Earth

"Earth, man... What a shithole."

―Johner (from Alien Resurrection)

Earth
System	Solar System
Suns	Sun
Moons	Luna
Class	Terrestrial
Diameter	12,756 km
Terrain	Forests, grasslands, deserts, jungles, wetlands, mountains, tundra, polar regions, oceans, lakes and rivers
Atmosphere	78% nitrogen, 21% oxygen, 0.9% argon, 0.1% others (carbon dioxide, water, etc.)
Climate	Many climate zones
Species	Humans Yautja Xenomorphs

Earth, also called the world and, less frequently, Gaia (and Terra in some works of science fiction) is the third planet from the Sun, the densest planet in the Solar System, the largest of the Solar System's four terrestrial planets and one of many astronomical objects known to accommodate life. The earliest life on Earth arose at least 3.5 billion years ago. Earth's biodiversity has expanded continually except when interrupted by mass extinctions. Although scholars estimate that over 99% of all species of life (over 5 billion) that ever lived on Earth are extinct, there are still an estimated 10–14 million extant species, of which about 1.2 million have been documented and over 86% have not yet been described. Over 7.3 billion humans live on Earth and depend on its biosphere and minerals for their survival. Earth's human population is divided among about two hundred sovereign states which interact through diplomacy, conflict, travel, trade and communication media.

Geographical features

As the homeworld of the Human species, Earth is the archetype by which they measure all other planets in terms of habitability. The ultimate goal of all terraforming efforts across the galaxy is to create an environment similar to that of Earth on any planet the humans attempt to colonize.

Earth is approximately 4.5 billion years old. It possesses an iron core that is solid at its center with a liquid layer encompassing it. This genereates a powerful magnetosphere that has kept Earth from losing its water and other volatile organic compounds. The core is surrounded by semifluid magma, on which the solid, yet light crust floats. The planet is geologically active, with plate tectonics causing volcanoes and natural springs to dot its surface. Earthquakes are common.

The planet lies in the liquid water zone of Sol, and water is found in abundance-oceans cover 70% of the planet. The 30% of the surface that is dry land is divided amongst four major landmasses (which Humans divide into seven continents) and thousands of islands spread across the oceans. There is a thin atmosphere that is maintained by the biomass on the planet's surface. It is 78% nitrogen and 21% oxygen, with the remainder a mix of trace gases including argon, carbon dioxide, and water vapor.

Earth spins on its axis once every 23 hours, 56 minutes, 4 seconds. The axis is tilted 23° from its orbital plane, which causes seasonal changes in its higher latitudes as it orbits Sol.

Earth held an abundance of natural resources well into the 22nd century, such as minerals and several substances produced as by-products by the planet's biomass, such as petroleum, coal, wood, and natural gas. Humans utilized these resources into an impressive technology base. However, over time the resources of Earth began to become exhausted, prompting Humans to search for other worlds which could be exploited.

Terrain and Climate

The geological activity of Earth has created a wide variety of terrain across its surface. Plate tectonics and erosion (by both the atmosphere and water) dominate the formation processes of surface features. There are mountain ranges, valleys, plains, mesas, and canyons, which in turn may be found in deserts, tundra, forests, grasslands, and icecaps at the poles. Earth may be classified into three general climate zones: the tropics, which straddle each side of the Equator, the polar regions located around the North and South Poles, and the temperate zones in-between. Each of these are divided into other zones which vary depending on the distance from the Equator, proximity to large bodies of water, and local geography, such as mountains.

Humans began to modify the terrain of Earth when they discovered agriculture around 8000 BCE. This enabled the development of great cities linked by trade routes stretching for thousands of miles over both land and ocean. Beginning in the 19th century, Humans began to alter the planetary climate with the introduction of industrial by-products. By the 24th century, much of Earth had become an arid wasteland. But over time, by the time of Alien Resurrection, It seems that there have been efforts to restore the Earth's ecology in some areas.

Species

Sentient

• Humans
• Yautja (Formerly)
• Engineers (Formerly)
• Xenomorphs

Semi-Sentient 

• Cats
• Dogs
• Ox
• Pig
• Cetacea (Dolphins/Whales)
• Corvidae (Crow family of birds)
• Elephants
• Non-Human hominids (ex: Chimpanzees)

Locations

Notable locations that have been the site of a Xenomorph or Predator activity:

Antarctica

• Bouvetøya, Antarctica, (Alien vs. Predator)

North America

• Neonopolis (New Way City) (Predator: Concrete Jungle)
• New Jersey (Predator: Bad Blood comic)
• Gunnison, Colorado (Aliens vs. Predator: Requiem)
• Los Angeles, California (Predator 2)
• San Drad, California (Alien vs. Predator)
• Nebraska

Central and South America

• Teotihuacan, Mexico (Alien vs. Predator)
• Republic of Val Verde, Central America, (Predator)

Europe

• Paris, France (Alien Resurrection)

Africa

• East Africa (Predator 2009 Comic)

Asia

• Vietnam (Predator: The Bloody Sands Of Time)

Australia

• Sydney, Australia (Aliens: Sentinels)

Trivia

• Gateway Station is in permanent orbit around Earth.
• In the unofficial Alien sequel, Alien 2: On Earth, the Aliens take over the Earth, as suggested by the film's "you may be next!" message. The conquest of Earth by the Xenomorphs is also a major plot point in many of the comics and novels of the Alien franchise.
• It is heavily insinuated in Alien Resurrection that some kind of catastrophe, or simply years of degradation, have made Earth uninhabitable or at least very unpleasant. At the end of the extended Special Edition of the movie, it is shown that Paris, France is in ruins, while the surrounding area is a desolate wasteland. The devastation may have something to do with the "Lacerta Plague", which is mentioned in the film by Annalee Call. However, Earth does not appear to have been entirely abandoned — the planet remains the designated home base of the USM Auriga. Johner's comment that Earth is "a shithole" by this time seems to imply that centuries of pollution, war and resource depletion have left Earth in a dilapidated state.
• In the SNES game Aliens vs. Predator, the colonists of Vega 4 send a distress call to "Earth-based authorities", implying Earth is once more the center of human activity by the year 2493. 
• In Alien Resurrection, when the Aurgia hits Earth, a large blast wave can be seen. The wave would have killed almost all life in central Africa.

Appearances

• Alien/novel/comic (mentioned only)
• Alien 2: On Earth
• Aliens/novel
• Predator/novel
• Aliens: Book One/novel
• Aliens: Book Two/novel
• Predator: Concrete Jungle (comic)
• Predator 2/novel/comic
• Aliens: Earth War/novel
• Alien vs. Predator (1994 video game)
• Alien Resurrection/novel/comic
• Aliens versus Predator (1999 video game)
• Alien vs. Predator/novel
• Predator: Concrete Jungle (video game)
• Aliens vs. Predator: Requiem
• Predators (comic)
• Predators (mentioned only)
• Prometheus
• Alien: Out of the Shadows (mentioned only)
• Alien: Sea of Sorrows
• Prometheus: Fire and Stone (mentioned only)