Something has been confusing me. There was an experiment that "slowed light down" to 45 mph in a supercooled medium, so relative to an outsider outside of the medium the light was "slow". I realise there is a "catch" with this and it's not actually slowing down that extremely. Or at all.
And that hypothetically if that medium was at 0K the light would stop completely.
The second thing I heard was that photons actually travel at C through any medium, and that the slowdown is almost mechanical - in that the photons get absorbed by a particle in the way inside a medium and then re-emitted, which takes time. But that the photons actually still always travel at C between the particles in that medium.
Can someone just confirm that this is right? And if not, why not?