John Wooding, age 10, of New Brunswick, New Jersey, for his question:

What causes the Old Moon in the New Moon's arms?

Sometimes the New Moon seems to hold a pale, ghostly ball in its bright curve. This dim light is called earthshine. It is sunshine that has reached the earth from the sun and then bounced back and fallen upon the face of the moon. The moonlight that falls on the earth earth is sunlight that has fallen upon the moon and then reflected on to us. The earth and the moon, however, reflect only a little of their total sunshine out into space. And only a small amount of this falls upon each other as moonlight and earthshine.

When the moon is new, we see a thin sliver of the side that is bathed in sunshine. The rest of its face is in the shadows of night. But this shadowy part of inQOn may be bathed in light reflected from the earth    somewhat like the moonlight that brightens up a dark night on the earth. Sometimes we see this earthshine as the Old Moon in the New Moon's arms. It traveled from the sun to the earth and only part of it was reflected to the moon as earthshine. And only a small part of the earthshine is reflected back again to the earth.