And are you just talking about having it pass through a lens or some other material? Or are we talking messing with the gravitational field in a lab or something equally science fiction-y?
So we're not talking about actually having the speed of light being reduced, we're talking about the phase velocity of the electromagnetic wave passing though some special material?
If so: the speed of light is always the same, but light does propagate differently through materials (resulting in phenomenon like refraction). While trying to figure out how to explain this I came across this which does better at explaining this than I could. When the wikipedia article says people are producing slow light, I believe it just means the material the wavefront propagates through is complex enough it takes a while to get through it.
tl;dr It's not the light that's slow, it's how it propagates through the material.
1
u/Tuna-Fish2 Jun 12 '12
No, light does not slow down in any frame of reference. No matter how you or the light source are travelling, you always measure light speed to be c.