Learning Plans & Activities
Defining Vocabulary Through Primary Source Analysis

In this lesson, students define the terms heliocentric and geocentric by analyzing models of the solar system.






Classroom teacher

Science teacher


Students will analyze a pictorial depiction of the solar system.

Students will compare their analysis with others to identify key similarities and differences.

Students will use comparisons, textual, and visual context clues to determine term definitions.


Select at least four images of solar systems from the set "Understanding the Cosmos: Changing Model of the Solar System and the Universe." Two should include geocentric models of the solar system. Two should include heliocentric models.

Possible options include:

  • Illustration of the Ptolemaic concept of the universe showing the Earth in the center
  • Copernicus' Sun-centered model of the cosmos'
  • M. Blundeuile his exercises
  • A plan or map of the Solar System projected for schools & academies
  • Collection of nine images including astronomical instruments


30-45 minutes


AASL National School Library Standards

I.D.3 Enacting new understanding through real-world connections.

III.A.2 Developing new understandings through engagement in a learning group.

Next Generation Science Standards

E-SS1-1 Support an argument with evidence, data, or a model.

Instructional Procedure

Have copies of primary source images in groups of four, two showing heliocentric models and two showing geocentric models. There should be enough copies for each student to have his or her own.

Begin the lesson by telling students they are going to determine the definition of two words, heliocentric and geocentric, by examining models or examples of those words. Share with students that they will work in groups of four. Each student will have a different image. Two of those images illustrate the term heliocentric. The other two illustrate the term geocentric.

Ask students to begin working individually with their own image. They should make observations about what they see making note of both things that they are familiar with and things that they are surprised to see. Encourage students to annotate on their image directly.

After four to five minutes, ask students to confer with the other three members of their group. Each individual should share what he or she noticed about their image and what they documented. After sharing, the group should look for similarities and differences between the four images.

Reminding students that two have an example of the term heliocentric and two have an example of the term geocentric, ask students to continue their discussion. The group's goals should include grouping the pairs of images together, attaching one of the two terms to the images, and being able to describe why they did this or give definitions they believe are correct for the individual terms.

After students have had an opportunity to go through these steps, each group can share their thinking about how they can define the terms heliocentric and geocentric.


The teacher may initially pair students with a single primary source or have students work in groups larger than four to provide additional support during the lesson.


Students providing their definitions for the two terms can be a group assessment. For individual assessments after the lesson, the teacher may want to provide an exit slip for each student asking him or her to describe an image as heliocentric or geocentric and provide evidence to support their choice.

Additional Resources

Bober, Tom. "Heliocentric, Geocentric: Using Library of Congress Ebooks to Explore Science-Related Primary Sources." Teaching with the Library of Congress (blog). January 13, 2015. https://blogs.loc.gov/teachers/2015/01/heliocentric-geocentric-using-library-of-congress-ebooks-to-explore-science-related-primary-sources/.

Owens, Trevor. "World, Sun, Solar System: Models of Our Place in the Cosmos." Teaching With the Library of Congress (blog). September 26, 2013. https://blogs.loc.gov/teachers/2013/09/world-sun-solar-system-models-of-our-place-in-the-cosmos/.

About the Author

Tom Bober is a school librarian, 2018 Library Journal Mover and Shaker, former Teacher in Residence at the Library of Congress, and author of the book Elementary Educator's Guide to Primary Sources: Strategies for Teaching. He is a Digital Public Library of America Community Rep, a member of the Teachers Advisory Board for the National Portrait Gallery, and a co-chair of the Education Advisory Committee of the American Archive of Public Broadcasting. Tom writes about student learning on AASL's Knowledge Quest blog and publications such as School Library Connection and American Libraries and has given workshops and spoken across the country. His foundation is built on over twenty years in public education, with six years as an elementary classroom teacher, seven years as a building and district instructional technology specialist, and over eight years in school libraries. Find him at https://tombober.com/ and on Twitter @CaptainLibrary.

MLA Citation Bober, Tom. "Defining Vocabulary Through Primary Source Analysis." School Library Connection, January 2010, schoollibraryconnection.com/Home/Display/2186236.

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Entry ID: 2186236

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