Galileo Galilei

About this figure

Galileo Galilei (1564-1642) was born in Pisa and spent his career moving between the mathematics chairs of two Italian universities, Pisa and Padua, before an invention he did not create made him famous. Spectacle-makers in the Netherlands had already built simple spyglasses; in 1609 Galileo heard of the device, worked out how to grind and combine lenses to sharpen and magnify it, and became the first person to turn one systematically on the night sky. What he saw he published within months in The Sidereal Messenger (1610): mountains and craters pockmarking the supposedly perfect surface of the Moon, a Milky Way resolved into countless individual stars, and four moons circling Jupiter, a miniature solar system that undercut the old assumption that everything in the heavens must orbit the Earth. He dedicated the discovery of Jupiter's moons to his patron Cosimo II de' Medici, naming them the "Medicean Stars," and the book made him a European celebrity almost overnight.

Galileo's other major early book, the Discourse on Bodies in Water (1612), was not astronomy but physics: a defense, against Aristotelian critics in Florence, of why some solids float and others sink, argued through careful attention to shape, density, and the behavior of water itself rather than received authority. That habit of testing inherited doctrine against observation and calculation ran through his whole career, and it put him on a collision course with the Catholic Church once he began defending the Copernican, sun-centered model of the cosmos. In 1616 Church authorities warned him against teaching Copernicanism as established fact; in 1632 he published his Dialogue Concerning the Two Chief World Systems anyway, arguing the case through three fictional speakers. The Roman Inquisition tried him in 1633, forced a recantation, and confined him for the rest of his life to house arrest at his villa in Arcetri, near Florence, where he eventually went blind.

House arrest did not stop him working. In 1638, with the help of Dutch publishers since no Italian press would touch it, he brought out Dialogues Concerning Two New Sciences, his last and in some ways most influential book, using the same three characters, Salviati, Sagredo, and Simplicio, from the earlier Dialogue. Framed as conversations that open with a visit to the Venetian Arsenal and its shipbuilders, it laid out his findings on the strength of materials and, above all, on motion: the mathematics of falling bodies and projectiles that would underpin the physics Isaac Newton built decades later. Galileo died at Arcetri on 8 January 1642, still formally a prisoner of the Inquisition; the Church did not lift the ban on his Dialogue until the 1820s.

Written by Epoch Voices. Not the figure’s own words.