Permutation City

She was about to object, but then it didn’t seem worth arguing. She’d done half the work, but this was Durham’s creation, whoever cut the ribbon.

She prodded the icon; it exploded like a cheap flashy fire-work, leaving a pincushion of red and green trails glowing on the screen.

“Very tacky.”

Durham grinned. “I thought you’d like it.”

The decorative flourish faded, and a shimmering blue-white cube appeared: a representation of the TVC universe. The Garden-of-Eden state had contained a billion ready-made processors, a thousand along each edge of the cube—but that precise census was already out of date. Maria could just make out the individual machines, like tiny crystals; each speck comprised sixty million automaton cells—not counting the memory array, which stretched into the three extra dimensions, hidden in this view. The data preloaded into most of the processors was measured in terabytes: scan files, libraries, databases; the seed for Planet Lambert—and its sun, and its three barren sibling planets. Everything had been assembled, if not on one physical computer—the TVC automaton was probably spread over fif-teen or twenty processor clusters—at least as one logical whole. One pattern.

Durham reduced the clock rate until the blue-white shimmer slowed to a stroboscopic flickering, then a steady alternation of distinct colors. The outermost processors were building copies of themselves; in this view, blue coded for complete, working processors, and white coded for half-finished machines. Each layer of blue grew a layer of white, which abruptly turned blue, and so on. The skin of this universe came with instructions to build one more layer exactly like itself (including a copy of the same instructions), and then wait for further commands to be passed out from the hub.

Durham zoomed in by a factor of two hundred, slowed down the clock rate further, and then changed the representation to show individual automaton cells as color-coded symbols. The processors were transformed from featureless blue or white boxes into elaborate, multicolored, three-dimensional mazes, rectilinear filigree alive with sparks of light.

In the throes of reproduction, each processor could be seen sprouting hundreds of pairs of fine red and green “construction wires,” which grew straight out into the surrounding empty space—until they all reached the same predetermined length, abruptly turned a tight one-hundred-and-eighty degrees, and then started growing back in the opposite direction. Glowing with elaborate moving striations, the wires zig-zagged back and forth between the surface of the mother computer and an unmarked boundary plane—until between them, they’d filled in the region completely, like some strange electronic silk weaving itself into a solid cocoon.

In close-up, the wires resolved into long lines of cells marked with arrowheads, some rendered in the brighter hues which represented “activated” states. Glowing stripes built from the binary code of bright and dim moved down the wire from arrow to arrow: the data of the blueprint for the daughter machine being shuffled out from the central memory.

With the clock rate slowed still further, the process could be followed in detail. Wherever a pulse of brightness reached the end of a construction wire, the transparent “Vacuum” of the null state was transformed into an “embryonic” cell, shown as a nondescript gray cube. Subsequent data told the new cell what to become—each pulse, or absence of a pulse, converting it into a slightly more specialized transition state, zeroing in on the particular final state required. The construction wires grew out from the mother computer using this principle, extending themselves by building more of themselves at their tips.

Having filled the entire region which the daughter machine would occupy, they then worked backward, retracting one step at a time; unweaving their zig-zag cocoon, and leaving behind whatever the blueprint required. The whole process looked grotesquely inefficient—far more time was spent on extending and retracting the wires themselves than on creating the cells of the daughter machine—but it kept the rules of the automaton as simple as possible.

Durham said, “This all looks fine to me. Okay to proceed?”

“Sure.” Maria had grown mesmerized; she’d forgotten her urgency, forgotten herself. “Crank it up.” At any speed where they could keep track of events at the level of individual processors—let alone individual cells—nothing useful would ever get done. Durham let the clock rate revert to the maximum they could afford, and the grid became a blur.

In contrast, the next stage would be painfully slow. Durham made coffee and sandwiches. All the overheads of running a Copy on a system of computers which was, itself, a simulation, addled up to a slowdown of about two hundred and fifty. More than four real-time minutes to a subjective second. There was no question of two-way communication—the TVC universe was hermetic, no data which hadn’t been present from the outset could affect it in any way—but they could still spy on what was happening. Every hour, they could witness another fourteen seconds of what the Copy of Durham had done.

Maria spot-checked at other levels, starting with the software running directly on the TVC grid. The “machine language” of the TVC computers was about as arcane and ridiculous as that of any hypothetical Turing machine, six-dimensional or not, but it had been simple enough to instruct a metaprogrammer to write—and rigorously validate—a program which allowed them to simulate conventional modern computers. So the processor clusters in Tokyo or Dallas or Seoul were simulating a cellular automaton containing a lattice of bizarre immaterial computers… which in turn were simulating the logic (if not the physics) of the processor clusters themselves. From there on up, everything happened in exactly the same way as it did on a real machine—only much more slowly.

Maria munched cheese and lettuce between thick slices of white bread. It was a Tuesday afternoon; most of the flats around them were silent, and the street below was lifeless. The neighboring office blocks had no tenants, just a few furtive squatters; where the sun penetrated the nearest building at just the right angle, Maria could see clothes hung out to dry on lines stretched between office partitions.

Durham put on music, a twentieth-century opera called Einstein on the Beach. He didn’t own a sound system, but he called up the piece from a library he’d bought for the Garden of Eden, and had a background task play it through his terminal’s speakers.

Maria asked, “What will you do with yourself when this is over?”

Durham replied without hesitation. “Finish the whole set of fifty experiments. Start Planet Lambert unfolding. Celebrate for about a week. Stroll down the main street of Permutation City. Wait for your little locking device to disengage. Wake up my passengers in their own private worlds—and hope that some of them are willing to talk to me, now and then. Start catching up on Dostoyevsky. In the original—”

“Yeah, very funny. I said you, not him.”

“I’d like to think of us as inseparable.”

“Seriously.”

He shrugged. “What will you do?”

Maria put her empty plate down, and stretched. “Oh… sleep in until noon, for a week. Lie in bed wondering exactly how I’m going to break the news to my mother that she can now afford to be scanned—without making it sound like I’m telling her what to do.”

“Perish the thought.”

Maria said simply, “She’s dying. And she can save herself—without hurting anyone. Without stealing food from the mouths of the next generation, or whatever it is she thinks makes being scanned such a crime. Do you really think she—honestly—doesn’t want to stay alive? Or wouldn’t want to, if she could think it through clearly, without all the guilt and moralizing bullshit her generation saddled her with?”

Durham wasn’t taking sides. “I don’t know her, I can’t answer that.”

“She was a child of the nineties. Her kindergarten teachers probably told her that the pinnacle of her existence would be fertilizing a rainforest when she died.” Maria thought it over. “And the beauty of it is… she can still do that. Scan her, put her through a meat grinder… scatter the results over the Daintree.”

“You’re a sick woman.”

“I’ll have the money soon. I can afford to joke.”

Their terminals chimed simultaneously; the first fourteen seconds of life inside were ready to be viewed. Maria felt the food she’d just swallowed harden into a lump like a closed fist in her gut. Durham told the program to proceed.

The Copy sat in a simple, stylized control room, surrounded by floating interface windows. One window showed a representation of a small part of the TVC lattice. The Copy couldn’t take the same God’s-eye view of the