What it shows
When distances between planets are drawn to the same scale as their sizes, space turns out to be almost entirely empty. Walking from the Sun to Neptune makes this gap between worlds felt in your legs.
The science
Pick one scale for distance, for example 1 metre for every 0.1 billion kilometres (so Earth is 1.5 m from the Sun). Every planet distance is then divided by the same number. At this scale the planets themselves are smaller than a grain of rice, which shows how far apart they are compared with their size.
Materials
Cost: free. Many items come from home or from waste; spare parts such as LEDs, motors and wire are in the store.
- A marble or bead about 1.4 cm wide for the Sun
- Mustard seeds, poppy seeds and pinheads for the planets (real planets at this scale would be dust specks, so these markers are still too big)
- A measuring tape or a 50 m rope with knots
- Chalk or small flags
- A notebook and a calculator
Safety
For this project: Work on the field with a teacher present, away from traffic and the school gate.
Never use mains electricity: power models with cells, batteries or a low-voltage adapter. Sharp and hot tools, flames and lab chemicals need an adult or your teacher beside you. Keep magnets, button cells and small parts away from young children, and wash your hands after making.
Step by step
8 steps. Do them in order, and test each part before you go on to the next. Write what you notice in a notebook as you go.
Look up the average distance of each planet from the Sun in million kilometres and write them in a table.
Choose the scale of 1 metre for every 100 million kilometres and divide each distance by 100 to get metres.
Check your answers: Earth about 1.5 m, Jupiter about 7.8 m, Neptune about 45 m.
Place the Sun ball at one end of the field and stretch the rope in a straight line.
Walk the rope with your tape and mark each planet distance with chalk or a flag.
Put a bead or seed at each marker and write the planet name on a card beside it.
Walk from the Sun to Neptune counting your steps and note how long it takes.
Draw the field plan in your notebook and write what you noticed about the empty space.
What you should see
A field model with eight markers from about 0.6 m to 45 m. The inner planets sit close to the Sun and the outer ones are spread far apart, and the tiny planet beads show how small they are next to the gaps.
Viva questions
A teacher or a judge will ask how it works. Try to answer each question before you open it, then compare.
01Why can a textbook not show planets to scale in distance and size together?
The page would have to be many metres long for the distances while the planets would shrink to dots.
02Which planet is about 1.5 m from the Sun in your model?
Earth.
03What unit is used for Earth’s distance from the Sun in astronomy?
One astronomical unit, about 150 million kilometres.
04Why is a scale needed?
It keeps every distance in the same proportion so they can be compared fairly.
Take it further
Add Pluto and the nearest star, and work out how many kilometres of your field the nearest star would need.
Change one thing, measure what happens, and add a table or chart of your readings: that is what turns a model into your own investigation.
Free ebooks for this project
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