On Sept. 21, 1956, Navy pilot Tom Attridge put his supersonic F11F Tiger into a shallow dive and test-fired two bursts from its 20mm cannon. Unfortunately, the jet was traveling so fast that it overtook its own rounds. One struck the engine, which failed on the way back to the airfield. Attridge crash-landed, losing a wing and a stabilizer but getting away safely. His Tiger had become the first jet aircraft to shoot itself down.

A puzzle sent to me by a Caltech grad student: A man is walking his dog on the beach. Each time he blows a whistle, the dog doubles its speed. If the dog starts at 2 meters per second, how many whistles does it hear? Answer: Fifteen — when the dog exceeds the speed of sound, it catches up with the earlier whistles.

(Thanks, John and Srivatsan.)