an autodidact meets a dilettante…

‘Rise above yourself and grasp the world’ Archimedes – attribution

is the moon really a harsh mistress?

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Eons ago, as a relatively young perpetual student type, I was wide awake late at night in my upper storey bedroom, my mind a blooming buzzing confusion of I know not who’s ideas. All I can really recall is that I couldn’t sleep for love nor money. I paced about my tiny enclosure like the sad polar bear did, in those years, in our local zoo.

Somehow, I managed to rise above myself for an instant and gaze out of the window. A perfectly full moon hung low and large in the sky. Eureka! It struck me like moonlightning – lunatics, werewolves, somnambulism, witches and warlocks. I was spellbound.

Well, not really. But for a wee while, this teensy personal experience affected my thinking about the power of the moon. But my skepticism, or what others have called my contrarian disposition, was soon doing battle with these loony feelings. All of this occurred well before the advent of the internet, but as a child I became addicted to encyclopaedias. We had a couple of full sets in the family home, and I loved disappearing into them on a regular basis. And this tendency to arm oneself with facts against the world – or not – is generally fixed from an early age.

So all of this is a preamble to a conversation I recently had with a young person who insisted that the full moon had distinct, if somewhat unquantifiable, effects on our behaviour, due to gravity, essentially. And water.

Of course, the reference here was to the moon’s tidal effects. These effects are quite powerful, and we are mostly made up of water, ergo…

And apparently it isn’t just about water. Gravity is one of the fundamental forces of nature, it’s exerted everywhere, and particularly by massive bodies. The moon is massive, ergo…

So let me take up the gravitational effects first. Why would there be any relationship between the moon’s gravitational effects and its fullness? A full moon is simply more visible, due to reflected light from the sun, not more massive or more proximal. Thus the gravitational effects are more or less constant. The moon’s orbit is not precisely circular, of course, though it’s very nearly so, and in any case its varying distance from the earth is is no way connected to its ‘fullness’ or otherwise.

However the moon is the principal cause of oceanic tides. The Geographical Society explains:

The moon’s gravitational pull is the primary tidal force. The moon’s gravity pulls the ocean toward it during high high tides. During low high tides, the earth itself is pulled slightly toward the moon, creating high tides on the opposite side of the planet.

So we have two effects here. The moon’s gravitational effect on the tides and any other earthly phenomena, and the moon’s psychological, and other, effects on subjects (including non-human species) due to the amount of light it reflects from the sun.

the moon’s gravity

The moon circles the earth while the earth circles (or orbits) the sun. Picture, then, the moon’s movements tracing something like a spring as it revolves around the revolving earth. Our planet, like all the others in our system, orbits the sun due to the enormous gravitational pull caused by its mass. But tidal forces are more closely related to distance than to mass. Also the tidal force, which is a calculable value*, is different from the actual tides, which are affected by many variables, such as the distribution of land and water over the earth, ocean depths, and endlessly changing weather conditions. The moon has a gravitational pull on land as well as sea, but fluids are far easier to move.

The tidal force causes oceanic waters to bulge towards the moon, when the moon is on that side. The force is at its greatest on the side of the earth closest to the moon, and at its weakest on the furthest side. It averages out around the centre. But interestingly, the oceans on the side opposite the moon also bulge out, as described in the Geographical Society quote above, causing two high tides and two low tides each day, as the earth rotates through the bulges. This is because the earth itself is distorted slightly by the tidal force, on a daily basis.

So much for the tides. The moon’s gravitational effect on humans, individually, is minuscule, and any effect would be constant, since the moon’s distance from earth is essentially unchanging (actually it’s spiralling away from us at a rate of just under 4cm per year, but don’t worry). It certainly doesn’t matter that we’re mostly water, because even the largest non-oceanic bodies of water exhibit barely discernible tidal effects. So, no, our blood doesn’t slosh about to a tidal rhythm.

Ah but hang on. It so happens that a full moon (and a new one) does have a planetary effect – but not due to light. The sun also affects us gravitationally, to a lesser degree, but sometimes in cahoots with the moon, so to speak. The SciJinks website explains:

When the earth, moon, and sun line up—which happens at times of full moon or new moon—the lunar and solar tides reinforce each other, leading to more extreme tides, called spring tides. When lunar and solar tides act against each other, the result is unusually small tides, called neap tides. There is a new moon or a full moon about every two weeks, so that’s how often we see large spring tides.

So much for gravity, by far the weakest of the four fundamental forces known today.

*Specified as the moon’s gravitational pull in a specific location on Earth, minus the moon’s average gravitational pull over the whole Earth

the full moon’s strange powers

So the other question is, does the full moon affect us (and/or wolves) psychologically, either due to tidal effects or, more likely, due to the light it floods us with every 29.5 days?

How to find out? It’s fair to say that, in the days before we lit up the earth’s surface with our inventions, the full moon’s regularly monthly light had a much greater impact than it does now. ‘Ill met by moonlight’, complained Oberon to proud Titania, and certainly a flood of moonlight would make secret nightly trysts and/or avoidings a trickier proposition, but such effects would be indirect rather than direct. As to direct effects, they might be expected to show up in statistics – more untoward activity (from murders to mad mutterings) showing up under full moons than not.

Well, the evidence so far is mixed and unconvincing. It would be impossible to list the number of studies, small and large, rigorous or otherwise, that have tried to establish or quantify a full moon effect, so I will simply briefly refer to some of the scientific articles trying to make sense of this mish-mash. The articles themselves are in the references.

Scientific American‘s 2009 article ‘Lunacy and the Full Moon’ provides fun historical detail, and a lot of stuff about the claim that the moon affects our waters, including our very watery brain. This goes at least as far back as Pliny the Elder. Their conclusion – the lunar lunacy effect is ‘a cultural fossil’.

An undated article from Healthline (presumably from the US) is rather more open-minded, if that’s the term. It mentions one study that found ‘nearly 81 percent of mental health professionals believe the full moon can make people ill’. Unsurprising but not very helpful. It also describes statistics which indicate no correlation between full moons and homicides, assaults or suicides. However, there is some evidence of a link between full moons and increased sleep latency – ‘the period between when you first fall asleep and when you enter the first stage of REM sleep… Increased latency means it takes a longer time to get to REM sleep’. Interesting, but not exactly a clincher for serious lunar impacts. Another small study (17 subjects!) suggested a link between the full moon and enhanced bipolar disorder.

Wikipedia is comprehensive and skeptical as always these days – I love Wikipedia! The very first sentence of its article ‘Lunar Effect’ gives an indication of what’s to come:

The lunar effect is a purported unproven correlation between specific stages of the roughly 29.5-day lunar cycle and behavior and physiological changes in living beings on Earth, including humans.

It gives short shrift to the lunacy claims, and reports on sleep studies:

A 2015 study of 795 children found a three-minute increase in sleep duration near the full moon, but a 2016 study of 5,812 children found a five-minute decrease in sleep duration near the full moon. No other modification in activity behaviors were reported, and the lead scientist concluded: “Our study provides compelling evidence that the moon does not seem to influence people’s behavior.”

Other possible lunar effects, on bad behaviour, health issues (including epilepsy), accidents, birth rates, and even the stock market, were found to be unproven at best. Effects on non-human creatures are largely limited to coastal species obviously affected by tides. Increased light levels during full moons may have some slight effect on plant growth.

Finally, New Scientist has a recent (albeit very brief) article which bucks the trend – at least for oysters. But maybe for other species too. A researcher, Frank Brown, decades ago, noted that oysters opened their shells for feeding at high tide, not surprisingly. He wondered whether the moon had anything to do with this, so he removed a bunch of oysters far from their location to see what would happen:

Brown kept the shellfish in a sealed darkroom, shielded from changes in temperature, pressure, water currents and light. At first, the oysters kept their rhythm, feeding each day in time with the New Haven tides. Then, something strange happened – their feeding times gradually shifted until they lagged 3 hours behind. Brown was mystified, until he realised that they had adapted to the local state of the moon: they were feeding at times when Evanston, if it were by the sea, would experience high tide. Despite having no obvious environmental cues, it seemed these shellfish were somehow tracking lunar cycles.

The article goes on to say that, though Brown’s evidence was largely dismissed, recent and growing evidence from ‘a range of fields’ backs him up. Unfortunately, no detail is provided. Disappointing.

All in all, the evidence for the moon’s effects on human behaviour is scant and rarely corroborated. Still, it makes for pleasant poetry, and all that.


Written by stewart henderson

January 26, 2022 at 8:10 am

Posted in moon, sun, tidal force, tides

Tagged with , ,

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