To begin this activity, scale the Earth to 16 inches. Many globes come in this size, especially the inflatable beach ball kind sold in many Nature stores. Once students understand that the size of the Earth as represented by the globe requires the use of scale, ask a student to guess the size of the moon compared to a 16 inch globe. Blow up a balloon to that estimated size of the moon. Ask another student to guess the distance at which the moon orbits the Earth at this scale. Place this balloon at that estimated distance from the globe. Then, to show the correct scaling of the Earth-Moon system when the Earth is 16 inches in diameter, blow up another balloon to 4.4 inches and place it at a distance 40.2 feet. Students are usually amazed at this scaling and are amazed even further when the Sun is also scaled. The size of the Sun at this scaling is 145.5 feet and the scaled distance is 15,700 feet, nearly 3 miles. (It is usually helpful to pick a local landmark three miles away to illustrate this distance). Back | Next |