When Galileo pointed his telescope toward the moon, he discovered rugged and mountainous landscapes similar to Earth’s terrain. In a short treatise, Galileo reproduced his observations through detailed illustrations. As Galileo’s treatise and telescope spread throughout Europe, many bold thinkers imagined trips to the moon. Astronomer Johannes Kepler told Galileo: "Provide ships or sails adapted to the heavenly breezes, and there will be some who will brave even that void." This quest to discover other worlds inspired centuries of observations and discoveries. Explorers and imaginative writers took up the challenge.