The Black Hole War

"This is a very interesting book, because it is a specific issue that he is discussing, which he uses as a springboard to discuss some of the deepest features of the laws of nature. The issue is: When black holes evaporate, as Stephen Hawking predicts that they will, does the information that went into them eventually come out, or is it completely destroyed and lost forever? If you throw an encyclopedia into a black hole, Hawking says if you wait millions of years the black hole eventually evaporates into photons scattered around the universe. Susskind asks if you captured all those photons, could you figure out what was in the encyclopedia that was thrown into the black hole? It sounds like an incredibly narrow and technical question, but it really is at the heart of how physics works. Is information conserved from moment to moment, or is the universe truly random? Yes. But what you are asking is whether in principle – obviously not in practice – if you can get everything it evaporated into, would you be able to reconstruct it? People have argued about this for years. The popular view now is yes, you could reconstruct the book that fell in. Hawking, Susskind and others argued about it for years, and eventually Hawking conceded. He admitted that what we know about quantum gravity seems to imply that information is not lost. The information contained in the book you threw into the black hole is still contained in the radiation it emits – at least in principle. Get the weekly Five Books newsletter Absolutely. There is no question in my mind that you can do better and better at understanding these ideas by reading books like this. There is a barrier, because the theories that we are talking about are intrinsically mathematical. But these books are not, there are no equations in them. They are translations of the science. It is like reading poetry in translation – you can get an idea of what is going on, even if you don’t have the original essence. It is our universe. We all live in it, and it is a basic feature of what makes us human beings that we are curious about how things work. When we are six years old, we are all little scientists doing experiments and asking questions. Eventually the difficulties of life beat that out of us, but I think it is never too late to recapture that original wondering curiosity we all had."