Talk:Black hole

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IP comment

The section on singularities could use the addition of this new article: http://io9.com/5596712/every-black-hole-may-hold-a-hidden-universe The scientist in the article describes a theory in which the singularity predicted by classic GR is not what happens at the center of the black hole. Sorry if I have done something wrong, the semi-protection of non-controversial pages has forced me to the talk page which I have never used before. Thanks. —Preceding unsigned comment added by 76.121.148.242 (talk) 07:26, 23 November 2010 (UTC)

That article is baloney. If there’s a universe inside a singularity, then that universe contains black holes, which contain universes, which contain black holes, etc, etc.

More interestingly, and amazingly, in 15 years there could be direct observational evidence of what is going on inside a black hole. See: http://arxiv.org/pdf/1011.5874

Briefly, this is what its about: Its estimated a few supermassive black hole mergers occur per year, in the center of merging galaxies. These mergers are preceded by about a month with a unique electromagnetic signature which along with the Laser Interferometer Space Antenna (LISA) can identify the host galaxy. Then the physical merger of these SMBHs will take seconds depending on size. If black holes are point singularities, at the merger nothing will be ejected of course. If black holes contain a distributed mass (perhaps a radiation star), a massive ejection or gamma ray burst will occur. 172.131.133.144 (talk) 01:26, 30 December 2010 (UTC)172.129.62.38 (talk) 16:48, 4 January 2011 (UTC)BG

Radiation ejection from supermassive black hole core mergers might not be possible due to a large (Schwarzchild radius)/(core radius) ratio, and the merger of smaller black hole cores could be much better candidates for radiation ejection. Estimates are a few potentially observable smaller black hole mergers occur annually, so this should be observable in our lifetimes. 172.163.67.59 (talk) 14:51, 6 February 2011 (UTC)BG

Black hole simulation improvement request (11th December 2010)

Thank you for this great article, it is very informative.

Please consider improving the black hole simulation so that the light gets attracted to the black hole. In the current simulation the light seems to get repelled away from the black hole. This is a bit confusing.

Or kindly explain why the light swells when it approaches the black hole.

Thank you.

Albertatambo (talk) 08:49, 11 December 2010 (UTC)

The simulation looks correct to me. Here is an illustration of why this leads to magnification: http://www.spacetelescope.org/enwiki/static/archives/images/screen/heic0814f.jpg Amaurea (talk) 17:51, 16 December 2010 (UTC)

I don't see how scientists have evidence to back up their conclusion with black holes, if they have never been able to get close enough to actually study them then how do they know they're real? i mean it could always be a colapsed star or unknown galisky.. who knows? ~Ashley —Preceding unsigned comment added by 68.56.145.145 (talk) 00:46, 20 January 2011 (UTC)

Edit request (21 January 2011)

"This temperature decreases with the mass of the black hole, making it difficult to observe this radiation for black holes of stellar mass." I put in a Citation needed tag for this and it was deleted. According to Leonard Susskind's book, "The Black Hole War..." temperature decreases as mass increases - the wording above makes it sound as if temperature decreases as mass decreases. This should be clarified and should include a proper citation. Later in the article it is stated with a citation that temperature is "proportional to" mass, but again, doesn't specify the direction of the proportion.

Doooook (talk) 01:37, 22 January 2011 (UTC)

Well, proportional means by definition that as one increases the other increases and vice versa. In the main article it correctly says that the temperature is proportional to the surface gravity, which is inversely proportion for mass. To prevent any possible confusion it even clarifies that this means that large black holes emit less radiation than small black holes. I don't see how there is any room for confusion there.

On the other hand I see how the statement in the lead can be misinterpreted. I'll have a go at clarifying it.TR 10:09, 22 January 2011 (UTC)

Concerning black holes' existence

I have read in the top of this discussion page that some user (unfortunately he/or she didn't signed the post) proposed to add explicitly in an statement the until-now hipothetical existence of black holes.

This seems to be an recurring issue here. As a matter of fact, this is an recurring issue in the physics community.

What this user received as a reply was:

... Also, it is unnecessary since the statement "a black hole is a region of space" does not say if such a region exists. The set of such regions in reality could be empty. ...

I think this is not a valid answer. I never assigned to Phylosophy 101, but I think that the set of things endowed with the attribute of being cannot be empty. So the statement "a black hole is a region of space" asserts that black holes do exist and they are a region of space.

I'm not trying to lecture no one here, but the thing is: people from inside the community are used to this question about the existence of black holes, but outsiders don't. And since astronomers are still searching for "That" ultimate evidence (the one they can call a "proof"), the existence of such objects must be considered hypothetical.

Why can't this be explicitly stated in this article? IMHO this is 'a must' to stand for a NPOV.

Cheers. Seneika (talk) 22:55, 28 January 2011 (UTC)

Please provide a high quality, reliable, academic source that states what you are proposing. Jehochman ^Talk 01:41, 29 January 2011 (UTC)

Surely I can. But can you be more specific? To what part of what I've said are you refering? Depending on it, I can cite every text book on general relativity or else I can cite books and papers related to astronomy. You see, I'm not talking of that part of the story regarded as fringe science. I'm talking simply of the state of art in relativity and astronomy. Seneika (talk) 10:53, 29 January 2011 (UTC)

You have to come up with a qualified source that states that black holes are considered hypothetical. You may find that this is not as easy as you would think. Dauto (talk) 03:00, 30 January 2011 (UTC)

In what follows I present a list of quotations accompanied by the sources. These are explicit references to endorse what I have proposed.

This first one is for historical purposes

"... these exotic objects remained a textbook curiosity until 1960's..."

Here we have it explicitly stated

"Testing the black hole hypothesis"

"Black holes are theoretical structures in spacetime predicted by the theory of general relativity"

and here several other quotations

"Observations of the binary X-ray source Cygnus X-1 in the early 1970's provided the first plausible evidence that black holes might actually exist in space."

"Do black holes exist?"

"...Evidence now suggests that black holes do exist"

"... the goal of confirming the detailed predictions of general relativity for their geometries is still for the future."

This is a good final one

"Although there is no conclusive evidence available for the existence of blackholes at the moment, presently the best candidates seem to be the binary stars in which one of the partners is visible and the other is supposed to be a blackhole."

I want to reiterate that my only intention is to put to the reader's eyes that the conception of black holes began as purely theoretical but now the scientists affirm to have strong reasons to belive that black holes do in fact exist. Nevertheless, there's no final conclusion on the subject, and this is a work in progress.

To my understanding, all this is implied in the article and may now be explicitly stated.

Cheers --Seneika (talk) 03:58, 1 February 2011 (UTC)

My references

The current first sentence makes absolutely no statement about the existence of black holes, it merely what a black hole is. There is no assertion (or even implication) of existence in that sentence. On the other hand, inserting the word "hypothetical", as the anon ip suggested, has the strong connotation that no such objects are thought to exist. Such as statement would thereby violate NPOV, as there is a significant portion of the community (especially within astrophysics) that believes that the existence of black holes is sufficiently proven. (For example by the absence of hard X-ray emissions for soft X-ray transients with masses above the TOV limit while in quiescence.)

The position of the community cannot (and thereby should not) summarized in a single word in the first sentence. The correct place in the lead to discuss this would be last paragraph that summarizes the observational evidence. This paragraph can do with some tweaking anyway. (In my opinion at least, it overemphasizes Sag A*, as compared to the emphasis given in the main article.) In tweak should be wary of WP:SYNTH however. (ie. no conclusion should be drawn, which cannot be directly attributed to a source).TR 09:32, 1 February 2011 (UTC)

I agree with you. Except for your first two sentences. When one reads

A 'black hole' is a region of space from which nothing, not even light, can escape.

one finds the existence of such objects to be implied, since it's being described without any reference to its nature. As a matter of fact, not all properties of black holes being described in the whole first paragraph are known observed (or observable) facts. These are theoretical predictions. If black holes and all its refered properties were observational facts then attributing to them some theoretical nature would be nonsense. But on the contrary, most of what is 'known' about black holes is found in the form of theoretical prediction. It would be different, for example, if one were talking about antiparticles, whose nature moved from theoretical to physical reality long ago.

I agree that in many cases a sentence like

A 'black hole' is a hypothetical region of space from which nothing, not even light, can escape.

comes in the form of an attempt to stablish one's own point of view (or even to demerit the research in this field). I am not supporting here the edition of that sentence to this form. On the other hand a sentence like

According to the general theory of relativity, a 'black hole' is a region of space from which nothing, not even light, can escape.^{[reference here]}

seems to be appropriate. The third paragraph could start with

Although there's no ultimate proof (or evidence) for the existence of black holes, astronomers have identified numerous stellar black hole candidates...^{[references to this statement here]}

In the way I'm proposing it, I don't think it would fall in WP:SYNTH or even WP:OR and would certainly satisfy WP:NPOV. --Seneika (talk) 13:09, 1 February 2011 (UTC)

The problem with a sentence like

According to the general theory of relativity, a black hole is a region of space from which nothing, not even light, can escape.^{[reference here]}

is that this definition of a black hole is independent of general relativity. Within any description of spacetime, a region which is not in the causal past of future timelike infinity (aka region from which nothing can escape) would be called a black hole. This exactly the reason that the "according to general relativity" phrase was removed in the past.

Some different variant may be needed. I'm not averse to adding some reference to general relativity to the first paragraph. In fact, I think it should be mentioned somewhere in the lead.

As for the sentence,

Although there's no ultimate proof (or evidence) for the existence of black holes, astronomers have identified numerous stellar black hole candidates...^{[references to this statement here]}

This might be too strong, since there is certainly a part of the community that would maintain that the ultimate proof has already been delivered. Considering this, such a sentence may actually violate NPOV.TR 13:55, 1 February 2011 (UTC)

But history tells us that a scenary where astronomers started to identify interesting black regions on space and developed the concept of a region of space from which nothing, not even light, can escape. is not the case. The way you put it, for example, the notion of a black hole would imply at least in the notion of spacetime. You see, these definitions are not paradigm-independent. Even the primordial idealization of a black hole, that of an object whose superficial gravity is so strong that even light cannot scape, implies in a theory for gravity. Many (I can't be sure if all of them) observational techniques to detect black holes are embued in the paradigm of such theory. It happens that our currently theory for gravity also dictates our notion of spacetime and it is general relativity. So why is a sentence beginning with "According to GR..." not appropriate? I think it would not only be appropriate, but also accurate. This whole article is written in an "According to GR..." style, BTW.--Seneika (talk) 16:12, 1 February 2011 (UTC)

First of all, starting with "According to GR..." implies that in other theories a black hole may be something different. In particular it suggests that the notion of a black hole has an existence independent of "an region of space which things may enter but not leave". In that sense it actually might have to opposite effect of what you are trying to achieve.

Secondly, the description of a black hole given in the first sentence is applicable to a whole slew of theories; not just GR, but also supergravity, f(R)-gravity, Hořava-Lifshitz gravity, causal sets, etc. Basically in any modern (alternative) theory of gravity A black hole is a region of space from which nothing, not even light, can escape. Not only is it applicable to such theories, but black hole solutions in such theories are actively studied (as one can see from looking at recent articles on the gr-qc ArXiv). Of course, the article further focuses on the properties of black holes as predicted by GR (although many (like hakwing radiation and gravitational red shift) are in fact independent of GR. GR is after all the currently accepted best model for gravity.TR 09:43, 2 February 2011 (UTC)

Regarding my second proposal of edit, that sentence can be modified in many ways. Take for example

Although the existence of an ultimate proof (or evidence) for the existence of black holes is not consensual, astronomers have identified numerous stellar black hole candidates...^{[references to this statement here]}

Isn't that accurate? Why mentioning this would be a violation of WP:NPOV? The lack of references to sources attesting the contrary wouldn't also be a problem? Otherwise just one side of the story will be told. IMHO, there is a difference between the assurance of neutrality in POV and the absence of POVs. One may say that this article lacks NPOV (or at least accuracy) by omission. The referencies I cite above present to the reader the current state of observations and of the understanding of the phenomenon (in a neutral manner, for what I could see). I'm not citing any controversial sources, just reviews found in journals like 'Nature' or 'Scientific American' and also known textbooks.

Just to finalize, I want to emphasize my opinion that somewere in this article this must be told (a bit on the lead and perhaps more in a subsection). --Seneika (talk) 16:12, 1 February 2011 (UTC)

To first respond to your final remark, I would like to draw your attention to the Observational evidence section, which IMO gives a fairly accurate summary of the observational status of black holes. In particular the black hole#Alternatives subsection gives a discussion the various reason why one might think that the current evidence is not enough.

However, talking about an "ultimate proof" is nonsense. An "ultimate proof" rarely (if ever) exists in science. Implying that it should be given is therefore misleading.TR 09:43, 2 February 2011 (UTC)

Edit request from Jofo2005, 29 January 2011

{{edit semi-protected}} |ref=harv}}</ref> which were shown to be rapidly rotating neutron stars by 1969.

 Done Next time, please state what you want changed more clearly (like, "please add the word were in the sentence..."). It makes it easier to tell what change needs to be made. Qwyrxian (talk) 06:03, 30 January 2011 (UTC)

Please clarify text in the article

The following text appears in the article, but I think it could be clarified:

In 1915, Albert Einstein developed his theory of general relativity, having earlier shown that gravity does influence light's motion. Though, a few months later, Karl Schwarzschild gave the solution for the gravitational field of a point mass and a spherical mass.

I think the text needs to explain (in a little more detail) the relevance of general relativity to the topic and what "solution" Schwarzschild was providing. Also unclear is the meaning of the "Though"? Is this meant to be a contrast of some sort? (Yes I more or less understand the physics; my concern is with what is being communicated.) Thanks!—RJH (talk) 22:59, 31 January 2011 (UTC)

It's probably worth spending a bit of time digging through the edit history, as this feels like a vestige from a past editing dispute. There should be a clearer version of that passage in there somewhere. --Christopher Thomas (talk) 23:24, 31 January 2011 (UTC)

I'm not sure how that sentence came about. I've changed it to "Only a few months later, ...". That makes at least some sense.TR 09:03, 1 February 2011 (UTC)

Improving the lead

Per WP:LEAD the lead section should summarize the main points of the article, reflecting the emphasis on those points given in the main text. As it currently is, the lead has the following issues with this:

• The history section is not covered in any way.
• Nothing is said about the formation and evolution of black holes.
• The lead currently spends two paragraphs on observations. In particular the evidence for the supermassive black hole at Sag A* is discussed in too much detail and thereby overemphasized.
• No mention is made of general relativity.

Remedying these points may also help alleviate the concerns of user:seneika raised above. I think the best way forward is to merge the current second and third paragraph about observational evidence and cut down on the detail. We then have space to add a paragraph on the history and a paragraph on the formation. Does this sound like a plan? TR 09:58, 2 February 2011 (UTC)

Suggestion for the first paragraph

I suggest changing the first paragraph to (something like):

A black hole is a region of space from which nothing, not even light, can escape. The theory of general relativity predicts that a very compact mass will deform the spacetime around it to form such a region. Around a black hole there is an undetectable surface called an event horizon that marks the point of no return. It is called "black" because it absorbs all the light that hits the horizon, reflecting nothing, just like a perfect black body in thermodynamics. Quantum mechanics predicts that black holes also emit radiation like a black body with a finite temperature. This temperature is inversely proportional to the mass of the black hole, making it difficult to observe this radiation for black holes of stellar mass.

The main change is to the second sentence, which now explicitly states that black holes are a prediction of general relativity.TR 11:02, 4 February 2011 (UTC)

suggestion for merger of second and third paragraph

I would like to suggest to following as a merger of the current second and third paragraph:

Despite its invisible interior, the presence of a black hole can be inferred through its interaction with other matter. Astronomers have identified numerous stellar black hole candidates in binary systems, by studying its interaction with its companion star. Moreover, there is growing consensus that supermassive black holes exist in the centers of most galaxies. In particular, there is strong evidence of a black hole of more than 4 million solar masses at the center of our Milky Way.

Maybe accretion discs should be mentioned more clearly?TR 11:02, 4 February 2011 (UTC)

Suggestion for a paragraph about history

This is a very rough draft for a paragraph summarizing the main points of the history section:

Objects whose gravity field is too strong for light to escape were first considered in the 18th century by John Michell and Pierre-Simon Laplace. The first modern prediction of a black hole in general relativity was found by Karl Schwarzschild in 1916, although its black hole nature was not fully realized for another 4 decades. For a long time black holes were considered a theoretical curiosity. This changed in the 1960s when theoretical work showed that black holes were a generic prediction of general relativity, and the discovery of neutron stars sparked interest gravitationally collapsed compact objects as a possible astrophysical reality.

Should it alos mention the work on gravitational collapse by Chandrashekar and TOV in 1930s?TR 11:02, 4 February 2011 (UTC)

suggestion for a paragraph about formation

The following is a suggestion about a blurb about the formation and evolution of BHs.

Black holes of stellar mass are expected to form when heavy stars collapse in a supernova at the end of their life cycle. After a black hole has formed it can continue to grow by absorbing mass from its surroundings. By absorbing other stars and merging with other black holes, supermassive black holes of millions of solar masses may be formed.

This is very rough. I'm not even sure if having a separate paragraph is necessary. I do however feel it is necessary to make the connection supernova->black hole, since that is something a wide audience may have heard about.TR 11:02, 4 February 2011 (UTC)

Other suggestions

It seems to me that sections 2,3 and 5 are affine. They're all about theory of black holes. I think merging them into a major section called 'Theory' would be nice. The usage of subsubsections may not be a bad idea. Take for example this (featured) article about acetic acid.

My suggestion is to structure the article in the form

• History

• Theory: current sections 2,3 and 5 and perhaps a subsection entitled 'concurrent theories'

• Observation: the current section 4 plus a section entitled 'Missions' (or a more appropriate title)

This 'concurrent theories' subsections may be a good idea to tell a little about of how other theories handle the concept of black holes. (Alternative theories is not really my expertise, so I think I couldn't contribute here for the moment, although I think they worth being mentioned)

In this 'Missions' subsection I'm proposing one would list projects related and/or dedicated to BH observation. As well as other sources of BH detection.

There's no mention to gravitational waves in the article. Was it decided to be kept that way?

Cheers. --Seneika (talk) 13:08, 2 February 2011 (UTC)

Could you elaborate what you think is the added value of this reorganization?

As for gravitational waves, I'm not sure what you want to mention about them. Since, no gravitational waves have been detected to date, they do not provide any real additional data on black holes. As for black hole mergers as a source of gravitational waves, that seems to be a subject better covered in the gravitational wave article.

As for further expansion with a "missions" section. The article already is fairly long, so I'm hesitant for further expansion. It may be worth while to consider if such discussions are better off in stellar black hole, X-ray binary or supermassive black hole, since missions typically try to observe a very specific class of objects.TR 14:47, 2 February 2011 (UTC)

I think a reorganization (not necessarily the one I've proposed) would help to make the article cleaner. Separating more clearly theory from observational fact. (Don't you agree that section 4.6 is kind of misplaced?)

Many theoretical aspects are used to explain what is observed about BHs, (many) other aspects, however, are (highly theoretical) predictions. IMHO this could be separated in a more logical way since little of what one reads in sections 2 and 3 are observational facts (although these are indeed facts about BHs). The structure of a BH fits better in 'theory'. The same is valid for 'Open questions'. Most of these topics are better discussed in their own respective articles.

You seem to be concerned in adding here only 'real additional' information about BHs. From this POV I can't attest the relevance of GWs. It was just a suggestion. (But it seems that in the near future gravitational radiation will most likely to be detected than thermal radiation from black holes, for example. Oscilatory normal modes of BHs is an active field of research that can lead to BHs 'finger prints').

In this same philosophy one can't attest the 'practical' relevance of any of those results arising from the semi-classical approaches (quantum evaporation, for example), yet these are found in this article (for the sake of completeness, I imagine).

About this 'missions' section it could be as little as a paragraph (smaller, for example, than section 5). Just a few comments about common sources of data on BHs.

In sum I think a reorganization would add the value of sections more clearly separated by their nature (history, theory and observation) resulting in a cleaner article.

Please don't interpret me as some one just arriving here with parachutes and saying whatever I want. I'm just pointing things I think could improve the article and, what is more important, I'm offering myself to do things, not just saying people to do it.

--Seneika (talk) 16:47, 2 February 2011 (UTC)

I actually think that the organization of the article is pretty clear. (Of course, I am biased in that respect, since I'm responsible for a lot of the current organization.) The first section provides a clear context of the subject by discussing its history. The second answers the "What", what is a black hole and what are its properties. The third answer the "How" and "When" questions; How and under what conditions do black holes originate. The fourth section section then explains what observational evidence exists for black holes. Section 4.6 is very much in its place, since it highlights the various caveats of the observational evidence. The last section then discusses several topics of current research. By nature, this discussions will be more technical than the previous sections, a best practice for technical articles is to have the most technical sections as last. This helps with the general accessibility.

About gravitational waves, as it stands the possibility of detecting anything using GWs is based on a lot of wishful thinking, given that no GWs have been detected to date. As such any speculation on what might be learned using GWs seems more in its place in the article on GWs and GW detectors. Once detection of GWs has become a reality, which might be soon, it might also be time to have a blurb here.TR 17:11, 2 February 2011 (UTC)

Despite my opinion that this is something that can't be, I thought at first that this article were intended to be relied mainly in 'astrophysical BHs'. I got this idea first reading the lead, were there's no reference to any theory (and by any I mean 'GR', since it's the only one reliably theory on the subject, according to the mainstream of Physics) ruling the definitions and concepts being proposed; and later our discussion confirmed that idea.

In practice, however, this article deals with a wide range of aspects regarding BHs. Not just what is observed and I agree this would be an impossibility, since most of the subject is highly theoretical.

In fact, most of these topics are strongly hypothetical. Take, for example, the case of the gravitational singularity inside a BH, whose existence or not is a matter of debate that extrapolates the realm of astronomy or astrophysics, since observation would be impossible by definition. Other examples range from inter-universe travel, to quantum evaporation (or vice-versa). These are examples of topics often appearing when one talks of BHs. In the present article this is no different, they're are here as well.

In this article it appears to be room left for topics not of only hypothetical nature but also especulative. This is easily seen in a sentence like

A phase of free quarks at high density might allow the existence of dense quark stars,[107] and some supersymmetric models predict the existence of Q stars.[108] Some extensions of the standard model posit the existence of preons as fundamental building blocks of quarks and leptons which could hypothetically form preon stars.[109]

Supersymetric models or anything outside the standard model is controversial isn't it? This is an example of a highly especulative subject appearing in the present article. Not to mention 'the possibility of travelling to another universe'.

Not that I want to advocate in favor of GWs, but when you say

Once detection of GWs has become a reality, which might be soon, it might also be time to have a blurb here.

I must ask why 'supersymetric models', 'extensions of the standard models' and even predictions of semi-classical approaches have a blurb here without having become 'reality' first. Did the level of 'wishful thinking' related to them garantee that? Isn't it a little arbitrage?

When one talks about the structure and evolution of BHs, I think it must be in a different tone of that when one speaks of the structure and evolution of the sun, for example.

Although the structure and evolution of 'ordinary' stars are also theory, represented in models, the high number of independent evidences attesting such models in this case allows one to talk about the structure of these stars without explicitly and repeatedly saying that this is theory. The same doesn't apply in the case of BHs. When you say that

The second answers the "What", what is a black hole and what are its properties.

it can't be left unclear that 'its properties' do not reffer necessarily to observed properties of BHs. As many of such properties are simply not observable and some are even hypothetical, it's not clear what is this 'what' being answered. For this reason I still suggest the existence of the section entitled 'Theory' with what is now section 2 being a subsection of it.

I'm not sure about what question is subsection 3.4 answering. (What 'when'?)

The whole of subsection 4.6 relies in highly especulative subjects. I'm still not convinced that it is in it's right place. There's already section 5 for 'Open questions'.

Off course, all this annoyance of mine stops making sense when one admits this article as a portal to whatever is related to BHs. But this is also not clear. --Seneika (talk) 22:57, 3 February 2011 (UTC)

The article tries to cover all aspects of BHs. Since most of what has been written about BHs is of theoretical nature, a lot of the article is concerned with theoretical aspects. (The lead at this point does not reflect this very accurately, which is why I started the section above to improve it.) In fact, the only section concerned with observation is the section called "observational evidence". The current section 4.6 completes the discussion of the observational evidence by relating what the possible alternative explanations are for the observed BH candidates. Part of the point is that any such explanation would require exotic speculative physics. The place of this section is in the "observational evidence" section, since it is about alternative explanations of the evidence, not about alternatives of black holes.

Obviously, the subject is very broad, which is why many of the (sub)sections have been written in WP:SUMMARYSTYLE, and refer to a main article for more detail.

I'm still not quite clear on what you want to say about GWs in this article. As far as I know, most discussion about BHs and GWs has been in the context of BH mergers as a possibly detectable source of GWs. This is a subject which is much more about GWs than Bhs (for example, if there were other similarly heavy compact objects, their merger would be just as interesting), and is thereby more suited for the GW article. As far as I know, there has been little to no (serious) discussion about using GWs to learn about BHs (unlike for example in cosmology, where you can find quite extensive discussions about what the GW background could teach us if we could the detect it). I could however be wrong about this. If there is documented discussion of this in secondary sources (review papers, textbooks, etc.) this would indeed warrant a short discussion in the "observational evidence" section.

I do agree that the article could make it clearer that black holes are a theoretical phenomenon for which we are searching for empirical verification, rather than an empirical phenomenon for which one searches for a theoretical explanation. Improving the lead could help with this.TR 10:03, 4 February 2011 (UTC)

I really don't know much about the aspects on which GW and BH subjects cross over each other. The little I know is found in reviews like (apparently this is already found in some textbooks). The picture is like this (I'll omit all the IFs I think should be in what follows, but assume for the moment that GWs and BHs do exist and are those predicted by GR. I'll be short because I know little and to respect the not-a-forum policy)

GWs may arrive to Earth comming from the more remote sources. Regardless their origin, GWs can be scattered by BWs. The interaction between GW and BH will cause the last to oscilate. The (quasinormal) modes of oscilation of the BH will be imprinted in the outgoing GW. Different BHs will have different modes of oscilation, scattering GW in their own peculiar way. This is belived (wished, hoped...) to provide a way (presumably the only possible way) to probe the presence of BHs directly.

AFAIK, the merger scenary presents a good candidate for detection of GWs. This scenary of scattering of GWs by BHs would present a probe for the presence of BHs. (Off course, GWs must then be assumed to exist). This is why I thought the subject to deserve a comment in this article (and because this seems to be a field of research in activity since the 70's relying in predictions of GR about BHs). Perhaps in section 4.6 then. Seneika (talk) 14:00, 5 February 2011 (UTC)

My references — Preceding unsigned comment added by Seneika (talk • contribs) 00:41, 6 February 2011 (UTC)

Note: this ref. to Davies isn't mine. I haven't manage to fix this... Seneika (talk) 00:48, 6 February 2011 (UTC)

It appears that there is enough information for a short subsection about the prospects of detecting BHs using gravitational waves, similar to the short subsection about detecting strong gravitational lensing by BHs, one or maybe two paragraphs long. I do not really have time to delve into this right now, so do you maybe feel like drafting a suggestion for such a section?TR 11:48, 6 February 2011 (UTC)

Sure. I can do that until the end of the week. Seneika (talk) 13:02, 8 February 2011 (UTC)

Edit Request (15th Feb 2011)

{{Edit semi-protected}}

The word "the" has been duplicated in the General Relativity section of the article.

http://en.wikipedia.org/wiki/Black_hole#General_relativity

"[...] to produce the the solution describing [...]"

 Done - DVdm (talk) 13:51, 15 February 2011 (UTC)

Main Image

The artist'S rendering At the top of the page could lead people to believe they'Re purely fictional bodies. I'm thinking if we use a double-stacked image instead, showing both the rendering of a black hole alone In space and an actual image from NASA of a galaxy with a central black hole. I'd suggest the recent image of NGC-4649 from the Chandra X-Ray Observatory.

--Ben Harkness (talk) 18:54, 25 February 2011 (UTC)