Donald Moffitt - Genesis 01

later, the ferry caught up with its target, and Bram caught his first glimpse of Lowstation.
    It was a gigantic hexagon some two thousand feet across, suspended in the blackness and turning with slow deliberation. In the naked vacuum of space it showed stark and clear. He could easily pick out the lines of the main timbers where the sheathing material had been seamed to them.
    Lowstation was a real antique—one of the first of the wood-framed space stations to be built after the Nar had acquired the code for the poplar genome from Original Man. It had started life as an equilateral triangle with thousand-foot sides. Even then, it had given good service with temporary environmental shells attached at the three points. Five identical triangles had been knocked together out of additional thousand-foot timbers floated in from the nursery wheel that grew them. Then the six wedges had been fitted together, and Lowstation was in business—still skeletal, to be sure, but starting to enclose itself a little at a time.
    In those days, they had still bothered to square off the timbers, in imitation of man, and that had been the biggest part of the job. Even so, assembling large space structures from ready-made framing elements that could theoretically be miles in length was still easier and cheaper than lofting flimsy plastic girders into orbit from the planetary surface.
    Poplar had not been much used as a building material on that long-vanished planet of man. Hardwood had better lateral strength and made better posts and beams. But poplar had one advantage: It grew fast and it grew straight, provided that it didn’t have to compete for its little piece of sky.
    It grew even faster in the low simulated gravity of a space wheel, and it grew just as straight: pointing itself at the hub along the lines of force. In a closed spoke of such a wheel, provided with air, water, and sunlight, its ultimate height was limited only by the radius of the wheel.
    Tensile strength is more important than rigidity in space construction, anyway, and a poplar trunk certainly could not be pulled apart by the usual one-g forces; plastic girders, assembled in segments, were more likely to do that. In fact, the poplar’s relative elasticity, adjusting to longitudinal stress, was an advantage.
    Later, the Nar learned to grow curved beams for arches and the curved perimeters of space wheels. You simply enclosed a wedge of a space wheel and moved a tubbed sapling in gradual stages along a straight floor that made a chord along the curved perimeter. The poplar, always yearning for the hub, would keep changing its direction of growth.
    Man, it was known from the records, had made wood-framed space stations and other structures the norm by the end of his twenty-first century. Even the larger ships used for intrasystem voyaging were wooden vessels fitted out with rocket units. For man, the space-grown poplar had brought about an era of cheap interplanetary expansion. And for the Nar, in the early stages of their own space age, it had done the same. But man had never taken the next obvious step. To teach the poplar tree to live and grow in vacuum.
    He would have been surprised to learn what the Nar had done with his gift.
     
    “Please fasten your harnesses,” the Nar attendant said gently from his pedestal in the center of the transfer vehicle’s oval cabin. “We will begin to decelerate shortly.”
    An obedient rustle of movement ran around the circlet of seats lining the cabin. A few adventurous souls who had been swimming in midair—to the annoyance of their fellow passengers—hauled themselves back to their seats along the lines they had been clipped to.
    The attendant waited until everybody had settled and announced: ‘Tm afraid that there will not be much to see during most of the approach, since we will of course be decelerating floor first.”
    There was a groan of disappointment from the passengers. The attendant, with a sympathetic swirling of arms, continued. “But our pilot has promised to invert us briefly at some point between deceleration thrusts so that, for a few minutes at least, you should have a fine overall view of the tree through the overhead dome.”
    Bram turned to Kerthin in the seat beside him. “Won’t that be marvelous?” he asked.
    She nodded without answering. She had regained her color, Bram was glad to see. The trip in the ferry up to Lowstation had been the worst part of it for her. The paneled corridors and