UFO

An unidentified flying object (UFO) is an aerial phenomenon that cannot be immediately identified or explained. This is primarily a Type 0 phenomenon and the majority of sightings can be explained. However a Type I civilization realizes that some of them had actually been monitoring technology or actual visits from extraterrestrials.

Type 0 explanations
UFOs are commonly seen as flying saucers or flying craft having disc or saucer-shaped bodies.
 * astronomical objects: stars; bolides; planets; the Moon
 * aircraft; aerial advertising; rocket launches, artificial satellites; kites; drones
 * balloons
 * atmospheric objects: birds; clouds; flares
 * other phenomena: mirages; ball lightning; searchlights
 * psychological effects: psychosis; suggestibility; mass psychogenesis; optical illusions; hallucinations
 * hoaxes

Because of the inclination from governments to cover up a potential alien threat, UFOs enter the mainstream culture of Type 0 societies but are passed off as conspiracy theories due to the lack of sufficient proof e.g. Area 51 and Roswell.

Hynek's scale
Josef Allen Hynek was an American astronomer and ufologist who devised this scale for close encounters which are events in which a person witnesses a UFO.

Close Encounters of the First Kind
Visual sightings of a UFO seemingly less than 150 m away, that show an appreciable angular extension and considerable detail.

Close Encounters of the Second Kind
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.

Close Encounters of the Third Kind
UFO encounters in which an entity is present—these include humanoids, robots, and humans who seem to be occupants or pilots of a UFO.

Close Encounters of the Fourth Kind
A UFO event in which a human is abducted by a UFO or its occupants.

Close Encounters of the Fifth Kind
A UFO event claiming direct communication between aliens and humans.

News

 * In June 2021, U.S. Defense and intelligence officials released the Pentagon UFO Report on what they know about a series of unidentified flying objects that have been seen by American military pilots.
 * Michio Kaku discussing with CNN about the United States hosting the first public hearing on the subject of UFOs in decades, and declassifying some related findings.