## Thursday, June 25, 2009

### Ten seconds

Many interesting problems can be stated in 10 seconds, like "what's the relationship between the brain and mind?" or "do you really love me?"

In Richard Feynman's wonderful book "Surely you're joking Mr. Feynman!", there is an interesting entry about how Feynman tries to answer any problem that can be stated in ten seconds with the accuracy of plus minus 10 percent, in just sixty seconds.

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One day I was feeling my oats. It was lunch time in the technical area, and I don't know how I got the idea, but I announced, "I can work out in sixty seconds the answer to any problem that anybody can state in ten seconds, to 10 percent!"

People started giving me problems they thought were difficult, such as integrating a function like 1/(1 + x^4), which hardly changed over the range they gave me. The hardest one somebody gave me was the binomial coefficient of x^10 in (1 + x)^20; I got that just in time.

They were all giving me problems and I was feeling great, when Paul Olum walked by in the hall. Paul had worked with me for a while at Princeton before coming out to Los Alamos, and he was always cleverer than I was. For instance, one day I was absent-mindedly playing with one of those measuring tapes that snap back into your hand when you push a button. The tape would always slap over and hit my hand, and it hurt a little bit. "Geez!" I exclaimed. "What a dope I am. I keep playing with this thing, and it hurts me every time."

He said, "You don't hold it right," and took the damn thing, pulled out the tape, pushed the button, and it came right back. No hurt.
"Wow! How do you do that?"
I exclaimed.
"Figure it out!"

For the next two weeks I'm walking all around Princeton, snapping this tape back until my hand is absolutely raw. Finally I can't take it any longer. "Paul! I give up! How the hell do you hold it so it doesn't hurt?"
"Who says it doesn't hurt? It hurts me too!"

I felt so stupid. He had gotten me to go around and hurt my hand for two weeks!

So Paul is walking past the lunch place and these guys are all excited. "Hey, Paul!" they call out. "Feynman's terrific! We give him a problem that can be stated in ten seconds, and in a minute he gets the answer to 10 percent. Why don't you give him one?"

Without hardly stopping, he says, "The tangent of 10 to the 100th."
I was sunk: you have to divide by pi to 100 decimal places! It was hopeless.

Excerpt from "Surely your're joking, Mr. Feynman!"
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The idea is not to require the exact answer. You need to work out only to 10 percent. Feynman's brilliance shines, among the mirthful laughter of the geniuses.

It is fun to extend the game to things other than those that are numerical. You can always come up with a pretty good qualitative appraisal of issues that can be stated within ten seconds, in just sixty seconds.