Abu Rayhan Al-Biruni was a great Persian Muslim scholar of the 10th and 11th centuries. Like many of the Muslim scholars, he believed that he could get closer to God if he understood his creation. Although his life and his contribution to science could be the focus of entire books, we will approach only the geographical aspect of his scientific work.

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Al-Biruni, is a Persian scholar who was born in 973 in Khwarazm, today known as Karakalpakstan (Uzbekistan). He studied under the famous astronomer and mathematician, Abu Nasr Mansur. By the age of 17 he was involved in scientific research. In 990 he determined the latitude of Kath (Uzbekistan) by observing the maximum altitude of the sun.

He wrote his Cartography which is about map projections. As well as describing his own projection of a hemisphere onto a plane. By the age of 22 he had studied a wide range of map projections and addressed them in treaties.

In 995 the rule by the Banu Iraq was overthrown in a coup. Al-Biruni fled at the outbreak of the civil war.

By the 4th June 1004 al-Biruni came back to his homeland. Abu’l Abbas Ma’mun became ruler and he provided important resources to al-Biruni’s scientific research.

Armed conflicts in the region interrupted the scientific work of Al-Biruni and made him leave Khwarazm around 1017.
Al-Biruni studied Indian literature, and translated many Sanskrit texts into Arabic. He also wrote treatises about Indian astronomy and mathematics. He was versed in astrology, astronomy, chronology, geography, grammar, mathematics, medicine, philosophy, religion, weights and measures.

He wrote his famous text, Shadows, around 1021. It is a precious legacy of the history of mathematics, astronomy, and physics. He is also the pioneer of what would be later known as polar coordinates.

Greek scientists, in particular Ptolemy, inspired Al-Biruni as for his conception of the spherical shape of the earth and its geographical components. In his al-Qānūn al-masūdī, he addressed the Greek astronomers’ theory of the earth and enhanced the debate of the distribution of land and sea with new knowledge and thinking.

In his Tahdīd he approaches climate change and stratigraphy. In India he interpreted the theories of the earth both of the Purānas (religious text about the history of the universe from creation to destruction) and of the Indian astronomers.

Al-Biruni made large contributions to geodesy and geography. He introduced techniques to measure the earth and distances based on triangulation. He claimed that the radius of the earth was 6339.6 km, by observing the height of a mountain in India. His Masudic canon reveals a table with the coordinates of six hundred places. Some of them were given by al-Khwarizmi (Persian scholar, 780-850).

Coming to the geographical organisation of the world, Al-Biruni accepted the Greek teaching of the seven climes, and also explained with deep precision the seven kešvars (Ancient Persians conceived the world as vast, round and surrounded by a high mountain) of traditional Persian geography and the seven dvīpas ( “peninsula, island” in Indian mythology) of the Indian Purānas.

Al-Biruni’s focus was mainly in the location of places relative to each other, their latitudes and longitudes, and the computation of their azimuths (angular measurement in a spherical coordinate system) of the qebla (direction to Mecca).

Al-Biruni did not meet problems for establishing local latitude. The longitude difference between two different places was his main obstacle. He managed to overcome it by assessing the longitudinal difference based on an amendment of the itinerary distance between two localities, using the latitude of each, and a determined value for the circumference of the earth. After establishing the longitudinal difference between any places of known latitude and Mecca has been determined, he managed to compute accurately the azimuth of the qebla.

Abu Rayhan al-Biruni died in 1048 in Ghazni (Afghanistan).

By Morad Ouasti