In this talk Dirac talks about his equations (based on Milne's) that the gravitational constant G is not constant. Has this been proven since his theory?
View: https://www.youtube.com/watch?v=-o8mUyq_Wwg
Some great links there. Thanks RodFYI, there are some past reports on G varying in astronomy.
Frequentist model comparison tests of sinusoidal variations in measurements of Newton's gravitational constant, http://adsabs.harvard.edu/abs/2016EL....11520006D, "Abstract In 2015, Anderson et al. (EPL, 110 (2015) 10002) have claimed to find evidence for periodic sinusoidal variations (period = 5.9 years) in measurements of Newton's gravitational constant. These claims have been disputed by Pitkin (EPL, 111 (2015) 30002). "
Does Newton’s gravitational constant vary sinusoidally with time? Orbital motions say no, http://adsabs.harvard.edu/abs/2016CQGra..33d5004I, "Abstract A sinusoidally time-varying pattern of the values of Newton’s constant of gravitation G measured in Earth-based laboratories over the last few decades has been recently reported in the literature. We put to the test the hypothesis that the aforementioned harmonic variation may pertain to G itself in a direct and independent way."
Does the Newtonian Gravity "Constant" G Vary?, http://adsabs.harvard.edu/abs/2015IAUGA..2254444N, "Abstract A series of measurements of Newton's gravity constant, G, dating back as far as 1893, yielded widely varying values, the variation greatly exceeding the stated error estimates (Gillies, 1997; Quinn, 2000, Mohr et al 2008). The value of G is usually said to be unrelated to other physics, but we point out that the 8^B Solar Neutrino Rate ought to be very sensitive. Improved pulsar timing could also help settle the issue as to whether G really varies."
'Big G': Scientists Pin Down Elusive Gravitational Constant, http://www.livescience.com/46385-new-gravitational-constant-measurement.html, "A fundamental constant that sets the size of the gravitational force between all objects has finally been pinned down using the quirky quantum behavior of tiny atoms. The new results could help set the official value of the gravitational constant, and may even help scientists find evidence of extra space-time dimensions, said study co-author Guglielmo Tino, an atomic physicist at the University of Florence in Italy."