High Quality Content by WIKIPEDIA articles! 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 refers to the gradual shift in the orientation of Earth`s axis of rotation, which, like a wobbling top, traces out a pair of cones joined at their apices in a cycle of approximately 26,000 years (called a Great or Platonic Year in astrology). The term "precession" typically refers only to this largest secular motion; other changes in the alignment of Earth`s axis — nutation and polar motion — are much smaller in magnitude.