From: Thomas Hockey et al. (eds.). The Biographical Encyclopedia of Astronomers, Springer Reference. New York: Springer, 2007, pp. 551-552 |
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Ibn al‐Bannāʾ:
Abū al‐ʿAbbās Aḥmad
ibn Muḥammad ibn ʿUthmān al‐Azdī
al‐Marrākushī
Julio Samsó
Born Marrakech,
(Morocco), 29 or 30 December 1256
Died 31 July 1321
Ibn
al‐Bannāʾ al‐Marrākushī, mathematician and
astronomer, was born in Marrakech where he studied a variety of subjects,
reportedly with at least 17 masters. However, he frequently went to Aghmāt,
near Marrakech, where he was a student of Abū ʿAbd
Allāh al‐Hazmīrī (died: 1279); it may have been due to
his influence that Ibn al‐Bannāʾ became interested in both
astronomy and astrology, and gained the reputation of being a Sufi. Ibn al‐Bannāʾ
was probably a practicing astrologer in the service of the Marīnid sultan
Abū Saʿīd (reigned: 1309–1331), and he is said
to have predicted the exact circumstances of the latter's death, which took
place some 10 years after his own. He was dedicated to his teaching, which
took place both in the great mosque of Marrakech and in his own home, and
he had at least eight disciples.
The
catalog of Ibn al‐Bannāʾ's works comprises about a 100 titles,
out of which some 50 are dedicated to mathematics and astronomy (including
astrology), but the list also includes Quranic studies, theology (uṣūl al‐dīn),
logic, law (fiqh), rhetoric, prosody, Sufism, the division of inheritances
(farāʾiḍ), weights and measures, measurement of surfaces (misāḥa),
talismanic magic, and medicine. His reputation is based mainly on his mathematical
works (especially arithmetic and algebra); he has been considered the last
creative mathematician in the Maghrib, meaning that he approached new problems
and gave original solutions. His works were extremely popular, and inspired
an enormous number of commentaries, which were still being written until the
beginning of the 20th century.
In the field of astronomy, Ibn al‐Bannāʾ is a clear
follower of the Andalusian tradition represented by the Toledan astronomer
Zārqālī, whose works reached him either directly or
indirectly. He wrote short works on the two varieties of universal astrolabes
(shakkāziyya and zarqāliyya) designed by this author,
as well as an astronomical handbook with tables (zīj) derived
ultimately from the research of Zārqālī. The title of this
zīj is Minhāj al‐ṭālib fī taʿdīl
al‐kawākib (The student's method for the computation
of planetary positions), and it became extremely popular in the Maghrib. There
were at least three commentaries, and it was still in use in the 19th century.
The direct source used by Ibn al‐Bannāʾ was the unfinished
zīj of Ibn Isḥāq,
which seems to have exercised the predominant influence in Maghribī astronomy
during the 13th and 14th centuries. Ibn al‐Bannāʾ's Minhāj
contains a selection of Ibn Isḥāq's tables accompanied
by a collection of canons that are easy to understand, which makes the zīj
accessible for the computation of planetary longitudes. This is accompanied
by some modifications of the structure of the tables, designed to make calculations
easier. Both the tables of the solar equation and those of the planetary and
lunar equations of the center are “displaced” (a constant is added to every
entry of the table in order to avoid negative values), a technique used for
the first time in the Maghrib. Although Ibn al‐Bannāʾ used
the standard structure, derived from the Handy Tables, for the tables
of the equation of the anomaly of Mars, Venus, and Mercury, he changed them
entirely in the cases of Jupiter and Saturn – planets that have small epicycles
– for which the equation of the anomaly is calculated in the same way as for
the Moon.
The Minhāj is not the only zīj produced by
Ibn al‐Bannāʾ, who prepared a summary of it entitled al‐Yasāra
fī taqwīm al‐kawākib al‐sayyāra (The simple
method for the computation of planetary positions). This smallest possible
form of a zīj, concerned mainly with the computation of planetary
longitudes, was prepared most likely for popular astrologers who, apparently,
were expected to learn the very short text of his canons by heart. The very
few numerical tables are also simplified as much as possible and, in the case
of the Moon, we go back to a simple model with only one inequality and a maximum
equation of 5° (either a rounding of the standard Indian value 4° 56' or of Ptolemy's
first lunar inequality of 5° 1′). The Yasāra met with some success, and Ibn al‐Bannāʾ
himself summarized it even further in his al‐Ishāra fī
ikhtiṣār al‐Yasāra
(How to summarize the Yasāra). The Yasāra was also
the subject of commentaries, adaptations, and corrections of defects such
as that written by Ibn Qunfudh al‐Qusanṭīnī
(1339–1407).
It
is evident from his writings that Ibn al‐Bannāʾ wrote mainly
for his students and always tried to be extremely brief and concise. He was
also interested in the practical applications of his knowledge. For example,
he wrote on the applications of geometry to land surveying, on the use of
arithmetic and algebra to solve problems of partitioning inheritances, on
weights and measures, and on the procedures for calculating with the Rūmī
ciphers (apparently derived from the Greek cursive alphanumerical system of
numeration), which were often used in Maghribī legal documents. In a
field more related to astronomy, Ibn al‐Bannāʾ wrote the Kitāb
fī al‐anwāʾ, a book on the pre‐Islamic Arabic
calendar system and meteorological predictor based on the heliacal risings
and acronychal settings. He was also interested in the problems of timekeeping
applied to Islamic worship and wrote short works, such as his Qānūn
fī maʿrifat
al‐awqāt biʾl‐ḥisāb (Rules to know
time by calculation [i. e., without instruments]), which seems to have
been directed toward the elementary astronomical education of muezzins and
imams who were responsible for the determination of prayer times and for the
fixing of the beginning of lunar months. Furthermore, Ibn al‐Bannāʾ
wrote a short report on the visibility of the New Moon of Ramaḍān of the year 1301 due
to the fact that the people of Fez had begun their fasting 1 day earlier than
those of Marrakech and Tlemcen. A similar practical/religious concern appears
in his two short texts on the qibla (direction toward Mecca): Ibn al‐Bannāʾ's
contemporaries were worried about the problem posed by the different orientations
of mosques, and he tried to ease their consciences by stating that all of
them had a correct orientation, which should not be changed in as much as
they had been established with due intellectual effort (ijtihād).
Surprisingly enough, this astronomer rejected the use not only of the imprecise
methods of folk astronomy but also of those of spherical astronomy, which
had given exact solutions to the problem since the 9th century. He gave two
reasons: The results obtained were not necessarily precise, for the differences
in geographical longitude between Mecca and other Islamic cities were not
reliably known; and the knowledge required could not be expected from a lay
Muslim.
A difficult problem is that of Ibn al‐Bannāʾ's attitude
toward astrology. It has been well established that he had been interested
in the subject during the early stages of his scholarly life and that he wrote
a number of short astrological works that have little originality and a very
limited interest. They do, though, bear witness to the fact that he is following
an Andalusian–Maghribī tradition that has certain characteristics different
from those of the Eastern Islamic one. On the other hand, it seems that he
wrote a nonextant work entitled Radd ʿalā al‐aḥkām
al‐nujūmiyya (Refutation of astrological judgments),
which seems to have been written in the second period of his scholarly life
(1290–1301). It is difficult to establish clearly whether Ibn al‐Bannāʾ
lost his faith in the scientific character of astrology since the Minhāj
(apparently written during the same period) describes techniques of mathematical
astrology and the Marīnid sultan Abū Saʿīd
reportedly consulted him as an astrologer.
Aballāgh, Muḥammad
(1994). Rafʿ al‐hijāb ʿan wujūh aʿmāl al‐ḥisāb li‐Ibn al‐Bannāʾ al‐Marrākushī. Taqdīm wa‐dirāsa
wa‐taḥqīq. Fez.
Calvo, E.
(1989). “La Risālat
al‐ṣafīḥa
al‐muštaraka ʿalà al‐šakkāziyya
de Ibn al‐Bannāʾ
de Marrākuš.” Al‐Qantara 10: 21–50.
——— (2004). “Two Treatises on Mīqāt from the Maghrib
(14th and 15th centuries A.D.).” Suhayl 4:
159–206.
Djebbar,
Ahmed and Muḥammad
Aballāgh (2001). Ḥayāt
wa‐muʾallafāt Ibn
al‐Bannāʾ al‐Murrākushī [sic] maʿa
nuṣūṣ
ghayr manshūra. Rabat. (This biobibliographical survey includes a very complete list of
editions and secondary literature. It updates the standard papers of H. P.
J. Rénaud [1937 and 1938].)
Forcada, Miquel (1998). “Books of Anwāʾ in al‐Andalus.” In The Formation of al‐Andalus, Part 2: Language, Religion, Culture and the Sciences,
edited by Maribel Fierro
and Julio Samsó, pp. 305–328. Aldershot: Ashgate.
al‐Khattābī, Muhammad al‐ʿArabī (1986).
ʿIlm al‐mawāqīt. Usūluhu wa‐manāhijuh. Muhammadiyya (Morocco).
King, David A. (1998). “On the History
of Astronomy in the Medieval Maghrib.” In Études philosophiques et sociologiques dédiées
à Jamal ed‐Dine Alaoui, pp. 27–61. Fez.
Puig, Roser (1987). “El Taqbīl
ʿalā risālat al‐ṣafīḥa al‐zarqāliyya de
Ibn al‐Bannāʾ
de Marrākush.” Al‐Qantara 8: 45–64.
Rénaud, H.
P. J. (1937). “Sur les dates de la vie du mathématicien arabe marocain Ibn
al‐Bannāʾ.” Isis 27: 216–218.
——— (1938).
“Ibn al‐Bannāʾ de Marrakech, Sûfî et mathématicien (XIIIe
– XIVe s. J. C.).” Hespéris 25: 13–42.
——— (ed.)
(1948). Le Calendrier d'Ibn al‐Bannâ de Marrakech (1256–1321 J. C.).
Texte arabe inédit, établi d'après 5 manuscrits, de la Risâla fiʾl‐anwâʾ,
avec une traduction française annotée et une introduction par H. P. J. Rénaud.
Paris: Larose.
Saʿīdān, Ahmad
Salīm (ed.) (1984). Al‐Maqālāt fī ʿilm al‐ḥisāb
li‐Ibn al‐Bannāʾ
al‐Marrākushī. Amman.
——— (ed.) (1986). Tārīkh al‐jabr fī
al‐ʿālam al‐ʿarabī.
Kuwait.
Samsó, Julio
(1998). “An Outline of the History of Maghribī
Zijes from the End of the Thirteenth Century.” Journal
for the History of Astronomy 29: 93–102.
Samsó,
Julio and Eduardol Millás
(1994).
“Ibn al‐Bannāʾ,
Ibn Isḥāq
and Ibn al‐Zarqālluh's Solar
Theory.” In Islamic Astronomy and Medieval Spain,
edited by Julio Samsó, X. Aldershot: Variorum.
——— (1998). “The Computation of Planetary
Longitudes in the Zīj of Ibn al‐Bannāʾ.”
Arabic Sciences and Philosophy 8: 259–286.
Suwaysī, Muhammad
(1969). Ibn al‐Bannāʾ, Talkhīṣ aʿmāl al‐ḥisāb. Tunis. (Edition, translation,
and commentary.)
Vernet, Juan
(1980). “La supervivencia de la astronomía de Ibn al‐Bannāʾ.”
Al‐Qantara 1: 445–451.
——— (ed.)
(1952). Contribución al estudio de la labor astronómica de Ibn al‐Bannāʾ.
Tetouan.