Posted on 03/26/2006 8:51:36 AM PST by PatrickHenry
Can anything travel faster than the speed of light? "No," is what Albert Einstein would likely say if he was alive today -- and he would be the man to ask, because scientists have been taking his word for it ever since the early 20th century.
According to Einstein's theory of special relativity, published in 1905, nothing can exceed the speed of light. That speed, explained Einstein, is a fundamental constant of nature: It appears the same to all observers anywhere in space.
The same theory says that objects gain mass as they speed up, and that speeding up requires energy. The more mass, the more energy is required. By the time an object reached the speed of light, Einstein calculated, its mass would be infinite, and so would the amount of energy required to increase its speed. To go beyond the infinite is impossible.
One hundred years of testing have only reinforced what Einstein wrote, said Donald Schneider, professor of astronomy and astrophysics at Penn State. "There is no experiment that has contradicted special relativity. We have accelerated sub-atomic particles to well over 99 per cent of the speed of light, but not equal to or exceeding the speed of light.
"Theoretically, strange things happen when you exceed the speed of light," Schneider added. Time travel, for one thing, and a breakdown in cause and effect. Schneider uses an example of hitting a target with a gun that shoots bullets faster than the speed of light. "Some observers would see the bullet hit the target before they saw the shooter fire the gun," he said. "Since one of the guiding principles of relativity is that all physical laws are the same to all observers, this violation of causality would be a big problem."
Another oddity: tachyons. In 1967, Gerald Feinberg, a physicist at Columbia University, proposed the existence of these faster-than-light particles. In their mirror world above the light-speed barrier, tachyons would require infinite energy to slow down to the speed of light.
Other concepts that have popped up include "wormholes" -- shortcuts through space-time that would permit point-to-point travel faster than light -- and "warp drives," a kind of bubble created in space in which relativity wouldn't apply.
Although they have become staples of science fiction, tachyons, worm holes and warp drives remain speculation, and many physicists dismiss their significance. There is, however, at least one real-world example of superluminal (i.e., faster-than-light) travel. It occurs when light passes through water.
In this dense medium, Schneider explained, light is slowed to three-fourths of its speed in a vacuum. In a nuclear reactor, charged particles flying off the radioactive rods through the water they are submerged in exceed this reduced speed.
Because these particles contain an electric charge, they emit energy, called Cherenkov radiation. Any particles they bump into become radioactive, giving the water a characteristic blue glow.
"It's not at all exotic," Schneider said. "Every time you look at the water in a nuclear reactor, the bluish glow you see is radiation produced by charged particles moving faster than the speed of light in the water."
Still, slowing light down in order to beat it is cheating, Schneider conceded. And although he's not closing his mind to the possibility that relativity will one day be amended, for now, he said, Einstein's theory is the final word.
Source: Penn State, by Joe Anuta
Nope, we even had a thread about this question not too long ago... although I can't seem to find it.
You can't just ADD speeds that way when dealing with relativisitic velocities. It works fine for slower relative velocities (like two cars passing one another on a racetrack) but not at all when the velocities approach light speed (like two particles passing one another in an accelerator).
The math is different, and in physics that's what counts. This website explains more, but is not really written for the layman, sadly.
http://math.ucr.edu/home/baez/physics/Relativity/SR/velocity.html
It might have just been science fiction, but there has been a lot of speculation that time travel is possible if you can manipulate matter and energy to the point where you could create and manipulate worm-holes and things like that. So perhaps the disks you refer to could lead to time travel if they were, say, the density of neutron stars and rotating at relativistic speeds. Such things are so far beyond our capabiltity to test that it's easy for theorists to come up with crazy ideas that are mathematically possible but completely impractical.
The short answer is, don't hold your breath for real time travel, but it's cool to think about anyway!
With that line of reasoning, you're never actually moving at all since you're staying stationary relative to your pants...
Of COURSE you're stationary with respect your pants! I mean, I HOPE they're not flying away from you right now...
They aren't flying away from me right now. but it has happened before... :-)
YES, illegals streaming across our unprotected southern border.
What the correlation represents is the limits of information. The reason why the two measurements get the correlated answers is because they're extracting the same piece of information...and this despite the fact that the information wasn't in a definite state until it was measured. (If it were in a definite state, it would have to obey Bell's Inequality; this is what sank Einstein's interpretation well after his death.)
I have seen it explained in the past is that if one changed the polarity filter Left for A then by observing that fact it 'magically determined' what the state of what B would be. If one reversed the polarity for A to Right, the B would magically become Left.
"correlation is not causality"
That is not the way I have seen Bell's Theorem presented time and time again. Why is it a "Theorem" anyway if it isn't univerally true?
If it were in a definite state, it would have to obey Bell's Inequality
I thought it did, that was the problem. The contradiction between this and Einstein's Theory.
and this despite the fact that the information wasn't in a definite state until it was measured.
Do you know that it was definitely wasn't in a 'definite state until measured?' How do you know? If you can't measure it in an "indefinite state" then you have a theory with no possible evidence. Therefore, how do you know?
Pardon my ignorance on the subject. I have followed this for years. It makes no sense. I personally think QM is wrong and hope to live long enough to see it dethroned. It is based upon a fallacy of reification (the Copenhagen Interpretation.) I think Bell's Theorem is wrong also.
But then, what do I know?
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