[apochromat]

BECs are exotic, but they are what prompted my questions.

I was thinking about Cerenkov radiation for several minutes after I wrote my previous reply, while I was also muddling over whether "nonrelativistic" was the appropriate term for me to have used.

After thinking about it some more, I suppose that such exotic phenomena are relativistic, but their conditions are so complex that naively-applied relativistic transformations won't fit.

[RightWhale]

Bose-Einstein Condensates are exotic alright, but we don't have to use them to wonder about relativity inside non-vacuum conditions. The simple glass in your telescope lens allows light to pass right on through fairly easily, yet what kind of relativistic effects are going on inside there? You could shoot a nuclear particle into that region at over the speed of light in the medium until it collided with something. Light slows down instantly at the air-glass interface, but the alpha particle keeps on trucking, moving faster than light for a while. What happens to relativity there?