I am always surprised by a Friday the 13th, which of course is ridiculous. A Friday the 13th does not sneak up on you; indeed, they are very predictable. By the rules of our Gregorian calendar, there must be at least one every year. If a leap year starts on a Sunday, there will be three: January, April, and July. And if a common year (non-leap) starts on a Thursday, there will be three then, too: in February, March, and November. And 2015 is a common year that starts on a Thursday: Don’t say I didn’t warn you.

Honey moons (though I’d never heard the term used non-matrimonially until last week) are predictable too: They happen annually, in June. That month’s full moon (which happen 12 to 13 times a year) is called the “honey” moon because, due to the sun’s position, it’s the one most likely to appear yellow-gold.

That these separate events might fall on the same day, while, yes, also predictable, is much more rare, and therefore more interesting: This month’s honey moon/Friday the 13th mash-up last occurred in 1919, and we won’t see one again until 2098. Well, not we, but, you know.

The range of human experiences hypothesized as connected to the phases of the moon—at one point or another in history, some of them still—includes: pregnancy, menstruation, birth, criminal activity, seizure, suicide, and sleep quality.

If any event that happens once in a lifetime is inherently cool—and I think it is, even if I swore I’d make myself go out into the street in the middle of the night to see that moon, and then got into bed and thought “Oh well”—it does not necessarily mean something. You wouldn’t know it from the spate of news stories that ran on the 12th and 13th: “Friday the 13th and Full Moon Collide: Should We Be Afraid?” “Got Goose Bumps? Friday 13th to Coincide With Full Moon.” Many of the stories I saw were facetious, and some were local-radio blog posts by people named Scoot, but their existence demonstrates recognition of a persisting interest (and maybe even belief) in their headlined inquiries.

It’s more than a bit of vague superstition: The study of the “lunar effect” (also known, derisively, as the “Transylvania effect”), or the idea that full moons directly influence human behavior, spans centuries. The word “lunacy” (and thereby “lunatic,” too) derives from the Roman goddess of the moon, Luna. Hippocrates wrote, “no physician should be entrusted with the treatment of disease who was ignorant of the science of astronomy.” Tradition and folklore built upon these ideas, and added their own; somewhere along the line, someone thought up werewolves.

The range of human experiences hypothesized as connected to the phases of the moon—at one point or another in history, some of them still—includes: pregnancy, menstruation, birth, criminal activity, seizure, suicide, and sleep quality. There have often been claims that some surgeons will refuse to operate during a full moon due to increased risk of blood loss; British politician David Tredinnick said as much in front of Parliament in 2009. Five years ago.

Two years before that, the BBC ran a story called “Crackdown on Lunar-Fuelled Crime,” in which a Sussex police spokeswoman revealed the force would be putting extra officers on patrol in Brighton during full moons. The story cites various academic studies as evidence for the moon’s ties to increased criminal activity; of course, it ends with an offhand mention of the 1994 movie Wolf, in which Jack Nicholson is bitten by a wolf, and therefore becomes one.

But still, those studies: There are tons of them. In the 1980s alone at least 40 studies examining the connection between the moon and “lunacy” were published; another 20-plus were dedicated to studying the connection between the moon’s phases and human birthrate. While some of these individual studies claimed to find proof of their hypotheses, severalsubsequentmeta-analyses and literature reviews have found no correlation between the fullness of the moon and human behavior. Rotton and Kelly’s 1985 meta-analysis of 37 studies found that phases of the moon accounted for no more than one percent of the variation in activities categorized as symptomatic of “lunacy.” They also found that most studies on the subject failed three crucial criteria for scientific study: replicability, statistical significance, and predictability.

In short, they were what my college statistics professor would have gleefully called “bunk."

Still, the belief persists. One survey found that 45 percent of college students believe that human beings are prone to “unusual behaviors” during full moons, and that percentage has often been much higher among, interestingly, mental health professionals. In looking for concrete reasons why people might continue to believe the moon can make us crazy, some researchers have considered more humdrum explanations; it’s possible that for people already prone to mental illness and/or seizure, sleep loss due to the moon’s brightness could provoke these symptoms further. As far as any bump in criminal activity goes, maybe it’s as simple as it being a little easier to see what you’re doing in the middle of the night.

Whether these factors have much (or anything) to do with persisting belief in the lunar effect, it’s hard to say. It’s hard to work backward from a great story—we’ve tied our health and fate and fortune to the full moon, become convinced we’re related to each other. Maybe it’s just because it feels so close.

In 1997, two Spanish researchers published a study called “Suicides and the Lunar Cycle” in Psychological Reports. In their introduction, the authors write: “The hypothesis of a relationship between the moon’s phases and human behavior is not supported by the evidence of a large number of studies conducted by many independent investigations all over the world.” You can almost hear the nervous pause. “In spite of this body of evidence,” they go on, “we want to test again for an hypothetical lunar influence on deaths by suicide.” They failed to find any significant correlation, but thank goodness they checked again, just in case.