Motivations for developing new theories of gravity have changed over the years, with the first one to explain planetary orbits (Newton) and more complicated orbits (e.g. Lagrange).
建立新的重力理論的動機隨著年代不同，最早先的動機是要解釋行星軌道（牛頓重力）以及更複雜的軌道（例如：拉格朗日）。