As the Moon orbits Earth, the angle between our viewing direction and incoming sunlight changes. This geometry changes the visible illuminated fraction. Ordinary phases are not Earth’s shadow crossing the Moon; lunar eclipses are a different event.
Space · Discover & try
Why does the Moon appear to change shape?
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Phase
The apparent shape of the sunlit Moon seen from Earth.
Waxing
The visible sunlit portion is growing.
Waning
The visible sunlit portion is shrinking.
Watch · Try · Explain
See how it works
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Eight checkpoints in a continuous cycle; north-pole orbital view and Northern Hemisphere Earth-view orientation. Sizes and distances are not to scale.
What to look for
- Compare the orbital view with the view from Earth.
- Find both half-lit quarter phases.
- Follow waxing phases through to full Moon.
Explain what you noticed
Why does the Moon appear to change shape?
Keep this idea: Moon phases come from our changing view of the Moon’s sunlit half.
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Source material checked 2026-10-28. Explanations and activities by Nepedia. Agency source links do not imply endorsement.
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