Never underestimate the fallibility of human perception, memory, and cognition. Experienced skeptics understand this, but we still can’t help being stunned at times by the misperceptions and bizarre beliefs of some fellow members of our species. It takes the occasional reminder. Yes – Sheri Shepard did not know that the world is not flat, that guy on the French version of Who Wants to be a Millionaire did not know that the Moon orbits around the Earth (and he listened to the 56% of the audience who thought the Sun was the correct answer), and yes millions of people actually believe that magic water (otherwise known as homeopathy) can treat illness.

It is also true that the moon is commonly mistaken for an unidentified flying object (UFO).

People are generally surprised to hear this for two reasons: they underestimate the human capacity to be fooled by misperception and they underestimate how unusual the moon may appear in certain viewing conditions. I also acknowledge that for some people they are simply unfamiliar with the appearance of the moon, not being in the habit of looking up at the nighttime sky, or apparently of paying significant attention to the details of the world around them.

A recent story about a South Wales resident who called 999 (the UK version of 911) to report a UFO did not provide enough details to say what factors were likely dominant in the misidentification. It does seem, however, that the police officer who responded to the call was able to quickly resolve the mystery. Here is the transcript from the call:

Control: “Alpha Zulu 20, this object in the sky, did anyone have a look at it?”

Officer: “Yes, it’s the moon. Over.”

Nice and succinct.

Astronomical objects are quite frequently mistaken for UFO’s – Venus and the moon being the most common. Optical illusions and strange viewing conditions contribute to this. There is the autokinetic effect, which can make stationary objects without any background reference appear to move. Also, in a moving vehicle an astronomical object may appear to follow you. Clouds and fog may obscure the object or give it an unfamiliar color.

But I think the most significant contributor to such misidentifications is the culture of belief. When people look up into the sky and see something strange they cannot identify they think – UFO. Their mind often too readily leaps to the conclusion that this could be something extraterrestrial, something truly exotic and unknown, something reportable. The public is trained to commit the argument from ignorance, rather than to be scientifically curious about what the object may be and to consider common and mundane possibilities. Could this be an aircraft, a satellite, an astronomical object, etc.?

Failing that, to simply be comfortable with the notion that there are many possible things they might see in the sky that they cannot identify without it being extraterrestrial – or even that unusual. Things like flares, ultralight aircraft, floating large lanterns, even outright hoaxes collectively are common enough, and may be impossible to identify by sight alone.

At least the UFO phenomenon provides frequent fun opportunities to teach the public how to think more critically. It provides numerous examples of the flaws of human perception and the power of suggestion. Mistaking the moon for a UFO can be a humbling experience – one that we can try to universalize. Humans should be humble in the knowledge of our own limitations.