On this day nearly four centuries ago, astronomer Galileo Galilei arrived in Rome. This was no vacation—he had been ordered there by the Catholic Church for a trial.
Galileo had previously taught astronomy at the University of Padua, where he promoted the dominant, Catholic Church-endorsed belief at the time—that the Earth sat at the center of the universe. But near the end of the 16th century, Galileo began to come to terms with Nicolaus Copernicus’ theory that Earth circles the sun, an idea already explored for centuries.
Galileo became convinced after he created his own telescope that gave him relatively crisp views of the cosmos for the time. This offered him a peek at details that confirmed the heliocentric model. For example, he saw sunspots, moons orbiting Jupiter, and the shifting phases of Venus.
Such sights poured cold water on Aristotle’s idea that the heavens were “perfect and unchanging,” a theory upheld by the church. Ultimately, Copernicus had prompted Galileo to “argue that he, not the theologians of the Catholic Church, had the right to study and interpret the natural world,” according to historian Mark A. Waddell.
After catching wind of Galileo’s beliefs, the cardinals of the Inquisition convened and decided to condemn Copernicus’ work in 1616. Galileo was ordered not to “actively promote Copernican ideas,” but it appears that his enemies planted a document in the records stating that he could never discuss the theory at all.
Read more: “Galileo the Science Publicist”
A few years later, Galileo learned that newly elected Pope Urban VIII was a fan of his work. The Pope’s behavior had convinced him that he could, in fact, explore the heliocentric model in his writing.
In 1632, he published Dialogue Concerning the Two Chief World Systems, in which characters debated heliocentrism versus geocentrism. Galileo thought this was a cautious choice, as it was theoretical and weighed both sides. But the Inquisition banned its sale, and Galileo, who was older and in poor health at the time, was sent to Rome for a reckoning in 1633.
There, he faced charges for breaking the rules he had agreed to in 1616, even though he might have never received all this information in the first place. Galileo testified, claiming he hadn’t done anything wrong. While he admitted he’d given the upper hand to heliocentrism in his book, it wasn’t because he believed in it: “Rather, he claimed he was simply showing off his debating skills,” according to Renaissance scholar Henry Kelly.
Ultimately, the church authorities found him guilty of “vehement suspicion of heresy,” a charge less severe than actual heresy. They banned his book, forced him to publicly renounce Copernican ideas, and sentenced him to house arrest. He died in 1642 at the age of 77.
It took more than three centuries for the Catholic Church to acknowledge that Galileo was right all along. In 1992, following a 13-year investigation, the church publicly addressed his persecution.
“The dispute between the Church and Galileo has long stood as one of history’s great emblems of conflict between reason and dogma, science and faith,” The New York Times wrote in 1992. “The Vatican’s formal acknowledgement of an error, moreover, is a rarity in an institution built over centuries on the belief that the Church is the final arbiter in matters of faith.” 
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Lead image: Joseph-Nicolas Robert-Fleury / Wikimedia Commons
