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.
He addressed the scape. "Sweep the sky." At any one moment, the ordinary view from the Island—a mere two-dimensional dome—could only encompass a narrow portion of the macrosphere's four-dimensional sky. But the hemisphere could he swept across the sky, scanning it like a Flatlander scanning ordinary space by rotating the plane of vis slit-like view. Orlando watched the sparse stars come and go, far fewer than he'd have seen from Atlanta beneath a full moon. Still, it was remarkable that he could make out so many, when they were scattered so widely and their light was spread so thin.
A brilliant rust-red point of light appeared in the east, then faded rapidly as the view swept over it: Poincare, the nearest star to the singularity, their first target for exploration. It would take forty megatau to reach Poincare, but no one was tempted to freeze themselves for the journey; there was too much to think about, too much to do. Orlando braced himself. "Now show me U-star." His exoself responded to the command, spinning his balls into hyperspheres, rebuilding his retinas as four-dimensional arrays, rewiring his visual cortex, boosting his neural model of the space around him to encompass five dimensions. As the world inside his head expanded, he cried out and closed his eyes, panic-stricken and vertiginous. He'd done this in sixteen dimensions to view the Orphean squid, but that had been a game, a dizzying novelty, like riding a comet or swimming with blood cells, adrenaline-pumping but inconsequential. The macrosphere was no game; it was more real than the Floating Island, more real than his simulated flesh, more real, here and now, than the ruins of Atlanta buried in a distant speck of vacuum. It was the space through which the polis sped, the arena in which everything he thought and felt was truly happening.
He opened his eyes.
He could see many more stars at once now, but they seemed more sparsely distributed; there was so much more emptiness to fill. Almost without thinking, he began joining up the dots, sketching simple constellations in his head. There were no striking figures here, no Scorpios or Orions, but a single line between two stars was a thing to be marveled at. His vision now stretched beyond its ordinary field in two orthogonal directions; Paolo's friend Karpal had suggested calling them quadral and quintal, but with no obvious basis for distinguishing between them Orlando seized on the collective term: the hyperal plane.
Networks in his new visual cortex and spatial map attached a raw perceptual distinction to the hyperal directions, but it still required a conscious effort to make cognitive sense of them. They were definitely not vertical; that realization carried the most immediate force. The direction of gravity, of his body's major axis, had nothing to do with them; if he was like a Flatlander seeing the world beyond his plane, that plane had always been vertical, and his slit-vision had now spread sideways. But the new directions weren't lateral, either; unlike a vertical Flatlander, his "sideways" was already occupied. When he consciously divided his visual field into left and right halves, all the purely hyperal pairs of stars lay solely in one half or the other, just like all the purely vertical pairs. And whatever common sense dictated as the only remaining possibility, there was no sense of the sky having gained depth, of the stars looming toward him like a holographic image leaping out of a screen.