3:25 PM local time: Fermi’s pile goes critical (it had almost gone critical a couple of hours earlier, but the imperturbable Enrico Fermi asks for his usual lunch break); the first test lasts 28 minutes with a power output of less than 0.5W to minimize the radioactivity produced. Richard Watts, a member of the instrumentation team, writes in the logbook: “We’re cooking!” Fermi remains calm (he was expecting the result). Leona Libby approaches him and asks, “When should we start worrying?” Fermi doesn’t respond: he’s focused on the instruments. After a full 28 minutes of criticality, Fermi orders “Zip!” to Zinn, who drops the safety rods. The pile shuts down immediately. It’s 3:53 PM. After turning off the pile, Wigner uncorks a flask of Chianti. Also present are Greenwalt (the future president of Du Pont) and Compton, who telephones Conant at Harvard to inform him that “the Italian navigator has landed in the New World” and that “he arrived earlier than expected.” “Are the natives friendly?” asks Conant: “Everybody landed safe and happy.” It is the first time that humans have induced nature to release, in a controlled and sustained way, the energy contained in the nucleus of the atom.
