These volunteers spent 40 days in a cave with no sunlight or way to tell time Montreal's Marina Lançon was one of 15 people who volunteered to spend 40 days in a French cave without any way to tell the time or communicate with the outside world — all in the name of science. Social Sharing CBC Radio · Posted: Apr 27, 2021 5:44 PM ET | Last Updated: April 27 Marina Lançon, pictured in the centre with a blue bandana and gray sweater, emerges from the Lombrives Cave in France with 14 other people after 40 days underground.(Renata Brito/The Associated Press)