Similarly, from the point of view of the moon, the earth also appears to go through phases. For example, in the above arrangement when the moon is nearly full, the moon sees mostly the nighttime side of the earth and the earth appears ``new.'' Conversely, when the moon is nearly new, the earth is nearly full.
The earthshine that we measure on the dark side of the moon, naturally, depends strongly on the phase of the earth. When the earth is new (at full moon), it hardly illuminates the moon at all and the earthshine is very dim. On the other hand, when the earth is full (at new moon), it casts the greatest amount of light on the moon and the earthshine is relatively bright. In fact, when the moon is a thin crescent, it is easy to see earthshine with your naked eye--the dark side of the moon is dimly visible because of the light reflected from the earth.
