In 1953, Enrico Fermi, John Pasta, Stanislaw Ulam and a young programmer named Mary Tsingou used one of the first computers, the MANIAC at Los Alamos, to watch a vibrating chain of weights share its energy out evenly, just as everyone expected. One day, the run was accidentally left going long past its cutoff, and when they came back the energy had flowed almost entirely back into the original wave, as if the chain remembered where it started. That surprise helped launch the modern science of Nonlinear Waves, and for decades Tsingou, who wrote the code, was left out of the problem's name.