Simple aspects of post-Newtonian gravitation

The physical ideas that are unified in general relativity have been separated out and their effects introduced as separate perturbations of Newtonian mechanics. Compression of space and proportional dilation of time contribute the main parts of all observed and expected quasistatic first-order post-Newtonian gravitational phenomena. In this approach, tests measuring trajectories are variants on a single refraction-in-a-nonuniform-medium experiment; their similarity has been obscured by the few small contributions from special relativity (in only the DeSitter and perihelion precessions) and from gravitation by the gravitational field (in only the perihelion precession).