http://www.destinationspace.net/ufo/watch/ce.asp [Broken]...For many, someone mentions Close Encounters and you immediately think of Steven Speilberg’s 1977 hit movie. But that movie was not just another wonderful creation originating from Speilberg’s imagination. Dr. J. Allen Hynek, long time official Project Blue Book consultant [https://www.physicsforums.com/showthread.php?t=58885] and founder of the Center for UFO Studies, coined not only the phrase, but also a system to classify different types of close encounters with UFOs.
...Close Encounters of the Second Kind: This is an encounter that meets the criteria of CE1 but the object leaves some type of evidence. Broken tree limbs, scorched earth, and a barren patch of lawn where grass does not grow for a long time are just a few types of interactions UFOs have been reported to have with their surroundings[continued]