Einstein's theory of gravitation implies that this energy must produce an infinite gravitational curvature of spacetime — something we most definitely do not observe. (scientificamerican.com)
The major reason is that Einstein's principle of equivalence, which correlates and consolidates the concepts of inertial and gravitational mass and which in turn introduces the curvature of spacetime in the general theory, has no analogue in Whitehead's theory.9 But perhaps more importantly for the purposes of this essay, Einstein's entire approach in special relativity presumes that the nature of causality in the universe has a direct bearing upon spatio — temporal structure. (religion-online.org)
It took Einstein to see that and develop the view of gravity as the curvature of spacetime induced by the presence of mass. (sciencenews.org)