What would life be like without a clock? Or more than that, what would it be like without the sun to even tell you if it was daytime or night time?
In 1962, Michel Siffre descended into a cave for two months to find out what would happen. His natural day lasted 24 1/2 hours – not a huge change – but other strange things happened, like five minutes feeling like two. He repeated the experiment with different people and himself and found that some people adopted a 48 hour day without even realising it, and one man slept for 33 hours non-stop. What I find most interesting is that most of these people couldn’t tell that their routines were changing so much.
This interview with Siffre gives a summary of these experiments, which are now famous for investigating how we sleep and measure time.