Theory of nutation of a nonrigid Earth

A general theory of terrestrial nutation is proposed assuming that the Earth is made up of four envelopes (atmosphere, mantle, fluid core, and solid core) and taking account of all important forces (viscous, electromagnetic, etc.). A theory for the effect produced on the Earth's nutation by viscous forces in the fluid core is developed based on experimental data on the viscosity of molten iron under pressure. The proposed theory predicts nutation in longitude and inclination with an rms deviation of 0.35 milliarcseconds.