The irregular movement of the Earth’s geographical poles over the surface, anticlockwise for the north pole and clockwise for the south. The effect is very small, the displacement of the pole being less than 10 m, but it produces slight but detectable changes in latitude and longitude of the order of 0″.3. This polar motion is a displacement of the poles with respect to the Earth, not the star background, and hence is quite distinct from precession, which is a variation in the direction of the Earth’s axis in space. It is named after the American astronomer Seth Carlo Chandler (1846–1913).