Origin of the Earth

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1. Steady State Theory – based on the perfect cosmological principle that the universe looks the same from any location at anytime. This theory holds that the universe is unchanging, it has no beginning and no end.
2. Big Bang Theory – presupposes that the vast universe grew out of something where all matter and energy were compressed to infinite density and heated to trillions of degrees (a beginning which was an immensely small particle of high-density state. The four basic forces of nature – gravity, electromagnetism, strong and weak atomic forces – were unified in that tiny particle. This particle exploded into a great fire ball releasing the basic forces. Rapid expansion
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Here is where the star leaves the main sequence. This collapse begins to create more and more pressure inside the star until it is sufficient to have the fusing process of helium begin in the core, while some of the remaining hydrogen burns just outside of it. The products of this helium burning is carbon and oxygen. The star swells, and depending on its size, either becomes a red giant or a red supergiant.
(ref. http://library.thinkquest.org/26220/stars/formation.html)


The Accretion theory

This assumes that the Sun passed through a dense interstellar cloud and emerged surrounded by a dusty, gaseous envelope. It thus separates the formation of the Sun from that of the planets thus losing problem 1.

The problem which remains is that of getting the cloud to form the planets. The terrestrial planets can form in a reasonable time but the gaseous planets take far too long to form. The theory does not explain satellites or Bode's law and must be considered the weakest of those described here.

The Protoplanet theory

This assumes that initially there is a dense interstellar cloud which will eventually produce a cluster of stars. Dense regions in the cloud form and coalesce; as the small blobs have random spins the resulting stars will have a low rotation rates. The planets are smaller blobs captured by the star. The small blobs would have higher rotation than is seen in the planets but the theory accounts for
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