Light wakes the world gently at this latitude. The sky softens as it slowly brightens, easing from a rich, deep blue into a curious green. The stars dim gradually―like music faded so skilfully that you feel a pang for its passing but listen all the more attentively as it quietens.

Back home I’m not one for prising my sleepy body from my quilt a single moment before I must, and so the magic of dawn too often passes me by. But here―in Glen Affric in the Scottish Highlands―I wake in the darkness, and, momentarily disorientated, I reach out to feel for the campervan curtains. Then gasp out loud at the clarity and density of the stars.

I’m not used to real dark anymore―the sky around my home on a slope of central Scotland is stained from the lights of industry and the sprawl of nearby towns―so the darkness that greeted me when I arrived at this Highland loch last night was unnerving, but welcoming too. It was cloudy, and I remembered that real dark is sometimes described as “velvet”; there is that texture to it, soft and alluring. But now the clouds have dispersed and that dark is just a canvas, a backdrop to the exhilarating starscape that adorns it. More vocabulary takes on refreshed meaning: “a pristine sky”. That’s exactly right―it’s clean, as if the stars have been polished. And another one: “gaze”―a sense of awe enshrined in the language; we watch birds and even whales, but we gaze at stars.

I get up and venture out into the darkness, step by step, the silhouettes of trees splintering the star-bright sky, and the sound of Loch Affric lapping gently at the rocky shore somewhere nearby.

And that’s when daylight starts to soften the sky, greening the blue way over there, edging a dimmer switch up ever so slightly until the stars are gone and the colours intensify in the autumn-tinged landscape all around me. The world around me is a forever of wooded mountains bathed in morning mist that lies in downy streaks among the trees. Lower down there are dark pines, and the soft yellows of birch just turning; then ghost trees stand behind them in black and white, like pencil drawings gently smudged, and above them is a layer of sky. Then higher still, improbably high: a ridge of pines up in the sky.

Here in this enchanted place, I can feel the light addressing me. It’s light that tells the green birch leaves to fade to soft ochre, tells the robin which song to sing, that touches these mountains with the colours of the spice rack: saffron, cinnamon and turmeric. Once upon a time, there were dark nights and light days. And that once upon a time lasted a very long time―three billion years―and life on Earth emerged, following a constant rhythm, tapping its collective toes to a steady beat: dawn-day-dusk-night, dawn-day-dusk-night. The length of the beats stretching and tightening gently in response to the seasons and the lunar cycle. Climates changed, continents drifted, mountains rose and oceans swirled and still Nature kept the beat: dawn-day-dusk-night. On and on and on.

And every living thing evolved and adapted to this rhythm. If the world’s a stage, the show is an elaborate dance created by Evolution, the flamboyant choreographer, in collaboration with the Cosmos as virtuoso lighting designer. They’re an inseparable partnership―every footstep of the dance takes its cue from the changing light. It’s performed by an astonishing cast of creatures, all flying, swimming, hiding, hunting, resting, growing and blossoming to the beat with breathtaking synchronicity. They’re all poised for their prompts: flowers ready to open their petals, frogs to croak a love song, birds to gather and fly south. Migration, predation, pollination and reproduction all respond to the intensity of the light.

And these cues come from the subtle lights of the night as well as the sun in the day. “Real” night, pristine and unpolluted, isn’t dark but a perpetual shifting, glowing light show put on by the moon, stars, planets and celestial activity. Many species of migratory birds are able to recognise the patterns of the stars and to adjust their navigation to the tilt and rotation of the sky. Dung beetles use the glow of the Milky Way to orient themselves, ensuring that they can roll their precious ball of dung in a straight line away from the competition of the dung heap. Hundreds of species of coral spawn simultaneously after the full moon, because a gene enables them to detect light with enough precision to track the phases of the moon. Whenever I talk about light, I’m also talking about darkness. I feel we’re inclined to underestimate the importance of darkness, just as much as we do light. There’s a presumption that the world goes to sleep at night because we do. Yet much of life on Earth is nocturnal, and darkness is essential, not just for the sleep and health and well-being of diurnal creatures, but for the rest of life that needs the dark to live and thrive, to travel and hunt and hide in.

Dusk and dawn are when we may notice the light change and feel its impact, but the colour and quality of natural light is changing constantly throughout the day. The shifts in frequency of the light spectrum, from blue morning to red evening, are subtle and often beyond our awareness, but they are not beyond our perception. The cues from lighting designer to cast keep coming, the messages changing: rest now, start to dig, become sexually aroused . . . The performers respond at every level: within the very cells of individual dancers; in their presence on the stage; and in the twists and turns and drama of the interaction between species. If we mess with these cues, what happens to the dance?