In popular culture, the term UFO–or unidentified flying object–refers to a suspected alien spacecraft, although its definition encompasses any unexplained aerial phenomena. UFO sightings have been reported throughout recorded history and in various parts of the world, raising questions about life on other planets and whether extraterrestrials have visited Earth. They became a major subject of interest–and the inspiration behind numerous films and books–following the development of rocketry after World War II.
READ MORE: Interactive Map: UFO Sightings Taken Seriously by the U.S. Government
The first well-known UFO sighting occurred in 1947, when businessman Kenneth Arnold claimed to see a group of nine high-speed objects near Mount Rainier in Washington while flying his small plane. Arnold estimated the speed of the crescent-shaped objects as several thousand miles per hour and said they moved “like saucers skipping on water.” In the newspaper report that followed, it was mistakenly stated that the objects were saucer-shaped, hence the term flying saucer.
The Roswell UFO Incident
The same year that Arnold saw the flying objects, rancher W.W. “Mac” Brazel came across a mysterious 200-yard long wreckage near an Army airfield in Roswell, New Mexico. Local papers reported it was the remains of a flying saucer. The U.S. military issued a statement saying that it was just a weather balloon, though the newspaper photograph suggested otherwise.
The flames of conspiracy were further fanned in the 1950s, when dummies with latex “skin” and aluminum “bones” that looked eerily like aliens fell from the sky across New Mexico and were hurriedly picked up by military vehicles. To those who believed in the earlier Roswell sightings, this seemed like a government cover-up. For the Air Force, these “dummy drops” were a way to test new ways for pilots to survive falls.
Fifty years later, the military issued a subsequent statement admitting that the Roswell wreckage was part of Project Mogul, a top-secret atomic espionage project.
Project Blue Book
Sightings of unidentified aerial phenomena increased, and in 1948 the U.S. Air Force began an investigation of these reports called Project Sign. Cold War tension was mounting, and the initial opinion of those involved with the project was that the UFOs were most likely sophisticated Soviet aircraft, although some researchers suggested that they might be spacecraft 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 Blue Book compiled reports of more than 12,000 sightings or events, each of which was ultimately classified as (1) “identified” with a known astronomical, atmospheric or artificial (human-caused) phenomenon or (2) “unidentified.” The latter category, approximately 6 percent of the total, included cases for which there was insufficient information to make an identification with a known phenomenon.
READ MORE: Meet J. Allen Hynek, the Astronomer Who First Classified UFO 'Close Encounters'
The Robertson Panel and the Condon Report
An American obsession with the UFO phenomenon was under way. In the hot summer of 1952, a provocative series of radar and visual sightings occurred near National Airport in Washington, D.C. Although these events were attributed to temperature inversions in the air over the city, not everyone was convinced by this explanation. Meanwhile, the number of UFO reports had climbed to a record high.
This led the Central Intelligence Agency to prompt the U.S. government to establish an expert panel of scientists to investigate the phenomena. The panel was headed by H.P. Robertson, a physicist at the California Institute of Technology in Pasadena, Calif., and included other physicists, an astronomer, and a rocket engineer. The Robertson Panel met for three days in 1953 and interviewed military officers and the head of Project Blue Book. They also reviewed films and photographs of UFOs.
Their conclusions were that (1) 90 percent of the sightings could be easily attributed to astronomical and meteorological phenomena (e.g., bright planets and stars, meteors, auroras, ion clouds) or to such earthly objects as aircraft, balloons, birds and searchlights; (2) there was no obvious security threat; and (3) there was no evidence to support the ETH. Parts of the panel’s report were kept classified until 1979, and this long period of secrecy helped fuel suspicions of a government cover-up.
READ MORE: Two Pilots Saw a UFO. Why Did the Air Force Destroy the Report?
A second committee was set up in 1966 at the request of the Air Force to review the most interesting material gathered by Project Blue Book. Two years later this committee, which made a detailed study of 59 UFO sightings, released its results as Scientific Study of Unidentified Flying Objects—also known as the Condon Report, named for Edward U. Condon, the physicist who headed the investigation. The Condon Report was reviewed by a special committee of the National Academy of Sciences. A total of 37 scientists wrote chapters or parts of chapters for the report, which covered investigations of the 59 UFO sightings in detail.
Like the Robertson Panel, the committee concluded that there was no evidence of anything other than commonplace phenomena in the reports and that UFOs did not warrant further investigation. This, together with a decline in sighting activity, led to the dismantling of Project Blue Book in 1969.
READ MORE: Why Mysterious Green Fireballs Worried the Government in 1948
In the 1950s and 60s, multiple UFO sightings were reported around Area 51 in Nevada, a site used variously by the CIA, U.S. Air Force, and Lockheed Martin to test flights of experimental aircraft, or “black aircraft.” Declassified documents show Area 51 was home to a Cold War program called Oxcart dedicated to creating a spy plane that would be undetectable in the air and could be used to gather information behind the Iron Curtain. The resulting SR-71 Blackbird, F-117 Nighthawk, and Archangel-12 (A-12) traveled at speeds upwards of 2,000 miles an hour. These mysterious planes helped fuel rumors that Area 51 was used to conduct experiments on extraterrestrial life and their spacecraft.
Other investigations of UFOs
Despite the failure of the ETH to make headway with the expert committees, a few scientists and engineers, most notably J. Allen Hynek, an astronomer at Northwestern University in Evanston, Ill., who had been involved with projects Sign, Grudge and Blue Book, concluded that a small fraction of the most-reliable UFO reports gave definite indications for the presence of extraterrestrial visitors. Hynek founded the Center for UFO Studies (CUFOS), which continues to investigate the phenomenon.
Aside from Project Blue Book, the only other official and fairly complete records of UFO sightings were kept in Canada, where they were transferred in 1968 from the Canadian Department of National Defense to the Canadian National Research Council. The Canadian records comprised about 750 sightings. Less complete records have been maintained in the United Kingdom, Sweden, Denmark, Australia, and Greece. In the United States, CUFOS and the Mutual UFO Network in Bellvue, Colo., continue to log sightings reported by the public.
In the Soviet Union, sightings of UFOs were often prompted by tests of secret military rockets. In order to obscure the true nature of the tests, the government sometimes encouraged the public’s belief that these rockets might be extraterrestrial craft but eventually decided that the descriptions themselves might give away too much information. UFO sightings in China have been similarly provoked by military activity that is unknown to the public.
Possible explanations for UFO sightings and alien abductions
UFO reports have varied widely in reliability, as judged by the number of witnesses, whether the witnesses were independent of each other, the observing conditions (e.g., fog, haze, type of illumination), and the direction of sighting. Typically, witnesses who take the trouble to report a sighting consider the object to be of extraterrestrial origin or possibly a military craft but certainly under intelligent control. This inference is usually based on what is perceived as formation flying by sets of objects, unnatural—often sudden—motions, the lack of sound, changes in brightness or color, and strange shapes.
READ MORE: The First Alien-Abduction Account Described a Medical Exam with a Crude Pregnancy Test
That the unaided eye plays tricks is well known. A bright light, such as the planet Venus, often appears to move. Astronomical objects can also be disconcerting to drivers, as they seem to “follow” the car. Visual impressions of distance and speed of UFOs are also highly unreliable because they are based on an assumed size and are often made against a blank sky with no background object (clouds, mountains, etc.) to set a maximum distance. Reflections from windows and eyeglasses produce superimposed views, and complex optical systems, such as camera lenses, can turn point sources of light into apparently saucer-shaped phenomena.
Such optical illusions and the psychological desire to interpret images are known to account for many visual UFO reports, and at least some sightings are known to be hoaxes. Radar sightings, while in certain respects more reliable, fail to discriminate between artificial objects and meteor trails, ionized gas, rain, or thermal discontinuities in the atmosphere.
READ MORE: This Scoutmaster Had a Run-in with a UFO. The Kids Saw it Too.
“Contact events,” such as abductions, are often associated with UFOs because they are ascribed to extraterrestrial visitors. However, the credibility of the ETH as an explanation for abductions is disputed by most psychologists who have investigated this phenomenon. They suggest that a common experience known as “sleep paralysis” may be the culprit, as this causes sleepers to experience a temporary immobility and a belief that they are being watched.