Transfer of Muslim Astronomy to the Christian West


 The home of Muslim astronomy in Europe, of course, was Spain. It was from Spain, that the early treatises on the astrolabe travelled North of the Pyrenees in the late 10th  century following exchanges between Lorraine and Muslim Spain. John, Abbot, of Gorze (in Lorraine) travelled to Spain as a result of exchanges between Abd Errahman III, caliph of Cordoba,  and the German emperor Otto the Great during the years 970-74. After three years spent in Muslim Spain, John in all probability brought back with him manuscripts of an Islamic scientific nature.[1] John was helped in his enterprise by Spanish Jews who understood Latin .[2] Soon after his return, Lorraine exhibited astronomical knowledge and usage of the astrolabe on the Islamic model.[3] Following John was Gerbert of Aurillac  (930-1003) (later Pope Silvester II), who also spent some time in Ripoll Catalonia, and subsequently introduced the astrolabe and the armillary sphere North of the Pyrenees.[4] Subsequently, Spain, in the words of Haskins, remained the home of astronomical tables and astronomical observation from the days of Maslama (al-Majriti) (d.1007) and al-Zarqali (1029-1087) to the days of Alfonso the Wise (1252-1284); the meridian of Toledo  was the standard of computation for the West.[5] In between, in the 12th century, it was also to Toledo that scholars flocked from all Christian lands to translate Muslim science from Arabic into Latin, local Spanish dialects and also Hebrew, and later on into French, German and English. Amongst such translators were the Italian Gerard of Cremona, who among others translated the Toledan tables of al-Zarqali and Jabir ibn Aflah's Islah al Majisti (Correction of the Almagest) a refutation of Ptolemy,[6] and John of Seville , who made translations that included the astronomical treatises of al-Battani and Thabit Ibn Qurra, al-Madkhal ila sinaat ahkam al-nujum (Introduction to the Predictions of the Stars) of al-Qabisi, and the treatise on the astrolabe by Al-Majriti.[7]


The introduction of Islamic astronomy into England was the work of Walcher of Malvern (also from Lorraine), who had come into possession of an astrolabe. It was he, who for the first time in Christian Europe, on 18 October 1092, used the astrolabe for serious observational purposes to determine the time of a lunar eclipse that he had observed in Italy; and this had momentous consequences on European astronomy.[8] Walcher relied heavily on Petrus Alphonsi, a Jewish convert to Christianity, who served in both Spanish and English royal courts, and who is also credited with the introduction of Muslim astronomy into England.[9] Petrus also assisted early English scholars including Adelard of Bath. One of his astronomical treatises, based on Muslim astronomy is preserved at Oxford University.[10] It includes a concordance of eras for the year 1115, a series of tables for the various planets, and an explanation of the use of the chronological tables. Adelard of Bath himself made a translation of Maslama's edition of Al-Khwarizmi 's astronomical tables in 1126.[11] The cathedral of Chartres in France is thought to have contained a manuscript of Adelard's version of Al-Khwarizmi’s tables.[12] Adelard also translated a treatise by Abu Ma'ashar: the Isagoge minor (Shorter Introduction to Astronomy). Following Adelard, another Englishman, Robert of Chester, made an adapted version of al-Battani’s and al-Zarqali's tables in 1149, whilst Roger of Hereford (fl. 1176) wrote astronomical tables for the meridian of Hereford based on the tables of Toledo  and Marseilles.[13]


In France, Muslim learning was mainly located in the southern regions that were then part of Spain. The southern French Jews, such as Abraham Ibn Ezra and the Tibbonide family, who mastered Arabic, local dialects as well as Latin , played a leading part in this spread of Islamic learning. By the 13th century, Montpelier was a well-known centre of Muslim astronomy (and also medicine). Marseilles, too, played its part, when in 1140, Raymond (of Marseilles) wrote Liber Cursuum Planetarum, an astronomical treatise with tables based on the Toledan Tables. He declared himself the first Latin ‘to acquire the science of the Arabs,'[14] obviously little aware of his predecessors: Gerbet, Walcher etc. Amongst Raymond's inspirations were al-Battani, Mash-Allah, and above all Al-Zarqali from whom Raymond's works are largely drawn.[15]


Although Islamic civilisation declined in the 13th century, its impact outlived it. When Alfonso of Castile (1223-84) sought to construct an armillary sphere, ‘the finest and best that had yet been made', he turned to the Muslims.[16] He had Al-Zarqali’s safiha was translated into Latin . Subsequently, Regiomontanus published a collection of problems on the ‘noble instrument of the safiha.'[17] Regiomontanus also studied Al-Farghani's Compendium of astronomy, which was translated into Latin by both Gerard of Cremona and Johanes Hispalensis.[18] Melanchthon published an edition based on the work of Regiomontanus at Nuremberg in 1537.[19]

The greatest Islamic impact on Renaissance scholars was on Copernicus. He relied heavily in his book De Revolutionibus not just on al-Zarqali and al-Battani but most of all on Ibn al-Shatir and the astronomers at the Maragha observatory for his planetary models and theory.[20] In the 1950s, Kennedy discovered that the geocentric planetary models of Ibn al-Shatir in Nihayat al-sul were mathematically identical with the heliocentric models of Copernicus.[21] Saliba made a very convincing demonstration of this borrowing by Copernicus.[22] North, equally, stresses that Copernicus made repeated uses of his Muslim predecessors, and traces the line of transmission to Italy at about the time Copernicus studied there.[23]

Just like Copernicus, the mathematician Laplace relied heavily on Ibn Yunus's tables from his Al-Zij al-Hakim, using the tables in his determination of the ‘Obliquity of the Ecliptic' and the ‘Inequalities of Jupiter’s and Saturn's; whilst the American Newcomb used its observations of eclipses in his investigations on the motions of the moon.[24]

Islamic astronomical knowledge also travelled East; in the year 1266, Jamal Eddin reached Peking taking with him an equatorial armillary sphere, a plane sundial for unequal hours, an equinoctial dial, a celestial globe and an astrolabe.[25]

[1] J. W. Thompson: Introduction of Arabic science into Lorraine in the tenth Century,'' ISIS 12 (1929): 187-91; M. C. Welborn: ‘Lotharingia as a center of Arabic and scientific influence in the eleventh century,' ISIS 16 (1931) pp.188-99.

[2] J.W. Thompson: The Introduction of Arabic Science; op cit; pp 189-90.

[3] M.C. Welborn: Lotharingia; J.W. Thompson: The Introduction of Arabic Science.

[4] R. Allen: Gerbert Pope Sylvester II; The English Historical Review (1892), pp 625-68;

D.R. Hill: Islamic Science, op cit, p. 221.

 [5] C.H. Haskins: Studies in the History of Mediaeval Science, (Frederick Ungar Publishing Co. New York. 1967 ed), p. 18.

[6] R.  Lemay: Gerard of Cremona; Dictionary of Scientific Biography; op cit; Vol 15; Supplement I; pp. 173-92.

[7] C.H. Haskins: Studies; op cit; p. 13.

[8] O. Pedersen: Astronomy, op cit, p. 312.

[9] See J.H.L. Reuter: Petrus Alfonsi: an examination of his works; their scientific content, and their background.’ Unpublished Ph.d thesis (Oxford; 1975), p. iii.

[10] C.H Haskins: Studies, op cit, p.  117.

[11] L. Cochrane: Adelard of Bath (British Museum Press, 1994).

[12] C.H. Haskins: Studies, op cit,  p. 90.

[13] G. Sarton: Introduction; Vol 2; op cit; p. 404.

[14] C.H. Haskins: Studies, op cit, p. 98.

[15] P.K. Hitti: History, op cit, p. 571.

[16] Carra de Vaux: Astronomy; op cit p. 396.

[17] Ibid, p. 394-5.

[18] Ibid, p. 381.

[19] Ibid, p. 381.

[20] John North: Astronomy and Cosmology (Fontana Press, London, 1994), at p. 195.

[21]  See: The Life and Work of Ibn al-Shatir, an Arab astronomer of the 14th century; Edited by E.S. Kennedy and I. Ghanem; Institute for the History of Arabic Science (Aleppo ; Syria ; 1976).

See also D.A. King: Astronomy, in Religion, Learning , (M.J. L. Young et al ed) op cit; p.284.

[23] J. North: Astronomy and Cosmology; op cit; p. 195.

[24] S. M. Ziauddin Alavi: Arab Geography in the Ninth and Tenth Centuries, Published by the Department of Geography Aligarh (Muslim University, Aligarh 1965), p. 36.

[25] B. Hetherington: A Chronicle; op cit; p. 159.