origine de la terre

The planet, on which we live and move about, is a huge sphere of radius of about 6400 km, but is itself a small member of the Solar System. Since the Solar System is the only one of its kind, so far known, the origin of the Earth and that of the Solar System as well, must have been due to some unique phenomenon that happened to occur in the Universe during some very remote past.

One of the earliest theories is the Nebular Hypothesis. Though untenable, it enjoyed the confidence of the persons in science for nearly two long centuries and, accordingly, deserves some consideration. The hypothesis assumed that during the very remote past there existed a large, hot, gaseous nebula rotating in space. Gradual cooling of this nebula led to its contraction and increase in speed of revolution about its axis. The equatorial zone of the nebula, therefore, bulged out due to greater and progressively increasing centrifugal force prevailing in that region and ultimately a gaseous ring separated out from the mass of the nebula.

The ring coalesced in the form of a globe and continued to revolve round the nebula, following the path marked by the pre-existing ring. In exactly similar manner, ten rings were formed. Nine of them gave rise to the planets and one, which broke down into smaller fragments, to the group of planetoids, while the remnant of the pre-existing nebula formed the central incandescent mass of the Solar System and is known as the Sun. The planets, thus formed, were originally gaseous but were subsequently cooled down into liquid and ultimately to the solid state.

This video demonstrates the formation of the Solar System, while this is an artistic music video nicely done.

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