The House of Wisdom, By Jonathan Lyons

Early in the 9th century, two teams of surveyors were dispatched to the Iraq desert to perform a complex series of measurements. As a result the scholarly Caliph Abdallal al-Mamun gained an accurate calculation of the world's circumference, some eight centuries before the Danish astronomer Tycho Brahe achieved the same feat.

Even more remarkably, the efforts of the two teams were dismissed as excessive by a contemporary trigonometrician: "There is another method that does not require walking in deserts." During the Crusades, the Arabs with their "highly evolved system of legal disputation" were aghast at Christian trial by ordeal. Contrasting our Dark Ages with Arabic enlightenment, Lyons explains how this disparity began to close as travellers brought Arab learning to the West.