Dynamics of Earth’s Rotation

This chapter is dedicated to a very simplified dynamical analysis of the Earth’s lunisolar precession, nutation and free (Eulerian) nutation. It starts by examining the intuitive explanation of the lunisolar precession put forward by Newton in his Principia . The chapter provides first an approximate description, sufficient to clarify the basis of the overall phenomenon, and then a more quantitative analysis. It examines the influence of the astronomical coordinates of the Sun and of the Moon on precession and nutation. The 1980 IAU Theory of Nutation was computed by determining the nutation in longitude and obliquity of a rigid Earth and introducing some modifications to allow for the non-rigidity. In addition to the small and periodic variation of latitudes and longitudes, modern techniques have confirmed and improved the determination of several phenomena proper to the Earth’s body.