is built up from the
’s or potentials, as it should be. Thirdly, outside matter, our equations reduce to
, and the curvature connoted by this relation is compatible with the existence of perfect flatness at infinity, i.e., with
at infinity.
Nevertheless, Einstein soon recognised that his equations could not correspond to reality. The fact was that matter appeared to be conserved in nature. By this we mean that matter disappears from here only to reappear there.[95] It followed that the tensor of curvature which would be identified with the presence of matter in the law of gravitation should likewise possess the attributes of conservation. Now the tensor possessed no such attributes; but a very similar tensor, also symmetrical and of the second order, namely,
