Talk:Dark matter

M87 paper seems to evidence of character not existence of dark matter.

In a recent edit @Paolosalucci added a section on M87. I don't understand how it fits in with the section "Observational evidence". Most or even all of the content in that section is about evidence for existence/ The added text ends with:

• Remarkably, the dark matter halo shows a very large central region with an about constant density.

To me this is an analysis of the character of the dark matter halo, not observational evidence for existence. Similarly the cited reference is assumes dark matter from beginning to end. It seems to me that this content belongs in Dark matter halo. A bit more needs to be said about the significance of the 'remarkable' part. Johnjbarton (talk) 23:38, 8 August 2024 (UTC)

I've removed this section since the relevance is unclear. It's one of the many pieces of evidence that dark matter exists if GR/Newtonian mechanics is valid, but I don't see how this contributes evidence for dark matter that the Bullet Cluster doesn't already do (Bullet Cluster does it better too, since it is explicitly difficult for modified gravity theories to explain). Banedon (talk) 01:47, 12 August 2024 (UTC)

Dubious history

Kelvin's and Poincare's "dark matter" has no apparent connection to our present idea of dark matter as different from ordinary matter. Kelvin's idea is plainly about dark stars, which he thought of as ordinary matter. I don't see how it belongs here. The real origin of the dark matter problem is in the study of galactic rotation. I suggest Kelvin and Poincare be deleted as irrelevant. Is there any reason to think they have any connection to the dark matter needed to explain gravitational behavior? If so, it should be in the history. Zaslav (talk) 21:01, 15 August 2024 (UTC)

Sorry, but the reliable sources clearly show the current version is fine.

• Bertone, Gianfranco, and Dan Hooper. "History of dark matter." Reviews of Modern Physics 90.4 (2018): 045002.

This is a top journal and the article has over a thousand citations. Johnjbarton (talk) 22:58, 15 August 2024 (UTC)

Proposal to delete the table "Some dark matter hypotheses"

The table labeled "Some dark matter hypotheses" is puzzling and it's content is not reliably sourced. Rather the categories appear to be invented for the table. The entries are a mix of mainstream candidates and fringe theories. No text helps readers sort out the content. In effect is it an overly long See Also section stuck in the middle of the article. Johnjbarton (talk) 03:16, 24 August 2024 (UTC)

Confusing footnote

Under "Some dark matter hypotheses" > Neutrinos > Standard Model there is a sourced footnote.

• The three neutrino types already observed are indeed abundant, and dark, and matter, but their individual masses are almost certainly too tiny to account for more than a small fraction of dark matter, due to limits derived from large-scale structure and high-redshift galaxies. (ref omitted for Talk page).

As I read this footnote it is an editorial statement that the reference provides evidence against the hypothesis that Standard Model neutrinos account for dark matter (which is what the ref says).

The table gives the impression of (poorly sourced) evidence for a ton different options. If a reader scans the table they conclude "Standard Model neutrinos" are an option. If they read the fine print, they learn it's not an option. To me this is a confusing way to present this information.

@Banedon how about starting the Composition section with a paragraph with this content as well as a reminder of the many aspects of the Standard Model which fail to make the cut for simpler reasons. The latter may seem simplistic but I think it would set up the far ranging search implied by the table. Johnjbarton (talk) 03:16, 8 October 2024 (UTC)

Well, the table also has "MACHO" even though that's been ruled out too. Feel free to make your changes, I'm not likely to revert. Banedon (talk) 04:11, 8 October 2024 (UTC)