We all know what lies at the end of a rainbow — that proverbial pot of gold, that something much sought after but impossible to attain. But how do rainbows come about, and what lies at their origins?
Essentially, a rainbow is born out of light, water and geometrical relation. When the sunlight hits water droplets suspended in the air, they act as a kind of curved mirror, refracting the light back out again from different angles. The phenomenon demonstrates beautifully the way light is composed of a spectrum of wavelengths, each of which appears to us in different colour — the red, orange, yellow, green, blue, indigo and violet stripes of the rainbow. The angle in which the sunlight enters and refracts from the droplet is the key to this vibrant display: red light is refracted at a steeper angle towards the ground (and our eye), while blue light is directed less vertiginously and thus appears lower in the rainbow arch. The same phenomenon can also emerge in bright moonlight, for example in the splashing of water at the base of a waterfall.
This elusive and visually striking spectacle has enticed thinkers, scientists, artists and believers since the dawn of time. In Europe, Aristotle was the first to try to produce a qualitative explanation for the phenomenon in the 300s BC, and for centuries to come, many subsequent theories were created in reaction to his. An 11th century Chinese polymath and statesman Shen Kuo hypothesised, very much in accordance with the modern scientific principles, that rainbows are formed through refraction of sunlight in water-drops in the air. In the 13th century Persia, astronomer Qutb al-Din al-Shirazi gave a fairly accurate explanation of the phenomenon, which his student Kamāl al-Dīn al-Fārisī elaborated with further mathematical accuracy.
But long before the empirical explanations became widespread, rainbows played an important role in various mythologies and belief systems around the world. The most common symbolic meaning of the rainbow is that of a bridge or pathway linking heaven and earth. In Greek mythology, the gods’ messenger Iris is a personification of a rainbow, acting as an intermediary between the deities and the mere mortals. Old Norse cultures considered the rainbow as a bridge to the heavens, to be used only by gods and those killed in battle. According to ancient Japanese beliefs, rainbow is a bridge along which the human ancestors Izanagi and Izanami descended to the planet, in order to create the earth from oceans and chaos. In Navajo traditions, rainbow recurs in sacred sand paintings as the path of the holy spirits.
In addition to facilitating spiritual traffic in myths, rainbows have given birth to a range of legends and superstitions. The familiar pot of gold, for example, comes from Irish folklore, where the Leprechauns — mischievous fairy cobblers — are said to hide their gold at the end of the rainbow and ferociously guard it. An ancient Chinese belief claims seeing a full rainbow can make you rich, but you shouldn’t point at it with your index finger — if you do, the rainbow will suck out all your bone marrow and you’ll end up crooked. (Sinister!)
The rainbow, emerging in a clear sky after the rain, might also be seen as a beacon of hope, and today the symbolic meanings attached to it are more in that line of thought. The rainbow stands for diversity and harmony featuring, perhaps most famously, in the LGBT pride flag. The flag’s first modern form was designed by San Francisco-based artists Gilbert Baker and Lynn Segerblom in 1978, and a slightly different version of a rainbow flag was used by peace protesters in the 1960s particularly in Italy, with the word ‘pace’ written on it.
Philosophically speaking, the rainbow symbolises the complex relationship between the real and the illusory. Being based on an optical illusion (and therefore shifting its location along with the spectator), the rainbow does not actually exist as a physical object. The meteorological phenomenon, nevertheless, is very real. In the eighteenth century, the Enlightenment sought to put an end to all the superstitions and myths relating to the rainbow by producing, once and for all, a detailed scientific explanation for it. In 1704, Newton published his discovery that white light consists of a mixture of colours in his opus titled Opticks, and the rainbow as a phenomenon became fully ‘dissected’.
But stories and beliefs tend to be resilient. By the end of the eighteenth century, Enlightenment’s beloved Rationalism was challenged by Romanticism — a cultural and intellectual movement that objected to the way Rationalism dismissed the role of history, tradition, myth and faith in holding a society together and was effectively pulling the carpet from under moral principles. In the early nineteenth century, Romantic art propelled a huge resurgence of legends, the supernatural, and celebration of mystery in life. “Do not all charms fly / at the mere touch of cold philosophy?” asked John Keats in his 1820 poem ‘Lamia’.
There was an awful rainbow once in heaven (he writes)
We know her woof, her texture; she is given
In the dull catalogue of common things.
Philosophy will clip an Angel’s wings,
Conquer all mysteries by rule and line,
Empty the haunted air, and gnomèd mine—
Unweave a rainbow.
Beautifully as Keats it puts it, the scientific dissection of natural phenomena does not need to be at odds with imagination. In fact, the ability to imagine, to dream, to look beyond the ordinary and to open your mind to the unknown and the ‘inexplicable’ all play an essential role in scientific discovery. Without the faculty of imagination, one would be forever stuck with what one already knows.
Such is the nature of the rainbow that it can capture the essence of entire philosophical, social and artistic debates: it is at once real and imaginary, an immutable fact and a trick of the eye. Still, what are mirages there for, if not to make us wonder?