TORRE DI PISA

The Leaning Tower of Pisa is one of the most remarkable architectural structures from medieval Europe. It is located in the town of Pisa, one of the most visited European cities. Even though the tower has been leaning since it was under construction, it has stood for hundreds of years, despite the fact that it looks as if it might fall any minute.

The tower was begun almost 900 years ago, in 1173, and after the first three of its eight stories were built, the ground started to sink, and the tower began to lean. It has continued leaning, a millimeter each year, and now leans 14 feet out of line.

Still, the lean does not stop thousands of tourists each year from climbing its 300 winding steps to the bell tower to view Pisa and the surrounding countryside. The height of the tower is 55.86 m (183.27 ft) from the ground on the low side and 56.70 m (186.02 ft) on the high side. The width of the walls at the base is 4.09 m (13.42 ft) and at the top 2.48 m (8.14 ft). Its weight is estimated at 14,500 metric tons (16,000 short tons). The tower has 296 or 294 steps; the seventh floor has two fewer steps on the north-facing staircase. Prior to restoration work performed between 1990 and 2001, the tower leaned at an angle of 5.5 degree but the tower now leans at about 3.99 degrees. This means that the top of the tower is displaced horizontally 3.9 meters (12 ft 10 in) from where it would be if the structure was perfectly vertical.

There has been controversy about the real identity of the architect of the Leaning Tower of Pisa. For many years, the design was attributed to Guglielmo and Bonanno Pisano a well-known 12th-century resident artist of Pisa, famous for his bronze casting, particularly in the Pisa Duomo. Bonanno Pisano left Pisa in 1185 for Monreale, Sicily, only to come back and die in his home town. A piece of cast with his name was discovered at the foot of the tower in 1820, but this may be related to the bronze door in the façade of the cathedral that was destroyed in 1595. However, recent studies seem to indicate Diotisalvi as the original architect due to the time of construction and affinity with other Diotisalvi works, notably the bell tower of San Nicola and the Baptistery, both in Pisa. However, he usually signed his works and there is no signature by him in the bell tower which leads to further speculation.
Galileo Galilei is said to have dropped two cannon balls of different masses from the tower to demonstrate that their speed of descent was independent of their mass. However, this is considered an apocryphal tale, its only source being Galileo's secretary.

I do find this really meaningful because – as I wrote before – gravity is to me the most real and measurable sign of the existence of God, that will soon reposition the worldwide economies in their natural places, or positions of strength. It has been leaning for so long -- nearly 840 years - it's natural to assume it will defy gravity forever. But the famous structure has been in danger of collapsing almost since its first brick was laid.
It began leaning shortly after construction began in 1173. Builders had only reached the third of the tower's planned eight stories when its foundation began to settle unevenly on soft soil composed of mud, sand and clay. As a result, the structure listed slightly to the north. Laborers tried to compensate by making the columns and arches of the third story on the sinking northern side slightly taller. They then proceeded to the fourth story, only to find themselves out of work when political unrest halted construction.
The tower sat unfinished for nearly 100 years, but it wasn't done moving. Soil under the foundation continued to subside unevenly, and by the time work resumed in 1272, the tower tilted to the south -- the direction it still leans today. Engineers tried to make another adjustment, this time in the fifth story, only to have their work interrupted once again in 1278 with just seven stories completed.
Unfortunately, the building continued to settle, sometimes at an alarming rate. The rate of incline was sharpest during the early part of the 14th century, although this didn't dissuade town officials or the tower designers from moving forward with construction. Finally, between 1360 and 1370, workers finished the project, once again trying to correct the lean by angling the eighth story, with its bell chamber, northward. By the time Galileo Galilei is said to have dropped a cannonball and a musket ball from the top of the tower in the late 16th century, it had moved about 3 degrees off vertical. Careful monitoring, however, didn't begin until 1911. These measurements revealed a startling reality: The top of the tower was moving at a rate of around 1.2 millimeters (0.05 inches) a year.
In 1935, engineers became worried that excess water under the foundation would weaken the landmark and accelerate its decline. To seal the base of the tower, workers drilled a network of angled holes into the foundation and then filled them with cement grouting mixture. They only made the problem worse. The tower began to lean even more precipitously. They also caused future preservation teams to be more cautious, although several engineers and masons studied the tower, proposed solutions and tried to stabilize the monument with various types of bracing and reinforcement.
The tower currently leans at 5.6 degrees. Another 1.4 degrees will be enough to bring 14,000 tons of intricately carved white marble crashing to the ground. At 7 degrees a model shows that walls cannot support the structure anymore. High-tension areas on the lower floors on the northern side can cause the bricks to pull apart.
However experts say the tower will lean for at least another 200 years. It may even stay upright — well, almost upright — forever. That's all thanks to a restoration project, which brought the tower back from the brink of collapse a decade ago. Restoration work undertaken from 1999 to 2001 stabilized the tower. Engineers placed weights on the structure's north end, while at the same time extracting soil from below, causing it to slowly sink back in that direction. The Leaning Tower of Pisa still leans south, but now it does so at just 3.99 degrees. Barring a large earthquake or other unforeseen catastrophe, engineers believe it will stay put for at least a few hundred years.

The tower itself with the study of gravity made by Galileo represent without any doubts to me that most of our today’s culture and way of understanding everything was born in the country where I was born about 50 years ago and made it possible to pass on to my own treasures, very much of this millenarian culture now part of our so-called Western culture.