Does Hawking deserve a Nobel prize for his singularity theorem?

[petergreat]

Hawking radiation is almost certainly not going to win him a Nobel prize, because experimental detection is beyond our technology. But how about the singularity theorem which he and Roger Penrose proved? This theorem convinced the physics community that black hole would indeed form in realistic situations found in our universe when massive stars run out of fusion fuel. Unlike Hawking radiation, the existence of black holes itself does have observational evidence, which the Nobel Committee requires. Maybe awarding him a Noble prize for the singularity theorem is a possible way of acknowledging this legendary wheel-chair genius? On the downside, I guess some people would argue that proving the singularity theorem doesn't carry that much physical significance, since the concept of black holes had been around for a long time, and the only thing Hawking and Penrose achieved was to silence the sceptics.

 

[Phyisab****]

Tag, I'd like to hear to pf communities opinion on this. I don't know anything about Hawking or what he's contributed, (so I should really just keep my mouth shut) but my knee jerk reaction is no.

 

[Frame Dragger]

Hawking radiation is almost certainly not going to win him a Nobel prize, because experimental detection is beyond our technology. But how about the singularity theorem which he and Roger Penrose proved? This theorem convinced the physics community that black hole would indeed form in realistic situations found in our universe when massive stars run out of fusion fuel. Unlike Hawking radiation, the existence of black holes itself does have observational evidence, which the Nobel Committee requires. Maybe awarding him a Noble prize for the singularity theorem is a possible way of acknowledging this legendary wheel-chair genius? On the downside, I guess some people would argue that proving the singularity theorem doesn't carry that much physical significance, since the concept of black holes had been around for a long time, and the only thing Hawking and Penrose achieved was to silence the sceptics.

I would argue that experiments on earthbound analogues of BHs (Sonic for instance http://dsc.discovery.com/news/2009/06/17/sonic-black-hole.html ) may (longshot granted) provide observations that corroborate the QM process of Hawking Radiation. Observing the emission of Phonons in a manner consistant with HR would be a coup for that view of BHs. As for silencing skeptics... that isn't a trivial matter. The actual question however is one that I think will fall along "party lines". Either you feel that Stephen Hawking has made enormous contributions to this field and deserves recognition, or you're Kip Thorne. Sorry, I meant to say that you're someone who appreciates the elegance of the math, but has to admit that right now one could argue it's pure untestable theory; impossible to confirm or refute (which is dead science).

I just don't know. I think I'd have to say yes, for his theorem and his incredible insight into the mechanics of rotating black holes. He probably deserves some kind of stellar honour for introducing generations of young people to physics; from the arcane to Hubble's view of Cosmology. Whether you credit the man for being what he is, and whether he would be a captivating figure out of the chair as any other man... is hard to know. I have to say, I hope he's right... it would be an amazing coup for theoretical physics on the order of confirming SR/GR piece by piece.

 

[atyy]

No. He should get it for Hawking radiation, with Bekenstein, after it's detected.

 

[Frame Dragger]

No. He should get it for Hawking radiation, with Bekenstein, after it's detected.

That would be incredibly satisying.

 

[Altabeh]

Hawking radiation is almost certainly not going to win him a Nobel prize, because experimental detection is beyond our technology. But how about the singularity theorem which he and Roger Penrose proved? This theorem convinced the physics community that black hole would indeed form in realistic situations found in our universe when massive stars run out of fusion fuel. Unlike Hawking radiation, the existence of black holes itself does have observational evidence, which the Nobel Committee requires. Maybe awarding him a Noble prize for the singularity theorem is a possible way of acknowledging this legendary wheel-chair genius? On the downside, I guess some people would argue that proving the singularity theorem doesn't carry that much physical significance, since the concept of black holes had been around for a long time, and the only thing Hawking and Penrose achieved was to silence the sceptics.

I think Nobel Committee has not done anything bad to him yet, because he is still happy that his other fella and co-workers have not been honored by such a precious prize in place of him and of course HR has yet to become realistic.

And I think, as most do, Sudarshan is the most glorious physicist active in the zone of elementary particles who was andante sacrificed for just a minor anachronism or stuff 5years ago and, instead, his co-worker Roy J. Glauber won the prize for Sudarshan's work!, as Sudashan once ironically said "The 2005 Nobel prize for Physics was awarded for my work, but I wasn’t the one to get it."

AB

 

[George Jones]

In The Nature of Space and Time, Hawking said/wrote,

"Instead, almost everyone believes that the universe, and time itself had a beginning at the big bang. This is a discovery far more important than a few miscellaneous unstable particles, but not one that has been so well recognized by Nobel prizes."

 

[Frame Dragger]

In The Nature of Space and Time, Hawking said/wrote,

"Instead, almost everyone believes that the universe, and time itself had a beginning at the big bang. This is a discovery far more important than a few miscellaneous unstable particles, but not one that has been so well recognized by Nobel prizes."

I would tend to agree with the man, but I'm not sure that fits Nobel criteria. That said, I'm not sure what to make of that statement, or its implications. Should the popularity of a theory lead to a Nobel, even when it is untested and some believe, untestable? *shrug*

 

[Naty1]

The Nobel prize for physics has had many components, including political and racial ones. Seems like there was a considerable past period when certain ethnicities were not recognized...that seems to have passed. The IPCC received oneusing about the most biased/flawed politically motivated studies imaginable. I have no idea what the specific Nobel criteria might be, but reasonable proof nor evidence does not seem to be required in some recent awards. It's their money so I guess they can dole it out any way they like.

 

[GRDixon]

how about the singularity theorem which he and Roger Penrose proved?

He should probably get the prize. But the Nobel committee has dropped the ball more than once. For example, George Gamow should certainly have gotten the prize for explaining tunneling (nuclear decay), etc., using quantum theory. For reasons unknown to perhaps all but a few old men, he was passed over.

 

[Frame Dragger]

There is also the fact that Stephen Hawking is ALREADY wealthier and better known than most Nobel Lauriates. Once upon a time, a Nobel was an instant rise to a kind of fame... that has waned over the last century. Now other routes exist to fund research or a fine retirement... or to show general acceptance.

 

[mgb_phys]

The IPCC received oneusing about the most biased/flawed politically motivated studies imaginable.

That's the Nobel PEACE prize - it is completely separate and awarded by politicians not scientists

 

[JesseM]

Has any physicist ever gotten a Nobel for purely theoretical work without experimental confirmation like the singularity theorem? As important as such work is in physics, I don't think the Nobel committee likes to give the award to anything non-experimental. And unless mini black holes can be created in near-future particle accelerators (which I think is only possible in theories with large extra dimensions), I don't see how we'd get experimental data on any of the properties of black holes that Hawking studied (Hawking radiation would be too weak to detect from astronomical black holes)

 

[mgb_phys]

He should probably get the prize. But the Nobel committee has dropped the ball more than once. For example, George Gamow should certainly have gotten the prize for explaining tunneling (nuclear decay), etc., using quantum theory. For reasons unknown to perhaps all but a few old men, he was passed over.

Fred Hoyle didn't get it for Stellar nuclear synthesis when everybody else in the field did.

 

[Frame Dragger]

Has any physicist ever gotten a Nobel for purely theoretical work without experimental confirmation like the singularity theorem? As important as such work is in physics, I don't think the Nobel committee likes to give the award to anything non-experimental. And unless mini black holes can be created in near-future particle accelerators (which I think is only possible in theories with large extra dimensions), I don't see how we'd get experimental data on any of the properties of black holes that Hawking studied (Hawking radiation would be too weak to detect from astronomical black holes)

It's a longshot, but it certainly shows that analgoues of the real beast could suffice. http://dsc.discovery.com/news/2009/06/17/sonic-black-hole.html

 

[Phrak]

Unlike Hawking radiation, the existence of black holes itself does have observational evidence, which the Nobel Committee requires.

What is the measurable different between a black hole and a proto black hole? A proto black hole, has a mass slightly greater than its radius.

 

[Frame Dragger]

What is the measurable different between a black hole and a proto black hole? A proto black hole, has a mass slightly greater than its radius.

Maybe he meant Primordial? I've seen people get the terms confused... unless he was taking a terribly roundabout way of saying "Star".

 

[Phrak]

Maybe he meant Primordial?

I'd like to see someone defend his assertion against the strong doubts as I've expressed in my signature below. Maybe I'm just too stupid to get it, but without it, I'll continue to think the black hole believers are happily delusional.

 

[JesseM]

I'd like to see someone defend his assertion against the strong doubts as I've expressed in my signature below. Maybe I'm just too stupid to get it, but without it, I'll continue to think the black hole believers are happily delusional.

Do you think it's delusional to think general relativity is probably correct at far lower energy densities than the Planck scale, and thus that its theoretical predictions about collapsing stars becoming black holes are very likely to be correct too? Or do you think that, even given the assumption that GR is correct on a theoretical level, it's delusional to think that various astronomical objects which appear to fit the profile for what GR would predict about black holes (like this one, which does have what seems to be an accretion disc and jets in photos...likewise, see here and here for photos of a jet from the center of M87 which is believed to contain a supermassive black hole) are in fact black holes?

 

[Altabeh]

I'd like to see someone defend his assertion against the strong doubts as I've expressed in my signature below. Maybe I'm just too stupid to get it, but without it, I'll continue to think the black hole believers are happily delusional.

Actually I feel you are a little bit too delusional about things that are not today talked about from the angle you see 'em because it's been a long time since they were discovered in the real world. You get to have a look at this http://www.physics.purdue.edu/astro/ListerPapers/Observational%20evidence%20for%20the%20accretion-disk%20origin%20for%20a%20radio%20jet%20in%20an%20active%20galaxy.pdf" which provides an observational evidence for the accretion disk origin for a radio jet or just visit Arxiv.org and start searching the relevant stuff in there to find over than 1,000 entries on the subject of accretion disks, removing your doubt in their existence!

AB

 

[Frame Dragger]

I'm going to go out on a limb here and assume that Phrak is aware of current imaging studies of (commonly accepted, by me as well) BHs. I think he's positing that something other than a singularity enshrouded by an event horizon is causing polar jets, and accretion discs. At this point however I'd say that's a pointless speculation. BHs are not wild theory, but the best working material a pretty well verified theory (GR) provides us with. Does that mean that the superdense object behaving like a BH is actually a point where... well... everything is destroyed utterly at the singularity? Who knows, and new theories to describe such a space aren't being developed by people who reject their existence entirely.

Personally, I don't think it matters right now, because the models of whatever is generating the artifacts observed in the images linked by JesseM and Altabeh must be VERY close to an object that would be hidden by an Event Horizon. Does it really matter if it's a String Theory "Fuzzball" behind that event horizon, or "Green Slime and Lost Socks"? No. Unless earthbound anaogues of BHs can show experimental evidence of HR, we'll just have to wait in even more precise mesurements. That said, from a purely phenomenological it doesn't matter one way or the other.

Singularities are predicted by GR, and the associated artifacts have PROBABLY been observed, and provide explanations of LGRBs, superluminal jets, etc... Before you stand on the mountaintop and shout that everyone is a fool for believing in, or working with, the best current observations backing up a well verified theory... offer YOUR brilliant explanation... and please, in the kind of detail you'd expect from someone with a view contrary to your own.

Finally... if you want to make a point in a serious discussion online, your signiture is not the best delivery mechanism. ;)

 

[stevebd1]

While I have no issue with current black hole theory, I do think the alternative http://en.wikipedia.org/wiki/Black_Star_(semiclassical_gravity)" sounds interesting.

Related paper-

'Small, dark, and heavy: But is it a black hole?' by Matt Visser, Carlos Barcelo, Stefano Liberati & Sebastiano Sonego (2009)

http://arxiv.org/abs/0902.0346

 

[Frame Dragger]

While I have no issue with current black hole theory, I do think the alternative http://en.wikipedia.org/wiki/Black_Star_(semiclassical_gravity)" sounds interesting.

Related paper-

'Small, dark, and heavy: But is it a black hole?' by Matt Visser, Carlos Barcelo, Stefano Liberati & Sebastiano Sonego (2009)

http://arxiv.org/abs/0902.0346

It is interesting, but as with formulations for naked singularities, gravstars, etc... it doesn't work in all of the multitutde of situations where (gravitational) singularities arise in GR. Before we go off inventing theories that are essentially baseless because we dislike the IDEA of a BH, maybe closer examination of these massive bodies is warrented?

 

[atyy]

It is interesting, but as with formulations for naked singularities, gravstars, etc... it doesn't work in all of the multitutde of situations where (gravitational) singularities arise in GR. Before we go off inventing theories that are essentially baseless because we dislike the IDEA of a BH, maybe closer examination of these massive bodies is warrented?

Visser's work is motivated by quantum gravity considerations. At present, there is no known way to extend the Einstein-Hilbert to the Planck scale. So the possibility that the EH action is only a low energy effective action is being explored. However, the Weinberg-Witten says that the EH action cannot be a low energy effective action if the high energy action is Lorentz invariant, 4 dimensional etc. Thus high energy actions without Lorentz invariance are being theoretically explored by Visser and Horava, among others. If Lorentz invariance is broken, there is an argument from Ted Jacobson that black holes can be perpetual motion machines, which suggests either that Lorentz invariance is not broken or that black holes do not exist.

 

[Frame Dragger]

Visser's work is motivated by quantum gravity considerations. At present, there is no known way to extend the Einstein-Hilbert to the Planck scale. So the possibility that the EH action is only a low energy effective action is being explored. However, the Weinberg-Witten says that the EH action cannot be a low energy effective action if the high energy action is Lorentz invariant, 4 dimensional etc. Thus high energy actions without Lorentz invariance are being theoretically explored by Visser and Horava, among others. If Lorentz invariance is broken, there is an argument from Ted Jacobson that black holes can be perpetual motion machines, which suggests either that Lorentz invariance is not broken or that black holes do not exist.

I think that the simple fact that there is no unification between the macroscopic and microscopic makes me leery of challenges to the existence of BHs such as those from Ted Jacobson. There are plenty of theories which are consistant with observations and GR/SQM, but they are unproven and maybe unrproveable. Alas. Then again, maybe BHs really are enshrouded singularities, or boundary conditions on which information is encoded a la The Holographic Principle. Nothing I've read from Visser or others is convincing in all of the many ways that collapse or accretion could lead to some BHs. In some cases they make more sense... but when has that ever mattered?

 

[atyy]

GR/SQM

What is SQM?

 

[Frame Dragger]

What is SQM?

Standard Quantum Mechanics.

EDIT: good point... could be Scaled, or Supersymmetric. Let's just say GR/QM

 

[Altabeh]

If Lorentz invariance is broken, there is an argument from Ted Jacobson that black holes can be perpetual motion machines, which suggests either that Lorentz invariance is not broken or that black holes do not exist.

But this is in a total disagreement with the mechanism of Kerr black holes, because they lose mass by the emission of massive particles and HR and therefore angular momentum and this means they will stop rotating someday. Though it is not proved practically that the primordial rotating black holes would become motionless today nor is it that HR exists in the real world, I can't completely disagree with the Jacobson's idea! What if the HR is just a theory?

AB

 

[atyy]

But this is in a total disagreement with the mechanism of Kerr black holes, because they lose mass by the emission of massive particles and HR and therefore angular momentum and this means they will stop rotating someday. Though it is not proved practically that the primordial rotating black holes would become motionless today nor is it that HR exists in the real world, I can't completely disagree with the Jacobson's idea! What if the HR is just a theory?

As I understand, Jacobson's idea (http://arxiv.org/abs/0804.2720) isn't relevant in standard GR or QFT on curved spacetime since those are have local Lorentz invariance.

People have suggested that there should be analogues of black holes in condensed matter systems, and that we should be able to detect Hawking radiation from them. But many of these suggestions don't have Lorentz invariance, so does that mean that we can have perpetual motion machines or that we can't have black hole analogues? These guys say we can't have perpetual motion machines, we can't have event horizons, but we can get Hawking radiation (http://arxiv.org/abs/gr-qc/0607008).

 

[Frame Dragger]

As I understand, Jacobson's idea (http://arxiv.org/abs/0804.2720) isn't relevant in standard GR or QFT on curved spacetime since those are have local Lorentz invariance.

People have suggested that there should be analogues of black holes in condensed matter systems, and that we should be able to detect Hawking radiation from them. But many of these suggestions don't have Lorentz invariance, so does that mean that we can have perpetual motion machines or that we can't have black hole analogues? These guys say we can't have perpetual motion machines, we can't have event horizons, but we can get Hawking radiation (http://arxiv.org/abs/gr-qc/0607008).

This is why, when I start talking about this kind of thing with friends who are NOT interested in theoretical physics, they walk away with their eyes rolling.

I don't know... and I don't know that anyone does for sure. GR and QM alone can only describe a BH to a certain extent... mostly up to the EH. To be honest however, even the exact flows in the accretion disk have only been partially modeled. I wouldn't assume that BHs are PMMs, violate Unitarity, or crush matter out of existence at a singularity before the math advances, or an analgoue DOES produce confirmatory evidene of an existing theory.

After all, what happens beyond the EH, stays beyond the EH for any external observer, unless it's encoded on the EH... *head hurts*.

If a BH loses mass through periods of NOT accreting, and emitting HR, to the point of eventual destruction (whatever form that takes) I fail to see how they can be perpetual motion machines, even in theory. They require angular momentum from their original collapsing body, or from infalling matter to rotate, and without infalling matter they slowly shrink and "get hotter". Seems like a strange thermodynamic process (or analogue thereof), but it seems limited.

 

[sezw]

i think if they gave obama a peace prize for continuing a war they should definitely give hawkins a nobel physics award

 

[mgb_phys]

i think if they gave obama a peace prize for continuing a war they should definitely give hawkins a nobel physics award

Sorry - is that supposed to make sense?
If they gave Halle Berry the oscar for the worst Bond movie in history - they should give Terry Pratchett the Booker prize for Good Omens.

 

[Frame Dragger]

Sorry - is that supposed to make sense?
If they gave Halle Berry the oscar for the history's worst Bond movie they should give Terry Pratchett the Booker prize for Good Omens.

1.) HAHAHAHAHHAAHA

2.) I think perhaps he doesn't grasp the division between one prize awarded by politicians, and the other which is awarded by academicians.

3.) That is a warped sense of parity indeed.

 

[JesseM]

I'm going to go out on a limb here and assume that Phrak is aware of current imaging studies of (commonly accepted, by me as well) BHs. I think he's positing that something other than a singularity enshrouded by an event horizon is causing polar jets, and accretion discs.

But is he positing that this would be possible in GR, or is he positing that GR is incorrect even in the classical limit? I think they've shown that, based on the mass of the objects inferred from orbiting stars and the maximum possible radius inferred from the radius at which the stars closest to them are orbiting, that they are definitely over the Schwarzschild limit, so according to GR there doesn't seem to be any way to escape the conclusion that they're black holes and not just really dense quark stars or whatever...

 

[Frame Dragger]

But is he positing that this would be possible in GR, or is he positing that GR is incorrect even in the classical limit? I think they've shown that, based on the mass of the objects inferred from orbiting stars and the maximum possible radius inferred from the radius at which the stars closest to them are orbiting, that they are definitely over the Schwarzschild limit, so according to GR there doesn't seem to be any way to escape the conclusion that they're black holes and not just really dense quark stars or whatever...

I agree, but presumably he's making an argument for something outside of GR. If we ignore "small" cases, there is no explaining M87's disc and jets, apparent mass and so forth unless it IS something massive within its own Schwarzschild Radius. That being the case, there will be an EH, and what is beyond that is beyond US.

 

[Phrak]

Do you think it's delusional to think general relativity is probably correct at far lower energy densities than the Planck scale, and thus that its theoretical predictions about collapsing stars becoming black holes are very likely to be correct too? Or do you think that, even given the assumption that GR is correct on a theoretical level, it's delusional to think that various astronomical objects which appear to fit the profile for what GR would predict about black holes (like this one, which does have what seems to be an accretion disc and jets in photos...likewise, see here and here for photos of a jet from the center of M87 which is believed to contain a supermassive black hole) are in fact black holes?

How long does it take for a black hole to form? How long does it take for its mass to increase? What is the age of the universe? What is the theoretical justification for claiming accreation disks, jets, and other evidence of black holes are not also evidence of pre-collapsed dense masses?

 

[Frame Dragger]

How long does it take for a black hole to form? How long does it take for its mass to increase? What is the age of the universe? What is the theoretical justification for claiming accreation disks, jets, and other evidence of black holes are not also evidence of pre-collapsed dense masses?

A googleplex, a snifter of brandy, 42, Chocolate covered raisins, airplane's have them, Shchwarzschild metric, Kerr metric and billions of solar masses in a tiny tiny area. Wait... did I get serious at the end there? I meant... pudding.

 

[JesseM]

How long does it take for a black hole to form? How long does it take for its mass to increase? What is the age of the universe? What is the theoretical justification for claiming accreation disks, jets, and other evidence of black holes are not also evidence of pre-collapsed dense masses?

Could you answer my question about whether you are willing to accept the likelihood that GR (plus quantum field theory on curved spacetime, perhaps) is correct when dealing with energy densities far below the Planck scale? In the context of GR your questions about black holes should all have well-defined answers, but perhaps you are questioning the validity of GR itself? Or maybe you accept GR, but wish to use a coordinate system (like Schwarzschild coordinates) where it takes an infinite coordinate time for a collapsing star to actually reach the Schwarzschild limit? (if the latter, note that all coordinate systems are equally valid in GR and there are plenty of coordinate systems where you can cross the event horizon in finite time, and any particle in the star will cross the horizon in finite proper time regardless of what coordinate system you choose)

 

[Phrak]

Could you answer my question about whether you are willing to accept the likelihood that GR (plus quantum field theory on curved spacetime, perhaps) is correct when dealing with energy densities far below the Planck scale? In the context of GR your questions about black holes should all have well-defined answers, but perhaps you are questioning the validity of GR itself?

No, I am not questioning general relativity. I'm mystified as to why you are asking the set of questions you are, but in any case...

Or maybe you accept GR, but wish to use a coordinate system (like Schwarzschild coordinates) where it takes an infinite coordinate time for a collapsing star to actually reach the Schwarzschild limit? (if the latter, note that all coordinate systems are equally valid in GR and there are plenty of coordinate systems where you can cross the event horizon in finite time, and any particle in the star will cross the horizon in finite proper time regardless of what coordinate system you choose)

But not all coordinate systems are applicable. Schwarzschild coordinates are applicable to good approximation. Our clocks and telescopes are attached to the Earth or Sun system. Populate the universe with clocks and dense objects. Not one clock will record formation of an event horizon.

..in GR and there are plenty of coordinate systems where you can cross the event horizon in finite time..

Yes...relative to another coordinate system containing the the coordinate singularity--assuming we have a black hole to start with. But this is putting the horse before the cart. The infalling clock has no event horizon to cross.

Let's assume one of your infalling coordinate systems and that the Earth is falling into a massive object. The massive object will not form an event horizon. Where are the applicable coordinate systems where we can say "lookie here. This is a picture of an accreation disk of a black hole."


I believe I've answered your questions. Will you answer mine?

 

[JesseM]

But not all coordinate systems are applicable. Schwarzschild coordinates are applicable to good approximation.

"Applicable" to what?

Our clocks and telescopes are attached to the Earth or Sun system. Populate the universe with clocks and dense objects. Not one clock will record formation of an event horizon.

What do you mean by "record formation"? Receiving light from an event on the horizon? In this case, the only clocks that will do so will be ones that cross the horizon themselves, but I don't see the problem with that.

Yes...relative to another coordinate system containing the the coordinate singularity--assuming we have a black hole to start with. But this is putting the horse before the cart. The infalling clock has no event horizon to cross.

Do you argue that because outside observers never see infalling clocks reach some finite proper time T, that implies an observer traveling with the clock would never see it reach T or beyond?

If so, someone could make the same sort of argument about the Rindler horizon, since after all, an accelerating observer who remains outside the horizon (like one of the ones at fixed coordinate position in Rindler coordinates) will never see anything cross it, the only way to see light from an event on the Rindler horizon is to cross the horizon yourself (which should not be too surprising, since from the perspective of an inertial frame the 'Rindler horizon' is just one edge of a future light cone). Note that the relationship between Rindler coordinates (where the Rindler horizon is at fixed coordinate position and it takes an infinite coordinate time to reach it) and inertial coordinates (where the horizon is moving outward at the speed of light and can be crossed in finite time) is very closely analogous to the relationship between Schwarzschild coordinates and Kruskal-Szekeres coordinates (where the event horizon expands outward at the speed of light). So if some accelerating observer who remained forever outside the Rindler horizon seriously argued that worldlines simply "end" before reaching the proper time T where they are supposed to cross it, what would your response be? I don't see how your position is any less implausible.

Let's assume one of your infalling coordinate systems and that the Earth is falling into a massive object. The massive object will not form an event horizon.

Why do you say that? It would certainly form an event horizon in finite time in Kruskal-Szekeres coordinates, to name one. On the right side of this diagram from the Gravitation textbook by Misner/Thorne/Wheeler, you can see a collapsing star in KS coordinates, the gray area representing the interior and the black curve representing the surface, with the event horizon as the line at a 45 degree angle labeled r=2M, t=infinity (the label referring to Schwarzschild coordinates):

Where are the applicable coordinate systems where we can say "lookie here. This is a picture of an accreation disk of a black hole."

What would a coordinate system have to do with a picture? A photo isn't "native" to any particular coordinate system.

I believe I've answered your questions. Will you answer mine?

Q: How long does it take for a black hole to form?
A: Too vague. Depends if you are talking about coordinate time in some system, or proper time of some clock...and of course it also depends on physical specifics like the mass of the black hole, the point of the collapse you want to start counting down from, etc.

Q: How long does it take for its mass to increase?
A: You mean, when a new object falls in? I don't think there's any well-defined way to measure the "mass" of an extended object in a coordinate-independent way, so this would presumably depend on your choice of coordinate system too, and how you define "mass" (see this page on the difficulty in defining 'energy' in GR in a non-local sense, since mass and energy are equivalent the problems should be the same)

Q: What is the age of the universe?
A: Again depends on what coordinate system/clock you use, but the most common definition uses a coordinate system whose definition of simultaneity is such that the universe's density is about the same everywhere at a give coordinate time (the average rest frame of the cosmic microwave background radiation), and whose time coordinate matches up with the proper time of a clock that remains at rest in this system. In this case the universe's age since the Big Bang is estimated at 13.7 billion years.

Q: What is the theoretical justification for claiming accreation disks, jets, and other evidence of black holes are not also evidence of pre-collapsed dense masses?
A: Because as long as you accept GR, and you accept the principle of "geodesic completeness" which says geodesics shouldn't just "stop" at some finite proper time when it's possible to extend the spacetime manifold in a way that allows them to continue and which respects the Einstein Field Equations everywhere, then for a sufficiently massive object collapsed below a certain radius, it can be proved that an event horizon must form and that whatever's inside cannot be a stable dense mass but will collapse into a singularity (that's what the singularity theorems mentioned at the start of the thread are all about).

 

[atyy]

Where are the applicable coordinate systems where we can say "lookie here. This is a picture of an accreation disk of a black hole."

Without jumping through the horizon, the closest I've seen is to try to verify that the metric is the Kerr metric close to the event horizon "Gravitational waves would probe nonlinear gravity and could reveal small corrections, such as extra long-range fields that arise in unified theories, deviations of the metric around massive black holes from the Kerr solution ..." http://arxiv.org/abs/0903.0100

 

[Altabeh]

If a BH loses mass through periods of NOT accreting, and emitting HR, to the point of eventual destruction (whatever form that takes) I fail to see how they can be perpetual motion machines, even in theory. They require angular momentum from their original collapsing body, or from infalling matter to rotate, and without infalling matter they slowly shrink and "get hotter". Seems like a strange thermodynamic process (or analogue thereof), but it seems limited.

It is limited and Kerr BHs can't get so much faster in their rotation than a limit of 1/72 of their total angular momentum. Don't ask how I got this limit (it is going to be explained in my PHD thesis.). So I'd guess the PMM stuff is way beyond being even wrong to believe in it!

AB

 

[Frame Dragger]

It is limited and Kerr BHs can't get so much faster in their rotation than a limit of 1/72 of their total angular momentum. Don't ask how I got this limit (it is going to be explained in my PHD thesis.). So I'd guess the PMM stuff is way beyond being even wrong to believe in it!

AB

Well, if a Kerr BH did rotate faster, it wouldn't have an EH anymore... or am I thinking of another solutioon. Anyway, thanks very much, I never really considered before this thread that a BHH in any way could be a PMM. I look forward to your thesis btw; good luck and soon(realtively speaking of course)-to-be congratulations.

 

[Altabeh]

Well, if a Kerr BH did rotate faster, it wouldn't have an EH anymore... or am I thinking of another solutioon. Anyway, thanks very much, I never really considered before this thread that a BHH in any way could be a PMM. I look forward to your thesis btw; good luck and soon(realtively speaking of course)-to-be congratulations.

Thank you so much. Actually my work itself makes use of Bondi mass as an infalling matter, so the BH would lose mass and therefore it would get smaller in its size but not motionless at all, but the Penrose process on the other hand gets involved to not let this happen because according to Penrose, in any case except BHs with accretion disks, the angular momentum of infalling particles decreases the total angular momentum of BH which itself is limited by the fact(?) that HR carries away angular momentum by the emission of rotating particles so it's going to make BH stop rotating. Here to have a PMM we need to know Penrose process is less happening than mine in a Kerr BH without an accretion disk. But the important thing is that in case of accretion disks, both make a BH rotate perpetually which only is possible if HR does not exist or it occurs so much slower than PP or my own process!

AB

 

[Frame Dragger]

Thank you so much. Actually my work itself makes use of Bondi mass as an infalling matter, so the BH would lose mass and therefore it would get smaller in its size but not motionless at all, but the Penrose process on the other hand gets involved to not let this happen because according to Penrose, in any case except BHs with accretion disks, the angular momentum of infalling particles decreases the total angular momentum of BH which itself is limited by the fact(?) that HR carries away angular momentum by the emission of rotating particles so it's going to make BH stop rotating. Here to have a PMM we need to know Penrose process is less happening than mine in a Kerr BH without an accretion disk. But the important thing is that in case of accretion disks, both make a BH rotate perpetually which only is possible if HR does not exist or it occurs so much slower than PP or my own process!

AB

Elegant, I love it. Makes perfect sense too, and next to rotational frame dragging, the Penrose process is my personal favourite!

 

[Phrak]

"Applicable" to what?

What do you mean by "record formation"? Receiving light from an event on the horizon? In this case, the only clocks that will do so will be ones that cross the horizon themselves, but I don't see the problem with that.

Do you argue that because outside observers never see infalling clocks reach some finite proper time T, that implies an observer traveling with the clock would never see it reach T or beyond?

If so, someone could make the same sort of argument about the Rindler horizon, since after all, an accelerating observer who remains outside the horizon (like one of the ones at fixed coordinate position in Rindler coordinates) will never see anything cross it, the only way to see light from an event on the Rindler horizon is to cross the horizon yourself (which should not be too surprising, since from the perspective of an inertial frame the 'Rindler horizon' is just one edge of a future light cone). Note that the relationship between Rindler coordinates (where the Rindler horizon is at fixed coordinate position and it takes an infinite coordinate time to reach it) and inertial coordinates (where the horizon is moving outward at the speed of light and can be crossed in finite time) is very closely analogous to the relationship between Schwarzschild coordinates and Kruskal-Szekeres coordinates (where the event horizon expands outward at the speed of light). So if some accelerating observer who remained forever outside the Rindler horizon seriously argued that worldlines simply "end" before reaching the proper time T where they are supposed to cross it, what would your response be? I don't see how your position is any less implausible.

Why do you say that? It would certainly form an event horizon in finite time in Kruskal-Szekeres coordinates, to name one. On the right side of this diagram from the Gravitation textbook by Misner/Thorne/Wheeler, you can see a collapsing star in KS coordinates, the gray area representing the interior and the black curve representing the surface, with the event horizon as the line at a 45 degree angle labeled r=2M, t=infinity (the label referring to Schwarzschild coordinates):

What would a coordinate system have to do with a picture? A photo isn't "native" to any particular coordinate system.

Q: How long does it take for a black hole to form?
A: Too vague. Depends if you are talking about coordinate time in some system, or proper time of some clock...and of course it also depends on physical specifics like the mass of the black hole, the point of the collapse you want to start counting down from, etc.

Q: How long does it take for its mass to increase?
A: You mean, when a new object falls in? I don't think there's any well-defined way to measure the "mass" of an extended object in a coordinate-independent way, so this would presumably depend on your choice of coordinate system too, and how you define "mass" (see this page on the difficulty in defining 'energy' in GR in a non-local sense, since mass and energy are equivalent the problems should be the same)

Q: What is the age of the universe?
A: Again depends on what coordinate system/clock you use, but the most common definition uses a coordinate system whose definition of simultaneity is such that the universe's density is about the same everywhere at a give coordinate time (the average rest frame of the cosmic microwave background radiation), and whose time coordinate matches up with the proper time of a clock that remains at rest in this system. In this case the universe's age since the Big Bang is estimated at 13.7 billion years.

Q: What is the theoretical justification for claiming accreation disks, jets, and other evidence of black holes are not also evidence of pre-collapsed dense masses?
A: Because as long as you accept GR, and you accept the principle of "geodesic completeness" which says geodesics shouldn't just "stop" at some finite proper time when it's possible to extend the spacetime manifold in a way that allows them to continue and which respects the Einstein Field Equations everywhere, then for a sufficiently massive object collapsed below a certain radius, it can be proved that an event horizon must form and that whatever's inside cannot be a stable dense mass but will collapse into a singularity (that's what the singularity theorems mentioned at the start of the thread are all about).

This is going nowhere but devolving into debate. My fault of course. I did kick it off accusations of delusional beliefs. I do appreciate the response very much however, as I haven't gotten any action on this forum, on this matter without kicking the sacred cow. When I get over a full schedule of real work, moonlighting, and all-important down time, I want to post some assertions in the venue of objective science that I hope you can tear into with equal objectivity.

 

[JesseM]

This is going nowhere but devolving into debate. My fault of course. I did kick it off accusations of delusional beliefs. I do appreciate the response very much however, as I haven't gotten any action on this forum, on this matter without kicking the sacred cow. When I get over a full schedule of real work, moonlighting, and all-important down time, I want to post some assertions in the venue of objective science that I hope you can tear into with equal objectivity.

No problem, if you want to start the discussion again later when you have more time, send me a message to let me know (I haven't been hanging out on this forum as much lately so I miss a lot of threads).