Mathematics 7–10 · Year 9

Solar system to scale on the oval: scientific notation and a 5.75 billion to one scale

Measurement and space

Practical, model not builtLow risk

This site has no interactive model of its own. Where a step or a material names a Concept Studio model, simulation or tool, it has not been built; an external simulation a step names (for example PhET) is not part of this site.

The idea

Dividing distances of hundreds of millions of kilometres by one scale factor turns them into paces on the oval, and writing both in scientific notation keeps the powers of ten under control.

Safety card

Low riskAn adult supervises

Hazards

sun exposure
uneven ground
small pins
other users of the oval

Controls

hats, sunscreen, water
pins pushed into a cork or cone, not left on the grass
book the oval
beads stay glued to their cards

Note

No chemicals or heat are used, so the NSW Department of Education Chemical Safety in Schools package does not apply; outdoor work follows the school's excursion and playground supervision rules.

What you need

A basketball (Sun, about 242 mm across), two beads about 2 mm across glued to small cards (Venus and Earth; the CSIRO build uses the heads of two unstruck matches, replaced here so that no match heads come into the classroom), one large-headed pin (Mars), two small-headed pins (Mercury and the Moon), as in the CSIRO build
50 m tape measure, cones or witches' hats, calculator
NASA planetary fact sheet values: distances from the Sun in millions of km (Mercury 57.9, Venus 108.2, Earth 149.6, Mars 228.0), Moon from Earth 0.384 million km; diameters in km (Mercury 4879, Venus 12 104, Earth 12 756, Mars 6792, Moon 3475); Sun radius 695 700 km

How to do it

Write each real distance in metres in scientific notation (Earth: 1.496 × 10^11 m).
Choose the scale: 1 m in the model represents 5.75 × 10^9 m, which makes the Sun a 0.242 m basketball. Compute each model distance by dividing.
Compute each model diameter in millimetres the same way and match it to an object.
Set the basketball at one end of the oval and pace out the model distances with the tape, placing a cone and object at each planet.
Stand at Earth and describe how large the Sun looks from there and how far apart neighbouring planets are compared with their own sizes; write the ratio of Mars's model distance to Mercury's and check it equals the ratio of the real distances.

What you should see

At 1 : 5.75 × 10^9 the model distances are Mercury 10.1 m, Venus 18.8 m, Earth 26.0 m, Mars 39.7 m, and the Moon 7 cm from Earth; the model diameters are Sun 242 mm, Earth 2.2 mm, Venus 2.1 mm, Mars 1.2 mm, Mercury 0.85 mm, Moon 0.6 mm. The four inner planets fit on a school oval while the Sun is a basketball and the Earth a 2 mm bead. The learner knows it worked when their computed distances match these to two significant figures and the ratio of any two model distances equals the ratio of the real ones.

What changes

This activity lists no variables to change, measure and keep the same.

Common misconceptions

Each of these ideas is wrong, and the activity is a chance to test it.

The planets are evenly spaced.
A model that fits on a page can show sizes and distances at the same scale.
Scientific notation changes the value rather than the way it is written.

Curriculum references

The NSW syllabus outcomes and Australian Curriculum v9 codes this activity supports. They are references, not a verified or complete curriculum alignment.

Mathematics K–10 Syllabus (2022), Stage 5 Numbers of any magnitude; page read 2026-09-22MA5-MAG-C-01
Australian Curriculum v9AC9M9M02AC9M9M05

Sources

The pages the author read to write this activity.

All Concept Studio activities