James Bradley discovered the Earth’s 18-year nutation motion. It would be necessary to wait longer to have the physical explanation demonstrated and precisely calculated. Jean-Baptiste d’Alambert and Leonhard Euler would precisely calculate the motion of the ellipsoidal Earth, deriving the precession of the equinoxes as 25,800 years, as Newton had already done (but already discovered by Hipparchus), and the 18-year nutation.
