Nightmarish lunation

Is there a Dark Side of the Moon? Yes, the same way there’s a dark side of the Earth. It’s called night time. On the moon, night time lasts two weeks. There is, however, something more mysterious called the Far Side of the Moon. One side of the Moon always faces the Earth. It’s impressive to think that, until the Soviet Union sent Luna 3 to the Moon, no one had any notion what the far side of the Moon looked like. The odd fact that the Moon stares at us fixedly from one side probably convinced more than a few observers that it was a flat disk (and by logical extension, that the Earth was too).

In fact, though, the Moon slightly tips its hand and shows us somewhat more than a pure hemisphere. This process is called lunation, and it is akin to the Moon bowing slightly as it dances around us, watching us all the while. If you take pictures of the Moon every night of the month, you get a sense of this pitching motion. I had seen this kind of thing before, but recently NASA’s astronomy picture of the day was an intense high speed version of lunation that gave me vertigo: APOD: 2005 November 13 – Lunation. For some reason, they chose to animate it at warp speed, and the result is disturbing, something like being fed upon by giant insect lit by a strobe. Menace and the Moon are friends for a reason.