National Geographic

Our brain profoundly alters its behavior andpurpose, dimming our consciousness. For awhile, we become almost entirely paralyzed. Wecan’t even shiver. Our eyes, however, periodi-cally dart about behind closed lids as if seeing,and the tiny muscles in our middle ear, even insilence, move as though hearing. We are sexuallystimulated, men and women both, repeatedly.We sometimes believe we can fly. We approachthe frontiers of death. We sleep.Around 350 B.., Aristotle wrote an essay, “OnSleep and Sleeplessness,” wondering just whatwe were doing and why. For the next 2,300 yearsno one had a good answer. In 1924 German psy-chiatrist Hans Berger invented the electroen-cephalograph, which records electrical activity``````Swathed in tubes andelectrodes, 10-year-old Francis Ajua awaits“lights out” for hisovernight sleep studyat Children’s NationalHealth System in Wash-ington, D.C. He wasbeing tested for sleepapnea, in which breath-ing repeatedly pauses.PREVIOUS PHOTOAt the Philharmonie deParis, composer MaxRichter leads a perfor-mance of Sleep, a min-imalist, scientificallyinformed piece thataims to guide listenersthrough a rejuvenatingrest. It lasts eight hours.Nearly everynight of our lives,we undergo astartlingmetamorphosis.46 NATIONAL GEOGRAPHIC