Poul Anderson - Tau Zero

“You can distinguish thatmuch detail already?” Reymont wondered; “Boudreau couldn’t.”

“I told you I have new equipment, with its balkiness now tinkered out,” Nilsson said. “You recollect that after Ingrid gave me some special lessons, I became able to work in free fall with a degree of efficiency. The precision of my data seems even more than hoped for when, ah, we instigated the project. Yes, I have a reasonably accurate map of that part of the clan which we might traverse. On such basis, I have calculated what options are open to us.”

“Get to the point. God damn you!” Reymont yelled. At once he curbed himself, inhaled, and said: “Apologies. I’m a little overwrought. Please go on. Once we get in where the jets have a decent amount of matter to work on, why can’t we brake?”

“We can,” Nilsson replied quickly. “Certainly we can. But our inverse tau is immense. Remember, we acquired it by passing through the densest attainable portions of several galaxies, en route to interclan space. It was necessary. I don’t dispute the wisdom of the decision. Nevertheless, the result is that we are limited in what paths we can take that intersect the space occupied by this clan. The paths form a rather narrow conoidal volume, as you might guess.”

Reymont gnawed his lip. “And it turns out there doesn’t happen to be enough matter in that cone.”

“Correct.” Nilsson’s head bobbed. “Among other things, the difference in velocity between us and these galaxies, due to the expansion of space, reduces the effectiveness of our Bussard engine more than it reduces the amount of deceleration required.”

His professorial manner was returning to him: “At best, we will emerge on the other side of the clan — after an estimated six months of ship’s time under deceleration, mind you — with a tau that remains on the order of ten to the minus third or fourth power. No further important change of velocity can be made in the space beyond, interclan space. Hence it would be impossible for us to reach another clan — given that high a value of tau — before we die of old age.”

The pompous voice cut off, the beady eyes looked expectant. Reymont met them rather than Telander’s sick, gutted stare. “Why am I being told this, and not Lindgren?” he asked.

A tenderness made Nilsson, briefly, another man. “She works cruelly hard. What can she do here? I thought I had best let her sleep.”

“Well, what can I do?”

“Give me … us … your advice,” Telander said.

“But sir, you’re the captain!”

“We have been over this ground before, Carl. I can, well, yes, I suppose I can make the decisions, issue the commands, order the routines, which will take us crashing on through space.” Telander extended his hands. They trembled like autumn leaves. “More than that I can no longer do, Carl. I have not the strength left. You must tell our shipmates.”

“Tell them we’ve failed?” Reymont grated. “Tell them, in spite of everything we did, we’re damned to fly on till we go crazy and die? You don’t want much of me, do you, Captain?”

“The news may not be that bad,” Nilsson said.

Reymont snatched at him, missed and hung with a raw noise in his throat. “We have some hope?” he managed finally.

The fat man spoke with a briskness that turned his pedantry into a sort of bugle call: “Perhaps. I have no worthwhile data. The distances are too vast. We cannot choose another specific galactic clan and aim for it. We would see it with too great an inaccuracy, and across too many millions of years” of time. However, I do believe we can base a hope on the laws of chance.

“Someplace, eventually, we could meet the right configuration. Either an especially large clan through whose galaxy-densest portions we can lay a course; or else two or three clans, rather close to each other, more or less along a straight line, so that we can pass through them in succession; or else one whose velocity with respect to us happens to be favorable. Do you see? If we could come upon something like that, we would be in reasonable shape. We would be able to brake in a few years of ship’s time.”

“What are the odds?” Reymont’s words clanked.

Now Nilsson shook his head. “I cannot say. Perhaps not too bad. This is a big and varied cosmos. If we continue sufficiently long, I should imagine we have a finite probability of encountering what we need.”

“How long is sufficiently long?” Reymont made a gesture to halt. ‘‘don’t bother answering. I can tell. It’s on the order of billions of years. Tens of billions, maybe. That means we’ve got to have a lower tau yet. A tau so low that we can actually circumnavigate the universe … in years or in months. And that, in turn, means we can’t start slowing as we enter this clan up ahead. No. We accelerate again. After we’ve passed through — well, we should have a shorter period of ship’s time in free fall than the current one has been, until we strike another clan. Probably there, too, we’ll find it advisable to accelerate, running tau still lower. Yes, I know, that makes it still harder to find a place where we can come to rest; but anything else gives us no measurable chance at all, right?”

“I expect we’ll be taking every opportunity to accelerate that we come upon, till we see a journey’s end we can make use of, if we ever do. Agreed?”

Telander shuddered. “Can any of us hold to it?” he said.

“We must,” Reymont stated. Once more he spoke crisply.’TU figure out a tactful way to announce your news. It was among the possibilities that have been discussed by nearly everyone. That helps. I’ll have the few men I can trust ready … no, not for violence. Ready with leadership, steadiness, encouragement. And we’ll embark on a general training program for weightlessness. No reason why it has to cause trouble. We’ll teach every last one of those groundlub-bers how to handle himself in zero gee. How to sleep. By God, how to hope!” He smote his palms together with a pistol sound.

“Don’t forget, we can depend on some of the women too,” Nilsson said.

“Yes. Certainly. Like Ingrid Lindgren.”

“Like her indeed.”

“M-hm. I’m afraid you will have to go rouse her, Elof. We’ve got to assemble our cadre — the unbreakables; the people who understand people — assemble them and plan this thing. Start suggesting names.”

The reaches of space-time cannot be numbered by man’s familiar integers; They cannot even be honestly counted by orders of magnitude. To feel this fact, recapitulate:

Leonra Christine spent most of a year getting within 1 per cent of light velocity. The time aboard was about the same, because the value of tau only began to drop sharply when she was quite near c . During that initial period, she covered half a light-year of space, approximately five trillion kilometers.

Thereafter the decrease became constantly more swift. Aided by the higher acceleration now possible, she required somewhat under two more years, in her own measure, to get about ten light-years from Earth. That was where she met her grief.

The decision being made to seek the Virgo cluster of galaxies, she must gain such a tau that she could bridge the distance in a tolerable shipboard time. At maximum acceleration — a maximum which increased as she traveled — she swung half around the Milky Way and into its heart in a little more than one year. According to the cosmos, it took better than a hundred millennia.

In the Sagittarian clouds, she won a tau which brought her out of her native galaxy in days. Then her people discovered that the vacuum between the family of star groups they were in and the Virgo assemblage at which theirplans were aimed, was not hard enough. They must go beyond the entire clan.