July 14, 2005
by Seth Shostak, Senior Astronomer, SETI Institute

The good news is that polls continue to show that between one and two-thirds of the public thinks that extraterrestrial life exists. The weird news is that a similar fraction think that some of it is visiting Earth.

Several recent television shows have soberly addressed the possibility that alien craft are violating our air space, occasionally touching down long enough to allow their crews to conduct bizarre (and, in most states, illegal) experiments on hapless citizens. While these shows tantalize viewers by suggesting that they are finally going to get to the bottom of the so-called “UFO debate”, they never do. That bottom seems perennially out of reach.

So what are the contentious issues here? First off, despite heated discussion by all concerned, let’s admit that interstellar travel doesn’t violate physics. It’s possible. After all, the Pioneer and Voyager probes are nearly three decades into an inadvertent interstellar journey right now. The kicker, of course, is that these craft will take 70,000 years to cover the distance to even the nearest stars (and they’re not aimed that way). With the physics we know, it’s extremely difficult to substantially, and safely, shorten that travel time. Sure, it might be theoretically possible to create worm holes or some other exotic facility for high-speed cosmic cruising; but that approach is entirely speculative.

And it’s not really the point. The problem I have with the claim that strange craft are prowling our planet is not with the transportation mode, but with the evidence. I’ll worry about how they got here once I’m convinced that they’ve really made the scene.

Well, have they? How good is the evidence? In the course of a recent TV broadcast in which I participated, guest experts who have long studied UFOs argued the case for their alien nature by showing photographs of putative saucers hovering at low altitudes. Some of these objects appeared as out-of-focus lights, while others resembled hubcap-shaped Frisbees caught in mid-trajectory.

Since the former are perforce ambiguous, the latter commanded more of my attention. How can we know they’re NOT hubcaps, tossed into the air by a hoaxer with a camera? The reply from one expert: “these photographs pass muster.” When quizzed on exactly which muster was mastered, the response was that “atmospheric effects give us a limit on the distance, and careful examination has ruled out photographic trickery.” Well, the former is pretty chancy, and relies on some assumption about atmospheric conditions (was it a smoggy day in Los Angeles?), and the latter proves nothing. A real shot of an airborne hubcap would, after all, be free of photographic trickery.

Additional evidence that is endlessly cited is “expert testimony.” Pilots, astronauts, and others with experienced eyes and impressive credentials have all claimed to see odd craft in the skies. It’s safe to say that these witnesses have seen something. But just because you don’t recognize an aerial phenomenon doesn’t mean that it’s an extraterrestrial visitor. That requires additional evidence that, so far, seems to be as unconvincing as the trickery-free saucer snaps.

What about those folks who have experienced alien beings first-hand? Abduction stories are an entirely separate field of study and one which I won’t address here, although I must confess that it’s intriguing to see photos of scoop marks on the flesh of human subjects, coupled with the claim that these minor disfigurements are due to alien malfeasance. But even aside from the puzzling question of why beings from distant suns would come to Earth to melon-ball the locals, this evidence is, once again, ambiguous. The scoops might be due to aliens, and then again, they could be the consequence of spousal abuse or many other causes.

When push came to shove, and when pressed as to whether there’s real proof of extraterrestrial visitation, the experts on this show backed off by saying that “well, we don’t know where they come from. But something is definitely going on.” The latter statement is hardly controversial. The former is merely goofy. If the saucers and scoopers are not from outer space, where, exactly, are they from? Belgium?

The bottom line is that the evidence for extraterrestrial visitors has not convinced many scientists. Very few academics are writing papers for refereed journals about alien craft or their occupants. Confronted with this, the UFO experts usually take refuge in two possible explanations:

(1) The material that would be convincing proof has been collected and secreted away by the U.S. government. While endlessly appealing, this is an argument from ignorance (tantamount to saying “we can’t show you good evidence because we haven’t got it”), and perforce implies that every government in the world has efficiently squirreled away all alien artifacts. Unless, of course, the extraterrestrials only visit the U.S., where retrieval of material that falls to Earth is supposedly a perfected art form.

(2) Scientists have simply refused to look carefully at this phenomenon. In other words, the scientists should blame themselves for the fact that the visitation hypothesis has failed to sway them.

This is not only unfair, it’s misguided. Sure, rather few researchers have themselves gone into the field to sift through the stories, the videos, and the odd photos that comprise the evidence for alien presence. But they don’t have to. This complaint is akin to telling movie critics that films would be better if only they would pitch in and get behind the camera. But critics can compose excellent and accurate evaluations of a movie without being participants in the business of making films.

The burden of proof is on those making the claims, not those who find the data dubious. If there are investigators who are convinced that craft from other worlds are buzzing ours, then they should present the absolute best evidence they have, and not resort to explanations that appeal to conspiratorial cover-ups or the failure of others to be open to the idea. The UFO advocates are not asking us to believe something either trivial or peripheral, for after all, there could hardly be any discovery more dramatic or important than visitors from other worlds. If we could prove that the aliens are here, I would be as awestruck as anyone. But I await a compelling Exhibit A.