Moon & phases

Moon phase

Also known as: lunar phasephases of the moonlunar cyclesynodic monthmoon cycle

A moon phase is a stage of the synodic lunar cycle, from new moon through full moon and back, set by the angle between the Sun and the Moon as seen from Earth.

The Moon does not produce its own light. What we see as its changing shape is the sunlit half of the Moon turned partly towards us or partly away from us. When the Moon stands in the same direction as the Sun, its lit side faces away from Earth and we see a new moon. When it stands opposite the Sun, the whole lit face looks towards us and we see a full moon. Everything in between is a gradual change of that angle.

One complete cycle from new moon to new moon is called the synodic month and lasts about 29.5 days. It is longer than the sidereal month of about 27.3 days, the time the Moon needs to return to the same place among the stars, because during that time Earth has also moved along its orbit and the Moon needs roughly two extra days to catch up with the Sun again.

Western astrology usually divides the cycle into eight phases, each covering about 45 degrees of separation between the Sun and the Moon: new moon, waxing crescent, first quarter, waxing gibbous, full moon, waning gibbous, last quarter and waning crescent, the last one often called the balsamic moon. The first half, from new to full, is the waxing half; the second, from full back to new, is the waning half. The two quarters mark the moments when the Moon is 90 degrees from the Sun, a square.

In the symbolic reading the new moon is linked with beginnings and quiet intentions, the crescent with first effort, the first quarter with decisions and friction, the gibbous phase with refining, the full moon with culmination, visibility and sometimes heightened emotion, the waning gibbous with sharing what was learned, the last quarter with letting go of what no longer fits and the balsamic moon with rest and closure. These are traditional images, not rules, and they are best read as a rhythm rather than as instructions.

Many astrologers also look at the phase at birth. The natal moon phase, sometimes called the lunation phase, follows the approach popularised by Dane Rudhyar: someone born near a new moon is said to act more instinctively and from within, someone born near a full moon to be more aware of others and of contrasts. Calculating it only needs the positions of the Sun and the Moon at the moment of birth.

Vedic astrology approaches the same cycle differently. It divides the month into two halves, shukla paksha, the bright waxing half, and krishna paksha, the dark waning half, and into thirty lunar days called tithis, each equal to 12 degrees of distance between the Moon and the Sun. Tithis play an important role in choosing auspicious times and in the Hindu calendar.

The moon phase is a simple and reliable astronomical fact, which makes it a good starting point for anyone exploring astrology: it can be observed in the night sky, and its meaning is about rhythm, timing and reflection rather than prediction.