Duration of Activity:
20 minutes.

Student Prerequisites:
From previous discussion and reading, students should have a basic understanding of the rotation (spin) and revolution (orbit) of the Sun and Earth. This lesson reinforces what students have learned in the "Adding the Moon: Using a Playground Model to Explore the Movement of the Sun, Earth, and Moon" lesson.

Materials:

• Styrofoam balls: 6-inch ball for the Sun, 3-inch ball for the Earth, 1 1/4-inch ball for the Moon
• Styrofoam disk: 8-inch round x 2-inch thick for base to hold Sun ball (Note: The relative sizes and distances of materials used in this model are not the scale of the Sun-Earth-Moon system.)
• 3 bamboo skewers (about 12 inches)
• Optional: Lamp with 200 watt bulb and shade removed to serve as Sun
• Optional: Extension cord for lamp

Teacher Preparation:
Allow 15 minutes to locate and prepare materials.

1. The Moon rotates or spins on its axis.
2. The Moon revolves or orbits around the Earth.
3. The Moon and Earth revolve around the Sun.
4. The motion of the Sun, Earth and Moon are cyclical.

Grade Level:
Grades 1-3

Procedure:

1. Choose a location in the classroom with ample room (approximately 10' x 10' ) to demonstrate the Sun-Earth-Moon model. Students may want to sit in a circle or semi-circle, with the model in the middle.
2. Insert one end of a skewer into the 6 inch Sun ball and the other end of the skewer into the Styrofoam disk to elevate and secure the Sun ball.
3. Put the 6-inch Sun ball or the lamp where all students can see it.
4. Review what students know about the Sun and Earth. Write answers on the board or KWL chart. Possible points to elicit about the Sun and Earth.
   The Sun:
   • Is our closest star.
   • Is at the center of the solar system (like the hub of a bicycle wheel).
   • Spins slowly compared to the Earth.
   • Spins counterclockwise when seen from above.
   • The Earth and other planets rotate on their axes and revolve or orbit around the Sun, but the Sun is in the center of the solar system and spins on its axis as well.
   • Is very hot and big—much bigger than Earth!
   • Is a light source and is always shining.

   
   The Earth:

   • Is our home planet.
   • Is much smaller than the Sun.
   • Rotates or spins.
   • Takes a day and a night (24 hours) to complete one spin.
   • Revolves or orbits around the Sun.
   • Takes one year to complete its orbit around the Sun.
     
     
5. Place a 3-inch ball on a 12-inch bamboo skewer to represent the Earth. Hold the skewer vertically so that the Earth can be held from above and rotated. (See photos) Remind students that the Earth spins counterclockwise, and that it is smaller than the Sun. Note: Stress to students that Sun/Earth/Moon model is not to correct size or distance scale. Explain that distances in space are vast and that this is a model to help us see the big picture.
6. Demonstrate the Earth orbiting around the Sun. Walk counterclockwise in a circle around the Sun and simultaneously turn the skewer counterclockwise to demonstrate the Earth's spin as it orbits the Sun.
7. Introduce the Moon. Ask, "What revolves around the Earth? What do you see in the sky almost every night and also during the day?"
8. Ask what students know about the Moon and write answers on the board or use KWL chart. Possible points to elicit about the Moon--

   The Moon:

   • It is smaller than the Earth (4 Moons can fit across the Earth's diameter).
   • It revolves or orbits around the Earth.

    

9. Break a 12-inch skewer in half and place a 1 1/4-inch styrofoam ball on the 6-inch skewer. Insert the other end of the skewer in the 3" Earth ball at the approximate "equator" (i.e. perpendicular to the longer skewer). (See photos)
10. Rotate the long skewer counterclockwise to demonstrate the spin of the Earth and the Moon orbiting the Earth. Note: Remind your students that the model is not to correct scale or distance.
11. While turning the Earth/Moon model, walk counterclockwise around the Sun to demonstrate that the Earth is rotating, that the Moon is revolving around the Earth, and that both are revolving around the Sun.
12. Explain to students that the motions they see demonstrated happen as a cycle and that the rotating and revolving never stop! Explain again that it takes a day and a night for the Earth to make one entire rotation and that it takes a whole year for the Earth to complete its long orbit around the Sun.

Assessment:
Ask student to model the movement of the Earth and Moon around the Sun to the rest of the class.

Bibliography:
See related books and websites.