How do black holes destroy information and why is that a problem?

How do black holes destroy information and why is that a problem?

This video is to answer a question that many of you asked about my video on quantum gravity, which is just how do black holes destroy information and what’s the problem with that.

To explain what is the problem, I first introduce the two major concepts in contemporary physics theories, which is the « state » of a system and the « evolution equation ». I explain the difference between time-reversibility and time-reversal invariance, and that there are no fundamental evolution equations which are irreversible. The only fundamentally irreversible process we know of is the measurement in quantum mechanics.

Black hole evaporation, however, seems to be fundamentally irreversible, already before a measurement is being made. This is the very problem, because that makes black hole evaporation incompatible with quantum theory.