Introduction

Abstract

As a teenager I built a reflecting telescope. After many hours of grinding a mirror, figuring, and assembling, I was ready for my first look at the heavens. I pointed it toward the Milky Way and began scanning the star clouds. It was a moment I’ll never forget. A sense of elation overcame me; the stars were like tiny diamonds—some solitary, others in pairs and threes. Some were blue, others faintly red. I remember thinking as I looked at them that any one of them could have a planet orbiting it, perhaps with a civilization on it. I tried to imagine what they would be like.