Second Golden Age of Humankind
According to the official Republic historical curriculum, the Second Golden Age of Humankind lasted from 2,452, with the signing of the Unification Treaty, to 4,026 AD.
The Unification Treaty united humanity for the first time under a common state. The separatist governments were reorganized as departments under a global federal state, the United Nations. The far-sighted leaders of the United Nations sought to extirpate the plague of group separatism that had caused so much suffering, and to promote a new, species-wide culture. With the species no longer fragmented and disunited, the Golden Age saw slow but steady growth and development in science, art, and economic output. The combination of a large population with highly automated technology meant there was little need for most individuals to work, and the UN channeled the population's surplus energies in positive, unifying directions.
The UN's efforts were assisted by two events: the discovery of the Architect ruins under the South Atlantic in 2,523 AD and the development of the Kingston-Brown fusion drive in 2,496 AD.
The exploration of Architect ruins provided a common cultural touchstone for the new global state. Three separate sites were found underwater in the south Atlantic during the 26th century. A second series of ruins was found on Mars in 2,988 AD. Although the ruins had been completely stripped of useable technology, the beautiful and stirring mosaic and sculptural art of the Architects set a high standard that the new, global human culture did its best to imitate.
Artistic Reconstruction of Architect
(Image Credit: http://en.wikipedia.org/wiki/Elder_Thing)
Space exploration and development was a second focus of the UN. The Kingston-Brown fusion drive made large-scale exploration and colonization of the solar system outside of the Earth-Moon system possible for the first time. Mining bases were set up on Mercury in the late 2800's, bases on Mars in the early 3000's to explore the Architect ruins, a major orbital station around Saturn in the 3100's to support exploration into the outer solar system, and smaller outposts scattered throughout the solar system.
The exploration program culminated in the launch of the first interstellar exploration ship from Saturn in 3789 AD. These primitive starships were only able to reach 0.1c, but, over the next two centuries, they explored most of the star systems within 10 LY of Earth.
The human population in 4,000 AD had stabilized at four billion. 50 million people lived in off-planet colonies in the Earth-Moon system, and another 200,000 were scattered throughout the rest of the solar system. The UN had forged a global, species-wide culture, defeating the virus of national identities. The average human enjoyed a luxurious existence supported by automated mining, manufacturing, and agriculture, his or her time dedicated to science, art, or personal pleasure.
The Second Golden Age came to an end on January 4th, 4,026 AD, when TYRANT reactivated under the South Pacific.