George, a physics professor, waving a sheet of paper, runs into the office of Ken, a math professor. “Ken. I’ve got it. I’ve finally got an equation that explains my data! Can you check it out for me?” Accustomed to George’s enthusiastic outbursts, Ken nodded. George handed him the paper. Ken scanned it for a moment. “Give me a couple of days, George.”

Four days later, George runs into Ken in the hallway. “Ken, have you looked at the equation?” Ken sighs and looks unhappy. “Yes, George, but I’m sorry to say it’s totally uninteresting. The equation is valid, of course, but only in the most trivial case where the numbers are real and positive.”