One day, astrobiologists could make the most fantastic discovery of all time: the detection of complex extraterrestrial life. As space agencies continue to search for life in our Universe, fundamental questions are raised: are we awake to the revolutionary effects on human science, society and culture that alien contact will bring? 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. From Newton to Kubrick, and Lucian to H. G. Wells, this is a fascinating account for anyone interested in the extraterrestrial life debate, from general readers to amateur astronomers and undergraduate students studying astrobiology.