SOURCE: "Tycho's Book on the Comet of 1577 and His System of the World," in Tycho Brahe: A Picture of Scientific Life and Work in the Sixteenth Century, Dover Publications, Inc., 1963, pp. 158-85.

In the following excerpt, originally published in 1890, Dreyer assesses Brahe 's De mundi—a monograph on the comet of 1577, which contains Brahe's elaboration of his planetary system. Dreyer additionally comments on the state of astronomy in the sixteenth century and the overall significance of Brahe's theories.

The year 1588 is one of great importance in the life of Tycho Brahe, not only because his firm friend and benefactor died in that year, but also because he then published a volume containing some of the results of his work at Uraniborg, and embodying his views on the construction of the universe. The subject specially dealt with in this volume was the great comet of 1577, the most conspicuous of...