Clues of observations practices Astronomy and natural sciences in late medieval Europe (Latin, Arabic and Hebrew)
3-4 December 2019,
ENS Paris Salle de l’IHMC
45 rue d’Ulm 75005 Paris
Escalier D, third floor
Org.: José Chabas, Matthieu Husson, Richard Kremer, Laure Miolo
Argument
A wealth of historical and philosophical studies of scientific observation has produced valuable methodological insights and a better understanding of different practices of observation in numerous historical contexts (e.g. L daston, 2011, K. Park 2011). Other studies have also demonstrated the links between observations and experiments and explored the medieval terminology of these interrelated notions, their connection to different kinds of reasonnings and computations (D. Jacquart, 1996). However, historical analysis of observation in pre-modern scientific traditions remains a complex task for the historian because of the difficulties to escape the various modern conceptions that flourished at least since the 18th centuries and the ideological weight attached to the study of the place of observation in a given scientific tradition. These general issues tends to obscure the historical sources themselves and the historian of pre-modern scientific traditions is therefore often faced with the fundamental problem of identifying clues of observation in them.
This situation is especially acute in the history of astral sciences where the evolving relations of observations, instruments, computations, and theory are central in particular to mathematical astronomy. As one of its important general aims regarding astronomical practices, ALFA seeks for a better understanding of the different kinds of observations practiced in the Alfonsine traditions, their mutual relations and their contexts. This enhanced understanding is a necessary step toward a survey of astronomical observations including, when pertinent, elements such as: dates, locations, actors involved, phenomena observed, methods used, or epistemic aims. Most Alfonsine astronomers were trained in arts faculties to natural philosophy and intermediate sciences (optics, music, meteorology…) with some of them pursuing their studies in medicine or theology. Moreover, some alfonsine astronomers wrote and worked in disciplines outside mathematical astronomy (e.g. Jean des Murs, Prodoscimo Beldomandi, …) and many manuscripts reflect this diversity of practices. Thus, it seemed important for us, in an initial approach to the topic, to include also these other disciplines as ideas, practices, ways of recording observations might well carry over from one discipline to another. In the same line of thought it essential to include sources in Hebrew and Arabic produced in Europe during the late medieval and early modern period or shortly before in order to trace transmission, interactions, overlap and contrast.
This workshop attempt to explore these issues by focusing first on clues of observation in the sources. In this way we hope to broaden the scope of what we are able to recognize as an observation in late medieval and early modern scientific practices and thus to build an enhanced understanding of how observations of various kinds nourished different sciences during these periods. This general aim can be addressed through multiple angles. These includes at least the following three broad categories:
- Documentary aspects and material culture of observations practices: What are the writing format of observation statements? How are observation reports materially integrated in larger textual structures, in curriculum? Can we find clues of observations beside the various kind of direct observations statements? In other words: can we identify indirect clues of observations in our sources? In the opposite: are all observation report truly reporting an observation? If case of “fake” observation report are found what does this mean for observation and its status? What kind of instruments, in a broad sense (e.g. including manuscripts), could be used in relation to observation? How do we know about these instruments, (e.g. through specific kinds of text dedicated to them, through archeological remains, through observation ‘records’ including chronicles, almanac or miniatures)? How are diagrams or numerical tables used in observation or in reporting observations?
- Temporality and collective aspects of observations practices: Are there kinds of observations made alone and others made in group? In case of group what are the roles of the different actors involved? How is information about the observation shared within the group? What is the temporality of observation? How does this affect the collective aspect of observation (in astronomy observation can often range on very long time span)? How does this affect the way information from observation are reported and transmitted? Who owned instruments, individuals, institutions? Were they made ad hoc or the result of a stabilised standardised production? Are they object of prestige or social symbols of specific kind of knowledge (e.g. astronomer are very often portrayed with an astrolabe on medieval miniatures)? What were materials employed for constructing instruments? What were their cost?
- Epistemological aspects of observations practices: What are the phenomena observed and defined by different kinds of observations? How are observations made visible in scientific reasoning of different sorts (computations, predictions, deductions, diagnosis)? How is observation used differently to legitimize the scientificity of a given discipline, its boundary, its methodology? How do instruments take part in various types of observations and contribute to shape them in theoretical ways? More fundamentally, what kind of skills are required to manipulate these instruments? What are the limitations of instruments? Is there a codification of observation practices with instruments?
In order to foster awareness about evidences of observations practices along these lines we will seek to set an open discussion between specialists of sciences, technologies and philosophies but also arts historians, historian of material culture interested in this endeavour. This discussion shall be articulated around specific case studies presented by the different contributors that address some of the question listed above or related ones.
Program
3 December 2019
9:15-10:00
Matthieu Husson: Welcome and Opening with a “flash talk” by Nick Jacobson
10:00-11:00
Benno van Danlen
Observations in Islamic Astronomy: Attested and Implicit
11:00-11:30 Break
11:30-12:30
Mohammed Mozzafari In absentia
Telling history in astronomical rigor: how the technical analyses can help us to better understand the ancient and astronomical corpus
12.30-14:00 Lunch Break
14:00-15:00
Emmanuelle Kuhry
Observation in university teaching : the case of the glossa anglicana
15:00-16h00
Josefina Rodríguez-Arribas
Astrolabes in Medieval Hebrew Sources: Features, Uses, and Availability
16:00-16:30 Break
16:30-17:30
Laure Miolo
Observational or non-observational practices? Lewis Caerleon and the solar eclipses of 1481, 1482 and 1485
4 December
9:00-10:00
Jarosław Włodarczyk
The Torquetum: Is It an Observing Instrument?
10:00-11:00
Richard Kremer
Observation in the margins? Astronomical measurements and armillary spheres, 1312-1544
11:00-11:30 Break
11:30-12:30
Laurence Moulinier-Brogi
L’examen de l’urine était-il nécessaire au diagnostic et au pronostic au Moyen Âge ?
12:30-14:00 Lunch break
14:00-15:00
Samuel Gesner
Ad salvandam diversitatem in motu fixorum: thinking about observation in assessing Werner’s trepidation theory
15:00-16:00
Matthieu Husson
Uses of observation in astronomical reasonings: John of Murs and John of Lignères on the eigth sphere
16:00-16:30 Break
16:30-17:00
Concluding discussion
Abstracts
Josefina Rodríguez-Arribas
Astrolabes in Medieval Hebrew Sources: Features, Uses, and Availability
My paper focuses on the contribution of Jews to the field of astrolabe knowledge. The Jewish chapter in the history of medieval instruments has been disregarded possibly because of the unchallenged assumption that Jews copied practically everything from Arabic and Latin sources. I will present an early fifteenth-century Hebrew treatise on the construction of astrolabes that is a good example of how often mathematical instruments and texts are engaged in a tacit conversation that only becomes audible putting them side by side. I will use this specific text to reflect on the construction, methods, materials, availability, contexts, and uses of astrolabes during the Middle Ages in Jewish contexts and their dialogue with non-Jewish texts and astrolabes.
Benno van Dalen (Bavarian Academy of Sciences and Humanities, Germany)
Observations in Islamic Astronomy: Attested and Implicit
From the late ninth century onwards, astronomers in the Islamic realm made observations in order to improve upon the parameter values of the planetary models in Ptolemy’s Almagest, which after more than six centuries were found to lead to incorrect predictions of heavenly phenomena. Among the most important and well-known observational programs are those under the caliph al-Maʾmūn in Baghdad and Damascus (ca. AD 830), that at Maragha (northwestern Iran, from 1258 onwards) under the supervision of Naṣīr al-Dīn al-Ṭūsī, and that at Samarqand (now in Uzbekistan, from 1428 onwards) instigated by the Timurid ruler Ulugh Beg. But also observations by private scholars such as al-Battānī (Raqqa in Syria, ca. 880–900) and smaller scale programs such as those carried out by Ibn al-Aʿlam in Baghdad and by al-Khujandī near Tehran (both in the 2nd half of the 10th century) are known to have taken place. [For an excellent overview, see Aydın Sayılı, The Observatory in Islam and its Place in the General History of the Observatory, Ankara: Turkish Historical Society, 1960 (reprinted: 1998).] Only in incidental cases did Islamic astronomers follow Ptolemy’s Almagest in describing accurately which observations they made and how they determined new values of the planetary parameters from these observations. In other cases we have only their astronomical tables (included in handbooks called zīj in Arabic and Persian, of which more than one hundred different ones survive), from which the used parameters can be extracted by numerical or statistical means. In my presentation I will show how a database of astronomical parameters and the careful comparison of values of these parameters underlying tables in primary sources can help us in judging whether some of these may be assumed to be based on original observations, even if these are nowhere explicitly mentioned in historical sources. For this I will use the example of the Islamic astronomers who worked for the Mongol rulers of China in the last quarter of the 13th century. The zīj that these astronomers produced is only extant in Chinese, is fully based on Ptolemy’s planetary models but on mostly new values of the underlying parameters.
Emmanuelle Kuhry (IRHT-CNRS Orléans)
Observation in university teaching : the case of the glossa anglicana
The Oxford gloss or glossa anglicana is the name given to a corpus of glosses copied around the texts of the corpus vetustius of the aristotelian treatises on nature. The gloss was compiled at the University of Oxford, probably before the end of the 1230’s, and was transmitted quite early to the continent. It is composed of a compilation of commentaries and believed to be the teaching material of the lessons on the libri naturales in the Faculty of Arts in the 13th century. The contribution will explore the question of the presence of clues of observation in or beside the corpus of the glossa anglicana on the De plantis and on the Meteora, and the form these clues take in the manuscripts. These elements will allow to broaden the discussion about the role of observation in university teaching in the 13th century.
Richard Kremer (Dartmouth College, ALFA project)
Observation in the margins? Astronomical measurements and armillary spheres, 1312-1544
In her well-known 2011 study of “Observation in the margins, 500-1500,” Katharine Park argued that “observation was ‘marginal’ to medieval scientific inquiry—too informal to have its own genre, let alone to be a regular part of training and practice of astronomers and astrologers” (p. 37). Texts derived from experientia or experimentum represent a well-established medieval genre, recording knowledge of “singular, specific, or contingent phenomena that cannot be grasped by deductive reasoning” (p. 17). Reports about rainbows, prisms, lodestones or the morphology of animals fall into this category. Observatio, on the other hand, referred to cyclical phenomena, to regular patterns that appear to continue over the long term like weather, celestial movements or the stable correlations of astrology. Written records of observations, e.g., eclipses or daily temperatures, are rare and scattered in medieval Europe, jotted into margins of manuscripts and lacking any fixed format.
Park fails to mention, however, an Oxford manuscript discovered by Thorndike in 1948 that contains five pages of astronomical observations of stellar and planetary longitudes, made in Paris with an armillary in the years 1312-1316 and recorded in a prose format as one of the several texts copied by the same scribal hand into the codex. An identical writing format was used 180 years later by the Nuremberg merchant, Bernard Walther, who recorded 30 years of armillary observations of celestial bodies. I have previously studied both these sets of extended observations, clearly cases of observation not in the margins. My goal now is to reconsider both texts, to think about the similarities in writing formats, instrumental and procedural designs, and astronomical motivation for armillary observatio. I will also look for evidence of other armillary observations during the Alfonsine era (and would welcome suggestions of mss to check!).
Laure Miolo (Observatoire de Paris, ALFA project)
Observational or non-observational practices? Lewis Caerleon and the solar eclipses of 1481, 1482 and 1485.
This paper will focus on Lewis Caerleon’s computations of the solar eclipses of 1481, 1482 and 1485. These calculations were performed by this Welsh physician and astronomer, trained in Cambridge, who served the Lancastrian faction. His detailed notes on the eclipses of 1481 and 1482 are contained in one manuscript (Cambridge, UL, Ee.III.61), which can be considered as his notebook. He conceived this codex as a compendium mainly dedicated to eclipse phenomena and their calculation. Both eclipses were calculating in different ways. However, they are closely linked to eclipse tables that Lewis Carleon drew for that purpose. The last extant eclipse calculation by Lewis Caerleon is the solar eclipse of March 1485 (London, BL, Royal 12.G.I and Cambridge, St John’s College, B.19 (41)). It is based on other tables that Lewis argued to have drawn and proved by observations. Furthermore, he mentioned that this eclipse was observed by him from the tower of London were he was imprisoned, because of his support to the Lancastrian cause. Through these three case studies and the vocabulary used by Lewis, I will try to find evidences of real observation practices and to highlight the importance of the vocabulary linked to observations within computational practices.
Jarosław Włodarczyk, (Institute for the History of Science, Polish Academy of Sciences)
The Torquetum: Is It an Observing Instrument?
The torquetum is a complex astronomical instrument which construction is known thanks to some descriptions, iconography and few extant examples. It was used in pre-telescopic astronomy from at least the 13th century. However the usefulness of the torquetum as an observing instrument remains unknown. It is my intention to introduce a preliminary analysis of the merits and limitations of the torquetum in determining the coordinates of heavenly bodies. For this purpose I shall refer to 1/ the results of the examination of the torquetum constructed by Hans Dorn of Vienna (c.1487) and conserved in the Jagiellonian University Museum in Cracow; 2/ written sources with samples of observations made with a torquetum; 3/ elements of a theory of the instrument which allow to trace down instrumental errors, both systemic and accidental.
Matthieu Husson (Observatoire de Paris, ALFA project)
Uses of observation in astronomical reasonings: John of Murs and John of Lignères on the eigth sphere
In this communication I want to compare two texts which are among the firsts to propose a reflection on the double motion of the eight sphere expressed in a tabular format by the so-called “Parisian Alfonsine tables”: John of Murs Expositio and John of Lignères Theorica planetarum. Both texts make uses of some sort of observational evidences in their argumentation. However the two texts present an interesting contrast. John of Murs argumentation is mainly articulated around computations and arithmetical reasoning with the tables. John of Lignères texts, as a theorica, is structured around a more geometric approach to the question. I want to analyse how observational evidence is presented and how it interact with other aspects of the argumentation in both contexts. This will help us understand what kind of clues of observation we can find in this type of sources.
Mohammed Mozzafari (Maragha Observatory) In absentia
Telling history in astronomical rigor: how the technical analyses can help us to better understand the ancient and astronomical corpus
History of observational astronomy in the medieval Islamic period is a field that investigates, at its core, the relation between the observational data (within the accuracy of pre-telescopic observational instruments and optical aids) and theoretical results (in the form of the ephemerides derived from astronomical handbooks with tables) or the fundamental parameters adopted in the medieval astronomical works (the motional parameters, like the mean motions in longitude and anomaly or the precession, and the structural parameters such as the eccentricities). This research area received little attention in the historical researches appeared in the modern period. Although a large bulk of the observational records carried out in the medieval Middle East, Andalus, and Northern Africa has seemingly lost forever, the number of the solar, lunar, and planetary observation reports preserved from this period is enough to reflect how and to what extent the Islamic astronomers, in both the classical period of the rise of astronomy in Islam (ca. 800–1050 AD) and the later period (after 1050 AD), attempted to make extensive, continuous, systematic, and purposed observations in sufficiently long periods in order to check the contemporary theories against observational data and/or determine unprecedented/updated values for the basic parameters of Ptolemaic astronomy. The main goals of the research in this field can be classified in the three classes as follows: 1. Evaluation of the surviving observational records in order to determine the errors committed for a variety of reasons, including the practical skills of the medieval observers of the sky, the probable systematic errors caused by the deficiencies in the instruments applied, and the intrinsic errors reflecting the limitations of the naked-eye observational equipments. 2. Determination of the degree of precision attained in fundamental parameters and/or the ephemerides, considering the theoretical limitations/deviations caused by substantial differences between the simple Ptolemaic models and the complicated modern planetary theories. 3. Determination of the errors in the ephemerides or the times of the occurrence of the synodic celestial phenomena (like conjunctions, eclipses, etc) as predicted from the medieval theories in comparison with the modern results. This is mainly to validate or disprove the statements made by the medieval astronomers on the applicability of the rival theories available to them.
In a broader view, the intrusion of modern astronomical evaluation of the historical data and theories (as I attempted to do so in my studies since 2012 until now) has valuable benefits for a better understanding of the development and evolution of astronomy in the medieval period: more importantly, it reveals that although the experimental techniques were not changed, a clear transition in the purpose and interpretation of the observational practice can be witnessed in medieval Middle Eastern astronomy. It shows why we sometimes encounter the interaction of astronomical traditions. We can understand the way in which such interactions paved the way for the definition and justification of astronomical phenomena or, in contrast, undermine the accuracy in the prediction of them, in particular, and in positional astronomy, in general. We can recognize the reasons why a specific hypothesis from a tradition was maintained, whereas another from other tradition was discarded. After all, we can gain new insights about the experimental correlation between observation and theory. The examples given in the talk will cast light on such aspects.
Samuel Gesner (Observatoire de Paris, ALFA project)
Ad salvandam diversitatem in motu fixorum: thinking about observation in assessing Werner’s trepidation theory
At the beginning of his 1522 treatise De motu octavae sphaerae Johannes Werner references some of his personal observations made in Nuremberg. In particular he describes the measurement of the zenithal distance of three fixed stars near the ecliptic around 1514. But he also mentions the determination of the latitude of Nuremberg. On the other hand he supposed an obliquity of 23;28,30 without further comment. This paper examines how Werner presents those observations and how he uses them — also in combination with historical observations made at the Ptolemaic and the Alfonsine eras — in making the case for his own, unconventional, trepidation model. Werner’s treatise on the Eighth Sphere was criticised by two illustrious astronomers, Copernicus and Tycho Brahe. Both took issue with Werner’s treatise not because of its unconventional way of ‘saving the phenomenon‘ of trepidation but with the observations of the phenomena itself. Their critique, nevertheless, targets fundamentally different aspects which highlights the complexity of any use of observation to buttress theoretical claims in early astronomy.
Laurence Moulinier-Brogi (Université Lumière lyon 2)
L’examen de l’urine était-il nécessaire au diagnostic et au pronostic au Moyen Âge ?
On connaît le vers salernitain : « regarde tout dans l’urine, mais ne crois pas que tu y voies tout ! ». Malgré cette réserve, l’analyse des urines du patient prit un essor considérable dans l’examen clinique à partir du XIIe siècle en Occident, avec des conséquences multiples : floraisons de textes et de commentaires universitaires sur la question, changement des règles de la consultation puisque le patient pouvait désormais être absent, et représenté par son seul urinal porté par un messager, apparition de diagrammes qualifiés de « roues des urines », permettant une appréhension et une mémorisation synoptique des 20 teintes que pouvait revêtir le fluide, autonomisation de ces aide-mémoires sous forme de roues pliables faciles à transporter, etc. Sans oublier l’appropriation de cette grille de lecture du corps par des imposteurs bien incapables de maîtriser d’autres éléments plus difficiles du diagnostic comme l’analyse du pouls. Or, malgré, ou à cause de la part centrale désormais revêtue par l’urine, des tentatives pour s’en passer se firent jour, et le premier à lancer en quelque sorte un pavé dans la mare de la sémiologie médicale fut un Anglais installé à Marseille qui, en 1220, composa un traité au titre novateur sinon provocant, « De l’urine non vue ». Loin de rester isolé, ce petit livre qui proposait de regarder non plus l’eau du corps mais l’état du ciel eut des émules, fit partie des lectures de certaines faculté et inspira d’autres auteurs jusqu’à l’époque moderne.