Exploring Planet Sizes and Distances

Part 1: Exploring Planet Sizes

1. Read through the Planet Sizes Student Worksheet.  This is where you will find the lesson jobs for each team.

2. Discuss Earth, the solar system, and why we need models to help study them.

•  Earth is the biggest thing we have ever touched, but Earth is not the biggest planet in the Solar System. We cannot just look up in the sky and see the whole Solar System and how it works. It is too big, and the planets are too far away.
• Models let us take objects that are vastly bigger than we can understand and bring them down to a size we can understand.

3. Show students the model Sun (the balloon blown up to 14 cm (5.5 in)). Based on the size of the model Sun, students will work in teams of four or five to answer questions 1-4 on the Planet Size Student Worksheet. These questions reveal what students currently think about planet sizes.

4. Discuss students’ predictions and pass out the Model Planet Cards.

5. Direct each team to choose an item from the material list and compare it to the planet on the cards. Complete the Planet Sizes Worksheet for each planet with their findings.

6. Go around the room, having each team’s reporter give reasons why they picked each object to use for a given planet.

7. Cut the Model Planet Cards to use in Part 2 for the walk. You may want to attach the cards to helium balloons for the walk to make the planets easy to see at a distance.

PART 2: WALKING PLANET DISTANCES

1. Before taking the class outside, introduce the “pace” as the “ruler” for this model. A pace is two steps one with each foot. One pace is about 1 meter. You can use a meter stick for reference and for practice “pacing.”

2. Have each team predict how far away the Earth card should be from the model Sun, using paces or meters.

3. Take your class outside to walk the model length of the Solar System. Take the cut-up master Model Planet Cards you made in Part 1.

4. For each planet, choose a team of students to be the official “pace setter” and “planet bearer” to fasten the planet at the correct distance.

5. Fasten the Sun to the ground (or tie a helium balloon to a nearby object). Tell class the number of paces to Mercury, and tell students to complete the chart on their Distance Between Planets worksheet. “Walk” to Mercury, fasten the Mercury Planet Card to the ground, and repeat the process for all planets.

NOTE: In this model, a spacecraft would move an average of 3cm (1 in) every 5 hours.

NOTE: Be sure to point out the asteroid belt between Mars and Jupiter. Neptune was the most distant planet in the Solar System from 1979 until 1999 when Pluto passed outside of Neptune’s orbit.

7. Back in the classroom, conclude the activity with Reflection Questions. (As a group activity or individually in science journal/notebook)

NOTE: Be sure to remind students that the planets do not really form a straight line. They all travel around the Sun at different speeds, so they are constantly changing positions.