Wilmer outlined the new ideas and defined the pattern of compressions that must have been applied to Alpha Centauri A, the larger star of the system, to induce a supernova explosion. He spoke clearly, but certainly not simply. Celine had to concentrate to follow, and she had heard it several times before. While he spoke Astarte sat cross-legged on the floor, grinned up at Nick Lopez, and unselfconsciously scratched her belly and bare thighs.

Nick did not seem upset at that. He listened closely to Wilmer’s every word, and when Wilmer talked of stellar resonance Nick nodded as though that idea was no more than common sense. He did not fidget, and he ignored the occasional beeping of the telcom unit. Twice he asked for additional details. Once he asked that a subtle point be repeated.

Celine decided that Saul was right. Nick Lopez was very smart. But in nine meetings out of ten he was bored, and that was when he wandered off to do other things.

Wilmer had reached the most controversial point in the presentation, the one that the Cabinet officers and government research heads had rejected out of hand. “So the compressive pulses couldn’t have occurred naturally,” he said. “They were induced by some other agent. That, and the fact that the directions of both the gamma-ray beam and the particle storm precisely intersect the solar system, indicate that the geometry for this event was arranged.”

“Arranged?” Lopez was frowning.

“Deliberately contrived. It didn’t just happen.”

This was the point where Wilmer was supposed to end the presentation, as he had ended it before. Celine was ready to defend his heretical suggestion of supernova intention when Wilmer nodded to Astarte and said, “That’s me done. Your turn up the gum tree.”

“Right.” Astarte came to her feet with a grace, fluidity, and energy that Celine envied. She glanced at Celine. “Hey, this’ll be new ter you as well. We just come up with it yes’day.”

Celine directed a lethal glare at Wilmer. Hadn’t he learned at his age that surprises in presentations were anathema?

But he remained oblivious, and Astarte went on, “We didn’t have the latest Sniffer results ’til two days ago. They agree with everything me and Wilmer calculated, and it’s the way we worried it might be. There’s one mode of the particle flux traveling a lot faster than the rest. It’s going to hit real early — mebbe as soon as a month. But there’s something else in the Sniffer data, and this one’s a real bugger.” Her chubby black face glowed with excitement, and she paused for effect before she exclaimed, “The particle charge-ter-mass mix is all fucked up!”

She stood up straight, as though waiting for applause.

“You’ll have to tell ’em more than that, Star,” Wilmer said. “Don’t assume they know the predicted energy spectra.”

“Or much else,” Lopez said. “What’s a particle charge-to-mass mix?”

“It’s like a— like a—” Astarte placed her fists together and rolled them around each other in a churning motion. “All right. Yer got yer supernova, right? The star blows up, and it’s hotter than hell.”

Lopez nodded. “Got that much.”

“Well, that’s when all the different element nuclei get made, everything from protons — hydrogen nuclei, they was there to start with — up to the nuclei of the transuranics, with hundreds of protons and neutrons in each of ’em. Most of the unstable ones and all the superheavy ones split down to something lighter real quick, so after that you’ve only got stable ones left. D’yer get that, too?”

She spoke to Nick Lopez slowly, as though to a rather backward child. He nodded gravely. “I get that, too.”

“All right. Now let’s take a few of them nuclei. Say helium, carbon, tin, and lead. Helium has two protons and two neutrons, carbon has six protons and six neutrons, tin has fifty protons and seventy neutrons, lead has eighty-two protons and a hundred and twenty-six neutrons. I’m simplifying because there’s isotopes, too, but that’s all right, in’t it?”

“Perfectly all right. The simpler, the better.”

“Now, there’s a different amount of each type of nucleus formed in the explosion, so naturally yer’d expect different proportions in what comes out of the supernova. But that’s only part of the story. The stuff don’t just fly out, bang, it’s gone. It gets accelerated, real hard, by electromagnetic fields. But the field can’t get a hold on the neutrons ’cause they got no charge. The field only pushes on protons. So the two protons in helium get grabbed by the field and slung away, and the two neutrons in the nucleus hang on tight and get a free ride. The helium nucleus shoots off just half as fast as a single proton would without a neutron. With carbon, it’s six protons get grabbed and flung, an’ they got six neutrons as freeloaders. So the carbon nucleus goes off same rate as the helium nucleus, neck and neck. But when you get to tin, there’s only fifty protons to boost and they have to carry seventy neutrons along. So they only finish up five-twelfths as fast as a proton, which means five-sixths as fast as helium or carbon. An’ when you get to poor old lead, eighty-two protons lumbered with a hundred and twenty-six neutrons, it can only go eighty-two two-hundred-and-eighths as fast as a proton. That’s slower yet, only seventy-nine percent as fast as helium or carbon. So you see, different nuclei come out from the supernova with different speeds. That means they fly different distances in the same time, which means they’ll arrive in the solar system at different times. And it all depends on the charge-ter-mass ratio of the particular nuclei. See?”

Astarte had uttered this in one great breathless spate of words. Celine understood, but she felt sure that Nick Lopez didn’t. He sat staring at Astarte with an unreadable expression on his face.

Finally he smiled, shook his head, and said, “I don’t see. But I don’t have to, do I? Because you started out telling me that this charge-to-mass-to-particle thing is wrong, which must mean it doesn’t come out the way you calculated it.”

“Too bloody true.” Astarte came close to Lopez and peered at him curiously. “Yer really listen, don’t yer?”

“Sometimes. I know what isn’t happening, but I still don’t know what is.”

“That’s because I haven’t told you yet. Hold your water, and we’ll explain.” Astarte looked to Wilmer. “You wanna do it, or you want me ter?”

“You keep going, girl. It’s your show.”

Astarte scowled at Wilmer and turned back to Lopez. “He’s a lazy bugger for everything bar physics, but I s’pose I oughta be used ter that by now. What we found in the Sniffer data wasn’t what we expected. We got something a lot more interesting. See, you can work out what the supernova chucked out, the proportions of different nuclei. And you can calculate how fast they should be going, and how they ought to have spread over time. What we found, the thing that’s real terrific, is that the Sniffer data shows groups of nucleus types, with some elements moving along together when according ter us they shouldn’t have been because they had different charge-to-mass ratios. And it turns out that the speed they’re moving is exactly as though they’re tied together physically. We found carbon linked with oxygen and iron and mercury.”

“They’ve formed molecules,” said Celine.

That earned the President of the United States, the most powerful woman in the world, a reproving look.

“We’re not dealing with atoms, you know,” Astarte said sternly. She turned to Lopez. “D’you see why that makes a difference?”

“I have no idea.”

“Well, you oughta be ashamed of yerself. A man in your position, building the shield an’ all, yer ought ter know some science. So I’ll tell yer some. Atoms are electrically neutral, they have the same number of electrons as the number of protons in the nucleus. But the particle flux isn’t electrically neutral — if it was, the shield wouldn’t be a damn bit of good, would it? The particles would go right on through without the EM field of the shield touching ’em. The particles in the storm are bare nuclei, charged, no electrons attached. Molecules are atoms with shared electrons. So how can you have molecules if you don’t have atoms with electrons?” Astarte shook an admonishing finger in Nick Lopez’s face. “Stands to reason you can’t.”