Four hundred years ago, the great astronomer Galileo Galilei (Ga-lih-lay-oh Ga-lih-lay) became the first person to turn his telescope toward the sky. Although his telescope was small and the view was blurry, his discoveries changed astronomy forever. Galileo was born in Pisa, Italy, in 1564. In 1609, he built his first telescope, using two pieces of carved wood held together with copper wire, leather and paper. Galileo saw detailed views of Earth's moon and the planets, including Mars. He is also credited with discovering four of Jupiter's moons and finding that the Milky Way is a collection of stars.
