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Incoming links: Eclipse
Eclipse Created 2026-10-18 Updated 2026-11-05
An eclipse occurs when an alignment of astronomical bodies obscures a source of light or places an illuminated body in another body's shadow. During a solar eclipse, the Moon interrupts the view of the Sun; during a lunar eclipse, the Moon enters Earth's shadow.
The monthly sequence of Moon phases is insufficient to produce monthly eclipses. The Moon's orbital inclination usually carries it above or below the required alignment. Eclipses become possible when the relevant phase occurs sufficiently near an orbital node.[ref]
Why Do Eclipses Happen? by NASA. Geometry: the inclined lunar orbit, eclipse seasons and the distinction between solar and lunar alignments
The finite apparent size of the Sun makes shadow geometry richer than a single dark cone: the umbra excludes the entire solar disk, whereas the penumbra excludes only part. An extended lamp and an opaque ball reproduce this distinction on a screen, allowing the shadow's sharp central region and softer surroundings to be compared without astronomical distances.