Genesis 9.8-17: Refraction and Dispersion

God's bow in the sky is practically inseparable from the story of Noah (Genesis 9:8-17, Lent 1B). On the walls of church nurseries it isn't unusual to find a child-friendly boat, charming animals, a benevolent Noah...and that rainbow. But what is decorative and colorful and familiar is also science. And that means theory and

discovery and history.

Dome of the Portinari Chapel. Basilica of Sant'Eustorgio. Milan, Italy. 1460-1468. 

The Dominican order began the rebuilding of the Basilica of Sant'Eustorgio in Milan, Italy, in the 13th century, and it served as the seat of the order in Milan. Between 1460 and 1468 the Portinari Chapel was added to the Basilica. Commissioned by banker Pigello Portinari, the chapel was designed by an unknown architect, though the style has some similarities to Brunelleschi's Pazzi Chapel.

One of the aspects of Portinari Chapel that differs wildly from Brunelleschi's earlier chapel is in the decoration of the dome. Both domes show the pattern of ribs dividing the dome and reaching up to an oculus in the center of the dome. But where the ribs of the earlier dome separate sections of undecorated plaster, the Portinari dome is filled with a rainbow-colored scale pattern: red on the outside, then yellow, then green, with blue next to the oculus. These are the four colors of the rainbow identified centuries earlier by Aristotle.

The presence of the rainbow in the dome is one of several indications that the Dominican order was interested in scientific exploration of the rainbow. Around 1310, Theodoric of Freiburg wrote De iride, a treatise on the rainbow, which is still considered correct in its explanation of how light passes through individual drops of water, refracting and dispersing, to create primary and secondary rainbows. Theodoric was a philosopher and scientist who was also a member of the Dominican order.

Though no Noah is present in the dome, the presence of the rainbow in a dome still carries the same idea as the Genesis account. A dome, after all, is nothing but an arc (like the shape of the rainbow) spun in a circle. Because the dome represents heaven, then God's bow is still displayed in the heavens, symbolizing the covenant God made and has kept with humanity since the days of Noah.

For thoughts on the gospel reading for Lent 1B (Mark 1:9-15), click here.

See a place where the rainbow connects to a moment in the life of Jesus on this week's Art&Faith Matters Facebook page.