Earth

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"O brave new world. What immortal hand or eye could frame thy fearful symmetry?"

―Clay Kaczmarek's Cluster #10.

Earth

The Earth is the third planet from the Sun and the densest and fifth largest planet in the Solar System, though most of its surface is covered in water. It is also the only known terrestrial object to harbor life. According to radiometric dating and other sources of evidence, Earth formed over 4.5 billion years ago.

Within the first billion years of Earth's history, life appeared in the oceans and began to affect the planet's atmosphere and surface, leading to the proliferation of aerobic and anaerobic organisms. Some geological evidence indicates that life may have arisen as much 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 the Earth, biodiversity has gone through long periods of expansion, occasionally punctuated by mass extinction events. Over 99% of all species^[32] that ever lived on Earth are extinct.^[33][34] Estimates of the number of species on Earth today vary widely;^[35][36][37] most species have not been described.^[38] Over 7.6 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 about 200 sovereign states.

Throughout much of its existence, a power struggle between the Assassin and Templar Orders has shaped many parts of history. The planet was revealed to be held together by mysterious artefacts which, if removed or disturbed, would cause devastating earthquakes and potentially destroy Earth entirely. Around 75000 BCE, Earth was struck by a coronal mass ejection, causing near extinction for both humanity and the Isu. When a second solar flare released on 21 December 2012, the Assassin Desmond Miles sacrificed himself to protect the Earth.

Physical Characteristics

Shape

The shape of Earth is approximately oblate spheroidal. Due to rotation, the Earth is flattened along the geographic axis and bulges around the equator. The diameter of the planet at the equator is twenty-seven miles larger than the pole-to-pole diameter. Thus, the point on the surface farthest from Earth's center of mass is the summit of the equatorial Chimborazo volcano in Ecuador. The average diameter of the reference spheroid is 7,198 miles. Local topography deviates from this idealized spheroid, although on a global scale these deviations are small compared to Earth's radius: The maximum deviation of only 0.17% is at the Mariana Trench(10,911 meters (35,797 ft) below local sea level), whereas Mount Everest, standing at 29,029 feet above sea level, represents a deviation of 0.14%.

In geodesy, the exact shape that Earth's oceans would adopt in the absence of land and perturbations such as tides and winds is called the geoid. More precisely, the geoid is the surface of gravitational equipotential at mean sea level.

Chemical Composition

Earth's mass is 5.97×10²⁴ kg. The planet's atmosphere is mostly nitrogen -- about seventy-eight percent. It also contains oxygen and 1.2% of other elements.

Internal structure

Earth's interior, like that of the other terrestrial planets, is divided into layers by their chemical and properties. The outer layer is a chemically-distinct silicate solid crust, which is underlain by a highly viscous solid mantle. The mantle itself is made up of silicon, iron, magnesium, aluminum, and oxygen. Beneath the mantle is an extremely low viscosity liquid outer core that lies above a molten inner core made up of iron and other metals. Underneath Earth's crust are plates that slowly move against each other.

Gallery

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  Earth during the 2012 coronal mass ejection
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  A Geomagnetic storm