Two professors of mathematics were staring away at the flagpole in front of the college building. A professor of physics walking by asked, “What seems to be the problem?” “We were wondering,” said the mathematicians, “how to measure the height of this flagpole.” The professor of physics set about unscrewing the pole from its moorings, laid it on the ground, borrowed a measuring tape and said, “It is exactly 20 feet long,” and walked away smoking his pipe.
Staring after the physics professor, one mathematician remarked to the other, “Smart Alec. We wanted to know the height, and he tells us the length.”