Greg Egan: Incandescence

The tunnel dipped and weaved erratically as it wound its way up. The wind was strong but steady, a nuisance but no great complication. Away from the well-trodden path that marked the easiest ascent, a riot of vegetation colored the light of the underlying rock. Roi resisted the urge to reach out and crush the inedible varieties; most of them had their uses, and as long as they didn't crowd out the food crops they deserved to be left to grow in peace. It was a familiar part of the winding down process to be aware of the weeds everywhere, without responding to the sight of them in the manner that was second nature when she was working.

The tunnel ended in a crowded chamber, where six routes leading up from the garmside edge converged. People were coming up out of the wind after finishing a variety of tasks, and while there was no need for most of these shifts to be synchronized, some kind of social cue seemed to have nudged the timing into a rather inconvenient lockstep. Roi recognized a few members of her own team crossing the chamber, but felt no desire to rejoin them.

At the edge of the flow of bodies a group of wretched males clung to the rock, begging to be relieved of their ripeness. Roi approached them to inspect their offerings. Each male had separated the two hard plates that met along the side of his body, to expose a long, soft cavity where five or six swollen globes sat dangling from heavy cords. Not all of the seed packets were plump and healthy, but Roi made a conscious effort not to be too finicky. With her own carapace split open along her left side, she used her mating claw to reach into the males' bodies, snip the globes free, and deposit them inside herself.

She stripped all the packets from the first three donors, and they shuddered with gratitude and disappeared into the crowd. When she took two globes from the fourth male and found that she was full, she muttered a few consoling words and left him wailing for further assistance.

The ripe seed packets secreted a substance that the males found extremely unpleasant, and while unplucked globes did shrivel up and die eventually, waiting for that to happen could be an ordeal. There were tools available for severing and discarding them, but that method was notoriously prone to spilling an agonizing dose of irritant. Something about a female's mating claw — something harder to mimic than its shape and its mechanical action — sealed the broken cord far more effectively than any tool.

As Roi continued across the chamber, a pleasant haze of contentment washed over her. The seed packets were battling for supremacy, but the poisons they were using against each other had a thoroughly positive effect on her. The battle was rendered more intense by a weapon of her own: a small quantity of crushed plant material that she replenished regularly. All of her competing suitors would die, valiantly trying to out-poison this thoroughly sterile rival.

Roi left the chamber by the least crowded route, intent now on finding a quiet crevice in which to recuperate. The wind would never fall completely silent unless she traveled all the way to the narrow calm space that divided the garmside from the sardside, but it wouldn't take long to reach some veins of less porous rock that offered a degree of shelter. There was no shelter from the geographical certainties of weight, but after so long working at the Splinter's edge she didn't need much lightening in order to feel unburdened.

Ahead of her, a lone male stood idle in the middle of the tunnel. He wasn't begging for help, and as she drew closer Roi could see that he carried no seeds. A moment later she recognized something else in his appearance: the visibly laboring heart of someone who'd ventured well beyond the weight he was accustomed to bearing.

The male was blocking the easiest way ahead, so Roi, undeterred by the weeds, climbed the tunnel wall to detour around him.

«It must be something simple,» he declared.

Roi paused courteously. «What must be, father?»

«Whatever underlies it all.»

«Of course.» Roi had no idea what he was talking about, so she could hardly dispute him.

She hesitated, then started to move on.

The male scrambled after her. «My name is Zak.»

«My name is Roi.» He was exerting himself valiantly to match her pace, but she took pity on him and slowed down a little. «I work among the crops, at the garm-sharq edge.»

Zak chirped approval. «Valuable work.»

Roi glanced behind them. If this was some kind of recruitment ambush, his team-mates were well hidden. «What do you do?»

«I doubt you will have heard of my task. In fact, lately I've been working alone.»

Roi didn't ask why he remained unrecruited; he was plainly quite old, and probably in poor health. Being stranded without team-mates was an unfortunate fate for anyone, but she had no power to change that for him. She certainly couldn't recruit him into her own team, in his condition.

«I spend a lot of time in the Calm,» Zak continued. «Near the Null Line.»

«I see.» Resting, hoping to recover from an illness? Or perhaps being weightless too long was the cause of his weakness. «Doing what?»

«Playing with some contraptions of mine. Trying to find something simple.»

«I don't understand. What is it you're looking for?»

Zak said, «I'm not sure. But I'll recognize it when I see it.»

They continued on in silence for a while. Roi didn't mind him accompanying her; he could hardly hijack her loyalty on his own, and she was relieved to see him heading for a level more conducive to his health.

«Do you ever wonder why we climb up to the Null Line from the garm and sard quarters,» Zak asked, «but down to it from the shomal and junub?»

«What is there to ponder?» Roi replied, amused. «That's just the way it is.» When Zak said nothing she added defensively, «Do you really think it's surprising? Any point you name must be above some places, and below others. So why shouldn't the four quarters be half and half?»

Zak said, «If you ascend to any other point and then continue on in the same direction, you cross between the two alternatives: the point that was originally above you is now below you. When you cross straight through the Null Line, that doesn't happen. If you go from garm to sard, the Null Line remains above you. If you go from shomal to junub, it remains below.»

Roi was tired, but she forced herself to concentrate. She might have let the matter drop for the sake of harmony, but something about Zak provoked her to disputation.

«At the Null Line you have no weight,» she said finally, «so there really is no up or down. That's the difference. If any other point stayed above you as you crossed through it, your weight would have to reverse suddenly, changing completely in a single step. At the Null Line it shrinks to nothing, so a change in direction is no change at all.»

«Exactly.» Her answer was clearly no revelation to Zak, but he sounded pleased that she'd made the effort to think it through. «That still doesn't explain the particular pattern, though. I can see no logical difficulty with a far simpler situation: our weight always pointing away from the Null Line, or always pointing toward it. Nor can I see any barrier to more complex arrangements. Why the four quarters? When you circle around the Null Line, why should it be above you, then below you, then above, then below? Why not six changes of direction, or thirty-six?»

Roi rasped annoyance. «And if it was thirty-six, you'd be asking why not four, or six.»

«Of course I would. But I don't believe it could ever be thirty-six.»

«You just told me you can see no reason why it shouldn't be!»

Zak said, «I can't see the reason yet. But four is small enough to point to something simple. If it was thirty, I could believe it might be thirty-six. Because it's four, though, I believe it must be four.»