 It also means that our volume integral will be constant for any enclosing surface, as long as we enclose all of the gravitating mass inside our surface.Because Stokes theorem guarantees that our surface integral is equal to the above volume integral, our surface integral will also be independent of the enclosing surface as long as the surface encloses all of the gravitating mass.By using Einstein's Field Equations

letting u=v and summing, we can show that R = -8 π T.

This allows us to rewrite our mass formula as a volume integral of the stress–energy tensor.