"Sunshine, our greatest source of potential power, is now largely wasted," we declared in October 1934. But that's not for lack of trying: Throughout history, humans have harnessed the sun's power with increasingly sophisticated contraptions. One of the first uses of solar energy came in 214 B.C., when Archimedes set Roman warships aflame with reflected sunlight. Things got more complex in 1874, when engineer August Mouchot delivered 0.5 horsepower from a solar-powered steam engine (the steam was generated by transferring heat from a
reflective silver-lined copper cone to a copper boiler). And in 1904, engineer Aubrey G. Eneas erected a 36-foot dish [below] in Pasadena, California, that tracked the sun with a "clock-controlled motor" and pumped out 2.5 horses from a 13-foot boiler. By the 1930s, solar energy heated homes, powered water pumps, and even cooked meals, but the falling price of fossil fuels in the 1930s caused interest in solar power to wane until the 1970s, when the looming energy crisis and recently developed photovoltaic cells made it hot again.