Tidal tensor
In Newton's theory of gravitation and in various relativistic classical theories of gravitation, such as general relativity, the tidal tensor represents: tidal accelerations of a cloud of (electrically neutral, nonspinning) test particles tidal stresses in a small object immersed in an ambient gravitational field The tidal tensor describes the relative acceleration due to gravity between two test masses separated by an infinitesimal distance. The component Φ a b {\displaystyle \Phi _{ab}} represents the relative acceleration in the a ^ {\displaystyle {\hat {a}}} direction produced by a displacement in the b ^ {\displaystyle {\hat {b}}} direction.