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Understanding planetary habitability is partly an extrapolation of the conditions on Earth, as this is the only planet known to support life. Planetary habitability is the measure of a planet 's or a natural satellite 's potential to develop and maintain environments hospitable to life. [1] Life may be generated directly on a planet or ...
The Gaia hypothesis ( / ˈɡaɪ.ə / ), also known as the Gaia theory, Gaia paradigm, or the Gaia principle, proposes that living organisms interact with their inorganic surroundings on Earth to form a synergistic and self-regulating, complex system that helps to maintain and perpetuate the conditions for life on the planet.
Currently most of the objects of mass between 10 9 kg to 10 12 kg (less than 1000 teragrams (Tg)) listed here are near-Earth asteroids (NEAs). The Aten asteroid 1994 WR12 has less mass than the Great Pyramid of Giza, 5.9 × 10 9 kg. For more about very small objects in the Solar System, see meteoroid, micrometeoroid, cosmic dust, and ...
Earth is the only celestial body known for sure to have generated living beings, and thus the only current example of a habitable planet. At a distance of 1 AU from the Sun, it is within the circumstellar habitable zone of the Solar system, which means it can have oceans of water in a liquid state. [ 22 ]
Of the Solar System's eight planets and its nine most likely dwarf planets, six planets and seven dwarf planets are known to be orbited by at least 300 natural satellites, or moons. At least 19 of them are large enough to be gravitationally rounded; of these, all are covered by a crust of ice except for Earth's Moon and Jupiter's Io . [ 1 ]
At time 2, the planet has rotated 360 degrees and the distant star is overhead again but the Sun is not (1→2 = one stellar day). It is not until a little later, at time 3, that the Sun is overhead again (1→3 = one solar day). Earth's rotation period relative to the International Celestial Reference Frame, called its stellar day by the ...
Earth is rounded into an ellipsoid with a circumference of about 40,000 km. It is the densest planet in the Solar System. Of the four rocky planets, it is the largest and most massive. Earth is about eight light-minutes away from the Sun and orbits it, taking a year (about 365.25 days) to complete one revolution.
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