Excerpted from John Glassie’s excellent biography of Athanasius Kircher, A Man of Misconceptions ©2012:
In 1610, twelve years before Kircher arrived in Cologne, Galileo Galilei, a mathematics professor in Padua, published a slim volume, Starry Messenger, about the observations he’d made with a new instrument he called the perspicillium, or the telescope. It was a very much improved-upon version of the spyglasses that had recently begun to appear in Europe. The configuration (a concave lens at one of a tube, and a convex lens at the other) was fairly simple, but Galileo’s handcrafted device made things appear, as he wrote, “nearly one thousand times larger and over thirty times closer” than they would with the naked eye. Among other discoveries, he observed four moons revolving around Jupiter. The most basic implication of this was clear to any student of natural philosophy willing to admit it. (At the Jesuit school of La Flèche in Anjou, a student named René Descartes is said to have written a sonnet celebrating the news.) If moons revolved around Jupiter, maybe earth wasn’t really the center of the universe, around which everything revolved. Galileo also reported that “the moon is not robed in a smooth and polished surface,” as Aristotelian doctrine had it, “but is in fact rough and uneven, covered everywhere, just like the Earth’s surface, with huge prominences, deep valleys, and chasms.”
The Church seemed willing at first to consider these findings. Clavius and other Jesuit astronomers held a reception for Galileo in Rome, and while Clavius declared telescopes “troublesome to operate,” he confirmed the existence of moons around Jupiter. On the question of the rough surface of the moon, however, the seventy-one-year-old astronomer couldn’t bring himself to believe his eyes. Perhaps the moon was just unevenly dense, he suggested. In a letter to the Church’s chief theologian, a group of Jesuit astronomers wrote together that they were “not sufficiently certain” about the matter. In other words, preconceived notions were such that Clavius couldn’t see through a telescope what modern people, who know the truth, can recognize with the naked eye.