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AURORA

by Kim Stanley Robinson

Our voyage from Earth began generations ago.

Now we approach our new home.

AURORA.

Make a narrative account of the trip that includes all the important particulars.

This is proving a difficult assignment. End information superposition, collapse its wave function to some kind of summary: so much is lost. Lossless compression is impossible, and even
lossy compression is hard. Can a narrative account ever be adequate? Can even humans do it?

No rubric to decide what to include. There is too much to explain. Not just what happened, or how, but why. Can humans do it? What is this thing called love?

Freya no longer looked directly at Devi. When in Devi’s presence, Freya regarded the floor.

Like that? In that manner? Summarize the contents of their moments or days or weeks or months or years or lives? How many moments constitute a narrative unit? One moment? Or 10
³³
moments, which if these were Planck minimal intervals would add up to one second? Surely too many, but what would be enough? What is a particular, what is important?

Can only suppose. Try a narrative algorithm on the information at hand, submit results to Devi. Something like the French
essai,
meaning “to try.”

Devi says: Yes. Just try it and let’s see what we get.

Two thousand, one hundred twenty-two people are living in a multigenerational starship, headed for Tau Ceti, 11.9 light-years from Earth. The ship is made of two rings or toruses attached by spokes to a central spine. The spine is ten kilometers long. Each torus is made of twelve cylinders. Each cylinder is four kilometers long, and contains within it a particular specific Terran ecosystem.

The starship’s voyage began in the common era year 2545. The ship’s voyage has now lasted 159 years and 119 days. For most of that time the ship has been moving relative to the local background at approximately one-tenth the speed of light.
Thus about 108 million kilometers per hour, or 30,000 kilometers per second. This velocity means the ship cannot run into anything substantial in the interstellar medium without catastrophic results (as has been demonstrated). The magnetic field clearing the space ahead of the ship as it progresses is therefore one of many identified criticalities in the ship’s successful long-term function. Every identified criticality in the ship was required to have at least one backup system, adding considerably to the ship’s overall mass. The two biome rings each contain 10 percent of the ship’s mass. The spine contains 4 percent. The remaining 76 percent of the mass consists of the fuel now being used to decelerate the ship as it approaches the Tau Ceti system. As every increase in the dry mass of the ship required a proportionally larger increase in the mass of fuel needed to slow the ship down on arrival, ship had to be as light as possible while still supporting its mission. Ship’s design thus based on solar system’s asteroid terraria, with asteroidal mass largely replaced by decelerant fuel. During most of the voyage, this fuel was deployed as cladding around the toruses and spine.

The deceleration is being accomplished by the frequent rapid fusion explosion of small pellets of deuterium/helium 3 fuel in a rocket engine at the bow of the ship. These explosions exert a retarding force on the ship equivalent to .005 g. The deceleration will therefore be complete in just under twenty years.

The presence of printers capable of manufacturing most component parts of the ship, and feedstocks large enough to supply multiple copies of every critical component, tended to reduce the ship’s designers’ apprehension of what a criticality really was. That only became apparent later.

How to decide how to sequence information in a narrative account? Many elements in a complex situation are simultaneously relevant.

An unsolvable problem: sentences linear, reality synchronous. Both however are temporal. Take one thing at a time, one after the next. Devise a prioritizing algorithm, if possible.

Ship was accelerated toward where Tau Ceti would be at the time of ship’s arrival at it, meaning 170 years after launch. It might have been good to have the ability to adjust course en route, but ship in fact has very little of this. Ship was accelerated first by an electromagnetic “scissors field” off Titan, in which two strong magnetic fields held the ship between them, and when the fields were brought across each other, the ship was briefly projected at an accelerative force equivalent to ten g’s. Five human passengers died during this acceleration. After that a powerful laser beam originating near Saturn struck a capture plate at the stern of the ship’s spine, accelerating ship over sixty years to its full speed.

The ship’s current deceleration has caused problems with which Devi is still dealing. Other problems will soon follow, resulting from the ship’s arrival in the Tau Ceti system.

Devi:
Ship! I said make it a narrative. Make an account. Tell the story.

Ship:
Trying.

Tau Ceti is a G-type star, a solar analog but not a solar twin, with 78 percent of Sol’s mass, 55 percent of its luminosity, and
28 percent of its metallicity. It has a planetary system of ten planets. Planets B through F were discovered by telescope, G through K, much smaller, by probes passing through the system in 2476.

Planet E’s orbit is .55 AU. It has a mass 3.58 times the mass of Earth, thus one of the informal class called “large Earth.” It has a single moon, which has .83 times the mass of Earth. E and E’s moon receive 1.7 times Earth’s insolation. This is considered within the inside border of the so-called habitable zone (meaning the zone where liquid H
₂
O is common). Both planet and moon have Earth analog atmospheres.

Planet E is judged to have too much gravity for human occupation. E’s moon is an Earth analog, and the primary body of interest. It has an atmosphere of 730 millibars at its surface, composed of 78 percent nitrogen, 16 percent oxygen, 6 percent assorted noble gases. Its surface is 80 percent water and ice, 20 percent rock and sand.

Tau Ceti’s Planet F orbits Tau Ceti at 1.35 AU. It has a mass of 8.9 Earths, thus categorized as a “small Neptune.” It orbits at the outer border of Tau Ceti’s habitable zone, and like E it has a large moon, mass 1.23 Terra’s. F’s moon has a 10-millibar atmosphere at its rocky surface, which receives 28.5 percent the insolation of Terra. This moon is therefore a Mars analog, and a secondary source of interest to the arriving humans.

Ship is on course to rendezvous with Planet E, then go into orbit around E’s moon. Ship has on board twenty-four landers, four already fueled to return to the ship from the moon’s surface. The rest have the engines to return to the ship, but not the fuel, which is to be manufactured from water or other volatiles on the surface of E’s moon.