9. Al-Battani
(244-317H/858-929AD)

He is Abu Abdullah Muhammad Ibn Jabir Ibn Sinan ar-Raqqi al-Harrani, known as al-Battani. He was named as ar-Raqqi after Raqqa, a township on the Euphrates in Iraq. He was known in the West in the Middle Ages as Albategnus or Albategni.

Al-Battani was born in "Battan" near Harran, located on one of the Euphrates tributaries. His date of birth is not accurate, but he was probably born in 235 H./858 AD. Concerning the date of his death, "historians agreed all that he passed away in 317 H./929 A.D.(54) near the city of Moussul in Iraq. He was regarded as one of the greatest Arab astronomers. He devoted all his life time from 264 H until his death to the observation of planets and stars. Al-Battani was first educated by his father Jabir Ibn al-Battani, who was also a well-known scientist. He then moved to Raqqa, where he studied the works of his predecessors, mainly Ptolemy's. He dedicated himself afterwards to research in the fields of astronomy, trigonometry, algebra, geometry and geography. He spent his professional life travelling between "Ar-Raqqah" and "Antakia" in Syria, where he set up an observatory bearing his name (al-Battani Observatory).

The Islamic Encyclopedia refers to al-Battani was famous for the observation of planets and was one of the leading figures in the fields of geometry,  planet positions and star calculus.  European scholars all agree that al-Battani was more versed in his science than was the Greek astronomer Ptolemy. The French astronomer Lalande said that al-Battani was among the 20 top level astronomers that existed in all the world(55).

Kadari Tawkan stated in his book "Arab Scientific Heritage in Mathematics and Astronomy"(56) that "Kajori" and "Halle" considered al-Battani among the most eminent observation scientists. Some  researchers called him Ptolemy of Arabs. Georges Sarton described him as the greatest astronomer of his time and one of the greatest scholars of Islam(57).

Contributions to Astronomy

Of his most important contributions in astronomy is his discovery of the azimuth and nadir and the determination of their points in the sky. He also determined with remarkable accuracy the inclination of the ecliptic, the length of the tropical year, the seasons and the true and mean orbit of the sun. He opposed Ptolemy's and showed that the position of the Sun's apogee is variable. His accurate observations of lunar and solar eclipses were used by Europeans (Dunthorne in 1749 AD) to determine the secular acceleration of motion of the Moon throughout a whole century.

He also rectified the orbits of the Moon and the planets and developed a table of their new positions. Besides, he checked the positions of several stars and included them in his famous table of planetary movements, which was used by astronomer for centuries.

"Nellino" recognizes that he "discovered a new theory which evidences his dexterity and ability to find out means to explain the states of the Moon at its birth(58).

Contributions in Mathematics

Al-Battani was among the first Arab scholars to have used the sine instead of chord. He also used the tangent et the cotangent in the spherical trigonometry. He attempted to use algebra in solving the problems in which Greeks used geometry. Al-Battani was among the founders of trigonometry and who endeavours to extend its scope(59).

Major Works

Among his major works, the following can be cited :

-"Zij Assabi" is by far his most important writing. It contains the findings of the observation of planets, he conducted in 299 Hegira, tables on the motions of the celestial bodies, he discovered as well as the various astronomical works he undertook from 264 to 306 H. It constituted the first "zij" or ephemeris ("zij" a Persian term referring to the old ephemerides) containing true and accurate information. The book was greatly influential in the development of astronomy and mathematics both during the Arab-Islamic renaissance or at the outset of the European renaissance. Several Arab scientists relied on it in their calculations, some of them quoted or interpreted parts of its content.

This book was translated in Latin by Tivok Platoof in the 12th century under the title "Sciencia de Sttellarum", "Science of Stars", and was printed in Nuremberg in 1537 AD. In the 13th century, the King of Castile, Alfonso X, ordered the translation of this Zij from Arabic into Spanish. An incomplete manuscript of this translation is in Paris. A copy of this book is available in the Vatican. Carlo Nellino published an edition of the Arabic original, copied from the copy of El Escorial in three volumes in Rome 1899-1907 accompanied by Latin translation and comments on some subjects.

- "Kitab Ma'rifat al-Buruj fima bayna Arba' al-Falak" in which al-Battani deals with the mathematical solution to the astrological problem to the observer's orientation; 

- "Rissala fi Mikdar al-Ittissalt";

- "Rissala fi Tahqiq Akdar al-Ittissalat";

In these last two treatises, al-Battani tackled the subject of the congruence of two planets as to latitude and longitude, whether they are in the same orbit, or one or both of them are outside this sphere.

-"Charh al-Maqalat al-Arba' Libatlimus". Ptolemy ended his "Almagest" with these four treatises in which he dealt with astrological issues and the influence of stars on secular matters.

- "Kitab Ta'adil al-Kawakib". Al-Battani studied the difference between the motions of planets within their orbits, as a constant value and their real motions which differ from one position to the other.

In summary, "Al-Battani was among the greatest geniuses of the world who developed important theories and enriched the human scientific heritage by adding new discoveries in astronomy, algebra and trigonometry. He became famous for his observations of planets and celestial bodies. Some of his findings continue to arouse the interest of scholars and their admiration(60).