James Webb Space Telescope finds evidence for alternate theory of gravity

I follow the lead author, Stacy McGaugh, via his blog where he posts discussions and musings about the latest research into the dark matter vs MOND debate: https://tritonstation.com/new-blog-page/

His arguments are very convincing and relatively clear. I am not an astrophysicist but I have two degrees in physics and have always found the dark matter theory to be lacking -- in absence of any evidence of causation whatsoever, dark matter can only be described trivially as "where we would put matter if we could to make our theory of gravity make sense," which is totally backwards from a basic scientific perspective.

Predictions based on modern MOND postulates are shown to be more and more accurate as our observational instruments continue to improve in sensitivity.

> which is totally backwards from a basic scientific perspective

This is not right, because if we have a situation where our theories and observations don't cohere, it's not given whether the theory requires modification or we're missing something in our observations (or both). A classical illustration is the orbit of Uranus being observed in the nineteenth century to be contrary to the predictions of Newtonian theory. Calculations were made assuming the truth of the Newtonian theory and that we were missing something in our observations - the position of Neptune was predicted and it was subsequently discovered.

On the other hand, the orbit of Mercury diverged from the prediction of Newton's theory. Again, a previously unobserved planet closer to the sun was postulated as being responsible, but in this case it really did require a modification to the theory of gravity: general relativity, which accurately predicted the 43 arcseconds per century of perihelion precession by which Mercury's orbit diverges from Newtonian predicitions.

GR has obviously made many other predictions, such as the gravitational bending of light, black holes, and gravitational waves, which have been vindicated.

So there's obviously a problem of the theory and observations not cohering, but whether the solution is a modification of the theory or a new form of matter is not clear in advance, and the latter is not unreasonable and certainly it's not unscientific to make as a hypothesis, to see where it leads.

The difficulty is in coming up with a theoretical framework that retains all the successful predictions of GR while also accounting for the galactic rotation curves.

One difference between dark matter and Neptune is that the existence of Neptune is falsifiable. The formulation of dark matter inherently is not. Falsifiable hypotheses is the cornerstone of science.

Is the existence of a planet so easily falsifiable? It hasn't been so long since the Planet Nine hypothesis started going around, and while we've observationally ruled out a big chunk of the original parameter space, there's still lots of room for a big dark dwarf planet to be floating around out there. It doesn't seem so different from how we've gradually been ruling out the parameter space for dark-matter observations.