It also moves with respect to the Earth's crust; this is called polar motion. Precession is a rotation of the Earth's rotation axis, caused primarily by external torques from the gravity of the Sun, Moon and other bodies. The polar motion is primarily due to free core nutation and the Chandler wobble. i got it from google.but put because the earth is caused primarily by external torques from the gravity of the Sun, Moon and other bodies. your welcome.
