Origin of the Earth Essays

1745 Words Mar 22nd, 2008 7 Pages
THEORIES OF THE ORIGIN OF THE UNIVERSE
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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This is known as the “Big Crunch”.

FORMATION AND DEATH OF STARS
1. BIRTH - A star is born in a huge cloud of gas and dust known as a nebula. This nebula is about 21 light-years (125 trillion miles) across. Part of the nebula begins to shrink under the pull of its own gravity. This forms a protostar which is about 60 million miles across. The star begins to take shape. The temperature continues to rise and nuclear fusion begins to take place. The pressure from inside the star finally equalizes the gravity pushing in, and the star stops contracting.
2. LIFE - In order for nuclear fusion to take place, there must be tremendous amounts of pressure and heat. This pressure crushes together elements to create more massive elements and energy. Stars begin fusing hydrogen first because it is the least dense and the easiest to fuse. Four hydrogen nuclei fuse together to form one nucleus of helium. By-products of this is the production of two positrons, two neutrinos, and the release of energy. Stars that are going through this hydrogen burning process are known to be on the main sequence. Stars spend most of their life (aprox. 90%) on the main sequence.
3. DEATH - A star will eventually use up most of it's hydrogen and be left with helium. At this time there is not enough pressure crushing down on the star to create a nuclear reaction with helium. Nuclear reactions cease inside the

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