undetectable. In other words, it is a preferred framein principle only, in practice all inertial frames must be equivalent, as in special relativity. ^ a b
in the General Theory of Relativity”. Physical Review 48: 73. Bibcode: 1935PhRv...48...73E. doi:10.1103/PhysRev.48.73. ^ Koks, Don: Explorations in Mathematical