What Are the 8 Stages of the Moon's Cycle, in Sequence?

It's hard to imagine our world without the moon lighting up the night sky. While the moon may seem like a constant companion, it actually undergoes various phases as part of a unique celestial choreography within our solar system.

If you've ever wondered why the moon appears to change every night, rises at different times, or what those unfamiliar names for the moon phases signify, the answer is out there. We'll explain the different phases of the moon and the workings of the lunar cycle — at least for our moon (other moons follow their own rules on different planets!).

Why Does the Moon Have Phases?

Earth revolves around the sun, while the moon orbits Earth. The moon is 'tidally locked,' which means it rotates on its axis at the same rate it orbits Earth. Unlike Earth, which rotates at a different speed than its orbit around the sun (resulting in both days and years), this tidal locking ensures that only one hemisphere of the moon is visible from Earth at all times.

The moon doesn't generate light of its own but instead reflects the sunlight. The sun illuminates different parts of the moon at various times, and since the same side of the moon always faces Earth, we see portions of the moon lit by the sun. Sometimes, we see the entire moon lit, such as during a full moon, and other times, it is completely dark, like during a new moon. The varying amounts of sunlight on the moon create its different phases.

The Four Primary Moon Phases

The moon experiences eight phases during each lunar cycle, which includes four primary and four secondary phases. The four main phases of the moon are:

These phases occur at precise moments each month, and you can check the exact time to determine when the moon will rise and be visible in your location as it reaches each phase.

The Four Secondary Moon Phases

The four secondary moon phases don’t have a fixed time; they are the transitional phases that the moon goes through between the primary phases. Each of these phases can last for about seven days. They include:

Generally, the names of the moon phases are quite logical, such as 'waxing' when the illuminated portion of the moon is increasing and 'waning' when it is decreasing. The 'crescent' phase is also easy to grasp, as the moon takes on a crescent shape during this time. One of the more unique terms in the lunar calendar is 'gibbous,' which broadly means convex, but in the context of astronomy, it refers to the phase when the moon is more than half, yet not fully illuminated.

Now, let's dive deeper into the entire lunar cycle and explore the different lunar phases in detail.

New Moon

If you've ever looked up at the night sky and couldn't spot the moon, it could be because we’re experiencing the new moon phase. During this phase, the side of the moon facing Earth is in complete darkness, as it is not being lit by the sun. As a result, it appears black — though it’s not actually visible at all, blending into the dark expanse of space around it.

Waxing Crescent Moon

The waning crescent phase happens between the new moon and the first quarter phase. During this time, the moon appears as a thin sliver in the night sky, gradually becoming more illuminated each night until it reaches the first quarter phase, where half of the moon is lit. These early days of the lunar cycle are also perfect for stargazing since the moon is faint and doesn’t overpower the view.

First Quarter Moon

The first quarter phase gets its name because it marks the point when the moon has completed one-quarter of its 29.5-day cycle. If you spot the moon during this phase, it will appear half-lit and half-dark. (Often, people will call it a 'half-moon.') As the moon passes through the first quarter phase, it starts to interfere with stargazing, and many avid stargazers either focus on the moon itself or take a break until later in the cycle, when the moon is less bright.

Waxing Gibbous Moon

After the moon passes the first quarter phase, it continues to brighten in the waxing gibbous phase. During this stage, the moon is not yet fully illuminated but is gradually becoming more so. This phase lasts about a week and is an excellent time to observe the moon using a telescope or binoculars, especially to examine the terminator line where the light and dark sections of the moon meet.

Full Moon

The full moon occurs when the entire hemisphere of the moon facing Earth is fully illuminated by the sun. This is the most familiar lunar phase, and many of us may have drawn a face on the full moon as children. While there is no actual 'man in the moon,' the surface features — including fascinating craters and 'mare' (basaltic plains created by ancient volcanic activity) — form various recognizable shapes.

Waning Gibbous Moon

Following the full moon phase, the moon's illuminated portion starts to shrink, marking the waning phase of the lunar cycle. The first phase in this period is the waning gibbous, where the moon remains more than half illuminated but not fully lit.

Third Quarter Moon

The third quarter moon is the last primary phase of the lunar cycle, occurring at a specific time each month. During this phase, the opposite half of the moon is illuminated compared to the first quarter. Depending on your location, you might not always observe the third quarter moon, as it may only be visible during daylight hours.

Waning Crescent Moon

The waning crescent phase wraps up the lunar cycle. Similar to the waxing crescent, the moon appears as a slender arc, growing dimmer as it nears the new moon phase and the start of a new cycle.