Naked singularity

wolram

From Wikipidia
In general relativity, a naked singularity is a gravitational singularity without an event horizon. The singularities inside black holes are always surrounded by an area which does not allow light to escape, and therefore cannot be directly observed. A naked singularity, by contrast, is a point in space where the density is infinite and which is observable from the outside.
The theoretical existence of naked singularities is important because their existence would mean that it would be possible to observe the collapse of an object to infinite density.
Computer simulations of the collapse of a disk of dust have indicated that these objects can exist, and thus the Cosmic censorship principle (stating that singularities are always hidden) does not hold. Stephen Hawking lost a bet about this question.
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From this a BH is only termed Black because of the event horizon
hiding it, and a naked singularity would be observable, as it seems
that science does not rule out the naked singularity, why do all the
observed phenomena have event horizons?

Chronos

Hawking conceded the bet to Thorne based on a theoretical technicality, which allows for the existence of a naked singularity. But these solutions are highly unstable. It cannot actually occur in the physical universe.

wolram

Chronos
Hawking conceded the bet to Thorne based on a theoretical technicality, which allows for the existence of a naked singularity. But these solutions are highly unstable. It cannot actually occur in the physical universe.
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I have read somewhere that a naked singularity is not possible in our
universe, but i have forgotten the facts, google dosent come up with
much either, what was the technicality?

Chronos

The tiniest disturbance - like the presence of other matter in the universe - will scare it into throwing on some clothes.

wolram

Chronos
Pleases give some referance.

Chronos

About the bet:
http://www.theory.caltech.edu/people...bet_story.html

Here is some technical discussion
Testing Cosmic Censorship in Kerr-like Collapse Situations
http://arxiv.org/abs/gr-qc/9710022

You can also google for the hoop conjecture.

wolram

Thanks Chronos.

Garth

The Big Bang is the naked singularity!

Garth

Chronos

Indeed, but not a gravitational singularity.

brightstar2005

the appeance of singularity indicates that something
is fundamentally wrong

ctrebor

Einstein said when he was confronted with the notion of a singularity existing within a black hole that, should a singularity exist it would twist all of spacetime up within itself and therefore it could'nt be true that singularities existed within black holes.

Einstein was right, singularities don't "exist" within black holes- instead a singularity is the consequence of a black hole and is "reached" through the black hole as part of the eventual collapse of the space-time structure of our universe. The singularity will only "exist" at the end of time- in fact beyond time itself, as the singularity which generated the Big Bang existed before time began. "Exist" is only a tentative word in this context... If one could look at our multidimensional universe from outside it is possible to conceive of the Singularity actually being at the "centre" of the universe and to be BOTH the source and the destination Singularity, "causing" the Big Bang and the Big Crunch, and the phenomenon of the accelerating rate of expansion of the universe.

Garth

If the Big Bang isn't a gravitational singularity then I don't know what is!

Is isn't a Schwarzschild solution singularity, but the density, pressure, temperatue and curvature as t -> 0 all become singular.

Garth

turbo-1

Indeed! Now if someone can please explain how that infinitely massive, dense, curved singularity decided to cut loose..... A simple black hole of any significant mass cannot hope to evaporate in the life of the universe, but that singularity somehow exploded at faster than light speed - or did it?

Bobster

Hmmm..interesting

JesseM

The big bang singularity is different from a black hole singularity, GR doesn't say there was a singularity sitting in a particular location in some preexisting space which exploded outward (although something like that is technically allowed by GR, it's called a 'white hole'), it says that all of space expanded from state of infinite density.

owl3951

If the pea instanton theory is correct, and I realize that is an "if," then the mass of the original singularity was about that of a pea.

However, what I wonder is, since the theory cannot account for the pre-existence (before the Bang) of the laws of our universe, how do we know the original Bang was not repeated, perhaps repeatedly? If the laws existed from the beginning, and it was inevitable that those laws would result in a pea instanton, then those same laws, continuing to exist in imaginary time, could have repeatedly created pea instantons.

Since the pea instanton theory would result in a total mass about 30 orders of magnitude under what appears to be the current mass of the universe, if 30 Bangs happened, as each shock wave "caught up" with the expanding universe, those shock waves would periodically increase universal inflation.

Of course, this would mean that conservation applied only to existing matter and energy. New matter and energy would result from each Bang.

Also, repeated Bangs may not affect this universe at all. They may create additional universes, all apparently with the same laws of physics our universe has.

So I guess this is sort of my vague objection to the pea instanton theory, at least until theory can account for the pre-existence of physical law. It seems no matter how hard Hawking tries, he eventually ends up begging the First Cause question. It is incredibly exciting, however, to watch him pursue this entire issue. What a mind!