798-865 Al-Farghani, Abu al-Abbas (Al-Fraganus)

798-865) * Al-Farghani, Abu al-Abbas (Al-Fraganus) * 

(Astronomy, Tehnik Sipil )al‐Abbas Ahmad ibn Muhammad ibn Kathir al-Farghani

Abu'l-Abbas Ahmad ibn Muhammad ibn Kathir al-Farghani, born in Farghana, Transoxiana, was one of the most distinguished astronomers in the service of al-Mamun and his successors.

He wrote "Elements of Astronomy" (Kitab fi al-Harakat alSamawiya wa Jawami Ilm al-Nujum i.e. the book on celestial motion and thorough science of the stars), which was translated into Latin in the 12th century and exerted great influence upon European astronomy before Regiomontanus. He accepted Ptolemy's theory and value of the precession, but thought that it affected not only the stars but also the planets. He determined the diameter of the earth to be 6,500 miles, and found the greatest distances and also the diameters of the planets.

Al-Farghani's activities extended to engineering. According to Ibn Tughri Birdi, he supervised the construction of the Great Nilometer at al-Fustat (old Cairo). It was completed in 861, the year in which the Caliph al-Mutawakkil, who ordered the construction, died. But engineering was not al-Farghani's forte, as transpires from the following story narrated by Ibn Abi Usaybi'a.

Al-Mutawakkil had entrusted the two sons of Musa ibn Shakir, Muhammad and Ahmad, with supervising the digging of a canal named al-Ja'fari. They delegated the work to Al-Farghani, thus deliberately ignoring a better engineer, Sind ibn Ali, whom, out of professional jealousy, they had caused to be sent to Baghdad, away from al-Mutawakkil's court in Samarra. The canal was to run through the new city, al-Ja'fariyya, which alMutawakkil had built near Samarra on the Tigris and named after

himself. Al-Farghani committed a grave error, making the beginning of the canal deeper than the rest, so that not enough water would run through the length of the canal except when the Tigris was high. News of this angered the Caliph, and the two brothers were saved from severe punishment only by the gracious willingness of Sind ibn Ali to vouch for the correctness of al-Farghani's calculations, thus risking his own welfare and possibly his life. As had been correctly predicted by astrologers, however, alMutawakkil was murdered shortly before the error became apparent. The explanation given for Al-Farghani's mistake is that being a theoretician rather than a practical engineer, he never successfully completed a construction.

The Fihrist of Ibn al-Nadim, written in 987, ascribes only two works to Al-Farghani: (1) "The Book of Chapters, a summary of the Almagest" (Kitab al-Fusul, Ikhtiyar al-Majisti)and (2) "Book on the Construction of Sun-dials" (Kitab 'Amal al-Rukhamat).

TheJawami, or  'The Elements' as we shall call it, was AlFarghani's best-known and most influential work. Abd al-Aziz alQabisi (d. 967) wrote a commentary on it, which is preserved in the Istanbul manuscript, Aya Sofya 4832, fols. 97v-114v. Two Latin translations followed in the 12th century. Jacob Anatoli produced a Hebrew translation of the book that served as a basis for a third Latin version, appearing in 1590, whereas Jacob Golius published a new Latin text together with the Arabic original in 1669. The influence of 'The Elements' on mediaeval Europe is clearly vindicated by the presence of innumerable Latin manuscripts in

European libraries.

References to it by medieval writers are many, and there is no doubt that it was greatly responsible for spreading knowledge of Ptolemaic astronomy, at least until this role was taken over by Sacrobosco's Sphere. But even then, 'The Elements' of AlFarghani continued to be used, and Sacrobosco's Spherewas evidently indebted to it. It was from 'The Elements' (in Gherard's translation) that Dante derived the astronomical knowledge displayed in the 'Vita nuova'and in the 'Convivio'

The astronomer, mathematician, and geographer, Abu al‐Abbas Ahmad ibn Muhammad ibn Kathir al-Farghani (798-865), known in Europe as Alfraganus, was probably born in the Farghana Valley in present day Uzbekistan. Under Abbasid Caliph Mamun’s patronage in Baghdad, he collaborated in the accurate measurement of the world’s diameter, and wrote ‘The Elements of Astronomy’ and his famous treatise on the mathematical principles of the astrolabe. The astrolabe became highly developed in the 9th century and was extremely valuable in Islam to define prayer times and the direction of Mecca.

Farghani moved to Cairo later in his life where he restored the Nilometer in 861.  Nilometer existed since the Pharaonic Period, the Umayyads (the first Arab dynasty) constructed a Nilometer on Roda Island (then Fustat)  around 715 AD. This structure was restored in 815, but was destroyed by a flood in 850. The Nilometer existent on Roda Island today was designed by al-Farqhani.His last years were spent in Egypt and he is buried in the Qarafa mausoleum in Cairo.

from Wikipedia. Nilometer and Manasterly Palace on Roda Island

The statue of al-Farghani, standing at the Manasterly Palace entrance and the Nilometer on Roda Island, was given by Uzbekistan in 2007.

A moon crater, Alfraganus, was named after al-Farghaniī in recognition of his contribution to science.

(Published in Obelisque Magazine, 2011. All rights reserved by Lesley Lababidi