Talk:Black hole

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    Something "might" escape[edit]

    It is time once again to point out the incompatibility of the definition of a black hole with Hawking radiation. According to the introduction: "nothing—including particles and electromagnetic radiation such as light—can escape from inside it".

    According to the Evaporation section: "If Hawking's theory of black hole radiation is correct, then black holes are expected to shrink and evaporate over time as they lose mass by the emission of photons and other particles."

    I have been stomped on for pointing this out before, but I'm sorry... it jumps out at me every time I read the article.192.249.47.204 (talk) 20:52, 1 March 2016 (UTC)

    And again Hawking radiation does not 9have to) come from inside the black hole.TR 21:45, 1 March 2016 (UTC)
    Yes, that was the previous explanation. However, that was before the "black holes ... shrink and evaporate over time as they lose mass by the emission of photons and other particles" was added to the article. Is there an explanation as to how this can occur without anything coming from inside?192.249.47.204 (talk) 20:25, 2 March 2016 (UTC)
    It depends on your definition of "from". At very small scales, quantum effects dominate and space becomes counter-intuitive. So from a macroscopic perspective the black hole is emitting radiation and losing mass, but no particle is travelling out from within the event horizon. VQuakr (talk) 20:41, 2 March 2016 (UTC)

    One particle/anti-particle pair is created near the event horizon by quantum fluctuations, one particle falls into the black hole and by quantum tunneling the other escapes the one that escapes carries the mass/energy away.Quantanew (talk) 14:43, 4 March 2016 (UTC)

    section on LIGO is wrong[edit]

    The masses in the LIGO section are mis-stated; there were 3 solar masses lost due to gravitational waves; this is kind-of a very central, important part of the result, so getting it wrong is ... not good. Also. The statement that there is "at least one" researcher who believes that LIGO was first to detect the event is absurd: there's a whole mass (about on-thousand) co-authors on the paper: making it sound like there's just one is goofy. 67.198.37.16 (talk) 02:08, 23 March 2016 (UTC)

    Since it's causing confusion, maybe we should just drop the "the first direct detection of black holes" line. Most sources seem to characterize it as an indirect detection of two black holes and the first direct detection of a collision event. Direct vs. indirect is subjective, but it's hard for me to see a definition of "direct" that would simultaneously admit LIGO, but exclude all the previous detections of black holes. Rolf H Nelson (talk) 07:49, 23 March 2016 (UTC)
    Specifically, its 29+36=62 with about 3 solar masses lost as waves. The WP article on this does get the details right. 67.198.37.16 (talk) 02:17, 23 March 2016 (UTC)
    Looking at the abstract, the uncertainty bars are +/- four solar masses, so that might be unwarranted precision. IMHO the current ~30 and ~60 are fine. Rolf H Nelson (talk) 07:49, 23 March 2016 (UTC)
    Hi @67.198.37.16: I'll edit the masses of the black holes accordingly. That said, I would argue that approximate masses are acceptable because the purpose of that section is to invoke the overall LIGO result as independent, compelling evidence of the existence of black holes; it doesn't purport to describe the LIGO result in detail, and it doesn't need to do so given its limited aims. As a result, some important details about the black-hole merger, such as the amount of mass converted into energy, aren't relevant within that context. (Obviously, they are critically relevant in the article dedicated to the LIGO detection, and I would not be OK with approximate masses in that article.)
    Hi @Rolf H Nelson: I think that "direct" is appropriate because the LIGO measurements show that the merging objects were so massive and compact that they must have been black holes. I am not aware of a credible alternative explanation for the observed waveform. As for the phrase "In what at least one researcher has characterized as the first direct detection of black holes," it establishes at the outset why the LIGO result is being mentioned as observational evidence for black holes. Would "In what has been characterized as the first direct detection of black holes" be more acceptable? Full disclosure: I wrote that phrase, but I'll be the first to admit that it could be improved upon. Thank you both for your thoughts, and best wishes, Astro4686 (talk) 03:07, 25 March 2016 (UTC)
    'I think that "direct" is appropriate because the LIGO measurements show that the merging objects were so massive and compact that they must have been black holes.' OK, but do you also believe "direct detection" is *inappropriate* for each and every of the various previous observations over the years that had already confirmed the existence of black holes? It seems to me that by your same criteria ("no other explanation for observation" -> "direct observation"), certain previous observations would also be "direct", in which case this isn't the *first* direct detection. Your proposal of "In what has been characterized as the first direct detection of black holes" is fine with me, but if you're asking my personal preference I would just yank the "direct observation of black holes" claim as being a minority viewpoint about a minor terminological distinction that's unimportant to most readers. Rolf H Nelson (talk) 05:54, 25 March 2016 (UTC)
    Hi @Rolf H Nelson: I've decided that I agree with you about removing 'direct detection.' This conversation has underscored how subjective that term is (and also that my previous thoughts about it were hasty and ill-conceived). Indeed, if one term requires such careful definition, then it's probably best to avoid it in the article. For what it's worth, I think that the best definition of a 'direct detection' is an observation showing that a BH candidate possesses an event horizon (i.e., the defining characteristic of a BH), and with the LIGO result, a separation of 350 km for two BHs with 36 M_sun and 29 M_sun *doesn't* fulfill that description (since the minimum detected separation of 350 km is still greater than the sum of the Schwarzchild radii). I think that you hit the nail on the head when you wrote, "Most sources seem to characterize it as an indirect detection of two black holes and the first direct detection of a collision event." Best Wishes, Astro4686 (talk) 09:03, 25 March 2016 (UTC)
    In a strict sense BHs cannot be observed directly by an outside observer because (by definition) a black hole exists only outside the causal past of any outside observer. However barring that technicality, the closest we are ever going to get to directly observing a BH is seeing the ringdown signal. The ringdown quite literally is the gravitational radiation emitted as the BH settles down to a stationary state. In that sense the LIGO observation is much much closer to being a direct detection of a BH than an other observation that came before it. Unfortunately, from LIGO observation it is only possible to see the dominant quasinormal mode in the ringdown (and even that is not very well constrained). The properties of the dominant QNM are pretty much determined by the presence (and geometry) of a photon sphere. Consequently, it is not quite possible to rule out various exotic alternatives that have a similar photon sphere. If for a future detection (when LIGO is running at full design sensetivity) we are able to isolate some of the overtones of the ringdown as well, then that will severely constrain the possible alternatives.TR 16:16, 25 March 2016 (UTC)
    Hi @TimothyRias: Thank you for your detailed explanation. If you have a moment, perhaps you might like to edit the section to explain some of this. I'd do it myself, but I lack your expertise with gravitational waves. Best Wishes, Astro4686 (talk) 17:08, 25 March 2016 (UTC)

    <<<unindent. Yes, I guess saying "approx 30 solar masses" is OK. I had the exact figures stuck in my head when I first read this, but now that they've faded away ... OK. The problem with "at least one researcher" is that most UFO sightings and paranormal phenomena involve "at least one researcher". This is much more credible than that. What makes this a "direct" sighting is that changes to the metric are directly measured, as opposed to inducing the metric from orbital precession, or gravitational lensing, M-sigma relation, etc. 67.198.37.16 (talk) 21:30, 4 April 2016 (UTC)

    Delete GIF please[edit]

    The GIF currently attached to the article is far too distracting. Please delete to make reading easier. — Preceding unsigned comment added by Rickmoede (talkcontribs) 18:28, 8 August 2016 (UTC)

    FWIW I personally like the animated GIF at the top of the article showing gravitational lensing, assuming that's what you're talking about. Is there a replacement image being proposed, or just deletion? Rolf H Nelson (talk) 04:55, 9 August 2016 (UTC)
    I do understand it to be a matter of personal taste in either instance, and I do find it distracting. While I see that it meets with WP:PERTINENCE more effectively than would a still, the problem is that Wikipedia's css doesn't allow for a maximum number of loops for animated gifs. Perhaps a good compromise would be to place it further down in the text so as the sidebar is moved up to the prominent position it should preferably have? I've gone WP:BOLD and moved it down as it does overwhelm the lead, but other editors are welcome to revert me. --Iryna Harpy (talk) 21:25, 10 August 2016 (UTC)

    Split?[edit]

    I don't know about anybody else, but it seems clearer to me if there was to be a clear disambiguation of astronomical black hole versus black hole solution. My recommendation would be to split this article into the above two recommendations, and link both from the disambiguation page, with some discussion about the relation between the two. At a minimum, my feeling is that the two above terms should have redirect pages to an appropriate location. — Preceding unsigned comment added by 70.247.163.128 (talk) 18:56, 13 August 2016 (UTC)

    Please sign all your talk page messages with four tildes (~~~~). Thanks.
    I don't think it would be a good idea to split theory and observation—on the contrary. We could however create redirect pages for both terms to this article. - DVdm (talk) 19:12, 13 August 2016 (UTC)
    My feeling is that it remains very unclear in this article which context one is speaking from. Redirects to sections here would probably do a lot to make the context clearer. I'm definitely not advocating for a divorce, but the rules of inference in the astronomical realm and in the theoretical realm are completely different, and I would like to see a better exposition of both of those lines of thought, however it can be accomplished. 70.247.163.128 (talk) 20:37, 13 August 2016 (UTC)
    Note also that there is sensible precedent for separating theory and observation. Best example I can think of would be electromagnetic field and magnet. 70.247.163.128 (talk) 21:15, 14 August 2016 (UTC)

    This does not really make sense to me. There really is no such thing as an "astronomical black hole" in the sense that there is phenomological class of objects that are observed and dubbed "black holes". Black holes in astronomy almost always appear as a theoretical explanation for other phenomological classes of objects such as quasars or active galactic nuclei. From that perspective there really is little sense in the split you suggest, since all we know about black holes is from theory. This knowledge will either fit observations (in which case they can be explained by black holes) or it doesn't (in which the observation cannot be explained by a black hole).TR 15:34, 15 August 2016 (UTC)

    Honestly, that's exactly the point. That phenomenological class is the astronomical black hole. It's informed by astronomical observation. The black hole solution, is informed by gravitational theory like General Relativity, and may ultimately be disjoint from observation. I think we agree on that. But if it turns out that current theory and observation are disjoint, it seems that you would suggest that black holes don't exist. My position would be that they exist theoretically, but not physically. This situation happens in many other theories, and while there may be a reality invalidated by observation, it doesn't invalidate the theoretical concept, except in implementation. I would again point to magnets. If it turned out that electromagnetic theory is not an accurate depiction of reality, then that in no way reduces the reality of observed physical magnets. The theoretical concept still carries weight, even if only as an effective description of the physical interactions. Moreover, I don't believe anyone would confuse a physical magnet with the idealization of a magnet that is captured by theory. I could argue that there's really no such thing as a physical magnet, it can all be reduced to the theoretical concept, but that is to gloss over a very real distinction between theory and experience which requires explanation. 70.247.163.128 (talk) 18:46, 20 August 2016 (UTC)
    But there is no phenomenological class of objects known as "black holes". There is many classes of phenomenological classes of objects that feature black holes in their theoretical explanation but there currently no class of observations that we would label "black holes" (and continue to do so even if they would fail to agree with current theoretical expectations). This mainly because we do not directly observe any of the qualities that would characterize it as a black hole. This might changes with the event horizon telescope, but currently this is the state of affairs.TR 16:57, 21 August 2016 (UTC)
    I see your point more clearly now, but if that's the case, then the tone of this article is way off (maybe you agree). If there's no objective astronomical definition of what constitutes a black hole, then the development of the article should be the development of the black hole solution with applications. Among the applications would be a possible explanation of astronomical phenomena, in particular, falsifiable astronomical models (astronomical black holes). Either way, though, I still see value in both black hole solution and astronomical black hole as descriptors. — Preceding unsigned comment added by 70.247.163.128 (talk) 19:26, 23 August 2016 (UTC)
    If there's no objective astronomical definition of what constitutes a black hole... Huh? And no, both proposed titles seem very contrived and I do not see any good reasons proposed for a split. VQuakr (talk) 01:21, 24 August 2016 (UTC)

    cut overbloated lede[edit]

    Lede too bloated and turgid. History in lede should be moved to history etc.--86.187.175.218 (talk) 23:17, 26 August 2016 (UTC)

    Reiteration[edit]

    quark stars exist, (quark-gluon soup stars), black hole single particles would immediately explode having an infinite decay potential — Preceding unsigned comment added by 2A02:587:4102:CF00:1963:F284:B24D:197C (talk) 05:02, 8 October 2016 (UTC)

    Added Archives[edit]

    I will add 5 access-dates and 11 archive urls to the citations in this page. Details:

    --Tim1357 talk|poke 17:04, 23 September 2016 (UTC)

    How can a black hole grow if mass cannot cross the event horizon for a distant observer?[edit]

    From the article:

    "To a distant observer, clocks near a black hole appear to tick more slowly than those further away from the black hole.[54] Due to this effect, known as gravitational time dilation, an object falling into a black hole appears to slow as it approaches the event horizon, taking an infinite time to reach it.[55] "

    OK, but it also says:

    "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 (M☉) may form."

    Aren't these two statements contradictory? If it takes an infinite amount of time for the falling object to reach the event horizon, how can the black hole grow? Sure, if you are the object, you will cross it. But for us distant (external) observers, the object never crosses, and therefore cannot add mass to the black hole; therefore, the article is not self-consistent. Can someone please resolve this? Thanks!

    Betaneptune (talk) 14:58, 12 October 2016 (UTC)

    The former statement says something about what distant observers see/feel/measure. The latter statement says something about what happens locally to the black hole itself. No contradiction. Also note that distant observers feel the influence of the total combined mass of the current BH and whatever in its neighbourhood. For further questions, per wp:talk page guidelines, you probably should try the wp:reference desk/science. HTH. - DVdm (talk) 17:10, 12 October 2016 (UTC)

    AST102[edit]

    This section contains student reviews related to Wikipedia:Wiki Ed/CUNY College of Staten Island/AST102 - Contemporary Theories of the Universe (Fall 2016).

    Reading this article makes me think that there are a lot of facts about black holes. For the most part there is but i feel that some of the facts that are thrown in there aren't reliable. While reading this article i clicked on the links and they all lead me to another wikipedia page. I find this interesting because i would think before i even clicked on the links that they would lead me too the actual source. At the end though where the references are located the links that i picked on were in fact reliable.

    In the first paragraph there is a sentence where i understand what they're trying to say, and which in fact is relevant. The sentence is "In many ways a black hole acts like an ideal black body, as it reflects no light.[4][5]" The only wrong flaw of this sentence is how it is worded. "An ideal black body" ? They could've just said the color black.

    No this article states a lot of point of views of how the black hole theory even came around. The only way i can see this article being biased is of wikipedia only stating the people that believed in the theory vs the people that didn't believe in it.

    Clicking on the links they give you down right detail on black holes. The articles explain the specifics around what a black hole is and everything around it.

    Jonathanp44 (talk) 03:43, 5 November 2016 (UTC)


    Critiques: There is a 5 paragraph lead section that summarizes and gives a general overview of what a black hole is→ this allows readers to get a general idea of the article topic before delving into the details This article is structured in a way that each subtopic within the black hole is given a headline Such a structure provides easy navigation for the reader to quickly find the exact information they are looking for There is an extensive list of the sources used and careful citation at the end to ensure its reliability and give credit


    The article Black Hole on wikipedia I noticed right away was of up to the standard quality by the green plus symbol on the top right hand corner which represents a good article. It does not have the symbol for a feature article however and that from reading it I figured was due to the lack of depth. There is a lot of content however, I do believe black holes encompass just so much that can be added to this article in order to put it on par with a potentially featured quality article. Mahwish.razi (talk) 23:24, 20 November 2016 (UTC)

    misleading lead[edit]

    Can we please have a better word choice in the lead? The claim that a black hole is a region is misleading, as it connotes spatial locality, and doesn't do justice to temporal configuration. Further, it would be fairer to characterize the black hole as a physical system, since it has many physical properties beyond simple location.

    Holistically, this also doesn't make sense in WP in general, as it is difficult to characterize a black hole as an astronomical object, if it is simply a location. I would do this myself, but apparently the article is locked. 75.139.254.117 (talk) 16:04, 22 February 2017 (UTC)

    This was discussed a few times before. IIRC, it seems that the claim that a black hole is a region is properly sourced. - DVdm (talk) 18:54, 23 February 2017 (UTC)