Lunar Formations and Astronomers from Muslim Civilisation
by Salim Al-Hassani - 1001 Book Chief Editor
Book Review of “Reflections on Observational Astronomy in the Medieval Islamic Period” by S. Mohammad Mozaffari
by Fatima Sharif
This chapter is organised in the following manner. Section one gives a brief overview about important periods in the history of Islamic Astronomy. This is done in order to highlight the significance of choosing to examine the fate of astronomy in Persia and not elsewhere. Section two gives a brief background to one of the most important observatories in the history of Islamic astronomy: the Maragha observatory. Section three highlights some of the most important astronomical contributions of the Maragha observatory. Section four describes the impact of this Islamic astronomical tradition upon the work of Copernicus. The final section gives concluding remarks about the fate of Islamic astronomy in Persian between the eleventh and sixteenth-centuries.
Figure 1. Constellation of Draco, Persia 16th c. (Source)
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Note: This paper explores the history of Islamic Astronomy in Persia between the eleventh and sixteenth centuries. It is a chapter from the doctoral thesis of Professor Mohamad Abdalla AM at Griffith University, titled ‘The Fate of Islamic Science Between the Eleventh and Sixteenth Centuries: A Critical Study of Scholarship from Ibn Khaldun to the Present.’ It has been republished on the Muslim Heritage website with the permission of Professor Abdalla, University of South Australia.
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Figure 2. Persian Miniature Paintings Wellcome L0045151- Zodiac; Persian; Astronomy; Astrology (Source)
Before proceeding to examine the development of astronomy in Persia, it is necessary to give a brief – but important – overview of two important periods of Islamic astronomy. The history of Islamic astronomy can be broadly divided into two major periods, the eleventh century being the dividing road between the two. [1] From the ninth to the eleventh century, astronomical work was “almost exclusively in the area of geometrical models inherited from Ptolemy, reworked and criticised on the bases of new observations.” [2] Ptolemy was one of the most influential Greek astronomers and geographers of his time. He postulated the geocentric theory of the world in a form that prevailed for 1400 years. Ptolemy’s geocentric description of the universe was based on “two postulates of ancient astronomy: the earth is stable at the centre of the world, and all celestial motion must be explained by a combination of uniform circular movements.” [3] It is a view of the world based on a fixed earth around which the sphere of the fixed stars rotates every day, carrying with it the spheres of the sun, moon, and planets. Ptolemy used geometric models to predict the positions of the sun, moon, and planets, using combinations of circular motion known as epicycles and eccentrics based on pervious work done by Hipparchus. [4] This view of the world was recorded in his famous work Almagest, which became available in Arabic under the caliph of Baghdad al-Ma’mun (813-33). [5] However, astronomers in Baghdad did not accept Ptolemy’s work on face value. They re-examined the theoretical base of his results, in order to revise the mechanisms he had proposed and recalculate the parameters of the different movements. [6]
Criticism of Ptolemy pointed out that his mathematical models that describe the behaviour of physical spheres were: “fundamentally flawed in that they implied a contradiction between the physical properties of those spheres and the manner in which their motions were described mathematically.” [7] From that perspective, the most outstanding problem that permeated the whole of Ptolemaic astronomy implied the uniform rotation of a sphere around an axis that did not pass through its centre. [8] This very problem was later identified by astronomers working in the Islamic civilization as the equant problem and was also identified for the same purposes by Copernicus (d. 1543) in the introduction to his Commentariolus, which was written around 1510-1515. [9]
Efforts to resolve this problem began in earnest in the Islamic civilization sometime around the middle of the thirteenth century. Many astronomers attempted to devise non-Ptolemaic mathematical models that would still describe the motions of the celestial spheres in accordance with observations but would, at the same time, remain consistent with the physical properties of those spheres. [10] In these attempts at model construction, two astronomers in particular (whose works are discussed later), Mu’ayyad al-Din al-Urdi (d. 1266) and Nasir al-Din al-Tusi (d. 1274), devised two new mathematical theorems, unknown in the earlier Greek tradition, would serve this purpose. [11] These theorems are now known in the literature as the “Tusi Couple” and the “‘Urdi Lemma.” For both Tusi and ‘Urdi, “the problem to be solved was exactly that posed by Ibn al-Haytham, and the solutions proposed by both (and later by Qutb al-Din al-Shirazi, a student of Tusi) betray the presuppositions and limitations that characterised the approach of the eleventh-century mathematician.” [12] This tradition continued with astronomers working in later centuries, particularly, Ibn al-Shatir (d. 1375) who worked in the central mosque of Damascus in the fourteenth century. [13]
Figure 3. Nizam al-Din Hassan bin Husayn Qumi Nishapuri, known as Nizam-i a’raj (fl. 1311); a commentary on Tusi’s al-Tadhkirah Fi ‘ilm al-Hay’a, signed ‘Ali bin Sufi bin Ibrahim Aqhari, Timurid Iran, dated December 1490 (Source)
In the eleventh century, Ibn al-Haytham (965-1039) criticised the work of Ptolemy in his work al-Shukūk ‘ala Batlamyūs (Doubts concerning Ptolemy), in which he highlighted all the “still unresolved inconsistencies” in three of Ptolemy’s works, but without proposing solutions. [14] Ibn al-Haytham stated, “The arrangement proposed for planetary motions in the Almagest were ‘false’ and the true arrangements were yet to be discovered.” [15] Ptolemy’s work was also criticised by an unknown astronomer in a book called al-Istidrāk ‘ala Batlamyūs, which has not yet been located. [16] This trend of criticising Ptolemy’s work became known as the astronomical school of Ibn al-Haytham, which lasted until other solutions were sought and found in the eastern part of the Muslim empire. [17]
Ibn al-Haytham’s work led Muslims to search for solutions to Ptolemy’s inconsistencies. In Andalusia (Muslim West) there were proposals to re-adopt Aristotelian principles. [18] The best representative of this school was al-Bitrūjī (end of twelfth century). These proposals, however, were philosophical solutions whose conclusions could not allow practical calculations to be made or to be verified by numerical observations. [19] This school was therefore unsuccessful in producing alternate results even though its philosophical processes “remain interesting.” [20]
In the Muslim East, the response was different in the sense that it was scientific and not philosophical, which gave rise to what is called “the great period of Islamic astronomy.” [21] This period witnessed the rise of research into the movement of heavenly bodies using non-Ptolemaic models. [22] This led to new contributions to astronomy, which eventually led to the Copernican heliocentric model of the universe – as shall be seen later on in this chapter. The essential part of that important research was done by a group of eminent scientists working in the Maragha observatory near Tabriz in northwest Iran. [23]
Figure 4. Central Tower of the Maragheh Observatory (Source)
Towards the end of the eleventh century (the supposed century of decline) a large and highly organised observatory was founded in Iran. [24] This observatory was founded by Malikshah (1072-92) and had amongst its eminent scientists Omar al-Khayyam. The plan was that this observatory was meant to operate for thirty years, but it only lasted for eighteen years – until the death of its founder. [25] It was the first official observatory that lasted for that long, and more importantly, it was in this tradition that the famous Maragha observatory was constructed in the second half of the thirteenth century, marking an important turning point in the history of astronomy. [26]
Figure 5. Painting of Al-Tusi and colleagues working on the Zij-i Ilkhani at the observatory (Source)
The Maragha observatory was known for the high quality instruments it possessed, a very important scientific library with about 400,000 books attached to it, [27] a foundry for the construction of the copper apparatus, [28] and the well organised work of “extremely high-calibre researches working in it.” [29] Amongst these researches were: Nasir al-Din al-Tusi (1201-74), Mu’ayyid al-Din al-‘Urdi (d.1266), Muhyi al-Din al-Maghribi, Fakhr al-Din al-Maraghi, Ali ibn ‘Umar alQazwini, Najm al-Din al-Abhari, Qutub al-Din al-Shirazi, and the Chinese scholar Fao Mun-ji, all of whom extended the astronomy of Ptolemy. [30] The astronomical contributions of some of these scientists will be examined later in the chapter. It should be noted that the reform to the Ptolemaic astronomy started before the establishment of the Maragha observatory, but reached its heights in the fourteenth century. In fact, some of the astronomers at Maragha had already started their reform work before joining the Maragha observatory, and it is perhaps because of this that they were invited to work at Maragha. [31]
Berggren [32] informs us that more recent research has shown that the reform movement of Ptolemaic astronomy began with Alhazen in the eleventh century. This reform movement was later developed at the Maragha observatory, and the first serious non-Ptolemaic models were proposed by al-‘Urdi in the mid thirteenth century, and were developed later in that century by al-Tusi and al-Shirazi. [33] These non-Ptolemaic models were the source of continued research through the seventeenth century. [34] The reform of astronomy was made successful primarily due to the ‘Tusi couple.’ Saliba’s book, A History of Arabic Astronomy: Planetary Theories during the Golden Age of Islam, [35] treats many aspects of this reform movement, in particular the Tusi couple and ‘Urdi’s Lemma, both of which played important roles in the whole development, as well as the discussion of the mathematical equivalence of earlier models developed by the Maragha school to those of Copernicus. [36]
In the Maragha observatory new set of astronomical tables – called Ilkhanian tables – were formulated. [37] Also, scientists working at Maragha were able to produce “better geometrical models than those of Ptolemy to account for the movements of celestial bodies.” [38] More importantly, this observatory initiated the establishment of other significant observatories in Samarkand, Istanbul and India. The most famous of these is the one built in Samarkand by Ulugh Beg, who was an eminent scientist. This observatory lasted until nearly 1500. [39]
Ironically, Hulagu Khan (who sacked Baghdad in 1256) financed the Maragha observatory with large sums of revenue for its maintenance. [40] The activity of al-Maragha observatory lasted until the early fourteenth century (1316) the date of the death of its last known director, Asīl al-Din, who directed it for fourteen years. [41]
Figure 6. Folio From The Akhlaq-i Nasiri of Nasir al-Din al-Tusi: School courtyard with boys reading and writing. Lahore, Mughal period, circa 1595 CE. (Source)
It was said above that Malikshah founded the most important observatory during the eleventh century. Amongst its greatest scientists was Omar al-Khayyam, who is known for his Rubaiyyat more than anything else. [42] Generally, however, the eleventh century did not witness new contributions in astronomy other than the “continuous and parallel developments observed in the preceding eras,” [43] with the exception of new technological contributions in the form of instrument making. [44] During the twelfth century “several proposals to improve the dominant Ptolemaic astronomy with several mathematical models,”[45] were suggested, but no notable contributions were made. [46] Original and influential contributions flourished later by astronomers of the Maragha Observatory. The following will show that astronomers of the Maragha observatory not only produced original work in astronomy, but also:
“left their imprint on later astronomical research, mainly in the Latin West, and may perhaps have laid the foundation for Copernican astronomy itself.” [47]
While al-‘Urdi made original contribution to a number of scientific disciplines, emphasis here will only be on his astronomical contributions – and the same is true regarding other astronomers discussed below. Al-‘Urdi was the first astronomer associated with the Maragha School to construct planetary models before 1259 AD. [48] Al-‘Urdi designed some of the instruments at the Maragha Observatory, but more importantly he was also the first astronomer to offer alternative models to those of Ptolemy, [49] which were developed later in the thirteenth century by Nasir al-Din al-Tusi and his student Qutb al-Shirazi, [50] and perfected by Ibn al-Shatir (Damascus) in the fourteenth century – whose planetary models “and those of Copernicus are virtually identical, with only minor differences in some parameters.” [51]
Al-‘Urdi was known as an expert maker of astronomical instruments who was brought from Syria to supervise the construction of the Maragha. [52] His Book Hay’a, written before leaving Syria, demonstrates his rejection of views and procedures done by earlier competent Islamic astronomers. [53] Furthermore, al-‘Urdi’s book clearly shows that he was not completely satisfied with “the ancient observations believed to be true, such as those of Hipparchus and Ptolemy,” [54] and “his reluctance to pass judgment on them without having been able to test them.” [55]
In the same book al-‘Urdi lauds the study of astronomy as a universal pursuit that does not vary with place or time “or religion.” [56] Mixing themes of Hellenic philosophy with others inspired by the Islamic revelation made al-‘Urdi’s astronomical arguments favour the promotion and perfection of Ptolemaic astronomy. [57] Al-‘Urdi only lamented that he could not carry his own observations but accepted the earlier observations of Ptolemy and only objected to Ptolemy’s hypothesis of mathematical models.
Figure 7. Manuscript of al-Urdi’s Risala fi Kayfiyyat al-Arsad wa-ma Yuhtaju Ila ‘ilmihi Wa-‘Amalihi Min al-Turuq al-Mu’addiya ila Ma’rifat ‘Awdat al-Kawakib. Copy created in Iran, dated 15th century (Source)
Ultimately, for al-‘Urdi the problem to be solved was exactly that posed by Ibn al-Haytham, and the solutions proposed by him and al-Tusi (and later by Qutb al-Din al-Shirazi, a student of Tusi) betray the presuppositions and limitations that characterised the approach of the eleventh century mathematician. [58] Al-‘Urdi remarked that:
Ptolemy, in his solar model opted for a single eccentric orb in preference to the combination of a concentric deferent and an epicycle (both moving with simple/uniform motions) because it was “simpler” to assume a single motion rather than two. [59]
Al-‘Urdi then declared that he seeks:
The simplest constructions possible by means of which the motions of the planets can be accomplished in a uniform circular manner, in accordance with what resembles and is appropriate for the nature of the heaven. [60]
But such an interpretation had to be satisfied by a dominant physical doctrine, and the observational evidence reported and argued in mathematical terms in Almagest. [61] These conditions existed for centuries, and “evidence of their unresolved interaction with one another had been embarrassingly visible in Ptolemy’s work itself.” [62] These conditions were not invented by Muslim astronomers but were given to them, [63] and so “they needed to be reconciled, at least in the eyes of those who accepted them as equally indispensable,” [64] such as Ibn al-Haytham, al-‘Urdi, al-Tusi, and, a century later, Ibn al-Shatir.
Al-‘Urdi sought to achieve such a reconciliation in the construction of his new planetary models. [65] Thus, he:
Utilised the concept to represent the mathematical character of the proposed devices as means of replacing a Ptolemaic variable-length vector rotating at constant velocity (the Ptolemaic equant vector) by linkages of constant-length vectors each rotating with a constant velocity, thereby disposing of the “impossible” constant-length deferent radius carrying the epicycle centre around at variable speed. [66]
Al-Urdi’s arguments against Ptolemy led to him to establish a new model of his own (‘Urdi’s Lemma), with which he was satisfied, consequently urging “the reader to accept it and to reject that of Ptolemy, since the latter had been shown to have been riddled with contradictions. [67] Later, Copernicus echoed al-‘Urdi’s original contribution in De Revolutionibus. [68] But to understand the possible relationship between the Copernican model and that of al-‘Urdi it is necessary to investigate the contributions of al–Tusi, al-Shirazi and Ibn al-Shatir. Since the emphasis of this chapter is on Persia, Ibn al-Shatir (who belongs to Damascus, Syria) will be referred to here, but examined in more details in the next chapter.
Figure 8. Iranian stamp for the 700th anniversary of his death (Source)
Known as Nasir al-Din al-Tusi, his proper name was Muhammad ibn Muhammad ibn al-Hasan al-Tusi. [69] He is one of the most influential figures in Islamic intellectual history. [70] He was a distinguished scholar in astronomy, mathematics, mineralogy, logic, philosophy, ethics and theology.
Al-Tusi was the head of the Maragha observatory, and is one of the most prolific Islamic polymaths, with 150 known treatises and letters to his credit. [71] He became famous for his treatise al-Tadhkira in which he discusses the problems with Ptolemy’s lunar model, and tries to find solutions to them. [72] Al-Tusi’s major contributions to astronomy consisted of his criticism of Ptolemaic astronomy, and the proposal of a new theory of planetary motion. [73]
Without going into technical details, [74] according to al-Tusi the problem in the Ptolemaic lunar model was its inability “to allow the centre of the epicycle to approach the centre of the universe and to draw away from it without having to incorporate the crank-like mechanism of Ptolemy.” [75] It was in that context that al-Tusi “proposed a new mechanism in his book Tahrir al-Majisti (‘A Redaction of the Almagest, composed in 1247).” In al-Tadhkira, al-Tusi:
Devised a new model of lunar motion, essentially different from Ptolemy’s. Abolishing the eccentric and the centre of prosneusis, he founded it exclusively on the principle of eight uniformly rotating spheres and thereby succeeded in representing the irregularities of lunar motion with the same exactness as the Almagest. His claim that the maximum difference in longitude between the two theories amounts to 10’ [10 minutes] proves perfectly true. In his model Nasir, for the first time in the history of astronomy, employed a theorem invented by him, which, 250 years later, occurred again in Copernicus, De Revolutionibus, III 4. [76]
The theorem referred to above concerns what Kennedy [77] called the “Tusi-couple.” The aim of al-Tusi with this result was to remove all parts of Ptolemy’s system that were not based on the principle of uniform circular motion. Once that was achieved using his “Tusi-couple”:
There was no longer any need for the eccentric deferent of Ptolemy, nor for his crank-like mechanism, both of which were originally required to bring the lunar epicycle closer to the earth at quadrature and further away at conjunction and opposition. [78]
Though al-Tusi made numerous other contributions to astronomy, however, his most important contribution was the so-called ‘Tusi couple.’ With the help of this theory (and ‘Urdi’s Lemma, examined above), and with the “technique of dividing the eccentricities of the Ptolemaic models, it was possible to transfer segments of these models from the central parts to the peripheries and back.” [79] In addition, the Tusi couple allowed “the production of linear motions as a combination of circular motions, and thus allowed someone like Ibn al-Shatir, and after him Copernicus, to create the effect of enlarging the size of the epicycle radius and of shrinking it by using uniform circular motion only or combination thereof.” [80]
Al-Tusi’s work was carried on by other astronomers of the Maragha School, which “succeeded in producing the non-Ptolemaic planetary models that were duplicated in the work of Copernicus.” [81] Al-Tusi’s original contribution in astronomy is considered “the most important departure from Ptolemaic astronomy before modern times.” [82] With the exception of Copernicus’ heliocentric thesis, “the novelty of Copernicus’ astronomy is already found in the works of al-Tusi and his followers, which probably reached Copernicus through Byzantine intermediaries.” [83]
Figure 9. ‘Ali ibn Muhammad ibn ‘Ali al-Husayni al-Jurjani, known as Al-Sayyid al-Sharif (d.1413), Sharh tadkira (a commentary on al-Tusi’s Kitab al-tadhkira, on astronomy), Persia, Timurid, dated 1410 (Source)
Figure 10. Epicyclic planetary model in a medieval manuscript by Qutb al-Din al-Shirazi. (Source)
Al-Shirazi joined the Maragha Observatory around 1262, and became Tusi’s foremost student. He remained at Maragha a long period before he moved to Khurasan, Baghdad, Konya, Sivas, Molatya, Tabriz and other areas. [84] Al-Shirazi wrote on optics, medicine, philosophy and astronomy. Here we shall consider his contributions in astronomy during his stay at the Maragha observatory.
Al-Shirazi emphasised the relation between the movement of the sun and the planets in the way that is found later in the writings of Regiomontanus, and which prepared the way for Copernicus. [85] In two of his most famous books, Nihaya and al-Tuhfat al-Shahiyya, al-Shirazi sought to reach a completely satisfactory planetary model, and the solutions he arrived at were amongst his most important achievements. [86] The details of this model are beyond the scope of this chapter, but can be found in the work of scholars like E. S. Kennedy. [87]
In his book Nihaya, Shirazi wanted to find solutions to the objections raised against Ptolemaic models. However, he did not arrive at any new model, though he concluded that Tusi’s models did not answer objections to the lunar model, and ‘Urdi’s model was preferred. [88] In his Tuhfa, Shirazi proposed a model of his own. Al-Shirazi’s model represents the height of the technique developed at Maragha to solve the problems of planetary motion. He also applied these techniques to the solution of the problem of the moon, trying to remove some of the obvious flaws in the Ptolemaic model. [89] It was shown above that al-Tusi found the equant of Ptolemy particularly unsatisfactory. In his Tadhkira he replaced it by adding two more small epicycles (Tusi couple) to the model of each planet’s orbit. Through this device al-Tusi was able to achieve his goal of generating the non-uniform motions of the planets by combinations of uniformly rotating circles. [90] The centres of the deferents, however, were still displaced from the earth.
Qutb al-Din al-Shirazi offered an alternative arrangement but this system too retained the philosophically objectionable eccentricity. [91] Ibn al-Shatir of Damascus was more successful, for he produced a model that “was greatly superior to that of Ptolemy,” [92] and “mathematically equivalent to those of Copernicus elaborated some 150 years after the time of Ibn al-Shatir.” [93] Ibn al-Shatir played the most significant role in the development of theoretical planetary models and overcome the problems associated with Ptolemaic planetary models. [94] However, he arrived at such a model building on the work of astronomers like al-Tusi, al-‘Urdi and al-Shirazi. [95]
Figure 11. Jamshid bin Mas’ud bin Mahmud al-Tabib al-Kashi, known as Ghiyath (d. 1429); Miftah al-Hisab signed ibn Muhammad Mu’min Taj al-Din al-Shirazi, Iran, dated 31 May 1656 (Source)
Figure 12. From Prof. George Saliba’s website showing both Tusi’s and Copernicus’ drawings (Source)
It was noted above that a completely concentric rearrangement of the planetary mechanisms was achieved by Ibn al-Shatir, who worked in Damascus in about 1350. By using a scheme related to that of al-Tusi, Ibn al-Shatir succeeded in eliminating not only the equant but also certain other objectionable circles from Ptolemy’s constructions. He thereby cleared the way for a perfectly nested and mechanically acceptable set of celestial spheres. Yet Ibn al-Shatir’s solution, along with the work of the Maragha astronomers, remained generally unknown in medieval Europe. [96]
According to Kennedy, [101] the resemblance between the work of Copernicus and the Islamic astronomers who preceded him are outstanding:
Figure 13. Ibn al-Shatir’s model for the appearances of Mercury, showing the multiplication of epicycles in a Ptolemaic enterprise. 14th century CE. (Source)
More recently, Saliba claims that early in his works, Copernicus – like the Muslim astronomers – was troubled by the mathematical inconsistencies of Ptolemy, “but it was the problem of the equant that disturbed him more than the geocentric cosmology.” [102] Furthermore, since Copernicus still viewed celestial motions as circular rather than elliptical and so still required the equant to describe elliptical motions, a heliocentric universe would not have solved the problem of the equant in any case. [103] Thus, according to Saliba, a close inspection of Copernicus’s work shows that the only two theorems Copernicus used that weren’t already in the classical Greek sources were the ‘Urdi Lemma and the Tusi Couple. [104] Copernicus was using the ‘Urdi Lemma and the Tusi Couple in the sixteenth century to solve precisely the same problems that faced the Islamic astronomers in the thirteenth century. [105]
The question that is being asked by scholars is how could someone like Copernicus become familiar with the ideas of ‘Urdi, al-Tusi and Ibn al-Shatir, when apparently he could not read Arabic, and as far as known the Arabic works had not been translated into Latin? [106] Recent research gives some interesting clues. For example, the Austrian-American historian Otto Neugebauer drew attention to “a Byzantine Greek manuscript, translated from Arabic, which contained some of the results obtained by the Islamic astronomers.” [107] Since “Copernicus did read Greek,” and he may have had the opportunity to see Byzantine Greek manuscript “early in the sixteenth century in the course of his studies in Italy (where the manuscript now resides).” [108]
More recently, Saliba has uncovered in different European libraries several Arabic manuscripts on planetary astronomy, including a copy of Tusi’s critique of Ptolemy. [109] The manuscripts “appear to have been owned by Copernicus’s contemporaries, who could read Arabic very well as evidenced by many Latin notes they left on the margins.” [110] But the question that is posed by Saliba is this: “Did those contemporaries, or their colleagues, ever communicate this knowledge to Copernicus?” [111] Others, like Stacewicz-Sapuntzakis and Andrea PontecorvoMartonffy, ask: is it “possible that Copernicus was not aware of the precise origins of these theorems, or that to acknowledge them might have proved difficult in the charged anti-Islamic atmosphere era of the early 16th century?” [112] But Saliba claims that, “we know that Copernicus had no qualms about mentioning other Islamic astronomers, such as al-Battani and Arzachel, among others, when he knew his sources. But when he did not know, as seems to be the case here, he simply remained silent.” [113]
Other recent studies by Saliba show that the astronomical works of al-Tusi were continued during the sixteenth century. Saliba studies on a commentary on the Tadhkira of Tusi himself, which was written by Shams al-Din al-Khafri (d. after 1525), shows that al-Khafri has gone far beyond all previous commentators in that he took it upon himself not only to explain the work of Tusi, but to complete that work and add to it all the parts left unfinished by Tusi. As a result, al-Khafri’s commentary contains at least five mathematical models of his own creation in addition to the ones he credited to others. [114]
Figure 14. Diagram of the famous Tusi couple as depicted in the 13th-century Arabic MS 319 (folio 28v) held at the Vatican Library (Source)
The aim of this chapter was to examine the fate of Islamic astronomy in Persia to see how far it fits with any of the four theoretical claims established in Chapter Four. This chapter demonstrated that Islamic astronomy in Persia flourished after the eleventh century. The period between the eleventh and sixteenth centuries was marked with intense astronomical activity. In the Maragha observatory in Persia, original contributions in astronomy (notwithstanding contributions in other scientific fields like mathematics) were made. The originality and importance of these contributions can be estimated by their impact upon later European astronomical research, which may perhaps have laid the foundation for Copernican astronomy itself.
This chapter also showed that in some of the most recent research in theoretical astronomy, historians of Islamic astronomy such as Saliba [115] have documented the highly original contributions of Mu’ayyad al-Din al-‘Urdi (d. 1266), Nasir al-Din al-Tusi (d. 1274), and Qutb al-Din al-Shirazi (d. 1311), between the thirteenth and sixteenth century. Such research shows that Ibn al-Shatir’s highly sophisticated alternatives to the Ptolemaic models for planetary motion were simply one development in a tradition of reform of Ptolemaic astronomy that began with Alhazen in the eleventh century. [116] The first serious models in this reform movement, which were proposed by al-Urdi in the mid-thirteenth century, were developed later in the century by Nasir al-Din al-Tusi and his student Qutb al-Din al-Shirazi. These non-Ptolemaic models continued to be explored through the seventeenth century. [117]
More recently, historians of Islamic science and astronomy as Goldstein, Hartner, King, Sabra, Saliba, and Kennedy, have painted a “portrait that almost fully assimilates the scientific activity in Arab astronomy of the twelfth, thirteenth, and fourteenth centuries with the activities of such modern scientists as Copernicus, Galileo, Tycho Brahe, and Kepler.” [118] Furthermore, studies by Neugebauer and Swerdlow establish that Islamic astronomy “must have had an impact on Copernicus himself, and only future research will reveal the exact nature of the channels of transmission from the East to the West that were responsible for this impact.” [119]
This case study, like the one before it, clearly shows that the idea that Islamic science “declined,” “decayed,” “froze,” or suffered any other uniform single-faceted fate is clearly erroneous. This case study further verifies that Ibn Khaldun’s theory is essentially closer to reality, but is incomprehensive since it says nothing about astronomy in Persia.
Figure 15. Iskandar Sultan horoscope. The personal horoscope of Iskandar b. Umar Shaykh b. Timur who ruled in Shiraz from 812/1409 to 817/1414. The horoscope was prepared in the second year of Iskandar’s rule. (Source)
[1] Régis Morelon, “General Survey of Arabic Astronomy,” in Roshdi Rashed (ed), Encyclopaedia of The History of Arabic Science, 1, (London: Routledge, 1996), p. 17.
[2] Ibid.
[3] Ibid, p.4.
[4] Ibid.
[5] Ibid., p.25.
[6] Ibid.
[7] A.I. Sabra, “Configuring the Universe: Aporetic, Problem Solving, and Kinematic Modeling as Themes of Arabic Astronomy,” Perspectives on Science, 6, Fall 1998, i3.
[8] Ibid.
[9] Ibid.
[10] Ibid.
[11] Ibid.
[12] Ibid.
[13] Ibid. Also see E.S. Kennedy, “An Islamic Response to Greek Astronomy: Kitab Tad dil Hay at al-Aflak of Sadr al-Sharia,” The Journal of the American Oriental Society, 117, n2, April-June 1997, p. 384 (2).
[14] Morelon, op. cit., p.17
[15] A. H. Sabra, “The Andalusian revolt Against Ptolemaic Astronomy,” in Everett Mendelsohn (ed), Transformation and Tradition in the Sciences (New York: Cambridge University Press, 1984), p. 134.
[16] George Saliba, “Arabic Planetary Theories after the eleventh century AD,” in Roshdi Rashed (ed), Encyclopaedia of The History of Arabic Science, op. cit., 1, p.74.
[17] Ibid.
[18] This was to be done by “abandoning epicycles and eccentrics and returning to homocentric spheres, which would be much more consistent form a ‘physical’ astronomy point of view.” Morelon, op. cit., p.17.
[19] Morelon, op. cit., p. 17.
[20] Ibid.
[21] Ibid. p. 18.
[22] Ibid.
[23] Ibid. p. 13.
[24] Ibid.
[25] Ibid.
[26] Ibid. Also see A. Sayili, The Observatory in Islam and its place in the general History of the Observatory (Ankara: The Turkish Historical Society, 1960), pp. 188-223.
[27] Ahmad Y Al-Hassan, “Factors behind the decline of Islamic science after the sixteenth century,” in Sharifah Shifa Al-Attas (ed.), Islam and the Challenge of Modernity: History and Contemporary Contexts (Kuala Lumpur: International Institute of Islamic Thought and Civilisation, 1996).
[28] Sayili, op. cit., p. 14.
[29] Ibid., p. 13.
[30] Ibid., p. 14. Also, Charles Coulston Gillispie (ed), Dictionary of Scientific Biography (New York: Charles Scriber’s Sons, 1976), XII, pp. 508-513.
[31] This is true in the case of Nasir al-Din al-Tusi and al-‘Urdi. See George Saliba, Kitab al-Hya’ah – The astronomical work of Mu’ayyad al-din al-‘Urdi (Centre for Arab Unity Studies, 1990), pp. 31f; and F J. Ragep, Nasir al-Din al-Tusi Memoir on Astronomy, 2 vol. (New York: Springer-Verlag, 1993), pp. 65f.
[32] J. Lennart Berggren, “Mathematics and Her Sisters in Medieval Islam: A selective review of work done from 1985 to 1995,” Historica Mathematica, 24, 1997, pp. 23-24.
[33] Ibid., p. 24.
[34] Ibid.
[35] George Saliba, A History of Arabic Astronomy: Planetary Theories during the Golden Age of Islam (New York: New York University Press, 1994).
[36] Berggren, op. cit., p. 24.
[37] Morelon, op. cit., p. 13.
[38] Ibid.
[39] Ibid. p. 14.
[40] Ibid. p. 13.
[41] Ibid. p. 14.
[42] Abdul Latif Samian, “The growth and Decline of Islamic astronomy,” Islamiyyat, 14, 1993, p. 19.
[43] Ibid.
[44] Ibid.
[45] Ibid.
[46] Ibid.
[47] George Saliba, “Arabic planetary theories after the eleventh century AD,” in Roshdi Rashed (ed.) Encyclopaedia of the History of Arabic Science, op. cit., 3, p. 59.
[48] Samian, op. cit., p. 21.
[49] Ibid.
[50] Berggren, 1997, op. cit., p.24.
[51] Toby Huff, The rise of early modern science (Cambridge: Cambridge University Press, 1993), p. 59.
[52] A. I. Sabra, 1998, op. cit.
[53] Ibid.
[54] Ibid.
[55] Ibid.
[56] Ibid.
[57] Ibid.
[58] Ibid.
[59] Ibid.
[60] Ibid.
[61] Ibid.
[62] Ibid.
[63] Ibid.
[64] Ibid.
[65] Ibid.
[66] Ibid.
[67] Saliba, 1996, op. cit., pp. 92-93.
[68] Ibid.
[69] Gillispie, op. cit., p. 508.
[70] Ibid.
[71] Owen Gingerich, “Islamic astronomy,” Scientific American, 254, April 1986, p. 74 (10).
[72] Saliba, op. cit. p. 93.
[73] Gillispie, op. cit., p. 511.
[74] For an explanation of such details see Saliba, 1996, op. cit. pp. 58-127.
[75] Saliba, 1996, op. cit., p. 93.
[76] W. Hartner, “Nasir al-Din al-Tusi ‘s lunar theory,” Physis – Riv. Internaz. Storia Sci. 11, 1969, pp. 287-304.
[77] E. S. Kennedy, “Late Medieval Planetary Theory,” Isis, 57, 1966, 1vii, pp. 367-78.
[78] Sabra, op. cit., p. 94.
[79] Saliba, 1996, op. cit. p. 125.
[80] Ibid.
[81] Huff, op. cit., p. 57.
[82] Gillespie, op. cit., p. 511.
[83] Ibid.
[84] Ibid, vol. XI, p. 248.
[85] Gillespie, op. cit., vol. XI, p. 250.
[86] Ibid.
[87] See for example E. S Kennedy, “Late Medieval Planetary Theory,” Isis, 57, 3, 1966, p. 376 and 373.
[88] Saliba, 1996, op. cit., pp. 97-98.
[89] Gillespie, op. cit, vol. XI, p. 251.
[90] Gingerich, op. cit.
[91] Ibid.
[92] Gillespie, vol. XI, op. cit., p. 251.
[93] David A. King, “The astronomy of the Mamluks,” Isis, 74, 1983, p. 539.
[94] Ibid., p. 538.
[95] Ibid.
[96] Gingerich, op. cit.
[97] Ibid.
[98] Ibid.
[99] Ibid.
[100] Ibid.
[101] E. S. Kennedy, “Late Medieval Planetary Theory,” Isis, 57, 1966, pp. 366-377.
[102] Saliba, “Greek astronomy and the medieval Arabic tradition: the medieval Islamic astronomers were not merely translators. They may also have played a key role in the Copernican revolution,” American Scientist, 90, 4, July-August 2002, p. 360(8).
[103] Ibid.
[104] Ibid.
[105] Ibid.
[106] Ibid.
[107] Ibid.
[108] Ibid.
[109] Ibid.
[110] Ibid.
[111] Ibid.
[112] Cited in: “In defence of Copernicus. (Letters to the Editors),” American Scientist, 90, 6, Nov-Dec 2002, p. 492 (1).
[113] Ibid.
[114] Saliba, “Writing the history of Arabic astronomy: problems and differing perspectives,” The Journal of the American Oriental Society, 116, 4, Oct-Dec 1996, p. 709 (10).
[115] Saliba, Kitab al-Hya’ah; the Astronomical Work of Mu’ayyad al-Din al-‘Urdi (Center for Arab Unity Studies, 1990); Saliba, A History of Arabic Astronomy. Planetary Theories during the Golden Age of Islam (New York University Press, 1994).
[116] J. Lennart Berggren, “Mathematics and Her Sisters in Medieval Islam: A selective Review of Work Done from 1985-1995,” Historia Mathematica 24, 1997, pp. 407-440.
[117] Ibid.
[118] Huff, op. cit., p. 57.
[119] Saliba, 2002, op. cit., pp. 125-126.
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