There are a few people in the world whose lives take place on the extremities of ordinary human experience. The vast majority of us work jobs and ignore emails. We look at traffic signs and try and get to 10,000 steps a day. We complain about the weak Wi-Fi signal and make plans for Friday evenings. The rest, a minority so small they might as well not count, do other things. They explore the deepest depths of oceans and wave a muleta in front of a charging bull. They jump off planes and surf giant waves. They climb mountains.