Explain how no one had created a dome with so large a span since antiquity and that the knowledge of this process had been lost.

What will be an ideal response?

Brunelleschi had to create new methods whereby the expanse of the dome could be supported during construction. Brunelleschi used a skeleton of eight large ribs alternating with eight pairs of thinner ribs beneath the roof, all tied together by nine sets of horizontal ties, which would be able to support themselves as the dome took form.