Charles Sheffield - Starfire

“You mean you can.”

“Yeah. Me and Wilmer.” Astarte picked up a shrimp, stared at it longingly, then put it down. “A star is stable because there’s a balance everywhere inside it between gravitational force inward and radiation pressure outward. So the star reacts ter the squeeze by contracting a bit, then the radiation pressure takes hold and pushes it back out. It overshoots a little bit, comes out a bit farther than it was ter start with, and oscillates. For some stars, like Cepheid variables, the wobble occurs naturally. But for most stars the oscillation will damp out — unless, just at the right moment, yer hit it again with another compressive pulse. And then you hit it again, and again, doing it each time at just the right moment. Then the oscillations don’t damp out at all. Yer get resonance.”

“Like soldiers,” Celine said, “marching over a bridge. They’re supposed to break step and not march together, otherwise the regular rhythm of their marching could hit the resonant frequency of the bridge and make it collapse.”

“I didn’t hear about that!” Star’s eyes widened with pleasure. “I love it. Have yer seen it happen?”

“No. Actually, I’m not sure it ever has. But people talk about it all the time as if it’s true.”

“Yer could do it. You’re the President, you’re in charge of the Army. Yer could take a whole bunch of troops, and a bridge, and tell ’em ter march over and not break step and see what happens.”

“Not if I want to stay President I couldn’t,” Celine said, and Wilmer added, “Star, unless I hear more astrophysics I’ll take that bottle away.”

“First yer tell me ter talk, and then when I’m talking you complain.” Astarte turned to Celine. “Anyway, an oscillating star’s not quite like troops walking over a bridge. It’s more like a pendulum, where if yer give it a bit of a nudge on each swing, the size of the swing gets bigger and bigger each time. But all of a sudden, instead of swinging back, the pendulum changes the way it moves.” Star made a complete revolution with her arm. “It goes right over the top and comes down on the other side. That’s what it does if it’s a pendulum. If it’s a star, it goes supernova. Like Alpha Centauri went supernova. Got it?”

“I think so.” Celine had been expecting something far more complicated, and this seemed remarkably clear and simple. “The star experiences a small impulsive force, applied regularly.”

“No.” Star scowled. “Maybe I shouldn’t have used the pendulum idea. Yer can’t hit a star with a regular squeeze, you have ter do it at intervals that vary with time, or it won’t work — and calculating the times gave us no end of trouble.”

“But the principle’s the same, isn’t it?” Celine was reluctant to abandon her nice mental picture. “I mean, instead of coming regularly, the squeezes come at certain calculated times. And if that goes on long enough, the whole star becomes unstable.”

“It does indeed,” Wilmer said, and Star added, “Becomes unstable, and explodes like a son of a bitch.”

“That makes perfect sense.” But Celine suspected that she was still missing something. “Why did you think I would find it hard to accept?”

“Not that part,” said Wilmer. “I felt sure you’d accept everything so far.”

“So what else is there?” Celine looked from Wilmer to Astarte, who had bent low over her plate, grabbed her veal chop in both hands, and was tearing a big piece off it with those crooked white teeth. “What haven’t you told me?”

Astarte stared at her silently over the lump of bloody meat and went on chewing steadily.

“We haven’t told you the part that’s hard to accept,” Wilmer said. “The oscillatory squeeze process that Star describes works perfectly. It allows us to reproduce every measurement that we’ve made since the beginning of the Alpha C supernova. But there’s something we’ve not discussed.”

He deliberately waited, until Celine said, “What?” She had a hollow feeling in the pit of her stomach, as if her worry button had just been pressed.

“The agent. What is it that can impose such a systematic, exactly timed compressive pulse on a whole star?”

“You mean, what physical process can produce that effect?”

“I wish I meant that, but I don’t.” Wilmer seemed upset, and to Celine that was a bad sign. Wilmer never became uncomfortable when physics was the subject. “We’ve racked our brains, Star and me, trying to come up with a natural explanation for what happened. And we can’t. The timing-sequence of the impulses needed to make Alpha C go pop is so peculiar and improbable, I don’t see how it could possibly arise naturally. Something or somebody produced that sequence by design. Something made that star system go supernova.”

While Celine stared in disbelief, Astarte said, “Tell her the rest. About the gamma pulse and the particle storm.”

“Oh, yes.” Wilmer rubbed the bald patch on the top of his head — already red and inflamed from his previous attentions. “It turns out that the right sequence of impulsive compressions needed to provide a supernova is not radially symmetrical. Certain modes of oscillation must be excited, and that in turn gives preferred directions of emission for gamma rays and for the charged particle beam. Everyone always assumed that the fact that the gamma-ray beam was aimed to hit Earth, twenty-seven years ago, was a piece of pure bad luck.”

“Wasn’t it?” Celine was wondering if she could ever explain to anyone else what Wilmer and Astarte had been saying. Not one of her colleagues had any previous experience with Wilmer, or understood his brilliance and intellectual honesty.

“It wasn’t bad luck,” Wilmer said, and Astarte nodded firmly.

“Calculations show that it can’t be an accident,” she added. “Yer see, the Sun moves at thirty-two kilometers a second relative ter Alpha Centauri. Ter have a narrow gamma-ray beam intersect the position of Sol, twenty-seven years ago, and then ter have the main front of the particle storm hit Sol again, in its new position tens of billions of kilometers away — that’s off the scale on the probability charts.

“Something made Alpha Centauri go supernova. And that same something arranged for the gamma pulse and the particle storm ter run right smack bang into our solar system.”

From the private diary of Oliver Guest.

A Proustian obsession with one’s own past is, to my mind, an indicator of mental illness.

And yet, sometimes, it is necessary.

Seth Parsigian had departed at midday telling me that he was going to “check out ideas” that might solve the problem of my inability to face a trip to Sky City. He did not tell me what those ideas were. I did not ask. Nor did he mention an intention to return. I knew the man. He would be back.

Meanwhile, there were the records. Parsigian left with me a mountain of data and conjectures relating to the twelve murders, together with the less-than-helpful advice “See what you can sift out of it, Doc.”

Sifting, however, was not what I had in mind when I sat down, early the same afternoon, to begin my review of the material that he had left with me. What I sought was that intangible sense of contact, the ineffable touch of another’s mind.

Murders, particularly murders of compulsion, represent consequence rather than cause. They occur as the result of some particular motivation. In my own case, it was-and is-a desire to match mental to physical perfection. What, then, motivated the murderer of teenage girls in Sky City? What had been in his mind before he killed?