At the dawn of the Fifth Millennium, about a thousand years ago, the first new habitat in geosynchronous orbit had been constructed. It was called Greenwich because it was positioned above Old Earth’s prime meridian. In the way of neighbors, it at first had nothing but rubble and worn-out robots. As soon as Greenwich was complete, however, construction of more habitats had spread outward from it. The human races and their robots had begun burning their way through the ring of raw material in both directions, consuming it like fire on a fuse.