* * *
Despite all his doubts and questions, Rees found the shifts following his acceptance the happiest of his life. As a fully fledged apprentice he was entitled to more than Grye's grudging picture-book sessions; now he sat in classes with the other apprentices and learned in a structured and consistent way. For hours outside his class time he would pore over his books and photographs — and he would never forget an ageing picture buried in one battered folder, a photograph of the blue rim of the Nebula.
Blue!
The magical color filled his eyes, every bit as clear and cool as he had always imagined.
At first, Rees sat, awkwardly, with apprentices some thousands of shifts younger than himself; but his understanding progressed rapidly, to the grudging admiration of his tutors, and before long he had caught up and was allowed to join the classes of Hollerbach himself.
Hollerbach's style as a teacher was as vivid and captivating as the man himself. Abandoning yellowing texts and ancient photographs the old Scientist would challenge his charges to think for themselves, adorning the concepts he described with words and gestures.
One shift he had each member of the class build a simple pendulum — a dense metal bob attached to a length of string — and time its oscillation against the burning of a candle. Rees set up his pendulum, limiting the oscillations to a few degrees as Hollerbach instructed, and counted the swings carefully. A few benches along he was vaguely aware of Doav languidly going through the motions of the experiment; whenever Hollerbach's fierce eye was averted Doav would poke at the swinging bob before him, elaborately bored.
It didn't take long for the students to establish that the period of the pendulum's swing depended only on the length of the string — and was independent of the mass of the bob.
This simple fact seemed wonderful to Rees (and that he had found it out for himself made it still more so); he stayed in the little student lab for many hours after the end of the class extending the experiment, probing different mass ranges and larger amplitudes of swing.
The next class was a surprise. Hollerbach entered grandly and eyed the students, bade them pick up the retort stands to which their pendulums were still fixed, and beckoned. Then he turned and marched from the lab.
The students nervously followed, clutching their retorts; Doav rolled his eyes at the tedium of it all.
Hollerbach led them on a respectable hike, out along an avenue beneath the canopy of turning trees. The sky was clear of cloud today and starlight dappled the plates of the deck. Despite his age Hollerbach kept up a good pace, and by the time he paused, under open sky a few yards beyond the edge of the flying forest, Rees suspected that his weren't the only young legs that ached a little. He looked around curiously, blinking in the direct starlight; since beginning classes he had scarcely had a chance to come out this way, and the apparent tilt of the riveted deck under his feet felt strange.
Solemnly Hollerbach lowered himself to the deck plates and sat cross-legged, then bade his students do the same. He fixed a series of candles to the plates. "Now, ladies and gentlemen," he boomed, "I would like you to repeat your experiments of our last class. Set up your pendulum."
There were stifled groans around the class, presumably inaudible to Hollerbach. The students began work, and Hollerbach, restless, got up and paced among them. "You are Scientists, remember," he told them. "You are here to observe, not judge; you are here to measure and understand..."
Rees's results were... odd. As Hollerbach's supply of candles burned through he went over his results carefully, repeating and testing.
At last Hollerbach called them to order. "Conclusions, please? Doav?"
Rees heard the cadet's breathy groan. "No difference," he said languidly. "Same result curve as last time."
Rees frowned. That was wrong; the periods he had measured had been greater than yesterday's — by a small amount, granted, but greater consistently.
The silence gathered. Doav shifted uneasily.
Then Hollerbach let him have it. Rees tried not to grin as the old Scientist tore into the cadet's sloppy methods, his closed mind, his laziness, his lack of fitness to wear the golden braids. By the end of it Doav's cheeks burned crimson.
"Let's have the truth," Hollerbach muttered, breathing hard. "Baert...?"
The next apprentice supplied an answer consistent with Rees's. Hollerbach said, "Then what has happened? How have the conditions of this experiment changed?"
The students speculated, listing the effect of the starlight on the pendulum bobs, the greater inaccuracy of the timing method — Hollerbach's candles flickered far more out here than in the lab — and many other ideas. Hollerbach listened gravely, occasionally nodding.
None of it convinced Rees. He stared at the simple device, willing it to offer up its secrets.
At last the student Baert said hesitantly, "What about gravity?"
Hollerbach raised his eyebrows. "What about it?"
Baert was a slender, tall boy; now he rubbed his thin nose uncertainly. "We're a little further from the Raft's center of gravity here, aren't we? So the pull of gravity on the pendulum bob will be a bit less..."
Hollerbach eyed him fiercely, saying nothing. Baert flushed and went on, "It's gravity that makes the bob swing, by pulling at it. So if gravity's less, the period will be longer... Does that make sense?"
Hollerbach rocked his head from side to side. "At least that's a little less dubious than some of the other proposals I've heard. But if so, what precisely is the relationship between the strength of gravity and the period?"
"We can't say," Rees blurted. "Not without more data."
"Now that," Hollerbach said, "is the first intelligent thing any of you have said this shift. Well, ladies and gentlemen, I suggest you proceed to gather your facts. Let me know what you find out." He stood, stiffly, and walked away.
The students dispersed to their task with varying degrees of enthusiasm. Rees went at it with a will, and for the next few shifts scoured the deck, armed with his pendulum, notepad and supply of candles. He recorded the period of the pendulum, made careful notes and drew logarithmic scale graphs — and more; carefully he observed how the plane of the pendulum's swing formed various angles with the surface, showing how the local vertical was changing as he moved across the face of the Raft. And he watched the slow, uncertain oscillations of the pendulum at the Rim itself.
At last he took his findings to Hollerbach. "I think I have it," he said hesitantly. "The period of the pendulum is proportional to the square root of its length... and also inversely proportional to the square root of the acceleration due to gravity."
Hollerbach said nothing; he steepled liver-spotted fingers before his face and regarded Rees gravely.
At length Rees blurted, "Am I correct?"
Hollerbach looked disappointed. "You must learn, boy, that in this business there are no right answers. There are only good guesses. You have made an empirical prediction; well, fine. Now you must check it against the body of theory you have learned."
Inwardly Rees groaned. But he went away and did so.
Later he showed his findings on the strength and direction of the Raft's gravitational field to Hollerbach. "The way the field varies is quite complex," he said. "At first I thought it might fall off as the inverse square of the distance from the center of the Raft; but you can see that's not true..."
"The inverse square law holds only for point masses, or for perfectly spherical objects. Not for something shaped like a dinner plate, like the Raft."
"Then what is...?"
Hollerbach merely eyed him.
"I know," Rees sighed. "I should go and work it out. Right?"
It took him longer than the pendulum problem. He had to learn to integrate in three dimensions... and how to use vector forces and equipotential surfaces... and how to make sensible approximating assumptions.
But he did it. And when he'd done that, there was another problem. And another, and still another...
It wasn't all work.
One shift Baert, with whom Rees struck up a diffident friendship, offered Rees a spare ticket to something called the Theatre of Light. "I won't pretend you're my first choice companion," Baert grinned. "She was a bit better looking than you... But I don't want to miss the show, or waste a ticket."
Rees thanked him, turning the strip of cardboard over in his hands. "The Theatre of Light? What is it? What goes on there?"
"There aren't too many theatres in the Belt, eh? Well, if you haven't heard, wait and see..."
The Theatre was situated beyond the tethered forest, about three-quarters of the way to the Rim. There was a bus service from the Raft's central regions but Baert and Rees chose to walk. By the time they had reached the head-high fence which surrounded the Theatre the deck appeared to be sloping quite steeply, and the walk had become a respectable climb. Out here on the exposed deck, far from the cover of the forest canopy, the heat of the star above the Raft was a tangible thing, and both of them arrived with faces slick with sweat.
Baert turned awkwardly, slippered feet gripping at the riveted slope, and grinned down at Rees. "Kind of a hike," he said. "But it'll be worth it. Do you have your ticket?"
Rees fumbled in his pockets until he found the precious piece of cardboard. Bemused, he watched as Baert presented the tickets to a doorkeeper and then followed Baert through a narrow gate.
The Theatre of Light was an oval some fifty yards along its long axis, which ran down the apparent slope of the deck. Benches were fixed across the upper part of the Theatre. Rees and Baert took their places and Rees found himself looking down the slope at a small stage which was fixed on stilts so that it rested at the local horizontal — so at an angle to the "tilted" deck — and beyond the stage, serving as a mighty backdrop to the show, he could see the center of the Raft tip away, a vast metal slope of boxy buildings and whirling, rustling trees.
The Theatre filled up rapidly. Rees estimated there was room for about a hundred people here, and he shivered a little, uncomfortable at the thought of so many people in one place.
"Drinks?"
He turned with a start. A girl, luminously pretty, stood beside his seat with a tray of glasses. He tried to smile back and form an answer, but there was something odd about the way she was standing...
Without effort or discomfort she was standing perpendicularly to the deck; she ignored the apparent tilt of the deck and stood as naturally as if it were level. Rees felt his jaw drop, and all his carefully constructed reasoning about the illusory tilt of the deck evaporated. For if she was vertical then he was sitting at an angle with nothing at his back—
With a stifled yell he tumbled backwards.
Baert, laughing, helped him up, and the girl, with an apologetic smile, presented him with a tumbler of some clear, sweet beverage. Rees could feel his cheeks burn like stars. "What was all that about?"
Baert suppressed his laughter. "I'm sorry. It gets them every time. I should have warned you, really..."
"But how does she walk like that?"
Baert's thin shoulders moved in a shrug. "If I knew it would spoil the fun. Magnetic soles on her shoes? The funny thing is, it's not the girl that knocks you over... It's the collapse of your own perceptions, the failure of your sense of balance."
"Yeah, hilarious." Rees sucked sourly at his drink and watched the girl move through the crowd. Her footsteps seemed easy and natural, and try as he might he failed to see how she kept her balance. Soon, though, there were more spectacular acts to watch. Jugglers, for instance, with clubs that swooped and soared in arcs at quite impossible angles, returning infallibly to their owners' hands.
During applause Rees said to Baert, "It's like magic."
"Not magic," the other said. "Simple physics; that's all there is to it. I guess this is making your miner's eyes pop out, eh?"
Rees frowned. On the Belt there wasn't a lot of time for juggling... and no doubt the labor of the miners was going to pay for all this, in some indirect fashion. Discreetly he glanced around at the rest of the audience. Plenty of gold and crimson braid, not a lot of black or the other colors. Upper Classes only? He suppressed a stab of resentment and returned his attention to the show.
Soon it was time for the main feature. A trampoline was set up to cover the stage and the crowd grew hushed. Some wind instrument evoked a plaintive melody and a man and a woman dressed in simple leotards took the stage. They bowed once to the audience, climbed onto the trampoline, and together began to soar high into the starlit air. At first they performed simple manoeuvres — slow, graceful somersaults and twists — pleasing to the eye, but hardly spectacular.
Then the couple hit the trampoline together, jumped high, met at the top of their arcs — and, without touching, they twisted around each other, so that each was thrown wide.
Baert gasped. "Now, how did they do that?"
"Gravity," Rees whispered. "Just for a second they orbited around each other's center of mass."
The dance went on. The partners twisted around each other, throwing their lithe bodies into elaborate parabolae, and Rees watched through half-closed eyes, entranced. The physicist in him analyzed the dancers' elaborate movements. Their centers of mass, located somewhere around their waists, traced out hyperbolic orbits in the varying gravity fields of the Raft, the stage and the dancers themselves, so that each time the dancers launched themselves from their trampoline the paths of their centers were more or less determined... But the dancers adorned the paths with movements of their slim bodies so deceptively that it seemed that the two of them were flying through the air at will, independent of gravity. How paradoxical, Rees thought, that the billion-gee environment of this universe should afford humans such freedom.
Now the dancers launched into a final, elaborate arc, their bodies orbiting, their faces locked together like facing planets. Then it was over; the dancers stood hand-in-hand atop their trampoline, and Rees cheered and stamped with the rest. So there was more to do with billion-strength gravity than measure it and fight it—
A flash, a muffled rush of air, a sudden blossom of smoke. The trampoline, blasted from below, turned briefly into a fluttering, birdlike creature, a dancer itself; the dancers, screaming, were hurled into the air. Then the trampoline collapsed into the splintered ruins of the stage, the dancers falling after it.
The audience, stunned, fell silent. The only sound was a low, broken crying from the wreckage of the stage, and Rees watched, unbelieving, as a red-brown stain spread over the remains of the trampoline.
A burly man bearing orange braids hurried from the wings and stood commandingly before the audience. "Sit down," he ordered. "No one should try to leave." And he stood there as the audience quietly obeyed. Rees, looking around, saw more orange braids at the exits from the Theatre, still more working their way into the ruins of the stage.
Baert's face was pale. "Security," he whispered. "Report directly to the Captain. You don't see them around too often, but they're always there... undercover as often as not." He sat back and folded his arms. "What a mess. They'll interrogate us all before they let us out of here; it will take hours—"
"Baert, I don't understand any of this. What happened?"
Baert shrugged. "What do you think? A bomb, of course."
Rees felt an echo of the disorientation he had suffered when the drinks girl had walked by. "Someone did this deliberately?"
Baert looked at him sourly and did not reply.
"Why?"
"I don't know. I don't speak for those people." Baert rubbed the side of his nose. "But there's been a few of these attacks, directed against Officers, mostly, or places they're likely to be. Like this.
"Not everyone's happy here, you see, my friend," he went on. "A lot of people think the Officers get more than their share."
"So they're turning to actions like this?" Rees turned away. The red-stained trampoline was being wrapped around the limp bodies of the gravity dancers; he wa
tched with an unshakeable sense of unreality. He remembered his own flash of resentment at Baert, not more than an hour before this disaster. Perhaps he could sympathize with the motives of the people behind this act — why should one group enjoy at leisure the fruits of another's labor? — but to kill for such a reason?
The orange-braided security men began to organize strip searches of the crowd. Resigned, not speaking, Rees and Baert sat back to wait their turn.
* * *
Despite isolated incidents like the Theatre attack Rees found his new life fascinating and rewarding, and the shifts wore away unbelievably quickly. All too soon, it seemed, he had finished his Thousand Shifts, the first stage of his graduation process, and it was time for his achievement to be honored.
And so he found himself sitting on a decorated bus and studying the crimson braids of a Scientist (Third Class), freshly stitched to the shoulder of his coverall, and shivering with a sense of unreality. The bus worked its way through the suburbs of the Raft. Its dozen young occupants, Rees's fellow graduate-apprentices, spun out a cloud of laughter and talk.
Jaen was studying him with humorous concern, a slight crease over her broad nose; her hands rested in the lap of her dress uniform. "Something on your mind?"
He shrugged. "I'm fine. You know me. I'm the serious type."
"Damn right. Here." Jaen reached to the boy sitting on the far side from Rees and took a narrow-necked bottle. "Drink. You're graduating. This is your Thousandth Shift and you're entitled to enjoy it."
"Well, it isn't precisely. I was a slow starter, remember. For me it's more like a thousand and a quarter—"
"Oh, you boring bugger, drink some of this stuff before I kick you off the bus."
Rees, laughing, gave in and took a deep draught from the bottle.
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