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
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 ...
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 ...
Can alkaline earth metals be used in quantum computing?
Nov 14, 2008 |
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(PhysOrg.com) -- "There are a number of different proposals for quantum computing," Andrew Daley tells PhysOrg.com. "These include solid state or semiconductor as well as atomic and molecular systems. We are considering atomic ...
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 ...
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 ...
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 ...
Banded rocks reveal early Earth conditions, changes
Space & Earth / Earth Sciences
Oct 11, 2009 |
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(PhysOrg.com) -- The strikingly banded rocks scattered across the upper Midwest and elsewhere throughout the world are actually ambassadors from the past, offering clues to the environment of the early Earth ...
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 ...
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, ...
Two More Earth's Chandler Wobble Jumps Revealed, Last in 2005
Sep 02, 2009 |
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(PhysOrg.com) -- The Chandler Wobble is a small variation in the rotation of the Earth on its axis. It has been known for some time that the phase of the Chandler Wobble jumped by 180 degrees in the 1920s, ...
Water in Earth's mantle may be associated with subduction
Space & Earth / Earth Sciences
Aug 19, 2009 |
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A team of scientists from Oregon State University has created the first global three-dimensional map of electrical conductivity in the Earth's mantle and their model suggests that that enhanced conductivity ...
Planet Smash-Up Sends Vaporized Rock, Hot Lava Flying (w/ Video)
Aug 10, 2009 |
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(PhysOrg.com) -- NASA's Spitzer Space Telescope has found evidence of a high-speed collision between two burgeoning planets around a young star.
Shaking the Earth: How Water Helps Tectonic Plates Slide in New Zealand
Space & Earth / Earth Sciences
Aug 05, 2009 |
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(PhysOrg.com) -- New Zealand is the site of one of the world’s youngest subduction zones, where the Pacific Plate of Earth’s crust dives beneath the Australian Plate. Now, a University of Utah study shows ...
Scientists discover Amazon river is 11 million years old
Space & Earth / Earth Sciences
Jul 29, 2009 |
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Researchers at the University of Liverpool have discovered that the Amazon river, and its transcontinental drainage, is around 11 million years old and took its present shape about 2.4 million years ago.
