One of actor/comedian/educator Bill Cosby's greatest old comedy routines is "Noah." Cosby replays the conversation between God and Noah as the Divine tells the clueless human about his watery plans and the need for an ark. True to Genesis 6:15-16, God tells Noah to build this boat with specific instructions: "the length of the ark three hundred cubits, its width fifty cubits, and its height thirty cubits."

Noah listens to all God's instructions with a stunned grin frozen on his face. Then finally sums up his complete incomprehension by asking, "Right. What's a cubit?"

A cubit, of course, is just a linear unit of measurement--the approximately 17-22 inches of the human forearm, the ancient world's equivalent of a "yard" or a "meter." (Editor's NOTE, and with apologies: This is a change from …