# Binet's Ellipsoid

Binet's Ellipsoid

Jacques Philippe Marie Binet showed that the angular momentum vector lies on the intersection of a sphere and an ellipsoid. The angular velocity along the principal axis of a freely rotating rigid body is described by Euler's equations from the point of view of an observer rotating with the body, a motion known as nutation (as in the case of a top). The angular velocity vector is a constant of motion viewed from the body system.