Earth

Earth
	The Blue Marble, the first full-view photograph of the planet ; taken by Apollo 17 astronauts in 1972
Designations
Adjectives	Earthly, terrestrial, terran, tellurian
Orbital characteristics
	Epoch J2000[1]
Aphelion	152100000 km[2]; (94500000 mi; 1.017 AU)
Perihelion	147095000 km[2]; (91401000 mi; 0.98327 AU)
Semi-major axis	149598023 km[3]; (92955902 mi; 1.00000102 AU)
Eccentricity	0.0167086[3]
Orbital period	365.256363004 d[4]; (1.00001742096 yr)
Average orbital speed	29.78 km/s[5]; (107200 km/h; 66600 mph)
Mean anomaly	358.617°
Inclination	7.155° to the Sun's equator;; 1.57869°[6] to invariable plane;; 0.00005° to J2000 ecliptic;
Longitude of ascending node	−11.26064°[5] to J2000 ecliptic
Argument of perihelion	114.20783°[5]
Satellites	1 natural satellite: the Moon; 5 quasi-satellites; >1 800 operational artificial satellites[7]; >16 000 space debris[8];
Physical characteristics
Mean radius	6371.0 km (3958.8 mi)[9]
Equatorial radius	6378.1 km (3963.2 mi)[10][11]
Polar radius	6356.8 km (3949.9 mi)[12]
Flattening	0.0033528[13]; 1/298.257222101 (ETRS89)
Circumference	40075.017 km equatorial (24901.461 mi)[11]; 40007.86 km meridional (24859.73 mi)[14][15];
Surface area	510072000 km2 (196940000 sq mi)[16][17][18]; 148940000 km2 land (57510000 sq mi; 29.2%); 361132000 km2 water (139434000 sq mi; 70.8%);
Volume	260 billion cubic miles [19]
Mass	5.97237×1024 kg (1.31668×1025 lb)[20] ; (3.0×10−6 M☉)
Mean density	5.514 g/cm3 (0.1992 lb/cu in)[5]
Surface gravity	9.807 m/s2 (1 g; 32.18 ft/s2)[21]
Moment of inertia factor	0.3307[22]
Escape velocity	11.186 km/s[5] ; (40270 km/h; 25020 mph)
Sidereal rotation period	0.99726968 d[23] ; (23h 56m 4.100s)
Equatorial rotation velocity	0.4651 km/s[24] ; (1674.4 km/h; 1040.4 mph)
Axial tilt	23.4392811°[4]
Albedo	0.367 geometric[5]; 0.306 Bond[5];
Atmosphere
Surface pressure	101.325 kPa (at MSL)
Composition by volume	78.08% nitrogen (N; 2; dry air)[5]; 20.95% oxygen (O; 2); 0.934% argon; 0.0408% carbon dioxide[28]; ~ 1% water vapor (climate variable);

Earth is the third planet from the Sun in the Solar System. It is the only planet known to have life on it. The Earth formed about 4.5 billion years ago.[29][30]

Quick facts: Designations, Adjectives, Orbital characteris... ▼

It is one of four rocky planets on the inner side of the Solar System. The other three are Mercury, Venus, and Mars.

The large mass of the Sun keeps the Earth in orbit through the force of gravity.[31] Earth also turns around in space, so that different parts face the Sun at different times. Earth goes around the Sun once (one year) for every 365¹⁄₄ times it turns around (one day).

Earth is the only planet in the Solar System that has a large amount of liquid water on its surface.[32][33][34] About 74% of the surface of Earth is covered by liquid or frozen water.[35] Because of this, people sometimes call it the blue planet.[36]

Because of its water, Earth is home to millions of species of plants and animals which need water to survive.[37][38] The things that live on Earth have changed its surface greatly. For example, early cyanobacteria changed the air and gave it oxygen. The living part of Earth's surface is called the "biosphere".[39]