The three brothers 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
Persian
Persian may refer to:
* People and things from Iran, historically called ''Persia'' in the English language
** Persians, the majority ethnic group in Iran, not to be conflated with the Iranic peoples
** Persian language, an Iranian language of the ...
scholars who lived and worked in
Baghdad
Baghdad ( or ; , ) is the capital and List of largest cities of Iraq, largest city of Iraq, located along the Tigris in the central part of the country. With a population exceeding 7 million, it ranks among the List of largest cities in the A ...
. They are collectively known as the Banū Mūsā (, "Sons of (or Moses)").
The Banū Mūsā were the sons of
Mūsā ibn Shākir, who was a well-known astronomer of
al-Ma'mun
Abū al-ʿAbbās Abd Allāh ibn Hārūn al-Maʾmūn (; 14 September 786 – 9 August 833), better known by his regnal name al-Ma'mun (), was the seventh Abbasid caliph, who reigned from 813 until his death in 833. His leadership was marked by t ...
, a son of the
Abbasid
The Abbasid Caliphate or Abbasid Empire (; ) was the third caliphate to succeed the prophets and messengers in Islam, Islamic prophet Muhammad. It was founded by a dynasty descended from Muhammad's uncle, Abbas ibn Abd al-Muttalib (566–653 C ...
caliph
Harun al-Rashid
Abū Jaʿfar Hārūn ibn Muḥammad ar-Rāshīd (), or simply Hārūn ibn al-Mahdī (; or 766 – 24 March 809), famously known as Hārūn al-Rāshīd (), was the fifth Abbasid caliph of the Abbasid Caliphate, reigning from September 786 unti ...
. After their father's death, the brothers received an education under al-Ma'mun’s direction, and were enrolled at the
House of Wisdom
The House of Wisdom ( ), also known as the Grand Library of Baghdad, was believed to be a major Abbasid Caliphate, Abbasid-era public academy and intellectual center in Baghdad. In popular reference, it acted as one of the world's largest publ ...
in Baghdad. There they undertook the translation of
ancient Greek
Ancient Greek (, ; ) includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Greek ...
works acquired from
Byzantium
Byzantium () or Byzantion () was an ancient Greek city in classical antiquity that became known as Constantinople in late antiquity and Istanbul today. The Greek name ''Byzantion'' and its Latinization ''Byzantium'' continued to be used as a n ...
, which they used to develop their own technological,
mathematical
Mathematics is a field of study that discovers and organizes methods, Mathematical theory, theories and theorems that are developed and Mathematical proof, proved for the needs of empirical sciences and mathematics itself. There are many ar ...
and
astronomical
Astronomy is a natural science that studies celestial objects and the phenomena that occur in the cosmos. It uses mathematics, physics, and chemistry in order to explain their origin and their overall evolution. Objects of interest include ...
ideas. They were some of the earliest scholars to adopt
Greek mathematics
Ancient Greek mathematics refers to the history of mathematical ideas and texts in Ancient Greece during Classical antiquity, classical and late antiquity, mostly from the 5th century BC to the 6th century AD. Greek mathematicians lived in cities ...
, but innovative in their approach to the concepts of
area
Area is the measure of a region's size on a surface. The area of a plane region or ''plane area'' refers to the area of a shape or planar lamina, while '' surface area'' refers to the area of an open surface or the boundary of a three-di ...
and
circumference
In geometry, the circumference () is the perimeter of a circle or ellipse. The circumference is the arc length of the circle, as if it were opened up and straightened out to a line segment. More generally, the perimeter is the curve length arou ...
by expressing them using numerical values instead of
ratio
In mathematics, a ratio () shows how many times one number contains another. For example, if there are eight oranges and six lemons in a bowl of fruit, then the ratio of oranges to lemons is eight to six (that is, 8:6, which is equivalent to the ...
s. They
made geodesic measurements to determine the length of a degree of
latitude
In geography, latitude is a geographic coordinate system, geographic coordinate that specifies the north-south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from −90° at t ...
, and so obtained a relatively accurate value for the
circumference of the Earth
Earth's circumference is the distance around Earth. Measured around the equator, it is . Measured passing through the poles, the circumference is .
Treating the Earth as a sphere, its circumference would be its single most important measuremen ...
.
The Banū Mūsā wrote almost 20 books, all but three of which are now lost. The most important of all their works was a
treatise
A treatise is a Formality, formal and systematic written discourse on some subject concerned with investigating or exposing the main principles of the subject and its conclusions."mwod:treatise, Treatise." Merriam-Webster Online Dictionary. Acc ...
on
geometry
Geometry (; ) is a branch of mathematics concerned with properties of space such as the distance, shape, size, and relative position of figures. Geometry is, along with arithmetic, one of the oldest branches of mathematics. A mathematician w ...
, ("''
Book on the Measurement of Plane and Spherical Figures''"), which was used extensively by medieval mathematicians. Their most famous extant work (of which the oldest and most reliable copy is in the
Topkapi Sarayi in
Istanbul
Istanbul is the List of largest cities and towns in Turkey, largest city in Turkey, constituting the country's economic, cultural, and historical heart. With Demographics of Istanbul, a population over , it is home to 18% of the Demographics ...
) is ("''
Book of Ingenious Devices
The ''Book of Ingenious Devices'' (, ) is a large illustrated work on mechanical devices, including automata, published in 850 by the three brothers of Persian descent, the Banū Mūsā brothers (Ahmad, Muhammad and Hasan ibn Musa ibn Shakir) ...
''"). It describes 100 inventions, many of which were pouring vessels, intended to entertain party guests. Some of their innovations, such as those that involved
fluid pressure
In physics, a fluid is a liquid, gas, or other material that may continuously move and deform (''flow'') under an applied shear stress, or external force. They have zero shear modulus, or, in simpler terms, are substances which cannot r ...
variations and
valve
A valve is a device or natural object that regulates, directs or controls the flow of a fluid (gases, liquids, fluidized solids, or Slurry, slurries) by opening, closing, or partially obstructing various passageways. Valves are technically Pip ...
s, remained unsurpassed until the modern period. One of those inventions includes an automatic flute player that may have been the first programmable machine or computer.
Biographical details
Early years
The Banu Musa were the three sons of
Mūsā ibn Shākir, who earlier in life had been a
highwayman
A highwayman was a robber who stole from travellers. This type of thief usually travelled and robbed by horse as compared to a footpad who travelled and robbed on foot; mounted highwaymen were widely considered to be socially superior to foo ...
and astronomer in
Khorasan
KhorasanDabeersiaghi, Commentary on Safarnâma-e Nâsir Khusraw, 6th Ed. Tehran, Zavvâr: 1375 (Solar Hijri Calendar) 235–236 (; , ) is a historical eastern region in the Iranian Plateau in West and Central Asia that encompasses western and no ...
of unknown pedigree. After befriending
al-Ma'mun
Abū al-ʿAbbās Abd Allāh ibn Hārūn al-Maʾmūn (; 14 September 786 – 9 August 833), better known by his regnal name al-Ma'mun (), was the seventh Abbasid caliph, who reigned from 813 until his death in 833. His leadership was marked by t ...
, who was then a governor of Khorasan and staying in
Merv
Merv (, ', ; ), also known as the Merve Oasis, was a major Iranian peoples, Iranian city in Central Asia, on the historical Silk Road, near today's Mary, Turkmenistan. Human settlements on the site of Merv existed from the 3rd millennium& ...
, Musa was employed as an
astrologer
Astrology is a range of Divination, divinatory practices, recognized as pseudoscientific since the 18th century, that propose that information about human affairs and terrestrial events may be discerned by studying the apparent positions ...
and
astronomer
An astronomer is a scientist in the field of astronomy who focuses on a specific question or field outside the scope of Earth. Astronomers observe astronomical objects, such as stars, planets, natural satellite, moons, comets and galaxy, galax ...
.
After Musa's death, the three orphaned children were cared for at the court of al-Maʾmūn, who made the senior Baghdad official
Ishaq ibn Ibrahim al-Mus'abi
Abu al-Husayn Ishaq ibn Ibrahim (, died July 850) was a ninth-century official in the service of the Abbasid Caliphate. A member of the Mus'abid family, he was related to the Tahirid governors of Khurasan, and was himself a prominent enforcer of ...
their guardian. Al-Ma’mun recognized their abilities, and enrolled them in the
House of Wisdom
The House of Wisdom ( ), also known as the Grand Library of Baghdad, was believed to be a major Abbasid Caliphate, Abbasid-era public academy and intellectual center in Baghdad. In popular reference, it acted as one of the world's largest publ ...
, an institution created by him as a centre for collecting, translating and studying books from other lands. In Baghdad, where they apparently lived for the rest of their lives, the three brothers studied
geometry
Geometry (; ) is a branch of mathematics concerned with properties of space such as the distance, shape, size, and relative position of figures. Geometry is, along with arithmetic, one of the oldest branches of mathematics. A mathematician w ...
,
mechanics
Mechanics () is the area of physics concerned with the relationships between force, matter, and motion among Physical object, physical objects. Forces applied to objects may result in Displacement (vector), displacements, which are changes of ...
, music,
mathematics
Mathematics is a field of study that discovers and organizes methods, Mathematical theory, theories and theorems that are developed and Mathematical proof, proved for the needs of empirical sciences and mathematics itself. There are many ar ...
and
astronomy
Astronomy is a natural science that studies celestial objects and the phenomena that occur in the cosmos. It uses mathematics, physics, and chemistry in order to explain their origin and their overall evolution. Objects of interest includ ...
, trained by a senior court
astrologer
Astrology is a range of Divination, divinatory practices, recognized as pseudoscientific since the 18th century, that propose that information about human affairs and terrestrial events may be discerned by studying the apparent positions ...
,
Yaḥyā bin Abī Manṣūr.
The three brothers, Moḥammad, Aḥmad, and Ḥasan, are often listed in what is assumed to be their order of seniority.
Accomplishments under the Abbasid Caliphate
The Banū Mūsā assisted al-Ma'mun's in his obsession to obtain and translate works from Greek into
Arabic
Arabic (, , or , ) is a Central Semitic languages, Central Semitic language of the Afroasiatic languages, Afroasiatic language family spoken primarily in the Arab world. The International Organization for Standardization (ISO) assigns lang ...
. They sent for
Greek texts from the
Byzantines, or travelled themselves to
Byzantium
Byzantium () or Byzantion () was an ancient Greek city in classical antiquity that became known as Constantinople in late antiquity and Istanbul today. The Greek name ''Byzantion'' and its Latinization ''Byzantium'' continued to be used as a n ...
to acquire them. During their working lives they used their wealth and energy towards the translation of these works. On his way home to Baghdad from Byzantium, Muhammad met and recruited
Thābit ibn Qurra
Thābit ibn Qurra (full name: , , ; 826 or 836 – February 19, 901), was a scholar known for his work in mathematics, medicine, astronomy, and translation. He lived in Baghdad in the second half of the ninth century during the time of the Abba ...
, a
money changer
Money is any item or verifiable record that is generally accepted as payment for goods and services and repayment of debts, such as taxes, in a particular country or socio-economic context. The primary functions which distinguish money are: med ...
from
Harran
Harran is a municipality and Districts of Turkey, district of Şanlıurfa Province, Turkey. Its area is 904 km2, and its population is 96,072 (2022). It is approximately southeast of Urfa and from the Syrian border crossing at Akçakale.
...
. Thābit went on to make important discoveries in algebra, geometry, and astronomy.
Under the direction of al-Ma'mun, the Banū Mūsā worked with the most talented men available, including
al-Khwarizmi
Muhammad ibn Musa al-Khwarizmi , or simply al-Khwarizmi, was a mathematician active during the Islamic Golden Age, who produced Arabic-language works in mathematics, astronomy, and geography. Around 820, he worked at the House of Wisdom in B ...
,
al-Kindi
Abū Yūsuf Yaʻqūb ibn ʼIsḥāq aṣ-Ṣabbāḥ al-Kindī (; ; ; ) was an Arab Muslim polymath active as a philosopher, mathematician, physician, and music theorist
Music theory is the study of theoretical frameworks for understandin ...
,
Al-Ḥajjāj ibn Yūsuf ibn Maṭar, and the mathematician and translator
Hunayn ibn Ishaq
Hunayn ibn Ishaq al-Ibadi (808–873; also Hunain or Hunein; ; ; known in Latin as Johannitius) was an influential Arab Nestorian Christian translator, scholar, physician, and scientist. During the apex of the Islamic Abbasid era, he worked w ...
, who became a close friend of one of the brothers, Muhammad.
Of the translators, three were paid about 500
dinars
The dinar () is the name of the principal currency unit in several countries near the Mediterranean Sea, with a more widespread historical use. The English word "dinar" is the transliteration of the Arabic دينار (''dīnār''), which was bor ...
a month. None of the brothers were medically trained, and relied upon Ishaq bin Hunayn and Thabit bin Qurra to translate Greek medical works. They exchanged ideas with other experts, including the astrologer
Abu Ma'shar al-Balkhi
Abu Ma‘shar al-Balkhi, Latinized as Albumasar (also ''Albusar'', ''Albuxar'', ''Albumazar''; full name ''Abū Maʿshar Jaʿfar ibn Muḥammad ibn ʿUmar al-Balkhī'' ;
, AH 171–272), was an early Persian Muslim astrologer, thought to be ...
, with whom Muhammed was in continuous contact.
The brothers are likely to have used portable instruments such as
armillary sphere
An armillary sphere (variations are known as spherical astrolabe, armilla, or armil) is a model of objects in the sky (on the celestial sphere), consisting of a spherical framework of rings, centered on Earth or the Sun, that represent lines o ...
s or dials when making their observations, which were recorded from around 847 to 869. From their Baghdad home, they observed stars in the
constellation
A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object.
The first constellati ...
Ursa Major
Ursa Major, also known as the Great Bear, is a constellation in the Northern Sky, whose associated mythology likely dates back into prehistory. Its Latin name means "greater (or larger) bear", referring to and contrasting it with nearby Ursa M ...
In 847–848, and measured the maximum and minimum
altitude
Altitude is a distance measurement, usually in the vertical or "up" direction, between a reference datum (geodesy), datum and a point or object. The exact definition and reference datum varies according to the context (e.g., aviation, geometr ...
s of the Sun in 868–869. They also observed the
September equinox
The September equinox (or southward equinox) is the moment when the Sun appears to cross the celestial equator, heading southward. Because of differences between the calendar year and the tropical year, the September equinox may occur from ...
in the city of
Samarra
Samarra (, ') is a city in Iraq. It stands on the east bank of the Tigris in the Saladin Governorate, north of Baghdad. The modern city of Samarra was founded in 836 by the Abbasid caliph al-Mu'tasim as a new administrative capital and mi ...
. To calculate the difference in
latitude
In geography, latitude is a geographic coordinate system, geographic coordinate that specifies the north-south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from −90° at t ...
between Samarra and
Nishapur
Nishapur or Neyshabur (, also ) is a city in the Central District (Nishapur County), Central District of Nishapur County, Razavi Khorasan province, Razavi Khorasan province, Iran, serving as capital of both the county and the district.
Ni ...
, they organized simultaneous observations of a
lunar eclipse
A lunar eclipse is an astronomical event that occurs when the Moon moves into the Earth's shadow, causing the Moon to be darkened. Such an alignment occurs during an eclipse season, approximately every six months, during the full moon phase, ...
.
Whilst working for al-Ma’mun, the Banū Mūsā travelled to a desert near
Sanjar
Sanjar (, ; full name: ''Muizz ad-Dunya wa ad-Din Adud ad-Dawlah Abul-Harith Ahmad Sanjar ibn Malik-Shah'') (6 November 1086 – 8 May 1157) was the Seljuq ruler of Khorasan from 1097 until 1118,[Mesopotamia
Mesopotamia is a historical region of West Asia situated within the Tigris–Euphrates river system, in the northern part of the Fertile Crescent. Today, Mesopotamia is known as present-day Iraq and forms the eastern geographic boundary of ...]
, with the aim of measuring the length of a degree of latitude along a
meridian, and from that verifying a value of obtained by the Greeks for the
Earth's circumference
Earth's circumference is the distance around Earth. Measured around the equator, it is . Measured passing through the poles, the circumference is .
Treating the Earth as a sphere, its circumference would be its single most important measuremen ...
. They first measured the altitude of the
Pole Star
A pole star is a visible star that is approximately aligned with the axis of rotation of an astronomical body; that is, a star whose apparent position is close to one of the celestial poles. On Earth, a pole star would lie directly overhead when ...
, and then, using pegs and a rope as they moved north, stopped again when the altitude of the star changed by one degree. They repeated the same measurement, this time travelling southwards. The process was repeated at al-Kufa. From their measurements, the brothers obtained a value for the circumference of the Earth of .
Under the patronage of the caliphs that followed al Ma’mun—
al-Mu'tasim
Abū Isḥāq Muḥammad ibn Hārūn al-Rashīd (; October 796 – 5 January 842), better known by his laqab, regnal name al-Muʿtaṣim biʾllāh (, ), was the eighth Abbasid Caliphate, Abbasid caliph, ruling from 833 until his death in 842. ...
,
al-Wathiq
Abū Jaʿfar Hārūn ibn Muḥammad al-Wathiq bi'Llah (; 18 April 81210 August 847), commonly known by his regnal name al-Wathiq bi'Llah (), was an Abbasid caliph who reigned from 842 until his death in 847.
Al-Wathiq is described in the so ...
, and
al-Mutawakkil
Ja'far ibn al-Mu'tasim, Muḥammad ibn Harun al-Rashid, Hārūn al-Mutawakkil ʿalā Allāh (); March 82211 December 861, commonly known by his laqab, regnal name al-Mutawwakil ala Allah (), was the tenth Abbasid Caliphate, Abbasid caliph, rul ...
—the brothers continued to acquire great wealth and become influential in court. They used much of their wealth to collect the works of ancient writers, a practise that was later copied by other scholars at the House of Wisdom.
The brothers were very active during the reign of al-Mutawakkil, who was interested in mechanics, and asked the Banū Mūsā to write on this subject. A son of al-Mu'tasim was educated by Ahmad, but the brothers' relations with the caliph are otherwise unknown. When close to death, al-Mu'tasim's successor al-Wathiq called together his astrologers, including Muhammed, who erroneously pronounced that the caliph would live for another 50 years.
Involvement in politics
The Banū Mūsā's employment by the caliphs for different
civil engineering
Civil engineering is a regulation and licensure in engineering, professional engineering discipline that deals with the design, construction, and maintenance of the physical and naturally built environment, including public works such as roads ...
projects, including their involvement in the building of the city of al-D̲j̲aʿfariyya for al-Mutawakki, led to them becoming involved in court politics. In 860, the Banū Mūsā and Mutawakkil’s architects were involved in obtaining land for a new city. The caliph’s advisor suggested that Muhammed and Ahmad bin Musa should be forced to contribute towards the expense of a new palace nearby.
The peak of Muhammad's political activity came towards the end of his life, when Turkish commanders were starting to take control of the state. After the death of al-Mutawakkil, Muhammad helped al-Mustaʿīn to become nominated as caliph. Denied the throne, Al-Mustaʿīn's brother besieged Baghdad, and Muhammad was sent to estimate the size of the attacking army. After the siege, he was sent to find out the terms for al-Mustaʿīn to abdicate.
Jaʻfariyya canal
It was during the reigns of al-Wathiq and al-Mutawakkil that internal rivalries arose between the scholars there. The Banū Mūsā became enemies of al-Kindi, and assisted in his persecution by al-Mutawakkil.
They criticized and ridiculed his treatise on the
astrolabe
An astrolabe (; ; ) is an astronomy, astronomical list of astronomical instruments, instrument dating to ancient times. It serves as a star chart and Model#Physical model, physical model of the visible celestial sphere, half-dome of the sky. It ...
, and caused al-Mutawakkil to have him beaten, removed from court, and his library confiscated. The library was returned back to him at a later date with the help of the Persian Jewish scholar
Sanad ibn Ali, who insisted the library was returned as a condition to him assisting the Banū Mūsā over his judgement concerning the construction of a canal for the city of al-Ja’fariyya.
Shortly before his death, Mutawakkil gave the Banū Mūsā overall responsibility for building the al-Ja’fariyya canal; they in turn delegated the work to Fargftani. The caliph discovered that, due to an engineering error, once built, the water in the canal would drain away. He decreed that the brothers would be
crucified
Crucifixion is a method of capital punishment in which the condemned is tied or nailed to a large wooden cross, beam or stake and left to hang until eventual death. It was used as a punishment by the Achaemenid Empire, Persians, Carthaginians, ...
beside the canal if this happened. Sanad bin Ah', who was the caliph's consultant
engineer
Engineers, as practitioners of engineering, are professionals who Invention, invent, design, build, maintain and test machines, complex systems, structures, gadgets and materials. They aim to fulfill functional objectives and requirements while ...
, agreed to proclaim—four months before the truth was to be revealed, and knowing that astrologers had predicted that the caliph was close to death—that no error had been made. The brothers were saved from execution when the caliph was
assassinated
Assassination is the willful killing, by a sudden, secret, or planned attack, of a personespecially if prominent or important. It may be prompted by political, ideological, religious, financial, or military motives.
Assassinations are orde ...
shortly afterwards.
Deaths
Of the three brothers, only the year that Mohammed died—January 873—is known.
Works
The Banū Mūsā wrote almost 20 books. Moḥammad was the most productive of the brothers; of his many works, one still exists. They worked together as well as separately: Jafar Muhammad was an expert on mathematics and astronomy, Ahmad excelled in technology, and al-Hasan in mathematics.
Muhammed knew the works of both Euclid and Ptolemy, and was considered by contemporaries to be an expert mathematician, astronomer, and
philosopher
Philosophy ('love of wisdom' in Ancient Greek) is a systematic study of general and fundamental questions concerning topics like existence, reason, knowledge, Value (ethics and social sciences), value, mind, and language. It is a rational an ...
.
All but three of the books attributed by scholars to the Banū Mūsā are now lost. Many of the lost works are named in the ''
Book of Ingenious Devices
The ''Book of Ingenious Devices'' (, ) is a large illustrated work on mechanical devices, including automata, published in 850 by the three brothers of Persian descent, the Banū Mūsā brothers (Ahmad, Muhammad and Hasan ibn Musa ibn Shakir) ...
'', their most famous work.
Astronomy and astrology
The Banū Mūsā are known to have made many astronomical observations in Baghdad.
("Book on the Mathematical Proof by Geometry that there Is not a Ninth Sphere Outside the Sphere of the Fixed Stars") is a lost book, reportedly written by Ahmed. Also referred to as the ("Book of Astronomy"), or the ("Book on the First Motion of the Celestial Sphere"), the work analysed the
Ptolemy
Claudius Ptolemy (; , ; ; – 160s/170s AD) was a Greco-Roman mathematician, astronomer, astrologer, geographer, and music theorist who wrote about a dozen scientific treatises, three of which were important to later Byzantine science, Byzant ...
's
geocentric model
In astronomy, the geocentric model (also known as geocentrism, often exemplified specifically by the Ptolemaic system) is a superseded scientific theories, superseded description of the Universe with Earth at the center. Under most geocentric m ...
of the cosmos, in which a ninth sphere is responsible for the motion of the heavens, and instead considered that the Sun, the Moon, the planets, and the stars all moved of their own volition.
The other astronomical or astrological works by the Banū Mūsā are:
* ("''The Book of Degrees''");
* ("Book on the Construction of the Astrolabe"), a work quoted by the 11th century Persian scholar
al-Biruni
Abu Rayhan Muhammad ibn Ahmad al-Biruni (; ; 973after 1050), known as al-Biruni, was a Khwarazmian Iranian scholar and polymath during the Islamic Golden Age. He has been called variously "Father of Comparative Religion", "Father of modern ...
;
* ("Book on the Solar Year"), which was once attributed to
Thābit ibn Qurra
Thābit ibn Qurra (full name: , , ; 826 or 836 – February 19, 901), was a scholar known for his work in mathematics, medicine, astronomy, and translation. He lived in Baghdad in the second half of the ninth century during the time of the Abba ...
;
*
("On the Visibility of the Crescent"), by Muhammad;
* ''Book on the Beginning of the World'', by Muhammad, now lost;
* A non-extant (an Islamic astronomical book used to calculate the positions of the Sun and objects in the night sky) by Ahmad was mentioned by the Egyptian astronomer and mathematician
Ibn Yunus
Abu al-Hasan 'Ali ibn Abi al-Said 'Abd al-Rahman ibn Ahmad ibn Yunus ibn Abd al-'Ala al-Sadafi al-Misri (Egyptian Arabic: ابن يونس; c. 950 – 1009) was an important Arabs, Arab Egyptians, Egyptian astronomer and Islamic mathematics, math ...
in his , written in ;
* A separate non-extant by the Banū Mūsā was mentioned by
Ibn Yunus
Abu al-Hasan 'Ali ibn Abi al-Said 'Abd al-Rahman ibn Ahmad ibn Yunus ibn Abd al-'Ala al-Sadafi al-Misri (Egyptian Arabic: ابن يونس; c. 950 – 1009) was an important Arabs, Arab Egyptians, Egyptian astronomer and Islamic mathematics, math ...
.
* A translation of a Chinese work called ''A Book of Degrees on the Nature of Zodiacal Signs'';
The calculation by Moḥammad and Aḥmad of the Sun’s mean motion in a year agreed with the result obtained by al-Bīrūnī—that a solar year was 365 days and less than 6 hours long. Aḥmad independently reached a similar conclusion in 851852. They observed the longitude of
Regulus
Regulus is the brightest object in the constellation Leo (constellation), Leo and one of the List of brightest stars, brightest stars in the night sky. It has the Bayer designation designated α Leonis, which is Latinisation of names, ...
from their house on a bridge in Baghdad in 840841, 847848, and 850851, and made observations of
Sirius
Sirius is the brightest star in the night sky. Its name is derived from the Greek word (Latin script: ), meaning 'glowing' or 'scorching'. The star is designated Canis Majoris, Latinized to Alpha Canis Majoris, and abbr ...
, Al-Bīrūnī used data about the Moon obtained by the Banū Mūsā in his astrological calculations.
Mathematics
The Banū Mūsā were some of the earliest scholars to adopt
Greek mathematics
Ancient Greek mathematics refers to the history of mathematical ideas and texts in Ancient Greece during Classical antiquity, classical and late antiquity, mostly from the 5th century BC to the 6th century AD. Greek mathematicians lived in cities ...
. They differed from the Greeks in their approaches to the concepts of
area
Area is the measure of a region's size on a surface. The area of a plane region or ''plane area'' refers to the area of a shape or planar lamina, while '' surface area'' refers to the area of an open surface or the boundary of a three-di ...
and
circumference
In geometry, the circumference () is the perimeter of a circle or ellipse. The circumference is the arc length of the circle, as if it were opened up and straightened out to a line segment. More generally, the perimeter is the curve length arou ...
, giving them numerical values rather than considering them in terms of
ratio
In mathematics, a ratio () shows how many times one number contains another. For example, if there are eight oranges and six lemons in a bowl of fruit, then the ratio of oranges to lemons is eight to six (that is, 8:6, which is equivalent to the ...
s.
''Book on the Measurement of Plane and Spherical Figures''
The most important of the works produced by the Banū Mūsā was the ("''
Book on the Measurement of Plane and Spherical Figures''"), of which a commentary was made by the persian polymath
Naṣīr al-Dīn al-Ṭūsī
Muḥammad ibn Muḥammad ibn al-Ḥasan al-Ṭūsī (1201 – 1274), also known as Naṣīr al-Dīn al-Ṭūsī (; ) or simply as (al-)Tusi, was a Persian polymath, architect, philosopher, physician, scientist, and theologian. Nasir al-Din al-Tu ...
in the 13th century.
A
Latin
Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...
translation by the 12th century Italian
astrologer
Astrology is a range of Divination, divinatory practices, recognized as pseudoscientific since the 18th century, that propose that information about human affairs and terrestrial events may be discerned by studying the apparent positions ...
Gerard of Cremona
Gerard of Cremona (Latin: ''Gerardus Cremonensis''; c. 1114 – 1187) was an Italians, Italian translator of scientific books from Arabic into Latin. He worked in Toledo, Spain, Toledo, Kingdom of Castile and obtained the Arabic books in the libr ...
appeared entitled and . This treatise on geometry, which is similar to Archimedes's ''On the measurement of the circle'' and ''On the sphere and the cylinder''.
was used extensively in the Middle Ages, and was quoted by authors such as Thābit ibn Qurra,
Ibn al-Haytham
Ḥasan Ibn al-Haytham (Latinization of names, Latinized as Alhazen; ; full name ; ) was a medieval Mathematics in medieval Islam, mathematician, Astronomy in the medieval Islamic world, astronomer, and Physics in the medieval Islamic world, p ...
,
Leonardo Fibonacci
Leonardo Bonacci ( – ), commonly known as Fibonacci, was an Italian mathematician from the Republic of Pisa, considered to be "the most talented Western mathematician of the Middle Ages".
The name he is commonly called, ''Fibonacci'', is f ...
(in his ),
Jordanus de Nemore
Jordanus de Nemore (fl. 13th century), also known as Jordanus Nemorarius and Giordano of Nemi, was a thirteenth-century European mathematician and scientist. The literal translation of Jordanus de Nemore (Giordano of Nemi) would indicate that he ...
, and
Roger Bacon
Roger Bacon (; or ', also '' Rogerus''; ), also known by the Scholastic accolades, scholastic accolade ''Doctor Mirabilis'', was a medieval English polymath, philosopher, scientist, theologian and Franciscans, Franciscan friar who placed co ...
. It includes
theorems
In mathematics and formal logic, a theorem is a statement (logic), statement that has been Mathematical proof, proven, or can be proven. The ''proof'' of a theorem is a logical argument that uses the inference rules of a deductive system to esta ...
not known to the Greeks. The book was re-published in Latin with an English translation by the American historian
Marshall Clagett
Marshall Clagett (January 23, 1916, Washington, D.C. – October 21, 2005, Princeton, New Jersey) was an American historian of science who specialized first in medieval science and later in Ancient Egyptian science. John E. Murdoch described him ...
, who has also summarized how the work influenced mathematicians during the
Middle Ages
In the history of Europe, the Middle Ages or medieval period lasted approximately from the 5th to the late 15th centuries, similarly to the post-classical period of global history. It began with the fall of the Western Roman Empire and ...
.
Other mathematical works
The other known mathematical works by the Banū Mūsā were:
* Three works relating to ''Conic Sections'', a book by the astronomer
Apollonius of Perga
Apollonius of Perga ( ; ) was an ancient Greek geometer and astronomer known for his work on conic sections. Beginning from the earlier contributions of Euclid and Archimedes on the topic, he brought them to the state prior to the invention o ...
. ''Conic Sections'' was first translated to Arabic by
Hilāl al-ḥimṣī and
Thābit ibn Qurra
Thābit ibn Qurra (full name: , , ; 826 or 836 – February 19, 901), was a scholar known for his work in mathematics, medicine, astronomy, and translation. He lived in Baghdad in the second half of the ninth century during the time of the Abba ...
. One of these three works, ("''Conic Sections of Apollonius''"), by Muhammed, was a recension of Apollonius's book.
* ("The Book of the Elongated Circular Figure"),
a mathematical treatise by al-Hasan—and the only one that is attributed to him— now lost. It contained a description of a procedure used to draw an
ellipse
In mathematics, an ellipse is a plane curve surrounding two focus (geometry), 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 ty ...
using a length of string, a technique that is now known as the "gardener's construction";
* or ("Reasoning on the Trisection of an Angle"), by Aḥmad;
The treatise attempted to solve the classical problem of
trisecting an angle
Angle trisection is a classical problem of straightedge and compass construction of ancient Greek mathematics. It concerns construction of an angle equal to one third of a given arbitrary angle, using only two tools: an unmarked straightedge an ...
.
The manuscript and medieval Latin translations are extant. The two known manuscripts containing the treatise, MS. Marsh 720 and MS. Thurston 3, are held in the
Bodleian Library
The Bodleian Library () is the main research library of the University of Oxford. Founded in 1602 by Sir Thomas Bodley, it is one of the oldest libraries in Europe. With over 13 million printed items, it is the second-largest library in ...
at
Oxford University
The University of Oxford is a collegiate research university in Oxford, England. There is evidence of teaching as early as 1096, making it the oldest university in the English-speaking world and the second-oldest continuously operating u ...
.
* ("Book on a Geometric Proposition Proved by Galen"). A lost book by Muhammed.
Technology
''The Book of Ingenious Devices''

("''The Book of Ingenious Devices''"), the only surviving work by Aḥmad, describes 100 inventions, 25 of which had a practical use. These include mechanical fountains, a "hurricane" lamp, self-trimming and self-feeding lamps, a form of
gas mask
A gas mask is a piece of personal protective equipment used to protect the wearer from inhaling airborne pollutants and toxic gases. The mask forms a sealed cover over the nose and mouth, but may also cover the eyes and other vulnerable soft ...
for use underground, and a
grabbing tool, constructed in the same way as a modern clamshell grab, for recovering underwater objects. The book's other inventions are ingeniously built pouring vessels, designed to puzzle guests at parties. It is thought that some of these models were never constructed.
The inventions employ innovative engineering ideas, such as automatic one-way and two-way
valve
A valve is a device or natural object that regulates, directs or controls the flow of a fluid (gases, liquids, fluidized solids, or Slurry, slurries) by opening, closing, or partially obstructing various passageways. Valves are technically Pip ...
s, mechanical memories, devices capable of responding to
feedback
Feedback occurs when outputs of a system are routed back as inputs as part of a chain of cause and effect that forms a circuit or loop. The system can then be said to ''feed back'' into itself. The notion of cause-and-effect has to be handle ...
, and delay mechanisms. Most of them were operated by water
pressure
Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and eve ...
. The trick vessels are unimportant in themselves; their significance for
historians of engineering is the means by which they were developed. Many of Ahmad's ideas were obtained from Greek texts such as
Philo of Byzantium
Philo of Byzantium (, ''Phílōn ho Byzántios'', ), also known as Philo Mechanicus (Latin for "Philo the Engineer"), was a Greek engineer, physicist and writer on mechanics, who lived during the latter half of the 3rd century BC. Although he wa ...
's ''Pneumatics'' (3rd century BCE) and
Hero of Alexandria
Hero of Alexandria (; , , also known as Heron of Alexandria ; probably 1st or 2nd century AD) was a Greek mathematician and engineer who was active in Alexandria in Egypt during the Roman era. He has been described as the greatest experimental ...
's ''Pneumatics '' (written in the 1st century CE). However, some of the devices, particularly when involving small variations in
fluid pressure
In physics, a fluid is a liquid, gas, or other material that may continuously move and deform (''flow'') under an applied shear stress, or external force. They have zero shear modulus, or, in simpler terms, are substances which cannot r ...
, and automatic control components such as valves, were developed by the Banū Mūsā.
The most important copies of the are:
* a complete manuscript held at the
Vatican Library
The Vatican Apostolic Library (, ), more commonly known as the Vatican Library or informally as the Vat, is the library of the Holy See, located in Vatican City, and is the city-state's national library. It was formally established in 1475, alth ...
(no. 317);
* a manuscript in two parts kept at the
Berlin State Library
The Berlin State Library (; officially abbreviated as ''SBB'', colloquially ''Stabi'') is a universal library in Berlin, Germany, and a property of the German public cultural organization the Prussian Cultural Heritage Foundation ().
Founded in ...
(Ahlward No. 5562) and Gotha (Pertsch No. 1349);
* the manuscript at the Topkapi Sarayi (A 3474), which is both the oldest and most reliable of the all the extant copies of the work.
Other works
The other technology-based works by the Banū Mūsā were:
* ("A Book on the Qarasṭūn"), a treatise on the weight balance, or
steelyard
The Steelyard, from the Middle Low German (sample yard), was the kontor (foreign trading post) of the Hanseatic League in London, and their main trading base in England, between the 13th and 16th centuries. The main goods that the League export ...
.
Thabit bin Qurra also wrote a book on the steelyard.
* ''A Book on the Description of the Instrument Which Sounds by Itself''. A copy of the manuscript is held in
Beirut
Beirut ( ; ) is the Capital city, capital and largest city of Lebanon. , Greater Beirut has a population of 2.5 million, just under half of Lebanon's population, which makes it the List of largest cities in the Levant region by populatio ...
. The Banū Mūsā 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 Musical note, note and performance information in several forms, typically CV/Gate, MIDI, or Open ...
, as described in the manuscript, as an example of an early 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 pun ...
.
* , a treatise containing a discussion between Ahmad and Sanad ibn Ali,
possibly about the difficulties encountered by the Banū Mūsā due to the failure by their agent
Al-Farghani
Abū al-ʿAbbās Aḥmad ibn Muḥammad ibn Kathīr al-Farghānī () also known as Alfraganus in the West (870), was an astronomer in the Abbasid court in Baghdad, and one of the most famous astronomers in the 9th century. Al-Farghani composed ...
to properly build the Jaʻfariyya canal.
See also
*
Inventions in the Muslim world
*
Mathematics in the medieval Islamic world
Mathematics during the Golden Age of Islam, especially during the 9th and 10th centuries, was built upon syntheses of Greek mathematics (Euclid, Archimedes, Apollonius) and Indian mathematics (Aryabhata, Brahmagupta). Important developments o ...
*
Science in the medieval Islamic world
Science in the medieval Islamic world was the science developed and practised during the Islamic Golden Age under the Abbasid Caliphate of Baghdad, the Caliphate of Córdoba, Umayyads of Córdoba, Spain, Córdoba, the Abbadid dynasty, Abbadids ...
Notes
References
Sources
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PDF version
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Further reading
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Digitized manuscripts and translations
Manuscript facsimile of the held in the
Princeton University Library
Princeton University Library is the main library system of Princeton University. With holdings of more than 7 million books, 6 million microforms, and 48,000 linear feet of manuscripts, it is among the largest libraries in the world by number of ...
(Islamic Manuscripts, Garrett no. 501H)
* ''The Book of Ingenious Devices'':
:
A manuscript facsimileheld in the
Vatican Library
The Vatican Apostolic Library (, ), more commonly known as the Vatican Library or informally as the Vat, is the library of the Holy See, located in Vatican City, and is the city-state's national library. It was formally established in 1475, alth ...
(Manuscript Vaticani Arabi 317), a copy of which was made by the philosopher al ‘Afrit.
:
A manuscript facsimileheld at the
Berlin State Library
The Berlin State Library (; officially abbreviated as ''SBB'', colloquially ''Stabi'') is a universal library in Berlin, Germany, and a property of the German public cultural organization the Prussian Cultural Heritage Foundation ().
Founded in ...
(Ms. or. quart. 739).
:
A manuscript facsimileheld at the
University of Erfurt
The University of Erfurt () is a public university located in Erfurt, the capital city of the German state of Thuringia. It was founded in 1379, and closed in 1816. It was re-established in 1994, three years after German reunification. Therefore ...
(Ms. orient. A 1349).
A manuscript facsimile of kept at
Columbia University
Columbia University in the City of New York, commonly referred to as Columbia University, is a Private university, private Ivy League research university in New York City. Established in 1754 as King's College on the grounds of Trinity Churc ...
, New York (via the
Internet Archive
The Internet Archive is an American 501(c)(3) organization, non-profit organization founded in 1996 by Brewster Kahle that runs a digital library website, archive.org. It provides free access to collections of digitized media including web ...
). The treatise is located from pp. 253265 (f. 116 to 122).
Translations
*
PDFversion)
*
*
External links
*
A list of works by the Banū Mūsāfrom the Islamic Scientific Manuscripts Initiative (ISMI) website
*
Pioneers of Engineering: Al-Jazari and the Banu Musa' TV episode from
Al Jazeera
Al Jazeera Media Network (AJMN; , ) is a private-media conglomerate headquartered in Wadi Al Sail, Doha, funded in part by the government of Qatar. The network's flagship channels include Al Jazeera Arabic and Al Jazeera English, which pro ...
(25 minutes)
*
{{DEFAULTSORT:Banu Musa
873 deaths
People from Baghdad
Astronomers from the Abbasid Caliphate
Mathematicians from the Abbasid Caliphate
9th-century Iranian mathematicians
Iranian engineers
Inventors of the medieval Islamic world
9th-century people from the Abbasid Caliphate
9th-century Iranian astronomers
9th-century inventors
Brother trios