Einstein had done more than set the soiled linen out for common display; he had slapped many faces. Most physicists—most scientists, even most Nobel Prize winners—contribute little or nothing to theory. They gather facts and hit upon techniques, but they do not alter the axioms that govern their work. Physicists like Einstein, Bohr, and Planck were unusual figures for having changed nature’s ground rules. Many proud scientists could ask themselves: if Einstein says that about Lenard, what might he say about me?

Despite their fatherly advice, Einstein defied his colleagues by making no public retraction. He even arranged for an open debate with Lenard at the annual meeting of the Society of German Scientists and Physicians. Einstein was going for a kill. He was right, of course. Lenard’s understanding of relativity theory was superficial and trivial. How much more fruitful a discussion about light quanta would have been. Einstein could have used an experimental partner just then. Lenard was among the few physicists whom Einstein had admired in his early days and Einstein’s first wife had studied under Lenard in Heidelberg. At about the time Mileva was there, a visiting Japanese physicist reported that Lenard’s lab was “perhaps the most active in Germany.” In 1901 Einstein wrote to Mileva, “I have just read a wonderful paper by Lenard on the generation of cathode rays by ultraviolet light. Under this beautiful piece I am filled with such happiness and joy that I absolutely must share some of it with you.” The “generation of cathode rays by ultraviolet light” was the old name for the photoelectric effect. Einstein’s letter refers to Lenard’s original publication proposing that electrons—what Lenard called cathode rays—are knocked from atoms by the light that strikes them. Almost two decades later, Einstein still could have used Lenard’s experimental vigor and imagination. He desperately needed to find some decisive experiment that would prove that quanta, not waves, caused the photoelectric effect.

Instead, Einstein scheduled a debate with Lenard that took place on September 23, 1920, in Bad Nauheim, a resort near Frankfurt in southwestern Germany. Before the Great War, Bad Nauheim had boasted an international clientele; aristocrats came from every European land and a few Americans were added for seasoning. The baths