Earth

**Earth** is the mother planet of Tomorrowland, the entire United Galaxy Space Force (UGSF) and the home of Terrans. The Earth is a planet in the Solar System and the third planet from the Sun and the only astronomical object known to harbor life. According to radiometric dating and other sources of evidence, Earth was formed over 4.5 billion years ago. Earth's gravity interacts with other objects in deep space, especially the Sun and the Moon, which is Earth's only natural satellite. The Earth orbits around the Sun in 365 days, a period known as an Earth sidereal year. During this time, Earth rotates its axis about 366.256 times.

Earth's axis of rotation is tilted with respect to its orbital plane, producing seasons on Earth. The gravitational interaction between Earth and the Moon causes tides, stabilizes Earth's orientation on its axis, and gradually slows its rotation. Earth is the densest planet in the Solar System and the largest and most massive of the four rocky planets.

Earth's lithosphere is divided into several tectonic plates that migrate across the surface over many millions of years. About 71% of Earth's surface is covered with water, mostly by oceans. The remaining 29% is land consisting of continents and islands that together contain many lakes, rivers and other sources of water that contribute to the hydrosphere. The majority of Earth's polar regions are covered in ice, including the Antarctic ice sheet and the sea ice of the ice pack. Earth's interior remains active with a solid iron inner core, a liquid outer core that generates Earth's magnetic field and a convicting mantle that drives plate tectonics.

With the first billion years of Earth's history, life appeared in the oceans and began to affect Earth's atmosphere and surface, leading to the proliferation of anaerobic and, later, aerobic organisms. Some geological evidence indicates that life may have arisen as early as 4.1 billion years ago. Since then, the combination of Earth's distance from the Sun, physical properties and geological history have allowed life to evolve and thrive. In the history of life, biodiversity was gone through the long periods of expansion, occasionally punctuated by the mass extinction events. Over 99% of all dinosaurs that ever lived on Earth are extinct. Estimates of the number of species on Earth today vary widely; most species have not been described. Over 7.7 billion humans live on Earth and depend on its biosphere and natural resources for their survival. Humans have developed diverse societies and cultures; politically, the world has around 200 sovereign states.

In all Virtual Galaga games, Planet Earth is the 2nd stage of the game. This stage features all ground targets and defense troops from the ground (Such as the Xevious ground units like Lograms, Zolbaks, Grobdas, Domograms, Sol Citadels, and etc.).

In Galaxy on Fire 2, Earth was once the homeworld of Terran race. It is the planet where the Terrans lived in and thrived, before migrating out to the rest of the galaxy. It is believed that a Grey had given them the technology to travel among the stars. The planet, along with the Solar System, has been lost (this never happens).

Alice mentioned Earth, so it's clear that Earth is still remembered by the Terran population, but it may have been destroyed during the Vossk fight (or maybe the UIMS could've destroyed the Earth by firing the Cannon Seed when the mission fails whenever the voice timer is up by using the Thunder Shot, or when the Dragoon gunship gets shot down by any enemies during Project Dragoon, or the entire Solar System was completely destroyed by Gourb's superweapon during The Rising of Gourb) or Tomorrowlandians kept a secret to protect it from enemy attacks, to the point that everyone forgot where it was.

Surprisingly, planet Earth can also be found in Star Ixiom and only appears in the Conquest Mode. When the text says "DEFEND PLANET EARTH" on the screen (image shown on the right), this means that Earth is under attack by any enemies. But, when the text says "DANGER PLANET EARTH" on the screen, you have to act fast, or else Earth would be destroyed and the mission will fail (don't let any single planet to be destroyed by any means necessary, or else you'll fail the mission). The refueling station in Earth, this time, it is the International Space Station (ISS) ***ITSELF*** (instead of the other stations that looks like the ISS).