Apples Float Because They Are 25% Air

The buoyant nature of an apple is a fascinating consequence of its cellular makeup. The flesh of an apple, which appears solid, is actually comprised of loosely arranged cells with significant air spaces in between them. This network of intercellular air pockets makes up a substantial portion of the apple's total volume, reducing its overall density to be less than that of water. According to Archimedes' principle, an object submerged in water experiences an upward buoyant force equal to the weight of the water (Review) it displaces. Because the apple's density is lower than water's, it displaces a volume of water that weighs more than the apple itself, causing it to float.

This natural buoyancy is not only responsible for the satisfying crunch of a fresh apple but also enables the traditional party game of apple bobbing. The origins of this activity are thought to stretch back to ancient times. Some historians suggest that when the Romans conquered Britain, their harvest celebrations, which honored Pomona, the goddess of fruit (Review) trees, merged with Celtic festivals. For the Celts, apples were mystical symbols of fertility and were used in divination rituals.

These ancient traditions evolved into a form of matchmaking. In one version of the game, young, unmarried people would try to bite into an apple floating in a tub of water. Successfully capturing an apple was believed to predict who would be the next to marry. This practice was later brought to America by Irish immigrants and transformed into the popular Halloween and autumn festival game we know today.