Moon phase explorer
Move through a lunar month and see how sunlight creates the Moon’s familiar phases.
Your experiment
How it works
The Sun lights half of the Moon. As the Moon orbits Earth, our viewing angle changes, revealing different fractions of that sunlit half. The repeating phase cycle is a synodic month.
Read the field note ↗About this model
A mean 29.53059-day cycle, not a precision lunar ephemeris. Date estimates can differ from the actual phase by about a day. The diagram uses a conventional northern-hemisphere orientation; the apparent tilt depends on location and time.
Moon phase explorer: common questions
Are phases caused by Earth’s shadow?
No. Ordinary phases are changing views of the sunlit half of the Moon. Earth’s shadow causes a lunar eclipse.
Why is the phase month longer than the orbit?
While the Moon orbits, Earth moves around the Sun. The Moon needs extra time to return to the same alignment with the Sun.
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