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Author Topic: Does the singularity exist?  (Read 2022 times)

Offline Fluid_thinker

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Does the singularity exist?
« on: 25/07/2013 13:41:44 »
Does the shell theorum apply to Black Holes?

That is, as you approach the centre of a black holes more mass is behind you, than in front of you.

If so, isnt the singularity impossible?


 

Offline JP

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Re: Does the singularity exist?
« Reply #1 on: 25/07/2013 15:34:32 »
No, because a black hole isn't a shell of mass that's hollow inside.  All the mass is tightly concentrated at or near the singularity.

The singularity is probably impossible for other reasons.  We say singularity because the equations break down and predict that all the mass goes to a point (non-rotating) or ring (rotating) black holes.  This indicates the density of matter becomes infinite, which is probably not physically possible and probably means that the equations of general relativity don't work at that scale and have to be amended to include quantum effects.  This is one of the big open problems in physics.
 

Offline syhprum

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Re: Does the singularity exist?
« Reply #2 on: 25/07/2013 17:15:56 »
Surely the density of the matter beyond the event horizon does not need to all that much greater than that of a neutron star I can never understand why it is believed to be a quasi infinite density singularity.
 

Offline njskywalker

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Re: Does the singularity exist?
« Reply #3 on: 26/07/2013 01:31:40 »
Scaler blackholes/singularities are the ROOTS of the universe .
 

Offline JP

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Re: Does the singularity exist?
« Reply #4 on: 26/07/2013 19:28:38 »
Surely the density of the matter beyond the event horizon does not need to all that much greater than that of a neutron star I can never understand why it is believed to be a quasi infinite density singularity.

To answer this question it helps to think about what causes a planet or star to have finite density in the first place.  Gravity always wants to pull everything together to a point (or a ring), but various forces act to hold the matter apart.  A planet is stable because repulsive forces between molecules making it up counteract gravity.  If we add more mass, gravity becomes stronger so at some point gravity overcomes that repulsive force.  When this happens, the planet collapses until an even stronger force steps up to hold the particles apart.  But once you go past a neutron star, no known force exists that could prevent further collapse. 

But most likely when you get very close to the singularity, quantum effects become important so you don't end up with a physical singularity.
 

Offline syhprum

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Re: Does the singularity exist?
« Reply #5 on: 26/07/2013 20:34:58 »
Is there any evidence from collider experiments that the density of neutron matter can never be exceeded ?
Neutrons are not of course fundamental particles a combination of Quarks and electrons. ?
 

Offline JP

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Re: Does the singularity exist?
« Reply #6 on: 26/07/2013 22:16:42 »
Good question, and a bit out of my depth.  It seems that a neutron star is well accepted, and a black hole is well accepted, but what happens between the two isn't.  There's a bit on it on this blog post here:
http://quibb.blogspot.com/2013/02/degenerate-matter-exotic-stars.html

So it seems I was wrong about the neutron star being the last step before black hole!  There might be other interim steps before you pass that critical limit.
 

Offline yor_on

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Re: Does the singularity exist?
« Reply #7 on: 28/07/2013 21:22:28 »
It was a interesting read JP, although some of it went far over my understanding, as relating Greens theorem to the question if information is 'stored'? Presented in the link following from the one you linked to, about black holes. Don't see how such a information would tell you if it was a apple or a orange falling in? When it comes to the question about what's inside a event horizon I don't know what to think, actually. I've also seen it defined such as everything inside a event horizon is 'the singularity', which then should makes any positional reference after passing that event horizon meaningless, applying the shell theorem. To me it makes sense to consider the inside of a event horizon as having a spatial existence, with a center, as defined from a 'inside'? This assumes that infalling matter do pass a event horizon though. If it doesn't?

But the Green theorem applied as a proof for information being stored is what really confuses me.

"There is a final alternative, however. It is possible that the fluctuations of the event horizon itself would store the impressions of the incoming (or outgoing) particles. Note that this requires the projection of the information in a four-dimensional space (three spatial dimensions plus time) onto a three-dimensional space (the surface of the event horizon is a two-dimensional surface, which again changes over time), but this poses no problem, and has sound mathematical justification; for a sufficiently "well-behaved function" on a space, the behavior of the function within a region is completely determined by the values of the function on its boundary. This result is known as Green's theorem"


The Green of Green Functions.
 

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Re: Does the singularity exist?
« Reply #7 on: 28/07/2013 21:22:28 »

 

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