The L5 Society was founded in 1975 by Carolyn and Keith Henson to promote the space colony ideas of Dr. Gerard K. O'Neill.
The name comes from the L4 and L5 Lagrangian points proposed as locations for the huge rotating space habitats that Dr. O'Neill envisioned. L4 and L5 are points of stable gravitational equilibrium located just outside the Moon's orbit at equal distances from both the Earth and the Moon.
An object placed in orbit around L5 (or L4) will remain there indefinitely without having to expend fuel to keep its position, whereas an object placed at L1, L2 or L3 (all points of unstable equilibrium) may have to expend fuel if it drifts off the point.
This is a preview for a Sony IMAX movie about the first space colony. The story is perceived through the eyes of the first child born in space.