6. Banu Musa Ibn Shakir
(Died in 259H/ 872AD) 

Musa Ibn Shakir lived in Baghdad during the rule the Abbasid Caliph al-Ma'mun and was among his closest courtiers. He was interested in astronomy and astrology. At his death, he left three children at small age. Al-Ma'mun took them under his wings and appointed Isshak Ibn Ibrahim al-Masbaghi to take care of them. This latter placed them in Bayt al-Hikmah (the House of Wisdom), which hosted an important library, an astronomic observatory, and a translation center of Greek philosophical and scientific works. Banu Musa brothers grew up in this scientific environment, and became among the outstanding scholars of Bayt al-Hikma. The three brothers, Muhamad, Ahmad and al-Hassan were known as Banu Mussa or the three brothers(28). The eldest of them, Abu Jaafar Muhamad was a scientist with extensive knowledge in geometry, stars and "Almajest". Ahmad was an expert and an innovator in the field of mechanical engineering. Al-Hassan had an in-depth mastery of geometry(29). The eldest of the three brothers died in 872AD.

Scientific Contributions

Ibn Musa brothers excelled in the fields of mathematics, astronomy, mechanics and geometry and contributed to their development by their important innovations and discoveries.

Their scientific contributions in mechanics appeared in the invention of a series of scientific tools and automatic devices, such as a number of farming machines, fountains which show numerous images with ascending waters. They also invented a number of household devices and toys as well as machines for loads traction, lifting or weighing.

Banu Musa brothers had an extensive expertise in general mathematics and put into use their mathematical knowledge in applied matters. They succeeded for instance in creating the elliptic form(30).

The method consists in planting two pins at two separate points, taking a thread measuring the distance between the two points. The threat must be tightened from both ends then put around the pins and a pencil inserted into the other folded end. When the pencil is turned clockwise the elliptic form is drawn.

In the fields of astronomy, Banu Musa brothers assessed the mean movement of the sun in the Persian calendar and developed calendars for the positions of planets. They also worked on meteorological changes and recorded the observations.

Banu Musa brothers played also an important role in the development of mathematics, astronomy and geometry through their treatises and by providing sponsor and support to translators and scientists. In this context, the German author Sigrid Hunkah said about Banu Musa brothers : "They sent envoys at their own expenses to the Byzantine Empire in search of ancient philosophical, astronomic, mathematical and medical manuscripts. They went until paying considerable amounts to buy Greek heritage and carry them home... In a house, close to the palace of al-Mutawakil, put at their disposal by this latter, a large team of translators from all parts of the country was working ceaselessly …"(31).

Major Works

Banu Musa brothers wrote in several scientific fields, such as geometry, land surveying, cones, astronomy, mechanics and mathematics. Their publications include the following :

- Kitab al-Hiyal, their most famous book, in which they compiled old mechanics as well as their personnel experiences. The annotator of this book, Mr. Ahmad Yussuf Hassan, says that the interest for Kitab al-Hiyal started in the West by the end of the 19th Century. The serious studies did not appear until the beginning of the 20th century, with the publication by Fiedeman and Hauser of study papers on this book. In 1979, Hill translated the book into English. Kitab al-Hiyal was published in 1981 by the Institute of Arab Scientific Heritage in Syria after its verification and annotation by Dr. Ahmad Yussuf Hassan and others;

- Kitab Missahat Al-Akr;

- Kitab Kismat Azzawaya ila Talatat Akssam Mutassawiya (Division of angle into three equal parts), translated by Gerard of Cremona into Latin;

- Kitab chalk al-Handassi, a book on geometrical form;

- Kitab Harakt al-Falak al-Ula (Stars First Motion).

It is worth noting that Banu Musa brothers worked closely with each other to the extent it becomes impossible to single out the work of each of them. The important thing is that they played an outstanding role in the development of mathematics, astronomy and geometry and had a great influence on their era.