I've probably got something wrong here, but bear with me. An electron is moving through a material faster than the speed of light in that material. I know particles tend to do this from time to time -- we have Cerenkov radiation. If a TV camera were attached to this electron in a way which would not slow it down (you know what I'm talking about), would it witness "tachyonic" behavior such as things going back in time and stuff like that? Granted, the object is moving slower than c, but if the light in the medium the electron is moving is moving slower still strange things can happen. Which aspects of relativity would be violated / seem to become irrational in situations like this? You obviously wouldn't get "negative lengths" from length contraction exceeding c. Basically, if all of the rules involve nothing exceeding the speed of light but the speed of light is itself slowed because of the medium, how would the particles in the scenario know that the speed of light they are experiencing is not c?