Computing the “Holy Wisdom” Oliver Hauck, Andreas Noback, Lars Grobe The church of Hagia Sophia – from the Greek: Ἁγία Σοφία, "Holy Wisdom" – built on the orders of Emperor Justinianis from 532 to 537 (AD) is the most im- portant building of an era which is generally characterised as the decline of the ancient world and the beginning of the mediaeval times. The building is well con- sidered to be one of the most outstanding masterpieces of architecture in the world having an extensive influence on European and islamic architecture in general . 1 A wide vaulted dome and the adjacent semidomes span the large open space of the main nave. Every hidden part of the space can be grasped by the eye by simply moving a few steps; nothing seems to be obscured by the architecture but the weight of the vaults. The actual cubic capacity is hidden by the flat relief of the precious decoration of the surfaces. The entire space seems to be enclosed only by a thin shell and the dome soaring over it . 2 This effect of lightness seems to be the main issue of the architectural concept, because it is supported by a careful light design. This outstanding quality already impressed the contemporary historian Procopius of Caesarea: “[…] it abounds exceedingly in sunlight and in the reflection of the sun's rays from the marble. Indeed one might say that its interior is not illuminated from without by the sun, but that the radiance comes into being within it, such an abundance of light bathes this shrine” 3 The meaning of these words is difficult to follow with the building we see to- day in mind: many windows have been closed due to structural problems and massive supports were added to prevent further collapses after several severe earthquakes that also resulted in vaste damages to the tesselation. So today there is distinctly less illumination coming through the windows and the yellow paint have another effect on indirect illumination than the tesselation had before. At the dome the effect can still be retraced: the 40 windows at the foot of the dome create a crown of light that nearly counterbalances the weight of the vault by covering the depth of the embrasures with the gloss of light in the golden mosaics. Further reading: Van Nice, Survey; Kähler, Sophia; Mainstone, Sophia; 1 Mark - Çakmak, Sophia; Kleinbauer - White - Matthews, Sophia; Stichel, Ein- blicke. Cf. Zaloziecky, Sophienkirche. 2 Procopius, aedificia I 1,30; English citation: Buildings, by H. B. Dewing, 3 as printed in Vol. VII of the Loeb Classical Library edition of Procopius, published in 1940 Cambridge