“Surely You’re Joking, Mr. Feynman”: Adventures of a Curious Character

by Richard Phillips Feynman

  Meanwhile some guys in the computing department came around and one of them said, “Hey, everybody; Feynman’s gonna show Staley how to open a safe, ha, ha, ha!” I wasn’t going to actually open the safe; I was just going to show Staley this way of quickly trying the back two numbers without losing your place and having to set up the first number again.

  I began. “Let’s suppose that the first number is forty, and we’re trying fifteen for the second number. We go back and forth, ten; back five more and forth, ten; and so on. Now we’ve tried all the possible third numbers. Now we try twenty for the second number: we go back and forth, ten; back five more and forth, ten; back five more and forth, CLICK!” My jaw dropped: the first and second numbers happened to be right!

  Nobody saw my expression because my back was towards them. Staley looked very surprised, but both of us caught on Very quickly as to what happened, so I pulled the top drawer out with a flourish and said, “And there you are!”

  Staley said, “I see what you mean; it’s a very good scheme”—and we walked out. Everybody was amazed. It was complete luck. Now I really had a reputation for opening safes.

  It took me about a year and a half to get that far (of course, I was working on the bomb, too!) but I figured that I had the safes beaten, in the sense that if there was a real difficulty—if somebody was lost, or dead, and nobody else knew the combination but the stuff in the filing cabinet was needed—I could open it. After reading what preposterous things the safecrackers claimed, I thought that was a rather respectable accomplishment.

  We had no entertainment there at Los Alamos, and we had to amuse ourselves somehow, so fiddling with the Mosler lock on my filing cabinet was one of my entertainments. One day I made an interesting observation: When the lock is opened and the drawer has been pulled out and the wheel is left on ten (which is what people do when they’ve opened their filing cabinet and are taking papers out of it), the bolt is still down. Now what does that mean, the bolt is still down? It means the bolt is in the slot made by the three discs, which are still properly lined up. Ahhhh!

  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 be 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 be 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 all the time, like a card sharp walking around all the time with a deck of cards.

  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!

  Of course I was able to open the safe because of my perpetual habit of taking the last two numbers off. While in Oak Ridge the month before, I was in the same office when the safe was open and I took the numbers off in an absentminded way—I was always practicing my obsession. Although I hadn’t written them down, I was able to vaguely remember what they were. First I tried 40-15, then 15-40, but neither of those worked. Then I tried 10-45 with all the first numbers, and it opened.

  A similar thing happened on another weekend when I was visiting Oak Ridge. I had written a report that had to be OKed by a colonel, and it was in his safe. Everybody else keeps documents in filing cabinets like the ones at Los Alamos, but he was a colonel, so he had a much fancier, two-door safe with big handles that pull four ľ-inch-thick steel bolts from the frame. The great brass doors swung open and he took out my report to read.

  Not having had an opportunity to see any really good safes, I said to him, “Would you mind, while you’re reading my report, if I looked at your safe?”

  “Go right ahead,” he said, convinced that there was nothing I could do. I looked at the back of one of the solid brass doors, and I discovered that the combination wheel was connected to a little lock that looked exactly the same as the little unit that was on my filing cabinet at Los Alamos. Same company, same little bolt, except that when the bolt came down, the big handles on the safe could then move some rods sideways, and with a hunch of levers you could pull back all those ľ-inch steel rods. The whole lever syst
em, it appeared, depends on the same little bolt that locks filing cabinets.

  Just for the sake of professional perfection, to make sure it was the same, I took the two numbers off the same way I did with the filing cabinet safes.

  Meanwhile, he was reading the report. When he’d finished he said, “All right, it’s fine.” He put the report in the safe, grabbed the big handles, and swung the great brass doors together. It sounds so good when they close, but I know it’s all psychological, because it’s nothing but the same damn lock.

  I couldn’t help but needle him a little bit (I always had a thing about military guys, in such wonderful uniforms) so I said, “The way you close that safe, I get the idea that you think things are safe in there.”

  “Of course.”

  “The only reason you think they’re safe in there is because civilians call it a ‘safe.’ ” (I put the word “civilians” in there to make it sound as if he’d been had by civilians.)

  He got very angry. “What do you mean—it’s not safe?”

  “A good safecracker could open it in thirty minutes.”

  “Can you open it in thirty minutes?”

  “I said a good safecracker. It would take me about forty-five.”

  “Well!” he said. “My wife is waiting at home for me with supper, but I’m gonna stay here and watch you, and you’re gonna sit down there and work on that damn thing for forty-five minutes and not open it!” He sat down in his big leather chair, put his feet up on his desk, and read.

  With complete confidence I picked up a chair, carried it over to the safe and sat down in front of it. I began to turn the wheel at random, just to make some action.

  After about five minutes, which is quite a long time when you’re just sitting and waiting, he lost some patience: “Well, are you making any progress?”

  “With a thing like this, you either open it or you don’t.”

  I figured one or two more minutes would be about time, so I began to work in earnest and two minutes later, CLINK—it opened.

  The colonel’s jaw dropped and his eyes bugged out.

  “Colonel,” I said, in a serious tone, “let me tell you something about these locks: When the door to the safe or the top drawer of the filing cabinet is left open, it’s very easy for someone to get the combination. That’s what I did while you were reading my report, just to demonstrate the danger. You should insist that everybody keep their filing cabinet drawers locked while they’re working, because when they’re open, they’re very, very vulnerable.”

  “Yeah! I see what you mean! That’s very interesting!” We were on the same side after that.

  The next time I went to Oak Ridge, all the secretaries and people who knew who I was were telling me, “Don’t come through here! Don’t come through here!”

  The colonel had sent a note around to everyone in the plant which said, “During his last visit, was Mr. Feynman at any time in your office, near your office, or walking through your office?” Some people answered yes; others said no. The ones who said yes got another note: “Please change the combination of your safe.”

  That was his solution: I was the danger. So they all had to change their combinations on account of me. It’s a pain in the neck to change a combination and remember the new one, so they were all mad at me and didn’t want me to come near them: they might have to change their combination once again. Of course, their filing cabinets were still left open while they were working!

  A library at Los Alamos held all of the documents we had ever worked on: It was a solid, concrete room with a big, beautiful door which had a metal wheel that turns—like a safe-deposit vault. During the war I had tried to look at it closely. I knew the girl who was the librarian, and I begged her to let me play with it a little bit. I was fascinated by it: it was the biggest lock I ever saw! I discovered that I could never use my method of picking off the last two numbers to get in. In fact, while turning the knob while the door was open, I made the lock close, so it was sticking out, and they couldn’t close the door again until the girl came and opened the lock again. That was the end of my fiddling around with that lock. I didn’t have time to figure out how it worked; it was much beyond my capacity.

  During the summer after the war I had some documents to write and work to finish up, so I went back to Los Alamos from Cornell, where I had taught during the year. In the middle of my work I had to refer to a document that I had written before but couldn’t remember, and it was down in the library.

  I went down to get the document, and there was a soldier walking back and forth, with a gun. It was a Saturday, and after the war the library was closed on Saturdays.

  Then I remembered what a good friend of mine, Frederic de Hoffman, had done. He was in the Declassification Section. After the war the army was thinking of declassifying some documents, and he had to go back and forth to the library so much—look at this document, look at that document, check this, check that—that he was going nuts! So he had a copy of every document—all the secrets to the atomic bomb—in nine filing cabinets in his office.

  I went down to his office, and the lights were on. It looked as if whoever was there—perhaps his secretary—had just stepped out for a few minutes, so I waited. While I was waiting I started to fiddle around with the combination wheel on one of the filing cabinets. (By the way, I didn’t have the last two numbers for de Hoffman’s safes; they were put in after the war, after I had left.)

  I started to play with one of the combination wheels and began to think about the safecracker books. I thought to myself, “I’ve never been much impressed by the tricks described in those books, so I’ve never tried them, but let’s see if we can open de Hoffman’s safe by following the book.”

  First trick, the secretary: she’s afraid she’s going to forget the combination, so she writes it down somewhere. I started to look in some of the places mentioned in the book. The desk drawer was locked, but it was an ordinary lock like Leo Lavatelli taught me how to open—ping! I look along the edge: nothing.

  Then I looked through the secretary’s papers. I found a sheet of paper that all the secretaries had, with the Greek letters carefully made—so they could recognize them in mathematical formulas—and named. And there, carelessly written along the top of the paper, was pi = 3.14159. Now, that’s six digits, and why does a secretary have to know the numerical value of pi? It was obvious; there was no other reason!

  I went over to the filing cabinets and tried the first one: 31-41-59. It didn’t open. Then I tried 59-41-31. That didn’t work either. Then 95-14-13. Backwards, forwards, upside down, turn it this way, turn it that—nothing!

  I closed the desk drawer and started to walk out the door, when I thought of the safecracker books again: Next, try the psychology method. I said to myself, “Freddy de Hoffman is just the kind of guy to use a mathematical constant for a safe combination.”

  I went back to the first filing cabinet and tried 27-18-28—CLICK! It opened! (The mathematical constant second in importance to pi is the base of natural logarithms, e:2.71828 …) There were nine filing cabinets, and I had opened the first one, but the document I wanted was in another one—they were in alphabetical order by author. I tried the second filing cabinet: 27-18-28—CLICK! It opened with the same combination. I thought, “This is wonderful! I’ve opened the secrets to the atomic bomb, but if I’m ever going to tell this story, I’ve got to make sure that all the combinations are really the same!” Some of the filing cabinets were in the next room, so I tried 27-18-28 on one of them, and it opened. Now I’d opened three safes—all the same.

  I thought to myself, “Now I could write a safecracker book that would beat every one, because at the beginning I would tell how I opened safes whose contents were bigger and more valuable than what any safecracker anywhere had opened—except for a life, of course—but compared to the furs or the gold bullion, I have them all beat: I opened the safes which contained all the secrets to the atomic bomb: the schedules for the production of the pl
utonium, the purification procedures, how much material is needed, how the bomb works, how the neutrons are generated, what the design is, the dimensions—the entire information that was known at Los Alamos: the whole shmeer! ”

  I went back to the second filing cabinet and took out the document I wanted. Then I took a red grease pencil and a piece of yellow paper that was lying around in the office and wrote, “I borrowed document no. LA4312—Feynman the safecracker.” I put the note on top of the papers in the filing cabinet and closed it.

  Then I went to the first one I had opened and wrote another note: “This one was no harder to open than the other one-Wise Guy” and shut the cabinet.

  Then in the other cabinet, in the other room, I wrote, “When the combinations are all the same, one is no harder to open than another—Same Guy” and I shut that one. I went back to my office and wrote my report.

  That evening I went to the cafeteria and ate supper. There was Freddy de Hoffman. He said he was going over to his office to work, so just for fun I went with him.

  He started to work, and soon he went into the other room to open one of the filing cabinets in there—something I hadn’t counted on—and he happened to open the filing cabinet I had put the third note in, first. He opened the drawer, and he saw this foreign object in there—this bright yellow paper with something scrawled on it in bright red crayon.

  I had read in books that when somebody is afraid, his face gets sallow, but I had never seen it before. Well, it’s absolutely true. His face turned a gray, yellow green—it was really frightening to see. He picked up the paper, and his hand was shaking. “L-l-look at this!” he said, trembling.

  The note said, “When the combinations are all the same, one is no harder to open than another—Same Guy.”

  “What does it mean?” I said.