Astronomy from Arabia
The birth of Astronomy
Arabic astronomy comprises the astronomical developments made in the Islamic world, particularly during the Islamic Golden Age (8th–15th centuries), and mostly written in the Arabic language. These developments mostly took place in the Middle East, Central Asia, Al-Andalus, and North Africa, and later in the Far East and India. It closely parallels the genesis of other Islamic sciences in its assimilation of foreign material and the amalgamation of the disparate elements of that material to create a science withIslamic characteristics. These included Greek, Sassanid, and Indian works in particular, which were translated and built upon. In turn, Islamic astronomy later had a significant influence on Indian, Byzantine and European astronomy (see Latin translations of the 12th century) as well as Chinese astronomy and Malian astronomy.
A significant number of stars in the sky, such as Aldebaran and Altair, and astronomical terms such as alhidade, azimuth, and almucantar, are still referred to by their Arabic names. A large corpus of literature from Islamic astronomy remains today, numbering approximately 10,000 manuscripts scattered throughout the world, many of which have not been read or cataloged. Even so, a reasonably accurate picture of Islamic activity in the field of astronomy can be reconstructed.
Ahmad Dallal notes that, unlike the Babylonians, Greeks, and Indians, who had developed elaborate systems of mathematical astronomical study, the pre-Islamic Arabs relied entirely on empirical observations. These observations were based on the rising and setting of particular stars, and this area of astronomical study was known as anwa. Anwa continued to be developed after Islamization by the Arabs, where Islamic astronomers added mathematical methods to their empirical observations. According to David King, after the rise of Islam, the religious obligation to determine the qibla and prayer times inspired more progress in astronomy for centuries.
The period of assimilation and syncretisation of earlier Hellenistic, Indian, and Sassanidastronomy. The first astronomical texts that were translated into Arabic were of Indian and Persian origin. The most notable of the texts was Zij al-Sindhind, an 8th-century Indian astronomical work that was translated by Muhammad ibn Ibrahim al-Fazari and Yaqub ibn Tariq after 770 CE under the supervision of an Indian astronomer who visited the court of caliph Al-Mansur in 770. Another text translated was the Zij al-Shah, a collection of astronomical tables (based on Indian parameters) compiled in Sasanid Persia over two centuries. Fragments of texts during this period indicate that Arabs adopted the sine function (inherited from India) in place of the chords of arc used in Greek trigonometry.
The first major Muslim work of astronomy was Zij al-Sindh by al-Khwarizmi in 830. The work contains tables for the movements of the sun, the moon and the five planets known at the time. The work is significant as it introduced Ptolemaic concepts into Islamic sciences. This work also marks the turning point in Islamic astronomy. Hitherto, Muslim astronomers had adopted a primarily research approach to the field, translating works of others and learning already discovered knowledge. Al-Khwarizmi’s work marked the beginning of nontraditional methods of study and calculations. This period of vigorous investigation, in which the superiority of the Ptolemaic system of astronomy was accepted and significant contributions made to it. However, Dallal notes that the use of parameters, sources and calculation methods from different scientific traditions made the Ptolemaic tradition “receptive right from the beginning to the possiblity of observational refinement and mathematical restructuring”. Astronomical research was greatly supported by the Abbasid caliph al-Mamun. Baghdad andDamascus became the centers of such activity. The caliphs not only supported this work financially, but endowed the work with formal prestige.
In 850, al-Farghani wrote Kitab fi Jawani (meaning “A compendium of the science of stars”). The book primarily gave a summary of Ptolemic cosmography. However, it also corrected Ptolemy based on findings of earlier Arab astronomers. Al-Farghani gave revised values for the obliquity of the ecliptic, the precessional movement of the apogees of the sun and the moon, and the circumference of the earth. The book was widely circulated through the Muslim world, and even translated into Latin.
Between 1025 and 1028, Ibn al-Haytham wrote his Al-Shuku ala Batlamyus (meaning “Doubts on Ptolemy”). While maintaining the physical reality of the geocentric model, he criticized elements of the Ptolemic models. Many astronomers took up the challenge posed in this work, namely to develop alternate models that resolved these difficulties. In 1070, Abu Ubayd al-Juzjani published the Tarik al-Aflak. In his work, he indicated the so-called “equant” problem of the Ptolemic model. Al-Juzjani even proposed a solution for the problem. In Al-Andalus, the anonymous work al-Istidrak ala Batlamyus (meaning “Recapitulation regarding Ptolemy”), included a list of objections to the Ptolemic astronomy.The period when a distinctive Islamic system of astronomy flourished. The period began as the Muslim astronomers began questioning the framework of the Ptolemaic systemof astronomy. These criticisms, however, remained within the geocentric framework and followed Ptolemy’s astronomical paradigm; one historian described their work as “a reformist project intended to consolidate Ptolemaic astronomy by bringing it into line with its own principles.
The period of stagnation, when the traditional system of astronomy continued to be practiced with enthusiasm, but with rapidly decreasing innovation of any major significance. A large corpus of literature from Islamic astronomy remains today, numbering around some 10,000 manuscript volumes scattered throughout the world. Much of this has not even been cataloged. Even so, a reasonably accurate picture of Islamic activity in the field of astronomy can be reconstructed.
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