Einstein's special relativity space-time Minkowski space non-Euclidean parallel postulate proved Euclid non-Euclidean geometries
Einstein's theory of special relativity involves a four-dimensional space-time, the Minkowski space, which is non-Euclidean. This shows that non-Euclidean geometries, which had been introduced a few years earlier for showing that the parallel postulate cannot be proved, are also useful for describing the physical world.
