Lesson Plans: Grades 9-12

Galileo and the Inevitability of Ideas

Created September 26, 2010


The Lesson


Persian Astrolabe

Modern Persian Astrolabe

Credit: Wikipedia Commons

Galileo has long stood as an emblem of intellectual freedom and the triumph of truth over superstition. Yet his achievements can also help students recognize the contingency of even the most inevitable-seeming historical developments and how the consequences of historic turning-points extend into our lives today.

Learning Objectives

  • To understand the historical significance of Galileo's scientific achievements
  • To explore the element of "inevitability" in our perception of historical developments
  • To examine the values underlying historic choices.

Preparation Instructions

Begin by reviewing what students may already know about Galileo, using the "Timeline of Galileo's Life and Era" accessible from The Galileo Project homepage. Create a timeline of Galileo's life (1564-1642) on your chalkboard and have students mark off events during those years to place his career in historical context. Remind students that Galileo's scientific work focused on motion, particularly the motion of falling bodies and projectiles. (Click "On Motion" at 1589 in the timeline for background.) Students may be familiar with the experiment in which Galileo supposedly dropped objects of different weights from the Leaning Tower of Pisa. Explain that Galileo approached science with a belief in the fundamental truth of mathematics that led him to search for mathematical relationships in the phenomena of nature. Yet in testing his ideas through experiment, he played an influential part in establishing the empirical method as a principal tool of scientific inquiry.

Lesson Activities

Activity 1. The Ptolemaic and the Copernican Systems

Focus on Galileo's role in the scientific revolution that gradually replaced the earth-centered Ptolemaic System with the sun-centered Copernican System. Have student research teams use the articles The Ptolemaic System and The Copernican System on these competing views of the universe. What kinds of evidence supported the Ptolemaic System? Why did it seem to make sense from a philosophical and theological point of view? What were the main arguments for the Copernican system? What problems did it solve? What evidence supported it? Why didn't the religious authorities condemn it from the start?

Activity 2. Galileo's trial before the Inquisition

Conclude this lesson by looking at Galileo's famous trial before the Inquisition in 1633, where he was found guilty of heresy for advocating the Copernican system in his book, Dialogue on the Two Chief World Systems. Students can research this event at The Galileo Project (click on "The Inquisition") and in library resources. Have students explain why the Inquisition believed that the Copernican system contradicted Scripture. Why couldn't the Inquisition agree with Galileo that Scripture tells us "how to go to heaven, not how the heavens go"? What was at stake for the Catholic Church in this confrontation, in terms of theology, philosophy, and political power? What was at stake for Galileo in terms of intellectual freedom and scientific inquiry?

Extending The Lesson

From our point of view, it might appear "inevitable" that Galileo's ideas would eventually prevail and even preposterous that anyone could be condemned for scientific work. Ask students to consider how some scientific developments raise similar issues today -- the possibility of cloning human beings, for example, or the potential uses of human genetic engineering

The Basics

Grade Level


Time Required

2 class periods

Subject Areas
  • History and Social Studies > Themes > Common Core
  • History and Social Studies > Place > Europe
  • History and Social Studies > Themes > History of Science and Technology
  • History and Social Studies > World > The Modern World (1500 CE-Present)
  • Compare and contrast
  • Critical analysis
  • Critical thinking
  • Data analysis
  • Evaluating arguments
  • Gathering, classifying and interpreting written, oral and visual information
  • Logical reasoning
  • Problem-solving
  • Using primary sources