Aristotle falls
While there, Galileo’s ongoing astronomical studies increasingly demonstrated that Aristotle had been wrong on numerous points. Aristotle believed the world was impure and changeable, whereas the heavens were perfect and unchanging. Galileo’s telescopic observations revealed many aspects of celestial change, and different patterns of planetary and lunar orbits. Through these observations, he became convinced that Copernicus (1473–1543) had been right: the earth orbits the sun, not the other way around.
Galileo’s timing, however, was unfortunate. Rome was turning hostile to Copernicus’s theories, and in 1615 declared them heretical. Galileo was accordingly warned by the Inquisition not to promote Copernican theories. He followed the edict for a while, but found ways to nevertheless continue researching and discussing the topic.
Enter the telescope
While there, Galileo’s ongoing astronomical studies increasingly demonstrated that Aristotle had been wrong on numerous points. Aristotle believed the world was impure and changeable, whereas the heavens were perfect and unchanging. Galileo’s telescopic observations revealed many aspects of celestial change, and different patterns of planetary and lunar orbits. Through these observations, he became convinced that Copernicus (1473–1543) had been right: the earth orbits the sun, not the other way around.
Galileo’s timing, however, was unfortunate. Rome was turning hostile to Copernicus’s theories, and in 1615 declared them heretical. Galileo was accordingly warned by the Inquisition not to promote Copernican theories. He followed the edict for a while, but found ways to nevertheless continue researching and discussing the topic.
In 1623, one of his patrons, Cardinal Maffeo Barberini, became Pope Urban VIII. After a number of interviews, Urban asked Galileo to write about the universe, but cautioned him only to deal with Copernican ideas in a hypothetical way. In 1630 the work was ready: Dialogo sopra i due massimi sistemi del mondo, tolemaico e copernicano (Dialogue on the Two Chief World Systems, Ptolemaic and Copernican), Galileo had heeded the pope’s warning, and the book carried a preface explicitly noting that it was all hypothetical. An outbreak of plague meant that he sent it to the censors in Florence rather than Rome. They approved the work, and it was published in 1632.
The Leaning Tower of Pisa - one of his earlier experiments
The final straw
The contents of the book were structured around a conversation between three characters: Salviati, who was really Galileo; Simplicio, who represented the old Aristotelian thinking; and Sagredo, who was a bright lay person. Despite Galileo’s careful preface, the book immediately caused a storm, because Galileo gave Simplicio — whom the others poked fun at throughout — the final line, and it was one the pope often said: that God, who could have created the universe any way he wanted, nevertheless made it the way we see it.
Urban immediately convoked a commission to investigate the book. It concluded that Galileo had not really dealt with Copernican theories hypothetically. They passed the file over to the Inquisition.
Galileo appeared before the Inquisition in Rome on 12 April 1633, and was questioned on the 1616 edict stating that he was forbidden to promote the Copernican theory. He submitted a letter he had kept from Cardinal Bellamine, which clarified that the restriction was only that he may not hold or defend the theory. This brought matters to an impasse. Eventually, Galileo noted that he had probably overstated the mark. On 22 June 1633 the Inquisition declared him to be vehemently suspect of heresy. He formally abjured, and was sentenced to life imprisonment, which was commuted to house arrest. The story that he whispered, “Eppur si muove” (And yet it moves) is apocryphal.
During his trial he had stayed with the Tuscan ambassador, and he had not been imprisoned or tortured. After the trial he was not formally confined, but stayed first at the Archbishop of Siena’s palace, before moving to a villa in the hills above Florence. He was now 70, and lived there, working and publishing, until his death nine years later, on 8 January 1642.