National Geographic Naked Science Close Encounters

Close encounter in ufology is an event where a person witnesses an unidentified flying object. This terminology and the system of classification behind it was started by astronomer and UFO researcher J. Allen Hynek, and was first suggested in his 1972 book The UFO Experience: A Scientific Study.

From 1950's sci-fi legends to modern-day UFO hunters, the notion of alien encounters has fascinated people for decades. Now, Naked Science explores whether Earth really might have been visited by beings from another planet.