The Abbasid Caliphate

The Abbasid Caliphate has only been mentioned so far as a target of the Assassins, but deserves more attention. Descended from Muhammad's uncle Abbas, the caliphate took power from the Umayyad caliphate and ruled from 750 until its conquest by Mongols in 1258.

That means that the Abbasid Caliphate was "in charge" during many of the Islamic interaction with Europe mentioned in this blog:

• Abu Ma'shar, the Father of Arab Astrology, who brought commentaries on Aristotle to Western Europeans
• The astronomer Abd al-Rahman al-Sufi, who reconciled Greek and Arab star charts
• Averroes the Commentator
• Avicenna the surgeon
• ...and, of course, it was during this time that Algebra came to be

Besides math and philosophy, the Abbasid Caliphate was at the forefront of technology, adopting the use of Chinese paper-making techniques and gunpowder. Arabs developed the sextant, windmills for industrial use, and kerosene from petroleum.

The Abbasid's first capital was Kufa, on the banks of the Euphrates, but they shortly chose a different city, whose only shortcoming was that it did not exist.

On 30 July, 762, that would change; but that's a story for tomorrow.

Abd al-Rahman al-Sufi, Astronomer

MS. Marsh 144, fol. 135v, Bodleian

The contributions of the Muslim world to astronomy are many, and I have only briefly touched on some of them (such as here). There were nine Muslim astronomers in particular who made major contributions. One of them was the Iranian Abd al-Rahman al-Sufi (7 December 903 - 25 May 986). His name indicates that he was a Sufi Muslim, like Rumi.

al-Sufi translated and expanded on the work of the Greeks, especially attempting to reconcile the Greek and Arabic star charts and constellations. In 964 he published Suwar al-Kawakib al-Thabitah, the "Book of Fixed Stars."* In it he gave the latitude and longitude of hundreds of stars for the year 964 from two views: from both the exterior and interior of a celestial globe. The oldest surviving manuscript known is in the Bodleian Library and was created about 1009 by al-Sufi's son. There was no English translation of this book until 2013.

Among the "firsts" that can be credited to al-Sufi's work are the following identifications:

Ursa Major

• "the little cloud" that we call the Andromeda Galaxy.
• the Large Magellanic Cloud*
• the Omicron Velorum star cluster
• a "nebulous object" in Vulpecula, now called "Al Sufi's Cluster"

He also describes the astrolabe and lists a thousand uses of it.

The significance of al-Sufi's work led the astronomical community to name other objects after him, such as a a lunar crater (Azophi) and 12621 Alsufi, a minor plant in the asteroid belt with a period of 2000 days.

*There is an argument that he could not have known of the Magellanic Cloud until the same time as Western European astronomers in the 15th century because of its position in the Southern Hemisphere.