For talking about slowing light down, apparently in Bose-Einstein condensate it can actually be stopped. That's pretty cool.

@Dodece. 'Bounce around' isn't quite factual either. The light gets absorbed and re-emitted by atoms which delays the propagation.

@Rath

I actually thought about including that. Then decided against doing so, because it wouldn't help to exactly clarify the situation. Once you bring that up then you open the door up to a whole slew of other interpretations. Like well then it isn't the same light, or the medium is really just a battery and so forth. I just went with the elegance of simplicity.

who is einstein?

Third president of America.

I was simplifying my explanation so (I thought) you could understand it. Of course light always travels at c regardless of medium. I mentioned phase velocity and group velocity and anyone wishing to read further should look those terms up.

I don't understand why you wasted people's time by making that up though.