Einstein thought that when dealing with gravity high velocities are not so important. So in 1912 he thought about gravity in terms of the principle of relativity and not in terms of the constant-speed-of-light postulate (special relativity). But then he engaged in a dispute with other scholars who claimed that he gave up the central postulate of his special theory of relativity. x

Max Abraham

Gunnar Nordström

Einstein’s Pathway to his Equivalence Principle 1905-1907

1912 – 1913 Static Gravitational Field Theory

1913 – 1914 “Entwurf” theory

Berlin “Entwurf” theory 1914

The Einstein-Nordström Theory

Dawn of “Entwarf theory”

1915 Relativity Theory

1916 General Theory of Relativity