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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 ninth-century Persian scholars who lived and worked in
Baghdad Baghdad (; ar, بَغْدَاد , ) is the capital of Iraq and the second-largest city in the Arab world after Cairo. It is located on the Tigris near the ruins of the ancient city of Babylon and the Sassanid Persian capital of Ctesiphon ...
. They are known for their '' Book of Ingenious Devices'' on automata (automatic
machine A machine is a physical system using power to apply forces and control movement to perform an action. The term is commonly applied to artificial devices, such as those employing engines or motors, but also to natural biological macromolecul ...
s) and mechanical devices. Another important work of theirs is the ''Book on the Measurement of Plane and Spherical Figures'', a foundational work on
geometry Geometry (; ) is, with arithmetic, one of the oldest branches of mathematics. It is concerned with properties of space such as the distance, shape, size, and relative position of figures. A mathematician who works in the field of geometry is c ...
that was frequently quoted by both Islamic and European mathematicians. The Banu Musa worked in astronomical observatories established in Baghdad by the
Abbasid The Abbasid Caliphate ( or ; ar, الْخِلَافَةُ الْعَبَّاسِيَّة, ') was the third caliphate to succeed the Islamic prophet Muhammad. It was founded by a dynasty descended from Muhammad's uncle, Abbas ibn Abdul-Mutta ...
Caliph al-Ma'mun as well as did 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. They are credited with inventing the first
music sequencer A music sequencer (or audio sequencer or simply sequencer) is a device or application software that can record, edit, or play back music, by handling note and performance information in several forms, typically CV/Gate, MIDI, or Open Sound Co ...
which was the earliest type of
programmable machine A program is a set of instructions used to control the behavior of a machine. Examples of such programs include: *The sequence of cards used by a Jacquard loom to produce a given pattern within weaved cloth. Invented in 1801, it used holes in punc ...
.


Life

The Banu Musa were the three sons of Mūsā ibn Shākir, who earlier in life had been a highwayman and astronomer in
Khorasan Khorasan may refer to: * Greater Khorasan, a historical region which lies mostly in modern-day northern/northwestern Afghanistan, northeastern Iran, southern Turkmenistan, Tajikistan, and Uzbekistan * Khorasan Province, a pre-2004 province of Ira ...
of unknown pedigree. After befriending al-Ma'mun, who was then a governor of Khorasan and staying in
Merv Merv ( tk, Merw, ', مرو; fa, مرو, ''Marv''), also known as the Merve Oasis, formerly known as Alexandria ( grc-gre, Ἀλεξάνδρεια), Antiochia in Margiana ( grc-gre, Ἀντιόχεια ἡ ἐν τῇ Μαργιανῇ) and ...
, Musa was employed as an
astrologer Astrology is a range of divinatory practices, recognized as pseudoscientific since the 18th century, that claim to discern information about human affairs and terrestrial events by studying the apparent positions of celestial objects. Di ...
and
astronomer An astronomer is a scientist in the field of astronomy who focuses their studies on a specific question or field outside the scope of Earth. They observe astronomical objects such as stars, planets, moons, comets and galaxies – in either ...
. 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 Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic pe ...
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 Thābit ibn Qurra. At some point Hunayn ibn Ishaq was also part of their team. The brothers sponsored many scientists and translators, who were paid about 500 dinars a month. Had it not been for the brothers' efforts, many of the Greek texts that they translated would have been lost and forgotten. After the death of al-Ma'mun, the Banu Musa continued to work under the Caliphs al-Mu'tasim, al-Wathiq, and
al-Mutawakkil Abū al-Faḍl Jaʿfar ibn Muḥammad al-Muʿtaṣim bi-ʾllāh ( ar, جعفر بن محمد المعتصم بالله; March 822 – 11 December 861), better known by his regnal name Al-Mutawakkil ʿalā Allāh (, "He who relies on God") was ...
. 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 of al-Kindi and contributed to his persecution by al-Mutawakkil. They were later employed by al-Mutawakkil to construct a
canal Canals or artificial waterways are waterways or engineered channels built for drainage management (e.g. flood control and irrigation) or for conveyancing water transport vehicles (e.g. water taxi). They carry free, calm surface f ...
for the new city of al-Jafariyya.


Mathematics and mechanics

The Banu Musa had a different view on area and circumference from the Greeks. In the research they translated, the Greeks looked at volume and area more in terms of ratios, rather than giving them an actual numerical value. Most of them based such measurements relatively on another object's size. In one of their surviving publications, the Kitab Marifat Masahat Al-Ashkal (The Book of the Measurement of Plane and Spherical Figures) Banu Musa gave volume and area number values. This is evidence that they were not just translating and reproducing the Greek sources. They were actually building on concepts and coming up with some of their own original works. The most popular of their publications was the ''Kitāb al-Ḥiyal'' (The Tricks Book), which was mostly the work of Aḥmad, the middle brother, was a book filled with one hundred mechanical devices. There were some real practical inventions in the book including a lamp that would mechanically dim, alternating fountains, and a clamshell grab. Eighty of these devices were described as "trick vessels" that showed a real mastery of mechanics, with a real focus on the use of light pressure. Some of the devices seem to be replications of earlier Greek works, but the rest were much more advanced than what the Greeks had done.


Astronomy

They made many observations and contributions to the field of astronomy, writing nearly a dozen publications over their astronomical research. They made many observations on the sun and the moon. Al-Ma’mun had them go to a desert in Mesopotamia to measure the length of a degree. They also measured the length of a year to be 365 days and 6 hours.


Politics

Although they were not made famous by their politics, they did have interests outside the world of science, mainly the oldest brother Muhammad. They were employed by the caliphs for many different projects, including the canal mentioned above, and they were also a part of a team of 20 hired to build the town of al-D̲j̲aʿfariyya for al-Mutawakkil. Taking on these types of civil projects naturally got them involved in the political scene in Baghdad. However, the height of Muhammad's political activity in the palace came towards the end of his life, during a time when Turkish commanders were starting to take control of the state. After al-Mutawakkil died, Muhammad helped al-Mustaʿīn get the nomination instead of the caliph's brother. When the caliph's brother besieged the city of Baghdad, Muhammad was sent to estimate the size of the army, and when the siege was over he was sent to get the terms of how al-Mustaʿīn would renounce the throne. This evidence shows where Muhammad ranked at that time. He was trusted and respected by the highest levels of authority at that time.


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 Automation describes a wide range of technologies that reduce human intervention in processes, namely by predetermining decision criteria, subprocess relationships, and related actions, as well as embodying those predeterminations in machines ...
, 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 Pneumatics (from Greek ‘wind, breath’) is a branch of engineering that makes use of gas or pressurized air. Pneumatic systems used in industry are commonly powered by compressed air or compressed inert gases. A centrally located and ...
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 Thābit ibn Qurra, but recent research has shown that it was actually by the Banu 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

* 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 Muhammad ibn Muhammad ibn al-Hasan al-Tūsī ( fa, محمد ابن محمد ابن حسن طوسی 18 February 1201 – 26 June 1274), better known as Nasir al-Din al-Tusi ( fa, نصیر الدین طوسی, links=no; or simply Tusi in the West ...
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 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 Roger Bacon (; la, Rogerus or ', also '' Rogerus''; ), also known by the scholastic accolade ''Doctor Mirabilis'', was a medieval English philosopher and Franciscan friar who placed considerable emphasis on the study of nature through emp ...
. Some theorems included in this book are not found in any work of the Greek mathematicians. * ''Conic Sections of
Apollonius of Perga Apollonius of Perga ( grc-gre, Ἀπολλώνιος ὁ Περγαῖος, Apollṓnios ho Pergaîos; la, Apollonius Pergaeus; ) was an Ancient Greek geometer and astronomer known for his work on conic sections. Beginning from the contributio ...
'', 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 In mathematics, an ellipse is a plane curve surrounding two focal points, such that for all points on the curve, the sum of the two distances to the focal points is a constant. It generalizes a circle, which is the special type of ellipse in ...
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 Aelius Galenus or Claudius Galenus ( el, Κλαύδιος Γαληνός; September 129 – c. AD 216), often Anglicized as Galen () or Galen of Pergamon, was a Greek physician, surgeon and philosopher in the Roman Empire. Considered to be o ...
''.


See also

* Nuʿaym ibn Muḥammad ibn Mūsā, the son of Abu Ja'far Muhammad, wrote a mathematical treatise. * Inventions in the Muslim world *
Islamic Golden Age The Islamic Golden Age was a period of cultural, economic, and scientific flourishing in the history of Islam, traditionally dated from the 8th century to the 14th century. This period is traditionally understood to have begun during the reign ...
*
Islamic science Science in the medieval Islamic world was the science developed and practised during the Islamic Golden Age under the Umayyads of Córdoba, the Abbadids of Seville, the Samanids, the Ziyarids, the Buyids in Persia, the Abbasid Caliphate an ...


References


Further reading

*
PDF version
* * * * * 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. * 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.


External links

* Manuscript edition o
Kitab al-Daraj
(a treatise on astrology). Princeton University Digital Library. {{DEFAULTSORT:Musa, Banu 873 deaths People from Baghdad Astronomers from the Abbasid Caliphate Mathematicians from the Abbasid Caliphate 9th-century Iranian mathematicians Iranian engineers Iranian scientists Medieval physicists Year of birth unknown Inventors of the medieval Islamic world 9th-century people from the Abbasid Caliphate 9th-century Iranian astronomers 9th-century inventors