Phases of the Moon. North is at top. As the Moon orbits the Earth, the amount of sunlight seen on its visible hemisphere varies in a regular 28-day cycle. This montage of images shows, from top left to bottom right: a waxing crescent Moon (4 days old); the Moon's first quarter (7 days old); a waxing gibbous Moon (11 days old); a Full Moon (14 days old); a waning gibbous Moon (18 days old); the Moon's last quarter (22 days old); and a waning crescent Moon (25 days old, bottom right). As the cycle progresses, the motion of the Moon in its orbit around the Earth moves its visible hemisphere into and then out of the sunlight. The lunar day dawns on a waxing Moon, and then the lunar night falls on a waning Moon. Photographed in Earth's northern hemisphere.