Divergence

Fiction by David Whitmarsh

It was my sister’s suggestion. “You need to get away, Samantha!” she said. “Make a fresh start. Can’t your company give you a transfer?”

I cursed her dumbass idea but it crept under my skin, kept pricking me whenever I let down my guard until I found myself scouring the vacancies list, looking for something far away. Then I actually found one: Almazir station, a one-year posting, big bonus, scary non-disclosure agreement, and a hefty penalty if I quit early. The dumbass idea had become a decision. I applied and I was accepted. That was eight months ago. They say that under the circumstances they won’t enforce the penalty clause.

Within a week I was locking the front door of my Darmstadt apartment, locking away those memories. I barely had time to catch my breath until the shuttle docked with the ship. There was time to reflect then: 30 days of nothing to do but contemplate the void outside and the void within me. I might have changed my mind then but I was committed. There was no way back. Thirty days later the limitless void outside my window was replaced by the red, red deserts of Mars 300 clicks below. Funny that looking down from so high never triggered me. I guess it needed a vertical face—a cliff or a wall—to awaken that demon.

The ship docked at the Ares Interchange and the momentum that brought me that far carried me along the gangway. In the arrivals hall a man in a scruffy pilot’s jumpsuit held a board with my name scrawled on it. Late twenties, early thirties, a relaxed kind of smile on his face. I kicked a little too hard against the rail to propel myself towards him and his outstretched arm caught me.

“Samantha?”

“Yeah, sorry about that. People call me Sam.”

“Hey, no problem.” He held out a hand to shake. “Herman. That all your baggage?” His eyes flicked towards the flight bag over my shoulder.

“Yeah.”

The stream of passengers crowded into the hall, gripping the rails while studying the departure boards for the cities and stations on and around Mars. Herman guided me away down a series of tubes and junctions and hatches into a cramped cockpit. The windows looked out onto the criss-crossing tangle of girders and modules, propellant tanks and docking ports that made up the Ares interchange. “Strap in,” he said. While he was calling traffic control for clearance to depart I picked out the winged shapes of a pair of shuttles and the long cylindrical hull and wide cooling vanes of the liner that had brought me from Earth.

“Look, there.” Herman pointed. A silvery ellipsoid manoeuvred into dock with delicate puffs of its thrusters. “Garcia’s Luminar.”

I’d read about it. The prototype commercial version of Garcia’s exotic quantum locality drive. It carried only six passengers but travelled at the speed of light, making in 12 minutes the journey that had taken me 30 days. As they began to roll off the production line they were going to monopolise the interplanetary passenger market. Our company would be left scrabbling for the bulk freight trade.

Clearance given, Herman backed us out of the dock and turned us around. A burst of thrust pressed me back into the seat, along the line of our orbit. The accelerometer on the panel before me registered half a g. I counted the seconds until the thrust cut out and did a little mental arithmetic. “Six hundred and forty kilometres apogee.”

He laughed. “An old space hand, hey?”

“First time off Earth.” He cocked an eyebrow and I hid a smile. “It’s just maths.”

“So, we have a little time. About thirty minutes before we get there but I guess you figured that out already, hey? Any questions.”

“Just one. What’s this project about?”

“Ahh, that’s a hard one. Everything’s compartmentalised. We get to know only enough to do our jobs.”

“Sure, I get it.” Herman was a shuttle pilot, a taxi driver. He wouldn’t need to know that much.

Small talk filled the time until Almazir turned from another point of light outside the cockpit window to a fat, lazily spinning cylinder. On the nearer face a thin spire protruded from the axis, a series of struts and modules sticking out at right angles. Workshops and engineering, Herman said. They held still as the cylinder rotated around the base of the spire. Herman flew us around to the opposite face where a smaller cluster of docking ports rose from the centre. With easy confidence he brought the shuttle into dock.

From the hatch it was a short kick down a passageway to the hub where I caught my first view of the interior. A thousand metres to the far face, five hundred metres to the rim turning slowly around me. A grid of narrow pedestrian streets and footpaths separated the buildings, some low and sprawling, some four or five stories high. A park filled half the width and a quarter of the circumference with grass, dwarf trees, and a lake. When I saw the ground as a cylinder wrapped around me I was fine, but as my brain began to interpret it as down, the panic surfaced. I closed my eyes and counted to ten like my therapist taught me, to ward off that cycle of self-destructive thoughts.

There was an induction, mostly a rehash of the contract terms, stressing the importance of security clearance levels. A silver-haired executive type introduced himself afterwards: Alex Ledermann, head of operations, my new boss. I’d have a day to rest and recover from the journey before starting work but he wanted me to meet some people right away. Faces and names I did my best to memorise but one needed no introduction. Ledermann knocked deferentially on an office door, within was the bald pate and permanent scowl of Arnauld Nouvier. That face had filled the news feeds when he’d received his Nobel prize three years earlier and again when he quit his post at Garcia shortly after. Garcia’s Lightstar had left that same week. A crew of four on their way to Alpha Centauri at the speed of light. Four years there, four years back. It was Nouvier’s breakthrough that had made that possible. And now he was at Almazir. My curiosity was well and truly piqued.

The apartment they allocated to me was bigger than the one I’d abandoned in Darmstadt and had a view over the park to the lake. It’s hard to describe just how strange it was to see that curved surface rippling. Beside the lake was the Garden Café Bar. The only place to eat and drink out, all in the open air. That’s where I met Marion Michaels.

A row of empty stools stood by the bar and a haphazard scattering of tables lay on the tiled apron by the lakeside. A half dozen people were clustered around one of them lost in earnest conversation. She was sitting by herself at another, her fair hair pulled tight to the scalp in a short ponytail, deep in concentration as she read her slab. I took my drink from the barman and walked over.

“Hi, mind if I join you? New here, don’t know anyone.”

“Sure,” she mumbled without looking up, the flick of a hand vaguely indicating the empty seat.

I sat, took a sip of my beer, looked out over the lake, my eyes followed the curve as it rose up to near vertical, and on to the roof of my apartment building. I was beginning to feel awkward in her silence when she put down the slab.

“Sorry,” she said, “I needed to finish that. Marion.”

I shook the outstretched hand.

“Sam.”

“New?”

“Yep.”

She picked up her glass, took a good swig.

“I’ve never been off Earth before,” I said, “it’s strange.”

“You’ll get used to it.” A brief glance in my direction, a tentative half-smile, and she drained her glass.

“Always this quiet?” I asked her.

“Not usually. People are busy gearing up for the launch.”

She answered my raised eyebrow.

“Casimir. The test article. Launch in two weeks.”

“Testing what?”

“What’s your security clearance?”

“Level three. Ledermann said he’d try and get me level two.”

“Ask me again when you’ve got it.”

“He said it just after I saw Arnauld Nouvier. I’m getting really curious.”

She gave me a long steely look. “Read Nouvier’s paper?”

“Relativity I can do. Quantum non-locality is way beyond me.”

“You should read it, if only the abstract.” She picked up her slab and stood. “Ok. Gotta go. Early starts, long days. Nice to meet you.”

Her heels clacked loud on the tiles. Ten paces away she stopped and called to me over her shoulder. “And the addendum, read the addendum.”

So, I finished my beer, strolled back around the lake to my empty apartment and started looking. It turned out Nouvier had published hundreds of papers, but only one that had earned him a Nobel. Quantum Gravity Non-local Phase Transitions at High Field Densities.

The abstract delved into abstruse implications of quantum loop gravity. I waded through a paragraph that might have been written in Sanskrit, until I reached the last sentence: If certain technical obstacles can be overcome, the first modal solution described can be utilised in the construction of a device capable of travel at relativistic speeds with moderate expenditure of energy, and freed from the constraints of the rocket equation. That I did understand, confirming that this was the paper where Nouvier had discovered a way to travel at the speed of light. Garcia S.A. had licensed his patents, and were now on the verge of making a great deal of money selling small, very expensive craft that could travel across the solar system almost instantaneously. Thirty-day voyages to Mars would soon be history. And in another four and a half years or so, the interstellar demonstrator Lightstar would return from Alpha Centauri, and the crew would have aged only the few days that they spent there.

There was nothing new here, this was history. This is what Garcia S.A. were doing, not us. “The Addendum,” Marion had said. I scrolled to the end of the paper. It is interesting to note that the second modal solution described suggests a mechanism for travel at super-relativistic speeds. However this is of academic interest only as to generate the enhanced Casimir effect requires a naked singularity, a practical impossibility. Also, Einstein teaches us that travel faster than light can lead to closed time-like curves, unless we invoke Everett in our solutions to the quantum non-localities.

Most of that I didn’t understand either, but travel faster than light jumped out at me, and I was sure it was no coincidence that the test article Marion had mentioned was called Casimir.

I was at the bar a little earlier the next day. It was even quieter. Just me and the barman. I asked him about Marion.

“Yeah, she’s here most evenings, probably be along shortly.”

“Not the most talkative person I’ve ever met.”

“Last night? I’ve never seen her so chatty.”

I turned at the sound of heels clacking.

“How do you make a naked singularity?” I asked her.

“Still on security level three?”

I nodded.

“You can’t. It’s impossible.”

“Hypothetically, wouldn’t it be dangerous?”

“Only to your career prospects if you told anyone.”

“How do you mean?”

“Black holes make for bad PR, that’s why we’re sitting out here in this recycled can rather than, say, down-town New York. But there’s no real danger. If someone hypothetically lost containment on a hypothetical naked singularity, it would evaporate. Explode.”

“That sounds dangerous.”

“...about as violently as a damp firecracker. They are tiny.”

“But what about...”

She shook her head, raised a hand. Topic closed. “Are you the one who figured out how to find TAU?”

“What’s TAU.”

“Thousand Astronomical Unit. It’s a probe from the mid twenty-first sent out to explore the interstellar medium. Finished its mission after 20 years and has been drifting dead and silent since, but it’s still the furthest human-made object from Earth.”

“Garcia’s Lightstar is most of the way to Alpha Centauri.”

“No. It’s not anywhere until it gets somewhere. So you’re not the one who figured out the tri-radial pulse?”

The tri-radial pulse was an answer to an incomprehensible question that had crossed my desk in Darmstadt the year before; a way of searching a large volume of space for a small dark object. “Ye-e-e-s, but no-one told me what it was for.”

“Shit. We really need to get you level two clearance.”

“Yeah.” I turned to get the barman’s attention, signalled for more beer. “It’s a long way to come here from Earth when I don’t even know what I’ve come for.”

“So why did you come?”

“There was nothing for me back there. Not since...”

She looked at me, waiting. Two beers landed on the table and she was still looking. I took a long drink. “What about you? Why did you come?”

“Maybe I was running away from something.”

Alex Ledermann looked up when I walked into his office. “Can I help you?”

“It won’t work.” I folded my arms, looking down at him across his desk.

“What won’t?”

“The tri-radial pulse.”

He leaned back in his chair. “Why not?”

“You only give me half the story, you only get half the answer.” It didn’t look like he was going to offer so I pulled up the chair and sat facing him. “The error bars on the target location are too narrow. If TAU is tumbling, the acceleration due to starlight becomes erratic, the search volume is considerably larger.”

His fingers tapped a rhythm on his desk for a moment. “Can you fix it?’

“Now that I know that the search is done by a probe with faster than light capability. Yes I can, as long as I have free access to the information I need.”

The look he gave was long, hard, stony as granite. “How do you know all this?”

Marion rang my doorbell while I was having breakfast.

“Level two! How did you persuade Ledermann?”

“I told him I’d seen Arnauld Nouvier, read his paper, and I couldn’t do anything useful if I was working in the dark.”

“Good. Now I can show you.” Her eyes gleamed, her whole body twitched with suppressed energy.

“What?” I found myself smiling at her infectious mood.

“Casimir, and everything.”

We took the lift up the north end wall. At the hub there was no gravity, the world span slowly around and I began to regret my breakfast. She led me through a hatch into a long wide tube, the inside of the spire I’d seen when arriving. Here, with no rotation, my stomach settled a little. She turned down a side corridor. A glass wall ran the length of one side of this passageway, giving a view into a much bigger space. Spotlights all around lit what looked like a satellite, about the size of a small car, bristling with manoeuvring thrusters and antennae. Two technicians wearing oxygen masks worked with hands deep in the probe’s innards—a nitrogen dock. The vacuum of space opens allows for materials that aren’t stable in the presence of oxygen or water vapour: certain magnesium alloys, anhydrous glasses, and so on. Working in a dock pressurised with nitrogen while wearing an oxygen mask is a hell of a lot easier than working in a pressure suit in vacuum.

“Casimir,” Marion said. “Proof of concept. One unmanned flight planned. This way...”

I followed to another maintenance bay. The craft inside had a rough hand-crafted look, its elliptical outline broken by flat windows. Workers and assembly robots clustered around it.

“This is Hawking, the manned version. Bound for Alpha Centauri.”

My level two clearance gave me access to the control room gallery on the day of the test. The big screen followed Casimir as they led it out of the depressurised nitrogen dock, then, after a seemingly endless systems check, it vanished in a blink. TAU, the probe it was being sent to find, was thirty-four light-days away. Travelling at the speed of light it would have been there and back in ten weeks. It reappeared after an hour. The view screen lit up with the video it had recorded: the TAU probe gently tumbling.

Pretty much everyone on the station was at the party afterwards, overflowing from the bar into the park. Marion partied hard, dancing and drinking more than I ever could. I found myself by the side of the lake chatting to Herman, the shuttle pilot. I was never sure what I could say to people about the work, with the silos and the security clearances. I could have asked him about his past, but then he’d have asked me about mine.

“I was trying to skip stones,” I said, “but with the curve on the surface I can’t get more than a couple of bounces.”

“Right-handed?”

“Yeah.”

“We need to trek round to the other side of the lake. Pick out some good stones while I get us a couple of drinks.”

I was rooting around in the raised beds when a shadow loomed from behind me: Marion, bottle in hand, hair falling loose half-hiding her face. She didn’t look too steady. I sat her down on the stone wall.

“What’s up?” I said.

“I was wondering why you came here. What you’re trying to forget.”

“Not forget. I’m just trying to move on.”

Marion raised her head enough to look at me through the parting curtain of her hair. “How’s that working out for you?”

It seemed an age since I’d turned the key in the lock, leaving that apartment, that life, behind. I’d hardly thought about it at all since arriving at Almazir. The work, the people. “I think, OK.”

Back at the bar, Herman emerged from the crowd, two bottles in his hands. I caught his eye and gave the slightest shake of my head. He sat down at an empty table where he could watch us discreetly.

“I lost someone,” I said.

“What were they like?”

For a moment I had no answer, then I didn’t know where to start. A bark of laughter escaped me. “Infuriating!” I cried out. “One moment like a stupid spoiled child, the next the kindest...” my words petered out and the tears ran.

“I’m sorry,” she said.

“It’s OK.” I wiped my eyes with the back of my hand. “What about you.”

“What about me.” She tipped her head back and raised the bottle to her lips but it was already empty. “I am trying to forget.” She stood and sent the bottle spinning through the air and into the lake. “Come on. I need another drink and you’re keeping our test pilot waiting.”

“Test pilot?”

“Herman. He’s the one who’s going to fly Hawking to Alpha Centauri.”

She was vanishing into the crowd at the bar by the time I reached the table. Herman handed me a beer. “Is she OK?”

“I’m not sure.”

“We should keep an eye on her.”

“What’s her story?”

He chewed his lip for a minute. “If she wants you to know she should be the one to tell you.”

A couple of weeks after, late in the evening, Herman and I were sitting at a table by the lakeside. I’d asked a question and he was in full flow.

“When I was little, Gagarin, Tereskova, Armstrong, were my heroes. I wanted to be like them, exploring the mysteries of the cosmos, going to places no-one had ever been.”

“Now you’re living your dream?”

“So I studied hard, went to pilot school and got a job with the company, and ended up a glorified bus driver. For ten years I shuttled passengers from one station to another, then they sent me deploying nav beacons wherever they said.”

I laughed at that, reaching to touch his hand. “Wherever I said! Planning nav beacon deployments was my job for a while.”

That brought a smile to his face. “But now, yes. I really am living my dream. I’ll be first to reach another star, first to travel faster than light.” His hand curled loosely around his beer glass, still half-full. “How about you? What brought you here?”

I reached across the table and took his hand. “I want to tell you, but not now. Now I want...”

Heels clomped across the tiles behind me, breaking the moment. “Damnedest thing,” Marion said, throwing herself down into an empty chair.

“What?” we chorused.

“We’ve been stripping down Casimir. CPU has the wrong serial number.”

Herman leaned forward. “How do you mean?”

“The week before launch, during checkout, we picked up an anomaly, we were thinking to swap out the CPU, but ran the tests a couple more times and it came up clean, so we left it.”

“So?” I said.

“The one I took out from Casimir today was the spare.”

“Someone swapped it after all,” Herman said.

“That wouldn’t be anyone’s job but mine, and even then, it should be on the worksheet.”

“Where’s the original,” I said, “the one that failed the test?”

“Can’t find it. We always keep components that fail for further investigation.”

“Put back in stores where the spare was?”

“If someone did that, I’ll throw ’em out the nearest airlock.” She sat, tight-lipped, tapping the table with her fingertips. “I’m going to go look. Coming?”

Herman and I looked at each other. Unspoken words.

“You go,” he said, “I’ll catch you later.”

Back up at the hub and along the spire and into a side passage with doorways on each side. She darted into one and I followed. A small storeroom, every wall lined with cupboards and storage bins. Every wall, no such thing as a floor or ceiling here. She took out a carton from one of the smaller cupboards, examined the label.

I waited. She turned it over, looked at the reverse, turned it back, looked at me with the strangest expression on her face.

“We didn’t swap it. This is the spare. Look, still sealed.”

It was taped up, the manufacturer’s seal unbroken.

She darted out into the passageway, turned left, away from the spire. I bumbled after her as fast as my clumsiness allowed, just in time to see her disappear into another room.

“Welcome to my world,” she said as I poked my head around the doorway. Structured chaos greeted me: workbenches, cupboards and storage bins, instruments and tools held to the walls by clips and stikpads, and Marion floating in the middle of it with the carton in one hand. She reached into one of the bins and took something out, pushed it so it drifted towards me in a leisurely straight line. I caught it: a rectangular block, chips and fibre guideways on one side, a row of optical connectors on the edge, a white label stuck on the otherwise featureless reverse face.

“That’s the unit I took from Casimir today,” she said, “and this,” holding up the carton, “is the spare. What’s the serial number on that one, just the last six digits.”

There was a bar code and a long number on the label, “ah, six-three-eight-zero-zero-four.”

She showed me the carton, same number on the box.

“Mix-up in manufacturing,” I suggested, “they’ve mislabelled the box?”

She slit the seal and pulled the unit out. The label on the back had the same number.

“Here,” she said, pointing, “there’s a mark on the casing. Identical. Corner of the label is missing. Identical. This is so weird.” She held the two units, one in each hand looking blankly from one to the other, and back. “I’m gonna have to talk to Ledermann about this.”

Something happened, something was going on. The senior technical and operations people were constantly in meeting rooms or gathered around terminals talking in hushed tones, falling silent when anyone approached. I asked Herman.

“I’m really not allowed to say. It’s a level one thing.”

I managed to pin down Marion in her workshop, bleary-eyed and sleep deprived.

“Casimir’s telemetry arrived,” she said, “it doesn’t make sense.”

“Surely that was five weeks ago?”

An exasperated sigh escaped her. “Telemetry! When Casimir reached TAU it sent data by laser so that if it didn’t make it back we’d at least know it got there. The signal comes the slow way, five weeks at light speed.”

“So what’s the problem?”

She showed me her slab, an image of TAU, slowly tumbling, just like the recorded images from Casimir after it returned. “This is the feed. We’ve been receiving these pictures for over twenty-four hours.”

“So?”

“It was only there an hour before jumping back. The telemetry says there’s a fault in the drive management CPU and it can’t come back.”

“But it did come back.”

“Exactly.”

Something was nagging at the back of my mind. The thing with the CPU serial numbers was weird enough but that wasn’t it. I asked the question anyway. “Did you find out what happened with the CPU modules?”

“Ledermann sent them to recycling, the incompetent sod.”

I’d seen plenty of stupidity from management in my time, but this had a different stink. Either they already knew what was happening or they didn’t want to know. A thought came to me: something I’d read. I picked up my own slab, found Nouvier’s paper, the addendum: ...travel faster than light can lead to closed time-like curves....

I showed her. “You know what that means?”

She frowned. “It says if you can travel faster than light, you can travel through time.”

“Is that what we’re doing?”

“You think Casimir is spending longer with TAU than the time it was away from here.” She held her head in her hand a moment. “I don’t know. I’m just the technician, the theory’s beyond me.”

I’d been lying awake for hours when the rest of the quote from the addendum popped into my mind: travel faster than light can lead to closed time-like curves, unless we invoke Everett in our solutions to the quantum non-localities.

“Who’s Everett?” I said out loud.

“Huh?” Herman stirred, half-turned towards me. “Everett?”

“Yes.”

“Theoretical physicist, twentieth century, quantum theory.”

“Oh.”

He turned back, settled down.

“Don’t worry about it,” he mumbled into his pillow, “doesn’t apply.”

“How do you mean?”

“Ahhh! It’s late. Tired. Tomorrow...”

None of which helped me sleep. I was still thinking about whether to get out of bed and go look it up when I found myself waking. Sleep had crept up on me, morning had come, Herman was already up and gone.

I flicked through my slab while drinking my morning coffee, trying to find out what I could about Everett.

I found it. I put down my coffee and called Marion. She answered.

“Marion! Everett! Many Worlds!”

She interrupted my babbling with a stern look and a raised eyebrow.

I drew a deep breath, swallowed.

“The addendum in Nouvier’s paper mentions ‘Everett’, OK? He was the one who first proposed the many-worlds interpretation of quantum mechanics. It says that there are enormous numbers of alternate realities. Every possible past or future is real.”

“And how is this relevant?”

“If Casimir shifts between realities when it jumps, that would explain everything.”

She flashed a smile. “Great imagination, you’ve been watching too much sci-fi. Chat about it later. See you in the bar.” As she reached to hang up her mouth turned down to a frown, even a grimace.

Ledermann had his head down, typing furiously on his keyboard when I entered. I stood and waited. After a couple of moments a finger pounded the full stop and he leaned back and looked up at me. “What can I do for you, Sam?”

I gave him the whole story. The CPUs, the telemetry, alternative realities. “We can’t launch Hawking,” I said, “until we understand what’s happening.”

“I’m going to tell you the same thing I told Marion. Hawking will launch on schedule in three months’ time. Stick to your job and stop speculating on things outside your area of expertise.”

“But the risk! He might never come back!”

He stood, he clenched his jaw, he leaned toward me, hands resting on the desk. “If you’re unwilling to do your job you are free to resign and return to Earth.”

Yeah, I was free to resign, but I’d still be bound by the non-disclosure agreement and there was the penalty clause in the contract.

She was already hunched over a beer when I got to the bar that evening.

“You get the talking to from Ledermann?” she said.

I nodded.

“He took Casimir’s CPUs, now they’ve cut off the telemetry. They’re trying to bury this.”

“Why are they so desperate to stick to the schedule?”

“Too much at stake. Nouvier wants to rub Garcia’s nose in it, since they refused to fund his FTL project.”

“Lost you.”

“When Lightstar arrives at Alpha Centauri, Herman will be there to greet the crew. He’ll be back with the pictures four years before them.”

Talk about stealing someone’s thunder. Marion’s brief moment of animation was over. She hunched forward again.

“So, what else?” I said, “what’s bugging you?”

“Everett. All possible histories and futures are real.”

I waited.

“Stupid,” she said. “Maybe in some other reality I’m still trying to get away from John.”

“John?”

“You know how lucky you are? You can look back and remember good times. Me, it’s only pain. He’s been dead two years and still he brings me pain.” She took a long drink, slammed the empty glass down.

I wanted to argue, I wanted to shout that I didn’t feel lucky, but looking at her face, I couldn’t.

Her chair creaked as she leaned back, face upward, eyes closed. “No. We were never both going to survive that.” Her voice long and drawn and low. “It was him or me.” She stood and clacked away without another word.

It was Herman’s turn to cook, we were at his apartment.

“Twice John Michaels and I crewed together. You get to know someone when you’re sharing a tin can in space for months.” Herman stirred as he spoke. “He was calm, quiet. Always seemed a reasonable guy on board, but he and Marion were toxic together. Shouting all the time—he wanted her to give up her career and raise kids, she wanted him to give up flying and stay at home where she could keep an eye on him.”

“How did he die?”

“They’d been fighting, he’d been drinking. Fell from a tenth-floor hotel balcony. Officially an accident, but suicide was suggested.”

Fell! I closed my eyes and counted to ten to suppress that image of the vertical face of a building, of an ice-crusted mountainside. When I opened them again Herman was there, a look of concern on his face. “You OK?”

Funny thing is, I was. I was fine. I kissed his cheek. “Is dinner ready?”

After we’d eaten he refilled my wine glass. “Can we talk about Everett?” I said as I picked it up, “what’s going on?”

He exhaled deeply. “What do you know?”

“For starters, that the Casimir that came back is from a different reality.”

“That was a surprise. The best theory Nouvier had was that so long as we didn’t return before we left, it would still be the same reality. He has a new theory now. Time is a local phenomenon, so is reality. Branching of the quantum multiverse propagates at the speed of light, cross the light-cone boundary and you’re in another reality.”

“What does that mean in practice?”

“Casimir travelled five light-weeks, the one that came back to us was from a reality that diverged from ours five weeks earlier. In that reality the CPU was replaced before launch.”

My brain jumped into overdrive. The Casimir we’d sent was stuck out there because we hadn’t changed the CPU, but that was one jump. The jump back again was another five weeks, and then there was the sequence of small jumps Casimir made as it homed in on TAU. They were only seconds long, not five weeks. Hawking was going to jump four years. Four years ago I’d just been widowed, I’d never heard of Almazir.

“You’ll come back to another reality,” I said. “The you that returns here could be from a reality where I never left Darmstadt.” He said nothing but his eyes told me he’d worked it out long ago. “But you’re going anyway.”

I left him then, heading back to my own apartment, turning it over as I walked. My last sight of my husband his pack was slung over one shoulder with the helmet, crampons, and ice-axe hanging from it. He was smiling, excited at his next challenge. As always I’d hidden my fear, buried my wish that he would find some less dangerous pastime. I could never have asked that of him; he’d already given up so much to follow me to Darmstadt. He’d never complained about it and they were good years we had together. By the time I was back in my apartment I was smiling to myself at those memories. Smiling, when before they’d have pulled me down into the depths of despair. My one regret was all the time we’d wasted planning for a future that never came. Then after I lost him my only thoughts were for the past. Lucky, Marion had called me. For a time I was, but if there was one lesson to learn it was that I had to start living in the present; the future only offered false promises.

The doorbell rang. I opened it.

“Things have changed since I first agreed to go.” Herman’s eyes roved from the floor to the door frame to the south wall of the habitat. “They can send someone else.”

I kicked him in the shin so he would look at me.

“Don’t be an idiot,” I said. He opened his mouth to speak. I didn’t let him.

The few short months before Hawking’s launch we spent together as much as we could. The thought that there were innumerable realities where we were doing the same was a comfort, even though there must be many more where things were very different. The letters were his idea. He wrote one to himself, for me to give to the Herman that returned. I wrote one for him to give to the Sam that he would meet. I gave him my address in Darmstadt in case I was still there, still a poor lost widow.

Launch day came too soon. I was allowed to join the small group that escorted him to Hawking’s bay. He gave me one last hesitant smile as the hatch closed.

Four weeks the mission was to last. Time for him to find and greet the crew of Lightstar. Everyone was relishing the shock that they would have. Everyone except me. It was the longest four weeks of my life. After Hawking was gone my work was done and my days were long and idle, every waking moment filled with apprehension, and too many waking moments. My thoughts turned to Marion and unanswered questions. Out of long-established habits I had avoided thinking about how her partner had died but the thought of falling no longer held such terror for me. I did some digging. Their names cropped up in media reports of the inquest in Miami. Witnesses reported sounds of an argument some time earlier, high levels of alcohol in his blood and hers. The coroner had been unable to reach a clear verdict as to whether he had fallen, jumped, or was pushed.

“It was him or me.” Those were Marion’s words to me. I didn’t know what she meant, and it was not my place to judge. We met a couple of times in the bar but she was more withdrawn than ever. Tight hair, furrowed brow, thin down-turned lips. Intense in her silence.

Hours before Herman was scheduled to return I was in the control room gallery, waiting. There was some uncertainty about exactly when and where Hawking would reappear; over such a distance, even a small imprecision makes hours of difference. They watched for Hawking’s beacon and I watched them, waiting, waiting, waiting. The scheduled time came and went and the lump in my throat grew tighter. Another hour. I squeezed my eyes closed, took a deep breath. I couldn’t stand any more. I gripped the arms of my seat intending to leave when a laconic voice drawled: “Beacon acquired.”

A cheer filled the room. I could feel the pulse racing in my neck, pounding in my temples. I gripped the chair arms tighter.

Ledermann spoke into his headset. “Hawking? Almazir station. Status, please.”

One second, two, three, and a voice echoed. “Hey, Almazir, good to be home, and have I got some pictures for you!”

I was enveloped in cold numbness. The world around me receded into a hazy distance, just like four years before when they told me I was a widow. The grief would come later but for now I sat in a detached stillness without thought or feeling. Watching. Ledermann pressed his hand to his earpiece and muttered into his microphone. Nouvier looked around at the flurry of activity, puzzled. Marion Michaels sat before her console head in her hands, shaking. She tore off her headset and ran from the room.

All I knew was that the voice was not Herman’s.

Alex Ledermann found me skimming stones on the lake. Herman had shown me how. From the southern shore, parallel to the axis where the line of the water surface is straight, and flick just at the right angle so that the coriolis force counters the bend in the trajectory on each bounce.

“I guess you’d rather be on your own now...” he said.

“Right.”

“... but we need your help.”

“Uh-huh!”

“You’re close to Marion Michaels, aren’t you?”

“Is anyone?”

“I mean...”

“I know what you mean. Get to the point.”

“We can’t find her, and the pilot...”

I stopped flicking stones, looked up at him.

“It’s John Michaels.”

He wanted me near to talk to Marion if she appeared so I accompanied him to the spire. Hawking had just docked when we got there. A group of figures pulled down the passage past Casimir’s bay. There with Nouvier and a couple of techs was a stranger, a dead man in a grubby flight suit.

Out of the corner of my eye I caught a movement: a technician in an oxygen mask with hands deep in an access panel in Casimir’s flank, her fair hair tied back tight: Marion. She stared at the group coming down the passage. The panel she had opened revealed the singularity containment. As soon as I saw her I knew what she intended, and why. John Michaels had brought her nothing but pain. It was him or me, she’d said.

In my mind it’s a succession of freeze frames. Marion, hands deep in Casimir’s flank, the group around John Michaels drifting down the passage towards me. Ledermann ahead of me, flying towards them, turning to look back when I shouted. Then the world turned bright white, then black.

I’ll be out of the infirmary soon, they say. I should make a full recovery, they say. The bones will knit, the burns will heal without too much scarring. She’d released the containment on Casimir’s singularity, not quite the damp firecracker she’d described. It blew out the bay, the passage, and everyone in it. Blew them all into the vacuum. Blew me back through the opening into the spire just as the emergency seal slammed down.

They found a letter amongst John Michaels’s effects, addressed to me, my handwriting on the envelope.

I haven’t opened it.