All manner of accomplishments and actions have been attributed to aliens, who for some reason seem to have a travel preference for the Americas. There are relatively few sightings or handiwork left behind on other continents. Some aliens are malevolent beings like the Robot Monster, while others like E.T. are friendly. Still others are neutral and satisfy themselves by scratching images on Ica rocks.

Aliens are also said to be responsible for Nazca lines, crop circles, destroying Atlantis, building Pyramids, reproduction experiments, Mayan temples, cattle mutilation, unpleasant prodding, New Mexico desert wreckage, and providing the blueprint for reverse engineering of advanced spacecraft. For all this, believers have yet to produce a confirmed alien artifact, souvenir, implant, or DNA sample. This is sometimes attributed to aliens having the ability to erase memories. More ad hoc reasoning explains why extraterrestrial creatures would travel unimaginable distances just to build stuff or screw with us and never engage in meaningful outreach or dialogue. It’s because the various alien populations have entered into a no-human contact agreement. This makes the lack of proof the proof.

We don’t know of any life on other planets, though there could be. There may be microbes, which would be significant but not that fascinating. There may be an equivalent of a mammal or reptile, which would be better but still not entirely cool. The best would be intelligent life, which I define as being able to appreciate what finding comparable life elsewhere means. For example, if intelligent life were discovered at the outer edge of the Milky Way, humans would comprehend this and understand the implications, whereas goats would not.

With billions of galaxies each having billions of stars, most of which are orbited by multiple planets, life could have developed on one or more of them. In the search for this life, astronomers look for traces of water and oxygen in the Goldilocks zone. On one hand, this could be myopic, as life may have other ways of developing. On the other hand, this is the only way we KNOW life can form, so it makes the most sense to look there first.

But if beings do exist elsewhere, the idea of them dropping by unannounced seems highly improbable due to the distance. Earthlings are 500 light seconds from the sun, but four light years away from the second nearest star, Alpha Centauri. That equals 24 trillion miles. Buck Rogers would need a sustained speed of 100 million miles per hour to get there in 30 years. By contrast, the fastest spacecraft to leave Earth, Voyager, travels at 40,000 miles an hour.

So aliens would need to travel at amazing speeds, plus keep a population housed, fed, clothed, medicated, entertained, cooperative, and sustained, probably for millenniums. Also necessary would be equipment repairs, plus planning and good fortune to avoid the perils of deep space. All this just to flatten some corn, scribble some artwork, or take skin samples from unwilling medical subjects.

Accounts of alien abduction have precursors in Medieval and ancient times. Some European nuns believed they had been seduced by demons. BCE Greek women reported that the gods Jupiter and Dionysus had incarnated as animals, then had sex with them, resulting in Minotaur and Centaur offspring. There were no reports of alien visitation until man began pondering interstellar travel in the late 19^th Century. Jules Verne and the 1902 movie A Trip to the Moon, which featured a rocket crashing into the lunar body’s eye, popularized the concept of otherworldly beings.

Whether holding a prod or a paintbrush, the aliens are described by witnesses as being about four feet tall, with heads shaped like inverted eggs, having large craniums, slanted eyes, usually earless and with very small noses. This mirrors how movies, novels, and comic books have usually portrayed them. The first widespread abduction tale was that of Betty and Barney Hill, who told their story following a hypnosis session in 1961. Hypnosis can have limited value in specific instances, but is an unreliable method of accessing lost memories, and can even be used to create false ones.

Mr. Hill reported that the aliens had “wraparound eyes.” Not coincidentally, beings with these features were broadcast 12 days earlier on The Outer Limits. After the Hills story became public, reports became commonplace as the cultural delusion and communal reinforcement took hold. It helped that this took place during the Cold War, a time of a technological and arms races against a mostly faceless Red Menace. The situation seems to have not been reversed in Soviet Union, as its citizens had no access to Invaders From Mars or Flash Gordon comics. Most reports indicate a period of forgetfulness after the encounter. Hypnosis or some other type of suggestion session is needed to lift the fog of being sprayed with alien amnesia juice.

Scientists and skeptics have answered many of the challenges. The crop circle ruse was uncovered by hidden night vision cameras. Erich von Däniken claimed to have alien artwork but this fraud was exposed. He had hired someone to paint spaceships and aliens on rocks and tried to pass them off as ancient. Cattle and other animals can take on an eerie, bloated appearance after scavengers eat their tongues, eyeballs, and other soft parts.

While science demands proof, the alien visitation position asks for considerably less evidence. Nevada businessman Robert Bigelow financed a survey to determine the frequency of alien abduction. It asked respondents if they had ever sensed a presence in the room, had an hour unaccounted for, seen unusual lights, noticed unexplained scars, or had a sensation of flying. Answering four of five yes was counted as evidence of having been snatched by aliens, an especially absurd illustration of magical thinking. It seems more like evidence for having fallen down drunk.