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 moons discovered orbiting a planet other than 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.


Last Update: 5 Jul 2011 (AMB)

Credit: The Galileo Project