Students create a scaled-down model of the solar system by calculating the planets' diameters and distances from the sun and then building the model outdoors.

## Objectives

- Students will develop a scaled-down model of the solar system.

## Materials

- Answer Key: Chart 1 and Answer Key: Chart 2 for the teacher.
- Copies of Chart 1 and Chart 2 for students.
- Metric measuring apparatus for length in meters
- Pencil
- Outdoor materials such as stones, twigs, etc.
- Large open outdoor area
- Calculator

## Procedure

**Teacher Notes:**Math skills are required in figuring the distances and diameters. Younger students may be given an already completed chart to do this activity. Older students can mathematically figure the distances and diameters and fill in the chart for themselves. The class should be divided into groups of four or five. Parts A and B (mathematical computations) of the lab activity should be done indoors. Part C of the activity will be done outdoors on the second day. The best solar system creation can be awarded a numerical grade or some other award.

**Part A: Calculating the scaled-down diameter of the planets**

- Distribute Chart 1 and review the diameters of the planets and sun with the students.
- Explain that students will be filling in Chart 1 by completing some calculations. The first set of calculations should be recorded under the heading "# Times Smaller than Sun".
- Explain and demonstrate the following on the board:
- The sun is 1,380,000 km in diameter. Assign the sun a diameter value of 1. To get the diameter value of Mercury, divide 1,380,000 km by 4989. The answer would be 277. Place this number in the part of the chart marked "# times smaller than the sun". Repeat this procedure for the other seven planets. For instance, Venus would be 1,380,000 km divided by 12,392 km.

- Once student have filled in the first part of the chart, explain that students need to assign a scaled-down value for each of the planets. Explain and demonstrate the following calculations on the board:
- Begin with the sun and assign the sun a value of 1 meter (1000 mm). Calculate the value of the planets by dividing 1000 by the number of times smaller you calculated that planet to be than the sun. For instance, Mercury will be calculated by dividing 1000 by 277. The answer will be 3.6 mm. This will be entered in the chart. Do this for each of the planets.

- Tell students that when the chart is complete, the last column will represent the diameter their group will use to represent each planet in the activity.

**Part B: Figuring the scaled-down distance of the planets from the sun**

- Distribute Chart 2 .
- Explain and demonstrate the following calculations on the board:
- Study Chart 2 , which lists the distance of the planets from the sun in millions of miles. Your group will convert these distances to astronomical units (AU). 1 AU is the distance of the earth from the sun. This means that 93 million miles is equivalent to 1 AU. In Chart 2 you will see the number 1 under AU for Earth. To find the astronomical unit for the other seven planets, you should divide each planet's distance from the sun by 93 million. For instance, Venus is 0.7 AU. To arrive at that figure, the distance of Venus from the sun, 67.27 million miles, is divided by 93 million. You will record 0.7 in Chart 2 under AU.

- Instruct students to follow this procedure for the remaining planets.
- Tell students that they will now calculate the relative distance from the sun by assigning a value of 1000 mm (1 meter) for the distance of the earth from the sun – l AU. Ask students to place 1000 mm in the last column on Chart 2. The distance from Venus to the Sun will be 700 mm.
- Instruct students to follow this procedure for the remaining planets.

**Part C: Creation of Scaled-Down Model**

- Instruct each group to take completed Charts 1 and 2 and a meter stick or metric tape measure outdoors.
- Explain that each group will use the data in the last column of Chart 1 to devise the appropriate diameter of the sun and the nine planets in millimeters. Rocks, twigs, straw, etc., can be used to build each planet and the sun.
- Explain to students that the sun should be at one end of the model, and the planets should be placed in the proper order away from the sun. To determine the appropriate distance of each planet from the sun, use the meter stick and information from the last column of Chart
- Tell students to measure the appropriate meters or millimeters for the distance of each planet from the sun.
- Instruct each group to create the sun and the planets in the appropriate scaled-down diameter and at the appropriate distance from the sun. Make the planets by using rocks, twigs, straws, etc., to form the outline of each planet in the appropriate size.
- Once students have concluded building their solar system model, inspect their creations.
- Allow each group to view the solar system created by other groups.

Excerpted from *Hands on Science Activities with Real-Life Applications* by Pam Walker and Elaine Wood.