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The Pluto Debate: The International Astronomical Union Defines a Planet Microgame

by Anthony Crider

Science isn't Usually Done by a Vote
In this game, students play one of nine astronomers arguing the definition of a planet at a 1999 debate in New York City and a 2006 meeting of the International Astronomical Union. During this game, students will do the following:

  • Compare the history of Pluto’s discovery to that of the asteroid Ceres
  • Describe the properties of the Kuiper Belt and its members
  • Plot the orbital and physical properties of planets, asteroids, and comets
  • Debate the necessity and value of scientific classifications



STEM, History of Science, Astronomy


20th and 21st Centuries; Contemporary Period


Notable Roles

Neil deGrasse Tyson, Julio Angel Fernandez, Rick Binzel

Themes and Issues  
Scientific understanding and process, Classifications

Player Interactions 
Factional, Competitive

Sample Class Titles
First Year Seminar, Introduction to Astronomy

Chaos and Demand on Instructor 
Low chaos level and low demand on instructor

Primary Source Highlights 
The Hunt for Planet X: New Worlds and The Fate of Pluto by Govert Shilling

Level 3
(what's that mean?

Using the Game

Class Time  
This game can be played over 1 to 3 sessions, depending on how much time you wish to devote to setup, debate, and debrief.

Possible Reacting Game Pairings
This game can be used on its own, or with other games. These pairings are meant to be illustrative rather than exhaustive or prescriptive. Pairings include: Trial of Galileo, or any of the STEM games

You can adjust the assignments based on the desired learning outcomes of your class. 

Class Size and Scalability
This game is recommended for classes with 9-27 students. All roles are designed to be doubled or tripled. 


Reacting Consortium members can access all downloadable materials (including expanded and updated materials) below. You will be asked to sign in before downloading.  


Students need a Gamebook, or in this case, a gamesheet, which includes directions, resources, and historical content.

.pdf file.

Role Sheets and Add'l Materials

Students also need a Role Sheet, which contains biographical information, role-specific resources or assignments, and their character's secret victory objectives. 

.pdf file.

.pdf file.

.pdf file.

Instructor's Guide

The Instructor's Guide includes guidance for assigning roles, presenting historical context, assignments, activities and discussion topics, and more.  

.pdf file.

Additional Resources 

Planet Data Plotter 
This is an online tool created for The Pluto Debate game. Students can use it to create plots to support their arguments. These "mini-papers" are typically handed out after the 1999 debate in New York and before the 2006 vote in Prague.



Anthony Crider

Tony Crider is a Professor of Astrophysics at Elon University in North Carolina. He received his Ph.D. in space physics and astronomy from Rice University in 1999 studying gamma rays and X-rays emitted by newly formed black holes. He continued this work as a National Research Council associate at the Naval Research Laboratory. Before moving to Elon, Dr. Crider taught at American University where he coordinated the Multimedia Design and Development program. His interest in science visualization led him to create virtual planetariums, telescopes, and lunar landscapes within the 3D online world of Second Life. In 2006, he co-founded the SciLands, an archipelago of Second Life islands dedicated to science education and outreach. After receiving a grant from the National Science Foundation to create and disseminate science role-playing games such as The Pluto Debate. Recently, he has taught classes both with and about virtual reality, and served as chair of the Reacting Consortium Board. His hobbies include protest photography, world percussion, and trying to understand his dog, Murphy.


Members can contact game authors directly

We invite instructors join our Facebook Faculty Lounge, where you'll find a wonderful community eager to help and answer questions. We also encourage you to submit your question for the forthcoming FAQ, and to check out our upcoming events


The Trial of Galileo: Aristotelianism, the "New Cosmology," and the Catholic Church, 1616-1633

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Are Atoms Real? 1860 Karlsruhe Conference of Chemistry

Climate Change
Climate Change in Copenhagen, 2009


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