A Professor of astro physics once told me that the speed of light is actually higher when light passes through cesium as its medium as opposed to vacuum or worse mediums.
I dont really find a consensus that this is true, apparently there where some experiments in around 2000, but it doesnt seem widely accepted - OR it doesnt matter. The implications of FTL even in such a restricted way, especially with regards to causality should be incredible. But apparently that is not the case.
How is light moving in a medium like cesium, at > c, not the same as without cesium and not a big deal?