Diaspora

"Not every bond does. If you throw enough hydrous together, the leptons fill up all the energy levels where they're confined tightly within the nucleus, so the outermost ones end up protruding sufficiently to be able to bind two atoms together with a respectable separation between the nuclei. You have to fill up the first two levels completely, which takes twelve leptons—so every stable molecule needs to contain a few judiciously placed atoms of number 13 or higher. Atom 27 can form fifteen covalent bonds; it's the closest thing in the macrosphere to carbon." The exhibit showed them a three-dimensional shadow of a five-dimensional, sixteen-atom molecule: one atom of 27, joined to fifteen hydrons. Paolo said, "Think of this as a souped-up version of methane. If you knock off any of these hydrons and substitute a side branch, you can build all kinds of elaborate structures."

Orlando was beginning to look besieged. As he glanced down the hall toward distant speculation on biochemistry and body plans, something caught his eve. "'U-star polymers.' What does 'U-star' mean?"

Paolo followed his gaze. "That's just another crane for the macrosphere. U is the ordinary universe, and the star is mathematical notation for its 'dual space'-that's a term used for all kinds of role-reversals. The universe and the macrosphere are both ten-dimensional… but one has six small dimensions and four large, the other has six large and four small. So they're inside-out versions of each other." He shrugged. "Maybe it's a better name. 'Macrosphere' captures the difference in size, but that hardly matters; once we're there, we'll be operating on roughly the same scale as any comparable lifeform. It's the fact that the physics has been turned inside-out that will make all the difference."

Orlando was smiling faintly. Paolo asked, "What?"

"Inside-out. It's nice to know that's the official verdict. It's how I've felt about it all along." He turned to Paolo, his expression suddenly, painfully naked. "I know I'm not flesh and blood. I know I'm software like every one else. But I still half believe that if anything happened to the polis, I'd be able to walk out of the wreckage into the real world. Because I've kept faith with it. Because I still live by its rules." He glanced down and examined an upturned palm. "In the macrosphere, that will all he gone. Outside will he a world beyond understanding. And inside, I'll just be one more solipsist, cocooned in delusions." He looked up and said plainly, "I'm afraid." He searched Paolo's face defiantly, as if daring him to claim that a journey through the macrosphere would be no different from a walk through an exotic scape. "But I can't stay behind. I have to be a part of this."

Paolo nodded. "Okay." After a moment he added, "But you're wrong about one thing."

"What?"

"A world beyond understanding?" He grimaced. "Where do you get that shit! Nothing is beyond understanding. A hundred more exhibits, and I promise you: you'll be dreaming in five dimensions."

16

DUALITY

Carter-Zimmerman polis, U*

Orlando stood outside the cabin and watched the last visible trace of his universe recede into the distance. The dome of sky above the Floating Island offered a pinhole view of the macrosphere, revealing only two faint stars; the station they'd built beside the singularity appeared just above the western horizon as a tiny, flashing white light, fading rapidly. The singularity itself was invisible at this distance, but the station's beacon echoed the regular stream of photons emanating from it to mark its position.

If the team on Swift ever stopped creating those photons, the singularity would vanish from sight. A massless anomaly in the vacuum, small as a subatomic particle, it would he almost impossible to find. But then, if no one was sending, no one would be listening either, so there'd be no point scouring the vacuum for the home universe; any data blasted back at the singularity would trigger beta decays in Swift's neutrons to no avail. Some people had expected the singularity to be surrounded by Transmuter artifacts, but Orlando hadn't been surprised to find the region abandoned, given the absence of machinery on the other side of the link.

The beacon seemed to dim with unnatural speed, as if the polis was accelerating away wildly. Yet another manifestation of the inverse-fourth law: anything that spread out in all directions thinned more rapidly here. Orlando watched the reassuring pulse of light fade from view, then managed to laugh at his visceral sense of abandonment. It was possible to be stranded anywhere. On Earth, he'd once almost died of exposure less than twenty kilometers from home. Scale meant nothing. Distance meant nothing. They'd either make it back, or they wouldn't and nothing this world could do to them could begin to compare to a slow death from cold and dehydration.