Lesson Plans: Grades 6-8

Galileo: Revealing the Universe

Created September 13, 2013


The Lesson


Galileo and the Doge

Giuseppe Bertini, Galileo Galilei Showing the Doge of Venice How to use the Telescope, 1858.

Credit: Wikimedia Commons.

… for the Galaxy is nothing else but a mass of innumerable stars planted together in clusters.

—Galileo Galilei, Sidereus Nuncius (Starry Messenger), 1610

Ancient astronomers constructed explanations of the motions of the celestial bodies based on mathematics, philosophy, and careful observations of the skies as visible to the human eye. They recorded the positions of these heavenly bodies over time. Based on this method, ancient astronomers concluded that Earth was the center of the universe and that all other objects in the sky revolved around it.

In the 2nd century CE, a Roman astronomer named Ptolemy refined this view, stating that all planets moved in perfect circles, attached to perfect spheres, all of which rotated around the Earth: a theory that predicted the paths of the planets fairly well. This view, accepted for 1,400 years, was challenged by new astronomers, aided by instruments that enabled them to see the skies as they had never been seen before. Chief among them was Galileo, bolstering his observations with a revolutionary telescope he invented.

He carefully explored the night sky, turning his telescope to what looked like “dark” parts and discovering that they were filled with stars too dim to be seen without the telescope’s enhancement. In 1610, he published his observations of the solar system and distant stars in a volume called Sidereus Nuncius, or Starry Messenger.

In this lesson, students will practice close reading of passages from Galileo’s Starry Messenger concerning his observations of the stars and constellations through a telescope. They will develop an understanding of how he constructed his arguments to challenge the established views of his time using new technology and logical reasoning.

Guiding Questions

  • What did Galileo see when he looked at the sky through his telescope?
  • How did Galileo’s observations change our view of the universe and the Earth’s place in it?

Learning Objectives

At the end of this lesson students will be able to:

  • Cite specific textual evidence to support analysis of a passage from Galileo’s Starry Messenger dealing with his observations of stars, constellations, and the Milky Way
  • Explain the significance of Galileo’s ideas to our understanding of the stars and the universe

College and Career Readiness Standards

Anchor Standard

CCSS.ELA-Literacy.CCRA.R.1: Read closely to determine what the text says explicitly and to make logical inferences from it; cite specific textual evidence when writing or speaking to support conclusions drawn from the text.

Science and Technical Subjects:

  • CCSS.ELA-Literacy.RST.6–8.4: Determine the meaning of symbols, key terms, and other domain-specific words and phrases as they are used in a specific scientific or technical context relevant to grades 6–8 texts and topics.
  • CCSS.ELA-Literacy. RST.6–8.7: Integrate quantitative or technical information expressed in words in a text with a version of that information expressed visually (e.g., in a flowchart, diagram, model, graph, or table);
  • CCSS. ELA-Literacy.RST.6–8.9: Compare and contrast the information gained from experiments, simulation, video or multimedia sources with that gained from reading a text on the same topic.

NGSS Earth and Space Science Strand (ESS):

  • ESS1: Earth’s Place in the Universe
  • ESS1.A: The Universe and Its Stars
  • ESS1.B: Earth and Solar System

Practice Skills

  • constructing and evaluating evidence-based arguments
  • engaging in discourse by explaining phenomena scientifically
  • evaluating and designing scientific enquiry, and
  • interpreting data and evidence scientifically
  • identify a variety of credible sources for research
  • collecting information from a variety of places
  • synthesizing information appropriately


In addition to addressing content in Earth and Space Science as articulated in the Next Generation Science Standards, the lesson also supports the development of ideas pertaining to Scale and Proportion, one of the NGSS’s crosscutting themes. For example, in Starry Messenger, Galileo reported that he saw at least ten times as many stars through the telescope as with the naked eye. From his observations he deduced that the nebulae and the Milky Way were collections of stars too small and far away to be seen as individual stars by the naked eye.

This lesson also helps to support the development of the following science and engineering practices as articulated in the National Research Council’s A Science Framework for K–12 Science Education:

  • Asking questions (for science) and defining problems (for engineering);
  • Constructing explanations (for science) and designing solutions (for engineering);
  • Engaging in argument from evidence;
  • Obtaining, evaluating, and communicating information.

Further Background

Preparation and Resources

Prerequisite skills: By the end of Grade 5, students should know that stars range greatly in size and distance from Earth and this can explain their relative brightness. You may wish to review these concepts with the class before beginning this lesson.

Students utilize close reading strategies, using passages from Galileo’s Sidereal Messenger (Sidereus Nuncius) in which he records his early observations of the moon, the stars (the belt of Orion and the Pleiades), and the moons of Jupiter. The science content will focus specifically on the stars and constellations. The student activity version (Launchpad) may be used to guide students through a sequence of activities outlined below. The activities may be taught with or without this aid.

The teacher may also wish to give students a brief explanation concerning the Sword and Belt of Orion, which Galileo mentions in Section 5 of the close reading of Activity 2. The Star Search interactive for Orion from the AAAS’s Science NetLinks may also be used.


Activity 1

Activity 2

Activity 3

Final Assessment

Other Tools and Worksheets

Lesson Extension (Optional)

Lesson Activities

Activity 1. Stargazing Before Galileo

This activity is designed to introduce students to the general state of astronomy up to the time of Galileo. Students listen, look, and read the text of the Stargazing video closely to discover key concepts and vocabulary as they progress.

The following questions for students after viewing the video necessitate an understanding of the academic vocabulary listed on both the teacher and student versions of the vocabulary handout.

  • What was the general understanding of the relative position of the earth to the sun before Galileo? What important model reflected this understanding?
  • What did early astronomers believe about the position of the stars relative to each other?
  • How did they group them in order to make sense of them?
  • What role did the Greeks play in applying mathematical models to the heavens? Why was this important?
  • What crucial observation did Aristotle make?
  • Which astronomer before Galileo proposed a different model of the solar system? What did he get right? What did he get wrong?
  • In his book Starry Messenger, what did Galileo write about? What did he do that was different than what had been done before?

Bridge to Activity 2.

In order to bring together what students have learned through the video about the state of astronomical observation and the close reading of Starry Messenger in Activity 2, assign a short homework assignment in looking at the night sky.

  • Have students locate a common, bright celestial object (the Moon or Venus, for example) and record how it appears to the naked eye;
  • Are its contours clearly demarcated? If the surface is visible, is it rough, smooth? How about color? Is there any other heavenly body near it?
  • Now ask them to use a device with some type of magnification to view this same body. This can be the zoom feature on a camera or smartphone, a pair of binoculars, or other hand lenses;
  • Tell students to record the magnification of the device and compare this view with what they could discern without the tool.


Activity 2. Close Reading of Galileo’s "Starry Messenger"

To help students gain an understanding of key scientific terms and concepts, as well as integrate textual and visual information, the teacher will model a guided close reading activity using the first of seven sections from Galileo’s Starry Messenger, which deals with his observations of the stars through a telescope.

Suggested reading methods are given in the teacher’s version of the close reading. The teacher may also wish to give students a brief explanation concerning the Sword and Belt of Orion, which Galileo mentions in Section 5 of the close reading. (Note: vocabulary items appear in most of the focus questions and on the teacher’s and student’s vocabulary lists.)

Formative Assessment

Have the students as a group think back to the state of astronomy before Galileo in Activity 1, and compare that to what he has noted here about the nature of the stars as seen through a telescope (as opposed, for example, to the planets). Ask them to write down some examples from the text that point to his overall argument for using such a scientific device. Encourage the class to refine their own answers and come to consensus about the best responses to the questions


Activity 3. Comparing Galileo’s Drawing of the Pleiades to NASA Photographs

Student will compare and contrast their knowledge about the Pleiades gained from a NASA photograph with that gained from Galileo’s drawings and descriptions of them in the Starry Messenger. The goal is to engage them in an analysis of the accuracy of the astronomer’s conclusions about these systems.

Have students use the star comparison graphic organizer, (also available from the student Launchpad), to compare and contrast Galileo’s drawings of the Pleiades system with the NASA photograph taken using modern space telescopes. (Optional vocabulary appears in the teacher’s and student’s vocabulary lists but not on the Launchpad.)

  • Using the organizer, model an initial compare and contrast exercise with the whole class before having students work independently;
  • Guide groups of 2–3 students in looking for differences in detail, scale, and clarity. (See the Launchpad for the student-led versions of these questions.)
  • Ask them to try and match the larger stars that Galileo drew to the ones seen in the NASA image. If they are having trouble making the comparison, remind them that they may need to reorient the images in order to match the stars and prompt them to look for visual clues that can help them do that. (You can use the images here to aid identification.)

Formative Assessment

Ask students to individually write a short paragraph stating how accurate Galileo was in his conclusions about the placement of the stars; their scale, and clarity, based upon modern astrophotography.



Students will incorporate their comparison of images from Activity 3 into their comparison of a news release from a NASA story about the Pleiades (“Hubble Refines Distance to Pleiades Star Cluster”). This story presents new scientific information about measuring distances to distant stars developed as a result of analysis of images from the Hubble Space Telescope. It will serve as a comprehensive review of student’s general understanding of measurement and distance obtained through their comparisons of the close reading with the drawing and the photograph.

After reading the news story, have students comment about the progress of astronomical observation by writing a short (one- to two-page) analysis comparing the current state of knowledge regarding the Pleiades nebula to what Galileo wrote in the passages from Sidereus Nuncius in Activity 2. Remind them to incorporate their comparison of images from Activity 3.


Extending The Lesson

Working with the constellation Orion presents a visually more challenging extension of the culminating activity of this lesson and will deepen students’ skills in analyzing complex scientific media and in making more subtle observations about the actual state of galaxies, with their dust and gas clouds.

This activity should be done by pairs of students or by individual students.

  • As above, have students use the fill out the star comparison graphic organizer, this time for the Orion system;
  • Instruct them to use the same types of categories and strategies that they used when comparing the images of the Pleiades. (If they are having trouble making the comparison, remind them that they may need to reorient the images in order to match the stars and prompt them to look for visual clues that can help them do that.)
  • You might also have them use the background on this constellation at the AAAS’s Science NetLinks interactive for the constellation Orion.

Instruct students to read the NASA story about the Orion nebula (“Hubble Panoramic View of Orion Nebulae Reveals Thousands of Stars”), which presents new scientific information on the density and variety of stars in the Orion nebula developed as a result of analysis of images from the Hubble Space Telescope.

After reading the news stories, have students comment about the progress of in astronomical observation of the understanding of the constellation by writing a short (one- to two-page) analysis comparing the current state of knowledge regarding the Orion nebula to what Galileo wrote about the constellation in the passages from Sidereus Nuncius in Activity 2. Instruct students to incorporate their comparison of images from the earlier part of this extension activity.

Further Resources

The Basics

Time Required

3 class periods

Subject Areas
  • Literature and Language Arts > Genre > Common Core
  • History and Social Studies > Themes > Common Core
  • History and Social Studies
  • History and Social Studies > Themes > History of Science and Technology
  • Literature and Language Arts > Genre > Essay
  • Literature and Language Arts
  • Essay writing
  • Gathering, classifying and interpreting written, oral and visual information
  • Textual analysis
  • Using primary sources
  • Maria Sosa, AAAS