An Etymological Dictionary of Astronomy and Astrophysics

In classical mechanics, the study concerned with the dynamics of an isolated system of two particles subject only to the Newtonian gravitational
force between them. The problem can be separated into two single-particle problems with the following solutions. The equation of the → center of mass is governed by the equation of the same form as that for a single particle. Moreover, the motion of either particle, with respect to the other as origin, is the same as the motion with respect to a fixed origin of a single particle of → reduced mass acted on by the same internal force. See also → three-body problem, → n-body problem.

See also: → two; → body; → problem.