Space technology and the potential habitation of the Solar System is lengthening the list of catastrophic threats posed to humanity, claims Daniel Deudney in his new book Dark Skies: Space Expansionism, Planetary Geopolitics, and the Ends of Humanity. It follows on from his prior arguments about nuclear weapons and a world government in Bounding Power: the threat of nuclear extinction requires systemic political and social change in the way humans govern the world.