On September 14, 1962, French scientist Michel Siffre emerged from a two-month stint of complete isolation in a cave, having lived without natural light for 63 days. Equipped with only a dim four-volt lamp, Siffre’s experiment was not geological, despite his profession as a geologist; he aimed to study the human body’s internal clock in the absence of sunlight.
During his time underground, Siffre’s perception of time changed drastically. He noted that his sleep patterns diverged from the typical 24-hour cycle, extending to approximately 25 hours. Consequently, those two months felt more like a single, continuous day. Siffre recounted this experience to Cabinet magazine, expressing how he lost track of daily activities and the distinction between wakefulness and sleep, remarking, “It’s like one long day.”
His research received backing from the French Army, which was interested in exploring whether soldiers could function without regular sleep intervals, while NASA aimed to understand the implications of extended periods away from the solar cycle on human sleep patterns. Upon his return to the surface, Siffre struggled with bright sunlight, requiring special sunglasses due to what felt like blinding glare, and needed assistance to walk, having become unaccustomed to movement after his extended isolation.
Siffre continued to contribute to the field of cave experimentation, overseeing subsequent studies. In 1964, he orchestrated a rescue operation after hearing suspicious silence from another subject’s microphone, only to discover the individual had simply fallen asleep for 34 hours.
In a later exploration in 1999, Siffre spent another three months underground, commemorating the turn of the millennium alone in the cave with champagne and foie gras, only to discover he had lost track of time and missed the actual New Year’s celebration by days.
Through his research within the depths of the Earth, Siffre highlighted the profound effects of prolonged darkness on human physiology, shedding light on the complexities of our biological rhythms.