And popping up through the murky atmosphere was a shower of orange sparks.
An alarm went off. Jun Davd picked up the interphone, said “I see them,” and hung up.
Bram was already busy at the computer touch board. Jun Davd leaned over his shoulder to see what he was entering, nodded approval, and started feeding in supplementary data from the tree’s sensors.
“What can they hope to accomplish?” Bram whispered when the answer appeared on the screen. “At best they’ve matched roughly for our present velocity. Those vehicles could be waiting for us in our projected flight path if we stopped accelerating in the next decihour. But we’re still boosting. They’ll only end up behind us, like the others, and get themselves vaporized in our drive exhaust.”
“Then they must expect us to stop accelerating,” Jun Davd said.
“Missiles,” exclaimed Alis Tonia Atli, then had to explain the specialized meaning of the word from her knowledge of twentieth-century earth history.
“No,” Jun Davd said. “We’d have seen them by now. At any rate, they wouldn’t do much better at catching us than those piloted craft. It has to be something faster.”
“A fusion exhaust,” said Dal. “Remember how reckless they were with it around the diskworld? They might not quail at using it this close to home. And they might not realize Yggdrasil’s combustible. If all they want to do is kill the probe and stop us, they. wouldn’t mind turning us into a ball of slag. We’d be another moon to settle on—bigger than most of those they use.”
“There’s nothing the size of their interstellar ship in orbit,” Jun Davd said. “I’m sure they launch them as soon as they make them. The largest objects I see in orbit are those bulky cylindrical structures attached to mirrors—” He stopped.
“Light,” Bram said. “Light would be fast enough.”
Jun Davd looked shaken. “I thought they had something to do with solar power. I can see that even now we don’t fully understand these creatures. They’ve mounted laser defenses against unwanted colonization by their brethren on Earth.”
Even as he spoke, the laser beams struck Yggdrasil. There was a flickering of images on the big screen as some of the antennae elements dispersed across Yggdrasil’s crown burned out, then the computer redistributed data to compensate. Bram saw the beams, hundreds of them, sending their threads of light through space in a complex skein that focused on Yggdrasil. The computer had assigned different colors to the threads to distinguish the types of lasers—violet, red, blue, green, magenta, and a deadly gray to represent x-rays.
One of the visitors went into hysterics, a little round man who was calmed by two women and given a glass of water.
Bram reached for the interphone before he remembered that he was no longer year-captain. He turned to Jun Davd. “Somebody should get Enyd to rotate the tree—distribute the heat absorption. Even though we’re boosting, another few percent of g wouldn’t—”
“We needn’t bother,” Jun Davd said. “We couldn’t get rotation started fast enough. Besides…”
He trailed off, looking thoughtful.
The tree continued to accelerate. One of the women with the hysterical man said soothingly, “See, we’re still going.”
“The sensitive part of the ramjet shaft’s in the umbrage of the leaves at this angle,” Jun Davd said. “And as for the leaves themselves, our sensors haven’t yet detected any fires.”
He was trying to suppress a smile. He gave up the effort and let his long face split in a big grin.
Bram took the call from Smeth when it came. He listened briefly, then hung up and addressed the expectant throng.
“Smeth wanted to warn us that we’re all a few pounds heavier—but I’m sure you’ve all noticed that already. The laser beams are giving us a small additional boost—enough to take a little of the load off the ramjet and turn more of its work into acceleration.”
A few of the people looked puzzled. Bram drew a breath and said, “Yggdrasil thrives on light. Up to and including x-rays—the Nar found space trees happily in orbit around x-ray stars.”
He added his own grin to Jun Davd’s. “When Yggdrasil felt things getting a little too hot, it turned its leaves reflective side out, in the lightsail mode. The dragonflies will take a while to realize it, but they’re helping to speed us out of their system.”
An hour later, they watched the second fleet of dragonfly ships fall into the consuming flame of the drive beam. Long before then, the lasers had been switched off.
As Yggdrasil sped past the orbit of the planet that had been called Pluto, Jun Davd sought Bram out during an intermission at one of Edard’s concerts. It was a Tenday later, and life in the tree was returning to normal. “The next time we meet them,” Jun Davd said, “they may be more advanced.”
“Then we’ll have to go far enough to be sure we won’t meet them,” Bram said.
Jun Davd did not reply directly. “Trist is looking for volunteers to help repair the antenna system,” he said.
“What’s the hurry? We don’t have a Message to broadcast anymore.”
“No. But we’d better start listening.”
Seven years of listening had taken their toll on Trist. He had the same ready smile, the same willingness to banter. But his ice-blue eyes had acquired something of the haunted look that Bram remembered from the years when Trist had monitored the spread of Nar civilization through the Whirlpool galaxy—until the wave of radiation from the exploding core had put a stop to the radio emissions forever.
Trist had monitored the Nar emissions for fifty thousand years. He had listened to the spread of dragonfly civilization for only fifty-odd years—about seven years in terms of tree time. But his eyes had aged at the same rate as the outside universe, Bram thought.
Trist looked up from his console as Bram entered the control booth. The Message Center had been stripped of its library over the centuries, as the archivists had gradually integrated its contents with the growing central databank. But its equipment—the leaning stacks of power and control elements that made long avenues down the cylindrical cavity—had been left intact and placed at the service of the astronomy department.
“They’ve reached Aldebaran now,” he said before Bram could speak.
“Red giant,” Bram said, searching his memory. “With a companion.”
“It’s a white dwarf now,” Trist said. “The dragonflies have settled both components. They’re not very fussy. Outer planets of the dwarf would be pretty cold but that wouldn’t bother the kind of creatures who settled Pluto. Any inner planets, if they survived the red giant phase and resolidified, wouldn’t be much more habitable. Airless slagballs.”
“How far?” Bram asked.
“About sixty light-years from Sol. It was one of the stars that stayed in the same neighborhood.”
A crawling sensation went down Bram’s spine. “Their technology’s improving. They’re spreading outward at about half the speed of light.”
Trist nodded. “Since we first met them at Delta Pavonis, the sphere of space they occupy has grown to a diameter of nearly one hundred twenty light-years. At this rate, it will take them only two hundred thousand years to overrun the entire galaxy.”
“Jun Davd said that we could flee to the opposite ends of the Milky Way and find them waiting for us.”
“If they learn how to attain relativistic speeds any time in the next few centuries, yes.” Trist was gloomy. “And if they don’t, they could come calling fairly soon, anyway.”
“The nearest large galaxy is two million light years away. Andromeda, former man called it.” Bram swallowed hard as he remembered the first breathtaking sight he’d had of the Milky Way’s sister galaxy, centuries ago, as a child at the observatory with Voth. “At one g, we could be there in thirty years, our time.”