Tau Zero

“That part is plain.” Boudreau leaned on the desk, shoulders hunched, brooding over the notes he had made. “I tell you, however, I have watched each single galaxy we passed through, or in observation distance of, these months. I have grown familiar with their types. And gradually those types are changing.” He jerked his head at the viewscope. “That up ahead, for instance, it is of the irregular sort, like the Magellanic Clouds at home—”

“I daresay, in these parts, the Magellanic Clouds count as home,” Foxe-Jameson murmured.

Boudreau chose to ignore the aside. “It should have a high proportion of Population n stars,” he went on.

“From here we should be able to see many individual blue giants. Instead, we see none.

“All the spectra I take, to the extent I can interpret them, they are becoming different from what is normal for the types. No kind of galaxy looks right any more.”

He raised his eyes. “Malcolm, what is happening?”

Foxe-Jameson appeared surprised. “Why’d you pick me to query?” he countered.

“I had only a vague impression at first,” Boudreau said. ‘‘I am not a real astronomer. Besides, I could not get accurate navigational sights. To obtain a value of tau, for instance, requires such a cat’s cradle of assumptions that — Bien, when I finally felt sure the nature of space was altering, I approached Charles Reymont. You know how he puts down panic-mongers, and he is correct in that. He told me to call in one of your team, quietly, and report the answer back to him.”

Foxe-Jameson chortled. “Why, you two pathetic beggars! Haven’t you anything else to stew about? Actually, I thought it’d be common knowledge. So common that none of us pros happened to mention it, starved though everyone is for fresh conversation. Makes a chap wonder what else he’s overlooking, eh?”

“Qu’est-ce que c’est?”

“Consider,” Foxe-Jameson said. He settled one thigh and buttock on the desk. “Stars evolve. They build heavier elements than hydrogen in thermonuclear reactions. If one is so big that it explodes, a supernova, at the end of its life, it scatters some of those atoms back into the interstellar medium. A more important process, though, if less spectacular, is the shedding of mass by smaller stars, the majority, in their red-giant stage on the way to extinction. New generations of stars and planets condense out of this enriched medium and add to it in their turn. Over the ages you get a rising proportion of metal-rich suns. That affects the over-all spectrum. But of course no star gives back more than a percentage of the material which formed it. Most matter stays locked in dense bodies, cooling toward absolute zero. So the interstellar medium becomes depleted. Space within the galaxies grows more clear. The rate of star formation declines.”

He gestured bow-ward. “Finally you reach a point where little or no further condensation is possible. The energetic, short-lived blue giants bum themselves out and have no successors. The galaxy’s luminous members are entirely dwarfs — at last nothing except cool, red, miserly Type Ms. Those are good for almost a hundred gigayears.

“I’d judge this galaxy we’re aimed for isn’t that far along yet. But it’s getting there. It’s getting there.”

Boudreau pondered. “Then we won’t gain as much speed per galaxy as we did before,” he said. “Not if the interstellar gas and dust are being used up.”

“True,” Foxe-Jameson said. “Don’t fret. I’m sure ample will remain for our purposes. Every bit doesn’t get collected in stars. Besides, we have the intergalactic medium, the intercluster, the interfamilial — thin, that, but usable at our present tau — and eventaully we should be getting work out of the interclan gas itself.”

He clapped the navigator’s back in friendly wise. “We’ve come about three hundred megaparsecs now, remember,” he said. ‘‘Which means about a thousand million years of time. You’ve got to expect some changes.”

Boudreau was less accustomed to astronomical concepts. ‘‘You mean,” he whispered, “the whole universe is growing enough older for us to notice?” It was the first time since his early youth that he had crossed himself.

The door to the interview room was shut. Chi-Yuen hesitated before pressing the chime button. When Lindgren let her in, she said timidly, “They told me you were here alone.”

“Writing.” The first officer stood somewhat slumped; nonetheless she topped the planetologist by a head. “A private place.”

“I hate to disturb you.”

“What I’m for, Ai-Ling. Sit down.” Lindgren went back behind her desk, which was covered with scrawled-on papers. The cabin hummed and trembled to irregular acceleration. More than a day of weight remained. Leonora Christine was bound through a clan of unprecedented size and opulence.

For a while, hope had lived that this might be the one where the ship could reach a halt within some member galaxy. Closer observation showed otherwise. Inverse tau had gotten too immense.

A faction had argued at general assembly that there ought to be limited deceleration anyhow, in order that requirements for stopping inside the next clan be less rigorous. One could not prove the contention wrong; not that much cosmography was known. One could only use statistics, as Nilsson and Chidambaran did, to prove that the likelihood of finding a resting place seemed greater if acceleration continued. The theorem was too involved for most persons to follow. The ship’s officers elected to take it on faith and maintain full forward thrust. Reymont had had to quell some individuals whose objections approached mutiny.

Chi-Yuen perched herself on the edge of a visitors’ chair. She was small and neat in high-collared red tunic, broad white slacks, hair brushed back with unwonted severity and held by an ivory comb. Lindgren contrasted in more than size. Her shirt was open at the neck, rolled up at the sleeves, smudged here and there; her hair was tousled, her eyes haunted.

“What are you writing, if I may ask?” Chi-Yuen ventured.

‘‘A sermon,” Lindgren said. ‘‘Not easy. I’m no writer.”

“You, a sermon?”

The left corner of Lindgren’s mouth twitched slightly upward. “Actually the captain’s address at our Midsummer Day festivities. He can still conduct divine service, after a fashion. But for this he requested me to, ah, inspirit the troops in his name.”

“He is not a well man, is he?” Chi-Yuen inquired low.

The humor flickered out in Lindgren. “No. I assume I can trust you not to blab that around. Even if everybody does suspect it.” She rested elbow on desk, forehead on hand. “His responsibility is destroying him.”

‘‘How can he blame himself? What choice has he except to let the robots move us onward?”

“He cares.” Lindgren sighed. “Also, mis latest dispute. In his condition, that was more than he could take. He’s not nervously prostrated, understand. Not quite. But he’s no longer able to buck people.”

‘‘Are we wise to hold a ceremony?” Chi-Yuen wondered.

“I don’t know,” Lindgren said in a worn-out voice. “I simply don’t. Now when — we aren’t a

She seized both arms of her chair. For a moment the blue eyes were wild and blind. Then the straining body eased, muscle by muscle; she leaned into the seat until its swivel joint tilted with a creak; she said flatly: “The constable persuaded me to go ahead with our rituals. Defiance. Reunification, after the past quarrel. Rededication, especially to that unborn baby. New Earth: We’ll snatch it from God’s grip yet. If God means anything, even emotionally, any more. Maybe I should lay off religion altogether. Carl didn’t give me any details. Only the general idea. I’m supposed to be its best spokesman. Me. That tells you a good deal about our condition, doesn’t it?”