grew up in one of the biggest forests in Switzerland and spent my childhood around nature. I became an explorer and have travelled to some of the most extreme places on the planet: a 70C summer in the Dasht-e Lut desert in Iran, and a month in the Verkhoyansk mountains in Russia which can reach -60C. I want to better understand humankind’s ability to adapt to extreme environments. When I was young, I read about a Frenchman called Michel Siffre who spent weeks alone in a cave in 1962 to see what would happen to his body rhythm. The idea of living without the structure of time became a dream, and when lockdown came, disrupting schedules people had kept all their lives, I saw a reason to repeat the experiment. I found a cave in the French Pyrenees where I could go with 14 others who volunteered to join the expedition; I made sure there was a gender balance and a good level of fitness. The aim was to see how living down there for 40 days and nights without clocks, sunlight or contact with the outside world would affect our sense of time. Inside the cave, we would not be allowed to speak with our friends or family, or receive updates about the outside world. The cave was huge, the biggest in Europe. It felt as if we were on the moon. It was dark, with just faint shades of yellow, red and orange, and quite cold, and smelt of rocks and humidity. We established three spaces inside: a living area with a kitchen, which had a gas cooker, tinned food, pasta and rice. Eight hundred metres away, we had our tents. Beyond that was a place for scientific research. On the lower level, you had to descend 90 metres with a rope to reach a lake area for drinking water and bathing, but it was too cold to do wash properly. There was only one absolute rule: we had to follow our natural rhythm. We mustn’t wake other people, or do anything that felt unnatural, but just follow our feelings: if I want to go to sleep, I go to sleep; if I want to eat, I eat. There was always at least one person awake. It’s a strange feeling, to wake and not have a watch to tell you if you’ve slept enough. But soon it felt freeing. I slept really well. When I woke up I would go for a walk on my own, just listening and looking at the cave, soaking in the calmness. For breakfast, I always had coffee, two eggs with chapati and chocolate. We had a lot of chocolate in the cave. We spent much of the time talking about our lives, the reason for our existence on Earth and how we can improve humanity. On expeditions, people are much more open to talking about themselves: pain, love, joy. We also fantasised about what was happening outside – whether the pandemic was over and bars and restaurants open, or if a new virus might have destroyed society, like in disaster films, and we’d be the last people alive on Earth. After a while, people got familiar with the cave and began to forget to do chores and work tasks. There were arguments over food and washing-up. It was impossible to organise group tasks in these conditions, so after 17 cycles, or sleeps, we had a big group meeting to clear the air. It was tense. It took hours of discussion. After that, we began to unite. We gave ourselves specific roles and each person had to teach others how to do the job, so if you weren’t awake someone else could do it. We began to coordinate more and a strong bond developed between us. Some even planned holidays and bike tours together. Two volunteers had birthdays while we were down there. The first one was easy, because it was after just two cycles. But the second, for a girl who turned 30, was much more difficult because it was in the middle of the experiment. We just decided: it’s today, your birthday. We played music and had some cake and candles. Afterwards we found out we had celebrated it four days late. In the end, we were happy there. Following your own rhythm is an incredible freedom. When we were told it was over, we didn’t feel ready to go out, but leaving was like a rebirth. There was the sun and blue sky. The trees were really green. My nose was ready for all these other smells. The breeze blew in my face and birds were singing. It was unbelievable. I think, as a society, we should reconsider the way we spend our time. We wake up because it’s time to wake up and to work, but we forget to listen to our bodies. For the first time, I felt free. If I had to live like this for a long time, it would be nice.