perhaps i missed something in the FAQ: what's the FE explanation for phases of the moon?
Lunar phase in FE refers to the appearance of the illuminated portion of the Moon as seen by an observer on Earth. The lunar phases vary cyclically as the Moon orbits the hub of the Earth, according to the changing geometry of the Moon and Sun, which rotate at slightly different velocities. One half of the lunar surface is always illuminated by the Sun, and is hence bright, but the portion of the illuminated hemisphere that is visible to an observer can vary from 100% (full moon) to 0% (new moon). The boundary between the illuminated and unilluminated hemispheres is called the terminator.
The Moon exhibits different phases as the relative geometry of Sun and Moon change, appearing as a full moon when the Sun and Moon are on opposite sides of the observer, and as a new moon it is not visible at night when they are on the same side of the observer. The phases of full moon and new moon are examples of syzygies, which occur when the Moon, observer, and Sun lie approximately in a straight line. The time between two full moons, or between successive occurrences of the same phase, is about 29.53 days (29 days, 12 hours, 44 minutes) on average. This synodic month is longer than the time it takes the Moon to make one orbit about the hub of the Earth with respect to the stars (the sidereal month), which is about 27.32 days. This difference is caused by the fact that the Moon system is orbiting about the Sun at the same time the Moon is orbiting about the hub of the Earth. The actual time between two syzygies is variable because the orbit of the Moon is elliptic and subject to various periodic perturbations, which change the velocity of the Moon.