Caesar’s last words in 44 B.C.E. were “Et tu, Brute?”* His last breath, shortly thereafter, consisted of 25 sextillion air molecules. Each of us breathes, with every breath, at least one molecule of those 25 sextillion air particles that were a part of Caesar’s last breath. (25 sextillion is 25 followed by 21 zeros and looks like this: 25,000,000,000,000,000,000,000)

The air we breathe consists primarily of nitrogen (78%), oxygen (21%), a smattering of water vapor, and traces of argon, carbon dioxide and other gasses.  Yes, surprisingly, CO2 only makes up 0.033% of air.  When you exhale, your exhaled breath is about 4% CO2.

Anything released into the atmosphere spreads quickly because air is constantly on the move.  Photons from the sun warms air at the equator more than air north or south and causes changes in temperature and pressure.  This creates winds and the expansion and contraction of the lower and higher atmosphere.  During the day the lower atmosphere expands and then at night it settles back down as it cools. Thus, air is being tousled, churned and mixed all the time.

“A breath seems like such a small thing compared to the Earth’s atmosphere, but remarkably, if you do the math, you’ll find that roughly one molecule of Caesar’s air will appear in your next breath. And it doesn’t stop there. In the same way, you might currently be inhaling Cleopatra’s perfume, German mustard gas and even particles exhaled by dinosaurs.” – Sam Kean, author of the book “Caesar’s Last Breath” in BBC Science Focus

At the smallest level, air molecules continuously jostle against one another at hundreds of miles per hour and ricochet like pool balls.  In a matter of weeks, the molecules in any given volume of air will circumnavigate the globe.  After a few years the original molecules will be evenly distributed throughout the lower atmosphere.  Air’s eternal cycling quality does not apply to many pollutants and organic compounds as they are often heavier (and so hang around) and/or are typically broken down by chemical reactions before they can complete their around the world trip.

So, when Caesar breathed his last breath he sent approximately 25^21 molecules of air mixture into the atmosphere.  Some of the CO2 probably got trapped and digested by plants in a nearby garden but the vast majority of his exhaled molecules began to fan out over an ever-widening area.  Within a decade, that breath had disbursed completely around the earth and most of it is still in circulation.  Thus, you breath some of everyone’s prior breaths with each inhale you take. We’re all connected!

*”Et tu, Brute” is Latin and translates in English to “Mmmmm, it smells like you are wearing Brut today.”