Using a nineteenth century approach, an effort to unify physics from the twentieth century has been attempted. A dynamic metric equation is found but it uses a simpler set of field equations than general relativity, a rank one tensor instead of two.
This theory makes several predictions. If weak gravitation effects are measured to second-order parameterized post-Newtonian accuracy, light will bend around the Sun 0.7 microarcseconds more than the Schwarzschild metric predicts. It remains to be seen if the complete 3-force equation matches all the data for a thin spiral galaxy. The polarization of gravitational waves will be scalar or longitudinal, not transverse as predicted by general relativity. A linear field theory for gravity can work elegantly beside the intellectual superstructure of electromagnetism, using analogy to complete the story of forces in Nature.