Analyses of the nutation terms based on the results of astronomical observations of time and latitude provide valuable information to promote studies on the constitution of the Earth's interior. Indeed, the results of analyses of the nutations agree well with those predicted by theory for a fluid core. This shows that the matter of the outer core, 3,000 km and more below the Earth's surface, is not only in a fused state but also is a "fluid" which can move in response to the external forces.

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... y additional studies on the nutation terms are now in progress, for example, to estimate an extreme value of viscosity of the fluid core, to discuss the possibility of the geomagnetic dynamo being driven by the precession, and so on.