Ngima Gyalzen Sherpa, a Nepalese mountain guide, still feels a chill in his heart when he remembers the moment he slipped and fell into a crevasse on Mount Everest, the highest summit in the world, in the spring of 2022. The Khumbu Icefall is one of the most dangerous passages on Everest. It is a huge mass of giant blocks of ice that move slowly but steadily towards the valley and which climbers have to overcome on their ascent to the peak. Most of them only manage thanks to local specialists who previously created a safe passage by installing a network of ladders and ropes – which they adapt …