[Tormod]

Okay, this question pops up now and then so let's have a new poll.

What do you think - can anything move faster than light?

[Thelonious]

Tormod said:

What do you think - can anything move faster than light?

In theory or in practice?

[bumab]

Yes. (mainly because I think people will figure out a way to do what the past has considered impossible).

But, I don't think it will be "moves faster then the speed of light" but rather, "gets from point A to point B faster then light could." Some sort of space warping, or moving into some other thing (warp field anyone?) where the distance between two places is smaller.

[GAHD]

I don't know what i think in that matter.

But then again, I'm rethinking how I look at movevement because of that question. Such an eternal puzzle.

[Fishteacher73]

I'm with bumab, I think that in terms of velocity, C is it. But thare could be other methods that could allow one to reach point B from A in a quicker manner than a straight line at C. What and how is up in the air, but with our understanding of how elastic space/time is, it seems somewhat reasonable that if we can streach it we can compress it as well.

[maddog]

I am not sure how answer the question... Theoretically possible if you expand what is definition of the
Lorentz Transformation by allowing Complex properties such that no mass particles crosses the C
boundary and massless particle move at C (or some harmonic of C). In this way symmetry is preserved
and Causality is not locally violated (assuming Tachyons don't openly interact with Tardyons).

Observably, no (this would violate the principle I said above).

Just a way of looking at it.

Maddog

[Qfwfq]

Tormod said:

can anything move faster than light?

If you mean "anything" then yes, quite likely. One thing that probably can't is causality, even by whatever shortcuts.

Theory doesn't actually rule out any superluminal velocity but, if something goes faster than light for some observers, it goes backward in time for others. The same would hold for causality, hence superluminal causality being possible makes the time-reversed causality possible and vice versa. This doesn't depend on how it would get from A to B, it's enough for the two to be at a spacelike separation.

If anyone can find a way to accomplish it, send me those lottery numbers and I'll play the ticket. Current jackpot €50 million! 1 euro is over a dollar thirty US.

[C1ay]

'Something' is such a broad term. If you could turn gravity on and off with a switch might it move faster than light? Could a magnetic field be propogated faster than light? Are there forces we haven't even discovered yet? Could they be faster than light. SInce the question is not limited to matter then I think it is entirely possible. Who knows, maybe even tachyons are real...

[sanctus]

And if something is as well what is defined as group velocity in optics then as well we got something moving faster than light.

[Qfwfq]

C1ay said:

If you could turn gravity on and off with a switch might it move faster than light? Could a magnetic field be propogated faster than light?

No, according to GR and no, according to electromagnetism (and SR).

[Qfwfq]

sanctus said:

And if something is as well what is defined as group velocity in optics then as well we got something moving faster than light.

When is group velocity superluminal?

[C1ay]

Qfwfq said:

No, according to GR and no, according to electromagnetism (and SR).

I realize that. I also realize that both of these are simply theories so there might be somethings we just don't know yet that they don't cover. That's just me though, I like to remain skeptical until someone proves something.

I wonder for instance. We use gavitational assist to accelerate space vehicles. Might it be possibles to use some type of electromagnetic assist to accelerate photons in the future? If so, could those photons travel faster than C? Just wondering.....

[Qfwfq]

C1ay said:

I also realize that both of these are simply theories so there might be somethings we just don't know yet that they don't cover.

Certainly. There are things that GR and EM don't fully cover. What we are talking of is, however, covered quite well by SR, which covers the very geometry of space-time. GR isn't quite as well tested as SR but there are things we don't expect to see ever being contradicted.

While people often say "but, they said the same about Newton's theory and then it turned out to be wrong..." I say that, in a certain fundamental sense, Newton wasn't wrong at all. SR should be viewed as a change more than as a contradiction to Newton's dynamics.

Our understanding became more complete with SR, and we don't find we can do anything that Newton's theory explicitly proves impossible. Not that we can now explicitly prove superluminal causality to be impossible, I haven't completely, totally, quite 100% lost hope for that jackpot.

[Qfwfq]

A few examples of "things" that certainly can "move" faster than light:

The locus of points on a surface, at which the phase of an incident wave is equal to a specified value, can move faster than the wave's phase velocity.

Phase velocity of electromagnetic waves in some dispersive media can be greater than c.

Correlation between measured values for a QM state may be instantaneous according to Born interpretation.

These things, especially the last one, can hardly be described as "something moving" and none of them amount to a propagation of causality.

[paultrr]

Qfwfq said:

If you mean "anything" then yes, quite likely. One thing that probably can't is causality, even by whatever shortcuts.

Theory doesn't actually rule out any superluminal velocity but, if something goes faster than light for some observers, it goes backward in time for others. The same would hold for causality, hence superluminal causality being possible makes the time-reversed causality possible and vice versa. This doesn't depend on how it would get from A to B, it's enough for the two to be at a spacelike separation.

If anyone can find a way to accomplish it, send me those lottery numbers and I'll play the ticket. Current jackpot €50 million! 1 euro is over a dollar thirty US.

I'd agree on that. Even Warp drive and wormhole cases don't actually get around causality. Both of those theories are pure theory since we have no experimental support at present for either. One might actually suggest that the theory on such moves superluminal while the experimental support in any of these areas tends to move rather at a turtle's pace.

But given time someone will find a way. Good Poll and you're right the question keeps coming up under a lot of varients.