From the Apologia booklinks section

An Indoor Solar System Activity Here is an activity you can do indoors to get an idea of how far the planets in the solar system are from one another. You will need 392 paper clips, 9 items that can be used to represent the planets (marshmallows, for example), and the floor of a pretty long (about 41-feet long) hallway. It is best to use a floor that does not have carpet, as the paper clips can get caught in the carpet. It is also best to use small paper clips. If you can find paper clips that are smaller than the standard 1.25-inch paper clips, a shorter hall can be used.

Procedure

1. Start at one end of the hall and put 4 paper clips end to end. Mercury orbits the sun at the end of the 4th paper clip. Put a marshmallow next to the end of the fourth paper clip to indicate Mercury is there.

2. Add 3 more paper clips to the line. Put a marshmallow next to the end of the last paper clip to indicate Venus is there.

3. Add 3 more paper clips to the line. Put a marshmallow next to the end of the last paper clip to indicate earth is there.

4. Add 5 more paper clips to the line. Put a marshmallow next to the end of the last paper clip to indicate Mars is there.

5. Add 37 more paper clips to the line. Put a marshmallow next to the end of the last paper clip to indicate Jupiter is there.

6. Add 44 more paper clips to the line. Put a marshmallow next to the end of the last paper clip to indicate Saturn is there.

7. Add 96 more paper clips to the line. Put a marshmallow next to the end of the last paper clip to indicate Uranus is there.

8. Add 108 more paper clips to the line. Put a marshmallow next to the end of the last paper clip to indicate Neptune is there.

9. Add 92 more paper clips to the line. Put a marshmallow next to the end of the last paper clip to indicate Pluto is there.