In Midnight Cave, Texas, Michelle Silver's tent shines with incandescent lights.
Leviathan Press:
Imagine if you were deprived of your senses of sight, hearing, and touch, how could you perceive time? Even if you have artificial light like Sever in the text, hearing, touch, and everything else is normal, but in an isolated environment, what will happen to your perception of time?
The passage of time is a subjective experience, and concurrent emotions can easily distort time. Specifically, when people are in a negative emotional state, time seems to be particularly slow (as it takes for years). Current research shows that dopamine plays an important role in time perception, causing us to either overestimate or underestimate the sense of passage of time.
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In 1962, a French spelier named Michel Siffre spent two months in a completely isolated underground cave with no clock, calendar, or sun (to tell him the time). He eats only when he is hungry and sleeps when he is sleepy, and his goal is to find out how the natural rhythms of human life are affected when they live "outside of time."
Over the next decade, Seaver organized a dozen additional experiments on time isolation underground, and finally, in 1972, he personally returned to a cave in Texas for six months. His work helped create the field of human chronobiology. Joshua Foer interviewed Sever by email.
On September 17, 1962, he arrived at Severre at Paris-Orly Airport.
Joshua Faure: In 1962, you were only 23 years old. What made you decide to live in complete isolation underground for 63 days?
Michelle Sever: You have to understand that I'm a trained geologist. In 1961, we discovered an underground glacier in the Alps about 70 km from Nice. At first, my idea was to prepare for a geological expedition to study the glacier for about 15 days underground, but after a few months, I said to myself, "Well, 15 days is not enough." I couldn't see anything. "So, I decided to stay for two months. And then I had this idea —it became an idea that would last my life. I decided to live like an animal: without a watch, in the dark, not knowing the time.
Fore: In the end, you stopped studying caves, but time.
Sieuffer: Yes, I invented a simple plan for scientific experiments. I sent a group of people to guard the entrance to the cave. I would contact them every time I got up, at dinner, and before I went to bed. My team didn't have the right to contact me proactively so I couldn't know what time was outside. Unconsciously, I created the field of human time biology. As early as 1922, it was discovered that rats had a built-in biological clock. My experiments have shown that humans, like lower mammals, have biological clocks.
In Silver's 1972 experiment in Texas, the reading material was well suited to the cave dwelling background: Plato (here alluding to the "parable of the cave" in Plato's Republic, Editor's Note).
Fore: When you first went underground, the temperature was below freezing and the humidity was as high as 98 percent. How do you pass the time?
Sever: I was poorly equipped, the camping place was small, and a lot of things were crammed together. My feet were always wet and my body temperature dropped to only 34 degrees Celsius (93 degrees Fahrenheit). My pastime was to read, write and do research in the caves. I also spend a lot of time thinking about my future.
In addition, every time I call the ground, I have to do two tests. First, I measure my pulse. Second, there will be a psychological test. I have to count from 1 to 120 at a rate of one number per second. With this test, we made a big discovery: It took me five minutes to count to 120. In other words, I mentally experienced real five minutes as if they were only two minutes.
Fore: Psychologist Elizabeth Loftus conducted an experiment in which she showed people a video of a bank robbery and asked them to estimate the duration of the robbery. Compared to the actual time, the participants overestimated by 500%. It seems that our subjective experience of time is highly variable. How do you feel the passage of time without a clock?
Sieuffer: My sense of time has been very badly disturbed. I went down to the ground on July 16 and went into the cave, planning to complete the experiment on September 14. When my ground team informed me that the day was finally here, I thought it was only August 20th. I felt like I was going to spend a month in the cave. My mental feeling of time was tripled.
Fore: What do you think is causing the huge disconnect between mental time and the real clock?
Sever: This is a big question that I've been studying for forty years. I believe that when you are in the middle of the night — the cave is completely dark, with only one light bulb — your memory cannot capture time. You will forget. You won't remember what you did a day or two ago. Only the two moments when you wake up and go to bed are changed. Beyond that, all the moments are completely in darkness. It was like an extremely long day.
Sever weighed himself. Experiments in Texas in 1972.
Fore: These kinds of isolation experiments can also be easily performed in the laboratory. Why do you always prefer to do it underground?
Sever: Labs are a great place to do these experiments, but you have to find people who are motivated enough. It is difficult to ask people to spend months in an experimental cabin. Between 1962 and 1972, a Professor in Germany conducted more than 150 isolation experiments in an artificial underground bunker, but they were all short-term experiments that lasted only about a month. The people we sent underground were originally cave explorers who were interested in the caves themselves and had a lot of motivation, so they were able to stay longer.
Fore: When you're underground, completely cut off from any human-defined measure of time, your body sleeps as long as it wants. It can be said that you got the perfect sleep. What was that like?
Sever: My sleep was perfect! My body chooses for itself when to sleep and when to eat. This is very important. Our study showed that my sleep/wake cycle wasn't 24 hours like that of people on the ground, but was slightly longer, about 24 hours and 30 minutes. But importantly, we demonstrated that there is an internal circadian clock that is independent of Earth's natural circadian cycle.
Interestingly, in my subsequent experiments with other study subjects, all "cavemen" demonstrated biological cycles of more than 24 hours. In fact, they are generally able to establish a 48-hour cycle: they move continuously for 36 hours, followed by about 12 to 14 hours of sleep. After we came up with this discovery, the French army gave me a lot of money. They wanted me to analyze how it was possible to double the soldier's waking activity time.
Seefour in the Cave (center) in 1964.
Fore: What did you find?
Sever: After experimenting on my own, I had a man in the cave for four months, and then a woman in the cave for three months. In 1966, another man did six months of experiments underground, and then we did two more experiments that lasted four months. We analyzed sleep phases—rapid eye movement (REM) phases, dreaming phases, and slow-wave sleep phases—and came up with another finding.
We demonstrated a correlation between the amount of time a person spends waking continuously and the amount of time he dreams the next night. Roughly speaking, ten more minutes of waking time per day, one more minute of REM sleep time in men. We also found that the more you dream, the shorter the reaction time when you are awake at the next stage. After we made this discovery, the French army tried to find drugs that could artificially increase the time of dreams, hoping to keep soldiers awake for thirty hours or more.
Fore: Ten years after your first quarantine experiment, you yourself went underground, this time in a midnight cave near Del Rio, Texas, for 205 days. Why do you want to go back?
Sieuffer: There are two reasons. First of all, I am interested in studying the effects of aging on mental time. My plan is to do experiments every ten or fifteen years to see if there are any changes in my brain's perception of time. Second, all but me, all the people I arranged to experiment with underground set up a 48-hour sleep/wake cycle. I decided to stay underground for six months and try to get this 48-hour cycle.
Faure: Why do people adjust to this 48-hour cycle?
Siefer: I don't provide a theory about that. I don't do theory. The 48-hour cycle is a fact. I observed this phenomenon, and I'm sure the truth of this finding is true, but no one knows what caused the sleep-wake cycle to undergo such a large desynchronization. Now that the Cold War is over, access to finance has become increasingly difficult. Today, only mathematicians and physiologists can go further on this issue.
In his 1972 experiment, Silver was covered with electrodes to monitor his heart, brain and muscle activity.
Fowl: Your first underground quarantine experiment took place in 1962, the same year that the Cuban Missile Crisis made the world acutely aware of the importance of bomb shelters, and the year before, Yuri Gagarin first went into space. How did these two events change the way we think about the underground?
Sever: I came at the right time. It was during the Cold War, and we didn't know anything about the human sleep cycle in outer space. Not only have the United States and Russia competed over manned spaceflight, but France has just begun its nuclear submarine program. The French headquarters had no clue how best to organize the sleep cycle of submarine personnel. That's probably why I got so much financial support. NASA deciphered my first experiment in 1962 and invested money in a complex mathematical analysis.
Fowl: What is there underground that both attracts us and scares us?
Sieuffer: Darkness. You need a light. If your lights go out, you're dead. In the Middle Ages, caves were inhabited by demons. But at the same time, the cave is a promising place. We went to the caves in search of minerals and treasures, one of the last places where we can still venture and discover new things.
Fore: You celebrate the millennium with foie gras and champagne in clamouse, 2,970 feet underground, but you're three and a half days late. You also missed your 61st birthday. Why did it take you almost thirty years to decide to go underground again?
Sieuffer: When I walked out of the midnight cave in 1972, I was in debt for $100,000. I grossly underestimated the cost of bringing my experiments from France to Texas, so I had to leave the field of chronobiology. Most of the data I got from that experiment hasn't been mathematically analyzed. In 1999, I decided to return to a cave in the south of France. I spent two months there studying the effects of aging on circadian rhythms. I was following in the footsteps of John Glenn, who returned to space at the age of 77.
Fowl: I know you're doing a "permanent underground site for human confinement and chronobiology experiments." Are you doing anything else?
Sever: The experiment in the cave is over. You can't do this kind of experiment anymore. When we first did it, I was young and we took all the risks. Now, researchers are limited. Now you have an ethics committee. Let me give you an example. In 1964, the second man to go underground after me had a microphone attached to his head. One day he slept 33 hours and we're not sure if he's dead or not. It was the first time we had seen a man sleep for so long. I thought, well, I'll go down into the cave and see what's going on. By the 34th hour, he was snoring, and we knew he was still alive. After a few minutes, he called the ground for us to take his pulse. Today, the doctor must wake him up, otherwise the risk is too great.
Fore: Have you ever managed to establish a 48-hour cycle?
Sieuffer: I've succeeded. In my 1972 experiment in Texas, for two periods my rhythm cycle was 48 hours, but they were irregular. I would stay awake for 36 hours straight, then 12 hours of sleep. I can't tell the difference between these long days and days that only last 24 hours. I studied the diaries I wrote in the caves, looking at them cycle by cycle, but there was no evidence of any difference in my perception of those days. Sometimes I slept two hours, sometimes I slept eighteen hours, but I couldn't tell the difference. I think it's an experience that we can all understand. It's a matter of mental time. This is a human problem. What is time? We don't know.
文/Joshua Foer、Michel Siffre
Translation/Bitter Mountain
Proofreading/Rabbit's Lingbo Microstep Original/www.cabinetmagazine.org/issues/30/foer_siffre.php