How can Hawking Radiation Escape?

How does a black hole radiate Hawking radiation, why isn't can it escape when everything else cant?
- Robbi (age 20)
England

The original version of this had the Hawking radiation get out by quantum tunneling. Those processes wouldn't be allowed classically, since they in effect would require a particle to have neagitive kinetic energy during its escape. Quantum mechanics does allow them. 

The current version of the story is a bit different. The black hole never quite forms, because processes near the event horizon slow down infinitely. (That's already true in the old picture.) So from the outside, the stuff that falls in seems to form a sheet just outside the event horizon. It can gradually leak out by something that looks much like Hawking radiation but isn't quite the same as the original version. How this outsider's descri[ption fits with the description from the in-falling point of view is a tough problem. You can google "black-hole firewall"  to find some of the current arguments.

Mike W.

(published on 08/31/2013)