The name comes from the and Lagrangian points in the Earth–Moon system proposed as locations for the huge rotating space habitats that O'Neill envisioned. and are points of stable gravitational equilibrium located along the path of the Moon's orbit, 60 degrees ahead or behind it. An object placed in orbit around will remain there indefinitely without having to expend fuel to keep its position, whereas an object placed at, or may have to expend fuel if it drifts off the point.
History
Founding of L5 Society
O'Neill's first published paper on the subject, "The Colonization of Space", appeared in the magazine Physics Today in September 1974. A number of people who later became leaders of the Society got their first exposure to the idea from this article. Among these were a couple from Tucson, Arizona, Carolyn Meinel and Keith Henson. The Hensons corresponded with O'Neill and were invited to present a paper on "Closed Ecosystems of High Agricultural Yield" at the 1975 Princeton Conference on Space Manufacturing Facilities, which was organized by O'Neill. At this conference, O'Neill merged the Solar Power Satellite ideas of Peter Glaser with his space habitat concepts. The Hensons incorporated the Society in August 1975, and sent its first 4-page newsletter in September to a sign up list from the conference and O'Neill's mailing list. The first newsletter included a letter of support from Morris Udall and said "our clearly stated long range goal will be to disband the Society in a mass meeting at."
The peak of 's influence was the defeat of the Moon Treaty in the U.S. Senate in 1980. Specifically, Society activists campaigned for awareness of the provisions against any form of sovereignty or private property in outer space that would make space colonization impossible and the provisions against any alteration of the environment of any celestial body prohibiting terraforming. Leigh Ratiner "played the key role in the lobbying effort, although he had energetic help from L-5 activists, notably Eric Drexler and Christine Peterson." Although economic analysis indicated the SPS/space colony concept had merit, it foundered on short political and economic horizons and the fact that the transport cost to space was about 300 times too high for individuals to fund when compared to the Plymouth Rock and Mormon colonies.
The L5 News was the newsletter of the Society reporting on space habitat development and related space issues. The News was published from September 1975 until April 1987, when the merger with the National Space Institute was completed and the newly formed National Space Society began publication of its own magazine, Ad Astra.
