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As theorized by Isaac Newton and Christiaan Huygens, [3]: 4 [4] [5] the Earth is flattened at the poles and bulged at the equator. Thus, geodesy represents the figure of the Earth as an oblate spheroid. The oblate spheroid, or oblate ellipsoid, is an ellipsoid of revolution obtained by rotating an ellipse about its shorter axis.
Spherical Earth or Earth's curvature refers to the approximation of the figure of the Earth to a sphere. The concept of a spherical Earth gradually displaced earlier beliefs in a flat Earth during classical antiquity and the Middle Ages. The figure of the Earth is more accurately described as an ellipsoid, which was realized in the early modern ...
In Greek antiquity the ideas of celestial spheres and rings first appeared in the cosmology of Anaximander in the early 6th century BC. [7] In his cosmology both the Sun and Moon are circular open vents in tubular rings of fire enclosed in tubes of condensed air; these rings constitute the rims of rotating chariot-like wheels pivoting on the Earth at their centre.
Earth is the third planet from the Sun and the only astronomical object known to harbor life. [23] This is enabled by Earth being an ocean 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.
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 lithosphere ).
Because astronomical objects are at such remote distances, casual observation of the sky offers no information on their actual distances. All celestial objects seem equally far away, as if fixed onto the inside of a sphere with a large but unknown radius, [1] which appears to rotate westward overhead; meanwhile, Earth underfoot seems to remain still.
Many of the subsystems are characterized as "spheres", coinciding with the shape of the planet. The four spheres (for which most of the other spheres are a subtype of) are the atmosphere, the biosphere, the hydrosphere and the geosphere. Earth's ecosphere lies it self within the heliosphere (the Sun's astrosphere). [4]
They were believed to explain the motions of the four terrestrial elements: Earth, Water, Air, and Fire. In modern texts and in Earth system science , geosphere refers to the solid parts of the Earth ; it is used along with atmosphere , hydrosphere , and biosphere to describe the systems of the Earth (the interaction of these systems with the ...