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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 a water world, the only one in the Solar System sustaining liquid surface water. Almost all of Earth's water is contained in its global ocean, covering 70.8% of Earth's crust.
The history of Earth is divided into four great eons, starting 4,540 mya with the formation of the planet. Each eon saw the most significant changes in Earth's composition, climate and life. Each eon is subsequently divided into eras, which in turn are divided into periods, which are further divided into epochs . Eon.
Earth's rotation. Earth's rotation or Earth's spin is the rotation of planet Earth around its own axis, as well as changes in the orientation of the rotation axis in space. Earth rotates eastward, in prograde motion. As viewed from the northern polar star Polaris, Earth turns counterclockwise . The North Pole, also known as the Geographic North ...
720,000 km/h (450,000 mi/h) [10] Orbital period. ~230 million years [10] The Solar System [d] is the gravitationally bound system of the Sun and the objects that orbit it. [11] It was formed 4.6 billion years ago when a dense region of a molecular cloud collapsed, forming the Sun and a protoplanetary disc.
Earth's inner core is the innermost geologic layer of the planet Earth. It is primarily a solid ball with a radius of about 1,220 km (760 mi), which is about 20% of Earth’s radius or 70% of the Moon 's radius. [1] [2] There are no samples of Earth's core accessible for direct measurement, as there are for Earth's mantle. [3]
Earth's crust is its thick outer shell of rock, referring to less than 1% of the planet's radius and volume. It is the top component of the lithosphere, a division of Earth's layers that includes the crust and the upper part of the mantle. [1] The lithosphere is broken into tectonic plates whose motion allows heat to escape the interior of ...
Earth science. Earth science or geoscience includes all fields of natural science related to the planet Earth. [1] This is a branch of science dealing with the physical, chemical, and biological complex constitutions and synergistic linkages of Earth's four spheres: the biosphere, hydrosphere / cryosphere, atmosphere, and geosphere (or ...
In geography and cartography, hemispheres of Earth are any division of the globe into two equal halves ( hemispheres ), typically divided into northern and southern halves by the Equator or into western and eastern halves by the Prime meridian. Hemispheres can be divided geographically or culturally, or based on religion or prominent geographic ...