Earth

Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surface is made up of the ocean, dwarfing Earth's polar ice, lakes, and rivers. The remaining 29% of Earth's surface is land, consisting of continents and islands. Earth's surface layer is formed of several slowly moving tectonic plates, interacting to produce mountain ranges, volcanoes, and earthquakes. Earth's liquid outer core generates the magnetic field that shapes Earth's magnetosphere, deflecting destructive solar winds.

Earth
A photograph of Earth taken by the crew of Apollo 17 in 1972. A processed version became widely known as The Blue Marble.[1][2]
Designations
Gaia, Terra, Tellus, the world, the globe
AdjectivesEarthly, terrestrial, terran, tellurian
Orbital characteristics
Epoch J2000[n 1]
Aphelion152100000 km (94500000 mi)[n 2]
Perihelion147095000 km (91401000 mi)[n 2]
149598023 km (92955902 mi)[3]
Eccentricity0.0167086[3]
365.256363004 d[4]
(1.00001742096 aj)
29.78 km/s[5]
(107200 km/h; 66600 mph)
358.617°
Inclination
−11.26064°[5] to J2000 ecliptic
2023-Jan-04[7]
114.20783°[5]
Satellites
Physical characteristics
Mean radius
6371.0 km (3958.8 mi)[9]
Equatorial radius
6378.137 km (3963.191 mi)[10][11]
Polar radius
6356.752 km (3949.903 mi)[12]
Flattening1/298.257222101 (ETRS89)[13]
Circumference
  • 510072000 km2 (196940000 sq mi)[15][n 5]
  • 148940000 km2 land (57510000 sq mi)
  • 361132000 km2 ocean (139434000 sq mi)
Volume1.08321×1012 km3 (2.59876×1011 cu mi)[5]
Mass5.97237×1024 kg (1.31668×1025 lb)[16]
(3.0×10−6 M)
Mean density
5.514 g/cm3 (0.1992 lb/cu in)[5]
9.80665 m/s2 (1 g; 32.1740 ft/s2)[17]
0.3307[18]
11.186 km/s[5] (40270 km/h; 25020 mph)
1.0 d
(24h 00m 00s)
0.99726968 d[19]
(23h 56m 4.100s)
Equatorial rotation velocity
0.4651 km/s[20]
(1674.4 km/h; 1040.4 mph)
23.4392811°[4]
Albedo
Surface temp. min mean max
Celsius −89.2 °C[21] 14 °C (1961–90)[22] 56.7 °C[23]
Fahrenheit −128.5 °F 57 °F (1961–90) 134.0 °F
Surface equivalent dose rate0.274 μSv/h[24]
Atmosphere
Surface pressure
101.325 kPa (at MSL)
Composition by volume
  • 78.08% nitrogen (N2; dry air)[5]
  • 20.95% oxygen (O2)
  • ~1% water vapor (climate variable)
  • 0.9340% argon
  • 0.0413% carbon dioxide[25]
  • 0.00182% neon[5]
  • 0.00052% helium
  • 0.00019% methane
  • 0.00011% krypton
  • 0.00006% hydrogen

Earth's atmosphere consists mostly of nitrogen and oxygen. More solar energy is received by tropical regions than polar regions and is redistributed by atmospheric and ocean circulation. Water vapor is widely present in the atmosphere and forms clouds that cover most of the planet. Greenhouse gases in the atmosphere like carbon dioxide (CO2) trap a part of the energy from the Sun close to the surface. A region's climate is governed by latitude, but also by elevation and proximity to moderating oceans. Severe weather, such as tropical cyclones, thunderstorms, and heatwaves, occurs in most areas and greatly impacts life.

Earth is an ellipsoid with a circumference of about 40,000 km. It is the densest planet in the Solar System. Of the four rocky planets, it is the largest and most massive. Earth is about eight light minutes away from the Sun and orbits it, taking a year (about 365.25 days) to complete one revolution. Earth rotates around its own axis in slightly less than a day (in about 23 hours and 56 minutes). Earth's axis of rotation is tilted with respect to the perpendicular to its orbital plane around the Sun, producing seasons. Earth is orbited by one permanent natural satellite, the Moon, which orbits Earth at 380,000 km (1.3 light seconds) and is roughly a quarter as wide as Earth. The Moon always faces the Earth with the same side through tidal locking and causes tides, stabilizes Earth's axis, and gradually slows its rotation.

Earth formed over 4.5 billion years ago. During the first billion years of Earth's history, the ocean formed and then life developed within it. Life spread globally and began to affect Earth's atmosphere and surface, leading to Earth's Great Oxidation Event two billion years ago. Humans emerged 300,000 years ago, and have reached a population of almost 8 billion today. Humans depend on Earth's biosphere and natural resources for their survival, but have increasingly impacted Earth's environment. Today, humanity's impact on Earth's climate, soils, waters, and ecosystems is unsustainable, threatening people's lives and causing widespread extinction of other life.


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