Did Islamic science really decline after the golden age, and how much did Europe take from it?

Historians disagree on both questions, and the disagreement is the interesting part. The conventional story, which Mohamad Abdalla calls the "decline theory", says there was a golden age from the end of the ninth to the end of the eleventh century and an "age of decline" afterwards. He notes that this has become the preferred paradigm in general academia. Even the dates are fuzzy: the golden age is said to have ended with the Siege of Baghdad in 1258, but some scholars extend it to around 1350, while Khan (2003) places the proper golden age between 750 and 950.

Why a decline? The economic historian Joel Mokyr has argued that al-Ghazali was a key figure in the decline of Islamic science, shifting culture away from scientific thinking. Others disagree: George Saliba points out that the golden age did not slow down after al-Ghazali, and places the golden age of astronomy in the period after him. Ahmad al-Hassan rejects lack of creative thinking as a cause and points instead to economic and political factors.

There is also evidence on the ground. The Maragheh observatory began construction in 1259, the year after Baghdad fell, and stayed active for more than 50 years with over a hundred astronomers. Samarkand's Ulugh Beg observatory, built in the 1420s, was similar in scale.

As for Europe, the 12th-century translators were scholars searching for new learning unavailable in western Europe. Gerard of Cremona is said to have gone to Toledo for love of the Almagest, and became its most productive translator, with more than 87 books of Arabic science. But some Greek works reached Latin directly, such as an earlier Almagest translation made from the Greek in Sicily, so the debt is real, but Arabic was not the only route.