The conventionality of simultaneity in Einstein’s practical chrono-geometry

While Einstein considered that sub specie astern the correct philosophical position regarding geometry was that of the conventionality of geometry, he felt that provisionally it was necessary to adopt a non-conventional stance that he called practical geometry. here we will make the case that even when adopting Einstein’s views we must conclude that practical geometry is conventional after all. Einstein missed the fact that the conventionality of simultaneity leads to a conventional element in the chrono-geometry, since it corresponds to the possibility of different space-time metrics (which, when changing, accordingly, the “physical part” of the theory, are observationally equivalent).