Johannes Kepler, Astronomia nova (Prague, 1609)
The discovery that overturned two millennia of astronomical thought
Kepler’s demonstration that planetary motion follows an elliptical path.
A considerable portion of St John’s manuscripts and early printed books contain scientific works. An exceptional treasure among these is a first edition of Astronomia nova by Johannes Kepler (1571–1630). First published in Prague in 1609, it stands among the most transformative works in the history of science. Written while Kepler served as Imperial Mathematician to Emperor Rudolf II, the book presents the results of nearly a decade of painstaking analysis of planetary observations, many inherited from Tycho Brahe.
Kepler rejected the long-held belief that the heavens moved in perfect circles. His work demonstrated that the orbit of Mars is elliptical, with the Sun at one focus. From this he derived two of the laws of planetary motion: that planets travel in ellipses and that they sweep out equal areas in equal times. These conclusions overturned centuries of classical and medieval cosmology. Moreover, they provided the mathematical foundation on which later astronomers, including Newton, would build.
Unlike many scientific treatises of its day, Astronomia nova reads almost as a working notebook. Kepler preserves false starts, revisions, and calculations, allowing the reader to follow the process of discovery step by step. The volume is therefore not only a statement of results but a rare record of scientific reasoning in action.
This copy was donated to St John’s College by John Edwardes in 1620.