Michel Siffre, who went into caves to study the human mind, dies at 85

On the morning of September 14, 1962, Reporters and spectators began to gather. In a hole in the ground, in a remote area in the Maritime Alps between France and Italy. After a few hours, workers tied a rope in the dark; and soon they were able to pull out a small, strong man named Michel Sever.

He had been inside the cave 375 feet underground for 63 days, with only a four-volt lamp for light. He was wearing dark glasses to reduce the glare of the sun, and had to be carried to a waiting helicopter.

This was no rescue: Mr. Severi, a geologist, was experimenting on himself, to see what would happen to his sense of time if he cut himself off from the natural flow of life day and night on the surface.

It turns out that a lot of things could have happened: He said the time he lived had “overlapped” with the time he lived. His daily rhythm of wakefulness and sleep had expanded from 24 to about 25 hours. What seemed like a month to him was actually two months on the surface.

“After a day or two, you don't remember what you did a day or two ago,” he said. Al-Khazana Magazine, an arts and culture magazine, in 2008“The only thing that changes is when you wake up and when you go to bed. Plus, everything is completely black. It's like a long day.”

Mr. Sèvre, who died on August 25 in Nice, was a pioneer in the field of chronobiology, the study of how the human body perceives time. Previous scientists had speculated that, contrary to the prevailing idea at the time, our internal clocks were independent of the solar cycle, even though we usually adapted to its influence. In decades of experiments that began with his descent in 1962, Sèvre proved it.

His death was announced by Family in a statementIn a separate statement, The French Explorers Association said: The cause was pneumonia, and he was 85 years old.

Mr. Sifry was inspired by the Cold War and the space race, and then funded by the government. His 1962 venture came just before the Cuban missile crisis, which prompted Americans to dig nuclear shelters in their backyards and wonder what new life might be underground.

The French army wanted to know if he could keep soldiers awake longer. NASA wanted to know how the sleep cycles of astronauts on a mission to Mars or beyond would be affected. Both supported his subsequent research.

During the 1960s, Mr. Siffry supervised more underground excursions by volunteers, all of them similarly isolated—he chose bat-free caves, for example, because their nocturnal habits served as a guide to the time of day.

His experiments continued for longer and longer, and the results were astonishing. Without the influence of the sun, the participants had wildly different circadian rhythms; some slept for 12 hours, but then had no problem staying awake for 36 hours—even though they counted those 48 hours as 24.

He returned to the Earth's interior in 1972, spending six months in a cave in South Texas. Electrodes were attached to his chest and head to measure various vital statistics, and he spent his time conducting a lengthy protocol of tests on himself.

At one point, feeling so lonely that he disconnected the sensors and nearly called off the mission, he calmed down ten days later, reconnected them, and ended his stay—at the time a world record for time spent underground. Once again, he thought he had only been underground for a short time.

“When we said to him, ‘OK, time to get out,’ he didn’t believe us,” Greg Passmore, a cave explorer who helped with the project as a teenager, said in an interview. “He said, ‘You know, you’re just kidding me.’”

Mr. Sivri emerged from this situation depressed and in debt. His wife, Natalie, decided to leave him. Even with government funding, his project had cost him a small fortune.

At the time, he also faced criticism from cave scientists, some of whom felt he disturbed fragile subterranean ecosystems, as well as skepticism from biologists, who questioned his work as being unspecialized.

Over time, Mr. Sifry's research has proven invaluable to other researchers, and represents a pivotal contribution to chronobiology – a field in which three scientists have been involved, Jeffrey C. Hall, Michael Rosbash, and Michael W. YoungHe won the Nobel Prize in Biology in 2017 for his discovery of the genetic basis of our internal clocks.

Michel Augustin Francis Sèvre was born on January 3, 1939 in Nice. His father, Jean, was a winemaker before World War II, a prisoner of war during the conflict and a tax official afterward. His mother, Lucie (Roques) Sèvre, was responsible for running the household.

He obtained a Bachelor's degree in Geology from the University of Paris in 1960.

Full information about the survivors was not immediately available.

After his descent in 1972, Mr. Severe turned to writing books and lecturing about caves. He spent time in Sri Lanka, searching for caves containing precious stones, and in Guatemala, exploring subterranean sites for evidence of pre-Columbian settlement.

He returned to Earth again, after hearing that John Glenn, the first American to orbit the Earth, had returned to space in 1998, when he was 77 years old.

He entered the cave in November 1999 and emerged in February 2000. He had taken foie gras and champagne with him to celebrate the new millennium, but his internal clock failed again – what he thought was New Year's Day was actually January 4, 2000.

Alain Delacouriere Contribute to research.