question
stringlengths 19
300
| answer
stringlengths 28
1.02k
|
|---|---|
Can many small, quieter speakers produce sound equivalent to a single larger, louder speaker?
|
Yes, due to a principle called constructive interference, the sound waves with matching and in phase frequencies will build on eachother, making the amplitude higher and the volume louder. Think of a crowd cheering in a stadium for a simple example. However, from an engineering point of view the sound would probably sound distorted unless you were listening in an open field, or the small speakers were very close together. This is because the holes you see in speakers are designed to 'spread' the sound out, and with multiple different speakers the waves could reach you at different times causing a very slightly dodgy sound (this may well be an insignificantly small error however)
|
What is the limit to how small speakers can get, whilst still producing a powerful sound?
|
I wouldn't say that there's a limit, more like a relationship. To produce sound speakers just vibrate to make pressure waves in the air. The frequency and amplitude of these waves determine what sound is produced. I don't think that there is a "limit" other than the fact that you need something to make the air move how you want it. It's just that the louder you want your music or sounds the be, the more air you'd need to move. And so the more air you want to move, the larger the surface of whatever moves it. I think some company has engineered a way to move a plastic film back and forth to produce sound, so it's really thin but still wide (think like a sheet of paper). The quality of sound is often pretty important. A lot factors into this like material choice and volume (size) of a speaker's housing. So it's not really a matter of how small can something be, it's more like how much volume and quality of sound do you want to sacrifice for size.
|
How big would the sun be compared to Venus during the transit?
|
The Sun is 1.4 million km wide. Venus is about 12,000 km wide, so the Sun is 116x wider than Venus. BUT during the transit, Venus will be much closer to the Earth than the Sun is so it will appear to be larger than 1/116th the diameter of the Sun. The angular diameter of Venus during the transit will be 58 arc seconds, and the Sun's will be 1891 arc seconds. So that's 58/1891 = 32.6 So the Sun will appear to be about 32.6x larger than Venus during the Transit.
|
What insects besides mosquitoes are common vectors for human disease?
|
Not a complete list by any means, but some off the top of my head include the reduviid bug (Chagas disease, via trypanosoma cruzii), the tsetse fly (African sleeping sickness, via trypanosoma brucei), the ixodes tick (Lyme disease via borrelia burgdorferi and many other diseases), deer flies (loa loa disease), blackflies (river blindness via onchocerca volvulus), sandflies (leishmaniasis), etc.
|
Why do planets have axial tilts which deviate greatly from the normal of their orbital plane?
|
I am no astronomer, but in the off chance this doesn't get answered, I'll give it a go. Their orbit around the sun, as you said, is planar. However, the gravitational force acting on each planetary body is relatively uniform. That is to say, the gravity pulls no more on the poles than anywhere else on the planet. The tilts, therefore, are not influenced by the sun's gravitational well. The planets' individual rotations and original tilts are due to formative collisions and other influencing forces.
|
I just read that there could be 100,000 more rouge planets in our galaxy than stars. Is this enough to account for dark matter?
|
The dark matter content of the galaxy is roughly 0.12 g/cm^3, as reported by the WMAP 9-year data. If we assume that each of the rogue planets has a mass equivalent to that of jupiter, that would account for: 1.898x10^27 kg * 10^5 planets = 1.898x10^32 kg. The volume of the milky way galaxy is around 10^63 m^3. If we assume that the planets are distributed evenly, this would contribute 1.898x10^32 kg / 10^60 m^3 = > 2x10^-28 kg/m^3, or around 10^-31 g/cm^3. This is an order of magnitude estimation, but clearly this is not nearly enough matter to account for the dark matter in the galaxy. Edit: formatting Edit: Dark matter density should be GeV/cm^3, not g/cm^3. Thanks to NJerseyGuy for the correction.
|
Why aren't there any pictures from the Moon that show the Earth at night?
|
The Earth-facing side of the moon will be on the light side of the Earth about half the time. But the moon is far away enough that usually one will be able to see a mix of night and day on Earth. Moreover, because the moon is so far away the night part of the Earth is nearly completely black (unlike say pictures from the shuttle or the International Space Station which at a few hundred miles up can still pick up human lights). For a famous example of this look at this picture of ["Earth rise"](_URL_0_). Note how the dark part of the Earth is from the perspective of the moon the lower part. In this picture, East-West replace North-South. That is, the Earth is being viewed on its side. That's in part because the lunar landings occurred in the equatorial region of the near side of the moon. It is a good exercise to try to visualize how this would change if one took the picture from nearer one of the lunar poles.
|
Why aren't there any pictures of a sunrise from the moon?
|
There must be pics of a "sunrise" from low Moon orbit, but I assume that's not what you mean. If you want to land on the Moon, it makes sense to do it in daylight, not darkness. But then it takes anywhere up to 2 weeks for the sun to set, then another 2 weeks of darkness until you get your sunrise. So if we ever decide to go to the Moon for several weeks at a time, that's when you'll get the pics you want. But I'm not sure how interesting such a photo would be actually. It would look the same as any other picture on the moon, but with the sun just closer to the horizon, and everything completely backlit. It's much different for us who have an atmosphere to scatter light of various colors around.
|
Is Sugar in the Raw really healthier than normal sugar?
|
The FDA has an [ambiguous definition](_URL_1_) for the use of the word "natural." Sugar is not a significant source of vitamins and minerals in a well-balanced adult diet; it is an inefficient source of these nutrients. The health concern with sugar products usually arises from two things: (1) the caloric content, which is about 4 kcal/g regardless of the type, and (2) the glycemic index, which is pretty much the same. All the monosaccharide sweeteners available on the American market, including brown rice extract, natural sugar, honey, and table sugar, will give you the same amount of metabolic energy, and will cause about the same rise in insulin, and should be all used with similar moderation. Hope that is some helpful information.
|
If gas giants are literally made just from gas, does that mean they have no solid ground to stand on?
|
Nobody really knows -- but it's possible that at the core of gas giants there is quite a lot of iron and other heavy elements. Possibly even more heavy material than the mass of the Earth. Of course they are incredibly hot and under incredible pressure -- so you can't exactly stand on these hypothetical cores.
|
Is it possible that there is a galaxy much closer to us than Andromeda, but it is on the other side of the milky way core?
|
Well, it is a good question. I guess that we can say so, since we can´t see with detail stars from the other side of the galaxy, we could have a close galaxy that we can´t detect because all the star´s brightness. But there is a counterpoint to it: wouldn´t that close galaxy keep getting closer to ours because of the gravitational effect of such a huge galaxy (with a big black hole)? PS: After talking with some fellow astrophysics, they said it is unlikely, but admited it´s not impossible.They say it´s a good point since neither of the galaxies in the Local Group it´s in the opposite direction of the Milky Way core.
|
If sugar is made by plants for energy could sugar be use like fertilizer?
|
Plants have not evolved under conditions where they can get nutrition by absorbing sugar from the ground, so the answer is "no". If you added sugar to the soil, though, microorganisms and fungi would happily find a way to pick up on it.
|
What reaction causes OxiClean to make red wine turn green immediately?
|
Red wine contains [anthocyanins](_URL_1_), which are colourful pigments that act as pH indicators. When in acidic solution, they're pink/red. When in basic solution, they're green/blue. [OxiClean has sodium carbonate](_URL_0_), which is a base. When added to wine - which is usually acidic - it brings the pH up so the colour of the stain changes.
|
Why doesn't it look or seem like Mars does not have tectonic plate movement or the resulting mountains?
|
Those topics have been the object of previous discussions. You'll find links to those threads here: _URL_2_? _URL_1_? _URL_0_?
|
What is the defining difference between moons and planets when in a Co-orbital configuration?
|
There's no strict definition, but one of the more popular ones is whether the barycentre (centre of mass) falls above or below the surface of the larger object. Said differently, whether the two bodies orbit a point within the planet or a point in the space between them.
|
Does changing tire size on a car change the mpg?
|
It will depend on more factors than simply the diameter of the tire. A larger diameter will give more resistance to change in its [rotational inertia](_URL_0_) than a smaller tire. When you are out next, pay attention to the diameters of different vehicles wheels. Less powerful vehicles (like the Prius, Smart car, etc.) which are designed for efficiency over speed will have smaller wheels because the motor would struggle to move the wheel with 20" diameter wheels on it. The larger diameter wheel may cover more distance in a single rotation than a smaller diameter wheel, but because of its moment of inertia it will take more energy to turn it a single revolution. Add to that the likelihood that a larger-diameter wheel (or simply a larger diameter tire) will most likely weigh more than a smaller one, the added weight will also have an effect on a vehicles mpg.
|
How sustainable is our landfill trash disposal model in the US? What's the latest in trash tech?
|
Landfill mining is worth a look, essentially digging through existing landfills and sorting things of economic value, recyclables, biodegradables, fuel sources, etc. while creating more space in the process. It is of course a costly undertaking, but there are MSW sites in the US that have profitably implemented landfill reclamation. Here's the EPA spiel on it with sources: _URL_0_
|
How do we have pictures of the Milky Way if the farthest satellite to travel from Earth just recently left our solar system?
|
We don't have photos of the Milky Way from a distant point of view because we are in it and we can't leave it. But we can see the Milky way from our inside point of view, you can see it in the sky with your naked eyes (not as a spiral shaped galaxy like your image) as a broad ribbon brighter than the rest of the sky. Your picture is the Andromeda Galaxy or M31, the closest galaxy to us. You can see it with your naked eyes as well. Here is a picture of the Milky Way : _URL_0_
|
Is there any real reason not to put hot food directly into the refrigerator?
|
The refrigerator’s thermostat will keep it running to maintain a safe temperature of 40° F or below. The main thing to worry about is breaking up portions to ensure they chill quickly enough. If you have a deep pot of food such as stew, or chili; place it into several smaller containers, otherwise it may retain heat for extended periods and increase the risk of bacterial growth. [USDA's refrigeration and food safety sheet!](_URL_0_)
|
Are there any ancient constellations that no longer exist due to the Suns orbit around the Galaxy or just the stars moving relative to us in general?
|
The stars that are close enough to be seen with the naked eye (and make up constellations) are also moving with respect to the solar system. This 'proper motion' of the stars makes them drift very slowly, on a timescale of thousands of years. For example, check out 100,000 years of evolution of the [Big Dipper.](_URL_0_) The present form is largely recognizable thousands of years into the past and future, but it will eventually probably deserve a name change to the "Big Dagger." The similar effect is also easily seen in the pole star. Polaris wasn't always the north star, and it won't always be. The precession of the earth's axis (like the wobble of a top) causes the axis to shift, so the positions of the stars in the night sky shift with a 26,000 year period. This doesn't change their relative positions, just their apparent positions in the sky. For example, in the past the star Thuban in the constellation Draco was the north star, and [lots of different stars have been historical north stars!](_URL_1_)
|
what determines the shape of a popped kernel of corn?
|
I don't know the answer, but you might be interested to look into [chinese popcorn making](_URL_0_). basically, they heat a tightly sealed iron cylinder with the popcorn in it, for an unbearable time, then they let it explosively decompress into a bag. Instead of the ordinary shape of popcorn as kind of an exploded flower, this process produces near-identical puffs of corn. In this context, the answers to most of your questions are simple: they're all pretty much identical spheres.
|
Does laughter have different accents?
|
The general consensus is no - laughter and human emotion in general are considered generally universal. However(!) there has been some more recent research that has determined that certain non-verbal communication (i.e. facial expression) may be "accented", allowing us to parse region or cultural background from nuanced differences in certain expressions (_URL_2_) One of the things that you may find interesting about this question is how people born deaf laugh *extremely* similarly to non hearing-impaired people, outside of things that may be more socially cued like the duration of a laugh and how loudly we laugh (i.e. hearing persons are more apt to laugh quieter and shorter) (_URL_2_) Laughter appears to be an innate thing in both humans and other animals and transcends many mitigating factors of other verbal communication types.
|
If you were to reflect a photon between two perfect mirrors endlessly, would it eventually run out of energy from exertion of radiation pressure?
|
If in the limit that your mirrors are very heavy and rigid, even if momentum is transfered, energy is not, so the photon stays the same forever. Total momentum is conserved and not accumlated because the photon 'hits both mirrors equally often'. Energy is conserved because the neither the photon energy nor the mirror energy change. The question is harder to answer if the mirrors are not very heavy. Then I think it depends on the details of your setup what will happen.
|
Why do we drink ethanol if there are safer alcohols?
|
Because no yeast makes 2-propanol as a by-product during fermentation. We drink ethanol because it's there.
|
Why is ethanol the only safe alcohol to drink?
|
The simple answer is that ethanol is metabolized into (relativly) non-toxic compounds by a rather well studied mechanism. _URL_0_. It is not the chemical itself that is always toxic, but what it turns into as the body breaks it down. Methanol metabolizes to Formic acid that damages the optic nerves causing its well known effect of blindness. Isopropyl alcohol metabolizes to Acetone, that is toxic to the central nervous system. Butanol metabolizes to carbon dioxide so it is less toxic, pretty safe compared to other short chain alcohols. If you want to know more just look up the particular alcohol you are interested in and see what it metabolizes into. EDIT: or read the MSDS for symptoms and specific affects.
|
Why is my vision tinted blue when I open my eyes after closing them in direct sunlight for an extended period of time?
|
You will probably have noticed that bright light sources look red with your eyes closed. This is because the eyelids let through up to about 20% of red wavelengths, while they only let through up to about 5% of green and blue wavelengths. The human eye contains three different types of cones: L-cones (which preferentially absorb red light), M-cones (which preferentially absorb green light), and S-cones (which preferentially absorb blue light). When you have your eyes closed in direct sunlight, it is mostly the red light reaching the retina. This [temporarily exhausts the L-cones](_URL_1_), causing an [after-image](_URL_0_). Essentially, what has happened is that your L-cones have become less responsive to light, meaning most of the visual signal your brain receives is now from the M-cones and S-cones. As a result, there is a perception of objects being tinted more blue or green than they usually are.
|
What happens to an eyelash when it gets stuck behind your eye?
|
Things don't get stuck behind your eye, because your eyeball isn't just like a ball in a socket with space between the two for stuff to get into. The place where the eyeball makes contact with the socket (the place at the top of the behind of your eyelid) is covered by a membrane and prevents things from going further. If an eyelash or anything gets behind your eyelid, you will feel it and your eyes will water more and you'll blink more, and it will eventually come out. Things can't go behind your eye. Source: contact lens wearer, I've had some panic moments that lead me to great discoveries.
|
What happens to an eyelash that gets stuck in your eye and never comes out?
|
Here's two previous discussions on the topic: _URL_1_ _URL_0_
|
Is a partial brain transplant possible?
|
Who suggested that as possible? With our current capabilities, no it's not possible. In the future will it ever be possible, no I don't believe so. Lastly, there is no "part of the brain that contains our identity" that we're aware of.
|
Is there an 'opposite' of ADHD?
|
disorders of the brain do not generally fall along a neat linear continuum the way that some disorders of the rest of the body (eg endocrine hypo or hyper activity) do. this is because disorders of behavior are incredibly complex. there is no such thing as the opposite of ADHD or schizophrenia or personality disorders. you could make some argument for depression being the opposite of mania, but even that is an oversimplification.
|
Is ADHD something someone either has or doesn't have? Or is it a spectrum, and we only call it ADHD if a subject crosses some threshold?
|
There's a difference between theory and practice here. In theory, either you have ADHD or you don't -- kind of like syphilis. You have it or you don't. So there is a definition of ADHD you can find in the DSM V, and in theory, if you meet the definition you have ADHD, and if you don't, you don't. In reality, it's a spectrum. People can have a little of it, or a lot of it. And fundamentally, how much ADHD you have is inversely proportional to how much dopamine function you have in the pre-frontal cortex. If you have high dopamine function, you can pay attention to boring things, catch your own mistakes, sit still for long periods of time, etc. If you have low dopamine function, you can't pay attention to boring stuff, you miss your own mistakes, and when you sit still for very long, you get more and more restless. Since dopamine function varies along a spectrum from low to moderate to high, ADHD symptoms vary on a spectrum from major to minor to nonexistent.
|
Why isn't Jupiter's atmosphere more uniform?
|
It has to do with the rotation. Jupiter is rotating really fast, especially for its size (~11 x Earth radius with a period of ~10 hours). This causes the Coriolis effect to be particularly intense, so the heated atmosphere at the equator gets bent into bands as it rises toward the poles. The same thing happens on Earth, but since we're rotating slower, our atmosphere doesn't get split into so many bands (here they're called [Hadley cells](_URL_0_)).
|
Why isn't the atmosphere of Jupiter homogeneous?
|
Heavier gases tend to get to deeper layers, what you would expect with no activity is an equilibrium that doesn't have a homogeneous mixture, but heavier gases in deeper layers. Jupiter's interior is still hot, while the outside is cooled by radiation (to space). In addition there is the "daily" cycle of sunlight. That leads to temperature gradients, and that leads to convection. Convection mixes up the different atmospheric layers in many individual cells and generates patterns in the atmosphere. There are many more things (interaction with the magnetic field, for example), but convection alone prevents an atmosphere in equilibrium.
|
Why does human hair grow so long? I've noticed that other apes and monkeys don't seem to have really long hair. Humans on the other hand can grow out the hair on their heads and get it pretty long.
|
Why does human hair grow so long? The anagen phase tends to last several years on scalps. Other apes have far shorter anagen phases. Humans have thinner shorter hair over much of their bodies because we evolved to be long distant runners and sweating allows for very quick cooling. Obviously this isn't the case with our heads and genitals, where hair grows far longer than other apes. Reason? Sexual preference, like peacock tails.
|
Why do people bite their nails?
|
It is classified as an impulse control disorder. Specifically it is considered within the obsessive compulsive spectrum. Nail biting isn't an advantageous trait and can actually lead to infections of both the mouth and fingers. There are actually quite a few habits like this that aren't helpful. Things like impulsive scratching and picking or biting of the skin, cheek biting and pulling out your own hair. So why do people do it? Well they can't help it. It has been suggested that when less severe, obsessive grooming habits would be advantageous. There are changes in neurotransmitter levels but as usual, we don't really know if this is a cause or an effect. I haven't heard of an animal "nail biting" but there are cases of excessive grooming leading to hair loss. This is usually the result of some kind of stress.
|
Do cats purr voluntarily? Do they get tired of it?
|
I would think that depends how much ability to voluntary behavior you think a non sapient animal has. The question was asked before. _URL_0_
|
Are the stars in the big dipper closer to Earth than other stars in the night sky and is that how they came to be a constellation?
|
[This image](_URL_0_) shows the Big Dipper head on, and from the side. Distances to astronomical objects are essentially impossible to judge from a human perspective on Earth. Stars that are much brighter, but further away, can far outshine nearby dim stars. A star's location on the sky or in a constellation usually has little to do with it's distance to stars that are visually nearby, except in the case of clusters or binaries. *Edit*: To answer the constellation question, yes; constellations are essentially just groupings of bright stars in a region on the sky that helps make observing and recording the movements of celestial objects easy. This was originally done for calendar keeping and astrology, but they're still useful features for astronomy and the general public today.
|
If we think there are multiple universes, why do we still use the term "universe" to explain a collection of galaxies? Wouldn't "multiverse" just be another name for universe and collection of galaxies just be called..a collection of galaxies?
|
ultimately, this problem boils down to a contended definition of "universe." Some people want it to be defined as "everything." Others want it to be defined as "everything within the continuous region of spacetime we occupy."
|
Does the creation of new memories cause older ones to decay?
|
_URL_0_ None of them exactly match 'new memories cause older ones to decay', in decay theory, memories fade independent of new memories, just time. Interference theory, old memories can be confused by new memories, or vice versa. Your idea is more along the lines of over-writing the hard-disk, which, afaik isn't considered as a cause for forgetting.
|
Particles in Space.. is Space a gas?
|
Space is filled mostly with hydrogen gas. Keyword: [interstellar medium](_URL_0_).
|
Is it possible for a small star to have a ring system like Saturn?
|
It's possible that a ring system could develop from the method you described, but it wouldn't last long (cosmically speaking). This depends on the size of the particles that the ring is made of. Tiny particles (about .5 mircometers, as given in the next source) are blown away by stellar radiation. For slightly larger particles the [Poynting–Robertson effect](_URL_1_) has a larger impact on the orbit. These particles fall *in* to the star. Simply put, they don't last in stable orbits around stars due to the absorption and re-emission of photons, which "pushes" them in. [The rings of Saturn](_URL_0_) consist of particles ranging from micrometer to meter scale. So, in your scenario, the small particles would be blown away by or sucked into the star. What you'd have left is an asteroid belt, made of meter-sized chucks of rock.
|
How do bats emit the sound they use for echolocation?
|
The same way as humans talk or shout, passing air over vocal chords. _URL_0_
|
Why do the moons surrounding the gas giants vary so much?
|
There's essentially two types of moon - those that are captured asteroids, which are obvious - they tend to be similar to most other asteroids and are irregular in shape. The other kind, i.e. Io, Europa, Titan, are basically mini-planets (in some cases not so mini). We don't actually know how these formed. They could be captured planetesimals that formed at the same time as the planets. However, it's also possible they formed out of a kind of quasi-circumstellar disc around the planet - so like mini-solar system but with, say, Jupiter at the middle instead of the Sun.
|
Why are the moons of the gas giants so different from one another?
|
Just looking at the satellites of Jupiter on Wiki, it looks like they each have a different semi-major axis (largest distance across the ellipse) ranging from 30 million to 127,000 kilometers. They probably all came from different places at different times and haven't all run into each other and combined because of the vast distances between them. I don't think its safe to assume most moons come from the byproducts of planet formation, I would bet many of them are captured asteroids that collected random elements based on their distance from the planet.
|
Is this really the orientation of the planets orbits relative to the motion of our solar system?
|
OP is asking simply if the plane of the solar system is inclined relative to the galactic plane. And the answer is yes. It's hard to tell from everyones existing replies, but yes.
|
With Venus the and Jupiter in view to us now so visible at dusk. Why are they not brighter at night? They disappear once it's completely dark.
|
They don't disappear from the sky, they just go below the horizon. Because of their angle relative to the Sun and Earth, they can only be seen at dusk and dawn. By the time it's fully dark, the Earth (and you) has rotated and is pointing in the wrong direction to be able to see them - after a certain time they will dip below the horizon and you won't be able to see them because the Earth is in the way. This is always the case for Venus, as it's closer to the Sun and as the Sun goes down, Venus isn't too far behind. On the other hand Jupiter, depending on its position relative to the Earth, can be seen in the dead of night.
|
will food rot/expire in outer space?
|
Yes it can do, it depends on the circumstances. Ordinary untreated food would rot if it was in a spaceship. 'Space food' eaten by astronauts tends not to rot, because it is treated and vacuum sealed. If you mean 'will food rot in the vacuum of empty space?' then the answer is that it won't rot exactly as there is no air; but it will undergo chemical changes. Bombarded by the solar wind and cosmic rays it will likely become ~~radioactive~~ irradiated and disintegrate into more stable compounds and form a kind of dust.
|
Why can't we taste our own tongues?
|
We can taste the inside of our mouth, but your brain no longer consciously interprets the taste signals coming from your tongue. The plastic feature of the brain is very good at processing necessary information and leaving out obsolete signals. Just like how you don't consciously think about your rib cage expanding with every breath (but you will probably notice it now since I have mentioned it), or how you don't notice your pants are touching your legs when you wear them. Your brain has also gotten so use to the flavor of the inside of your mouth, that it now perceives it as normal, but if you were to make out with someone you would definitely notice a difference. Just like how your house has a certain smell to it, but you don't notice anything because that is "normal" to you. But if you walk in a strangers house you will notice the smell.
|
Why do pitches sound flat when you yawn?
|
There are little tubes called Eustachian Tubes that connect the ear to the throat. When you yawn, the pressure changes in the ear causing the popping sound you sometimes hear. Sound is just a pressure wave so if you change the pressure in your ear sound will be distorted slightly in this case slightly flat.
|
On a physical level, is there a difference between PTSD and extreme anxiety that does not stem from a traumatic event?
|
Therapy would be very similar. Acute stress disorder becomes PTSD after three months if the person is still experiencing symptoms such as flashback, intrusive thoughts, avoiding, nightmares, and somatic symptoms. Medicine for anxiety and depression can be used for ASD, PTSD, and anxiety. Anxiety is mostly an over stimulation of fight/flight/freeze that leads to somatic symptoms, avoiding, and hyper arousal. cognitive based therapy can be effective for both. Both therapies will involve coping skills, exposure, and looking at how thoughts, feelings, and actions go together to effect behavior.
|
Why do women's menstrual cycles synchronize?
|
They don't. That belief is from a paper from 1971 which has been found to be flawed. A study published last year in the journal Human Nature looked at 186 women living in dorms for a full year and found no evidence for synchrony. The authors also reviewed the original 1971 study and argued that its findings were due to chance. _URL_0_ _URL_1_
|
Why does human hair turn grey? Would most other mammal's fur also turn grey if they lived long enough?
|
Some animals definitely go grey, although to a lesser extent than most humans - thing silverback gorillas, or 'frost' on an old dog's muzzle. I don't know how common it is, though, or if it occurs more in domesticated or zoo specimens than their wild counterparts due to generally living longer. For animals that rely on camouflage I expect it's a trait that would be quite strongly selected against, by making individuals expressing it more vulnerable to predators at a life stage where they may already be getting slower.
|
Is it possible to have a moon orbiting around another moon, which orbits a planet?
|
Yes, its possible (and if you think about it the Moon orbiting the Earth which orbits the Sun) is sort of similar, (with the caveat that the Sun is a star). However due to tidal effects of the main planet and moon it is unlikely to be stable for millions of years. This isn't as big of an effect with Sun - Earth - Moon as stars are significantly more massive than planets (e.g., the Sun is roughly million times earth mass or 1000 mass of Jupiter).
|
How does gasoline expire/go bad?
|
Gasoline definitely *does* go bad. Leave a can of gas in your storage shed for a year and then try to run your lawnmower on it, and you'll find out! Wikipedia has [some information](_URL_0_) on how this happens, but here's the short version: The gasoline you buy from the gas station is not a single chemical. It's a mixture of various oil-based chemicals, and if you leave it sitting for too long, two things happen. First, the chemicals can start to separate. Second, the more volatile compounds evaporate away. If the can isn't properly sealed, water vapor from the air can react with some of the chemicals in the gasoline, too.
|
How close is the shape of our Sun to a sphere?
|
The amount that a rotating sphere is "squashed" (gets an equatorial bulge) by centrifugal effects can be measured by its oblateness, with a perfect sphere having zero oblateness. Earth is 0.0033528, while the Sun is 0.000006, much closer to a sphere due to its much stronger gravity and slower rotation.
|
If light has energy, it has momentum. But if it has momentum doesnt that mean it also has mass?
|
As you surmised, p = mv only applies to classical motion of objects well below the speed of light.
|
Does taking antibiotics affect the gut bacteria in any way?
|
That is correct. Side effects may include any number of stomach problems, including diarrhea and the various Pepto symptoms. Depending on how broad spectrum the drug is, you may experience worse or longer lasting side effects.
|
If a drunk person donated blood, would the recipient of the blood be drunk immediately?
|
It depends on the blood alcohol level of the donor and the tolerance of the receiver. As the blood is given by transfusion it is diluted roughly 1:10 (1 blood conserve 500ml, in total blood of 5 liters, very roughly). So if a hardcore alcoholic very close to death (bac of 0.5%) were to give blood, you might feel a mild alcoholization (bac 0.05%). So in principle, yes, in practice not so much unless you transfuse huge amounts of blood. And in that case you are probably not awake to experience the effects anyways.
|
If I donated blood while drunk, would the recipient of my blood be drunk when they receive it?
|
Short answers: No to the thread title, yes to your description. Longer answers: Being "drunk" is a bit of a subjective term, but let's stick to the legal definition of higher than 0.08 BAC. So let's say you're HAMMERED at a 0.30 BAC. Standard donation is one pint, which represents approximately 10-15% of your blood. If the recipient got just your one pint, it would be diluted into their other blood. So, if one pint of 0.30% blood is transfused into a sober recipient, their BAC would become approximately 0.03-0.04, not drunk. Although yes, the alcohol would be transfused. To get "drunk" through a blood transfusion, the recipient would need to receive 3+ pints of your blood (or similarly high BAC blood, since they'd never let you donate 3 pints).
|
Do animals and insects with shorter life spans, lets say flies, evolve faster that humans or other animals/mammals/insects with longer life spans?
|
The rate of evolution is dependent on the rate of reproduction. Mutations are a random process so the more offspring a creature produces, the more likely a mutation will occur that is beneficial and gives the creature an advantage under given circumstances. Flies have short lifespans but have many offspring. This is why fruit flies are heavily studied.
|
Why do I get sick as a passenger in a car while I don't when I'm driving?
|
Passengers tend to look at things inside the car (like a book or a computer), while drivers always look at the road. The road's movements in the eye correspond to the movements detected by the inner ear. The movements in the car don't. If you want to not get sick in a car, either look at the horizon or keep your eyes closed.
|
Why do some people get motion sick as a car passenger but not as a driver?
|
Motion sickness is caused by your brain perceiving motion without your eyes perceiving the motion. When you're driving your brain senses the motion and your eyes confirm it by looking at the landscape moving past you. But, when you're sitting in the backseat and not looking out the window, your brain senses the movement but your eyes tell you you're siting still (because the car interior isn't moving) and this causes motion sickness. Similarly, if you're indoors on a boat and can't see the boat moving along the water but you can feel the boat jerking around you're going to start to feel pretty shitty
|
Sometimes when I look in the Sun's general direction I sneeze. Why does this happen?
|
What you're experiencing is called the [photic sneeze reflex](_URL_0_). While there is no clear scientific explanation for the sneezing effect, the likeliest theory so far is that sudden exposure to bright light causes confusion in the nerve signals.
|
Is milk the best thing to drink after eating something spicy? Why or why not?
|
Milk will more effectively relieve the burn on your tongue than water. The reason for this is that the burn is caused by a chemical called capsaicin in the spices. A chemical in milk, casein, disengages the capsaicin and allows it to be washed away. Water doesn't contain any casein, so it is not effective.
|
Do plants and animals have a common ancestor?
|
Yes, the most recent common ancestor of plants and animals lived about 1.6 billion years ago, and was neither plant nor animal. The [Last Universal Common Ancestor](_URL_0_) was more like 3.8 billion years ago.
|
Do plants and animals have a common ancestor?
|
While there is no fossil evidence of one genetic evidence does suggest that there was a common ancestor between all kingdoms of life. It's now referred to as the last universal common ancestor (LUCA) and it is represented on phylogenetic trees as the intersection between all the branches of life. For plants and animals more specifically there is a more recent common ancestor. Both plants and animals belong to the eukarya branch of the tree, which means they have more genetically in common than with the other branches and that their common ancestor occured some time after LUCA.
|
Why do birds, insects, squirrels, and other animals move in short, jerky motions?
|
It's a matter of size. It takes a lot more energy for a large animal to accelerate/decelerate a limb or such. On the scale of an insect, beating their wings is relatively easy. Here's the wikipedia article on the [Square-Cube Law] (_URL_0_) in regard to biomechanics.
|
Were there fires on Earth before land plants evolved?
|
The Oxygen Crisis aka the Great Oxygenation Event was generated by Cyanobacteria in the oceans - this is the time at which the earth's Banded Iron Formations were generated, essentially oxygen-as-waste-product photosynthetic bacteria rusted out the Oceans which were saturated with ionic iron. So there was plenty of Oxygen around even before land plants evolved. In fact oxygenation of the oceans and then the atmosphere is what allowed for the generation of an ozone layer and it's UV shield which is what allowed for the evolution of surface dwelling organisms. Some sources: _URL_1_ _URL_0_ A user friendly pdf slide show: _URL_2_
|
How were forest fires contained 150 years ago, especially in remote areas like the west?
|
Forest fires are a lot worse now than they were a long time ago. So chances were better in the 1800s that the fire would burn itself out without destroying half the forest. Minute Earth did an excellent video on the topic, I'll just summarize below: The shift in the fires' sizes has to do with the "reactionary" policy put in place in the 1980s (I think it was the 80s?) where legislators said "all fires are bad, extinguish them right now!" That led to a build up of forest litter, which should have been cleaned by a periodic fire, but now has dried out into tinder, decades worth of tinder. Now, with the ridiculous underfunding of the national parks service, the only money available to fix things is used to fight the massive tinder fires, rather than be proactive with controlled burns. There has been a shift recently, you'll hear on the news that a fire has been contained rather than extinguished, but a ton of work still has to be done.
|
Can we accurately know the color of dinosaurs skins?
|
Quoting one of the sources listed below, color in animals are made in two different ways. Either using pigments that absorb light or by using structures that scatter the light. Scientists have been able to find remnants of pigments in fossilized feathers and have been analysing them. _URL_8_ However a recent study found that the pigments could be changing during the fossilization process and "[Our results] suggest that some previous reconstructions of the original plumage colors of fossils may not be accurate". _URL_9_
|
How many photons do we see per star?
|
It depends on the star, of course, how bright it is and how far away it is and also what frequency you're looking in. The brightest night star, Sirius, is 25 times as luminous as the sun but 8 light years away, which means an area the size of your eyeball gets about 10^-10 Watts. If you divide that by the energy of the most common energy photons from Sirius, you get about 100,000,000 per second. If you do x-ray astronomy and look at distant galaxies, you are lucky to get a few photons per hour.
|
Do trees have a lifespan?
|
Most organisms (including most trees) will start to die more often (mortality rate) as they get older (once matured). This gives you an average age they will live to. Some organisms though have an unchanging or even decreasing mortality rate as they get older. They basically don't age and are called biologically immortal. However the longer a life form is alive (even if they aren't aging) the more likely they are to die from some other cause so they will still have an average age they will live to. Here is the wikipedia article title [list of long-living organisms](_URL_0_).
|
Do countries where people commonly wear face masks when sick have much fewer cases of flu or common colds than others?
|
Just as an add-on, generally the mask's are seen as beneficial for reducing flu and such but only because you help protect other's from your coughs/sneezes. It doesn't really help ***you*** as much specifically unless everyone uses it. (unless I have a misconception, then I apologise)
|
Do countries (Japan, China) where a large part of the population wear face/dust masks have statistically lower occurrences of airborne illness/infections compared to countries (US) that don't wear masks?
|
No. Face masks are not effective at stopping airborne pathogens, and if there is a dust issue that your body cannot handle on its own, you're going to need a full on gas mask. Surgeons don't wear face mask to keep themselves healthy, they wear them so that their spit and phlegm doesn't get into a patient's open wound. If it was effective, we would be doing it too. *Edit for spelling*
|
Do giraffes get struck by lightning more often than other animals?
|
Thanks for all of the info, guys. I posted this after waking up from a dream in which giraffes were being struck by lightning, of all things.
|
Do giraffes get struck by lightning more often than other animals?
|
Lightning travels down the path of least resistance from its origin to the ground. Now, factors like local climate and altitude have a much bigger impact than animal height, but *all else being equal*, a giraffe would be very, very slightly more likely to get struck by lightning than other animals.
|
Do giraffes get struck by lightning more often than other animals?
|
Turns out another redditor before you had the same question: [_URL_1_](_URL_0_)
|
If two vehicles, each going half the speed of sound, passed each other within inches, would they experience a sonic boom?
|
While the relative speed between the two vehicles would be equal to the speed of sound, the speed of each vehicle relative to the fluid through which it is traveling would still be less than the speed of sound. Thus sonic boom would not be possible
|
If passing the speed of sound in a vehicle produces a sonic boom, would something similar happen if you could pass the speed of light?
|
Yes. A charged particle moving through a medium faster than the local speed of light creates a conical optical shockwave akin to that from a supersonic object. This is the so-called Čerenkov effect, and is famously responsible for the blue glow in nuclear reactors.
|
If diamonds are made of just carbon, is it possible to get a diamond to catch fire?
|
The ignition point of diamond is between 850 and 1000 degrees Celsius in air. A propane torch can reach temperatures of 2000 degrees C. [Here's](_URL_1_) someone heating a diamond up and then tossing it in liquid oxygen to set it aflame. [Antoine Lavoisier](_URL_0_), thought of by some as the father of modern chemistry, famously discovered that diamond is a crystalline form of carbon by burning it.
|
Diamonds are just carbon, so what would it take to burn them?
|
2 packs of dry yeast (about 2 tablespoons) 1 pint of hydrogen peroxide 1 large jar at least a quart in size Pour the peroxide and yeast into the jar, cover with the lid, and swirl gently. It will release pure oxygen. You can prove this by lighting a small twig, put out the flame so just a spark is left on the end, then insert the twig tip into the jar where it will burst into flame. Just wanted to point out that there is a simple kitchen method of producing pure oxygen. There are other ways to release oxygen from hydrogen peroxide, but yeast is simple, effective, and readily available. What use would a jar of pure oxygen be? It can dramatically speed up the metabolism of seed. I've used it several times to get very old (more than 15 years) tomato seed to germinate.
|
How come seeds don't sprout in the fruit they come from?
|
Hormones. Abscisic acid and gibberellins to be precise. The first one promotes seed inhibition and keeps them dormant while the other one promotes seed growth. As long as the ratio is high enough the seeds won't start sprouting. Source: Myself, 6 years biology education.
|
Why aren't planets tidally locked to the sun, the way moons are tidally locked to their planet?
|
[A lot of planets in other solar systems are tidally locked.](_URL_0_) Tidal forces decrease with the cube of distance rather than the square (this is why the moon has a bigger effect on the tides than the sun), so locking occurs much more readily in objects that are close together, e.g. big moons around planets, planets very close to stars. Mercury has a spin-orbit resonance, although it's not tidal locking. Over very very long times (longer than the sun is expected to last) it is possible for tidal locking to occur, but it hasn't occurred yet because our solar system is too spread out.
|
Why are most major moons in the solar system tidally locked to their planet, but most planets are not tidally locked to the sun?
|
The moon has a diameter of about 2000 miles, and a orbital radius of about 200,000 miles. This means that its close side is 1% closer to the earth than its far side. On the other hand, the Earth has a diameter of around 8,000 miles and an orbital radiusof around 90 million miles, which means the difference in distance between the close and far sides is about .009%. As a result, the difference in gravity between the close and far sides of the moon are much stronger than the difference in gravity between the close and far sides of the earth, which is why the moon is tidally locked and the Earth is not.
|
Why does it burn so much if even a tiny amount of water is inhaled through the nose?
|
Well, from an evo-devo standpoint, there's a very good reason for the human body to have extreme aversion to water going down your nose. The alveoli in the lung collapse on contact with water, so it makes sense that organisms that had an extreme aversion to even the tiniest bit of water going down their nose would avoid getting pneumonia and thus, live long enough to reproduce and outcompete their fellows.
|
Why doesn't the alcohol made by fermenting wine or beer need to be distilled?
|
Need to be distilled to what purpose? Usually, distilled products have a much higher alcohol content than beer or wine. This high alcohol content can only be achieved through distillation. A typical wine yeast cannot work when the alcohol content exceeds 12-16 % (varies wildly). Point is, if you want high alcohol content you need distillation. If not you don't need it.
|
Why can we digest fats but not plastics when both are mostly hydrocarbon chains?
|
1) The carboxylic acid changes the chemistry of fatty acids compared to plastic hydrocarbons massively. It looks subtle on paper, but it is like the difference between a stick and an arm (with a hand!) in terms of chemical functionality. 2) Plastic/polymeric hydrocarbons are very chemically inert and there is therefore a larger energy barrier to chemical transformations (and therefore use as an energy source). 3) The enzymes evolved over many millions of years to be exquisitely selective for fatty acids, not plastics.
|
Can monkeys whistle?
|
To direct this discussion let's ask, what is a whistle? I would define it as a reverberation in the mouth initially caused by the sound generated from constricted flow through the pursed lips. Can other apes purse their lips? Absolutely. Can they exhale and control the shape if their mouth? Absolutely. I would argue that they physically can whistle, but they must attempt to. But the anecdotal evidence others have provided has demonstrated that they at least have before.
|
Why does seemingly everything in the universe rotate?
|
Stars and galaxies form when a cloud of gas - scattered about more or less randomly in all directions - collapses under its own gravity. See [here](_URL_0_) for an excellent video showing the process of galaxy formation. Planets are thought to form from some of the leftover gas and dust which didn't end up in the star - the gas and dust form a disk, and clumps form, again due to gravity. Now, it's next to impossible to form something in this way and *not* have it rotate. Think about a star: only if the cloud of gas is perfectly spherical and distributed evenly in all directions will it collapse into something non-rotating. If some of the molecules in the gas are moving in different directions, that motion doesn't just vanish when the star forms, it's left over and goes into the star's rotation. Similarly for galaxies, planets, and so on.
|
What would happen if I shine a laser in a room full of mirrors?
|
Reflection is never perfect unless it's total internal reflection, so each bounce some of the light will be absorbed by the mirror until it diminishes in size. Also, if at any point, the laser hits you, then that light will obviously be absorbed. After some amount of time there will be a steady state achieved, where the amount of laser light exiting the laser pointer is equivalent to the amount of light absorbed by the various surfaces. It's hard to guess how large the laser size will become without knowing some specifics like the material of the mirror, the frequency of the laser, and the quality of collimation, and what kind of gas is in the room (this is where temperature might come into play, but I'm guessing it's a smaller effect than the others. The presence of dust particles probably plays a bigger role in scattering).
|
What would happen if a laser was shot in a room that is completely mirrors?
|
You would very likely injure yourself, but nothing much more. Mirrors actually absorb a significant amount of light, that's why they appear *very* slightly dark. After some 10 or 20 bounces, the intensity is down to a pretty low level. The intensity goes down exponentially with the number of bounces.
|
Why does the sound from a boiling kettle seem to go quiet just before it starts to fully boil?
|
My best guess: When the water is cold only the water closest to the stove gets hot and stars to boil. The small bubbles that form makes a hissing sound that gets louder and louder as more water gets hot. When all the water gets near the boiling point the water starts to boil as a whole. At this point all of the water stars to absorb the heat from the stove and make bubbles everywhere. So the sound goes from a sharp hissing sound to a soft bubbling sound.
|
When heating up water in a kettle, why does it get quiet right before boiling?
|
The noise is caused by [cavitation](_URL_0_), vapor bubbles forming and imploding in the water. The layer nearest the bottom of the kettle is the first to boil. The water vapor bubbles rise toward the surface and into cooler layers, which recondenses the vapor. The collapsing bubbles cause the noise. The bubble production increases, getting louder and louder until all the water is hot enough to allow the bubbles to reach the surface, and the noise drops off dramatically. It's another moment or two before the vapor pressure builds up enough to make the kettle whistle.
|
What actually increases risk of lung cancer when smoking?
|
Disclaimer: I’m not an expert at this and would love to be corrected if I’m wrong. Many cancerous processes, including some in the lung, are induced by a process called metaplasia, where cells of one type change to another type, usually in response to an injury. At the risk of making a teleological argument, the way I think of it is that the cell is changing from a type that isn’t great at dealing with external exposures (pseudostratified columnar epithelium) to a type that can deal with these exposures better (squamous epithelium, similar to what makes up the skin). In theory, this is an great way for the body to adapt to unexpected conditions such as smoke in the lungs. However, any time you have cells that are changing programming like this, it increases the risk of mutations that lead to cancer. This is a rather crude explanation, so hopefully someone with a better understanding of the precise molecular biology can chime in.
|
If our eyes could see in any range of the electromagnetic spectrum, which part of the spectrum would the night sky appear brightest?
|
The [Chromoscope](_URL_0_) may be relevant to your interests. It lets you visualize the sky in various wavelengths.
|
Why do domestic mammals (dogs, cats, cows, horses) have tails?
|
Most mammals have tails, though some have lost it through evolution when it no longer fills any meaningful function. In these cases, they still have at least some functionality. Cats use their tails for balance and communicating, dogs also use their tails to communicate and cows and horses swat flies and other irritating insects with their tails.
|
How large is the Milky Way, as opposed to other galaxies of the same type?
|
The Milky Way is a barred spiral galaxy. It has a central main arm, with a few other sub arms. We are pretty big for a barred spiral, 130,000 ly and all. It probably looks a bit like [UGC 12158](_URL_0_) I do not understand what you mean by "flat disk" galaxy. There is no such classification in the standard labelling for galatic evolution. There are Spirals, Ellipticals, Irregular and Lenticular. No, it is definitely not an elliptical. Ellipticals do not have distinct spiral arms, and are mostly filled with old, metal poor stars, and are distinct for a lack of gas to form new stars. The Milky Way is almost the complete opposite. Take a look at [M87](_URL_1_), a well known elliptical galaxy. Now compare that with the previous picture. They look nothing alike (well except that they are bright).
|
[Sponsored Content] What is the difference between generic and brand-name drugs?
|
Pharmaceutically? Nothing. There are VERY strict guidelines in place, all drugs have to be exactly the same in make up. Psychologically? A lot. Say you pay £0.45 for a pack of generic paracetamol, psychologically this WILL NOT work as well* as £4 pack of panadol. (Exactly the same active ingredients, excuse the british currency/drug names) Also name brand drug companies will put a LOT more money and time into marketing. Studies into placebos have shown that the colour of the drug, the size of the capsule and even the colour of the packaging all massively influence the perceived outcome of taking the drug. Edit: * When is say work as well I mean how well it is perceived to have worked. But then again, in the case of some drugs such as anti-depressants this doesn't matter as much.
|
I have a question about an object placed on a planet with/without friction. Does it rotate at the same rate as the planet?
|
Well, consider the force diagram on an object at rest, with friction. You have gravitational force towards the center of the earth. You don't need to consider friction unless the object is in motion. So it seems the object would have an unstable equilibrium at its rest position. For your example of the statue, this means it would remain in that position until a miniscule force is applied in a direction that is not parallel or antiparallel to the gravitational force. There's a little bit of funny business due to noninertial reference frames, though. Centrifugal force (normally miniscule) would make the frictionless objects drift in some direction depending on the location of the object relative to the earth's axis of rotation, and the Coriolis force would do something similar. So the objects that rely on friction to remain stationary (i.e. not bolted into the ground) will move relative to the center of the earth. Cool!
|
How come if a person eats raw meat they get sick, but animals are just fine eating it?
|
We can eat raw met without getting sick. Fish and red meat especially. It's poultry and pork where most of that comes from, and largely due to our industrial farming practices. In other countries (Non USA) they don't need to refrigerate their eggs and in some places (Japan, notably) you can have your chicken cooked "rare" - something you would never ever see in the US. The meat is only as healthy as the animal. So you might initially think that large industrial farms would produce meat with a lot of health problems where wild game would be much more safe to eat, but actually wild game is loaded with parasites. Something like 90% of ALL trichinosis cases in North America come from people eating bear meat. We can eat raw meat and stay healthy....just needs to be that the animal that meat came from was healthy to start with
|
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.