Incandescence

„Once we can describe both speed and direction in the same framework, it makes sense to understand natural motion and spin as two aspects of the same thing. When an object is weightless, that means its velocity is simply following the geometry it encounters: there is no rock, no claw, pushing against it, so the only thing that can influence it is the way empty space itself is shaped. Similarly, when an object isn't spinning, the directions it carries with it must be following that same general rule. We know that the directions tied to the rock of the Splinter aren't following that rule, because of the swerve weight“ — the sideways weight of motion connected to the Splinter's spin—„that we see if we treat those directions as fixed. But I believe the directions tied to the frame of the Rotator obey the same laws as natural motion, and that is why we can declare that it's the Splinter that is spinning, not the frame, however compelling the opposite scenario must seem to a casual observer.“

In Tan's view, at every point in space and every moment in time it ought to be possible to summarise the effects of the local geometry with a simple mathematical rule for the way directions and velocities were „naturally carried“ along any given path. Zak had proposed that circular orbits around the Hub, with a certain period that depended on their size, comprised one form of natural motion. Tan wanted to find a single rule that could account for that, and also the behavior of the Rotator: a single template into which he could insert a direction or a velocity in order to calculate how much (if at all) it was changing, compared to the dictates of geometry. Feed in the Splinter's velocity, and the answer would be: this is natural motion, there is no change. Feed in the direction garm and the answer would be: this direction is constantly turning, at a certain rate, around the shomal-junub axis. Feed in any direction tied to the Rotator's frame, and the answer would be: there is no change.

If Tan's ideas were dizzyingly abstract, the next speaker proved to be an antidote. Bard had been a miner, searching out and extracting metal, and he had a bluntly practical approach to his new team's work that side-stepped speculation in favor of tangible results.

„We have no way of knowing exactly why the weights changed in the past,“ Bard declared. „The Splinter seems to have shifted closer to the Hub, but it isn't clear what made that happen. Was it a gradual effect, spread over many generations, or was there a sudden, violent change in the wind that forced us off our earlier path and into our present orbit?

«The wind on the garmside pushes us faster along our orbit, which tends to move us away from the Hub, while the wind on the sardside acts to slow us down and bring us closer to the Hub. If everything about the Splinter was perfectly symmetrical, the two influences would balance exactly. I doubt that the symmetry is perfect, but even if it's not, we've been unable to measure the consequences in the short time that this team has existed.»

«However,» he continued, «whether these dangerous shifts come slowly or quickly, it seems likely to me that the Splinter would be safer if we could move it further from the Hub. If we could reduce the weights, taking them back to the values they had before the last division, there would be a far greater margin for surviving any subsequent change.»

Zak interjected, «I agree with everything you've said, but how do you propose to move us?»

«We cut a tunnel,» Bard replied, «through the sardside. Maybe two or three tunnels. If the Splinter now feels roughly the same force from the wind on the garmside as it does on the sardside, we can shift the balance by letting some of the sardside wind pass right through, delivering no force.»

«If we empty out a tunnel on the sardside, won't that shift the center of the Splinter garmwards?» Ruz protested. «If the Calm moves garmwards, the sardside will grow larger.»

«We can move the rubble anywhere we like,» Bard countered. «We won't toss it out into the Incandescence. If we pack it into some small, empty tunnels that already lie sard of the excavation, the center of the Splinter will move sardwards, and it's the garmside that will grow.»

Bard unfurled a scroll of skin. He had drawn up a plan, which showed two tunnels piercing the Splinter from rarb to sharq.

Roi said, «The mouths will be open directly to the Incandescence! How could anyone survive working there?»

«For the final few spans we'll simply loosen the rock and then withdraw the workers,» Bard explained. «The wind itself will finish the job.»

«How wide will these tunnels be?» she asked.

Bard gave a noncommittal rasp. «As wide as possible. As wide as we can make them.»

«What's that going to do to the sardside crops?»