Talk:Rotating black hole

Ergospheres

Which event horizon is the ergosphere located outside of? тəzєті 18:07, May 14, 2005 (UTC)

I have read in other sources that the outer event horizon remains stationary while the inner one moves out. Which on is it?

Rings of Dense Mass

if a massive donet shaped disk would rotate. Then from a distance it's centre could still have a mass of a blackhole. While in theory the disk mass would not have to be at a collapsing state. The ring can grow in mass and in size without a need of a colapse. And mass in centre me teared appart, while some mass will be jetsioned out like plume. It could have also have properties like magnetism (as seen in a MEC). Such theoretical rings of dense mass how are they called, and is there research in this direction as an alternative to blackholes ?

Frames of Reference

The article doesn't mention frames of reference at all. If you are rotating at the same speed (angular velocity) as a black hole wouldn't you 'see' a non-rotating blackhole? —Preceding unsigned comment added by 77.99.150.12 (talk) 07:56, 9 December 2008 (UTC)

A rotating reference frame is non-inertial in every sense, and angular momentum measurements taken in a rotating reference frame must take this into account. Angular momentum measurements taken from a rotating reference frame are invalid unless the angular velocity of the frame is subtracted. Iameditingstuff (talk) 05:33, 1 May 2011 (UTC)

Possibility of Time Travel

I think the whole section on time travel should be deleted. A lot of it is very hand-wavey and vague. There are also what appear to be original derivations here. There's no real references, which is also a serious problem. But the kicker is that this section, IMHO, belongs in the time travel article in a much clearer, cited form, written by somebody who understands it, without . I propose removing it. Opinions? Other objections have been made that haven't been addressed, so I'd say if I haven't heard anything, I'll delete it by 12/1/2011. Joel Frederico (talk) 22:21, 23 October 2011 (UTC)

On a more professional note, this should be written in a more neutral tone. The idea that time travel is possible is not one I've heard a physicist put forward without a lot of caveats. The closest my GR professor got was saying that there are some rather strange solutions that are possible if you allow an object to not be torn apart by tidal forces, and give it a form of propulsion. The solutions are hard to understand physically and even harder to interpret, but they are solutions. But there are no discussions of what solutions lead to these interpretations. It makes it all highly suspect to me as a physicist. Unfortunately, time travel wasn't really addressed in my class ("Intro to GR"), so I don't know what the consensus is. Joel Frederico (talk) 22:21, 23 October 2011 (UTC)

I agree that this section should be deleted and am about to delete the section. I'm quite knowledegable in this field, and I'm quite certain that the discussion is quite simply wrong. First, the closed time like loops which exist in the Kerr black hole need not be (and probably are not) generic features of black holes, rotating or otherwise. Second, even in the Kerr block hole spacetime, there is no way to escape to the original exterior region -as this article claims- from the very definition of a black hole. 86.161.97.191 (talk) 06:04, 19 November 2011 (UTC)

Deletion Nomination

It seems like this article should be deleted. It doesn't have any properly sourced information that isn't contained in any of the other black hole related articles (especially the "black hole" article, "Kerr metric" article, and "Kerr–Newman metric" article). It is also very poorly written... it doesn't seem to have been given any attention by somebody who has actually taken General Relativity in university. —Preceding unsigned comment added by 74.14.156.248 (talk) 04:54, 29 April 2011 (UTC)

This article serves as a simple introduction and a disambiguation page. From the chart one can choose which specific metric one wants to look at. People who do not already know the names of the specific metrics should appreciate this article for that reason. JRSpriggs (talk) 09:10, 29 April 2011 (UTC)

Why not give the article some time to develop.... or improve it yourself? Also I'm concerned about the article statement "This is because anything happening inside the black hole horizon cannot affect events outside it." Isn't the accretion disk affected by a spinning black hole? 172.162.44.231 (talk) 01:40, 15 April 2012 (UTC) BG

Circular form of event horizon

There is no evidence for this. In the contrary, there are several voices for an elliptical shape. So I do replace the image with an international version. → User: Perhelion 12:42, 30 June 2016 (UTC)

Sorry, I didn't see that your edit was just before mine, otherwise I would have come to the talk section first. But back to topic: it's not circular, it's spherical (topologically)! I know of coordinate systems where the EH is a sphere and others where it is an ellipsoid but none of where the ergosphere AND the EH are BOTH ellipsoids. The event horizon does have constant r, which is also obvious from the equation you have linked in your image description. The old version is backed up by PHYS 486, page 17 and there are also some ellipsoide versions like the one on page 35 here, but what is the coordinate system you are using in the updated version of the illustration?--Yukterez (talk) 05:05, 10 July 2016 (UTC)

Please update with: "Amplification of waves from a rotating body" and "Magnetic reconnection as a mechanism for energy extraction from rotating black holes"

Please add some short information on this paper to the article, possibly to a new section. It's currently featured in 2020 in science (July) like so (you could also edit it there):

Scientists demonstrate that it may be possible – for advanced extraterrestrial civilizations – to harvest rotational energy from black holes 51 years after it has been proposed to be possible and 49 years after an experiment to test the theory has been proposed.

--Prototyperspective (talk) 14:40, 23 October 2020 (UTC)

Information on this study could be added as well. It's currently featured in 2021 in science like so:

Astrophysicists report that energy extraction – with high efficiency – from rotating black holes with a high spin via reconnection of magnetic field lines of an externally supplied magnetic field that accelerates escaping plasma particles is possible. Advanced civilizations may be capable of doing so.

and:

Astrophysicists report a new way for energy extraction from rotating black holes that have a high spin. Reconnection of magnetic field lines of an externally supplied magnetic field would accelerate plasma particles escaping the black hole. Advanced civilizations may be capable of harnessing energy this way with high efficiency. This may be relevant to the search for extraterrestrial intelligence and the accuracy of the Kardashev scale.

--Prototyperspective (talk) 18:37, 27 February 2021 (UTC)

References

All celestial objects - planets, stars (Sun), galaxies, black holes - spin

I added... All celestial objects - planets, stars (Sun), galaxies, black holes - spin. 2601:589:4801:5660:B1C7:7A45:9E90:1C31 (talk) 15:15, 20 June 2021 (UTC)

Citation for all objects in the universe spin, or remove

There is no concrete evidence that black holes spin, therefore it is inaccurate to have the article say without a doubt that ALL objects in the universe spin.

"This is because anything happening inside the black hole horizon cannot affect events outside of it."

Incorrect. Gravity is being generated within the black hole, and certainly affects things outside of it. — Preceding unsigned comment added by 2A02:F6D:8484:0:D0FE:943B:D5AD:E1D1 (talk) 19:47, 26 April 2024 (UTC)