On the 4th of March 1926 three brothers and a fourth man set out on a hike to Koncordiaplatz on Switzerland’s Aletsch glacier, the largest in the Alps. They never returned. When their bodies were discovered in 2012, scientists and mathematicians were able to work out what happened to the men 86 years earlier.
The film above explains how they did it using a mathematical model, which maps the motion of the ice.
For more stories like this on Switzerland follow us on Facebook and Twitter.