Question about the Scharnhorst effect

[Dmitry67]

http://en.wikipedia.org/wiki/Scharnhorst_effect

I see 2 different interpretations:
1. There is no violation of causality. Light in vacuum is traveling slightly slower then c. Between 2 plates it is traveling faster then light in vacuum but still slightly slower then c
2. c is a speed of light in vacuum, so it is traveling faster then c between 2 plates

I tend to think that 1 is correct... But I am not sure... any ideas?

 

[turbo]

Einstein did not believe that the speed of light (c) was constant from place to place in a vacuum, as he explained in his 1920 book "Relativity: the Special and General Theory".

http://www.bartleby.com/173/22.html

In the second place our result shows that, according to the general theory of relativity, the law of the constancy of the velocity of light in vacuo, which constitutes one of the two fundamental assumptions in the special theory of relativity and to which we have already frequently referred, cannot claim any unlimited validity. A curvature of rays of light can only take place when the velocity of propagation of light varies with position. Now we might think that as a consequence of this, the special theory of relativity and with it the whole theory of relativity would be laid in the dust. But in reality this is not the case. We can only conclude that the special theory of relativity cannot claim an unlimited domain of validity; its result hold only so long as we are able to disregard the influences of gravitational fields on the phenomena (e.g. of light).

Please refer to the quote in my sig for a little clarification on his motivation.

 

[tiny-tim]

Hi Dmitry67!

I see 2 different interpretations:
1. There is no violation of causality. Light in vacuum is traveling slightly slower then c. Between 2 plates it is traveling faster then light in vacuum but still slightly slower then c
2. c is a speed of light in vacuum, so it is traveling faster then c between 2 plates

I tend to think that 1 is correct... But I am not sure... any ideas?

I'm with you …

the existence of a speed, c, on which all observers agree is a matter of geometry …

the speed of light is a matter of physics, and has to be ≤ c …

but I'm not sure either. ​

 

[Vanadium 50]

I think we need to be a little careful here. First, there is no experimental verification of the Scharnhorst effect. It may not even be possible to verify this: at long wavelengths, quantum mechanics gets in the way of precise speed measurements, and at short wavelengths the approximation of a perfect conductor breaks down. It's entirely possible that there is no physical configuration possible to see this effect - if it's really one part in 10³⁰, or 10³⁵ it's entirely possible that idealizations like "perfect conductor" fail just like idealizations like "rigid rods" fail in SR.

Second, it's certain that QED is not the right theory to give you 35 digits of precision. You'll need the full-blown electroweak theory, and you might even need to worry about GR effects. It's far from clear that the rigorously correct calculation would give the same answer.

Third, it's also far from clear that even if such a thing actually did permit signals infinitesimally faster than c, you could use this to send a signal backwards in time. Such an arrangement would involve two interpenetrating Scharnhorst regions - at a bare minimum, edge effects would have to be considered.

Finally, if you had "Lorentz c" faster than "light c", that would give the photon a mass (not observed), and would permit charge non-conservation (also not observed).

 

[cesiumfrog]

Light in vacuum is traveling slightly slower then c.

At what speed in who's reference frame?

Actually, can anyone explain that in the context of astrophysical gamma ray delays?

 

[Halfbaker]

Or 3: c = the speed of light in a vacuum and light travels faster between to conductive plates because the vacuum is modified. In other words the Scharnhorst effect actually changes the value of c locally.