The Earth’s Variable Rotation

Far from being uniform, the Earth s rotation displays a rich spectrum of variations. Short and intermediate fluctuations are caused by internal movements in the Earth. Longer term changes arise from tidal deformations caused by the Sun and the Moon. The length of day is (very!) gradually increasing; the Moon is receding from us; Polaris has not always been our North Star; the globe nutates and wobbles like a giant top spinning through space - these phenomena and more will be discussed with the help of illustrations.