Astro101 - ＂Is information destroyed by a black hole？＂

When Hawking originally proposed that black holes evaporate, he did a calculation where he applied quantum theory to the matter, to the particles that are coming out from the black hole, like the electrons and positrons, but nobody knew, in fact still nobody really knows completely, how to apply it to the gravitational field. So he did what's called a semi-classical approximation. He applied classical physics to the black hole and quantum theory to the particles coming out. And when he did that, he found that because if you don't use quantum mechanics for the black hole itself, the surface of the black hole is this rigid, I mean it's this firm boundary of what could escape, and therefore anything that goes into a black hole, any information that goes in, the information cannot escape. And so he argued that the information would go into a singularity or get lost if the black hole evaporated completely, which he believed, and now most of us do believe, that this information would be forever lost from the universe.