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Why Does the Leaning Tower of Pisa Lean?

In 1172, Donna Berta di Bernardo donated sixty silver coins to the local cathedral for the purchase of stones to be used in the base of a new bell tower.

The next year, construction on the tower began and almost immediately there were problems. The tower site sat on soft ground composed mostly of clay, fine sand, and shells (the city sits between the Arno and the Serchio rivers). By the time the builders finished the second floor in 1178, the tower was beginning to lean.

Soon, construction was halted for almost 100 years, as Pisa fought wars against Genoa, Lucca and Florence. This may have been a lucky break, as modern analysis says that the tower definitely would have toppled had construction continued without time for the soil to settle.

When work on the tower started again, it was leaning 0.2 degrees north of vertical, but by the time the workers started on the seventh floor, the tower was tilting one degree south. Around this time, construction stopped again for unknown reasons.

Don't Lean on Me

Over the next century, construction continued intermittently.

The tower’s lean gained another 1.6 degrees. To counteract the lean, the builders made the remaining floors taller on the south side of the tower. But the weight of the additional floors only made the foundation sink further, making the lean worse. Having done what they could, the builders finished up and officially completed the tower around 1370.

Since the tower’s completion, engineers and architects from all over the world have monitored the lean and tried to correct it. These attempts have involved adding grout to the foundation masonry, wrapping plastic-coated steel pieces around the tower up to the second floor, pouring a concrete ring around the base of the tower, laying lead counterweights to the north side, installing anchored cable counterweights, and extracting soil from underneath the north side.

After the removal of more than 70 metric tons of soil in 2008, engineers announced that the Tower had been stabilized enough that it had stopped moving for the first time since construction began. Its lean is now only about 4 degrees (prior to the all the restoration attempts, the lean was 5.5 degrees), or about 13 feet past perfectly vertical. The Leaning Tower of Pisa should be stable for at least the next 200 years.

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History
The Secret World War II History Hidden in London's Fences

In South London, the remains of the UK’s World War II history are visible in an unlikely place—one that you might pass by regularly and never take a second look at. In a significant number of housing estates, the fences around the perimeter are actually upcycled medical stretchers from the war, as the design podcast 99% Invisible reports.

During the Blitz of 1940 and 1941, the UK’s Air Raid Precautions department worked to protect civilians from the bombings. The organization built 60,000 steel stretchers to carry injured people during attacks. The metal structures were designed to be easy to disinfect in case of a gas attack, but that design ended up making them perfect for reuse after the war.

Many London housing developments at the time had to remove their fences so that the metal could be used in the war effort, and once the war was over, they were looking to replace them. The London County Council came up with a solution that would benefit everyone: They repurposed the excess stretchers that the city no longer needed into residential railings.

You can tell a stretcher railing from a regular fence because of the curves in the poles at the top and bottom of the fence. They’re hand-holds, designed to make it easier to carry it.

Unfortunately, decades of being exposed to the elements have left some of these historic artifacts in poor shape, and some housing estates have removed them due to high levels of degradation. The Stretcher Railing Society is currently working to preserve these heritage pieces of London infrastructure.

As of right now, though, there are plenty of stretchers you can still find on the streets. If you're in the London area, this handy Google map shows where you can find the historic fencing.

[h/t 99% Invisible]

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Guillaume Souvant, Getty Images
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This Just In
For $61, You Can Become a Co-Owner of This 13th-Century French Castle
Guillaume Souvant, Getty Images
Guillaume Souvant, Getty Images

A cultural heritage restoration site recently invited people to buy a French castle for as little as $61. The only catch? You'll be co-owning it with thousands of other donors. Now thousands of shareholders are responsible for the fate of the Château de la Mothe-Chandeniers in western France, and there's still room for more people to participate.

According to Mashable, the dilapidated structure has a rich history. Since its construction in the 13th century, the castle has been invaded by foreign forces, looted, renovated, and devastated by a fire. Friends of Château de la Mothe-Chandeniers, a small foundation formed in 2016 in an effort to conserve the overgrown property, want to see the castle restored to its former glory.

Thanks to a crowdfunding collaboration with the cultural heritage restoration platform Dartagnans, the group is closer than ever to realizing its mission. More than 9000 web users have contributed €51 ($61) or more to the campaign to “adopt” Mothe-Chandeniers. Now that the original €500,000 goal has been fulfilled, the property’s new owners are responsible for deciding what to do with their purchase.

“We intend to create a dedicated platform that will allow each owner to monitor the progress of works, events, project proposals and build a real collaborative and participatory project,” the campaign page reads. “To make an abandoned ruin a collective work is the best way to protect it over time.”

Even though the initial goal has been met, Dartagnans will continue accepting funds for the project through December 25. Money collected between now and then will be used to pay for various fees related to the purchase of the site, and new donors will be added to the growing list of owners.

The shareholders will be among the first to see the cleared-out site during an initial visit next spring. The rest of the public will have to wait until it’s fully restored to see the final product.

[h/t Mashable]

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