P2- 7.4 - the early universe

  • Created by: Grace
  • Created on: 06-05-13 11:04
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  • 7.4- The early universe
    • most scientists believe that the universe was created by the Big Bang about 13 billion years ago.
      • At first the universe was a hot glowing ball of radiation
      • In the first feew minuets the nuclei of the lightest elements formed
      • As the universe expanded, over millions of years, its tempurature fell. Uncharged atoms were formed
    • Before galaxies and stars formed, the universe was a dark patchy cloud of hydrogen and helium.
      • eventually dust and gas were pulled together by gravitational attraction to form stars
        • The resulting intense heat started off nuclear fusion reactions in stars, so they began to emit visible light and other raditation
    • Very large groups of stars are called galaxies.
      • Our sun is one of the many billions of stars in the milky way galaxy.
      • the universe contains billions of galaxies
      • A galaxy is a collection of billions of stars held together by their own gravity .
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