INTRODUCTION For most of human history, our understanding of the cosmos was based not on scientific evidence, but on our direct observations of the night sky as we gazed up at its sparkling, dark expanse. We once imagined the sky to be something like a hollow, spherical shell surrounding the Earth, and stars as bright points on that shell. When we began to notice that some of those bright points took different paths across the sky than the rest, we altered our explanation: the Earth was encased not by one sphere, but by many perfectly transparent crystal spheres nested inside one another and spinning in different directions. Onto these, we mapped constellations, the sun, and the moon. Our old theories about how the universe worked were flawed, but stargazing was still key to some of humanity's most important achievements. Calendars based on the movement of the sun, moon, and stars were important to the development of early agriculture. Navigation based on the positions of the constellations helped explorers sail the globe. The importance of the stars in our history is undeniable.

With so many of us spending a majority of our time indoors and living in light-polluted cities, our stargazing is often limited to occasionally noticing the moon on a particularly luminous night. Even the Milky Way--our own home galaxy that appears as a soft stream of light stretching across the sky--is impossible to see when drowned out by the artificial light of our modern world. We can forget the magic of the night sky. To take a moment and gaze up is to connect to an ancient human experience, and can be a great source of wonder and awe. This book is a tour of the night sky, centered on the old names and stories still in use by astronomers today. It will cover the most brilliant features of our solar system: the constellations, the moon, the bright stars, and the visible planets. And it will delve into less familiar celestial phenomena too, like the outer planets and deep space. Through it all, we'll explore some of the ancient mythology behind our night sky, as well as the basic science behind what we see--and don't see--in the stars.