About Earth; the important data

Earth is the third planet from the sun and is the largest of the terrestrial planets in the Solar System in terms of diameter, mass and density. It is also referred to as the World, the Blue Planet and Terra. Home to millions of species including humans, Earth is the only place in the universe where life is known to exist. Scientific evidence indicates that the planet formed some 4.54 billion years ago and life appeared on its surface within a billion years. Since then, Earth’s biosphere has significantly altered the atmosphere and other abiotic conditions on the planet.
Scientists believe the Earth began its life about 4.54 billion years ago. The Earth formed as cosmic dust lumped together to form larger and larger particles until 150 million years had passed. At about 4.4 billion years, the young Earth had a mass similar to the mass it has today. The continents probably began forming about 4.2 billion years ago as the Earth continued to cool. The cooling also resulted in the release of gases from the lithosphere, much of the which formed the earth’s early atmosphere. Most of the Earth’s early atmosphere was created in the first on million years after solidification (4.4 billion years ago). Carbon dioxide, nitrogen and water vapors dominated this early atmosphere. The table given below describes the three major stages of the development of the atmosphere.Earth’s outer surface is divided into several rigid segments or tectonic plates that gradually migrate across the surface over periods of many millions of years. About 71% of the surface is covered with salt-water ocean, the remainder consisting of continents and islands. Liquid water, which is necessary for all known life, is not known to exist on any other planet’s surface. Earth interacts with other objects in outer space, including the Sun and the Moon. At present, Earth orbits the sun once for every roughly 365.26 times it rotates about its axis, which is equal to 365.26 solar days. The Earth’s of rotation is tilted 223.4 degree away from perpendicular to its orbital plane, producing a seasonal variation on the planet’s surface. Earth’s only known natural satellite , the moon, which began orbiting it about 4.53 billion years ago, provides ocean tides, stabilizes the axial tilt and gradually slows the planet’s rotation. A cometary bombardment during the early history of the planet played a role in the formation of the oceans. Long term periodic changes in the Earth’s orbit, caused by the gravitational influence of other planets, are believed to have given rise to the ice ages that have intermittently covered significant portions of Earth’s surface in glacial sheets.

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