Banū Mūsā

The Banū Mūsā brothers (بنو موسى, "Sons of Mūsā") were three 9th century Persian scholars, of Baghdad, active in the House of Wisdom:

• Abu Ja'far Muhammad ibn Mūsā ibn Shākir (before 803 – 873), who specialised in astronomy, engineering, geometry and physics.
• Ahmad ibn Mūsā ibn Shākir (803 – 873) (أحمد بن موسى بن شاكر) , who specialised in engineering and mechanics.
• Al-Hasan ibn Mūsā ibn Shākir (810 – 873) (الحسن بن موسى بن شاكر) , who specialised in engineering and geometry.

The Banu Musa were the sons of Mūsā ibn Shākir, who had been a highwayman and later an astrologer to the Caliph al-Ma'mūn. At his death, he left his young sons in the custody of the Caliph, who entrusted them to Ishaq bin Ibrahim al-Mus'abi, a former governor of Baghdad. The education of the three brothers was carried out by Yahya bin Abu Mansur who worked at the famous House of Wisdom library and translation centre in Baghdad.

Works

Book of Ingenious Devices

The Banu Musa brothers invented a number of automata (automatic machines) and mechanical devices, and they described a hundred such devices in their Book of Ingenious Devices. Some of these inventions include:

• Valve and plug valve
• Float valve
• Feedback controller
• Automatic flute player
• Programmable machine
• Mechanical trick devices
• Hurricane lamp
• Self-trimming lamp (Ahmad ibn Mūsā ibn Shākir)
• Self-feeding lamp
• Gas mask
• Grab
• Clamshell grab
• Fail-safe system
• Differential pressure

The Banu Musa also invented "the earliest known mechanical musical instrument", in this case a hydropowered organ which played interchangeable cylinders automatically. According to Charles B. Fowler, this "cylinder with raised pins on the surface remained the basic device to produce and reproduce music mechanically until the second half of the nineteenth century. The Banu Musa also invented an automatic flute player which appears to have been the first programmable machine.

Book on the motion of the orbs

In physics and astronomy, Muhammad ibn Musa was a pioneer of astrophysics and celestial mechanics. In the Book on the motion of the orbs, he was the first to discover that the heavenly bodies and celestial spheres were subject to the same laws of physics as Earth, unlike the ancients who believed that the celestial spheres followed their own set of physical laws different from that of Earth.

Astral Motion and The Force of Attraction

In mechanics and astronomy, Muhammad ibn Musa, in his Astral Motion and The Force of Attraction, discovered that there was a force of attraction between heavenly bodies, foreshadowing Newton's law of universal gravitation.

On mechanics

Ahmad (c. 805) specialised in mechanics and wrote a work on pneumatic devices called On mechanics.

Premises of the book of conics

The eldest brother, Ja'far Muḥammad, wrote a critical revision on Apollonius' Conics, called the Premises of the book of conics.

The Book of the Measurement of Plane and Spherical Figures

The Banu Musa's most famous mathematical treatise is The Book of the Measurement of Plane and Spherical Figures, which considered similar problems as Archimedes did in his On the Measurement of the Circle and On the Sphere and the Cylinder.

The elongated circular figure

The youngest brother, al-Hasan (c. 810), specialised in geometry and wrote a work on the ellipse called The elongated circular figure.

See also

• Inventions in the Muslim world
• Islamic Golden Age
• Islamic science
• Islamic astronomy
• Islamic mathematics

Notes

References

• 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
• Golden Age of Persia, Richard Nelson Frye, pp. 162-163.
• 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.