Sol III

Earth

The Blue Marble photograph of Earth, taken during the Apollo 17 lunar mission in 1972
Orbital characteristics
Epoch J2000
Aphelion	152100000 km (94500000 mi; 1.017 AU)
Perihelion	147095000 km (91401000 mi; 0.98327 AU)
Semi-major axis	149598023 km (92955902 mi; 1.00000102 AU)
Eccentricity	6998167086000000000♠0.0167086
Orbital period	365.256363004 d (1.00001742096 yr)
Average orbital speed	29.78 km/s (107200 km/h; 66600 mph)
Mean anomaly	7000625904740362451♠358.617°
Inclination	6999124878307980194♠7.155° to the Sun's equator; 6998275533383683093♠1.57869° to invariable plane; 6993872664625997166♠0.00005° to J2000 ecliptic
Longitude of ascending node	3000803464756118225♠−11.26064° to J2000 ecliptic
Argument of perihelion	7000199330266505796♠114.20783°
Satellites	1 natural satellite: the Moon 5 quasi-satellites >1 700 operational artificial satellites >16 000 space debris
Physical characteristics
Mean radius	6371.0 km (3958.8 mi)
Equatorial radius	6378.1 km (3963.2 mi)
Polar radius	6356.8 km (3949.9 mi)
Flattening	6997335280000000000♠0.0033528 1/7002298257222101000♠298.257222101 (ETRS89)
Circumference	40075.017 km equatorial (24901.461 mi) 40007.86 km meridional (24859.73 mi)
Surface area	510072000 km2(196940000 sq mi) 148940000 km2 land (57510000 sq mi; 29.2%) 361132000 km2 water (139434000 sq mi; 70.8%)
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(7000100000000000000♠1 g; 32.18 ft/s2)
Moment of inertia factor	0.3307
Escape velocity	11.186 km/s (40270 km/h; 25020 mph)
Sidereal rotation period	7004861641003520000♠0.99726968 d (23h 56m 4.100s)
Equatorial rotation velocity	0.4651 km/s (1674.4 km/h; 1040.4 mph)
Axial tilt	6999409092629495479♠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 14.9 °C 56.9 °C Fahrenheit −128.5 °F 58.7 °F 134.3 °F
Atmosphere
Surface pressure	7005101325000000000♠101.325 kPa (at MSL)
Composition by volume	78.08% nitrogen (N 2; dry air) 20.95% oxygen (O 2) 0.930% argon 0.0402% carbon dioxide ~ 1% water vapor (climate-variable)

Earth is the third planet from the Sun and the only astronomical object known to harbor life. According to radiometric dating and other sources of evidence, Earth formed over 4.5 billion years ago.Earth's gravity interacts with other objects in space, especially the Sun and the Moon, Earth's only natural satellite. Earth revolves around the Sun in 365.26 days, a period known as an Earth year. During this time, Earth rotates about its axis about 366.26 times.

Earth's axis of rotation is tilted with respect to its orbital plane, producing seasons on Earth. The gravitational interaction between Earth and the Moon causes ocean tides, stabilizes Earth's orientation on its axis, and gradually slows its rotation. Earth is the densest planet in the Solar System and the largest of the four terrestrial planets.

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 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.