Attention aspiring ufologists: July 2 is World UFO Day. It's a day to raise awareness of what some think are extraterrestrial visits to our planet. The day roughly corresponds to the date of perhaps the most well-known UFO story. In July 1947, debris was discovered on a ranch northwest of Roswell, N.M., that some think came from an alien spacecraft. Eye witnesses claimed they saw alien bodies at the crash site. An initial statement from the Air Force said a "flying saucer" had crashed. Later the service said the debris came from a weather balloon. Decades later, the Air Force issued a report saying the debris was likely from experimental surveillance balloons. Any "aliens" observed in the desert were in fact "anthropomorphic test dummies" that were in the balloons, according to the 1994 report. The Air Force also investigated UFOs from 1947 to 1969 under Project Blue Book to determine if any sightings threatened national security. It concluded there was no threat and none of the "unidentified" objects were extraterrestrial vehicles. But one UFO expert says the government has covered up the truth about Roswell and the existence of extraterrestrial visits in general. "It's cosmic Watergate," said Stanton Friedman, a nuclear physicist who has studied UFOs for more than 40 years. He added, "We're dealing with the biggest story of the millennium." More via USA Today.