The size of the solar system

# The size of the solar system

You can read about the diameters of the Earth, Sun, Moon and Planets in thousands of kilometres and the distances between them in millions of kilometres, but the only real way to understand the size of the solar system is to make a model.

Once you have made the model you will understand why you cannot make a scale drawing of the solar system, unless you happen to have a piece of paper bigger than a football field....

This model assumes you and your friends are all about eleven years to thirteen years old - if you are all much older or younger the number of paces between the planets will be different.

You will need

• A number of friends, at least six but up to eleven
• A large fairly flat field. A football field will take you as far as Mars but several football fields will be needed if you are going to include all the planets as far as Neptune
• A football
• A large lump of plasticine (or other modelling clay)
• A tablespoon of granulated sugar or table salt (in a container!)
• A ruler (at least 100mm)
• Some pieces of card or paper, one for each child, and a felt tip pen
• In the full model Neptune is more than a thousand paces from the Sun, so if you do have a big enough field to go as far as Neptune mobile phones might be useful for you to keep in touch with each other

You all start together in one corner of the field. Label the pieces of card as you go.

• The Sun is a football in this corner.
• Mercury is a lump of plasticine about 1mm in diameter 15 paces from the Sun
• Venus is a lump of plasticine nearly 2mm in diameter 12 paces beyond Mercury
• The Earth is a lump of plasticine nearly 2mm in diameter 10 paces beyond Venus
• The Moon is a lump of plasticine about 0.5mm in diameter 6 cm from the Earth
• Mars is a lump of plasticine about 1mm in diameter about 20 paces beyond the Earth
• The asteroids are a tablespoon of salt or sugar 48 paces beyond Mars - in real life they are spread out in a circle all round the Sun.
• Jupiter is a lump of plasticine 20mm in diameter 93 paces beyond the asteroids
• Saturn is a lump of plasticine about 17mm in diameter 162 paces beyond Jupiter
• Uranus is a lump of plasticine about 7mm in diameter 360 paces beyond Saturn
• Neptune is a lump of plasticine about 7mm in diameter 410 paces beyond Uranus

Neptune is therefore more than 1000 paces from the Sun. On this scale it will take you at least a month to walk to our nearest star!

You can find out more about the planets by going to the Planets Page of my Web Site. This Page also explains why Pluto is not a Planet any more.

© Barry Gray September 2008