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.

Comments

So?

[Anonymous Coward]

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.

Re:So?

[Fragnet]

You do know. There's information on and within both phones that's a record of which owner they had.

Re:So?

[Leuf]

What if I make two different ice sculptures from the same source of water with the same mass but different shapes. After they melt it's impossible to tell which one was which. That's not a paradox.

Re:So?

[michelcolman]

Of course you are simplifying down to a ridiculous level, and I do understand that information is a pretty powerful concept in physics that carries a lot more weight than you would think, but still, I did not find anything useful in this article. The title of the Slashdot Summary was very promising: "why the black hole information paradox is such a problem", so I was hoping to finally see this question answered, but no, same old same old. Information gets conserved in all experiments we do outside black holes, so we kind of assume this must be some cosmic requirement (why?), and for some reason which is never properly explained we just can't accept that black holes would destroy information. Because... well, why exactly? Why is it such a problem that information would simply disappear in a black hole?

Why would it be such a problem if information did simply disappear? Oh my god, entropy might go down in an isolated system, it's the end of physics as we know it! No it's not. Entropy is just a trick that works because of the statistically enormously small probability of it going down in a large macroscopic system without spending energy on it, but isn't that really all it is? Why does it get treated like one of the most important truths in the universe?

Re: So?

[Anonymous Coward]

Yet your ice example doesn't involve reducing etropy in a closed system, so there is retained consequences to what you did (physical information is different from entropy, but related). Making two black holes with the same energy but different entropy gives the same result without more careful thought about black hole formation...

Re:So?

[willworkforbeer]

Obvious non-physicist here, but in absolute terms, information theory says that the original systems' (ice sculptures) information -- every particle's directions etc. was not destroyed, though it may be terribly difficult to ascertain by us at a later time.

I don't pretend to understand why, but the fundamental premise is that information is a conserved property.

Re:So?

[Anonymous Coward]

Of course you are simplifying down to a ridiculous level, and I do understand that information is a pretty powerful concept in physics that carries a lot more weight than you would think

In physics, sure. In biology, not so much. One would expect random events like mutations to decrease information and be a destructive process. That's what you need to turn a single-celled organism into a man - you need lots more information and you need it to be highly ordered. Where did it come from? How did it move from a less highly ordered state to a more highly ordered state when nothing else we observe does this on its own?

These questions are taboo because they've become associated with theology, something many biologists find thoroughly distasteful. How that makes them less valid or how social taboos help to advance science, that is a mystery to me. But it's like asking a Puritan to talk about the merits of Satanism.

Re:So?

[localman]

I also found the article's use of "paradox" and "problem" to be a bit grating. We are observing something here we don't understand, and maybe that's anathema to a physicist who thinks we already understand everything (hint: we don't), but it's not that shocking to me.

However with the last two paragraphs of the article he clears things up a bit:

Whenever there’s a conflict between what our best theories predict [...] that’s an omen of scientific advance. That paradox is such a problem because it tells us that something about our present understanding is, in some way, incomplete. Is there a new law of physics? Is there a new application of the currently existing laws that we’ve missed? Are these quantities not fundamentally conserved after all? Is the information really encoded in the final state somehow? Will quantum gravity eventually make this all clear?

We hope to have the answer to this. But in the meantime, this paradox means we have a problem, and hence that we have more to learn. And for anyone curious about the scientific truths of the Universe, that’s an incredible thing: evidence that there’s still a whole lot more to be figured out.

Well okay then. It's not so much a paradox or a problem as a (not totally unexpected to me) indication that our physics theories do not yet account for everything going on in the universe. Taken out of the framework of "paradox" and "problem" that is exciting - maybe we'll tease some new information about how the universe works by researching this further. Now that's exciting. Just let's not get ahead of ourselves as being all-knowing quite yet.

Re:So?

[Anonymous Coward]

I think the reason is that there isn't anything preventing time running in reverse (other than 2nd law of thermodynamics, which is only statistical, I guess...), but if the information required to do so is lost then you can't.

Personally, I still don't see why they feel it is so important, but it seems they do.

Re:So?

[Anonymous Coward]

Which leads to the obvious question, where'd the information come from in the first place? Because the Universe as described didn't begin as a bunch of particles but instead as merely energy. So at some point the energy formed into matter and hence either there was a magical substrate of information floating around that correlated with the energy or we at some level recognize that this whole information paradox is absurd.

I mean, hell, the very basis for the information paradox springs about precisely because virtual particles are created, presumably with information, out of nothing. And they're otherwise destroyed through annihilation into nothing if not near a black hole.

In short, it all seems a non-sequitur.

Re:So?

[willworkforbeer]

I mean, hell, the very basis for the information paradox springs about precisely because virtual particles are created, presumably with information, out of nothing. And they're otherwise destroyed through annihilation into nothing if not near a black hole.

In short, it all seems a non-sequitur.

Again, as an obvious non-physicist, I think this is exactly why the models break down at t=10^-32 seconds or thereabouts... all the information of the Big Bang theoretically fits into the current information theory, but breaks down at the 'singularity'.

And I also think that the 'nothing' from which virtual particles emerge and subsequently disappear, is not 'nothing' in the sense of absolute nothing. There are fields and energies in the vacuum, so there is always something.

Again, showing my abject ignorance, but these questions are why physicists are so excited about seemingly obscure problems mentioned in The Fine Summary. The preservation of information, the initial conditions preceding the Big Bang, and reconciling non-determinism with information theory... all fascinating stuff.

Re:So?

[Bengie]

Particles aren't information, they're made of information. Energy is made of information. It takes information to describe something. Anything that can be described is made of information.

Re:So?

[Anonymous Coward]

In physics, sure. In biology, not so much....These questions are taboo...

No, in this particular case it is not so much taboo as just fundamentally misunderstanding things. Physical information in physics has a specific definition about the number of possible states within a system. Hand waving about the complexity of different stages of life doesn't show any impact in the amount of physical information in the system.

Re: So?

[Anonymous Coward]

The two different stars arenmade of different material ... if onenof your ice sculptures was made of piss you would know which is which

Re:So?

[Crashmarik]

I think the reason is that there isn't anything preventing time running in reverse (other than 2nd law of thermodynamics, which is only statistical, I guess...), but if the information required to do so is lost then you can't.

Personally, I still don't see why they feel it is so important, but it seems they do.

Oddly enough time does have an arrow and it never does seem to run backwards.

Re:So?

[Bengie]

It doesn't run forward either. Funny how that works. It just is.

Re:So?

[GerryHattrick]

So - when the pretty bubbles in my bath go down the plughole, is there some 'information' in my cesspit that tells me how they were configured? What's 'entropy' anyway?

Re:So?

[Crashmarik]

Odd I can't seem to remember the future.

Re: So?

[Anonymous Coward]

AC doesn't believe in evolution, more at 11

Re:So?

[Anonymous Coward]

If you can only see what's behind you, you're going backwards.

But, really, the arrow of time and the complete lack of problem AFAICT is because if you want to reverse a simple operation like the collusion of two billiard balls, you have the forward situation where you have hit one ball and then let it go. In the other direction you need TWO balls to move and then let it go.

Moreover, there is no a priori state for the "forward" direction. The collision of two gas molecules don't CARE how they meet. But the reverse case, if it is to BE reverse, DOES care. Get the force in the wrong direction for either of them, or the wrong strength, and they won't meet and bounce the opposite path.

IOW even for the simplest scenario, you multiply the necessary condition and have a required outcome, therefore the probability of this coming about is reduced to the probabilities of their occurences overlapping.

What you CAN get is the opposite EVENT, where two moving billiard balls hit and one stops and the other one goes on alone. They may not be the SAME balls, going at the same speed, or coming back to hit your pool cue tip and forcing your hand back, but the reverse event can happen and, in a random set of balls flying about, will happen eventually.

Entropy and time reversibility are merely consequences of the requirement for a specific event set being unlikely to happen spontaneously, whereas setting UP a specific event will happen every time.

Re:So?

[lgw]

Obvious non-physicist here, but in absolute terms, information theory says that the original systems' (ice sculptures) information -- every particle's directions etc. was not destroyed, though it may be terribly difficult to ascertain by us at a later time.

  I don't pretend to understand why, but the fundamental premise is that information is a conserved property.

This is just not true in quantum mechanics, at least if we're talking about what it's possible to observe (not merely practical). The QM definition of entropy is information loss (or that's my best attempt to translate the math to English - I've only studied QM a bit). QM entropy is a bit different from thermo and statistical entropy, though at large enough scales it all works out the same.

There's a remarkable new idea linking black holes to quantum entanglement, going under the name ER=EPR that, if true, will change how we think about both and may finally be a stepping stone to a quantum gravity theory that's actually useful. YouTube has several lectures by Leonard Susskind on the idea, as he and Stanford have been awesome about brining his lectures to the public.

That idea changes how we'd even state the black hole paradox, because in QM the only way you measure anything is to become entangled with it. So it may be that the information isn't lost, it's just unavailable to those not entangled with the black hole (but what exactly that means as the black hole evaporates is anyone's guess, and perhaps my favorite open question in physics).

Re:So?

[Anonymous Coward]

You're fundamentally not understanding what physical information is, as in the precise definition relevant to discussion of quantum mechanics and physical information theory. Energy and particles are not made of information, things that can be described are not made of information. Physical information describes the number of possible states within a system. Don't try to infer the meaning from informal definitions of information used in the IT world and colloquial language.

Re: So?

[Anonymous Coward]

The universe is a closed system, pretty much by definition. Indeed, it's THE closed system.

Re:So?

[Anonymous Coward]

That's also not what the paradox is about. It would be more like taking two different ice sculptures -- one made of methane ice and the other of water ice -- and not being able to tell the difference between the two after they melt. Everything we know says we should be able to see that both 'puddles' (black holes) have different properties as a result of forming from different sources, but they actually appear different only in their mass, electric charge, and angular momentum.

Re:So?

[Bengie]

Time is a perception, like color. You can know the past and future based on information. Cause and effect gives determinism to the Universe. Unless you don't believe in cause and effect, the basis of science.

Re:So?

[Bengie]

Energy and particles are not made of information

Yet they cannot exist without information. Energy and information are like space and time, you can't describe one without the other.

Re:So?

[Bengie]

The QM definition of entropy is information loss

Yet quantum theory explicitly states information cannot be lost. Information not being lost is a corner stone of quantum theory. Your simplification is outright wrong.

Re:So?

[Anonymous Coward]

ER=EPR doesn't set out to (and even at its most speculative, doesn't attempt to) change the terms of black hole complementarity; it just tries to resolve the AMPS (Polchinksi et al.) firewall paradox.

If you drop an entangled pair into a black hole, unless the Einstein Equivalence Principle is wrong, it will stay entangled as it crosses the event horizon. When the black hole eventually evaporates, unless the entangled pair emerges simultaneously (and it can be shown that this is almost impossible), what happens to the entanglement energy? "Firewalls at the receding horizon" is one possible answer, but again that answer conflicts with the EEP. "Entanglement monogamy is wrong" is another possible answer (and does away with the firewall), but that answer conflicts with unitarity. "They remain entangled somehow even though the horizon separates the partners" is a third possible answer, and the one which ER=EPR tries to add some theoretical flesh to.

ER=EPR not only is a huge reversal of the "no hair" conjectures of black holes, it adds wormholes *everywhere*, and embraces this by suggesting (without much explanation so far) that these ER wormhole networks can provide a post-semiclassical gravity theory that is worth the calculational and conceptual burden of wormholes everywhere. (One such problem is that superpositions are basis dependent and a change of basis will also change a huge swath of these wormholes. The useful metrics in General Relativity all appear to behave much better than that seems to imply (so far).)

Re:So?

[Anonymous Coward]

They aren't taboo questions at all -- moreover, your key one has a pair of clear answers: system scope and scope of random fluctuations. Except in carefully contrived laboratory experiments, nothing alive on Earth exists in anything close to a thermodynamically closed system. There is plenty of energy from off-planet feeding into the electron transport chains that manipulate genetic information, so they do not all have to be thermodynamically favourable ones. They can be simply other natural examples of a larger increase in entropy elsewhere in the universe leading to a local decrease in entropy. Heck, the entire solar system is an example of that, assuming the solar nebular disk model is correct.

The observable is almost certainly a closed system (it's usually taken to be THE closed system), but it's big and so not only supports local apparent violations of entropy increase by transfer, it also supports it by random fluctuation -- examples of these abound in molecular clouds, and explain the formation of large scale structures in the universe (and that's supported by the small anisotropies in the cosmic microwave background, for instance).

As to the taboo -- the whole scientific field of evolutionary development explores exactly the questions you raise in your first paragraph. I doubt you can find many evo-devo researchers who even consider how their work relates to origin-of-life/origin-of-species/stages-of-life/biological-metamorphosis stories incorporated into various religious scriptures.

Re:So?

[LarryOlson]

Time does microscopically run backwards sort of, microscopically,

"The truth of the second law is ... a statistical, not a mathematical, truth, for it depends on the fact that the bodies we deal with consist of millions of molecules... Hence the second law of thermodynamics is continually being violated, and that to a considerable extent, in any sufficiently small group of molecules belonging to a real body." -- James Clerk Maxwell
Quote is from http://olsonb.com/

However this could just be information re-configuring to temporary low entropy states, therefore when entropy decreases, it is only re-configuring information to a new low entropy state, so not technically going back in time literally:
https://www.quora.com/Does-ent...

Re:So?

[LarryOlson]

remembering the future is not something we do since the brain has not had that information enter the brain yet, you could remember the future if you used equations and a computer program that predicted the future and fed the future into your brain - this was sort of Leibniz's dream that all of the universe could be calculated by equations and all arguments could be sorted out using equations. Essentially Leibniz was a computer programmer predicting Google before computers even existed.. he invented calculus ironically at the same time as Newton did.

Re:So?

[Anonymous Coward]

the fundamental premise is that information is a conserved property

Thanks.

If so, then it seems that information is never created nor destroyed.

If information is never created, then all the information that exists must have been present (in some form) immediately after the Big Bang.

Essentially, the universe was "born" with the knowledge of exactly what would happen to every particle within it. That seems to imply that what we call "free will" doesn't really exist.

Am I on the right track here?

Re:So?

[LarryOlson]

maybe information gives us the illusion that there is physical matter here... If you were the character running around in grand theft auto and you bent down to touch your shirt pocket, does your shirt pocket actually exist physically in grand theft auto? The information is stored on a hard drive and in the computer memory, but the character inside grand theft auto doesn't have an actual shirt that he is touching... So if you give the character A.I. where he can think about his universe, does he think his shirt is information, or is it physical?

Re: So?

[Anonymous Coward]

nugh, argh, it ain't. Try a bit of reading into the topic of "Virtual Particle Fluctuations" that continually create and destroy instances of matter. However from our macro point of view it looks stable and still the same thing but it is not. Obligatory Quote: "This is not the Universe your looking for".

Re: So?

[lokedhs]

It's past 11 already. Where is my additional information?

Re:So?

[Fragnet]

How did it move from a less highly ordered state to a more highly ordered state when nothing else we observe does this on its own?

That's easy to answer: Energy was expended in moving from a less to a more ordered state. The general rule is that entropy almost always increases.

Re:So?

[Anonymous Coward]

Gibbs Rule #10 ... there are no coincidences.

Re:So?

[Anonymous Coward]

So true ... with your frontal lobe only running at a fixed frequency to create the observers perception ... we are always too late to the party.

Re:So?

[lgw]

We're both technically correct (the best kind of correct). Entanglement means you can know everything (everything it's possible to know) about a system and yet know nothing about it's individual parts. As systems evolve they become entangled, and the information about the individual components is lost. Sure the total "count of bits of information" is conserved, but that's just a constraint on the allowed states of the system, and the actual details become increasingly vague.

Re:So?

[lgw]

it just tries to resolve the AMPS (Polchinksi et al.) firewall paradox

Sure, I understand that's where it started.

ER=EPR not only is a huge reversal of the "no hair" conjectures of black holes, it adds wormholes *everywhere*,

And that sure seems likely to end up resolving the information-loss paradox, given the "no hair" theory is the cause of that.

it adds wormholes *everywhere*, and embraces this by suggesting (without much explanation so far) that these ER wormhole networks can provide a post-semiclassical gravity theory that is worth the calculational and conceptual burden of wormholes everywhere.

Well, I think the point of that is to try to explain where geometry comes from, in space. Once you ask that question, it's a Hell of a mystery. Where does the geometry of space come from? It's not clear it even existed until the universe cooled to the point there were slower-than-light particles, and thus time and distance. Saying entanglement between "adjacent loci" is the same as wormholes purports to be capable of explaining that - I'm not sure I get that, but intuitively it seems OK - points plus connections between points could give rise to geometry, but above a certain temperature you don't have the entanglement and it all breaks down.

Ehh, or it could all be BS. We'll see.

Re: So?

[Anonymous Coward]

You and who ever modded up this post should do said reading. Quantum fluctuations, virtual or not, do not violate conservation of energy and do not make the universe any less closed. Work like QFT that takes these into account, producing some of the most accurate quantitative predictions ever in physics, basically show that what we see and measure already includes the effects of the vacuum, including on the microscopic level.

Re:So?

[mooterSkooter]

How did irony come into the invention of calculus, even if it was at the same time as Newton?

Seriously, I often wonder how to use the word irony, ironically.

Re:So?

[tendrousbeastie]

"cause and effect, the basis of science"

Not since around 1925 it isn't.

Re:So?

[whodunit]

Information gets conserved in all experiments we do outside black holes, so we kind of assume this must be some cosmic requirement (why?), and for some reason which is never properly explained we just can't accept that black holes would destroy information. Because... well, why exactly? Why is it such a problem that information would simply disappear in a black hole?

I'm no physicist, so I don't fully grasp the concept of "information" and all its intangibles myself, but just from the description given in the article:

n the Universe as we understand it, there are certain properties of matter and energy that contain information. A particle like a proton or an electron contains not only a mass, an electric charge and a spin, but also other quantum properties like baryon number, lepton number, weak hypercharge, color charge, and quantum entanglements connecting one particle to another.

- I can discern that "information" is intrinsically linked to matter and energy. I also remember from high school science that energy cannot be destroyed; it can only change states, and that mass is technically just energy in a specific form (such as gasoline in your car, the burning of which the engine converts into kinetic energy to move the vehicle down the road.) Now just what these "numbers" or "charges" are I don't know and don't care, but I also know the periodic table of the elements has a bunch of numbers like that which list their (miniscule) weight, number of orbiting electrons, and other shit like that. In other words it's a complete description of what state the energy is currently in using science geek numbers. I also remember from high school science that velocity isn't just how fast something is going, but how fast it's going and in what direction? So I can naturally work out that this must be the same kind of thing, just using crazy-ass quantum stuff I don't understand.

Now scientists are screaming because the real-world metadata is missing and they don't know where it went. Who cares? Well, I know that mass/energy can't be destroyed, only transferred. That's something everyone knows and it's pretty dang intuitive. But since the scientists can't find the information on what happens to the mass/energy in the black hole, they're flipping their wigs... and I can understand. Mass/energy is changing form when that black hole vacuums it up and utterly rips it apart down to the subatomic whatever - big surprise there. But where the hell did it go?

Now the article states that all the information goes into the black hole - duh, obviously - but the black hole itself doesn't change one bit, and that's where you SHOULD find the information encoded. To borrow the earlier analogy, when heat energy goes into an ice sculpture, it melts into a puddle. The ice sculpture and the puddle are still the same mass and all, but their states; their "information" sure as hell isn't the same, and you can see it easily. But, as the article says, "as far as we can tell, black holes are completely described by only three properties: their mass (governed by the total amount of matter and energy that went into them), their electric charge, and their angular momentum." And that's strange, because energy cannot be destroyed, so if energy is leaving source A and entering recipient B, you expect to see B changing somehow. The mass/energy entering the black hole and not coming out isn't surprising. You knock a golf ball into the hole, and you can't see it anymore. Big frikkin surprise. But if you knock sixty golf balls into that same hole, and they keep going in without overflowing - well, the damn thing must be shredding them like the monster noise in your sink to fit them all in. Stands to reason; if the matter changes state it can fit just fine. But if that's what's going on, why can't you hear the damned monster noise? It's spooky.

Or another analogy from an unsophisticated layman like myself. An F-18 drops a G

Re:So?

[michelcolman]

It's not that the black hole doesn't change. It does change: it gets heavier and its spin and charge may change. No energy was lost. This is about entropy, not energy.

A better analogy than your F18 would be an extremely powerful garbage compactor. You put a bunch of documents in, together with a lot of other garbage, for a total of several cubic meters, and compact it to a cubic millimeter. Guess what, you can't read the documents anymore.

I do realise that this kind of comparisons is a bit silly, and you might still possibly retrieve the information by prying open the little compacted cube (or at least, every bit of ink would have made a tiny change in the final cubelet, which might be noticed in careful analysis) but maybe at some point, when atoms stop being atoms, you reach a point where information really is destroyed. Not energy, the mass of the cube will still be there, you just won't be able to tell anymore what the original garbage was made of. So what? I really fail to see why that would be a big deal.

Re:So?

[Anonymous Coward]

Ugh. Don't bring the "free will" philosophical claptrap into this. Whether free will does or does not exist is basically a question of semantics whether the universe is deterministic or not. In a deterministic universe, all of your decisions flow from the preconditions and the fully deterministic laws of nature. In the non-deterministic universe, all of your decisions flow from the preconditions and the semi-random laws of nature. In either scenario, people are just leaves on the wind. Our actions are just microscopic turbulence left over from the formation of the universe. "Free will" is what you make of it. Some definitions are consistent with either possibility for the universe, some with one or the other, and some are inconsistent and don't seem to describe a real thing at all.
A lot of the nonsense around free will is obvious even without considering the deeper nature of the universe itself. Many of the most important decisions people make are obviously shaped by the world around them from the time and place of their birth and from their upbringing and genetic factors, etc.

Re:So?

[Bengie]

Actually, Causality is the one thing the entire Universe and all frames of reference agree upon.

Re:So?

[Anonymous Coward]

You can't forget it either.

Re: So?

[beastofburdon]

Something which is infinite cannot be closed.

Re:So?

[beastofburdon]

Just because humans can't perceive time running backwards does not mean that it cannot happen.

Re:So?

[painandgreed]

Information gets conserved in all experiments we do outside black holes, so we kind of assume this must be some cosmic requirement (why?), and for some reason which is never properly explained we just can't accept that black holes would destroy information. Because... well, why exactly? Why is it such a problem that information would simply disappear in a black hole?

Because the idea that physics is the same everywhere is one of the assumptions that our physics, especially relativity, is based upon. By stating that the physics at point A is the same as at point B allows us to make some assumptions and delete some variables via symmetry. This gives us the general theory of relativity not to mention science itself, which so far has been shown to be upheld. If the the physics in a black hole is different from the physics outside of it, then it most certainly is the end of physics as we know it because assumptions of physics as we know it is based on it all being the same everywhere.

Whoa..

[bhcompy]

This is some high brow shit for Sunday morning

Re:Whoa..

[Anonymous Coward]

Yeah, it's supposed (used?) to be good here all the time, not just sunday mornings.

I RTFA, but...

[Anonymous Coward]

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.

Re:I RTFA, but...

[Bengie]

Conservation of information is a property of causality.

Re:I RTFA, but...

[michelcolman]

But would destroying information violate causality? Would you be able to do something contradictory like the grandfather paradox or something like that by destroying information? I really don't see the problem.

Re: I RTFA, but...

[Anonymous Coward]

No, it is more subtle than that. Conservation of information is closely tied to time reversal symmetry and energy conservation as a result of Noether's theorem. But in general it is not tied to casaulity.

Re: I RTFA, but...

[Anonymous Coward]

No, it is more subtle than that. Conservation of information is closely tied to time reversal symmetry and energy conservation as a result of Noether's theorem. But in general it is not tied to casaulity.

If we had a list of observations of backwards time then I see how this could be a relevant problem. Until then it sounds like: just because you can reverse some signs and run your equations backwards doesn't mean that all math has a physical reality.

Re:I RTFA, but...

[Anonymous Coward]

"But would destroying information violate causality?"

Because information is made of matter and energy? AKA when we think of "information" it's not a non material thing, when we gather "information" from the environment, electromagnetic waves are hitting your eyes and through a series of reactions causing a signal to be sent to your brain to be processed and interpreted. The whole process is physical from top to bottom.

Re: I RTFA, but...

[Anonymous Coward]

Until then it sounds like: just because you can reverse some signs and run your equations backwards doesn't mean that all math has a physical reality.

Nope, Noether's theorem is quite specific, and if there are certain symmetries in your equations (i.e. you can just reverse some signs for on example), then there exists certain conservation laws. If there is time symmetry in the equations, then it is a necessary consequence of the equations that energy is conserved. This has nothing to do with reality of math or if time can actually be reversed... either the particular equations are correct or not. If they are correct, then all logical consequences of the equations are also correct.

Re:I RTFA, but...

[Bengie]

For every unique cause is a unique effect. You can know what the cause was based on the effect. If the effect disappears, you can't know what the cause was. Anyway, if information is destroyed, that means the energy it represented is destroyed which means it cannot contribute to the mass of a system. It's contradictory to say the mass of a blackhole increases if the information is destroyed. A blackhole is created by too much information and it is itself a blob of information. The question isn't "why does a blackhole destroy information", but "what mechanism does a blackhole use to allow information to be recovered".

Re:I RTFA, but...

[Bengie]

Because information is made of matter and energy?

You got that reversed. Matter and energy is made of information. Universally unique information.

Re:I RTFA, but...

[HairyNevus]

Yea, I don't see why this is a problem, anymore than any other thing in physics today.

I think what they're trying to say is: "Black Holes Matter".

*ducks*

Re:I RTFA, but...

[Anonymous Coward]

For every unique cause is a unique effect.

This is not a requirement of causality, and nor is a requirement of most physics, only a consequence of current theories. Causality only requires that a cause precedes an effect, with a more complicated definition of "precede" in relativity. There is no uniqueness requirement, and macroscopic physics doesn't follow this, yet follows conservation of information.

The question isn't "why does a blackhole destroy information", but "what mechanism does a blackhole use to allow information to be recovered".

No, only if you make a bunch of assumptions. The whole point of the problem is that it is still open ended, even if there are some proposals to deal with it. The question is why black holes destroy information or how information is recovered... but is the information destroyed or recovered, i.e. is there something wrong with information conservation, something wrong theory of black holes, or is there a recovery method that hasn't been figured out yet.

Re:I RTFA, but...

[Anonymous Coward]

"Matter and energy is made of information. Universally unique information."

Information is a property of a system and its possible states. Matter and energy is not made of information, especially unique information, considering how QFT and QM are built upon indistinguishable particles.

Re:I RTFA, but...

[Anonymous Coward]

How is this not +5 funny?

Re: I RTFA, but...

[LarryOlson]

it's not a case of the equations being correct or not, it's whether they are useful models (approximations). An example is the speed of light constant. It may be a white lie that it is a constant. It probably is constant, but it also could just be an approximation.. maybe it fluctuates such a small amount that it is undetectable. Also the theory of gravity when Newton started out, wasn't correct 100 percent, but was a useful model for the time being.

Conservation of energy has already been violated by virtual particles popping in to existence temporarily and then disappearing. The laws of thermodynamics are models or approximations. The second law especially is violated all the time microscopically, but macroscopically it holds true in engineering

A macroscopic equation can be correct to a degree, but break down in other cases. So to claim that it is either correct or not, is simply naive - math is a model, it doesn't represent reality exactly. If we ever are able to represent reality exactly, it might be something like Leibniz's dream.

Re: I RTFA, but...

[Anonymous Coward]

Conservation of energy has already been violated by virtual particles popping in to existence temporarily and then disappearing

Virtual particles follow conservation of energy.

SciShow Space - Has Stephen Hawking Solved a Black

[morcego]

https://www.youtube.com/watch?...

Information encoded on the event horizon.

[Anonymous Coward]

Leonard Susskind discusses this in a talk he gave a few years ago.
https://www.youtube.com/watch?v=2DIl3Hfh9tY
Pretty entertaining.

a black hole

[Anonymous Coward]

if you take two things we don't quite fully understand called "black holes", one made we think from the collapse of one type of "star" that we think we understand, and the second from the collapse of a different type of star that we don't, you can't tell which is which.

right ?

Artificial black holes

[CrimsonAvenger]

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....

Why caps?

[Anonymous Coward]

"the Black Hole Information Paradox"

"some types of Physics."

Neither of these things should be capitalized. Science education is important, but so is language education.

Re:Why caps?

[TimSSG]

"the Black Hole Information Paradox"

"some types of Physics."

Neither of these things should be capitalized. Science education is important, but so is language education.

Look up the rules for the capitalization of titles. Tim S.

Not high brow -- low brow junk science

[Anonymous Coward]

It's building a even bigger steaming pile of conjecture and speculation.
 
Not that much unlike Percival Lowell's martian civilization and canal fantasies.

"no hair" Theorem

[l2718]

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.

blue upside down head fixie riding hiptard

[Hognoxious]

Are there any paradoxes concerning StartsWithABang and a sockpuppet?

Big Crunch

[CanEHdian]

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?

Re:Big Crunch

[Bengie]

Taken as a whole, the past present and future of a system can be described by its information at any point in time. Just think of forensics. It uses present information to figure out the state of the past. When talking about information at the Universe level, you can figure out the state of the past Universe perfectly assuming you have perfect access to all of the present information in the Universe.

The other way to look at it is destroying information destroys the energy it represents. Since energy also represents mass, if you destroy information, how does the mass of a blackhole increase? By definition destroying the information destroys the mass the information represents meaning the blackhole does not gain mass from in-falling matter/energy. That makes no sense.

Re:Big Crunch

[Anonymous Coward]

The deterministic view of the universe is severely undermined by quantum mechanics. Even with perfect information in the present, if you accept the statistical nature of QM, you will not be able to determine the past or future with perfect certainty. Chaotic behavior further confounds our ability to predict the evolution of a system even if you thought QM was hogwash, which it isn't.

Re:Big Crunch

[LarryOlson]

I think the term "heat death" should actually be renamed to "equilibrium death"... When the universe is in equilibrium due to the second law of thermodynamics, there aren't any cold spots or hot spots you just have equilibrium. Think of it: if it was all hot, it wouldn't be hot - it would be neutral.. all the cold spots would even out with the hot spots. Frozen planets would no longer be frozen, they would equal out at one temperature, hot planets would no longer be hot, they would all even out.

An interesting article on the subject: http://olsonb.com/articles/hea...

Isaac Asimov asked the computer in science fiction "how can we reverse entropy" or "how can we reverse the heat death of the universe"..

Re:Big Crunch

[Anonymous Coward]

One or a few Planck second(s) before the singularity, all the information in the universe should still be there.

Question:

Is there a principle of symmetry that says that if information can't be destroyed then information can't be created either?

In other words: Aren't we supposed to be able to project all particle interactions both forward and backward in time? And wouldn't that fact imply that information is never created or destroyed?

If information can neither be created nor destroyed, then it would be interesting to note that all the information in the universe was present at one Planck second after the Big Bang. I wonder what implications that would have for the concept of "free will"?

Re:Big Crunch

[CanEHdian]

Yes, equilibrium death is a better term. It's the universe in a uniform state. If it's uniform, there are only a few parameters needed to describe the universe.There is no way to "hide" more information than that within the universe itself.

Re:Big Crunch

[LarryOlson]

the past, present, and future of a system can be described by its information only if you store that information somewhere: example taking a video tape of a soccer game means you can relive the soccer game over and over again, but only because you stored that information on the video tape or SD card. So where is the universe storing all this meta information about information?

Once you delete files off your hard drive, the information becomes scrambled - but you could only get the data back if you video taped every particle movement(heat) coming from the hard drive, but that video tape you took required you to store all the information! So without the video camera, how are you going to find out the information? the universe has no video camera unless humans make video tapes.. This is an interesting area of physics that people don't fully understand. As Daniel Sheehan says, the universe is actually getting richer with more entropy. If we were just a low entropy system we would be in a boring universe that looked like a clump of mass and nothing else (before the big bang).

meh

[Khashishi]

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.

Re:meh

[Rei]

And we, outside the black hole, will "see" everything that the person inside the black hole sees as the black hole evaporates - albeit in a form mangled beyond recognition by the extreme forces at play.

They fall in, and in their reference frame, they're chasing an event horizon (the apparent horizon) that always recedes away from them and which they never hit, until they're torn apart. We see them approach, see their time slow down, get dimmer and dimmer and more and more distorted, but never really "get there" - and as the black hole evaporates, the spot where we could theoretically still see their image stretched out around the event horizon moves inwards and inwards as it does. It's the same causal series of events, just in the former case perceived as happening quickly, while in the latter case happening over trillions of trillions of years, and far too distorted and dim to make literal observations practical.

Black holes no longer seem that exotic when you just think of them as areas where (from an outside perspective) time has just slowed down to a near halt during the collapse of a massive star, and slowly leaks back out.

Re:meh

[Intron]

There is no "inside the black hole". It's a singularity - no volume, no structure. The event horizon is a boundary, not a container.

Re: meh

[Anonymous Coward]

It makes no sound at all.
Sound is only sound when it is heard.
Do you call the wind sound? How about a river? What difference is there in hearing vs feeling a firework show?

What a falling tree does is push air out the way.
A sound event only happens if there is a lifeform around to hear it.
Sound isn't a physical component of the universe, a measurable quality in the strict physics sense, it is a biological sensation, a result of kinetics applied to clumps of matter

Re: meh

[Hognoxious]

What if there's a tape recorder?

Re:meh

[Anonymous Coward]

"Black hole" is not synonymous with just the singularity but refers to a larger object with several structural components including an event horizon. The region inside the event horizon is frequently referred to as the inside in literature and even textbooks.

Re:meh

[Tough Love]

Just because we cannot see the internal degrees of freedom does not mean that they do not exist.

If internal (hidden) degrees of freedom are impossible to detect then they are metaphysics and do not exist in the real world. If hidden degrees of freedom are merely impractical to detect, or beyond our science to detect, then they may exist. If hidden degrees of freedom have predictive value then they probably exist. However as of today, no theory relying on hidden degrees of freedom has shown any predictive value, in spite of huge numbers of research dollars having been tossed down that hole. Hidden degrees of freedom do exist in some form: they are the super massive black hole of science funding.

Re: meh

[alvinrod]

If a tree falls in the forest and lands on a mime, does anyone care?

Re:meh

[Howitzer86]

I've considered this as well, though I don't think the person has to constantly chase the event horizon. In holes large enough, they can exist just fine inside of it, with the horizon constantly chasing them and experience less gravitational sheering than you experience right now on Earth. The problem I have with common black holes evaporating is that it would require the universe to entropy to the degree that background radiation doesn't get in the way of these holes evaporating.

So it could be a while, if it happens at all.

A new problem I hadn't considered though: if common black holes do evaporate at all, their emission will return some lost energy to the universe, perhaps enough to keep other black holes from evaporating... slow the entropy of the universe or even halt it.

I'm not a scientist though, so I'm sure I got a lot wrong here.

Re: meh

[Anonymous Coward]

Sound is only sound when it is heard.

I think you'll find that what you're describing is not the common scientifically used definition of sound.

How about

[Anonymous Coward]

we first find out what the Universe is made out of?

Like maybe figuring out what 95% of the Universe is might help a tad. No?

Isn't this navel gazing? I understand it keeps the grant money flowing, but really...

So when is information lost?

[ultranova]

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?

Re:So when is information lost?

[Intron]

Since the front part is traveling at the local speed of light, the back part of the infalling observer can't detect the front part reaching the event horizon.

Re:So when is information lost?

[Anonymous Coward]

Nothing is seen to accelerate to the speed of light in any frame for something falling into a black hole. For an object free-falling into a black hole, it is easy to show with the math, or various diagrams of the process, that components of the object closer and further away will remain in the light cone of the object. In other words, if you free fell into a black hole, you would not see parts of you or your spaceship disappear, nor would you see it going the speed of light. For that matter, you wouldn't be able to even tell if/when you reached the event horizon if in a spaceship with no windows, and would only be able to do so with windows if you watched for the angle between stars in the sky to reach a certain amount of distortion.

Re:So when is information lost?

[Bengie]

Yet scientists claim passing the horizon should be unnoticeable.

Because the event horizon is relative and different for all observers. One observer may see someone approaching the event horizon, but the one approaching the horizon may see that the horizon is still far away. "Passing" the horizon would be unnoticeable for the in-falling observer because from their frame of reference, they haven't passed it yet. Of course I don't think any observer would ever see any other object reach the event horizon, yet alone get past it.

Re:So when is information lost?

[Bengie]

I used to think the event horizon was when acceleration was the speed of light, but it's not. It's when the escape velocity is the speed of light. An ever increasing blackhole would have an event horizon where the gravitational acceleration of the event horizon would asymptotically approach zero. All the event horizon means is you cannot have enough initial energy to gravitationally escape the blackhole.

I don't know the math, but all they say is you can't gravitationally escape the blackhole, but they don't say you can't escape the blackhole. No frame of reference ever passes into the blackhole. My guess is that as space contracts, it will look like other objects are moving further an further away. At some point an object make look as if it is moving away faster than light, meaning it is out of your light cone. You can still attempt to approach it and get closer to where it was but not where it is, but you'll never interact with it again. The other side of things is if you start to approach the object before it recedes faster than light, you may theoretically be able to interact with it again, given enough time.

Re:So when is information lost?

[Anonymous Coward]

Because the event horizon is relative and different for all observers.

The event horizon is an absolute horizon, not an apparent horizon, and is the same for all observers.

Re:So when is information lost?

[Tough Love]

At some point an object make look as if it is moving away faster than light, meaning it is out of your light cone. You can still attempt to approach it and get closer to where it was but not where it is, but you'll never interact with it again.

If an object is out of your light cone then you may not interact with it so it cannot appear to be moving away faster than light. Not only that (correct me if I am wrong please) the object always was out of your light cone, and you were never able to interact with it.

Re:So when is information lost?

[Intron]

So you are saying that light from the front of the spaceship (inside the event horizon) will still reach me sitting in the back (outside the event horizon)?

Re:So when is information lost?

[Anonymous Coward]

In free fall, yes, the light from the front of the space ship will reach you sitting in the back because you are also falling too, and will in essence catch up with the light (bad way to think about it, but the point is the front of the spaceship will not leave your past light cone). If you are using a force to remain outside the event horizon, any portion of the spaceship approaching the event horizon will redshift and fade (and also ultimately require infinite force to hold on to if it crosses the event horizon). If you are applying a force while falling in, there is a bunch of in between conditions that requires more information to calculate the result.

Re:So when is information lost?

[Anonymous Coward]

"correct me if I am wrong please"

Ok, consider the cosmological horizon in an expanding universe -- distant galaxies will cross that and you will never see their photons again. But they were in your past light cone prior to that, before the metric expansion of space took them across the horizon; an ancient galaxy that appears in our sky as half across the horizon certainly didn't only half exist in our past.

Rather more extremely, assuming cosmic inflation; there is matter well beyond the horizon now that local matter was causally connected to only before inflation.

Various models of stellar black hole formation propose a formation of a horizon of substantial radius forming all at once within a collapsing star. This matter never crosses from inside to outside, even though that's true of all the matter of the star that is not behind the horizon at its formation. (It's really difficult to get stellar black hole models that accord with available evidence to date without this sort of thing happening). The internal matter of the star can't be said never to have had a causal connection with an observer of the black hole. In fact, exactly that causal connection is what motivates TFA.

A better article

[Anonymous Coward]

http://www.scientificamerican.com/article/stephen-hawking-hasn-t-solved-the-black-hole-paradox-just-yet/

Re:An easy fix to Black Hole spending

[Anonymous Coward]

is to make sure another Democrat like Obama never gets elected.

Except that he didn't increase spending and did improve the economy, while Republicans did the opposite.

Credit where credit is due.

[SeanCurry]

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.

Why C

[Anonymous Coward]

So why is the speed of light the limit? Why can *nothing* travel faster than the speed of light.

Re:Why C

[Anonymous Coward]

I guess somebody slept through Modern Physics 101.

Re:Why C

[Bengie]

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.

Re:Why C

[Tough Love]

Good luck with your new theory.

Re:Why C

[Tough Love]

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.

steaming pile

[goombah99]

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.

Re:steaming pile

[Crashmarik]

Well that article sure was not worth reading.

It's an Ask Ethan, just not on medium.com this time. Gotta wonder how the guy got slashdot to be his personal PR machine.

Easy

[Anonymous Coward]

The information is sucked out of this world... Two different types of stars have different masses and angular momentums, so the black holes can can be separated anyway. If the atoms are crushed into quark soup or beyond the only thing that is left is some kind of superposed quantum state. Is it possible to detect individual gas atom's quantum state from a Bose-Einstein Condensate without decondensing it, for example?

This isn't the case in this universe

[Anonymous Coward]

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 what fell in with these two is still there, falling in. Not quite finished yet.

And when you smoosh them together, they ALSO take forever to fall in. The spacetime at the event horizon for both will compress (from our point of view) indefinitely and the two will "merge" but from this inertial frame out here in the rest of the universe (where we are looking to find this "information" to come out,they won't actually meet on this side of eternity.

Once eternity HAS passed,then the stuff will thereafter be able to fall in at a faster and faster rate, but due to being imaginary mass travelling at faster than light speed, we will not be able to get any of that out because we'd have to pull with imaginary strength through the event horizon and get it back to the event horizon from the other side, where it will take ANOTHER infinite time to reach the event horizon. And then AFTER that second infinite time, you can get something out.

But then after two infinities of time having passed, you don't know that you have the same thing out and have no more new information out of it than you would get if you measured the spin of an entangled proton whose partner was off in another galaxy.

Re:This isn't the case in this universe

[sexconker]

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.

This is correct for a black hole of a fixed size.

However, if we presume black holes exist, there must be a mechanism for their creation.
If there is a mechanism for their creation, then there is a point at which there is no black hole and there is a point at which there is a black hole, with a non-zero radius to its event horizon.
Thus, there is a mechanism by which a black hole grows and its event horizon expands.
Whether or not this growth is fed by mass falling into a black hole doesn't matter. What matters is the fact that they grow.

Given a growing black hole with someone stuck forever at the event horizon (as viewed by an outside observer), the event horizon will expand as the black hole grows, enveloping the person who was stuck.

If you believe in the concept of a singularity, then this has the effect of destroying information. This is important because if we allow for the destruction of "information" then we're violating the laws of thermodynamics, which are kind of important to our understanding of things at the real-world level.
If we throw out the concept of the singularity, then we lost the big bang and the picture of the universe as we "know" it gets thrown in the trash. This is why so many physicists do a lot of make believe experiments and math to try to "solve" the "problem" of black holes destroying information. The singularity and the big bang are religious icons to many.

If singularities destroy information, then there are huge implications that should affect the real world. We don't see these effects (we see the laws of thermodynamics holding true), thus either singularities don't destroy information or they don't exist.

Re:This isn't the case in this universe

[Tough Love]

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.

Re:This isn't the case in this universe

[Anonymous Coward]

"If you believe in the concept of a singularity, ..."

The information conservation issue has to do with the existence of event horizons, not singularities. You could propose whatever you want for the structure of a black hole inside the event horizon, and still be stuck with the quantum mechanics issues of the horizon.

Re:This isn't the case in this universe

[Pikoro]

)

*whew* That was bugging the hell out of me.

ice sculpting black holes

[goombah99]

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.

I can answer this with only high school biology.

[Anonymous Coward]

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.

And the order doesn't exist on any longer form than it does for a closely packed body of amoebas, who only react to the chemical signal gradients in the surrounding water and change shape or express chemicals based on that stimulus.

Your toenail doesn't interact with what the follicle inside your ear. So the existence of cells in those two locations being in your human body does NOT indicate that these two cells have to engage in some sort of "information of knowledge" about their respective actions.

Moreover, the thermodynamic complaint of the accretion of planets and stars and so forth based on "How can it become LESS ordered????" is based on a false assertion of the laws of thermodynamics. To create a more ordered system you have to expend work on it and this work entails necessary losses, and this necessary loss is the second law of thermodynamics. So when the gas clouds collapse, they collapse because work is done on the molecules by gravitational attraction. The condensation doesn't happen unless there is frictional losses and this loss is what the 2nd law says should happen. That loss is via ejection of matter or the emission of less-organised (because they're leaving, therefore becoming LESS condensed) photons of radiation. ALL of the potential energy of the cloud that would pull those molecules into the condensed object PLUS THE KINETIC ENERGY THAT WOULD MAKE IT FLY APART AGAIN is lost to the rest of the universe, increasing the overall entropy.

How can you not tell them apart?

[Ecuador]

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...

Re:How can you not tell them apart?

[Pikoro]

But as soon as they turn black, the cops will shoot them so I guess we'll never know.

Re:An easy fix to Black Hole spending

[Anonymous Coward]

I don't see a claim he increased spending at all... but he definitely spent money the USA doesn't have to spend until the deficit is like a giant black hole. Typical Democrat and your sorry apologist excuses.

Shoelaces CAPTCHA: exclude

[Anonymous Coward]

At the heat death of the universe, time stops and space disappears, setting up the next big bang. Since all the laws are still the same, the new universe will unfold exactly as the old one did, right down to your lack of shoelaces. There's your information, always was and always will be. To the fetus the womb is its universe: to the child the universe is its womb.

Re:Shoelaces CAPTCHA: exclude

[Tough Love]

Thanks for clearing that up. I can get back to my facebook updates now.

The information is just dispersed

[presidenteloco]

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.

Re:The information is just dispersed

[Anonymous Coward]

I'd have to go back to grad school to re-learn the math, but here's the TL;DR. If the Hawkin radiation were containing information then it shouldn't be able to "leak" out.

Re:The information is just dispersed

[peragrin]

Random means exactly that. If there is a pattern how ever hidden it means it is no longer random.

You can't take a melted ice sculpture and remake it .. It won't be exact. Only close.

Re:The information is just dispersed

[LarryOlson]

Indeed when the information is reconfigured it is not erased, this is the mistake Hawking made thinking it was gone for good.

Another interesting debate is Jack Semura and Todd Duncan who think information is erased in entropy (Laynes Law? definition of words problem?)
https://www.quora.com/Are-Todd...
Another article on the subject:
http://olsonb.com/articles/jac...

Re:The information is just dispersed

[mooterSkooter]

You could remake it, if you looked a the temperatures of all the surrounding particles and 'rewound' it all backwards. I think that was the point op was trying to make.

Re:The information is just dispersed

[Bengie]

Hawking never said what was happening, he only made an observation and could not think of a mechanism with which to allow information to be available.

Re:The information is just dispersed

[Agent0013]

You could remake it, if you looked a the temperatures of all the surrounding particles and 'rewound' it all backwards. I think that was the point op was trying to make.

So I can look at a homeopathic preparation and wind it back to tell what it was prepared with. So your are indeed telling us that homeopathy works and that water has memory!

Re:The information is just dispersed

[presidenteloco]

The Kolmogorov-Chaitin definition of random says something to the effect that if there is no process simpler/shorter than the process which produced the sequence/arrangement of events which could predict what that sequence/arrangement of events would have been (and would evolve to next), then the sequence/arrangement is random. It is equivalent to saying that the process which produced the sequence/arrangement is maximally complex.

So if there is a deterministic pattern but it (or its originaing/generating process) is complex enough to be inherently unpredictable, then it is random.

Keeping the world safe for Quantum Mechanics....

[claykarmel]

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.

Wrong question = wrong answer

[Anonymous Coward]

"Preservation of information" is a laughable concept considering everything locally measurable is defined exclusively in the context of interaction with something else. There is no evidence for existence of anything independent of interaction. Gabbing away about unavailability of properties of inaccessible things you can't interact with is a truly worthless exercise.

Re:Wrong question = wrong answer

[raftpeople]

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."

Re:Wrong question = wrong answer

[Anonymous Coward]

So when you say wrong question = wrong answer you mean the wrong answer becomes the wrong question, since you are assigning the wrong answer to the wrong question? You are programming in C aren't you..

// wrong answer is assigned to wrong_question
wrong_question = wrong_answer;
if (wrong_question == wrong_answer) {
    cout("my name is Dennis Ritchie and I confused everyone");
}

Isn't theory testable?

[MarkH]

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 ?

After reading TFA, what I don't get is...

[minogully]

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?

Re:After reading TFA, what I don't get is...

[Anonymous Coward]

"the conservation of information, shouldn't also break down and therefore results in a paradox."

Because the issue with conservation of information is at the event horizon, not with the inside of the event horizon and the singularity, the latter of which is where there could be some big problems but is also involves a lot of speculation.

"Who gets to decide which laws break down and which ones don't?"

Who ever can do the math and find the contradiction...

Re:After reading TFA, what I don't get is...

[iggymanz]

because the paradox is OUTSIDE the black hole. From our point of view, everything slows going into a black hole until the event horizon is reached. Information would be stuck there except the hole evaporates by hawking radiation (virtual pairs formed having one particle free to leave)

Re:After reading TFA, what I don't get is...

[Agent0013]

because the paradox is OUTSIDE the black hole. From our point of view, everything slows going into a black hole until the event horizon is reached. Information would be stuck there except the hole evaporates by hawking radiation (virtual pairs formed having one particle free to leave)

Since when does a new particle going into a black hole mean it is losing mass? It seems to be gaining mass to me as it now has one more particle. Perhaps they don't actually evaporate, or they don't do it because of extra things falling into them.

Their mass, electric charge, and spin

[shoor]

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.

That's funny

[Art3x]

"The most exciting phrase to hear in science, the one that heralds new discoveries, is not 'Eureka' but 'That’s funny...'" --- Isaac Asimov

Re:That's funny

[LarryOlson]

When they discovered we were not designed by Jesus and evolved from ape like creatures, did they say "eureka", "that's funny", or "oh shit". I'm not sure.

Why is that a problem?

[Anonymous Coward]

We'll never see a black hole, we're never going to visit one, ever. In 50 years time nobody will care. In 100 years time, nobody will remember what a black hole is, just as all of science will have been forgotten. It's the end of the road, sorry.

Re:Why is that a problem?

[Anonymous Coward]

We'll never see a black hole...

The Event Horizon Telescope will likely start producing images of the event horizon of Sgt A* in the next couple years.

Re: Why is that a problem?

[Anonymous Coward]

And? Supposing it doesn't get defunded what are you going to achieve? Outer space may as well be made of peanut butter, it makes no difference. We're not going to explore it. As the age of science slowly draws to an agonizing end and technology begins its march backward, the biggest irony is that, after all, religion and superstition will end up outliving reason.

Re: Why is that a problem?

[Anonymous Coward]

You claimed we would never see one, but are just basing that on your gut feeling and pulling stuff out of your rear. If you can't even get the next couple years right, why should we believe your conjectures about the distant future of subjects you are unfamiliar with?

Re: Why is that a problem?

[Anonymous Coward]

Just wait and see. I hope you will make it. I really do. But I'm afraid the end of computers and the internet will be too much for you. I'm sorry.

Re: Why is that a problem?

[Anonymous Coward]

Got any more assumptions you want to make in order to have the world confirm to your notions? I actually grew up in a house without electricity due to parents with bad money problems, and know how to grow food and hunt. Many coworkers in my lab also camp, hunt, and fish. On the other hand, I would be more concerned about what you would do without the internet, as you would have to face a real world with real people that often don't conform to the image your ego makes to protect itself.

Re:Why is that a problem?

[david_thornley]

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.

Re:I can answer this with only high school biology

[Man Eating Duck]

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.

Stupid

[Anonymous Coward]

Why is this such a big deal. If you take 2 eggs and scramble them down to amino acids, you wouldn't know which amino acid belonged to which egg.

Diameter isn't needed to describe a black hole?

[Anonymous Coward]

From the article:

black holes are completely described by only three properties: their mass (governed by the total amount of matter and energy that went into them), their electric charge, and their angular momentum (which describes their spin).

I was surprised that diameter is not one of these properties. Has it been determined that the diameter can always be exactly calculated exactly from the other three properties? If so, that would be surprising to me, because I would imagine that the observational data we have obtained so far would not be precise enough to make the claim that the diameter isn't a necessary property. And on the theoretical side, if we can't (by definition) see inside a black hole, how could they rule out that different black holes might have different densities?

Here's the issue...

[Ungrounded Lightning]

(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.

Re:Here's the issue...

[Anonymous Coward]

I've always wondered what happens when you tear a black hole into pieces that aren't massive enough to be black holes anymore? There doesn't seem to be any reason it can't happen. Nothing can escape the event horizon of a black hole of course, but how does that work when the event horizons of two black holes pass through each other? Is it guaranteed somehow that mass can only be transferred from the inside of one event horizon to the other, or is it possible for forces to cancel and some matter to actually escape the event horizon of one of the black holes? If it does, does the information return to the universe?

For that matter, if the problem is one of the total information that describes the system, what's the difference between the amount of information in whatever is ejected as Hawking radiation and whatever went in? If a black hole forms, sucks in a certain amount of matter and energy, then the black hole evaporates, returning that amount of matter/energy to the rest of the universe, exactly how is that different than if the matter and energy hadn't gone into the event horizon in the first place?

Re:Here's the issue...

[Anonymous Coward]

The radius of an event horizon is linear with mass. If we just assume the event horizons don't deform and you brought two black holes close enough for their event horizons to touch, they would be separated by the sum of their Schwarzchild radii... except the mass of the system would be the sum of their mass and the event horizon for the system would hence then also be the sum of their Schwarzchild radii. In other words, there is no way for the event horizons to bump each other without the black holes basically forming a larger black hole that would hold both. The actual behavior of the event horizon in a collision is much more complicated and computationally very difficult, but works out such that any point that was behind an event horizon remains so. There is no method using just GR alone to get the event horizon to recede.

Re:Here's the issue...

[david_thornley]

I've always wondered what happens when you tear a black hole into pieces that aren't massive enough to be black holes anymore? There doesn't seem to be any reason it can't happen.

You're talking about taking stuff out of a black hole and putting it somewhere outside the event horizon. That doesn't happen. As I understand it, for everything in the black hole the spacetime distortion is such that the future points inward, so the only way to escape would be to have some sort of way to move outside the timewise nature of world lines, and this means FTL travel, which implies time travel.

I also don't understand the "aren't massive enough to be black holes anymore". Black holes don't have to be supermassive, just concentrated.

QM random number generator seed cracked by kiddie

[LarryOlson]

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.

An event horizon is finite in range and resolution

[dsmatthews9379]

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?

Re:Particles aren't information,bits are physical?

[LarryOlson]

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..

Re:Keeping the world safe for Quantum Mechanics...

[lokedhs]

Hawking already accepted Susskind's position when he admitted defeat in the bet with John Preskill.

Re:Particles aren't information,bits are physical?

[Anonymous Coward]

the problem with particles not being information, is something string theory is trying to solve where everything is just composed of bits or qubits

No, string theory is just trying to find an underlying structure that has various modes of excitement that produce the diverse particle zoo we see. This is not the same as it is trying to make everything composed of bits and/or qubits.

This is an open area of study and anyone who claims to know everything about the subject is ignorant (not saying you are)

The problem here seems to be not that there are people around claiming to know everything, but that there are multiple, prolific and confident posters that keep trying to post what is and is not information without bothering to look up the definition of information in physics. It is jargon for a very specific definition, and yet several people wax at length using their own vague interpretation every time one of these stories gets posted. After they've been told multiple times how they've misinterpreted things and asking them to read some basic background on the topic, at some point people seem to demonstrate they are not interested in learning about a topic.

How to tell two black holes apart?

[Anonymous Coward]

Of course one can tell them apart, even if they have exactly [?] the same mass:

They are almost by definition in different places.

Photonic Destruction

[Anonymous Coward]

Let's say you have a distant star (10 million light years away) that has been radiating photons for 10 million of years. Now, as an observer located on Earth you apprehend that a new star has appeared in your visual space. The photons you are registering with the rods and cones in your eyeballs somehow get turned into the classical information that you perceive as a point of light. Are the photons that were incident upon the rods and cones recoverable or are they effectively converted into electromagnetic oscillations that are in turn ultimately re-radiated as more numerous low-energy photons (heat)? I ask this because you do not need a black hole to illustrate how information is destroyed. If you absorb the photons it indicates that another observer located further away (but along the same line) will not be able to receive the information. Under what circumstances could that observer reconstruct the information? I do not think such a reconstruction is possible due to teh fact the original information was destroyed (resulting in a mental image). The *information* was destroyed, not the energy. Am I missing something here?

Re:Photonic Destruction

[Anonymous Coward]

The energy from the photons is still there, and there is still the possibility of photons being re-emitted by the matter that absorbed it. Physical information is about the number of possible states in a system, so that hasn't changed.