11. For a survey of current work toward creating a quantum theory of gravitation , see quantum gravity. 12. In particular, no successful theory of gravitation based on a particle theory has yet been proposed. 13. In any metric theory of gravitation , all gravitational effects arise from the curvature of the metric. 14. Scalar theories of gravitation include conformally flat theories and stratified theories with time-orthogonal space slices. 15. Cartan ( 1922, 1923 ) suggested a simple generalization of Einstein's theory of gravitation . 16. The first attempts to present a relativistic ( classical ) field theory of gravitation were also scalar theories. 17. Technically, general relativity is a theory of gravitation whose defining feature is its use of the Einstein field equations. 18. He later succeeded in producing an alternative theory of gravitation , General Relativity, which obeys the principle of locality. 19. Alley developed some of the earliest important laboratory tests of Albert Einstein's theories of alternative theories of gravitation . 20. Vacuum Bianchi type V and VI ( 0 ) cosmological models in a new scalar-tensor theory of gravitation .
