Understanding Seasons - A Model From the University of Wisconsin SpacePlace Background Seasons are not caused by the Earth being sometimes closer to and sometimes farther away from the Sun. Seasons are caused by the tilt of the Earth's axis. When the Northern Hemisphere tips toward the Sun, we have summer and the Southern Hemisphere has winter. It is colder in the winter because the days are shorter, nights are longer, and the Sun is lower in the sky. It is hotter in the summer because the days are longer, nights are shorter, and the Sun is higher in the sky. At the equinoxes day and night are equal in length. You can build a model of the sun and Earth to help students understand the effect of the tilt of the earth on the seasons. Materials Needed: 1 Styrofoam ball 1 large paper clip 2 paper fasteners Crayons or markers 2 tagboard circles (one slightly larger than the other) You can use 2 different sizes of paper plates. pencil scissors ruler Activity: Cut out the smaller of the two circles. In the middle of the circle draw the sun. Draw the dividing lines on the circle. You will need four parts. Label them going counter clockwise around the circle - Winter Solstice, Vernal Equinox, Summer Solstice, and Autumnal Equinox. Decorate each quarter with things that you enjoy doing during each season. Cut out the large circle. Using one of the paper fasteners, connect the two circles. Try to put the fastener as close to the middle of the two circles as possible. Take the paper clip and bend the outside prong towards you about 23 degrees. Bend the inside prong in, closing the end to make a circle. Insert the paper fastener in the circle and place the paper clip contraption to the edge of the larger circle. Draw a circle around the Styrofoam ball to represent the equator and attach the ball to the end of the paper clip was bent (23 degrees). Now, being careful to always keep the Earth (Styrofoam ball) lifted in the same direction, move the larger circle around and see how our seasons occur. Copyright 1999 Journey North. All Rights Reserved. Please send all questions, comments, and suggestions to our feedback form