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Why the Black Hole Information Paradox Is Such a Problem
New submitter TheAlexKnapp writes: Here's a really nice explanation of the Black Hole Information Paradox for those who are unfamiliar with it. The article lays out the basic gist — that right now if you take two black holes, one made from the collapse of one type of star, and the second from the collapse of a different type, you can't tell which is which. Ethan Siegel points out that Hawking's big announcement was really just a small step heading towards a possible solution, and highlights that the paradox highlights the incompleteness of our understanding of some types of physics.
If I take two random iPhones from random strangers, I won't know which iPhone came from which stranger just by looking at the outside of them. But we don't call that a paradox.
This is some high brow shit for Sunday morning
Yea, I don't see why this is a problem, anymore than any other thing in physics today.
Conservation of information is a quantum property. Black holes are a concept from general relativity (or a poor approximation in classical mechanics). Wake me when a verified theory of quantum gravity exists where this problem still exists... until then, this isn't news.
https://www.youtube.com/watch?...
morcego
Leonard Susskind discusses this in a talk he gave a few years ago.
https://www.youtube.com/watch?v=2DIl3Hfh9tY
Pretty entertaining.
So, presumably we can't tell whether any particular black hole is artificial either?
Shame, artificial black holes look like such a wonderful way for an advanced (for really advanced values of advanced) civilization to get both power and waste disposal taken care of....
"I do not agree with what you say, but I will defend to the death your right to say it"
In general relativity (our theory of classical gravity, without quantum effects), there are several "no hair" theorems, saying that several types of black holes are completely determined by a few overall parameters (say mass, charge and angular momentum) and without regard to their history.
We don't yet have a theory of quantum gravity, so we don't know if the quantum state of a black hole does retain information. It probably has to, but this is not understood. By the way, in any case classical GR would be an excellent approximation except in the case of very small black holes, so any information retained will not be actually accessible.
Black holes are just a toy.
Suppose gravity wins out after all, and the universe ends in a Big Crunch. One or a few Planck second(s) before the singularity, all the information in the universe should still be there. How?
Suppose entropy wins and the universe ends in heat death. For bonus points assume all protons have decayed. All the information should still be preserved. How?
When the copyright term is "forever minus a day", live every day like it's the last.
Just because we cannot see the internal degrees of freedom does not mean that they do not exist. Someone who is inside the black hole can detect events that fall past him/her/it that we cannot see from outside the black hole. Does a tree falling in the woods make a sound if nobody was there to hear it? Yes.
AFAIK from the point of view of an outside observer, it takes forever for a falling object to reach the event horizon. Given this, no object can ever be seen actually crossing said horizon; even the original star's collapsing matter is still just above it (or, alternately, it's just short of collapsing beyond it's Schwarzschild radius), merely very hard to see due to gravitational redshift. So... it seems to me that there's no two points in time for any outside observer where said observer could say information has been lost somewhere between them, and thus no paradox to explain.
Of course, by the same token, event horizon should be extremely noticeable to an infalling observer, since no part of them can enter before any other (since any part that's closer to the horizon will take forever to cross it from the point of view of any that's further), thus falling would be like being squeezed through jelly that keeps getting more and more rigid as you get closer to the horizon, culminating in you getting squeezed into a 2-dimensional shape against it. Yet scientists claim passing the horizon should be unnoticeable. Do we have anyone here who can actually work the equations and figure out what happens to observers who aren't point-like?
Forget magic. Any technology distinguishable from divine power is insufficiently advanced.
The credit should go to Gerard T' Hooft for the holographic principle and this work for which he received a Nobel Prize. Hawking is just slurping up media credit because he's a household name. Let's not get into the whole Edison/Tesla thing and get it right folks.
Well that article sure was not worth reading. But still it's an interesting question. One thing I don't understand is why the matter entering the black hole can't leave it's information behind in the conventional universe. I don't think that it is true that information is attached to the mass itself. As I understand it information content is a property of the universe. My understanding is that if you were to write down the position, momentum (or rather the density matrix, since things aw Quantum) ans any other wuatnum states of every bit of matter, one would have a desription of the state of the universe. If you then ran Bzip on this one would have an estimator of the amount of incompressible information contained in that description. If you put something into a black hole where it's simpler to describe then that bzip file size gets smaller so information disappeared. But if in the act of heading towards the black hole the energy the accelerating particle radiates cdistrurbs the universe and makes it more complicated to describe then the size of the bzip file increases. My hypothesis is that as matter enters the black hole all of it's information has been radiated away except for information about it's mass (or equivalently mass energy). Thus the Bzip file stays the same size.
Some drink at the fountain of knowledge. Others just gargle.
I'm not an astrophysicist either but I think that your mention of ice sculptures hits the nail on the head. When an ice sculpture melts the organization of the ice vanishes. But it also cools the air. The information content of the cold air increases. So the answers is the system preserves the information. Likewise when something is sucked into a blackhole it contributes it's mass but the organizational information it had (position, momentum, internal quantum states) is gone. On the otherhand as it's charges separate and accelerate it radiates and that radiation disturbs the rest of the universe. Thus my non-astrophycist guess is that those two exactly balance just like the ice sculptures warming chills the environment.
Some drink at the fountain of knowledge. Others just gargle.
I mean, with a sufficient supply of donuts you can assign a couple of cops to each star, and when they turn to black holes you can tell which is which as long as you don't lose sight of them...
Violence is the last refuge of the incompetent. Polar Scope Align for iOS
So when the black hole evaporates by giving off Hawking radiation, who's to say the information (albeit all mixed together) isn't coming out in the particular spatio-temporal pattern of emanation of the radiation?
Sure, the radiation seems (and is effectively to any observer) random, but it is well known that a random bitstring (k-random bitstring) can encode information, and in fact can be the most compact encoding of information.
Random simply means you don't have the means or supplementary information to deduce/detect the pattern. It does not mean that no pattern is there.
Where are we going and why are we in a handbasket?
Susskind wrote a very interesting book on this topic, too. The Black Hole War, subtitled, "my battle with Steven Hawking to make the world safe for Quantum Mechanics". I was hoping someone in the thread would know if Steven Hawking's announcement was an acceptance of Susskind's position, or similar to it, or something else.
It's more accurate to say "speed of information propagation". Light so happens to propagate at or very near the maximum rate of information through space-time.
If a black hole can be modelled as below from centre to event horizon a) A point gravity source b) A solid sphere with mass distributed evenly c) a distribution curve of mass from event horizon to centre d) a 2d shell and empty middle. Then won't behaviour of objects near eh be different and detectable ?
Why is it that the article can state things like "the known laws of physics break down" inside a black hole, yet insist that this particular law of physics, the conservation of information, shouldn't also break down and therefore results in a paradox.
Who gets to decide which laws break down and which ones don't?
Why isn't it all or nothing?
Thanks for clearing that up. I can get back to my facebook updates now.
When all you have is a hammer, every problem starts to look like a thumb.
The article says that all that is preserved, that is, information still obtainable, from a black hole is mass, electric charge, and spin (or angular momentum). I think also their plain old momentum is also preserved. What's interesting is that these are the first properties of matter to be discovered and understood in the study of physics. Newton describes mass and conservation of momentum, including angular momentum, and Benjamin Franklin discovered conservation of electric charge. I wonder if it's just a coincidence early, easy to understand qualities are the ones you can still get out of a black hole.
In theory, theory and practice are the same; in practice they're different. (Yogi Berra & A. Einstein)
Because anything falling in takes infinite time to reach the event horizon, at which point they cannot exit (or, from our point of view, continue in) and are trapped on the event horizon and cannot be detected at all
So from our point of view, all or nearly all the mass of a black hole exists at the event horizon? From our point of view, a particle or its remnants may approach the event horizon arbitrarily closely. What happens when the event horizon expands? Does the particle still take infinite time to reach the event horizon?
IOW, doubting your assertion about infinite time.
When all you have is a hammer, every problem starts to look like a thumb.
Good luck with your new theory.
When all you have is a hammer, every problem starts to look like a thumb.
So why is the speed of light the limit?
Figure that out and get a Nobel prize, never mind taking the crown for greatest thinker of all time. But you are unlikely to get there as an anonymous coward.
When all you have is a hammer, every problem starts to look like a thumb.
From Stephen Hawkings notes:
"And then I was reading slashdot and anonymous coward said all of this preservation of information stuff is a laughable concept, that's why I've switched professions from math/physics to web site dev. I'm working on a website for balancing checkbooks, should be really cool."
"The most exciting phrase to hear in science, the one that heralds new discoveries, is not 'Eureka' but 'That’s funny...'" --- Isaac Asimov
I can answer this with only high school biology.
No, you can't.
There is no more "more information" in a human body than there is in a mass of single celled organism of equivalent mass. Indeed on the scale of DNA (usually the source of this "misconception": that DNA is a measure of information), each cell of a single celled organism may have MORE DNA "information" than the human genome does.
I don't think you understand what "informaton" in this setting means. Hint: Altoug DNA information would probably qualify in a very roundabout way (as would the the information pertaining to a detailed description of a hen's egg), the informaton they're concerned about here is a lot more fundamental, and exists at a far lower level than DNA. We're talking wich particular types of fundamental particles went into the thing, and indeed which particular particles went in and what particular quantum properties *they* had.
Are you a grammar Nazi? I'm trying to improve my English; please correct my errors!
(Assuming I have this correctly.):
A rule of physics had been that information is not destroyed. (It can be scrambled beyond recovery by any reasonable process, but it's still there.)
Black holes make the information inside them inaccessible - no message gets out. Ok, it's still there but you can't get to it. All you can measure about a black hole is its mass, electric charge, and spin. All those other quantum numbers get hidden.
But Hawking radiation - according to the first formulation - is vacuum virtual particle pairs, appearing near the event horizon, where one got trapped by flying through the event horizon, releasing enough extra energy for the other one to become permanent and fly up the gravity well and away. The lost energy of the particle creation and ejection comes out of the total mass/energy of the black hole, so it shrinks a bit.
It's almost as if a particle tunneled out of the hole, but not really. The type of particle pair is random. If they're charged, the electric field can bias the probability of which one falls in, gradually discharging the hole. But the other fields don't leave memory, so, for instance, you get equal amounts of matter and antimatter, regardless of what you originally squeezed into a black hole.
But the evaporation of the hole leaves nothing behind. So if you built the hole out of mostly anti-matter you get half of it back as antimatter and half as normal matter, changing the matter/antimatter balance of the universe.
Oops!
(If this is correct, perhaps the explanation for the predominance of normal matter in the observed universe is that more anitmatter than matter got squeezed into early black holes, to emerge, if at all, as 50/50? You heard it here first!)
Matter/antimatter and related conservation of this-and-that laws is part of the information that's not supposed to go missing. Even if you DON'T violate those conservations, Hawking radiation was supposed to be random. So when the black hole evaporates (in a blaze of glory right at the end), all the information that went beyond the event horizon is still lost, replaced with an equal amount of purely random noise.
There has been a big discussion in physics on whether the information actually is lost. It got a LOT hotter when a scientist computed how much information should be inside the event horizon of a black hole and discovered that it was exactly proportional to the area of the event horizon, at one bit per plank-length-scaled patch. This led to speculation that maybe the infalling information doesn't actually fall in, but "gets stuck" on, or just above, the event horizon and might be returned to the rest of the universe during the evaporation process.
There were different camps on this, with Hawking being in the "lost" camp and others (including Susskind, who gives public lectures to laymen) in the "maybe it's not lost" camp.
Now Hawking may have been convinced, or convinced himself, that maybe the info isn't lost, and switched positions on the argument. This is big news.
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
If you accept the statistical nature of QM, then you might want to consider that we are just apes trying to understand QM. What if QM has a random number generator seed behind it (i.e. a C program) or the random number generator is encrypted with something we just haven't quite figured out yet? The hidden variables theory from Einstein implies that there might be state (i.e. Einstein was literally claiming we are a C program, but he didn't know how to program.. so he didn't realize what he was implying, only I realize it...well me and Nick Bostrom).... While people are busy cracking games and creating keygens, some of us are busy cracking the universe encryption... script kiddies become universe kiddies.
http://simulation-argument.com...
Enjoy the red pill - I'll give you some milk so that the pill goes down well.
How can you fit more information into an event horizon than it can hold? Isn't an event horizon a given size, a 2D spherical surface, existing in a universe that is limited by the resolution of the Planck distance? So how can I encode as much, about as many in-falling particles, as I like into it? If Hawking does not explain that adequately his theory is nonsense. Where he is going to find room to move to do this is a mystery, perhaps he will declare it to not be 2D after all and rather, a fractional dimension greater then 2 and less than 3? Perhaps this +2 dimensionality is a measure of the information it has already absorbed?
the problem with particles not being information, is something string theory is trying to solve where everything is just composed of bits or qubits, but the question is, do these bits of information exist as physical dots, substrings that are part of the string - what are the bits? This is an open area of study and anyone who claims to know everything about the subject is ignorant (not saying you are)
I'm not a huge fan of string theory since it isn't so testable (it's more like String Hypothesis).
You end up with a tautology, where information is represented physically, but are physical things represented by information
Then you end up with meta information about the information - where are these Hidden Variables that einstein spoke of? Is there state, like a C program, and is someone keeping track of the state using assignment in a procedural program, or monads in a functional program?
Again this brings us to silly things like the simulation argument (Nick Bostrom) which are so silly they could be true.
When Einstein spoke of hidden variables, he was unknowingly implying that we are living in a C or Lisp program. Or something like it. variables
" A state variable is one of the set of variables that are used to describe the mathematical 'state; of a dynamical system. Intuitively, the state of a system describes enough about the system to determine its future behaviour in the absence of any external forces affecting the system." --Wikipedia, not realizing they are describing the universe as a computer system..
Hawking already accepted Susskind's position when he admitted defeat in the bet with John Preskill.
)
*whew* That was bugging the hell out of me.
"Freedom in the USA is not the ability to do what you want. It is the ability to stop others from doing what THEY want"
Understanding the Universe tends to pay off, decades or more down the line. Computers would not be nearly as cheap as they are without a good understanding of quantum mechanics.
"When you have eliminated the unacceptable, whatever is left, however improbable, must be the truthiness" - Holmes