Now, if I turn the wheel away from ten a little bit, the bolt comes up; if I immediately go back to ten, the bolt goes back down again, because I haven’t yet disturbed the slot. If I keep going away from ten in steps of five, at some point the bolt won’t go back down when I go back to ten: the slot has just been disturbed. The number just before, which still let the bolt go down, is the last number of the combination!
I realized that I could do the same thing to find the second number: As soon as I know the last number, I can turn the wheel around the other way and again, in lumps of five, push the second disc bit by bit until the bolt doesn’t go down. The number just before would be the second number.
If I were very patient I would he able to pick up all three numbers that way, but the amount of work involved in picking up the first number of the combination by this elaborate scheme would be much more than just trying the twenty possible first numbers with the other two numbers that you already know, when the filing cabinet is closed.
I practiced and I practiced until I could get the last two numbers off an open filing cabinet, hardly looking at the dial. Then, when I’d be in some guy’s office discussing some physics problem, I’d lean against his opened filing cabinet, and just like a guy who’s jiggling keys absent-mindedly while he’s talking, I’d just wobble the dial back and forth, back and forth. Sometimes I’d put my finger on the bolt so I wouldn’t have to look to see if it’s coming up. In this way I picked off the last two numbers of various filing cabinets. When I got back to my office I would write the two numbers down on a piece of paper that I kept inside the lock of my filing cabinet. I took the lock apart each time to get the paper—I thought that was a very safe place for them.
After a while my reputation began to sail, because things like this would happen: Somebody would say, “Hey, Feynman! Christy’s out of town and we need a document from his safe—can you open it?”
If it was a safe I knew I didn’t have the last two numbers of, I would simply say, “I’m sorry, but I can’t do it now; I’ve got this work that I have to do.” Otherwise, I would say, “Yeah, but I gotta get my tools.” I didn’t need any tools, but I’d go back to my office, open my filing cabinet, and look at my little piece of paper: “Christy—35, 60.” Then I’d get a screwdriver and go over to Christy’s office and close the door behind me. Obviously not everybody is supposed to be allowed to know how to do this!
I’d he in there alone and I’d open the safe in a few minutes. All I had to do was try the first number at most twenty times, then sit around, reading a magazine or something, for fifteen or twenty minutes. There was no use trying to make it look too easy; somebody would figure out there was a trick to it! After a while I’d open the door and say, “It’s open.”
People thought I was opening the safes from scratch. Now I could maintain the idea, which began with that accident with Staley, that I could open safes cold. Nobody figured out that I was picking the last two numbers off their safes, even though—perhaps because—I was doing it
I often went to Oak Ridge to check up on the safety of the uranium plant. Everything was always in a hurry because it was wartime, and one time I had to go there on a weekend. It was Sunday, and we were in this fella’s office—a general, a head or a vice president of some company, a couple of other big muck-a-mucks, and me. We were gathered together to discuss a report that was in the fella’s safe—a secret safe—. when suddenly he realized that he didn’t know the combination. His secretary was the only one who knew it, so he called her home and it turned out she had gone on a picnic up in the hills.
While all this was going on, I asked, “Do you mind if I fiddle with the safe?”
“Ha, ha, ha—not at all!” So I went over to the safe and started to fool around.
They began to discuss how they could get a car to try to find the secretary, and the guy was getting more and more embarrassed because he had all these people waiting and he was such a jackass he didn’t know how to open his own safe. Everybody was all tense and getting mad at him, when CLICK!—the safe opened.
In 10 minutes I had opened the safe that contained all the secret documents about the plant. They were astonished. The safes were apparently not very safe. It was a terrible shock: All this “eyes only” stuff, top secret, locked in this wonderful secret safe, and this guy opens it in ten minutes!