As the sun rises over Stockholm—a bit before 4 a.m.—I surf the Internet to check out music videos. I’m preparing to appear on the BBC radio show “Private Passions” as a guest DJ, and they’ve asked me to choose half an hour of music, mostly classical-ish. Four hours later, I’m not done. I’m having too much fun: exploring, not selecting. I walk to campus humming.

A brilliant visitor from Beijing shows me a fantastic discovery. (We are both guests of the Nordic Institute for Theoretical Physics, a gift from Scandinavia to the...