Editing Riverworld (section)

===Overview===
Starting in the "late twenty second century", the Riverworld has been engineered by an alien race to consist solely of a single long [[river|river-valley]] which snakes across its entire surface. The river's source is a small North Polar sea, from which it follows a course tightly zig-zagging across one hemisphere before flowing into another, along an equally labyrinthine path, to the same sea. The river has an average depth of {{convert|1.5|mi|km}}, and its width ranges from {{convert|6.8|mi|km}} to {{convert|24.8|mi|km}}. It is shallow near the shore but plunges to enormous depths towards the channel. The banks are generally smooth and gentle, expanding into wide plains on either side, then assuming jagged hills before an impenetrable [[mountain range]]. The valley averages {{convert|9|mi|km}} in width, but includes narrows and occasional widenings into lakes with islands. From source to mouth, the original supposition of the river's length is 20,000,000 miles, as said by Alice Hargreaves and attributed to Peter Frigate, shortly after the defeat of Hermann Goering.  (Books I, II, and III later state the river is {{convert|10000000|mi|km}} long). There are no seasons, and daily variations are metronomic. The only animal life consists of fish and soil worms. The vegetation is lush and of great variety, including trees, flowering vines, several kinds of fast-growing bamboo, and a resilient mat of grass which covers the plains. The Riverworld has no visible moon, but a great number of stellar objects in the sky, including gas sheets and stars close enough to show a visible disk.

The story of Riverworld begins when 36,006,009,637 humans, varying from the first ''[[Homo sapiens]]'' until the early 21st century, are simultaneously [[resurrection|resurrected]] along the river.  Of these, 20% are from the 20th century, due to the high population thereof. Originally the cutoff year was given as 2008 in ''To Your Scattered Bodies Go'', but this later was [[retcon|modified]] to 1983 in ''The Dark Design''. Purportedly, the cut-off indicated the point at which most of the human race had been purposefully annihilated by [[First contact (science fiction)|first contact]] with aliens visiting Earth. The protagonists later find this a creative fiction, produced by the masterminds of the resurrection. Undercover agents of these masters placed on the Riverworld would identify themselves as having died after 1983 so as to be recognized by fellow agents.

In each area are initially three groups of people: a large group from one time period and place, a smaller group from another time and place, and a very small group of people from random times and places (most of the 20th- and 21st-century humans are part of this last group).