W. Wayt Gibbs

6 min read Caltech’s SSPD-1 [shown here in an artist’s conception] has been testing the feasibility of beaming solar energy from space to Earth’s surface. The idea of powering civilization from gigantic solar plants in orbit is older than any space program, but despite seven decades of rocket science, the concept—to gather near-constant sunlight tens of thousands of kilometers above the equator, beam it to Earth as microwaves, and convert it to electricity—still remains tantalizingly