Earth's surface

Earth

The Blue Marble photograph of Earth, taken during the Apollo 17 lunar mission in 1972
Orbital characteristics
Epoch J2000
Aphelion	152,100,000 km (94,500,000 mi) (7011152100643076810♠1.01673 AU)
Perihelion	147,095,000 km (91,401,000 mi) (7011147094903845957♠0.9832687 AU)
Semi-major axis	149,598,023 km (92,955,902 mi) (7011149598022990632♠1.000001018 AU)
Eccentricity	6998167086000000000♠0.0167086
Orbital period	7007315581497635456♠365.256363004 d  (7000100001742095999♠1.00001742096 yr)
Average orbital speed	29.78 km/s (18.50 mi/s) (107,200 km/h (66,600 mph))
Mean anomaly	7002358617000000000♠358.617°
Inclination	7000715500000000000♠7.155° to the Sun's equator; 1.57869° to invariable plane; 0.00005° to J2000 ecliptic
Longitude of ascending node	2998887393600000000♠−11.26064° to J2000 ecliptic
Argument of perihelion	7002114207830000000♠114.20783°
Satellites	1 natural satellite: the Moon 5 quasi-satellites >1,400 operational artificial satellites >16,000 space debris
Physical characteristics
Mean radius	6,371.0 km (3,958.8 mi)
Equatorial radius	6,378.1 km (3,963.2 mi)
Polar radius	6,356.8 km (3,949.9 mi)
Flattening	6997335280000000000♠0.0033528 1/298.257222101 (ETRS89)
Circumference	40,075.017 km (24,901.461 mi) (equatorial)  40,007.86 km (24,859.73 mi) (meridional)
Surface area	510,072,000 km2 (196,940,000 sq mi)  148,940,000 km2 (57,510,000 sq mi) (29.2%) land  361,132,000 km2 (139,434,000 sq mi) (70.8%) water
Volume	7021108320999999999♠1.08321×1012 km3 (7011259876000000000♠2.59876×1011 cu mi)
Mass	7024597237000000000♠5.97237×1024 kg (7024597236001731600♠1.31668×1025 lb) (7024596565000000000♠3.0×10−6 M☉)
Mean density	5.514 g/cm3 (0.1992 lb/cu in)
Surface gravity	9.807 m/s2 (32.18 ft/s2) (7000100000000000000♠1 g)
Moment of inertia factor	0.3307
Escape velocity	11.186 km/s (6.951 mi/s)
Sidereal rotation period	7004861641003520000♠0.99726968 d (23h 56m 4.100s)
Equatorial rotation velocity	1,674.4 km/h (1,040.4 mph)
Axial tilt	23.4392811°
Albedo	0.367 geometric 0.306 Bond
Surface temp. min mean max Kelvin 184 K 288 K 330 K Celsius −89.2 °C 15 °C 56.7 °C Fahrenheit −128.5 °F 59 °F 134 °F
Atmosphere
Surface pressure	7005101325000000000♠101.325 kPa (at MSL)
Composition by volume	78.08% nitrogen (N2)(dry air) 20.95% oxygen (O2) 0.930% argon 0.0402% carbon dioxide ~ 1% water vapor (climate-variable)

Earth (Greek: Γαῖα Gaia; Latin: Terra), otherwise known as the world (especially in geopolitics and geography), is the third planet from the Sun and the only object in the Universe known to harbor life. It is the densest planet in the Solar System and the largest of the four terrestrial planets.

According to radiometric dating and other sources of evidence, Earth formed about 4.54 billion years ago.Earth's gravity interacts with other objects in space, especially the Sun and the Moon, Earth's only natural satellite. During one orbit around the Sun, Earth rotates about its axis over 365 times; thus, an Earth year is about 365.26 days long. Earth's axis of rotation is tilted, producing seasonal variations on the planet's surface. The gravitational interaction between the Earth and Moon causes ocean tides, stabilizes the Earth's orientation on its axis, and gradually slows its rotation.

Earth's lithosphere is divided into several rigid tectonic plates that migrate across the surface over periods of many millions of years. About 71% of Earth's surface is covered with water, mostly by its oceans. The remaining 29% is land consisting of continents and islands that together have many lakes, rivers and other sources of water that contribute to the hydrosphere. The majority of Earth's polar regions are covered in ice, including the Antarctic ice sheet and the sea ice of the Arctic ice pack. Earth's interior remains active with a solid iron inner core, a liquid outer core that generates the Earth's magnetic field, and a convecting mantle that drives plate tectonics.