Beginning more than a hundred years ago, science fiction writers, early filmmakers, and, later, serious scientists explored the possibilities of human beings expanding beyond Earth to dwell in the Solar System. Whether on the Moon, on Mars, in hollowed-out asteroids, or in constructed space stations, the dream of our species breaking free from this wet rock on which we evolved has been a source of fascination. We're getting closer now to having the technological capability to make the attempt. Some would argue, in fact, that we could have had thriving colonies on the Moon for decades now, had the US and the USSR not cut back on their space programs in the 1970s. Join discussion...