Earth

Earth’s Characteristics
– Third planet from the Sun
– Water world with liquid surface water
– Global ocean covers 70.8% of Earth’s crust
– Land hemisphere contains most of Earth’s landmasses
– Earth’s crust consists of moving tectonic plates

Earth’s Atmosphere
– Dynamic atmosphere composed primarily of nitrogen and oxygen
– Water vapor present, forming clouds that cover most of the planet
– Greenhouse gases, including carbon dioxide, maintain average surface temperature
– Regional differences in captured energy drive atmospheric and ocean currents
– Different climate regions and weather phenomena exist due to these currents

Earth’s Structure
– Rounded into an ellipsoid with a circumference of about 40,000km
– Densest planet in the Solar System
– Largest and most massive of the four rocky planets
– Rotates around its own axis in about 23 hours and 56 minutes
– Orbited by one permanent natural satellite, the Moon

Earth’s Formation and History
– Formed 4.5 billion years ago from gas in the early Solar System
– Ocean formed during the first billion years
– Life developed within the ocean
– Great Oxidation Event occurred two billion years ago
– Humans emerged 300,000 years ago and spread across every continent except Antarctica

Earth’s Future
– Solar luminosity will increase by 10% over the next 1.1 billion years and by 40% over the next 3.5 billion years
– Increasing surface temperature will accelerate the inorganic carbon cycle
– Concentration of carbon dioxide will decrease to levels lethally low for plants
– Earth’s long-term future is tied to that of the Sun
– Possibility of global catastrophic risks in the future

Earth’s Physical Characteristics
– Earth has a rounded shape with an average diameter of 12,742 kilometers (7,918mi).
– The shape of Earth is an ellipsoid, bulging at its Equator.
– Earth’s surface is farthest out from its center of mass at its equatorial bulge.
– Earth’s surface is the boundary between the atmosphere and the solid Earth and oceans.
– Most of Earth’s surface is ocean water, covering 70.8% or 361 million km² (139 million sq mi).

Earth’s Surface Topography
– Earth’s surface topography comprises the topography of the ocean surface and the shape of Earth’s land surface.
– The oceanic crust forms large oceanic basins with features like abyssal plains, seamounts, and submarine canyons.
– The land surface varies greatly and consists of mountains, deserts, plains, plateaus, and other landforms.
– Earth’s surface is continually shaped by internal plate tectonic processes, weathering and erosion, and biological processes.
– Earth’s surface topography is influenced by earthquakes, volcanism, ice, water, wind, temperature, and the growth and decomposition of biomass.

Plate Tectonics
– Boundaries where two plates slide past one another laterally
– Plate boundaries can result in earthquakes, volcanic activity, mountain-building, and oceanic trench formation
– Tectonic plates ride on the asthenosphere, a solid but less-viscous part of the upper mantle
– Oceanic crust is subducted under leading edges of plates at convergent boundaries
– Upwelling of mantle material at divergent boundaries creates mid-ocean ridges

Earth’s Interior Layers
– Earth’s interior is divided into layers based on chemical and physical properties
– Outer layer is the solid crust, separated from the mantle by the Mohorovičić discontinuity
– Crust thickness varies from about 6 kilometers (3.7mi) under oceans to 30-50km (19-31mi) for continents
– Asthenosphere is a low-viscosity layer on which the lithosphere rides
– Outer core is an extremely low viscosity liquid, while the inner core is a solid

Chemical Composition
– Earth’s mass is approximately 5.97×10^24 kg
– Composed mostly of iron, oxygen, silicon, magnesium, sulfur, nickel, calcium, and aluminum
– Core primarily composed of iron, with smaller amounts of nickel, sulfur, and trace elements
– Crust mostly composed of various oxides, particularly silicate minerals
– Iron is the most abundant element in Earth’s core

Internal Heat
– Major heat-producing isotopes within Earth are potassium-40, uranium-238, and thorium-232
– Center temperature may reach up to 6,000°C (10,830°F), with pressure up to 360GPa (52 million psi)
– Early in Earth’s history, heat production was higher due to isotopes with short half-lives
– Mean heat loss from Earth is 87mW m, with a global heat loss of 4.42×10^13W
– Heat is transported through mantle plumes, plate tectonics, and convection. Source:  https://en.wikipedia.org/wiki/Earth

Earth (Wikipedia)

"Planet Earth" redirects here. For other uses, see Earth (disambiguation) and Planet Earth (disambiguation).

Earth is the third planet from the Sun and the only astronomical object known to harbor life. This is enabled by Earth being a water world, the only one in the Solar System sustaining liquid surface water. Almost all of Earth's water is contained in its global ocean, covering 70.8% of Earth's crust. The remaining 29.2% of Earth's crust is land, most of which is located in the form of continental landmasses within one hemisphere, Earth's land hemisphere. Most of Earth's land is somewhat humid and covered by vegetation, while large sheets of ice at Earth's polar deserts retain more water than Earth's groundwater, lakes, rivers and atmospheric water combined. Earth's crust consists of slowly moving tectonic plates, which interact to produce mountain ranges, volcanoes, and earthquakes. Earth has a liquid outer core that generates a magnetosphere capable of deflecting most of the destructive solar winds and cosmic radiation.

Earth

Earth as seen from outer space; the image, known as The Blue Marble, was taken by the crew of Apollo 17 on 7 December 1972
Designations
Alternative names	The world, the globe, Sol III, Terra, Tellus, Gaia, Mother Earth
Adjectives	Earthly, terrestrial, terran, tellurian
Symbol	and
Orbital characteristics
Epoch J2000
Aphelion	152097597 km (94509065 mi)
Perihelion	147098450 km (91402740 mi)
Semi-major axis	149598023 km (92955902 mi)
Eccentricity	0.0167086
Orbital period (sidereal)	365.256363004 d (1.00001742096 aj)
Average orbital speed	29.7827 km/s (107218 km/h; 66622 mph)
Mean anomaly	358.617°
Inclination	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
Time of perihelion	2023-Jan-04
Argument of perihelion	114.20783°
Satellites	1, the Moon
Physical characteristics
Mean radius	6371.0 km (3958.8 mi)
Equatorial radius	6378.137 km (3963.191 mi)
Polar radius	6356.752 km (3949.903 mi)
Flattening	1/298.257222101 (ETRS89)
Circumference	40075.017 km (24901.461 mi), equatorial 40007.86 km (24859.73 mi), meridional
Surface area	Total: 510072000 km2 (196940000 sq mi) Land: 148940000 km2 (57510000 sq mi) – 29.2% Water: 361132000 km2 (139434000 sq mi) – 70.8%
Volume	1.08321×1012 km3 (2.59876×1011 cu mi)
Mass	5.972168×1024 kg (1.31668×1025 lb)
Mean density	5.5134 g/cm3 (0.19918 lb/cu in)
Surface gravity	9.80665 m/s2 (1 g; 32.1740 ft/s2)
Moment of inertia factor	0.3307
Escape velocity	11.186 km/s (40270 km/h; 25020 mph)
Synodic rotation period	1.0 d (24h 00 m 00s)
Sidereal rotation period	0.99726968 d (23h 56 m 4.100s)
Equatorial rotation velocity	0.4651 km/s (1674.4 km/h; 1040.4 mph)
Axial tilt	23.4392811°
Albedo	0.367 geometric 0.306 Bond
Temperature	255 K (−18 °C; −1 °F) (blackbody temperature)
Surface temp. min mean max Celsius −89.2 °C 14.76 °C 56.7 °C Fahrenheit −128.5 °F 58.568 °F 134.0 °F
Surface equivalent dose rate	0.274 μSv/h
Absolute magnitude (H)	−3.99
Atmosphere
Surface pressure	101.325 kPa (at sea level)
Composition by volume	78.08% nitrogen (N2; dry air) 20.95% oxygen (O2) ≤1% water vapor (climate variable) 0.9340% argon 0.0415% carbon dioxide 0.00182% neon 0.00052% helium 0.00017% methane 0.00011% krypton 0.00006% hydrogen

Earth has a dynamic atmosphere, which sustains Earth's surface conditions and protects it from most meteoroids and UV-light at entry. It has a composition of primarily nitrogen and oxygen. Water vapor is widely present in the atmosphere, forming clouds that cover most of the planet. The water vapor acts as a greenhouse gas and, together with other greenhouse gases in the atmosphere, particularly carbon dioxide (CO₂), creates the conditions for both liquid surface water and water vapor to persist via the capturing of energy from the Sun's light. This process maintains the current average surface temperature of 14.76 °C, at which water is liquid under atmospheric pressure. Differences in the amount of captured energy between geographic regions (as with the equatorial region receiving more sunlight than the polar regions) drive atmospheric and ocean currents, producing a global climate system with different climate regions, and a range of weather phenomena such as precipitation, allowing components such as nitrogen to cycle.

Earth is rounded into 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 384,400 km (1.28 light seconds) and is roughly a quarter as wide as Earth. The Moon's gravity helps stabilize Earth's axis, and also causes tides which gradually slow Earth's rotation. As a result of tidal locking, the same side of the Moon always faces Earth.

Earth, like most other bodies in the Solar System, formed 4.5 billion years ago from gas in 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 has been altering Earth's atmosphere and surface, leading to the Great Oxidation Event two billion years ago. Humans emerged 300,000 years ago in Africa and have spread across every continent on Earth with the exception of Antarctica. Humans depend on Earth's biosphere and natural resources for their survival, but have increasingly impacted the planet's environment. Humanity's current impact on Earth's climate and biosphere is unsustainable, threatening the livelihood of humans and many other forms of life, and causing widespread extinctions.