Subject: Conventional Wisdom – the Discovery of Jupiter’s Moons
Event: Galileo Galilei Discovers the Moons of Jupiter, 1610
In 1610, the Italian astronomer Galileo Galilei (1564-1642) made a discovery that changed not just the world but also the heavens. Although Galileo did not invent the telescope, he did make significant improvements that increased its magnification. He was also among the first to turn the telescope to the night sky and record observations of the stars. This is exactly what he was doing on the night of January 7, 1610, when he observed what he first thought were three fixed stars near Jupiter. Further examination revealed that instead of stars, he was seeing natural satellites orbiting Jupiter. Later he discovered a fourth satellite. Today we know these satellites as Callisto, Europa, Ganymede, and Io: the Galilean Moons of Jupiter.
Galileo’s discovery was much more significant than just discovering the moons of a distant planet. What he saw in his telescope called into question the conventional wisdom of the geocentric theory, which said that all celestial bodies rotated around the Earth, the center of the universe. Geocentrism dated back to ancient astronomy and the Old Testament. As a Catholic, Galileo realized that his discovery was at odds with the teachings of the powerful Roman Catholic Church.
Years earlier, in 1514, the Polish monk and mathematician Copernicus had theorized the heliocentric theory, which put the Sun not the Earth at the center of the universe. Copernicus did not have a telescoper, however, so his theory lacked the kind of solid proof that would challenge the orthodoxy of the geocentric model. Galileo’s discoveries provided the concrete proof that confirmed Copernicus’ theory.
In 1616, the Catholic Inquisition rejected heliocentrism and ordered Galileo to abandon his claims, but he refused to remain quiet. In 1632, he published “Dialogue Concerning the Two Chief World Systems,” where he juxtaposed the arguments for the geocentric universe and the heliocentric universe. After the publication of his book, Galileo was charged with heresy and tried by the Inquisition in Rome. In June 1633, he was put under house arrest and his publications were banned. On June 22, 1633, Galileo was found guilty of heresy and sentenced to life imprisonment. Ordered to kneel, he was directed to read a statement recanting his theory.
Probably the most famous quotation attributed to Galileo is a brief statement that he supposedly made at the end of his trial: “Eppur si muove” (“And yet it moves).” This statement — which is probably more legend than fact — would be a contradiction of the Catholic Church’s view of the Earth that stands still at the center of the universe. Even though under house arrest, Galileo continued his scientific work until his death in 1642.
Today his views have been vindicated, and not only is he seen as the father of astronomy, but he is also seen as the father of modern science (1).
In 1992, 350 years after the Catholic Church condemned Galileo, Pope John Paul II issued a formal statement admitting that the church was wrong: the Earth does move (2).
Recall, Retrieve, Recite, Ruminate, Reflect, Reason: How did Galileo’s discovery of Jupiter’s moons upend conventional wisdom?
Challenge – Where the Experts Were Wrong: Obviously we know from history that the Catholic Church was wrong about the geocentric universe. Research another example from history of where the experts were wrong.
1-Levesque, Paul. “Skywatch: Galileo’s Discovery of the Moons of Jupiter Disrupted Conventional Wisdom. Quad-City Times. 4 Oct. 2020.
2-Cowell, Alan. “After 350 Years, Vatican Says Galileo Was Right: It Moves.” New York Times 31 Oct. 1992.