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Samizdata, derived from Samizdat /n. - a system of clandestine publication of banned literature in the USSR [Russ.,= self-publishing house]
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No possibility … This is the New York Times quote of the day, from Stephen Hawking, he of the technologically enhanced vocal chords:
“I’m sorry to disappoint science fiction fans, but if information is preserved there is no possibility of using black holes to travel to other universes.”
Until now I have taken it for granted that any idea that black holes might ever make a contribution to long haul transport was black pudding in the sky. But now I am not so sure.
I do not know exactly what Hawking means about information being preserved, just as I am seldom completely clear what he means about most things, but the rest of this quote reads so very like those it-will-never-float it-will-never-fly only-six-computers-will-ever-be-needed electric-guitar-groups-will-never-catch-on prophecies which are periodically gathered together into anthologies of Things They Wish They Had Not Said, that I suddenly find myself becoming more optimistic about the possibility that one might one day be able to hail a Black Hole Cab and take a trip to another universe.
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Who Are We? The Samizdata people are a bunch of sinister and heavily armed globalist illuminati who seek to infect the entire world with the values of personal liberty and several property. Amongst our many crimes is a sense of humour and the intermittent use of British spelling.
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Essentially, and I could be waaaayyyyy out here, what he is saying is:
1. Back in the 70’s he reckonned that nothing could escape a blackhole. Other people said, well then squire where does all the stuff go to? Hawking said he wasnb’t sure.
2. Hawking then started a slow recant with a prediction that you could have radiation bleeding off a black hole over time. “Hawking Radiation”. If that was the case, then perhaps “information” might be able to escape. Still, Hawking was pretty sure this was not the case.
3. Now Hawking is pretty sure that over time a black hole will die and that anything that falls into it, will, in some form be returned to the universe i.e. this one and not another. All the black hole does is store it for a while.
This does deal with the problem of Singularities (a point with no dimensions) which one would have to suppose were in Black Holes. Now it looks like that is the case.
There are some heretical physicists still out there who say that there are no black holes, just super massive stars that behave light we assume a black hole would but are actually not…
I think I’ll go and lie down now.
Either way, using a black hole for travel was probably unlikely. Better to build a wormhole, Steven Baxter gives a working example in his novel Timelike Infinity.
There are also some cosmological theories which are getting fairly well believed that the amount of information within a closed system is dependant on and limited by the surface area, not the volume. In this case, the full state information of everything which ever fell into a black hole is recorded on its event horizon.
Somewhat deeper theories state that a universe can be represented by a model based on an n dimensional volumen or an n-1 dimenstional surface and both will give the same answers. The two are formal ‘dual’s of each other, ie one is a transform of the other.
At this point I am probably swinging a bat well out of my league.
I did my 2nd year undergraduate project on black holes, so maybe I can help.
1. In the 70s, Hawking proved the “No-Hair Theorem” which states that a stationary black hole is completely specified by it mass, electric charge and angular momentum. It can contain no other information about the matter from which it was formed.
2. He also proved that a black hole emits radiation (Hawking radiation) via quantum mechanical processes, so over enough time, a black hole will evaporate.
3. In the standard model of particle physics, there are several quantities which must be conserved, for example, “baryon number” which is the number of protons plus the number of neutrons, minus the number of anti-protons minus the number of anti-neutrons.
This gives us a problem. A star contains lots of protons and neutrons, but virtually no anti-protons or anti-neutrons, so has a very large baryon number. If it’s heavy enough, it will form a black hole when it dies. About 10^60 years later, it will have evaporated due to Hawking radiation. According to points 1 and 2, the end product of the evaporated black hole will have equal numbers of protons+neutrons and anti-protons+anti-neutrons, so the baryon number of is zero, whereas the initial star had a very large baryon number. According to point 3, however, the baryon number should have remained unchanged. This is the information paradox.
Its resolution should lie within the realm of quantum gravity, of which we do not yet have a satisfactory theory. The two possible outcomes are: the standard model of particle physics is wrong – once gravity is accounted for in quantum theory, we may find that the conservation laws that we observe in our present experiments do not hold at higher energies; or, the No-Hair Theorem is wrong, that quantum theory should allow black holes to contain information about baryon number etc.
According to the press reports, Hawking now thinks that the No-Hair Theorem is wrong.
Are you still awake? Have I been of any help?
Except this is Stephen Hawking publicy saying he was wrong about something. Not some stupid environmentalist dweeb asserting he’s right even though any homeless drunk can tell he’s full of it.
Sylvain,
I think Brian’s referring to a famous quote from, I think, Arthur C. Clarke:
One famous example is Lord Kelvin(Link), who is reputed to have said that “Heavier-than-air flying machines are impossible”, “X-rays will probe to be a hoax” and “Radio has no future”.
Nothing to do with “stupid evironmentalist dweebs”.
I do not know exactly what Hawking means about information being preserved, just as I am seldom completely clear what he means about most things, but the rest of this quote reads so very like those it-will-never-float it-will-never-fly only-six-computers-will-ever-be-needed electric-guitar-groups-will-never-catch-on prophecies which are periodically gathered together into anthologies of Things They Wish They Had Not Said,
Of course the examples cited were real world phenomena and were proven false in a short period of time as individual tastes and choices were made. A lot of people crashed and a lot of people drowned (and a lot of saxophone players were unemployed) while testing and exploration took place. All of which occured in a time and space that was directly at hand, and technological strides were spurred on by need.
The existence of black holes, understanding their function, and exploiting them, exists in theory and the horizon on proving their existence and exploiting them, much less needing to, is certainly well off in the future. Considering space travel thus far has collected a few rocks from the moon, puts some satellites in orbit, and is constructing a relatively useless international tin can, I’m going to assume that zooming around the universe via time-space distorting mechanisms is well off in the future of which I am not in.
Man obviously isn’t going to travel anywhere linearly, so positing some time-space distortion is a must. For those that need some idea that man will populate the universe, and need such notions to fuel some cosmological/psychological drive, more power to them. As long as no resources are coerced from individuals in funding ‘research’ I ulitmately don’t care. Unfortunately most ‘research’ in such areas are funded or co-funded by extorted resources, by States and State funded institutions of higher education.
So those who don’t think black holes (if they exist) will ever be exploitable can be fobbed off as flat-earthers. Meanwhile, proponents can be labeled dreamers. Necessity IS the mother of invention, and when the time comes, and understanding is gained by need, versus casual curiousity, there is a possibility that man can find ways to distort time/space at least in launching himself vast distances and into the future. If man were able to travel to and from, and choose the time-space of re-entry (just as if he had found a way to travel linearly at several thousand times the speed of light) then man will have had mastered time travel. If so, I think we would have some plain notion that man is traveling through time. Conspiracy theories of crashes in the desert, and posterior explorations by bug eyed aliens (especially of the trailer park set) aside we have little or no evidence that men from the future have come back in time. The only possible signatures that I can see are contagions that seem to come from nowhere or are not directly tracable to an ancestor. I’d think visiters from the future would bring microbes with them, some of which we would not have resistance to. That would be about it as far as I can see.
Mr. Wood;
A third resolution is that black holes never form, therefore the information is never lost.
I think that Hawking’s work answers something that has puzzled me for a long time about black holes, which is how can they exist? The intense gravitational field causes time to slow down. In fact, nothing can ever actually fall in to a black hole because it takes literally forever to get to the event horizon. But that applies to the matter that fell in to form the black hole in the first place. Shouldn’t it take forever as well? The answer, I was told, was an effect called “extinction” whereby the state of the infalling matter becomes so close to that of a real black hole that it’s indistinguishable. But there’s the kicker – it’s still not really a black hole.
I’ll bet that what Hawking has done is show that the collapse of a black hole goes far enough to create Hawking radiation but not far enough to erase things like baryon number. Therefore, when the black hole finally evaporates that information is recovered.
True, although that would require a much more radical reformulation of General Relativity. Sufficiently massive black holes don’t require particularly extreme densities in order to form.
That’s not correct. It’s true that a distant observer never sees the matter reach the event horizon because of the time dilation effect, but an observer falling into the black hole will cross the event horizon without noticing anything any more unusual than strong tidal forces and a strong gravitational lens effect and he will reach the singularity in finite time.
I’ve not read his paper (have I committed myself to doing so, now that I’ve got involved in a discussion about it?), but judging from this piece(Link) I expect it has more to do with quantum mechanics than time dilation. Relevant quote:
“Gary Gibbons, a physicist at Cambridge University, said Hawking’s newly defined black holes did not have a well-delineated event horizon that hid everything in them from the outside world.”
Now he has my undivided attention. I think I’d better go read the paper too.
Maybe one universe’s black hole is feeding another universe’s Big Bang. I mean, here we have a black hole, where material is “exiting” to a place unknown. Then we have the Big Bang theory, where material is “entering” from a place unknown. 😉
There is an interesting blog posting to be written on famous people who have recanted, but were right in the first place. Some examples:
Einstein (the cosmological constant) and Nozick (libertarianism) spring to mind.
“Man obviously isn’t going to travel anywhere linearly, so positing some time-space distortion is a must.”
Sez who? Given a long enough lifespan, people can go anywhere. Given a ship traveling sufficiently close to the speed of light, it won’t seem like a very long trip to the people inside; although it will be an awfully long time to the people left behind. But given a long enough lifespan, that won’t matter so much.
“For those that need some idea that man will populate the universe, and need such notions to fuel some cosmological/psychological drive, more power to them.”
My “psychological drive” is simply that progress is good, and properly constituted human societies are capable of it. As long as we keep our freedom, we can go anywhere eventually.
“Considering space travel thus far has collected a few rocks from the moon, puts some satellites in orbit, and is constructing a relatively useless international tin can, I’m going to assume that zooming around the universe via time-space distorting mechanisms is well off in the future of which I am not in.”
I’m not going to assume that. Medical research is our friend.
My personal psychological drive to get man off of the earth is rooted in species survival fear: all our eggs are in one basket.
FTL would alleviate that even more than colonies in the outer planets and slow-ships going everywhere, obviously!
Except this is Stephen Hawking publicy saying he was wrong about something.
That’s probably a good operational definition of a scientist, someone who publicly admits they were wrong, and doesn’t think it is a bad thing. However, the manner of the announcement was that of great triumph, a classic Hawking self-promotion–he’s changed his theory, it’s better, and (implicitly) no-one else could have done it.
It’s not a matter of density, but of time.
Here’s the thought experiment. You jump in to a black hole. I, the distant observer, watch you fall in. While I’m waiting for you to cross the event horizon (which takes forever in my reference frame), the black hole evaporates and the event horizon disappears. Therefore, in my reference frame, you can never cross the event horizon. Relativity lets you do a lot of re-arranging of the order of space-time events, but it doesn’t let you change the set of events. Alternately, at what point do you, the infalling observer, see the black hole evaporate? Before or after you cross the event horizon?
P.S. Can I mention how much I hate the anti-Spambot garbage? Could you at least put out a cookie on Preview so I don’t have to type the frigging code every time I want to see if my comment looks right and makes sense?
You’ve missed my point. The time dilation effect has no bearing on whether the black hole forms or not. It just means that a distant observer doesn’t see the matter cross the event horizon. To prevent the possibility of black holes forming would require a reformulation of General Relativity. The point about density is that a sufficiently massive black hole can form from matter which is at the density of everyday matter, about which we have a lot of information. So there isn’t really any possibility of solving the problem by invoking unforseen behaviour of matter at high densities.
Reference frames don’t actually make much sense in General Relativity (other than local reference frames). What happens is that the light I send back just before I cross the event horizon is red-shifted, so that you see my blue shirt turn red, then infra-red, then radio and very quickly you can no-longer see me. The light that I send back as I cross the event horizon remains at the event horizon and never reaches you. (However, that doesn’t mean that the light is stationary; it is still travelling at 186,000 miles/second relative to a local observer.)
I think I see what you’re trying to say. For a stellar-mass black hole, it only takes a few micro-seconds for an infalling observer to cross the event horizon and reach the singularity, so I wouldn’t see the black hole evaporate at all, I’d be long dead.
The time dilation effect has to be modified when the Hawking radiation is taken into account. If the black hole is evaporating, its distortion of space-time weakens, so the time dilation effect that retards the light I send back to you weakens too. The net effect is that the light I send back as I cross the event horizon does indeed reach you along with the last of the Hawking radiation. So you see me cross the event horizon after all, at the very moment that you see the black hole disappear.
You don’t have to type the code when you’re only hitting preview, only when you’re actually posting. (To the management: It might be worth making that clear in the instructions.)
Cydonia:
There is an interesting blog posting to be written on famous people who have recanted, but were right in the first place. [..] Nozick (libertarianism) spring to mind
Nozick only recanted libertarianism if you’re using a very narrow definition. As he said in his interview with Julian Sanchez:
“Yes [he would still self-apply the L-word]. But I never stopped self-applying. What I was really saying in The Examined Life was that I was no longer as hardcore a libertarian as I had been before. But the rumors of my deviation (or apostasy!) from libertarianism were much exaggerated.”