Christopher Clavius

Jesuit astronomer

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In calendar: The Gregorian calendar
…bull that the Jesuit astronomer Christopher Clavius (1537–1612) began to draw up, using suggestions made by the astronomer and physician Luigi Lilio (also known as Aloysius Lilius; died 1576).
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In calendar: The date of Easter
…omitting most centennial leap years, Clavius decided that, when the cycle of epacts reached an ordinary centennial year, the number of the epact should be reduced by one; this reduction became known as the solar correction.
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In mathematics: Foundations of geometry
The Italian researchers Christopher Clavius in 1574 and Giordano Vitale in 1680 showed that the postulate is equivalent to asserting that the line equidistant from a straight line is a straight line. In 1693 John Wallis, Savilian Professor of Geometry at Oxford, attempted a different demonstration, proving that…
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