"Kaltenegger's breezy narrative style invites you to experience with her the challenges and joys of being a scientist on the frontier of discovery." ―Neil deGrasse Tyson, Astrophysicist, American Museum of Natural History "Horizon-expanding... [Kaltenegger] has something of Sagan’s knack for eliciting wonder." ―The Times "A superb testament to the scientific virtue of curious wonder." ―Wall Street Journal 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. But once you look for life elsewhere, you realize it is not so simple. How do you find it over cosmic distances? What actually is life? As founding director of Cornell University's Carl Sagan Institute, astrophysicist Lisa Kaltenegger has built a team of tenacious scientists from many disciplines to create a specialized toolkit to find life on faraway worlds. In Alien Earths, she demonstrates how we can use our homeworld as a Rosetta Stone, creatively analyzing Earth's history and its astonishing biosphere to inform this search. With infectious enthusiasm, she takes us on an eye-opening journey 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! And the best contenders for