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?
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).
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Originally Posted by Helle Gannestad (Utøya massacre survivor)
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So many questions! This is what I get for going to bed .
Originally Posted by AV1611VET
1. Why do stagecoach wheels turn backwards in movies?
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.
Originally Posted by AV1611VET
2. Does a vacuum cleaner work in a vacuum?
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!
Originally Posted by AV1611VET
Why is snow white?
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.
Originally Posted by AV1611VET
If 15 people make 15 posts in 15 minutes, how long does it take 1 person to make 1 post?
Depends on how long they can sleep for .
Originally Posted by Jazmyn
Where do flour weevils come from?
Originally Posted by Jazmyn
no no flour weevils, the ones in packets of flour, they are unexplained...
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.
Originally Posted by IzzyPop
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?
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.
In essence, the act of measuring the photon changes how it behaves, and restricting its behaviour makes it act more like a particle than a wave. It doesn't change from a particle to a wave, or vice versa, it just changes its behaviour such that we might identify it as one or the other.
My personal opinion is that it's all particles, and sometimes particles are so queer that they look like waves.
Originally Posted by dewaddict84
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.
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.
Originally Posted by Michael
Where does dark energy come from?
Originally Posted by catzrfluffy
what is dark matter?
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.
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.
Originally Posted by pgp_protector
Is their a simple way to explain spin of sub atomic particles ?
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.
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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?
Almost certainly: one in a million chances occur nine times out of ten.
Originally Posted by faith guardian
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).
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.
But if you start moving towards the photon at some very high speed (say, 2/3 c), you won't catch up on the photon: you'd still measure it to be moving at c. This is because, when you measure its speed using the rod and clocks, you see the rod start to contract (compared to a handy spare metre rod on your ship) and you'd see the clocks start to tick slowly (compared to a handy clock on your ship).
Basically, as you approach lightspeed, length contracts and time dilates in such a way that lightspeed stays lightspeed.
Now, this is all just a result of the axiom that light is constant. But why is it constant? Well, light is an EM wave, and you can use Maxwell's laws of electromagnetics to derive its speed. It's just the nature of light to travel at this awesome high speed. And if it travels at the same speed, regardless of how fast you're travelling, then time and space must contract in order to compensate.
So, if you like, time dilation and space contraction are the reason light is constant.
__________________ "I am a scientist... when I find evidence that my theories are wrong, it is as exciting as if the evidence proved them right."
- Stargate: SG1
"A scientific man ought to have no wishes, no affections, -- a mere heart of stone."
- Charles Darwin
"What can be asserted without proof can be dismissed without proof."
- Christopher Hitchens
"Protecting the sanctity of marriage against people who want to get married"
- Anonymous
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& amp; amp; amp; amp; amp; quot ; Abo u t Jesus of Nazareth,&amp ;amp ;amp ;amp ;amp ;amp ;amp ;amp ;quo t; they replied.
what exactly is a black hole, why does it attract even light?
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).
Black holes have extremely powerful gravity fields. According to general relativity, mass warps space around it, which makes objects move towards said mass. This happens with light as well: it's travelling along in a straight line, but space itself is warped towards the black hole. This means that light travels towards the hole.
If you're close to a black hole and you turn on a torch, space is so warped that any light trying to escape will end up bending back in on itself and travelling back towards the black hole.
So it's basically a very, very, very dense object that warps spacetime so much that even light is affected.
__________________ "I am a scientist... when I find evidence that my theories are wrong, it is as exciting as if the evidence proved them right."
- Stargate: SG1
"A scientific man ought to have no wishes, no affections, -- a mere heart of stone."
- Charles Darwin
"What can be asserted without proof can be dismissed without proof."
- Christopher Hitchens
"Protecting the sanctity of marriage against people who want to get married"
- Anonymous
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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.
...
I had a seventh grade english teacher tell me that.
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they told me if I voted for John McCain that I would get a President like Bush that would violate the airspace and sovereignty of an allied nation with a military force to assassinate a foreign national of another allied country and then their dead body would be dumped in the ocean. and they were right.
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?
No, since it was not predicted in a dicworld novel but in but a hitchhikers book.
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Courage is the price that life exacts for granting peace. The soul that knows it not, knows no release from little things; Knows not the livid loneliness of fear, nor mountain hights where bitter joy can hear the sound of wings. How can life grant us boon of living, compensate for dull gray ugliness and pregnant hate unless we dare the soul's dominion? Each time we make a choice, we pay with courage to behold restless day, and count it fair.
Amelia Earhart
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.
I'll concede for the sake of argument that we can measure the amount of "missing mass" in lensing data, and also thereby eliminate MOND theory from consideration as it relates galactic rotation patterns. I'll even concede that there is a logical and empirical way to "test" SUSY theory via LHC and whatever future experiments we might perform at the level of particle physics. So far however no SUSY theory has been shown to be valid and standard particle physics theory 'explains' everything we've seen in lab experiments to date. No new exotic forms of matter are necessary. In an Occum's razor argument, as it relates to particle physics theory itself, SUSY theory is toast. There is really no need for it.
Only astronomers seem to have a great need to find a new and exotic form of matter to validate their original "approximations" of the amount of mass in a galaxy. If they can't find some exotic material, their theory is DOA. While there is evidence of "missing mass" in lensing data, our technology is still *extremely* primitive. We can't even count individual stars in distant galaxies, we have to "guestimate" them. We simply blew the calculations. That doesn't mean the some new or exotic form of matter exists, it only means our estimation techniques are primitive and need to be adjusted.
But they don't emit or absorb EM radiation: they are, quite literally, dark.
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.
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. .
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.
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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.
Without wishing to turn this into too much of a derail, didn't you just make a comment about how assuming properties of something is bad?
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