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Science project idea

Planet sizes compared with fruit and seeds from the kitchen

The eight planets differ hugely in size. With the Earth as a peppercorn, Jupiter is a large orange and the Sun would be a ball taller than a child, so everyday objects show the true sizes far better than equal-sized clay balls.

Make it yourself8 numbered steps, the materials and the science, all free.Go to the stepsGet a ready-made kitReady-made models, kits and spare parts in the store under Science.Browse ScienceAsk on WhatsAppAsk the head office whether a model or kit for this idea is available.Send a message

What it shows

The eight planets differ hugely in size. With the Earth as a peppercorn, Jupiter is a large orange and the Sun would be a ball taller than a child, so everyday objects show the true sizes far better than equal-sized clay balls.

The science

The Earth is about 12,700 kilometres across and Jupiter about 143,000 kilometres, roughly 11 times wider. If the Earth is a 4 millimetre peppercorn, Jupiter is about 45 millimetres, the size of a small orange. The Sun, 109 times wider than the Earth, would be about 44 centimetres across. Choosing objects whose sizes match these ratios makes the comparison honest.

Materials

Cost: free. Many items come from home or from waste; spare parts such as LEDs, motors and wire are in the store.

  • A peppercorn, a mustard seed, a pea, a coriander seed, a large orange, a small orange, two lemons
  • A tray or a board
  • Labels
  • A measuring tape
  • A chart of planet diameters

Safety

This project uses safe, everyday materials. Still, read the rules below with a parent before you start.

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.

All the safety rules

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.

  1. Copy the diameters: Mercury 4,900 km, Venus 12,100, Earth 12,700, Mars 6,800, Jupiter 143,000, Saturn 120,000, Uranus 51,000, Neptune 49,000.

  2. Decide that the Earth is the peppercorn and measure it; it should be about 4 millimetres.

  3. Work out with an adult how big each other planet should be by comparing with the Earth.

  4. Pick a kitchen object closest to each size: mustard seed for Mercury, pea for Venus, coriander seed for Mars, oranges and lemons for the gas giants.

  5. Lay them on the tray in order from the Sun and label each.

  6. Draw a circle 44 centimetres across on a chart paper to represent the Sun and stand it behind the tray.

  7. Ask visitors to guess which object is the Earth before you tell them.

  8. Write two sentences on the card about which planet surprised you most.

What you should see

A tray of eight correctly sized objects in order, with a Sun circle behind that makes even Jupiter look small.

Viva questions

A teacher or a judge will ask how it works. Try to answer each question before you open it, then compare.

1Which is the biggest planet?

Jupiter.

2About how many Earths would fit across Jupiter?

About 11.

3Which planet is nearly the same size as the Earth?

Venus.

4Is the Sun a planet?

No, it is a star.

Free ebook: Viva Questions for Science Projects

Take it further

Use the same scale to place the Moon, a tiny seed about 1 millimetre across, 12 centimetres from the peppercorn.

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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