"But the Intruder's moving considerably faster than that," Assembly-Prime Wu-sin objected.
"Exactly," Roth nodded. "They're apparently using an after-accelerator of some sort to boost their exhaust speed. But this takes energy, requiring extra fuel."
"I see," Nordli rumbled. "They have to carry extra hydrogen which can't be replaced in the interstellar medium. So they periodically dive into a star to replenish their tanks?"
"It would seem so."
"Dr. Du Bellay, you're an expert on alien cultures, correct?" Nordli asked.
"To some extent, sir," Du Bellay said, "bearing in mind we've so far studied only dead civilizations, and only a handful of those."
"Yes. In your opinion, what are the chances of communicating with these aliens? And what are the chances that would make any difference in their actions?"
Du Bellay frowned. "I'm afraid the answer to both questions is very poor," he said slowly. "It's true that various scientists have developed so-called 'first-contact primers' in case we ever came across a living intelligent species. But it's also true that teaching any of our language to an alien would take considerable time, and we haven't got that time. No ship ever built could match speeds with the Intruder, so we would have to give everything to them in short, high-density data bursts. And even assuming they were equipped to receive whichever wavelengths we use, they have only seven or eight hours—in their time frame—to decipher it."
"I have to concur with Dr. Du Bellay," Carey spoke up. "As a matter of fact, we've already sent out a series of tachships to try precisely what he suggested, but we don't expect anything to come of it."
"Perhaps we could signal our existence some other way," Evelyn Woodcock, Nordli's assistant, suggested. "Say, a fusion drive pointed at them, blinking off and on. They couldn't miss that."