Science Common Sense

312 - What causes the phases of the moon?

The phases of the moon happen because of the way the Earth, sun, and moon move. The moon is like a ball that goes around the Earth. As it moves, different amounts of sunlight shine on it. There are 8 main phases:

1. New moon - The side of the moon facing the Earth isn't lit by the sun.
2. Crescent moon - A little bit of sunlight shines on the right side of the moon.
3. First quarter moon - Half of the moon's right side is lit by the sun.
4. Gibbous moon - More and more of the moon's right side is lit.
5. Full moon - The whole side of the moon facing the Earth is lit by the sun.
6. Gibbous moon (again) - More and more of the moon's left side is lit, but it's decreasing on the right.
7. Last quarter moon - Half of the moon's left side is lit by the sun.
8. Crescent moon (again) - A little bit of sunlight shines on the left side of the moon.

It takes about a month for the moon to go through all the phases.