Torsion Balance Tests

Celestial Variations in G
The Equivalence Principle Torsion Balance tests are incredibly reliable precision machines which are used to measure the Equivalence Principal to increasing sensitivity. Experimenters have designed Torsion Balance tests to try and detect the gravity variations caused by the sun, moon, and the tidal forces. It was found that the gravitational influence of the sun, moon, or the tidal forces could not be measured as manifest of the attraction of the bodies in the experiments. Variations to "gravity" did not appear.

Princeton Experiment
From The Pendulum Paradigm: Variations on a Theme and the Measure of Heaven and Earth, by Professor Martin Beech, we read the following on p.176:



Essentially, the experiment is summarized as follows:

The masses were not attracted to the sun in the experiment, to an accuracy of one part in one hundred billion.

Moscow State University Experiment
The experiment was repeated and improved by researchers at Moscow State University. The title of the paper states the conclusion:

Verification of the Equivalence of Inertial and Gravitational Mass V. B. Branginsky and V. I. Panov Full Text Link (Archive)

Repetitions
Additional experiments of this class are described (Archive). The first two experiments in this list are the Princeton and Moscow State experiments above:

The Eöt-Wash experiments were repeated by others:

https://plato.stanford.edu/entries/physics-experiment/app4.html (Archive)

Eöt-Wash Hill Experiments
From No Easy Answers: Science and the Pursuit of Knowledge by Professor Allan Franklin (bio), on p.70 we read a summary of the Eöt-Wash hillside experiments with the rotating torsion balance:

Study Link

An Eöt-Wash presentation explains (Archive) that the influence of an external source mass on these type of experiments would be a violation of the Equivalence Principle (EP).



One will notice from the graphic above that any horizontal pulling phenomenon would violate the Equivalence Principle which states that gravity operates exactly like a rocket ship accelerating upwards at 1G with no other gravitating bodies around.

Short Range Variations in G
Over shorter ranges, such as with the Cavendish Experiment, it has been seen that an attraction was found, but the attraction is not consistent. This inconsistency suggests that there are dominating effects at that range creating or modifying those results and that the experiment has not yet been properly refined to remove all sources of error.

On the topic of the Cavendish Experiment, the Encyclopedia Britannica article Experimental Study of Gravitation says:

For further information see the Cavendish Experiment

History of the Torsion Balance
The history of the Torsion Balance experiments began in 1889, with Barron Rosland von Eötvös' attempt to detect the Coriolis force.

Foundations of Modern Cosmology By Professor John F. Hawley, and Katherine A. Holcomb

From p.219 of the above text we read:

Interpretation of Torsion Balance Experiments: Selective Gravity
The paradox that external celestial gravity from the Sun and other effects cannot be felt by the test bodies in the torsion balance experiments of Dicke, Eötvös, and others, is acknowledged and addressed by mainstream science with the concept of selective gravity. In the book Gravitation by physicists Charles W. Misner, Kip S. Thorne, and John Archibald Wheeler, on the topic of the Dicke-Eötvös experiments, we read the following at the bottom of p.1055 (Archive):

The reader is left to decide whether this answer of "preferred curves" is sufficient or valid.