Aliens threaten to destroy the Earth in any number of sf books and movies. In most cases, daring space heroes defeat them and all returns to normal. In the rare cases when they don’t, it usually spells the end of the human race, at least as an independent civilisation; individuals might survive, but only by hitching a ride to safety with more benevolent aliens.
The big idea of Belt Three is that neither of these extremes happens. By cosmic coincidence, the Worldbreakers arrive during a quite narrow window in human development: we’re not advanced enough to defeat them, but we’re advanced enough to survive. Three hundred years later, people live in cities built into the asteroid belts that once made up the planets. The Worldbreakers are still around, destroying these debris pieces one by one (they’re slow but thorough), and populations scramble to evacuate whenever they approach. To build the world of Belt Three I tried to imagine what life would be like under these conditions.
The details of the evacuation of Earth would leave a large mark on the society that would emerge. I’d read somewhere that there may have been a human population bottleneck around 70,000 years ago, in which the human race was reduced to a few thousand individuals, and I decided that a similar thing happened here: only around a thousand families managed to evacuate in time. These near-future refugees had more resources than our prehistoric ancestors, though, and they also managed to save banks of genetic material from a larger population, and the technology to create clones from this material. However, a flaw in the hurriedly-designed cloning system meant that the clones were sterile. Three centuries later, the most important social divide is between the “true-born” ruling class and the “tank-born” majority, and the mythology of the thousand surviving families is an important part of true-born identity.
Secondly, the way people understand their place in history wouldn’t be as straightforward as “alien robots destroyed the planets and now we’re living in the debris.” That’s too cold for most people to find comforting. Instead, various religious groups offer their own explanations for the Worldbreakers; and because these religions pull in different directions, the society-wide consensus has become a sort of agnostic shrug: “No one knows what the Worldbreakers are.”
I find religion fascinating, and I wanted to make it an important part of my worldbuilding. I decided that creating a single dominant religion would be too neat, so I invented several small religious groups. The one that features most prominently is Scriberism, which teaches that the Worldbreakers are angels sent by God to dismantle the universe and bring the spiritually pure into paradise. At the highest level of the religion, believers purify themselves then board ships that fly into a Worldbreaker’s energy beam. Other religions include the Arkites, who interpret the Worldbreakers as a second Flood, which will eventually end and reveal a new set of planets; the Eternalists, who believe that the planets are destroyed and recreated in an endless cycle; and the True Belters, who believe that the planets are a myth and the universe has always consisted of belts and asteroid cities.
Outside of religion, society’s received wisdom would reflect its circumstances in more subtle ways, common assumptions that no one questions because no one thinks about them at all. Whatever the Worldbreakers are, everyone knows that they can’t be fought, and that the human race is living through its last few hundred years. That’s enough time to grab the best life you can for yourself and (if you’re a true-born) your children, but not long enough to think about grand projects for improving the world. For someone who’s grown up with the idea of the doomed human race, it wouldn’t be frightening, and might even be a source of comfort; nothing you do really matters, so there’s nothing to worry about. When one character has this belief challenged, they react not with hope but with bafflement.
That’s some of the thinking that went in to the background of the novel. In the foreground is the idea that there are always a few individuals who don’t accept society’s commonly accepted wisdom. The main character isn’t such an individual (at least not at first), but the pirate who kidnaps him is: she knows it’s impossible to strike back against the Worldbreakers, but she’s on a personal quest do do so anyway, and she’ll tear down any part of belt-dwelling society that tries to stop her.