** Straight Dope Staff Report What’s with news reports about things traveling faster than light**
** Straight Dope Staff Report What’s with news reports about things traveling faster than light**
If nothing travels faster than the speed of light, then how do you represent the speed of one photon (leaving the “top” of the sun) away from another (leaving the “bottom” of the sun)?
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I think you are missing a few of the facts.
Scientists at CERN claim to have made particles travel at 3 times the speed of light. The controversy is whether the particles that exited the particle accelerator are teh same particles that entered it.
One thing that often confuses people when talking about
relativity is that there is the “speed of light” and then
there is the “speed of light”. (You can probably see why
it’s confusing.) In one case, the phrase means a velocity
that light travels. This may or may not be the ultimate
limit of how fast information can be transferred between
to points. For instance, in glass light propagates much
slower than in, say, air. Heck, in germanium light goes
only one fourth as fast as in air.
The other meaning is more properly called Einstein’s
constant and is often represented as “c”. This happens
to be how fast light appears to travel in a vacuum. So
you could say, “the speed of light in a vacuum” but that
is less than rigorous and a mouthful besides.
The sooner everybody starts saying “Einstein’s constant”
the sooner the frontiers of ignorance will be given another
shove back.
- jam
Mark IV asked:
One of the basic questions of relativity. Addition of velocities is not directly linear like at non-relativistic speeds. You have to include the relativity term.
Please read How Do You Add Velocities in Special Relativity?
Jamoross, we could call it Einstein’s constant (I like that), but then we have to put up with people complaining that we’re “worshipping Einstein”. (No, I’m not being facetious. I’m following an exchange on relativity elsewhere with a certain person who espouses that view.)
Yeah, like we worship Planck, Boltzmann, and Hubble. Anyone that worries about worship among particle physicists and cosmologists doesn’t understand them. Sure, many do consider all Einstein’s work to be a done deal, but there will always be some that consider making a modification to relativity to be their main goal as a scientist.
I also like ‘Einstein’s constant,’ though I’ll probably mostly continue referring to it as simply ‘c’.
I have to say, I like the idea of calling it “Einstein’s Constant”, as well… I’ll have to see if I can get that to catch on around here. Of course, I usually use C, but sometimes that can get a bit awkward.
The added advantage here is that, should the photon be discovered to have a minutely tiny rest mass, we could still keep special relativity intact.
I believe that Einstein proposed not that nothing can go faster than the speed of light, but that nothing can reach the speed of light. There are particles called Tachyons that go faster than the speed of light, they just cannot slow down to the point where they reach it.
MonkeyKong, that’s addressed in the other thread currently running on this topic: Special relativity allows for the possibility that tachyons might exist, but there is absolutely no evidence of any sort, theoretical or experimental, to suggest that they actually do exist. Furthermore, even if they do exist, they probably can’t interact with ordinary matter at all, or you’d get time travel paradoxes. If something can’t possibly interact with us at all, we might as well say it doesn’t exist.