UFOs 
This is a general overview of the subject of UFOs. There is a vast amount of information on this topic, so we encourage you to research some on your own and read more. There are interesting articles on our Message Board, check it out!!
According to Wikipedia, an Unidentified Flying Object (UFO) is the popular term for any aerial phenomenon whose cause cannot be easily or immediately identified. This term was coined by the U.S. Air Force in 1952. Studies show that only a small percentage of reported UFOs are actual hoaxes. 80% of Americans believe the U.S. government is witholding information on UFOs.
History
Unexplained aerial observations have been reported throughout history (some undoubtedly were astronomical, such as comets, meteors, or planets).
Quick Historical UFO Facts:
- Certain objects in medieval paintings seem similar in shape to the popularized icon of what we typically
(currently)
visualize as a UFO. - As early as 1878, a large circular flying object was seen by a farmer in the U.S.
- There were 3 red egg shaped and circular objects flying in formation observed west of San Fransisco in 1904.
- Many sightings were reported during WWII by Allied and Axis pilots.
- The most famous cases include the Roswell incident in the 1940s and the Betty and Barney Hill abduction in 1964.
Identification
The most common identified sources of UFOs are
- astronomical objects
- aircraft
- balloons
- atmospheric objects and phenomena
- light phenomena
- Hoaxes
UFO Hypotheses
It has been suggested by some that all or most of human technology and culture is based on extraterrestrial contact. The following hypotheses have been proposed to account for unsolved UFO cases.
- The Extraterrestrial hypothesis by Edward Condon in 1968 can be defined as "The idea that some UFOs may be spacecraft sent to Earth from another civilization, or on a planet associated with a more distant star."
- The Interdimensional hypothesis - that UFOs are objects crossing over from other dimensions or a parallel universe - was popularly proposed by Jacques Vallee.
- The paranormal/occult hypothesis (a varient of Interdimensional Hypothesis) was invoked to explain paranormal aspects sometimes associated with UFO reports.
- The psychological hypothesis: what people report as UFO experiences is the result of psychological misperception and strongly influenced by popular culture.
- Natural phenomena causes UFO events
- Earthquake lights/Tectonic Strain hypothesis: UFOs are caused by strains in the Earth's crust near earthquake faults, which can also supposedly induce hallucinations.
- UFOs are military flying saucers, which are top secret or experimental craft unfamiliar to most people
Physical Evidence
Besides merely reports of sightings, there are sometimes claims of indirect or direct physical evidence. Some of the categories of physical evidence include
- Radar contact and tracking, sometimes from more than one site.
- Photographic evidence
- Claims of physical trace evidence from landings, which include ground impressions, burned soil, burned or broken foliage, magnetic anomalies, radiation levels, and metallic traces.
- Physiological effects on people and animals including temporary paralysis, skin burns, and rashes
- Animal/cattle mutilation cases
- Biological effects on plants, such as increased or decreased growth
- Electromagnetic interference effects
- Remote radiation detection
- Actual hard physical evidence cases
UFO Categorizations
Typical categorizations include
- Saucer, toy-top, or disk-shaped crafts
- Large triangular crafts or triangular light patterns
- Cigar-shaped craft with lighted windows
- Shapes such as crescents, boomerangs, spheres, diamonds, etc.
One of the popular classification systems is the Vallee system, which classifies UFOs into 5 broad types with 3 to 5 subtypes. The other popular system is the Hynek system, which divides the object by appearance then subdivided further into "close encounters."