MOGging Milgrom

On topic of fancy theories being wrong, let's get back to Milgrom's Modified Newtonian Dynamic. This "MOND" was supposed to obviate the need for "dark matter" in explaining galaxies' overly-fast spin. Against my better judgement perhaps, I'd believed Triton Station. h/t the Turtle, last Tuesday John Moffat submitted Scalar-Tensor-Vector Gravity - which Moffat's calling MOG, just plain modified-gravity. I'll get into Moffat, later this week.

Milgrom makes predictions concerning wide-angle binaries. That radius is √[G_NM/a₀]; a₀ is an acceleration which is zero for pure Newton, 1.2 × 10^-10 m/s² for Milgrom. Moffat calculates 7000 AU for our Sun which runs beyond even a Planet Nine conjecture (although some comets might help us here). If the mass is that of the Centauri barycentre which is 1.988, 2.11 with Prox; we're looking at 10,168 AU. Even α/prox Centauri at their 2017 poorly-constrained maximum semimajor isn't more than 9400 AU. So - to the extent testable, a difficult test here.

But what if we had a wideangle binary of smaller stars. Next problem: those are hard to see in the first place, and we'd have to watch them for some time; which is time we often hadn't had, faint stars being only recently found. We hadn't the tech nor patience to do that from Earthside. Enter the Gaia 'scope, out on STL2.

Gaia has been watching a few of those binaries from our vantage. Following DR3, we've constrained a₀ to a maximum of 0.1032 × 10^-10 m/s² - and a negative minimum. Here's a 25 November update. Ol' Isaac, who never had a clue about any "a₀" so just left it zero, is vindicated. Milgrom, and followers like Triton, are hereby pantsed.