• DOI:10.1086/350839
• Corpus ID: 120700705

Theory and Observation in Medieval Astronomy

@article{Goldstein1972TheoryAO,
  title={Theory and Observation in Medieval Astronomy},
  author={Bernard R. Goldstein},
  journal={Isis},
  year={1972},
  volume={63},
  pages={39 - 47}
}

• B. R. Goldstein
• Published 1 March 1972
• Physics
• Isis

T HERE IS NO MODERN STUDY of the relationship between theory and observation in medieval astronomy, as far as I am aware. A number of modern astronomers, foremost among them Simon Newcomb, have discussed medieval observations with regard to their accuracy and usefulness for the determination of certain astronomical parameters.' Moreover, historians of astronomy have devoted much effort to the elucidation of various medieval modifications of ancient theories.2 But the impression one gains from reading these many studies is that theory and observation developed in isolation from one another. In the course of my researches I began to realize that this picture was seriously in need of revision and that some medieval astronomers had a much better understanding of the procedures and aims of ancient scientists than they have been given credit for. They not only held the view, already prevalent in antiquity, that observations should be used to test and construct theories, but they succeeded in applying it as well. One difficulty they faced was that the formidable achievements of Ptolemaic astronomy seemed to allow little room for improvement. Indeed, the theoretical advances introduced by Kepler rested on the observations of Tycho Brahe, which were clearly more accurate than those available to medieval astronomers. This paper is not intended to exhaust all known discussions of theory and observation in medieval astronomy, but simply to call attention to some illustrative passages that I have recently uncovered. That the passages are largely drawn from Hebrew and Arabic sources is not entirely a reflection of my own interests, for the evidence seems to suggest that these questions were not as actively pursued in the Latin West. One may note that observations of phenomena not discussed in the Almagest, such as planetary brightness, transits, and even comets, were introduced to resolve problems arising out of Ptolemaic astronomy. Moreover, at least one lunar theory introduced in the Middle Ages was based on a new set of observed lunar positions, and Levi ben Gerson, who constructed it, had reason to believe it was superior to Ptolemy's lunar theory. Finally, solar eclipses were used to test and modify astronomical theories, although Ptolemy did not record or use any such observations in the Almagest. In effect, the ancient texts served as a point of departure for subsequent developments in astronomy and were not understood as setting firm limits on the range of topics worthy of consideration. Throughout the history of astronomy, beginning with the Babylonian astronomers,