Moon Phase

Moon phases are caused by the changing geometry between the Sun, Earth, and Moon. As the Moon orbits Earth, we see different portions of its illuminated half, creating the phase cycle.

A complete Moon cycle (synodic month) takes approximately 29 days, 12 hours, 44 minutes, and 3 seconds, or 29.53058770576 days. This is the time between two consecutive new moons.

The eight Moon phases in order are: new moon, waxing crescent, first quarter, waxing gibbous, full moon, waning gibbous, last quarter, and waning crescent. After the waning crescent, the cycle returns to new moon.

A solar eclipse only occurs during a new moon, when the Moon passes between the Sun and Earth, casting its shadow on Earth.

A synodic month (29.53 days) is the time between identical lunar phases, while a sidereal month (27.32 days) is the time it takes the Moon to complete one orbit relative to the stars.