People have always looked to the sky for inspiration, imagining a world that is above our own. Looking at the stars reminds us that the world is more marvelous, more ordered yet more mysterious than we often recognize in the bustle of day-to-day life, even as its operation of days and nights rely on the stars above as the cosmic markers of our own daily rhythms. Yet the omnipresence of hand-held devices and digital clocks has made us forgetful of this reality, and thanks to the effects of the light of electric cities (as well as environmental pollution), most of us have very little sense of what the night sky must have looked like to people before such inventions of the industrial and digital revolution. Yet for the ancients, the sky's sweeping expanse held a more definitive and immediate role. The structure of the cosmos represented stability and orde