The Moon produces no light of its own. During its four week orbit (Lunar Month), half of its surface is always illuminated by the Sun.

Day by day, the changing position of the Moon, relative to the Earth and Sun, creates the phases from full to new Moon.

For a few days the Moon disappears as it lies in the same direction as the Sun. This is the time of the New Moon when sunlight falls on its far side.

01_Moon Phases

On rare occasions the Moon passes directly between the Earth and Sun causing a Solar Eclipse, this can only occur at a New Moon.

04_Solar Eclipse

A Lunar Eclipse however can only occur at Full Moon, this is when the Moon passes into the shadow of the Earth.

03_Lunar Eclipse

04_Lunar Eclipse Points

Tides are also controlled by the Moon in conjunction with the Sun though the Moon is the dominant player in this. The relative positions of Sun, Earth and Moon, and the rotation of the Earth account for the tidal effect and the extremes of tidal range that result in Spring and Neap tides, and is shown very simply in the following diagram:


Click on image to see animation


A more detailed explanation of the tidal effects is given in the following links:

and tide prediction tables are to be found on the National Tidal and Sea Level Facility.