[Steuard]

I don't mean this unkindly, but I am always so baffled when I see how common this take is. I mean, sure, say this about string theory (the field I was trained in): fine. I don't agree, but I see the point.

But dark matter? You think we wanted this "weird particle or something very like it that we persistently can't find" situation? No! The reason that the overwhelming majority of cosmologists and astrophysicists pretty solidly believe that dark matter exists (after a whole lot of skepticism when it was first proposed) is that there is very strong evidence for it from at least three radically different sets of experimental data. [Patterns in how galaxies rotate (the original), gravitational lensing to locate and quantify mass in galaxy clusters (including cluster collisions like the "Bullet Cluster"), and the overall history of cosmological evolution.] And not only do all three lines of evidence indicate "dark matter exists", but as I understand it, they all independently indicate a consistent amount of dark matter (relative to the observable ordinary matter).

People have tried to come up with modified theories that eliminate the need for dark matter for years and years (once they gave up suggesting the observations themselves might be faulty): it would be so much more satisfying, especially in light of our continued failure to find any sort of "stuff" that the dark matter might be made of. But as I understand it, every modification of basic theory that's so far been proposed to give a different explanation of one of those pieces of evidence has had nothing at all to say about the other two. And while maybe you could come up with a different theory modification to account for each line of evidence separately, at that point the coincidence starts to seem far less plausible even than "particle we can't find". ("Our otherwise solidly established theories are wrong in three very specific but unrelated ways, each tuned to match the effects we'd see from the exact same amount of dark matter.")

And yet somehow, the notion has taken root among a whole bunch of non-experts that this is all somehow a conspiracy or a group delusion or a stubborn self-interested refusal to consider other answers. I'll never pretend that science is perfect or immune to groupthink! But for goodness sake, aim that skepticism in some direction where the observational evidence is less overwhelming. (And before you just pick another field to go after, maybe first think carefully about what factors led you to disagree with the experts on this one where it really, really wasn't justified.)

[austin-cheney]

The problem is not group think or conspiracies as you believe. I suspect you believe that must be the counter-position due to emotional investment and low empathy.

The problem is misplaced confidence. The accuracy of opinions/predictions is almost always inversely proportional to the confidence of the claimant. If there were observational evidence then that would alone be a sufficient qualifier and overstated confidence wouldn’t be necessary. It’s bad logic that I explained here: https://news.ycombinator.com/item?id=38203818

[Steuard]

> The accuracy of opinions/predictions is almost always inversely proportional to the confidence of the claimant.

I recognize the sort of phenomenon you're pushing back against here, and there's legitimate value in consciously trying to counterbalance the all too human tendency to nod along to overconfident proclamations of truth.

But even so, the claim you're making here is absurd when treated as a general rule. Expertise is a real thing that people can have. Yes, there are countless places where a genuine expert will express caution and give carefully qualified statements about what is "true", and that's good. It's especially common for topics close to the frontiers of human knowledge. But there are also a whole lot of places where an expert will be willing to say "it's basically safe to take ____ as true", and where if asked they'll be able to back that up with copious explanations and evidence.

If I tell you that tomorrow morning the sun will rise in the east rather than the west, I will say it very confidently, and I will be right. If I tell you as a physicist that this bowling ball I'm about to drop from the second floor window will accelerate toward the ground at a rate very close to 9.8 m/s^2 (maybe only a smidge less due to air resistance, given the short time involved), I will be right. You trust your life every day to countless engineers who have at some point said, "The design and fabrication process we have implemented has involved enough rigor and enough quality control and enough margin of safety that I'm willing to stake my career on it being safe." And the vast majority of the time, for each essential bolt in your car and each fuel line on your airplane and each support beam in your office building, they are right.

So here, in the case of dark matter, the community of astrophysicists and cosmologists has assembled over the past 50-ish years a tremendous array of evidence from multiple independent directions that all seems to paint a consistent picture of some type of matter with quite specific properties. Many of them were highly skeptical at first, and there are still some actively looking for radically different explanations. But the vast majority of those experts have considered all of this positive evidence for "dark matter" and have become convinced that something very close to the Lambda-CDM model must be more or less true.

It's not at all clear to me what more you want from them. I mean, heck, the gravitational lensing results (especially as applied to something like the Bullet Cluster) could be considered a successfully tested prediction of the dark matter model, since those measurements weren't even possible until well after most of the community had become reasonably convinced that dark matter was real. The fact that we haven't yet answered the question "how does dark matter fit with the rest of our understanding of particle physics and astronomy?" is fascinating, but the existence of open questions doesn't on its own mean that all that observational data somehow doesn't count!

[austin-cheney]

Sigh. The cosmological model came into being after several years of academic discussions and finally crystallized around 1978, I believe. Plans for the Hubble didn’t even exist then. All people knew is what they could see from Earth surface and it was fine until later observations became absurdly contradictory comparing the math to known physics from agreed upon physics almost a century earlier. So… you solve for the math. You aren’t going to get a better cosmological model by observing distant galaxies from Earth surface. The only other options are abandoning the entirety of the cosmological model without a replacement or abandoning Einstein physics, which is worse.

That still does not make something entirely without evidence thrust into existence. It certainly doesn’t explain the level of emotional investment. Your only arguments supporting your position are purely social conduct: expertise, agreement, confidence, and apparent sadness. These are not observations. They are not physics proofs. They aren’t even measurements. They are the equivalent of the church calling Galileo a heretic. You call my opinion absurd only because it, according to your own words, inconveniences you, god forbid.

Actual science has been slowly chipping away at the social stupidity of this subject. Here is yet another potential example: https://news.ycombinator.com/item?id=38215274