- #1

Gonzalo Chumillas

- 3

- 0

I asked this question previously in a Spanish forum, but nobody know :( And I think it is a very simple question.

Thank you and sorry for my basic English.

You are using an out of date browser. It may not display this or other websites correctly.

You should upgrade or use an alternative browser.

You should upgrade or use an alternative browser.

- B
- Thread starter Gonzalo Chumillas
- Start date

- #1

Gonzalo Chumillas

- 3

- 0

I asked this question previously in a Spanish forum, but nobody know :( And I think it is a very simple question.

Thank you and sorry for my basic English.

- #2

m4r35n357

- 654

- 148

The angular momentum of the black hole is simply the angular momentum of the body that it formed from. It is detectable via the phenomenon of Frame Dragging.

I asked this question previously in a Spanish forum, but nobody know :( And I think it is a very simple question.

Thank you and sorry for my basic English.

Point of order: If I can answer it, it isn't advanced ;)

- #3

m4r35n357

- 654

- 148

Of course, it can change as it engulfs infalling material.The angular momentum of the black hole is simply the angular momentum of the body that it formed from. It is detectable via the phenomenon of Frame Dragging.

Point of order: If I can answer it, it isn't advanced ;)

- #4

Gonzalo Chumillas

- 3

- 0

The angular momentum of the black hole is simply the angular momentum of the body that it formed from. It is detectable via the phenomenon of Frame Dragging.

Point of order: If I can answer it, it isn't advanced ;)

Thanks. It seems to be advanced for Spanish forums, since nobody know :D

- #5

Vitro

- 130

- 47

That's a good question, and personally I don't know if we can relate the angular momentum or "spinning" of a black hole with the casual meaning of rotating or spinning.

I asked this question previously in a Spanish forum, but nobody know :( And I think it is a very simple question.

Thank you and sorry for my basic English.

From a quantitative perspective one applies the conservation laws to determine that the angular momentum of a black hole plus that carried by any material blasted away at the formation is equal to the angular momentum of the star that collapsed. Then later any type of matter or energy with angular momentum that is absorbed or emitted by the black hole will add or remove angular momentum from it. But is it (the singularity?) rotating in the usual everyday meaning of the word? No idea, the question itself might be meaningless.

- #6

Gonzalo Chumillas

- 3

- 0

- #7

Stollaxel Stoll

- 7

- 0

From the perspective of an outer observer all the material that builds the black hole is stuck on the horizon because of the infinite time dilation at its surface. This material is, from that perspectice, frozen right above the horizon, but angular momentum has to be conserved so it becomes space itself that rotates (with time standing still on the surface). Because there is, still speaking from the outer perspective, nothing inside black holes (not even spacetime, see the Schwarzschild paraboloid, which has a hole in the middle where the Schwarzschildradius begins), what you get is a rotating shell. For the infalling particle the story is a bit different, but as long as we are talking about the black hole from the outside.A black hole does not have a conventional surface, like a basketball.

- #8

haael

- 538

- 35

Rotating black hole (or in some interpretations even elementary particles) has nonzero torsion.

- #9

PeterDonis

Mentor

- 39,036

- 16,788

The torsion is coupled to the curvature and this is known as frame-dragging.

I don't think this is correct. Frame dragging is an effect that appears in standard GR, where the connection is torsion-free.

Rotating black hole (or in some interpretations even elementary particles) has nonzero torsion.

This doesn't look correct either. A rotating black hole is described by the Kerr solution in standard GR, again with a torsion-free connection.

- #10

PeterDonis

Mentor

- 39,036

- 16,788

From the perspective of an outer observer all the material that builds the black hole is stuck on the horizon because of the infinite time dilation at its surface.

This is not correct. A black hole is a vacuum solution; there is no "material" anywhere.

The rest of your post does not look correct either. It is very important in this subject to look at the actual math, not at heuristic pop science descriptions.

- #11

PeterDonis

Mentor

- 39,036

- 16,788

Maybe, the angular momentum can be understood as a distortion in the adjacent space-time around the black hole, not the black hole itself.

This is actually a good heuristic way of understanding, not just the angular momentum, but the mass of the hole (or indeed of any isolated object). If you go far away from the object and measure the geometry of spacetime, you will find certain aspects of that geometry that correspond to "mass" and "angular momentum". For example, you can put test objects in orbit about the isolated object and measure their orbital parameters, and from those measurements you can compute the mass and angular momentum of the isolated object.

Share:

- Replies
- 18

- Views
- 478

- Last Post

- Replies
- 9

- Views
- 432

- Replies
- 114

- Views
- 3K

- Last Post

- Replies
- 4

- Views
- 319

- Last Post

- Replies
- 34

- Views
- 744

- Last Post

- Replies
- 11

- Views
- 326

- Replies
- 63

- Views
- 2K

- Last Post

- Replies
- 24

- Views
- 513

- Replies
- 16

- Views
- 391

- Last Post

- Replies
- 11

- Views
- 599