His 1981 book "" was an exercise in futurology. O'Neill narrated it as a visitor to Earth from a space colony beyond Pluto. The book explored the effects of technologies he called "drivers of change" on the coming century. Some technologies he described were space colonies, solar power satellites, anti-aging drugs, hydrogen-propelled cars, climate control, and underground magnetic trains. He left the social structure of the 1980s intact, assuming that humanity would remain unchanged even as it expanded into the Solar System. Reviews of "2081" were mixed. "New York Times" reviewer John Noble Wilford found the book "imagination-stirring", but Charles Nicol thought the technologies described were unacceptably far-fetched.