Physicist Jim Al-Khalili travels through Syria, Iran, Tunisia and Spain to tell the story of the great leap in scientific knowledge that took place in the Islamic world between the 8th and 14th centuries. He travels to Syria to discover how, a thousand years ago, the astronomer and mathematician Al-Biruni estimated the size of the earth to within a few hundred miles of the correct figure. In Cairo, he tells the story of the physicist Ibn al-Haytham, who helped establish the science of optics.

• Jim Al-Khalili