Earth is the third planet from the Sun and the only object in the Universe known to harbor life. According to radiometric dating and other sources of evidence, Earth formed over 4.5 billion years ago.

Earth’s gravity interacts with other objects in space, especially the Sun and the Moon, Earth’s only natural satellite. Earth revolves around the Sun in 365.26 days, a period known as an Earth year. During this time, Earth rotates about its axis about 366.26 times.

Planet Earth

Earth’s axis of rotation is tilted with respect to its orbital plane, producing seasons on the Earth. 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-globe-continents_oceans

Earth’s location in the Universe

The following outline is the location of the earth in the observable Universe. (From the human point of view)

Universe – all of time and space and its contents.
Observable universe – spherical region of the Universe comprising all matter that may be observed from Earth at the present time, because light and other signals from these objects have had time to reach Earth since the beginning of the cosmological expansion.
Laniakea Supercluster – galaxy supercluster that is home to the Milky Way and approximately 100,000 other nearby galaxies. Includes the prior defined local supercluster, the Virgo Supercluster, as an appendage.
Virgo Supercluster – one of the approximately 10 million superclusters in the observable universe. It spans 33 megaparsecs (110 million light-years) and contains at least 100 galaxy groups and clusters, including the Local Group.
Local Group – specific galaxy group that includes the Milky Way and at least 53 other galaxies, most of them dwarf galaxies.
Milky Way Galaxy – a specific barred spiral galaxy
Orion Arm – a spiral arm of the Milky Way
Solar System – the Sun and the objects that orbit it, including 8 planets, the 3rd planet closest to the Sun being Earth
Earth’s orbit – a path through which the Earth travels around the Sun. The average distance between the Earth and the Sun is 149.60 million kilometers (92.96 million miles).

Earth’s Major Plates

Earth’s lithosphere is divided into several rigid tectonic plates that migrate across the surface over periods of many millions of years. 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.

  • Pacific Plate
  • African Plate
  • North American Plate
  • Eurasian Plate
  • Antarctic Plate
  • Indo-Australian Plate
  • South American Plate

Earth’s Continents

  • Asia
  • Africa
  • North America
  • South America
  • Antarctica
  • Europe
  • Australia

About 71% of Earth’s surface is covered with water, mostly by 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 Oceans

  • Arctic Ocean
  • Atlantic Ocean
  • Indian Ocean
  • Pacific Ocean
  • Southern Ocean

Life and Biodiversity

Within the first billion years of Earth’s history, life appeared in the oceans and began to affect the Earth’s atmosphere and surface, leading to the proliferation of aerobic and anaerobic organisms. Some geological evidence indicates that life may have arisen as much as 4.1 billion years ago.

Since then, the combination of Earth’s distance from the Sun, physical properties, and geological history have allowed life to evolve and thrive.

In the history of the Earth, biodiversity has gone through long periods of expansion, occasionally punctuated by mass extinction events. Over 99% of all species that ever lived on Earth are extinct. Estimates of the number of species on Earth today vary widely; most species have not been described.

Human Population

Earth’s human population reached approximately seven billion on 31 October 2011. Over 7.6 billion humans live on Earth and depend on its biosphere and natural resources for their survival. Humans have developed diverse societies and cultures; politically, the world has about 200 sovereign states.

Projections indicate that the world’s human population will reach 9.2 billion in 2050. Most of the growth is expected to take place in developing nations. Human population density varies widely around the world, but a majority live in Asia. By 2020, 60% of the world’s population is expected to be living in urban, rather than rural, areas.

Habitable Area

It is estimated that one-eighth of Earth’s surface is suitable for humans to live on – three-quarters of Earth’s surface is covered by oceans, leaving one-quarter as land. Half of that land area is desert (14%), high mountains (27%), or other unsuitable terrains. The northernmost permanent settlement in the world is Alert, on Ellesmere Island in Nunavut, Canada. (82°28′N) The southernmost is the Amundsen–Scott South Pole Station, in Antarctica, almost exactly at the South Pole. (90°S)

Countries

Independent sovereign nations claim the planet’s entire land surface, except for some parts of Antarctica, a few land parcels along the Danube river’s western bank, and the unclaimed area of Bir Tawil between Egypt and Sudan. As of 2015, there are 193 sovereign states that are member states of the United Nations, plus two observer states and 72 dependent territories and states with limited recognition. Earth has never had a sovereign government with authority over the entire globe, although some nation-states have striven for world domination and failed.

United Nations

The United Nations is a worldwide intergovernmental organization that was created with the goal of intervening in the disputes between nations, thereby avoiding armed conflict. The U.N. serves primarily as a forum for international diplomacy and international law. When the consensus of the membership permits, it provides a mechanism for armed intervention.

Notable Geographers

  • Alexander von Humboldt (1769-1859), one of the founders of modern geography, he traveled extensively and pioneered empirical research methods that would later develop primarily into biogeography and physical geography but also anticipated population geography and economic geography. Humboldt University of Berlin is named after Alexander and his brother Wilhelm von Humboldt.
  • Carl Ritter (1779–1859), considered to be one of the founders of modern geography and first chair in geography at the Humboldt University of Berlin, also noted for his use of organic analogy in his works.
  • Xavier Hommaire de Hell (1812–1848), research in Turkey, southern Russia, and Persia
  • Élisée Reclus (1830–1905), known for his monumental 19 volume The Earth and Its Inhabitants, he coined the term social geography and his thinking anticipated the social ecology and animal rights movements, where he advocated anarchism and veganism as part of an ethical life.
  • Peter Kropotkin (1842–1921), one of the first radical geographers, he was a proponent of anarchism and notable for his introduction of the concept of mutual aid.
  • Friedrich Ratzel (1844–1904), environmental determinist, invented the term Lebensraum
  • Paul Vidal de la Blache (1845–1918), founder of the French School of geopolitics and possibilism.
  • Sir Halford John Mackinder (1861–1947), author of The Geographical Pivot of History, co-founder of the London School of Economics, along with the Geographical Association.
  • Jovan Cvijić (1865–1927), a Serbian geographer and a world-renowned scientist. He started his scientific career as a geographer and geologist and continued his activity as an anthropogeographer and sociologist.
  • Carl O. Sauer (1889–1975), critic of environmental determinism and proponent of cultural ecology.
  • Walter Christaller (1893–1969), economic geographer and developer of the central place theory.
  • Richard Hartshorne (1899–1992), a scholar of the history and philosophy of geography.
  • Torsten Hägerstrand (1916–2004), a key figure in the quantitative revolution and regional science, developer of time geography and indirect contributor to aspects of critical geography.
  • Milton Santos (1926–2001) winner of the Vautrin Lud Prize in 1994, one of the most important geographers in South America.
  • Waldo R. Tobler (born 1930), developer of the First law of geography.
  • Gamal Hamdan (born 1928), an Egyptian thinker, intellect, and professor of geography. Best known for The Character of Egypt, Studies of the Arab World, and The Contemporary Islamic World Geography, which form a trilogy on Egypt’s natural, economic, political and cultural character and its position in the world.
  • Yi-Fu Tuan (born 1930) Professor Emeritus at University of Wisconsin–Madison, a key figure behind the development of humanist and phenomenological geography and the most prominent Chinese-American geographer. Recipient of the Vautrin Lud Prize in 2012.
  • David Harvey (born 1935), world’s most cited academic geographer and winner of the Lauréat Prix International de Géographie Vautrin Lud, also noted for his work in critical geography and critique of global capitalism.
  • Evelyn Stokes (1936–2005). Professor of geography at the University of Waikato in New Zealand. Known for recognizing inequality with marginalized groups including women and Māori using geography.
  • Allen J. Scott (born 1938), winner of Vautrin Lud Prize in 2003 and the Anders Retzius Gold medal 2009; author of numerous books and papers on economic and urban geography, known for his work on regional development, new industrial spaces, agglomeration theory, global city-regions and the cultural economy.
  • Edward Soja (1941-2015), noted for his work on regional development, planning and governance, along with coining the terms synekism and postmetropolis.
  • Doreen Massey (1944-2016), a key scholar in the space and places of globalization and its pluralities, winner of the Vautrin Lud Prize.
  • Denis Cosgrove (1948–2008), Alexander von Humboldt Professor of geography at UCLA in California. Specialized in cultural geography and landscapes.
  • Michael Watts, Class of 1963 Professor of Geography and Development Studies, University of California, Berkeley
  • Nigel Thrift (born 1949), developer of non-representational theory.
  • Derek Gregory (born 1951), famous for writing on the Israeli, U.S. and UK actions in the Middle East after 9/11, influenced by Edward Said and has contributed work on imagined geographies.
  • Cindi Katz (born 1954), who writes on social reproduction and the production of space. Writing on children’s geographies, place, and nature, everyday life and security.
  • Gillian Rose (born 1962), most famous for her critique: Feminism & Geography: The Limits of Geographical Knowledge (1993), which was one of the first moves towards a development of feminist geography.

Features of Earth

Earth is the third planet from the Sun, the densest planet in the Solar System, the largest of the Solar System’s four terrestrial planets, and the only astronomical object known to harbor life.

  • Earth’s Age:
  • Earth’s Size:
  • Earth’s radius:
  • Satellites of Earth: 
  • World map:
  • Gravity:
  • Natural environment:

Major Astronomical Events on Earth

  • Meteor showers
  • Meteorite falls
  • Tides
  • Eclipse – This includes both a lunar eclipse and solar eclipse.
  • Equinox – This includes both the March equinox and the September equinox.
  • Solstice – This includes the Summer solstice, June solstice, Winter solstice, and December solstice
  • Manhattanhenge

Beyond Earth

The first human to orbit Earth was Yuri Gagarin on 12 April 1961. In total, about 487 people have visited outer space and reached orbit as of 30 July 2010, and, of these, twelve have walked on the Moon.

Normally, the only humans in space are those on the International Space Station. The station’s crew, made up of six people, is usually replaced every six months.

The farthest that humans have traveled from Earth is 400,171 km, achieved during the Apollo 13 mission in 1970.

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April 14, 2018 3:31 pm Published by

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