Viewpoint No. 113 3

Islamic Astronomy from “Star Wars” to Star Tables

Glen M. Cooper explores the cosmos as seen by Islamic scholars through history.

Astronomy had a long and fruitful life in the and rulers in Islamic world, where ancient Greek astronomy terms of a grand was transformed into a fully institutionalised cosmological endeavour employing a comprehensive and scheme written predictive theory that was consistent with in the stars, physical principles as then understood. which both Astronomy in the ancient world was justified the motivated by different concerns than what current dynasty drives the science today. Its principal aim was and permitted to divine the future from planetary positions, knowledge of which eventually could be calculated using the political past data and theoretical models. Astrologers future. These have been associated with imperial courts interests in since ancient Mesopotamian times. There, in a political and his- kind of ancient “star wars”, they vied with each torical astrology other for the most accurate predictions. Meso- were inherited potamian stargazers accumulated centuries by the Muslim of observational data, and invented math- Abbasid dynasty ematical methods for predicting astrologically (750-1258 CE). significant planetary configurations. The most While the Mesopotamian cultures provided obvious differ- incentive and data for astronomy, the Greeks ence between were more concerned with integrating this modern and knowledge into a cosmology, with geometri- Islamic astron- cal models and a physics. The culmination of omy is that the these efforts was the Almagest, the work of latter is primarily the 2nd Century mathematical astronomer, mathematical Nasir al-Din al-Tusi at the observatory in Maragha, Persia. Ptolemy, who, using the Mesopotamian data, and predictive, Image courtesy of the British Library. produced the most powerful system of predic- and the former tive astronomy yet known, the Almagest. He has other obser- also developed a comprehensive astrology, vational goals, which, because of its mathematical preci- such as describing the physics of other worlds. ying speeds, Ptolemy had postulated that one sion, acquired the air of genuine science. The As noted earlier, the predictive character of of the spheres responsible for moving these Almagest showed how to derive mathemati- astronomy derived from its use in astrological planets rotated uniformly around a pole that cal models of the planets from observational forecasting. The Ptolemaic models were to an did not coincide with its own centre, which, data. Ptolemy’s methods were the foundation extent instrumentalist, namely, useful for gen- although it gives good mathematical results, of Islamic astronomy. erating planetary positions rather than being is physically impossible. Muslim astronomers Prior to Islam, the rulers of the Sasanian Per- strictly physically consistent. There were some invented new mathematical devices that sian Empire (224-651 CE) fostered a dynamic thinkers, however, such as al-Tusi, who desired produced the same effects without violating astrological tradition, which they employed to present a unified physics and cosmology of physical principles. for a variety of purposes. For example, the the heavens. Through his efforts and those of Observatories as institutions that housed state religion, Zoroastrianism, espoused a his followers, several of Ptolemy’s models that a collective effort to gather positional data chiliastic/millennialist view of history, and contained physically absurd elements were about the stars and planets were an Islamic thus invited astrological activity. Astrologi- replaced with physically consistent ones. For invention. Programs of observation began cal histories rationalised significant events example, in order to explain some planets’ var- under the 9th-century Abbasid rulers, but

Viewpoint 113.indd 3 30/06/2017 08:26:39 4 Viewpoint No. 110

Above left: Ulugh Beg observatory, cour- tesy of Alaexis via Wikimedia Commons.

Right: An Arabic translation of the astro- nomical tables of Ulugh Beg, courtesy of the Library of Congress.

culminated in the grand observatories of Maragha (13th C.) under the Ilkhanids, and Samarkand (15th C.) under the Timurids. The main goal of these observatories was to improve the planetary tables (zijes; sing. zij) used to calculate planetary positions. Unlike modern observatories, their Islamic anteced- ents were useful only until all the data had been gathered over a period of decades at most. The main structural feature of the Islamic observatory was the meridian quadrant, which measured the planets’ elevations as they crossed the meridian. (See above). In addition, there were more portable instru- ments, including armillary spheres, quadrants, and other devices for measuring celestial posi- tions by hand. The way to improve upon data from earlier observatories was to build a larger plished. However, the most famous observa- sciences. meridian quadrant in order to obtain more tory was established at Maragha in northwest- The majority of those who used astronomi- precise observations, which in turn improved ern Iran by the Mongol Ilkhanid ruler Hulegu cal information did so in the form of tables, the accuracy of the zij tables. This basic design (d.1265) in 1259, under the direction of Nasir and so did not require advanced mathematics. persisted for centuries, and even found its way al-Din al-Tusi (d.1374). The first observatory Along with planetary models, Ptolemy had into Tycho Brahe’s 16th Century Uraniborg. to be supported by a religious endowment also shown how to use tables for the relatively (The main difference there was that, whereas (waqf), it not only produced an improved zij easy calculation of planetary positions. Only the Ptolemaic tradition had astronomers (Zij-i Ilkhani), but also began a major reform of basic arithmetic was needed, since the tables taking observations at major conjunctions Ptolemaic astronomy. This resulted in a new of various functions already had complex or at other significant times of the planetary tradition of planetary theory that culminated trigonometry built into them. cycles in order to extrapolate the rest using in the models of Ibn al-Shatir (d.1375), ele- In the Islamic tradition, such tables were the model, Tycho observed the planets on the ments of whose contributions Copernicus called “zijes”, from a Persian word that means days between, and thus had a far more precise incorporated in his own revolutionary treatise, “thread”, because their cross-hatched appear- set of data). On the Revolutions (1543). The Samarkand ance, with numbers in the spaces, resembles The Abbasid Caliph al-Ma’mun (r.813-833) observatory, established and supervised by a woven cloth (see illustration, above). Zijes founded two observatories at Baghdad and the Timurid ruler and astronomer Ulugh Begh were typically a collection of such tables along Damascus, respectively, where some of the (d.1449), produced a new zij (Zij-i Sultani), and with instructions for their use, including tables initial updates to the Almagest were accom- supported a flowering of the mathematical for converting between calendars, for Islamic

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prayer times, and for determining planetary longitudes, based on the number of elapsed days and hours since a known position, or “epoch”. Zijes were calculated using math- Cocktail parties ematical models of the planetary motions, which in turn were based on observational parameters that were determined at the observatories. So, advances in astronomy under starlight were expressed in new zijes, which were the result of more accurate parameters or better Pedro Ruiz-Castell highlights the role of amateur astronomy as a models, or both. form of sociability under Franco’s dictatorship. To simplify the process further for the eve- ryday practitioner, yearly almanacks were pro- duced, which used the zijes to determine all of the celestial data for the upcoming year on a daily basis, much like a modern ephemeris. Islamic astronomy was interconnected with all of the other sciences, in a comprehensive cosmology inherited from Aristotle. Through their unrelenting critique of ancient astron- omy and natural philosophy, Islamic astrono- mers laid the groundwork for the scientific advances of both the European Late Middle Ages and the Scientific Revolution. Coper- nicus, Brahe, Kepler and many others used methods developed in Islamic astronomy to critique and eventually replace the ancient cosmology.

The opening of Aster’s new premises, 3 June 1949. Source: Aster, 1 (1949), p. 49.

Glen M. Cooper The Spanish Civil War (1936-1939) was a by academics and senior amateurs. Despite Claremont McKenna College devastating conflict that marked the begin- encouraging and promoting systematic ama- [email protected] ning of one of the longest European dictato- teur work –such as the methodical observa- rial regimes of the twentieth century. Franco’s tion of variable stars–, SADEYA seemed to dictatorship signified a break with the past in have problems accommodating the enthusi- many political, ideological, and social aspects, asm of young people. This situation led to the including cultural expressions and intellectual creation of new amateur astronomical associa- traditions. It also brought important changes tions in Spain during the central decades of from an institutional perspective and meant the twentieth century. the purge and forced exile of many Spanish The foundation of such new non-pro- scientists and lecturers. Moreover, the years fessional astronomical associations proves of hunger and misery that characterised post- particularly relevant for historians of science, Bibliography war Spain were of intense social propaganda since the development of amateur science and mandatory recatholisation. This included was much more difficult to oversee by the dic- • Sayili, Aydin. The Observatory in Islam: And the practice of science, which was submit- tatorial regime –as it was less dependent on Its Place in the General History of the Observa- ted to the Catholic doctrine. The case of the precepts of official science. Moreover, such tory. Ankara, 1960. astronomy is particularly obvious, since the initiatives may be understood as attempts to • Blake, Stephen P. Astronomy and Astrology in observation and study of the heavens was develop new spaces for scientific sociability, the Islamic World. Edinburgh, 2016. seen as a tool to offer evidence in favour of in response to the new political and socio- • Saliba, George. Islamic Science and the Mak- the existence of God and the Creation. economic conditions of the dictatorship. The ing of the European Renaissance. Cambridge, As a result, astronomy remained fairly popu- search for valuable instructional and cultural MA, 2007. lar in Spain during these years. The severe resources that provided astronomy was com- • King, David A. In Synchrony with the Heavens: new regulations established by the dictatorial bined, during these years, with the explora- Studies in Astronomical Timekeeping and regime during the post-war years, however, tion of new and fresh spaces for socialisation Instrumentation in Medieval Islamic Civilization. had a strong impact in the normal life of the sought by young people. Volume One: The Call of the Muezzin. Leiden, Astronomical Society of Spain and America A good example is that of the Agrupación 2004. (SADEYA). Furthermore, new young amateurs Astronómica Aster, founded in Barcelona in • King, David A. Volume Two: Instruments of felt uneasy with how the main Spanish astro- 1948 by a group of secondary school stu- Mass Calculation. Leiden, 2005. nomical association was organised and run dents. Aster eventually became responsible

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ISSN: 1751-8261 MAGAZINE OF THE BRITISH SOCIETY FOR THE HISTORY OF SCIENCE

Contents

Canine Cosmonauts 1-2

Islamic Astronomy 3-5

Stargazing under a Dictator 5-6

Looking at Earth 7

Visions of the Universe 8-9

From Sweden to Space 10

A History of Dark Matter 11

Interview - Anna Maerker 15

BJHS, Viewpoint, BSHS info. 16

Editorial

I This issue is devoted to the history of those who have gone in pursuit of knowl- edge of the furthest reaches of the cosmos. We begin with an article by Amy Nelson on the non-human explorers sent into space (1-2). Missions to space are also the focus of articles by Nina Wormbs, who asks why Swedens aim for the stars (10), and Robert Poole, who takes us on a journey through space historiography (7). Astronomy is the focus of articles by both Glen Cooper (3-5) and Pedro Ruiz- Castell (5-6), though each explores a very Canine Cosmonauts different context! Marek Kukula discusses the role of photography in astronomy, and Amy Nelson tells us about the dogs who led humans into space there are details of how that work contin- ues today (and an exhibition to attend! They were a motley crew. Most of the small, Many people saw the dogs as experimental 8-9). Last, but by no means least, Jaco de mixed-breed dogs enlisted as experimental re- subjects playing a critical role in the produc- Swart provides a fascinating insight into search subjects by scientists at the Institute of tion of knowledge about the environmental the history of the hunt for dark matter (11). Aviation and Space Medicine in Moscow be- conditions of space travel. Others viewed You’ll also notice a link to a survey asking gan their lives as strays. Pointy and flop-eared, them in ways that drew on the historic interac- for your views on Viewpoint (6): please do spotted and solid-colored, with hints of terrier, tions of people and dogs, identifying them as spend 5 minutes to give us your thoughts spaniel, or spitz in their ancestry, they could scouts bravely blazing the trail to outer space, on the magazine! not have understood the role they played as victims sacrificed on the altar of geopolitics, Contributions to the next issue should in our most Promethean project – the quest or as faithful servants of humanity. be sent to [email protected] by 15th to send humans into outer space and return The most famous space dog was also the August. them safely to earth. But their significance was most controversial. When Laika became the Alice White, Editor apparent to the scientific community and the first living creature to orbit the earth on 3 global public that followed each chapter of November, 1957, she instantly became a the unfolding race to conquer outer space. global celebrity. Her photograph appeared in

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