# Discovery of New Blackholes

1. Oct 26, 2007

### riverkee

I am going to ask some questions based on my curiosity and my complete lack of knowledge and understanding of the Universe. My biggest hope is those answering can be understanding and patient, and not see it as an opportunity to to be arrogant.

Are wormholes still a possible theory of what lies at the end of black holes? If so, would that matter sucked into the black holes be scattered throughout our own universe and/or others? Could the matter from a galaxy billions of light years away, whose light we only see now, and has long disappeared, been the makings for own solar system or galaxy?

If this is so, is it possible the total matter in the Universe, as we see it, is slightly less than perceived as it sort of recycles from one point in Universe to another leaving only light ahead of it's present?

Curious question from a curious guy.

2. Oct 26, 2007

### Chris Hillman

Probably not. Well, it depends. Actually, it's hard to say

You sound a bit defensive--- I hope that is not based upon experience at PF (I see this is your first post here, at least under the handle "riverkee")!

Information about what books you've read would be more useful than a disclaimer of all knowledge. I'll try to take a stab at your questions on the assumption that you've read some popular science books, but please do not mistake my attempts to informally convey some sense of numerous subtle issues for "arrogance". Your questions appear to involve many difficult points which cannot be truly explained without considerable mathematical machinery and prior mastery of much background material. I'm trying to answer as best I can without saying anything which is terribly misleading.

(Yah, now I sound defensive! )

It depends upon what you mean by "wormhole".

1. The hypothetical objects known as "stable wormholes", which would maintain long-lived "shortcuts" to distant locations , have never risen beyond the level of a theoretical speculation not supported by convincing evidence, in fact a speculation which many (but not all) physicists regard as theoretically dubious for a variety of reasons.

2. The first "wormhole" discussed in theoretical physics was the so-called "Einstein-Rosen bridge", an old name for what is now called the "throat" of the "maximal analytic extension of the Schwarzschild vacuum", a spacetime used to model a highly idealized nonrotating black hole, nowadays often called the "eternal Schwarzschild vacuum" model. It turns out that while in this model the throat does in some sense connect two universes, it pinches off too rapidly for an astronaut to get through. More important, this "eternal" model is physically implausible; more reasonable models of nonrotating black holes depict black holes formed by gravitational collapse of a star, e.g. the "Oppenheimer-Snyder model". These models have a different "conformal structure" once one passes through the event horizon; their internal structure does not feature throats.

3. Similarly, the most idealized models of charged black holes ("eternal Reissner-Nordstrom electrovacuum"), uncharged but rotating black holes ("eternal Kerr vacuum", and rotating charged holes ("eternal Kerr-Newman electrovacuum") have throats, but in theory the throats in "eternal Kerr-Newman electrovacuum" would not pinch off. However, it turns out that once again these models are not plausible once when passes through the even horizon. More realistic models are believed not to have throats, although it seems they might feature a "weak null singularity" in addition to a "strong spacelike singularity", and it is possible that objects which fall into a real hole and which miss the strong singularity might pass through the weak singularity unharmed. Unfortunately, gtr itself declares its inabilty to predict what might happen after that! Before you ask, it is not clear that any of the speculative theories being discussed in connection with quantum gravity would resolve the question, although there appears to be room for hope that this might happen should a successful theory of quantum gravity ever appear.

No. At least, I think that is the best short answer based upon what we currently know about gtr.

There is a long-standing but so far untested prediction by Hawking which is goes outside the domain of gtr into quantum field theory, namely "Hawking radiation", which has led to the suggestion that black holes might very slowly "evaporate". There is controversy over what kind of "stuff" would "come out" in this process, but I think the best short answer is that this wouldn't be very much like restributing matter within our own universe.

The prediction of Hawking radiation is thought to be valid, but it is based upon a tricky approximation and it has not yet been directly supported by experiment or by observation. However, it is consistent with a body of notions called "black hole mechanics" which makes sense in the context of gtr, and has been more rigorously established. According to this, gravitation theories such as gtr should share some "thermodynamical" characteristics, and the most important characterization of a "black hole" should be "thermodynamical". An interesting program being pursued by several groups around the world seeks to lay the groundwork for "analogue black holes" which might one day result in a direct test of the prediction of Hawking radiation (and a Nobel Prize).

The issue of black evaporation (and the related information paradox) is far trickier than the prediction of Hawking radiation and IMO must still be regarded with caution. However, again, analog black holes might one day allow a direct test (another Nobel Prize).

Classically: perhaps, depending upon what gtr proves to say about the internal structure of realistic black hole models. This would then raise some philosophical difficulties about how one might test this even in principle (after falling through an event horizon, how would an intrepid explorer report his findings should he survive?)

In quantum gravity? Who knows? I think the safest brief characterization is that very little is yet known with confidence about what a successful theory of quantum gravity might look like, despite a great deal of work, in part because the theories so far explored are quite challenging, and in part because there is almost no clear experimental or observational evidence to guide theorists.

Via vanishing into black holes? And reappearing after a few billion years? I think the best short answer is almost certainly not. In particular, evaporation times for stellar mass black holes (if black holes do indeed evaporate) would be much longer than that!

You might be asking about "pre-Big Bang cosmology", another speculation which has been kicked about for some time. That depends upon yet another set of ideas, including Penrose's "Weyl curvature hypothesis" and "dark energy".

There is a notion of supernovae blowing out stellar material, which forms dust clouds and may be later recycled to make new stars, but this recycled matter would certainly not have been "inside" a black hole, not even if the collapsing core of the supernova forms a hole.

OK, your questions were pretty vague, so I think that's the best I can do towards vaguely (non)-answering them.

http://relativity.livingreviews.org/Articles/lrr-2006-3/index.html (review of tests of competing gravitation theories, e.g. gtr, Brans-Dicke)

http://relativity.livingreviews.org/Articles/lrr-2007-4/index.html (review of some of the available evidence bearing on cosmology, specifically that bearing on determination of cosmological distances and expansion rates)

http://www.arxiv.org/abs/gr-qc/0604102 (review of exact solutions of the EFE, including some discussion of the global structure of Kerr vacuum etc.)

http://relativity.livingreviews.org/Articles/lrr-2004-1/index.html (reviews conformal structure, although mostly focused on the regions very far away from black hole models, rather than "deep inside" them!)

http://relativity.livingreviews.org/Articles/lrr-2005-12/index.html (review of analog gravity)

http://www.arxiv.org/abs/0710.4474 (reviews speculations about hypothetical "traversable wormholes", hypothetical "time machines", and hypothetical "warp drives"; beware the authors abuse of terminology "solution"; according to him, any Lorentzian manifold is a solution of the EFE, which is dangerously close to claiming that gravitation theories are "vacuous by design")

http://www.arxiv.org/abs/0710.4919 (one flavor of speculation about hypothetical "pre-Big-Bang" epochs)

http://www.arxiv.org/abs/0710.2696 (speculation about hypothetical creation of traversable wormholes in the LHC)

Last edited: Oct 26, 2007
3. Oct 28, 2007

### Seele

True, it is a theoretical possibility that worm holes are the almost permanent resident inside some black holes, but certainty I don't believe that they exist within all black holes. A worm hole is more or less the complete collapse of space-time, being so warped by mass, it can do nothing more than collapse under the intense force of matter.

Though it is also true that black holes are in no way a permanent feature of the universe, they do, in fact, evaporate over a determined amount of time. This is caused by their slight temperature, and the correlation between energy and mass. Thus we can safely conclude on very solid grounds that over a period of time a black hole will radiate all of it's available mass, and simply disappear.

So from this I wouldn't necessarily conclude that mass scattering is in due to the consumption and scattering of material by black holes, it's just to rare of a process to have much significance.

4. Oct 28, 2007

### Chris Hillman

Careful!

Hi, Seele, for some reason you seem to have ostentatiously ignored several recent PF posts including Post #2 just above in which I tried to carefully warn against several serious misconceptions. This is disappointing.

It would be well to qualify that. See how I described what gtr says about various aspects of "black holes" in these PF posts (listed roughly in ascending chronological order, for my convenience in avoiding listing any post twice):
• [post=1165040]here[/post], comparing static observers in the Schwarzshild vacuum with Rindler observers in the Minkowski vacuum,
• [post=1165377]here[/post], about coordinate speeds and light cones in the Schwarzschild vacuum,
• [post=1165767]here[/post] about light bending and instability of the "circular photon orbit" at $r=3 m$ in the Schwarzschild vacuum,
• [post=1165784]here[/post] and [post=1173126]here[/post] about the interpretation of the Schwarschild radial coordinate (and comparing various distinct and operationally significant notions of "distance in the large"; see also [post=1165747]this[/post]),
• [post=1166525]here[/post] and [post=1174400]here[/post] about Kottler lambdavacuum (Schwarzschild with lambda) and an the stability of orbits,
• [post=1168221]here[/post], where I briefly describe the Aichelburg-Sexl ultraboost of a non-rotating black hole and its relation with pp-wave solutions,
• [post=1168311]here[/post] about "mass inflation" in the Poisson-Israel model of a black hole interior, and [post=1176876]here[/post] about black hole interiors generally,
• [post=1168389]here[/post], comparing various black hole models and mentioning the "teleological" nature of the event horizon,
• [post=1166597]here[/post] and [post=1168394]here[/post] about exact solutions of the EFE (which include the Schwarzschild vacuum, Kerr vacuum, OS dust ball, and other black models),
• [post=1172751]here[/post], [post=1172788]here[/post], [post=1176905]here[/post], [post=1165703]here[/post], and [post=1176891]here[/post] about varous common misconceptions concerning black holes,
• [post=1172563]here[/post] about the Oppenheimer-Snyder collapsing dust ball model,
• [post=1173087]here[/post] about closed timelike curves inside the "eternal Kerr vacuum" model,
• [post=1176675]here[/post] about the plausiblity of event horizons,
• [post=1178324]here[/post], [post=1209282]here[/post] and [post=1347429]here[/post] about the physical experience of various observers near/inside a black hole,
• [post=1179816]here[/post] about "quasi-Keplerian orbits" in the Schwarzschild vacuum,
• [post=1181763]here[/post] about "gravitational time dilation" near a black hole, and comparing de Sitter versus Lense-Thirring precession of the spin axes of gyroscopes in orbit around a (possibly rotating) black hole,
• [post=1193049]here[/post] about locally flat spatial hyperslices in the Schwarzschild vacuum,
• [post=1193952]here[/post] about comparing some coordinate charts on the Schwarzschild vacuum,
• [post=1204486]here[/post] about "tipping over of light cones" (e.g. in the Kerr vacuum as often it is often graphically represented in terms of the well-known Boyer-Lindquist chart),
• [post=1325023]here[/post] about stationary versus static spacetimes (e.g. Kerr versus Schwarzschild),
• [post=1331559]here[/post], about the "effective potential" governing geodesics in the exterior of the Schwarzschild vacuum,
• [post=1332546]here[/post] about the Vaidya null dust (which can be used to model the formation of a black hole due to the collapse of a spherically symmetric shell of incoherent EM radiation) and some other simple exact solutions with nonzero energy-momentum-stress tensors; see also [post=1181699]this[/post] about the form of the contribution of an EM field to the energy-momentum-stress tensor (e.g. in Reissner-Nordstrom or Kerr-Newman electrovacuum solutions),
• [post=1337471]here[/post] about gravitational waves from black hole mergers,
• [post=1341478]here[/post] about the optical appearance of a black hole to a nearby external observer,
• [post=1342096]here[/post] and [post=1172569]here[/post] about black hole mergers generally,
• [post=1350550]here[/post] about dropping a small object into a black hole,
• [post=1351759]here[/post] about "singularities" in gtr,
• [post=1165130]here[/post] and [post=1482542]here[/post] about gtr generally,
• [post=1484417]here[/post] about black holes versus "point masses",
• in my Post #2 above, comparing various features which have been called "wormholes" in the gtr literature (with greater or lesser accuracy and greater or lesser degrees of physical plausibility)
My point is that gtr is a subtle subject and as the posts to which I was responding in the posts I cited above show (IMO), failure to think and write very carefully inevitably leads to confusion and misconceptions.

I think you are talking about the throat of something like the "eternal Schwarzschild vacuum" solution, which pinches off before any particle can get through. The whole point of the (dubious) speculation about hypothetical "stable wormholes" is that these would be filled with mysterious "stuff" which would in principle hold the wormhole open indefinitely. One problem with such speculation is that the "stuff" required probably doesn't exist. The basic problem with the putatively stable throat(s) of something like the Reissner-Nordstrom electrovacuum is that it is unstable against small perturbations due to infalling matter or radiation. As I already mentioned.

As I already explained, such statements are theory dependent. The classical black hole concept is well established in the context of gtr, which in turn is one of the most highly tested theories devised so far. The notion of Hawking radiation is so far only a theoretical concept, one which goes outside gtr and which has not yet been tested experimentally, but nonetheless is generally believed to be true on theoretical grounds, even though the theoretical arguments for it involve approximations rather than any exact and well-tested theory (such as gtr). The notion of black hole evaporation is another theoretical concept which also goes outside gtr, is even less well established than the existence of Hawking radiation, and again has not been tested.

Solidity is in the eye of the beholder, obviously. I feel it is terribly misleading not to provide the context which I described above.

I really doubt the OP was asking about scattering by black holes

Last edited: Oct 28, 2007