| From: Thomas Hockey et al. (eds.). The Biographical Encyclopedia of Astronomers, Springer Reference. New York: Springer, 2007, pp. 92-24 |
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Banū Mūsā
Josep Casulleras
Jaʿfar Muḥammad
Born Baghdad, (Iraq),
beginning of the 9th century
Died January or
February 873
Abū
al‐Qāsim Aḥmad
Born Baghdad, (Iraq),
beginning of the 9th century
Died Baghdad, (Iraq),
9th century
Ḥasan
Born Baghdad, (Iraq),
beginning of the 9th century
Died Baghdad, (Iraq),
9th century
The
three brothers, the three sons of Musā ibn Shākir, generally known
under the single name of the Banū Mūsā, were among the most
important scientists of Baghdad in the 9th century; they played a prominent
role as private patrons of scientific translations and research, and excelled
in the fields of astronomy, mechanics, and mathematics.
It is quite impossible to write separate biographies of them. Their
father, Mūsā ibn Shākir, is described as a reformed bandit
who became a renowned astronomer or astrologer and a close friend of Maʾmūn
(reigned: 813–833) before he was a caliph, while residing in Marw in Khurāsān.
After Mūsā's death, the brothers became the wards of Maʾmūn,
who cared for their education and sent them to the House of Wisdom (Bayt
al‐ḥikma), which was the major
scientific institution in his time. After finishing their education, the Banū
Mūsā collaborated with Maʾmūn and his successors in a
variety of activities, which ranged from scientific matters (such as geodetic
surveys) to managerial affairs (such as contracting for the building of public
works and structures), thus becoming wealthy and powerful. This allowed them
to devote a great deal of their acquired fortune to sponsoring scientific
research. They actively sought classical works by ancient writers and sent
agents or went themselves to Byzantium to purchase manuscripts that they translated
on returning to Baghdad. On one such trip, Muḥammad
met the famous mathematician and translator Thābit
ibn Qurra of Ḥarrān and brought him back
to Baghdad, where Thābit joined the circle of scientists and translators
who were working under the patronage of the Banū Mūsā. The
Nestorian Christian Ḥunayn ibn Isḥāq (died: circa
877), considered one of the most prolific and significant translators of 9th‐century
Baghdad, was also part of the Banū Mūsā team. In sum, these
brothers promoted to a great extent the movement of translations that made
it possible to assimilate the main classical scientific works into Arabic.
Their significance to science and astronomy is not limited to this sponsorship
of translations alone; like the scholars gathered around them, the Banū
Mūsā also authored very important original scientific works of which
there is a known list of some 20 books on astronomy, mechanics, and mathematics.
Almost a dozen of the works attributed to the Banū Mūsā
are related to astronomical research. Muḥammad, the eldest son, wrote a treatise On the Visibility of the
Crescent, a Book on the Beginning of the World, and a book variously
known under the titles of Book on the Motion of Celestial Spheres (Kitāb
Ḥarakāt al‐aflāk), Book of Astronomy (Kitāb al‐Hayʾa),
or Book on the First Motion of the Celestial Sphere (Kitāb
Ḥarakāt al‐falak al‐ūlā), which contains a critique
of the Ptolemaic system of the Universe. In it Muḥammad
explains the daily motion of the heavens by the rotation of all the spheres
of the Sun, the Moon, the five planets, and the fixed stars, denying the existence
of the 9th sphere, which is the origin of movement in Ptolemy.
Aḥmad is reportedly
the author of a Book on the Mathematical Proof by Geometry That There Is
Not a Ninth Sphere Outside the Sphere of the Fixed Stars, two texts on
two questions that he discussed with his contemporary Sanad
ibn ʿAli, and a zīj
(astronomical handbook), which is mentioned by the Egyptian astronomer Ibn
Yūnus, who also says that there is another zīj by
the three brothers. Finally, listed under the name of the Banū Mūsā
are: A Book of Degrees on the Nature of Zodiacal Signs, regarding which
it is stated in the manuscript that it is a translation of a Chinese work;
a Book on The Construction of the Astrolabe, quoted by Bīrūnī;
and, a Book on the Solar Year. The latter has traditionally been attributed
to Thābit ibn Qurra, but recent research has shown that this is most
likely a misattribution and that the treatise is actually by the Banū
Mūsā. The majority of these books are now lost; however, the list
of titles and the studies on the extant works show that the Banū Mūsā
dealt extensively with the major concerns of astronomy in their time. Moreover,
the interest of the Banū Mūsā in astronomy is also attested
by reports that the brothers were involved in various activities, such as
leading the astronomical observations that were made in Baghdad during the
course of the 9th century or collaborating in the expeditions mounted by Maʾmūn
for the purpose of making a geodetic measurement of the length of a degree
along a terrestrial meridian.
The Banū Mūsā produced major work in the field of mechanics.
Their efforts show important advances over those of their Greek predecessors:
writers such as Philo of Byzantium (end of third century BCE) and Hero of
Alexandria (middle of first century), whose works were extensively known by
Muslim engineers. The Banū Mūsā also wrote many works in the
field of mathematics, many devoted to geometrical problems. One of their most
important works, Book on the Measurement of Plane and Spherical Figures,
was the object of a recension by Naṣīr al‐Dīn al‐Ṭūsī in the 13th century and
of a Latin translation by Gerard
of Cremona in the 12th century under the titles Liber trium fratrum
de geometria and Verba filiorum Moysi filii Sekir. This treatise
was one of the fundamental texts on geometry in the Middle Ages, and its contents
(in both the Arabic and European contexts) are found in authors such as Thābit
ibn Qurra, Ibn al‐Haytham,
Leonardo Fibonacci of Pisa (died: 1250), Jordanus de Nemore (died: 1260),
and Roger Bacon
(died: circa 1292). The other works on geometry attributed to the Banū
Mūsā are three books related to the Conic Sections of Apollonius
of Perga (third century BCE), a Book on a Geometric Proposition
Proved by Galen, a Reasoning on the Trisection of an Angle (by
Aḥmad), and a Book
on an Oblong Round Figure. The latter concerns the ellipse and contains
a description of what is known as the gardener's construction, a procedure
for drawing an ellipse by means of a string fastened to two pegs and based
on the fact that the sum of the two focal radius vectors of any point belonging
to a given ellipse is constant.
Finally,
the family tradition of the Banū Mūsā seems to have been continued
to a certain extent by a son of the eldest brother, Nuʿaym
ibn Muḥammad ibn
Mūsā, who wrote Book on Geometric Propositions.
Selected References
Al‐Dabbagh, J. (1970). “Banū Mūsā.” In
Dictionary of Scientific Biography, edited by Charles Coulston Gillispie.
Vol. 1, pp. 443–446. New York: Charles Scribner's Sons.
Al‐Hassan, Ahmad
Y. (2001). “Mining and Metallurgy.” In The Different Aspects of Islamic
Culture. Vol. 4, Science and Technology in Islam. Part 2, Technology
and Applied Sciences, edited by A. Y. al‐Hassan, Maqbul Ahmed and
A. Z. Iskandar, pp. 85–87. Beirut: UNESCO.
Banū Mūsā ibn Shākir (1981). Kitāb
al‐Ḥiyal,
edited by A. Y. al‐Hassan. Aleppo.
Clagett, Marshall (1964). Archimedes in the Middle Ages.
Vol. 1, The Arabo‐Latin Tradition. Madison: University of Wisconsin
Press.
Hill,
D. R. (trans.) (1979). The Book of Ingenious
Devices. Dordrecht: D. Reidel.
——— (1993). “Mūsa,
Banū.” In Encyclopaedia of Islam. 2nd ed. Vol. 7, pp. 640–641.
Leiden: E. J. Brill.
——— (1993). Islamic
Science and Engineering. Edinburgh: Edinburgh University Press.
——— (2001). “Mechanical
Technology.” In The Different Aspects of Islamic Culture. Vol. 4, Science
and Technology in Islam. Part 2, Technology and Applied Sciences,
edited by A. Y. al‐Hassan, Maqbul Ahmed and A. Z. Iskandar, pp. 165–192.
Beirut: UNESCO.
Hogendijk, Jan P. (2003). “The Geometrical Problems of Nuʿaim ibn Muḥammad
ibn Mūsā (9th century).” SCIAMVS 4: 59–136.
Rashed,
R. (1995). Les mathématiques infinitésimales du IXe au XIe siècle.
Vol. 1, Fondateurs et commentateurs: Banū Mūsā, Ibn Qurra,
Ibn Sinān, al‐Khāzin, al‐Qūhī, Ibn al‐Samḥ,
Ibn Hūd. London.
Rosenfeld, B. A. and Ekmeleddin Ihsanoğlu (2003). Mathematicians,
Astronomers, and Other Scholars of Islamic Civilization and Their Works
(7th–19th c.). Istanbul: IRCICA, pp. 34–36.
Youschkevitch,
Adolph P. (1976). Les mathématiques arabes (VIIIe‐Xvesiècles): Traduction
française de M. Cazenave et K. Jaouiche. Paris:
J. Vrin.