O'Neill became interested in the idea of space colonization in 1969 while he was teaching freshman physics at Princeton University. His students were growing cynical about the benefits of science to humanity because of the controversy surrounding the Vietnam War. To give them something relevant to study, he began using examples from the Apollo program as applications of elementary physics. O'Neill posed the question during an extra seminar he gave to a few of his students: "Is the surface of a planet really the right place for an expanding technological civilization?" His students' research convinced him that the answer was no.