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Is it possible to surgically change a person's voice?
You might want to be more specific. The voice, being controlled by physical parts of your body, can of course be changed by surgically altering those parts. The only vocal surgery I'm aware of are the pitch-altering surgeries which are used to raise or lower a person's pitch, commonly because they are either transgender or feel their current pitch is atypical.
Can daily sunscreen use make you more vulnerable to the sun?
Sunscreen doesn't make you more prone to burning, but being pale does. That said, as public service advertising has drilled in to me (Aussie) for as long as I can remember, "tanning is skin cells in trauma, theres nothing healthy about a tan." So while consistent sunscreen use can make you more pale, which means you are more likely to burn, being more tanned and tanning rather than burning is not at all better for you.
Do plants that have red or purple leaves still use chlorophyll?
Yes, most non-green plants you see do use chlorophyll. High amounts of other photosynthetic pigments (like red-purple anthrocyanins) simply mask the green color. [One source tells me](_URL_0_) that the extra anthrocyanin is photo-protective against UV at the cost of low light level efficiency. People also breed for over expression of non-green pigments to make colorful ornamentals. For exceptions, some parasitic plants like dodder don't have any chlorophyll. Also some plants temporarily go through stages without active chlorophyll, such as autumn coloration or etiolated seedlings.
Chemically, what is the difference between refined and unrefined sugars?
Unrefined (brown) sugar is what you get when you press sugarcane or sugar beets and dry it to crystals. Beet sugar is rarely sold unrefined though, because people don't like the beet taste. Refined sugar is just purified to be almost pure sucrose, removing the [molasses](_URL_0_), which is most easily defined as 'all the other stuff'. Even the molasses is still mostly sucrose though. Raw sugar is [96-98%](_URL_1_) sucrose, while white sugar is 99% sucrose. Sucrose is sucrose, there's no chemical difference. The only significant difference is really in taste and appearance, not in nutritional content or any proven health benefits. Sugar is refined simply to taste like sugar (sucrose), and less like sugar _cane_ or sugar _beets_.
How many times could the earth fit into the sun?
You are. The sun's diameter is 109 times that of the earth, but that does not translate into volume at all. Spherical volume is 4/3 pi r^3 where r is the radius of the sphere. Assuming r of the earth is 1 unit, then it's cubed value is 1 as well. The sun, at 109, would be 1295029. That is their ratio. You are correct: whoever was responsible for that is dumb.
Are there any variable alternatives to fossil fuels for cargo ships.
Nuclear cargo ships have been [built and demonstrated](_URL_0_), but the bottom line is that they just aren't economically viable. This is due to a combination of factors, such as the need for highly trained staff, safety, security and regulatory requirements, and the fact that marine reactor technology is highly controlled due to its dual-use capability (i.e. military).
Why is it very common to sneeze in pairs?
["Scientists have yet to come up with a good explanation for why most people sneeze the predictable two or three times, while others are wracked by staccato attacks. But the answer seems to lie in an individual’s unique immunological and neurological constitution."](_URL_0_) Side note that is excellent for parties: another term for sneezing is "sternutation" or "sternutatory reflex". **Edit**: Don't believe everything you read in that link. For instance, I am skeptical about ~160 kph (100 mph) being the typical sneeze velocity. From an evolutionary perspective, multiple (but not too many) sneezes might be beneficial in terms of their combined effort to successfully discharge the irritant.
Are viruses alive? And if not, then what are they?
There are individual genes within plant and animal genome that act like viruses; they reproduce themselves and hop around in the genome, but we don't say that they're alive, rather that they are a part of a living organism. Right now, we usually define living things as cells. Why? Because cells contain genetic information and the means to reproduce this genetic information as a self-contained unit. An individual bacterium, given the correct nutrients, grown at the correct temperature well be able to make many more bacteria; while an individual particle of HIV or influenza simply cannot do so. Maybe an analogy will help: Imagine a virus is like a USB memory stick, while a cell is like a computer. The memory stick contains information, but it's useless without something to read it. edit: I should mention, I haven't heard a huge amount of controversy on the topic, possibly because it's mostly a semantic argument at this point.
Are the "gas giants" really just giant balls of gas, or do they have a surface of some sort?
Underneath the gas there is a region of what is thought to be metallic hydrogen. Here is a [diagram](_URL_0_) of Jupiter. I believe that these structures were ascertained by measuring the gravitational influence on probes as they fly North-South around the planets.
Can microwaves harm you if you stand close to them while they are cooking food?
The microwave oven is perfectly safe to stand next to. The metal cage you see lining the inside of the microwave is a Faraday cage that prevents the electromagnetic radiation from getting out. Don't worry about the holes you see in the metal cage, their size is specifically designed to increase its effectiveness at the frequency that the microwave operates at (2.4GHz), so nothing harmful will get out.
Is there enough matter in the asteroid belt to build a planet?
The mass of the asteroid belt is about 18 x 10^-10 the mass of the sun or 3.6 x 10^21 kg. This is about 5% the mass of our Moon. So would this be called a planet? The IAU definition is > 1) is in orbit around the Sun, > 2) has sufficient mass to assume hydrostatic equilibrium (a nearly round shape), and > 3) has "cleared the neighbourhood" around its orbit. 1 and 2 would definitely be true. And as for 3, if we put all the asteroids together, then there wouldn't be anything left in the asteroid belt so it would have cleared it's neighborhood. So even though it would be very puny, it could be considered a planet. But baring this artificial formation, it won't form any planet because the pieces wouldn't have enough gravity to clear the neighborhood naturally. _URL_1_ _URL_0_
Is there anything in our universe that is truly random?
As far as we know, quantum mechanical processes are truly random- certainly they are random to the extent that we have no mechanism for predicting the outcome of a quantum process with certainty (we can only predict probabilistically), and there is strong evidence (Bell's theorem) that any theory which is able to predict such processes must be nonlocal. Since nonlocality has its own problems, it's reasonable to conclude that there is likely no theory which can exactly predict the outcome of quantum processes. Interestingly, quantum mechanics also challenges the premise of your question, since by the Heisenberg uncertainty principle your 'omniscient being' would still be unable to simultaneously access position and momentum information to arbitrary precision for a particular particle (or any other pair of measurements with a nonzero commutator.) So in terms of modern physics the question isn't totally well-posed.
Are there truly different sizes of infinity? Or is our definition of infinity in English is different than mathematical infinity?
The cardinality of the set of natural numbers and the set of rational numbers is actually the same- that is to say, they can be mapped 1:1. Mathematicians call this a *countable* infinity, because you can construct a list which would eventually reach all the numbers (please any actual mathematicians expand on this). On the other side, there's another type of infinity to which the real numbers belong to. Essentially, there is no way to construct a list which contains all the real numbers from any interval, so it is a different type of infinity. This type is conveniently called uncountable infinity.
Are there animals that don't sleep?
[There are some fish that don't sleep](_URL_0_). The implication of the article here seems to be that sleep is involved in processing visual stimuli and forming memories. So species which are not in need of this function tend to sleep less or not at all. This would also explain in part why sleeping is so common among animals (sight and memory are key adaptations for survival).
Can helium bond with other elements or with itself?
TL;DR: no. _URL_0_ Helium is too inert for any normal molecules to be formed from it. There are some interactions that occur at high pressure and some non-covalent interactions that are very weak but nothing has been discovered that really resembles the covalent sort of molecules that we normally think of. The heavier noble gasses can form some fairly unstable compounds from interactions between their d and f orbitals which bypass the filled valence shell.
Are Induced Pluripotent Stem Cells as advantageous as Embryonic Stem Cells, research wise?
Short answer is no. While iPS cells have a lot of potential, they simply are not as undifferentiated as ES cells. This means ES cells can be used for a wider variety of purposes more effectively. Potentially we could find a way to program them like ES cells, but it's kind of a ridiculous step when ES cells are merely a moral problem to fundamentalists. There are other issues, including that some of the hacks we use to reprogram the cells can sometimes make them oncogenic. Needless to say, they're useful, but they really don't hold a candle to ES cells yet. Interesting review _URL_0_
Why is childbirth so painful for women (or all mammals for that matter)?
This has been asked a few times recently. Searching for [childbirth](_URL_1_) gives: [Why is human childbirth so painful and difficult?](_URL_2_) [Why do we, as humans need assistance during childbirth? ](_URL_0_) [Why have humans not evolved to have painless childbirth?](_URL_3_)
Is childbirth painful for all mammals?
Whilst we don't have a hard and fast measure of how painful other animals find anything, it seems that for many animals it is not nearly as painful. My reason for believing this is that the human pelvis has changed so much to allow bipedal upright walking that it has severely shrunk the exit as it were. I've also seen videos of animals, particularly livestock, casually walking about then plopping out a calf, not the best evidence, but a little.
Why do lightbulbs always seem to burn out right when you turn them on, and not while they're already on?
Sometimes lights do burn out when they're on but basically it's because at the moment of being turned on lightbulbs experience a small surge of power that's greater than they get when they are running. This can push them to burn out.
Do girls really mature faster than boys?
Yes, they do. [here](_URL_1_)'s the wikipedia article about puberty. The wikipedia article cites a bunch of studies. It is generally considered to be scientific fact that the onset of puberty starts earlier in girls than boys, and that the puberty process ends earlier in girls than in boys *on average*. Naturally, its possible for a given boy to start puberty and thus mature to adulthood faster than a given girl, but it is the exception rather than the norm. Edit: To address the concerns below. Because this question was directed to askscience rather than askreddit, I feel it's appropriate to answer with the most unbiased terms possible. "Maturity" being defined as the [state of being fully developed](_URL_0_), onset and completion of puberty seemed as fair and impartial a measurement as possible.
Why do black holes evaporate faster the smaller they are?
No. Many black holes form when the whole core of a star collapses into itself. For stars big enough, there's just too much mass there, and therefore too much gravity, for the collapse to stop. They're not microscopic at all, even in the beginning.
What is the science behind bread going stale?
There are two main processes at work. The first is the migration of moisture from the bread to the atmosphere; even though we think of bread as 'dry' there's still a good deal of water left behind, bound up in the structure of the bread. As this moisture leaves the bread and goes into the surrounding air, the drying bread changes texture and loses some flavor. Additionally, the starch in bread undergoes a process known as *retrogradation* where the starch molecules align and crystallize, and the bread changes from soft to crunchy. In bread this effect is mitigated by the presence of protein and fats (if present in the recipe) but you can really see this at work in white rice. Leave white rice in the refrigerator overnight and it turns from light fluffy grains to crystalline shards of nasty.
Research suggests that using electronics before bed hurts your sleep because the screen causes a suppression in the release of melatonin - would looking at electronics (with screens) help to wake us up in the morning?
Perhaps. However, remember that it's actually blue light coming from the screen than tricks the brain into thinking that it's daytime and since sleeping during the day would decrease your chance of survival, the brain evolved to suppress melatonin secretion during daytime. In short, blue light at night suppresses melatonin production and makes you less sleepy. I actually use a blue light filter program to reduce the effect and it works. So, exposing yourself to blue light in the morning should drive your sleep away.
How can light be affected by gravity if it has no mass?
Here are two ways to think about this: (1) Gravity acts on energy, not mass, and photons have energy. (2) In the language of general relativity, gravity is a curvature of spacetime, so the path a photon takes follows the spacetime curvature when and where the photon is traveling.
Why is cloning a human so much harder than cloning a sheep?
It's not that it's harder, but there are a ton of ethics behind cloning a human. If you clone a sheep and it comes out with 5 legs, it's a whoops moment. People may get angry about it, but nowhere nearly as angry as cloning a human and comes out with 3 legs or some other deformity. Can't really euthanize humans, like you can an animal and any society being ok with it.
Is it possible for a moon to have a moon?
Theoretically, yes, although I'm not sure of any that we know of currently. What you seem to be asking for is a satellite for a satellite, and a number of examples of that already exist. The moon orbits Earth, as the Earth orbits the Sun, and in turn, our Solar System is spiraling round the Milky Way. It's a chain of command, and its completely plausible for our Moon to have a satellite orbiting it. EDIT: Okay, so there've been a couple of responses saying that a satellite and a moon are two different things, and that based off the definition of the word 'moon', this is impossible. That's fine and dandy and all, but simply saying saying 'No' probably isn't what OP is asking for. Yes, our moon cannot have a 'moon', but that problem originates with the definition of the word, however, if we simply ignore the minor discrepancy and look the the question subjectively, OP is asking if our moon can have a satellite, and the answer to that is 'Yes.'
When someone gets a transplant of an organ that they have two of, like a kidney, does the new organ have to come from the same side of the donor's body as the one it's replacing?
Doesn't matter. They don't even put a transplanted kidney anyplace near the original location, anyway, and usually don't remove the old kidneys either. See [this image for a good example](_URL_0_). Which side they transplant a kidney to depends really on the surgeon's preference or the recipient's anatomy, and not on what side the organ came from in the donor. [source: I am a kidney recipient]
Can you really "train" your liver to become more tolerant to alcohol?
You can't train your liver to tolerate more damage. The tolerance comes from adjusting to the impairment that alcohol puts you in. You are still going to face the same health issues, it just will take you more to reach a drunk state.
If alcohol damages our livers, why does our alcohol tolerance increase?
The liver does have some specific cellular alcoho tolerance effects, but the liver is not the primary place that tolerance occurs. Keep in mind that alcohol is not a drug with acute cellular/neuronal action. It is readily absorbed throughout the body. Tolerance to alcohol occurs at the molecular level at many places in the body. This involves lots of mechanisms including changing the activity of chanel protein production, interacting with membrane lipids, interacting with auxiliary proteins, modulation of membrane protein expression, and altering the spatial organization of membrane proteins. Also, we don't really understand how any of the mechanisms listed above specifically affect alcohol intoxication behaviorally.
Why are people still gay?
In some species, like the one I study named *Cygnus atratus*, about 25% of the pair bonds formed are pairs between two males. The males will then either steal a nest, or have a temporary 3some with the female and run her off. The cygnets of these homosexual pair tend to have a higher degree of fitness because they're protected by two males. One could hypothesize that it could be an adaption similar to altruism (which is what I'm studying). In people, it could just be a hormonal imbalance early in development that makes a male's brain be more structured like a females so that when puberty hits and hormones are plentiful, it has the activational effect of preferring male companions. At least from my readings, only observational studies have been done about this phenomena.
How much rainfall would it take for California to get out of the drought?
The Cali drought isn't just simply a liquid precipitation deficit problem. It's a combination of lack of rain, plus very high temperatures, plus a decline in snowpack. So your answer will depend on how you want to deal with those other variables. Are you asking "if we ignore the persistent warming trend and decline in snowpack, then what would be..."?
Do the gas giants have a solid core?
Nobody really knows for sure. However, satellites have measured gravity of some of the gas giants (non-spherical objects have non-spherical gravitational influence), and these measurements have suggested that solid cores exist in all the gas giants. However, the inference of these cores is both very difficult and uncertain. For example, Jupiter is thought to have a "rocky" core comprising somewhere between 5-15% of its total mass. However, the term "rocky" is used loosely, because we know very little about the actual composition (in part because we simply don't know all of the properties of the materials at the temperature and pressure of Jupiter's core). The story is pretty much the same with the other gas giants.
Do gas giants have a solid core?
most likely they do, but even if they didn't they would still have gravity. Gravity just depends on mass, gases and liquids have mass, and at the ridiculous pressures at the center of gas giants the the gas becomes a very dense fluid so even if there's no rocky core, the center of the planets would still be quite dense and thus massive
Why does the sun look yellow, rather than a more intense blue?
It's due to the atmosphere preferentially scattering shorter (bluer) wavelengths of the sunlight and leaving the longer (redder) wavelengths to hit your eye. This effect is more and more pronounced as the sun heads towards the horizon, making it a rather striking red/orange when it's setting. The blue light that is scattered, in turn, gets scattered repeatedly across the sky and makes it appear blue. Edit: [Rayleigh scattering](_URL_0_) has more info on that.
Would making gasoline "fizzy" by adding oxygen - in the same way CO2 is added to soft drinks - make it more combustible?
It's not possible. Carbonating a drink causes the chemical reaction CO2 + H2O - > H2CO3 to happen. H2CO3 is only stable under pressure and decays back to H2O and CO2 when the pressure is relieved. This decay is also endothermic, which causes carbonated drinks to feel cooler. O2 gas cannot react in such a reversible way with gasoline. Any reaction of O2 and gasoline would immediately cause combustion (because that's what combustion is). O2 also doesn't go into solution in any relevant amount.
Why is Ebola not as contagious as, say, influenza if it is present in saliva, therefore coughs and sneezes ?
It really does't have to do with the capsid. Ebola can be aerosolized in the lab. If monkeys breathe in this aerosol, they will get Ebola and die. So, the capsid can protect the virus just fine, at least for a time. Yes, other viruses are more hardy in the environment than Ebola, other are less. But Ebola can be aerosolized artificially. In humans, when we sneeze and cough, the aerosol that is generated comes mainly from the upper respiratory tract (the nose and mouth and upper trachea). The upper respiratory tract is not an efficient site of replication for Ebola. Ebola is not shed in high quantities into the mucosa of the nose and mouth. This is main reason why Ebola is not transmissible person-to-person. Add to this that the virus does not survive well in the environment, it dies when dried or exposed to UV light, etc, and it's pretty clear why it is not aerosol transmitted.
My bottle of bleach claims to kill 99.9% of all household germs.
What kind of bleach is it? [Clorox regular bleach](_URL_0_), for one example, is a registered disinfectant. Based on the US EPA [website](_URL_1_) disinfectants are "used on hard inanimate surfaces and objects to destroy or irreversibly inactivate infectious fungi and bacteria but not necessarily their spores." I'm not sure what time frame or concentrations are required for this definition, but I did find one article that looked at the effectiveness of 10% bleach on the spores of Bacillus anthracis, the causitive agent of anthrax. The [article](_URL_2_) clearly demonstrated that anthrax spores can be killed by bleach, however if the spores are at a very high concentration, or if they are exposed to bleach for too little time (30 minutes at high concentrations) some can survive. So if there is a lower cut off for time of exposure required to kill a spore, Bacillus anthracis spores could be one example of that 0.1% of germs that could survive.
Why does the the spicy taste seem to stay around longer than all of the other tastes?
The hotness of spicy tastes is not sensed using taste buds: it's essentially a burn-like irritation that directly stimulates the nerve fibers. This is an example of [chemesthesis](_URL_0_). Not quite sure why the sensation persists longer, though.
Why does Jupiter have a much more detailed "surface structure" (red spot, cloud bands) than the other gas giants?
Someone asked a very similar question about Uranus awhile ago. The responses seem to answer you as well _URL_0_
Why do new avian influenza variants seem to originate in the far east and/or China?
People in these regions tend to live in close quarters with animals, particularly poultry and pigs which increases the odds of a virus making an interspecies jump to humans. "...small-holder raising of animals with close interaction between humans, poultry, and pigs continues, providing the opportunity for interspecies transmission of influenza viruses (32). H9N2 viruses are widespread in poultry in [southern China] (11), and interspecies transmission to pigs is now documented." _URL_0_
Why don't we all get Dementia or Alzheimer's? They wouldn't be stopped by natural selection, they happen after middle age, usually
This isnt specific to dementia, but you are assuming that there is no natural selection after middle age which is an unfounded assumption. There are hypotheses that some selection occurs after humans stop reproducing. Grandfathers and mothers being around to help raise their grandchildren may help ensure their grandchildrens survival and thus the survival of their genes [Wikipedia](_URL_0_).
Why do we use optical telescopes for space exploration?
You see different things in different parts of the electromagnetic spectrum (see [Multiwavelength Milky Way](_URL_0_)). Different sources will emit differently because of different physics, thus we need telescopes across the spectrum to study these phenomena. Also, you cannot calibrate a radio telescope to see at visible wavelengths. Crudely put, a radio telescope views light in a wave-like regime and measures voltages in electronics whereas optical telescopes view light in a particle-light regime and measures the light hitting a detector. Another major engineering difference is that in order to see something, the deformities of your "mirror" need to be of the order of the wavelength of light that you want to see. So mirrors on optical telescopes need to be very smooth. Low-frequency radio telescopes can be basically wire meshes.
Why do we only have two sets of teeth?
Because our two sets of teeth last long enough for us to successfully reproduce. Tooth loss is the main reason why animals die in nature, they can't get enough energy and get diseases etc from infections or fall prey to predators. Our ancestors were probably frugivorous (fruit eaters) so they ate relatively soft foods and didn't wear down the teeth like grazing or browsing animals do. Also there is a trade off in development which may relate to the strength of our jaws (which might be weakened if we were continually growing new teeth) and the energy required to produce more teeth. Energy investment in our ancestors was slanted towards brain size which led to tool use and that allowed them to continue eating even after they had lost their teeth (by mashing up foods). But I think the main thing is that they are strong enough to last until after the typical age of reproduction so there was no selective pressure favouring continuous tooth growth.
Why do we have two sets of teeth in our lifetime?
I've got a follow up question, why only baby and adult teeth why can't we grow replacement teeth?
Why does the far and near sides of the moon look so different?
I saw it in a documentary a while back and searched for a source online: [link](_URL_0_) The idea is basically that the Moon cooled faster than the Earth after the violent event that created him, because he is smaller. The Earth, still hot, then radiated its heat onto the near side of the moon, which led to the geological differences between near and far side. It is described in more detail in the linked article.
How do we influence qubits in quantum computers?
That depends on the type of qubit. Qubits have physical implementation, just like classical bits (voltage across a transistor). The most common implementations are superconducting qubits, cold atom qubits, and photonic qubits, each of which has various advantages and disadvantages. Superconducting qubits are commonly manipulated by microwave pulses into the qubit antenna line, cold atom qubits are manipulated by timed on-resonant laser pulses which induce Rabi oscillations in the qubit state, and photonic qubits are manipulated in many different ways depending on the encoding, such as by applying phase shifts and directional coupling to the various basis states, by using light modulators, or by scattering successive photons off of a natural or synthetic atom.
When someone is sick with an infectious illness and they sneeze on a surface, how long does a bacteria or virus survive on that surface? What eventually makes them die off or go away?
Viruses haver varying times they con survive, since we don't know which one you have, and do not know the current conditions in the house it hard to say. Like a poster said before 3 weeks is a good cover all your bases. When you sneeze thing can become aerosolized, these particles will stay aloft longer than droplets. Most virus's die from UV exposers, also they can dehydrate and die. The flu seems to stay around 2-8 hrs Or rhinovirus is 2-4 hrs on surfaces. _URL_0_ _URL_1_
Why are some tyres made of solid rubber?
Toughness and consistency under load. Air filled tires are really great for soaking up bumps in the road and conforming to changing surface conditions, but are much more fragile than a solid tire. Solid tires keep their shape under heavy loads (like a forklift picking up lots of weight), and most warehouses are designed with flat floors, so comfort and compliance aren't an issue.
What would happen if you fired a gun in space?
A modern cartridge doesn't require air to fire and will operate in the vacuum of space. The bullet will travel at muzzle velocity until another force (like the gravity of any celestial body it passes by) acts on it.
How can we reliably tell the difference between male and female voices?
To answer your second question, it depends which direction the transition is in. For F to M, testosterone treatments will naturally increase the weight and thickness of the vocal cords which lowers the pitch. In M-to-F you cannot decrease the size of the vocal cords so voice training can be utilized alternatively. This is actually one of the newest fields of research in my University's speech department.
Why is the last sip or two of a cup of coffee so much more bitter than the rest of the cup?
Totally not trying to be a smart ass(I'm just not sure what kind of answer you're asking for), but isn't the simple answer a matter of the ground up coffee particles settling in the cup near the bottom? Much like a smoothie eventually separates into layers based on their density, same thing in coffee. Only it's just coffee beans and water. If say you decide to make the world's most balanced coffee, aka the perfect amount of coffee that distributes it's particles completely evenly through water, you would notice no difference in bitterness.
Why do scars form? Why does the body never fully heal the wound?
When your body is damaged, your body “panics” to seal up and protect the wound. It lays down a random mess of tissue (scar tissue) to simply cover up the wound and protect the body. Some times, the scar tissue is unable to re-learn how to be normal tissue again, and the scar is formed.
How do we know that different animals see more colors than us?
TL;DR: Two main ways: behavioral tests and examining retinal cone cells using a micro\-spectrophotometer. u/totes_original_uname provided some good background information about how color perception relies on the wavelength of light, but I take your question to be asking about methodology \- that is, how human researchers know what animals can see. There are two main ways: behavioral tests and through examining cells in the animal's retina. An example of a behavioral test might be to reward an animal for correctly identifying whether two colors are identical or different, and then presenting many combinations of identical or similar colors. Given enough time, the animal will learn the task and we can estimate the colors that the animal can and cannot distinguish. We can also remove the retinal cone cells responsible for color vision and analyze the wavelengths to which they respond, which can give us a sense of what colors the animal sees. [Here](_URL_0_) is an example of a paper that does just that.
Are gravitons and the higgs boson the same thing?
No, a Higgs boson is a massive spin-0 particle, while a graviton is a massless spin-2 particle. A graviton would facilitate interaction between massive (and also massless) objects.
Do photons have mass? Am I heavier in light than I am in shade?
Photons are massless particles. They don't have mass, but they do have momentum. As to whether you're heavier in the light or shade, I can't really say.
If human cells all contain the same genetic code and very only in the expression of genes, then why can researchers not take a dermal cell, change what genes it expresses, and "create" a different type of cell such as a stem cell?
To put it simply, they [can and do](_URL_1_). I should mention that the process isn't quite as simple as switching the expression profile of the cell from 'dermal' to 'stem' in one go. Our ability to fine-tune expression within cells is limited. Instead, a now-common way of changing differentiated cells into stem cells is by causing them to transiently express certain [transcription factors](_URL_0_), which causes them to revert to a more stem-like state. These induced cells are not the exact same as embryonic stem cells, though they share some important qualities.
Assuming the universe is infinite in volume; it would mean that any event thathas even the slightest chance of existing, will exist an infinite number of times, including humanity, including you... right?
No. You misunderstand the concept of "infinite". Just because something is infinite, it doesn't mean it contains *all* possibilities, much less that each of those possibilities repeats "several" times, or an infinite number of times, or even once. Take an example from an earlier one of today's threads on mathematics: the number 0.1001000100001000001... (a) is clearly infinite, (b) is clearly non-repeating, (c) does not even contain all possible *numbers*, much less number *sequences*, much less *repeated* sequences. Similarly, there could be an infinite number of stars in a steady-state, infinite and eternal universe, without a single one of them ever becoming a blue-white star of a specific size, of a specific composition, in a specific location, travelling in a specific direction, at a specific speed, rotating at a specific rate, deteriorating at *another* specific rate, radiating a specific spectrum, and so on.
How exactly do people get vitamin D from exposure to sunlight?
Our skin contains [7-Dehydrocholesterol](_URL_0_). This is a precursor to Vitamin D. When Ultraviolet light (UVB) of the right wavelength reaches the skin, it reacts with 7-Dehydrocholesterol, to produce Vitamin D.
If refraction is caused by the absorption and reemission of photons, why don't materials only refract certain wavelengths of light?
Refraction is an emergent property of a material, that is, it only arises when there is a large number of atoms that the light is passing through. For instance, if you have 5 carbon atoms, that group of carbon atoms will not have the refractive properties of a diamond which is made of carbon. So, how do large collections of atoms have continuous absorption patterns? Because large collections of atoms have many more absorption methods than simple electron promotion. Collections of atoms can vibrate and oscillate, using two to n atoms (where n is some large number) which allows a nearly continuous absorption pattern as they are many, many combinations.
Is there a giant rocky planet ?
If a rocky planet is sufficiently large, its gravity will draw in hydrogen and helium from the interplanetary medium and it will build up an atmosphere and end up like a gas giant. If it is close enough to its star, the solar wind can strip this hydrogen proto-atmosphere away as it forms, so larger rocky planets can exist closer to stars. It isn't exactly known where the rocky/gassy cutoff is, from what I've red it's about five times the mass of Earth.
Helium is running out, Hydrogen is explosive: is there a party balloon gas mix that would be buoyant, more readily available and have minimal flammability?
There are a few gasses that are lighter than air but most of them are impractical, the only reasonable gas other than hydrogen or helium is methane, but that kind of catches on fire. Neon is also lighter than air but it's comically expensive. Sans engineered gases that are probably prohibitively expensive and probably don't exist, no.
Was alzheimer's effecting older people durring victorian era?
Sure, they just called it senile dementia. The severe degradation of one's faculties in old age has been attested since at least the Classical era. Interestingly, Dr. Alzheimer first started seeing Auguste Deter, the first patient from which he developed the definition of the disease, in 1901, the year Victoria died.
If the universe is expanding, what is it taking the place of?
The universe isn't "contained within" anything, as humans would visualize it. The universe is *all that exists* so you cannot be "outside" of it, like we think of being outside of a house. We evolved to deal with things in our immediate three-dimensional world; we literally lack the biological capacity to comprehend the true nature of the universe. "Outside the universe" is a concept we simply can't grasp.
Did Native Americans who lived in climates similar to Europe develop lighter skin?
Do Eskimos have any place in this discussion?
The rate of universal expansion is accelerating to the point that light from other galaxies will someday never reach us. Is it possible that this has already happened to an extent? Are there things forever out of our view? Do we have any way of really knowing the size of the universe?
Yes, there are galaxies from which we will never receive any light at all. (Any galaxy beyond a current distance of about 65 Gly.) There are also galaxies whose light we have already received in the past but which are currently too far away for any signal emitted from us *now* to reach them some time in the future. (Any galaxy beyond a current distance of about 15 Gly.) The farthest points from which we have received any light at all as of today are at the edge of the observable universe, currently at a distance of about 43 Gly. For more details, [read this post](_URL_0_).
Why can't we just keep accelerating in space?
Continually adding thrust requires continuously ejecting fuel, and only so much fuel can be taken in a given rocket. To take more fuel requires a bigger rocket which requires more fuel to accelerate, etc.
What's happening on a cellular level when you have an itch?
The sensation of an itch is associated with, on a cellular level, with histamine-selective C-fiber nociceptors in the uppermost layers of the skin. Nociceptors are neurons that relay information about damaging stimuli to the brain, which then relays back commands to get away from that stimuli -- this is called the pain reflex. Interestingly, the activation of these histamine-selective C-fiber nociceptors results in the scratch reflex, where instead of moving away from the stimulus, our body moves towards it in order to relieve itself. Overall, on a cellular level, itch (and the subsequent scratch reflex) seems to result from the activation of these specific neurons by histamine; the exact mechanism is an area of active research.
Why is it that when I put in my correct password into the computer, it logs in almost immediately, but when I put in a wrong password, it takes significantly longer to reject me?
It's a deliberate pause that serves two purposes. The first is that it makes it take years for someone to try all possible passwords (called a brute force attack). The second is that if the computer always responded as quickly as possible a sophisticated attacker could measure the slight difference (nanoseconds) it takes the computer to reject a password to infer how many characters in the password are correct (called a timing attack); by making all rejections take the same amount of time this information leak is plugged.
How does your brain determine whether a sound is loud enough to wake you up?
Sound feeds into the brain's arousal pathways, in the reticular activating system. It is a weak input (vision is much stronger), but it is there. The sound inputs will activate reticular activating system neurons, which will "turn on" the brain by sending acetylcholine to the thalamus and activating the Nucleus Basalis to send acetylcholine to the cerebral cortex. The thalamus is likely to be the more important target, though. The reticular activating system is in different states of suppression in different phases of sleep. The sound level necessary to wake someone changes dramatically depending on where they are in their sleep cycle.
If both Hydrogen and Oxygen are flammable, how come you can't light Water on fire?
This is a very simplistic view, but I think it helps understand what is going on. When something combusts, it usually becomes oxidized. For instance, when wood burns, you have oxidation of carbon, leading to the production of CO2. When hydrogen burns in the presence of oxygen, you are similarly left with H2O. So in a way, water is hydrogen that has already been burned.
Did cocoa trees, coffee plants, and tea plants all evolve the production of caffeine independently, or do they share a common ancestor that made caffeine?
They evolved caffeine production independently. This is an example of convergent evolution, whereby different species develop similar characteristics independently. The caffeine sources even vary--seeds, leaves, etc. The chemical structure of caffeine isn't the most complex. _URL_1_ Article: _URL_0_
Why don't females have Adam's apples?
They do, they just aren't as pronounced as they are in males. Male adam's apples tend to be at a 90 degree angle, whereas women's tend to be at a 120 degree angle. So, they do, it's just not that obvious.
Would discovering that the universe was actually infinite or finite change anything regarding our understanding of physics?
Having a definite answer would certainly pose more questions, such as why. These questions, and their inevitable potential answers could change our understandings but I can't think of anything offhand that would change instantly. If you don't know that space is infinite, you study and learn what you can observer. If you know that space is infinite, you study and learn what you can observe. You also probably question how it can stretch infinitely. If you know that space is certain size, you question why. What is special about that particular size. We can also begin to ask specific questions, such as does gravity have a pull at any length?
Why do celestial bodies spin? What keeps them spinning? Have we discovered any that don't spin?
Because of conservation of angular momentum. Objects form from smaller stuff colliding and sticking together. If you have two or more objects, unless they collide head on, the final object has angular momentum and will be spinning. It's incredibly unlikely that anything in space was formed from objects colliding head on with each other.
What will happen to the planets that aren't destroyed when the sun supernovas?
The biggest thing to consider it that our sun will not supernova but will expand to encompass the Earth and then contract to about the size Earth. [Here is a short video](_URL_0_)
About how far up would an average helium party balloon float if let go right after being filled?
It would go up until the density of the air equaled the density of the helium within the balloon. These densities will vary based on the pressure of helium in the balloon as well as the temperature of the helium and surrounding atmosphere, as well as the elevation of the release point (it will float "higher" above Death Valley than it will above sea level, and higher above sea level than it will above, say, Denver).
What would a triple star system's orbit look like? (Both from a planet in the system, and from a view outside the system)
Generally, the only stable orbits are nice elliptical orbits between two objects - or what is effectively two objects from their distance. So Alpha Centauri for instance consists of two stars of about equal mass to each other (and to the sun) orbiting each other at a distance equal to about the orbit of Saturn, plus a third star (Proxima Centauri) which is about 0.2 light-years away that orbits the other two stars. So similarly with planets, you will either have to orbit one star so closely that you basically only feel its gravity (the other stars only altering your orbit slightly), or you'll orbit the whole system from such a large distance that the three stars basically feel like one large star.
How do accents form?
I wish I was further into my studies with linguistic anthropology and could really answer this... I'll come back in a couple years armed with a degree and an answer to this question. but in the meantime... I think you're talking about the origins of accents in general, but an interesting bit about how children develop accents/language is categorical perception and the early production of babbling. when a baby is born, they can perceive phonemic differences across all languages, but by the end of the first year, monolingual children can only differentiate between sounds in their native language. around 11-12 months is also when babbling starts to reflect sounds and patterns in their home language -- even before speech production they start to form their accents, in a way. (source - psycholinguistics textbook) [edit- grammar]
How do accents form?
While groups of people who share an accent speak alike, no two individuals speak exactly alike. There's natural variation. When a language community is isolated from other speakers of that language, it is free from reinforcement from outside and those variations are allowed to evolve independently and gain their own distinctive character. It's not just accents either. Together with vocabulary and grammar, they make up a dialect. There are several examples of vocabulary differences between UK and US English, e.g. loo vs. toilet, lorry vs. truck, etc.
How do accents form?
Actually, some areas in America, particularly in the [Appalachians](_URL_0_), have a dialect similar to British dialect from the 18th century. Languages are always evolving and are reinforced by interaction with others. A fast changing dialect is due to interaction with people outside of a person's origin and acquired new pronunciations over time. While isolation has the opposite effect and reinforces the dialect of that region. Appalachian is a perfect example, the people living there are isolated from people outside of their community, so the language doesn't evolve in the same direction as other regions and continues to reinforces the original dialect of that region.
What is the difference between a white surface and a mirror?
I talk about this in a fair amount of detail [here](_URL_3_), but to quickly summarize, the textbook answer is that the surface of a mirror is flat and reflects specularly where the surface of white stuff is rough and reflects diffusively. See [here](_URL_2_). However, as is often the case, the "textbook" answer has some real issues with it. If that was really true then how can you have things like brushed aluminum or glossy white paint? Another key effect is so-called "sub-surface scattering". Light that is reflecting off something like a white T-shirt, ISN'T just coming from a surface reflection. Rather much of it is [entering](_URL_1_) (see also [this](_URL_0_)) and being scrambled and refracted somewhat before working its way back out at funny angles. It's this change in character that is acquired due to interactions with the interior of the material that really separates the two.
If all the mass of the universe was distributed evenly, would space still be a vacuum?
It wouldn't be a perfect vacuum, but it's not to begin with. The average density of the universe is around 10^-27 kg/m^(3). The best we've managed in a laboratory is around 10^-18 kg/m^(3). So it would be about a billionth the density of that.
If boiling water kills all germs - would it be safe to boil faeces and then eat it? How long could we boil it for and what would survive?
You would kill the bacteria in the faeces but it would still contain the various toxic materials produced by your gut fauna. Reingesting that is not a good idea.
Dreams are said to be very short in real time, so why is it that when people talk in their sleep it's at normal speed?
Because most dreams happen in [real time](_URL_0_). Time dilation in dreams is mostly a myth.
Why, sometimes, does only one of my nostrils get plugged up when I have a cold and/or allergies?
Turbinates are fleshy glands on the side wall of your nose. There are three turbinates in each nostril. In a dependent position, when you you sleep on the right side, with the right turbinate down, after a time, this right turbinate fills up with fluid, and expands so that it pushes against the septum in the mid line and blocks one nostril. Sleeping in the opposite position will relieve this. Another possible explanation is a deviated nasal septum which causes one nostril to be narrow and the other wider. In this situation, the wider nostril being more exposed to allegens has more swollen turbinates and the cycle alternates.
Do all organisms exhale carbon dioxide? If not then which organisms don't exhale CO2 and what do they exhale instead?
All animals do, at least. Organisms that are autotrophic, or producers, take in c02 and expel 02 as a waste product of photosynthesis. The major autotrophs are plants and cyanobacteria. This is what is meant when you hear the expression "plants make oxygen."
If the universe is expanding and galaxies are spreading apart, why are we set to eventually collide with Andromeda?
The Milky Way and the Andromeda galaxy are within the Local Group of galaxies and are gravitationally bound to each other, meaning that their bulk velocity is such that they can't escape each others' gravity. The universe is expanding only outside of such gravitationally bound systems. Once two objects are close enough to become bound to each other, they fall together rather than falling away from each other. Besides the recessional velocity due to the expansion of space between galaxies, galaxies also have what's known as [peculiar velocity](_URL_0_), essentially their random velocity through space relative to [the rest frame of the Cosmic Microwave Background](_URL_1_). This essentially shows up as a scatter in the distance-redshift plot of the [Hubble Law](_URL_2_). Over short distances (millions or tens of millions of light years), peculiar velocity can be larger than the Hubble Flow.
Can a gas be more concentrated when dissolved in water than when it's in the atmosphere?
Not exactly the same thing, but a liter of gasoline has more hydrogen in it than a liter of liquid hydrogen. Liquid H2 has a very low density due to some interesting quantum effects, and the dense bonding of hydrogen to carbon actually stores more hydrogen than pure hydrogen!
My beer was very cold but not frozen, then I when I opened it, it foamed up then overflowed and I ended up with a bottle of frozen foam. What happened?
the pressure in the bottle was lowering the freezing temperature. as soon as you let the pressure out, the freezing temperature returned to normal; since the beer was colder than that it changed phases.
Are there lone groups of "planets" in the distance between stars?
Groups? Doubtful. Rouge planets do get kicked out of solar systems during their formation, or systems with complicated and unstable orbits can eventually kick out a planet (or gravitational interaction with a nearby stellar mass object). There's an article on r/science where they measured Saturn's gravitational influince on the inner planets, they found that if saturn's orbit was inclined by 20 degrees from the ecliptic, Mars would get kicked out. At 30 degrees, Earth would get kicked out too. _URL_0_
If the liquid wax is what burns in a candle, why doesn't a pool of liquid wax go up in flames? Why only the wick?
It's not the liquid wax that burns, it's the vapors. The liquid gets drawn up the wick, and vaporized when it reaches the flame proper, and is burned then (as a general rule, most everyday things that burn do so as a gas: it's the only way to get a sufficient mixture with the oxygen it reacts with while burning).
Why do we lose control of our pee and poop when extremely scared?
One of my med school profs believes this is urban legend. The science behind it backs it up, as well. Urination and defecation are parasympathetic processes, which requires the relaxation of the sympathetic nerves that tighten internal sphincters (external sphincters are somatic, or voluntary muscles). The fight-or-flight response is sympathetically-driven, so if anything those sphincters are getting even tighter. This is the explanation for why some people have a hard time urinating if there is a long line of people waiting behind them -- the social pressure to hurry make them nervous, so they can't relax and pee. Edit: spelling
Why does a pot of boiling water produce more steam almost immediately after you turn off the stove?
on a gas stove the exhaust gases from the burning fire are very hot. those hot gases rising up around the pot of boiling water subdue the condensation of water vapor. Turn off that heat source and the steam mixes with cooler air and more vapor is visible. Electric coils would have a similar effect of heating air which rises around the pot until you move it off the heat source.
Why does more steam come out of a pot when I turn off the heat?
It's not steam, it's condensed water. When the heat source is turned off, the air above the water cools slightly and water condenses out.
Is there heat in space?
Your teacher maybe wasn't as clear as he should be. He can legitimately say there is no conductive-heat. But there can still be radiative heat (in the form of photons). _URL_0_
Does bacteria grow in your nalgene water bottles over time?
Water bottles and nalgene bottles will both produce biofilms of bacteria, mainly along the screw top mouth pieces. It's important to wash them probably at least once a week. If you hand wash it with a paper towel, you may notice some black 'dirt' coming off of it which is what built up. Dish soap and water will definitely work.
Does Bacteria Grow When You Keep Reusing Your Water Bottles?
Yes, definitely! A few years ago a few of my lab mates and I did a study on what bacteria lived on ourselves and various things around our lab. The place with the most bacteria and diversity was on my Nalgene water bottle! I wrote up an article describing what we did and how we used DNA sequencing to identify the various bacterium [here at this link](_URL_0_). Edit: By "on my Nalgene water bottle" I meant "on the inside surface of my Nalgene water bottle" in case there was any confusion.
If microwaves work by creating vibration in the water molecules of food, why does your plastic or ceramic container come out so hand-burning hot?
Water is not the only thing that can be excited into motion by microwaves, the motion being converted into heat.
Why is it ok to keep baked good that contain egg/milk out at room temperature but not fried or scrambled eggs.
Baked goods typically have very little water per unit volume so they are reasonably inhospitable to bacteria. Also for most baked goods you've cooked the eggs and milk all the way through, killing any resident bacteria. So they'll last about a week. With scrambled or fried eggs you don't always cook the egg all the way through. Especially if you like your eggs a little runny or sunny side up.
Why is the ocean so blue and almost crystal clear in some places, while in other places it’s murky and green?
It boils down to how much life there is in the water. That crystal clear, blue tropical water? It's pretty much dead and devoid of biomass. That murky green seawater of the Pacific Northwest, and so forth is full of plankton, algea, and other biomass. Why is this? The colder waters tend to have upwellings that deliver nutrients into the water which feed this. The other contributor is agricultural runoff from shore which also adds to the nutrient load.