Reflect and refract
When was the last time you looked out the window and said, “Oh look! There’s a many-coloured refraction of light from drops of water!”? Well – OK, if you said that last week then feel free to skip the next paragraph, but most of us refer to the sudden splash of colours in the sky as a rainbow, an eye-catching natural phenomenon which has been rich in cultural significance throughout human history.
The science behind rainbows is reasonably straightforward: when sunlight hits a raindrop, it slows down and is refracted, or made to change direction. The raindrop acts as a tiny prism, splitting the white light into all its individual hues. Some of this light is reflected back and further refracted on entering the air again, dispersing outwards to create the spectrum of shades whose names we probably all remember from the school playground.
“No! Richard of York Gave Battle In Vain,” I remember my six-year-old friend Maria explaining at school in order to settle a long-standing argument between us over which colour came first in the sequence, blue or green. (Americans may be more familiar with a shady character called Roy G Biv.) It’s worth bearing in mind that dividing the visible part of the spectrum into seven shades is not so much an objective truth as an idea of Isaac Newton’s, who felt that the number was significant; other cultures are known to label the spectrum differently.
Somewhere over the moonbow
There is, appropriately, diversity among rainbows, and the language used to designate them: there are double rainbows, supernumerary rainbows (additional bands of pastel pinks and greens), and the “haunting beauty” of lunar rainbows (or moonbows). Another branch of the rainbow family is less well-known: the haloes, triggered by light refracting through ice crystals (rather than water) to produce a host of wonderfully-named light shows such as the circumzenithal arc (which looks like an upside-down rainbow), the parhelion (or sun dog), and the corona.
Our English word rainbow is of Germanic origin (and very similar to its German cognate Regenbogen), with bow meaning, essentially, “a bent line”. Our Mediterranean neighbours see it quite differently: while for the French it is a straightforward arc-en-ciel or “arc in the sky”, the Italians call it an arcobaleno (or “lightning bow”) and the Spanish, an arco iris (or “Iris arc”, named after the Greek goddess who is a messenger between the gods and humanity). In Chinese it’s a 彩虹 (cǎihóng) and in Russian, a радуга (or “RAH-doo-gah”. The etymology of the word is uncertain, but it may be related to радостный, which translates as glad or joyous.)
The lovers, the dreamers, and me
In the Judeo-Christian world the rainbow has traditionally been regarded as a communication from the divine, first appearing in the sky above Noah and his floating ark as a promise from God that he would never send another flood to destroy humanity. The cultural legacy of this story is the western tendency to view rainbows as a kind of silver lining to every storm: or as Dolly Parton memorably said, “The way I see it, if you want the rainbow you gotta put up with the rain.”
A search through the Oxford English Corpus reveals that in current usage the word rainbow is often found in close proximity to words like star, cloud, unicorn, sunshine, and butterfly, in order to paint a picture of – often tongue-in-cheek – escapist sentimentality. We associate rainbows with romance, and also with the innocence of children (think of the British children’s TV programme of that name, or the children’s organization, the Rainbows.)
At the end of the rainbow
In many traditional cultures, the rainbow is a dangerous and destructive spirit to be avoided. Pre-Christian Northern European folklore, however, focuses on what can be found at the elusive rainbow’s end. Norse mythology regards the rainbow as a bridge leading to Asgard, the land of the gods, while Irish legends claim a pot of gold can be found at the end of the rainbow, guarded by a leprechaun. This may partly explain the enduring affection for Over the Rainbow, first popularized by Judy Garland in 1939, and more recently voted the defining “song of the twentieth century” in America.
This idea of the elusive, evasive rainbow, always tantalizingly one step ahead of us but never within reach, is an interesting one: the Oxford English Dictionary dates the concept of chasing rainbows, meaning to pursue a “useless quest”, as far back as 1450. Science has always maintained that finding the end of a rainbow is impossible because it’s an optical illusion which requires a certain amount of distance from the viewer to be seen. However, the relatively recent rise of the camera phone now allows us to snap photos of rainbows apparently touching down in rather mundane places like the middle of a dual carriageway. These images perhaps lend credence to people’s claims to have driven right through a rainbow, often describing it as a semi-mystical experience. Such stories may express a subconscious wish on the part of many to look for the transcendent in everyday life, and seem to echo Keats’ lament in the early nineteenth century that Isaac Newton had “destroyed the poetry of the rainbow by reducing it to a prism”, which he elaborated on in his 1819 poem Lamia:
Philosophy will clip an Angel’s wings,
Conquer all mysteries by rule and line,
Empty the haunted air, and gnomed mine –
Unweave a rainbow…
This last phrase was picked up by Richard Dawkins in his 1998 book, Unweaving the Rainbow, in which he makes the opposite argument: that an understanding of scientific principles can only increase our appreciation of the wonders of the universe, rather than diminish it.
All the colours of the rainbow
The word rainbow has long been used as a modifier to signify a wide range of related and typically colourful things, and as human civilization has progressed, the rainbow has come to be associated with a similar theme: that of diversity, inclusion, and acceptance. In fact, the most common collocates of rainbow in the Oxford English Corpus (leaving animal names such as trout, runner, and lorikeet aside) are flag, coalition, and nation. The rainbow flag has a long history of being used by many ethnic groups, political parties, and religious movements over the centuries, but since the late 1970s has been most often associated with the LGBT movement, where it stands for diversity and gay pride. A rainbow coalition can refer to either the established American movement for social change, or any political alliance of several different groups, while rainbow nation is a term attributed to Archbishop Desmond Tutu to describe South Africa’s racial and ethnic diversity.
As I’m finishing this article, news comes in that Tate Britain have just acquired “one of the quintessential images of nineteenth century British art”, John Constable’s Salisbury Cathedral from the Meadows. The painting features the cathedral after a storm and is dominated by a striking rainbow, which the artist himself explained as representing “the exhilaration of the returning sun”. Nearly two centuries later, the rainbow still stands as a symbol of hope and the promise of a better, more enlightened future for us all.