Why do scientists believe white holes are impossible?

[Phrak]

But as long as you're looking for reasons, here's the big one: gravity is a one-way force. There is no counterpart to it.

But you've got it wrong. Gravitional force is time-evolution symmetric. As much as theory admits black holes, it admits white holes. It really does become a question of entropy, where we should ask, how should the observed entropy of the universe find correlation with white holes/blackholes?

 

[Dmitry67]

Schwarzschild is just an idealization for the eternal flat spacetime around an object.
Realistic solution depends on the consmological model (open, closed universes).
So white holes are not compatible with Big Bang consmology.

 

[Phrak]

Schwarzschild is just an idealization for the eternal flat spacetime around an object.
Realistic solution depends on the consmological model (open, closed universes).
So white holes are not compatible with Big Bang consmology.

Then neither are black holes. Replace t with -t in the schwarzschild solution, and you have replaced a black hole with a white hole.

 

[Dmitry67]

The difference is (in the open universe) that we have only 13 billion years of the time BEFORE today but the eternity AFTER. So our position in time is very asymmetric. So you can't just change the sign of t

 

[stevebd1]

If I read Hawking's original papers, 30 years ago, he wrote there that for all purpose white holes would be indistinguishable from black holes, at least for an outside observer. The rate of matter "evaporation" from a white all is identical to the rate of radiation from a black hole. I stress again, in the original papers of Hawking 30 years ago, I don't know about now. So from this point of view, there is no more or no less observational evidence for white or black holes !

Hypothetically, an over-extremal rotating 'black' hole would behave like a white hole based on-

$$\kappa_\pm=\frac{r_+-r_-}{2(r_\pm^2+a^2)}$$

where $\kappa_\pm$ is the Killing surface gravity at the outer (r₊) and inner (r_-) event horizon where-

$$r_\pm=M\pm\sqrt{M^2-a^2}$$

where M=Gm/c² and a=J/mc

The inner and outer event horizons would disappear (the coordinate radii would technically swap places) and $\kappa_\pm$ would become negative if a>M. While there is a mechanism in place for the formation of black holes (where a<M), there isn't one for the over-extremal solution. Either they would have had to have always existed or there is a mechanism as yet unknown (the notion of http://www.sciam.com/article.cfm?id=naked-singularities" seems to have made a recent reappearance). Also, it would be interesting to see how temperature and entropy would fit into such a solution.

 

[Dmitry67]

P.S. Phrak
But of course, I agree with you, in the 'closed' universe for example, the solution is different because the big cranch would affect the black hole. The same is true for the Big Rip.

stevebd1,
Super-extreme black holes! My favourite subject!
I really like closed time-like loops around them!
I don't understand why people are so afraid of such things.
Do you have any interesting links about the naked singularities? I mean, it is hard to believe that you can not convert underextreme black hole into a superextreme one by throwing matter at proper angles inside.

 

[stevebd1]

It's a slightly old paper but it has an interesting proposal that from within the inner event horizon, the Cauchy horizon would have properties similar to that of a white hole (i.e. you may be in time like space but if you were to try and push back through the Cauchy horizon, you would be repelled). It also has an alternative proposal to calculating the entropy of a spinning black hole which would imply S=0 at a/M=1, apparently complying with Nernst theorem.

'Entropy of Kerr-Newman Black Hole Continuously Goes to Zero when the Hole Changes from Nonextreme Case to Extreme Case' by ZHAO Zheng, ZHU Jian-yang and LIU Wen-biao
http://cpl.iphy.ac.cn/qikan/manage/wenzhang/0160698.pdf

Abstract: 'A new formulation of the Bekenstein-Smarr formula of a Kerr-Newman black hole is given. The re-defined black hole entropy continuously goes to zero as the black hole temperature approaches absolute zero, which satisfies the Nernst theorem. Our new result suggests that the Kerr-Newman black hole should be regarded as a composite thermodynamic system composed of two sub-systems, its outer horizon and its inner horizon. There exists a new quantum thermal effect, "Hawking absorption", near the inner horizon of the black hole.'

This paper proposes something similar regarding entropy-

'Black Holes, Entropy and the Third Law' by A. J. Meyer, II
http://arxiv.org/abs/physics/0608080

 

[Dmitry67]

Thank you, will read!

Also, could you tell me if my recipe is right:

1. take two almost extreme BH
2. rotating on the same axis, same direction
3. If you merge them together (when they approach each other from the poles), the result is also an almost-extreme heavier BH
4. But if they approach each other so they are not only rotating, but also rotating around each other, then the additional momentum makes the final BH super-extreme - guaranteed.

 

[stevebd1]

4. But if they approach each other so they are not only rotating, but also rotating around each other, then the additional momentum makes the final BH super-extreme - guaranteed.

Earths orbit reduces the rotation of the sun, the same applies to the moon and Earth. If you had two black holes with high angular momentum encounter each other, their individual spin would reduce while the angular momentum of their combined orbit would increase and they would become tidally locked before combining to create a larger black hole but the sum of the overall angular momentum would remain approx. the same (if anything it would probably reduce marginally).

EDIT:
The difference in the before and after angular momentum would probably be radiated as gravitational waves.

 

[Dmitry67]

Yes, because Sun ratates much faster then Earth around it.

But anyway I was wrong: for a BH to be extreme, angular momentum must be proportional to a square of mass.

So if we take 2 extreme BH (J=M)
Merge them J+J=2J, M+M=2M
the result is an underextreme BH: 2J<4M

 

[Ultrastar 1]

You are offering a solution for which there is no problem. White holes don't exist for the same reason unicorns don't exist.


But as long as you're looking for reasons, here's the big one: gravity is a one-way force. There is no counterpart to it.

You know what? The last time I looked, this is an astrophysics fourm meaning that anything of scientific interest can be dicussed here. If you object my theory, that is fine, but next time give me a valid answer for why white holes do not exist.

 

[Ultrastar 1]

It would bo cool to see if they do exist. you are right theoreticaly they do not. but where do the black holes go? maybe a new universe. maybe that is what we call the big bang. new material from another universe.

No. I can assure you that the big bang was not material form another unviverse. I believe in the multiverse theory, but I don't think that the material came from another unverse. Here is why: the mutiverse theory of quantom physics says that there is a huge number of parallel universes, and that anything that can happen, will happen. Well, what are the odds that an inter-demnsional bridge just came into our universe, and caused the big bang? One in millions. Also, to answer your question, "where do black holes go?" Well, they go pertty much nowhere. The gavitational energy that sucks in matter and light ito the black hole is always circulating around the core of the collapesed star. And I think that this is so because this circulation is responsable for rotating the accrettion disk due to the angular momentom produced. So, the bottom line: black holes go nowhere.

 

[cristo]

You know what? The last time I looked, this is an astrophysics fourm meaning that anything of scientific interest can be dicussed here. If you object my theory, that is fine, but next time give me a valid answer for why white holes do not exist.

First, a warning for you (and others) to read the PF rules pertaining to overly speculative posts. This thread will be kept on a tight leash, but I'll leave it open for now.

Here is why: the mutiverse theory of quantom physics says that there is a huge number of parallel universes, and that anything that can happen, will happen. Well, what are the odds that an inter-demnsional bridge just came into our universe, and caused the big bang? One in millions.

Why are the odds "one in millions"? This is the fundamental flaw with multiverse theory: you cannot say anything about probability when the only universe you can observe is this one. Furthermore, you're not even using your observations, you're just speculating and throwing numbers about. What justification do you have for being able to do this? And how do you know that this "inter-universe bridge" doesn't occur in this and every universe?

 

[Solistics]

Couldn't you consider the big bang as a white hole? where mater just comes spilling out at a single moment.

 

[DaveC426913]

Couldn't you consider the big bang as a white hole? where mater just comes spilling out at a single moment.

No. That is not at all how the Big Bang happened. For starters, there was no matter in the BB. Matter couldn't even condense until well after it had expanded and cooled.

 

[Solistics]

than what came out the bb?

something had to come out of it in order to create the universe.

 

[Chronos]

Pure energy emerged from the 'big event', by science as we know it. The first 'particles' were unable to condense until about 3 minutes thereafter.

 

[Archosaur]

keep in mind that the bb singularity wasn't a point in space. It was space. Nothing came out of it. There was no "out of it". It expanded faster than you can imagine.

 

[Ultrastar 1]

Im not exactly sure what they are but I will try to find out. (Ring or kerr singularities.)

 

[Ultrastar 1]

Ok. Enough with the math. I prefer if you only contributed theories and ideas. No math please. That goes for everyone.

 

[Ultrastar 1]

Then neither are black holes. Replace t with -t in the schwarzschild solution, and you have replaced a black hole with a white hole.

The soultion does not apply in this case. The schwarzschild wormhole has shown to be unstable. Therefore, it cannot transport matter from a black hole to a white hole.

 

[Ultrastar 1]

We are getting way off topic. What does the Earth's orbit have to do with white holes? This thread is for white holes and black holes only. Nothing else.

 

[Ultrastar 1]

P.S. Phrak
But of course, I agree with you, in the 'closed' universe for example, the solution is different because the big cranch would affect the black hole. The same is true for the Big Rip.

stevebd1,
Super-extreme black holes! My favourite subject!
I really like closed time-like loops around them!
I don't understand why people are so afraid of such things.
Do you have any interesting links about the naked singularities? I mean, it is hard to believe that you can not convert underextreme black hole into a superextreme one by throwing matter at proper angles inside.

Super extreme black hloles have nothing to with white holes. Plz stay on topic.

 

[Mr. Paradox]

But you have to admit that super extreme black holes are really cool

 

[DaveC426913]

But you have to admit that super extreme black holes are really cool

Well if they're really cool, then super-duper-mega-zowee black holes are ultra-hip-boffo cool.

Or are super extreme black holes something real? Reference?

 

[Ultrastar 1]

Well if they're really cool, then super-duper-mega-zowee black holes are ultra-hip-boffo cool.

Or are super extreme black holes something real? Reference?

Good point. But still super black holes have nothing to do with this thread.

 

[Ultrastar 1]

But you have to admit that super extreme black holes are really cool

Well, I think that super black holes are an interesting subject, but they do not belong here.

 

[Archosaur]

super extreme = super massive = super?

 

[Archosaur]

Also, I propose the addition of "super nifty" black holes to the black hole family.

 

[Vanadium 50]

You know what? The last time I looked, this is an astrophysics fourm meaning that anything of scientific interest can be dicussed here

I prefer if you only contributed theories and ideas. No math please. That goes for everyone.

Well, I think that super black holes are an interesting subject, but they do not belong here.

I think it's best to leave the decision of what does and does not belong here to the mods. After all, it's their job.