Over at Starts with a Bang, Ethan Siegel expressed exasperation that Nature and New Scientist are paying attention to (and lending too much credibility to) an astronomical theory Ethan views as a non-starter, Modified Netwonian Dynamics (or MOND):
[W]hy is Nature making a big deal out of a paper like this? Why are magazines like New Scientist declaring that there are cracks in dark matter theories?
Because someone (my guess is HongSheng Zhao, one of the authors of this paper who's fond of press releases and modifying gravity) is pimping this piece of evidence like it tells us something. Guess what? Galaxy rotation curves are the only thing MOND has ever been good for! MOND is lousy for everything else, and dark matter -- which is good for everything else -- is good for this too!
So thanks to a number of people for bringing these to my attention, because the record needs to be set straight. Dark matter: still fine. MOND: still horribly insufficient. Now, maybe we can get the editors and referees of journals like this to not only do quality control on the data, but also on the reasonableness of the conclusions drawn.
In a comment on that post, Steinn took issue with Ethan's characterization of MOND:
Ethan - this is not a creationism debate.
Hong Sheng is a top dynamicist and he knows perfectly well what the issues are. The whole point of science at this level is to test models and propose falsifiable alternatives.
MOND may be wrong, but it is not evil.
Cold Dark Matter is a likelier hypothesis, by far, but it has some serious problems in detail, and the underlying microphysics is essentially unknown and plagued with poorly motivated speculation.
MOND has always approached the issue from a different perspective: that you start with What You See Is What You Get, and then look for minimal modifications to account for the discrepancies. It is a phenomenological model, and makes little attempt to be a fundamental theory of anything. Observers tend to like it because it gives direct comparison with data and is rapidly testable.
I think Leslie Sage knew what he was doing when he published this paper.
In a subsequent post, Ethan responded to Steinn:
Yes, Steinn, it is evil to present MOND as though it is a viable alternative to dark matter.
It is evil to spread information about science based only on some tiny fraction of the available data, especially when the entire data set overwhelmingly favors dark matter and crushes MOND so as to render it untenable. It isn't evil in the same way that creationism is evil, but it is evil in the same way that pushing the steady-state-model over the Big Bang is evil.
It's a lie based on an unfair, incomplete argument. It's a discredited theory attacking the most valid model we have at -- arguably -- its only weak point. Or, to use a favorite term of mine, it is willfully ignorant to claim that MOND is reasonable in any sort of way as an alternative to dark matter. It's possibly worse than that, because it's selectively willful ignorance in this case.
And then I look at the effect it has. It undermines public understanding of dark matter, gravity, and the Universe, by presenting an unfeasible alternative as though it's perfectly valid. And it isn't perfectly valid. It isn't even close. It has nothing to do with how good their results as scientists are; it has everything to do with the invalid, untrue, knowledge-undermining conclusions that the public receives.
And yes, I find that incredibly evil. Do you?
I have no strong views on MOND or Cold Dark Matter, but given that my professional focus includes the methodology of science and issues of ethics in science, I find this back and forth really interesting.
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