The solar system and all the planets are always moving. Each of the planets revolve around the sun. They also rotate on their axis. When a portion of the earth faces the sun, it is daytime, and they part that is away from the sun is experiencing nighttime. The cylce of light and dark is continuous, except at the North and South pole. The earth, which is the third planet in the Solar System, roates around the sun for different season, and spins on its axis for different times of day. While it is daytime here in America, it is nighttime on the other side of the world and vise versa. While we are eating lunch, they are sleeping, while we are sleeping, they are eating lunch, and so on and so forth.