During the period of time known as the Dark Ages (5th to 15th centuries), much scientific progress occurred in the Muslim world. The scientific research of the Islamic scientists is often overlooked due to the conflict of the Crusades and “it’s possible, too, that many scholars in the Renaissance later downplayed or even disguised their connection to the Middle East for both political and religious reasons.” The Islamic Abbasid caliphs gathered many classic works of antiquity and had them translated into Arabic within the House of Wisdom in Baghdad, Iraq. Islamic philosophers such as Al-Kindi (Alkindus), Al-Farabi (Alpharabius), and Averroes (Ibn Rushd) reinterpreted Greek thought in the context of their religion. Ibn Sina (980 – 1037), known by the Latin name Avicenna, was a medical researcher from Bukhara, Uzbekistan responsible for important contributions to the disciplines of physics, optics, philosophy and medicine. He is most famous for writing The Canon of Medicine, a text used to teach student doctors in Europe until the 1600s.
The Abbasid Caliphate at its height, in 830 CE
Important contributions were made by Ibn al-Haytham (965 – 1040), a mathematician from Basra, Iraq considered one of the founders of modern optics. Ptolemy and Aristotle theorised that light either shone from the eye to illuminate objects or that light emanated from objects themselves, whereas al-Haytham (known by the Latin name Alhazen) suggested that light travels to the eye in rays from different points on an object. The works of Ibn al-Haytham and Abū Rayhān Bīrūnī eventually passed on to Western Europe where they were studied by scholars such as Roger Bacon and Witelo. Omar Khayyám (1048–1131), a Persian scientist, calculated the length of a solar year to 10 decimal places and was only out by a fraction of a second when compared to our modern day calculations. He used this to compose a calendar considered more accurate than the Gregorian calendar that came along 500 years later. He is classified as one of the world’s first great science communicators – he is said to have convinced a Sufi theologist that the world turns on an axis. Muḥammad ibn Jābir al-Ḥarrānī al-Battānī (858 – 929), from Harran, Turkey, further developed trigonometry (first conceptualised in Ancient Greece) as an independent branch of mathematics, developing relationships such as tanθ = sinθ / cosθ. His driving force was to obtain the ability to locate Mecca from any given geographical point – aiding in Muslim rituals such as burial and prayer, which require participants to face the holy city, as well as making the pilgrimage to Mecca (known as the hajj).
A page from al-Khwārizmī’s Algebra
Furthermore, Nasir al-Din al-Tusi (1201–1274), an astronomer and mathematician from Baghdad, authored the Treasury of Astronomy, a remarkably accurate table of planetary movements that reformed the existing planetary model of Roman astronomer Ptolemy by describing a uniform circular motion of all planets in their orbits. This work led to the later discovery, by one of his students, that planets actually have an elliptical orbit. Copernicus later drew heavily on the work of al-Din al-Tusi and his students, but without acknowledgment. The gradual chipping away of the Ptolemaic system paved the way for the revolutionary idea that the Earth actually orbited the Sun (heliocentrism). Jābir ibn Hayyān (721 – 815) was a chemist and alchemist from Iran who, in his quest to make gold from other metals, discovered strong acids such as sulphuric, hydrochloric and nitric acids. He was the also first person to identify the only substance that can dissolve gold – aqua regis (royal water) – a volatile mix of hydrochloric and nitric acid. It is disputed whether Jabir was the first to use or describe distillation, but he was definitely the first to perform it in the lab using an alembic (from ‘al-inbiq’). The most famous Arabic mathematician is considered to be Muḥammad ibn Mūsā al-Khwārizmī (780 – 850), who produced a comprehensive guide to the numbering system developed from the Brahmi system in India, using only 10 digits (0-9, the so-called “Arabic numerals”). Al-Khwarizmi also used the word algebra (‘al-jabr’) to describe the mathematical operations he introduced, such as balancing equations, which helped in several problems.