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Al-Khwarizmi Persian Mathematician, Astronomer and Geographer part one

October 1, 2016 by  

Nasser Kanani, (Prof. Dr.Ing. Dr. Habil.) Berlin
Al-Khwarizmi was a Persian mathematician, astronomer and geographer who disseminated the Indian numbers throughout the Islamic world and introduced them as “Arabic” numerals to the West. He founded the mathematical branch algebra, which is why he is referred to as the “father” of algebra, and his name has become what is known today as “algorithm,” meaning how to find the solution for a given problem. Without al-Khwarizmi’s “Arabic” numerals and his “algorithm” the invention of the modern computer would have never been possible. In recognition of his services to the scientific world NASA has named a crater on the moon after him (photo below).

Name and Epithets
Al-Khwarizmi’s full name was Abu Jafar or Abu Abdallah Muhammad ibn Musa al-Khwarizmi. The last part of his name refers to his birth place, Khwarizm in the Greater Khorasan), which then occupied the eastern part of the Greater Iran. Khwarizm or Chorasmia was part of the Persian Empire, and its name appears in Achaemenid inscriptions as Huvarazmish. The remainders of Khwarizm belong nowadays partly to Uzbekistan and partly to Turkmenistan.
Al-Khwarizmi is also known by two epithets: al-Majusi and al-Qutrubbulli. The first epithet, meaning magician (a Zoroastrian priest), indicates that his Persian ancestors and parents were adherents of the Zoroastrianism founded by the Old Persian prophet Zoroaster. The second epithet refers to a viticulture district of Baghdad by the name of Qutrubbull which was famous for its wines, touring minstrels, and carpe diem atmosphere.

Birth and Death
Al-Khwarizmi was born around 783 CE1 probably in the city of Kath in Khwarizm. He died around 850 CE in Baghdad after having served three Muslim Caliphs: al-Ma′mun (813-833), al-Mu′tasim (833-842) and al-Wathiq (842-847)2.

Education and Religious Belief
Only few details of al-Khwarizmi’s life are known with certainty. He must have studied mathematics and astronomy vigorously when he was an adolescent, since as a young man he was already an accomplished mathematician and astronomer. In the course of his academic training he must also have made the acquaintance of scientific manuscripts, which were written in Pahlavi3 and Sanskrit.
The pious preface to his book on algebra clearly shows that al-Khwarizmi was an orthodox and devout Muslim. This fact gives rise to assume that either both his parents abandoned their Zoroastrian religion and converted to Islam after the conquest of Khwarizm by the Muslim Arabs in 712 CE, or he himself became later a Muslim.

At al-Ma′mun’s Court
The young al-Khwarizmi drew the attention of al-Ma′mun, who was the younger son of Harun al-Rashid, the legendary Abbasid caliph (786-809), and his Persian wife Marajil. He had been appointed governor of the Greater Khorasan by his father and his capital was the city of Merv, nowadays in Turkmenistan.
Al-Khwarizmi was invited to join al-Ma′mun’s courtiers and soon became a member of his scientific entourage.
When al-Ma′mun was appointed caliph in 813 CE he decided to rule the Islamic Empire, which stretched from the Mediterranean Sea to India, from his capital Merv and continued to do so for six years. However, in 819 CE he was forced by many conflicting circumstances to leave Merv for Baghdad and entered the Islamic capital on August 11, 819.
Al-Khwarizmi accompanied the new caliph to Baghdad and there became one of the scholars at the House of Wisdom.

House of Wisdom
The House of Wisdom was originally a scientific institute initiated by Caliph Harun al-Rashid for translating books on alchemy and medicine, logic and philosophy, astrology and astronomy, mathematics and geography from Pahlavi, Greek and Sanskrit into Arabic. It soon became a center of learning where educated men gathered and translated scientific works.
Its point of culmination reached the House of Wisdom during the caliphate of al-Ma′mun, a patron of the sciences, and developed into the largest repository of books in the world accumulating a huge collection of knowledge. Many learned scholars from all over the Islamic Empire set out for the House of Wisdom to study and teach mathematics and astronomy, medicine and alchemy, geography and cartography, and other sciences. They were engaged in translating all the known scientific works as a consequence of which the Arabic language started to flourish. Thus, al-Ma′mun’s era became the Golden Period of the Islamic civilization.
Under Ma′mun’s patronage, and the spirit of openness towards other religions and cultures that he fostered, many scholars from all over the empire gravitated towards Baghdad, drawn by a vibrant sense of optimism and freedom of expression.

Scientific contributions
Al-Khwarizmi made contributions in various fields of science including astronomy, geography and cartography as well as mathematics. He also wrote a treatise on Hebrew Calendar called “Extraction of the Jewish Era” and authored some treatises on mechanical devices such as astrolabes and sundials. After all he was one of the developers of the astrolabes and sundials and by writing these treatises he wished to prove his astronomical abilities.
Al-Khwarizmi’s talents were holistic and ranged from one subject to another. He never hesitated to explore new dimensions in fields that intrigued him, and turned out to be a scientist of great merit paving the way for further development of many sciences.
Prior to discussing some of al-Khwarizmi’s major works, it should be pointed out that even though he was a brilliant mind, discovered astronomy, geography and mathematics in a way no one had before, and wrote on his own findings, some of his achievements can be traced back to the Babylonian, Indian, Greek and Persian sources. He reviewed the existing knowledge in various fields and left his own mark in a way that his achievements could continue their legacy till present time. Unfortunately, not all the works written by him have survived.

Astronomical Works
Following al-Ma′mun’s order two lavishly equipped observatories were constructed around 823 CE, one in Baghdad and the other one in Damascus, so that al-Khwarizmi and his fellow astronomers could perform their astronomical research and make their own discoveries. It should be added that the knowledge of astronomy was also critical for certain religious exercises such as determining which direction to pray and ascertaining the times for the first sighting and setting of the crescent moon at the start and end of the holy month of Ramadan.

Zij al-sind-hind
Most of al-Khwarizmi’s contributions were in the field of astronomy. He produced a considerable amount of astronomical tables, called Zij, containing calendars and calculations of the true positions of the sun and the moon and five planets known at his time. His development of this kind of astronomical tables was a significant contribution to the field of astronomy.
Al-Khwarizmi’s major astronomical work known as Zij al-sind-hind was based primarily on Persian and Hindu astronomical sources and to some extent on Greek texts. It is known that the original tables in his Zij employed the Persian solar year and date of origin corresponding to the era of Yazdegerd III,4 16 June 632 CE. The Indian text on which al-Khwarizmi had based his treatise was one that had been given to the court in Baghdad around 770 CE as a gift from an Indian political mission.
The original Arabic version of Zij al-sind-hind was lost. A Latin translation that has survived in its entirety indicates that the original text consisted of 37 chapters and 116 tables containing astronomical and astrological calculations as well as detailed data on the sun and the moon and other celestial bodies. It also encompassed tables of solar and lunar eclipse and parallax5 as well as tables for trigonometric functions such as sines, cosine and tangents. Al-Khwarizmi’s astronomical work marked the turning point in the Islamic astronomy. Hitherto, Muslim astronomers had been translating works of others and learning already discovered knowledge. Al-Khwarizmi, on the contrary, not only expounded extensively the works of ancient astronomers, but also performed his own research. As a sign of service to the Muslim faith, he developed a method to calculate the time of visibility of the new moon, indicating the beginning of the month of Ramadan.

Geographical Works
From among al-Khwarizmi’s geographical works two are in particular worth mentioning, one is “The Image of the Earth” and the other “The World Map of al-Ma′mun”.

“The Image of the Earth”
Around 1875 a German specialist in Middle Eastern and Oriental studies by the name of Wilhelm Spitta (1853-1883) discovered in Cairo a geographical manuscript entitled “The Image of the Earth”. On its cover it was attributed to Musa al-Khwarizmi. The Italian scholar Carlo Alfonso Nallino (1872-1938) was the first to recognize in it al-Khwarizmi’s work on geography commissioned by Caliph al-Ma′mun.6
As it turned out “The Image of the Earth”, a major work in the field of geography in its own right was based on Geographike Hyphegesis put forward Ptolemy7 around 150 CE. According to the American scholar, Walter B. Bevens:
“First extensive use of Ptolemy known is by ibn Musū al-Khwarizmi in his work, Kitab ṣurat al-arḍ. In this work, al-Khwarizmi produces an elaboration of Ptolemy’s material made with liberties taken to make it more acceptable to Muslim thought.”۸
Al-Khwarizmi, however, not only revised Ptolemy’s views, but also made some considerable alterations in his Geography in that he improved or corrected Ptolemy’s data with more accurate values for sites in Africa, Asia and the Middle East. Based on his own findings, al-Khwarizmi provided better values for the length of the Mediterranean Sea than Ptolemy.9
Al-Khwarizmi’s “The Image of the Earth,” which was finished in 833 CE, provided the latitudes and longitudes of more than 2400 sites in the known world, including oceans, seas, rivers, mountains, islands and cities as well as other geographical features, in particular in the Islamic world. This is easily comprehensible when one takes into consideration that where more local knowledge was available to al-Khwarizmi such as the regions of Islam, Africa and the Far East then his work was considerably more accurate than that of Ptolemy. As for Europe, al-Khwarizmi seems to have used Ptolemy’s data.
An interesting aspect of “The Image of the Earth” was the classification of weather zones. Al-Khwarizmi had ordered the inhabited quarters of the world in different climates.10 His contribution in the field of geography has been praised by Nallino as follows: “His geography is not a servile imitation of the Greek model, but an elaboration of Ptolemaic material made with more independence and ability than is displayed by any European writer of that period.”۱۱

The World Map of al-Ma′mun
At al-Ma‘mun’s behest al-Khwarizmi cooperated with a team of geographers to create a map of the known world to be called “The World Map of al-Ma′mun”. The Caliph wanted his geographers to create a world map that accurately depicted the shape of the world, which would enable him to recognize countries and regions conquered by the Muslims.
The only one surviving copy of “The Image of the Earth” does not contain such a map. However, the German scholar, Hubert Daunicht,12 and the Indian scientist, Razia S. Jafri13, have been able to reconstruct the missing map from the list of coordinates given in “The Image of the Earth”.
to be continued

Notes:
۱٫ The United Nations Educational, Scientific and Cultural Organization, UNESCO, has declared the year 1983 as the 1200th birth anniversary of al-Khwarizmi.
۲٫ The most recent date associated with the name of al-Khwarizmi is 847. This year died Caliph al-Wathiq, and al-Khwarizmi is mentioned among the persons who were present at his death.
۳٫ Pahlavi or Pehlevi, also known as Middle Persian, was the Middle Iranian language of the Sassanid era (224-654 CE).
۴٫ Yazdegerd III was the last king of the Sasanian Empire (Reign: 632-651 CE)
۵٫ Parallax refers to the phenomenon that objects in the further distance appear to move slower than the objects closer to the observation post.
۶٫There is only one surviving copy of “The Image of the Earth”, which is kept at the Strasbourg University Library. A Latin translation is kept at the Biblioteca Nacional de España in Madrid; the complete title translates as “Book of the Image of the Earth, with its Cities, Mountains, Seas, all the Islands and Rivers, Written by Abu Jafar Muhammad ibn Musa al-Khwarizmi, According to the Geographical Treatise Written by Ptolemy the Claudian.”
۷٫ Claudius Ptolemy (90-168 CE), Greek mathematician, astronomer and geographer
۸٫ Walter Bascom Bevens: “Al-Yaman and the Ḥaḍramawt: Translation from Medieval Arabic Geographers and Analysis,” a dissertation submitted to the Department of Oriental Studies of the University of Arizona, 1988, p. 15
۹٫ Edward S. Kennedy: “Mathematical Geography,” in “Encyclopaedia of the History of Arabic Science,” Volume 1, edited by R. Rashed in collaboration with R. Morelon, published by Routledge, London New York, 1996, p. 185
۱۰٫ The classical “Tetragonus mundus” (four-fold world view, or dividing the Earth in four quarters) is often attributed to the Greek philosopher Aristotle (384-322 BCE) even though the roots are older.
۱۱٫ Carlo Alfonso Nallino: “Al-Ḫuwarizmi e il suo rifacimento della Geografia di Tolomeo” (A-Khwarizmi and his Reconstruction of the Geography of Ptolemy,” in Atti della R. Accademia dei Lincei, fifth series, Memorie, Classe di scienze morali, storiche e filologiche, Vol. II, 1896, pp. 11-53
۱۲٫ Hubert Daunicht: “Der Osten nach der Erdkarte al-Ḫuwārizmīs: Rekonstruktion der Karte,” Band I-IV, Bonner orientalistische Studien, Selbstverlag des Orientalischen Seminars, 1968/70
۱۳٫ Razia S. Jafri: “Al-Kharazmiʼs Geographical Map of the World Based on the Book Surat al-ard,” Soviet Committee of the International Association for the Study of the Cultures of Central Asia, Dushanbe, 1985

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