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Surely You’re Joking, Mr. Feynman

ModernLib.Net / Áèîãðàôèè è ìåìóàðû / Feynman Richard P., Hutchings Edward, Leighton Ralph / Surely You’re Joking, Mr. Feynman - ×òåíèå (ñòð. 6)
Àâòîðû: Feynman Richard P.,
Hutchings Edward,
Leighton Ralph
Æàíð: Áèîãðàôèè è ìåìóàðû

 

 


If it was contour integration, they would have found it; if it was a simple series expansion, they would have found it. Then I come along and try differentiating under the integral sign, and often it worked. So I got a great reputation for doing integrals, only because my box of tools was different from everybody else’s, and they had tried all their tools on it before giving the problem to me.

Mindreaders

My father was always interested in magic and carnival tricks, and wanting to see how they worked. One of the things he knew about was mindreaders. When he was a little boy growing up in a small town called Patchogue, in the middle of Long Island, it was announced on advertisements posted all over that a mindreader was coming next Wednesday. The posters said that some respected citizens—the mayor, a judge, a banker—should take a five-dollar bill and hide it somewhere, and when the mindreader came to town, he would find it.

When he came, the people gathered around to watch him do his work. He takes the hands of the banker and the judge, who had hidden the five-dollar bill, and starts to walk down the street. He gets to an intersection, turns the corner, walks down another street, then another, to the correct house. He goes with them, always holding their hands, into the house, up to the second floor, into the right room, walks up to a bureau, lets go of their hands, opens the correct drawer, and there’s the five-dollar bill. Very dramatic!

In those days it was difficult to get a good education, so the mindreader was hired as a tutor for my father. Well, my father, after one of his lessons, asked the mindreader how he was able to find the money without anyone telling him where it was.

The mindreader explained that you hold onto their hands, loosely and as you move, you jiggle a little bit. You come to an intersection, where you can go forward, to the left, or to the right. You jiggle a little bit to the left, and if it’s incorrect, you feel a certain amount of resistance, because they don’t expect you to move that way. But when you move in the right direction, because they think you might he able to do it, they give way more easily and there’s no resistance. So you must always be jiggling a little bit, testing out which seems to be the easiest way.

My father told me the story and said he thought it would still take a lot of practice. He never tried it himself.

Later, when I was doing graduate work at Princeton, I decided to try it on a fellow named Bill Woodward. I suddenly announced that I was a mindreader, and could read his mind. I told him to go into the “laboratory”—a big room with rows of tables covered with equipment of various kinds, with electric circuits, tools, and junk all over the place—pick out a certain object, somewhere, and come out. I explained, “Now I’ll read your mind and take you right up to the object.”

He went into the lab, noted a particular object, and came out. I took his hand and started jiggling. We went down this aisle, then that one, right to the object. We tried it three times. One time I got the object right on—and it was in the middle of a whole bunch of stuff. Another time I went to the right place but missed the object by a few inches—wrong object. The third time, something went wrong. But it worked better than I thought. It was very easy.

Some time after that, when I was about twenty-six or so, my father and I went to Atlantic City where they had various carnival things going on outdoors. While my father was doing some business, I went to see a mindreader. He was seated on the stage with his back to the audience, dressed in robes and wearing a great big turban. He had an assistant, a little guy who was running around through the audience, saying things like, “Oh, Great Master, what is the color of this pocketbook?”

“Blue!” says the master.

“And oh, Illustrious Sir, what is the name of this woman?”

“Marie!”

Some guy gets up: “What’s my name?”

“Henry.”

I get up and say, “What’s my name?”

He doesn’t answer. The other guy was obviously a confederate, but I couldn’t figure out how the mindreader did the other tricks, like telling the color of the pocketbook. Did he wear earphones underneath the turban?

When I met up with my father, I told him about it. He said, “They have a code worked out, but I don’t know what it is. Let’s go back and find out.”

We went back to the place, and my father said to me, “Here’s fifty cents. Go get your fortune read in the booth back there, and I’ll see you in half an hour.”

I knew what he was doing. He was going to tell the man a story, and it would go smoother if his son wasn’t there going, “Ooh, ooh!” all the time. He had to get me out of the way.

When he came back he told me the whole code: “Blue is ‘Oh, Great Master,’ Green is ‘Oh, Most Knowledgeable One,’” and so forth. He explained, “I went up to him, afterwards, and told him I used to do a show in Patchogue, and we had a code, but it couldn’t do many numbers, and the range of colors was shorter. I asked him, ‘How do you carry so much information?’”

The mindreader was so proud of his code that he sat down and explained the whole works to my father. My father was a salesman. He could set up a situation like that. I can’t do stuff like that.

The Amateur Scientist

When I was a kid I had a “lab.” It wasn’t a laboratory in the sense that I would measure, or do important experiments.

Instead, I would play: I’d make a motor, I’d make a gadget that would go off when something passed a photocell. I’d play around with selenium; I was piddling around all the time. I did calculate a little bit for the lamp bank, a series of switches and bulbs I used as resistors to control voltages. But all that was for application. I never did any laboratory kind of experiments.

I also had a microscope and loved to watch things under the microscope.It took patience: I would get something under the microscope and I would watch it interminably. I saw many interesting things, like everybody sees—a diatom slowly making its way across the slide, and so on.

One day I was watching a paramecium and I saw something that was not described in the books I got in school—in college, even. These books always simplify things so the world will be more like they want it to be: When they’re talking about the behavior of animals, they always start out with, “The paramecium is extremely simple; it has a simple behavior. It turns as its slipper shape moves through the water until it hits something, at which time it recoils, turns through an angle, and then starts out again.”

It isn’t really right. First of all, as everybody knows, the paramecia, from time to time, conjugate with each other—they meet and exchange nuclei. How do they decide when it’s time to do that? (Never mind; that’s not my observation.)

I watched these paramecia hit something, recoil, turn through an angle, and go again. The idea that it’s mechanical, like a computer program—it doesn’t look that way. They go different distances, they recoil different distances, they turn through angles that are different in various cases; they don’t always turn to the right; they’re very irregular. It looks random, because you don’t know what they’re hitting; you don’t know all the chemicals they’re smelling, or what.

One of the things I wanted to watch was what happens to the paramecium when the water that it’s in dries up. It was claimed that the paramecium can dry up into a sort of hardened seed. I had a drop of water on the slide under my microscope, and in the drop of water was a paramecium and some “grass”—at the scale of the paramecium, it looked like a network of jackstraws. As the drop of water evaporated, over a time of fifteen or twenty minutes, the paramecium got into a tighter and tighter situation: there was more and more of this back-and-forth until it could hardly move. It was stuck between these “sticks,” almost jammed.

Then I saw something I had never seen or heard of: the paramecium lost its shape. It could flex itself, like an amoeba. It began to push itself against one of the sticks, and began dividing into two prongs until the division was about halfway up the paramecium, at which time it decided that wasn’t a very good idea, and backed away.

So my impression of these animals is that their behavior is much too simplified in the books. It is not so utterly mechanical or one-dimensional as they say. They should describe the behavior of these simple animals correctly. Until we see how many dimensions of behavior even a one-celled animal has, we won’t be able to fully understand the behavior of more complicated animals.

I also enjoyed watching hugs. I had an insect book when I was about thirteen. It said that dragonflies are not harmful; they don’t sting. In our neighborhood it was well known that “darning needles,” as we called them, were very dangerous when they’d sting. So if we were outside somewhere playing baseball, or something, and one of these things would fly around, everybody would run for cover, waving their arms, yelling, “A darning needle! A darning needle!”

So one day I was on the beach, and I’d just read this book that said dragonflies don’t sting. A darning needle came along, and everybody was screaming and running around, and I just sat there. “Don’t worry!” I said. “Darning needles don’t sting!”

The thing landed on my foot. Everybody was yelling and it was a big mess, because this darning needle was sitting on my foot, And there I was, this scientific wonder, saying it wasn’t going to sting me.

You’re sure this is a story that’s going to come out that it stings me—but it didn’t. The book was right. But I did sweat a bit.

I also had a little hand microscope. It was a toy microscope, and I pulled the magnification piece out of it, and would hold it in my hand like a magnifying glass, even though it was a microscope of forty or fifty power. With care you could hold the focus. So I could go around and look at things right out in the street.

So when I was in graduate school at Princeton, I once took it out of my pocket to look at some ants that were crawling around on some ivy. I had to exclaim out loud, I was so excited. What I saw was an ant and an aphid, which ants take care of—they carry them from plant to plant if the plant they’re on is dying. In return the ants get partially digested aphid juice, called “honeydew.” I knew that; my father had told me about it, but I had never seen it.

So here was this aphid and sure enough, an ant came along, and patted it with its feet—all around the aphid, pat, pat, pat, pat, pat. This was terribly exciting! Then the juice came out of the back of the aphid. And because it was magnified, it looked like a big, beautiful, glistening ball, like a balloon, because of the surface tension. Because the microscope wasn’t very good, the drop was colored a little bit from chromatic aberration in the lens—it was a gorgeous thing!

The ant took this ball in its two front feet, lifted it off the aphid, and held it. The world is so different at that scale that you can pick up water and hold it! The ants probably have a fatty or greasy material on their legs that doesn’t break the surface tension of the water when they hold it up. Then the ant broke the surface of the drop with its mouth, and the surface tension collapsed the drop right into his gut. It was very interesting to see this whole thing happen!

In my room at Princeton I had a bay window with a U-shaped windowsill. One day some ants came out on the windowsill and wandered around a little bit. I got curious as to how they found things. I wondered, how do they know where to go? Can they tell each other where food is, like bees can? Do they have any sense of geometry?

This is all amateurish; everybody knows the answer, but I didn’t know the answer, so the first thing I did was to stretch some string across the U of the bay window and hang a piece of folded cardboard with sugar on it from the string. The idea of this was to isolate the sugar from the ants, so they wouldn’t find it accidentally. I wanted to have everything under control.

Next I made a lot of little strips of paper and put a fold in them, so I could pick up ants and ferry them from one place to another. I put the folded strips of paper in two places:

Some were by the sugar (hanging from the string), and the others were near the ants in a particular location. I sat there all afternoon, reading and watching, until an ant happened to walk onto one of my little paper ferries. Then I took him over to the sugar. After a few ants had been ferried over to the sugar, one of them accidentally walked onto one of the ferries nearby, and I carried him back.

I wanted to see how long it would take the other ants to get the message to go to the “ferry terminal.” It started slowly but rapidly increased until I was going mad ferrying the ants back and forth.

But suddenly, when everything was going strong, I began to deliver the ants from the sugar to a different spot. The question now was, does the ant learn to go back to where it just came from, or does it go where it went the time before?

After a while there were practically no ants going to the first place (which would take them to the sugar), whereas there were many ants at the second place, milling around, trying to find the sugar. So I figured out so far that they went where they just came from.

In another experiment, I laid out a lot of glass microscope slides, and got the ants to walk on them, back and forth, to some sugar I put on the windowsill. Then, by replacing an old slide with a new one, or by rearranging the slides, I could demonstrate that the ants had no sense of geometry: they couldn’t figure out where something was. If they went to the sugar one way and there was a shorter way back, they would never figure out the short way.

It was also pretty clear from rearranging the glass slides that the ants left some sort of trail. So then came a lot of easy experiments to find out how long it takes a trail to dry up, whether it can be easily wiped off, and so on. I also found out the trail wasn’t directional. If I’d pick up an ant on a piece of paper, turn him around and around, and then put him back onto the trail, he wouldn’t know that he was going the wrong way until he met another ant. (Later, in Brazil, I noticed some leaf-cutting ants and tried the same experiment on them. They could tell, within a few steps, whether they were going toward the food or away from it—presumably from the trail, which might be a series of smells in a pattern: A, B, space, A, B, space, and so on.)

I tried at one point to make the ants go around in a circle, but I didn’t have enough patience to set it up. I could see no reason, other than lack of patience, why it couldn’t be done.

One thing that made experimenting difficult was that breathing on the ants made them scurry. It must be an instinctive thing against some animal that eats them or disturbs them. I don’t know if it was the warmth, the moisture, or the smell of my breath that bothered them, but I always had to hold my breath and kind of look to one side so as not to confuse the experiment while I was ferrying the ants.

One question that I wondered about was why the ant trails look so straight and nice. The ants look as if they know what they’re doing, as if they have a good sense of geometry. Yet the experiments that I did to try to demonstrate their sense of geometry didn’t work.

Many years later, when I was at Caltech and lived in a little house on Alameda Street, some ants came out around the bathtub. I thought, “This is a great opportunity.” I put some sugar on the other end of the bathtub, and sat there the whole afternoon until an ant finally found the sugar. It’s only a question of patience.

The moment the ant found the sugar, I picked up a colored pencil that I had ready (I had previously done experiments indicating that the ants don’t give a damn about pencil marks—they walk right over them—so I knew I wasn’t disturbing anything), and behind where the ant went I drew a line so I could tell where his trail was. The ant wandered a little bit wrong to get back to the hole, so the line was quite wiggly unlike a typical ant trail.

When the next ant to find the sugar began to go back, I marked his trail with another color. (By the way he followed the first ant’s return trail back, rather than his own incoming trail. My theory is that when an ant has found some food, he leaves a much stronger trail than when he’s just wandering around.)

This second ant was in a great hurry and followed, pretty much, the original trail. But because he was going so fast he would go straight out, as if he were coasting, when the trail was wiggly. Often, as the ant was “coasting,” he would find the trail again. Already it was apparent that the second ant’s return was slightly straighter. With successive ants the same “improvement” of the trail by hurriedly and carelessly “following” it occurred.

I followed eight or ten ants with my pencil until their trails became a neat line right along the bathtub. It’s something like sketching: You draw a lousy line at first; then you go over it a few times and it makes a nice line after a while.

I remember that when I was a kid my father would tell me how wonderful ants are, and how they cooperate. I would watch very carefully three or four ants carrying a little piece of chocolate back to their nest. At first glance it looks like efficient, marvelous, brilliant cooperation. But if you look at it carefully you’ll see that it’s nothing of the kind: They’re all behaving as if the chocolate is held up by something else. They pull at it one way or the other way. An ant may crawl over it while it’s being pulled at by the others. It wobbles, it wiggles, the directions are all confused. The chocolate doesn’t move in a nice way toward the nest.

The Brazilian leaf-cutting ants, which are otherwise so marvelous, have a very interesting stupidity associated with them that I’m surprised hasn’t evolved out. It takes considerable work for the ant to cut the circular arc in order to get a piece of leaf. When the cutting is done, there’s a fifty-fifty chance that the ant will pull on the wrong side, letting the piece he just cut fall to the ground. Half the time, the ant will yank and pull and yank and pull on the wrong part of the leaf, until it gives up and starts to cut another piece. There is no attempt to pick up a piece that it, or any other ant, has already cut. So it’s quite obvious, if you watch very carefully that it’s not a brilliant business of cutting leaves and carrying them away; they go to a leaf, cut an arc, and pick the wrong side half the time while the right piece falls down.

In Princeton the ants found my larder, where I had jelly and bread and stuff, which was quite a distance from the window. A long line of ants marched along the floor across the living room. It was during the time I was doing these experiments on the ants, so I thought to myself, “What can I do to stop them from coming to my larder without killing any ants? No poison; you gotta be humane to the ants!”

What I did was this: In preparation, I put a bit of sugar about six or eight inches from their entry point into the room, that they didn’t know about. Then I made those ferry things again, and whenever an ant returning with food walked onto my little ferry I’d carry him over and put him on the sugar. Any ant coming toward the larder that walked onto a ferry I also carried over to the sugar. Eventually the ants found their way from the sugar to their hole, so this new trail was being doubly reinforced, while the old trail was being used less and less. I knew that after half an hour or so the old trail would dry up, and in an hour they were out of my larder. I didn’t wash the floor; I didn’t do anything but ferry ants.

Part 3. Feynman, the Bomb, and the Military

Fizzled Fuses

When the war began in Europe but had not yet been declared in the United States, there was a lot of talk about getting ready and being patriotic. The newspapers had big articles on businessmen volunteering to go to Plattsburg, New York, to do military training, and so on.

I began to think I ought to make some kind of contribution, too. After I finished up at MIT, a friend of mine from the fraternity, Maurice Meyer, who was in the Army Signal Corps, took me to see a colonel at the Signal Corps offices in New York.

“I’d like to aid my country sir, and since I’m technically minded, maybe there’s a way I could help.”

“Well, you’d better just go up to Plattsburg to boot camp and go through basic training. Then we’ll be able to use you,” the colonel said.

“But isn’t there some way to use my talent more directly?”

“No; this is the way the army is organized. Go through the regular way.”

I went outside and sat in the park to think about it. I thought and thought: Maybe the best way to make a contribution is to go along with their way. But fortunately I thought a little more, and said, “To hell with it! I’ll wait awhile. Maybe something will happen where they can use me more effectively”

I went to Princeton to do graduate work, and in the spring I went once again to the Bell Labs in New York to apply for a summer job. I loved to tour the Bell Labs. Bill Shockley the guy who invented transistors, would show me around. I remember somebody’s room where they had marked a window: The George Washington Bridge was being built, and these guys in the lab were watching its progress. They had plotted the original curve when the main cable was first put up, and they could measure the small differences as the bridge was being suspended from it, as the curve turned into a parabola. It was just the kind of thing I would like to be able to think of doing. I admired those guys; I was always hoping I could work with them one day.

Some guys from the lab took me out to this seafood restaurant for lunch, and they were all pleased that they were going to have oysters. I lived by the ocean and I couldn’t look at this stuff; I couldn’t eat fish, let alone oysters.

I thought to myself, “I’ve gotta be brave. I’ve gotta eat an oyster.”

I took an oyster, and it was absolutely terrible. But I said to myself, “That doesn’t really prove you’re a man. You didn’t know how terrible it was gonna be. It was easy enough when it was uncertain.”

The others kept talking about how good the oysters were, so I had another oyster, and that was really harder than the first one.

This time, which must have been my fourth or fifth time touring the Bell Labs, they accepted me. I was very happy. In those days it was hard to find a job where you could be with other scientists.

But then there was a big excitement at Princeton. General Trichel from the army came around and spoke to us: “We’ve got to have physicists! Physicists are very important to us in the army! We need three physicists!”

You have to understand that, in those days, people hardly knew what a physicist was. Einstein was known as a mathematician, for instance—so it was rare that anybody needed physicists. I thought, “This is my opportunity to make a contribution,” and I volunteered to work for the army.

I asked the Bell Labs if they would let me work for the army that summer, and they said they had war work, too, if that was what I wanted. But I was caught up in a patriotic fever and lost a good opportunity. It would have been much smarter to work in the Bell Labs. But one gets a little silly during those times.

I went to the Frankfort Arsenal, in Philadelphia, and worked on a dinosaur: a mechanical computer for directing artillery. When airplanes flew by the gunners would watch them in a telescope, and this mechanical computer, with gears and cams and so forth, would try to predict where the plane was going to he. It was a most beautifully designed and built machine, and one of the important ideas in it was non-circular gears—gears that weren’t circular, but would mesh anyway. Because of the changing radii of the gears, one shaft would turn as a function of the other. However, this machine was at the end of the line. Very soon afterwards, electronic computers came in.

After saying all this stuff about how physicists were so important to the army the first thing they had me doing was checking gear drawings to see if the numbers were right. This went on for quite a while. Then, gradually the guy in charge of the department began to see I was useful for other things, and as the summer went on, he would spend more time discussing things with me.

One mechanical engineer at Frankfort was always trying to design things and could never get everything right. One time he designed a box full of gears, one of which was a big, eight-inch-diameter gear wheel that had six spokes. The fella says excitedly “Well, boss, how is it? How is it?”

“Just fine!” the boss replies. “All you have to do is specify a shaft passer on each of the spokes, so the gear wheel can turn!” The guy had designed a shaft that went right between the spokes!

The boss went on to tell us that there was such a thing as a shaft passer (I thought he must have been joking). It was invented by the Germans during the war to keep the British minesweepers from catching the cables that held the German mines floating under water at a certain depth. With these shaft passers, the German cables could allow the British cables to pass through as if they were going through a revolving door. So it was possible to put shaft passers on all the spokes, but the boss didn’t mean that the machinists should go to all that trouble; the guy should instead just redesign it and put the shaft somewhere else.

Every once in a while the army sent down a lieutenant to check on how things were going. Our boss told us that since we were a civilian section, the lieutenant was higher in rank than any of us. “Don’t tell the lieutenant anything,” he said. “Once he begins to think he knows what we’re doing, he’ll be giving us all kinds of orders and screwing everything up.

By that time I was designing some things, but when the lieutenant came by I pretended I didn’t know what I was doing, that I was only following orders.

“What are you doing here, Mr. Feynman?”

“Well, I draw a sequence of lines at successive angles, and then I’m supposed to measure out from the center different distances according to this table, and lay it out.

“Well, what is it?”

“I think it’s a cam.” I had actually designed the thing, but I acted as if somebody had just told me exactly what to do.

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.


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