In UFOlogy, a close encounter
is an event where a person observes evidence of extra-terrestrial
visitation of the Earth
. Close encounters are categorized into three degrees or "kinds," thus:
- A close encounter of the first kind is a sighting of an unidentified flying object or objects. Reports of fast-moving lights in the night sky or "flying saucers," unattributable to human technology, can all be considered close encounters of the first kind.
- A close encounter of the second kind is an observation of physical evidence of extra-terrestrial visitation. Footprints, heat or radiation damage to terrain and Crop circles, though controversial, are all examples of close encounters of the second kind.
- A close encounter of the third kind is an observation of an alien or aliens associated with the craft.
More recently, some groups have referred to alien abductions as close encounters of the fourth kind, and encounters in which humans and aliens communicate as close encounters of the fifth kind.
It is remarkable that this system qualifies encounters on the basis of the observer's experience, as opposed to the evidence available, or even the falsifiability of the claim.
The classification system was first suggested by UFOlogist J. Allen Hynek in his 1972 book The UFO Experience: A Scientific Study.