The Role of Islam in the Rise of Astronomy


 Hoskin and Gingerich provide a good introductory section on Islamic astronomy in one of their latest works.[1] In a five or so pages, they detail how observation of the faith confronted Muslims with problems they had to resolve, which led to their developing aspects of mathematical astronomy to resolve such problems.[2] The following is a brief outline of this section, which, without a doubt, will not express the argument as eruditely as Hoskin and Gingerich did.

The religious practices of Islam generated three specific challenges to which mathematical astronomers attempted to find solutions. The first arose out of the lunar calendar, each month beginning with the new moon, when the lunar crescent was first sighted in the evening sky. If the crescent was seen, it would signify the beginning of the month, such as the month of fasting (Ramadhan,) or the end of it, etc. The problem remains that skies are not always clear, and even if they were, watchers in different places might not see the moon. To resolve this problem, Muslim astronomers followed criteria found in Indian sources, as well as those found in Ptolemy, which, however helpful, failed to provide adequate answers. Muslim astronomers had to compile sophisticated tables to assist in the resulting calculations, leading to the production of almanacs with information on the possibility of sightings around the beginning of each month.

The second religious requirement that involved astronomy concerned the times of prayer, the number of which was five: sunset, nightfall, daybreak, midday and afternoon. The timing of the latter two, plus that of a voluntary mid-morning prayer, corresponds to the ends of the third, sixth and ninth of the (variable) hours of daylight. Finding the exact time of the day from the altitude of the sun or the time of night from the altitude of bright stars was resolved in Baghdad  in the 9th century. By this century, the medieval equivalent of the six modern trigonometric functions had been recognised, whereas Ptolemy had operated with only a single chord. Islamic astronomers discovered basic trigonometric identities that greatly simplified calculations involving triangles on the celestial sphere. The institution of the muwaqqit, time keeper, in mosques, gave competent astronomers a central institutional foundation from which to operate, and it led to a rapid increase in the quantity and quality of astronomical writings.   

The third challenge relates to the orientation of both prayers and mosques in direction towards Makkah  from any place in the world. Muslim astronomers applied their minds to resolve the problem of how to determine the qibla (sacred orientation) mathematically using available geographical data. Formulae in spherical trigonometry were developed and tables calculated from them. One outstanding achievement, dating possibly from the 11th century, was the development of cartographic grids for Makkah-centred world maps, from which one could read off the qibla and distance to Makkah directly.[3]


Highlighting further the intricate link between faith and science is the fact that in the Islamic experience, both science and faith rose simultaneously (8th century), a unique fact in history, and Islamic science and power declined simultaneously, too, in the 13th century. This matter will be examined at greater length in the final part of this work. Here, the instance of astronomy is very enlightening as far as proving a direct link between the faith and the enthusiasm for scientific query, going further than the factor of religious necessity already looked at in the previous paragraphs. We read incessantly accounts by Muslim astronomers declaring their enthusiasm for the science in their quest for religious truth, stimulated by the fact that Islam is free of miracles, and thence, reason is the road towards religious discovery. Hence, one of Islam’s earliest astronomers, Habash Al-Hasib (d. 865) says:

‘Among the very favours which God bestowed upon the people of past generations… He had endowed them with intellects through which it became possible for them to gain clear and precise knowledge, so that this capacity of theirs led them to a discriminating and penetrating enquiry into the constitution of the heavenly spheres and the laid out land, their harmonious relations, and their mutual adaptations and connections. They thereby grasped the implications of God’s words and penetrated the inner meaning of his tidings. They thus inferred from the visible features of the firmament its more secret implications and from its appearances its hidden truths; they reached the conviction that it has a creator who brought it into being and originated it and that there was no question of a process whereby some of its parts caused existence of others.’[4]

Al-Battani  (d. 929), likewise, says of astronomy that it is a field of endeavour with an invigorating effect on the intellect and sharpens the faculty of reflection, and that this science makes possible the knowledge of the length of the year, the months, the different times and seasons, the positions of the sun and the moon as well as their eclipses, and the courses of the planets and their direct and retrograde motions, the alterations of their forms, and the arrangements of their spheres, which leads people, who reflect deeply and persistently, to the proof of the unity of God and to the comprehension of His majesty, to His immune wisdom, infinite power, and to the grasp of the excellence of His act.[5] Then, as frequently found in books on astronomy, al-Battani quotes from the Qur’an in support of ideas such as those expressed above. He cites verses such as the following, adding that many others of the same nature could be mentioned:

‘Verily, in the creation of the heavens and of the earth, and in the succession of the night and of the day, are marvels and signs for men of understanding heart. (Sura III; verse 187); Blessed be He who has placed in the heaven the signs of the zodiac, who has placed in it the lamp of the sun and the light giving moon. (XXV; 62). It is he who has appointed the sun for brightness, and the moon for a light, and has ordained her station that you may learn the number of years and the reckoning of time (X; 5)… 

Speaking to al-Qifti (d. 1248), Al-Sabti (d. 1226) stated that there was no heresy in astronomy, and that ‘on the contrary, it is a road leading to faith and to a knowledge of the power of God… through a study of what He has ordered and arranged.’[6]

Al-Urdi (d. 1266) holds that the excellence of each science comes either from the excellence of its subject or from the solidity of its proofs, or that it may come from both, and he says that this latter case is true of astronomy; for its subject matter deals:

‘with God’s most admirable achievements, the most magnificent He has created, and the most sagacious of His acts, and its proofs are geometrical and arithmetical and therefore clear and final,’[7]

and he concludes that astronomy leads to the science of theology and gives evidence of God’s magnificence.[8]

This is a common line amongst most Muslim astronomers, all acknowledging the same fervour for the science on the same lines, and all bringing together science, theology, the magnificence of creation and fabulousness of the universe.


Just as the foundations of Islamic astronomy are not Greek, Islamic astronomy is no reproduction of Greek astronomy, either.

[1] M. Hoskin and O. Gingerich: Islamic Astronomy; in The Cambridge Concise History of Astronomy; ed by M. Hoskin (Cambridge University Press; 1999), pp. 50-62.

[2] Ibid; at pp. 52-7.

[3] Ibid.

[4] A. Sayili: The Introductory section of Habash’s Astronomical Tables; Ankara Universitesi Dil ve Tarikh Cografya Fakultesi Dergisi; vol 13; No 4 (1955), p. 140.

[5] Al-Battani : Al-Zij Al-Sabi; Ed. Nallino (Rome; 1944), vol 5; pp. 6-7.

[6] Ibn al-Qifti: Tarikh al-Hukama; ed. Lippert (Berlin; 1903), pp. 228-9.

[7] Al-Urdi: Kitab al-Hay’a; Ms. Konya; Yusuf Aga Library; No 6829; p. 1b.

[8] Ibid.