基地系列
Asimov estimates that his Foundation series takes place nearly 50,000 years into the future, with Hari Seldon born in 47,000 CE. Around this time, the future emperor Cleon I is born in the imperial capital Trantor, 78 years before the Foundation Era (FE) and the events of the original Foundation trilogy. After Cleon inherits the crown, the mathematician Hari Seldon comes to Trantor from Helicon to deliver his theory of psychohistory that predicts the fall of the empire, which triggers the events of "Prelude to Foundation". "Forward the Foundation" picks up the story a few years later, with the emperor being assassinated and Seldon retiring from politics.