Half of the Moon is in Darkness

We only see the Moon because sunlight reflects back to us from its surface. During the course of a month, the Moon circles once around the Earth. If we could magically look down on our solar system, we would see that the half of the Moon facing the Sun is always lit (see image below). But the lit side does not always face the Earth! As the Moon circles the Earth, the amount of the lit side we see changes. These changes are known as the phases of the Moon and it repeats in a certain way over and over.

Cartoon of Moon-Earth Orbit, illustrating the phases of the moon. The cartoon is labeled Moon Earth Sun as viewed from above our solar system. The Earth sits in the center of eight moons at different places in the lunar cycle. To the right the Sun shines on the Moon Earth system, creating shadows on the moon, which we view as phases.

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StarChild Authors: The StarChild Team
StarChild Graphics & Music: Acknowledgments
StarChild Project Leader: Dr. Laura A. Whitlock
Curator: J.D. Myers
Responsible NASA Official: Amber Straughn