The Inner Sphere is an astrographical and political region of space, and an administrative sector of the Central Galactic Union, with historical precedent as a province of the Terran Empire. It is defined as an area of space within a 500 light-year radius around the Sol System. It is a region of great importance to human history; it contains the Sol System and Earth, the cradle of humanity, as well as many of the first human colonies. It is a densely-populated region of space with a high level of development and standards of living. The economies of its constituent worlds are largely characterized by technology, commerce, and the public sector, as well as light industry. The capital world of the Union is located within the Inner Sphere, as are many important military, business, and government centers.

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