title list | over_18 list | post_content stringlengths 0 9.37k ⌀ | C1 list | C2 list | C3 list |
|---|---|---|---|---|---|
[
"Is there an energetic difference between light observed from stars and light created from inside our atmosphere?"
] | [
false
] | Not sure if I'm wording this correctly in the title, but I was thinking about how one might be able to look at stars better from inside a dense area of light pollution, and started to wonder if light observed from stars is different than light from a streetlamp. | [
"No, photons of the same type are indistinguishable from one another, regardless of their source. Two photons with the same energy are identical."
] | [
"Would starlight exhibit more defined polarization than street lamps?"
] | [
"No, the polarization from both those sources is random. "
] |
[
"What is the difference between cutting a material and breaking/ripping it?"
] | [
false
] | For example if I cut a piece of paper with scissors, I get a nice, clean separation between the two pieces. However, if I rip it using my hands, the break is very jagged/serrated, and isn't smooth at all. The same is true for lots of other materials (i.e cutting verse ripping bread). What is the difference, on an atomic/molecular level, between cutting something and breaking or ripping it? | [
"When you cut a piece of paper, the pressure you're applying is localized along the blade of the scissors. This pressure is enormous (Pressure is Force/Area, and the area on the tip of a blade, as you can imagine, is extremely tiny), so the paper breaks effortlessly along the blade.",
"When you tear a piece of p... | [
"You are correct, but while we're on the subject, a serrated blade is effective because the notches change the way the pressure is applied. Instead of being applied evenly along the edge, a serrated blade applies force mostly at the pointy bits, increasing the pressure at those bits greatly. In addition, due to the... | [
"Why thank you! I like to make the best of a situation."
] |
[
"What is meant by \"clinical effect\" and \"domains\" in this context?"
] | [
false
] | Hi! I am studying a program in Sweden which will allow me to work as a counsellor. I'd be super grateful if anybody wants to take time out of their day to help me! :) A study can be found if searched for via google, with the title: Positive Effects of Methylphenidate on Social Communication and Self-Regulation in Children with Pervasive Developmental Disorders and Hyperactivity It's on the website of NCBI. Within the study, under 'Discussion', in the last paragraph, the word "clinical effect" is mentioned: "the greatest clinical effect was seen with the medium dose" (Jahromi., et al 2008). Precisely what is meant by "clinical effect" in that context? Another sentence found in the last paragraph under discussion is: "there may be greater disparity in dose-response across different domains for optimal change" (Jahromi., et al 2008). Precisely what is meant by "domains"? Thanks in advance! | [
"The study will have defined the clinical effect but according to the title they are likely metrics of self regulation and social communication.",
"Domains in this context would mean categories of behavior. That is, one dose may be more effective for improving social communication, whereas another dose may improv... | [
"\"Clinical effect\" means \"what the drug did for the patient.\" \"Clinical\" tends to refer to a range of medical settings where actual patients and things they care about are involved, in contrast to laboratory research or \"basic science.\" If methylphenidate binds at a specific molecular target, that's not a c... | [
"Positive Effects of Methylphenidate on Social Communication and Self-Regulation in Children with Pervasive Developmental Disorders and Hyperactivity ",
"police-ical thank you sooo much for the explanation. I was thinking that they weren't being that specific when using those terms, but I did not want to run th... |
[
"What to electronic stopwatches or digital clocks use keep time?"
] | [
false
] | I've always wondered how a digital stopwatch knows how much a minute is? Is it filled with quartz that resonates or something? I've always though that was in analog watches EDIT:oh shit I meant "what do" not "what to" mod help! And "use to" ugh... | [
"Quartz clocks rely on a quartz crystal and the piezoelectric effect to tell time. Send an electric current through a quartz crystal and it will vibrate at a very constant and known frequency. Count the oscillations and you can use them to mark time.",
"http://en.wikipedia.org/wiki/Quartz_clock"
] | [
"Quartz is used in many electronic/digital watches. ",
"Analogue watches use mechanical resonators (not quartz) as they are mostly mechanical. For example, some will use springs and a two way ratchet type device."
] | [
"There is a tiny, very precisely manufactured tuning fork made out of quartz. Quartz is piezoelectric and thus will produce a current when it is deformed and will deform when a current is applied. The vibrations are sensed via electronic circuitry and maintained by continuous application of voltage.",
"The signal... |
[
"If the moon causes high and low tide due its gravitational forces, does the sun also cause its own variation of high and low tide as well?"
] | [
false
] | null | [
"Yes, it does. However, the effect of the Sun on the tides is quite a bit weaker than that of the Moon. At first glance, this seems contradictory because the gravitational pull of the Sun is stronger than the one of the Moon.",
"But the tidal force isn't proportional to the gravitational force itself, but rather ... | [
"Calculable differences, yes, but ",
", not so much. Jupiter, being teh second most massive object in the solar system, is too far and not massive enough to have a measurable effect at its distance. ",
"That said, ",
" object of any mass will have a ",
" effect on us, gravitationally."
] | [
"Yes, it actually comes from the gravitational formula.",
"Using Fg(r) = GmM/(r^2)",
"The tidal force is:",
"Ft = Fg(R-r) - Fg(R+r)",
"Where R is the distance between the two objects and r is the radius of the object your calculating the tidal force on (usually the Earth). You can see that if R >> r, the ti... |
[
"How do antibacterial medicines work on a cellular/molecular level?"
] | [
false
] | I've always been told that antibiotics kill bacteria, but I've never really understood how they work. Also, if they are made to kill cells, what stops them from killing our own tissue cells? Thanks! | [
"I'm definitely no expert, but from what I understand they function by interfering with the bacteria's essential structures or processes. Breaking apart its cell membrane, preventing it from making proteins, etc. And they don't affect human cells because the functional parts of the antibiotic are very specific, and... | [
"That makes a lot of sense, thanks for responding!"
] | [
"Antibacterial (or antimicrobials {there is an important difference}) have four main ways of working. Some kill bacteria, some stop bacteria from growing or dividing.",
"Disrupt bacterial cell wall\nBeta-lactams (like the first discovered antibiotic penicillin)\nPolymixin",
"Disrupt bacterial cell membrane\nGly... |
[
"If an electrical current in a wire generates a magnetic field, would an observer moving with the flow of electrons along that wire measure the same magnetic field as stationary observers measuring the field around the same wire?"
] | [
false
] | This is a hypothetical thought experiment, and a variation of the stationary observer vs. observer on a speeding train analogy commonly used with relativity. Suppose you have a very long wire with a direct current traveling through it. Along one side of the wire are stationary people who are measuring the magnetic field generated by the current through the wire. On the other side is someone also measuring the magnetic field, but who is traveling down the wire at the exact same speed as the flow electrons through the wire, so that the electrons 'appear stationary' to him. Will both the stationary and moving observers measure the same magnetic field around the wire? | [
"An observer moving with the flow of electrons would notice positively charged protons moving in the opposite direction, so they'd get the same magnetic field. If you get rid of the wire and just have a beam of electrons, then they wouldn't notice the magnetic field. How much of the field is electric and how much i... | [
"Sort of like how momentum depends on your reference frame.",
"Not sort of. Exactly :-) Both can be expressed as 4-vectors and transform identically."
] | [
"not really, the electromagnetic field F_μν is an antisymmetric tensor (=6 components) that contains both the magnetic and electric field. ",
"https://en.wikipedia.org/wiki/Electromagnetic_tensor#Relationship_with_the_classical_fields",
"even classicaly, the magnetic field isn't even a 3 vector, but a pseudo v... |
[
"How successful is social work and assistance in reducing poverty in the long term?"
] | [
false
] | What is the effectiveness of social workers and assistance in reducing poverty rates Hi everyone i want to ask social sciences what the effectiveness of reducing poverty is. This is also relevant because I am curious to know hwo effective it is in reducing crime by reducing poverty. Is this a dream or is there evidence to back it up | [
"Is reducing poverty the goal? Don't social workers help people with bad mental problems, enabling them to live on their own and have a better quality of life? ",
"",
"Some people can't contribute to society and are a resource drain, fiscally speaking, that doesn't mean helping them live a better life is ine... | [
"Social workers do a huge variety of different things beyond just counseling. Hospitals and clinics often employ social workers to help patients navigate the healthcare system: locating transportation to appointments, connecting them with resources for government assistance so they can buy formula, etc. Schools oft... | [
"That doesn't mean that helping those people isn't a net benefit, even if you only recoup value from their family and children. Individual benefit, social benefit, and economic benefit are different sides of the same coin. People who experience less mental health burden have better life trajectories. Even brief dep... |
[
"What's the evolutionary impetus behind homosexuality?"
] | [
false
] | null | [
"1) There are some theories I've heard out there, for why a certain level of homosexuality is evolutionarily preferable, but they've always seemed half-baked to me. Then again, I am not an expert in the field.",
"2) The appearance of a trait in a population does not have to be advantageous - it simply has to not... | [
"I've heard it argued that homosexuality is not advantageous for the individual's reproduction, but rather that having fully functioning childless adults does benefit the tribe's chances. Sort of the animal kingdom version of having a gay uncle who gives you fashion advice, dating tips, and loves babysitting.",
"... | [
"not every trait evolved through natural selection and are advantageous. some ways that non-advantageous traits can evolve are genetic drift or random selection of traits. An example of traits evolving without natural selection is if a small group of a population separates from the main group and start to have babi... |
[
"What brings the quantum and wave theory together?"
] | [
false
] | null | [
"What do you mean by \"wave theory\"?"
] | [
"Considering light as a wave , experiments such as Young's double slit experiment prove the wave theory of light. ",
"So my question is , how do we explain presence of both of those theory at the same time ?"
] | [
"Light is a wave even in classical physics. But the way you're using \"wave theory\" sounds like it's the same thing as quantum mechanics, so there's no need to reconcile them."
] |
[
"How do they synchronize atomic clocks?"
] | [
false
] | I was reading some information about atomic clocks and saw that there are over 200 of them in the world and wondered do they all have the same time? How did they figure out the exact time in the first place? If a new atomic clock is built how is the initial time set? The problem i see is that the clocks are accurate to the nano second but even using a computer it would take more than a nano second to set the clock's initial time so how do they do it? Also when they compare the times of clocks that are in different locations there is a significant amount of time it takes to send messages between locations so how do they properly account for this, such as the time to send a radio/satellite transmission from a clock in Washington DC to London | [
"On a very basic level it is ",
" to synchronize clocks, since different clocks tick at different rates due to the local strength of the gravity field.",
"The \"universal\" time is defined as an average of a large number of reference clocks as kept by national institutions. The best an institution can do is to ... | [
"Then there's also ",
"Relativity of Simultaneity",
" which basically says that any events that are in different locations can't be said to be happening at the same time because it depends on the observer."
] | [
"Well there are already a set of highly synchronized atomic clocks floating about in space in the form of GPS, so that's the main way that new clocks are synchronized. There is also the more generalized ",
"two-way time transfer",
" method which gives more precision than GPS.",
"In general, it's not a problem... |
[
"Can someone give an explanation about (fast) metabolism and why people tend to be skinny?"
] | [
false
] | From what I understand there is no such thing as a truly "fast metabolism". A vast majority of people who seem to think they have a fast metabolism actually do not eat a high enough caloric diet to contribute to significant weight gain (although they may binge eat which makes it seem like they eat a lot). I however believe that some people (myself included) do have relatively fast metabolisms. I've been tracking calories for over 6 months and I easily average 3000+ calories a day (I weigh 140 lbs and am 5'7). A rough estimation on my daily caloric needs are: bodyweight in lbs * 16; 140 lbs*16=2240) I eat well over that number and my weight is fairly stable. Going to the gym should not burn off an average of 750 calories through the whole week since I basically only do weight lifting with no cardio. I also don't exactly eat healthy.. I eat whatever I want. Theres talk about different body types (ecto/meso/endo-morphs) but I don't quite understand scientifically why those body types occur outside of people who tend to have different hormonal (testosterone in particular) production rates, but that contribues more to muscle gain. So can anyone explain why this would be the case? Does ethnicity, muscle mass:body mass ratio, or maybe a genetic predisposition to stay fairly thin? I can grasp on how people can be overweight much easier than how people can be thin by watching diet, but when a thin person eats a lot and isn't careful about what they eat, I'm at a loss. | [
"I eat whatever I want",
"Just because you eat whatever you want does not mean you are eating a lot.",
"Also, it's not so surprising that once you went off GOMAD, but didn't replace those calories, your weight dropped back to what it was before."
] | [
"Fat-free mass (FFM) was the best single predictor of resting energy expenditure (REE).\nThis basically means muscle mass is what mostly determines your basal metabolism.",
"From what I understand; the fact that you do weight lifting doesn't directly burn a lot of calories. But because it increases your BMI throu... | [
"Perhaps its not about metabolism but rather efficiency of digestion. You consume 3000 calories but your body might not be absorbing them. I have trouble keeping the weight on and I have a strong inclination that it is related to how poorly I chew my food. I don't tend to chew thoroughly and I very aware of it. ... |
[
"Why is it colder on mountains than on the ground?"
] | [
false
] | [deleted] | [
"this is not really true. the temperature distribution through the atmosphere is more complicated than simply going from high to low temperature. Different layers of the atmosphere have different absorption of sunlight, e.g. Ozone in the stratosphere absorbs UV light. Therefore the stratosphere is much warmer than ... | [
"Sunlight doesn't heat air directly very efficiently because air is mostly transparent. Instead, sunlight heats the ground and the seas, which in turn heat the layers of air directly on top of them. At the top of the atmosphere, on the other hand, there's an effectively infinite heat sink: space. This creates a tem... | [
"The air gets heated up over the surface. The higher in the atmosphere you go the lower the pressure will be. This is logical since there is less air above you that can exert pressure downwards through its weight. So the air pressure drops with increasing height in the atmosphere. \nNow if you take an air parcel at... |
[
"Why are there more right handed people than left handed people?"
] | [
false
] | [deleted] | [
"It is still unknown. There are several theories however. The main theories were generally that there was a genetic cause similar to Situs inversus. However the most popular models for a genetic cause have recently been shown to be unlikely from a large genome mapping study done in twins.",
"http://www.nature.com... | [
"Are other primates right and left handed as well?",
"Yes.",
"If so, is there a prevalence of right-handedness in other primates?",
"For chimpanzees, most likely, yes, however it's different. See ",
"this study",
":",
"The results of our study indicate that wild chimpanzees exhibit task-specific populat... | [
"Are other primates right and left handed as well?",
"Yes.",
"If so, is there a prevalence of right-handedness in other primates?",
"For chimpanzees, most likely, yes, however it's different. See ",
"this study",
":",
"The results of our study indicate that wild chimpanzees exhibit task-specific populat... |
[
"I'm racing light, I'm traveling half its speed, but light is still traveling light speed (relative to me)??"
] | [
false
] | My friend told me that, for reasons he couldn't explain, even if I was traveling half the speed of light, light would still be traveling light speed from my point of view. | [
"yes. This is true. Light always travels at the same speed regardless of who's looking at it or how you're moving relative to it. Everyone will see it travel at the speed of light. This is one of the fundamental ideas that led to Einstein's theory of relativity."
] | [
"Light travels at about 300,000 km/second. But seconds are relative.",
"When you travel at half the speed of light, time slows down for you, making those seconds longer, and giving light more time to travel that distance relative to you."
] | [
"as is distance. The distance in front of you also contracted as compared to an outside observer."
] |
[
"How is information wirelessly transferred from one place to another?"
] | [
false
] | For example, what happens when I send a picture to someone over text? | [
"Big picture, the cell phone represent the data (say text) as some sequence of (say binary) numbers. These numbers are used to create different waveforms which are then sent out from an antenna using electromagnetic waves. Another antenna receives these waveforms, recovers the original numerical sequence, and then ... | [
"I guess an accurate description would be \"error mitigation code\"?"
] | [
"And, back in the day, you could do morse (or binary) with a spark-gap transmitter. You're forbidden from doing that now, because there's lots of noise on frequencies adjacent to the one you're using.",
"https://en.wikipedia.org/wiki/Spark-gap_transmitter"
] |
[
"How would one go about synthesizing elements from raw materials?"
] | [
false
] | null | [
"You mean like, constructing elements from protons, neutrons, and electrons?",
"That's basically nuclear fusion, and we can't even turn two hydrogen atoms into helium with any kind of reliability at the moment. It's a combination of engineering challenges as well as a lack of a theoretical framework that really ... | [
"You can totally isolate electrons and protons and store them. It's actually pretty easy with charged particles. We do it in our lab all the time."
] | [
"Unfortunately, you can't isolate a proton or an electron and store it somewhere, so you can't make an element-maker. (A charged species cannot exist alone.) Through neutron bombardment and some types of disproportionation you can technically turn some elements into very close neighbors on the periodic table, but t... |
[
"Why does it feel like I'm pushing air out of my ears when I plug my nose and try to push air through it anyway?"
] | [
false
] | null | [
"There are tubes linking the back of your throat to your middle ear.",
"They are called the ",
"Eustachian Tubes.",
"They are what you use when your ears 'pop' in an airplane or lowered air pressure for any other reason."
] | [
"Yes. The pharyngotympanic tube (aka Eustachian tube) connects your nose to the space behind your eardrum. You can damage your eardrum by putting too much pressure on it. ",
"However, if you are blowing your nose, you might have an infection, and that infection might be spreading through the pharyngotympanic tube... | [
"When you blow your nose and feel an almost painful pressure in your ears, is this genuinely dangerous?"
] |
[
"If the earth was a cube instead of a sphere, what would gravity be like at the edges?"
] | [
false
] | null | [
"Gravity will pull you towards the center of the cube. if you stood near the center of a face, it would be like gravity normally is here on earth. However, as you move towards the edges, the pull of gravity still points towards the center of the cube, making it seem as if you were climbing uphill. You effectively a... | [
"This is mostly correct, with one interesting and perhaps non-intuitive clarification: gravity will pull you \"towards the center of the cube\"... only approximately. That is, the direction of the gravitational field at various points on the surface of the cube do ",
", in general, point ",
" toward the center... | [
"Calculating the gravitational field of a uniform cubical object is not exceptionally complicated mathematically, and the OP isn't implying that a planet as large as the Earth could assume the shape of a cube. ",
"This is a \"what if\" question with a scientifically valid answer.– entirely appropriate for ",
"... |
[
"Is there a medical term for not being able to speak fluently? (details inside)"
] | [
false
] | [deleted] | [
"Two terms match what you are describing:",
"1) Disarthria - this is a condition where a patient cant coordinate their tongue, lips, lungs or vocal chords in a manner which allows speech to be comprehensible. This can be caused by neurological damage, or physical deformity.",
"2) Aphasia- this is very similar t... | [
"Dysarthria?"
] | [
"I think this is it. Thanks. :)"
] |
[
"Could you, theoretically, uncook something?"
] | [
false
] | null | [
"One could argue that the easiest way to 'uncrack an egg' is to use the material that makes up the cracked egg to ultimately make feed for a chicken, which will produce a new egg. Because chickens are by far the most efficient way we know of to produce un-cracked chicken eggs.",
"Still, a global enough accounting... | [
"The other comments answer your question pretty well, but I think it's worth noting that there are ",
" conditions under which ",
" the effects of cooking can be reversed. See this Ig Nobel prize-winning report on how to unscramble egg whites: ",
"http://onlinelibrary.wiley.com/doi/10.1002/cbic.201402427/abst... | [
"Depends. It'd be fairly easy to uncook, say, a fruit salad. But I'm going to assume you mean something more like a cake. And in that case the short answer is no, due to entropy. The second law of thermodynamics says that during the course of any chemical reaction, the amount of entropy (or lack of order) in a clos... |
[
"How well connected is the human brain to the rest of the body? How many points (nerves, arteries, connecting tissue) would need to be severed to \"cleanly\" remove it without definite loss of function - assuming it could be kept alive at all?"
] | [
false
] | I'm trying to understand how a full brain transplant might be possible (assuming those severed connections could be reconnected and healed on the other side, of course) - I have the mental image of the brain floating about in the skull with just the brainstem and nerves for the eyes coming out and linking it to the body - though surely it is not this simple, right? | [
"If you want some nightmare fuel, look up the head transplant experiments of the 50s and 60s.",
"One of the big barriers to brain/head transplantation is that there isn't an effective method to reconnect nerve tissue (severed nerves do not heal to a functional state, this is why spinal cord injuries can result in... | [
"https://en.m.wikipedia.org/wiki/Head_transplant",
" At this point in time we don’t have the technology or understanding to achieve anything close to that. The brain is connected to the rest of the body through the spinal cord, which has nerves that extend down the spine and out to every other part of the body. T... | [
"Which has changed very recently due to both stem cell therapy, and artificial bypass devices."
] |
[
"If we as scientifically advanced as we are now, were in the universe as it was after only ~1M years old, and we looked into the sky, what would we see?"
] | [
false
] | null | [
"I got an equation",
". T = 3 * 10",
" K /sqrt(t).",
"I got ",
" 5,342 K when t = 1,000,000 * #seconds/year."
] | [
"I get 5,342 K when t= 1,000,000 * 365 * 24 * 3600 seconds.",
"So according to ",
"this",
" \"we\"'d see an orange glow everywhere at night. Of course no life as we know it could possibly exist at such temperatures."
] | [
"You're right, what Calculator was showing me was just the denominator. Wish I had a Casio..."
] |
[
"What would happen to a person if they slept ~24 hours each day?"
] | [
true
] | [deleted] | [
"I think they already invented it: ",
"coma"
] | [
"TIL people in coma wake up everyday to workout."
] | [
"Interesting question, though I doubt there is any experimental studies (and I couldn't find any) on it given it represents such an abnormal and ill-advised use of sedatives. Plus the question is confounded by the fact that many hypnotics are addictive and have their own negative health effects (ex: suppression of ... |
[
"Why does Venus have extremely cold parts in its atmosphere?"
] | [
false
] | Apparently there are parts in Venus's atmosphere that reach -175 C while on the surface it is 450+C. | [
"It doesn't completely exclude it - take a look at the location of Venus in Fig. 3a and the text about Venus below it.",
"They directly call out Venus as an outlier for lacking a stratospheric inversion, precisely because of the reason I stated above: even at the height where most atmospheres have a temperature m... | [
"Every thick atmosphere - Earth, Venus, Jupiter, Saturn, Uranus, Neptune, and Titan - follow a characteristic property of being warmer down deep in the atmosphere, and colder as one goes higher in the atmosphere.",
"For rocky bodies, sunlight warms the surface, so that area is the hottest. That warmth must then b... | [
"No, this is definitely not the reason why Venus' upper atmosphere is cold.",
"Any atmosphere will have a cold trap somewhere high above the surface where the atmosphere is no longer opaque to infrared radiation. It has nothing to do with the presence/absence of the magnetosphere. See my detailed answer ",
"her... |
[
"Is it possible to use a large magnifying glass to amplify the Moon's rays to warm up a given smaller area, since the Moon reflects the sun's light?"
] | [
false
] | Basically, using that large magnifying glass would burn anything during the day, but could potentially just be "warm" at night. Eh? | [
"In the context of optics on telescopes, permanent eye damage can occur in observing the moon without a moon filter, which typically blocks around 90% of incoming light. ",
"The flux received from the moon is about ",
"10",
" the solar luminosity. On Earth we get ",
"10",
", which is still around 10",
... | [
"In the context of optics on telescopes, permanent eye damage can occur in observing the moon without a moon filter, which typically blocks around 90% of incoming light.",
"This makes no sense to me. The full moon's apparent magnitude is -12.6, which is equal to ",
"approximately 4.6 W/m",
". According to ",
... | [
"Yes, it is possible. Light is light, and with enough intensity it can heat anything, no matter which wavelength it is.",
"There's a common misconception that only infrared light causes heating, but that's because we're used to heat radiation from relatively cold objects at 50-5000 °C, which have emission peaks i... |
[
"How can a cell phone potentially be dangerous when Microwaves are less powerful than visible light?"
] | [
false
] | null | [
"Intensity is analogous to brightness (not frequency). If you stand in front of an extremely bright light, it can burn you. The same is true for a very bright microwave source."
] | [
"I see. Can a microwave or visible light ever become bright enough that it goes from burning you to, like, breaking apart your DNA (like a gamma ray)?"
] | [
"Only indirectly, by breaking up molecules via heating you up too much. Visible and microwave light doesn't have high enough frequency to directly cause ionization."
] |
[
"Why is the diameter of an insulated wire important to how much current a wire can carry if electricity only travels on the outside of a conductor?"
] | [
false
] | So, I saw on some science program a while back a demonstration of the Faraday Cage, except it was two men in chain mail being struck by a lightning generator and suffering no consequences, as the charge travels on the outside of the chain mail.However, from way back when I was doing physics experiments in secondary school,I remember that the amount of charge a material could conduct or carry was influenced by the diameter of the conducting material, suggesting that the current flowed not only on the outside surface of the wire, but also through it's core. I am confused. Is it just that wires with bigger diameters have a larger surface area? Anyone have any thoughts? | [
"Actually, most wire that is stranded is that way for flexibility, not to work against skin effect. Because the strands are uninsulated and touching each other, the current always stays in the outermost strands at high frequency, conducting from strand-to-strand as those strands move towards the center of the bund... | [
"Actually, most wire that is stranded is that way for flexibility, not to work against skin effect. Because the strands are uninsulated and touching each other, the current always stays in the outermost strands at high frequency, conducting from strand-to-strand as those strands move towards the center of the bund... | [
"Correct. Also, it should be noted that DC currents are not effected by skin effect, and do use the entirety of the wire(s). "
] |
[
"Which combinations of foods give you gas?"
] | [
false
] | Please, lets avoid combinations which you don't even sound appetizing together so you would not even eat it. Like asparagus and cottage cheese for example. | [
"http://en.m.wikipedia.org/wiki/Flatulence#section_1",
" says that farts are mostly nitrogen & CO2 - I assume the nitrogen is from the air, and the CO2 is what's left after respiration. The other gases are Methane & Hydrogen. From my basic chemistry knowledge, I know that Hydrogen comes from a reaction between an... | [
"Actually, farts (at least a percentage) come from bacteria in your intestines."
] | [
"Derp. Slipped my mind. Thank you!"
] |
[
"Could \"dark energy\" be proof that the universe has negative curvature?"
] | [
false
] | null | [
"His is a bit of a confusing explanation with the \"total energy\" thing; what he means is that ",
", that is fixing the value of the Hubble constant, there is a critical value of the energy density that makes the Universe spatially flat. ",
"What we measure is that summing the energy contributions (matter and ... | [
"Wow, my brain feels like a buzzing beehive of questions right now, but most of them I'll probably have to save for other posts.",
"That dark energy is already accounted for makes sense now, but how does energy balance translate to a spatial geometry, moreover a flat one? Insofar as one could plug a resultant \"z... | [
"Wow, my brain feels like a buzzing beehive of questions right now, but most of them I'll probably have to save for other posts.",
"That dark energy is already accounted for makes sense now, but how does energy balance translate to a spatial geometry, moreover a flat one? Insofar as one could plug a resultant \"z... |
[
"Why don't objects thousands of light years in size appear distorted?"
] | [
false
] | null | [
"No one answered, so looked into it, did some rough estimations. ",
"Closest side of Andromeda to earth, ~2.5million Light years\nDiameter of Andromeda, ~100,000 light years\nOff angle of Andromeda, ~154.29°",
"Using these estimations, \nthe further side of the galaxy is ~2.59 million LY away. ",
"If a galaxy... | [
"No one answered, so looked into it, did some rough estimations. ",
"Closest side of Andromeda to earth, ~2.5million Light years\nDiameter of Andromeda, ~100,000 light years\nOff angle of Andromeda, ~154.29°",
"Using these estimations, \nthe further side of the galaxy is ~2.59 million LY away. ",
"If a galaxy... | [
"No one answered, so looked into it, did some rough estimations. ",
"Closest side of Andromeda to earth, ~2.5million Light years\nDiameter of Andromeda, ~100,000 light years\nOff angle of Andromeda, ~154.29°",
"Using these estimations, \nthe further side of the galaxy is ~2.59 million LY away. ",
"If a galaxy... |
[
"Why can't we see all matter in the universe?"
] | [
false
] | null | [
"You said it yourself:",
"we can not see the light from the edges of the universe because the light has not reached us yet",
"How could we possibly see matter if the light from that very same matter hasn't reached us yet? The universe is likely infinite, so we expect there to be plenty of matter far beyond our ... | [
"I was saying we should be able to see all matter even if we see it in a previous state what it is in real time."
] | [
"If all matter was connected at one point, then the light would have started to emit from it as soon as the explosion occurred, and assuming nothing can move faster than the speed of light we should see all matter."
] |
[
"Can astronomers see further back in time than Hubble eXtreme Deep Field?"
] | [
false
] | [deleted] | [
"Yes. We can see back to the cosmic microwave background. That's about 380.000 years after the beginning of the big bang. There's an argument that you could look back even further by looking at the neutrinos from the early universe, but that's far beyond our technology"
] | [
"With galaxies, sometimes but the XDF is definitely the biggest sample of extremely-distant galaxies we have. Beyond that, we can see the ",
"cosmic microwave background",
", light which has been travelling nearly unimpeded since 380,000 years after the Big Bang. That's the earliest light we'll ever be able to ... | [
"Main problem with neutrinos is that they so reluctantly react with matter.",
"http://en.reddit.com/r/askscience/comments/1ov09y/if_i_put_a_camera_in_a_completely_dark_room_and/ccw6a4i",
"a light-year of solid lead [...] would stop about half of them"
] |
[
"Does it become more difficult to increase the temperature of a substance the hotter it gets?"
] | [
false
] | null | [
"Couple reasons, at higher temperatures, the heat capacity for many substances from ",
"solids",
" to ",
"gases",
" gain access to more ways to soak up energy, for instance a gas molecule might start being able to use another vibrational mode.",
"The other reason and perhaps more important one when dealin... | [
"There are two things to consider: how much energy it takes to raise the temperature of an object (heat capacity), and how fast you can get energy into the object (heat transfer rate). ",
"Heat capacities do change with temperature, but for many substances the change isn't big and you can assume it's constant. ",... | [
"Ideally NO. However many things as they get hot, like gasses at very high temperatures start resonating. (the components of the gas particles start resonating against each other). The heat energy goes into these intra-particle resonances, which means the temperature does not rise as quickly as before. ",
"So as ... |
[
"Could an atomic bomb be destroyed with some type of non atomic bomb, such as dynamite, and not detonate the atomic bomb in the process?"
] | [
false
] | null | [
"Easily. Indeed if a nuclear bomb is fully armed with all safeties removed it would still be almost impossible for an outside explosion to cause a proper nuclear detonation.",
"All known current nuclear weapons use chemical explosives to compress a subcritical mass of plutonium or uranium, the increased density t... | [
"Yes.",
"Modern weapons are designed to be ",
"one-point safe",
". So if you set off a conventional high explosive charge near a nuclear weapon and the resulting shockwave initiates the high explosive in the nuclear weapon, the system remains subcritical, or if it momentarily becomes supercritical, it doesn't... | [
"And this has actually happened. Multiple times.",
"The US, during the cold war, had nuclear bombers in the air at all times to be ready to respond to a first strike. Because this meant incredibly long shifts for bomber crews, there were several accidents with dropped nuclear payloads, and in 1966, a nuclear arme... |
[
"Can 2 massless particles occupy the same space at the same time?"
] | [
false
] | I can speculate that there are some physical forces that may prevent or at least make this possibility unlikely but I'm not exactly sure which ones as I am merely an interested layman. Thank you for any responses even if they cannot explicitly answer or any good sources of information on massless particles. | [
"Yes, so can two massive particles if they have an integer spin."
] | [
"To be clear, lasers do not need to occupy the same point in space-time, but the photons in lasers can occupy the same point in space-time. This is the current theory, but some people still debate that."
] | [
"The only massless particles which (AFAIK) have been shown to exist are photons.",
"FYI, there is plenty of evidence both for the existance and masslessness (or at least near-masslessness) of gluons. The Wikipedia article seems to suggest that this evidence has met the 5-sigma standard to claim gluons as discove... |
[
"Is it possible that a man would be unable to produce offspring of a certain gender?"
] | [
false
] | As I understand it, the gender chromosome is decided by the man, because the woman passes on an X chromosome and the man passes on an X or a Y. What I'm asking is would it be possible that a man's sperm only transmits a specific chromosome, forcing all of his offspring to be the same gender? | [
"Generally people with trisomy of the sex chromosomes aren't fertile (or at least have a very hard time reproducing). If they do reproduce, they would be able to pass on the extra chromosome.",
"An extra X chromosome would have some similar effects to trisomy-21. In XX females, one of the X chromosomes is inact... | [
"Generally people with trisomy of the sex chromosomes aren't fertile (or at least have a very hard time reproducing). If they do reproduce, they would be able to pass on the extra chromosome.",
"An extra X chromosome would have some similar effects to trisomy-21. In XX females, one of the X chromosomes is inact... | [
"Turner Syndrome is 45X, not 47XXX. Individuals with Turner Syndrome do have cognitive issues, most individuals with a 47XXX karyotype never find out about it, because there is no real phenotype associated with it."
] |
[
"AskScience AMA Series: I'm Seth Shostak, Senior Astronomer at the SETI Institute and host of Big Picture Science, and I'm looking for aliens. AMA!"
] | [
false
] | For nearly 60 years, scientists have been using sophisticated technology to find proof of cosmic companions. So far, they've not turned up any indications that anyone is out there. What, if anything, does that mean? And what are the chances that we will trip across some other galactic inhabitants soon... or ever? I will be on to answer your questions at 11am (PT, 2 PM ET, 18 UT). AMA! Links: EDIT: Please note the corrected time at which our guest will be joining us. | [
"Is there a standard protocol globally on what to do if a serious candidate signal is found, who to contact first etc.?"
] | [
"You saying that when the aliens finally text us back, we leave them on read? That's an alpha move right there"
] | [
"There is a protocol ... two versions, discussed and approved at the International Academy of Astronautics. But in fact, it simply says to check the signal, tell everyone, and restrain from a reply until the world is on-board."
] |
[
"Thousands of meters under the ocean the pressure is extreme; does that mean that small movements produce extreme friction and extreme heat?"
] | [
false
] | null | [
"The viscosity of water doesn't change much with pressure",
", so there isn't much difference in friction between the surface and extreme depths."
] | [
"No. Pressure comes from all sides pretty much equally, so it \"balances out\". It's not like moving in one direction you have to \"fight against the pressure\", because the same pressure is backing you up from behind."
] | [
"I'm using the word \"friction\"---in a very loose way---because that's how the OP phrased it, but it isn't really friction in the sense of two solids in contact. The correct terminology is drag, which will be influenced in large part by fluid viscosity. Sorry for any misunderstanding."
] |
[
"\"A Kugelblitz is a concentration of light so intense that it forms an event horizon\" from Wiki. Light is made up of photons and photons do not have mass. How can a massless energy form a black hole?"
] | [
false
] | null | [
"Any individual photon is massless, but a system of photons can easily be massive. To demonstrate for two photons traveling in opposite directions, ",
"m",
" = E",
" - p",
" = 4p",
"p",
" ",
"If some system has rest mass, we can describe the gravitational curvature of that system. If you have an eye... | [
"Special relativistic mathematics isn't additive, weird right? Think of it more like a triangle, the energy side and momentum side form a hypotenuse called mass. So even if systems of photons are massive, each individual photon is still perfectly massless. "
] | [
"Maybe thinking of it in these terms will help:",
"The definition of rest mass for any ",
" of particles is: the sum of all the energies of the system's constituent parts (divided by c",
"), in the system's center-of-momentum frame.",
"If you have a system made up of, say, 2 photons moving in different dir... |
[
"What is the protection status for the Russian Sputnik and the Cuban Vaccine compared to moderna, Pfizer, Johnson and astrazeneca?"
] | [
false
] | I can't seem to find statistics and comparable numbers. | [
"You could compare the efficacy number, but it's important to know ",
"what it means",
".",
"A vaccine’s efficacy is measured in a controlled clinical trial and is based on how many people who got vaccinated developed the ‘outcome of interest’ (usually disease) compared with how many people who got the placeb... | [
"Sputnik seems to be highly efficient. Studies state efficacies of 70-80% for one dose and over 90% for two doses against asymptomatic infections. \nSource: ",
"https://www.nature.com/articles/d41586-021-01813-2",
"But it's definitely everything other than trivial to compare the efficiency of the different vacc... | [
"One of the downsides of the adenovirus based vaccines (jnj/azn) is that your body tends to get good at attacking other aspects of the adenovirus after exposure. Not necessarily the spike proteins they put on it. There's a lot of history with humans and that virus. So we are quite adapted to fight it. It would prob... |
[
"Do they need to replenish air on the ISS?"
] | [
false
] | It seems like they'd lose a little air with each spacewalk and shuttle docking/undocking. Do shuttles replenish the air along with supplies, or do they vacuum out chambers before exposing them to space? Or is the amount lost so negligible that it hasn't been an issue yet? | [
"They probably do, but I would think that the oxygen that is used up by the people on board would be much more than any lost through docking etc.",
"Here's",
" a link about how they make oxygen on the ISS"
] | [
"do they vacuum out chambers before exposing them to space",
"It's worth noting that if they didn't vacuum chambers before opening them to space, it would be a rather rude surprise to anyone in the chamber. The sudden uncontrolled decompression would launch anyone or anything not bolted down into space, as the ai... | [
"Thanks, this is the answer I was looking for. Any sort of a source for this?",
"EDIT: On further review, it seems this isn't quite true:\n",
"http://www.boeing.com/defense-space/space/spacestation/components/joint_airlock.html",
"\n\"Before spacewalkers open its hatch to the vacuum of space, the Crew Lock is... |
[
"Hypothetically, could anaphylactic shock be treated by sending the victim bungee-jumping or other adrenaline-inducing experience?"
] | [
false
] | Here's what I'm thinking: * EpiPen's active ingredient is adrenaline * the body produces adrenaline naturally during exciting experiences * so when lacking medical adrenaline, could inducing the body to produce it be better than doing nothing? However: * nearly dying would surely induce adrenaline anyway? | [
"Another question: Wouldn't the fact that you probably think your dying during anaphylactic shock cause you to pump out adrenaline anyway? Why doesn't this solve its own problem?"
] | [
"So following people with peanut allergies around with a loaded handgun is now considered not helpful? What a world..."
] | [
"So following people with peanut allergies around with a loaded handgun is now considered not helpful? What a world..."
] |
[
"How can astronomers figure out the \"day\" length on a gas planet?"
] | [
false
] | It's easy to determine the day length on a rocky planet or celestial body with thin/no atmosphere, but how can you determine the rotation period in a planet where there's no ground? The speed of the gas should not be taken as refference (I'm guessing), since the gas may be rotating at different speeds on various locations of the planet. Bonus: How could astronomers figure out Titan and Venus? Both have pretty thick and opaque atmospheres, so I'm guessing some other light frequencies, like infrared maybe? | [
"A good example here is Jupiter, because each atmospheric band rotates at a slightly different speed to another - this is called differential rotation. Jupiter's polar regions rotate about 5 minutes slower than it's equator, at 9h 55m, while it's equator takes 9h 50m. The official speed of rotation of Jupiter is me... | [
"keep in mind how slow it already rotated.",
"think of it as a percent change. it isnt 6.5 minutes on 24 hours. it is 6.5 minutes on 243 days (the length of the venus day). that is only 0.00186% difference. Likely measurement error. It is extrememly hard to measure with that kind of accuracy. It could also had ju... | [
"Wow, 6.5 minutes? How can a planet's rotation slow down that much in a short period of time?"
] |
[
"Why is it, that when you put your finger close to a small, unfocused light-source, it appears to block the light out from the opposite side?"
] | [
false
] | See for a crudely drawn example. I notice this when I look at my alarm clock at night or a small speck of light coming from a window curtain. It's like the shadow starts from the opposite side and merges with your finger and I don't get why that happens. | [
"I just posted this elsewhere:",
"Short answer, optics.",
"It is somewhat hard to explain in words, but easy to understand in concept. ",
"So, I drew you a picture.",
"http://i.imgur.com/A0B8n.jpg",
"Ok:",
"As you move the finger down towards the top of the arrow, light is blocked starting from lower on... | [
"This doesn't actually explain the phenomenon. All this explains is why images are inverted on our retina."
] | [
"I suggest you look at it again. It explains why the object is blocked from the far side as opposed to the close side when you start blocking it as well as why images are inverted.",
"Anyways:",
"Imagine you move your blurry finger towards the blurry arrow from the top. Naturally, you will block light from the ... |
[
"Why do we hear about an increase of conditions like ADHD and allergies in children now?"
] | [
false
] | 10 to 20 years ago, you wouldn't have heard much about ADHD or Ritolin, or about peanut allergies, or gluten allergies, and the like. I agree that there would be cases here and there, but now it is so commonplace that it is a fact of life that someone you know has ADHD or an allergy of some kind. Is this simply because of increased education and knowledge? Or have both been overdiagnosed or minor cases being shoved under the same umbrella? | [
"As the texts define conditions and diagnostic test become availble it is more readily diagnosed. Also since there is a lag between scientific research and even the best field physician there is typically a corresponding lag in diagnosis and treatment for 'new' disorders/diseases."
] | [
"How about something like peanut allergies? I have known of the existence of such allergies before the 90s/00s, but it's only in recent years that it has become such a contemporary issue. Has there really been an explosion of peanut allergy cases (and quite notably in children), or are we now just more sympathetic ... | [
"Honestly that may have to due with 'defective' or normally disaventageous genes being passed on and concentrated within our population due to modern interventions."
] |
[
"Is nuclear power cost-effective or efficient?"
] | [
false
] | Most debates on the viability of nuclear power seem to focus on safety and carbon-emission issues. However, I’ve heard some argue that when you add up all the energy it takes to maintain a nuclear plant (i.e. costs of building, running and eventually decommissioning the plant, and the costs of mining the fuel and disposing of the waste) and weigh that expended energy against the total energy over the life of an average nuclear plant, the net output is minimal when compared to other more abundant power sources. Is there any truth to this? | [
"Hopefully we'll find a way to store it in the atmosphere like coal."
] | [
"Hopefully we'll find a way to store it in the atmosphere like coal."
] | [
"First thing to think about, is big fleets like exelon are running their plants at big profits. ",
"Second thing to recognize, is the majority of a plant's costs are for the staff on site. Fuel and capital make up less than 20% of the yearly budget. This makes it beneficial to keep the plant online even if they a... |
[
"When someone increases their flexibility (via stretching/yoga/exercise), what is actually happening at a molecular level?"
] | [
false
] | null | [
"I'd like to add to this by saying that it is (most likely, but maybe someone can back me up) also due to material changes taking place in your connective tissue. Your tendons, ligaments, and a lot of the muscle tissue that surrounds the sarcomeres are made up of collagen, which is a string-like fibrous molecule. I... | [
"Flexibility is increased by reducing the reflexive muscle tension that occurs when a joint is flexed past a certain point. For example, there is no connection travelling across your groin that prevents you from doing the splits. It's muscle tension in each leg that automatically kicks in. This means that increasin... | [
"Thought experiment: Suppose we take a very inflexible person and chop off their head (or whatever part of the body is responsible for producing the reflexive muscle tension). Would this person now be able to do the splits without damaging the muscles and ligaments involved?"
] |
[
"How could I figure out the distance a projectile (flying upwards at high speed) is from the surface of a planet, while taking into consideration that gravity weakens as it gets higher?"
] | [
false
] | [deleted] | [
"You're seriously overthinking this. If you know the initial velocity, you know the initial kinetic energy. If you know the current velocity, you know the current kinetic energy. Any difference between the two must be what's gained in gravitational potential, which you can then plug into the formula to solve for al... | [
"Getting the max height is straightforward:",
"Work out the initial kinetic energy of the object ( 1/2 m v",
" ) ",
"Work out the current gravitational potential energy of the object (-G M m / r ) ",
"Add the two energies, and then solve for the new r",
"M is the Earth's mass, m is the object's mass.",
... | [
"I couldn't think of a simple analytical solution, and my guess is there isn't one. I would break it down into a problem that can be solved numerically without too much trouble:",
"http://i.imgur.com/q4VVEMA.png",
"EDIT: I screwed up the derivative... here's something a bit better: ",
"http://i.imgur.com/whKu... |
[
"Who would live longer without food: a 200 lbs overweight man or a 170 lbs normal weight man carrying 30 lbs of lard to consume."
] | [
false
] | null | [
"I imagine it would be close, but factors to take into consideration would be, ",
"200lb guy would burn more calories a day on average, although most of his digestive system would shut down due to lack of food intake, this would drastically reduce the amount of calories he needs per day.",
"The 170lb guy would ... | [
"There's more to survival than just calorie intake; vitamins play a huge role as well. A human can go about a month just on their own body fat, but if they supplement that with vitamins they can go a whole year. It would be important to examine what vitamins are contained in lard to make a good guess as to who woul... | [
"There are many variables at play here so it's not too easy. The main variable why I would bet ",
" the fat guy is the efficiency.",
"\nFor instance, there are (male) ultra runners that need only ~700kcal per day (laying on a couch).",
"\nFeel free to do the math yourself with a few assumptions on these varia... |
[
"Why are the most common DC voltages for ICs and other electrical components 3.3v and 5v? Why not 4.4, or 6, or 7v?"
] | [
false
] | null | [
"It's a rather boring answer, currently it is because these voltages are easily available, and very safe. However the reason they are availible is very interesting! ",
"The reason historically that 5V and 3.3V are so important is due to the Logic levels used within circuit types.",
"Long ago, when logic circu... | [
"MOSFETs aren't different from CMOS. CMOS is made with MOSFETs"
] | [
"Now few circuits ever use either 3.3 or 5V to drive logic, however these are often the supply as USB is everywhere.",
"Well, a lot of microcontrollers still use 3.3 or 5V especially for communication I think. You might not find these voltages inside of CPU often but there are many machines that value compatibili... |
[
"Why do antibiotics mess with birth control pills?"
] | [
false
] | If possible, I would prefer both the long complicated explanation and the simpler version, just so I can be sure I understand everything. | [
"CYA = cover your arse...same thing for most pharmacists...we will inform you you should probably use back up while on the birth control although we all know that the potential for it to be changed by the majority of antibiotics is highly unlikely..liability...and some just have not seen the data that most birth co... | [
"This is actually not the case, and is only true with a few antimicrobial agents.",
"Pharmacokinetic evidence demonstrates that ",
", including ampicillin, ciprofloxacin, clarithromycin, doxycycline, metronidazole, ofloxacin, roxithromycin, temafloxacin, and tetracycline. However, reduced steroid levels have be... | [
"Pharmacist here: The traditional mechanism of interaction for OCPs and antibiotics is not actually a CYP interaction. For example, the typical interaction (based on a few cases) is with amoxicillin, which has no effect on your CYPs. Also if that was the case, would Biaxin give you like super contraceptive control?... |
[
"Is there a theoretic limit to how small hidden cameras can get?"
] | [
false
] | A comment on another thread said that in the near future there could be hidden cameras 1/1000th the size of a grain of rice recording people. Is it actually possible (not with todays technology but in theory) for a camera that size to record people in reasonably high resolution. | [
"One limiting factor would be the size of the optics. The angular/spatial resolution of an imaging device depends on the diameter of its aperture. The smaller the diameter the lower the resolution. Assuming you are imaging in visible light, at the size you mentioned, the spatial resolution of your camera at 2 meter... | [
"Couldn't storage be connected to remotely? Some form of wireless connections."
] | [
"Another thing limited by the size of the optics is, pretty intuitively, the amount of light gathered. An extremely small sensor would either need a long exposure to form a reasonable image, have a low resolution so individual \"pixels\" (sensor elements) would be larger, or settle for extremely noisy images - at s... |
[
"Do all species of mammals produce identical twins?"
] | [
false
] | null | [
"Probably, but we don't really know because we haven't really checked. Articles below may be helpful:",
"\n",
"http://www.bbc.com/earth/story/20160830-first-identical-twin-dogs-discovered",
"\n",
"https://medicine.yale.edu/obgyn/kliman/placenta/twins/",
"Still, although it's likely that most/all mammals p... | [
"\"Multiple births\" or multiple young in a litter are technically instances of fraternal twins, that is, each offspring is from a separate egg + sperm combination with all the offspring conceived during the same birth. So, we can say that fraternal twins (multiple young) are more common than identical twins among ... | [
"Why would this be true for identical twins more than fraternal twins? I ask because in most other mammals multiple births seems to be completely normal."
] |
[
"Do animals have dominant sides?"
] | [
false
] | [deleted] | [
"Yes, sometimes they do. It's often referred to as laterality.\nJust a few examples:",
"From hand to mouth in the evolution of language: The influence of vocal behavior on lateralized hand use in manual gestures by chimpanzees (",
")",
"We report evidence that chimpanzees exhibit preferential use of the right... | [
"Apparently No. Even animals closest to humans like primates/great apes don’t seem to show a similar motor asymmetry, except in captivity when they tend to mimic their captors. There's an interesting article by Corballis about this subject called 'From mouth to hand', but basically humans developed an asymmetry at ... | [
"Horses usually have a dominant side with regard to asymmetrical gaits (canter and gallop). A horse will find it easier to start those gaits on its dominant side, and also has an easier time curving its spine toward that side (sometimes described as the hollow side). Dressage trainers spend a lot of time working on... |
[
"How far are we from being able to design and engineer new proteins?"
] | [
false
] | The thought that led me to this question is in regards to the enzyme rubisco. If we were to develop a replacement for the enzyme that was better optimized for today's atmospheric conditions (rather than the high CO2, low O2 environments it evolved in), it's my guess that it would vastly improve agricultural efficiency. Can we do anything like this yet/how would we make this happen? | [
"We already do engineer proteins. In fact, my lab is one of the labs that does protein engineering, although not of rubisco. There are other labs that engineer proteins, but it is far from a solved problem. At this point it's more of an art form than a true engineering discipline with formalized rules of design ... | [
"Simply put, we can and we do. One way that I know of how it is done is that the DNA coding for a protein, say rubisco, is put into a environment, but with many also possible base changing conditions. Thus, we form a lot of mutations, and then filter the mutations based on whether they perform what we want the ne... | [
"Sorry I don't really have the time right now to reply, but jzmddf15314 is spot on!!",
"We are just starting to rational design proteins for designer function, but we don't really understand basic things such as how proteins fold and something really basic to do with water (forget what it is) which relates to fol... |
[
"How do doctors prevent things like bedsores and pneumonia and other medical problems related to an extended stay in a hospital in a comatose person?"
] | [
false
] | [deleted] | [
"nurses are tasked with shifting a comatose patient's weight in bed regularly (every 2 hrs at least) to avoid development of pressure ulcers. if a person is in a coma and on a ventilator to assist with breathing, they may get ventilator-associated pneumonia (VAP). comatose people usually have a feeding tube of some... | [
"As answered below, they can be moved by nurses regularly. However for those who can't move in the long term, they usually have beds that shift the pressure around. If you can imagine a mattress full of beanbag beans, with air pumped into the mattress, they can shift the air pressure and with the design of the be... | [
"why is it they don't get pneumonia or bedsores?",
"They do. Quite a bit more than folks who are not in their condition. Stasis/Pressure ulcers and poor clearance of debris from the airways are thought to be the reasons.",
"The first means of prevention is vigilance in daily care-- special equipment, turning p... |
[
"Why aren't absorption spectra canceled out by emission spectra?"
] | [
false
] | As far as I understand, when atoms lose energy, they emit light. Because this energy is quantized, atoms only emit a few very specific frequencies as the electrons drop from different energy levels. For example, as a hydrogen electron drops from n3 to n2, it releases a photon producing light with a wavelength of 6.57*10 Therefore, hydrogen atoms, when losing energy, emit a few wavelengths of light that create a recognizable spectrum. Absorption spectra work the opposite way: atoms absorb specific amounts of energy. Hydrogen atoms the same wavelengths that they Absorption spectra can be used to identify elements. How is that possible? If you shine a light at a cloud of hydrogen gas, it will absorb its characteristic frequencies and let the rest through, causing the absorption spectrum--but doesn't it then emit those same frequencies, filling in the black gaps and leaving a full spectrum? | [
"There are a few reasons that emission spectra don't mask absorption spectra:",
"Absorption only happens in one direction. Emission happens in all directions. Absorption is detected when the sample is on the line between the light source and the detector. Emission, on the other hand, involves light getting spi... | [
"The radiation that is re-emitted is emitted at a random angle. If your light is coming from a particular direction, that means a relative loss of intensity. "
] | [
"Emission energy is usually less than absorption energy.",
"For more, see ",
"Stokes shift",
"."
] |
[
"Do computer chips have fault tolerance?"
] | [
false
] | As I understand it , many IC chips are collections of transistors. In the case of CPU's which have 10's to 100's if millions of them, If 1 transistor fails can it still work? | [
"No, generally CPUs are not designed for transistor failure, the cost of doing this would be way higher than just designing for a low failure rate and throwing out chips that do have issues. The probability of a single transistor failure is very very low, and the rate of failure in an entire chip (with billions of ... | [
"Yup. It's is called processor yield. The biggest contributing factor is the size of the actual die (usually measured in mm",
" ). The larger the die, the more likely that a flaw will be present.",
"The process of disabling sections is especially prevalent with graphics cards which can have hundreds of processi... | [
"Depends on how complex chip and what transistor died. CPU may still perform all of it's operations except one. If it's rarely or never used operation then you won't notice. Simple logic chips often have several independent modules. If one dies, others still work fine."
] |
[
"Pregnancy 24h (or more) after ovulation?"
] | [
false
] | Hey, I've read some articles about getting pregnant and most of them are saying that getting pregnant 24h or more after ovulation are nil, but why aren't they exactly 0%? If ovulation egg dies my logic suggests me that it's impossible to get pregnant. Apart from shifting ovulation and irregular cycles, why isn't it 0%? | [
"The human estrous cycle lasts roughly 28 days (of course, like everything else about the human body, that can vary for all sorts of reasons). It's split into two parts, each which lasts about 14 days. The ",
" is basically when the ovaries make the egg. The ovarian follicle releases an egg. It then becomes what'... | [
"Ok, so time is being increased to let's say 48h if two eggs would be released, but my question was if after 5 days there is 0% of pregnancy? Im confused because it sounds like woman can get pregnant even after few days after ovulation."
] | [
"You can certainly get pregnant a few days after you *thought* ovulation occurred. There's a reason they sell those predictor kits: because it's hard to know exactly when it happened.",
"",
"Anecdotally, you can sort of tell by watching for a spike in horniness (as well as things like mucus.) But you can't c... |
[
"Can anyone tell me what language this is if it even is a language? (link in comments)"
] | [
false
] | null | [
"/r/linguistics",
" might be able to tell you."
] | [
"It's almost certainly Syriac or, perhaps, Nabataean."
] | [
"Im fairly certain that it is not arabic but urdu. At least that is what my friend from saudi arabia believes. unfortunately i have no one to reference for urdu exactly but arabic and urdu are similar. ",
"you can see if it compares ",
"http://en.wikipedia.org/wiki/Urdu"
] |
[
"Is the speed of light an arbitrary constant or is there a reason why it is what it is?"
] | [
false
] | null | [
"The value for the speed of light is not a fundamentally meaningful physical thing. By this I mean the fact that it has a value is a result of humans giving it a value, and there's no real sense in which it ",
" to have a value as far as the universe is concerned.",
"The reason the speed of light has a value is... | [
"That's rather circular; the permeability of free space is generally defined to be the constant that makes Maxwell's equations work in terms of the speed of light. That is, it's defined in term of the ",
"."
] | [
"I think when people say the speed of light was slower a better way of phrasing the question would be what would the universe look like if we travelled at larger fractions of the speed of light, which is a relevant question. "
] |
[
"Can someone explain how gas chromatography works?"
] | [
false
] | I need to understand how the actual process works for a college paper (I study archaelogy) but I'm having a hard time figuring it out with only a highschool chemistry background. Can any kind souls explain how it works, or link me to any good sources on the subject? | [
"In essence any chromatography is separating compounds into their constituent elements, and gas is just another way to do that. Chromatography uses mobile and stationary phases, with the mobile phase in gas chromatography being typically an inert gas like helium or argon, and this carries the sample to the detector... | [
"Why do we call it chromatography then?",
"It's called that because the earliest separations of this kind of technique, the results were shown as coloured bands. It's a historical naming convention.",
"I also read somewhere that for the type of result im looking for they use a FID detector for organic compounds... | [
"GC (and other chromatography methods like HPLC) separate mixtures into individual compounds through the fact that they pass through different stuff at different speeds because they interact differently with the 'stuff'. With HPLC the 'stuff' in question is a gel, with GC it's the inside of the wall of a tube. ",
... |
[
"What is the gold-colored wrapping on spacecraft and rover wiring?"
] | [
false
] | What is the gold wrapping on the wiring on Curiosity? Is it different from other, similarly colored coverings used on other spacecraft and rovers? | [
"https://en.wikipedia.org/wiki/Kapton",
"It's a lightweight insulator that keeps it's properties over large temperature ranges and doesn't have problems with outgassing in vacuums.",
"Here's some on Amazon",
"http://www.amazon.com/Gold-Kapton-Tape-Polyimide-36yds/dp/B0049KTIAU"
] | [
"Kapton is love, kapton is life. It's seriously the duct tape of space. You wouldn't believe how many things we use it for our experiments. Ours even comes with ESA certified print."
] | [
"They have a similar function as the other reflective coatings: reflect radiation. I'm pretty sure those are a metalized polyamide or polyester film.",
"See this page for product details and a video that suggests this is the insulation in question: ",
"http://www.dunmore.com/products/multi-layer-films.html"
] |
[
"Does running the car's A/C at 65F require less power than running it at 60F?"
] | [
false
] | Or when I set the A/C at a higher temperature it just means that the cold air from the A/C is mixed with hot air from the outside? | [
"It depends on the system in your car.",
"In some cars, the dial sets the temperature of the air blowing at you. The A/C compressor runs the whole time, cooling one air stream as much as it can. That cool air gets mixed with a certain percentage of warm air, which you get \"free\" from the heat of the engine, so ... | [
"That is true if you're calculating the minimum required energy in physical terms. It's not necessarily the same as how much energy the car actually expends to do it.",
"A car may waste energy by design, cooling air too much, and then bringing it to the right temperature by mixing in hot air from the heater core.... | [
"That is true if you're calculating the minimum required energy in physical terms. It's not necessarily the same as how much energy the car actually expends to do it.",
"A car may waste energy by design, cooling air too much, and then bringing it to the right temperature by mixing in hot air from the heater core.... |
[
"Statistics - How do you reconcile number of votes vs voting percentages?"
] | [
false
] | This is something i've thought about for a bit and have been unable to reconcile in my mind how it works. I've taken statistics classes in the past and I know some statistical mathematics, but it's not something i'm excessively knowledgeable about. My question is best framed with a scenario. Let's assume i run an online shopping site, or some contest or anything that is run by community driven votes. Say, for example, in my shop, I have categories people can rate the product on, 1-5, and one of these categories happens to be "fun". So now let's say, at some point, I want to list all of my widgets by 'fun', highest rated fun to lowest rated. When I pull together my list of data, let's say I have Widget A which has 1000 votes, 750 of which are 5-star fun votes Now let's say I also have Widget B which has 500 votes, all of which are 5 star fun votes. What's the proper way to tell which is "most fun" of these two widgets? Widget B obviously has a full 5-star 'fun' rating, but Widget A has more ratings than Widget B that are 5-star, but it's average might be something like 4.5 stars or something. Is it Widget A because its percentage of fun is 100%? This scenario doesn't seem right to me because where's the cut-off? If i have Widget C that has 3 votes, all 5-star, this one probably shouldn't be rated higher than Widget B, so why should Widget A? Is it Widget B because it has more high-rating votes? This scenario doesn't feel right to me either because having a 4.5 star 'fun' widget rated above a 5-star fun widget seems wrong too. | [
"Honestly it depends on what you're trying to capture. There isn't a right way to make this decision in every scenario. There are a few instances in which we can say something, so let's focus on them, and then try to figure out possible ways to make the decision you're trying to make.",
"Suppose Widget A has 100 ... | [
"The simplest answer is that Widget B is the \"most fun\".",
"This is because in the case of Widget A, you can say with high confidence that it is rated \"most fun\" 75% of the time. By the ",
"law of large numbers",
", this rating is probably quite accurate. If you assume for a moment that Widget B has the... | [
"So, essentially, the 'easiest' way is to just normalize everything by percentage and toss out outliers that have a low vote count?"
] |
[
"Does friction exist on a subatomic scale?"
] | [
false
] | As I understand it, friction is the result of electrostatic forces between different objects interacting (electrons and protons attracting and repelling each other). So if you were to take two neutrons and rub them together, would there be any friction? | [
"Friction is a macroscopic effect. There are no meaningful analogs at the atomic or sub-atomic scale. At the atomic scale there are interaction cross-sections and various types of forces somewhat generalized as bonds and weak interactions such as van-der-waals forces and things like fermi-level interactions, cooper... | [
"Well, friction isn't a result of the electrostatic forces themselves. For instance, if a two electrons scatter off each other (due to their repelling charges), no energy is lost to 'friction' in that process. Nor does an electron in an atom lose energy with time (unless it changes states).",
"What we mean by fri... | [
"Those are arrays of 30x30 carbon atoms in a matrix. It is one million times larger than atomic scale, as in there are 1000 atomic surfaces interacting with 1000 other atomic surfaces. Each atom only interacts with a few atoms at a time. The scale occurs over time. Friction needs the persistence of interacting with... |
[
"Does street light affect plant growth?"
] | [
false
] | [deleted] | [
"I did a similar experiment in the 6th grade. We planted several plants in pots and left them in different locations. The four groups were:",
"\n - Sunlight only",
"\n - Artificial light only",
"\n - Sunlight + artificial (your streetlight scenario)",
"\n - no light",
"The sunlight + artificial light gr... | [
"The plant with no light grew an extremely long stem...it kept growing taller in an attempt to emerge from the soil.",
"This made me very sad..."
] | [
"You've got a great question, and a good experimental set up to test it, but you missed one key assumption. Is the light from that street light the same as the light from the sun? It is not. The wavelengths of light emitted from the street light are barely a fraction of the various wavelengths that come from the... |
[
"How do we get tanks filled with just Helium?"
] | [
false
] | Or any type of gas that comes in tanks really | [
"Gases have different boiling points, most of which are far below the freezing point of water. If you cool a sample of gas to the point that all of it liquefies, the different gases can be boiled off one by one. If the gases don't have significantly different boiling points, a process called gas centrifugation ca... | [
"Isn't the helium concentration in the air very low mostly due to it being too light for the earth to keep in its atmosphere? Just like hydrogen?"
] | [
"Right, the concentration in the atmosphere is about 5 ppm, which is evidently the equilibrium established between the out-gassing rate from the earth and the diffusive loss rate into space. Hydrogen is much lower, around 0.5 ppm."
] |
[
"Why do viruses, such as smallpox, chickenpox, and monkeypox, cause random lesions and blisters?"
] | [
false
] | Viruses like smallpox lead to blisters, rashes, and or lesions on the surface of the skin. How does the virus cause this an why do the 'pox' tend to appear randomly on the body. What decides the location of these marks and their density or cluster formation? | [
"For chicken pox, you inhale the varicella zoster virus, and it replicates in your lungs. As your body fights back, T cells come into the tissue and become infected by the virus. These T cells then get reprogrammed by the virus to traffick to hair follicles, where they cause secondary infection, and spread in the s... | [
"To put it short and simple: lesions are caused by your body fighting back or a virus spreading. ",
"There are mechanisms of cells detecting their own malfunction or being detected by the immune system. Viral infection is such a malfunction. Usually, a process called apoptosis kicks in, where infected cells die o... | [
"Wow I did not know varicella zoster had such a complex infection / replication cycle.",
"Username does not check out, since it doesn’t do justice to your ability to drop such a cool knowledge bomb."
] |
[
"How different are brains in \"normal\" people, and their structure, genetics and other things?"
] | [
false
] | [deleted] | [
"This answer to that really depends on the scope that you're looking at. In terms of brain structures and regions (cerebellum, amygdala, etc.), you can safely bet that most healthy people have these structures, the way most healthy people have fingers and a nose. When you zoom in to the actual neural networks and p... | [
"In my experience there is quite a bit more variability than you would otherwise think. A good friend and talented scientist has one cerebral hemisphere twice the size of the other. Another friend who is a mid-size business CEO is missing a temporal pole. Fairly significant alterations in standard brain structures ... | [
"http://www.npr.org/sections/health-shots/2015/03/16/392789753/a-man-s-incomplete-brain-reveals-cerebellum-s-role-in-thought-and-emotion",
"\n",
"http://www.scientificamerican.com/article/strange-but-true-when-half-brain-better-than-whole/",
"\n",
"http://www.iflscience.com/brain/man-tiny-brain-lived-normal... |
[
"How has Earth's diameter changed during it's lifetime?"
] | [
false
] | null | [
"Since the moon-forming impact (the last major addition of mass) it's probably shrunk a little as the interior cooled and condensed, but so far as we can tell there have been no dramatic changes for the last few billion years of good geological record."
] | [
"Due to spin down of the Earths rotation the oblateness will have reduced. So the equatorial radius will have increased and the polar radius increased. Probably not by much."
] | [
"According to a study conducted by NASA, the earth is growing, but by such an insignificant amount that it is not worth mentioning. There are geological changes happening all over the globe such as high-latitude countries like Norway rising in elevation in response to the removal of the weight of Ice Age ice sheet... |
[
"How did National Geographic get these shots from inside a caterpillar? Are they faked?"
] | [
false
] | [deleted] | [
"They are models. \n",
"http://channel.nationalgeographic.com/series/in-the-womb/3708/Overview#tab-Videos/06709_00",
" "
] | [
"I'm in my second year studying Film and Television so I'm no expert, but I'm 90% sure those \"inside the caterpillar\" shots are only well-produced puppetry. ",
"Other than the fact that the larvae look like latex and foam, no camera lens that small could produce such a wide angle of vision and have a large enou... | [
"That is almost as cool as if they had a camera inside the caterpillar...almost."
] |
[
"Does nystagmus (or other conditions) affect the eyes natural frequency?"
] | [
false
] | null | [
"What do you mean by natural frequency of the eye?"
] | [
"Ah, looks like you mean the resonance frequency. That has to do with the material/physical structure of the eye (i.e. a fluid-filled sphere). Nystagmus is characterized by uncontrolled rapid eye movement. I'm not sure what one would have to do with the other."
] | [
"Okay I’m simply a physics student so my understanding and definition may be iffy. But it’s basically that since particles with energy vibrate, and practically everything has them, everything vibrates. The natural frequency of something is the frequency it tends to oscillate at when there’s nothing disturbing it (e... |
[
"Not 100% sure how to word this. In a similar environment to Earth's, in a perfectly equal atmosphere and composition, would life evolve in exactly the same way as ours? How much of it is up to chance?"
] | [
false
] | null | [
"I'm sorry but I need more information. Do you mean a planet striking similar to earth? Or do you mean a copy/paste atom by atom version of the ancient earth, just to see how it happens the second time around?",
"I doubt it much matters because we only have one planet with life on it for our data set. Life cou... | [
"Hmm. Let's say, in this specific question that it's an exact copy/paste version of physical earth. "
] | [
"I doubt we would have an identical set of animals, but you will see some pretty common elements since things like eyes have evolved independently and we have evidence for that.",
"And can I assume that dinosaurs were made extinct at the same time too etc."
] |
[
"Phantom Itches: Why do I sometimes feel a sense of itchiness in one place (ex: abdomen) that can only be relieved by scratching another place (ex: inner elbow)?"
] | [
false
] | This question was brought up today while leading a nature walk with boy scouts. We were talking about the itchiness and duration of mosquito bites on different parts of the body. The conversation moved to itchiness in general. One of the parents said, out of the blue, that she'll sometimes have an itchy spot on her body (example: abdominal area) that can only be satisfied when she scratches another part (example: the bottom of her foot). She described it as a "phantom itch". I believe I have occasionally experienced the same thing, although I can't think of a specific instance at the moment. Anyway, is this a crazy question? What is that called, and why does it happen? | [
"Disclaimer: I'm not an expert.",
"What you're describing in the second paragraph is known as 'referred pain'. The following Wikipedia article has information on referred itch, which is likely what the OP is asking about (although I'm not sure if you're correct in the assumption that you can learn where the stimu... | [
"Disclaimer: I'm not an expert.",
"What you're describing in the second paragraph is known as 'referred pain'. The following Wikipedia article has information on referred itch, which is likely what the OP is asking about (although I'm not sure if you're correct in the assumption that you can learn where the stimu... | [
"Are you trying to tell me I'm not a doctor?",
"No, and I'm not sure why you'd think that I was implying that. I felt as though I was adding to your post for the benefit of the OP and those that may come across this page. I expressed uncertainty about something that you claimed to be fact, and given that you're n... |
[
"What would happen to a black hole and all of the matter it has trapped (theoretically) if it were to encounter another object with a gravity density higher than its own not including other black holes?"
] | [
false
] | null | [
"Thank you for your submission! Unfortunately, your submission has been removed for the following reason(s):",
"For more information regarding this and similar issues, please see our ",
"guidelines.",
"If you disagree with this decision, please send a message to the moderators."
] | [
"I am fine with your first part as I guess it would be speculative and not definitive. This is why I was asking the question in the first place. If we are going that route though Black Holes themselves are speculative and cannot be confidently confirmed with any available data as you have stated for my question so ... | [
"Hi,",
"a few points",
"1) black holes are definitely not speculative. Black holes are proven and sound science. We've had a bit of a black hole denialism epidemic in the last days for reasons that are beyond me, so you might have stumbled upon some weird content in the comment section. But black holes are soli... |
[
"Is glycogen stored randomly throughout the liver or is it pretty much in every liver cell?"
] | [
false
] | [deleted] | [
"This all sounds VERY weird and the experiment should not be associated with glycogen whatsoever. once you put the liver into water, the electrolyte balance is so messed up that it will stop all cell functions. ATP is needed for glycogen breakdown and all ATP production has stopped. there is no way you are measurin... | [
"That’s not the best way of looking at the liver. The functional unit of the liver is the liver acinus of rappaport which are a diamond snapped and connects two central veins and two portal triads. if you imagine a lune between the triads, the hepatocytes (liver cells) closest to this line will be considered in zon... | [
"My initial statement (i was alluding to the zone model when talking about parts approximate to the portal vein) is wrong as i now just realized. Zone 1 includes most oxidative reactions as the blood there is rich in oxygen. Glykogen synthesis not requiring as much oxygen as lets say cholesterol biosythesis or Bet... |
[
"I have well water, people say not to \"waste water\" (mean let the tap run) but is that even possible since the water will collect back in the aquifer?"
] | [
false
] | How long does it take to reach the aquifer if the well is 300 ft deep? Or is it a general reminder as to not get in the habit? | [
"It depends on how may people are using the aquifer and how quickly the aquifer recharges. The time it takes water to percolate down to an aquifer varies quite a lot, from 1 day to 10,000 years, all depends on the soil. Most of the big aquifers in the US recharge between 70 and 700 mm per year, but that's a differe... | [
"Yes, or sometimes never at all. That's called ",
"fossil water",
" (ie analogous to fossil fuels)."
] | [
"Aquifer recharge depends on a great many things. So, how long will it take for water you pour on your lawn to percolate down to your 300ft well? Without coming out to your house and getting a borehole log, it's hard to say. You can have a myriad of well scenarios. Your well could be in the upper, unconfined Aquife... |
[
"How many strains of coronavirusare most likely out there?"
] | [
false
] | null | [
"Not sure why you’re getting such weird answers, but there are 7 main strains of the coronavirus in humans. ",
"The four mundane ones are referred to as “HCoV”, such as HCoV-HKU1. ",
"These strains are constantly present in humans and are known for causing common colds, and very rarely leading to complications.... | [
"When people say there are many strains(1000+), they are mostly referring to small nucleotide shifts(technically a new strain). For reference these shifts are like moving one piece in a 32,000+ piece puzzle.(less than .001% difference) Coronaviruses are relatively stable (for a virus...) In that there will be thous... | [
"No. Meaning recent infection with a human beta coronavirus might lead to resistance to serious symptoms when encountering nCoV-19"
] |
[
"Red blood cell count recovery after donating blood"
] | [
false
] | hey ! The red cross is at my university this week so I decided that I wanted to give blood. I give whenever I can, and I usually give double red. When I tried to give blood today they denied me saying that my red blood cell count wouldn't be high enough yet, and that I am suppose to wait 16 weeks between donations. This seems far too long to me. You're telling me that my body cant recover from an event, which didn't even affect my daily living, in less than 16 weeks?? I'm a pharmaclology student, so I'm pretty familiar with how amazing the human body is, and I find it hard to believe that it would take that long to synthesis new red blood cells. So thats my question, how long does it take for the body to synthesize red blood cells after a donation, or any event actually which would lead to blood loss? | [
"The problem is how fast you can replenish your iron supply to prevent you from getting anaemia after your second or third donation.",
"In the UK, they have just changed the rules from every 16 weeks to every 12 weeks (for ",
" donors only). There is, obviously, a safety factor involved too, so every ten weeks ... | [
"If thats the case couldn't they just check your iron level like they do anyway everytime, to make sure its at an adequate level?"
] | [
"They could, but it would not be sufficient as you have iron deposited around your body, outside the blood. When you give blood, the iron in the blood is replenished from these deposits first, so ",
" are the ones that need stocking up. This means that you can a perfectly good amount of iron in the blood and yet ... |
[
"Does the optical fiber reflect all types of light?"
] | [
false
] | I just finished watching a video demonstration showing a fiber optic cable struck by two types of lasers, one green and one red. The cable transmitted the green light beam without problems, while the red one could not cross it. How does this happen? | [
"I think you mean 550 nm for green light as 650 nm would be a slightly different shade of red."
] | [
"I don't know about the specific experiment you watched, but it is very difficult to reflect all types of light (it's also very difficult to have 100% reflection). Optical fibers can be tailored for specific wavelengths or at least more efficient at certain wavelengths. Since optical fibers reflect light multiple t... | [
"There’s a few different reasons. The simplest one is likely what happened, you may know that different coloured light has different wavelengths, red light has a wavelength of 665 nm while green light is 550 nm. ",
"The diameter of the core of the fibre optic cable can exclude wavelengths of light which are too b... |
[
"Is the mass of virtual particles accounted for in the mass of the galaxies?"
] | [
false
] | As I understand it, virtual particles pop in and out of existence by some probabilistic model. On a small scale, I'd imagine this amounts to nothing,, but on a galactic level, shouldn't there be some quantifiable minimum total mass that they would contribute at all times? And if so, has this been considered as a candidate for dark matter? | [
"Vacuum bubbles (virtual processes involving no real particles and only virtual particles) do contribute to the energy of the vacuum.",
"This is not particularly denser in galaxies than in intergalactic space, and is also unable to get denser or thinner; it's not a real substance that forms a halo on a galaxy lik... | [
"There is no experimental evidence that vacuum energy is/contributing to the gravity cosmological constant. ",
"There is extensive experimental evidence of the equivalence principle which among other things implies the universal coupling of gravity with all forms of energy-momentum, with no possibility of an exce... | [
"Turns out you cannot use that argument for ρ as this rests on Newton's law which in turn comes from Poisson's equation for the potential assuming ρ is fast decreasing. ρ is constant so it crumbles.",
"Using GR, constant energy density makes the Universe slow down in expansion. This is what normal (baryonic or da... |
[
"Why do sharks have small notches in their tail fins?"
] | [
false
] | I'm wondering if it's just a random evolution fluke or something to due with dynamics, or maybe a weird sex thing. | [
"That's a good question, and there doesn't seem to be an answer. That notch is called the subterminal notch, and most elasmobranchs have them, except for most of Batoidea. I would have expected some use for hydrodynamics or flexibility, but I can't find any discussion about its purpose."
] | [
"Flexibility seems pretty spot on for great whites but then theres others that are a bit more asymmetrical. "
] | [
"Asymmetry in general is caused by the fact that sharks don't have swim bladders like bony fish. Asymmetrical tails generate more lift, which sharks need to... not sink. Can't speak to the notch though."
] |
[
"why aren't there animals the size of dinosaurs anymore?"
] | [
false
] | null | [
"The largest known animal to ever live is the Blue Whale, which still exists."
] | [
"Please see this thread - ",
"http://www.reddit.com/r/askscience/comments/spsqi/why_arent_there_larger_land_animals_today_like/"
] | [
"Because it's a lot easier to survive if you can't be seen and can live off less nutrients due to smaller mass."
] |
[
"According to studies alcohol shrinks the brain but alcohol does not in fact kill brain cells. So how does the brain shrink from alcohol?"
] | [
false
] | null | [
"Hi!",
"This study deals with the exact problem you described. (",
"https://pubs.niaaa.nih.gov/publications/arh314/377-388.htm#:~:text=Chronic%20alcohol%20consumption%20leads%20to,of%20neurodegeneration%20and%20brain%20damage.",
")",
"In short; while it's true that alcoholics tend to have a smaller brain si... | [
"I read on Healthline that it's the Wernicke-Korsakoff syndrome which may be caused by a thiamine deficiency which may be caused by heavy drinking rather than the alcohol itself that results in a loss of neurons. Here's the article: ",
"https://www.healthline.com/health/does-alcohol-kill-brain-cells"
] | [
"Interestingly, the study I found fed animals vitamin-rich food to corcumvent this variable. Your argument is correct, but the study seems to have already taken the possibility into account.",
"Edit: I quote: ",
"In most cases, complete vitamin-enriched diets are used to assure that alcohol is the damaging agen... |
[
"Is gold a better blocker of ionising radiation than lead?"
] | [
false
] | It's denser, but is the expense the reason why it is not more commonly used? | [
"The expense is most definitely the reason. Currently the price of lead is hovering around $2/kg. The price of gold is around $54,000/kg.",
"Using ",
"this table of half-value layers",
", you can see that tungsten, which is very close to the density of gold, offers an energy attenuation of gamma radiation app... | [
"Someone with more experience in nuclear physics than I have may correct me on this, but theoretically, gold should be a better shield against ionizing radiation because of its density.",
"Lead shielding is typically in the form of lead bricks stacked around your cyclotron/beam dump/whatever, so you can imagine h... | [
"Mostly the cost and density combination. Most extremly dense materials are extremly expensive (or radioactive) - but not lead."
] |
[
"I've been wondering about orientation in the universe."
] | [
false
] | [deleted] | [
"The universe doesn't have a top or bottom. If you look far enough away, it's pretty much the same in every direction. If you were to pick a universal direction, you could pick the direction of the ",
"cold spot",
" in the cosmic microwave background."
] | [
"Keep in mind that we don't actually have north, east, south, west on earth. They are just ideas, that can exist anywhere. They symbolize direction for us and symbols are completely subjective. This is why the map is upside down in Australia. There is no top or bottom to the earth (nor the universe) , in the same w... | [
"The notions of North, East , etc ... on earth, are only relevant because the earth rotates on itself.",
"Imagine a round sphere in space that is not moving at all. Could you determine where the north pole is on that sphere ? No, because it does not make sense. You could choose randomly a point to be the north po... |
[
"How did engineers on Apollo 11 and similar missions test their code for bugs for the final mission without having to shoot a test rocket into orbit?"
] | [
false
] | Or at least, I very much assume they didn't have the budget for a test rocket, even with the Space Race. | [
"They did test them with manned and unmanned launches. The computers were also hand built and specially designed for their purpose. A crash and subsequent recovery of a computer was almost seamless and it also used a lot of redundancy to make sure they wouldn't fail. ",
"For its era it was very advanced at well d... | [
"We did have test rockets.",
"AS-201 in 1966 - Saturn IB and Block I Command and Service Module (CSM); suborbital to Atlantic Ocean; qualified heat shield to orbital reentry speed.",
"AS-203 in 1966 - Saturn IB test to make sure the engines restarted in space",
"AS-202 - Saturn IB suborbital flight around to... | [
"Great answer.",
"Or at least, I very much assume they didn't have the budget for a test rocket, even with the Space Race.",
"However large you think the Apollo Program's budget was, it was bigger than that."
] |
[
"Does lower revs always mean lower fuel consumption when driving?"
] | [
false
] | Obviously it'll vary from car to car, but in general in any one car if the engine is at lower revs, will I use less fuel? Are there exceptions? I can do 30 in 5th quite happily, will that use less than doing it in 4th or 3rd due to revving slower? What other cost considerations come into play? | [
"Short answer is no. and doing 30 in 5th gear probably isn't the best idea.",
"Keeping in mind that this is not my speciality, and most of my answer is taken from what a few of my mech friends have told me and a quick google search there are a TON of variables in engines that affect efficiency. One of those does ... | [
"You are looking for the sweet spot in terms of volumetric efficiency (at what speed does the engine make the most power for each revolution of the engine), air resistance and drive train friction. If your car has an onboard computer, you can set to instant fuel economy reading and drive the same route at the same ... | [
"If your car doesn't have an onboard computer with fuel economy readings, you can use a vacuum gauge instead - most of them will show the range at which you get the best fuel efficiency. I'm not sure how easy they are to get, but my old car had one fitted by its previous owner and while it wasn't as accurate as an ... |
[
"Can astronauts create artificial gravity by spinning the craft very fast?"
] | [
false
] | Can the spaceships used be made to spin fast enough on the horizontal that it would create an artificial gravity? If so, why have they not tried this? Or maybe they have and I haven't read about it. | [
"The term \"artifical gravity\" is a bit of a misnomer, since it implies we are actually able to create gravitational force. To answer your question though, yes, we can create the perception of gravity through centripetal force. Have you ever ridden ",
"Gravitron-type",
" rides at an amusement park? Its the ... | [
"Never seen ",
"2001: A Space Odyssey",
"? Part of the problem is, we haven't built a spacecraft big enough yet to use artificial gravity without making the astronauts throw up. If you spin it \"very fast\", that's what will happen, so you have to make it big and spin it slowly.",
"Here's a PDF about a Clarke... | [
"Well, I don't know what you mean by spinning a spaceship on the horizontal, but we have known for years that by spinning a spacecraft you can utilize centripedal force to give the feeling of gravity. Imagine a spinning wheel, with astronauts walking around on the inner rim. Check ",
"this link",
" for more inf... |
[
"Does all light have the same speed?"
] | [
false
] | null | [
"I was under the impression that the light still travels at ",
" however ",
" to slow down due to being absorbed and re-emitted?"
] | [
"As far as we know, yes. For an overview of recent tests, see the first three paragraphs of ",
"http://en.wikipedia.org/wiki/Speed_of_light#Propagation_of_light"
] | [
"I say enough theory. This is what is ",
" in nature (please be aware this does not detail the interactions of light inside matter!!):",
"1) Light travels at a speed that depends on the medium it travels in. The parameters that affect the speed in a medium are intrinsic to the medium - the relative permittivi... |
[
"What is the control system for the heart?"
] | [
false
] | I got into a discussion about high blood pressure earlier today and got to thinking, "how does the blood pressure actually rise?" From what I understand, arteries get clogged up from various material and therefore the heart works harder to push the blood throughout the body. But does the heart know to pump harder? I think of the heart as a pump with a constant power input; let's say it pumps cc/cycle. If there is a clog at an outlet, blood would not be able to move out as quickly and create a build up of blood in the heart. Now what I'm confused about is what causes the heart to learn it has to pump harder in order to get the correct fluid flow? My logic is if the heart works at cc/cycle, an organ can't just "know" it requires more power to push the fluid out. I'm guessing there is some maximum expansion in the heart's walls where the elasticity forces the blood out at cc/cycle even with the blockage. I'm imagining a rubber orb with (for simplicity) one inlet and one outlet. When the outlet is reduced in size, the output velocity will increase but output volume would be the same due to the rubber wall's k-constant. So is there a mechanical explanation to how the heart reacts to blockages? Also, if you are knowledgeable on this topic can you please give similar explanations to the rise in high blood pressure? I'll probably have to edit this cause I'm terrible with words, so please bear with me. | [
"You're on the right track in thinking about \"stretch.\" Certain parts of the heart wall (in the myocardium, aorta, and some other areas) have stretch receptors that serve to determine the resistance. Tat can help signal the heart to pump harder. ",
"This happens pretty indirectly, though. Those stretch receptor... | [
"What about the sino-atrial node? It also ties in to heart function, but more on a demand from high CO2 in the blood."
] | [
"The actual node is what controls the pace of the heart. It is attached to the vagus nerve and some sympathetic nervs that either slow the heart down or speed it up. The node itself is just responsible for keeping the pace. High CO2 in the blood would be detected more indirectly by chemoreceptors that primarily det... |
[
"Can someone please simplify time dilation?"
] | [
false
] | null | [
"The first few chapters of ",
"this",
" are pretty good."
] | [
"Thank you!!"
] | [
"You’re welcome. Please come back with any follow up questions :)"
] |
[
"Is the density of the materials that makes up Neutron stars and White dwarves a result of the properties of the material, or the gravitational feilds in which the materials reside?"
] | [
false
] | Also, what would happen if said material was placed in a low gravity situation, such as on earth? | [
"Neutron stars occur when the mass of the core left after all fusion has stopped. The mass of which these occur:",
"White dwarf > 1.4sol<neutron star > 3sol ",
"(Sol= solar mass= mass of the sun) past 3 Sol a black hole is formed. As the name suggests the star is just a incredibly dense core of neutrons which a... | [
"If I understand what your asking correctly, unless there was another force stronger than that of the gravity acting between the neutrons then it would remain the same "
] | [
"He's asking if you took neutron star matter onto earth or something. The answer is \"I hope there's nothing you like around\" since outside of the intense gravity of a star with over 1.4 solar masses, those neutrons are going to start decaying and expanding. It's no longer energetically favorable to be in that sta... |
[
"If the universe is 46.5 billion light-years across and has been constantly expanding since the Big Bang then how big would it have been back at the time of the Big Bang?"
] | [
false
] | null | [
"You're confusing the size of the universe with the amount of the universe OBSERVABLE from Earth (the observable universe). As far as we know the universe is infinite in extent now and it was infinite in extent then, even if it is \"larger\" (i.e. any two points are further away than they were) today.",
"It's im... | [
"46.5 billion light years is the he size of the observable universe. The farther back in time you go the closer you get to the earliest things that you can see, those stars would have also expanded away from you less",
"We can only see about 12.7 billion light years away, but those stars that were 12.7 light yea... | [
"Did we have to adjust our calculations when we discovered that the expansion is accelerating because of dark energy?"
] |
[
"How many more calories per day do you burn if you have a high fever?"
] | [
false
] | null | [
"A simple way to calculate body caloric requirement is to use the ",
"Harris - Benedict Equation.",
" This is a calculation that uses gender, weight, height and age to estimate your daily basal caloric requirement. There are a number of factors that can be used to adjust the equation (daily exercise, sickness, ... | [
"According to ",
"this",
" section of a United Nations University website, a rise of 1 degree Celsius requires a 13% increase in BMR. It also states the effects can vary among different infections. Wikipedia's ",
"source",
" seems to indicate that around 70% of caloric usage is consumed by baseline BMR. Thi... | [
"Would that mean an increase of 13% in energy consumed?"
] |
[
"Recommended reading on carbon dating?"
] | [
false
] | [deleted] | [
"The Greatest Show on Earth",
" by Richard Dawkins."
] | [
"Carbon dating is used for things under about 50 000 to 60 000 years old so when Christians say scientists are wrong to carbon date things to billions of years old you can say, \"That's because they didn't!\""
] | [
"The site ",
"http://www.c14dating.com/",
" is excellent."
] |
[
"How warm could the earth get (due to climate change, not due to the sun exploding)?"
] | [
false
] | null | [
"If global warming is caused by the burning of fossil fuels, which thus release CO2 that previously had been trapped ",
"This is only the current largest contributor, there are many factors which can cause global warming, some of them are anthropogenic (ie. caused by humans), such as burning fossil fuels, some of... | [
"That's exactly my point- it seems unlikely that burning through as much as we do, and are continuing to do would raise the temperature by much much more than a mere 2 degrees C. It seems like it would be much more dramatic than that. I have a feeling that we're underestimating our impact. "
] | [
"The full answer would require something very in-depth, but I know that even in the relatively short time frame since the mass extinction of the dinosaurs, the average global temperature has been ",
"more than 10 degrees C above today's average",
". Given human action on the planet, I would expect the actual ch... |
[
"How is water able to stay in gaseous form in air (water vapour) well below its condensing temperature?"
] | [
false
] | null | [
"All liquids have what's called a vapor pressure. Essentially, if you leave the liquid sitting open to air it evaporates, often very slowly, until there's a certain concentration (partial pressure) of it in the air. The vapor pressure also depends on temperature, which is why hot air can be more humid than cold air... | [
"I loved posing this to physics students:\n“What temperature does water boil?”\n“212” (in US and these were first years)\n“I put a few drops of water on the table and come back a while later and the drops are gone, what happened”\n“It evaporated”\n“Did it ever get that hot?”\n.....\nSo we need another explanation, ... | [
"When you have less than 100% humidity, water is constantly evaporating. If you leave a glass of water in your house for long enough, it will eventually all evaporate off like you expect. It is just a relatively slow process. The kinetics of evaporating water in the atmosphere is controlled by 2 things"
] |
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