"But then what keeps these pebbles together? Why doesn't that repulsive force blast them apart?"

"They must be locked chemically. I suspect they were originally formed under great pressure — pressure that defeated the repulsion we're observing. Now that their constituent atoms are bonded, they stay together, but it would take great effort to combine the pebbles into bigger groupings."

"Oh, hell," said Rissa. "You know what I'm thinking…"

Jag's four eyes went wide. "The Slammers! We've only ever seen what their weapon did to one of our probes.

Perhaps if they turned it on a world, this might be the result.

Quite the doomsday device: not only does it destroy the planet, but it also imparts a force to the rubble to prevent it from ever collecting back together to form another world."

"And now there's an open shortcut leading from here to the Commonwealth worlds. If they were to come through-"

At that moment, Jag's wall beeped, and the elderly face of Cynthia Delacorte appeared on it. "Jag, it's — oh, hi, Rissa…

Listen, thanks for sending up those samples. Do you know that this stuff sinks into normal matter?"

Jag lifted his upper shoulders. "Incredible, isn't it?"

Delacorte nodded. "I'll say. It's not normal baryonic matter. It's not antimatter, of course. We'd have been blown out of the skies if it were. But where normal protons and neutrons consist of combinations of down quarks and up quarks, this stuff is made of matte quarks and glossy quarks."

Jag's fur danced excitedly. "Really?" "I've never heard of those kinds of quarks," said Rissa.

Jag made a sound like she was a fool, but Delacorte nodded. "Since the twentieth century, humans have known of six flavors of quarks — up, down, top, bottom, strange, and charmed. In fact, six was the maximum number allowed for under the old Standard Model of physics, so we'd pretty much given up looking for more, which turned out to be a big mistake." She looked pointedly at Jag. "The Waldahudin had only found the same six flavors, too. But when we met the Ibs, they were aware of two more, which we refer to by opposing lusters, glossy and matte.

There's no way you can get them by breaking down normal matter,' but the Ibs had 'done unique work pulling matter out of quantum fluctuations.

In their experiments, luster quarks were sometimes produced, but only at very, very high temperatures. What we've got here are the first-known naturally occurring luster quarks."

"Incredible," said Jag. "You've noticed thefardint things carry no charge? What explains that?"

Delacorte nodded, then looked at Rissa. "Electrons have a charge of negative one unit, up quarks have a positive two-thirds charge, and down quarks have a negative one-third charge. Each neutron is made of two downs quarks and an up, which means the net charge is zip.

Meanwhile, each proton consists of one down and two ups, which gives a charge of positive one. Since atoms have equal numbers of protons and electrons, they have an overall neutral charge."

Rissa understood that the explanation had been for her benefit. She nodded at the wall monitor for Delacorte to go on.

"Well, this luster-quark matter consists of what I'm calling para-neutrons and para-protons. Para-neutrons consist of two glossy quarks and one matte, and para-protons consist of a pair of mattes plus a glossy. But neither glossies nor mattes carry any charge whatsoever — so regardless of how you combine them, there's no charge on the nucleus.

And without a positive nucleus, there's nothing to attract negatively charged electrons, so a luster-quark atom is solely a nucleus; it has no electron orbital shells. The bottom line is that luster matter isn't just electrically neutral. Rather, it's nonelectrical; it's immune to electromagnetic interactions."

"Gods," said Jag. 'q'hat would explain why it can sink into solid objects. It would probably pass through completely unhindered if it weren't for drag caused by the regular-matter carbon grains and hydrogen polluting it, and — of course! That explains why we can see it, too. If it were purely luster quarks, it would be invisible, since the reflection and absorption of light depend on vibrating charges.

We're just seeing the interstellar dust that's caught gravitationally inside the luster matter, like sand in jelly."

He looked at the wall screen. "All right — it doesn't interact electromagnetically. What about the nuclear forces?"

"It is affected by both the strong and the weak nuclear force," said Delacorte. "But those forces are so short-range, I doubt we'd get any interaction through them with regular matter except at incredibly high pressures and temperatures."

Jag was quiet for a moment, considering. When he next spoke, his barking was subdued. "It's incredible," he said.

"We knew the Slammer weapon could break chemical bonds, but changing regular matter into luster matter is-"

"What was Saul Ben-Abraham like?" asked Glass.

Keith looked around the forest simulation, thinking of all the ways he could describe the man who had been his best friend. Tall.

Boisterous. A guffaw that could be heard a kilometer away. A guy who could identify any song in three notes. A man who could drink more beer than anyone Keith had ever met — he must have had a bladder the size of

Iceland. Finally, Keith settled on, "Hairy."

"I beg your pardon?" said Glass.

"Saul had a great beard," said Keith. "Covered most of his face. And he had this one giant eyebrow, like a chimp had laid its forearm across his head. The first time I ever saw him in shorts, I was amazed. The guy looked like sasquatch."

"Sasquatch?"

"A mythical primate from my part of Earth. I still remember seeing him in shorts for the first time and saying, gee, Saul, you've got hairy legs. He let out that great laugh of his and said, 'Yes — like a man.'" I said it was more like ten men." Keith paused. "God, how I miss him Friends like that, who mean that much to you, come along perhaps once in a lifetime."

Glass was quiet for several seconds. "Yes," he said at last. "I suppose that's true."

"Of course," said Keith, "there was more to Saul than just a thick coat of fur. He was brilliant. The only person I've ever met who I thought might be brighter than him is Rissa. Saul was an astronomer. He's the person who discovered the Tau Ceti shortcut, from its footprint in hyperspace. The guy should have won a Nobel prize for that… but they don't like to award them posthumously."

"I appreciate your loss," said Glass. "It's as if — oh, excuse me. My reckoner says I've got an incoming thought package. Will you excuse me for a little while?"

Keith nodded, and Glass took an odd step, sort of sideways, and disappeared. Doubtless he'd gone through a door hidden by the forest simulation filling the docking hay — the only direct visual evidence Keith had had that he wasn't actually back on Earth. Well, if there was a door, Keith wanted to find it. He patted the air in the spot that Glass had disappeared from, but there was nothing. There had to be a wall somewhere around, though. The bay wasn't that big. Keith began to walk, figuring he was bound to hit a wall eventually. He continued on for perhaps five hundred meters without encountering any obstruction.

Of course, if his — he started to think the word "captor," again, but fought it down and substituted "host" instead — if his host were being clever, he could have manipulated the images to make.Keith think he was walking in a straight line when he was really going in a circle.

Keith decided to rest. As much as he tried to find time to work out in Starplex's Earth gym, which had gravity set to a full standard gee, he'd lost some muscle tone because of all the time he spent in the lighter Wald-standard gravity used in the ship 's common elements. He really should take Thor Magnor up on his offer of playing handball; Keith and Saul had played the game regularly, but he'd given it up when Saul had died.