In which your correspondent learns a valuable lesson.

When I took MIT's Physics Junior Lab, we did about seven or eight experiments each semester. However, we were required to submit, each semester, only one written report. For each of the the remainder of the experiments, we underwent an oral examination. (We had to bring our lab notebooks to the oral exam, and sometimes they would be examined, but we did not have to write a report.)

My lab partner and I were at the oral examination for the experiment on plasma physics. Our professor asked me to define the Langmuir length (also called the Langmuir distance). I started in on what was, I'm afraid, a lengthy explanation, which I suppose I thought would show off my knowledge of the subject.

Our (famous and distinguished) professor interrupted me.

"No, not like that," he said. "That's not the kind of answer I want. Here's the kind of answer I want. Imagine you've had dinner with your girlfriend. You've had a little wine. Now you're in bed. She asks you, 'say, what's the Langmuir length?' What you want to do is give her the briefest possible answer, and then fuck. That's the kind of answer I want. Now, try again. What's the Langmuir length?"

I provided a one-sentence answer; he approved; we went on.