The extraterrestrial hypothesis (ETH) proposes that some unidentified flying objects (UFOs) are best explained as being physical spacecraft occupied by extraterrestrial life or non-human aliens, or non occupied alien probes from other planets visiting Earth.
Origins of the term extraterrestrial hypothesis are unknown, but use in printed material on UFOs seems to date to at least the latter half of the 1960s. French ufologist Jacques Vallée used it in his 1966 book Challenge to science: the UFO enigma. It was used in a publication by French engineer Aimé Michel in 1967, by James E. McDonald in a symposium in March 1968 and again by McDonald and James Harder while testifying before the Congressional Committee on Science and Astronautics, in July 1968. Skeptic Philip J. Klass used it in his 1968 book UFOs–Identified. In 1969 physicist Edward Condon defined the “extraterrestrial hypothesis” or “ETH” as the “idea that some UFOs may be spacecraft sent to Earth from another civilization or space other than Earth, or on a planet associated with a more distant star,” while presenting the findings of the much debated Condon Report. Some UFO historians credit Condon with popularizing the term and its abbreviation “ETH”.
Although ETH as a word is a comparatively new concept, one which owes much to the flying saucer sightings of the 1940s–1960s, its origins can be traced back to a number of earlier events, such as the now-discredited Martian canals and ancient Martian civilization promoted by astronomer Percival Lowell, popular culture including the writings of H. G. Wells and fellow science fiction pioneers such as Edgar Rice Burroughs, who likewise wrote of Martian civilizations, and even to the works of figures such as the Swedish philosopher, mystic and scientist Emanuel Swedenborg, who promoted a variety of unconventional views that linked other worlds to the afterlife.
In the early part of the 20th century, Charles Fort collected accounts of anomalous physical phenomena from newspapers and scientific journals, including many reports of extraordinary aerial objects. These were published in 1919 in The Book of the Damned. In this and two subsequent books, New Lands (1923) and Lo! (1931), Fort theorized that visitors from other worlds were observing Earth. Fort’s reports of aerial phenomena were frequently cited in American newspapers when the UFO phenomenon first attracted widespread media attention in June and July 1947.
The modern ETH—specifically, the implicit linking of unidentified aircraft and lights in the sky to alien life—took root during the late 1940s and took its current form during the 1950s. It drew on pseudoscience, as well as popular culture. Unlike earlier speculation of extraterrestrial life, interest in the ETH was also bolstered by many unexplained sightings investigated by the U.S. government and governments of other countries, as well as private civilian groups, such as NICAP and APRO.
Historical reports of extraterrestrial visits
An early example of speculation over extraterrestrial visitors can be found in the French newspaper Le Pays, which on June 17, 1864, published a story about two American geologists who had allegedly discovered an alien-like creature, a mummified three-foot-tall hairless humanoid with a trunk-like appendage on its forehead, inside a hollow egg-shaped structure.
H. G. Wells, in his 1898 science fiction classic The War of the Worlds, popularized the idea of Martian visitation and invasion. Even before Wells, there was a sudden upsurge in reports in “Mystery airships” in the U.S. For example, the Washington Times in 1897 speculated that the airships were “a reconnoitering party from Mars” and the Saint Louis Post-Dispatch wrote, “these may be visitors from Mars, fearful, at the last, of invading the planet they have been seeking.” Later there was a more international airship wave from 1909-1912. An example of an extraterrestrial explanation at the time was a 1909 letter to a New Zealand newspaper suggesting “atomic powered spaceships from Mars.”
From the 1920s the idea of alien visitation in space ships was commonplace in popular comic strips and radio and movie serials such as Buck Rogers and Flash Gordon. In particular, Flash Gordon serials have Earth being attacked from space by alien meteors, ray beams, and biological weapons. In 1938 a radio broadcast version of The War of the Worlds by Orson Welles, using a contemporary setting for H. G. Wells’ Martian invasion, created some public panic in the United States.
The 1947 U.S. flying saucer wave
On June 24, 1947, at about 3:00 p.m. local time, pilot Kenneth Arnold reported seeing nine unidentified disk-shaped aircraft flying near Mount Rainier. When no aircraft emerged that seemed to account for what he had seen, Arnold quickly considered the possibility of the objects being extraterrestrial. On July 7, 1947, two stories came out where Arnold was raising the topic of possible extraterrestrial origins, both as his opinion and those who had written to him. In an Associated Press story, Arnold said he had received quantities of fan mail eager to help solve the mystery. Some of them “suggested the discs were visitations from another planet.”
When the 1947 flying saucer wave hit the U.S., there was much speculation in the newspapers about what they might be in news stories, columns, editorials, and letters to the editor. For example, on July 10, U.S. Senator Glen Taylor of Idaho commented, “I almost wish the flying saucers would turn out to be space ships from another planet,” because the possibility of hostility “would unify the people of the earth as nothing else could.” On July 8, Dewitt Miller was quoted by UP saying that the saucers had been seen since the early nineteenth century. If the present discs weren’t secret Army weapons, he suggested they could be vehicles from Mars or other planets or maybe even “things out of other dimensions of time and space.” Other articles brought up the work of Charles Fort, who earlier in the 20th Century had documented numerous reports of unidentified flying objects that had been written up in newspapers and scientific journals.
Even if people thought the saucers were real, most were generally unwilling to leap to the conclusion that they were extraterrestrial in origin. Various popular theories began to quickly proliferate in press articles, such as secret military projects, Russian spy devices, hoaxes, optical illusions, and mass hysteria. According to Murrow, the ETH as a serious explanation for “flying saucers” did not earn widespread attention until about 18 months after Arnold’s sighting.
These attitudes seem to be reflected in the results of the first US poll of public UFO perceptions released by Gallup on August 14, 1947. The term “flying saucer” was familiar to 90% of the respondents. As to what people thought explained them, the poll further showed that most people either held no opinion or refused to answer the question (33%), or generally believed that there was a mundane explanation. 29% thought they were optical illusions, mirages or imagination, 15% a US secret weapon, 10% a hoax, 3% a “weather forecasting device”, 1% of Soviet origin, and 9% had “other explanations”, including fulfillment of Biblical prophecy, secret commercial aircraft, or related to atomic testing.