I saw an ad on TV today that really caught me by surprise. It showed a nighttime, starry scene with a crescent moon rising (or perhaps setting) over a calm tropical sea. The moon appeared to be just a few degrees above the horizon. In the foreground was a long-neck bottle of beer; the gimmick was that the crescent moon fit into the opening in the bottle just like a slice of lemon.

The visual image immediately struck me as wrong, and in seconds I realized what the problem was: the lunar terminator,
the dividing line between the night and dark halves, was perpendicular to the horizon. This is impossible. The crescent moon is always near the sun and rises or sets just before or after it. The terminator is at right angles to a great circle connecting the sun and moon. The illuminated half of the moon will always point towards the sun, in the graphic it was pointing parallel the horizon.

The only time and place where a configuration like this is possible is winter in extremely high latitudes, and then only under certain conditions, like during a "midnight sun" situation with the moon on the ecliptic. Even then, the angles and illumination weren't quite right, and the scene was clearly meant to be in the tropics. It occurred to me that today, only an astronomy buff would be expected to notice this. A century ago, almost anyone would have taken one look at the scene and immediately known it was bogus.

People today, even those who spend a lot of time outdoors, like farmers and sailors, rarely look at the sky anymore. And they never have depended on the moon for direction finding, as a calendar or a clock, or even for illumination.

I certainly hope someone who helped put that commercial together is reading this. I have a message just for you: I didn't notice the name of the brand of beer, and I don't want to know.