Where is knowledge?

The Free Fall

“…His first mention of the rotating disk in print was in his 1912 paper dealing with the static gravitational fields of 1912; and after the 1912 paper, the rotating-disk argument occurred in Einstein's writings only in the 1916 review article. 45 Einstein did not mention the rotating disk problem in any of his papers on gravitation theory from 1907 through 1915. 46 The initial motivation for presenting the rotating disk thought experiment in 1916 was to show that coordinates of space and time have no direct physical meaning; since coordinates have no direct physical meaning Euclidean Geometry breaks down.…”

“…66 The context in which Einstein presented the point coincidence argument was his rejection of his Hole Argument and his commitment and acceptance of general covariance. 67 There are actually two versions of the Point Coincidence Argument, which have been called "the private" and "the public" one. 68 The private version was formulated in letters.…”

“…He could now say he wanted to prove that symmetry is a property which is independent of the reference system. Using (9) and the symmetry condition for tensors, A µν = A νµ , Einstein managed to prove that, A στ ' = A τσ '. 98 He ended the section with anti-symmetric tensors, 99 which he had presented in his 1914 review article.…”