"a jet aircraft on a cloudless night began its landing flight-path twenty miles due east from the airport where it was due to land. for the first five miles of its descent, the noise from the jet's engine and exhaust disturbed no-one. at the sixth mile, an ornithologist, birdwatching on a reservoir, was irritated by the jet-noise just enough to give the aircraft a quick glance. He turned into a swan. at the seventh mile a naturalist and his wife saw the aircraft through their bedroom net-curtains and were turned into crows. at the eighth mile, four children in a school dormitory saw the aircraft through a skylight and turned into herons. at t