Surely You're Joking, Mr. Feynman! (13 page)

The lieutenant couldn’t get any information from anybody and we went happily along, working on this mechanical computer, without any interference.

One day the lieutenant came by and asked us a simple question: “Suppose that the observer is not at the same location as the gunner–how do you handle that?”

We got a terrible shock. We had designed the whole business using polar coordinates, using angles and the radius distance. With X and Y coordinates, it’s easy to correct for a displaced observer. It’s simply a matter of addition or subtraction. But with polar coordinates, it’s a terrible mess!

So it turned out that this lieutenant whom we were trying to keep from telling us anything ended up telling us something very important that we had forgotten in the design of this device: the possibility that the gun and the observing station are not at the same place! It was a big mess to fix it.

Near the end of the summer I was given my first real design job: a machine that would make a continuous curve out of a set of points–one point coming in every fifteen seconds–from a new invention developed in England for tracking airplanes, called “radar.” It was the first time I had ever done any mechanical designing, so I was a little bit frightened.

I went over to one of the other guys and said, “You’re a mechanical engineer; I don’t know how to do any mechanical engineering, and I just got this job

“There’s nothin’ _to_ it,” he said. “Look, I’ll show you. There’s two rules you need to know to design these machines. First, the friction in every bearing is so-and-so much, and in every gear junction, so-and-so much. From that, you can figure out how much force you need to drive the thing. Second, when you have a gear ratio, say 2 to 1, and you are wondering whether you should make it 10 to 5 or 24 to 12 or 48 to 24, here’s how to decide: You look in the Boston Gear Catalogue, and select those gears that are in the middle of the list. The ones at the high end have so many teeth they’re hard to make. If they could make gears with even finer teeth, they’d have made the list go even higher. The gears at the low end of the list have so few teeth they break easy. So the best design uses gears from the middle of the list.”

I had a lot of fun designing that machine. By simply selecting the gears from the middle of the list and adding up the little torques with the two numbers he gave me, I could be a mechanical engineer!

The army didn’t want me to go back to Princeton to work on my degree after that summer. They kept giving me this patriotic stuff, and offered a whole project that I could run, if I would stay.

The problem was to design a machine like the other one–what they called a director–but this time I thought the problem was easier, because the gunner would be following behind in another airplane at the same altitude. The gunner would set into my machine his altitude and an estimate of his distance behind the other airplane. My machine would automatically tilt the gun up at the correct angle and set the fuse.

As director of this project, I would he making trips down to Aberdeen to get the firing tables. However, they already had some preliminary data. I noticed that for most of the higher altitudes where these airplanes would be flying, there wasn’t any data. So I called up to find out why there wasn’t any data and it turned out that the fuses they were going to use were not clock fuses, but powder-train fuses, which didn’t work at those altitudes–they fizzled out in the thin air.

I thought I only had to correct the air resistance at different altitudes. Instead, my job was to invent a machine that would make the shell explode at the right moment, when the fuse won’t burn!

I decided that was too hard for me and went back to Princeton.

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Testing Bloodhounds
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When I was at Los Alamos and would get a little time off, I would often go visit my wife, who was in a hospital in Albuquerque, a few hours away. One time I went to visit her and couldn’t go in right away so I went to the hospital library to read.

I read an article in _Science_ about bloodhounds, and how they could smell so very well. The authors described the various experiments that they did–the bloodhounds could identify which items had been touched by people, and so on–and I began to think: It _is_ very remarkable how good bloodhounds are at smelling, being able to follow trails of people, and so forth, but how good are _we_, actually?

When the time came that I could visit my wife, I went to see her, and I said, “We’re gonna do an experiment. Those Coke bottles over there (she had a six-pack of empty Coke bottles that she was saving to send out)–now you haven’t touched them in a couple of days, right?”

“That’s right.”

I took the six-pack over to her without touching the bottles, and said, “OK. Now I’ll go out, and you take out one of the bottles, handle it for about two minutes, and then put it back. Then I’ll come in, and try to tell which bottle it was.”

So I went out, and she took out one of the bottles and handled it for quite a while–lots of time, because I’m no bloodhound! According to the article, they could tell if you just touched it.

Then I came back, and it was absolutely obvious! I didn’t even have to smell the damn thing, because, of course, the temperature was different. And it was also obvious from the smell. As soon as you put it up near your face, you could smell it was dampish and warmer. So that experiment didn’t work because it was too obvious.

Then I looked at the bookshelf and said, “Those books you haven’t looked at for a while, right? This time, when I go out, take one book off the shelf, and just open it–that’s all–and close it again; then put it back.”

So I went out again, she took a book, opened it and closed it, and put it back. I came in–and nothing _to_ it! It was easy. You just smell the books. It’s hard to explain, because we’re not used to saying things about it. You put each book up to your nose and sniff a few times, and you can tell. It’s very different. A book that’s been standing there a while has a dry uninteresting kind of smell. But when a hand has touched it, there’s a dampness and a smell that’s very distinct.

We did a few more experiments, and I discovered that while bloodhounds are indeed quite capable, humans are not as incapable as they think they are: it’s just that they carry their nose so high off the ground!

(I’ve noticed that my dog can correctly tell which way I’ve gone in the house, especially if I’m barefoot, by smelling my footprints. So I tried to do that: I crawled around the rug on my hands and knees, sniffing, to see if I could tell the difference between where I walked and where I didn’t, and I found it impossible. So the dog _is_ much better than I am.)

Many years later, when I was first at Caltech, there was a party at Professor Bacher’s house, and there were a lot of people from Caltech. I don’t know how it came up, but I was telling them this story about smelling the bottles and the books. They didn’t believe a word, naturally because they always thought I was a faker. I had to demonstrate it.

We carefully took eight or nine books off the shelf without touching them directly with our hands, and then I went out. Three different people touched three different books: they picked one up, opened it, closed it, and put it back.

Then I came back, and smelled everybody’s hands, and smelled all the books–I don’t remember which I did first– and found all three books correctly; I got one person wrong.

They still didn’t believe me; they thought it was some sort of magic trick. They kept trying to figure out how I did it. There’s a famous trick of this kind, where you have a confederate in the group who gives you signals as to what it is, and they were trying to figure out who the confederate was. Since then I’ve often thought that it would be a good card trick to take a deck of cards and tell someone to pick a card and put it back, while you’re in the other room. _You say_, “Now I’m going to tell you which card it is, because I’m a bloodhound: I’m going to _smell_ all these cards and tell you which card you picked.” Of course, with that kind of patter, people wouldn’t believe for a minute that that’s what you were actually doing!

People’s hands smell very different–that’s why dogs can identify people; you have to _try_ it! All hands have a sort of moist smell, and a person who smokes has a very different smell on his hands from a person who doesn’t; ladies often have different kinds of perfumes, and so on. If somebody happened to have some coins in his pocket and happened to be handling them, you can smell that.

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Los Alamos from Below
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[Adapted from a talk given in the First Annual Santa Barbara Lectures on Science and Society at the University of California at Santa Barbara in 1975. ‘Los Alamos from Below” was one of nine lectures in a series published as _Reminiscences of Los Alamos_, 1943–1945, edited by L. Badash _et al_., pp. 105–132. Copyright C 1980 by D. Reidel Publishing Company, Dordrecht, Holland.]

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.

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 fellas 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 how our process of separating isotopes worked, 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 was perfectly right. Another guy would say, well, maybe, but there’s this other possibility we have to consider against it.

So everybody is disagreeing, all around the table. I am surprised and disturbed that Compton doesn’t repeat and emphasize his point. 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 fella 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. 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 fellas 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.