In 1962, explorer Michel Siffre began experiments by locking himself underground for months under conditions without light and no concept of time. He uses an electrocardiogram to monitor his body’s vital signs and record his eating and sleeping schedule. When Siffre came out of the ground, the results of this pioneering experiment showed that his body kept a regular circadian rhythm. Although he does not receive any external signals, he still sleeps, wakes up and eats at certain times. From here the concept of “circadian rhythm” was born.
Later, scientists discovered that this circadian rhythm is based on the body’s hormone regulation. We have this ability thanks to a time management system in the brain. This system consists of a biological clock that tells us how many hours in a day and a calendar that tells us the seasons of the year. They are located in a specific location in the brain. In the dark cave, Stiffre relied on the most primitive clock in the pineal gland in the hypothalamus.
Here are a few basics about how the pineal gland works. One protein, CLK, activates genes that stimulate us to wake up and makes another protein called PER. When enough PER accumulates, these proteins disable the gene that makes CLK and make us fall asleep. Then, because the CLK content in the body decreases, the PER content also decreases. As a result, the gene that makes CLK activates again and the cycle continues. The alternation between CLK during the day and PER at night contributes to the formation of the circadian clock in our body.
To increase accuracy, the pineal gland also relies on external signals such as light, food, sound, and temperature. Siffre lacks these signals underground, but in everyday life, these signals help regulate the biological clock more precisely.
For example, the morning light when shining into the eyes will help wake us up. Light travels through the optic nerve to the lobe and announces it’s morning. When this happens, the hypothalamus in the brain halts the production of melatonin, a hormone that helps induce sleep. At the same time, it stimulates the production of vasopressin and noradrenalin in the brain, which helps control our sleep cycles.
In addition, the mechanism of action of the biological clock is also based on the communication of information between pairs of neurons. Since the communication time between two neurons is usually equal, the cerebral cortex uses them to calculate the elapsed time, from which we get the perception of time. While in the cave, Siffre made an interesting discovery. Every day, he challenges himself to count to 120 at the rate of one number per second. Over time, instead of taking 2 minutes, it took him 5 minutes to count to 120.
From there, it was shown that the solitary life in the dark cave had distorted Siffre’s concept of time despite the efforts of his brain to help him maintain the concept of time. Which makes us wonder what time really is? Does each of us experience time differently? Does one person ever feel that a day is longer than another?