Astronomy of the Arabs


In that vast wilderness that occupies the largest area of the Arabian Peninsula, it was necessary for the Arabs to find what could guide them through it; otherwise, they would have been lost and faced death. People of the desert are in the habit of moving and traveling, looking for water, food, and grass; thus, finding a way to observe and identify locations was a necessity.

With the dawn of Islam and the commandment of prayer and fasting, it became also a necessity to determine the directions to face Al-Aqsa Mosque, and later the Ka’aba, at five specific times daily; as well as identifying the months of the Hijri Calendar and determining the new moons as festivals and fasting of Muslims depend totally on the sightings of the Moon and its phases. Stellar guidance was mentioned in the Qur’an, and there are verses that call for meditation and observation of the universe’s creation.

All these introductions and reasons made astronomy one of the necessities for survival among the Arabs, and urged them to dig deep in observation, analysis, establishment of theories, and the invention of astronomical instruments to monitor the sky day and night.

There is no doubt that the contributions of the Arabs in astronomy in the Middle Ages or the Golden Age of the Arab Civilization are well known everywhere. It is enough to know that the names used to this day for the stars and planets discovered by the Arabs more than 1,500 years ago are Arabic names, as well as some astronomical terms; such as almucantar, azimuth, and alidade.

Perhaps one of the most important sources that reached us in the field of observational astronomy is the Book of Fixed Stars by Abd al-Rahman al-Sufi, who died in 376 AH/976 CE. The book described the planets in the sky, which amounted to forty-eight planets that were thoroughly illustrated as imagined by the Arabs then without the use of complex modern machines in our time. After al-Sufi’s death, his daughter Arajoza Bint al-Sufi resumed his observations, in addition to the development of observational and approximation instruments by scholars of the Islamic civilization of the time.

We can also only imagine how Ibn al-Haytham—who died in 430 AH/1040 CE—with the means available at his age, wrote a treatise entitled The Trace on the Moon’s face, in which he addressed and scientifically analyzed the topography of the Moon and its volcanic craters.

Before al-Sufi and Ibn al-Haytham (aka Alhazen), there was Abu Abdullah al-Battani—born in 240 AH/854 CE. He was one of the most significant scientists in astronomy and observation in the world, prompting some people to call him Ptolemy of the Arabs. If you have studied trigonometry and trigonometric functions—sine, cosine, and tangent—for example, you have to know that this man is credited for their existence.

If we go back to the second hijri century/eighth century CE, we will find al-Khwarizmi (aka Algoritmi), whose name was linked with algebra for his great contributions, the effects of which resonated in astronomy and observation, where the first book was the Astronomical Tables of Sind and Hind, which became the turning point in Islamic observational astronomy.

The book observed the movement of the Sun, the Moon, and the five planets known at the time, where he entered concepts translated from Indian and taken from Ptolemy to the Arab astronomy, developed them, and from which he initiated new discoveries in astronomy.

We cannot talk about observational astronomy without mentioning Maragheh observatory, located in the west of Maragheh, in Azerbaijan, which was founded by astronomer, mathematician, chemist, physicist, philosopher, and physician Nasir al-Din Tusi in 657 AH/1259 CE.

Maragheh observatory was attended by many scholars, such as: Qutb al-Din al-Shirazi, Ibn al-Shater, Najm al-Din al-Qazwini, Ali Qushji, Abdul Ali al-Birjandi, and Shams al-Din al-Khafri, Muhyi al-Din al-Maghribi, Ibn al-Fuwati and many others. The Observatory contained more than 400,000 volumes, which made it the first academy for scientific research in the field of astronomy and observation that revolted against the principles and ideas of Ptolemy in astronomy.

On the other hand, al-Biruni (Abu Rayhan)—born in 362 AH/963 CE in the capital of the Khwarezmian Empire—was described as one of the greatest minds that the Islamic civilization has ever known; he excelled in astronomy and observation. His designs of astrolabes and observational instruments for sites, stars, and planets, and their development were groundbreaking for astronomy and observation, and preparatory for the invention of the mechanical clock. Al-Biruni was the first to invent the vertical astrolabe in the first decade of the eleventh century, and he was also the first to say that the Earth rotates around its own axis.

The list of scientists and contributions goes on and on as the manuscripts of astronomy and observational methods in the written Arab heritage mount to thousands that still need to be exposed or re-discovered. Indeed, astronomy was a necessity for survival of the Arab Muslims, and for the application of their holly religion; this article is thus but a drop in the ocean of the contributions of the Arab Civilization in that area.

Top Image: By Ala ad-Din Mansur-Shirazi - Istanbul University Library, Esposito, John L. (2008) Iszlám (Vallások földrajza), Budapest: National Geographic, p. 358 ISBN: 978-963-9810-42-6., Public Domain,

This article was first published in print in SCIplanet, 2015 Winter issue.

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