'Flying saucer' was a term coined following the reported sighting by Kenneth Arnold, on June 24, 1947, of nine luminous objects in the sky over Washington state. Arnold, a businessman and part-time deputy sheriff was piloting a private plane when he saw the unusual lights heading south from the direction of Mount Baker toward Mount Rainier at what he estimated was a supersonic speed. In describing to reporters later how the objects moved he said that they hugged the contours and appeared to undulate "like a saucer skipping over water." By the time, the story appeared in print his words had been distorted to the phrase "flying saucer." Arnold's sighting, and the great publicity it received, triggered the great saucer flap of 1947. Various theories have been put forward to account for the incident, including an especially plausible one which involves the little understood phenomenon of earthlights.