Physicists have been searching for variations in the coupling of materials to gravity for more than a century, and by some measure, for more than a millenium.
Every experiment anyone has ever tried has come up empty. The equivalence principle is a postulate (Einstein's "happiest idea") that underlies General Relativity, making it essential to test.
(Source: This is literally what I do for a living.)
https://en.wikipedia.org/wiki/Equivalence_principle#Tests_of...
Every experiment anyone has ever tried has come up empty. The equivalence principle is a postulate (Einstein's "happiest idea") that underlies General Relativity, making it essential to test.
(Source: This is literally what I do for a living.)