In Caesar‘s Last Breath, renowned author Sam Kean tells „the epic story of the air around us“. From the famous analogy that we all breathe some air molecules of Caesar‘s (or indeed anyone‘s) last breath in our lifetime, on to “Earth’s early atmosphere”, the first experiments with oxygen, „nitrous highs“, the democratic behaviour of all gases and the building of bombs, the chemistry of air never ceases to fascinate.
Most of the book covers the beginnings of air as we know it, the part it plays in the way humans inhabit the earth, and how we learnt to „harness” air through scientific endeavors. In the final chapter though, Sam Kean envisions the future of air, how humans will migrate to other planets once our home planet has become uninhabitable for us, or rather once we have rendered it uninhabitable. In his imagined future scenario – half prophecy half eulogy – humans, now called „exonauts“, are landing on another planet for the first time:
„The first sip of air might well bring death. Some trace gas – something we didn‘t even know we should worry about – might sear his lungs or paralyze his neurons. Much more likely, this strange air would burn his throat a little, not unlike a newborn‘s first breath. Things might smell funny, too, damp or dank or rotten. But there probably wouldn‘t be any reason to panic or grasp. He‘d probably just laugh a little in relief, and take a few deep breaths to clear his lungs.
As he did so, something amazing would happen. All the nitrogen and other gases in his lungs, the air he‘d carried with him from home, would trickle forth and escape. After all that distance, the tiny bit of air from his home planet would burst forth and consecrate the air of his new home. The atmosphere of Earth and this new planet would now be forever intertwined. The same thing would happen when the other exonauts removed their helmets and washed their lungs out, adding their own Earth-born molecules to the mix. And because the average person always carries within her lungs a molecule or two that Julius Caesar breathed during his final moments, several Ceasar molecules would now pirouette upward and carry his story forth on this new planet.
There‘s no reason to limit ourselves to Caesar, either. As more and more people began descending from the mother ship and emptying their lungs, molecules that Harry Truman breathed at Mount Saint Helens; molecules that mingled with the nitrous oxide in Humphry Davy‘s lungs and that whirled around Mount Everest while James Clerk Maxwell wondered what made the sky blue – all of them would join in this new planet, too. As would a few molecules from your own life, the air coursing through your lungs during your first wail in the delivery room, your first kiss, your final breath years and years hence.
When we speak of endings, we say dust to dust, ashes to ashes, but that‘s not quite right – there‘s more to it. Every molecule in our bodies started off life as a gas, and long after our demise, when the big red bloated sun swallows everything around us, all those atoms will return to a gaseous state. A few lucky molecules could even get a second chance somewhere else. Some tiny bit of you – molecules that danced inside your body, maybe even that formed your body – could live on in a distant world. The idea of some part of me living on after I die sounds a lot like the stories of heaven I used to hear as a kid – except that here it‘s really true, it really will happen. We‘ve talked all book about the millions and billions and septillions of stores swirling around us, coursing into and out of our lungs every second. You can capture the entire history of the world in a single breath. Journeying to another planet will inevitably, in some small way, keep those stories alive a little longer. Dust to dust, gases to gases.“