Now back to the physics: In terms of angles, the tower now leans at 3.99 degrees. Working delicately for about four years, they reduced the lean by 17 inches. Then engineers in the 1990s figured they needed to remove soil underneath the non-leaning side, inject more cement, and stabilize the structure with steel cables. That didn’t work so well, it just made the ground heavier, which made it subside more. One was to inject cement into the ground under the tower to stabilize it. That started a few different restoration efforts.
The tower was leaning more, about 1/20th of an inch every year, which would increase as the tower’s center of gravity shifted. The structure continued to decline into the 20th century, when engineers realized they had a problem. Workers tried to compensate by making the columns on the other side slightly bigger to even out the lean. Not long after it was built, the ground under one side started to sink under the weight of the stones. The tower was built back in 1173 with marble, so the assumptions of modern engineering don’t really apply. Our question in Italy: Will it lean forever, or will it eventually fall? Over a couple Italian beers, we plotted the physics. I’ve always thought it strange that an engineering screw-up based on poor planning and shoddy construction has become one of the Seven Wonders of the World. There are many symbols of Italy-gondolas, Sophia Loren, gelato-but none is more iconic than the Leaning Tower of Pisa.
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