Stephen Baxter: Exultant

There was a punch in the small of his back, the ghost of hundreds of gravities as the Claw kicked its way out of the star’s gravity well.

The neutron star whipped away into darkness. The arch had already collapsed.

And in the last instant he glimpsed the Xeelee, behind him. No longer an implacable, converging foe, it was folding over, as if its graceful wings were crumpled in an invisible fist.

The Assimilator’s Claw hung in empty space, far from the neutron star. The crew tended their slight wounds, and tried to get used to still being alive. They saw to their ship’s systems; the encounter with the quagmites had done a good deal of damage to the GUTdrive.

And they reconstructed what had happened during those crucial moments at the magnetar.

At its heart the magnetic field embracing the flare had been as strong as any field since the first moments of the universe itself. At such field strengths atoms themselves were distorted, forced into skinny cylindrical shapes; no ordinary molecular structure could survive. Photons were split and combined. Even the structure of spacetime was distorted: it became birefringent, Pirius learned, crystalline.

It was this last which had probably done for the Xeelee. Nobody knew for sure how a nightfighter’s sublight drive worked. But the drive seemed to work by manipulating spacetime itself. In a place where spacetime crystallized, that manipulation could no longer work — but the Claw’s much cruder GUTdrive had kept functioning, despite the quagmites.

All that was straightforward enough. Just physics.

“But what I can’t get my head around,” Pirius told Dans’s Virtual, “is how you appeared out of nowhere, and squirted down the right evasive maneuver for us, based on a knowledge of the flare’s evolution before it happened.”

Dans said tinnily, “It was just an application of FTL technology. Remember, every FTL ship—”

“Is a time machine.” Every child learned that before she got out of her first cadre.

“I pulled away. Out of trouble, I watched the flare unfold, recorded it. I took my time to work out your optimal path — how you would have avoided destruction if you’d had the time to figure it out.”

Pirius said, “But it was academic. You got the answer after we were already dead.”

“And I had to watch you die,” said Dans wistfully. “When the action was over, the Xeelee out of the way, I used my sublight to ramp up to about a third lightspeed. Then I cut in the FTL.”

Cohl understood; “You jumped back into the past — to the moment just before we hit the flare. And you fed us the maneuver you had worked out at leisure. You used time travel to gain the time you needed to plot the trajectory.”

“And that’s the Brun maneuver,” Dans said with satisfaction.

“It’s some computing technique,” Cohl mused. “With the right vectors you could solve an arbitrarily difficult problem in a finite time — break it into components, feed it back to the source…”

Pirius was still trying to think it through. “Time paradoxes make my head ache,” he said. “In the original draft of the timeline, Claw was destroyed by the flare, and you flew away. In the second draft, you flew back in time to deliver your guidance, and then you — that copy of you — flew into the neutron star.”

“Couldn’t be helped,” Dans said.

He could see she was waiting for him to figure it out. “But that means, in this new draft of the timeline, we survived. And so you don’t need to come back in time to save us. We’re already saved.” He was confused. “Did I get that right?”

Hope said, “But there would be a paradox. If she doesn’t go back in time, the information that future- Dans brought back would have come out of nowhere.”

Cohl said, “Yes, it’s a paradox. But that happens all the time. A ship comes limping back from a lost battle. We change our strategy, the battle never happens — but the ship and its crew and their memories linger on, stranded without a past. History is resilient. It can stand a little tinkering, a few paradoxical relics from vanished futures, bits of information popping out of nowhere.” Cohl evidently had a robust view of time-travel paradoxes. As an FTL navigator, she needed one.

But Pirius’s only concern was Dans. “So can you save yourself?”

“Ah,” Dans said gently. “Sadly not. More than one Xeelee chased us after all. If I hadn’t hung around to work out your course I might have got away. I’m all that’s left, I’m afraid. Little pixellated me…”

“Dans” — Pirius shook his head — “you gave your life for me. Twice.”

“Yeah, I did. So remember.”

“What?”

She glared at him. “When you get back to Arches, leave my stuff alone.” And she popped out of existence.

For long minutes they sat in silence, the three of them in their blisters.

“Here’s something else,” Cohl said at last. “To get back to Arches from here we’ll have to complete another closed-timelike-curve trajectory.”

“A what?… Oh.” Another jump into the past.

“We’ll arrive two years before we set off on the mission.” She sounded awed.

Hope said, “I’ll meet my past self. Lethe. I hope I’m not as bad as I remember.”

“And, Pirius,” Cohl said, “there will be a younger version of Dans. A third version. Dans won’t have to die. None of this will be real.”

Pirius really did hate time paradoxes. “Time loops or not, we lived through this. We will remember. It’s real enough. Navigator, do you want to lay in that course?”

“Sure…”

Hope said dryly, “You might want to delay a little before kicking off for home, Pilot. Take a look.” He projected a Virtual into their blisters.

It was a shape, drifting in space. Pirius made out a slender body, crumpled wings folded. “It’s the fly,” he breathed.

Hope said, “We have to take it back to base.”

Cohl said, “We captured a Xeelee? Nobody ever did that before. Pirius, you said you wanted to make your name stand out. Well, perhaps you have. We’ll be heroes!”

Hope laughed. “I thought heroism is anti-Doctrinal?” Pirius brought the greenship about and sent it skimming to the site of the derelict. “First we need to figure how to grapple that thing.”

As it turned out — when they had got hold of the Xeelee, and with difficulty secured it for FTL flight, and had hauled it all the way back to the base in Arches Cluster — they found themselves to be anything but heroes.

This was the energetic heart of a large galaxy, a radiation bath where humans had to rely on their best technological capabilities to keep their fragile carbon-chemistry bodies from being fried. But to the quagmites it was a cold, dead place, in a dismal and unwelcoming era. The quagmites were survivors of a hotter, faster age than this.

They were drawn to the neutron star, for in its degenerate-matter interior there was a hint of the conditions of the warm and bright universe they had once known. But even here everything was frozen solid, comparatively. They were like humans stranded on an ice moon, a place where water, the very stuff of life, is frozen as hard as bedrock.

Still, every now and again there was a spark of something brighter — like the firefly speck which had come hurtling out of nowhere and skimmed the surface of the neutron star. The quagmites lived fast, even in this energy-starved age. To them the fractions of a second of the closest approach to the neutron star were long and drawn-out. They had plenty of time to come close, to bask in the warmth of the ship’s GUTdrive, and to feed.