The largest and ablest collection of mathematicians in Italy belonged to the Society of Jesus. When he started serious study of mathematics, Galileo sought and obtained the advice and approval of their leader, Father Christopher Clavius. He had to break off relations in 1606, when the Venetian state expelled the Jesuits from its territories. Galileo restored the connection soon after returning to Florence in 1610 as “Mathematician and Philosopher to the Grand Duke of Tuscany.” Again he had an urgent need for Clavius’s endorsement. The astonishing discoveries he had made in 1609/10 by turning his telescope on the heavens challenged credulity. By the end of 1610 he had the confirmation he wanted. Clavius’s group of mathematicians invited him to their headquarters in Rome to celebrate the “message from the stars,” as Galileo had entitled the book in which he had announced his discoveries, and to toast the messenger.
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