I had a lot of interesting experiences with Bethe. The first day when he came in, we had a calculator, or glorified adding machine, a Marchant that you work by hand. And so he said, “Let’s see.” The formula he’d been working out, he says, “involves the pressure squared; the pressure is 48; so the square of 48 is –

I reach for the machine.

He says, “It’s about 2300.” So I plug it out just to find out.

He says, “You want to know exactly? It’s 2304.” And it came out 2304.

So I said, “How do you do that?”

He says, “Don’t you know how to take squares of numbers near 50? If it’s near 50, say 3 below (47), then the answer is 3 below 25 – like 47 squared is 2200, and how much is left over is the square of what’s residual. For instance, it’s 3 less and the square of that is 9, so you get 2209 from 47 squared.”

So he knew all his arithmetic, and he was very good at it, and that was a challenge to me. I kept practicing. We used to have a little contest. Every time we’d have to calculate anything we’d race to the answer, he and I, and I would lose. After several years I began to get in there once in a while, maybe one out of four. You have to notice the numbers, you see – and each of us would notice a different way. We had lots of fun.

El que escribe es Richard Feynman. El texto forma parte de “Los Alamos From Below: Reminiscences 1943-1945″. Pueden ver el texto completo, con varias historias sobre el tiempo que Feynman pasó en Los Alamos en:

http://calteches.library.caltech.edu/34/3/FeynmanLosAlamos.htm