In a 1611 book published by the Academy of the Lynx, the Jesuit astronomer Christoph Scheiner argued that sunspots are little planets circling the Sun like Venus. Galileo answered Scheiner with this book. Galileo’s detailed, full-page copperplate engravings set a new standard for presenting evidence about the Sun. Galileo’s study of sunspots is a masterpiece of data visualization. The spots move together. They move slowly, each taking about a month to travel across the solar disk. Their shape is irregular; they form and disappear with irregular timing. The spots foreshorten as they approach the edge of the solar disk. All this proves they lie on or very near the surface, and are not little planets. Sunspots therefore suggest that the Sun and the heavens are corruptible, a tenet contrary to Aristotle but already accepted by some scientists and theologians.