True darkness, it turns out, can be experienced but does not exist. If you have been down a deep mine where the guide tells you to turn off your lamp you will have seen – in not seeing – something close to it: an utter nothingness in which your body and mind seem to shrink and expand at the same time. On a school trip to Big Pit in South Wales my entire class fell into a moment of unprecedented and never-to-be-repeated silence, a gasped amazement at the disappearance and invisibility of ourselves. Just for a moment everything vanished – and then the whooping and squealing started. 

This double impulse, of delight and terror, runs through Into the Dark, Jacqueline Yallop’s exploration of what she describes as ‘an anomaly… a non-existent state which most of us would claim to experience as a real thing’. Down that mine we were surrounded by light we could not see. According to quantum physics, Yallop explains, there is no true darkness. Photons exist throughout the known universe and beyond it. Nasa’s New Horizons spacecraft is now four billion miles from Earth and still picking up a glow from the darkest quadrants of space – either from undiscovered galaxies or another unknown origin.

Irish Gaelic has four different terms for the transition of afternoon to nightfall

Isaac Newton identified darkness as an absence of light; before him it was believed to be a force or entity, light’s opposite, a thing. And the thingness of darkness clings on. Our language for it evolved from the physical blackness of dark. ‘Pitch-dark’ comes from the tar used to waterproof wooden ships; pitch ‘reminds us that dark is viscous, tangible, impenetrable’, Yallop writes, while ‘dark’ itself seems to descend from Old High German tarchanjan, meaning danger, mystery, concealing.

The Greek skotos captures the way we often understand darkness, meaning both night’s blackness and misery’s gloom. Yallop travels through literary engagements with darkness – Dylan Thomas’s crowblack sea is here, along with Conrad’s Congo – and she excels in its visual story. A page painted black by Robert Fludd in his 1617 history of the divine and human worlds, representing his conception of the beginnings of creation and the infinities beyond it, links with Kazimir Malevich’s 1915 ‘Black Square on a White Ground’ and Pierre Soulages’s outrenoir – ‘beyond black’ – galleries of black canvases.

Soulages’s work, Yallop says, ‘gouges, folds and sculpts the dark, which is charged, relentless’. As a viewer, you are ‘thrown in on yourself, back on yourself’. Soulages claimed that his pictures were poetic objects capable of receiving ‘what each person is ready to invest’, and it is these qualities of darkness, its powers to fill or drain us, to enfold or engulf or balm us, which inspires Yallop’s quest.

Her father is falling into dementia when the book opens, and in an overlit care home at the close. Searching for different ways to approach the void that is overcoming him leads Yallop to range beyond European ideas of darkness, founded in perceptions of the non-light and non-white as justifications for imperial, sexualising and enslaving instincts, towards much more various and valuable conceptions of the dark. She cites the Maori academic Carl Mika’s call to treat ‘obscurity, invisibility and endarkenment benevolently’.

Medieval Europe worried about the power of the dark to conceal ill deeds and erase status, requiring citizens to carry torches, households to hang out lanterns and contracts to be signed before dusk, darkness being the realm ofthe untrustworthy. But away from the spreading glare of artificial light there were, and are, richer and more sinuous relationships with dark. Irish Gaelic has four different terms for the transition of afternoon to nightfall, from idirsholas, ‘between light’, to amhdhorchacht, meaning raw, uncooked darkness, referring to the sky at dusk. Maori days begin at nightfall and the dark itself is wonderfully divided into the great night, the long night, the deep night and the intense night, through 11 distinct terms culminating in Te Po-tahuri-mai-ki-taiao, meaning ‘the night of turning towards the revealed world’.

A cultural historian and novelist, Yallop finds spaces in between the binaries of light and dark. A section on shadows has the 18th-century French scientist Claude-Nicolas Le Cat declaring them ‘holes in the light’, and the great Japanese writer Jun’ichiro Tanizaki pointing out that ‘were it not for shadows there would be no beauty’. The 19th-century physicist Lord Rayleigh discovered what would be called the ‘Rayleigh scattering’ of light, which explains the colour of clear sky and blue snow shadows so luminously captured by Monet and Van Gogh. Yallop traces the 19th-century craze for silhouette portraiture (invented by Louis XV’s finance minister Étienne de Silhouette, who cut representative shapes out of black paper in his downtime) back to bronze outlines of deities distributed throughout the Roman empire. Further back, in the Pech Merle caves in France, the silhouette of a woman’s hand waves to us from her work in the darkness of a deep cavern 20,000 years ago. 

In what might seem a literally dark time in a metaphorically dark year, Yallop’s book makes a welcome companion, gently and thoughtfully enquiring. In the Maori understanding of night, as in the lives of the Pech Merle caves, she finds protection, reverence, ceremony, safety and comfort.

If night and darkness sometimes become confused here, it is no wonder. The associative structure of the book suits its subjects. The fact is, we need darkness. The Milky Way, ‘the clustered, textured, shift-shimmer arch of stars, dense and deep’, is invisible to 80 per cent of the world’s population, and 99 per cent of USA’s, she reports. This is sad, if only because to gaze on a span of our galaxy’s 400 billion stars is to feel our true proportion. My screeches with my classmates at the apparently utter darkness of Big Pit were gleeful as much as alarmed. Darkness seemed to make us all wild sprites, as small and free as photons, invisible, ineffable, but resoundingly – so resoundingly – there.