To model the light and dark areas of Earth during equinox, use aluminum foil and a 2-inch (5-cm) Styrofoam ball. With a blackmarker, make two dots opposite each other on the ball. Draw small circles around each dot to represent the Arctic and Antarctic Circles. Again use the marker to draw a circle around the middle of the ball between the poles. This circle represent the equator, which divides earth into two parts called the Northern Hemisphere and the Southern Hemisphere. Mold the foil around the ball so that it covers half of the ball from pole to pole to pole, as shown in the diagram. The foil covering represent the half of Earth that is not lighted by sunlight.
Notice that both the Northern and Southern hemispheres have an equal amount of lighted and darkened regions. This is because the poles of Earth are parallel to the Sun. This occurs twice during Earth’s movement about the Sun, once in March, which is called the vernal (spring) equinox and once in autumn, which is called the autumnal equinox.
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