The rotation of the Earth includes precession, nutation, variations of the rotation rate and polar motion.
地球自转运动包括岁差和章动，极移和日长的变化。
2
The moment ofprecession and nutation is a prerequisite to explain these phenomena and one main way of building nutational serial of rigid Earth.
岁差章动力矩是解释这些现象的前提条件，也是建立刚体地球章动序列的最主要方法之一。
3
It is the result of a process called precession, where the Earth behaves like a spinning top, which takes 26,000 years and has at the moment moved the zodiac by about a month.