Discover the Mysterious Phases of the Moon

The moon's cycle of phases is due to the fact that the moon is illuminated by the sun. The moon's orbital path around Earth causes the different amounts of sunlight to be reflected off the lunar surface. When the moon is between the Earth and the sun, the side of the moon facing us is in darkness. This is a new moon, when less than one-half of the moon's surface is illuminated. As the moon orbits, we start to see more of the illuminated half, and the moon appears to grow from a thin crescent to a full circle. This is called the waxing phase, and is made up of the crescent, quarter, and gibbous phases. When the moon is on the opposite side of the Earth from the sun, the entire illuminated half of the moon is facing us and we see a full moon. This is the full moon phase. As the moon continues in its orbit and we start to see less of the illuminated half, the moon appears to shrink back down to a crescent. This is the waning phase, and is made up of the gibbous, quarter, and crescent phases.
The cycle of the moon's phases takes about 29.5 days to complete.