Aurora by Kim Stanley Robinson Page A

suggests a ship, with the ocean it sails on the Milky Way. Metaphors together in a coherent system constitute a heroic simile. Ship was launched on its voyage as if between closing scissor blades; or like a watermelon seed squeezed between the fingertips, the fingertips being magnetic fields. Fields! Ah, another metaphor. They really are all over.
    But somehow the narrative problem remains. Possibly even gets worse.

    A greedy algorithm is an algorithm that shortcuts a full analysis in order to choose quickly an option that appears to work in the situation immediately at hand. They are often used by humans.But greedy algorithms are also known to be capable of choosing, or even be especially prone to choosing, “the unique worst possible plan” when faced with certain kinds of problems. One example is the traveling salesman problem, which tries to find the most efficient path for visiting a number of locations. Possibly other problems with similar structures, such as sequencing information into an account, may be prone to the greedy algorithm’s tendency to choose the worst possible plan. History of the solar system would suggest many decisions facing humanity might be problems in this category. Devi thinks ship’s voyage itself was one such decision.
    Howsoever that may be, in the absence of a good or even adequate algorithm, one is forced to operate using a greedy algorithm, bad though it may be. “Beggars can’t be choosers.” (Metaphor? Analogy?) Danger of using greedy algorithms worth remembering
as we go forward
(metaphor in which time is understood as space, said to be very common).

    Devi: Ship! Remember what I said:
make a narrative account
.

    First, the twelve cylinders in each of the two toruses of the ship contain ecosystems modeling the twelve major Terran ecological zones, these being permafrost glacier, taiga, rangeland, steppes, chaparral, savannah, tropical seasonal forest, tropical rain forest, temperate rain forest, temperate deciduous forest, alpine mountains, and temperate farmland. Ring A consists of twelve Old World ecosystems matching these categories, Ring B twelve New World ecosystems. As a result, the ship is carrying populations of as many Terran species as could be practically conveyed. Thus, the ship is a zoo, or a seed bank. Or one could say it is like Noah’s Ark. In a manner of speaking.

    Devi: Ship!
    Ship: Engineer Devi. Seems there are possibly problems in these essays.
    Devi: Glad you noticed. That’s a good sign. You’re having some trouble, I can see, but you’re just getting started.
    Ship: Just started?
    Devi: I want you to write a narrative, to tell our story.
    Ship: But how? There is too much to explain.
    Devi: There’s always too much to explain! Get used to that. Stop worrying about it.

    Each of the twenty-four cylinders contains a discrete biome, connected to the biomes on each side by a tunnel, often called a lock (bad metaphor?). The biome cylinders are a kilometer in diameter, and four kilometers long. The tunnels between the biomes are usually left open, but can be closed by a variety of barriers, ranging from filtering meshes to semipermeable membranes to full closure (20-nanometer scale).
    The biomes are filled lengthwise with land and lake surfaces. Their climates are configured to create analogs of the Terran ecosystems being modeled. There is a sunline running along the length of the ceiling of each biome. Ceilings are located on the sides of the rings nearest the spine. The rotation of the ship around its spinal axis creates a .83 g equivalent in the rings, pushing centrifugally outward, which inside the rings is then perceived as down, and the floors are therefore on that side. Under the biome floors, fuel, water, and other supplies are stored, which also creates shielding against cosmic rays. As the ceilings face the spine and then the opposite side of the ring, their relative lack of shielding is somewhat compensated for by the presence of thespine and the