Banū Mūsā

This article is about the 9th century Baghdad scholars. For the Iberian dynasty sometimes called the Banū Mūsā, see Banu Qasi.

Banū Mūsā

An illustration of a self-trimming lamp from Ahmad's On Mechanical Devices, written in Arabic.
Born	9th-century
Era	Islamic Golden Age
Region	Baghdad
Main interests	Astronomy, Geometry
Notable ideas	Application of arithmetic to geometry
Major works	Book of Ingenious Devices, Book on the Measurement of Plane and Spherical Figures
Influenced by Apollonius of Perga, Ptolomy, Galen, Al-Maʾmūn, Mūsā ibn Shākir, Yahya ibn Abi Mansur
Influenced Thabit ibn Qurra, Hunayn Ibn Ishaq, Ibn al‐Haytham, Naṣīr al‐Dīn al‐Ṭūsī, Gerard of Cremona, Leonardo Fibonacci, Jordanus de Nemore, Roger Bacon

The Banū Mūsā brothers ("Sons of Moses"), namely Abū Jaʿfar, Muḥammad ibn Mūsā ibn Shākir (before 803 – February, 873), Abū al‐Qāsim, Aḥmad ibn Mūsā ibn Shākir (d. 9th century) and Al-Ḥasan ibn Mūsā ibn Shākir (d. 9th century), were three 9th-century Islamic scholars of Baghdad who are known for their Book of Ingenious Devices on automata (automatic machines) and mechanical devices. Another important work of theirs is the Book on the Measurement of Plane and Spherical Figures, a foundational work on geometry that was frequently quoted by both Islamic and European mathematicians.

The Banu Musa worked in astronomical observatories established in Baghdad by the Abbasid Caliph al-Ma'mun as well as doing research in the House of Wisdom. They also participated in an 9th-century expedition to make geodesic measurements to determine the length of a degree.

Life

The Banu Musa were the three sons of Mūsā ibn Shākir, who earlier in life had been a highwayman and astronomer in Khorasan of unknown pedigree. After befriending al-Maʾmūn, who was then a governor of Khorasan and staying in Marw, Musa was employed as an astrologer and astronomer. After his death, his young sons were looked after by the court of al-Maʾmūn. Al-Maʾmūn recognized the abilities of the three brothers and enrolled them in the famous House of Wisdom, a library and a translation center in Baghdad.

Studying in the House of Wisdom under Yahya ibn Abi Mansur, they participated in the efforts to translate ancient Greek works into Arabic by sending for Greek texts from the Byzantines, paying large sums for their translation, and learning Greek themselves. On such trips, Muhammad met and recruited the famous mathematician and translator Thabit ibn Qurra. At some point Hunayn Ibn Ishaq was also part of their team.

After the death of al-Ma'mun, the Banu Musa continued to work under the Caliphs al-Mu'tasim, al-Wathiq, and al-Mutawakkil. However, during the reign of al-Wathiq and al-Mutawakkil internal rivalries arose between the scholars in the House of Wisdom. At some point the Banu Musa became enemies to al-Kindi and contributed to his persecution by al-Mutawakkil. They were later employed by al-Mutawakkil to construct a canal for the new city of al-Jafariyya.

Works

The Banu Musa wrote almost 20 books the majority of which are now lost.

Automata

Most notable among their achievements is their work in the field of automation, which they utilized in toys and other entertaining creations. They have shown important advances over those of their Greek predecessors.

• The Book of Ingenious Devices describes 100 inventions; the ones which have been reconstructed work as designed. While designed primarily for amusement purposes, they employ innovative engineering technologies such as one-way and two-way valves able to open and close by themselves, mechanical memories, devices to respond to feedback, and delays. Most of these devices were operated by water pressure.

• Qarasṭūn, a treatise on weight balance.

• On Mechanical Devices, a work on pneumatic devices, written by Ahmad.

• A Book on the Description of the Instrument Which Sounds by Itself, about musical theory.

Astronomy

• Book on the First Motion of the Celestial Sphere (Kitāb Ḥarakāt al‐falak al‐ūlā), containing a critique of the Ptolemaic system. Muhammad in this book denied the existence of the Ptolemaic 9th sphere which Ptolemy thought was responsible for the motion.

• Book on the Mathematical Proof by Geometry That There Is Not a Ninth Sphere Outside the Sphere of the Fixed Stars, by Ahmad.

• Book on The Construction of the Astrolabe, quoted by al-Biruni.

• Book on the Solar Year, was traditionally attributed to Thabit ibn Qurra, but recent research has shown that it was actually by the Bani Musa.

• On the Visibility of the Crescent, by Muhammad.

• Book on the Beginning of the World, by Muhammad.

• Book on the Motion of Celestial Spheres (Kitāb Ḥarakāt al‐aflāk), by Muhammad.

• Book of Astronomy (Kitāb al‐Hayʾa), by Muhammad.

• A book of zij, by Ahmad

• Another book of zij, listed under the Banu Musa, mentioned by Ibn Yunus.

Astrology

Cover of Kitāb al-Daraj (The book of degrees), by Ahmad, as found in the Saladin library, from before 1193 AD.

• A translation of a Chinese work called A Book of Degrees on the Nature of Zodiacal Signs.

• Kitāb al-Daraj (The book of degrees), by Ahmad.

Mathematics

• Book on the Measurement of Plane and Spherical Figures, later edited by Naṣīr al‐Dīn al‐Ṭūsī in the 13th century. A Latin translation by Gerard of Cremona appeared the 12th century under the titles Liber trium fratrum de geometria and Verba filiorum Moysi filii Sekir. This treatise on geometry was used extensively in in the Middle Ages, quoted by authors such as Thābit ibn Qurra, Ibn al‐Haytham, Leonardo Fibonacci (in his Practica geometriae), Jordanus de Nemore, and Roger Bacon. Some theorems included in this book are not found in any work of the Greek mathematicians.

• Conic Sections of Apollonius of Perga, a recension of the Greek work, which was first translated to Arabic by Hilāl al-ḥimṣī and Thābit ibn Qurra.

• Book on an Oblong Round Figure, which contains a description of procedure used to draw an ellipse using a string, now called the gardener's construction.

• Reasoning on the Trisection of an Angle, by Aḥmad.

• A treatise containing a discussion between Ahmad and Sanad ibn ʿAli.

• Book on a Geometric Proposition Proved by Galen.

See also

• Their book, Book of Ingenious Devices.
• Nuʿaym ibn Muḥammad ibn Mūsā, the son of Abu Ja'far Muhammad, wrote a mathematical treatise.
• Inventions in the Muslim world
• Islamic Golden Age
• Islamic science

References

• Casulleras, Josep (2007). "Banū Mūsā". In Thomas Hockey et al. The Biographical Encyclopedia of Astronomers. New York: Springer. pp. 92–4. ISBN 978-0-387-31022-0.  (PDF version)
• Masood, Ehsad (2009). Science and Islam A History. Icon Books Ltd. pp. 161–163. 
• Al-Darrbagh, J. (1970). "Banū Mūsā". Complete Dictionary of Scientific Biography. Encyclopedia.com. 
• Pingree, D. (1988). "Banū Mūsā". Encyclopædia Iranica. 
• O'Connor, John J.; Robertson, Edmund F., "Banu Musa brothers", MacTutor History of Mathematics archive, University of St Andrews .

Further reading

• Rashed, Roshdi (1996). Les Mathématiques Infinitésimales du IXe au XIe Siècle 1: Fondateurs et commentateurs: Banū Mūsā, Ibn Qurra, Ibn Sīnān, al-Khāzin, al-Qūhī, Ibn al-Samḥ, Ibn Hūd. London  Reviews: Seyyed Hossein Nasr (1998) in Isis 89 (1) pp. 112–113; Charles Burnett (1998) in Bulletin of the School of Oriental and African Studies, University of London 61 (2) p. 406.
• D El-Dabbah, The geometrical treatise of the ninth-century Baghdad mathematicians Banu Musa (Russian), in History Methodology Natur. Sci., No. V, Math. Izdat. (Moscow, 1966), pp. 131–139.
• Ramon Guardans, A Brief Note on the anwā' Texts of the Late Tenth Century, in: Variantology 4. On Deep Time Relations of Arts, Sciences and Technologies In the Arabic-Islamic World and Beyond, ed. by Siegfried Zielinski and Eckhard Fürlus in cooperation with Daniel Irrgang and Franziska Latell (Cologne: Verlag der Buchhandlung Walther König, 2010), pp. 177–193. [1]
• Claus-Peter Haase, Modest Variations — Theoretical Tradition and Practical Innovation in the Mechanical Arts from Antiquity to the Arab Middle Ages, in: Variantology 4. On Deep Time Relations of Arts, Sciences and Technologies In the Arabic-Islamic World and Beyond, ed. by Siegfried Zielinski and Eckhard Fürlus in cooperation with Daniel Irrgang and Franziska Latell (Cologne: Verlag der Buchhandlung Walther König, 2010), pp. 195–213. [2]

External links

• Manuscript edition of Kitab al-Daraj (a treatise on astrology). Princeton University Digital Library.