Construction of the cathedral began one hundred years before
construction of the dome was even considered. In fact, until the design
competition of 1418, no one was sure how the massive dome could be completed.
Filippo Brunelleschi became the man whose name is forever associated with
Florence’s most recognizable architectural feature—his dome.
The story of the dome (or more correctly, two domes, one
inside of the other), like Brunelleschi, is remarkable. Truly unprecedented in
world history, Brunelleschi’s plan for completion of the dome called for no internal
scaffolding or support on which or from which masons would build the two brick domes.
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| Brunelleschi admiring his dome |
The architectural genius of Brunelleschi—a goldsmith and
clockmaker by trade—called for eight teams of masons, each working on a
different panel of the dome(s), to raise their separate portion so that they
all converged at the top. Precise measurements of each successive layer of
bricks, which were gradually diminishing, as the dome grew taller, required perfect
horizontal and perpendicular coordination (while using the precise sloping inward
angle).
Brunelleschi’s solution to this essential dilemma remains a
mystery although in 1490 historian, Bartolomeo Scala theorized that
Brunelleschi stretched a stiffened cord from the precise center point to mark
the radius of the circle, which would mark the location and angle of each brick
relative to the midpoint. He believed the cord was shortened in successive
layers as the radius decreased from 70’ at the bottom to only 10’ at the top of
the outer dome. Several theories exist regarding how Brunelleschi could have
avoided slack in the cord, but no one has determined how he marked the centerline
of the dome. (Consider this: wooden poles, like ship’s masts were used on
smaller domes throughout Europe and the Middle East, but Brunelleschi’s dome
would have required a tree the size of a California Redwood!)
A secretive, rather mysterious man, Brunelleschi was
responsible for many, many contributing designs as well. For example, he
created an ox-driven wench to lift massive sandstone “belts” hundreds of feet
into the air (as well as more than 4,000,000 bricks). He designed the crane to
lift and center the cupola and lantern that sit atop the outer dome. (He was
even hired to design the massive—and massively unsuccessful—ship that carried
and sank losing hundreds of tons of granite in the River Arno. He then designed
the salvage efforts.)
Brunelleschi lived just long enough to see the cathedral
consecrated by St. Antoninus, the Archbishop of Florence in 1446. He died one
month later.
On a related note:
I’m on record regarding my thoughts on the connectivity of
life. Get this:
Filipo Brunelleschi was a friend of renowned mathematician,
Paolo Toscanelli. Having taught Brunelleschi the geometry of Euclid, Toscanelli
was repaid years in ways that truly changed the world.
As a hermit-like loner, Toscanelli spent most of his adult
life completing complex mathematical operations and studying the celestial
heavens. In 1475 when given the chance to climb to the top of Brunelleschi’s
dome, (with permission, of course) Toscanelli placed a bronze plate at the base
of the lantern at the apex. Designed to direct the sun’s rays to the floor of
the cathedral 300’ below, Toscanelli transformed the Duomo into a massive
sundial. Due to the dome’s height and stability, Toscanelli’s “sundial” allowed
him to gain unprecedented knowledge of the sun’s motions (and that of the earth
traveling around it) resulting in greater accuracy of the summer solstice and
vernal equinox (which made the church people happy because it resulted in a more
accurate determination of the date of Easter each year).
Toscanelli’s “sundial went beyond that. In the modern age of
global positioning it might be easy to forget that maritime navigation, especially
in the vastness of the open ocean, was once a very tricky and often lethal
business. Long-range navigation was accomplished with the aid of an astrolabe,
an instrument that astronomers used to calculate the position of the sun and
other stars relative to the horizon. By 1252 Spanish astronomers had compiled
the Alfonsine Tables, which were used by sailors to calculate relative
positions. Two hundred years later, navigation was still dependent on the
Tables, and inaccuracies made trans-oceanic travel dubious at best. Toscanelli
was able to correct and refine the Alfonsine Tables through the data collected
by his “sundial.”
As far back as 1459 Toscanelli interviewed a number of
Portuguese sailors familiar with India and the west coast of Africa in an attempt
to create an accurate world map. In 1474 Toscanelli was convinced that access
to India was possible via the Atlantic. His pleas to the king of Portugal fell
on deaf ears, but in 1481 a Genoese sea captain named Christopher Columbus
contacted Toscanelli regarding his theory. (Toscanelli estimated the distance
at approximately 6,500 miles. It's more like 25,000. Hey, even Babe Ruth struck our some of the time.)
Despite Columbus’s claim that neither maps not mathematics
were of any use to him, there is very little doubt that Columbus’s historic
voyages were made possible because of Toscanelli’s calculations taken from data
compiled under Brunelleschi’s dome.
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