Also called an orbital lift, a space elevator is a super-strong cable attached to the earth at the equator, extended up beyond geostationary orbit. A counterweight at the top keeps the cable taught. At the altitude of geostationary orbit, the lift has the same linear velocity as a satellite at that altitude - since the orbital period is 24 hours. Thus, the energy to put something into orbit is only as much as it takes to climb to that altitude.

Arthur C. Clarke admitted it was far-off technologically but estimated that "The Space Elevator will be built about 50 years after everyone stops laughing."