The moon is nearing its fullest phase, with 98.9% illumination as of January 2, 2025. Observers may notice prominent craters and dark patches on the lunar surface tonight. The next full moon is expected tomorrow, January 3rd, following a previous full moon on December 4th.
Understanding Lunar Cycles
The moon completes one full cycle – from new moon to new moon – in approximately 29.5 days. This period, known as the lunar cycle, dictates how much sunlight illuminates the visible side of the moon as it orbits Earth. While the same side of the moon always faces our planet, the amount of lit surface changes, creating the different phases we observe.
The Eight Main Moon Phases
NASA defines eight distinct phases in the lunar cycle:
- New Moon: The moon appears dark because it’s positioned between Earth and the sun. The side facing us is not lit.
- Waxing Crescent: A sliver of light appears on the right side (in the Northern Hemisphere), growing each night.
- First Quarter: Half of the moon is illuminated, appearing as a half-moon shape.
- Waxing Gibbous: More than half of the moon is lit, but it hasn’t reached full illumination yet.
- Full Moon: The entire visible face of the moon is brightly lit, creating a spectacular night sky sight.
- Waning Gibbous: The moon begins to lose light on the right side (in the Northern Hemisphere), shrinking each night.
- Third Quarter (Last Quarter): Another half-moon, but with the left side illuminated.
- Waning Crescent: A thin sliver of light remains on the left side before disappearing entirely, signaling the start of a new cycle.
The lunar cycle has historically been used for timekeeping and navigation, and continues to influence cultural practices and scientific study today. Understanding these phases provides insight into Earth’s natural satellite and its impact on our planet.
