The most detailed treatment of the issue comes from international relations scholar Dr. Daniel Deudney and his book Dark Skies: Space Expansionism, Planetary Geopolitics, and the Ends of Humanity. It’s an involved argument, but the basic idea is this: humans being what we are, the move into space creates at least two forms of existential peril: the risk of nuclear conflict on Earth due to a scramble for space territory, and the risk of heavy objects being thrown at Earth if humans are allowed to control things like asteroids and massive orbital space stations.
