Talk:Rotating black hole/Archive 1

message: Peanut gallery here.  Stationary BH needs to be explained/defined.  What does it mean? -- non- orbiting?  No discussion or references to non-stationary bh?  Why not?  embedded in flat space time?  What?  —Preceding unsigned comment added by 69.40.245.3 (talk) 22:58, 23 August 2008 (UTC)
thread_title:  stationary with angular momentum? 

message: The section "Two event horizons" is contradicting itself. As the spin increases, do they move father away from each other or towards each other? Also, it should probably state what the spin speed is where the even horizons merge, because clearly one of the two needs to change its direction at some critical spin speed. — Timwi 11:19, 21 Feb 2005 (UTC)
replies: text: Ergosphere is not a horizon - a test particle can escape from there. This should be spelled out better in the article.
What I want to be explained is a transition of "Cauchy horizon". *That one* seems to be more like a "real" second horizon. As I understand it now, outer horizon is a lot like Schwarzschild hole's horizon (+ some rotation), but "Cauchy horizon" sits inside and it is basically a radius at which rotation is so strong that it actually allows you to STOP FALLING and enter an funny "orbit" where as you fly, you do not only return to the same place (just like the satellite of Earth) but to the same TIME too.
Can someone improve the picture in the article (one with ergospere and event horizon) and add Cauchy horizon? How big is it? Is it spherical or oblate or what? 89.103.91.47 (talk) 15:47, 29 June 2008 (UTC)
thread_title:  Two event horizons 

message: This article needs to be expanded quite a bit. Some questions that I as a layman with no real physics background do not understand:
* Why are there two event horizons? 
* What is a photon sphere? 
* What distinguishes the two event horizons?
* If I can only move closer to the singularity while inside the outer event horizon, why can I move away from it again once I pass the inner event horizon?
* Why would I (possibly) emerge in a different universe/part of the universe after passing the inner event horizon and then leaving it again?
* Why would I (no matter which universe/part of the universe I end up in) be able to leave the black hole's outer event horizon after using it for "wormhole travelling"? I.e., why would the black hole actually be *useful*?
* What does the image "Space-Time Diagram for a Spinning Black Hole" (:Image:Space-Time Diagram for a Spinning Black Hole.gif) mean?
The image in particular is bugging me a lot - it's wholly unclear what is being displayed, I can't make sense of the labels (particularly "Our Universe" etc.), and there is no explanation of what it shows. -- Schnee (cheeks clone) 21:05, 18 August 2005 (UTC)
thread_title:  Explanations needed 

message: Since these are Kerr blackholes is there any particular reason the Penrose process is given before explaining who Kerr and Newman are?  Sophia 12:46, 5 September 2006 (UTC)
thread_title: Why is [[Roy Kerr]] not given top billing?

message: Gunnar Nordström was a Finn with a Swedish name, and thus his name had the letter ö, which is used in Finnish and Swedish. Ø is incorrect, because this particular letter is used only in Danish and Norwegian.195.16.202.19 10:26, 30 November 2006 (UTC)
thread_title: Nordström, not Nordstrøm

message: Apparently a few people don't understand what an event horizon is, in the context of a black hole. It's the surface at which, and within which, light cannot escape to future null infinity. It is conceptually nonsensical to talk about more than one per object, just as it's conceptually nonsensical to talk about two people of different heights that are both "the tallest person in the world". By definition, there can only be one such surface surrounding any given object. If there were an "inner" one of some sort, it would fail the criteria, and be a non-horizon of any fucking sort.
I think it's time this shit got deleted, instead of provoking more confused brow-furrowing from the peanut gallery, to be answered by people who took physics classes off the side of a fucking Crackerjack box.
--76.209.50.222 08:58, 20 February 2007 (UTC)
replies: text: Your frustration I understand but your language needs to be toned down! I agree that the definition of an event horizon is nonsensical if there is more than one but I'm not up to date enough with this field to say for sure that there isn't some bizarre definition somewhere. If you are the most up to date person here then be bold and get rid of it. It's certainly the mainstream view and any editor who wants to keep the "2 horizons" version will have to explain why.  Sophia 12:32, 20 February 2007 (UTC)
replies: text: Actually, I see the sense of two or more horizons. An event horizon encloses a region which nothing can leave. If Kerr hole has two horizons, it just means that once you crossed outer horizon, you cannot leave the hole, and when you cross inner horizon, you cannot leave even inner horizon's enclosed area (and go into outer horizon's enclosed area).  —Preceding unsigned comment added by 89.103.91.47 (talk) 15:39, 29 June 2008 (UTC)
thread_title:  Can we finally get rid of this "two event horizons" BS? 

message: Unless I get feedback, I'm going to make some changes soon (Say by 3 November 2007). I'm not sure when and why this was split from Kerr metric, but I'll respect the decision. I believe most of this page should be moved back to the Kerr page. It is generally believed that there should be an enormous class of not explicitely known rotating black hole solutions which are neither Kerr or Kerr-Newman. The ergosphere and Penrose process should be moved to the Kerr page (with a link from the Kerr-Newman page), since it's not clear that a general rotating black hole will have such structures, whereas Kerr and Kerr-Newman do. The "two event horizons" section is a mess here and clearly (and correctly!) explained on the Kerr page, so it should be cut. The Kerr and Kerr-Newman section should stay. "Kerr black holes as wormholes" should be cleaned and then moved to the Kerr page. The "see Also" and "references" look OK, but Wald's book and the one by Hawking and Ellis should probably be added. Any suggestions before I do this?  91.37.231.178 22:44, 29 October 2007 (UTC)
replies: text: You sound like you know what you are doing and we so badly lack knowledgeable editors in these areas. If it make more sense then please don't respect the split as it was likely done by someone who had just watched "The sky at night" or something! I only know a little of this area, having had the pleasure of taking Prof Kerr to dinner  when he came to give a talk to our Astrosoc at Uni. As they say - "be bold" and thanks for the work you will be putting in.  Sophia 06:45, 24 August 2008 (UTC)

text: I am also a physicist. 91.37.231.178 is absolutely right that this page has serious errors. If only he had completed his work. Nvf (talk) 23:23, 13 January 2011 (UTC)
thread_title:  Proposed changes 

message: 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)
replies: text: 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)
thread_title:  frames of reference 

message: 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)
replies: text: 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)
thread_title:  Deletion Nomination