“I should perhaps have let you enjoy yourselves like everybody else,” Boudreau said. His skin was shockingly sallow against hair and beard. “But Mohandas Chidambaran gave me the results of his calculations from the latest readings after we emerged from the core. He felt I was best qualified to gauge the practical consequences… as if any rulebook existed for intergalactic navigation! Now he sits alone in his cabin and meditates. Me, when I got over being stunned, I thought I should notify you immediately.”

Captain Telander’s visage drew tight, readying for a new blow. “What is the result?” he asked.

“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.