Donald Moffitt - Genesis 01

It’s because only by diving straight through the interior of the galaxy, where the H-II regions are thickest, we can scoop up enough ionized gas to build up our gamma factor to the point we need. We also get a bonus. We pick up some of the rotational energy of the galactic core itself when we whip around it. By the time we head out of the galaxy, we’ll be traveling at a speed of—” His eyeballs rolled back in his head while he mumbled figures to himself. “—call it a fraction of the speed of light represented by a decimal point followed by ten nines. Apply the relativity equations and anyone can see that’ll give us a gamma factor of about seventy thousand.”
    Ang, the blonde girl from the string quartet, was part of the group listening to Jao. She was leaning forward with an adoring expression on her face. Jao winked at her.
    “Excuse me,” someone ventured timidly, “but what do those figures mean?”
    “What do they mean?” Jao bellowed in outrage. ‘They mean that while the outside universe ticks off thirty-seven million years, we make the crossing between galaxies in only about five hundred years, our time.”
    “Plus the detour through the center of the galaxy,” someone pointed out.
    Jao decided his questioners were hopeless. “The detour will only add about another forty years of subjective time to the journey,” he said, spacing his words carefully. “And if you don’t like it, I might as well warn you that we’ll have to perform the same maneuver at the other end in order to brake. Fortunately, the Milky Way’s a good match in mass and configuration.”
    “Still,” his listener demurred, “that’s a long time for a bunch of people to spend shut up in a spaceship.”
    “Want me to skip the detour?” Jao growled. “Fine. How would you like me to drop a couple of nines off that string of figures I mentioned? That’d give us a gamma factor of—” Again, the eyes rolled back. “—seven oh seven point one. And you could spend fifty thousand years twiddling your thumbs while we make the crossing.”
    “He has a point, Jao,” Bram said. “No matter how big we build this ramjet—and I’m assuming it might be as big as Lowstation—won’t it be rather close quarters?”
    “Yes,” Jao’s blonde admirer said. “What about that?”
    Jao scowled, clearly stung by the criticism. He thought hard for a moment or two, then a beatific expression crossed his face. “Why not?” he mumbled to himself.
    He turned to them with a broad smile. “We’ll travel in style,” he said. “We’ll live in a tree.”
     

Prologue Two

EXODUS
     
    The passengers who came crowding onto the bridge at the pilot’s invitation were mostly elderly. But they all seemed to be in marvelous health, and they were quite as lively and eager as the younger people among them as they grabbed safety lines and hauled themselves to the viewports for a look at their destination.
    A handsome, erect old man of about seventy, with deep-etched features and an impressive white mane, took the elbow of the trim, gray-haired woman beside him and steadied her as she took her turn at the port.
    “There it is, Mim,” he said. “Our home for the next five hundred years.”
    She drew closer to him. “Oh, Bram!” she said. “It’s beautiful!”
    The star tree floated in space before them, looking like a perfect green globe. From the cargo vessel’s angle of approach—head on toward the center of the crown—the matching ball of root growth could not be seen, nor could the stubby trunk which connected them.
    Hanging beside the green puff was a brassy skewer with a trumpet end—Jao’s hydrogen-scooping robot vehicle. The flaring bell looked solid enough from a distance, but Bram knew it was as insubstantial as gossamer. It was hundreds of miles in diameter and had to spin to maintain its shape. Still, its electromagnetic fields would shield the tree from the howling storm of radiation into which it would sail at near-light speeds, and the tree’s own reflective leaves, bred to handle anything up through X-rays, would take care of stray ionization—and even soak up the energy and use it.
    Space tugs—tiny motes to the eye—were maneuvering to haul an enormous crystalline tether whose colossal links were forged of viral monofilament; the probe’s long shaft would be threaded between the tree’s two hemispheres at right angles to the hidden trunk. At relativistic speeds, the probe would tow the tree; for