Moon Phases

New Moon

The new moon is the phase when the Moon and Sun share the same ecliptic longitude, meaning the Moon is roughly between Earth and the Sun. At this time the lunar disk is not visible to the naked eye (except during a solar eclipse).

Waxing Crescent

After the new moon the illuminated portion of the Moon begins to grow (this is referred to as “waxing”). The waxing crescent is the phase between the new moon and the first quarter, when less than half the Moon is illuminated and the crescent shape is visible.

First Quarter

In this phase the Moon has moved about a quarter of the way around Earth relative to the Sun, so half of the Moon’s visible surface is illuminated. The first quarter is one of the four major phases in the lunar cycle.

Waxing Gibbous

Following the first quarter the illuminated portion continues to increase, more than half the Moon is lit, but it is not yet full. This phase is called the waxing gibbous.

Full Moon

The full moon occurs when Earth is between the Sun and the Moon (or more precisely when their ecliptic longitudes differ by about 180°), so the near side of the Moon is fully illuminated. It is a key major phase.

Waning Gibbous

After the full moon the illuminated portion begins to shrink (this is “waning”). The waning gibbous phase is when more than half the Moon is still lit but the brightness is decreasing.

Last Quarter

Also known as the last quarter, this major phase occurs when the Moon has moved about three-quarters of the way around Earth relative to the Sun, and half of the visible Moon is illuminated (but the opposite half compared to the first quarter).

Waning Crescent

In this final intermediate phase the illuminated portion decreases to a thin crescent once again, before the Moon arrives back at the new moon phase and the cycle repeats.

Lunar Cycle

The Moon goes through a repeating cycle that takes about 29.5 days. This cycle is caused by the changing angles of the Sun, Earth, and Moon. As the Moon orbits Earth, different portions of its sunlit side become visible to us.

It begins with the new moon, when the Moon lies between Earth and the Sun and appears dark. Over the next days it grows into a crescent, then a half moon, and eventually a full moon when Earth is between the Sun and the Moon. After that, the bright portion starts shrinking again.

This cycle has helped humans track time for thousands of years. Many calendars, festivals, and farming activities are still linked to lunar phases. Even today, the lunar cycle influences tides, wildlife behavior, and cultural traditions all around the world.

Read more about Moon phases and Lunar Cycle on Wikipedia.