In July 1962, 23-year-old French geologist and speleologist Michel Siffre undertook a radical self-experiment: to live in complete isolation inside a glacier cave in the Scarasson mountain in the Ligurian Alps—130 meters below the surface—for over two months. Inspired by the space race and the psychological challenges astronauts might face, Siffre aimed to understand how the human body perceives time in the absence of natural cues like sunlight or clocks.
“This idea came to me—this idea that became the idea of my life,” Siffre later told Cabinet Magazine. “I decided to live like an animal, without a watch, in the dark, without knowing the time.”
No Watch, No Light, Just the Body Clock
Siffre’s experiment was simple in structure but profound in outcome. He abandoned his watch, deprived himself of sunlight, and instructed his surface team not to share any time-based information. The only equipment he carried was basic camping gear and a flashlight. He would notify the surface crew whenever he woke up, ate, or went to sleep, helping them monitor his natural rhythm without interfering with it.
Through this extreme isolation, Siffre made an unexpected yet revolutionary discovery: the body runs on its own internal clock. “Without knowing it, I had created the field of human chronobiology,” he said.
Time, Warped by the Mind
To delve deeper into his own perception of time, Siffre conducted psychological tests during his stay. In one test, he was asked to count from 1 to 120 at the rate of one digit per second. He believed it took him two minutes. In reality, five minutes had passed.
This distortion, he explained, demonstrated that psychological time compresses when devoid of external reference points. “My psychological time had compressed by a factor of two,” he said, noting how the absence of light, routine, and context distorts the brain’s ability to measure time.
Siffre also reported significant effects on memory and cognition. “After one or two days, you don’t remember what you have done a day or two before,” he recalled. The days merged into each other, becoming what he described as “one long day.” Without natural light or any sense of calendar days, the brain loses track of time’s passage entirely, he concluded.
Following the success and scientific interest generated by his initial cave expedition, Siffre returned to similar experiments multiple times. In the 1970s, he spent six months isolated in a cave in Texas. His final underground venture ran from November 1999 to February 2000, during which he infamously missed the turn of the millennium by four days—convinced New Year’s Eve had not yet arrived.
In some experiments, Siffre and his team found that people, when completely removed from time cues, could shift to a 48-hour sleep-wake cycle, doubling the standard circadian rhythm that governs most human lives.
A Legacy Set in Stone—and Silence
Michel Siffre passed away on August 24, 2024, at the age of 85 due to pneumonia. Yet his pioneering efforts in self-experimentation and time research live on in disciplines ranging from sleep science and space medicine to cognitive psychology.
His findings have influenced how researchers think about human performance in space, deep-sea missions, and environments of extreme isolation. Siffre proved that time is not just something we measure—it’s something we psychologically construct. And in doing so, he changed the way science understands the ticking of the human mind.
“This idea came to me—this idea that became the idea of my life,” Siffre later told Cabinet Magazine. “I decided to live like an animal, without a watch, in the dark, without knowing the time.”
No Watch, No Light, Just the Body Clock
Siffre’s experiment was simple in structure but profound in outcome. He abandoned his watch, deprived himself of sunlight, and instructed his surface team not to share any time-based information. The only equipment he carried was basic camping gear and a flashlight. He would notify the surface crew whenever he woke up, ate, or went to sleep, helping them monitor his natural rhythm without interfering with it.
Through this extreme isolation, Siffre made an unexpected yet revolutionary discovery: the body runs on its own internal clock. “Without knowing it, I had created the field of human chronobiology,” he said.
In 1972, a French scientist locked himself in a pitch-black cave 440 feet underground for 180 days.
— Suyash (@suyashadvait) April 4, 2025
No light.
No time.
No human contact.
He wanted to uncover the secrets of the human mind—and what he found was literally TIME-BENDING:
Michel Siffre was a geologist and researcher… pic.twitter.com/jmMiymRIKP
Time, Warped by the Mind
To delve deeper into his own perception of time, Siffre conducted psychological tests during his stay. In one test, he was asked to count from 1 to 120 at the rate of one digit per second. He believed it took him two minutes. In reality, five minutes had passed.
This distortion, he explained, demonstrated that psychological time compresses when devoid of external reference points. “My psychological time had compressed by a factor of two,” he said, noting how the absence of light, routine, and context distorts the brain’s ability to measure time.
Siffre also reported significant effects on memory and cognition. “After one or two days, you don’t remember what you have done a day or two before,” he recalled. The days merged into each other, becoming what he described as “one long day.” Without natural light or any sense of calendar days, the brain loses track of time’s passage entirely, he concluded.
Following the success and scientific interest generated by his initial cave expedition, Siffre returned to similar experiments multiple times. In the 1970s, he spent six months isolated in a cave in Texas. His final underground venture ran from November 1999 to February 2000, during which he infamously missed the turn of the millennium by four days—convinced New Year’s Eve had not yet arrived.
In some experiments, Siffre and his team found that people, when completely removed from time cues, could shift to a 48-hour sleep-wake cycle, doubling the standard circadian rhythm that governs most human lives.
A Legacy Set in Stone—and Silence
Michel Siffre passed away on August 24, 2024, at the age of 85 due to pneumonia. Yet his pioneering efforts in self-experimentation and time research live on in disciplines ranging from sleep science and space medicine to cognitive psychology.
His findings have influenced how researchers think about human performance in space, deep-sea missions, and environments of extreme isolation. Siffre proved that time is not just something we measure—it’s something we psychologically construct. And in doing so, he changed the way science understands the ticking of the human mind.
You may also like
James Corden sparks gasps with X-rated joke about Dame Judi Dench's sex life at awards
Stock markets LIVE: FTSE 100 plummets as Trump sparks recession fears in new Black Monday
Carlo Ancelotti teases huge Real Madrid change for Arsenal showdown
Springtime Celebrations: Festivals in Switzerland This April
How Singapore's unique monetary policy works
