CHill on a Mission: The Leaning Tower of Pisa

The following excerpts about the Leaning Tower of Pisa are from a research paper I did for my college writing class this past April as I prepared and looked forward to my cruise to Europe.

Approximately 12 miles from the port of Livorno, Italy, a haven for cruise ships, lies the quaint town of Pisa: “Pisa boasts such a beautiful square that the Pisans refer to it as the field of miracles” (Levy & Salvadori, 2002, p. 155). The centerpiece of Pisa is the famed Leaning Tower. The tower is actually only one part of a three piece complex named La Piazza dei Miracoli. The tower, a baptistery, and the Cathedral of St. Mary the Virgin make up the plaza. This plaza is considered one of the great masterpieces of Italian Architecture (Ciagá, 2006). An observation made by one of my friends was; “One thing that struck me as ironic is that it is the bell tower to a fairly nice looking church that no one cares anything at all about”

Over 800 years ago construction began on the bell tower of this complex. In 1173, under the leadership of Bonnano Pisano, the structure began to rise. For no apparent reason, after five years and three stories were completed, construction halted. At the time someone mentioned they felt the tower was leaning. The tower then sat idle for nearly 100 years until 1272, when Giovanni di Simone continued work on the project. This architect actually made an attempt to correct the initial lean by placing the next three stories at a backwards angle in an attempt to straighten out the tower. In 1278 work once again stopped without reason, although some attribute it to Italy’s constant state of war, and the tower sat incomplete once again. Finally, almost 200 years after it was begun, the belfry, and thus the tower, was finally completed. At its completion, the initial lean of the tower was 1.6 degrees. The tower stood 180 feet high and measured 51 feet in diameter.

With its Leaning Tower, the city of Pisa became a tourist destination. In 1989, 700,000 visitors climbed the steps to the top. Sources vary the amount of steps from 293 to 297 possibly attributed to the fact that the north staircase has less steps that the south because of the lean. Even after the tour to the top was closed to the public in 1990 as crews began repair efforts, thousands of tourists still flocked to the site to behold its majesty. The tower remained closed for more than a decade, re-opening to much fanfare in 2001. When the tower was first closed for repairs, the lean had been increasing 1/20 of an inch per year. While not a large fraction when viewed, if one does the math the tower increased its lean over 30 inches in the six centuries since it was completed.

The reason for the tower’s lean has been attributed to poor quality soil. Although it has a 13 foot foundation, almost immediately after construction began, the tower began to sink into the soil, a soil mostly composed of clay over a buried riverbed. John Burland, the soil mechanics professor from England who is largely responsible for saving the tower, compares its construction in a Newsweek article “to a child’s carelessly stacking toy bricks on a carpet” (p. 50). Even though the tower has been leaning since its early days, according to Matthys Levi and Mario Salvador at the time of the original publication in 1991 of Why Buildings Fall Down the tower had been righting itself, possibly due to heavy rains softening the earth, or to previous efforts to repair the tower. However, the tower’s self righting efforts were not going to save it without further aid. One amazing fact shows that if a tower built like that of Pisa with similar materials on similar ground were to lean 5.4 degrees, the laws of physics say it would fall. When Burland and his team began their efforts to save the tower, it stood 5.5 degrees off. An interesting fact according to Burland who says: “no matter how many calculations we made, the tower should not have been standing at all”

The decade long process of saving the tower was not without drama. At one point, due to engineers accidentally removing an important part of the foundation, the tower moved 2.5 millimeters instantly. The measurement of 1/20 of an inch is approximately 1.3 millimeters; therefore the tower lurched nearly twice as far in an instant as it normally moved in a year. Burland and his team developed all types of ideas to fix the tower. One idea said to balance it with hot air balloons. An even crazier idea discussed redoing the landscape around the tower to make it look straight. Engineers dried the soil with steam pipes, anchored the tower to the ground with steel cables, and buried 600 tons of lead on the north side (not visible), all with little success. The plan that finally started the true fix came about when Burland thought of slowly removing soil from under the tower and letting it slowly settle into place. After wrapping the tower with an almost two inch thick cable to support it, the crew drilled holes, inserted pipes and removed roughly 70 tons of soil in increments of 20 liters at a time, which allowed the tower to straighten about six inches. The commission to save the tower estimates that they have added 300 years to the life of the tower. The lean now stands at five degrees and art historians figure it leans today as much as it did for Galileo.

Speaking of Galileo, he was a native Pisan, and it is thought by many that he made is his apparent gravity defying experiment off the tower of Pisa. He attempted to prove that objects of different weights will fall at the same speed. Although authorities believe the results of the experiment: many scientists no longer believe this story [that the experiment occurred at the tower]

The city of Pisa has over 100,000 residents, and although we know how many climb the tower in an average year, the number that just visits the site is unknown. Although opinions differ about the overall experience when visiting the tower, everyone I spoke to discussed picture taking. My friend said, “My family enjoyed taking the classic pictures where we are holding up the tower”. Another response stated: “One thing I had fun doing was watching people posing for pictures. Everyone likes to take the picture where it looks like they’re holding up the tower, so you can stand there and see people all around in these totally ridiculous poses, holding up air”. I have a picture of myself looking like I am holding up a rock at Garden of the Gods in Colorado, and had thought that it would be fun to have a similar picture with the tower. It appears several people have already beaten me to that, and I am going to re-think that idea.

In a city with so much history, isn’t it odd that “the tower is the city’s only claim to fame, and the only reason it’s famous at all is because someone messed up the math?” When I am climbed to the top I remebered, with a huge smile on my face, something I read when doing the paper: “the Pisans never wanted the tower to be straightened out. Who would travel halfway around the world to see the straight tower of Pisa? Enjoy the pics and have a great weekend.