Has the speed of light been constant since the big bang?

[Bharath Siva]

Just wondering if the speed of light in vacuum has always been constant since the big bang. Is there any evidence (theoretical or experimental) that the speed of light could have been faster or slower in the early universe or just after the big bang? How about at the big bang itself? Was the speed of light exactly the same at the point of the big bang as it is now?

 

[PeterDonis]

This Usenet Physics FAQ article may be helpful:

http://math.ucr.edu/home/baez/physics/ParticleAndNuclear/constants.html

 

[bcrowell]

It is not meaningful to ask whether a universal constant has changed over time if the constant is one like c that has units. For a more detailed discussion, see http://physics.stackexchange.com/questions/34874/has-the-speed-of-light-changed-over-time and Duff, "Comment on time-variation of fundamental constants," http://arxiv.org/abs/hep-th/0208093 .

This Usenet Physics FAQ article may be helpful:
http://math.ucr.edu/home/baez/physics/ParticleAndNuclear/constants.html

Also: http://math.ucr.edu/home/baez/constants.html