## Satellites and Scale in the Earth-Moon System

In this activity, students will make a scale model of the Earth-Moon system. It may be better to initially conceal the intent however. Step by step instructions for the students are given in the provided slides. Below is an outline of the activity. The written lesson plan is pending revision.

Materials: Play dough (commercially available or homemade in equivalent amounts), rulers (two per group), tape measures, support slides.

1. Have students begin with half a standard size (5 oz) container of play dough per group of 2-3 students. Provide at least two rulers (stiff plastic preferred) per small group.
2. Ask the students to divide their half container of dough into 50 approximately equal pieces. Having the students think about what to do before they begin dividing their dough is highly recommended. For a mathematics connection, have the groups of students share their strategies with the class.
3. Ask the students to select a representative piece from their 50, and set it aside.
4. Put the remaining 49 pieces back together, and form two spheres, one large and one small.
5. Inform the students that they have just created a scale model in size for the Earth and Moon. The Earth is approximately four times the diameter of the Moon. Have the students measure their model Earth and Moon to see if their model is close to this ratio of 4:1.
6. Next, ask the students to predict how far apart the Earth and Moon should be on their scale model  "If we could shrink down the real Earth and real Moon to this size, how far apart would they be?"
7. Tell the students, as shown on the slides, that the Moon is about 30 Earth diameters away from the Earth. Have them measure out that distance using the diameter of their Earth model times 30. Flexible tape measures, such as those used for sewing work well.
8. Have the students predict where the C/NOFS spacecraft carrying CINDI (or the International Space Station) would be found on their scale model of the Earth-Moon system.
9. Provide students the measured distance between the Earth and Moon: 384,000 km. From the "How High is Space?" activity, the distance for satellites in low Earth orbit is about 1/1000th the Earth-Moon distance. So if the distance between the Earth and Moon is 1.5 m, or 1500 mm, the distance for low Earth orbit is only about 1.5 mm!

Additional slides, linked above, discuss adding the Earth-Moon system to the paper model in "How High is Space?"

University of Texas at Dallas 2012