What Do We Mean by “The Old Moon in the New Moon’s Arms”?
“Earth-shine,” in astronomy, is the name given to the faint light visible on the part of the moon not illuminated by the sun, due to the illumination of that portion by the light which the earth reflects on her. It is most conspicuous when the illuminated part of the disc is at its smallest, as soon after new moon. This phenomenon is popularly described as “the old moon in the new moon’s arms.”