# Question combining - black holes & conservation of angular momentum

1. Jun 11, 2013

### ruspj

had a thought. suspect that i am wrong but not sure where. no idea of the maths involved but suspect

As an object approaches the speed of light relativistic forces come into play – effecting time dilation density etc

Can the same theory be rearranged to show that

As you approach the density & time dilation involved at the event horizon of a black hole the conservation of angular momentum would accelerate any rotating matter to the speed of light?

If this is true could the event horizon of a black hole become an extremely narrow ring? Circling its own common center of gravity – material approaching the speed of light at the same time that it forms an event horizon?

If an object of this type existed could they reach galactic sizes ?

Could its diameter, density, rotation, frame dragging of such an object account for the observed effects associated with dark matter ?

Last edited: Jun 11, 2013
2. Jun 11, 2013

### ruspj

ouch :)
i said " no idea of the maths involved " at the start also meaning no understanding of them.

heard a few times from reputable audiobooks that the centrifugal force is indistinguishable from the force of gravity. i have taken this to also mean another manifestation of the same force.

being a manifestation of gravity the centrifugal force should relativistic effects when taken to extremes identical to gravity.

The conservation of angular momentum force is inseparable from the centrifugal force

i was also thinking of the conservation of angular momentum increasing rotation in the same way that any mass is increased with speed is increased. with diverging relativistic effects.

I suspected that the centrifugal forces pulling out and the gravitational forces pulling in could converge forcing such collapsing matter into an extremely narrow ring.
Possibly to the point of a narrow stream of orbiting particles, maybe described as a ring of singularity

the comment about frame dragging was a thought that if such a ring was created the space within that ring could become a frame dragged disc of space

thanks for the reply but if possible is there a simpler non mathematical explanation of if/where i am wrong

Last edited: Jun 11, 2013
3. Jun 11, 2013

### WannabeNewton

I accidentally deleted my post whilst trying to edit it, sorry about that. Regardless, PeterDonis has an excellent blog post related to centrifugal forces in the Schwarzschild geometry (specifically, near Schwarzschild black holes) that may be of use to you: https://www.physicsforums.com/blog.php?b=4327 [Broken]

The problem is that when it comes to topics like this it is near impossible to correctly and comprehensively explain things without math. Unfortunately, you are throwing together a bunch of terms from general relativity that don't actually relate to one another in the way you are describing. Also, there is no gravitational force in general relativity.

Last edited by a moderator: May 6, 2017
4. Jun 11, 2013

### ruspj

is where i am wrong:

knowing that mass is increased when approaching relativistic speeds.
and suspecting that rotational speed is increased in the in the same way ( due to centrifugal ) when approaching relativistic mass/density

or relativistic effects not increasing speeds in the same way

suspected that math could be rearranged to do this in a similar way to e=mc2 can be rearranged to something like m=e/c2 with the same meaning

never even seeing the appropriate math before i wont understand it lol
was thinking someone would point out a simple mistake with the concept rather than needing the math

Last edited: Jun 11, 2013
5. Jun 12, 2013

### yenchin

It's quite confusing for me to try to understand what you want to say. Do you mean angular momentum of a *particle* near a black hole, or are you asking about rotating black hole itself? It seems to me like that latter case from your description. If so, a rotating black hole is described by the Kerr solution in general relativity. The singularity is a ring instead of a point. The black hole itself is like an oblate sphere. Does that help?

See e.g. http://www.daviddarling.info/encyclopedia/K/Kerr_black_hole.html.

6. Jun 12, 2013

### yenchin

Here's lots of math for you :tongue: It's a very recent preprint, in case you missed it.
http://arxiv.org/abs/1306.1019v1