how to see a rainbow

Surely one of the best things about living in a rainy landscape, like the west of Scotland, is the frequency of its rainbows?

Blown in from the Atlantic, the westerly fronts move quickly here: it’s a place of characteristic sun and showers, where one always has to make the most of the time between weathers.

If you like walking in Scotland, you are going to a see an awful lot of rain, but that also means you’ll get to see a lot of rainbows!

Tom and I love rainbow spotting. On one memorable occasion, we were driving north along Loch Lomond on a day of swirling, heavy mist, through which a low sun was breaking through on the horizon. Illuminated above the loch, a huge, curious and utterly beautiful rainbow accompanied our journey for about twenty miles. We sat in silence as the landscape came alive with colour.

What a joy it is, when desultorily pottering around the house on grey day, to look out of the back window and to suddenly see this.

. . . or to be able to stop, stand and watch the movement of light and colour across a steel-hued sea on a cold winter walk.

I find it impossible not to stop, pause, and take a moment to wonder at the colourful beauty of a rainbow every single time I see one, and it is really no surprise to find that they have played an important role in many cultures. So here’s my completely subjective 10-point exploration of how to see a rainbow, and how rainbows have been seen (please do add in your own rainbow-related experiences and associations in the comments section, at the end).

1. Optical practicalities

Rainbows are quite complex optical phenomena, whose appearance depends on the confluence of many factors. Rain (or mist) must be heading in towards you, and the sun (or very rarely, the moon) must be shining quite brightly behind you, at a point on the horizon at an angle of less than 42 degrees.

Each droplet in a rainbow acts as a mini prism, refracting and reflecting light into the eye of its beholder. Light enters the upper part of a raindrop and is reflected downwards towards the eye, dividing itself into the spectrum’s different coloured wavelengths. Red light is bent the least and violet the most, with the other shades falling into line to form concentric bands.

Rainbows only occur when the sun is fairly low in the sky. If you are lucky enough to spot a rainbow in the evening, you’ll be able to observe it rising in the sky in adverse proportion to the sinking, setting sun.

Sometimes it’s possible to see a secondary rainbow (always situated eight degrees in the sky above the first). The colours of the secondary bow reverse those of the primary, with the red band sat at the bottom and violet at the top. This is because, in the secondary bow, light initially enters the lower part of the raindrop before undergoing two refractions and two reflections. The intensity of light is reduced by this repeated reflection process and so the secondary bow always appears more indistinct.

When you are lucky enough to spot a classic, semi-circular, rainbow, you’ll notice that the arc of sky beneath it appears to be a little lighter. This is because rays refracted through the raindrops at angles of less than 42 degrees tend to mix together and form white light rather than the bow’s distinctly coloured spectrum.

2. Persian rainbows

We only now know how and why our eyes see rainbows because scientists have puzzled over such matters for centuries.

Everyone has heard of Isaac Newton, but fewer (in the west) are perhaps aware of the two great Persian optical innovators, whose work preceded (and certainly influenced) that of Newton: Ḥasan Ibn al-Haytham (often Latinised / Anglicised as Alhazen) and Kamāl al-Dīn al-Fārisī. Alhazen’s Kitāb al-Manāẓir (Book of Optics (1011-1021) described the physiology of the eye, and proposed a theory of the way light bends and refracts through luminous bodies that was extremely influential in the Arab world and later, across Europe, after translation into Latin.

Influenced by Ibn al-Haytham’s work, Kamāl al-Dīn al-Fārisī’ conducted rainbow-related optical experiments with a camera obscura and a glass sphere acting as a scaled-up model of a raindrop. His Kitab Tanqih al-Manazir (Revision of the Optics (1309)) proposed dividing the spectrum into a group of 5 primary and 23 secondary colours, and provided the first mathematically correct explanation of a rainbow’s doubled process of refraction and reflection.

3. The rainbow covenant

In the biblical book of Genesis, Noah, his family, and the animals are waiting out the terror of the earth-destroying deluge in their ark. A rainbow appears in the sky, and God says to Noah: “I do set my bow in the cloud and it shall be for a token of a covenant between me and the earth. And it shall come to pass, when I bring a cloud over the earth, that the bow shall be seen in the cloud and I will remember my covenant, which is between me and you and every living creature.”

In this biblical story, then, a rainbow is the sign of the coming calm after the storm, of an era of tranquility following a time of great hardship. God’s rainbow covenant with Noah – the promise of an end to all suffering – is surely one of the rainbow’s most potent and enduring meanings across time. In many different contexts, for many different cultures, rainbows have come to symbolise peace, tranquility and protection.

4. Rainbow protectors

In the Navajo Nation’s great seal, the rising sun, shining low in the sky on the eastern horizon, illuminates an encircling westward rainbow which surrounds and protects land, crops, animals and people.

Rainbows fulfil a similar encircling and protective function in the healing rituals of Navajo sandpainting, as well as the woven fabrics and other artefacts such rituals inspire. In this beautiful design, a colourful rainbow yéii extends itself from the east to surround the northern, southern and western edges of the cloth, protecting everything within its compass. Just as a rainbow connected Noah to his creator in the biblical story, so Navajo tradition suggests the rainbow as a link between the human and the spiritual, between earth and heaven.

5. Iris

Happily zipping back and forth between the realms of the human and the heavenly is Iris – Greek messenger of the gods. Sometimes depicted as a traveller along a rainbow road, sometimes clad in a glorious cloak of rainbow-hues, or sometimes a sort of embodied rainbow in herself, Iris can be a malign trickster or a kindly interceder (depending on her mythological story). Iris is the word for rainbow in Spanish, Russian and other languages.

6. Colour herself

In 1778, Angelica Kauffman was commissioned to produce a series of ceiling paintings for the Royal Academy of Arts in its then home of Somerset House. Kauffman, who had been born in Switzerland in 1741, was one of just 2 women artists to be included among the 36 founding members of the Royal Academy (the other being Mary Moser). Kauffman’s commission was to depict the four elements of art: Invention, Composition, Design and Colour. In Neoclassical theories of painting, colour was generally regarded as inferior to the other elements because it was associated with the material craft of mixing and applying pigments, rather than with elevated intellectual ideas. Colour, it was argued, was about making a mess, not aesthetic genius. But Kauffman made Colour the most striking and creative of her four roundels, and this image became the most frequently reproduced of her ceiling paintings, in the contemporary mezzotint prints which were then the popular medium of her fame. A dynamic female figure, swathed in vital red and gold, sweeps the arc of a rainbow across the sky with the brush she holds in her right hand. The rainbow is creative colour itself, and the female figure is both art and artist. After Kauffman, it was to be a century and a half before another woman was admitted to the Royal Academy (Dame Laura Knight, in 1936).

7. Rainbow Power

If a rainbow is a sign from heaven, connecting the realms of the human and the divine, then such connections are epitomised in this famous portrait of Queen Elizabeth I of England: an image that’s both utterly extraordinary and genuinely weird (in the way only Tudor portraiture can be). Elizabeth, who was almost 70 years of age when this painting was commissioned, is depicted as an arrestingly beautiful young woman with bare décolletage, direct, challenging gaze, and perfect, whiter-than-white complexion. The inner lining of her mantle is embroidered with life-like eyes and ears, suggesting, (in a manner not entirely unambiguously positive), the inviolable queen as the embodiment of an all-seeing, all-hearing, all-knowing nation state. In her right hand she holds out a rainbow, behind which she stands, and above which is emblazoned the motto “non sine sole iris” – without the sun, there is no rainbow.

Elizabeth, then, is a figure whose power is equivalent to that of the sun, and perhaps, too, to the omnipotent God who set his bow upon the cloud after the deluge: she’s divinity here on earth. When I look at this image, I see an extraordinary spectacle, or performance, of monarchical power, with the rainbow as an obvious accoutrement of that power, but there’s also a lot to question. If this queen is the sun, why on earth does her rainbow appear as a colourless, transparent tube, rather than as an arc of coloured light? (The argument that pigments have faded only in this area of the painting is somewhat unconvincing). Is Elizabeth, who holds the rainbow, an embodiment of godly peace and prosperity or a potential harbinger of conflict? (If an archer’s bow might be set peaceably upon a cloud, then it could also be used as a weapon, whose bellicose associations are perhaps reinforced by the tiny be-jewelled gauntlet that’s pinned to the queen’s lace). As emblematically rich an image as it is an ambiguous one, scholars from many disciplines and different schools of thought have argued about the rainbow portrait and its curious symbols for decades. What do you think the rainbow means?

8. It was a hard thing to undo this knot

There are many poems about rainbows. Here is my all-time personal favourite, by Gerard Manley Hopkins, composed some time between 1884 and 1889.

It was a hard thing to undo this knot.
The rainbow shines, but only in the thought
Of him that looks. Yet not in that alone,
For who makes rainbows by invention?
And many standing round a waterfall
See one bow each, yet not the same to all,
But each a hand’s breadth further than the next.
The sun on falling waters writes the text
Which yet is in the eye or in the thought.
It was a hard thing to undo this knot.

Strictly speaking, a rainbow has no objective reality at all- it is merely a transient optical phenomenon that exists in the eye (and brain) of a single beholder. Two people, standing adjacent to one another beside a waterfall will see two different rainbows, cast by the sun’s rays through two different sets of water droplets, an experience that is never self-identical and which never points to a thing which two rainbow-observing people might agree upon as having any sort of actual, material existence. Hopkins poses the rainbow’s knotty conundrum, unravels it, and then ties it back up again in ten deft lines that are as fleeting and ephemeral as the phenomenon they describe.

9. Everyday wonder

Isn’t the very best thing about a rainbow the wonder it inspires? Given the right weather conditions and the time of day, a rainbow can appear quite literally anywhere, and immediately transform the most mundane of surroundings into glorious, marvellous spaces. Such a combination of the mundane and the marvellous is brilliantly captured in this woodcut print by Hiroshige. This humble area, on Edo’s southern fringes, was known as Kurumacho or Ushico – Ox Town or Cart Town – and we know we are in the right place because of the gigantic wheel and axel whose lines cut across the rainbow arching elegantly above the boats, the water, the reddening horizon. A pair of wee dogs play together on the dockside, worrying the remains of a straw sandal, while two discarded watermelon rinds litter the ground, providing a punning visual echo of the rainbow’s concentric form and structure. It’s a beautiful, completely ordinary moment, on a late summer’s evening, at the shabby edges of the city. Here’s the transience of all earthly things, and their beauty too.

10. A rainbow means inclusion

For centuries, then, rainbows have captured the human imagination as emblems of peace, hope, and togetherness and in no contemporary context does this resonate more strongly than that of gender equality and inclusion. For the LGBTQ+ community, rainbows are powerful, global symbols of shared identity, mutual recognition – and proud defiance too. Next week, the football (soccer) world cup will begin in a place where the legitimacy of the rainbow flag has been questioned, and the sale of rainbow-coloured toys to children has been prohibited. In the face of continuing prejudice, suffering and inequality, it’s more important now than ever to embrace the colourful wonder of the rainbow, and celebrate its ultimately optimistic message of joy, peace and solidarity.

With thanks to Tom for many years of rainbow photography.

Do you have a favourite rainbow memory? Are rainbows associated with particular myths, mottos or superstitions where you come from? Please share your own rainbow-related experiences in the comments!