Around 1588, Galileo was asked by the Florentine Academy to settle a dispute over the shape of Dante’s hell, and took it seriously: a cone with its roof centred on Jerusalem, as wide as the Earth’s radius and at least 600 kilometres thick, the roof reasoned from Brunelleschi’s dome. He backed the Florentine Manetti over the Lucchese Vellutello — and the scaling problem he hit, a roof that thick collapsing under its own weight, is by Mark Peterson’s account where his physics began.