Earth

Earth
EUMETSAT · Attribution · source
Name	Earth
Type	Terrestrial planet
Mass	5.972×10^24 kg
Radius	6,371 km
Orbital period	365.256 days
Moons	1 (Luna)

Earth Earth is the third planet from the Sun and the largest of the four terrestrial planets in the Solar System. It hosts a diverse range of environments and is the only known astronomical object to support life, with complex interactions among the Luna, the Sun, and processes observable across the Milky Way neighborhood. Modern understanding of the planet integrates data from missions by agencies such as NASA, European Space Agency, Roscosmos, China National Space Administration, and JAXA.

Overview

Earth orbits the Sun at an average distance of about 1 astronomical unit and is a member of the Inner Solar System along with Mercury, Venus, and Mars. Its axial tilt produces seasons similar to those studied in paleoclimate records from sites like Greenland Ice Sheet Project and Vostok Station. The planet's magnetic field, studied through observations by missions like Parker Solar Probe and Voyager 1, interacts with the solar wind and creates phenomena such as the aurorae visible near polar regions including Antarctica and Northern Canada.

Physical characteristics

Earth is an oblate spheroid with equatorial bulge quantified by measurements from GRACE and GOCE. Surface features include continents—such as Eurasia, Africa, North America, South America, Antarctica, and Australia—and major oceans like the Pacific Ocean, Atlantic Ocean, Indian Ocean, Southern Ocean, and Arctic Ocean. Climatic zones span from polar ice caps at Greenland and Antarctica to tropical regions around the Equator including the Amazon Basin and Congo Basin. The single natural satellite, Luna, stabilizes axial tilt and influences tidal regimes experienced along coasts such as Baja California and Bay of Bengal.

Geology and internal structure

Earth's internal differentiation produced a metallic core, a silicate mantle, and a crust; seismology from earthquakes recorded by instruments in regions like Japan and California reveals a liquid outer core and solid inner core. Plate tectonics, a paradigm refined by studies of the Ring of Fire, explains continental drift evident in the fit of South America and Africa and in orogenic belts such as the Himalayas formed by the collision of Indian Plate and Eurasian Plate. Volcanism at locations like Mauna Loa, Mount Etna, and Eyjafjallajökull drives crustal renewal, while passive margins such as the Atlantic coast preserve sedimentary records used by paleontologists working at sites like La Brea Tar Pits and Hell Creek Formation to study mass extinctions including the one at the end of the Cretaceous.

Atmosphere and climate

The atmosphere, composed mainly of nitrogen and oxygen, includes layers defined and named by radio and satellite studies conducted by NOAA, Met Office, and ECMWF. Greenhouse gases including carbon dioxide and methane are monitored globally by programs such as Mauna Loa Observatory and initiatives associated with the Intergovernmental Panel on Climate Change. Climate phenomena like the El Niño–Southern Oscillation, monsoons, and North Atlantic Oscillation influence weather patterns across regions including India, West Africa, and Western Europe. Human-driven emissions and natural feedbacks are examined in assessments tied to international agreements like the Paris Agreement and meetings of the United Nations Framework Convention on Climate Change.

Biosphere and ecology

Life on the planet spans microorganisms to megafauna, with major biomes such as tropical rainforests in the Amazon Rainforest, coral reef systems like the Great Barrier Reef, and tundra ecosystems in Siberia. Biodiversity hotspots identified by conservation organizations including IUCN and WWF face pressures from land-use change, invasive species, and climate change, evident in case studies from Madagascar, Borneo, and the Galápagos Islands. Biogeochemical cycles—carbon, nitrogen, phosphorus—are studied across research stations such as Scripps Institution of Oceanography and initiatives like the Long Term Ecological Research Network.

Human presence and civilization

Human societies developed urban centers from ancient sites such as Mesopotamia and Angkor Wat to modern megacities like Tokyo, Delhi, Shanghai, and New York City. Cultural and scientific institutions—British Museum, Smithsonian Institution, Louvre, universities such as Oxford, Harvard University, and Peking University—drive advances in technology, medicine, and the humanities. Global systems of trade and governance are managed through organizations like the United Nations, World Bank, and World Health Organization, while conflicts and cooperation are recorded in treaties and events including the Treaty of Westphalia and the Cold War.

Exploration and observation

Systematic exploration began with ancient navigation across bodies like the Mediterranean Sea and expeditions such as those of Christopher Columbus and Ferdinand Magellan, advancing to polar expeditions by Roald Amundsen and Ernest Shackleton. Modern remote sensing uses satellites from programs like Landsat, Copernicus Programme, and missions including Hubble Space Telescope and ICESat to monitor land, ocean, and cryosphere. Human spaceflight conducted by organizations such as Roscosmos, NASA, and private companies like SpaceX has enabled observations from low Earth orbit aboard the International Space Station and lunar reconnaissance by missions like Artemis program.

Category:Planets