April 1, 2025

The Leaning Tower of Pisa and Galileo Galilei

Pisa is a port town located 90 kilometers west of Florence, at the mouth of the Arno River where it flows into the Ligurian Sea.

During its peak (11th–13th centuries), Pisa reigned over the Mediterranean as a maritime trading state alongside Venice, Genoa, and Amalfi.

In the 16th century, when Pisa gained fame as a university city, Galileo Galilei was born here.

Galileo taught at the University of Pisa and solidified the institution's reputation in the sciences.

Speaking of Pisa, one cannot overlook the Leaning Tower, Italy’s most famous building.

Construction of this bell tower, an annex to the adjacent cathedral (Duomo), began in the 12th century—during Japan’s Heian period.

Due to the weak foundation on the marshy ground, the tower began to tilt shortly after construction started.

Despite several interruptions in the building process, the tower was completed in the 14th century (Japan’s Muromachi period), about 200 years after its inception, with a tilt of approximately five degrees.

The tilted tower’s height measures 55.2 meters on the northern side and 54.5 meters on the southern side, creating a 70-centimeter difference.

The topmost level is displaced by three meters relative to the base.

Galileo Galilei famously conducted an experiment using this tilted tower.

He challenged Aristotle’s claim that "the speed of a falling object is proportional to its weight"—a widely accepted idea in ancient Greece.

To disprove this, Galileo dropped two lead cannonballs of different sizes from the southern tip of the tower's roof.

Lead cannonballs were used because their high density and small volume minimized air resistance.

The result?

Both cannonballs hit the ground simultaneously.

This confirmed that "in the absence of air resistance, the speed of a falling object is independent of its weight."

Galileo later published this groundbreaking discovery in the 17th century in his work Dialogue Concerning Two New Sciences, which introduced the famous Law of Falling Bodies.

As mentioned in the Florence episode, Galileo Galilei applied the method of "direct observation and verification" to his work in astronomy and physics.

He emphasized observation and believed that experiments were essential to validate his theories.

While this approach is considered fundamental today, it was revolutionary at the time, standing in opposition to deeply rooted traditions and the powerful Catholic Church.

Nevertheless, Galileo remained undeterred, continuing his research with unyielding faith in his own convictions.