Astronomy in Islam
Between the time of Ptolemy and that of Copernicus, a period of over a thousand years, astronomy knows no notable development in Europe. In the Islamic world, by cons, important progress will occur between the ninth and eleventh centuries, both in the mathematical tools of astronomy in observing the sky.
Al-Khwarizmi
The most notable scholar of the ninth century Persian Al-Khwarizmi. He wrote the first book on algebra, al-Jabr Hisab w'al-muqabala and founded the same time this discipline. He introduced and spread the use of numbers we use today (they are called for Arab although they are actually from India). Its main direct contribution to the astronomy book will Sindhind zij, based on Hindu astronomy, in which he sets the tables on the position of the Sun, Moon and planets, and studying a variety of subjects such as eclipses or visibility of the moon.
Al-Farghani
Around the same time, the Persian Al-Farghani writes Astronomy Elements (Kitab fi al-Harakat al-Samawiya Jawami wa al-Ilm Nujum), a book based on the Ptolemaic astronomy. It also introduces new ideas, for example that the precession must affect the apparent position of the planets, not just the stars. This book will play a significant role in Western Europe when it was translated into Latin in the twelfth century.
Al-Battani
Around the late ninth century, the dominant figure is the Arab astronomer Al-Battani will observe the sky from Syria and make measurements of outstanding accuracy for its time. It will thus determine the length of the solar year, the value of the precession of the equinoxes and the obliquity of the ecliptic. He would also like to establish a catalog of 489 stars.
From a theoretical point of view, his main work, Kitab al-Zij is of fundamental importance as it introduces for the first time trigonometry in the study of the celestial sphere. This new approach will prove more powerful than the geometrical method of Ptolemy. This book will be translated into Latin in the twelfth century and influence many major European figures of the sixteenth and seventeenth centuries.
Al-Khujandi
In 994, the astronomer Al-Khujandi, from the current Tajikistan, built a huge mural sextant to Ray observatory near Tehran, the first instrument for more accurate measurements than the arc minute. He uses it in particular to determine a more precise value of the obliquity of the ecliptic.
Al-Biruni
Around the same time appears another scholar, al-Biruni, from near the Aral Sea. Like its predecessors, it is interested in many subjects such as mathematics and geography. In astronomy, he distinguished himself by his observations of lunar and solar eclipses, but also by a more modern approach to the experimental method, especially when analyzing errors which undermine its actions and those of Al-Khujandi.
Omar Khayyam
In the eleventh century Persian Omar Khayyam, now best known for his poetry, is interested also in various subjects, particularly algebra and astronomy. It creates new astronomical tables, but is especially remarkable in determining the length of the solar year with extreme precision for the time.
This golden age of Islamic astronomy will end in the twelfth century. The works of this prosperous period will gradually be translated into Latin, particularly in Toledo, Spain, and spread in Europe. It will be through these translations that European scholars of the late Middle Ages rediscover the theories of Ptolemy and will take note of progress made in the Muslim world.
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