Copernicanism Deserves Support

For the time being, Galileo was a celebrity. Word of his observations and discoveries spread throughout Rome. In 1611, he was invited to attend a grand banquet at the Collegio Romano, where Jesuit mathematicians certified his discoveries. While there, he gained a membership to the Accademia dei Lincei (Lincei National Academy) by Federigo Cesi, an Italian natural scientist who suggested the word telescope for Galileo's invention. Cesi remained a supporter of Galileo for the rest of his life.

By 1612, Galileo had made enough observations of Jupiter's moons to establish accurate periods, but since he had forgotten to consider the motion of the Earth around the Sun, his conclusions were inconsistent. He had also made extensive observations of Saturn, which at first appeared to him as three bodies, a large one in the center with two smaller ones on each side (the smaller bodies being, in reality, the rings). He also determined that Venus had phases, as the Moon did, and concluded that the planet must orbit the Sun and not the Earth. All these discoveries pointed to a rotating Earth that in turn revolved around the Sun. He argued his conclusions publicly, claiming that this was proof enough to condemn the Ptolemaic system in favor of the Copernican. His opponents, however, argued that if the Earth were spinning, everything would fly off. They argued further that if the Earth truly were spinning, cannonballs dropped from a high tower could not fall straight down. As the Earth rotated, they would drop behind the tower while they fell. Galileo knew differently, but he could not convince them that the Earth was in motion.

Then, in 1614, a well-known preacher named Tommaso Caccini labeled Galileo a heretic, along with any other mathematician who dared to support the Copernican system. His sermon started rumors of a scandal. By the next year, Caccini was confident enough to offer an official declaration to the Roman Inquisition, which was an organization within the Catholic Church that was in

Consequences of Nonconformity

Giordano Bruno (1548—1600) was an Italian astronomer who also embraced the Copernican theory of a heliocentric solar system. He openly disagreed with the Catholic Church's accepted Ptolemaic theory of a geocentric solar system and sought to teach Copernicanism. The church denounced him, and Bruno fled Italy, fearing punishment for his beliefs. For a few years, he taught abroad, but in 1592 he was located, arrested, and tried by the Roman Inquisition. After years spent in the courts, in 1600, Bruno—who never abandoned his beliefs—was burned at the stake in Rome. Bruno was made an example of the consequences to be suffered if one were to publicly turn from the church.

charge of suppressing known heretics. Galileo wrote a lengthy letter to the influential Monsignor Piero Dini in Rome defending his views, but the cardinals Robert Bellarmine and Paolo Antonio Foscarini warned Piero Dini and Galileo to treat the Copernican theory as merely a suggestion.

The Inquisition

Galileo wrote another letter, this one to the grand duchess Christina of Lorraine, again defending his views but also addressing the relationship between science and scripture. According to Stillman Drake's translation of an excerpt of the letter in his Discoveries, Galileo wrote:

I hold the Sun to be situated motionless in the center of the revolution of the celestial orbs while the Earth rotates on its axis and revolves about the Sun. I support this position not only by refuting the arguments of Ptolemy and Aristotle, but by producing many counter arguments; in particular, some which relate to physical effects whose causes can perhaps be assigned in no other way. There are astronomical arguments derived from many things in my new celestial discoveries that plainly confute the Ptolemaic System while admirably agreeing with and confirming the contrary hypothesis. These men (Galileo's opponents) have resolved to fabricate a shield for their fallacies out of the mantle of pretended religion and the authority of the Bible.

The letter did no good. The Roman Inquisition continued its investigation and while it did not take action against Galileo, in 1616 it officially announced that to support Copernicanism was heretical and went against the teachings of the church and God. Galileo traveled to Rome in order to defend himself in person, figuring he had enough evidence to back a defense and his belief in Copernicanism. In the end, however, Pope Paul V forbade him to hold Copernican views.

In 1618, he lost the confidence of the Jesuits when three bright comets appeared in the sky. Galileo wrote about them in Discorso delle comete (Discourse on the comets, 1619), the theory of which was published under the name Mario Guiducci, one of his pupils.

(As a result of the warning given to him from the Roman Inquisition, Galileo published no works under his own name between 1616 and 1623). Discorso delle comete was written as a lecture in direct response to an earlier lecture given by the Jesuit mathematician Orazio Grassi of Collegio Romano called De tribus cometis (On the three comets), in which Grassi's explanation of the location of the comets attempted to discredit the Copernican theory. Galileo's views published in Discorso delle comete attacked this interpretation of these bodies and their location in the heavens. (At the time, Grassi was writing under a surname and Galileo did not know he was attacking the Jesuits until it was too late.) Grassi countered Galileo's Discorso delle comete with a work he called Libra (The balance). In 1622, Galileo wrote yet another counter to Grassi, entitled Saggiatore (The assayer), in which Galileo formulated the new principles of the scientific method. That is to say, it brought about the agreement of theory through experimentation and observation rather than speculation through debate. In 1623, Roman censors granted Galileo the right to publish Saggiatore. He dedicated this book to his longtime admirer Maffeo Barberini, recently elected as the new Pope Urban VIII.

By this time, Galileo's health was starting to fail; however, this did not keep him from beginning work on his famous book Dialogo sopra i due massimi sistemi del mondo, tolemaico copernicano (Dialogue concerning the two chief systems of the world—Ptolemaic and Copernican), also known simply as The Dialogue. Galileo was given permission to write The Dialogue providing he presented the Ptolemaic theory in tandem with the Copernican theory, the latter of which he was directed to treat as hypothetical. In this book, he used the two characters to argue against each other. Galileo used his (ultimately false) theory on the relationship between the Moon and the effect it had on the tides as strong argument in support of Copernicanism.

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