Full Moon

Causes and timing

Full illumination happens when the Sun, Earth and Moon are nearly collinear, with Earth between the other two. The instant of exact opposition (the astronomical "full moon") may differ from the night when the Moon appears most round because of time zones and the observer's horizon. At full moon the Moon typically rises at sunset and sets at sunrise.

Cultural and calendar roles

Across cultures the full moon has long anchored festivals, religious observances and agricultural timing. Examples include the Mid‑Autumn Festival, Buddhist Vesak and Hindu Purnima. Many traditional calendars are lunar or lunisolar, using the full moon as a monthly milestone; others count months from the new moon, with the full moon near midmonth.

Observable variations and named full moons

Not all full moons look the same. When a full moon coincides with the Moon's perigee it is called a "supermoon" and appears slightly larger and brighter; the opposite is a "micromoon." Names such as "Harvest Moon" or "Hunter's Moon" reflect seasonal timing. A "blue moon" is a colloquial term for an extra full moon in a calendar period, while "blood moon" is often used informally for a total lunar eclipse.

Physical effects and myths

Gravitational alignment during full and new moons contributes to spring tides — larger tidal ranges — because the Sun and Moon reinforce each other's pull. Popular beliefs about strong effects on human behavior, crime or sleep persist, but scientific evidence is limited or mixed; some studies show small correlations while many find none.

Observation tips and notable phenomena

Full moons offer good opportunities for casual observation and photography, though surface detail looks flatter due to direct illumination. The best time to view lunar topography is near quarter phases when shadows enhance relief. When a full moon passes through Earth's shadow a total lunar eclipse can color the Moon red and reveal fine details of Earth's atmosphere.