Bee explains The Equivalence Principle
That is what Einstein explains in his thought experiment with the elevator. If you are standing in the elevator (that is just a local patch, theoretically infinitesimally small) you can’t tell whether you are pulled down because there is a planet underneath your feet, or because there is a flying pig pulling up the elevator.
Einstein’s elevator postulates isotropic vacuum. Fundamental indistinguishability of mass and weight fails for anistropic vacuum interaction with test mass. Isotropic vacuum through Noether’s theorem conserves angular momentum. BRST invariance in perturbational string theory inserts the Equivalence Principle. Anisotropic vacuum must *not* contradict prior observation in massed (e.g., atoms) and massless (e.g., EM) sectors.
Vacuum chiral pseudoscalar background: 1) Big Bang matter is favored over antimatter, 2) inflation is fueled by the pseudoscalar field that concurrently dilutes to trace contemporary values, 3) Weak interaction chirality is sourced, 4) biological homochirality is sourced… teleparallel gravitation theory with spacetime torsion (chiral like Lorentz force in electrodynamics) is set to go. EM is unaffected if the chiral interaction is configuration-dependent (requires left and right shoes) . Ordinary stuff is also inert. Opposite chirality mass distributions’ divergence is 10^(-12) relative or smaller – detetable but not commonly seen. A parity Nordtvedt effect does not obtain given chiral L-configuration protein amino acids (e.g., meat) cancel chiral D-configuration natural sugars (e.g., wood).
Theory is a whore. Observation is real. Perform the parity Eötvös experiment (pdf) – the only Equivalence Principle violation mechanism that has never been tested.