Earth

Earth

"The Blue Marble" photograph of Earth, taken by the Apollo 17 mission. The Arabian peninsula, Africa and Madagascar lie in the upper half of the disc, whereas Antarctica is at the bottom.

The Blue Marble photograph of Earth, taken during the Apollo 17 lunar mission in 1972

Orbital characteristics

152,100,000 km (94,500,000 mi)
(1.01673 AU)

147,095,000 km (91,401,000 mi)
(0.9832687 AU)

Semi-major axis

149,598,023 km (92,955,902 mi)
(1.000001018 AU)

0.0167086

365.256363004 d
(1.00001742096 yr)

Average orbital speed

29.78 km/s (18.50 mi/s)
(107,200 km/h (66,600 mph))

358.617°

7000715500000000000♠7.155° to the Sun's equator;
1.57869° to invariable plane;
0.00005° to J2000 ecliptic

Longitude of ascending node

−11.26064° to J2000 ecliptic

Argument of perihelion

114.20783°

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)

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)

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

1.08321×10¹² km³ (2.59876×10¹¹ cu mi)

5.97237×10²⁴ kg (1.31668×10²⁵ lb)
(3.0×10⁻⁶ M_☉)

5.514 g/cm³ (0.1992 lb/cu in)

Surface gravity

9.807 m/s² (32.18 ft/s²)
(1 g)

Moment of inertia factor

0.3307

Escape velocity

11.186 km/s (6.951 mi/s)

Sidereal rotation period

0.99726968 d
(23h 56m 4.100s)

Equatorial rotation velocity

1,674.4 km/h (1,040.4 mph)

23.4392811°

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

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, otherwise known as the world, (Greek: Γαῖα Gaia; Latin: Terra) 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.

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