Sky as a bridge:Astronomical interactions

in Eurasia through the ages 

Rajesh KochharPresident IAU Commission 41: History of AstronomyMathematics Department, Panjab University, Chandigarh, India

Indian Institute of Science Education & Research, Mohali, Punjab, India

rkochhar2000@gmail.comTalk given at IAU General Assembly, Honolulu, 10 August 2015

• Sky has always been seen as the heritage of the whole humankind. People have been curious about their sky. They have also been curious about the curiosity of others. Accordingly, astronomy has advanced through pooling of intellectual resources and cross-fertilization of ideas. There is broad connectivity in the world history of astronomy. Astronomy is a multi-stage intellectual cumulus where each stage has built on the previous ones and carried the studies forward.

• The growth of astronomy has not occurred in a steady manner, but in spurts, with different centres playing a pre-eminent role at different times.

• The trajectory of development that culminated in modern astronomy has a number of important milestones: Mesopotamia (Iraq) >Hellenistic world> India >Muslim culture zone > Europe.

• China does not figure in the above sequence, because it did not influence Europe. Also note that the Roman empire did not contribute to astronomy, but focused on law and engineering. This general observation remains valid because Claudius Ptolemy belongs to the Hellenistic tradition, even though his epoch is c. 100 CE and place of work Rome.

• The reason for general Roman disinterest in astronomy is probably this. Since astronomy was the strong point of the Hellenistic Greeks whom the Romans had vanquished, the new victors consciously distanced themselves from it.

• At the same time , as a counter-example , it should be noted that the 6th - 4th century BCE Persian Achaemenid empire in Mesopotamia had no difficulty in continuing the earlier astronomical tradition.

• This raises an important question. When regime changes, what activities are continued and what are abandoned? What is the dynamics of continuity or the break?

An interesting correlation needs to be noted. The level and quality of astronomical activity has been related to a nation’s GDP. Prosperous, self-assured, resurgent, assertive nations have tended to become patrons of astronomy. It is as if having established their superiority or supremacy over fellow human beings, they wanted to unravel the mysteries of the sky on behalf of the whole humankind.

This can be seen from recent developments. Europe’s decline began with the First World War and the centre of astronomical activity shifted to USA. After the Second World War reconstruction, Europe, unitedly this time, took to astronomy with renewed vigour. Japan’s economic strength manifested itself in its technology-backed astronomical projects. And now, China , Korea and Japan together wish to become an astronomical power.

• We can distinguish between two successive phases in the human pursuit of astronomy over the millennia: (i) the geocentric phase, and (ii) the heliocentric, telescopic phase. Interestingly, in both the phases, the initial impulse came not from love of stars but fear ; fear of the skies in the first phase; and the fear of the waters (that is, oceanic voyages before scientific navigation), in the second phase.

• The first phase ended with Copernicus who was a man of two parts. His laborious mathematical work is in continuation with that of his predecessors. At the same time he represents a drastic break with the past by postulating the earth’s motion around the sun.

• My concern here is with the first phase. Today, we look at the universe as if from the outside. For us, it is no more than a field station and a laboratory for discovering natural laws and testing theories. In earlier times, when the world was anthropo-centric, cosmic environment was from human affairs. The sky was partly a divinity to be feared and appeased. Partly, it was a phenomenon to be observed and utilized.

• As creator, God would surely keep a watch on the Earthians. His messages and signals would be communicated through movements in the sky.

• His wrath would be conveyed by the appearance of unexpected phenomena, like comets, meteors, and eclipses. They would call for post-facto propitiation of the gods.

• Fortunately, the divine wrath was invariably short-lived.

Planetary orbits represented cosmic order and were a means of assurance of divine benevolence. Ever increasing understanding of their orbits decreased the distance between the human beings and the divinities, and permitted the former to establish an ex-ante (before the event) negotiatory relationship with the latter.

• The beginnings of astronomy (and mathematics) are related to the requirements of the ritual in early cultures. Ritual was a means of securing divine approval and support for terrestrial actions. To be effective, it had to be elaborate and well-timed, so that a careful distinction could be made between auspicious and inauspicious times. Since planetary orbits were the timekeepers provided by nature, their study became important.

Egypt and Babylonia

• Alexander’s (356-323 BCE) military campaigns against the Persian empire which began in 334 BCE and brought him up to river Indus in the Indian subcontinent paved the way for intellectual interaction over a vast region. After his death, Greek-speaking dynasties came to power in Egypt (Ptolemaic, in 323 BCE) and Mesopotamia (Seleucid, in 312 BCE).

• Both these countries had an older civilization , big food surplus, vast geography, and high levels of practical knowledge and  technological developments. The combination of these with the classical Greek intellectual tradition produced remarkable results of long-lasting value.

• Alexandria in Egypt was founded in 331 BC and emerged as a major centre for scientific activity. The vastness of Egypt made possible the celebrated experiment by Eratosthenes (c. 275-192 BC) to measure the circumference of the earth, using Alexandria and Aswan ( modern name) as reference stations. (Similarly, the vastness of British India permitted the measurement of the great meridional arc under George Everest.)

• Scientific activity in Alexandria came to an end in 144 BC, when the king Ptolemy VIII expelled all intellectuals and scholars from the city. Alexandria itself was conquered by the Romans in 30 BC.  The Egyptian solar calendar travelled to Europe with the Romans and became the basis for Julian/Gregorian calendar.

• In Babylonia, the Greeks had the advantage of inheriting a rich and well-preserved astronomical tradition. Babylonia had maintained a tradition of making and recording astronomical observations and a mechanism (cuneiform) for storing and preserving the records. The Greeks could use records going back to 8th century BCE

• I think it needs to be appreciated that the Greco-Babylonian astronomy was characterized by a combination of continuity and break. The Greeks had now access to old data which had been taken by others. They could pursue astronomy as an intellectual discipline without being overwhelmed by its divine dimension. India, for instance, could never really decouple scientific astronomy from the sacred.

• An accurate luni-solar calendar (with seven extra months in 19 years) was introduced in Babylonia in 383 BCE (Ref. 1). During the Achaemenid period itself, 12-equal part zodiacal belt was introduced (Ref. 2). The seven-day week, inspired by the seven planets, butwith its peculiar ordering of days, was a much older construct, from Chaldean times. They all now became known in the outside world.

India

• Greco-Babylonian astronomical elements were brought into India from the northwest by the Indo-Greeks. Through a long-drawn and hardly understood process, they were incorporated into the Indian mainstream. Revitalized Indian mathematical astronomy (known as Siddhantic astronomy ) appears in a full-blown form in the 499 CE text composed by Aryabhata.

• The Siddhantic tradition remained active for more than a thousand years. The most remarkable feature of ancient Indian astronomical tradition was the development of approximate mathematical solutions for astronomical calculations. Thus Diophantine and Pell equations were solved. In the 14th century Kerala-based astronomers ( Madhava) discovered infinite series for sine, cosine and arctangent functions and for pi.

• The European names associated with these ‘discoveries’, made more than 200 years later, are Colin Maclaurin, Isaac Newton, James Gregory and Gottfried Wilhelm Leibniz. The European names associated with these ‘discoveries’, made more than 200 years later, are Colin Maclaurin, Isaac Newton, James Gregory and Gottfried Wilhelm Leibniz. Appreciation of pioneering mathematical work in the astronomical context is a recent phenomenon.

• In its own time, the influence of Siddhantic astronomy spread westwards as well as eastwards.

• Even though Siddhantic astronomy received new inputs from Greco-Babylonian astronomy ( including an accurate luni-solar calendar, week and zodiac), many features of the old, Vedic, astronomy were advisedly retained. The moon’s position at night was marked with respect to bright stars/ star groups (known as nakshatras) visible near it. The number originally was 28 , but was later brought down to 27.

• Both the Chinese and the Arabs have a similar system, respectively known as Hsiu and Manzil, comprising 28 names. The Indian as well as the Arabic list begins with Beta Arietis, which marked spring equinox in about 300 CE. The first entry in the Chinese list is Alpha Virginis, which marked the autumn equinox at the same epoch.

• There is an interesting interplay between scriptures, astronomy and mythology in the case of eclipses which needs to be noticed because of its transmission outside India.

• Mythology was upgraded to keep pace with astronomy. Astronomy in turn adopted mythological terms to maintain continuity with scriptures.

• Post-Rigveda Vedic mythology attributed eclipses to a demon called Rahu. Even when scientific cause of the eclipses became known, the demon was not banished, but accommodated in the new scheme of things.

• The demon was cut into two, so that the head and torso corresponded to the ascending and descending lunar nodes, respectively. They were designated Rahu and Ketu.

• Indian mythology now had demons who came by appointment!

• Athe term Keru was an old one given an extra meaning. Vedic mythology used the term ketu to denote comets, meteors, etc. (Ref. 3). It continued to be used in that sense also.

Muslim culture zone

• In later Iranian (and Arabic) mythology the Rahu and Ketu become the head and the tail of the dragon Al –Djawzahr. Ketu as comet came to be known as al-Kayd (Ref. 4).

• Of greater significance was the incorporation of Indian scientific astronomy into Arabic science.

• In about 773 CE, al-Fazari, on orders from the second caliph al-Mansur (reign 754 -775 AD) translated a Sanskrit astronomical text into Arabic. This was the Arabia’s first introduction to the Indic numerals. Historically, far more significant is the work of the mathematician al-Khwarizmi who flourished during the reign of caliph al-Mamun ( reign 813-833 CE) and became the conduit for transfer of Indian mathematical knowledge to Europe.

• The significance of al-Khwarizmi’s work can be quickly seen from the fact that the English language owes three common terms, algebra, (trigonometrical) sine and algorithm, to 12th century Latin translation of his works.

• The term Algebra comes from the title of his book which contains the Arabic word al-jabr.

• The Latin/English term sine comes from his algebra. Indian astronomy introduced the term jya , which literally meant a bowstring and was given the technical meaning of half-chord. Also called jiva, it was rendered in Arabic as jaib. Now, jaib was an existing word in Arabic meaning fold of a dress; this was literally translated as sinus in Latin.

• In the translation of al-Khwarizmi’s book on arithmetic, his name was Latinized to Algoritmi which in turn gave rise to the term algorithm.

China, Korea, and Japan

• While India’s interaction with the Muslim culture zone was two-way, interaction with east Asia and southeast Asia was largely unidirectional. Indian influences reached China by land and further to Korea and Japan. There was an independent channel to Tibet. East India was in regular touch with Indonesia, Thailand, Burma, etc. through sea.

• Buddha personally was firmly against astrology, so that while Buddhism flourished in India, astronomy went into decline. By the time Buddhism was exported to East Asia, astronomy/ astrology had become part of it. Unlike the traditional Chinese focus on portents, Indian mathematical astronomy could prepare horoscopes for the benefit of individuals.

• Interaction with east Asia was driven by Buddhism and was characterized by translation of Buddhist and other texts. It began in the first century CE during the Later Han period (25–220 CE) and continued into the politically unstable Three Kingdom period (220-265 CE).

• Indian inputs continued intermittently even after that, with the most detailed incorporation of Indian astronomy coming during the Tang Dynasty (618-906 CE). Indian-origin documents found in China and Tibet are important from the point of view of history of India also, because they provide textual information which carries a firm date.

• Notwithstanding earlier pre-Siddhantic (pre-499 CE) translations, China’s systematic introduction to Indian astronomy began in early 8th century. Unlike in India, where almanac-making was a social/religious affair, in China it enjoyed state support. An astronomer of Indian descent Qutan Xida [Gautam Siddha] prepared an astronomical treatise, Jiu-zhi-li in 718 CE. Its elements in turn were employed by the well known Chinese astronomer Yi-Xing (687-727 CE) in his famous calendar Da-yan-li.

• Far more significant was the contribution of the Indian Buddhist monk, Jin Ju Zha, whose Qi Yao Rang Zai Jue contains detailed ephemerides of Rahu and Ketu. It was incorporated into calendrical calculations of the Tang dynasty Yuanhe era, Year I (806 CE).

• Being 180 degrees apart, the nodes Rahu and Ketu are not independent variables. Recognizing this, Jin Ju Zha’s while employing Rahu to denote the ascending node, boldly decided to use Ketu to denote lunar apogee (Ref.5). This shows that Indian astronomical influences were not superficial, but became part of the Chinese mainstream.

The making of Copernicus

• As we know, planetary orbit calculations became very simple once Kepler enunciated his laws and introduced the concept of elliptical orbits. Before that, Ptolemy’s mathematical model for calculating planetary orbits by using circles alone remained influential for a very long time. One aspect of Ptolemy’s model, the equant, which permitted non-uniform circular motion, was recognized as a problem.

• An important astronomical development was the 1269 CE establishment of the Maragha Observatory ( East Azerbaijan, Iran) which preceded Ulugh Beg’s Samarqand Observatory by 150 years. Important names associated with Maragha are al-Tusi (1201-1274), al-Urdi (d 1266), al-Shatir ( d. c. 1375), and al-Khafiri (fl 1525).

• Did the Maragha work on improving Ptolemy model by such theoretical constructs as al-Tusi couple and al-Urdi lemma remain a dead end or did it influence later developments?

• There is no doubt that Copernicus’s planetary models exhibit some striking similarities to those of the Maragha astronomers. Did Copernicus know of the previous work or did he develop his model entirely independently? The question has been discussed for the last seven decades. The general opinion seems to be that Copernicus was indeed influenced by Maragha (Ref. 6) . However, Copernicus’ independence is still being argued for (Ref. 7).

• Copernicus explicitly cites five Islamic scholars, but they all belonged to 12th century CE or earlier. He does not quote any later author. This however does not necessarily mean that he did know of their work. Copernicus’ target audience was Europe. He would quote authors who were part of a learned man’s library in Europe. He may have consulted obscure works and not cited them.

• Was the work of al-Tusi and others available in Europe? It was. Al-Tusi’s models seem to have been known to Copernicus’ contemporaries, like Giovanni Battista Amico and Girolamo Fracastaro. A Greek manuscript, probably dating from 13th century and in the Vatican since the 15th century, mentions al-Tusi’s work. This also could have been seen by Copernicus (Ref. 6).

• To me, it appears natural that a researcher addressing a difficult problem of long-standing duration would first of all acquaint himself with the work done before him. Whether Copernicus re-invented al-Tusi couple or not, his laborious mathematical work is in continuation with that of his predecessors. The break with the past came not from his calculations but from his hypothesis that the earth goes around the sun.

Concluding remarks

• History of astronomy (and science) was particularly important for the 19th century Europe. As authors of the powerful knowledge system of modern science, Europeans claimed cultural and racial superiority, and by extension right to rule, over others. Accordingly, as an article of faith, the origin of modern science and the entire trajectory of its development were placed within the geographical limits of Europe.

• In this framework, an unresolved monolithic period of antiquity was created that extended from the 6th century BCE ( Greek philosopher Thales) to 2nd century CE ( Greek astronomer Ptolemy).

• No distinction was made between the Hellenic and the Hellenistic phases; and there was no question of investigating the antecedents of the Hellenistic science. It is noteworthy that in the hybrid Hellenistic period, the classicist Aristotle did not enjoy the type of reputation Europe bestowed  on him later.

• In 1819, a British text book writer in India paid glowing tributes to al-Tusi’s commentary on Euclid , already popular in India, saying that it had been enriched ‘ with great variety of explanatory notes, new demonstrations, and additional propositions, which cannot fail to be studied with advantage by all who wish to enter deeply into the science themselves, or explain its principles to others’ .

• And yet, in the Arabic-language text book he was writing for students in government-run madrasas ( traditional Muslim school), he removed ‘all that is not Euclids’ so as ‘to guard the accuracy of the text’ (Ref. 8). It is remarkable that Muslim students were to be told about Euclid but not about the contribution of Muslim scientists who carried on from him.

• Similarly, Indians were informed that there was nothing original in their astronomy, and that it was a tame imitation of the Greek. This put Indians perennially on the defensive. As recently as 1970, an otherwise well-regarded Indian historian of astronomy tamely submitted that the borrowings from the Greeks were in astrology rather than astronomy (Ref. 9), as though the distinction made any sense while talking of 2000 years ago.

• The next challenge to European historical ingenuity was presented by India’s contributions to chemistry. The author of an ancient Sanskrit chemistry text (Rasa-sara ) declared in the colophon at the end of the text that he had composed the work after consulting the traditions and opinions of the Buddhists. Commenting on it, the British experts declared with a straight face that that by Buddhists, ‘the author probably meant the Muhammadans’ (Ref. 10).

• Surely Arabs would have liked to hear that. But they were instead told that their role in the world history of science had been no more than as librarians and archivists for preserving Greek science till Europe was in a position to take its heritage back.

• The American philosopher, Thoreau, made a very perceptive observation: ‘A man is wise with the wisdom of his time only, and ignorant with its ignorance’.

• Euro-centric historiography was consistent with Europe’s requirements and philosophy of the 19th century. Anti-Euro-centrism and ultra-nationalism would be a continuation of the same.

Cultural Copernicanism

• The theoretical framework that I have developed for historical analysis of the colonial period can be described as Cultural Copernicanism. Cosmological principle, named in honour of Copernicus, states that the universe does not have any preferred direction or location. Its cultural counterpart part would similarly assert that no cultural, geographical or ethnic area can be deemed to be a benchmark to be used to evaluate and judge others. This framework manifestly rejects Euro-centrism as well as anti-Euro-centrism.

•What we need is a world history of astronomy, written with rigour and detachment and on behalf of the whole humankind.

Thank you

References

1. Fotheringham, J.K. (1934) The Calendar in The National Almanac for 1935 (London: H.M. Stationery Office), pp. 754-770; see p.756

2. Evans, James (1998) The History and Practice of Ancient Astronomy (New York: Oxford), p. 15

3. Kochhar, Rajesh (2010) Rahu and Ketu in mythological and astronomological contexts. Indian Journal of History of Science, Vol 45, pp. 287-297.

4. Hartner , W. (1965) Al-Djawajahar. Encyclopedia of Islam, Vol. 2 (Leiden: Brill), pp. 501-502.

5. Niu, Wei-Xing (1995) ‘An inquiry into the astrological meaning of Rahu and Ketu.’ Chinese Astronomy and Astrophysics, Vol. 19, No. 2, pp. 259-266.

6. Ragep, F. Jamil (2007) Copernicus and his Islamic predecessors: Some historical remarks. History of Science, Vol. 45, pp. 66-81.

7. Blasjo, Viktor (2014)A critique of the arguments for the Maragha influence on Copernicus. Journal of History of Astronomy, Vol. 45, pp. 183-195.

8. The Second Report of Calcutta School Book Society’s Proceedings, 1819, App. IV, p. 37.

9. Chatterjee, Beena ( 1970), The Khandakhadyaka of Brahmagupta, Vol. 1 ( Delhi: Motilal Banarasidass), p. 290.

10. Ray, Prafulla Chandra (1918) Essays and Discourses (Madras: G.A. Natesan), p. 91.