The discoveries of the scientist who lived in a dark cave – 09/18/2024 – Science

It’s very likely that you check the time several times a day, whether on your watch or cell phone.

Time plays a fundamental role in our lives. That’s why even the oldest civilizations sought a way to measure it, using the sun as a reference.

But what would happen if we didn’t know when it was day and when it was night? And what if we also didn’t have a device that recorded the passage of time?

This is what a young French geologist named Michel Siffre (1939-2024) asked himself in the 1960s.

Siffre’s doubt arose during the so-called space race — the dispute between the United States and the Soviet Union for the conquest of space.

In 1961, Soviet cosmonaut Yuri Gagarin (1934-1968) became the first human to travel into space. He spent 108 minutes in orbit around the Earth.

But Siffre wondered: What would happen if humans spent more time in space? How would that affect our sleep cycle?

To answer these questions, instead of traveling outside the Earth, Siffre preferred to go a little deeper into the Earth’s crust.

Caveman

Michel Siffre died on August 25th in Nice, France, at the age of 85. He was a speleologist, that is, a scientist who studied caves.

In 1962, at just 23 years old, he performed one of the most famous experiments in the history of human chronobiology—a branch of science that he himself helped create, dedicated to understanding the mechanism of our biological rhythms.

The scientist camped alone for two months in a cave 130 meters underground. His only source of light was a mining lamp, which he used sparingly to prepare his food, read and write in his diary.

“Deciding to live like an animal, without a watch, in the dark and without knowing the time,” he said in 2008, in an interview with American journalist Joshua Foer, from Cabinet magazine.

Siffre carried out his experiment on an underground glacier in the Alps, which he had discovered a year earlier.

“I stationed a team at the cave entrance,” he said. “I decided to call them when I woke up, when I ate, and just before I went to sleep. My team had no right to call me, so I would have no idea what time it was outside.”

With this, he was able to demonstrate that human beings have a “biological clock”. But the surprise was to discover that this clock did not follow a 24-hour cycle, as is usually the case in our daily lives.

Slowed down time

During the eight weeks he spent in the cave, Siffre ate and slept only when his body demanded it.

In addition to informing the team on the surface whenever this happened, the scientist also performed two checks: he took his own pulse and counted to 120. And it was this second procedure that brought one of the most astonishing conclusions of the study.

The goal was for Siffre to take one second per number to count from 1 to 120, while his collaborators recorded the actual time. And that’s how they realized that the scientist kept a much slower time record.

“It took me five minutes to count to 120,” he reported. “In other words, psychologically, I experienced five real minutes as if they were two.”

The scientist felt time pass more slowly inside the cave, without any natural or artificial reference to day and night.

This feeling of time slowing down was confirmed when Siffre finally left the cave. Two months had passed, but the scientist was convinced that he had only been confined for a month.

“My psychological time had been cut in half,” he noted.

48 hours

Michel Siffre’s findings indicated that without nature’s guided circadian rhythms of sunrise and sunset, our bodies apparently maintain an internal clock that runs on roughly 48-hour cycles.

This theory was supported by other experiments carried out by the French speleologist throughout his more than 50-year career. He used himself and other people as objects of study.

After his 1962 “breakup” (as he called the experiment), Siffre conducted five more cave studies with volunteers, including one woman, each lasting three to six months.

Siffre noted that they all fell into the 48-hour cycle. “They had 36 hours of continuous activity, followed by 12 to 14 hours of sleep,” he said.

“After this discovery, the French army gave me a large amount of funding. They wanted me to look at how it would be possible for a soldier to duplicate his activity in a waking state,” the scientist revealed to Cabinet magazine.

The French Ministry of Defense was also interested in his experiments for another reason. They had just launched their nuclear submarine program and wanted to see what effects long missions would have on the health of sailors.

And they weren’t the only ones interested. The US space agency NASA also wanted to understand the effects caused by long-duration space missions.

The two organizations funded Siffre’s second personal project. And in 1972, 10 years after his first stay in the Alpine cave, the scientist returned to live underground—this time in the United States, for a much longer period of time.

His goal was to spend six months in Midnight Cave, near Del Río, in the US state of Texas.

“My interest was to study the effects of aging on psychological time,” he explained. “My plan was to do an experiment every 10 to 15 years to see if the way my brain perceives time changes.”

He also acknowledged that he wanted to clarify why “every other person who had been underground had a 48-hour sleep/wake cycle except me.”

This experiment ended up lasting 205 days (about seven months). And the scientist also entered the 48-hour cycle, but not on a regular basis.

“I had 36 hours of continuous wakefulness followed by 12 hours of sleep,” he said. “I couldn’t feel the difference between those long days and the ones that were only 24 hours long.”

“Sometimes I would sleep two hours or 18 hours and I couldn’t tell the difference,” he recalls. “I think that’s an experience we can all have.”

“It’s the problem of psychological time. It’s the problem of human beings. What is time? We don’t know.”