The Jurassic and Cretaceous followed and created the continents we know today. The idea of continental drift explains how a giant land mass or supercontinent called Pangaea, which existed about 240 million years ago, soon broke into two – Laurasia and Gondwanaland, during the Triassic period.The idea of continental drift is the leading explanation on the theory of plate tectonics. Through periods of hundreds of millions of years, the supercontinents have assembled and then broke apart.The continuous loss of heat from Earth’s interior helped continents form through plate tectonics.There are two models that propose that the landmass steadily grew to present-day forms, or, more likely that it grew rapidly early on in Earth’s history, followed by a long-term steady continental area. A crust formed when the molten outer layer of Earth cooled to form a solid.When the Earth’s magnetic field was established it helped to prevent the atmosphere from being stripped away by the solar wind.The atmospheric greenhouse kept the oceans from freezing when the newly formed Sun had only 70% of its current luminosity.It is believed that water vapour condensed into the oceans, being augmented by water and ice from asteroids, protoplanets and comets.
Slowly, the Earth’s atmosphere and oceans were formed by volcanic activity and outgassing. The planets grow out of that disk through gravity pulling swirling dust and gas.
The theory states that a solar nebula partitions a volume out of a molecular cloud by gravitational collapse which begins to spin and flatten into a circumstellar disk.The duration for this formation has been estimated at about 10 to 20 million years. The Earth is believed to have formed around 4.5 billion years ago.
Observations continued, ideas caught up and finally, it was established that Earth was a planet among many others. Later, in the 17th century, Galileo Galilei observed and discovered Jupiter and that it had moons of its own, and that Venus went through phases like the Moon. Copernicus’ idea was highly opposed as it negated the common knowledge about the Solar System and man’s place in it. In the 16th century, Polish mathematician/astronomer Nicolaus Copernicus created the heliocentric model of the Solar System – where everything orbited the Sun. Soon after, the Greek astronomer Ptolemy proposed the idea that planets were tiny spheres and made circles as they orbited Earth. Some believed that the Earth was flat, while the Ancient Greeks such as Plato correctly deduced that the Earth was a sphere. Since ancient times, the Earth was taught to be at the centre of the Universe, with the other celestial objects orbiting around it. Equatorial inclination to orbit: 23.4393 degrees. Length of year (single revolution around the sun): 365.26 days. Length of solar day (single rotation on its axis): 23.934 hours. Those who inhabit Earth can be referred to as Earthlings, Earthers, Terrans or Gaians. The old English version of these words became “eor(th)e” or “ertha”, which later transformed into “Earth”. Despite not being directly named after figures in mythology, the Greek equivalent to Earth is Gaia – terra mater – mother Earth, and Roman equivalent was Tellus – the fertile soil. Unlike other planets, it wasn’t named after a Greek or Roman god. The name “Earth” is at least 1,000 years old, and it is a Germanic word which simply translates to “the ground”. It is currently the only known planet where life is present. Earth is the third planet from the Sun and the fifth largest planet in the Solar System, with the highest density. Click any of the example images below to view a larger version.
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