Riviting and timely, a look at the research that is transforming our understanding of the cosmos in the quest to discover whether we are alone.For thousands of years, humans have wondered whether we are 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. What is life, actually? How do you find it over cosmic distances? And where are we the aliens?As director of the Carl Sagan Institute at Cornell University, astronomer Lisa Kaltenegger works with teams of tenacious scientists building the uniquely specialized tool kit to find life on alien worlds. In Alien Earths, she provides an insider's view of what scientists are learning from Earth's history and its astonishing biosphere. With an infectious enthusiasm. she takes us on an eye-opening journey to a dozen of the most unusual exoplanets that have shaken our worldview - planets covered in oceans of lava, lonely wanderers lost in space, and planets with more than one sun in the sky! And she dives into the worlds of science fiction, using these imagined other worlds to entertainingly describe how close they come to reality.With the James Webb Space Telescope, other smaller telescopes, and the pioneering work Dr. Kaltenegger is carrying out in her labs, we live in an incredible epoch of exploration. With Dr. Kaltenegger as our witty and knowledgable tour guide, we discover not merely new continents, like the explorers of old, but whole new worlds circling other stars. This riveting account will appeal to anyone who has ever gazed at the night sky in wonder.