The document discusses how day and night occur on Earth due to its rotation. It explains that when one side of Earth faces the Sun it is daytime there, while the opposite side faces away from the Sun and experiences nighttime. Shadows form when light is blocked by an object, and as the position of the Sun changes during the day, one's shadow also changes in length and direction pointing away from the Sun. The Earth rotates on its axis and revolves around the Sun in an elliptical orbit, which causes the seasons over the course of a year.