Thread by @DudeDarkmatter

What we have here is a failure to communicate.

https://twitter.com/sq1learning/status/1034498966455508992

Over and over I see statements from esteemed colleagues - genuinely brilliant people - that are simply incorrect, for simple lack of fact checking. Like “using only two out of 10 pieces” of evidence. How does one count? Or “MOND doesn’t and dark matter does.” Does what, exactly?

I understand their attitude. I had the same reaction when I first encountered MOND. Indeed, when I first realized that MOND made specific predictions about low surface brightness galaxies, my immediate thought was “Good. I have the data to falsify this stupid theory.”

That was my starting point. Same as theirs. Trouble was, against my hopes and expectations, MOND nailed all these predictions. So what am I suppose to say, that it is wrong?

OK, I thought. MOND must fail somehow else. A survey of the literature showed many claims to falsify it. Good, fine. But why did it get these predictions right? Twenty years on, I still haven’t heard a satisfactory answer.

Worse, I made the mistake of reading the papers that claimed to falsify MOND. More often than not, they falsified straw men, not MOND. So I re-did the analyses. LOTS of them. Over and over, the results were ambiguous or actually favored MOND. We just weren’t giving it a chance.

I’ve reviewed the evidence lots of times.
xxx.lanl.gov/abs/astro-ph/9…
xxx.lanl.gov/abs/astro-ph/9…
arxiv.org/abs/astro-ph/0…
arxiv.org/abs/astro-ph/0…
arxiv.org/abs/1112.3960
arxiv.org/abs/1404.7525
Etc. there are a lot more than ten items to consider, and MOND get a lot more than two right.

These “2 outta 10” kind of statements are not scientific evaluations of the situation. They are political assertions meant to belittle the opposition. They get repeated enough that the echo chamber makes them seem true, but they’re made in ignorance of a wealth of scholarship.

It boils down to an attitude I’ve often heard expressed, that I once shared: “anything before MOND!” Ok. But that’s a sentiment, not a form of evidence. Science can be hard. It was the hardest thing to admit that maybe I’d been wrong to be so sure it HAD to be dark matter.

Because I was. I was sure the dark matter had to be WIMPs, in fact. I was very derisive towards other ideas. I was wrong.

Other people get to be wrong too. This is something every scientist has to face up to personally. What evidence would cause a change of mind? It isn’t science if it isn’t falsifiable. I hear lots of assertions that MOND has been falsified, and a few hold water. What about DM?

By the standards we set in the ‘90s, CDM has been falsified many times. We just chose to ignore those, because the idea is flexible enough to accommodate pretty much anything. No cusps in NFW halos? No problem. Got feedback. Mass function not steep enough? Got feedback.

Over and over we’ve adjusted our predictions to accommodate unforeseen data. This has been going on for so long, people seem to think this is how science is suppose to work. Nope. The perpetual need for revision upon revision is a sign we’re barking up the wrong tree.

I don’t know what’s right. But I use to think I did. Those who seem to think they do know are arguing from a perspective I know to be wrong. I was there. Worse, they’re command of the observational constraints is selectively biased by cognitive dissonance.

The answer here just isn’t as simple as often portrayed. If you don’t understand that, you are missing out on some important facts.