Americans sleep less than seven hours a night, about two hours less than a century ago. In our restless floodlit society, we often think of sleep as an adversary. Nearly every night of our lives, we undergo a startling metamorphosis. Our brain profoundly alters its behavior and purpose, dimming our consciousness. For a while, we become almost entirely paralyzed. We can’t even shiver. Our eyes, however, periodically dart about behind closed lids as if seeing, and the tiny muscles in our middle ear, even in silence, move as though hearing. We are sexually stimulated, men and women both, repeatedly. We sometimes believe we can fly. We approach the frontiers of death. We sleep.
Around 350 B.C., Aristotle wrote an essay, “On Sleep and Sleeplessness,” wondering just what we were doing…
