Earth is a planet because it is an object in space big enough to have its own gravity, is spherical, and moves around a sun. Earth moves in an almost circular orbit around the Sun. It also rotates around an axis, an imaginary line that goes through its center. Earth's rotation around its axis causes day and night, with one day being one full rotation of Earth. Earth's axis is tilted with respect to the Sun, and the combination of the tilt of Earth and its orbit around the Sun causes the seasons. When the northern part of Earth is tilted toward the Sun and the southern part is tilted away from the Sun, the northern part will be warmer and the southern part cooler. The reverse is true when Earth is in a different location in its orbit and the southern part is tilted toward the Sun and the northern part away from the Sun. Satellites are machines that orbit Earth and gather information and photographs that are sent to scientists on Earth. Pronunciation guide. 24 pages filled with engaging, colorful illustrations. Reading Level 1-3, Interest Level 2-5, Word count 377, Lexile measure 660L.