At the outset of the Second World War, Feynman desires to contribute to the military effort. Eventually, he takes a summer job working on a computer for aiming artillery. He finds that it is fun to design machines, though it is an engineering job rather than science. He learns that the best designs are ones that make use of the most reliable pre-existing parts, not something that the workers invent themselves from scratch. He is successful enough that the army offers to put him in charge of another project, but because it makes little scientific sense to him, he declines and returns to graduate studies at Princeton.

While Feynman is working on the atomic bomb in New Mexico, his wife becomes ill and must be hospitalized. Feynman recently read an article about bloodhounds’ excellent sense of smell, and to pass the time while visiting his wife, he decides to experiment with whether people also have a better sense of smell than most assume. The experiment shows that he can, indeed, tell which objects his wife has recently touched, though the human sense of smell is not nearly as acute as dogs’. Having discovered this, Feynman turns his sniffing game into a party trick in which he first appears to be a “faker” but proves the truth of his point by scientific experiment.