18 November 2011
Vol 334, Issue 6058

About The Cover

Cover image expansion

COVER Nighttime view of present-day Chicago, USA. Since the 1893 Chicago World's Fair introduced alternating current to the public, demand for electrical power has soared. Increased use of power from renewable resources will require new materials to store energy or generate power to ensure proper load balancing, as discussed in the special section beginning on p. 921. Image: Jim Richardson/National Geographic/Getty Images.