Please assign one of the following roles to each member of your group. If you have 5 people, you should have either 2 explorers or 2 skeptics. If you have only 3 people, ask one person to be both skeptic and explorer.

Leader
• Directs sequence of steps
• Keeps group "on track"
• Insures all participate
• Checks the time
Explorer
• Explores the meaning of the question
• Suggests ways of answering the question
• Ensures all possibilities are explored
Skeptic
• Helps group avoid coming to agreement too quickly
• Suggests alternative ideas
• Looks for errors in reasoning
Recorder
• Acts as a scribe for the group
• Checks for understanding by all
• Insures all members agree
• Summarizes conclusions

Note that in the following exercise, the words heliocentric and geocentric refer to viewpoints rather than the specific models discussed in the text. The geocentric perspective is the view from Earth looking up into the southern sky, while the heliocentric perspective is the view of the Solar System looking down from above. Don't get confused!