In the twenty-first century, humanity had developed technology to scan a person’s brain and turn them into a computer program. Many people escaped into the polises, underground computer systems where you could live indefinitely in abstraction, where you could simulate any reality you wanted. Humanity fragmented into the fleshers who remained beings tied to the physical world, the Coalition of Polises, and the gleisners who were computer programs that inhabited physical, robotic bodies. The fleshers had even fragmented within themselves: there were the statics who had not modified their DNA and the exurberants, who came in all shapes, sizes, and colors. There was war, at least between the gleisners and the fleshers, and it seems that some fleshers had been forced to become gleisners. There was mistrust on all sides, and Earth was divided into areas, with satellites that enforced the zones, at least with regards to the digital humans.

The citizens of a polis could reproduce, and the polis also created orphans from no parents, with some fields set randomly. The mind seed activated programs called shapers which iteratively created the structures of the mind, handing themselves off to more shapers. The resulting mind had both positive and negative feedback loops that enabled it to learn: the positive loops were reward circuits and were balanced by the dampening negative feedback to determine when something was not helpful. So the mind reached out to its inputs and tried things randomly, stumbling on the correct sequences to the polis library, the central abstract 3D ‘scape where citizens met, the challenge/response sequence to identify citizens, language, and social relations, and learning how to interact by building on the sequences that . When the mind became self-aware, it was granted citizenship in the polis.

One such orphan named itself Yatima. Ve was intrigued both with mathematics of ver’s friend Blanca and with emotions and art from vis friend Inoshiro, although ve did tend toward mathematics as ver’s first love. Inoshiro convinced ver to visit the fleshers in Atlanta by inhabiting some abandoned gleisner bodies. There was suspicion, but Orlando and his wife, and friends were glad to have visitors. The original inhabitants of Atlanta had died, and Orlando Venetti and the others were bridgers, who saw their purpose in life as bridging communication between others.

Some time later, the gleisner’s noticed from their solar-system sized gravity wave detectors that a pair of binary neutron stars in a system named Lacerta relatively near earth were spiraling in much faster than predicted. They were losing so much energy that they would combine in several days and release a gamma ray burst so strong it would cause reactions in the atmosphere that would make Earth unlivable for centuries. Ionshiro and Yatima visited Atlanta again, where the fleshers were much more suspicious this time, and thought that the whole thing might be a trick. They were especially suspicious when they offered that they could join the polis. The bridgers did manage to get a virtual conference of the fleshers through the flesher communications network. Some believed them and started to make preparations; many did not. Atlanta tried to make preparations, but there was no time and the storm that resulted from the gamma rays killed everyone. Inoshiro and Yatima stayed, and they could not bear people dying, so at the last minute they shot as many people as they could with the Introdus device to digitize them, even though not violating autonomy of a person was a sacrosanct principle.

Inoshiro retreated within himself with grief. Yatima emigrated to the Carter-Zimmerman polis, which planned to take to the stars to create a Diaspora of clones and escape destruction that way. The gleisner’s had already sent ships to the stars, but Carter-Zimmerman thought they could create a wormhole using the fact that basic particles were already connected via wormholes, they just had to find a useful pair. After creating a particle accelerator with the diameter of Pluto, they did succeed in widening a wormhole, but it turned out that the theory was partially incorrect—you could travel through the wormhole, but it still took the same distance. Disappointed, they went the slow way.

Blanca’s clone going to the star Fomalhaut discovered that the world was not made of four + six dimensions as had previously been thought (the six were microscopically small), but four + twelve. This was close to heresy in Carter-Zimmerman, but ver transmitted it back to the Earth polis anyway, which was fortunate, since that polis collided with something enroute and was destroyed.

The polis to the star Vega found life on the water planet Orpheus. Vega had such intensive ultraviolet radiation that life could only survive deep under the ocean, where it took the form of “Wang Carpets”. Organic molecules self-assembled into Wang tiles, which have mathematical properties that enable them to do computations. Analysis of the carpets showed that the edges of the carpets were the information of the computation and were computing a wide variety of life, similar in concept to what the polises did.

Orlando, who had been digitized in his dying moments in Atlanta, was woken up on the way to the star Voltaire because of unusual spectra from the fourth planet, Swift. Despite being too close to the star to retain its water, it still had water. Closer inspection of the spectral lines revealed that all the elements on Swift were the heavy versions. This helped them stay bound to the planet, but also made an unmistakable signature that the planet had been engineered. There was life on the planet, confined to puddles when it rained at night. Most creatures secreted a film that protected the puddle from evaporation, but eventually the heat was too great and the film burst. The creatures were able to withstand drying out (at about a 30% rate), but this was not the interesting thing. The original inhabitants of the planet, dubbed Transmuters, had used the phase shifts of the neutrons to chain together wormholes that encoded a message in every neutron. The message turned out to contain a two-dimensional movie, which appeared to show binary neutron star collisions in the galaxy, eventually showing the Lacerta collision, and then a thousand years after that, a collision at the galactic core large enough to wipe out life in the entire galaxy.

Blanca had discovered that the Transmuters had done something else, too: the neutrons had also tied our universe to another universe, in which our universe was just one fundamental particle. This macrosphere was five+one dimensions (plus six microscopic ones), the mathematics of which predicted some interesting physics. First, there were no stable orbits. Second, stars were rare, and of course there could be no planets since there were no stable orbits. Third, the physics of the chemistry predicted that the nuclear reactions would happen at a much cooler temperature, and that life (if any) would live on the surface of the stars because they would be much cooler than in our universe.

Carter-Zimmerman built a polis in the macrosphere, and then about 100 of them cloned themselves, to look for the Transmuters and ask about the coming galactic destruction of life. If the Transmuters confirmed their understanding of the message, all the citizens would clone to the macrosphere, and then clone back to the original universe after the event. The Transmuters were not to be found, but there were some interesting mollusk-like creatures that appeared to have sculpted their environment to be completely safe. Orlando cloned himself a number of times each more natively five-dimensional, with the result that the seventh clone was able to communicate with the Hermits, who said that they remembered the Transmuters, who had continued on after leaving an artifact at the pole. Orlando offered to merge back with the clones, but the seventh clone was more at home in the robot with the Hermits, most of the others wanted to terminate now that their translation role was finished, and only the first clone wanted to merge.

A few, mainly Yatima and Orlando’s son Paolo continued outwards through macrospheres in search of the Transmuters. In the third macrosphere, the polis was hacked into by creatures that were light-years in size, but because of that they functioned too slowly to communicate with them and over a thousand Exception Handlers bridged the gap. They Handler casually answered their question about why the neutron star orbits unexpectedly decayed: because each point had an infinite number of macrospheres, and itself was the macrosphere of an infinite number of subuniverses, and these combined to pull on the stars. But they said that the Transmuters had talked for a while and then moved on. So they reported that destruction was on its way, but then Yatima and Paolo continued in search of the Transmuters. The Transmuters started leaving artifacts that appeared to be data cubes, which made them easier to follow. Some hundred trillion macrospheres later they finally came to macrosphere without a data artifact, but no Transmuters anywhere to be found.

After some confusion, Yatima realized that the Transmuters had done one tau of computation in each macrosphere; they had computed their simulations externally. In addition, they had arranged the artifacts into a sculpture of a four-legged creature with four arms (the five-dimensional equivalent of a bipedal creature), one of which was pointed up. They had done everything there was to do, so they ceased. Yatima and Paolo could not go back: there had been a many slippages and communications failures along the way so they would be unable to find many of the singularities to return, and in any case, billions of years had passed. Even if the universes had not died their heat deaths, the cultures of the cloned polises would have evolved unrecognizably. Having achieved his goal of finding the Transmuters, Paolo decided to cease, but Yatima was not ready yet, and ve headed to the Mines, where one “mined” mathematical concepts by slowly understanding the concepts others had discovered until they were intuitive, and eventually one came to the seam, the coal face, where the concepts had not yet been found.

Diaspora is the “hardest” science fiction book I have read. Not only was the reading slow due to heavy use of mathematical topology which I only vaguely understood, but the book an exploration of the mathematics of life and the universe. Unlike, say, Isaac Asimov, who sketches enough of the universe to have people do things within it, David Egan has fleshed out people enough to explore not one idea of life, but at least seven concrete lifeforms (two forms of computational life, two forms of fleshers, the Wang Carpets, the life on Swift, and the Hermits), as well as ideas on wormholes, and a five dimensional universe. The book is simply mind expanding at every turn.

The flip side is that as far as Story goes, it is disjointed and sketchy, made up of quasi-short stories connected by a quest for immortality. Characters come and go in the service of ideas. One could consider the ideas as a story, progressing from a mind seed to a self-aware computational creature, to a Diaspora of cloned computational creatures on a thousand stars attempting to interact with each other, to “outer” universes, to an externalized computational sculpture across millions of dimensions and macroverses.

In some sense this resembles C.S. Lewis’ “onwards and upwards” at the end of Narnia, except it is a nihilistic vision. At the end of a quest which separated them from their community, Yatima and Paolo found the Transmuters only to discover that they had ceased, and so while the quest was ended, in some sense it was incomplete. Paolo considers that he has fulfilled his life like the Transmuters and ceases, but this is hardly a Lewisian ever-more beautiful and fulfilling exploration with a community expanding both forward and backward in time (backward because you are reunited with past community). Yatima ends by being alone, but it is a futile act of self-fulfillment, because no one else will benefit from vis discoveries because the communications were severed in both time and space. Nor is there any indication that Yatima will have the polis create new citizens, and so ve will remain alone until ve feels that ver has fulfilled verself. The polis achieved immortality, but ultimately chooses to die.

This is a cold, stark world, with a cornucopeia of rich ideas, and feels sort of like a companion to Asimov’s emotionally rich people but worlds that are a shell, much as a warehouse is an undecorated shell compared to a home. As a story, it is a little slow going. But wow, one should read it because the ideas are so crazily expansive.

Review: 8
The lack of coherent Story brings the review value down, as the ideas are consistently expansive and well-fleshed out. The book just keeps expanding, it is sort of like an essay of ideas, or like a series of musical variations that keeps exploring the same theme with very different results.