validity of the ETH, which violate Occam's razor. Scientific Historically, ufology has not been considered credible in mainstream science. The scientific community has generally deemed that UFO sightings are not worthy of serious investigation except as a cultural artifact. Studies of UFOs rarely appear in mainstream scientific literature. When asked, some scientists and scientific organizations have pointed to the end of official governmental studies in the U.S. in December 1969, following the statement by the government scientist Edward Condon that further study of UFOs could not be justified on grounds of scientific advancement. Status as a pseudoscience Jacques Vallée, a scientist and ufologist, claimed there were deficiencies in most UFO research, including government studies. He criticized the mythology and cultism often associated with UFO sightings, but despite the challenges, Vallée contended that several hundred professional scientists — a group both he and Hynek termed "the invisible college" — continued to study UFOs quietly on their own time. Studies UFOs have become a prevalent theme in modern culture, and the social phenomena have been the subject of academic research in sociology and psychology. Sturrock panel categorization Besides anecdotal visual sightings, reports sometimes include claims of other kinds of evidence, including cases studied by the military and various government agencies of different countries (such as Project Blue Book, the Condon Committee, the French GEPAN/SEPRA, and Uruguay's current Air Force study). A comprehensive scientific review of cases where physical evidence was available was carried out by the 1998 Sturrock panel, with specific examples of many of the categories listed below. Radar contact and tracking, sometimes from multiple sites. These have included military personnel and control tower operators, simultaneous visual sightings, and aircraft intercepts. One such example was the mass sightings of large, silent, low-flying black triangles in 1989 and 1990 over Belgium, tracked by NATO radar and jet interceptors, and investigated by Belgium's military (included photographic evidence). Another famous case from 1986 was the Japan Air Lines flight 1628 incident over Alaska investigated by the Federal Aviation Administration (FAA). Photographic evidence, including still photos, movie film, and video. Claims of physical trace of landing UFOs, including ground impressions, burned or desiccated soil, burned and broken foliage, magnetic anomalies, increased radiation levels, and metallic traces. (See, e. g. Height 611 UFO incident or the 1964 Lonnie Zamora's Socorro, New Mexico encounter of the USAF Project Blue Book cases.) A well-known example from December 1980