The Inconstant Moon

Romeo: Lady, by yonder blessed moon I swear,

That tips with silver all these fruit-tree tops—

Juliet: O, swear not by the moon, the inconstant moon,

That monthly changes in her circled orb,

Lest that thy love prove likewise variable.

Romeo and Juliet. Act ii. Sc. 2. 12

As I was thinking about the lunar cycle and the moon's phases, I remembered a conversation I had with a friend a few years ago who was trying to understand the mechanics of the moon phases, and I realized I didn't really get it either (or had just forgotten).

Well, since we're here, let's quickly and painlessly get up to speed on the moon’s phases. Here's a diagram to help:

That's the Earth in the center with the moon circling. The outer moon figures show the phases as seen from the Earth. It's really just about the positioning of the moon with respect to the sun and the Earth. It also relates to the fact that the moon seems as though it doesn't rotate (although it does, once for every revolution around the Earth).

Well, I don't want to get too technical. After all, it's getting late. The image above of the moon and the Earth's atmosphere is courtesy of NASA, taken from the International Space Station. The NASA images are amazing, and we're just getting started!

As for Romeo and Juliet, maybe if he'd sworn by the moon, things would have turned out differently. We'll never know. The moon may seem inconstant, but it is reliable in its cycle, waxing and waning as it has for millenia. It takes human minds to apply moral judgments to natural phenomena. I'm pretty sure the moon doesn't care.