fullmoon

A full moon is the lunar phase in which the Moon’s near side is fully illuminated as seen from Earth. It occurs when the Sun and Moon are on opposite sides of the Earth, so the Sun’s light fully illuminates the side facing us. The full moon repeats roughly every 29.53 days, the length of the synodic month. From Earth, the Moon’s apparent diameter is about 0.5 degrees, and at full illumination its brightness reaches around magnitude −12.7, making it one of the brightest objects in the night sky.

Frequency and calendar notes: Most calendar months contain one full moon; occasionally a month contains two. The second full moon in a calendar month is commonly called a blue moon. The timing of full moons depends on the Gregorian calendar and time zones, but the 29.53-day cycle remains constant in astronomy.

Observational variants: A full moon near perigee (the closest point in the Moon’s orbit to Earth) appears larger and brighter and is popularly called a supermoon; near apogee it looks smaller and is sometimes referred to as a micro-moon. The Moon’s phase also influences tides, with higher and lower tides at full and new moons in what are known as spring tides.

Cultural and historical aspects: Full moons have long held significance in calendars, folklore, and art across cultures. Names for full moons in different months have included Harvest Moon, Hunter’s Moon, Wolf Moon, and Cold Moon. In modern usage, terms such as blue moon, supermoon, and harvest moon describe calendar timing and observational variations of the full moon.