[another cricket]

There is one possible mechanism by which the speed of light may have changed. If there are large (order 1 mm) extra dimensions, some models predict that the compactification scale (the radius of curvature for the extra dimensions) will "relax" slightly over time after the universe forms. A tiny change in the speed of light may be a signature of that relaxation. If this is the case, relativity is unmolested. What we are seeing is the principle of relativity applied to a universe whose geometric structure is changing slightly over time.

Ouch! Can we have an ice pack over here? I think I sprained something trying to wrap my brain around this.

Did you say that if the shape of the universe is changing it could effect the speed of light?

a.cricket

[balrog666]

There is evidence to suggest that the fine-structure constant, [alpha] — a measure of the strength of the electromagnetic interaction between photons and electrons — is slowly increasing over cosmological timescales. As
[alpha] = e2/[h]c (where e is the electronic charge, [h] is Planck's constant and c is the speed of light), this would call into question which of these fundamental quantities are truly constant.

Anybody got a nice physics symbol font?