Epistemic Change in the Discourse on Comets in the 17th Century

Epistemic Change in the Discourse on Comets in the 17th Century. The Popularization of Knowledge in the Fields of Natural Philosophy, Astrology and Theology


Depiction of the cometary orbit in an anonymous pamphlet of 1665


This project is a research on vernacular pamphlets and broadsides on comets in the 17th century. It aims at a reconstruction of the early-modern discourses on this issue over about a hundred years starting with the great comet of 1577 and ending with the comets of the early 1680s. In historiography, the one of 1577 was long seen as the one with which Tycho Brahe, Michael Mästlin and others enfostered a new view on comets at odds with the still influential peripatetic tradition, according to which comets were seen as meteorological phenomena in the upper regions of air below the moon which would have led to an observable parallax. Since these mathematical astronomers could not determinate any parallax, they were forced to conclude that comets are supralunar objects belonging to the heavenly realm. The comets in the early 1680s, at the end of the period taken under scrutiny, were the first to be detected with a telescope – introduced into astronomical practice around 1610 – and by comparing historical and new observational data could be identified as periodic cosmic bodies. On that occasion, Edmond Halley was able to accurately calculate the path of the comet of 1682 and rightfully predicted its future return.

In the pamphlets, natural philosophical, astrological and theological approaches to the phenomenon comet were amalgamed in manifold ways. Thus, the different views on comets as natural objects, as a divine memento or as a sign to be astrologically interpreted inspired different forms of presentation and argumentation. These forms were often interwoven and elements of one field could be used to support claims of another. This study aims at a clarification of the ways in which these interconnections were established and what role they played in developing varied views on comets. Moreover, this project takes into account the repercussions of the cometary discourse on the disciplinary fields it was embedded in. The important astrological judgement of a comets significance as a harbinger of calamity and disaster and, to a lesser extent, also the theological-religious view of comets as signs of God that had to be deciphered, had to be based on observational data. Therefore, these interpretations indirectly fostered astronomical and natural philosophical knowledge. Natural doctrines were disseminated through the pamphlets and fulfilled certain purposes in the different areas of interpretation. In this context, astronomical knowledge was combined with edification and astrological advise. Furthermore, theoretical considerations on the nature of comets were often incorporated in the publications reflecting current debates and developments.

Although principally conservative in character, the vernacular pamphlets and broadsides helped to establish a new view on comets also in laymens audiences. On the other hand, observations accomplished also by non-experts and distributed through these publications, were on display to be examined and commented on by learned scholars as Tycho Brahe or Johannes Kepler in their Latin tracts for specialists. The popular discourse on the nature and meaning of comets reflects the existence of an early-modern astronomical culture connected to, rather than separated from, the academic world. Both realms influenced each other profoundly. Thus, also epistemic boundaries and the basic principles of the fields for which comets were relevant were continuously negotiated during the early modern period.