The full moon (revisited)

That idea that the full moon effects human behavior is largely taken for granted, and is probably nearly as old as speculation itself. The word "lunacy" suggests that the ancient Romans (who worshiped the moon goddess, Luna) subscribed to this idea, but I doubt they were the first.

Today, this belief remains largely unquestioned. And why not? The moon causes the tides; informs the advice given by the Farmer's Almanac; (allegedly) regulates human menstrual cycles; and makes wolves howl. So it was only very recently that I even bothered to give this little tidbit of common knowledge much thought. But one day, I ventured to wonder if the moon really was periodically wresting my precious inhibitions from me, and if so, how I could put a stop to it.

Can the moon really effect our behavior/ physiology? If so, is the effect truly more pronounced when it's full? And if not, what about claims that women are "in sync" with the moon?

I've generally encountered two different explanations as to how the full moon allegedly effects us: I will call them the gravity theory; and the moonlight theory. The proponents of the gravity theory tend to say things like:

"Everyone knows that the moon has an immense effect on the ocean, and everyone knows that people are - like the ocean - mostly made of water, so the moon must effect us too, right?"

Well actually, no. In fact, it is incredibly easy to calculate the gravitational "pull" that the moon exerts on you, and it turns out that taking an elevator has a vastly greater effect on your physiology; and I don't mean to play up the physiological effect of elevators.The moon's effect on the ocean is due to two things: the size of the ocean; and the fact that is fluid. People - puny, viscus things that they are - are actually effected much differently than the ocean, regardless of their percentage water content.

And anyway, according to the gravity explanation it is the new moon - not the full - that should have the greater effect, as it is only then that the gravitational influence of the sun and the moon are complimentary, as you can see in the image above. But, again: even with the sun and moon so ganging up on you, their combined gravitational influence on you really is incredibly infantesimal..

The moonlight theory on the other hand, holds that:

"To animals the world over, the full moon is associated with a change in behavior, often by acting as a mating signal. So isn't it possible that some sort of human "sensitivity" to the light of a full moon might be a kind of vestigial instinct, inherited from our evolutionary ancestors?"

First of all, even if this were true, modern dwellings and illumination techniques often obscure the moon's light altogether. But the best point to be made here is that there just really is no evidence that the full moon has any special effect on humans; we just don't seem to act any differently when the moon is full.

Don't get me wrong: full moon is beautiful to look at, can provide great lighting, which can help you feel romantic, and I'm sure that the knowledge the moon was full might has helped convince many a person to act like an idiot on more than one occasion. But the idea that such behavior can be directly caused by a full moon is, I think, false. And there really is little in the way of objective evidence to contradict me.

"So then what about the apparent correlation between the moon and human female menstruation?"

Ladies, if I may be so bold as to propose it, this apparent correlation is almost certainly just a coincidence! As the astronomer George O. Abell wrote:

"The moon's cycle of phases is 29.53 days, while the human female menstrual cycle averages 28 days (although it varies among women and from time to time with individual women); this is hardly even a good coincidence! The corresponding estrus cycles of some other mammals are 28 days for opossums, 11 days for guinea pigs, 16 to 17 days for sheep, 20 to 22 days for sows, 21 days for cows and mares, 24 to 26 days for macaque monkeys, 37 days for chimpanzees, and only 5 days for rats and mice. One could argue, I suppose, that the human female, being more intelligent and perhaps aware of her environment, adapted to a cycle close to that of the moon, while lower animals did not. But then the 28-day period for the opossum must be a coincidence, and if it is a coincidence for opossums, why not for humans?"

Since we entirely lack any decent explanation as to how it might be otherwise, this seems to me be an etirely reasonable assumption. Moreover, according to Wikipedia, no study has ever "demonstrated the synchronization of women's menstrual cycles with the lunar cycle."

This means that virtually all the talk of the supposed "emotional/physiological effects" of the moon is, as far as I can tell, full of it. And I think that's just fascinating.

(Special thanks to Dr. Alf!)