Los Alamos From Below: Reminiscences 1943-1945, by Richard Feynman


WHEN I say "Los Alamos From Below"' I mean that, although in my field at the present time I'm a slightly famous man, at that time I was not anybody famous at all. I didn't even have a degree when I started to work with the Manhattan Project. Many of the other people who tell you about Los Alamos - people in higher echelons - worried about some big decisions. I worried about no big decisions. I was always flittering about underneath.

            So I want you to just imagine this young graduate student that hasn't got his degree yet but is working on his thesis, and I'll start by saying how I got into the project, and then what happened to me.

            I was working in my room at Princeton one day when Bob Wilson came in and said that he had been funded to do a job that was a secret, and he wasn't supposed to tell anybody, but he was going to tell me because he knew that as soon as I knew what he was going to do, I'd see that I had to go along with it. So he told me about the problem of separating different isotopes of uranium to ultimately make a bomb. He had a process for separating the isotopes of uranium (different from the one which was ultimately used) that he wanted to try to develop. He told me about it, and he said, “There's a meeting --.”

            I said I didn't want to do it.

            He said, “All right, there's a meeting at three o'clock. I'll see you there."

            I said, “It's all right that you told me the secret because I'm not going to tell anybody, but I'm not going to do it."

            So I went back to work on my thesis - for about three minutes. Then I began to pace the floor and think about this thing. The Germans had Hitler and the possibility of developing an atomic bomb was obvious, and the possibility that they would develop it before we did was very much of a fright. So I decided to go to the meeting at three o'clock.

            By four o'clock I already had a desk in a room and was trying to calculate whether this particular method was limited by the total amount of current that you get in an ion beam, and so on. I won't go into the details. But I had a desk, and I had paper, and I was working as hard as I could and as fast as I could, so the fellows who were building the apparatus could do the experiment right there.

            It was like those moving pictures where you see a piece of equipment go bruuuuup, bruuuuup, bruuuuup. Every time I'd look up, the thing was getting bigger. What was happening, of course, was that all the boys had decided to work on this and to stop their research in science. All science stopped during the war except the little bit that was done at Los Alamos. And that was not much science; it was mostly engineering.

            All the equipment from different research projects was being put together to make the new apparatus to do the experiment - to try to separate the isotopes of uranium. I stopped my own work for the same reason, though I did take a six-week vacation after a while and finished writing my thesis. And I did get my degree just before I got to Los Alamos - so I wasn't quite as far down the scale as I led you to believe.

            One of the first interesting experiences I had in this project at Princeton was meeting great men. I had never met very many great men before. But there was an evaluation committee that had to try to help us along, and help us ultimately decide which way we were going to separate the uranium. This committee had men like Compton and Tolman and Smyth and Urey and Rabi and Oppenheimer on it. I would sit in because I understood the theory of the process of what we were doing, and so they'd ask me questions and talk about it. In these discussions one man would make a point. Then Compton, for example, would explain a different point of view. He would say it should be this way, and he would be perfectly right. Another guy would say, well, maybe, but there's this other possibility we have to consider against it.

            I'm jumping! Compton should say it again! So everybody is disagreeing, all around the table. Finally, at the end, Tolman, who's the chairman, would say, “Well, having heard all these arguments, I guess it's true that Compton's argument is the best of all, and now we have to go ahead."

            It was such a shock to me to see that a committee of men could present a whole lot of ideas, each one thinking of a new facet, while remembering what the other fellow said, so that, at the end, the decision is made as to which idea was the best - summing it all up without having to say it three times. So that was a shock. These were very great men indeed.

            It was ultimately decided that this project was not to be the one they were going to use to separate uranium. We were told then that we were going to stop, because in Los Alamos, New Mexico, they would be starting the project that would actually make the bomb. We would all go out there to make it. There would be experiments that we would have to do, and theoretical work to do. I was in the theoretical work. All the rest of the fellows were in experimental work.

            The question was - What to do now? Los Alamos wasn't ready yet. Bob Wilson tried to make use of this time by, among other things, sending me to Chicago to find out all that we could find out about the bomb and the problems. Then, in our laboratories, we could start to build equipment, counters of various kinds, and so on, that would be useful when we got to Los Alamos. So no time was wasted.

            I was sent to Chicago with the instructions to go to each group, tell them I was going to work with them, and have them tell me about a problem in enough detail that I could actually sit down and start to work on it. As soon as I got that far, I was to go to another guy and ask for another problem. That way I would understand the details of everything.

            It was a very good idea, but my conscience bothered me a little bit because they would all work so hard to explain things to me, and I'd go away without helping them. But I was very lucky. When one of the guys was explaining a problem, I said, “Why don't you do it that way?" In half an hour he had it solved, and they'd been working on it for three months. So, I did something! Then I came back from Chicago, and I described the situation - how much energy was released, what the bomb was going to be like, and so forth.

            I remember a friend of mine who worked with me, Paul Olum, a mathematician, came up to me afterwards and said, “When they make a moving picture about this, they'll have the guy coming back from Chicago to make his report to the Princeton men about the bomb. He'll be wearing a suit and carrying a briefcase and so on - and here you're in dirty shirtsleeves and just telling us all about it, in spite of its being such a serious and dramatic thing."

            There still seemed to be a delay, and Wilson went to Los Alamos to find out what was holding things up. When he got there, he found that the construction company was working very hard and had finished the theater, and a few other buildings that they understood, but they hadn't gotten instructions clear on how to build a laboratory - how many pipes for gas, how much for water. So Wilson simply stood around and decided, then and there, how much water, how much gas, and so on, and told them to start building the laboratories.

            When he came back to us, we were all ready to go and we were getting impatient. So they all got together and decided we'd go out there anyway, even though it wasn't ready.

            We were recruited, by the way, by Oppenheimer and other people, and he was very patient. He paid attention to everybody's problems. He worried about my wife who had TB, and whether there would be a hospital out there, and everything. It was the first time I met him in such a personal way; he was a wonderful man.

            We were told to be very careful - not to buy our train ticket in Princeton, for example, because Princeton was a very small station, and if everybody bought train tickets to Albuquerque, New Mexico, in Princeton, there would be some suspicions that something was up. And so everybody bought their tickets somewhere else, except me, because I figured if everybody bought their tickets somewhere else. . .

            So when I went to the train station and said, “I want to go to Albuquerque, New Mexico, “ the man says, “Oh, so all this stuff is for you!" We had been shipping out crates full of counters for weeks and expecting that they didn't notice the address was Albuquerque. So at least I explained why it was that we were shipping all those crates; I was going out to Albuquerque.

            Well, when we arrived, the houses and dormitories and things like that were not ready. In fact, even the laboratories weren't quite ready. We were pushing them by coming down ahead of time. So they just went crazy and rented ranch houses all around the neighborhood. We stayed at first in a ranch house and would drive in in the morning. The first morning I drove in was tremendously impressive. The beauty of the scenery, for a person from the East who didn't travel much, was sensational. There are the great cliffs that you've probably seen in pictures. You'd come up from below and be very surprised to see this high mesa. The most impressive thing to me was that, as I was going up, I said that maybe there had been Indians living here, and the guy who was driving stopped the car and walked around the corner and pointed out some Indian caves that you could inspect. It was very exciting.

            When I got to the site the first time, I saw there was a technical area that was supposed to have a fence around it ultimately, but it was still open. Then there was supposed to be a town, and then a big fence further out, around the town. But they were still building, and my friend Paul Olum, who was my assistant, was standing at the gate with a clipboard, checking the trucks coming in and out and telling them which way to go to deliver the materials in different places.

            When I went into the laboratory, I would meet men I had heard of by seeing their papers in the Physical Review and so on. I had never met them before.”This is John Williams, “ they'd say. Then a guy stands up from a desk that is covered with blueprints, his sleeves all rolled up, and he's calling out the windows, ordering trucks and things going in different directions with building material. In other words, the experimental physicists had nothing to do until their buildings and apparatus were ready, so they just built the buildings - or assisted in building the buildings.

            The theoretical physicists, on the other hand, could start working right away, so it was decided that they wouldn't live in the ranch houses, but would live up at the site. We started working immediately. There were no blackboards except for one on wheels, and we'd roll it around and Robert Serber would explain to us all the things that they'd thought of in Berkeley about the atomic bomb, and nuclear physics, and all these things. I didn't know very much about it; I had been doing other kinds of -things. So I had to do an awful lot of work.

            Every day I would study and read, study and read. It was a very hectic time. But I had some luck. All the big shots except for Hans Bethe happened to be away at the time, and what Bethe needed was someone to talk to, to push his ideas against. Well, he comes in to this little squirt in an office and starts to argue, explaining his idea. I say, “No, no, you’re crazy. It'll go like this." And he says, “Just a moment, “ and explains how he's not crazy, I'm crazy. And we keep on going like this. You see, when I hear about physics, I just think about physics, and I don't know who I'm talking to, so I say dopey things like, “No, no, you're wrong, “ or "You're crazy." But it turned out that's exactly what he needed. I got a notch up on account of that, and I ended up as a group leader under Bethe with four guys under me.

            I had a lot of interesting experiences with Bethe. The first day when he came in, we had a calculator, or glorified adding machine, a Marchant that you work by hand. And so he said, “Let's see." The formula he'd been working out, he says, “involves the pressure squared; the pressure is 48; so the square of 48 is --

            I reach for the machine.

            He says, “It's about 2300.” So I plug it out just to find out.

            He says, “You want to know exactly? It's 2304." And it came out 2304.

            So I said, “How do you do that?"

            He says, “Don't you know how to take squares of numbers near 50? If it's near 50, say 3 below (47), then the answer is 3 below 25 - like 47 squared is 2200, and how much is left over is the square of what's residual. For instance, it's 3 less and the square of that is 9, so you get 2209 from 47 squared."

            So he knew all his arithmetic, and he was very good at it, and that was a challenge to me. I kept practicing. We used to have a little contest. Every time we'd have to calculate anything we'd race to the answer, he and I, and I would lose. After several years I began to get in there once in a while, maybe one out of four. You have to notice the numbers, you see - and each of us would notice a different way. We had lots of fun.

            Well, when I was first there, as I said, the dormitories weren't ready. But the theoretical physicists had to stay up there anyway. The first place they put us was in an old school building - a boys' school that had been there previously. I lived in a thing called the Mechanics' Lodge. We were all jammed in there in bunk beds, and it wasn't organized very well because Bob Christie and his wife had to go to the bathroom through our bedroom. So that was very uncomfortable.

            The next place we moved to was called the Big House, which had a balcony all the way around the outside on the second floor, where all the beds were lined up next to each other, along the wall. Downstairs there was a big chart that told you what your bed number was and which bathroom to change your clothes in. Under my name it said "Bathroom C"' but no bed number! By this time I was getting annoyed.

            At last the dormitory was built. I went down to the place where rooms were assigned, and they said, you can pick your room now. You know what I did? I looked to see where the girls' dormitory was, and then I picked a room that looked right across - though later I discovered a big tree was growing right in front of the window of that room.

            They told me there would be two people in a room, but that would only be temporary. Every two rooms would share a bathroom, and there would be double-decker bunks in each room. But I didn't want two people in the room.

            The night I got there, nobody else was there, and I decided to try to keep my room to myself. Now my wife was sick with TB in Santa Fe, but I had some boxes of stuff of hers. So I took out a little nightgown, opened the top bed, and threw the nightgown carelessly on it. I took out some slippers, and I threw some powder on the floor in the bathroom. I just made it look like somebody else was there. OK? So, what happened? Well, it's supposed to be a men's dormitory, see? So I came home that night, and my pajamas are folded nicely, and put under the pillow at the bottom, and my slippers put nicely at the bottom of the bed. The lady's nightgown is nicely folded under the pillow, the bed is all fixed up and made, and the slippers are put down nicely. The powder is cleaned from the bathroom and nobody is sleeping in the upper bed.

            Next night, the same thing. When I wake up, I rumple up the top bed, I throw the nightgown on it sloppily and scatter the powder in the bathroom and so on. I went on like this for four nights until everybody was settled and there was no more danger that they would put a second person in the room. Each night, everything was set out very neatly, even though it was a men's dormitory.

            I didn't know it then, but this little ruse got me involved in politics. There were all kinds of factions there, of course - the housewives faction, the mechanics faction, the technical peoples faction, and so on. Well, the bachelors and bachelor girls who lived in

the dormitory felt they had to have a faction too, because a new rule had been promulgated: No Women in the Men's Dorm. Well, this is absolutely ridiculous! After all, we are grown people! What kind of nonsense is this? We had to have political action. So we debated this stuff, and I was elected to represent the dormitory people in the Town Council.

            After I'd been in it for about a year and a half, I was talking to Hans Bethe about something. He was on the big Governing Council all this time, and I told him about this trick with my wife's nightgown and bedroom slippers. He started to laugh.”So that's how you got on the Town Council, “ he says.

            It turned out that what happened was this. The woman who cleans the rooms in the dormitory opens this door, and all of a sudden there is trouble: Somebody is sleeping with one of the guys! Shaking, she doesn't know what to do. She reports to the chief charwoman, the chief charwoman reports to the lieutenant, the lieutenant reports to the major. It goes all the way up, through the generals to the Governing Board.

            What are they going to do? What are they going to do? They're going to think about it, that's what! But, in the meantime, what instructions go down through the captains, down through the majors, through the lieutenants, through the chars' chief, through the charwoman? "Just put things back the way they are, clean then up, and see what happens." OK? Next day, same report. For four days, they worried up there about what they're going to do. Finally they promulgated a rule: No Women in the Men's Dormitory! And that caused such a stink down below that they had to elect somebody to represent the ......

            I would like to tell you something about the censorship that we had there. They decided to do something utterly illegal and censor the mail of people inside the United States - which they have no right to do. So it had to be set up very delicately as a voluntary thing. We would all volunteer not to seal the envelopes of the letters we sent out, and it would be all right for them to open letters coming in to us; that was voluntarily accepted by us. We would leave our letters open; and they would seal them if they were OK. If they weren't OK in their opinion, they would send the letter back to us with a note that there was a violation of such and such a paragraph of our "understanding."

            So, very delicately amongst all these liberal-minded scientific guys, we finally got the censorship set up, with many rules. We were allowed to comment on the character of the administration if we wanted to, so we could write our senator and tell him we don't like the way things are run, and things like that. They said they would notify us if there were any difficulties.

            So it was all set up, and here comes the first day for censorship: Telephone! Briiing!

            Me: "What?"

            "Please come down.

            I come down.

            "What's this?"

            "It's a letter from my father."

            "Well, what is it?"

            There's lined paper, and there's these lines going out with dots - four dots under, one dot above, two dots under, one dot above, dot under dot...

            "What's that?"

            I said, “It's a code."

They said, “ Yah, it's a code, but what does it say?"

I said, “I don't know what it says."

            They said, “Well, what's the key to the code? How do you decipher it?"

            I said, “Well, I don't know."

            Then they said, “What's this?"

            I said, “It's a letter from my wife - it says TJXYWZ TWIX3."

            "What's that?"

            I said, “Another code."

            "What's the key to it?"

            "I don't know."

            They said, “You're receiving codes, and you don't know the key?"

            I said, “Precisely. I have a game. I challenge them to send me a code that I can't decipher, see? So they're making up codes at the other end, and they're sending them in, and they're not going to tell me what the key is."

            Now one of the rules of the censorship was that they aren't going to disturb anything that you would ordinarily do, in the mail. So they said, “Well, you're going to have to tell them please to send the key in with the code."

I said, “I don't want to see the key!"

They said, “ Well, all right, we'll take the key out."

            So we had that arrangement. OK? All right. Next day I get a letter from my wife that says, “It's very difficult writing because I feel that the _____ is looking over my shoulder." And where the word was, there is a splotch made with ink eradicator.

            So I went down to the bureau, and I said, “You're not supposed to touch the incoming mail if you don't like it. You can look at it, but you're not supposed to take anything out."

            They said, “Don't be ridiculous. Do you think that's the way censors work - with ink eradicator? They cut things out with scissors."

            I said OK. So I wrote a letter back to my wife and said, “Did you use ink eradicator in your letter?" She writes back, “No, I didn't use ink eradicator in my

letter, it must have been the____ and there's a hole cut out of the paper,

            So I went back to the major who was supposed to be in charge of all this and complained. You know, this took a little time, but I felt I was sort of the representative to get the thing straightened out. The major tried to explain to me that these people who were the censors had been taught how to do it, but they didn't understand this new way that we had to be so delicate about.

            So, anyway, he said, “What's the matter, don't you think I have good will?"

            I said, “Yes, you have perfectly good will but I don't think you have power." Because, you see, he had already been on the job three or four days.

            He said, “We'll see about that!" He grabs the telephone, and everything is straightened out. No more is the letter cut.

            However, there were a number of other difficulties. For example, one day I got a letter from my wife and a note from the censor that said, “There was a code enclosed without the key, and so we removed it."

            So when I went to see my wife in Albuquerque that day, she said, “Well, where's all the stuff?"

            I said, “What stuff?"

            She said, “Litharge, glycerine, hot dogs, laundry.”

            I said, “Wait a minute - that was a list?"

            She said, “Yes."

            "That was a code, “ I said.”They thought it was a code - litharge, glycerine, etc." (She wanted litharge and glycerine to make a cement to fix an onyx box.)

            All this went on in the first few weeks before we got each other straightened out. Anyway, one day I'm piddling around with the computing machine, and I notice something very peculiar. If you take 1 divided by 273 you get .004115226337... It's quite cute, and then it goes a little cockeyed when you're carrying; confusion occurs for only about three numbers, and then you can see how the 10 10 13 is really equivalent to 114 again, or 115 again, and it keeps on going, and repeats itself nicely after a couple of cycles. I thought it was kind of amusing.

            Well, I put that in the mail, and it comes back to me. It doesn't go through, and there's a little note: "Look at Paragraph 17B." I look at Paragraph 17B. It says, “Letters are to be written only in English, Russian, Spanish, Portuguese, Latin, German, and so forth. Permission to use any other language must be obtained in writing." And then it said, “No codes."

            So I wrote back to the censor a little note included in my letter which said that I feel that of course this cannot be a code, because if you actually do divide 1 by 273 you do, in fact, get all that, and therefore there's no more information in the number .004115226337... than there is in the number 273 - which is hardly any information at all. And so forth. I therefore asked for permission to use Arabic numerals in my letters. So, I got that through all right.

            There was always some kind of difficulty with the letters going back and forth. For example, my wife kept mentioning the fact that she felt uncomfortable writing with the feeling that the censor is looking over her shoulder. Now, as a rule, we aren't supposed to mention censorship. We aren't, but how can they tell her? So they keep sending me a note: "Your wife mentioned censorship.” Certainly my wife mentioned censorship. So finally they sent me a note that said, “Please inform your wife not to mention censorship in her letters.” So I start my letter: "I have been instructed to inform you not to mention censorship in your letters." Phoom, Phoooom, it comes right back! So I write, “I have been instructed to inform my wife not to mention censorship. How in the heck am I going to do it? Furthermore, why do I have to instruct her not to mention censorship? You keeping something from me?"

            It is very interesting that the censor himself has to tell me to tell my wife not to tell me that she's .... But they had an answer. They said, yes, that they are worried about mail being intercepted on the way from Albuquerque, and that someone might find out that there was censorship if they looked in the mail, and would she please act much more normal.

            So I went down the next time to Albuquerque, and I talked to her and I said, “Now, look, let's not mention censorship.” But we had had so much trouble that we at last worked out a code, something illegal. If I would put a dot at the end of my signature, it meant I had had trouble again, and she would move on to the next of the moves that she had concocted. She would sit there all day long, because she was ill, and she would think of things to do. The last thing she did was to send me an advertisement which she found perfectly legitimately. It said, “Send your boyfriend a letter on a jigsaw puzzle. We sell you the blank, you write the letter on it, take it all apart, put it in a little sack, and mail it." I received that one with a note saying, “We do not have time to play games. Please instruct your wife to confine herself to ordinary letters.”

            Well, we were ready with the one more dot, but they straightened out just in time and we didn't have to use it. The thing we had ready for the next one was that the letter would start, “ I hope you remembered to open this letter carefully because I have included the Pepto Bismol powder for your stomach as we arranged.” It would be a letter full of powder. In the office we expected they would open it quickly, the powder would go all over the floor, and they would get all upset because you are not supposed to upset anything. They'd have to gather up all this Pepto Bismol ... But we didn't have to use that one. OK?

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 begins to wonder what's 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 71 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.

Well, 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, “Well, 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.”

            Well, 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. OK?

            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!

            After I was able to open the filing cabinets by picking the locks, they got filing cabinets that had safe combinations. Now, one of my diseases, one of my things in life, is that anything that is secret I try to undo. And so the locks to those filing cabinets represented a challenge to me. How the hell to open them? So I worked and worked on them. There are all kinds of stories about how you can feel the numbers and listen to things and so on. That's true; I understand it very well -- for old-fashioned safes. But these had a new design so that nothing would be pushing against the wheels while you were trying them, and none of the old methods would work.

            I read books by locksmiths, which always say in the beginning how they opened the locks when the safe is under water and the woman in it is drowning or something, and the great locksmith opened the safe. And then in the back they tell you how they do it, and they don't tell you anything sensible. It doesn't sound like they could really open safes that way - like guess the combination on the basis of the psychology of the person who owns it! So I always figured they were keeping the method a secret, and like a kind of disease, I kept working on these things until I found out a few things.

            First, I found out how big a range you need to open the combination, how close you have to be. And then I invented a system by which you could try all the necessary combinations - 8,000, as it turned out, because you could be within two of every number. And then I worked out a scheme by which I could try numbers without altering a number that I had already set, by correctly moving the wheels, so that I could try all the combinations in eight hours. And then finally I discovered (this took me about two years of researching) that it's easy to take the last two numbers of the combination off the safe if the safe is open. If the drawer was pulled out, you could turn the number and see the bolt go up and play around and find out what number it comes back at, and stuff like that. With a little trickery, you can get the combination off.

            So I used to practice it like a cardsharp practices cards, you know - all the time. Quicker and quicker and more and more unobtrusively I would come in and talk to some guy. I'd sort of lean against his filing cabinet, and you wouldn't even notice I'm doing anything. I'm not doing anything - just playing with the dial, that's all, just playing with the dial. But all the time I was taking the two numbers off! And then I would go back to my office and write the two numbers down, the last two numbers of the three. Now, if you have the last two numbers, it takes just a minute to try for the first number; there's only 20 possibilities, and it's open. OK? It takes about three minutes to open a safe if you know the last two numbers.

            So I got an excellent reputation for safe-cracking. They would say to me, “Mr. Schmultz is out of town, and we need a document from his safe. Can you open it?"

            I'd say, “Yes, I can open it, but I have to go get my tools.”

            I didn't need any tools, but I'd go to my office and look up the number of his safe. I had the last two numbers for everybody's safe in my office. I'd put a screwdriver in my back pocket to account for the tool I claimed I needed. I'd go back to the room and close the door. The attitude is that this business about how you open safes is not something that everybody should know because it makes everything very unsafe. So I'd close the door and then sit down and read a magazine or do something. I'd average about 20 minutes of doing nothing, and then I'd open it. Well, I really opened it right away to see that everything was all right, and then I'd sit there for 20 minutes to give myself a good reputation that it wasn't too easy, that there was no trick to it. And then I'd come out, sweating a bit, and say, “It's open. There you are."

            Once, however, I did open a safe purely by accident, and that helped to reinforce my reputation. It was a sensation, but it was pure luck.

            I went back to Los Alamos after the war was over to finish some papers, and there I did some safe opening that - well, I could write a safecracker book better than any previous safecracker book. It would start by explaining how I opened the safe - absolutely cold, without knowing the combination - which contained more secret things than any safe that's ever been opened. I opened the safe that contained the secret of the atomic bomb - all the secrets, the formulas, the rates at which neutrons are liberated from uranium, how much uranium you need to make a bomb, how much was being made and available, all the theories, all the calculations, the WHOLE DAMN THING!

            This is the way it was done.

            I was trying to write a report. I needed some material but it was a Saturday. I thought everybody worked. I thought it was like Los Alamos used to be. So I went down to get some documents from the library. The library at Los Alamos had all these documents in a great vault with a lock and dial of a kind I didn't know anything about. Filing cabinets I understood, but I was an expert only on filing cabinets. Not only that, but there were guards walking back and forth in front with guns. I couldn't get that vault open. OK?

            But then I thought, wait! Old Freddy DeHoffman is in charge of deciding which documents now can be de-classified. He had to run down to the library and back so often, he got tired of it. And he got a brilliant idea. He would get a copy made of every document in the Los Alamos library. And he'd stick them in his files. He had nine filing cabinets, one right next to the other in two rooms, full of all the documents of Los Alamos.

            I went up to his office. The office door was open. It looked like he was coming back any minute; the light was lit. So I waited. And, as always when I'm waiting, I diddled the knobs. I tried 10-20-30 - didn't work. I tried 20-40-60 - didn't work. I tried everything, because I'm waiting, with nothing to do.

            Then I began to think. You know, I have never been able to figure out how to open safes cleverly, so maybe  those locksmith people don't either. Maybe all the stuff they tell me about psychology is right. I'm going to open this one by psychology.

            The first thing the book says is: "The secretary is very often nervous that she will forget the combination.” She's been told the combination, but she might forget, and the boss might forget. She has to know. So she nervously writes it somewhere. Where? List of places where a secretary might write combinations, OK? It starts right out with the most clever thing: You open the drawer, and on the wood along the outside of the drawer is written carelessly a number, as if it is an invoice number. That's the combination number. So. It's on the side of the desk, OK? I remembered that; it's in the book.

            The desk drawer was locked, but I picked the lock easily. I pulled out the drawer, looked along the wood. Nothing. All right, all right. There were a lot of papers in the drawer. I fished around among the papers, and finally I found it, a nice little piece of paper which has the Greek alphabet - alpha, beta, gamma, delta, and so forth - carefully printed.

            The secretaries have to know how to make those letters and what to call them when they're talking about them, right? So they each had a copy of the thing. But - carelessly scrawled across the top is, pi is equal to 3.14159. Well, why does she need the numerical value of pi? She's not computing anything. So I walked up to the safe. 31-41-59 - doesn't open. 13-14-95 doesn't open. 95-14-13 - doesn't open. For 20 minutes I turned pi upside down. Nothing happened.

            So I started walking out of the office, and I remembered in the book about the psychology, and I said, “You know, it's true. Psychologically, DeHoffman is just the kind of a guy to use a mathematical constant for his safe combination. And the other important mathematical constant is e.” So I walk back to the safe. 27-18-28 - click, clock, it opens.

            I checked, by the way, that all the rest of the filing cabinets had the same combination.

            Well, I want to tell about some of the special problems I had at Los Alamos that were rather interesting. One thing had to do with the safety of the plant at Oak Ridge. 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 practising 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 - and though we would send them instructions, they never got it right.

            So finally 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 says, “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 says.

            Huh! Explode?

            And so the Army said, “You see! We shouldn't have let any information get to them! Now they are all upset.”

            Well, it turned out that the Army had realized how much stuff we needed to make a bomb -- 20 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. And so 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. So, 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. Christie'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 Christie 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 Christie, and said, you have all the stuff, so go. Christie got pneumonia; I had to go.

            I never traveled on an airplane before. I traveled on an airplane. 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. ”It looks like this. There are some generals coming. They are going to put off some of us number 3's.”

            "It's all right, “ I said, “I'm a number 2."

            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 2 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 short-term 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 home that night, and I 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 be 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!

            So 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. And that was good because the plant would have blown up if nobody had paid attention to this problem.

            Well, there was a Lieutenant Zumwalt who took care of me, and 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. So 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 or not 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.

            So in five minutes he said, “All right, Mr. Feynman, go ahead."

            So 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 turned out to be a tremendous genius to them.

            I was a god coming down from the sky! Here were all these phenomena that were not understood and never heard of before - but I knew all about it; I could give them facts and numbers and everything else. So, from being rather primitive back there at Los Alamos, I became a super-genius at the other end.

            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 re-design 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. OK?

            How do you look at a plant that ain't built yet? I don't know. Well, 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 cover, a stack of large, long 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 start to explain it to me, because they think I am a genius. Now, one of the things they had to avoid in the plant was accumulation. So 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, down-up-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?"

            I don't know what to do. (You are not going to believe this story, but I swear it's absolutely true - it's such sensational luck.) I thought, what am I going to do? I got an idea. Maybe it's a valve? So, in order to find out whether it's a valve or not, 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 number 3, 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 up and down, back and forth, back and forth, and they both look at each other and they tchk, tchk, tchk, and 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.


Well, 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. So 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 explosion, so you can figure out exactly how much energy was released and so on - required much more calculating than we were capable of. A rather clever fellow by the name of Stanley Frankel realized that it could possibly be 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. But she was the multiplier, and she was the adder, and this one cubed, and we had index cards, and all she did was cube this number and send it to the next one.

            We went through our cycle this way until we got all the bugs out. Well, 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. So 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.

            And so 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 arctangent 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.

            And so 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 - and so forth.

            So my boys really came through, and all that had to be done was to tell them what it was, that's all. 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 bunch 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 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 Christie 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."

            So 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 there was nothing else 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 died in Albuquerque, and I had to go down. I borrowed Fuchs' car. He was a friend of mine in the dormitory. He had an automobile. He was using the automobile to take the secrets away, you know, down to Santa Fe. He was the spy. I didn't know that. I borrowed his car to go to Albuquerque. The damn thing got three flat tires on the way. I came back from there, and I went into the room, because I was supposed to be supervising everything, but I couldn't do it for three days.

            It was in this mess. There's white cards, there's blue cards, there's yellow cards, and I start 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 50 cards and you make a mistake at card number 39, it affects 37, 38, and 39. The next, card 36, 37, 38, 39, and 40. 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 10 cards around the error. And because 10 cards could be put through the machine faster than the deck of 50 cards, they would go rapidly through with this other deck while they continued with the 50 cards with the disease spreading. But the other thing was computing faster, and they would seal it all up and correct it. OK? Very clever.

            That was the way those guys worked, really hard, very clever, 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. So I left them alone and everything came out. We solved the problem in time and that's the way it was.


I would like to tell a little about some of the people I met. I was an underling at the beginning. I became a group leader. But 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, 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. So that was quite a lesson to me.

            Then there was Von Neumann, the great mathematician. We used to go for walks on Sunday. We'd walk in the canyons, and we'd often walk with Bethe, and Von Neumann, and 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, from the corner.

            In the morning of the day he's due to come next time, I get a telephone call.

            "Hello - Feynman?"

            "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. OK."

            So, at 8 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. Blah, blah, 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."

            So forth, back and forth. I was always dumb about one thing. 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. Just as I was lucky with that blueprint, I'm lucky in my life that I can do this.

            So, 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 says 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, he 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."

The next thing that happened, of course, was the ' I 'test, after we'd made the calculations. 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 just arrived when the buses were leaving, so I went straight out to the site and we waited out there, 20 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 20 seconds or something to go, for people who were far away like we were. Others were closer, 6 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. OK.

            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 ain't it. That's an after-image.” So I look back up, and I see this white light changing into yellow and then into orange. The clouds form and then they disappear again; the compression and the expansion forms and makes clouds disappear. Then 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 of the fire going out, the heat.

            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 Mr. 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's kicking the doorstop, you see, and I said, “Yes, the doorstop certainly is appropriate for this door.” The doorstop was a 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. So 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 anymore, 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 St? ... 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 about 30 years now, isn't it? So I've been wrong for 30 years about it being useless making bridges and I'm glad that those other people had the sense to go ahead.


"Los Alamos From Below'' has been adapted from a talk given by Richard P. Feynman, Richard Chace Tolman Professor of Theoretical Physics at Caltech, in the First Annual Santa Barbara Lectures on Science and Society, given at the University of California at Santa Barbara in 1975. This was one of nine lectures presented in a series of "Reminiscences of Los Alamos, 1943-1945." The lectures are now being edited for publication by Dr. Lawrence Badash of the Department of History, UCSB.