The pleasure of finding things out

• The fragility of knowledge

  I often liked to play tricks on people when I was at MIT. One time, in mechanical drawing class, some joker picked up a French curve (a piece of plastic for drawing smooth curves -- a curly, funny-looking thing) and said, "I wonder if the curves on this thing have some special formula?"

  I thought for a moment and said, "Sure they do. The curves are very special curves. Lemme show ya," and I picked up my French curve and began to turn it slowly. "The French curve is made so that at the lowest point on each curve, no matter how you turn it, the tangent is horizontal."

  All the guys in the class were holding their French curve up at different angles, holding their pencil up to it at the lowest point and laying it along, and discovering that, sure enough, the tangent is horizontal. They were all excited by this "discovery" -- even though they had already gone through a certain amount of calculus and had already "learned" that the derivative (tangent) of the minimum (lowest point) of any curve is zero (horizontal). They didn't put two and two together. They didn't even know what they "knew."

  I don't know what's the matter with people: they don't learn by understanding; they learn by some other way -- by rote, or something. Their knowledge is so fragile!

• The map of a cat

  When the course began, Harvey started out by drawing a great, big picture of a cell on the blackboard and labeling all the things that are in a cell. He then talked about them, and I understood most of what he said.

  After the lecture, the guy who had invited me said, "Well, how did you like it?"

  "Just fine," I said. "The only part I didn't understand was the part about lecithin. What is lecithin?"

  The guy begins to explain in a monotonous voice: "All living creatures, both plant and animal, are made of little bricklike objects called 'cells'..."

  "Listen," I said, impatiently, "I know all that; otherwise I wouldn't be in the course. What is lecithin?"

  "I don't know."

  I had to report on papers along with everyone else, and the first one I was assigned was on the effect of pressure on cells -- Harvey chose that topic for me because it had something that had to do with physics. Although I understood what I was doing, I mispronounced everything when I read my paper, and the class was always laughing hysterically when I'd talk about "blastospheres" instead of "blastomeres," or some other such thing.

  The next paper selected for me was by Adrian and Bronk. They demonstrated that nerve impulses were sharp, single-pulse phenomena. They had done experiments with cats in which they had measured voltages on nerves.

  I began to read the paper. It kept talking about extensors and flexors, the gastrocnemius muscle, and so on. This and that muscle were named, but I hadn't the foggiest idea of where they were located in relation to the nerves or to the cat. So I went to the librarian in the biology section and asked her if she could find me a map of the cat.

  "A map of the cat, sir?" she asked, horrified. "You mean a zoological chart!" From then on there were rumors about some dumb biology graduate student who was looking for a "map of the cat."

  When it came time for me to give my talk on the subject, I started off by drawing an outline of the cat and began to name the various muscles.

  The other students in the class interrupt me: "We know all that!"

  "Oh," I say, "you do? Then no wonder I can catch up with you so fast after you've had four years of biology." They had wasted all their time memorizing stuff like that, when it could be looked up in fifteen minutes.

  From Surely You're Joking, Mr.Feynman!, a book by Richard P. Feynman

Next: The gadgets of teaching - hands-on labs