Speed of light

[kermit911]

Can the speed of light change?  Make it faster or slower?

[kempie]

Yes, as it passes through matter it slows according to the density of the medium.  This is why light refracts (bends) as it passes through glass or water.

[slimfandango]

Scientists now do it fairly frequently, especially with lasers. And they make it verrrrrry slow indeed!
So much for 'c' being absolute! (in a vacuum, I know, I know)

[dosset]

at the sub atomic level particle information travels faster than speed of light

[anthomson]

Persumably the reason light travels slower thru a solid is because it is interacting with the particles in the solid. i.e. the photon hits a particle, is absorbed (destroyed) but the energised particle then generates a new photon. So in a way a single photon cannot be slowed down.I did hear of an experiment which actually stopped light but think this worked on the same principle, you don't actually stop the photons but store their energy in another form until you are ready to realise them (As new photons). I don't think particles can travel faster than light but 'thought' experiments in quantum physics suggest that remote particles might be somehow be instantiously 'aware' of each other.