Natural high

摘要

How does it feel to be on top of the world? The iconic photograph of Tenzing Norgay on the summit of Mount Everest on 29 May 1953 (far left) might give a clue. He and Edmund Hillary were the first people to reach the highest point on Earth. But they couldn't have done it without their innovative kit. John Hunt, who led the team, ascribed their success to the oxygen equipment (bottom). They took two systems with them. The first mixed oxygen in tanks with the ambient air and had been used successfully on Everest before. The second was a brilliant experiment: a system that recycled exhaled air through a cylinder of soda lime to remove carbon dioxide, allowing the air to be reused so fewer bottles of oxygen were needed. Tom Bourdillon, the team member who designed the recycling system, was able to make fast progress on his ascent with partner Charles Evans - but the system broke down when the pair reached Everest's south summit on 26 May, denying them the chance to reach the peak first.