The Science of the Leaning Tower of Pisa

A silly tourist trap?

Perhaps, but the Leaning Tower of Pisa has been a must-see attraction for centuries, which in itself is a reason to go.

Pisa's most famous son, Galileo Galilei, is said to have climbed to the top of the famous bell tower in 1590 and dropped two cannonballs of different masses to prove that gravity would result in both falling at the same speed.

Indeed they did, thus disproving Aristotle's theory of gravity.  For almost 2,000 years, it had been accepted as scientific fact that objects fall at a rate proportional to their masses.

Anyone who has seen a leaf float down versus a rock plummeting understands why no one before Galileo challenged the wisdom of a venerated ancient Greek, but that difference in velocity is caused by the air itself creating friction that counteracts gravity subject to aerodynamics including shape of the objects.

In a vacuum, even a feather and a brick would fall at the same speed.

Galileo also invented an astronomical telescope --- though not the very first telescope --- with which he examined the heavens.  His observations led him to emphatically agree with the theory of Polish Renaissance mathematician Nicolaus Copernicus that the sun, not the earth, was at the center of our solar system.

Such blasphemy could not be tolerated by the Catholic Church, so Galileo was tried by the Inquisition and forced to recant his theories, which was about the worst thing that anyone could do to a brilliant scientist.

Galileo would become known as the Father of Modern Science, because he based his theories on real world experimentation and empirical observation rather than strictly on faith.

Galileo spent the remainder of his life under house arrest, but he would be vindicated by history, eventually also being called the Father of Observational Astronomy and the Father of Modern Physics.

It wasn't until 1992 that the Catholic Church finally agreed that Galileo was correct.

Long before Galileo rose to fame, infamy and then historical renown, Pisa was an important Mediterranean port for the Roman Empire and a hub of trade activity.

In addition to being a natural harbor on the Mediterranean coast, it had two major navigable rivers, the Arno and the Serchio.  This favorable location allowed it to prosper even as empires claiming it rose and fell.

With great wealth brought by trade, the city-state of Pisa eventually became a military naval power in its own right.  They fought in the First Crusade to re-take Jerusalem, sacking a few Mediterranean ports along the way.

At its zenith, the city-state of Pisa was more important to the Byzantine Empire than even Venice.

There are other beautiful historical buildings in Piazza dei Miracoli (Square of Miracles) besides the famous bell tower, and because of far more open area around them, it is somewhat easier to take in their grandeur than for historic buildings in Florence, where center-city growth has encroached upon them.

The star of Pisa, of course, remains its Leaning Tower, which has looked like it could fall over at any time for over 850 years.

Construction began in 1173, and within five years, the lean had already begun due to having laid an insufficient foundation only ten feet deep in soft soil in an area subject to possible earthquakes.  We actually encountered similar conditions in a Los Angeles house hunt with our son Jay when we learned one house could not be remodeled without consideration of "expansive soils."

By the completion of the second floor, the tilt of the tower base was pronounced, and construction ceased.

Meanwhile, wars with Genoa, Florence and Lucca distracted attention from the failed project for almost a century, during which period the soil had time to settle.

Engineers reasoned that if one side was built taller than the other, they could sort of straighten the tower out.  This added a curve to the structure, but it continued to tilt as it rose to its full height of 183 feet in stages, culminating in 1372 with the addition of the bell chamber.

Despite ever-so-slowly tilting a bit more each year, the Leaning Tower of Pisa never toppled over.

By 1990, however, the tower was leaning 5.5 degrees, forcing immediate action to save it for posterity.

With modern construction techniques, civil engineers worked from 1993 to 2001 to reduce the angle to 3.97 degrees, allowing many more generations of travelers to arrive and take pictures of loved ones seeming to either hold the 16,000-ton tower up with a finger or push it over with a kick.

Is Pisa worth seeing?

I think so, especially in conjunction with a visit to Florence.

That evening, we enjoyed a delicious Tuscan meal, but not in Pisa.  Instead, we dined at Toscana, one of the complimentary alternative dining venues aboard Oceania Riviera.  We made that reservation before leaving home in anticipation of capping off a great day in Tuscany with an approriate meal.  I thought it was the best dining experience on the cruise, even if I no longer remember exactly what we ate beyond the whimsically-sculpted artesanal bread and fresh olive oil.

I should note that our port was not in Pisa but rather Livorno, because the Roman Empire port of Pisa now lies about seven miles off the Mediterranean Coast, a result of accumulated alluvial deposits from the Arno and Serchio Rivers as well as naturally-occurring climate change over the centuries.