Aron Ralston knew he would die before the next morning’s sunrise. Five days earlier he’d been walking a trail in a narrow desert canyon in Utah and had climbed down from a large chockstone along his route. A chockstone is a huge boulder that’s wedged between other stones or canyon walls. This one may have been there for hundreds of years, but when Ralston came down, he somehow loosened the boulder, and it fell on him. When it stopped, the stone was wedged against both canyon walls, and his right wrist was between one of those walls and the boulder.