Talk:Black hole/Archive 14

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Archive 12

Question about paragraph

The no-hair theorem states that, once it achieves a stable condition after formation, a black hole has only three independent physical properties: mass, charge, and angular momentum. Any two black holes that share the same values for these properties, or parameters, are indistinguishable according to classical (i.e. non-quantum) mechanics.

This statement actually seems to imply that black holes are distinguishable via quantum mechanics. Is that true? It seems unlikely. If so, it seems sufficient just to say that they "are indistinguishable". Regards, RJH (talk) 16:08, 16 September 2011 (UTC)

The theory for a quantum black hole is still incomplete so the correct answer is that we don't know yet for sure. The answer to that question is related to the information paradox. There is no consensus yet but many theoreticians think that the no-hair theorem is not preserved by quantum mechanics. Dauto (talk) 18:17, 16 September 2011 (UTC)

Thanks. So... I'm curious as to how would you go about explaining that to somebody's grandmother? It would seem that the theorem is thus satisfied for observers beyond a certain distance (outside the quantum realm). Regards, RJH (talk) 22:40, 22 September 2011 (UTC)

Simulated image

Wikipedia needs to remove the main simulated photo of a black hole. The best evidence for a black hole, is the tracking of the orbits of twenty eight stars. This is not even close to what the picture depicts. — Preceding unsigned comment added by 122.58.140.51 (talk) 23:02, 15 November 2011 (UTC)

And? I don't see any relation between your argument and your conclusion.T R 07:16, 16 November 2011 (UTC)

I would speculate that the poster is arguing that the image in the lead should show as "real" image of a black hole as is practical, rather than a conjectured illustration as is shown at present. Something like this or this is probably what the poster has in mind, although there are likely copyright issues. Personally, I don't have an issue with the current image. Regards, RJH (talk) 21:24, 18 November 2011 (UTC)

I recall hearing a few years back that someone had actually managed to image the inner edge of the accretion disk of Sag A* using radio interferometry. Is that image kicking around, and is it US-government licensed? Or am I misremembering? --Christopher Thomas (talk) 21:35, 18 November 2011 (UTC)

I'm not sure; there might be. What I have heard is that there are attempts under way to try and capture the silhouette of a SMBH with a large angular diameter, such as Sgr A* or M87.[1][2] Hopefully we'll hear some results in the near future. Regards, RJH (talk) 19:45, 20 November 2011 (UTC)

Wikipedia Is Not A Fan Page For Stephen Hawking

The facts are a theorist demonstrated he miscalculated his 1974 theories and Hawking afterwards claimed he was wrong. Three different non-tabloid and reliable news sources I cited all state he claimed he was wrong. The Time Magazine source even stated the theorist's name.JoetheMoe25 (talk) 12:52, 26 September 2011 (UTC)

He wasn't wrong about the thing you claimed he was wrong about. There is nothing wrong with Hawking's original calculations, they still stand. What he (now thinks he) was wrong about is his original position on the black hole information paradox. His original position was that information would simply be lost. In 2004, he conceded that stringy corrections would probably cause the information to be encoded in the Hawking radiation.

And for the record, news sources are notoriously unreliable when it comes to science reporting, and do not qualify as WP:RSs for this type of article.T R 13:03, 26 September 2011 (UTC)

Your claim is baseless. They wrote articles about Hawking's own statements from a Dublin Conferenece. What you claimed about what Hawking conceded also is the same what I stated: he claimed in 2004 his 1974 theories about black holes were wrong. See Wikipedia:Fancruft.75.72.35.253 (talk) 13:23, 26 September 2011 (UTC)

The fact that you think we said the same thing says enough about your understanding of the subject. You stated that Hawking conceded that his prediction that black holes radiated was wrong. This prediction still stands. The bet that he conceded was about further speculation about what happens to the information that went into the black hole. There were two main positions on this. One championed by the like of Hawking and Unruh, that the information was simply lost. The other championed by among others Preskill that quantum back reactions would somehow encode this information in the Hawking radiation. Preskill and Hawking at some point made a bet on this. In 2004, in the face of the AdS/CFT microstate descriptions of black holes, Hawking conceded this bet, and changed position that in all likelihood, information is conserved.

However, all parties still agree that QFT predicts that black holes radiate, as predicted by Hawking in 1974.T R 13:41, 26 September 2011 (UTC)

TimothyRias, this is not a Hawking fanpage. One article that was sourced even states Hawking Admits He Was Wrong.JoetheMoe25 (talk) 00:59, 30 September 2011 (UTC)

Yes, but not about the thing you say he was wrong. (And stop throwing around random accusations of people being fan of stuff).T R 05:47, 30 September 2011 (UTC)

Yes, he did admit he was wrong in 1974 and presented a new theory. The fact that you are erasing this information suggests you are a fan trying to hide the fact that he was wrong, so there's no bias assumption.JoetheMoe25 (talk) 00:28, 28 October 2011 (UTC)

Quote one source:"Renowned physicist Stephen Hawking on Wednesday put forward a radically-revised version of his theory on the nature of black holes, which formed where stars collapse.

He told a Dublin conference that black holes did not destroy everything they consumed but instead eventually fired out "mangled" matter and energy.

Until now, he had argued that matter sucked into the gravitational vortex of a black hole was completely destroyed and no information about it ever reappeared apart from a generic form of radiation, now called "Hawking radiation."JoetheMoe25 (talk) 00:37, 28 October 2011 (UTC)

With respect, Timothy Rias is a graduate physics researcher at a prominent university, specialising in black holes and quantum gravity. You are not. Why don't you pay attention to what he's written, try to understand it, then you might learn something.

What Rias wrote to you above is exactly accurate:

There is nothing wrong with Hawking's original calculations, they still stand. What he (now thinks he) was wrong about is his original position on the black hole information paradox. His original position was that information would simply be lost. In 2004, he conceded that stringy corrections would probably cause the information to be encoded in the Hawking radiation.

We deal with the debate that there has been about the black hole information paradox further down the article. It's an interesting topic, but it's a detail compared to the main point: that quantum field theory predicts that black holes should radiate like a black body with a temperature proportional to the surface gravity of the black hole; i.e. as fully thermodynamic objects. This is the key point for the introductory survey to make, with the minimum of confusion or distraction. Jheald (talk) 00:49, 28 October 2011 (UTC)

I'm afraid your nonsense is not convincing. You don't have to be a top physicist to know when people admit their mistakes. Hawking admitted he was wrong about exactly what I typed. Also, don't think that I'm either so stupid or gullible to believe Rias is a "graduate physics researcher at a prominent university" just because you claim he is. This is not a Hawking fanpage.JoetheMoe25 (talk) 03:58, 27 December 2011 (UTC)

Let's Please Try To Be Mature

I find the continuous erasing of my properly resourced edits to be self-centered and childish. Immature arguments, like assuming that I'm not a "graduate physics researcher at a prominent university" just because I wrote something you didn't agree with, are quite insulting and prejudice. I will find an administrator who is neutral and will prevent this vandalism from continuing if I find it to be erased again. Please read the Consensus policy JoetheMoe25 (talk) 04:30, 27 December 2011 (UTC)

Several editors have repeatedly explained to you why your edits were reverted. A full treatment of the topic is at black hole information paradox and Thorne–Hawking–Preskill bet. What you are doing now - re-adding the material after multiple editors have asked you not to - is called "edit warring". Please stop doing it; it will get you blocked. --Christopher Thomas (talk) 05:41, 27 December 2011 (UTC)

Weasel Words

Shouldn't these "weasel words" warnings should be removed? They all appear to be in properly sourced statements. — Preceding unsigned comment added by 66.30.48.132 (talk) 22:29, 15 February 2012 (UTC)

No exact definition!!!

There is no exact definition of black hole becaue quantum gravity has not yet been proved. — Preceding unsigned comment added by 67.80.107.41 (talk) 15:34, 17 February 2012 (UTC)

Edit request: bulge

We have this: "It is now widely accepted that the center of (nearly) every galaxy (not just active ones) contains a supermassive black hole.[102] The close observational correlation between the mass of this hole and the velocity dispersion of the host galaxy's bulge, known as the M-sigma relation, strongly suggests a connection between the formation of the black hole and the galaxy itself." -- but no explanation of the concept of the galaxy's "bulge." I haven't found an explanatory spot in Wikipedia to link to. Came here looking for an explanation of this bulge after reading http://www.sciencedaily.com/releases/2012/02/120227162801.htm . Thanks -- Jo3sampl (talk) 11:29, 28 February 2012 (UTC)

The relevant wiki article is Bulge (astronomy), roughly speaking this is the central part of a galaxy in which the distribution of stars is roughly spherical. I have added a link to the word bulge in the article here. Thank you for pointing this out.T R 12:11, 28 February 2012 (UTC)

Hawkings Radiation?

I am afraid that no such radiation exists; and, the fictive notion that black holes even exist is wishful thinking. — Preceding unsigned comment added by 71.71.87.169 (talk) 15:01, 5 March 2012 (UTC)

Whether it exists or not is not at issue. What is at issue is the proven fact that if you crush enough mass together it will create a black hole, and that hawking radiation will cause the black hole to slowly evaporate. If you have some valid sources that contradict that statement, please share them. Fresheneesz (talk) 23:50, 1 April 2012 (UTC)

Bullshit about bending space time and infinities

There's a lot of popular-media bullshit about bending space time and such. These things are visual aids, not real science. Real science is about energy, and the energy of normal light (up to gamma rays) decay to 0 energy before crossing the event horizon. There are no "paths" that bend in space time. That is bullshit.

Also bullshit is this articles use of infinities and singularities. A singularity is a conceptual idea related to black holes - one that every scientist knows cannot exist. Infinities do not exist. Every time we see an infinity, its an indicator that we did something wrong or that the equation we're solving has no solution (ie the scenario we created cannot happen). I'm a little confused why people throw them around like they're real.

Fresheneesz (talk) 00:34, 2 April 2012 (UTC)

General relativity describes spacetime as a curved surface. "Space" and "time" are where you choose to draw coordinate axes on a local patch of that surface (there are many possible choices; only light-like directions remain the same in different reference frames). Freely-falling objects follow paths called geodesics. On a flat surface, a geodesic is a straight line. On a curved surface, the path is curved. That is what popular media are attempting to describe when they refer to "bending space and time".

Within the event horizon of a black hole, all possible "forward in time" paths point inwards. That, not energy arguments, is why escape is not possible from within the horizon.

The equations of general relativity do indeed result in a mathematical singularity when applied to black holes. The exact physical interpretation of this is open to question. As is already described in the black hole article, it's usually taken to mean that our description of gravity under those conditions is incomplete. The most conservative interpretations - ones that add the least new/unknown physics - take it at face value, and call it a gravitational singularity: a point-like (or ring-like) region where all of the black hole's mass is contained, where our description of it breaks down.

While your distaste for the idea of a singularity is shared by some scientists, Wikipedia's job is to describe black holes as they are understood by the scientific community, as reflected in sources. The subset of WP:RS that describes standards for this is at WP:SCHOLARSHIP. --Christopher Thomas (talk) 00:56, 2 April 2012 (UTC)

Removed dubiously sourced sentence

I removed the following sentence:

"It is called "black" because it absorbs all the light that hits the horizon, reflecting nothing, just like a perfect black body in thermodynamics."

And it's supposed source:

Davies, P. C. W. (1978). "Thermodynamics of Black Holes" (PDF). Reports on Progress in Physics. 41 (8): 1313–1355. Bibcode:1978RPPh...41.1313D. doi:10.1088/0034-4885/41/8/004.

because I couldn't find anything that would indicate the sentence is actually sourced from that document. First of all, pages 1313-1355 don't exist in that PDF, so whoever sourced it must have either been sourcing some kind of journal. Unfortunately, the pdf isn't it.

Fresheneesz (talk) 23:53, 1 April 2012 (UTC)

I've changed it back. You made quite a few changes, not just removing that sentence, and IMO most leave the lede in worse shape. Also, the reference does indeed back up the statement you flagged above.

My PDF reader numbers the pages in the document as 1313-1355, and they're also printed at the bottom of each page (in the footer text); I'm not sure what your reader is doing for that to not be the case for you as well.

The abstract at the start of the paper (first page) mentions "thermal radiation", so I'd say it's reasonably certain that the body discusses it as well. Hawking radiation _has_ a black body radiation distribution. The thermodynamic arguments made by Hawking and Bekenstein all pointed towards black holes acting as though they were perfect black-body objects with a nonzero temperature, and Hawking was the one who worked out a mechanism for that to occur. --Christopher Thomas (talk) 00:44, 2 April 2012 (UTC)

I have added Schutz' book as another source for this statement. - DVdm (talk) 11:29, 2 April 2012 (UTC)

Naive question perhaps

Does time cease to move forward at the point of a gravitational singularity? For that matter what are the effects of gravitational time dilation at the absolute central point of a large mass? I wasn't sure whether these were relevant things for the page, which is why I am asking. I don't mean to just discuss the topic without a contribution to the page.137.111.13.167 (talk) 04:44, 21 May 2012 (UTC)

These are described at gravitational singularity, which is linked from this page. The short answer is, the equations of general relativity produce a mathematical singularity at that point, so they don't give an answer (and in fact say that no answer is consistent with the equations). This is usually interpreted to mean that general relativity is not an accurate description of gravity at the singularity itself.

For an extended mass (one that isn't a black hole, but is instead spread out like a normal object), gravitational time dilation at the centre works exactly the way you'd expect from potential energy arguments (time inside runs a bit slower, so that blue-shift and red-shift going into and out of the gravity well produce consistent observations). This is explained in more detail at gravitational time dilation.

For general questions, you can probably find faster answers at the reference desk page. --Christopher Thomas (talk) 05:59, 21 May 2012 (UTC)

Edit request on 30 May 2012

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The statement, “A black hole is a region of spacetime whose gravitational field is so strong that nothing which enters it, not even light, can escape”, taken from Wald, Robert M., General Relativity (1984) is dated. 21st publications clearly show this statement to be false. This is discussed by Aranoff in “Basic Assumptions and Black Holes”, Physics Essays 22, 559 (2009), and by Aranoff in Teaching and Helping Students Think and Do Better (2007). It is also discussed by Hynecek, “The Galileo effect and the general relativity theory”, Physics Essays 22, 4 (2009). This paper makes the following statement, “The Schwarzschild metric, which is the vacuum solution of Einstein field equations, is clearly a nonphysical metric and predicts the existence of such absurdities as black holes.”

It is surprising that people still accept old incorrect ideas!

The reasoning is simple. Due to time dilation, it takes forever to reach the black hole, and so it is meaningless to speak about the “inside”. The puzzle is that why then do so many discuss the inside. There is another solution of the equations for the viewpoint of an observer falling down the black hole. According to this solution, he enters the black hole in a finite time. However, this solution is not valid, as mathematicians have proven that at the center of the black hole there is a singularity, that is, the solution is not valid.

Sanford123445 (talk) 00:19, 30 May 2012 (UTC)

Not done - This is neither an edit request, nor correct (by a sensible reference frame). Egg Centri c 21:07, 31 May 2012 (UTC)

Concerning Information Loss

The article states that information describing matter absorbed by the black hole is lost, but I was under the impression that this was dis-proven, and later confirmed to be false by Hawkings. I believe the holographic principle was shown to (at least theoretically) account for the information. Regardless, I think it might be wise to mention the controversy that had arisen around that argument.

Peekama (talk) 20:34, 31 May 2012 (UTC)

This is mentioned in the article at Black hole#Black hole unitarity, and is discussed at length at Black hole information paradox. There is strong circumstantial evidence to believe that information is preserved, and at least two attempts at proving this (Hawking's attempt and other arguments based on the holographic principle), but to the best of my knowledge neither proof is universally accepted as correct yet. --Christopher Thomas (talk) 21:32, 31 May 2012 (UTC)

Subtle quibble about opening lead sentence

Three times ([3], [4], [5]) user TimothyRias has changed the opening lead sentence from

A black hole is a region of spacetime where gravity is so strong that nothing that enters the region, not even light, can escape.

to

A black hole is a region of spacetime deformed by gravity such that nothing, not even light, can escape.

The sentence is sourced by Wald, p 299 (http://books.google.com/books?hl=en&id=9S-hzg6-moYC&pg=PA299), saying:

Basically, we wish to define a black hole as a "region of no escape" like region II of Figure 6.11, i.e. in physical terms a region of spacetime where gravity is so strong that any particle or light ray entering that region never can escape from it.

I know it's a bit of a quibble, but Timothy's version says that a black hole is deformed by gravity, which i.m.o. sort of puts the cart before the horse. I think that the original version (i.e. Wald's) subtly but carefully avoids doing that. So I propose we stick with Wald's version: a region of spacetime where... — What say others? - DVdm (talk) 07:17, 4 June 2012 (UTC)

The problem with the version you propose is that it wrongly suggests that gravity in a black hole is strong. As you may be well aware, this is not the case. The surface gravity of a black hole is inversely proportionate to its mass, and as a result the gravity at the horizon of a BH can be quite weak. This is not as much a problem in Wald's book, where a) the remark is made in the context of a textbook of GR allowing the reader to be aware of this issue, b) it is meant as a brief synopsis to give intuition for the technical definition discussed right after. Quite to the point the technical definition does not make any reference to "gravity being strong" it only focuses on the spacetime geometry preventing particles from escaping. Please not that ref 1 in the article references the whole discussion on pg 299 and 300 leading up to the formal definition.

In the past the sentence actually read: "A black hole is region of spacetime from which nothing can escape." Which is the most accurate reflection one can make of the technical definition presented in Wald. There have however been several requests to somehow reference gravity in the opening sentence. Which has prompted the "deformed by gravity" addition.

The problems with stating that gravity is strong in the opening sentence are examplified by the edit that was made by user:Cadiomals on May 16 in which the opening sentence was changed to "A black hole is a region of spacetime whose gravitational field is so strong that nothing which enters it...". Which went from merily misleading to flat out false.

On the other hand, I do understand your objection to stating that "a region of spacetime is deformed by gravity". (After all, gravity IS the deformation of spacetime) I'll think about this a bit, to try to devise a better formulation.T R 08:23, 4 June 2012 (UTC)

Let's just stay with the source. After all, it's Wald, right? And trying to devise a better formulation would be a bit wp:ORish, no? - DVdm (talk) 19:07, 4 June 2012 (UTC)

No, devising a better formulation has nothing to do with OR. (In fact, not doing so could be considered plagiarism). Taken out of context, the sentence from Wald is very much misleading, to point of being plain false. If you insist on staying close to the source we should go back to "A black hole is a region of spacetime from which nothing can escape". Because that is an accurate paraphrase of the technical definition given by Wald on page 300.T R 21:06, 4 June 2012 (UTC)

I don't see how it could be plagiarism, as the sentence was already paraphrased. Without the opening paragraph of section 12.1 on page 299, translating what he says on page 300 to "A black hole is a region of spacetime from which nothing can escape, " would of course be top-shelf wp:OR. So, if we agree that the opening sentence and the paraphrase is indeed very much misleading, to point of being plain false, then I propose we dump Wald and find another source with a text-based definition that is not misleading.

This is just a quibble, really, and besides, despite its 1056 watchers, no-one else seems to care anyway. - DVdm (talk) 06:54, 5 June 2012 (UTC)

On the subject of watchers caring, I _did_ consider nominating this for WP:LAME a few days ago, but the entries on that list have it beat by quite a margin. On a more serious note, it's probably worth posting a short note at WT:ASTRO and WT:PHYS asking for more opinions (I can see arguments for both versions, but don't have strong feelings either way). --Christopher Thomas (talk) 08:24, 5 June 2012 (UTC)

I really don't get what your trouble is here. Besides are rather misled tendency to stick too literally to sources, you have provided no argument against the current opening sentence. On the other hand, you have not respond to my objections to calling the gravity of a black hole "strong".T R 10:24, 5 June 2012 (UTC)

Some possible alternatives:

"A black hole is a region of spacetime where gravity prevents anything, including light, from escaping."

or

"A black hole is a region of spacetime where the local geometry prevents any signal from reaching a distant observer." (This is probably the most literal plain English paraphrase of the technical definition "A black hole is a region of spacetime not in the causal past of future null infinity" presented on page 300 of Wald. I don't think it is very suitable though.)

I am basically fine with almost anything that does not say that "gravity is strong" in a black hole. (Because that simply is not true)T R 10:37, 5 June 2012 (UTC)

^(ec)

The current opening sentence says that a black hole is deformed by gravity, which—as we agreed upon above—is not a good formulation.

If (1) Wald talks about a region of spacetime where gravity is so "strong" that such and such, and (2) Wald is considered to be reliable, and (3) we use Wald as a source, then I don't see any reason to respond to objections to calling the gravity of a black hole "strong".

Anyway, I don't mind leaving the strongness out of it, so how about

"A black hole is a region of spacetime where gravity prevents anything that enters the region, including light, from escaping.

where I have taken your first alternative and added the entering of the region, which seems to be typical for Wald's formulation. - DVdm (talk) 10:49, 5 June 2012 (UTC)

I would leave out the "entering of the region" bit, as it can be misread as implying that somehow it is possible for things that did not enter the region to leave. Again this is not as much a concern for Wald, because of a) his readership can be expected not to make that mistake b) his statement is imbedded in a more careful discussion that would dismiss such questions. Since physically this comes down to samething, it is safer (and better for a general readership) to omit the "entering the region" bit. (Much in the same way that we say "anything" rather than "any particle".)T R 11:06, 5 June 2012 (UTC)

Ok, let's go for your first alternative then. Sounds good for me. - DVdm (talk) 11:14, 5 June 2012 (UTC)

Moved religious material to talk page

I've moved the following recently added material here:

== Black Holes in religion and culture == In [[Quran]] chapter 81 (At-Takwir) verses 15-19 say: ''"So verily, I swear by the stars that are veiled . And by the sweeping (stars) that move swiftly and hide themselves. And by the night as it departs; And by the dawn as it brightens; Verily, this is the Word (this Qur'an brought by) a most honorable messenger [Jibril (Gabriel), from Allah to the Prophet Muhammad (Peace be upon him)"''. Some Muslim scholars suggest that this could be a reference to the black holes.<ref>http://www.answering-christianity.com/mahir/black_holes_miracle.htm</ref>

My concerns are that a) there is no demonstration that this represents a noteworthy view even among religious scholars, b) the source is a web page that doesn't seem to me to meet WP:RS. I also feel that a "religious discussion of black holes" section is inappropriate to the article period, but sufficient demonstration of cultural noteworthiness might change my mind about that. This has not been demonstrated so far. --Christopher Thomas (talk) 21:42, 15 June 2012 (UTC)

This material is irrelevant and has nothing to do with black holes. Nobody, especially any cosmologist, honestly believes that this refers to black holes. It was written in the 5th century. They had no idea what black holes or even stars really were back then. Dr. Morbius (talk) 01:08, 16 June 2012 (UTC)

Reference edit request

Hi, I have found a free fulltext for reference [74]. Can somebody with edit access replace current links (that lead to sites charging ~ 30 EUR) with this link? — Preceding unsigned comment added by Shooshpanchick (talk • contribs) 00:05, 23 June 2012 (UTC)

Done; thanks for the link! --Christopher Thomas (talk) 00:23, 23 June 2012 (UTC)

Classical mechanics is reversible

The following sentence was removed by User:TimothyRias with the edit summary “rremove silly sentence (classical physics is abound with dissipative systems that are not reversible)”:

Classically, the laws of physics are the same run forward or in reverse (T-symmetry). Liouville's theorem dictates conservation of phase space volume, which can be thought of as "conservation of information", so there is some problem even in classical physics.

Well... Actually the equations of motion are reversible in classical mechanics; what's not reversible is the boundary condition that says that the past had very low entropy. You don't normally see an egg unbreaking, but that's for entropic reasons, and if you could take a broken egg and exactly invert the momentum of each particle it would. Maybe the original sentence was misleading if worded like that because “the laws of physics” are usually taken to include the second law of thermodynamics, but I feel that something to that effect should still be included in the article. Comments? Ideas? ― A. di M. 16:44, 28 June 2012 (UTC)

Well actually in classical physics it is quite common to have systems which are truly dissipitive. Basically, any friction term in classical physics will cause this. The (unreferenced) sentence in the article is referening to the hypothetical case of a completely fundamental classical theory of the world. (Which does not exist, and taking the classical limit leads to thermal physics which has information loss. (At the level of continuum mechanics, the information about the details of an ice sculpture do dissappear when it melts. In fact, this is exactly analaguous to the information loss in black holes when viewed from an AdS/CFT perspective.)T R 17:02, 28 June 2012 (UTC)

Proper time and big rip

An observer could pass the event horizon of a massive black hole in proper time before being spaghettified. An outside observer will never see him cross the event horizon. Assuming the universe ultimately ends in the big rip, what will both observers see, and does the first one really pass the event horizon, or is the universe ripped apart before he gets there? Ssscienccce (talk) 19:31, 2 July 2012 (UTC)

Something for the wp:Reference desk/Science. Here we're supposed to discuss the article, not the subject. - DVdm (talk) 19:51, 2 July 2012 (UTC)

space,atoms and every thing inside it....!

There is a question that does the god particle really exists? a few days ago there was a new's that the scientist at genova have have found the higgs boson particle really exists.this new discovery has completed the 14 fundamental particle in the making of the universe or this higgs boson is not that on which the scientis were searching for the last 40 years or this particle is something else that could force the scientist on new basics again?....that would again put the mankind to it's first step of understanding the universe wholly

First off all what is higgs boson? it is a fundamental sub atomic part in the atom that has been known to create the universe.It is the thing which gives mass to every thing in this universe — Preceding unsigned comment added by 120.60.3.240 (talk) 18:07, 22 July 2012 (UTC)

First, this article is about black holes, not the Higgs boson.

Second, article pages are for discussing how the article should be changed, not for asking about the article's subject. Per the big green banner at the top of this page, general questions don't belong on article talk pages.

The place to ask questions like this is the science reference desk. --Christopher Thomas (talk) 20:47, 22 July 2012 (UTC)

infinite density?

The entry says "The singular region can thus be thought of as having infinite density." But then the gravity would be infinite and the event horizon would stretch indefinitely, no? 78.128.185.183 (talk) 22:22, 27 August 2012 (UTC)

Density is only infinite at an infinitely small point (the singularity). Extrapolating that to behavior far from the singularity gives you undefined results (as you end up dividing by zero in there). That's part of why the presence of a singularity in the mathematical description of black holes is usually taken as an indication that the description isn't correct in that region. --Christopher Thomas (talk) 22:35, 28 August 2012 (UTC)

Edit request on 16 September 2012

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If one read the text of this article it seems there is a chronological error in reference [9] 1915 cannot be the year of Droste's (a Lorentz student) independent finding of the Schwarzschild solution. It's too early. There was not enoug time to publish a solution that year, because Einstein's first publication on general relativity, if I remember well, was in November of that year. Schwarzschild found a few months later the solution that now carries his name, and the text in Wikipedia says that a few months later Droste found independently the same solution. Therefore I suppose it was published in 1916 or even the following year. One have to go to the original reference in Koninklijke Nederlandsche Akademie van Wetenschappen Proceedings 17 (3): 998–1011 to findRafael Rosende (talk) 01:24, 16 September 2012 (UTC) out the correct year.

The transcription in Wikipedia reads:

«In 1915, Albert Einstein developed his theory of general relativity, having earlier shown that gravity does influence light's motion. Only a few months later, Karl Schwarzschild found a solution to Einstein field equations, which describes the gravitational field of a point mass and a spherical mass.[8] A few months after Schwarzschild, Johannes Droste, a student of Hendrik Lorentz, independently gave the same solution for the point mass and wrote more extensively about its properties.» Rafael Rosende (talk) 01:24, 16 September 2012 (UTC)

I've asked other editors from WT:PHYS to take a look at this, as I'm afraid I don't have the literature familiarity to confirm this myself. Good catch noticing it, though! --Christopher Thomas (talk) 08:59, 16 September 2012 (UTC)

I'll look in to it. It appears that the paper by Droste referenced here [6] is not the one in which he presented his final solution for the full covariant version of the GR field equations. (Instead he was working with older preliminary versions presented by Einstein.)T R 10:23, 16 September 2012 (UTC)

Ok, I have figured this out (and corrected the article). The Droste paper that the text was referring to was presented to the KNAW on May 27, 1916 (Einstein's paper was presented in Nov 1915, and Schwarzschild submitted his paper Jan 1916). However, the reference referred to an earlier paper by Droste with almost the same title. (I think I may have introduced this error, when completing missing data from the references awhile back, when the KNAW's digital archives had not been published.) Anyway, it should be fixed now. Good Catch.T R 11:07, 16 September 2012 (UTC)

blackhole

Can or has a blackhole ever inverted ? It appears to me things that weren't thought possible are plausable in the feild of science. You can email me at davereinhart@ymail.com — Preceding unsigned comment added by Niners1849dave (talk • contribs) 06:38, 10 October 2012 (UTC)

Please sign your talk page messages with four tildes (~~~~). Thanks.

This is not really the place for asking questions about the subject — see wp:talkpage guidelines. You might try asking this at the wp:Reference desk/Science. Good luck. - DVdm (talk) 07:36, 10 October 2012 (UTC)

Magnetic field?

Sun has magnetic field, does BH have a magnetic field with n/s-polar-spots? And after reading MECO article, I think that MF could could be detected by "pass near" BH particle's (photons) polarity (core spin).

Ps. Is a black doughnut possible? (d'Oh) "The term "black hole" was first publicly used by John Wheeler" should be at top of article.

(As a whole I regard article wee bit too scientific in writing as a non-native reader. <-- delete) (84.231.0.235 (talk) 15:11, 18 October 2012 (UTC))

Note that wikipedia talk pages are not for asking general questions about a subject. For general questions you can try the wp:Reference desk/Science.

The short answer is: "Yes, a rotating charged black hole has a magnetic field."T R 15:31, 18 October 2012 (UTC)

First sentence - egregious error

The first sentence is outdated and the citation that accompanies it is dreadfully archaic, causing a directly logic contradiction in the introduction. This **must** be corrected.

First sentence of article: "A black hole is a region of spacetime where gravity prevents anything, including light, from escaping.[1]"

Indented line

full citation: pp. 299-300 Wald, Robert M. (1984). General Relativity. University of Chicago Press. ISBN 978-0-226-87033-5.

Then **in the same paragraph** "Quantum mechanics predicts that black holes emit radiation like a black body with a finite temperature."

Either 'nothing escapes' or they emit radiation. One or the other is true...and anyone who has studied astrophysics or astronomy in the last 15 years knows that **all** black holes emit radiation of some type.

I can't help but see the first sentence as some sort of attempt to maintain an old dogma in astrophysics that has been proven wrong. See: Hawking-Susskind debate and 'Hawking Radiation'

There are surely editors who can find an appropriate way to change this. It must be done. — Preceding unsigned comment added by 67.5.228.126 (talk) 20:03, 31 August 2012 (UTC)

follow up by the guy who asked this question: the last section of the article discusses the alleged 'information paradox' that according to disproven dogma could theoretically be an 'unsolved problem' in physics...however at then very end we see this, with cite:

"Over recent years evidence has been building that indeed information and unitarity are preserved in a full quantum gravitational treatment of the problem."[123] full cite: Mathur, S. D. (2011). "The information paradox: conflicts and resolutions". XXV International Symposium on Lepton Photon Interactions at High Energies.

This section also mentions another Hawking-involved 'debate' that has, essentially by all scientific measures, been proven in favor of no violation of any thermodynamic laws, information theory laws, etc....matter and energy go in, radiation comes out...i'm grossly oversimplyfying of course, but the first sentence of the article...'nothing escapes' really is just incorrect no matter how you look at it!

Please let's make this better! Think of the children... — Preceding unsigned comment added by 67.5.228.126 (talk) 20:14, 31 August 2012 (UTC)

These have both been addressed in previous talk-page threads; older threads can be accessed via the archive box at the top. To briefly summarize:

The General Relativity description of black holes is still the baseline description. This is where "nothing can escape from inside" and "all world-lines inside end at a pointlike or ringlike gravitational singularity" come from.
Hawking radiation does not represent world-lines crossing the event horizon. From far away, it looks like a thin film at the Planck temperature hovering about a Planck distance over the horizon (no horizon-crossing needed). Mathematically, you can express it in terms of energy bookkeeping among virtual particles (with the ones we observe originating outside of the horizon), or in terms of quantum tunnelling (the black hole tunnels from a system state of "no particles outside" to "particles exist outside"). Either way, no horizon-crossing.
There's been very strong circumstantial evidence for a while that black holes do not destroy information, but instead a) have a microstate (which they don't in the GR description), b) encode incoming entropy in that microstate, and b) couple that entropy back out into the outbound Hawking radiation. That said, my understanding is that the arguments for this are not universally considered proven, just very likely (it depends on what you think about the assumptions they make or how they set up the problem).

Long story short, the article starts with the simplest accepted description of black holes (that given by General Relativity), and then describes modifications to that description that are expected to be true but whose descriptions are either incomplete or not yet considered fully proven. --Christopher Thomas (talk) 21:09, 31 August 2012 (UTC)

The first line simply gives the definition of what is meant by a black hole. Anything that does not satisfy that definition is not a black hole. (Yes, this means that the quantum gravitational version of a black hole may not in fact be a black hole.)T R 22:12, 31 August 2012 (UTC)

Not sure everyone is using such a narrow definition. I think most people would continue to call things such as Sgr A* “black holes” even if Hawking radiation was shown to exist beyond a reasonable doubt. OTOH, I think the current wording of the article is fine – the reader just has to interpret the verb “prevent” more... er... ‘flexibly’ (FLOABW) if quantum effects are taken into account. — A. di M. 12:16, 2 September 2012 (UTC)

Hawking radiation does not originate from within the BH horizon, so that would never be a problem for this definition. Also, I think most people are using this narrow definition. When people talk about black holes, they mean the incredibly weird solutions of GR that have event horizons. In astrophysics, people just talk about compact objects that might correspond to black holes.T R 21:29, 2 September 2012 (UTC)

I think that most people don't distinguish between those meanings. For those that do understand the distinction, I've gotten the impression that "black hole" will still be the label assigned to this type of compact object in most situations, per A. di M.'s statements. Uncertainty over the equations of state of nuclear matter doesn't prevent us from using the term "neutron star", for example (even if the original assumption about their composition was an oversimplification).

As for clarifying this distinction in the article, the lede originally had text along the lines of "black holes are objects described by General Relativity as having Foo properties", in order to stem the tide of "Black holes don't exist!" and "Black holes are actually X!" edits back in the day (by focusing the scope down to the GR description), but if memory serves that was taken out a long time ago. It might be worth going back to something similar ("Black holes are objects predicted by GR as having Foo properties. When quantum mechanical effects are taken into account, they are also expected to have Bar and Baz properties.") --Christopher Thomas (talk) 21:49, 2 September 2012 (UTC)

From OP....thanks for the well written responses wikipedians...I'm a noob (obv) but I appreciate the thoughtful feedback...I obviously have a point but there are reservations...

This should clear everything up: "First images of particle jets at edge of a supermassive black hole" http://arstechnica.com/science/2012/09/first-images-of-particle-jets-at-edge-of-a-supermassive-black-hole/?comments=1#comments-bar

Link to academic article: http://arxiv.org/abs/gr-qc/0311038

Black Holes are **definitely not** "a region of spacetime where gravity prevents anything, including light, from escaping"

The first sentence of the whole article **MUST** be changed. It is blatantly not true. We have photographic evidence now.

Please, don't citation troll me, or jargon troll me, or Cambridge dogma troll me, or qualifications troll me, or in any way troll me...don't just say "Oh we covered this"....if it is such a resolved issue, then why can't you just type it out...why must I be linked to another windbag discussion that is nebulous at best in regards to the reasoning of leaving the incorrect sentence unchanged?

I stand by my original post. I do not feel anyone has offered a legitimate refutation of my original points, and now, this new evidence, imaged by NASA's Event Horizon Telescope makes it unbearable to see this simple, egregious error go unfixed.

Black Holes **ARE NOT** regions of space where nothing even light escapes...please fix or explain...and reference my Original Post above — Preceding unsigned comment added by 67.5.218.99 (talk) 22:21, 28 September 2012 (UTC)

From OP...one response to this objection from Christopher from above: "Long story short, the article starts with the simplest accepted description of black holes (that given by General Relativity), and then describes modifications to that description that are expected to be true but whose descriptions are either incomplete or not yet considered fully proven."

A simple explanation does **NOT** completely contradict itself in two paragraphs...first sentence says 'nothing escapes'...second paragraph says 'radiation always espaces'....it is **NOT** more 'simple' to explain black holes by being completely contradictory!!!

I feel I have completely answered this objection to my suggestion for edit. There are many, many qualified persons who could, deftly and in one sentence explain the basic properties of a black hole without actively stating disproven facts ('nothing escapes'), and thereby contradicting itself blatantly several times later.

Please edit first sentence of the Black Hole article. — Preceding unsigned comment added by 67.5.218.99 (talk) 22:27, 28 September 2012 (UTC)

You misunderstand where those jets come from. Per relativistic jet, they're produced by interactions in the accretion disc of infalling matter outside the event horizon.

Regarding your second objection, as has been explained several times on this talk page, including my own earlier response, Hawking radiation also originates outside the event horizon.

If you feel that statements in the lede are inaccurate, feel free to provide references to appropriate sources backing up your position, and make sure you're clear on what the sources actually say (per comments about polar jets, above). --Christopher Thomas (talk) 00:22, 29 September 2012 (UTC)

From OP...Thanks for the response, [User talk:Christopher Thomas|talk]...I disagree strongly but thanks... I'd like to hear a few more points of view. Christopher should not be the only one making this judgement. I don't have a direct response now, b/c I feel it will devolve into an argument over definitions of non-scientific words like 'inside'...(ex: 'If it's not **inside** the event horizon then it isn't 'in' the black hole...so therefore it can't go 'out')

I won't have that discussion. This is **obviously** a question of wording and not science. In other words, this is politics...let's make this change. — Preceding unsigned comment added by 71.34.75.149 (talk) 19:10, 15 October 2012 (UTC)

You can jump high or low, but this wont change the fact that black holes are defined as "regions of space from which nothing can escape". As is supported by authoritative sources. (Or if you wish in more technical language: "a region of spacetime that is not in the casual past of future timelike infinity" But I am sure that you agree that that is not a suitable formulation for the lede.)

As has been said several times before, the (suspected) fact that black holes emit Hawking radiation does not contradict this definition because Hawking radiation does not originate inside the black hole. Exactly, how this radiation would allow black holes to evaporate is a subject that continues to baffle theorists. (It is essentially the black hole information paradox) Currently, the most advanced answers to this paradox boils down to "things can come out of a black hole because they never go in". (As weird as that sounds.)T R 22:19, 15 October 2012 (UTC)

(edit conflict) Strictly speaking, there is indeed an inconsistency in the first paragraph: The first sentence is phrased as a general definition of the term black hole, not obviously limited to a purely GR treatment. The part about the quantum mechanical prediction implies a slightly different definition, which encompasses also the region where the Hawking radiation originates. I think the easiest solution (without going too much into details in the lede) is what Christopher Thomas suggested above: "Black holes are objects predicted by GR as having Foo properties. When quantum mechanical effects are taken into account, they are also expected to have Bar and Baz properties." — HHHIPPO 22:23, 15 October 2012 (UTC)

That suggestion would be very much flawed, because the definition given in the first sentence is, in fact, not limited to GR, but applies to any (metric) theory of gravity. (i.e. it is just as applicable to alternative theory such as Supergravity, Brans-Dicke, TeVeS, Conformal Gravity, you name it). I also don't quite see how the statement: "Quantum mechanics predicts that black holes emit radiation" implies a different definition. If it makes people feel better we could instead write: "Quantum mechanics predicts that event horizons emit radiation", which is closer to the what QM actually predicts.T R 06:13, 16 October 2012 (UTC)

Good point regarding the first sentence, I agree that should stay general rather than GR-specific. What I meant by the different definition in QM is this: QM says black holes emit radiation, so its definition of 'black hole' includes some region from which radiation can be emitted (namely the event horizon or the first Planck length outside it). Now we earlier defined 'black hole' as a region from which radiation can't escape. I think for a non-expert reader who reads only this lede that's at least confusing.

I would usually use 'black hole' in the sense of 'an object that has an event horizon', with the source of Hawking radiation considered still part of the object. I'm not sure though if that can be phrased lead-friendly. Anyway, we don't need to discuss all the tiny details in the lede, we should just avoid a phrasing that can too easily be understood as self-contradicting. Maybe 'event horizons emit radiation' is not too bad, that shows immediately that the radiation is not coming from the interior. — HHHIPPO 18:25, 16 October 2012 (UTC)

From OP...Thanks TR , HHHIPPO, TimothyRias, others...I appreciate the thoughtful discussion...sorry i'm a noob w/ my text formatting

TR wrote this: "If it makes people feel better we could instead write: "Quantum mechanics predicts that event horizons emit radiation", which is closer to the what QM actually predicts."

HHHIPPO and TR both are going the direction I was hoping for...I think making the event horizon distinction does add complexity, it is closer to the most accurate wording for an opening sentence. Black Holes are a complex phenomenon...the first sentence on the entry will inevitably reflect that. — Preceding unsigned comment added by 71.34.75.149 (talk) 23:38, 23 October 2012 (UTC)

//fixed-thank you//

final edit from OP...thanks wikipedians! It has been great watching this edit unfold. The changes to the first paragraph are excellent. Good work, and thanks for putting up with my bad text formatting!

please edit/remove this as necessary...don't want to clutter this talk page

i would hope this interchange gets archived somewhere, idk, i think it's great evidence for wikipedia's superiority...— Preceding unsigned comment added by 71.34.75.149 (talk) 18:40, 28 October 2012 (UTC)

Moved here from top of section, restored section title — HHHIPPO 19:00, 28 October 2012 (UTC)

You're welcome, this is how it's supposed to work. This discussion will be moved to an archive automatically after two months. — HHHIPPO 19:00, 28 October 2012 (UTC)

Suggestion - effect on human bodies

Just a suggestion, but I think it might be useful to explain what the effect of a black hole would be on human bodies. --The Lord of the Allosaurs (talk) 15:54, 26 October 2012 (UTC)

Situation of black holes

The article states in the beginning that black holes are situated in spacetime. However, spacetime is just an abstraction, it is just a mathematical model astronomists can use to think about all kinds of objects in space. Therefore, black holes are not situated in spacetime - they are situated in space itself that is not an abstraction and thus space exists in concrete reality and black holes too if way say that they are situated in space. --Hartz (talk) 15:09, 2 November 2012 (UTC)

I don't see the word "abstraction" used anywhere in the spacetime article. Dr. Morbius (talk) 17:53, 2 November 2012 (UTC)

Maybe they consider it evident. Reification (hypostatization) – a fallacy of ambiguity, when an abstraction (abstract belief or hypothetical construct) is treated as if it were a concrete, real event or physical entity. In other words, it is the error of treating as a "real thing" something which is not a real thing, but merely an idea. Spacetime is merely an idea, not a real thing. It is called a concept of spacetime. --Hartz (talk) 18:04, 2 November 2012 (UTC)

The article does not say that black holes are situated in spacetime, but that they are regions of spacetime. If you think indeed that spacetime is an abstraction, then you might also consider black holes to be abstractions. On the other hand, if you prefer to look at spacetime as someting more tangible (--see article Spacetime: "The term spacetime has taken on a generalized meaning beyond treating spacetime events with the normal 3+1 dimensions. It is really the combination of space and time."), then of course your black hole becomes dramatically less abstract too. Anyway, the opening lead sentence is pretty well backed by a rather solid —albeit a somewhat technical— source. - DVdm (talk) 21:38, 2 November 2012 (UTC)

Black holes are not abstractions - they are observable reality and therefore there is no need to consider them as abstractions (comparable to stars and planets), black holes are concrete. Spacetime cannot be looked at as more tangible, because it cannot be looked at, it is unobservable as it is an abstract concept. Similarly the United States cannot be looked at - you do not see the United States, it is unobservable. If the state of California is a region of the United States, then California is situated in the United States. The United States is an abstract concept and the state of California is also, and therefore it does make sense to talk about an abstract concept as a part of an abstract concept. However, for example the Missisippi river is situated in the physical geography of a land mass, not in the United States in reality, but an abstract concept called United States spans over this land mass. --Hartz (talk) 06:16, 3 November 2012 (UTC)

By your logic, black holes also cannot be situated in the Universe, because the Universe is an abstraction that cannot be observed. Your welcome to that opinion, but it defies common sense. Not to mention, that your statement spacetime is more abstract than space makes even less sense. Spacetime has physical properties (curvature) which can be observed. Space cannot be viewed separately from spacetime. In fact, one of the consequences of relativity is that space cannot be viewed (visually) directly. What you see is always a null hypersurface of spacetime.T R 07:26, 3 November 2012 (UTC)

Ok. That's your view. Everyone is entitled to their beliefs. Please see the comment from DVdm below. --Hartz (talk) 16:29, 4 November 2012 (UTC)

Some views are just more equal than others.T R 06:57, 5 November 2012 (UTC)

Re Hartz: Based upon the reader's preference of what spacetime is and whether they think it is abstract or not (—and both views seem to be common, and implicitly expressed in our article about spacetime—), they can decide the same thing about the level of abstractness of black holes. That sounds like a fair deal, and a properly sourced one. And of course it is not for us to impose one view upon the reader. - DVdm (talk) 09:55, 3 November 2012 (UTC)

Ok. Then this article should give voices to both views. Although, the view that spacetime is concrete is wrong, haha :) (in good jest) --Hartz (talk) 16:29, 4 November 2012 (UTC)

No, it should not, because your view on this makes no sense at all in this context. For the most common concept of space (essentially equal time slices in Minkowski time), it will never (by definition) contain a black hole. The whole concept of black holes only makes sense in relation to the causal structure of spacetime.T R 06:57, 5 November 2012 (UTC)

Everyone is entitled to their beliefs. I do not understand the "causal structure of spacetime" you mentioned. I would suggest you to ditch the "concept of space" for a while (and forget the untrue spacetime and all other abstractions) and look at the space itself in its concrete form at night, and realize that the Earth is part of a solar system, the solar system is part of a galaxy, and in the center of the galaxy is situated a supermassive black hole. The supermassive black hole does not care about your Minkowski time, concept of space, spacetime or concept of black holes at all - neither does the Moon or the Earth's core. These all exist without any abstractions or human thought. Observations of phenomena should always be first, then calculations follow. Astronomy as a field is full of theorists and crackpots. I heard a comment lately that string theory should be accepted without empirical evidence, and this reflects the level of the science. I wonder if someone suggests that we should fly into a black hole because it might be a wormhole according to a theory! *facepalm* --Hartz (talk) 16:59, 5 November 2012 (UTC)

Your are entitled to your opinion. However, it is kinda of ignorant and based on several incorrect assumptions. (Basically, you are wrongly extrapolating physics as you observe in everyday life to extreme situations. We know these assumptions to be incorrect.)T R 17:45, 5 November 2012 (UTC)

I'm sorry, that I incorrectly bashed astronomy as I intended to bash the current state of cosmology. Wrongly extrapolating physics from everyday life sounds interesting as laws of physics are universal, but it is thought that some laws of physics might break down in certain situations, but this remains unproven (until we can examine black holes closer). --Hartz (talk) 08:38, 6 November 2012 (UTC)

That laws of physics are universal is an assumption. Moreover, there are many "laws of physics" that work perfectly in everyday life, but that fail miserably in more extreme (but experimentally accessible) situations. Newtonian mechanics en Galilean relativity are good examples. (And it is those laws that you are wrongfully extrapolating)

It is also good that science has not followed your dogma of "observation should precede theory". Because without essential theoretical groundwork, we would still be stuck in the 19th century. (The laser, is a good example of a piece of technology that would have never been discovered without first being theoretically discovered.)

Anyway this discussion, no longer has any bearing on improving this article. Therefore, per WP:TPG, it should be discontinued.T R 09:13, 6 November 2012 (UTC)

I haven't read the whole thread (just the first couple comments and skimmed the rest), but I agree that it would make more sense to say “a region of space” than “a region of spacetime” (though the OP's arguments for this are weak). — A. di M. 16:42, 14 November 2012 (UTC)

Why? Per definition, a black hole is a region of spacetime that is not in the causal past of future timelike infinity. On the other, hand in many common time foliations (such as the Schwarzschild one) do not intersect this region. As such the statement "a black hole is a region of space" does not really make that much sense.T R 07:31, 15 November 2012 (UTC)

Misleading phrase

The first time I read the following sentences:

"The shape of the event horizon of a black hole is always approximately spherical.[Note 2][53] For non-rotating (static) black holes the geometry is precisely spherical, while for rotating black holes the sphere is somewhat oblate."

I thought they were wrong. The event horizon of a rotating black hole is still a spherical surface (the ergosphere is oblate). After rereading it several times I think the sentence just refers to the geometry on the outside. But it could be rephrased as

"For non-rotating (static) black holes the geometry (outside the black hole) is precisely spherical, while for rotating black holes it is somewhat oblate."

or something similar.

141.2.249.114 (talk) 13:56, 9 November 2012 (UTC) Thomas Schönenbach 9th of November 2012, 14:54 CET

Falling into a black hole at the speed of light

In Caleb Scharf's recent book, Gravity's Engines, he mentions that as an object hits the event horizon of a black hole, it will be travelling at the speed of light, and presumably with infinite energy, which has come from somewhere! Given the opening quotes from Mitchell, would it not be appropriate to provide an explanation of this interesting fact somewhere in the article? Very good article, by the way! 51kwad (talk) 08:17, 13 November 2012 (UTC)

No, because that interesting fact is bonkers. Dauto (talk) 17:07, 13 November 2012 (UTC)

Travelling at the speed of light relative to what? This question, if you think about it, highlights the flaw in Scharf's statement.82.0.143.29 (talk) 19:49, 16 February 2013 (UTC)

If you do the calculation using Newtonian mechanics, you find that you are travelling at the speed of light when you reach the event horizon. However, black holes do not even exist in Newtonian mechanics, so it's entirely inappropriate to do that. — Preceding unsigned comment added by 86.26.13.2 (talk) 02:12, 28 November 2012 (UTC)

rewriting the topic

According to Vasily Yanchilin in his book The Quantum Theory of Gravitation (2003) black holes do not exist (big masses do). Einstein invented the general theory of relativity a century ago when quantummechanics did not yet exist to explain that the speed of light is constant. The special theory of relativity stays valid if understood thus that the propagation of electromagnetic waves is related to the potential of the total mass of the universe (Mach principle), which is the same in all directions at a certain time and a certain place but decreases with the expansion of the universe. So in the past the speed of light was bigger and the supernovae Ia standard has to be revised. This means that accellerated expansion of the universe, the cosmological constant, negative energy, inflation and black holes become phantasy. (The Nobel prize physics 2011 has to be returned as well as the Spinoza premium 2011). Einstein made the mistake not taking time as connected to physical processes. Everybody agrees that near mass the unit of length gets smaller and thus distances become bigger. The atom there shrinks and electrons will rotate faster since no change appears in electric charge. Time is measured according activities of those electrons. So near mass the second shrinks and the duration of physical processes likewise, while the unit of length shrinks but distances become bigger. Then consider the movement of a photon passing a mass. It will obey the principle of least action, taking as big steps as possible (low frequencies) and a minimum number of these. If Einstein were right the photon's track would be a hyperbole. (Check). So the general theory of relativity is wrong. It can neither explain the red shift of sunlight, as such in this theory originates from overcoming gravitation and slower time on the sun, while not the sum of both is measured. Yanchilin gives new interpretation. This russian scientist presents a beautiful new theory on gravitation, taking as hypothesis that near mass the Heisenberg uncertainty decreases: In the half of a particle nearest to an external mass there will be less transitions (in the Heisenberg sphere) towards the more distant half than in the opposite way. The netto result is movement of the particle towards the external mass. Negative gravitation then cannot exist. I add that such makes understandable why no mass is felt when a thing is not near something else unless a force is applied. At the edge of the universe everything looses speed and direction, gets undetermined and things cannot exist anymore. Potential and speed of light become zero. Yanchilin calls this chaos in contrast to the universe where mass determines the physical laws. In the past with a smaller universe this was more classic. The enormous speed at the Big Bang contrasts sharply with standstill of time at supposed black holes. For derivation of the new correct formula of an interval see the book, available at the Library of Congress. Jitso Keizer, www.janjitso.blogspot.com, janjitso@hotmail.com — Preceding unsigned comment added by 130.37.93.67 (talk) 11:46, 28 December 2012 (UTC)

Summary: “This russian scientist presents a beautiful new theory on gravitation...” — Preceding unsigned comment added by 86.140.51.175 (talk) 23:00, 1 March 2013 (UTC)

Lead to article

The lead (introduction?) to this subject is so poor as to be virtually nonsensical. Complex the matter may be, but normal sentence order and deductions which might follow, and so forth should still be followed.

For example, the second sentence states that GR predicts the existence of black holes. It does not. As the lead itself states, further down, GR theoretical work showed the existence of Black Holes could or might be or ought to be construed as a prediction of GR. GR itself did not make any such statement as to the existence of such. That is an important difference.

Another example, the prediction of Quantum Mechanics re: radiation. It is still a prediction. As far as the lead suggests - and I dont know otherwise - no radiation has yet been measured. So why is that statement in the lead at all and not in a part of the article (if there is such) where theoretical/predictive assumptions might be explored.

There are other examples.

I don't want to re-write a well-looked after article. But I would suggest that the good folk who edit this go back and tidy-up that introduction. 213.114.45.61 (talk) 10:44, 29 November 2012 (UTC)

Sorry, but I find it hard to make any sense of your comments.

With your first comment are you trying to say that the existence of black holes does not follow from general relativity?

As for your second point: Yes Hawking radiation is a theoretical predicition and has not been observed. Strictly, speaking the same is true for black holes. I don't see what this has to do with being mentioned in the lead or not.T R 12:36, 29 November 2012 (UTC)

Not only do black holes not follow from general relativity, but GR in fact precludes their existence. See this paper: htttp://arxiv.org/pdf/physics/0402088v1.pdf

Black holes are nothing more than a hypothetical construct that spun out of control because they sound "cool" and get the pop-science journalism crowd excited. — Preceding unsigned comment added by 65.94.245.240 (talk) 01:35, 24 January 2013 (UTC)

arXiv is not a peer-reviewed journal, and no meaningful consensus exists regarding its stated theories. As such, it has no place in this article. Please see http://en.wikipedia.org/wiki/Wikipedia:FRINGE for more information on using reliable scientific sources. 74.134.243.62 (talk) 07:09, 8 March 2013 (UTC)

Distracting animation

Hi. The article itself is very good and well-written, but one animation that runs constantly makes reading very hard and distracting. I'm talking about the one with the caption "Simulation of gravitational lensing by a black hole, which distorts the image of a galaxy in the background (larger animation)". It runs on its own and there is no way to stop it. Can it please be changed to start upon clicking, just like all the other animations on the page? Thank you. — Preceding unsigned comment added by 109.121.91.251 (talk) 12:16, 5 January 2013 (UTC)

I wish there was an easy way to do that, but with gifs there isn't. It would have to be converted to a different format. RockMagnetist (talk) 18:29, 29 March 2013 (UTC)

OK, I understand. Thank you for answering. — Preceding unsigned comment added by 109.121.91.251 (talk) 23:29, 6 April 2013 (UTC)

Recent reverts

I moved these comments here from my talk page. RockMagnetist (talk) 16:21, 28 March 2013 (UTC)

http://en.wikipedia.org/wiki/Black_hole ...As predicted by general relativity, the presence of a mass deforms spacetime in such a way that the paths taken by particles bend towards the mass.[46] At the event horizon of a black hole, this deformation becomes so strong that there are no paths that lead away from the black hole.

http://en.wikipedia.org/wiki/Event_horizon ...Third, the description of black holes given by general relativity is known to be an approximation and it is expected that quantum gravity effects become significant in the vicinity of the event horizon.

http://en.wikipedia.org/wiki/Quantum_gravity ...However, there are certain physical phenomena such as singularities that are "very small" spatially (volume) yet are "very large" from mass and energy perspectives. Such objects cannot be understood with current models of quantum mechanics, nor can they be explained by general relativity. This situation highly motivates the search for a theory of quantum gravity. — Preceding unsigned comment added by Cserez (talk • contribs) 15:26, 28 March 2013 (UTC)

I presume you're questioning my recent reverts of your edits. Those quotes are perfectly consistent with the edits I made. Actually, the only discussion of the role of quantum gravity that is supported by citations is in this article. Instead of replacing some of the existing lead, I suggest adding a sentence summarizing the limits of general relativity. RockMagnetist (talk) 16:29, 28 March 2013 (UTC)

Infinite loop

Light from the collapsing material takes longer and longer to reach the observer, with the light emitted just before the event horizon forms is delayed an infinite amount of time.

This sentence is in an infinite loop. — Preceding unsigned comment added by 76.27.233.125 (talk) 03:39, 31 March 2013 (UTC)

this is crazy!

Imagine how great of a force the black hole has..... It is puzzling me, cuz its such a far out topic. — Preceding unsigned comment added by 97.92.150.20 (talk) 02:17, 13 June 2013 (UTC)

Edit request on 15 August 2013

This edit request has been answered. Set the |answered= or |ans= parameter to no to reactivate your request.

Astrophysics research update

New research out of Stanford U from the physicist Leonard Susskind may be able to address the quantum mechanical paradox of Hawking Radiation. Using traditional Relativity, all matter and radiation going into a hole is lost to the universe forever. Hawking showed with Quantum Mechanics that the horizon isn't opaque, but that radiation can leak from the hole as radiation. It failed to address the loss of information unique to the matter that fell into the hole.

Susskind may have solved the information paradox by confining all the energy that has ever fallen into the hole in a firewall of energy just below the event horizon. Using this technique, all the energy that has ever fallen into a hole will leak out in time.

http://www.nytimes.com/2013/08/13/science/space/a-black-hole-mystery-wrapped-in-a-firewall-paradox.html?ref=science&_r=0&pagewanted=all Paradoxsquared (talk) 23:50, 15 August 2013 (UTC) {{EPs|n}}the linked article is very fuzzy, and more should become publicly discussed before it should be added to the article. Martijn Hoekstra (talk) 21:01, 23 August 2013 (UTC)

Advice seems inappropriate

The line "...after attaining a certain ideal velocity, it is best to free fall the rest of the way." reads like something Bear Grylls would say in an episode of Man vs Wild. Is it really appropriate here? The Wikipedia pages for deserts and jungles don't have "it is best to..." advice, so it seems odd that this info be given for black holes. Kansaikiwi (talk) 23:25, 24 August 2013 (UTC)

Thank you for your suggestion. When you believe an article needs improvement, please feel free to make those changes. Wikipedia is a wiki, so anyone can edit almost any article by simply following the edit this page link at the top.
The Wikipedia community encourages you to be bold in updating pages. Don't worry too much about making honest mistakes—they're likely to be found and corrected quickly. If you're not sure how editing works, check out how to edit a page, or use the sandbox to try out your editing skills. New contributors are always welcome. You don't even need to log in (although there are many reasons why you might want to).

The entire Singularity section could do with some proper cleanup, actually. Martijn Hoekstra (talk) 09:58, 27 August 2013 (UTC)

How long does it take for black holes to become static?

The article talks about static black holes, but doesn't indicate whether existing black holes are static. Existing black holes quickly become static ("no-hair") outside the event horizon, but I can't find a reference stating how fast the black hole interior region reaches a symmetric equilibrium despite all the lumpy matter that went into its creation. I guess the basic question here is, are the simplified models discussed in the article considered good approximations to existing black holes? If there are currently no static black holes in nature, maybe the text should note that. Rolf H Nelson (talk) 23:26, 14 September 2013 (UTC)

Semi-protected edit request on 1 January 2014

ṯhttp://en.wikipedia.org/w/index.php?action=edit&preload=Template%3ASubmit+an+edit+request%2Fsemi-preload&editintro=Template%3AEdit+semi-protected%2Feditintro&preloadtitle=Semi-protected+edit+request+on+1+January+2014&section=new&title=Talk%3ABlack+hole&create=Submit+an+edit+request# — Preceding unsigned comment added by 1.38.31.4 (talk) 11:04, 1 January 2014 (UTC)

Semi-protected edit request on 7 February 2014

I can understand protecting the page, but I was wondering if a few of the gramatical errors could be removed, over all, I think it's a good article. — Preceding unsigned comment added by Armchairphysicist (talk • contribs) 18:13, 7 February 2014 (UTC)

let be more clear- I would just like to see "these data" changed to "this data" in the last paragraph in the intro Armchairphysicist (talk) 18:31, 7 February 2014 (UTC)

Copyedited Rolf H Nelson (talk) 02:40, 8 February 2014 (UTC)

Planck star

Planck star redirects here, but the term is not mentioned in the article. Paradoctor (talk) 16:04, 16 February 2014 (UTC)

Wikipedia:Articles for deletion/Planck star was closed as merge and redirect. (without the merge, it is an improper redirect). The following needs to be merged into the article,
A '''Planck star''' is a type of star proposed to exist inside [[black hole]]s.<ref>https://medium.com/the-physics-arxiv-blog/6cf7ec0ed28b</ref>
or the redirect deleted or reverted. --SmokeyJoe (talk) 02:04, 24 February 2014 (UTC)

How Black Holes Are Created?

Black holes are created when a star dissipates or in other words, runs out of helium or hydrogen, it's main resources. Our star, the sun, will change its form after the world is destroyed thankfully. Why I say this is, when the sun grows older, the sun expands to 1,000 times it's size! The sun will have burnt our planet to a crisp by then. ParanormalPanda (talk) 04:01, 9 January 2014 (UTC)

Please ask at the wp:reference desk/Science. Here we duscuss the format and content of the article, not the subject—see wp:talk page guidelines. Good luck at the ref desk! - DVdm (talk) 08:31, 9 January 2014 (UTC)

I'm not familiar with the protocol here, and don't know where to place this comment. The second sentence of the article states "The theory of general relativity predicts that a sufficiently compact mass will deform spacetime to form a black hole." I don't believe this is a true statement. I have not located any article in the literature that proves this claim. A citation would be in order. 2001:5B0:2BFF:EF0:0:0:0:3D (talk) 23:40, 23 February 2014 (UTC)

Added a cite to the cosmic censorship hypothesis and hedged with "usually". If someone wants to revert the "usually" they can do so, I'm ambivalent about it. Rolf H Nelson (talk) 04:02, 25 February 2014 (UTC)

I am required to submit references to peer reviewed articles in which gravitational collapse to a black hole is demonstrated. 2001:5B0:2BFF:EF0:0:0:0:3D (talk) 04:38, 1 March 2014 (UTC)

Golden Age of General Relativity

Could someone change this to link directly to the correct section? I can't get it to work with the "see also" coding. TJSwoboda (talk) 18:15, 14 March 2014 (UTC)

Try Template:See_also#See_also:_Link_to_section. Paradoctor (talk) 22:40, 14 March 2014 (UTC)

Overall position of article- do they exist or not?

In several places, the article suggests that the existence of black holes is predicted by quantum physics & astrophysics, but points out that direct observation from the surface of the earth has so far yielded only "candidates". I suggest, therefore, that in opening paragraph at least, & at several points throughout the article, it should be pointed out that black holes are a 'predicted' or 'theoretical' phenomenon, at least until we can stand outside at night & point at one! at the moment, the article assumes their existence has been proved, without supporting this assertion. duncanrmi (talk) 13:09, 25 January 2014 (UTC)

Outside at night is probably not the best of places. Try here - DVdm (talk) 14:40, 25 January 2014 (UTC)

Would info from this article be appropriate? It does say that his paper has yet to pass peer review. --FF9 (talk) 22:15, 25 January 2014 (UTC)

Perhaps we should wait a few months until he changes his mind again. DVdm (talk) 22:23, 25 January 2014 (UTC)

Is Hawking now taking on himself in the naked singularity bet?:

Original bet: http://www.theory.caltech.edu/people/preskill/old_naked_bet.html New bet: http://www.theory.caltech.edu/people/preskill/new_naked_bet.html Wikipedia's view on what one is: https://en.wikipedia.org/wiki/Naked_singularities — Preceding unsigned comment added by 67.168.187.66 (talk) 04:56, 26 January 2014 (UTC)

As far as I can tell, all physicists believe that black holes (broadly speaking) exist, and the existence of black holes is generally reported as fact, for example [7]. Therefore the lede does not need to have any caveats at this time, unless someone can point to sources that say otherwise. Rolf H Nelson (talk) 04:28, 29 January 2014 (UTC)

It would be nice if the phenomenon/theory/model were presented with more discipline. I suggest that the article should be clear as to whether the basis is astronomy, astrophysics or cosmology. Astronomy is a science of readily observable facts. I don't believe that there is any strong astronomical data that helps in describing the nature of a black hole, unlike the nature of the moon. Astrophysics is a science based on data and established theory. Black holes in astrophysics appear to be an extrapolation of what is known, there being no experimental data on physics inside a black hole. Cosmology is modelling, with a lot of detail for the number of constraining experiments, containing more mathematics than observed facts, and the facts of cosmology should be presented with explicit tentativeness.

In particular, I think that the "theory ... predicts" language of the second sentence of the lede should precede the factually absolute first sentence.

Most of the rest of the article appears fine, as in not prone to mislead as to the certainness of the information. However, the section beginning "The simplest black holes have mass but neither electric charge nor angular momentum" calls for a mention that this is describing a model, something inferred, and is not describing something ever physically observed. --SmokeyJoe (talk) 07:27, 29 January 2014 (UTC)

The first sentence, "A black hole is a region of spacetime from which gravity prevents anything, including light, from escaping", can be taken as a rough definition rather than as a fact, even if you don't agree that black holes should be presented as facts. If someone still wants to say it's a hypothetical or theoretical region, I'm open to being convinced, but you'll need to start by producing a modern source that uses such terminology. Rolf H Nelson (talk) 07:59, 29 January 2014 (UTC)

That said, if you're talking about the actual properties of black holes, then yes, that's a source of active controversy, so please be bold and try to fix it. I agree "the facts of cosmology should be presented with explicit tentativeness" in many cases, but we need to look at them on a case-by-case basis; at an extreme, surely you'd agree that "the universe is expanding" doesn't need to be presented tentatively! Rolf H Nelson (talk) 07:59, 29 January 2014 (UTC)

"A black hole is defined as a region of spacetime from which gravity prevents anything, including light, from escaping" I think reads much better. --SmokeyJoe (talk) 02:09, 24 February 2014 (UTC)

[8] looks like scholars present black holes as fact when summarizing, so we probably should as well. For example the abstract to [9] reads "the nuclear black hole (M) in NGC 3706" rather than "the hypothetical nuclear black hole (M) in NGC 3706." Rolf H Nelson (talk) 04:07, 25 February 2014 (UTC)

No, scholars writing of black holes would be assuming that their audience knows what black holes are. I'm thinking of Wikipedia readers who may not have ever studied any physics. Of course we, and nobody, would talk of a "hypothetical nuclear black hole (M) in NGC 3706". I think black holes are universally considered much more than a hypothesis. There is little doubt (I assume), that there is a black hole in NGC 3706. There may be doubt as to what exactly is a black hole, when looking at it up close. I know that the lede suddenly worked better when someone suggested reading it as a definition. The black hole is is the region inside the event horizon, without getting hung up on what is the event horizon, and this region contains whatever structure, if any, there is inside. The black hole, as defined, is different to the mass (of whatever unknown form/structure) is inside. I was thinking, musing, as to whether this article should distinguish more between what is observed (or inferred from observations) and what is theoretical. Maybe it's not important. --SmokeyJoe (talk) 06:20, 25 February 2014 (UTC)

I generally agree. However, I would like to clarify the position of the community on the existence of black holes. There is lots of circumstantial evidence for the existence of black holes. So much so, that until somebody comes up with a better explanation of our observations, most physicists/astrophysicists/astronomers are working under the assumption that black holes exist. However, what is currently missing is direct evidence for the defining characteristic of black holes: the presence of an event horizon. Until that confirmed (e.g. by observing the ringdown in the gravitational wave signal from a black hole binary merger), most people in the field (in particular the astrophysicists working on black holes) also consider the distinct possibility that the objects observed in active galactic nuclei and compact binaries are not black holes but something more exotic.

In that sense, the status of black holes is very similar to that of gravitational waves. (or the Higgs boson a few years back). Based on circumstantial evidence most people do not doubt their existence, but in the absence of direct physical evidence nobody is really certain.T R 14:03, 7 April 2014 (UTC)

Current new News

Great article! I'll be 'watching' and adding to TALK. The animation of graphics in this article is amazing--congratulations.

Headline-1: Weird Corkscrew-Shaped Light Unleashed by Universe's Most Powerful Explosions

http://www.space.com/25707-corkscrew-shaped-light-gamma-ray-bursts.html

QUOTE: "This artist's impression of a gamma-ray burst shows the two intense beams of relativistic matter emitted by the black hole. To be visible from Earth, the beams must be pointing directly towards us. ... The discovery, unveiled Wednesday (April 30) in the journal Nature, contradicts what theoretical models have always predicted about so-called circularly polarized light in gamma-ray bursts and has at least one scientist completely [surprised]." Very nice picture. Credit: NASA/Swift/Mary Pat Hrybyk-Keith and John Jones-- AstroU (talk) 23:05, 2 May 2014 (UTC) -- PS:FYI for future editing.