Cast in the Shadows

The moon wanes thru week’s end, until Sunday, December 5, when the new moon passes directly between the sun and the earth, disappearing from view.

Of course, the moon is still there. However, the side facing us is cast in the darkness of its own shadow, rendering it invisible to us. But the so-called dark side of the moon faces the sun full-on, reflecting all that light away from earth. Like the tree falling in a forest with no one to hear it, the dark side of the moon is only dark in as much as we see it — or don’t.

Over eons, the pull of earth’s gravity has slowed the rotation of the moon, until now it is locked in orbit around us, always keeping the same face toward us. As the angle between earth, moon and sun changes, so does the amount of moon illuminated for us to see, causing the moon’s phases. But just as here on earth, half of the moon’s surface is always fully bathed in sunlight. 

Scan the southeast horizon Friday before dawn for the last of the thin waning crescent moon. It rises at 5am, just two hours before the sun. High above shines brilliant Venus, and higher still Saturn.

By Tuesday the nascent moon has returned, a thin sliver visible low in the southwest after sunset, around 4:43pm. Once you spot the moon, look between it and the horizon for the piercing light of Mercury, at its best evening apparition this week. Lower still is much dimmer Mars. Binoculars may help your search, but both planets are visible to the unaided eye.

Take heart as the days grow shorter, as Wednesday, December 8, marks a turning point of sorts. When the sun dips beneath the southwest horizon at 4:43, it will be the earliest sunset of the year, almost two weeks before solstice. On the flip-side, the latest sunset won’t come until two weeks after solstice.