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tommac
2010-Mar-05, 12:10 PM
Can quantum/gravitational fluxuations that happen inside an event horizon be detected external to the EH?

For example, say the singularity was able to fluxuate and move over say one planck length and back would that "move" be noticeable from external to the EH?

Ken G
2010-Mar-05, 01:21 PM
The usual claim is that only the mass, spin, and charge of the singularity can have any effects on the world outside its event horizon. All other information is swallowed by the black hole as completely as it swallows light itself. This prompted Hawking to wonder if the lost information could be recovered when the black hole eventually evaporates. He first thought it could not, but later was convinced that the information does radiate away, so to "see" the effects of the wobble you discuss, I think Hawking would say you'd have to wait until the hole evaporates to get that information.

WayneFrancis
2010-Mar-05, 02:13 PM
my first question to you would be if you had a ball sitting on a table and it moved a Planck length and back would that be noticeable?

Because it is you I'm going to have to ask "Where are you going with this and what is your real question?"

tommac
2010-Mar-05, 06:17 PM
my first question to you would be if you had a ball sitting on a table and it moved a Planck length and back would that be noticeable?
no you wouldnt but it also isnt a singularity, nor is it very massive, nor is it bending space-time so that light ( or gravity??? ) could escape ...


Because it is you I'm going to have to ask "Where are you going with this and what is your real question?"

Just Freestylin'

tommac
2010-Mar-05, 06:21 PM
The usual claim is that only the mass, spin, and charge of the singularity can have any effects on the world outside its event horizon. All other information is swallowed by the black hole as completely as it swallows light itself. This prompted Hawking to wonder if the lost information could be recovered when the black hole eventually evaporates. He first thought it could not, but later was convinced that the information does radiate away, so to "see" the effects of the wobble you discuss, I think Hawking would say you'd have to wait until the hole evaporates to get that information.

Yes but we are talking about the singularity ... the point of all of the mass ...

For example, can a black hole move? if it moves doesnt that mean that the singularity is moving and thus the EH and the rest of the general topology along with it? Well if the BH can move then why cant the singularity jiggle?

Wouldnt that jiggle send out gravitational waves etc ... I am not proposing anything just was wondering if the singularity is a point or as small or smaller than the planck legnth then wouldnt it be prone to the quantum jiggles? If it does jiggle, would the jiggle be detected outside of the EH?

tommac
2010-Mar-05, 06:25 PM
I think Hawking would say you'd have to wait until the hole evaporates to get that information.

From my understanding the release of information is contained in the radiation. By information I think he usually refers to a bit of information ... not sure if the location of the singularity would be considered "information" unless we are discussing the holographic principle. In which case I think the location is stored in bits.

DrRocket
2010-Mar-05, 06:26 PM
The usual claim is that only the mass, spin, and charge of the singularity can have any effects on the world outside its event horizon. All other information is swallowed by the black hole as completely as it swallows light itself. This prompted Hawking to wonder if the lost information could be recovered when the black hole eventually evaporates. He first thought it could not, but later was convinced that the information does radiate away, so to "see" the effects of the wobble you discuss, I think Hawking would say you'd have to wait until the hole evaporates to get that information.

But a black hole does have a position, so if it moves you would notice that. Now a duisplacement by a Planck Length by anything is going to be rather difficult to detect, but that is a different issue.

As a note, Hawking did indeed concede his bet with Preskill, but Kip Thorne, who was also a party to that bet, has not conceded. Hawking's position is not universally accepted, and as far as I can tell it relies on the AdS/CFT correspondence of Maldecena. The AdS/CFT correspondence is widely accepted by string theory types, but it is in fact an open cojecture dating back to about 1997. Susskind has declared victory over Hawking as well, in his book The Black Hole War but I find that book also rather long on claims and short on proof. He makes use of the AdS/CFT correspondence without even calling attention to that fact, or to the fact that it is still unproved.

DrRocket
2010-Mar-05, 06:40 PM
Yes but we are talking about the singularity ... the point of all of the mass ...

For example, can a black hole move? if it moves doesnt that mean that the singularity is moving and thus the EH and the rest of the general topology along with it? Well if the BH can move then why cant the singularity jiggle?

Wouldnt that jiggle send out gravitational waves etc ... I am not proposing anything just was wondering if the singularity is a point or as small or smaller than the planck legnth then wouldnt it be prone to the quantum jiggles? If it does jiggle, would the jiggle be detected outside of the EH?

You seem to have some misconceptions regarding singularities.

Try reading this (http://arxiv.org/PS_cache/math/pdf/0603/0603190v3.pdf).

tommac
2010-Mar-05, 06:52 PM
But a black hole does have a position, so if it moves you would notice that. Now a duisplacement by a Planck Length by anything is going to be rather difficult to detect, but that is a different issue.
The thought would be that if it did jiggle and the signal could make it outside the EH then there should be ( or would there be ? ) gravitational waves rippling the EH.



As a note, Hawking did indeed concede his bet with Preskill, but Kip Thorne, who was also a party to that bet, has not conceded. Hawking's position is not universally accepted, and as far as I can tell it relies on the AdS/CFT correspondence of Maldecena. The AdS/CFT correspondence is widely accepted by string theory types, but it is in fact an open cojecture dating back to about 1997. Susskind has declared victory over Hawking as well, in his book The Black Hole War but I find that book also rather long on claims and short on proof. He makes use of the AdS/CFT correspondence without even calling attention to that fact, or to the fact that it is still unproved.

I think Susskind was saying that there was proof at the point of the original debate, but that they were able to duplicate the confirm using string theory.

However what I dont agree with is his idea of the black hole complementarity.

tommac
2010-Mar-05, 06:55 PM
You seem to have some misconceptions regarding singularities.

Try reading this (http://arxiv.org/PS_cache/math/pdf/0603/0603190v3.pdf).

OK ... read it ... do you have a particular thing that I have a misconception about? Or a particular line that I was supposed to read? It all seems very straightforward.

DrRocket
2010-Mar-05, 07:06 PM
OK ... read it ... do you have a particular thing that I have a misconception about? Or a particular line that I was supposed to read? It all seems very straightforward.

Good. Then you recognize that the singularity is not a set of points in spacetime and therefore is not "the point at which all the mass is concentrated".

So, now what is your point ?

Ken G
2010-Mar-06, 01:29 AM
But a black hole does have a position, so if it moves you would notice that. Now a duisplacement by a Planck Length by anything is going to be rather difficult to detect, but that is a different issue.
It seemed to me tommac was asking about gravitational radiation from the central singularity. I think the only things that could radiate such that we could see it would be new matter approaching the event horizon. So if you want a black hole to "move", you'd have to hit it with something from the outside, something we would see by its external effects directly.

In other words, you can make gravitational radiation from outside an event horizon and have it cross the event horizon, but I don't think you can scatter it from the central singularity-- that would not affect the external solution. However, you might be able to tease out the fact that such scattering did occur if you wait until the Hawking radiation comes out much later, but for any of the black holes thought to exist, that would be impossible to actually do. That seems to be the main problem with Hawking radiation-- it is aesthetically interesting, filling in various gaps in our expectations, but the only kinds of black holes for which it would ever be observable are simply not known to exist at all.

loglo
2010-Mar-06, 08:00 AM
It seemed to me tommac was asking about gravitational radiation from the central singularity. I think the only things that could radiate such that we could see it would be new matter approaching the event horizon. So if you want a black hole to "move", you'd have to hit it with something from the outside, something we would see by its external effects directly.

In other words, you can make gravitational radiation from outside an event horizon and have it cross the event horizon, but I don't think you can scatter it from the central singularity-- that would not affect the external solution. However, you might be able to tease out the fact that such scattering did occur if you wait until the Hawking radiation comes out much later, but for any of the black holes thought to exist, that would be impossible to actually do. That seems to be the main problem with Hawking radiation-- it is aesthetically interesting, filling in various gaps in our expectations, but the only kinds of black holes for which it would ever be observable are simply not known to exist at all.

I wonder if the lack of noticeably radiating black holes is a reflection of a deeper principle that is complementary to the "no naked singularity" principle.
Hawking's argument against information loss from black holes seems about as vague as the particle-antiparticle picture of Hawking radiation. There seems plenty of room for new principles to emerge.

Ken G
2010-Mar-06, 11:01 PM
I agree, and the principles get even more vague when translated by the likes of Hawking and Thorne into language that I can understand, so it's hard to tell the true source of the vagueness in that process. The end result is not much you could hang your hat on. I would say that while we are still struggling to even detect gravitational radiation, and Gravity Probe B had difficulties, and the Pioneer Anomaly has not been completely resolved, the empirical state of affairs is in enough of a muddle that the vagueness in the theory of Hawking radiation is not our biggest problem at the moment.

DrRocket
2010-Mar-07, 12:10 AM
It seemed to me tommac was asking about gravitational radiation from the central singularity. I think the only things that could radiate such that we could see it would be new matter approaching the event horizon. So if you want a black hole to "move", you'd have to hit it with something from the outside, something we would see by its external effects directly.

In other words, you can make gravitational radiation from outside an event horizon and have it cross the event horizon, but I don't think you can scatter it from the central singularity-- that would not affect the external solution. However, you might be able to tease out the fact that such scattering did occur if you wait until the Hawking radiation comes out much later, but for any of the black holes thought to exist, that would be impossible to actually do. That seems to be the main problem with Hawking radiation-- it is aesthetically interesting, filling in various gaps in our expectations, but the only kinds of black holes for which it would ever be observable are simply not known to exist at all.

You might get something from two orbiting black holes. Or from coalescing black holes. Maybe a Scotch and soda would help too.

Hawking radiation is, as you say, a pretty weak process. I have no idea if it extends to gravitational radiation. Even the theory of Hawking radiation is based on quantum field theory in highly curved spacetime and there are some serious difficulties with that. We really need a unification of gravitation with quantum mechanics just for that, and if we had it then presumably the question of graviton radiation in addition to photon radiation from the Hawking mechanism might be answerable.

Ken G
2010-Mar-07, 02:10 PM
You might get something from two orbiting black holes. Or from coalescing black holes. Yes, those sound like processes that we could detect, moreso than what is described in the OP.


Hawking radiation is, as you say, a pretty weak process.Indeed, I imagine it might hold some kind of record for the phenomenon that is the most discussed and taken seriously while also being the farthest from ever being detected from any real object currently expected to exist.

TampaDude
2010-Mar-08, 03:45 AM
You seem to have some misconceptions regarding singularities.

Try reading this (http://arxiv.org/PS_cache/math/pdf/0603/0603190v3.pdf).

Wow...math...my head hurts... :lol:

So, the black hole is the physical matter that creates the intense gravitational field, and the singularity is the distortion in spacetime created by that gravitational field? Am I in the ballpark here???

Tensor
2010-Mar-08, 04:14 AM
You seem to have some misconceptions regarding singularities.

Try reading this (http://arxiv.org/PS_cache/math/pdf/0603/0603190v3.pdf).

Man, that's got some handy explanations and equations in there. I especially like the mathematical formulazation of the twin paradox.

WayneFrancis
2010-Mar-09, 04:38 AM
no you wouldnt but it also isnt a singularity, nor is it very massive, nor is it bending space-time so that light ( or gravity??? ) could escape ...


Black holes move relative to other objects. Heisenberg uncertainty principle really kills what you are suggesting I think. IE Random movements of a BH might occur but I still don't see how this is any different then random movements of a star. A movement of 1 planck length wouldbe near impossible to detect as I understand it as this is the highest frequency possible in nature. Even so this isn't really saying anything about the BH that we didn't already know. I would guess the amplitude of the GW would be a function of the mass of the BH and the distance of the detector from the BH.

What do you think it should tell us?

DrRocket
2010-Mar-09, 04:49 AM
Man, that's got some handy explanations and equations in there. I especially like the mathematical formulazation of the twin paradox.

Yes, it is a nice compact article. The theorem regarding proper time along generic world lines as compared to those in free fall is the rigorous way to resolve the so-called Twin Paradox.

More importantly it gives some insight into the real nature of singularities associated with general relativity. Popularizations tend to distort their nature and cause people to reach unfounded conclusions.

Since Tommac read and understood it (it took about 5 minutes for him to reply to that effect), discussions can now proceed on a more firm theoretical and mathematical footing. Mathematics makes things much more precise and clear, so with his new appreciation for the tensor formulation of general relativity, it should be much simpler now to answer Tommac's questions accurately -- no need to over-simplify with attendant distortions of the truth.

WayneFrancis
2010-Mar-11, 04:27 AM
Yes, it is a nice compact article. The theorem regarding proper time along generic world lines as compared to those in free fall is the rigorous way to resolve the so-called Twin Paradox.

More importantly it gives some insight into the real nature of singularities associated with general relativity. Popularizations tend to distort their nature and cause people to reach unfounded conclusions.

Since Tommac read and understood it (it took about 5 minutes for him to reply to that effect), discussions can now proceed on a more firm theoretical and mathematical footing. Mathematics makes things much more precise and clear, so with his new appreciation for the tensor formulation of general relativity, it should be much simpler now to answer Tommac's questions accurately -- no need to over-simplify with attendant distortions of the truth.

I eagerly await the future conversation.

tommac
2010-Mar-12, 10:11 AM
I guess where I was going / questioning with this was that if the EH would fluctuate even by just a Planck length that information could escape / radiate. If the singularity either as a point mass or as the sum of all the mass inside the EH would jiggle, that is that its point placement relative to the EH changed slightly, that the shape/area of the EH would also change slightly resulting in loss of bits of information.


Black holes move relative to other objects. Heisenberg uncertainty principle really kills what you are suggesting I think. IE Random movements of a BH might occur but I still don't see how this is any different then random movements of a star. A movement of 1 planck length wouldbe near impossible to detect as I understand it as this is the highest frequency possible in nature. Even so this isn't really saying anything about the BH that we didn't already know. I would guess the amplitude of the GW would be a function of the mass of the BH and the distance of the detector from the BH.

What do you think it should tell us?

Jeff Root
2010-Mar-12, 12:01 PM
I see that nobody replied to this question.



So, the black hole is the physical matter that creates the intense
gravitational field, and the singularity is the distortion in spacetime
created by that gravitational field? Am I in the ballpark here???
It's almost the other way around. The black hole is the whole thing.
The singularity is the place where the matter is located, at the
center of the black hole. The event horizon is the place where
the gravitational field is so intense that even light moving directly
away from the singularity can't escape. The term "black hole" is often
synonymous with the volume inside the event horizon, or with the
event horizon itself. It is rarely synonymous with the singularity, or
with the matter causing the black hole. More often, it refers to the
event horizon, everything inside the event horizon, and the highly-
distorted space close to the event horizon. At a minimum, the space
within 3 Schwarzschild radii of the center. 3 R is the location of the
last stable orbit -- the closest that any massive object can orbit a
black hole without spiralling in. 1.5 R is the photon sphere -- the
place where light could theoretically orbit a non-rotating black hole.
Such an orbit is extremely unstable, so is highly unlikely to actually
happen. The slightest deviation from a perfect circle causes the
photon to either spiral in or fly away.

-- Jeff, in Minneapolis

tommac
2010-Mar-12, 12:15 PM
The term "black hole" is often
synonymous with the volume inside the event horizon


The locally observed volume I would assume right? This is one of the BH items that still confuses me because space ( of the space-time ) seems to not exist indide the event horizon ... at least to external observations.

Jeff Root
2010-Mar-12, 03:29 PM
From MY outside observer's point of view, there is definitely an inside to
the event horizon -- I just can't ever detect anything come from it. I do
not put much significance on the fact that in Schwarzschild co-ordinates,
outside observers see the hands of a ticking clock slow to a stop as it
falls to the event horizon. It has nothing to do with what is actually
happening to the clock or the nature of the space interior to the event
horizon. Anyone actually going close enough to a black hole to observe
things falling in would see them simply fade out extremely rapidly as they
reach the event horizon. Time dilation probably wouldn't be detectible
without a slow-mo playback of a recording of the event.

-- Jeff, in Minneapolis

Jeff Root
2010-Mar-12, 03:47 PM
My understanding is that in "normal" spacetime, space is the dominant
character, while inside the event horizon, time becomes dominant. The
closer you get to the center, the more dominant time is, and the less
significant space becomes. At the event horizon, time and space are
equals. the funnel-shaped curve of gravitational field strength graphs
that relation. Space is on the horizontal axes; time is on the vertical
axis. In "normal" spacetime, the curve is nearly flat. At the event
horizon, the curve is at a 45-degree angle. Approaching the center,
the curve becomes closer and closer to vertical.

-- Jeff, in Minneapolis