The mountaineering physicist

The pion, a kind of subatomic particle consisting of a quark and anti-quark, was first observed by Giuseppe Occhialini, César Lattes and Cecil Powell of the University of Bristol in 1947. The team used sensitive photographic plates, known as nuclear emulsions, to collect evidence of the pion. The pion is more likely to be observable at high altitudes as it has a short lifespan and many pions that enter the Earth’s atmosphere decay before reaching sea level. Fortunately, Occhialini had worked as a rock-climbing guide and was skilled in both physics and rope work. The team exposed their nuclear emulsions at an altitude of 2,877 m on the Pic du Midi in the French Pyrenees, capturing the first traces of the pion.