The full moon occurs when the moon is directly opposite the sun in Earth's sky — the entire visible face is lit, and the moon rises as the sun sets. It is the brightest phase, and the only one during which a lunar eclipse is possible (when Earth's shadow passes across the moon). Full moons have their own folk names in many cultures: the Harvest Moon nearest the autumn equinox, the Wolf Moon of January, the Blue Moon when two occur in one calendar month.
