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Galileo Ordered to Give Up Copernican Heresy (February 26, 1616)

Galileo and the InquisitorsToday in Odd History, the Inquisition delivered an injunction to Galileo Galilei, an Italian nobleman famous for his studies of mathematics and physics, ordering him to stop defending the Copernican theory that the Earth revolves around the Sun.

The idea that the Sun, and not the Earth, was the center of the solar system was not new. Aristarchus of Samos, who lived around 300 BCE (Before the Common Era), proposed a heliocentric universe. Archimedes, whom Galileo greatly admired, referenced Aristarchus's model in his Sand-Reckoners. But Ptolemy and Aristotle believed in a geocentric universe, and their works formed the foundation of European learning during the Middle Ages and into the Renaissance. And the Catholic Church found the geocentric model easier to reconcile with certain biblical passages, such as Joshua 10:12-14, which states that God caused the Sun to stand still in response to Joshua's prayer. The geocentric model also seemed to be verified by observation: Looking up into the night sky, without a telescope, one can clearly see that the stars wheel around the Earth.

The geocentric concept was so firmly engrained in the European consciousness that it was never seriously questioned, until Nicholas Copernicus published De Revolutionibus Orbium Coelestium ("On the Revolutions of the Celestial Orbs") in 1543, just before his death. The book was dedicated to Pope Paul III, and prefaced with a statement (written, as it turned out, by Andreas Osiander, and not by Copernicus himself) that the model it espoused was only a mathematical hypothesis, and did not pretend to represent the actual construction of the universe. The book attracted a great deal of attention, but very little controversy. No one took the heliocentric hypothesis seriously, but its mathematical constructions were adapted to the geocentric model and formed the basis for a new set of astronomical charts, which were much more accurate than the old ones.

In 1608, however, Hans Lipperhey, in the Netherlands, requested a patent on a combination of lenses that brought far-away objects into near focus. The patent was denied, but by 1609, a number of manufacturers were making low-power spyglasses available for public sale. Galileo began to experiment with these devices, and soon created a 20-power telescope through which he discovered the moons of Jupiter, the rings of Saturn, and the properties of sunspots. In 1610, he observed that Venus goes through phases, like the Moon, which proved Venus revolves around the Sun. Galileo published several books about his findings, and began discussing his findings with other scientists, most notably Benedetto Castelli, a former student who was teaching mathematics at the University of Pisa.

The Church was beginning to look at Galileo askance by now. He had the patronage of Cardinal Maffeo Barberini, who would later become Pope Urban VIII, but that was not enough. In February 1615, Niccolo Dorini, a Dominican friar, filed a written complaint against him with the Inquisition. With it, he enclosed a copy of a letter Galileo had written to Castelli, in which he discussed the relationship between science and religion. The Inquisition also took a deposition from Tommaso Caccini, another Dominican friar, who had preached a sermon against Galileo in December of 1614, and who had doubtless been embarrassed when his superiors apologized to Galileo in January. Galileo went to Rome in December, to defend his hypotheses, but not before he had written the famous Letter to the Grand Duchess Christina, in which he expanded upon his letter to Castelli. The Letter was not published, but it was widely circulated, and it could hardly have helped his case. In January 1616, he sent a treatise on the tides to Cardinal Alessandro Orsini, arguing that here was proof that the Earth moves. By February, the Inquisition's panel of consultants had concluded that the heliocentric model was not only absurd, but heretical, and that the idea that Earth moves was at least erroneous, if not actually blasphemous. Galileo was ordered not to discuss the theory, in writing or in speech, and to cease either believing it or defending it. In March, De Revolutionibus Orbium Coelestium was placed on the list of forbidden books, until it could be "corrected."

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