Last week, the Lunar and Planetary Laboratory of the University of Arizona honoured the retirement of Dr Randy Jokipii, Regent’s Professor of Planetary Sciences … and the man who directed my doctoral dissertation. It’s customary at such events to downplay the scientific work of the honouree, and praise instead the “life lessons” taught. But Jokipii was not my father, my pastor or my guru; he taught me physics. I chose to work for him for the simple reason that I thought he was the smartest guy in the department. (I still think so.) His field, cosmic ray physics, was far from what I had done before, or since. That was another attraction: I wanted to be challenged to learn new stuff. I got what I wanted. Under his direction, I spent two years applying techniqu