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Hawking Gracefully, Formally Loses Black Hole Bet
Liora writes "Today at the 17th International Conference on General Relativity and Gravitation in Dublin, Cambridge University professor Stephen Hawking said in his talk titled The Information Paradox for Black Holes that he was wrong about the formation of an event horizon in a black hole, and that matter is not destroyed in a way defying subatomic theory, as he had previously believed. According to the talk's short, "the way the information gets out seems to be that a true event horizon never forms, just an apparent horizon." A New York Times story and a Wired story are available, both apparently based on Reuters information." (This is the formal announcement promised last week.)
I once asked the Slashdot editors why they didn't replace reg-required NYT links with reg-free links. They pointed out that there is a chance that the NYT could get its panties in a wad, and do something stupid. Lawsuits, goatse redirects, the works. Lawsuits... that would just be wrong!
Anyway, here's the obligatory reg-free link:
Are you looking at ME?
(Courtesy of these fine folks)
You don't understand it? It's pretty straightforward: a black hole has an event horizon, but nothing ever actually crosses it. The information can be retrieved from the black hole because it was never inside the event horizon.
"They redundantly repeated themselves over and over again incessantly without end ad infinitum" -- ibid.
Technically, the article said Hawking said that black holes do not lead to another universe. So if you want to think that there are other universes, you just have to look elsewhere.. String theory posits high dimensionality and "universes next door"; I'll remain parallel universe agnostic for the moment, but Hawking's point seems to have been that black holes do not eat information, and so they return the matter to the universe, and so he says, black holes are not an exit. If Hawking said definitively that our universe was the only existence, I would listen but I think unless we actually poke a hole into another universe with funky clues like, only 2 spatial dimensions (we could just be making a tesseract) or something, parallel universes will remain mostly philosophical.
Summary: Parallel universes aren't ruled out (at least by this article) so keep dreaming big! We'll need those other universes when entropy runs out in this one. Even better, ask someone who knows string theory whether the idea of multiple universes would be ruled out IF Hawking is right. Remember, he just lost a bet. He may be sure this time, but who's to say some bright kid 200 years from now won't have a different perspective... blah blah hypothetical
"A witty saying proves nothing." ~Voltaire
"d'Oh!" ~Homer
Black holes were first predicted in 1783 by a geologist named John Mitchell.
All that was needed to predict something odd would happen at this mass was the concept of escape velocity and that light had a velocity, both of which have been known for quite some time.
More info can be gotten at:
http://en.wikipedia.org/wiki/Black_hole
http://notanumber.net/
Yes. You're missing 200 years of Black Hole history.
The notion of a body whose gravitational force is so strong that not even light can escape was put forward in the late 1700s, first by a British geologist and later by Pierre Laplace. The solution of General Relativity that would come to be recognized as a Black Hole was put forward by Karl Schwarzschild in 1915, only a short time after Einstein had presented his theory of General Relativity. Schwarzschild developed his solution while serving with the German army, on the Russian front. Chandrasekhar's work was initiated in the 1920s. The idea of "Frozen Stars" remained known to physicists, but wasn't the focus of as much attention as it is nowadays. It wasn't until the late 60s and early 70s that they began to attract more attention, and around that time the phrase "Black Hole" appeared.
A great deal of Hawking's work has been devoted to Black Holes, and he is responsible for a number of significant developments in our understanding of them. In fact, "significant development" doesn't quite do it credit, as some of his ideas were so counter-intuitive (the notion of Black Holes radiating, for one!) as to be totally unexpected. But he definitely did not invent the concept of a Black Hole!
m5brane
Once it was clear that light moves at a finite speed, an English geologist, John Michell realized that one could imagine an object with a gravitational escape velocity greater than c. Such an object would appear black. Of course, the term "black hole" didn't appear until much later.
... by someone who doesn't know physics.
t ml)
The Euclidean path integral over all topologically trivial metrics can be done by time slicing and so is unitary when analytically continued to the Lorentzian. On the other hand, the path integral over all topologically non-trivial metrics is asymptotically independent of the initial state. Thus the total path integral is unitary and information is not lost in the formation and evaporation of black holes. The way the information gets out seems to be that a true event horizon never forms, just an apparent horizon.
The Euclidean path integral is the latest trick in quantum gravity.
The original problem with quantum gravity was that as you "quantitized" space into discrete units, explaining gravity in terms of particles like 'gravitons' and trying to do the math was possible for simplistic interactions like tree diagrams where time generally flowed one way - but extremely hairy and full of infinities if you started looking at loop diagrams where time can flow both ways.
So people like Roger Penrose came at it from a different direction, starting off with definining space-time in a quantitized manner (spin networks, quantum foam, whatever you want to call it) which had the side effect that complex examples of spin networks acted a lot like 3-dimensional Euclidean space.
Once people started talking about space-time like this, math started showing up that helped describe events and the progression of events in this space-time, including the Euclidean path integral which attempts to measure the end result of an interaction of particles in this type of space-time.
(Good link talking about path integrals and how they were a problem with quantum definition of gravity: http://www.damtp.cam.ac.uk/user/gr/public/qg_qc.h
Anyways, it sounds like he's saying: All this new math is great and if the world were a simple place, yeah, black holes would probably have an event horizon and the math to prove it is simple.
But the world is more complex than you think and doing the math for "the real world" shows that the closer you get to the end result, the less and less predictable the end result will be, even though overall it looks like it has a defined end result (i.e. it looks like it _should_ have an event horizon). In reality it's constantly shifting around - and likely this amount of shifting around is representative of the original information/particle system that went into its formation but you won't be able to trace it backwards and extract what the original information was.
This will probably tie into time dialation which will make it be: We never get to the end result event horizon that 'should' be there and in the process of never getting there, the black hole will have a nice jiggly event horizon as a result of all that information - but so jiggly we can't tell what went in to it, all we can do is measure the jiggliness.
What he hasn't explained is how he knows this and the math behind it.
Crap I'm bored.