Qasmuna blinked and caught Talasea's hand. Her smile was painful.

Despite the distance of years, the Irenian understood what had happened in an instant. The paleness of Qasmuna's iris, the haziness of her cornea, the redness of her sclera, the way she sought light to the limit of blindness, the picture it painted was simple yet merciless.

“Neovascular glaucoma,” whispered Qasmuna, “my ophthalmologist says it is due to a short episode of heavy radiation exposure. I don't know how it happened. When I was taken out of the shadow zone of that drive, as the Al-Awaidh broke and spiralled out in a sunward vector; or perhaps when I witnessed the glimmers of a particle lance, diffracted through stellar dust. It doesn't matter. It's old, slow-burning, inevitable. My peripheral vision has already degraded to the point I can't even see the entirety of your face. I have six months, maybe a year, before blindness.”

“Your optic nerve and retina can be replaced with vegetal analogues. You will see again.”

“You are aware of what it entails, yes? They burn your optic nerve with lichens, then inject you with stem cells and commensal algae to rebuild your eyes. After twelve months of darkness, you wake from the great darkness with golden pupils, and your sight is changed. Your neural pathways are rewritten in the process, so blue is still blue, red is still red, a sphere is still a sphere and a smile is still a smile, but deep down, you know; that the world is not the same and that the root that runs to your visual cortex lies, not because it seeks to lie to you, but because it cannot do otherwise. You are a human with the eyes of a plant, and the world will never sing the same. It terrifies me.”

Radio waves were scattered across the atmosphere, dots and waves linking aircraft together — white wings and clear frames, high in the sky of Elora. Talasea was nestled in the thin cockpit of her Kármán skimmer, fortress of warmth and life in the freezing air of the stratosphere. Through the teardrop-shaped canopy poured in the candlelight of the main star, drenching her face in gold. It was an ancient sun, seven billion years down the evolutionary course of cosmic candles, teetering at the edge of the main sequence, yet not fallen. Sleek pearlescent frame and variable geometry wings angled in inversion, the Kármán skimmer was a thing of beauty — useless, but all spaceplanes were, superseded by skyhooks, orbital fountains and geostationary elevators, new altars of the interstellar age. It drifted through the layers of the stratosphere with the serene slowness of a drop of oil strolling at the surface of a river. Talasea's voice was soft and kind.

“Elora orbital, this is Cradle One, requesting permission to begin powered ascent.”

“Elora orbital control to Cradle One, you are good to go, happy flying.”

The Irenian pushed the throttle of the Kármán skimmer all the way up to the military power setting and the spaceplane responded in kind. Biofuel was pumped from the wing tanks and into the engine — thick, dark red liquid, the blood of flowers growing on the night side of tidally locked worlds. The jet engine swallowed the cold air and the Kármán skimmer abandoned its glider allure to transition into a runner. The cockpit hummed, vapour exuded and sublimed from the wings as they locked their shape into a delta. Mach 1, Mach 2, Mach 3, Mach 4 — as it passed the Mach 6 mark, at six thousand and five hundred kilometers per hour, the jet engine opened as a flower under the rain and turned into a scramjet. The Kármán skimmer had become an eager raindrop falling upwards, seeking a path of least resistance.

As the aircraft reached the mesosphere, the scramjet started losing thrust. The icy air in front of its gaping maws had become too thin for sustenance. Talasea flicked a switch and the engine performed its second metamorphosis. The flower died, retracting its petals under an invisible storm. It ceased to hunger for dark red blood, instead seeking hydrogen and oxygen. A white flame appeared in the wake of the skimmer. The teardrop had turned into a winged rocket. Underneath the thermal tiles of the fuselage gleamed a sea of high clouds, stretching their tendrils across the horizon. Elora's nascent space elevator cut the sky in two, thirty thousand kilometers of wire dangling from the edge of the world. Talasea grazed the back of her passenger's hand.

“Are you alright, Qasmuna?”

She nodded and Talasea pulled the stick towards her, increasing their rate of ascent.

Orange leaves dangled in the cool wind that rustled through the pseudotrees. The forest was warm, the mountains heavy with snow. Elora had just entered its stellar autumn, as its old star dimmed its light for six months straight. Local life had slowed down, many of the most complex symbiotic creatures falling in nigh-hibernation, just aware enough to seek for rays of sunlight falling in-between the trees. Talasea held Qasmuna in her arms, sheltering her from the rising mist.

“It is getting cold,” Talasea murmured, “we should return home, lest the birds start taking us for trees.”

“I would love to be a tree,” answered Qasmuna, “they do not have to worry about anything. They are trees.”

“Careful, now. You are on Elora. Our trees can think and dream. Perhaps they could even hear you.”

“Do they have eyes?”

Talasea extended her arms towards a furred pseudolizard that had been observing them for the better part of the afternoon, perched on its branch. The creature slithered towards the Irenian, snuggling against her neck in search of warmth and the sweet contact of her ocean-colored skin. Talasea patted the lizard on the head and it pawed her neck in response.

“The trees, I do not think so. But everyone else in the forest, yes. Eloran ecosystems are one interconnected symbiote, and I mean this not as a poetic manner of speech, but as a simple reality of this world. Maybe this lizard is going to report you to the trees. Who knows what they are up to? Conspirators, the lot of them.”

“I wonder if they will consider me as one of their own, when I have eyes as a forest and a root in my brain. Do tell, Tali. Do you think trees are afraid of seeing as a human?”

And now the Kármán skimmer ran a race against its own wake, wings three-quarters retracted and hugging the hull which creaked and vibrated under the coruscant song of the closed-cycle rocket engine. G-forces pushed Talasea and Qasmuna against their seats like a giant's palm leaning on their chests, but they didn't mind — for they were spacers at heart, daughters of this kinetic age. Freed from the shackles of air-breathing propulsion, so close to the edge of the atmosphere, the great skimmer exulted. Talasea kept an eye on the needle of the altimeter. The spaceplane was very close to Elora's orbital velocity and its wings played with the edges of the Kármán line, of that universal frontier which, one hundred kilometers up on Earth-like planets, materialized the limit between the void and the atmosphere. It was a convention, it was a fiction, for above continued the scattered particles of the exosphere, hundreds and thousands of kilometers out before the solar wind could blow them away into oblivion — but a strong fiction it was, neatly delineating the world between aircraft and spacecraft, between the flyers and the burners, between the drifters and the torches, between the realms of the blue and the realms of the black, between the last colours Qasmuna would ever see truly.

The windy warmth of a short stellar spring undulated in the forest, flowing around the hills, curving wheat fields and pseudo-oaks in its wake as it created a shifting landscape. Talasea and Qasmuna had left their bicycles on the side of the old path, abandoning the light of the young wood for the shade of the old trees. Talasea kissed Qasmuna in the neck. The Irenian was happy and exhausted, drunk on her lover's perfume and the sweet scent of spring. They had nothing left to say. It would thus be the end, thought Qasmuna. One last afternoon, one last hour of love before a year of darkness — and after that, the world would be changed without return, the colours and the shapes different yet her brain tricked into accepting as the same. It was the old question once again, the old doubt — are others really seeing the world as I do? What I call red, is it red for them? Or is it what I would call green, but by language and custom the other considers it red and thus we are all in broad accordance as to what the world actually is? Childhood questions, naive and meaningless — it didn't matter as long as humans as a whole agreed on the broad colors and shapes of the universe. But now it was her own continuum that was to be broken, this tunnel vision of hers to be replaced by the bright clarity of an algae's brightness sensors sharpened and educated into an eye, and — she was convinced of it now — with her old sight would go away the sincerity of the world. There would be a flash of suspended animation and she would find herself unable to trust reality anymore, spending every waking moment wondering as to whether or not red was red and green was green, and blue, and—

“Come,” said Talasea, “I have one last gift before the night.”

Qasmuna stood up and, helped by the Irenian, climbed back on her bicycle. They rode down the hill and towards the little village, stopping by the coral-woven hangars that rested by the deep blue lake. They entered. A slender spaceplane rested in an alveolar niche of the warehouse, grazed by the golden afternoon pouring through the bay windows. Qasmuna ran her hands alongside the edge of the variable geometry wings, feeling the silky surface against the palm of her hand. The spaceplane summoned images of a sea creature accustomed to the abyss, even though it yearned for the void.

“You never told me you had a Kármán skimmer…”

“It is not mine. I am merely keeping it in good shape for a friend who might fly it once again if she ever finds her way back to Elora from the deep black. She is a tideless, nearing three hundred years old. Her eyes are made of sap, bark and transparent leaves — but it is not why I want you to fly with me.”

One hundred and fifty-seven kilometers above the Eloran surface, Talasea cut the engines of the Kármán skimmer.

The world below had contracted its colours in a singular end of the spectrum. The ocean gleamed in lapis and cobalt that turned into teal and sapphire where the ancient, eroded continents would draw closer to the surface of Elora's shallow oceans. At the other end of the curved horizon, the planet was spread across a sea of ultramarine blue that dissolved into underexposed darkness along the exact line where sunlight came to die. In-between the atmosphere erupted in suzerain blue, fiery hue born out of the Rayleigh scattering of photons pulsed away by the sun.

For as long as Talasea could keep the spaceplane straddling the edge of space, Qasmuna watched. She gazed and gazed and gazed, gorging herself on colours that pierced the funeral veil on her eyes, the infinite hues of space intertwined with the fragile envelope of a garden world.

Blue, blue, blue; azure, the empress of colours, the tint of liquid water and the promise of life, the Cherenkov rays of electrons in radioactive water, the Doppler shift of spaceships exiting a faster-than-light translation, the formidable glow of fusion engines brought at the edge of the divine, it was the fundamental colour of this kinetic age, the heraldry of Qasmuna's heart, the promise of the eternal traveller. She closed her eyes. It would be the last true colour she would ever see, it would be Talasea's gift.

At the edge of night, a Kármán light.