Christoph Clavius, S.J. (1538 - 1612) was one of the foremost astronomical authorities of the late sixteenth and early seventeenth centuries. He is also known for his early printed edition of Euclid's Elements and for his important role in the formulation, promulgation, and defense of the Gregorian calendar reform. He taught mathematics in Rome for nearly half a century, and in the process firmly established mathematical studies in the curriculum of the far-flung and influential network of Jesuit colleges. The many books he wrote cover all aspects of the traditional field of mathematics and include also applied aspects such as instruments and practical computation.
Clavius was born in Bamberg, Germany, but traveled to Rome in his 16th year to join the Society of Jesus, then undergoing explosive growth. He was sent to Coimbra for education, then brought back to Rome for advanced studies where he passed most of the rest of his career.
Clavius steadfastly defended the Ptolemaic cosmology-- a Renaissance hybrid of Ptolemaic planetary theory, Aristotelian cosmology, Christian theology, and astronomical developments from Islamic and Latin scholarship of the Middle Ages. Clavius expended much ink defending Ptolemaic cosmology and its methodological underpinnings from challenges by strict Aristotelians (Averroists), Copernicus, and others.
When Galileo announced his world-shaking telescopic discoveries in 1610, Clavius and his Jesuit students (who had already been experimenting with telescopes) were some of the first and most influential astronomers to confirm the accuracy of Galileo's observations. Clavius, however, never agreed (and he was correct in this) that Galileo's work established the truth of the Copernican theory. However, he did admit, in the final edition of his Sphere Commentary, published in 1611 just before his death, that Galileo's observations presented a fundamental challenge to the traditional astronomy-- a challenge that his successors were obliged to face.
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