Earth

Earth 🜨
Photograph of Earth, taken by the Apollo 17 mission. The Arabian peninsula, Africa and Madagascar lie in the lower half of the disc, whereas Antarctica is at the top.
A photograph of Earth taken by the crew of Apollo 17 on December 7, 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]
Volume1.08321×1012 km3 (2.59876×1011 cu mi)[5]
Mass5.97217×1024 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 (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 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 the magnetosphere of the Earth, deflecting destructive solar winds.

The atmosphere of the Earth consists mostly of nitrogen and oxygen. Greenhouse gases in the atmosphere like carbon dioxide (CO2) trap a part of the energy from the Sun close to the surface. Water vapor is widely present in the atmosphere and forms clouds that cover most of the planet. More solar energy is received by tropical regions than polar regions and is redistributed by atmospheric and ocean circulation. A region's climate is governed by latitude, but also by elevation and proximity to moderating oceans. In most areas severe weather, such as tropical cyclones, thunderstorms, and heatwaves, occurs 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, like most other Solar System bodies formed 4.5 billion years ago from gas of the early Solar System. 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 the Great Oxidation Event two billion years ago. Humans emerged 300,000 years ago, and have reached a population of 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.[26]

  1. ^ Petsko, Gregory A. (28 April 2011). "The blue marble". Genome Biology. 12 (4): 112. doi:10.1186/gb-2011-12-4-112. PMC 3218853. PMID 21554751.
  2. ^ "Apollo Imagery – AS17-148-22727". NASA. 1 November 2012. Archived from the original on 20 April 2019. Retrieved 22 October 2020.
  3. ^ a b Cite error: The named reference VSOP87 was invoked but never defined (see the help page).
  4. ^ a b Cite error: The named reference IERS was invoked but never defined (see the help page).
  5. ^ a b c d e f g h i j Cite error: The named reference earth_fact_sheet was invoked but never defined (see the help page).
  6. ^ Cite error: The named reference Allen294 was invoked but never defined (see the help page).
  7. ^ "HORIZONS Batch call for 2023 perihelion". ssd.jpl.nasa.gov. NASA/JPL. Retrieved 3 July 2022.
  8. ^ Cite error: The named reference ucs was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference hbcp2000 was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference usno was invoked but never defined (see the help page).
  11. ^ a b World Geodetic System (WGS-84). Available online Archived 11 March 2020 at the Wayback Machine from National Geospatial-Intelligence Agency.
  12. ^ Cite error: The named reference cazenave_ahrens1995 was invoked but never defined (see the help page).
  13. ^ Cite error: The named reference IERS2004 was invoked but never defined (see the help page).
  14. ^ Cite error: The named reference WGS-84-2 was invoked but never defined (see the help page).
  15. ^ Cite error: The named reference Pidwirny 2006_8 was invoked but never defined (see the help page).
  16. ^ Cite error: The named reference earthmass was invoked but never defined (see the help page).
  17. ^ Cite error: The named reference NIST2008 was invoked but never defined (see the help page).
  18. ^ Cite error: The named reference Williams1994 was invoked but never defined (see the help page).
  19. ^ Cite error: The named reference Allen296 was invoked but never defined (see the help page).
  20. ^ Cite error: The named reference Cox2000 was invoked but never defined (see the help page).
  21. ^ Cite error: The named reference asu_lowest_temp was invoked but never defined (see the help page).
  22. ^ Jones, P. D.; Harpham, C. (2013). "Estimation of the absolute surface air temperature of the Earth". Journal of Geophysical Research: Atmospheres. 118 (8): 3213–3217. Bibcode:2013JGRD..118.3213J. doi:10.1002/jgrd.50359. ISSN 2169-8996.
  23. ^ Cite error: The named reference asu_highest_temp was invoked but never defined (see the help page).
  24. ^ United Nations Scientific Committee on the Effects of Atomic Radiation (2008). Sources and effects of ionizing radiation. New York: United Nations (published 2010). Table 1. ISBN 978-92-1-142274-0. Retrieved 9 November 2012.
  25. ^ "Trends in Atmospheric Carbon Dioxide: Recent Global CO2 Trend". Earth System Research Laboratory. National Oceanic and Atmospheric Administration. 19 October 2020. Archived from the original on 4 October 2020.
  26. ^ Nations, United. "What Is Climate Change?". United Nations. Retrieved 17 August 2022.


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