[jjoonathan]

> one of the particles to fall in and the other to escape. This results in a loss of mass of the black hole (told you it was weird)

How does the energy to create the virtual particles come from the black hole (which it has to in order for the accounting to work: -2+1=-1)? Is it a "Quantum Field Theory doesn't care about the event horizon" type thing?

[pdonis]

It doesn't take any energy to create virtual particles; virtual particle pairs are constantly being created and destroyed everywhere, according to Quantum Field Theory, but when they're created, on average, they have zero net energy: one has positive energy and one has negative energy. (Note that this is a heuristic description and not every quantum field theorist would agree with it. The only really unambiguous way to describe the process is using math; but translating math into everyday language is often difficult because our intuitions don't really match up with what the math is telling us. I'm doing the best I can.)

However, if a virtual particle pair happens to be created just outside a black hole's horizon, the hole's tidal gravity can pull the negative energy particle inside the horizon before it can be annihilated by the positive energy particle. The positive energy particle can then escape. Effectively, this means the positive energy particle's energy is taken from the hole's mass, so the hole's mass decreases slightly.