Christopher Clavius

Christopher Clavius, who lived from 1538 to 1612, was a Jesuit German mathematician, physicist and astronomer, head of the mathematicians at the Collegio Romano and a member of the Vatican commission that accepted the calendar proposed by Aloysius Lilius, now known as the Gregorian calendar. Born in Bamberg, he joined the Jesuit order in 1555, attended the University of Coimbra in Portugal and studied theology at the Collegio Romano, where he was ordained in 1564. He proposed the calendar reform adopted in 1582 by order of Pope Gregory XIII and later wrote defences and an explanation of it. Within the Jesuit order he was almost single-handedly responsible for adopting a rigorous mathematics curriculum, and his commentary on Sacrobosco's De Sphaera ran to at least 16 editions between 1570 and 1618. In the 1585 edition he placed the nova of 1572 beyond the Moon, independently of Tycho Brahe. He adhered to the geocentric model and was treated with great respect by Galileo, who visited him in 1611.