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Mostly harmless. Earth (or the Earth) is the third planet of the star called in English the Sun or Sol; it is the only planet known to be capable of supporting life.

File:Earth-apollo17-thumb.jpg

View of Africa, Antarctica and 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. click here for larger image

Physical characteristics

  • Average orbital radius: 149,600,000 km (1 AU) from Sun
    • Aphelion: 152,000,000 km
    • Perihelion: 147,000,000 km
  • Diameter: 12,756.3 km
  • Mass: 5.972×1024 kg
  • Rotation period: 23 hours, 56 minutes
  • Orbital period: 365.2 days
  • Axial tilt: 23.45°

Water covers over 70% of Earth's surface and divides it into five oceans and seven continents. It has a relatively thick atmosphere composed of 76% nitrogen, 21% oxygen, 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.

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 a solid inner nickel-iron 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.

The inner core of Earth was recently discovered to 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.

Earth is the only known place in the universe that supports life, notably humans. Scientists have not ruled out the possibility of the existence of life in other places in the universe, and some think it likely.

Some planetologists believe that the Earth is only marginally able to support life. The evidence is that 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 1/3 to 1/4 of an orbit. Life in these zones exhibits extreme cold-adaptations including anti-freeze blood, exothermic metabolisms, insulation and long-term estivation.

Earth is unusual in its solar system in having a terrestrial planet-like Moon that is about 1/4 of Earth's diameter, usually called simply "the Moon," although natural satellites orbiting other planets are also called "moons." The name "Luna" is sometimes used for Earth's moon instead. 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. 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 lack of iron and volatile elements. See Giant impact theory.

Paleontological evidence shows that Earth's axial tilt is stabilized by tidal interactions with its moon. Without this stabilization, the rotational axis would be chaotically unstable, as it is with any sphere. If Earth's axis of rotation where 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 - may provide additional information.

Why Earth is Wet

Earth is the only planet in our solar system, or the known universe whose surface has liquid water. Earth's solar orbit, vulcanism, gravity, greenhouse effect, magnetic field and oxygen 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 the greenhouse effect, the Earth's water would freeze.

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 the reason 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 tidal effects, continuously emits water from the interior.

It is known that Lunar tides keep the crust broken, and therefore aid the recycling of carbon and water as limestone fields are subducted into magma and volcanically emitted as gaseous carbon dioxide and steam.

Without Lunar tides, some planetologists speculate that Earth's crust would have solidified. Its crust would have accreted all available carbon as limestone. This would remove the carbon needed by the biosphere. As the greenhouse effect failed, the result would be an ice planet similar to mars. The oxygen would all combine with surface minerals, and then as the water sublimed, the hydrogen would be cracked from the water and scoured away by the solar wind, creating a desert.

Geography: Map references: World, Time Zones

Area:

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

Coastline: 356,000 km

Maritime claims:

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: the greatest ocean depth is the Mariana Trench at 10,924 m in the Pacific Ocean

Elevation extremes: (measured relative to sea level)

Natural resources:

  • The Earth's crust contains large deposits of fossil fuels (coal, oil, natural gas, methane clathrate). These deposits are used 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 from the land.

Some of these resources 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 sq km (1993 est.)

Natural hazards: large areas subject to severe weather (tropical cyclones), natural disasters (earthquakes, landslides, tsunamis, volcanic eruptions)

Environment - current issues: large areas subject to overpopulation, industrial disasters, pollution (air, water, acid rain, 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.)

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:

Data code: none; there is no FIPS 10-4 country code for the World, so the Factbook uses the "W" data code from DIAM 65-18 "Geopolitical Data Elements and Related Features," Data Standard No. 3, March 1984, published by the Defense Intelligence Agency; see the Cross-Reference List of Country Data Codes appendix

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

Legal system: see international law

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 output. Externally, the nation-state, as a bedrock economic-political institution, is steadily losing control over international flows of people, goods, funds, and technology. Internally, the central government often finds its control over resources slipping as separatist regional movements - typically based on ethnicity - gain momentum, e.g., in many of the successor states of the former Soviet Union, in the former Yugoslavia, in India, and in Canada. In Western Europe, governments face the difficult political problem of channeling resources away from welfare programs in order to increase investment and strengthen incentives to seek employment. The addition of 80 million people each year to an already overcrowded globe is exacerbating the problems of pollution, desertification, underemployment, epidemics, and famine. Because of their own internal problems and priorities, the industrialized countries devote insufficient resources to deal effectively with the poorer areas of the world, which, at least from the economic point of view, are becoming further marginalized. Continued financial difficulties in East Asia, Russia, and many African nations cast a shadow over short-term global economic prospects. The introduction of the euro as the common currency of much of Western Europe in January 1999, while strengthening prospects for an integrated economic powerhouse, poses serious economic risks because of varying levels of income and cultural and political differences among the participating nations. (For specific economic developments in each country of the world in 1999, see the individual country entries.)

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.)

GDP - composition by sector:

  • agriculture: NA%
  • industry: NA%
  • services: NA%

Household income or consumption by percentage share:

  • lowest 10%: NA%
  • highest 10%: NA%

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

Labor force: NA

Labor force - by occupation: agricultue NA%, industry NA%, services NA%

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.

Industrial production growth rate: NA%

Electricity - production: 12,342.7 billion kWh (1994)

Electricity - production by source:

  • fossil fuel: NA%
  • hydro: NA%
  • nuclear: NA%
  • other: NA%

Electricity - consumption: 12,342.7 billion kWh (1994)

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

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.)

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

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

Communications: Telephones - main lines in use: NA

Telephones - mobile cellular: NA

Telephone system:

  • domestic: NA
  • international: NA

Radio broadcast stations: AM NA, FM NA, shortwave NA

Radios: NA

Television broadcast stations: NA

Televisions: NA

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

Highways:

  • total: NA km
  • paved: NA km
  • unpaved: NA km

Ports and harbors: Chiba, 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.)

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; Greek: Gaea, Aztec: Coatlicue, Inca: Pachamama, Maya: Bacabs, Norse: Midgard, Egyptian: Geb, China: Hou ji, Sumerian: Enlil, Maori: Papa.

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