Strata Study Guide

Kin Arad is a human planetary engineer working for the Company , a human organisation that "builds" habitable planets with techniques and equipment salvaged from the Spindle Kings , an extinct alien race, excelling in terraforming. The expressed aim of the Company's planet building is to create branches of humanity diverse enough to ensure the whole species' survival for eternity, since the Earth's population in the past has been decimated due to the lethal Mindquakes , epidemic mass deaths caused by too much homogeneity among the populace.

All planets built by the Company are carefully crafted with artificial strata containing false fossils, indistinguishable from the real thing. On occasion, however, mischievous Company employees will attempt to place anomalous objects in the strata as practical jokes, like running shoes or other out-of-place artefacts, hoping to cause confusion among future archaeologists when the planets' beginnings have been long forgotten. The Company does not allow this however, and secretly monitors the generated strata in order to detect this, fearing such actions may cause the collapse of entire civilizations when the artefacts are eventually unearthed.

Kin and two aliens, the four-armed frog-like, paranoid and muscular Kung Marco and Silver, a bear-like Shand , historian and linguist by profession, are recruited by the mysterious Jago Jalo for an expedition. Jalo, a human who more than a thousand years ago embarked on a relativistic journey has made a stunning discovery: a flat Earth. However, when the team rendezvous on the Kung homeworld, the violent Jalo unexpectedly has a heart attack and dies. Shocked by the large amounts of weapons on-board Jalo's spaceship, Kin has misgivings about the expedition, but Silver and Marco see the possibility of reaping great technological rewards and launch the vessel. When the expedition finally arrives at Jalo's pre-programmed coordinates, they find a flattened version of the mediaeval Eastern hemisphere of Earth, clearly artificial. It rotates around its hub inside a gigantic hollow sphere with tiny "stars" affixed to the interior, complete with a small sun, moon and fake planets revolving around it.

After their ship is hit by one of the orbiting "planets", Kin, Marco and Silver are forced to abandon ship and land on the flat Earth with the help of their lift-belt equipped suits. A return from the flat Earth now seems impossible, unless they are able to find its mysterious builders, so they embark on a journey to a structure they have spotted at the hub of the Disc, the only thing which does not match geographically with the Earth they know. En route, they encounter the superstitious Medieval inhabitants of the Disc, who believe the end of the world is near, due to increasingly chaotic climate (caused by the Disc's machinery breaking down), the recent disappearance of one of their planets and the general devastation caused by the ship's crash. They also discover a number of other differences. What Kin Arad knows as Reme is called Rome on the Disc, and there is a strange Christos cult that is completely unfamiliar to Kin Arad. Also, Venus is conspicuously lacking its giant (lunar-sized) moon Adonis , which dominates the sunset sky on the Earth Kin knows, and led humanity to a heliocentric world view early on. Since only the Eastern hemisphere of Earth is represented, the continent of America is completely missing; the travellers rescue a party of Vikings in the process of searching for Vinland, when their ship is about to sail over the edge of the world.

In addition, there are real "magical" creatures and objects on the Disc, demons and magic purses and flying carpets– all of them, the travellers realise, highly advanced and sophisticated technological constructs like the Disc itself. Indeed, the world itself is an extremely old and sophisticated automated system. At the very end of the story, Kin comes to suspect that the builders of the flat world in fact constructed the universe as a whole, with the evidence of previous races being hoaxes and the flat world being an inside joke, analogous to the false strata Kin and the Company themselves manufacture, and the occasional hoaxes put in these strata by rebellious employees.

Kin and the others eventually reach the hub and Kin makes contact with the Disc's controlling systems. She is told that, despite advanced robotic maintenance, sheer entropy build-up threatens the Disc's further existence. The machines offer their advanced technology, in exchange for Kin's construction of a real replacement Earth for the flat planet's inhabitants. Kin agrees; the implication being that the world she will build is in fact our own Earth. Kin is excited about the massive task at hand; just like Ringworld 's Louis Wu, whom she parallels, she is over two hundred years old, and thus constantly in danger of growing tired of life.