Defending Copernican system wasn’t easy


Last week, we began discussing Galileo Galilee’s relationship with the Catholic Church.

Galileo was an advocate of the Copernican system. He argued that the sun is at the center of the cosmos and that Earth and the other planets orbit the sun.

The church advocated the Ptolemaic system. Ptolemy’s system involved a complex system of orbits within orbits called epicycles that allowed the Earth to stay at the center of things.

Using a self-designed and constructed telescope, Galileo systematically studied the telescopic sky for the first time. He felt like he discovered proof of flaws in the Ptolemaic model. Among them were Jupiter’s four “Galilean” satellites, the phases of Venus, and the sun’s rotation as determined by sunspots.

In 1610, Galileo rushed his findings into print. “The Sidereal Messenger” was to become one of the most influential works in astronomical history.

But not immediately. Galileo had two impediments working against him. For one thing, most people refused to believe what Galileo had seen with his own eyes.

We moderns tend to embrace new technology. In Galileo’s day, many influential people refused to look through the telescope. They feared that the images were false and might mislead them. Some saw the telescope as demonic in that regard.

Others looked but didn’t see anything. Galileo’s telescope was particularly demanding to use. The image would miss the eye unless it was in precisely the right spot above the eyepiece.

Add to that the uniqueness of the experience. Anyone who has done public work in astronomy will tell you that the first look through a telescope (or a microscope or any optical instrument, for that matter) requires a radical change in thinking. Your mind must learn to process what you’re seeing — or that you’re seeing anything at all.

As a result, his critics had a field day. The more sympathetic of his opponents said his conclusions were wrong. His harshest critics said he was lying about his observations.

“The Sidereal Messenger” made Galileo famous, however. He was appointed chief mathematician and philosopher to Florence’s Grand Duke of Tuscany.

In 1611, he visited Rome, where church officials treated him respectfully. He engaged in long and friendly discussions with Cardinal Barberini, a powerful prelate who would later become Pope.

Galileo’s friendship with the Cardinal provided some protection from conservatives in the church, but that friendship would, somewhat ironically, contribute to his undoing 20 years later.

The second issue was Galileo’s abrasive personality. Modern commentators describe him as “forceful,” “outspoken” and “tactless.” He enjoyed debating, and he was good at it. He took every opportunity in letters, public debates, and lectures to defend his discoveries.

His sometimes tactless approach to argument led him to create powerful enemies within the church, particularly during and after his 1611 visit.

Thus, by 1616, Galileo was at the center of a raging controversy. When Galileo again visited Rome that year, Pope Paul V decided that he would try to end Galileo’s fractious behavior once and for all.

Cardinal Bellarmine met with Galileo privately and ordered him to cease debate on the matter immediately. The meeting would later become the leading cause of the scientist’s Inquisitional undoing.

Historians have not been able to determine the actual instructions Bellarmine gave Galileo, but the results were pretty obvious.

Galileo did not discuss his telescopic findings and their connection to Copernicanism for several years afterward. All books that defended the Copernican model were banned, including “The Sidereal Messenger.”

Seven long years passed. They were particularly difficult for the argumentative and impatient Galileo. Can we blame him? Church officials ordered him to sit on revolutionary discoveries using a radical new technology. Who among us could have stayed silent?

But Galileo did, perhaps because he feared excommunication from the church. Or perhaps he remembered Giordano Bruno, who was burned at the stake a few years earlier for publicly expounding Copernicanism. Perhaps both.

Instead, Galileo decided to work within the system. Pope Paul V died in 1621. His successor, Gregory XV, died two years later. Galileo waited.

Gregory was succeeded by Galileo’s friend Cardinal Barberini, who took the papal name Urban VIII. Galileo immediately traveled to Rome, hoping that Urban would lift the 1616 prohibitions.

Next week: That meeting and its catastrophic ramifications on Galileo’s life and work.

Tom Burns is the former director of the Perkins Observatory in Delaware.

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