Moon Phases
Moon Phase Calendar
What are Moon Phases?
Moon phases refer to the different appearances of the Moon as seen from Earth throughout its 28-day lunar cycle. The Moon doesn’t actually change shape and the Moon doesn’t produce its own light; instead, its phases are the result of how much of the Moon’s surface is illuminated by the Sun, as the Moon orbits Earth. The changing phases happen because of the Moon’s position relative to the Earth and Sun.
Credit: NASA/JPL-Caltech
The Eight Moon Phases
New Moon
The New Moon marks the beginning of the lunar cycle. During this phase, the Moon is positioned between the Earth and the Sun, so the side of the Moon that is illuminated by the Sun is facing away from Earth. As a result, the Moon appears dark and is not visible from Earth.
Waxing Crescent
After the New Moon, the Moon begins to move away from the Sun. The illuminated portion of the Moon starts to grow, creating a thin crescent shape. This phase is called the Waxing Crescent because the light is increasing, or “waxing.”
First Quarter
The First Quarter occurs when half of the Moon is illuminated. It is called the “first” quarter because it marks the first time the Moon has completed one-quarter of its orbit around Earth. During this phase, we see the right half of the Moon lit up.
Waxing Gibbous
In the Waxing Gibbous phase, the Moon is more than half illuminated, but it is not yet full. The light is still increasing, and the shape appears more than a half-circle but less than a full circle.
Full Moon
The Full Moon occurs when the entire face of the Moon is fully illuminated by the Sun. This happens when the Earth is between the Sun and the Moon. A Full Moon is visible from Earth and appears as a complete circle of light in the night sky.
Waning Gibbous
After the Full Moon, the Moon begins to move away from the Sun. The illuminated portion starts to shrink, or “wane.” The Waning Gibbous phase is when more than half of the Moon is still lit, but it’s starting to decrease.
Third Quarter
The Third Quarter is similar to the First Quarter but in the opposite direction. It occurs when half of the Moon is illuminated again, but this time, it’s the left half. It marks the third quarter of the lunar cycle.
Waning Crescent
The Waning Crescent is the final phase before the cycle begins again with the New Moon. During this phase, only a small sliver of the Moon is visible, and the light is continuing to decrease, or “wane.”
