Mathematics

The first thing Caius did was reduce the oxygen.

Not because the math required it — Voss had not yet done the math, not formally, not with the precision that was his particular form of prayer — but because the gauge was moving faster than it should have been, and the leak that had started as a steady trickle now showed every sign of being something worse.

Caius reached up to the environmental panel above his head. The controls were designed for someone with more room to maneuver, someone who was not sharing thirty inches of red-lit air with another man's breathing. His fingers found the flow regulator, a small dial recessed into the panel, and turned it counterclockwise until the indicator needle dropped from nominal to minimum viable.

The change was immediate. The air did not thin — not yet, not perceptibly — but the quality of it shifted. The ventilator's hum dropped half an octave, a sound that registered somewhere below conscious hearing and told the body that the world had just become a fraction less habitable.

Voss noticed. Of course Voss noticed. He noticed everything that could be measured, and everything in the pod was measurable except the one thing that mattered.

'What did you set it to.'

Voss's voice came from under the emergency blanket. The foil had settled over him like a second skin, catching the red light in ripples that moved with his breathing. He had not turned his head. He was looking at the environmental display on the wall above Caius's shoulder, the one that showed oxygen partial pressure and CO2 accumulation and atmospheric temperature, and his eyes were doing what his hands could not — reading the numbers, filing them, preparing to run them through the machinery of a mind that had been trained to find the worst-case scenario and call it realism.

'Minimum viable,' Caius said. 'Point-one-four partial. Enough to keep us conscious.'

'For how long.'

It was not really a question. Voss already knew the answer, or could calculate it, or was calculating it now behind the stillness of his face and the red light and the foil that crinkled every time he exhaled.

'Longer than point-one-six would,' Caius said.

Voss made a sound that was not quite a laugh. It was a single exhale, sharper than the ones before it, and the foil crackled in response like something alive. 'That is not an answer, Lieutenant.'

Lieutenant. The word landed in the thirty inches between them and stayed there, a title that had been stripped from Caius seven years ago and that Voss used anyway, because it was protocol, because it was distance, because the alternative was a name Voss had not spoken since the inquiry and would not speak now, when names cost oxygen and oxygen had just become a limited resource.

Caius did not correct him. He had stopped correcting him years ago, somewhere between the second and third year of silence, when he had realized that the title was not a mistake but a choice — Voss's way of keeping the distance measured, catalogued, filed in the same mental cabinet where he kept stress tolerances and failure modes and the arithmetic of structural collapse.

'Point-one-four partial,' Voss repeated, and now his voice had changed, the way it always changed when he was running numbers. The edges smoothed out. The clipped precision of command gave way to something more fluid, the engineer surfacing from beneath the officer, a man who trusted equations more than he trusted people and had seven years of evidence to prove he was right. 'At current metabolic rate and assuming a consumption curve that accounts for two adult males at rest — rest, not sleep, because neither of us is sleeping — and factoring in the leak rate at three microfracture points with a combined effective aperture of approximately point-oh-four millimeters...'

Caius let him talk. It was easier than talking himself, and it served the same purpose — filling the silence with something other than the silence, keeping the air moving with words instead of the things that words could not contain.

Voss's calculations filled the pod the way the cold was filling it: gradually, then all at once. He factored in the O2 reserve in the emergency tank, the rate of atmospheric loss through the microfractures, the metabolic cost of his own injury and Caius's body mass and the ambient temperature that was dropping half a degree every twenty minutes as the pod's thermal regulation diverted power to the beacon. He did it aloud, because Voss had always done his best thinking aloud, had always needed the sound of his own voice to anchor the numbers in reality, as if speaking them made them true in a way that thinking them did not.

The cold had started in the corners — the seams where the hull plates joined, the edges of the viewport, the thin gap between the floor grating and the outer skin. It announced itself the way the microfractures had announced themselves: not as an event but as a condition, a thermodynamic erosion that the pod's failing thermal regulation could not counteract and did not try to. The beacon was drawing forty percent of remaining power, and the beacon was the only thing that mattered, the only thing that might bridge the fifty-eight-minute gap between when they lost consciousness and when the rescue window opened.

Caius felt it in his fingers first. His hands, which had held the suture needle steady through Voss's flinch and Voss's blood and the terrible intimacy of bare skin under red light, were now stiffening at the joints. He flexed them under the emergency blanket, the foil crinkling in his lap, and watched the O2 gauge drop another increment.

Voss was still talking. The numbers had become a kind of incantation, a spell against the dark, the engineer's version of a prayer. He was calculating the oxygen consumption curve against the leak rate, integrating the variables, arriving at a number that Caius could see coming the way you see a wave coming — first a line on the horizon, then a wall, then something that was going to hit you whether you were ready or not.

'Four hours,' Voss said. 'Twelve minutes. That is the point at which partial pressure drops below consciousness threshold. Assuming no further degradation of the hull, which is an assumption I would not make, and assuming the beacon continues to transmit at current power draw, which is an assumption I would also not make.'

He paused. The pause was worse than the numbers. It was the pause that told Caius Voss had already run the second calculation, the one that mattered, and was deciding whether to speak it.

'The rescue corridor transfer window opens in five hours twenty,' Voss said. 'At the earliest. If Command registered the Mayday immediately — if they launched without delay — if the burn is maximum — five hours twenty. That is the optimistic projection.'

The gap between the numbers was not large when you wrote it down. An hour. Eight minutes. On a mission planning document, a gap of sixty-eight minutes would be classified as acceptable margin, a risk factor within operational tolerance, the kind of number that got a footnote and a sign-off.

But sixty-eight minutes of unconsciousness in a pod that was drifting away from the rescue corridor at a steady half-degree per hour — that was not a gap. That was a void. That was the difference between being alive when the rescue ship arrived and being a debris signature on a long-range scanner, sixty-eight minutes too late to matter.

Caius did not say any of this. He had spent seven years learning that some things did not need to be said, and the arithmetic of their situation was one of them. The math spoke for itself. It had always spoken for itself. It was the only thing in Caius's life that had never lied to him.

Voss shifted under the blanket. The foil rustled, a sound that was too bright for the space it occupied, and when he spoke again his voice had lost the fluidity of calculation and returned to something harder, something that had edges.

'It would not have mattered,' Voss said. 'The blankets. The oxygen rationing. Any of it. The numbers were the numbers before you opened the kit, and they are the numbers now.'

'I know,' Caius said.

It was the same thing he had said before, when Voss told him the beacon would keep broadcasting. The same words, two syllables, carrying the same freight of meaning that was not the meaning of the words. He meant that he had known the numbers before Voss spoke them — had known them since the moment he saw the leak rate on the diagnostic panel and did the math himself, faster than Voss had done it. Caius had always been faster at math and had never told anyone, because being fast at math was not useful for a pilot. It might have been useful for something else, something he had not let himself want and would not let himself want now, in a metal box at the edge of survivable time.

He also meant that knowing did not change anything. It never had.

The silence that followed was different from the silence that had preceded the suturing, and different from the silence that had followed it. The first silence — the seven-year silence — had been a wall, a structure, something built and maintained and reinforced by two men who had both decided, independently and without consultation, that not speaking was better than speaking and hearing what the other might say. The second silence — the silence after the suturing, after Caius had touched Voss's skin and Voss had let him — had been a truce, a cessation of hostilities, the kind of silence that happens when two armies have fought to exhaustion and neither has the strength to raise a weapon.

This silence was heavier. It was freighted with something that had not been present in the first two: the awareness that this cramped metal box, this thirty-inch space between two men who had not spoken in seven years, was very likely the last thing either of them would see.

It was not a thought that arrived all at once. It accumulated, the way the cold was accumulating in the corners and in Caius's fingers and in the place behind his sternum where certain truths had been stored for so long that he had forgotten they were there. It accumulated in the space between Voss's breaths, between the environmental monitor's chirps, between each increment the O2 gauge dropped with the patience of something that had all the time in the world and was not sharing any of it.

Voss was the one who broke it.

'Why,' Voss said, 'did you come back.'

The question did not land. It hovered in the red-lit air between them, a question that had been waiting for approximately four hours and was now being asked, and the fact that it had been asked in English rather than mathematics was the only reason Caius understood it.

Voss was not asking about the math. The math he could do himself — had already done himself, aloud and in his head and probably a third time just to be sure, because Voss never did anything once that he could do three times and still doubt. The math was unambiguous. The math was a wall, the same way the seven-year silence had been a wall, and Voss had arrived at the wall and found that it could not be climbed or circumvented or reduced to component variables. So he had turned away from the math and toward the one equation that could not be solved with numbers.

Why Caius had come back for him in the engineering bay.

Why Caius had dragged him through emergency bulkheads and sealed them both in a pod designed for one.

Why Caius had taken the suture needle from Voss's broken fingers and stitched the wound in his side with hands that did not shake and breathing that had hitched exactly once, when Voss flinched — a hitch that neither of them had acknowledged and neither of them had forgotten.

Caius did not answer.

The silence that filled the space where his answer should have been was not the same silence as the one that had preceded the question. It had a shape. A weight. A temperature. It was the silence of a man who had spent seven years not answering a different question and had gotten very good at it, and the silence of another man who had spent seven years not asking and was now asking and was receiving the same answer he had always received: nothing.

Voss's breathing changed. A fraction of a second added to the exhale, a hesitation in the inhale that had not been there before. The foil over his chest rippled with it, the red light catching the edges of the crinkles and throwing them back as something that was almost movement, almost speech.

'I am asking,' Voss said. His voice had lost the fluidity of the engineer and gained something else, something that Caius had not heard in seven years and could not name and would not name, because naming things cost oxygen. 'Why you came back for me. That is not a complicated question, Lieutenant. That is not an equation. That is six words.'

Caius's hands were still. They were always still, except when they were not, and the exception was something he had learned to anticipate and control and bury so deep that even he could not find it most days. His hands were still now, folded under the emergency blanket that he still had not draped over himself, the foil cold against his palms where the cold had seeped through the hull and into the metal and into everything that touched the metal, which was everything.

He could feel Voss waiting.

He could feel the gap between the question and the answer widening, the way the gap between their location and the rescue corridor was widening — half a degree per hour, a deviation that was negligible on any given second and catastrophic when you added up all the seconds between now and when the rescue ship would arrive. If it arrived. If Command had registered the Mayday. If the burn was maximum. If the arithmetic of survival had variables that had been solved and not just postponed.

He did not answer.

The O2 gauge dropped another increment. The environmental monitor chirped. The cold continued to seep through the hull fractures, and the stars outside the viewport continued to keep their counsel, and inside the pod, two men who had spent seven years not speaking to each other sat in a silence that had become, without either of them acknowledging it, the third kind — the kind that had a door at the end of it, and the door was closing, and neither of them knew how to walk through it before it shut.

Voss did not ask again.

The question was still there, suspended in the thirty inches between them, unanswered and unanswerable and somehow more present for having been spoken aloud. It hung in the red light the way the cold hung in the corners, accumulating, waiting — a variable that had not been solved and would not be solved tonight, if tonight was the word for the absence of daylight, if day was a concept that still applied in a metal box at the edge of survivable time, if time itself was still a thing that could be measured in anything other than the increments of the O2 gauge and the distance between one silence and the next.

Caius finally pulled the second emergency blanket over his shoulders. The foil crackled — bright, brittle, a sound that belonged in a different kind of space — and settled around him, reflecting his own body heat back toward the source, a closed loop of warmth that was already failing.

He did not look at Voss.

He stared at the O2 gauge, which was ticking downward with the patience of something that had been waiting longer than either of them had been alive and would wait longer than either of them would be alive, and he did not answer the question that had been asked, and he did not answer the questions that had not been asked, and he did not think about the engineering bay or the seconds before the breach or the sound that Voss's body had made when he hit the pod floor.

He thought about the oxygen consumption curve and the leak rate and the thermal budget and the transmission frequency of the beacon and the distance to the rescue corridor.

The math was easier than the question.

It had always been easier.

The O2 gauge dropped another increment, and the cold continued to fill the spaces that the numbers had left behind.