Egg drop tests: how tough is the egg?

A learning journey by Arthur Lee, assisted by Google AI NotebookLM

Figure caption: Panels a and b are taken from the paper: Challenging common notions on how eggs break and the role of strength versus toughness, Nature Communications Physics, . The paper has a lot of data measuring forces. These two panels encapsulate the key finding about the toughness of eggs in the horizontal orientation versus the vertical orientation (sharp or blunt end dropped). The experimental results challenge the commonly held belief that eggs are tougher to break oriented vertically.

Not all the readings in my learning journey are in climate policy decision texts, heavy histories, memoirs, legislations and regulations, science, and economics journal articles. I came across this Nature Communications Physics article back in May 2025 that is scientifically interesting and a bit of fun, breaking news that seem so … ordinary, so … everyday mundane activity – cracking the egg. Do you prefer to crack the egg on its end or on its side?

I reviewed the Nature Communications Physics article:

Antony Sutanto, Suhib Abu-Qbeitah, Avishai Jeselsohn, Brendan M. Unikewicz, Joseph E. Bonavia, Stephen Rudolph, Hudson Borja da Rocha, and Tal Cohen, Challenging common notions on how eggs break and the role of strength versus toughness, .  https://www.nature.com/articles/s42005-025-02087-0.pdf

From the MIT News article, 8 May 2025:

‘The annual egg drop competition is a highlight of first-year orientation in the MIT Department of Civil and Environmental Engineering. “Every year we follow the scientific literature and talk to the students about how to position the egg to avoid breakage on impact,” says Tal Cohen, associate professor of civil and environmental engineering and mechanical engineering. “But about three years ago, we started to question whether vertical really is stronger.”

That curiosity sparked an initial experiment by Cohen’s research group, which leads the department’s egg drop event. They decided to put their remaining box of eggs to the test in the lab. “We expected to confirm the vertical side was tougher based on what we had read online,” says Cohen. “But when we looked at the data — it was really unclear. ‘

What started out as a normal, annual rite of passage for first year undergraduate students at MIT’s Civil and Environmental Engineering became a curiosity-driven research project that also included researchers in mechanical engineering, mathematics, and researchers from Tel Aviv University and the University of Galway, Ireland. The results of the project showed that commonly held belief about a certain everyday truth isn’t necessarily so.

Here is a video of a drop test.

https://youtu.be/FrNqzY6SM7Y?si=EDedtzQL65kJH0m9

I asked Google AI NotebookLM to produce a written brief of the results (). I also generated an AI-podcast to talk about the results. The AI-podcasters bantered back-and-forth to educate me and entertain me (with puns, eggsactly).

Strength versus toughness

In material science, particularly as illustrated by the egg experiments in the paper, the fundamental difference between strength and toughness lies in how a material responds to applied forces and energy before failure.

Here's a breakdown:

• Strength (Peak Force) In the context of the egg study, "strength" is often intuitively associated with the peak force an object can withstand before it cracks. The experiments revealed that the peak force required to break an egg is independent of its orientation (vertical or horizontal). Both vertically and horizontally loaded eggs sustained similar peak forces, around 46.0 ± 6.61 Newtons (N) and 45.2 ± 5.52 N, respectively. A common misconception equates higher stiffness with higher strength, suggesting that an egg can sustain more force when loaded vertically. However, the paper clarifies that stiffness and peak force are not always directly correlated; a stiffer object doesn't necessarily achieve a higher peak force.
• Toughness (Energy Absorption) Toughness is defined as the amount of kinetic energy an object can absorb before failure. This is quantified by the area under the force-displacement curve up to the point of fracture. The study found that eggs loaded horizontally exhibit approximately 30% greater displacement upon cracking compared to vertically loaded eggs. This indicates that the horizontal orientation results in decreased stiffness (or increased compliance). Because the peak force is similar regardless of orientation, the greater displacement in the horizontal orientation means that these eggs can absorb approximately 30% more energy before failure, making them tougher.

Why the Distinction Matters:

The distinction between strength (peak force) and toughness (energy absorption) is crucial, especially in dynamic loading situations like a drop.

• Challenging Conventional Wisdom: The study directly challenges the commonly held belief that an egg is strongest when dropped vertically on its end. This idea is often based on an appeal to "common sense" or analogies to structural arches, which efficiently transmit vertical loads under static conditions. However, this notion is incorrect for dynamic impacts.
• Dynamic Impact vs. Static Loading: While static loading might suggest stiffness is advantageous, for a dynamic impact (like a drop), the ability to absorb kinetic energy is paramount for remaining intact. The experiments demonstrated a statistically significant decrease in the likelihood that an egg breaks when oriented horizontally as opposed to vertically. This is because the horizontal orientation, being more compliant, allows the egg to "bend" and dissipate impact energy over a greater distance. As an analogy, the sources explain that when a person falls, they bend their knees rather than locking them straight. Bent knees are "weaker" or more compliant, but this compliance makes them tougher and "stronger" during impact by experiencing a lower force over a longer distance. The same principle applies to the egg.
• Implications for Education and Design: The findings highlight the importance of precise language and the dangers of relying on "common sense" in physics education, particularly in activities like the "egg drop challenge". Educators often introduce students to structural mechanics and impact using the egg drop challenge. Educators frequently reinforce the incorrect notion that vertical orientation is stronger. Beyond eggs, these insights have wide-ranging implications for understanding the mechanical failure of other ubiquitous shell structures in nature, such as turtle shells, sea shells, human skulls, and outer membranes of viruses and bacteria. This understanding can inform the design of protective equipment and drug delivery systems. The research underscores a broader scientific principle: the value in challenging widely accepted "truths" through rigorous empirical evidence and an open mind, rather than intuition.

The research paper presents several key results derived from extensive static compression and dynamic drop tests, challenging conventional wisdom regarding egg strength.

Key Results in the Data from the Journal Article:

The core findings are illustrated through force-displacement and energy absorption charts, as well as drop test success rates:

• Peak Force is Independent of Orientation:

    ◦ Description of Data: Static compression tests involved applying force until cracking. Data collected fro experimental force-displacement curves show force increasing linearly before a sharp drop at fracture. Numerical simulations showed similar trends.

    ◦ Key Finding: Despite expectations, the peak force required to break an egg was found to be similar regardless of its orientation. Eggs loaded vertically withstood approximately 46.0 ± 6.61 N, while horizontally loaded eggs withstood around 45.2 ± 5.52 N. This indicates that, for static loads, the maximum force an egg can sustain (its "strength" in terms of peak force) does not depend on whether it's oriented vertically or horizontally.

• Horizontal Orientation Leads to Greater Displacement and Lower Stiffness:

    ◦ Description of Data: The data showed that horizontal force-displacement curves extend further along the displacement axis before fracture compared to vertical curves.

    ◦ Key Finding: Although peak force is similar, eggs loaded horizontally exhibited approximately 30% greater displacement upon cracking (0.213 ± 0.022 mm) compared to vertically loaded eggs (0.161 ± 0.015 mm). This implies that the horizontal orientation results in decreased stiffness (or increased compliance), meaning it deforms more before breaking. This increased compliance is also seen in dynamic impacts, leading to a larger contact time with the platen for horizontal drops.

• Horizontal Orientation Leads to Greater Energy Absorption (Toughness):

    ◦ Description of Data: Figure 1e is a violin plot showing the distribution of energy absorbed before cracking for horizontal and vertical orientations, clearly indicating a higher absorption for horizontal. The p-value of < 0.0001 shown in the chart indicates a statistically significant difference.

    ◦ Key Finding: Because the peak force is similar but horizontal eggs show greater displacement, they can absorb approximately 30% more energy before failure. The study defines toughness as the amount of kinetic energy an object can absorb before failure, concluding that eggs are tougher when loaded horizontally. This statistical difference in energy absorption is significant.

• Dynamic Drop Tests Corroborate Static Results:

    ◦ Description of Data: Tests were done (8, 9, 10 mm) in horizontal, sharp-end vertical, and blunt-end vertical orientations. Data from numerical simulations show simulated force-time curves for vertical and horizontal drops, with sharp drops indicating cracking.

    ◦ Key Finding: Drop tests demonstrated a statistically significant decrease in the likelihood that an egg breaks when oriented horizontally as opposed to vertically (on either end). Fewer horizontal eggs cracked when dropped from the same height compared to vertical ones. Simulations showed that fracture occurred for vertical drops at 8.6 mm, but horizontal eggs could withstand drops up to 0.3 mm higher without cracking.

• Crack Patterns Differ by Orientation:

    ◦ Key Finding: Horizontal compression typically results in cracks propagating along the egg's equator, splitting it open. Vertical compression often leads to spiral crack patterns from the contact point of the blunt end, causing shell caving.

Key Recommendations from the Journal Article:

The study offers crucial recommendations stemming from its findings, particularly in educational and scientific contexts:

• Challenge Conventional Wisdom with Empirical Evidence: The study directly challenges the widely held belief that eggs are strongest when dropped vertically. It emphasizes the importance of relying on rigorous empirical evidence and an open mind rather than intuition or "common sense" when approaching scientific questions, especially in physics education. This highlights the value of scientifically testing "received wisdom".

• Emphasize Specificity of Language in Science Education:

    ◦ The research highlights how imprecise language and improper framing can lead to misunderstanding and miseducation.

    ◦ It clarifies that while eggs are indeed stiffer when loaded vertically (true), this does not mean they can sustain more force or are less likely to fracture during dynamic impact. The common misconception equates stiffness with "strength" in all senses.

• Distinguish Between Strength (Peak Force) and Toughness (Energy Absorption):

    ◦ The critical distinction is that for dynamic impacts, materials need to be tough, not stiff, to survive a fall.

    ◦ Toughness is the ability to absorb kinetic energy by allowing reversible deformation over a greater distance. This is analogous to bending one's knees during a fall to absorb impact, where "weaker" (more compliant) legs are actually "tougher" and "stronger" during impact by experiencing lower force over a longer distance.

• Reframe the "Egg Drop Challenge" for Better Physics Intuition:

    ◦ The findings are particularly relevant for educators using the "egg drop challenge" to teach structural mechanics and impact. The study provides a revised framework to help budding scientists and engineers better understand how objects and structures react to impact and dynamic loads. Instead of focusing on stiffness or peak force, the challenge should emphasize designing for energy absorption.

• Broader Implications for Shell Structures: The insights gained from studying eggshells have wide-ranging implications for understanding the mechanical failure of other ubiquitous shell structures in nature, such as turtle shells, sea shells, human skulls, and the outer membranes of viruses and bacteria. This understanding can inform advancements in the design of protective equipment and drug delivery systems.

Last note

Somehow, I preferred to crack my eggs on the side, just a good way for a one-handed crack-and-open to get the yolk and albumin onto the pan. The article made me pause and think about this ordinary activity, not taking it for granted anymore. 😊

Arthur Lee

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