Permutation City

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?"