The Planet Chikyu is one of two main planetary locations within the Spectral Shadows series on which the majority of the saga takes place.
This planet contains several other locations crucial to the saga, including Rubicon Forest, The Ommandeer Family Shrine, the world nation Polithsania, the capitol city Babylon, The Animal Research Center, The Hole and The Rhoades Mansion.
Chikyu has a relatively Earth-like history up to the time of the early 1960's, at which point the planet was invaded by The Empire of Astral Pirates who attempted to bring the planet under their control, but met resistance from former World War 2 pilot Harrison James who organized a moderately successful rebellion.
Finding the rebellion too costly to defeat, the pirates turned to political means of absorbing the planet into their empire. With the assassination of the Polithsanian president in 1963, a new president was installed who helped unite that planet under a single world government, which then voted to become part of the empire of its own free will.
From that point on the parallels between Earth history and Chikyu history become slightly altered. The Pirates bring new technology to Chikyu, as well as opening up commerce and migration from other planets.
The history of Chikyu is fated to end in 1979, but because of the advances supplied by the empire, certain aspects of Earth's early 80's happen before the planet's demise.
The rebellion against the empire continues, in spite of the voluntary acceptance of imperial rule, but it must continue as an underground movement, as the general populace no longer endorses it. This underground rebellion becomes the motivation for the counter culture of the late 60's, replacing the Vietnam war, which never happens on Chikyu. Rather, young humans find themselves conscripted into the imperial military to fight wars on other planets, which are generally meaningless to the population of Chikyu, but are treated as sacred by those who fall under the guidance of imperial propaganda.
This practice of conscription is discontinued in 1974 as a means of driving a final stake into the heart of the rebellion. The rebellion then loses all favor on Chikyu, and those who continue to rebel against the empire are considered outlaws.