12/12/2025
Full Story:
At Los Alamos during the Manhattan Project, security was often more “procedural” than truly robust, and Feynman’s curiosity locked onto that gap. He first noticed that sensitive papers were sometimes kept in ordinary filing cabinets, and he learned to pick the simple locks to get what he needed, largely as a puzzle and a prank, not to steal anything. When the lab switched to filing cabinets with combination dials, he treated them as an even better challenge and kept experimenting until he understood their quirks. In one account, he explains that if a cabinet was already open you could often infer the last two numbers of the combination, and with those in hand the first number becomes a small search, so opening the cabinet could take only a few minutes.
One of the most famous episodes happened when he returned after the war and needed a document on a weekend. He went to the office of the declassification officer, Freddy de Hoffmann, and while waiting he started “testing” the combination lock. Following the kind of tricks described in safecracker lore, he looked for a written clue and spotted a sheet where “pi = 3.14159” was scribbled, tried variants, failed, then made a sharper psychological guess: a mathematically minded person might use the constant . He tried 27-18-28 and the cabinet opened, and he discovered multiple cabinets were set to the same combination.
After taking the document he needed, he left a pointed calling card to prove the breach and embarrass the complacency, writing a note like: “I borrowed document no. LA4312 — Feynman the safecracker,” and in other cabinets he left extra notes signed “Wise Guy” and “Same Guy” to underline that identical combinations made the “other” safes no harder at all. When de Hoffmann later found the bright note, the story goes that he turned visibly pale and panicked, suddenly realizing how exposed the “top secret” material really was.
