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The Greifswald lights, German Democratic Republic. - Thousands witnessed an organized formation of seven lights that hovered for 30 minutes in the night sky over the Greifswald nuclear power plant near Peenemünde, in 1990. Several witnesses, including a Russian nuclear physicist working at the station, managed to film the incident.

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The Greifswald lights, German Democratic Republic - The incident drew a skeptical response from many, though the fact the lights appeared to hang in the sky for half an hour could not be explained. One of the reasons given was that the lights were flares fired into the sky by the Russian or Polish navy. The reunification of Germany was due to take place six weeks later and some thought this was in some way a diplomatic protest to prevent or delay the union from taking place.

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The Warrenton sightings, South Africa - In 1994, a farmer claimed to have seen what he thought was a small, noisy air craft traveling at speed through the night sky alongside a larger 'mother ship.'

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The Warrenton sightings, South Africa - The noise the ship made was compared with that of a helicopter, or the engine of a Volkswagen beetle. Four other people witnessed the 1994 sighting, which was never properly explained.

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The Kolkata sighting, India - In 2007, a report carried in The Times Of India cited several witnesses claiming to have seen a flying object moving at high velocity through the skies over Kolkata. The sightings were reported between 3.30 am and 6.30 am.

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The Kolkata sighting, India - Those who witnessed the event affirmed that the object was able to alter its form, from a spherical shape something resembling a triangle. Specialists contacted by the Times of India could not explain the phenomenon.

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The Vancouver sighting, Canada - On February 20, 2011 several people in Vancouver reported seeing an object hovering in the sky that emitted green and red lights, as shown in this vídeo.

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The Vancouver sighting, Canada - However, after reviewing the footage, experts concluded that the UFO was in fact a kite fitted with LED lights.

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The Captain William Schaffner incident, North Sea - On September 9, 1970 Royal Air Force pilot William Schaffner was flying over the North Sea when he spotted a strange object ahead of his plane, hovering over the water in the North Sea. He decided to investigate, but a few minutes later radio communication with Captain Schaffner's aircraft was lost.

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The Captain William Schaffner incident, North Sea - Schaffner's plane was later found ditched in the sea. Oddly, the canopy was closed and there was no trace of the pilot. This remains one of the most intriguing of cases involving a so-called UFO, and as The Telegraph reported at the time, there seems no answer as to what might have happened other than the RAF captain was practicing night time low altitude target training when his aircraft inexplicably crashed.

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Incident of the Berwyn range, Wales - On the night of January 23, 1974 several villagers living in the mountainous region of Berwyn in northern Wales reported seeing bright lights in the sky accompanied for a while by a very loud noise.

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Incident of the Berwyn range, Wales - Despite the scare the incident provoked, it was subsequently dismissed as a UFO sighting after the British Ministry of Defense confirmed that a falling meteor created the light, and after hitting the ground produced the subsequent tremor, which measured 3.5 on the Richter scale—the noise heard by the villagers.

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The Yenikent complex incident, Turkey - Throughout 2007, 2008, and 2009, a night watchman at the Yenikent complex called Yalcin Yalman was able to film on several occasions what many believe to be UFOs hovering in the skies over Turkey.

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The Yenikent complex incident, Turkey - The visual recordings, now considered one of the most compelling pieces of evidence that alien life exists beyond our world, have been confirmed as genuine and free of any manipulation. They can be seen here.

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The Belgian wave of UFOs - The Belgian UFO wave was the term used to describe a series of sightings of unidentified flying objects that took place between November 1989 and April 1990 in Belgium. Thousands of people reported seeing various objects in the sky, triangular in shape with lights attached to the base.

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The Belgian wave of UFOs - Despite the huge volume of sightings reported by the public at the time, no photographs or video footage was ever officially released to confirm the event. A photograph that emerged in 1990 and released to the press was later proved to be an altered image.

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The lights of Lubbock, Texas - Between August and September 1951, several unusual light formations were spotted in the skies above Lubbock, in Texas. Witnesses described seeing about 20 to 30 lights arranged in a 'V' pattern. The incident is one of the first in the United States reported as a UFO sighting. 

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The lights of Lubbock, Texas - The same year the United States Air Force investigated the incident and concluded that the lights had been caused by a plover, a small wading bird. However, this bizarre explanation was later recounted by the USAF and no other reason was given.

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The Tehran incident, Iran - On September 19, 1976 Iranian military forces detected an unidentified flying object in the skies above the capital, Tehran.

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The Tehran incident, Iran - As two Iranian air force jets approached the mystery object the pilots lost radio communications with the ground. As they prepared to open fire on the UFO, their weapons systems also failed. It was only after leaving the vicinity of the strange craft that they resumed full control of their aircraft.

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The sighting by Jimmy Carter - In 1973, before he held office as the President of the United States, Jimmy Carter, governor of the state of Georgia, reported seeing an unidentified flying object.

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The sighting by Jimmy Carter - The case only became public after Carter was in the White House. By the late 1970s, when he was no longer president, the US press used the sighting by Carter to open up a debate about UFO sightings.

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The São Paulo sightings, Brazil - In 1986, 20 UFOs appeared on Brazilian military forces radars. An air force jet was scrambled to intercept them but the objects eventually disappeared from screens.

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The São Paulo sightings, Brazil - Several conspiracy theories subsequently surfaced regarding the sightings, but the general consensus is that the 'objects' were in fact pieces of debris from the decommissioned Salyut-7 Soviet space station, disintegrating as it fell out of orbit and into the Earth's atmosphere.

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The 'Roswell Incident' - The 'Roswell Incident' continues to catch the imagination of the public and media around the world. In 1947, two men out hunting claimed to have seen US Army personnel recover an alien spacecraft from the desert near Roswell.

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The 'Roswell Incident' - The United States military denied any such incident occurred, and continues to do so today. The explanation offered by the authorities is that the army was engaged on a secret mission to recover a surveillance device.

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The case of Kenneth Arnold, Washington - In 1947, an American businessman named Kenneth Arnold claimed to have seen several disc-shaped objects flying over Mount Rainier, in Washington state.

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The case of Kenneth Arnold, Washington - The objects reported by Arnold were renamed 'flying saucers,' a description he subsequently popularized when recalling the incident.

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The lights of Rendlesham Forest, England - The Rendlesham Forest incident is the name given to a series of sightings that occurred in 1980 after a supposed landing of an unidentified flying object in Rendlesham Forest.

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The lights of Rendlesham Forest, England - The UK Ministry of Defense never considered the event a threat to national security. As such, the incident was never officially investigated.

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The Levelland case, Texas - In Levelland in 1967, the engines of several vehicles stopped working after drivers encountered a bright, egg-shaped object in the sky. The cars restarted after the mystery object disappeared.

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The Levelland case, Texas -

A subsequent police investigation concluded that the engines were disabled as a result of an electrical storm. However, this explanation continues to be refuted by those who believe in UFOs and alien life-forms.

See also:The government's secret radiation experiments on United States citizens

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