-distribution, while
represents the characteristics of the matter exciting the field. There are ten of these gravitational equations corresponding to the various values from 1 to 4 which we must assign to the indices i and k (space-time being four-dimensional). And here we must note that the tensor
represents matter much more fully than does the
of classical science, for the various components of
refer to such additional characteristics as the momentum, the vis viva and the conditions of stress existing in the interior of matter. We may infer, therefore, that whereas in classical science the mass of the matter was solely responsible for the creation of a gravitational field, in the present case all the additional characteristics mentioned above contribute their share.
Similar considerations would hold for the gravitational field outside matter, and as a result, were the sun to be rotating with greater speed on its axis, the gravitational field it would produce would be slightly different. In the case of the planet Jupiter and its moons, it would appear possible to submit to an observational test this additional disturbance caused by the rotation of the central mass on the satellites moving around it. As yet, however, no checking up of the theory has been possible on this point.