Galileo, himself, though he lectured on Ptolemaic theory until 1605, had been converted to Copernicanism by a work of Kepler. In 1611 he openly declared for Copernicanism. His own observations convinced him that the Copernican system was correct, and in the classic Dialogue on the Great World Systems he defended it strongly.
Galileo's rebelion is all over this book, damn good book.
