Nutation is the mathematically predictable change in the direction of the earth's axis of rotation due to changing external torques from the sun, moon and planets.
(Nutation; is; the mathematically predictable change in the direction of the earth's axis of rotation due to changing external torques from the sun, moon and planets)
Nutation
is
the mathematically predictable change in the direction of the earth's axis of rotation due to changing external torques from the sun, moon and planets