Rachel Hansen, BHP Teacher
Iowa, USA

I bet Galileo threw his hands in the air at least a few times during his nine years of house arrest. The Roman Inquisition sentenced him to lifetime imprisonment after finding him guilty of heresy. What had Galileo done to deserve such a punishment? He made a claim ⎼ although an incorrect one ⎼ that the Sun, not the Earth, was at the center of the Universe. Wrong or right, Galileo directly challenged the widely accepted view of the Roman Catholic Church, and that’s really all that mattered.

Today, the Catholic Church operates one of the most important centers for observational astronomy, using powerful telescopes to provide evidence of the changing shape and dimension of galaxies over time. These efforts to pioneer new scientific discoveries are in sharp contrast with the attitudes of the Catholic Church in the past. Despite their historical views, the Catholic Church slowly shifted their thinking over time. What caused the Church to change its mind? What causes anyone (or any institution) to change their beliefs? This is the topic of study in Unit 2.

Why Do Individuals Change Their Minds?

In Unit 2, students embark on an investigation of the evolution of human thought over time. Why do individuals change their minds? What does it take for entire societies to change their way of thinking?

When we begin this unit, I ask my students to recall a time when they changed their minds. We discuss the factors that go into such big decisions. When did you stop believing in Santa Claus? The Tooth Fairy? The Easter Bunny? Why? I like to recite to them this line from one of my favorite Taylor Mali poems: “Changing your mind is one of the best ways of finding out whether or not you still have one.” And with that, we are off in search of the answer to how we arrived at our current view of a centerless Universe.

There are a few essential concepts and skills that align well with this driving question: thresholds, claim testing, and interdisciplinary perspectives. Here’s how we put them to work in our classroom.

Thresholds: When is the truth undone? These are the moments that mark a significant change in thinking. Under the right Goldilocks Conditions (improved technology to gather better evidence, trustworthy experts, an approving government, an accepting society), individuals throughout a society may let go of their old thinking in favor of something new. Each time this happens in history, it becomes a threshold moment for us to study. In this unit, those moments center on scientific thinkers like Ptolemy, Galileo, Copernicus, Newton, Leavitt, and Hubble.

  • Changing Views Timeline: This activity, found in Lesson 2.1, is an excellent way to build upon students’ understanding of scale from Unit 1 and incorporate a new idea, thresholds of increasing complexity, which was introduced in Lesson 2.0. Students examine different scientists’ views of the Universe by creating a story arc of how their thinking progressed over time. Each student group must construct a timeline of the life of a single scientist, share it with the class, and then add it to the class timeline. In creating a physical timeline, students need to consider how much detail is required to capture the larger narrative. Examining the individual as part of the larger narrative requires a shift in scale. Ultimately, students will have to evaluate and decide where the threshold moments occur in our changing view of the Universe.
We construct a timeline on the back wall of our classroom. It remains there for the unit so that we can refer to it during other activities, discussions, and the Investigation. Photo by Rachel Hansen.

Claim Testing: What factors facilitate a change in thinking? Who is an authority? Why should we take their opinions seriously? What makes for high quality, reliable evidence? Does the claim even make sense? Using all four of the claim testers (authority, evidence, intuition, logic), we can begin to unpack the kinds of claims that were being made in each of those threshold moments on the Changing Views Timeline.


  • Views of the Universe Debate: This activity (found in Lesson 2.1) is the perfect follow-up to the Changing Views Timeline. At this point, students have a tremendous amount of background knowledge on each of the scientists. It’s the perfect opportunity to sharpen their claim testing skills and introduce the concept of collective learning ⎼ the idea that these scientists built upon one another’s knowledge. We spend a single 50-minute class period on the debate. Student groups are assigned a scientist to represent and prepare positions on the following questions:
    • What were the most important cultural and scientific influences on the development of this view of the Universe?
    • How did our views of the Universe stay the same and change over the time period from Copernicus to Hubble?
    • How does the development of this view of the Universe contribute to collective learning (either by building on previous views of the Universe or by laying the foundation for later views, or both)?

Interdisciplinary Perspectives: How do we know what to believe? The experts and evidence we examine represent several different disciplines: science, religion, and politics. Evaluating such a broad spectrum of viewpoints helps stitch together the narrative as a whole and place it in the appropriate historical context.

  • What Are Disciplines? After watching an introduction to cosmology and astrophysics in Lesson 2.2, students should be better prepared to think about the value of interdisciplinary thinking. Fully understanding our changing view of the Universe requires more than just a single historian’s point of view. I highly recommend this revamped activity, What Do You Know? What Do You Ask?, which requires students to assemble the best possible team to evaluate whether Mars could be inhabited by humans someday. Each expert brings a different set of skills to the project, and therefore, a different set of questions. Students get to practice disciplinary questioning, which helps them to see its value. Diversity fosters innovation and creativity. As historians, it’s also exactly what we need to understand the big picture.


You’ll remember we kicked off Unit 2 talking about times in our lives when we changed our minds. By the end of this unit, students understand that changing your mind requires serious thought. It takes the right conditions at just the right moment. It’s not easy to persuade society to abandon their old ways.

All of this ultimately leaves my students puzzled that it took until 1992 for the Vatican to pardon Galileo of any wrongdoing, even though the Church conceded they were wrong about the whole Earth-centered Universe thing sometime in the early nineteenth century. My students want justice for Galileo, even when I remind them his ideas were wrong (much to their credit, they cite historical context for his error). I like to think that Galileo is somewhere looking down on us, throwing his hands up in the air with a smug look on his face.

About the author: Rachel Hansen is a high school history and geography teacher in Muscatine, IA. Rachel teaches the BHP world history course over two 90-day semesters to about 50 ninth- through twelfth-grade students each school year.


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