From fast cars and aeroplanes to computer encryption – mathematics underpins so much of modern life. In this episode, Jim Al-Khalili uncovers how, between the 9th and 14th centuries, mathematicians from the Islamic world helped mathematicise science and lay the foundations of algebra. He looks at the modern mathematics behind flight, and behind the record-breaking fastest car in the world, tracing the route back from these achievements to the legacy of the Persian mathematician Al Khwarizmi. We also discover the role that the Islamic world played in giving us the modern numeral system that we take for granted in everyday life. And, in the Sulemaniye Library in Istanbul, Jim uncovers a rare text by Al Kindi – perhaps the world’s earliest mathematical code breaker.