The Universe is everything that exists; it is infinite and eternal. A cosmos is finite and temporal. The
Cosmos, in which this website, its author, and its reader exist, is the only one we know of; but it is reasonable to suppose that the Universe contains more than one, perhaps indeed an infinitude of them. It may well be that every possible cosmos exists, i.e. every one that contains no internal contradictions.
A polycosm is a group of interconnected cosmoses. A metachronic polycosm is a group of alternate histories, located sideways in time. A tectonic polycosm is a group of artificial cosmoses, or cosmions, created by superhuman beings or a far-future supercivilization.
Right now, in the Hypostatic Cosmos, a/k/a The Real World, history is reaching a crux. In the future history I prefer, the American nation and the West as a whole survive and triumph; in the future history I dread, they go under. China and Islam will then contend for domination of the world.
Various alternative histories exist in the author's imagination. In one of these histories, which I call The Prime Line or TPL, civilization survives and advances for, oh, a hundred thousand years or so, until our remote descendants have the power to create whole self-contained worlds of space-time, with natural laws made to order.
The Carolojohannine Polycosm is recursive. In TPL, an SF writer named Peter Gower (Lost Generation, 1895 cohort) wrote two series of novels about the planets Maldek and Counter-Earth, which actually exist in various other alternate histories. In one of these, Contraterran colonies on Earth founded antediluvian civilizations that begot contemporary supercivilizations with the power of metachronic travel. A cosmion based (in part) on Gower's writings will also have been created during the Cosmogenic Age.