It’s been years (5-6) since I was into cosmology. And the last few subjects I was looking at was Hawking’s radiation and information paradox. Well it seems that very soon the paradox is no more.
Began as just a fascinating idea, popularized with a “catchy name”:http://www.usd.edu/phys/courses/phys300/gallery/clark/wheeler.html , and brought to the masses via many science fictions. Black hole, as most people know, sucks everything into it. It just gets bigger and bigger as more things falls inside. And nothing ever escapes.It is black because light cannot travel away from it and onto our eyes. That was the original idea.
But then Stephen Hawking proposed his idea of how “something” can actually escape from a black hole. With a simple mechanism of virtual particle pairs created at the surface (called event horizon), it can happen that half of the pair (with negative mass) falls into the black hole, and the other half (with positive mass) escapses. To us outside this will just looked like the black hole “emit” a particle and lost some mass. We call the particles coming out “Hawking’s radiation”. And we can actually see black holes because of their radiations. Some of them are “quite bright”:http://antwrp.gsfc.nasa.gov/apod/ap991017.html indeed.
This is good news. So black hole doesn’t just expand and end up eating the whole universe. Actually most of them will spew out lots and lots of things when they get big enough. This is all and well, except there is a something missing. According to the then theory (sometimes called the quasi-classical theory), Hawking’s radiation are totally random. In other words, you cannot tell what fell inside by looking at what comes out of it. This bugs many people. Something is loss. The information.
Well, as with many cases in the history of Sciences. The solution that is good, but not good enough, can be improved on by the advancement of the theory behind. It was in the 70’s that Hawking thought of black hole’s radiation. And at the time, the universe still consist of point particles.
Now it is made of “String”:http://turing.wins.uva.nl/~rhd/string_theory.html . And with String Theory-based model of the black hole. Scientists had come up with a proof that the information is, after all, not lost. Mystery solved.
According to “this article”:http://www.newscientist.com/news/news.jsp?id=ns99996151 in “New Scientist”:http://www.newscientist.com , Hawking himself also has a few word on this matter. To quote:
I have solved the black hole information paradox and I want to talk about it.
This is what he said to the chairman of the “GR17”:http://www.gr17.com/ (the 17th International Conference on General Relativity and Gravitation, to be held between 18th – 23rd July 2004 in Dublin, Ireland). Now how do you say no to that? The chairman admitted he just went with the reputation and accpeted it.
I think I will stop here, I have already went in over my head. But it is a very fascinating story. And you can find out more at this excellent “web page”:http://superstringtheory.com/blackh/index.html which tell the story nicely, with the dirty details if you are so inclined.