Try it: a peppercorn Earth
- Find a ball about as big as a soccer ball, and one peppercorn.
- Put the ball down outside, on the footpath or in the park. That is the Sun.
- Measure about 25 metres together, or use big grown-up steps as a rough estimate.
- Hold up the peppercorn. That is the Earth, and you are standing on it.
- Look back at the ball. That is how far away the Sun is, and how big.
You need: a ball about 23 cm across, a peppercorn, and somewhere to walk about 25 metres.
A picture inside a picture
Draw your room on a scrap of paper. Put that drawing on a bigger page for your home, then a bigger one for your street. Each bigger picture includes the smaller place. These are pretend maps, not measured plans.
Grown-up notes
Each line is marked Fact well established,
Model a deliberate simplification, or
Unsure not yet known.
Play another way
Pick one invitation, then let your child lead. Watching, pointing or changing her mind all count; there is no answer to pass.
- Keep a finger near the home dot as you zoom out. Wonder which bigger place will surround it next.
- Zoom back in. Is it a new home, or the same home seen another way?
- Compare the planet parade with the peppercorn activity. The parade compares sizes; the walk helps us feel distances.
Another connection: Why is there day and night?
The idea
- FactEvery place sits inside a bigger one: home in a street, the street in a city, the city in a country, the country on a planet, and the planet among others going around a star.
- FactSydney is on Australia's east coast, towards the south. It is Australia's biggest city, with about 5.6 million people.
- FactAll of Australia is south of the equator. It is the sixth-largest country in the world, about 7.7 million square kilometres.
- FactEarth is a ball about 12,700 km across.
- FactEight planets go around the Sun. In order: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune. Earth is the third.
- FactJupiter is about 11 times as wide as Earth, and the Sun about 109 times as wide.
- FactThe Sun is about 150 million km away. Its light takes about eight minutes to reach us.
What the pictures simplify
- ModelEven steps. The slider gives each place the same room, but the jumps are wildly different. Street to city is about a hundred times bigger; Earth out to Neptune is about 350,000 Earth-widths.
- ModelThe planets picture is not to scale. The planets are drawn far too big and far too close together, and they stand still. If Earth were a peppercorn, the Sun would be a soccer ball 25 metres away and Neptune a small marble about 750 metres away. The "Try it" walk shows this.
- ModelThe planet parade. There the sizes are true compared with each other, including the edge of the Sun. The gaps are not, and the row is a size comparison, not a picture of the planets' positions in space.
- ModelThe home, street and city are made up. They are a typical Sydney house and street, not a real address. The city picture is a sketch of Sydney's shape: sea to the east, the harbour running west into a river, a bay to the south. The red dot's spot in the city is arbitrary.
- ModelCoastlines are rough. The lands on the globe are drawn with a few dozen corners each. Small islands are left out.
- ModelThe Earth has no clouds, no night side and no Moon here. The Moon is left out because, at this size, it would sit more than ten screens away.
Questions she may ask
- Why don't people fall off the bottom? FactThe Earth pulls everything towards its middle. "Down" means towards the middle of the Earth, wherever you are standing. Space has no top or bottom; maps put north at the top only out of habit.
- What about Pluto? FactPluto is still there. Since 2006 astronomers have called it a dwarf planet, because it is small (smaller than our Moon) and shares its part of space with many other icy bodies.
- Is the Sun a planet? FactNo. The Sun is a star: a huge ball of glowing hot gas. The stars at night are suns too, very much further away.
- What is past the planets? FactOther stars, a very long way off. Our Sun is one of an enormous number of stars in a group called the Milky Way.
- Does space end? UnsureNobody knows yet.
- Does anyone live on the other planets? FactNo people do. UnsureWhether anything at all lives anywhere else, nobody knows yet.
Words this guide teaches
City: lots and lots of streets and homes together. Country: a big piece of the world with its own name, like Australia.
Planet: a large, round world that goes around a star. Earth goes around the Sun.
Go further
Sydney Observatory, on Observatory Hill near the Harbour Bridge. The grounds are free to walk around by day. Going inside and
looking through the telescopes is by booked tour, and there are family tours for younger children. Conservation work is under way,
so check the Observatory's page for
what is running before you go.
Sources
Checked November 2026. The peppercorn figures are arithmetic from the NASA table. The answers about gravity,
Pluto, stars and the Milky Way are standard astronomy, not taken from a linked page.