Myths surrounding Halloween and the moon are abundant in our culture. Full moons on Halloween are thought to bring out every sort of nightmare, from werewolves to witches. Ask any emergency room tech, police officer or campus security guard, and you will quickly discover that a belief in the full moon’s effects is widely held. Add the fear of the full moon to the inherent spookiness of Halloween, and the devil seems so much more plausible.

So, how scared should we be of the full moon this Halloween? Well, the next full moon to coincide with Halloween will be a blue moon! In 2020, the moon will be full on Oct. 1, followed by another full moon on Halloween. For this year, at least, we are safe. What about in 2020? Well, let me try to debunk a few myths.

As a planetarium operator in college, people often wanted to share their theories about the full moon with me. I heard any number of theories, from the stronger gravity of a full moon to a brighter sky at night as causes for alarm. Let us start with the idea that the full moon has a stronger gravitational pull than any other moon.

Full moon mythsYou may have heard that the moon’s gravity is a primary cause of the ocean tides, and this is true. However, the moon phases are often misunderstood. The full moon has no stronger gravitational pull on the earth than any other phase. As the moon travels around the earth in an elliptical orbit, light from the sun strikes the moon and reflects that light back into space. During certain days of the month, your location on earth is more-or-less aligned with that reflected light. This is what causes the moon phases. The distance of the moon to the earth remains roughly constant throughout the lunar cycle ~ which means moon’s gravitational pull on the earth is roughly constant, as well.

As for the brighter night sky as an explanation for full-moon hysteria, in modern times, at least, there does not seem to be any correlation at all. Before the ubiquity of artificial light, there may have been more activity on bright nights, but scientists don’t have any data to support that theory. A 1996 study conducted by two psychologists and an astronomer (Ivan Kelly, James Rotton and Roger Culver) found that there was no correlation between human activity and the lunar cycle. So, why do we believe so deeply that the crazies come out during the full moon?

One strong theory for why people believe in the moon myths is that many people suffer from something called confirmation bias. We see confirmation bias in all areas of the media and politics today. Confirmation bias is the perfectly human act of searching for evidence that supports our own beliefs, while ignoring evidence that disproves our ideas. So this year, when something strange happens on the night of a full moon, take a moment and think back to the last strange happening in your life. Was there a full moon?

Either way, Happy Halloween! I’ll see you in 2020.

By R.J. Linton