In 1963 a schoolboy in Tanganyika named Erasto Mpemba, making ice cream in a cooking class and short of room in the fridge, put his mixture in while it was still hot, and it froze ahead of the other boys’. His physics teacher told him that was “Mpemba’s physics, not the universal physics.” Later a visiting physicist, Denis Osborne, took questions at his school and Mpemba asked his. The class laughed. Osborne didn’t; he had no answer, so he went home and had a technician try it. They published together in 1969, and the boy’s name went on the effect. In 2016 two researchers ran the careful version and concluded, “somewhat sadly”, that there was no evidence for it worth the name, though the argument isn’t over. So the teacher may turn out to have been right about the water. He was still wrong about the question, and no fridge was ever going to show that.