The Soufflé Principle, Up Side: It Must Rise

The physical law that animates the soufflé was discovered a few decades after its invention by—appropriately—a French scientist and balloonist, J. A. C. Charles. Charles’s law is this: all else equal, the volume occupied by a given weight of gas is proportional to its temperature. Heat an inflated balloon and the air will take up more space, so the balloon expands. Similarly, put a soufflé in the oven and its air bubbles heat up and swell, so the mix expands in the only direction it can: out the top of the dish.