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Comment by MattPalmer1086 | Hacker News Reader

A really interesting result. On it's own, it doesn't destroy dark matter as a theory, but it's putting quite a large dent in it.

Obviously will need additional work and review, it's only one paper. Maybe there are mistakes or factors not fully considered.

There have been a number of other papers recently on measuring wide binaries. Different papers claimed different results on these.

Still, it's certainly something that merits a lot more attention. We may be looking at needing some new theory of gravity (maybe not MOND, but something other than dark matter).

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> A really interesting result. On it's own, it doesn't destroy dark matter as a theory

It refutes LCDM though. No DM halos could be responsible for this behaviour this far out. And this isn't the first time LCDM has been refuted by evidence before they tweaked it with yet more parameters/epicycles to make it fit.

It's been clear for awhile now that neither particle dark matter nor MOND are adequate explanations for observations. MOND clearly matches some data better and with fewer parameters (like this), and DM others, like cluster-scale lensing. New thinking is needed, and hopefully this paper will surprise people into taking MOND-like approaches a little more seriously.

Presuming the behavior is real and not an artifact of the model. This is a statistical technique, needing specially selected targets in order to be observed reliably - and also assuming those targets themselves are typical.

There's plenty of observations which can accidentally vanish because of subtle problems with assumptions, so declaring a total refutation is beyond premature.

Like to wit, if MOND is real then you've really got to explain how sometimes it also selectively just bails out on some galaxies apparently[1].

I'm tired of people trotting out "epicycles" to attack theories they don't like: you're gonna be adding a lot of those to get a MOND which can explain all the data as well (which is to say, it's a trite insult and not useful argument).

[1] https://en.wikipedia.org/wiki/NGC_1052-DF2

Iirc, the udg makes sense if the distance to it is off by something like 25% and the orientation of rotation is off by a bit. Those parameters are very hard to measure in UDGs.

> I'm tired of people trotting out "epicycles" to attack theories they don't like

That's disingenuous. LCDM has a long history of failing to successfully predict later observations and adding parameters to fit the data, where MOND has made many successful a priori predictions without any added parameters since the 1980s. This is not just a matter of not liking something, successful predictions vs. post-hoc curve fitting strikes at the very core of what it means to be a good scientific theory. See:

From Galactic Bars to the Hubble Tension: Weighing Up the Astrophysical Evidence for Milgromian Gravity, https://www.mdpi.com/2073-8994/14/7/1331

As I said, neither approach is fully satisfactory, and we need new thinking about this problem.

Consider also that the author of the linked blog post seems to be a (pretty strong) advocate for MOND, it did read as somewhat biased

He is a bit more nuanced than that, I've been reading the blog for quite some time.

He has pointed out areas where MOND falls short in other posts, but it is true that he thinks that LCDM has some serious flaws, and that MOND like theories have a better predictive record.

It's just that from a more complete point-of-view, there are many other areas than rotation curves that depend on dark matter and has been modelled to really require the specific properties of DM that the lambda-CDM model has, and it's just a bit worrisome every time a blog post talks exclusively about rotation curves. Sounds good that he writes about more of the issues elsewhere! The real picture might require a new blend of both DM and MOND of course..

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