UFO means Unidentified Flying Object.
First, for the record, I believe in UFOs, but only in the sense that I recognize that it's nearly impossible to identify every object seen flying (or hovering, or floating...) in the sky. Once something has been seen and has gone, there's a limit to what people who didn't see it can say about it.
The real question is whether or not UFOs are visitors from extra-terrestrial civilizations. I think not.
For most of my career as an astronomer, I have worked either directly or indirectly for NASA. This connection has on many occasions led people to tell me their UFO stories. They usually go something like this: "My friend saw such and such a while ago. He thinks it was a UFO." By that they mean an alien spacecraft. "What do you think it was?" If I take the bait, I'm left in the position of trying to discuss an event which I didn't witness, usually with a person who also didn't witness it. All we have are the few details to be gleaned from the second-hand story. In some ways it's even worse when the person talking to me was the witness, because then they are free to remember details which contradict any possible explanations as I provide them. Just to let you know in advance, since I wasn't there, I can't tell you what it was. But that doesn't mean it's what you want it to be.
I have spent hundreds, maybe thousands of nights observing the skies, at major observatories, with small telescopes, and often with just a pair of binoculars or with my naked eyes. And I have seen lots and lots of phenomena, like satellites, the space shuttle, meteors (including the occasional exploding bolide), weird cloud formations, lightning displays near and far, helicopters and aircraft with an assortment of lighting arrangements, and aurorae. But I have never seen anything which made me think it might be an extra-terrestrial spacecraft. I know many other astronomers who like me have spent a great deal of their time observing, and none of us have seen something that we thought might be caused by extra-terrestrial intelligence. If aliens occasionally drop into the Earth's atmosphere for a visit, it seems that astronomers would be more likely to have seen 'em than most, but alas, there are no credible reports.
Using my experience as a guide, I am often able to come up with an explanation for folks of what they might have seen, often fairly convincing, at least to me. But frequently it's just an exercise in frustration, as some people will believe what they want to believe, and there's not much you or I can do about it. So now I rarely take the bait.
However, there is someone who does take the bait. In fact, he's made a career of it. This person is the late Philip Klass, who in his lifetime wrote several good books demolishing even the strongest cases for aliens as the root cause of UFOs. Rather than discuss individual UFO cases, I refer the reader to his books for more information.
Klass has made a number of interesting general findings in his investigations. I've posted his UFOlogical principles separately. Below, I cover some of the same ground.
From my reading and discussion with various people, I make the following observations:
The classic example is how the typical UFO encounter has evolved over the years. Early UFO encounters reflected the shape of spacecraft in popular science fiction like the Flash Gordon series: they were cylindrical, like rockets. But as a result of 1950s science fiction movies, everyone began to see flying saucers. Today, UFO abductions are the rage.
Another example which predates the 20th century is the existence of mythical airships. In 1896, scattered reports appeared in newspapers that people had witnessed dirigibles in the sky. By 1897, sightings were reported across the country. Jerome Clark, a UFO researcher and the author of the UFO Encyclopedia, researched the legend and concluded that the sightings were a mixture of sightings by people with too much imagination and hoaxes.
The best example is how people will report the size of a UFO when they admit they did not know how far away it was. You cannot know one without the other, and if the uncertainty in the distance to an object is, say 1.5 to 5 km, an object of a given angular diameter has an uncertainty in its actual diameter of a factor of 3.
A classic example happened during the 1991 Solar eclipse in Mexico, which many people videotaped. The skies don't have to darken by much for Venus to become visible, and when this happened, some observed it with their videocameras, not knowing what it was. In a typical videotape, the image of Venus jiggled haphazardly as the camera moved around, making the observer think that they were looking at a maneuvering spacecraft.
My own personal recollection along these lines involves a sheriff's deputy in Cheyenne, Wyoming, who observed Venus near the horizon under a low cloud deck and reported it as a UFO. The Denver TV stations and newspapers reported the sighting, and the deputy denied that the object could possibly have been Venus, as he had seen Venus countless times and knew what it looked like.
To go back to my story from Cheyenne, months later, the deputy admitted publically that in fact he had probably just seen Venus, which was low in the west that night, between a ridge line and a low cloud deck. In the Denver papers, the story was buried in the back pages, while the TV stations ignored it completely.
No matter where the observer moves, the direction to celestial object won't change over short timescales. So if someone is driving along a straight road in a car, and they see the UFO over their left shoulder, it will remain over their left shoulder as foreground objects pass by, giving the impression that it is chasing them. Anyone who has driven with small children probably remembers them asking at some time why the Sun was following them.
At first glance, this mutual sighting sounds like hard evidence, but as Philip Klass has repeatedly explained, most radar screens contain false echoes, especially in marginal weather conditions, so there is almost always something on the screen in the right place when a sighting is reported.
Once a UFO sighting has made the news, people spend more time looking at the skies, and they now have more expectations. The result is predictable: more UFO sightings. These make the news, leading to more sightings, and the whole cycle feeds on itself until the media loses interest. After all, it's no longer new news when the 34th UFO sighting has been made.
Just because it wasn't "A" doesn't make it "B". It makes it "not A," that's it. This problem is known as the false dichotomy, since "A" and "B" are never the only choices.
In the 1980s, when UFO sightings had grown somewhat mundane, the new rage became UFO abductions. The testimony about the abductions was almost always extracted under hypnosis, and initially, the two psychologists hypnotizing the witnesses were Dr. John Mack at Harvard and Dr. Leo Sprinkle at the University of Wyoming. Most of Sprinkle's victims inevitably reported a fairly benign encounter, while Mack's victims often described more degrading experiences like anal probes and sexual assault. So which is the more likely scenario: victims of the bad aliens sought out John Mack, while the other victims found their way to Leo Sprinkle, or Mack and Sprinkle were suggesting the stories to people under hypnosis? The real problem from my perspective is that when these people awoke, they believed these things had really happened to them. In a way, Mack was sexually assaulting his victims by planting the pain and experience of a sexual assault in their memory.
So what's behind the UFO sightings that can't be explained? Who knows? I sure don't. There are many possibilities. A given UFO sighting which can't be shown to be Venus, the Moon, or anything else for that matter is no more proof for flying saucers than it is for floating giant cockroaches in elaborate disguise.
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Last modified 11 February, 2009. © Gregory C. Sloan.