One morning several years ago a black triangular-shaped object flew over my home in the San Gabriel Mountains in southern California. It was almost completely silent, made rapid turns and accelerations, and was so nonreflective it looked like a hole in the sky, almost otherworldly. It was, in fact, the B-2 Stealth Bomber, looping around to make another run over the Pasadena Rose Parade on January 1, an annual tradition. But had I not known what it was and seen it first, say, out in the desert at dusk, I might easily have thought it a UFO.

For decades black triangular-shaped objects have been labeled UFOs. Now a cohort of military, aviation and political observers would like to change the label to a less pejorative phrasing—Unidentified Aerial Phenomena (UAP)—and their efforts to be taken seriously have resulted in a new book by investigative journalist Leslie Kean entitled UFOs: Generals, Pilots, and Government Officials Go on the Record (Crown, 2010). Kean asks readers to consider that such sightings represent “a solid, physical phenomenon that appears to be under intelligent control and is capable of speeds, maneuverability, and luminosity beyond current known technology,” that the “government routinely ignores UFOs and, when pressed, issues false explanations,” and that the “hypothesis that UFOs are of extraterrestrial or interdimensional origin is a rational one and must be taken into account.”

How much data do we have, and can they help us distinguish between UAPs and what I call Completely Ridiculous Alien Piffle (CRAP), such as crop circles and cattle mutilations, alien abductions and anal probes, and human-alien hybrids? According to Kean, “roughly 90 to 95 percent of UFO sightings can be explained” as “weather balloons, flares, sky lanterns, planes flying in formation, secret military aircraft, birds reflecting the sun, planes reflecting the sun, blimps, helicopters, the planet Venus or Mars, meteors or meteorites, space junk, satellites, sundogs, ball lightning, ice crystals, reflected light off clouds, lights on the ground or lights reflected on a cockpit window,” and more. So the entire extraterrestrial hypothesis is based on the residue of data after the above list has been exhausted. What’s left? Not much.

For example, Kean opens her exploration “on very solid ground, with a Major General’s firsthand chronicle of one of the most vivid and well-documented UFO cases ever”—the UFO wave over Belgium in 1989–1990. Here is Major General Wilfried De Brouwer’s recounting of the first night of sightings: “Hundreds of people saw a majestic triangular craft with a span of approximately a hundred and twenty feet and powerful beaming spotlights, mov­ing very slowly without making any significant noise but, in several cases, accelerating to very high speeds.” Even seemingly unexplainable sightings such as De Brouwer’s, however, could simply have been an early experimental model of a stealth bomber (U.S., Soviet, or otherwise) that secret-keeping military agencies were understandably loath to reveal.

In any case, compare De Brouwer’s narrative with Kean’s summary of the same incident: “Common sense tells us that if a government had developed huge craft that can hover motionless only a few hundred feet up, and then speed off in the blink of an eye—all without making a sound—such technology would have revolutionized both air travel and modern warfare, and probably physics as well.” Note how a 120-foot craft becomes “huge,” how “moving very slowly” changes to “can hover motionless,” how “without making any significant noise” shifts to “without making a sound,” and how “accelerating to very high speeds” transforms into “speed off in the blink of an eye.” This language transmutation is common in UFO narratives, making it harder for scientists to provide natural explanations.

In all fields of science there is a residue of anomalies unexplained by the dominant theory. That does not mean the prevailing theory is wrong or that alternative theories are right. It just means that more work needs to be done to bring those anomalies into the accepted paradigm. In the meantime, it is okay to live with the uncertainty that not everything has an explanation.