Galileo Galilei was an Italian astronomer and physicist who worked as a lecturer in 1589 at the University of Pisa. From 1592 to 1610, he worked at the University of Padua.
He conducted his famous experiments about freely falling bodies when he was a lecturer at the University of Pisa. He opposed Aristotle's view of the universe and so lost favor with the authorities of the university. He was asked to leave and had to accept another teaching position at the University of Padua. He worked for 18 years at Padua, when he achieved great fame as a physicist.
He invented the telescope and studied the motion of planets and the sun. He explained why objects float on water. He also published a number of scientific papers, including "The Operation of the Geometrical and Military Compass" and "Discourse on Bodies in Water."