Part 2 Sleep, Rewritten: Why Kids Sleep, Adults Don’t, and How to Restore the Signal
Light is not just something you see. Light is information. It tells every cell in your body what time it is, what hormones to release, what genes to express, and what state to prepare for. Before food, before supplements, before sleep routines, light is the primary organizer of human biology. Children live in a world where light signals still make sense. Adults do not. A child’s day usually begins with natural light or at least a gradual increase in brightness. Their eyes receive a clear signal that morning has arrived. Cortisol rises smoothly. Body temperature climbs. Appetite turns on. Movement follows. As the day goes on, light exposure naturally peaks and then fades. By evening, darkness arrives without negotiation. The signal is clean. The system knows what to do. Adults live in a different reality. They wake up in darkness. They turn on overhead lights that mimic noon at 6am. They stare into phones inches from their face. They spend most of the day indoors under artificial lighting that never changes. Then, late at night, when biology expects darkness, they flood their eyes with bright screens again. From the brain’s perspective, this is chaos. Circadian rhythm is often described like a clock. That metaphor is misleading. A clock keeps time even if the environment is wrong. Circadian rhythm is more like a conductor leading an orchestra. If the conductor is confused, the musicians don’t just play late. They play out of sync. Light is the conductor. The master clock in the brain, the suprachiasmatic nucleus, does not care what time your phone says it is. It cares what your eyes report. Specialized cells in the retina measure brightness, wavelength, and timing. They send that information directly to the brain’s timing center. From there, signals cascade to hormones, metabolism, digestion, immune function, body temperature, and sleep-wake cycles. This system evolved under one condition only. Bright light during the day. Darkness at night. There was no evolution for indoor lighting, night screens, or social schedules that shift daily. Biology assumes consistency. Modern life provides variability.