,
, etc., the strains and stresses existing in its interior. If we are dealing with non-coherent matter, we may ignore these strains and stresses.
We see that the curvatures of space-time are connected with the various conditions of the matter. If we heat it, we increase its energy, its molecules vibrate faster, and the curvatures of space-time, hence the field of gravitation, are affected correspondingly. We may also note that whereas the density of mass of the matter at a point, namely,
, affects the curvature
, the momentum components of the matter
