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Earth science 25.3


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Earth science 25.3

  1. 1. 25.3 The Universe <br />
  2. 2. Galaxy <br />A group of stars, dust, and gases held together by gravity.<br />
  3. 3. Galaxy Cluster <br />A system of galaxies containing from several to thousands of member galaxies.<br />
  4. 4. Hubble’s Law<br />A law that states that the galaxies are retreating from the Milky Way at a speed that is proportional to their distance.<br />
  5. 5. Big Bang Theory<br />The theory that proposed that the universe originated as a single mass, which subsequently exploded.<br />
  6. 6. Key Concept<br />The milky Way is a large spiral galaxy whose disk is about 100,000 light-years wide and about 10,000 light-years thick at the nucleus.<br />
  7. 7. Key Concept<br />In addition to shape and size, one of the major differences among different types of galaxies is the age of their stars.<br />
  8. 8. Key Concept<br />The red shifts of distant galaxies indicate that the universe is expanding.<br />
  9. 9. Key Concept<br />The big bang theory states that at one time, the entire universe was confined to a dense, hot, supermasive ball. Then, about 13.7 billion years ago, a violent explosion occurred, hurling this material in all directions.<br />