THE IRIS OF THE EYE WAS TOO BIG TO HAVE BEEN FABRICATED AS A single rigid object. It had been built, beginning about nine hundred years ago, out of links that had been joined together into a chain; the two ends of the chain then connected to form a loop. The method would have seemed familiar to Rhys Aitken, who had used something like it to construct Izzy's T3 torus. For him, or anyone else versed in the technological history of Old Earth, an equally useful metaphor would have been that it was a train, 157 kilometers long, made of 720 giant cars, with the nose of the locomotive joined to the tail of the caboose so that it formed a circular construct 50 kilometers in diameter. An even better analogy would have been to a roller coaster, since its purpose was to run loop-the-loops forever. The "track" on which the "train" ran was a circular groove in the iron frame of the Eye, lined with the sensors and magnets needed to supply electrodynamic suspension, so that the whole thing could spin without actually touching the Eye's stationary frame. This was an essential design requirement given that the Great Chain had to move with a velocity of about five hundred meters per second in order to supply Earth-normal gravity to its inhabitants. Each of the links had approximately the footprint of a Manhattan city block on Old Earth. And their total number of 720 was loosely comparable to the number of such blocks that had once existed in the gridded part of Manhattan, depending on where you drew the boundaries-it was bigger than Midtown but smaller than Manhattan as a whole. Residents of the Great Chain were acutely aware of the comparison, to the point where they were mocked for having a "Manhattan complex" by residents of other habitats. They were forever freeze-framing Old Earth movies or zooming around in virtual-reality simulations of pre-Zero New York for clues as to how street and apartment living had worked in those days. They had taken as their patron saint Luisa, the eighth survivor on Cleft, a Manhattanite who had been too old to found her own race. Implicit in that was that the Great Chain-the GC, Chaintown, Chainhattan-was a place that people might move to when they wanted to separate themselves from the social environments of their home habitats, or indeed of their own races. Mixed-race people were more common there than anywhere else.
( Neal Stephenson )
[ Seveneves ]
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