Scientific activity in medieval Europe was maintained by the activity of a number of significant scholars, active in a wide range of scientific disciplines and working in Greek, Latin, and Arabic-speaking cultures. This list provides a brief summary of their work. Early Middle Ages Anatolius of Laodicea (early 3rd century – 283), a bishop of Laodicea, one of the foremost scholars of his day in the physical sciences. Nemesius (?-c. 390), a bishop of Emesa whose De Natura Hominis blended theology with Galenic medicine and is notable for his ideas concerning the brain. He also may have anticipated the discovery of the circulatory system. Isidore of Miletus (ca. 442 – ca. 537) was a renowned Byzantine scientist and mathematician. He was one of the two main Byzantine Greek architects (Anthemius of Tralles was the other) that Emperor Justinian I commissioned to design the cathedral Hagia Sophia in Constantinople from 532 to 537. He taught stereometry and physics at the universities, first of Alexandria then of Constantinople, and wrote a commentary on an older treatise on vaulting. Isidore is also renowned for producing the first comprehensive compilation of Archimedes' work, the Archimedes palimpsest. Anthemius of Tralles (ca. 474 – ca. 534), a Byzantine professor of geometry and architecture, authored many influential works on mathematics and was one of the architects of the famed Hagia Sophia, the largest building in the world at its time. His works were among the most important source texts in the Arab world and Western Europe for centuries after. John Philoponus (ca. 490–ca. 570), also known as John the Grammarian, a Christian Byzantine philosopher, launched a revolution in the understanding of physics by critiquing and correcting the earlier works of Aristotle. In the process he proposed important concepts such as a rudimentary notion of inertia and the invariant acceleration of falling objects. Although his works were repressed at various times in the Byzantine Empire, because of religious controversy, they would nevertheless become important to the understanding of physics throughout Europe and the Arab world. Paul of Aegina (ca. 625–ca. 690), considered by some to be the greatest Christian Byzantine surgeon, developed many novel surgical techniques and authored the medical encyclopedia Medical Compendium in Seven Books. The book on surgery in particular was the definitive treatise in Europe and the Islamic world for hundreds of years. The Venerable Bede (ca. 672–735), a Christian monk of the monasteries of