For thousands of years, humans have wondered whether we're alone in the cosmos. Now, for the first time, we have the technology to investigate. The question should have an obvious answer: yes or no. But once you try to find life elsewhere, you realize it is not so simple. How do you find it over cosmic distances? What actually is life? Astronomer Lisa Kaltenegger works from Carl Sagan’s former office at Cornell University, where she built a team of tenacious scientists from many disciplines to find life on faraway worlds, using Earth’s diverse biosphere and its history as a Rosetta Stone. With infectious enthusiasm, she provides an eye-opening insider’s guide to the most unusual exoplanets that have shaken our worldview – planets covered in oceans of lava, lonely wanderers lost in space, and others with more than one sun in their sky – as well as the best contenders for Alien Earths. She also shows how close imagined scifi worlds come to reality. We live in an incredible new epoch of exploration. As our witty and knowledgeable tour guide, Professor Kaltenegger shows how we discover not merely new continents, like the explorers of old, but whole new worlds circling other stars – and how we could spot life there. Worlds from where aliens may even be gazing back at us. What if we're not alone?