Watch the moon rise at sunset on 12/5-7.
The Moon passes through the bright stars of the Great Winter Circle this week, a fitting backdrop for the most northerly Full Moon of the year, which occurs on 6th at 7:27 am Eastern Standard Time. December’s Full Moon is popularly known as the Moon Before Yule, Cold Moon, or Long Night Moon. The latter is particularly appropriate as we approach the year’s longest nights around the time of the Winter Solstice. Watch Luna glide just a degree north of the bright star Aldebaran on the night of December 5th. On the following night her bright crisp disc hovers above the figure of Orion, the Hunter.
For most folks living in the mainland United States this week begins the series of phenomena associated with the winter solstice. For the next 10 days we will experience the earliest sunsets of the year. Here in Washington they occur at 4:46 pm EST. By the 12th the sunset time slowly begins to creep a bit later; however, the time of latest sunrise is still advancing. That event falls on the several days before and after January 4th. Thus, when we measure the total length of daylight/night, we find that the year’s shortest day indeed does fall on the solstice on December 21st. This “lag” in the times of sunrise and sunset is a result of our method of keeping time by using a standard second and by the slightly elliptical orbit of the Earth around the Sun. If we still used sundials for keeping time the effect wouldn’t exist.