Basic Facts: Distance, Size, and Mass

Abstract

The aim of the present introductory chapter will be to introduce to the reader the Moon as a celestial body, and to review its basic properties such as the distance, size, and mass, the knowledge of which will constitute a necessary prerequisite for proper understanding of the structure and other physical characteristics of the Moon to be discussed in the main part of this book. To the astronomer the Moon has indeed been a friend of old standing; and at least a rudimentary knowledge of its motion goes very far back in the history of mankind on this planet; for since prehistory times the waxing and waning of lunar phases and the light changes accompanying them provided the first astronomical basis for the reckoning of the time. Whenever we go sufficiently far back in the history of almost any primitive civilization, we find them invariably dependent on the lunar, rather than the solar, calendar: the month became a unit of time long before the concept of the year emerged from accumulating observations; and the Moon as the graceful carrier of this knowledge thus gained entrance, as a female deity, to the pantheons of most ancient nations.