Does stiffness or toughness count? Researchers drop 180 eggs

Cambridge. Is a raw egg more fragile if it falls upright or on its side? This question plays a role not only in kitchen mishaps, but also in the so-called "Egg Drop Challenge." This is the name of a popular school experiment, often used in physics classes. The task: Using everyday items such as straws, paper, or string, students must build a safety capsule for the egg that will allow it to land safely on the floor from different heights.

A US research team from the Massachusetts Institute of Technology (MIT) in Cambridge has now officially dedicated itself to the question of whether the egg breaks more quickly when oriented sideways or upright, and has dropped an egg 180 times from different heights.

The team's finding, reported in the journal Communications Physics, is that eggs are less fragile when dropped horizontally rather than vertically. The authors have thus refuted what they believe is a widespread belief that eggs are less likely to break when dropped upright. This assumption is even found in tutorials and teaching materials, the study states.

In the US experiment, more than half of the eggs dropped upright from a height of eight millimeters broke, regardless of which end the egg was facing down. In contrast, fewer than 10 percent of the eggs dropped from a horizontal position broke.

Even at slightly greater drop heights, the proportion of broken eggs was significantly lower when the eggs were oriented horizontally. The team also conducted tests using a special device to determine the pressure at which the eggs broke.

The researchers explain the proven effect by saying that eggs are more flexible in the middle and can therefore absorb more energy there before breaking. On average, eggs can absorb around 30 percent more energy when dropped horizontally, according to the study. This makes them tougher, according to the study's definition – which should not be confused with stiffness.

The team also sees this confusion as a reason for the common misconception that eggs are more stable when oriented vertically: The physical properties of stiffness, toughness, and strength are often confused. Eggs are indeed stiffer when compressed upright, but this does not mean they are also tougher—and therefore less fragile.

RND/dpa