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
Scientific debate sparked over carbon sink data
Nov 18, 2009 |
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(PhysOrg.com) -- According to research published this week in Nature Geoscience, emissions of carbon dioxide continue to outstrip the ability of the world’s natural ‘sinks’ to absorb carbon. ...
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 ...
Space station gets new research module
Space & Earth / Space Exploration
Nov 12, 2009 |
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(AP) -- A cargo ship has delivered a Russian research module to the International Space Station.
Rosetta spacecraft may help unravel cosmic mystery (w/ Video)
Space & Earth / Space Exploration
Nov 12, 2009 |
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When Europe's comet chaser Rosetta swings by Earth tomorrow for a critical gravity assist, tracking data will be collected to precisely measure the satellite's change in orbital energy. The results could help ...
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 ...
Atomic Particles Help Solve Planetary Puzzle
Space & Earth / Earth Sciences
Nov 10, 2009 |
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(PhysOrg.com) -- A University of Arkansas professor and his colleagues have shown that the Earth's mantle contains the same isotopic signatures from magnesium as meteorites do, suggesting that the planet formed ...
Cave study links climate change to California droughts
Space & Earth / Earth Sciences
Nov 10, 2009 |
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California experienced centuries-long droughts in the past 20,000 years that coincided with the thawing of ice caps in the Arctic, according to a new study by UC Davis doctoral student Jessica Oster and geology professor ...
New evidence supports 19th century idea on formation of oil and gas
Chemistry / Analytical Chemistry
Nov 04, 2009 |
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Scientists in Washington, D.C. are reporting laboratory evidence supporting the possibility that some of Earth's oil and natural gas may have formed in a way much different than the traditional process described ...
Texas A&M prof to predict weather on Mars
Space & Earth / Space Exploration
Nov 04, 2009 |
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Is there such a thing as "weather" on Mars? There are some doubts, considering the planet's atmosphere is only 1 percent as dense as that of the Earth. Mars, however, definitely has clouds, drastically low temperatures and ...
Rosetta's final Earth boost
Space & Earth / Space Exploration
Nov 04, 2009 |
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ESA's comet chaser Rosetta will swing by Earth for the last time on 13 November to pick up energy and begin the final leg of its 10-year journey to comet 67P/Churyumov-Gerasimenko. ESA's European Space Operations ...
Atlantis 'Go' For Launch to Station on Nov. 16
Space & Earth / Space Exploration
Oct 29, 2009 |
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(PhysOrg.com) -- NASA's space shuttle Atlantis is targeted to begin an 11-day flight to the International Space Station with a Nov. 16 launch from the Kennedy Space Center in Florida. Liftoff is scheduled ...
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 ...
Rosetta probe lined up nicely for Earth approach
Space & Earth / Space Exploration
Oct 28, 2009 |
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(PhysOrg.com) -- Following the first and primary trajectory correction manoeuvre 22 October, Rosetta is lined up nicely for the approach to Earth. The manoeuvre provided an 8.8 cm/s change in orbital velocity ...
Like a hungry teen, life on Earth had big growth spurts
Space & Earth / Earth Sciences
Oct 27, 2009 |
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Twice in the Earth's history, living creatures underwent astonishing growth spurts, and each time, new organisms emerged that were a million times larger than anything that had existed before.
Paradigm shift: How Galileo's spy glass upended science
Space & Earth / Space Exploration
Oct 23, 2009 |
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Today it would hardly pass muster as a child's plaything, but the telescope Galileo used 400 years ago this week to peer into the heavens overturned the foundations of knowledge, changing our perception of ...
