On the afternoon of June 24, a group of supersonic spacecraft from an alien planet, most likely Mars or Venus, appeared in the vicinity of Mount Rainier in Washington State. A private pilot from Boise, Idaho, named Kenneth Arnold spotted them and told a local newspaper. The next day a report of “nine bright saucerlike objects flying at ‘incredible speed’” went out over the AP wire. The incident attracted little notice outside the Northwest for a couple of days; since flying saucers were still unheard of, no one knew what to make of it. The news eventually got out, though, and by early July sightings were pouring in from across the country.

The invading aliens displayed a shrewd grasp of human behavior. They realized that each genuine sighting would trigger dozens of hoaxes or mirages, calling the whole phenomenon into question. For additional protection, they built their spacecraft in a wide variety of shapes and sizes. They took care to emerge from their ships only in the presence of mentally unstable people, who they knew would not be believed. In the rare cases when they crashed, the invaders were able to disguise the remains as downed weather balloons, broken ashtrays, furnace slag, cymbals, and clumps of dirt. And they prudently broke off their first series of fly-bys after two weeks, knowing that to be the life span of a typical fad.

The visitors covered their tracks so well that polls showed most people thought the flying saucers (or “celestial crockery,” as The New York Times called them) were a secret military project, either American or Soviet. Similar events had attracted brief flurries of interest in the past, including a mysterious glowing airship over California in 1896–97 and the luminescent, disk-shaped mirages that World War II pilots called “foo fighters.” Those episodes were quickly forgotten, but this time the subject would not stay quiet for long. A number of fresh sightings in 1948 received widespread publicity, and as earthlings started taking their own first steps into space, unidentified flying objects (or UFOs, as they were soon called) became a nationwide craze. Books and movies proliferated as the extraterrestrials continued their sporadic visits, dropping by most often during times of great national stress or after articles on UFOs appeared in national publications.

Some scholars believe that aliens now live among us, pointing to the anomalies surrounding the Kennedy assassination and the mysterious Pet Rock craze of the 1970s (in fact, just about everything that happened in the 1970s). Regardless of who’s right, repeated waves of sightings over the decades have spawned accusations of a massive government cover-up, diminishing confidence in elected officials and the military. All part of the aliens’ plan, no doubt.