The moon takes approximately 27 and 1/3 days to orbit the Earth, but due to the Earth's movement, it appears to return to the same position in the sky after 29 and a half days, a period known as a lunar month. During this cycle, the moon undergoes eight distinct phases, caused by the varying amounts of its sunlit portion visible from Earth. These phases are a result of the changing positions of the Sun, Earth, and moon, rather than an actual change in the moon's shape. All About the Moon part 2