Astronomers have long noted that the Earth does not rotate uniformly about an axis fixed in the planet, that both the length-of-day and the direction of the rotation axis vary periodically and irregularly by small amounts. These variations are an immediate consequence of the Earth not being a rigid body. In this book Professor Lambeck discusses the irregular nature of this motion and the geophysical mechanisms responsible for it. A complete analysis of these causes requires a discussion of solid Earth physics, magnetohydrodynamics, oceanography and meteorology. The study of the Earth's...