Ammianus Marcellinus and three-dimensional rainbows

We examine Ammianus Marcellinus' scientific digression on the rainbow, where the rainbow colors are listed in an unusual order. We suggest an explanation for the order and conclude that, according to a scientific theory current at the time, the rainbow was viewed as a three-dimensional arrangement in the sky, with colored bands positioned at different distances from the observer. This perspective aligns with the rejection of the Aristotelean rainbow theory, which is an evolution of ideas observable in its intermediate stages in Seneca’s “Natural Questions” and in the commentary on Aristotle’s “Meteorology” written by Alexander of Aphrodisias.