On June 24, 1947, pilot Kenneth Arnold claimed he saw gleaming aircraft he later described as "saucerlike objects." He had no photos to bolster the first and most famous report of a flying saucer. In Fate magazine, Arnold wrote: "I would have given almost anything that day to have had a movie camera." 

His vision of saucer-shaped craft was quickly embraced by popular culture, showing up in comics, movies, even children's toys. Astronomer Carl Sagan noted that depictions of UFOs in entertainment often have a strong influence on how observers perceive phenomena in the sky. Sure enough, over the next few years UFO sightings increasingly mentioned silvery, saucer-shaped objects. Such UFO iconography is reinforced by a cultural feedback loop: a report offers intriguing new details; the entertainment industry amplifies those images; and future sightings "confirm" their existence. Hoaxes--pie-plate photos, crop circles, Alien Autopsy: (Fact or Fiction?) on the Fox network--abet the process, no matter how conclusively debunked. Just as the ancients were inclined to see gods and flaming chariots in the skies, modern humans became primed to see saucers and aliens whenever something strange appeared overhead. 

UFO sightings evolve with the culture. By the `60s, classic saucer images had started to fade. Instead, people began reporting more direct contact with aliens (who often resembled the big-eyed creatures seen in the TV movie The UFO Incident). But a darker strain emerged, when tales of gray aliens performing experiments on human abductees flourished. UFO stories sometimes took on spiritual dimensions: Aliens were godlike creatures coming to save our planet--or transport us to a better one. 

In recent years, most UFO reports have grown far less sensational; many sightings these days simply describe lights in the sky. 

Arnold regretted not having a camera at hand during his sighting. Today camera phones and video cameras are ubiquitous. And yet clear, detailed images have all but disappeared from the photographic record. Even the clearest recent images are little more than glowing dots and squiggles. 

1950	1955
Marine Corps officer and aviation enthusiast Donald Keyhoe's first book contends that the Air Force is covering up evidence of UFOs.	While it may not have lived up to its tagline as "the greatest shock film of all time," this sci-fi B-movie classic features Ray Harryhausen's special-effects magic as animated flying saucers with now-standard shapes obliterate practically every international landmark.

1967

Teenage brothers Dan and Grant Jaroslaw claim to snap sensational Polaroids of a UFO over Lake St. Clair, near Detroit. The images make front-page news and survive initial expert scrutiny, but the boys later admit it's a hoax.

1975

Nearly two years before Star Wars, James Earl Jones stars in this re-enactment of Betty and Barney Hill's alleged alien abduction outside Groveton, N.H., in 1961.

1977

UFOs evolve from sleek saucers to clusters of lights in Steven Spielberg's Close Encounters of the Third Kind. The film brings religious overtones to the topic, implying that belief in aliens is a matter of faith, not science. E.T.: The Extra-Terrestrial (1982) echoes that theme. Together, the films gross over $1 billion.

1983

More than 300 people in the Hudson Valley report seeing V- and boomerang-shaped lights in March 1983. It's a hoax by pilots flying out of Stormville, N.Y., who rig their planes with extra lights before formation flights.

1987

Horror novelist Whitley Strieber describes his abduction by "the visitors." A 1989 movie based on the book stars Christopher Walken; in 1999, the National UFO Conference names Strieber "UFOlogist of the Year."

1987

Ed Walters takes photos of a purported spacecraft over the Florida panhandle--but accidentally leaves the model (made of Styrofoam plates and bowls) in his house when he moves, and new owners find it.

2008

On March 14, 2008, residents of Wesley Chapel, Fla., are spooked by a hovering, rotating triangle of blue lights and a blinking red light. The sheriff's office confirms it's a hoax--a homemade balloon with lights.