How Big is the Solar System



Students will make an accurate outdoor scale model of the solar system using common objects.


1 ball (8″ diameter), 2 pins, 2 peppercorns, 1 chestnut or pecan, 1 hazelnut or acorn, 2 coffee beans, index card, LOTS of space¬†outdoors


Affix the peppercorns and nuts to index cards, and push each pin through a card so that students can see the size of the pinhead. Each card will represent a planet, and the large ball will represent the sun. Show these items to the students and ask them how far apart they must be to accurately represent the distances between the planets. Lead the students outside to a space you have chosen in advance and set down the sun.

Using the list below, walk the students through the solar system placing the planets down as you go. At each stop, remind students of the actual sizes and distances of each planet. Remember that a pace is equal to two steps, so count out paces every time a particular foot hits the ground. You may decide to select one or a few students as pace counters so that you may speak during the walk.


Challenge students to calculate the scale of this model of the Solar System. Using this scale, how far would you have to walk to reach Proxima Centauri? How large would a human be?

Discuss the pros and cons of manned and robotic space missions.