My “Old Earth” stories are the product of many impulses. But the very first was a trip to Australia for the Worldcon of 1999. After the con, my wife and I toured the island continent. Many overseas attendees took the same opportunity, and we encountered such exotic fauna as the Bushy-bearded Editor of Analog (Stanleius Schmidtus).
And I enjoyed my first one-to-one with a kangaroo, in a nature park north of Melbourne. Close to the kangaroos seemed extraordinary, with those remarkable levered back legs. To my (non-biologist’s) eye, they were like examples of alternative bio-engineering, aliens from the imagination of Niven or Vinge. Of course kangaroos and the rest of the native fauna evolved differently because of Australia’s long isolation from the other continents.
From that experience bubbled up the idea of a world with “stratified time.” I wanted to concoct a world in which the passage of time and its effects were manifest and intrusive, just as it was for me in that brief kangaroo moment. So how would it be if time ran at different rates in different placesin fact, at different altitudes? If time ran faster the higher up you climbed, you could perhaps reside on top of Australia’s Uluru and live out a life of decades, while mere hours passed down on the plain.
I could quickly think of many tales to be spun out of such a premise, some of which have emerged in the subsequent stories. “PeriAndry’s Quest” is a story of social impact; the longer-lived upper crust living at the bottom of the cliff exploit the (relatively) short-lived caste further up. In “The Time Pit” the strata of time are exploited in warfare. And in “Climbing the Blue” my hero deliberately accelerates his own life to save his wife; he grows old seeking a cure for her disease, while she stays young.
The vision came before the science, but how might such a time-pit world come about? Of course in relativity theory a black hole is something like my time pit; if you fell towards the event horizon, as seen by an outside observer, your elapsed time would seem to slow to vanishing. Every gravity well, including Earth’s, has similar properties, though on Earth the stratification is negligible to the senses. I wanted to see such effects built into a human-scale world, where climbing a staircase is enough to deliver a noticeable difference in time flowbut without such inconveniences as a black hole’s ferocious tidal forces.
Old Earth is an artefact. I imagined a far-future civilisation able to shape space and time to arbitrary ends in a way unimaginable to us, just as our Neolithic-farmer ancestors could surely not have imagined our modern mastery of materials technology and biotech, say. In the back of my mind, I think, was Greg Bear’s work, which has featured such artefacts of spacetime as the “Way” of Eon and its sequels. Is a time pit possible, however? Not within relativity theory, but relativity appears to be just one asymptote of a much deeper theory we’ve yet to assemble: quantum gravity. The possibilities opened up by quantum gravity ideas seem to me so wide that right now what is physically possible to an arbitrarily advanced technology is only loosely constrained. In other words, all bets are off!
Later another input came when I began work on my Destiny’s Children series of novels. These are a return to my “Xeelee Sequence” universe, which has roots that now go back nearly twenty years, God help me. While Destiny’s Children is about an episode at the centre of the Sequence’s grand narrative, I also began to think about the very far future of my universe. Having the pre-existing framework of the “Sequence” in place seems to enable me to think more deeply about the construction of such a future, and what trends might shape it.
For example, in Destiny’s Children humans are busily building a galactic empire. But what happens after the wave of colonisation has come and gone? On Earth, even if mankind were to disappear tomorrow, a future alien archaeologist would be able to deduce the existence of intelligence from the great mixing-up of the world’s flora and fauna we’ve caused since the age of explorationsuch as the transporting of science fiction fans to the heart of Australia. So it will be after the starships have gone; Earth will be left with an “ecology” composed of fragments transported purposefully or accidentally across interstellar distances.
And it would be a true ecology, given enough time, a mosaic, not just a heap of fragments. If you have a different biochemistry to mine I may not be able to eat you. But I could perhaps use your skeleton as a supporting frame, or live off some by-product of yours, such as carbon dioxide or methane. In our present world there are productive symbioses of creatures such as birds and elephants, and bacteria and humans, far removed from each other on the evolutionary tree. Why not symbioses between colonists from different stars?
And then there’s technology. Already our tools enjoy an evolution of their own that has run parallel to ours since we’ve been toolmakersthat is, since hominids have walked the Earth. Right now this evolution is still shaped by our desires, but in the future, when machines become too complicated for us to build, and perhaps even smarter than us, this may no longer be true. And what then? In a far enough future you may find technological “species” with almost as deep an evolutionary pedigree as our own. And the machines will surely engage in symbiotic and other relationships with the other inhabitants of their world which may have nothing to do with the intent of the long-dead designers of their remote ancestors. Thus the wild weapons of “The Time Pit” and the predatory mobile buildings of “The Lowland Expedition.”
And so the ecology of future Earth could be a complex mixture of “native” (pre-technological) life, life forms with origins on other worlds, and much-evolved technological relicsand all locked into an ecology every bit as interconnected and interdependent the “entangled ban” of which Darwin eloquently wrote in The Origin of Species.
So the threads for my “Old Earth” stories came together. We are in the far future of the Xeelee Sequence universe. In a dangerous age, engineers built a shell of stratified spacetime over an exhausted Earth. Its inhabitants live slow enough that the feeble trickle of remnant interior heat sustains them. On the surface is a post-interstellar, post-technological ecology. Swimming slowly in their pond of slow time, the engineers’ descendants have been projected into the safety of the remote future. I have been feeling my way into this world with short fiction, rather as I did in the early days of my Xeelee project, my Manifold work and others, because I’ve found it’s a good way to develop such complicated ideas.
It’s fun to allow the characters in the stories to deduce the past history of their world from traces in their present, just as real-world geologists and biologists have decoded our own deep history from rocks and fossils. But everything about Old Earth has been, if not made by intelligence, then modified. Just as in our time, Old Earth philosophers argue against “intelligent design” and hold to the belief that everything is the product of the working-out of natural law. But on Old Earth, as in any far future shaped by intelligence we can imagine, the Creationists are right!