Wednesday, August 6, 2008

The black hole: Does it or doesn't it destroy information?

Here John Johnson Jr. interviews Stanford's Leonard Susskind, whose claim to fame is that he is Stephen "black hole" Hawking's nemesis (Los Angeles Times. July 26, 2008). Susskind has printed Hawking's letter conceding that information is not necessarily lost in a black hole:
I was a particle physicist when I was invited to an event at Werner Erhard's house in 1981. Erhard [founder of the est self-awareness movement] admired scientists and liked to listen to them debate. At one of his events, I met Stephen Hawking. Stephen discovered an amazing fact, which is that black holes evaporate. It's like a puddle of water out in the sun.
Susskind thinks that was wrong.
It violates one of the fundamental principles of physics, which says nothing is ever lost completely. You may say, "How can you say information isn't lost? I can erase information on my computer." But every time a bit of information is erased, we know it doesn't disappear. It goes out into the environment. It may be horribly scrambled and confused, but it never really gets lost. It's just converted into a different form.
I am not sure what that means. If information is horribly scrambled and confused, it isn't just converted to a different form, it can be basically lost.

If I told you that my late cat's name was &*&^^%**!, how would that help you figure out what the cat's name was, without any regular encoding/decoding system in place?

Something about all this doesn't make sense, and I am not surprised to learn that Susskind is one of many anti-intelligent design folk who would love to believe there is a zillion universes (so absolutely anything could be true about our universe and it wouldn't prove anything, right?):
Since the early 1980s, some cosmologists have argued that multiple universes could have formed during a period of cosmic inflation that preceded the Big Bang. More recently, string theorists have calculated that there could be 10 [to the]500 universes, which is more than the number of atoms in our observable Universe. Under these circumstances, it becomes more reasonable to assume that several would turn out like ours. It’s like getting zillions and zillions of darts to throw at the dart board, Susskind says. “Surely, a large number of them are going to wind up in the target zone.” And of course, we exist in our particular Universe because we couldn’t exist anywhere else. It’s an intriguing idea with just one problem, says Gross: “It’s impossible to disprove.” Because our Universe is, almost by definition, everything we can observe, there are no apparent measurements that would confirm whether we exist within a cosmic landscape of multiple universes, or if ours is the only one. And because we can’t falsify the idea, Gross says, it isn’t science. (Geoff Brumfiel, "Outrageous Fortune," Nature, Vol 439:10-12 (January 5, 2006).)

[ ... ]

Susskind, too, finds it “deeply, deeply troubling” that there’s no way to test the principle. But he is not yet ready to rule it out completely. “It would be very foolish to throw away the right answer on the basis that it doesn’t conform to some criteria for what is or isn’t science,” he says. (Geoff Brumfiel, "Outrageous Fortune," Nature, Vol 439:10-12 (January 5, 2006)
Notice he says that about the multiverse, but not about intelligent design of our universe - for which we have evidence.

Note: I seem to recall a Canadian physicist once telling m that Hawking had admitted the same thing to him too. Maybe he should have got a letter ...