> you meant "inertial frame of reference"

Actually no. The speed of light is constant in ALL frames of reference, whether inertial or not. The math just gets more complicated in non-inertial frames. (That's the difference between special and general relativity.)

UPDATE: it's actually a little more complicated than that. See http://en.wikipedia.org/wiki/Propagation_of_light_in_non-ine...

> I'm sure that the effects are tiny for the LHC

Actually, gravity is a pretty significant factor. See e.g.:

http://www.astronomy.ohio-state.edu/~pogge/Ast162/Unit5/gps....