There once was a dream of cities in space — vast cylindrical habitats, self-sufficient and populated by millions who would look down on the Earth from their lofty perch.
Back in the 1970s, one serious scientist believed that by now this dream would have been a reality. That scientist was Princeton University professor of physics, Gerard K. O'Neill, and, for a few years, his dream of living in space made him a household name. He appeared on television, wrote a best-selling book and was invited to testify before the U.S. Congress about his vision for the future.
