title list | over_18 list | post_content stringlengths 0 9.37k ⌀ | C1 list | C2 list | C3 list |
|---|---|---|---|---|---|
[
"Can you help me identify this bone I found my dog chewing? I think it is a humerus bone."
] | [
false
] | From doing a simple search for bone images, I am guessing it is the bottom part of the Humerus bone. But i have no idea which animal and if it is indeed part of the Humerus. I would like to have an expert weigh in. Here are the pics. | [
"I am no expert, but it looks cut and based on my Asian grandparent's cooking, I would say it is from some sort of pork soup. So it is probably a pig.\n",
"http://www.thechinesesouplady.com/wp-content/uploads/ingredients/meat/pork/pork_marrow_bones2.jpg"
] | [
"Why does it look like its been cut?"
] | [
"It looks to me like part of the knee of a pig."
] |
[
"What methods are used to rescue very endangered species?"
] | [
false
] | What methods are used to prevent very endangered species from going extinct? Or, if we don't try to prevent them from going extinct do we do anything to try to preserve DNA? By "very endangered" I'm talking about species with a population of less than 250 in the world. For example, the is critically endangered, with ... | [
"There are a number of diffrent theories about how stuff should be done. \nOne that has been effective is the Kakapo-project i New Zealand. ",
"Basicly what they did was rid a few Islands of Everything that had not been there when the parrot was around in numbers. ",
"Wikipedia",
" "
] | [
"Well there are so many different solutions because each endangered animals is faced with its own unique set of problems. So what are ",
" of the causes to animals becoming endangered:",
": illegal hunting, over hunting, prize/trophy hunting, sustenance hunting (for food). ",
" create spaces where you cannot ... | [
"Question: What is the minimum number of animals you can start with to completely save the species? If you only had 1 or 2 breeding pairs, wouldn't they die out due to inbreeding? "
] |
[
"Is it t possible for identical twins to have different traits such as hair color or eye color?"
] | [
false
] | null | [
"Physically, they are identical in every way.",
"Not true. Identical twins are almost completely genetically identical but this doesn't mean they are completely physically identical. In the case of eye colour and hair colour, these traits are strongly determined by genetics so will mostly be the same. However ev... | [
"I would assume some other forms of life experience could also alter the hair of identical twins, such as more time in the sun for one of them resulting in more bleaching."
] | [
"Physically, they are identical in every way.",
"Not true. Identical twins are almost completely genetically identical but this doesn't mean they are completely physically identical. In the case of eye colour and hair colour, these traits are strongly determined by genetics so will mostly be the same. However ev... |
[
"How are mathematical constants computed on calculators?"
] | [
false
] | Such as pi, e, etc. I know in the old days before calculators they had tables for stuff like that with hundreds of decimal places for constants, but how do calculators do it now? Do they just have memory space that hold all of that same information or do they run some equation to get the number? | [
"I believe they are stored in calculator's memories, the manual will even tell you the precision in terms of decimal digits of these constants if I remember correctly. ",
"As for their computation on computers, if needed to a high precision:",
"e is pretty simple: since the Taylor series for e",
" is: 1 + x +... | [
"On a handheld calculator with like 8 decimal points, it would serve no purpose for pi to be stored or calculated to any higher precision. All the extra digits would be obliterated the first time you added it to another number. I would assume they just store it as a constant value.",
"I'm curious on your source f... | [
"I don't know what's done in practice, but if you know how many terms you want to evaluate, it seems like you could avoid overflow by factoring. For instance, to evaluate",
"1 + x + x",
"/2 + x",
"/6",
"you can factor this to",
"1 + x * (1 + x/2 * (1 + x/3))",
"In practice you can compute this as follow... |
[
"What is the fidelity of human sensory perception/judgement?"
] | [
false
] | null | [
"This question is a bit too broad. This area of research is called psychophysics and has been going on for a long time. These measurements have been done for all of the things you list and many others besides but there is no centralized exhaustive list that I'm aware of. Do you have a specific question in mind?"
] | [
"I recommend making a new post with exactly that question. Happy to answer it there"
] | [
"Yeah i had that thought after i posted this, apologies.",
"My specific question is the title i guess, my other questions were more or less my way of trying to define my thought with my limited vocabulary haha. ",
"The question that prompted me to post this was how accurately a human could tell the difference i... |
[
"Why is accelerating more fun or exciting than driving at a constant speed of 100mph?"
] | [
false
] | [deleted] | [
"Except for small bumps in the road, you can't feel any difference from going 100mph versus 0. When accelerating, you'll feel the normal force of your seat pushing you forward."
] | [
"One of the effects of relativity is that all constant-velocity reference frames look the same. That means that if your speed/direction of travel doesn't change, you can't actually tell that you're moving. (Of course you can refer to something outside, like the trees outside the car window, but that's cheating.) On... | [
"G's"
] |
[
"What is happening in an operating system when a process is \"Not responding\"?"
] | [
false
] | I'm taking a course on operating systems right now, so I know a little about how processes work. An OS switches context between processes several times a second, and this makes it seem as though all your processes are running simultaneously (and on multicore systems many of them actually are running simultaneously). So... | [
"Here",
" is a nice post from Raymond Chen explaining part of your question.",
"Generally, the OS checks if an app hasn't retrieved messages from the message queue in a long time (a couple of seconds) and if it hasn't - the app is \"not responding\".",
"Usually the app is stuck performing a heavy computation ... | [
"This is pretty much dead on. I have written a lot of software in which I never multi-threaded so my stuff always appeared as if it was dead. If software multi threads it can usually leave the UI active for the user and the error message is a lot less likely to happen."
] | [
"For a simple demonstration of a thread try this page: ",
"http://afshinm.github.io/50k/",
"The \"web workers\" thingy here is an implementation of threads in you browser, the interesting aspect is that the \"children thread\" doesn't block the \"main thread\", two threads are working in parallel (opposed to se... |
[
"How high pressure does it take to transform liquid water into ice at room temperature?"
] | [
false
] | On high mountain tops water boils and turns to steam at a much lower temperature because of the lower atmospheric pressure. Is there somewhere in the sea deep enough to turn the water into solid ice? And can we recreate such pressure with today's tech to solidify water at normal room temperature? | [
"We need ~10 kbar of pressure to freeze (pure) water into solid ice at 25",
" C according to ",
"this diagram",
". At the Mariana Trench, apparently we only reach ~1 kbar according to ",
"Wiki's second paragraph",
".",
"You can create such a pressure in a ",
"diamond anvil cell",
", actually you can... | [
"Your phase diagram doesn't go to a high enough pressure! If it were to keep going up in pressure, you'd see that you actually can form solid ice at room temperature. ",
"Here is a better diagram: ",
"http://en.wikipedia.org/wiki/Ice#Phases",
"and here is an experiment where they've done this: ",
"http://ww... | [
"I believe it's the other way around. If you compress ice, it turns into water. Ice takes up more room than water, so you can't compress water into regular ice. You can compress water into other solid forms (called Ice II to Ice XV), but they do not have the same crystal structure as normal ice."
] |
[
"Why is the moon's horizon not directly perpendicular to the sun?"
] | [
false
] | I'm not sure if I worded that question correctly, but hopefully someone can help me out. I was walking close to sunset time last night (I live in Pennsylvania, I figure that has something to do with it) and I noticed something I never had before. If I looked at the moon, I could obviously see the horizon, as it's not a... | [
"I definitely know the light was from the sun, no doubt. It just didn't appear that way from my angle (which is why I was so boggled). The sun was just above the horizon in the west, and the moon was, like you said, almost in a \"noon\" position (middle of its visibility time here in PA). It was more to the south, ... | [
"What you saw has nothing to do with rotation or time delay. After all, the speed of light is ",
" fast, so there's not much time delay between the Sun and the Moon and the Sun and the Earth.",
"The moon is approaching full, which means it was probably close to overhead or even a little in the East when you wer... | [
"A compass and a protractor always seem to work well. You can figure out what direction (Azimuth, as it's called) and elevation (Altitude) each object is, then do some fancy spherical geometric calculations to figure it out."
] |
[
"Do we know any Neuroscience on Lucid Dreaming?"
] | [
false
] | I know dreaming as is is already lacking a whole lot of completeness, much less understanding how lucidity will manifest itself thereof. But with whatever it is we do know and understand, what's the best science to explain one of the most powerful experiences the human mind is capable of without foreign substance/manip... | [
"This article",
" does a fair job of discussing dreaming and it's out the Psychiatry Department at Harvard. I think it's readable by a non-scientist, but if you have specific questions, feel free to ask.",
"In studying the physiological correlates of lucid dreaming (Voss et al., 2009), it \nwas found that ther... | [
"But we already knew the brain could do all those things. In fact, it's doing that stuff ",
" when you're awake. The lucid dreaming research hasn't really informed us on how exactly it works. Also, your internal imagery isn't photoreal. It seems perfectly realistic because you only imagine a certain level of deta... | [
"Wow. I wasn't sure there would be much if any actual science of lucidity, other than philosophical/scientific speculation! This is very interesting. And this was already ~2 years ago. It's exciting to think about how there really are many fields unexplored and incomplete that can still be constructed by the few wh... |
[
"Why is it that when we use time less than a second we use a metric system but not for anything more than a second?"
] | [
false
] | null | [
"Not everything has to have a deep reason. Some conventions are just accidental. "
] | [
"Then once we get to year, we go back to a decimalized metric system (megayear, gigayear, etc.). It's just a funny convention, and likely related to our daily lives being so intertwined with the night-day cycle. Perhaps someone more familiar with history of science can give more details."
] | [
"Yeah I tried looking at in online but, the answers were usually \"cause that's how it is\" type answers which bothered me. I feel like we could measure days as 86.4 ks. "
] |
[
"How do we perceive the color brown?"
] | [
false
] | The color brown isn't part of the electromagnetic spectrum and usually results by mixing colors. Are there cones in our eye that perceived mixed signals as brown? Is it perceived later down the line at the occipital lobe due to the stimulation of multiple cones? | [
"You're right in that there is no wavelength of light that is brown. But our eyes don't perceive wavelengths anyway. Our eyes have 3 kinds of cones that measure 3 parts of the electro magnetic spectrum, and our brain turns any combination of signals from the 3 types of cones into a color. Brown means the eyes perce... | [
"To clarify, we have one type of rod, not 3, and those rods respond to a variety of wavelengths of light (but peak - ie respond most easily/strongly at a particular wavelength).",
"We have 3 other types of photoreceptors called cones which “peak” at different wavelengths (but, again, each type of cone responds to... | [
"Yes, but still it gets created by mixing spectral colors AND these colors are picked up by the cones. How else should it work?",
"\nTop comment wrote basically the same thing like I did 5 hours earlier. The only difference is I didn't point to the fact that brown is a mix of wavelengths."
] |
[
"Is the brain's pain center(s) capable of distinguishing between physical pain and emotional pain?"
] | [
false
] | null | [
"A recent paper published in ",
" showed that the brain has a similar physiological response to emotional pain (social rejection) than it does to physical pain. So while different receptors may be used to initiate that reaction (since there may not necessarily be a physical stimuli that causes emotional pain), it... | [
"There is an overlap between the two. When you put people under an MRI scan, some of the same regions light up. These regions are the ones that \"feel\" that you are in pain, not the sensory areas themselves. ",
"In one study, they compared participants who had just been dumped and where looking at pictures of th... | [
"Does empathy also play a role here? I am not somebody who vivedly experiences other people's emotions, but I know people that do.",
"They will sit there and weep with someone, even if they don't really know why. ",
"The way I understand it, we have a \"pain center\" in our brains that deals with all the signal... |
[
"Why are traits such as acute vision/hearing/smell not propagated through evolution."
] | [
false
] | [deleted] | [
"Well to begin with, your opening premise isn't correct. We do not have dull senses. For instance, cats have a visual acuity of about 0.1 degrees [1] while humans have about 0.02, i.e. we can resolve things 5 times better than cats [2]. Now, yes, there are some animals that have higher visual acuity, and some that ... | [
"Humans also have a history of hunting in \"packs\". This would reduce the need for ears that can pinpoint the exact location of a noise, or need to pickup on things as finely as a lone predator."
] | [
"Humans have a better ability to localize the source of sounds than dogs do actually."
] |
[
"why is my body still able to feel the motion of waves after having left the beach?"
] | [
false
] | this mostly occurs right before i am about to fall asleep. | [
"Our brains are very good at compensating when external stimulus throws us off. There are great experiments, for example, showing how our brains will gradually adjust to wearing special goggles with mirrors that flip everything the wrong way. Over time, the brain adjusts.",
"The brain also adjusts to coping with ... | [
"Is this how it works wearing a hat and then taking it off, but still feeling the hat hours after its come off?"
] | [
"Or when a cast comes off, in a more extreme example. Yes, likely the same compensatory/adaptation system."
] |
[
"If extinct species are brought back by implanting recovered DNA in the zygote of similar existing species would we expect epigenetics to make significant changes to the development of the baby?"
] | [
false
] | I'm not sure I really understand what the process of making an extinct species baby would be but if we could do it could we ever make a real mammoth or a real neanderthal or would they be effected by the surrogate mother. Also, (these are more ethics/implications of science question - not sure how appropriate it is for... | [
"The short answer is yes, we would expect changes, but the extent to which these changes would ultimately affect the phenotype of a successfully cloned extinct animal are difficult to predict. ",
"This type of project",
" has indeed been attempted with the ",
"Pyrenean Ibex",
" in 2009 and the efforts are ... | [
"Look I'm really not trying to step on your toes but I have a few problems with your contribution. If you look to the bullet points under the goal of what this subreddit is for you'll see what I'm referring to: ",
"we undoubtedly would treat them as lesser-slave-beings.\n\"Well they are not as smart as we are, t... | [
"You are absolutely correct, I got caught up in the moment and wanted to share. I will now try and correct my lack of scholarship (see below). For better reference, my speculation and opinions are based on my training in molecular and cell biology. ",
"\n A number of blogs and news sources report that a man... |
[
"How did different civilisations develop sounds/letters that others cannot pronounce?"
] | [
false
] | What I mean is for example,in japanese, there is no letter "L", just a thick R, in dutch & french there is the "gh" pronunciation, in arabic & certain other languages there are many letters not present in other languages, what I mean by this is why do people from other civilisations not have the ability to pronounce ce... | [
"Well, you don't pronounce letters, you pronounce phonemes. Letters give some hints as to what the phonemes are, but there's not a 1:1 relationship, and with English and many other languages there really aren't even any hard to fast rules - the the a and hat is the phoneme æ, while the a in all is the phoneme o:. A... | [
"You are assuming people had access to the entire range of sounds when they first made up words, when it's likely they simply stuck with whatever sound they uttered first. Think of it as a random seed that then dictates in what directions the language evolves in."
] | [
"if you adopt a japanese kid and teach it only english, he will pronunce everything OK.",
"But he would also effectively be part of the civilization of the parent from whatever English speaking country that adopted him. "
] |
[
"What is physically happening when someone gets sick and can't smell/\"taste\" anything?"
] | [
false
] | I understand that what we perceive or accept to be "taste" is actually our sense of smell and that the sensation of taste (bitter, salty, sweet, sour, savory) is mostly unaffected by illness. So what is physically happening and why can't one smell "taste" anything? | [
"Well to address your first question, you can be suffering from congestion during a sinus infection but be able to breathe through your nose. Sometimes the infection can produce dense congestion in the deep sinuses without a lot of mucous coming out of the nose. However, when you chew food the aroma's and chemica... | [
"You're right that a significant portion of taste is smell. When your nose is congested, and you breath through your mouth, scents don't reach your olfactory (sense of smell), so flavors are diminished. You can reproduce this simply by holding your nose. It's hard to tell the difference between a very small piec... | [
"When your nose is congested",
"Why then when someone ",
" no congestion (their nose isn't stuffy/blocked up and they can breathe freely) would the sense of smell still be diminished or non existent?",
"Is there a mucous coating covering something specific to smell that doesn't come off easily and/or takes t... |
[
"How did early cyanobacteria develop the means for photosynthesis?"
] | [
false
] | As a preface I am somewhat of an armchair scientist so please feel free to correct me anywhere I am mistaken. Please forgive any formatting problems as well, I'm on mobile at the moment. I understand that these algae were likely the first prolific organisms on Earth, and their presence provided our atmosphere with oxyg... | [
"How did the mechanisms of the light and dark reactions evolve? For example, the water-splitting happens through the manganese oxocluster; did this originate from inorganic sources? Similarly with the huge variety of photopigments that absorb the light. Also, how did the key dark reaction enzyme rubisco develop? So... | [
"How did the mechanisms of the light and dark reactions evolve? For example, the water-splitting happens through the manganese oxocluster; did this originate from inorganic sources? Similarly with the huge variety of photopigments that absorb the light. Also, how did the key dark reaction enzyme rubisco develop? So... | [
"Sorry, that's a little too specific and out of my field to answer right away, but it's an interesting topic. I've always stayed out of plant biology (and other photosynthesizers).",
"Here's a review that does a good quick summary of the various parts of photosynthesis and what we know from 2010. ",
"http://www... |
[
"I’ve heard that humans can see more shades of green than any other colour, is this true? If so, would it be advantageous to outfit street lights with green hued bulbs for safety purposes?"
] | [
false
] | null | [
"It's true we are able to discern more shades of green than any other color, this isn't really helpful for streetlights. The purpose of those is to illuminate an area, not project an image with subtle shading gradations. So, the only real priority is that the light is bright enough for the intended purpose. Color f... | [
"The yellow streetlights also have gaps in their color production, leading to things like green cars appearing black, since the light doesn’t produce green."
] | [
"The yellow fo street lights has two benefits. First sodium tubes are cheaper and have better service lives than many alternatives and secondly, yellow light is marginally better at penetrating foggy conditions, so safer for drivers."
] |
[
"How do we know that a Hydrogen atom only has one proton and one neutron?"
] | [
false
] | Extrapolate this to all the elements. What experiments were preformed so that we know how many protons and neutrons each element has? Thanks! | [
"Hydrogen only has one proton. An atom with one proton and one neutron is a ",
"deuterium",
" atom.",
"Watch the BBC's ",
"documentary",
" (watch all the episodes!) on the periodic table. It explains much of how we learned about ",
"stoichiometry",
". Many early studies were based on gases, since the ... | [
"There are many ways to study the atomic mass and structure of a nucleus. One of the most direct being mass spectroscopy, whereby ionized molecules are passed through a magnetic field, which will apply a force to the molecules and bend their path by an amount dependent on their mass. In this way we can determine th... | [
"Hydrogen doesn't usually have any neutrons. It can have as many as six or seven (I forget) with various degrees of stability, but in its overwhelmingly most common form — something like 998 atoms out of a thousand — it's got none at all."
] |
[
"If I were to drop a glass marble into an infinitely deep body of water, would it eventually crack or continue to be compressed indefinitely?"
] | [
false
] | Doesn't have to be a marble but a sphere seemed like an easy shape to choose and glass seems brittle. I guess my question could be more general if I rephrased to: Can a sphere be uniformally compressed indefinitely and retain its shape (not dimensions) or would another effect come into play? | [
"Well...at some depth of your infinite water, the water would start undergoing nuclear fusion, (if you substitute \"infinite body of water\" for \"extremely large hydrogen gas cloud\", this is what leads to star formation).",
"It would not be like in a roadrunner cartoon where the marble just gets compressed into... | [
"On its way down the pool, the marble would crack, and then turn into a fine powder",
"This reads like your speculation. The atoms are being pushed ",
" by hydrostatic pressure. What is the driving force for a crack to open, or powder to form?"
] | [
"Wouldn't the marble just float somewhere in the water column where water gets to the same density as the marble?"
] |
[
"Why is exercise good for your heart, but stress is bad?"
] | [
false
] | null | [
"Stress has a lot to do with cardiac health.",
"According to this Kaiser ",
"Permanante page on effects of stress",
": \"Stress is linked to high blood pressure, abnormal heartbeat (arrhythmia), blood clots, and hardening of the arteries (atherosclerosis). It's also linked to coronary artery disease, heart at... | [
"It does ",
"not boost the immune system",
". Cortisol is the primary stress hormone and in stress (e.g. fight or flight) it suppresses non-essential body functions temporarily like the immune system so all your energy can go into fighting or running away. ",
"Here is ",
"another source from Utah Universi... | [
"No universal conclusions can be drawn about boost/suppress \"the immune system.\" There are many subsystems in the immune system that respond differently to cortisol, and there is not perfectly consistently directionality to response to stress, either short or long term. Both skyskimmer and TalvRW are reasonably c... |
[
"How is the plane of polarised light rotated by a particular 'handedness' of optical isomer?"
] | [
false
] | I know the basics of optical isomerism and that if both the left and right isomers are in a 50:50 ratio, the racemic mixture will have no net effect on the plane of light passing through it. What I cannot fathom is exactly how light interacts with a particular isomer to be rotated at all. Is the light absorbed and remi... | [
"Optical activity is a type of ",
"birefringence",
". Optically active isomers act differently on the left handed and right handed (circular) components of the light's polarization vector, resulting in a net rotation.",
"More thoroughly, the trick is to express (linear) polarization as the sum of two circular... | [
"Well, for ",
"bi-isotropic materials",
", specifically Pasteur media (chiral and reciprocal), linear polarization can't exist within the media. You can actually show this using Maxwell's equations and the constitutive relations for bi-isotropic materials.",
"So, an incident linearly-polarized wave gets split... | [
"SR is not a \"fudge factor\", it is the difference of the two RIs [SR=RI(LH)-SR(RH)]. ",
"Also, my understanding is that the two enantiomers do NOT have different refractive indices for plane polarized light, only for circularly polarized light.",
"See ",
"andand89's reply",
"."
] |
[
"What evidence (if any) would there be if a massive asteroid struck earth in the middle of the Pacific Ocean?"
] | [
false
] | Okay so this thought only came to me after reading an article about Scientists/Geologists now thinking there may have been a large comet impact some 13,000 years ago, but they do not have a crater to prove it. If a huge asteroid struck way back when, say in a part of the Pacific farthest from all land (the middle in si... | [
"How big an object are you talking about?",
"a Big object would leave behind gravitational and magnetic variation which we can measure. ",
"A lot like they have done with the Chicxulub crater"
] | [
"Well - you'd get an thin event layer with minerals which are typical of impact environment: Coesite, Stishovite, micro-diamonds, perhaps even buckyballs. This horizon be best preserved in surrounding pelagic muds as well as ponds and lakes in continental environments."
] | [
"Hard for me to say since I don't know much about the subject. Something that would be 'catastrophic' if it hit land...something that would wipe out a continent. A few km in diameter? Maybe something like this would make it through 5-6 miles of water to the ocean floor?"
] |
[
"Why does a discharged battery bounce higher than a fully charged battery?"
] | [
false
] | As seen in this video , why does this happen? | [
"The battery starts out as a caustic liquid and a ",
"manganese dioxide powder",
", metal bits and a membrane. As the corrosion reaction between those two proceeds, the powder changes to manganese oxide which could result in expansion, but also the powder granules becoming chemically and mechanically connected.... | [
"My bad, I didn't even watch the video, I assumed it was the one that made the front page. And that's apparently because I'm an ass. I made my own video though and found yes there is a difference but can one tell a 1.2 from a 1.5 reliably between 2 batteries of the same brand, no not really unless you drop from a f... | [
" cut open a battery. If it is not charged, you will spray dangerous chemicals everywhere. If it is charged, you will spray dangerous chemicals everywhere, which carry a strong charge. This will probably result in electrical fire, pain and other bad things."
] |
[
"I've heard that yeast grows better in an acidic environment. Why is that?"
] | [
false
] | [deleted] | [
"I work in a place with industrial fermenters (but I work indirectly with the fermenters). However, from the literature I have, yeast that are fermenting produce acid on their own and will drop the pH of the solution. ",
"My information also mentions that yeast tolerate a lower pH better than bacteria. Bacteri... | [
"This has been confirmed via people who do work with the fermenters every day. I also gleaned some other insightful information. Typically, you'll need some enzymes to break the long chain sugars down into the monosaccarides necessary for yeast to use. These enzymes work best at a particular pH range so the pH o... | [
"My theory with high school biology knowledge:",
"Some fermenting bacteria produce ethyl alcohol right? Since they normally increase the pH of the solution, dropping the pH might increase the rate of their reactions and growth. "
] |
[
"Do dogs actually enjoy playing fetch? Or do they think that is what they are supposed to do because they get appraisal when they return the ball?"
] | [
false
] | null | [
"There has actually been quite a bit of research having to do with two points explored in this thread. ",
"Do dogs experience joy? Do they have emotions? I don't know, but this ",
"blog",
" by Patricia McConnell, one of the leading Ph.D.'s in animal behavior frequently discusses this and does a great job of... | [
"There has actually been quite a bit of research having to do with two points explored in this thread. ",
"Do dogs experience joy? Do they have emotions? I don't know, but this ",
"blog",
" by Patricia McConnell, one of the leading Ph.D.'s in animal behavior frequently discusses this and does a great job of... | [
"Praise, not appraisal. Appraisal means evaluation, not praise."
] |
[
"How can a VTOL capable aircraft, like the V-22 Osprey, remain stabilized when added cargo throws off the balance of the aircraft?"
] | [
false
] | [deleted] | [
"There are calculations made by the Loadmaster (actual title of the person responsible) before each flight to making sure aircraft maintains a stable CoG with the addition of cargo and extra people. The loadmaster also packs the cargo in such a way so that it can be unloaded effectively, for example on military air... | [
"Your question made me think of this:",
"http://www.youtube.com/watch?v=eWeXgvot2TI",
"As cadialg said a Loadmaster would ensure the weights are positioned correctly. Unfortunately, while passengers or crew members do not effect CoG that much a tank or heavy weight coming loose can be catastrophic."
] | [
"I don't know about the V22 in particular, but when it comes to cargo, calculations are usually done before the flight so the cargo is positionned in a way where it will not change the position of the CoG too much.",
"As for crew members affecting the CoG, one guy moving from one end of the heli to the other woul... |
[
"How does the chemical structure of Taq Polymerase give it such a high resistance to heat?"
] | [
false
] | [deleted] | [
"In order to understand why Taq Polymerase can tolerate high temperatures, it may help to understand where the enzyme comes from in the first place. ",
"In deep water hydrothermal vents, you will find certain bacteria, T. aquaticus, that will thrive in temperatures and conditions that most organisms couldn't. Tem... | [
"First, I appreciate you responding. I understand the background of Taq and the environmental conditions T. aquaticus lives in, but what I really want to understand, which you seemed to give me a good head start, is the ability of Taq to not denature at such high temps. and the chemistry behind why. My final goal i... | [
"I always thought, taq polymerase would contain an increased amount of disulfide bridges. This seemed logical, because H-bridge bonds in proteins are about 25 - 40 kJ/mol strong and the S-S is about 270 kJ/mol strong. But quickly googling it I found a supplier offering a taq that is supposed to contain no S-S bonds... |
[
"Is the sun capable of causing an EMP on earth substantial enough to do significant damage to the electrical grid?"
] | [
false
] | I've seen articles that argue how society would break down if the electrical grid were to be shut down but these articles often conflate the effects of a weaponized EMP designed to do just that with what common sense tells me are the far less significant effects of a solar flare compressing the magnetic field of earth.... | [
"Yes. This actually occurred once before. This was prior to the wide spread use of electricity in homes but after the widespread use of the telegraph. The EMP pulse was so strong that operators were able to send messages without being connected to batteries using the electricity generated in the wires by the pulse.... | [
"I don't like to call it an EMP but it can still cause currents in any conductor. We call them ",
"geomagnetically induced currents (GIC)",
" and they can be destructive to the power grid. The most exciting demonstration of this was in 1859 where the most massive ever recorded flare, referred to as ",
"the Ca... | [
"https://en.wikipedia.org/wiki/March_1989_geomagnetic_storm",
"This happened in the era of electricity too, not just the Carrington flare."
] |
[
"Once light is produced does it ever stop?"
] | [
false
] | I just had a conversation with my Grandfather concerning the light that comes from distant suns and how we can still see that light even if the star is no longer there. So now we're curious if light ever stops moving forward once it's been produced. | [
"It won't stop unless it hits something. The light emitted by a distant star will continue to travel through space until it is absorbed by some particle of matter. This can be an interstellar gas cloud, a planet or another star. These will obviously only block part of the light. In addition, light can be pulled int... | [
"Photons are absorbed by matter and push electrons to higher energy levels. If/When the electron falls back to a lower energy level, it emits a photon. The wavelength and/or energy level of the photon (depending on how you want to look at it) determines how high an energy level the electron reaches and vice versa."... | [
"I have a slightly off topic question. I hope you may shed some light on it (pun). So as far as I know space itself is expanding. Was there light created at the advent of the Big Bang that did not hit anything and was able to keep going? If so could light outrun the expansion of the universe? Seeing as both the cre... |
[
"Is it possible for a line/function to have a complex (imaginary) slope?"
] | [
false
] | null | [
"Functions from C to C can have imaginary slope: just take f(x) = ix. This is a perfectly valid function sending complex numbers to complex numbers.",
"Things get complicated because you can move in more than one direction in C, but the same sort of idea applies to such functions, the slope is the \"rise over run... | [
"Something fun to think about:",
"We know from algebra that a line is perpendicular to a given line y = m*x if its slope is -1/m. Can a line be perpendicular to itself? It sounds absurd but we can approach the question with arithmetic. We'd need m to satisfy",
"m = -1/m",
"m",
" = -1",
"m = i, -i",
"Wha... | [
"Sure, why not? I can define a function y = (a + b",
"x. Plotting it is a little tricky. If you restrict x to be a real number, then one possible way to plot this function would be as a 3-D plot: one axis is the X-axis, one axis is the real Y-axis, and one axis is the imaginary Y-axis. You would still see it as a... |
[
"Since you can train cats and dogs to respond to their name, could you train any mammal to respond to it's name?"
] | [
false
] | [deleted] | [
"Basically all animal organisms have the ability to learn. If you activate a signal and then torture (or awesomely love) an animal, they will learn that the signal will soon result in torture (or awesome love). If you define the signal as their name, they will respond to it."
] | [
"Do you have a citation for this? Isn't a sponge an animal?"
] | [
"From the best of my knowledge a sea sponge is indeed an animal. I'm not explicitly knowledgeably about the nervous system of sea sponges (nor taxation studies) and it may well be possibly they are not intelligent enough to have intelligence be an evolution pressure in their evolution.",
"Most animals are higher... |
[
"If you get a transplant (heart, liver, etc) can you feel pain from that area. If so, why?"
] | [
false
] | Title says it all. If you get a transplant of any kind, can you feel pain in that transplanted organ. If so, how does this happen? Do the nerves or whatever reconnect? How does the brain fix those connections? Thanks in advance. | [
"No, you cannot feel pain in the transplanted organ*.",
"This ends up being very important for certain things like kidney transplants. Normally, if your ureter (the tube connecting kidney to bladder) gets stopped up, it is incredibly painful. This is the pain experienced during a kidney stone. After a transpla... | [
"No and yes. ",
"No because you generally do not reconnect the nerves, mostly because the function of the organ is generally independent of innervation, because you don't have to transplant the new organ to the same place the old one was, because results are poor with no proven advantage and increased morbidity ... | [
"So doctors can reconnect/repair nerves, just not spinal nerves, is that correct?"
] |
[
"What is the difference between the way a white material reflects light and a mirror reflects light?"
] | [
false
] | If I understand correctly, we perceive white materials as white because they reflect most/all of the visual spectrum. It seems like mirror surfaces also reflect most/all light, yet my mirror isn't white. What is the difference between the way in which these materials reflect light? | [
"Mirrors produce ",
" -- light comes in at some angle and goes back out at an equal angle wherever it hits.",
"A generic white object, however, produces ",
" -- light come in at one angle but is reflected at a broad range of angles.",
"You can read more in this ",
"discussion",
"."
] | [
"A white body is one with a rough surface that reflects all incident rays completely and uniformly in all directions. Light is scattered in all directions. ",
"In a mirror (and other transparent media), the light is not scattered. The incident rays of light are reflected or refracted ",
", so you get most of th... | [
"We see colors based on how light interacts with matter - for example, a green object lit by white light absorbs everything except for green light, so we see what isn't absorbed. The object has modified the spectrum of light from the source that now hits your eye.",
"Furthermore we think of color as a property an... |
[
"Is it possible for a particle to be made of only neutrons?"
] | [
false
] | I've recently learned the functions and such of an atom, and was wondering if it would be possible for a particle to be made of only neutrons, and what would be the implications of such a particle? | [
"There are multi-neutron resonances, but no bound states. For example, the dineutron and the tetraneutron. Because they’re unbound, they decay on timescales of 10",
" seconds."
] | [
"That is the half life (order of magnitude). Only 0.1% survive 10 times the half life, only 0.0001% survive 20 times the half life and so on, so they are totally gone very fast."
] | [
"Thats the half-life, or the mean lifetime. It’s an order of magnitude estimate, and both of those quantities are of the same order of magnitude."
] |
[
"How exactly do we feel pain from hot things?"
] | [
false
] | [deleted] | [
"Nah - Some nociceptors are definitely myelinated... First, we gots Aδ fiber axons. They are very myelinated and as a result the signal is sent really fast... they can allow an action potential to travel at a rate of about 20 meters/second towards the CNS. We also have slow C fiber axons. These only conduct at spee... | [
"We have nocioreceptors (pain) in our skin. They are unmeylinated free nerve endings. When they sense a change in temperature they depolarize causing a action potential. This goes up our lateral spinothalamic tract, then up to the VPL nucleus of the thalamus. From there we are aware that we are in pain but not exac... | [
"yhea iIjust left out the A delta receptors I was talking about c fibers specifically just for basics."
] |
[
"Do all vector quantities obey superposition?"
] | [
false
] | In my recent physics courses, we've studied electrical and magnetic fields. Both of these quantities obey superposition (fields created by independent sources can be summed using vector addition). Are there any similar quantities that DON'T follow this simple pattern? | [
"As a nice example of a nonlinear (pseudo)vector quantity in classical EM, you may have learned about the Poynting vector in your courses, it is related to the momentum carried by an electromagnetic field configuration, and is proportional to S = E x B. (vector cross product). ",
"Imagine we have some field confi... | [
"Everything nonlinear. That includes electric and magnetic fields if they are strong enough (the linear addition is only a really good approximation), gravity if strong enough (black holes), air resistance, ..."
] | [
"The question that you are asking is confusing two different ideas. Superposition is a property of a system. In contrast a vector is an element of a set (a vector space). Vector fields (like B and E) assign a vector to every point in space.",
"We often mathematically represent physical quantities as a vector fiel... |
[
"The space suit used on the moon, could they also be used on mars?"
] | [
false
] | null | [
"No. They were designed for the moon's gravity, about 1/6 earths. Mars gravity is twice the moons so the space suits would weigh twice as much, and therefore render the astronaut virtually immobile. Actually a light-enough space-suit for Mars exploration remains a significant problem.",
"Edit: the apollo space su... | [
"LAYMAN: The moon suits had liquid cooling because it's so hot on the moon. It's very cold on Mars, so that part of the suit would not be appropriate. ",
"Here",
"'s a prototype NASA's looking at."
] | [
"Those were designed over 40 years ago. I strongly suspect they'd provide a newer version."
] |
[
"Why did we evolve the inability to eat raw meat safely?"
] | [
false
] | Assuming that we evolve beneficial traits over time and that our ancestors were likely able to eat raw meat. Why would we evolve to not be able to eat raw meat? Surely that's disadvantageous? | [
"We are able to eat raw meat, provided it is fresh (or properly fermented/preserved) we just generally choose not to for three main reasons:",
"First, cooked meat tastes better. Incidentally, ",
"this doesn't seem to be limited to humans",
". Because this preference isn't limited to humans, we know it's not... | [
"I would add, in most countries irradiation can be used to sterilize meat: killing any bacteria or parasites present and rendering it completely safe to eat raw or undercooked. However, due to people's fears and misunderstandings about the process, it is treated as a food additive, and has to be labeled \"treated w... | [
"Second, cooking meat removes parasites....Essentially all wild animals carry parasites, often in significant numbers.",
"This is what I came here to say, and really want to emphasise. Wild animals are (relatively speaking) ",
"riddled with parasites",
"."
] |
[
"How will cooling as a result of the AMOC current stopping interact with general global warming?"
] | [
false
] | says that if this ocean current stops, it could make parts of the northern hemisphere colder. Would that mean just colder winters, or year-round? Would there still be more heat waves in summer? Would it make equatorial regions even hotter? | [
"Some housekeeping first, when commenting in AskScience, please ",
"remember our guidelines",
" for answering questions, specifically that answers should be based on peer reviewed sources when possible (and there are abundant sources in this case, so it's not a big ask) and should be free of speculation.",
"N... | [
"Neither of these are likely outcomes (or maybe even possible outcomes) based on the sources above. Coming at this from the perspective of the Jackson et al, results, as for an \"ice age in Europe\", weakening/destabilization of the AMOC certainly leads to cooling of Europe but not necessarily to the point where yo... | [
"What is the likelihood of catastrophic outcomes like ice age in Europe or desertification in the American northeast coast?"
] |
[
"Whats the main difference between a sociopath, psychopath and a narcissist?"
] | [
false
] | null | [
"Poor judgment and failure to learn by experience ",
"Failure to follow any life plan.",
"Can you expand on these two? As I understand it all of the APD types are essentially caused by a lack of empathy and a lack of fear/anxiety (and likely a blunting of emotions in general). These two traits you listed stand... | [
"Hmm... that's a good point, a reduced negative feedback enforcement. Psychopaths are very logical though so you would think they would say, \"hey, this clearly doesn't work, let me try something else.\" Plus it kind of goes contrary to the perception that many psychopaths are ",
" successful, arguably more so th... | [
"There is a lot of overlap between them. The main point of a narcissist is someone who thinks they are wonderful, and they cannot comprehend or tolerate the idea that they are not wonderful. Narcissists can be very entertaining (think Jenna from 30 Rock) and very gracious so long as you do not run counter to thei... |
[
"Why does the Spin commute with the position but not with the momentum?"
] | [
false
] | null | [
"Yes, the spin Hilbert space is separate from the coordinate-space. These operators don’t care about each other because they act in different spaces. If you have some state describing a position and a spin, this state lives in a tensor product space. And when you say you have a “spin operator”, what you actually ha... | [
"Spin operators commute with both position and momentum operators."
] | [
"Oh, why the spin commute and the orbital angular momentum not?\nIt is because the spin lives in a space of finite dimension and the others in one of infinite dimension?"
] |
[
"What happens whith the excess of kinetic energy that isn't being acumulated when a rocket is flying at light speed and keeps thrusting in perfect vacum?"
] | [
false
] | I'm sorry, another light speed question. What happens with that energy? Does it just disappear? | [
"Well, a rocket can't fly at light speed so the question doesn't really make sense. "
] | [
"If a rocket is flying just under light speed but continually being accelerated (so its kinetic energy must increase), the kinetic energy will increase without bound without the rocket ever reaching the speed of light. The full equation for kinetic energy is KE = mc",
"/sqrt(1-(v/c)",
") - mc",
", which reduc... | [
"Those are not the same thing at all..."
] |
[
"Does the Planck charge have any relation to the natural world?"
] | [
false
] | I'm reading about Planck units, and the Wikipedia for the Planck Charge states that its value is about 11.706 times greater than the elementary charge, . Why is there this mismatch? Is there no connection at all between and the Planck charge? I thought Planck units were fundamental units, derived from the nature of the... | [
"Though all charge seems to be quantized in units of 1/3 e.",
"Actually, you can still say that charge is quantized in units of e, regardless of the 1/3. This is because charge only ",
" in unit increments of e. So for example, an up quark (+2/3) changing into a down quark (-1/3) exhbiits a change of 1e, and ... | [
"I thought Planck units were fundamental units",
"They're not, there's not anything special about planck units.",
"So, does this mean that e isn't elementary after all? Yet, every time we observe electric charge, it's always in integer multiples of e.",
"Quarks have non-integer charge, an up quark has, +2/3 e... | [
"No, not really. It's just the natural unit formed with the choice of constants used in the Planck system, where Coulomb's constant is 1, so the force between two charges is just e",
" /r",
" . The ratio of the fundamental and Planck charge is the square root of the fine structure constant. There are other sets... |
[
"Why is the polio vaccine still needed in the US?"
] | [
false
] | null | [
"I’m guessing that near eradication in the US population, which has large numbers of people visiting from other countries, is not considered to be enough to keep such a horrible disease at bay. Im young enough to have gotten immunized, and I would hope that everyone else in the world will be too one day, but we are... | [
"Hepatitis A is also transmitted via a fecal-to-oral route and the US has several outbreaks right now. Advances in water cleanliness in the US are great, but not foolproof. Ask Flint, Michigan. Ask anyone who uses well water. Contamination of food and water can and does happen every day, even in the first world. Th... | [
"It's a virus. It doesn't wave a little white flag just because you chased it outside your national borders with vaccines. Evolution doesn't just quit.",
"It improves and it waits because that's all evolution really knows how to do. The ascension of the antivaxx movement in the U.S. may create a situation where o... |
[
"Why is it that animals such as birds are \"scared\" of humans, while smaller insects like flies are not?"
] | [
false
] | [deleted] | [
"Birds have a lot more \"brainpower\", which is metabolically expensive but gives them greater behavioral flexibility than insects. In general, birds are more capable of learning about humans (or even recognizing them as distinct entities), while insects rely on high reproductive rates and a series of inflexible b... | [
"Not only brain power. It's mainly the quality of sight. Insect eyes do not enable recognizing a human as such. Even dragonflies (with their relatively enormous eyes) have very poor eye sight compared with birds.",
"http://cronodon.com/BioTech/Insect_Vision.html"
] | [
"Please remember that AskScience is not for guesses or speculation, no matter how logical it may seem. Thanks!"
] |
[
"Did Neanderthals make the cave paintings ?"
] | [
false
] | In 2018, Dirk Hoffmann et al. published a Uranium-Thorium dating of cave art in three caves in Spain, claiming the paintings are 65k years old. This predates modern humans that arrived in europe somewhere at 40k years ago, making this the first solid evidence of Neanderthal symbolism. . Widely covered, This of course ... | [
"Well, neanderthals existed concurrently with humans and were just as smart as us. They eventually interbred with humans and faded/melded into homo sapiens. (As homo sapiens are breeding machines, Homo Neanderthalis couldn't keep up.) I would say its entirely possible that the paintings could have been drawn by the... | [
"Furthermore, assumptions like this sometimes form the basis for entire scientific careers.",
"Reminds me of what happened with dating when humans moved to North America. You basically had to have an entire old guard die before evidence would be accepted that humans in NA predated Clovis. You had evidence of pre-... | [
"Furthermore, assumptions like this sometimes form the basis for entire scientific careers.",
"Reminds me of what happened with dating when humans moved to North America. You basically had to have an entire old guard die before evidence would be accepted that humans in NA predated Clovis. You had evidence of pre-... |
[
"What do bees see?"
] | [
false
] | A few days ago I learned that bees don't have the ability to see the color red, just like us humans can't see UV. What do they see when something is red? | [
"It's tough to really say what bees \"see\". We can, however, point out what they ",
" see. It's important to note that not all bees are red-colorblind, and even then, most can discriminate shades of yellow and orange. As for the red flowers that don't have shades of yellow or orange to help bees out, it looks... | [
"Whoa -- this is awesome! Thanks for sharing -- going to play with this for an hour or four."
] | [
"Whoa -- this is awesome! Thanks for sharing -- going to play with this for an hour or four."
] |
[
"When selling your blood plasma, does the payment outweigh the cost of energy and nutrients (food) to replace the lost plasma?"
] | [
false
] | null | [
"Also be sure to factor in the several hours/days afterwards during which you will feel very lethargic and likely not be able to do anything productive. Overall it is not worth doing it for the money - it is primarily a selfless act so I imagine the money is meant more as compensation than actual pay"
] | [
"In the modern world food calories are cheap. Two pounds of flour or around 1 kg is around $1.50. Let's say that prepared it costs double that, so $3 per kg. According to ",
"the label",
" 30 g is 100 calories. So, then you are paying $3 for 3000 calories. That's ridiculously cheap when you think that is proba... | [
"My ",
" is that most people eat more of most nutrients than they need, and that selling plasma would mostly mean a more-efficient use of the same diet, rather than an increase in eating. Even if the plasma requires increased eating to replace, much would depend on the ",
" of food required. (Would you want "... |
[
"Would bee hives grow larger if we didn't harvest their honey?"
] | [
false
] | null | [
"Not significantly. Not removing the honey instead triggers swarming and the foundation of new hives, or they get to a point the queen can't lay enough in a day to grow the population.",
"Honey is a hives food stores for winter. Adults need only carbohydrates to survive since they do not grow or repair and honey ... | [
"Adults need only carbohydrates to survive since they do not grow or repair and honey provides that.",
"That is fascinating in itself. To have a final rigid form that needs no protein is so ",
".",
"Meanwhile we just shed skin cells like they are going out of style."
] | [
"This is one reason why I consider bees to be more like appendages, with the hive being the “individual” in the sense we think of with most animals. "
] |
[
"A marine biologist friend of mine told me that studies have shown that animals who are in overpopulated habitats are much more likely to exhibit homosexual behavior. Is there any validity to this?"
] | [
false
] | If so could I get some elaboration on why this happens? | [
"There are the ",
" by John B Calhoun.",
"Essentially he created a perfect system where there were no predators, plentiful food and the initial rats were all healthy - the only constraint was available space. This allowed extensive breeding, particularly early on when there was a lot of spare area.",
"Then th... | [
"This purpose of the experiments was not to portend some imminent doom for humanity, in fact Calhoun was trying to be positive. He wanted to change cities, his remedy to the behavioural sink was creativity. By changing society and changing how we designed our cities we could avoid becoming mired, stagnant, and even... | [
"Fuck that's scary"
] |
[
"Does all the nuclear fuel in an atomic bomb undergo fission, or is some scattered before it can go critical?"
] | [
false
] | Is it possible that some fissile material is blown away by the force of the explosion before it can start reacting itself? On a related note, could the detonation of a nuclear weapon in close proximity to a reactor's fuel rods (unshielded for this hypothetical) cause them to explode? | [
"Most of it does not undergo fission, only a small fraction actually does.",
"It takes about 0.22 Moles of fission reactions to produce 1 kiloton of energy. So for the nuclear weapon that destroyed Nagasaki (21 kilotons) it took about 4.6 Moles of fission reactions to produce that amount of destructive power. Pu-... | [
"Since the other comments addressed your questions I would add a little bit about what determines the efficiency. The efficiency depends on a few factors, the largest being how long the super critical mass is held together. In the case of a gun type weapon, you are shooting a plug into a cylinder. In that case t... | [
"It is because the number of atoms involved in each fission generation is an exponential function.",
"Assume each generation is twice the size of the previous. The last one is half of all the energy release, the one before it is 1/4th of the total and the 3rd to last is 1/8th."
] |
[
"How did scientists find out the composition of DNA?"
] | [
false
] | I was reading journal which discusses the possibility that a bacterium could use arsenic instead of phosphorus in its DNA which turned out to be false. This led me to wonder how scientists first isolated different components of DNA and what technique they used. I was also wondering what modern techniques could be used ... | [
"You mean elemental composition? Well, ",
"Miescher",
" first isolated DNA, extracting it from infected medical bandages. It was already known in Miescher's time that it contained phosphorus, I believe from ashing experiments. At the time it was routine to decompose compounds using acid, basic, and high tempera... | [
"The question was about chemical composition, not sequence. XRF has never been used for sequencing. All the technologies you describe depend on a lot of prior knowledge of DNA, and aren't applicable to characterizing the chemistry of an unknown substance. "
] | [
"It only becomes straightforward ",
" somebody has already figured out what the protocol should be!"
] |
[
"Are there any materials that are plasma at room temperature?"
] | [
false
] | If different materials, can have different melting or boiling points, that's should apply to plasma too, right? | [
"Because it takes energy on the order of electron volts (eV) to ionize an atom and 1 eV corresponds to a \"temperature\" (actually kT) of around 10,000 K, there are no materials that are plasmas at room temperature without any external electric or magnetic fields. However, there is a whole category of plasmas calle... | [
"Yes, neon lighting is another example of a low temperature plasma. It consists of a low-density neon gas with a high voltage applied to it."
] | [
"Would that be true for neon lamps as well?"
] |
[
"Does the body become physically dependent on caffeine for energy, or does the body just build up a tolerance?"
] | [
false
] | Let's say one were to drink 5 cups of coffee per day for 6 months straight, then quit suddenly. Aside from physical withdrawals such as headaches etc, you wouldn't be any less tired than you were pre testing, right? | [
"To oversimplify greatly:",
"Caffeine is an adenosine antagonist. It takes up spaces where the neurotransmitter adenosine should bind without activating them. In other words, it \"mutes\" your body's response to that neurotransmitter. Adenosine, to simplify grossly, slows down your neurological processes, you ... | [
"Tip of my hat to you sir!"
] | [
"I understood that caffeine intake corresponds to an increase in adrenaline. Am I wrong to understand that adrenaline gives you energy?"
] |
[
"Is their a psychological or physical benefit to tennis players who \"moan\", \"groan\" or scream every time they hit the ball?"
] | [
false
] | I was visiting my grandma the other day. While watching tennis I noted how some players "moan","groan", or scream with every hit they give. It annoyed me terribly so I asked my grandma (who watches a lot of tennis) why they do it and she couldn't give me answer. She did, however, note that it only started a couple of y... | [
"Comming from a martial arts background where we scream at the end of some of our techniques, here's why we do it:",
"1) Psychological - anything that distracts or disrupts the other person's concentration is a benefit to you. It doesn't take much when two people are evenly matched. If you're outclassed, this ... | [
"Not sure if this the reason they started grunting, but seems like a good reason to do it.",
"In the current study, 33 undergraduate students watched tennis players hitting balls across the tennis court. Each shot was either quiet or contained a brief \"unnh\" noise that occurred as the player struck the ball.",
... | [
"There is a physical advantage to it. The power of a tennis shot is largely generated in the hips, torso and shoulders, to get the most power you have to generate rotation in all 3 sections which requires clenching the abdomen. You can do it gently which is fine, but when you put in maximum force you are going to c... |
[
"If a cop had to fine someone for playing music too loud, wouldn't the sound meter's distance from the source be critical?"
] | [
false
] | null | [
"Sound intensity drops with the square of the distance to the source. So yes, in that sense, where the meter is located does matter.",
"However, the specific wording of the legislation determines the procedure for determining if a source is \"too loud.\" For instance, (anecdotally) I got a noise violation ticke... | [
"SPL (Sound Pressure Level)=20∙log(P/Pref), where P is the pressure due to the sound source and Pref is a reference pressure, typically 20 microPascals, the (approximate) lower threshold of human hearing at 1000 Hz. You would use a SPL meter to measure the sound, you can even use a smartphone nowadays. A differen... | [
"This seems like it's a legal issue more than a science issue. In order for the cops to come because of a noise complaint, someone has to call them and complain. In that case, the cops would probably determine the noise level at the complainer's distance from the sound source. Sure, the sound gets louder as you ... |
[
"Is water cycle present in Antarctica?"
] | [
false
] | I was wondering, as Antarctica does not often experience temperatures above zero degrees Celsius, if snow just accumulates or if there is a water cycle present on the continent | [
"Sure there is a water cycle, it's just a bit different than the other continents. Snowfall is driven by winds carrying moisture in from the oceans. Water molecules can return from the ice to the atmosphere via sublimation, which is like evaporation but is a phase change directly from the solid (ice) to gas (wate... | [
"Yes, the glaciers ",
"flow downhill into the ocean.",
" Although they move rather slowly, typically 1 meter per day, glaciers can be quite thick so there is a significant transport of frozen water toward the coast."
] | [
"I can understand how sublimation works, but I have another question about glaciers: Does the snow shifts from inland to the coast then? "
] |
[
"How different would the Earth be today if the Permian-Triassic extinction event did not occur?"
] | [
false
] | I know this is an oddly specific question, and I couldn't find anything using the search bar. I'm just curious how this would have effected Earth and biodiversity as a whole. | [
"It is impossible to answer precisely what current biodiversity and faunal composition would look like in that hypothetical never-never land of \"what ifs\".",
"The most we can say is that natural selection would have continued to operate, but with a greater number of lineages to choose fromthan those who were cu... | [
"I think another important thing to note is that the Permo-Triassic extinction paved the way for archosaurs replacing synapsids as the dominant clade of lifeforms - so no P-Tr may mean no dinosaurs, and most likely not humans as we know them today, since many adaptations seen in humans and other modern mammals aros... | [
"And humans would never have evolved, right?"
] |
[
"Sophomore in Electrical Engineering.. looking for projects?"
] | [
false
] | Hello all. As I said in the title, I am in college for Electrical Engineering. I'm doing good in all my classes and such, but I'm looking for something extra to do in my time (other than video games); I'd like to possibly build some circuits or do something to further my learning. However, I'm at a dead spot, and can't... | [
"Maybe consider doing research? I know it's different in biology than engineering since you don't need to do research in engineering to get a job, but I can honestly say that research was the most rewarding part of my college career. Your professors will all have their own research projects; look around to see what... | [
"Look at your department's course catalog and find an upper-level course/elective or two that sound really interesting to you. Find out who teaches those courses. Chances are that their research is related to the elective that they teach, but look into it on the professors' web pages. Send them a quick email int... | [
"Thank you- I'll look around and ask my professors if they're doing any or know of any cool projects."
] |
[
"Can maglev trains go uphill?"
] | [
false
] | Conventional trains are incapable of going up very steep hills because of the low friction between its wheels and the track. So how would a maglev train with zero friction and only gravity and drag to worry about perform going up an incline? Would the linear motor be able to drive the train up a steep hill? And how ste... | [
"sure. The magnets both levitate and propel the train. It's just a matter of having enough power to overcome the incline. In this regard the maglev train would perform better than a traditional train because a maglev train does not rely on wheels and friction."
] | [
"To add to that - magnetic levitation happily works vertically as well, ",
"here",
" is an article about magnetic elevators and ",
"here",
" is their (a bit flashier) advertisement video.",
"I have no real engineering insight into how energy efficient they would really be on a large scale, the article see... | [
"See item #15 on this page:",
"http://northeastmaglev.com/frequently-asked-questions-about-scmaglev",
"The SCMAGLEV is capable of climbing a 4 percent gradient while maintaining its maximum operational speed of 311 mph (500 km/h). The system is capable of climbing steeper inclines, but with constant electromagn... |
[
"How do we know what the earth's mantle, core, etc. are made of?"
] | [
false
] | null | [
"/u/DMos150",
" is talking about seismic tomography. Otherwise that's a good summary. I'll just add a bit more detail. There are also other seismic techniques that are used, such as receiver functions, that get at some other details, but the end goal is the same - it tells you something about earths structure.",
... | [
"The study of the Earth's interior is done using a technique with the delightful name \"Seismic tomography.\"",
"When an earthquake occurs, the shock waves don't just ripple across the surface, but travel into and through the Earth. We can only detect waves on the surface, but by studying the different speeds and... | [
"I think most methods have been explained, but not all(on mobile, might have missed something, sorry for that)\nBasically, there are direct methods, such as the drillings in Kola Peninsule (Russia) that went 12023 m deep (continent) and the drillings in Costa Rica , 2km deep in the ocean\nOfc 12 km isn't anything c... |
[
"How does rocket fuel not freeze in space?"
] | [
false
] | Just curious, I was watching the film "The Day After Tomorrow" and the helicopter's fuel instantly froze causing it to crash. How does this not happen to rockets in space where the temperature is near absolute zero? Are the ships just incredibly well insulated? | [
"In space most things are in a vacuum, which is a very good insulator. Think about vacuum flasks for an example. And close to the Earth there are few places close to absolute zero. For example the lunar surface which was explored during the Apollo program was generally very warm, because it was exposed to the sun. ... | [
"good insulation ",
" solid fuel is already frozen. LOX freezes at 54K, which makes it likely to be used up before it becomes solid. ",
"Most ships burn up their fuel before they just start cruising, which is where they would be before they froze."
] | [
"Water freezes slower than vodka, since water has a higher specific heat capacity, but vodka freezes at lower temperatures than water, because it has a lover melting point.",
"Be careful to use the specific meaning of words correctly in here, as people are sensitive to inaccuracies.",
"Also, some simple explosi... |
[
"mainly an astronomy/optics question: Could we built a Telescope using the Sun as the objective? Is there any other large natural object in our solar system that would help us focus light from thousands of light-years away? Is collective astronomy observation even feasible?"
] | [
false
] | The idea is to place an array of photon sensors around the earth and combine the output of these sensor devices to build one unique picture of an object thousands of light-years behind the Sun. Let alone the technological/commercial barriers, is this physically even possible? | [
"I'm unclear what exactly you are trying to do. Are you trying to take a picture of something behind the sun?",
"Since our planet orbits the sun, at some point in our orbit we are on the other side and can certainly train our own telescopes at the object.",
"Thousands of light years is very close (where I work... | [
"Are you talking about using the gravitational lensing of the sun to focus light? If so, then I should point out that gravitational lensing from massive objects doesn't have the same useful properties as a telescope lens. Here's wikipedia: ",
"Unlike an optical lens, maximum 'bending' occurs closest to, and min... | [
"Possibly",
", but not from Earth. Your telescope would need to be at least 550 AU out, and it would be pretty much limited to a single target."
] |
[
"How does your stomach know when to stop digesting food and move it into the small intestine?"
] | [
false
] | null | [
"A hole in the stomach means a direct route for bacteria and air to get into the abdominal cavity. So a bowel or stomach perf almost always leads to infection. ",
"But yeah it also leads to incredibly profound pain and tenderness. The acid is very very irritating to the lining of that cavity and the organs inside... | [
"It's not -good-, but it's not like movies portray acid. ",
"",
"Think about vomiting and acid reflux. If you puke, particularly on an empty stomach, you got a mouth full of stomach acid. It's not that bad, as far as causing damage to your body goes. However, repeated, long-term exposure to stomach acid, a... | [
"Really the fact that you’re about to get super infected is more of a concern than stomach acid is. "
] |
[
"How stable is a person's personality over time?"
] | [
false
] | null | [
"Personality is highly, but not perfectly stable (either rank-order or mean-level change). However, change may well be a heritable individual difference. ",
"Roberts & Delvecchio (psych bulletin, 2000) did a study on this and found that the test-retest correlations between the \"Big Five\" personality traits (agr... | [
"The answer depends on how personality is measured, how long a period of time is elapsing, the age period covered. The most common instrument is some version of the NEO Big Five, which assesses neuroticism, extraversion, openness, agreeableness, and conscientiousness. From adolescence to early adulthood, the rank ... | [
"This comment has been overwritten by an open source script to protect this user's privacy. ",
"If you would like to do the same, add the browser extension ",
"GreaseMonkey",
" to Firefox and add ",
"this open source script",
". ",
"Then simply click on your username on Reddit, go to the comments tab,... |
[
"Is it true that you are unable to learn second language as proficiently as a native speaker when you are in your mid twenties?"
] | [
false
] | I have seen this , and now Im wondering if I'll be ever able to learn another language the way I would like to which is as proficiently as a native speaker. | [
"This depends entirely on what you mean by native. Can you get really good? Absolutely! Can you discuss everything under the sun? Sure!",
"Can you pick up the phonemic contrasts that this language has that yours lacks? Possibly. Probably not to native performance levels.",
"Are there other tests that can be use... | [
"It is very clear from a wide number of experimental investigations that there is a very big difference between people learning a language as a child and learning a language as an adult. Some of these are things caused by developmental differences, as predicted by the ",
"Critical Period Hypothesis",
", but oth... | [
"This is laughably, demonstrably false. Let me give you a simple example: new words. Can adults beyond the age of 35 gain vocabulary? You bet!",
"There's also a bunch of evidence about neuroplasticity into adulthood being more of a thing than really old stuff claims - see the below references for a slew of eviden... |
[
"Does a 1000W PC output about the same amount of heat as a 1000W heater?"
] | [
false
] | Assuming the PC is pulling 1000W from the wall, does it produce the same amount of heat output as a 1000W heater? if no, then where else does the energy go because the PC is not moving? | [
"If there actually is 1000W of electrical current going through the PC from the wall socket, then yes, it's generating just as much heat as a 1000W heater doing the same thing.",
"However, just because a PC has a 1000W PSU doesn't mean that it actually draws 1000W on average. Or ever, for that matter. How much po... | [
"If it's a monitor that gets its power from the PC, such as a laptop screen, yeah. My impression is that most standalone monitors have a separate power cord, their connection to the PC being for data only. And a machine with a 1000W PSU is unlikely to be a laptop.",
"Also, inside a closed room without many transp... | [
"Short answer. Every measurable watt the computer takes from the wall will be converted to heat.",
"Longer answer. No, sub fractional amounts of energy will be put into objects that increase their potential energy. Some energy that is taken from the wall going into processes that do not have a 100% conversion t... |
[
"Would filling the tires of different racing vehicles (cars, bikes, etc.) with a lighter-than-air gas like helium give the racer any kind of significant advantage?"
] | [
false
] | null | [
"That's exactly why. Nitrogen is inert & won't fluctuate (as much) throughout the variable daily temperatures. So instead of 28psi on a cold morning moving to 32psi in the warm afternoon, the pressure just stays where it was initially filled by nitrogen. This helps with tire longevity, as running your tires even a ... | [
"That's exactly why. Nitrogen is inert & won't fluctuate (as much) throughout the variable daily temperatures. So instead of 28psi on a cold morning moving to 32psi in the warm afternoon, the pressure just stays where it was initially filled by nitrogen. This helps with tire longevity, as running your tires even a ... | [
"The extra weight you would have to add for thermal control would make the whole exercise a waste of time."
] |
[
"Why do only a few concentrated acids dissolve glass?"
] | [
false
] | I'm assuming it doesn't have anything to do with the pH of the acids, since triflic acid is stable in glass while hydrofluoric acid eats through it. What, chemically, allows some acids to react with the oxides in glass? | [
"Common glass consists primarily of silica (SiO2). In order to dissolve glass you must break the Si-O bonds in silica. These bonds are very strong, so you must form even stronger bonds for dissolution to occur. Si-F bonds are also quite strong. When HF reacts with silica it will form H2SiF6 or SiF4. Both are water ... | [
"HF isn't such a strong acid, if I recall correctly. The F atom radius is too small. It's weaker than e.g. HCl. there are quite some acids stronger than this.",
"HF isn't classified as a \"strong\" acid, but it is highly corrosive. Strong vs Weak acids refers to how well they deprotinate in solution. Strong aci... | [
"You're going to confuse a lot of amateur chemists with this \"strong acid\" claim. Most people don't know know the difference between pKa and pH and will think back to their highschool chemistry definition of \"strong acids dissociate completely in water\".",
"But you're right, it's not a terribly strong acid wi... |
[
"What would a nuclear explosion in space look like?"
] | [
false
] | We see hollywood special effects setting off explosions and nukes going off in shows like Battlestar Galactica but what would an nuclear explosion reasonably removed from a planet's gravity well look like? | [
"Searched",
"Relevant ",
"discussion",
"Original question by ",
"shishkebob202",
"Just read an article that mentioned the banning of nuclear tests in space and it got me thinking. If a nuclear weapon was detonated in some remote part of space or in a vacuum, would it have the same effect? Might vary accor... | [
"Excellent bot. For anyone reading this, I have to add that starfish prime invariably comes up in discussions of space nukes, and it always irritates me because even though it was detonated in a vacuum, it wasn't technically outside the atmosphere - it was well within the ionosphere and thus could interact with the... | [
"Yes, this is correct. Starfish Prime is interesting but not a case study for what a nuclear detonation would look like in 'real' outer space.",
"From everything I've read, a nuclear detonation in the vacuum of space would look more or less like a flashbulb going off - a brilliant flash of light, and not much els... |
[
"Why is there static on my radio whenever my cellphone is near?"
] | [
false
] | null | [
"Mobile phones communicate using radio waves. Analogue radio antenna, speaker cables, and other wires can act as antenna and pick up the radio waves transmitted by the phone, which produces an electrical signal, which you hear as noise on the attached speakers. The noise and bursts you hear is how the phone encodes... | [
"Is ",
"this",
" the noise you're talking about? It's the \"GSM noise.\" I'm not an expert in physics, broadcasting, or antennae so I'm going to stop talking here."
] | [
"That is exactly it."
] |
[
"What causes the shape of ferrofluids introduced to a magnetic field?"
] | [
false
] | null | [
"Generally, the ferrofluid follows the pattern of the magnetic field itself, concentrating in areas of high field. The \"spike\" pattern is the result of ",
"normal-field instability",
", which occurs because the particles are more easily magnetized in air than \"inside,\" surrounded by other particles. Basical... | [
"I wrote the ",
"Ferrofluid#Normal-field instability",
" section. :) I tried to make it as vivid as possible. Does it need... more explanation? Simpler language?",
"Ninja edit: Maybe it needs a diagram?"
] | [
"OH wow really? Yes a diagram would be phenomenal. Possibly an explanation that relates the simple laws of magnetic fields and relates them directly to the corrugations? Anyway, thanks for contributing to the world! Ahaha"
] |
[
"Are there any planets in the universe that are as big--or possibly bigger--than our sun?"
] | [
false
] | Furthermore, would they even be habitable due to the incredible force of gravity? | [
"No if they were the size of our sun they would be considered stars because they would presumably be fusing hydrogen in their core. If they weren't fusing hydrogen, they'd be considered a brown dwarf."
] | [
"What do you mean by 'big', do you mean mass or radius? Anyway, the answer to both is no. If a were more massive than the sun, it would be a star. If had a mass comparable to the Earth or even Jupiter, but a radius larger than the sun, then the planet would not be stable and would collapse to something the size ... | [
"Wouldn't it be stable if the internal temperature were high enough? I'm thinking of a very low density gas giant held up by high temperatures. It wouldn't strictly be \"stable\" because it would gradually shrink as it radiated away heat, but the same is true of Jupiter."
] |
[
"How does a single propeller plane not roll?"
] | [
false
] | So, suppose an airplane with a single propeller spinning in a clockwise direction. So, by the conservation of angular momentum, the body of the plane must spin in anticlockwise direction. How do plane resist that and fly straight. | [
"The ailerons compensate for the propeller and engine torque with aerodynamic forces."
] | [
"Yes. This is most notably seen on large single engine WW2 warbirds with their very powerful piston engines. They have very high engine torque that is tricky to compensate for as you throttle up or down."
] | [
"It has to be noted, though, that the air resistance of the wings intrinsically counters the roll tendency to an extent. Even untrimmed, a usual GA plane won't go into a wild roll due to engine torque. There's also additional effects, like asymmetries in prop wash and asymmetric blade effects at higher angle of at... |
[
"Does every cloud represent an area of lower air pressure than the air that surrounds it?"
] | [
false
] | I did some googling but couldn't find an answer to this specific question - if I see a cloud can I assume that that location in the atmosphere has a measurably lower pressure than the air surrounding it? | [
"Not necessarily pressure, but temperature. Clouds form when the ambient air temperature reaches the dew point, this is the temperature at which water condenses at to form a cloud. Low pressure systems tend to bring clouds with them but are not the direct cause."
] | [
"I think you’re under the impression that density and pressure are related and on a very very small scale that may be true but in terms of the entire atmosphere, the pressure difference in a cloud vs the atmosphere is miniscule at best. Clouds will only form once the dew point is reached, pressure doesn’t play a bi... | [
"I guess I got focused on pressure since \"clouds\" that are man made (such as wingtip vortices, or the shock cones around trans / supersonic aircraft) are formed by the pressure differential... at least I think so, but now you've got me wondering if it's another misunderstanding lol. Thank you for responding, I a... |
[
"Which would burn more calories by: running a mile, walking a mile, or are they the same?"
] | [
false
] | I think this may boil down to a biomechanics problem and is probably affected by running and walking form. If that's the case, you can assume the most energy-efficient walking and running form. | [
"Complicated question. The efficiency of muscles depend very much on the posture and the kind of movement and is not the same for running and walking. Although newer studies would be much more reliable, here is a 1976 paper talking about the exact thing. ",
"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1283673/",... | [
"OTOH, when running you take longer strides, reducing the amount of 'accelerations'. "
] | [
"Every step you take accelerates your leg and foot from zero (resting on the ground) to twice your velocity in order to get the foot in front of you, then decelerates the foot to rest it on the ground. If F=ma then the faster you go, the more force needed since the acceleration needed is greater by a factor of two.... |
[
"What is the etymology of the first four prefixes in organic chemistry?"
] | [
false
] | Meth-, Eth-, Prop-, But-, Pent-, Hex-...etc. Why dont the first four follow the numeral prefixes and where did they come from? | [
"The first alkanes, or rather, alkyl components, were named after where they were first isolated from. This is before we knew things like how many carbon atoms were in them, so a numbering scheme wouldn't have been possible.",
"\"Methyl\" comes from (EDIT: archaic \"methylene\", which is methanol) - which comes f... | [
"Methyl predates methanol (1840 vs. 1892), so the reverse is actually true. Methyl in turn comes from methylene (1835), which is where the wood connection comes in, with ",
" meaning wine and ",
" meaning wood being combined with the suffix ",
". "
] | [
"This is etymologically true, but \"methylene\" isn't a separate chemical, it's a (modern) chemical group. The archaic use of \"methylene\" just refers to methanol, as the etymology implies."
] |
[
"Why are the majority of human beings right-handed? Why aren't we all just ambidextrous?"
] | [
false
] | I recently read that ~90% of humans are right-handed and that a similar ratio of right-handedness has been observed in apes. But why? Is/was there some evolutionary benefit or is it just a cultural practice? Why aren't we all 100% ambidextrous? | [
"Most theories have the start of the influence way too late in evolution to matter, ie ones that are a result of writing, or things based on teaching styles.",
"My favorite theory that seems to come early enough though is the Throwing Madonna theory, discussed ",
"here",
". It basically says that early in hu... | [
"Have they isolated a gene for left-handedness? If not then it may not have a genetic component which is why it hasn't disappeared."
] | [
"I've never heard that theory before, so thanks! Seems like it could answer the question. ",
"As far as I'm aware, there's no specific gene for left-handedness but rather a combination of genes. For example, artists and creative personalities tend to have a higher ratio of left-handedness than the general populat... |
[
"When you get a limb amputated, specifically what happens to the veins and circulation?"
] | [
false
] | [deleted] | [
"Med student here",
"Let's take for example an amputated leg.\nThe lower leg is cut off, bleeds a lot, veins and arteries constrict to help stop the bleeding, blood starts to clot, the wound starts to heal and not very much actually changes (except you lost part of a limb, sorry).",
"You should know that the bl... | [
"Basically they scar down. I've done a TMA before and basically we go in and then just cauterize the bleeding vessels until there's no more blood. If they're infected, then we do a delayed closure and just leave a flap."
] | [
"Very helpful, thank you."
] |
[
"Is carrying a 100kg object on Mars harder than carrying a ~38kg object on earth?"
] | [
false
] | Since inertia is always based on mass - yet the 'weight' of an object is based on gravity - would it be more difficult to carry an object weighing 100kg on mars vs 38kg on earth - assuming both have the same physical dimensions of course. My initial thought is that although I can more easily lift the object, walking wi... | [
"The term 'carry' is a bit ill defined from a physics perspective as it would depend very much on the path taken. If we compare two situations where we were pushing a 100kg rock on a skateboard on both Earth and Mars, one would have to do the same work against inertia in both cases.",
"So the works against inert... | [
"Inertia only affects acceleration. On mars it would be slightly harder to start moving with the 100kg object. Once you are walking the objects inertia is irrelevant. Well it matters again when you stop. As for the difficulty of inertia when starting it's hard to say, given I've never tried. You walk at about 5km/h... | [
"'Carry' meaning holding the entire object yourself without the use of wheels.\nFor an somewhat real-world example - grab 2 of those 18L water-cooler jugs (that's about 36kg) and walk 20 meters with them - it's very tiring, and walking like that requires very deliberate steps which seems to fight inertia a lot. Now... |
[
"How do spiders spin up a really long horizontal web between two bushes?"
] | [
false
] | Whenever I’ve hiked along a trail and torn apart a spiders web, I’ve always wondered that to myself. Often times it’s just a single strand. How does a spider manage to cross two bushes with a web, seemingly building a bridge between them? | [
"Generally they let out a very light pilot strand that is allowed to blow in the wind. The spider can tell from vibrations in the strand if it has stuck itself to something far away. It then pulls on the strand to tighten it, and uses it as a catwalk to initiate construction of the remainder of the web.",
"See fo... | [
"Oh don't worry, that's not what I'm talking about. The spider stands still, and just lets the silk strand wave in the wind. The spider doesn't move until the silk catches on something else.",
"Ok, now worry: spiders can totally fly. It's called \"ballooning\". Just search youtube for that and have fun."
] | [
"Oh don't worry, that's not what I'm talking about. The spider stands still, and just lets the silk strand wave in the wind. The spider doesn't move until the silk catches on something else.",
"Ok, now worry: spiders can totally fly. It's called \"ballooning\". Just search youtube for that and have fun."
] |
[
"Is everything provable?"
] | [
false
] | null | [
"Consider this. Take your conjecture, and treat it as an axiom. The system may be trivial, and may not work, but your conjecture will certainly be provable.",
"The word proof is meaningless without an axiom system. The incompleteness theorem says that no sufficiently powerful axiom system can be complete. There a... | [
"Yes you can, in fact people do all the time. Mathematics is not driven by experiments, but by arriving at conclusions from assumed axioms."
] | [
"Yes you can, in fact people do all the time. Mathematics is not driven by experiments, but by arriving at conclusions from assumed axioms."
] |
[
"If Mercury's orbit was tidally locked, how cold would the dark side be?"
] | [
false
] | null | [
"There are permanently shadowed crater floors on Mercury at below 102K (-276 degrees farenheit)"
] | [
"This is goddamned fascinating. Ok, so stupid question, how is this possible? I know there's no atmosphere, but how is it possible that the extreme heat doesn't effect the rest of the planet? I don't know shit about space."
] | [
"I thought that Mercury had a very, very thin atmosphere. "
] |
[
"How long is the time delay with a live digital tv transmission?"
] | [
false
] | I have a cable Tivo box and when I change from a regular digital channel (say ESPN) to ESPN HD, I notice that the HD Channel is a few seconds behind. So my question is: how much behind, under normal circumstances, is the digital live tv broadcast? I am assuming that it involves a compression and decompression time, reg... | [
"As little as 1 second for ATSC broadcasts, but live programs sometimes add a few seconds of delay to avoid \"bloopers\". Cable and internet services add several more seconds. You're correct that in the analog days it was almost instantaneous. "
] | [
"You're correct that in the analog days it was almost instantaneous. ",
"Or about 0.25 seconds for a satellite relay. To as low as 0.016 seconds for a coast to coast microwave link."
] | [
"It can vary a lot. The regular channel is also \"behind,\" you just don't have anything else to compare it to. Every bit of equipment in the broadcast can add a delay - the machine that adds the captions, the one that mixes between cameras, and so on. Most of the delay comes from encoding for broadcast and decodin... |
[
"Anyone that works in Ecology. Is an Ecology/Bio/something similar major required to get a job in the field?"
] | [
false
] | I'm a 3rd year physics + math major and my main plan was to teach, but I'm starting to get really interested in ecology. Is there a possibility of getting a job in ecology without a degree in it? I'm thinking of trying to talk to my bio professor who I chat with a lot to see if I could get into some research here as an... | [
"A job, not so much. Even if you were a ecology major, and undergraduate degree doesn't mean too much. You have to go to grad school to get a real job working in biology.",
"That being said, you should definitely take a few classes if you're interested but more importantly TRY TO FIND UNDERGRAD RESEARCH. It's the... | [
"This isn't necessarily true, it depends on the kind of ecology work you do. Environmental management and protection and a lot of other \"practical\" areas have jobs for people with a B.A.",
"I would also recommend graduate school depending on what kind of ecology you are in to. I think there are a lot of things ... | [
"If you live in Canada, it really helps to speak French because a lot of the jobs are with the federal government."
] |
[
"If the ISS didn't move but just hovered at its present altitude, would it still be zero gravity there?"
] | [
false
] | null | [
"Short answer: gravity on the ISS is functionally equal to that on the surface of Earth. The ISS experiences zero g because it's constantly in free fall. \nIn Newtonian physics f =(G* m1* m2) / r",
"\nOnly the r changes is the scenario you suggest. The radius of Earth is ~6300 km, the ISS orbits at 400 km above ... | [
"There is no such thing as \"not moving\" in space (or in physics for that matter) if the ISS wasn't moving perpendicularly to gravity's pull it would be falling towards Earth. ",
"Maybe you meant what is it was geostationary (aka always above the same point of Earth) ? Then yes, astronauts would still experience... | [
"There is no such thing as \"not moving\" in space (or in physics for that matter) if the ISS wasn't moving perpendicularly to gravity's pull it would be falling towards Earth.",
"I take the question to mean if it were held in place at the same altitude, but stationary relative to the ground below it. This could ... |
[
"If you go off a huge jump riding something much heavier than yourself, like a ride-on lawnmower, or a bicycle made of cast iron, do you travel higher/farther than the thing you're riding on if you let go of it mid-flight?"
] | [
false
] | Does that object essentially serve as a catapult? I'm just trying to picture the two trajectories - of the person and of the object. Thanks! | [
"If there weren't any air, it would make no difference. However, the air resistance probably affects you more than it affects your cast iron bike. You'll travel less far if you let go."
] | [
"Id like to add that as long as no additional energy is added to the system, its center of mass will land in the same spot as if it were still joined, even if it is in parts. So if you pushed the cart backwards, you would in turn go forwards to ensure that your center of mass stays the same trajectory."
] | [
"That's incredible. I have a strong math/science background, but physics has always seemed so arbitrary to me, in the sense that there are many explanations that I could believe for how objects are supposed to act, so many explanations that just seem plausible. So it's cool when the correct explanation ends up bein... |
[
"Why do shockwaves form at the leading and trailing edge of objects moving at supersonic speeds?"
] | [
false
] | I've just started to study shockwaves this year at university and we've been shown images of double-wedge aerofoils with leading edge and trailing edge shocks. I understand why shocks form but what I don't understand is why you have them at both edges. Is it just the flow coming off the upper and lower surface and hit... | [
"the leading edge of the wedge produces an attached oblique shockwave that doesn't reduce the speed of the flow below Mach 1.0 if the freestream flow is supersonic.",
"Since the flow is still supersonic, passing over the corner in the center of the double wedge airfoil creates an expansion wave which increases th... | [
"...uh. Can you explain that to me but dumber?"
] | [
"Firs, understand that shockwaves are a discontinuity in a fluid flow. What this means is that whenever you have a shockwave, you are essentially witnessing a line in space across which fluid properties change suddenly. Continuum Mechanics says a shockwave is infinitesimally thin. Gas dynamics can prove the actu... |
[
"Is it possible to shake a certain distance of air (maybe with a sound wave or other method) so that it could disrupt the stability of a flying drone?"
] | [
false
] | [deleted] | [
"While I'm not sure if this is even remotely practical, the underlying physics makes me think it might at least be plausible. ",
"For one, every object has a resonant frequency. If you drive an oscillation in the object at that frequency the amplitude of oscillation gets big (e.g., a child on a swing has a specif... | [
"Static air cannon?",
"I have a small toy one that will send a solo cup flying from across the room. \nI've seen truck bed mounted ones knock over stacks of hay bales. I'm betting that would take out a drone. ",
"I don't know if that fits your description but it would work. "
] | [
"Mechanically breaking the drone with sound seems too impractical. Surely there is a way to screw with its accelerometer and make it crash.",
"Low frequency sound would shake it and cause a lot of noise. If you knew the PID coefficients you might be able to build a custom sound profile to make it overcorrect. ",... |
[
"How is quantitative easing fundamentally different from inflation?"
] | [
false
] | null | [
"Quantitative Easing means the central bank creates new money, and distributes the new money out to people (by buying assets from them at market price). It increases the 'liquidity' in the economy, there is more cash and fewer assets.",
"Inflation means the amount that the prices of goods and services increases ... | [
"If you think of money like you do anything else in a marketplace, you understand that it has a price, a supply, and a demand. The price is the value of the money - how much stuff can you exchange it for. Inflation is a decrease in the price of money - one dollar can't be exchanged for as much stuff as before. Whe... | [
"Also keep in mind the assets that are being purchased are financial instruments issued by the banks that are buying them back. It's as though they're maturing their bonds \"early\", meaning the main benefactors are firms that hold lots of government bonds--most often banks. ",
"Increasing the money supply can ca... |
[
"Is there any evidence to suggest that any living creature has exited the earth's atmosphere before modern science made it reasonably accessible?"
] | [
false
] | null | [
"Much of the debris from the ",
"Chicxulub impact",
", believed to be responsible for the ",
"Cretaceous-Paleogene extinction event",
", was ejected into space, probably carrying microbial life with it. Most of it fell back to earth along ballistic trajectories, but mathematical models of the impact indicat... | [
"There was never confirmation of microbes on Mars, or being ejected from Mars. "
] | [
"There was never confirmation of microbes on Mars, or being ejected from Mars. "
] |
[
"How do they build highways in loose sand?"
] | [
false
] | My question is basically only what is in the title, I am trying to find out how paved roads in the desert are made. Normally, constructors lay down a subbase on the subgrade (which in this case is sand) then a base course over that and then the pavement. The subgrade is supposed to hold the whole weight of the road, ho... | [
"Well it is possible because of a foundation technique known as pile foundation.",
"Piles are basically circular concrete columns that have been reinforced under the ground. There are two types of pile available",
"End bearing pile",
"Friction pile.",
"End bearing pile is the pile which transfers load to th... | [
"So it's like the ones they use for tall buildings in desert? Is this what they use in the MENA countries for example? ",
"Just to see if I imagine it right, they put the friction (or end bearing where possible) piles in the sand and then build a new foundation on that (like the floor of a building) and then laye... | [
"I think you have a misconception how a desert looks. It's not just loose sand, desert terrain goes from loose sand to hard ground. Only about 20% is the dune filled sandy type usually depicted as desert. In most you'll find solid foundations where you can build roads like everywhere else."
] |
[
"Is all radiated heat in the form of infrared radiation?"
] | [
false
] | null | [
"No, thermal radiation ranges over the entire electromagnetic spectrum. The peak of the black-body curve at room temperature lies inside the infrared region, which is why people tend to associated infrared radiation with thermal radiation."
] | [
"So, the technical term is \"Blackbody Radiation.\" This is Electromagnetic radiation that is given off by all objects warmer than absolute zero.....so, all objects.",
"The wavelengths given off are a continuous spectrum, but there is a frequency where the peak intensity occurs, as well as a minimum wavelength cu... | [
"Heat as we feel it is in thermal violations of the molecules of our body. Lots of different types of electromagnetic radiation can cause molecules to vibrate. Objects around room temperature tend to emit infrared radiation, but as you heat up objects they emit other types a lot, visible and ultraviolet especially.... |
[
"Could one have some immune cells removed, exposed to a pathogen, then re-inserted back into their body?"
] | [
false
] | If it is too difficult or impossible to make an injected version of a vaccine, is this method possible? Does this method already exist? Would it be too expensive to do this on a population scale? Could you possibly remove B cells, T cells, leukocytes, etc from an individual and have them fight a disease in vitro? | [
"People in this thread are heavily misinformed and/or speculating beyond the science as far as constraints are involved. This can be done, and has been done, and is being done to combat disease today. ",
"Provenge",
" is an FDA approved anti-prostate cancer immunotherapeutic drug that is derived from the haemat... | [
"Good point, I had been restricting my thinking to antigen presentation happening outside the body as well."
] | [
"Even if you could, what would be the point? I mean, why go to all the trouble of isolating something as complicated as the human immune system to make antibodies outside the body and then re-introduce them when you could just inactivate a virus and let your immune system do the work in vivo?"
] |
[
"We are able to freeze embryos and bring them back to life. Why are we unable to do the same with fully grown humans?"
] | [
false
] | null | [
"The main problem with cryogenics is that when we freeze things, crystals form. These crystals are what kills the organism upon unfreezing by lysing cells. In smaller subjects, we can introduce whats called a cryoprotectant, which slows the ",
" of cooling reducing the size and number of crystals formed. It is ea... | [
"In theory I suppose it could be possible, but it's very very unlikely to happen soon. Blood is a very complex fluid, replacing it with another that performs a different action is a very difficult thing to do."
] | [
"In theory I suppose it could be possible, but it's very very unlikely to happen soon. Blood is a very complex fluid, replacing it with another that performs a different action is a very difficult thing to do."
] |
[
"I it possible to continuously accelerate at the same rate (relative to an observer on the object) without reaching the speed of light?"
] | [
false
] | Lets say that and object was accelerating at a constant rate, say 10m/s/s, and there was an observer on the object. Would it be possible for the object to appear to keep its constant acceleration from the perspective of the observer on the object but appear to have its acceleration slow down as it approached the speed ... | [
"You can move with constant (and nonzero) proper acceleration and you will never reach c."
] | [
"According to relativistic kinematics, yes this is what will happen if you accelerate with a constant force. However in reality it is not usually feasible to apply a constant force forever, because that requires an energy source and a propellant. One option is to use a Bussard Ramjet, which absorbs interstellar hyd... | [
"The rapidity will increase without bound."
] |
[
"Are there wildfires in the Amazon?"
] | [
false
] | I was just watching , and they were [showing clips of fly over sections of the Amazon rainforest]( Ignoring the source/wording/topic of that show (I am not intending to argue about the source, you'll get the gist of what I'm asking if it's on mute while you're watching). When I was watching that "fly over the rainfore... | [
"It's mostly due to the weather conditions. Fires thrive and grow in hot, dry conditions. The West coast is often very dry and quite hot at this time of year. Comparatively, the Amazon, being a rainforest is much more wet and humid which greatly reduces fire activity.",
"Humidity actually has such a huge effect o... | [
"Forests burn because they do. They've been around for a lot longer than we humans have been around and living amongst them. In precontact times, several First Nations would use fire to maintain the health of the forests in their area through what amounts to prescribed burns.",
"While the trees can be reasonably ... | [
"I'm both thankful and disappointed in this response - thankful that you explained it, but disappointed because I was hoping for a much more complex and interesting explanation... (Sorry if I'm being unclear, I am not disappointed in ",
" response!)",
"Thanks so much for taking the time to reply, and I hope you... |
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