The belief that UFOs are evidence of extraterrestrial visitors is gaining traction once again. While tales of mysterious objects in the sky have appeared in art and literature for centuries, the modern UFO phenomenon took off in the 1940s.

During World War II, “foo fighters” were reported over Europe’s battlefields, and in 1947, Kenneth Arnold’s encounter with multiple flying objects coined the term “flying saucer,” bringing the concept into mainstream awareness.

Though interest in UFOs waned slightly by the early 2000s, today more people than ever believe we might be visited by beings from other worlds.

In the 1990s, polls suggested that around 20% of Americans believed UFOs were of alien origin. Today, that figure has risen to over 34%, reports The Week.