 Although Galileo seriously considered the priesthood as a young man , at his father 's urging he instead enrolled at the University of Pisa for a medical degree . In 1581 , when he was studying medicine , he noticed a swinging chandelier , which air currents shifted about to swing in larger and smaller arcs . To him it seemed , by comparison with his heartbeat , that the chandelier took the same amount of time to swing back and forth , no matter how far it was swinging . When he returned home , he set up two pendulums of equal length and swung one with a large sweep and the other with a small sweep and found that they kept time together . It was not until the work of Christiaan Huygens , almost one hundred years later , that the <unk> nature of a swinging pendulum was used to create an accurate timepiece . Up to this point , Galileo had deliberately been kept away from mathematics , since a physician earned a higher income than a mathematician . However , after accidentally attending a lecture on geometry , he talked his reluctant father into letting him study mathematics and natural philosophy instead of medicine . He created a <unk> , a forerunner of the thermometer , and in 1586 published a small book on the design of a hydrostatic balance he had invented ( which first brought him to the attention of the scholarly world ) . Galileo also studied <unk> , a term encompassing fine art , and in 1588 obtained the position of instructor in the Accademia delle Arti del <unk> in Florence , teaching perspective and chiaroscuro . Being inspired by the artistic tradition of the city and the works of the Renaissance artists , Galileo acquired an aesthetic mentality . While a young teacher at the Accademia , he began a lifelong friendship with the Florentine painter <unk> , who included Galileo 's lunar observations in one of his paintings . 
