Abstract

Simon Marius argued in his 1614 Mundus Iovialis that telescopic observations of stars supported Tycho Brahe over Copernicus. Prior to the advent of the telescope, Brahe’s was a powerful voice against the Copernican theory. Brahe used observations and calculations regarding the sizes of stars to produce what, at the time, appeared to be a formidable scientific case against Copernicus. The advent of the telescope raised questions about the true sizes of stars. Marius appears to have been the first astronomer to argue that the telescope supported Tycho. Today Marius’s support for Tycho might seem to have been an error. Yet it in fact illustrates Marius’s skill as an astronomer. It also contrasts Marius favorably with Galileo, who also made telescopic studies of stars but did not share all his results. The tricky nature of telescopic observations of stars in the early seventeenth century, and why Marius was right, even though he was wrong, will be the focus of this paper.