“Now you’re doing what I did, according to Jun Davd—thinking of the black hole only as a gravitational resource and not paying enough attention to whatever mischief it might be causing among all those close-packed stars and dust clouds.”
“Astronomers worry too much.”
“The centers of galaxies are active places. And this one’s more active than most. I’m not just thinking about radiation, I’m thinking about material particles. Are we going to be in danger?”
Jao sucked thoughtfully at his upper lip. The bushy gray mustache there was beginning to turn a faded orange. “Barring the chance of hitting a star or planet, our magnetic fields and our relativistic state of grace ought to do a pretty good job of protecting us. Do you have any idea of how much energy we’re carrying at this point? The universe is in more danger from us than we are from it!”
Bram refrained from smiling. “What about a dust particle?”
“Tear it apart. Whip it on through. Use it.”
“Can we handle that stew of radiation coming from the central parsec?”
“Handle it?” Jao snorted. “We’ll use it.”
Bram said nothing and waited. After a moment Jao flushed.
“All right,” he said. He squatted and scratched a diagram on the smooth wood of the floor with a stylus from his wrist pouch. Bram bent over to see.
There was an obtuse angle with a dot gouged at its vertex. Intersecting the dot was a shallow arc whose horns curved well forward of the dot to embrace the angle.
“This is us, here,” Jao said, tapping the dot. He traced the two lines forming the angle with his stylus. “Our umbrella is opened out to about this angle now, and it’ll keep opening out farther as we pick up speed. Theoretically, if we reached gamma infinity, the cone of the field would open all the way out to a flat disk, but the point is that the field thrives on anything that’s thrown at it. It all goes to feed the engine and make more gamma and a wider intake area. So we have nothing to worry about from up front. And from the rear, of course, all the dangerous wavelengths are dopplered down past the radio end of the spectrum by now.”
“And from the sides?” Bram prompted, though the answer was plain to see in the diagram.
Jao grinned hugely. “You’ve just taken a ride outside,” he said. “You saw for yourself how far forward the star-bow is displaced by now.” He tapped the two horns of the arc with his stylus. “By the time we hit the core, we’ll be snug within what amounts to a dopplered lens with a curvature that looks like this. Any hard radiation forward of the red-shifted meniscus intersects the nappe of the cone made by the field.”
“How long before we swing around the galactic center?”
“At the rate we’re picking up speed in this hydrogen soup, probably in the next few days.”
“Should I cancel Bobbing Day?”
“Don’t even whisper such a thing!” Jao exclaimed in mock horror. “I’ll try to slow us down as much as possible by avoiding the thickest parts of the H-II clouds. With any luck, we’ll squeak through Bobbing Day and All-Level Eve before Yggdrasil starts to squeak and groan.”
“And then?”
“Then we batten down.”
“How much longer can we broadcast the Message?”
“Let’s go see Trist and ask him.”
The Message Center was in the thickest part of the trunk, near the spreading root system, for maximum protection. It was, after all, the most important part of the treeship and the ultimate reason for the mission.
Bram looked down the length of the enormous cylindrical cavity, which was brilliantly lit by the abundant electrical power that was a by-product of the fusion drive. The circular tracks that had been worn all the way around the walls marched dizzyingly into the distance till they blended together. They had been scraped into the wooden surface over a period of time by the necessity of pushing thousands of pieces of heavy equipment another thirty degrees farther along every year.
The equipment itself—data banks, towering stacks of naked capacitors, oscillators, control elements for the thousands of phased array antennae planted in Yggdrasil’s crown and roots—made several broad avenues down the center of the chamber’s temporary floor, leaning crazily inward.
A work gang of young huskies had already started the next move, sweating and hauling at the heavy housings with levers, ropes, and their own backs and shoulders. It was a tremendous job once a year, but it was a lot easier than carting everything across space from bough to bough.
They found Trist in a control booth, eating a tomato sandwich with one hand and tracing geometric diagrams on a touch screen with the other. His face lit up with pleasure when he saw them.
“What brings you two to the upper depths?” he asked.
“We’re going around the bend a little earlier than we thought,” Jao said. “The skipper wanted a status report on the Message.”
Trist took a bite of his sandwich, then put it down. “We’ll be completing one last abbreviated cycle sometime later today, and I think that about finishes it.” He shrugged. “Of course, I’ll keep it going till we’re out of the galaxy. Beamed backward in the microwave frequencies. But it’ll be a very long shot, no pun intended.”
“Your signals have dopplered too far to be receivable, is that it?” Bram said.
“No, that’s not the real problem. Even with a gamma factor of twenty thousand, we’re still intelligible, pulse by pulse. The microwaves focused sternward lengthen into radio waves, and the long waves we send ahead of us compress into microwaves for anyone who happens to be listening on the radar frequencies. With the frequency continually adjusted for Doppler shift, of course. No, the trouble is the pulses are too far apart now because of time dilation. We’ve got a problem of information density.”
“How long is your abbreviated cycle?”
“Twenty days.” Trist grimaced. “We’re down to the genetic code for the Nar themselves, plus a minimum number of simple organisms from which a biologically sophisticated civilization might cobble together a supporting mini-ecology. Plus a Great Language module, of course. And a Small Language dictionary with human loan words. And a capsule history. And a highly abridged cultural package.” He peered at Bram. “We’ve got a touch symphony by your touch brother Tha-tha in the cultural package, by the way.”
Bram found himself looking past Trist, through the window of the control booth, at what he could see of the library. Miles of shelves, containing everything the Nar knew about themselves and their world. The old touch sagas were there, unintelligible to any race but the Nar. The message of Original Man was there in its entirety.
Not all of it could be broadcast, of course. But the Nar had wanted the departing humans to have it all. In the fullness of time, it might come in handy.
Out of it all, a Nar committee had prepared their Message. Or rather a series of Messages, progressively edited. The first took a year to broadcast. Now the Message was down to twenty days.
But if a touch symphony by Tha-tha was still included, then there must also be plans for a touch reader. A future generation of reincarnated Nar, here in the inner galaxy, might yet have access to a smattering of their heritage.
Jao was already figuring in his head. “Twenty days,” he said. “That works out to almost a thousand years for receiving it—with no repeats. The Message of Original Man had only a fifty-year cycle, and it was received by a very patient folk.” He shook his shaggy head. “I can see why you think the program’s finished, Trist.”
“And on our way out of the galaxy,” Trist said, “if our gamma’s up to what you say it’s going to be, we’ll have a Message cycle of close to four thousand years. With the tail out of range of the head.”