The aim of the present book will be to summarize the results of the
space exploration of the Moon in the past fifteen years -culminating in
the manned Apollo missions of 1969-1972 -on the background of our
previous acquaintance with our satellite made in the past by
astronomical observations at a distance. Astronomy is one of the oldest
branches of science conceived by the inquisitive human mind; though
until quite recently it had been debarred from the status of a genuine
experimental science by the remoteness of the objects of its study. With
the sole exception of meteoritic matter which occasionally finds its way
into our labora- tories, all celestial bodies could be investigated only
at a distance: namely, from the effects of attraction exerted by their
mass, or from the ciphered messages of their light carried by
nimble-footed photons across the intervening gaps of space. A dramatic
emergence oflong-range spacecraft -capable of carrying men with their
instruments not only outside the confines of our atmosphere, but to the
actual surface of our nearest celestial neighbour - has since 1957
thoroughly changed this time- honoured picture. In particular (as we
shall detail in Chapter 1 of this book) space astronomy ofthe Moon is
barely 15 years old. But relative infant as it is by age, it has already
provided us with such a tremendous amount of new and previously inacces-
sible scientific data as to virtually revolutionalize our subject.