Dialogue Concerning the Two Chief World Systems, Ptolemaic and Copernican, Second Revised Edition

The book is primarily astronomical and philosophical in content, being concerned with the arguments for and against the motion of the earth. Galileo's discoveries and researches in astronomy -- the phases of Venus, the satellites of Jupiter, and the motion of sunspots -- share the main scenes with his cogent and derisive attacks upon aristotle and his followers. The discussion of the Second Day contains many of Galileo's fundamental contributions to physics -- inertia, the laws of falling bodies, centrifugal force, and the pendulum -- as well as important historical steps in mathematics toward analytic geometry and calculus. Galileo's explanations, written in the infancy of modern science, can hardly fail to be understood today by both layman and scientist.