Isidore of Miletus

Isidore of Miletus (born about 475) was a Greek mathematician and architect who taught stereometry, the geometry of solid figures, and physics at Alexandria and Constantinople. With Anthemius of Tralles he designed Hagia Sophia in Constantinople for the emperor Justinian I, built from 532 to 537. He wrote a commentary on Hero of Alexandria's treatise on vaulting and is thought to have been responsible for the design of the dome.

The church's main hall measures about 70 by 75 meters. Its dome sits on four pendentives, curved triangles of masonry that carry a round dome over a square plan. Building materials were brought from Egypt, Syria, Libya and Rome. Earthquakes in 553 and 557 weakened the dome, and it collapsed in 558. Isidore's nephew, Isidore the Younger, rebuilt it about 6 meters higher and with ribs, finishing by 562. After part of that dome fell in an earthquake of 989, the Armenian architect Trdat repaired it.

In mathematics Isidore compiled and checked the works of Archimedes, working with the mathematician Eutocius. He is credited with a compass for drawing parabolas. Part of the so-called Book XV of Euclid's Elements, which Euclid did not write, is attributed to him.