For use with Activity 5, Worlds in Comparison. Each group will need 3 lbs. of modeling dough; a plastic knife; a bread board or sheet of waxed or parchment paper for cutting modeling dough; Handout 1, Instructions; and Handout 2, Planet Name Worksheet.
Used with permission from the Astronomical Society of the Pacific, 390 Ashton Ave., San Francisco, CA 94112. Originally developed by Dennis Schatz (Pacific Science Center) for Family ASTRO. Adapted by Anna Hurst. Copyright 2006, Astronomy from the Ground Up, Astronomical Society of the Pacific.
Setting Up the Activity
This activity works best if the Handout 2 worksheets with the planet names are placed side-by-side on a table, arranged to match the order from the Sun. In front of these sheets place Handout 1, the modeling dough, and the plastic knife on the breadboard or waxed paper. Be sure there is enough room in front of the table for the group to work together. It is crucial to have the indicated amount of modeling dough for each group. If there is less than 3 lbs., the Pluto piece will be too small to see! We recommend 3 lbs. each and urge you to try the activity for yourself before leading it.
Suggestions for Introducing the Activity
For any of these scale model activities, it is useful to start by exploring the notion of models. Playthings, such as dolls or toy cars, can be a useful reference for talking about scale models.
This activity is designed as a self-guided station activity. Nevertheless, if you choose to do so, it can also be a facilitated activity from the beginning. If you facilitate this activity from the start, begin by asking the participants which planet they think is the largest. Which is the smallest? For whatever planet they say is the largest (it will most likely be Jupiter), ask them: If we could combine all the planets together into a big ball, what fraction of that ball would the largest planet be? Might it be 1/9 or 1/5, for example? End the introduction by telling them they will get a better idea after completing this activity.
Note: If groups will use previously used modeling dough of various colors, reassure participants that mixing colors is fine — after all, many planets are multicolored!
Doing the Activity
Participants start by reading the instructions handout, but they should get into working with the modeling dough as quickly as possible. They should follow the instructions as to how to divide their modeling dough and place the parts in the proper planet boxes. Each time the modeling dough is divided and parts are combined to make a planet, be sure participants roll the combined parts around in their hands until the planet has a ball shape.
Ask the group what discoveries they made regarding the sizes of the planets. Were there any surprises? Direct the discussion so they realize the smaller planets (except Pluto) are the inner planets, while the larger planets are the outer planets. Note that more than 96% of the combined volume of the planets is in Jupiter and Saturn (approximately 60% in Jupiter and 36% in Saturn). Those giant planets really are giants.