Einstein's contributions to our ideas of time and space, and to our
knowledge of the universe in general, are of so momentous a nature,
that they easily take their place among the two or three greatest
achievements of the twentieth century. This little book attempts
to give, in popular form, an account of this work. As, however,
Einstein's work is so largely dependent upon the work of Newton and
Newton's successors, the first two chapters are devoted to the latter.