-- "The B-52 bombers are flying examples of the Ship of Theseus paradox. Take a 2,000-year-old ship and gradually replace every plank. How old is the ship? 'I would be surprised if there's an original rivet in any of those airplanes we have out on the ramp,' Col. Robert Durkin, then commander of the 28th Bombardment Wing—a B-52 unit in South Dakota—told a reporter in 1983." --