Figures and Mirrors in Demetrios Triklinios's 'Selenography'

This article is about the interplay between diagrammatic representation, the mediation of mirrors, and visual cognition. It centres on Demetrios Triklinios (fl. ca. 1308–25/30) and his treatise on lunar theory. The latter includes, first, a discussion of the lunar phases and of the Moon's position in relation to the Sun, and second, a narrative and a pictorial description of the lunar surface. Demetrios Triklinios's Selenography is little-known (though edited in 1967 by Wasserstein) and not available in translation into a modern scholarly language. Therefore, one of the main goals of the present article is to introduce its context and contents and to lay down the foundations for their detailed study at a later stage. When discussing the Selenography, I refer to a bricolage consisting of the two earliest versions of the work preserved in Bayerische Staatsbibliothek, graecus 482, ff. 92r–95v (third quarter of the fourteenth century) and Paris, Bibliothèque nationale de France, graecus 2381, ff. 78r–79v (last quarter of the fourteenth century). I survey the available evidence concerning the role of Demetrios Triklinios (the author), John Astrapas (?) (the grapheus or scribe-painter), and Neophytos Prodromenos and Anonymus (the scribes-editors) in the production of the two manuscript copies. Next, I discuss the diagrams included in the Selenography and their functioning in relation to Triklinios's theory concerning the Moon as a mirror reflecting the geography of the Earth, on the one hand, and to the mirror experiment described by Triklinios, on the other. Finally, I demonstrate how, even though the Selenography is a work on lunar astronomy, it can also be read as a discussion focusing on the Mediterranean world and aiming at elevating its centrality and importance on a cosmic scale.

John Couch Adams: mathematical astronomer, college friend of George Gabriel Stokes and promotor of women in astronomy

John Couch Adams predicted the location of Neptune in the sky, calculated the expectation of the change in the mean motion of the Moon due to the Earth’s pull, and determined the origin and the orbit of the Leonids meteor shower which had puzzled astronomers for almost a thousand years. With his achievements Adams can be compared with his good friend George Stokes. Not only were they born in the same year but were also both senior wranglers, received the Smith’s Prizes and Copley medals, lived, thought and researched at Pembroke College, and shared an appreciation of Newton. On the other hand, Adams’ prediction of Neptune’s location had absolutely no influence on its discovery in Berlin. His lunar theory did not offer a physical explanation for the Moon’s motion. The origin of the Leonids was explained by others before him. Adams refused a knighthood and an appointment as Astronomer Royal. He was reluctant and slow to publish, but loved to derive the values of logarithms to 263 decimal places. The maths and calculations at which he so excelled mark one of the high points of celestial mechanics, but are rarely taught nowadays in undergraduate courses. The differences and similarities between Adams and Stokes could not be more striking. This volume attests to the lasting legacy of Stokes’ scientific work. What is then Adams’ legacy? In this contribution, I will outline Adams’ life, instances when Stokes’ and Adams’ lives touched the most, his scientific achievements and a usually overlooked legacy: female higher education and support of a woman astronomer. This article is part of the theme issue ‘Stokes at 200 (part 2)’.

Ptolemy

The chapter surveys the work of Ptolemy (Claudius Ptolemaeus), who wrote on astronomy, cosmology, astrology, geography, optics and harmonics and who placed several fields of study into forms that remained definitive until the Renaissance. His astronomical Syntaxis (or Almagest) gave theories of the motions of the sun, moon, and planets that were highly successful in representing the angular motions of the bodies, although his lunar theory exaggerated the variation in distance. The cosmological consequences of this world view were developed in a separate work, the Planetary Hypotheses. Of the surviving ancient treatises on astrology, Ptolemy’s is the most rationalized and orderly and attempts to justify this art in terms of philosophy. His geographical work provides instructions for projecting a world map and an extensive gazetteer of sites. In both his astronomy and his harmonics Ptolemy built and described a suite of instruments. His book on optics includes experiments aimed at determining a law of refraction.

The First Jewish Astronomers: Lunar Theory and Reconstruction of a Dead Sea Scroll

ArgumentThe Astronomical Book of Enoch describes the passage of the moon through the gates of heaven, which stand at the edges of the earth. In doing so, the book describes the position of the rising and setting of the moon on the horizon. Otto Neugebauer, the historian of ancient science, suggested using the detailed tables found in later Ethiopic texts in order to reconstruct the path of the moon through the gates. This paper offers a new examination of earlier versions of the Astronomical Book, using a mathematical analysis of the figures and astronomical theories presented throughout the Aramaic Astronomical Book; the results fit both the data preserved in the scrolls and the mathematical approach and religious ideology of the scroll's authors better than the details found in the late Ethiopic texts. Among other new insights, this alternate theory also teaches about the process of the composition of the Astronomical Book in the first centuries of its composition.

Methodological Issues concerning the Astronomy of Qumran

In the 21st issue of Dead Sea Discoveries, Dennis Duke and Matthew Goff offered their collaboration as physicist and Dead Sea Scrolls scholar in order to study the lunar theory of the Aramaic Astronomical Book (aab). They use the astronomical model of lunar elongation—the angular distance between the moon and the sun on the observed heavenly sphere—to compute the times of the moon’s visibility and invisibility. They conclude that the times written on the Aramaic fragments are closer to reality than the times written in the Babylonian sources of the aab. This paper concludes that lunar elongation is not the best explanation of the astronomical data of the aab, and Duke and Goff’s computations should be refined according to some astronomical, cosmological, textual, and historical considerations.