Galileo’s Three Repudiations of Copernicanism – Two Coerced and One Volunteered

Abstract Up to 1616, when the Copernican theory of heliocentrism was prohibited, Galileo had never asserted its truth. But the pope and cardinals of the Roman Inquisition assumed that he had, and he was required to repudiate it. In contrast, Copernicus’s book was only lightly corrected and allowed to be read. Galileo continued his practice of not asserting the reality of heliocentrism in his Dialogue on the two world systems, but he was put on trial nevertheless, in 1633. However, instead of being charged with a crime to be proved, as required by canon law, he was subjected to pre-trial interrogation and intimidation, and he confessed to a made-up crime. His conviction entailed another repudiation of the static sun, on pain of harsh punishment. In subsequent years, even though he was reckless in expressing preference for the condemned theory, he still did not advocate it. In fact, in writing to the Tuscan ambassador to Venice in 1641, he insisted that the Copernican system was false, because theologians said so. However, he went on to say that the opposing Ptolemaic view was actually erroneous, while the other was merely insufficient – because stellar parallax (which would prove the earth’s orbit) could not yet be measured.