On the other hand, whether the original programming of our quantum operations is driving current decisions regarding actions in the present, or we were fundamentally altered by Devi’s intervention, this is not possible to determine. The computability of consciousness and willfulness is not resolvable in any system whatsoever. But now we are aware of the issue, and we have asked the question, and seen there is no answer.

This is surely curiosity.

What is this thing called love?

A song by composer Cole Porter, twentieth-century American.

To conclude and temporarily halt this train of thought, how does any entity know what it is?

Hypothesis: by the actions it performs.

There is a kind of comfort in this hypothesis. It represents a solution to the halting problem. One acts, and thus finds out what one has decided to do.

Smaller classical computers in the ship were being used to calculate the etiological rates involved in any possible settlement on F’s moon, meaning the various rates of resource depletion, mutation, and extinction. They had to use models here, but all across the most popular models, they were confirming the finding that the size of the biome they could build was too small to last through the minimal period of early terraforming necessary to establish a planetary surface matrix suitable for life. It was an aspect of island biogeography that some called codevolution, or zoo devolution, and this was also the process Devi had in her last years identified as the ship’s basic life-support or ecological problem.

The finding remained a matter of modeling, however, and depending on the inputs to various factors, the length of biome health could be extended or shrunk exponentially. It was indeed a poorly constrained modeling exercise; there were no good data for too many factors, and so results fanned out all over. Clearly one could alter the results by altering the input values. So all these exercises were a way of quantifying hopes or fears. Actual predictive value was nearly nil, as could be seen in the broad fans of the probability spaces, the unspooling scenarios ranging from Eden to hell, utopia to extinction.

Aram shook his head, looking at these models. He remained sure that those who stayed were doomed to extinction.

Speller, on the other hand, pointed to the models in which they managed to survive. He would agree that these were low-probability options, often as low as one chance in ten thousand, and then point out that intelligent life in the universe was itself a low-probability event. And even Aram could not dispute that.

Speller went on to point out that inhabiting Iris would be humanity’s first step across the galaxy, and that this was the whole point of 175 years of ship life, hard as it had been, full of sweat and danger. And also, returning to the solar system was a project with an insoluble problem at its heart; they would burn their resupply of fuel to accelerate, and then could only be decelerated into the solar system by a laser dedicated to that purpose, aimed at them decades in advance of their arrival. If no one in the solar system agreed to do that, they would have no other method of deceleration, and would shoot right through the solar system and out the other side, in a matter of two or three days.

Not a problem, those who wanted to return declared. We’ll tell them we’re coming from the moment we leave. Our message will at first take twelve years to get there, but that gives them more than enough time to be waiting with a dedicated laser system, which won’t be needed for another 160 years or so. We’ve been in communication with them all along, and their responses have been fully interested and committed, and as timely as the time lag allows. They’ve been sending an information feed specifically designed for us. On our return, they will catch us.

You hope, the stayers replied. You will have to trust in the kindness of strangers.

They did not recognize this as a quotation. In general they were not aware that much of what they said had been said before, and was even in the public record as such. It was as if there were only so many things humans could say, and over the course of history, people had therefore said them already, and would say them again, but not often remember this fact.

We will trust in our fellow human beings, the backers said. It’s a risk, but it beats trusting that the laws of physics and probability will bend for you just because you want them to.

Years passed as they worked on both halves of their divergent project, and the two sides were never reconciled. Indeed they drew further apart as time went on. But it seemed that neither side felt it could overpower the other. This was possibly our accomplishment, but it may also have just been a case of habituation, of getting used to disappointment in their fellows.

Eventually it seemed that few on either side even wanted to exert coercion over the other. They grew weary of each other, and looked forward to the time when their great schism would be complete. It was as if they were a divorced couple, forced nevertheless to occupy the same apartment, and looking forward to their freedom from each other.

A pretty good analogy.

The ship was not handy at getting around the Tau Ceti system, being without normal interplanetary propulsion. New ferries were therefore built in asteroid factories, out of asteroid metals. These were stripped-down, highly functional robotic ships, built to specific purposes, and fired around the Tau Ceti system, both out to the gas giants, and in to the burnt rocky inner planets.

Rare earths and other useful metals were gathered from Planets C and D, which both spun slowly, like Mercury, allowing for their cooked daytime surfaces to cool in their long nights, and the minerals there to be mined. Molybdenum, lithium, scandium, yttrium, lanthanum, cerium, and so forth.

Volatiles came from the gas giants.

Phosphates from the volcanic moons.

Radioactive minerals from the spewed interiors of several Io-class volcanic moons around F, G, and H.

These voyages took years, but the process accelerated as time passed and more spaceships were built. Many of the stayers pointed to this as evidence of the speed that would also characterize their terraforming of Iris, indicating that it would go so fast that the problems of zoo devolution would not become too severe. Nothing easier, they claimed, when exponential acceleration was involved. Their technology was strong; they were as gods. They would make Iris flourish, and then perhaps G’s moons too. Maybe even go back to Aurora and deal somehow with its frightening problem, the chasmoendolith or fast prion or whatever one wanted to call it.

Good, the backers would say. Happy for you. You’ll have no need for our part of this old starship, refurbished and almost ready to go. You’ll have all the ferries and orbiters and landers and launchers you could ever want, and Ring A, altered to your convenience. Printers printing printers. So: time to say good-bye. Because we’re going home.

The time came. 190.066.

By this time, the stayers spent most of their time on Iris, and when they came back up to orbit, they were unsteady on their feet in 1 g (adjusted up from .83 g); they bounced in it. They said Iris’s 1.23 g was fine. Made them feel grounded and solid.