question
stringlengths 19
300
| answer
stringlengths 28
1.02k
|
|---|---|
how can pi be calculated out to millions of digits?
|
I suggest that you peruse [this wikipedia article](_URL_0_). It talks about the history of how pi used to be calculated before talking about the current methods used.
|
What causes the sexual side effects of SSRI medications?
|
No one really knows for sure why SSRIs cause sexual dysfunction in some patients. SSRIs affect the release and uptake of not just serotonin but other neurotransmitters such as noradrenaline and dopamine as well. Each SSRI within the drug class affects the body's neurotransmitter systems slightly differently. The effects of modulating multiple neurotransmitter systems is most likely the cause. Here is an article if you wish to read more: _URL_0_
|
If something travels at faster than speed of sound without generating any noise, then still there will be sonic boom?
|
A sonic boom isn't generated from the propulsion system of any machine. Sound is pressure waves. A supersonic object creates a pressure cone where it is splitting the air. The boom you hear is when the cone intersects your ear. A supersonic bullet has a miniature sonic boom without producing any other noise. So, yes, there is still a sonic boom.
|
Why haven't the constellations ever changed?
|
They do, just too slowly to notice. The star that moves fastest across the sky is [Barnard's Star](_URL_0_), which covers a degree in about 350 years. Most stars in the familiar constellations are much slower. Betelgeuse, for example, has moved a few percent of a degree since the pyramids were built. I believe the constellation star with the fastest proper motion is Sirius. Occasionally stars explode but this is a rare occurrence; to my knowledge no star in a constellation has ever exploded. Historical supernovae like the one in 1054 appeared to be "new stars" in the sky, hence 'nova.'
|
Why don't our constellations change?
|
They do change, they are always changing. They have not remained the same pattern through history. However they tend to move pretty slowly compared to human time scales which is why they might have appeared similar just a few thousand years ago. - _URL_0_
|
Is it possible for the same organ to be transplanted to different people throughout its life span?
|
As has been said in previous threads on this topic, generally the answer is no. There was a recent [report](_URL_0_) of it being done successfully, but they did it shortly after it was transplanted in to the first patient. Basically, the first recipient started to reject it very quickly, and they new it wouldn't help that patient for long. So, they gave a try to transplanting it in to someone else and it worked. I feel like when people ask this question, they are picturing waiting for someone to die after having the organ for a while, and then retransplanting it. I still don't think that's a possibility, but this case opens the idea to pulling the transplanted organ from someone that initially rejects it and trying to transplant it in to someone else. I think this was the first time this was ever done.
|
How much more likely am i to get cancer from smoking weed then cigarettes or not smoking at all?
|
There are more known carcinogens in tobacco smoke than cannabis smoke. There's some limited research to suggest that tobacco is objectively more cancer causing than cannabis smoking. _URL_0_ That said, there are several ways to consume cannabis without any cancer risk. Whereas tobacco is extremely toxic no matter how you ingest it.
|
Why is space cold if there is untold billions of stars throwing out heat in all directions?
|
Because the stars are very far apart, and so the energy they are emitting gets spread out over large expanses of space.
|
If meditation is good for the brain, is the opposite of mediation(chaotic, unfocused thoughts) bad for the brain?
|
I think you're going to have to explain your premise before anyone can answer your question. In what way do you think meditation is "good" for the brain? Do you have a source that states that meditation is "good for the brain" so we can form an objective definition for what that might mean?
|
Do most mammals have an approximately even ratio of males to females?
|
No, and it appears to vary tied to things like population density (Kruuk et al. 1999) and hormone levels at conception (James, 2008). References: Clutton-Brock, T. H., & Iason, G. R. (1986). Sex ratio variation in mammals. Quarterly Review of Biology, 339-374. James, W. H. (2008). Evidence that mammalian sex ratios at birth are partially controlled by parental hormone levels around the time of conception. Journal of Endocrinology, 198(1), 3-15. Kruuk, L. E., Clutton-Brock, T. H., Albon, S. D., Pemberton, J. M., & Guinness, F. E. (1999). Population density affects sex ratio variation in red deer. Nature, 399(6735), 459-461.
|
Is it possible to have hearing loss without any actual physical damage to the ear?
|
Hearing is entirely a conscious experience so brain damage can cause loss of hearing without ear damage.
|
Is it possible for planets to collide in orbit?
|
Someone else correct me if I'm wrong please. I believe one of the qualifiers for a body to be a planet is that it has cleared/absorbed any other bodies from its orbit. Therefore, there should be nothing else in its path of that size to hit.
|
Do aromatic molecules have a defined smell, or do different animals smell things differently?
|
Smell cannot be objective. It is a sense that only has a definition with regards to human beings. An object does not inherently have a smell (or color for that matter), it releases molecules (or certain wavelengths of light in case of color) which are characteristic of the object. How those molecules (photons) induce a reaction in an organism will be organism-dependent.
|
What happened to the hole in the ozone layer?
|
Here's a neat article about it: _URL_0_ Though I know most don't come here for a long read so here's the tl;dr: The hole being discovered contributed greatly to its reversal. Had it not been, it would have been quite a catastrophe. It's expected to be completely healed by 2050.
|
How come the rate of skin cancer has increased even though we spend less time in the sun than our ancestors?
|
I would like to see some confirmation that the rate of skin cancer is actually increased. If it is so, it could be because we're getting better at diagnosing it, or: > previous generations would toil all day in the fields ... while wearing long sleeved shirts and hats.
|
How does sun exposure cause skin cancer many years later?
|
For a normal cell to become cancerous, it must develop specific traits through mutation of its DNA - [the hallmarks of cancer](_URL_0_). One mutation event (such as a sunburn) can cause, for instance, a gene that regulates the cell cycle to stop functioning. This cell then passes this mutation to its offspring as it divides. In later years, another mutation event might occur in one of the progeny cells that carry this mutation, giving that cell two mutations. In this way, DNA damage is cumulative, and it takes many years and many mutation events for cancer to occur. [Lots of discussion here](_URL_1_) edit: mangled a sentence due to lack of coffee
|
If I chew gum it will stay soft but if I drink some cold water it seems to harden, so why does my saliva not have this effect on the gum but water does?
|
Assuming the water is colder than your saliva, the gum is hardening because it is cooled off by the water. Your saliva simply is not cold enough to cause a noticeable change in texture. And never apologize for asking a question, that is how we learn. Hope this helps.
|
What happens inside the corn when you make popcorn?
|
Heating of the water molecules causes 1) a pressure build-up within the kernel and 2) the starches retain more water molecules than they would at low pressures. Eventually, the pressure exceeds the strength of the outer shell, and the kernel "pops." When it pops there is an immediate drop in pressure for the starch molecules that were inside of the kernel and retaining water. Those water molecules go from being soluble in the starch to non-soluble vapor, which causes a foaming action. (This drop in pressure is analogous to opening a soda bottle and causing bubble to form.) The change from a liquid to a gas causes rapid expansion of the nearby starch molecules and gives a low density structure. I presume that the resulting corn is white because you are seeing the exposed starch, which is white just like corn starch you buy from the store. tl;dr Water vapor in the kernel from heating causes the popping and leads to a foamed starch that is mostly air.
|
Why can we discern male handwriting from female handwriting?
|
You've obviously never graded large stacks of papers. I can tell you from 6 years of teaching, four of that high school, that there really isn't much rhyme or reason to how males and females write. I've had plenty of female students with horrid handwriting, and a few males students with some of the most beautiful penmanship I've ever seen. That said, I would hypothesize that there is something to how some males *tend* to write, and how some females *tend* to write. Add in differences in socialization, different rates of dyslexia, and a smattering of attention to detail (or lack there of) and it's not hard to see why *some* males *tend* to have messier handwriting than *some* females.
|
Why does our sight get worse as we age?
|
The rule of thumb is that a 70 year old sees half as much light as a 50 year old, who sees half as much light as a 20 year old & nbsp; Mechanisms that reduce the amount of light with age include clouding of the aqueous humors, yellowing of the lens, and reduced responsiveness of the retina & nbsp; Visual acuity is reduced by hardening of the lens, weakening of the ciliary muscles, and reduced range of pupil dilation - all of which lead to reduced ability to properly focus and adapt to changing light conditions & nbsp; Lighting recommendations for facilities like nursing homes include increased illuminance, higher contrast ratios, and fewer light level changes throughout the facility
|
What is the advantage of using rubbing ethanol vs rubbing isopropanol? What is the point of selling rubbing ethanol?
|
If they don't make it inedible it's taxed as liquor. Isopropyl alcohol is toxic to consume (in significant quantities) so it's way easier to sell untaxed and to minors. Ethanol requires all sorts of things added to it to make it inedible. With that said, ethanol is easier to produce (any old yeast will do) and it's easier to make food safe (but then it's taxed). With that said, there are differences, but not much, so I'm sure someone needs ethanol for some lab work or something.
|
The difference between ethanol (drinking alcohol) and isopropanol (rubbing alcohol) is CH2. What about this chemical difference makes ethanol safe to drink, but not rubbing alcohol?
|
Both ethanol and isopropanol act as central nervous system depressants, meaning that at toxic concentrations, these substances can lead to effects such as respiratory depression and coma. Fortunately for us, we have evolved a way to metabolize ethanol. Humans produce an enzyme called alcohol dehydrogenase, which has a specific pocket in it that fits the molecular structure of ethanol exactly and breaks it down upon binding. The reason we evolved this is likely to [break down ethanol produced by bacteria in our digestive tract as food is broken down](_URL_0_). Unfortunately, due to that extra CH2, isopropanol does not fit into our alcohol dehydrogenase enzyme. As a result, we can't break it down, and toxicity is reached at much lower levels.
|
Radiation poisoning: why are nausea and vomiting the first symptoms?
|
Rapidly dividing cells are particularly sensitive to radiation, and the cells that make up the lining of your GI tract and the cells in bone marrow that replenish red and white blood cells need to divide fairly rapidly to function. That's why nausea/vomiting/diarrhea/hair loss/pancytopenia are such common side effects of radiation or chemotherapy (which also targets dividing cells).
|
A common symptom of severe radiation exposure is nausea and vomiting shortly after. What biological mechanism is affected by the radiation to result in these symptoms so soon after exposure?
|
Vomiting is caused by the rapid death of cells in the lining of the GI tract. The sudden loss of stomach lining causes vomiting. The reason this occurs is because the cells in the GI tract lining replicate very quickly and have one if the shorter life cycles of any cell type. Cells that have their DNA damaged by radiation, though, can’t replicate properly. This process is accelerated by apoptosis of heavily damaged cells. When that happens, the stomach lining degrades quickly, leading to vomiting. A similar process is responsible for the loss of hair, flaking of skin, and aplastic anemia after acute exposure. Rapidly replicating cells show the effects of DNA damage sooner than cells that replicate slowly.
|
How much does CO2 from carbonated beverages contribute to greenhouse gas emissions? Can this be measured?
|
None. There's a natural carbon cycle on Earth. When a tree dies and rots, it releases CO2 but then the next tree is able to photosynthesis that back into O2. The problem with burning fossil fuels is that we're bringing carbon up from underground and introducing new carbon into the cycle. The CO2 bubbles in your soda came from the air so when you release them they're just returned to the cycle from which they came.
|
If allergies are caused by an over active immune system, does that mean someone with bad allergies is more likely to get sick as their immune system is constantly "preoccupied"?
|
My guess is no. Allergies are caused by your body over reacting to an allergen. An allergen is an antigen (provokes the production of antibodies) that can provoke type 1 hypersensitivity. When your body responds to these outside antigens it excretes histamine and a few other monoamines. Histamine is big one though. If you have ever taken benedryl (Diphenhydramine) you have taken a H1 receptor antagonist that blocks those receptors which are working over time from Histamine acting as an agonist and causing a lot of those uncomfortable effects. The immune system being preoccuied though? I'm no medical doctor, but like I said I'm guessing no. Allergies are just a body responding to antigens (sometimes more than it should) and allergies are only a small part of what your immune system takes care of. You have all kinds of immune responses, barriers, antibodies etc. You should be safe.
|
Does a photon "leaving" the sun (yet close to it) move slower because it's affected by its gravity?
|
As near as we can tell, photons are massless particles (which makes more sense if you consider light as an EM wave instead of a particle). Gravity does not change the speed at which light propagates, but it can change its frequency ([gravitational redshift](_URL_1_)). Gravity can also change the direction light travels (here is a [previous comment](_URL_0_) where I explained why gravity changes the direction light travels).
|
Why is so much easier to balance on a moving bike than a stationary one?
|
While you are moving, you can make corrections in your trajectory (by adjusting your balance or shifting the handlebars) in order to keep your balance. At slow speed, the correction required becomes larger (since you are moving over a smaller distance), hence why it is easier to balance a bike at speed. When you are stationary, you can't make corrections at all, and you have to balance through other means. Most of these involve turning your front tire to the side and being able to move backwards and forwards (either from being on a hill or riding a non-freewheel bike).
|
When someone gets a transplant, if you wait long enough, do all the organ's donor cells get replaced by the recipients cells?
|
This would depend slightly on the organ, but in general I would say no. First of all, the "all our cells get replaced in x years" factoid is not true. Second, replacement of cells within an organ, if it happens at all, falls to the resident [adult stem cells](_URL_0_), which are likely to have been transplanted from the donor, since they reside in the organ.
|
Would an EMP blast have an effect on our brains?
|
A quick Google search... _URL_1_ _URL_0_ So yes, if the EMP blast was large enough it could have an effect.
|
Would an EMP blast affect human brains?
|
An electromagnetic pulse works on the displacement of electrons (as far as my understanding goes). The electrical activity of the brain is mediated by sodium and potassium, which are vastly heavier than individual electrons. That being said, a study showed that electromagnetic pulses can affect different areas of the brain: (_URL_0_)
|
At what stage in the evolution of life did sleep become a necessity for certain organisms?
|
Sleep is actually a fairly poorly understood aspect of biology. We haven't even been able to answer why we sleep, let alone at what point it became necessary. Any more specific answer you get will be one of pure speculation and not something supported by the facts.
|
If Earth had rings like Saturn, how would it appear on the sky?
|
depends on where you are on the surface. at the equator you might not even be able to see it, although theoretically it would travel accross the sky passing your zenith. farther you go to the poles the thicker the rings would look and the lower in the horizon the rings would be
|
How do "airless tires" work?
|
Are you talking about that picture of a bicycle tire that was on the front page recently? There's nothing magical about airless tires compared to pneumatic tires. The support that pneumatic tires provide through air pressure is instead provided by the material itself. Obviously this requires a significantly larger amount of material. This makes airless tires heavier and reduces fuel efficiency for that reason, as well as the increased rotational inertia associated with the larger mass. One thing to remember is that the pressure on tires is actually not substantially large compared to the strength of a typical material. Even a weak material like rubber can support several thousand pounds per square inch.
|
If identical twins are genetically identical, why do they have different finger prints?
|
Fingerprints are developed in the womb and the shapes that they form are not strictly controlled by DNA but are more a result of environment and random chance.
|
Why do identical twins have different fingerprints?
|
Fingerprints aren't coded for genetically. Fingerprint development takes place in the womb as the fetus touches surrounding structures. As such, the exact position in the womb, the density of the womb’s amniotic fluid, the general chaos in the womb, as well as the activity of the fetus determine how every individual ridge will form.
|
Why does healing skin itch, prompting one to scratch off scabs and promote infection?
|
Wound contraction. When an injury heals dry it scabs, in the final portion of the proliferative phase of healing the skin is being tightened with myofibroblasts and in turn, alpha-smooth muscle actin which pulls (or pushes, however you want to look at it) the wound closed. This hurts, relatively. Those small pain signals being sent to your brain register as an itch. Weak sources: _URL_0_ _URL_1_ To answer your question about scratching, evolution and the human anatomy is far from perfect.
|
Instead of the Universe expanding, could all mass be shrinking?
|
No, because the measurements indicating that the universe is expanding have nothing much to do with mass and everything to do with the red shift of light.
|
Why are there six types of quarks instead of two?
|
As far as we know all the quarks (and all the leptons) are elementary, in the sense that they are not made of smaller constituents. Many of them are known to be (if not pointlike), smaller than 10^(-18) m. [Composite models have been proposed](_URL_0_), but they don't yet successfully simplify the theory, and research activity along these lines has decreased. So, the simple answer to your question, "Why are there six types of quarks instead of two?" is, "We don't know."
|
What is the difference between the six types of quarks?
|
There are three "generations" of increasing size, and in each generation there is a quark with 2/3 the charge of a proton and another with 1/3 the charge of an electron. The first generation is up/down, the second is strange/charm, the third is top/bottom. Starting in the 1950s, more and more particles were being discovered and it was thought that these were fundamental, but by grouping them in terms of common properties like charge and spin it was deduced that all of them could be explained as being made up by a small number of constituent particles, which were termed quarks. Quarks aren't really Planck scale; their interactions relevant over femtometers, which is much much larger than the Planck length, and their mass is much much smaller than the Planck mass. Planck's constant has units of angular momentum, not energy, so you can't equate it to an energy to determine a mass.
|
Why is visible light blocked by opaque matter, but not other wavelengths of EM waves (gamma rays, radio waves, etc.)?
|
Your question is somewhat redundant. Opaque matter is opaque precisely because it absorbs or deflects visible light. Different materials are opaque in different parts of the spectrum. So far as I know no material is transluscent or opaque across the spectrum, though some are opaque or translucent at various points.
|
Why are our fingers different lengths?
|
The different lengths of each finger allow you to concentrate your grip strength on the central fingers while the edge fingers apply precision. Each of the fingers contributes a different percentage to your grip strength It's roughly 25%, 35%, 25%, 15%: _URL_0_ If they were all the same length, they'd all apply the same force since the grip of any finger is approximately correlated with its length: _URL_1_ If your fingers were all the same length and any torsion were involved, the outer two fingers would be forced to bear the majority of the load. You'd lose precision and in the worst case, maybe even a finger.
|
[Medicine] Why has the number of cases of autism increased so rapidly over recent years?
|
It's just diagnosed a lot more in recent times. The incidence probably hasn't changed much. In my opinion it's become something of a "fad diagnosis." Some children may be misdiagnosed with it. One of the problems is the etiology of autism is poorly understood. It may in fact represent a somewhat arbitrary group of symptoms that could be the result of several different conditions.
|
Has the rate of Autism actually increased over the years?
|
> Can it be definitively said if the incidence of severe/full blown cases of Autism, how most of the public sees them, has actually went up? It is my understanding that the answer is 'yes'. Even controlling for higher awareness and proper diagnostics leading to an increase, the overall rate has increased and I will explain what the hypothesis I am familiar with is. The citizenry of modern nations, all around the world, now have access to much better medical care than they have ever had. We are able to treat and even cure many more illnesses than before and our standard of living has improved. As a result, many people that would have previously died are now surviving to reproduce. Given that people of less robust constitution or even people with straight up illnesses are now reproducing, this has had the direct effect of slightly increasing the rate of congenital defects across the board, including many forms of what is now called autism. That is the strongest hypothesis I am familiar with.
|
If space wasn't a vacuum could we hear the sun?
|
From my rudimentary math that might not be quite right I got that the sun would have to generate 1,670,000,000,000,000,000,000 Watts in order to be heard as 225 dB on Earth (225 dB pretty much being the threshhold where your eardrums are guaranteed to rupture). In comparison a jet engine generates roughly 1,000,000 Watts. In my completely unqualified opinion, I would think this to be unlikely and thus the sun would not be heard from Earth. Edit: ALso for reference, the loudest sound ever recorded on earth was the eruption of Krakatoa which could make someone go deaf up to 16km away. The sun would have to be loud enough to make you go deaf 150 million km away. Edit for maths: 225 dB = 10*log10(I/Io) = & amp;gt; I = .0059 W/m^2. I = Power / (4*pi*r^2) where r = 150,000,000,000 m (distance from earth to sun, this assumed all power is generated on the surface of the sun which may not be the case.) Power = 1.67*10^21W. Edit: deep meant 21 not 12
|
Will a large cup of coffee hold heat longer than a small cup of coffee?
|
Yes, because of the [relationship between surface area and volume](_URL_0_), a larger cup will not have a proportionately large surface area in which heat transfer could occur. This is also something you can easily test at home.
|
How much mass does the sun lose per second as light - photons - alone?
|
Let's find out! If we go to [the sun's Wikipedia page](_URL_0_) and look at the infobar on the right, it says, in "Physical Characteristics," it says solar luminosity is 3.846×10^26 W, or 3.846×10^26 J/sec. So every second, it sends out 3.846×10^26 J. Now we just plug in the most famous formula ever: e=mc^2 3.846×10^26 J = m×(299792458 m / s)^2 3.846×10^26 J = m×8.98755179 × 10^16 m^2 s^-2 4279252114.33 kg = m So, the sun loses about 4.3 billion kilograms a second.
|
Is there evidence that severe or uncontrolled migraine headaches can cause any permanent damage?
|
Yes there is. Same article, different mirrors: _URL_1_ _URL_0_ Ctrl+F and search for "lesion". It is mentioned several times that migraine sufferers have increased risk of deep white matter lesions.
|
What does this type of double bond mean?
|
A crossed double bond is used to denote the presence of geometric isomers - see for example [this article](_URL_0_) (FYI - link directly to a PDF) from IUPAC, in particular where it's mentioned on pg. 1961. It's not the preferred way of doing so any longer, but can still be encountered on occasion.
|
Is it actually necessary to boil pasta? (Could I make spaghetti if I let it sit for days in cold water?)
|
Here's your chance to actually _do_ science! Try it out and see what happens. I recommend checking every 15 minutes for the first hour, 30 minutes for the second hour, etc.
|
How effective would alcohol be in stopping a sore throat in the long term?
|
Questions like this get asked often, the simple answer is "it wouldn't help." Alcohol at high concentrations (say 70%) can kill many bacteria on contact but each time you ingest alcohol, you suppress the immune system. You may "disinfect" your throat for a moment or two, but the immune suppression will cause the infection to flare up again worse than before.
|
If birds are thought to have evolved from reptiles, how did they develop warm bloodedness?
|
Actually theres new data coming forth that points toward dinosaurs actually being warm blooded. _URL_0_
|
Since birds descended from ancient reptiles, how did they go from cold-blooded to warm-blooded?
|
A lot of theories are listed [here](_URL_1_). I dunno. It's worth noting that "warm-blooded" and "cold-blooded" are no longer considered good descriptors of reality. You can sort of use the terms relatively, but because there are a number of mechanisms that affect this, different critters may have their "blood warmed" in different ways. *Most* animals have some sort of mechanism for this. To pick an example, the swordfish has a mechanism that keeps the temperature up at the eyes and brain. Dinosaurs *may* have generated heat by [dint of sheer size](_URL_0_). Some animals actually mix it up a little: A few breeds of birds' blood drops to ambient temperature at night but warms up during the day.
|
Given an infinitely powerful computer, what are the minimum preconditions it would need to simulate a universe similar to our own?
|
We don't know the answer to this yet. It depends on what the fundamental rules of physics end up being. It could simulate *very nearly* a universe that is very similar to our own excepting the very early stages of the big bang and maybe certain quantum processes would be adjusted by "fudge factors" rather than a fundamental understanding of why those factors exist. For instance, dark energy is such a fudge factor. We know it's there, how it behaves on the large scale, how much there is. What exactly it does or how it works we don't know.
|
Could a computer in our universe theoretically contain enough information to exactly simulate our own universe?
|
I'm not sure it would be possible - wouldn't you need more than one particle to store the information about a single particle, hence you'd need a computer bigger than the universe is in order to model the universe? Then there's another problem that just occurred to me - if the computer you were using to model the universe existed, it would be within the universe, which means the computer would have to be modelling itself modelling itself modelling itself... etc. and now my brain is bleeding and coming out my eyes.
|
Can other animals see different colors?
|
Ooh, an excuse to talk about [bee-vision!](_URL_0_) Flowers aren't trying to impress you. They want to advertise to bees, and like many insects bees can see into the low end of ultraviolet. Many flowers have extra patterns and [nectar guides](_URL_1_) on them that only a bee could see. Don't get too jealous of bee-vision though - bee eyes [are very different from yours](_URL_3_). They get colors we don't, but their world is likely a pixelated schmear due to lack of image-forming eyes. They don't do well on vision tests. Bees are [not alone either](_URL_2_) - some birds have UV vision too, and some snakes can "see" infrared.
|
Why does water extinguish fire?
|
AFAIK its purely temperature. Common fire (there are lots of uncommon fire that can take place even underwater) is basically the combination of carbon + oxygen. The trick is that C and O don't normally combine at low temperatures, so they need to be heated. Water does this in several ways, first it has a pretty high specific heat, which means it can absorb a lot of heat energy, cooling down fire to temperatures unable to continue burning. Secondly, when water undergoes state transition, boiling, it also cools. This has the effect of not letting the surrounding material get hotter than the boiling point of water, which is below the combustion point of most common materials.
|
Why does water extinguish fire?
|
Because it blocks its access to oxygen, and because it cools things down (because water has high capacity). CO2 extinguishers only block access to oxygen (usually because water is for some other reason dangerous, like in electrical fires). Yes, it could. Put a wood fire in a closed container and it extinguishes when it converts enough of oxygen to CO2.
|
Does darkness exist or is it just the absence of light?
|
Darkness is just sufficiently low enough levels of visible light. Whether or not absences exist is a different type of question.
|
Is darkness just the absence of light, or is it an independent phenomenon?
|
Darkness is indeed the absence of visible light. However, even in a pitch black room, there will be some light which your eyes cannot see and light you can see, but of which there is too little to trigger the photosensitive cells in your eyes.
|
Why does milk violently froth when reaching its boiling point?
|
Milk contains a variety of [emulsifying](_URL_1_) compounds to keep everything as a liquid to begin with. These compounds also function as [surfactants](_URL_0_), which is why blowing bubbles in milk is so much more rewarding than in water. When the milk boils, the water in which everything is dissolved is converting into gas and forming bubbles. When you boil pure water, those bubbles can escape. When you boil milk, those bubbles are trapped by the surfactants, and thus form a froth.
|
Why are the solar panels on the ISS orange when the ones on Earth are blue?
|
It’s not exactly well documented, but from what I could find, it has to do with their construction. Each solar array is made of two large, retractable blankets of solar cells. They were sent up folded like an accordion, because unfolded they’re almost twice as long as the shuttle’s cargo bay. The cells are laid out in a grid, and layered between sheets of [Kapton](_URL_0_) which is what gives them the orange hue. Kapton is flexible and non-conductive, so it’s often used in flexible electronics electronics. It also has great heat resistance, which is necessary because the panels can get up to 150°C.
|
How long did the impact winter that killed the dinosaurs last?
|
A recent study suggest it wasn't much more than 3-4 years, but that it was extremely intense: [Link](_URL_0_) Can recommend the video linked at the bottom; most landmasses end up at sub-freezing temperatures!
|
Does the air inside the tires of a moving car move inside them?
|
Yes, in multiple ways. When the tire is stationary, the air molecules are still constantly moving and bumping into both each other and the sides of its container. When the tire is moving, the molecules that hit the sides of the container (the spinning tire) are flung in the direction of the spin, causing the air to generally spin in the same direction as the tire, albeit in a delayed fashion (the air will be delayed to get "up to speed" as well as delayed to stop spinning inside the tire when the tire stops). ~~However, the air molecules do not actually move any faster than they normally do -- they just change direction.~~ EDIT: There is a change of velocity in the air molecules when spinning, however while the change is relatively small compared to their velocity when the tire is at rest, there is a change present. Although, the heat caused by the friction of the road on the tire contributes considerably more velocity to the air molecules in comparison.
|
How do radio stations transmit information (song title, artist, "like us on facebook", etc) along with music?
|
This should provide your answer _URL_0_ Basically your normal FM radio is working by superimposing the audio onto a base frequency A reciever than can pick up the RDS infomation will also look for additional data broadcast on a different carrier frequancy in parallel to that of the main broadcast Older radios are not looking for this information and because it is not interpreted as sound because it as at a different frequency to the main broadcast, outside of the usual FM range.
|
How does radio stations transmit the name of the song currently broadcasted?
|
The system is called RDS: _URL_0_ It's a way to transmit a small digital information on the same frequency as the analog FM signal, without interfering with eachother..
|
If Photons don't have a mass/charge, why don't they go through matter?
|
I remember in a Sixty Symbols video in which professor Moriarty explained that photons are absorbed by matter. In the very small spectrum of light that we can observe, ROYGBIV, the rays are absorbed into a matter and light is produced by the electrons they excite. Something see through like glass has an energy activation level that is too high for a photon to excite those electrons, which is why glass is see through, light just passes right on through. When you take an X-Ray, the x-radiation excites the electrons in your body and produces an image to scanners that can see that light. We cannot, however, observe that spectrum of wavelength and that is why when you take an X-Ray you do not see your leg flashing when the radiation is bombarding your leg. Hope this helps. I can answer only with a very limited scope of knowledge. Source: _URL_0_
|
Why does acceleration due to gravity stay constant no matter the mass of the falling body while gravitational force increases when mass increases?
|
The two relevant equations are: F= G × m × M × r^-2 and F= m × a The former equation gives the gravitational force between two objects; the latter states that the force on an object is equal to its mass times its acceleration. In the first equation, let's fix M as the mass of the earth, and consider the amount of acceleration that mass has on a smaller object m, like a bowling ball or a feather. Well, we have two equations for the force, F, so let's equate them: G × m × M × r^-2 = m × a Note that m appears on both sides; so we can divide it out. G × M × r^-2 = a Now we have a formula for the amount of acceleration experienced by an object in Earths gravitational field; but note it doesn't depend on m, so it doesn't matter if the object is a bowling ball or a feather. All that matters is the gravitational constant G, the mass of the Earth M, and the distance between the object and the Earth, r.
|
Does gravitational acceleration increase mass?
|
Mass doesn't actually increase with relative velocity. In modern parlance, mass is the invariant quantity that was previously referred to as "rest mass". Energy is more complicated. An object's energy depends the frame its measured in, and the faster an object is moving in a given frame, the higher its energy will be. For a curved spacetime, however, such as the region around a black hole, there is no universal inertial frame of reference, and so defining an object's energy is more complicated than asking "What is its energy relative to an outside observer?" That said, in the usual Schwarzschild coordinates, the energy of an object falling into a black hole does increase over time. Note: It actually goes to infinity as the object approaches the horizon, but this is a peculiarity of the coordinates.
|
When will humans become hairless and why did we lose our need for hair?
|
It is doubtful we will lose it any time soon, we currently like how it looks and select for those that have nice hair. One theory for why we lost our body hair is that losing it greatly helped us keep cool and also may have reduced parasites that reside in fur. _URL_0_
|
how can some mouth wash or toothpaste restore enamel?
|
Fluoride strengthens [teeth](_URL_3_) by [being absorbed while brushing or rinsing](_URL_2_). It displaces a hydroxide group in a chemical that makes up the enamel of your teeth ([hydroxyapatite](_URL_1_) -- > [fluorapatite](_URL_0_)) and takes its place in the tooth structure. Fluorapatite is a stronger and more resistant compound, which helps strengthen and "restore" enamel. However, *regrowth* of enamel is still an emerging science and not currently a common process.
|
Why do you forget your dreams?
|
Using this as a reference: _URL_0_ , Wikipedia suggests > "Certain brain chemicals necessary for converting short-term memories into long-term ones are suppressed during REM sleep." So it would seem that unless you make the conscious effort to remember your dreams upon waking, they'll likely fade quite rapidly.
|
When a car brakes, will the decelleration be linear or will it decellerate quicker at some speeds and slower at others?
|
The force of deceleration will be constant (assuming the brakes are applying constant pressure). Because the force of deceleration is constant, the decrease in speed is linear. Because the decrease in speed is linear, the distance it takes you to stop is *quadratic* with respect to your starting speed. E.g., if it takes you 10m to stop from 50km/h, then it will take you 40m to stop from 100km/h. It's the reason why PSAs such as [this one](_URL_0_) focus on what, at first glance, seems like a trivial difference in speed (60km/h vs 65km/h). Because stopping distance varies quadratically, small differences in speed can be important.
|
Diamonds require millennia of heat and pressure to form, yet we cab create them artificially. Could we take organic waste an create artificial fossile fuels?
|
Sure, we can create hydrocarbon fuels from waste. The problem is that it uses more energy than we get out of the fuel at the end.
|
If scientists can synthesize diamonds from carbon, why can't they do the same with fossil fuels?
|
> What am I missing? The economic side of the equation. People have been able to manufacture [synthetic fuels](_URL_0_) for a while now. The method you described is just not cost-effective (remember you have to input the heat and pressure).
|
Are all of the fossil fuels on and in earth made up of carbon dioxide that was once in the atmosphere?
|
Short answer: yes. Way back (4 billion + years ago) the atmosphere was 25% CO2. The CO2 dissolved into the oceans and then formed carbonate rocks. From there it worked its way through rocks, soil, and life, to eek back into the atmosphere just barely. For perspective, C is distributed on our planet like this (by mass): Sediments: 7.4e7 Pg Ocean: 3.8e4 Pg Atmosphere: 7e2 Pg Biosphere: 7e3 Pg The lithosphere *clearly* dominates. So our emitting CO2 back to the atmosphere is in total, small in terms of the total carbon reservoirs. But the atmosphere hasn't seen CO2 like this for awhile, and back when it was last like this, the earth was quite different.
|
Some scientist hypothesis that Solar Wind stripped away most of Mars atmosphere. Could Earths atmosphere also be suitable to being stripped away by solar winds?
|
I am surprised that you have not received an adequate answer thus far so I will do my best to recollect an old NOVA episode about mars. From what I can remember the reason that Mars had its atmosphere stripped away by the solar wind is because the magnetic field that surrounded the planet weakened because the core cooled/ stopped spinning as fast. *Think of the core as a gigantic spinning magnet* This allows more charged particles (solar wind) to enter the atmosphere and therefore strip it away. The Earth, on the other hand, still has a strong magnetic field from our core, which protects us and our atmosphere from the wrath of the Sun.
|
Is the universe expanding at the atomic level as well?
|
No. The metric expansion of space takes place in the sparse areas of space between distance interstellar objects. Within those structures the fundamental interactions dominate. E.g. gravity keeps our solar system together (and the space it occupies), electromagnetism keeps molecules together, strong force keeps atoms together. The expansion happens in parts of the universe where there is little or no matter to keep space from expanding. > So sometime in the distant future could the expansion begin effecting gravitational forces that hold large mass objects together, and then eventually the weak and strong nuclear forces so that atoms will fall apart? Yes, this is hypothetically possible. It is known as [the big rip](_URL_0_).
|
[Human Body] What happens with the lactose in people who are lactose intolerant to cause gas/diarrhea?
|
In healthy people Lactose is broken down by the enzyme Lactase, lactose intolerance is the lack of this enzyme. So the sugar Lactose moves through the body until it reaches the large intestine. There, bacteria break it down. They break it down into smaller sugars, Glucose and Galactose, and release gasses such as Hydrogen. The released gasses are what causes flatulence and bloating. The sugars in the large intestine change the concentration of sugars in the water in the gut so water flows into the gut from the blood leading to very watery faeces and therefore Diarrhoea.
|
Why do people think they sleep better during a thunderstorm?
|
The rain creates white noise that is soothing to most sleepers because it offers a low level of auditory stimulation. If it is completely silent, sounds that may happen that the white noise would cover up increases your sympathetic signaling in the ANS with the possibility of rousing you. Also it keeps your brain from creating artificial auditory stimuli.
|
Does deeper sleep during thunderstorms relate biologically to a decrease in predator activity?
|
[Here](_URL_1_) is the link that got me thinking about this. edit: I meant to link to [this reddit post](_URL_0_) but copied the wrong link.
|
Does the perceived size of the moon actually increase as it moves from the horizon to overhead? Or is it just an optical illusion?
|
You win the bet. The moon does *seem* larger to the eye near the horizon, but it's an illusion. Images like [this one](_URL_0_) allow a direct comparison of the apparent size of the moon at different points above the horizon and show that it's constant.
|
Marine biologists use submarines with bright lights to film deep sea creatures, many of which have very large, sensitive eyes. Are the retinas of these animals damaged by these lights, and do they try to avoid the subs?
|
Marine Biologist here, to answer your question the most truthful answer is "we dont know". Thats due to a lack of research, species specific responses and difficulty of accessing the deep sea. But that's not very fun or elaborate. [An interesting report here](_URL_0_) covers most of the bases. It seems in most species, bright light exposure temporarily removes the ability to respond to light stimuli. After some time to re-acclimate, the fish respond normally again. That would obviously vary with species, intensity and exposure time etc. The only true permanent damage stems from UV exposure which wouldnt be emitted by ROV sub white lights. EDIT: Reworded to avoid taser like vocabulary
|
How damaging are submarine lights to deep sea animals' eyes?
|
this is a great question but a similar one was asked before. "Research subs usually use red light when in the deep sea since 99.8% of animals can't see it (red is the first wavelength filtered out in seawater so there is no red light at depth. Almost all deep sea organisms don't even have photoreceptors to see it) and it's not harmful. The white lights are mostly used for filming purposes. But yeah, they absolutely are being blinded most of the time." source_____________________________________________ _URL_0_
|
If we viewed a star "going supernova" in real time, would it look like a violent explosion, or does it take a long time?
|
A type I supernova begins when the star undergoes electron degeneracy collapse - meaning that all the electrons and protons in the star undergo reverse decay and merge into neutrons. The process takes about 20 seconds, which is a pretty amazing speed for anything to happen on the scale of a red giant. But other posters are right, the actual explosion (which happens when the outer layers of the star rebound against the newly-formed neutron core) would take several minutes to become apparent. Though still, that's incredibly fast for an enormous, billions-year-old star. edit: gilded! Thanks guys! (Not really, but I just always wanted to say that.) edit: gilded *for real!* Thanks! It's like my very own supernova.
|
Why do we design vehicles to be aerodynamic (laminar?) while dimpled golf balls are designed to create turbulence to get them to travel farther?
|
If the ball was aerodynamic to begin with, dimples wouldn't be necessary. The dimples help mitigate the drag the overall shape causes.
|
Can you shoot a bullet in space?
|
Yes. While there is no oxygen in space, the cartridge of the gun contains oxidizers. I leave the math of "how long" to the reader.
|
If you are the recipient of an organ transplant and you get a DNA test, is it possible to get the reults of the donor?
|
Depends on the type of organ transplanted and the way the test is administered. A bone marrow recipient getting a blood-based test would certainly have interesting results. Getting a cheek swab, on the other hand, probably wouldn't turn up anything of the donor.
|
Are all the stars I see at night in the Milky Way?
|
All stars in the night sky that are visible are stars in the Milky Way. They're also stars that are close by in the Milky Way; none are more than a few hundred light years away. Andromeda and the Magellanic Clouds are visible, and are significantly further away, but it's impossible to make out individual stars in those groups.
|
How do our eyes see the stars much better than a camera?
|
They dont, if you could remove an eye and plug it into a printer, open the shutter for a tiny fraction of a second the picture you would get would be more or less jack. Now take a camera, have the shutter open and close about once a second for minutes, have a powerful computer that stabilises the image, adjusts light sensitivity, and plugs in gaps by recreating complete parts out of imagination/expectation and you would probably get a much better image than our eye. Its obviously not the hardware, its the software.
|
How do we know what the Milky Way looks like?
|
You can trivially measure with great accuracy the angle or direction a star is positioned at relative to earth. By various methods [explained here](_URL_0_) you can relatively accurately estimate the distance. When you know the distance and angle of a great number of stars or larger structures like arms or groups of stars or nebulae you can reconstruct a model of the galaxy. Our milky way models are quite inaccurate because closer stars block the view to further away stars. It happens very often that a photograph of another spiral galaxy is used for illustration of some article that deals with the milky way. Often the fact that this is not the actual milky way is omitted. Of course we cannot get an actual photograph of the milky way.
|
How do we know what the Milky Way looks like?
|
We know what the Milky Way looks like from direct observation and measurement. We know it's flat because there is a bright strip in the sky. We know it has arms because we can measure the position of stars within our galaxy and map their location and star density of regions (certain directions and distances will have different amounts of stars, consistent with spiral arms.) The galactic bulge is fairly evident. The bar shape in our galactic center has been observed with [space telescopes](_URL_1_). Looking out of our galaxy we see other galaxies that are disc shaped, have arms, have a galactic bulge, have bars, have dust clouds, have the same overall color, etc. [This leads us to conclude our galaxy looks very similar to these.](_URL_0_)
|
What are the emissions of burning gasoline?
|
The wiki page is a good source: _URL_0_ All cars are not created equal, and older cars can produce much more exhaust than cleaner cars: _URL_1_ In perfectly clean burning, the carbon from gasoline is turned into CO2, the oxygen and hydrogen is burned into water, and nitrogen into N2. Burning is a wild and chaotic event, however, and impure compounds such as CO and NO2 can form, to say nothing of evaporated gasoline, and particles of soot.
|
Can a planet with a large mass rotate fast enough to reduce gravity?
|
Yes. Partly because of Earths rotation, at the equator you weigh only 99.6% of what you would weigh at the pole. Let's address your question specifically. Neptune has an equatorial radius of 24,765 km and a volume of 57.74 Earths. That means, if it was the same density as Earth, it would have a mass of 3.45×10^(26) kg. Hence, without any rotation at all, acceleration due to gravity on our hypothetical planets equator would be G×M×r^(-2)=37.5 m/s^(2). We want Earth-style gravity, which is 9.8 m/s^(2). Hence, the centrifugal acceleration must be 27.7 m/s^(2). Using a=rw^2, we have 27.7 m/s^(2)=24,765,000 m × w^2 or w=1.06×10^(-3). That's how many radians a second we're rotating. Divide 2pi by this quantity to get the length of the day in seconds, and we have 5941 seconds, or 1 hour 39 minutes. **So, in order for a Neptune-sized mass of rock with Earths density to have Earth-like gravity at the equator, it would have to have a day of length 1 hour 39 minutes.**
|
Would it be possible to discover new elements on a foreign planet? If so, how would they differ from the ones we have on earth?
|
New elements, not likely. New isotopes, maybe. New minerals, absolutely.
|
If looking at distant galaxies is like looking into the past, and if we had a telescope that could see the big bang, could we see it looking out from any spot around Earth?
|
You can not *see* the Big Bang. The earliest you can *see* is the [CMB](_URL_0_) (Cosmic Microwave Background) which is about 380,000 years *after* the big bang. Yes... we can see this from every point on earth and we have mapped it very well (WMAP Survey) - and this has helped us prove the Big Bang as well as Expansion of the Universe. The reason you can't go back before the CMB is prior to the CMB the temperatures and densities of the universe were so high that photons were almost instantly absorbed after being emitted - so no light can reach us from that time because it didn't persist. Once the universe cooled and inflated enough - light could persist. This earliest light has now red-shifted into the microwave spectrum and is the CMB.
|
If stars have more planets than previously thought, would this "add " enough mass to galaxies so we don't need dark matter for explaining their dynamics?
|
This can't explain astronomical observations. There is about 4-5 times as much mass as we can see in star form, and planets typically weigh at most a few tens of a percent of their stars, but often much less. If planets weighed more than stars, we wouldn't see the orbits that we do. There was an idea that the missing mass might be in the form of starless brown dwarf planets or other massive objects (the MACHO hypothesis), but their existence has largely been ruled out by the non-observation of microlensing.
|
How does LSD cause hallucinations?
|
I can get you started, but I won't be able to answer all of it. LSD is a serotonergic psychedelic, along with drugs like DMT and psilocybin, which means that it binds to serotonin receptors. It acts as a partial agonist for these receptors, particularly 5-HT2a. Its action at the 5-HT2a receptor site is *probably* responsible for its psychedelic effects. I really can't tell you anything more in-depth than that, unfortunately. It's worth adding that there is no true answer to your question, because no one knows the exact reason that LSD causes hallucinations. But someone can probably get you pretty close.
|
(Human Body) How do hallucinogens like lsd and shrooms affect the brain to induce hallucinations?
|
It really has to do with where in the brain the receptors are that LSD binds to. These receptors are serotonin 2A receptors, and a large amount of them are in the prefrontal cortex (PFC). The PFC does a lot of higher-order processing, including visual processing. So stimulating these receptors here activates lots of neurons in a way that triggers hallucinations. LSD in general doesn't just act on these receptors, so it has a lot of other effects. But the main hallucinogenic properties are thought to be due to the serotonin 2A activation. Fun side-note: most anti-psychotic drugs block these receptors to inhibit signaling on these neurons, therefore reducing/preventing hallucinations.
|
What causes the rapid pressure increases in the cabin of my vehicle while the rear windows are down and the car is moving at highway speeds?
|
The noise you are speaking of is caused by buffeting, which has to do with the aerodynamics of the car. [Here is a link](_URL_0_) to a Car Talk discussion of the phenomena.
|
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.