Earth  

The Blue Marble, taken from Apollo 17
Orbital characteristics (Epoch J2000)
Aphelion	152,097,701 km (1.016 710 333 5 AU)
Perihelion	147,098,074 km (0.983 289 891 2 AU)
Semi-major axis	149,597,887.5 km (1.000 000 112 4 AU)
Semi-minor axis	149,576,999.826 km (0.999 860 486 9 AU)
Orbital circumference	924,375,700 km (6.179 069 900 7 AU)
Orbital eccentricity	0.016 710 219
Sidereal orbit period	365.256 366 d (1.000 017 5 a)
Synodic period	n/a
Max. orbital speed	30.287 km/s (109,033 km/h)
Average orbital speed	29.783 km/s (107,218 km/h)
Min. orbital speed	29.291 km/s (105,448 km/h)
Orbital inclination to ecliptic	0.000 05° (7.25° to Sun's equator)
Longitude of the ascending node	348.739 36°
Argument of the perihelion	114.207 83°
Satellites	1 (the Moon) (see also 3753 Cruithne)
Physical characteristics
Aspect Ratio	0.996 647 139
Ellipticity	0.003 352 861
Radius:
Equatorial	6,378.135 km
Polar	6,356.750 km
Mean	6,372.795 km
Diameter:
Equatorial	12,756.270 km
Polar	12,713.500 km
Mean	12,745.591 km
Circumference:
Equatorial	40,075.004 km
Meridional	40,007.849 km
Mean	40,041.455 km
Surface Area	510,065,284.702 km²
Land	148,939,063.133 km² (29.2 %)
Water	361,126,221.569 km² (70.8 %)
Volume	1.0832×1012 km³
Mass	5.9736×1024 kg
Density	5,515 kg/m³
Equatorial surface gravity	9.7801 m/s² (0.997 32 g)
Escape velocity	11.186 km/s
Sidereal rotation period	0.997 258 d (23.934 h)
Rotational velocity (at the equator)	465.11 m/s
Axial tilt	23.439 281°
Right ascension of North pole	0° (0 h 0 min 0 s)
Declination	90°
Albedo	0.367
Surface temperature - min - mean - max	185 K (-88 °C) 287 K (14 °C) 331 K (58 °C)
Surface pressure	100 kPa
Adjective	Earthling or Terrestrial
Atmospheric constituents
nitrogen	77 %
oxygen	21 %
argon	1 %
carbon dioxide	0.038%
water vapor	trace (varies with climate)
edit

Earth is the third planet from the Sun. It is the largest of the solar system's terrestrial planets, and the only planetary body that modern science confirms as harboring life. Scientific evidence indicates that the planet formed around 4.57 billion (4.57×10⁹) years ago, and shortly thereafter (4.533 billion years ago) acquired its single natural satellite, the Moon. Image File history File links Earth_symbol. ... Image File history File links Download high resolution version (3000x3002, 6358 KB) The Blue Marble: This photo is of Africa, Antarctica, and the Arabian Peninsula as taken en route to the Moon by Apollo 17s Harrison Schmitt on December 7, 1972. ... The Blue Marble is a famous photograph of the Earth taken on 7 December 1972 by the crew of the Apollo 17 spacecraft at a distance of about 45,000 kilometers or about 28,000 miles. ... Apollo 17 was the eleventh manned space mission in the NASA Apollo program, and was the sixth and last mission to date to land on the Moon. ... In physics, an orbit is the path that an object makes, around another object, whilst under the influence of a source of centripetal force, such as gravity. ... In astronomy, an epoch is a moment in time for which celestial coordinates or orbital elements are specified. ... The J2000. ... Another view of Keplerian orbital elements. ... A kilometre (American spelling: kilometer), symbol: km is a unit of length in the metric system equal to 1000 metres (from the Greek words χίλια (khilia) = thousand and μέτρο (metro) = count/measure). ... The astronomical unit (AU or au or a. ... The semi-major axis of an ellipse In geometry, the term semi-major axis (also semimajor axis) is used to describe the dimensions of ellipses and hyperbolas. ... In geometry, the semi-minor axis (also semiminor axis) applies to ellipses and hyperbolas. ... The circumference is the distance around a closed curve. ... In astrodynamics, under standard assumptions any orbit must be of conic section shape. ... The sidereal year is the time for the Sun to return to the same position in respect to the stars of the celestial sphere. ... A day (symbol: d) is a unit of time equal to 24 hours. ... In astronomy, a Julian year is a unit of time defined as exactly 365. ... The orbital period is the time it takes a planet (or another object) to make one full orbit. ... The orbital speed of a body, generally a planet, a natural satellite, an artificial satellite, or a multiple star, is the speed at which it orbits around the barycenter of a system, usually around a more massive body. ... Kilometre per hour (American spelling: kilometer per hour) is a unit of both speed (scalar) and velocity (vector). ... kilometre per second is an SI derived unit of both speed (scalar) and velocity (vector), signified by the symbol km/s or km s-1. ... Kilometre per hour (American spelling: kilometer per hour) is a unit of both speed (scalar) and velocity (vector). ... Kilometre per hour (American spelling: kilometer per hour) is a unit of both speed (scalar) and velocity (vector). ... Inclination is one of the six orbital parameters describing the shape and orientation of a celestial orbit and is the angular distance of the orbital plane from the plane of the reference (usually planets equator or the ecliptic), stated in degrees. ... A degree (in full, a degree of arc, arc degree, or arcdegree), usually symbolized °, is a measurement of plane angle, representing 1／360 of a full rotation. ... The Sun is the star at the center of our Solar system. ... The Longitude of the ascending node () is one of the orbital elements used to specify the orbit of an object in space. ... The argument of the perihelion is one of the orbital elements describing the orbit of a planet. ... Moons of solar system scaled to Earths Moon The common noun moon (not capitalized) is used to mean any natural satellite of the other planets. ... Crust composition Oxygen 43% Silicon 21% Aluminium 10% Calcium 9% Iron 9% Magnesium 5% Titanium 2% Nickel 0. ... (also known as Earths second moon ) 3753 Cruithne is an asteroid in orbit around the Sun. ... In mathematics, an ellipse (from the Greek for absence) is a plane algebraic curve where the sum of the distances from any point on the curve to two fixed points is constant. ... In classical geometry, a radius of a circle or sphere is any line segment with one endpoint on the circle (i. ... The equator is an imaginary circle drawn around a planet (or other astronomical object) at a distance halfway between the poles. ... For other uses of the word pole, see Pole (disambiguation). ... The radius of the Earth is the distance from the Earths centre to its surface at mean sea level. ... For the geometric term, see diameter. ... The circumference is the distance around a closed curve. ... Meridional is a geographic term that means along a north-south direction, or relative to a meridian (opposite: zonal, east-west). ... A spheroid is a quadric surface in three dimensions obtained by rotating an ellipse about one of its principal axes. ... Square kilometre (US spelling: Square kilometer), symbol km², is an SI unit of surface area. ... Volume, also called capacity, is a quantification of how much space an object occupies. ... A cubic kilometre (symbol km³) is an SI derived unit of volume. ... Mass is a property of physical objects that, roughly speaking, measures the amount of matter they contain. ... The international prototype, made of platinum-iridium, which is kept at the BIPM under conditions specified by the 1st CGPM in 1889. ... Density (symbol: ρ - Greek: rho) is a measure of mass per unit of volume. ... Kilogram per cubic metre is the SI measure of density and is represented as kg/m³, where kg stands for kilogram and m³ stands for cubic metre. ... It has been suggested that gravitation be merged into this article or section. ... Metres per second squared is the SI derived unit of acceleration (scalar) and (vector), defined by distance in metres divided by time in seconds and again divided by time in seconds. ... g (also gee, g-force or g-load) is a non-SI unit of acceleration defined as exactly 9. ... In physics, for a given gravitational field and a given position, the escape velocity is the minimum speed an object without propulsion, at that position, needs to have to move away indefinitely from the source of the field, as opposed to falling back or staying in an orbit within a... On a prograde planet like the Earth, the sidereal day is shorter than the solar day. ... A day (symbol: d) is a unit of time equal to 24 hours. ... The hour (symbol: h) is a unit of time. ... Axial tilt is an astronomical term regarding the inclination angle of a planets rotational axis in relation to its orbital plane. ... A degree (in full, a degree of arc, arc degree, or arcdegree), usually symbolized °, is a measurement of plane angle, representing 1／360 of a full rotation. ... Right ascension (RA; symbol α: Greek letter alpha; celestial longitude) is the astronomical term for one of the two coordinates of a point on the celestial sphere when using the equatorial coordinate system. ... In astronomy, declination (dec) is one of the two coordinates of the equatorial coordinate system, the other being either right ascension or hour angle. ... The albedo is a measure of reflectivity of a surface or body. ... Temperature is the physical property of a system which underlies the common notions of hot and cold; the material with the higher temperature is said to be hotter. ... The kelvin (symbol: K) is the SI unit of temperature, and is one of the seven SI base units. ... It has been suggested that Centigrade be merged into this article or section. ... diurnal (daily) rhythm of air pressure in northern Germany (black curve is air pressure) Atmospheric pressure is the pressure above any area in the Earths atmosphere caused by the weight of air. ... The pascal (symbol Pa) is the SI unit of pressure. ... General Name, Symbol, Number nitrogen, N, 7 Chemical series nonmetals Group, Period, Block 15, 2, p Appearance colorless Atomic mass 14. ... General Name, Symbol, Number oxygen, O, 8 Chemical series Chalcogens Group, Period, Block 16, 2, p Appearance colorless Atomic mass 15. ... General Name, Symbol, Number argon, Ar, 18 Chemical series noble gases Group, Period, Block 18, 3, p Appearance colorless Atomic mass 39. ... Carbon dioxide is an atmospheric gas comprised of one carbon and two oxygen atoms. ... Water (from the Old English word wæter; c. ... A planet is generally considered to be a relatively large mass of accreted matter in orbit around a star that is not a star itself. ... The Sun is the star at the center of our Solar system. ... Presentation of the solar system (not to scale) The solar system comprises our Sun and the retinue of celestial objects gravitationally bound to it. ... A Earths solar system has four terrestrial planets: Mercury, Venus, Earth and Mars. ... Wikimedia Commons has media related to: Science For the scientific journal named Science, see Science (journal). ... Look up life and living in Wiktionary, the free dictionary. ... The age of the Earth is estimated to be 4. ... The word billion and its equivalents in other languages refer to one of two different numbers, depending on whether the writer is using the long or short scale. ... A year is the time between two recurrences of an event related to the orbit of the Earth around the Sun. ... The word billion and its equivalents in other languages refer to one of two different numbers, depending on whether the writer is using the long or short scale. ... Moons of solar system scaled to Earths Moon The common noun moon (not capitalized) is used to mean any natural satellite of the other planets. ... Crust composition Oxygen 43% Silicon 21% Aluminium 10% Calcium 9% Iron 9% Magnesium 5% Titanium 2% Nickel 0. ...

Lexicography

Earth is sometimes known as Terra in some languages, after the Roman goddess Terra. Its astronomical symbol consists of a circled cross, representing a meridian and the equator; a variant puts the cross atop the circle (Unicode: ⊕ or ♁). Besides words derived from Terra, such as terrestrial, terms that refer to the Earth include tellur- (telluric, tellurion, from the goddess Terra's alternate name, Tellūs) and geo- (geocentric, geothermal; from the Greek goddess Gaia). Roman mythology, the mythological beliefs of the people of Ancient Rome, can be considered as having two parts. ... // Mythology Terra or Tellus was a primeval Roman goddess, mother of Fama. ... Chinese Celestial symbols on an antique bronze mirror Astronomical symbols are symbols used to represent various celestial objects, theoretical constructs and observational events. ... Meridian is: Meridian (astronomy): an imaginary circle perpendicular to the horizon. ... The equator is an imaginary circle drawn around a planet (or other astronomical object) at a distance halfway between the poles. ... Technical note: Due to technical limitations, some web browsers may not display some special characters in this article. ... The adjective telluric is derived from a Latin word for earth or Mother Earth, Tellus, and is used in terms related to the Earth such as: telluric planet (a planet which is Earth-like in the sense that it is primarily composed of silicate rocks) telluric current (an extremely low... Tellurian is a variant spelling of tellurion, an instrument that depicts how day, night and the seasons are caused by the movement of the Earth on its axis and around the sun; it is similar to an orrery. ... The geocentric model (in Greek: geo = earth and centron = centre) of the universe is a paradigm which places the Earth at its center. ... Geothermal power is electricity generated by utilizing naturally occurring geological heat sources. ... Gaia (World Book «JEE uh») (land or earth, from the Greek ; variant spelling Gaea—see also also Ge from ) is a Greek goddess personifying the Earth. ...

The English word Earth has cognates in many modern as well as defunct - including ancient - languages. Examples in modern tongues include aarde in Dutch, Erde in German and arde in Arabic. The root also has cognates in extinct languages such as ertha in Old Saxon and ert (meaning 'ground') in Middle Irish. It is derived from Old English eorðe. Taking into account metathesis, we can find cognates of the word Earth in the Latin terra and in the modern Romance languages (i.e. tierra in Spanish). Arabic (; , less formally, ) is the largest member of the Semitic branch of the Afro-Asiatic language family (classification: South Central Semitic) and is closely related to Hebrew and Aramaic. ... Old Saxon, also known as Old Low German, is a Germanic language. ... my children are my life ... Note: This page contains phonetic information presented in the International Phonetic Alphabet (IPA) using Unicode. ... Metathesis is a sound change that alters the order of phonemes in a word. ... Latin is an ancient Indo-European language originally spoken in the region around Rome called Latium. ... The Romance languages, also called Romanic languages or New Latin languages, are a subset of the Italic languages, specifically the descendants of the Latin dialects spoken by the common people in what is known as Latin Europe (Italian/Portuguese/Spanish Europa latina, Catalan Europa llatina, French Europe latine, Romanian Europa...

Although a link to such Indo-European languages has not been proved, several Semitic languages have similar-sounding words for Earth: aard in Arabic, irtsitu in Akkadian, araa in Aramaic, erets in Phoenician (which appears in the Mesha Stele), and ארץ (arets, or erets when followed by a noun modifier) in Hebrew. The Indo-European languages are a group of languages several hundred languages and dialects (specifically 443 according to the SIL estimate), including most of the major language families of Europe, as well as many languages of Asia, which belong to a single superfamily. ... 14th century BC diplomatic letter in Akkadian, found in Tell Amarna. ... Akkadian (lišānum akkadÄ«tum) was a Semitic language (part of the greater Afro-Asiatic language famaily) spoken in ancient Mesopotamia, particularly by the Assyrians and Babylonians. ... Aramaic is a Semitic language with a 3,000-year history. ... Phoenician was a language originally spoken in the coastal region then called Phoenicia /Canaan (now Lebanon, coastal Syria and northern Israel ). Phoenician is a Semitic language of the Canaanite subgroup, closely related to Hebrew and Aramaic. ... The stele as photographed circa 1891 The Mesha Stele (popularized in the 19th century as the Moabite Stone) is a black basalt stone, bearing an inscription by the 9th century BC Moabite King Mesha, discovered in 1868. ... Hebrew (עִבְרִית ‘Ivrit) is a Semitic language of the Afro-Asiatic language family spoken by more than 7 million people, mainly in Israel, the West Bank, the United States and by Jewish communities around the world. ...

Physical characteristics

Main article: Structure of the Earth

Earth cutaway from core to exosphere. Partially to scale

The Earth consists of several atmospheric, hydrologic, and mainly geologic layers. Its components are the atmosphere, the hydrosphere, the crust, the mantle, and its core. The biosphere is a tiny layer in this composition and is usually not considered part of the physical layers of the Earth. Earth cutaway from core to exosphere. ... Geology (from Greek γη- (ge-, the earth) and λογος (logos, word, reason)) is the science and study of the Earth, its composition, structure, physical properties, history and the processes that shape it. ... Earth and atmosphere cutaway illustration. ... Earth and atmosphere cutaway illustration. ... Atmosphere may refer to: a celestial body atmosphere, e. ... Water covers 70% of the Earths surface. ... Geology (from Greek γη- (ge-, the earth) and λογος (logos, word, reason)) is the science and study of the Earth, its composition, structure, physical properties, history, and the processes that shape it. ... Layers of Atmosphere (NOAA) Earths atmosphere is a layer of gases surrounding the planet Earth and retained by the Earths gravity. ... Hydrosphere (Greek hydro- means water) in physical geography, describes the collective mass of water found on, under, and over the surface of a planet. ... Crust is any solid, outer layer on a fluid or soft body. ... Earth cutaway from core to exosphere. ... CORE may refer to: The Congress of Racial Equality in the USA. The Coordinated Online Register of Electors in the United Kingdom. ... The biosphere is that part of a planets outer shell—including air, land, surface rocks and water—within which life occurs, and which biotic processes in turn alter or transform. ...

The geologic component layers of the Earth are located at the following depths below surface:

• 0 to 60 km - Lithosphere (locally varies between 5 and 200 km)
  • 0 to 35 km - Crust (locally varies between 5 and 70 km)
  • 35 to 60 km - Uppermost part of mantle
• 35 to 2890 km - Mantle
  • 100 to 700 km - Asthenosphere
• 2890 to 5100 km - Outer Core
• 5100 to 6378 km - Inner Core

The tectonic plates of the Lithosphere on Earth. ... Earth cutaway from core to exosphere. ... Dont be afraid of big words. ...

Earth in the solar system

It takes the Earth 23 hours, 56 minutes and 4.091 seconds (1 sidereal day) to rotate around the axis connecting the north pole and the south pole. From Earth the main apparent motion of celestial bodies in the sky (except meteors which are within the atmosphere and low-orbiting satellites) is the movement to the west at a rate of 15 °/h = 15'/min, i.e., a Sun or Moon diameter every two minutes. On a prograde planet like the Earth, the sidereal day is shorter than the solar day. ... The word axis has several meanings: In mathematics, axis can mean: A straight line around which a geometric figure can be rotated. ... The North Pole is the northernmost point on any planet. ... Location of the South Pole in the Antarctic continent. ... A burst of meteors A meteor is the visible path of a meteoroid that enters the Earths (or another bodys) atmosphere, commonly called a shooting star or falling star. ...

Earth orbits the Sun every 365.2564 mean solar days (1 sidereal year). From Earth, this gives an apparent movement of the Sun with respect to the stars at a rate of ca. 1 °/day, i.e., a Sun or Moon diameter every 12 hours eastward. The sidereal year is the time for the Sun to return to the same position in respect to the stars of the celestial sphere. ...

The orbital speed of the Earth averages about 30 km/s (108,000 km/h), which is enough to cover one Earth diameter (~12,700 km) in 7 minutes, and one distance to the Moon (384,000 km) in 4 hours.

Earth has one natural satellite, the Moon, which revolves with the Earth around a common barycenter, from fixed star to fixed star, every 27.32 days. When combined with the Earth-Moon system's common revolution around the Sun, the period of the synodic month, from new moon to new moon, is 29.53 days. Moons of solar system scaled to Earths Moon The common noun moon (not capitalized) is used to mean any natural satellite of the other planets. ... Crust composition Oxygen 43% Silicon 21% Aluminium 10% Calcium 9% Iron 9% Magnesium 5% Titanium 2% Nickel 0. ... The barycenter (from the Greek βαρύκεντρον) is the center of mass of two or more bodies which are orbiting each other, and is the point around which both of them orbit. ... In Egyptian mythology, Month is an alternate spelling for Menthu. ...

The direction in which the Earth turns

Viewed from Earth's north pole, the motion of Earth, its moon and their axial rotations are all counterclockwise. Image File history File links Rotating_Earth. ... Image File history File links Rotating_Earth. ... A clockwise motion is one that proceeds like the clocks hands: from the top to the right, then down and then to the left, and back to the top. ...

The orbital and axial planes are not precisely aligned: Earth's axis is tilted some 23.5 degrees against the Earth-Sun plane (which causes the seasons); and the Earth-Moon plane is tilted about 5 degrees against the Earth-Sun plane (otherwise there would be an eclipse every month). Axial tilt is an astronomical term regarding the inclination angle of a planets rotational axis in relation to its orbital plane. ... A season is one of the major divisions of the year, generally based on yearly periodic changes in weather. ...

The Hill sphere (sphere of influence) of the Earth is about 1.5 Gm (930 thousand miles) in radius, within which one natural satellite (the Moon) comfortably orbits. A Hill sphere approximates the gravitational sphere of influence of one astronomical body in the face of perturbations from another heavier body around which it orbits. ... Crust composition Oxygen 43% Silicon 21% Aluminium 10% Calcium 9% Iron 9% Magnesium 5% Titanium 2% Nickel 0. ...

In an inertial reference frame, the Earth's axis undergoes a slow precessional motion with a period of some 25,800 years, as well as a nutation with a main period of 18.6 years. These motions are caused by the differential attraction of Sun and Moon on the equatorial bulge due to the Earth's oblateness. In a reference frame attached to the solid body of the Earth, its rotation is also slightly irregular due to polar motion. The polar motion is quasi-periodic, containing an annual component and a component with a 14-month period called the Chandler wobble. Also, the rotational velocity varies, a phenomenon known as length of day variation. Precession refers to a change in the direction of the axis of a rotating object. ... Rotation (green), Precession (blue) and Nutation (red) of the Earth Nutation is a slight irregular motion (etymologically a nodding) in the axis of rotation of a largely axially symmetric object, such as a gyroscope or a planet. ... This article needs to be wikified. ... The Chandler wobble is a small variation in Earths axis of rotation, discovered by American astronomer Seth Carlo Chandler in 1891. ... A day (symbol: d) is a unit of time equal to 24 hours. ...

In modern times, Earth's perihelion is always about January 3, and aphelion is about July 4 (near the winter and summer solstices, which are on about December 21 and June 21, respectively). For other eras, see precession and Milankovitch cycles. This article is about several astronomical terms (apogee & perigee, aphelion & perihelion, generic equivalents based on apsis, and related but rarer terms. ... January 3 is the 3rd day of the year in the Gregorian calendar. ... This article is about several astronomical terms (apogee & perigee, aphelion & perihelion, generic equivalents based on apsis, and related but rarer terms. ... July 4 is the 185th day of the year (186th in leap years) in the Gregorian Calendar, with 180 days remaining. ... Diagram of the Earths seasons Solstice is an astronomical term regarding the position of the Sun in relation to the earths equator. ... December 21 is the 355th day of the year (356th in leap years) in the Gregorian calendar. ... June 21 is the 172nd day of the year (173rd in leap years) in the Gregorian calendar, with 193 days remaining. ... Precession refers to a change in the direction of the axis of a rotating object. ... Milankovitch cycles is the name given to the collective effect of changes in the Earths movements upon its climate. ...

The Earth is sometimes referred to as the Third Planet from the Sun because, of the nine planets of our solar system, Earth is the third closest planet to the sun.

The Moon

Earthrise as seen from the Moon on Apollo 8, 24 December 1968. Due to tidal locking, from any point on the Moon's surface, the Earth does not rise or set, but is always located in the same position in the sky.

Main article: Moon

The Moon, sometimes called 'Luna', is a relatively large terrestrial planet-like satellite, whose diameter is about one-quarter of the Earth's. With the exception of Pluto's Charon, it is the largest moon in the Solar system relative to the size of its planet. The natural satellites orbiting other planets are called "moons", after Earth's Moon. Download high resolution version (1024x92, 2 KB)Subject: Illustration of the Earth and the Moon at maximum distance from each other as seen from the Sun. ... Download high resolution version (1024x92, 2 KB)Subject: Illustration of the Earth and the Moon at maximum distance from each other as seen from the Sun. ... Apollo 8 was the second manned mission of the Apollo space program, in which Commander Frank Borman, Command Module Pilot James Lovell and Lunar Module Pilot William Anders became the first humans to leave Earth orbit and to orbit around the Moon. ... December 24 is the 358th day of the year in the Gregorian Calendar (359th in leap years). ... 1968 (MCMLXVIII) was a leap year starting on Monday (the link is to a full 1968 calendar). ... Tidal locking makes one side of an astronomical body always face another, like the Moon facing the Earth. ... Crust composition Oxygen 43% Silicon 21% Aluminium 10% Calcium 9% Iron 9% Magnesium 5% Titanium 2% Nickel 0. ... The semi-major axis of an ellipse In geometry, the term semi-major axis (also semimajor axis) is used to describe the dimensions of ellipses and hyperbolas. ... Crust composition Oxygen 43% Silicon 21% Aluminium 10% Calcium 9% Iron 9% Magnesium 5% Titanium 2% Nickel 0. ... For more uses of the term Pluto, see Pluto (disambiguation). ... Charon (shar-ən or karr-ən, Greek Χάρων) is the largest satellite of Pluto. ... Moons of solar system scaled to Earths Moon The common noun moon (not capitalized) is used to mean any natural satellite of the other planets. ...

The gravitational attraction between the Earth and Moon cause the tides on Earth. The same effect on the Moon has led to its tidal locking: Its rotation period is the same as the time it takes to orbit the Earth. As a result, it always presents the same face to the planet. This article is about tides in the ocean. ... Tidal locking makes one side of an astronomical body always face another, like the Moon facing the Earth. ...

As the Moon orbits Earth, different parts of its face are illuminated by the Sun, leading to the lunar phases: The dark part of the face is separated from the light part by the solar terminator. In astronomy, a phase of the Moon is any of the aspects or appearances presented by the Moon as seen from Earth, determined by the portion of the Moon that is visibly illuminated by the Sun. ... World map with terminator A composite image showing the terminator crossing Europe and Africa The terminator is the line between the illuminated, day side and dark, night side of a planetary body (also known as the grey line). It is defined as the locus of points on a moon or...

The Moon may dramatically affect the development of life by taming the weather. Paleontological evidence and computer simulations show that Earth's axial tilt is stabilised by tidal interactions with the Moon. Some theorists believe that, without this stabilization against the torques applied by the Sun and planets to the Earth's equatorial bulge, the rotational axis might be chaotically unstable, as it appears to be with Mars. If Earth's axis of rotation were to approach the plane of the ecliptic, extremely severe weather could result, as this would make seasonal differences extreme. One pole would be pointed directly toward the Sun during summer and directly away during winter. Planetary scientists 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 insight. Axial tilt is an astronomical term regarding the inclination angle of a planets rotational axis in relation to its orbital plane. ... In physics, torque can be thought of informally as rotational force. Torque is measured in units of newton metres, and its symbol is Ï„. The concept of torque, also called moment or couple, originated with the work of Archimedes on levers. ... Mars is the fourth planet from the Sun in the solar system, named after the Roman god of war (the counterpart of the Greek Ares), on account of its blood red color as viewed in the night sky. ... The plane of the ecliptic is well seen in this picture from the 1994 lunar prospecting Clementine spacecraft. ... Composite satellite image showing the progress of a hurricane weather system approaching the East Coast of the United States Weather comprises all the various phenomena that occur in the atmosphere of a planet. ... Planetary science, also known as planetology or planetary astronomy, is the science of planets, or planetary systems, and the solar system. ... On a prograde planet like the Earth, the sidereal day is shorter than the solar day. ... Axial tilt is an astronomical term regarding the inclination angle of a planets rotational axis in relation to its orbital plane. ...

The Moon is just far enough away to have, when seen from Earth, very nearly the same apparent angular size as the Sun (the Sun is 400 times larger, but the Moon is 400 times closer). This allows total eclipses and annular eclipses to occur on Earth. Photo taken during the French 1999 eclipse An eclipse (Greek verb: ecleipo, to cease existing or calypse, to cover ) is an astronomical event that occurs when one celestial object moves into the shadow of another. ...

Earth and Moon to scale.

The most widely accepted theory of the Moon's origin, the giant impact theory, states that it was formed from the collision of a Mars-size protoplanet with the early Earth. This hypothesis explains (among other things) the Moon's relative lack of iron and volatile elements, and the fact that its composition is nearly identical to that of the Earth's crust. Download high resolution version (1024x92, 2 KB)Subject: Illustration of the Earth and the Moon at maximum distance from each other as seen from the Sun. ... Download high resolution version (1024x92, 2 KB)Subject: Illustration of the Earth and the Moon at maximum distance from each other as seen from the Sun. ... The Big Splash The giant impact theory (or Big Splash or Big Whack; cf. ... In cosmogony, a protoplanet is a quasi-planetoid which is slightly larger than a planetesimal and orbits within a solar nebulas protoplanetary discs. ...

Earth also has at least one co-orbital asteroid, 3753 Cruithne. An asteroid is a small, solid object in our Solar System, orbiting the Sun. ... (also known as Earths second moon ) 3753 Cruithne is an asteroid in orbit around the Sun. ...

Geography

Main article: Geography

Physical map of the Earth ( Medium) ( Large 2 MB)

Map references: Image File history File links Physical_world. ... Image File history File links Physical_world. ... Image File history File links Physical_world. ... Download high resolution version (4000x2949, 1546 KB)Physical World Map 2004-04-01 CIA World Factbook; Robinson Projection; standard parallels 38°N and 38°S File links The following pages link to this file: Wikipedia:WikiProject Maps/World World map Categories: CIA World Factbook images ...

Time Zones, Coordinates. Time zones are areas of the Earth that have adopted the same standard time, usually referred to as the local time. ... See Cartesian coordinate system or Coordinates (elementary mathematics) for a more elementary introduction to this topic. ...

Biggest geographic subdivision

Continents, Oceans Dymaxion map by Buckminster Fuller shows land mass with minimal distortion as only one continuous continent A continent (Latin continere, to hold together) is a large continuous landmass. ... The worlds oceans as seen from the South Pacific Ocean (from Okeanos, Greek for river, the ancient Greeks noticed that a strong current flowed off Gibraltar, and assumed it was a great river); covers almost three quarters (71%) of the surface of the Earth, and nearly half of the...

Area:

• Total: 510.073 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 km (not counting shared boundaries twice) To help compare sizes of different areas, here is a list of areas between 100 million km² and 1,000 million (American billion) km². See also areas of other orders of magnitude. ... Square kilometre (US spelling: Square kilometer), symbol km², is an SI unit of surface area. ... A landform comprises a geomorphological unit. ... Water (from the Old English word wæter; c. ...

Coastline: 356,000 km

Maritime claims: see United Nations Convention on the Law of the Sea United Nations Convention on the Law of the Sea Opened for signature ??? at ??? Entered into force November 16, 1994[1] Conditions for entry into force 60 ratifications Parties 149[2] The term United Nations Convention on Law of the Sea (UNCLOS, also called simply the Law of the Sea or...

• Contiguous zone: 24 nautical miles (44.4 km) claimed by most, but can vary
• Continental shelf: 200 m depth claimed by most or to depth of exploitation; others claim 200 nautical miles (370.4 km) or to the edge of the continental margin
• Exclusive fishing zone: 200 nautical miles (370.4 km) claimed by most, but can vary
• Exclusive economic zone: 200 nautical miles (370.4 km) claimed by most, but can vary
• Territorial sea: 12 nautical miles (22.2 km) 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 nautical miles (370.4 km)
• 42 nations and other areas are completely landlocked (see list of landlocked countries)

A nautical mile is a unit of length. ... The continental shelf is the extended perimeter of each continent, which is covered during interglacial periods such as the current epoch by relatively shallow seas (known as shelf seas) and gulfs. ... A landlocked country is one that has no coastline. ...

Environment and Ecosystem

Main article: Biosphere

Earth is the only place in the universe where life is absolutely known to exist, and some scientists believe that biospheres might be rare. The planet's lifeforms are sometimes said to form a "biosphere". This biosphere is generally believed to have begun evolving about 3.5 billion (3.5×10⁹) years ago. The biosphere is that part of a planets outer shell—including air, land, surface rocks and water—within which life occurs, and which biotic processes in turn alter or transform. ... The rare Earth hypothesis is a response to the Fermi paradox which explains why we might expect a planet such as Earth to be very rare. ... The biosphere is that part of a planets outer shell—including air, land, surface rocks and water—within which life occurs, and which biotic processes in turn alter or transform. ... A speculatively rooted phylogenetic tree of all living things, based on rRNA gene data, showing the separation of the three domains, bacteria, archaea, and eukaryotes, as described initially by Carl Woese. ...

The biosphere is divided into a number of biomes, inhabited by broadly similar flora and fauna. On land, biomes are separated primarily by latitude. Terrestrial biomes lying within the Arctic and Antarctic Circles are relatively barren of plant and animal life, while most of the more populous biomes lie near the Equator. In ecology, a biome is a major regional group of distinctive plant and animal communities best adapted to the regions physical environment. ... In Botany a Flora (or Floræ) is a collective term for plant life and can also refer to a descriptive catalogue of the plants of any geographical area, geological period, etc. ... Fauna is a collective term for animal life. ... Latitude, sometimes denoted by the Greek letter φ, gives the location of a place on Earth north or south of the Equator. ... World map showing the five major circles of latitude A sign along the Dalton Highway marking the location of the Arctic Circle The Arctic Circle is one of the five major circles of latitude that mark maps of the Earth. ... Zoomable PDF of the map this is based on The Antarctic Circle is one of the five major circles of latitude that mark maps of the Earth. ... Divisions Land plants (embryophytes) Non-vascular plants (bryophytes) Marchantiophyta - liverworts Anthocerotophyta - hornworts Bryophyta - mosses Vascular plants (tracheophytes) Lycopodiophyta - clubmosses Equisetophyta - horsetails Pteridophyta - true ferns Psilotophyta - whisk ferns Ophioglossophyta - adderstongues Seed plants (spermatophytes) †Pteridospermatophyta - seed ferns Pinophyta - conifers Cycadophyta - cycads Ginkgophyta - ginkgo Gnetophyta - gnetae Magnoliophyta - flowering plants Adiantum pedatum (a fern... Phyla Porifera (sponges) Ctenophora (comb jellies) Cnidaria (coral, jellyfish, anenomes) Placozoa (trichoplax) Subregnum Bilateria (bilateral symmetry) Acoelomorpha (basal) Orthonectida (parasitic to flatworms, echinoderms, etc. ... The equator is an imaginary circle drawn around a planet (or other astronomical object) at a distance halfway between the poles. ...

A familiar scene on Earth which simultaneously shows the lithosphere, hydrosphere and atmosphere

Image File history File links Download high resolution version (1600x1200, 364 KB) 90 mile beach, Lakes Entrance File links The following pages link to this file: Tourism Beach Wikipedia:Featured picture candidates Lakes Entrance, Victoria Wikipedia:Featured picture candidates/90 mile beach ... Image File history File links Download high resolution version (1600x1200, 364 KB) 90 mile beach, Lakes Entrance File links The following pages link to this file: Tourism Beach Wikipedia:Featured picture candidates Lakes Entrance, Victoria Wikipedia:Featured picture candidates/90 mile beach ... 90 mile beach Australia A beach or strand is a geological formation consisting of loose rock particles such as sand, shingle, cobble, or even shell along the shoreline of a body of water. ...

Climate

Main article: 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 metres of water per year to less than a millimetre. In geography, temperate latitudes of the globe lie between the tropics and the polar circles. ... The equator is an imaginary circle drawn around a planet (or other astronomical object) at a distance halfway between the poles. ... The tropics are the geographic region of the Earth centered on the equator and limited in latitude by the two tropics: the Tropic of Cancer in the north and the Tropic of Capricorn in the southern hemisphere. ... Subtropical (or semitropical) areas are those adjacent to the tropics, usually roughly defined as the ranges 23. ...

Ocean currents, particularly the spectacular thermohaline circulation which distributes heat energy from the equatorial oceans to the polar regions, are important determinators of climate. The thermohaline circulation is a term for the global density-driven circulation of the oceans. ...

Terrain

Main article: Extreme points of the world

Elevation extremes: (measured relative to sea level) It has been suggested that The worlds most northern be merged into this article or section. ... For considerations of sea level change, in particular rise associated with possible global warming, see sea level rise. ...

• Lowest point on land: Dead Sea −417 m
• Lowest point overall: Mariana Trench in the Pacific Ocean −10,924 m [1]
• Highest point: Mount Everest 8,844 m (2005 est.)

The Jordan River flowing into the Dead Sea The Dead Sea (Arabic البحر الميت, Hebrew ים המלח) is the lowest exposed point on the Earths surface. ... To help compare different orders of magnitude this page lists lengths between 100 m and 1 km. ... Mariana Trench location The Mariana Trench (or Marianas Trench) is the deepest known submarine trench, and the deepest location in the Earths crust itself. ... To help compare different orders of magnitude this page lists lengths between 10 and 100 km (104 to 105 m). ... Mount Everest is the highest mountain on Earth, meaning its summit is higher above sea level than that of any other mountain. ... To help compare different orders of magnitude this page lists lengths between 1 km and 10 km (103 and 104 m). ... 2005 (MMV) was a common year starting on Saturday of the Gregorian calendar. ...

Natural resources

Main article: Natural resource

• Earth's crust contains large deposits of fossil fuels: (coal, petroleum, 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 Earth's crust by the action of erosion and plate tectonics. These ore bodies form concentrated sources for many metals and other useful elements.
• 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 mineral 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. Coal rail cars in Ashtabula, Ohio Fossil fuels, also known as mineral fuels, are hydrocarbon-containing natural resources such as coal, petroleum and natural gas. ... Coal is a fossil fuel extracted from the ground by underground mining or open-pit mining (strip mining). ... Pumpjack pumping an oil well near Sarnia, Ontario Petroleum (from Greek petra – rock and elaion – oil or Latin oleum – oil ), crude oil, sometimes colloquially called black gold, is a thick, dark brown or greenish liquid. ... Natural gas (commonly referred to as gas in many countries, but note that gas is also an American and Canadian shortening of gasoline) is a gaseous fossil fuel consisting primarily of methane. ... Burning ice. Methane, released by heating, burns; water drips. ... Iron ore (Banded iron formation) Manganese ore Lead ore Gold ore An ore is a mineral deposit containing a metal or other valuable resource in economically viable concentrations. ... Severe soil erosion in a wheat field near Washington State University, USA. Erosion is the displacement of solids (soil, mud, rock, and other particles) by the agents of wind, water, ice, movement in response to gravity, or living organisms (in the case of bioerosion). ... Plate tectonics (from the Greek word for one who constructs and destroys, τεκτων, tekton) is a theory of geology developed to explain the phenomenon of continental drift, and is currently the theory accepted by the vast majority of scientists working in this area. ... Hot metal work from a blacksmith In chemistry, a metal (Greek: Metallon) is an element that readily forms ions (cations) and has metallic bonds, and metals are sometimes described as a lattice of positive ions (cations) in a cloud of electrons. ... A chemical element, often called simply element, is a chemical substance that cannot be divided or changed into other chemical substances by any ordinary chemical technique. ... The biosphere is that part of a planets outer shell—including air, land, surface rocks and water—within which life occurs, and which biotic processes in turn alter or transform. ... A tree trunk as found at the Veluwe, The Netherlands Wood derives from woody plants, notably trees but also shrubs. ... Pharmacology (in Greek: pharmacon is drug, and logos is science) is the study of how chemical substances interfere with living systems. ... In ecology, the word ecosystem is an abbreviation of the term, ecological system. ... Topsoil is the uppermost layer of soil, usually the top six to eight inches. ... In ecology, the word ecosystem is an abbreviation of the term, ecological system. ... Coal rail cars in Ashtabula, Ohio Fossil fuels, also known as mineral fuels, are hydrocarbon-containing natural resources such as coal, petroleum and natural gas. ... A non-renewable resource is Natural resource that cannot be re-made or re-grown. ... The word civilization (or civilisation) has a variety of meanings related to human society. ... Environmentalism is the support or involvement with the environmental movement by environmentalists. ...

Land use

• Arable land: 10%
• Permanent crops: 1%
• Permanent pastures: 26%
• Forests and woodland: 32%
• Urban areas: 1.5%
• Other: 30% (1993 est.)

Irrigated land: 2,481,250 km² (1993 est.) 1993 (MCMXCIII) was a common year starting on Friday of the Gregorian calendar and marked the Beginning of the International Decade to Combat Racism and Racial Discrimination (1993-2003). ...

Natural and environmental 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. Composite satellite image showing the progress of a hurricane weather system approaching the East Coast of the United States Weather comprises all the various phenomena that occur in the atmosphere of a planet. ... Cyclone - Wikipedia, the free encyclopedia /**/ @import /skins-1. ... This article is about weather phenomena. ... This article is about weather phenomena. ... Global earthquake epicenters, 1963–1998 An earthquake is a sudden and sometimes catastrophic movement of a part of the Earths surface. ... It has been suggested that Mudslide be merged into this article or section. ... The tsunami that struck Malé in the Maldives on December 26, 2004. ... Eruption redirects here. ... Union City, Oklahoma tornado (1973) A tornado is a violent spinning storm typically shaped like a funnel with the narrow end on the ground. ... A special type of sinkhole - formed by rainwater leaking through the pavement and carrying dirt into a ruptured sewer pipe Sinkholes, also known as sinks, dolines, and cenotes, are formed by the collapse of cave roofs and are a feature of landscapes that are based on limestone bedrock. ... Look up Flood in Wiktionary, the free dictionary A flood (in Old English flod, a word common to Teutonic languages; compare German Flut, Dutch vloed from the same root as is seen in flow, float) is an overflow of water, an expanse of water submerging land, a deluge. ... A drought or an extreme dry periodic climate is an extended period where water availability falls below the statistical requirements for a region. ...

Large areas are subject to man-made pollution of the air and water, acid rain and toxic substances, loss of vegetation (overgrazing, deforestation, desertification), loss of wildlife, species extinction, soil degradation, soil depletion, erosion, and introduction of invasive species. Environmental Pollution is the release of harmful environmental contaminants, or the substances so released. ... Acid rain is defined as any type of precipitation with a pH of below 5. ... Deforestation is the conversion of forested areas to non-forest. ... Ship stranded by the retreat of the Aral Sea Desertification is the degradation of land in arid, semi arid and dry sub-humid areas resulting from various factors including climatic variations and human activities. ... Various species of deer are commonly seen wildlife across the Americas and Eurasia. ... In biology, a species is the basic unit of biodiversity. ... In biology and ecology, extinction is the ceasing of existence of a species or group of taxa. ... Retrogression and degradation are two regressive evolution processes associated with the loss of equilibrium of a stable soil. ... Severe soil erosion in a wheat field near Washington State University, USA. Erosion is the displacement of solids (soil, mud, rock, and other particles) by the agents of wind, water, ice, movement in response to gravity, or living organisms (in the case of bioerosion). ... It has been suggested that Invasive plants be merged into this article or section. ...

Long-term climate alteration due to enhancement of the greenhouse effect by human industrial carbon dioxide emissions is an increasing concern, the focus of intense study and debate. Global mean surface temperatures 1856 to 2005 Mean temperature anomalies during the period 1995 to 2004 with respect to the average temperatures from 1940 to 1980 Global warming is an increase in the average temperature of the Earths atmosphere and oceans. ... The greenhouse effect, first discovered by Joseph Fourier in 1824, and quantified by Svante Arrhenius in 1896, is the process by which an atmosphere warms a planet. ... Carbon dioxide is an atmospheric gas comprised of one carbon and two oxygen atoms. ...

Human geography

Earth at night, composite of pictures taken between October 1994 and March 1995

Main article: Human

On 25 February 2005 the United Nations Population Division issued revised estimates and projected that the world's population will reach 7 billion by 2013 and swell to 9.1 billion in 2050. Most of the growth is expected to take place in developing nations. Download high resolution version (2400x1200, 534 KB)Composite image of the Earth at night, created by NASA and NOAA. NASA Description: This image of Earth’s city lights was created with data from the Defense Meteorological Satellite Program (DMSP) Operational Linescan System (OLS). ... Download high resolution version (2400x1200, 534 KB)Composite image of the Earth at night, created by NASA and NOAA. NASA Description: This image of Earth’s city lights was created with data from the Defense Meteorological Satellite Program (DMSP) Operational Linescan System (OLS). ... Binomial name Homo sapiens Linnaeus, 1758 Subspecies Homo sapiens idaltu(extinct) Homo sapiens sapiens Homo (genus). ... February 25 is the 56th day of the year in the Gregorian Calendar. ... 2005 (MMV) was a common year starting on Saturday of the Gregorian calendar. ... The world population is the total number of humans alive on the planet Earth at a given time. ... 2013 (MMXIII) will be a common year starting on Tuesday of the Gregorian calendar. ... Centuries: 20th century - 21st century - 22nd century Decades: 2000s 2010s 2020s 2030s 2040s - 2050s - 2060s 2070s 2080s 2090s 2100s Years: 2045 2046 2047 2048 2049 - 2050 - 2051 2052 2053 2054 2055 The year 2050 (MML) in the Gregorian calendar corresponds to to 5810-5811 in the Hebrew Calendar. ... A developing country is a country with low average income compared to the world average. ...

Nearly all humans currently reside on Earth: 6,411,000,000 inhabitants (January 5, 2005 est.). It is estimated that only 1/8th of the surface of the Earth is suitable for humans to live on - 3/4 is covered by oceans, and half of the landmass is unsuitable, being desert, high mountain, etc. Coastal areas constitute the highest density. Binomial name Homo sapiens Linnaeus, 1758 Subspecies Homo sapiens idaltu(extinct) Homo sapiens sapiens Homo (genus). ... January 5 is the 5th day of the year in the Gregorian calendar. ... 2005 (MMV) was a common year starting on Saturday of the Gregorian calendar. ... Binomial name Homo sapiens Linnaeus, 1758 Subspecies Homo sapiens idaltu(extinct) Homo sapiens sapiens Homo (genus). ... The worlds oceans as seen from the South Pacific Ocean (from Okeanos, Greek for river, the ancient Greeks noticed that a strong current flowed off Gibraltar, and assumed it was a great river); covers almost three quarters (71%) of the surface of the Earth, and nearly half of the... A dune in the Egyptian desert In geography, a desert is a landscape form or region that receives little precipitation - less than 250 mm (10 in) per year. ... Mount McKinley in Alaska has one of the largest visible base-to-summit elevation differences anywhere For other uses of this term, see Mountain (disambiguation). ...

Two humans are presently in orbit around Earth on board the International Space Station. The station crew is replaced with new personnel every six months. During the exchange there are more, and sometimes others are also traveling briefly above the atmosphere. ISS Statistics Crew: 2 As of August 21, 2005 Perigee: 352. ... Currently, the most common technology for space transport is rocket propulsion, which expels matter to provide a net forward thrust. ...

In total, about 400 people have been outside Earth (in space) as of 2004. Out of those only twelve humans have ever walked on a world other than Earth: the men of Apollo 11, 12, 14, 15, 16 and 17, who walked on the Moon between 1969 and 1972. 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ... Apollo 11 was an American space mission, part of the Apollo program and the first manned mission to land on the Moon. ... Apollo 12 was the sixth manned mission in the Apollo program and the second to land on the Moon. ... Apollo 14 was the eighth manned mission in the Apollo program and the third mission to land on the moon. ... Apollo 15 was the ninth manned mission in the Apollo program and the fourth mission to land on the Moon. ... Apollo 16 was the tenth manned mission in the Apollo program and the fifth mission to land on the Moon. ... Apollo 17 was the eleventh manned space mission in the NASA Apollo program, and was the sixth and last mission to date to land on the Moon. ... Crust composition Oxygen 43% Silicon 21% Aluminium 10% Calcium 9% Iron 9% Magnesium 5% Titanium 2% Nickel 0. ... 1969 (MCMLXIX) was a common year starting on Wednesday For other uses, see Number 1969. ... 1972 (MCMLXXII) was a leap year that started on a Tuesday. ...

See also space colonization. Artists conception of a space habitat called the Stanford torus, by Don Davis Space colonization, also called space settlement and space humanization, is the hypothetical permanent autonomous (self-sufficient) human habitation of locations outside Earth. ...

The northernmost settlement in the world is Alert, Ellesmere Island, Canada. The southernmost is the Amundsen-Scott South Pole Station, in Antarctica, almost exactly at the South Pole. Alert is the northernmost permanent settlement in the world. ... Ellesmere Island, Nunavut. ... -1... Location of the South Pole in the Antarctic continent. ...

There are 267 administrative divisions, including nations, dependent areas, other, and miscellaneous entries. Earth does not have a sovereign government with planet-wide authority. Independent sovereign nations claim all of the land surface except for some segments of Antarctica. There is a worldwide general international organization, the United Nations. The United Nations is primarily an international discussion forum with only limited ability to pass and enforce laws. ... One of the most influential doctrines in history is that all humans are divided into groups called nations. ... An international organization (also called intergovernmental organization) is an organization of international scope or character. ... Main articles: League of Nations and History of the United Nations The term United Nations was coined by Franklin D. Roosevelt during World War II, to refer to the Allies. ... International law, is the body of law that regulates the activities of entities possessing international personality. Traditionally, that meant the conduct and relationships of states. ...

Descriptions of Earth

Earth has often been personified as a deity, in particular a goddess (see Gaia and Mother Earth). The Chinese Earth goddess Hu-Tu is similar to Gaia, the deification of the Earth. As the patroness of fertility, her element is Earth. In Norse mythology, the Earth goddess Jord was the mother of Thor and the daughter of Annar. A deity or a god, is a postulated preternatural being, usually, but not always, of significant power, worshipped, thought holy, divine, or sacred, held in high regard, or respected by human beings. ... Ceres, the Roman goddess of agriculture A goddess is a female deity, in contrast with a male deity known as a god. A great many cultures have goddesses, sometimes alone, but more often as part of a larger pantheon that includes both of the conventional genders and in some cases... Gaia (World Book «JEE uh») (land or earth, from the Greek ; variant spelling Gaea—see also also Ge from ) is a Greek goddess personifying the Earth. ... Mother Earth is a common metaphorical expression for the Earth and its biosphere as the giver and sustainer of life. ... Norse or Scandinavian mythology comprises the pre-Christian religion, beliefs and legends of the Scandinavian people, including those who settled on Iceland, where the written sources for Norse mythology were assembled. ... Jord was, in Norse mythology, the goddess of the Earth. ... Thor carries his hammer and wears his belt of strength in this illustration from an 18th century Icelandic manuscript. ... In Norse mythology, according to the Gylfaginning, Annar (Old Norse Annarr second, another) was the father of Jörd Earth by Nótt Night. The form Ónar (Old Norse Ónarr gaping) is found as a variant. ...

Since Earth is rather large, it is not immediately obvious to the naked eye viewing from the surface that it is an oblate spheroid, bulging slightly at the equator and slightly flattened at the poles. In the past there were varying levels of belief in a flat Earth because of this, but ancient Greek philosophers and, in the Middle Ages, thinkers such as Thomas Aquinas knew that the Earth was a sphere. The notion of a Flat Earth refers to the idea that the inhabited surface of the Earth is flat, rather than curved (see Spherical Earth). ... The Middle Ages formed the middle period in a traditional schematic division of European history into three ages: the classical civilization of Antiquity, the Middle Ages, and modern times, beginning with the Renaissance. ... Saint Thomas Aquinas [Thomas of Aquin, or Aquino] (c. ...

Prior to the introduction of space flight, this belief was countered with deductions based on observations of the secondary effects of the Earth's shape and parallels drawn with the shape of other planets. Cartography, the study and practice of mapmaking, and vicariously geography, have historically been the disciplines devoted to depicting the Earth. Surveying, the determination of locations and distances, and to a somewhat lesser extent navigation, the determination of position and direction, have developed alongside cartography and geography, providing and suitably quantifying the requisite information. Currently, the most common technology for space transport is rocket propulsion, which expels matter to provide a net forward thrust. ... Cartography or mapmaking (in Greek chartis = map and graphein = write) is the study and practice of making maps or globes. ... Surveyor at work with a leveling instrument. ... There are several traditions of navigation. ...

The technological developments of the latter half of the 20th century are widely considered to have altered the public's perception of the Earth. A photo taken of Earth by Voyager 1 inspired Carl Sagan to describe the planet as a "Pale Blue Dot". Earth has also been described as a massive spaceship, with a life support system that requires maintenance, or as having a biosphere that forms one large organism. See Spaceship Earth and Gaia theory. (19th century - 20th century - 21st century - more centuries) Decades: 1900s 1910s 1920s 1930s 1940s 1950s 1960s 1970s 1980s 1990s As a means of recording the passage of time, the 20th century was that century which lasted from 1901–2000 in the sense of the Gregorian calendar (1900–1999 in the... A NASA artists rendition of a Voyager spacecraft The Voyager 1 spacecraft is an 815-kilogram unmanned probe of the outer solar system and beyond, launched September 5, 1977, and currently operational. ... Carl Edward Sagan (November 9, 1934 – December 20, 1996) was an American astronomer, astrobiologist and highly successful science popularizer. ... Pale Blue Dot is a photograph of the Earth taken by the Voyager 1 spacecraft at the range of 3. ... Ariane 5 lifts off with the Rosetta probe on 2nd of March, 2004. ... This article is about life support systems for outer space or underwater. ... The biosphere is that part of a planets outer shell—including air, land, surface rocks and water—within which life occurs, and which biotic processes in turn alter or transform. ... In biology and ecology, an organism (in Greek organon = instrument) is a complex adaptive system of organs that influence each other in such a way that they function as a more or less stable whole and have properties of life. ... The phrase spaceship Earth is believed to have been derived from a passage in Henry Georges best known work, Progress and Poverty (1879). ... A Gaia theory is a class of scientific models of the biosphere in which life fosters and maintains suitable conditions for itself by affecting Earths environment. ...

For descriptions of the Earth in (science) fiction, see Earth in fiction. Earth Although nearly all fictional work features the Earth, this page describes its fictional place in the Universe. ...

See also

• Ecology: Millennium Ecosystem Assessment
• Economy: World economy
• History:
  • Origin and evolution of the solar system
  • Geologic time scale
  • Timeline of evolution
  • Human History
• Legal system: Anarchy, International law
• Political: List of countries
• Geology
  • Earthquake
  • Plate tectonics
• Degree Confluence Project
• Equatorial bulge
• Earth in fiction
  • Journey to the Center of the Earth
  • Hollow Earth
• Extraterrestrial life
• Globus Cassus
• Extremes on Earth

A conceptual outline for the program The Millennium Ecosystem Assessment (MA) is a research program that focuses on ecosystem changes over the course of decades, and projecting those changes into the future. ... The world economy can be represented in various ways, and broken down in various ways. ... Presentation of the solar system (not to scale) The solar system comprises our Sun and the retinue of celestial objects gravitationally bound to it. ... The geologic time scale is used by geologists and other scientists to describe the timing and relationships between events that have occurred during the history of the Earth. ... This timeline outlines the major events in the development of life on planet Earth. ... The history of the world, in popular parlance, is human history, from the first appearance of Homo sapiens to the present. ... In the realist theory of International Relations, the anarchical system that all states find themselves in is the lack of clear organisation of states into a hieracical order that is found within states. ... International law, is the body of law that regulates the activities of entities possessing international personality. Traditionally, that meant the conduct and relationships of states. ... This is an alphabetical list of countries of the world, including both internationally recognized and generally unrecognized independent states, inhabited dependent territories, as well as areas of special sovereignty. ... Geology (from Greek γη- (ge-, the earth) and λογος (logos, word, reason)) is the science and study of the Earth, its composition, structure, physical properties, history and the processes that shape it. ... Global earthquake epicenters, 1963–1998 An earthquake is a sudden and sometimes catastrophic movement of a part of the Earths surface. ... Plate tectonics (from the Greek word for one who constructs and destroys, τεκτων, tekton) is a theory of geology developed to explain the phenomenon of continental drift, and is currently the theory accepted by the vast majority of scientists working in this area. ... The goals of the Degree Confluence Project are to visit each of the latitude and longitude integer degree intersections on Earth, and post photographs of each location on the World Wide Web. ... An equatorial bulge is a planetological term which describes a bulge which a planet may have around its equator, distorting it into an oblate spheroid. ... Earth Although nearly all fictional work features the Earth, this page describes its fictional place in the Universe. ... Journey to the Center of the Earth DVD Journey to the Center of the Earth is an 1864 science fiction novel by Jules Verne (published in the original French as Voyage au centre de la Terre. ... The phrase hollow earth refers to the esoteric idea that the planet Earth has a hollow interior, almost always associated with the idea that it has a habitable inner surface. ... The existence of extraterrestrial life remains hypothetical though human beings continue to search Extraterrestrial life is life that may exist and originate outside the planet Earth. ... Globus Cassus is a utopian project for the transformation of Planet Earth into a much bigger, hollow, artificial world with an ecosphere on its inner surface. ... It has been suggested that this article or section be merged with Extreme points of the world. ...

References

• NASA's Earth fact sheet
• Discovering the Essential Universe (Second Edition) by Neil F. Comins (2001)
• space.about.com - Earth - Pictures and Astronomy Facts

External links

Wikimedia Commons has media related to:

Earth

• USGS Geomagnetism Program
• [2] (pdf) - density, pressure, gravity, P-wave and S-wave seismic wave velocities, and Poisson's ratio as a function of depth
• 3D Map from NASA World Wind (184.3 MB).
• 3D Map from Google - Google Earth search system.
• [3] Nasa Earth Observatory - the Blue Marble (very high resolution images)

• Planets - Earth A kid's guide to Earth.

Image File history File links Commons-logo. ... The Wikimedia Commons (also called Commons or Wikicommons) is a repository of free content images, sound and other multimedia files. ... Density (symbol: ρ - Greek: rho) is a measure of mass per unit of volume. ... Pressure (symbol: p) is the force per unit area acting on a surface in a direction perpendicular to that surface. ... It has been suggested that gravitation be merged into this article or section. ... p-wave and s-wave from seismograph A seismic wave is a wave that travels through the Earth, often as the result of an earthquake or explosion. ... When a sample of material is stretched in one direction, it tends to get thinner in the other two directions. ... Screenshot of World Wind showing USGS Urban Ortho-Imagery of Huntington Beach, Los Angeles World Wind is a virtual globe developed by NASA for use on personal computers running Microsoft Windows. ... A megabyte is a unit of information or computer storage equal to one million bytes. ... Google Earth is a free virtual globe formerly known as Earth Viewer. ... Presentation of the solar system (not to scale) The solar system comprises our Sun and the retinue of celestial objects gravitationally bound to it. ... Atmospheric characteristics Atmospheric pressure trace Potassium 31. ... Adjective Venusian or (rarely) Cytherean (*min temperature refers to cloud tops only) Atmospheric characteristics Atmospheric pressure 9. ... Crust composition Oxygen 43% Silicon 21% Aluminium 10% Calcium 9% Iron 9% Magnesium 5% Titanium 2% Nickel 0. ... For the Roman god, see Mars (god). ... Adjective Jovian Atmospheric characteristics Atmospheric pressure 70 kPa Hydrogen ~86% Helium ~14% Methane 0. ... Adjective Saturnian Atmospheric characteristics Atmospheric pressure 140 kPa Hydrogen >93% Helium >5% Methane 0. ... Adjective Uranian Atmospheric characteristics Atmospheric pressure 120 kPa (at the cloud level) Hydrogen 83% Helium 15% Methane 1. ... Adjective Neptunian Atmospheric characteristics Surface pressure ≫100 MPa Hydrogen - H2 80% ±3. ... For more uses of the term Pluto, see Pluto (disambiguation). ... The Sun is the star at the center of our Solar system. ... For the Velvet Chain album, see Asteroid Belt (album). ... Artists rendering of the Kuiper Belt and more distant Oort cloud. ... The scattered disc (or scattered disk) is a distant region of our solar system, thinly populated by a subset of the family of trans-Neptunian objects known as scattered disk objects (SDOs). ... This image is an artists rendering of the Oort cloud and the Kuiper Belt. ... See also Lists of astronomical objects Category: ... Presentation of the solar system (not to scale) The solar system comprises our Sun and the retinue of celestial objects gravitationally bound to it. ... Below is a list of solar system objects with diameter >500km: The Sun, a spectral class G2 star Mercury Venus Earth Moon Mars Jupiter Io Europa Ganymede Callisto complete list of Jupiters natural satellites Saturn Tethys Dione Rhea Titan Iapetus complete list of Saturns natural satellites Uranus Ariel... This is a list of solar system objects by radius, in decreasing order. ... This is a list of Solar system objects by mass, in decreasing order. ...