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.[2]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 a 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.[3] After befriending al-Ma'mun, who was then a governor of Khorasan and staying in Marw, Musa was employed as an astrologer and astronomer.[4] After his death, his young sons were looked after by the court of al-Maʾmūn.[5] 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.[6]Studying in the House of Wisdom under Yahya ibn Abi Mansur,[4] 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.[5] On such trips, Muhammad met and recruited the famous mathematician and translator Thābit ibn Qurra. At some point Hunayn ibn Ishaq was also part of their team.[2]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.[1]
Works
The Banu Musa wrote almost 20 books the majority of which are now lost.[2]
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.[2]
- 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.[5]
- Qarasṭūn, a treatise on weight balance.[6]
- A Book on the Description of the Instrument Which Sounds by Itself, about musical theory.[6]
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.[2]
- 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 Solar Year, was traditionally attributed to Thābit ibn Qurra, but recent research has shown that it was actually by the Bani Musa.[2]
- 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
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