Cassini's laws

Three empirical laws describing the rotation of the Moon about its centre of mass, stated by Jacques Cassini (1677-1756) in 1721: 1. The Moon rotates eastwards about an axis fixed within it, with constant angular velocity in a period of rotation equal to the mean sidereal period of revolution of the Moon about the Earth. 2. The inclination of the mean plane of the lunar equator to the plane of the ecliptic is constant. 3. The poles of the lunar equator, the ecliptic and the Moon's orbital plane all lie on one great circle, in that order.