The reason given in most places about why one cannot escape out from an event horizon is the fact that the escape velocity at the event horizon is equal to the speed of light, and no one can go faster than speed of light. But, you don't really need to reach the escape velocity to get away from a ...

I'm struggling to understand a hopefully silly implication about light clocks on trains. The train is in motion. SR and all that. Bob is on the side of the tracks watching. We're going to get super specific and say that the emitter for the light clock is an LED with a collimator. Problem 1: The l...