In order to "see" objects or systems that are too small or too big, scientists build scale models. The parts of the scale model keep their same relationship to each other but the model is much smaller or much larger than the actual object.

Think of a model car as an example. In building a scale model of the solar system, you will find that the solar system is largely empty space.

• Students will use a scale model to demonstrate the relative distances in the solar system and the relative sizes of the sun and the planets.

• Students will research the nine planets and the sun and report on their characteristics and features during a trip through the solar system.

• 1 large orange
• 1 tennis ball
• 1 hula hoop covered with yellow paper
• 2 cherry tomatoes
• 2 garbanzo beans
• 1 pea
• Several BBs
• Globe
• Glue or scotch tape
• Books, pictures, posters and other research material about the solar system

For each student:

• A garbanzo bean
• BB
• Metric ruler
• Piece of paper (26 cm long)

1. Use a toy car or airplane to demonstrate the concept of scale to the class. Explain how the same scale had to be used to keep everything in proportion. Explain that since the solar system is so vast, we will build a scale model of it, using common objects.

2. Use the globe to represent the earth and explain to the students that the softball represents the moon in this scale model. Ask the students how far apart to put the "earth" and "moon" to represent the actual distance to scale. Have several pairs of students determine the distance. Ask the class to pick the one they think is most accurate. Then ask a student to hold the globe while you move the "moon" 40 feet away. That is the scaled distance.

3. Pass out the paper and ruler. Ask the students how to fit the distance between the earth and moon, 240,000 miles onto the piece of paper. List all ideas on the board. If no student comes up with it, point out that using a scale of 1 cm = 10,000 miles will allow us to fit that distance on the paper. Have students calculate length of the line to represent the distance in centimeters. (240,000 mi. divided by 10,000 mi./cm will equal 24 cm)

4. Distribute a garbanzo bean and BB to each student. The garbanzo bean represents the earth and the BB, the moon. Have the students paste or tape the garbanzo bean at one end of the 24 cm line and the BB at the other to build their earth and moon model. Review the concept of scale model. (Collect and save for the solar system tour.)

5. Using the scale 1 cm = 10,000 miles complete the chart that scales the diameter and distance from the sun of each planet. (See attached chart for students, for teachers, and in Spanish. ) Students could work on this individually or it could be done as a whole class activity with the chart reproduced on the board or a transparency.

6. After completing the scaling exercise, use common objects to represent the various planets and present them to the class. End with the sun and hold the earth-moon model constructed previously in the center of the sun to show its vastness. If it takes astronauts three days to travel from the earth to the moon, how long would it take them to travel across the sun? The sun is a sphere: How many earths would fit inside it? (1,000,000 earths). The sun is over 100 times larger than the earth.

   PLANET	COMPARABLE OBJECT
   Mercury	BB
   Venus	garbanzo bean
   Earth	garbanzo bean
   Moon	BB
   Mars	pea
   Jupiter	large orange
   Saturn	tennis ball
   Uranus	cherry tomato
   Neptune	cherry tomato
   Pluto	BB
   Sun	hula hoop covered with yellow paper

   Days Two - Four (optional)

7. If you are having the students do reports on the planets, the students should form their teams of experts. Assign two to three students to each planet plus the earth's moon and the sun. Student research can take place in class or as a homework assignment, but leave two or three days for the investigation and preparation of the report. The reports will be oral and presented during a walk through the solar system. (If the teacher is going to present the information and not have students do the reports, plan to do the walk the next day.)

   In student or teacher reports, the following information can be included:

   a. What is the gravitational pull of the celestial body?
   b. Would we weigh more or less than on earth?
   c. What is the celestial body made of?
   d. What is its temperature range?
   e. How long is its day (the time it takes to turn on its axis?)
   f. How long is its year (the time it takes to orbit the sun?)
   g. What is its atmosphere?
   h. Describe special features (moon, rings, volcanos, etc.)
   i. Could life exist on this celestial body? Why or why not?
   j. Has man done any exploration of this celestial body? How?

   Note: Report should point out to the students that all planets move in the same direction and in nearly the same plane around the sun, but they never are lined up in a row coming from the sun.

   Day Five (optional)

8. The walk has to be prepared for by the teacher the day before the class goes on its trip. The class goes on a walk through the solar system. You will need a very long flat area for your walk. A very long school playground, a football field, or perhaps the sidewalk out side of the school can be used. The day before, find a place to secure the "sun" ( a fence or post). This location should be at the farthest end of the area you will be pacing off the solar system. Use the scaled distances that the class completed and pace off the distances from the sun to each planet. You may want to mark the spot for each planet the day before or do the pacing with the whole class so they can see the measurement system. If you have a very long area, you probably can get to Jupiter, but no farther. Pluto would be two miles from your sun in this scale.

9. On the day of the trip, students should have journals or notebooks to take notes on the trip, their team reports and their earth-moon scale model. The teacher should have the sun and other objects representing the planets, and something to use for evaluating the reports.

10. Walking through the solar system: The class goes to the designated location and the teacher hangs up the sun if not already displayed. At the sun, the expert team gives its report. Then the class paces off the distance to Mercury, if not previously marked. The expert team gives its report. Continue on through the solar system. Make sure to notice how the sun changes as you get farther away. When you get to earth, use the garbanzo bean and BB model to experience a solar eclipse. Hold the garbanzo bean to your eye and line up the BB with the sun to simulate the eclipse. Visit as many planets as you have space for. The reports on the outer planets can be completed in the class room.

1. Ask students to write about what surprised them the most about their trip. Ask them what they enjoyed the most. What were three new things they learned? Write two questions they still have about the solar system. Share responses.

2. Assess students on the thoroughness and accuracy of their planet reports. Did they answer all the questions ? Were they able to answer questions asked by other students? Was their presentation clear?

3. Collect the students notes and score their thoroughness and accuracy, using a rubric.

Explore the concepts of gravity, weight, mass, micro-gravity and free fall and the concept of orbiting.

Language Arts:

Select some short stories or excerpts from science fiction to share with the class. Have students write their own science fiction adventure about a visit to another planet.

Social Studies:

Have students research the impact of Copernicus' and Galileo's ideas on the society of their time. How are new ideas accepted? Examine the pro's and con's of space exploration today.

Art:

Have students create and build their own space station out of used and recycled materials.