Galileo Galilei was an Italian astronomer, physicist and engineer born in 1564 in Pisa, Italy. He made many important scientific discoveries through his use of the telescope, including observing mountains and craters on the moon, the phases of Venus, and the four largest moons of Jupiter. Galileo also supported Copernicus' theory that the Earth and planets revolve around the sun, which brought him into conflict with the Catholic Church and led to his imprisonment. Galileo made many contributions to the scientific revolution through his innovative use of the telescope and his willingness to challenge established scientific beliefs of the time.