Hawking's Information Paradox solution

Certainly, but first could someone please change the title to reflect Stephen's real name It's HAWKING !!!

Grrr, wrote this post once already yesterday and lost it as (I assume) the EvC server went down. Thanks for fixing the title...Ok, some misconceptions here to clear up...A black hole "ends" when it has evaporated all of its mass away. There is therefore no matter left to destroy. That is quite key to actual problem, in that there doesn't seem to be anything left in the "remnant" to store the lost information. But we'll get back to that later...Matter can be destroyed or "annihilated" as we say. By matter, we mean fermions: electrons, quarks, etc - the stuff that gives solidity to the universe. I'm sure you've heard that an electron and a positron (both matter) can annihilate and leave just a pair of photons (not matter). In this precise context you cannot use vague terms such as "energy" or "heat" which only apply at much larger scales when looking at bulk behaviour.As we start to consider quantum gravity, various possibilities are introduced. One of these is the idea of baby universe: branches of space-time separating off from the trunk space-time via black-holes and similar phenomena. One of Hawking's proposed solutions to the information problem used baby universes (dating back to the 80s). These are not alternate or "other" universes as such. Imagine a treee as the whole of our space-time. Take a horizontal slice through the tree at a particular height, and that gives a picture of how we consider our universe with thes ebaby universes: a central area (the x-section of the trunk) and lots of smaller distinct isolated areas (x-sections of the branches). It looks like lots of separate universes. But when you look at the whole tree, you realise that it is all one big connected space-time.Finally, the information paradox itself: if say a tea-cup falls into a black-hole, eventually it will be re-radiated out via Hawking Radiation. However, the radiation is completely thermal and there will be no way of determining that the radiation had once been a tea-cup. This is contrary to everything we know about quantum mechanics. Information has gone missing. Where is it? The baby universe idea is that information may filter into the baby universe via the black hole, and from the point of view of our observation, information has been lost. But when the baby universe is counted as part of our universe (as it should) then nothing has been lost.Sorry, this is not great. I had a much longer and better piece written yesterday that the aether-net swallowed. Just a bit rushed at the moment.

Yes, and I went into some detail on this in my "lost" post. There was something immensely elegant about Black Hole Thermodynamics, how it almost-unified thermodynamics with quantum field theory and black holes. It did seem to make so much sense that the black hole should radiate purely themally, and that was what all the (admittedly semi-classical) quantum gravity mathematics suggested. However, as soon as it became apparant that we had black holes in string theory, attempts were made to push through the nice semi-classical work into the real hardcore non-perturbative (or at least higher-order perturbative) quantum theory to see if corrections could be found that would show that the radiation was not purely thermal, and indeed encoded the infomration that had fallen into the black hole. The discovery of AdS/CFT correspondance pushed this further to the point where calculations these days are highly suggestive that information is re-radiated. There may well still be baby universes but we don't need them to solve the infomration paradox.

Theoretically yes, practically no. But if Hawking had been right, then it would have also have been "theoretically no", which has profound implications for physics. No, this really has nothing to do with the issue. In this case, the electron/positron pair "come from" the pair of photons. Photons are simply excitations of the quantum electrodynamic field (think of isolated waves upon an ocean). Electrons are a different kind of excitation of the quantum electrodynamic field, with particular properties that we describe as matter, but they are still like isolated waves (of a different kind) upon this same ocean. Given the right circumstances, photons waves can combinme to become electron waves.Dark matter and dark energy are yet other varieities of waves upon this ocean. You yourself are an amazingly complex stable arrangement of waves upon this ocean. No, everything that falls into a black hole will eventually radiate out, unless the universe should recollapse (unlikely given current evidence) in which case some black holes will not have evaporated to extinction before the big crunch. Heh, heh... well, if you will pick a subject at the frontiers of human knowledge, be prepared for a few headaches!

Very much so. Mass of a simple space-time is a difficult enough concept, without the added complications of a branching universe. You essentially measure mass across a slice of space-time; the question is what kind of slice?You are right, the rubber sheet analogy does require the Earth's gravity to work, but it is only an analogy. In reality, mass/energy at a particular point in space-time helps define the curvature of space-time at that point. There is no action at a distance, no gravitational force.Curvature at a point helps define the curvature at neighbouring points, and hence the effect of the mass/energy propegates out through space-time. As SG has pointed out, a particle will follow a straight line through space-time, which will appear curved to us (orbits, projectile motion) because of our reduced 3d perspective. Simple as that.Particles that are sufficiently massive to create non-negligible curvature are a little more complicated to work with, but the same principles apply (e.g. the Earth moving on its orbit through space) Again, gravitational forces are our naive interpretation of the warping. Spae-time is not warped by 'gravitational forces'. Mass, energy, and momentum (and most importantly space-time curvature) all generate space-time curvature. Oh, also a cosmological constant, which is important for the accelerating Universe.At present we have no need to introduce any other concepts to explain the large-scale structure of the Universe.Edited by cavediver, : No reason given.

Yes, it can be. As I said, space-time curvature generates space-time curvature - not in an out-of-control positive feedback cycle, but in a self-supporting type of notion.Quick analogy off the top of my head: imagine a long strip of paper (space-time) How can we add some humps to the paper? Easy, stick some blocks (matter) under the strip to prop up bits of it. What if we have no blocks? Well how about putting a few knots in the paper itself. That will introduce similar (if somewhat contorted) humps, without the need of adding anything else.There are an infinite variety of vacuum solutions of General Relativity: space-times that contain no matter, no extra energy, nothing except the space-time itself. They are far from trivial, like our paper above with its knots.The classic Schwarzschild solution, our most simple black hole, is one such solution. Despite everything you may think you know about black holes, this one has no matter whatsoever. Yet there it is with its event horizon and singularity, but with all of its 'gravitational field' generated purely from the space-time itself. It even has a mass if you try to measure it using any of the usual methods, again generated purely from the curved space-time. We have long (~100 years) assumed it to be zero for no good reason other than to fit with observation. Now observation dictates it has a small value, and suddenly we are interested in the reason. Nothing has changed, we have just had a prod to our laziness. The problem is the GR leaves the CC as a free parameter. The theory does not dictate the value. This is a huge clue to the idea that GR is not a final theory but an emergent theory (perhaps not as huge a clue as its non-quantum nature)But GR itself is untouched by the discovery of a non-zero CC, or the existence of 'dark energy' (you listening, RAZD? ) The great thing about the observed CC is that it is pushing us into considering a deeper theory sooner than we had anticipated.Edited by cavediver, : No reason given.

A true CC is constant in time and space. It would arise from some deeper theory about which we know little - perhaps some aspect of M-theory or something not even yet considered.A pseudo-CC would be a dynamic field - essentially a new particle - that varies very slowly across space and time. It would take its place in family of fields (particles) of which we are aware, and again would arise from some deeper theory, as do all of the fields: space-time, strong, electroweak, matter, etc.The observed very small CC could be the remainder of the above two working aainst each other, similar to the idea that observed matter is the slight left-over discrepancy of the original matter/anti-matter annihilations.

Any being that "travels" along the dimensions of our existence (time and/or space) does not merit the term "god". 10 dimensional beings are as far below god as we are. Yes. Up to 4d, it has some good bits and bad bits. After that, the scientific term is "pure bollocks".

In this case it is more simple - it's just wrong As in, when we talk about extra dimensions in physics (string theory, M-theory, SuperGravity, etc) it has very little if anything to do with the concepts shown in that video. Where the ideas in that video come from (for d>4) I have no idea, but it's not part of extra-dimensional physics as we practise it. My first work was in 26 dimensions. I wonder how he'd explain those extra 16 Fundemental physics is weird and exciting enough - it doesn't need "bollocks" like this!Edited by cavediver, : Corrected imbecilic use of language

Of course, I spent long enogh working on it. I am severely critiquing the website, but not because it is for laymen and is simplistic. It is just making stuff up that bears no relation to how we view the extra dimensions.If we consider the first three dimensions as spatial, then it is reasonable to describe the fourth as time as our observable Universe is 3+1 dimensional. So apart from making a poor job of the explanations, it is ok up to there.But it then goes on to describe the higher dimensions as related to time (incorrect) and having something to do with an Everett-like quantum many-worlds picture (wacko and truly bizarre).All are valid parts of theoretical physics: string theory, extra dimensions, even extra time dimensions and many-worlds, etc; but randomly mixing up these concepts, inventing incorrect relationships between them, and then presenting this as some authoritive layman guide is why this website is a load of bollocks.Edited by cavediver, : typos

That's not reason enough just to make stuff up and try and pass it off as physics! Theoretical physics is not some wishy-washy science where anything goes. Otherwise I could make up some really fun stuff involving sploorions and ultra-sploorions that are seven and two/thirds dimensional. The multi-dimensional aspects of various theories are predicted by the precise mathematics of those theories. Yes it is, but General Relativity itself does not specify the dimension of space-time. GR works in any number of dimensions. It is the deeper theories - the attempts at theories of everything - that actually specify the dimensions of existence. And these theories tell us the properties of these dimensions. And no existing theory comes close to talking about the crap on that website. Great insight Yes, theoretically this is possible in certains circumstances. And then you go and ruin it Time is one of the dimensions - the other dimensions are spatial. They don't have the properties of time, becasue they are not time, they are space! The time dimension, unsurprisingly, is the dimesnion that has properties of time... In most theories, the higher dimensions are curled up at the Planck-scale and are unobservable as yet.

Then why are you posting in the Science Forums? No, that site is posing as physics, and is simply wrong. If it were to put a disclaimer at the front saying "the ideas presented here are not the concensus of scientists working in this field and are purely my own ideas" I would have no complaint.And why would I ever take M-Theory or String Theory on faith??? They are mathematical theories that show some exciting relation to reality. One day they may explain much of reality... or they may not. For now they are possibilities. There is no faith involved at all.

Sorry, we're talking science. We don't "prove" things in science. And any theory that I discuss in the positive will have solid roots in the bedrock of the Standard Model, i.e. is built upon existing science, not the whims and fancies of those who would rather pursue their own version of "science". oh no... M-theory and string theory are regarded as *possibly* representing some part of reality by the great majority of theoretical physicists. Your ideas and that site's are certainly not so regarded. I believe the onus is on you to provide some evidence However, if you would like to ask me to explain some of the aspects of those theories that lead us to believe that they *may* have something to do with reality, I would be delighted. Please quote me where I suggest this, as I cannot seem to find it at the moment... To think that as a theoretical physicist I have been working under this false assumption for so many years. Thank you for putting me straight. I owe you one... Edited by cavediver, : No reason given.

Cool Though it probably deserves a new thread. Can you propose one? I'd do it myself but I get a bit self-conscious with "in this thread I would like to explain..." I'd rather answer questions.