an Italian mathematician at the University of Padua, directed a new scientific instrument, the telescope, toward the heavens. Having heard
that a Dutch artisan had put together two lenses in a way that magnified distant ob- jects, Galileo built his own such device. Anyone who has looked through a tele- scope can appreciate his excitement. Ob- jects that appeared one way to the naked eye looked entirely different when magni- fied by his new “spyglass,” as he called it. The surface of the moon, long believed to be smooth, uniform, and perfectly spheri- cal, now appeared full of mountains and craters. Galileo’s spyglass showed that the sun, too, was imperfect, marred by spots that appeared to move across its surface. Such sights challenged traditional sci- ence, which assumed that “the heavens,” the throne of God, were perfect and thus never changed. Traditional science was shaken even further when Galileo showed that Venus, viewed over many months, appeared to change its shape, much as the moon did in its phases. This discovery provided evidence for the relatively new
