In physics, Whitehead's thought has had some influence. He articulated a view that might perhaps be regarded as dual to Einstein's general relativity, see Whitehead's theory of gravitation. It has been severely criticized. Yutaka Tanaka, who suggests that the gravitational constant disagrees with experimental findings, proposes that Einstein's work does not actually refute Whitehead's formulation. Whitehead's view has now been rendered obsolete, with the discovery of gravitational waves. They are phenonena observed locally that largely violate the kind of local flatness of space that Whitehead assumes. Consequently, Whitehead's cosmology must be regarded as a local approximation, and his assumption of a uniform spatio-temporal geometry, Minkowskian in particular, as an often-locally-adequate approximation. An exact replacement of Whitehead's cosmology would need to admit a Riemannian geometry. Also, although Whitehead himself gave only secondary consideration to quantum theory, his metaphysics of processes has proved attractive to some physicists in that field. Henry Stapp and David Bohm are among those whose work has been influenced by Whitehead.