Gravitational Physics

Affine theories of gravitation ignore the EP, instead modeling gravitation as spacetime torsion. The two entirely different approaches give wholly identical predictions, with one class of exceptions: affine theories predict at least three classes of Equivalence Principle violation based upon test mass physical spin test mass polarized electron spin[2 , or test mass atomic lattice opposite geometric parity[3]. The first two are theoretically too small to observe.

Testing for reproducible Equivalence Principle violation is therefore of major interest. No violation beyond experimental error was ever observed. Test mass opposite parity EP experiments have never been performed. The proper test of spacetime geometry may be test mass geometry. Somebody should look.

Historic Equivalence Principle Tests {Link without Title}

Method
500?	Philoponus {Link without Title}	"small"	Drop Tower
1590?	Galileo {Link without Title}	2·10-2	Pendulum, Drop Tower
1686	Newton {Link without Title}	10-3	Pendulum
1832	Bessel {Link without Title}	2·10-5	Pendulum
1910	Southerns {Link without Title}	5·10-6	Pendulum
1918	Zeeman {Link without Title}	3·10-8	Torsion Balance
1922	Eötvös {Link without Title}	5·10-9	Torsion Balance
1923	Potter {Link without Title}	3·10-6	Pendulum
1935	Renner {Link without Title}	2·10-9	Torsion Balance
1964	Dicke,Roll,Krotkov {Link without Title}	3·10-11	Torsion Balance
1972	Braginsky,Panov {Link without Title}	10-12	Torsion Balance
1976	Shapiro, et al. {Link without Title}	10-12	Lunar Laser Ranging
1981	Keiser,Faller {Link without Title}	4·10-11	Fluid Support
1987	Niebauer, et al. {Link without Title}	10-10	Drop Tower
1989	Heckel, et al. {Link without Title}	10-11	Torsion Balance
1990	Adelberger, et al. {Link without Title}	10-12	Torsion Balance
1999	Baeßler, et al. {Link without Title}	5·10-13	Torsion Balance
2005?	MiniSTEP {Link without Title}	10-17	Earth Orbit

• "Accuracy" is the measurable difference/average of the weight vectors of the contrasted (sets of) test masses.