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:

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.