Space Science · Earth, Moon & Sky

Moon Phase Modeling: Why Does the Moon Seem to Change Shape?

Use a light-and-ball model to explain why the Moon's visible illuminated part changes as the Moon orbits Earth, and test common phase misconceptions.

Lesson plan

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Lesson overview

Use a physical model to explain that the Sun illuminates half of the Moon while our view of the lit half changes.
Connect Moon positions in the model with visible phase patterns such as crescent, quarter, gibbous, and full.

The Sun illuminates half of the Moon at a time.
As the Moon orbits Earth, our viewpoint lets us see different amounts of the illuminated half.
That changing view creates the repeating pattern of Moon phases.