Extraterrestrial UFO hypothesis

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UFOs and ufology
Notable sightings and hoaxes
Kenneth Arnold sighting 1947 wave Roswell Mantell crash Chiles-Whitted Gorman dogfight McMinnville photos Mariana film 1952 flap Sightings in outer space Flatwoods monster Barney and Betty Hill 'Swamp gas' Travis Walton Rendlesham Forest Belgian wave Calvine photo Alien autopsy hoax Phoenix Lights Pentagon UFO videos
Government investigations
Operação Prato - Brazil Project Magnet - Canada GEIPAN - France Institute 22 - Soviet Union Flying Saucer Working Party - UK Project Condign - UK History of government investigations - US All-domain Anomaly Resolution Office - US NASA's UAP independent study team - US Condon Committee - US Project Blue Book - US Unidentified Anomalous Phenomena Disclosure Act - US
Conspiracy theories
Area 51 Bob Lazar Majestic 12 Men in black Serpo
Religions
Aetherius Society Church of the SubGenius Heaven's Gate Nation of Islam Raëlism Scientology Unarius Academy of Science
Lists of organizations, sightings, studies, etc.
UFO organizations Reported UFO sightings Sightings by country Investigations of UFOs by governments Identification studies of UFOs Ufologists Alleged extraterrestrial beings
v t e

The extraterrestrial hypothesis (ETH) proposes that some unidentified flying objects (UFOs) are best explained as being physical spacecraft occupied by extraterrestrial intelligence or non-human aliens, or non-occupied alien probes from other planets visiting Earth.