The Leaning Tower of Pisa: Ingenious design and ongoing stability efforts

The Tower of Pisa, since its completion in 1372, has continually leaned. However, due to intentional design decision the risk of toppling has been reduced. The constructors ingeniously shaped it like a banana, positioning its center of gravity slightly behind the geometric center of its base. This structural trick allowed it to lean further than a straight tower.

Due to its unique structural features, the leaning Tower of Pisa has maintained its iconic tilt for over 800 years, enduring earthquakes and storms while remaining stable. Engineers consistently monitor its tilt, ready to intervene if it reaches a critical inclination.

The reason why the tower is standing is simple. Every object possesses a center of gravity, the point where its mass is concentrated for balance. This concept is crucial for understanding why the Tower stands despite its lean. For any object to remain upright, its center of gravity must fall within its base. The Tower, weighing approximately 14,500 metric tons with a top-heavy geometry, has its center of mass lower than the top floor, causing it to lean such that a vertical line from its outer edge meets the ground 4 meters from its base.

It should be mentioned that in the early 1600s, Galileo Galilei used the Tower's unique lean to conduct gravity experiments, demonstrating that an object's mass doesn't affect its falling speed. Even then, the Tower's tilt was less pronounced than today.

In 1990, when the Tower reached a tilt of 5 degrees, engineers warned that its center of gravity was approaching the edge of its base, risking collapse. To stabilize the Tower, engineers closed the monument for about a decade, a project that eventually cost 30 million EUR.

Today, despite its current 4-degree tilt, a vertical line from its center of gravity still falls within its base, ensuring stability. However, to prevent future stability issues the structure is monitored with sensors. Overall, although the risk of collapse under normal conditions is not very high, engineers are concerned about its stability if a significant earthquake occurs. Therefore, they use the knowledge they have gained from past stabilization efforts to maintain the Tower and ensure that it will withstand possible strong seismic loads.