3

I just watched a BBC Horizon episode where they talked about the Hawking Paradox. They mentioned a controversy about information being lost but I couldn't get my head around this.

Black hole thermodynamics gives us the formula $$S ~=~ \frac{A k c^3 }{4 \hbar G}=4\pi k\dfrac{M^2}{M_P^2}.$$

where $M_P$ is the Planck mass. And we also have Einstein's famous $E = M c^2$, which mean that mass can be turned into energy, right? Hence information is either lost or it is preserved, but now in energy-form instead of mass-form.

I can't understand why radiation from black holes would be any different than an atomic bomb for example, where mass is also turned into energy?

riemannium
  • 6,843
Joakim
  • 41

1 Answers1

8

Radiation normally contains subtle correlations. For all practical purposes you can't use it, but it's there. Hawking radiation is, according to the theory, perfectly thermal and does not contain any more information than the temperature itself. The problem is that then the process of black hole evaporation is not reversible, in principle. Unlike all other processes that we know of (which might be irreversible in practice, but are reversible in principle). That irreversibility (which implies non-unitarity) is incompatible with quantum mechanics. That is the problem in a nutshell. It is really a conflict between quantum mechanics and semi-classical general relativity.

There are many more things to be said but I get the impression you haven't done a lot of reading about this and details would be rather pointless. I suggest you browse around for a bit with that starting point in mind.

WIMP
  • 2,685