One day, astrobiologists could make the most fantastic discovery of all time: the detection of complex extraterrestrial life. And how is it possible to imagine the unknown? In this book, Mark Brake tells the compelling story of how the portrayal of extraterrestrial life has developed over the last two and a half thousand years. Taking examples from the history of science, philosophy, film and fiction, he showcases how scholars, scientists, film-makers and writers have devoted their energies to imagining life beyond this Earth.