A little bit later he tried again. “There are some generals coming. They are going to put off some of us number threes.”
“It’s all right,” I said. “I’m a number two.”
He probably wrote to his congressman—if he wasn’t a congressman himself—saying, “What are they doing sending these little kids around with number two priorities in the middle of the war?”
At any rate, I arrived at Oak Ridge. The first thing I did was have them take me to the plant, and I said nothing. I just looked at everything. I found out that the situation was even worse than Segre reported, because he noticed certain boxes in big lots in a room, but he didn’t notice a lot of boxes in another room on the other side of the same wall—and things like that. Now, if you have too much stuff together, it goes up, you see.
So I went through the entire plant. I have a very bad memory but when I work intensively I have a good shortterm memory and so I could remember all kinds of crazy things like building 90-207, vat number so-and-so, and so forth.
I went to my room that night, and went through the whole thing, explained where all the dangers were, and what you would have to do to fix this. It’s rather easy. You put cadmium in solutions to absorb the neutrons in the water, and you separate the boxes so they are not too dense, according to certain rules.
The next day there was going to be a big meeting. I forgot to say that before I left Los Alamos Oppenheimer said to me, “Now, the following people are technically able down there at Oak Ridge: Mr. Julian Webb, Mr. So-and-so, and so on. I want you to make sure that these people are at the meeting, that you tell them how the thing can he made safe, so that they really understand.”
I said, “What if they’re not at the meeting? What am I supposed to do?”
He said, “Then you should say: Los Alamos cannot accept the responsibility for the safety of the Oak Ridge plant unless—!”
I said, “You mean me, little Richard, is going to go in there and say—?”
He said, “Yes, little Richard, you go and do that.”
I really grew up fast!
When I arrived, sure enough, the big shots in the company and the technical people that I wanted were there, and the generals and everyone who was interested in this very serious problem. That was good because the plant would have blown up if nobody had paid attention to this problem.
There was a Lieutenant Zumwalt who took care of me. He told me that the colonel said I shouldn’t tell them how the neutrons work and all the details because we want to keep things separate, so just tell them what to do to keep it safe.
I said, “In my opinion it is impossible for them to obey a bunch of rules unless they understand how it works. It’s my opinion that it’s only going to work if I tell them, and Los Alamos cannot accept the responsibility for the safety of the Oak Ridge plant unless they are fully informed as to how it works! ”
It was great. The lieutenant takes me to the colonel and repeats my remark. The colonel says, “Just five minutes,” and then he goes to the window and he stops and thinks. That’s what they’re very good at—making decisions. I thought it was very remarkable how a problem of whether or not information as to how the bomb works should be in the Oak Ridge plant had to be decided and could be decided in five minutes. So I have a great deal of respect for these military guys, because I never can decide anything very important in any length of time at all.
In five minutes he said, “All right, Mr. Feynman, go ahead.”
I sat down and I told them all about neutrons, how they worked, da da, ta ta ta, there are too many neutrons together, you’ve got to keep the material apart, cadmium absorbs, and slow neutrons are more effective than fast neutrons, and yak yak—all of which was elementary stuff at Los Alamos, but they had never heard of any of it, so I appeared to be a tremendous genius to them.
The result was that they decided to set up little groups to make their own calculations to learn how to do it. They started to redesign plants, and the designers of the plants were there, the construction designers, and engineers, and chemical engineers for the new plant that was going to handle the separated material.
They told me to come back in a few months, so I came back when the engineers had finished the design of the plant. Now it was for me to look at the plant.
How do you look at a plant that isn’t built yet? I don’t know. Lieutenant Zumwalt, who was always coming around with me because I had to have an escort everywhere, takes me into this room where there are these two engineers and a loooooong table covered with a stack of blueprints representing the various floors of the proposed plant.
I took mechanical drawing when I was in school, but I am not good at reading blueprints. So they unroll the stack of blueprints and start to explain it to me, thinking I am a genius. Now, one of the things they had to avoid in the plant was accumulation. They had problems like when there’s an evaporator working, which is trying to accumulate the stuff, if the valve gets stuck or something like that and too much stuff accumulates, it’ll explode. So they explained to me that this plant is designed so that if any one valve gets stuck nothing will happen. It needs at least two valves everywhere.
Then they explain how it works. The carbon tetrachloride comes in here, the uranium nitrate from here comes in here, it goes up and down, it goes up through the floor, comes up through the pipes, coming up from the second floor, bluuuuurp—going through the stack of blueprints, downup-down-up, talking very fast, explaining the very very complicated chemical plant.
I’m completely dazed. Worse, I don’t know what the symbols on the blueprint mean! There is some kind of a thing that at first I think is a window. It’s a square with a little cross in the middle, all over the damn place. I think it’s a window, but no, it can’t be a window, because it isn’t always at the edge. I want to ask them what it is.
You must have been in a situation like this when you didn’t ask them right away. Right away it would have been OK. But now they’ve been talking a little bit too long. You hesitated too long. If you ask them now they’ll say “What are you wasting my time all this time for?”
What am I going to do? I get an idea. Maybe it’s a valve.
I take my finger and I put it down on one of the mysterious little crosses in the middle of one of the blueprints on page three, and I say “What happens if this valve gets stuck?”—figuring they’re going to say “That’s not a valve, sir, that’s a window.”
So one looks at the other and says, “Well, if that valve gets stuck—” and he goes up and down on the blueprint, up and down, the other guy goes up and down, back and forth, back and forth, and they both look at each other. They turn around to me and they open their mouths like astonished fish and say “You’re absolutely right, sir.”
So they rolled up the blueprints and away they went and we walked out. And Mr. Zumwalt, who had been following me all the way through, said, “You’re a genius. I got the idea you were a genius when you went through the plant once and you could tell them about evaporator C-21 in building 90-207 the next morning,” he says, “but what you have just done is so fantastic I want to know how, how do you do that?”
I told him you try to find out whether it’s a valve or not.
Another kind of problem I worked on was this. We had to do lots of calculations, and we did them on Marchant calculating machines. By the way, just to give you an idea of what Los Alamos was like: We had these Marchant computers—hand calculators with numbers. You push them, and they multiply divide, add, and so on, but not easy like they do now. They were mechanical gadgets, failing often, and they had to be sent back to the factory to be repaired. Pretty soon you were running out of machines. A few of us started to take the covers off. (We weren’t supposed to. The rules read: “You take the covers off, we cannot be responsible …”) So we took the covers off and we got a nice series of lessons on how to fix them, and we got better and better at it as we got more and more elaborate repairs. When we got something too complicated, we sent it back to the factory but we’d do the easy ones and kept the things going. I ended up doing all the computers and there was a guy in the machine shop who took care of typewriters.
Anyway we decided that the big problem—which was to figure out exactly what happened during the bomb’s implosion, so you can figure out exactly how much energy was released and so on—required much more calculating than we were capable of. A clever fellow by the name of Stanley Frankel realized that it could possibly he done on IBM machines. The IBM company had machines for business purposes, adding machines called tabulators for listing sums, and a multiplier that you put cards in and it would take two numbers from a card and multiply them. There were also collators and sorters and so on.
So Frankel figured out a nice program. If we got enough of these machines in a room, we could take the cards and put them through a cycle. Everybody who does numerical calculations now knows exactly what I’m talking about, but this was kind of a new thing then—mass production with machines. We had done things like this on adding machines. Usually you go one step across, doing everything yourself. But this was different—where you go first to the adder, then to the multiplier, then to the adder, and so on. So Frankel designed this system and ordered the machines from the IBM company because we realized it was a good way of solving our problems.
We needed a man to repair the machines, to keep them going and everything. And the army was always going to send this fellow they had, but he was always delayed. Now, we always were in a hurry. Everything we did, we tried to do as quickly as possible. In this particular case, we worked out all the numerical steps that the machines were supposed to do—multiply this, and then do this, and subtract that. Then we worked out the program, but we didn’t have any machine to test it on. So we set up this room with girls in it. Each one had a Marchant: one was the multiplier, another was the adder. This one cubed—all she did was cube a number on an index card and send it to the next girl.
We went through our cycle this way until we got all the bugs out. It turned out that the speed at which we were able to do it was a hell of a lot faster than the other way where every single person did all the steps. We got speed with this system that was the predicted speed for the IBM machine. The only difference is that the IBM machines didn’t get tired and could work three shifts. But the girls got tired after a while.
Anyway we got the bugs out during this process, and finally the machines arrived, but not the repairman. These were some of the most complicated machines of the technology of those days, big things that came partially disassembled, with lots of wires and blueprints of what to do. We went down and we put them together, Stan Frankel and I and another fellow, and we had our troubles. Most of the trouble was the big shots coming in all the time and saying, “You’re going to break something!”
We put them together, and sometimes they would work, and sometimes they were put together wrong and they didn’t work. Finally I was working on some multiplier and I saw a bent part inside, but I was afraid to straighten it because it might snap off—and they were always telling us we were going to bust something irreversibly. When the repairman finally got there, he fixed the machines we hadn’t got ready and everything was going. But he had trouble with the one that I had had trouble with. After three days he was still working on that one last machine.
I went down. I said, “Oh, I noticed that was bent.”
He said, “Oh, of course. That’s all there is to it!” Bend! It was all right. So that was it.
Well, Mr. Frankel, who started this program, began to suffer from the computer disease that anybody who works with computers now knows about. It’s a very serious disease and it interferes completely with the work. The trouble with computers is you play with them. They are so wonderful. You have these switches—if it’s an even number you do this, if it’s an odd number you do that—and pretty soon you can do more and more elaborate things if you are clever enough, on one machine.
After a while the whole system broke down. Frankel wasn’t paying any attention; he wasn’t supervising anybody. The system was going very, very slowly—while he was sitting in a room figuring out how to make one tabulator automatically print arc-tangent X, and then it would start and it would print columns and then bitsi, bitsi, bitsi, and calculate the arc-tangent automatically by integrating as it went along and make a whole table in one operation.
Absolutely useless. We had tables of arc-tangents. But if you’ve ever worked with computers, you understand the disease—the delight in being able to see how much you can do. But he got the disease for the first time, the poor fellow who invented the thing.
I was asked to stop working on the stuff I was doing in my group and go down and take over the IBM group, and I tried to avoid the disease. And, although they had done only three problems in nine months, I had a very good group.
The real trouble was that no one had ever told these fellows anything. The army had selected them from all over the country for a thing called Special Engineer Detachment—clever boys from high school who had engineering ability. They sent them up to Los Alamos. They put them in barracks. And they would tell them nothing.
Then they came to work, and what they had to do was work on IBM machines—punching holes, numbers that they didn’t understand. Nobody told them what it was. The thing was going very slowly. I said that the first thing there has to be is that these technical guys know what we’re doing. Oppenheimer went and talked to the security and got special permission so I could give a nice lecture about what we were doing, and they were all excited: “We’re fighting a war! We see what it is!” They knew what the numbers meant. If the pressure came out higher, that meant there was more energy released, and so on and so on. They knew what they were doing.
Complete transformation! They began to invent ways of doing it better. They improved the scheme. They worked at night. They didn’t need supervising in the night; they didn’t need anything. They understood everything; they invented several of the programs that we used.
So my boys really came through, and all that had to be done was to tell them what it was. As a result, although it took them nine months to do three problems before, we did nine problems in three months, which is nearly ten times as fast.
But one of the secret ways we did our problems was this. The problems consisted of a hunch of cards that had to go through a cycle. First add, then multiply—and so it went through the cycle of machines in this room, slowly, as it went around and around. So we figured a way to put a different colored set of cards through a cycle too, but out of phase. We’d do two or three problems at a time.
But this got us into another problem. Near the end of the war, for instance, just before we had to make a test in Albuquerque, the question was: How much energy would be released? We had been calculating the release from various designs, but we hadn’t computed for the specific design that was ultimately used. So Bob Christy came down and said, “We would like the results for how this thing is going to work in one month”—or some very short time, like three weeks.
I said, “It’s impossible.”
He said, “Look, you’re putting out nearly two problems a month. It takes only two weeks per problem, or three weeks per problem.”
I said, “I know. It really takes much longer to do the problem, but we’re doing them in parallel. As they go through, it takes a long time and there’s no way to make it go around faster.”
He went out, and I began to think. Is there a way to make it go around faster? What if we did nothing else on the machine, so nothing else was interfering? I put a challenge to the boys on the blackboard—CAN WE DO IT? They all start yelling, “Yes, we’ll work double shifts, we’ll work overtime,” all this kind of thing. “We’ll try it. We’ll try it!”
And so the rule was: All other problems out. Only one problem and just concentrate on this one. So they started to work.
My wife, Arlene, was ill with tuberculosis—very ill indeed. It looked as if something might happen at any minute, so I arranged ahead of time with a friend of mine in the dormitory to borrow his car in an emergency so I could get to Albuquerque quickly. His name was Klaus Fuchs. He was the spy, and he used his automobile to take the atomic secrets away from Los Alamos down to Santa Fe. But nobody knew that.
The emergency arrived. I borrowed Fuchs’s car and picked up a couple of hitchhikers, in case something happened with the car on the way to Albuquerque. Sure enough, just as we were driving into Santa Fe, we got a flat tire. The two guys helped me change the tire, and just as we were leaving Santa Fe, another tire went flat. We pushed the car into a nearby gas station.
The gas station guy was repairing somebody else’s car, and it was going to take a while before he could help us. I didn’t even think to say anything, but the two hitchhikers went over to the gas station man and told him the situation. Soon we had a new tire (but no spare—tires were hard to get during the war).
About thirty miles outside Albuquerque a third tire went flat, so I left the car on the road and we hitchhiked the rest of the way. I phoned a garage to go out and get the car while I went to the hospital to see my wife.
Arlene died a few hours after I got there. A nurse came in to fill out the death certificate, and went out again. I spent a little more time with my wife. Then I looked at the clock I had given her seven years before, when she had first become sick with tuberculosis. It was something which in those days was very nice: a digital clock whose numbers would change by turning around mechanically. The clock was very delicate and often stopped for one reason or another—I had to repair it from time to time—but I kept it going for all those years. Now, it had stopped once more—at 9:22, the time on the death certificate!
I remembered the time I was in my fraternity house at MIT when the idea came into my head completely out of the blue that my grandmother was dead. Right after that there was a telephone call, just like that. It was for Pete Bernays—my grandmother wasn’t dead. So I remembered that, in case somebody told me a story that ended the other way. I figured that such things can sometimes happen by luck—after all, my grandmother was very old—although people might think they happened by some sort of supernatural phenomenon.
Arlene had kept this clock by her bedside all the time she was sick, and now it stopped the moment she died. I can understand how a person who half believes in the possibility of such things, and who hasn’t got a doubting mind—especially in a circumstance like that—doesn’t immediately try to figure out what happened, but instead explains that no one touched the clock, and there was no possibility of explanation by normal phenomena. The clock simply stopped. It would become a dramatic example of these fantastic phenomena.
I saw that the light in the room was low, and then I remembered that the nurse had picked up the clock and turned it toward the light to see the face better. That could easily have stopped it.
I went for a walk outside. Maybe I was fooling myself, but I was surprised how I didn’t feel what I thought people would expect to feel under the circumstances. I wasn’t delighted, but I didn’t feel terribly upset, perhaps because I had known for seven years that something like this was going to happen.
I didn’t know how I was going to face all my friends up at Los Alamos. I didn’t want people with long faces talking to me about it. When I got back (yet another tire went flat on the way), they asked me what happened.
“She’s dead. And how’s the program going?”
They caught on right away that I didn’t want to moon over it.
(I had obviously done something to myself psychologically: Reality was so important—I had to understand what really happened to Arlene, physiologically—that I didn’t cry until a number of months later, when I was in Oak Ridge. I was walking past a department store with dresses in the window, and I thought Arlene would like one of them. That was too much for me.)
When I went back to work on the calculation program, I found it in a mess: There were white cards, there were blue cards, there were yellow cards, and I started to say, “You’re not supposed to do more than one problem—only one problem!” They said, “Get out, get out, get out. Wait—and we’ll explain everything.”
So I waited, and what happened was this. As the cards went through, sometimes the machine made a mistake, or they put a wrong number in. What we used to have to do when that happened was to go back and do it over again. But they noticed that a mistake made at some point in one cycle only affects the nearby numbers, the next cycle affects the nearby numbers, and so on. It works its way through the pack of cards. If you have fifty cards and you make a mistake at card number thirty-nine, it affects thirty-seven, thirty-eight, and thirty-nine. The next, card thirty-six, thirty-seven, thirty-eight, thirty-nine, and forty. The next time it spreads like a disease.
So they found an error back a way, and they got an idea. They would only compute a small deck of ten cards around the error. And because ten cards could he put through the machine faster than the deck of fifty cards, they would go rapidly through with this other deck while they continued with the fifty cards with the disease spreading. But the other thing was computing faster, and they would seal it all up and correct it. Very clever.
That was the way those guys worked to get speed. There was no other way. If they had to stop to try to fix it, we’d have lost time. We couldn’t have got it. That was what they were doing.
Of course, you know what happened while they were doing that. They found an error in the blue deck. And so they had a yellow deck with a little fewer cards; it was going around faster than the blue deck. Just when they are going crazy—because after they get this straightened out, they have to fix the white deck—the boss comes walking in.
“Leave us alone,” they say. I left them alone and everything came out. We solved the problem in time and that’s the way it was.
I was an underling at the beginning. Later I became a group leader. And I met some very great men. It is one of the great experiences of my life to have met all these wonderful physicists.
There was, of course, Enrico Fermi. He came down once from Chicago, to consult a little bit, to help us if we had some problems. We had a meeting with him, and I had been doing some calculations and gotten some results. The calculations were so elaborate it was very difficult. Now, usually I was the expert at this; I could always tell you what the answer was going to look like, or when I got it I could explain why. But this thing was so complicated I couldn’t explain why it was like that.
So I told Fermi I was doing this problem, and I started to describe the results. He said, “Wait, before you tell me the result, let me think. It’s going to come out like this (he was right), and it’s going to come out like this because of so and so. And there’s a perfectly obvious explanation for this—”
He was doing what I was supposed to be good at, ten times better. That was quite a lesson to me.
Then there was John von Neumann, the great mathematician. We used to go for walks on Sunday. We’d walk in the canyons, often with Bethe and Bob Bacher. It was a great pleasure. And von Neumann gave me an interesting idea: that you don’t have to be responsible for the world that you’re in. So I have developed a very powerful sense of social irresponsibility as a result of von Neumann’s advice. It’s made me a very happy man ever since. But it was von Neumann who put the seed in that grew into my active irresponsibility!
I also met Niels Bohr. His name was Nicholas Baker in those days, and he came to Los Alamos with Jim Baker, his son, whose name is really Aage Bohr. They came from Denmark, and they were very famous physicists, as you know. Even to the big shot guys, Bohr was a great god.
We were at a meeting once, the first time he came, and everybody wanted to see the great Bohr. So there were a lot of people there, and we were discussing the problems of the bomb. I was back in a corner somewhere. He came and went, and all I could see of him was from between people’s heads.
In the morning of the day he’s due to come next time, I get a telephone call.
“Hello—Feynman?”
“Yes.”
“This is Jim Baker.” It’s his son. “My father and I would like to speak to you.”
“Me? I’m Feynman, I’m just a—”
“That’s right. Is eight o’clock OK?”
So, at eight o’clock in the morning, before anybody’s awake, I go down to the place. We go into an office in the technical area and he says, “We have been thinking how we could make the bomb more efficient and we think of the following idea.”
I say, “No, it’s not going to work. It’s not efficient… Blab, blab, blah.”
So he says, “How about so and so?”
I said, “That sounds a little bit better, but it’s got this damn fool idea in it.”
This went on for about two hours, going back and forth over lots of ideas, back and forth, arguing. The great Niels kept lighting his pipe; it always went out. And he talked in a way that was un-understandable—mumble, mumble, hard to understand. His son I could understand better.
“Well,” he said finally, lighting his pipe, “I guess we can call in the big shots now.” So then they called all the other guys and had a discussion with them.
Then the son told me what happened. The last time he was there, Bohr said to his son, “Remember the name of that little fellow in the back over there? He’s the only guy who’s not afraid of me, and will say when I’ve got a crazy idea. So next time when we want to discuss ideas, we’re not going to be able to do it with these guys who say everything is yes, yes, Dr. Bohr. Get that guy and we’ll talk with him first.”
I was always dumb in that way. I never knew who I was talking to. I was always worried about the physics. If the idea looked lousy, I said it looked lousy. If it looked good, I said it looked good. Simple proposition.
I’ve always lived that way. It’s nice, it’s pleasant—if you can do it. I’m lucky in my life that I can do this.
After we’d made the calculations, the next thing that happened, of course, was the test. I was actually at home on a short vacation at that time, after my wife died, and so I got a message that said, “The baby is expected on such and such a day.”
I flew back, and I arrived just when the buses were leaving, so I went straight out to the site and we waited out there, twenty miles away. We had a radio, and they were supposed to tell us when the thing was going to go off and so forth, but the radio wouldn’t work, so we never knew what was happening. But just a few minutes before it was supposed to go off the radio started to work, and they told us there was twenty seconds or something to go, for people who were far away like we were. Others were closer, six miles away.
They gave out dark glasses that you could watch it with. Dark glasses! Twenty miles away, you couldn’t see a damn thing through dark glasses. So I figured the only thing that could really hurt your eyes (bright light can never hurt your eyes) is ultraviolet light. I got behind a truck windshield, because the ultraviolet can’t go through glass, so that would be safe, and so I could see the damn thing.
Time comes, and this tremendous flash out there is so bright that I duck, and I see this purple splotch on the floor of the truck. I said, “That’s not it. That’s an after-image.” So I look back up, and I see this white light changing into yellow and then into orange. Clouds form and disappear again—from the compression and expansion of the shock wave.
Finally, a big ball of orange, the center that was so bright, becomes a ball of orange that starts to rise and billow a little bit and get a little black around the edges, and then you see it’s a big ball of smoke with flashes on the inside, with the heat of the fire going outwards.
All this took about one minute. It was a series from bright to dark, and I had seen it. I am about the only guy who actually looked at the damn thing—the first Trinity test. Everybody else had dark glasses, and the people at six miles couldn’t see it because they were all told to lie on the floor. I’m probably the only guy who saw it with the human eye.
Finally, after about a minute and a half, there’s suddenly a tremendous noise—BANG, and then a rumble, like thunder—and that’s what convinced me. Nobody had said a word during this whole thing. We were all just watching quietly. But this sound released everybody—released me particularly because the solidity of the sound at that distance meant that it had really worked.
The man standing next to me said, “What’s that?”
I said, “That was the Bomb.”
The man was William Laurence. He was there to write an article describing the whole situation. I had been the one who was supposed to have taken him around. Then it was found that it was too technical for him, and so later H. D. Smyth came and I showed him around. One thing we did, we went into a room and there on the end of a narrow pedestal was a small silver-plated ball. You could put your hand on it. It was warm. It was radioactive. It was plutonium. And we stood at the door of this room, talking about it. This was a new element that was made by man, that had never existed on the earth before, except for a very short period possibly at the very beginning. And here it was all isolated and radioactive and had these properties. And we had made it. And so it was tremendously valuable.
Meanwhile, you know how people do when they talk—you kind of jiggle around and so forth. He was kicking the doorstop, you see, and I said, “Yes, the doorstop certainly is appropriate for this door.” The doorstop was a ten-inch hemisphere of yellowish metal—gold, as a matter of fact.
What had happened was that we needed to do an experiment to see how many neutrons were reflected by different materials, in order to save the neutrons so we didn’t use so much material. We had tested many different materials. We had tested platinum, we had tested zinc, we had tested brass, we had tested gold. So, in making the tests with the gold, we had these pieces of gold and somebody had the clever idea of using that great ball of gold for a doorstop for the door of the room that contained the plutonium.
After the thing went off, there was tremendous excitement at Los Alamos. Everybody had parties, we all ran around. I sat on the end of a jeep and beat drums and so on. But one man, I remember, Bob Wilson, was just sitting there moping.
I said, “What are you moping about?”
He said, “It’s a terrible thing that we made.”
I said, “But you started it. You got us into it.”
You see, what happened to me-what happened to the rest of us—is we started for a good reason, then you’re working very hard to accomplish something and it’s a pleasure, it’s excitement. And you stop thinking, you know; you just stop. Bob Wilson was the only one who was still thinking about it, at that moment.
I returned to civilization shortly after that and went to Cornell to teach, and my first impression was a very strange one. I can’t understand it any more, but I felt very strongly then. I sat in a restaurant in New York, for example, and I looked out at the buildings and I began to think, you know, about how much the radius of the Hiroshima bomb damage was and so forth … How far from here was 34th Street? … All those buildings, all smashed—and so on. And I would go along and I would see people building a bridge, or they’d be making a new road, and I thought, they’re crazy, they just don’t understand, they don’t understand. Why are they making new things? It’s so useless.
But, fortunately, it’s been useless for almost forty years now, hasn’t it? So I’ve been wrong about it being useless making bridges and I’m glad those other people had the sense to go ahead.
Safecracker Meets Safecracker
“It’s all right,” I said. “I’m a number two.”
He probably wrote to his congressman—if he wasn’t a congressman himself—saying, “What are they doing sending these little kids around with number two priorities in the middle of the war?”
At any rate, I arrived at Oak Ridge. The first thing I did was have them take me to the plant, and I said nothing. I just looked at everything. I found out that the situation was even worse than Segre reported, because he noticed certain boxes in big lots in a room, but he didn’t notice a lot of boxes in another room on the other side of the same wall—and things like that. Now, if you have too much stuff together, it goes up, you see.
So I went through the entire plant. I have a very bad memory but when I work intensively I have a good shortterm memory and so I could remember all kinds of crazy things like building 90-207, vat number so-and-so, and so forth.
I went to my room that night, and went through the whole thing, explained where all the dangers were, and what you would have to do to fix this. It’s rather easy. You put cadmium in solutions to absorb the neutrons in the water, and you separate the boxes so they are not too dense, according to certain rules.
The next day there was going to be a big meeting. I forgot to say that before I left Los Alamos Oppenheimer said to me, “Now, the following people are technically able down there at Oak Ridge: Mr. Julian Webb, Mr. So-and-so, and so on. I want you to make sure that these people are at the meeting, that you tell them how the thing can he made safe, so that they really understand.”
I said, “What if they’re not at the meeting? What am I supposed to do?”
He said, “Then you should say: Los Alamos cannot accept the responsibility for the safety of the Oak Ridge plant unless—!”
I said, “You mean me, little Richard, is going to go in there and say—?”
He said, “Yes, little Richard, you go and do that.”
I really grew up fast!
When I arrived, sure enough, the big shots in the company and the technical people that I wanted were there, and the generals and everyone who was interested in this very serious problem. That was good because the plant would have blown up if nobody had paid attention to this problem.
There was a Lieutenant Zumwalt who took care of me. He told me that the colonel said I shouldn’t tell them how the neutrons work and all the details because we want to keep things separate, so just tell them what to do to keep it safe.
I said, “In my opinion it is impossible for them to obey a bunch of rules unless they understand how it works. It’s my opinion that it’s only going to work if I tell them, and Los Alamos cannot accept the responsibility for the safety of the Oak Ridge plant unless they are fully informed as to how it works! ”
It was great. The lieutenant takes me to the colonel and repeats my remark. The colonel says, “Just five minutes,” and then he goes to the window and he stops and thinks. That’s what they’re very good at—making decisions. I thought it was very remarkable how a problem of whether or not information as to how the bomb works should be in the Oak Ridge plant had to be decided and could be decided in five minutes. So I have a great deal of respect for these military guys, because I never can decide anything very important in any length of time at all.
In five minutes he said, “All right, Mr. Feynman, go ahead.”
I sat down and I told them all about neutrons, how they worked, da da, ta ta ta, there are too many neutrons together, you’ve got to keep the material apart, cadmium absorbs, and slow neutrons are more effective than fast neutrons, and yak yak—all of which was elementary stuff at Los Alamos, but they had never heard of any of it, so I appeared to be a tremendous genius to them.
The result was that they decided to set up little groups to make their own calculations to learn how to do it. They started to redesign plants, and the designers of the plants were there, the construction designers, and engineers, and chemical engineers for the new plant that was going to handle the separated material.
They told me to come back in a few months, so I came back when the engineers had finished the design of the plant. Now it was for me to look at the plant.
How do you look at a plant that isn’t built yet? I don’t know. Lieutenant Zumwalt, who was always coming around with me because I had to have an escort everywhere, takes me into this room where there are these two engineers and a loooooong table covered with a stack of blueprints representing the various floors of the proposed plant.
I took mechanical drawing when I was in school, but I am not good at reading blueprints. So they unroll the stack of blueprints and start to explain it to me, thinking I am a genius. Now, one of the things they had to avoid in the plant was accumulation. They had problems like when there’s an evaporator working, which is trying to accumulate the stuff, if the valve gets stuck or something like that and too much stuff accumulates, it’ll explode. So they explained to me that this plant is designed so that if any one valve gets stuck nothing will happen. It needs at least two valves everywhere.
Then they explain how it works. The carbon tetrachloride comes in here, the uranium nitrate from here comes in here, it goes up and down, it goes up through the floor, comes up through the pipes, coming up from the second floor, bluuuuurp—going through the stack of blueprints, downup-down-up, talking very fast, explaining the very very complicated chemical plant.
I’m completely dazed. Worse, I don’t know what the symbols on the blueprint mean! There is some kind of a thing that at first I think is a window. It’s a square with a little cross in the middle, all over the damn place. I think it’s a window, but no, it can’t be a window, because it isn’t always at the edge. I want to ask them what it is.
You must have been in a situation like this when you didn’t ask them right away. Right away it would have been OK. But now they’ve been talking a little bit too long. You hesitated too long. If you ask them now they’ll say “What are you wasting my time all this time for?”
What am I going to do? I get an idea. Maybe it’s a valve.
I take my finger and I put it down on one of the mysterious little crosses in the middle of one of the blueprints on page three, and I say “What happens if this valve gets stuck?”—figuring they’re going to say “That’s not a valve, sir, that’s a window.”
So one looks at the other and says, “Well, if that valve gets stuck—” and he goes up and down on the blueprint, up and down, the other guy goes up and down, back and forth, back and forth, and they both look at each other. They turn around to me and they open their mouths like astonished fish and say “You’re absolutely right, sir.”
So they rolled up the blueprints and away they went and we walked out. And Mr. Zumwalt, who had been following me all the way through, said, “You’re a genius. I got the idea you were a genius when you went through the plant once and you could tell them about evaporator C-21 in building 90-207 the next morning,” he says, “but what you have just done is so fantastic I want to know how, how do you do that?”
I told him you try to find out whether it’s a valve or not.
Another kind of problem I worked on was this. We had to do lots of calculations, and we did them on Marchant calculating machines. By the way, just to give you an idea of what Los Alamos was like: We had these Marchant computers—hand calculators with numbers. You push them, and they multiply divide, add, and so on, but not easy like they do now. They were mechanical gadgets, failing often, and they had to be sent back to the factory to be repaired. Pretty soon you were running out of machines. A few of us started to take the covers off. (We weren’t supposed to. The rules read: “You take the covers off, we cannot be responsible …”) So we took the covers off and we got a nice series of lessons on how to fix them, and we got better and better at it as we got more and more elaborate repairs. When we got something too complicated, we sent it back to the factory but we’d do the easy ones and kept the things going. I ended up doing all the computers and there was a guy in the machine shop who took care of typewriters.
Anyway we decided that the big problem—which was to figure out exactly what happened during the bomb’s implosion, so you can figure out exactly how much energy was released and so on—required much more calculating than we were capable of. A clever fellow by the name of Stanley Frankel realized that it could possibly he done on IBM machines. The IBM company had machines for business purposes, adding machines called tabulators for listing sums, and a multiplier that you put cards in and it would take two numbers from a card and multiply them. There were also collators and sorters and so on.
So Frankel figured out a nice program. If we got enough of these machines in a room, we could take the cards and put them through a cycle. Everybody who does numerical calculations now knows exactly what I’m talking about, but this was kind of a new thing then—mass production with machines. We had done things like this on adding machines. Usually you go one step across, doing everything yourself. But this was different—where you go first to the adder, then to the multiplier, then to the adder, and so on. So Frankel designed this system and ordered the machines from the IBM company because we realized it was a good way of solving our problems.
We needed a man to repair the machines, to keep them going and everything. And the army was always going to send this fellow they had, but he was always delayed. Now, we always were in a hurry. Everything we did, we tried to do as quickly as possible. In this particular case, we worked out all the numerical steps that the machines were supposed to do—multiply this, and then do this, and subtract that. Then we worked out the program, but we didn’t have any machine to test it on. So we set up this room with girls in it. Each one had a Marchant: one was the multiplier, another was the adder. This one cubed—all she did was cube a number on an index card and send it to the next girl.
We went through our cycle this way until we got all the bugs out. It turned out that the speed at which we were able to do it was a hell of a lot faster than the other way where every single person did all the steps. We got speed with this system that was the predicted speed for the IBM machine. The only difference is that the IBM machines didn’t get tired and could work three shifts. But the girls got tired after a while.
Anyway we got the bugs out during this process, and finally the machines arrived, but not the repairman. These were some of the most complicated machines of the technology of those days, big things that came partially disassembled, with lots of wires and blueprints of what to do. We went down and we put them together, Stan Frankel and I and another fellow, and we had our troubles. Most of the trouble was the big shots coming in all the time and saying, “You’re going to break something!”
We put them together, and sometimes they would work, and sometimes they were put together wrong and they didn’t work. Finally I was working on some multiplier and I saw a bent part inside, but I was afraid to straighten it because it might snap off—and they were always telling us we were going to bust something irreversibly. When the repairman finally got there, he fixed the machines we hadn’t got ready and everything was going. But he had trouble with the one that I had had trouble with. After three days he was still working on that one last machine.
I went down. I said, “Oh, I noticed that was bent.”
He said, “Oh, of course. That’s all there is to it!” Bend! It was all right. So that was it.
Well, Mr. Frankel, who started this program, began to suffer from the computer disease that anybody who works with computers now knows about. It’s a very serious disease and it interferes completely with the work. The trouble with computers is you play with them. They are so wonderful. You have these switches—if it’s an even number you do this, if it’s an odd number you do that—and pretty soon you can do more and more elaborate things if you are clever enough, on one machine.
After a while the whole system broke down. Frankel wasn’t paying any attention; he wasn’t supervising anybody. The system was going very, very slowly—while he was sitting in a room figuring out how to make one tabulator automatically print arc-tangent X, and then it would start and it would print columns and then bitsi, bitsi, bitsi, and calculate the arc-tangent automatically by integrating as it went along and make a whole table in one operation.
Absolutely useless. We had tables of arc-tangents. But if you’ve ever worked with computers, you understand the disease—the delight in being able to see how much you can do. But he got the disease for the first time, the poor fellow who invented the thing.
I was asked to stop working on the stuff I was doing in my group and go down and take over the IBM group, and I tried to avoid the disease. And, although they had done only three problems in nine months, I had a very good group.
The real trouble was that no one had ever told these fellows anything. The army had selected them from all over the country for a thing called Special Engineer Detachment—clever boys from high school who had engineering ability. They sent them up to Los Alamos. They put them in barracks. And they would tell them nothing.
Then they came to work, and what they had to do was work on IBM machines—punching holes, numbers that they didn’t understand. Nobody told them what it was. The thing was going very slowly. I said that the first thing there has to be is that these technical guys know what we’re doing. Oppenheimer went and talked to the security and got special permission so I could give a nice lecture about what we were doing, and they were all excited: “We’re fighting a war! We see what it is!” They knew what the numbers meant. If the pressure came out higher, that meant there was more energy released, and so on and so on. They knew what they were doing.
Complete transformation! They began to invent ways of doing it better. They improved the scheme. They worked at night. They didn’t need supervising in the night; they didn’t need anything. They understood everything; they invented several of the programs that we used.
So my boys really came through, and all that had to be done was to tell them what it was. As a result, although it took them nine months to do three problems before, we did nine problems in three months, which is nearly ten times as fast.
But one of the secret ways we did our problems was this. The problems consisted of a hunch of cards that had to go through a cycle. First add, then multiply—and so it went through the cycle of machines in this room, slowly, as it went around and around. So we figured a way to put a different colored set of cards through a cycle too, but out of phase. We’d do two or three problems at a time.
But this got us into another problem. Near the end of the war, for instance, just before we had to make a test in Albuquerque, the question was: How much energy would be released? We had been calculating the release from various designs, but we hadn’t computed for the specific design that was ultimately used. So Bob Christy came down and said, “We would like the results for how this thing is going to work in one month”—or some very short time, like three weeks.
I said, “It’s impossible.”
He said, “Look, you’re putting out nearly two problems a month. It takes only two weeks per problem, or three weeks per problem.”
I said, “I know. It really takes much longer to do the problem, but we’re doing them in parallel. As they go through, it takes a long time and there’s no way to make it go around faster.”
He went out, and I began to think. Is there a way to make it go around faster? What if we did nothing else on the machine, so nothing else was interfering? I put a challenge to the boys on the blackboard—CAN WE DO IT? They all start yelling, “Yes, we’ll work double shifts, we’ll work overtime,” all this kind of thing. “We’ll try it. We’ll try it!”
And so the rule was: All other problems out. Only one problem and just concentrate on this one. So they started to work.
My wife, Arlene, was ill with tuberculosis—very ill indeed. It looked as if something might happen at any minute, so I arranged ahead of time with a friend of mine in the dormitory to borrow his car in an emergency so I could get to Albuquerque quickly. His name was Klaus Fuchs. He was the spy, and he used his automobile to take the atomic secrets away from Los Alamos down to Santa Fe. But nobody knew that.
The emergency arrived. I borrowed Fuchs’s car and picked up a couple of hitchhikers, in case something happened with the car on the way to Albuquerque. Sure enough, just as we were driving into Santa Fe, we got a flat tire. The two guys helped me change the tire, and just as we were leaving Santa Fe, another tire went flat. We pushed the car into a nearby gas station.
The gas station guy was repairing somebody else’s car, and it was going to take a while before he could help us. I didn’t even think to say anything, but the two hitchhikers went over to the gas station man and told him the situation. Soon we had a new tire (but no spare—tires were hard to get during the war).
About thirty miles outside Albuquerque a third tire went flat, so I left the car on the road and we hitchhiked the rest of the way. I phoned a garage to go out and get the car while I went to the hospital to see my wife.
Arlene died a few hours after I got there. A nurse came in to fill out the death certificate, and went out again. I spent a little more time with my wife. Then I looked at the clock I had given her seven years before, when she had first become sick with tuberculosis. It was something which in those days was very nice: a digital clock whose numbers would change by turning around mechanically. The clock was very delicate and often stopped for one reason or another—I had to repair it from time to time—but I kept it going for all those years. Now, it had stopped once more—at 9:22, the time on the death certificate!
I remembered the time I was in my fraternity house at MIT when the idea came into my head completely out of the blue that my grandmother was dead. Right after that there was a telephone call, just like that. It was for Pete Bernays—my grandmother wasn’t dead. So I remembered that, in case somebody told me a story that ended the other way. I figured that such things can sometimes happen by luck—after all, my grandmother was very old—although people might think they happened by some sort of supernatural phenomenon.
Arlene had kept this clock by her bedside all the time she was sick, and now it stopped the moment she died. I can understand how a person who half believes in the possibility of such things, and who hasn’t got a doubting mind—especially in a circumstance like that—doesn’t immediately try to figure out what happened, but instead explains that no one touched the clock, and there was no possibility of explanation by normal phenomena. The clock simply stopped. It would become a dramatic example of these fantastic phenomena.
I saw that the light in the room was low, and then I remembered that the nurse had picked up the clock and turned it toward the light to see the face better. That could easily have stopped it.
I went for a walk outside. Maybe I was fooling myself, but I was surprised how I didn’t feel what I thought people would expect to feel under the circumstances. I wasn’t delighted, but I didn’t feel terribly upset, perhaps because I had known for seven years that something like this was going to happen.
I didn’t know how I was going to face all my friends up at Los Alamos. I didn’t want people with long faces talking to me about it. When I got back (yet another tire went flat on the way), they asked me what happened.
“She’s dead. And how’s the program going?”
They caught on right away that I didn’t want to moon over it.
(I had obviously done something to myself psychologically: Reality was so important—I had to understand what really happened to Arlene, physiologically—that I didn’t cry until a number of months later, when I was in Oak Ridge. I was walking past a department store with dresses in the window, and I thought Arlene would like one of them. That was too much for me.)
When I went back to work on the calculation program, I found it in a mess: There were white cards, there were blue cards, there were yellow cards, and I started to say, “You’re not supposed to do more than one problem—only one problem!” They said, “Get out, get out, get out. Wait—and we’ll explain everything.”
So I waited, and what happened was this. As the cards went through, sometimes the machine made a mistake, or they put a wrong number in. What we used to have to do when that happened was to go back and do it over again. But they noticed that a mistake made at some point in one cycle only affects the nearby numbers, the next cycle affects the nearby numbers, and so on. It works its way through the pack of cards. If you have fifty cards and you make a mistake at card number thirty-nine, it affects thirty-seven, thirty-eight, and thirty-nine. The next, card thirty-six, thirty-seven, thirty-eight, thirty-nine, and forty. The next time it spreads like a disease.
So they found an error back a way, and they got an idea. They would only compute a small deck of ten cards around the error. And because ten cards could he put through the machine faster than the deck of fifty cards, they would go rapidly through with this other deck while they continued with the fifty cards with the disease spreading. But the other thing was computing faster, and they would seal it all up and correct it. Very clever.
That was the way those guys worked to get speed. There was no other way. If they had to stop to try to fix it, we’d have lost time. We couldn’t have got it. That was what they were doing.
Of course, you know what happened while they were doing that. They found an error in the blue deck. And so they had a yellow deck with a little fewer cards; it was going around faster than the blue deck. Just when they are going crazy—because after they get this straightened out, they have to fix the white deck—the boss comes walking in.
“Leave us alone,” they say. I left them alone and everything came out. We solved the problem in time and that’s the way it was.
I was an underling at the beginning. Later I became a group leader. And I met some very great men. It is one of the great experiences of my life to have met all these wonderful physicists.
There was, of course, Enrico Fermi. He came down once from Chicago, to consult a little bit, to help us if we had some problems. We had a meeting with him, and I had been doing some calculations and gotten some results. The calculations were so elaborate it was very difficult. Now, usually I was the expert at this; I could always tell you what the answer was going to look like, or when I got it I could explain why. But this thing was so complicated I couldn’t explain why it was like that.
So I told Fermi I was doing this problem, and I started to describe the results. He said, “Wait, before you tell me the result, let me think. It’s going to come out like this (he was right), and it’s going to come out like this because of so and so. And there’s a perfectly obvious explanation for this—”
He was doing what I was supposed to be good at, ten times better. That was quite a lesson to me.
Then there was John von Neumann, the great mathematician. We used to go for walks on Sunday. We’d walk in the canyons, often with Bethe and Bob Bacher. It was a great pleasure. And von Neumann gave me an interesting idea: that you don’t have to be responsible for the world that you’re in. So I have developed a very powerful sense of social irresponsibility as a result of von Neumann’s advice. It’s made me a very happy man ever since. But it was von Neumann who put the seed in that grew into my active irresponsibility!
I also met Niels Bohr. His name was Nicholas Baker in those days, and he came to Los Alamos with Jim Baker, his son, whose name is really Aage Bohr. They came from Denmark, and they were very famous physicists, as you know. Even to the big shot guys, Bohr was a great god.
We were at a meeting once, the first time he came, and everybody wanted to see the great Bohr. So there were a lot of people there, and we were discussing the problems of the bomb. I was back in a corner somewhere. He came and went, and all I could see of him was from between people’s heads.
In the morning of the day he’s due to come next time, I get a telephone call.
“Hello—Feynman?”
“Yes.”
“This is Jim Baker.” It’s his son. “My father and I would like to speak to you.”
“Me? I’m Feynman, I’m just a—”
“That’s right. Is eight o’clock OK?”
So, at eight o’clock in the morning, before anybody’s awake, I go down to the place. We go into an office in the technical area and he says, “We have been thinking how we could make the bomb more efficient and we think of the following idea.”
I say, “No, it’s not going to work. It’s not efficient… Blab, blab, blah.”
So he says, “How about so and so?”
I said, “That sounds a little bit better, but it’s got this damn fool idea in it.”
This went on for about two hours, going back and forth over lots of ideas, back and forth, arguing. The great Niels kept lighting his pipe; it always went out. And he talked in a way that was un-understandable—mumble, mumble, hard to understand. His son I could understand better.
“Well,” he said finally, lighting his pipe, “I guess we can call in the big shots now.” So then they called all the other guys and had a discussion with them.
Then the son told me what happened. The last time he was there, Bohr said to his son, “Remember the name of that little fellow in the back over there? He’s the only guy who’s not afraid of me, and will say when I’ve got a crazy idea. So next time when we want to discuss ideas, we’re not going to be able to do it with these guys who say everything is yes, yes, Dr. Bohr. Get that guy and we’ll talk with him first.”
I was always dumb in that way. I never knew who I was talking to. I was always worried about the physics. If the idea looked lousy, I said it looked lousy. If it looked good, I said it looked good. Simple proposition.
I’ve always lived that way. It’s nice, it’s pleasant—if you can do it. I’m lucky in my life that I can do this.
After we’d made the calculations, the next thing that happened, of course, was the test. I was actually at home on a short vacation at that time, after my wife died, and so I got a message that said, “The baby is expected on such and such a day.”
I flew back, and I arrived just when the buses were leaving, so I went straight out to the site and we waited out there, twenty miles away. We had a radio, and they were supposed to tell us when the thing was going to go off and so forth, but the radio wouldn’t work, so we never knew what was happening. But just a few minutes before it was supposed to go off the radio started to work, and they told us there was twenty seconds or something to go, for people who were far away like we were. Others were closer, six miles away.
They gave out dark glasses that you could watch it with. Dark glasses! Twenty miles away, you couldn’t see a damn thing through dark glasses. So I figured the only thing that could really hurt your eyes (bright light can never hurt your eyes) is ultraviolet light. I got behind a truck windshield, because the ultraviolet can’t go through glass, so that would be safe, and so I could see the damn thing.
Time comes, and this tremendous flash out there is so bright that I duck, and I see this purple splotch on the floor of the truck. I said, “That’s not it. That’s an after-image.” So I look back up, and I see this white light changing into yellow and then into orange. Clouds form and disappear again—from the compression and expansion of the shock wave.
Finally, a big ball of orange, the center that was so bright, becomes a ball of orange that starts to rise and billow a little bit and get a little black around the edges, and then you see it’s a big ball of smoke with flashes on the inside, with the heat of the fire going outwards.
All this took about one minute. It was a series from bright to dark, and I had seen it. I am about the only guy who actually looked at the damn thing—the first Trinity test. Everybody else had dark glasses, and the people at six miles couldn’t see it because they were all told to lie on the floor. I’m probably the only guy who saw it with the human eye.
Finally, after about a minute and a half, there’s suddenly a tremendous noise—BANG, and then a rumble, like thunder—and that’s what convinced me. Nobody had said a word during this whole thing. We were all just watching quietly. But this sound released everybody—released me particularly because the solidity of the sound at that distance meant that it had really worked.
The man standing next to me said, “What’s that?”
I said, “That was the Bomb.”
The man was William Laurence. He was there to write an article describing the whole situation. I had been the one who was supposed to have taken him around. Then it was found that it was too technical for him, and so later H. D. Smyth came and I showed him around. One thing we did, we went into a room and there on the end of a narrow pedestal was a small silver-plated ball. You could put your hand on it. It was warm. It was radioactive. It was plutonium. And we stood at the door of this room, talking about it. This was a new element that was made by man, that had never existed on the earth before, except for a very short period possibly at the very beginning. And here it was all isolated and radioactive and had these properties. And we had made it. And so it was tremendously valuable.
Meanwhile, you know how people do when they talk—you kind of jiggle around and so forth. He was kicking the doorstop, you see, and I said, “Yes, the doorstop certainly is appropriate for this door.” The doorstop was a ten-inch hemisphere of yellowish metal—gold, as a matter of fact.
What had happened was that we needed to do an experiment to see how many neutrons were reflected by different materials, in order to save the neutrons so we didn’t use so much material. We had tested many different materials. We had tested platinum, we had tested zinc, we had tested brass, we had tested gold. So, in making the tests with the gold, we had these pieces of gold and somebody had the clever idea of using that great ball of gold for a doorstop for the door of the room that contained the plutonium.
After the thing went off, there was tremendous excitement at Los Alamos. Everybody had parties, we all ran around. I sat on the end of a jeep and beat drums and so on. But one man, I remember, Bob Wilson, was just sitting there moping.
I said, “What are you moping about?”
He said, “It’s a terrible thing that we made.”
I said, “But you started it. You got us into it.”
You see, what happened to me-what happened to the rest of us—is we started for a good reason, then you’re working very hard to accomplish something and it’s a pleasure, it’s excitement. And you stop thinking, you know; you just stop. Bob Wilson was the only one who was still thinking about it, at that moment.
I returned to civilization shortly after that and went to Cornell to teach, and my first impression was a very strange one. I can’t understand it any more, but I felt very strongly then. I sat in a restaurant in New York, for example, and I looked out at the buildings and I began to think, you know, about how much the radius of the Hiroshima bomb damage was and so forth … How far from here was 34th Street? … All those buildings, all smashed—and so on. And I would go along and I would see people building a bridge, or they’d be making a new road, and I thought, they’re crazy, they just don’t understand, they don’t understand. Why are they making new things? It’s so useless.
But, fortunately, it’s been useless for almost forty years now, hasn’t it? So I’ve been wrong about it being useless making bridges and I’m glad those other people had the sense to go ahead.
Safecracker Meets Safecracker
I learned to pick locks from a guy named Leo Lavatelli. It turns out that picking ordinary tumbler locks—like Yale locks—is easy. You try to turn the lock by putting a screwdriver in the hole (you have to push from the side in order to leave the hole open). It doesn’t turn because there are some pins inside which have to be lifted to just the right height (by the key). Because it is not made perfectly, the lock is held more by one pin than the others. Now, if you push a little wire gadget—maybe a paper clip with a slight bump at the end—and jiggle it back and forth inside the lock, you’ll eventually push that one pin that’s doing the most holding, up to the right height. The lock gives, just a little bit, so the first pin stays up—it’s caught on the edge. Now most of the load is held by another pin, and you repeat the same random process for a few more minutes, until all the pins are pushed up.
What often happens is that the screwdriver will slip and you hear tic-tic-tic, and it makes you mad. There are little springs that push the pins back down when a key is removed, and you can hear them click when you let go of the screwdriver. (Sometimes you intentionally let go of the screwdriver to see if you’re getting anywhere—you might be pushing the wrong way, for instance.) The process is something like Sisyphus: you’re always falling back downhill.
It’s a simple process, but practice helps a lot. You learn how hard to push on things—hard enough so the pins will stay up, but not so hard that they won’t go up in the first place. What is not really appreciated by most people is that they’re perpetually locking themselves in with locks everywhere, and it’s not very hard to pick them.
When we started to work on the atomic bomb project at Los Alamos, everything was in such a hurry that it wasn’t really ready. All the secrets of the project—everything about the atomic bomb—were kept in filing cabinets which, if they had locks at all, were locked with padlocks which had maybe only three pins: they were as easy as pie to open.
To improve security the shop ouffitted every filing cabinet with a long rod that went down through the handles of the drawers and that was fastened by a padlock.
Some guy said to me, “Look at this new thing the shop put on—can you open the cabinet now?”
I looked at the back of the cabinet and saw that the drawers didn’t have a solid bottom. There was a slot with a wire rod in each one that held a slidable piece (which holds the papers up inside the drawer). I poked in from the back, slid the piece back, and began pulling the papers out through the slot. “Look!” I said. “I don’t even have to pick the lock.”
Los Alamos was a very cooperative place, and we felt it our responsibility to point out things that should be improved. I’d keep complaining that the stuff was unsafe, and although everybody thought it was safe because there were steel rods and padlocks, it didn’t mean a damn thing.
To demonstrate that the locks meant nothing, whenever I wanted somebody’s report and they weren’t around, I’d just go in their office, open the filing cabinet, and take it out. When I was finished I would give it back to the guy: “Thanks for your report.”
“Where’d you get it?”
“Out of your filing cabinet.”
“But I locked it!”
“I know you locked it. The locks are no good.”
Finally some filing cabinets came which had combination locks on them made by the Mosler Safe Company. They had three drawers. Pulling the top drawer out would release the other drawers by a catch. The top drawer was opened by turning a combination wheel to the left, right, and left for the combination, and then right to number ten, which would draw back a bolt inside. The whole filing cabinet could he locked by closing the bottom drawers first, then the top drawer, and spinning the combination wheel away from number ten, which pushed up the bolt.
These new filing cabinets were an immediate challenge, naturally. I love puzzles. One guy tries to make something to keep another guy out; there must be a way to beat it!
I had first to understand how the lock worked, so I took apart the one in my office. The way it worked is this: There are three discs on a single shaft, one behind the other; each has a notch in a different place. The idea is to line up the notches so that when you turn the wheel to ten, the little friction drive will draw the bolt down into the slot generated by the notches of the three discs.
Now, to turn the discs, there’s a pin sticking out from the back of the combination wheel, and a pin sticking up from the first disc at the same radius. Within one turn of the combination wheel, you’ve picked up the first disc.
On the back of the first disc there’s a pin at the same radius as a pin on the front of the second disc, so by the time you’ve spun the combination wheel around twice, you’ve picked up the second disc as well.
Keep turning the wheel, and a pin on the back of the second disc will catch a pin on the front of the third disc, which you now set into the proper position with the first number of the combination.
Now you have to turn the combination wheel the other way one full turn to catch the second disc from the other side, and then continue to the second number of the combination to set the second disc.
Again you reverse direction and set the first disc to its proper place. Now the notches are lined up, and by turning the wheel to ten, you open the cabinet.
Well, I struggled, and I couldn’t get anywhere. I bought a couple of safecracker books, but they were all the same. In the beginning of the book there are some stories of the fantastic achievements of the safecracker, such as the woman caught in a meat refrigerator who is freezing to death, but the safecracker, hanging upside down, opens it in two minutes. Or there are some precious furs or gold bullion under water, down in the sea, and the safecracker dives down and opens the chest.
In the second part of the book, they tell you how to crack a safe. There are all kinds of ninny-pinny, dopey things, like “It might be a good idea to try a date for the combination, because lots of people like to use dates.” Or “Think of the psychology of the owner of the safe, and what he might use for the combination.” And “The secretary is often worried that she might forget the combination of the safe, so she might write it down in one of the following places—along the edge of her desk drawer, on a list of names and addresses … and so on.
They did tell me something sensible about how to open ordinary safes, and it’s easy to understand. Ordinary safes have an extra handle, so if you push down on the handle while you’re turning the combination wheel, things being unequal (as with locks), the force of the handle trying to push the bolt down into the notches (which are not lined up) is held up more by one disc than another. When the notch on that disc comes under the bolt, there’s a tiny click that you can hear with a stethoscope, or a slight decrease in friction that you can feel (you don’t have to sandpaper your fingertips), and you know, “There’s a number!”
You don’t know whether it’s the first, second, or third number, but you can get a pretty good idea of that by finding out how many times you have to turn the wheel the other way to hear the same click again. If it’s a little less than once, it’s the first disc; if it’s a little less than twice, it’s the second disc (you have to make a correction for the thickness of the pins).
This useful trick only works on ordinary safes, which have the extra handle, so I was stymied.
I tried all kinds of subsidiary tricks with the cabinets, such as finding out how to release the latches on the lower drawers, without opening the top drawer, by taking off a screw in front and poking around with a piece of hanger wire.
I tried spinning the combination wheel very rapidly and then going to ten, thus putting a little friction on, which I hoped would stop a disc at the right point in some manner. I tried all kinds of things. I was desperate.
I also did a certain amount of systematic study. For instance, a typical combination was 69-32-21. How far off could a number be when you’re opening the safe? If the number was 69, would 68 work? Would 67 work? On the particular locks we had, the answer was yes for both, but 66 wouldn’t work. You could he off by two in either direction. That meant you only had to try one out of five numbers, so you could try zero, five, ten, fifteen, and so on. With twenty such numbers on a wheel of 100, that was 8000 possibilities instead of the 1,000,000 you would get if you had to try every single number.
Now the question was, how long would it take me to try the 8000 combinations? Suppose I’ve got the first two numbers right of a combination I’m trying to get. Say the numbers are 69-32, but I don’t know it—I’ve got them as 70-30. Now I can try the twenty possible third numbers without having to set up the first two numbers each time. Now let’s suppose I have only the first number of the combination right. After trying the twenty numbers on the third disc, I move the second wheel only a little bit, and then do another twenty numbers on the third wheel.
I practiced all the time on my own safe so I could do this process as fast as I could and not get lost in my mind as to which number I was pushing and mess up the first number. Like a guy who practices sleight of hand, I got it down to an absolute rhythm so I could try the 400 possible back numbers in less than half an hour. That meant I could open a safe in a maximum of eight hours—with an average time of four hours.
There was another guy there at Los Alamos named Staley who was also interested in locks. We talked about it from time to time, but we weren’t getting anywhere much. After I got this idea how to open a safe in an average time of four hours, I wanted to show Staley how to do it, so I went into a guy’s office over in the computing department and asked, “Do you mind if I use your safe? I’d like to show Staley something.”
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!”
What often happens is that the screwdriver will slip and you hear tic-tic-tic, and it makes you mad. There are little springs that push the pins back down when a key is removed, and you can hear them click when you let go of the screwdriver. (Sometimes you intentionally let go of the screwdriver to see if you’re getting anywhere—you might be pushing the wrong way, for instance.) The process is something like Sisyphus: you’re always falling back downhill.
It’s a simple process, but practice helps a lot. You learn how hard to push on things—hard enough so the pins will stay up, but not so hard that they won’t go up in the first place. What is not really appreciated by most people is that they’re perpetually locking themselves in with locks everywhere, and it’s not very hard to pick them.
When we started to work on the atomic bomb project at Los Alamos, everything was in such a hurry that it wasn’t really ready. All the secrets of the project—everything about the atomic bomb—were kept in filing cabinets which, if they had locks at all, were locked with padlocks which had maybe only three pins: they were as easy as pie to open.
To improve security the shop ouffitted every filing cabinet with a long rod that went down through the handles of the drawers and that was fastened by a padlock.
Some guy said to me, “Look at this new thing the shop put on—can you open the cabinet now?”
I looked at the back of the cabinet and saw that the drawers didn’t have a solid bottom. There was a slot with a wire rod in each one that held a slidable piece (which holds the papers up inside the drawer). I poked in from the back, slid the piece back, and began pulling the papers out through the slot. “Look!” I said. “I don’t even have to pick the lock.”
Los Alamos was a very cooperative place, and we felt it our responsibility to point out things that should be improved. I’d keep complaining that the stuff was unsafe, and although everybody thought it was safe because there were steel rods and padlocks, it didn’t mean a damn thing.
To demonstrate that the locks meant nothing, whenever I wanted somebody’s report and they weren’t around, I’d just go in their office, open the filing cabinet, and take it out. When I was finished I would give it back to the guy: “Thanks for your report.”
“Where’d you get it?”
“Out of your filing cabinet.”
“But I locked it!”
“I know you locked it. The locks are no good.”
Finally some filing cabinets came which had combination locks on them made by the Mosler Safe Company. They had three drawers. Pulling the top drawer out would release the other drawers by a catch. The top drawer was opened by turning a combination wheel to the left, right, and left for the combination, and then right to number ten, which would draw back a bolt inside. The whole filing cabinet could he locked by closing the bottom drawers first, then the top drawer, and spinning the combination wheel away from number ten, which pushed up the bolt.
These new filing cabinets were an immediate challenge, naturally. I love puzzles. One guy tries to make something to keep another guy out; there must be a way to beat it!
I had first to understand how the lock worked, so I took apart the one in my office. The way it worked is this: There are three discs on a single shaft, one behind the other; each has a notch in a different place. The idea is to line up the notches so that when you turn the wheel to ten, the little friction drive will draw the bolt down into the slot generated by the notches of the three discs.
Now, to turn the discs, there’s a pin sticking out from the back of the combination wheel, and a pin sticking up from the first disc at the same radius. Within one turn of the combination wheel, you’ve picked up the first disc.
On the back of the first disc there’s a pin at the same radius as a pin on the front of the second disc, so by the time you’ve spun the combination wheel around twice, you’ve picked up the second disc as well.
Keep turning the wheel, and a pin on the back of the second disc will catch a pin on the front of the third disc, which you now set into the proper position with the first number of the combination.
Now you have to turn the combination wheel the other way one full turn to catch the second disc from the other side, and then continue to the second number of the combination to set the second disc.
Again you reverse direction and set the first disc to its proper place. Now the notches are lined up, and by turning the wheel to ten, you open the cabinet.
Well, I struggled, and I couldn’t get anywhere. I bought a couple of safecracker books, but they were all the same. In the beginning of the book there are some stories of the fantastic achievements of the safecracker, such as the woman caught in a meat refrigerator who is freezing to death, but the safecracker, hanging upside down, opens it in two minutes. Or there are some precious furs or gold bullion under water, down in the sea, and the safecracker dives down and opens the chest.
In the second part of the book, they tell you how to crack a safe. There are all kinds of ninny-pinny, dopey things, like “It might be a good idea to try a date for the combination, because lots of people like to use dates.” Or “Think of the psychology of the owner of the safe, and what he might use for the combination.” And “The secretary is often worried that she might forget the combination of the safe, so she might write it down in one of the following places—along the edge of her desk drawer, on a list of names and addresses … and so on.
They did tell me something sensible about how to open ordinary safes, and it’s easy to understand. Ordinary safes have an extra handle, so if you push down on the handle while you’re turning the combination wheel, things being unequal (as with locks), the force of the handle trying to push the bolt down into the notches (which are not lined up) is held up more by one disc than another. When the notch on that disc comes under the bolt, there’s a tiny click that you can hear with a stethoscope, or a slight decrease in friction that you can feel (you don’t have to sandpaper your fingertips), and you know, “There’s a number!”
You don’t know whether it’s the first, second, or third number, but you can get a pretty good idea of that by finding out how many times you have to turn the wheel the other way to hear the same click again. If it’s a little less than once, it’s the first disc; if it’s a little less than twice, it’s the second disc (you have to make a correction for the thickness of the pins).
This useful trick only works on ordinary safes, which have the extra handle, so I was stymied.
I tried all kinds of subsidiary tricks with the cabinets, such as finding out how to release the latches on the lower drawers, without opening the top drawer, by taking off a screw in front and poking around with a piece of hanger wire.
I tried spinning the combination wheel very rapidly and then going to ten, thus putting a little friction on, which I hoped would stop a disc at the right point in some manner. I tried all kinds of things. I was desperate.
I also did a certain amount of systematic study. For instance, a typical combination was 69-32-21. How far off could a number be when you’re opening the safe? If the number was 69, would 68 work? Would 67 work? On the particular locks we had, the answer was yes for both, but 66 wouldn’t work. You could he off by two in either direction. That meant you only had to try one out of five numbers, so you could try zero, five, ten, fifteen, and so on. With twenty such numbers on a wheel of 100, that was 8000 possibilities instead of the 1,000,000 you would get if you had to try every single number.
Now the question was, how long would it take me to try the 8000 combinations? Suppose I’ve got the first two numbers right of a combination I’m trying to get. Say the numbers are 69-32, but I don’t know it—I’ve got them as 70-30. Now I can try the twenty possible third numbers without having to set up the first two numbers each time. Now let’s suppose I have only the first number of the combination right. After trying the twenty numbers on the third disc, I move the second wheel only a little bit, and then do another twenty numbers on the third wheel.
I practiced all the time on my own safe so I could do this process as fast as I could and not get lost in my mind as to which number I was pushing and mess up the first number. Like a guy who practices sleight of hand, I got it down to an absolute rhythm so I could try the 400 possible back numbers in less than half an hour. That meant I could open a safe in a maximum of eight hours—with an average time of four hours.
There was another guy there at Los Alamos named Staley who was also interested in locks. We talked about it from time to time, but we weren’t getting anywhere much. After I got this idea how to open a safe in an average time of four hours, I wanted to show Staley how to do it, so I went into a guy’s office over in the computing department and asked, “Do you mind if I use your safe? I’d like to show Staley something.”
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!”