Close encounter

In ufology, a close encounter is an event in which a person witnesses an unidentified flying object. This terminology and the system of classification behind it was started by astronomer and UFO researcher J. Allen Hynek, and was first suggested in his 1972 book The UFO Experience: A Scientific Inquiry. He introduced the first three kinds of encounters; more sub-types of close encounters were later added by others, but these additional categories are not universally accepted by UFO researchers, mainly because they depart from the scientific rigor that Hynek aimed to bring to ufology.

Sightings more than 500 feet (150 m) from the witness are classified as "Daylight Discs," "Nocturnal Lights," or "Radar/Visual Reports." Sightings within about 500 feet are subclassified as various types of "close encounters." Hynek and others argued that a claimed close encounter must occur within about 500 feet to greatly reduce or eliminate the possibility of misidentifying conventional aircraft or other known phenomena.

Hynek's scale became well known after being referenced in a 1977 film, Close Encounters of the Third Kind, which is named after the third level of the scale. Posters for the film recited the three levels of the scale, and Hynek himself makes a cameo appearance near the end of the film.

Hynek devised a sixfold classification for UFO sightings: They are arranged according to increasing proximity.

Lights in the night sky.

UFOs seen in the daytime, generally having discoidal or oval shapes.

UFO reports that have radar confirmation. These seem to offer harder evidence that the objects are real, although radar propagation can often be unreliable .

Visual sightings of an unidentified flying object seemingly less than 500 feet away that show an appreciable angular extension and considerable detail.

A UFO event in which a physical effect is alleged. This can be interference in the functioning of a vehicle or electronic device; animals reacting; a physiological effect such as paralysis or heat and discomfort in the witness; or some physical trace like impressions in the ground, scorched or otherwise affected vegetation, or a chemical trace.

UFO encounters in which an animated creature is present. These include humanoids, robots, and humans who seem to be occupants or pilots of a UFO.

The UFO researcher Ted Bloecher proposed six subtypes for the close encounters of the third kind in Hynek's scale.

...
Wikipedia