Law of Areas

Law of Areas 

a law describing the motion of a material particle or the center of mass of a body under the influence of a central force. It states that the path of the particle is a plane curve lying in a plane passing through the center of force and that the radius vector drawn from the center of force to the particle sweeps out equal areas in equal intervals of time—in other words, the particle moves with a constant areal velocity. The law was discovered by J. Kepler for the case of the motion of planets about the sun and published in 1609. It was proved for the general case by I. Newton in 1687.