Galileo Galilei's Dialogue Concerning the Two Chief World Systems is one of the most important scientific treatises ever written. Using the dialogue form, a genre common in classical philosophical works, Galileo masterfully demonstrates the truth of the Copernican system over the Ptolemaic one, proving, for the first time, that the earth revolves around the sun.

Stillman Drake (1910-1993) was emeritus professor of the history of science at the University of Toronto. His many translations and scholarly works on Galileo include Galileo at Work and Cause, Experiment, and Science, both published by the University of Chicago Press.