Welcome to decade eight, third millennium, when the effects of the phase-change in the structure of the solar system are finally becoming visible on a cosmological scale.
There are about eleven billion future-shocked primates in various states of life and undeath throughout the solar system. Most of them cluster where the interpersonal bandwidth is hottest, down in the water zone around old Earth. Earth's biosphere has been in the intensive care ward for decades, weird rashes of hot-burning replicators erupting across it before the World Health Organization can fix them – gray goo, thylacines, dragons. The last great transglobal trade empire, run from the arcologies of Hong Kong, has collapsed along with capitalism, rendered obsolete by a bunch of superior deterministic resource allocation algorithms collectively known as Economics 2.0. Mercury, Venus, Mars, and Luna are all well on the way to disintegration, mass pumped into orbit with energy stolen from the haze of free-flying thermoelectrics that cluster so thickly around the solar poles that the sun resembles a fuzzy red ball of wool the size of a young red giant.
Humans are just barely intelligent tool users; Darwinian evolutionary selection stopped when language and tool use converged, leaving the average hairy meme carrier sadly deficient in smarts. Now the brightly burning beacon of sapience isn't held by humans anymore – their cross-infectious enthusiasms have spread to a myriad of other hosts, several types of which are qualitatively better at thinking. At last count, there were about a thousand nonhuman intelligent species in Sol space, split evenly between posthumans on one side, naturally self-organizing AIs in the middle, and mammalian nonhumans on the other. The common mammal neural chassis is easily upgraded to human-style intelligence in most species that can carry, feed and cool a half kilogram of gray matter, and the descendants of a hundred ethics-challenged doctoral theses are now demanding equal rights. So are the unquiet dead; the panopticon-logged Net ghosts of people who lived recently enough to imprint their identities on the information age, and the ambitious theological engineering schemes of the Reformed Tiplerite Church of Latter-day Saints (who want to emulate all possible human beings in real time, so that they can have the opportunity to be saved).
The human memesphere is coming alive, although how long it remains recognizably human is open to question. The informational density of the inner planets is visibly converging on Avogadro's number of bits per mole, one bit per atom, as the deconstructed dumb matter of the inner planets (apart from Earth, preserved for now like a picturesque historic building stranded in an industrial park) is converted into computronium. And it's not just the inner system. The same forces are at work on Jupiter's moons, and those of Saturn, although it'll take thousands of years rather than mere decades to dismantle the gas giants themselves. Even the entire solar energy budget isn't enough to pump Jupiter's enormous mass to orbital velocity in less than centuries. The fast-burning primitive thinkers descended from the African plains apes may have vanished completely or transcended their fleshy architecture before the solar Matrioshka brain is finished.
It won't be long now …
Meanwhile, there's a party brewing down in Saturn's well.
Sirhan's lily-pad city floats inside a gigantic and nearly-invisible sphere in Saturn's upper atmosphere; a balloon kilometers across with a shell of fullerene-reinforced diamond below and a hot hydrogen gas bag above. It's one of several hundred multimegaton soap bubbles floating in the sea of turbulent hydrogen and helium that is the upper atmosphere of Saturn, seeded there by the Society for Creative Terraforming, subcontractors for the 2074 Worlds' Fair.
The cities are elegant, grown from a conceptual seed a few megawords long. Their replication rate is slow (it takes months to build a bubble), but in only a couple of decades, exponential growth will have paved the stratosphere with human-friendly terrain. Of course, the growth rate will slow toward the end, as it takes longer to fractionate the metal isotopes out of the gas giant's turbid depths, but before that happens, the first fruits of the robot factories on Ganymede will be pouring hydrocarbons down into the mix. Eventually Saturn – cloud-top gravity a human-friendly 11 meters per second squared – will have a planet wide biosphere with nearly a hundred times the surface area of Earth. And a bloody good thing indeed this will be, for otherwise, Saturn is no use to anyone except as a fusion fuel bunker for the deep future when the sun's burned down.
This particular lily-pad is carpeted in grass, the hub of the disk rising in a gentle hill surmounted by the glowering concrete hump of the Boston Museum of Science. It looks curiously naked, shorn of its backdrop of highways and the bridges of the Charles River – but even the generous kiloton dumb matter load-outs of the skyhooks that lifted it into orbit wouldn't have stretched to bringing its framing context along with it. Probably someone will knock up a cheap diorama backdrop out of utility fog, Sirhan thinks, but for now, the museum stands proud and isolated, a solitary redoubt of classical learning in exile from the fast-thinking core of the solar system.
"Waste of money," grumbles the woman in black. "Whose stupid idea was this, anyway?" She jabs the diamond ferrule of her cane at the museum.
"It's a statement," Sirhan says absently. "You know the kind, we've got so many newtons to burn we can send our cultural embassies wherever we like. The Louvre is on its way to Pluto, did you hear that?"
"Waste of energy." She lowers her cane reluctantly and leans on it. Pulls a face: "It's not right."
"You grew up during the second oil crunch, didn't you?" Sirhan prods. "What was it like then?"
"What was it …? Oh, gas hit fifty bucks a gallon, but we still had plenty for bombers," she says dismissively. "We knew it would be okay. If it hadn't been for those damn' meddlesome posthumanists —" Her wrinkled, unnaturally aged face scowls at him furiously from underneath hair that has faded to the color of rotten straw, but he senses a subtext of self-deprecating irony that he doesn't understand. "Like your grandfather, damn him. If I was young again I'd go and piss on his grave to show him what I think of what he did. If he has a grave," she adds, almost fondly.
Memo checkpoint: log family history, sirhan tells one of his ghosts. as a dedicated historian, he records every experience routinely, both before it enters his narrative of consciousness – efferent signals are the cleanest – and also his own stream of selfhood, against some future paucity of memory. But his grandmother has been remarkably consistent over the decades in her refusal to adapt to the new modalities.
"You're recording this, aren't you?" she sniffs.
"I'm not recording it, Grandmama," he says gently, "I'm just preserving my memories for future generations."
"Hah! We'll see," she says suspiciously. Then she surprises him with a bark of laughter, cut off abruptly: "No, you'll see, darling. I won't be around to be disappointed."
"Are you going to tell me about my grandfather?" asks Sirhan.
"Why should I bother? I know you posthumans, you'll just go and ask his ghost yourself. Don't try to deny it! There are two sides to every story, child, and he's had more than his fair share of ears, the sleazebag. Leaving me to bring up your mother on my own, and nothing but a bunch of worthless intellectual property and a dozen lawsuits from the Mafiya to do it with. I don't know what I ever saw in him." Sirhan's voice-stress monitor detects a distinct hint of untruth in this assertion. "He's worthless trash, and don't you forget it. Lazy idiot couldn't even form just one start-up on his own: He had to give it all away, all the fruits of his genius."