Earth

Earth is the homeworld of the human species and the capital world of the United Earth Government. Located in the Sol system, Earth is the most populous world within SolCore and the Human Sphere overall. Earth's only major natural satellite, Luna, is also home to a major human colony.

Prehistory
There is evidence suggesting that the planet was visited by one or more ancient civilizations millions of years ago and potentially up until as recently as 300,000-100,000 BCE. Though no unambiguous traces of these visits remain, their existence can be inferred from the presence of decidedly terrestrial out-of-place biota on various extrasolar worlds.

Modern era
By the mid-22nd century, the effects of anthropogenic climate change had begun to take their toll, causing extreme weather, deglaciation and consequently elevated sea levels, as well as desertification. Although the mass adoption of nuclear power for most of Earth's energy needs in the second half of the 21st century had slowed down the process, considerable damage had already been done; for one, entire coastal regions were forced to erect massive seawalls or be submerged. This caused significant human suffering, with intercontinental migrations, poverty, resource wars, and runaway urbanization. As Earth's nations were weakened by global strife, many movements on the off-world colonies sought to assert their autonomy and even gained a foothold on Earth. These crises would come to a head in the Rainforest Wars, which both exacerbated the planet's climate issues and led to a massive death toll and devastation particularly in South America.

In the late 22nd century, the nascent UEG launched the Earth Reclamation Initiative, an ambitious plan encompassing a series of projects to curtail and eventually reverse the ongoing climate crisis. Although previous eco-reclamation projects had been launched by various actors, they had so far been limited in scope and failed to impart long-term change on the global scale. The UEG's projects, developed in tandem with terraforming efforts on Mars and Venus, spanned centuries, with some being concluded only at the cusp of the 26th century. The Initiative involved large-scale reforestation as well as the eventual pioneering of mechanical atmosphere processors and weather-control technologies, made possible by the virtually limitless energy available via fusion power, to expedite the process. This process came with considerable political upheaval and controversy due to the sometimes-draconian measures taken in problem areas. Alongside various contemporaneous civil conflicts, it also led to national governments losing virtually any of the sovereignty they still had remaining. By the 25th century, when Earth's climate had stabilized to such an extent that such crisis conditions were no longer seen as viable or justified, local re-nationalization efforts enjoyed only partial success.

Over the 23rd and 24th centuries, massive arcologies were constructed to contain millions who had once lived in endless slums. In these planned communities, some of which were built in areas that had once been only sparsely inhabited such as Greenland and Siberia, millions of destitute Earthers were given housing and basic amenities. A system of global basic income was instituted as automation continued to render most basic jobs obsolete. Early on, these grand housing projects enjoyed mixed success, and the bare-minimum approach taken in the planning of the arcologies or megascrapers led to a myriad social problems within, and several became notorious as hotbeds of crime. Once the system had fully settled into its routine, however, the grimy stigma associated with "arco-life" faded somewhat, though it was still an existence characterized by aimlessness. The idle populace had their basic needs provided for them along with the metaphorical bread and circuses in the form of an infinitude of free, corporate-produced mass media and entertainment. The only way out of this was to migrate off-world, though by the 23rd century, the pioneering spirit of the Golden Age of Space Colonization had long waned and the colonies were no longer the virgin frontiers they had once been. Still, a new life off-world did provide an outlet to many Earthers even before the floodgates opened with the discovery of slipspace travel and the beginning of expansion beyond Sol, first in relatively small numbers the First Wave and then en masse in the subsequent Domus Diaspora. By the late 24th century, colonists no longer needed to be carefully vetted, and colonization companies were practically throwing able-bodied Earthers onto colony ships. This was the first true mass exodus off Earth, and it would continue up until the 26th century.

Society and culture
Earth is often regarded (at least by Earthers themselves) as the cultural heart of the Human Sphere. The stereotypical Earthers are often academics, artists, designers of many varieties, and miscellaneous socialites mingling in slick upper-class penthouse parties. By the 26th century, few Earthers are truly destitute; even those worst-off are provided basic housing and income by the UEG. This is virtually a necessity, given that society has long been so thoroughly automated that there simply are not enough jobs to go around, effectively rendering a significant portion of the planet's population unemployed for life. While this suits some just fine, giving them ample time to pursue their personal passions, it has led to a critical lack of meaning in life to many, sometimes termed "Earther Angst". One way to offset the populace's collective malaise has historically been continual expansion. This is commonly perceived as brain drain, with Earth's best and the brightest generally moving on from their cushy but boring lives on Earth to tame the wild frontier or enlist in the UNSC. This has changed in the post-war era as Earth and all of SolCore have their own reconstruction projects to contend with, and the standard of living is no longer as high in many places.

All this, however, only applies to the formal citizens of Earth. The supposed comfort of Earth life has made it an appealing destination for some colonials, particularly ones who have fallen on hard times. Earth is notoriously the most difficult planet in the Human Sphere to immigrate to, and not only due to its strict immigration policies; one of the stated goals of the Domus Diaspora was, after all, to make the planet less crowded. While Earth's capacity to support its massive population has stabilized since then, thanks to the use of new technologies, other barriers for entry are economic in nature. With the price of the dingiest apartment cells in a Singapore megascraper, one could buy an entire house on an Outer Colony like Gao. This effectively makes all but the wealthiest Outer Colonials penniless should they migrate to Earth. With Earth's limited job prospects, it also makes earning a living difficult. Standard government welfare requires Earth citizenship, which as of the end of the Human-Covenant War has a waiting line measured in the millions. Due to the effective elimination of manual labor jobs, the only work available tends to be highly specialized in nature, and most of these jobs are already filled by Earthers. One of the most reliable ways to fast-track one's way to Earth has historically been service in the UNSC, which not only pays competitively but also reflects favorably upon those seeking Earth citizenship. Despite these obstacles, Earth was flooded with refugees over the course of the Covenant War, despite the government's efforts to funnel them elsewhere in the system, including Mars and the Jovian Moons. Disappointed with the harsh reality that awaited them, most of these refugees would end up back on a colony ship bound for a new world at the first opportunity as the Phoenix Initiative's reclamation efforts began.

Governance and politics
Under the UEG, Earth is divided into administrative territories known as protectorates. Grouped based loosely on the United Nations geoscheme, each of these regions encompasses several of the old nation-states' territories. The protectorate system was created in the early 23rd century in response to various crises and was intended to streamline Earth's governance as well as the UEG's relationship with its administrative regions (specifically, to prevent the larger countries and transnational entities from dominating within the UEG), though this change did not come without controversy. Today, countries largely exist as provinces or cultural subregions, handling administration within their own territories but having little power outside. Many of the classical nation-states have either dissolved completely or no longer maintain any appreciable government, having given up their governing functions to either the protectorate system or larger transnational unions, a development already well underway before the advent of the UEG. Although Earth experienced a revival of national identity in the second half of the 25th century, this only enjoyed success in some regions. National territories on Earth are still frequently known by their old, pre-UEG names in colloquial usage, though one novel development in Standard English has been the use of national endonyms for countries rather than the classical exonyms.

Space elevators
Earth has an array of space elevators, six of which are located in major cities also known as "tether cities". These have become commercial hubs of global significance.
 * Mombasa
 * Quito
 * Pontianak - home to the Borneo Space Tether
 * Macapá - home to the Amazon Tether
 * Havana - home to the antiquated Centennial Orbital Elevator.
 * Aranuka - ocean platform home to the Pacific Tether before its destruction during the Covenant invasion. Not regarded as a full "tether city" due to its low-capacity nature.
 * Zanzibar - home to a new tether built after the war to replace the Mombasa one. Formerly an industrial wasteland after various reclamation projects failed to attract interest to the region following 22nd-century conflicts, Zanzibar is now a key development area within Dar es-Salaam's commercial sphere.

Orbital space
Despite the UNSC's efforts to clean up much of the space debris formed in the first centuries of human space exploration, Earth's orbital space is home to hundreds of thousands of artificial satellites, along with several large stations and habitats in the Earth-Luna L4 and L5 Lagrange points in particular. Space traffic around the planet is managed by multiple AI-controlled STC systems operating in synchrony, and craft operating within orbital space must relinquish override controls to their engines and weapons to the traffic control for safety reasons. Before approaching Earth, incoming craft are often instructed to wait in parking swarms in Earth-Sol Lagrange points and are subsequently directed to docking facilities either on orbital stations or on Luna. As with other planets with similarly steep gravity wells, few interstellar craft or even large intrasolar vessels ever land on Earth itself; travel to groundside spaceports is mainly conducted via orbital shuttles or space elevators. Earth's orbital infrastructure, along with large parts of the elaborate space traffic control system, suffered heavy damage during the Battle for Earth. Despite attempts to clear up Earth's orbital space prior to the battle by pushing nonessential stations to further orbits or even deorbiting others, orbital debris continued to present problems for over a decade since, leading to various flight restrictions. As the STC system was rebuilt, the communication system incorporated the newest superluminal communications technology only partly adopted in the pre-Battle for Earth network, enabling the traffic control operators and AIs to coordinate across the entire Sol system without light lag.