Caesar's Last Breath

Caesar's Last Breath 23 May, 2025 How many molecules from Caesar’s last breath do we inhale with each breath we take? Shockingly, the answer is about one molecule—we actually do share breaths with Caesar! And, by extension, every breath we take is composed of the previous breaths of everyone who ever lived—Socrates, Lincoln, Einstein, etc. Isn’t that crazy? This is a classic exercise in Fermi estimation—it even has a book named after it. It’s a beautiful introduction to the power of napkin math, showing how much you can figure out with just a few back-of-the-envelope numbers. Estimating quantities is a valuable skill—if you’re not convinced, check out Nabeel Qureshi's blog. It’s easier and more fun than it seems, and I find myself enjoying it more as I realize how often I land within an order of magnitude. Let’s walk through Caesar’s Last Breath together! We need to determine the volume of Earth’s atmosphere, and the volume of a breath. If we assume that a breath diffuses evenl ... Read full article.