Full Moon. The lunar phases arise as the Earth-Moon-Sun angle changes as the Moon orbits the Earth. The Moon is full (14 days into its 28-day cycle) when the Earth-facing side is fully lit by the Sun. Darkness will then encroach as the lunar night advances over the Earth-facing side of the Moon. This image, published in 2015, uses data from the Lunar Reconnaissance Orbiter. The image is part of a sequence of lunar phases (see images C030/3708-3714), orientated for the northern hemisphere.