A scale model uses one rule to shrink real distances. Here 1 astronomical unit, or AU, becomes 1 cm. One AU is Earth’s average Sun distance, about 150 million km. Planet sizes must shrink by the same rule if we want one true scale. Most classroom planet dots are far too large. Safety: No small loose beads and no outdoor distance walk. Stop: Stop at the paper model; no long outdoor route or tiny bead model is needed.

Materials: Two scrap sheets overlapped to form a flat strip at least 35 cm long; Ruler marked in millimetres; Pencil 1. Draw a 31 cm baseline. Put the Sun at 0. Use these rounded average distances, measured from the Sun, not from the previous planet: Mercury 0.4 cm; Venus 0.7 cm; Earth 1.0 cm; Mars 1.5 cm; Jupiter 5.2 cm; Saturn 9.5 cm; Uranus 19 cm; Neptune 30 cm. 2. Mark and label all eight positions. For Mercury and Venus use the nearest millimetre marks, 4 mm and 7 mm. Write: positions compare average orbital distances; planets are not normally lined up this way. 3. Add matching size references: Sun diameter about 0.093 mm; Earth diameter about 0.00085 mm. These calculated values use Sun 1,392,000 km and Earth about 12,750 km. Do not try to draw them accurately. Label all visible marks oversized symbols. 4. Write a second consistent model: a 24 cm Sun gives an Earth about 2.2 mm wide, about 26 m away. Do not measure this route; compare the supplied sizes and distance on paper. 5. Circle the empty distance between Earth and Jupiter. Explain why a pea-sized Earth beside a small beach-ball Sun can give a false size impression. Done: Finish eight distance marks and both size-limit notes. Explain one mismatch in an oversized-dot model. Proof: Keep the strip and consistent 24 cm Sun comparison. Note adult help with ruler placement. Stop: Stop at the paper model; no long outdoor route or tiny bead model is needed.