Galileo Galilei was born on February 15, 1564, in Pisa, Italy. He studied medicine and philosophy. At the age of 26, he became professor of mathematics in Pisa. In 1609, Galileo constructed his own telescope, with which he discovered the moons of Juptiter, the rings of Saturn, mountians on the Moon, and sunspots. His advocacy of the teachings of Copernicus brought him into conflict with the Inquisition. He was then ordered to Rome, where he was interrogated and held in custody. On the threat of torture, he recanted his teachings and denied his discoveries. The pope allowed him to retire to his villa in Arcetri in 1633, where he produced his main work on the laws of gravity and inertia. Galileo Galilei died on January 8, 1642 in Arcetri near Florence.