Idea #619 – Climbing the steps of the Leaning Tower of Pisa to feel the effects of gravity
Piazza del Duomo is home to a collection of monuments known all over the world: the Leaning Tower of Pisa. On a vast green expanse surrounded by the city walls, the ancient Ospedale della Misericordia and the Palazzo dell’Arcivescovato, the Piazza del Duomo in Pisa forms one of the most famous built landscapes in the world.
The four masterpieces of medieval architecture – the cathedral, the baptistery, the campanile (the “Leaning Tower”) and the cemetery – were erected between the 11th and 14th centuries close to each other, constituting a unique set of monuments. A striking atmosphere permeates the site, emanating from the interplay of marble and mosaics, the alliance of bare walls and vaulted galleries, triangular pediments and heavy domes, all enhanced by the striking effect produced by the inclination of the campanile.
Construction of the building began on August 9, 1173, some ten years after work began on the cathedral, and spanned two centuries. By the time the addition of the third story was completed, around 1178, the tower had begun to tilt and construction was suspended for 90 years. The tower began to lean only a few years after construction began. Located on a particularly ungrateful site, the fluvial-marine alluvial plain of the mouth of the Arno, the tower undergoes subsidence due to differential settlements and leans even more since there are no foundations. Looking at it from the east or the west, “we see that it leans less up than down, because its plumb has visibly been gradually corrected during its construction: its successive builders have no doubt quickly understood that the basement of the site was not stable.”
Paradoxically, the tower was able to withstand no less than four strong earthquakes because the clay soil which is at the origin of its instability is also responsible for its capacity not to collapse in the event of an earthquake. From 1272, the four upper floors were therefore built diagonally to compensate for the inclination.
Construction then stopped again from 1301 to 1350 and it was not until 1372 that the last stage of the bells, of smaller diameter, was completed. Its inclination, which varies with time, is currently close to 4 °. According to specialists, it even seems that the tower is gradually recovering, under the effect of a deformation. Fortunately, the tower has undergone significant stabilization work, with injection of concrete to create new foundations and ensure sustainability. During its ascent, you will be surprised by the effect of gravity which confronts your inner ear…
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Where is it ?
Pisa Tower, Pisa Italia.