Caesar's Last Breath

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Caesar's Last Breath


To develop a deeper understanding of the nature of science and technology advancements, and the connections between science and society, through an exploration of the substances that make up the air we breathe.


This lesson uses the book Caesar’s Last Breath: Decoding the Secrets of the Air Around Us by Sam Kean. This book was selected as a finalist for the 2018 AAAS/Subaru SB&F Prize for Excellence in Science Books in the Young Adult category. SB&F, Science Books & Films, is a project of the American Association for the Advancement of Science.

Caesar’s Last Breath explores the substances that make up the air we breathe and covers a broad range of topics, from discussions of physical and chemical properties to engaging stories about how people made discoveries about the gases around us, how technology was developed to harness the properties of gases, and how humans have impacted the atmosphere.

While Caesar’s Last Breath explains scientific concepts related to the atmosphere and its components, it’s the stories related to these concepts—such as how they were discovered or how they were applied—that really draws in the reader. In interviews about Caesar’s Last Breath, Sam Kean talks about using stories with heroes and villains to make the science more accessible. The book’s stories around how these discoveries were made go beyond the limited descriptions that might be found in science textbooks (if they are mentioned at all), providing an opportunity for students to learn about and consider what is involved in the practice of science and the connections between science and society, not just the science facts in isolation. In this lesson, students focus on concept strands that come up repeatedly throughout the book related to the history and practice of science and the interconnections between science and society. Students also explore topics in a range of science and technology fields such as physics, chemistry, and geosciences, but learning goals in these areas are not directly assessed in this lesson.

The book is organized into three sections:

  • “Making Air: Our First Four Atmospheres” looks at how the atmosphere has evolved starting when the Earth first formed, and science and engineering advancements related to the main components of the air.
  • “Harnessing Air: The Human Relationship With Air” looks at the science and technology advances that let humans use the properties of gases in daily life.
  • “Frontiers: The New Heavens” looks at how humans have changed the atmosphere, or at least tried to.

All but the last chapter are paired with an Interlude that covers a shorter story thematically linked to the chapter.

Caesar’s Last Breath is written for general audiences, and very little prerequisite science knowledge is needed. Students should have a general familiarity with the states of matter and atom and molecular theory, likely covered in the middle grades. However, multiple chapters deal with science and technology advancements driven by political and military priorities and the related ethical considerations, most notably the stories about nuclear testing and the development of chemical weapons in Germany during World War I. Therefore, some knowledge of World War I, World War II, and the Cold War are important to provide the context to understand and discuss these chapters.

Caesar’s Last Breath identifies and addresses many misconceptions. An important misconception that students may have about the practice of science is that science discoveries are usually made by individuals working alone. This can be reinforced by stories about scientific discoveries because it is often simpler to talk about one or a few people rather than including everyone who contributed. Though the author’s interest in finding heroes and villains can at times reinforce this misconception, students may notice references to the teams behind the main hero—such as Anton Lavoisier’s wife Anne-Marie pointing out issues with the theory of phlogiston in Chapter Three, or the stories about the former Manhattan Project researchers and “computers.” If students seem to have this misconception during discussions or presentations, you may want to ask questions to make them think about all the work that goes into discoveries, such as, “Who else may have played a role in those experiments?”

Students may also have a misconception that the atmosphere is unchanging. This is addressed directly in the first section of the book. In addition, students will watch a webinar by Sam Kean called Caesar’s Last Breath and the Fascinating Science and History of the Air We Breathe in the Development section to help address this misconception.

Ideas in this lesson are also related to concepts found in this Next Generation Science Standard:

  • HS-PS2-6. Communicate scientific and technical information about why the molecular-level structure is important in the functioning of designed materials.

Ideas in this lesson are also related to concepts found in these Common Core State Standards:  

  • CCSS.ELA-Literacy.RST.11-12.1 Cite specific textual evidence to support analysis of science and technical texts, attending to important distinctions the author makes and to any gaps or inconsistencies in the account.
  • CCSS.ELA-Literacy.RST.11-12.2 Determine the central ideas or conclusions of a text; summarize complex concepts, processes, or information presented in a text by paraphrasing them in simpler but still accurate terms.
  • CCSS.ELA-Literacy.RST.11-12.6 Analyze the author’s purpose in providing an explanation, describing a procedure, or discussing an experiment in a text, identifying important issues that remain unresolved.
  • CCSS.ELA-Literacy.RST.11-12.7 Integrate and evaluate multiple sources of information presented in diverse formats and media (e.g., quantitative data, video, multimedia) in order to address a question or solve a problem.
  • CCSS.ELA-Writing.WHST.9-12.2 Write informative/explanatory texts, including the narration of historical events, scientific procedures/ experiments, or technical processes.
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Planning Ahead

If possible, have classroom copies of Caesar's Last Breath on hand. 

Because of the length of the book, this lesson plan is structured by assigning students to focus on one of eight chapters (and the accompanying interlude), and then, in groups, present a summary of that chapter to the rest of the class. The length of the lesson can vary depending on how long it takes your students to read their chapter and complete the reading log. Below is list of the key activities and estimates of the time required:

  • Introduction activities (described in Motivation Section): all in-class, lasting 30-45 minutes
  • Viewing  American Chemical Society (ACS) webinar and filling out the student sheets: if students watch the video outside of class, allow a few days or a weekend; if viewing in-class, allow 35 minutes for viewing the video (32:45 minutes)
  • Video sheet check-in and reading assignment introduction: in-class, 30 minutes
  • Reading the chapter and completing the reading log: mostly out-of-class, with occasional check-ins to ensure students are on-track, allow at least a week
  • Students working in groups to develop and give their presentations: a couple in-class periods for groups to discuss chapters and plans, plus at least one week mostly out-of-class to develop the presentations

You may consider assigning students to one of the three sections (with three chapters each) instead of just one chapter. In that case, plan on at least two to four weeks for the reading, and a week to a week and a half for the presentations.

This lesson focuses on learning goals related to how science and engineering is practiced and the connections between science and society, which are brought up throughout the book. The book also touches on concepts from specific science and technology fields, and many of these topics come up only in one chapter. When planning, consider if any chapters (or parts of chapters) are especially relevant to your class topics; if so, you may want to have all students read those chapters or passages.  

Caesar’s Last Breath makes many allusions to works and involves topics that may be part of Language Arts or History classes, providing an opportunity to make connections to your students’ other classes. For example, you could have a focused discussion on the relevant topic and corresponding passages from Caesar’s Last Breath:


  • Bleak House by Charles Dickens
  • Cat’s Cradle by Kurt Vonnegut
  • Poet Samuel Coleridge (a participant in Chapter Four)
  • Poetry references to Walt Whitman, Robert Frost, e e cummings (see Poetry Across the Sciences on incorporating poetry into science teaching)

 History topics

  • French Revolution
  • World War I
  • World War II
  • Cold War

Some resources you may find useful in preparing are:

  • This Lab Out Loud interview is aimed at educators with a behind-the-scenes discussion with Sam Kean, including choices he made in writing the book (24 minutes; the interview starts at around 3 minutes).
  • This C-SPAN interview with Sam Kean provides a taste of what the book covers  (9 minutes, 44 seconds).


Start with the exercise described on the first page of the introduction to Caesar’s Last Breath. Ask your students to take some slow, deep breaths and think about what’s in the air they are breathing. See below for some suggested questions. You want to make sure the students begin to think not just about the specific facts, but how they were discovered and how that information may have been used.

  • What’s in the air you just inhaled?
  • Where do you think those substances come from?
  • Do you think the air is the same as what someone would have breathed a hundred years ago?
  • How would you find out what’s in the air? 
  • How do you think scientists found out what is in the air?
  • Why do you think people decided to study the components of the air?
  • How have scientists and engineers used that knowledge? How has that affected our world?

(Answers may vary. Encourage your students to explain their answers.)

Next, present students with the thought exercise that the book is named for: "What are the odds that in the next breath you take, there will be a molecule of Julius Caesar’s last breath?" You can describe it yourself or ask students to read Sam Kean’s description of the scenario in the book’s introduction with the paragraph starting, “Even more startling…” (In the hardcover, this starts on p. 4.) Students should stop reading at the paragraph that ends with: “You can open a vein into the ocean, but you don’t expect a pint of blood to wash ashore two thousand years later.” (In the hardcover, this is near the top of page 7.) Instead of having them read Kean’s solution, ask them to speculate and consider what information they would need to reason out the answer—key questions and the book’s answers are listed below. Students should then reason out the thought experiment in class and you can help them with the math involved if they don't know how to do it themselves.

  • How much air is in a breath? 
    (A normal breath is about half a liter, but for Caesar’s last breath the book assumes a full lungful of air is expelled, resulting in 1 liter of air.)
  • Are those molecules still around or did they break down or cycle out of the atmosphere? 
    (Most of those molecules aren’t very reactive, so would not break down or be cycled out of the atmosphere.)
  • Would the molecules in the last breath spread across the world? How quickly? 
    (The rates of gas diffusion in the atmosphere would spread 1 liter of air across the world, in all latitudes and longitudes, within one year.)
  • How many molecules are in that last breath? 
    (With a few chemistry equations and temperature and pressure assumptions, that 1 liter of air translates to 25 sextillion (2.5 X 1022 molecules.)
  • How big is the atmosphere?
    (The book describes atmosphere of the Earth as having a volume of about 2 billion cubic miles and that 1 liter is 0.00000000000000000001 percent of the atmosphere (that’s 19 zeros between the decimal and the 1: 1 X 10-20. It may be easier for students to calculate by using the actual volume rather than a percent: converting 2 billion cubic miles to liters gives about 8 X 10­21 liters (or 8 sextillion).)

For a basic calculation: the number of molecules in Caesar’s last breath is about three times the number of liters of air in the atmosphere, so each half liter breath we take is likely to contain one molecule of Caesar’s last breath.


Caesar’s Last Breath is a long book with three sections. While later chapters may briefly refer to earlier information or anecdotes, each chapter or section can be read on its own. Each chapter (except the last) is followed by a short interlude, a more focused story related to the theme of the chapter. The chapter and interlude should be read together. For this lesson, you should separate the class into groups and assign each one of the first eight chapters to read (optionally, you can ask them to read an entire section). The groups will then present the main concepts, facts, and stories to the rest of the class. If you would like a more focused class discussion on certain concept strands or technical topic, you may want to assign just a subset of chapters. See the Caesar's Last Breath teacher sheet for suggestions.

To give students an introduction, they should use their Caesar's Last Breath student esheet to watch Caesar’s Last Breath and the Fascinating Science and History of the Air We Breathe for homework. They should answer the questions on their Caesar's Last Breath student sheet and you can find answers to the questions on the teacher sheet.

In this presentation, Sam Kean discusses the first four atmospheres, the theme of the first section, and this will provide students with an overview of the science behind the changes to Earth’s atmosphere. It also introduces the story of Einstein trying to invent a better refrigerator. There are three quiz-style polls (at 6:00, 15:00 and 28:23), which the students do not have to do. The presentation ends at 32:45 and the Q&A session can be skipped.

After students have watched the webinar, you should go over the questions on the student sheet as a lead-in to introducing the concept strands and giving students their reading log assignments. In particular, focusing the discussion on the story of Einstein and refrigeration and the related questions can help introduce students to the idea that the stories in Caesar’s Last Breath are as much or more about the practice of science and how society and science connect as they are about the scientific facts. You can ask questions about what the students learned beyond the chemistry and physics, following up on the questions about what motivated the research and how it (and related work) impacted society.

From there, you should provide the students with the Caesar's Last Breath Reading Log and introduce the concept strands that are listed. The strands fall into two general categories:

  • The Practice of Science: Strands 1-3 relate to the process of scientific inquiry and engineering advancement. Students will read about how science advances by building on past work and incorporating new information; how science findings can correct misconceptions in addition to finding new information; and the importance of publicly communicating scientific findings as well as factors that can conflict with that goal.
  • Science and society: Strands 4-6 are about how science and society are interconnected. Students will explore the way that science impacts society and how society impacts science, as well as the related issue of science and ethics.

Whether you introduce the concepts yourself or direct the students to review them on their own, you will want to give them a chance to ask questions and make sure they understand the strands. You may want to note that the strands do have areas of overlap, and some topics may fall into multiple strands. For example, for some topics, science impacts society and society impacts science may be a feedback loop. In the reading log, students should summarize the stories and scientific facts and concepts and keep track of concept strands for each chapter and interlude pair.

Next, assign students to read one of the first eight chapters and the interludes of the book. Unless you opt to assign whole sections instead of individual chapters, the ninth chapter should be skipped as it differs greatly from the other chapters. Determine how much time students will need to read the chapter and interlude and fill out the reading log. You could plan to allow a minimum of one week, and likely more time, for students to read the chapter and complete the reading log.

To monitor student progress, you should ask students to make sure they have their reading logs in class with them a couple of days during each week you've allotted for them to complete the reading. Allow time for students to ask any questions they may have about the section they're reading and check their logs to make sure they're working on them.

Once students have finished their reading logs, they should meet with the other students in their sections to go over what they learned and plan a presentation. They should work together to pull out the most important points from their section. Students can use the Caesar's Last Breath Presentation student sheet to help them organize their ideas, and you should provide them with format and organization requirements for their presentations. You should plan for one to two in-class sessions of 30-45 minutes for students to discuss the most important points from their reading logs.


For the assessment, student should use their discussion notes and the other sections on the presentation student sheet to develop a presentation about the chapter they read. You should determine the format, length, and organization of the presentation based on your class topics and resources. Allow students adequate time to develop their presentations—another one to two weeks.

For the content of the presentations, the main sections should include a storyline summary, the important scientific discoveries and technology advancements, and each of the concept strands. More detailed suggestions are included in the student presentation sheet.

For an optional activity, you can extend the lesson and add another assessment by assigning students to write an essay about the context and conditions of one of the scientific or technological advancements described in the book. Though the essay should include a description of the scientific finding or engineering achievement, it should focus on the practice of science and science and society learning goals, based on questions such as:

  • Why was the advancement made in that time and place?
  • Were there social, economic, or political conditions that drove the discovery?
  • Were there technological advancements that were required to make the discovery possible?
  • What were the short-term impacts of the discovery? Long-term impacts?

Depending on your class, you may ask students to do research on their topic and provide additional context on the time and place the discovery was made and/or the impacts of the discovery.

For the assessment, consider developing a detailed rubric that relates to your class topics and curriculum. A sample presentation rubric that focuses on the content is listed on the Caesar's Last Breath Assessment teacher sheet. If you use this, you should also have a corresponding rubric related to the presentation skills and organization that is appropriate to the chosen format and your students’ level.

There are several resources on the Internet that describe the use of rubrics in the K-12 classroom, a few of which are highlighted here.

To learn more about rubrics in general, see Make Room for Rubrics on the Scholastic site.

For specific examples of rubrics, more information, and links to other resources, check out the following sites:

Finally, you can go to Teacher Rubric Makers on the Teach-nology.com website to create your own rubrics. At this site you can fill out forms to create rubrics suitable for your particular students, and then print them instantly from your computer.


Air Masses is a 9-12 Science NetLinks lesson that helps students develop an understanding of air masses and the role they play in weather and climate.

Poetry Across the Sciences is a K-12 Science NetLinks tool with resources for using poetry to enrich science teaching. The resource could be used in incorporating some of the poems that are alluded to into the lesson, and even includes references to two poets referenced in Caesar’s Last Breath, e e cummings and Robert Frost.

Earth Simulator is a 6-12 Science NetLinks Science Update about the Earth Simulator, a supercomputer for modeling earth systems including the atmosphere – a modern successor to Lewis Fry Richardson’s work described in Chapter Eight, Weather Wars.

Climate Change is a Science NetLinks collection of resources such as lessons and tools related to climate change.

Making It Rain is an article and podcast episode by 99% Invisible about the attempts at weather control, providing additional information and a different perspective on the Weather Wars discussed in Chapter Eight, Weather Wars. The article text and podcast script are similar but not identical; the podcast includes interviews and audio recordings such as news bulletins, and the article has photographs and videos.

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