SPELUNKER SCIENTISTS: From June 4 to July 6, 1938, Nathaniel Kleitman (at left in both photos) and his student Bruce Richardson camped out in Mammoth Cave in Kentucky to study the body’s ability to conform to a non–24-hour cycle. The cave, 140 feet underground with no natural light, provided a location free from visual cues of day and night or temperature fluctuations—it was a constant and chilly 54 °F. The men brought lanterns to regulate their exposure to light, a table, and a bunk bed, and staked out a spot in a rock chamber about 26 feet high by 65 feet wide inside the cave. Each “day” they slept for 9 hours, worked for 10, and rested for another 9 hours. The researchers measured the daily rhythm of body temperature, finding an endogenously generated 24-hour body temperature cycle, despite the self-imposed 28-hour cycle. Still, Richardson, who was 20 years old at the time, felt he was better able to adjust to the new pattern after just a week in the cave. In contrast, Kleitman, then 43, found that his body clock did not move towards a non–24-hour schedule—he would get tired at 10 o’clock at night and feel awake and alert eight hours later.SUBHADEEP DUTTA GUPTA
Even though we spend about one-third of our lives sleeping, probing how sleep works seemed a trivial, soft science to most researchers in the early 20th century. But the nightly habit intrigued Nathaniel Kleitman, who launched the world’s first sleep laboratory at the University of Chicago after joining the physiology department in 1925.
UNIVERSITY OF CHICAGO“When he began, I think he was the only man on the planet devoting his full time to the study of sleep,” says William Dement, a sleep researcher at Stanford University and one of Kleitman’s students. “Kleitman always said his interest in sleep was sparked by the question of what was required for us to stay awake.”
Kleitman often used himself as a subject in his sleep research, particularly on sleeplessness—whether in a pitch-black cave in Kentucky, in an underwater submarine during World War II, or on a trek above the Arctic Circle. To test one of his hypotheses—that the 24-hour clock could be ...
