dark matter is not a theory

This is a dense video, I highly recommend it though: ▶ this video TLDW: there's a lot of evidence on why the phenomena we watch is mostly favored to be described as 'something' that is conveniently called dark matter as opposed to a revision of gravity.

If you've got the time, these YouTube videos are a nice counterpoint to a lot of popular communication and discussion on dark matter: Dark matter is not a theory: ▶ this video That dark matter video aged like milk: link the tl;dr is that "dark matter" is a bit of a misnomer. (But also a fun name so it's probably here to stay through sheer memetic momentum.) Dark matter is not actually a hypothesized kind of matter. Dark matter is just an unresolved discrepancy between theory and observation. I'll say that again: "dark matter" is not an attempt at explaining the discrepancy; dark matter is the discrepancy. There are some hypotheses that postulate some kind of as-yet-unobserved matter that could resolve the discrepancy, but these hypotheses are not the actual problem that we call "dark matter". And not all hypotheses postulate unobserved or exotic matter. Some of them suggest alternative physics, others suggest measurement error.

IANAP (physicist) The only the matter portion of the universe is 85% dark matter (26.8% of mass-energy content of the universe). As for the question; I don't think it's right to assume that dark matter really is exotic matter. It's just a set of observations. It's something that behaves like matter (with respect to density scaling) but only seems to interact gravitationally. Some theories posit that it's some unknown particles, others that they are primordial black holes, and some that gravity just behaves differently (MOND). I really enjoyed Dr Angela's videos on Dark Matter [1,2] [1] link [2] ▶ this video

There's a good cosmology YouTuber who basically explains: dark matter is not a theory, it's a set of observations. Galaxies behave like there's a halo of invisible mass surrounding them, one that varies in density per-galaxy. The halos even perturb as expected in galaxy collisions. But nobody's got a coherent theory on what that halo is. ▶ this video

If you're interested in learning more I recommend you watch "dark matter is not a theory"[1]. We consistently, across many measures, observe the effect of substantially more mass than we expect using traditional understandings of dynamics. People have been aware of it, under different names, for about 90 years now. [1] ▶ this video

Interesting that you should link that video. Its title card says "Angela Collier". Here's a more recent video by the physicist[0]. Re: where it says "using simulations with dark matter", we can't simulate DM because it doesn't have any properties beyond our observations. All we do is distribute amounts of it to match observations. It could be "Dyson spheres with EM shields" and the results would be the same. [0] ▶ this video

As far as I know it's from here: ▶ this video As I said elsewhere in this thread, I think she's trying to make some meta point but ends up just muddying the water.

"Dark matter is not a theory"[0] Dark matter, do we need it? what is it? where is it? how much? Full rap mp3[1] [0] ▶ this video [1] link

I also don't know why MOND remains so popular. Angela Collier talks about Dark Matter here: ▶ this video And talks more about how often MOND is brought up in comments on her own video: link

Angela Collier (astronomy post-doc) takes the position that dark matter isn't an theory, but an observation ▶ this video

Doing something professionally just means doing it for money and with the authorization of others, not necessarily doing it well. We all know about professional software developers who are forced by their profession, that is, the fact that they do it under contract X for company Y managed by person Z, to do things that they know are complete crap. I mean, SAP is professional. Microsoft or Google lock-in? Highly professional! Shiny even. Supporting RSS? Not professional. A gimmick you're allowed, like what you do outside of work. Or even more brutal: Ignaz Semmelweis. That he was a professional didn't help him, the super mega cereal professionals undid his efforts without blinking, and without anyone even realizing it at the time. At the same time, people just make stuff up without any rigor, just take climate change denial and whatnot. So it's not that not being a professional is any positive indicator, either. I just think that if you do something others don't already do, they cannot authorize you, by definition. They don't know what they're even talking about, while thinking they do. Not their fault, not your fault, but if you don't do you, "you" will not be done, and the world will never know. Of course, in the end the results have to hold up, my point is not to give license to "questioning everything" as code for just spouting non-sequiturs. But I wouldn't dissuade "randoms" from pursuing scientific fancies because the professionals got it, because frankly, they don't. No