maanfases

Maanfases, or moon phases, describe the changes in the Moon’s apparent shape when viewed from Earth. They result from the changing geometry between the Sun, the Moon, and the Earth and from how much of the Moon’s sunlit hemisphere is visible to an observer on our planet. The cycle repeats roughly every 29.5 days, a period known as the synodic month.

The standard sequence is New Moon, Waxing Crescent, First Quarter, Waxing Gibbous, Full Moon, Waning Gibbous, Last Quarter, and Waning Crescent. During a new moon the Moon sits near the Sun and is usually not visible; at full moon the Moon is opposite the Sun and fully illuminated. The terms waxing and waning describe whether the visible illuminated portion is growing or shrinking. The exact shape of each phase depends on the observer’s latitude and the Moon’s orbital inclination; libration can cause slight variations in how much of the lunar limb is seen over time.

Moonrise and moonset times shift by about one hour per day, influencing when each phase is best observed. The Moon’s phases have been used for calendars, tides, and agricultural timing in many cultures and remain a fundamental topic in observational astronomy.