Eggs have long been a staple in both culinary arts and science classrooms, often serving as a didactic model to explore principles of physics and engineering. A new study published in Communications Physics is now upending a widespread assumption about the resilience of eggshells in impact scenarios, particularly those mimicking the classic ‘egg drop challenge.’ Contrary to popular belief, this research reveals that eggs are less likely to crack when dropped on their side rather than vertically — an insight with intriguing implications both in education and in understanding the mechanical properties of biological materials.
The ‘egg drop challenge’ is a common experiment designed to demonstrate principles of impact resistance and material toughness. Students construct protective contraptions around an egg and drop it from predetermined heights, aiming to prevent the egg from cracking. Conventional wisdom, often reinforced by school curricula and popular science explanations, posits that eggshells are stronger when the egg lands point-first — vertically — because this orientation supposedly minimizes the likelihood of fracture. The new research led by Tal Cohen and colleagues challenges this deeply ingrained assumption with compelling experimental evidence.
Cohen’s team undertook a rigorous, controlled series of 180 drop tests to quantitatively analyze how chicken eggs respond to impacts from different orientations. They dropped eggs vertically and horizontally from three heights: 8, 9, and 10 millimeters onto a hard surface. The results were striking: eggs dropped vertically cracked at significantly lower drop heights compared to those dropped horizontally. More specifically, over half of all vertically dropped eggs cracked even at the lowest tested height of 8 millimeters, if falling on either end, while fewer than 10 percent of eggs dropped horizontally exhibited cracks at the same height. This disproves the entrenched notion that vertical drops are safer for eggshell integrity.
To complement the drop tests, the researchers performed compression experiments to further characterize the mechanical behavior of eggs under different loading conditions. Remarkably, the force required to compress and crack the eggs was nearly identical for both vertical and horizontal orientations — approximately 45 newtons. Nevertheless, eggs loaded horizontally exhibited greater compressive deformation before fracturing, indicating superior ability to absorb energy in that orientation. This suggests that while vertical loading imparts stiffness to the egg, it does not enhance its toughness, or ability to endure energetic impacts.
From a materials science perspective, this distinction between stiffness, strength, and toughness is pivotal. Stiffness describes the rigidity or resistance to deformation, strength corresponds to the maximum stress a material can withstand, and toughness refers to the energy a material absorbs before fracturing. The egg’s response to vertical compression is characterized by greater stiffness but lower toughness, making it more brittle and susceptible to cracking. Conversely, horizontal compression exploits the shell’s increased flexibility around the equator, allowing the eggshell to deform more and dissipate impact energy without failing.
The findings highlight the inadequacy of equating stiffness with toughness in teaching materials and popular explanations about eggshell resilience. As the authors note, confusion between these mechanical properties has perpetuated myths regarding how eggs break under impact. This study provides clarity by disentangling these concepts and demonstrating their concrete consequences in a tangible system. Such nuanced insight enriches our understanding of biological structures and the complex interplay between form and function.
Beyond the immediate educational ramifications, these results bear significance for bio-inspired engineering, where biological materials like eggshells serve as templates for designing lightweight but strong structural components. The differential capacity of eggshells to endure impact depending on orientation may parallel how engineered materials respond to dynamic loads in real-world applications — from vehicular crashworthiness to aerospace structure resilience. Future research could explore these analogies, leveraging the egg’s natural architecture to innovate more efficient, damage-tolerant materials.
At a microscopic scale, the egg’s shell is a composite of calcium carbonate crystals organized in a complex hierarchical pattern, reinforced by an organic matrix. This architecture inherently balances mechanical strength and toughness, critical for protecting the developing embryo. The new data suggest that this composite’s anisotropy — variation in mechanical properties with direction — manifests in its macroscopic response to loading orientation, conferring increased flexibility and energy absorption when compressed laterally. This insight furthers our appreciation of how evolutionary pressures sculpt material properties in biological systems.
This research also prompts a reevaluation of laboratory protocols and educational demonstrations involving eggshell mechanics. Many teaching settings traditionally promote vertical dropping as the default method for the egg drop challenge, often without considering the orientational dependence of fracture risk. By integrating these findings, educators can foster a more accurate and nuanced pedagogical approach, encouraging students to think critically about the factors determining material failure, rather than relying on oversimplified narratives.
The study’s methodology deserves particular mention. The team’s systematic use of three distinct drop heights and large sample sizes (60 eggs per orientation-height combination) lends statistical robustness to their conclusions. The complementary compression tests also provide mechanistic understanding beyond empirical observation, bridging descriptive and explanatory perspectives. Such rigor is commendable and sets a benchmark for future investigations into the mechanical behavior of complex biological materials.
In summary, this groundbreaking research overturns a commonly held belief about egg fracture mechanics by demonstrating that eggs are more resistant to cracking when dropped on their side rather than vertically. This occurs because horizontally loaded eggshells can endure greater deformation before failure, highlighting the importance of toughness over mere strength or stiffness in impact resilience. These insights not only benefit educational practice but open avenues for bio-inspired design strategies in engineering. The humble egg, a symbol of fragility, proves to be a sophisticated natural structure with untapped lessons for science and technology.
Subject of Research:
Not applicable
Article Title:
Challenging common notions on how eggs break and the role of strength versus toughness
News Publication Date:
8-May-2025
Web References:
http://dx.doi.org/10.1038/s42005-025-02087-0
References:
Cohen, T. et al. (2025). Challenging common notions on how eggs break and the role of strength versus toughness. Communications Physics. DOI: 10.1038/s42005-025-02087-0
Image Credits:
Not specified
Keywords
Eggshell fracture, impact resistance, material toughness, mechanical anisotropy, bio-inspired engineering, stiffness vs toughness, egg drop challenge, calcium carbonate composite, dynamic loading, structural mechanics
