STEVEN ZUCKER:
We're in Florence. And we're standing
outside of the Duomo. BETH HARRIS: The
cathedral of Florence, and we're looking up
at Brunelleschi's dome. STEVEN ZUCKER: It's huge. Until St. Peter's, it
was the highest dome that had ever been raised. And in its width, it was
as wide as the Pantheon. BETH HARRIS: Almost. STEVEN ZUCKER: If you
think about the Duomo itself had been planned
in the 14th century. BETH HARRIS: The
plan was to build a dome that had a span nearly
equal to that of the Pantheon. STEVEN ZUCKER: And of
course, the Pantheon had been built in
the ancient world. And that technology
had largely been lost. BETH HARRIS: So
first and foremost, what Brunelleschi did was
an amazing engineering achievement. The challenge was
how to build a dome this wide without
wooden centering. Generally, when you
build an archway-- and the dome is
really just an arch-- STEVEN ZUCKER: In the round. BETH HARRIS: --in the round--
you put up a wooden framework. STEVEN ZUCKER: So
this is the wood to actually support
the dome until it can be locked in
place by the keystone. BETH HARRIS: Exactly. So you don't even
really need mortar to hold it together because
you've got the keystone. STEVEN ZUCKER: The problem
is that this was so big, they couldn't actually
get enough lumber, and lumber that was strong
enough, to hold the thing up until they could
lock it in place. BETH HARRIS: And
so there was no way to do wooden scaffolding
or centering to hold it up as it was being built. So how do you build this
dome that inclines inward and not have it fall down? STEVEN ZUCKER:
There's two problems. You've got that issue. And then you've got the problem
of it wanting to splay outward. BETH HARRIS: A dome exerts
pressure not only down, but down and out. And so one of the
biggest challenges is how to raise
the dome and deal with that downward
and outward pressure, not cracking the
walls underneath. STEVEN ZUCKER: Now,
in the ancient world, for the Pantheon, for example,
they had dealt with that by just creating sheer bulk. In other words, the walls
got to be 10 feet thick. BETH HARRIS: I think,
actually in the Pantheon, they're something like 20
feet thick of concrete. STEVEN ZUCKER: But Brunelleschi
couldn't do that here. So what he's done
instead is, first of all, he made the decision to make
the dome as light as possible. And that means that
it's basically hollow. It's a double shell. And within the
shell is a staircase that snakes around that allows
one to actually get to the top. And if you look, you can see
people just below the lantern, up at the top of the dome,
taking in the view of the city. BETH HARRIS: He
also created ribs. STEVEN ZUCKER: Which are doing
a lot of the weight bearing. BETH HARRIS: And then in between
each of the major ribs, which are visible on
the outside, there are two within
that we can't see. STEVEN ZUCKER: And those
are actually locked in place by a series of
horizontals, as well. So there's this whole
skeletal structure that's actually holding
this piece together. I think, most
importantly, he was able to develop a system where,
as the dome was being raised up, as each course of
stone and brick was added, it was actually locking
itself in place. And so it was self sustaining. BETH HARRIS: Another
way that Brunelleschi dealt with the downward
and outward thrust was to create chains
inside the dome made out of stone and wood, locked
together with iron, like a girdle, to
hold the dome in and to counter that
downward and outward thrust. STEVEN ZUCKER: You might think
of an old-fashioned wooden barrel that has a couple
of iron rings around it to help keep the wood together. BETH HARRIS:
Brunelleschi created cantilevered scaffolding. STEVEN ZUCKER: That could
rise as the building went up. BETH HARRIS: And so the
workmen had a place to work. Brunelleschi also built new
kinds of pulleys and hoists to bring up his heavy,
massive pieces of stone to the top of the dome. So he created this ox hoist,
just these remarkable machines that no one had
ever seen before. STEVEN ZUCKER: He actually
even designed a special barge to go down the Arno
to be able to bring the materials to
the city itself. If you think about the sheer
quantity of material that had to be imported, and
had to be hoisted up, and had to be put
in place, it is just this remarkable project. BETH HARRIS: Bricks that had
to be created, stone that had to be quarried and brought
here, platforms for the workmen to work on, machines
to hoist everything. And I think it was
Alberti who said something like, what Brunelleschi
did, he did without-- STEVEN ZUCKER:
--without a precedent. BETH HARRIS: Without having
any example to lean on. STEVEN ZUCKER: Utter invention. Now, we think that Brunelleschi
may have gone to Rome and may have studied
ancient architecture as well as sculpture there. But there is no precedent
in the ancient world, even, for what Brunelleschi
accomplished here. BETH HARRIS: Now, it's important
to say that the dome is not hemispherical, like the
dome on the Pantheon. STEVEN ZUCKER: It's
actually kind of tall. BETH HARRIS: Right. It's kind of pointed. In a way, it has more
of a Gothic shape than a classical shape. But in that way, it matches
the Gothic church itself. If you look closely, you
can see these exedrae, or blind tribunes,
that Brunelleschi added around the
outside of the dome. They actually look
very classical compared to the
Gothic church there. In fact, look like
Roman triumphal arches. So there's this curious
classical moment here in an otherwise
very Gothic church. STEVEN ZUCKER: And
it's a church that is not only Gothic, but
really referring back to the Tuscan
Romanesque tradition. Especially in terms of the
polychromy, the colored marbles, which Brunelleschi
also carries up into the barrel just below the dome itself. But ultimately, you've
got Brunelleschi, who, through his
engineering genius, is solving a problem the
Western tradition had never been capable of solving before. How does one span
this enormous space? And in order to do it, he's
surpassing the ancients that he's even here
paying reverence to.