GENERAL KNOWLEDGE

Detailed explanation-1: -Aside from the long-term motions, the Earth’s rotational axis and poles have two shorter periodic motions. One, called the Chandler wobble, is a free nutation with a period of about 435 days.

Detailed explanation-2: -Nutation (from Latin nūtātiō ‘nodding, swaying’) is a rocking, swaying, or nodding motion in the axis of rotation of a largely axially symmetric object, such as a gyroscope, planet, or bullet in flight, or as an intended behaviour of a mechanism.

Detailed explanation-3: -The cause of nutation lies chiefly in the fact that the plane of the Moon’s orbit around Earth is tilted by 5.15° from the plane of Earth’s orbit around the Sun. The Moon’s orbital plane precesses around Earth’s in 18.6 years, and the effect of the Moon on the precession of the equinoxes varies with this same period.