Al-Ma'mun (The Scholar Caliph)

Abu al-Abbas Abdallah al-Ma'mun was the seventh Abbasid Caliph, reigning from 813 to 833 CE, revered as the greatest scholar-caliph in Islamic history. The son of Harun al-Rashid and a Persian mother, Al-Ma'mun prevailed over his brother Al-Amin in the Fourth Fitna civil war, ruling over an empire at the absolute pinnacle of intellectual and scientific brilliance.

Passionate about philosophy, mathematics, and astronomy, Al-Ma'mun vastly expanded the House of Wisdom (Bayt al-Hikma) in Baghdad. He sent diplomatic expeditions to Constantinople to purchase Greek manuscripts, commissioning Hunayn ibn Ishaq to translate Aristotle, Plato, Euclid, and Galen into Arabic. He patronized mathematician Al-Khwarizmi, who developed algebra and algorithms under his sponsorship. An astronomer in his own right, Al-Ma'mun constructed observatories in Baghdad and Damascus, and dispatched surveyors to the desert plains of Sinjar to measure a degree of the Earth's meridian, calculating the circumference of the Earth with astounding accuracy (within 2% of the modern value). He championed rationalist Mu'tazilite theology, establishing an era of scientific preeminence that illuminated the medieval world.