People have long questioned whether life exists on other planets and whether we have been visited by creatures from another world. The next few weeks mark a major anniversary in America's history with unidentified flying objects.

The first chapter of this strange controversy began a little more than a century ago when thousands of people across the United States reported seeing cigar-shaped airships in the skies over 19 states.

Sociologist Mark Rodeghier is Director of the J. Allen Hynek Center for UFO Studies in Chicago, one of this country's oldest UFO investigative organizations.  He says although many newspapers and scientists reported the sightings to be hoaxes or hallucinations, some people thought they were real.
"There was a wave of what are called 'airship reports' in the late 1890s. This was the period of 'yellow journalism' in the U.S. And after first taking a little bit of a serious interest in this subject, most newspapers began to make fun of it all.  The public on the other hand, a number of them, at least initially, took it seriously," says Rodeghier.

These airships constituted the first major wave of UFO sightings in the world.   Occurring at a time when technology could not duplicate what witnesses described, these reports ignited a national furor.   

David Jacobs of Temple University in Philadelphia is one of this country's foremost historians on the topic of UFOs. "What we do know is that we have a full gamut of sighting types -- close-up sightings, sightings of objects on the ground, sightings of objects doing strange maneuvers. Every person had a different explanation for what people were seeing.  None of them really took into account the evidence,? says Jacobs. ?Now in 1896 and 1897, they might have been right.  But they were shoot from the hip explanations; they were not carefully evaluated explanations. This is what we find in the United States now." 

Flying Saucers
This is the sound of a UFO as recorded in March 1981 by two police officers near Portland, Oregon. They reportedly saw an orange, glowing sphere about 10 meters in diameter, hovering motionless above the Columbia River. They watched it for about 10 minutes.  Then the sound grew louder and the UFO flew away.

That sighting was witnessed by several other people and remains unexplained.

This report is similar to others in the modern era of UFO sightings, which began on June 24, 1947.

"That's the day when Kenneth Arnold, a businessman and private pilot, reported seeing nine disc-shaped objects flying near Mount Rainier in Washington state," says Rodeghier.
"His report got immediate publicity, worldwide. And it began what people have called the 'flying saucer craze.' Before this, there had been scattered, sporadic reports.   Newspapers really didn't cover it at all nor did any other media,? says Rodeghier. ?But from that day onward, people in the United States heard about UFOs, people reported UFO sightings and, most important perhaps, the government took it seriously.?

Because Kenneth Arnold was a reputable citizen, skepticism about the incident soon faded as newspaper headlines around the world carried the now popular phrase "flying saucer".

Soon pilots, scientists, engineers, persons holding elective office as well as farmers, truck drivers and children began to report much the same things the world over.   But the immediate reaction of many of those who had not seen these objects was hostile.  They could not believe it happened.

The Roswell Incident
For six decades, controversy about unidentified flying objects has raged over the alleged crash of a flying saucer near Roswell, New Mexico.
"Something very, very unusual crashed into the New Mexico desert on the second of July in 1947.  And whatever it was, the United States government went to the site and recovered the object," says William Moore, another prominent UFO investigator and an expert on the so-called "Roswell Incident".

?The Air Force issued an official press release, stating that they had recovered the wreckage of a crashed flying saucer.  And that press release literally went all over the world and made headlines," says Moore. "Clearly something crashed.  The question is: 'What was it?'"

The U.S. military soon retracted its story, stating that what had crashed was a weather balloon.  Decades later, the official explanation changed to a top-secret test for monitoring nuclear explosions in the Soviet Union.

But alleged witnesses say they handled the remains of an alien spaceship...and its crew.

Richard Berendzen, an astronomer at American University here in Washington, has investigated a number of UFO reports. "UFO believers claim there is a massive conspiracy, one which has suppressed evidence since at least the Second World War," says Berendzen.

"In the case of UFOs, you're talking about a conspiracy that would have involved the scientific community, the military, as well as the U.S. State Department and the White House, this country if not many other countries, not for one administration but for many administrations,? says Berendzen. ?And yet, no one has ever broken the story.  No one has ever really presented the verifiable information."

If, as many people suspect, our planet has been visited by creatures from another world, it would be the most momentous development in human history.

But has it really happened?  For now, only you can decide.

This story was first broadcast on the English news program, VOA News Now. For other Focus reports click here.