It is stated that the speed of light “slows down” when passing through a medium; passing through Bose-Einstein Condensate can slow light to the speed of a bycicle…even bring it to a complete halt!
Only in the absence of a medium, a vaccuum, does light travel at it’s maximum velocity per Relativity…299,792,458 meters per second.
What if we had some kind of “super-vaccuum”, something with negative density?
Somewhere on these boards someone posited the existence of negative temperatures…below Absolute Zero…which are actually quite hot, so at least the mathematics exist to describe negative physical quantities.
Can Relativity allow for and describe a speed greater than c in a negative density super-vaccuum?
“negative temperatures” is, to my mind, a misleading label. It usually simply indicates a population inversion, and is the unfortunate result of extending a model past its useful range.
There are interesting results with metamaterials (like negative refractive indices), but I can’t think of anything “vacuumier” than vacuum, or has hyper-vacuum effects.
I suppose there are some situations which could be regarded as “vacuumier than vacuum”, such as the space between two Casimir plates. But those all have other effects on light which still end up slowing it down.
The only thing I can think of that would make a vacuum more of a vacuum is “dark energy” as an expansive force. It does affect the speed of light if you consider that the light remains at light speed while space itself stretches out.
Correct me if I’m wrong, but I was under the impression that c is a constant, which happens to be equal to the speed of electromagnetic energy in a vacuum, for reasons requiring several paragraphs of dense physics to explain. That the “speed of light” is below c when passing through material objects is irrelevant. Correct?
There is some speculation that what we consider to be vacuum might actually be a “false vacuum”. The true vacuum would be a lower-energy configuration of space than the current vacuum. The current vacuum would merely be a local minimum, preventing space from spontaneously decaying into the true vacuum. However, a sufficiently high-energy event could jolt a local area of space out of its false vacuum state, allowing it to decay to the true vacuum. The result would be a bubble of true vacuum that would expand at the speed of light, destroying all matter in its wake until the entire universe was converted to the new true vacuum state.
If you’re going to destroy the entire universe, that’s the way to do it!
The interesting thing there is you could see it coming. Depending on where it started you might have millions of years of forwarning or just a couple dozen. I wonder how far away in time and space such a disaster would have be before people didnt give a darn.
I was (not) thinking that far off stars would blink out before nearby ones, forgetting of course that all light we see, whether coming from far or near, is ARRIVING here at the same time.
No, a Big Rip you can see coming. You’d see the dark energy getting stronger and stronger, with galaxy clusters, galaxies, etc. being torn apart well before the time planets and atoms got torn apart. There still wouldn’t be anything you could do about it, but at least you’d know.