As a result of all these experiences with the censor, I knew exactly what could get through and what could not get through. Nobody else knew as well as I. And so I made a little money out of all of this by making bets.

One day I discovered that the workmen who lived further out and wanted to come in were too lazy to go around through the gate, and so they had cut themselves a hole in the fence. So I went out the gate, went over to the hole and came in, went out again, and so on, until the sergeant at the gate began to wonder what was happening. How come this guy is always going out and never coming in? And, of course, his natural reaction was to call the lieutenant and try to put me in jail for doing this. I explained that there was a hole.

You see, I was always trying to straighten people out. And so I made a bet with somebody that I could tell about the hole in the fence in a letter, and mail it out. And sure enough, I did. And the way I did it was I said, You should see the way they administer this place (that’s what we were allowed to say). There’s a hole in the fence seventy-one feet away from such-and-such a place, that’s this size and that size, that you can walk through.

Now, what can they do? They can’t say to me that there is no such hole. I mean, what are they going to do? It’s their own hard luck that there’s such a hole. They should fix the hole. So I got that one through.

I also got through a letter that told about how one of the boys who worked in one of my groups, John Kemeny had been wakened up in the middle of the night and grilled with lights in front of him by some idiots in the army there because they found out something about his father, who was supposed to be a communist or something. Kemeny is a famous man now.

There were other things. Like the hole in the fence, I was always trying to point these things out in a non-direct manner. And one of the things I wanted to point out was this—that at the very beginning we had terribly important secrets; we’d worked out lots of stuff about bombs and uranium and how it worked, and so on; and all this stuff was in documents that were in wooden filing cabinets that had little, ordinary common padlocks on them. Of course, there were various things made by the shop, like a rod that would go down and then a padlock to hold it, but it was always just a padlock. Furthermore, you could get the stuff out without even opening the padlock. You just tilt the cabinet over backwards. The bottom drawer has a little rod that’s supposed to hold the papers together, and there’s a long wide hole in the wood underneath. You can pull the papers out from below.

So I used to pick the locks all the time and point out that it was very easy to do. And every time we had a meeting of everybody together, I would get up and say that we have important secrets and we shouldn’t keep them in such things; we need better locks. One day Teller got up at the meeting, and he said to me, “I don’t keep my most important secrets in my filing cabinet; I keep them in my desk drawer. Isn’t that better?”

I said, “I don’t know. I haven’t seen your desk drawer.” He was sitting near the front of the meeting, and I’m sitting further back. So the meeting continues, and I sneak out and go down to see his desk drawer.

I don’t even have to pick the lock on the desk drawer. It turns out that if you put your hand in the back, underneath, you can pull out the paper like those toilet paper dispensers. You pull out one, it pulls another, it pulls another … I emptied the whole damn drawer, put everything away to one side, and went back upstairs.

The meeting was just ending, and everybody was coming out, and I joined the crew and ran to catch up with Teller, and I said, “Oh, by the way let me see your desk drawer.”

“Certainly,” he said, and he showed me the desk.

I looked at it and said, “That looks pretty good to me. Let’s see what you have in there.”

“I’ll be very glad to show it to you,” he said, putting in the key and opening the drawer. “If,” he said, “you hadn’t already seen it yourself.”

The trouble with playing a trick on a highly intelligent man like Mr. Teller is that the time it takes him to figure out from the moment that he sees there is something wrong till he understands exactly what happened is too damn small to give you any pleasure!

Some of the special problems I had at Los Alamos were rather interesting. One thing had to do with the safety of the plant at Oak Ridge, Tennessee. Los Alamos was going to make the bomb, but at Oak Ridge they were trying to separate the isotopes of uranium—uranium 238 and uranium 235, the explosive one. They were just beginning to get infinitesimal amounts from an experimental thing of 235, and at the same time they were practicing the chemistry. There was going to be a big plant, they were going to have vats of the stuff, and then they were going to take the purified stuff and repurify and get it ready for the next stage. (You have to purify it in several stages.) So they were practicing on the one hand, and they were just getting a little bit of U235 from one of the pieces of apparatus experimentally on the other hand. And they were trying to learn how to assay it, to determine how much uranium 235 there is in it. Though we would send them instructions, they never got it right.

So finally Emil Segre said that the only possible way to get it right was for him to go down there and see what they were doing. The army people said, “No, it is our policy to keep all the information of Los Alamos at one place.”

The people in Oak Ridge didn’t know anything about what it was to be used for; they just knew what they were trying to do. I mean the higher people knew they were separating uranium, but they didn’t know how powerful the bomb was, or exactly how it worked or anything. The people underneath didn’t know at all what they were doing. And the army wanted to keep it that way. There was no information going back and forth. But Segre insisted they’d never get the assays right, and the whole thing would go up in smoke. So he finally went down to see what they were doing, and as he was walking through he saw them wheeling a tank carboy of water, green water—which is uranium nitrate solution.

He said, “Uh, you’re going to handle it like that when it’s purified too? Is that what you’re going to do?”

They said, “Sure—why not?”

“Won’t it explode?” he said.

Huh! Explode?

Then the army said, “You see! We shouldn’t have let any information get to them! Now they are all upset.”

It turned out that the army had realized how much stuff we needed to make a bomb—twenty kilograms or whatever it was—and they realized that this much material, purified, would never be in the plant, so there was no danger. But they did not know that the neutrons were enormously more effective when they are slowed down in water. In water it takes less than a tenth—no, a hundredth—as much material to make a reaction that makes radioactivity. It kills people around and so on. It was very dangerous, and they had not paid any attention to the safety at all.

So a telegram goes from Oppenheimer to Segre: “Go through the entire plant. Notice where all the concentrations are supposed to be, with the process as they designed it. We will calculate in the meantime how much material can come together before there’s an explosion.”

Two groups started working on it. Christy’s group worked on water solutions and my group worked on dry powder in boxes. We calculated about how much material they could accumulate safely. And Christy was going to go down and tell them all at Oak Ridge what the situation was, because this whole thing is broken down and we have to go down and tell them now. So I happily gave all my numbers to Christy and said, you have all the stuff, so go. Christy got pneumonia; I had to go.

I had never traveled on an airplane before. They strapped the secrets in a little thing on my back! The airplane in those days was like a bus, except the stations were further apart. You stopped off every once in a while to wait.

There was a guy standing there next to me swinging a chain, saying something like, “It must be terribly difficult to fly without a priority on airplanes these days.”

I couldn’t resist. I said, “Well, I don’t know. I have a priority.

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.”