Look at the 2-body gravitational system -- let&#x27;s say Earth-Moon.  Let&#x27;s put our non-rotating reference frame at the barycenter.  At any given moment, Earth has a definite position and velocity, and the Moon has a definite position and linear velocity.  If we know these positions and velocities (and masses), we can derive anything else we&#x27;d like to know about the system.  Including its angular momentum.<p>This would also be true of any system such that the size is large enough to render the quantum spins statistically close to zero.