Space is huge and explaining the vastness of space can be a tall order, especially to kids. The team at Double Helix, our partner publication, has brought this big concept down to Earth by creating a scale model of our inner solar system.
You can create your own scale model using materials from around your home. It is a great activity to do with young people… or the young at heart. We were able to complete it in less than an hour but if you don’t have the materials on hand it will take longer.
You will need
- Ruler
- Tape measure
- Basketball
- Matchsticks
- Sewing pins with small and large heads
- Plastic cups or witches’ hats
- Pen
- Calculator (optional)
- Phone with measuring app (optional)
| Space object | Actual diameter | Model diameter | What we used |
| Sun | 1,392,700 km | 242 mm | Basketball |
| Mercury | 4,879 km | 0.8 mm | Pin with small head |
| Venus | 12,104 km | 2.1 mm | Matchstick |
| Earth | 12,742 km | 2.2 mm | Matchstick |
| Moon | 3,476 km | 0.6 mm | Pin with small head |
| Mars | 6,790 km | 1.2 mm | Pin with large head |
What to do
Go to a local park with your model space objects, cups and tape measure. How big should the park be? The inner solar system will be about 40m wide; the distance to Jupiter will be about 136m.
Pick a quiet area of the park to place your model Sun. We recommend picking a spot close to the park boundary, so you have plenty of room to spread out. The table below tells you the distances between space objects in real life and in your model.
So, our scale is 1m: 5,740,000 km.
| Space objects | Actual distance | Model distance |
| Sun to Mercury | 58,000,000 km | 10.1 m |
| Mercury to Venus | 51,000,000 km | 8.9 m |
| Venus to Earth | 40,000,000 km | 7.0 m |
| Earth to Moon | 384,400 km | 0.07 m or 70 mm |
| Earth to Mars | 79,000,000 km | 13.7 m |
Use the tape measure to practice pacing out exactly 1 meter. This might be two steps, one big step or one big jump. Choose a method that you’ll be able to repeat many times. You can also use an app to measure distances.
Put the basketball down. That’s your Sun.
With one foot next to your Sun, pace out 10 meters. Place your Mercury object here and mark it with a cup or a witch’s hat.
With one foot next to Mercury, pace out 9 more meters away from your Sun. Place your Venus object here and mark it with a cup or a witch’s hat.
With one foot next to Venus, pace out 7 more meters. Place your Earth object here and mark it with a cup or a witch’s hat. Look up – how big does the basketball appear now?
Use a ruler or tape measure to measure 7cm from your Earth, and put your Moon object here.
With one foot next to Earth, pace out 13.5 more meters. Place your Mars object and yet another cup or witch’s hat.
Congratulations! You’ve completed a scale model of the inner solar system.
A scale model can help us relate the astronomical gaps between the planets to distances we can understand and compare. Most illustrations of the solar system have to blow up the planets relative to their orbits so you can see them.
There’s a solar system sculpture at scale at St Kilda Beach in Melbourne. Sweden claims the biggest scale model, which stretches across the entire country! The University of Colorado has a 1:10bn scale model which inspired other sculptures, and it claims to be “materials efficient,” but Cosmos materials are likely to be entirely recycled!
Adding Jupiter to your solar system
What would it take to complete your solar system model? The outer planets are much further so it’s unlikely the whole model will fit in your park.
For example, the next planet, gas giant Jupiter is 778,000,000km from the Sun. That’s 136 metres away from your basketball.
Going further
At the edge of our solar system lies the Oort cloud, which could stretch 15 trillion (that’s a 15 followed by 12 zeros) kilometres away from the Sun. In your model that would be 2,600 kilometres away.
How about the nearest star (other than the Sun)? Proxima Centauri is 4.2 light years away, which is equal to about 40 trillion kilometres. In your model, that would be about 7,000 kilometres – a flight from Australia to Japan
If you enjoyed this activity, we invite you to sign up for Double Helix Extra, a fortnightly newsletter delivering science activities, news, quizzes and more for kids and curious adults.
