Bearing the Heavens: Tycho Brahe and the Astronomical Community of the Late Sixteenth Century (review)

The Danish nobleman Tycho Brahe (1546–1601) practiced a unique combination of feudalism and science on the small island of Hven, which the King of Denmark assigned to him, together with an appropriate income, to build an observatory, perfect astronomy, cast horoscopes, reflect glory on the monarchy, and teach doctors astrology. Tycho had two fiefs on Hven. One was the island and its inhabitants, who owed him the labor with which he built a palace observatory (Uraniborg) with guest rooms, a library, and an alchemical laboratory; another observatory (Stjerneborg) stocked with instruments unusually large and accurate for their time; and outbuildings, orchards, fish ponds, and vegetable gardens. Uraniborg stood at the centre of a formal square garden patrolled by large dogs and enclosed by massive walls. Hven's second fief was the bounteous information produced by the instruments and their attendants—Tycho's students and visitors—who found it the more difficult to leave the island the higher their mathematical skills and the lower their social status. Tycho guarded his measurements as carefully as he did his palace until he published them from his own press, also located on Hven.

All historians of science know that Tycho lost half his nose in a duel; that he invented a planetary system in which the sun, carrying the planets, circles around an immobile earth; that he exploded the rigid solid heavens of late scholasticism by showing that comets moved freely through the spaces that the solids were supposed to occupy; that he fought continually over his priority as a world builder; that his unprecedented program of sustained regular measurement of celestial coordinates made a hoard that could revolutionize astronomy; and that his last mathematical assistant, Johannes Kepler, whom he engaged at Prague after a new Danish king had expelled him from Hven, made the revolution.

Mosley's Bearing the Heavens is a late entry in a professional historical literature that goes back to, and depends upon, Tycho's work and correspondence published more than seventy-five years ago.¹ Some notable recent exploitations of this and cognate material—by Thoren, Christianson, and Gingerich and Westman—have recounted Tycho's life and work, the doings on Hven, and the travels of sixteenth-century astronomers in detail.² They have left Mosley with slim pickings, mainly in the correspondence, for what his publisher's blurb describes as a "ground-breaking" book. He appears to have the tools for deep excavation in the Tychonic mines—the languages, the sciences, energy, resourcefulness, and patience—but, despite his several claims to have found the mother lode that his predecessors missed, his prodigious digging has uncovered no new seams and not many nuggets. Among the by-products of Mosley's systematic industry are lists of the owners of Tycho's books during his lifetime, an extensive bibliography, and an index of Tycho's correspondents.

Mosley devotes much of his book to the Epistolae astronomicae, a collection of letters put together, annotated, and published by Tycho in 1596 as the first volume of a series that he did not continue. The reasons for this publication, as Mosley reconstructs them, were to distribute (and advertise) information about the stars and about Hven, and to curry favor with the son of Landgrave Wilhelm IV of Hesse-Kassel, whose correspondence figures prominently in Tycho's book. Mosley squeezes the Epistolae for information about instruments, gifts, world systems, travel, books, and letters. He is able to affirm, what only people bamboozled by recent histories of the book would doubt, that correspondence and books were important to the advancement of science. In his most useful and original chapter, which discusses Tycho's celestial spheres and their manufacture in the Netherlands, Mosley enlarges on the theme of travel undertaken to see, sell, deliver, or copy books and instruments.

One promising direction in which Mosley heads but does not travel far is indicated by his title, Bearing...