3D Game Programming

14.6 Understanding the Phases

The moon has four main phases: new, first quarter, full, and third quarter.

New is when the moon is in between Earth and the sun. Since the sun is

shining on the side of the moon that we cannot see, we do not see the moon

at this time (also, it’s in the same part of the sky as the sun).

First quarter means that the moon is one-quarter of the way around its orbit.

It doesn’t mean that it’s one-quarter lit up—as you can tell, it’s half full.

When the moon is two-quarters (also known as one-half) of the way around

Earth, it’s full. The part of the moon that we see is completely lit up.

You know what third quarter is. The moon is three-quarters of the way around

Earth, and again it’s half lit.

In between the new moon and the quarters, the moon is a crescent.

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Understanding the Phases • 131

Prepared exclusively for Michael Powell