Astronomical Images : Cosmological spheres and orbs (the order of spheres in the Ptolemaic worldview)

Christophorus Clavius

Astronomical Images

<p style='text-align: justify;'>Christoph Clavius (1538-1612) was a distinguished Jesuit professor of the Collegio Romano. He published many mathematical and astronomical textbooks, and was regarded as 'the Euclid of his times'. He was also one of the architects of the Gregorian calendar reform. As an educator, he played a very important role in the history of science and the Society of Jesus, although he was a firm defender of crystalline spheres and Ptolemaic astronomy. He had connections with Galileo, Tycho Brahe, and other 'new' scholars, and he witnessed and tried to adapt Galileo's new astronomical discoveries with telescopes, but he never gave up Aristotelian cosmology. Christoph Clavius was also an important commentator of Sacrobosco's <i>De sphaera</i>. There were many editions of <i>In sphaeram Joannis de Sacro Bosco commentarius</i>, which first appeared in 1570, and the last edition was in 1618. Clavius's text was not only a textbook used in Jesuit colleges, but also an influential astronomical work in its own right. This is a typical diagram of crystalline spheres from Christoph Clavius' <i>In sphaeram Joannis de Sacro Bosco commentarius</i> (1585). It depicted an eleven-layer cosmos model, which listed from the inner to the outer sphere: the Moon, Mercury, Venus, Sun, Mars, Jupiter, Saturn, the firmament, the 'ninth heaven', 'the prime mover', and the Empyrean heaven. Due to different explanations of precession, there were also ten-layer or twelve-layer crystalline spheres since the Middle Ages. Clavius adopted a twelve-sphere cosmos in his later editions of <i>Sphaeram</i>.</p>