Solar System Scaled Down: Lesson on Proportions by Marie Caldwell and Karyn Carson

Materials
• 10 pr. scissors
• several rolls of masking tape
• measuring tapes or meter sticks
• magic markers
• scale model of Earth, moon and Sun where 400,000km = 1 meter
• table of distances and diameters of planets and Sun (enough copies for all students)
• scale model of solar system where 400,000km = 1 mm
• calculator

Objectives
• To construct a scale model of the solar system using one scale for diameters of the planets and distances from those planets to the sun.

Procedure
1. To construct a scale model of the solar system using one scale for diameters of the planets and distances from those planets to the Sun.
2. Let students know that the objective is for them to make a scale model of the solar system using one scale.
3. Introduce scale of Earth and moon, (write this information on the board) where:
400,000km = 1 m
Diameter of Earth = 12,760 km
Diameter of Moon = 2,127 km

Ask the students to figure out how big the Earth and the moon would be using the scale.
4. Now ask students to guess how big and how far away the sun would be using this scale. Where would it be in the room? Use follow up questions to find where they think it would be.
5. Write the diameter of the Sun and the distance from the Earth to the Sun on the board:
Diameter of Sun = 1,399, 858 km
Distance from Earth to Sun = 150,000,000 km

Tell the students to figure out, using the scale, how big and how far away the sun would be.
6. Ask students to make educated guesses about how far away 375 meters is. "Is it in this room?", "Could it fit in this building?", etc.
7. Go outside to show 375 meters and sun. (already set up at end of block.)
8. Go inside and pass out table of measurements. Split class in half (or into groups of 10, depending on number of students), Ask students to come up with their own scale models of the solar system. Emphasize the fact that their planets must be visible and also made to scale. Let students know that they are free to go outside, in the hall (be quiet), or where ever they need to.
9. Be there to answer questions or help.
10. Have students demonstrate models.

Wrap Up
• Show model of solar system (400,000 km = 1 mm). Point out that this model would not have satisfied our requirements because the planets are too small to draw.
• Ask students to think about and verbalize the point of the lesson. What did they get from it? (Ratio and proportion, get a more true sense of the solar system and where me are in it.) Did they think it was fun? Do they think middle school kids would like it?
 Planets Distance from Sun (km) Distance from Sun (AU*) Diameter (km) Scale distance from Sun Scale diameter Mercury 58,000,000 0.39 4900 Venus 108,000,000 0.72 12,000 Earth 150,000,000 1.00 12,760 Mars 228,000,000 1.52 6,800 Jupiter 778,000,000 5.20 143,000 Saturn 1,427,000,000 9.54 120,000 Uranus 2,871,000,000 19.00 52,000 Neptune 4,497,000,000 30.30 50,000 Pluto 5,913,000,000 39.50 2,300 SUN -- -- 1,399,830

The Department of Mathematics Education
University of Georgia