Short answer: apples float because they are less dense than water. A surprisingly large fraction of an apple's volume is intercellular air space—often around one quarter—so the fruit's average density is low enough for buoyancy to support it.
Solid-looking fruit, lots of tiny air spaces
Apple tissue is built from cells with gas-filled spaces between them. Penn State Extension notes that roughly 25% of an apple's volume can be air, while University of Wisconsin Extension gives the same figure as the reason apples float.
Buoyancy depends on average density, not whether something “feels heavy.” When an apple displaces water whose weight equals the apple's weight, the upward buoyant force balances gravity and the apple stays at the surface.
Not every apple is identical
Variety, maturity and internal disorders can change the amount of gas and liquid in the tissue. The exact density therefore varies from fruit to fruit. The useful rule is simpler: a typical fresh apple contains enough low-density air space to be less dense than water.
Quick follow-ups
FAQ
Is 25% of every apple exactly air?
No. It is a useful approximate figure; actual air-space fraction and density vary by variety and condition.
Would an apple float in every liquid?
Not necessarily. Floating depends on the relative densities of the apple and the liquid.
Check the evidence
Sources
- Troubleshooting Problems when Canning Applesauce — Penn State Extension
- Fun Apple Facts — University of Wisconsin Extension
- Buoyancy — Smithsonian National Air and Space Museum
Sources are linked for verification. FactToon summarizes them in our own words and does not reproduce their articles or images.