page_title: Earth
section_title: Habitability
hierarchical_section_title: Earth / Habitability
caption_attribution_description: English&#160;:Valley of the Ten Peaks and Moraine Lake, Banff National Park, Canada. Mountains from left to right: Tonsa (3057 m), Mount Perren (3051 m), Mount Allen (3310 m), Mount Tuzo (3246 m), Deltaform Mountain (3424 m), Neptuak Mountain (3233 m) Francais&#160;: Lac Moraine dans le Parc national Banff, au Canada.
context_page_description: Earth is the third planet from the Sun and the only astronomical object known to harbor life. According to radiometric dating estimation and other evidence, Earth formed over 4.5 billion years ago. Earth's gravity interacts with other objects in space, especially the Sun and the Moon, which is Earth's only natural satellite. Earth orbits around the Sun in 365.256 solar days, a period known as an Earth sidereal year. During this time, Earth rotates about its axis 366.256 times; that is, a sidereal year has 366.256 sidereal days.
  Earth's axis of rotation is tilted with respect to its orbital plane, producing seasons on Earth. The gravitational interaction between Earth and the Moon causes tides, stabilizes Earth's orientation on its axis, and gradually slows its rotation. Earth is the densest planet in the Solar System and the largest and most massive of the four rocky planets.
  Earth's outer layer is divided into several rigid tectonic plates that migrate across the surface over many millions of years. About 29% of Earth's surface is land consisting of continents and islands.
context_section_description: A planet that can sustain life is termed habitable, even if life did not originate there. Earth provides liquid water—an environment where complex organic molecules can assemble and interact, and sufficient energy to sustain metabolism. The distance of Earth from the Sun, as well as its orbital eccentricity, rate of rotation, axial tilt, geological history, sustaining atmosphere, and magnetic field all contribute to the current climatic conditions at the surface.
caption: The Rocky Mountains in Canada overlook Moraine Lake.
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