“Surely You’re Joking, Mr. Feynman”: Adventures of a Curious Character

He had proved that when a bacterium makes a new one, there’s a whole molecule, intact, which is passed from one bacterium to another—a molecule we now know as DNA. You see, we always think of everything dividing, dividing. So we think everything in the bacterium divides and gives half of it to the new bacterium. But that’s impossible: Somewhere, the smallest molecule that contains genetic information can’t divide in half; it has to make a copy of itself, and send one copy to the new bacterium, and keep one copy for the old one. And he had proved it in this way: He first grew the bacteria in heavy nitrogen, and later grew them all in ordinary nitrogen. As he went along, he weighed the molecules in his density gradient centrifuge.

The first generation of new bacteria had all of their chromosome molecules at a weight exactly in between the weight of molecules made with heavy, and molecules made with ordinary, nitrogen—a result that could occur if everything divided, including the chromosome molecules.

But in succeeding generations, when one might expect that the weight of the chromosome molecules would be one-fourth, one-eighth, and one-sixteenth of the difference between the heavy and ordinary molecules, the weights of the molecules fell into only two groups. One group was the same weight as the first new generation (halfway between the heavier and the lighter molecules), and the other group was lighter—the weight of molecules made in ordinary nitrogen. The percentage of heavier molecules was cut in half in each succeeding generation, but not their weights. That was tremendously exciting, and very important—it was a fundamental discovery. And I realized, as I finally got to my office, that this is where I’ve got to be. Where people from all different fields of science would tell me stuff, and it was all exciting. It was exactly what I wanted, really.

So when Cornell called a little later, and said they were setting everything up, and it was nearly ready, I said, “I’m sorry, I’ve changed my mind again.” But I decided then never to decide again. Nothing—absolutely nothing—would ever change my mind again.

When you’re young, you have all these things to worry about—should you go there, what about your mother. And you worry, and try to decide, but then something else comes up. It’s much easier to just plain decide. Never mind—nothing is going to change your mind. I did that once when I was a student at MIT. I got sick and tired of having to decide what kind of dessert I was going to have at the restaurant, so I decided it would always be chocolate ice cream, and never worried about it again—I had the solution to that problem. Anyway, I decided it would always be Caltech.

One time someone tried to change my mind about Caltech. Fermi had just died a short time before, and the faculty at Chicago were looking for someone to take his place. Two people from Chicago came out and asked to visit me at my home—I didn’t know what it was about. They began telling me all the good reasons why I ought to go to Chicago: I could do this, I could do that, they had lots of great people there, I had the opportunity to do all kinds of wonderful things. I didn’t ask them how much they would pay, and they kept hinting that they would tell me if I asked. Finally, they asked me if I wanted to know the salary. “Oh, no!” I said. “I’ve already decided to stay at Caltech. My wife Mary Lou is in the other room, and if she hears how much the salary is, we’ll get into an argument. Besides, I’ve decided not to decide any more; I’m staying at Caltech for good.” So I didn’t let them tell me the salary they were offering.

About a month later I was at a meeting, and Leona Marshall came over and said, “It’s funny you didn’t accept our offer at Chicago. We were so disappointed, and we couldn’t understand how you could turn down such a terrific offer.”

“It was easy,” I said, “because I never let them tell me what the offer was.”

A week later I got a letter from her. I opened it, and the first sentence said, “The salary they were offering was—,” a tremendous amount of money, three or four times what I was making. Staggering! Her letter continued, “I told you the salary before you could read any further. Maybe now you want to reconsider, because they’ve told me the position is still open, and we’d very much like to have you.”