Lunar Cycles • A visual guide
Eclipses
When sunlight is interrupted
Solar and lunar eclipses involve the same three bodies. The difference is which one casts the shadow, and where that shadow falls.
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Solar eclipse: the Moon between us and the Sun
At new moon, a close alignment can place the Moon’s shadow on Earth. Observers in the affected region see the Moon cover some or all of the Sun. What is visible depends on the alignment and the observer’s location.
Lunar eclipse: Earth’s shadow on the Moon
At full moon, a close alignment can carry the Moon through Earth’s shadow. It may pass through the faint outer shadow, or partly or completely into the darker inner shadow. These produce penumbral, partial, and total lunar eclipses.
Why eclipses are occasional
The Moon’s tilted orbit usually carries it above or below the alignment needed for an eclipse. New and full moon describe phase; an eclipse also needs the right three-dimensional geometry. The lunar nodes help explain when that alignment is possible.