CLASS 7 · LEARNING KNOWLEDGE

Moon motion and calendar – basic principles

How it works

The Moon orbits the Earth in about 27.3 days relative to the stars (sidereal month), but about 29.5 days pass from new moon to new moon (synodic month). The lunar phases arise from the different illumination of the Moon as seen from the Earth. Some calendars are based on the solar year, others on the Moon, and lunisolar calendars combine both. The most important lunar phases are new moon, waxing moon, full moon, and waning moon. The motion of the Moon influences calendars and timekeeping, for example through leap months in lunisolar calendars.

Note
The lunar phases arise from the position of the Sun, Earth, and Moon relative to one another. The duration of a synodic month (new moon to new moon) is longer than that of a sidereal month (one orbit of the Moon around the Earth relative to the stars), because the Earth is also moving around the Sun during that time.

An example

Which lunar phase follows directly after the new moon?

Directly after the new moon comes the waxing moon. Reason: After the new moon, the Moon begins, as seen from the Earth, to be illuminated more by the Sun again, so the phase of the waxing moon begins.

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Own explanation and own practice exercises by AmyMath. Subject reference framework: Astronomy. The topic assignment may vary by federal state.