More Than Just a Trick of the Light
Even children know a rainbow is created by the interaction between sunlight and raindrops. Today, we know a lot about the phenomenon, but previously, it was the subject of myths, tales, and superstition, and scholars have obsessed over rainbows for thousa
In Nordic mythology, Bifröst is a burning rainbow bridge that reaches between Midgard (Earth) and Asgard (the realm of the gods). The bridge is guarded by the god Heimdall. Indigenous Australian cultures see the rainbow as a creative force, and the Abrahamic religion, a covenant.
With the advent of the Greek philosophers, people started to prefer scientific methods over the world of myths.
Aristotle (384-322 BC) imagined that the rainbow was an incomplete reflection of the Sun in an irregular “mirror” on the surface of a cloud – made up of myriads of droplets and located in a hemisphere known as the “meteorological hemisphere”. According to Aristotle, the Sun was also located in this hemisphere. The light was reflected by the hemisphere to produce the rainbow. This explanation comes quite close to the correct one, only people did not understand the raindrops' function, and they thought that we get visual impressions via light beams radiating from the eye – hence the expression “cast a glance at something.”
Aristotle’s explanation was not questioned until the early 1300s, when Dominican scholar Theodoric (approximately 1250-1310) realized the relation between a rainbow and the shape of raindrops by experimenting with ballshaped bottles filled with water. He discovered that a rainbow was the result of light refracted and reflected in the interior of raindrops, hitting the eye at a specific angle.
However, his discovery was forgotten, and not until René Descartes (1596-1650) of France, who undoubtedly knew Theodoric’s work, made the same experiments did we get an explanation of the rainbow in 1637. The explanation was so good that it largely holds water today. It was the culmination of a thousand years of trying to understand and explain the phenomenon. Nevertheless, some nature philosophers still preferred Aristotle's model as late as in the second half of the 17th century.