The Starry Messenger, published in 1610, introduced Europe to Galileo's telescopic observations of the night sky. While spots on the moon had not escaped notice, Galileo tried to show how bright spots on the dark side of the moon indicated mountains and valleys. Notice the continuing arc of the bright ridge on the top crater and the bright interior curve of the bottom crater. Galileo argued that this was proof that the geography of the moon resembled that of the earth and that it was not a perfect, incorruptible sphere.