Defending Copernicus and Galileo: The Ship's Mast Experiment
Maurice A. Finocchiaro

Abstract: Although recent works on Galileo's trial have reached new heights of erudition, documentation, and sophistication, they typically exhibit over-inflated complexities; neglect 400 years of historiography; and make little effort to learn from Galileo. I am working on a book aiming to avoid these lacunae. I argue that the Copernican Revolution required that the earth's motion be not only constructively supported with new reasons and evidence, but also critically defended from numerous old and new objections. This defense in turn required not only the destructive refutation but also the appreciative understanding of those objections in all their strength. A major Galilean accomplishment was to elaborate such a reasoned, critical, and fair-minded defense of Copernicanism. Galileo's trial (1613-1633) can be interpreted as a series of ecclesiastic attempts to stop him from defending Copernicus. And an essential thread of the controversy (from 1633 to our own day) about Galileo's trial is the emergence of numerous arguments claiming that his condemnation was right, as well as the defense of Galileo from such criticisms. My general thesis is that the defense of Galileo can and should have the reasoned, critical, and fair-minded character which his own defense of Copernicus had. After a summary of this general project, I illustrate it with an account of selected aspects of the history and the logic of the anti-Copernican argument based on the experiment of dropping a rock from the top of the mast of a ship.