Extraterrestrial Hypothesis in U.S. UFO Investigations: From Project Sign and Grudge to Blue Book at Wright-Patterson

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ETH is the idea that some unidentified flying objects come from other worlds, and in the United States it was one possible explanation investigated by Project Sign, then Project Grudge in 1952, and by Project Blue Book (1952–1969) at Wright-Patterson Air Force Base in Dayton, Ohio, as researchers studied sightings of flying saucers and related phenomena, showing that there is still uncertainty about where unidentified aerial phenomena originate.

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Other articles where extraterrestrial hypothesis is discussed: unidentified flying object: Flying saucers and Project Blue Book: … from other worlds, the so-called extraterrestrial hypothesis (ETH). Within a year, Project Sign was succeeded by Project Grudge, which in 1952 was itself replaced by the longest-lived of the official inquiries into UFOs, Project Blue Book, headquartered at Wright-Patterson Air Force Base in Dayton, Ohio. From 1952 to 1969 Project…