Of the nine planets in our solar system, Earth is the third nearest to (or from) the Sun. Earth varies in distance from the Sun during the year. The Sun is 94 million miles (150,400,000 km) in summer and 91 million miles (145,600,000 km) in winter.

Earth is subject to four motions in its movement through space: rotation about its axis, revolution around the Sun, precessional motion (a slow conical movement or wobble) of the axis, and the solar motion (the movement of the whole solar system with space). Of the four motions affecting Earth, only two are of any importance to meteorology.

The first motion is rotation. Earth rotates on its axis once every 24 hours. One-half of Earths surface is therefore facing the Sun at all times. Rotation about Earths axis takes place in an eastward direction. Thus, the Sun appears to rise in the east and set in the west. (See fig. 1-2-3.)

The second motion of Earth is its revolution around the Sun. The revolution around the Sun and the tilt of Earth on its axis are responsible for our seasons. Earth makes one complete revolution around the Sun in approximately 365 1/4 days. Earths axis is at an angle of 23 1/2 to its plane of rotation and points in a nearly fixed direction in space toward the North Star (Polaris).

Privacy Statement - Press Release - Copyright Information. - Contact Us - Support Integrated Publishing