Galileo's Journal Date: 7 Jan 1610 Galileo Galilei made these sketches after discovering four moons orbiting Jupiter in January 1610. The moons, later named Io, Europa, Callisto and Ganymede, were the first discovered beyond Earth.
Their discovery also led to the demise of the popular theory that Earth was the center of the universe and an understanding that the planets in our solar system orbit the Sun.
Image Credit: The Galileo Project, Rice University.
