Stephen Hawking said he got it wrong
- Thread starter K.I.L.E.R
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Well there's been speculation that Black Holes can be used to travel far distances(think of movies like Wing Commander and Event Horizon(where the people actually travel to hell)). Just how far though, nobody knows.
It's been speculation though.
US
It's been speculation though.
US
'None. Stephen Hawking is overrated.'
Err no. Unfortunately Hawkings isn't up to date with some of the quantum theories of gravity floating around, so his solution will probably be classical, however he is also one of the foremost experts on the subject in the world. His reputation precedes him, he's been right a number of times, and well everyone is kinda interested in the specifics (that will be revealed at a conference next week).
The field is actually getting a surge of interest in the last few months, and everyone seems to have a different pet solution.
Essentially the problem is the following. Evolve a quantum state that is by nature a unitary process, and collapse it into a blackhole. Eventually the black hole will evaporate by well known processes that Hawkings discovered back in the 70s. The outgoing state is now thermal and mixed. Quantum mechanics says that you can't evolve a quantum state into a mixed state. What happened?
Up until recently, people have sorta assumed that this was essentially unsolvable unless you had a correct theory of the microscopics of the affair, read a quantum theory of gravity. There were several papers by string theorists that claimed to have resolved the process.
What will be interesting is seeing how all these competing theories actually mix and match (or not at all). The problem is, in principle, measurable so one day we will now.
Err no. Unfortunately Hawkings isn't up to date with some of the quantum theories of gravity floating around, so his solution will probably be classical, however he is also one of the foremost experts on the subject in the world. His reputation precedes him, he's been right a number of times, and well everyone is kinda interested in the specifics (that will be revealed at a conference next week).
The field is actually getting a surge of interest in the last few months, and everyone seems to have a different pet solution.
Essentially the problem is the following. Evolve a quantum state that is by nature a unitary process, and collapse it into a blackhole. Eventually the black hole will evaporate by well known processes that Hawkings discovered back in the 70s. The outgoing state is now thermal and mixed. Quantum mechanics says that you can't evolve a quantum state into a mixed state. What happened?
Up until recently, people have sorta assumed that this was essentially unsolvable unless you had a correct theory of the microscopics of the affair, read a quantum theory of gravity. There were several papers by string theorists that claimed to have resolved the process.
What will be interesting is seeing how all these competing theories actually mix and match (or not at all). The problem is, in principle, measurable so one day we will now.
Deepak said:Why not go inside a black hole and end this speculation once and for all.....
Yeah i'd love to travel years and years accross the universe, to the nearest black hole, to see how quickly i can die!!
Deepak said:I guess it would extremely dark inside a black hole (since light can't pass through it) so we should carry candles + matchstick...
And we can hold those with our new molecularly-fucked-up fingers!
Joe DeFuria
Legend
I'd visit a black hole...I'd just like to see Maximillian again...he's probably lonely...
Deepak said:I guess it would extremely dark inside a black hole (since light can't pass through it) so we should carry candles + matchstick...
If you were inside the event horizon of a black-hole you *would* be able to see out of it. You'd see stars in the sky just like you would anywhere else in space. Black-holes are "black" because light can't get out, not because light can't get in.
For super-massive black-holes in particular the effects of crossing the event horizon are relatively minor I believe (discounting ther fact that you're now trapped there, and have to wait for eternity to find out whether Mr Hawking was correct, and black-holes do evaporate, or whether dropped a sign somewhere in his maths).
If one observes photons travelling away from just outside an event horizon around a black hole, they appear to be red shifted due to having to "climb out" of a gravitational well. Put simply, they lose energy and hence drop in frequency due to the potential. The converse is true - sit at an event horizon and watch photons "drop" in; they will gain energy and be blue shifted.
davefb said:
Well, the black hole itself is invisible, the matter gravitating around it can be seen though.
davefb said:
Accretion of matter into a black-hole can release energy in the form of electromagnetic radiation, both in the visible and other wavebands (depending on the exact mechanism). It's not the actual process of the matter crossing the event horizon that releases the energy though, there's usually some dissipative process going on, often in the form of a hot disc of material surrounding the black-hole.
Black-holes effectively have no hard surface, so there's nothing for the infalling matter to bang into if you like, which is the way that gravitational energy is released in accretion onto other compact objects (white dwarfs and neutron stars). The gravitional energy has to be released in other ways, otherwise it simply gets advected into the black-hole never to be seen again.
davefb said:
The usual definition of the boundary of the black-hole is the event horizon, which is the surface inside which the escape velocity exceeds the speed-of-light. Google for "Schwarzschild Radius", that'll tell you everything you want to know and a whole pile you probably don't
Since black holes evaporate they are not completely black. According to general relativity the superstrong gravitational field around a black hole constantly creates pairs of particles and anti particles. Sometimes one of the "twins" escapes while the other falls into the black hole.
Hawkings says that the event horizont moves in space and this lets information to escape the black hole.
Hawkings says that the event horizont moves in space and this lets information to escape the black hole.