For years, scientists at the Laboratory for Circadian & Sleep Disorders Medicine of Harvard University Medical School have been studying the effects of light on the human biological clock. The research shows that when normal sleep routines are disrupted, the body's clock can go haywire, leaving factory workers and other swing-shifters prone to poor performance and accidents. Both the Three Mile Island and Chernobyl accidents, for example, occurred on the graveyard shift. Now, lab director Charles A. Czeisler and the university have patented a way to reset the body's clock forward or backward quickly--using precisely controlled exposure to bright lights.
To help power-plant workers adjust to night duty, for instance, Light Sciences Inc. in Braintree, Mass., which is commercializing the technology, installs a computer-controlled lighting system in a plant's control room. The technique is also helping prepare NASA's shuttle astronauts.