Talk:Dark matter/Archive 8

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Dark Matter is a controversal hypothesis, and not an accepted theory. This fact becomes more prominent, and more and more scientists openly critizise it, and show its shortcomings, in widely public articles or peer-review papers in some of the highest ranked science journals. A few examples:

• Is Dark Matter Real? by Sabine Hossenfelder, Stacy S. McGaugh in Scientific American
• A whirling plane of satellite galaxies around Centaurus A challenges cold dark matter cosmology, in Science (02 Feb 2018)
• Rotation curves of galaxies and the stellar mass-to-light ratio in Monthly Notices of the Royal Astronomical Society
• many many other examples...

I would suggest to explicitly mention in the introduction that it is a controversal hypothesis or (potentially one of the most important) open problem in physics. My edits have been removed, thus i hope this discussion will lead to a conclusion. --Mario23 (talk) 04:06, 6 December 2019 (UTC)

I'm strongly against this. Are there problems with it, sure, but there are even more problems with all the modified gravity theories out there, and Lambda-CDM remains the standard model of cosmology. To quote from the Scientific American article, "Right now a few dozens of scientists are studying modified gravity, whereas several thousand are looking for particle dark matter." This clearly shows dark matter isn't controversial. Banedon (talk) 04:21, 6 December 2019 (UTC)

i would like to note that this user, Banedon, is the person who keeps reverting attempts to introduce justified attempts explaining the hypothetic and controversial character of this concept. i would like to get confirmations about the potential conflicts of interests here. If the person works withon the field (or in a close relation, etc), the opinion should be taken cautiosly. --Mario23 (talk) 10:11, 6 December 2019 (UTC)

I have a conflict of interest insofar as I am something of an expert on cosmology, yes. What about you? Do you have an undeclared conflict of interest? Banedon (talk) 08:55, 7 December 2019 (UTC)

The current version of the lead reflects the scientific consensus, so far as I know as a regular reader of Scientific American and New Scientist. It states the prevailing theory and describes minority views in the last paragraph. I also strongly disagree with bringing a charge of conflict of interest just because of a difference of opinion. Dudley Miles (talk) 13:49, 7 December 2019 (UTC)

Its existence is not debated, but its nature. Rowan Forest (talk) 18:47, 7 December 2019 (UTC)

No. Advocates of

MOND deny the existence of dark matter. Dudley Miles (talk

) 20:04, 7 December 2019 (UTC)

The phenomenon is not debated, however the solution via Dark Matter is. Outside the field of dark matter/cosmology research, in the bigger community of physics, is not taken serios as a solution, see recent surveys. Also inside cosmology, it is questioned. Otherwise, how would you describe a 1year old paper in Science (one of the most prominent journal for scientific research) that questions its existance already in the title? --Mario23 (talk) 23:44, 7 December 2019 (UTC)

The Science paper suggests there may be problems with the formation of dwarf galaxies in

ΛCDM models. That's not the same as arguing that dark matter doesn't exist. Modest Genius ^talk

18:11, 3 January 2020 (UTC)

I thank all participants of this discussion for the argument. I would suggest to write a slightly more careful introduction, to inform the public that astronomical phenomena are observed that require modification of the standard models, and dark matter is one potential solution. --Mario23 (talk) 23:44, 7 December 2019 (UTC)

One example, even at the wikipedia list of [unsolved problems of physics], it is asked whether the phenomena observed are related to unseen mass or modifications of gravity theory. --Mario23 (talk) 23:54, 7 December 2019 (UTC)

What kind of controversy are we writing about? There is currently no theory of gravity consistent with both quantum mechanics and general relativity, but the fact that gravity exists is not controversial. As well as I know it, though I don't follow it all that carefully, there is little controversy on the existence of dark matter, but just the form of it. Gah4 (talk) 11:19, 8 December 2019 (UTC)

I propose changing the first sentence of the article from "Dark matter is a form of matter..." to "Dark matter is a proposed form of matter..." as a remedy to the conflict above. This modification keeps the article true without bringing about the appearance of other more likely theories. The truth is as easy to correct as the inclusion of one word. As of now the first sentence of the article is an unproven claim that does not accurately convey the situation to the readers. Npavanel (talk) 01:12, 10 December 2019 (UTC)

The first sentence already says that dark matter is thought to account for approximately 85% of the matter in the universe; "proposed" would be redundant with "thought to". Probably a harmless addition, but a needless one.

As to the more general point, dark matter is the mainstream standard position, and for good reasons. A tiny sliver of the physics community being dissatisfied with it is not really relevant for our purposes here. Wikipedia follows the mainstream scientific consensus; it does not try to lead. XOR'easter (talk) 02:46, 10 December 2019 (UTC)

Exactly. Dark matter as matter is by far the most popular option. The following sentences explain this in more detail. --mfb (talk) 14:30, 10 December 2019 (UTC)

I think the current lead accurately reflects the uncertainties, throughout it uses language like thought to account for, it's presence is implied by, not yet been observed directly, if it exists. Inserting "proposed" into "dark matter is a form of matter" would, as XOR'easter said, be redundant. More broadly, as others said previously dark matter is by far the most widely accepted hypothesis, it is most certainly not 'controversial' in that sense and the existence of other ideas is acknowledged in the fourth paragraph (which to be honest gives them much higher recognition than they generally receive in the astronomical community). Physdragon (talk) 02:05, 11 December 2019 (UTC)

The nomenclature “dark matter” is widely accepted — frankly, nearly uniformly so — which makes it uncontroversial in the scientific sense, i.e. that something’s at work, keeping the whirling zippies zipping and not zapping — if I may frame it so profoundly — is not in dispute… even if the specifics remain as yet tantalizingly opaque, no pun intended! “Not wholly explained” for an observed phenomenon is leagues away from “controversial,” and “defies intuitive explanation” kinda describes everything interesting. This article seems already written very carefully to present theory as theory, keeping close to current cosmology as-is. If anything, the article is over-cautious in giving undue weight to weak countervailing notions by mentioning them in the lead section, when they ought only be under current section 7 “Alternative hypotheses.” I wouldn’t change the lede. -Danopticon (talk) 15:30, 14 December 2019 (UTC)

By the way, both are hypotheses, and I fixed the bias at the MOND article previously stating that MOND is a "theory" while dark matter is a "hypothesis". Rowan Forest (talk) 19:45, 14 December 2019 (UTC)

Thank you for your effort Rowan. I think your edits are unfortunatly one-sided. Now MOND is described as hypothesis, and dark matter is written as the standard. Obviously, epistemologically, both are hypothesis. May I aks you to add or remove the hypothesis in the lead sentence of both articles. Thank you for trying to help here Rowan! Mario23 (talk) 02:00, 16 December 2019 (UTC)

Hello. Both subjects are hypotheses, and the purpose of this discussion is precisely on how to verbalize that, and clarify what is hypothetical and is not. I have a minimal knowledge on astrophysics so I'm standing on the sidelines on that. Rowan Forest (talk) 02:15, 16 December 2019 (UTC)

Dark matter is on so much more solid footing than MOND that I think it's ridiculous to treat them as equals - if we do then all the wildest theories such as how dark matter is actually invisible antimatter, how the Michelson-Morley experiment actually discovered aether instead of disproved it, etc, are also "theories" or "hypotheses". Banedon (talk) 03:38, 16 December 2019 (UTC)

I was pointed here by a note on

WT:AST. Dark matter is not a controversial theory. It is not a complete or proven theory either, so its details (such as the mass of the dark matter particles) remain matters of debate and alternative models are under active study. However, the overwhelming consensus of professional astronomers is currently that dark matter (of some unknown form) exists. That might change as additional evidence emerges, but it is not currently 'controversial'. Modest Genius ^talk

18:11, 3 January 2020 (UTC)

My favorite example is always gravity. There is no question that gravity exists, but also no theory consistent with both general relativity and quantum mechanics. As well as I know, having been to talks but not studied it much, the consensus is that dark matter exists, but with no consistent theory, which sounds about like gravity. I don't recommend jumping off tall objects, claiming that there is no theory, so you won't get hurt when you fall. Gah4 (talk) 18:40, 3 January 2020 (UTC)

 Administrator note Banedon does not have a conflict of interest in relation to this topic. El_C 19:17, 7 December 2019 (UTC)

Banedon wrote "I have a conflict of interest [...]" --Mario23 (talk) 23:44, 7 December 2019 (UTC)

Then the sentence continues: insofar as I am something of an expert on cosmology — being an expert is not a conflict of interest. El_C 15:29, 8 December 2019 (UTC)

Should the use of velocity be clarified when discussing rotational curves? Graham W. Griffiths (talk) 13:43, 14 January 2020 (UTC)

In my opinion, this article still does a poor job of leading into a broad discussion of dark matter topics. I see some reasons for that:

• The article seems to present dark matter as some sort of theory of matter, rather than a gravitational theory.
• There seems to be poor leading from the idea of dark matter itself as a theory (attempting to explain certain phenomena) into the more varied particular theories that might explain certain observations. In paticular, there seems to be a schizophrenic insistence that dark matter as a theory is true, despite not bringing forward the "leading contender" more specific sub-theory/theories that would substantiate this appropriately. Another aspect of this is undue weight on the theory being true, rather than the observations being true.
• Additionally, there seems to a "cart before the horse" mindset when it comes to dark matter candidates. Because the aforementioned natural leading to subtheories is absent, dark matter candidates are presented without the context of the theories they are embedded within, so the reader is unable to get any sense of why any particular theory might have more validity than another.

In fact, the more I look at it, the more I feel it is missing a section entitled "Theoretical models", which could go before the section currently titled "Theoretical classification". This section could describe the general concepts behind dark matter models, and how they each attempt to address the observations presented in the section immediately prior (observations). Note that this might also tie in more cleanly with the historical presentation, as an account of the development of models and their strengths and weaknesses might also be brought out in discussion. — Preceding unsigned comment added by 96.40.48.159 (talk) 223:09, 10 May 2020 (UTC)

Fixed above signature---Steve Quinn (talk) 20:56, 11 May 2020 (UTC)

Please provide explanations for reversions - more than "weasel words". It is ridiculous to revert without explanations. The above is a critique of this article, please treat it as such. ---Steve Quinn (talk) 21:27, 11 May 2020 (UTC)

I think the article is much better organized. I only have problems with "proposed" in the lead and changing a subtitle from "Alternate hypothesis" to "Alternative gravitational models". However, "proposed" might be useful in the lead, this I don't know. So, please let's discuss. ---Steve Quinn (talk) 22:11, 11 May 2020 (UTC)

Some of this has been discussed in the above section last December. Here is a link to that discussion [1]. ---Steve Quinn (talk) 22:58, 11 May 2020 (UTC)

The more I study this the more problems I see with what the IP opened the discussion with. But I think some of the regular editors (who have more expertise than me) could comment here. That would be helpful. I don't regularly edit this article. ---Steve Quinn (talk) 23:12, 11 May 2020 (UTC)

Wondering if the unit for energy density in the second line is correct. I feel like energy density should be in Joules per cubic meters but then again maybe it is supposed to be density (not energy density). I don't know though if the terminology is different when talking about dark matter.

Huldar98 (talk) 10:05, 29 May 2020 (UTC)

J/m^3 and kg/m^3 are effectively the same thanks to Mass–energy equivalence. I don't think it's a big deal which unit is used. Banedon (talk) 14:15, 29 May 2020 (UTC)

I think the juxtaposition is unfortunate and not helpful to the reader. Units of mass kind of imply "mass", whereas the term "mass" is used to mean something quite different from "mass–energy". —Quondum 21:12, 14 June 2020 (UTC)

I am having difficulty understanding what is meant in this edit. If some dark matter theories are ruled out by observations, this leaves others, which hardly acts as a strong motivation to to seek other theories. The statement would have mede more sense from the reader's perspective (but I'm not saying that it would be accurate) if it said, say, "observations which do not fit any dark matter theories [in a GR background]". I also do not see why in the original form ("observations which do not fit some dark matter theories"), "This gave undue weight to alternative theories of general relativity." Explanation is needed to be able to make sense of this. —Quondum 11:26, 15 June 2020 (UTC)

Reference 28 seems to be a duplicate of 26 and 27 (the early Zwicky papers). Shouldn't reference 28 be removed?

I've tried to fix it by removing the duplicated references. It's possible to believe the duplicate happened because somebody moved text with its references around. TowardsTheLight (talk) 19:33, 21 September 2020 (UTC)

This article just reads like its schizophrenic at times, and this is because contributions are being made by authors with multiple points of view. Some authors are operating under the assumption that Dark Matter exists and other authors are not. This contradiction is very confusing for lay readers. I am going to make a minor edit in one sentence to just help a little bit, but we need to talk about this article more to resolve disputes within the article. Perhaps we could present a dialectic on Dark Matter within the article. However, when writers say that Dark Matter is hypothetical and hasn't been directly detected, and then other writers state, as fact, that Dark Matter accounts for 85% of the mass in the universe, readers get confused. — Preceding unsigned comment added by CessnaMan1989 (talk • contribs) 15:53, 4 October 2020 (UTC)

Sorry I forgot to sign my comment beforeCessnaMan1989 (talk) 17:48, 4 October 2020 (UTC)

Another example of confusion between dueling concepts of Dark Matter is whether or not Dark Matter is being inferred due to General Relativity or Newton's Laws. I think this is problematic for this article. @Parejkoj:, I'm pretty sure Dark Matter is inferred today because of the motion of large bodies not moving in accordance with both General Relativity and Newton's Laws, but General Relativity is the "deeper", more accurate theory of Gravity than Newtonian Physics so General Relativity is what is used to most accurately measure the motion of bodies in space. GR is used for the ad hoc explanation of Dark Matter today. CessnaMan1989 (talk) 17:57, 4 October 2020 (UTC)

Seconded - until proven otherwise, I propose dark matter be referred to as "hypothesis", instead of fact or theory. Facts are indisputable elements that can be readily utilised, and theories are successfully tested working explanations with sufficient evidence to corroborate, that can be built on; hypothesis, like dark matter, are suggestions, often made off observations, and flimsy building material. There are plenty of solid observations that correlate with dark matter, but nothing has been solidly proven to the point of theory, especially when competing suggestions and theories of considerable weight exist. 67.164.37.103 (talk) 06:03, 29 October 2020 (UTC)

Dark matter has not been directly detected and we still do not know what it is composed of. Simultaneously, there is no other viable explanation for the various observed features of the universe, as listed in the article. To User:CessnaMan1989: you do not need GR demonstrate the existence of missing mass in a variety of situations (e.g. rotation curves), but you do for others (BAO, lensing). To User:67.164.31.103: I think you need to spend some time at Hypothesis, as you have a misunderstanding of theory vs. hypothesis in science. - Parejkoj (talk) 16:52, 3 November 2020 (UTC)

I see what you're saying about GR, Parejkoj, so I think it's understandable to refer to Newton's Laws instead of GR in that situation. However, there are other explanations besides dark matter for the observed features of the universe including Emergent Gravity and MOND. CessnaMan1989 (talk) 18:24, 18 November 2020 (UTC)

Overall, I think the article should stress that Dark Matter is still theoretical even though most astronomers and physicists believe it exists. CessnaMan1989 (talk) 19:34, 18 November 2020 (UTC)

As discussed in section 3, and most specifically in section 3.4 with regards to reference 67: https://doi.org/10.1086%2F508162 ("A Direct Empirical Proof of the Existence of Dark Matter"), there is enough evidence that a very strong argument can be made that we do, in fact, have direct proof that there is matter which does not interact electromagnetically and makes up the majority of the matter within the universe. The only thing that's hypothetical is the particle which dark matter may consist of. As such, usage of the term hypothetical is reasonable, especially in reference to it being particulate, but it is acceptable to refer to dark matter as being factual. LewriBaedi (talk) 18:17, 24 February 2021 (UTC)

I tweaked the article to "26%". 73.85.202.201 (talk) 13:01, 1 March 2021 (UTC)

"as reported by the

Planck spacecraft". 73.85.202.208 (talk

) 13:02, 3 March 2021 (UTC)

From what I found, it seems the results from the Planck mission were that the percentages are now estimated to be 68% Dark Energy, 27% Dark Matter, and 5% Ordinary Matter. [1] NeonGenesisEvan (talk) 00:01, 10 May 2021 (UTC)

I am not going to edit this article but new information about distribution of Dark Matter may need to be included to be up-to-date https://www.bbc.co.uk/news/science-environment-57244708Thelisteninghand (talk) 19:05, 28 May 2021 (UTC)

In the intro section, it is said of MOND that: "These models attempt to account for all observations without invoking supplemental non-baryonic matter.". This statement is problematic, as the source it links to is a MOND cosmology simulation using light sterile neutrinos. Sterile neutrinos are hypothetical particles outwith the standard model and are non-baryonic, hence the source does not back up this claim.

This discussion of MOND should be rewritten with discussion of how MOND requires dark matter to explain all observations.

LewriBaedi (talk) 18:05, 1 June 2021 (UTC)

I removed the source, it doesn't directly support the statement and if it's used then lots of other MOND papers could be cited. The statement seems obvious enough as to not require citation, as well. Banedon (talk) 03:45, 4 June 2021 (UTC)

Two recent papers undermine one of the assumptions behind dark matter:

Deur, Alexandre (2021-03). "Relativistic corrections to the rotation curves of disk galaxies". The European Physical Journal C. 81 (3): 213. doi:10.1140/epjc/s10052-021-08965-5. ISSN 1434-6044. Check date values in: |date= (help)
Ludwig, G. O. (23 February 2021). "Galactic rotation curve and dark matter according to gravitomagnetism". The European Physical Journal C. 81 (2): 186. doi:10.1140/epjc/s10052-021-08967-3. ISSN 1434-6052.

Those two papers directly refute the second sentence of the Dark Matter intro: "Its presence is implied in a variety of astrophysical observations, including gravitational effects that cannot be explained by accepted theories of gravity unless more matter is present than can be seen."

Where is the best place in the page on Dark Matter to include that info? Johnjordano (talk) 20:59, 18 June 2021 (UTC)

Do not include first the papers do not "refute" anything since people have been writing these kind of "I can explain galaxy rotation curves too" papers for decades, second they do not explain the other gravitational effects that require more matter such as the Bullet Cluster or CMB, and third Lambda-CDM remains the gold standard as can be seen by e.g. the recently-published DES papers. Not every paper deserves to be cited. Banedon (talk) 04:01, 19 June 2021 (UTC)

Banedon Banedon, thank you for the info. - On the other "I can explain galaxy rotation curves too" papers you refer to: I'm aware of many of them, like MOND, that attempt to explain galaxy rotation curves by introducing new forces or modifications to existing ones. I'm unaware of other earlier papers that show that the galaxy rotation curves can be explain by classic GR without introducing new particles or forces. Can you provide examples? And if there are a set of papers that do explain galaxy rotation curves without the need for new particles or forces, and if those papers are credible, wouldn't that be the type of thing that should be included somewhere in this wikipedia article? - About your point that "they do not explain the other gravitational effects that require more matter such as the Bullet Cluster or CMB". You are right. The math to apply GR to galaxy or other mass distributions is difficult. That type of work, attempting to apply GR to the mass distributions in things like Bullet Cluster, has not been done yet to the best of my knowledge by those authors or anyone else. Johnjordano (talk) 04:32, 19 June 2021 (UTC)

[2] for example. "And if there are a set of papers that do explain galaxy rotation curves without the need for new particles or forces, and if those papers are credible, wouldn't that be the type of thing that should be included somewhere in this wikipedia article?" -- because they are likely to be wrong. They are going against a mountain of observational evidence, after all. If they gain more widespread acceptance then sure (and this article would have to be massively rewritten) but as of right now that is not the case. Banedon (talk) 06:49, 19 June 2021 (UTC)

The article starts with "Dark matter is believed to be a form...". This is not a scientific statement. My edit https://en.wikipedia.org/w/index.php?title=Dark_matter&oldid=1031733482 was reverted by @Banedon: (pinging for attention to this section). All I did was remove "believed", and added the other alternative from the linked citation, while stating that dark matter is more accepted, per the citation. I do not work in dark matter, but I am of a scientific mind, and that intro is a really bad start to the article. The edit notice said "Because there is not enough baryonic matter to account for all the missing matter. See [https://en.wikipedia.org/wiki/Dark_matter#Composition". That is not in disagreement with my edit. The intro should encompass what's in the article. zmm (talk) 11:15, 3 July 2021 (UTC)

MACHOs are not really a viable solution any more, when considering all cosmological observations. I don't see how "believed" is "unscientific" - it accurately describes the scientific consensus on the question. - Parejkoj (talk) 16:24, 3 July 2021 (UTC)

@Parejkoj: I still think "believed" is problematic. Please hear me out. Given that the article says, "General relativity is well-tested on solar system scales, but its validity on galactic or cosmological scales has not been well proven," the lede is not true to the article, and the word belief carries the wrong tone, as Wiktionary says: 'Mental acceptance of a claim as true.' A more apt description IMO would be: "Dark matter is a theoretical form of matter—commonly accepted in the scientific community—that accounts for approximately...". This removes the unscientific connotations of believed and stays true to the source that says: "the most common view...". Believed on its own like this is begging for a ^{[by whom?]} template. zmm (talk) 16:50, 3 July 2021 (UTC)

I think Zm14's proposed rewrite is an improvement (although personally, I would remove the m-dashes). Schazjmd (talk) 17:21, 3 July 2021 (UTC)

No, "believed" is not problematic. By your cited definition, it means mentally accepting a claim as true. Are you saying scientists cannot mentally accept a claim as true? Of course they can, and they can use scientific processes for doing so. How is it any better to say "more accepted"? I have a problem with: "Dark matter is a theoretical form of matter"? We don't really know that it is a form of matter. Is the word "theoretical" used to indicate some doubt about it? Or to say that there is a theory for believing it to be a form or matter? Either way, I don't think it helps. Roger (talk) 22:33, 3 July 2021 (UTC)

Two things. First your edit inserts "Normal baryonic matter could still account for the discrepancy in what is known as massive compact halo objects, though the "most common [scientific] view" is that dark matter is exotic" into the article, and as Parejkoj pointed out there are good reasons to believe dark matter is non-baryonic. If there's anyone out there who works on dark matter who also thinks MACHOs account for all the dark matter, I am not aware of who they are, so this gives a fringe position undue weight. Secondly, for the word 'believed', I don't see what your problem is with it. There are lots of papers that use the word 'believed' in their text, e.g. [3] which says "Collapsing shells form horizons, and when the curvature is small classical general relativity is believed to describe this process arbitrarily well." If someone actually tags the word with ^{[by whom?]} then we'll just add "by scientists". Banedon (talk) 22:47, 3 July 2021 (UTC)

The insertion of MACHOs was triggered by "believed" -- my aim was NPOV: merely utilizing the linked citation. If it's outdated, then let's use a better source.

Allow me to offer an analogy to my issue with "believed". Imagine the Sun article started with "The Sun is believed to be the star at the center of the Solar System". This is clearly weird on so many levels, so is the "believed" here. My previous suggestion may not have been the best, but I think it's an improvement that can be improved on. Let's start with what we know: 1. Dark matter hasn't been directly observed 2. it makes up 85% of the matter in the universe 3. all candidates are just hypotheses at the moment. So, the intro should just begin with that, for example:

Dark matter makes up 85% of the universe by mass according to indirect observations.[insert citation] The leading hypothetical candidate(s) as of [insert year], among many, is(are) [x].[insert citation] Its presence is implied ...

I already see on this talk page concerns with POV issues. All I'm saying is, the lede gets off the wrong foot. Even "believed by scientists" would not be a good description. I hope this helps even by a little. zmm (talk) 23:38, 3 July 2021 (UTC)

I also see no issue with the word believe being used in this manner, A theory is a belief, policy, or procedure proposed or followed as the basis of action^[1]. Your example also makes sense since at one point it was believed that the Earth was in fact once at the centre of the solar system. Believed or theorized are interchangeable as a theory is a belief based on observed or calculated information. Your definition given for belief only supports the usage in the article as a theory is a mental acceptance of a claim is true, in this case dark matter. It has not been proven that it actually exists. McMatter ^(talk)/_(contrib) 00:19, 4 July 2021 (UTC)

The lede is awkward and not the best wording. Would something like this work? Dark matter is a form of matter that has not been detected directly but whose whose existence is inferred from otherwise unexplained gravitational effects. NPguy (talk) 19:52, 4 July 2021 (UTC)

We don't know for sure that dark matter is a form of matter. Roger (talk) 20:00, 4 July 2021 (UTC)

We do know for sure that it is, see the technical definition section. Banedon (talk) 22:28, 4 July 2021 (UTC)

I don't see an issue with writing "The Sun is believed to be the star at the center of the Solar System" either. It sounds curiously hesitant, but it's not wrong. I don't like your version of the lede because my conception of lede is that it will begin with "Dark matter is [what it is]", but if people prefer it then so be it. Banedon (talk) 22:28, 4 July 2021 (UTC)

Scientists on an individual level are free to believe in whatever they want. The body of work that is science is modeling nature, observing, refining said model, and so on. Dark matter not being for sure even matter at the moment makes it hypothetical, and the lede should be upfront without weasel words—that includes "believed by scientists". I agree "is" is needed after "Dark matter", so here's another proposal:

Dark matter is a hypothetical solution to a discrepancy in the observed matter in the universe. As of [insert year], the leading candidates are [x, y, z].[citation] It accounts for approximately 85% of the matter [...]

I appreciate the discussion, and I hope now I have gotten my point across much better. Over to you. zmm (talk) 14:47, 5 July 2021 (UTC)

Addendum:

Having checked the technical section of the article, a further refinement can be (see added explanatory footnote):

Dark matter is the invisible non-baryonic matter^[a][2] that accounts for approximately 85% of the matter in the universe and about 27% [...]

I fully appreciate all those that are OK with the colloquial sense of "believed", but it remains a weasel word, so does "believed by scientists", according to Wikipedia's manual of style:

As stated in the MOS it's a word to watch out for, however in this case it is not a weasel word as it is following the thought that it is a theoretical concept and we should not speak about about it as fact, believe relays this effectively. McMatter ^(talk)/_(contrib) 20:50, 5 July 2021 (UTC)

"invisible non-baryonic" should convey the same more professionally instead of words (believed and thought) to watch out for. For more emphasis, "yet to be discovered" can be added. Reading my latest suggestion, which is based on the article, and uses the same citation, in one sentence I get what the topic is about, instead of the vagueness (may be not to those familiar with the topic) of the current sentence. If I may ask, what's wrong in my latest suggestion (again, it's right off the article)? I see that it does zero harm, and in fact improves the prose, whether you think it's a MOS issue or not. zmm (talk) 21:12, 5 July 2021 (UTC)

"believed to be" is redundant since "thought" was already there 3 months ago

"believed to be" was added only three months ago by an IP address (so it's not an established intro), with the reason "adding context". Wasn't "thought" enough? Prose improvements aside, I'll be removing the redundancy. zmm (talk) 21:52, 5 July 2021 (UTC)

I reverted your change, as it changed the meaning of the sentence from Dark Matter being a theory to being fact, which it is not. The thought is how much of total matter it is guessed to comprise. McMatter ^(talk)/_(contrib) 22:16, 5 July 2021 (UTC)

After very careful consideration, I completely see your point. "Believed" in this case is being used in the uncertain sense, which IMO is better replaced with "a hypothetical". The latter removes any uncertainty in the intended meaning. I believe this will not change the meaning of the sentence (I sure do hope so), so I'll go ahead with an edit, based on what I just wrote. zmm (talk) 22:37, 5 July 2021 (UTC)

Addendum: the article already makes use of the various variations of the word "hypothesis" ~20 times (Ctrl+F "hypoth"), so it should be perfectly fine in the lede. zmm (talk) 22:45, 5 July 2021 (UTC)

Addendum 2: the local description (shows on app under the title) already says the same: "Hypothetical form of matter comprising most of the matter in the universe." zmm (talk) 23:03, 5 July 2021 (UTC)

Under Direct detection it says "The DAMA/NaI and more recent DAMA/LIBRA experimental collaborations have detected an annual modulation in the rate of events in their detectors,[131][132] which they claim is due to dark matter. This results from the expectation that as the Earth orbits the Sun, the velocity of the detector relative to the dark matter halo will vary by a small amount. This claim is so far unconfirmed and in contradiction with negative results from other experiments such as LUX, SuperCDMS[133] and XENON100.[134]" but months ago it was reported that the annual variation reported was an artifact of the annual resetting of the noise floor. DAMA had never released their data, and now it seems their statistics were incompetent at best. Is that controversial ? It should be easy to find the reports from earlier this year (I will soon). - Rod57 (talk) 00:24, 11 November 2021 (UTC)

See title. 2A02:AA11:9102:3D80:94D9:4928:F250:4A62 (talk) 17:19, 4 April 2022 (UTC)

According to the article, Zwicky "obtained evidence of unseen mass he called dunkel Materie ('dark matter')". An IP editor changed "dunkel" to "dunkle" [4] but this was soon reverted [5]. It seems to be the case that the IP editor's version with "dunkel" is correct German: see de:Dunkle Materie, wikt:Dunkle Materie, and various books and papers such as [6]. It appears that Zwicky first used the term as "dunkle (kalte) Materie" in 1933 [7] (see pg. 122). The article was published in Helvetica Physica Acta (Vol. 6, p. 110-127), written in German and although Zwicky was already at Caltech at that time. There's a publication "The Early History of Dark Matter" by Sidney van den Bergh [8] that gives some historical considerations. The phrase itself can be found much earlier in other contexts, for example in Goethe [9]. We currently have the wrong spelling in Dark matter, Fritz Zwicky, and Coma Cluster. I'll correct the spelling, although it seems to me that the German phrase could be just as well left out. --Amble (talk) 21:19, 2 June 2022 (UTC)

IP has restored the edit [10] -- appears correctly now. --Amble (talk) 21:20, 2 June 2022 (UTC)

I looked around online and both "dunkel" and "dunkle" appear to be mean "dark" in German. Dunkel v. Dunkle. Dunkle seems to have added connotations such as "shady", "dubious", "questionable". I don't have access to the Zwicky paper to check, but some books that discuss it use the dunkel spelling[11][12] while others use dunkle.[13][14] Schazjmd (talk) 21:21, 2 June 2022 (UTC)

I only find the spelling "dunkel Materie" in English-language books and papers, not in any written in German. See above where I linked to Zwicky's original paper, which does indeed have "dunkle". I understand the distinction to be simply proper agreement of adjective + noun in German grammar, not any special shade of meaning. --Amble (talk) 21:26, 2 June 2022 (UTC)

That is correct (native speaker here). When the adjective dunkel is used as an attribute with a feminine noun, it becomes dunkle. --Wrongfilter (talk) 21:51, 2 June 2022 (UTC)

That's interesting, Wrongfilter, thanks for the explanation! And Amble, thanks for fixing the misspellings. Schazjmd (talk) 21:54, 2 June 2022 (UTC)

I have had several discussions with astronomy/astrophysics students this semester.
Each time I have had to correct broad, incorrect assumptions on the nature of Dark Matter.
And, in each case, students were using this article/references to base those assumptions.

We cannot discuss Dark Matter the same way we discuss Iron, Electro-Magnetism, or Tuesday.
Dark Matter is literally Whatever stuff or mechanism that is making our observed measurements different than our predictions above a certain scale.
It is no more or less than that until we have a better understanding of why things don't work as accounted for.

Let me give you a simple example:

   Imagine a jar(1kg) with 10 cookies(100g) in it.

   On day 1 you measure the jar + cookies at 2kg.
   You add 1 more cookie to the jar and measure 2.1kg.
   Later that day, you take 2 cookies out of the jar.

   On day 2 you measure the jar + cookies at 1.95kg.
   You add 3 more cookies, and now measure 2.21kg.

   On day 3 you measure it at 2.28kg.
   You take 4 cookies out and measure it again at 1.81kg.

   On day 4 you measure it at 1.79kg.
   You then take all 8 cookies out of the jar and they each measure exactly 100g on their own.
   You measure the empty jar at exactly 1kg.

   What is causing your measurements to come out differently when things are combined? We don't know.
   The system as a whole sure ACTS like there is more/less mass than what we expect.
   If others replicate the study they also get unexpected numbers. But everyone's numbers are also slightly different.

   Let's agree to call [reason for the big and slight differences] Dark Cookies.

That's it. There isn't anything more to say. (Yet)
Note that I didn't say, or imply that there WAS more/less mass, only that there must be a reason that things don't appear to work the same when measured individually.

But it's difficult to talk about some abstract idea of [why something doesn't seem to make sense]. So we gave it a name. But the very name we gave it implies something that we very-much-so should not be implying. But we can't change the name now. So instead, we need to go out of our way to SAY that we are not making that implication.

Dark Matter is not just Matter that we can't observe. (Unless proven otherwise)
It's just shorthand for...

   Shrug
   That galaxy acts like it has a mass of [ X ]. But we can only see mass of about [X × 0.45] no matter how hard we look.
   And that one over there acts like it has a mass of [ Y ]. But we only see about [ Y × 0.51 ].

2601:19A:C101:1459:54C3:A185:F7E7:85DF (talk) 03:40, 9 December 2021 (UTC)

Is there a point to this extended commentary? NPguy (talk) 19:31, 10 December 2021 (UTC)

I don't think this is accurate. Dark energy could arguably be described this way, but dark matter is specifically restricted to being massive objects of some kind that don't currently interact in dynamically significant ways except through gravity. In current usage, cold (nonrelativistic) dark matter is almost always assumed due to hot/warm DM being mostly ruled out, so "dark matter" typically means a perfect fluid with w=0 ("dust") that is almost completely decoupled from the Standard Model. In particular MOND and other proposed explanations of the same observations are *not* considered to be "dark matter". Maybe you were thinking of dark energy? Patallurgist (talk) 05:33, 27 July 2022 (UTC)

The current text [1] categorizes primordial black holes (in a footnote) as non-baryonic matter, but then cites a contradicting source stating that those silly astronomers do in fact classify all black holes as baryonic matter. (It's also confusing because a paragraph later we repeat that ordinary stars are made of baryons, but without the disclaiming footnote.) Any objections to simplifying the explanation of baryonic matter to:

Most of the ordinary matter familiar to astronomers, including planets, brown dwarfs, red dwarfs, visible stars, white dwarfs, neutron stars, and black holes, is called baryonic matter (referring to the baryons that dominate the mass of most ordinary matter).

Rolf H Nelson (talk) 07:01, 2 November 2022 (UTC)

If I understand correctly, the (admittedly loosely worded) Mach's Principle says that impulse-mass doesn't really exists, it is merely a side-effect of the accelerating object's weight-mass interacting with the combined weight-mass of the entire Universe. Because of that M. P. and the Dark Matter theory likely have a lot of intersection, which could be discussed in the article. 78.131.76.69 (talk) 21:38, 15 December 2022 (UTC)

Dark matter supposedly forms a "halo" around a galaxy (or exists in the halo region). As a layman, I came to this article seeking an explanation of why its distribution around a galaxy isn't roughly the same as the distribution of visible matter. I understand that it can't form stars, because it isn't subject to the strong nuclear force; but that doesn't explain why it forms a spherical halo, rather than a rotating disk.

I've read many popsci articles about DM, and its distribution isn't generally discussed except in terms of the evolution of structure in the early universe.

Is this just another question about dark matter that nobody knows the answer to?

MrDemeanour (talk) 15:28, 3 May 2023 (UTC)

Good point: the basic reason is under "It lacks an efficient means to lose energy", but not spelled out as such. I'm not sure where would be a better place in the article to explain this. - Parejkoj (talk) 16:03, 4 May 2023 (UTC)

I have reverted this edit which points to a poll at a conference. My main reason is that this poll is hardly notable for an encyclopedia simply because science does not work via polls. More concretely, it is not clear how representative this conference is, what the credentials of the participants are, how many there were ("only three" - out of how many?). The conference web site is not very enlightening (I recognise only one name with certainty). The cited source is a spreadsheet on google docs, these things are rather volatile and not suitable. --Wrongfilter (talk) 09:43, 15 July 2023 (UTC)

I disagree with this on multiple fronts. Science does not work via polls, but the section in the article starts with "The prevailing opinion among most astrophysicists", making clear that this is an opinion. It will remain an opinion until either dark matter is discovered or a better alternative model (presumably based on modified gravity) is found. I wrote in the original edit that 25 answered no to the question "does dark matter exist", so it's three out of 28 respondents (also the conference had a lot more than 28 participants, it's just that only 28 responded to the poll + gave an answer to this question). That you recognize only one name doesn't mean much, because there are lots of cosmologists in the world and I doubt anyone recognizes all of them. More pertinent is whether the other people listed actually are cosmologists, and I don't think that's in dispute. The source is a Google Docs because the results of the poll were shared in a Google Docs (note the document isn't editable).

I would agree the source isn't very reliable or scientific. It's probable that people responded based on different interpretations of the question, e.g. it's difficult for me to think that most cosmologists believe the universe is flat. A curvature of exactly 0 would be highly unusual, even though current measurements indicate it is 0 within experimental bounds. But it is still a source for "The prevailing opinion among most astrophysicists [is that dark matter exists]", unless you are aware of a better source. Banedon (talk) 01:19, 17 July 2023 (UTC)

@Wrongfilter: since no response after two weeks. Banedon (talk) 06:31, 1 August 2023 (UTC)

Since I've already expressed my opinion I was hoping for other people to chime in. I did not write the article or that section; I check changes or additions when I see them, and when I deem them unacceptable I revert to the status quo. The current formulation ("prevailing opinion") is not great either, nor is its reference (a well-known cosmologist, but a blog post from 11 years ago). I think that whole sentence can be dropped at no loss. What I know from direct experience is that dark matter is the model that is used by the overwhelming majority of papers in extragalactic astronomy for the interpretation of observational data, for simulations and theoretical analysis, while alternative models are rarely used. This reflects an opinion on the epistemological value of the dark-matter model. Read this way, the existing formulation is just about acceptable, but really, I would now advocate its removal. --Wrongfilter (talk) 08:24, 1 August 2023 (UTC)

I'm no scientist so I'm really asking a question here rather than advocating for a correction, but where does the 85% figure come from? The linked NASA article says that it's 27%, unless I'm reading it wrong: "But it is an important mystery. It turns out that roughly 68% of the universe is dark energy. Dark matter makes up about 27%. The rest - everything on Earth, everything ever observed with all of our instruments, all normal matter - adds up to less than 5% of the universe." What am I misreading here? Mpaniello (talk) 13:55, 11 August 2023 (UTC)

ETA: Never mind, figured it out. It's 27% of the entire universe, 85% of all matter. That'll teach me not to read closely. Sorry for wasting anyone's time. Mpaniello (talk) 13:58, 11 August 2023 (UTC)

Dark Matter is described in the first book of the Bible. One might say that it is hidden in plain site. "In the beginning G-d created the heavens and the earth. The earth was formless and void [tohu v’vohu], and darkness was over the surface of the deep, and the Spirit of G-d was moving over the surface of the waters. Then G-d said, “Let there be light”; and there was light." This is describing Dark matter. One can deduce that light came out of darkness. The absence of darkness does not create light whereas the absence of light does create darkness. That makes sense because darkness pre-dated light. 2600:6C51:627F:101E:828:DCD6:527D:F2BD (talk) 06:29, 1 August 2023 (UTC)

The Talk page is for discussing improvements to the article. This comment doesn't propose or discuss any improvement. If it is meant as a proposed addition, even just part of it, I would revert it as

WP:Fringe (although most probably someone will beat me to it). MrDemeanour (talk

) 10:52, 1 August 2023 (UTC)

biblical nonsense stories and science do not mix, there is no evidence for god, there is some evidence that there may be dark matter, or our maths models are wrong, but still, nothing in there leaves room for a mystical being who can allegedly make everything but is incapable of being detected in any testable way! 82.9.90.69 (talk) 19:09, 24 August 2023 (UTC)

Them that got eyes let them see . 2607:FB91:F83:8036:143B:5D20:2B64:789E (talk) 15:18, 10 September 2023 (UTC)

Right now the article lists black holes under both baryonic dark matter and also non-baryonic dark matter, which is clearly contradictory. Banedon (talk) 04:08, 3 October 2023 (UTC)

"While the matter from which black holes form is mainly baryonic matter, once swallowed by the black hole, this distinction is lost." -- COSMOS (the Swinburne University of Technology Online Astronomy Encyclopedia.) We should probably just say that, but I'm sure someone would prefer a peer reviewed source instead. But it's definitely the right answer because primordial black holes could form from either, and direct collapse would be from baryonic matter, and we don't know which the early JWST quasars are. Sandizer (talk) 05:33, 3 October 2023 (UTC)

Yesterday I put mentions of atomic dark matter into the article, and this was reverted, first by user:Parejkoj and then by user:DVdm, supposedly because the reference was too recent and was a preprint. But this is a misuse of those policies. The reference I gave (as I said in my edit comment) was given as a source of other references. I did not give it as support for what the paper is saying (something about "mirror stars"). So it doesn't matter whether the paper is recent or a preprint. I'm just giving it for the sake of its introduction, which surveys some of the previous theoretical work on the subject of atomic dark matter. It's not as though I'm putting some fact into our article that needs support or "verification"! You have to think about what the purposes of Wikipedia policies are, rather than just go around applying them however you like, undoing the contributions of other editors.

The "Bold, revert, discuss cycle" is really flawed, and is NOT mandated. The "discuss" part usually gets nowhere, so the reverter wins. The problem is that it encourages people to revert, even though

See

wp:BURDEN

: "The burden to demonstrate verifiability lies with the editor who adds or restores material, and it is satisfied by providing an inline citation to a reliable source that directly supports the contribution."

And that IS mandated, a

wp:policy. Don't let others do the work. Do it yourself. You were warned about this many times before. - DVdm (talk

) 17:43, 8 January 2024 (UTC)

The solution seems simple enough: If the article you linked to is merely an indirect citation, why not change to it a direct one but citing its references? For some reason I couldn't download the preprint to check.NPguy (talk) 18:13, 8 January 2024 (UTC)

@NPguy: I'm not sure what you meant by an indirect citation. The paper I referenced has lots of citations of previous work. I actually think it's better to put it than to put one or several of the articles it references, because in its introduction it discusses things a bit, and that is useful to a Wikipedia reader who wants to understand the subject a little. It's better than having to look at a whole bunch of references, if I put a bunch into our article. I am no expert on atomic dark matter. I don't know what other papers are good introductions. I improved out article by putting in three mentions of atomic dark matter. They should not be taken out just because somebody thinks my reference doesn't "verify" something, as though I'm tryin' to prove something! I'm just giving a useful reference, that's all. I don't know what DVdm is talking about when he says I have been warned about this. Sometimes people accuse me of original research if I put some simple calculation or observation into an article, such as at Talk:Atmosphere of Earth. DVdm reverted an edit of mine of the article on gravity, because I didn't prove with a reliable reference that the information I added was interesting!

The link to my reference works, for me. Eric Kvaalen (talk) 13:22, 10 January 2024 (UTC)

Regarding " I don't know what DVdm is talking about when he says I have been warned about this": see

• User talk:Eric Kvaalen#Alpha Centauri
• User talk:Eric Kvaalen#Hunic superterrane moved to draftspace
• User talk:Eric Kvaalen#Plutonium-238
• User talk:Eric Kvaalen#Date of Easter
• User talk:Eric Kvaalen#September 2022
• User talk:Eric Kvaalen#Original research regarding this revert of your edit to Gravity
• Wikipedia:Administrators'_noticeboard/IncidentArchive972#Removal_of_a_request_on_the_Talk_page_of_Criticism_of_Windows_10

- DVdm (talk) 15:00, 10 January 2024 (UTC)

@Eric Kvaalen: I took a brief look at the paper. It's not a good source. You're not wrong that it contains relevant citations, but it's not focused on atomic dark matter. In the context of a Wikipedia article, the kind of source we need is a review article on atomic dark matter itself – an article that discusses the motivation for the model, its relative strengths and weaknesses, its successes so far (if any), and prospects for testing it in the future. The paper you linked is not it; it's focused on "mirror stars", and the relation between mirror stars and atomic dark matter is a priori unclear. I don't have time to do it myself, but I would start with a Web of Science search for "atomic dark matter" and filter for review articles. Banedon (talk) 04:29, 11 January 2024 (UTC)

@Banedon: Yes, it would be nice to have a review article on the subject of atomic dark matter. (I don't see why you say that the relation between mirror stars and atomic dark matter is a priori unclear. You can't have stars, with nuclear fusion, if you don't have atoms.) But nevertheless, my edit was an improvement to the article, and therefore should not be reverted. The article didn't mention atomic dark matter at all!

As for DVdm's list of my "sins", none of them have to do with giving a reference that was too recent or a preprint. And I think I make some very good points in all those discussions on my talk page. Eric Kvaalen (talk) 08:38, 13 January 2024 (UTC)

The relation is a priori unclear because stars and dark matter are a priori different things. These terms you're using are not obvious, including to people who work in the general field. Without more text on what these terms are, I do not think your edit was an improvement; it's like reading a thesis that is generally well-written but contains a poorly-written paragraph about some interesting topic. Being about an interesting topic does not make the paragraph an improvement.

I'm not interested in the DVdm's list of your "sins" - that's a conduct dispute, not a content one. Banedon (talk) 07:05, 15 January 2024 (UTC)

Putting these here to remember to check in on later:

• Oncins (2022) "Constraints on PBH as dark matter from observations: a review", comes with a video
• Bernard Carr et al. (2023) "Observational Evidence for Primordial Black Holes: A Positivist Perspective"
• Su, Li, and Feng (2023) "An inflation model for massive primordial black holes to interpret the JWST observations"
• Depta et al. (2023) "Do pulsar timing arrays observe merging primordial black holes?"

All four are pretty juicy relative to the dark matter composition question, which is why I'm a bit reluctant to add until they pass review. Sandizer (talk) 02:21, 5 October 2023 (UTC)

Probably worth checking in on those peer review statuses, as https://iopscience.iop.org/article/10.3847/2041-8213/ad1bf0 states as an unqualified premise that AGN were around from z ≳ 15 (see the second line in the Discussion section.)

... Carr et al. 2024 made it in Physics Reports: https://www.sciencedirect.com/science/article/pii/S0370157323003976 -- it's a pretty ambitious review with 68 pages and 451 references.

From the Conclusions: "much of the evidence point towards dark matter in PBHs with around a solar mass ... naturally explained if PBHs form at the QCD epoch and this is our preferred scenario." Sandizer (talk) 20:59, 15 February 2024 (UTC)