Joke of the day:

A farmer asks an engineer, a physicist, and a mathematician to build him the largest possible pen out of a fixed amount of fencing.

Without giving it a second thought, the engineer builds the farmer a large, circular pen.

After a moment's consideration, the physicist builds a long straight piece of fence, and says, "We can consider the length of the fence to be infinite," pointing out that fencing off half the globe would be a more efficient solution.

The mathematician laughs gently at both of them, builds a tiny pen around himself, and says "I declare myself to be on the outside."

(Via Forward Biased.)