Published in Learning & Leading with Technology, vol. 28, no. 4, Dec/Jan 2000-2001.Making scale models of the Sun, the planets, and the Moon is a splendid activity for learning and teaching about fractions, ratios, proportions, geometry, and the Solar System. Models of the orbits of planets as they go 'round and 'round the Sun can range from a model that fits in a classroom to walking/biking models that are many kilometers in diameter. Note: Some Internet links may no longer work.