Throughout its more than 4,500 years of history, the Great Pyramid of Gizathe tomb of Pharaoh Cheops, has witnessed the rise and fall of empires, the erosion of the desert and also the earthquakes in an area with very intense seismic activity. This is crucial, because while the Alexandria Lighthouse or the Colossus of Rhodes succumbed to the Earth’s tremors, the 138-meter-high mass has remained immovable.
The secrets Their longevity has been a topic of conversation for decades among Egyptologists, engineers and architects who tried to understand why they were still standing. And it is logical, because every physical object has a “natural frequency” of vibration, and this is crucial because when the seismic waves of an earthquake coincide with the frequency of an object, a very important amplification effect is produced.
It is an effect that we can see, for example, on a swing, since we push it at the exact moment so that it goes higher and higher. And this is where the “superpower” of the Great Pyramid lies.
What does it consist of? According to a study published in Scientific Reports, the pyramid and the ground on which it sits dance to completely different rhythms. This means that the pyramid has a natural vibration frequency which is around 2.3 Hz. For its part, the surrounding terrain of the Giza Plateau vibrates at a drastically lower frequency, close to 0.6 Hz.
This mathematical gap is a true structural lifesaver, since, since there is no coincidence between the frequency of the stone mass and that of the ground during a seismic event, resonance is practically impossible. Waves from the earthquake pass through the area, but the pyramid does not amplify the vibration, dispelling the danger of a catastrophic collapse. It is, in modern terms, perfect passive seismic isolation behavior.
Extreme geometry. This frequency decoupling is one part of the equation, since the focus is also on the impeccable architectural design and geometric of construction, which provides a uniform structural response to any mechanical stress.
All this is thanks to the ingenuity of Egyptian engineers who created an artificial monolith that defies the laws of destruction through several characteristics, such as greatly lowering the center of gravity. And, unlike modern structures that are slender, in pyramids the vast majority of stones are concentrated in their lower third. This makes the building virtually impossible to overturn, regardless of the violence of the transverse shaking.
More reasons. The square pyramid shape is not just an aesthetic or religious choice, but it is the most stable geometric figure that exists to withstand compression. Symmetry ensures that when seismic waves shake the building, the load and stress are distributed equally across all faces, avoiding critical fracture points.
The internal chambers. One of the details that the investigation has pointed out is the unsuspected role of the famous internal chambers of the pyramidlike the King’s Chamber. Historically, they have been analyzed from a funerary perspective, but it is now suggested that, together with the impressive granite discharge blocks, they also act as a system to dissipate energy.
In this way, seismic waves that manage to penetrate the structure encounter abrupt changes in the density of the matter, which causes the waves to refract and disperse.
Did they do it on purpose? This is the question we can ask ourselves after reading all this, and the most plausible answer is that the Egyptians did not handle all these technical concepts, but they were absolute masters of empirical engineering. Through observation, trial, error and a deep knowledge of the materials, they arrived at the optimal solution so that they would last for life.
They built for eternity based on massive stability and, in doing so, accidentally designed a building that meets the same safety parameters that we demand of our most critical infrastructure today to prevent them from collapsing in an earthquake.
Images | Jeremy Bishop
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