“What about?”

“Stuff. New information. But we can’t do it here and now.” He jerked his head backward. “Too many ears.”

Maddy doubted that. Wilmer Oldfield and Astarte Vjansander were making enough noise to cover anything that Seth said.

They were arguing. Anyone sitting in front of them had no choice but to listen. Maybe that was why Seth was so annoyed.

“Stands ter reason,” Astarte was saying. “Yer can calculate and theorize and speculate ’til your eyeballs pop, but you still won’t know ’less you measure. We have to do it.”

“Do you think anyone but us cares?” Wilmer hissed. “Look at it from their point of view. We say, you have to build a system to detect and deflect particle bundles.”

“They do, too. Or they’re dead.”

“Of course they are. So they listen to us, and they buy what we say, and they change all their plans. What do you think they’ll do if now we say, by the way, deflect some of them particle bundles but not all of ’em because we need some? You can try that if you want, but not me. You’ll be lucky if they don’t grab you and whale your fat black butt.”

“Yer think you’re the only one allowed ter do that, don’t yer, you dirty old bugger? You’re a fossil, Wilmer Oldfield. You’re all mouth and beer gut. Yer stopped thinking twenty years ago, and you don’t have the brains and nerve of a paralytic parrot.”

“Better a paralytic parrot than a jumped-up outback madonna who thinks if she just wiggles her tits in Bruno Colombo’s face she can talk him into anything.”

“Not Bruno Colombo, you soft old ponce. I said Nick Lopez.”

“Colombo, Lopez, makes no difference. For starters, look at the bloody energy problem—”

Maddy leaned over to Seth. “What’s all that about?”

“Technical discussion.” Seth stared gloomily out of the port, to where a sunlit Earth loomed thirty times the size of a full Moon. “Far as I can tell, she wants to slow down a few of the bundles and catch them. Then they’d be able to study ’em and find out what sort of structure the bundles have. He’s telling her no one would ever agree. I’m with him. I want to get rid of particle bundles, not sit an’ play with ’em.”

The musical chime of a bell interrupted his final words. It came from an invisible address system. “Two minutes,” said John Hyslop’s voice. “Station One?”

There was a five-second silence, then an unfamiliar man’s reply: “Station One ready.”

“Confirmed. Station Two?”

“Station Two all set.” Lauren Stansfield’s voice came from directly behind Maddy, and a fraction of a second later the words were repeated from the address system.

“Confirmed. Station Three?”

As the count went on, Maddy wondered where the other stations were located. Some of them, from what John had said, must be at the points where the thrustors would fire; engineers there would be alert for buckling plates or failing seals. Lauren Stansfield and Torrance Harbish were doing the same thing, monitoring from their bird’s-eye view on the extended central axis.

“All stations confirmed. Twenty seconds.”

Maddy listened closely to John’s voice. It was calm, but with an odd undercurrent of excitement. She thought, That weirdo, he’s enjoying this. If I were a failing component, I’d get more of his attention than I do now. Engineers!

The soft chime of the bell was back, counting off the final seconds. Everyone in the observation chamber fell silent. All of them were looking in the same direction: out and down, to where the mirror-matter thrustors sat on Sky City’s broad disk.

The countdown was over. Maddy followed their gaze and saw nothing. That was surely the site of one of the thrustors; John had pointed it out to her on the Sky City hologram only two days ago. So why wasn’t it working?

She stared again, and realized it was. Not the gaudy orange flare of rockets that you became used to in launches to Earth orbit, but a thin, near-invisible line of blue plasma stabbing out from the thrustor. Unless you followed it from its source you would never know it was there.

Was that it? Was that frail, gossamer strand of light, with eleven more like it, supposed to hoist the million-ton bulk of Sky City a hundred thousand kilometers to the end of the shield? The idea seemed preposterous.

Maddy turned. Lauren Stansfield and Torrance Harbish were calmly working their equipment. John Hyslop’s voice came again over the address system. “Station Seven, we’re showing an anomaly.”

“Correct.” It was a man’s voice, one that Maddy did not recognize. “We have structural give in the main support beam. There’s no danger of overall failure, but it’s throwing the line of thrust off by a couple of degrees. Do you want us to try to do something about it locally?”

“I don’t think so. Just wait a moment.” There was a pause of a few seconds, then John’s voice again. “General rotation will average most of it out. If we have to, we’ll compensate with a reduced thrust on the opposite side. Hold as you are.”

“We’re holding.”

“Station Two? Do you see anything?”

Torrance Harbish said into his throat microphone, “We verify Station Seven off-line thrust. Everything else is nominal.”

“Noted. You may switch to automatic recording.”

Harbish said, “Changeover in process.” And then, in a less formal tone, “Good show, John. We’re wrapping up here. Expect us in the control room in about five minutes.”

Two more minutes, and he and Lauren Stansfield had set the scopes to automatic mode and left. Wilmer Oldfield and Astarte Vjansander followed, still bickering. Maddy turned to Seth Parsigian. “You want to talk?”

“Not yet.” His sallow face was thoughtful. “Got some stuff I have to do first. I’ll come to your rooms when I’m ready to chitchat.”

“If you do come, don’t do it late at night — I found out how much I hate that. And let me tell you how to reach my quarters.”

“Don’t need to; I already know. But I got a question for you. Have you been workin’ on the Argos Group deliveries?”

“Not up here. I worked deliveries down on Earth, years ago.”

“That’s all right, then. See you.” Seth slipped out of his seat and was gone.

Maddy was alone in the observation chamber. She could go back to her rooms and wait for Seth, but she lacked the will to do so. This was a better place for thinking, here with the great wheel of Sky City below her and the silent stars above.

There was plenty to think about. Far beyond Sky City, out beyond the shield and more than four light-years away, lay the source of the particle storm. Maddy was in no danger. In principle, particle bundles spit out by the Alpha Centauri supernova could hit Sky City right this very minute, and she would be protected by the bulk of the massive structure.

Each particle bundle averaged four trillion separate nuclei, but each bundle was still minute, its mass less than a billionth of a gram. Even so, each one packed enormous energy. Maddy had heard Astarte’s casual comment a few days earlier. “Yeah, they’re little, but yer don’t want ter underestimate them. They’re really smoking. Traveling close to a tenth of light speed — not really relativistic, but getting up there — and energy goes like the square of velocity. Every one of the little buggers packs as much of a wallop as a half-gram pellet traveling at a third of a kilometer of a second — that’s the speed of a bullet as it comes out of the muzzle of a handgun. A particle bundle can do a lot more damage to human tissue than a bullet, too, because the particles in it are all charged. If the bundle comes apart inside you when it hits, that’s still worse. We still don’t know if that will happen or not.”

Maddy was protected by Sky City, but Earth was not. She looked to her left, where the hazy globe hung in the heavens. She could see the moving day-night boundary of the terminator, but the planet itself seemed exactly the same size as before. She held up her hand and measured the width of Earth between thumb and first finger. The space city was leaving its orbit, but you would never know by looking. Acceleration was imperceptible. It would be days before Earth began to shrink in the sky.