Relativity Postulate

[IDMclean]

c is constant because in the simple electromagnetic equation: [math]\frac{E}{B} = \nu[/math]. When E and B are equal they equal c. This is simplification as there are other factors involved but for educational purposes it should be sufficent.

 

This ratio is the important because c is the rate at which a propagating electric field will regenerate a propagating magnetic field, and vice versa. This forms electromagnetic fields.

 

It is constant and invariant because it doesn't matter your frame of reference, your co-ordinant choice, or any of that. This ratio is always the same, so long as the laws that make up Electromagnetics, Electrodynamics, Magnetodynamics, and other such hold true under observation.

 

So in short, it would seem that the constant of light, c, is invariant because for the system to operate without regulating into nothingness, and amplifing into discord, c must remain constant. This does not mean that the speed of light is invariant, only that the rate at which equal electric and magnetic fields regenerate one another remains constant. It has been observed that the signal speed of light can vary according to the medium that the light progresses through.

 

In the case of the Casimir Vacuum it has been found that photons can propagate through the medium at faster than c signal speeds.

 

Tachyons

[coldcreation]

snip

 

what about when the gravity of a body bends light--any affect on the speed of the light?

 

snip.

 

Nope. For all intents and purposes, light is traveling in a straight (geodesic line), taking the shortest distant between the observer and the source, even when, interestingly enough, when deflected as it grazes the surface of a massive body along the line of sight toward an observer.

 

Her Einstein right again: c in vacuo is a fundamental constant of nature.