al-Battānī

Arab astronomer and mathematician

• Born: 858
• Birthplace: Near Haran, Mesopotamia (now in Turkey)
• Died: 929
• Place of death: Qasr al-Jiss, region of Sāmarrā (now in Iraq)

Al-Battānī examined and corrected, through application of trigonometry, astronomical theories first put forward by the second century Alexandrian Ptolemy.

Early Life

Born near Haran, the young al-Battānī (ahl-bah-TAH-nee) moved with his and several other families to Rakka on the Euphrates River midway on the caravan route between Aleppo and the Upper Mesopotamian city of Mosul. This migration may be explained in part by the nisba, or nickname, retained by the future Islamic astronomer. “Al-Sabi՚” may refer to his family's earlier adherence to the so-called Sabian sect, which was reputed to follow a mixture of Christian and Islamic principles. Whatever the family's original religious orientation, al-Battānī's later fame was won under the banner of Islam, the faith he ultimately followed. After his move to Rakka as a youth, al-Battānī spent the remainder of his life in the same geographical and cultural environment.

No specific information is available on al-Battānī's formal education. It is not known, for example, whether his original training was obtained in a fully secular “scientific” or in a religious setting. It was as a youth in Rakka, however, that al-Battānī decided to devote himself to careful study of ancient texts, especially those of Ptolemy, which provided him with the knowledge needed to carry out the series of astronomical observations that would make him famous, not only in the Islamic world but in the medieval European West as well.

Life's Work

Al-Battānī, known to the West as Albatenius, contributed greatly to advances in the field of trigonometry . To carry out key calculations, he relied on algebraic rather than geometric methods. Like his somewhat lesser known later follower Abul Wefa (940-998), al-Battānī focused much of his attention on the theories of the second century Alexandrian astronomer Ptolemy. Several Islamic scholars before him had been intrigued by Ptolemy's approach to the phenomenon of the oscillatory motion of the equinoxes. Al-Battānī's contemporary Thābit ibn Qurrah (c. 836-901) tried to account for this by supplementing Ptolemy's theory, merely adding a ninth sphere to the Greek scientist's assumption of eight spheres; al-Battānī, however, remained doubtful. He was convinced that trigonometry should be developed more effectively for the purpose of achieving greater precision in already known methods of making these and other astronomical calculations. This goal led him to explore and expand the relevance of sines. His use of the Indian sines, or half chords, enabled him to criticize Ptolemy's conclusions in several areas.

For example, Ptolemy had insisted that the solar apogee was a fully immobile phenomenon. Al-Battānī, however, was able to observe that in the seven centuries since Ptolemy's time, there had been a notable increase in the Sun's apogee. His further observations suggested that the apogee was affected by the precession of the equinoxes. To explore this theory required a substantial revision of methods of proposing equations to represent the passage of time in accurate astronomical terms; room had to be made for accommodating slow secular variations. As part of this process, al-Battānī set out to correct Ptolemy's theory of the precession of the equinoxes.

The phenomenon of eclipses was also a field incompletely pioneered by Ptolemy. Interest in this subject motivated al-Battānī to make a variety of studies that aided subsequent astronomers in their calculations to determine the time of the visibility of the new moon. His treatment of the phenomena of lunar and solar eclipses provided the basic information that would be used by European astronomers as late as the eighteenth century. Most notably, Richard Dunthorne used al-Battānī's work in his 1749 study of the apparent acceleration of the motion of the Moon. In addition, mention of solutions al-Battānī proposed for the field of spherical trigonometry appears in many earlier European works, including those of Regiomontanus (1436-1476).

In a somewhat more practical vein easily appreciated by the layperson, al-Battānī's observations allowed him to determine the length of the tropic year and, significantly, the precise duration of the four seasons of the year.

One of the most original areas of al-Battānī's work involved the use of horizontal and vertical sundials. Through their use, he was able to denote the characteristics of a so-called “horizontal shadow” (umbra extensa). These he used to reveal cotangents, for which he prepared the first-known systematic tables. Similarly, his study of “vertical shadows” (umbra versa) provided pioneer data for calculating tangents.

Most of al-Battānī's important findings in the field of astronomy were contained in his major work, Kitāb al-zij (c. 900-901, book on astronomy; best known as Zij, De motu stellarum, or De scientia stellarum). As the Latin titles suggest, this magnum opus was first circulated widely among scholars of the early period of the European Renaissance. The work was translated originally by Robertus Retinensis in Spain in the twelfth century. In the thirteenth century, King Alfonso X of Spain had a direct Arabic-to-Spanish translation prepared. De scientia stellarum later gained added attention from modern scholars such as the Italian C. A. Nallino, who edited and translated the Latin text, providing essential commentaries that enhance contemporary understanding of the Islamic scholar's original contributions.

Unfortunately, modern scholars’ familiarity with other important writings by al-Battānī is limited to what can be gleaned from references to them in other Islamic authors’ works. A “Book of the Science of Ascensions of the Signs of the Zodiac,” a commentary on Ptolemy's Apotelesmatika tetrabiblos, and a third work on trigonometry, for example, are all lost in their original versions.

Significance

The scholarly career of al-Battānī provides an example of the diversity of pre-Islamic sources that contributed to the rise of Islamic science. It also illustrates the importance of such scientists’ work in saving traces of pre-Islamic contributions to knowledge during the Dark Ages of European history, when much of the classical heritage of Western civilization was lost. To speak of al-Battānī's role as that of an interim transmitter of knowledge, however, would be to miss the essential importance of scientific endeavors in his era. It is clear, for example, that al-Battānī was dissatisfied with interpretations offered by his classical and Indian forerunners. By the time his work of reinterpretation was translated for transmission to the European world, it reflected numerous original contributions. Thus, in regard to the reemergence of Western science during the classical revival period of the Renaissance, it can be said that many of the principles on which it was based came from Islamic sources.

The fact that such advances in several fields of “pure” science were actively sponsored by the early Islamic caliphs themselves assumed to be primary guardians of the religious interests of their realm is of major significance. In al-Battānī's age, knowledge was still recognized as something necessarily derived from syncretic sources. Tolerance for the exploration of different secular scientific traditions did not, however, survive many successive generations. Narrowness of views in the eastern Islamic world a mere century and a half after al-Battānī's contributions would make the role of Western translators of Arabic scientific works just as vital to the conservation of cumulative knowledge in world culture as the work of Islamic translators and commentators had been after the end of the classical era. Outstanding figures such as al-Battānī, therefore, definitely span world civilizations and reflect values that are universal. These are easily recognized as such beyond the borders of their chronological time or geographic zone.

Bibliography

Anawati, G. “Science.” In The Cambridge History of Islam, edited by P. M. Holt, Ann K. S. Lambton, and Bernard Lewis. 1970. Reprint. Cambridge, England: Cambridge University Press, 1977. This chapter places the general field of science within the overall framework of Islamic civilization and explores interrelationships between religious and scientific attitudes toward knowledge and how each of the two domains was affected by developments in the other. The body of the chapter consists of a field-by-field review of the most important Islamic accomplishments, including advances in arithmetic, algebra, geometry, trigonometry, optics, mechanics, astronomy and astrology, and medicine.

Bakar, Osman. The History and Philosophy of Islamic Science. Cambridge, England: Islamic Texts Society, 1999. Discusses questions of methodology, doubt, spirituality and scientific knowledge, the philosophy of Islamic medicine, and how Islamic science influenced medieval Christian views of the natural world.

Bell, E. T. The Development of Mathematics. New York: McGraw-Hill, 1945. This comprehensive work on mathematics begins with a historical review of the field from the first-known texts through each successive stage of discovery, ending at the mid-point of the twentieth century. Includes the chapter “Detour Through India, Arabia, and Spain, a.d. 400-1300.” Covers the specific contributions of Islamic scholars such as al-Battānī and examines topical subsections of the field of mathematics, including geometry, invariance, and others. Bibliographical references.

Cajori, Florian. A History of Mathematics. 1931. 5th ed. Providence, R.I.: AMS Chelsea, 2000. This classic work has several important characteristics that still merit mention. It covers standard non-Western mathematical traditions (Hindu and Islamic). The author gives detailed information on individual mathematicians’ original findings.

Hogendijk, Jan P., and Abdelhamid I. Sabra, eds. The Enterprise of Science in Islam: New Perspectives. Cambridge, Mass.: MIT Press, 2003. A collection surveying the history of Islamic science, including mathematics and astronomy. Illustrations, bibliography, index.

Kennedy, Edward S. Astronomy and Astrology in the Medieval Islamic World. Brookfield, Vt.: Ashgate, 1998. Discusses astronomy, astronomers, math, and mathematicians during the Islamic Middle Ages. Includes an index.

Nasr, Seyyed Hossein. Islamic Science: An Illustrated Study. London: World of Islam Festival, 1976. Contains an attractive collection of illustrations that bring to life the world of Islamic science. These include intricate miniatures depicting cosmic charts and photographs of astronomical instruments and remains of observatories similar to the ones that would have been used in al-Battānī’s time. Glossary and bibliography.

Nasr, Seyyed Hossein. Science and Civilization in Islam. Cambridge, Mass.: Harvard University Press, 1968. This survey text deals only with scientific endeavors in Islamic civilization, which allows it to examine individual contributions thoroughly. Extensive bibliography.

Sabra, Abdelhamid I. Optics, Astronomy, and Logic: Studies in Arabic Science and Philosophy. Brookfield, Vt.: Variorum, 1994. A history of science, specifically optics and astronomy, in the Muslim world of al-Battānī’s time. Illustrations, index.

Stephenson, F. Richard. Historical Eclipses and Earth’s Rotation. New York: Cambridge University Press, 1997. Explores “Solar and Lunar Eclipses Recorded in Medieval Arab Chronicles,” “Observations of Eclipses by Medieval Arab Astronomers,” and “Eclipse Records from Medieval Europe.” Illustrations, bibliography, index.