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Erde (Planet) Tero Tierra Terre Aarde Ziemia Terra Jorden

Atmospheric characteristics Pressure 101.325 kPa nitrogen 78% oxygen 21% argon 1% carbon dioxide water vapor trace

Earth (or "the Earth" or "Terra") is the third planet from the Sun in its (that is, our) solar system and the only one in the universe known to be inhabited by living organisms.

''View of Africa, Antarctica and the Arabian Peninsula from Apollo 17. This picture was taken as Apollo 17 left Earth orbit en route to the Moon. Taken on December 7, 1972.''

Structure
The interior of Earth is, like the other terrestrial planets, divided into an outer silicaceous solid crust, with a highly viscous mantle, an outer core that is less viscous than the mantle, and an inner core. The planet is big enough to have the core differentiated into an liquid outer core, which gives rise to a weak magnetic field due to the convection of its electrically conductive material, and a solid inner core.

New material contantly finds its way to the surface through volcanoes and cracks in the ocean floors. Much of the Earth's surface is less than 100,000,000 years old.

Interior
The interior of the Earth reaches temperatures of 5270 K. The planet's internal heat was originally released during its accretion (see gravitational binding energy), and since then additional heat has continued to be generated by the decay of radioactive elements such as uranium, thorium, and potassium. The heat flow from the interior to the surface is only 1/20,000 as great as the energy received from the Sun.


 * 0-60 km -- Lithosphere
 * 0-30/35 km -- Crust
 * 30/35-2900 km -- Mantle
 * 100-700 km -- Asthenosphere
 * 2900-5100 km -- Outer Core
 * 5100-~6375 km -- Inner Core

The Core
The average density of Earth is 5,515 kg/m3|undefined. Since, the average density of surface material is around 3000 kg/m3, that means there must be denser materials within the core. It is thought that the core is largely composed of nickel and iron, with other dense elements such as lead and uranium either being too rare to be significant or being felsic-seeking in nature (and thus concentrated in the crust rather than the core).

The Earth was entirely molten about 4.6 billion years ago. Gravity would have caused denser substances to sink towards the center in a process called chemical differentiation, while less dense substances would have migrated to the crust.

The inner core is generally believed to be solid and to be composed entirely of iron and some nickel. Some believe it may be entirely composed of a single iron crystal. The inner core is surrounded by the outer core, which is believed to be liquid iron mixed with liquid nickel.

Recent evidence has suggested that the inner core of Earth may rotate slightly faster than the rest of the planet, completing one additional rotation every 600 years. It is not known exactly why this occurs, but it is thought to be a result of the circulation of the liquid outer core and interaction with Earth's magnetic field.

Mantle
The Earth's mantle extends to a depth of 2900 km. It is largely composed of substances rich in iron and magnesium. The melting point of a substance depends on the pressure it is under. As there is intense and increasing pressure as one travels deeper into the mantle, the lower part of this region is thought solid while the upper mantle is plastic, (semi-molten).

Why is the inner core thought solid, the outer core thought liquid, and the mantle solid/plastic? The melting point of iron rich substances are higher than pure iron. The core is composed almost entirely of pure iron, while iron rich substances are more common outside the core. So, surface iron-substances are solid, upper mantle iron-substances are semi-melted (as it is hot and they are under relatively little pressure), lower mantle iron-substances are solid (as they are under tremendous pressure), outer core pure iron is liquid as it has a very low melting point (despite enormous pressure), and the inner core is solid due to the overwhelming pressure found at the center of the planet.

Crust
The crust ranges from 5-35 km in depth. It is composed of silicon-based rocks.

Biosphere
Earth is the only place in the universe where life has been reliably observed.

Some planetologists believe that the Earth is only marginally able to support life. Life is practically nonexistent at the poles, and increases in density from the poles to the equator. The so-called "temperate" zones are unable to support life for a third to a quarter of an orbit. Life in the temperate zones exhibits extreme cold-adaptations including world-spanning migrations, anti-freeze blood, exothermic metabolisms, insulation and long-term estivation.

Atmosphere and hydrosphere
Water covers 71% of Earth's surface (97% of it being sea water and 3% fresh water ) and divides it into five oceans and seven continents. It has a relatively thick atmosphere composed of 78% nitrogen, 21% oxygen, and 1% argon, plus traces of other gases including carbon dioxide and water. The atmosphere acts as a buffer between Earth and the Sun. The layers, troposphere, stratosphere, mesosphere, thermosphere, and the exosphere, vary around the globe and in response to seasonal changes.

Earth is the only planet in our solar system, or even the known universe, whose surface has liquid water. Earth's solar orbit, vulcanism, gravity, greenhouse effect, magnetic field and oxygen-rich atmosphere seem to combine to make Earth a water planet.

Earth is actually beyond the outer edge of the orbits which would be warm enough to form liquid water. Without some form of a greenhouse effect, the Earth's water would freeze. Paleontological evidence indicates that at one point after blue-green bacteria (Archaea) had colonized the oceans, the greenhouse effect failed, and the Earth froze solid for 10 to 100 million years.

On other planets, such as Venus, gaseous water is cracked by solar ultraviolet, and the hydrogen is ionized and blown away by the solar wind. This effect is slow, but inexorable. It is believed to be why Venus has no water. Without hydrogen, the oxygen interacts with the surface and is bound up in solid minerals.

On Earth, a shield of ozone absorbs most of this energetic ultraviolet high in the atmosphere, reducing the cracking effect. The magnetosphere also shields the ionosphere from direct scouring by the solar wind.

Finally, vulcanism, aided by the moon's tidal effects, continuously emits water vapor from the interior. Earth's plate tectonics recycle carbon and water as limestone fields are subducted into magma and volcanically emitted as gaseous carbon dioxide and steam.

The Moon
Earth is unique in its solar system in having "the Moon", named Luna, a huge terrestrial planet-like satellite that is about 1/4 of Earth's diameter. The moons orbiting other planets are so called after Earth's moon.

Some scientists believe that the moon may be essential to the existence of life on the Earth. Without the moon, the Earth would freeze to a solid crust, as Venus and Mars have. As a result, carbon rock would cease to be recycled, eventually causing life to fix all gaseous Carbon and then die. Without life, Oxygen would slowly combine with surface rocks, and the ozone layer would disappear. At this point, sublimated water vapor would begin to be cracked by solar ultraviolet, and the Earth's hydrogen would be eliminated by the solar wind. In less than a hundred million years, Earth would resemble Mars.

The moon may enable life by moderating the weather, as well. Paleontological evidence shows that Earth's axial tilt is stabilised by tidal interactions with its moon. Without this stabilization, the rotational axis might be chaotically unstable, as it is with a sphere. If Earth's axis of rotation were to approach the plane of the ecliptic, extremely severe weather could result as one pole was continually heated and the other cooled. Planetologists who have studied the effect claim that this might kill all large animal and higher plant life. This remains a controversial subject, however, and further studies of Mars - which shares Earth's rotation period and axial tilt, but not its large moon or liquid core - may provide additional information.

By coincidence, the Moon is just far enough away to have, when seen from the Earth, the same apparent angular size as the Sun. This allows a total eclipse to occur on Earth.

Also, the Moon is tidally locked: its rotation period is the same as the time it takes to revolve around the Earth, meaning it always presents the same face to the planet, seeming to disappear and reappear as the solar terminator line moves around the moon.

The origin of the Moon is presently unknown, but one popular theory has it that it was formed from the collision of a Mars-sized protoplanet into the early Earth. This theory explains (among other things) the Moon's relative lack of iron and volatile elements. See Giant impact theory.

Geography
Map references:

World, Time Zones

Area:
 * total: 510.072 million km2
 * land: 148.94 million km2
 * water: 361.132 million km2
 * note: 70.8% of the world's surface is covered by water, 29.2% is exposed land

Land boundaries: the land boundaries in the world total 251,480.24 km (not counting shared boundaries twice)

Coastline: 356,000 km

Maritime claims: see United Nations Convention on the Law of the Sea
 * contiguous zone: 24 nm claimed by most, but can vary
 * continental shelf: 200 m depth claimed by most or to depth of exploitation; others claim 200 nm or to the edge of the continental margin
 * exclusive fishing zone: 200 nm claimed by most, but can vary
 * exclusive economic zone: 200 nm claimed by most, but can vary
 * territorial sea: 12 nm claimed by most, but can vary
 * Note: boundary situations with neighboring states prevent many countries from extending their fishing or economic zones to a full 200 nm; 43 nations and other areas that are landlocked include Afghanistan, Andorra, Armenia, Austria, Azerbaijan, Belarus, Bhutan, Bolivia, Botswana, Burkina Faso, Burundi, Central African Republic, Chad, Czech Republic, Ethiopia, Holy See (Vatican City), Hungary, Kazakhstan, Kyrgyzstan, Laos, Lesotho, Liechtenstein, Luxembourg, Malawi, Mali, Moldova, Mongolia, Nepal, Niger, Paraguay, Rwanda, San Marino, Slovakia, Swaziland, Switzerland, Tajikistan, The Former Yugoslav Republic of Macedonia, Turkmenistan, Uganda, Uzbekistan, West Bank, Zambia, Zimbabwe

Climate:
Two large areas of polar climates separated by two rather narrow temperate zones from a wide equatorial band of tropical to subtropical climates. Precipitation patterns vary widely, ranging from several meters of water per year to less than a millimeter.

Terrain:
Elevation extremes: (measured relative to sea level)
 * Lowest point on land: Dead Sea -408 m
 * Lowest point overall: Marianas Trench in the Pacific Ocean -10,924 m
 * Highest point: Mount Everest 8,850 m (1999 est.)

Natural resources

 * The Earth's crust contains large deposits of fossil fuels: (coal, oil, natural gas, methane clathrate). These deposits are used by humans both for energy production and as feedstock for chemical production.
 * Mineral ore bodies have been formed in the Earth's crust by the action of erosion and plate tectonics. These ore bodies form concentrated sources for many metals and other useful elements.
 * The Earth's biosphere produces many useful biological products, including (but far from limited to) food, wood, pharmaceuticals, oxygen, and the recycling of many organic wastes. The land-based ecosystem depends upon topsoil and fresh water, and the oceanic ecosystem depends upon dissolved nutrients washed down from the land.

Some of these resources, such as fossil fuels, are difficult to replenish on a short time scale, called non-renewable resources. The exploitation of non-renewable resources by human civilization has become a subject of significant controversy in modern environmentalism movements.

Land use

 * arable land: 10%
 * permanent crops: 1%
 * permanent pastures: 26%
 * forests and woodland: 32%
 * other: 31% (1993 est.)

Irrigated land: 2,481,250 km2 (1993 est.)

Natural hazards:
Large areas are subject to extreme weather such as (tropical cyclones), hurricanes,or typhoons that dominate life in those areas. Many places are subject to earthquakes, landslides, tsunamis, volcanic eruptions, tornadoes, sinkholes, floods, droughts, and other calamities and disasters.

Environment - current issues:
Large areas are subject to overpopulation, industrial disasters such as pollution of the air and water, acid rain and toxic substances, loss of vegetation (overgrazing, deforestation, desertification), loss of wildlife, soil degradation, soil depletion, erosion

Human population:
6,080,671,215 (July 2000 est.)

As of 2003, there is a permanent human presence in space, in the International Space Station, of three people, who are from time to time replaced.

Age structure:
 * 0-14 years: 29.92% (male 932,832,913; female 885,970,165)
 * 15-64 years: 63.17% (male 1,942,402,264; female 1,898,479,062)
 * 65 years and over: 6.91% (male 184,072,470; female 235,017,660) (2000 est.)

 Population growth rate: 1.3% (2000 est.)

Birth rate: 22 births/1,000 population (2000 est.)

Death rate: 9 deaths/1,000 population (2000 est.)

Sex ratio:
 * at birth: 1.05 male(s)/female
 * under 15 years: 1.05 male(s)/female
 * 15-64 years: 1.02 male(s)/female
 * 65 years and over: 0.78 male(s)/female
 * total population: 1.01 male(s)/female (2000 est.)

Infant mortality rate: 54 deaths/1,000 live births (2000 est.)

Life expectancy at birth:
 * total population: 64 years
 * male: 62 years
 * female: 65 years (2000 est.)

Total fertility rate: 2.8 children born/woman (2000 est.)

Government:
Administrative divisions: 267 nations, dependent areas, other, and miscellaneous entries

Legal system: See international law

Economy
Economy - overview: Growth in global output (gross world product, GWP) rose to 3% in 1999 from 2% in 1998 despite continued recession in Japan, severe financial difficulties in other East Asian countries, and widespread dislocations in several transition economies, notably Russia. The US economy continued its remarkable sustained prosperity, growing at 4.1% in 1999, and accounted for 23% of GWP. Western Europe's economies grew at roughly 2%, not enough to cut deeply into the region's high unemployment; the EU economies produced 20% of GWP. China, the second largest economy in the world, continued its strong growth and accounted for 12% of GWP. Japan grew at only 0.3% in 1999; its share in GWP is 7%. As usual, the 15 successor nations of the USSR and the other old Warsaw Pact nations experienced widely different rates of growth. The developing nations varied widely in their growth results, with many countries facing population increases that eat up gains in outp

GDP: GWP (gross world product) - purchasing power parity - $40.7 trillion (1999 est.)

GDP - real growth rate: 3% (1999 est.)

GDP - per capita: purchasing power parity - $6,800 (1999 est.)

Inflation rate (consumer prices): all countries 25%; developed countries 1% to 3% typically; developing countries 5% to 60% typically (1999 est.) note: National inflation rates vary widely in individual cases, from stable prices in Japan to hyperinflation in a number of Third World countries

Unemployment rate: 30% combined unemployment and underemployment in many non-industrialized countries; developed countries typically 4%-12% unemployment (1999 est.)

Industries: dominated by the onrush of technology, especially in computers, robotics, telecommunications, and medicines and medical equipment; most of these advances take place in OECD nations; only a small portion of non-OECD countries have succeeded in rapidly adjusting to these technological forces; the accelerated deployment of new industrial (and agricultural) technology is complicating already grim environmental problems in some regions.

Yearly electricity - production: 12,342.7 billion kWh (1994)

Yearly electricity - consumption: 12,342.7 billion kWh (1994)

Yearly exports: $5.6 trillion (f.o.b., 1999 est.)

Exports - commodities: the whole range of industrial and agricultural goods and services

Exports - partners: in value, about 75% of exports from the developed countries

Yearly imports: $5.6 trillion (f.o.b., 1999 est.)

Imports - commodities: the whole range of industrial and agricultural goods and services

Imports - partners: in value, about 75% of imports by the developed countries

Debt - external: $2 trillion for less developed countries (1999 est.)

Yearly economic aid - recipient: traditional worldwide foreign aid $50 billion (1997 est.)

(Note: All exports, imports, debts and economic aid listed are between nations on Earth. There are currently no significant extraterrestrial imports or exports.)

Internet Service Providers (ISPs): 13,119 (1999)

Transportation
Railways:
 * total: 1,201,337 km includes about 190,000 to 195,000 km of electrified routes of which 147,760 km are in Europe, 24,509 km in the Far East, 11,050 km in Africa, 4,223 km in South America, and 4,160 km in North America; note - fastest speed in daily service is 300 km/hr attained by France's Societe Nationale des Chemins-de-Fer Francais (SNCF) Le Train a Grande Vitesse (TGV) - Atlantique line
 * broad gauge: 251,153 km
 * standard gauge: 710,754 km
 * narrow gauge: 239,430 km

Ports and harbors: Chiba, Halifax, Nova Scotia, Houston, Kawasaki, Kobe, Marseille, Mina' al Ahmadi (Kuwait), New Orleans, New York, Rotterdam, Yokohama

Military
Military expenditures - dollar figure: aggregate real expenditure on arms worldwide in 1999 remained at approximately the 1998 level, about three-quarters of a trillion dollars (1999 est.)

Yearly military expenditures - percent of GDP: roughly 2% of gross world product (1999 est.)

Solar system: Sun - Mercury - Venus - Earth - Mars - Asteroids - Jupiter - Saturn - Uranus - Neptune - Pluto - Comets

In addition to being a planet, earth is also one of the Chinese five elements. In this sense, it means soil.

Some other names for 'Earth' are;
 * Aztec: Coatlicue
 * Chinese: Hou ji
 * Danish: Jorden
 * Dutch: Aarde
 * Egyptian: Geb
 * Estonian: Maa
 * French: Terre
 * German: Erde
 * Greek: Gaea
 * Hebrew: HaOlam
 * Incan: Pachamama
 * Italian: Terra
 * Japanese: Chikyuu
 * Latin: Terra
 * Maltese: Dinja
 * Maori: Papa
 * Mayan: Bacabs
 * Norse: Midgard
 * Norwegian: Jorden
 * Polish: Ziemia
 * Portuguese: Terra
 * Russian: Zemlya
 * Serbo-Croatian: Zemlja
 * Slovene: Zemlja
 * Spanish: Tierra
 * Sumerian: Enlil

The Earth has often been personified as a deity, often a goddess. See Gaea and Mother Earth. In Norse mythology, Earth was the son of Nott and Annar.

See also: earthquake, Earth's magnetic field, equatorial bulge