# Talk:Black hole

https://news.osu.edu/black-hole-is-closest-to-earth-among-the-smallest-ever-discovered/
Write both observed AND theorized (if you hide theory vs data science doesn't evolve).

Replace the dashes for commas.
Introduce John Michell and Pierre Simon in the beginning of the second paragraph. Meaning put the subjects who discovered it first.

The redirect Spatial singularity has been listed at redirects for discussion to determine whether its use and function meets the redirect guidelines. Readers of this page are welcome to comment on this redirect at Wikipedia:Redirects for discussion/Log/2025 October 4 § Spatial singularity until a consensus is reached.  Thepharoah17 (talk) 20:27, 4 October 2025 (UTC)

The article quotes Arthur Eddington, but why? What is encyclopedic about:

Arthur Eddington commented on the possibility of a star with mass compressed to the Schwarzschild radius in a 1926 book, noting that Einstein's theory allows us to rule out overly large densities for visible stars like Betelgeuse because "a star of 250 million km radius could not possibly have so high a density as the Sun. Firstly, the force of gravitation would be so great that light would be unable to escape from it, the rays falling back to the star like a stone to the earth. Secondly, the red shift of the spectral lines would be so great that the spectrum would be shifted out of existence. Thirdly, the mass would produce so much curvature of the spacetime metric that space would close up around the star, leaving us outside (i.e., nowhere)."
As a reader I suppose that I should "know why" this content is "silly" or "obvious" or whatever. But all I get is confused. What is the point? Johnjbarton (talk) 03:23, 12 October 2025 (UTC)

I think including the text of the quote from the second reference there (Black Holes and Time Warps) would be good, as it gives useful context for the quote. The context of the surrounding paragraphs is "how were people conceptualizing black holes and stellar collapse in the first decades after GR was published?", and I think this fits within that. - Parejkoj (talk) 20:13, 26 October 2025 (UTC)

Cannot find anything in the source (Black Hole Binaries, Jeffrey E. McClintock, Ronald A. Remillard) that backs up this statement Merlin.anthwares (talk) 10:40, 13 October 2025 (UTC)

It's hard to find but it's on page 9 of the black hole binaries source, in the second paragraph under 4.1.5 Accretion onto black holes. 
Quote from the source: "Thus a gas element of mass m that is destined to enter the BH starts far out with negligible binding energy. However, when it reaches the ISCO it will have radiated 0.057mc^2 for a Schwarzschild BH or 0.42mc^2 for an extreme Kerr BH." Shocksingularity (talk) 22:57, 13 October 2025 (UTC)
@Shocksingularity, Thank you, this answers my questions!
The sentence below is misleading though and it may be beneficial to clarify that unlike nuclear fusion (where mass is converted to energy) the gas mass itself isn't directly turned into energy; rather, the energy is released from the gravitational/rotational potential as the gas falls toward the black hole:
This process of accretion is one of the most efficient energy-producing processes known.
The sentence contains indirect implication that gas mass is turned into energy (up to 40% compared to 0.7% of nuclear fusion). The source does not confirm this implication. Merlin.anthwares (talk) 00:05, 14 October 2025 (UTC)
My proposal for addressing this issue is outlined below:
Replace
This process of accretion is one of the most efficient energy-producing processes known. Up to 40% of the rest mass of the accreted material can be emitted as radiation. In nuclear fusion only about 0.7% of the rest mass will be emitted as energy.
with
A gas particle moving towards a black hole releases binding energy as it gets closer. By the time it reaches the ISCO it will have given off a significant amount of energy - about 0.057mc2 for a non-rotating black hole or 0.42mc2 for a rapidly rotating one. Most of this energy (about 90%) is released in a relatively small area, within about 20 times the black hole's gravitational radius from its centre. Merlin.anthwares (talk) 10:30, 28 October 2025 (UTC)
The change entered seems fine, but overall the paragraph confuses me. It starts with high speed then claims "resulting friction" which makes sense only if there are collisions. Density is not discussed so the picture is incomplete. Then we read about release of "binding energy" of gas particles but its not clear what is bound to what and why it would be released. From the discussion above I gather that the gravitational acceleration creates kinetic energy which is partially dissipated as radiation during collisions between the accelerated gas particles. Johnjbarton (talk) 03:35, 12 November 2025 (UTC)
Hi @Johnjbarton! Thank you for the review!
I agree that further clarification is needed. Below is my understanding of why the energy is released (based on section 4.1.5 Accretion onto black holes of the source - McClintock, J. E.; Remillard, R. A. (2006). "Black Hole Binaries"):
As the gas flows toward a black hole, its gravitational potential energy is converted into kinetic energy (orbital motion). Viscous dissipation then converts some of this kinetic energy into heat, which is radiated away. The closer the gas gets to the black hole, the more gravitational potential energy is released, and the more energy is available to be radiated. In a rotating black hole, the stronger gravity and closer ISCO allow more gravitational potential energy to be released, resulting in more energy radiated overall.
If these considerations align with the source, I can come up with a change to the wording to clarify energy release process. Merlin.anthwares (talk) 11:20, 12 November 2025 (UTC)
That's great and very helpful, thanks. I do have two concerns. First we should make it clear that this is a model still being developed, eg something like "The best-known such model is the thin accretion..." in McClintock. Second is this description in the right place? The section is on observations, maybe we should improve "Accretion disk" section with these ideas. Johnjbarton (talk) 17:12, 12 November 2025 (UTC)
Good points, please see a proposed change to the sentence below:

According to the established model of black hole accretion, by the time the matter of the disk reaches the ISCO it will have given off a significant amount of energy - about 0.057mc2 for a non-rotating black hole or 0.42mc2 for a rapidly rotating one.

I also agree that this information belongs to "Properties and structure - External Geometry - Accretion disk" section. The section actually contains description of how gravitational energy is converted into radiation (probably can be enhanced as well). Merlin.anthwares (talk) 13:20, 15 November 2025 (UTC)

A critical part of the article has dubious sourcing:

Though only a few dozen black holes have been found so far in the Milky Way, there are thought to be hundreds of millions, most of which are solitary and do not emit any significant amount of radiation.
cites:

"ESO Instrument Finds Closest Black Hole to Earth". European Southern Observatory. 6 May 2020. Archived from the original on 6 May 2020. Retrieved 2 April 2021.
However this work has been subsequently reanalyzed. See "5.4. Thermally Contracting Stripped Stars" in

Marchant, P., & Bodensteiner, J. (2024). The evolution of massive binary stars. Annual Review of Astronomy and Astrophysics, 62.
HR 6819 was not a hidden black hole so it is not an indicator of other hidden black holes. (I also think the bit about "solitary" is wild speculation).
Moreover this critical aspect of black holes needs solid secondary sourcing, not a press release about a primary source. Johnjbarton (talk) 15:56, 13 October 2025 (UTC)

Here's one reference that might be relevant, on theoretical estimates for the stellar mass black hole population of the Milky Way:  "Counting black holes: The cosmic stellar remnant population and implications for LIGO" by Elbert et al. (2018). (link to NASA/ADS) Aldebarium (talk) 20:11, 13 October 2025 (UTC)
Thanks! That paper is cited by
Wiktorowicz, G., Wyrzykowski, Ł., Chruslinska, M., Klencki, J., Rybicki, K. A., & Belczynski, K. (2019). Populations of stellar-mass black holes from binary systems. The Astrophysical Journal, 885(1), 1.
which has additional info.
I added a bit under Observation. I think we could have a subsection "Population". In addition to the counts, there is work around the mass pattern of population.  The assumptions in these studies are subtle, eg many are directed at predicting binary. They are mostly driven by gravitational wave detection grant justifications. Johnjbarton (talk) 02:36, 14 October 2025 (UTC)

If you're looking through the page history, you may notice I have added quite a few cleanup tags to the article. I am currently working on improving this article to FA-status, and was adding some tags to questionable locations in the article. I have added more in-depth explanations in my user subpage as well. So if you have questions/comments/concerns, feel free to reply here or use the talk page of my forementioned user subpage.
BTW, I am going to go back through and work on cleaning up the areas, I'm not just drive-by tagging here. Shocksingularity (talk) 02:16, 14 October 2025 (UTC)

I have somehow accumulated a number of BH books, mostly history related so let me know if I can help there.  I added much better sources and I think there are generally good BH reviews around.
I whacked on some of the content, trying to go by steps in case you disagree. Johnjbarton (talk) 02:45, 14 October 2025 (UTC)
Thank you for the help! I don't know as much about the history as the science stuff itself, so feel free to help if you'd like! :D Shocksingularity (talk) 04:53, 14 October 2025 (UTC)
Some of the items on your User list I would dispute but I'm unsure if/how I should comment. These may simply be quick notes that will resolve upon further work. Johnjbarton (talk) 16:06, 15 October 2025 (UTC)
You can use the talk page! :) Shocksingularity (talk) 18:24, 15 October 2025 (UTC)

Just stumbled upon Outline of black holes. Johnjbarton (talk) 23:48, 15 October 2025 (UTC)

In a recent topic here, I mentioned that I had made a user subpage with information about improvements to this article. Recently, @ZergTwo suggested that I copied it here, so below is some of the improvements that I think could be made to the article. Feel free to discuss or dispute them in the replies here or on my user subpage's talk page. If you do fix something, I'd appreciate if you could cross it out on the subpage by adding 
 and 
 around the list entry for the thing you fixed.


### General
Possibly add a section about effects such as spaghettification, gravitational lensing, gravitational redshift, gravitational time dilation. Some of them are covered in other topics but not in a ton of depth. I'd personally add the section below properties and structure.


### Lead
Definition of a black hole in first sentence: What definition are we using here?


### History
Add information about black hole discoveries post 1970s through theoretical physics, not just observation. I know there's been some


### Properties and structure
I have made the following change to the organization of the properties and structure section.

Arrange the topics starting from the outermost part of the black hole and continuing radially inward. For example, ergosphere -> ISCO -> plunging region -> photon sphere -> event horizon -> singularity


#### Lead
the image does not fit with the text, which really has little to do with BH anatomy


#### Physical properties
Add subsection about mass
The table of black hole classifications feels kind of awkwardly placed


#### Event horizon
Copyedit grammar
Add a better transition to the explanation of gravitational time dilation
Explain what "singular behavior" means in this context
The topology p5 could be elaborated on/explained


#### Singularity
Copyedit grammar
Clarify what it means that the "singular region" contains "all the mass of the black hole solution"
"Solution"?
From what reference frame is this true? Because for an outside observer, all of the mass of the BH appears to be frozen on the EH
A mention of the Cauchy horizon as the boundary between causality and noncausality in spinning/charged BHs would be useful in p3
Elaborate on why the violations of causality would not survive a "proper quantum treatment" or remove this statement
Not sure p4 is WP:NPOV. Some physicists eg Kip Thorne do believe that singularities will probably turn out to exist even despite quantum interactions, the article kinda implies there is a consensus in physics that they won't
p5 needs general copyediting/improvement of wording


#### ISCO
Detechnicalize this


#### Plunging region
Explain where this is relative to other parts of the BH environment (eg ISCO)
Generally expand this section


#### Other
A section about the accretion disks and relativistic jets here would be good. Accretion is mentioned in a part of the observation section, but it more specifically refers to the detection of BHs via their disks/jets vs the properties of the disks/jets themselves.
More information is needed about BH interiors other than just the singularity.
A section about the Cauchy horizon/inner horizons
Possibly mention mass inflation (singularity)?
Possibly mention shock singularity?
Things you might see falling into a BH (eg gas, dust)
How the outside world would appear for an infalling observer


### Formation
#### Lead
Clarification needed in p2
p2: "The Kerr solution, the no-hair theorem, and the laws of black hole thermodynamics showed that the physical properties of black holes were simple and comprehensible, making them respectable subjects for research." Not only is this not WP:NPOV, it also doesn't explain why the Kerr solution/no-hair/thermodynamics show they are simple and comprehensible. Also, "simple" is very subjective here, a lot of physicists would disagree
provide examples of "other processes" by which BHs could be formed


#### Gravitational collapse
Add more information about the end of star lifespan and how it becomes a BH
Add example of how a star could gain matter w/o raising its temp to become a BH
Explain why its temperature affects its ability to gravitationally collapse


#### Primordial black holes and the big bang
p1: Give examples of models/predictions
Possibly mention PBH as a possible source of dark matter
p2: Explain the negative pressure/positive energy density/repulsive gravitational field thing more clearly


#### High energy collisions
What would the mass of a BH formed via particle collision be vs Planck mass?
p2: Clarify whether BHs evaporating in such a short timespan would be detectable


### Evolution
#### Growth
Possibly mention vampirism by the BH on a star in its binary as a method of accretion


#### Evaporation
Format the equation as math text
Give update on Fermi telescope
Mention what happens at the very end of BH lifespan -- does it just disappear? afaik we aren't 100% sure yet


### Observational evidence
#### Direct interferometry
p4: Centrifugal balance thing is kinda confusing


#### Detection of gravitational waves from merging black holes
Clarify why the objects being close together before the merge must mean they were BHs
p2: Why is the ringdown the most direct way of observing a BH?
Explain what frequency, damping time, and decay time of the dominant mode are
Explain why/how they are determined by the photon sphere
Give example of theoretical non-BH compact object that could have a photon sphere


#### Stars orbiting Sagittarius A*
What observational evidence that it might have an EH?


#### Accretion disk
Should this go in the properties and structure section?


#### Galactic nuclei
Do we need that many examples of SMBH candidates


#### Microlensing
Clarify definition of lensing/microlensing
Stars orbiting a BH is not lensing?


#### Alternatives
Explain what more of these alternatives actually are/their properties


### Open questions
Add information about SMBHs in high-redshift galaxies


#### Entropy and thermodynamics
In dark mode the image is light gray text on a white background
"The link with the laws of thermodynamics was further strengthened by Hawking's discovery in 1974 that quantum field theory predicts that a black hole radiates blackbody radiation" How was it strengthened?
"The radiation also carries away entropy, and it can be proven under general assumptions that the sum of the entropy of the matter surrounding a black hole and one quarter of the area of the horizon as measured in Planck units is in fact always increasing. This allows the formulation of the first law of black hole mechanics as an analogue of the first law of thermodynamics, with the mass acting as energy, the surface gravity as temperature and the area as entropy." clarify this section a bit
Elaborate a little more on the holographic principle


#### Information loss paradox
How is the info represented on the EH?
"full quantum gravitational treatment of the problem" explain.
" According to quantum field theory in curved spacetime, a single emission of Hawking radiation involves two mutually entangled particles. The outgoing particle escapes and is emitted as a quantum of Hawking radiation; the infalling particle is swallowed by the black hole." This is an oversimplified representation of Hawking radiation and not really how it works. Replace w/ something else
Explain monogamy of entanglement a little more here. At present it's a bit confusing.
Explain firewall paradox more
Explain more potential resolutions to the paradox, possibly in a subsection


### In science fiction
Need more examples than just Interstellar
Shocksingularity (talk) 02:35, 26 October 2025 (UTC)

@Johnjbarton You've been working on this article. What do you think of this list? ZergTwo (talk) 00:05, 27 October 2025 (UTC)
@ZergTwo I checked the first set of changes and others now and then by Shocksingularity and they seemed reasonable. So rather than discuss every detail I planned to wait until things settle down. I'd like to save energy for a complete read through. Johnjbarton (talk) 00:14, 27 October 2025 (UTC)

I wonder if the first sentence of the paragraph about topology is worth including? 

The topology of the event horizon of a black hole at equilibrium is always spherical, meaning that it has a shape that could be deformed into a sphere.
The issue seems highly technical, hypothetical, or perhaps mathematical. The sentence which follows it

For non-rotating black holes, the geometry of the event horizon is precisely spherical, while for rotating black holes, the event horizon is oblate.
seems entirely adequate for the issue. Johnjbarton (talk) 14:25, 30 October 2025 (UTC)

Looking back at that, I honestly agree. I was trying to make it less technical, but I feel like it just sounds more confusing now and I don't feel like it's super important. Shocksingularity (talk) 03:17, 8 November 2025 (UTC)

The section on singularity is difficult to be sure. I think most popular descriptions over-emphasize singularity because it is a easy way to get extra drama. Technical sources seem to me to say that singularities are an important mathematical aspect of black hole solutions, but every different solution may or may not have a singularity and they can have different characteristics. These are not observable nor do they seem to have direct observable consequences. To say this another way: singularities are properties of mathematical solutions but they may or may not be properties of black holes. I would lead the section with something along these lines to set the reader up to notice the variety of claims in the section.
A related but uncited source:

Lan, C., Yang, H., Guo, Y., & Miao, Y. G. (2023). Regular black holes: a short topic review. International Journal of Theoretical Physics, 62(9), 202. "Regular black holes (RBHs) are a collection of black holes (BHs) that have coordinate singularities (horizons) but lack essential singularities in the entire spacetime."
I think its is a better topic/source than "Nonsingular Black Holes in ƒ (R) Theories" which seems to be a niche of a niche.
I think a paragraph on fuzzball model would be better outside of the Property/singularity section. Johnjbarton (talk) 17:07, 2 November 2025 (UTC)

Just saw this. Thank you for the advice and the source. I will definitely use it when I look back over that section after I finish adding info about jets & Cauchy horizons (in progress right now). Shocksingularity (talk) 03:15, 8 November 2025 (UTC)
I have added your source, and changed the lead so that the section discussing attitudes towards singularities is first. I may move the part about fuzzball once I find a good place to put it (probably in alternative models). Shocksingularity (talk) 02:39, 16 November 2025 (UTC)

Add a sentence to qualify this sentence: "They can prolong the experience by accelerating away to slow their descent, but only up to a limit." (Under Properties and Structure > Internal Geometry > Singularity) Stephen Hawking states in A Brief History of Time that, due to time dilation effects, accelerating away from the singularity actually decreases the time an observer experiences before meeting the singularity. DevLehen (talk) 21:59, 11 November 2025 (UTC)

 Not done. Is there any evidence that he said that? If so, please provide a reliable source. NotJamestack (talk) 22:03, 11 November 2025 (UTC)
The issue are discussed in detail in the cited source:
Lewis, G. F., & Kwan, J. (2007). No Way Back: Maximizing survival time below the Schwarzschild event horizon. Publications of the Astronomical Society of Australia, 24(2), 46-52.
In my opinion no additional material on this fantasy topic is encyclopedic. Johnjbarton (talk) 23:54, 11 November 2025 (UTC)
Ok, I have been looking for where I found it for a while, and it turns out it is not from Hawking, sorry about that. I do know I read it somewhere, and it does fit with the "geodesics maximize proper time."
Thank you for referring me to that paper.
In fact, the paper you referenced even discusses that this is a common misconception and provides an explanation to how the seeming contradiction between the geodesic time and its results can be reconciled by considering that the singularity is a different event for a rocketeer vs a free faller.
The paper also gives significance to the initial conditions, even stating that "In dropping from rest at the event horizon, the firing of a rocket does not extend the time left, it only diminishes it."
In my opinion, the Wikipedia section provides an inadequate discussion of this topic and needs clarification. DevLehen (talk) 20:39, 12 November 2025 (UTC)
I don't think readers of an encyclopedia are additionally informed by detailed discusses of this kind. The source claims this is a useful device for teaching general relativity but that is not our goal here. I agree that the discussion may be inadequate so I removed the sentence. The sources still verify the preceding claim. Johnjbarton (talk) 20:54, 12 November 2025 (UTC)
Thank you so much! DevLehen (talk) 20:55, 12 November 2025 (UTC)

This concerns the revert of my recent edit. The explanation ("my phrasing was not helpful"), ironically, is not helpful to me in addressing the issue, so maybe it can be cleared out here.
The reason for my edit was that on-the-face interpretation of the current phrasing is that a free-falling observer would see the universe blue-shifted. As far as I understand, the opposite is true (edit: or rather, at least in the direction opposite to the black hole the background would be red-shifted), and the simplest example of an observer that would see entirely blue-shifted universe is a stationary one, not free-falling. This is a factual error that needs to be addressed in one way or the other, in my opinion. L3erdnik (talk) 18:55, 17 November 2025 (UTC)

I think the latter part of that paragraph needs a rework; the "settles in a stationary way" in particular didn't help matters. I think the difficulty lies in distinguishing "free falling" vs. "at rest in the Schwarzschild metric" (which is not really the same as "at rest" or "stationary" in the normal sense) observers without resorting to referring directly to the math and spacetime diagrams. I'm not sure how to go about that. - Parejkoj (talk) 19:05, 19 November 2025 (UTC)
I think the revert link should be this one.
In my opinion neither version is appropriate. The source here is
Krasnikov, S. (2008). "Falling into the Schwarzschild black hole. Important details". Gravitation and Cosmology. 14 (4): 362–367. arXiv:0804.3619. Bibcode:2008GrCo...14..362K. doi:10.1134/S0202289308040129.
The source makes three points about a falling observer, they
won't see the whole history of the universe
won't cross the event horizon at the speed of light
won't see the singularity
and a fourth point that the singularity is not in the "center" because the space is cylindrical and time dependent.
The source only mentions blue shifts as needed by a falling astronaut wishing to communicate with one not falling.
It's possible that the Kip Thorne source says something on this topic, IDK. Johnjbarton (talk) 22:17, 19 November 2025 (UTC)
I was the one who added that source. When I was originally writing, I was going to be more specific about not seeing the whole history of the universe at the EH (since that's a very common misconception about BHs) but I couldn't find a good way to word it so I made it less specific.
The Kip Thorne source mentions that an observer falling into a BH would observe blueshift unless they were travelling quickly into the BH. Shocksingularity (talk) 02:53, 23 November 2025 (UTC)
IMO we should just do without this sentence. It does not add enough to the sub topic Event horizon. Johnjbarton (talk) 03:11, 23 November 2025 (UTC)
I agree. However, if the redshifts and blueshifts seen by an observer FALLING into a black hole were to be discussed somewhere else, it would probably be better to cite the "Seeing relativity" paper (third reference of the current article) since they discuss that exact issue in detail (section VIII) and it is publicly available, in contrast to Kip Thorne's book. L3erdnik (talk) 04:12, 23 November 2025 (UTC)

I think most of "Accretion of matter" belongs in "Evolution" not Observation Johnjbarton (talk) 03:51, 20 November 2025 (UTC)

Agreed. A good location for it could be right after the "Growth" section. Aldebarium (talk) 17:43, 20 November 2025 (UTC)

@EatingCarBatteries The WP:Good article content needs sources so I don't think an excerpt is practical here. Johnjbarton (talk) 23:59, 22 November 2025 (UTC)

That is true, but I feel that it is still better than what it was before. Before, it was just a description of Nolan's Interstellar without any other context or references. Despite being a good example, it felt out of place and cherry picked because of its popularity and cult following.
Black holes in fiction, which is the article embedded, is also marked as a good article. I guess I figure that if the reader would want to see the references of the text they would naturally click the link at the top. EatingCarBatteries (contributions, talk) 00:38, 23 November 2025 (UTC)