I missed it by a day, but February 15, 1564 was the birthday of Galileo, in Pisa, Italy. Herewith: a short bio to tie in with the International Year of Astronomy.
Among other things, he gave us the Law of the Pendulum which would later be used to regulate clocks; He constructed a “spyglass” (later called telescope) based on rumors and information coming out of Holland about such a device, without ever seeing one.
His designs improved quickly, and on January 7, 1610, he was the first to see three of the moons of Jupiter.
Famous for being charged with heresy for supporting the Copernican model of the universe which suggested the Earth was not the center of the universe, he was fortunately cleared of all charges.
More info available at Galileo Galilei