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JohnD
2015-Aug-27, 10:42 AM
Stephen Hawking has said that information that falls into to a Black Hole may be preserved in the event horizon "as a 2D hologram".
Ooooookaaaay, I think.
Then he says that the information would be in "chaotic, useless form," adding: "For all practical purposes the information is lost."

Chaos is not random, it is order that is very sensitive to the original conditions, so that it is impossible to recover those conditions.
Then it is not 'information'.
So what is Hawking on about? The information disappears.

John

Immortan Furiosa
2015-Aug-27, 10:52 AM
I don't understand much of what Hawking has written, and this may well turn out to be correct, but my first thought is: "This is a 73 year old man, maybe someone should vet what he says before it gets published."

So if I take a page of Shakespeare, cut it into individual letters and place them in a pile, is the information lost or does it exist but in a chaotic and useless form? I would say it is no longer information if it is unusable, but I'm no scientist.

swampyankee
2015-Aug-27, 11:11 AM
The math community appropriated and unilaterally redefined a perfectly good word, which is being used by Hawking in its normal sense.

John Mendenhall
2015-Aug-27, 11:23 AM
I think the information is still there but it cannot be recovered. The point is it has not been destroyed.

Squink
2015-Aug-27, 03:02 PM
Are we talking a wall of entropy here, or a perfect, reversible data compression system?
This is a very strange way to talk about it.
Perhaps someone needs to beat the heck out of information theory.
All I'm getting is the feeling of hands waving in the air.
We need to see at least a smidgeon of an equation here.

ShinAce
2015-Aug-27, 07:19 PM
Are we talking a wall of entropy here, or a perfect, reversible data compression system?
This is a very strange way to talk about it.
Perhaps someone needs to beat the heck out of information theory.
All I'm getting is the feeling of hands waving in the air.
We need to see at least a smidgeon of an equation here.

Bingo! I personally doubt he's talking about information as an immutable object (how the public might interpret it). He's talking about information entropy.

Dr. Hawking is considered an expert on black hole entropy. The field of information theory does exist. I just want to put that out there.

I think he's saying that information is never destroyed. After all, that must be the case if the entropy of a closed system tends to increase(2nd law of thermodynamics). All he's doing is adding that an event horizon is a fast way to scramble(or 'thermalize') information.

Imagine a pin dropping to the ground during an earthquake. Is the sound of the pin dropping preserved. Of course it is. Will it be heard by anyone? Would it be unreasonable to say that the information falling into a black hole is like the pin? That it is drowned out by 'noise'.

malaidas
2015-Aug-27, 11:17 PM
Yes, the problem here is contextual meaning i am guessing as well. The term information is a tricky one, because it can apply in many different ways and leads to a great deal of apparently nonsensical statements. For years I had huge issues with the assertion that quantum entanglement didn't violate C because no information was being passed because I wasn't understanding what was being said.

Selfsim
2015-Aug-28, 07:55 AM
All this just sounds like to me is that Hawking has formally yielded to the 't Hooft/Susskind version of the Holographic Principle and is prepared to lecture publically about it.

Information can be reassembled if one knows how to do this. I think Susskind etal have stated that no-one would know how to reassemble the information spread over a BH's event horizon(?)

grapes
2015-Aug-28, 09:03 AM
I don't understand much of what Hawking has written, and this may well turn out to be correct, but my first thought is: "This is a 73 year old man, maybe someone should vet what he says before it gets published."

Careful! I resemble that remark!


So if I take a page of Shakespeare, cut it into individual letters and place them in a pile, is the information lost or does it exist but in a chaotic and useless form? I would say it is no longer information if it is unusable, but I'm no scientist.
Imagine you were to carefully shuffle them into a pile. Would it still be unusable? What if your shuffles were reversible?

The math community appropriated and unilaterally redefined a perfectly good word, which is being used by Hawking in its normal sense.
Here's a link to reporting about the talk at the Hawking Radiation Conference in Stockholm, Sweden:
http://www.sci-news.com/physics/science-stephen-hawking-black-holes-information-03172.html

In context, I'd say Hawking was actually using "chaos" in the mathematical sense.

Ken G
2015-Aug-28, 09:07 AM
Yes, I'd say the whole debate brings us smack into the question, "what is information." We know how we use information, but does it have some kind of separate existence from how we use it? When we say information is lost, do we mean like we lose our keys (where we know the keys still exist, but we don't have access to them), or do we mean like forgetting where we put the keys? The difference is in whether or not we regard information as something that fundamentally involves us, or not-- are we talking about the keys themselves, or our memories about the keys? The place where this distinction gets particularly muddled is the realm of quantum mechanics, because so far the answer of which type of "lost information" we are talking about actually depends on our interpretation of quantum mechanics, so not even on our predictions surrounding any experiment we've ever actually done.

For example, Bohr once said "there is no quantum world", expressing the Copenhagen view that information is like a memory of where we put our keys, it's something that if we have no ability to access, it is not information to us. But in the many worlds view, we are only privy to some tiny mutually coherent eddy in the full information of a vast superposition of mutually incoherent swirls, much like we now view our presence on one planet out of a vast universe of similar planets. So the many-worlds view of lost information in the quantum domain is like losing the keys themselves, and how the keys are not themselves lost. What has been missing is an operational definition of the difference between these two types of information, and a black hole event horizon is a problematic place to try and find such an operational definition, given the notorious difficulties in doing observations there. On the other hand, it might be just the place where that distinction has relevance.

I'd say the need is to find an observation of the quantum realm, or of event horizons, that comes out A for one version of lost information, and B for the other. Until we have that, I have a sense that these theorists can pretty much argue until they are blue in the face, but all they are doing is trying to anticipate what cannot actually be anticipated-- unless their argument leads to the recognition of such an observable ramification.
(ETA: changed the analogy a little.)

Cougar
2015-Aug-28, 01:16 PM
....my first thought is: "This is a 73 year old man, maybe someone should vet what he says before it gets published."

I generally have an "assumption of cleverness" with respect to scientists who are much more educated than I am. And Hawking, of course, is known as a very deep thinker. Recently, however, some of his claims have made me somewhat skeptical of the cleverness assumption. And I wasn't too impressed by the recent book he wrote with Leonard Mlodinow.

From the linked article, it is not that clear what Hawking is claiming...


He formulated the idea that information is stored in the form of what are known as super translations.
“The idea is the super translations are a hologram of the ingoing particles,” he explained....
“This information is emitted in the quantum fluctuations that black holes produce, albeit in chaotic, useless form. For all practical purposes the information is lost,” he said.


The information loss problem has a long history, and the problem with what Hawking seems to be saying here was pointed out long ago: the quantum fluctuations that black holes produce are fully describable by their thermal characteristics. But the matter falling into a black hole is describable by a quantum state, which contains more information than a simple thermal characteristic. Where does that extra information go? It appears it is simply lost to the universe outside the black hole.

Hawking has invented a new term describing a new process: "super translations." In the ATM forum, such new terms typically raise a red flag. With Hawking, perhaps it's a yellow-caution flag (but of course, that should be so with any new scientific claim). So he says the super translations are a hologram of the ingoing particles on the surface of the black hole. So the hologram maintains the information. Yes, we know, from a respectful distance, that due to gravitational time dilation infalling objects appear to "freeze" at the event horizon, which is a theoretical 2D surface. But that appearance is temporary and very brief as the redshift of the object essentially goes to infinity, in which case, it's unclear how any information about that infalling object could be recovered.

Naively I wonder if Hawking's "super translations" attempt a new and super-clever way to recover quantum information from a mere thermal emission? This would not seem to be possible.

JohnD
2015-Aug-28, 08:09 PM
What is "information"?
It is the organisation of something, bits, letters, shapes, so that it means something.
If the medium has lost its organisation, the information been lost.

JOhn

ShinAce
2015-Aug-28, 09:34 PM
By that logic, if the index of your hard drive(its organisation) is lost, then all the data has been lost. There are people who make a living by recovering data from hard drives, and we would all agree. Your logic is therefore false.

The real problem is "how is the information organized?" If you don't know, then it is 'effectively' lost. If you know, then it's not lost. By that analogy, Hawking is saying that we don't know how information is organized.

Information, in a classical sense, is something with a yes/no answer. The number of questions you need for a full description is the amount of information. But you could potentially ask redundant questions, and store too many bits. That excess of bits relates to the entropy of that information.
See: http://tnt.phys.uniroma1.it/twiki/pub/TNTgroup/AngeloVulpiani/machta.pdf
"Entropy, information, and computation by J. Machta"

Information, in a quantum sense, is a whole new beast. Information can be computed. Computations can be reversible in the quantum world. Reversible computations can happen with no energy lost. Therefore, it is possible in the quantum world to perform calculations without any expenditure of energy. That simply isn't true of today's electronic computers.

Information is, in my opinion, even more baffling than the concepts of time and energy. It really does seem to be integral to the universe, but no one is sure exactly how. Hawking, being a theoretical physicist, enjoys these types of challenges. Hence he's working on it.

Does that help you understand what Hawking might be talking about? Because the truth is, the subject matter he's dealing with is above our pay grades. Then there's stuff about entanglement which I still haven't worked with.

Cougar
2015-Aug-29, 12:52 PM
What is "information"?

I could be wrong, but the baryon number (https://en.wikipedia.org/wiki/Baryon_number), which is conserved in nearly all the interactions of the Standard Model, is a bit (or byte) of information. This information appears to be lost and never recoverable when baryons fall into a black hole, thus violating this strict conservation law... and bothering physicists.

Squink
2015-Aug-29, 01:02 PM
thus violating this strict conservation law... and bothering physicists.We clearly need to promote an major information theory initiative. The stuff is bothering a lot of people in a lot of different fields of endeavor.

swampyankee
2015-Aug-29, 02:20 PM
One of the problems that seems to be present is that if the "information is there, but you can't recover it," one can argue that you've lost information: the information about how those bits are arranged. After all, "Call me Ishmael" has information that "l chalmlemes ai" lacks.

JohnD
2015-Aug-29, 03:31 PM
By that logic, if the index of your hard drive(its organisation) is lost, then all the data has been lost. There are people who make a living by recovering data from hard drives, and we would all agree. Your logic is therefore false.

The real problem is "how is the information organized?" If you don't know, then it is 'effectively' lost. If you know, then it's not lost. By that analogy, Hawking is saying that we don't know how information is organized.


I don't think that Hawking was referring to the loss of an index, as on a disk, where the information data is stored anywhere the system can find space, keeping tabs on where it is in the index. He speaks of the information being in ""chaotic, useless form", unlike the data on a disk which is broken up into chunks with complete internal congruity. The only interpretation that fits that statement is SY's example, disordered lettering, a nonsensical anagram. Decyphering seeks to restore the information in a message that has been disordered, but the cypher always follows a rule, so that it can be read by the desired recipient. A message that has been disordered by a chaotic rule could never be regained, even if we know the cypher!

Yes, the components whose ordering imparted the information are still present, but the information is lost. Is that what Hawking means, on a sub-atomic level?

John

John

Selfsim
2015-Aug-30, 01:28 AM
I don't think that Hawking was referring to the loss of an index, as on a disk, where the information data is stored anywhere the system can find space, keeping tabs on where it is in the index. He speaks of the information being in ""chaotic, useless form", unlike the data on a disk which is broken up into chunks with complete internal congruity. The only interpretation that fits that statement is SY's example, disordered lettering, a nonsensical anagram. Decyphering seeks to restore the information in a message that has been disordered, but the cypher always follows a rule, so that it can be read by the desired recipient. A message that has been disordered by a chaotic rule could never be regained, even if we know the cypher!

Yes, the components whose ordering imparted the information are still present, but the information is lost. Is that what Hawking means, on a sub-atomic level?In general, temperature is Hawking's "chaotic information".

Specifically: temperature is the increase in the energy of a system, when you add one bit of entropy.

(This was the outcome of Jacob Bekenstein's work on black holes, but Hawking was probably the first to see what Bekenstein had not recognised).