There was a key difference, however, between how vertically and horizontally squeezed eggs deformed in the compression experiments—namely, the former deformed less than the latter. The shell’s greater rigidity along its long axis was an advantage because the heavy load was distributed over the surface. (It’s why the one-handed egg-cracking technique targets the center of a horizontally held egg.)
But the authors found that this advantage when under static compression proved to be a disadvantage when dropping eggs from a height, with the horizontal position emerging as the optimal orientation. It comes down to the difference between stiffness—how much force is needed to deform the egg—and toughness, i.e., how much energy the egg can absorb before it cracks.
Cohen et al.’s experiments showed that eggs are tougher when loaded horizontally along their equator, and stiffer when compressed vertically, suggesting that “an egg dropped on its equator can likely sustain greater drop heights without cracking,” they wrote. “Even if eggs could sustain a higher force when loaded in the vertical direction, it does not necessarily imply that they are less likely to break when dropped in that orientation. In contrast to static loading, to remain intact following a dynamic impact, a body must be able to absorb all of its kinetic energy by transferring it into reversible deformation.”
“Eggs need to be tough, not stiff, in order to survive a fall,” Cohen et al. concluded, pointing to our intuitive understanding that we should bend our knees rather than lock them into a straightened position when landing after a jump, for example. “Our results and analysis serve as a cautionary tale about how language can affect our understanding of a system, and improper framing of a problem can lead to misunderstanding and miseducation.”
DOI: Communications Physics, 2025. 10.1038/s42005-025-02087-0 (About DOIs).