Project Sign in 1948 wrote a highly classified opinion (see Estimate of the Situation) that the best UFO reports probably had an extraterrestrial explanation, as did the private but high-level French COMETA study of 1999. A top secret Swedish military opinion given to the USAF in 1948 stated that some of their analysts believed the 1946 ghost rockets and later flying saucers had extraterrestrial origins. (see Ghost rockets for document). In 1954, German rocket scientist Hermann Oberth revealed an internal West German government investigation, which he headed, that arrived at an extraterrestrial conclusion, but this study was never made public. Classified, internal reports by the Canadian Project Magnet in 1952 and 1953 also assigned high probability to extraterrestrial origins. Publicly, however, Project Magnet, nor later Canadian defense studies, ever stated such a conclusion.

Another highly classified U.S. study was conducted by the CIA's Office of Scientific Investigation (OS/I) in the latter half of 1952 after being directed to do so by the National Security Council (NSC). They concluded UFOs were real physical objects of potential threat to national security. One OS/I memo to the CIA Director (DCI) in December read, "...the reports of incidents convince us that there is something going on that must have immediate attention... Sightings of unexplained objects at great altitudes and traveling at high speeds in the vicinity of major U.S. defense installations are of such a nature that they are not attributable to natural phenomena or any known types of aerial vehicles." The matter was considered so urgent, that OS/I drafted a memorandum from the DCI to the NSC proposing that the NSC establish an investigation of UFOs as a priority project throughout the intelligence and the defense research and development community. They also urged the DCI to establish an external research project of top-level scientists to study the problem of UFOs, now known as the Robertson Panel, to further analyze the matter. The OS/I investigation was called off after the Robertson Panel's negative conclusions in January 1953.[33]

Some public government conclusions have indicated physical reality but stopped short of concluding extraterrestrial origins, though not dismissing the possibility. Examples are the Belgian military investigation into large triangles over their airspace in 1989–1991 and the recent 2009 Uruguay Air Force study conclusion (see below).

Some private studies have been neutral in their conclusions, but argued the inexplicable core cases called for continued scientific study. Examples are the Sturrock Panel study of 1998 and the 1970 AIAA review of the Condon Report.

However, the initially classified USAF Regulation 200-2, first issued in 1953 after the Robertson Panel, which first defined UFOs and how information was to be collected, stated explicitly that the two reasons for studying the unexplained cases were for national security reasons and for possible technical aspects involved, implying physical reality and concern about national defense, but without opinion as to origins. (For example, such information would also be considered important if UFOs had a foreign or domestic origin.) The first two known classified USAF studies in 1947 also concluded real physical aircraft were involved, but gave no opinion as to origins. (See American investigations immediately below) These early studies led to the creation of the USAF's Project Sign at the end of 1947, the first semi-public USAF study.

It has been claimed that all UFO cases are anecdotal[30] and that all can be explained as prosaic natural phenomena. On the other hand, it has been argued that there is limited awareness among scientists of observational data, other than what is reported in the popular press.[3][31]

Controversy has surrounded the Condon report, both before and after it was released. It has been claimed that the report was "harshly criticized by numerous scientists, particularly at the powerful AIAA … [who] recommended moderate, but continuous scientific work on UFOs".[9]. In an address made to the AAAS, James E. McDonald stated that he believed science had failed to mount adequate studies of the problem, criticizing the Condon report and prior studies by the US Air Force for being scientifically deficient. He also questioned the basis for Condon's conclusions[32] and argued that the reports of UFOs have been "laughed out of scientific court."[8] J. Allen Hynek, an astronomer whose position as USAF consultant from 1948 made him perhaps the most knowledgeable scientist connected with the subject, sharply criticized the report of the Condon Committee and later wrote two nontechnical books that set forth the case for investigating seemingly baffling UFO reports.

No official government investigation has ever publicly concluded that UFOs are indisputably real, physical objects, extraterrestrial in origin, or of concern to national defense. These same negative conclusions also have been found in studies that were highly classified for many years, such as the UK's Flying Saucer Working Party, Project Condign, the US CIA-sponsored Robertson Panel, the US military investigation into the green fireballs from 1948 to 1951, and the Battelle Memorial Institute study for the USAF from 1952 to 1955 (Project Blue Book Special Report #14).

There has been little mainstream scientific study of UFOs, and the topic has received little serious attention or support in mainstream scientific literature. Official studies ended in the U.S. in December 1969, subsequent to the statement by Edward Condon that the study of UFOs probably could not be justified in the expectation that science would be advanced.[9] The Condon report and these conclusions were endorsed by the National Academy of Scientists, of which Condon was a member. However, a scientific review by the UFO subcommittee of the AIAA disagreed with Condon's conclusion, noting that at least 30% of the cases studied remained unexplained, and that scientific benefit might be gained by continued study.

Investigations
UFOs have been subject to investigations over the years that vary widely in scope and scientific rigor. Governments or independent academics in the United States, Canada, the United Kingdom, Japan, Peru, France, Belgium, Sweden, Brazil, Chile, Uruguay, Mexico, Spain, and the Soviet Union are known to have investigated UFO reports at various times.

Among the best known government studies are the ghost rockets investigation by the Swedish military (1946–1947), Project Blue Book, previously Project Sign and Project Grudge, conducted by the United States Air Force from 1947 until 1969, the secret U.S. Army/Air Force Project Twinkle investigation into green fireballs (1948–1951), the secret USAF Project Blue Book Special Report #14 [28] by the Battelle Memorial Institute, and Brazilian Air Force Operation Saucer (1977). France has had on ongoing investigation (GEPAN/SEPRA/GEIPAN) within its space agency CNES since 1977, as has Uruguay since 1989.

A public research effort conducted by the Condon Committee for the USAF, which arrived at a negative conclusion in 1968, marked the end of the US government's official investigation of UFOs, though documents indicate various government intelligence agencies continue unofficially to investigate or monitor the situation.[29]

Allen Hynek was a trained astronomer who participated in Project Bluebook after doing research as a federal government employee. He formed the opinion that some UFO reports could not be scientifically explained. Through his founding of the Center for UFO Studies and participation at CUFOs he spent the rest of his life researching and documenting UFOs. The movie Close Encounters of the Third Kind had a character loosely based on Hynek. Another group studying UFOs is Mutual UFO Network. MUFON is a grass roots based organization known for publishing one of the first UFO investigators handbooks. This handbook went into great detail on how to document alleged UFO sightings.

Jacques Vallée, a scientist and prominent UFO researcher, has argued that most UFO research is scientifically deficient, including many government studies such as Project Blue Book, and that mythology and cultism are frequently associated with the phenomenon. Vallée states that self-styled scientists often fill the vacuum left by the lack of attention paid to the UFO phenomenon by official science, but also notes that several hundred professional scientists continue to study UFOs in private, what he terms the "invisible college". He also argues that much could be learned from rigorous scientific study, but that little such work has been done.[3]

This shows the report Kenneth Arnold filed in 1947 about his UFO sighting.

This shows Kenneth Arnold holding a picture of a drawing of the crescent shaped UFO he saw in 1947.

The Kenneth Arnold sightings

The post World War II UFO phase in the United States began with a famous sighting by American businessman Kenneth Arnold on June 24, 1947 while flying his private plane near Mount Rainier, Washington. He reported seeing nine brilliantly bright objects flying across the face of Rainier.

Although there were other 1947 U.S. sightings of similar objects that preceded this, it was Arnold's sighting that first received significant media attention and captured the public's imagination. Arnold described what he saw as being "flat like a pie pan", "shaped like saucers and were so thin I could barely see them… ", "half-moon shaped, oval in front and convex in the rear. … they looked like a big flat disk" (see Arnold's drawing at right), and flew "like a saucer would if you skipped it across the water". (One of the objects, however, he would describe later as crescent-shaped, as shown in illustration at left.) Arnold’s descriptions were widely reported and within a few days gave rise to the terms flying saucer and flying disk.[23] Arnold’s sighting was followed in the next few weeks by hundreds of other reported sightings, mostly in the U.S., but in other countries as well. After reports of the Arnold sighting hit the media, other cases began to be reported in increasing numbers. In one instance a United Airlines crew sighting of nine more disc-like objects over Idaho on the evening of July 4. At the time, this sighting was even more widely reported than Arnold’s and lent considerable credence to Arnold’s report.[24]

American UFO researcher Ted Bloecher, in his comprehensive review of newspaper reports (including cases that preceded Arnold's), found a sudden surge upwards in sightings on July 4, peaking on July 6–8. Bloecher noted that for the next few days most American newspapers were filled with front-page stories of the new "flying saucers" or "flying discs". Reports began to rapidly tail off after July 8,[25] when officials began issuing press statements on the Roswell UFO incident, in which they explained debris found on the ground by a rancher as being that of a weather balloon.[26]

Over several years in the 1960s, Bloecher (aided by physicist James E. McDonald) discovered 853 flying disc sightings that year from 140 newspapers from Canada, Washington D.C, and every U.S. state except Montana.[27]

•   On January 25, 1878, The Denison Daily News wrote that local farmer John Martin had reported seeing a large, dark, circular flying object resembling a balloon flying "at wonderful speed." Martin also said it appeared to be about the size of a saucer, the first known use of the word "saucer" in association with a UFO.[16]
•   On February 28, 1904, there was a sighting by three crew members on the USS Supply 300 miles west of San Francisco, reported by Lt. Frank Schofield, later to become Commander-in-Chief of the Pacific Battle Fleet. Schofield wrote of three bright red egg-shaped and circular objects flying in echelon formation that approached beneath the cloud layer, then changed course and "soared" above the clouds, departing directly away from the earth after two to three minutes. The largest had an apparent size of about six suns.[17]
•   1916 and 1926: The three oldest known pilot UFO sightings, of 1305 cataloged by NARCAP. On January 31, 1916, a UK pilot near Rochford reported a row of lights, like lighted windows on a railway carriage, that rose and disappeared. In January 1926, a pilot reported six "flying manhole covers" between Wichita, Kansas and Colorado Springs, Colorado. In late September 1926, an airmail pilot over Nevada was forced to land by a huge, wingless cylindrical object.[18]
•   On August 5, 1926, while traveling in the Humboldt Mountains of Tibet's Kokonor region, Nicholas Roerich reported that members of his expedition saw "something big and shiny reflecting the sun, like a huge oval moving at great speed. Crossing our camp the thing changed in its direction from south to southwest. And we saw how it disappeared in the intense blue sky. We even had time to take our field glasses and saw quite distinctly an oval form with shiny surface, one side of which was brilliant from the sun.” [19] Another description by Roerich was, "...A shiny body flying from north to south. Field glasses are at hand. It is a huge body. One side glows in the sun. It is oval in shape. Then it somehow turns in another direction and disappears in the southwest." [20]
•   In the Pacific and European theatres during World War II, "Foo-fighters" (metallic spheres, balls of light and other shapes that followed aircraft) were reported and on occasion photographed by Allied and Axis pilots. Some proposed Allied explanations at the time included St. Elmo's Fire, the planet Venus, hallucinations from oxygen deprivation, or German secret weapon.[21][22]
•   On February 25, 1942, U.S. Army observers reported unidentified aircraft both visually and on radar over the Los Angeles, California region. Antiaircraft artillery was fired at what was presumed to be Japanese planes. No readily apparent explanation was offered, though some officials dismissed the reports of aircraft as being triggered by anxieties over expected Japanese air attacks on California. However, Army Chief of Staff Gen. George C. Marshall and Secretary of War Henry Stimson insisted real aircraft were involved. The incident later became known as the Battle of Los Angeles, or the West coast air raid.
•   In 1946, there were over 2000 reports, collected primarily by the Swedish military, of unidentified aerial objects in the Scandinavian nations, along with isolated reports from France, Portugal, Italy and Greece, then referred to as "Russian hail", and later as "ghost rockets", because it was thought that these mysterious objects were possibly Russian tests of captured German V1 or V2 rockets. Although most were thought to be natural phenomena like meteors, over 200 were tracked on radar and deemed to be "real physical objects" by the Swedish military. In a 1948 top secret document, the Swedish military told the USAF Europe in 1948 that some of their investigators believed them to be extraterrestrial in origin.

History
Unexplained aerial observations have been reported throughout history. Some were undoubtedly astronomical in nature: comets, bright meteors, one or more of the five planets that can be seen with the naked eye, planetary conjunctions, or atmospheric optical phenomena such as parhelia and lenticular clouds. An example is Halley's Comet, which was recorded first by Chinese astronomers in 240 B.C. and possibly as early as 467 B.C.

Other historical reports seem to defy prosaic explanation, but assessing such accounts is difficult. Whatever their actual cause, such sightings throughout history were often treated as supernatural portents, angels, or other religious omens. Some objects in medieval paintings can seem strikingly similar to UFO reports.[13] Art historians explain those objects as religious symbols, often represented in many other paintings of Middle-Age and Renaissance.[14]

Shen Kuo (1031–1095), a Song Chinese government scholar-official and prolific polymath inventor and scholar, wrote a vivid passage in his Dream Pool Essays (1088) about an unidentified flying object. He recorded the testimony of eyewitnesses in 11th-century Anhui and Jiangsu (especially in the city of Yangzhou), who stated that a flying object with opening doors would shine a blinding light from its interior (from an object shaped like a pearl) that would cast shadows from trees for ten miles in radius, and was able to take off at tremendous speeds.[15]

Studies have established that the majority of UFOs are observations of some real but conventional object—most commonly aircraft, balloons, or astronomical objects such as meteors or bright planets—that have been misidentified by the observer as anomalies, while a small percentage of reported UFOs are hoaxes.[5] Between 5% to 20% of anomalous sightings can be classified as unidentified in the strictest sense (see below for some studies).

The possibility that all UFO sightings are misidentifications of known natural phenomena[6] inspired some debate in the scientific community about whether scientific investigation was warranted given the paucity of available empirical data.[7][8][9][10][11] Very little peer-reviewed literature has been published in which scientists have proposed, studied or supported non-prosaic explanations for UFOs.[12] Nevertheless, UFOs as a cultural phenomenon continues to be the subject of serious academic research[12] and amateur investigators continue to advocate that UFOs represent real and unexplained events, whether or not they are associated with alien encounters.

Unidentified flying object

Unidentified flying object (commonly abbreviated as UFO or U.F.O.) is the popular term for any apparent aerial phenomenon whose cause cannot be easily or immediately identified by the observer. The United States Air Force, which coined the term in 1952, initially defined UFOs as those objects that remain unidentified after scrutiny by expert investigators,[1] though today the term UFO is colloquially used to refer to any unidentifiable sighting regardless of whether it has been investigated. UFO reports increased precipitously after the first widely publicized U.S. sighting, reported by private pilot Kenneth Arnold in June 24 1947, that gave rise to the popular terms "flying saucer" and "flying disc." The term UFO is popularly taken as a synonym for alien spacecraft and generally most discussions of UFOs revolve around this presumption.[2] UFO enthusiasts and devotees have created organizations, religious cults have adopted extraterrestrial themes, and in general the UFO concept has evolved into a prominent mythos in modern culture.[3] Some investigators now prefer to use the broader term unidentified aerial phenomenon (or UAP), to avoid the confusion and speculative associations that have become attached to UFO.[4] Another widely known acronym for UFO in Spanish, Portuguese, French, and Italian is OVNI (Objeto Volador No Identificado, Objeto Voador Não Identificado, Objet volant non identifié or Oggetto Volante Non Identificato).

The "modern" mansion
Mansions built during the last and present centuries usually have specially designed rooms meant to accommodate leisure activities of a particular kind. Many will have a conservatory or greenhouse, while others will have an infinity pool or a home theatre. Some have all of these features. The relative importance of these specially designed rooms changes with the times: At the beginning of the 20th century no true mansion would have been built without a room to house a private library or office, while at the beginning of the 21st century the presence of a room designed for a home theatre or cinema is a must. Most recently, mansions have been built with integrated domotics.

A modern mansion today may not necessarily be limited to a single house standing alone. Compounds, or a grouping of larger houses have become more popular. The Kennedy Compound is an example of one family building surrounded by large houses on a single plot.

Latin America

In Latin America, with its feudal colonial and post-colonial past, the grand rural estate, the Hacienda, Estancia, in Portuguese speaking Brazil Fazenda or Estância, with the mansion as its stately center, is a characteristic feature.

Naturally mansions followed European architectural styles. Whereas until the second half of the 19th century Portugal and Spain as the colonial (or former colonial) powers were the eminent models for architecture and upperclass lifestyle, towards the end of the 19th century they were sometimes replaced by then more dominant powers like France or England.

In comparably developed, densely populated countries like Mexico, feudal estates and their mansions were as grand and stately as in the Mediterranean old world, whereas where estates were founded in the sparsely populated remote areas like the Pampa of Argentina or Uruguay, where iron pillars, doors, windows, furniture had to be brought from Europe by ship and afterwards oxcart, buildings were smaller, but normally still aspiring to evoke a stately impression, often featuring the Mirador (the lookout or tower, see also belvedere) In Venezuela, the traditional Spanish Mansion with the garden in the center of the property are usually referred as "Quinta".

The Breakers, in Newport, Rhode Island, is one of the most famous 19th century mansions in the United States.