Dirac and the gravitational constant G

[RobbyQbit]

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

 

[rod]

Interesting. If G is not constant, then what happens to measurements like the gravitational redshift for the Sun using GR? This has been tested using G as a constant.

New measurements of the solar spectrum verify Einstein's theory of General Relativity, https://phys.org/news/2020-10-solar-spectrum-einstein-theory-relativity.html

The solar gravitational redshift from HARPS-LFC Moon spectra *,** A test of the general theory of relativity, https://arxiv.org/pdf/2009.10558.pdf, 06-Oct-2020 "ABSTRACT Context. The general theory of relativity predicts the redshift of spectral lines in the solar photosphere as a consequence of the gravitational potential of the Sun. This effect can be measured from a solar disk-integrated flux spectrum of the Sun’s reflected light on Solar System bodies. Aims. The laser frequency comb (LFC) calibration system attached to the HARPS spectrograph offers the possibility of performing an accurate measurement of the solar gravitational redshift (GRS) by observing the Moon or other Solar System bodies. Here, we analyse the line shift observed in Fe absorption lines from five high-quality HARPS-LFC spectra of the Moon."

 

[rod]

FYI, 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."

 

[Unclear Engineer]

Rod,

I don't see any problem with the measurements supporting GRT in the solar system measurements, even if it is assumed that the gravitational constant varies with time over the age of the universe. We are taking measurements over an extremely small portion of the time, as well as the space of the evolution of the universe. So long as gravity does not have its constant varying by large amounts in very limited volumes or amounts of time, we would only see the effects when looking at great distances, perhaps to locations with substantially different conditions than here around Earth. And, to some degree, that is what we do see - observations show indications of attraction and repulsion that we can't explain using only the physical laws we have derived here near Earth over the past couple od centuries. That is where the hypotheses for dark matter and dark energy come from.

 

[RobbyQbit]

FYI, 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."

Some great links there. Thanks Rod

 

[RobbyQbit]

Dirac was a modest Physicist and often gave credit to other Physicists like Einstein. He resolved differences between Schrödinger and Heisenberg. His colleagues in Cambridge jokingly defined a unit called a "dirac", which was one word per hour. He was quiet but brilliant. During all that quietness he was in deep thought. He was a genius.

 

[rod]

Unclear Engineer in post #4 discussed G varying with time over the age of the universe. "I don't see any problem with the measurements supporting GRT in the solar system measurements, even if it is assumed that the gravitational constant varies with time over the age of the universe."

I suspect there could be problems here. G was a repulsive force during inflation, study Alan Guth. Example, https://ui.adsabs.harvard.edu/abs/2020arXiv200610384S/abstract, “The biggest blunder of his life”, Einstein’s cosmological constant, was introduced since his static space would have collapsed, so he added it to his equation in order to hold back gravity and achieve a static universe. After Hubble’s discovery of the expansion of the universe, Einstein’s cosmological constant was forgotten until modern times, when inflation used the option that gravity could be a repulsive force. To allow for the repulsive gravity, we require negative pressure, thus a small part of repulsive gravitational material existed in the early universe and led to the creation of everything.”

G varying between repulsive and attractive force must be carefully balanced I would think or G much too strong as an attractive force Varying values for G likely impact observations and measurements of the Galilean moons at Jupiter, exoplanet studies, the receding Moon from Earth, and the issue with Mercury orbit and what GR demonstrated correctly about how Mercury moves around the Sun. How the Big Bang created G when it violates the conservation law of energy I do not know. Consider that today we have a GRB reported with 10^55 erg released. How much energy created at the BB event and how did this energy create G (when inflation uses repulsive G)? G varying may be fun to model, but could destroy the universe too

 

[Atlan0001]

The Planck Horizon constant of a collapsed, collapsing, constant of infinity down and in and the Big Bang Horizon constant of a collapsed, collapsing, constant of infinity up and out are exactly the same collapsed Horizon constant permanently (always) opposing itself from two self-opposing directions.

Rod, you've looked to the outer rim of the observable spherical shell of universe one way or another from both sides of the sun as an astronomer and student of physics. You've also seen maps of the universe layers including the outermost rim layers. Which universe layer is the largest layer of all having the greatest extent of coverage regarding the shell? Regarding the Horizon? The outermost Horizon, which at once, at exactly the same time, is the innermost Horizon? Two background constants, two dimensions of one background Horizon that are in fact one force self-opposed and opposing coalescing between them a third dimensional force constant (G)?

(Which I identify as something else, duality as the strong binding force.)