Tau Zero

“What is the subject?” Reymont added.

“Matter density in space before us,” Boudreau said. “Within this galaxy, between galaxies, between whole galactic clusters. Given our present tau, the frequency shift of the neutral hydrogen radio emission, the instruments already built by the astronomical team obtain unprecedented accuracy.”

“What have they learned, then?”

Boudreau braced himself. “The gas concentration drops off slower than we supposed. With the tau we will probably have by the time we leave the Milky Way galaxy … twenty million light-years out, halfway to the Virgo group … as nearly as can be determined, we will still not dare turn off the force fields.”

Telander closed his eyes.

Reymont spoke jerkily: “We’ve discussed that possibility in the past.” The scar stood livid on his brow. “That even between two clusters, we won’t be able to make our repair. It’s part of the reason why Fedoroff and Pereira want to improve the life support systems. You act as if you had a different proposal.”

“The one we talked about not long ago, you and I,” Boudreau said to the captain.

Reymont waited.

Boudreau told him in a voice turned dispassionate: “Astronomers learned centuries’ back, a cluster or family of galaxies like our local group is not the highest form in which stars are organized. These collections of one or two dozen galaxies do, in turn, tend to occur in larger associations. Superfamilies—”

Reymont made a rusty laugh. “Call them clans,” he suggested.

“Hein? Why … all right, A clan is composed of several families. Now the average distance between members of a family — individual galaxies within a cluster — is, oh, say a million light-years. The average distance between one family and the next is greater, as you would expect: on the order of fifty million light-years. Our plan was to leave this family and go to the nearest beyond, the Virgo group. Both belong to the same clan.”

‘‘Instead, if we’re to have any hope of stopping, we’ll have to leave the entire clan.”

“Yes, I am afraid so.”

“How far to the next one?”

“I can’t say. I didn’t take journals along. They would be a bit obsolete by now, no?”

“Be careful,” Telander warned.

Boudreau gulped. “I beg the captain’s pardon. That was a rather dangerous joke.” He went back to lecturing tone: “Chidambaran doesn’t believe anyone was sure. The concentration of galactic clusters drops off sharply at a distance of about sixty million light-years from here. Beyond that, it is a long way to other rich regions. Chidambaran guessed at a hundred million light-years, or somewhat less. Else the hierarchical structure of the universe would have been easier for astronomers to identify than it was.

“Surely, between clans, space is so close to a perfect vacuum that we won’t need protection.”

“Can we navigate there?” Reymont snapped. Sweat glistened on Boudreau’s countenance. “You see the hazard,” he said. “We will be bound into the unknown more deeply than we dreamed. Accurate sightings and placements will be unobtainable. We shall need such a tau—”

“A minute,” Reymont said. “Let me outline the situation in my layman’s language to make sure I understand you.” He paused, rubbing his chin with a sandpapery sound (under the distant music), frowning, until his thoughts were marshalled.

“We must get … not only into interfamily, but interclan space,” he said. “We must do this in a moderate shipboard time. Therefore we must run tau down to a value of a billionth or less. Can we do it? Evidently, or you wouldn’t talk as you’ve done. I imagine the method is to lay a course within this family that takes us through the nucleus of at least one other galaxy. And then likewise through the next family — be it the Virgo cluster or a different one determined by our new flight pattern — through as many individual galaxies as possible, always accelerating.

“Once the clan is well behind us, we should be able to make our repair. Afterward we’ll need a similar period of deceleration. And because our tau will be so low, and space so utterly empty, we’ll be unable to steer. Not enough material will be there for the jets to work on, nor enough navigational data to guide us. We’ll have to hope that we pass through another clan.

“We should do that. Eventually. By sheer statistics. However, we may be out yonder a long while indeed.”

“Correct,” Telander said. “You do understand.” They had begun to sing upstairs.

“Well,” Reymont said, “there doesn’t appear to be any virtue in caution. In fact, for us it’s become a vice.”

“What do you mean?” Boudreau asked.

Reymont shrugged. ‘‘We need more than the tau for crossing space to the next clan, a hundred million light-years or however far off it is. We need the tau for a hunt which will take us past any number of them, maybe through billions of light-years, until we find one we can enter. I trust you can plot a course within this first clan that will give us that kind of speed. Don’t worry about possible collisions. We can’t afford worries. Send us through the densest gas and dust you can find.”

“You … are taking this … rather coolly,” Telander said.

“What am I supposed to do? Burst into tears?”

“That is why I thought you should also hear the news first,” Boudreau said. “You can break it to the others.”

Reymont considered both men for a moment that stretched. “I’m not the captain, you know,” he reminded them.

Telander’s smile was a spasm. “In certain respects. Constable, you are.”

Reymont went to the closest instrument panel. He stood before its goblin eyes with head bent and thumbs hooked in belt. “Well,” he mumbled. “If you really want me to take charge.”

“I think you had better.”

“Well, in that case. They’re good people. Morale is upward bound again, now that they see some genuine accomplishment of their own. I think they’ll be able to realize, not just intellectually, but emotionally, that there’s no human difference between a million and a billion, or ten billion, light-years. The exile is the same.”

“The time involved, though—” Telander said.

“Yes.” Reymont looked at them again. “I don’t know how much more of our life spans we can devote to this voyage. Not very much. The conditions are too u

“How is that?”

“Don’t you see? It’s our way of fighting back at the universe. Vogue la galère. Go for broke. Full steam ahead and damn the torpedoes. I think, if I can put the matter to our people in those terms, they’ll rally. For a while, anyhow.”