Banū Mūsā brothers
They were some of the earliest scholars to adopt Greek mathematics, but innovative in their approach to the concepts of area and circumference by expressing them using numerical values instead of ratios.
They made geodesic measurements to determine the length of a degree of latitude, and so obtained a relatively accurate value for the circumference of the Earth.
The most important of all their works was a treatise on geometry, Kitāb Maʿrifah masāḥat al-ashkāl al-basīṭah wa-al-kuriyyah ("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) is Kitab al-Hiyal al-Naficah ("Book of Ingenious Devices").
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.
[2] 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 their guardian.
[3][4] Al-Ma’mun recognized their abilities, and enrolled them in the House of Wisdom, an institution created by him as a centre for collecting, translating and studying books from other lands.
[8] On his way home to Baghdad from Byzantium, Muhammad met and recruited Thābit ibn Qurra,[9] a money changer from Harran.
[13] Whilst working for al-Ma’mun, the Banū Mūsā travelled to a desert near Sanjar, in northern Mesopotamia, with the aim of measuring the length of a degree of latitude along a meridian, and from that verifying a value of 25,000 miles (40,000 km) obtained by the Greeks for the Earth's circumference.
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.
[12][17] 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.
[9] Kitāb bayyana fīhī bi-ṭarīq taʿlīmī wa-madhhab handasī annahū laysa fī khārij kurat al-kawākib al-thābitah kurah tāsiʿah[20] ("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.
[9] Also referred to as the Kitāb al-Hay’a ("Book of Astronomy"), or the Kitāb Ḥarakāt al-falak al-ūlā ("Book on the First Motion of the Celestial Sphere"), the work analysed the Ptolemy's geocentric model 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.
[7] The most important of the works produced by the Banū Mūsā was the Kitāb maʻrifat masāḥat al-ashkāl al-basīṭah wa-al-kurīyah ("Book on the Measurement of Plane and Spherical Figures"), of which a commentary was made by the persian polymath Naṣīr al-Dīn al-Ṭūsī in the 13th century.
[5][26] A Latin translation by the 12th century Italian astrologer Gerard of Cremona appeared entitled Liber trium fratrum de geometria and Verba filiorum Moysi filii Sekir.
[27] The book was re-published in Latin with an English translation by the American historian Marshall Clagett, who has also summarized how the work influenced mathematicians during the Middle Ages.
However, some of the devices, particularly when involving small variations in fluid pressure, and automatic control components such as valves, were developed by the Banū Mūsā.
