Waking up to the moon sneaking away in a blue sky and above sunlit fields and woods has been an inspiration for many artists. Here you see yesterday’s morning moon: egg-shaped, low, and about 245,075 miles to our northwest, but still visible until it “set” (disappeared over the horizon) at 9:12 a.m. My amateur understanding of the phenomenon, for what its worth, follows.
Morning moons often occur on clear days shortly after the full moon. That’s when the moon is setting later and later and becomes “high” enough to be visible in daylight. This month, for example, the moon here rose full (fully illuminated) on January 13 and set at 7:21 the following morning, but it wasn’t high enough in our view to see after daylight.
Yesterday, the moon was “waning” (less and less of it was being illuminated by the sun as time was going by). It was a “gibbous” moon (“GIB-us,” not “JIB-us,” from the Latin word for “hump”). That is, the moon is gibbous when the area visible to us is more than 50 percent and in the process of decreasing or increasing.
At 50 percent illumination, the moon reaches one fourth of its cycle (“first quarter moon”) or three fourths of its cycle (“third quarter moon”). At other times, as the moon’s surface is becoming more and more visible to us, it is said to be a “waxing” moon (from the Old English for “to grow”). Whether waxing or waning, the moon’s illuminated part will eventually be crescent-shaped due to the angle of sun rays; the crescent and other moon phases are not caused by the earth’s shadow (except in a relatively rare lunar eclipse).
(Image taken in Brooklin, Maine, on January 17, 2025.)