Caesar’s Last Breath
Decoding the Secrets of the Air Around Us
Sam Kean
Little, Brown, and Company
(c) 2017 by the author

In the kingdom of non-fiction books, there’s a land that can be described as “commodity biographies”. Here, the authors take an item or substance of great familiarity, and write about how it has influenced and has been influenced by human history. (e.g Cod: A Biography of the Fish that Changed the World by Mark Kurlansky). Given air’s ubiquity, it’s kind of hard to write a biography for it. Kean’s book can be better described as a collection of independent essays that together tell a history of Earth’s atmosphere and our understanding of it.

The title comes from the old high school chemistry exercise on the diffusion of gases in the atmosphere. How many molecules from the air in Julius Caesar’s last breath our in our lungs right now? For Kean, answering this question requires a detailed account of Caesar’s last minutes before getting in to the mathematics. It’s a good prologue to the subject of our atmosphere.

The first few chapters cover the atmosphere’s origin and early development, in terms of the major gases in each stage. The one on the Earth’s early vulcanism is a biography of Harry Truman, the guy who refused to leave Mount St. Helens when it exploded back in 1980. Then it’s on to nitrogen, and the Oxygen Catastrophe, which involves terms like the “Big Splat” and “Big Burp”. The middle section covers how mankind put certain gases to good use. The last few chapters get into pollution and man’s effects on the atmosphere. There’s a fair bit of overlap in the sections, and “interludes” between the main chapters.

There’s a lot of good information in here, some of which I’d never come across before. The discovery/invention of nitroglycerine. Albert Einstein’s refrigerator patents. The atmospheric physics behind what Project Mogul (the program that gave us “crashed UFO” at Roswell) was trying to do.

And Kean does it all with a light touch, leavening the science with the right amount of humor to make the entire book a pleasant read. Given that the last section is on our effects (deliberate or accidental) on the atmosphere, it would be all too easy to end with gloom and doom about carbon dioxide, methane, and global warming. Instead, he leaves things on an optimistic note that brings us back full circle to Caesar’s Last Breath. Since we’ve all got at least a few molecules of that dying gasp in our lungs, when the day comes when an explorer steps out onto an alien planet, doffs her helmet, and takes a deep breath of completely new air, some of those molecules will emerge as part of the First Breath on a new world.