Viewing black holes

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Viewing black holes

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Published by munch 09-14-2007

A couple questions have been bothering me for a while. We all know the event horizon is an area beyond which no information can pass to the outside universe. However, if I was to hover just outside the event horizon, wouldn't I be able to take information from outside the event horizon as I see it?

Furthermore, what's to stop me from sending a series of probes, each one penetrating deeper into the event horizon, and having the probes relay information from as far into the event horizon as I want? (This is assuming the probes can boost the energy of the redshifted information coming from further in.) I know this shouldn't be possible, but I can't think of any reason it wouldn't work. Can anyone prove me wrong?

By Jay-qu on 09-14-2007

Re: Viewing black holes

Well assuming you have sufficiently indestructible probes, and lots of fuel to keep your self hovering at the event horizon, once anything passes beyond that point the curvature of space is so great that not even traveling at the speed of light will allow you to escape. So if your probes couldnt send you any information in any form, even if they where in 'arms reach' of yourself.

By munch on 09-15-2007

Re: Viewing black holes

Right, but doesn't the event horizon mark where information can't escape to normal "flat" space? The idea is the information doesn't have to escape, it just needs to reach the next probe out. Although the information that does escape isn't the same that the innermost probe received, it should contain the same information.

By Jay-qu on 09-15-2007

Re: Viewing black holes

yes, the curvature of space at the event horizon prevents any information from traveling further away from the center of the hole.

By munch on 09-15-2007

Re: Viewing black holes

Ok, but the idea is that a series of probes could relay copies of the information from inside the event horizon. I know information from inside the horizon can't escape, but it's not necessarily that information that escapes, it's information about what the probes see and relay to the next probe in sequence.

I'm thinking of maybe a picture file, for example. Probe 1 takes a picture and sends it out to probe 2. It's redshifted into radio range when probe 2 receives it, but once it gets the entire picture, it re-broadcasts it as, say, a gamma ray burst. Probe 3 gets the redshifted gamma ray burst as radio, makes its own gamma ray transmission, and so on until probe n transmits into flat space.

That's what shouldn't work.

By CraigD on 09-15-2007

General relativity and quantum mechanics

Quote:

Originally Posted by munch

However, if I was to hover just outside the event horizon, wouldn't I be able to take information from outside the event horizon as I see it?

Furthermore, what's to stop me from sending a series of probes, each one penetrating deeper into the event horizon, and having the probes relay information from as far into the event horizon as I want? (This is assuming the probes can boost the energy of the redshifted information coming from further in.) I know this shouldn't be possible, but I can't think of any reason it wouldn't work.

According to General Relativity, it would be impossible for a probe even a tiny distance within the event horizon of a black hole to send a signal of any kind to one even a tiny distance outside it. If a probe were positioned part within and part outside the event horizon, it would be unable to communicate within itself – a very severe problem, as at some location, the photons of magnetic force holding its matter together would be unable to “communicate”, and it would fall apart, despite the fact that the gravitational tidal force of a sufficiently massive black hole is small enough to not cause too much strain for commonplace materials to hold together.

According to quantum mechanics, it should be possible to send a signal across the event horizon of a black hole by manipulating the distribution of mass within it, effecting the Hawking radiation produced outside it. According to General Relativity again, however, such manipulation might take an infinite amount of time relative to an observer outside the event horizon.

Neither of these theories (Relativity and Hawking radiation) are uncontroversial when applied to the vicinity of the event horizon of a black hole, so what would actually happen is debatable. Reconciling gravity with quantum mechanics – a theory of quantum gravity - would help settle this debate, but is a very difficult problem.

By munch on 09-16-2007

Re: Viewing black holes

Huh. I thought the event horizon wasn't static... like the closer you got to the Swartzchild radius, the further into the black hole you could see. It still doesn't make sense, but I guess relativity isn't supposed to make sense.

By Jay-qu on 09-16-2007

Re: Viewing black holes

Quote:

Originally Posted by munch

like the closer you got to the Swartzchild radius, the further into the black hole you could see. It still doesn't make sense, but I guess relativity isn't supposed to make sense.

Im not sure where you got that from, but I am pretty sure its false. Relativity makes sense insofar as its self consistent and is a great description of the world we see around us.

By von Faulkenstein on 09-17-2007

Re: Viewing black holes

Interesting question and answers. I did find out from Wikipedia that--

"In July 2005, Stephen Hawking published a paper and announced a theory that quantum perturbations of the event horizon could allow information to escape from a black hole, which would resolve the information paradox. Basically, his argument assumes the unitarity of the AdS/CFT correspondence which implies that an AdS black hole which is dual to a thermal conformal field theory, is unitary."

Could such an event(if found to be correct) take place that would present some such information about a black hole?

By munch on 09-17-2007

Re: Viewing black holes

I remember reading about that too. I think it had something to do with quantum displacement of the singularity. In any event, Stephen Hawking owes Kip Thorne an encyclopedia set, since he originally bet black holes don't store information. And since Hawking never pays off a wager until he's absolutely convinced it's true, I take information preservation at face value.

That raises another question. Has Hawking ever won a bet with Thorne?

Quote:

Relativity makes sense insofar as its self consistent and is a great description of the world we see around us.

General mechanics is a great description of the world we see. For most practical purposes, no one really needs relativity, as it does tend to complicate things so. Most of us won't ever encounter a situation that requires it.

Plus, relativity is the main reason I gave up on physics, so I do hold a bit of a grudge there.

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