Book excerpt: In The Siesta and the Midnight Sun, award-winning science writer Jessa Gamble explores the continuing significance of the biological clocks that governed our lives before modern technology annihilated the night. She describes experiments that show both rats and people adhere to a 24-hour schedule even when deprived of daylight. When our days are disrupted by shift work, jet lag or space travel, things go wrong. The disastrous chemical leak at Bhopal, India and the calamitous launch of the Space Shuttle Challenger both were caused partly by sleepless workers. Insomnia is rampant in the Western world.