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Earth is the third planet from the Sun and the only astronomical object known to harbor life.This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water.
The following outline is provided as an overview of and topical guide to the planet Earth: . Earth – third planet from the Sun, the densest planet in the Solar System, the largest of the Solar System's four terrestrial planets, and the only astronomical object known to harbor life.
The first eon in Earth's history, the Hadean, begins with the Earth's formation and is followed by the Archean eon at 3.8 Ga. [2]: 145 The oldest rocks found on Earth date to about 4.0 Ga, and the oldest detrital zircon crystals in rocks to about 4.4 Ga, [34] [35] [36] soon after the formation of the Earth's crust and the Earth
Earth is the third planet from the Sun with an approximate distance of 149.6 million kilometres (93.0 million miles), and is traveling nearly 2.1 million kilometres per hour (1.3 million miles per hour) through outer space.
Earth's atmosphere contains 78% nitrogen and 21% oxygen, which is the result of the presence of life. [103] [104] The planet has a complex climate and weather system, with conditions differing drastically between climate regions. [105] The solid surface of Earth is dominated by green vegetation, deserts and white ice sheets.
The Earth's radius is the distance from Earth's center to its surface, about 6,371 km (3,959 mi). While "radius" normally is a characteristic of perfect spheres, the Earth deviates from spherical by only a third of a percent, sufficiently close to treat it as a sphere in many contexts and justifying the term "the radius of the Earth".
Planetary atmospheres are affected by the varying insolation or internal energy, leading to the formation of dynamic weather systems such as hurricanes (on Earth), planet-wide dust storms (on Mars), a greater-than-Earth-sized anticyclone on Jupiter (called the Great Red Spot), and holes in the atmosphere (on Neptune). [69]
A terrestrial planet with an arid surface consistency similar to Earth's deserts. Mars: Gas dwarf: A low-mass planet composed primarily of hydrogen and helium. GJ 1214 b: Gas giant: A massive planet composed primarily of hydrogen and helium. Saturn, Jupiter, 70 Virginis b: Helium planet: A theoretical planet that may form via mass loss from a ...