At exactly new moon (the moon is called new when it lies between the earth and sun), the moon comes above the horizon at the same time as the sun and sets with it. A few days after new moon we sometimes see what is called the old moon in the young moon's arms, the dimly lighted portion being illuminated by light reflected from the day side of the earth. This earthlight at the moon is at least 50 times greater than moonlight at the earth. Its somewhat ruddy color is caused by the sunlight having passed twice through our atmosphere. The bright crescent, which is the young moon's arms enclosing the old moon, is the sun-illuminated portion of the moon.
Wi' the auld moon in her arms."
—Old Scotch Ballad.
After "new moon" the moon appears a little to the east of the sun as a thin semicircle, the horns of which always point to the cast. The horns point to the east because the sun sets in the west and the illuminated part of the moon is on the side nearest to the sun, a fact sometimes forgotten by artists. The thin crescent of the moon gradually becomes broader as the moon moves away from the sun and in the course of four or five days increases to a semicircle.
And with increasing horns forsook the Sun;"
—Lucan's Pharsalia.
The semicircle then increases to an oval and by the time the moon is behind the earth with the earth between it and the sun, the oval has increased to a full circle. Each day the moon rises about 50 minutes later than on the preceding day and in the course of a month changes from a crescent—a quarter—a full shining face, to a quarter, a crescent and again a slender new moon. It has now
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