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I'm enjoying these physics-related threads so...
Ask a physicist anything .
what is dark matter?
It's an optical illusion created by the imager (either the camera or our eyes) not taking enough frames per second. By the time we take a second frame, the wheel has turned 350°: it's just short of where it was in the first frame. Repeat this, and you get a wheel that turns backwards 10° per frame. You can see it on the wheel of a car when it slows down; there's a point when it looks like it's going backward.1. Why do stagecoach wheels turn backwards in movies?
No, because the vacuum created by a hoover isn't nearly as pure as the vacuum of space. Everything would get sucked out the nozzle, even if you put it on setting #11!2. Does a vacuum cleaner work in a vacuum?
Ice sheets are generally transparent, but they are highly reflective at certain angles. Snow is just irregular ice, so it has lots of miniature ice sheets at pretty much every angle. So, no matter where you are, there will always be some 'sheets' in the snow that are at just the right angle to reflect light back at you. Which is why it's white.Why is snow white?
Depends on how long they can sleep for .If 15 people make 15 posts in 15 minutes, how long does it take 1 person to make 1 post?
Where do flour weevils come from?
According to Artistotle, they are what happens when individual rice grains rot (just as mice are rotting hay, flies are rotting meat, etc). But it's more likely that weevils got in and laid eggs, attracted to the smell of yummy rice.no no flour weevils, the ones in packets of flour, they are unexplained...
It behaves like a wave because, when it goes through two slits, it interferes with itself, creating the interference pattern. But it behaves like a particle when it can only go through one slit, because it can no longer interfere with itself.Real physics question coming up with a little background...3,2,1...
The 'whys' are somewhat important for me to actually achieve understanding. This would be one major reason that quantum physics holds such a problem for me. I can't grasp the whys that underlie it. I can feel it right beyond my grasp, I think I can almost grab hold of it and then it eludes me.
Now on to specifics. The infamous double slit experiment. I don't get how light can act as a particle if we are watching and a wave if we are not. Any help?
According to general relativity, gravity waves travel at the speed of light. So if the Moon poofed out of existence, we'd both see it vanish and we'd see the tides go funny, at the same time.Ooooo!
If a massive object comes in at the speed of light and smacks the moon that's right above me, which happens first: We see the moon dissappear, or the tide starts to go out?
ie: Does the effects of gravity influence instantaneously, at the speed of light, or slower.
Where does dark energy come from?
Dark matter and energy are just that: matter and energy which are dark. We know they exist, because we can measure how much mass is out there. But they don't emit or absorb EM radiation: they are, quite literally, dark.what is dark matter?
Yes: it's just a numeric property, like charge or mass, and we call it 'spin' because its units are the same as classical spin. It doesn't actually spin, though. It's just a handy (if misleading) term.Is their a simple way to explain spin of sub atomic particles ?
Almost certainly: one in a million chances occur nine times out of ten.If you jump off a cliff and someone distracts you just before you land so that you forget you're falling and are about to land, do you really end up flying like predicted in certain DiscWorld novels?
If you're next to a really long measuring stick which has accurate clocks all along it at, say, every metre mark, you could measure the speed of light using them.More seriously:
Do you have a good way to explain to my brother in law about the somewhat counterintuitive nature of light? (that you can't go faster than it can, that the speed of light is constant, even relative to observers moving at or near the speed of light themselves etcetera).
A black hole is an object that's become so dense that its gravity pulls it in even further (every object has a sphere associated with it, and if that object is squished to within that sphere, no known force can overcome gravity from squishing the object further. For example, Earth's sphere is about the size of a tennis ball).what exactly is a black hole, why does it attract even light?
Depends on how you define the terms, but it's a solid. It's an urban legend that it's a just very viscous liquid, and some people even point to medieval glass that bulges at the bottom. Truth is, that was just the style at the time.
If you jump off a cliff and someone distracts you just before you land so that you forget you're falling and are about to land, do you really end up flying like predicted in certain DiscWorld novels?
Dark matter and energy are just that: matter and energy which are dark. We know they exist, because we can measure how much mass is out there.
You simply "assumed" these properties by the way. That really an ad hoc assertion since you can't produce either one, let alone demonstrate DE or DM do not emit or absorb EM radiation. You simply *ASSUME* this is true, otherwise standard theory is DOA.But they don't emit or absorb EM radiation: they are, quite literally, dark.
I am really fascinated by that rationalization and the fact you also display an atheist icon. If you were a theist, it wouldn't be ironic that you put your faith in "unseen mass and energy" but you refuse to consider the possibility that the unseen mass and energy is also aware and aware of you. Then again if you are a Wicca, maybe you aren't actually an atheist. I do find it fascinating when atheists put their faith in "dark energy" but not God. That is amusing from an empirical perspective.So we have these vast quantities of mass out there. We normally deduce properties by looking at their spectra (e.g., a star that emits mostly this and that light is made up of 99% Hydrogen), but because dark matter doesn't have a spectrum, we can't deduce that much about it. .
If you were a theist, it wouldn't be ironic that you put your faith in "unseen mass and energy" but you refuse to consider the possibility that the unseen mass and energy is also aware and aware of you.