This book tells the story of the early modern astronomer Johannes Kepler's Somnium, which has been regarded by science historians and literary critics alike as the first true example of science fiction. Kepler began writing his complex and heavily-footnoted tale of a fictional Icelandic astronomer as an undergraduate and added to it throughout his life. The Somnium fuses supernatural and scientific models of the cosmos through a satirical defense of Copernicanism that features witches, lunar inhabitants, and a daemon who speaks in the empirical language of modern science....