The new views of the cosmic system required a new physics—Galileo knew that what he saw through the telescope signaled the end of the Ptolemaic and Aristotelian systems. We explore Galileo's attempts to create a new physics while emphasizing the new methods, goals, and worldview embodied in his system, and how this brought him into conflict with the church. We look at parallel developments in physics, particularly William Gilbert's work on magnetism and its impact.