Unlike a total solar eclipse, when the disk of the sun is completely blackened, an eclipsed moon does not vanish completely from the sky. Rather it is still bathed in some sunlight streaming past the Earth and, significantly, through its atmosphere. That has a dramatic effect on the color of the moon. Solar light contains all of the colors of the visible spectrum, but as it reaches our atmosphere, the higher frequency blue wavelengths are scattered out—which is what gives our sky its characteristic color. Red and orange wavelengths pass right through. In the case of a lunar eclipse, that means the moon is bathed in a reddish glow—hence the blood moon handle.
There are other names for a full moon at this time of year when a lunar eclipse is not taking place. According to the Old Farmer’s Almanac, a March full moon is also called a worm moon—a name attributed to the earthworms that typically emerge from the ground in early spring, or to the beetle larvae that also emerge from the branches of trees in the post-winter thaw. Indigenous American tribes have also dubbed the March full moon the Eagle Moon, the Goose Moon, or the Crow Comes Back Moon, heralding the reappearance of these animals in the Spring.
