?-1558

French mathematician who provided a unique theory to the celestial rather than conventional terrestrial origin of comets. In a period of critical rethinking on the legitimacy of the four elements and placement of atmospheric and celestial phenomena, Pena, royal mathematician at Paris, followed other unconventional thinkers in these matters, accepting the logic of Copernicanism and the rejection of wholesale Aristotelianism. In his treatise on geometrical optics of lens and mirrors (Euclidis Optica et Catoptrica, 1557), Pena noted that a comet's tail pointed away from the Sun, prompting him to theorize that comet's were made of some celestially transparent substance that refracts light and causes combustion and thus the tail.