Al-Farghani

Al-Farghani

Abū al-ʿAbbās Aḥmad ibn Muḥammad ibn Kathīr al-Farghānī, also known in the West as Alfraganus, was a Persian Muslim astronomer. He was one of the most famous astronomers who flourished in the 9th century. The crater "Alfraganus" on the Moon is named in his honor.

His life

It is accepted that al-Farghani was born in the early 9th century, that he was alive in 861, and that he died shortly afterward.

He pursued his education in Fergana, the cultural center of the time. Then he went to Baghdad. Al-Farghani, who made a name for himself in a short time, established himself in the field of astronomy and mathematics. During the reigns of the Abbasid caliphs al-Ma'mun, al-Muʿtaṣim, al-Wāthiq and al-Mutawakkil, he carried out important scientific research and wrote many works. The caliph al-Mutawakkil sent al-Farghani, an authority in his field, to Egypt in 861 to direct the construction of the nilometer on the island of Rawda and to oversee the measurement work, in order to carry out measurements on the banks of the Nile.

Astronomy

Al-Farghani was among the first to criticize an astronomy that did not conform to the principles of reason. He did not accept that the celestial bodies were, as Ptolemy and his followers claimed, certain irrational spiritual bodies. He proved that they possessed rational, definite, homocentric and eccentric circular motions. He examined the volumes and sizes of the universe and the planets and their distances from one another. His calculations were accepted as unchanging measures in Western astronomy until Copernicus and were used for centuries. Al-Farghani stated that the length of the Sun's radius was 3,250 Arab miles. This was equal to 6,410,000 meters and 3,990 English miles.

Al-Farghani is the scholar who first discovered, in the history of science, that the Sun too is in motion relative to itself. Until his time the motion of the celestial bodies was known. But al-Farghani was the first scholar to discover that the Sun too has an orbit and rotates on its own axis from west to east. Moreover, in his astronomical studies that continued for 41 years, he calculated the distance between the parallels of latitude.

Al-Farghani also found a method for predicting solar eclipses in advance. By this method he determined in advance that a solar eclipse would occur in 842, and on that day he made observations and studies on the subject. He presented new evidence that the Earth is round.

Al-Farghani went to Cairo in 856 and published a work titled On the Construction of the Astrolabe.

Al-Farghani made very great contributions to the science of astronomy and to its development through his work. The crater Alfraganus on the Moon is named in his honor.

Elements of Astronomy

Elements of Astronomy is one of the most important works al-Farghani wrote on astronomy. The book, estimated to have been written in 833, is a descriptive and adequate summary of Ptolemy's book the Almagest. This book was translated into Latin in the 12th century by Gerard of Cremona under the title Liber de Aggregationibus Scientie Stellarum et Principiis Celestium Motuum and was a very popular work in Europe until the time of Regiomontanus. The work was translated into Latin a third time by Jacob Christmann under the title Muhammedis Alfragani Arabis Chronologia et astronomica elementa and printed in Frankfurt in 1590 and 1618. This translation was based on the Hebrew translation of the work made by Jacob Anatoli. Jacob Anatoli's Hebrew translation was made under the title Qizzur Almagesti in 1231–1235. This translation most likely used Gerard of Cremona's translation. Anatoli's translation has 3 more chapters than al-Farghani's. The last of these (Chapter 33) concerns geography and gives the positions of places on the Earth and the lengths of days.

The work was finally translated into Latin by the Dutch orientalist Jacob Golius in the 17th century, based on the Leiden copy, under the title Muhammedis Fil. Ketiri Ferganensis, qui Vulgo Alfraganus Dicitur. Elementa Astronomica. Arabice & Latine. Cum Notis ad Res Exoticas sive Orientales, quae in iis Occurrunt, and was printed in Amsterdam in 1669.

This work was used as a handbook until the astronomy book titled The Sphere, written by the 13th-century scientist Sacrobosco. Sacrobosco made use of this work in writing his own book. Moreover, the conception of the universe in Dante's famous work the Divine Comedy is taken from al-Farghani.

Mechanics

Al-Farghani also carried out work in the fields of physics and mechanics. He built an instrument called the Miqyās al-Jadīd (New Measure) that measured the speed and level of the waters of the river Nile, whose design he himself prepared and whose construction he oversaw.

Apart from astronomy and mechanics, al-Farghani carried out work in the fields of mathematics and mathematical geography.

Beginning with the caliph al-Ma'mun and up to the time of al-Mutawakkil, al-Farghani took his place among the leading scholars of the time through the research he carried out in al-Jazira (Mesopotamia), the works he wrote, and the measuring instruments he devised. His work in the fields of astronomy, mathematics, geography and mechanics helped significantly in the development of these branches of science. He strengthened their foundations and paved the way for new developments. In later periods, scholars concerned with the same subjects benefited from al-Farghani's works. His influence is seen upon all the scholars of Turkestan of that era.

Al-Farghani's influence is also seen upon European scholars. His works translated into Latin were taught for centuries in European universities. The zijes he prepared were among the works most made use of by the French mathematicians d'Alembert and Laplace.

His works

Usūl ʿIlm al-Nujūm: a work concerning the stars. The book's other titles are: al-Madkhal fī al-Majisṭī, al-Madkhal ilā ʿIlm Hayʾat al-Aflāk, Kitāb al-Fuṣūl al-Thalāthīn.

al-Kāmil fī al-Usṭurlāb: concerning the construction of the astrolabe. It is also known under the title Fī Ṣanʿat al-Usṭurlāb.

Sources

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