Q&A: Black Holes

Q:
What are "ergosphere" and "stationary limit", and what is an "event horizon"?

A:
A "stationary limit" is a surface around the outside of a rotating black hole. Any object which passes through this surface is always in motion - it's pulled by the distortion of space caused by the rotating black hole. The "event horizon" is a surface that exists closer to the black hole. Any object which passes through this surface can never be seen again. Nothing, not even light, can escape from inside the event horizon (this is how the event horizon is defined and that's why they're called black holes). An "ergosphere" is the region in between the event horizon and the stationary limit.

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