<P> In astronomy , axial precession is a gravity - induced , slow , and continuous change in the orientation of an astronomical body 's rotational axis . In particular , it can refer to the gradual shift in the orientation of Earth 's axis of rotation , which , similar to a wobbling top , traces out a pair of cones joined at their apices in a cycle of approximately 26,000 years . The term `` precession '' typically refers only to this largest part of the motion ; other changes in the alignment of Earth 's axis -- nutation and polar motion -- are much smaller in magnitude . </P>
a single period of precession of earth 's axis is completed in about
approximately 26,000 years