What happens to spacetime inside a black hole?
What kind of time reversal takes place inside the event horizon of black holes? Many people are fascinated by the famous “event horizon” of a black hole, the boundary of the region out of which nothing can escape. The mechanism that gives it this property is strange and amazing–it has to do with the idea of causality. Merlin from the King Arthur legends was supposed to have lived his life backwards–the first thing he experienced was his death and the last was his birth, hence his ability to foretell the future. To us, however, time feels as though it flows only forward. This feeling actually comes from the more general property of causality. In a region like the one here on Earth, you can only remember events that meet 2 criteria: (1) it has to have been in the past, and (2) it has to have happened at a distance no more than what light could have travelled since it happened. The second rule is just the familiar light speed limit. The first is called causality, and it’s why you won’t
