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Video transcript

we're in Florence and we're standing outside of the Duomo the Cathedral of Florence and we're looking up at Brunelleschi's dome it's huge until st. Peters it was the highest known that had ever been raised and in its width it was as wide as the Pantheon almost if you think about the Duomo itself had been planned in the 14th century the plan was to build a dome that had a span nearly equal to that of the Pantheon and of course the Pantheon had been built in the ancient world and that technology had largely been lost right 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 in the dome is really just an arch in in the round in the round you put up at wooden framework so this is the wood to actually support the dome until it can be locked in place by the Keystone exactly so you don't even really need Mordor to hold it together because you've got the Keystone the problem is is 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 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 there's two problems you've got that issue and then you've got the problem of it wanting to splay outward 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 now in the Asian world for the Pantheon for example they had dealt with that by just creating sheer bulk in other words the walls got to be ten feet thick I think actually in the Pantheon have something like 20 feet thick of concrete 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 bay basically hollow it's a double shell and within the shell is a staircase it snakes around that allows one actually get to the top and if you look you can see people just below the lantern up at the top of the dome but taking in the view of the city he also created ribs you're doing a lot of the weight bearing and then in between each of the major ribs which are visible on the outside there are two within that we can't see 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 another way the 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 you might think of an old-fashioned wooden barrel that has a couple of iron rings around it to help keep the wood together Brunelleschi created cantilevered scaffolding that could rise as the building went up 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 we created this ox hoist the just is remarkable machines that no one had ever seen before 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's just this remarkable bricks bricks that had to be created stone that had to be quarried and brought here platforms for the workmen to work on machines waste everything and I think it was Albert II who said something like what Brunelleschi did we did without precedent right without having any example to not utter invention now we think the 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 no it's important to say that the dome is not hemispherical like the dome on the pants actually kind of tall 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 xzj or blind tributes 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 and otherwise very gothic church and is 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 you you