as much kinetic energy as New Horizons gained, causing its orbit around the sun to slow by a small amount. A year on Jupiter today is slightly longer than it was before--all because humans wanted to [get] a good look at Pluto." The New Horizons spacecraft weighs a little over half a ton, including fuel. So what would happen if Earth had a very close fly-by with a gigantic asteroid? Would it have enough of an effect to change the way we calculate years or months or minutes or seconds or anything? I realize that New Horizons' effect on Jupiter's orbit was minuscule, but then again, the leap second that we recently experienced, temporarily-caused some pretty significant issues (such as T-Mobile experiencing 5 minutes of hard downtime as a result). If the same thing that we did to Jupiter happened to us on a much larger scale, would could the possible repercussions be, if any? | [
"One second is defined as the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium 133 atom. This exact amount was chosen as it was the number of transitions that occured in the the previous standard second called Ephe... | [
"So, ",
"/u/rubynorails",
", we can put some numbers to this for context.",
"The average orbital speed of Earth is 30 km/s, and that of 1036 Ganymed is 17 km/s. If we just took these speeds, and assumed they were traveling towards one another with the precise trajectory required for a gravity assist, we can d... | [
"which would cause the length of a year to elongate by about a third of a second.",
"A normal person would be afraid of the chances of 1036 Ganymed hitting the earth. As a sysadmin I'm afraid of the many leap seconds that would cause…"
] |
[
"Is damage of radiation linearly dependent of radiation exposure?"
] | [
false
] | Two questions: Is staying out in the sun for 10 hours straight the same in terms of risk of cancer as ten hours spread out over a larger timeframe? A simalir is wether a single, large dose of radiation has the same effect as several smaller ones? | [
"It's a difficult question to answer, but for the purposes of radiation protection, cancer risk is considered proportional to dose and is not time dependent, in accordance with the ",
"Linear No-Threshold model",
". Now that is certainly not true with biological damage in general. For instance, the spreading ou... | [
"No, these exposures are not at all the same. ",
"The key is that cells have a tremendous capacity to repair DNA in the hours just after exposure. If it has a chance to repair damage after a small exposure before more piles on, the success rate will be higher."
] | [
"DNA can be repaired, and in fact most radiation damage is successfully repaired. By giving cells time to repair between exposures the final result is less permanent damage.",
"That's why radiation therapy is usually spread over multiple sessions: to give normal cells a chance to repair and recover."
] |
[
"If breaking the sound barrier causes a sonic boom, what would breaking the light speed barrier do?"
] | [
false
] | null | [
"A charged particle moving faster than the phase velocity of light in a medium emits ",
"Cherenkov radiation",
"."
] | [
"Sound travels faster in water than in air. Light works the same way, it moves faster through some materials than other.",
"For example, the speed of light through water is lower than c (speed of light in vacuum). When you have a nuclear reactor immersed in liquid coolant, the charged particles released by the re... | [
"As Cherenkov radiation has already been mentioned, the problem with any object going faster than the speed of light (in a vacuum) is that the math breaks down. The Lorentz factor (gamma) shows up in a lot of the equations of special relativity, and it's equal to:",
"1 / sqrt( 1 - v",
" / c",
" )",
"When v... |
[
"If all the objects and respective distances in our solar system were shrunk to 1/10 their current measure, would the orbital relationships stay the same? More specifically, does gravity function in the same way at different scales?"
] | [
false
] | This would assume no effect from forces outside our solar system. | [
"Newton's Law of Gravitation relates the force between two objects by F=GMm/r",
" If both the sun and earth had their masses cut but 90% and the same for the distance between them, the gravitational force of attraction would remain the same. ",
"The earth (basically) orbits in a circle. The force required to mo... | [
"Gravitationally, there shouldn't be many differences.",
"In other aspects, however, things would change. The problem here is that the size of objects is not so important in orbital mechanics; their mass is more so. And if you'd scale the mass of everything down by 10, some of the objects would probably be of a d... | [
"That was super helpful and fascinating. Thanks for taking my question on! Would this continue to be the case no matter how much smaller things get? "
] |
[
"If we were to lose 90% of bees over the next 10 years, how would this impact human life? And what technologies and ways will we use to cope with this loss of pollinators?"
] | [
false
] | null | [
"I have heard that in China they are already employing people to go out into the fields with paint brushes to pass pollen from flower to flower. Seems like a bit of a dyer situation if it comes to that... but hey if your unemployed theres some hope for you"
] | [
"Our crops are clones in that they are genetically identical, but they still have to be pollinated."
] | [
"I dont know about that, many crops still have to be harvested by hand. Im sure that pollination would have to be quite delicate so as not to harm the plant too. So I'm not sure there would be a plausible way to automate it. ",
"Also with respect to bees dying, you would not only have to think of all the crops we... |
[
"Claim: shampoo is harmful to you hair, and the 'no poo' movement is the response. Would someone take a scientific look at this?"
] | [
false
] | The basic contention is chemicals in shampoo strip too much natural oil out of your hair, leaving it dry and unhealthy. The alternative is no cleanser, or commonly baking soda solution cleaner and apple cider vinegar conditioner. Could someone explain the science behind shampoo, and see if the 'no poo' movement has legitimacy? Bonus points for a scientific source of best hair health practices. No poo articles: "If you wash your hair every day, you're removing the sebum," explains Michelle Hanjani, a dermatologist at Columbia University. "Then the oil glands compensate by producing more oil," she says. | [
"Ok, everybody, let's try this again, but with citations this time!"
] | [
"When a thread gets out of control like this, the general AskScience way is to wipe the speculation clean. Speculation and guesses aren't what we do here.",
"And I didn't delete ",
" comment. There's somebody with links to previous discussions we've had, and a couple followup questions."
] | [
"Your dermatologist claims (as does, as far as I can find on Google, the \"no poo\" activists) that the removal of sebum will drive the sebaceous glands to compensate for the loss and produce more sebum — so-called ",
" — but this seems to be a myth that is not supported by evidence. According to ",
"this artic... |
[
"What is the mechanism causing separate atom nuclei to repel?"
] | [
false
] | null | [
"Nuclei have positive change, so they repel each other due to electrostatic forces."
] | [
"Are the electrostatic forces you're referring to also considered the electromagnetic forces? How do these electrostatic forces interact with gravity, electromagnetic forces, the strong, and weak force?"
] | [
"Yes, electrostatic forces are electromagnetic."
] |
[
"I recently learned COVID has a lipid membrane but I was taught in school that viruses are DNA or RNA packed inside a protein shell, so how many different virus physiologies are there and what exactly is COVID made out of?"
] | [
false
] | As the title said, I was taught that viruses are a protein shell with a DNA packed in that inject their DNA (or RNA) into the host cell. Now I learn that some viruses actually have membranes and multiple membrane proteins, which is much more complex than the image I have in my mind. Now I'm wondering about how many different phenotypes of viruses there are, is it a binary thing, some are a protein shell and some are a membrane, or more of a spectrum? Do we know? | [
"The estimate I remember seeing, but don't ask me to cite it, is that 60% of viruses are \"icosahedral\" ",
" (EDIT: vague, see below). So most viruses you hear about are like this, which is what you see in school textbooks, eg the classic bacteriophages, the common cold, polio, hpv, rotavirus.",
"Some viruses ... | [
"Viruses fall (to my knowledge) into 3 key morphology categories: Icosahedral (or isometric, such as herpes/rhino viruses etc), helical (Influenza, Ebola, measles), and head and tail virus (such as many bacteriophage T7,T4, T4like etc) (There are also outliers like poxviridae (as highlighted in a comment) that dont... | [
"The estimate I remember seeing, but don't ask me to cite it, is that 60% of viruses are \"icosahedral\", meaning they have a protein shell.",
"All viruses have a \"protein shell\", the capsid. Its primary function is protecting the genome until it can be released into the host cell. There's different types of th... |
[
"Why do patches of still water persist behind the wake of a boat?"
] | [
false
] | [deleted] | [
"I believe it relates back to wave motion and how it interacts with one another. \nWave nature by force is in the constructive or destructive. ",
"What you are seeing is the destructive wave motion. The boat pushes through sending off wake and destroying the waves that are sent from surrounding shorelines or othe... | [
"You get the same effect from a kayak or sailboat, the oil may be part of it, but not a compete explanation. It has something to do with turbulence, but I can't say how. If you look closely at that flat water section in the wake there are lots of small eddies."
] | [
"It could be turbulence, I'm not sure of the exact indepth mechanics of fluid dynamics anymore. ",
"Bossier330 has a sound idea, to build off it a bit, the motion of the propeller churning the water up could result in denser water rising up to the surface for a brief amount of time as well"
] |
[
"Is it actually bad to consume too much soybeans or soy milk because of the estrogen?"
] | [
false
] | null | [
"Nope. read this, and then read the citations.... ",
"http://www.livestrong.com/article/519107-soy-estrogen-in-men/",
"then read this, particularly the last paragraph or two: \n",
"http://examine.com/faq/is-soy-good-or-bad-for-me.html"
] | [
"This",
" came from the same site. I think there really hasn't been a long enough time period to truly understand what the effects could be. "
] | [
"Soy milk cartons I come across in the US has a fine print stating that it is 'Not to be used as infant formula'."
] |
[
"Could dark energy be used to harvest electricity using temperature differentials?"
] | [
false
] | In a video I watched recently, it was theorized that empty space is not empty, but has a dark energy that is the reason for the expanding universe. Also mentioned was how that energy also gives empty space a radiant temperature. Sterling Engines run off temperature differentials, so if dark energy is a force that also creates heat, could it be harnessed to generate electricity? If not temperature differentials, are there better competing theories? (I'm intentionally ignoring the size such a system would need to be, and efficiency of the system, just asking if it's even feasible) | [
"Conceivably, yes. But there's the added problem that in order to get an energy differential, you'd need a space with even less energy. I.e., \"turn off\" dark energy in a given volume.",
"However, even given all that...",
"https://en.wikipedia.org/wiki/Dark_energy",
"The density of dark energy (~7×10",
"... | [
"Dark energy is EVERYWHERE. All work occurs in disparity-- and in doing so you even out that disparity. If the energy is the same amount in all locations, you can't really do anything with it."
] | [
"Do you know of other options for harvesting this radiant energy for electricity? "
] |
[
"Why do different blood types exist?"
] | [
false
] | null | [
"Blood type is an example of a polymorphic trait. This means that it is a heritable difference in phenotype determined by the genes at a single locus. As all polymorphic traits, blood types arose after certain selective processes caused certain (mutant) blood types to be more fit than others. For example, blood typ... | [
"Clarification: The gene for sickle cell is a mutation in hemoglobin, the protein that carries oxygen in your blood, and has nothing to do with ABO blood groups from the OP's questions.",
"Also, carrying a single copy of the sickle cell gene is enough to protect against malaria, but these individuals do not have ... | [
"Clarification: The gene for sickle cell is a mutation in hemoglobin, the protein that carries oxygen in your blood, and has nothing to do with ABO blood groups from the OP's questions.",
"Also, carrying a single copy of the sickle cell gene is enough to protect against malaria, but these individuals do not have ... |
[
"what would happen if two supermassive black holes (like those in the center of 2 large galaxies) collided?"
] | [
false
] | null | [
"This simulation was of rotating (Kerr) black holes, which most black holes are theorized to be. While black holes rotate, they induce \"frame drag\" which is basically space-time moving in the same direction as the rotation. Think of swirling your finger in a pool - your finger is the black hole, the water space-t... | [
"Nothing overly special. They fall into each other, creating a new black hole of a mass of the two combined. Lots of gravitational waves would be generated, which could spur star formation near-by, but that's about all. Check out ",
"this",
" article for some details and a video.",
"The cool thing is what hap... | [
"I've looked up ",
"this",
" video, but found that even in the slow motion segments there comes, in all but the first simulation, a dramatic and discontinuous change in the last moments of merger. Why such a discontinuity?",
"And a ",
"link",
" for those wanting to know what Ringdown means."
] |
[
"What medical tools / drugs does NASA outfit space shuttels/ISS and what kind of medical dificulties have been encountered by astronauts and dealt with them?"
] | [
false
] | [deleted] | [
"This page seems to give a pretty good overview of what medical emergencies have occured.",
"And this page",
" says that shuttles carried medical kits that could be used by 2 trained crew members. "
] | [
"Related question: What is the shortest amount of time between going from a regular working \"day\" in the ISS to shaking hands with someone on the ground? Say a serious medical emergency occurs that needs immediate attention by a trained and equipped hospital staff, how fast can enough people needed to deorbit and... | [
"People seem to forget the I in ISS stands for \"international\". Why does everyone assume only NASA does space stuff? Every NASA heavy launch now goes up on Russian engines."
] |
[
"Through a narrow slit in my blinds a beautiful colour image of the street below is projected onto my ceiling. How is this possible?"
] | [
false
] | This might be difficult to accurately describe. The blinds are polished paint and the slit through which the light passes is about 50cm in horizontal length. Here's the tricky point: the gap in the (venetian) blinds is over 1 cm wide but is covered by a lip from the outer blind. The light isn't passing directly through the slit but being reflected off the exterior left hand blind and then the interior surface of the lip of the right hand blind. How is it that this can create clearly defined, undistorted colour images? Many thanks. | [
"pics?"
] | [
"Can you take a picture of the blinds so we know the exact setup? "
] | [
"Yes. If you can get the right lens in from of the slit, you can bring the image into focus too."
] |
[
"When an ejaculate is thicker, does that mean it has a higher sperm count?"
] | [
false
] | [deleted] | [
"Short answer: no, it is likely to have ",
" sperm count.",
"In a healthy male, abstinence time is strongly correlated to seminal viscosity. After ejaculating, seminal viscosity decreases in a linear fashion with respect to time. ",
"Source",
"In a healthy male, abstinence time is the primary determinant ... | [
"Your efforts are both a testament to the availability of information on the internet and how little you value your free time. Kudos."
] | [
"I have other, much more important things I should be writing, so obviously I'm writing stuff here."
] |
[
"Are trees immortal?"
] | [
false
] | [deleted] | [
"In theory, many plants could be essentially immortal. For instance, many cultivated plants that are propagated via cuttings or tissue culture are effectively the same organism over thousands of years. Plants do not die of cancer and they do not have organs in the sense that animals do.",
"Many trees die when the... | [
"Here",
" is a more complete explanation, but in a nutshell:",
"Plants have cell walls. If the DNA of a specific cell causes a mutation that inspires abnormal growth, it's kind of stuck in place. This doesn't mean it won't form a tumor (plants form galls, and ",
" may be used to produce tumors in plants that ... | [
"Plants do not die of cancer ",
"Why don't plants die of cancer?"
] |
[
"If all the rivers leading to oceans slowly wash dirt into the sea, will there eventually be no dry land?"
] | [
false
] | Water evaporates, forms clouds, and then rains. Some of that rain evaporates again, but some of it will go into tributaries, streams, and rivers. Some of those will go into the sea. The water going into the sea washes dirt away with it. Will this process on a large enough time scale level out all the dry mass till the entire planet is encased in unbroken water? | [
"Erosion is only half of the equation. Mountains are also being slowly formed by the action of plate tectonics, driven by the heat of the earth's core. Today's earth is in a near steady-state balance between erosion washing the continents away and plate tectonics pushing up new ground. In the long term, when ear... | [
"New crust is created at divergent plate boundaries, such as the mid-ocean ridges between the North American and Eurasian Plates, the boundary between on the eastern edge of the Pacific plate, and along the edge of the Antarctic plate. In all of these places, new crust is created as two opposing plates move away. ... | [
"In some areas, like the Great Lakes, the elevation is actually rising since the ",
"land is still bouncing back from the weight of the glaciers being lifted."
] |
[
"how does voltage get distributed in a weird circuit"
] | [
false
] | I came across this weird circuit that looks like this So I'm not sure how will the voltage be distributed when the two imput wires connect to the object. I understand that parallel circuits have the same voltage as they both have the same potential difference in the sense of Pd=p(final)-p(initial). But in this case since there are two imputed wires I am unsure of the voltage of the object. Also, how do I calculate the total effective resistance and current? Thanks for the help.(please ignore the other stuff on the right if the picture) | [
"You're not really using standard schematic symbols, so I'm having a hard time understanding what you've drawn. What is the \"logic box\"?",
"BTW: this might be better over in ",
"/r/AskElectronics",
" "
] | [
"It can we assumed to be just another appliance I'm just unsure about the voltage across it how to determine resistance and current when um presented with a circuit similar to this where two wires from different branches are brig connected to an electrical load. Thanks for the help."
] | [
"No, I mean ",
" on the diagram is the \"logic box\"."
] |
[
"Has our Sun ever \"ate\" or engulf a planet?"
] | [
false
] | null | [
"After the creation of our solar system the sun was surrounded by a disk of debris, consisting mostly of dust and small chunks of rock. At this point the sun must have been eating anything that lost too much speed to stay in orbit, but nothing of considerable size existed yet. When these formed their orbital speeds... | [
"Early in the solar system it definitely did but I don't think you could call the stuff it engulfed 'planets'. They were mostly rocks and debris. In the future however at the end of it's life approximately 4-5 billion years from now the Sun will expand and swallow up the inner planets. "
] | [
"It probably did in the early Solar System days, but there's no way to prove that it happened. We do know the Sun eats comets fairly often though, and have ",
"good observations of that",
".",
"The Sun will eventually swallow Mercury and Venus in a few billion years as it swells at the end of its life. The ... |
[
"If you run around a track twice, the first time slowly, the second time much faster so that the average for the two laps is twice the speed of the first lap. People are getting infinite speed for the second lap. Why?"
] | [
false
] | This question pops up in Veritasium's new . People are getting infinite speed for the answer. If you run the first lap at 6 km/h and then the second lap at 18 km/h you get an average of 12 km/h. That average is 2v . How is this not correct? You can also check people's answers and the third answer to a Youtube comment . There are also multiple answer videos that say the same thing. Help me not be confused. | [
"If you run the first lap at 6 km/h and then the second lap at 18 km/h you get an average of 12 km/h.",
"You can't average velocities in this way. You can only do this if the time is equal for the two velocities. In this case, that's not true, since it's the distance that is equal.",
"To illustrate, assume that... | [
"The unstated principle here is speeds should be weighted by time -- the runner spent three times as long running slow, so 6 km/h gets weighted three times as much:",
"(3*(6 km/h) + 1*(18 km/h))/(3 + 1) = 9 km/h.",
"Or equivalently, we should take ",
"harmonic mean",
" of the velocities rather than arithmet... | [
"It's not about weighting, it's the definition of the term. Speed is the ratio of distance to time. Instantaneous speed is defined as the derivative of distance with respect to time, and average speed is defined as just total distance divided by total time. Since that's your definition, that's how you calculate it.... |
[
"How good is a raptor's hearing? Does it go beyond the human range?"
] | [
false
] | Hi there asksciencers! I have a question out of mere curiousity. Hawks and other raptors are well renowned for their sense of sight. But so far all google searches have turned up that raptors (excluding owls) have 'good' hearing with no comment to the definition of 'good'. How good is a raptor's sense of hearing? Does it go above the human hearing range for infrasonic frequencies? Any papers or sources I could read? | [
"Birds generally have a more limited range of hearing, and inferior thresholds, to humans. Humans are restricted to 20 Hz -> 20 kHz. For certain ultrasonic hearing in birds has been investigated and has not been found (over 20 kHz), and also low infrasonic frequency hearing has not been found, but is less well inve... | [
"I want to thank you for using the term 'raptor' correctly. The idiots in Toronto named their basketball team \"The Raptors\" when they really meant \"Velociraptors\". I keep hoping they'll fix the logo to show a bird, but we are talking Toronto sports teams here ..."
] | [
"While going a bit further off-topic, it's fun to note that Toronto's mascot bears little resemblance to a velociraptor, which is narrower and about the size of an elongated chicken. Largely because of Jurassic Park, the animal people think is a velociraptor is in fact a ",
"Deinonychus",
". Even its name, \"... |
[
"What causes the body to produce dental tartar, and how does tartar control toothpaste reduce the amount of tartar buildup on the teeth?"
] | [
false
] | null | [
"Tarter is caused by a bacteria that resides in your mouth, plaque. When plaque builds up it creates a biofilm. If you leave this biofilm on your teeth it will eventually harden which is commonly known as tartar. Toothpaste uses a combination of “cleaning” chemicals that interact with the biofilm to dispel it, howe... | [
"Your saliva has minerals, calcium, sodium, etc, that are used to build a mini-coral-like reef in your mouth."
] | [
"Toothpaste also has various abrasives that help to physically remove the films when combined with the brushing action"
] |
[
"If I were to leave my fully charged laptop turned off and unplugged for five years, could I still start it up on battery only?"
] | [
false
] | Average run-of-the-mill HP laptop, fully charged. I unplug it, turn it off, leave it at room temperature, and then I wait five years. Will I still be able to turn it on using battery power, or is the battery somehow discharged? | [
"Most likely not. All batteries suffer from a phenomenon called \"self discharge\", which is the slow reduction of capacity when a battery is not in use. Rechargeable batteries have higher self discharge rates than non-rechargeable batteries.",
"Lithium ion batteries that are used in laptops and many other mobile... | [
"This is likely because it's an old laptop. The older laptops would charge the battery to 100% then continuously give it a small constant charge to keep it there. This was bad for the life of the battery. Newer laptops have more intelligent charging algorithms and sensors so they know when and how much to charge... | [
"Exactly right. Plus if their voltage is too low, they will never hold a charge again. "
] |
[
"Hypothetically, what would happen if a neuron synapses onto it's own dendrites?"
] | [
false
] | If you could somehow get a neuron's dendrites to connect to it's synapses what would happen if an action potential was triggered? | [
"So this does happen, and it's called an \"Autapse\" as in an auto-synapse And I've written a couple papers on it even. A specific class of inhibitory interneurons does do this, and it does it very strongly, in fact, it's one of the strongest synapses in the brain, and certainly in the cortex. So what this means is... | [
"I don't have any conclusive proof that they form by accident. An experiment that would prove me wrong is finding a cell type that has lots of autapses, but doesn't ever connect to other cells of the same type. We really only have three cell types to build up our correlation, so it's shakey.",
"I mean, the \"by a... | [
"This is so damn cool. Thanks for taking the time to explain it! :D"
] |
[
"Are Photons everywhere?"
] | [
false
] | If were looking at light from a galaxy a million light years away, are there photons everywhere in between the telescope and origin point? If so does this mean that photons are potentially everywhere? | [
"Technically yes. However, obviously an object can intersect between the viewer and the light source cutting off that particular source of photons for some time.",
"So, for example, if you are observing light from 1 million light years away, and an object intersects at 500,000 light years, you won't see the ligh... | [
"Could you clarify what you mean by \"photons everywhere in between the telescope and origin point?\" Do you mean a continuous stream of photons that lie along a line between the origin point and the telescope?"
] | [
"OP's context:",
"http://www.reddit.com/r/science/comments/se8py/by_taking_advantage_of_a_rare_cosmic_zoom_lens_a/c4db8k4"
] |
[
"Is there a way to convert black and white photographs into accurate full-color photographs?"
] | [
false
] | [deleted] | [
"Is there a reason why multiple colours can translate into a single black and white \"colour\"? Why doesn't each individual colour appear as a slightly different shade in the black and white photo?"
] | [
"Is there a reason why multiple colours can translate into a single black and white \"colour\"? Why doesn't each individual colour appear as a slightly different shade in the black and white photo?"
] | [
"As others have noted, it is not possible to produce an accurate colour image from a single black and white photo because you lose the hue and chroma of the original image.",
"It is, however, possible to reconstruct a colour image from three black and white images using red, green, and blue filters separately. Th... |
[
"How does one select for specific traits when breeding animals? And what traits can you select for?"
] | [
false
] | I am curious about animal husbandry and how to create hybrids through the selection of specific traits. what I want to know is how this is done, and what traits you can select for and which ones are at random. for example can you select for speed and for athleticism? or for intelligence? or for strength? what traits are not hereditary? | [
"You can theoretically select for any trait, and you do so by picking the most outstanding members of a generation with respect to that trait and pairing them to breed the next generation. The members of the next generation will likely vary from somewhat worse than their parents to somewhat better than their paren... | [
"Most traits you are likely to think of, including all the ones you listed, can be inherited and thus selected for. The heritability of different traits varies though, you can try googling your trait of interest and 'heritability' (ie 'strength heritibility' or 'milk fat heritability') and you should find a number ... | [
"So, very importantly, you can only truly know if traits are hereditary by breeding individuals that have the trait for several generations then looking to see if the trait is still present in the population. Biology is complicated, so sometimes you can get two individuals with traits that look identical on the sur... |
[
"Can an electromagnetic an wave exist only within certain frames of reference?"
] | [
false
] | I was once pointed out this paradox by a physics teacher: My teacher already told us that this is still an unsolved paradox, and that Maxwell Equations and relativistic electrodynamics still hasn't a clear answer. I had been believing him for a decade, but the question poped-up in my head recently. Was my teacher right? | [
"There is a ",
"-paradox-",
" surrounding what you say, it is not however (at least to my knowledge) an \"open question\". Just a subtle consideration of electrodynamics in the context of general relativity. The starting place for the resolution is that falling charges do indeed emit EM radiation, like for exam... | [
"a charged particle and a neutral particle fall equally fast in a gravitational field, despite the fact that the charged one loses energy by radiation",
"Where does the radiation energy come from? The gravitational and kinetic energy should be the same in either case.",
""
] | [
"Sorry for the much-delayed response. Apologies. And a double apology because I fully must admit that general relativity (GR) is basically the opposite end of physics from my specialty and I'd rather be vague than give you wrong information. So take everything I'm saying with a beach of salt. ",
"However, the hea... |
[
"Dark Matter - Why not neutrons?"
] | [
false
] | [deleted] | [
"Free neutrons (those not bound in nuclei) will decay with a half life of about 11 minutes. The decay products are a proton, electron, and and (anti electron) neutrino. The proton and electron are charged, and so couldn't really be ",
" matter. The neutrinos aren't a separate hypothesis. Even if the universe was ... | [
"He's talking about the weak nuclear force, not that it interacts weakly with gravity."
] | [
"It's not new at all. Neutrons are made of quarks, and quarks have electric charge. This gives rise to a magnetic dipole moment for the neutron that will interact with magnetic fields. This is well measured."
] |
[
"@Earthquake Engineering, in simple terms, what's the precise connection between response spectrum and time history for a building"
] | [
false
] | [deleted] | [
"You seem to be trying to create a model for the building, which is not exactly what the original question asked.",
"There are several methods to find the components of a spectrum by parametric analysis, it's an ongoing research. The most common methods are based on the ",
"Pisarenko's method",
", like the ",... | [
"You transform a time series into a spectrum by using a ",
"Fourier transform",
". Any math library will have a version of it."
] | [
"Is that answer correct or wrong? Don't you do something like the following?",
"--> Output is the earthquake response spectrum"
] |
[
"Are there forests of fruit trees in the wild? Or do they naturally only form isolated clumps?"
] | [
false
] | [deleted] | [
"OK, first of all, every tree produces fruits. Fruits are (essentially) just the parts of a plant that bear seeds. Even gymnosperms (things like pine trees) produce structures (such as cones) that can be considered fruit using this simple definition. ",
"Second of all, when you say \"forest\" you seem to be imagi... | [
"/u/ilexmucronata",
" is correct, but I can add a little more. The fruit that we get at the store, which is what OP is probably imagining, is largely the result of careful cultivation by humans. Many of the varieties that we eat could not grow in the wild (or at least not as we envision them). Apples, for exa... | [
"Your first question made me think of food forests, not fruit forests. I'm not sure if you've ever heard of them, but I thought you would enjoy what information I could offer.",
"I learned about food forests in my Permaculture course and it was my favourite section of the course. It was understood that food fores... |
[
"Where is the North Pole of Uranus?"
] | [
false
] | How did it get sideways? Some kind of impact? | [
"Uranus has a rotational inclination of ",
"82 degrees",
", putting its pole closer to the solar system's plane than earth's tropics. ",
"I haven't read specifically about Uranus, but I'm familiar with planetary accretion. The young solar system was more spherical, less uniform in the orbits of the planetoids... | [
"I think the question should be \"where are the poles of Uranus\"",
"Since the usual convention used by most people seems to be Up is North, then Uranus doesn't really have a pole that's North. It's closer to an East and West Pole.",
"P.S. However, the definition currently endorsed by the International Astron... | [
"causing it's orbital tilt",
"That'd be ",
" tilit; Uranus orbits almost exactly within the solar plane."
] |
[
"What is the difference among CT scans, PET scans, and MRIs? More specifically, what is each one used for?"
] | [
false
] | What might a CT scan find that a PET scan or MRI might not? How does a doctor decide which one to order? | [
"Within each of the studies you mentioned there are subcategories and a lot of technical differences, but I will give you broad function/purpose in general terms:",
"CT (Computed tomography) is basically really high resolution X-ray that is obtained in 2-D and then can be reconstructed in 3D. Helical CT is prett... | [
"Not sure how they specifically decide what to use what for, but a PET scan starts with a radioactive chemical being injected, and it’s absorbed into the organs and tissues being studied. The scan measures blood flow, oxygen use, and glucose metabolism which helps doctors identify the abnormal amongst the normal. "... | [
"Also for detecting stress fractures, using radio-labelled bone growth cells, as they are invisible in X-rays."
] |
[
"What stops black holes from imploding on themselves?"
] | [
false
] | I'm familiar with theories and what we know. My background is in BioChem, MolecularBio, and Computer Science (I was bored in college) and I can't get enough of space talk. I was looking at the new equations for determining the densities of new planets based on their orbitals between each other when I though "Can we then determine the "weight" of a black hole"? If so, we can get the density? Then I thought, can it be dense enough where it would collapse in on itself? Then what? When it comes to astrophysics, I'm still a noob and will be for a very very long time. Oh great reddit, please help fuel another one of my infatuations with space. | [
"They are imploded on themselves."
] | [
"Infinite density doesn't require infinite mass, only a finite mass in an infinitely small volume."
] | [
"Yes. A black hole exists as a point with infinite density. While it is used to characterize the size of black holes, the Schwarzcshild radius says nothing about mass distribution, only the amount of mass at the singularity."
] |
[
"Why are certain saurians believed to have sails versus humps?"
] | [
false
] | [deleted] | [
"Consensus these days is that (outside of theropods), large dinosaurs were ",
"homeothermic ectotherms",
". They did not produce heat for the sake of producing heat like a mammal does, but rather given their size and the inability to dispel heat allowed to them be homeothermic while maintaing ectothermal meta... | [
"I don’t think the consensus is that all non-avian dinosaurs were cold blooded. I’d list references, but you can find that information in anything written after the early 90’s. Also Dimetrodon wasn’t a dinosaur."
] | [
"If Spinosaurus' elongated spines, like those of a bison, were needed for anchoring muscle tissue, other similarly-built dinosaurs (e.g. Tyrannosaurus rex) should have had comparable features.",
"edit: phrasing"
] |
[
"What happens during storms on other planets? Does it rain some other liquids besides water, is there lightning, etc."
] | [
false
] | After reading about how difficult it was to calculate the length of a day on Neptune because it has no visible surface due to stormy weather and various gases, I am curious to learn what actually happens during a storm. I figured it would be too cold for any liquid or gas to exist on Neptune since it is so far from the sun, but apparently it does, so what can one expect? | [
"I'm not sure exactly what you mean by \"what can one expect?\", but....",
"On Venus for example, it rains sulfuric acid, but the rain never reaches the surface. Instead, it evaporates well above the surface, while still in the atmosphere. The Soviet probes that landed on Venus also detected quite a bit of ligh... | [
"H20 as a liquid is fairly rare because H2O is only liquid in a ",
"small window of pressure and temperature",
". Even though Earth is really \"wet,\" water only makes up a small part of Earth as a whole. Deserts, icy tundras, and inner/out core are all nearly void of liquid water. ",
"That being said, H20 is... | [
"It would be awesome, but Venus is probably the worst environment in the Solar System. Try to build a probe able with its electronics and gears fully functional after having been in space for months, then suddenly exposed to 460 C temperatures, 93 atmospheres of pressures and sulphuric acid vapour all around. ",
... |
[
"How can we tell that the universe is flat and infinite if we can't be affected by anything outside the observable universe?"
] | [
false
] | I understand that our observations tell us that the universe is flat, and that this implies that the universe is either infinite, or that it extends very, very far beyond the observable universe. But if nothing outside the observable universe can affect anything inside, how can matter outside the observable universe have an effect on the curvature inside? Isn't the flatness of the universe information from outside the part we can observe? | [
"We assume that the universe we can't see is the same as the universe we can see. We can make this assumption because the universe we can see is the same everywhere, and there's no reason to think it's different anywhere else. So we can measure what we can see, and extrapolate to what we can't."
] | [
"we can't know for sure. But when we extrapolate the measurements of our observable universe, it seems very likely to be the case."
] | [
"Thanks a lot. I had my thinking a little backwards, but you and shavera cleared it up very nicely."
] |
[
"Visible Light"
] | [
false
] | [deleted] | [
"Goodness. Inquisitive minds want to know! There's more questions than I have fingers! :P Let me reformat this in a list, and reply to the list, since I don't have all the answers.",
"1a. What's the deal with magenta then, which seems to be weirdly absent from the spectrum? ",
"1b. What frequency is it [mage... | [
"Why is one way of representing hues linear, and the other cyclic?",
"Perhaps the more fundamental question is not why are these representations somewhat different, but why are they so similar? Why are they both one-dimensional? The answer is that it's a complete mathematical accident. We have three kinds of cone... | [
"Yes. The liquid crystals in a LCD monitor simply acts as a \"light valve\" on the polarized backlight, and UV light can be polarized (e.g., the setup in circular dichroism).",
"Not that I know of. The primary reason is that non-XMen cannot see UV light. The secondary reason that the backlight has no UV compon... |
[
"Are they searching for a single particle in the search for black matter or is it believed the answer to the unobservable majority of mass within the known universe has multiple solutions?"
] | [
false
] | Everytime I hear about dark matter it sounds like they are talking about a single particle. I don't know the gist of it, but in my head it sounds more probable that the great unobservable mass consists out of a lot of different things we still can't observe. If we can only observe about 10% of the universe and this consists out of millions of things, it kind of would be crazy the other 90% would consist out of a single thing right? I understand dark matter could be the stepping stone to finding out more, but I have no clue what the exact theories are on this. So that's why I'm asking here! Edit: I can't change the title which is why it still says black matter instead of dark matter. In my defense, I am from Holland and just asked the question as it popped up in my mind. | [
"It's unknown whether the missing mass will turn out to mostly be one particle or several or... something else. There are a lot of candidates that are being explored, though.",
"Particle physicists have come up with a lot of dark matter candidates. ",
"This",
" paper reviews some of them, and they are a stran... | [
"You're entirely correct to say that neutrinos are a form of dark matter. For a time they were even thought to be ",
" dark matter. So whoever it was that took umbrage is just misinformed.",
"But as you say, in the 80s pioneering computer simulations of how cosmic structures form (in particular by the DEFW or \... | [
"Check out the ",
"wikipedia article",
"; I've linked directly to a table of hypotheses, some of which are already 'known' components of dark matter (but none of which is known to account for all of it, so far), and some of which are theoretical or hypothetical."
] |
[
"How can the corona of the sun be hotter than the surface?"
] | [
false
] | null | [
"The top comment is not correct. Nobody knows how the corona is heated. It is an excellent question to ask but no one can answer you for certain.",
"The comment suggest flares but they have been ruled out. They simply do not provide the energy that is needed where it is needed; they are too occasional and they ar... | [
"If one is in a hot gas it's possible to cool off below its temperature if it has a low enough density, because it will be heating you more slowly than you're losing heat via thermal radiation.",
"However if you were in the Sun's corona you would get extremely hot (thousands of degrees) because of the intense sun... | [
"It's an aura of plasma which surrounds the Sun and other celestial bodies and can be seen during a ",
"solar eclipse",
". The sun's corona is much hotter (by a factor from 150 to 450) than the surface of the sun, something which is sometimes termed as an apparent paradox."
] |
[
"I understand how we distinguish whether sounds are coming from the left or right (difference in when sound hits the ears)... but how does my body tell that a particular sound is in front of or behind me?"
] | [
false
] | null | [
"This is one of the great examples that shows how complex some parts of the brain's signal processing truly are. It boils down to the ",
"Head-related transfer function",
". As sound travels through your head/body, there are subtle changes made to the signal. Your brain learns how to tell the difference betw... | [
"Followup question: would this mean that a sound in a medium in which it acts differently, say water, would be more difficult to pinpoint?"
] | [
"Based on ",
"this paper",
", then yes, localization is more difficult underwater."
] |
[
"How do Significant Digits and Standard of Error work in other Bases?"
] | [
false
] | I have a pretty solid understanding of significant digits in base 10. What are the repercussions of using significant digits in a small base (eg base 2) or a large base (eg base 60)? Bonus: how to keep the same significant digits (in meaning) when switching bases. | [
"Significant figures are a quick way of displaying uncertainty, which is more accurately stated using the ± sign:",
"5.4 (2 significant figures) means 5.4 ±0.1 or 5.4 ± 0.05. ",
"In base 2 (approximately):",
"5.3= 101.0100",
"5.4=101.0110",
"5.5=101.1000",
"So your number is about\n101.011 ± .001, or ju... | [
"I've always found it helpful to think of it as writing the uncertainty in terms of magnitude. In this case, the base determines the range of the magnitude. Base ten has 10 units per magnitude, while base 2 would have 2 units per magnitude. Smaller base has less range of uncertainty in your magnitude."
] | [
"Just to clarify one bit. Sorry for being a stickler. ",
"5.4 (2 significant figures) means 5.4 ±0.1 or 5.4 ± 0.05.",
"Shouldn't that be 5.40 ± 0.05"
] |
[
"Why hasn't the \"Big Bang\" or any similar event occurred again?"
] | [
false
] | null | [
"Hmm, let's see what I can remember and how I can explain this.",
"1) we don't really know ",
" caused the Big Bang, because the cause of the Big Bang came before the start of the Universe, and we don't have any info on that time period... because the Universe wasn't around.",
"2) we do observe, however, that... | [
"Not technically right. It happened before the start of time, but that doesn't mean that there was no universe before the Bang, matter was just very dense but it still existed in the universe",
"Not really right right either. What we can say is that if you 'run time backwards' you eventually reach an extremely ho... | [
"the cause of the Big Bang came before the start of the Universe, and we don't have any info on that time period... because the Universe wasn't around.",
"Not technically right. It happened ",
" at the start of ",
", but that doesn't mean that there was no universe before the Bang, matter was just very dense ... |
[
"How long did the transformation from a hunter gatherer society to an agrarian one take?"
] | [
false
] | Did it happen all at once, or in certain parts of the world first? What role did language play in this? What was an average number of people in a group in a hunter gatherer society? How about agrarian? | [
"Exactly how long is really up for debate, but this is a process that takes millennia. Hunter-gatherers don't simply start farming one day (not the first ones, anyway), but experiment with crop cultivation, manage herds, etc. Over time, in places where agriculture developed, the plants and animals began to become d... | [
"Did moving to agrarian methods help the development of language significantly? I could imagine language would be more important in a larger society than one with just 25 people. How about writing? ",
"If it didn't have that much do to with language, did it at least potentially help unify it? If each 'tribe' of 2... | [
"Writing systems only develop in places with agriculture, but the writing systems themselves are related to administration and control by the state, essentially (record-keeping). States can't develop without agriculture, but agriculture itself does not lead to writing. And there are many societies that were fully a... |
[
"Zika virus has been known about for 70 years, why is it only now a big issues? Has it always caused microcephaly, or is this new?"
] | [
false
] | null | [
"We don't know.",
"Could be a recent mutation in ZV.",
"Could be that there's always been a link to microcephaly, but that ZV didn't infect enough people for anyone to notice — there is some debate as to whether the sheer number of people infected with ZV is increased in the last few years.",
"(Which could be... | [
"Alternatively, it could be due to host related factors. For instance, the people in Brazil might be more predisposed to complications during infection with Zika virus than people in Africa or Asia due to a different genetic makeup of the immune system. However, the Brazilian population has a pretty heterogenous ge... | [
"On the BBC Science Hour they gave the following hypothesis. Zika is so common in Africa that everyone gets infected fairly early in childhood and then develops immunity, so that Zika disease in women during pregnancy almost never happens and microcephaly rarely shows up. When the virus was recently imported to Bra... |
[
"What's the practical use of complex numbers?"
] | [
false
] | I know it's used in physics (if I remember correctly it's related to quantum mechanics, and electricity among other things), but I don't understand how we use an unknown number (the square root of -1) to describe things in nature? Where does it appear and in what way? | [
"The complex numbers are just the algebraic completion of the real numbers, so if you have an algebraic equation involving real numbers, then it's perfectly possible that you might need to use complex numbers to write down the solution - even though everything you measure is \"real\".",
"It's very unfortunate tha... | [
"i isn't an \"unknown number\". It is a symbol that represents something. Mathematically we can treat that symbol as the square root of -1 and the math follows the rules of what we want to happen. ",
"For example, in some disciplines, i is used to represent the y-axis (x-axis has the real component, y-axis uses t... | [
"Complex numbers are wonderful to represent sinusoidal signals. Let's say that you have the signals a = A*sin(wt) and b = B * sin (wt+c), what's the sum of those signals? You can use a trigonometric formula to solve it. ",
"Or you could represent each of those functions with a complex number. If you add those co... |
[
"How often does oxygen concentration change in the atmosphere in a given area on a day-to-day basis, taking into consideration weather conditions such as rain, windiness, or humidity?"
] | [
false
] | null | [
"The atmosphere is generally well mixed. A fundamental law of geophysical fluid dynamics is the conservation of mass. So if mass is in motion through advection, divergence, etc, it is being replaced. The old saying “warm air holds more water vapor” is not correct. What happens is that temperature shifts the sat... | [
"Outside of 'extreme circumstances', the concentration of oxygen in the atmosphere would typically vary on the order of 0.02 to 0.03%. The reason for this is that the relative concentration of oxygen in the atmosphere is immense compared to every other gas (outside of nitrogen).",
"To increase the oxygen concentr... | [
"Not very much. Here's some data from the Scripps Institute of Oceanography, which has monitored oxygen and CO2 levels at their pier for 30 years now.",
"http://scrippso2.ucsd.edu/assets/pdfs/plots/daily_avg_plots/ljo.pdf",
"It's not daily data, unfortunately, it's roughly weekly, but it gives you a good idea.... |
[
"Is it possible that our universe is part of a much larger system?"
] | [
false
] | null | [
"Yes. There are many theories concerning what's outside of our universe though the evidence for any one of them is extremely scarce.",
"One of the most popular theories is called ",
"eternal inflation",
" or sometimes bubble universe theory. It says that there is ever expanding (->eternal inflation) multivers... | [
"Pardon the ignorance but if we found that the universe is part of a larger system, wouldn't we have to define that whole system as \"the universe\" and then come up with another name for our local systems? Much like until the 19th century astronomers thought that out galaxy was the only one and therefore the whole... | [
"This is more of a linguistic issue than a scientific one. One one hand, the work \"universe\" and its Latin origin have always been used for the entirety of existence, from the solar system in classical times to the billions of galaxies in the observed universe in the 20th century. On the other hand, the word \"at... |
[
"Has there been any attempt to create one of the elements thought to be in the island of stability?"
] | [
false
] | Is it even possible to create such large nuclei? How does one go about to create one? | [
"The principle behind creating heavy elements is bombarding particles together to supply sufficient neutrons/protons. The island of stability is centered around very heavy isotopes, which require far more neutrons than protons. There is not enough access to the stable, heavy isotopes needed for synthesis to even co... | [
"In part because the heavy isotopes you'd need have half lives which are of the order of the tiniest fractions of seconds. So it's not (yet) feasible to manipulate them for further experiments/reactions "
] | [
"If you don't mind, why don't we have access to the heavy isotopes?"
] |
[
"In terms of evolution, why is vitamin D synthesis dependent on exposure to sunlight?"
] | [
false
] | null | [
"I'm not sure which direction you are thinking about this from, so I will answer both questions simplistically. Feel free to ask for clarification.",
"All organisms which use the chemical (as far as I'm aware) from phytoplankton to mushrooms to mammals synthesize vitamin D by the use of sunlight, (or by eating so... | [
"Plus whatever's abundant in nature we will evolve to rely on , it's free and saves the body energy to make it itself , which is why things are essential and non essential for human nutrition. essential nutrients are abundant compared to non essential which are scarce and that's why we make the non essential nutri... | [
"Vitamin D is a fat soluble vitamin found in nature as one of three types Vitamin D1, Vitamin D2, and you guessed it, Vitamin D3. As with all other substances on earth there is a finite amount of each. The absorption of these vitamin components is dependent on an intact brush border in the proximal small intestine.... |
[
"Are nebulae and gas clouds in space dense enough that sound could travel through them?"
] | [
false
] | I'm basically wondering if in a nebulae you could hear stars being created | [
"Not any that you could hear if you were hanging out there in a spacesuit, but even in sparser regions of the interstellar medium especially energetic events like supernovae can create shockwaves that propagate for many light-years. In theory an immensely large and sensitive receiver could record these sounds, and ... | [
"Once propagating, a sonic boom is not any different than a normal sound wave. "
] | [
"On a human scale, they are extremely diffuse. For example: the Cat's Eye nebula has an estimated average density of about 5x10",
" particles per cubic centimeter. Our atmosphere at sea level has about 2.7x10",
" molecules per cubic centimeter - 16 orders of magnitude difference. A human floating in a nebula wo... |
[
"How were the most recently discovered Elements (ie. 113, 117, 119 ect.) documented, when their half lives are so short?"
] | [
false
] | null | [
"Depending on the lifetime of the nuclide and your experimental setup, you may or may not have time to directly detect it before it decays. If not, you can just detect its decay products and infer what the original nucleus was.",
"The shortest nuclear lifetimes are in the order of 10",
" seconds, and those ones... | [
"119 hasn't been discovered yet.",
"The elements were discovered via their decays: The short half life is an advantage. If one of these would be stable we wouldn't have found it.",
"If you see a nucleus undergo a series of alpha decays then the element number decreases by 2 in each step. Eventually you'll reach... | [
"Yes, exactly. This is how exotic isotopes of lighter elements are routinely discovered, like the recent discovery of calcium-60 that got some media attention.",
"All you need is particle identification; we have many techniques for achieving that."
] |
[
"Can light be turned to microwave through the Doppler effect?"
] | [
false
] | I know that light can change color due to shift in wavelength due to the Doppler effect. If the source/observer moved at the right speed, can a visible light change its wavelength to that of a microwave? and if so does it act the same way as a microwave? To anyone that isn't familiar with the topic. | [
"Absolutely. This is why the Cosmic Microwave Background is microwaves, and not visible light.",
"The opposite is true as well. If you travel extremely fast towards the sun, its light would appear to you as x-rays or gamma rays."
] | [
"so therefore you would get radiated with gamma rays? So you'd be dead. Great."
] | [
"Yeah remember this as we discuss interstellar spaceships that travel at large fractions of the speed of light. That motion blue-shifts the light of stars along the direction of travel to increasingly higher energy. "
] |
[
"How were the number of atoms in a mole determined?"
] | [
false
] | I'm trying to do a bit of reading on this and what I've read so far doesn't seem to get at it. I get the definition of there being 6.02x10 atoms in 12 grams of carbon 12, but how did they 'count' the atoms in those 12 grams? | [
"First, a bit if history. Avogadro had made the idea of a mole as you described (12 grams of carbon in carbon 12), but he didn't actually create the constant of 6.02x10",
" What's important is that moles have been around.",
"Michael Faraday worked in the 1830s on electrolysis, and he had been able to calculate ... | [
"Knowing the mass is the easy part... it was first DEFINED to be a specific mass in terms of carbon, so that was piece of cake. ",
"Then, to go from one element to another, that is an easy task too because we know the atomic masses of elements quite precisely as well. (H=1; C=12, etc) "
] | [
"I don't understand; how did they know how much mass a mole of hydrogen is? Does it have to do with the molar masses of elements or did they use known reactions to algebraically determine how much a mole is?"
] |
[
"What determines the colour of a flame?"
] | [
false
] | I've been told before that the blue/red-orange colour of a flame is due to the blackbody radiation from hot bits of soot etc. in the flame, rather than emission from heated air. If that's the case, why is the colour different when the flame has other elements, such as sodium or lithium. Is it a matter of soot being a relatively large object? | [
"It is true that the red/orange hues in a common flames (camfires, candles) is due to blackbody radiation of soot particles as result of incomplete combustion.",
"Other colors appear because the large energies released during combustion excite electrons in molecules causing them to jump/increase their energy leve... | [
"The red/orange in flames is radiation from soot particles in incomplete combustion which is pretty common to find in things like burners, candles and campfires. The blue (and other colors in other flames) is from electrons jumping energy levels which you've described well."
] | [
"That makes sense, thank you."
] |
[
"If a dog bites someone, at what point can you be sure that the dog was not rabid?"
] | [
false
] | null | [
"First off, when I say “dog bite” I’m referring to a dog biting a human, in case that wasn’t clear.",
"If by “transmission” you mean transmission to the dog, then yes, I understand that the dog may or may not have rabies at the time it bites a human. That is the premise of this whole question. But no, it is not i... | [
"If the dog had rabies at the time of the bite but did not transmit to the person then the dog will develop symptoms within X days and die within Y days. Those numbers are relatively small (from what I understand less than a month, but my question, again, is what the average and maximum value of X?).",
"If the do... | [
"No, you can not test a dog for rabies because the only test is to kill the dog and test the brain. ",
"Sorry but I’ve stated my specific question a few times now, not sure how else I can ask it."
] |
[
"What would happen to my body in space (vacuum) if I had an endless supply of oxygen through a mask, water, food and the temperature was 20 degrees Celsius"
] | [
false
] | I ask specifically with oxygen/heat/cold/food not being an issue. I'm more curious how the absence of air pressure would affect my body. What would I end up dying of? | [
"Temperature is based upon the kinetic energy in the molecules/atoms in a region of space. A vacuum cannot have any temperature because it does not contain matter. (At a simplistic level, anyway--I'm ignoring all sorts of \"virtual pairs\" stuff.) ",
"Your skin is actually pretty porous, thus in a vacuum, the lig... | [
"You have many things happening in this situation (and it should be noted that cold isn't an immediate problem, you don't lose heat super fast through radiation): ",
"Fluids exposed to the vacuum would start boiling to vapor (fluid in mucus membranes, mouth, eyes, etc) and fluids in the muscles and body start to ... | [
"eventhorizon is not explaining it quite right - he got latched onto the wrong topic for your initial question.",
"To explain the issue with lungs: Imagine trying to breathe when an elephant is sitting on your chest - you could imagine it would be difficult, no? That would be because outside pressure is preventin... |
[
"Could entanglement be used for long-distance communication (and if not, why)?"
] | [
false
] | null | [
"Your question is answered in the ",
"FAQ",
"."
] | [
"I have just noticed the reply, and quickly checked the FAQ, found the matching question, and looked at the first linked thread, which continues to leave me dissatisfied. The first answer reads: ",
"Short version: Because you're measuring a fundamental aspect of a particle (let's say spin in this case), and you t... | [
"What is \"system resolution\"?",
"You may be using a different interpretation of communication as the one used when proving the ",
"no-communication theorem",
". The point is that there is no information you can communicate using entanglement that couldn't also be communicated classically without entanglemen... |
[
"Would it be possible to light a piece of wood on fire with water vapor?"
] | [
false
] | Would water vapor at an extremely high temperature be able to ignite wood or would it just heat it up until it just disintegrated? | [
"Yes, it's very much possible.",
"Heck, many years ago we demonstrated exactly that capability, only using the fire-retardant treated paper towels in the chemistry lab. To this day I have no idea how hot that steam was; the source was a boiling flask on top of a burner, with a copper coil attached to the stopper... | [
"Yes. ",
"Here's",
" a simple demonstration on how it's possible. "
] | [
"It depends on whether oxygen is present or not. If oxygen is present, and the steam has the capacity to raise the temperature of the wood above its ignition temperature, then yes. If the environment is starved of oxygen, the wood will be converted into a sort of mushy pulp.",
"This is how pulp is made for paper ... |
[
"Why does the water recede from the shore before a tsunami?"
] | [
false
] | [deleted] | [
"Yes and generation mechanisms depressing the water like landslides or underwater avalanches will cause the trough to arrive first. "
] | [
"This will happen when the trough of the wave hits the land (rather than the crest). If the crest hits first, the water won’t recede, and the wave will be bigger than the normal waves.",
"Source (and a much more detailed explanation):\nInternational Tsunami Information Center FAQ\n",
"http://itic.ioc-unesco.org... | [
"It doesn't always do that. Waves go up and down - sometimes \"up\" comes first, sometimes \"down\" comes first. It depends on the cause of the tsunami."
] |
[
"How to identify a substance?"
] | [
false
] | In general if someone finds a solid/liquid/gas. Then what are steps taken to figure out what is the chemical composition of it? | [
"Infrared spectroscopy",
" is a common technique used to identify unknown samples. Whilst it won't tell you exactly what your sample is, the portions of the EM spectrum that are absorbed will tell you what bonds are present in your sample.",
"An O-H bond absorbs a different frequency to a C-H bond and so forth.... | [
"If you want to determine the ",
" something is made out of, you use something like ",
"AES",
", where you basically blast apart the matter into a vapor of atoms, and measure the absorption/emission spectrum of the atoms. Each element has a unique set of absorption/emission frequencies (through which the elem... | [
"Depends on your budget, the state of matter (solid, liquid, gas), and the reason for analysis (i.e. Hazmat). ",
"If it's a metal, portable XRF, if it's liquid ICP-MS, or GCMS, or even flame atomic absorption, there are literally hundreds of ways and I would need more info to tell you which would be the best for ... |
[
"Is it true that a human can outrun (endurance) nearly every other animal on the planet?"
] | [
false
] | I have just heard of this and was intrigued. A bit of Google-Fu turned up in discover, but it was the only thing I could find. I wondered whether the guys and gals in had heard of this before or knew the answer. edit: Thinking about it, I realise that there would be many variables (hydration, fitness, weather, weight etc...) which would effect the outcome. | [
"Not my field at all.",
"There's an old BBC episode [1] which tracked some African endurance hunters kill a few elk over the course of a day. They used superior tracking skills and the ability to carry water to help exhaust the animal. They were also obviously in peak physical shape.",
"[1] ",
"http://www.you... | [
"Funny, I just watched a TED talk on this subject: ",
"Are we born to run?"
] | [
"As an avid distance runner with distance runner friends who occasionally drag their dogs out for a few miles, I doubt many other animals could outrun a human in peak physical condition.",
"I don't think there are many dogs, cats, gazelle, etc., who could cruise at 7 min/mile for 16-18 miles, which is what a fair... |
[
"What percentage of the earth does the sun directly shine on?"
] | [
false
] | Thanks to my 12 year old son I'm on a mission to get an answer to this. This one might sound silly because '50%' could be the right answer but I suspect it might not be. If you have the Sun a large star, radiating light towards tiny earth - would the edges of the sun in reference to the earth actually 'encroach' so that the direct sunlight hits over 50% of the surface of the earth? The question probably involves some geometry and knowledge of the relative size differences and also the distance of the sun to the earth. Help? | [
"(supporting picture (very rough Paint drawing without legend): ",
"http://i.imgur.com/rUmZVKz.png",
" )",
"50% is an obvious starting guess, but you're correct in noting that the sun being larger than the earth, will shine just a bit \"over the edge\". To compute just how much is not straightforward.",
"Le... | [
"We can improve the approximation a bit without too much extra work. Particularly, we can improve the approximation of the slope of the red line.",
"Suppose the Sun is the circle",
"S(x) = sqrt(R",
"-x",
")",
"and the Earth is the circle",
"E(x) = sqrt(r",
"-(x-D)",
")",
"where R is radius of Sun,... | [
"An added twist is that our atmosphere scatters sunlight in all kinds of directions.",
"Another important effect is atmospheric refraction (which is different from atmospheric scattering). Direct sunlight is bent over the horizon by the atmosphere. As a result, you see the sun on the horizon after it has geometri... |
[
"Do insects ever interact with their larvae?"
] | [
false
] | [deleted] | [
"Honey bees ",
" (and related honey bee species) feed their larvae from hatching until they cap the cell and pupation starts ",
"up to 800 times per day",
". The larval stage is is a 6 day time period. They feed pollen and secretions from their own mandibular glands. They remove dead/dying/diseased larva and... | [
"Ants also interact with their larvae. They feed them, tend to them, some species use them for silk production.",
"Tending to larvae seems to be relatively common in the sphecoid wasps (stinging wasps) like social wasps, bees, and ants. This would make sense since they're mostly social and have colonies."
] | [
"Post hatching parental care is known for insects...see this publication for a beetle species and take a look at the reference cited section for other examples:",
"https://www.nature.com/articles/srep29323"
] |
[
"How do the kalahari dirt circles form?"
] | [
false
] | I was watching BBC's Africa serie (stunningly beautiful documentary btw) and in the first episode they talk about Kalahari desert and they mention those mysterious dirt circles. What are the hypothesis for their formation. The second picture on this slide show is what I'm refering to | [
"The non mobile version of the article: ",
"http://en.wikipedia.org/wiki/Fairy_circle_(Africa)"
] | [
"http://en.m.wikipedia.org/wiki/Fairy_circle_(Africa)",
"Carbon monoxide from an unknown source appears to be the culprit."
] | [
"Not a full answer more a hypothesis"
] |
[
"How rapidly would a flamethrower deplete the oxygen in an enclosed space?"
] | [
false
] | Hypothetical: A person is in a bunker that is sealed. They have a flamethrower, and fire it. Is there a noticeable depletion of oxygen? How long would the fire have to be sustained in order to deplete oxygen in an area maybe 3000 cubic feet in volume? EDIT: I guess a better question is "How long until you suffocate in that enclosed space?" | [
"3000 cubic feet of air would contain about 1520 moles of oxygen. Wikipedia says that modern flamethrowers use propane.",
"Propane combusts as follows:",
"C3H8 + 5 O2 -> 3 CO2 + 4 H2O",
"So 1520 moles of oxygen could combust 304 moles of propane. 304 moles of propane has a mass of 13.4 kg.",
"Unfortunately,... | [
"I'm running a pen and paper RPG online via a forum with a bunch of buddies from undergrad. It's in a sci-fi setting, and one of them just decided to use a flamethrower in a bunker that is sealed shut. ",
"I want to have a good basis for forcing them to take suffocation checks and damage. "
] | [
"Your analysis is good for civilian \"weed burners\". ",
"Military flamethrowers, however, use gelled gasoline (napalm) as fuel, with propane used as a constant-on ignition system. ",
"Wiki.",
"Suffocation is one of the effects flamethrowers were used for, along with the ability to flow into buried fortific... |
[
"Is thrust exerted from a light emission source via the expulsion of light?"
] | [
false
] | null | [
"Yes, it's called radiation pressure and it's extremely weak. It's roughly equivalent to the power of the light emitted divided by the speed of light. So a 60 Watt lightbulb, if perfectly efficient and unidirectional, would give 200 nanonewtons of force."
] | [
"If what you mean is, if you put a laser out in space and turned it on, would the laser accelerate due to the thrust of the laser light? The answer is yes, by Newton's third law of motion, or simply by conservation of momentum (light carries momentum). "
] | [
"Yes, this is why we don't have satellites that run purely on solar power.",
"We do have objects in orbit that drive on ion thrust. We accelerate ions in an electric grid to high speeds and eject them from the end of the craft.",
"The main drawback of this is that this method does not produce enough thrust as c... |
[
"Why does minus attract plus and vice versa?"
] | [
false
] | I understand that plus attracts minus, and minus attracts plus. I also know that two similar charges (+ and + or - and -) repel eachother. The thing is, I've never learned , and I can't find any explanation. | [
"The reason is that the photon has spin 1. ",
"Forces are mediated by particles; electrical forces are mediated by photons. Now particles have intrinsic angular momentum, called spin. The way things work out, if the force mediating particle as an odd spin (such as the photon, with spin 1), like sign charges re... | [
"It doesn't always. You're thinking of ",
", which comes in two types +/-, like-kinds repelling, opposite attracting. There are other types of forces with other types of charges.",
"Gravity has only one kind of 'charge', mass, which is attractive (like 'charges' attract). [Yes I know gravity is better expres... | [
"So what causes photons to have spin in the first place?"
] |
[
"Does a photon have any space-filling properties?"
] | [
false
] | null | [
"A photon is a boson (integer spin). You can have as many bosons as you want in the same location.",
"Particles that comprise matter are fermions (half integer spin). They stay in their assigned seats and keep their distance."
] | [
"Let's say that the math for that would give me nightmares. Because you can't just say \"oh there's some point with a lot of electromagnetic energy in it.\" You'd have to account for the flow of the energy in and out of that point too. Maybe someone can answer that question, I just can't."
] | [
"Hang on a second. There are a number of errors there. You can't just substitute ",
"² into an equation like that, for starters. And second, you're ignoring the uncertainty principle and pretending that photons are cannonballs.",
"The bottom line is no, you can't make a black hole with laser beams."
] |
[
"If right now, and by now I mean southern hemisphere autumn and northern spring, I took a deciduous tree from the southern hemisphere and transplanted it to a very similar climate in the northern hemisphere, what would happen?"
] | [
false
] | Would the tree stop dropping its leaves and sprout new buds, would it shut down for a few seasons to readjust its internal clock, or just die? | [
"If the tree uses photoperiod to measure seasonal change, it will probably be fine, as it will only shed it's leaves when it detects a change in the length of day. If we're assuming it hasn't already dropped the leaves for the southern hemisphere winter, the tree will probably just interpret this as a super long su... | [
"It would no doubt just assume it went through a ",
" short winter and start regrowing leaves again.",
"Same reason transplanting a human from a warm climate to a cold one won't cause that person to freeze, they'll just start wearing warmer clothes. Humans and trees decide what to do based on environmental con... | [
"But what about if it is ALREADY in the process of shedding its leaves? Also, what if it has already completed this?"
] |
[
"What is a muscle knot?"
] | [
false
] | What cause "knots" in the muscles and why do they feel the way they do? | [
"The medical term is myofascial trigger points. There is some debate about what causes muscle knots but it seems to be connected to an abnormal build up of protein after a release of lactic acid.",
"Muscles that form knots are muscles that have gone into a muscle spasm either due to injury, overuse, or a sedentar... | [
"This seems like a good place to ask: Does foam rolling work to relieve this condition?"
] | [
"As a swimmer I can say that with bihkram yoga, and a ice bath, the foam roller does an amazing job. I do it once a week to detox from all the lactic acid build up in my muscle (sweating a ton and stretching) as well as rolling my self after."
] |
[
"Why are cathodes known as negative electrodes and cations known as positively charged ions?"
] | [
false
] | This might be more of an english question if anything, but I always get these mixed up in experience with science courses. Sorry if it’s a silly question, but I have always been confused at the similarity of the words. This question also obviously applies to the opposite of these terms, anode and anion. | [
"The negatively charged cathode attracts positively charged cations, the positively charged anode attracts negatively charged anions. The prefixes cat- and an- on their own do not mean positive or negative."
] | [
"I believe there's also an historical side of this as well, the names and polarities were decided sort of arbitrarily before we knew what the charge carriers were (aka electrons), and by the time we figured out we had assigned them incorrectly it was too late. I could be mistaken on this, but I ",
" to remember i... | [
"Cations move to the cathode, anions move to the anode.",
"It makes sense if you don't understand what positive and negative charges are. Same with the magnetic field. The north pole of a magnet will point north - which means Earth's magnetic field has the magnetic South Pole at the North Pole."
] |
[
"If you're in a plane that breaks the speed of sound, does the noise outside of the cabin suddenly fall completely silent, since you're moving away from the sound waves the plane is creating before they reach your ears?"
] | [
false
] | I've tried to find a video of a plane going supersonic filmed from inside the cabin to answer this, but so far I've found nothing of the sort. | [
"No. The cabin is still vibrating and transferring those vibrations to the air inside of the cabin.",
"EDIT: Maybe I misread your question, are you asking if someone was listening to the plane from outside the cabin while it was supersonic? Or if something outside of the cabin that wasn't the plane itself, made n... | [
"No. Despite the misconception that the sonic boom is the noise created the moment the plane breaks the sound barrier, the sonic boom is actually caused by the bow wave of sound waves created by the plane, and is actually one continuous stream of noise that onlookers will only hear for an instant as the wave reache... | [
"You hear noises inside the cabin (subsonic or not) through vibrations on the outside surface of the vehicle, which are transmitted to a locally subsonic medium (the cabin air) as pressure waves. I would say no, the average passenger wouldn't notice any difference. In fact, if anything it would probably get loude... |
[
"Do light photons experience time dilation?"
] | [
false
] | null | [
"Photons do not have a valid reference frame and thus can not experience anything. ",
"If you ignore the reference frame part, you ",
" say that they experience maximum time dilation where time stops completely. I would be careful with that statement though. "
] | [
"I'd love to give you an answer, but that's not even valid as a hypothetical question due to the invalidity as a reference frame. Kinda like saying \"if an orange was an apple, how good of an apple would it be?\""
] | [
"If you ignore the reference frame part, you could say that they experience maximum time dilation where time stops completely. I would be careful with that statement though. ",
"Perhaps the best way to phrase it is to not speak from the viewpoint of the photon, but rather to simply say that the proper time distan... |
[
"gravity - size, mass and the effects"
] | [
false
] | ok so i posted on softscience and a replier directed me here, heres the thread: so yeah, a really in-depth explanation is requested here, thanks in advance. | [
"Next time post the actual question:",
"hey quick question guys, 1 my intuition isnt enough to answer. does the size of an object matter when it comes to gravity? if you have a chunk of matter that maintains its mass at any size, is its gravitational field affected? eg: if the earth was crushed into the size of a... | [
"To be a bit more clear:",
"Far away, the size doesn't matter. When you start getting close, the finite size may be important. The size is important ",
" it is comparable to the \"gravitational radius\" of that mass, which is to convert mass into a length: R_s = 2 GM/c",
" (this is the \"Schwarzschild radius\... | [
"would you be able to put multiple super dense objects close together? wouldnt they just collide with each other?"
] |
[
"AskScience AMA Series: Cosmology experts are here to talk about our projects. Ask Us Anything!"
] | [
false
] | We are four of 's cosmology panelists here to talk about our projects. We'll be rotating in and out throughout the day (with more stable times in parentheses), so send us your questions and ask us anything! (8-11 EDT)- I'm a theoretical cosmologist interested in how we can explain the accelerated expansion of the Universe, in a way that's theoretically satisfying, by modifying the laws of gravity rather than invoking a mysterious dark energy. Most of my work over the last couple of years has been on a theory called massive gravity, in which gravitons are massive (in Einstein's theory of general relativity they're massless, like photons), and a closely-related theory called bigravity, in which there are two spacetime curvatures (or equivalently two gravitational fields). I've just finished my PhD and will be starting a postdoc in the fall. (10- EDT)- My research is primarily focused on constraining the cosmological parameters related to dark energy. Currently, I'm involved in a project focused on finding new galaxy clusters using CMB and galaxy survey data. (13-15 EDT) - I do research at a major US university. My primary focus is on large-scale redshift surveys (namely, SDSS and DESI), studying properties of dark energy (observational constraints, time-evolution, etc.) and galaxy/QSO clustering. (10-12 EDT) - I'm a graduate student studying computational physics. My research involves simulating compact bodies like neutron stars and white dwarfs to calculate their physical properties. For example, I'm interested in neutron star mergers as a site of heavy metal nucleosynthesis and as a source of gravitational waves. | [
"Honestly, it was probably watching a bunch of stupid videos on youtube when I was in high school. I always liked science, but having Mind Blowing Content",
" on demand about quantum mechanics and relativity and space and Neil deGrasse Tyson really made me think, \"Holy ",
", I need to do ",
" with my life.\"... | [
"There are ",
"articles",
" for ",
"each",
" of these on Wikipedia, although they're aimed mostly at people with a working knowledge of theoretical physics. (Full disclosure: pretty big chunks of these articles are my work.)",
"Our best theory of gravity to date is Einstein's theory of general relativity,... | [
"When you graduate from college, believe it or not, you're not finding a job. You're going back to school. ",
"After you've got a 4 year degree, you apply to grad school, and you basically retake all the same classes but in much more depth, and you start on research. The research is about 4-5 years of work that u... |
[
"Is yeast necessary for the production of alcohol during decomposition? Or is alcohol just a consistent byproduct of decomposition?"
] | [
false
] | null | [
"Yeast metabolize sugars and replicate and in the process generate CO2 and ethyl alcohol, among other things. When alcohol levels reach a certain level it becomes toxic to the yeast and the production comes to a halt, unless they run out of available sugars first. Some yeasts are more tolerant of alcohol levels tha... | [
"Alcohol is not a consistent byproduct of decomposition in general, but it is a common byproduct of a particular ",
" of decomposition, namely fermentation. Fermentation is a nice old fall-back (The other common byproduct of fermentation is acid; for example, when your muscles run out of oxygen they begin to fer... | [
"Alcohol is the waste product of anaerobic catabolism of sugars in the glycolytic pathway (also called fermentation) - if there was enough oxygen in the solution, you'd instead have CO2 production from the yeast, which is what is produced by aerobic respiration via the TCA cycle."
] |
[
"Does the conjecture P = NP in computational complexity theory assert that encryption is unreliable?"
] | [
false
] | I'm a philosophy grad student and came across the PvNP question recently in some literature. I was wonder that since P=NP asserted that the class of problems with efficiently checkable solutions (finding an algorithm in polynomial-time) is equivalent to the class of problems with efficiently solvable problems, that it concomitantly asserts that encryption based on prime factorization could be solvable in polynomial-time. Not that anyone makes this conjecture it seems, but an interesting consequence to think about. | [
"I mean, the answer to your question is \"Yes\".",
"More specifically, if it turns out that P=NP, encryption will be much less secure than it currently is and that because we don't know if it's true then we don't know if encryption is actually secure.",
"It's possible that P=NP but the algorithm that we prove e... | [
"Let's start with some things about integer factorisation & discrete logarithm, two problems on which encryption schemes (such as RSA or Diffie-Hellman key exchange) are based:",
"quasi-polynomial",
"NP ∩ coNP",
"and those make us sufficiently certain these problems are ",
" to base an encryption scheme on.... | [
"You're correct that we can't prove factor-based encryption schemes are impossible to break in polynomial time with a classical algorithm. It is theoretically possible that someone could publish an algorithm that busts our banking system wide open tomorrow, or that some government agency like the NSA is already si... |
[
"How do scientist take pictures and videos of incredibly microscopic things?"
] | [
false
] | I was going through the Nikon Small World competition and was baffled by how scientist were able to produce their videos. Thing first place video was of a zebrafish embryo growing its elaborate sensory nervous system | [
"The specific technique used in the zebrafish embryo video was Selective Plane Illumination Microscopy (SPIM) which is designed to image small organisms without the photons damaging the organism. Instead of lenses projecting an image onto a plane like a normal camera, this method scans the organism with a sheet of ... | [
"SPIM is also called Light-sheet Fluorescent Microscopy and it has only come to be a commonly used microscopy technique in the last ~5-6 years due to technical advances in cameras, computing power and data storage. The data sets used to create a single movie are huge! It has the advantage of being gentle to living ... | [
"We are actually capable of imaging things below the diffraction limit now (200-250 nm, roughly half the wavelength of visible light). This is done with super resolution microscopy, and we're able achieve resolution down to 20 nm, with some laboratories claiming they've gone even further down.",
"Since we can't s... |
[
"If two identical twin females marry a set of identical twin males and have children and had a DNA test on each others children would it say that Sister A's kids actually belonged to Sister B because of the identical DNA?"
] | [
false
] | I've had this question in my head for a long time. Like, genetically could it look like the other twins children are her own? I've always wondered about things like that. I mean how identical is their DNA? | [
"A test of all children of the two couples would show up as if all children had the same two parents. Strictly genetically speaking, since it was two pairs of identical twins reproducing, all of those children would be (genetic) siblings, not (genetic) cousins. ",
"Our modern paternity testing's sensitivity would... | [
"To clarify, the type of genetic test commonly used to determine paternity would not be able to tell them apart. A much more thorough (and expensive) test would probably be able to tell them apart, but it might require a huge number of genes to be tested. "
] | [
"I don't believe the OP is asking if the children are genetically identical to each other, the OP is asking if paternity/maternity can still be ascertained by DNA testing and the answer is no."
] |
[
"When Intel or AMD build a CPU, do they know in advance how high the CPU will be able to clock?"
] | [
false
] | I know they probably have targets but I was wondering if there was some method they use to simulate the physical properties of the CPU before production. | [
"CPU developers have to find the maximum clock speed at which their architecture will be stable. They should have a pretty good idea of where this stable speed is, since they developed the architecture and roughly know the limitations of the hardware design, but there's a lot of testing to find the true maximum.",
... | [
"A great deal of really expensive or vendor-proprietary software involving graph theory to model circuits, propagation delays, etc. likely running on supercomputers of previous generations of CPUs. Basically, the longest propagation delay possible through a circuit dictates its maximum clock speed. I've personally ... | [
"you know already how fast the silicon gates can switch and the whole cpu is designed in VHDL so you can simulate the clock cycles on a computer, I think you have a fairly good idea before you build it, but obviously what the simulated cpu and the actual do might differ, however I imagine they debug it as much as p... |
[
"Why would someone be prohibited from donating blood after a clinical trial?"
] | [
false
] | null | [
"Drug trial?",
"They don't know how long it takes the body to remove 100% of the drug and there may be some random contraindication with someone receiving your blood. Like a random freak allergy that just appears.",
"I wasn't allowed to have unprotected sex for like 6 months after mine for a similar reason"
] | [
"It depends on the nature of the clinical trial and the treatment that the donor received. A general statement is that donors who receive a systemic experimental medication as part of a clinical trial should be deferred for 12 months unless stated otherwise by the sponsor of that trial. Source: ",
"https://www.us... | [
"That depends on the trial. ",
"If it's a medication trial, it's still unclear how long the medication can be present in the blood, and how long after taking the medication the participant can still have negative effects. You don't want to put the recipient or donor at risk unnecessarily. ",
"If it's a non-medi... |
[
"What is the biological purpose of rejecting blood types?"
] | [
false
] | How would this have evolved? Only with modern medicine could we get enough foreign blood in our bodies to have a reaction, and even that seems to serve no protective role. | [
"You're probably referring to the ABO system as well as the Rh system, but for a fun fact, there are ",
"many 'minor' blood type differences",
" on top of those. ",
"Blood antigen variation is thought to be a response to pathogens like viruses spreading from person to person and carrying some component of me... | [
"From an evolutionary perspective, the different ABO types served as a mechanism to avoid disease. ",
"Depending on blood type, people are more or less susceptible to particular pathogens. Type O people, for example, are more susceptible to cholera and plague, while people with type A are more susceptible to smal... | [
"Rejecting other blood types is a by-product of your immune system being able to identify foreign substances (antigens) in your body. It is really just an immune response. This response is generated like any other immune response, your body detects something and determines that it is not one of your cells. One of t... |
[
"Why are we so confident Leptons to be truly the most fundamental particles of Nature?"
] | [
false
] | In Science, shouldn't we always give the benefit of doubt to our lack of knowledge? How are we so confident the Leptons are truly point like particles. Do they have no dimensions? Also, how likely is the discovery of something even more fundamental? | [
"We are not so confident. There are many ",
"searches",
" for effects related to a hypothetical compositeness of our current fundamental particles and no one is claiming that what we have now is the last brick.",
"However what we know for sure is that a point particle model describes perfectly all data we hav... | [
"Why are we so confident Leptons to be truly the most fundamental particles of Nature?",
"Leptons aren't considered to be more fundamental than other elementary particles; they share the same \"fundamental\" status as quarks and the force-carrier bosons.",
"But we are reasonably confident (don't confuse reasona... | [
"The mistake is mine then ... but I definitely remember your username being filed in my \"crackpot\" bin, and a glance through your post history confirms why I remember it. Do you cite ",
" sources at all besides that one nutty WordPress blog?",
"Edit: Oh. I see the blog is yours. With lots of rambling writi... |
[
"What actually happens to electronics when they are damaged by water, why do they often not work when dried out again?"
] | [
false
] | null | [
"Semiconductor reliability engineer here. (Thanks for posting a question in my area of expertise!) ",
"Water has various bad effects on electronics: ",
"Causes a \"short circuit\" or electrical \"leakage\". Instead of following the wires it is supposed to, it travels along the water. This can cause malfunctio... | [
"It was probably moderately purified DI (DeIonized) water. An aqueous rinse followed by a rinse in a drying agent is a common practice, to get rid of solder flux residues, which can be much more harmful than water. Although some manufacturers use \"no clean\" fluxes making this step unnecessary. ",
"I didn't m... | [
"The OP said nothing about temporary exposure to tap water. Certainly a brief immersion (such as a dunk in the toilet) minimizes the risk of any of those things. OP also did not specify a particular electronic device. ",
"So I'll address your bullet points one by one:",
"porous layers inside of the IC (um no,... |
[
"Einstein's Principal of Equivalence states that gravity and acceleration are the same thing. But wouldn't acceleration have a limit (speed of light) while gravity is infinite? Would the discovery of gravitons disprove this principal?"
] | [
false
] | null | [
"Acceleration isn't a speed. What do you mean?",
"The existence of gravitons has little to nothing to do with the equivalence principle, it could be true with or without them."
] | [
"You can never accelerate to the speed of light but you aren't taking into account any relativistic principles here. From the point of view of an accelerating object it can accelerate forever."
] | [
"You can never accelerate to the speed of light but you aren't taking into account any relativistic principles here. From the point of view of an accelerating object it can accelerate forever."
] |
[
"Why does Helium liquefy at a lower temperature than Hydrogen?"
] | [
false
] | I would have thought it was related to the molecular weight of the molecule, but that is not the case? Although "naturally occurring" hydrogen is diatomic, the total mol wt is still less than helium and yet it condenses at a much higher temperature. So why does helium condense at such a low temperature, relative to other gases? For reference (from Wikipedia), boiling points of various gases: Background - I'm working on a helium recovery project and I was curious about the history of helium and its physical properties and why there really is no substitute for it's use in the science and medical fields. | [
"Boiling points are a product of the overall strength of the intermolecular forces at play between the molecules in solution.",
"Since the species you mentioned have no dipoles, the only forces at play are London dispersion forces (or Induced Dipole - Induced Dipole forces). These forces occur when molecules spon... | [
"But even if it is elongated, how would a dipole form if the two nuclei are identical? Is it just that the molecular hydrogen is easier to polarize than an isolated atom is, so dipoles tend to form most of the time?"
] | [
"As far as your main question goes, Helium is the lightest noble gas. Not really an explanation, but it at least makes sense that it doesn't strongly attract itself, and why it doesn't take a lot of energy to make the molecules scatter everywhere.",
"Concerning it's irreplaceability, medicine mostly just wants i... |
[
"When we take footage of the ocean floor that isn't reached by sunlight, are the lights used for filming harmful to the ocean life?"
] | [
false
] | null | [
"Generally not. ",
"You might be drawing an analogy to 'if i sit in the dark for a while, a bright light is really bright - imagine if i lived in the dark!', but it isn't really like that.",
"Most of the visible spectrum doesn't penetrate too far, with only the blue end of the visible spectrum penetrating to th... | [
"Water can absorb a very large amount of energy without heating up by any significant degree. Heat will also diffuse fairly readily to surrounding water and wont remain localized."
] | [
"Adding on to this, water has the highest specific heat capacity of any stable and abundant liquid, meaning it takes an IMMENSE amount of energy to heat it up. Specifically, it takes 4,184 joules to heat 1 kg of water by 1° Celsius (consider that an entire kilogram of copper takes only 385 joules to increase temp. ... |
[
"Ambidexterity"
] | [
false
] | Is there any reason everyone cant be ambidextrous? I remember when I was little a teacher would come around and ask us which hand was easier to write with, and then told us to stick with it. I had no preference so I switched off when one hand got tired and I feel like other students would do the same thing. If you start early enough is there any scientific evidence why anyone cannot be ambidextrous? | [
"Just a reminder for commenters: Please don't post your personal anecdotes in AskScience."
] | [
"The brain is divided into two hemispheres.",
"There are typically right-handers, and non-right-handers. They're classified this was because non-right-handers have a brain with relatively equal hemispheres.",
"Most people can become ambidextrous through practice, but it only comes easy to a small percent of the... | [
"I may be a little late to this, but I have recently been practicing my handwriting with both of my hands and I have reached a point where I can write legibly with both hands. My left doesn't quite have the speed my right hand, the dominant one, does, but it is still legible."
] |
[
"Is the universe 13.8 billion years old, or is the observable universe 13.8 billion years old?"
] | [
false
] | I've tried googling and researching this to no avail. If our best telescopes and other sensors can only see so far into the universe, how do we supposedly know the age of the whole thing? Edit: Didn't know whether to put Physics or Astronomy for the flair. It's Astrophysics, isn't it? A mixture of both? | [
"It's a good question! ",
"For the sake of argument, let's say that 'the universe' is infinite. Here, by 'the universe', i mean everything that exists.",
"We know from our observations of the cosmic microwave background (",
"CMB",
") that to a very good approximation, the universe is both homogeneous and ... | [
"This is also a very excellent question.",
"It is true that space is mostly a vacuum. But it is not ",
" empty. Between the galaxies, the average density is somewhere on the order of one proton (and one electron) per cubic metre.",
"The thing that puzzles me, though, is that i don't know whether or not spac... | [
"...by 'the universe', i mean everything that exists.",
"I honestly don't know what I'm talking about, so bear with me when I ask: Isn't there a whole lot of ",
" in space? Does that exist?"
] |
[
"Why did the luner module get cold in Apollo 13? Why didn't the vacuum of space act as a thermos and keep the astronauts toasty warm?"
] | [
false
] | null | [
"All objects radiate away energy as a function of their temperature. So while it's not an instantaneous process, over time the module loses heat into space."
] | [
"Especially when secondary systems are disabled to save power, which would normally generate more heat."
] | [
"Yes. This is also true. Now over short times, the vacuum of space ",
" make a good insulator. If for instance the astronauts happened to find their module deep in the ocean (ignoring the pressure which would crush them), the heat drain from the water would kill them much faster than the equivalent heat lost to v... |
[
"Given the right circumstances could flora become sentient?"
] | [
false
] | null | [
"define sentient."
] | [
"I would think this very fact would make it extremely unlikely, bordering on impossible, for a plant to evolve sentience. Theres nothing plants could do to actually use this intelligence, they'd just sit there and think. And think some more. And think some more. All that energy used in thinking and building and mai... | [
"Given the right circumstances, I suppose just about any organism could eventually evolve sentience, however, plants developing sentience is highly unlikely and here's why: Plants have no nervous system, they don't even have the evolutionary beginnings of higher thought. Also, sentience would have no evolutionary b... |
[
"Book list for science subreddits?"
] | [
false
] | Could we try to compile a list of well-regarded books in the various fields represented here? Here are some examples similar to what I had in mind: It would be nice to have labels distinguishing how in depth a book is. It might be ideal to have a format similar to 's list or to have a subreddit dedicated to this subject in the vein of . Features to consider: 1) Individual suggestions can be upvoted or downvoted. 2) Individual suggestions should allow people to describe/discuss the pro's and con's of a title. 3) If in , perhaps panelists' suggestions should take priority. I'll try to xpost this to . (Would've posted there originally but they only accept links.) | [
"Feynman Lectures on Physics",
"Any else by him is also wonderful."
] | [
"Introductory reading for biology, molecular biology and biochemistry:",
"Campbell biology",
"Molecular biology of the cell",
"Lehninger principles of biochemistry"
] | [
"This'd give you a good start if you wanted to get a good (and easy-to-understand) familiarization with what archaeology is all about. There are many other well-regarded books, but I don't think most people want \nto invest the kind of time needed to read them all. ",
"Rathje's ",
"Deetz's ",
"Trigger's ",
... |
[
"Did membranes evolve before cells?"
] | [
false
] | I was told this recently, for the first time, so went online to try and find out if this was the case, but couldn't find any evidence toward it (fossils, etc.), how it happened, or even just an article relating to it. If anyone could explain, or even just link me to some relevant information, it would be much appreciated! | [
"One theory for the origin of life is that bubbles of phospholipids (lipids with a charged polar end that are attracted to water, and a nonpolar end that are repelled by water) formed bilayers (as in extant cells), which allowed for the evolution of nucleic acids and proteins that we see in life today. So yes, cel... | [
"One neat observation is that certain types of lipids can spontaneously form lipid bilayer vesicles (i.e. liposomes). In 2003, ",
"a study",
" was published that showed how the same clay environment that is capable of catalyzing the polymerization of RNA nucleotides is also capable of catalyzing the formation o... | [
"The current theory is that cellular membrane was present before or at least at the same time of the first cells.",
"the fat that make up our cell's membrane is very easy to have in nature and naturally will form into a ball."
] |
[
"Will a black hole created by compressing a pencil (hypothetically) and a black hole created by a collapsed star have the same gravitational strength?"
] | [
false
] | null | [
"Gravitational influence is directly proportional to its mass."
] | [
"But, of course, a black hole's density is what gives it it's commonly-portrayed properties. "
] | [
"Not exactly. At say one kilometer from each source the gravitational force is much greater with the collapsed star. In fact the pen black hole would have same gravity as a normal pen. However once you reach the event horizon,where the escape velocity is greater than the speed of light, of each case the gravity... |
[
"Why do mutations occur at all during DNA replication? How/why do the proteins that replicate DNA mess up?"
] | [
false
] | null | [
"It's because the process is not as organized as we have learned it. We tend to think of intracellular reactions as they're supposed to work. Only thymine is supposed to bond to adenine. Only a specific type of ligand bonds to a certain receptor etc. this type of thinking leaves it hard to imagine what's actually g... | [
"/u/jimmyth3xplod3r",
" spoke about the bigger \"why?\" question in terms of evolution and the necessity of mutations to generate diverse progeny, but I will come at your question from the angle of biochemistry / protein chemistry regarding the replication machinery.",
"Disclaimer: I will be speaking about the ... | [
"All of the answers here are brilliant. I'll just add that DNA can also take mutation-inducing damage from outside sources such as ionising radiation and toxic chemicals like free radicals, which are generated by various cellular mechanisms. On a molecular level, a DNA base's structure can be altered by such reacti... |
[
"Are there any materials that become softer when cooled and harder when heated?"
] | [
false
] | Materials made of iron for example become very soft and malleable when heated but extremely brittle and hard when cooled -- are there any materials that have the opposite effect? | [
"Plastic deformation (ie. permanent deformation) generally occurs by the passage of dislocations through a material - you can think of them as defects in the crystal that let it move a bit like a caterpillar - (",
"https://www.nature.com/nmat/journal/v9/n4/images/nmat2737-f1.jpg",
"). Heating things up lets the... | [
"Not all nickel super alloys. Inconel while exceptionally strong does not get strong with temperature"
] | [
"Yeah all Ni superalloys exhibit this effect - in certain inconels it might just offset the drop in strength due to temperature though, so you wouldn't see an explicit strength increase."
] |
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