Earth
hideEarth is the third planet from the Sun, and the largest of the terrestrial planets in the Solar System in terms of diameter, mass and density. It is also referred to as the World, the Blue Planet, and Terra.
Home to millions of species, including humans, Earth is the only place in the universe where life is known to exist. The planet formed 4.54 billion years ago, and life appeared on its surface within a billion years. Since then, Earth's biosphere has significantly altered the atmosphere and other abiotic conditions on the planet, enabling the proliferation of aerobic organisms as well as the formation of the ozone layer which, together with Earth's magnetic field, blocks harmful radiation, permitting life on land. The physical properties of the Earth, as well as its geological history and orbit, allowed life to persist during this period. The world is expected to continue supporting life for another 1.5 billion years, after which the rising luminosity of the Sun will eliminate the biosphere.
Earth's outer surface is divided into several rigid segments, or tectonic plates, that gradually migrate across the surface over periods of many millions of years. About 71% of the surface is covered with salt-water oceans, the remainder consisting of continents and islands; liquid water, necessary for all known life, is not known to exist on any other planet's surface. Earth's interior remains active, with a thick layer of relatively solid mantle, a liquid outer core that generates a magnetic field, and a solid iron inner core.
Earth interacts with other objects in outer space, including the Sun and the Moon. At present, Earth orbits the Sun once for every roughly 366.26 times it rotates about its axis. This length of time is a sidereal year, which is equal to 365.26 solar days. The Earth's axis of rotation is tilted 23.4° away from the perpendicular to its orbital plane, producing seasonal variations on the planet's surface with a period of one tropical year (365.24 solar days). Earth's only known natural satellite, the Moon, which began orbiting it about 4.53 billion years ago, provides ocean tides, stabilizes the axial tilt and gradually slows the planet's rotation. Between approximately 4.1 and 3.8 billion years ago, asteroid impacts during the Late Heavy Bombardment caused significant changes to the surface environment.
Both the mineral resources of the planet, as well as the products of the biosphere, contribute resources that are used to support a global human population. The inhabitants are grouped into about 200 independent sovereign states, which interact through diplomacy, travel, trade and military action. Human cultures have developed many views of the planet, including personification as a deity, a belief in a flat Earth or in Earth being the center of the universe, and a modern perspective of the world as an integrated environment that requires stewardship.
For more information about Earth, read the full article at
Wikipedia.
This text uses material from Wikipedia and is available under the GNU Free Documentation License.
News tagged with earth
Study: Earth more sensitive to carbon dioxide than previously thought
Space & Earth / Earth Sciences
Dec 06, 2009 |
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In the long term, the Earth's temperature may be 30-50% more sensitive to atmospheric carbon dioxide than has previously been estimated, reports a new study published in Nature Geoscience this week.
Turbulence around heat transport
Dec 03, 2009 |
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(PhysOrg.com) -- Heat transport in the earth's mantle and in the atmosphere is probably not as effective as previously thought.
Forest deal at Copenhagen must avoid creating 'carbon refugees'
Dec 03, 2009 |
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Forest dwellers must be included in the design of the upcoming forest deal at Copenhagen in order to avoid a humanitarian crisis, according to a scientist at the University of Leeds.
Superior Super Earths
Space & Earth / Space Exploration
Nov 30, 2009 |
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Super Earths are named for their size, but these planets - which range from about 2 to 10 Earth masses - could be superior to the Earth when it comes to sustaining life. They could also provide an answer to ...
San Francisco vs Amsterdam in green city rivalry
Dec 02, 2009 |
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San Francisco and Amsterdam set an online stage for an environmental rivalry regarding which city is more nature-friendly.
Professor foresees rising Antarctic snowmelt
Space & Earth / Earth Sciences
Dec 03, 2009 |
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The 30-year record low in Antarctic snowmelt that occurred during the 2008-09 austral summer was likely due to concurrent strong positive phases for two main climate drivers, ENSO (El Niño - Southern Oscillation) and SAM ...
Russia: no space for space tourists
Space & Earth / Space Exploration
Nov 26, 2009 |
2.7 / 5 (3) |
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(AP) -- A top Russian space official says there is no space for tourists wishing to fly to the International Space Station.
Partial lunar eclipse will take place on 31st December
Space & Earth / Space Exploration
Dec 03, 2009 |
not rated yet |
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(PhysOrg.com) -- In a lunar eclipse, the Earth, Sun and Moon are almost exactly in line and the Moon is on the opposite side of the Earth from the Sun.
Rosetta bound for outer Solar System after final Earth swingby (w/ Video)
Space & Earth / Space Exploration
Nov 13, 2009 |
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(PhysOrg.com) -- This morning, mission controllers confirmed that ESA’s comet chaser Rosetta had swung by Earth at 8:45 CET as planned, skimming past our planet to pick up a gravitational boost for an epic ...
Rotating Space Elevator Propels its Own Load
May 21, 2009 |
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(PhysOrg.com) -- The idea of the space elevator just got a little crazier. While the “traditional” concept involved using rocket propulsion or laser light pressure to propel loads up a cable anchored to Earth, ...
Reversals of Earth's Magnetic Field Explained by Small Core Fluctuations
Apr 23, 2009 |
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(PhysOrg.com) -- Based on studies of old volcanic basalt, scientists know that the Earth’s magnetic field reverses at irregular intervals, ranging from tens of thousands to millions of years. Volcanic basalt ...
Ancient ocean chemistry: Effects of biological oxygen production 100 million years before it accumulated in atmosphere
Space & Earth / Earth Sciences
Oct 29, 2009 |
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(PhysOrg.com) -- Scientists widely accept that around 2.4 billion years ago, the Earth's atmosphere underwent a dramatic change when oxygen levels rose sharply. Called the "Great Oxidation Event" (GOE), the ...
Scientists propose new hypothesis on the origin of life
Space & Earth / Earth Sciences
Sep 04, 2009 |
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The Miller-Urey experiment, conducted by chemists Stanley Miller and Harold Urey in 1953, is the classic experiment on the origin of life. It established that the early Earth atmosphere, as they pictured it, ...
Early life on Earth may have developed more quickly than thought (w/ Video)
Space & Earth / Earth Sciences
Nov 11, 2009 |
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The Earth's climate was far cooler -- perhaps more than 50 degrees -- billions of years ago, which could mean conditions for life all over the planet were more conducive than previously believed, according ...
Moon geology could solve three mysteries of early Earth
Space & Earth / Earth Sciences
Dec 08, 2008 |
4.1 / 5 (37) |
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(PhysOrg.com) -- Not much is known about the Earth before 4 billion years ago, the earliest period in the planet’s 4.5-billion-year history. Because Earth has lost almost all geological records of this era ...
