A colleague points out to me a recent preprint by Bertone & Tait titled A New Era in the Quest for Dark Matter. Most of the narrative is a conventionalist response to the failure of experimental dark matter searches, posing a legitimate question in this context. Where do we take it from here?
There is one brief paragraph mentioning and dismissing the possibility that what we call the dark matter problem might instead be some form of new dynamics. This is completely pro forma, and I wouldn’t have given it a second thought had my colleague not griped to me about it. It contains the following gem:
“The success of these efforts however remained limited at most to rotation curves of galaxies, and it is today clear that the only way these theories can be reconciled with observations is by effectively, and very precisely, mimicking the behavior of cold dark matter on cosmological scales.”
This is enormously revealing about the sociological attitudes in the field. Specifically, the attitude common among particle physicists who work on dark matter. Now, that’s a lot of people, and there are many individual exceptions to the general attitude I’m about to describe. But these are exceedingly common themes, so lets break it down.
There are two distinct issues packed into this one sentence. The first amounts to the oft-repeated talking point, “MOND fits rotation curves but does nothing else.”
“…these efforts however remained limited at most to rotation curves of galaxies…”
(emphasis added.) This is simply incorrect.
Nevertheless, this sentiment has been asserted so many times by so many otherwise reasonable and eminent scientists that the innocent bystander may be forgiven for thinking there is some truth to this statement. There is not. Indeed, it is a perfect example of the echo chamber effect – someone said it without checking their facts, then someone else repeated it, and so on until everyone knows this to be true. Everyone says so!
To be sure, I shared the same concern initially. Difference is, I did the fact checking. It surprised the bejeepers out of me to find that the vast majority of observations that we usually ascribe to dark matter could just as well be explained by MOND. Often better, and with less effort. This is not to say that MOND is always better, of course. But there is so much more to it that I’m not going to review it yet again here.
If only there were some way for scientists to communicate. In writing. Preserved in archival journals. Reviews, even…
A Tale of Two Paradigms: the Mutual Incommensurability of ΛCDM and MOND
The Third Law of Galactic Rotation
Modified Newtonian Dynamics (MOND): Observational Phenomenology and Relativistic Extensions
Modified Newtonian Dynamics as an Alternative to Dark Matter
Testing the Hypothesis of Modified Dynamics with Low Surface Brightness Galaxies and Other Evidence
Testing the Dark Matter Hypothesis with Low Surface Brightness Galaxies and Other Evidence
or if those are too intimidating, review talks at conferences
The Trials and Tribulations of Modern Cosmology: The Good, the Bad, and the Just Plain Ugly
Observational Constraints on the Acceleration Discrepancy Problem
Dynamical Constraints on Disk Galaxy Formation
The world has many experts on dark matter. I am one of them. It has rather fewer experts on MOND. I happen to be one of those, because I made the effort to learn about it. Being an expert on dark matter does not make one an expert on MOND – it’s painful to realize you’re at the wrong peak in the Dunning-Kruger curve. Becoming an expert is hard and time consuming, so I appreciate why many people don’t want to invest their time that way – MOND is a fringe idea, after all. Or so I thought, until I bothered to learn about it. The more I learned, the more I realized it could not so easily be dismissed.
But MOND can easily be dismissed if you remain ignorant of it! This attitude is what I call the arrogance of ignorance. Many scientists who are experts on dark matter don’t know what MOND is really, or what all it does and does not do successfully. They don’t need to! (arrogance). It can’t possibly be true! (ignorance).
The result is a profoundly unscientific status quo. If you hear someone assert something to the effect that “MOND fits rotation curves and nothing else” then you know they simply don’t know what they’re talking about.
I haven’t yet broken down the second part of statement above, but I’ve probably outraged enough people for one post. That’s OK – the shoe deserves to be on the other foot. Being outraged is what is to be an astronomer listening to particle physicists opine about dark matter. Their general attitude is that astronomers can’t possibly have anything to teach them about the subject. Never mind that 100% of the evidence is astronomical in nature, and will remain so until we get a laboratory detection. Good luck with that.
9 thoughts on “The arrogance of ignorance”
Good post, Prof. McGaugh (as always). On a personal note I want to apologize to you for the many times I bothered you with my own speculations at a time when I now understand I was on the Left side of the Dunning Kruger graph. I may be on the Right side now, but still close to the minimum of the curve.
No worries. I fear we’re all in the middle most of the time.
Thanks for the post.
I noticed that there is not available a good introductory textbook about galactic dynamics/Mond for physicists. You want to address physics students and to get them to specialise to astrophysics ( before they get brainwashed by dark matter dogma).
I loved the Sanders book about dark matter, but it’s outdated and too much history of rotation curves. Milgrom’ s reviews are difficult to read as an introductory text. You have a much better writing style anyhow. My suggestion: take ‘ Observational Phenomenonlogy ….’ and transform it into a textbook available on Amazon. I will be the first to preorder it:)
You are correct, and the thought had occurred to me. Sometime in my copious spare time… I prefer to do cutting-edge science; I find writing reviews and textbooks rather grinding. It would be good to transmit things I know, but I’m more motivated by things I don’t know, if you see what I mean.
If you ever do want to get serious about doing such a book I would be honored to do the grunt work for you!
Perhaps you could do an outline, then I would fill in the details with information from “The Mond Pages”.
Of course this is probably just another silly idea.
I see precisely what you mean … (Research etc.) ….but I also see clearly that such an introductory text is missing. You already have tons of material…..
In general : the acceleration scale a0 is what theotists should get excited about. I can not see that anyone else ( except Milgrom/ Bekenstein) has started from that premise. All other approaches start from somewhere else and hope to end up with some scale approx. a0 ( for example Verlinde : from deSitter spacetime deduce a0 ). I think it should be the other way round : start with a0 ( microphysical origin) and explain cosmological acceleration.
Thanks again for post.
You are correct, but I am a finite resource.
David Merritt has a book in the works along these lines. Look for it next year from Cambridge University Press.
Prof, I just want to tell you how much I enjoy reading your blog. I’ve probably done this before, my memory’s not so good these days.
Kids like to ignore where we came from and your perspective on recent cosmology should be compulsory reading for them. How we learned to love Lambda is a hoot. I will be quoting much in my own blogs which I sometimes dump in viXra so no-one will read them. Sorry, I don’t suppose a citation in viXra counts much.
Thanks for the inspiration.
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