ola and developed his treatise on the center of gravity of solid bodies. In 1589, he became professor of mathematics at Pisa University; in 1592, professor at the University of Padua; and in 1610, was appointed chief mathematician and philosopher to the Grand Duke of Tuscany, Cosimo II de Medici. He made his reputation first as a mathematician, and then through the application of mathematics, as a physical scientist. Galileo initiated experiments concerning the laws of bodies in motion, which brought results which were contradictory to the accepted teachings of Ptolomey. Strong antagonism was aroused amongst scholars. He found that bodies did not fall with velocities that were proportional to the weights and proved after several years of experiments and observation that the velocity of falling bodies is proportional to the time in motion. While at the University of Padua where he spent 18 years in residence, he received reports of a simple magnifying instrument which had been developed in Holland by a lens grinder. In 1609, using the information and skills he had garnered, he constructed the first complete astronomical telescope by which to explore the heavens, the stars and the planets. Looking through his new spyglass, he made some discoveries which shook the foundations of the Aristotelian cosmos. First, he saw that the moon was not a perfect sphere, but pocked with mountains and valleys like the earth. Second, and more astonishing, Jupiter had at least four satellites. No longer could it be said that heavenly bodies revolve exclusively around the earth. Finally, he observed the phases of Venus, the only explanation of which is that Venus moves around the sun and not the earth. The response to these discoveries ranged from enthusiastic to downright hostile. The leading Jesuit astronomer of the day, Christopher Clavius, was skeptical; but once the Roman college acquired an improved telescope, he saw for himself that Galileo was rig...
