Taken from “Surely You're Joking, Mr.
Feynman!” Adventures of a Curious Character by Richard Phillips Feynman as told to Ralph Leighton edited by
Edward Hutchings
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 be. 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.
As
director of this project, I would be 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.