AL-FARGHANI
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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
al-Samawiya 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 al-Mutawakkil 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, al-Mutawakkil 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). The Jawami, or 'The Elements'
as we shall call it, was Al- Farghani's best-known and most
influential work. Abd al-Aziz al-Qabisi (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 in mediaeval 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 Al-Farghani continued to be used, and Sacrobosco's Sphere
was 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'.