Famous Hawking Black Hole Bet Resolved? 500
Mick Ohrberg writes "In 1997 the three cosmologists Stephen Hawking, Kip Thorne and John Preskill made a famous bet as to whether information that enters a black hole ceases to exist -- that is, whether the interior of a black hole is changed at all by the characteristics of particles that enter it. It now looks like Stephen Hawking and Kip Thorne may owe John Preskill a set of encyclopedias of his choice, since physicists at Ohio State University 'have derived an extensive set of equations that strongly suggest that the information continues to exist -- bound up in a giant tangle of strings that fills a black hole from its core to its surface.'"
Hawking radiation (Score:5, Informative)
The article though is a bit hand-wavy over why the information is preserved in this new theory... (I guess Nth dimensional maths doesn't appeal to the reporter
Effectively this is a conjecture - if the strings continue to exist, then they'd have the same size as the black hole appears to have. The throwaway statement " That means a black hole can be traced back to its original conditions, and information survives." seems a bit of a stretch though
Simon
Re:status of string theory (Score:3, Informative)
this is also why quite a few people feel its more philosphy than science
Re: encyclopaediae (Score:3, Informative)
Re:Simple question maybe (Score:5, Informative)
I'm sure the bet will be collected... (Score:1, Informative)
Paul
Re:It was a Playboy subscription... (Score:3, Informative)
Hawking/Thorne bet [k12.wa.us]
Ain' the web grand?
Yeah, Stephen lost that one. Word has it that Kip's wife was a bit miffed about the payoff.
KFG
Re:Simple question maybe (Score:2, Informative)
Re:Almost - wrong bet though (Score:3, Informative)
In 1975, he bet Kip Thorne a subscription to Penthouse (the loser would get it mailed to his home) that a celestial mystery named Cygnus X-1 would turn out to be a black hole.
Re:Is it me (Score:3, Informative)
Re:status of string theory (Score:5, Informative)
String theory certainly does predict a number of things that are easily testable
Yes, it's a theory, yes it's kinda off-the-wall and feels a bit contrived, but, studying it, I gotta say that it's pretty if nothing else. It's elegant enough and compelling enough - in terms of what it promises to explain - that it's worth following until it's found to actually be wrong.
A quantum theory of gravity might not be so motivating to you, but if you're a physicist, it's worth trying something wonky to get to it. (Speaking of which, Quantum Loop Gravity - also very wonky - is awesome).
And, as for "quite a few people" finding it too philosophical
Re:Hawking radiation (Score:5, Informative)
As I understand it, the idea is that the particle and the anti-particle come into being at the same place, moving in different dirrectsion, and the anti-particle is more prone to being pulled in somehow due it its being the opposite of the other mass in the black hole. The particle escapes, generating the black-body radiation, and the anti-particle enters the black whole and collides with a corresponding particle, leaving existance as the original particles came into existance - messed up I know.
If anyone is curious, (stolen from The Universe in a Nutshell by Stephen Hawking, the temp of a black hole is
Temp = (h * c^3)/(8 * pi * k * G * M)
where h is planck's constant, c is the speed of light, G is Newton's gravitational constant, k is Boltzman's costant,T is temp, and M is the mass of the black hole.
Re:Hawking radiation (Score:3, Informative)
BUT:
If an anti-particle enters the black hole, it LOSES mass. So its a process in which energy is emitted outside of the event horizon and the mass inside the event horizon is decreased. That no mass actually transfered out of the black hole is only a semantic problem (like tunneling, ect).
I cant really speak about the asymetry that enables this process, because its a few years about my quantum physics level, but it could be possible.
Btw: There are theories that the resulting radiation isnt REALLY blackbody radiation, but only "shaped" like BR, but with an "overlayed" information contend.
Re:Hawking radiation (Score:5, Informative)
The abstract from the NPB article is
It has been found that the states of the 2-charge extremal D1-D5 system are given by smooth geometries that have no singularity and no horizon individually, but a `horizon' does arise after `coarse-graining'. To see how this concept extends to the 3-charge extremal system, we construct a perturbation on the D1-D5 geometry that carries one unit of momentum charge P. The perturbation is found to be regular everywhere and normalizable, so we conclude that at least this state of the 3-charge system behaves like the 2-charge states. The solution is constructed by matching (to several orders) solutions in the inner and outer regions of the geometry. We conjecture the general form of `hair' expected for the 3-charge system, and the nature of the interior of black holes in general.
If your institution is a subscriber you can get the full text from here [sciencedirect.com]
Re:Hawking radiation (Score:5, Informative)
Except that the pair of virtual particles are an entangled pair and if one catches the escaped one and measures its quantum state, one then knows the quantum state of the one that fell in. Catch enough of them and you know about an appreciable fraction of the black hole (in theory!)
Now, how the black hole doesn't gain mass from the anti-particle I'm not quite sure
The energy that was used to create the virtual pair came from the black hole's gravitational field, thus robbing the hole temporarily of mass. For each "virtual" particle that escapes as Hawking radiation, that mass is lost permanently so the mass of the hole goes down, over time. Now remember that this loss can only happen at the event horizon; if the black hole is very large, the tidal force (the gravity gradient) at the event horizon will be weak and thus the rate of particle loss will be very low. For very small black holes the tidal force at the event horizon will be enormous and almost all virtual pairs close to the boundary will separate in this way.
So large black holes will simmer coldly, shrinking only with glacial slowness if at all, and small ones will be hot and shrink very rapidly indeed - finally disappearing altogether in an brief, intense burst of radiation, according to Hawking's theory.
Re:Hawking radiation (Score:5, Informative)
Now, how the black hole doesn't gain mass from the anti-particle I'm not quite sure...
The black hole doesn't gain mass, because the particle that fell in has negative energy. Remember, you can't create energy from nowhere, but you can "borrow" some from the vacuum temporarily ... that's where the virtual pairs come from. They borrow energy from the vacuum, which they have to give back after a time (roughly) Delta T < hbar/E, where E is the energy of the particle pair.
Now, if one half of the pair falls across the event horizon, it isn't coming back. The particle that escapes the hole becomes "real" because it has no one to annihilate with, so it carries off energy E/2. But since you can't yank energy out of the vacuum indefinitely, the particle that fell in had to be carrying energy -E/2 ... which isn't a problem, because it isn't a "real" particle, so it's energy need not be consistent with your expectations from freshman physics.
So, where does that energy E/2 that goes into the escaping particle come from? The only place it can: the black hole. Remember, a negative amount of energy fell in. So the hole has to lose some mass in the process. Which is why we say that the black hole "emits" particles.
The mathematical details are, of course, much nastier than that, but that's the gist of things...
Re:Is it me (Score:5, Informative)
I actually recently responded to a similar accusation against physicsists, and you can read my reply here [slashdot.org]. That response has more examples listed of 'kludges' in physics, but I'll talk about a few in more depth in this post.
What you've just described is known as phenomenology. In other words, trying to come up with some sort of basic theory to match the given data. Examples include Planck's original quantizing of radiation into discrete quanta, which turned out to be right. Another example is the Landau theory of 2nd-order phase transitions, where one builds a power-series expansion of the free energy in powers of something called the 'order parameter'. This is a total hack, but in many cases can adequately describe phase transitions (including superconductivity).
In fact, there are many kinds of physics theories, some termed 'macroscopic' in which case they're phenomonoligical, and describe what's going on, but don't adequately describe the 'physics' of the system. Then there's the microscopic theories that talk specifically about particle interactions, and follow directly from quantum mechanics, statistical mechanics, E&M, etc. The goal is to make these two approaches mesh.
For example, superconductivity could be described fairly well using the Ginzberg-Landau expansion, where the order parameter described above is complex, instead of real. Many things can be described this way, including Josephson Junctions and fluxoid quantization of superconducting loops. (Ginzberg just won the Nobel Prize in physics in 2003. Landau, if he were still alive, would have probably won it too, and it would have been his 2nd physics nobel prize). This approach worked fairly well, but physicists weren't sure why that was.
But then in 1957 Bardeen/Cooper/Schrieffer came up with the BCS theory of superconductivity, which explicitly describes how the electrons can pair up into Cooper pairs. Electrons want to repel, but in the right crystal lattice an electron-phonon-electron interaction (ie, a local distortion of the lattice) can produce an attractive interaction. BCS describe how this attraction comes about, how the energy gap forms, and how the electron pairs can carry a resistanceless supercurrent. BCS won the Nobel Prize in Physics in 1972.
This was microscopic vs macroscopic development of superconductivity. Two years later, physicist Gor'kov was able to show that the Ginzberg-Landau theory comes as a limiting case of the BCS theory. Hence, microscopic meets macroscopic, and everybody's happy.
So yes, physicists do look for something to fit the problem, but they don't just stop there. They also try to make those hacks or kludges match up directly from physical laws of the universe. That's what physics is about.
Re:Hawking radiation (Score:5, Informative)
A particle and an antiparticle both have a positive mass. The "virtual particle" mechanism means that for periods of times short enough, the measurement of the space right outside the hole is uncertain enough that there "might" be a pair of antiparticles there. So they are there. While they're there, one of them falls into the hole - it doesn't matter which one - while the other gains potential energy from its mate falling in, and escapes. Yaay.
But you can't get something from nothing. Some mass escaped from the vicinity of the hole, so some mass has to disappear from the vicinity of the hole. So the hole loses mass.
How's that for handwavy?
Re:Hawking radiation (Score:2, Informative)
I think this is not the case, since an anti-particle has the same (positive) mass as its normal-matter equivalent. An anti-proton is as heavy as a proton, but it has opposite charge.
Re:Hawking radiation (Score:5, Informative)
I'm the reporter, and you're absolutely right -- It doesn't!
Proud to be slashdotted,
Pam Gorder
Re:Hawking radiation (Score:3, Informative)
Exactly, you beat me to this. This is the explanation I have heard when in college with the addition that while it is a quasi-classical explanation (i.e. event horizon is classical, but space is not,) there always will be some handwaving involved.
Re:Hawking radiation (Score:2, Informative)
Actually, the physics applies. If they didn't match, I would be highly suspect of the result. Try to remember, in this case, the observer is not moving relative to the black hole, so low-velocity physics is sufficient.
Re:Is it me (Score:4, Informative)
By using theoretical physics, we've discovered some great observational results. Remember, not all theories have been just about quantum physics. The redshifting of stars, atomic decay, the curvature of space, the relativity of time.
These get back to us as profound statements about our existance: the approximate age of the universe, carbon dating objects, the formation of solar system.
Funny how the very large and very small are related.
Re:Hawking radiation (Score:4, Informative)
Re:Oh really, come on, get a clue! (Score:2, Informative)
fact is not a more emphatic form of theory, true. However, the advantage Physics has in working in a constructed language (math) is that we can go from a set of premises (astrophysicists and regular physicists differ as to which to accept) and arrive at logically confirmable conclusions.
While we can't ever definitely verify results experimentally, we can check closely enough to determine that these conclusions are good enough approximations to work from.
I guess what I'm saying is you don't have to accept, say, the Theory of Relativity...but if you want to talk me out of it, you'd better have a damned good alternative, because it fits the data and flows in a very straightforward manner from some premises that I buy into.
Universal Information Preservation... (Score:5, Informative)
What makes this interesting, is that as the matter slows down (an effect of time dialation), one can theoratically see more and more of the strings/string-structure (as higher and higher vibrational harmonics appeared to freeze out from the string's wild oscillations.) This in fact would mean that the available information about every string of matter that ever fell into any given black hole remains in the univerese as an observable phenomenon frozen at the surface of the black hole. Clearly this protects the conservation of information regarding all matter within the universe (as distinct from the space between the event horizon and the singularity which is a very different kind of place, and one that responds to different considerations as described by the Preskill's work.)
By the way if you ever want to read a great book on strings, and get a fantastic oveview of both Relativity and Quantum Mechanics, "The Elegant Universe" is a superb read. That and the authors subsequent comments about the strengths and weaknesses of both String Theory, and Quantum Loop Gravity point to an as yet undiscovered world view that will cleanly answer these dichotomies, the way these threories answer the dichotomy between Relatitivity and Quantum Mechanics.
Genda
"God not only plays with dice, he sometimes throws them where they cannot be seen..." -- Stephen Hawking
Re:Hawking radiation (Score:5, Informative)
Newton can actually say nothing about space around a black hole, at least not anything insightful. He just thinks that the gravity is pretty intense. He knows nothing of the spacetime warpage and all of the weirdness that goes with it. For example, he'd tell you nothing of the extreme time-dialation. All of this (from GR) is inherently part and parcel to the world of a black hole.
And if you stop and consider the Newtonian derivation of the Schwartschild radius (due to Laplace, I *think*), you should quickly see that it revolves around setting the escape speed of something to the speed of light. If that's not relativistic, what is? The speed of the observer is at best a red herring. (Arguably, citing it indicates a fundemental misunderstanding of relativity.)
Now, as for matching or not: stop and consider the history of relativity. The whole *point* of Einstein's work was that it *doesn't* match Newton's results. Newton predicts no time dilation for fast objects, no gravitational red shift, no gravitiational lenses, no gravitiational radiation. All of these things have been observered. Are you "highly suspect" of them?
Re:I've often wondered if... (Score:1, Informative)
The event horizon of a black hole cannot shrink, except in the case of Hawking radiation, which is completely negligible for any stellar-sized black hole. In particular, if you put two black holes close to each other, their horizons will deform and grow in size. They will emit a bunch of gravitational (not Hawking) radiation in the process, because the final merged black hole is not as big as the sum of the two original holes (as measured in area).
Re:Hawking radiation (Score:2, Informative)
Yeah, but they're virtual. You need a horizon to produce real particles from the vacuum.
Energy conservation. It works with horizons, because horizons allow one real particle to acquire a positive energy relative to an external observer, and the other (the one that falls in) to acquire a counterbalancing negative energy relative to that same observer -- the fact that the horizon separates the infalling particle from the observer is what allows the particle to have negative energy. The net energy remains zero. If there's no horizon, that can't happen.
Re:Some questions from a non-physicist (Score:2, Informative)
Real particles can't tunnel outside the light cone (faster than light), which is what would be necessary to get out of the horizon. If you're talking about the vacuum production picture of Hawking radiation, there is a sense in which it can be interpreted in terms of tunneling [arxiv.org].
Why should it explode? There is no limit to how much mass a black hole can contain. The more mass you dump in, the bigger it gets.
Not really [ucr.edu].
No. Quantum entanglement can't be used to transmit information [ucr.edu], regardless of whether there is a black hole around.
See also sections 9, 10, and 11 of this FTL FAQ [ucr.edu].
Re:Hawking radiation (Score:3, Informative)
I'm not an astrophysist but I think that's wrong. I don't think anything is accelerated beyond the speed of light--even within a black hole!!! Can someone else shed some light on this? I don't see why something would pass speed of light inside a black hole...
I think that is not correct either. Physics does NOT break down at the event horizon (from what I know). Rather, physics breaks down at the singularity deep within the black hole. I think the event horizon is well understood. (Actually you may mean something else--in which case you would be right. You are correct if you say that Newtonian Physics breaks down at the event horizon. However, Einstein's Relativity Theory can be used at the event horizon. However, inside the singularity, everything breaks down. We* need quantum gravity, which merges quatum physics and relativity. We haven't developed quatum gravity yet).
Having said that, we don't know what happens inside the black hole. Since nothing can escape, we have practically no observational evidence of anything inside. So all we have are theories.
BTW, someone correct me if I'm wrong in any of this. I am not 100% sure either--since I'm not in the field
(* When I say 'we', I'm talking about humanity. I'm not saying *I* am part of this whole thing. I never even took physics in university
Sivaram Velauthapillai
Re:Hawking radiation (Score:2, Informative)
The black hole doesn't gain mass, because the particle that fell in has negative energy. Remember, you can't create energy from nowhere, but you can "borrow" some from the vacuum temporarily ... that's where the virtual pairs come from.
The virtual particle approach to Hawking radiation seems to be more of a perturbative approximation that has caught on in the popular press than a reasonable description of reality. It may be more natural to describe the radiation in terms of the Unruh effect, which predicts a thermal spectrum around uniformly accelerating bodies - quasistationary objects near the event horizon are bathed in thermal radiation, and this is gravitationally redshifted as it propagates to the distant observer.
This avoids the rather cumbersome notions of negative energy and virtual particles which people tend to find counterintuitive. I have a recent post here [slashdot.org] which gives some relevant information and links.
Re:Hawking radiation (Score:2, Informative)
As I understand it, the idea is that the particle and the anti-particle come into being at the same place, moving in different dirrectsion, and the anti-particle is more prone to being pulled in somehow due it its being the opposite of the other mass in the black hole.
Unfortunately for your theory, particles and antiparticles behave essentially identically near a heavy object, so neither type is favored and (assuming the particle description of the mechanism is accurate - which it isn't) you can expect an equal number of particles and antiparticles to fall in. At least, Hawking's calculations didn't take your proposed mechanism into account.
The particle escapes, generating the black-body radiation, and the anti-particle enters the black whole and collides with a corresponding particle, leaving existance as the original particles came into existance - messed up I know.
If an antiparticle were to enter a black hole, it would add to the mass. If it were to collide with a corresponding particle whilst in transit, there would be some kind of radiation released into the hole, conserving total mass-energy. The perturbative explanation people like to give explains the mass theft in terms of the particle-antiparticle pair "borrowing" energy from the vacuum in order to exist, and the event horizon splitting them before they can recombine, causing the energy debt to be furnished by the black hole.
Re:Wait a second..? (Score:4, Informative)
This is where your mistake lies. The very foundation of the black hole is in it's mind boggling mass density. The absolute mass is important only in formation, because with too little mass gravitational forces are not able to compress matter enough to create the black hole.
You could get a black hole (complete with event horizon and Hawking radiation) by compressing earth into a radius less than about 9mm. Indeed, the less mass a black hole has, the smaller it is, and the larger the space curvature is on it's event horizon. Therefore all effects coming from space curvature are stronger for them, which also includes Hawking radiation. This especially means that finally black holes "explode": the more it radiates, the faster it gets smaller, and therefore it radiates even more in even shorter time scales, until it radiated it's complete mass away.
Of course, as soon as the black hole gets down to a size near the planck length (a mindboggling small length where quantum gravity effects are huge), we already know that all semiclassical reasoning must fail, therefore we cannot really say anything about what will happen at the last moment of a black hole, until we have a successfull theory of quantum gravity (or have watched black holes exploding, of course).
Re:Some questions from a non-physicist (Score:2, Informative)
Re:Hawking radiation (Score:3, Informative)
a=b+c (step 1) implies that a-b-c=0
Thus the division that occurs between step 5 and step 6 is division by zero.
"Proof" #2:
Step 4 - (I've an interest in mathematical vocabulary and notation, so this makes me curious. In the US we call this the "binomial" formula. What's your nationality?)
In going from step 4 to step 5, you are misapplying the following theorem:
If x>0 and y>0, and if x^2=y^2, then x=y.
Clearly in step 4, the expression on the right-hand side of the equality is negative. There is no other theorem that lets you "take the square root of both sides of an equation.
[/pedant]