Incandescence

struggled to remain calm; it was hard enough being weightless anywhere, but at least in the tunnels there’d been rock all around her to assuage the feeling that she was constantly falling. Here, out in the middle of the chamber with only Zak’s flimsy web to hold on to, the confusion and contradictions were starker. The fact was, Roi had no trouble supporting herself with the weakest of single-clawed grips, and even if she released that claw-hold accidentally she’d easily have time to regain it. She had probably never been in less danger of falling in her life. So why did the lack of weight, the very thing that guaranteed her safety, also make her feel that she was forever on the verge of being dashed against the walls of the chamber?

“Here at the Null Line, with no wind and no weight to confuse us, how do things move?” Zak took a stone from his carapace and tossed it gently away from them. “What do you see?”

Roi said cautiously, “As far as I can tell, that stone moved smoothly in a straight line until it hit the wall.”

“Good. I don’t expect you to be certain about anything from one crude experiment, but for the sake of argument let’s suppose that’s true: weightless things move smoothly in a straight line. And I’ll tell you something more from my own experience, which you can confirm for yourself when you feel more confident: once I’ve given myself a push and started moving across the chamber, it doesn’t matter how fast I make myself travel; except for the slight touch of the air passing over me I really can’t feel any difference. Weightlessness is weightlessness, as long as you’re moving smoothly, and the only thing that stops you moving smoothly is contact with a wall, or a wire.”

Zak led her to a small apparatus attached to the wire that marked the Null Line. It was a tube of susk cuticle, containing a spring with a stone at one end, much like the one she used to measure weights. Here, of course, the spring was unstretched, and the stone lay beside a mark on the tube that indicated no weight at all.

The end of the tube opposite the stone was attached to the wire by a small loop that allowed it to pivot. Zak flicked the tube and set it spinning, the free end sweeping out a circle while the other remained fixed. “What do you see?”

“The spring is stretched now,” Roi observed. “As if the stone had weight.”

“Yes.” Zak reached over and gave the tube another sharp tap, setting it moving faster. “And now?”

“It’s stretched even more. As if the weight had increased.”

“Good. Now let’s put some numbers to this.”

Zak took a sheet of cured skin from his carapace, and had Roi count while the tube spun around, to judge how quickly it made each revolution. Six times, they spun the tube and recorded both the time it took to complete a circle and the weight indicated by the stretching of the spring. A special kind of pointer that could only move one way under pressure from the stone made it possible to read the weight off the scale after the tube was brought to a halt; squeezing the pointer made it narrower and allowed it to be slid back, resetting the weight.

Zak said, “Multiply the weight by the time, and then by the time again.”

Roi stared at the skin, as if the answers might simply leap into her mind, but nothing happened. “I can’t do that,” she admitted. She understood the concept, but when it came to manipulating actual figures she had only been taught how to add and subtract. “None of my teams ever needed multiplication.”

“All right, don’t worry, I’ll teach you later.” Zak moved down the list of figures, rapidly scratching in the results. Although the individual times and weights varied greatly, the numbers produced by his calculation—weight by time, by time again—were all similar, all close to two hundred and seventy.

Roi was mystified. “Two hundred and seventy? What does that mean?”

“Nothing. Ignore the particular value, it’s just a measure of such things as how fast you count, and how we assign numbers to weights. The important thing is, we always get the same value, however fast or slow the stone is moving. There’s a rule here, there’s a pattern.”

“Not a very simple one,” Roi protested.

“Be patient.”

Zak modified the experiment, shifting the spring and the stone further along the tube, doubling the stone’s distance from the pivot. Six more times they spun the tube. When Zak calculated the same quantity again, it was no longer fixed around two hundred and seventy, but had doubled to five hundred and forty.

He repeated the experiment again, then again, each time with the spring shifted further.

“Now we divide by the distance. Weight multiplied by time, by time again, divided by distance.” All the numbers this new calculation produced were more or less the same, regardless of the distance from the pivot. By combining all the variables in this way, a constant value again emerged.

Roi had no idea why. She said, “Spinning the tube around gives the stone weight, I can understand that much. But these numbers.”

Zak replied, “Why does the stone acquire weight?”

She stared at the apparatus, and struggled to articulate the reason why this phenomenon hadn’t greatly surprised her. “A stone without weight moves in a straight line. This stone moved in a circle, so it couldn’t still be a stone without weight.”

“All right, that’s logical. But what made it move in a circle, when I struck it? As opposed to the one that flew straight across the chamber?”

“This one’s tied to a spring. The spring holds it back.”

“Exactly,” Zak said. “The spring forces it to follow a circle, frustrating its preference to move in a straight line. And the effort, the toll this takes on the spring, shows in the spring’s extension. Just as the effort it takes for the spring to keep the stone from falling, when they’re far from the Null Line, shows in the same way.”

Roi couldn’t see how this comparison explained anything. “The stone following a straight line is simple, for sure. So the spring has to fight to complicate the motion, to make it a circle instead. But what’s simple about all the different ways that stones fall, all around the Splinter? Keeping them still, keeping them from falling, seems much simpler to me.”

Zak chirped approval. “A fair comment. All I can do is ask for a little more patience.” He held up the skin. “This is where the numbers start to help us. You say the spring has to fight to complicate the motion of the stone, to bend it away from the straight line it would prefer to follow. How can we make that hypothesis precise, though?” He sketched the spring and the stone, then drew in a circle—the path that the stone actually followed—and a straight line, the path it would have followed had it not been tied down.

“How far would the stone travel in a count of one, if the spring wasn’t there?” Zak marked off a small section of the straight path. “And how far does it actually travel?” He marked a similar section of the circular path. “What is the difference?” He joined the two marks with a third line, an indication of how far the stone had deviated. “The length and direction of this line is a measure of the effort the spring needs to make, to pull the stone away from its natural motion into the path it actually follows. I call this a weight line, because that’s what it measures. I believe weight is nothing more than the difference between preferred and actual motion.”

“So where does the pattern in the numbers come from?” Roi demanded.

Zak said, “Think about the way the weight line changes as we change the two things we can alter in the experiment. If we make the distance from the stone to the pivot greater, everything I’ve drawn simply grows in proportion to that distance, including the weight line itself. But if we increase the time it takes for the stone to make one complete rotation, then the distance the stone would travel, or does travel, in a count of one gets smaller. However, not only do those two paths get shorter, the angle between them shrinks as well. So all in all, the separation of their endpoints—the weight line—shrinks in proportion to the rotational period multiplied by itself.

“The pattern in the numbers bears all of this out. The value I calculated reverses these two influences on the weight, canceling their effect, yielding a constant result.”

Roi found it difficult to follow the details of Zak’s calculations, but if she stepped back and looked at the overall picture, it was a startling idea. Weight is the difference between preferred and actual motion. What her body felt as it pressed against the floor of a tunnel was a kind of struggle against falling, a struggle she could only perform with the aid of the rock beneath her. What she felt now, the absence of that struggle, only seemed dangerous because in a more normal place any such lapse would be punished with serious injury if it lasted more than a heartbeat or two.

“All right,” she said. “The principle you’re asserting is simple enough, and I think I understand what’s happening with the spinning tube. How can this explain the pattern of weights across the whole Splinter?”

Zak said, “For that, we need another experiment.”