People know little about the moon. Popular astronomy and planetarium websites report that to many in their audiences, it comes as a huge surprise even to learn that the moon is visible in daylight. How can we reach adulthood so unobservant of our surroundings that never once did we look up to notice the moon out during the day?
Hollywood audiences apparently take no issue, either, with outdoor establishing shots that tell us a scene takes place at night—and in which, by some unwritten rule, the moon always appears full. I love how the smugglers in “Poldark,” who you’d think might have wanted to move their goods under cover of darkness, always work under a full moon. Then a show’s plot will advance by a week or two, until another scene takes place at night—can you guess whether the moon has changed its phase?
In earlier times, paying attention to the moon held higher stakes than it does today. It could be useful, or even affect survival, to know and predict the lunar cycle. Archaeologists have studied coastlines in Africa with intertidal zones where early humans dependent on molluscs for their food supply had to have a “sophisticated knowledge of the relationship between lunar-driven tides and intertidal foraging.”
Those “early modern humans could recognize the relationship between lunar cycles, tidal systems and [availability of molluscs] and thus design symbolic calendar systems that allowed them to time their visits to the coast so as to make productive use of the coastal zone.” Attunement to the lunar cycles mattered a lot, as foragers could risk drowning in the rising waters if they ignored or miscalculated the lunar—and therefore tidal—cycle.
Often throughout history, too, armies seeking to conduct post-sundown warfare have selected a date when the moon was full to enhance visibility for their nocturnal foray, or a new moon to ambush the enemy under maximum darkness.
Scientific studies still support the validity of relationships between animal behavior and the moon. But does the lunar cycle directly affect human behavior? Anecdotal evidence abounds, especially in places like police stations, crisis hotlines, birthing centers, and emergency rooms.
But hard evidence for the connection tends to crumble in the face of large-scale statistical analysis. Formal studies, many summarized in a Current Biology review article “Human Responses to the Geophysical Daily, Annual and Lunar Cycles,” examine claims of a monthly spike in so-called lunacy, rates of criminal behavior and traffic accidents; these claims, along with supposed correlations between lunar phase and stock-market performance, have all been soundly debunked.
Study after study has failed to support a causal connection between lunar phases and human physiology. Scientists explain that, to begin with, the gravitational force that generates the tides depend on the alignment among earth, moon, and sun, rather than specifically the moon’s phase in relation to earth, “so a full moon does not mean a specific gravitational effect on earth.” Secondly, the idea that our bodies are mostly made up of water and therefore we might host internal “tides” is contradicted by the fact that the moon’s pull is actually a very weak effect, not strong enough to stir most bodies of water (lakes, even the smaller oceans), much less to govern ebbs and flows inside a human body.
Even the most obvious monthly human rhythm—our menstrual cycle—shows no clear evidence of direct influence by the position of the moon. Yet based on the coincidental similarity in the average length of these cycles, cultures around the world link femaleness with the moon in their mythologies, legends, and spiritual practices.
Some evidence does suggest that people’s sleep can be disrupted when the night sky displays more light (such as the three or four nights closest to the full moon). As certain psychological conditions are exacerbated by sleep deprivation, this effect may partly account for anecdotes about the resulting incidents. Such an effect, hugely reduced by the advent of bright artificial lighting after sundown, may have been great enough in past times and still in remote places to keep lunar-phase myths alive.
We choose which cycles to focus on, to note in our diaries, and to invest with significance. Knowing that seasonal changes and circadian (daily) rhythms deeply affect our bodies—sleep patterns, appetites, activity levels—it makes sense, as a practice of self-awareness, to keep daily cycles in mind, a connection that the original meaning of the words “diary” and “journal” already invites.
Some calendar points constructed by culture, too, like weekdays versus the weekend, record-keeping and financial deadlines pegged to the turn of the month, or recurring tasks on a work calendar, tend to fold themselves in to the account of a journal, corresponding to rhythms that matter in our lives. Diaries kept by observant Christians often punctuate their week with Sunday (First Day or Sabbath); in diaries I’ve studied, especially if the writer is a churchgoer, Sunday’s entries may provide a pause to express religious sentiments or reflections.
The question of the lunar month holds a place of quixotic tension in this calendar. Like many journal-keepers, I’ve often followed an impulse to track lunar phases and even let my awareness of the moon’s current phase (last quarter, new moon) prompt the shape or direction of a journal entry. For no rational or scientific reason, I enjoy starting a new volume on the day of a full moon or a new moon.
Paying attention to the moon, even if it doesn’t directly control our physiology, may still have value. Observing your surroundings, such as to notice the moon visible in the sky at morning or midday, and to know where we stand in the lunar cycle, connects you with something beyond yourself.
Humans who menstruate, if attuned to the unfolding sensations in our bodies, can learn to take better care of ourselves by recognizing and working with the inherent “monthliness” of hormonal/menstrual cycles rather than denying or resisting them. Discovering a pattern that may be highly individual, we learn how different points around this cycle are associated, for us, with changing emotional states and physical sensations in semi-predictable ways.
Like the similarly odd fact that our sun and moon appear to share an almost identical diameter as viewed from Earth, the preponderance of scientific evidence suggests that any link between lunar phase and human physiology is nothing but coincidence. And links with other perceived connections, such as higher incidences of “lunacy” or crime, simply don’t hold up under statistical examination.
So, let’s accept that the moon exerts no effect on us, and only stirs large bodies of water like the oceans. Maybe as journal-keepers we simply observe those forces the moon exerts on Earth—the ebb and flow of tides, the fluctuation of crescent and gibbous moons, of lighter and darker night skies—as stations that usefully mark our own path through the seasons and the dozen or so full moons that make a year.
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