Can you believe that a man-made structure would last 800 years? The Leaning Tower of Pisa proves that even a man-made building can last a long time. After 848 years of its construction, it attracts a large number of people.
The construction of the bell tower began on August 9, 1173 when Pisa was among the most powerful city-states in Italy, a seafaring empire with commercial colonies across the Mediterranean from Majoren to Constantinople. The credit of building the “Piazza dei Miracoli,” the splendiferous assemblage of Romanesque tower goes to the city’s affluent traders who wanted to flaunt their wealth.
It is often said the tower was built with stolen money. After sacking Palermo in 1063, the city government needed to display all the treasures that adventurers had brought back from Sicily.
Although financial resources were available, the architects seem to have made a blunder when they selected an area with soft alluvial silt to put the structure. It was probably a buried river a bed. As a result, from the start, the tower tilted north. To save from further tilting north, they built columns and arches on the north taller than those on the south.
The building of the tower did not run smoothly. When the second storey was built, the tower began to sink on one side.
The builders tried to offset their mistake by adding taller columns and arches on the south side of it. After five years, the construction work had to be stopped. By then, they had partially built the fourth storey. If they had continued with the work, the tower would have collapsed immediately.
Although the tower was tilting almost from the inception, the builders did not want to give up their ambitious project. If they had wanted, they could have put up the tower elsewhere. They were rather resilient in their attitude that they did not want to accept defeat.
Columns and arches
Nothing virtually happened for 100 years. When the work resumed, the ground beneath the tower had compressed.
The unfinished part of the tower was leaning towards the south where the soil was soft.
To avert any disaster, they built more columns and arches on the south. They also placed stones on the north of the tower to balance the tilt. The builders managed to complete the seventh storey in 1278.
However, the construction work had to be suspended again. In 1360, another team of builders added the belfry angling it northwards to offset the worsening situation.
During the next five centuries, the tower dipped farther south. It subsided three metres below ground level, burying most of the elegant foundation arcade. In 1838, a sunken walkway was excavated around the base of the tower.
When Benito Mussolini was in power, 80 tonnes of concrete were poured into the foundation to strengthen it. However, the tower shifted farther southwards. It is said Mussolini was ashamed of the Tower of Pisa. He considered it a mistaken construction and an embarrassment to Italy’s reputation.
Lead weights
In the latter part of the 20th century, Italians realised that the tower was facing an imminent catastrophe. The Government appointed a panel of experts to suggest the ways and means of saving the tower from collapse. The panel consisted of 14 experts from different parts of the world.
It functioned under the Prime Minister of Italy. The panel decided to straighten the tower to stop it from falling. Salvatore Settis, an Italian educator said, “Because the original builders constructed the tower in direct response to the movement of the subsoil, we wanted to respect that interaction.”
In the 1990s, the Government sought the services of John Burland, a Professor of Soil Mechanics at London’s Imperial College of Science, Technology and Medicine. He proposed stacking 660 tonnes of lead weights onto the north side of the tower as a temporary measure.
When he tried it on the computer, it proved to be a disaster. However, after a few months, the lead weights were put into place. Although they managed to stop the southward lean, the professor came under heavy criticism for creating a monstrous eyesore.
After some time, engineers decided to install a concrete ring around the tower base, attach ten cables to it and anchor them 45 metres into compacted sand. The plan misfired when the engineers inadvertently cut through steel pipes connected to the tower. With all such attempts, the tower tilted south at an unprecedented speed. Then the engineers decided to add 300 more tonnes of lead ingots to halt the lean. Finally, they abandoned the cable solution.
As nobody could stop the tilt, experts explored new methods. They decided to remove the soil from under the high end of the tower. However, the operation produced a different result. The tower suddenly started veering towards the south again. When the British expert John Burland was about to tender his resignation, a gale blowing from the Alps moved the tower north again. While the extraction of soil continued vigorously, the heavy lead ingots were removed from the tower.
Aristotelian doctrine
One of the axioms in the Aristotelian doctrine of mechanics was that the heavier of two falling bodies would reach the ground before the other and that their velocities would be in proportion to their weights.
Galileo Galilee maintained that all bodies will fall through the same height in the same time if they are not unequally retarded by the resistance of the atmosphere.
He gathered together some of the leading followers of Aristotelian philosophy and showed them what he meant. With scorn written on his face, he ascended to the top of the Leaning Tower of Pisa and let fall two objects of unequal weights. His assembled enemies saw the two bodies strike the ground at the same time.
During World War II, American soldiers had orders to tear down all buildings in Italy ruled by Mussolini. However, when they saw the Leaning Tower of Pisa they were impressed by its beauty and did not want to destroy it.
Pisa where the Leaning Tower is located was particularly amenable to Romantic poets, such as Lord Byron and P.B. Shelley. They enjoyed extended holidays in Pisa where each has a street named after them. Mia Verita, a modern poet, went into raptures when she saw the Leaning Tower of Pisa and wrote the following poem:
The tower of Pisa leans into the future
She leans into the future
marble arches stretching wide
Poor engineering, Mussolini and war
are just a few things she’s survived
Over 14,000 metric tons
compressed in marshy ground
among a square of miracles
Golgotha’s holy soil surrounds
Constructed to display and flaunt
stolen goods and war-time plunder
Her victory intrigues and haunts
while softened soil pulls her under
She climbs 186 feet to the air
tips her hat to the southern sky
she tilts in medieval grandeur
stands as centuries pass her by
Her leaning tells a story
a crown upon her dome
a pillar of Romanesque glory
to those who call Pisa home.