这个假说所包括的第三种运动叫做岁差。
precession, basically is the change in the direction of earth's axis of rotation.岁差,基本上是地球自转轴方向的改变。
It will take me a million years to explain even just the basics of this movement as precession is quite complex.哪怕是这个运动的基本原理,我也要花一百万年才能解释清楚,因为旋进是相当复杂的。