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Earth
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This article is about scientific information on the Earth. For the Earth's geography, see World. For religious beliefs, see creation myth. For other uses, see Earth (disambiguation).
Earth  
Famous "Blue Marble" photograph of Earth, taken from Apollo 17.
Orbital characteristics
Epoch J2000
Aphelion
152,097,701 km
1.0167103335 AU
Perihelion
147,098,074 km
0.9832898912 AU
Semi-major axis
149,597,887.5 km
1.0000001124 AU
Eccentricity
0.016710219
Orbital period
365.256366 days
1.0000175 yr
Average orbital speed
29.783 km/s
107,218 km/h
Inclination
Reference (0)
7.25° to Sun's equator
Longitude of ascending node
348.73936°
Argument of perihelion
114.20783°
Satellites
1 (the Moon)
Physical characteristics
Mean radius
6,371.0 km[1]
Equatorial radius
6,378.1 km[2]
Polar radius
6,356.8 km[2]
Flattening
0.0033528[2]
Circumference
40,075.02 km (equatorial)
40,007.86 km (meridional)
40,041.47 km (mean)
Surface area
510,072,000 km²[3]
148,940,000 km² land  (29.2 %)
361,132,000 km² water (70.8 %)
Volume
1.0832073×1012 km³
Mass
5.9736×1024 kg
Mean density
5.5153 g/cm³
Equatorial surface gravity
9.780327 m/s²[4]
0.99732 g
Escape velocity
11.186 km/s 
40,270 km/h
Sidereal rotation
period
0.997258 d
23h 56m 04.09054s[4]
Equatorial rotation velocity
465.11 m/s
Axial tilt
23.439281°
Albedo
0.367
Surface temp.
   Kelvin
   Celsius
min
mean
max
184 K
287 K
331 K
−89 °C
14 °C
57.7 °C
Adjectives
Terrestrial, Terran, Telluric, Tellurian, Earthly
Atmosphere
Surface pressure
101.3 kPa (MSL)
Composition
78.08% Nitrogen (N2)
20.95% Oxygen (O2)
0.93% Argon
0.038% Carbon dioxide
About 1% water vapor (varies with climate)[5]
Earth (pronounced [ˈɝːθ] (help·info))[6] is the third planet from the Sun and is the largest of the terrestrial planets in the Solar System in diameter, mass and density. It is also referred to as the Earth, Planet Earth, the World, and Terra.[7]
Home to millions of species,[8] including humans, Earth is the only place in the universe where life is known to exist. Scientific evidence indicates that the planet formed 4.54 billion years ago,[9][10][11][12] and life appeared on its surface within a billion years. Since then, Earth's biosphere has significantly altered the atmosphere and other abiotic conditions on the planet, enabling the proliferation of aerobic organisms as well as the formation of the ozone layer which, together with Earth's magnetic field, blocks harmful radiation, permitting life on land.[13]
Earth's outer surface is divided into several rigid segments, or tectonic plates, that gradually migrate across the surface over periods of many millions of years. About 71% of the surface is covered with salt-water oceans, the remainder consisting of continents and islands; liquid water, necessary for all known life, is not known to exist on any other planet's surface.[14][15] Earth's interior remains active, with a thick layer of relatively solid mantle, a liquid outer core that generates a magnetic field, and a solid iron inner core.
Earth interacts with other objects in outer space, including the Sun and the Moon. At present, Earth orbits the Sun once for every roughly 366.26 times it rotates about its axis. This length of time is a sidereal year, which is equal to 365.26 solar days.[16] The Earth's axis of rotation is tilted 23.4° away from the perpendicular to its orbital plane,[17] producing seasonal variations on the planet's surface with a period of one tropical year (365.24 solar days). Earth's only known natural satellite, the Moon, which began orbiting it about 4.53 billion years ago, provides ocean tides, stabilizes the axial tilt and gradually slows the planet's rotation. A cometary bombardment during the early history of the planet played a role in the formation of the oceans.[18] Later, asteroid impacts caused significant changes to the surface environment.

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