Talk:Black hole

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Not a good sign when the first sentence is wrong

The article starts with "A black hole is a region of spacetime exhibiting gravitational attraction so strong that nothing—no particles or even electromagnetic radiation such as light—can escape from it" and citing the book by Wald. But in the same book, the next sentence says "However this notion is not properly captured by defining a black hole". It's not fair for a so good book to cite it wrongly. The horizon is not about how strong is gravity. For a supermassive BH, gravity could be very weak at the horizon while for a small black hole any object would be destroyed by tidal forces long time before reaching horizon. SO NO, horizon is not about how strong is gravity. In relativity, time is fundamental component, without it, one can't understand. Time is also affected and therefore the future light cone, which rotates toward the interior of the black hole. Once an observer reaches the horizon, his future is inside the black hole. It's not about how strong is gravity but about deforming the causal structure. — Preceding unsigned comment added by 201.241.20.145 (talk) 02:07, 13 April 2020 (UTC)

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The first sentence does not say that the horizon is about how strong gravity is. It does not even mention the horizon, so I don't think there's a problem with it. Your objection is covered by one of the following sentences, and further down in the article. - DVdm (talk) 07:19, 13 April 2020 (UTC)

Note that the first sentence does not mention "gravitational force" or "gravitational field" being strong. It says "gravitational attraction" this is purposefully a bit vague, to cover the much more technical description of curvature of spacetime leading to the formation of trapped surfaces and a event horizon, which are accurately (but in precisely) covered by the accessible description "strong gravitational attraction".TR 11:06, 13 April 2020 (UTC)

I don't personally like it either, I'd prefer something like "with a strong gravitational field that nothing can escape from", but the current text is well-sourced, so we should just leave it unless someone has a strong source that words it better. In any case, I don't think it's actually causing anyone to be confused about the basic idea of what a typical black hole is.

There's also some room for a "black hole for laymen" article that explains the causal structure in a more accessible way, either by expanding https://simple.wikipedia.org/wiki/Black_hole or creating an article in the Category:Introductory articles series.Rolf H Nelson (talk) 06:30, 14 April 2020 (UTC)

Note that a statement like "with a strong gravitational field that nothing can escape from" is categorically wrong for the reasons mentioned by the IP above. The gravitational field at the horizon can be quite weak.TR 13:46, 14 April 2020 (UTC)

Sure, but the horizon is not mentioned. - DVdm (talk) 13:59, 14 April 2020 (UTC)

Nonetheless, the strength of the gravitational field has nothing to do with things not being able to escape.TR 16:54, 14 April 2020 (UTC)

But the opening sentence does not mention the gravitational field either, let alone its strength. It looks like Wald gave that line quite some thought . - DVdm (talk) 17:02, 14 April 2020 (UTC)

Exactly, which is why I was commenting that changing it to something like "with a strong gravitational field that nothing can escape from", as was suggested, would be bad.TR 17:28, 14 April 2020 (UTC)

Ok, and good one, this. - DVdm (talk) 17:58, 14 April 2020 (UTC)

Yeah, fair point on that one. Ceoil (talk) 02:46, 16 April 2020 (UTC)

Full protection

Ceoil, Deacon Vorbis, please resolve your dispute in the usual way, through talk page discussion. Thank you. El_C 02:21, 16 April 2020 (UTC)

Its seems to me you dont understand the tools you are wielding. Protection against a two well established editors? Ceoil (talk) 02:44, 16 April 2020 (UTC)

Yes, Ceoil. Established editors do not get to edit war, just the same as newcomers. El_C 02:45, 16 April 2020 (UTC)

Ok, but this is becoming tedious, my original point on your talk stands: if you dont understand the tool or the rules, best say nothing. DVdm, no offence to you at this point. Ceoil (talk) 02:48, 16 April 2020 (UTC)

I realize you wish to make me the target of your frustration, but that makes it neither fair nor reasonable. El_C 02:50, 16 April 2020 (UTC)

i'd prefer if you went back to DVdm's version and lifted full protection; my additions were only matters of style, I thought. You overshot here, with no appreciation of content protection. Ceoil (talk) 02:55, 16 April 2020 (UTC)

I saw an edit war where exceeding 3RR by the participants was a real risk, so I acted quickly. I thought that was to my credit. Anyway, happy to oblige. El_C 02:56, 16 April 2020 (UTC)

Semi-protected edit request on 12 June 2020

In the last paragraph of the introduction please chenge "On 11 February 2016, the LIGO collaboration announced the first direct detection of gravitational waves," with "On 11 February 2016, the LIGO and Virgo collaboration announced the first direct detection of gravitational waves, Geppo.Cagnoli (talk) 09:14, 12 June 2020 (UTC)

 Done: [1]. - DVdm (talk) 09:25, 12 June 2020 (UTC)

It's "shredded", not "shred"

The fourth paragraph contains the word "shred" used as a past tense. This should be "shredded".50.205.142.50 (talk) 15:46, 24 June 2020 (UTC)

No, it's being used as a past participle rather than a simple past tense, and both shred and shredded can be used in that sense. –Deacon Vorbis (carbon • videos) 15:51, 24 June 2020 (UTC)

Doesn't look like its being used as a past participle to me. The sentence: "Stars passing too close to a supermassive black hole can be shred into streamers that shine very brightly before being "swallowed." has the simple sentence "Stars can be shred." The main verb, "can be shred", is present tense in the potential mood which is made with auxiliary verbs plus the infinitive verb form ("to shred" without the "to"). Were you to rewrite the sentence out of the potential mood in the the indicative mood, the main verb "can be shred" would change to "are shred".Tachypaidia (talk) 14:21, 14 July 2020 (UTC)

The infinitive here is "be shred", which is passive, which formed from of the appropriate tense of "to be" and the past participle of shred.TR 15:47, 14 July 2020 (UTC)

The infinitive here is "shred" with it marked periphrastically for the passive voice with "be". Regrettably, this is often omitted in spoken English, such as "the chicken is too hot to eat" which actually means something else than what is commonly intended. — Preceding unsigned comment added by Tachypaidia (talk • contribs) 07:31, 15 July 2020 (UTC)

Please consider the use of subjunctive mood in scientific writing: —Beast: "He's speaking the truth." Beast's owner: "How do you know?" Beast: "He's speaking in the subjunctive." —The Star Beast (Robert Heinlein). In other words, the article's text can be read in subjunctive mood, meaning that the article text "be shred" deals with possibility, which is an appropriate way to state an inference. --Ancheta Wis   (talk | contribs) 19:40, 14 July 2020 (UTC)

Semi-protected edit request on 22 July 2020

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[b]Black hole in mythology[/b]

Black hole in Puranas is called as third eye of god Shiva & also called as Vishnu Chakra Or Krishna Chakra - Black hole is also known as Goloka abode of god Krishna. Gita Says abode of god Krishna is where light cannot reach.

Black hole in Puranas is also known as Rudras - Puranas Says there are countless Rudras but only 11th(Eleventh) Rudra is known as god Shiva. God Krishna says in Gita that I am god Shiva.

In Ramayan god Rama was king for 11,000(Eleven Thousand) years & some Ramayan says nobody knows how many years god Rama was king - It means god Rama was immortal & he is still king & he is Still Living Somewhere. It means god Rama was avtar of god Shiva. There is no other information of 11th(Eleventh) number found in any texts books of hindu mythology.

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Please Remove These Lines

I Have Studied At Least 200 Books On Hindu Mythology.

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Please Remove These Lines Vikram ght (talk) 14:29, 22 July 2020 (UTC)

 Already done. These line don't appear in the article, so there's nothing to remove. –Deacon Vorbis (carbon • videos) 14:35, 22 July 2020 (UTC)

Supernovae

Do my eyes deceive me? Is there no mention of the word "supernova" in the entire article? Lithopsian (talk) 19:37, 27 August 2020 (UTC)

I have just added some info and a link to supernova, in the gravitational collapse part. --JimenaAstro (talk) 22:11, 27 August 2020 (UTC)JimenaAstro

I removed part of what you added because it included an incorrect definition of what a planetary nebula is. Planetary nebulae are not supernova remnants and they aren't related to black hole formation. It would still be useful to have a little more text on the connection between supernovae and black hole formation though. Aldebarium (talk) 22:21, 27 August 2020 (UTC)

I just (preliminary) restored properly sourced content that was removed by user Aldebarium (talk · contribs). Comments welcome. - DVdm (talk) 22:26, 27 August 2020 (UTC)

Hi Aldebarium (talk · contribs), thank you for your comments and edits. The mention to planetary nebulae was there before, I did not add it. I just expanded on the supernova event, but did not feel like removing the planetary part completely. I agree that planetary nebulae are not supernova remnants (and are not related to black hole formation). I added a brief mention to supernova in the introduction and will now have a look at the gravitational collapse part to see how we can express it better. Thank you! JimenaAstro (talk) 22:32, 27 August 2020 (UTC)JimenaAstro

OK- sorry then, I misunderstood where that text came from. I agree with including more information on the connection between supernovae and black hole formation in general, so my main reason for the deletion was just to remove the incorrect stuff about planetary nebulae. Aldebarium (talk) —Preceding undated comment added 22:35, 27 August 2020 (UTC)

 Jood job here! - DVdm (talk) 22:37, 27 August 2020 (UTC)

Aldebarium (talk · contribs) Please try to conform closer to what's directly stated in reliable sources. Rolf H Nelson (talk) 05:04, 28 August 2020 (UTC)

I'm not sure what you're referring to, but if you mean the part about Type Ia supernovae, I was working on removing that in my next edit. I didn't write that, it was there before, and I agree it doesn't belong there. Aldebarium (talk) 05:07, 28 August 2020 (UTC)

It would probably be appropriate to also mention something about the (upper) mass gap that sets an effective maximum mass for stellar black holes.TR 06:49, 28 August 2020 (UTC)

Semi-protected edit request on 7 October 2020

Recently, a quantum thermodynamical description for the interior of a Reissner-Nordström black hole, was proposed by Musmarra and Bellini. J. I. Musmarra, M. Bellini. "Quantum thermodynamics in the interior of a Reissner-Nordström black-hole". Physics of the Dark Universe. vol. 30, 100710 (2020).[2]. Mago.ratanga (talk) 22:55, 7 October 2020 (UTC)

 Not done. It's not clear what changes you want to make. –Deacon Vorbis (carbon • videos) 22:56, 7 October 2020 (UTC)

Temperature proportionality

Regarding this and this edit by user Spyglasses and this and this revert by user Deacon Vorbis, see Kip Thorne who writes that Hawking concluded that the temperature is proportional to the hole's surface gravity. So it looks like Deacon Vorbis is correct. - DVdm (talk) 14:17, 10 October 2020 (UTC)

References

Semi-protected edit request on 3 November 2020

The reference no. 177 Shipman, H. L.; Yu, Z; Du, Y.W (1 January 1975). "The implausible history of triple star models for Cygnus X-1 Evidence for a black hole". Astrophysical Letters.

 is incorrect in detail: Shipman appears to be the single author of the article, see

https://ui.adsabs.harvard.edu/abs/1975ApL....16....9S/abstract

It should read e.g.

Shipman, H. L. (February 1975). "The implausible history of triple star models for Cygnus X-1 Evidence for a black hole". Astrophysical Letters. Intophysics (talk) 19:22, 3 November 2020 (UTC)

Agreed. Looks like the doi link is bad? VQuakr (talk) 20:02, 3 November 2020 (UTC)

 Done Fixed. XOR'easter (talk) 20:14, 3 November 2020 (UTC)

Black hole definition refinement

According to me, the current definition for a black hole ("A black hole is a region of spacetime where gravity is so strong that nothing—no particles or even electromagnetic radiation such as light—can escape from it.") should be refined to be able to cope with the observations of two black holes merging together. According to the current definition, recently observerd merging of black holes would not possible since none of the merging black holes would be able to loose matter to the other black hole. The refinement could be something like: "without the nearby presence of any other significant object". WDeeraa (talk) 23:47, 26 January 2021 (UTC)

If some reliable source would directly support that, there would be no problem to add it. Without a source this would be wp:original research, which is not allowed on Wikipedia. - DVdm (talk) 00:02, 27 January 2021 (UTC)

Definitions are arbitrary. We already have List of gravitational wave observations, LIGO observations of inspiral events, which document mergers of black holes with other black holes (such as GW150914), and other mergers of black holes with neutron stars, etc. In other words, these objects are observed to entrap each other; there is no need for definitions to allow their existence. --Ancheta Wis   (talk | contribs) 01:56, 27 January 2021 (UTC)

In a BBH merger nothing escapes from within the black holes. There is no need to change anything.TR 13:29, 27 January 2021 (UTC)

In a Binary Black Hole system you could argue that nothing escapes between the two black holes (although I believe that the ultra-strong gravitational fields will influence each other, therefore also both event horizons, which will allow exchange of matter at a certain stage).

But when the two black holes merge to become one bigger black hole, the current definition of a black hole does not hold.

Also since the mass of the resulting black hole is less than the sum of the two merging black holes (for example GW190521: 85 M_☉ + 66 M_☉ → 142 M_☉), there is a significant loss of mass which cannot be explained with the current definition.

Maybe the addition of a note to solve the lack of a source? WDeeraa (talk) 21:54, 28 January 2021 (UTC)

We solve the lack of a source by not doing adding the content. All content, including footnotes, needs to be verifiable. VQuakr (talk) 22:13, 28 January 2021 (UTC)

I repeat, there is nothing wrong with the current description of a black hole as "a region of spacetime from which nothing can escape", in the case of merging black holes. In fact, this remaining true is instrumental in certain approaches to numerical relativity used to model such a merger. If you wish to claim otherwise you will need to provide a source.TR 15:37, 29 January 2021 (UTC)