Earth, the third planet from the Sun, is unique in the Universe as it is currently the only planet known to support life. It has a single natural satellite, the Moon, and is the fifth largest planet in the Solar System.
Earth's distance from the Sun is thought to be one of the key reasons why it is home to widespread life. Our planet occupies what scientists sometimes call the Goldilocks zone. Its distance from our star means it is neither too hot, nor too cold to support liquid water - thought to be a key ingredient for life. Astronomers are searching for rocky planets like ours in the Goldilocks zones of other stars.
BBC Earth has exciting videos about volcanoes, earthquakes and more.
Photo: The Earth rising behind the Moon taken by the Apollo 16 crew (NASA)
Our life-filled home is unique in the Universe (so far).
Scientists tell the story of Martian meteorite ALH84001's discovery.
Each year scientists hunt for meteorites in Antarctica because the ice and snow make it easier to spot dark space rocks. In 1984, the team found a special Martian meteorite that came to be known as ALH840001. In the 1990s a NASA team announced that they had found tiny fossils in this rock. Many in the scientific community are critical of this finding.
Rocks from Mars can make the long journey to Earth.
Asteroids and comets have struck Mars with so much force that rocks from the planet's surface were ejected into space. Some of those rocks have made the journey to Earth, falling through the atmosphere to become meteorite deposits.
The early Solar System was a shooting gallery.
Professor Brian Cox explains how the orbiting gas giants may have caused an enormous asteroid and comet bombardment in the inner Solar System 3.6 billion years ago. Earth and the other planets were peppered by asteroids and comets.
Brian Cox looks at what makes the two planets so different.
Professor Brian Cox looks at how greenhouse gases made Earth and Venus so different today.
If life can exist in solid ice on Earth, what about Europa?
Professor Brian Cox goes to caves in Iceland to find microbial life that survives in solid ice. Astrobiologists theorise that if life can live in solid ice on Earth, it may be able to survive on Jupiter's icy moon Europa
Earth, also known as the World,Terra, or Gaia, 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 celestial body known to accommodate life. The Earth's biodiversity has evolved over hundreds of million years, expanding continually except when punctuated by mass extinctions. It is home to over eight million species. There are over 7.2 billion humans who depend upon its biosphere and minerals. The Earth's human population is divided among about two hundred independent states that interact through diplomacy, conflict, travel, trade, and media.
According to evidence from sources such as radiometric dating, the Earth was formed around four and a half billion years ago. Within its first billion years,life appeared in its oceans and began to affect its atmosphere and surface, promoting the proliferation of aerobic as well as anaerobic organisms and causing the formation of the atmosphere's ozone layer. This layer and the geomagnetic field block the most life-threatening parts of the Sun's radiation, so life was able to flourish on land as well as in water. Since then, the combination of the Earth's distance from the Sun, its physical properties, and its geological history have allowed life to persist.
The Earth's lithosphere is divided into several rigid segments, or tectonic plates, that migrate across the surface over periods of many millions of years. 71 percent of the Earth's surface is covered with water, with the remainder consisting of continents and islands that together have many lakes and other sources of water that contribute to the hydrosphere. The Earth's poles are mostly covered with ice that includes the solid ice of the Antarctic ice sheet and the sea ice of the polar ice packs. The Earth's interior remains active, with a solid iron inner core, a liquid outer core that generates the magnetic field, and a thick layer of relatively solid mantle.
The Earth gravitationally interacts with other objects in space, especially the Sun and the Moon. During one orbit around the Sun, the Earth rotates about its own axis 366.26 times, creating 365.26 solar days, or one sidereal year.[n 6] The Earth's axis of rotation is tilted 23.4° away from the perpendicular of its orbital plane, producing seasonal variations on the planet's surface with a period of one tropical year (365.24 solar days). The Moon is the Earth's only natural satellite. It began orbiting the Earth about 4.53 billion years ago (bya). The Moon's gravitational interaction with the Earth stimulates ocean tides, stabilizes the axial tilt, and gradually slows the planet's rotation.