Xeelee: An Omnibus: Raft, Timelike Infinity, Flux, Ring by Stephen Baxter Page A

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