Look no further than one J. Allen Hynek, an astronomer and ufologist who had the distinction of both working for Project Bluebook -- the U.S. Air Force investigation into UFO phenomena -- and for publishing a moderately famous book on the subject, The UFO Experience: A Scientific Inquiry. Hynek is the founder of the Center for UFO Studies and, as much as such a thing is possible, is considered a reliable authority on unidentified flying object investigations. In the aformentioned UFO Experience, Hynek laid out three kinds of close encounters to categorize the various UFO reports that he had analyzed (and, most often, debunked) during his tenure as adviser to the Air Force and as a civilian investigator:
- Close encounter of the first kind, wherein a UFO is merely observed
- Close encounter of the second kind, wherein physical evidence of a UFO is recovered
- Close encounter of the third kind, wherein the occupants of a UFO are observed
For his part, Vallée did not explicitly endorse the alien abduction defintion of fourth kind of close encounter, but merely described them as "cases when witnesses experienced a transformation of their sense of reality." Vallée was equally circumspect as to the definition of a close encounter of the fifth kind, the most involved and potentially definitive UFO interaction of the revised close encounter scale.
So, what events comprise a close encounter of the fifth kind?