The Earth refers to the third planet located in the Solar System. It is the same as the real life planet Earth. It is the main setting of the Captain Earth series, and its evolutive roots are of pivotal importance for the plot.
The Earth is in many aspects similar to its real life counterpart, except there are slight differences or emphasized elements that grant differencies. The most important of them is the revelation that the Earth is the only planet in the Solar System with a knowly evolved especies capable of manifesting Orgone Energy which is the the target of the Kiltgangs and the motive of their attacks on Earth, to drain said energy, but if such event occurs, the planet would be devoid of life.
Although its potential for Orgone Energy is noted, at the time the Kiltgangs arrived at Earth, the planet did not suit their needs, so they decided to remain dormant until the planet could evolve with their mothership stationed in Uranus. Although the specific amount of time is unknown, it is hinted due to the Kiltgang's immortality that they may have awaited centuries, if not also milleniums. To facilitate their future assault on Earth, they sent their ship the Blume along a created living weapon Hana Muto known to them as the "Princess of Blume" to Earth, where she remained dormant.
The many events revolving the Kiltgangs, including the involvement of Macbeth Enterprises in the development of the Designer Child program. Caused several Earth bases to develop somewhat more advanced technology than seen in the real life Earth. These technological developments include the construction of an Orbital Space Ship known as the Tenkaido which monitors spacial activity and hosts a couple of selected humans to participate in the Kivotos Plan. The creation of large mecha robots such as the Star Emblem, the Earth Engine and the Nebula Engine for self-defense against the Kiltgangs as well as several specially developed armed satellites known as Impacters.