Some aspects of the physics of the Moon

Abstract

The development of the study of the Moon falls into three distinct phases. The Moon’s orbit provided a critical test of Newtonian theory, and observation of the motion of the Moon was a central problem in astronomy for over 2½ centuries. The discrepancies between this so-called ‘theory of the Moon’ and its observed motion yielded most important results: the secular and irregular changes in the Earth’s rotation rate, the evolution of the Moon’s orbit through geological time and the internal distribution of density within the Moon. The subject of the Moon’s motion remains today a lively one with many unsolved problems: laser ranging to the Moon provides a new technique for their solution. The study of the evolution of the Moon’s surface started with the famous paper by G. K. Gilbert in 1893 when, for the first time, clear evidence was produced that the craters had an impact origin. The recognition that the Moon’s surface is extremely old- little changed because of the absence of the forces of erosion so important in the terrestrial biosphere-provided a strong impetus for the develop­ment of the accretion theory of the origin of the Earth and planets. From the study of the frequency distribution of craters, dating of the lunar surface has developed and the understanding of the evolution of the surface much improved by the application of the principles of geology.