Dialogue Concerning the Two Chief World SystemsGalileo Galilei
About Dialogue Concerning the Two Chief World Systems
Galileo published the in Florence in 1632. Four days of conversation among Salviati (the Copernican), Sagredo (the open-minded layman), and Simplicio (the Aristotelian) compare the Ptolemaic and Copernican systems. The book is written in Italian, for a public beyond the universities.
Day One attacks the Aristotelian distinction between corruptible earth and incorruptible heavens, citing sunspots, new stars, and the Moon's rough surface. Day Two argues for the Earth's daily rotation and answers objections from falling bodies and cannon fire with the relativity of motion, including the thought experiment of observations made below decks on a smoothly moving ship. Day Three treats the annual motion around the Sun, the phases of Venus, the moons of Jupiter, and the explanation of retrograde motion. Day Four offers Galileo's theory of the tides as physical proof of the Earth's motion, a theory that later physics discarded.
The Inquisition found Galileo "vehemently suspect of heresy." The Dialogue entered the Index. It remains the great literary argument that the Earth moves, set against Ptolemy and Aristotle and written so that a serious general reader could follow the fight.