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
Antarctica to Pyramids -- lights dim for Earth Hour (Update)
Mar 28, 2009 |
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(AP) -- From an Antarctic research base to the Great Pyramids of Egypt and beyond, the world switched off the lights on Saturday for Earth Hour, dimming skyscrapers, city streets and some of the world's most ...
Texas School Standards: Age of the Universe Erased
Apr 07, 2009 |
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(PhysOrg.com) -- The fight over the new education and curriculum standards for the public schools in Texas has been long and publicized. Most of the publicity, though, focuses on the school board's focus on ...
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, ...
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 ...
Giant impact near India -- not Mexico -- may have doomed dinosaurs
Space & Earth / Earth Sciences
Oct 15, 2009 |
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A mysterious basin off the coast of India could be the largest, multi-ringed impact crater the world has ever seen. And if a new study is right, it may have been responsible for killing the dinosaurs off 65 ...
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 ...
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, ...
Earth's original ancestor was LUCA, study on origins of life
Biology /
Dec 17, 2008 |
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Here's another argument against intelligent design. An evolutionary geneticist from the Université de Montréal, together with researchers from the French cities of Lyon and Montpellier, have published a ground-breaking study ...
NASA Launches 'Eyes on the Earth 3-D'
Space & Earth / Earth Sciences
Mar 13, 2009 |
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(PhysOrg.com) -- New interactive features on NASA's Global Climate Change Web site give the public the opportunity to "fly along" with NASA's fleet of Earth science missions and observe Earth from a global ...
Moon geology could solve three mysteries of early Earth
Space & Earth / Earth Sciences
Dec 08, 2008 |
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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 ...
Scientists Give a Hand(edness) to the Search for Alien Life
Apr 22, 2009 |
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(PhysOrg.com) -- Visiting aliens may be the stuff of legend, but if a scientific team working at the National Institute of Standards and Technology is right, we may be able to find extraterrestrial life even ...
Deep Impact Films Earth as an Alien World
Space & Earth / Space Exploration
Jul 18, 2008 |
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(PhysOrg.com) -- NASA's Deep Impact spacecraft has created a video of the moon transiting (passing in front of) Earth as seen from the spacecraft's point of view 31 million miles away. Scientists are using ...
Researchers Find Ancient Evidence of 'Snowball Earth'
Space & Earth / Earth Sciences
Jul 11, 2008 |
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LSU scientist Huiming Bao, along with colleagues from UCLA and China, recently discovered some of the first atmospheric evidence in support of the “Snowball Earth” hypothesis. This theory suggests that Earth was entirely ...
Plate tectonics started over 4 billion years ago, geochemists report
Space & Earth / Earth Sciences
Nov 26, 2008 |
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(PhysOrg.com) -- A new picture of the early Earth is emerging, including the surprising finding that plate tectonics may have started more than 4 billion years ago — much earlier than scientists had believed, ...
International scientists set boundaries for survival
Sep 23, 2009 |
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Human activities have already pushed the Earth system beyond three of the planet's biophysical thresholds, with consequences that are detrimental or even catastrophic for large parts of the world; six others ...
